US2363658A - Finishing system - Google Patents

Description

Patented Nov. 28, 1944 UNITED STATES PATENT "OFFICE FINISHING SYSTEM Gerard Quick Decker, 3rd, Yeadon, Pa., assignor to E. I. du Pont de Nemours & Company. Wilmington, DeL, a corporation of Delaware No Drawing. Application March 27,1942, a

Serial No. 436,454

7 Claims.. (Cl. 117-57) casionally possible, in cases in which woodsof very dense structure are finished to obtain a relatively blister-free and fairly smooth film as a decorative and protective coating. The present general practice in finishing wooden articles with baking coating compositions is to kiln dry the article and later applying the finishing coniposition at room temperature. This treatment, however, does-not overcome the difliculty of producing a, satisfactory smooth finish of the desired appearance. The use of force dried or baking enamel compositions is desirable in the wood finishing industry for economic reasons and further because such compositions produce coatings of improved appearance and increased service life.

With the present and prospective shortage and so difficulty of obtaining metal for the manufacture of various commercial articles, it becomes increasingly necessary to we wood in place thereof. There follows then the desirability of obtaining means for producing decorative and protective coatings on the wooden surfaces which will be equal to or compare favorably with finishes produced by similar compositions used on metal surfaces.

The principal object of this invention is therefore the provision, of means for obtainingaon wooden surfaces smooth decorative and protective finishes by the use 'of force dried or baking enamel coating compositions.

Another object is the provision ofsuch means for producing satisfactorily smooth decorative and protective coatings on fibrous base material,

such as those prepared from pressed wood fibres, wallboard, etc.

Still another object is the provision of a finishing system for wood and similar fibrous material which is simple, practical and economical.

Other objects will be apparent as the description of the invention proceeds.

These objects are accomplished by the use of a finishing'system which includes (a) heating the article to be finished at a temperature equal to or above that at which the subsequent coating composition is to be baked, (b) applying the coating'composition while the article at substantially the same temperature at which it is heated, i. e., before it has appreciably cooled, and baking the article to which the coating composition has been applied. Subsequent coatings may be thereafter applied without the preheating step.

The invention will be more fully understood by the following examples which are given by way of illustration and not limitation except in- 10 sofar as defined in the appended claims. The

parts are by weight. I

i Example I A panel of birch wood which had been previously filled by conventional means well known in the wood finishing art was heated in a hot.

air oven, the temperature of which was maintained at approximately 280 F. for about 45 minutes. The panel was removed from the oven 0 and the filled surface immediately sprayed with a synthetic resin pigmented primercomposition, the temperature of the panel remaining at approximately 270" F. -The primer composition was composed of the following ingredients and prepared by means well known in the art of preparing such compositions.

Primer composition Parts Barium base titanium dioxide pigment 45.0 Urea formaldehyde monohydric alcohol resin l 4.0 45% soya bean oil modified glyceryl phthalate 19.0

Butyl alcohol 2.0

moi-seamen solvent 30.0

The primed birch panel was then baked for 40 approximately one hour at 270 F. after which it was removed from the. baking oven, allowed to cool and subjected to a light sanding treatment on the primed surface. To the primed and sanded surface was then applied by means of sprayin a pigmented enamel and the composition bakedfor one hour at approximately 260 F. The composition of the pigmented enamel was as, follows:

Pigmented enamel Titanium dioxide pigment- 30.0 Melamine-formaldehyde-butanol resin 7.0 Urea-formaldehyde butanol resin 11.0 43% Dehydrated castor oil modified glyceryl phthalate 14.0 Butyl alcohol 18.0 Aromatic hydrocarbon solvent 20.0

The finished panel possessed a smooth, blisterfree. hi h luster and hard surfaced finish which Parts would be considered highly acceptable in the or other composition was applied as above, pos-.

sessed a roughened surface due to the blister formation during the baking operation. Such a finish would not be acceptable in the wood finishing industry particularly where finishes similar to those obtained on metal surfaces are desired.

' The preliminary filling operation may be omittedif desired and its use will be determined largely by the type and character of the wood being finished. Under certain conditions the primer enamel coating may be dispensed with and the finishing enamel applied directly'to the pre-heated wood while still at a temperature approximately equal to or above that at which the enamel is to be baked. Primer coatings are,

' however, preferred where particularly good adhesion of the finish to the wood is desired or necessary and where optimum appearance and filling are desired. Such modifications will be readily apparent to those skilled in the art of applying finishing compositions and are well within the purview of the present invention.

Further the primer composition and the final enamel may be applied in a heated condition if desired. After the application of the primer or other composition to the preheated hot wood and the composition is baked, subsequent applications of finishing com-positions may be made without repeating the preheating operation. The

finish may be applied in a single coat or in a plurality of coatings. EXAMPLE II The sprayed panel was baked at approximately 225 F. for about 45 minutes, after which it'was removed from the baking oven, allowed to cool to approximately room temperature and then subjected to a sanding treatment.

The cooled, primed and sanded surface was then coated by spraying with a pigmented enamel composition of the following formula:

Enamel composition F. for about one hour. The resulting finish was continuous, smooth and free from blisters, and possessed a high luster. It was hard and tough and excellently adhered to the wood surface.

A similar poplar panel finished according to unsatisfactory product. The finish on this panel.

was blistered and rough and possessed in general an unacceptable appearance.

The examples show the application of the finishing system of the present invention tobirch wood as representative of a hard, dense type wood and to poplar wood representing the softer, less dense type wood. These two types of wood are the most commonly used in industries where finishing with a decorative and protective composition is desirable or necessary. Other commonly used woods are maple, clear white pine, gumwood, etc. The present invention is applicable alike to the hard, dense types as well as to the softer and more porous types of wood. The time and temperature of heating before the application of the coating composition which'is later to be baked will be governed by the particular type of wood to be coated and the temperature at which the coating composition is to be baked. The selection of the proper conditions will be readily apparent to those skilled in the art. Temperatures ranging between 160 F. and 325 F. have been found to be satisfactory for the most types of wood and decorative and protective coating compositions commonly used.

. The use of temperatures appreciably above 325 Raw castor oil 2.0 1 Butyl alcohol 7.0 Hydrocarbon solvent 25.0

F. is not practical and most baking type decorative and protective coating compositions are formulated to be baked at not lower than 150 F. It is important that the entire mass of-the wooden article to be coated reaches the temperature to which it is subjected in the pre-heating treatment and that it is not permitted to cool appreciably below the temperature at which the subsequently applied coating composition is to be baked before the coating composition is applied. The time of preheating will also'fbe governed to some extent by the size, thickness, previous treatment, etc., of the wooden article. For example, it has been found that a panel V inch present invention. In addition to those noted in Parts Titanium dioxide pigment-.. 29.0 Urea-formaldehyde-butanol resin 14.0 43% dehydrated castor oil modified glyceryl phthalate 20.0 Butyl alcohol 11.0 Hydrocarbon solvent ...L 26.0

the examples may be mentioned baking enamels of drying and semi-drying oil modified alkyd resins; urea-formaldehyde-monohydric alcohol resins; phenol and substituted phenol-formaldehyde resins; amino triazine and substituted amino triazine-formaldehyde resins; oleoresinous vehicles containing drying oils as China-wood, linseed,'etc.; oils with natural or synthetic resins; and mixtures thereof are some which are suitable. Particularly useful are the so-designated high temperature bake compositions, the ,use of which heretofore as a wood finish has been materially restricted or not practically feasible be- 2,868,858 cause of the unsatisfactory results produced.

While it is usually desirable to use the coating compositions pigmented, they may in certain applications be usedunpigmented. In such instances it is usually desirable or necessary to use a filler on the wood before the preheating treatment and subsequent application of the finpresent surfaces materially improved for easy sanding but there may be a slight sacrifice in toughness of coating.

The finishing compomtions may be applied by any of the well known conventional means as by spraying, dipping, brushing, roller coating, etc.,

the particular means chosen being governed by the article to be finished, available equipment, economic considerations, etc.

The present invention is useful in the finishing of various articles of wood in common use which require hard, tough and smooth finishes having decorative as well as protective properties. Among such articles may be mentioned kitchen cabinets and general utility cabinets, wood fur niture, toys, bowling pins, bar and counter fixtures, ofiice furniture, wood refrigerator cabinets, etc. Many other applications will be apparent to those skilled in the art of decorative and protective coating compositions. The invention is particularly useful where so-called high bake enamels are desired or necessary to be used.

The principal advantage of the present invention is the provision of means for producing on wooden surfaces hard, tough and smooth decorative and protective finishes. A further advantage is-that force driedor baking enamels. particularly high bake enamels may be used for finishing wood surfaces resulting-in smooth finishes free from blisters and other surface imperfections commonly met with in the usual wood finishing systems. Another advantage is the provision of a finishing system for fibrous woody materials as compressed wood fibre panels, wall board, etc. A still further advantage is the provision of a finishing system for wood in which baking compositions may be used to produce uniformly satisfactory results and which is simple,

practical, and economical. The advantages oifered by the present invention are of particular significance and importance under present conditions of the scarcity of metal usually used in the fabrication of many commercial articles. This scarcity has necessitated extensive replacement of metal by wood which has presented new and difficult finishing problems since the usual metal finishing systems are not ordinarily applicable to the finishing of wood.

It is apparent that many widely diiferent embodiments of this invention may be made without departing from the spirit and scope thereof, and

therefore, it is not intended to be limited except as indicated in the appended claims.

I claim: I

1. The process of coating wood surfaces which comprises heating the said surface to a temperature between about 150 F. and 325 F., appiying thereto while hot an enamel composition. containing a. film-forming agent dispersed in a solvent, said film-forming agent being one which dries to a tough durable fihn without decomposition at temperatures between 150 F. and 325 F., and maintaining the said temperature while the coated surface is exposed until the enamel is substantially dry.

2. The process of claim 1 in which the coating composition contains urea-formaldehyde resin. 1 a

3. The process of claim 1 in which the coating composition contains an oil modified alkyd resin.

4. The process of claim 1 in which the coating composition contains a drying oil vehicle.

5. The process of claim 1 in which the coated surface is heated to about 225 F. for about one hour after the composition has been applied.

.6. In the process of finishing wood surfaces which have been primed and are subsequently coated with a liquid baking type enamel, the improvement which comprises heating the said wood. surface to about 150 F. to 325 F. before and while the enamel is applied, and thereafter maintaining all baking temperature While the coated surface is exposed until the enamel is substantially dry, said enamel containing a filmforming agent which dries to a tough durable film without decomposition at temperatures between 150 F. and 325 F.

7. The process of finishing wood surfaces which comprises heating the said surface to a temperature of approximately 280 F. until thoroughly heated, applying a primer composition theretoat about 280 F. which has approximately the following composition:

Soya bean oil modified glyceryl phthalate-- 10.0 Solvent 32.0

allowing the coated surface to cool, sanding the primed surface, heating the surface to about 260 F. and while at such temperature applying an enamel having substantially the following composition:

Parts Pigment 30.0 Melamine-formaldehyde-butanol resin 7.0 Urea-formaldehyde-butanol resin 11.0 Dehydrated castor oil modified glyceryl 'phthalate 14.0 Solvent 30.0

and maintaining the said temperature, until free from solvents.

CERTIFICATE OF CORRECTION.

Novenber 28, 19 411..

GERARD QUICK DECKER, 3RD. I

It is hereby certified that error appears in the printed specification of the above numbered p'atent requiring correction as follows: Page 5, secand (301m, line k2, claim 7, for "about 2 0 F. read -about 270 F.--

land that the said Letters Patent should be read with this correction there-' in the t the same inay conform to the record of the case in the Pstent Office.

Sigaed and sealed this 201m day of February, A. D. 191

Leslie Frazer (Sea1) Acting Commissioner of Patents.