Food Science Packaging – Michael D. Schmal, Ernest E. Bachert, John A. Menges, Robert R. Witt, M&Q IP Leasing Inc
Abstract for “Thermoplastic Elastomer Films”
The present invention relates to thermoplastic-elastomer bags and films made from thermoplastic films, as well as to methods and materials for making thermoplastic bags and films. The present invention’s thermoplastic elastomer film is made from thermoplastic elastomers as well as non-elastic polymers. The present invention makes bags from blended monolayer thermoplastic film that includes a mixture of thermoplastic and non-elastic polymers. The present invention’s blended monolayer thermoplastic films are used in food handling, particularly in the meat packaging sector and in cooking bag applications. The co-extruded film of the present invention is also useful in food handling, particularly in the meat packaging industry, and in meat casing applications.
Background for “Thermoplastic Elastomer Films”
Thermoplastic films are used to preserve and protect food products. Polypropylene, nylon, ethylenevinylidene chloride, polyethylene, nylon and polyethylene are all common compositions. To combine films, an optional adhesive layer can be used.
Bags made of conventional films can be used for steam or hot water cooking, but they are not suitable for high-temperature cooking applications such as beef cooking. They either stick to or melt food products that are kept in the bag. Bags made from materials that are easily removed from food products during cooking is desirable. Because they are heated, conventional bags cannot be used in high-pressure meat casing applications.
Bags with good mechanical properties and low costs are also desirable. Food packaging is always looking for stronger and more durable bags that resist tearing and abrasion to isolate food products from outside environments. This will prevent contamination. To achieve desired mechanical properties such as tear resistance or durability, conventional bags are often thickened at an additional cost.
“The food packaging industry is also looking for materials that can be made at lower costs. Food packaging companies are trying to cut costs by using thinner films. Bags made from thin films require less material to make. The cost of making a bag is directly related to how much thermoplastic elastomer was used. To reduce material and hence the cost of making the bag, it is desirable that thinner films are used. In order to lower the material cost, it is important to increase the sealing strength of traditional bags. Bags with higher seal strengths require a thinner film and thus less thermoplastic elastomer.
“Conventional bags should be able to protect the environment from moisture and gases. Good barrier properties are desirable, including the ability to reduce or eliminate moisture, gas migration through the bag, and other such qualities. Because oxygen migration can cause bag contents, such as meat products to spoil or discolor, it is important to minimize it.
“Resealing thermoplastic films can be achieved by applying heat and pressure to the film surfaces. This will cause a fusion bond between layers. Heat sealed cylindrical bags can be imperfectly sealed as the heat required to seal the tubular stock folds will cause the film’s barrier properties to be damaged by melting or thinning. Poor seals can be a problem when using heat shrinkable film for cooking. This is because the seals are more susceptible to heat shrinking and elevated temperatures. Many manufacturers now use mechanical closure devices or ultrasonic sealing techniques to seal traditional films.
Ultrasonic sealing techniques are not recommended for sealing thermoplastic elastomer film, such as copolyester films. This is because the films’ elastic structure dampens ultrasonic energy transmission and prevents complete sealing of this particular type of bag. When thermoplastic elastomer film is used, mechanical sealing devices such as clips, rings, or the like are preferred. These mechanical sealing devices are typically made from a metal or plastic material.
Mechanical sealing devices can have several undesirable features. If they are lost in food products, mechanical sealing devices can cause contamination. The metal sealing devices can’t be used in microwave ovens to cook or defrost the food product in the bags. Additionally, the metal clips can sometimes get lost in the product which can lead to customer complaints. It is therefore desirable to have sealing methods for thermoplastic elastomer bags which eliminate the need of a mechanical device. This also solves the sealing issues associated with ultrasonically and heat sealed bags.
“There is an urgent need for better thermoplastic elastomer film and methods to make bags from these films, which overcomes the drawbacks of conventional films and methods to make bags made of conventional films.”
The present invention relates to thermoplastic-elastomer bags and films made from thermoplastic films, as well as to methods and materials for making thermoplastic bags and films. The present invention’s thermoplastic elastomer film is made from thermoplastic elastomers as well as non-elastic polymers. The present invention makes bags from blended monolayer thermoplastic films. These films can be made with a mixture of thermoplastic and non-elastic polymers, or co-extruded multilayer films that contain at least one layer each of thermoplastic and non-elastic elastomers. The present invention’s blended monolayer thermoplastic films are used in food handling, particularly in the meat packaging sector and in cooking bag applications. The multi-layered co-extruded films of the present invention can also be used in the food processing industry, particularly in the meat packaging industry, and in meat casing applications.
The films of the invention are co-extruded multilayered films with at least one layer each of thermoplastic elastomer or non-elastic polymer. Polyether-ester block polyolymers and polyester-ester blocks copolymers are the preferred thermoplastic elastomers. Another embodiment of the invention uses polyether-ester or polyester-ester copolymers as well as non-elastic Polyesters. These are mixed in a melt to create a single-layered film. Polyether-ester block polyolymers are the preferred thermoplastic elastomers.
The films of the invention have improved mechanical properties. They are stronger and more resistant to tearing and abrasion. These films have a higher tensile modulus and are therefore more rigid. This makes it easier to use these films for making bags. Films with a higher tensile yield strength require more force to cause them to stretch beyond their elastic regions. This allows for a controlled stretch to pack meat. High tensile yield strengths produce uniformly sized sausages when used in meat casings. The films of the invention make tighter and more consistent meat casings when they are used in pressurized applications. This is because they have lower tensile elongation than conventional films. Tensile yield extension is the amount of elongation before the film stretches out and becomes elastic. The films of the invention have a higher tensile break length than monolayer films made of thermoplastic elastomer. This allows them to be used in almost all meat packaging applications because they will stretch less before they are broken.
The present invention makes bags from thermoplastic films. They are then bonded together using a variety of sealing techniques. These include wire impulse sealing techniques and impulse sealing techniques. The bags of the invention are preferred to be made using ultrasonic sealing techniques. Bags are made using ultrasonic sealing techniques called star sealing. The present invention also includes the following features.
“DESCRIPTION DU DRAWINGS”
“The many features and benefits of the invention can be better understood by those who are skilled in the art. Refer to the detailed description and the drawing below.
“FIG. “FIG.
“FIG. “FIG.
“FIG. “FIG.
“FIG. 2A is a side-view of an exemplary blow extrusion apparatus for multilayered thermoplastic films.
“FIG. 2B is a side-view of an exemplary blow extrusion apparatus for blended thermoplastic monolayer films;
“FIG. “FIG.
“FIG. “FIG.
“FIG. 5A is a side-view of an exemplary star sealing machine bag machine.
“FIG. “FIG.
“FIG. FIG. 6 shows a top view showing the star seal bag machine. 5A;”
“FIG. 7 is a frontal view of an exemplary twist fixture.
“FIG. FIG.8 is a rear view of FIG.8’s twist fixture. 7;”
“FIG. “FIG.
“FIG. “FIG.
“FIG. “FIG. 11. This is a top-view of an exemplary star sealing machine with a plurality twisting members.
The present invention relates to thermoplastic-elastomer bags and films made from thermoplastic films, as well as to methods and materials for making thermoplastic bags and films. The present invention’s thermoplastic elastomer film is made from thermoplastic elastomers as well as non-elastic polymers. The present invention makes bags using blended monolayer thermoplastic Elastomer films. These films can be made from a mixture of thermoplastic and non-elastic polymers, or co-extruded multilayer films that contain at least one layer each of thermoplastic and non-elastic elastomers. The present invention’s blended monolayer thermoplastic films are used in food handling, particularly in the meat packaging sector and in cooking bag applications. The co-extruded film of the present invention is also useful in food handling, particularly in the meat packaging industry, and in meat casing applications. As used herein ?bag? Bags at traditional definition include vacuum bags, bags, pouches and sacks. They also refer to containers that hold meat products for transportation and packaging. Casings are food product casings that contain food products. This includes but is not limited to sausage casings and keilbasa cases, lunch meat casings and hot dog casings. Products can be food products, meat products or explosive products.
The films and bags of this invention have improved mechanical properties. They can be used to isolate food products from the environment. This prevents any contamination from entering the bag. These improved mechanical properties allow for lower-thickness films to make bags, which in turn lowers the cost of bags made from the films.
“Improved mechanical characteristics include increased tensile strength and thus higher resistance to tearing, abrasion and tearing, elevated melting points and increased tensile module, higher yield strengths, lower yield elongation and higher tensile breaking strength. The films of the invention have a higher tensile modulus and thus are more rigid. This makes it easier to use these films for making bags. Films with a higher tensile yield strength require greater force to cause them to stretch beyond their elastic regions. This allows for a controlled and controlled stretch when packaging meat. High tensile yield strengths films produce a uniformly sized sausage when used in a meat casing. The films of the invention make tighter and more consistent meat casings when they are used in pressurized applications. This is because the films have a lower tensile yield extension than conventional films. Tensile yield extension is the amount of elongation before the film stretches out and yields beyond its elastic limit. The films of the invention have a higher tensile break length, which allows them to be used in almost all meat packaging applications.
The films and bags of this invention have improved barrier properties. They can reduce or eliminate moisture, gas migration through bags made from the films. The thermoelastomer films are less likely to cause oxygen migration and more moisture transmission than conventional bags. Both the multilayered thermoplastic thermoplastic films are made from the thermoplastic film.
“The addition non-elastic polyesters as thermoplastic elastomers to multi-layered films or as a component in blended films makes it easier for ultrasonically star sealing bags made of the films of this invention, as opposed to bags made of conventional materials.” The ultrasonic seal is also stronger than those made from conventional materials or heat sealing methods.
Bags containing non-elastic polyester and a thermoplastic elastic elastomer are not able to adhere to food products. Blended monolayered thermoplastic films have better nonstick properties because the non-elastic polyester content in the blended film is decreased. Multi-layered coextruded bags have the added advantage of having a film layer made of substantially thermoplastic rubber in contact with food products. The film layer of substantially thermoplastic rubber elastomer will not adhere to foods products, particularly meat products. Bags made of multi-layered coextruded films have all the advantages of cost, mechanical properties, and barrier properties, but they do not adhere to meat products during transportation, storage, or cooking applications.
The present invention provides two methods of making thermoplastic film: co-extruding multi-layered thermoplastic films and extruding blended monolayer thermoplastic movies. Multi-layered films can be made by co-extruding non-elastic and thermoplastic polyester in separate layers. The melt mixture of non-elastic polyester, thermoplastic elastomer, and thermoplastic elastomer is used to make blended monolayer thermoplastic films.
“In one embodiment, the method for fabricating bags according to the present invention includes making tubular-shaped films called tubular stock and sealing the bag with at least one ultrasonic seal called a star seal. The present invention also allows for heat sealing to seal non-tube shaped films and tubular stock.
“FIG. “FIG. FIG. FIG. 1B shows a cross-sectional view of an exemplary monolayer blended thermoplastic elastomer (BMT) film. The films of this invention are co-extruded multilayered films 1 with at least one layer each of thermoplastic elastomer 2 or non-elastic polymer 3. Blended monolayer thermoplastic-elastomer films are also included in the films of this invention. Polyether-ester block polyolymers and polyester-ester blocks copolymers are the preferred thermoplastic elastomers. Another embodiment of the invention uses polyether-ester or polyester-ester copolymers as well as non-elastic Polyesters. These are mixed in a melt to create a single-layered film. Polyether-ester block polyolymers are the preferred thermoplastic elastomers.
Polyether-ester block copolymers, which are multi-block co-polymers that have crystallizable and low-crystallinity segments, alternate frequently. Melt trans-esterification is a method of making thermoplastic elastomers from a caboxylic acid or its methyl ester, a polyalkyleneoxide, and a short-chain diol. The Encyclopedia of Polymer Science and Technology Vol. 12 contains a comprehensive description of non-elastic polyesters and polyether-ester-block copolymers. 12, pages 76-177 (1985), which are herein incorporated as reference.”
“Films according to the present invention are co-extruded multilayered films that contain at least one layer each of thermoplastic epoxy 2 and non-elastic polymer 3 that are about 95 percent to approximately 5 percent of total film thickness. The preferred thickness of the thermoplastic layer 3 is between about 10 percent and about 50 percent, while the thickness of the non-polyester layer 3 ranges from approximately 90 percent to around 50 percent.
Blended mono layer films of the present invention include films that contain between 10 and 90 weight percent thermoplastic rubber elastomer, and 90 to 10 weight percent non elastic polyester. Blends are preferred to include about 40 to 60 weight percent of thermoplastic elastomer, and 60 to 40 weight percent of non-elastic Polyester. Blends with 50 to 50 percent thermoplastic Elastomer and 50 percent non-elastic Polyester are preferred.
“In one embodiment, the polyesterester block copolymers are the repeating alternating ester units (cystallizable polyester segments A) and low-crystallinelinity polyester segments. Segment A should have a molecular mass of about 400 to approximately 6000. Segment B should have a molecular mass of approximately 100 to about 550.
Segment A is made from at least one dicarboxylic acid, and at most one glycol. Segment A crystallizable with a preferable crystallinity of about 35 % and more preferably, about 50 %. A group of aliphatic, cycloaliphatic, and aromatic diboxylic acid suitable for use is selected. Dicarboxylic acids with aromatic dicarboxylic compounds are preferred. Preferred aromatic dicarboxylic acids are selected from the group comprising phthalic, isophthalic or terephthalic acid, naphthalenedicarboxylic acids and diphenyldicarboxylic acids. The dicarboxylic acid should have between 8 and 16 carbon atoms. Terephthalic acid is the preferred dicarboxylic acid. It is more preferable to repeat A segments of butylene-terephthalate units.
“Suitable polyalkylene glycols for segment A include long-chain glycols with terminal and near terminal hydroxy group. The preferred alkylene glycols can be selected from the following groups: polyethylene oxide; poly(1,2- and 1,3,3) propyleneoxid; polybutyleneoxid or copolymers thereof. The preferred alkylene glycol is polybutylene oxide.
Segment B contains repeating units that are derived at least from one diol or a dicarboxylic acids. Segment B has a low crystallinity and a crystallinity of less than 30%. You can use aliphatic and cycloaliphatic diols as well as aromatic dihydroxy compounds. The most preferred diols are those with between 2 and 15 carbon atoms. These include ethylene, propylenes, butylenes, tetramethylenes, and others. Butanediols and tetramethylene diols are even more popular diols. Equivalent ester-forming derivatives of diols can also be useful, such as ethylene carbonate or ethylene oxide. The formula for a suitable alkylene carbonate is:
“?O?(CR2)x?O?C?”
“where R is a hydrogenatom, an alkyl or an aryl group and x is between about 2 and about 20. It is preferable that R be a hydrogen atom with x=6. The alkylene carbonate, therefore, is hexamethylenecarbonate.
“The composition segments A, and B can vary within large limits. They are primarily determined based on the desired mechanical properties. Copolyester rubber elastomers with a higher A content have a greater stiffness and higher melting points. Copolyester Elastomers with a high amount of B are more flexible, and have a lower melting temperature. The copolyester rubber elastomers have a weight ratio of about 10:80 to 80:10. The preferred weight ratio is between about 10:60 and about 60,10, but more preferably between about 60/40 and about 40:60.
Non-elastic polyesters can be made using the invention if they are derived from a dicarboxylic and a diol. Alkylene glycols with long chains that facilitate crystal formation are preferred diols. Non-elastic crystallinity of polyester should be at least 35% and more preferably about 50%. The preferred alkylene glycols can be selected from the polyethylene oxide, poly(1,2- and 1,3) propyleneoxid, polybutyleneoxid or combinations thereof. The preferred alkylene glycol is polybutylene oxide. The preferred dicarboxylic acid group includes phthalic and isophthalic acids, as well as combinations thereof. Terepthalic acids are preferred, so non-elastic polyesters made of butylene triphthalate are preferred. Optionally, the dicarboxylic acid and the diol can be substituted provided that the substituted group doesn’t hinder crystal formation.
“Films according to the present invention should be made using extrusion processes well-known in the art. Perry’s Chemical Engineering Handbook (Ch. 18, pp. 29, pp.
“FIG. 2A is a side-view of the exemplary blown film extrusion device for multi-layered coextruded films. The multi-layered coextruded films made according to the invention are obtained by pouring thermoplastic resin pellets 4 into a resin hopper 5 on a first extruder 6, and then pouring non elastic polyester resin pellets 7 into a resin hopper 8 on a second extruder 8. You can use any type of extruder, including single-, double-, or tandem extruders. The thermoplastic elastomer pellets 4 are fed into 6’s first extruder. Non-elastic polyester pellets 7 are fed into 9’s second extruder. To form thermoplastic elastic polyester resin pellets 4, and non-elastic resin pellets 7, respectively, the first extruder 6, and second extruder 9, melt the thermoplastic rubber resin pellets 4. The optional additives may be added to the melted resins 10, 11 and 12 in first extruder 6, and second extruder 9, respectively, and/or mixed with resin pellets 4, and 7. A die 12 connects the first extruder 6 to the second extruder 9.
The first extruder 6 pushes melted resins 10, 11 and 12 through die 12, to form a film made of thermoplastic Elastomer 2, or the first layer, and a non-elastic Polyester 3, or the second layer. The preferred die 12 allows a film of thermoplastic elastic film 2 and a second non-elastic polymer 3 to be extruded simultaneously, forming a multi-layered film 1.
“Thermoplastic Elastomer Film 2 and non elastic Polyester Film 3 exit die 12. They are chilled by being in contact with a region of lower temperature and pressure than the temperature and pressure within first extruder 6 or second extruder 9. The ambient temperature and pressure are typically the ambient atmosphere. However, it may also be a chill roller. A sudden drop in temperature and pressure causes thermoplastic elastomer 2 and non elastic polyester 3 to become multi-layered films upon cooling. A winder gathers the layered film and winds it into rolls.
“In a preferred embodiment, multi-layered film 1 can be co-extruded using a blow-blown extrusion process. The die 12 connecting first and second extruders 6 in a blow film process is annular or ring-shaped so that first and second extruders 6 force thermoplastic elastomer films 2 and non elastic polyester films 3 from die 12. An aperture 14 is located in the middle of die 12. The aperture 14 is circular or annular in shape and allows a blowing agent, such as a blower, to inflate tube 13, of thermoplastic film 2 and non elastic polyester film 3, when it exits die 12. The tube 13’s diameter is increased and its thickness decreased by the blowing agent. Tube 13 is blown against the collapsing frame 16. This guides the tube to a pair of rolling rollers 17. The tube 13 is flattened by the rollers 17 to create a tubular stock. For transportation and storage, the tubular stock 18 can be wound into a roll 26. The interior layer of thermoplastic films is preferred to be thermoplastic elastomer 2 and non-elastic polyethylene film 3. It is preferable that the thermoplastic elastomer be in direct contact with products stored in bags made of films of the invention.
“FIG. 1C is a cross-sectional view of an exemplary multilayered thermoplastic elastomer (TME) film. Referring to FIG. FIG. 1C shows another preferred embodiment of the multi-layered film 1. It includes at least one additional layer, 81. Each layer 81 is made of a thermoplastic block copolymer, thermoplastic polyester or combination thereof. To make the multilayered thermoplastic movie 1, co-extrude the first layer 2, then the second layer 3 and each of the additional layers 81. This will form the multilayered thermoplastic movie 1. The multi-layered thermoplastic film can also be made by extruding each layer individually: the first layer 2, second layer 3 and each additional layer 81. The second layer 3, which is the second layer of multi-layered thermoplastic film 1 is placed on the first layer 2, and each layer 81 on the second layer. To form multilayered thermoplastic film 1, the first layer 2, second layer 3 and each of the at least one additional layer 81 are rolled between heated rollers. Alternativly, the multilayered thermoplastic movie 1 can be made by placing an interleaving adhesive layer 82 between the first and second layers. An interleaving adhesive layer (82) is placed between the layers 81 and 82.
“FIG. 2B is a side-view of an exemplary blow extrusion apparatus for blended thermoplastic films. The mixture of thermoplastic elastomer pellets 4 with non-elastic poly resin pellets 7 is used to make blended monolayer thermoplastic films 24. This results in a mixture 19 that is nearly homogenous. The blended mixture is then poured into an extruder 21’s resin hopper 20. You can use any type of extruder, including single-, double-, or tandem extruders. You can add any optional additives to each extruder, or you may use resin pellets 4, 7 and 8. Blend 19 is fed into extruder 21 by resin hopper 20. Mixing the blend 19 in extruder 21 creates a melt mix 22 which includes non-elastic polyesters and thermoplastic elastomers. Extruder 21 pushes melt mix 22 through a die 23, at the end extruder 21. Extruder 21 pushes melt blend 22 through die 23, to form a mixed monolayer thermoplastic film 24. The blended monolayer thermoplastic films 24 encounters a lower temperature and pressure than the extruder 21. The ambient temperature and pressure are typically the ambient atmosphere. However, it may also be a chilling roller. The temperature and pressure drop abruptly causes the blended film 24’s solidification upon cooling. A winder 25 gathers the monolayer blended thermoplastic film 24 and winds it into rolls 26.
In a preferred embodiment, melt mix 22 is extruded using a blown-film extrusion process. The die 23 at the end 21 of the extruder 21 is annular or ring-shaped so that the melt mix 22 is forced out of die 23 into the form of a tube 27. An aperture 28 is located in the middle of die 23. The aperture 28 is circular or annular in shape and allows a blowing agent, to inflate tube 27 when it exits die 23. Tube 27 is formed by the blowing agent, which increases its diameter and reduces the thickness the mixed monolayer thermoplastic film 24, forming it. Tube 27 is blown against the collapsing frame 30, which guides tube 27 to a pair 31 of rollers. A pair of rollers 31 flatten tube 27, forming a tubular stock. For transportation and storage, the tubular stock of film 32 can be wound into a roll 26.
“The films should be as thin as possible to reduce the resin required to make food product bags. They also need to have a high gas and moisture transmission rate and rugged durability. Each individual thermoplastic elastomer 2 and non-elastic Polyester 3 have a gauge thickness between about 0.0001 and 0.01 inches. Preferably, the films of this invention have a gauge thickness of between about 0.0005 and about 0.0035 inches. Even better, they should range from approximately 0.001 to about 0.25 inches.
“The films can optionally be stretch oriented. “Stretch-oriented” is an alternative term. The term “stretch-oriented” is used herein to refer to the process and the resultant product characteristics. It involves stretching and cooling a resinous, polymeric material to adjust its molecular structure by physical alignment of molecules. This results in improved mechanical properties such as tear strength, tensile strength, shrink properties, as well as optical properties. The present invention uses stretch-orientation to decrease the moisture and gas transmission rates, i.e., increase the film’s moisture vapor barrier functionality. It also increases toughness and shrinkability in comparison with films that are not stretch-oriented.
The film sheets can be optionally stretched by heating the quenched sheet to the orientation temperature, and then stretching it. The temperature of a particular film’s orientation will depend on the resinous polymers or blends that make it, so there will be a wide range of temperatures. The orientation temperature can be described as being above or below room temperature, but it will not be the melting point. It will usually be close to the glass transition temperature for the resins from the film.
“The process of stretching film at the orientation temperature range can be done in many ways, such as by using a?double bubble? or ?tenter framing? techniques. These techniques, along with others, are well-known in the art. They involve stretching the film in either the transverse or cross direction (TD), and/or in the machine or longitudinal direction (MD). Uniaxial orientation is achieved when the stretching force applies in only one direction. Biaxial orientation is achieved when the stretching force can be applied in both directions. The film is stretched and then quickly cooled to set the molecular arrangement. This type of quenched and oriented film is known to be heat-shrinkable. The film will return to its original dimensions if heated at a temperature below its melting point.
After quenching has locked-in the molecular arrangement, the film sheets can be heat-set. This involves heating the oriented film to near its orientation temperature and restraining it in its stretched dimensions. This is also known as “annealing”. This process results in a film that is significantly less susceptible to shrinkage, but retains many of the benefits of orientation such as improved tensile strength, optical properties, and lower gas and moisture transmission.
The present invention makes bags from thermoplastic films. They are then bonded together using a variety of sealing techniques. These include wire impulse sealing techniques and impulse sealing techniques. Hot knife heat sealing is another option. The bags of the invention are preferred to be made using ultrasonic sealing techniques. Bags are made using ultrasonic sealing techniques known as star sealing.
“Thermoplastic and elastomer films should be made from tubular stock so that bags can be made by sealing one end or both ends of a tube of tubular film, then cutting one edge to make the bag mouth. You can also make bags from flat sheets of film by sealing the edges of three superimposed sheets or by folding a rectangle sheet in half and sealing those sides closest to the folded side.
“FIG. FIG. 3 shows a side-view of an exemplary bag made from tubular stock and star sealed. FIG. FIG. 4 shows a side-view of an exemplary star sealing. Referring to FIG. Referring to FIG. 3. and FIG. 4. A bag 33 can be made according to the invention using ultrasonic sealing equipment capable of forming an “star seal 34”. The star seal 34 is made by tightly twisting, bunching and/or gathering a tube stock of film into an awd, thereby creating wadded tubular stocks. To seal the wadded tubular stock, ultrasonic sealing techniques are used to create a star seal.
“FIG. 5A is a side-view of an exemplary star sealing bags machine. FIG. FIG. FIG. 6 shows a top view showing the star seal bag machine. 5. As shown in FIG. 5A, FIG. FIG. 5A, FIG. FIG. 5B and FIG. 6. One embodiment of an acceptable ultrasonic seal machine 35 includes a gathering Horn 36, a twisting fixture 37, an anvil 38, an ultrasonic sealing horn 39, and at least one guide member 40. A first clamp 41, a 2nd clamp 42, as well as a cutting member 43.
“Gathering Horn 36” includes an elongated aperture 44 to receive tubular stock 45 from the roll of tubular stock 46. It also has a front surface 47, and a back side 48. The front surface 47 and the back surface 48 are connected by an elongated aperture 44. The circumference of the elongated aperture 44 shrinks from the front 47 to the back 48. The elongated aperture 44 narrows from the front surface 47 to the back surface 48 into a rope-like structure called wadded tubular Stock 49 as it passes through gathering Horn 36.
“FIG. FIG. 7 and FIG. 8. are front and back views of an exemplary twist fixture. 8 shows front and back views of an example twist fixture. Referring to FIG. 6, FIG. 6, FIG. 7. 8. Twisting fixture 37 also includes an air tube 50, a geared wrench 51, and at least one twisting piece 52. The operative attachment of the geared-ratchet 51 to the air cylinder 50 is to the geared wrench 51. It articulates with the geared regulator 51. The operative attachment of a geared ratchet 51 to at least one twisting piece 52 is a length 53 of gear teeth on an elongated 54 member. The gears 55 are operatively attached to gear ratchet 51. It has a front surface 56 and a back surface 57%. An aperture 58 is formed for wadded tubular stock 49. The aperture 58 connects the front surface 56 and back surface 57. The aperture 58 narrows between the front surface 56 and the back surface 57 so that the circumference decreases from one side to the other. The front surface of aperture 58 is oval-shaped, and it’s elongated. Aperture 58 on the back surface 57 has a circular shape. Through aperture 58, wadded tubular stock 49 can be found in twisting member 52.
“Twisting fixture37 articulates from a non-twisted position to an twisted position. Air cylinder 50 is in a resting position. Gear ratchet 51 biases away from twisting members 52. Air cylinder 50 is biased toward twisting member 52 by the geared ratchet51. This causes twisting member 52’s x-axis to turn around in a twisting position. Twisting can be achieved by placing wadded tubular stock 49 inside twisting member 52, while twisting 52 is in an untwisting posture and articulating twisting 52 from a nontwisting to a twisting state. To form twisted tubular stocks 59, twisting member 52 can be articulated from a twisting to a nontwisting position. (See FIG. 5).”
“FIG. 9 shows a frontal view of another exemplary embodiment with a plurality twisting members 60. FIG. 9 shows how each of the plurality twisting parts 60 is connected with another twisting part 60. This allows the geared ratchet 51, to articulate the plurality twisting pieces 60.
“Referring to FIG. FIG. 5A and FIG. 5A and FIG. Anvil 38 has a contact surface of 61 that is contactable with sealing-horn 39. Contact surface 61 is used for ultrasonic sealing. Twisted tubular stock 59 can be disposed of on it. Contact surface 61 is the location of an ultrasonic sealing area 62, in which twisted tubular stocks 59 are sealed. Optionally, contact surface 61 can be coated with knurling in order to give the seal a roughened appearance.
Ultrasonic sealing Horn 39 can be any conventional ultrasonic seal horn such as a Branson series 2000, capable of producing ultrasonic vibrations in the range of 15 to 45 KHz. The sealing horn 39 is mounted to a drive shaft 63, which pivotally moves to allow the sealing horn 39 to be moved between a sealing and non-sealing positions. The sealing horn 39 is biased away form anvil 38 in the non-sealing state. The sealing position has the sealing horn 39 biased towards anvil 38 by drive shaft 64. The sealing position is set up so that the twisted tubular stock placed upon the anvil 38 can be sealed. Twisted tubular Stock 59 is sealed tubular Stock 64, while star seal 34 is formed by sealing horn 39.”
“A minimum of one guide member 40 forms guide pathway 65 from the ultrasonic seal zone 62 to the first clamp 41. After an ultrasonic sealing cycle has been completed, sealed tubular stock 64 is removed from the ultrasonic seal zone 62 via guide pathway 65. Guide member 40 may be a guide aperture or guide bar, at most one guide plate, at minimum one guide pin, and at most one guide bar. The preferred guide member 40 is a pair or more of pins.
First clamp 41 is a standard clamp that holds twisted tube stock 59 in place during the ultrasonic seal cycle. First clamp 41 also holds wadded tube stock 49 until it is twisted into twisted tubular stocks 59. First clamp 41 can be moved between an open and closed position. First clamp 41 is closed during the twisting process, where wadded tubular material 49 is twisted into twisted tubular stock (59), and during the sealing cycle when star seal 34 forms. First clamp 41 is biased towards wadded tubular stocks 49 and twisted tubular stocks 59 when it is in the open position. First clamp 41 in the closed position is biased towards wadded tubular material 49 during the twisting process and toward twisted tubeular stock 59 throughout the sealing cycle. This ensures that wadded stock 49 and twisted stock 59 remain in place.
The second clamp 42 is a conventional clamp that moves sealed tubular stock 65 between the first clamp 41 and cutting member 43. Second clamp 42 is designed to hold sealed tubular stocks 64. It twists member 52 to make the tubular stock 64 the desired length. Then, it pushes previously sealed bags through member 43. Second clamp 42 can be moved between a forward and back position. Second clamp 42 is located proximate to first clamp 41. It is biased away from cutting members 43. Second clamp 42, which is located proximate to cutting member 43, is in the back position. It biases away from first clamp 41.
“Cutting member 43 has an upper blade (66) and a lower blade (67). The cutter member 43’s action causes reciprocal slicing movement between the upper and lower blades 66, 67, and 64 through the sealed tubular stock 64 at the point where it is separated from the star seal 34 to form a bag 33. To ensure safety, an optional fingerguard 68 is placed on one side and a cutter protector 69 on the opposite side of cutting member 43. This reduces the chance of injury to the user while operating the device.
“FIG. “FIG. FIG. The method described in FIG. 10 is accomplished by an ultrasonic seal device that can tightly twist and thereby wax tubular stock made of films of this invention. An exemplary bag made from tubular stock can be made by loading tubular stock 74 and activating the first clamp 75. Then, twist 76 and ultrasonic sealing 777. Finally, advance 79 and cut 80.
Ultrasonic sealing techniques are used to seal thermoplastic elastomer films and seal cylindrical bags. Because a thinner film can be used for making bags, the methods of increasing seal strength in thermoplastic-elastomer bags allow bags to be made at lower costs. These methods eliminate the need to use mechanical sealing devices, and eliminate heat sealing problems.
“Methods for star sealing bags can be achieved by using a sealing device following the following steps. Referring to FIG. 5, FIG. 5, FIG. 6. and FIG. 11. tubular stock 45 is loaded onto an ultrasonic sealing device 35 according to loading steps 74. This involves pulling a sheet 45 of tubular material from a roll of film, and then advancing it towards a gathering Horn 36. This wads the tubular stocks 45 into a rope-like configuration to make wadded tubular Stock 49. The wadded tubular stock 49 passes through aperture 58 on the twisting member 52 to reach an ultra sonic seal zone 62. Wadded tubular stock 49 passes through the ultra sonic sealing area 62. It is then allowed to unwad under its own power. At least one guide member 40 is used to hold wadded tubular stocks 49 and help with orientation during the sealing cycle. Wadded tubular stocks 49 are advanced past a first clasp 41 which holds wadded stock 49 during twisting and aids the guide member 40 with positioning wadded stock 49 during the sealing cycle. Wadded tubular stock 49 is also prevented from twisting beyond the first clamp 41 by the first clamp 41. The second clamp 42 is used to attach wadded tubular stock 49 to the second clamp. Wadded tubular stock 49 can then be advanced by cutting member 43.”
“Once the 45-pound tubular stock is loaded onto the ultrasonic seal machine 35, the operation of the ultrasonic seal machine 35 to star seal it is completed by activating the first clamp 41 in accordance with actuating step75 from an open position into a closed position and then actuating the geared ratchet 51 to move from an untwisted position to one that is twisted by the air cylinder 50 to perform twisting steps 76. The geared ratchet 51 rotates around an x-axis, forming twisted tubular stocks 49 in ultrasonic sealing area 62.
“After wadded tubular material 49 has been twisted to create twisted tubular stocks 59, the ultrasonic seal horn 39 is activated from a nonsealing position into a sealing position. This allows it to apply ultrasonic energy on twisted tubular stocks 59 to form star sealing 34. The ultrasonic sealing horn 39 uses ultrasonic energy on twisted tubular stocks 59 to seal the twisted tubular stocks 59 against anvil 38, according to sealing step 777.
“The seal time is the amount of time that energy is applied to the sealing horn while the bag is operatively associated with it. The sealing time, i.e. the amount of energy applied to the sealinghorn while the bag is operatively connected with the sealinghorn, should be set between 0.75 and 2 seconds. The bag size and the material used to make the bag can affect the setting. It can be adjusted from 0.25 to 10 seconds. It may be necessary to decrease the seal time if the star seal 34 seems too thin.
“After the ultrasonic seal horn 39 moves from the sealing position into a non sealing position, the air cylinder 50 turns the geared ratchet 51 to a non twisting position. Contemporaneously, first clamp 41 is actuated from a closed position to an open position according to untwisting/un-clamping step 78. Second clamp 42 grabs sealed tubular stocks 64 and advances them from the forward to the back positions. Sealed tubular stock 64 then goes through twisting member 52 until it reaches the desired length according to advancing step. Second clamp 42 pushes previously sealed bags into cutting members 43, which cuts bag 33 according to cutting steps 80.
“FIG. 11. This is a top view showing an exemplary star sealing machine with a plurality twisting members. A plurality of rolls of film (preferably 71) are used to make bag 33. A plurality if film 71 is used, multiple tubular stocks 72 are advanced via a plurality twist members 60. A plurality 60 of twist members are oriented such that multiple wadded tubular stocks 73 can be used simultaneously with one ultrasonic seal horn, sealing the horn 39. Star sealing is preferable from 6 to 9 wadded tubular stock at a time. It is preferable to seal the container completely automated.
After bags have been made, they are filled with food products. The bags are sealed to prevent contamination. A rotating product table with vacuum nozzles to evacuate the bags before sealing is a preferred example of fully automated food product packaging. This automated process allows for complete packaging of food products with minimal operator involvement and little to no interaction between operators and food products. A single operator is preferred to place the open-ended bags from the bagging station onto empty vacuum tubes. The evacuation and sealing are done automatically.
“The films can also used in vacuum bag applications, as described in U.S. Pat. No. No. Low-pressure molding of various plastics, rubber, resin bonded products such as reinforced plastics and laminates is possible with films. The present invention is used for vacuum bagging by applying film to the product’s surface to create a laminate. The film adheres to the product. The film is placed over a vacuum bag and sealed around the perimeter. The vacuum bag is attached to a vacuum pump and air is drawn from the vacuum bag. The vacuum bag, laminate and product are loaded into an oven/autoclave to allow heat and pressure to cure the laminate. The vacuum bag and product are kept at a reduced or atmospheric pressure. However, the pressure inside the autoclave chamber increases. To create a strong, dense article, the vacuum bag and product are compressed together. The laminate between them is then consolidated. Vacuum bags are a low-pressure method of bonding and laminating at 10 to 300 pounds per square inch. This system can be used for many purposes and can accommodate workpieces of all shapes and sizes. The only limitation is the size of the autoclave. A single-sided tool, of minimal construction and cost, can be sufficient in many cases. Only the tool must be rigid and impermeable at all temperatures.
“In addition, the films can be used as a casing material to build explosives. Individual explosive charges, or a group of explosive charges, are packaged in casings for use by the construction industry. The present invention has improved mechanical and barrier properties that are ideal for packaging and caging individual explosive charges, or a series of explosive ones.
“EXAMPLES”
The following examples are intended to demonstrate certain embodiments of the invention and their advantages. Any percentages, unless otherwise stated, are based on weight.
“Multi-Layered TPE-E Films”
“The barrier and physical properties of both films were measured and tested as follows. Tensile modulus refers to film stiffness. ASTM test D-645 measured that Test Film A is approximately five-and-a-half times stiffer than Elastic Film. Test Film A’s extra stiffness makes it easier for bags made of the film to be handled and to be manufactured. The following table summarizes the Tensile Modulus Test Results:
“TABLE 1\nTensile Tensile\nModulus Modulus\n(psi) (psi)\nMD Std. Dev. TD Std. Dev.nElastic film?35172?808?34101?2590nTestfilm A 190448 2711 202895 1260
Tensile yield strength is the force needed to cause a film’s elastic region to stretch or yield beyond its limit. The raw test results show that Test Film A requires 80% more force than the Elastic Film measured by ASTM testD-882. Table 2 summarizes the test results as follows:
Summary for “Thermoplastic Elastomer Films”
Thermoplastic films are used to preserve and protect food products. Polypropylene, nylon, ethylenevinylidene chloride, polyethylene, nylon and polyethylene are all common compositions. To combine films, an optional adhesive layer can be used.
Bags made of conventional films can be used for steam or hot water cooking, but they are not suitable for high-temperature cooking applications such as beef cooking. They either stick to or melt food products that are kept in the bag. Bags made from materials that are easily removed from food products during cooking is desirable. Because they are heated, conventional bags cannot be used in high-pressure meat casing applications.
Bags with good mechanical properties and low costs are also desirable. Food packaging is always looking for stronger and more durable bags that resist tearing and abrasion to isolate food products from outside environments. This will prevent contamination. To achieve desired mechanical properties such as tear resistance or durability, conventional bags are often thickened at an additional cost.
“The food packaging industry is also looking for materials that can be made at lower costs. Food packaging companies are trying to cut costs by using thinner films. Bags made from thin films require less material to make. The cost of making a bag is directly related to how much thermoplastic elastomer was used. To reduce material and hence the cost of making the bag, it is desirable that thinner films are used. In order to lower the material cost, it is important to increase the sealing strength of traditional bags. Bags with higher seal strengths require a thinner film and thus less thermoplastic elastomer.
“Conventional bags should be able to protect the environment from moisture and gases. Good barrier properties are desirable, including the ability to reduce or eliminate moisture, gas migration through the bag, and other such qualities. Because oxygen migration can cause bag contents, such as meat products to spoil or discolor, it is important to minimize it.
“Resealing thermoplastic films can be achieved by applying heat and pressure to the film surfaces. This will cause a fusion bond between layers. Heat sealed cylindrical bags can be imperfectly sealed as the heat required to seal the tubular stock folds will cause the film’s barrier properties to be damaged by melting or thinning. Poor seals can be a problem when using heat shrinkable film for cooking. This is because the seals are more susceptible to heat shrinking and elevated temperatures. Many manufacturers now use mechanical closure devices or ultrasonic sealing techniques to seal traditional films.
Ultrasonic sealing techniques are not recommended for sealing thermoplastic elastomer film, such as copolyester films. This is because the films’ elastic structure dampens ultrasonic energy transmission and prevents complete sealing of this particular type of bag. When thermoplastic elastomer film is used, mechanical sealing devices such as clips, rings, or the like are preferred. These mechanical sealing devices are typically made from a metal or plastic material.
Mechanical sealing devices can have several undesirable features. If they are lost in food products, mechanical sealing devices can cause contamination. The metal sealing devices can’t be used in microwave ovens to cook or defrost the food product in the bags. Additionally, the metal clips can sometimes get lost in the product which can lead to customer complaints. It is therefore desirable to have sealing methods for thermoplastic elastomer bags which eliminate the need of a mechanical device. This also solves the sealing issues associated with ultrasonically and heat sealed bags.
“There is an urgent need for better thermoplastic elastomer film and methods to make bags from these films, which overcomes the drawbacks of conventional films and methods to make bags made of conventional films.”
The present invention relates to thermoplastic-elastomer bags and films made from thermoplastic films, as well as to methods and materials for making thermoplastic bags and films. The present invention’s thermoplastic elastomer film is made from thermoplastic elastomers as well as non-elastic polymers. The present invention makes bags from blended monolayer thermoplastic films. These films can be made with a mixture of thermoplastic and non-elastic polymers, or co-extruded multilayer films that contain at least one layer each of thermoplastic and non-elastic elastomers. The present invention’s blended monolayer thermoplastic films are used in food handling, particularly in the meat packaging sector and in cooking bag applications. The multi-layered co-extruded films of the present invention can also be used in the food processing industry, particularly in the meat packaging industry, and in meat casing applications.
The films of the invention are co-extruded multilayered films with at least one layer each of thermoplastic elastomer or non-elastic polymer. Polyether-ester block polyolymers and polyester-ester blocks copolymers are the preferred thermoplastic elastomers. Another embodiment of the invention uses polyether-ester or polyester-ester copolymers as well as non-elastic Polyesters. These are mixed in a melt to create a single-layered film. Polyether-ester block polyolymers are the preferred thermoplastic elastomers.
The films of the invention have improved mechanical properties. They are stronger and more resistant to tearing and abrasion. These films have a higher tensile modulus and are therefore more rigid. This makes it easier to use these films for making bags. Films with a higher tensile yield strength require more force to cause them to stretch beyond their elastic regions. This allows for a controlled stretch to pack meat. High tensile yield strengths produce uniformly sized sausages when used in meat casings. The films of the invention make tighter and more consistent meat casings when they are used in pressurized applications. This is because they have lower tensile elongation than conventional films. Tensile yield extension is the amount of elongation before the film stretches out and becomes elastic. The films of the invention have a higher tensile break length than monolayer films made of thermoplastic elastomer. This allows them to be used in almost all meat packaging applications because they will stretch less before they are broken.
The present invention makes bags from thermoplastic films. They are then bonded together using a variety of sealing techniques. These include wire impulse sealing techniques and impulse sealing techniques. The bags of the invention are preferred to be made using ultrasonic sealing techniques. Bags are made using ultrasonic sealing techniques called star sealing. The present invention also includes the following features.
“DESCRIPTION DU DRAWINGS”
“The many features and benefits of the invention can be better understood by those who are skilled in the art. Refer to the detailed description and the drawing below.
“FIG. “FIG.
“FIG. “FIG.
“FIG. “FIG.
“FIG. 2A is a side-view of an exemplary blow extrusion apparatus for multilayered thermoplastic films.
“FIG. 2B is a side-view of an exemplary blow extrusion apparatus for blended thermoplastic monolayer films;
“FIG. “FIG.
“FIG. “FIG.
“FIG. 5A is a side-view of an exemplary star sealing machine bag machine.
“FIG. “FIG.
“FIG. FIG. 6 shows a top view showing the star seal bag machine. 5A;”
“FIG. 7 is a frontal view of an exemplary twist fixture.
“FIG. FIG.8 is a rear view of FIG.8’s twist fixture. 7;”
“FIG. “FIG.
“FIG. “FIG.
“FIG. “FIG. 11. This is a top-view of an exemplary star sealing machine with a plurality twisting members.
The present invention relates to thermoplastic-elastomer bags and films made from thermoplastic films, as well as to methods and materials for making thermoplastic bags and films. The present invention’s thermoplastic elastomer film is made from thermoplastic elastomers as well as non-elastic polymers. The present invention makes bags using blended monolayer thermoplastic Elastomer films. These films can be made from a mixture of thermoplastic and non-elastic polymers, or co-extruded multilayer films that contain at least one layer each of thermoplastic and non-elastic elastomers. The present invention’s blended monolayer thermoplastic films are used in food handling, particularly in the meat packaging sector and in cooking bag applications. The co-extruded film of the present invention is also useful in food handling, particularly in the meat packaging industry, and in meat casing applications. As used herein ?bag? Bags at traditional definition include vacuum bags, bags, pouches and sacks. They also refer to containers that hold meat products for transportation and packaging. Casings are food product casings that contain food products. This includes but is not limited to sausage casings and keilbasa cases, lunch meat casings and hot dog casings. Products can be food products, meat products or explosive products.
The films and bags of this invention have improved mechanical properties. They can be used to isolate food products from the environment. This prevents any contamination from entering the bag. These improved mechanical properties allow for lower-thickness films to make bags, which in turn lowers the cost of bags made from the films.
“Improved mechanical characteristics include increased tensile strength and thus higher resistance to tearing, abrasion and tearing, elevated melting points and increased tensile module, higher yield strengths, lower yield elongation and higher tensile breaking strength. The films of the invention have a higher tensile modulus and thus are more rigid. This makes it easier to use these films for making bags. Films with a higher tensile yield strength require greater force to cause them to stretch beyond their elastic regions. This allows for a controlled and controlled stretch when packaging meat. High tensile yield strengths films produce a uniformly sized sausage when used in a meat casing. The films of the invention make tighter and more consistent meat casings when they are used in pressurized applications. This is because the films have a lower tensile yield extension than conventional films. Tensile yield extension is the amount of elongation before the film stretches out and yields beyond its elastic limit. The films of the invention have a higher tensile break length, which allows them to be used in almost all meat packaging applications.
The films and bags of this invention have improved barrier properties. They can reduce or eliminate moisture, gas migration through bags made from the films. The thermoelastomer films are less likely to cause oxygen migration and more moisture transmission than conventional bags. Both the multilayered thermoplastic thermoplastic films are made from the thermoplastic film.
“The addition non-elastic polyesters as thermoplastic elastomers to multi-layered films or as a component in blended films makes it easier for ultrasonically star sealing bags made of the films of this invention, as opposed to bags made of conventional materials.” The ultrasonic seal is also stronger than those made from conventional materials or heat sealing methods.
Bags containing non-elastic polyester and a thermoplastic elastic elastomer are not able to adhere to food products. Blended monolayered thermoplastic films have better nonstick properties because the non-elastic polyester content in the blended film is decreased. Multi-layered coextruded bags have the added advantage of having a film layer made of substantially thermoplastic rubber in contact with food products. The film layer of substantially thermoplastic rubber elastomer will not adhere to foods products, particularly meat products. Bags made of multi-layered coextruded films have all the advantages of cost, mechanical properties, and barrier properties, but they do not adhere to meat products during transportation, storage, or cooking applications.
The present invention provides two methods of making thermoplastic film: co-extruding multi-layered thermoplastic films and extruding blended monolayer thermoplastic movies. Multi-layered films can be made by co-extruding non-elastic and thermoplastic polyester in separate layers. The melt mixture of non-elastic polyester, thermoplastic elastomer, and thermoplastic elastomer is used to make blended monolayer thermoplastic films.
“In one embodiment, the method for fabricating bags according to the present invention includes making tubular-shaped films called tubular stock and sealing the bag with at least one ultrasonic seal called a star seal. The present invention also allows for heat sealing to seal non-tube shaped films and tubular stock.
“FIG. “FIG. FIG. FIG. 1B shows a cross-sectional view of an exemplary monolayer blended thermoplastic elastomer (BMT) film. The films of this invention are co-extruded multilayered films 1 with at least one layer each of thermoplastic elastomer 2 or non-elastic polymer 3. Blended monolayer thermoplastic-elastomer films are also included in the films of this invention. Polyether-ester block polyolymers and polyester-ester blocks copolymers are the preferred thermoplastic elastomers. Another embodiment of the invention uses polyether-ester or polyester-ester copolymers as well as non-elastic Polyesters. These are mixed in a melt to create a single-layered film. Polyether-ester block polyolymers are the preferred thermoplastic elastomers.
Polyether-ester block copolymers, which are multi-block co-polymers that have crystallizable and low-crystallinity segments, alternate frequently. Melt trans-esterification is a method of making thermoplastic elastomers from a caboxylic acid or its methyl ester, a polyalkyleneoxide, and a short-chain diol. The Encyclopedia of Polymer Science and Technology Vol. 12 contains a comprehensive description of non-elastic polyesters and polyether-ester-block copolymers. 12, pages 76-177 (1985), which are herein incorporated as reference.”
“Films according to the present invention are co-extruded multilayered films that contain at least one layer each of thermoplastic epoxy 2 and non-elastic polymer 3 that are about 95 percent to approximately 5 percent of total film thickness. The preferred thickness of the thermoplastic layer 3 is between about 10 percent and about 50 percent, while the thickness of the non-polyester layer 3 ranges from approximately 90 percent to around 50 percent.
Blended mono layer films of the present invention include films that contain between 10 and 90 weight percent thermoplastic rubber elastomer, and 90 to 10 weight percent non elastic polyester. Blends are preferred to include about 40 to 60 weight percent of thermoplastic elastomer, and 60 to 40 weight percent of non-elastic Polyester. Blends with 50 to 50 percent thermoplastic Elastomer and 50 percent non-elastic Polyester are preferred.
“In one embodiment, the polyesterester block copolymers are the repeating alternating ester units (cystallizable polyester segments A) and low-crystallinelinity polyester segments. Segment A should have a molecular mass of about 400 to approximately 6000. Segment B should have a molecular mass of approximately 100 to about 550.
Segment A is made from at least one dicarboxylic acid, and at most one glycol. Segment A crystallizable with a preferable crystallinity of about 35 % and more preferably, about 50 %. A group of aliphatic, cycloaliphatic, and aromatic diboxylic acid suitable for use is selected. Dicarboxylic acids with aromatic dicarboxylic compounds are preferred. Preferred aromatic dicarboxylic acids are selected from the group comprising phthalic, isophthalic or terephthalic acid, naphthalenedicarboxylic acids and diphenyldicarboxylic acids. The dicarboxylic acid should have between 8 and 16 carbon atoms. Terephthalic acid is the preferred dicarboxylic acid. It is more preferable to repeat A segments of butylene-terephthalate units.
“Suitable polyalkylene glycols for segment A include long-chain glycols with terminal and near terminal hydroxy group. The preferred alkylene glycols can be selected from the following groups: polyethylene oxide; poly(1,2- and 1,3,3) propyleneoxid; polybutyleneoxid or copolymers thereof. The preferred alkylene glycol is polybutylene oxide.
Segment B contains repeating units that are derived at least from one diol or a dicarboxylic acids. Segment B has a low crystallinity and a crystallinity of less than 30%. You can use aliphatic and cycloaliphatic diols as well as aromatic dihydroxy compounds. The most preferred diols are those with between 2 and 15 carbon atoms. These include ethylene, propylenes, butylenes, tetramethylenes, and others. Butanediols and tetramethylene diols are even more popular diols. Equivalent ester-forming derivatives of diols can also be useful, such as ethylene carbonate or ethylene oxide. The formula for a suitable alkylene carbonate is:
“?O?(CR2)x?O?C?”
“where R is a hydrogenatom, an alkyl or an aryl group and x is between about 2 and about 20. It is preferable that R be a hydrogen atom with x=6. The alkylene carbonate, therefore, is hexamethylenecarbonate.
“The composition segments A, and B can vary within large limits. They are primarily determined based on the desired mechanical properties. Copolyester rubber elastomers with a higher A content have a greater stiffness and higher melting points. Copolyester Elastomers with a high amount of B are more flexible, and have a lower melting temperature. The copolyester rubber elastomers have a weight ratio of about 10:80 to 80:10. The preferred weight ratio is between about 10:60 and about 60,10, but more preferably between about 60/40 and about 40:60.
Non-elastic polyesters can be made using the invention if they are derived from a dicarboxylic and a diol. Alkylene glycols with long chains that facilitate crystal formation are preferred diols. Non-elastic crystallinity of polyester should be at least 35% and more preferably about 50%. The preferred alkylene glycols can be selected from the polyethylene oxide, poly(1,2- and 1,3) propyleneoxid, polybutyleneoxid or combinations thereof. The preferred alkylene glycol is polybutylene oxide. The preferred dicarboxylic acid group includes phthalic and isophthalic acids, as well as combinations thereof. Terepthalic acids are preferred, so non-elastic polyesters made of butylene triphthalate are preferred. Optionally, the dicarboxylic acid and the diol can be substituted provided that the substituted group doesn’t hinder crystal formation.
“Films according to the present invention should be made using extrusion processes well-known in the art. Perry’s Chemical Engineering Handbook (Ch. 18, pp. 29, pp.
“FIG. 2A is a side-view of the exemplary blown film extrusion device for multi-layered coextruded films. The multi-layered coextruded films made according to the invention are obtained by pouring thermoplastic resin pellets 4 into a resin hopper 5 on a first extruder 6, and then pouring non elastic polyester resin pellets 7 into a resin hopper 8 on a second extruder 8. You can use any type of extruder, including single-, double-, or tandem extruders. The thermoplastic elastomer pellets 4 are fed into 6’s first extruder. Non-elastic polyester pellets 7 are fed into 9’s second extruder. To form thermoplastic elastic polyester resin pellets 4, and non-elastic resin pellets 7, respectively, the first extruder 6, and second extruder 9, melt the thermoplastic rubber resin pellets 4. The optional additives may be added to the melted resins 10, 11 and 12 in first extruder 6, and second extruder 9, respectively, and/or mixed with resin pellets 4, and 7. A die 12 connects the first extruder 6 to the second extruder 9.
The first extruder 6 pushes melted resins 10, 11 and 12 through die 12, to form a film made of thermoplastic Elastomer 2, or the first layer, and a non-elastic Polyester 3, or the second layer. The preferred die 12 allows a film of thermoplastic elastic film 2 and a second non-elastic polymer 3 to be extruded simultaneously, forming a multi-layered film 1.
“Thermoplastic Elastomer Film 2 and non elastic Polyester Film 3 exit die 12. They are chilled by being in contact with a region of lower temperature and pressure than the temperature and pressure within first extruder 6 or second extruder 9. The ambient temperature and pressure are typically the ambient atmosphere. However, it may also be a chill roller. A sudden drop in temperature and pressure causes thermoplastic elastomer 2 and non elastic polyester 3 to become multi-layered films upon cooling. A winder gathers the layered film and winds it into rolls.
“In a preferred embodiment, multi-layered film 1 can be co-extruded using a blow-blown extrusion process. The die 12 connecting first and second extruders 6 in a blow film process is annular or ring-shaped so that first and second extruders 6 force thermoplastic elastomer films 2 and non elastic polyester films 3 from die 12. An aperture 14 is located in the middle of die 12. The aperture 14 is circular or annular in shape and allows a blowing agent, such as a blower, to inflate tube 13, of thermoplastic film 2 and non elastic polyester film 3, when it exits die 12. The tube 13’s diameter is increased and its thickness decreased by the blowing agent. Tube 13 is blown against the collapsing frame 16. This guides the tube to a pair of rolling rollers 17. The tube 13 is flattened by the rollers 17 to create a tubular stock. For transportation and storage, the tubular stock 18 can be wound into a roll 26. The interior layer of thermoplastic films is preferred to be thermoplastic elastomer 2 and non-elastic polyethylene film 3. It is preferable that the thermoplastic elastomer be in direct contact with products stored in bags made of films of the invention.
“FIG. 1C is a cross-sectional view of an exemplary multilayered thermoplastic elastomer (TME) film. Referring to FIG. FIG. 1C shows another preferred embodiment of the multi-layered film 1. It includes at least one additional layer, 81. Each layer 81 is made of a thermoplastic block copolymer, thermoplastic polyester or combination thereof. To make the multilayered thermoplastic movie 1, co-extrude the first layer 2, then the second layer 3 and each of the additional layers 81. This will form the multilayered thermoplastic movie 1. The multi-layered thermoplastic film can also be made by extruding each layer individually: the first layer 2, second layer 3 and each additional layer 81. The second layer 3, which is the second layer of multi-layered thermoplastic film 1 is placed on the first layer 2, and each layer 81 on the second layer. To form multilayered thermoplastic film 1, the first layer 2, second layer 3 and each of the at least one additional layer 81 are rolled between heated rollers. Alternativly, the multilayered thermoplastic movie 1 can be made by placing an interleaving adhesive layer 82 between the first and second layers. An interleaving adhesive layer (82) is placed between the layers 81 and 82.
“FIG. 2B is a side-view of an exemplary blow extrusion apparatus for blended thermoplastic films. The mixture of thermoplastic elastomer pellets 4 with non-elastic poly resin pellets 7 is used to make blended monolayer thermoplastic films 24. This results in a mixture 19 that is nearly homogenous. The blended mixture is then poured into an extruder 21’s resin hopper 20. You can use any type of extruder, including single-, double-, or tandem extruders. You can add any optional additives to each extruder, or you may use resin pellets 4, 7 and 8. Blend 19 is fed into extruder 21 by resin hopper 20. Mixing the blend 19 in extruder 21 creates a melt mix 22 which includes non-elastic polyesters and thermoplastic elastomers. Extruder 21 pushes melt mix 22 through a die 23, at the end extruder 21. Extruder 21 pushes melt blend 22 through die 23, to form a mixed monolayer thermoplastic film 24. The blended monolayer thermoplastic films 24 encounters a lower temperature and pressure than the extruder 21. The ambient temperature and pressure are typically the ambient atmosphere. However, it may also be a chilling roller. The temperature and pressure drop abruptly causes the blended film 24’s solidification upon cooling. A winder 25 gathers the monolayer blended thermoplastic film 24 and winds it into rolls 26.
In a preferred embodiment, melt mix 22 is extruded using a blown-film extrusion process. The die 23 at the end 21 of the extruder 21 is annular or ring-shaped so that the melt mix 22 is forced out of die 23 into the form of a tube 27. An aperture 28 is located in the middle of die 23. The aperture 28 is circular or annular in shape and allows a blowing agent, to inflate tube 27 when it exits die 23. Tube 27 is formed by the blowing agent, which increases its diameter and reduces the thickness the mixed monolayer thermoplastic film 24, forming it. Tube 27 is blown against the collapsing frame 30, which guides tube 27 to a pair 31 of rollers. A pair of rollers 31 flatten tube 27, forming a tubular stock. For transportation and storage, the tubular stock of film 32 can be wound into a roll 26.
“The films should be as thin as possible to reduce the resin required to make food product bags. They also need to have a high gas and moisture transmission rate and rugged durability. Each individual thermoplastic elastomer 2 and non-elastic Polyester 3 have a gauge thickness between about 0.0001 and 0.01 inches. Preferably, the films of this invention have a gauge thickness of between about 0.0005 and about 0.0035 inches. Even better, they should range from approximately 0.001 to about 0.25 inches.
“The films can optionally be stretch oriented. “Stretch-oriented” is an alternative term. The term “stretch-oriented” is used herein to refer to the process and the resultant product characteristics. It involves stretching and cooling a resinous, polymeric material to adjust its molecular structure by physical alignment of molecules. This results in improved mechanical properties such as tear strength, tensile strength, shrink properties, as well as optical properties. The present invention uses stretch-orientation to decrease the moisture and gas transmission rates, i.e., increase the film’s moisture vapor barrier functionality. It also increases toughness and shrinkability in comparison with films that are not stretch-oriented.
The film sheets can be optionally stretched by heating the quenched sheet to the orientation temperature, and then stretching it. The temperature of a particular film’s orientation will depend on the resinous polymers or blends that make it, so there will be a wide range of temperatures. The orientation temperature can be described as being above or below room temperature, but it will not be the melting point. It will usually be close to the glass transition temperature for the resins from the film.
“The process of stretching film at the orientation temperature range can be done in many ways, such as by using a?double bubble? or ?tenter framing? techniques. These techniques, along with others, are well-known in the art. They involve stretching the film in either the transverse or cross direction (TD), and/or in the machine or longitudinal direction (MD). Uniaxial orientation is achieved when the stretching force applies in only one direction. Biaxial orientation is achieved when the stretching force can be applied in both directions. The film is stretched and then quickly cooled to set the molecular arrangement. This type of quenched and oriented film is known to be heat-shrinkable. The film will return to its original dimensions if heated at a temperature below its melting point.
After quenching has locked-in the molecular arrangement, the film sheets can be heat-set. This involves heating the oriented film to near its orientation temperature and restraining it in its stretched dimensions. This is also known as “annealing”. This process results in a film that is significantly less susceptible to shrinkage, but retains many of the benefits of orientation such as improved tensile strength, optical properties, and lower gas and moisture transmission.
The present invention makes bags from thermoplastic films. They are then bonded together using a variety of sealing techniques. These include wire impulse sealing techniques and impulse sealing techniques. Hot knife heat sealing is another option. The bags of the invention are preferred to be made using ultrasonic sealing techniques. Bags are made using ultrasonic sealing techniques known as star sealing.
“Thermoplastic and elastomer films should be made from tubular stock so that bags can be made by sealing one end or both ends of a tube of tubular film, then cutting one edge to make the bag mouth. You can also make bags from flat sheets of film by sealing the edges of three superimposed sheets or by folding a rectangle sheet in half and sealing those sides closest to the folded side.
“FIG. FIG. 3 shows a side-view of an exemplary bag made from tubular stock and star sealed. FIG. FIG. 4 shows a side-view of an exemplary star sealing. Referring to FIG. Referring to FIG. 3. and FIG. 4. A bag 33 can be made according to the invention using ultrasonic sealing equipment capable of forming an “star seal 34”. The star seal 34 is made by tightly twisting, bunching and/or gathering a tube stock of film into an awd, thereby creating wadded tubular stocks. To seal the wadded tubular stock, ultrasonic sealing techniques are used to create a star seal.
“FIG. 5A is a side-view of an exemplary star sealing bags machine. FIG. FIG. FIG. 6 shows a top view showing the star seal bag machine. 5. As shown in FIG. 5A, FIG. FIG. 5A, FIG. FIG. 5B and FIG. 6. One embodiment of an acceptable ultrasonic seal machine 35 includes a gathering Horn 36, a twisting fixture 37, an anvil 38, an ultrasonic sealing horn 39, and at least one guide member 40. A first clamp 41, a 2nd clamp 42, as well as a cutting member 43.
“Gathering Horn 36” includes an elongated aperture 44 to receive tubular stock 45 from the roll of tubular stock 46. It also has a front surface 47, and a back side 48. The front surface 47 and the back surface 48 are connected by an elongated aperture 44. The circumference of the elongated aperture 44 shrinks from the front 47 to the back 48. The elongated aperture 44 narrows from the front surface 47 to the back surface 48 into a rope-like structure called wadded tubular Stock 49 as it passes through gathering Horn 36.
“FIG. FIG. 7 and FIG. 8. are front and back views of an exemplary twist fixture. 8 shows front and back views of an example twist fixture. Referring to FIG. 6, FIG. 6, FIG. 7. 8. Twisting fixture 37 also includes an air tube 50, a geared wrench 51, and at least one twisting piece 52. The operative attachment of the geared-ratchet 51 to the air cylinder 50 is to the geared wrench 51. It articulates with the geared regulator 51. The operative attachment of a geared ratchet 51 to at least one twisting piece 52 is a length 53 of gear teeth on an elongated 54 member. The gears 55 are operatively attached to gear ratchet 51. It has a front surface 56 and a back surface 57%. An aperture 58 is formed for wadded tubular stock 49. The aperture 58 connects the front surface 56 and back surface 57. The aperture 58 narrows between the front surface 56 and the back surface 57 so that the circumference decreases from one side to the other. The front surface of aperture 58 is oval-shaped, and it’s elongated. Aperture 58 on the back surface 57 has a circular shape. Through aperture 58, wadded tubular stock 49 can be found in twisting member 52.
“Twisting fixture37 articulates from a non-twisted position to an twisted position. Air cylinder 50 is in a resting position. Gear ratchet 51 biases away from twisting members 52. Air cylinder 50 is biased toward twisting member 52 by the geared ratchet51. This causes twisting member 52’s x-axis to turn around in a twisting position. Twisting can be achieved by placing wadded tubular stock 49 inside twisting member 52, while twisting 52 is in an untwisting posture and articulating twisting 52 from a nontwisting to a twisting state. To form twisted tubular stocks 59, twisting member 52 can be articulated from a twisting to a nontwisting position. (See FIG. 5).”
“FIG. 9 shows a frontal view of another exemplary embodiment with a plurality twisting members 60. FIG. 9 shows how each of the plurality twisting parts 60 is connected with another twisting part 60. This allows the geared ratchet 51, to articulate the plurality twisting pieces 60.
“Referring to FIG. FIG. 5A and FIG. 5A and FIG. Anvil 38 has a contact surface of 61 that is contactable with sealing-horn 39. Contact surface 61 is used for ultrasonic sealing. Twisted tubular stock 59 can be disposed of on it. Contact surface 61 is the location of an ultrasonic sealing area 62, in which twisted tubular stocks 59 are sealed. Optionally, contact surface 61 can be coated with knurling in order to give the seal a roughened appearance.
Ultrasonic sealing Horn 39 can be any conventional ultrasonic seal horn such as a Branson series 2000, capable of producing ultrasonic vibrations in the range of 15 to 45 KHz. The sealing horn 39 is mounted to a drive shaft 63, which pivotally moves to allow the sealing horn 39 to be moved between a sealing and non-sealing positions. The sealing horn 39 is biased away form anvil 38 in the non-sealing state. The sealing position has the sealing horn 39 biased towards anvil 38 by drive shaft 64. The sealing position is set up so that the twisted tubular stock placed upon the anvil 38 can be sealed. Twisted tubular Stock 59 is sealed tubular Stock 64, while star seal 34 is formed by sealing horn 39.”
“A minimum of one guide member 40 forms guide pathway 65 from the ultrasonic seal zone 62 to the first clamp 41. After an ultrasonic sealing cycle has been completed, sealed tubular stock 64 is removed from the ultrasonic seal zone 62 via guide pathway 65. Guide member 40 may be a guide aperture or guide bar, at most one guide plate, at minimum one guide pin, and at most one guide bar. The preferred guide member 40 is a pair or more of pins.
First clamp 41 is a standard clamp that holds twisted tube stock 59 in place during the ultrasonic seal cycle. First clamp 41 also holds wadded tube stock 49 until it is twisted into twisted tubular stocks 59. First clamp 41 can be moved between an open and closed position. First clamp 41 is closed during the twisting process, where wadded tubular material 49 is twisted into twisted tubular stock (59), and during the sealing cycle when star seal 34 forms. First clamp 41 is biased towards wadded tubular stocks 49 and twisted tubular stocks 59 when it is in the open position. First clamp 41 in the closed position is biased towards wadded tubular material 49 during the twisting process and toward twisted tubeular stock 59 throughout the sealing cycle. This ensures that wadded stock 49 and twisted stock 59 remain in place.
The second clamp 42 is a conventional clamp that moves sealed tubular stock 65 between the first clamp 41 and cutting member 43. Second clamp 42 is designed to hold sealed tubular stocks 64. It twists member 52 to make the tubular stock 64 the desired length. Then, it pushes previously sealed bags through member 43. Second clamp 42 can be moved between a forward and back position. Second clamp 42 is located proximate to first clamp 41. It is biased away from cutting members 43. Second clamp 42, which is located proximate to cutting member 43, is in the back position. It biases away from first clamp 41.
“Cutting member 43 has an upper blade (66) and a lower blade (67). The cutter member 43’s action causes reciprocal slicing movement between the upper and lower blades 66, 67, and 64 through the sealed tubular stock 64 at the point where it is separated from the star seal 34 to form a bag 33. To ensure safety, an optional fingerguard 68 is placed on one side and a cutter protector 69 on the opposite side of cutting member 43. This reduces the chance of injury to the user while operating the device.
“FIG. “FIG. FIG. The method described in FIG. 10 is accomplished by an ultrasonic seal device that can tightly twist and thereby wax tubular stock made of films of this invention. An exemplary bag made from tubular stock can be made by loading tubular stock 74 and activating the first clamp 75. Then, twist 76 and ultrasonic sealing 777. Finally, advance 79 and cut 80.
Ultrasonic sealing techniques are used to seal thermoplastic elastomer films and seal cylindrical bags. Because a thinner film can be used for making bags, the methods of increasing seal strength in thermoplastic-elastomer bags allow bags to be made at lower costs. These methods eliminate the need to use mechanical sealing devices, and eliminate heat sealing problems.
“Methods for star sealing bags can be achieved by using a sealing device following the following steps. Referring to FIG. 5, FIG. 5, FIG. 6. and FIG. 11. tubular stock 45 is loaded onto an ultrasonic sealing device 35 according to loading steps 74. This involves pulling a sheet 45 of tubular material from a roll of film, and then advancing it towards a gathering Horn 36. This wads the tubular stocks 45 into a rope-like configuration to make wadded tubular Stock 49. The wadded tubular stock 49 passes through aperture 58 on the twisting member 52 to reach an ultra sonic seal zone 62. Wadded tubular stock 49 passes through the ultra sonic sealing area 62. It is then allowed to unwad under its own power. At least one guide member 40 is used to hold wadded tubular stocks 49 and help with orientation during the sealing cycle. Wadded tubular stocks 49 are advanced past a first clasp 41 which holds wadded stock 49 during twisting and aids the guide member 40 with positioning wadded stock 49 during the sealing cycle. Wadded tubular stock 49 is also prevented from twisting beyond the first clamp 41 by the first clamp 41. The second clamp 42 is used to attach wadded tubular stock 49 to the second clamp. Wadded tubular stock 49 can then be advanced by cutting member 43.”
“Once the 45-pound tubular stock is loaded onto the ultrasonic seal machine 35, the operation of the ultrasonic seal machine 35 to star seal it is completed by activating the first clamp 41 in accordance with actuating step75 from an open position into a closed position and then actuating the geared ratchet 51 to move from an untwisted position to one that is twisted by the air cylinder 50 to perform twisting steps 76. The geared ratchet 51 rotates around an x-axis, forming twisted tubular stocks 49 in ultrasonic sealing area 62.
“After wadded tubular material 49 has been twisted to create twisted tubular stocks 59, the ultrasonic seal horn 39 is activated from a nonsealing position into a sealing position. This allows it to apply ultrasonic energy on twisted tubular stocks 59 to form star sealing 34. The ultrasonic sealing horn 39 uses ultrasonic energy on twisted tubular stocks 59 to seal the twisted tubular stocks 59 against anvil 38, according to sealing step 777.
“The seal time is the amount of time that energy is applied to the sealing horn while the bag is operatively associated with it. The sealing time, i.e. the amount of energy applied to the sealinghorn while the bag is operatively connected with the sealinghorn, should be set between 0.75 and 2 seconds. The bag size and the material used to make the bag can affect the setting. It can be adjusted from 0.25 to 10 seconds. It may be necessary to decrease the seal time if the star seal 34 seems too thin.
“After the ultrasonic seal horn 39 moves from the sealing position into a non sealing position, the air cylinder 50 turns the geared ratchet 51 to a non twisting position. Contemporaneously, first clamp 41 is actuated from a closed position to an open position according to untwisting/un-clamping step 78. Second clamp 42 grabs sealed tubular stocks 64 and advances them from the forward to the back positions. Sealed tubular stock 64 then goes through twisting member 52 until it reaches the desired length according to advancing step. Second clamp 42 pushes previously sealed bags into cutting members 43, which cuts bag 33 according to cutting steps 80.
“FIG. 11. This is a top view showing an exemplary star sealing machine with a plurality twisting members. A plurality of rolls of film (preferably 71) are used to make bag 33. A plurality if film 71 is used, multiple tubular stocks 72 are advanced via a plurality twist members 60. A plurality 60 of twist members are oriented such that multiple wadded tubular stocks 73 can be used simultaneously with one ultrasonic seal horn, sealing the horn 39. Star sealing is preferable from 6 to 9 wadded tubular stock at a time. It is preferable to seal the container completely automated.
After bags have been made, they are filled with food products. The bags are sealed to prevent contamination. A rotating product table with vacuum nozzles to evacuate the bags before sealing is a preferred example of fully automated food product packaging. This automated process allows for complete packaging of food products with minimal operator involvement and little to no interaction between operators and food products. A single operator is preferred to place the open-ended bags from the bagging station onto empty vacuum tubes. The evacuation and sealing are done automatically.
“The films can also used in vacuum bag applications, as described in U.S. Pat. No. No. Low-pressure molding of various plastics, rubber, resin bonded products such as reinforced plastics and laminates is possible with films. The present invention is used for vacuum bagging by applying film to the product’s surface to create a laminate. The film adheres to the product. The film is placed over a vacuum bag and sealed around the perimeter. The vacuum bag is attached to a vacuum pump and air is drawn from the vacuum bag. The vacuum bag, laminate and product are loaded into an oven/autoclave to allow heat and pressure to cure the laminate. The vacuum bag and product are kept at a reduced or atmospheric pressure. However, the pressure inside the autoclave chamber increases. To create a strong, dense article, the vacuum bag and product are compressed together. The laminate between them is then consolidated. Vacuum bags are a low-pressure method of bonding and laminating at 10 to 300 pounds per square inch. This system can be used for many purposes and can accommodate workpieces of all shapes and sizes. The only limitation is the size of the autoclave. A single-sided tool, of minimal construction and cost, can be sufficient in many cases. Only the tool must be rigid and impermeable at all temperatures.
“In addition, the films can be used as a casing material to build explosives. Individual explosive charges, or a group of explosive charges, are packaged in casings for use by the construction industry. The present invention has improved mechanical and barrier properties that are ideal for packaging and caging individual explosive charges, or a series of explosive ones.
“EXAMPLES”
The following examples are intended to demonstrate certain embodiments of the invention and their advantages. Any percentages, unless otherwise stated, are based on weight.
“Multi-Layered TPE-E Films”
“The barrier and physical properties of both films were measured and tested as follows. Tensile modulus refers to film stiffness. ASTM test D-645 measured that Test Film A is approximately five-and-a-half times stiffer than Elastic Film. Test Film A’s extra stiffness makes it easier for bags made of the film to be handled and to be manufactured. The following table summarizes the Tensile Modulus Test Results:
“TABLE 1\nTensile Tensile\nModulus Modulus\n(psi) (psi)\nMD Std. Dev. TD Std. Dev.nElastic film?35172?808?34101?2590nTestfilm A 190448 2711 202895 1260
Tensile yield strength is the force needed to cause a film’s elastic region to stretch or yield beyond its limit. The raw test results show that Test Film A requires 80% more force than the Elastic Film measured by ASTM testD-882. Table 2 summarizes the test results as follows:
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