US965152A - Waterproof leather board and process of preparing the same. - Google Patents

Description

' UNITED STATES PATENT OFFICE.

EDGAR S. IBU'FPUM, DE NEWTON, AND WILLIAM W. CARTER, OF NEBDHAM, MASSACHU SETTS, ASSIGN'ORS' TO THE NEWTON COMPANY, OF NEWTON,- MASSACHUSETTS, A

CORPORATION OF MAINE.

WATERPROOF LEATHER BOARD AND PROCESS OF PREPARING THE SAME.

1% Drawing.

Specification of Letters Patent. Application filed January 29, 1909. Serial No. 474,966.

Patented July 26, 1910.

To all whom it may concern:

Be it known that we, EDGAR S. BUFFUM,

residing at Newton, in the county of Mid-' dlesex and State of M'Sssachusetts, and WIL- LIAM W. CARTER, residing at Needham, in the county of Norfolk and State of Massachusetts, both citizens of the United States,

have invented certain new and useful Improvements in Waterproof Leather Board and Processes of Preparing the Same, of which the following is a specification.

/ f This invention relates to the waterproofof leather fibers only, or whether it is made up in part from such fibers and in part from fibers of other material suitablefor the pun.

pose; I I

it has long been desired to produce an edective and homogeneously waterproof leatherboard, but sofar as we are aware no one has ever succeeded in accomplishing this result prior to our present invention, and we believe that those ,Who have dealt with this iroblem have failed to recognize the wide distinction between leather fibers, on the one hand, and Vegetable fibers such as form the basis of ordinary paperyon the other hand. The leather is oi animal origin and nitrogemodified by the tanning process,-which has entirely changed the normal relations of the animal fiber substance to water, the fibers having lost their colloidal character and dil with it their power of becoming greatly distended by absorption of water whether pure water or water containing other substances in solution.

We have discoveredthat a thoroughl andhomogeneously waterproofed' leather oard results from our process, which consists essentially in subjecting the pulp fibers to an alkaline treatment and then precipitating upon and throughout the fibers suitable waterproofing agents in an amount sufiicient to produce an actual permanent waterproofing: of the final product when finishedi- We be lieve that the result of'the jalkalin'e treatment is greatly'to increase the receptivity of the leather fibers to the waterproofing agents, and this is-probabl'y due to the effect I of the alkaline treatment in'restoring to a substantial extent the. ori inal colloidal character of the leather ber substance treated, whereby the action of the waterproofing a ents is rendered vastly more effective. T e alkali used in our process also has the important function of neutralizing and converting into soluble salts the acids, '21. e., the tannic acid, chromic acid or their equivalents, Which were employed in sheeting the transformation of the raw-hide into leather, thereby preventing the remature precipitation of the waterproo ng com-- pounds Within the pulp mixture, as well as removing the acids from the leather fibers and leaving them receptive to the water-- proofing treatment as already indicated.

It is an important feature of our process that the treatment is applied to the disintegrated fibers of the pulp materials employed and may be carried'on'in the beater, thereby securing. a very thorough incorporation: of "the various chemicals employed with the fibers of the pulp. We will now describe the processin iwhat we have found to be a highly satisfactory and eificient form, but it will be understood, as hereinafter explained, that instead or using insoluble compounds of the fatt acids as the waterproofing agent other well :sizing agents may be employed for the purpose, neous in character, and has been profoundly own The process is carried on in a heater or ihollander, in which the pulp mixture is ground in the usual manner until it attains the desired degree of: fineness. ;ture is then added an alkaline substance ;such as caustic soda or potash, ammonia, llime, sodium carbonate, gate, borax or thelike alkaline treatment is that the various acids;

To this mixotassium carbonne result of this and weak acid com ound's contained in the mixture, and particularly the tannic' or chrome aclds'contained in or derived-fromthe leather, combine'with the alkalineneuatralizingagent employed and thereafter exist in the mixture as solublesalts of the alkali used.- With the mixture produced as justidescribedthe're is mixed it solution of 'jsoap; in which term we include "any com- ,pound Whichis soluble in water orwin the pulp mixture-and is formed by thechemical? .mix a soluble sulfi union of an alkali (sodium, potassium or ammonium) with one or more of the fatty acids, 2'. e., the acids of the fats, oils and resins. The mixture thus produced is operated upon in the beater long enough to secure an equal distribution of the soap upon the fibers of the pulp, about an hour being usually required for this purpose, and

there is then added thereto a precipitant which will react with the soap and form by the union of the fatty acids with the base of the precipitant a compound which is insoluble in water or in the liquid portion of the pulp mixture. Among the precipitants which may be used are alum, aluminum sulphate, and copperas, any of which compounds will re-act with the soap as above set forth and deposit an insoluble precipitate upon the fibers of the pulp. The pulp mixture is then operated upon in the beater for another interval, usually about an hour, and is thereafter treated in the usual manner to produce the desired sheet or other article by the employment of machines such as are commonly used for this purpose.

In practice, the choice of the precipitant will vary according to the desired color of the final product. For example, if a black leatherboard is desired, we use copperas for the preeipitanhin which case, if the leather in the pulp was bark-tanned, the soluble salts resulting from the alkaline treatment above referred to will re-act with the iron of the copperas to form a black coloring compound. If the leather was chrometanned and a black roduct is desired we with thepulp and then employ copperas' as a precipitant, with the same result. In this case the soluble sulfid can bemixed with the soap and introduced therewith into the pulp mixture. If the precipitant employed is alum, aluminum sulfate or calcium chlorid the resultin product will have, a natural or reddish co or. 1

The proportion of neutralizing agent employed must be governed largely by the acidity ofthe pulp, and ordinarily'we employ soda ash for the neutralizing agent. According to our experience from 2 to 5 lbs. of dry soda ash for each hundred pounds of dry leather scrap or fiber will usually suflice for this purpose. The quantity of solid soap ordinarily required is about 10% by weight of the leather scrap or fiber, and the quantit of precipitant used should be such as-wil r -act completelywith the soap 60 or waterproofing compound and with that portion of the salts formed by the union of the neutralizing a ent with-the acids derived -from the pp which can be recipitate'd by the precipltating agent; e have found that ordinarily about one half of the last mentioned salts can be precipitated, and

corresponding to the percentages of soda ash and waterproofing compound above given, the quantity of precipitant required will ordinarily be from 8 to 13% by weight of the leather scrap, if copperas is the precipitant employed, or from 6 to 10% by weight 'of the leather scrap if aluminum sulfate is the precipitant employed. It will be understood that the exact quantities and proportions of the neutralizing alkali, the soap and the precipitant will vary in different cases, and may be determined by chemical analysis of the pulp mixture.

The alkali necessary to effect the neutralization of the pulp mixture may be mixed with the soap employed, if desired, before the mixture so produced is introduced into the pulp, but in practice we refer to add to the soap only so much alka i as will certainly be required, the remainder of the alkali being separately added to the mixture if analysis shows that such an addition is necessary.

The scrap leather employed in practicing our invention will contain in most cases both bark-tanned and chrome-binned leather, so that it will usually be desirable to add a certain amount of soluble sulfidto the pulp mixture when a black leatherboard is wanted. The proportion of solid sulfid required will usually be about 5% by weight of the chrome-tanned leather scrap employed.

By the term chrome-tanned leather as herein used we intend to refer to all leather commercially known by that name, which is commonly used to denote any leather tanned by the use of inorganic chemical compounds of various sorts.

Instead" of employing a soap compound as the source of the insoluble precipitate which is deposited u on the fibers of the pulp we may use for t e same purpose any one or more of a variety of other well-known substances or compounds which will remain in solution when added to the pulp mixture and will ield an insoluble precipitate u on the additlon of a suitable precipitant. "or example, a colloidal substance such as albumen, casein, or gluten may be used for this purpose, as any of these substances will be precipitated in insoluble form from the substantiall neutral pulp mixture by the addition 0 various precipitants well known to chemists, including. the precipitants hereinbefore referred to.. We prefer, however, to

kaline treatment, precipitating insoluble waterproofing compounds in sand mixture, and subsequently forming the pulp into the desired product.

2. The herein described rocess of producing a waterproof leatherl ioard which consisls in preparing a ulp mixture containing fibers of tanned leat er, renderingthe same receptive to waterproofing agents by an alkaline treatment, mixing therewith a soluble compound of fatty acids and alkaline bases, adding thereto a precipitant adapted to react with the fatty acids to deposit an insoluble precipitate upon the fibers of the pulp, and subsequently forming the pulp into the desired product.

3. The herein described process of producing a waterproof leatherboard which consists in preparing a pulp mixture containing fibers of tanned leather, rendering the same receptive to waterproofing agents by means of alkaline re-agents adapted to combine with the acids derived from the leather to form soluble compounds thereof, mixing therewith a soluble compound of fatty acids and alkaline bases, adding thereto a precipit-ant adapted to re-act with said soluble comonj thefibers of the pulp, and su 3e pounds to deposit an insoluble precipitaite se uent y forming the pulp into the desired pro not.

4. The herein described process of producing a waterproof and colored leatherboard which consists in preparin a pulp mixture containing fibers of tanne ing the same rece tive to waterproofing agents by an alka ine treatment, mixing pulp into the desired product.

5. A waterproof leatherboard made from pulp containing disintegrated fibers of tanned leather and having insoluble waterproofing compounds deposited by recipitation upon and thereby int-imatel; mixed with the fibers of which it is composed,.sub-

stantially as described.

In testimony whereof, we have hereunto subscribed our names this 27th day of January, 1909.

. EDGAR S. BUFFUM.

WILLIAM W. CARTER.

Witnesses:-

JOSEPH T. BRENNAN, E. D. Crnmwrox.

leather, render-