EP0190069A1 - Treatment of a fibrous sheet obtained by paper-making techniques in view of improving its dimensional stability, and application, particularly in the field of floor or wall coverings - Google Patents

Abstract

The invention relates to a treatment process for improving the dimensional stability of a fibrous sheet obtained by papermaking process, and of which at least part of the fibers are cellulosic fibers, said process consisting in impregnating the sheet with a chemical composition containing at least one wetting agent and one binder.

Description

Treatment of a fibrous sheet obtained by the papermaking process in order to improve its dimensional stability and application in particular in the field of floor or wall coverings.

The invention relates to improving the dimensional stability of a fibrous sheet by supplying said sheet of chemicals in solution followed by a drying phase.

By "fibrous sheet" is meant here a material prepared by the papermaking route and comprising fibers of which at least a part is made up of hydrophilic fibers, in particular cellulosic; this material may, where appropriate, comprise a mineral and / or organic filler which is not a binder, an organic binder and one or more adjuvants conventional in stationery.

It is known that for certain applications, in particular floor or wall covering supports, posters, offset printing papers, papermakers and processors seek a high dimensional stability with respect to water or ambient humidity.

In the field of floor coverings, new supports have been used for a few years to replace asbestos cartons which were stable against water and humidity but presented a danger to the health of users. The substitute products are glass veil and mineral asbestos-free felt.

Mineral felts, although more economical for the transformer, are less interesting in terms of their dimensional stability, compared to glass veils which are at least as stable as asbestos felts with respect to humidity and water. .

The poor dimensional stability of mineral felts is mainly due to the cellulose fibers they contain. As the fibers are very hydrophilic, their dimensions vary greatly depending on the ambient humidity.

Papermakers have conducted a lot of research to improve the dimensional stability of such fibrous sheets.

The treatment of cellulosic supports is known by impregnation with resins of the melamine-formaldehyde type which can somewhat limit the water uptake of the cellulose fibers and thus improve dimensional stability. However, the improvement thus obtained is not very noticeable. (Cf. "Paper-cardboard-films-complex", June 1979 p.l4-l6).

It is also known that this improvement can be obtained by replacing cellulose with increasing amounts of hydrophobic fibers such as, in particular, mineral fibers and in particular glass fibers or rock wool, as well as to a certain extent synthetic fibers.

• - à l'épairage de la feuille lors de sa formation sur machine à papier,
• - à l'aspect de surface de support qui est à l'origine de défauts lors de la transformation ultérieure de ce support, tels que le peluchage et le relargage de ces fibres lors de l'enduction avec une matière synthétique.

But those skilled in the art know that large quantities of glass fibers are harmful:

• - the peeling of the sheet during its formation on a paper machine,
• - The appearance of the support surface which is the source of defects during the subsequent transformation of this support, such as the fluffing and salting out of these fibers during coating with a synthetic material.

It is also known that the improvement in dimensional stability can be obtained independently of the rate of hydrophobic fibers by chemical treatment of the fibrous sheet using wetting agents intended to make the cellulose fibers inert with respect to water and ambient humidity. A product known for this use in stationery is polyethylene glycol (hereinafter abbreviated as PEG) which is notably cited in "Paper, Cardboard, Films, Complexes", June 1979, p.14-16. Products of the same family of polyglycols and derivatives are described for the same use in documents US-A-4291101 of Nippon Oil and Fats Co. (polyoxyalkylene glycol monoacrylates and polyoxyalkylene glycol monomethacrylates) and EP-A-18961 of Rockwool AB ( polyoxyalkylenes).

• - cloquage du matériau synthétique couché sur le support lors du traitement thermique devant provoquer l'expansion (160-200°C) du fait de la dégradation à la chaleur de certains mouillants tels que le PEG.
• - inhibition de l'expansion du matériau synthétique, d'où une épaisseur irrégulière de la couche synthétique après expansion,
• - mauvais accrochage du matériau synthétique sur le support.

However, those skilled in the art know, in the field of supports for floor or wall coverings, that the supply of chemical wetting agents, in particular PEG, must be limited due to the loss in mechanical characteristics of the paper impregnated with such products and the difficulties encountered during the subsequent transformation of the support using a synthetic material such as plastisol (mixture of PVC and plasticizers, cf. EP-A-18961):

• - blistering of the synthetic material coated on the support during the heat treatment which should cause expansion (160-200 ° C) due to the degradation with heat of certain wetting agents such as PEG.
• - inhibition of the expansion of the synthetic material, hence an irregular thickness of the synthetic layer after expansion,
• - bad attachment of the synthetic material to the support.

Since the quantities of wetting agents which can be used for impregnating the fibrous sheet are limited, the possibilities of improving the dimensional stability with these chemicals are also limited.

All these techniques have therefore not so far made it possible, without major drawbacks, to obtain a sufficient improvement in the dimensional stability of the mineral felts, compared with that of the glass veils.

Furthermore, the treatment of cellulosic supports is known by impregnation with binders and wetting agents for purposes other than improving dimensional stability.

The wetting agent can in fact, as a surfactant, be used to modify the characteristics of the binder.

• - améliorer la dépose des liants sur les fibres papetières (cf. FR 1 250 132)
• - assouplir le papier imprégné de latex ou de bitume (cf. FR 2 481 333 et US 2 801 937)
• - ou tout simplement abaisser la tension superficielle des matériaux hydrophobes contenus dans les papiers ou les non- tissés imprégnés de latex ou de bitume pour en accroître le pouvoir absorbant vis-à-vis des liquides (cf. EP 42 259, US 1 995 623 et GB 770 730).

The wetting agent can be used in particular for:

• - improve the deposit of binders on paper fibers (cf. FR 1 250 132)
• - soften the paper impregnated with latex or bitumen (cf. FR 2 481 333 and US 2 801 937)
• - or quite simply lower the surface tension of hydrophobic materials contained in papers or nonwovens impregnated with latex or bitumen to increase their absorbency vis-à-vis liquids (cf. EP 42 259, US 1 995 623 and GB 770 730).

However, none of these documents aims to obtain a significant improvement in dimensional stability compared to the stationer's knowledge of the effects of wetting agents. Moreover, in the prior art, the doses of wetting agents used remain low relative to the weight of binder.

An object of the invention is to obtain an improvement in the dimensional stability of the coating supports for floor or wall coverings using a new chemical treatment.

Another object of the treatment of the invention is, with equal dimensional stability, to be able to reduce the rate of mineral fibers in the supports for floor or wall coverings.

Another object of the treatment of the invention is the improvement of the dimensional stability of other paper carriers containing cellulose fibers.

According to the invention, it has been found that the dimensional stability of the fibrous sheet with respect to moisture and water is remarkably improved when the fibrous sheet containing cellulose fibers is impregnated with a chemical mixture comprising at least one wetting agent and at least one binder, the impregnated sheet then being dried.

It has indeed been observed with surprise that the mixture of wetting agent and binder makes it possible to obtain a dimensional stability markedly greater than that which could have been obtained by impregnating the fibrous sheet with the wetting agent alone or the binder alone, and that the resulting stability is greater than the result one would have hoped for by adding the two effects.

The result is all the more astonishing, since in fact the binders alone bring little or no improvement in the dimensional stability of the fibrous sheet.

Without being able to identify the exact mechanisms of the synergistic action of the wetting agent and the binder, it seems that the amounts of wetting agent used are sufficient for, in addition to the possible fixing of a certain amount of wetting agent on the binder, allow satisfactory wetting of the cellulose.

The binder to be used is an organic binder of natural or synthetic origin since mineral binders and cements have the drawback of having too long a setting time. The organic binder bonds the constituents of the fibrous sheet to one another and can strengthen the physical properties of the paper sheet.

• - les polymères styréne-butadiène,
• - les polymères acryliques,
• - les polychlorures de vinyle
• - les copolymères acétate de vinyle-chlorure de vinyle-éthylène,

et/ou un liant hydrosoluble tel que, notamment :

• - l'amidon,
• - les alcools polyvinyliques,
• - les copolymères polyamide/polyamine-épichlorhydrine qui sont en outre utilisés comme agents de résistance humide en papeterie.

The binder according to the invention is a synthetic latex, such as, in particular:

• - styrene-butadiene polymers,
• - acrylic polymers,
• - polyvinyl chloride
• - vinyl acetate-vinyl chloride-ethylene copolymers,

and / or a water-soluble binder such as, in particular:

• - starch,
• - polyvinyl alcohols,
• - polyamide / polyamine-epichlorohydrin copolymers which are also used as wet strength agents in stationery.

The preferred synthetic latexes have a surface tension of less than 40mN / m.

Wetting is understood to mean any hygroscopic chemical having a low surface tension and allowing the sheet to quickly take up large amounts of water even at low ambient humidity. In doing so, the sheet remains dimensionally stable during the evolution towards a higher humidity.

• - les polyéthylène glycols,
• - les polyoxydes d'alkylène.

The wetting agent according to the invention is a chemical product preferably belonging to the family of polyglycols and its derivatives. In particular, products such as:

• - polyethylene glycols,
• - polyalkylene oxides.

According to the invention the treatment of the fibrous sheet can be carried out directly on a paper machine or on a autonomous impregnation or coating installation. The treatment can therefore be carried out by the papermaker or by a processor.

The fibrous sheet is treated by any impregnation process known to those skilled in the art. Possible devices are in particular spraying devices, impregnators, but the size press is preferred, which is the device commonly used on paper machines.

Impregnation of the fibrous sheet may only be carried out on one side but it is preferable to use devices allowing impregnation on both sides.

On the technical level, the implementation of the invention by impregnation or by coating of the fibrous sheets does not pose any particular problem to the skilled person.

The characteristics of the invention will be better understood thanks to the nonlimiting examples which follow.

In the context of the development of the invention, studies have been carried out on fibrous sheets of different compositions.

For each study, the effect of the wetting agents alone and the binders alone was considered before comparing to the effect of the mixtures of wetting agents and binders.

In what follows, the proportions between wetting agents and binders are given as an indication and correspond for the supports studied to the best compromises of mechanical strength and dimensional stability obtained.

The mixture will generally contain at least 15 parts by dry weight of wetting agent for 85 parts by dry weight of binder. However, the selection of specific binders makes it possible to introduce less than 15 parts of wetting agent into the impregnation composition.

It goes without saying that those skilled in the art will be able to change these proportions according to the support used and the goal sought, and replace all or part of the cellulose fibers with other hydrophilic fibers.

• - de combiner plusieurs latex, notamment pour limiter les problèmes de pelage du plastisol rencontrés avec les latex styréne-butadiène,
• - d'introduire dans le mélange d'imprégnation des additifs secondaires connus en papeterie tels que : des pigments, des colorants, des dispersants, des antimousses, des fongicides, des bactéricides, des agents de collage.

In addition, it is possible depending on the applications:

• to combine several latexes, in particular to limit the problems of peeling plastisol encountered with styrene-butadiene latexes,
• - to introduce into the impregnation mixture secondary additives known in stationery such as: pigments, dyes, dispersants, antifoams, fungicides, bactericides, sizing agents.

• - eau
• - antimousse
• - mouillant
• - latex synthétique
• - "aquapel"

The best procedure for obtaining size press baths is, for baths containing no water-soluble binder, to mix successively:

• - water
• - defoamer
• - wetting
• - synthetic latex
• - "aquapel"

• - liant hydrosoluble
• - eau
• - antimousse
• - mouillant
• - "aquapel".

For baths containing a water-soluble binder

• - water-soluble binder
• - water
• - defoamer
• - wetting
• - "aquapel".

STUDY 1 - Coating supports for floor or wall coverings

The impregnations were carried out for this first study on a fibrous sheet which is a support of intermediate composition with respect to the sheets with a high content of latex by mass described respectively in patent applications EP10 ₀ 720 and EP145522 filed by the Applicant.

The sheet is obtained according to the manufacturing process described in patent applications EP6390 and EP100720 from:

The sheet was impregnated by means of a size press fed with pure, wetting or binding products, and their mixtures.

The dry matter deposit on the sheet is adjusted by a more or less significant dilution of the impregnation solution with water.

In order to prevent the appearance of foam on the industrial machine, an anti-foam was selected and added to the bath.

Finally, an alkaline sizing agent based on dimeric alkyl ketene was incorporated into the impregnation solution to reduce the surface absorption of water in the sheet after treatment.

The doses of antifoam and sizing agents added to the various impregnation baths are identical for all the tests (both for pure products and for mixtures).

The antifoam is added at a rate of 0.05% relative to the total volume of the final bath.

• - de 5% en poids de produit commercial par rapport au poids de mouillant sec pour les bains contenant un mélange de liant et de mouillant.
• - de 5% en poids de produit commercial par rapport au poids sec de produits purs pour le mouillant ou le liant en général ou par rapport au poids commercial pour la Nadavine LT (copolymère polyamide/polyamine-épichlorhydrine).

The bonding agent is added correctly:

• - 5% by weight of commercial product relative to the weight of dry wetting agent for baths containing a mixture of binder and wetting agent.
• - 5% by weight of commercial product relative to the dry weight of pure products for wetting agent or binder in general or relative to the commercial weight for Nadavine LT (polyamide / polyamine-epichlorohydrin copolymer).

1st part: Impregnation with pure products

The results are collated in Table I A - wetting agents

• - le PEG 400 de poids moléculaire 400,
• - le BEROCEL 404, à base de polyoxydes d'alkylène et produit par la Société BEROL.

The two wetting agents used are:

• - PEG 400 with molecular weight 400,
• - BEROCEL 404, based on polyalkylene oxides and produced by the company BEROL.

1-The PEG 400

We verified the fact reported in the prior art that the _P EGs of low molecular weight degrade when the temperature increases. To meet the requirements of the application targeted with the support studied, PEG 400 was selected after various tests.

PEG 400 indeed has good efficiency for dimensional stability and low thermal degradation for temperatures encountered during the envisaged subsequent transformation phase. It is also possible, if necessary, to reduce the sensitivity of PEG to temperature, by the introduction into a size press of suitable stabilizing agents.

The tests carried out show that at heavy removal, PEG 400 improves the dimensional stability of the sheet (Prüfbau measurements) but considerably affects the mechanical characteristics. There is a drop in resistance to cold and hot traction, rigidity and delamination tensile strength (abbreviated below in RTD).

During baking the leaf turns yellow: this loss of whiteness is due to the presence of PEG.

Heavy deposits cause bubbling or blistering of the plastisol layer during gelation (160 C) and expansion (200 ° C).

In addition, heavy deposits do not allow the removal of hard spots on the surface of the plastisol which are defects due to linting; the impregnation bath of the press-sizing machine does not in fact have a sufficient binding power to bind the glass fibers to the surface of the sheet.

Removal obtained with a bath of PEG 400 diluted to 35% of dry extracts makes it possible to obtain a better compromise between the gain in dimensional stability and the loss in mechanical characteristics. Rigidity and traction, especially when hot, remain insufficient.

2-BEROCEL 404

The dimensional stability is lower than that obtained, with equal deposits, with PEG 400.

The improvement over raw support is insufficient. It has not been observed on the type of sheet studied, that this product makes it possible to limit the bubbling of plastisol during coating and expansion, as reported in the document EP-A-18961.

• - perte de rigidité,
• - perte de résistance à la traction à froid,
• - forte perte de résistance à la traction à chaud.

On the other hand, for equivalent dimensional stability on the sheets impregnated with PEG 400 or BEROCEL 404, the even more particularly harmful impact of BEROCEL 404 on the mechanical properties of the sheet is noted, in particular:

• - loss of rigidity,
• - loss of resistance to cold traction,
• - strong loss of resistance to hot traction.

The pure alkylene polyoxides do not allow this type of fibrous sheet to provide dimensional stability while avoiding the negative effects already known to those skilled in the art.

B - binders 1-synthetic latex

The improvement over the raw sheet in dimensional stability is too small to be of interest.

It is noted however that the best results are obtained at equivalent deposits and for latexes of the same chemical composition, with the latexes having the lowest surface tension (thus latex 3718 in the family of styrene butadiene latexes used).

2-Water-soluble binders a) pol ^y amide / polyamine-epichlorohydrin polymers

The products (Nadavine LT, Kymène 577 HV ...) have practically no influence on the dimensional stability and they do not harm the mechanical characteristics.

No particular difficulty appeared during the transformation: in particular no bubbling of the plastisol.

The impregnation of the sheet has surprisingly improved the RTD by almost 100% without boring during processing.

This result is all the more surprising since the strong deposits of latex, hitherto necessary for improving the RTD, lead to very marked bubbling of the plastisol during processing.

b) starch and polyvinyl alcohols (PVA)

No improvement in dimensional stability is noted.

2nd part - Impregnation with mixtures

The results are collated in Table II.

A- Wetting agents and latex

It has been found that the impregnation of the fibrous sheet with a bath comprising both a wetting agent and a latex makes it possible, for the same application by wetting, to greatly improve the dimensional stability compared to impregnation with a wetting agent. pure.

The result is all the more surprising since the latexes used alone provide, under the best conditions, only a slight improvement in dimensional stability (Table I).

By comparing the results obtained with those of pure wetting agents, we see that with equivalent dimensional stability, the binder-wetting mixture makes it possible to considerably limit the amounts of wetting agent deposited and on the other hand effectively combat the negative effects of these wetting agents for the further processing.

On all the examples corresponding to a total deposit of 13 g of dry extract of latex-wetting mixtures or of pure wetting agents, it can be seen that the impregnation with the latex-wetting mixture makes it possible to deposit twice as little wetting agent for the same level. dimensional stability and also to significantly enhance the mechanical properties, in particular rigidity and cold and hot pulls, while eliminating the greasy feel, the effect of transparency and the problems of oiling.

• - une meilleure rigidité,
• - une meilleure blancheur après étuvage,
• - de meilleures tractions à froid et à chaud sans inconvénient majeur sur le bullage et la régularité de l'épaisseur de la couche de plastisol.

With equal dimensional stability and for the same latex, reading of Table II makes it possible to observe that the mixtures with PEG make it possible to reduce the deposition by wetting and therefore to obtain better results in terms of physical characteristics compared to polyoxides of alkylene. In particular, in addition to the dimensional stability:

• - better rigidity,
• - better whiteness after baking,
• - better cold and hot traction without major drawback on bubbling and the regularity of the thickness of the plastisol layer.

Due to the low deposition by wetting, another advantage of PEG over BEROCEL 404 is the absence of bubbling of plastisol for the leaves treated with a latex-PEG 400 mixture, unlike those treated with a latex-BEROCEL404 mixture.

In addition, it is again apparent by comparing the results obtained with the styrene-butadiene latexes that the best results correspond to the latexes having surface tensions as low as possible.

It is also noted in Table II that the use of mixtures containing styrene-butadiene latex causes a sharp drop in the RTD values vis-à-vis mixtures containing other latexes.

This is due to the fact that the sheets used for this study are not very porous and that styrene-butadiene creates a barrier against plasticizers. There is a low penetration of these during coating with plastisol, therefore less cohesion between the treated sheet and the plastisol layer.

B-Wetting agents and water-soluble binders 1- Polyamide / polyamine-epichlorohydrin wetting agents and polymers (Nadavine LT)

If we compare the results obtained for a deposition of 13g / m2 of dry matter of PEG-Nadavine mixture and of pure PEG, we note a significant gain in dimensional stability which is accompanied by an improvement in rigidity, hot and cold and a decrease in yellowing at temperature.

It is noted that the results obtained with the KYMENE- _P EG mixture are comparable to those relating to the Nadavine-PEG mixture.

The examples in Table II also demonstrate the advantage of PEG-Nadavine mixtures over BEROCEL 404- _Na davine mixtures both in terms of dimensional stability and physical characteristics.

2- Wetting and starch or PVA

It is noted in Table II that there is, with equal deposition in dry extract and with equal dimensional stability, an improvement in rigidity and whiteness compared to PEG 400 alone.

STUDY 2 - Porous mass-free latex-free support

The results are collated in Table III.

The support used was obtained from:

It was verified by this study that the results obtained with the coating support for floor and wall coverings are found for this type of paper.

Having noted the technical and economic advantages of using PEG 400, the tests were only carried out with this wetting agent.

The preparation of the baths is analogous to that of Study 1.

1st part: Impregnations with pure products.

The high deposition PEG provides a good improvement in dimensional stability but it causes a loss of traction when hot and a loss of rigidity compared to the characteristics of the raw sheet.

Latex or Nadavine LT does not improve dimensional stability.

2nd part: Impregnations with mixtures 1- PEG 400 + Nadavine LT mixture

Comparing tests 1112 and 1116, it can be seen that at equivalent deposits of mixture or of pure wetting agent, the dimensional stability of the sheet is three times greater.

There is also an improvement in the stiffness and the hot pull as well as a reduction in the fluffing of the fibers on the surface of the sheet.

2- PEG 400 + latex mixture

The latex is DM 122.

It is found by comparing tests III 2 and III 5 that with a lower deposition of dry matter of the mixture, an equivalent dimensional stability is obtained.

At equivalent dimensional stability, impregnation with the mixture makes it possible to reduce the deposition of PEG 400 by more than half and to improve hot traction and rigidity.

The presence of latex in the impregnation bath increases the binding power of the bath and makes it possible to eliminate the linting of the fibers on the surface of the sheet.

STUDY 3 - Poster paper which must remain stable during large atmospheric variations

The results are collated in Table IV.

La préparation des bains est analogue à celle de l'Etude 1. lère partie - l'imprégnation avec les produits pursThe support used was obtained from:

The preparation of the baths is analogous to that of Study 1. 1st part - impregnation with pure products

Nadavine LT and latex have no influence on dimensional stability.

PEG improves dimensional stability but there is a drop in cold traction and stiffness.

The hot pull being irrelevant for this type of paper was not measured.

Part 2 - Impregnation with mixtures

The latex used is latex 3720.

The blends again allow for greater dimensional stability while providing less PEG 400 to the sheet.

The mixtures make it possible to limit the losses of physical characteristics compared to the values measured for the paper before impregnation.

Mixing reduces the greasy appearance of the paper. It has been found for papers impregnated with a mixture of wetting agent and binder according to the invention an improvement in the solidity of the paper which allows in particular a better rendering of the prints in plain background.

ETU _D E 4 - Tests on industrial coating materials for coatings of floor or wall

In order to verify the experimental results obtained in the laboratory, two industrial tests were carried out on a FOURDRINIER type paper machine.

I - Test E1183

It is a sheet loaded with a high level of latex obtained according to the process described in French patent application EP145522.

The sheet has the following composition:

This sheet was impregnated on its two faces by passing through the press-glue machine of the machine with a bath comprising:

Dry extract of the final mixture 48%.

The removal obtained was 25 g / m2 dry (total of the 2 faces). It is noted that this impregnation with a BEROCEL 404-latex 6171 mixture made it possible to improve the dimensional stability but to the detriment of the hot traction (Table V).

The performance of the impregnations with the previous bath and a new bath in which the BEROCEL 404 was replaced by the same amount of PEG 400.

To obtain the same dimensional stability, the deposit in a BEROCEL 404-latex mixture is twice as important as for the PEG 400-latex mixture (Table V bis).

In addition, the PEG 400-latex mixture provides better rigidity and better heat traction.

This test made it possible to verify the advantage of impregnating the sheet with a PEG 400-latex mixture to improve the dimensional stability.

II- Test E1193

It is an unfilled sheet with a high latex content obtained according to the process described in patent applications EP 6390 and EP100720.

The sheet has the following composition:

This sheet was directly impregnated on both sides on the paper machine with a bath comprising:

Dry extract of the final mixture 31%.

The removal obtained was 25 g / m2 dry (total of the two faces).

The results of Table VI show that the impregnation bath based on PEG 400 and latex makes it possible to greatly improve the dimensional stability of the sheet.

It is noted that this impregnation only causes a small loss in rigidity and in cold traction.

The loss in hot traction is more noticeable but its level remains satisfactory. Also note an improvement in RTD.

Impregnation with the PEG 400-latex bath allows a better level of dimensional stability to be obtained without significantly degrading the essential mechanical characteristics of the sheet (Table VI).

STUDY 5 - Mineral wall covering support

It is a thin sheet filled with low latex content which is obtained according to the process described in European patent application EP6390.

For this type of application, it is easily understood that it is desired to obtain as good dimensional stability as possible.

It has been noted during preliminary studies that the use of wetting agents alone too disturbs the essential physical characteristics (loss of rigidity, traction and opacity).

It has been verified that in this type of application the use of mixtures providing less wetting and therefore less disturbing the essential physical characteristics leads to a good improvement in dimensional stability without the drawbacks of wetting agents alone.

Le grammage est de 130g/m2.A sheet having the following composition was therefore impregnated with different baths and impregnations:

The grammage is 130g / m2.

The dimensional stability was measured on a FENCHEL type device. The test piece was baked 2 minutes at 200 ° C before testing and the measurement of the elongation carried out after 8 "minutes of immersion in water.

The dimensional stability of the raw sheet is 0.85%.

Impregnation 1

The bath supplying the press-sizing machine includes:

Dry extract of the final mixture 30%.

The removal was carried out at a rate of 10.3 g / m2 dry (total of the 2 faces).

The dimensional stability measured is 0.35%, ie a gain of more than 50% compared to the raw sheet.

Impreanation 2

Latex 3726 was replaced in impregnation bath 1 by an equivalent quantity of CE 35 latex.

The dry extract of the final mixture was 30%.

The removal was carried out at a rate of llg / m2 dry (total of the 2 faces).

The dimensional stability is 0.27%, again a very significant gain in dimensional stability.

Impregnation 3

The impregnation bath no longer contains synthetic latex but Nadavine LT.

The bath includes:

Dry extract of the final mixture 25%.

The removal was carried out at a rate of 11.1 g / m2 dry (total of the 2 faces).

The dimensional stability is again 0.27%.

STUDY 6 - INFLUENCE OF IMPREGNATION ON THE FIBERGLASS RATE

For certain applications, a high dimensional stability is sought which can only be obtained by the addition of high levels of reinforcing fibers in the mass of the paper.

The presence of significant amounts of reinforcing fibers may have technical drawbacks depending on the end use of the paper obtained, or economical due to the cost of certain qualities of reinforcing fibers such as polyester fibers.

It may therefore be desirable to obtain the desired level of dimensional stability for the final sheet while limiting the amounts of reinforcing fibers introduced.

Considering glass fibers, the stationer knows that such fibers improve the dimensional stability of paper sheets; they are in particular used for this purpose in the composition of coating supports for floor coverings, wall hangings and posters. However, it is known to the papermaker that adding too large amounts of glass fibers is harmful (cf. the beginning of this thesis).

We therefore carried out a comparative study to highlight the usefulness of the chemical treatment of the invention for reducing the levels of glass fibers while maintaining, or even improving, the dimensional stability of the paper sheet.

• 25 parties en poids sec de fibres cellulosiques,
• 50 parties en poids sec de craie,
• 2,5 ou 4 parties en poids sec de fibres de verre
• 5 parties en poids sec de latex.

The supports are obtained from:

• 25 parts by dry weight of cellulosic fibers,
• 50 parts by dry weight of chalk,
• 2.5 or 4 parts by dry weight of glass fibers
• 5 parts by dry weight of latex.

The results of this study are reported in Table VII.

• - la stabilité dimensionnelle dépend bien du taux de fibres de verre pour les papiers non traités selon l'invention, et que
• - la stabilité dimensionnelle des supports contenant 2,5 parties de fibres de verre et imprégnées selon l'invention est très nettement supérieure à celle du support non imprégné et contenant 4 parties de fibres de verre.

We have verified that:

• the dimensional stability does depend on the level of glass fibers for the untreated papers according to the invention, and that
• - The dimensional stability of the supports containing 2.5 parts of glass fibers and impregnated according to the invention is very clearly greater than that of the non-impregnated support and containing 4 parts of glass fibers.

STUDY 7 - INFLUENCE OF THE WET / BINDER RATIO ON THE LEVEL OF DIMENSIONAL STABILITY

In the field of floor coverings and wall coverings, there is known, due to the release of volatile products such as moisture contained in the support, a phenomenon of blistering of the synthetic material coated on the support during the heat treatment necessary to cause pre-gelation or expansion (160-200 ° C)) of said material.

To verify the effect of the wetting agents of our impregnating compositions, we have carried out tests by varying the wetting / binder ratio in different impregnating compositions and by comparing various wetting agents.

The results of this study are shown in Table VIII.

• a) Pour des mélanges d'un mouillant et d'un liant donnés, la diminution du rapport mouillant/liant permet de supprimer le phénomène de cloquage tout en conservant un très net avantage en stabilité dimensionnelle par rapport au support brut.
• b) Avec un même liant, une même dépose et des rapports mouillant/liant comparables, on obtient en remplaçant le PEG 400 par le PEG 600 une stabilité dimensionnelle améliorée et un cloquage sensiblement équivalent.
• c) Dans les mêmes conditions d'utilisation qu'au paragraphe b), le BEROL 404 donne d'aussi bons résultats que les PEG 400 et 600 quant au cloquage mais le BEROL 404 est moins efficace que ces PEG pour améliorer la stabilité dimensionnelle.

It emerges from these tests that:

• a) For mixtures of a given wetting agent and a binder, the reduction in the wetting / binder ratio makes it possible to eliminate the blistering phenomenon while retaining a very clear advantage in dimensional stability compared to the raw support.
• b) With the same binder, the same removal and comparable wetting / binder ratios, one obtains by replacing PEG 400 with PEG 600 improved dimensional stability and substantially equivalent blistering.
• c) Under the same conditions of use as in paragraph b), BEROL 404 gives as good results as PEG 400 and 600 in terms of blistering, but BEROL 404 is less effective than these PEG in improving dimensional stability.

Test VIII-4 shows that the quantity of PEG 400 can be significantly reduced while obtaining a net gain in dimensional stability compared to the raw support.

STUDY 8 - INFLUENCE OF THE CHOICE OF LATEX ON DIMENSIONAL STABILITY

In this study, we show that not all latexes have the same effectiveness in improving dimensional stability according to the treatment method of the invention.

We carried out impregnation tests using the same base composition comprising 15 parts by dry weight of PEG 400 and 85 parts by dry weight of latex.

• 25 parts en poids sec de fibres cellulosiques (20° SR)
• 4 parts en poids sec de fibres de verre
• 50 parts en poids sec de latex styrène butadiène carboxylé.

The support to be impregnated is the same for all the tests, it is an industrial support for wall hanging (E 1235 IN 3) whose grammage is 154 g / m obtained from a composition comprising:

• 25 parts by dry weight of cellulosic fibers (20 ° SR)
• 4 parts by dry weight of glass fibers
• 50 parts by dry weight of styrene butadiene carboxylated latex.

The deposit is 15 g / m of dry products for all the tests.

The results are reported in Table IX.

• - selon la nature chimique du latex et à tension superficielle équivalente, le niveau de stabilité dimensionnelle obtenu peut être très différent, et que :
• - pour des latex de même nature chimique, ce sont ceux qui ont la plus basse tension superficielle et la plus haute température de transition vitreuse qui conduisent aux meilleurs résultats. Ce sont les latex les plus mouillants et les plus rigides qui conduisent, en combinaison avec le PEG, aux meilleures stabilités dimensionnelles.

We observe that :

• - depending on the chemical nature of the latex and at equivalent surface tension, the level of dimensional stability obtained can be very different, and that:
• - for latexes of the same chemical nature, it is those which have the lowest surface tension and the highest glass transition temperature which lead to the best results. These are the wettest and most rigid latexes which, in combination with PEG, lead to the best dimensional stability.

• - par la compatibilité chimique du latex choisi avec les produits utilisés dans les étapes ultérieures éventuelles de transformation du support imprégné, par exemple la compatibilité du latex avec le plastisol utilisé pour la fabrication de revêtement de sol.
• - par la tension superficielle et la température de transition vitreuse du latex.

The choice of latex will therefore be guided:

• - By the chemical compatibility of the latex chosen with the products used in the possible subsequent stages of transformation of the impregnated support, for example the compatibility of the latex with the plastisol used for the manufacture of floor coverings.
• - by the surface tension and the glass transition temperature of the latex.

Example IX-6 of this study shows that it is possible to obtain a very good improvement in dimensional stability, even with a wetting / binder ratio of 15/85. It also shows the use of specific binders which allows to use less wetting agent in the impregnation mixture to obtain a still remarkable level of dimensional stability compared to that of the raw support.

ANNEX 1 METHODS USED TO MEASURE PHYSICAL CHARACTERISTICS Cold traction

Pull-ups carried out in accordance with standard NF Q 03-004 of November 1971.

• Dimension de l'éprouvette 15mm/100mm
• Durée de la traction 20 + 5 s

This standard corresponds to the international standard ISO 1924/1976

• Dimension of the test piece 15mm / 100mm
• Duration of traction 20 + 5 s

Hot pull

Pull-ups performed according to the same procedure as above. However, the tractions are carried out on test tubes located in an oven maintained at the temperature of 200 ° C.

Rigidity Taber

Taber stiffness was measured following the instructions in TAPPI T 489 OS-76.

Whiteness

The whiteness was determined using a photovoltaic by measuring the reflectance of a light flux at 457 mm. The measurements were carried out in accordance with TAPPI T 4520M-83.

Elongation at humidity

This measurement was carried out using a special cabinet allowing different degrees of relative humidity to be obtained (manufacturer PRUEFBAU).

The measurements were carried out in accordance with German standard DIN 53130.

Bullage

The values indicated correspond to a visual classification of the surface states.

Traction delamination - RTD

This is a traction measurement using a dynamometer on a 5cm wide test tube.

The test piece is cut from a sheet covered with a layer of expanded plastisol.

To carry out the measurement, delamination is started in the support sheet coated with the plastisol layer. The two parts are attached to the jaws of the dynamometer.

The value of the recorded traction corresponds to the force which must be exerted to detach the layer of expanded plastisol from the support.

Claims (8)

1. Treatment method intended to improve the dimensional stability of a fibrous sheet obtained by the papermaking process and of which at least a portion of the fibers are hydrophilic fibers, in particular cellulosic fibers, by impregnating the sheet with a chemical composition comprising at least one wetting agent and at least one organic binder, characterized in that the binder or binders are of the synthetic latex or water-soluble binders type. 2. Method according to claim 1, characterized in that the impregnation bath contains at least 15 parts by dry weight of wetting agent per 100 parts by dry weight of binder and wetting agent. 3. Method according to any one of claims 1 or 2, characterized in that the binder is a synthetic latex and that the impregnation bath is obtained by successively mixing: - some water - antifoam - wetting agent - synthetic latex - and a bonding agent. 4. Method according to any one of claims 1 to 3, characterized in that a synthetic latex is used having a surface tension of less than 40mN / m. 5. Method according to any one of claims 1 or 2, characterized in that a water-soluble binder is used as binder and that the impregnation bath is obtained by successively mixing: q - the water-soluble binder - some water - antifoam - wetting agent - and a bonding agent. 6. Method according to any one of claims 1, 2 or 5, characterized in that an aqueous solution of polyamide / polyamine-epichlorohydrin resin is used as water-soluble binder. 7. Method according to any one of claims 1 to 6, characterized in that a chemical compound from the family of polyglycols and their derivatives is used as a wetting agent. 8. Method according to claim 7, characterized in that polyethylene glycol is used as a wetting agent.