COMPOSITION TO INHIBIERUNG FROM SHATTER CRACKS IN PLASTIC ARTICLES AND PROCEDURES TO THEIR APPLICATION

In United States patents 5,073,280, 5,009,801 and 4,929,375, there is disclosed both bottle washing and lubricant compounds which can, inter alia, inhibit the stress crack formation ordinarily encountered when exposing a poly (alkylene) terephthalate article, such as a beverage bottle, to an alkaline environment. This phenomenon is well known and has been widely documented.

The development of this technology is predicated on the fact that "fatty acid" lubricants in the alkaline pH range are highly desirable in a bottling operation because of their ability to not only clean the conveyors, because of the soap generated by the interaction between a caustic neutralizing compound and the fatty acid, but because of their ability to neutralize any excess acidity encountered during spillage of a soda pop or the like. However, it is these fatty acid lubricants which contribute to the stress cracking because of their alkalinity. To minimize this, the art taught neutralization of the fatty acid lubricants. However, neutralization, i.e. pH 7.0 diminishes the lubricating capabilities as well as the cleaning capabilities of these compounds. Thus, in the prior copending application solutions were sought to find a fatty acid lubricant which could inhibit the stress cracking phenomenon while still being a good lubricant and cleaner. This, initially, and in accordance with the teachings of U.S. Patent No. 4,929,375, it was believed that by admixing a hydrophilic-substituted aromatic hydrocarbon having either an alkyl or aryl side chain, such as sodium xylene sulfonate or the like with an alkyl amine saponifying agent that there could be provided to the art a fatty acid lubricant which was highly dilutable and, therefore, highly efficacious in the lubrication of the poly (alkylene) terephthalate articles, and which was believed to inhibit stress crack formation even at a pH 7.

Then, as the technology evolved and as disclosed in the '801 patent, it was found that stress crack inhibition of PET articles actually did occur with fatty acid lubricants at pH greater than 7. Specifically, it was found that the hydrophilic substituted aromatic hydrocarbon was acting as a stress crack inhibitor in the lubricant concentrate.

Subsequently, and as disclosed and taught in the '280 patent, it was found that, at use levels, the amine was the primary stress crack inhibitor, but which stress cracking inhibition capabilities were enhanced and buttressed by the aromatic hydrocarbon.

However, in order to be highly efficacious as a stress crack inhibiting lubricant, the dilution ratios of the concentrate could not be achieved in the manner comparable to that disclosed in the '375 patent. Thus, to date, the art has witnessed the development of a fatty acid lubricant which exhibits both excellent lubricating properties, cleaning properties and, concomitantly, inhibits stress crack formation in PET articles in an alkaline environment. Moreover, at least in a bottling operation, it is highly desirable that a lubricant be efficacious in lubricating the tracks upon which the various types of containers translate i.e. cans, glass and PET articles. The fatty acid lubricants disclosed in the above-referred to patents are efficacious in conjunction with any of these types of containers. Thus, the lubricants disclosed in the above-referred to patents are "universal" lubricants in their application to various beverage containers and their ability to inhibit the stress cracking ordinarily encountered with PET articles. However, and as noted, the dilutability of these lubricants, as the stress cracking properties has been enhanced, has diminished. Thus, it would be highly desirable to provide a "universal" fatty acid-based lubricant which could approach the dilution levels disclosed in the '375 patent.

Moreover, because of the cost of raw materials, the art has looked to alternatives for fatty acid lubricants, i.e. synthetic diamine lubricants, such as disclosed in PCT International Publication Nos. WO 92/130580, U.S. Patent No. 5,062,978, and various other prior art.

These lubricants provide adequate lubricity and cleaning and are much lower in production cost. However, the ability to inhibit or minimize the stress cracking capabilities of PET articles in a alkaline environment and their corrosivity renders these lubricants suspect. For example, in Weber, United States patent 5,062,978, the amines are neutralized by the addition of acids which form pH neutral salts with amines to provide an acidic or in essence pH neutral lubricant. In practising the teachings of Weber, it is necessary that the pH be in the range of 5 to 8.

Thus, while providing high dilution capabilities, it would also be desirable to provide a synthetic diamine lubricant which is stress crack inhibiting, while being still applicable to other types of beverage containers.

It is to these purposes to which the present invention is directed.

The present invention provides an aqueous cationic diamine-based lubricant composition having a pH greater than 8 comprising a synthetic diamine lubricant, a water-soluble amine as a hydrotrope agent for said diamine lubricant where the diamine lubricant is unneutralized.

For a more complete understanding of the present invention references made to the following detailed description and accompanying examples.

In accordance with the invention, a cationic diamine-based lubricant at a pH greater than 8, generally comprises:

1. (a) a diamine lubricant,
2. (b) a water-soluble amine hydrotrope, and (c) water.

The lubricant is prepared from a lubricant concentrate comprising, by weight:

1. (a) from 0.5 to 15 percent of the diamine,
2. (b) from 1 to 45 percent of the hydrotrope, and
3. (c) from 40 to 95 percent of water.

Preferably, the concentrate comprises:

1. (a) from 2 to 10 percent of the diamine.
2. (b) from 5 to 20 percent of the hydrotrope, and
3. (c) from 60 to 90 percent of water.

The lubricant is prepared by diluting the concentrate with water in a volumetric ratio of concentrate to water ranging from 1/200 to 1/2000 and, preferably, from 1/500 to 1/1000.

Heretofore, and as shown in the prior art, synthetic diamine lubricants have been neutralized with a weak acid, such as acetic acid or the like. Herein, no such neutralization occurs. Rather, the unneutralized diamine, which is alkaline, is hydrotroped into aqueous solution using the water soluble amine. It is noteworthy that, traditionally, the synthetic diamine lubricants are oil soluble. Therefore, the use of the water-soluble amine enables the formation of an water-soluble lubricant having a pH greater than 8 therefrom.

Any water-soluble amine which can hydrotrope the diamine can be used herein. Among the useful amines are monoamines, diamines, triamines, tetraamines, pentaamines and the like. These amines may be substituted or unsubstituted. Preferably, ethoxylated amines are employed.

Representative of the useful amines are those water-soluble amines enumerated hereinabove.

Preferably, the hydrotrope or solubilizing agent is an oxyalkylated amine solubilizing agent selected form the group consisting of oxyalkylated N-alkylamines and oxyalkylated N-alkyl-alkylenediamines.

The oxyalkylated amine solubilizing agent is selected from the group consisting of oxyalkylated N-alkylamines, and oxyalkylated N-alkyl-alkylene diamines. Examples of oxyalkylated N-alkylamines are the oxyalkylated fatty amines such as oxyalkylated N-cocoamine, N-stearylamine, N-palmitylamine, and the like. The N-alkyl group should have from 8 to 24 carbon atoms, preferably 12-20 carbon atoms, and more preferably, 15-18 carbon Atoms. This group may be unsaturated, having from 1-4 sites of unsaturation, preferably 1-2 sites of unsaturation. Such amines correspond to the formula: R - NHC where R is a C₁₈ - C₂₄ alkyl or alkenyl group.

The polyolalkylene ether portion of the oxyalkylated N-alkylamine is preferably derived completely from ethylene oxide, and is thus a polyoxethylated N-alkylamine. However, block and heteric polyoxyethylene/polyoxypropylene copolymeric N-alkylamines are also suitable, particularly, hose block copolymers having an internal polyoxyethylene block capped with a polyoxypropylene block. Use of other alkylene oxides such as butylene oxide, amylene oxide, and the higher alkylene oxides such as the Vikolox® alkylene oxides having from 8-18 carbon atoms in the alkylene residue are also suitable. If alkylene oxides with a C₈ or greater alkylene residue are used, then not more than about 4 moles of said alkylene oxide, preferably 2 moles should be used, as a cap. Preferably, the oxyalkylation is performed with substantially all ethylene oxide. From 6 to about 40 moles, preferably from 10 to about 30 moles, and most preferably, from 12 to about 16 moles of ethylene oxide should be used.

The N-alkyl-alkylenediamines correspond to the formulae:

These are oxyalkylated preferably in the same manner as the oxyalkylated alkylamines, i.e. under suitable oxyalkylation conditions known to the skilled artisan. R₁ is preferably a C₈-C₂₀ linear or branched alkyl group, optionally containing unsaturation, more preferably a C₁₂-C₁₈ alkyl, and most preferably C₁₅-C₁₈ alkyl. R₂ is an alkylene residue containing from 2 to 6 carbon atoms, preferably 3-6 carbon atoms, for example 1,3-propylene, 1,4-butylene, 1,5-pentylene, or 1,6-hexylene (1,6-hexamethylene). Most preferably, R₂ is trimethylene, R₁ is C₁₃-C₁₅, and the oxyalkylation is all ethylene oxide derived. A suitable oxyalkylated N-alkyl alkylenediamine is Synprolam® 35 3NxlO, available from Imperial Chemical Inc. (ICI).

The oil-soluble synthetic diamines used herein as the lubricant are diprimary amines having an alkylene residue which may be straight chain or branched, containing from 12 to 24 carbon atoms, preferably 15-20 carbon atoms, and most preferably 16-18 carbon atoms. Preferably, the alkylene group further contains unsaturation. Examples of suitable diamines are oleyidiamine, linoleyldiamine, stearyldiamine, 2-ethyldodecane diamine, and the like. Such diamines are available from several commercial sources, oleyldiamine, for example, as Adogen® 572 from Sherex Chemical. Mixtures of diamines may be used.

Within the practice of the present invention the water soluble hydrotrope is, preferably, selected from the group consisting of tallow (ethoxylated) amine, cocoa (ethoxylated) amine and mixtures thereof.

The lubricant solutions, which are advantageously supplied in the form of concentrates which are subsequently diluted for use, also may contain additional ingredients such as corrosion inhibitors, bacteriocides, fungicides, mildewcides and other antimicrobial agents, such as quaternary ammonium compounds and the like. Likewise, the composition may contain sludge preventing compounds, to obviate the sludge encountered in breweries on glass and cans.

The lubricant concentrate may also contain a hardness sequestrant or chelant, for the purpose of sequestering Mg⁺ and Ca⁺ ions present in the water. The sequestrant may comprise either an organic or inorganic sequestrant. Useful organic sequestrants are alkali metal salts of ethylene diamine tetracidic acid (EDTA), gluconic acid, phosphonic acid, nitrilotriacetic acid (NTA) and the like, as well as mixtures thereof. Examples of inorganic sequestrants are the phosphate hardness sequestrants, such as sodium tripolyphosphate. Although any of the enumerated sequestrants may be effectively integrated herein, preferably, the alkali metal salt of EDTA is employed. Na EDTA sold under the trademark Versene R and available from Dow Chemical Corporation is utilized herein. Where used, and as noted, the hardness sequestrant is present in an amount of between 2 and 15 parts by weight based on total concentrate weight.

In preparing the synthetic amine lube, the components are mixed together at ambient temperatures.

The pH of the lubricant is equal to or greater than 8 so that it can be considered as an alkaline lube.

It has been observed that the synthetic diamine lube exhibits enhanced lubricity, and depending upon the choice of water soluble amine can inhibit stress cracking in PET articles at high dilution. Because of the alkaline nature of the lubricant it is effective in neutralizing acidic spillages such as soda pop and the like. Also, these amine lubes exhibit reduced corrosivity.

For a more complete understanding of the present invention, references made to the following non-limiting examples. In the examples, which are to be construed as illustrative, rather than limitative, of the present invention, all parts are by weight absent indications to the contrary.

This example illustrates the preparation of a synthetic diamine lubricant in accordance with the present invention.

Into a suitable container equipped with stirring means and at ambient temperatures were mixed the following:

Concomitantly, the utilization of the water soluble amines and, in particular, the ethoxylated amines, enables the production of synthetic diamine lubricants which can be used on various containers and articles with a lessening of corrosivity, excellent lubricity and cleaning.