US2121703A - Cork treated paper pulp - Google Patents

Description

artists CfiiiPtK TREATED Fr ll? PUMP lilo Leonard Larson, Willa, llliell... ghee to ailelt @crporation of America, Will ton, libel" a corporation of Delaware No Drawing. Application March t, 11935,

' Serial No. 9.9%

t @lai This invention relates to products comprising a combination of cellulose fiber and cork, and more particularly to water-laid sheets composed of paper pulp and comminuted cork.

An object of this invention is the production of an absorbent, porous, resilient, flexible, and pliable paper. A further object is to provide a process for the production of a paper comprising naturally or artificially crinkled cellulosic fibers and comminuted cork uniformly distributed throughout the sheet. A still further object is to improve the resiliency and the flexing properties of absorbent paper formed from naturally or artificially crinkled fibers.

These objects are accomplished by dispersing J cork and naturally or artificially crinkled fibers in water by the process described herein, and forming a sheet therefrom by regular paper making procedures.

Because of the nature of the pulp from which the present products are made it is not possible to obtain a sheet in which the fibers and cork are uniformly distributed by the typical paper making operations of mixing and beating which are used when the sheets are made from a mixture of. ordinary paper pulp and cork. The higher porosity and more open structure of the crinkled fibers used in the present process would,

unless the special procedure outlined herein were used, permit the cork to fioat through the pulp mass toward the top, thus preventing the formation of a sheet having the required uniformity oi distribution of the cork throughout the sheet.

I have discovered that an absorbent and resilient paper comprising artificially or naturally.

crinkled fibers and comminuted cork uniformly distributed throughout the sheet can be prepared by the following process: A stable suspension of comminuted cork is prepared by dispersing it in boiling water in which a wetting agent is dissolved, allowing the suspension to cool to room temperature, and then adding a dispersing agent. The combined action of the wetting agent at elevated temperatures and the dispersing. agent forms a stable suspension of the comminuted cork in water. The stable suspension of. cork is mixedin a heater with artificially crinkled chemical wood pulp in suitable proportions. l The mixture is beaten until uniform distribution of cork and fibers is obtained. The pulp is then diluted to a paper making consistency and formed into a sheet by procedures well known to the art.

Crinkl d fibers such as those made in accordance with United States Patent 1,857,100 .are advantageously used in the present process. Naturally crinkled fibers, such as cotton linters, or cotton rag properly converted into pulp, or

any fiber crinkled to an extent which gives a pulp at least no slower than 100 seconds freeness as measured by the freeness tester described in the mentioned patent, may also be used in making my new products.

The artificially crinkled fibers are made, as fully described in the patent, by wetting ordinary paper pulp, that is pulp composed of cellulose fibers having a mean length of 1.5 to 4 mm., with caustic of mercerizing strength, and promptly washing out the strong caustic as soon as thorough mixing 'of; the pulp with the caustic solution has been effected by means of a rapid and efficient dispersing means. In accordance with this method the absorbent pulp used in the examples of the present invention was made as One hundred parts by weight of kraft pulpas wet lap (40% fiber, water) and 150 parts by weight of 25.2% solution of sodium hydroxide at 25 C. are fed simultaneously and in proportionate rates into a pulper consisting of ribbed discs rotating in opposite directions at high speed. The clearance between the faces of 'the discs is approximately 0.150". The time required for the fibers wet with caustic solution to pass through the pulper, is approximately 15 seconds. The mass delivered from the pulper is drowned in water or a dilute solution of sodium hydroxide. The fibers are then washed with water until neutral and converted into wet lap.

In carrying out the process of this invention,-

either ground cork or shredded cork may be used. I prefer to use a ground cork, the major portion of which will not pass through an mesh screen and only a small portion of which "will pass through a 30 mesh screen.

A stable suspension of the ground cork is prepared as follows: The ground cork is sifted into a dilute water solution of a wetting agent at C., and with rapid agitation to keep the cork dispersed. The boiling temperature is maintained for several minutes, after which the suspension is allowed to cool to room temperature.

1 if-hydration of the fibers is desired, although in the preferred practice of this invention, the hydration of the fibers is held to a minimum. The pulp is then converted into a sheet and dried by regular paper making procedures on a Fourdrinier or cylinder paper machine.

In the preferred practice of my invention, the sheet should contain not less than 20% nor more than 35% by weight of cork. The minimum amount of cork that can be used is approtely 10%; the maximum amount that should be used is approximately 50%.

It is desirable to add an agent,to the pulp that will strengthen the sheet so that the sheet will have better working properties in subsequent impregnating operations. A heavy boiling starch such as corn starch added to the pulp in the beater in an amount equal to approximately 10% by weight based on the cork and fiber weight has been found very suitable for this purpose.

The following examples are further illustrative of the methods used in carrying out my invention:

Example I A beater was charged as follows: 1

, 7 Parts by weight Water 4,500 Artificially crinkled kraft pulp as wet lap 356 Fiber 142 1 Water 214 3.7% suspension of ground cork 1,000

6.0% solution of corn starch The furnish was beaten for 15 minutes with the roll set in a light brushing position. The stock was then diluted to a paper'- making consistency and formed into sheets on a laboratory sheet mold. The sheets were pressed between wool felts and dried at 100 C.

The 3.7% suspension of cork was prepared as follows: Thirty-seven parts of ground cork were "added with stirring to 922.4 parts of boiling water-1:.

containing 2.4 parts of sulfonated higher alcohol consisting chiefly of dodecyl sulfate'and 1.2 parts of pine oil. The boiling temperature was maintained for minutes and the suspension was agitated during this time. The suspension was then cooled to room temperature and 37 parts of a 10% solution of casein were added. The casein solution was prepared by standard procedure using 7.5% sodium hydroxide based on the casein as the solubiiizing agent.

The artificially crinkled kraft wet lap was prepared by the preferred process described above. A southern pine kraft pulp was used.

The sheets prepared by the above process were exceedingly pliable, resilient,. and absorbent.

Physical data on properties of the sheets follow:

Weight of 10" x 10" sheet -.'grams 27.4 Thickness i. inch- 0.075 Density (grams per cubic centimeter) 0.222 Mullen bursting strength 15.0 Porosity (Gurley densometer: 400 cc. air

displacement) second- 0.70 Kerosene absorption tandard roofing i felt test) percent- 400.0

The sheets produced on a laboratory mold have higher kerosene absorption, porosity, etc., than a sheet made on a Fourdrinier paper machine. For example, a sheet made from the above described stock on a plant scale would have a, kerosene absorption of 315%i%, with a corresponding change in thickness, density, and porosity.

Example II The following example illustrates the incorporation of linseed oil into the pulp in order to improve. the strength and softness of the sheet.

The beater was charged as follows:

/ Parts by weight Water 4,500 Artificially crinkled kraft pulp as wet iap 356 Fiber 142 Water"; 214 Linseed oil treated suspension of ground cork" 1,149

3.7% suspension of ground cork.-- 1,000 20.0% water emulsion of heat bodied linseed oil 74 i 3.0% solution of alum. 75

Total 1,149

The furnish was beaten for 15 minutes with the roll well up so that the drying oil would not be rubbed ofi from the surface of the cork particles. The stock was then diluted to a paper making consistency and sheets were formed on a laboratory sheet mold. The sheets were pressed between wool felts and dried at-100 C.

The artificially crinkled kraft pulp wet lap and the 3.7% suspension of ground cork were prepared as described under Example I. The emulsion of linseed oil was prepared as follows: Twenty parts of heat bodied linseed oil (viscosity of S. at C. on Gardner-Hoidt scale) and 2 parts of linseed oil acids were mixed and added to 78 parts of a 0.35% water solution of sodium hydroxide, with high speed agitation.

The wetting and dispersing agents used in preparing the stabilized suspension of cork may be any of the substances of these classes of materials known to function in general as efflcient wetting and dispersing agents. For the present purpose the wetting agents are substances which increase the ability of water to wet the surface of the cork. Examples of such agents are the sulfuric esters of the higher alcohols, i. e., the sulfates of dodecyl, cetyl or 9,10-octadecenyl alcohols or the sodium salts of these sulfates, true sulfonic acids, alkylated naphthalene sulfonic acids, and sulfated or sulfonated compounds in general such as those of the long chain ethers.

The amount of wetting agent must be suill-' cient to cause thorough wetting of the cork with water. Excellent results are obtained with 9% wetting agent based upon the weight of the cork, although smaller amounts may be used. I prefer to use a mixture of the higher alcohol sulfate and pine oil in the ratio of 2 parts by weight to 1 part by weight respectively.

The process of wetting the cork should be accomplished for economical reasons with the minimum ratio of wetting solution to cork consistent with satisfactory results. This may be done, for example, by mixing the hot wetting solution and the cork in a steam-jacketed mechanical mixer. This would be a batch opera tion. For a continuous operation, pulpers known to the trade may be used for mixing the cork and boiling hot wetting solution. These pulpers are designed to operate on high consistency mixes such as 15 to 30%, and wetting is furthered by pressure exerted on the mix in the pulper.

As the dispersing agent I have found the ammonium or sodium salt of casein to be very effective. Gelatin and animal .glue are likewise effective dispersing agents. persing agent is preferably 10% by weight based upon the cork, although larger or somewhat smaller amounts can be used.

The pulp consisting of crinkled fibersv and comminuted cork prepared by the process of this invention may be treated with waterproofing agents such as rosin size, soaps, or wax emulsions, and a precipitant such as alum. The pulp may also be treated with dyes and with pigments such as clay, calcium carbonate, lithopone, titamum-dioxide, etc. Materials other than starch, rubber, and drying oils may be used as strengthening agents. In general the pulp may be modified with any aqueous solution, dispersion, or emulsion capable of depositing an insoluble coating on the fibers and cork by the addition of an agent such as alum. For example, the pulp may be modified with aqueous dispersions or emuls'ions of resins, drying oil varnishes, cellulose esters or ethers, etc.

The present invention makes possible the manufacture of paper or' felted products comprising crinkled fibers containing uniformly distributed cork particles, thereby combining the properties of high absorbency and high saturating strength contributed by the crinkled fibers with the resilience, flexibility and other desirable properties contributed by the cork. The process described herein, however, may be advantageously applied to the manufacture of cork containing paper products from the straight fibers of ordinary paper pulp. Although the pasty mass of the ordinary paper pulp will hold the cork particles more or less satisfactorily so that good distribution can be obtained by ordinary mixing, the present process nevertheless will bring about a markedly more uniformdistribution of the cork.

The products of this invention are useful in the production of pyroxylin or rubber coated products for book bindings, upholstery, linings for trunks, suitcases, etc. They are also useful in the shoe industry as shoe caps, counters, and inner soles. In eachof these uses the sheet is impregnated with an impregnant that will impart to the sheet the required properties of strength and flexibility. The products of this invention are chiefly useful as a base for impregnation processes and they are particularly useful in the production of hard surface fioor covering. The sheet is converted into a floor covering material by first. printing a pattern through the sheet With a drying 'oil paint, curing the paint, saturating the sheet with a clear saturant to fill all the voids, and finally applying to the surface one or more finishing coats of lacquer or varnish. .The present products The amount of disare especially valuable for the manufacture of floor coverings because of the large capacity of the material for'saturant and its high resiliency and flexibility. The products of this invention are also very useful as press blankets, such for example as blankets on the bed of printing machines, plate presses, etc., because of their resiliency, flexibility, strength and surface adapted ments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as. delfined in the appended claims.

I claim:

1. A process for causing substantiallyuniform distribution of comminuted cork into paper pulp which comprises forming a dispersion of the cork in water containing a wetting agent and a dispersing agent, and intimately mixing the dispersion with the paper pulp.

2. A process for manufacturing a water-laid sheet comprising cellulose fiber and comminuted cork which comprises forming a dispersion of the cork in water containing a wetting agent and a dispersing agent, mixing the dispersion with cellulose fiber, and depositing a sheet from the mixture.

3. The process set forth in claim 1 in which the pulp comprises crinkled paper making fibers mercerizing activity and promptly separating the caustic from the pulp.

'7. A process for making a cellulose fiber and cork compositionwhich comprises forming a dispersion ofcork in water containing a wetting agent and a dispersing agent, and intimately mixing the dispersion with paper pulp admixed with starch.

8. The process set forth in claim 1 in which the pulp comprises crinkled paper making fibers in substantial amount and in which said cork dispersion is one of 15% to- 30% consistency.

LOUIS L. LARSON.