US1894050A - Coating composition - Google Patents

Description

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Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE FRANCIS B. MORTON, OF PAR-LIN, NEW JERSEY, ASSIGNOR TO E. I. DU PONT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELA- WARE COATING COMPOSITION No Drawing. Application filed June 27,

This invention relates to coating compositions and more particularly to a coating composition for leather, imitation leather, and the like.

A pigmented finish for leathers was developed during the recent war, due to the shortage of dyestuffs for coloring leather encountered at that time. It was composed of pigments of maximum hiding power incorporated in alkaline solutions of shellac or casein to which were added various other ingredients, such as wax emulsions, albumen, water soluble oils and glycerine. By the use of this pigmented finish a uniform color was obtained on the leather, whereas a dyed leather was not uniform in color due to the fact that some portions of the leather absorbed more dye thanothers. In addition, the pigmented finish covered stains and blemishes so that leather which was formerly suited only for blacks could be used for other colors. This pigmented finish was, however, seriously defective in that it rubbed off easily on a wet cloth since the binder was soluble in water, and in many cases the finish produced a. brittle film on the leather which easily cracked off. More recently there has been used a nitrocellulose pigmented finish for grain leather, applied by spraying, in which a mixture of nitrocellulose and suitable softeners is substituted as a binder in place of the water soluble binders used in the original type of pigmented finish. This nitrocellulose finish is objectionable in that its properties are such that it cannot be ironed out with a hot flat iron, nor can it be glazed with a glazing machine. Still more recently, these objections were overcome by the incorporation of adherent oils, such as neats-foot oil. However, although such films containing adherent oils showed a marked improvement in quality over prior art finishes in all respects, it was felt that the adhesive properties were not the maximum obtainable, since in some instances there was a tendency toward stripping from the base material.

This invention has as an object the production of a finish for leather, imitation leather, and the like which is not water soluble and which maybe ironed with a hot flat iron and 1928. Serial No. 288,808.

glazed with a glazing machine without inurious results to the finish. A further obect is the production of such a finish which will have improved qualities of adhesion. Other objects will appear hereinafter.

These objects are accomplished by the fol lowing invention which consists in adding or ganic acids to the nitrocellulose finish containing an adherent oil.

I have discovered that a finish having improved qualities of adhesion may be obtained by the addition of organic acids, such as lactic acid. The following formulae represent a preferred composition at spraying consistency and the range for the materials at which a workable finish can be obtained Color coat Range Per cent by weight Per cent lhtrocellulosav 2.5 2. 5, Neats-Ioot oil l i 5.0 1 to 8 Dibutyl phthalate 1. 5 0 to 2.5 85% lactic acid. s. 3, 1 1 to 10 Pigment or dye 5, 0 0.1 to 10 Clear top coat Range n 7 Per cent by weight Per c-mt Nitrocellulose M 2.5 2.5 Neat's-ioot oil 2. 5 1 to 8 75% lactic acid 3. 1 1 to 10 The lactic acid is a. solution of lactic acid in water and in place of lactic acid Imay use other organic acids, such as formic acid, tartaric acid, acetic acid, oxalic acid, or any other acid or substance that acts as an acid.

The range for the amount of nitrocellulose in the above compositions will depend on its viscosity and the method of application, and may be from 1 to 10. Compositions are, therefore, base on 2.5% nitrocellulose, as the ratio of the non-volatile ingredients is an important factor. The amount of pigment will depend on the type used, its oil absorption value, its hiding power and the effect which is desired. When transparency, or socalled depth of finish, is desired lakes or even dyes may be used. The pigments should preferably be inert in their action towards nitrocellulose and resistant to fading on exposure to light-f In the example given above,

dibutyl phthalate is not absolutely essential, its presence being due to the fact that the pigment may be ground on colloid rolls in the same manner as pigment is incorporated in celluloid, by grinding in a plastic of dibutyl phthalate and nitrocellulose, which method gives extremely good dispersion. The pigment may also be ground on buhr mills or roller mills in part or all of the neats-foot oil in the manner customary in the paint industry. The ratio of pigment to colloid or oil durin grinding will depend on the character of the pigment and the particular colloid or oil used, as is well known to those skilled in the art. It is not necessary that the adherent oil be the only oil present. Castor, ra eseed, linseed, or other animal or vegeta le oils may be present, so long as there is sufiicient adherent oil to counteract the effect of these oils, which used alone produce a finish which cannot be successively glazed or ironed. Also more dibutyl phthalate or other cellulose plasticizer than 1s required to make a suitable colloid may be present with the adherent oil. In such cases, the pigment Ethy,

ma' be ground on buhr mills or other mills wit part or all of such oils or plasticizers. In place of neats-foot oil, I may use other oils which, for the sake of convenience, I term adherent oils. These are specifically cod liver, sperm, lard, olive, egg and a mixture of cocoanut and paraffin oils. It is to be understood that the term adherent oils is meant to include the specific oils mentioned and is used for lack of a group classification which covers all these oils.

It is not absolutely essential to use adherent oil in all of the coats, but only in the top coat, since stickiness is due to the condition of the surface. For example, a top coat of clear or enamel containing neats-foot oil may be used over nitrocellulose colored coats of the old type. They may also be used over the water soluble type of colored coat but, due to deficient adhesion, the nitrocellulose type of colored bottom coat is to be preferred. The lactic acid may be used in coating compositions containing nitrocellulose, with or without oils or plasticizers, but those coating compositions containing an adherent oil Will be found superior. It has been found that the adhesion of the clear or pigmented finish to the leather may be improved by Washing the leather with lactic acid, or any other of the above mentioned acids, before applying the finish, in which case it is not necessary to add the acid to the finish. This method, however, does not produce as good results as when the acid is added to the finish.

The preferred nitrocellulose colored and clear coats may be made into finished mixtures by the customary methods employed in the lacquer and enamel industry. The colors are ground in a nitrocellulose plastic and the ground stock is then dissolved in suitable mixers with a thinner containing active solvents and diluents. The clear solutions are made by dissolving nitrocellulose in suitable mixers with a mixture of active solvents and diluents and adding the proper amount of ad herent oil. Clear solutions ma also be made from concentrated solutions 0 nitrocellulose by adding the proper amount of thinner and adherent oil. The following formula: represent a preferred enamel and a clear solution:

Enamel Per cent by weight *Red enamel- 95.24 85% lactic acid i 4.76

' Red enamel Nitrocellulose plastic Per cent Per cent Indian red lron oxide plg- N itroeellulose 43. inept 11.11 Dibutyl phthalate 20.2) Nitrocellulose plastic.. 8. 56 Denatured alcohol 30. 10 Neats-Ioot oilm F.

.40 MIND .16 .63 .15

Clear solution Per cent by welght *Clear solut1on 95.25 85% lactic ac1d i 4.75

' Clear solution N ltxocellulose baa Per cent Per cm! Nitrocellulose base e3. 50 Ethyl acetate 43 20 Neats-(oot oil-20 F-- 4.00 Butyl acetate.-. 10.00 Ethyl acetate 20. (X) Toluol 22 50 we (I) The above finishes may preferably be applied in two coats, one colored coat followed by a clear coat, and they should be applied by spraying as this method is found to be the most practicable one.

. While in the examples I have described nitrocellulose compositions, my invention may be utilized in compositions containing any cellulose derivative.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I claim: r

l. A coating'composition which contains nitrocellulose, neats-foot oil and lactic acid in proportions such that when applied to leather and dried the composition willform its a non-tacky, strongly adherent film which can be ironed with a hot iron and glazed in a glazing machine. 7

2. A coating composition which contains nitrocellulose, neats-foot oil, a plasticizer and lactic acid in proportions such that when applied to leather and dried the composition will form a non-tacky, strongly adherent film which can be ironed with a hot iron and glazed in a glazing machine.

8. A coating composition which contains nitrocellulose, neats-foot oil, a pigment and lactic acid in proportions such that when applied to leather and dried the composition will form a non-tacky, strongly adherent film which can be ironed with a hot iron and glazed in a glazing machine.

A. A coating composition which contains nitrocellulose, neatstoot oil, a plasticizer, a pigment and lactic acid in proportions such that when applied to leather and dried the composition will form a non-tacky, strongly adherent film which can be ironed with a hot iron and glazed in a glazing machine.

5. A coating composition which comprises a cellulose compound, an oil from the group consisting of neats-foot, cod liver, sperm, lard, olive, egg, and a mixture of cocoanut and paraflin oils, and an organic acid, said ingredients being in proportions such that when applied to leather and dried the composition Will form a non-tacky, strongly adherent film which can be ironed with a hot iron and glazed in a glazing machine.

6. A coating composition which comprises a cellulose ester, an oil from the group consisting of neats-foot, cod liver, sperm, lard, olive, egg, and a mixture of cocoanut and paraflin oils, and an organic acid, said ingredients being in proportions such that when applied to leather and dried the composition will form a non-tacky, strongly adherent film which can be ironed with a hot iron and glazed in a glazing machine.

7. A coating composition which comprises nitrocellulose, an oil from the group consisting of neats-foot, cod liver, sperm, lard, olive, egg, and a mixture of cocoanut and paraifin oils, and an organic acid, said ingredients being in proportions such that when applied to leather and dried the composition will form a non tacky, strongly adherent film which can be ironed with a hot iron and glazed in a glazing machine.

8. A coating composition which comprises nitrocellulose, an oil from the group consisting of neats-foot, cod liver, sperm, lard, olive, egg, and a mixture of cocoanut and paraflin oils, and an organic acid from the group including lactic, formic, tartaric. acetic and oxalic acids, the said ingredients being in proportions such that when applied to leather and dried the composition will form a non-tacky, strongly adherent film