EP0067076B1 - Process for the continuous manufacture in an aqueous environment of fibrous webs containing latex or a similar composition and/or a phenoplastic or aminoplastic, webs so obtained and their optional reuse - Google Patents

Description

The present invention relates to a new process for the continuous production in an aqueous medium of sheets of fibrous materials - and in particular paper - containing latex in their mass.

The invention also relates to the sheets of fibrous material which can be obtained using this method.

The global need for special papers is growing. This is particularly true for water-resistant papers intended for the manufacture of abrasives, adhesives, artificial leathers, etc. It is mainly latex which gives these special papers their impermeability, their flexibility and their resistance, and it is mainly the phenoplasts or the aminoplasts which allow the laying of various suitable plasters that the manufacture of these various special papers requires.

• - la feuille continue de matière fibreuse est enroulée normalement lors de sa production sur un mandrin pour former une bobine,
• - la bobine obtenue est ensuite passée en longueur continue sur une autre machine en un, deux, trois -ou même plus- passages qui ont pour but le dépôt sur une ou les deux faces de la feuille de matières fibreuses, de diverses couches (latex, résines, etc.).

To produce these various special papers, we generally proceed as follows:

• - the continuous sheet of fibrous material is wound normally during its production on a mandrel to form a coil,
• - the coil obtained is then passed in continuous length on another machine in one, two, three - or even more - passages which aim at depositing on one or both sides of the sheet of fibrous materials, various layers (latex , resins, etc.).

It is only then that the sheet, after proper drying, is again wound into a reel. This means that in order to obtain the desired paper, it is necessary to repeat the winding and unwinding operations a plurality of times, each time applying a new layer. This obviously puts a heavy burden on the cost price of a coil. Until now, we have never succeeded in operating at once (for example by mixing the raw or refined pulp with latex) to lead directly to the desired paper. This may be due to the presence of adhesions and deposits of latex (or resins) in the circuit for implementing the mixture or on the sheet-making machine, phenomena which make continuous production impossible quickly. This can also be due to the very poor retention of latex and resins on the fibrous material. The fact remains that despite the evidence of a spectacular lowering of the cost price if latex (or other additives) could be added to the very mass of the dough, this simplification of manufacture has never been successful yet. we have always resorted to a plurality of passages, long and expensive.

In US-A-2,563,897 and US-A-2,601,597, a process has been described in which a precipitation agent is added to the aqueous suspension of fibers, followed by an aqueous suspension of latex particles. These latex particles are therefore precipitated, that is to say agglomerated with fibers. The retention tests carried out by the Applicant have shown that the retention of the latex particles to the fibers is relatively low. This therefore results in a loss of latex particles, during the manufacture of the sheets of paper. In addition, the sheets of paper thus obtained do not have the desired uniformity.

The object of the present invention is therefore to provide a new process for the continuous production of this latex-containing fibrous material, which better meets the needs of the practice than the methods aiming at the same object previously known, in particular in that it not only eliminates a whole series of coating steps by making paper from fibrous materials containing latex perfectly bonded to the fibers, but also to obtain paper that is perfectly homogeneous, more homogeneous and more resistant than that obtained by previously known methods.

• - ajustement du pH entre 4 et 5,5,
• - addition d'un électrolyte dont la polarité est de signe contraire à celle du latex utilise,
• - addition du latex sous forme d'une suspension de fines particules divisées et stabilisées à un pH acide compris entre 4et 5,
• - réajustement du pH du mélange aux valeurs précitées.

The subject of the present invention is a process for the continuous manufacture in an aqueous medium of sheets of fibrous materials containing latex in their mass, characterized in that the pulp containing the fibrous materials is prepared before being admitted to the manufacturing circuit and the manufacturing table, as follows, and respecting the order indicated:

• - pH adjustment between 4 and 5.5,
• - addition of an electrolyte whose polarity is of opposite sign to that of the latex used,
• - addition of latex in the form of a suspension of fine particles divided and stabilized at an acidic pH between 4 and 5,
• - readjustment of the pH of the mixture to the above values.

According to the invention, the fibrous material can consist of paper pulp and / or glass fibers and / or synthetic fibers and / or textile fibers.

The process described in the present invention is more particularly suitable for the production of papers whatever the starting paper pulp: mechanical pulp, semi-chemical pulp, chemical pulp, unbleached chemical pulp, bleached chemical pulp, soda pulp, sulphate paste, kraft paste, bisulfite paste, rag paste, macerated straw paste, leached straw paste, etc.

By pursuing the study of the various operating conditions, and in particular the physical, chemical, physico-chemical parameters, the quality of the raw materials and the problem of recovery, the applicant has succeeded in bringing a whole series of improvements and improvements which have resulted in the production of fibrous mixtures of exceptional quality, both in the field of industrial and medical adhesive papers, as in the field of highly refined papers up to a dripping index of 95 ° SR (method of SCHOPPER-RIEGLER).

According to a particularly advantageous embodiment of the process which is the subject of the present invention, the polyelectrolyte used is a high molecular weight polyelectrolyte, greater than 15,000, with a strong positive potential.

It is precisely by examining the evolution of the electrostatic charges of fibrous mixtures that the applicant has found that by using on the one hand, a polyelectrolyte with a strong positive potential and on the other hand On the other hand, fine latex particles stabilized at acid pH, the internal cohesion of the prepared material is achieved by extremely fine crosslinking of the latex molecules on the fibrous materials, thus constituting an intimate graft of two elements (fiber and latex) by intermediate of the polyelectrolyte used. This crosslinking is remarkably homogeneous and reproducible in a very reliable manner. It is this crosslinking which gives the fibrous sheets in accordance with the present invention their properties which differ completely from those of the sheets containing the latex prepared according to the processes of the prior art (cf. for example the French documents -fr-A-2 388 915, 2 429 291, FR-A-2 357 676, FR-A-2 447 420).

According to an advantageous embodiment of the process which is the subject of the present invention, the latex used is natural latex.

According to another advantageous embodiment of the process which is the subject of the present invention, the latex used is an artificial latex (chlorobutadiene polymer or acrylic latex in particular).

In accordance with the invention, the latex solution used has a solids content of between 5 and 50%, and preferably between 7 and 75%, its viscosity (Brookfield) is between 30 and 650 centipoises at 25 °, and the amount of latex is between 3 and 75% (in dry product) relative to the total dry weight of fibrous materials).

According to an advantageous embodiment of the process which is the subject of the present invention, the diameter of the divided latex particles is between 0.01 and 0.5 μ. and preferably between 0.1 and 0.2u ..

According to an advantageous embodiment of the subject of the invention, the polyelectrolyte solution used has a solids content of between 0.2 and 10%, and the amount introduced into the suspension of fibrous materials is between 0.1 and 3.5% of the dry product relative to the total dry weight of the latex for the first addition and between 0.1 and 2% of the dry product relative to the total dry weight of fibrous materials, for the second addition.

According to the invention, the antifoam solution has a solids content of between 2 and 20%, and the amount added to the total mixture is between 0.05% and 0.25% of the total dry weight of fibrous materials.

According to an advantageous embodiment of the process which is the subject of the present invention, the pH is adjusted using hydrochloric acid and / or sulfuric acid and / or alumina sulfate.

In accordance with the invention, the solution of phenolic resin (or aminoplast) has a content of approximately 50 to 85% in solid matter, a viscosity (Brookfield) of between 5,500 and 7,000 centipoise, and the amount added to the mixture (in dry product) is between 0.01 and 50% relative to the total dry weight of the fibrous materials.

_. According to a particularly advantageous embodiment of the subject of the invention, the fibrous material also contains in its mass, dyes and pigments and / or fungicides and / or insecticides and / or flame retardants and / or bonding agents and / or an inert mineral filler.

In accordance with the invention, it is possible to apply, during the manufacture of the sheet of fibrous materials, on one or both sides of said sheet, various products taken from the group which comprises: starches, carboxymethylcelluloses, suspensions acrylics, polyvinyl alcohols, flame retardants, fungicides, insecticides, colorants, barriers to organic solvents, bonding agents, magnetic coating agents, mineral and organic fillers.

All these applications are made possible precisely thanks to the simplification of the process according to the invention, which allows the addition in the mass of the fibrous material, latex and / or resins.

In accordance with the invention, the fibrous material used is a fibrous material based on pulp recycled from waste paper, the added latex consists of a mixture of ethylacrylate and acrylonitrile copolymers and its proportion relative to the dry weight of the materials fibrous is between 40 and 55%.

• - d'amidons (solubilisés ou insolubilisés)
• - de carboxyméthylcelluloses(solubilisées ou insolubilisées)
• - de suspensions acryliques de toute nature,
• - des alcools polyvinyliques (solubilisés ou insolubilisés)
• - des solutions barrières aux solvants organiques
• - des agents de collage naturels ou synthétiques
• - des produits liants, etc...

The process according to the present invention makes it possible to obtain papers of excellent quality meeting the standards and criteria of usual use, while starting from a recycled pulp from old paper. This can be obtained thanks in particular to the presence of fine particles of crosslinked latex and thanks to the possibility of subjecting the sheet, after its formation in the so-called "wet" manufacturing part, to various treatments and applications, and in particular, applications:

• - starches (solubilized or insolubilized)
• - carboxymethylcelluloses (solubilized or insolubilized)
• - acrylic suspensions of any kind,
• - polyvinyl alcohols (solubilized or insolubilized)
• - barrier solutions to organic solvents
• - natural or synthetic bonding agents
• - binding products, etc ...

As an example of a special treatment (valid for both ordinary papers and for waste paper based on waste paper), the treatment which gives papers non-stick properties should be mentioned more particularly.

• - déposition sur une face du support d'une couche antiadhésive permettant ultérieurement le bobinage et le déroulement du produit fini pour utilisation,
• - déposition sur l'autre face du support initial (et sur une autre machine) d'une couche adhésive.

Adhesive papers (medical, industrial, technical) are currently manufactured from a paper support of 50 to 160 g / m ² . This support is impregnated with a polymer or copolymer or a mixture of polymers (generally based on styrene) in one or two passes. This operation finished, this impregnated support paper is subjected to two operations carried out in a solvent medium:

• - deposition on one side of the support of a non-stick layer subsequently allowing the winding and unwinding of the finished product for use,
• - deposition on the other side of the initial support (and on another machine) of an adhesive layer.

The Applicant has found that the process according to the present invention makes it possible to apply the layers non-stick in aqueous media. This facility is considerable, since the introduction of solvents in the papermaking workshops posed serious problems.

In accordance with the present invention, the layer of non-stick material is formed by an aqueous suspension of carboxymethylcellulose with a content of between 0.01 and 10% and brought for 5 to 25 minutes at 90-95 ° C.

According to a particularly advantageous embodiment of the subject of the present invention, the suspension of carboxymethylcellulose additionally contains from 0.01% to 85% of polyester and / or from 0.01% to 85% of polyester and / or 0.01% to 75% of a silicone emulsion with anionic or nonionic potential stabilized in an aqueous medium at a pH between 5 and 6.

The present invention also relates to sheets of fibrous materials obtainable according to the process according to the invention. According to the invention, the internal cohesion of this sheet is ensured by very fine and homogeneous crosslinking of the latex particles on the fibers which constitutes an intimate graft between the fibers and the latex particles produced by means of the polyelectrolyte. The paper thus obtained and which can be used for many industrial uses (abrasive papers, adhesive papers, tear-proof papers for bags, posters, etc., papers for the preparation of artificial leather, paper for free covers, papers for waterproof envelopes, papers for the manufacture of bags for vacuum cleaners, etc.), has excellent mechanical characteristics which classify it among the best, thanks in particular to its breaking length, to its burst strength, to its breaking strength by tensile strength, its suitability for thermoforming, its high resistance to use in an aqueous medium, its resistance to repeated bending, etc.

Another extremely important characteristic of the paper according to the invention is its homogeneity demonstrated by the electron microscope and which clearly differentiates it from all the other papers currently on the market.

The present invention relates to the reuse and recovery of the fibrous materials obtained in accordance with the process described. One of the advantages and not least of the process according to the present invention lies in the possibility of relatively easily recycling any fibrous material obtained according to the present invention, and this unlike all papers containing latex and prepared according to the processes of the prior art.

This repulpability and recycling operation is characterized in that it is carried out in an aqueous medium, cold, in the presence of a wetting agent and in the presence of a small amount (0.01 to 0.15% relative to the volume of water and 0.2 to 1.5% relative to the weight of dry fibrous materials) of chloride ions and / or sulfate ions and / or sulfamate ions. It is of course the extremely fine crosslinking of the latex molecules on the fibrous material which explains the easy repulbability of the papers prepared in accordance with the present invention. In addition to the foregoing arrangements, the invention also comprises other arrangements which will emerge from the description which follows.

The present invention relates in particular to the process and the installations for manufacturing sheets of fibrous materials (and in particular paper) containing, in their mass, latex or the like and / or phenoplasts or aminoplasts and the sheets of fibrous materials thus obtained, thus that the means specific to the implementation of these methods, as well as the overall methods and the production lines in which the methods and the installations in accordance with the present invention are included.

The invention can be better understood using the additional description which follows, which refers to examples of implementation of the process which is the subject of the present invention, using the installation shown diagrammatically by way of non-limiting example in the appended drawing, to an analytical experimentation report and to a recycling installation shown diagrammatically in the appended drawing.

It should be clearly understood, however, that these examples, report and installation are given solely by way of illustration of the subject of the invention, of which they do not in any way constitute a limitation.

PREPARATION EXAMPLES: EXAMPLE 1 Preparation of the Paper Containing the Latex in Its Mass

The fibrous material from a pulp factory is introduced into the tank 1 in the presence of water and coloring matter if necessary, and undergoes appropriate stirring therein allowing the fibrous particles to be suspended. The solids content of the mixture is adjusted to about 2.5%. The prepared fibrous suspension is conveyed to the storage tank 2, then to section 3, known as refining and hydration of the fiber, so that the fibrous material undergoes the structural modifications necessary for subsequent sheet forming. In the particular case of paper, the structural modification must give the mixture a drip index according to the SCHOPPER-RIEGLER method, between 10 and 50 ° SR.

The fibrous material thus prepared is then introduced into the mixing tank 8.

• a) le latex à caractère anionigue (ou une suspension acrylique) de viscosité Brookfield comprise entre 30 et 650 centipoises ayant un haut pouvoir filmogène à partir de 0° C, est introduit dans la cuve 4 munie d'une agitation adequate, pour y subir une dilution aqueuse en vue de constituer une solution dont la teneur en solides soit comprise entre 5 et 50 %.
• b) Dans la cuve 5 munie d'une agitation appropriée et d'un moyen de chauffage (serpentin ou double enveloppe par exemple), on prépare une solution aqueuse d'un polyélectrolyte de polarité contraire à celle du latex (à caractere cationigue dans le cas présent: par exemple une polyamine soluble dans l'eau). La teneur en solides de la préparation doit être comprise entre 0,2 et 10 %.
• c) La cuve 6 munie d'une agitation appropriée sert à la preparation d'une solution aqueuse d'un produit antimousse. La dilution est ajustée de manière que la teneur en solides soit comprise entre 2 et 20 %.
• d) La cuve 7 munie d'une agitation appropriée est utilisée pour le stockage d'une solution de résine (phénoplastes ou aminoplastes) contenant entre 55 et 85 % de matières solides et d'une viscosité Brookfield comprise entre 5500 et 7500 centipoises (à 25°C).

During this time, the following reagents and raw materials are prepared:

• a) the latex of anionic nature (or an acrylic suspension) of Brookfield viscosity of between 30 and 650 centipoises having a high film-forming power from 0 ° C., is introduced into the tank 4 provided with adequate stirring, in order to undergo there an aqueous dilution in order to constitute a solution whose solids content is between 5 and 50%.
• b) In the tank 5 provided with appropriate stirring and a heating means (coil or double jacket for example), an aqueous solution of a polyelectrolyte of polarity opposite to that of the latex (of cationic character in the present case: for example a water-soluble polyamine). The solid content of the preparation should be between 0.2 and 10%.
• c) The tank 6 provided with appropriate stirring is used for the preparation of an aqueous solution of an anti-foam product. The dilution is adjusted so that the solids content is between 2 and 20%.
• d) The tank 7 provided with appropriate stirring is used for the storage of a resin solution (phenoplasts or aminoplasts) containing between 55 and 85% of solid matter and a Brookfield viscosity of between 5500 and 7500 centipoise (at 25 ° C).

• La matière fibreuse préalablement préparée et introduite dans la cuve 8, est amenée sous agitation à un pH compris entre 4 et 5,5, et de préférence entre 4 et 4,5 par addition d'un acide qui peut être l'acide chlorhydrique, l'acide sulfurique ou le sulfate d'alumine. La solution d'électrolyte préparée dans la cuve 5 est introduite dans le mélange fibreux de la cuve 8 sous agitation, dans une proportion comprise entre 0,1 et 3,5 % de produit sec par rapport au poids sec total de latex mis en oeuvre dans l'étape suivante, et plus particulièrement entre 0,5 et 2,5 %. La solution d'antimousse préparée dans la cuve 6 est incorporée au mélange de la cuve 8, sous agitation, dans un rapport de produit sec de 0,05 à 0,25 % du poids sec total de matières fibreuses. Le pH est ensuite réajusté, si nécessaire, aux valeurs indiquées précédemment. La solution de latex préparée dans la cuve 4 est alors ajoutée par injection dans le mélange de la cuve 8, sous agitation appropriée, dans une proportion comprise de préférence entre 3 et 60 % de produit sec par rapport au poids sec total de matières fibreuses. Au mélange ainsi obtenu dans la cuve 8, il convient d'ajouter sous agitation appropriée, une dose complémentaire de l'électrolyte préparé dans la cuve 5, comprise entre 0,01 et 2 % en produit sec par rapport au poids sec total de matières fibreuses, pour s'assurer du dépôt et de la fixation complète du latex sur la matière fibreuse employée. La solution de résine phénolique stockée dans la cuve 7 est ensuite introduite sous agitation lente dans le mélange de la cuve 8, dans une proportion en produit sec comprise entre 1 et 50 % par rapport au poids sec total de matières fibreuses. Le pH du mélange final ainsi obtenu dans la cuve 8 est ensuite réajusté, si nécessaire, aux valeurs indiquées précédemment. La totalité de la préparation est alors acheminée dans la cuve de stockage 9, puis dans la cuve 10 alimentant le circuit de fabrication d'une-machine de fabrication d'une bande continue de papier.

We then operate as follows:

• The fibrous material previously prepared and introduced into the tank 8 is brought with stirring to a pH of between 4 and 5.5, and preferably between 4 and 4.5 by addition of an acid which may be hydrochloric acid, sulfuric acid or alumina sulfate. The electrolyte solution prepared in tank 5 is introduced into the fiber mixture of tank 8 with stirring, in a proportion of between 0.1 and 3.5% of dry product relative to the total dry weight of latex used in the next step, and more particularly between 0.5 and 2.5%. The antifoam solution prepared in tank 6 is incorporated into the mixture of tank 8, with stirring, in a dry product ratio of 0.05 to 0.25% of the total dry weight of fibrous materials. The pH is then readjusted, if necessary, to the values indicated above. The latex solution prepared in tank 4 is then added by injection into the mixture of tank 8, with appropriate stirring, in a proportion preferably between 3 and 60% of dry product relative to the total dry weight of fibrous materials. To the mixture thus obtained in tank 8, an additional dose of the electrolyte prepared in tank 5 should be added with appropriate stirring, between 0.01 and 2% as dry product relative to the total dry weight of materials fibrous, to ensure the deposit and complete fixation of the latex on the fibrous material used. The phenolic resin solution stored in the tank 7 is then introduced with slow stirring into the mixture of the tank 8, in a proportion of dry product of between 1 and 50% relative to the total dry weight of fibrous materials. The pH of the final mixture thus obtained in tank 8 is then readjusted, if necessary, to the values indicated above. The entire preparation is then conveyed to the storage tank 9, then to the tank 10 supplying the manufacturing circuit of a machine for manufacturing a continuous strip of paper.

• - amidons solubles ou insolubilisés de toute nature,
• - carboxyméthylcelluloses solubles ou insolubilisées,
• - suspensions acryliques,
• - alcools polyvinyliques,
• - solutions pour traitement ignifuge, fongicide, insection,
• - matières colorantes,
• - solutions barrieres aux solvants organiques en général,
• - agents de collage synthetiques,
• - enduction magnétique,
• - charges minérales,
• - produits de synthèse, etc...

The suspension contained in the tank 10 undergoes continuously in section 11, an aqueous dilution bringing the total quantity of solids in the mixture, at distribution point 12, to a value between 0.2 and 1.5%. The distribution point 12 continuously feeds the section 13 for forming the sheet, usually called "wet part", in which the sheet is formed by removing the water from the mixture through a rotating metallic (or plastic) cloth. . The drained water, then sucked in by vacuum, is recovered at point 13a to be recycled at 1 and 11. The sheet calibrated in width at the end of part 13, is conveyed to the wringing section by pressure 14, then that the excess width or trim is recovered at point 13b, to be recycled in the storage tank 8. The sheet thus formed continuously, is then conveyed to the drying section 15 in which each side of the sheet is dried alternatively using the drum dryer battery. The solids content of the sheet at the entrance to the drying section 15 is generally between 25 and 50%. After drying in section 15, the sheet can be passed, if desired, into a coating section 16 where different products, or simply water, can be applied to one or both sides. In the particular case of papermaking, the usual name for this coating material can be taken from nonlimiting examples, the press or "Size-Press", the different coating processes on one or two sides such as champion systems, air knife, drag blade, etc. The passage of the sheet during continuous production in this coating section is optional. It can be used to provide additional, specific and specific properties to the products used in this section, and for the creation of new materials from a continuous sheet containing in its mass fibrous materials, latex or acrylic suspensions, phenolic resins. By way of nonlimiting examples, the following products can be used in section 16 after appropriate preparation in tanks 17, 18, 19, dosed, mixed or not in tank 20, sieved and diluted adequately in section 21:

• - soluble or insoluble starches of any kind,
• - soluble or insolubilized carboxymethylcelluloses,
• - acrylic suspensions,
• - polyvinyl alcohols,
• - solutions for fire-retardant treatment, fungicide, inspection,
• - coloring matter,
• - barrier solutions to organic solvents in general,
• - synthetic bonding agents,
• - magnetic coating,
• - mineral fillers,
• - synthetic products, etc ...

In the case of a passage in section 16, the sheet is then re-dried simultaneously, on each side, in section 22. If this optional treatment in section 16 is not used, the sheet passes directly from the section 15 in section 22. On leaving section 22, the sheet can be engaged in section 23, with a view to imparting it with additional or particular properties by a thickness calibration treatment, embossing or frosting. The sheet can also be engaged in section 24 where it undergoes radiation at high temperature making it possible to ensure, if necessary, complete polymerization of the materials composing it.

As for the treatment in section 16, the treatments in sections 23 and / or 24 are optional, but these additional operations can bring properties for particular uses. If sections 23 and / or 24 are not used, the sheet is fed directly into section 25 where it is wound on a reel.

Example 2: Preparation of a backing paper for abrasives

• - 76,3 % de fibres de bois résineux, blanchies
• - 0,35 % d'électrolyte à caractère cationique
• - 0,10 % d'antimousse
• - 20 % de latex à caractère anionique
• - 3,25 % de résine phénolique.

This paper contains (expressed as% of the dry product):

• - 76.3% of softwood fibers, bleached
• - 0.35% cationic electrolyte
• - 0.10% antifoam
• - 20% latex with anionic character
• - 3.25% phenolic resin.

This sheet of paper is prepared continuously, as described in Example 1, however without passing through section 16, but with passage through section 23 for calibration, then directly to section 25.

Example 3: Preparation of a backing paper for abrasives, printable

• - 75 % de fibres de bois résineux, blanchies
• - 0,30 % d'électrolyte cationique
• - 0,10 % d'antimousse
• - 20 % de latex anionique
• - 3,20 % de résine phénolique
• - 1 % d'amidon de maîs oxydé
• - 0,20 % d'urée-formol
• - 0,20 % d'agent de collage.

This paper contains (expressed as% of the dry product):

• - 75% of softwood fibers, bleached
• - 0.30% cationic electrolyte
• - 0.10% antifoam
• - 20% anionic latex
• - 3.20% phenolic resin
• - 1% oxidized corn starch
• - 0.20% urea-formaldehyde
• - 0.20% sizing agent.

This paper is prepared with passage in sections 16 → 22 → 23 → 25.

Example 4: Preparation of a backing paper for adhesives

• - 73 % de fibres de bois résineux, blanchies
• - 26,5 % de latex anionique
• - 0,45 % de polyélectrolyte cationique
• - 0,05 % d'antimousse.

This paper contains (expressed as% of the dry product):

• - 73% of softwood fibers, bleached
• - 26.5% anionic latex
• - 0.45% cationic polyelectrolyte
• - 0.05% antifoam.

This paper is prepared according to the process described in Example 1, with a direct passage from section 15 to section 25.

Example 5: Preparation of a printable backing paper for adhesives

• - 70 % de fibres de bois résineux, blanchies
• - 28,3 % de latex anionique
• - 0,45 % d'électrolyte cationique
• - 0,05 % d'antimousse
• - 0,20 % d'urée-formol
• - 1 % d'amidon de maïs oxydé.

This paper contains (expressed as% of the dry product):

• - 70% of softwood fibers, bleached
• - 28.3% anionic latex
• - 0.45% cationic electrolyte
• - 0.05% antifoam
• - 0.20% urea-formaldehyde
• - 1% oxidized corn starch.

This paper is prepared according to the process described in Example 1, with the passage in sections 16 → 22 → 2!

Example 6: Preparation of a paper intended for the manufacture of bags for vacuum cleaners

• - 48,5 % de fibres de bois de résineux, écrues
• - 48,5 % de fibres de bois de résineux, blanchies
• - 2,85 % de latex de type anionique
• - 0,15 % d'électrolyte de type cationique

This containing paper (expressed as% of the dry product):

• - 48.5% softwood fibers, unbleached
• - 48.5% of softwood fibers, bleached
• - 2.85% anionic type latex
• - 0.15% cationic electrolyte

This paper is prepared according to the process described in Example 1, with the passage in the following sections: Section 15 → Section 22 → Section 25.

Example 7: Preparation of a paper intended for the manufacture of tear-resistant envelopes

• - 63 % de fibres de bois de résineux, blanchies
• - 36 % de latex de type anionique
• - 1 % d'electrolyte de type cationique

This paper contains (expressed as% of the dry product):

• - 63% of softwood fibers, bleached
• - 36% anionic type latex
• - 1% cationic electrolyte

This paper is prepared as described in Example 6.

Example 8 Preparation of a Paper with a Non-Adhesive Layer

The procedure is as described in Examples 4 and 1, with passage in the following sections: 1 to 15, then 16 → 22 → 23 → 25.

• - fibres de bois résineux, blanchies: 73 %
• - complexe d'éthylacrylate et d'acrylonitrile stabilisé à pH 4,2-4,5:26,5 %
• - polyamine à haut poids moléculaire: 0,45 %'

The product, before entering section 16, has, for example, the following composition: (expressed as dry product):

• - softwood fibers, bleached: 73%
• - ethylacrylate and acrylonitrile complex stabilized at pH 4.2-4.5: 26.5%
• - high molecular weight polyamine: 0.45% '

(for example the polyelectrolyte sold under the brand "Primafloc C-3"

by ROHM & HAAS)

- defoamer: 0.05%

• on introduit, sous agitation, dans l'eau, une dose de carboxyméthylcellulose en poudre ou en granules, de façon à constituer une solution dont la teneur (exprimée en sec) soit comprise entre 0,05 et 5 %. On porte ensuite cette solution à une température de 90-95°C et on maintient à cette température pendant 20 minutes environ, puis on laisse refroidir.

The non-stick formulation is prepared in tank 17 as follows:

• a dose of carboxymethylcellulose in powder or granules is introduced, with stirring, into water, so as to constitute a solution the content of which (expressed as dry) is between 0.05 and 5%. This solution is then brought to a temperature of 90-95 ° C and maintained at this temperature for about 20 minutes, then allowed to cool.

An aqueous emulsion of silicone previously stabilized at a pH of 5.2 is poured into the tank 18 containing water until a concentration of approximately 20% of silicones is obtained.

In tank 19, an aqueous solution is prepared containing approximately 20% (expressed as dry matter) of polyester emulsion previously stabilized at pH 5.4, an emulsion whose Brookfield viscosity (at 25 ° C) is between 200 and 1 000 centipoises.

• 80-120 parties de solution 17
• 2-15 parties de solution 18
• 2-25 parties de solution 19

The three solutions (17,18,19) ready, they are mixed in the tank 20 as follows:

• 80-120 parts of solution 17
• 2-15 parts of solution 18
• 2-25 parts of solution 19

The dry extract of the solution contained in the tank is between 2 and 8%.

• - fibres de bois résineux, blanchies: 71 %
• - copolymère acrylique: 26 %
• - polyélectrolyte: 0,43 %
• - antimousse: 0,04 %
• - matière anti-adhèsive (déposée sur une seule face): 2,53 %

This solution thus obtained is deposited on a single face of paper, which, after the passages in sections 22-23-25, has the following composition:

• - softwood fibers, bleached: 71%
• - acrylic copolymer: 26%
• - polyelectrolyte: 0.43%
• - defoamer: 0.04%
• - non-stick material (deposited on one side): 2.53%

Example 9: Recovering used paper

The installation necessary for the recycling of old latex-based paper is shown schematically in Figure 2.

• - fibres de bois résineux écrues: 45,5 %
• - fibres de bois résineux blanchies: 45,5
• - latex: 8,85 %
• - polyélectrolyte: 0,15 %

Is introduced into the tank 101 containing 2000 liters of water containing 0.1% bleach p / volume, 500 kg of waste and trimmings of a paper which has, for example, the following composition:

• - unbleached softwood fibers: 45.5%
• - bleached softwood fibers: 45.5
• - latex: 8.85%
• - polyelectrolyte: 0.15%

The agitator 102 is started, and agitated until about 80% of the paper is disintegrated. This disintegration is verified by the usual control procedures in stationery. At this stage, there are still some very fine agglomerates known in stationery jargon as "buttons" or "pastilles". n then passes the mixture thus obtained through a disintegration device 105, called a "defiler" (for example, defasterer of the "Hydraflaker" brand produced by BLACK CLAWSON), by recycling the juice via the piping 105 to the tank 101 .

For this operation, the repulpability time in the tank 101 was 25 minutes, the re-tacking time 15 minutes, or a total of 40 minutes to make the 500 kg of fibrous material reusable, directed towards reuse by the piping 104.

Example 10: Recovery of used paper with very high latex content

• - Fibres de résineux blanchies: 51,2 %
• - Latex type éthylacrylate/acrylonitrile: 45 %
• - Polyélectrolyte: 1,8 %
• - Agent de collage synthétique: 0,20 %
• - Phénoplastes: 2 %
• - Carboxyméthyleellulose: 0,8 %

Composition of the starting paper:

• - Bleached softwood fibers: 51.2%
• - Ethylacrylate / acrylonitrile type latex: 45%
• - Polyelectrolyte: 1.8%
• - Synthetic bonding agent: 0.20%
• - Phenoplasts: 2%
• - Carboxymethylellulose: 0.8%

The procedure is as described in Example 2, but 0.15% bleach w / volume is introduced. The disintegration time was 40 minutes and the de-tacking time was 15 minutes, or 55 minutes for the 500 kg of material used. The raw material thus recovered is reused in a conventional printing-writing support manufacture at a rate of 10% of dry product relative to the total dry weight of the support produced.

ANALYTICAL EXPERIMENTATION REPORT

The tables below summarize the main characteristics of the products obtained in accordance with the process of the present invention (Examples 9 and 10), compared with commercial products containing latex.

Table 1 summarizes the mechanical characteristics and Table II represents the characteristics of a paper in which a fibrous material based on recycled pulp was used:

It results from an examination of the figures summarized in Table I, that the mechanical qualities of the paper in accordance with the present invention are superior, and this even for the latex content which is 50% lower than that of a commercial paper. .

The papers obtained according to the process according to the present invention not only have excellent physical resistance, but their suitability for printing coated sheets is quite good, both in exposure and in ink, clarity and color rendering .

Table 11 reflects the particularly advantageous qualities obtained by the process in accordance with the present invention, on the basic fibrous materials consisting exclusively of recycled pulp from waste paper.

It follows from the above description that, whatever the methods of implementation, production and application adopted, a process is obtained for the continuous preparation of sheets of fibrous materials containing in their mass latex or the like. and / or phenoplasts or aminoplasts, which has, compared to processes aiming at the same goal, previously known, significant advantages such as the advantage of supplying, by a simple and economical method, papers of excellent quality for very numerous industrial uses. , and in particular papers for abrasives in dry or aqueous medium, backing papers for adhesives, backing papers for artificial leathers, backing papers for book covers, papers for albums, papers for tear-proof posters, papers advertising papers, papers for adhesive labels and for stickers in general, paper backing for metallization, paper backing for washable draperies, papers for vacuum cleaner bags, papers for filtration, papers for books, documents, magazines, heavily and frequently handled, papers for the production of banknotes, papers for thermoforming in general, and all paper supports requiring very high resistance to tearing, folding, wear, water, while retaining very great flexibility, as well as high mechanical resistance.

• - l'avantage de présenter un temps d'essorage du matelas fibreux sur une toile de formation de feuille d'une machine à papier, inférieur à 15 secondes et même, dans certaines conditions, compris entre 4 et 10 secondes,
• - l'avantage de retenir tout le latex (ou analogue) mis en oeuvre par une reticulation complète sur la matière fibreuse utilisée, assurant ainsi une absence totale de particules de latex non fixées dans les eaux d'égouttage, supprimant ainsi tout exces de consommation de matière première et tout le problème de nettoyage de circuits de fabrication ou de pollution des effluents de l'usine.

In addition to these advantages, two other very important advantages should be mentioned, namely:

• the advantage of having a spinning time of the fibrous mat on a sheet-forming canvas of a paper machine, less than 15 seconds and even, under certain conditions, between 4 and 10 seconds,
• - The advantage of retaining all the latex (or the like) used by complete crosslinking on the fibrous material used, thus ensuring a total absence of non-fixed latex particles in the drainage water, thus eliminating any excess consumption of raw material and the whole problem of cleaning production circuits or pollution of factory effluents.

As is apparent from the above, the invention is in no way limited to those of its modes of implementation work, production and application which have just been described more explicitly; on the contrary, it embraces all the vaiiantes which may come to the mind of the technician in the matter, without departing from the framework defined by the claims.

Claims (13)

1. A process for the continuous manufacture in an aqueous medium of sheets of fibrous materials containing latex in their mass, characterised in that the pulp containing the fibrous materials is prepared as follows and in the sequence indicated before being admitted to the manufacturing circuit and manufacturing table:

- adjustment of the pH between 4 and 5.5,

- addition of an electrolyte whose polarity is of the opposite sign to that of the latex or the like used,

- addition of the latex in the form of a suspension of fine divided and stabilized particles at an acidic pH of between 4 and 5,

- readjustment of the pH of the mixture to the aforesaid values.

2. A process according to claim 1, characterised in that the polyelectrolyte used is a polyelectrolyte of high molecular weight, above 15 000, having a highly positive potential.

3. A process according to claim 1 or 2, characterised in that the fibrous material is formed of paper pulp, glass fibres, synthetic fibres, textile fibres, or by a mixture thereof.

4. A process according to any one of claims 1 to 3, characterised in that the latex used is natural latex.

5. A process according to any one of claims 1 to 3, characterised in that the latex used is a chlorobutadiene polymer or acrylic latex.

6. A process according to any one of claims 1 to 5, characterised in that the latex solution used has a solids content of between 5 and 50%, and preferably between 7 and 15%, in that its Brookfield viscosity is between 30 and 650 centipoises at 25° C and in that the quantity of latex is between 3 and 75% of dry product with respect to the total dry weight of fibrous materials.

7. A process according to any one of claims 1 to 6, characterised in that the diameter of the latex particles of the suspension is between 0.01 and 0.5V.

8. A process according to any one of claims 1 to 7, characterised in that the polyelectrolyte solution has a solids content of between 0.2 and 10%, and the quantity introduced into the suspension of fibrous materials is between 0.1 and 3.5% of the dry product with respect to the total dry weight of the latex.

9. A process according to any one of claims 1 to 8, characterised in that the fibrous material also contains in its mass dyes and pigments and/or fungicides and/or insecticides and/or fire-resistant products and/or sizing agents and/or an inert mineral filler.

10. A process according to claim 1, characterised in that the addition of the latex suspension to the pulp containing the fibrous material is effected by injection.

11. A process according to any one of claims 1 to 10, characterised in that the fibrous material used is a fibrous material based on recycled waste paper pulp, the latex added is in the form of a mixture of ethylacrylate and acrylonitrile copolymers and its proportion with respect to the dry weight of the fibrous materials is between 40 and 55%.

12. A process for the re-utilization and recovery of sheets obtained by the process according to any one of claims 1 to 11, characterised in that these sheets are repulped and recycled in an aqueous medium, in the cold state, in the presence of a wetting agent and in the presence of a quantity of between 0.2 and 1.5% with respect to the weight of the dry fibrous materials, of chloride ions and/or sulphate ions and/or sulphamate ions.

13. A sheet of fibrous materials containing latex in its mass, obtainable by the process according to any one of claims 1 to 11, characterised in that the internal cohesion of this sheet is provided by a very fine and homogeneous reticulation of the latex particles on the fibres, which forms an intimate graft between the fibres and the latex particles, said graft being provided by means of the polyelectrolyte.

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