US2076159A

US2076159A - Art of making leatherboard

Info

Publication number: US2076159A
Application number: US13669A
Authority: US
Inventors: Herman W Richter
Original assignee: GEORGE O JENKINS Co
Current assignee: GEORGE O JENKINS Co
Priority date: 1935-03-29
Filing date: 1935-03-29
Publication date: 1937-04-06
Anticipated expiration: 1954-04-06

Description

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beaten UUHI PATENT QFFECE ART OF MAKING LEATHERBOARD Herman W. Richter, Bridgewater, Mass, assignor to George 0. Jenkins Company, Bridgewater, Mass, a corporation of Massachusetts No Drawing. Application March 29, 1935, Serial No. 13,669

9 Claims.

This invention relates to the art of making light colored leatherboard. In certain of its aspects the invention is in the nature of an improvement on the invention disclosed in Patent No. 1,975,556 issued to me on October 2, 1934.

As explained in my prior patent, leatherboard, which is often termed heeling board, is a material made from a furnish composed principally of leather scrap or waste (sole leather cuttings,

skivings, etc.) by board making processes, which involve disintegration in a beating engine and subsequent formation into sheets or slabs on a Wet machine. Leatherboard manufactured by this process is of a rather dark, unattractive hue, due undoubtedly to the presence of iron-tannate inks formed in the leatherboard during its fabrication by chemical reaction between the tannins present in the leather scrap and the iron of the fabricating apparatus.

My prior invention depended upon the fact that the iron-tannate inks or saddening material can be destroyed or eliminated by the application of very dilute solutions of bleaching agents, so as to liberate the natural color of the leather fiber, without injuriously affecting its durability or other desirable qualities. In my previous patent I have mentioned a number of suitable acid reducing reagents which can be used to liberate the natural color of the leather fiber. Of those mentioned oxalic acid has been found to be most acceptable in commercial operation. The customary mode of carrying out the process prior to the present invention consisted in dipping the board in a dilute aqueous solution of oxalic acid of about 3% concentration. This concentration of bleaching agent results in a palecolored product that takes the usual light stains and dressings without the undesirable darkening or discoloration so characteristic of untreated leatherboard. A 2% solution does not produce so pale a board and a 4% concentration throws the shade more on the reddish side, which is not as desirable as a pale color. Furthermore, a concentration in excess of 3% appears to impair to a certain extent some of the desirable qualities of the leather fiber, particularly its flexibility. Hence, in the process as commercially practiced under my prior patent it was always considered necessary to maintain a careful control to insure the desired change in color of the product and to avoid a harmful excess in concentration.

It is the primary object of the present invention to modify the process disclosed in my prior patent in such a manner as to reduce to a minimum or to obviate entirely the necessity for carefully controlling the conditions under which the process is practiced.

Another object is to modify the process of my prior patent in such a manner as to reduce to a minimum the amount of chemical necessary to produce a desired eifect.

Another object is to provide a simple and economical method for bleaching sheet material containing leather fiber.

The invention is based upon the discovery or observation that soluble binoxalates have a far greater bleaching action on saddening materials present in leatherboard than has oxalic acid. 'For instance, a 1.75% aqueous solution of an alkali binoxalate such as potassium binoxalate (salt of sorrel) appears to have substantially the same bleaching eifect as that produced by a 3% oxalic acid solution. Since a 3% solution of oxalic acid contains 2.14 grams anhydrous oxalic acid per grams of solution and a 1.75% solution of potassium binoxalate contains .54 gram, .575 gram or .615 gram of anhydrous oxalic acid per 100 grams of solution (depending upon the number of molecules of water of crystallization), it is obvious that the use of the acid salt instead of the acid itself results in a considerable economy. A 1.75% solution of binoxalate contains less anhydrous oxalic acid than a 1% solution of oxalic acid, yet it produces a bleaching effect substantially equal to that produced by a 3% oxalic acid solution.

It is to be noted that the binoxalates are considerably less soluble in water than oxalic acid. Oxalic acid is soluble to the extent of 10% while both sodium and potassium binoxalate are soluble only to the extent of about 2%. It, therefore, follows that by using a soluble binoxalate instead of oxalic acid, the necessity for a careful control of the process is reduced to a minimum or obviated entirely. For, it is no longer possible to introduce into the leatherboard sufiicient oxalic acid to produce a reddish board or to injuriously affect the leatherboard fiber.

The bleaching agent may be applied to the material to be treated in various ways. I prefer to dip the finished sheet of leatherboard into a 1.75% solution of potassium binoXalate (salt of sorrel) or sodium binoxalate until the desired bleaching effect is produced. If a uniform effect throughout the board is desired, the board is left in the bleaching solution until complete penetration takes place. As in the case of my prior patent, by arresting the process before complete penetration occurs, I can simulate the difference in shade which can be observed between the grain surface and the center of any out section of hide leather.

The foregoing constitutes the essential and distinctive thought of my invention, but it is to be distinctly understood that the same may be combined with various details and expedients without materially affecting the peculiar results obtained and that changes and modifications may be resorted to without departing from the spirit of the invention or the scope of the appended claims, in which I intend to claim all the patentable novelty inherent in my invention.

I claim:

1. The method of bleaching leatherboard which consists in treating the leatherboard with an aqueous solution of an alkali binoxalate.

2. The method of bleaching leatherboard which consists in treating the leatherboard with an aqueous solution of potassium binoxalate.

3. The method of bleaching leatherboard which consists in treating the leatherboard with an aqueous solution of potassium binoxalate, the concentration of the solution being approximately 1.75%.

4. The method of bleaching leatherboard which consists in dipping the leatherboard into an aqueous solution of an alkali binoxalate.

5. The method of bleaching leatherboard which consists in dipping the leatherboard into an aqueous solution of potassium binoxalate.

6. The method of bleaching leatherboard which consists in dipping the leatherboard into an aqueous solution of potassium binoxalate, the concentration of the solution being approximately 1.75%

7. The method of making a sheet of leatherboard having substantially the same difference in shade between its grain surface and center as has a cut section of hide leather, which method consists in subjecting a sheet of leatherboard to the bleaching action of an aqueous solution of an alkali binoxalate for a period of time insufficient to permit complete penetration of the solution.

8. The method of making a sheet of leatherboard having substantially the same difference in shade between its grain surface and center as has a cut section of hide leather, which method consists in subjecting a sheet of leatherboard to the bleaching action of an aqueous solution of potassium binoxalate for a period of time insufficient to permit complete penetration of the solution.

9. A method for bleaching a sheet material containing leather fiber which consists in subjecting the material to the action of an aqueous solution of potassium binoxalate.

HERMAN W. RICHTER.