CA2103206C - Multi-layer beverage tubing - Google Patents
Multi-layer beverage tubing Download PDFInfo
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- CA2103206C CA2103206C CA 2103206 CA2103206A CA2103206C CA 2103206 C CA2103206 C CA 2103206C CA 2103206 CA2103206 CA 2103206 CA 2103206 A CA2103206 A CA 2103206A CA 2103206 C CA2103206 C CA 2103206C
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Abstract
A multi-layer tubing for beverages is provided, with the tubing including a beverage contact layer formed from a first thermoplastic material, a second layer formed from a second thermoplastic material wherein the second thermoplastic material is coextruded with the first thermoplastic material, a gas barrier layer bonded to the second thermoplastic material and formed from a material resistant to gas diffusion, and an outer layer bonded to the material resistant to gas diffusion and formed from a third thermoplastic material.
Description
_1_ Docket No. 664.00002 Field of the Tnventi~"
This invention relates to tubing, such as that used to convey beverages, and, more particularly, to multi-layer tubing.
Background o the Th~~pntion Tubing used in the beverage industry has several special performance criteria that must be met. Unfortu-nataly, oftentimes these criteria are competing in that the fulfillment of one of the criterion necessarily leads l0 to a failure in another. Likewise, while the use of thermoplastic materials in the manufacture of beverage tubing can afford a performance advantage, it can likewise create special problems specific to the thermoplastic material used.
For example, tubing used to transfer syrups and carbonated beverages can be designed with thermoplastic materials that~will not impart taste or odor to the bever- .
age but will then be susceptible to stress cracking.
Other thermoplastic materials have inherent stress crack resistance, butltend to impart a taste to the beverage.
Thus, thermoplastic beverage tubing is often made to compromise between low taste transmission and stress crack resistance.
This invention relates to tubing, such as that used to convey beverages, and, more particularly, to multi-layer tubing.
Background o the Th~~pntion Tubing used in the beverage industry has several special performance criteria that must be met. Unfortu-nataly, oftentimes these criteria are competing in that the fulfillment of one of the criterion necessarily leads l0 to a failure in another. Likewise, while the use of thermoplastic materials in the manufacture of beverage tubing can afford a performance advantage, it can likewise create special problems specific to the thermoplastic material used.
For example, tubing used to transfer syrups and carbonated beverages can be designed with thermoplastic materials that~will not impart taste or odor to the bever- .
age but will then be susceptible to stress cracking.
Other thermoplastic materials have inherent stress crack resistance, butltend to impart a taste to the beverage.
Thus, thermoplastic beverage tubing is often made to compromise between low taste transmission and stress crack resistance.
In addition, due to the relatively high perme-ability of these thermoplastic materials, beverages can - become contaminated by the ingression of vapors and/or liquids. Cleaners, pesticides, and disinfectants can come in contact with the tubing. When installed in under-the floor conduits, water can collect around the tubing, become stagnant and effect contamination thereof. When held in relatively close proximity, aggressive liquids, such as root beer, can permeate out through one tube and into an adjacent tube thereby affecting the flavor of the beverage in that tube.
Similarly, these thermoplastic materials can have inherently low resistance to permeation by carbon dioxide gas so that carbonated drinks tend to lose their carbonation.
The use of a gas barrier layer can offer excel-lent resistance to permeation by oxygen, carbon dioxide gas, and organic hydrocarbons, thus keeping the proper flavor and carbonation in the beverage within the tubing and the unwanted flavors outside the tubing. However, the tubing with a gas barrier layer in the outermost layer in a thermoplastic beverage tube may not perform well when carbonated beverages are used. The carbon dio~Cide gas from the carbonated beverage, while being impeded by the barrier layer, can cause a build-up in pressure sufficient to blister the 'outer gas barrier layer. Hence, the need to compromise between low taste transmission and control of gas permeation and tube blistering (in carbonated applications) has existed.
Similarly, these thermoplastic materials can have inherently low resistance to permeation by carbon dioxide gas so that carbonated drinks tend to lose their carbonation.
The use of a gas barrier layer can offer excel-lent resistance to permeation by oxygen, carbon dioxide gas, and organic hydrocarbons, thus keeping the proper flavor and carbonation in the beverage within the tubing and the unwanted flavors outside the tubing. However, the tubing with a gas barrier layer in the outermost layer in a thermoplastic beverage tube may not perform well when carbonated beverages are used. The carbon dio~Cide gas from the carbonated beverage, while being impeded by the barrier layer, can cause a build-up in pressure sufficient to blister the 'outer gas barrier layer. Hence, the need to compromise between low taste transmission and control of gas permeation and tube blistering (in carbonated applications) has existed.
Finally, to prevent leakage of beverage between beverage tubing and a metal fitting thereon, it is impor-taut that there be close, sealing contact between the thermoplastic tube material and the metal. Generally, a narrow', metal band clamp forces the tubing onto barbs on the fitting. If the thermoplastic material used is one that will not impart taste or odor to the beverage, then the stresses exerted by the clamp can lead to stress cracking in the vicinity of the clamp. If a stiff gas barrier layer is used at the inner surface of a beverage tube, it can be difficult to maintain close, sealing contact with the metal fitting since the stiff material tends not to conform to the barbs on the fitting without the use of excessive force exerted through the clamp. The need for excessive force on the clamp can lead to cutting or cracking of the outer layer of the tubing.
Thus, there is a need for beverage tubing that effectively avoids taste transmission, and resists stress cracking, vapor and/or liquid permeation, loss of carbon ation, and tube blistering.
Summary of the Inven -i ~., The, present invention is specifically directed to overcoming the above-enumerated problems in a novel and simple manner.
According to the invention, a multi-layer tubing for beverages is provided, with the tubing including a beverage contact layer formed from a first thermoplastic material, a second layer formed from a second thermoplas-tic material wherein the second thermoplastic material is coextruded with the first thermoplastic material, a gas barrier layer bonded to the second thermoplastic material and formed from a material resistant to gas diffusion, and an outer layer bonded to the material resistant to gas diffusion and formed from a third thermoplastic material.
Through use of a multi-layer construction, the tubing can obtain the benefit of the performance advantag es afforded by a specific thermoplastic material used to form a layer while compensating far its deficiencies through the use of another thermoplastic material in a different layer. The manner and order in which the layers are put together also contributes to the benefits to be achieved through a multi-layer construction.
Preferably, the first thermoplastic material imparts low taste and resists odor transgression to the beverage, the second thermoplastic material is coextruded with the first thermoplastic material so that the forma-tion of stress cracks in the beverage contact layer is minimized, the material resistant to gas diffusion is bonded to the coextruded second thermoplastic material by a first layer of adhesive material therebetween, and the third thermoplastic material is bonded to the material resistant to gas diffusion by a second layer of adhesive material therebetween with the outer layer being of suffi-cient thicknesslto prevent blistering of the gas barrier layer in use.
In a preferred form, the first thermoplastic material is low density polyethylene or polypropylene.
_5-Preferably, the second thermoplastic material is linear low density polyethylene, ethylene vinyl acetate, or a -' thermoplastic elastomer. Even more preferably, the ther moplastic elastomer is a polypropylene-based thermoplastic elastomer. In another preferred form, the third thermo plastic material is linear low density polyethylene, ethylene vinyl acetate, a thermoplastic elastomer, or polyvinyl chloride. Even more preferably, the thermoplas-tic elastomer is a polypropylene-based thermoplastic elastomer. In yet another preferred form, the material resistant to gas diffusion is ethylene vinyl alcohol.
In one exemplary embodiment, the first and second layers of adhesive materials are the same material.
In another exemplary embodiment, the second and third thermoplastic materials are the same material. In yet another exemplary embodiment, the second and third same thermoplastic materials are one of either linear low density polyethylene, ethylene vinyl acetate, or a thermo-plastic elastomer. In yet another exemplary embodiment, the thermoplastic elastomer is a polypropylene-based thermoplastic elastomer.
brief Descr i nt i nn Of the Dratoi nrr Fig. 1 is a cross-sectional view of a multi-layer beverage tubing.
Vita>>ed Description of thA n,.~~°"~
Fig. 1 shows a cross-sectional view of a multi-layer tubing l0 for transporting beverages 12 _6_ therethrough. With the introduction of beverage bundles, several tubes are disposed in close proximity carrying different beverages and syrups to the dispenser.
The beverages 12 to be transported by the tubing 10 will normally be carbonated beverages but can also be noncarbonated beverages or beverage syrups. Carbonated beverages include three chief ingredients: syrup, water, and carbon dioxide. The syrup provides the flavor and generally contains sugar and some flavoring material, which may be from natural fruit or, more often, synthetic flavors. Fruit acids, such as citric acid, are commonly used as an important constituent of syrups to accentuate the other flavoring used. The carbon dioxide is usually pressurized and is combined with water by cooling the water to near freezing to increase the solubility of the carbon dioxide in the water.
Referring to Fig. 1, an innermost layer or beverage contact layer 14 is formed from a first thermo-plastic material 16 that imparts low taste and odor to the beverage 12 as it flows through the tube 10. The first thermoplastic material is highly stable and inert.
Preferably, the first thermoplastic material 16 is low density polyethylene or polypropylene.
Because the first thermoplastic material 16 generally will not have good environmental stress cracking resistance, a second layer 18, formed from a second ther moplastic material 20, is coextruded therewith so that the formation of stress cracks in the beverage contact layer vis minimized. The second thermoplastic material 20 exhib ,its excellent inherent environmental stress crack resis-tance but will generally have a decreased stability to - oxidation during the extrusion process and is therefore more likely to impart a taste or odor to the beverage 12 than the first thermoplastic material 16. Preferably, the second thermoplastic material 20 is one of either linear low density polyethylene, ethylene vinyl acetate, or a thermoplastic elastomer. Even more preferably, the ther moplastic elastomer is a polypropylene-based thermoplastic elastomer.
Die lines from the extrusion process lower the environmental stress crack resistance along those lines.
Coextruding the thermoplastic beverage contact layer 16 with a surrounding, concentric second thermoplastic layer 20 allows the two thermoplastic resins 16 and 20 to come together in the molten state so that the outer surface of the thermoplastic beverage contact layer 14 can not cool with die lines and can not come in contact with any envi-ronmental stress cracking agents. Since stress cracks are propagated at the outer surface of the tube, the use of the second thermoplastic layer 18 protects the thermoplas-tic beverage contact layer 14 and affords the tube 10 improved environmental stress crack resistance'while the use of an inner thermoplastic beverage contact layer 14 provides low taste and odor properties.
Because the thermoplastic beverage contact layer 14 and the second thermoplastic layer 18 have relatively high permeability, a gas barrier layer 22 can be bonded to the second thermoplastic layer 18. The gas barrier layer 2~.~32~6 _8_ 22 is concentric with and circumscribes the second layer 18 and coextruded beverage contact layer 14. The gas barrier layer 22 is formed from a material resistant to gas diffusion 24. Preferably, the gas resistant material 24 is a seamless, coextruded layer of ethylene vinyl alcohol. The ethylene vinyl alcohol provides excellent resistance to permeation by oxygen or organic hydrocar-bons, thus isolating the flavor of the beverage 12 in the tube 10 from external contaminating agents. When several different beverages 12 are used in different beverage tubes 10 in close proximity to one another and one of the beverages 12 is root beer, the gas barrier layer 22 is of particular importance since gas chromatography mass spec-troscopy evidence exists showing that the root beer fla-vor, notorious for permeating through conventional tubes not employing such a layer, does not permeate through applicants tubing 10 incorporating the gas barrier layer 22.
A relatively thick outer layer 26 formed from a third thermoplastic material 28 can be bonded to the gas barrier layer 22. The third thermoplastic material 28 exhibits excellent stress crack resistance, provides the tube 10 with improved kink resistance, and holds the barrier layer 22 down, eliminating blistering in applications involving carbon dioxide or carbonated beWer-ages. furthermore, by having the barrier layer 22 sandwiched between the second and third thermoplastic layers 18, 2C, the barrier layer 22 is protected, which is especially important under the clamp at the fitting, and allows the thermoplastic beverage contact layer 14 to conform more readily to the barbed fitting providing better sealing performance. Preferably, the third thermo-plastic material 28 is one of either linear low density polyethylene, ethylene vinyl acetate, a thermoplastic elastomer, or polyvinyl chloride. Even more preferably, the thermoplastic elastomer is a polypropylene-based thermoplastic elastomer.
To bond the gas barrier layer 22 to the second to thermoplastic layer 20, a first adhesive layer 3o can be used. The adhesive resin employed must be compatible with both the second thermoplastic material 20 and the gas resistant material 24. Likewise, to bond the gas barrier layer 22 to the third thermoplastic layer 26, a second adhesive layer 32 is used. Both adhesive layers 30 and 32 provide the barrier layer 22 with improved resistance to blistering in carbonated applications and resistance to separation of the layers during flexing.
While the thicknesses of the layers can vary, generally the thermoplastic beverage contact layer 14 and the second thermoplastic layer 18 are approximately the same thickness, while the third thermoplastic outer layer 26 is approximately 1.5 times as thick as either one of the beverage contact layer 14 or second thermoplastic layer 18. The barrier layer 22 and the,adhesive layers 30 and 32, by comparison, are relatively thin with their thicknesses being anywhere from 5 to 15 times thinner than the thickness of either one of the beverage contact layer 14 or second thermoplastic layer 18. In an exemplary embodiment where the tube wall is .06 inches thick, the thicknesses are as follows: beverage contact layer 14 and - second thermoplastic layer 18 - .015 inches; first adhe sive layer 30 - .003 inches; gas barrier layer 22 - .001 inches; second adhesive layer 32 - .002 inches; and outer thermoplastic layer - .024 inches.
To manufacture the tube 10, a three-stage con-tinuous extrusion process is employed. In stage one, the beverage contact layer 14 and second thermoplastic layer 18 are coextruded. A dual walled tube is formed in one extrusion die and cooled in water. In stage two, three layers are simultaneously extruded from one extrusion die coating the dual-layered tubing. The three layers are:
the first adhesive layer 30 which fuses to the second thermoplastic layer 18, the barrier layer 22 which is fusion compatible with the adhesive layers 30 and 32, and the second adhesive layer 32 which is fusion compatible with the barrier layer 22 and the outer thermoplastic layer 26. A relatively thick outer layer 26 is then applied to the five-layer tube, fusing to the second adhesive layer 32 in the final stage. This is a conven-tional, single component extrusion coating operation, thereby creating the complete multi-layer tube 10 with each layer fused to the adjacent layer.
To convert the tube 10 for use in high pressure environments, yarn reinforcement can be used (not shown) between the thick outer layer 26 and the second adhesive layer 32. To produce the reinforced hose or tube 10, the reinforcement is a pair of spirally opposed textile yarn layers applied to the five-layer tube immediately prior to the application of the outer layer 26. Fusiori between the second adhesive layer 32 and the outer layer 26 occurs through the interstices of the reinforcement layer.
Examtile 1 A tube formed using low density polyethylene as the beverage contact layer offers flexibility and low taste properties but does not have good resistance to environmental stress cracking. Therefore, a second layer l0 of linear low density polyethylene with excellent inherent environmental stress crack resistance is coextruded with the low density polyethylene.
An ethylene vinyl alcohol layer is used to provide excellent barrier resistance to oxygen, carbon 15 dioxide, and organic hydrocarbons, thereby protecting the fluid inside the tube from contamination by the exterior environment, flavor transfer from other nearby tubes, and oxidation. The excellent resistance to permeation by carbon dioxide preserves the carbonation in carbonated 20 fluids.
The relatively thick outer layer of linear low density, polyethylene provides further stress crack resis-tance as well as physical protection. The similarity in the physical properties of the various polyethylene layers 25 enables the multi-layer composite tube to be coupled to the fitting in the same fashion as single component poly-ethylene tubing.
Examtile 2 For added flexibility, the thick outer layer can be formed from ethylene vinyl acetate instead of linear low density polyethylene, which will stall be fusion compatible with the second adhesive layer used with the linear low density polyethylene.
ESA
For even greater flexibility, both the thick outer layer and the second layer can be formed from ethyl ene vinyl acetate. Due to the improved resilience of the ethylene vinyl acetate, stress crack resistance is still preserved.
Example 4 The structures of Examples 1 or 3 can be modi Pied so that polyvinyl chloride is used in the outer layer. Although it does have a low coefficient of fric tion, the abrasion resistance of linear low density poly ethylene is not exceptional. Ethylene vinyl acetate has a high coefficient of friction but relatively low abrasion resistance and low resistance to thermal softening.
Flexible polyvinyl chloride is an excellent choice for flexibility, abrasion resistance, and resis-tance to thermal softening. The use of. polyvinyl chloride allows for a much thicker outer layer to greatly improve the kink resistance.
When polyvinyl chloride is used for the thick 4outer layer, the second adhesive layer has to be modified _1~_ to provide fusion to the ethylene vinyl alcohol barrier layer as well as the polyvinyl chloride outer layer.
Ex~ple 5 In some cases, it may be important to reduce ingression into the tube by the fluid or certain organic components of the fluids generally associated with the flavor itself. A different choice for the beverage con tact layer may be used, such as polypropylene.
Polypropylene provides a more inert surface to reduce the absorption of flavor-carrying chemicals into the beverage contact layer. This is particularly important in applica-tions where it is desired to change the beverage being carried by the tube without flavor carry-over to the next beverage to be used in the tube.
While polypropylene provides low taste proper-ties and resistance to environmental stress cracking, it sacrifices flexibility. Using thermoplastic elastomer blends based on polypropylene in the second layer and outer layer affords the multi-layer composite tube good flexibility and kink resistance. When using a thermoplas-tic elastomer, care, should be taken to make the proper choice of adhesive for the first and second 'adhesive ' layers, so that they fuse to both the thermoplastic elas-tomer and the ethylene vinyl alcohol barrier layer.
The foregoing disclosure of specific embodiments is intended to be illustrative of the broad concepts comprehended by the invention.
Thus, there is a need for beverage tubing that effectively avoids taste transmission, and resists stress cracking, vapor and/or liquid permeation, loss of carbon ation, and tube blistering.
Summary of the Inven -i ~., The, present invention is specifically directed to overcoming the above-enumerated problems in a novel and simple manner.
According to the invention, a multi-layer tubing for beverages is provided, with the tubing including a beverage contact layer formed from a first thermoplastic material, a second layer formed from a second thermoplas-tic material wherein the second thermoplastic material is coextruded with the first thermoplastic material, a gas barrier layer bonded to the second thermoplastic material and formed from a material resistant to gas diffusion, and an outer layer bonded to the material resistant to gas diffusion and formed from a third thermoplastic material.
Through use of a multi-layer construction, the tubing can obtain the benefit of the performance advantag es afforded by a specific thermoplastic material used to form a layer while compensating far its deficiencies through the use of another thermoplastic material in a different layer. The manner and order in which the layers are put together also contributes to the benefits to be achieved through a multi-layer construction.
Preferably, the first thermoplastic material imparts low taste and resists odor transgression to the beverage, the second thermoplastic material is coextruded with the first thermoplastic material so that the forma-tion of stress cracks in the beverage contact layer is minimized, the material resistant to gas diffusion is bonded to the coextruded second thermoplastic material by a first layer of adhesive material therebetween, and the third thermoplastic material is bonded to the material resistant to gas diffusion by a second layer of adhesive material therebetween with the outer layer being of suffi-cient thicknesslto prevent blistering of the gas barrier layer in use.
In a preferred form, the first thermoplastic material is low density polyethylene or polypropylene.
_5-Preferably, the second thermoplastic material is linear low density polyethylene, ethylene vinyl acetate, or a -' thermoplastic elastomer. Even more preferably, the ther moplastic elastomer is a polypropylene-based thermoplastic elastomer. In another preferred form, the third thermo plastic material is linear low density polyethylene, ethylene vinyl acetate, a thermoplastic elastomer, or polyvinyl chloride. Even more preferably, the thermoplas-tic elastomer is a polypropylene-based thermoplastic elastomer. In yet another preferred form, the material resistant to gas diffusion is ethylene vinyl alcohol.
In one exemplary embodiment, the first and second layers of adhesive materials are the same material.
In another exemplary embodiment, the second and third thermoplastic materials are the same material. In yet another exemplary embodiment, the second and third same thermoplastic materials are one of either linear low density polyethylene, ethylene vinyl acetate, or a thermo-plastic elastomer. In yet another exemplary embodiment, the thermoplastic elastomer is a polypropylene-based thermoplastic elastomer.
brief Descr i nt i nn Of the Dratoi nrr Fig. 1 is a cross-sectional view of a multi-layer beverage tubing.
Vita>>ed Description of thA n,.~~°"~
Fig. 1 shows a cross-sectional view of a multi-layer tubing l0 for transporting beverages 12 _6_ therethrough. With the introduction of beverage bundles, several tubes are disposed in close proximity carrying different beverages and syrups to the dispenser.
The beverages 12 to be transported by the tubing 10 will normally be carbonated beverages but can also be noncarbonated beverages or beverage syrups. Carbonated beverages include three chief ingredients: syrup, water, and carbon dioxide. The syrup provides the flavor and generally contains sugar and some flavoring material, which may be from natural fruit or, more often, synthetic flavors. Fruit acids, such as citric acid, are commonly used as an important constituent of syrups to accentuate the other flavoring used. The carbon dioxide is usually pressurized and is combined with water by cooling the water to near freezing to increase the solubility of the carbon dioxide in the water.
Referring to Fig. 1, an innermost layer or beverage contact layer 14 is formed from a first thermo-plastic material 16 that imparts low taste and odor to the beverage 12 as it flows through the tube 10. The first thermoplastic material is highly stable and inert.
Preferably, the first thermoplastic material 16 is low density polyethylene or polypropylene.
Because the first thermoplastic material 16 generally will not have good environmental stress cracking resistance, a second layer 18, formed from a second ther moplastic material 20, is coextruded therewith so that the formation of stress cracks in the beverage contact layer vis minimized. The second thermoplastic material 20 exhib ,its excellent inherent environmental stress crack resis-tance but will generally have a decreased stability to - oxidation during the extrusion process and is therefore more likely to impart a taste or odor to the beverage 12 than the first thermoplastic material 16. Preferably, the second thermoplastic material 20 is one of either linear low density polyethylene, ethylene vinyl acetate, or a thermoplastic elastomer. Even more preferably, the ther moplastic elastomer is a polypropylene-based thermoplastic elastomer.
Die lines from the extrusion process lower the environmental stress crack resistance along those lines.
Coextruding the thermoplastic beverage contact layer 16 with a surrounding, concentric second thermoplastic layer 20 allows the two thermoplastic resins 16 and 20 to come together in the molten state so that the outer surface of the thermoplastic beverage contact layer 14 can not cool with die lines and can not come in contact with any envi-ronmental stress cracking agents. Since stress cracks are propagated at the outer surface of the tube, the use of the second thermoplastic layer 18 protects the thermoplas-tic beverage contact layer 14 and affords the tube 10 improved environmental stress crack resistance'while the use of an inner thermoplastic beverage contact layer 14 provides low taste and odor properties.
Because the thermoplastic beverage contact layer 14 and the second thermoplastic layer 18 have relatively high permeability, a gas barrier layer 22 can be bonded to the second thermoplastic layer 18. The gas barrier layer 2~.~32~6 _8_ 22 is concentric with and circumscribes the second layer 18 and coextruded beverage contact layer 14. The gas barrier layer 22 is formed from a material resistant to gas diffusion 24. Preferably, the gas resistant material 24 is a seamless, coextruded layer of ethylene vinyl alcohol. The ethylene vinyl alcohol provides excellent resistance to permeation by oxygen or organic hydrocar-bons, thus isolating the flavor of the beverage 12 in the tube 10 from external contaminating agents. When several different beverages 12 are used in different beverage tubes 10 in close proximity to one another and one of the beverages 12 is root beer, the gas barrier layer 22 is of particular importance since gas chromatography mass spec-troscopy evidence exists showing that the root beer fla-vor, notorious for permeating through conventional tubes not employing such a layer, does not permeate through applicants tubing 10 incorporating the gas barrier layer 22.
A relatively thick outer layer 26 formed from a third thermoplastic material 28 can be bonded to the gas barrier layer 22. The third thermoplastic material 28 exhibits excellent stress crack resistance, provides the tube 10 with improved kink resistance, and holds the barrier layer 22 down, eliminating blistering in applications involving carbon dioxide or carbonated beWer-ages. furthermore, by having the barrier layer 22 sandwiched between the second and third thermoplastic layers 18, 2C, the barrier layer 22 is protected, which is especially important under the clamp at the fitting, and allows the thermoplastic beverage contact layer 14 to conform more readily to the barbed fitting providing better sealing performance. Preferably, the third thermo-plastic material 28 is one of either linear low density polyethylene, ethylene vinyl acetate, a thermoplastic elastomer, or polyvinyl chloride. Even more preferably, the thermoplastic elastomer is a polypropylene-based thermoplastic elastomer.
To bond the gas barrier layer 22 to the second to thermoplastic layer 20, a first adhesive layer 3o can be used. The adhesive resin employed must be compatible with both the second thermoplastic material 20 and the gas resistant material 24. Likewise, to bond the gas barrier layer 22 to the third thermoplastic layer 26, a second adhesive layer 32 is used. Both adhesive layers 30 and 32 provide the barrier layer 22 with improved resistance to blistering in carbonated applications and resistance to separation of the layers during flexing.
While the thicknesses of the layers can vary, generally the thermoplastic beverage contact layer 14 and the second thermoplastic layer 18 are approximately the same thickness, while the third thermoplastic outer layer 26 is approximately 1.5 times as thick as either one of the beverage contact layer 14 or second thermoplastic layer 18. The barrier layer 22 and the,adhesive layers 30 and 32, by comparison, are relatively thin with their thicknesses being anywhere from 5 to 15 times thinner than the thickness of either one of the beverage contact layer 14 or second thermoplastic layer 18. In an exemplary embodiment where the tube wall is .06 inches thick, the thicknesses are as follows: beverage contact layer 14 and - second thermoplastic layer 18 - .015 inches; first adhe sive layer 30 - .003 inches; gas barrier layer 22 - .001 inches; second adhesive layer 32 - .002 inches; and outer thermoplastic layer - .024 inches.
To manufacture the tube 10, a three-stage con-tinuous extrusion process is employed. In stage one, the beverage contact layer 14 and second thermoplastic layer 18 are coextruded. A dual walled tube is formed in one extrusion die and cooled in water. In stage two, three layers are simultaneously extruded from one extrusion die coating the dual-layered tubing. The three layers are:
the first adhesive layer 30 which fuses to the second thermoplastic layer 18, the barrier layer 22 which is fusion compatible with the adhesive layers 30 and 32, and the second adhesive layer 32 which is fusion compatible with the barrier layer 22 and the outer thermoplastic layer 26. A relatively thick outer layer 26 is then applied to the five-layer tube, fusing to the second adhesive layer 32 in the final stage. This is a conven-tional, single component extrusion coating operation, thereby creating the complete multi-layer tube 10 with each layer fused to the adjacent layer.
To convert the tube 10 for use in high pressure environments, yarn reinforcement can be used (not shown) between the thick outer layer 26 and the second adhesive layer 32. To produce the reinforced hose or tube 10, the reinforcement is a pair of spirally opposed textile yarn layers applied to the five-layer tube immediately prior to the application of the outer layer 26. Fusiori between the second adhesive layer 32 and the outer layer 26 occurs through the interstices of the reinforcement layer.
Examtile 1 A tube formed using low density polyethylene as the beverage contact layer offers flexibility and low taste properties but does not have good resistance to environmental stress cracking. Therefore, a second layer l0 of linear low density polyethylene with excellent inherent environmental stress crack resistance is coextruded with the low density polyethylene.
An ethylene vinyl alcohol layer is used to provide excellent barrier resistance to oxygen, carbon 15 dioxide, and organic hydrocarbons, thereby protecting the fluid inside the tube from contamination by the exterior environment, flavor transfer from other nearby tubes, and oxidation. The excellent resistance to permeation by carbon dioxide preserves the carbonation in carbonated 20 fluids.
The relatively thick outer layer of linear low density, polyethylene provides further stress crack resis-tance as well as physical protection. The similarity in the physical properties of the various polyethylene layers 25 enables the multi-layer composite tube to be coupled to the fitting in the same fashion as single component poly-ethylene tubing.
Examtile 2 For added flexibility, the thick outer layer can be formed from ethylene vinyl acetate instead of linear low density polyethylene, which will stall be fusion compatible with the second adhesive layer used with the linear low density polyethylene.
ESA
For even greater flexibility, both the thick outer layer and the second layer can be formed from ethyl ene vinyl acetate. Due to the improved resilience of the ethylene vinyl acetate, stress crack resistance is still preserved.
Example 4 The structures of Examples 1 or 3 can be modi Pied so that polyvinyl chloride is used in the outer layer. Although it does have a low coefficient of fric tion, the abrasion resistance of linear low density poly ethylene is not exceptional. Ethylene vinyl acetate has a high coefficient of friction but relatively low abrasion resistance and low resistance to thermal softening.
Flexible polyvinyl chloride is an excellent choice for flexibility, abrasion resistance, and resis-tance to thermal softening. The use of. polyvinyl chloride allows for a much thicker outer layer to greatly improve the kink resistance.
When polyvinyl chloride is used for the thick 4outer layer, the second adhesive layer has to be modified _1~_ to provide fusion to the ethylene vinyl alcohol barrier layer as well as the polyvinyl chloride outer layer.
Ex~ple 5 In some cases, it may be important to reduce ingression into the tube by the fluid or certain organic components of the fluids generally associated with the flavor itself. A different choice for the beverage con tact layer may be used, such as polypropylene.
Polypropylene provides a more inert surface to reduce the absorption of flavor-carrying chemicals into the beverage contact layer. This is particularly important in applica-tions where it is desired to change the beverage being carried by the tube without flavor carry-over to the next beverage to be used in the tube.
While polypropylene provides low taste proper-ties and resistance to environmental stress cracking, it sacrifices flexibility. Using thermoplastic elastomer blends based on polypropylene in the second layer and outer layer affords the multi-layer composite tube good flexibility and kink resistance. When using a thermoplas-tic elastomer, care, should be taken to make the proper choice of adhesive for the first and second 'adhesive ' layers, so that they fuse to both the thermoplastic elas-tomer and the ethylene vinyl alcohol barrier layer.
The foregoing disclosure of specific embodiments is intended to be illustrative of the broad concepts comprehended by the invention.
Claims (20)
1. A tubing for beverages, said tubing comprising:
a beverage contact layer formed from a first thermoplastic material;
a second layer farmed from a second thermoplas-tic material coextruded with said first thermo-plastic material of the beverage contact layer;
a gas barrier layer bonded to said second ther-moplastic material and formed from a material resistant to gas diffusion; and an outer layer bonded to said material resistant to gas diffusion and formed from a third thermoplastic material.
a beverage contact layer formed from a first thermoplastic material;
a second layer farmed from a second thermoplas-tic material coextruded with said first thermo-plastic material of the beverage contact layer;
a gas barrier layer bonded to said second ther-moplastic material and formed from a material resistant to gas diffusion; and an outer layer bonded to said material resistant to gas diffusion and formed from a third thermoplastic material.
2 The tubing of claim 1 wherein said first thermoplastic material is low density polyethylene, said second and third thermoplastic materials are linear low density polyethylene, and said material resistant to gas diffusion is ethylene vinyl alcohol.
3. The tubing of claim 1 wherein said first thermoplastic material is low density polyethylene, said second thermo-plastic material is linear low density polyethylene, said third thermoplastic material is ethylene vinyl acetate, and said material resistant to gas diffusion is ethylene vinyl alcohol.
4. The tubing of claim 1 wherein said first thermoplastic material is low density polyethylene, said second thermo-plastic and third thermoplastic materials are ethylene vinyl acetate, and said material resistant to gas diffu-sion is ethylene vinyl alcohol.
5. The tubing of claim 1 wherein said first thermoplastic material is low density polyethylene, said second thermo-plastic material is one of linear low density polyethylene and ethylene vinyl acetate, said third thermoplastic material is polyvinyl chloride, and said material resis-tant to gas diffusion is ethylene vinyl alcohol.
6. The tubing of claim 1 wherein said first thermoplastic material is polypropylene, said second and third thermo-plastic materials are thermoplastic elastomers, and said material resistant to gas diffusion is ethylene vinyl alcohol.
7. The tubing of claim 1 wherein said gas barrier layer is bonded to said material resistant to gas diffusion by a first adhesive layer, and said outer layer is bonded to said material resistant to gas diffusion by a second adhesive layer, and wherein said beverage contact layer and said second layer are each approximately .015 inches in thickness, said first adhesive layer, said gas barrier layer, and said second adhesive layer each have thicknesses in the range of approximately .001 inches to .003 inches, and said outer layer is approximately .024 inches in thickness.
8. A tubing for beverages having a multi-layer construc-tion said tubing comprising:
a beverage contact layer formed from a first thermoplastic material which imparts low taste and resists odor transgression to the beverage;
a second layer formed from a second thermoplas-tic material adjacent said beverage contact layer, said first thermoplastic material coextruded with said second thermoplastic mate-rial so that the formation of stress cracks in said beverage contact layer of the tubing is minimized;
a gas barrier layer bonded to said second ther-moplastic material and formed from a material resistant to gas diffusion, said material resis-tant to gas diffusion bonded to said coextruded second thermoplastic material by a first layer of adhesive material therebetween; and an outer layer bonded to said material resistant to gas diffusion and formed from a third thermoplastic material, said third thermoplastic material bonded to said material resistant to gas diffusion by a second layer of adhesive material therebetween, said outer layer being of sufficient thickness to prevent blistering of said gas barrier layer in use.
a beverage contact layer formed from a first thermoplastic material which imparts low taste and resists odor transgression to the beverage;
a second layer formed from a second thermoplas-tic material adjacent said beverage contact layer, said first thermoplastic material coextruded with said second thermoplastic mate-rial so that the formation of stress cracks in said beverage contact layer of the tubing is minimized;
a gas barrier layer bonded to said second ther-moplastic material and formed from a material resistant to gas diffusion, said material resis-tant to gas diffusion bonded to said coextruded second thermoplastic material by a first layer of adhesive material therebetween; and an outer layer bonded to said material resistant to gas diffusion and formed from a third thermoplastic material, said third thermoplastic material bonded to said material resistant to gas diffusion by a second layer of adhesive material therebetween, said outer layer being of sufficient thickness to prevent blistering of said gas barrier layer in use.
9. The tubing of claim 8 wherein said first thermoplastic material is selected from the group consisting of low density polyethylene and polypropylene.
10. The tubing of claim 8 wherein said second thermoplas-tic material is selected from the group consisting of linear low density polyethylene, ethylene vinyl ace-tate, and a thermoplastic elastomer.
11. The tubing of claim 10 wherein amid thermoplastic elastomer is a polypropylene-based thermoplastic elastomer.
12. The tubing of claim 8 wherein said third thermoplas-tic material is selected from the group consisting of linear low density polyethylene, ethylene vinyl ace-tate, a thermoplastic elastomer, and polyvinyl chloride.
13. The tubing of claim 12 wherein said thermoplastic elastomer is a polypropylene-based thermoplastic elastomer.
14. The tubing of claim 8 wherein said material resistant to gas diffusion comprises ethylene vinyl alcohol.
15. The tubing of claim 8 wherein said first and second layers of adhesive material comprise the same materi-al.
16. The tubing of claim 8 wherein said second and third thermoplastic materials comprise the same material.
17. The tubing of claim 16 wherein said same material is selected from the group consisting of linear low density polyethylene, ethylene vinyl acetate, and a thermoplastic elastomer.
18. The tubing of claim 17 wherein said thermoplastic elastomer is a polypropylene-based thermoplastic elastomer.
19. The tubing of claim 8 wherein said beverage contact layer and said second layer are each approximately .015 inches in thickness, said first adhesive layer, said gas barrier layer, and said second adhesive layer each have thicknesses in the range of approximately .001 inches to .003 inches, and said outer layer is approximately .024 inches in thickness.
20. A tubing for beverages having a multi-layer construc-tion, said tubing comprising:
a beverage contact layer formed from a first thermoplastic material which imparts low taste and resists odor transgression to the beverage;
a second layer formed from a second thermoplastic material adjacent said beverage contact layer, said beverage contact layer coextruded with said second layer so that the formation of stress cracks in said beverage contact layer of the tubing are minimized, wherein said second thermoplastic material is selected from the group consisting of linear low density polyethylene, ethylene vinyl acetate, and polypropylene based thermoplastic elastomers;
a gas barrier layer bonded to said second thermo-plastic material and formed from a material resis-tant to gas diffusion, said material resistant to gas diffusion bonded to said coextruded second ther-moplastic material by a first layer of adhesive material therebetween, wherein said material resis-tant to gas diffusion comprises ethylene vinyl alco-hol; and an outer layer bonded to said material resistant to gas diffusion and formed from a third thermoplastic material, said third thermoplastic material bonded to said material resistant to gas diffusion by a second layer of adhesive material therebetween, said outer layer being of sufficient thickness to prevent blistering of said gas barrier layer in use, wherein said third thermoplastic material is selected from the group consisting of linear low density polyethyl-ene, ethylene vinyl acetate, and polypropylene based thermoplastic elastomers, wherein said first and second layers of adhesive material are the same material and said second and third thermoplastic materials are the same material.
a beverage contact layer formed from a first thermoplastic material which imparts low taste and resists odor transgression to the beverage;
a second layer formed from a second thermoplastic material adjacent said beverage contact layer, said beverage contact layer coextruded with said second layer so that the formation of stress cracks in said beverage contact layer of the tubing are minimized, wherein said second thermoplastic material is selected from the group consisting of linear low density polyethylene, ethylene vinyl acetate, and polypropylene based thermoplastic elastomers;
a gas barrier layer bonded to said second thermo-plastic material and formed from a material resis-tant to gas diffusion, said material resistant to gas diffusion bonded to said coextruded second ther-moplastic material by a first layer of adhesive material therebetween, wherein said material resis-tant to gas diffusion comprises ethylene vinyl alco-hol; and an outer layer bonded to said material resistant to gas diffusion and formed from a third thermoplastic material, said third thermoplastic material bonded to said material resistant to gas diffusion by a second layer of adhesive material therebetween, said outer layer being of sufficient thickness to prevent blistering of said gas barrier layer in use, wherein said third thermoplastic material is selected from the group consisting of linear low density polyethyl-ene, ethylene vinyl acetate, and polypropylene based thermoplastic elastomers, wherein said first and second layers of adhesive material are the same material and said second and third thermoplastic materials are the same material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13065693A | 1993-10-01 | 1993-10-01 | |
| US08/130,656 | 1993-10-01 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2103206A1 CA2103206A1 (en) | 1995-04-02 |
| CA2103206C true CA2103206C (en) | 2005-06-28 |
Family
ID=22445715
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2103206 Expired - Lifetime CA2103206C (en) | 1993-10-01 | 1993-11-16 | Multi-layer beverage tubing |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2103206C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102317063A (en) * | 2008-11-06 | 2012-01-11 | 德泰克动力流体技术公开有限公司 | Multi-layer tube for an automatic transmission |
| WO2014132036A1 (en) * | 2013-02-28 | 2014-09-04 | Valpar Industrial Limited | Improved beverage dispensing tubing |
-
1993
- 1993-11-16 CA CA 2103206 patent/CA2103206C/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102317063A (en) * | 2008-11-06 | 2012-01-11 | 德泰克动力流体技术公开有限公司 | Multi-layer tube for an automatic transmission |
| WO2014132036A1 (en) * | 2013-02-28 | 2014-09-04 | Valpar Industrial Limited | Improved beverage dispensing tubing |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2103206A1 (en) | 1995-04-02 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20131118 |