US2087094A - Metallic finish - Google Patents

Description

Patented July 13, 1937 METALLIC FINISH John Dorman'McBurney, Newburgh, N. 'Y., and

Edgar Hugo Nollau, Wilmington, Del, assignors to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application March 21, 1936, Serial No. 70,106

8 Claims.

This invention relates to metallic surface coated articles having highly lustrous finishes, and especiallyto the production of such coatings by means of metallic powders.

This case is a, continuation in part of our 00- pending cases Serial Nos. 661,418 and 705,618 filed March 17, 1933 and January 9, 1934, respectively.

Heretofore lustrous metallic surfaced articles have been produced by adhering to or combining with a base material one of'the various metal foils which has been highly polished or otherwise suitably surfaced. By the term metal foil is meant a continuous sheet of metal having an approximate thickness from 0.0001 to 0.05 of an inch, but the thickness may be varied in special circumstances and thicker or thinner sheets may be included in the class. generally as metallic covered articles, as metallic covered papers or metallic'covered fabrics and the like, and they are used for various-purposes.

It is among the objects of the invention to provide articles with a finish of high metallic luster. Another object of the invention is to provide methods whereby metallic powders may be used to produce highly lustrous or mirror-like metallic finishes. L

Other objects of the invention will be apparent in connection-with the following description.

The objects of the invention are attained generally by applying leaf-like particles of reflective 'metal to the surface to be treated, suitably causing them to adhere thereto; and applying orienting and lustre-producing operations whereby the particles are brought into position and condition to give a lustrous mirror-like surface appearance. The particles of metal powder may desirably have highly reflective surfaces. The invention is illustrated by the following embodiments.

Example I To a suitable paper base, for example, such a paper as that having the trade name Gloscote, is applied one coat of an anchoring composition consisting of 43.8% of a China-w'ood-linseed oil modified polyhydric alcohol-'polybasic acid resin, 53.5% of thinner consisting of a mixture of mineral thinner and high flash naphtha, and a quantity of cobalt and manganese drier (introduced a as linoleate) which corresponds to 0.1% metalhe cobalt and 0.1 ;.v metallic manganese based on These articles are known the drying oil content of the resin. The detailed formulation of this composition is as follows:

Solids 43.88 {13.74 9.87

Thinner 53.13

Drier Soi- 1.93%

Following the application of this composition by means of a doctor knife whereby 0.4-2.0 ounces per square yard are deposited, the coated material is passed through a '72 foot drying chamber heated by steam coils so that a temperature of 15 -200 F. is realized, forced draft being employed during the operation to remove the solvent vapors. The rate of coating is five yards per minute. After leaving the drying chamber, the coated surface is brought into contact with alu- 20 minum powder and the excess powder is then removed by mechanical bufling equipment composed of a series of oppositely revolving brushes.

Following a second brushing treatment in a simi- 25 lar bufling equipment, the material is baked by fe'stooning in a chamber at a temperature of approximately F. for a period of two hours and is then ready for use. The finished product is a sheet resembling a metal foil surface of high luster which can be embossed or printed.

No limitation is placed on the specific method of drying the material. In this and other examples, instead of festooning the material, it may be passed over a series 01' heating coils or drums. 35 Very good results have been obtained by passing the coated material over two'heated drums having diameters of 5 and 7 feet, respectively. The two Example II To a suitable rigid base, for example, sheet 50 steel, is appliedone coat of the following anchoring composition: 1

mineral thinner Manganese linoleate solution Drier 801. 2.99%

in mineral thinner Following the application of this composition by means of a doctor knife, or other suitable means, whereby 0.4 to 2.0 ouncesper square yard is deposited, the coated material is passed at a speed of 15 feet per minute through a '72 foot drying chamber heated to 180-200 F. Forced draft is employed during the operation to remove the solvent vapors. After leaving the drying chamber, the coated surface; while still very slightly tacky, "is brought into contact with aluminum powder and the excess powder is removed by mechanical bufling equipment, One particularly suitable type is composed of a series of oppositely revolving brushes. Following the second brushing, the material is treated as indicated in Example I. The finished product is a sheet of high luster resembling a metal foil surface. It may be embossed or printed.

In the foregoing examples the coatings of anchoring composition are cured until the surfaces are just tacky enough to retain an adherent thin layer of the metallic powder. Although some of the powder is ever so slightly embedded in the coating, the layer of powder is so thin and the cure of the coating is such that substantially all the particles constitute an adherent or surface layer so that when further brushing operations are performed the particles are arranged flatwise which may or may not be in overlapping relation on the surface of the coating. The degree of cure or tack of the coating must admit of the subsequent brushing and luster-producing operations. It very nearly approximates or may beidentical with that which is known as dust free as defined by H. A. Gardner on Page 110 of Physical and Chemical Examination of Paints, Lacquers and Varnishes (1927). This publication describes the condition of dust free as that at which the finger can be drawn lightly over the surface of the coating without the same feeling sticky.

In brushing the powder meiit is applied, the

first set of brushes assists in sweep n of! the excess of powder and adherently fixing or slightly embedding"the'particles on the surface as referrerito above but other means of removing the execs of powder may be used. The second or acids, and 27.2 parts by weight of phthalic anhydride' to a temperatureof 200-225 C. in a vessel fitted with a reflux condenser, stirringdevice, and temperature recording'instmmentpuntil the acid number of the resulting product-ls less than 10. Other proportions of oil maybe used as for example by heating 17.0 parts by weight of glycerol, 28.0 parts by weight of China-wood oil acids, and 27.0 parts by weight of phthalic anhydride to a temperature of 200225 C. until the acid number of the product is under 50, at which point 10 to 20 parts of a solvent for the resulting resin is added to cool the hot reaction mixture and thus reduce the reaction rate. The solvent added may be toluene,-xylene, ethyl acetate, butyl acetate, gasoline, or the like.

Although sheet steel and paper are recited in the foregoing examples as the base materials,

many other flexible as well as semi-flexible and rigid base materials can be used, such as cardboard, wood, Prestwood, "Celotex", leather, regenerated cellulose, cellulose derivative articles such as those prepared from the nitrate, acetate, propionate and other esters, as well as ethyl and benzyl cellulose and other ethers. A coated fabric in which a cellulose nitrate composition is used to coat the fabric may also receive the high luster metallic surface by means of the process of this invention. It is desirable that the base to receive the high luster metallic surface should be smooth.

Other adhesives or anchoring compositions than those mentioned in the examples can be used such as mixtures of rosin modified phenolformaldehyde resin and oil modified polyhydrlcalcohol-polybasic acid resin, or varnishes of the linseed or China-wood oil type may be used. Cellulose nitrate adhesives may also be used: one containing about 4 parts by weight of cellulose nitrate to one part by weight of a softener, such as di-butyl phthalate, dispersed in suitable media, such as methyl, ethyl, butyl or amyl acetate, methyl or ethyl alcohol, with or without the addition of aromatic or straight chain hydrocarbons is particularly useful. Such compositions are well known to those versed in the coating art and are merely mentioned as examples and not by way of restriction.

The adhesive composition is applied by any suitable coating means, such as a doctor knife, roll coating, or spraying, and may be used either as prepared, or thinned with a thinner such as high flash naphtha, petroleumspirits mixture, or the like. vary between 0.4 and 2.0 ounces per square yard, 0.9 ounces per square yard being preferred.

The described partial drying or curing of the adhesive base may desirably be done by passing through a heating chamber at temperatures between and 280 F. The particular type of base material will determine the temperature of the drying chamber, to wit, surfaces which contain oils which exude cannot be dried at the temperature of exudation.

In place of the aluminum powder disclosed in the above example, copper bronze, silver bronze, tin bronze, gold bronze, or any other metal or metallic alloy, in fact, any metal which is capable of being prepared in finely divided flakes or leaflike form may be used. -While this invention is well adapted to produce highly reflective surfaces, easily tarnished metals may be used for special artistic effects.

The powder may be applied by means of any suitable dusting equipment, after which the material is subjected to a frictioning or 'burnishing action, as by brushing the surface with brush rolls revolving in opposite directions. This operation is one of the most important in the The amount of resin applied may process of this invention in that it must suitably orient the metallic particles to give the high luster. I

The baking following the brushing operation, or series of brushing operations, is preferably carried out as indicatedin the examples; Higher or lower temperatures with suitable shorter or longer periods of time may, however, be used.

The finished product, a metallic surface of extremely high luster, is entirely satisfactory for most purposes, but where desired it may be given a final treatment with any suitable clear or transparent coating composition.

The product of the present invention may be used for many purposes now satisfied by the use of metal foils.- For example, it may be used for producing high luster metallic finishes on rigid, semi-rigid and flexible surfaces, thus avoiding the necessity of attaching sheets or foils of metal to the base materials. Materials having the high luster metallic finish are particularly useful for decorative purposes, but they are also useful as surface, finishes which-are more resistant to weathering than the unfinished base material. On light-transmitting base materials such as glass, regenerated cellulose, and cellulose esters and ethers, the finish presents a mirror when viewed by reflected light while the material is still semi-transparent to direct light. On wood and plaster casts the finish may be appliedchiefiy for decorative purposes but it will i also act as a protective covering. Highly orna- I hereinbefore.

mental effects may be obtained by using colored bronzes, for example, aluminum bronze colored with various organic dyestuffs.

Similarly, the invention may be embodied in ornamental papers, book jackets, wrapping ma-- terials such as cigarette and food wrappers, moving picture screens, outdoor signs and the like,

As applied to materials which are to be flexed or subjected to distortion, the finish is especially durable as for example against damage by flexing or by stretching the base material.

One form of ornamental material may be made by superimposing ornamental figures or designs on the base material, or in case the material has been precoated, by superimposing the design on the coating. The ornamental shapes or figures may be made by printing, stamping, painting or the like, using the coating or anchoring materials heretofore indicated. The superimposed design of anchoring material is cured to the dust free condition, the metal powder is applied and the'article is finished in the manner described Inasmuch as the metal powder adheres to the superimposed design or anchoring material, only that part, of the base material which is covered bythe anchoring material will be given the mirror-like finish by this operation.

However, it will be apparent that the base material may be an uncoated material or a coated material, the necessary requirement being that the powder shall be non-adherent to the base material or less adherent to the base material than to the superimposed design of anchoring material.' In this manner a variety of ornamental eifects can be produced by the suggested variations in design by the use of different types of base materials so that more or less or none of the powder will adhere to the base material and by varying the kind and color of the powder.

The product of the present invention combines the advantages of the high luster of a metallic surface with the flexibility and other advantageous properties of a flexible backing such as a paper or fabric. Aluminum powder has been applied to paper and other flexible and nonfiexible materials as a component of a coating composition. The resulting metallic surface produced by such compositions does 'not have a high luster and appears under high magnification to be made up of thin, leaflike particles standing on edge and otherwise heterogeneously disposed without orientation in any definite direction or fiatwise in overlapping relation so as to provide the described mirror surface. The structure and the appearance of the prior art coatings are highly suggestive of an etched metallic surface in contrast to the highly polished or lustrous metallic surface of smooth character and-mirror-like appearance characteristic of the present invention. The combination of metal foil to flexible or semi-rigid base materials, while affording a high luster, is deficient in that the finished product cannot be repeatedly folded without breaking the metal and it is not com- ,bined so intimately with flexible base material as to have the same strength as the base material.

Furthermore, such combined products are rather stiff which limits their uses for many purposes. In the materials produced in accordance with the present invention the metal surface is extremely thin and tough, and it becomes to a great extent an integral part of the base to which it is applied so that it has substantially the same strength as the base material. It is not readily removed by scratching, distorting, or cracking as is the case of metal foil facings. A waterproof surface essentially impermeable to gases, grease, and the like is produced by this highly lustrous oriented metallicffinish. The product further shows advantages over paper and other materials backed with metal foil in that the surface produced in accordance with the invention lends itself much more satisfactorily to printing and embossingadvantages obviously of considerable importance in a decorative as well as in a utilitarian material. Thus in various physical characteristics the products of the present invention have distinctive desired characteristics of practical value not possessed by coatings composed of foil or powder mixtures of the prior art.

As many apparently widely difierent embodi-' ments of this invention may be made without departing from the spirit and scope thereof,'it is to be understood that the invention'is not limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

l. The method of producing a high metallic luster on rigid surfaces, which comprises applying on said surface an anchoring composition containing about 43.8% China-wood oil-linseed oil modified polyhydric alcohol-polybasic acid resin, about 53.5% thinner, and about 3% drier containing .l% of cobalt and .l% manganese in the form of linoleate, passing the coated material through a drying chamber heated to -215 F. at a rate such that the composition will be cured therein for about 4.8 minutes, removing solvent vapors during the curing, applying a liberal dusting of aluminum powder while the surface is still slightly tacky,'sweeping off the excess powder, buifing the coated surface until a mirror-like finish is produced, baking at approximately 226 F. for approximately-45 seconds to harden the anchoring composition and coating the surface with a clear protective coat.

2. The method of making a mirror-like metallic surface on an article which comprises applying a coating of adhesive to the article, curing the adhesive until it is in a dust free" condition such as that which can be produced as described herein by depositing on sheet steel 0.4 to 2.0 ounces per square yard of a composition containing 43.8% of China-wood-linseed oil modifled polyhydric alcohol-polybasic acidresin,53.5% of a mixture of mineral thinner and high flash naphtha and the remainder drier solution, and passing the sheet through approximately a 72 foot drying chamber heated to 180 to 280 F. at a rate of about feet per minute, distributing over the dust free coating a metal pow- 15 der the individual particles of which have light reflecting faces, removing non-adherent particles, and brushingly orienting the adhering particles to bring the light reflecting faces into the plane of the surface of the coating to form a metallic finish of mirror-like reflectivity.

3. The method of making a mirror-like metallic surface on an article which comprises applying a coating of adhesive to the article, curing the adhesive until it is in a dust free" condition such as that which can be produced as described herein by depositing on sheet steel 0.4 to 2.0 ounces per square yard of a composition containing 43.8% of China-wood-linseed oil modifled polyhydric alcohol-polybasic acid resin, 53.5 of a mixture of mineral thinner and high flash naphtha and the remainder drier solution,'and passing the sheet through a 72 foot drying chamber heated to 180 to 280 F. at a rate of about 15 feet per minute, distributing over the coating of dust free hardness metal 'powder the individual particles of which have light reflecting faces, removing non-adherent particles, brushingly orienting the adhering particles to bring the light reflecting faces into the plane of the sur- 40 face of the coating to form a metallic finish of mirror-like reflectivity, and then heating to harden the coating.

4. The method of making a mirror-like surface on an article which comprises coating the article with a coating composition containing as a film-forming ingredient material selected from the class consisting of phenol-formaldehyde resins, polyhydric alcohol-polybasic acid resins,

and cellulose nitrate, curing the coating until a "dust free condition is reached which is just tacky enough to retain a firmly adherent thin layer of metallic powder, distributing over the tacky coating leaf-like metallic powder the individual particles of which have light reflecting faces to procure adherence of a thin layer of the particles over the surface, removing the nonadherent powder, and brushingly orienting the adhering particles until the reflecting faces thereof are brought substantially into the plane of the surface of the coating and a surface of mirror-like reflectivity is produced.

5. The method in accordance with claim 4, in which the article is coated with a composition comprising an oil modified polyhydric alcoholpolybasic acid resin.

6. The method in accordance with claim4, in which the metal powder comprises aluminum.

7. 'I'he method of making an article having a highly polished metallic surface which comprises applying a coating composition comprising an oil modified polyhydric alcohol-polybasic acid synthetic resin on a flexible cellulosic base material of the class which consists of cellulose and cellulose derivatives, hardening the coating until the dust-free stage is reached which is just tacky enough to retain a firmly adherent thin layer of metallic powder, applying over the coating a dusting of metal powder, the individual particles of said powder having light reflecting faces, removing non-adherent particles, orienting in/ overlapping relation on the surface of the coating the particles adhering to said surface to bring the light reflecting faces into a continuous plane parallel to the surface of the coating, and finally hardening the coating, and applying a clear surface coat thereover. 1

8. The product of claim 4 in which the highly reflective mirror-like finish comprises a hardened coating composition to which the leaf-like metallic particles are firmly bonded, said flm'sh being highly resistant to abrasion and cracking.

JOHN DORMAN MCBURNEY. EDGAR HUGO NOLLAU.