FR2505896A1 - Fibrous sheet e.g. paper prodn. - using pulp contg. latex and phenoplast or aminoplast resin - Google Patents

Abstract

Fibrous sheets are produced by (a) adjusting the pH of the pulp to 4-5.5, pref. 4-4.5, (b) adding an electrolyte having a polarity opposite to that of the latex or the like added in step (e), (c) adding an antifoam, (d) readjusting the pH to 4-5.5, if necessary, (e) adding a latex or the like, pref. by injection; (f) adding an electrolyte having the same characteristics as in (b), (g) opt. adding resins (phenoplasts or aminoplasts) and (h) readjusting the pH to the above values if necessary. The pulp is then processed into a sheet by conventional paper-making techniques. By incorporating the latex in the pulp prior to processing into a sheet, the process eliminates a series of coating steps involving winding and unwinding of continuous fibrous sheets as in prior art. The sheet obtd. is also more homogeneous and uniform than obtd. previously. The process is applicable to any type of pulp (e.g. mechanical, chemical, kraft or bisulphite). The sheets obtd. allow recovery of the fibrous materials in aq. medium.

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 or the like and / or phenoplasts or aminoplasts, as well as to sheets obtained using this process.

 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.

To produce these various special papers, one generally proceeds as follows - the continuous sheet of fibrous material is wound nor
improperly when produced 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 to deposit on one or both sides
sheet of fibrous material, various layers
(latex, resins, etc ...).

 It is only then that the sheet, after proper drying, is rewound 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 raw or refined pulp - with latex) to lead directly to the desired paper. This may be due to the presence of latches and deposits of latex (or resins) in the cir cuit for processing the mixture or on the sheet-making machine, phenomena which make continuous production impossible quickly. This may 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.

 The object of the present invention is therefore to provide a new process for the continuous production of fibrous materials containing a waterproofing agent such as latex, which better meets the needs of the practice than the processes aiming at the same goal. previously known, in particular in that it makes it possible not only to suppress a whole series of coating steps by carrying out the manufacture of paper from fibrous materials containing latex in their bulk, but also to obtain perfectly homogeneous paper - more homogeneous and more regular than that obtained by previously known methods.

The subject of the present invention is a process for the continuous manufacture in an aqueous medium of sheets of fibrous materials containing in their mass latex or the like and / or phenoplasts or aminoplasts, characterized in that the pulp containing the fibrous materials is prepared before its admission to the manufacturing circuit and the manufacturing table, as follows, and respecting the order indicated - adjustment of the pH between 4 and 5.5, and preferably between 4
and 4,5, - addition of an electrolyte whose polarity is of sign
contrary to that of the latex (or the like) used, - addition of an antifoam, - readjustment of the pH between 4 and 5.5, if necessary, - addition, preferably by injection, of the latex or the like, - second addition of electrolyte (with the same ca
characteristics as indicated above), - possibly addition of resins (phenoplasts or
aminoplasts), - readjustment of the pH to the values indicated above, if
necessary.

 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.

 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 solid content of between 5 and 50%, and preferably between 7 and 15%, its viscosity (Brookfield) is between 30 and 650 centipoise at 250, and the amount of latex is between 3 and 60% (in dry product) relative to the total dry weight of fibrous materials).

 According to an advantageous embodiment of the subject of the invention, the electrolyte is a polyelectrolyte, its 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 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 (as 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, dyes, 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 into the mass of the fibrous material, latex and / or resins.

 The present invention also relates to sheets of fibrous materials obtained according to the process according to the invention. 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 book covers, papers for envelopes raincoats, papers for making bags for vacuum cleaners, etc.), has excellent mechanical characteristics that rank it among the best, thanks in particular to its breaking length, its burst strength, its resistance 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.

 In addition to the foregoing provisions, the invention also comprises other provisions, 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 manufacturing 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 'nonlimiting example in the accompanying drawing.

 I1 must be understood however that the examples of implementation which will be described below, as well as the installation described in what follows and shown in the drawing, are given solely by way of illustration of the object of the invention, but in no way constitutes a limitation.

 The paper machine shown in the accompanying drawing will be described in detail in Example 1 below.

EXAMPLE 1
Preparation of the paper containing the latex in its mass
The fibrous material from a pulp mill 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 t. The prepared fibrous suspension is conveyed into the storage tank 2, then into 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-RIECLER method, between 10 and 500 SR.

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

Meanwhile, the following reagents and raw materials are prepared: a) anionic latex (or an acrylic suspension
que) of Brookfield viscosity between 30 and 650 cen
tipoises having a high film-forming power from OOC,
is introduced into the tank 4 provided with a suitable agitation
quate, to undergo an aqueous dilution with a view to consti
kill a solution with a solid content
between 5 and 50%.

b) In the tank 5 provided with appropriate agitation and a
heating means (coil or double jacket by
example), an aqueous solution of a poly is prepared
electrolyte of opposite polarity to that of latex (
cationic character in the present case: for example
a water-soluble polyamine). Solid content
of the preparation must be between 0.2 and 10%.

c) The tank 6 provided with appropriate agitation is used for the pre-
treatment of an aqueous solution of an anti-foam product.

The dilution is adjusted so that the content of so
lides is between 2 and 20%.

d) The tank 7 provided with appropriate agitation is used
for the storage of a resin solution (phenoplasts
or aminoplasts) containing between 55 and 85% of matter
solids and a Brookfield viscosity between 5500
and 7,500 centipoises (250C).

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 fibrous 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 comprised 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.

 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, that the excess width or trim is recovered at point 13b, to be recycled in the storage tank 9. 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, by way of nonlimiting examples, the size press or "Size-Press", the different coating processes on one or two faces such as champion systems, air gap, drag blade, etc. The passage of the sheet during continuous production in this coating section is optional. I1 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, resins As non-limiting 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 in such a way suitable in section 21 - soluble or insolubilized starches of any kind, - soluble or insolubilized carboxymethylcelluloses, - acrylic suspensions, - polyvinyl alcohols, - solutions for flame retardant treatment, fungicide, insecticide, - coloring matters, - 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. At the exit from section 22, the sheet can be engaged in section 23, with a view to giving it complementary or specific properties by a thickness calibration, embossing or glazing treatment.

The sheet can also be engaged in section 24 oA 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 provide 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
This paper contains (expressed as% of the dry product) - 76.3% of bleached resinous wood fibers - 0.35% of electrolyte with a cationic character - 0.10% of antifoam - 20% of latex with an 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
This paper contains (expressed as% of the dry product): - 75% of resinous wood fibers, bleached - 0.30% of cationic electrolyte - 0.10% of antifoam - 20% of 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 b 23) 25.

EXAMPLE 4
Preparation of backing paper for adhesives
This paper contains (expressed as% of the dry product) - 73% of bleached resinous wood fibers - 26.5% of anionic latex - 0.45% of cationic polyelectrolyte - 0.05% of 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 backing paper for printable adhesives
This paper contains (expressed as% of the dry product) - 70% of bleached resinous wood fibers - 28.3% of anionic latex - 0.45% of cationic electrolyte - 0.05% of 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) 25.

EXAMPLE 6
Preparation of paper for the manufacture of vacuum cleaner bags
This paper contains (expressed as% of the dry product): - 48.5% of softwood fibers, unbleached - 48.5% of softwood fibers, bleached - 2, X5% of 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 paper for the production of tear-resistant envelopes
This paper contains (expressed as% of the dry product) - 63% of bleached softwood fibers - 36% of anionic type latex - 1% of cationic type electrolyte
This paper is prepared as described in Example 6.

 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, backing papers for metallization, backing papers 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 supports- papers requiring very high resistance to tearing, folding, wear, water, while retaining great flexibility, as well as high mechanical resistance.

 As is apparent from the above, the invention is in no way limited to those of its modes of implementation, embodiment and application which have just been described more explicitly; on the contrary, it embraces all the variants which may come to the mind of the technician in the matter, without departing from the scope, or the scope, of the present invention.

Claims (1)

CLAIMS 2 - Process according to Claim 1, characterized in that the fibrous material can consist of paper pulp and / or glass fibers and / or synthetic fibers and / or textile fibers. necessary aminoplasts), - readjustment of the pH to the values indicated above, if teretic as indicated previously, - possibly addition of resins (phenoplasts or contrary to that of the latex or analogous used, - addition of an antifoam, - readjustment of the pH between 4 and 5.5, if necessary, - addition, preferably by injection, of latex or the like, - second addition of electrolyte having the same characteristics and 4.5, - addition of an electrolyte whose polarity is of sign  1 - Process for the continuous production in an aqueous medium of sheets of fibrous materials containing in their mass latex or the like and / or phenoplasts or aminoplasts, characterized in that the paste containing the fibrous materials is prepared before being admitted to the circuit and the manufacturing table, as follows and respecting the order indicated - pH adjustment between 4 and 5.5 and preferably between 4  30- Method according to any one of Claims 1 and 2, characterized in that the latex used is natural latex.  40- Method according to any one of Claims 1 and 2, characterized in that the latex used is an artificial latex (chlorobutadiene polymer or acrylic latex in particular).  5 - Process according to any one of Claims 1 to 4, characterized in that the latex solution used has a solid content of between 5 and 50% and preferably between 7 and 15%, in that its viscosity (Brookfield) is between 30 and 650 centipoise to 25 and in that the amount of latex is between 3 and 60% (as dry product) relative to the total dry weight of fibrous materials.  60- Process according to Claim 1, characterized in that the electrolyte is a polyelectrolyte, its solution has a solid 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 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.  7 - Process according to Claim 1, characterized in that the antifoam solution has a solid content of between 2 and 20%, and the amount added to the total mixture is between 0.05% and 0.25% by weight total dry of fibrous materials.  8 - Process according to Claim 1, characterized in that the pH is adjusted using hydrochloric acid and / or sulfuric acid and / or alumina sulfate.  9 - Process according to Claim 1, characterized in that the solution of phenolic resin (or aminoplast) has a content of approximately 50 I 85% in solid matter, a viscosity (Brookfield) of between 5,500 and 7,000 centipoises , and the amount added to the mixture (as dry product) is between 0.01 and 50% relative to the total dry weight of fibrous materials.  10 - Process according to any one of Claims 1 to 9, characterized in that the fibrous material contains, in addition 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.  11 - Method according to any one of Claims 1 to 10, characterized in that one can apply during the manufacture of the sheet of fibrous materials on one or both sides of said sheet, different products taken from the group which includes starches, carboxymethylcelluloses, acrylic suspensions, polyvinyl alcohols, flame retardants, fungicides, insecticides, dyes, barriers to organic solvents, bonding agents, magnetic coating agents, mineral and organic fillers.  120- Method according to Claim 1, characterized in that the addition of latex into the paste containing the fibrous material is carried out by injection.  13 - Sheet of fibrous materials, characterized in that it is obtained by the process according to any one of Claims 1 to 12.