CA2253060A1 - Environmentally friendly beverage contact layer of thermoplastic tubing - Google Patents

Abstract

This invention relates to a new and economically viable method for making a THERMOPLASTIC Multilayer Tubing which comprises of at least three layers in which the inner layer P.J.1 is a BARRIER layer which does not allow the permeation and diffusion of vapours, gases, moisture, aroma and flavors. The P.J.1 layer which is totally inert, odourless, non-soluble in water, alcohols, beverages, syrups and alike is the contact layer. The P.J.I is a copolyester with a general formula (C10H8O4)n without any hazardous ingredients and has a melting point range about 160°C and density between 0.9 and 1.0 g/mL.
The outer surface layer comprises of polyethylene, P.E., with general formula (C2H4)n having melting point range about 180°C. It is bonded to the non permeable P.J.1 layer by P.J.2 layer which is chemically stable plastic material under processing condition and is composed of having a general formula C8H16O and density about 0.9 and melting point about 55°C.
The applicants have developed processing conditions for P.J.1 which meet the attributes of desired tubing and solves the long standing problem of vapour and flavour transmission and adsorption in beverage carrying and dispensing. The film form of P.J.1 can finds its application in the food packaging industry to prevent loss of moisture, flavour and taste.
The realization is that P.J.1 is environmentally friendly, and it is envisioned to have numerous potential applications. These applications can draw upon the P.J.1's properties at competitive cost.

Description

_..'.i~ENTIR!
Page 1 of 25 From: Dr. Raj N. Pandey CHEMISAR LABORATORIES INC.
248 Silvercreek Parkway N.
Guelph, Ontario, Canada N1H lE7 Phone: (519) 836-2313 (519) 836-5023 Subject: New Patent Application in Canada Title: ENVIRONMENTALLY FRIENDLY BEVERAGE
CONTACT LAYER OF THERMOPLASTIC
TUBING
Inyentors . Raj N. Pandey, Rupesh N. Pandey and Terry L. Jackson Asslgtlee . Dr. Raj N. Pandey Replication No.
CONTENT : Draft Application, including:
o Abstract of the Disclosure, o Specification, o Claims, o Formal drawings, o Formal documents November 19, 1998 BACKGROUND OF THE INVENTION
The thermoplastic tubings used in beverage industry must be non-permeable so as not to cause contamination or become contaminated when in close proximity of other liquids or beverages.
The tubing used for example to transfer syrup or carbonated beverages must not impart taste or odour to the beverage material and must not be susceptible to stress cracking.
The tubing must be environmentally friendly and should not contribute any possible inorganic or organic contaminant to the beverage contained or flowing through it. Ideally such a tubing should be economically viable and environmentally friendly in that the water or beverages contained in it do not get contaminated. lf, for example, water meeting drinking water criteria of U.S.
Environmental Protection Agency (U.S. E.P.A.) or drinking water Objectives of Ontario, Canada, is passed through the tubing the test results before passing and after should be the same.
Unfortunately, the plastic tubings in current practices suffer from self and cross contamination problems mainly due to permeability and transmission properties which alters the taste, odours and sometimes on long term may pose a safety problem to human health. The other problems of lesser importance are related to carbonated beverages in which dissolved carbon dioxide is found to permeate through the tubing and thereby lowering the carbon dioxide content in the beverage.
The phenomena of the environmental problem which is getting prominent recognition in recent years over the world in general, as well as in Canada, and the U.S. in particular pertains to health. The scrutiny is related to the transmittance of volatile organics (C, to C,o hydrocarbons) from the solid tube composed of thermoplastic polymeric material to the liquid it contains. Such materials may or may not contribute to taste and odour problem and therefore may not be perceived by humans by sensory mechanism. In carefully designed experiments, GC/MS analysis performed of air samples collected by evacuation or pressure differential techniques on many tubes currently in use for beverage dispensing industries, have found them to contain hydrocarbons. When the empty tubes are purged with inert gases such as Helium or Nitrogen and the stream is analyzed by the techniques of GC/MS, hydrocarbons are found in the stream.
When a typical tube is filled with distilled water and allowed to stand at room temperature and the water is analyzed by the technique of GC/MS, hydrocarbons are often detected. The source of these hydrocarbons are related to the polymeric thermoplastic material itself and they were most likely formed during heating and melting of the polymer in the extrusion of the tubing and remained captured during and after cooling. The volatile organic materials formed in the molten state of the polymer resin and held in the tube are able to diffuse through the tubing's inner layer and contaminate the beverages in contact with it. This phenomenon is found with most tubing manufactured from polyethylene and related materials. Polyethylene and related materials, with the exception of these environmental drawbacks, are low cost materials and meet various other attributes of the tubing materials and therefore have been marketed economically and predominantly.
In recent years considerable attention has been given to solving this problem.
Tubing made of alternative materials such as fluorocarbon, nylon, polypropylene, saran etc.
have certainly added improvements and have shown a performance advantage with regards to the transmission and diffusion of flavours. However there is a loss of flexibility of the tubing.
Additionally, the cost is of the order of three to four times higher. Furthermore, fluorocarbons have high softening points (320°C). This property not only makes it difficult to extrude but is also an energy intensive process. While very tough, translucent fluorine containing polymer always carnes a potential concern of the formation of corrosive HF gas in a molten condition in the extrusion process in contact with the other polymerrs containing carbon and hydrogen in their molecules such as polyethlene.
One preferred method of making beverage tubing which can offer a potential solution to circumventing the environmental problem is to incorporate an inner fluid contact layer of environmentally friendly and non-permeating materials. This inner layer can then function as a barner layer. The barner layer would thus provide environmental protection and safety against permeation of carbon dioxide, oxygen and contaminating volatile organic hydrocarbons from the outer layers. Due to the inert, odourless, non-soluble and non-permeable nature of the inner layer, the flavour and taste remain unaffected.
The making of a barrier layer with desirable properties has been the subject of considerable research interest and difficulty in the beverage dispensing industry.
Materials such as fluorocarbon, nylon, Ethylene vinyl alcohol (EVOH) and polyvinyl chloride (PVC) are now commonly used. EVOH and nylons are found to lose with time, their vapour and gas barrier properties after exposure to water or increased humidity. Although polyvinyl chloride itself is safe, it is formed from vinyl chloride monomer which is carcinogenic.
Among the various known barriers in use, fluorocarbon ranks among the best in regard to its inertness and non-permeable properties. However, it is the most expensive.
There is another recognized problem with tubing with a fluorocarbon or polypropylene inner layer. These materials are stiff which often require excessive force in clamping, which may result in cutting or cracking of the inner layer of the tubing and are extremely difficult to bond to the other layers of the tubing.

Most recently, with the introduction of many new pungent flavours, it has become increasingly difficult to flush out a tube in order to change beverage flavours in a dispenser system. With the more pungent flavours such as root beer and cherry, it is virtually impossible to remove the absorbed flavour from current state-of the-art tubes.
Therefore, there exists a need for a simple, economically viable, and contaminant free thermoplastic tubing with an environmentally friendly inner barrier layer which effectively overcomes the inherent difficulties of stiffness, gas and flavour transmission, and flushability facing the beverage industry.
As follows, the present invention is considered to have overcome many of the difficulties discussed and offers a simple and economical solution to vapour and gas transmission for a wide range of applications.

SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an efficient and economical method for making a novel barrier layer tubing for beverage applications and a novel barrier film layer for food packaging industries where the preservation of aroma, taste and moisture transmission is of paramount importance.
In accordance with the invention, there is thus provided a process for making a tubing for beverage dispensing which comprises of an environmentally friendly inner layer, P.J.1, made up of copolyester with molecular formula (C,oHg04) without any hazardous ingredients. This layer is bonded to the outer polyethylene layer by terpolymer, P.J.2, with molecular formula (C~H,~O)°.
Applicant has found quite unexpectedly that by using carefully controlled conditions an inner layer P.J.1 can be efficiently bonded via P.J.2 to the non-compatible polyethylene layer.
According to the invention, a three-layer tubing for beverages is provided.
The beverage contact layer of about 0.1 mm is formed from a first thermoplastic material P.J.I
under careful extending temperature between 250-270°C, under the atmosphere nitrogen or carbon dioxide or a mixture of both which have passed through a proprietary filter for achieving the non-brittle property of tubing. In the preparation of the test films, the preferred rate of reaching said temperature was found to be 15°C per minute. A thin film of about 0.1 mm of terpolymer material can then be coated by the art of extrusion at 150°C for bonding the outer layer of about 1 mm of Polyethylene also at I50°C and at pressure of about 1000 psi.
The outer layer may be either linear low density polyethylene, ethylene vinylacetate or any other variety of thermoplastic material suitability selected for the purposes of the outer layer which offers the desired flexibility.

g The absence of stiffness, brittleness, and inertness with the other desired attributes such as cost makes P.J.1 a perfect non-permeable material of choice and makes this invention to be so much attractive.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the present invention will be more apparent from the following description of a prefer ed embodiment as illustrated by way of examples in the accompanying drawings in which:
FIG. 1. is a view of the tubing for dispensing beverages in accordance with one embodiment of the invention.
FIG. 2. is a diagrammatic illustration of a film making in accordance with another embodiment of the invention.
FIG.3. is a diagrammatic illustration of experimental set-up used to perform the permeability test.

In the process which is schematically illustrated in FIG. 1 a tubing with three layers is shown for transporting beverage (BEV) through the tubing. Beverages are normally dispensed through several tubes in close proximity canying different beverages and syrup to the dispenser. The beverages may include colas, alcohols, carbonated and non-carbonated drinks, and other liquid form drinks. The carbonated beverages are comprised of ingredients such as syrup, and water to which carbon dioxide has been added. ~ The syrup has the flavoring material which may be derived from natural fruit or synthetic materials. The carbon dioxide solubility is normally increased by pressure or by lowering the water temperature near freezing.
As shown in Figure 1 the beverage (BEV) flows through the inner layer of and its taste and odour are unaffected. The inner layer, P.J. l, is non-permeable, chemically inert and perfectly stable and therefore functions as a protective layer for the beverage contained for dispensing.
The contaminating middle and outer layer are unable to transmit the organic volatiles through this low cost amazing barner.
As shown later by GC/MS analysis the barrier layer P.J.1 does not allow the permeation of various kinds of beverages through it including among them the very invasive root beer. This finding is in contrast to commonly used barriers layers which have been discussed before.
According to embodiment of this invention the barrier layer, P.J.1 need not be thick. In a typical example P.J.1 can be about 0.10 mm or more, the P.J.2 layer about 0.10 mm or more and the outer layer about 1.0 mm or more. The strength of the inner layer is sufficient to contain the carbonated drinks under pressure and eliminating the blistering problem. Under the processing conditions of temperature and pressure, the inner layer does not suffer from cracks and stiffness as is common to the other materials. The processing and extrusion conditions do not require any significant modification to the capital and operational raw material costs of the extrusion process and therefore economically attractive in providing safe beverage dispensive tubing by switching to this inner layer.
To convert the tube for application in high pressure environments, yarn reinforcement can be used as is known to the art. The following non-limiting examples further illustrate the invention.

The elemental analysis of innerlayer, middle layer and outer layer materials were performed for material balance using Carlo Erba instrument. The carbon and hydrogen analysis was performed by combusting a known weight of sample at 1000°C in the presence of O2.
The resulting gases namely COZ and H20 produced were determined by standard techniques of gas chromatography.
The percentage Carbon and Hydrogen in the samples of materials were calculated from the combustion of NBS Standards. The Oxygen analysis was performed by the pyrolytic technique.
The elements such as N, S and halogens were not detected. As can be seen from the results in Table 1 there was a good mass balance within the experimental error. These results indicate that the composition of the materials used contain carbon, hydrogen and oxygen only and that there is good agreement between theorical and experimental values.

Composition by Weight Elements Inner Layer FoundMiddle Layer Outer Layer Found Found C 62.44 (62.50)* 75.03 (75.00)* 85.78 (85.71 )*

H 4.16 (4.16) 12.60 ( 12.50) 14.37 ( 14.28) O 33.46 (33.33) 12.48 ( 12.50 - -Total I 100.06 I 100. I 1 I 100.15 * Values in brackets are calculated expected values.

A thin film P.J.I of polyester of formula (C~oHeO4)~ in range of thickness of about O.l mm to about 0.5 mm were prepared in the laboratory as shown in Figure 2. In this method the polyester, P.J.1 in pellet form is uniformly spread over bottom die and the top die is placed on it. The die/P.J.1/die set is protected from the flowing stream of nitrogen which has been pretreated in passing through PJD and purges the entire system of GC oven which is programmed to increase linearly from room temperature to 320°C at rate of 15°C per minute. Once the temperature on the thermocouple is recorded to about 270°c the die set is taken out and pressed immediately to about 1000 psi or sufficient to the thickness of the film required. The thickness of the film can be controlled by applied pressure. The die set is cooled in water and film removed for testing. Such a processing condition of temperature and inert atmosphere is necessary otherwise the film produced becomes brittle and does not conform.
A group of five films produced in this way were immersed in distilled water and contents boiled in a beaker for an hour and cooled to room temperature and the water with the film in it kept for 7 days then the water was analyzed by Inductively Coupled Plasma for various metals. The anions were analyzed by standard technique of Ion Chromatography. The results are presented in Table 2. These results indicate that the film P.J.1 does not add any impurity and water remains unaffected and meets the drinking water criteria as shown in Table 2.

Sample Water Parameter TestedExtract with P.J.1MAC* (mg/L) Film concentrations (mg/L) Aluminum N.D. 0.10 Arsenic N.D. 0.025 Barium N.D. 1.0 Boron N.D. 5.0 Cadmium N.D. 0.005 Chromium N.D. 0.05 Iron N.D. 0.30 Nickel N. D. 0.01 Lead N. D. 0.0 I

Mercury <0.001 0.001 Manganese N.D. 0.05 Selenium N.D. 0.01 Uranium N.D. 0.10 Nitrite (as N) <0.1 1.0 Nitrate (as N) <0.1 10.0 N.D. = Not Detected Detection limit - 0.005 mg/L
** MAC = Maximum Acceptable Concentration as a Drinking Water Objective - Health Related In another experiment a second batch of P.J.1 films were kept immersed in distilled water for a period of 2 weeks. The water was then analyzed for organic volatile impurities by technique of GC/MS using Hewlett Packard GC/MS with Tekmar Purge and Trap. The results are presented in Table 3. These results clearly indicate that the film P.J. I does not impart any organic volatile impurity and that the water remains unaffected to its original environmental state.

Parameters Extract Sample Maximum Drinking Water with P.J.1 Water Limit Concentrations Concentration (m~-) (mg~L) Benzene N. D. 0.005 Toluene N.D. 0.02 Xylene N.D. 0.30 Ethyl Benzene N.D. 0.002 Volatile OrganicsN.D. 0.01 TrichloroethyleneN. D. 0.05 Trihalomethane N.D. 0.35 N.D. = Not Detected (<0.001 mg/L) The inner layer film, P.J.1, was prepared by the method described above and was subjected to permeability performance test. The apparatus shown in Figure 3 which is self explanatory was used. The film membrane is firmly placed as shown and it divides the cell into two compartments A and B. The transmittance of vapours and gases from A to B can occur only through the membrane. Septum 1 and Septum 2 are provided for withdrawal of samples for analysis by standard technique of gas chromatography.
In a typical water vapour transmittance determination experiments the technique involved passing of helium (or nitrogen) through a bubbler which contained water to humidify the helium. By opening and closing of valves 1 and 2, the side A of the cell was saturated with water vapour.
The side B was kept dry by flowing the stream of dry helium. The membrane was allowed to equilibrate with saturated water vapour for at least 24 hrs in a steady state.
The chromatographic analysis for water both from Side A and Side B of the cell were performed. The presence of water was detected on Side A and not on side B. Even after creating differential pressure by lowering the pressure on Side B the water was not detected on Side B implying that the film membrane does not allow transmission of water vapour. Later helium was replaced by carbon dioxide and then oxygen and permeability experiments were repeated under steady state condition. Carbon dioxide and Oxygen were not detected on the Side B of the cell. These results are presented in Table 4 and indicate that the film membrane of P.J.1 does not transmit water vapour, carbon dioxide and oxygen in contrast to polyethylene membranes of the same thickness or more and under identical conditions. Therefore the novel polyester as an inner layer is found to be an excellent barrier.

Permeant Film MembraneTemp. ConcentrationConcentration (barrier) (C) Permeant Sideof Permeant on A of Cell Side B of Cell Water Polyester 23-24 Saturated N.D.

(P.J.1 ) COz Polyester 23-24 Saturated N.D.

(P.J.1 ) OZ Polyester 23-24 Saturated N. D.

(P.J.1 ) N.D. = Not detected Polyester = Copolyester of formula (C,~H804)~

l5 In another embodiment of experiments the water in the bubbler (Figure 3) was replaced by alcohol, acetone and pentane and steady state was allowed to attain. The concentration of permeant were measured by gas chromatography. The results of analysis clearly showed that the PET (P.J.1) membrane does not allow permeation of organic volatiles. These results are shown in Table 5. The P.J.1 is therefore a material of choice to prevent transmission of organics.

Permeant Film MembraneTemp. ConcentrationConcentration (barrier) (C) of Permeant of Permeant ambient Side A Side B

Ethyl AlcoholPolyester 23-24 Steady State N.D.

(P.J.1 ) Saturation Acetone Polyester 23-24 Steady State N.D.

(P.J.1 ) Saturation Pentane Polyester 23-24 Steady State N.D.

(P.J.1 ) Saturation Pentane Polyethylene 23-24 Steady State Detected Saturation N.D. = Not Detected Polyester = Copolyester of formula, (C~~,HRO4)n In preferred embodiment, permeability measurements were carned out with actual beverages using Cola, Root Beer, Beer and Scotch Whisky. The apparatus of Figures 3 was modified and side A was saturated with each of the beverages and tested individually. In steady state condition the permeability results are reported in Table 6. In a separate study, the widely used barrier layers EVOH (ethylene vinyl alcohol), nylon-6 and nylon-11 have been found to permeate to some extent when methyl salicylate (a flavour component) was used as the permeant. This observation does not appear favourable in addition to the high cost of these materials. The low cost P.J.1 material with superior transmission properties is the most logical choice put forward by the virtue of this invention.

ti Permeant Film Temp Concentrationon Concentra Membrane (C) Permeant Permeant ambient Side A Side B

Cola 1 Polyester 23-23 Saturated N.D.

(P.J.1 ) Cola 2 Polyester 23-24 Saturated N.D.

(P.J.1 ) Root Beer Polyester 23-24 Saturated N.D.

(P.J.1 ) Beer Polyester 23-24 Saturated N. D.

(P.J.1 ) Scotch WhiskyPolyester 23-24 Saturated N.D

(P.J. l N.D. = Not Detected Polyester = Copolyester of formula, (C,oHg04)~

For the application in beverages dispensing such as the tubing of this invention, the tube must preferably be washable or flushable with water. The disc of polyester was soaked in two major colas and Beer for 24 hours at room temperature. The treated discs were successively washed with 10 ml distilled water. The wash solutions were collected and analyzed by GC/MS. 5 ml of wash samples were taken in Tekmar Purge and Trap system and analyzed by Hewlett-Packard GC/MS. The results of analysis presented in Table 7. These results indicate that the film surface is flushable implying that the surface adsorption is insignificant.

Detection in Wash Cola Detected Detected N.D. N.D. N.D.

Cola Detected Detected N.D. N.D. N.D.

Beer Detected Detected N.D. N.D. N.D.

N.D. = Not Detected Commonly used beverage dispensing tubings available in market were tested for the release of contaminating gases and vapours upon purging or creating pressure differential by evacuation.
The P.J.I disc was tested by evacuation only.
Each experiment on commercial beverage tubing comprised of purging with helium a certain length of tubing by flowing a stream of helium through the inner layer of the tube and analyzing gases and vapours released upon purging by Purge & Trap / GC-MS technique. The results are presented in Table 8. As can be seen from the results of Table 8 the polyester disc P.J.I does not release any such contaminant and therefore environmentally safe.

Source Test Contaminants of Method Found Tubings Commercial tubings Helium C, - C,o currently used in marketPurge & Trap Hydrocarbons for Beverage Dispensing Commercial tubings Evacuation C, - C,o currently used in market Hydrocarbons for Beverage Dispensing Copolyester (P.J.I Evacuation None disc)

Claims (20)

1. A novel and environmentally friendly tubing for carrying and dispensing of beverages.
The said tubing has numerous attributes:
The beverage contact layer has been chosen from low cost thermoplastic material which is copolyester of general formula (C10H8O4). This material has not been used as an inner contact layer in beverage tubings.
A second layer is formed from a second thermoplastic material with a general formula C8H10O which serves to strongly bond the third plastic outer layer to the beverage contact layer.
The third plastic layer is low cost polyethylene with formula (C2H4)n and is non-compatable to the inner contact layer and therefore a bonding layer is required.

2. The inner layer is the gas barrier layer which is inert, odourless, non-soluble in water, alcohols, beverages, syrups and alike.

3. The tubing of Claim 1 wherein said inner layer can be modified copolyester with variation in composition and substituent groups.

4. The tubing of Claim 1 wherein the middle bonding layer can be co-extruded with other materials having adhesive properties. The outer layer can be of low density or high density polyethylene, polypropylene, ethylene vinyl acetate, polyvinyl chloride or ethylene vinyl alcohol or any other form of thermoplastic suitable for this purpose.

5. The tubing of Claim 1 wherein the said contact layer is about 0.1 mm thickness, with middle layer about 0.1 mm in thickness and the outer layer is about 1.0 mm or more.

6. The optimum formation of inner layer of polyester free from stiffness, odour and colour changes can preferably be attained by passing nitrogen or other inert gas through a pretreatment filter which consists of silica gel and activated carbon. For the purposes of this invention a trade name "P.J.D." is given to the pretreatment filter.

7. The inner layer of Claim 1 wherein the bonding layer can be chosen from other materials with adhesive properties and a thermoplastic elastomer.

8. The tubing of Claim 1 wherein said thermoplastic elastomer is polypropylene-based.

9. The tubing in Claim 1 wherein the said tubing may comprise of inner, middle and outer layers of the same copolyester.

10. The tubing in Claim 1 wherein the said beverage contact layer are each approximately the same thickness or different thickness.

11. The tubing in Claim 1 wherein the thickness of inner contact layer can vary.

12. The tubing in Claim 5 wherein the thickness of inner contact layer can vary from 0.001 inches to 0.003 inches, and the said outer layer to about 0.024 inches in thickness.

13. A tubing for beverage having multiple layers, said tubing comprising:
a beverage contact layer formed from copolyester which does not impart taste, flavour and resists odour transmission to the beverage and from the beverage.

14. Under the conditions of temperature, heating rate chosen the inner layer does not develop cracks.

15. The film and sheets can be formed from P.J.1 which can lead the way in the food packaging industry.

16. The films and sheets provide thermally stable, inert and nonpermeable material which may allow freezer-to-oven service in the food market.

17. Various sizes of films and discs can be made which will find applications as an inert liners or caps for environmental sampling bottles replacing expensive fluorocarbon liners.

18. The film liners of P.J.1, being less expensive than fluorocarbon and meeting EPA criteria for drinking water contact material, therefore may find various applications in drug packaging.

19. The material P.J.1 can replace applications of polypropylene and EVOH for certain retort applications.

20. The P.J.1 material does not contain Chlorine atoms in its molecule and being nonpermeable, can lead to various medical applications where toxicological concerns are associated with thermoset materials and chlorine-bearing materials.