Finished paper for casings and process of preparing same
United States Patent r191 Maeno et al.  
 FINISHED PAPER FOR CASINGS AND PROCESS OF PREPARING SAME Inventors: Hit-00 Maeno, Osaka; Yoshiyuki Matsumoto, Agawa, both of Japan Assignee: Kanegafuchi Kagaku Kogyo Kabushiki Kaisha, Osaka, Japan Filed: June 30, 1972 Appl. No.: 268,108  
 US. Cl. 162/176; 260/217; 106/168; 427/339 Int. Cl 544d l/44 Field of Search 117/157, 166, 62, 62.1, 117/63; 99/176; 260/217 References Cited UNITED STATES PATENTS 6/1964 Underwood 117/157 X Apr. 15, 1975 OTHER PUBLICATIONS Ott, Emil et al., Cellulose &amp; Cellulose Derivatives, Pan 11, 1954, pp. 982, 995, 996, QD321089 1954.  
 Primary ExaminerMichael R. Lusi&#39;gnan Attorney, Agent, or FirmMoonray Kojima 57] ABSTRACT Finished paper for casings and method of preparing the same. The method comprises impregnating a thin base paper with excess alkali cellulose Xanthate solution, subjecting the impregnated paper to an alcohol treatment to produce regenerated cellulose and then water washing and drying the treated paper.  
 9 Claims, 4 Drawing Figures PATENTEDAPR 1 51975 3,877,  
 4 &#39;fllllllllll, v 1 X l IO -3- 7 g I. 9  
 FIG.2  
 FINISHED PAPER FOR CASINGS AND PROCESS OF PREPARING SAME BACKGROUND OF INVENTION This invention relates to finished paper for casings and method of preparing same.  
  For reinforcing the texture of paper made of a cellulose it has been common practice to process the base paper with regenerated cellulose serving as a water absorptive reinforcing binder. One method solidifies and fixes regenerated cellulose at crossing points of the fibers in the base paper. Another method applies regenerated cellulose on the surface of the relatively thick paper so as to set the regenerated cellulose into a form of extremely thin film.  
  Although such conventional methods encounter no substantial problems in case the amount of regenerated cellulose deposited on the base paper is relatively small, such methods encounter many difficulties when thin Japanese paper of about to gm/m thickness is used as base paper, and regenerated cellulose is de posited thereon in large quantity.  
  In the latter case, even if the base paper is tough, such as one composed mainly of bast fibres, when it is impregnated with an alkali cellulose xanthate solution, the paper composing fibres are rapidly weakened in their mutual intertwining strength due to swelling caused by alkali. Also the hydrogen bonding force between the cellulose molecules is greatly reduced due to the presence of moisture. Consequently, the original shape of the base paper is deformed under its own weight. It is therefore necessary to treat the paper immediately after coating or impregnation with an alkali cellulose xanthate solution, with an acid salt solution (such as, for example, a mixture solution of sulfuric acid and Glaubers salt) to thereby salt out, solidify and regenerate the deposited alkali cellulose xanthate. The alkali cellulose xanthate provides film-like smooth surface. The aforementioned process is employed in the manufacture of rayon, staple fibres or cellophane.  
 Cell.  
 Cell.C-0.Na+ H s0 ce11.+ na so CS According to this formula, only the surface contacted with the acid salt solution is first instantaneously reacted and solidified to form an extremely thin film of regenerated cellulose. This film acts to retard penetration of the treating solution into the nonreacted layer thereby excessively decelerating the cellulose regenerating speed. Also, a large liquid treating tank in which the paper must be immersed for a long time, is required, thus resulting in elevated costs. Furthermore, the film prevents release of gases (such as odoriferous CS thus by-produced during the reaction inside of the film, thereby producing tarnish. There are also byproduced sulfides which make the after-treatment difficult to perform. Because of these undesirable factors, it is highly difficult to solidify and set regenerated cellulose into the fibers in a commercially acceptable manner.  
 SUMMARY OF INVENTION The present inventors have successfully discovered, after considerable experimentation and study, an effective processing method which is free of the above defects. With the present invention even when a relatively thin base paper, such as about 15 to 30 gm/m is used, it is possible to obtain on an industrial scale, a regenerated cellulose processed paper in which the deposition of dry regenerated cellulose can be from 20 to gm/m or more. It was also found that the invention was operable without producing pollution.  
  More specifically, according to the invention which encompasses an improved method for producing converted paper to be used for casings, such as used for stuffing sausages, etc, a thin, such as a Japanese paper, base paper made of cellulose is absorbed or impregnated with a large quantity of an alkali cellulose xanthate solution and then subjected to an alcohol treatment to produce regenerated cellulose. Thereafter the thus treated base paper is washed with water and then dried.  
  Advantageously, the inventive method enables rapid formation of regenerated cellulose which is industrially adaptable. Manufacturing costs are reduced. Also the product may be coated with a large amount of regenerated cellulose and have high wet strength. Moreover, release of waste material which can pollute the environment is avoided.  
 BRIEF DESCRIPTION OF DRAWING FIG. 1 depicts an illustrative apparatus used in the practice of the invention;  
 FIG. 2 depicts a casing made of the inventive paper;  
  FIG. 3 depicts an alternative casing made of the inventive paper; and  
  FIG. 4 depicts another alternative casing made of the inventive paper.  
 DETAILED DESCRIPTION OF DRAWING In the present invention, the following chemical reaction is utilized:  
  c ONa+ ROH- R 0 O-Na Cell.  
 R is the component part ofthe alcohol used, which alcohol may be a lower alcohol such as, for example, methyl or ethyl. Regeneration of cellulose may be easily effected by the above reaction which produces xanthates from lower alcohol. The substitution reaction is completed almost instantaneously by shifting from left to right in the above formula) quantitatively. it has the advantage that since only alcohol which has higher permeability than the acid salt solution, participates in the reaction, there is by-produced no decomposed substance inside the coating. In contrast, the conventional acid neutralization method produces such decomposed material. Hence, no offensive odors or unwanted residues are produced during the reaction. Accordingly, it is highly simple to remove impurities from the inventive product and to wash the product. It is also possible to dispense with the pre-heating and drying treatments which were indispensible steps in the conventional viscose processing to prevent deformation of the original shape of the base paper before the acid treatment. Furthermore, the present invention is quite noteworthy in that it eliminates pollution.  
  According to the present invention, it is possibble to dispose of the slight amount of residues or by-products isolated from, but still in the alkali cellulose xanthate solution during the alcohol treatment in a simple manner by washing with water. From the post reaction alcohol treating liquid, alcohol and carbon bisulfide may be recovered. It is desirable that the alcohol used in the reaction have a high purity. Hence, the used alcohol containing s [R- c O&#39;Na,  
 when re-used after storage, should be neutralized with an acid at a low temperature (at about the temperature of cold water).  
 Carbon bisulfide (CS which was decomposed and fractionated in the reaction s R ti ONa HCl NaCl cs ROH,  
 is precipitated due to the difference in specific gravities. Thus, it is possible to separate and recover high purity alcohol from the high boiling point fractionates. Accordingly, the waste liquid may be neutral and, if necessary, the admixtures therein can be readily precipitated away.  
  Turning now to the drawing, in FIG. 1, there is shown an example of a flat plate processing apparatus in which the present inventive method may be practiced. The base paper 3 is drawn out of a tank 2 containing a highly concentrated alkali cellulose xanthate solution 1. It is successively delivered into a portion of treating tank 5 containing liquid alcohol, such as ethyl or methyl alcohol, on one side of a partition plate 6 contained therein and lifted up from another portion on the opposite side thereof to be further carried to the washing and drying steps not shown. The used alcohol treating liquid in tank 5 is discharged out from the bottom thereof into sealed tank 7 in which the liquid is neutralized with an acid supplied thereinto from a pipe 8. The resulting neutralized liquid is then fed into an alcohol still 10 provided with a steam jacket 9, wherein alcohol is fractionated.  
  The fractionate is further guided into a cooler 11 wherein the fractionate is cooled and liquified to separate low boiling point CS The C5,, freed alcohol is received in tank 12 from which it is again recycled and supplied into alcohol tank 5 through a pipe 13. Waste fluid or liquid is separated and released away from the bottom of still 10. CS separated in cooler 11 is recovered separately and suitably treated to ensure perfect preclusion or elimination of offensive odors and other possible hazards.  
  The following is an example embodying the invention method.  
  Manila hemp, linter, staple fibre available on the open market and powdery (or fibriform) polyvinyl alcohol were blended at ratios of 70, l0, l7 and 3 percent by weight, respectively, and the blend was then subjected to a cylinder paper machine the same as in a foundrinier machine.) to produce a thin Japanese paper having a thickness of about 14 to 20 gm/m by using a normal process. The Japanese paper was then used as base paper 3.  
  Thereafter, an alkali cellulose xanthate solution, which had been adjusted to cellulose concentration of 8.5 percent, Hottenroth number of 11, and caustic soda content of less than 6.0 percent (the lower the better the results), was supplied into and held in tank 2 of FIG. 1. The base paper 3 was immersed in the solution in the aforementioned manner so that the base paper was sufficiently impregnated with the solution. The amount of impregnation may be varied slightly according to the shape of the paper and the intended use, but usually it is on the order of 700 to 800 gm/m in the case of one time immersion and on the order of 400 gm/m in case of placing two sheets in layers or in case of performing immersing twice. Blending of powdery polyvinyl alcohol in the base paper is to provide reinforcement to the base paper and to enable it to withstand the force of gravity or handling after the impregnation treatment. About 3% blending of the alcohol, as used in this example, provides sufficient endurance even in the case of one time immersion as discussed above.  
  The impregnated base paper, upon being lifted up from the treating liquid or xanthate solution, is passed around a roll 14 having a compact smooth surface in such a manner that the paper is closely placed on the surface of the roll so as to prevent deformation of the paper shape. It is then charged into treating tank 5 containing ethyl alcohol, wherein the paper is immersed for a duration of several minutes to about ten minutes or longer until the reaction by alcohol is completed. Thereafter, if necessary, the thus treated paper is further subjected to washing with water and drying to thereby complete the entire process.  
 The cellulose processed paper obtained in accordance with this invention can be effectively used for making casings, such as for packing foodstuff, such as for example, high quality ham, sausages, etc.  
  Casing materials require high wet strength since they must resist internal pressure exerted during the stuffing process when the casing is wetted. They must also be suitably flexible to withstand contracting and stiffening during smoking operation when the finished article is finally shaped. The cellulose processed paper of this invention easily meets such requirements since the paper is coated with a film of thick regenerated cellulose to provide high wet strength.  
  The finishing into a cylindrical casing may be achieved in the following manner. The processed paper, for example, may be&#39;joined at opposite ends to form a vertical joint 15 as shown in FIG. 2. In an alternative method, the papermay be formed into a strip 20 and coiled spirally as shown in FIG. 3. In a further alternative method, as illustrated in FIG. 4, the strip shaped paper 21 is first coiled spirally in one direction to form a cylindrical body and then again coiled spirally in the opposite direction to thereby finish the casing into a double coiled cylindrical casing. The overlapped base paper portions of the cylindrical casing may be either joined during the step of alcohol setting, by application of an alkali cellulose xanthate solution or bonded in a separate step by using a suitable adhesive (such as cellulose ester, cellulose ether polyamide, epoxy resin, butyral resin, formal resin or the like).  
  As above described, the method of the invention has many advantages over the conventional methods in which alkali cellulose xanthate is salted out and solidi- Cell.  
 fled by an acid salt solution to thereby produce regenerated cellulose. For example, it is possible with the present invention to coat the base paper with a large quantity of regenerated cellulose in a short time and to obtain cellulose processed paper which is relatively free of impurities and has high wet strength. The inventive method produces such paper at low cost and without pollution. The thus obtained paper is especially suited for making of casings.  
  The foregoing description is intended to be only illustrative of the principles of the invention. Numerous other variations and modifications thereof would be apparent to the worker skilled in the art. All such variations and modifications are to be considered to be within the spirit and scope of the invention.  
 What is claimed is:  
  1. Method of preparing paper suitable for use as a casing, comprising the steps of A. impregnating said paper with an alkali cellulose xanthate solution; B. treating the impregnated paper with lower monoalcohol thereby to regenerate cellulose; and C. washing the resulting paper with water and thereafter drying.  
  2. The method of claim 1, wherein said lower monoalcohol is selected from the group consisting of ethyl alcohol and methyl alcohol.  
  3. Method of claim 1, wherein said step of treating with said alcohol produces dry regenerated cellulose to an amount of 20 to gmlm and said paper is between 15 to 30 gm/m in thickness.  
  4. Method of claim 1, wherein said treating step employs the following chemical reaction:  
 H II  
  C O&#39;Na ROH-Q R C O-Na Cell.  
 wherein R is a component of a lower alcohol.  
  5. Method of claim 1, wherein said alkali cellulose xanthate solution has a cellulose concentration of 8.5 percent, a Hottenroth number of l 1, and caustic soda content of less than 6.0 percent.  
  6. Method of claim 1, wherein said impregnation of said paper with alkali cellulose xanthate is on the order of 700 to 800 gm/m.  
  7. Method of claim 1, wherein said paper contains polyvinyl alcohol in an amount of about 3%.  
  8. Method of claim 1, wherein said treating step is for a period of time sufficient for the reaction of alcohol and the impregnated paper to be completed.  
  9. A casing paper prepared by the process of claim 1.