EP0006390B1 - Process of forming a fibrous web by the papermaking technique in order to improve the binding and retention, web obtained by this process and its use as a substitute material for asbestos products and as a printing or writing support - Google Patents

Description

The present invention relates to a new process for the preparation of a fibrous sheet by the papermaking process, including the precipitation of binder and fillers, in order to improve the bonds, the mechanical properties, the retention of fillers and thus allow the reduction of material losses and water pollution. It also relates to the fibrous sheet obtained according to this process and its application in particular in the field of coatings to replace asbestos and in the field of print-write supports.

It is known that paper and cardboard mainly consist of noble cellulosic fibers (that is to say originating in particular from softwood pulp and / or hardwood) in association, where appropriate, with a mineral filler (in particular the talc, kaolin, calcium carbonate, magnesium carbonate) and a binder, and that they may also contain auxiliary agents such as in particular bonding agents, retention agents, anti-siime agents and brighteners optical.

In the field of asbestos replacement, it is known that, in the published French patent application No. 2,357,676, a process has been proposed for preparing a fibrous sheet from plant or animal fibers, d 'a mineral filler and a binder. However, this process has many drawbacks (poor retention and poor mechanical properties of the final product, in particular) and could not be exploited industrially.

In addition, we know that in the past, technical solutions have been advocated using specific retention agents to solve the retention problem, see for this purpose British patents n ° 1 407 100, 1 338 759, 1 372 146 and 1,338,513, and Americans No. 2,657,991 and 3,184,373.

We also know that the increasingly high prices of noble cellulose fibers have led the paper industry to seek alternative products and raw materials. Among the technical solutions which have been envisaged, there may be mentioned those which consist in increasing the content of mineral filler introduced into the mass in order to decrease the consumption of fibers. However, it turns out that these solutions generate (i) a significant reduction in the mechanical properties of the sheet substrate (in particular the tensile strength, the burst strength, and, above all, the internal cohesion and the rigidity) and ( ii) difficulties in manufacturing and use (because the fragility of the sheet substrate can be the source of a reduction in production rates in order to avoid breakages on the machine and consequently waste) .

Thus, the technical solution proposed by French patent n ° 1 033 298, which consists in preparing a thick paper from fibers and a mineral filler, is not particularly suitable in the field of print-write supports, because it leads to a soft end product. Furthermore, the technical solution proposed by the aforementioned US patent No. 3,184,373, which consists in preparing a print-write medium from fibers, a mineral filler and a mixture of retention agents, is unsatisfactory in the sense that the flocs formed by the fibers and the mineral filler are weakly linked due to the absence of a binding agent: moreover, said flocs are unstable and do not withstand turbulence in the head circuits of the paper machine, as indicated in said American patent, column 7 lines 37 et seq.

According to the invention, it is recommended to solve the problem of improving the bonds and the retention, a new technical solution including the precipitation of a binder and a mineral filler, and which is based on the use of an agent flocculant before and after the introduction of the binder and which is directly usable when we want to increase the mineral filler content to have a high mineral filler-fibers weight ratio between 2 and 9, or when we want to improve the mechanical properties of papers existing, or finally when it is desired to increase the rate of remaining mineral filler of a paper having a mineral filler-fibers weight ratio of between 0 and 2 without affecting its mechanical properties.

One of the aims of the invention is to propose a unique process making it possible to prepare (a) a fibrous sheet intended to replace asbestos in the field of covering panels, in particular floor covering panels, and (b) a sheet fiber intended for use in the field of print-write media and special papers.

Another object of the invention is to provide a sheet product which is rot-proof and / or non-flammable and which has good dimensional stability in the dry state, in the wet state and under heat, and good properties of thermal and acoustic insulation, so that asbestos can be replaced, as we know that the use of the latter involves (i) the use of complicated installations entailing significant investment and operating costs and (ii) the compliance with very strict safety and hygiene rules, to avoid any risk of absorption or inhalation of asbestos fibers and dust.

Another object of the invention is to improve the mechanical properties of fibrous sheets useful in particular in the field of printing-writing and more precisely the two important properties of internal cohesion and rigidity. On a technical level, it is proposed to improve the mechanical properties of existing papers, without modifying the content of non-binding mineral filler, and, on an economic level, it is proposed to increase the content of non-binding mineral filler on papers and to overcome the drawbacks of the reduction in all of the mechanical properties, in particular the cohesion internal, the rigidity and the tear that the increase in said mineral filler content generates.

Among the advantages of the invention, there may be mentioned in particular the savings in material and energy (higher dryness on entry into the dryer of loaded papers, hence faster drying), and, in addition, an increase in the production speed (especially in the manufacture of roto-offsets).

• a) les applications visant le domaine des revêtements en remplacement notamment de l'amiante, à partir d'une feuille fibreuse ayant un rapport pondéral charge minérale non liante-fibres compris entre 2 et 9, et avantageusement compris entre 3 et 9 ;
• b) les applications visant le domaine des supports d'impression-écriture et de papiers spéciaux à partir d'une feuille fibreuse ayant un rapport pondéral charge minérale non liante-fibres compris entre 2 et 9, et utilisable en tant que support pour héliogravure, offset, flexographie, typographie, impression taille-douce, photocopie, papier chèque, étiquette, couché classique, couché moderne, édition, affiches publicitaires (ignifugées ou non ignifugées), journaux, annuaires, écriture (manuscrite ou avec machine à écrire), cahiers, cartonnettes, couvertures, ou encore support pour reprographie, pour papier diazo, support abrasif, anti-adhérent ou stratifié.

Among the applications of the process of the invention, one can notably mention:

• a) applications targeting the field of coatings to replace in particular asbestos, from a fibrous sheet having a weight ratio of non-binder mineral filler-fibers of between 2 and 9, and advantageously between 3 and 9;
• b) applications targeting the field of printing-writing supports and special papers from a fibrous sheet having a non-binder mineral-to-fiber weight ratio of between 2 and 9, and usable as rotogravure support, offset, flexography, typography, intaglio printing, photocopying, check paper, label, classic coated, modern coated, publishing, advertising posters (flame retardant or non flame retardant), newspapers, directories, writing (handwritten or with typewriter), notebooks , cardboards, covers, or even support for reprography, for diazo paper, abrasive support, non-stick or laminate.

By "fibrous sheet or even" sheet substrate here is meant a composite material prepared by the papermaking process and comprising fibers, an organic binder and at least one flocculant; this composite material can, where appropriate, also comprise a non-binding mineral filler and one or more conventional additives in stationery.

By “mineral sheet” here is meant a particular fibrous sheet prepared by the papermaking route and comprising fibers, a binder and a mineral filler, and in which the quantity of mineral filler is relatively large compared to that of the fibers.

By “base mixture” here is meant a mixture constituted by the fibers and the non-binding mineral filler.

By “improvement of the mechanical properties” is meant here the improvement of the mechanical properties of the existing fibrous sheets, on the one hand, and the maintenance of the mechanical properties when the content of non-binding mineral filler in the said sheets is increased, on the other hand .

In the following, the weight ratio of non-binder mineral filler to fibers has been designated by the letter R.

• a) on prépare une suspension aqueuse renfermant 100 parties en poids sec d'un mélange de base ayant un rapport pondéral charge minérale non liante-fibres R compris entre 2 et 9 ;
• b) on introduit dans cette suspension 0,01 à 4 parties en poids sec de floculant ;
• c) on introduit dans le mélange résultant 0,2 à 30 parties en poids sec de liant organique ;
• d) on introduit dans le mélange résultant 0,01 à 6 parties en poids sec de floculant ; et
• e) on forme une feuille fibreuse à partir de la suspension aqueuse résultante selon une technique papetière puis essore et sèche ladite feuille.

The process for the preparation according to the invention of a fibrous sheet with a view to improving the bonds, the retention, in which a sheet is formed wet from an aqueous suspension containing fibers, an organic binder, a flocculant and a non-binding mineral filler, said process, in which the flocculant is introduced into the aqueous suspension containing the base mixture being characterized in that successively:

• a) an aqueous suspension is prepared containing 100 parts by dry weight of a base mixture having a weight ratio of non-binding mineral filler-fibers R of between 2 and 9;
• b) 0.01 to 4 parts by dry weight of flocculant are introduced into this suspension;
• c) 0.2 to 30 parts by dry weight of organic binder are introduced into the resulting mixture;
• d) 0.01 to 6 parts by dry weight of flocculant are introduced into the resulting mixture; and
• e) a fibrous sheet is formed from the resulting aqueous suspension according to a papermaking technique then wringed and dried said sheet.

• au stade 1, on prépare une suspension aqueuse en introduisant successivement 100 parties en poids de mélange de base, 0,01 à 4 parties en poids de floculant, le liant organique et 0,01 à 6 parties en poids de floculant, puis forme une feuille que l'on essore et sèche ;
• au stade 2, on soumet, si nécessaire, la feuille ainsi obtenue à au moins un traitement complémentaire.

According to an advantageous mode of implementation, one operates in two stages:

• in stage 1, an aqueous suspension is prepared by successively introducing 100 parts by weight of base mixture, 0.01 to 4 parts by weight of flocculant, the organic binder and 0.01 to 6 parts by weight of flocculant, then forms a leaf which is wrung and dried;
• in stage 2, the sheet thus obtained is subjected, if necessary, to at least one additional treatment.

In general, the additional treatment in stage 2 depends on the application envisaged, since the sheet obtained in stage 1 can be used as a basic support for any type of surface treatment (mechanical treatment, such as smoothing, calendering or graining; or chemical treatment such as surfacing or coating on a machine or outside a paper machine).

From the practical point of view, in particular for preparing a printing-writing medium and a product intended for replacing asbestos, it is preferred to use stage 1 then stage 2.

All the fibers are suitable for the preparation of the mineral sheet according to the invention, with the exclusion, of course, of asbestos fibers because of the difficulties mentioned above even if their use does not raise any technical problem. Among the fibers that are recommended, mention may in particular be made of natural organic fibers (such as cellulosic fibers, leather fibers, vegetable fibers) and synthetic fibers (such as polyamide, polyalkylene and polyester fibers), and mineral fibers (such as glass, ceramic, calcium sulfate and carbon fibers). It is of course possible to use mixtures of these fibers as well as the recovery fibers from waste paper and textiles. The fibers that can be used are 0.1 to 8 mm in length (for example: 0.2-3 mm for cellulose fibers, 3-6 mm for glass fibers and 0.1-0.3 mm for rock wool fibers ). The use of calcium sulphate fibers and in particular acicular gypsum fibers first requires saturation of the dilution waters with calcium sulphate (2 to 3 g / 1) so as not to dissolve said fibers in the suspension of the mixture. basic.

By way of illustration, a certain number of usable fibers has been given in table 1. The fibers cellulosics used alone or in combination with other fibers will have a Schopper-Riegler (SR) degree of between 15 and 65.

The preferred fibers are cellulose fibers because, although relatively expensive, they are still less expensive than other fibers. According to a preferred embodiment, it is recommended to use celulosic fibers in combination with polyalkylene fibers (in particular polyethylene and polypropylene). The use of polyalkylene fibers makes it possible to reinforce the solidity of the whole (internal cohesion in particular) and the dimensional stability. Indeed, these fibers which melt or soften at 120-200 ° C make it possible to reinforce the mechanical characteristics (adhesion in the dry state and in the wet state, dimensional stability), to confer on the paper a certain thickness (which , for a given thickness and grammage, reduces material costs), to reduce the quantity of binder and, if necessary, the quantity of glass fibers to be used, in particular in the production of covering panels, to promote drainage (higher speed, better production cost) during the formation of the sheet, and to reduce linting (in particular to avoid hard spots and surface irregularities). The hot treatment (at approximately 120-200 ° C for approximately 4 to 2 minutes) of the mineral sheets containing polyalkylene fibers can be carried out on the paper machine, or at the user's place (for example during the drying of the vinyl coating for 3 minutes at 180 ° C) outside the paper machine.

Among the mixtures of fibers containing polyalkylene fibers, it is advantageous to make use of mixtures of cellulosic fibers-polyethylene fibers (75:25) by weight and (16: 9) by weight, of the mixture of cellulosic fibers-polyethylene fibers-fibers of glass (16 9: 2) by weight, and a mixture of cellulosic fibers-polyethylene fibers-rock wool fibers (16 8: 3) by weight.

The binder to be used in stage 1 is an organic binder of natural or synthetic origin since mineral binders and cements have the drawback of having a long setting time. The organic binder bonds the constituents of the fibrous sheet to one another, can strengthen the physical properties of the fibrous sheet and acts as a stiffening agent. Among the binders which are suitable, mention may in particular be made of those in Table III below.

Advantageously, 2 to 15 parts by weight of binder will be used, per 100 parts by weight of the base mixture.

In the field of printing-writing media and special papers, the most interesting binder is starch which is a product consisting of a straight chain polymeric substance, amylose, and a three-dimensional polymeric substance, amylopectin, and more particularly starch containing 50 to 6,000 anhydroglucose units (in the linear polymer) per molecule, such as native starch (especially obtained from potato) and native corn starch, which contain 100 to 6000 anhydroglucose units (in the linear polymer) per molecule, and starches modified by chemical or enzymatic route (phosphoric esters of carboxymethylated starch, and enzymatically degraded starch) which contain from 50 to 3000 anhydroglucose units per molecule. These starches react, either with aluminum ions or with the synthetic cationic flocculants mentioned below, to form a complex which has a good affinity for the fiber and the filler. It is also possible to use ionically modified starches.

Starch having 50 to 6,000 anhydroglucose units (in the linear polymer) per molecule, is the preferred binder in the sense that (i) it surprisingly contributes to obtaining rigidity, "slamming and" striking paper (it acts as a stiffening agent which is important because we know that the increase in the load introduced into the support interferes, among other things, with the stiffness of the paper: a paper that is too soft "does not pass well rapid offset) (ii) it advantageously replaces the latexes which are expensive binders, and (iii) facilitates the repulping of broken parts.

In the field of coatings, the preferred binders are starch as indicated above, and especially latexes, in particular acrylic latexes such as L9 and L10 and styrene-butadiene latexes such as L12 and L13 (see Table III).

It is essential that, during the implementation of stage 1, the flocculant is introduced before and after the addition of the binder. Before adding the binder, it allows (i) the cationization of the fibers and, when a non-binding mineral filler is present, the precipitation of said filler on the fibers, and (ii) the flocculation of the binder when it is incorporated to the mixture constituted by the fibers and the flocculant or by the fibers, the filler and the flocculant. After the addition of the binder, it completes the flocculation thereof, strengthens the cohesion of the flocs, improves the overall retention and promotes drainage.

Of course, it is possible to use either the same flocculating agent before and after the addition of binder, or else different flocculating agents, or finally mixtures of flocculating agents.

Among the flocculants which are suitable, mention may in particular be made of metal salts such as in particular aluminum, iron (II), iron (III), zinc and chromium salts such as halides, sulfates and phosphates, and the others substances indicated in Table IV below. The preferred flocculant according to the invention is poly aluminum chloride which is a substance also known under the name of aluminum hydroxychloride, having the general formula (HO) _y Al _x Cl _{z ― y ― x} and which is in particular marketed by the Péchiney-Ugine-Kuhlmann Company under the brand name of "WAC".

The non-binding mineral fillers which are introduced, if necessary, in stage 1 according to the invention, are those which are commonly used in the paper industry and have a particle diameter less than or equal to 80 μm. The mineral fillers given in Table II below are particularly suitable after. The preferred filler consists here of calcium carbonate, talc, kaolin and their mixtures, the diameter of the particles being advantageously between 2 and 50 μm. Without departing from the scope of the invention, it is possible to use a filler coated with a polymeric substance improving the retention of said filler; for this purpose, it is possible to use charges which are coated and ready to use, or else to coat the charges before their incorporation into the aqueous suspension of the fibers.

As indicated above, the amount of non-binding mineral filler may depend on the application envisaged.

For example, it will be possible to obtain a fibrous sheet having a grammage in particular between 350 and 800 g / m ² , intended to be used in the field of coatings to replace asbestos where R is between 2 and 9 and advantageously 3 and 9 .

For example, it is also possible to obtain a fibrous sheet having a grammage of between 40 and 400 g / m ² , in particular 40-200 g / m ² , intended to be used in the field of printing-writing supports and special papers, when R is between 0.2 and 9. Are included in this case very loaded papers having an R between 2 and 9 and advantageously 3 and 9 for which, according to the invention, a large part of the fibers has been replaced by a less expensive filler than said fibers while favorably solving the technical problem of rigidity.

Other conventional additives in paper mills can intervene, if necessary, in stage 1, such as for example water-repellent agents (also called bonding agents), antibiotic agents, lubricating agents, anti-foaming agents or foam-breaking agents , optical brighteners, shading dyes. Among the suitable adjuvants, mention may be made in particular of the water-repellent agents in Table V and the auxiliary agents such as the substances A7 (optical brightener) and A10 (anti-foam) in Table VII.

According to one characteristic of the invention, the water-repelling agent is introduced in stage 1 after the organic binder and before 2 ^* fraction of flocculant. The amount of water repellent may be between 0.05 and 10 parts, advantageously between 0.05 and 5, and preferably between 0.1 and 3 parts by dry weight per 100 parts by weight of the base mixture, the agents preferred water repellents being substances H1 and H4 in Table V.

If necessary, at stage 1, at the same time as or after the water-repellent agent, is introduced at least one auxiliary agent chosen in particular from the group consisting of resistance agents in the wet state (0.1 to 5 parts by weight per 100 parts by weight of the base mixture), anti-foaming agents (0.05 to 0.2 parts by weight per 100 parts by weight of the base mixture), optical brighteners (0.1 to 0.3 parts by weight per 100 parts by weight of the base mixture), the shading dyes (in sufficient quantity) and, where appropriate, the lubricating agents (0.2 to 5 parts by weight per 100 parts by weight of the basic mixture: for example 0.2 to 3 parts by weight if R is low, and 1 to 5 parts by weight if R is relatively higher).

• A) améliorer l'aspect, l'uni de surface, augmeter (le cas échéant) la résistance superficielle et uniformiser les propriétés porométriques de la feuille pour une meilleure aptitude à l'impression ;
• B) diminuer le pouvoir absorbant vis-à-vis de l'eau, et éventuellement des solvants et des plastifiants ;
• C) obtenir une blancheur et/ou une opacité et/ou une brillance plus élevée ;
• D) renforcer les propriétés mécaniques à l'état sec et/ou humide ;
• E) augmenter la rigidité ; et
• F) obtenir les propriétés particulières telles qu'ignifugation, anti-adhérence, ingraissabilité, thermoscellabilité, et des effets spéciaux tels que effets barrières et imputrescibilité (résistances aux champignons et aux bactéries).

The sheet obtained in stage 1 is subjected, if necessary, to one or more additional treatments. on paper machine or outside paper machine, in particular for:

• A) improve the appearance, the surface uniformity, increase (if necessary) the surface resistance and standardize the porometric properties of the sheet for better printability;
• B) reduce the absorbency vis-à-vis water, and possibly solvents and plasticizers;
• C) obtain a whiteness and / or an opacity and / or a higher gloss;
• D) strengthen the mechanical properties in the dry and / or wet state;
• E) increase rigidity; and
• F) obtain the particular properties such as fireproofing, anti-adhesion, grease-proofness, heat-sealability, and special effects such as barrier effects and rot-proofing (resistance to fungi and bacteria).

The means to be used, for this purpose, are in particular the size-press or sizing press, the roll coater, the roll coater, the metal coater, air coater or the coater scrapes. In addition to these means, there are means for transforming the surface appearance (smoothing, calendering and / or graining).

In general, stage 2 is characterized in that at least one substance is chosen chosen from the group consisting of mineral fillers, organic binders and conventional adjuvants in stationery such as in particular sizing agents, dispersing agents, pigments, fluorescent agents, shading dyes, lubricating agents, viscosity modifying agents, anti-foaming agents, insolubilizing agents and antibiotics.

Of course stage 2 is implemented according to the objectives sought. For printing-writing, the aim is in particular the surface uniformity and the quality of the printability. For the manufacture of special papers, certain properties are targeted such as fireproofing, rot-proofing, resistance to oils, hydrophobicity, heat-sealability, non-sticking, coloring, conductivity and resistivity. resistance to chemical and physical eradication, barrier effect against solvents, waxes and paraffins. For the replacement of asbestos, the reduction in absorbency vis-à-vis water, solvents and plasticizers, dimensional stability, rot-proofing and, where appropriate, fireproofing are sought.

From a practical point of view, at least one binder will be used in stage 2, in particular a binder from Table VI given below, and, where appropriate, at least one substance chosen from non-binding mineral fillers (as described above in stage 1) auxiliary agents (such as those given in table VII below), and special adjuvants (such as those given in table VIII below).

In stage 2, among the products which are suitable for improving the printability qualities of the fibrous sheet, mention may be made for surfacing or sizing, in particular cellulose derivatives such as starches, carboxymethylcellulose, ethylcellulose, alginates, natural or synthetic binders, such as polyvinyl alcohol, gelatin, casein, dextrins, polymers or copolymers in emulsion. These products can be combined with a conventional sizing agent for stationery products such as dimeric alkyl ketenes, wax and / or paraffin emulsions, styrene, acrylic, vinyl dispersions, acrylonitriles, styrene-butadiene complexes, trivalent chromium of stearic acid or saturated fatty acids, organo-polysiloxannes.

The fibrous sheet can be, in stage 2, coated one or more times, on one or two sides with a pigmented layer. Among the products which are suitable for producing the coating bath, there may be mentioned in particular: conventional fillers of the stationery industry, such as those of the base mixture. For this use, the particles must be finer: pigments with 70 to 95% of particles less than or equal to 5 µm are preferably used. These fillers are generally previously dispersed with mineral dispersants (sodium polyphosphates) and / or organic dispersants (in particular polyacrylates), and must be combined with one or more natural or synthetic binders.

The amount of dry matter deposited in stage 2 can be variable, and in particular between 1 and 150 g / m ² , taking into account the different coating means that can be used and the final properties required. As an indication, in non-pigmented size-press, 1 to 10 g / m ² of dry matter may be applied. By pigmented coating with a Champion doctor blade you can apply between 3 and 30 g / m ² of dry matter on one side in a single pass. On an air knife we can apply 5 to 40 g / m ² of dry matter on one side in a single pass.

In rigid or flexible trailing blade, 5 to 40 g / m ² of dry matter can be applied to one face in a single pass.

Among the products which are suitable for reducing the absorbency vis-à-vis water, and possibly solvents and plasticizers, it is possible in particular to use the conventional sizing agents of the stationery already mentioned above.

Among the products which are suitable for reinforcing the physical characteristics in the dry and / or wet state one can in particular use the natural or synthetic binders, and the agents of resistance in the wet state already mentioned above.

Among the products which are suitable for improving the flammability properties by promoting the contact with the flame the formation of a carbon structure, mention may in particular be made of nitrogen compounds (in particular urea-formaldehyde and melamine-formaldehyde resins), derivatives of boron (in particular, ammonium borate, boric acid and its metal salts) ammonium sulfamate and antimony derivatives. Of course, the flame retardant reinforces, if necessary, the fire resistance properties which are imparted by the mineral filler introduced in stage 1, and, if necessary, by the mineral filler introduced in stage 2. Advantageously , use 2 to 15 parts by weight of flame retardant per 100 parts by weight of fibrous sheet to be treated.

Among the products which are suitable for improving the anti-adhesion, mention may in particular be made of organopolysiloxannes, trivalent chromium complexes of stearic acid or saturated fatty acid and waxes. Advantageously, 0.1 to 5 g of non-stick agent will be used per m ² of fibrous sheet to be treated.

Among the products which are suitable for improving the greasiness, mention will in particular be made of ammonium phosphate bis- (N-ethyl-2-perfluoroalkyl-ethyl sulfonamide) (trade name: Scotch-ban). Advantageously, 0.5 to 1% by weight of such an agent will be used relative to the weight of the fibrous sheet to be treated.

The barrier and / or heat-sealable properties of the fibrous sheet can be obtained by coating 1 or 2 faces with emulsion polymers or copolymers and in particular with ethylene-vinyl acetate copolymers, acrylic copolymers, vinylidene chloride copolymers.

Resistance to the development of molds and fungi can be obtained by additional surface treatment with a conventional bactericide and / or fungicide agent from the paper mill.

• - 100 parties en poids d'un mélange de base choisi constitué par les fibres et la charge minérale non liante ;
• - 0,02 à 10 parties en poids d'agent floculant ;
• - 2 à 30 parties en poids de liant ; et le cas échéant,
• - 0,05 à 10 et avantageusement 0,05 à 5 parties en poids d'agent hydrofugeant ; et en ce que le rapport pondéral (R) charge minérale non liante-fibres est compris entre 2 et 9.
• Après le stade 2, on obtient une feuille fibreuse à laquelle on a notamment apporté par enduction, imprégnation au moins un liant et, le cas échéant, au moins une substance choisie parmi les charges minérales non liantes, les agents auxiliaires et les adjuvants spéciaux.

Thanks to stage 1, a fibrous sheet is obtained from the papermaking process ... from a flocculant, a binder, and a mineral filler, characterized in that it contains:

• - 100 parts by weight of a selected base mixture consisting of the fibers and the non-binding mineral filler;
• - 0.02 to 10 parts by weight of flocculating agent;
• - 2 to 30 parts by weight of binder; and optionally,
• - 0.05 to 10 and advantageously 0.05 to 5 parts by weight of water-repellent agent; and in that the weight ratio (R) non-binding mineral filler-fibers is between 2 and 9.
• After stage 2, a fibrous sheet is obtained to which it has in particular been provided by coating, impregnation of at least one binder and, where appropriate, at least one substance chosen from non-binding mineral fillers, auxiliary agents and special additives.

The best mode of implementing the method of the invention has been described below.

Stage 1

The fibers are suspended at 10-50 g / l and in particular at 30-50 g / l in water [if cellulosic fibers are used these will have been previously defibrated and refined to a degree SR of 15 to 65] (for example an SR from 15 to 60) and advantageously from 15-15.5 to 40-45 when R is between 2 and 9 if calcium sulphate fibers are used these will be suspended in water saturated with calcium sulphate (2 to 3 g / I) and all dilution water will also be saturated with calcium sulphate; if fibers of another nature are used (mineral fibers and synthetic organic fibers), these will either be defibrated separately, or dispersed with vigorous stirring in a vat containing the refined cellulosic fibers; for certain applications where the S.R. degree is not very high (S.R. less than 35) it may be advantageous to refine the cellulosic fibers and the synthetic organic fibers together. The mineral filler under vigorous stirring is suspended in water at 300-600 g / l in a second tank then mixed with the fibers in a load-fiber weight ratio of between 2 and 9 (part of the mineral filler can if necessary, from the reinsertion of already loaded papers such as old paper and broken machine). The basic mixture is thus obtained.

The generally cationic mineral or synthetic flocculant is diluted in water from 1 to 10 times, then is introduced into the mixture consisting of fibers and the non-binding mineral filler, at a dose of 0.01 to 4, in particular 0, 01 to 3 parts as is per 100 parts by weight of the base mixture. Advantageously, an inorganic flocculant and preferably aluminum polychloride will be used.

The binder, preferably native starch for the printing-writing application, after having been previously baked at 80-90 ° C, or a latex in aqueous emulsion, is then incorporated into the mixture with stirring, at a concentration of between 15 and 100 g / I either batchwise or preferably continuously in the head circuits before the other additives. Can then be incorporated, either discontinuously in a mixing tank, or continuously in the overhead circuits: a water repellency agent, a whitening agent, one or more shading dyes, an anti-foaming agent, or breeze -foam, and possibly the lubricant.

The flocculating agent is again incorporated before the headbox (at a dose of 0.01 to 6, in particular from 0.01 to 5 parts by weight, per 100 parts by weight of the basic mixture) which, generally at this stage is still a mineral flocculant, in particular polychloride of aluminum which has an important role on flocculation, retention and drainage. These last two properties can be improved, if necessary, by also adding a conventional stationery retention agent.

The following additives: wet strength agents and antibiotics (bactericides and / or fungicides) are preferably introduced into the base mixture before the binder.

The resulting suspension is spun on a canvas of a paper machine. The nature of the canvas will have an important role on retention depending on the grammage of the mineral sheet and the speed of manufacture. We can for example use fabrics with plain fabric, knitting, simple twists. We can use, for example, plain fabric canvases 28 x 22 cm, 28 x 24 cm, 32 x 26 cm, 36 x 32 cm, or link canvases 26 x 25 cm, 28 x 27 cm. For the replacement of asbestos and for material thicknesses greater than 400 µm, spinning can be carried out under a low linear load of 0.5 to 35 kg / cm.

After formation of the sheet, a conventional pressing is carried out in the wet part by means of one or more coating presses, rising presses, offset presses or multiple presses, the presses being dressed or naked, then drying.

The fibrous sheet obtained in stage 1 can have a variable grammage depending on the desired applications. We can thus have a grammage between 40 and 800 g / m ² . It is observed that the fibrous sheet of stage 1 is dried much faster than a sheet of conventional cellulosic paper. Indeed, it is possible to gain, from the first dryers, more than 20 dryness points. This advantage is very appreciable and allows a substantial gain in production and a reduction in energy consumption.

Stage 2

The sheet obtained in stage 1 is subjected to one or more treatments on a paper machine or outside of a paper machine.

The quantities of materials deposited on the fibrous sheet during these surface treatments are very variable and obviously depend on the objectives sought and the manufacturing means used. In traditional printing-writing applications, these surface treatments can be of the type commonly used on cellulosic supports. For special applications, their nature will depend on the desired properties. In general, aqueous baths of 10 to 600 g / l will be used.

Other advantages and characteristics will be better understood on reading which will follow nonlimiting examples but given by way of illustration.

Example 1 Stage 1

A suspension of acicular gypsum fibers of 1.5 mm of average length is prepared at a concentration of 10 to 50 g / I in water saturated with CaS0 ₄ (approximately 2 to 3 g / I) and of cellulose fibers ( pulped and refined for a fattening level of 15 to 35 degrees SR). For 100 parts by weight of a basic mixture [comprising 2 to 9 parts by weight of mineral filler (kaolin) and 1 part by weight of fibers (55 to 90% by weight of acicular gypsum fibers and 45 to 10% in weight of cellulosic fibers)] successively the following additives are introduced to make a sheet on a paper machine:

Note: the bactericide and fungicide is preferably incorporated to the base mixture before the flocculant ^(1st fraction) and the binder ..

It is spun slightly in the wet part and then dried. This produces a flexible sheet of 350 to 800 g / _m 2.

Stage 2

The sheet thus obtained is impregnated by means of an aqueous bath comprising 200 to 400 g / l of the following formulation: flame retardant [ammonium sulfamate-ammonium phosphate-ammonium borate

The desired recovery is 20 to 50 g / m ² after drying. The material thus obtained can, if necessary, be slightly smoothed. A mineral sheet is obtained having flame retardant properties and useful in the field of asbestos replacement.

Example 2 Stage 1

From 100 parts by weight of the basic mixture [talc-cellulosic fibers in the weight ratio (3: 1) to (9: 1)] and the following additives:

Stage 2

The sheet thus obtained is impregnated by means of an aqueous bath comprising 300 to 500 g / l of the following formulation:

The desired recovery is 10 to 50 g / m ² (in dry matter). An asbestos replacement product is obtained with flame retardant properties.

Example 3

The sheet obtained in stage 1 of Example 2 is treated using an aqueous impregnation bath containing 200 to 400 g / l of the following formulation:

The recovery required after drying is 20 to 40 g / m ² . We obtain a product useful for replacing asbestos and not fireproof.

Example 4

Talc (500 g / l) of water is dispersed with vigorous stirring, then it is incorporated into a dispersion of cellulosic fibers refined to a degree SR of between 15 and 35. Per 100 parts by weight of a mixture of base [comprising 2 to 9 parts by weight of talc and 1 part by weight of cellulosic fibers] the following additives are successively introduced to make a sheet on a paper machine:

A sheet of 350 to 800 g / m ² is produced after draining, pressing, then drying, which is smoothed, if necessary, at the end of the paper machine. A non-flame retardant asbestos replacement product is obtained.

Example 5

The sheet obtained in Example 4 is subjected to a finishing treatment according to the operating methods described respectively in Example 1 (stage 2), in Example 2 (stage 2) and in Example 3, thus obtaining three impregnated mineral sheets which are good substitutes for asbestos.

Example 6

The procedure is as indicated in Example 4 starting from a basic mixture comprising kaolin (3 to 9 parts by weight) and slightly refined cellulosic fibers (1 part by weight) (SR degree between 15 and 35), a mineral sheet with properties similar to that of Example 4 is obtained.

The finishing of this sheet is carried out by impregnation as indicated in Example 5. An asbestos replacement product is obtained.

Example 7

The procedure is as indicated in Example 4, starting from a basic mixture comprising talc (2 to 9 parts by weight) and a mixture of F22 fibers (1 part by weight) consisting of cellulose fibers (95% by weight). and glass fibers (5% by weight). A mineral sheet is obtained which can be impregnated according to the methods described in Example 5 for the replacement of asbestos.

Example 8

A mineral sheet is prepared according to the method described in Example 4 from 100 parts by weight of a basic mixture [talc-cellulosic fibers (85:15) by weight] with the difference that the 10 parts by weight of binder L10 of example 4 are replaced by 5 parts by weight of binder L1 (total amount of L1: 7 parts by weight). This sheet is impregnated as indicated in Example 5. A replacement product for asbestos is obtained.

Example 9

A mineral sheet is prepared according to the method of example 4 from 100 parts by weight of a basic mixture [kaolin-cellulosic fibers (80:20) by weight] with the difference that the binder L10 of the example 4 is replaced by an equivalent amount of polychloroprene.

This sheet has better flame resistance than that of the material of Example 4. Of course, it is impregnated as indicated in Example 5. A replacement product for asbestos is obtained.

Examples 10 to 16

Several mineral sheets intended for replacing asbestos were prepared from the base mixtures and the other ingredients given in Table IX where the comparison products were also recorded (CP 1-CP 4).

The product of Example 10 is a sheet which has excellent mechanical properties in the dry state and in the wet state. Compared to a sheet according to the invention prepared with the same ingredients but without polyethylene fibers (the mixture F 21 comprising 16 parts by weight of F 1 and 9 parts by weight of F 11, being replaced by 25 parts by weight of F 1), the sheet of Example 10 leads to an improvement in internal cohesion by (40%), in tensile strength (by 15%) and in dimensional stability (by 30 to 40%).

Trials have been undertaken to study the importance of using the flocculant before and after the binder. Forms (without lubricant) were prepared to compare the sheets according to the invention with sheets prepared with the same ingredients but incorporating all the flocculant before or respectively after the binder. The results of table X below show that to obtain the same grammage as example 11 and respectively example 15, CP 1 and CP 2 and respectively CP 3 and CP 4 lead to significant losses under canvas. In addition, the preparation of CP 1 and CP 2 results in a slowing down of the drainage of 30 to 70% (for CP 1) and from 10 to 15% (for CP 2) compared to example 11.

In Table XI below, the physical and mechanical properties of mineral sheets according to the invention were compared with an asbestos sheet, here examples 1-4 having been obtained from a basic mixture of ratio R ( 85: 15), and Example 12 of an R report (83: 27).

In Table XII below, a sheet (A) of 400 g / m ² and 0.6 mm thick prepared according to the method of Example 4 (from a base mixture of talc - cellulosic fibers (85:15) by weight) with an asbestos sheet (B) 400 g / m ² and 0.6 mm thick. The results relate to sheets A and B and the materials obtained by laminating A or B on several supports (drywall, fiber cement and wood agglomerate), and are expressed in decibels (dB) as a function of the frequency (Hz) of the source. sound.

où

• Q est la puissance dissipée (en calorie/seconde),
• S est la surface de l'échantillon (en cm²),
• e est l'épaisseur de l'échantillon (en cm), et
• Δt est le gradient de température en °C

Finally, the thermal insulation was determined according to the following technique: a heating plate is placed between two identical samples whose thermal conductivity is to be measured; the assembly is pressed between two metal plates maintained at constant temperature; thermocouples continuously measure the temperature difference between the heating plate and each of the external plates; the heating plate is supplied with constant power then when the steady state is reached, the temperature distribution is linear inside the material to be studied, and the thermal conductivity is expressed by the relationship.

or

• Q is the power dissipated (in calories / second),
• S is the surface of the sample (in cm ² ),
• e is the thickness of the sample (in cm), and
• Δt is the temperature gradient in ° C

From the standpoint of thermal insulation, the sheet A of the invention (λ = 13.8 x 10. ⁵ cal / cm - sec - ° C) is much more interesting than the asbestos sheet B (λ = 26.5 x 10 ⁵ cal / cm · s · ° C).

All of these results and those of Tables XI and XII make it possible to conclude that the mineral sheets according to the invention have properties greater than or equal to those of asbestos.

From a practical point of view, the sheets according to Examples 1 to 16 can be used in particular for floor and wall coverings. The flame retardant sheets, if necessary, can be laminated, in particular on plasterboard panels, in order to create safety ceilings.

Example 17

By proceeding as indicated in Example 4, a sheet of 80 g / m ² is prepared which is smoothed, if necessary, at the end of the paper machine. This sheet can be used as a basic support for printing-writing.

Examples 18-20

The sheet obtained in Example 17 is subjected to a complementary treatment according to the methods of Example 1 (stage 2), of Example 2 (stage 2) and respectively of Example 3; three mineral sheets are obtained which can be used in the field of printing-writing.

Example 21

The procedure is as indicated in Example 4 by preparing a sheet of 80 g / m ² from a basic mixture comprising kaolin (3 to 9 parts by weight) and weakly refined cellulosic fibers (degree SR between 15 and 35). A mineral sheet is obtained having properties similar to those of Example 17 and which can be subjected to one of the complementary treatments of Examples 18 to 20.

Example 22

A sheet of 80 g / m ² is prepared according to the methods given in Example 7 from a base mixture comprising 2 to 9 parts by weight of talc and one part by weight of fiber F 22. A sheet is obtained mineral which can be treated according to the methods of Examples 18 to 20.

Example 23

A mineral sheet of 80-120 g / m ² is prepared according to example 4. This sheet is coated in size-press with an aqueous starch bath at 100 g / I for a recovery (in dry matter) of 2 to 4 g / m ² . A coating is then carried out on one or both sides of this sheet by means of a pigmented bath containing 400 to 500 g / l of the following formulation:

The recovery in dry matter is 10 to 20 g / m ² per side (if necessary, the bath may include one or more shading dyes).

The resulting material is, after drying, smoothed and then calendered. It has a good aptitude for offest printing. If necessary, it can be coated again outside the paper machine, in particular by means of an air knife, a trailing blade or a roll coater.

Example 24

The procedure is as indicated in Example 8 to prepare a sheet of 80-120 g / m ² . This sheet is then treated according to the methods of one of examples 18 to 20 to give a print-write support.

Example 25

A sheet of 40-200 g / m ² is prepared according to the methods described in Example 9. This sheet is then treated according to the methods of one of Examples 18 to 20 to give a print-write support.

Example 26

A mineral sheet of 93 g / m ² is prepared according to example 4 from a basic mixture [talc - cellulosic fibers (85:15) by weight]. This sheet is coated in size-press with an aqueous starch bath (100 g / I) containing an optical brightener and a blue shading dye (in sufficient quantity) for a recovery in dry matter of 2 g / _M ² . After smoothing, a sheet of paper for printing-writing having the following properties is obtained:

Examples 27 to 37

By implementing stage 1 from the quantities given in table XIII, supports are obtained having very good dimensional stability (high ash rate), good flatness, and an opacity of 83 to 85 for variable grammages. between 65 to 70 g / m ² . These layer supports are very acceptable for printing-writing and have a lower cost than conventional supports in this field.

In Table XIII, the amounts of the base mixture (mineral filler and fibers) are expressed in parts by weight, and the amounts of all the other ingredients are expressed in percentage by weight relative to the weight of the base mixture.

The sheet of Example 37 is perfectly suited as a basic support for wall covering.

Examples 38 to 57

From Examples 27 to 37, using stage 2 according to the methods of Table XIV (where the concentration and the composition of the treatment bath have been recorded), the mineral sheets of Examples 38 to 57 of Table XV are obtained. .

The size-press treatments give the mineral leaf good resistance to IGT tearing. Helio-tests are also good.

Among the specific applications, the following are cited:

The mineral sheet of Example 46 has in the AFNOR text (alcohol flame) a charred surface <60 cm ² (classification M1). There is no flame, nor points of ignition on the sheet. This support can be used for example as an advertising poster in places receiving the public.

The mineral sheet of Example 47 coated on one side has good printability and good resistance to oils (turpentine-test> 1,800 seconds). Type of use: labels for oil bottles, especially as the sheet has a good flatness, and does not fold in contact with water.

Examples 48 and 49 concerning a 1-sided or 2-sided coating for magazines (offset, rotogravure) and a 1-sided coating for labels (in particular for beer bottles).

The mineral support of Example 50, of good dimensional stability, melamine in size-press, can be used as an abrasive support. Its advantage is independently of the lower cost of the base support, a reduction in the resumption of resin for the total impregnation (less cellulosic fibers, talc is hydrophobic).

The mineral support of Example 51 is heat sealable and can be used in the packaging field.

The mineral sheet of Example 52 non-stick on one side can be used as transfer paper for coating of polyvinyl chloride or polyurethane.

The PVDC coating (2 layers) gives the mineral sheet of Example 53 a good impermeability to water vapor. The product obtained is useful in the field of food packaging.

The product of Example 54 essentially has good flexibility, good resistance to washing (plynometer> 500 rubs), good aptitude for gravure printing. The presence of polyethylene fibers in its composition promotes deep embossing (better permanence after washing). This support can be used as a wall covering.

The sheet of Example 55 has mainly good resistance to water, and can be used as a diazo support.

In Table XVI, the properties of mineral sheets obtained in stage 1 are indicated (examples 27, 28 and 32).

In Table XVII, a number of sheets obtained in stage 2 (examples 38, 39, 46 and 48) were compared with comparison products CP 5 and CP 6 (obtained from a standard cellulosic support having been subjected to a size-press with starch) and CP 7 (a classic cellulosic magazine). In this comparison it was found that “the IGT printability” is good, that the fireproofing classification according to the AFNOR standard is “M 1 for the product of example 46 and that the heli-test is“ good for the example 48 and CP 7.

Example 58

The procedure is as indicated in Example 10 (see Table IX) to obtain a mineral sheet having a basis weight of 80-120 g / m ² , and which has excellent mechanical properties in the dry and wet state due to the presence of polyethylene fibers. This sheet can be processed according to the methods described in Table XIV.

Example 59

Tests have been undertaken to study the importance of the use of the flocculant before and after the binder in the field of printing-writing for a loaded paper (example 59; R> 2). Formulas were prepared according to the indications in Table XXII where the quantities are given in part by weight (stage 1 only), the total quantities of flocculant being identical for Ex. 59, CP 13 and CP 14. The results, with regard to concerns the losses under fabrics, given in table XXIII confirm those of table X relating to the replacement of asbestos.

(See Tables on pages 14-34)

Claims (12)

1. Method for the preparation of a fibrous sheet by paper-making means with a view to improving the bond and/or retention, in which a sheet is formed by wet method from an aqueous suspension containing fibers other than asbestos fibers, said latter being excluded, an organic binder, a flocculating agent and, a non-binding mineral filler, in which the flocculating agent is introduced in the aqueous suspension containing the basic mixture constituted by the fibers and the non-binding mineral filler, said method which is carried out with industrial paper-making machines being characterized in that it consists in, successively:

a) preparing an aqueous suspension containing 100 parts by dry weight of a basic mixture having a non-binding mineral filler-fibers weight ratio (R) ranging between 2 and 9 ;

b) introducing in said suspension 0.01 to 4 parts by dry weight of flocculating agent,

c) introducing in the resulting mixture 2 to 30 parts by weight of mineral binding agent ;

d) introducing in the resulting mixture 0.01 to 6 parts by dry weight of flocculating agent ; and

e) forming a fibrous sheet from the resulting aqueous suspension according to a paper-making technique, then in de-watering and drying said sheet.

2. Method according to claim 1, characterized in that the resulting dry sheet is subjected to a surface treatment.

3. Method according to any one of claims 1 and 2, characterized in that, after addition of the binding agent in step c) and before addition of the flocculating agent in step d), a water-proofing agent is introduced in the aqueous suspension.

4. Method according to claim 3, characterized in that 0.05 to 5 parts by dry weight of water-proofing agent are used for 100 parts by weight of basic mixture.

5. Method according to any one of claims 1 and 2, characterized in that the organic binder is a starch containing in its amylose linear polymer part 50 to 6 000 anhydroglucose units per molecule.

6. Method according to claim 5, characterized in that the starch is the native starch of potato or native corn starch.

7. Method according to any one of claims 1 and 2, characterized in that the organic binder of step c) is a starch pre-cooked to 80-90 °C and containing 6 000 anhydroglucose units per molecule.

8. Method according to claim 2, characterized in that step 2 comprises at least one treatment selected from the group constituted by the mechanical surface treatments and the chemical surfacing and coating treatments.

9. Method according to claim 8, characterized in that the treatment of step 2 comprises the addition of a binder by means of an aqueous bath of 10 to 600 g/I, containing, if necessary, at least one substance chosen from the group constituted by the non-binding mineral fillers, the auxiliary agents, and the special adjuvants, fire-proofing agents, antibiotics and non-stick agents.

10. Fibrous sheet, characterized in that it is prepared according to the process of any one of claims 1 to 9, and in that it has a weight of 40 to 400 g/m².

11. Fibrous sheet, useful in particular in the field of coverings as a replacement for asbestos, characterized in that it is prepared according to the method of any one of claims 1 to 9 and in that it has a weight of 350 to 800 g/m².

12. Fibrous sheet according to claim 10 or 11, characterized in that it has been subjected to a surface treatment by chemical process so as to have a dry-material regain of 1 to 150 g/m²,