US2921829A - Wood stains and method of preparing - Google Patents

Description

United States Patent WOOD STAINS AND NIETHOD OF PREPARING Leo J. Noyak, Dayton, Ohio, assignor to Commonwealth Engineering Company of Ohio, Dayton, Ohio No Drawing. Application June 25, 1956 Serial No. 593,384

3 Claims. (31. 8-6.5)

This invention relates to staining compositions and more particularly to a composition for staining wood, paper and the like cellulose containing substances and to a method of producing the same.

Briefly, the invention provides a brown colored stain as prepared from diazonium salts such as benzenediazonium chloride. The staining composition comprises an alkaline degradation product made from diazotized aniline or the like amine, the resultant brown colored substance which is extracted with a petroleum is fast to light and has been found to be especially useful for staining wood surfaces.

It is an object of the invention to provide a staining solution comprising the degradation products of benzenediazonium salts as the coloring or staining agent. Useful staining compositions are provided which are non-grain raising and fast to light by dissolving or dispersing suitable quantities of the brown colored, diazotate as extracted in organic solvents such as toluol, xylol, solvent naphtha and low carbon chain aliphatic alcohols such as methanol, ethanol, etc., or suitable mixtures of these organic solvents, the petroleum solvents being preferred because of their higher solvent power.

The wood stains of the prior art may be looked upon as of three types, first, the water type, second, the oil type, and third the spirit type. The water stains generally consist of aqueous solutions of aniline dyes, which are applied in any desired manner, as by brushing to the wood surface to be stained. The dye in such water stains is in a form that is non-bleeding and non-fading, but these Water stains have certain objectionable characteristics. For example, such water stains have the very highly undesirable effect of raising the grain. The surface must then be sanded, but because of the grain-raising efiect of the water stain, a thin shellac coating must be applied to the stained wood in order to stiffen the fibers in order that they may be uniformly sanded. When an open grained wood is used, it is necessary after the sanding operation to apply a filler to the surface over which the varnish or lacquer is applied. The grain-raising efiect of the water stains seriously militates against their effectiveness. Furthermore the water stains have indifferent penetration, the dye remaining substantially on the top surface of the wood instead of impregnating the fibers.

The oil stains have the desirable property of penetrating into the wood surface, but they are open to several material objections. Owing to the preliminary treatment given the dyes to render them available in the oil stain compositions, the resultant product is not light fast, and it is also subject to the so-called bleeding effect. Furthermore any excess of fatty acid present in such compositions affects the practicability and the durability of the surface finish, producing such effects as retarded drying and as checking.

The spirit stains, which utilize aniline dye bases so treated as to be soluble in alcohol, are not used very extensively because they are also subject to a number of undesirable qualities, such as lack of penetration into the ice wood surface, and lack of permanency of color and fading qualities similar to those of the oil-type stains. The spirit stains are also subject to the bleeding effect, and in many instances also give rise to grain raising.

Among the objects and advantages of the present invention is the production of wood stains which shall have the property of penetrating the wood surface to which they are applied without producing any substantial grain raising, and which at the same time will not exhibit the fading and bleeding properties of the prior art stains.

Other objects and advantages will appear from the more detailed description set forth below, it being understood however that this more detailed description is given by way of illustration only, and not by way of limitation.

The invention will be more fully understood by the following specific examples:

Example I Aniline is diazotized with sodium nitrite and hydrochloric acid while retained at a temperature of about 5 C. using an ice bath. The aniline is dissolved in water containing approximately three equivalents of hydrochloric acid. While the solution is held at a temperature of 0 to 5 C., an aqueous solution of sodium nitrite is added in small portions until the solution, as shown by starch-iodine indicator comprises excess nitrous acid and forming a benzenediazonium chloride solution.

The resultant benzenediazonium solution cooled to about 10-20" C. is poured into a strong sodium hydroxide solution (aqueous solution containing 10-30% by weight sodium hydroxide), the alkali being present in excess of that required to form the sodium salt to decompose the benzenediazonium chloride to form the desired product. The solution is thenacidified with hydrochloric acid and the brown product is extracted with toluene to provide a staining composition. Preferably the product formed by acidification is neutralized or at least partially so, the pH being in the range of about 4 to 6.5 prior to extracting. This may be done by carefully introducing the hydrochloric acid so that excess acid is avoided.

The brown colored product or dye, although not definitely known chemically, appears to be sodium isodiazotate with a minor proportionate amount (5-20% by weight) of benzenenitrosoamine. In general the greater the acidity the more benzenenitrosoamine present. A 20-30% solution of the brown colored sodium' isodiazotate in petroleum solvent makes a suitable staining composition.

Example 11 Ten grams of aniline and twenty grams of concentrated hydrochloric acid (40% HCl) are dissolved in grams of distilled or tap water. The solution is thereafter cooled to O5 C. and there is added slowly with stirring a solution of 10 grams sodium nitrite in 30 cc. of water, at a temperature of 0 to 5 C. The temperature should not be allowed to rise above about 10 C. The resulting solution of benzenediazonium chloride is then poured slowly with stirring into approximately cc. of an aqueous solution of sodium hydroxide (30% NaOH). The resultant alkaline solution is then acidified with strong hydrochloric acid until the solution has a pH of about 6.0 and the solution is allowed to come to room temperature.

The brown colored product is then extracted with toluene to produce the brown colored staining product.

A concentration containing approximately 30% of the brown colored extract in the petroleum solvent produces a satisfactory stain for wood. Where a more concentrated stain is desired, the brown colored oily extract may be increased to the desired proportionate amount in the solvent.

- 3 Example Ill A dark oily stain product is produced similarly as in Example II utilizing methyl aniline as the amine in producing the diazotized alkaline me'tal brown colored extract. The stain when applied as a 50% concentration on wood produced a dark brown stain having good light fastn'essri r -In preparing the diazotiz ed color product in accordance with the invention, other alkaline solutions may be utilized such as potassium hydroxide and/ or mixtures of alkaline metal hydroxides. Further, other amines such as the heterocyclic amines may be used to produce different shade colored products for use as a stain.

The alkaline degradation products as are produced form diazotized aromatic color products which are immiscible with water but are readily soluble in petroleum solvents such as benzene, xylene, etc., as well as mixtures of the same with lower aliphatic alcohols as aforementioned. The stain provides aproduct which is especially useful for staining wood and a dye which is fast to light. This is shown from tests made wherein wood surfaces stained with the product of this invention are subjected to prolonged exposure under ultra-violet light for a period of 72 hours or longer. 7 In the above examples other organic solvents having a petroleum base or mixture thereof with aliphatic alcohols may be us'ed'as the solvent for application of the stain.

It will be understood that while there have been given herein certain specific examples of how the stain can be produced and utilized in the practice of this invention, it is not intended thereby to limit the invention thereto or to the specific materials, proportions or conditions set forth inasmuch as those skilled in the art will readily appreciate that such details may be varied and substitution made in the practice of the invention. The same is accordingly understood to come within the scope and spirit of this invention and as more particularly set forth in the appended claims.

What is claimed is:

l. A process for producing a wood stain which com prises the steps of diazotizing'aniline with sodium nitrite and hydrochloric acid and neutralizingthe resultant benzenediazonium solution with sodium hydroxide, acidifying the resultant product, and extracting the brown coloring constituent with toluene to provide a staining composition comprising a. mixture of sodium isodiazotate and benzenenitrosoamine, said solution having a pH of between about 4.0 and 6.5.

2. A process for producing a wood staining composition comprising providing a diazotized amine solution, alkalizing said solution with alkali metal hydroxide to produce vthe alkali metal salt of benzenediazonium 'chloride, acidifying the resultant alkaline solution of benzeneisodiazotate and recovering the brown colored constituent therefrom, said brown colored constituent comprising a mixture of alkali metal isodiazotate and benzenenitrosoamine, and dispersing said constituent in an organic solvent vehicle.

3. A brown colored dye solution useful as a wood staining composition consisting of a mixture of alkali metal isodiazotate and benzenenitrosoarnine dissolved in toluol, said benzenenitrosoamine comprising from 5 to 20% by weight of the mixture.

References Cited in thefile of this patent UNITED STATES PATENTS

Claims (1)

1. A PROCESS FOR PRODUCING A WOOD STAIN WHICH COMPRISES THE STEPS OF DIAZOTIZING ANILINE WITH SODIUM NITRITE AND HYDROCHLORIC ACID AND NEUTRALIZING THE RESULTANT BENZENEDIAZONIUM SOLUTION WITH SODIUM HYDROXIDE, ACIDIFYING THE RESULTANT PRODUCT, AND EXTRACTING THE BROWN COLORING CONSTITUENT WITH TOLUENE TO PROVIDE A STAINING COMPOSITION COMPRISING A MIXTURE OF SODIUM ISODIZOTATE AND BENZENENITROSOAMINE, SAID SOLUTION HAVING A PH OF BETWEEN ABOUT 4.0 AND 6.5.