US2075025A - Coating compositions and processes of preparing the same - Google Patents

Description

Patented Mar. 30, 1937 UNI ED I STATES COATING COMPOSITIONS AND PROCESSES OF PREPARING THE SAME Joseph B. Diets, Roanoke, Va., and Harry G.

Stauffer and Edmund F- Oefiinger, Philadelphia, Pa., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del.;a

of Delaware corporation No Drawing. Application July 27, 1933, Serial No. 682,460

3 Claim.

This invention relates to coating compositions and more particularly to those coating compositions specifically designed for application directly over wood to be followed by one or more coats of 5 furniture varnish or similar finishing material and even more particularly to shellac substitute. Shellac substitutes now in common use consist mainly of simple solutions of alcohol soluble fossil gums such as Pontianak and Manila. In the art 10 of varnish manufacture it is common practice to treat such acidic gums as rosin with lime in order to decrease the acidity and increase the hardness.

The treatment is usually carried out in a molten condition of the gum although liming is some- 15 times carried out in solution in a volatile solvent.

Heating is resorted to in all cases in order to facilitate the reaction and in order to take up as much as possible of the lime or other basic material which has been added. Fossil gums such as Pontianak and Manila which are not as acidic in nature or as fusible as rosin are not treated in this manner.

Shellac itself, is, at the present time, quite expensive for application directly over wood to be followed by a further coat or coats of furniture varnish or similar finishing material. The substitutes now on the market generally give a great deal of difflculty in the sanding operation which generally follows the application of shellac or 30 shellac substitute, since they do not cut smoothly and have a tendency to gum up the paper and roll up on the surface of the work itself. They are also rather slow in drying and do not become sufficiently hard to provide a proper base for sub- 35 sequent coats.

This invention has as an object the preparation of an improved coating composition.

Another object of this invention is the preparation of a coating composition specifically de- 40 signed for application directly over wood to be followed by one or more coats of finishing material similar to furniture varnish.

A further object is the preparation of an improved shellac substitute of sanding properties 45 superior to the substitutes now available and even superior to shellac itself. A still further object is the preparation of a shellac substitute drying more rapidly than the coating materials com- 0 monly used for the same purpose, cheaper than materials now commonly used and at the same time at least equal to shellac in its other properties. A still further object is the preparation of a, shellac substitute miscible if appropriate sol- 55 vents are used with the common lacquer type (Clfi l-26) sealers containing such materials as cellulose ni- I trate or acetate. I a

The above objects are accomplished by the following invention wherein alcohol soluble fossil gums, such as Pontianak and Manila, dissolved in volatile solvents, such as alcohols or mixtures thereof with other volatile solvents, are partially neutralized at comparatively low temperatures. For the successful practice of the invention it is essential that the neutralization be stopped before it is complete. Otherwise, a large amount of insoluble material is formed and the resulting solution is not stable. Satisfactory shellac substitutes cannot be prepared if the neutralization is carried too far.

The following examples serve to illustrate the manner of carrying outthe invention and the type and proportion of ingredients used.

Example 1 Parts by weight Pontianak g 250 Sodium carbonate 8 50/50 mixture of alcohol and toluol 750 v Total 1008 Example 2 Parts by weight Manila g 250 Sodium carbonate 8 50/50 mixture of alcohol and toluol 750 Total---" 1008 Example 3 Parts by weight Pontianak g 250 Magnesium carbonate 8 75/25 mixture of alcohol and toluol 750 Total 1008 Example 4 Parts by weight Manila gum 250 Magnesium carbonate 8 75/25 mixture of alcohol and toluol- 750 Total 1008 Example 5 Parts by weight Pontianak g I 250 Barium carbonate." 8 Alcohol 750 Total 08 trample Parts by weight Manila g 250 Barium carbonate 8 5 Alcohol 750 Total 1008 Example 7 Parts by weight Pontianak g 250 Sodium hydroxide 3 Alcohol 750 Total 1003 Example 8 Parts by weight Manila gum- 250 Sodium hydr 3 Alcohol 750 Total 1003 Example 9 Parts by weight Pontianak gum 250 Potassium hydroxide 4 Alcohol 700 Total 954 Example 10 Parts by weight Pontianak gum 250 Potassium carbonate 8 50/50 mixture of toluol and alcohol 750 Total 1008 Example 11 Parts by weight Pontianak gum 250 Slaked lime 3 /50 mixture of toluol and alcohol 750 45 v Total 1003 The above solutions are obtained by merely agitating together the ingredients at room temperature. The ingredients may be added in anydesired order. The coating materials made in accordance with the above examples dry more rapidly to a stage at which they can be sanded than shellac itself or its known substitutes, and their sanding properties are also superior. The film laid down is harder and more satisfactory 'for the application of subsequent coats. The compositions are also miscible with the common lacquer type cellulose if .appropriate solvents are used.

The Manila gum of the above examples had an acid number of 132 and was completely soluble in alcohol. Such Manila is called a "soft Manila as opposed to the higher melting "hard Manila of acid number about 118. The Pontianak had an acid number of 108.5; the neutralization resulted in a drop of acid number of about five points based on the gum present.

Although the above examples recite the use of such gums as Pontianak and Manila and such solvents as alcohol and toluol, other gums and 7 solvents having similar characteristics may be substituted if desired. Any copal completely soluble in ethyl alcohol may then be used. As solvents, propyl, butyl, or amyl alcohols may also be used, either alone, or mixed with esters such 5 as ethyl acetate, propyl acetate, etc or hydrocarbons such as benzol or xylol or other solvent or mixed solvent for the fossil gum.

The neutralization should be substantial, the optimum results being obtained at neutralizations such as those obtained in the above examples. The neutralization should not, however, be carried to the point where any precipitation occurs, since this aifects very adversely the properties of the resulting compositions.

Variation in the total percentage of volatile ingredients may be from to 60% of the total. The ratio of alcohol to aromatic hydrocarbons may be varied in such a way that the solvent mixture may contain from 25% alcohol to alcohol. Ethyl alcohol and a mixture of ethyl alcohol and toluol represent the preferred solvents because of the ready solubility of the fossil gums in these solvents, the freedom of these solvents from dangerous physiological effects and their relatively cheapness. The temperature to be used in the treatment is limited by the boiling point of the solvent used, but in general it is not carried much beyond 100 C. and is more advantageously carried out at temperatures approximating room temperature. Other neutralizing agents may also be used such as calcium carbonate, basic iron salts as well as basic salts of other metals, barium carbonate, barium hydroxide, and salts of alkali or alkaline earth metals which will react basic in water solution etc. The treatment may also be applied to shellac, the acid number drop being in the neighborhood of 36 points from the original acid number of shellac of 84.6. This improves the property of the shellac coating composition noticeably but not to the extent that Pontianak and Manila compositions are improved. The preferred compositions of our invention are those containing partially neutralized Pontianak and soft Manila, because of the very great improvement in properties obtained.

This invention makes possible the economical production of shellac substitutes which dry more rapidly than those known to the art and more rapidly reach the stage in drying where they can be sanded. These compositions, in addition, have improved sanding properties since they do not have any tendency to clog the paper as is the case with many shellac substitutes now available. These compositions are at least the equal of shellac for use as under-coaters, and are, at the same time, cheaper. The compositions are miscible with the common lacquer type sealers and if appropriate solvents are used become suiliciently hard on drying to provide a proper base for subsequent coats.

As many apparent and widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that we do not limit ourselves to the foregoing examples or description except as indicated in the following claims.

We claim:

1. A shellac substitute, consisting of a copal resin of the class consisting of Pontianak and soft Manila in solution in a volatile solvent mix ture comprising ethyl alcohol and toluol together with an alkaline compound of metal selected from the alkali and alkaline earth groups in the proportion of less than eight parts of the alkaline compound to 250 parts of the resin.

2. A substantially clear coating composition consisting of a resin selected from the class consisting of Pontianak, soft Manila, and shellac in solution and a neutralizing agent which has an alkaline reaction in water, said agent being present in amounts suflicient to reduce the acidity of the resin substantially but insumcient to effect precipitation of the resins.

3. A substantially clear coating composition consisting of a copal resin in solution in a solvent containing alcohol togethei; with a compound of an alkali or alkaline earth metal which has an