Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/25—Cellulose

Definitions

• the present invention relates to a process of manufacture of a waterproof paper or cloth having a high mechanical resistance especially in the wet state, and likewise possessing a very high 5 chemical resistance, said paper being particularly suitable as packing paper and for the manufacture of paper bags of the type used for example for carrying plaster or other materials.
• Said process is essentially characterized by the fact that the paper pulp, that is to say, the cellulose fibres, previously obtained by any of the usual known means, but preferably by a chemical method and superficially hydrated, are impregnated with an alkaline solution offreshly prepared cellulose thiosulfocarbonate, which is then subjected to the action of a suitable coagulant producing a precipitation of hydrocellulose which constitutes the binder of the cellulose fibres.
• Such coagulated hydrocellulose exists in the paper according to the invention in a form similar to that in which it exists in artificial silk. As such hydrocellulose has a very high tensile strength, the paper thus obtained is likewise very resistant.
• Coagulation may be effected by means of any of the numerous coagulants used for viscose, subject, however, to the proviso that its acidity shall be considerably diminished as otherwise it has been found that the sudden change from the alkaline state of the thiosulfocarbonate solution has a harmful eil'ect on account oi the acid condition of the coagulant bath,'and destroys the homogeneousness of the fibre-binder mixture of thepaper. It is therefore necessary to arrange matters so that .the changes about the neutral point will be as small as possible, that is to say that the solution to coagulate shall have the minimum of alkalinity and the coagulant the minimum of acidity necessary to render the operation successful.
• coagulants having the same composition and concentration as those used in the preparation of viscose silk would result in valueless products completelyfilled with gas bubbles.
• a good quality of the product according to the present invention can only be obtained by diminishing the quantity of bi-sulfate, or sulfuric or M hydrochloric acid etc. contained side by side with the neutral salts in the coagulants of viscose to reduce it to or 1/20 of the usual concentrations.
• the strong acids are replaced by weak 15 acids, as for example sulfurous acidor bi-sulfites.
• Another method consists in providing two 00- agulant baths: a first saline bath having a neutral or alkaline chemical reaction, and a second slightly acidulated bath which promotes coagula- 20 tion.
• a first saline bath having a neutral or alkaline chemical reaction and a second slightly acidulated bath which promotes coagula- 20 tion.
• the cellulose thiosulfocarbonate may be impregnated by soaking the already formed paper in a solution of thiosulfocarbonate, it being possible to facilitate penetration by previously moistening the paper with a very dilute alkaline solution of thiosulfocarbonate as also by the vacuum producedunder the paper web if a paper couchso ing machine is used.
• hyposulfate or an alkaline sulfide may be added to the wash water.
• the invention is likewise concerned with a process for preparing in the cold the alkaline cellulose from which the solution of cellulose thiosulfocarbonate is derived.
• Another advantage of the process is that it avoids the formation of hemicelluloses which are produced when the temperature of the reaction exceeds a certain value and which result in unusable products.
• the products based on regenerated cellulose are generally softened after coagulation with glycerine or gluclose. Such softening effect disappears in the wash and leaves a brittle product which has undergone considerable contraction.
• soap micella Such drawbacks are avoided by adding a small proportion of soap to the solution of cellulose thiosulfocarbonate, before coagulation, soap is preferably added in the form of a solution of soft soap, and more particularly in the form of resinous soap which possesses the property of not precipitating with hydrated lime, and as castor oil soap, which prevents the regenerated cellulose from contracting.
• the soap micella The soap micella:
• the impregnation it is first of all necessary to wait a few minutes between the moment when the product is applied and the leaf coagulates. In the case of continuous manufacture, such waiting period is obtained by causingthe leaf to zig-zag through two rows of rolls placed in front of the coagulation tanks. To avoid tear, the paper web may be transported on conveyor cloths, or it may be passed round lightly constructed drums of large diameter.
• the product is applied by means of rubbercoated cylinders.
• it is often impossible Such to obtain a uniform web on account of the air included in the starting paper web which prevents the cellulose solution from penetrating.
• the web obtained then reveals opaque patches having irregular forms, This may be avoided if the web of paper is slightly moistened with water on one side, and if the moistened web is then applied against a heated cylinder.
• the contact with the cylinder causes the water to be converted into steam, which can only escape by passing through the web, driving before it the air contained therein and taking its place.
• Another means of obtaining a homogeneous impregnation consists in the use of a perforated cylinder provided internally with cells, some of which are in communication with a suction device, similarly to cellular filters, while the cells at the points at which the paper engages with and leaves the cylinder are open to the atmosphere.
• the product is then applied by means of a coating roller to one side of the paper before it reaches the suction cylinder. While the paper passes on this cylinder, the product is drawn through all its pores and when the strip is taken ofl, the other side is likewise printed and the whole equalized and the excess removed by means of two straining rolls.
• a process for the manufacture of a water proof and highly resistant paper and the like comprising refrigerating an alkali solution, treating cellulose with said solution to form alkaline cellulose, preparing cellulose thiosulphocarbonate from said alkaline cellulose, impregnating the material to be treated with a freshly prepared solution of said cellulose thiosulphocarbonate and precipitating hydrocellulose in the material by means of a coagulant.

Landscapes

• Paper (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=8987789

Family Applications (2)

Family Applications After (1)

Country Status (5)

Cited By (4)

• 0
  • BE BE404058D patent/BE404058A/xx unknown
  • BE BE395388D patent/BE395388A/xx unknown
• 1932
  • 1932-04-19 FR FR735525D patent/FR735525A/fr not_active Expired
• 1933
  • 1933-01-17 FR FR42723D patent/FR42723E/fr not_active Expired
  • 1933-04-11 GB GB10801/33A patent/GB410310A/en not_active Expired
  • 1933-04-14 US US666224A patent/US2011156A/en not_active Expired - Lifetime
  • 1933-07-19 FR FR44155D patent/FR44155E/fr not_active Expired
• 1934
  • 1934-07-13 US US735090A patent/US2033351A/en not_active Expired - Lifetime
  • 1934-07-14 GB GB20696/34A patent/GB425666A/en not_active Expired
  • 1934-07-18 DE DEN36947D patent/DE625546C/de not_active Expired

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