Coating composition for glass containers

Abstract: A coating composition for glass containers containing medium chain fatty acid triglyceride, medium chain fatty acid triglyceride and/or long chain unsaturated triglyceride and squalane, or (a) at least one selected from medium chain fatty acid triglyceride, long chain unsaturated triglyceride and liquid paraffin and (b) fatty acid isopropyl as essential ingredient(s).

Description: The present invention relates to a scratch masking composition for glass containers, which is coated onto the outer surface upon recycling class containers for beer, juice or mineral water, to enhance the appearance as well as masking scratches, to a scratch masking emulsion, and to a method of masking scratches on glass containers The glass containers for beer, juice, mineral water, etc. are repeatedly used by a collection system. When repeatedly using these bottles, scratches can generate on the outer surface due to mutual rubbing of bottles in the filling and distribution process to injure the appearance and to decrease the commercial value of bottled beverages. Upon recycling, therefore, it is necessary to coat a coating agent onto the portion of scratches, thus masking the scratches inconspicuous and enhancing the appearance at the same time. The portions of bottles violently generating the scratches are approximately fixed; for example, in the case of common beer bottles in Japan, the generation of scratches are violent at the positions of 1 to 2 cm, 5 to 7 cm and 13 to 15 cm from the bottom. For this reason and other various conditions, partial coating such as two or three-stripe coating, wherein the coating liquor is applied only onto the portions of violent scratches, is generally carried out. However, the scratches sometimes generate at positions other than those fixed positions, thus improvement in the working process is required for beautifully finishing even such portions. In order to cope with such problems, some coating compositions for the scratches of glass containers have so far been proposed. For example, in Japanese Unexamined Patent Publication No. Sho 57-179053, a composition using dimethylpolysiloxane together with aminomethylpolysiloxane is disclosed. Also, in Japanese Unexamined Patent Publication No. Sho 59-145259, a composition having liquid paraffin as a major ingredient and using small amounts of higher alcohol fatty acid ester and polyhydric alcohol fatty acid ester in combination is disclosed. Furthermore, in Japanese Unexamined Patent Publication No. Sho 62-128951, a composition containing acetylated glycerine fatty acid ester as an essential ingredient has also been disclosed. While these are favorable compositions for said partial coating processes, they are unsuitable in several points when considering overall coating process by the shower or spray method of coating liquor or with sponge aiming at the improvement in the partial coating process and the beautiful finishing of overall bottle surface. If considering the coating liquor for overall coating, such matters that it dries rapidly, that it does not allow slippage where handled, that it does not adversely affect the label (exudation and easy stripping off) and that it allows good transportability (no rubbing in the printed area of label) are desired in addition to the performance desirable for the coating liquor by the conventional system (masking property, appearance, non-tackiness, water resistance and washing property). JP-A-59 105 094 relates to lubricants for deep-drawing in the manufacture of metal containers for beverages and specifically describes the deep-drawing of a vinyl-coated Al sheet after application of tricaprylin. JP-A-54 137 020 discloses a protective coating to prevent cracking in glass bottles during filling, transportation or selling. the protective coating is prepared by dissolving a non-ionic surfactant such as sorbitan monooleate, monoglyceride or polyglyceride in an organic solvent. JP-A-47 030 760 relates to a staining composition containing fatty acid, triglyceride and a hydrocarbon. DE-A-1 792 455 discloses the use of fatty acid ethyl and/or isopropyl ester as additive for cosmetic and pharmaceutical preparations and cleaning agents. It has been the problem underlying the present invention to provide a scratch masking composition for glass containers yielding a good masking property, appearance, non-tackiness, water resistance and washing property, which further dries rapidly, does not allow slippage where handled, does not adversely affect the label and allows good transportability. As a result of diligent investigations for obtaining a scratch masking composition for glass containers having solved said problems, the inventors have reached the invention. Accordingly, the present invention provides a scratch masking composition for glass containers comprising (a) at least one triglyceride selected from the group consisting of medium chain C 8 -C 12 fatty acid triglycerides and long chain unsaturated fatty acid triglycerides, and (b) a fatty acid isopropyl ester, wherein said components (a) and (b) are present in the ratio (by weight) of (a)/(b) from 20/80 to 90/10. The medium chain fatty acid triglyceride (hereinafter abbreviated as MCT) to be used in the invention can be obtained by completely esterifying three hydroxyl groups of glycerine with 3 moles of medium chain fatty acid. The medium chain fatty acid includes saturated fatty acids with 8 to 12 carbon atoms, concretely caprylic acid, capric acid and lauric acid. These fatty acids can be used solely or as mixtures. The long chain unsaturated triglyceride to be used in the invention includes triglycerides comprising solely or mixed long chain unsaturated fatty acids, i.e, palmitoleic acid, oleic acid, elaidic acid, linolic acid and linolenic acid, or mixtures of these unsaturated fatty acids partially mixed with long chain saturated fatty acids (such as palmitic acid or stearic acid). As concrete examples, soybean oil, rape seed oil and olive oil may be mentioned, but the invention is not confined to these. The fatty-acid isopropyl ester to be used in the invention is a fatty acid ester of isopropyl alcohol obtainable by reacting fatty acids derived from natural oils and fats, e.g. lauric acid, myristic acid, palmitic acid or oleic acid, with isopropyl alcohol. In the invention, the formulation ratio of ingredient (a) to ingredient (b) is also important. If the formulation ratio of (a)/(b) is within a range of 0/100 to 20/80, some of the masking properties, appearance, water resistance and transportability would be insufficient in the coating performance required and, if the formulation ratio of (a)/(b) is within a range of 90/10 to 100/0, non-tackiness, washing properties, drying properties and slip-down properties would be insufficient. Hence, in order to satisfy all of these performance, it is necessary for the formulation ratio of (a)/(b) to be within a range of 20/80 to 90/10. The composition of the invention is used by emulsifying the ingredients of the composition into water. As the surfactant to be used as emulsified into water, the use of at least two kinds selected from nonionic surfactants including sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, glycerine fatty acid ester, polyoxyethylene glycerine fatty acid ester, polyglycerine fatty acid ester, sucrose fatty acid ester, polyoxyethylene nonylphenyl ether, or polyoxyethylene alkyl ether, is desirable, but the invention is not confined to these. The composition of the invention may contain, besides the essential ingredients, a small amount of, for example, dimethylsilicone oil and liquid paraffin, which are commonly used ingredients of coating agents for bottles. Example (1) Coating method Coating compositions as shown in Table 1 were converted to 12 % emulsion with a homogenizer. Into each of these solutions, a beer bottle with scratches after washing (dipping into 2 % aqueous solution of NaOH for 10 minutes at 70 °C, then washing and drying) was momentarily dipped at room temperature and thereafter it was dried for 24 hours at 35 °C in a ventilated environment. (2) Evaluation method 1) Masking property of scratched portions Comparative judgment was made using Comparative Articles 1 through 9 in Table 1 as references. 2) Appearance of unscratched smooth surface The coated state of clean smooth surface without scratches was observed. 3) Extensibility What state the coating agent stayed in on the smooth glass surface was evaluated. 4) Tackiness and slip property The tackiness and slip property when in the coated state were evaluated by touching with a tip of a finger. 5) Water resistance After dipping a coated bottle into water for 24 hours at room temperature, it was taken out to evaluate the remaining state of coating agent. 6) Washing property A coated bottle was treated for 10 minutes at 70 °C with 2 % aqueous solution of NaOH to observe the degree of washout of coating agent of the coated bottle. 7) Transportability Coated bottles after labeling were placed in a plastic container, and subjected to the vibration test according to JIS Z0232 where the transportability (degree of rubbing of labels) has observed. (3) Expression of evaluation o ○ Superior ○ Excellent, ▵ Poor, X Very poor (Effect of the invention] The comparative evaluation on the results of coating compositions of the Inventive Articles 1 through 11 and the Comparative Articles 1 through 9 is shown in Table 2. As shown in this table, the Comparative Articles 1 through 9 had ▵ to X for four items or more among nine items of coating performance. Whereas, the Inventive Articles 1 through 11 exhibited the results above the level for all of nine items showing the progressiveness.

Claims: A scratch masking composition for glass containers comprising (a) at least one triglyceride selected from the group consisting of medium chain C 8 -C 12 fatty acid triglycerides and long chain unsaturated fatty acid triglycerides, and (b) a fatty acid isopropyl ester, wherein said components (a) and (b) are present in the ratio (by weight) of (a)/(b) from 20/80 to 90/10. A scratch masking emulsion comprising the scratch masking composition in accordance with claim 1 and a surfactant. A method for masking scratches on glass containers comprising emulsifying a scratch masking composition in accordance with claim 1 to provide a scratch masking emulsion: and coating said glass container with said scratch masking emulsion.

Inventors: ISONAGA TERUTO, KAMIRYO EIJI, SHIBATA MASATOSHI, SHINOHARA KIYOSHI, ISONAGA, TERUTO, KAMIRYO, EIJI, SHIBATA, MASATOSHI, SHINOHARA, KIYOSHI, SHINOHARA, KIYOSHI, HIGASHIKORI DORMITORY OF
Applicants: KIRIN BREWERY, RIKEN VITAMIN CO, KIRIN BREWERY COMPANY LTD., RIKEN VITAMIN CO., LTD.
Application year: 1991
Main classification: C03C17
IPC codes: C03C17