US3450303A - Reusable lined beverage containers - Google Patents

Description

June 17, 1969 50550 ETAL 3,450,303

REUSABLE LINED BEVERAGE CONTAINERS Filed Jan. 17, 1966 INVENTORS JOSEPH F. 50550 a? as: 6536/4 BY MW at" A ORNEYS United States Patent 3,450,303 REUSABLE LINED BEVERAGE CONTAINERS Joseph F. Bosso, Lower Burrell, and Gene Gerek, Cheswick, Pa., assignors to PPG Industries, Inc., a corporation of Pennsylvania Filed Jan. 17, 1966, Ser. No. 520,948 Int. Cl. B65d 25/14, 25/34 US. Cl. 22064 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates to containers suitable for packaging beverages, and more particularly to such containers having a sanitary liner which is sufiiciently chemically resistant to be cleaned and reused.

Metal containers for beverages, such as beer and soft drinks, are usually made from aluminum or tinplate. Because such beverages exert corrosive action upon the metal a sanitary liner is ordinarily applied to the internal surface of the container in order to protect the container and to prevent contamination of the beverage during storage. The materials that can be used for the liner are limited, since the liner must not introduce any undesirable or toxic materials to the packaged product, and should not affect its taste. Taste is especially troublesome with beverages because very small taste differences are easily noticed in such products.

While several more or less satisfactory products are known for lining of ordinary food and beverage containers, these are designed for use with relatively small inexpensive cans which are discarded after use. There is now, however, increasing interest in containers of larger size which can be stored at ordinary ambient temperatures for extended periods of time. These may range from containers holding several quarts or gallons, for home use, to large storage containers and tank trucks holding hundreds or thousands of gallons.

Because of the cost of these larger containers, it is impracticable to discard them after they are used but once, and it is necessary that they be reused several times in order to make such containers economically feasible. This is true even with those designed for home use. It is necessary, however, to rigorously clean the container before each usage, since during its use and return there may be introduced therein various contaminants, dirt, etc.

The preferred cleaning agent is aqueous sodium hy- 6 droxide, Which is a reliable and sanitary cleaning agent but which is extremely corrosive and which attacks many coatings.

Thus, it is seen that any coating utilizable as a liner for the above-described containers must have a number of ice properties which are difiicult to obtain in combination. These include the following:

(1) The lining must not contribute or absorb any taste when in contact with beer, wine, soda and similar beverages for extended periods.

(2) The lining must be resistant to repeated washings with sodium hydroxide solution. A test which is employed to determine suitability in this regard subjects the coating to thirty washings with 5 percent aqueous sodium hydroxide at about 180 F. for five to ten minutes each, after which the lining should show no defects.

(3) The lining must be flexible enough to withstand severe external impacts during handling without cracking. This is quite important since the container may be dropped during use or while it is being returned for reuse, but it is diificult to inspect the interior of the container for cracks, etc.

(4) The lining should have good adhesion without the use of a primer, and the adhesion must be retained dur ing handling and use.

(5) Both relatively thick coatings and relatively thin coatings of the lining material must retain the above properties. In commercial use relatively thick coatings are applied (ranging as high as 30 mils) in order to insure complete coverage, but some small portions may only receive thin layers, i.e., 3 to 5 mils. Adequate flexibility and impact resistance of such coatings is difiicult to achieve.

(6) It is desirable that the coating composition not contain any solvent or other volatile component, so that the coating can be applied to the interior of large containers having a relatively small opening without the necessity for difiicult and tedious procedures to remove residual volatile components.

Conventional sanitary liner coatings do not meet the above qualifications. For example, those coatings which are extensively employed in sanitary liners for small cans, are not usable in the above type of containers because their adhesion, impact resistance and resistance to repeated cleanings are inadequate. Other materials proposed for use in lining of beer and beverage cans are similarly unsatisfactory because they do not meet one or more of the above criteria.

There have now been discovered certain coating compositions which when cured in the manner described herein meet all of the above described properties and which provide highly desirable liners for the beverage containers described above. These coating compositions consist essentially of a mixture of a polyglycidyl ether of a polyhydric compound having an epoxide equivalent between about and about 400, and an epoxy ester of dimerized fatty acid having an opoxide equivalent between about 350 and about 950, cured with a non-volatile, polyfun'ctional aromatic amine catalyst.

The polyglycidyl ether component is ordinarily made by reacting an oxirane compound, such as epichlorohydrin, 1-chloro-2,3,epoxybutane, l-bromo-2,3,epoxypentane or other epoxide, with a polyhydric compound, usually a polyhydric phenol. While trihydric phenols can be used, the preferred compounds are bisphenols such as bis(4-hy droxy phenyl)2,2-propane (which is known as Bisphenol A) and similar compounds, such as 4,4-dihydroxybenzophenone, bis(4-hydroxyphenyl)-l, l-ethane, bis (4-hydroxyphenyl)-1,1-isobutane, bis(2- hydroxynaphthyl) -methane, and the like. Polyglycidyl ethers derived from polyhydroxy alcohols, such as sorbitol, pentaerythritol, polyalkyl alcohol and the like, may also be used.

As indicated, the polyglycidyl ether should have a relatively low epoxide equivalent, between about 100 and about 400, this being important in order to achieve the combination of properties described above. A specific preferred polyglycidyl ether is the reaction product of epichlorohydrin and Bisphenol A having an epoxide equivalent between about 175 and about 210 and a molecular weight of from about 350 and about 400.

The epoxy ester component of the composition is an epoxy ester of dimerized fatty acid or mixture of fatty acids, the fatty acid or acids being any of those derived from vegetable and marine oils, such as linseed oil, soybean oil, tung oil, castor oil, and the like. The preferred dimer acid is dimerized linoleic acid. The epoxy ester is made by reacting the aforesaid acid material with an epoxy compound, which may be epichlorohydrin or the similar compounds mentioned above, or with a relatively low molecular weight polyepoxide, such as the diglycidyl ether of Bisphenol A or a similar reaction product of epichlorohydrin and 'a polyhydric compound. The epoxide equivalent of the epoxy ester should be between about 350 and about 950, this again being necessary in order to attain the desired properties. A preferred epoxy ester is the ester of epichlorohydrin and dimerized linoleic acid having an epoxide equivalent between about 390 and about 470. Another preferred epoxy ester is the similar product made by reacting dimerized linoleic acid with the reaction product of Bisphenol A and epichlorohydrin having an epoxide equivalent of 185 to 192. Such epoxy ester has an epoxide equivalent between about 650 and 750.

It is important that the composition be cured using a non-volatile polyfunctional aromatic amine catalyst. Examples of such catalysts include metaphenylenediamine, 4,4-methylenedianiline, orthophenylenediamine, triaminotriphenylmethane, and similar materials. A specific preferred catalyst is a eutectic mixture of metal-phenylenediamine and 4,4'methylenedianiline, which is available commercially in admixture with a small amount of 1,2-epoxy- 3-phenoxypropane as a diluent. The 1,2-epoxy-3-phenoxypropane serves to liquify the catalyst composition for convenience, and is present in the amount necessary to provide the desired viscosity.

The proportions of the components are also important to the obtention of coatings having the properties described herein. The polyglycidyl ether component should be present in an amount between about 30 and about 80 parts by weight, and the epoxy ester corespondingly should be present in an amount between about 20 and about 70 parts by weight. The amount of catalyst employed is especially important and should be between percent and 30 percent of the total weight of the polyglycidyl ether and the epoxy ester. In the preferred coatings, a mixture of equal parts of the polyglycidyl ether and the epoxy ester is cured with 20 percent by weight of the aforesaid catalyst.

The containers to which the above composition is applied are usually made of a metal such as aluminum although tinplate (cold rolled steel to which a thin layer of tin has been applied) can also be employed, as can other materials, which need not always be metal. The containers can be of various sizes and shapes, although as indicated, the invention is of particular utility with larger containers, i.e., holding several quarts or more. One container with which the coatings herein are especially desirable is a beverage container in the form of a small aluminum keg having one relatively small opening, located in one end.

One commercial embodiment of such a container has a capacity of about one gallon of beverage, the gross volume being somewhat greater to permit pressurizing with a gas, if desired. Such a container is illustrated in the drawing herein. As shown the container 1 with a single opening 2 has a lining 3 consisting of the cured, composition of the invention.

The compositions are applied by blending the catalyst with the mixture of the polyglycidyl ether and the epoxy ester, and then applying this to the internal surface of the container. Generally a flow coating procedure is utilized in which the composition is introduced into the container and the container is then rotated in several directions in order to distribute the coating over the interior surface. The catalyzed composition cures relatively slowly at room temperature, it remaining fluid for a period of twenty-four to forty-eight hours and then slowly curing to the hard finished coating. For this reason, elevated temperatures are generally employed in order to accelerate the rate of cure. Heating also aids in the coating process by reducing the viscosity of the composition.

Curing time can vary considerably, depending upon the desired time and the available temperature, which are correlated. Common curing schedules are from 350 F. to 500 F. for 2 to 30 minutes. Faster curing at ambient temperatures can also be obtained by addition of accelerators, such as aliphatic amines or hydroxyl compounds. Examples of accelerators include ethylene diarnine, diethylene triamine, triethylamine, phenol, ethanolamine, Bisphenol A, and the like. Such accelerator-s do not replace the catalyst and are typically utilized in very small amounts, e.g., between 1 and 5 percent of the total weight of polyglycidyl ether and epoxy ester.

Set forth below are several examples of the invention and the manner in which the compositions are produced and applied. In these examples, as throughout this specification, all parts and percentages are by weight unless otherwise indicated.

Example 1 Fifty parts of polyglycidyl ether (made from the reaction of epichlorohydrin with Bisphenol A and having a viscosity of -160 poises at 25 C. and an epoxide equivalent of 185 to 192) were thoroughly blended with an equal amount of epoxy ester made from epichlorohydrin and dimerized linoleic acid and having an epoxide equivalent of 390 to 470. To this, there were added 20 parts of a catalyst composition consisting of a eutectic mixture of m-phenylenediamine and 4,4'-methylene dianiline along with a small amount of 1,2-epoxy-3-phenoxypropane sufficient to make the viscosity of the catalyst mixture 20 poises at 25 C. This composition was coated on the interior surface of several keg-shaped containers similar to that shown in the accompanying drawing and made of aluminum 0.115 inch thick. The containers were 8 inches high and 7 inches in diameter, with a gross capacity of slightly over 1 gallon, and had a single o'pening 4 inch in diameter, through which 50 grams of the above composition were added. The containers were then rotated on several different axes so as to coat the entire inner surface, and were heated to 500 F. for 5 minutes. They were then cooled and rinsed with water.

Tests of the above containers established their suitability for packaging beverages as described above. These tests included the following:

Taste tests.Several taste tests were carried out, with in each instance the taste being evaluated as to whether the coating altered the taste, either by introducing a different taste to the contents or removing any of the original taste. Among the tests were:

(1) Water is boiled in the container for 30 minutes, cooled and tasted.

(2) Cola beverage is added to the water from (1) and tasted (with some materials a taste difference is noted in this test where none is observed in the water itself).

(3) The container is packed with one gallon of cola, sealed and stored for 1 month; it is then opened and the cola tasted.

(4) The container is packed with one gallon of beer and sealed. The beer is pasteurized by heating at F. for 30 minutes, and then cooled and tasted.

The containers containing the above coating passed each of the above tests with no observable taste differences.

Flexibility-The container is filled (one gallon) with Water, sealed and then dropped from a height of 30 feet onto a steel bar. The container is then cut open and the coating examined for an cracks, especially in the area of impact. The above containers showed no cracks in this test.

Adhesion.The coating in the area of impact'in the flexibility test above is covered with pressure sensitive adhesive tape, which is then removed quickly. Any loss of adhesion is evidenced by removal of some of the coating. No loss of adhesion was noted with the above coatings.

Caustic resistance-Resistance of the coating to caustic cleaning agents is tested by placing the coating in 5 percent aqueous sodium hydroxide solution at 180 F. for '10 minutes and flushing with Water. This is repeated 30 times. As an alternate test the coating is subjected to the hot caustic solution for 300 minutes continuously. The coating is then examined for any defects. The above coatings satisfactorily passed this test.

Example 2 Example 1 is repeated except that there are employed 70 parts of the polyglycidyl ether and 30 parts of the epoxy ester. Similar results are obtained.

Example 3 Example 1 is repeated except that there are employed 40 parts of the polyglycidyl ether and 60 parts of the epoxy ester. Similar results to those of Example 1 are again obtained.

Example 4 Example 1 is repeated except that the epoxy ester is made by esterifying dimerized linoleic acid with a polyglycidyl ether of Bisphenol A having an epoxide equivalent of 185-192 and a molecular weight of 350-400. The epoxy ester has an expoxide equivalent of 650 to 750. The product satisfactorily passes the above tests.

Example 5 Example 1 is again repeated using as the polyglycidyl ether the reaction product of Bisphenol A and epichlorohydrin having an epoxide equivalent of 180-18 8 and a viscosity of 6595 poises at 25 C. Again, satisfactory results are obtained.

Example 6 A composition suitable for spraying and curing at ambient temperatures (203 0 C.) is produced by adding 2 parts of diethylene triamine to the composition of Example 1. This composition is useful, for instance, to line .the interior sunfaces of large tank-cars and the like to be used for transporting or storing wine, beer, caustics and other liquids.

The above examples illustrate the invention in its prefered embodiments, but there can be employed in place of the corresponding components of the examples other materials as described herein. For example, other polyfunctional aromatic amines, such as o-phenylenediamine and triaminotriphenylmethane, can be used, as can epoxy esters made from other fatty acids, such as dimerized soybean acids.

The outstanding combination of properties provided by the compositions described and exemplified above is not obtainable with other types of coatings. Illustrating this was a series of tests employing the procedure of Example 1 but utilizing various resinous coating materials. Among those tested were the following, all of which were unsatisfactory:

Powdered epoxy resin Polyethylene Ethylene-vinyl acetate copolymer Vinyl chloride-vinyl acetate copolymer Polyamide (nylon) Polyglycidyl ether and epoxy ester (as in Example 1) cured with diethylene triamine Polyglycidyl ether (as in Example 1) cured with catalyst of Example 7 Polyglycidyl ether (as in Example 1) and phenol-formaldehyde resin Polyglycidyl ether (as in Example 1) cured with diethylene triarnine Polyglycidyl ether (as in Example 1) cured with triethylene tetramine Polyglycidyl ethyl (as in Example 1) cured with ethylene diamine Polyglycidyl ether (as in Example 1) cured with polyamide (Versamid 125) According to the provisions of the patent statutes, there are described above the invention and what are now considered to be its best embodiments. However, within the scope of the appended claims, it is to be understood that the invention can be practiced otherwise than as specifically described.

We claim:

1. A container suitable for packing beverages having its internal surface coated with a cured coating composition consisting essentially of (a) from about 30 to about parts by weight of a polyglycidyl ether of a poly hydric phenol having an epoxide equivalent between about and about 400; and

(b) from about 20 to about 70 lparts by weight of an epoxy ester of dimerized vegetable or marine oil fatty acid having an epoxide equivalent between about 350 and about 950; said compositions having been cured with from 10 percent to 30 percent, based on the total weight of '(a) and (b), of a non-volatile poly functional aromatic amine catalyst.

2. The container of claim 1 in which said polyglycidyl ether is a polyglycidyl ether of a polyhydric phenol.

3. The container of claim 2 in which said polyhydric phenol is bis(4-hydroxyphenyl)-2,2-protpane.

4. The container of claim 1 in which said epoxy ester is the ester of epichlorohydrin and dimerized linoleic acid.

5. The container of claim 1 in which said epoxy ester is the ester of dimerized linoleic acid and a reaction product of epichlorohydrin and his (4-hydroxyphenyl)-2,2- propane.

6. The container of claim 1 in which said catalyst is meta-phenylenediamine or 4,4-methylenedianiline, or a mixture thereof.

7. The container of claim 1 in which said catalyst is a. eutectic mixture of mcta-phenylenediamine and 4,4- methylene dianiline containing a minor amount of 1,2- epoxy-3-iphenoxypropane.

8. The container of claim 1 in which said surface is aluminum.

9. The container of claim 1 in which said cured layer has an average thickness of from 10 to 20 mils.

10. An aluminum container suitable for packing beer, having all of its internal surfaces coated with a 10 to 20 mil average thickness layer of a cured composition consisting of (a) from about 30 to about -80 parts by weight of a polyglycidyl ether of a polyhydric phenol having an epoxide equivalent between about 100 and about 400; and (b) from about 20 to about 70 parts by weight of an epoxy ester of dimerized vegetable or marine oil fatty acid, having an epoxide equivalent between about 350 and about 950; said composition having been cured with from 10 percent, to 30 percent, based on the total weight of (a) and 7 (b), of a non-volatile polyfunctional aromatic amine catalyst.

11. The container of claim 10 in which said catalyst is a mixture of meta-phenylenediamine and 4,4'-methylenedianiline.

12. The container of claim 10 in which said polyglycidyl ether has an epoxide equivalent between 175 and 210, and said epoxy ester has an epoxide equivalent between 390 and 470.

13. The container of claim 10 in which said composition contains equal parts of said polyglycidyl ether and said epoxy ester, and the amount of said catalyst is 20 percent of the total weight of the polyglycidyl ether and epoxy ester.

References Cited UNITED STATES PATENTS 2,940,986 6/ 1960 Newey 260-18 X 3,378,600 4/1968 Hodges et al 117-432 X FOREIGN PATENTS 569,227 1/ 195 9 Canada.

RALPH S. KENDALL, Primary Examiner.

U.S. Cl. X.R.

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