WO1999050201A1

WO1999050201A1 - Method for damp-proofing gypsum plaster

Info

Publication number: WO1999050201A1
Application number: PCT/FR1999/000627
Authority: WO
Inventors: Christine Franzoni; Sandrine Goubet; Evelyne Prat; Laurent Rocher; Mustapha Sari
Original assignee: Rhodia Chimie
Priority date: 1998-03-31
Filing date: 1999-03-18
Publication date: 1999-10-07
Also published as: HU221659B1; HUP0101570A2; EP1068160A1; AU2842999A; FR2776655B1; PL343151A1; FR2776655A1; HUP0101570A3; RU2199500C2

Abstract

The invention concerns a method for damp-proofing gypsum plaster, characterised in that it consists in adding to the gypsum plaster, at least a compound (A) comprising at least an alkylhydrogenopolysiloxane, at least a hydrocolloid (B) comprising at least a galactomannan, and at least a polysaccharide (C) comprising at least a gum.

Description

1

PLASTER WATER REPELLENT PROCESS

The present invention relates to a process for waterproofing plaster and wet plaster objects.

Plaster, with the chemical formula CaS0 ₄ .1 / 2 H ₂ O, results from calcination at a temperature of about 140 ^β C from natural or synthetic gypsum.

When calcination is carried out at atmospheric pressure, β plaster (construction plaster) is obtained.

If this calcination is carried out at a pressure higher than atmospheric pressure, plaster α is obtained. Calcination of gypsum (CaS0 ₄ .2 H ₂ 0) at a temperature above 600 ° C, will produce anhydπte (CaSO ₄ ) . There are also synthetic anhydrites, such as, for example, fluoroanhydrite. It should be noted that the anhydπte (CaSO ₄ ) can also exist in the natural state, in the form of rock.

Calcium sulphate in semi-hydrated or anhydrous form (α, β plasters, and synthetic or natural anhydrates), when mixed with water or mixing can lead to the formation of gypsum with the formula CaSO ₄ .2 H ₂ O. Gypsum is a water sensitive product and has a solubility of around 2.0 g / l at 20 ° C.

In the context of the present invention, the term "plaster" will denote all the aforementioned phases, which, after rehydration, give gypsum (CaSO ₄ .2 H ₂ O).

In the different plaster applications, it is important to have a material that has long-lasting mechanical properties. Likewise, it is important that the hardened material retains the original properties (shape, color, etc.) after contact with moisture. For this it is necessary to waterproof the plaster, that is to say to make it not very sensitive or even completely insensitive to the penetration of water.

It was with the aim of improving the resistance of plaster to water that we had to treat plaster on the surface or in the mass. In the case of water repellency in the mass, the treatment takes place in situ, at the time of the manufacture of the manufactured articles in plaster, in general, by addition of a water repellant compound in the mixing water.

The use of al ylhydrogenopolysiloxanes alone to waterproof the plaster in the mass is already known. After hydrolysis, the alkylhydrogenopolysiloxanes lead, in general, to the formation of hydrophobic alkylhydrogenopolysiloxane networks. The major drawback of alkylhydrogenopolysiloxanes when used alone, as water repellents, is that under certain operating conditions, in particular at high temperature (from about 120 ^β C), these compounds can partially give rise to dust of silica, which by its character powdery, may affect the operation of the conveying devices This will result in a shutdown of the installations, thus penalizing the manufacturing

Furthermore, depending on the pH of the plaster, more or less violent releases of hydrogen can occur with alkylhydrogenopolysiloxanes used as water repellant, which poses safety and manufacturing quality problems.

In addition, the antifoaming property of alkylhydrogenopolysiloxanes poses problems of recycling the plasters which contain them.

Finally, problems of water repellency can be encountered using alkylhydrogenopolysiloxanes alone with certain types of plaster, in particular with plasters of synthetic origin.

The main object of the present invention is to overcome the drawbacks mentioned above by proposing an improved water-repellency process for plaster using alkylhydrogenopolysiloxanes in a reduced quantity, and which makes it possible to obtain and keep a material whose sensitivity to water penetration is considerably reduced in a sustainable manner

These aims are achieved by the present invention which relates to a plaster water-repellency process using in particular an alkylhydrogenopoly-siloxane (A), a hydrocolloid (B), and a polysaccharide (C) comprising at least one gum By process "plaster water repellency" means a process which makes the plaster impermeable to the penetration of liquid water, both from the outside to the inside and from the inside to the outside of the plaster, while retaining plaster permeability in both directions to water vapor

The subject of the invention is a process for waterproofing plaster, characterized in that at least one compound (A) comprising at least one alkylhydrogenopolysiloxane, at least one hydrocolloid (B) comprising at least one galactomannan is added to the plaster , and at least one polysaccharide (C) comprising at least one gum

The method according to the present invention can, in addition, allow easy recycling of the treated plasters.

It can also, under certain conditions, lead to a waterproof plaster of the above type, the mechanical properties of which are preserved or even improved.

In addition, the method according to the present invention can lead to a good quality of water repellency even with plasters of synthetic origin.

More particularly, the method of the invention consists in mixing with a plaster powder, at least one compound (A) comprising at least one alkylhydrogenopoly-siloxane, at least one hydrocolloid (B) comprising at least one galactomannan, at least one polysaccharide (C) comprising at least one gum, and water

The first essential constituent used in the process of the invention is the compound (A) which consists of at least one alkylhydrogenopolysiloxane 99- / 50201

The alkylhydrogenopolysiloxanes (A) can be of various natures. They can be linear or cyclic, or a mixture of linear and cyclic, of average formulas (I) and (II):

RH R <

Ro - SiO-t-SiO SiO-r-Si - R;

R, H R,

(")

SiO- -siσ

RH H

(II)

in which :

• a and b are whole or fractional numbers, defined as:

° 0 <a <500, preferably 0 <a <99 ° 0 <b <500, preferably 1 <b <100 ° 5 <a + b <1000, preferably 10 <a + b <150 • c and d are whole or fractional numbers, defined as:

° 0 <c <5, preferably 0 <c <3 ° 1 <d <10, preferably 1 <d <5 ° 3 <c + d <10, preferably 3 <c + d <5

• R _{1 f, which are} identical or different, represent a monovalent hydrocarbon radical containing 1 to 8 carbon atoms chosen from: a linear or branched alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, tert-butyl, n-hexyl, n- radicals octyl, ° phenyl unsaturated radicals, optionally substituted by a methyl radical and / or an ethyl radical, • when b> 0, R ₂ , identical or different, represent a hydrogen atom and / or a monovalent hydrocarbon radical comprising 1 to 8 carbon atoms chosen from

° linear or branched alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, tert-butyl, n-hexyl, n-octyl radicals, ° the unsaturated phenyl radicals, optionally substituted by a methyl radical and / or an ethyl radical,

When b = 0, at least one of the radicals R ₂ represents a hydrogen atom, the other radicals R ₂ , which are identical or different, representing a monovalent hydrocarbon radical having 1 to 8 carbon atoms chosen from:

° linear or branched alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, tert-butyl, n-hexyl, n-octyl radicals, ° phenyl unsaturated radicals, optionally substituted by a methyl radical and or an ethyl radical. Preferably, the compound (A) consists of at least one linear alkylhydrogenopolysiloxane of average formula (I) in which:

• the radicals R ^ and R ₂ represent the linear alkyl radicals comprising 1 to 3 carbon atoms chosen from the methyl, ethyl, propyl radicals and preferably methyl, • a and b are whole or fractional numbers, defined as:

° 0 <a <99, preferably 0 <a <50 ⁰ 1 <b <100, preferably 10 <b <80 ° 10 <a + b <150, preferably 20 <a + b <100 The compound (A ) mentioned above consists of at least one alkylhydrogenopolysiloxane which can have a viscosity of at most 200 mPa.s, and preferably from 5 to 50 mPa.s. In the remainder of the description, the viscosity is determined with a BROOKFIELD viscometer at 25 ° C. and 20 revolutions / minute.

An important parameter for the definition of the alkylhydrogenopolysiloxanes (A) of the invention is the percentage of the hydrogen radicals (≡SiH units). The best results are obtained with alkylhydrogenopolysiloxanes (A) preferably having a percentage of ≡SiH units of between 0.05 and 5% by weight of hydrogen relative to the weight of compound (A), and preferably between 0.3 and 2% by weight of hydrogen relative to the weight of compound (A).

The alkylhydrogenopolysiloxanes (A) are usually in the form of an oil.

They can be used in the pure state, diluted in an organic solvent, in emulsion, or in the form of powder when they are fixed on a pulverulent support.

They will be used, preferably, in the pure state, in the form of an aqueous emulsion, or of emulsifiable concentrates, in the presence of suitable surfactants. Usually, the alkylhydrogenopolysiloxanes are present in an amount of at least 0.3% by weight relative to the plaster powder, in order to have the water-repellency properties required according to the water-repellency standards: O 99/50201

water absorption <5% after 2 hours of immersion water absorption <10% after 24 hours of immersion

The present invention makes it possible to reduce the usual dose of alkylhydrogenopolysiloxanes (A), to an amount of at most 0.25%, and preferably at most 0J5% by weight relative to the plaster powder in order to satisfy the above-mentioned standards. .

The second essential constituent used in the process of the invention is the hydrocolloid (B) which consists of at least one galactomannan.

Galactomannans are polysaccharides constituted by a chain of monomers of the mannose and galactose type. Among the galactomannans, guar gum is chosen more particularly.

Guar gum is a natural hydrocolloid stored as a reserve material in the endosperm of the guar seed. It is also a galactomannan whose molecule has a very specific configuration. The skeleton of the macromolecule consists of a long chain of mannose units linked together by a 1,4-β-glycosidic bond. Statistically, a molecule of mannose on two carries, as branching, a galactose fixed by a bond 1, 6-α.

Natural guar gum can undergo chemical modifications allowing its properties to vary considerably, while retaining the basic characteristics. Thus, the free hydroxyl groups of guar gum can be substituted by etherification or esterification reactions producing, for example, carboxyalkylated, hydroxyalkylated, and phosphate derivatives. The etherification or esterification reactions are known per se, in particular in the chemistry of cellulose and starch. It is also possible to substitute the free hydroxyl groups of guar gum to produce cationic and amphoteric guars.

In the context of the present invention, the hydrocolloid (B) is preferably chosen from nonionic galactomannans in which at least part of the hydroxyl groups is substituted by hydroxyalkyl groups. More particularly, the hydrocolloid (B) is a nonionic guar gum in which at least part of the hydroxyl groups is substituted by hydroxyalkylated groups, the alkyl group of which contains from 2 to 4 carbon atoms. These nonionic guars, also called hydroxyalkyl ethers, can be chosen from hydroxyethyl guars, hydroxypropyl guars, and hydroxybutyl guars. (B) is preferably a hydroxy propyl guar.

The guar hydroxyalkyl ethers according to the invention can be prepared according to methods known to a person skilled in the art, for example that described in Canadian patent No. 1075727, in particular by reaction of a guar gum with an oxide. alkylene, for example ethylene oxide, propylene oxide, and butylene oxide, in the presence of a catalyst such as an alkali hydroxide such as NaOH, an alkaline earth metal, or 'ammonia.

The reaction can take place at a temperature varying between 15 ° C and 130 ° C. Usually, in guar gum, each mannose and / or galactose monomer) can have, on average, three hydroxyl functions capable of reacting with alkylene oxide. Thus, the degree of molar substitution of a hydroxyalkyl ether of a polymer in general, and of a hydroxyalkyl ether guar in particular, can be defined as the number of moles of alkylene oxide added per unit of hexose in a polymer in general, and in guar in particular.

The degree of molar substitution of the hydrocolloid (B), and in particular of the guar hydroxyalkyl ether according to the invention, can be between 0.2 and 0.9, and preferably between 0.3 and 0.7 .

The weight average molecular weight (Mw) of the hydrocolloid (B) can vary between 50,000 and 2,000,000, and preferably between 200,000 and 1,500,000.

The weight average molecular weight (Mw) is represented by the following formula:

M _{W =} ∑i N; [M _d ] 2

∑i N, i in which:

N _j = number of moles of polymer of species i, M _j = molecular weight of polymer of species i.

The hydrocolloid (B) is usually in the form of a solid. Its incorporation into a given medium makes it possible to modulate the viscosity and the rheological properties of said medium according to the specific requirements desired.

Thus, for a dispersion at 1% of hydrocolloid (B) in a given medium, in particular in water, the viscosity is advantageously at most 1500 mPa.s. This viscosity is more particularly between 500 and 1100 mPa.s, for example around 1000 mPa.s.

The hydrocolloid content (B) is between 0.05% to 0.5% by weight, preferably between 0.05% and 0.3% by weight, and more particularly between 0J0% and 0.25% by weight compared to plaster powder.

As commercial hydrocolloid products (B), non-limiting examples will be cited of the products of the commercially available series, mention may in particular be made of RHOXIMAT RH 148, JAGUAR HP 140, JAGUAR 8000, JAGUAR 8200, the JAGUAR 8801, and the JAGUAR HP 8 from the RHODIA Company. The third essential constituent used in the process of the invention is the polysaccharide (C) comprising at least one gum. O 9950201

Polysaccharides can include all natural and modified gums.

Natural gums include extracts of algae such as agar, algin, carrageenan, plant exudates such as gum arabic, karaya gum, tragacanth gum, ghatti gum, gums from seeds such as guar gum, locust bean gum, tara gum, tamarind gum, pectins, and gums obtained by fermentation such as xanthan gum.

The natural gum is preferably guar gum.

The modified gums come from chemical modifications of the abovementioned natural gums. By chemical modification is meant more particularly reactions of the hydroxyalkylation and carboxyalkylation type.

The polysaccharide (C) according to the present invention consists of at least one gum which is chosen from the abovementioned natural gums. They have preferably undergone at least partial depolymerization. The term “depolymerization” is understood to mean the cleavage of a polymer making it possible to obtain polymers of lower molecular weights.

The depolymerized polysaccharide can be characterized by its degree of polymerization (DP). The degree of polymerization is generally calculated by dividing the molecular mass of the depolymerized polysaccharide by 162; 162 being the equivalent molecular weight of a neutral hexose, which is the neutral monomer of said polysaccharide.

In the context of the present invention, the polysaccharide (C) can have a degree of polymerization of between 60 and 50,000, preferably between 150 and 6,500, even more preferably between 100 and 500. The depolymerization can be carried out by:

- oxidative route in the presence of alkali,

- basic route in the presence of air,

- enzymatic route, or

- acid depolymerization. These depolymerization methods are known per se. We could refer for example to:

- EP 0130946 for the oxidative depolymerization process in the presence of alkali and basic in the presence of air,

- "Novo Enzyme", Novo Industri, AS Denmark, with regard to enzymatic depolymerization, and

- "Sâurehydrolyse glykozidischer Bindungen", Jozsef Szejtli, 1975, VEB Fachbuchverlag, Leipzig, for acid depolymerization. 8

The teaching of these references is of course incorporated here into the present application.

Preferably, the polysaccharides (C) are obtained by oxidative depolymerization in the presence of alkali or basic depolymerization in the presence of air from natural gums.

The weight average molecular mass (Mw) of the polysaccharide (C) can vary between 10,000 and 8,000,000, preferably between 30,000 and 1,000,000, and even more preferably between 20,000 and 70,000.

Like the hydrocolloid (B), the polysaccharide (C) is usually in the form of a solid.

The incorporation of the polysaccharide (C) in a given medium makes it possible to modulate the viscosity and the rheological properties of said medium according to the specific requirements desired.

Thus, for a dispersion at 10% of polysaccharide (C) in a given medium, in particular in water, the viscosity is advantageously at most 2500 mPa.s. This viscosity is more particularly between 500 and 1500 mPa.s.

The content of polysaccharide (C) is between 0.01% and 0.5% by weight, preferably between 0.05% and 0.5% by weight, and more particularly between 0J% and 0.30% by weight compared to plaster powder. As commercial products of polysaccharides (C), non-limiting examples will be cited of the products in the commercially available series, mention may in particular be made of MEYPROGAT 7, MEYPROGAT 30, MEYPROGAT 90, MEYPRODOR 100 from the company RHODIA , and FIBERON®.

The water-repellency of the plaster can be carried out according to methods known to those skilled in the art, for example by mixing a plaster powder, a compound (A) comprising at least one alkylhydrogenopolysiloxane, a hydrocolloid (B) comprising at least one galactomannan, a polysaccharide (C) comprising at least one gum, and water.

One can proceed, for example, as follows: i) premix the compound (A), the hydrocolloid (B), and the polysaccharide (C) in the mixing water, ii) introduce the plaster into the premixing, iii) shape the plaster and allow it to set, and iv) dry the plaster in an oven until constant mass. The mixing water may contain other additives (which can also be introduced into the fresh dough), in particular plaster thinning or dispersing agents, and / or foaming agents. O 99/50201

As fluidizing or dispersing agent, mention may be made of condensed phosphates, sodium tripolyphosphate, sodium hexametaphosphate, methyl, ethyl or sodium poly (meth) acrylates, poly (meth) acrylic acids, poly (meth) acrylic amides, organic phosphonates in particular methylene phosphonate, polysulfonates in particular lignosulfonates, petroleum sulfonates, polystyrene sulfonates, sulfonated polycondensates in particular sulfonated polycondensate of naphthalene and formaldehyde, polymaleates in acid form and / or alkaline salt, tannins, lignins, glucosides, gluconates, alginates, phosphoesters, and phosphoglasses. These compounds and others are described in: "Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, Volume 7, 1979, pages 833-846", the teaching of which is incorporated here into the present description.

Mention may be made, as foaming agents, of families of alkyl ether sulfate sodium or ammonium surfactants, sodium or ammonium lauryl ethers sulfates, sodium cocoamphodiacetates dialkyisulfosuccinates, ethoxylated alcohols, ethoxylated fatty alcohols , sucroglycerides, castor oil or ethoxylated coconut oil, and betaine. As such, commercial foaming agents can be used, for example RHODASURF 860 P, RHOCAFOAM AN 45, RHOCAFOAM AMP 10, RHOCAFOAM AB 20, RHOXIMAT TG 80, RHOCAFOAM AN 30, marketed by RHODIA.

As already mentioned, the hydrocolloid (B) and the water-soluble polymer (C) are usually in the form of a solid. The compound (A) can be in the form of a pure oil, diluted in solution, in emulsion as defined above, or in the form of an emulsifiable concentrate. Emulsifiable concentrate means that the compound (A) additive with surfactants, allows a setting immediate emulsion in case of contact with water. In such a case, the subject of the invention will be a plaster water-repellency process, characterized in that a composition comprising:

- at least one hydrocolloid (B) comprising at least one galactomannan in solid form as defined above, - at least one polysaccharide (C) comprising at least one gum as defined above, and

- At least one compound (A) comprising at least one alkylhydrogenopolysiloxane as defined above, in the form of pure oil, diluted in solution, in emulsion, or in the form of emulsifiable concentrate. When the compounds (A), (B), and (C) are all solids, the premix will be in the form of a pulverulent composition.

Since compounds (B) and (C) are usually in solid form, the problem of compound (A) arises. 10

As already indicated, the compound (A) is preferably an oil. It is made solid, preferably, by impregnation of a solid mineral support, for example silica, calcium carbonate, plaster (CaSO ₄ J / 2 H ₂ O), gypsum, or any other inert mineral or organic filler. . The impregnation is carried out in a known manner, by bringing the solid support into contact with the pure compound (A), or with a solution or an emulsion comprising the compound (A).

The operation is generally carried out by soaking the solid support in a determined pure volume of compound (A), or in a determined volume of a solution or an emulsion comprising the compound (A). It is also possible to impregnate the solid support by soaking it in pure compound (A), or in the solution or emulsion comprising compound (A), and removing the excess solution by draining.

The placing on a support can also be carried out by spraying the pure compound (A), or the solution or the emulsion comprising the compound (A) directly on the support in a mixer, for example of the Lodige or Forberg type.

Thus, the subject of the invention will also be a pulverulent composition comprising:

- at least one hydrocolloid (B) comprising at least one galactomannan as defined above, - at least one polysaccharide (C) comprising at least one gum as defined above, and

a solid based on at least one supported compound (A), the compound (A) comprising at least one alkylhydrogenopolysiloxane as defined above.

The invention also relates to molded objects or in the form of tiles or plates. These objects are obtained from plaster which has undergone the water repellency treatment as described in the whole of the description.

Finally, the subject of the invention is the product comprising at least one compound (A) comprising at least one alkylhydrogenopolysiloxane corresponding to general formulas (I) and (II), at least one hydrocolloid (B) comprising at least one galactomannan as defined above, and at least one polysaccharide (C) comprising at least one gum, as a combination product for joint use in a plaster waterproofing process.

Joint use means use of the three constituents (A), (B), and (C) together to obtain the desired water-repellent property; (A), (B), and (C) can be introduced simultaneously or separately into the plaster.

Concrete but nonlimiting examples of the invention will now be given. O 99/50201

11

EXAMPLES Example 1

Material:

The material described below is the same for all the examples. It includes: - a Rayneri mixer and 4-blade propeller, used at a speed of 1200 rpm.

- stainless steel molds for 4 x 4 x 16 cm ³ test tubes

- a 2 liter polypropylene beaker

- a ventilated oven HERAEUS type UP 6420

Products: Four sets of three plaster test tubes are prepared with 3600 g of plaster

(CaSO ₄ J / 2H ₂ O).

Series 1 is the control plaster (without water repellency).

Series 2 is added with 0.3% by weight relative to the plaster powder of polymethylhydrogenosiloxane blocked at the end of the chain by methyl groups of formula (CH ₃ ) 3-Si-0- [SiH (CH3) -O] _x -Si (CH ₃ ) 3 with 45 <x <80; also called RHOXIMAT H 68, in the form of pure oil.

Series 3 is added with 0J% by weight relative to the plaster powder of RHOXIMAT H 68, in the form of pure oil.

Series 4 corresponds to plaster added with 0J% by weight relative to the plaster powder of RHOXIMAT H 68, and 0J5% by weight with respect to the guar plaster powder RHOXIMAT RH 148 which is a mass hydroxypropyl guar molar of approximately 1,200,000 and molar degree of substitution of approximately 0.6, and 0J5% by weight relative to the plaster powder of MEYPROGAT 7 which is a depolymerized guar of molecular mass of approximately 47,000 and DP of approximately 300. Whatever the sample prepared, the amount of water added is such that the water / plaster ratio always remains equal to 0.75.

Preparation:

- According to the prepared sample, introduce water, polymethylhydrogenosiloxane (RHOXIMAT H 68), hydroxypropyl guar (RHOXIMAT RH 148), depolymerized guar (MEYPROGAT 7) in the beaker. Shake for 15 seconds.

- Add the plaster in 15 seconds and remix in 15 seconds.

- Leave to stand for 30 seconds and remix for 30 seconds.

- Pour the plaster into the mold, pack, level and leave to set (duration approximately 30 minutes) - Once set, unmold and dry the plaster samples 40 hours at 40 ° C in the ventilated oven. 12

Evaluation of the hvdrofuαes properties of these test pieces:

At the exit of the oven, the plaster samples are left to cool to about 23 ° C and 65% relative humidity.

They are immersed in drinking water, at a height of around 1 cm, and are weighed every hour for 8 hours, then after 24 hours.

Expression of results:

The quantity of water absorbed is expressed in% of the dry weight of the test piece at time t, according to the formula:

E% -_ E2 - E1 x 100 E1

E1 = mass of the test piece at time t = 0 E2 = mass of the test piece at time t

Each formula is tested on a series of 3 plaster test pieces. The results summarized in Table I correspond to the average of the 3 tests; they are given with an accuracy of + 2% absolute.

Table I

Water absorption (%)

Sample

2 hours 24 hours

Series 1: Sample plaster 38 49

Series 2: Plaster + 0.3% H 68 ^a 3 9

Series 3: Plaster + 0J% of H 68 ^to 37 39

Series 4: Plaster + 0.1% H 68 ^a + 0.15% RH

1 4 148 * + 0.15 from MEYPROGAT 7

^a H 68 signifies RHOXIMAT H 68 ^fa RH 148 signifies RHOXIMAT RH 148 There has been an improvement in the water repellency properties of additive plaster by reduced amounts of RHOXIMAT H 68, guar RHOXIMAT RH 148, and MEYPROGAT 7, and this in a lasting manner for at least 24 hours.

Example 2

Spreading test The spreading test is carried out on a paste obtained by mixing 300 g of dry mixture and 150 g of water using a Rayneri mixer according to the following procedure: 13

• pour in 30 seconds, a dry mixture containing:

- 99.6% plaster

- 0J% citric acid

- 0.3% of RHOXIMAT RH 148 + MEYPROGAT 7 mixture, in a 500 ml container containing water;

• knead at a speed of 250 revolutions / minute;

• increase the mixing speed in 15 seconds up to 1000 rpm,

• continue mixing for 75 seconds at 1000 rpm.

Citric acid is a plaster retardant. While the RH 148 + MEYPROGAT 7 mixture represents 0.3% of the total mass, the proportions in which each compound is present can vary.

The measurement of spreading of the dough is done for example using a shaking table of the EUROMATEST type, with a cylindrical mold with a diameter of 7.5 mm and a height of 50 mm. The mold is filled with dough and then the spread, that is to say the diameter of the initial wafer, is measured at 5, 10 and 15 shots. Successive shocks are spaced one second apart.

The spreading results, summarized in Table II, will be expressed in mm and reflect the diameter of the dough at different stages. Table II: Spreading test

number of strokes Plaster M 7 RH 148 M 7 / RH 148: 50/50

0 90 90 70 80

5 135 130 110 125

10 150 145 125 140

15 160 155 135 150

M7 represents MEYPROGAT 7

RH 148 represents RHOXIMAT RH 148

It is observed that the fluidity of the fresh dough, characterized by spreading measures, is only slightly affected by the presence of MEYPROGAT 7 and RHOXIMAT RH 148, which allows said dough to be shaped according to the usual methods .

The combination of the two MEYPROGAT 7 + RHOXIMAT RH 148 products provides the best compromise between fluidity and retention. 14

Example 3

Material:

The equipment as well as the operating method of example 1 are identical to this example. Products:

Four sets of three plaster samples are prepared with 3600 g of plaster (CaSO ₄ J / 2H ₂ O).

Series 1 is the control plaster (without water repellency).

Series 2 is added with 0.5% by weight relative to the plaster powder of a 60% polymethylhydrogenosiloxane emulsion blocked at the end of the chain by methyl groups of formula (CH ₃ ) 3-Si-O- [SiH (CH3) -O] _x -Si (CH ₃ ) 3 with 45 <x <80; also called RHOXIMAT HD 879.

Series 3 is added with 0J7% by weight relative to the plaster powder of a 60% emulsion of RHOXIMAT HD 879. Series 4 corresponds to plaster with 0J7% by weight relative to the plaster powder of '' an emulsion at 60% RHOXIMAT HD 879, and 0.15% by weight relative to the RHOXIMAT RH 148 guar plaster powder, also called RH 148, which is a hydroxypropyl guar with a molar mass of approximately 1 200,000 and a degree of molar substitution of approximately 0.6, and 0J5% by weight relative to the plaster powder of MEYPROGAT 7 which is a depolymerized guar with a molecular mass of approximately 47,000 and a DP of approximately 300.

Whatever the sample prepared, the amount of water added is such that the water / plaster ratio always remains equal to 0.75.

Evaluation of the hydrofoil properties of these test pieces: At the exit of the oven, the plaster test pieces are left to cool to approximately

23 ° C and 65% relative humidity.

They are immersed in drinking water, at a height of around 1 cm, and are weighed every hour for 8 hours, then after 24 hours. Each formula is tested on a series of 3 plaster test pieces. The results summarized in Table III correspond to the average of the 3 tests; they are given with an accuracy of + 2% absolute. O 99/50201

15

Table III

Water absorption (%)

Sample

2 hours 24 hours

Series 1: Control plaster 35 37

Series 2: Plaster + 0.5% HD 879 ^e 2 5 emulsion

Series 3: Plaster + 0J7% HD emulsion ^879th June 26

Series 4: Plaster + 0J7% HD 879 ^e emulsion + 0J5

1 5% of RH 148 + 0.15% of MEYPROGAT 7

c HD 879 means RHOXIMAT HD 879

There has been an improvement in the water-repellent properties of plaster added with a combination of the two products MEYPROGAT 7 + RHOXIMAT RH 148, and this in a lasting manner over 24 hours.

Claims

O 99/5020116 CLAIMS

1. A water-repellency process for plaster, characterized in that at least one compound (A) comprising at least one alkylhydrogenopolysiloxane, at least one hydrocolloid (B) comprising at least one galactomannan, and at least one polysaccharide (C).

2. Method according to claim 1, characterized in that at least one compound (A) comprising at least one alkylhydrogenopolysiloxane, at least one hydrocolloid (B) comprising at least one galactomannan, is mixed with a plaster powder a polysaccharide (C), and water.

3. Method according to one of claims 1 and 2, characterized in that the compound (A) consists of at least one linear and / or cyclic alkylhydrogenopolysiloxane of average formulas (I) and (II):

RH

R ₂ - SiO -f-SiO SiO- -Si - ₅

R, H Ri

(D

y "olϋ" y SiO "

H

_ ^R 1_ cd

(H)

in which :

• a and b are whole or fractional numbers, defined as:

° 0 <a <500, preferably 0 <a <99 ° 0 <b <500, preferably 1 <b <100

° 5 <a + b <1000, preferably 10 <a + b <150

• c and d are whole or fractional numbers, defined as:

° 0 <c <5, preferably 0 <c <3 ° 1 <d <10, preferably 1 <d <5 17

° 3 <c + d <10, preferably 3 <c + d <5

• R _1? identical or different, represent a monovalent hydrocarbon radical containing 1 to 8 carbon atoms chosen from:

^D linear or branched alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, tert-butyl, n-hexyl, n-octyl radicals,

^D the unsaturated phenyl radicals, optionally substituted by a methyl radical and or an ethyl radical,

• when b> 0, R ₂ , identical or different, represent a monovalent hydrocarbon radical containing 1 to 8 carbon atoms chosen from: ^α linear or branched alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, tert-butyl, n -hexyl, n-octyl, ° phenyl unsaturated radicals, optionally substituted by a methyl radical and or an ethyl radical,

⁰ linear or branched alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, tert-butyl, n-hexyl, n-octyl radicals, ° phenyl unsaturated radicals, optionally substituted by a methyl radical and or an ethyl radical.

4. Method according to any one of claims 1 to 3, characterized in that the compound (A) consists of at least one linear alkylhydrogenopolysiloxane of average formula (I) in which: • the radicals R ^ and R represent the alkyl radicals linear comprising 1 to 3 carbon atoms chosen from methyl, ethyl, propyl, and preferably methyl,

• a and b are whole or fractional numbers, defined as:

° 0 <a <99, preferably 0 <a <50 ° 1 <b <100, preferably 10 <b <80

° 10 <a + b <150, preferably 20 <a + b <100

5. Method according to any one of claims 1 to 4, characterized in that the compound (A) consists of at least one alkylhydrogenopolysiloxane having a viscosity of at most 200 mPa.s, and preferably from 5 to 50 mPa. s.

6. Method according to any one of claims 1 to 5, characterized in that the alkylhydrogenopolysiloxanes (A) have a percentage of ≡SiH units included 18

between 0.05 and 5% by weight of hydrogen relative to the weight of compound (A), and preferably between 0.3 and 2% by weight.

7. Method according to any one of claims 1 to 6, characterized in that the compound (A) consists of at least one alkylhydrogenopolysiloxane in the form of an oil.

8. Method according to any one of claims 1 to 7, characterized in that the compound (A) is present in an amount of at most 0.25% by weight relative to the plaster powder, and preferably d 'at most 0J5% by weight relative to the plaster powder.

9. Method according to any one of claims 1 to 8, characterized in that the hydrocolloid (B) is a nonionic guar in which at least part of the hydroxyl groups is substituted by hydroxyalkylated groups in which the alkyl group contains 2 to 4 carbon atoms.

10. Method according to claim 9, characterized in that the hydrocolloid (B) is chosen from hydroxyethyl guars, hydroxypropyl guars, and hydroxybutyl guars.

11. Method according to any one of claims 9 or 10, characterized in that the degree of molar substitution of the hydrocolloids (B) is from at least 0.2 to at most 0.9, and preferably the degree of molar substitution is between 0.3 and 0.7.

12. Method according to any one of claims 1 to 11, characterized in that the molecular weight of the hydrocolloid (B) varies between 50,000 and 2,000,000, and preferably between 200,000 and 1,500,000.

13. Method according to any one of claims 1 to 12, characterized in that the hydrocolloid (B), in dispersion at 1% in water has a viscosity between at most 1500 mPa.s, and preferably between 500 and 1100 mPa.s.

14. Method according to any one of claims 1 to 13, characterized in that the hydrocolloid content (B) is between 0.05% to 0.5% by weight, preferably between 0.05% and 0, 3% by weight, and more particularly between 0J0% and 0.25% by weight relative to the plaster powder. 19

15. Method according to any one of the preceding claims, characterized in that the hydrocolloid (B) is a solid.

16. Method according to any one of the preceding claims, characterized in that the polysaccharide (C) consists of at least one gum chosen from natural gums.

17. Method according to the preceding claim, characterized in that the gum has undergone at least partial depolymerization.

18. Method according to the preceding claim, characterized in that the gum has undergone an oxidative depolymerization in the presence of alkali or basic depolymerization in the presence of air.

19. Method according to the preceding claim characterized in that the polysaccharide (C) has a degree of polymerization (DP) of between 60 and 50,000, preferably between 150 and 6,500, even more preferably between 100 and 500.

20. Method according to any one of the preceding claims, characterized in that the molecular mass of the polysaccharide (C) varies between 10,000 and 8,000,000, preferably between 30,000 and 1,000,000, and even more preferably between 20,000 and 70,000.

21. Method according to any one of claims 1 to 20, characterized in that the polysaccharide (C), in 10% solution in water, has a viscosity of at most 2500 mPa.s, and preferably included between 500 and 1500 mPa.s.

22. Method according to any one of the preceding claims, characterized in that the content of polysaccharide (C) is between 0.01% and 0.5% by weight ^ preferably between 0.05% and 0.5% by weight , and more particularly between 0J% eι% by weight relative to the plaster powder.

23. Method according to any one of the preceding claims, characterized in that a plastering or dispersing agent and / or a foaming agent are added to the plaster.

24. Plaster waterproofing process, characterized in that a composition comprising: 20

- at least one hydrocolloid (B) comprising at least one galactomannan in solid form as defined in any one of claims 9 to 15,

- at least one polysaccharide (C) comprising at least one gum as defined in any one of claims 16 to 22 and - at least one compound (A) comprising at least one alkylhydrogenopolysiloxane as defined in any one of claims 1 to 8, in the form of pure oil, diluted in solution, in emulsion, or in the form of emulsifiable concentrate.

25. Pulverulent composition comprising: - at least one hydrocolloid (B) comprising at least one galactomannan as defined in any one of claims 9 to 15,

- at least one polysaccharide (C) comprising at least one gum as defined in any one of claims 16 to 22 and

a solid based on at least one supported compound (A), the compound (A) comprising at least one alkylhydrogenopolysiloxane as defined in any one of claims 1 to 8.

26. An object molded or in the form of tiles or plates obtained from water-repellent plaster according to the method as defined in any one of claims 1 to 24.

27. Product comprising at least one compound (A) comprising at least one alkylhydrogenopolysiloxane as defined in any one of claims 1 to 8, at least one hydrocolloid (B) comprising at least one galactomannan as defined in any one of claims 9 to 15, and at least one polysaccharide (C) comprising at least one gum as defined in any one of claims 16 to 22 as a combination product for joint use in a plaster waterproofing process.