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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/76—Processes or apparatus for adding material to the pulp or to the paper characterised by choice of auxiliary compounds which are added separately from at least one other compound, e.g. to improve the incorporation of the latter or to obtain an enhanced combined effect
  • D21H23/765—Addition of all compounds to the pulp
• • 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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/76—Processes or apparatus for adding material to the pulp or to the paper characterised by choice of auxiliary compounds which are added separately from at least one other compound, e.g. to improve the incorporation of the latter or to obtain an enhanced combined effect

Definitions

• the present invention relates to a process for the preparation of sheet materials, of fibrous structure and of cellulose base, in particular by wet papermaking and constituting paper, nonwoven or cardboard, ennobled by impregnation of elastomeric resins.
• the present invention thus makes it possible to obtain, from a process using a papermaking production line, fibrous sheets based on cellulose, in particular smooth or creped and ennobled by various synthetic materials of elastomeric or plastomeric nature.
• the process thus makes it possible to obtain cartons having specific properties originating from the impregnation of products made up of said resins and allowing the use of the material thus obtained in numerous applications such as artificial leathers and the production of shoes and leather goods, high value printing sheets, gummed papers or labels as well as abrasive layer supports; the invention also makes it possible to obtain pressure-sensitive adhesive tapes, substrates usable in tapestry (floor or wall coverings); the invention also makes it possible to produce materials for technical uses, in particular for winding and protecting filiform elements such as cables or electrical cables, as well as envelopes of various shapes, in particular sterilization envelopes.
• drying cylinder tends to retain on its surface the sheet during drying therefore having only weak mechanical properties which comes to tear with rupture in the continuity of the course.
• the cylinders are regularly fouled by the deposits of resins, which leads to the need for regular stops for cleaning operations, resulting in a lowering of the general production yield.
• a first solution consisted in coating the drying cylinders and rollers with a non-stick resin with a low coefficient of friction such as fluorocarbon resins.
• a solution has also been recommended allowing the manufacture of a sheet based on cellulose fibers containing an elastomeric impregnation and in which organic electro-positive cationic compounds are incorporated into the starting material in order to reduce the zeta potential.
• the invention makes it possible to manufacture paper products containing a large proportion of finishing composition in the form of polymers and elastomers or plastomers and without any risk of deposition of elements originating from the finishing resin along the machinery and in particular at level of drying rollers.
• the invention relates firstly to a process for the wet preparation of sheet materials of fibrous structure based on cellulose, such as paper, cardboard, nonwovens or the like, of the type in which the fibrous web structure is enriched with finishing materials made up of synthetic polymers and more particularly resins of the elastomer or plastomer type, and moreover of the type in which the wet sheet formed on the endless fabric, passes through an impregnation press, to receive there a finishing product of the type consisting of an elastomer or plastomer resin before drying on heating rollers, and the method is characterized in that the finishing product feeding the impregnation press with a view to its impregnation in the wet sheet consists of an aqueous dispersion of an elastomeric or plastomeric resin and in that this liquid bath receives as an adjuvant of f manufacturing an active product capable of causing the spontaneous coagulation of said resin above a given temperature with release of a quantity of water, thus capable of constitu
• a first primer for the subsequent attachment of the elastomeric resin and this first primer consists of a retention product capable of lowering the zeta potential of the mass.
• said first retention primer consists of a polymer with long polyelectrolyte chains.
• said first attachment primer is chosen from the family comprising dispersions of polychloroprene, polybutadiene-styrene, polymethacrylate and polyvinyl acetate.
• the preparation of the starting paste comprises the incorporation of a second primer for the subsequent attachment of the elastomeric resin, this second primer consisting of a synthetic elastomeric resin, chosen to be different and compatible with the elastomeric resin. constituting the finishing product or subsequent impregnation and presented in the form of an aqueous dispersion.
• said second attachment primer is introduced into the paper pulp after a period of time greater than 15 minutes and preferably of the order of 20 minutes after the introduction of the first primer.
• said second finish is chosen from the family comprising polychloroprene, polybutadiene acrylonitrile, polyacrylate, polyvinyl acetate, polyvinylbutadiene-styrene, as well as their mixture or their copolymers.
• the impregnation bath supplying the impregnation press for impregnating the paper sheet with the aqueous dispersion of elastomeric or plastomeric resin is maintained at a pH of less than 5 and of preferably between 4 and 4.5.
• the pH is adjusted by adding acids, chosen from the group comprising maleic acid and paratoluenesulfonic acid, but it will be seen that in these certain cases the pH can change between 4 and 11.
• the impregnation bath supplying the impregnation press is provided at a concentration of between 15 and 45% of dry matter relative to the total.
• the impregnation bath supplying the impregnation press and containing the dispersions of elastomeric or plastomeric resins is produced from an aqueous dispersion of resins chosen from natural latex, polybutadiene acrylonitrile, polyvinyl acetate, polybutadiene styrene, the butadiene acrylonitrile and styrene copolymer, the copolymers of acrylic esters and vinyl acetate, as well as their mixture or copolymers.
• the coagulation agents of the elastomeric resin consist of gelling agents such as the polycondensation products of long-chain aliphatic polyols and more especially the polyesters of propylene ethylene , methyl ester of polyvinyl alcohol, polyoxyethylene.
• the impregnation bath supplying the impregnation press comprises adjuvants consisting of viscosity regulators such as polyvinyl alcohols, polyacrylamides, polyacrylic acid with the addition of ammonia.
• the impregnation bath also carries manufacturing adjuvants chosen from softening, plasticizing and hydrophilic agents, such as polyglycol, trietanolamine or glyoxal, emulsifiers for adjusting the coagulation temperature of the elastomeric resin, metal sensors. heavy such as ethylenediamine tetra acetic acid as well as dyes and fillers.
• softening, plasticizing and hydrophilic agents such as polyglycol, trietanolamine or glyoxal, emulsifiers for adjusting the coagulation temperature of the elastomeric resin, metal sensors.
• heavy such as ethylenediamine tetra acetic acid as well as dyes and fillers.
• the method comprises a coating phase, after drying, and on at least one face, using a protective varnish chosen from the family comprising the chloride dispersions.
• a protective varnish chosen from the family comprising the chloride dispersions.
• the corresponding face of the sheet receives a coating of product chosen from the family comprising the complexes of stearic acid and chromium trivalent, melamine resins, long chain fatty acids, melamine formalins and water soluble and crosslinkable formalin ureas.
• a long fiber paste is used which allows sufficient absorption and resistance adapted to the use for which the product is intended; the long-fiber, bleached, semi-bleached or unbleached pulp is not very refined (16 to 30 ° SR); the medium is maintained at a substantially neutral pH, between 6.5 and 7.5; it will be noted however that all the pastes, including the recycled pastes can be used within the framework of the finishing process according to the invention.
• the fibers in a conventional and conventional manner are disintegrated in the pulper and possibly refined and in the paste thus produced is then introduced a first bonding composition or a first finish constituting a retention product and chosen from the products designated under the registered trademarks Retaminol (Bayer), Cartaretine (Sandoz), Percol (Allied Colloid); this first primer is introduced in a proportion of between 0.1 and 3% of the total.
• a second primer is introduced into this dough consisting of a relatively hard and polar polymer, giving off a fairly large surface energy; preferably this polymer is an elastomer and it is dispersed in the fibrous mass in very fine particles in the form of an aqueous dispersion; a great aptitude for adhesion between the elastomers is thus obtained, or dispersion of elastomers or plastomers with the fibers of the pulp.
• polychloroprene, polybutadiene acrylonitrile, polyacrylate and polyvinyl acetate have been noted.
• This second elastomeric primer is introduced in a proportion of 0.1 to 3% of the total.
• the retention product introduced into the paste lowers the zeta potential and at the same time reduces the degree of refining by fixing the fines and by crosslinking between the long-chain polyelectrolyte molecules and the cellulose fibers of the sheet. .
• the successive additions - at determined intervals - of auxiliary products to the dough distribute very finely over the surface of the fiber where they present - in the form of a veil - an adhesive base excellent for "soft" latex subsequent and constituting the main finishing product.
• the prepared and surface-modified dough will be brought to the top of the machine at a concentration of 0.4% in water.
• the necessary quantity of crosslinking resin (4 to 8%) is added thereto continuously.
• the sheet is then formed on the endless canvas to be finally dried.
• the formation of the sheet is done without obstacle to the felting of the fiber, that is to say without hindrance to the formation of water bridges which naturally bind the fibers together.
• the fibrous material leaving the endless fabric is dried to a humidity level of 8 to 15% and it then has an adequate absorption power which can be adjusted initially by refining the dough.
• the sheet is then introduced into the impregnation press, at the aforementioned degree of humidity (8 to 15%) to be introduced into the impregnation bath comprising between 15 and 45% of elastomeric resin or plastomer in the form of an aqueous dispersion.
• the impregnation bath based on elastomeric resin comprises, according to a characteristic element of the invention, the incorporation of a component constituting a gelling agent capable of causing coagulation of the elastomeric resin from a certain thermal level.
• the impregnation bath is maintained at a temperature below said pre-adjusted coagulation temperature so that the dispersion is stable at the level of the impregnation bath.
• the elastomeric polymer or plastomer of the impregnation bath can be chosen from the same family as the elastomers used as a second finish (in the dough preparation phase); however the polymer of the impregnation bath will be different in each case from that already used for the preparation of the surface of the fibers as a second bonding primer.
• the choice of the elastomeric impregnation resin will be determined with a view to good adhesion, that is to say good compatibility from the chemical and physical point of view between the two formulas, that is to say between the elastomer used as a second attachment primer and the elastomer for impregnation in the sheet.
• the pH of the impregnation bath is maintained at an acid value corresponding to a pH between 4 and 5 and preferably between 4 and 4.5, by adding in particular maleic acid or paratoluenesulfonic acid; adjusting the pH to obtain coagulation at the programmed temperature.
• the sheet After passing through the impregnation press and absorption of the quantity of dispersion provided, the sheet is led to the drying devices, in particular by infrared radiation and passage over heating rollers.
• the thermal rise to which the impregnated sheet is subjected then causes coagulation of the dispersion of elastomeric resin within the fibrous structure; this coagulation is accompanied by a release on the two surfaces of the sheet of a certain amount of water; it thus occurs when passing over the heating rollers a wet interface which opposes "dry” contact between the elastomeric resin and the surface of the roller and consequently prevents any parasitic deposition of this resin on the roller.
• the sheet thus formed can then receive surface coatings on one or on two sides.
• These coatings can be a simple protective varnish, but more commonly and more usefully, it will cause the establishment of layers giving antinomic properties from one side to the other, namely on one side a varnish of non-stick and hydrophobic character, while on the other side a layer facilitating the subsequent attachment of an adhesive mass or any other element to obtain a self-adhesive assembly.
• Film forming temperature greater than 10 ° C.
• BASF Polysar products with higher proportions of butyl and octyl esters
• the styrene content is between 50 and 65%.
• the film formation temperature is above 10 ° C.
• products with a styrene content of approximately 30% were chosen, the film formation temperatures of which are less than 5 ° C.
• the surface preparation can be carried out with polychloroprene dispersions having a low tendency to crystallize, the impregnation with an impregnation press compensating for this effect. Very good results are obtained with a subsequent impregnation based on polybutadiene-acrylonitrile latex and polyvinyl acetate latex or blends of these with types of polychloroprene latex (Dupont, Bayer) which do not crystallize.
• Polyvinyl acetate is suitable for surface preparation, not only as a homopolymer but also as a copolymer with acrylates maleinates and other derivatives of polyvinyl alcohol, especially since these are highly polymerized types with film forming temperatures above 10 ° C.
• an impregnating product - with regard to the uses mentioned at the beginning - it is used only as a cutting partner for the latexes of nitril, butadienestyrene or acrylic esters.
• the polyethers of propylene-ethylene, the methylether of polyvinyl alcohol, the polyoxyethylenes are coagulating agents, called “gelling agents” like other products of polycondensation of different aliphatic diols with long chains. They have the property of becoming insoluble in water during a rise in temperature after which, there is spontaneously a general coagulation of the dispersion. At the same time, the entire amount of water is released We work at pH values below 5.
• Polyvinyl alcohol also gives hydrophilicity.
• Polyglycol, triethanolamine, glyoxal have softening, plasticizing and hydrophilic functions.
• Certain resins can be used for the physical reinforcement of the fiber to fiber bond (rosin resin, rosin ester) or for the chemical crosslinking of fibers (melamine formaldehyde resins, phenolformaldehyde resins). Under very specific conditions (high temperature, energy-rich rays), the combinations of urea-formaldehyde, melamine-formaldehyde and phenol-formaldehyde also crosslink the impregnation product.
• One of the aspects of the invention which also contributes to the finishing of the paper, is the application of protective varnish to one side of the sheet.
• different preparations can be used: - or those based on trivalent chromium complexed with stearic acid - or those based on melamine resins and long chain fatty acids (Sunsize) which give good covering varnishes.
• the most suitable resins are formaldehyde melamines and water-soluble crosslinkable ureas. These coatings can be called "release" coatings commonly used for adhesive tapes.
• Latex Polysar PL 3540 100.0% Butylstearate 10 -15% latex Arcopal N 300 0.65% of latex Nopco NDW 0.1 - 0.3% of latex Chromium stearochloride complex (Cr +++) 4.0% latex or Sunsize 134/137 3 - 6% of the latex 2) DOW DL 86824 Latex 100.0% Palatinol 12.0% latex Sunsize 137 1 - 4% of latex Arcopal N100 1.8% of latex Nopco NDW 0.3O% of latex Chinaclay 6.9% of latex 3) Latex Polysar PL 7560 100.0% Palatinol C 10.0% latex Latecol D 0.36% of latex MF 400 resin 4.64% of latex Arcopal N300 1.5% of latex Nopco NDW 0.10% latex Triethanolaminemonostearate 4.40% of latex
• an integral impregnation of the paper is carried out in order to constitute a pre-anchoring capable of improving the efficiency and the resistance of the adhesive layer deposited subsequently.
• the following basic formulas were used:
• the invention also covers various variants which allow, by the use of elastomeric resins, in particular natural or synthetic latexes, to obtain an impregnation of the sheet while adopting a pH lying in a wider range than previously mentioned and likely to be between 3 and 33.
• the primers generally deposited by the transformers in the form of a coating layer tend over time, because of the migration of the charges, to deplete the adhesive capacity of the adhesive mass. This results in a gain in efficiency of the adhesive mass anchored to the paper having undergone the pre-anchoring impregnation according to the invention.
• the method according to the invention is therefore a factor in improving the quality and efficiency as well as a source of substantial savings; the transformer can indeed obtain identical efficiency while benefiting from a weight saving in the use of the adhesive mass of between 15 and 30%.

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• Paper (AREA)

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Citations (3)

• 1989
  • 1989-05-31 FR FR8907198A patent/FR2647819B1/fr not_active Expired - Fee Related
• 1990
  • 1990-05-31 DE DE1990604499 patent/DE69004499T2/de not_active Expired - Fee Related
  • 1990-05-31 EP EP19900401474 patent/EP0406039B1/de not_active Expired - Lifetime

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