US2340846A - Wax emulsion - Google Patents

Description

Patented Feb. 1

WAX EMULSION Chester G. Landes, Stamford, Conn, assignor to American Cyanamid Company,

New York,

N. Y., a corporation of Maine No Drawing. Application January 18, 1941, Serial No. 375,025

4 Claims. This invention relates to improved wax com-.

positions, particularly wax emulsions useful as sizes and liquid coating compositions.

Wax emulsions prepared by emulsifying mineral wax with common tallow soaps are known and have enjoyed widespread usage in the paper and textile industries as sizes and liquid coating compositions. In some cases the wax is modified with small amounts of montan wax or other partially saponiflable wax. I have now discovered that these emulsions may be greatly improved in several respects while retaining those excellent properties that have led to their pres ent wide use. Not only is the sizing efliciency of these wax emulsions improved when prepared in accordance with my invention but also their stability to mechanical agitation. acidity, and hard water is increased, their foaming tendencies reduced, and most important, their corrosive effect on metallic shipping containers is eliminated.

Wax emulsions prepared with soaps of palmitic, oleic, stearic and other fatty acids containing 16 or more carbon atoms have been found to react with metallic shipping containers, of both iron and galvanized iron, in a very marked and distinctive manner. This action on the container produces at least two undesirable results: First, the wax size-emulsion corrodes the metallic container with resultant contamination of the wax emulsion by products of the corrosive action and secondly, there is formed on the walls of the container hard growths which sometimes extend into the size emulsion a distance of an inch or more. These hard particles may become dislodged and become mixed with the size which necessitates straining of the emulsion before use. Even with this precaution size spots are too frequently found in the finished paper.

I have now discovered that the action on the metallic shipping container can beentirely eliminated and the wax size also improved in stability, foaming characteristics and sizing efficiency if the emulsion is prepared with fatty acid soaps in which the fatty acids contain not more than 14 carbon atoms. I have also discovered that my wax sizes may be further improved in color, sizing efficiency and stability by the use of candelilla wax in place of the crude montan wax sometimes employed in conventional wax sizes.

I prefer to prepare my wax size by melting together a mineral wax, such as crude scale wax, candelilla wax and a fatty acid of 14 carbon atoms or less and pour these into hot water (about 180 F.) having dissolved therein sumcient caustic potash to saponify all the fatty acid and part of the candelilla wax. The hot mixture is agitated for a short time in a high speed mixer and then passed through a pressure homogenizer at about 165 F. to obtain a stable than 14 carbon atoms.

- candelilla wax with parailin, it is possible to rewax emulsion containing 40-60% total solids. It will be understood, of course, that other conventional methods of preparing wax emulsions may be utilized to prepare my new wax size compositions.

The greater part of the fatty acids employed must contain not more than 14 carbon atoms if the full advantages of my invention are to be obtained. I prefer to use lauric acid because of the commercial availability of this material. Myristic acid has been employed and it also enables me to obtain the advantages heretofore mentioned over the use of fatty acids containing 16 or more carbon atoms. Although myristic acid differs from palmitic acid by 2 carbon atoms the difference in the effect of wax emulsions prepared with these two materials on shipping drums is very pronounced. Just why the emulsions prepared with lower fatty acids are less corrosive is not known and is very surprising in View of the fact that the lower'fatty acids are considered to be of greater acidity and should therefore be more corrosive to metals. I have also prepared satisfactory wa'x emulsions with the aid of soaps prepared from caprylic and capric acids and these emulsions did not react with iron or galvanized containers to form insoluble lumps or nodules. In most cases it will be found cheapest and most convenient to use one of the readily available commercial fatty acid products consisting of a mixture of fatty acids most of which contain les A commercial coconut oil fatty acid, for example, contains roughly 15% caprylic and capric acids, 45% lauric acid, 20% myristic acid, 15% palmitic acid and 5% of'other higher fatty acids. A it has been found that fatty acids of more than 14 carbon atoms may be used in amounts up to about 50% of'the total fatty acids required in my wax emulsions without encountering serious corrosion difliculties, the

commercial fatty acid mixtures such as described above are very useful and are meant to be included within the scope of my invention.

The amount of fatty acids used depends on several factors. When the wax component is entirely a mineral wax it may be necessary to use as much as 20% of fatty acid soap base on the weight of the wax in order to obtain a stable emulsion. By using increasing amounts of a saponifiable or partially saponifiable wax such as duce the fatty acid soap content of my size composition to around 2% of the total wax content. The alkali will also vary; enough ordinarily is used to saponify all of the fatty acid, and when a saponifiable wax is used enough should be employed to partially saponify it. Instead of canstic potash I may use soda ash, caustic soda, ammonia, triethanolamine, morpholine and other bases which form water-soluble soaps with fatty acids.

nstead of candelilla wax, which is my preferred mineral wax adjunct since its use enables me to obtain a. superior size, other partially or completely saponiflable waxes such as carnauba, bleached or crude montan and Japan wax may be substituted in whol or in part. In some instances it is possible to use paraifin wax with put modification by saponiflable waxes. Howev'er'theaise o1 some saponifiable wax is preferred,

preferably up to about 40% of the total wax content, since such a wax improves the stability of the emulsion, enables me to useless fatty acid. soaps in its preparation, and improves the sizing characteristics of the wax emulsion.

In order to illustrate my improved wax size an emulsion containing 40% total solids was prepared by melting together 29.17% by weight of crude scale wax, 7.0% candelilla wax and 2.9% of a 50-50 mixture of laur'ic and stearic acids. 60 parts of water containing .93 part by weight of KOH were heated to 185 F. and the molten wax-acid mixture added thereto with vigorous agitation. The mixture was allowed to cool to 165 F. and then forced through a pressure homogenizer whereby a light colored creamy wax.

emulsion of th oil-in-watertype was obtained. Although wax emulsions prepared with stearic acid are more corrosive to containers than those prepared with oleic acid the substitution of one halfor more of the stearic acid by a fatty acid of 14 carbon'atoms or less almost entirely eliminates corrosion difilculties. I

For comparative purposes, another wax mulsion was prepared in the same way except that an equivalent amount of crude montan wax was used instead of candelilla wax and all of the fatty acid used was oleic.- This last composition represents a commercially available wax size which has been regarded in the trade as giving fairly satisfactory sizing results.

These two wax size emulsions were tested in an actual mill trial in which a boar liner stock consisting of 75% white paper cuttings and 25% unbleached sulflte pulp were beater sized. The heater furnish consisted of 1100 pounds of the above mentioned stock, 18 pounds (dry weight) wax size emulsion, pounds dry rosin size and 50 pounds alum. Two runs were made, one with the conventionally prepared oleic acid-containing wax size emulsion and one with my new improved lauric acid-containing wax size emulsion. Actual tests which represent the average results obtained on a number of samples are given in the following table:

Table Surface water Lactic acid absorption Wax Wax size conpenetration Cobb test, ahsnr tion spots minimz- (Penescope) gin/sq. crn., dm per seconds water at ft F. minu cs Olcio acid s ap. 78 7.76 9.3 4.7 Laurie acid scorn I20 7.. 20.0 3.0

The distinct superiority of my new wax size over a similar size prepared with fatty acids of 16 or more carbon atoms was also demonstrated in like manner in a mill run in which wax size was used in the beater and also as a surface size on the calenders at a 20% solids content. Hand sheets sized with l rosin and l/;;% wax emulsion also showed better water and ink resistance and slower lactic acid penetration when using my ize prepared with lauric acid in comparison with hand sheets sized with oleic acid prepared wax sizes.

Further tests also demonstrated the superiority of my improved wax sizes. Awax size emulsion prepared entirely from wax and lauric acid soap was compared with a simila wax emulsion prepared entirely from wax and oleic acid soap. Both emulsions when diluted to a 5% solids concentration foamed when shaken in a bottle. However, the size prepared with oleic acid still had some foam over the liquid after standing for a period of several minutes but th foam collapsed almost immediately over the size dispersion prepared with lauric acid. It was also found that the oleic acid prepared wax emulsion attacked a heavily galvanized can in a period of about 24 hours whereas after a period of several months there was no visible evidence of attack by the lauric acid prepared wax size. The lauric acid prepared size also had greater mechanical and hard water stability and a uniformly smaller particle size.

My improved wax size emulsions may be used with rosin sizes, starch, casein, resins, pigments and the like. They may be used in the paper industry as a beater, tub, or calender size with various types of furnishe in the production of glassine, book, hanging and wrapping papers, carton and container board and other-stocks. In the textile, leather and other industries my improved wax emulsions also find utility in the same manner and for the same uses in which other wax sizes and finishing agents have been used.

What I claim is:

1. A stable emulsified wax size composition non-corrosive to galvanized containers comprising a major proportion of a mineral wax, a minor proportion of a partially saponifiable wax, 2 to 20% by weight based on the total wax content of the size comprising a water-soluble fatty acid soap th major proportion of which is a s p of a saturated fatty acid of from 8 to 14 carbon atoms and water.

2. A stable emulsified wax size composition noncorrosive to galvanized containers containing 40 to 60% total solids by weight comprising a major proportion of a mineral wax, a minor proportion of candelilla wax, 2 to 20% by weight based on the total wax content of the size comprising a water-soluble fatty acid soap the major proportion of which is a soap of a saturated fatty acid of from 8 to 14 carbon atoms and water.

3. A stable emulsified wax size composition noncorrosive to galvanized containers containing 40 to 60% total solids by weight comprising a major proportion of a mineral wax, a minor proportion of a partially saponifiabl wax, 2 to 20% by weight based on the total wax content of an emulsifying agent consisting essentially of a water-soluble fatty acid soap of cocoanut oil fatty acids, and water.

4. A stable emulsified wax size composition noncorrosive to galvanized containers containing 40 to 60% total solids byweight comprising a major proportion of crude scale wax, a minor proportion of candelilla wax, 2 to 2.0% by weight based on the total wax content of a water-soluble soap of saturated fatty acids of which the soap of lauric acid predominates and water.

CHESTER G. LANDES.