Title of Invention	"JOINTING COMPOUND OR PLASTER FOR CONSTRUCTION ELEMENTS, ITS METHOD OF PREPARATION AND METHOD OF PRODUCING A STRUCTURE"
Abstract	Jointing compound or plaster for construction elements comprising, in percentages by weight with respect to the total weight of plaster: 50 to 85% of a mineral filler , such as calcium carbonate ; 1 to 20% of an organic binder dispersible in an aqueous phase , such as polyacrylic ; 1 to 15% of a silicate-based agent other than the mineral filler, such as talc ; 0.2 to 5% of a hydrophobic agent which is a silicone derivative, such as siliconate ; 0.05 to 5% of polyvinyl alcohol; and water to make up to 100%. The jointing compound or plaster can be advantageously used as a filling plaster and also as a finishing plaster.

Title of Invention

"JOINTING COMPOUND OR PLASTER FOR CONSTRUCTION ELEMENTS, ITS METHOD OF PREPARATION AND METHOD OF PRODUCING A STRUCTURE"

Abstract

Jointing compound or plaster for construction elements comprising, in percentages by weight with respect to the total weight of plaster: 50 to 85% of a mineral filler , such as calcium carbonate ; 1 to 20% of an organic binder dispersible in an aqueous phase , such as polyacrylic ; 1 to 15% of a silicate-based agent other than the mineral filler, such as talc ; 0.2 to 5% of a hydrophobic agent which is a silicone derivative, such as siliconate ; 0.05 to 5% of polyvinyl alcohol; and water to make up to 100%. The jointing compound or plaster can be advantageously used as a filling plaster and also as a finishing plaster.

Full Text	_ 1 _ JOINTING COMPOUND OR PLASTER FOR CONSTRUCTION ELEMENTS, ITS METHOD OF PREPARATION AND METHOD OF PRODUCING A STRUCTURE The present invention relates to a jointing compound or plaster for construction elements, particularly paper-faced plasterboards, its method of preparation and a method of producing a structure such as a partition, a wall covering or a ceiling. It is well known to use plasterboards for producing partitions, coverings for vertical or inclined elements, or for producing ceilings, whether suspended or not. These boards generally consist of a core, essentially made of plaster, covered on each of its sides with a sheet, which serves both as reinforcement, and as facing and which may consist of paperboard or of mineral fibres. The subject matter of the International application published under number WO-A-9702395 is a method of constructing finishings, in which plasterboards are joined together with a first plaster and the joints between the boards are finished off with a complementary plaster having the following composition: 50 to 85% of a mineral filler; 1 to 20% of an organic binder dispersible In an aqueous phase ; 0.2 to 5% of a hydrophobic agent; 1 to 15% of a workability agent (water-retaining agent/thickener); 0.1 to 2% of a slip agent; 1 to 12% of a complementary slip agent; 0.1 to 5% of a dispersant; 0.001 to 0.015% of a pigment; 0.1 to 0.3% of a biocide ; 0.1 to 0.3% of an antifoam agent; and water. - 2 - The colour of this plaster is matched as best as possible to that of the facing paper. However, such a plaster is a finishing plaster, which means that it cannot be used for filling the space between two boards, especially because it does not allow good bonding and adhesion of the jointing tape. It is therefore necessary to have two plasters: a first plaster, called filling plaster, used to fill the space between two boards, and a second plaster, called finishing plaster, which finishes off the junction- between the two boards. Furthermore, such a plaster has too great a shrinkage after hardening. The colour of the filling plaster is of little matter as it will be covered with the finishing plaster. On the other hand, it must, after drying, have a negligible shrinkage as it is applied with a significant thickness. However, the colour of the finishing plaster is important as it must be as close as possible to that of the facing of the plasterboard. But it is not necessary for the shrinkage of the finishing plaster after drying to be very low, since this plaster is applied only with a small thickness. The aforementioned application WO-A-9702395 therefore does not address the problem of shrinkage after drying, since this does not matter for the application as a finishing plaster. It would therefore be beneficial to have a plaster, which could serve both as filling plaster and as finishing plaster. Such a plaster would therefore have to have one or more, preferably all, of the following properties: good adhesion to the paper constituting the facing of the plaster board; -3- good bonding and good adhesion of the jointing tape ; a colour identical to that of the facing paper; a negligible shrinkage after drying (for example, less than 20% as determined by the ring test); water absorption as close as possible to that of the facing paper, so as to avoid having to use a primer coat before wallpapering or painting ; moderate adhesion of the paper constituting the wallpaper, so as to make it possible for it to be stripped off subsequently one or more times ; and easy paintability. The Applicant has therefore carried out extensive research for the purpose of developing such a plaster. It has now succeeded in doing so and consequently proposes a plaster having the following composition: in percentages by weight with respect to the total weight of plaster: 50 to 85% of a mineral filler; 1 to 20% of an organic binder dispersible in an aqueous phase ; 1 to 15% of a silicate-based agent; 0.2 to 5% of a hydrophobic agent which is a silicone derivative ; 0.05 to 5% of polyvinyl alcohol; and water to make up to 100 %. When the constituents are mixed, no chemical reaction takes place. However, it has been found that the plaster produced has unexpected synergistic properties, namely, that the plaster produced can be used as a filling plaster as well as a finishing plaster and also that it can be easily spread during application of the plaster to the surface. -3A- A second aspect of the present invention is a method of preparing the plaster, in which the constituents of the plaster are mixed in any desired order. A third aspect of the present invention is a method of producing a structure, comprising juxtaposing of construction elements, filling the space between the construction elements by means of a filling plaster, laying a tape, and covering the tape by - 4 - means of a finishing plaster and is characterized in that the same plaster is used as filling plaster and as finishing plaster. Further characteristics and advantages of the invention will now be described in detail in the description, which follows. Plaster according to the invention The plaster according to the invention therefore comprises, in percentages by weight with respect to the total weight of plaster: 50 to 85% of a mineral filler; - 1 to 20% of an organic binder dispersible in an aqueous phase; 1 to 15% of a silicate-based agent; 0.2 to 5% of a hydrophobic agent which is a silicone derivative; 0.05 to 5% of polyvinyl alcohol; and water to make up to 100%. As mineral filler, any mineral filler commonly employed for the manufacture of a jointing compound or plaster may be used. In general, the mineral filler will be light in colour, preferably white, and the mean diameter dso of which is in general between 5 and 35 microns, so that the plaster after drying gives a smooth finish corresponding to that of the facing of the board. As examples of mineral filler, mention may be made of calcium carbonate, anhydrous or dihydrated calcium sulphate, magnesium carbonate, dolomite, silicas, silicates, aluminates and other such materials. Preferably, calcium carbonate CaCO3 is used. - 5 - The mineral filler preferably represents between 50 and 70% of the total weight of the plaster. According to one embodiment, the binder/silicate-based agent weight ratio is between 0.5 and 2. According to one embodiment, the binder/hydrophobic agent weight ratio is between 1.5 and 10. According to an advantageous embodiment of the invention, the mineral filler furthermore includes perlite, preferably expanded and even more preferably hydrophobic perlite. The amount of perlite is then generally between 2 and 5%. As organic binder dispersible in an aqueous phase, mention may be made of polyvinyl acetate homopolymers (plasticized or unplasticized), ethylene/vinyl acetate copolymers (plasticized or unplasticized EVAs), ethylene/vinyl versatate copolymers, vinyl acetate/vinyl versatate copolymers, polyacrylics, vinyl acetate/acrylic copolymers, styrene/acrylic copolymers, styrene/butadiene copolymers, vinyl acetate/vinyl versatate/vinyl maleate terpolymers, vinyl acetate/vinyl versatate/acrylic terpolymers, acrylic terpolymers and blends thereof. The proportion of organic binder is preferably between 2 and 12% of the total weight of the plaster. The silicate-based agent (different from the mineral filler) preferably comprises talc and/or mica and/or a clay. Preferably, a mixture of talc and mica is used. The proportion of silicate-based agent is preferably between 3 and 10% of the total weight of the plaster. The hydrophobic agent is a silicone derivative. As silicon derivatives, mention may be made of siliconates, 6 - silanes, hydrogenated silicone oils, silicone emulsions, aminosilicone emulsions, alkylsiloxane resins, such as hydrogenomethyl-polysiloxane and aminated polydimethyl-siloxane, and mixtures thereof. Preferably, a resin of the aminated polydimethyl-siloxane type is used as silicone derivative. The proportion of silicone derivative is preferably between 0.5 and 3% of the total weight of the plaster. Advantageously, the proportion of silicone derivative is chosen so as to allow a joint to be produced which has the same surface properties as those of the facing paper. These surface properties are decolouration or colouration owing to the effect of the natural colour, reflectance and surface water absorption. These properties are described in detail in application WO-A-9702395 (the content of which is incorporated as reference) , to which reference may be made for further details. It is understood that the technical characteristics described in that application apply mutadis mutandis to the present application. The proportion of polyvinyl alcohol is preferably between 0.05 and 1% of the total weight of the plaster. According to an advantageous embodiment, the plaster furthermore includes starch and/or a starch derivative. The proportion of starch and/or starch derivative is in general between 0.05 and 5%, preferably between 0.1 and 1%, of the total weight of the plaster. The plaster according to the invention may be prepared by mixing its constituents in any order. -7- Of course, provided that the proportions assigned to each of the essential constituents are respected, it is possible to introduce into the plaster according to the invention, as secondary ingredients, additives normally used to facilitate the processing of the other constituents or for conferring additional particular properties on the plaster. By way of examples of such additives, mention may be made of water-retaining agents or thickeners, slip agents, dispersants, antigels, pigments, biocides and antifoams. These additives are described, for example, in the application WO-A-9702395 (the content of which is incorporated by reference), to which reference may be made for further details. The plaster according to the invention can be used for producing, by means of plasterboards, many types of structures, such as partitions, wall coverings or ceilings, whether suspended or not. The plaster according to the invention is particularly suitable for producing a structure by means of paper-faced plasterboards. Of course, the plaster according to the invention may be used merely as a finishing plaster, a conventional plaster providing the function of a filling plaster. Method according to the invention The production of a structure by means of plasterboards generally comprises the juxtaposition of plasterboards, the filling of the space between the boards by means of a filling plaster, the laying of a tape, the covering of the tape by means of the filling plaster and the covering of the filling plaster with a finishing plaster. Surprisingly, the Applicant has succeeded in producing a structure using, as filling plaster and as - 8 - finishing plaster, one and the same plaster. This is achieved by: (1) the plaster that has been developed and has been described hereinabove; and/or (2) by matching the content of hydrophobic agent (silicone) of the finished or completed joint (namely filled and finished) with the content of hydrophobic agent (silicone) of the facing of the board; and/or (3) by increasing the binder content of the plasters of the type of those described in the application WO-A-9702395 and, optionally, the content of silicate-based agents (other than the mineral filler). With regard jzo point (1), the plaster has been described in detail above. With regard to point (2), the matching of the silicone contents of the facing and of the plaster was not clearly demonstrated in the application WO-A-9702395. The invention therefore proposes to optimize the plaster content/facing content weight ratio, of between 3 and 10, with preferred content values for the facing and the board. With regard to point (3) , the adhesion to tape was not discussed and not demonstrated in the application WO-A-9702395, since the adhesion to tape is not a criterion for finishing plasters. The invention therefore proposes to increase the binder content and/or to add polyvinyl alcohol to plasters of the type described in that application WO-A-9702395 in order to optimize the adhesion to tape (without the other properties being affected). According to an additional and advantageous characteristic of the invention, plasterboards which have - 9 - a paper facing, the silicone content of the coating of which is between 0.1 and 1%, are joined together. According to another characteristic, the content of the hydrophobic' or silicone agent of the plaster is between 0.5 and 3%. The plaster content/facing content weight ratio is between 3 and 10 for the optimization described above. This therefore constitutes an excellent compromise between easy painting, effective retention of the wallpaper, strippability of the wallpaper and good adhesion of the plaster to the facing of the plasterboard, as will become apparent on reading the examples which follow. European Patent Application No. EP 521 804 in the name of the Applicant describes a paper for covering plasterboards, and the plasterboards covered with this paper. These boards are very suitable for use with the plaster according to the invention. Examples The following examples are given purely by way of illustration and imply no limiting character. Example 1 A control plaster, the composition of which is in accordance with the aforementioned international application WO-A-9 702 395, and plasters A to F according to the invention were prepared. The various plasters were composed, apart from the essential constituents, of additives normally used in the manufacture of plasters and well known to those skilled in the art. - 10 - The composition of the various plasters is given in the following table: - 11 - 12 - (1): hydrophobic expanded perlite; (2): resin of the aminated polydimethylsiloxane type; (3): modified cellulose ether; > (4): synergistic mixture of aromatic {non-metallic, non-phenolic) compounds. Example 2 Tests were carried out on the adhesion of the PREGYLISS 35 setting plaster from the Lafarge Platres range to boards as described in the aforementioned application EP-A-521 804, having: a) a coating containing 0% silicone; b) a coating containing 0.2% silicone; c) a coating containing 0.4% silicone. It was found that too high a silicone content in the coating was unfavourable to good bonding of the conventional setting plaster (adhesion value at best 0.25 MPa). Example 3 Adhesion tests were carried out under the conditions described in paragraph 6.5 of the draft European Standard CEN2 4INI75 of January 19 98, whi ch covers the characteristics of coatings on specimens of the control plaster and plasters A to F of Example 1, with boards having a silicone content in the coating of 0.4%. The tape adhesion was determined under the conditions described in "Guide Technique - Enduits de traitement des joints entre plaques de piatre - Modalites d'essais" [Technical Guide - Plasters for treating joints between plasterboards - Test methods] of Specialist Group No. 9 of the Commission of the CSTB responsible for drawing up technical literature (January 1999) . - 13 - The results are given in the table below. 5 it is clearly apparent that all the plasters according to the invention have a higher performance than the control plaster. Example 4 Joints as indicated in Example 3 were produced. A wallpaper was then pasted onto them in the conventional way. Next, for the purpose of determining the impact of the silicone content of the coating of the facing paper of the boards on the stripping behaviour, a steam-stripping test was carried out. It was found that stripping was more difficult when the boards have a coating containing no silicone. Thus, wallpaper was applied and then removed several times. The results are the same .as for the first stripping. However, it was noted that, on boards with a silicone coating, at each stripping operation markedly 14 - more adhesive was removed than on boards with a non-silicone coating. Example 5 A test was carried out to determine the shrinkage after drying, The following results were obtained; The shrinkage of the plaster according to the invention is less than that of the control. Example 6 A test was carried out under the conditions described in the application WO-A-9702395 in order to determine the L, a and b* values (CIE 1916 standard, Minolta CR310 1 apparatus). The following values were obtained, the middle column giving the average value for the plasters according to the invention and the right-hand column for the board according to application EP-A-521 804 used in Example 3. The differences between the plaster and the board are imperceptible to the eye. The surface characteristics, as expressed according to the aforementioned application WO-A-9702395, are therefore very good. The plaster according to the invention may be a setting plaster or a drying plaster; preferably it is a - 15 - drying plaster. In the latter case, the drying plaster is advantageously a plaster called ready-mix plaster, that is to say one into which water has already been incorporated. -16-WE CLAIM : 1. Jointing compound or plaster for construction elements comprising, in percentages by weight with respect to the total weight of plaster: 50 to 85% of a mineral filler; 1 to 20% of an organic binder dispersible in an aqueous phase ; 1 to 15% of a silicate-based agent other than the mineral filler; 0.2 to 5% of a hydrophobic agent which is a silicone derivative ; 0.05 to 5% of polyvinyl alcohol; and water to make up to 100%, 2. Plaster as claimed in claim 1, comprising starch and/or a starch derivative. 3. Plaster as claimed in claim 2, wherein the proportion of starch and/or starch derivative is between 0.05 and 5%. 4. Plaster as claimed in any one of the preceding claims, wherein the silicate- based agent comprises talc and/or mica and/or a clay. 5. Plaster as claimed in any one of the preceding claims, wherein the silicate- based agent is a talc/mica mixture. -17- 6. Plaster as claimed in any one of the preceding claims, wherein the binder/silicate-based agent weight ratio is between 0,5 and 2, 7. Plaster as ciaimed in any one of the preceding claims, wherein the binder/hydrophobic agent weight ratio is between 1.5 and 10. ^t\|( 8. Plaster as claimed in any one of the preceding claims, wherein the mineral filler also comprises perlite, preferably expanded perlite. 9. Plaster as claimed in claim 8, wherein the mineral filler comprises between 2 and 5% perlite with respect to the total weight of the plaster. 10. Plaster as claimed in any one of the preceding daims, wherein the organic binder dispersible in an aqueous phase is chosen from the group consisting of polyvinyl acetate homopolymers (plasticized or unplasticized), ethylene/viny! acetate copoiymers (plasticized or unplasticized EVAs) , ethylene/vinyl versatate copoiyrners, vinyl acetate/vinyl versatate copoiymers, polyacrylics, vinyl acetate/acrylic copoiymers, styrene/acrylic copoiymers, styrene/butadiene copoiymers, vinyl acetate/vinyl versatate/acrylic terpolymers, vinyl acetate/vinyl versatate/vinyl maleate terpolymers, acrylic terpolymers and blends thereof. -18- 11. Plaster as claimed in any one of the preceding claims, wherein the silicone derivative is chosen from the group consisting of siliconates, silanes, hydrogenated silicone i oils, silicone emulsions, aminosilicone emulsions, alkylsiloxane resins, such as hydrogenomethylpolysiloxane and aminated polydimethylsiloxane, and mixtures thereof. 12. Plaster as claimed in any one of the preceding claims, wherein the mineral filler comprises calcium carbonate CaCO3. 13. Plaster as claimed in any one of the preceding claims, comprising, in percentages by weight with respect to the total weight of plaster: 50 to 70% of a mineral filler; 2 to 12% of an organic binder dispersible in an aqueous phase ; 3 to 10% of a silicate-based agent; 0.5 to 3% of a hydrophobic agent which is a silicone derivative ; 0.05 to 1% of polyvinyl alcohol; 0.1 to 1% of starch and/or a starch derivative ; and water to make up to 100%. 14. Method of preparing a plaster as claimed in any one of the preceding claims, comprising mixing in percentages by weight with respect to the total weight of plaster: -19- 50 to 85% of a mineral filler; 1 to 20% of an organic binder dispersible in an aqueous phase ; 1 to 15% of a silicate-based agent other than the mineral filler; 0.2 to 5% of a hydrophobic agent which is a silicone derivative ; 0.05 to 5% of polyvinyl alcohol; optionally 0.1 to 1% of starch and/or a starch derivative ; and water to make up to 100%, said mixing being carried out in any desired order. 15. Method of producing a structure, comprising : juxtaposing plasterboards having a paper facing ^filling the space between the boards by means of a filling piaster ; laying a tape ; covering the tape by means of the filling piaster, and covering the filling plaster with a finishing plaster, characterized in that the silicone content of the finishing plaster/silicone content of the facing weight ratio is between 3 and 10. 16. Method as claimed in any one of the preceding claims, wherein the silicone content of the coating of the facing paper is between 0,1 and 1%. 17. Method as claimed in Claim 15 or 16, wherein the same piaster is used as filling plaster and also as finishing plaster. -20- 18. Method as claimed in Claim 17, wherein the plaster has a binding agent content such that the binder/silicate-based agent weight ratio is between 0.5 and 2. 19. Method as claimed in Claim 17, wherein the plaster has a binding agent content such that the binder/hydrophobic agent weight ratio is between 1.5 and 10. 20. Method as claimed in Claim 17, wherein the plaster used is the plaster as claimed in any one of Claims 1 to 13. 21. Method of producing a structure, comprising : juxtaposing plasterboards having a paper facing ; filling the space between the boards by means of a filling plaster ; laying a tape ; covering the tape by means of the filling plaster ; and covering the filling plaster with a finishing plaster, characterized in that the filling and finishing plaster is a plaster as claimed in any one of claims 1 to 13. Jointing compound or plaster for construction elements comprising, in percentages by weight with respect to the total weight of plaster: 50 to 85% of a mineral filler , such as calcium carbonate ; 1 to 20% of an organic binder dispersible in an aqueous phase , such as polyacrylic ; 1 to 15% of a silicate-based agent other than the mineral filler, such as talc ; 0.2 to 5% of a hydrophobic agent which is a silicone derivative, such as siliconate ; 0.05 to 5% of polyvinyl alcohol; and water to make up to 100%. The jointing compound or plaster can be advantageously used as a filling plaster and also as a finishing plaster.

Full Text

_ 1 _
JOINTING COMPOUND OR PLASTER FOR CONSTRUCTION ELEMENTS, ITS METHOD OF PREPARATION AND METHOD OF
PRODUCING A STRUCTURE
The present invention relates to a jointing compound or plaster for construction elements, particularly paper-faced plasterboards, its method of preparation and a method of producing a structure such as a partition, a wall covering or a ceiling.
It is well known to use plasterboards for producing partitions, coverings for vertical or inclined elements, or for producing ceilings, whether suspended or not.
These boards generally consist of a core, essentially made of plaster, covered on each of its sides with a sheet, which serves both as reinforcement, and as facing and which may consist of paperboard or of mineral fibres.
The subject matter of the International application published under number WO-A-9702395 is a method of constructing finishings, in which plasterboards are joined together with a first plaster and the joints between the boards are finished off with a complementary plaster having the following composition:
50 to 85% of a mineral filler;
1 to 20% of an organic binder dispersible In an aqueous phase ;
0.2 to 5% of a hydrophobic agent;
1 to 15% of a workability agent (water-retaining agent/thickener);
0.1 to 2% of a slip agent;
1 to 12% of a complementary slip agent;
0.1 to 5% of a dispersant;
0.001 to 0.015% of a pigment;
0.1 to 0.3% of a biocide ;
0.1 to 0.3% of an antifoam agent; and
water.

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The colour of this plaster is matched as best as possible to that of the facing paper.
However, such a plaster is a finishing plaster, which
means that it cannot be used for filling the space
between two boards, especially because it does not allow
good bonding and adhesion of the jointing tape. It is
therefore necessary to have two plasters: a first
plaster, called filling plaster, used to fill the space
between two boards, and a second plaster, called
finishing plaster, which finishes off the junction-
between the two boards.
Furthermore, such a plaster has too great a shrinkage after hardening. The colour of the filling plaster is of little matter as it will be covered with the finishing plaster. On the other hand, it must, after drying, have a negligible shrinkage as it is applied with a significant thickness.
However, the colour of the finishing plaster is important as it must be as close as possible to that of the facing of the plasterboard. But it is not necessary for the shrinkage of the finishing plaster after drying to be very low, since this plaster is applied only with a small thickness. The aforementioned application WO-A-9702395 therefore does not address the problem of shrinkage after drying, since this does not matter for the application as a finishing plaster.
It would therefore be beneficial to have a plaster, which could serve both as filling plaster and as
finishing plaster. Such a plaster would therefore have to have one or more, preferably all, of the following properties:
good adhesion to the paper constituting the
facing of the plaster board;

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good bonding and good adhesion of the jointing tape ;
a colour identical to that of the facing paper;
a negligible shrinkage after drying (for example, less than 20% as
determined by the ring test);
water absorption as close as possible to that of the facing paper, so
as to avoid having to use a primer coat before wallpapering or
painting ;
moderate adhesion of the paper constituting the wallpaper, so as to
make it possible for it to be stripped off subsequently one or more
times ; and
easy paintability.
The Applicant has therefore carried out extensive research for the purpose of developing such a plaster.
It has now succeeded in doing so and consequently proposes a plaster having the following composition: in percentages by weight with respect to the total weight of plaster:
50 to 85% of a mineral filler;
1 to 20% of an organic binder dispersible in an aqueous phase ;
1 to 15% of a silicate-based agent;
0.2 to 5% of a hydrophobic agent which is a silicone derivative ;
0.05 to 5% of polyvinyl alcohol; and
water to make up to 100 %.
When the constituents are mixed, no chemical reaction takes place. However, it has been found that the plaster produced has unexpected synergistic properties, namely, that the plaster produced can be used as a filling plaster as well as a finishing plaster and also that it can be easily spread during application of the plaster to the surface.

-3A-
A second aspect of the present invention is a method of preparing the plaster, in which the constituents of the plaster are mixed in any desired order.
A third aspect of the present invention is a method of producing a structure, comprising juxtaposing of construction elements, filling the space between the construction elements by means of a filling plaster, laying a tape, and covering the tape by

- 4 -
means of a finishing plaster and is characterized in that the same plaster is used as filling plaster and as finishing plaster.
Further characteristics and advantages of the invention will now be described in detail in the description, which follows.
Plaster according to the invention
The plaster according to the invention therefore comprises, in percentages by weight with respect to the total weight of plaster:
50 to 85% of a mineral filler; - 1 to 20% of an organic binder dispersible in an
aqueous phase;
1 to 15% of a silicate-based agent;
0.2 to 5% of a hydrophobic agent which is a
silicone derivative;
0.05 to 5% of polyvinyl alcohol; and
water to make up to 100%.
As mineral filler, any mineral filler commonly employed for the manufacture of a jointing compound or plaster may be used. In general, the mineral filler will be light in colour, preferably white, and the mean diameter dso of which is in general between 5 and 35 microns, so that the plaster after drying gives a smooth finish corresponding to that of the facing of the board.
As examples of mineral filler, mention may be made of calcium carbonate, anhydrous or dihydrated calcium sulphate, magnesium carbonate, dolomite, silicas, silicates, aluminates and other such materials.
Preferably, calcium carbonate CaCO3 is used.

- 5 -
The mineral filler preferably represents between 50 and 70% of the total weight of the plaster.
According to one embodiment, the binder/silicate-based agent weight ratio is between 0.5 and 2.
According to one embodiment, the binder/hydrophobic agent weight ratio is between 1.5 and 10.
According to an advantageous embodiment of the invention, the mineral filler furthermore includes perlite, preferably expanded and even more preferably hydrophobic perlite. The amount of perlite is then generally between 2 and 5%.
As organic binder dispersible in an aqueous phase, mention may be made of polyvinyl acetate homopolymers (plasticized or unplasticized), ethylene/vinyl acetate copolymers (plasticized or unplasticized EVAs), ethylene/vinyl versatate copolymers, vinyl acetate/vinyl versatate copolymers, polyacrylics, vinyl acetate/acrylic copolymers, styrene/acrylic copolymers, styrene/butadiene copolymers, vinyl acetate/vinyl versatate/vinyl maleate terpolymers, vinyl acetate/vinyl versatate/acrylic terpolymers, acrylic terpolymers and blends thereof.
The proportion of organic binder is preferably between 2 and 12% of the total weight of the plaster.
The silicate-based agent (different from the mineral filler) preferably comprises talc and/or mica and/or a clay. Preferably, a mixture of talc and mica is used.
The proportion of silicate-based agent is preferably between 3 and 10% of the total weight of the plaster.
The hydrophobic agent is a silicone derivative. As silicon derivatives, mention may be made of siliconates,

6 -
silanes, hydrogenated silicone oils, silicone emulsions, aminosilicone emulsions, alkylsiloxane resins, such as hydrogenomethyl-polysiloxane and aminated polydimethyl-siloxane, and mixtures thereof.
Preferably, a resin of the aminated polydimethyl-siloxane type is used as silicone derivative.
The proportion of silicone derivative is preferably between 0.5 and 3% of the total weight of the plaster.
Advantageously, the proportion of silicone derivative is chosen so as to allow a joint to be produced which has the same surface properties as those of the facing paper. These surface properties are decolouration or colouration owing to the effect of the natural colour, reflectance and surface water absorption. These properties are described in detail in application WO-A-9702395 (the content of which is incorporated as reference) , to which reference may be made for further details. It is understood that the technical characteristics described in that application apply mutadis mutandis to the present application.
The proportion of polyvinyl alcohol is preferably
between 0.05 and 1% of the total weight of the plaster.
According to an advantageous embodiment, the plaster furthermore includes starch and/or a starch derivative.
The proportion of starch and/or starch derivative is in general between 0.05 and 5%, preferably between 0.1 and 1%, of the total weight of the plaster.
The plaster according to the invention may be prepared by mixing its constituents in any order.

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Of course, provided that the proportions assigned to each of the essential constituents are respected, it is possible to introduce into the plaster according to the invention, as secondary ingredients, additives normally used to facilitate the processing of the other constituents or for conferring additional particular properties on the plaster. By way of examples of such additives, mention may be made of water-retaining agents or thickeners, slip agents, dispersants, antigels, pigments, biocides and antifoams. These additives are described, for example, in the application WO-A-9702395 (the content of which is incorporated by reference), to which reference may be made for further details.
The plaster according to the invention can be used for producing, by means of plasterboards, many types of structures, such as partitions, wall coverings or ceilings, whether suspended or not.
The plaster according to the invention is particularly suitable for producing a structure by means of paper-faced plasterboards.
Of course, the plaster according to the invention may be used merely as a finishing plaster, a conventional plaster providing the function of a filling plaster.
Method according to the invention
The production of a structure by means of plasterboards generally comprises the juxtaposition of plasterboards, the filling of the space between the boards by means of a filling plaster, the laying of a tape, the covering of the tape by means of the filling plaster and the covering of the filling plaster with a finishing plaster.
Surprisingly, the Applicant has succeeded in producing
a structure using, as filling plaster and as

- 8 -
finishing plaster, one and the same plaster. This is achieved by:
(1) the plaster that has been developed and has
been described hereinabove; and/or
(2) by matching the content of hydrophobic agent
(silicone) of the finished or completed joint (namely filled and finished) with the content of hydrophobic agent (silicone) of the facing of the board; and/or
(3) by increasing the binder content of the
plasters of the type of those described in the
application WO-A-9702395 and, optionally, the
content of silicate-based agents (other than
the mineral filler).
With regard jzo point (1), the plaster has been described in detail above.
With regard to point (2), the matching of the silicone contents of the facing and of the plaster was not clearly demonstrated in the application WO-A-9702395.
The invention therefore proposes to optimize the plaster content/facing content weight ratio, of between 3 and 10, with preferred content values for the facing and the board.
With regard to point (3) , the adhesion to tape was not discussed and not demonstrated in the application WO-A-9702395, since the adhesion to tape is not a criterion for finishing plasters. The invention therefore proposes to increase the binder content and/or to add polyvinyl alcohol to plasters of the type described in that application WO-A-9702395 in order to optimize the adhesion to tape (without the other properties being affected).
According to an additional and advantageous characteristic of the invention, plasterboards which have

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a paper facing, the silicone content of the coating of which is between 0.1 and 1%, are joined together. According to another characteristic, the content of the hydrophobic' or silicone agent of the plaster is between 0.5 and 3%. The plaster content/facing content weight ratio is between 3 and 10 for the optimization described above.
This therefore constitutes an excellent compromise between easy painting, effective retention of the wallpaper, strippability of the wallpaper and good adhesion of the plaster to the facing of the plasterboard, as will become apparent on reading the examples which follow.
European Patent Application No. EP 521 804 in the name of the Applicant describes a paper for covering plasterboards, and the plasterboards covered with this paper. These boards are very suitable for use with the plaster according to the invention.
Examples
The following examples are given purely by way of illustration and imply no limiting character.
Example 1
A control plaster, the composition of which is in accordance with the aforementioned international application WO-A-9 702 395, and plasters A to F according to the invention were prepared.
The various plasters were composed, apart from the essential constituents, of additives normally used in the manufacture of plasters and well known to those skilled in the art.

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The composition of the various plasters is given in the following table:

- 11

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(1): hydrophobic expanded perlite;
(2): resin of the aminated polydimethylsiloxane
type;
(3): modified cellulose ether; > (4): synergistic mixture of aromatic {non-metallic,
non-phenolic) compounds.
Example 2
Tests were carried out on the adhesion of the PREGYLISS 35 setting plaster from the Lafarge Platres range to boards as described in the aforementioned application EP-A-521 804, having:
a) a coating containing 0% silicone;
b) a coating containing 0.2% silicone;
c) a coating containing 0.4% silicone.
It was found that too high a silicone content in the coating was unfavourable to good bonding of the conventional setting plaster (adhesion value at best 0.25 MPa).
Example 3
Adhesion tests were carried out under the conditions described in paragraph 6.5 of the draft European Standard CEN2 4INI75 of January 19 98, whi ch covers the characteristics of coatings on specimens of the control plaster and plasters A to F of Example 1, with boards having a silicone content in the coating of 0.4%.
The tape adhesion was determined under the conditions described in "Guide Technique - Enduits de traitement des joints entre plaques de piatre - Modalites d'essais" [Technical Guide - Plasters for treating joints between plasterboards - Test methods] of Specialist Group No. 9 of the Commission of the CSTB responsible for drawing up technical literature (January 1999) .

- 13 -
The results are given in the table below.

5 it is clearly apparent that all the plasters according to the invention have a higher performance than the control plaster.
Example 4
Joints as indicated in Example 3 were produced. A wallpaper was then pasted onto them in the conventional way.
Next, for the purpose of determining the impact of the silicone content of the coating of the facing paper of the boards on the stripping behaviour, a steam-stripping test was carried out.
It was found that stripping was more difficult when the boards have a coating containing no silicone.
Thus, wallpaper was applied and then removed several times. The results are the same .as for the first stripping. However, it was noted that, on boards with a silicone coating, at each stripping operation markedly

14 -
more adhesive was removed than on boards with a non-silicone coating.
Example 5
A test was carried out to determine the shrinkage after drying, The following results were obtained;

The shrinkage of the plaster according to the invention is less than that of the control.
Example 6
A test was carried out under the conditions described in the application WO-A-9702395 in order to determine the L*, a* and b* values (CIE 1916 standard, Minolta CR310 1 apparatus). The following values were obtained, the middle column giving the average value for the plasters according to the invention and the right-hand column for the board according to application EP-A-521 804 used in Example 3.

The differences between the plaster and the board are imperceptible to the eye. The surface characteristics, as expressed according to the aforementioned application WO-A-9702395, are therefore very good.
The plaster according to the invention may be a setting plaster or a drying plaster; preferably it is a

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drying plaster. In the latter case, the drying plaster is advantageously a plaster called ready-mix plaster, that is to say one into which water has already been incorporated.

-16-WE CLAIM :
1. Jointing compound or plaster for construction elements comprising, in
percentages by weight with respect to the total weight of plaster:
50 to 85% of a mineral filler;
1 to 20% of an organic binder dispersible in an aqueous phase ;
1 to 15% of a silicate-based agent other than the mineral filler;
0.2 to 5% of a hydrophobic agent which is a silicone derivative ;
0.05 to 5% of polyvinyl alcohol; and
water to make up to 100%,
2. Plaster as claimed in claim 1, comprising starch and/or a starch derivative.
3. Plaster as claimed in claim 2, wherein the proportion of starch and/or
starch derivative is between 0.05 and 5%.
4. Plaster as claimed in any one of the preceding claims, wherein the silicate-
based agent comprises talc and/or mica and/or a clay.
5. Plaster as claimed in any one of the preceding claims, wherein the silicate-
based agent is a talc/mica mixture.

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6. Plaster as claimed in any one of the preceding claims, wherein the
binder/silicate-based agent weight ratio is between 0,5 and 2,
7. Plaster as ciaimed in any one of the preceding claims, wherein the
binder/hydrophobic agent weight ratio is between 1.5 and 10. ^t|(
8. Plaster as claimed in any one of the preceding claims, wherein the mineral
filler also comprises perlite, preferably expanded perlite.
9. Plaster as claimed in claim 8, wherein the mineral filler comprises between
2 and 5% perlite with respect to the total weight of the plaster.
10. Plaster as claimed in any one of the preceding daims, wherein the organic
binder dispersible in an aqueous phase is chosen from the group consisting of
polyvinyl acetate homopolymers (plasticized or unplasticized), ethylene/viny!
acetate copoiymers (plasticized or unplasticized EVAs) , ethylene/vinyl versatate
copoiyrners, vinyl acetate/vinyl versatate copoiymers, polyacrylics, vinyl
acetate/acrylic copoiymers, styrene/acrylic copoiymers, styrene/butadiene
copoiymers, vinyl acetate/vinyl versatate/acrylic terpolymers, vinyl acetate/vinyl
versatate/vinyl maleate terpolymers, acrylic terpolymers and blends thereof.

-18-
11. Plaster as claimed in any one of the preceding claims, wherein the silicone
derivative is chosen from the group consisting of siliconates, silanes,
hydrogenated silicone i oils, silicone emulsions, aminosilicone emulsions,
alkylsiloxane resins, such as hydrogenomethylpolysiloxane and aminated
polydimethylsiloxane, and mixtures thereof.
12. Plaster as claimed in any one of the preceding claims, wherein the mineral
filler comprises calcium carbonate CaCO3.
13. Plaster as claimed in any one of the preceding claims, comprising, in
percentages by weight with respect to the total weight of plaster:
50 to 70% of a mineral filler;
2 to 12% of an organic binder dispersible in an aqueous phase ;
3 to 10% of a silicate-based agent;
0.5 to 3% of a hydrophobic agent which is a silicone derivative ;
0.05 to 1% of polyvinyl alcohol;
0.1 to 1% of starch and/or a starch derivative ; and
water to make up to 100%.
14. Method of preparing a plaster as claimed in any one of the preceding
claims, comprising mixing in percentages by weight with respect to the total
weight of plaster:

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50 to 85% of a mineral filler;
1 to 20% of an organic binder dispersible in an aqueous phase ; 1 to 15% of a silicate-based agent other than the mineral filler; 0.2 to 5% of a hydrophobic agent which is a silicone derivative ; 0.05 to 5% of polyvinyl alcohol;
optionally 0.1 to 1% of starch and/or a starch derivative ; and water to make up to 100%, said mixing being carried out in any desired order.
15. Method of producing a structure, comprising : juxtaposing plasterboards
having a paper facing ^filling the space between the boards by means of a filling
piaster ; laying a tape ; covering the tape by means of the filling piaster, and
covering the filling plaster with a finishing plaster, characterized in that the silicone
content of the finishing plaster/silicone content of the facing weight ratio is
between 3 and 10.
16. Method as claimed in any one of the preceding claims, wherein the silicone
content of the coating of the facing paper is between 0,1 and 1%.
17. Method as claimed in Claim 15 or 16, wherein the same piaster is used as
filling plaster and also as finishing plaster.

-20-
18. Method as claimed in Claim 17, wherein the plaster has a binding agent
content such that the binder/silicate-based agent weight ratio is between 0.5
and 2.
19. Method as claimed in Claim 17, wherein the plaster has a binding agent
content such that the binder/hydrophobic agent weight ratio is between 1.5
and 10.
20. Method as claimed in Claim 17, wherein the plaster used is the plaster as
claimed in any one of Claims 1 to 13.
21. Method of producing a structure, comprising : juxtaposing plasterboards
having a paper facing ; filling the space between the boards by means of a filling
plaster ; laying a tape ; covering the tape by means of the filling plaster ; and
covering the filling plaster with a finishing plaster, characterized in that the filling
and finishing plaster is a plaster as claimed in any one of claims 1 to 13.
Jointing compound or plaster for construction elements comprising, in percentages by weight with respect to the total weight of plaster:
50 to 85% of a mineral filler , such as calcium carbonate ; 1 to 20% of an organic binder dispersible in an aqueous phase , such as polyacrylic ; 1 to 15% of a silicate-based agent other than the mineral filler, such as talc ; 0.2 to 5% of a hydrophobic agent which is a silicone derivative, such as siliconate ; 0.05 to 5% of polyvinyl alcohol; and water to make up to 100%.
The jointing compound or plaster can be advantageously used as a filling plaster and also as a finishing plaster.

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Patent Number

210305

Indian Patent Application Number

IN/PCT/2002/01588/KOL

PG Journal Number

39/2007

Publication Date

28-Sep-2007

Grant Date

26-Sep-2007

Date of Filing

27-Dec-2002

Name of Patentee

LAFARGE PLATRES

Applicant Address

500 RUE MARCEL DEMONQUE ZONE DU POLE TECHNOLOGIQUE, AGRO PARC, F-84915 AVIGNON, FRANCE

Inventors:

#	Inventor's Name	Inventor's Address
1	BONETTO CHRISTIAN	70 RUE DE LA FONTAINE, F-84300 CAVAILLON,
2	BOURNE-CHASTEL PASCEL	560 CHEMIN DES VOCADES F-84210, SAINT-DIDIER, FRANCE
3	PETIT ALAIN	17 LOTISSEMENT LES VERTES PRAIRIES, F-84800 ISLE SUR SORGUE, FRANCE

PCT International Classification Number

C04B 26/02

PCT International Application Number

PCT/FR01/02269

PCT International Filing date

2001-07-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	00/09393	2000-07-18	France