US1780844A - Applying nitrocellulose varnishes - Google Patents

Description

o sures and blistering and are likely to come off or they present other physical disadvan-' Patented Nov. 4, 1930 UNITED STA TEs PATENT OFFIC APPLYING NITROCELLULOSE VARNISHES No Drawing. Application filed November 30, 1926, Serial 'No. 151,827, and in Germany December 4, 1 925.;

This invention has reference to improvements in varnish coatings of nitrocellulose and the like, and it is intended to devise means of producing a better adhesion of the 6 nitrocellulose coating to the article to be treated than it was possible to obtain by the means heretofore suggested. The invention has also for its object to generally improve,

the process of manufacture of such varnishes and varnish coats, as well as the quality of such products. Other objects and advantages will appear from the specification and claims.-

For the purpose of coating articles with varnishes or lacquers, such as for instance in the case of the coating of automobiles and other vehicles and the like, oil varnishes have been employed almost exclusively until recently. The long duration of the drying required for such varnishes was, however, a serious drawback which has become particularly annoying with the introduction of the so-called series-method of manufacture of automobiles and the like, so that it became necessary to devise means of substituting a suitable, but more rapidly drying product for the oil varnishes heretofore employed. Asa partial substitute for oil varnishes it has been suggested to make use of cellulose-ester varnishes. While these varnishes and lacquers dry very quickly, there is the inconvene ience that such varnishes fail to possess sufiicient body, inasmuch as the celluloseestercan only be dissolved in the solvents employed at very low concentrations. Such thin varnishes or lacquers will accordingly requiremore successive coats, which will to a large extent compensate the advantage of more rapid dryin thereof. Besides, such varnishes are lia le to showfistageous features, and there is the additional difficulty that such methods are rather expensive by the great amounts of valuable solvents required.

The nitro-cellulose-varnishes and lacquers have become important, since it has become possible to manufacture nitro-cellulose yielding comparatively thinly liquid solutions by means of which varnishes or lacquers with about 20 to 40 percent solids can be obtained that can be applied in jets or by sprinkling. To this class of varnishes belongs for instance the Du-Pont-Errtee-Duco-Finish. These Duco-varnishes show the drawback, however, that they do not adhere directly to sheet metal surfaces, so that it becomes necessary to provide for grounding the surfaces twice with oil paint. This previous grounding of I the surface requires at least two days, particularly in cases where stopping or filling is necessary; and there is also the inconvenience that these Duco-varnishes produce a dull surface, which is objectionable in manycases.

, Now this invention'is adapted to overcome all these drawbacks and disadvantages resulting in the application of coats of nitrocellulose-varnishes. It has been ascertained in the course of my experiments that the intermediate layer intended to secure such coats of celluloid-like nature to the underlying surface, instead of consisting of. a grounding of oil-paint or varnish, may comprise a suitably compounded solution of nitro-cellulose; and by this means a very quick completion of the entire coating process with the simultaneous reliable fixing of the coat to the surface of wood, sheet metal or the like is made possible. In accordance with this invention it has been found advantageous to employ intermediate layers of nitro-cellulose possessing a solubility which is different from the other coats. These difi'erent solubilities do not refer to the slight variations of solubility exhibited by the ordinary collodion-cotton with a content of nitrogen from, say 10.5% to 12.5%, but the invention refers particularly to the different solubilities of the kinds of nitrot-cellulose containing more than 12.6% of nitrogen, the so-called gun-cottons, the solubility of which in etheralcohol is less than that of the ordinary collodion-cotton. A grounding coat composed of this kind of nitro-cellulose-solutions will so as not to produce any dissolving action upon the fastening intermediate layer. This varnish or lacquer obtained from the kinds of "nitro-cellulose above specified having morethan 12.6% of nitrogen may be compounded in the usual manner with softening agents, coloring pigments, natural and artificial resins-and varnishes. This grounding varnish may moreover be employed as a ploy modifications of nitro-cellulose with different solubilities and varying contents of nitrogen with advantage, by which means the durability of the entire coating of varnish is greatly increased. Hence, the entire method of the application of varnishesin accordance with this invention therefore comprises for instance the applying of a'suitable solution of gun-cotton nitrocellulose as the ground, then the application of the coating varnish of any desirable adjustable hardness, and the application of the gloss-varnish by sprinkling orby jets; Each of these three varnish layers containing easily volatile solvents dries very rapidly, about one to two hours drying being generally suificient for every varnishing and painting operation at 25 Centigrade up to the rubbing and burnishing of the coatings.

.A numerical example may explain still more clearly the method of theinvention. To an iron sheet there is applied by means of t a brush or otherwise a primary grounding layer by using a lacquer of the following composition:

10% low-viscous nitrocellulose of 12.8% N., 5% rosin-ester, 8% butylphtalate, 20% butyl-acetate, 17% propyI-acetate, 15%

ethyl-acetate, 15% propanol, 10% pigment."

-After the drying of this grounding coat a second layer. of varnish is applied which may becom'posed of the following constituents:

13% low-viscous nitrocellulose of 12% N.,

7% butylphtalate, 10% butanol, 35% methand, 25% toluol, 4% castor oil, 6% pigment,

It should, of course, be understood that the n vention is susceptible ofmodifications, and that no limitations on the invention are intent and a lower ether-alcohol solubility than the nitrocelluloses used in the subsequent coating solutions.

. 2. In a method of applying coatings of nitrocellulose varnishes upon bases with the aid of a primary binding layer, the applying as primary binding layer, of a nitrocellulose solution comprising a nitrocellulose having a substantially higher nitrogen content and a lower ether-alcohol solubility than 5 the. nitrocelluloses used in the subsequent coating solutions, and the employing for these subsequent coatings, of nitrocelluloses which differ considerably amongst them selves in respect of solubility and nitrogen content.

3. In a method of applying coatings of nitrocellulose varnishes to surfaces with the a1d of a primary binding layer, the employment as primary binding layer, of a guncotton-nitrocellu-lose having a nitrogen content above 12.6% and incomplete ether-alcohol solubility, and the employment for the further coatings, of nitrocelluloses differing considerably amongst themselves in respect of solubility and nitrogen content.

4. In a method of applying coats of nitrocellulose varnishes to surfaces of work with the aid of a primary bindinglayer, the using for the primary binding layer, of a nitrocellulose having a nitrogen content above 12.6%, and for the following layers, of nitrocelluloses having another nitrogen content than the nitrocellulose of the primary coatin In a method for producing superimposed layers of nitrocellulose varnishes differing from one another in content of nitrogen and degree of ether-alcohol solubility using as nitrocellulose of the grounding layer a nitrocellulose of a substantially higher nitrogen content and a lower ether-alcohol solubility than the nitrocelluloses of the subsequent coatings.

- 6. In a method for producing superimposed layers of nitrocellulose varnishes, constituting the grounding layer by a nitrocel-' .lulose having a nitrogen content above 12.6%

and an incomplete ether-alcohol solubility,

whilst the other layers have another nitrogen content than the nitrocellulose of the groundlayer.

In testimony whereof I afiix my signature.

HANS F. SOHULZ.

tended other than those imposed by the scope