US3511751A - Method of modifying cellulose xanthate paper prior to in situ regeneration by embossing and product thereby - Google Patents

Description

" Us. or. 162-117 United States Patent ABSTRACT OF THE DISCLOSURE Process for modification of paper to impart to it properties of woven or knitted fabric. Process comprises converting cellulose paper to alkali cellulose, conversion of alkali cellulose to cellulose xanthate by reaction with carbon disulfide, thereby loosening the fibers, pressing an embossing die against the surface of the treated paper to orient the fibers in the manner of a textile fabric, and soaking the sheet in an acid coagulating bath. Paper properties'may be further improved by treatment with a surface active agent, polyvinyl alcohol, or glycerol. Wrinkle resistance, folding endurance, elongation, wet strength, and other properties of the paper are improved by the process.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a method of modifying paper to impart to the paper the characteristics typical of textile fabrics. The invention aims at the preparation of modified or converted paper having the characteristics of textile fabrics, namely, softness, high extensibility, high wet strength, and wrinkle and scuff resistance, by altering the characteristics or, in other aspect, altering the defects of the paper, namely, stillness, low wet strength, and poor wrinkle and scuff resistance.

Description of the prior art Paper is an article of manufacture prepared by intertwining vegetable fibers in an aqueous medium into a web and drying the web to allow the fibers to recover their resiliency, while aggulatinating the fibers at their intersections. This gives dimensional stabilty and strength to the paper thus formed.,Accordingly, paper fibers are intertwined and agglutinated with each other essentially in an unoriented state or in random alignment.

On the contrary, textile fabric is an article of manufacture prepared by twisting fibers into yarns and subjecting the yarn to weaving or knitting processes. Comparing the properties of paper and of textile fabrics, paper has a poorer drapability and a lower extensibility than textile fabric because, in paper, the fibers are intertwined and agglutinated with each other in an unoriented state so that a stress imposed on a portion of the paper would hardly be distributed to other portions of the paper. On the other hand, textile fabric fibers are twisted together and each fiber is secured by frictional force between adjoining fibers so that textile fabric has a low tendency to scuff. In addition, textile fabric is prepared by weaving or kniting which will give the resulting textile fabric a retainability of the form of the textile fabric and, to the fibers forming the fabric, an alignment in regular direc- Patented May 12, 1970 ice tions so that the textile fabric has high extensibility, tensile sterngth, and good drapability.

Ordinary methods of making paper comprise a step of felting Ifibers by means of a machine provided with a vibrating screen and the resulting paper has a structure which makes it difficult to change the relative locations of fibers forming the paper by mechanical treatment. Accordingly, if a paper is cockled in the state in which the fibers form the paper, the fibers will retain the original agglutinated state and an uneveness will be formed on the paper.

SUMMARY OF THE INVENTION The present invention essentially comprises chemically treating a paper to loosen the combinations among the fibers forming the paper and then pressing a woven or knitted fabric against the surface of the paper to cause orientation of the fibers forming the paper in regular directions.

That is to say, the characteristics of textile fabric are imparted to paper by pressing a textile fabric to a paper which has been treated to convert the unoriented, immobile structure of the fibers to a mobile state so as to move and orient the fibers in parallel and perpendicular directions to the directions of the yarns in the textile fabric.

The method of the present invention comprises soaking a paper in an aqueous alkali to convert the cellulose fibers forming the paper to alkali cellulose, treating the alkali cellulose with carbon disulfide to convert it to cellulose xanthate in the form of paper, thereby, to make the fibers mobile with respect to each other, pressing a textile fabric, as a forming die, against the surface of the cellulose xanthate sheet, and coagulating the soy embossed cellulose xanthate sheet, and regenerating the cellulose in an acidic coagulating bath. The products obtained by the method of the present invention, of course, may be employed in the fields in which textile fabrics have been employed as they have the properties of textile fabrics. In addition, they may be used in fields where papers have usually been employed. Thus, the products prepared by the methods of the present invention have great versatility.

DETAILED DESCRIPTION OF THE INVENTION In the practice of the present invention, there may be used as converting paper, any of printing, hand-writing, drawing, wrapping, absorbing and Japanese papers. Preferably, the papers used are those having low size and filler contents and high strength, such as, e.g., kraft paper.

As the embossing-element, there may be employed woven or knitted fabrics formed of yarns of organic or inorganic fibers or fine metallic wires or metallic or synthetic resinous sheet materials having grains of such textile fabrics transferred to their surfaces from such textile fabrics in any conventional manner.

The present invention will be illustrated in detail by the following examples.

Example 1 A kraft paper was soaked in an 8% aqueous caustic soda solution for 1 minute and the sheet of alkali cellulose thus formed was taken out of the aqueous caustic soda solution and squeezed to remove excess aqueous caustic alkali. The sheet was then soaked in carbon disulfide at 25 C., for 30 minutes, squeezed to remove excess carbon disulfide, and interposed between two sheets of a plain cotton fabric. The assembly so formed was compressed under a pressure of -kg./sq. cm. for seconds. After removal of the cotton fabric, the sheet of cellulose xanthate was soaked in a coagulating bath containing sulfuric acid in a concentration of 120 g./l. for 3 minutes to coagulate and regenerate the cellulose and was then washed with water and dried.

The properties of the converted paper thus obtained are summarized in Table 1 together with those of the untreated paper.

TABLE 1 Untreated Treated Thickness (mm. 0. 082 Areal weight (g./sq. m.) 53. 2 Decrease in area (percent 17. 4 Loss in Weight (percent) 1 6 Tensile strength (kg. sq

T.'D.'::::::::::::: iii? Elongation at break (percent) Wet strength (kg/sq mm) 121) 0.01 0. 7 Folding endurance (times).

127 100, 000 weaknesses-(asst):- 6

'IJ? 55 110 Garley s stiffness (mg) 150 52 Customs abrasion (times)- 300 3 000 Shrinkage (percent) 0. as i). 05

In the above data, tensile strength and elongation at break were measured on test pieces of mm. width at a rate of drawing of 45 .mm./ min. The tensile strength was calculatedon the basis of the thickness at the thickest portions. Folding endurance was measured by means of a Schopper folding tester. Wrinkle resistance and shrinkage were measured in accordance with JIS (Japanese Industrial Standard) L-l006 (test method for woollen fabrics).

As indicated by Table 1, the treated paper had remarkably altered properties compared with the untreated one and there was obtained a further improvement in softness by post-treating the treated paper with a surface active agent or the like.

For instance, by soaking the treated paper in a 1% aqueous solution of a cationic surface active agent (sold under a trade name of Softex KW by Kate Soap Co., Japan), at 40 C., for 3 minutes and subsequently drymg, the wrinkle resistance was improved about 30 from 116 to 145. There was obtained a further improvement in wrinkle resistance, i.e from 116 to 165, by a slightly post-treatment employing a 10% aqueous solution of glycerol. By employing an aqueous solution of glycerol added with polyvinyl alcohol, in addition to softness, tensile strength was also enhanced. For instance, by posttreatment in which a treated paper was soaked in an aqueous solution containing 4% of polyvinyl alcohol of a degree of saponification of 88% and an average molecular weight of 1725 and 4% of glycerol for 3 minutes and then dried, the tensile strength, elongation at break and wrinkle resistance were improved compared with those of the original treated paper from 2.2 kg./sq. mm. to 2.8 kg./sq. mm. from to and from 116 to 165, respectively.

Example 2 A kraft paper of the same quality as the one employed in Example 1 was treated with an aqueous alkali and then carbon disulfide in the same manner as in Example 1 and interposed between two sheets of a twilled fabric. The assembly was compressed under a pressure of 3 kg./sq. cm. for 10 seconds and, after removal of the twilled fabric, the paper was then soaked in an aqueous solution containing 100 g. of sulfuric acid and 100 g. of sodium sulfate per litre of water for 5 minutes, and then was washed with water and dried. In the treated paper thus obtained, the fibers were oriented in regular directions corresponding to the grain of the twilled fabric.

The properties of the treated paper are summarized in Example 3 A ground wood paper was soaked in an aqueous caustic soda of 12% concentration for 1 minute and the alkali cellulose thus formed was squeezed to remove excessive alkali solution and was then soaked in carbon disulfide at 25 C. for 20 minutes. The cellulose xanthate sheet thus formed was squeezed to remove excessive carbon disulfide and interposed between two sheets of a plain cotton fabric and the resulting assembly was compressed under a pressure of 10 kg./sq. cm. After removal of the cotton cloth, the cellulose xanthate sheet was soaked in an aqueous sulfuric acid solution containing g. of sulfuric acid per litre for 3 minutes and then washed with water and dried. The properties of the treated paperthus obtained are shown in Table 3.

I claim: 1. A method of modifying paper and like cellulosic containing randomly oriented fibers comprising soaking the cellulosic sheet material in an alkaline solution to convert the cellulose to alkali cellulose, treating the so formed alkali cellulose sheet with carbon disulfide to convert the alkali cellulose to cellu lose xanthate, thereby, to loosen the agglutination of fibers with each other and to make the fibers relatively mobile, pressing an embossing die having the grain of textile fabric against the surface of the fibrous sheet to orient in regular directions the unoriented or randomly aligned fibers in the sheet, and soaking the so oriented sheet in an acidic coagulation bath to coagulate the cellulose Xanthate and regenerate the cellulose. I 2. A method as in claim 1 in which the embossing die is a woven fabric.

3. A method as in claim 1 in which the embossing die is a knitted fabric.

4. A method, as in claim 1, in which the embossing die is a woven or knitted fabric of line metallic wires.

5. An article of manufacture produced by the method of claim 1. q

6. A method of modifying paper and like cellulosic sheet materials containing randomly oriented fibers,

soaking the oellulosic sheet material in an alkaline solution to convert the cellulose to alkali cellulose,

treating the so formed alkali cellulose sheet with carbon disulfide to convert alkali cellulose to cellulose xanthate, thereby, to loosen the agglutination of fibers with each other and to make the fibers relatively mobile,

pressing an embossing die having the grain of textile fabric against the surface of the fibrous sheet to orient in regular directions the unoriented or randomly aligned fibers in the sheet,

soaking the so oriented sheet in an acidic coagulation bath to coagulate the fibers and regenerate the cellulose xanthate to cellulose sheet, and

subjecting to the said regenerated cellulose sheet a post-treatment with a solution containing at least one component selected from the group consisting of a surface active agent, polyvinyl alcohol, and glycerol.

7. A method, as in claim 6, in which the embossing die is a woven fabric.

8. A method, as in claim 6, in which the embossing die is a knitted fabric.

of claim 6.

I References Cited UNITED STATES PATENTS S. LEON BASHORE,

Smith et a1. 8l22 X Lilienfeld 8-122 Richter 8-122 X Sanford et a1 162-117 X Bridgeford 162177 Primary Examiner A. L. CORBIN, Assistant Examiner US. Cl. X.R. 20 8122; 117-157; l62146, 1570, 176, 177