WO2010003867A1

WO2010003867A1 - Dispersant for dispersing matter comprising gypsum

Info

Publication number: WO2010003867A1
Application number: PCT/EP2009/058295
Authority: WO
Inventors: Antonius Wibowo; Rodney Walter Parr; Gavin Charles Tindall; David Ross
Original assignee: Huntsman International Llc
Priority date: 2008-07-08
Filing date: 2009-07-02
Publication date: 2010-01-14

Abstract

The present invention relates to dispersant, suitable for dispersing matter comprising gypsum, e.g. for dispersing such matter in aqueous dispersion, and to a method to produce such dispersant. The dispersant comprises a first structural element corresponding to the formula: wherein: R1 and R2 being a hydrogen atom or C1-C4 alkyl; R3 being an aromatic or substituted aromatic group, e.g. a sulphonated substituted aromatic group, an alkyl substituted aromatic group or a sulphonated alkyl substituted aromatic group.

Description

DISPERSANT FOR DISPERSING MATTER COMPRISING GYPSUM

The present invention relates to a dispersant, suitable for dispersing matter comprising gypsum or gypsum composition, e.g. for dispersing such matter in an aqueous dispersion, and to a method to produce such dispersant.

Various dispersants, such as salts of lignosulphonate and salts of naphthalene sulfonate formaldehyde condensate, have been used to improve the fluidity of gypsum slurry, while using a reduced amount of water. Reduction in water usage reduces costs in the form of reduction of water cost and energy cost for drying the slurry.

Salts of lignosulfonate may provide water reduction, but they retard the set times of gypsum. Salt of naphthalene sulphonate formaldehyde condensation improves the fluidity of gypsum slurry, but the amount of water to be used remains relatively large.

Copolymer of (meth)acrylic acid with (meth)acrylic acid esters of polyalkylene glycols have been used as high water reducing admixture in cement and concrete application for many years. The copolymer can be used in much lower dosages than naphthalene sulphonate formaldehyde condensate, but they are not very suitable for gypsum application due to long retardation of setting time.

US3544344 discloses an alternative dispersant, which however causes the plaster composition to retard. The dispersant is backbone copolymer, being a copolymer of styrene and maleic anhydride, to which alkoxy polyalkylene glycol is grafted.

It is an object of the present invention to provide a good dispersant for dispersing gypsum or gypsum containing matter.

It is a further object to provide a process for providing a dispersant for dispersing gypsum or gypsum containing matter. It is an advantage of some embodiments of the present invention to provide a dispersant for dispersing matter comprising gypsum, i.e. a gypsum dispersant, that gives a reduction of water usage in making slurry comprising said matter comprising gypsum. Some embodiments of the present invention provide a shorter curing time to the matter comprising gypsum, i.e. a dispersant with less retarding as compared to the dispersants in the prior art. It is an advantage of some embodiments of the present invention to provide a dispersant for dispersing matter comprising gypsum, thereby providing slurry that has a shorter curing time, while still, having acceptable flow properties. It is a further advantage that the gypsum dispersant of the present invention is used at less dosage than the dispersant in the prior art to give the same fluidity at a given amount of gypsum and water.

The above objective is accomplished by a dispersant suitable for dispersing matter comprising gypsum according to the present invention, such as dispersants for dispersing gypsum, i.e. gypsum dispersants.

According to a first aspect of the present invention, a dispersant suitable for dispersing matter comprising gypsum is provided. The dispersant, being a copolymer of various repeating elements, comprises

• a first structural element (A), corresponding to the formula:

wherein:

Rl and R2 being a hydrogen atom or C1-C4 alkyl; 81720

R3 being an aromatic or substituted aromatic group, e.g. a sulphonated substituted aromatic group, an alkyl substituted aromatic group or a sulphonated alkyl substituted aromatic group; a second structural element (D) corresponding to the formula:

wherein:

Rl 3 and Rl 4 being a hydrogen atom or C1-C4 alkyl;

Rl 5 being a hydrogen atom or a group represented by the formula -COOM; each M representing a hydrogen atom, an alkali metal atom, an alkali earth metal atom, an ammonium ion, alkylamine ion, a substituted alkylamine ion or the residue of an organic ammonium group; at least a first further structural element (Bl, B2, Cl, C2), wherein this at least one further structural element corresponding to one of a first formula, a second formula, a third formula and a fourth formula, the first formula being

the second formula being 81720

the third formula being

the fourth formula being

wherein:

R6 and R9 and Rl 2 each representing a hydrogen atom or a group represented by the formula -COOX, or a group represented by the formula -(CO)₁-O(AO)_nX, or a group represented by the formula -(CH₂)_p0(A0)_nX, or a group represented by the formula - CONH(AO)_nX;

R4, R5, R7, R8, RlO and RI l each representing a hydrogen atom or

Cl-C4 alkyl; 81720

in which each p is a number in the range of 0 to 3; each r is a number in the range of 0 to 1 ; each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X represents a hydrogen atom or C1-C4 alkyl.

It is understood that a plurality of different structural elements B 1 , B2, Cl and/or C2 may be present, each having the same or different values for p, r and/or n and/or the same or different AO groups and/or the same or different X groups.

In the dispersant, the mol ratio of the second structural element (D) over the total of the further structural elements (Bl, B2, Cl, C2) is in the range of 1 : 1 to 10: 1. The mol ratio of the first structural element (A) over the second structural element (D) is in the range of 1: 1 to 4: 1.

According to some embodiments of the present invention, the mol ratio of the second structural element (D) over the total of the further structural elements (Bl, B2, Cl, C2) may be in the range of 1 : 1 to 4: 1 , preferably in the range of 1.25 : 1 to 4: 1.

According to some embodiments of the present invention, the mol ratio of the first structural element (A) over the second structural element (D) may be in the range of 1 ,5 : 1 to 4:1, preferably in the range of 2:1 to 4:1, even more preferred in the range of 2: 1 to 3: 1.

According to some embodiments of the present invention, each n may be a number in the range of 20 to 80, such as 25 to 80, typically in the range of 20 to 60, e.g. the range of 25 to 60. 81720

R3 is thus selected from the group consisting of an aromatic substituted aromatic group (e.g. an aromatic C6 or ClO group), e.g. a sulphonated substituted aromatic group, an alkyl substituted aromatic group or a sulphonated alkyl substituted aromatic group. The substituted compounds may be H-, alkyl-, fluoro or bro mo-substituted.

The use of a first structural element is believed to reduce the curing time or "setting time" of the slurry, in which the dispersant according to the present invention is used to disperse the gypsum of the matter comprising such gypsum.

In particular, the use of R3 being an aromatic group, such as a phenyl-group, is believed to improve, i.e. reduce, the curing time of the slurry, in which the dispersant according to the present invention is used to disperse the gypsum of the matter comprising such gypsum.

It was found that the provision of the first and second structural elements cause the dispersant to link with the gypsum particles to be dispersed in a suspension. Also the carboxylic- groups of the second structural element, optionally also present as Rl 5, cause the dispersant to link with the gypsum.

The at least one further structural element, such as the first and the second further structural element, and optionally even more further structural elements, causes the gypsum to disperse, in particular in aqueous suspension.

A first further structural element according to the fourth formula may be present by reaction of a first further structural element according to the third formula, wherein R12 is a group represented by the formula -COOX. The Rl 2 carboxylic group may react with the hydrogen of the amine present in the first further structural element according to the third formula "Cl" , resulting in a further functional group according to the fourth formula "C2" with eliminating H2O. According to some embodiments of the present invention, the dispersant may comprise at least a second further structural element (Bl , B2, Cl , C2) being different from the first further structural element, the second further structural element corresponding to one of the first, second, third or fourth formula.

According to some embodiments of the present invention, the formula of the first further structural element may correspond to a first or a second formula, the formula of the second further structural element corresponding to the third or the fourth formula.

According to some embodiments of the present invention, R6 or R9 of the first further structural element may represent o a hydrogen atom or o a group represented by the formula -COOX, or o a group represented by the formula -(CO)₁-O(AO)_nX, or o a group represented by the formula -(CH2)_p0(A0)_nX; and

Rl 2 of the second further structural element may represent o a hydrogen atom or o a group represented by the formula -COOX, or o a group represented by the formula - CONH(AO)_nX in which each p is a number in the range of O to 3; each r is a number in the range of O to 1 ; each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X represents a hydrogen atom or C1-C4 alkyl. It is understood that a plurality of different further structural elements may be present, each having the same or different values for p, r and/or n and/or the same or different AO groups and/or the same or different X groups.

It is understood that Rl and R2 may mutually be identical or different. R3 may be identical or different from Rl and/or R2, in case one or both of Rl or R2 is a C1-C4 alkyl group.

According to some embodiments of the present invention, R3 may be an aromatic C6- group, i.e. a phenyl group.

According to some embodiments of the present invention, Rl and R2 may be hydrogen atoms.

It is understood that Rl 3 and R14 may mutually be identical or different. Hydrogen groups for both Rl 3 and Rl 4 are advantageous.

In case the dispersant comprises more than one further structural element, the groups R6, R9 and/or R12, as the case may be, may mutually be identical or different.

In case the dispersant comprises at least one further structural element having a formula according to the first formula, R4 and R5 may be identical or different, and optionally are both hydrogen atoms.

Similarly, in case the dispersant comprises at least one further structural element having a formula according to the second formula, R7 and R8 may be identical or different, and optionally are both hydrogen atoms. 81720

Similarly, in case the dispersant comprises at least one further structural element having a formula according to the third or the fourth formula, RlO and Rl 1 may be identical or different, and optionally are both hydrogen atoms.

Some embodiments of a dispersant according to the present invention may comprise only further structural elements having a formula according to the first formula. Alternatively, a dispersant may comprise a plurality, i.e. 2 or more, different further structural elements, which all have a formulation according to the first formula.

Alternatively, a dispersant according to the present invention may comprise only further structural elements having a formula according to the second formula. A dispersant may comprise a plurality, i.e. 2 or more, different further structural elements, which all have a formulation according to the second formula.

As a further alternative, a dispersant according to the present invention may comprise only further structural elements having a formula according to the third or the fourth formula. A dispersant may comprise a plurality, i.e. 2 or more, different further structural elements, which all have a formulation according to the third or the fourth formula.

A dispersant according to the present invention may comprise one of more different further structural elements having a formula according to one of the first, second, third or fourth formula, and one or more further structural elements, each of these further structural elements having a formula according to one or more other formulas from the first, the second, the third or the fourth formula.

Hence a dispersant according to the present invention may comprise a first further structural element having a formula according to the first formula, a second further structural element having a formula according to the second formula and a third further structural element having a formula according to the third or the fourth formula. 81720

R4, R5, R7, R8, RlO and Rl 1, as the case may be, may mutually be identical or different.

The AO representing oxyalkylene groups having 2 to 4 carbon atoms may be provided by either random addition or block addition. The AO are preferably ethylene oxide groups (EO) or propylene oxide groups (PO). The use of EO only is preferred.

The dispersant, also referred to as a gypsum dispersant, is suitable to disperse matter comprising gypsum in aqueous suspension. The term of gypsum include calcium sulphate hemihydrate, calcined gypsum, stucco and gypsum. It is understood that the gypsum may be available in several forms, e.g. Dihydrate - CaSO^H₂O (commonly known as land plaster), Hemihydrate - CaS04. /2H2O (commonly known as stucco, calcined gypsum, plaster of paris), and anhydrite - CaSθ4 (or anhydrous calcium sulphate).

Alternatively the matter comprising gypsum may be cementitious binder, which includes Portland cement, cement in accordance with European and American standard as well as other cement standard, masonry cement, and may also include limestone powder, pozzolans, PFA (Pulverized Fuel Ash) or fly ash, GGBS (ground granulated blastfurnace slag), silica fume or microsilica, metakaolin and ultrafine amorphous colloidal silica(nano-silica).

The dispersant hence is a polymeric dispersant for dispersing matter comprising gypsum.

According to some embodiments of the present invention, the weight average molecular weight of the dispersant may be in a range of 1000 to 500000.

Preferably the weight average molecular weight (MW) of the dispersant is in a range of 10000 to 150000. 81720

It was found that sufficient to superior dispersing effects are obtained when the MW is chosen within the range of 1000 to 500000, preferably between 10000 and 150000. When the molecular weight is too large or too small, the dispersant may exhibit a too poor dispersing effect. The weight average molecular weight is determined by gel permeation chromatography using polystyrene as a standard reference material.

In the dispersant according to the invention, more first structural elements (A) are present in comparison to the second structural element (D). The mol ratio of the first structural element (A) to the second structural element (D) is in the range of 1 : 1 to 4: 1, such as preferably in the range of 1.5: 1 to 4: 1 , such as in the range of 2: 1 to 4: 1 , e.g. in the range of 2:1 to 3:1.

The mol ratio of second structural element (D) over total amount of moles of further structural elements, i.e. the sum of moles of all further structural elements, is in the range of 1 : 1 to 10: 1 , such as in the range of 1 : 1 to 7: 1 , preferably 1 : 1 to 4: 1 , preferably in the range of 1.25:1 to 4: 1, e.g. 2:1 to 3:1.

In case of presence of further structural elements according to the first and/or second formula, and presence of further structural elements according to the third and/or fourth formula, the number of moles of further structural elements according to the first and second formula (Bl and/or B2) is preferably larger than the number of moles of further structural elements according to the third and/or fourth formula (Cl and/or C2). The number of moles of further structural elements according to the first and second formula (Bl and/or B2) is preferably more than 50% of the total number of moles of further structural elements (Bl and/or B2 and/or Cl and/or C2). The number of moles of further structural elements according to the first and second formula (Bl and/or B2) may represent 50% to 100% of the total number of moles of further structural elements (Bl and/or B2 and/or Cl and/or C2). Hence only further structural elements according to the first and second formula (Bl and/or B2) may be present. As an alternative though, only 81720

further structural elements according to the third and/or fourth formula (Cl and/or C2) may be present.

According to a second and a third aspect of the present invention, a process for manufacturing a dispersant, suitable for dispersing matter comprising gypsum, is provided.

The process according to the second aspect of the present invention comprises providing the first component (A'), polymerizing this component with a second component (D') thereby providing an intermediate polymer, and grafting additional components (B', C) to the intermediate polymer, thereby providing a dispersant suitable for dispersing matter comprising gypsum according to the first aspect of the present invention.

The process according to the second aspect of the present invention comprises the steps of

• providing a first component (A'), corresponding to a formula:

R¹I R'2

HC^=C

R'3 wherein:

R' 1 and R'2 being a hydrogen atom or C1-C4 alkyl; R'3 being an aromatic group, an aromatic substituted aromatic group (e.g. an aromatic C6 or ClO group), e.g. a sulphonated substituted aromatic group, an alkyl substituted aromatic group or a sulphonated alkyl substituted aromatic group;

• providing a second component (D') being maleic acid or corresponding to the formula: 81720

R'13 R'14

R¹15 COOM wherein:

R' 13 and R' 14 being a hydrogen atom or C 1 -C4 alkyl; R' 15 being a hydrogen atom or a group represented by the formula -COOM; each M representing a hydrogen atom, an alkali metal atom, an alkali earth metal atom, an ammonium ion, alkylamine ion, a substituted alkylamine ion or the residue of an organic ammonium group; • polymerizing said first and said second component, providing an intermediate polymer structure having carboxylic acid groups;

• grafting at least a first further component (B', C) to at least some of the carboxylic acid groups of the intermediate polymer for providing a polymeric dispersant, wherein said at least one further component corresponding to a formula

H₃C (AO)n OH ^

or a formula

H₃C (AO)n NH₂ (_C>)

wherein: each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X representing a hydrogen atom or Cl -C4 alkyl. 81720

The amounts of moles of the first, the second and the at least a first further component being chosen such that in the dispersant provided,

• the mol ratio of a second structural element (D) originating from component (D') to which no of said further component is grafted over the total of further structural elements (Bl, B2, Cl, C2) originating from component (D') to which at least one further component (B', C) is grafted is in the range of 1 :1 to 10:1,

• the mol ratio of a first structural element (A) originating from the first component (A') over the second structural element (D) originating from said second component (D') to which no of said further component is grafted is in the range of 1 :1 to 4:1.

Thus R3' may be selected from the group consisting of an aromatic group, an aromatic substituted aromatic group (e.g. an aromatic C6 or ClO group), e.g. a sulphonated substituted aromatic group, an alkyl substituted aromatic group or a sulphonated alkyl substituted aromatic group. The substituted compounds may be H-, alkyl-, fluoro or bro mo -substituted.

The first component is a polymerizable aromatic or substituted aromatic component such as styrene, methyl styrene, dimethylstyrene, trimethylstyrene, ethyl styrene, isopropylstyrene, propylstyrene, 4-tertbutyl styrene, fluorostyrene, trifluoromethylstyrene, pentafluorostyrene, difluoro styrene, bromostyrene, 4-ethoxystyrene, 4-tert-butoxystyrene, vinylbenzoic acid, or styrene sulphonate. Styrene is preferred.

According to some embodiments of the present invention, grafting at least a first further component (B', C) to at least some of the carboxylic acid groups of the intermediate polymer may comprise grafting of at least a first and a second, mutually different, further component (B', C), wherein both the first and the second further component corresponding to a formula 81720

H₃C (AO)n OH /_βn or a formula

H₃C (AO)n NH₂ (_C>) wherein: each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X representing a hydrogen atom or Cl -C4 alkyl.

According to some embodiments of the present invention, the formula of the first further component may correspond to a formula

H₃C (AO)n OH /_βn wherein: each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X representing a hydrogen atom or Cl -C4 alkyl; the formula of the second further component corresponding to a formula

H₃C (A0)n NH₂ (_C>) wherein: each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X representing a hydrogen atom or Cl -C4 alkyl.

n may be a number in the range of 20 to 80, such as 25 to 80, typically in the range of 20 to 60, e.g. the range of 25 to 60.

According to some embodiments of the present invention, grafting the first and the second further component may comprise grafting of the first further component, and thereafter grafting said second further component. 81720

According to some embodiments of the present invention, grafting the first and the second further component may comprise grafting the first and the second further component simultaneously.

During polymerization of first component A' and second component D', D' comprises one or more -COOH groups. After polymerization and grafting, the final polymer may be neutralized with NaOH or alkylamine or NH3, providing -COOM groups in the dispersant obtained.

The second component are polymeriseable carboxylic acids or poly(carboxylic) acids, such as acrylic acid, methacrylic acid, crotanic acid, maleic anhydride, maleic acid, itaconic anhydride, itaconic acid, citraconic aid, and furmaric acid, and their alkali metal salt, alkaline metal salts, ammonium salts, alkylamine salts, and substituted alkylamine salts. Maleic anhydride and maleic acid are prefered.

The at least one, and optionally more than one further component are grafted on the intermediate polymer, more particular on the carboxylic acid groups of the intermediate polymer.

A further structural element according to the third or fourth formula of the resulting dispersant, being a dispersant according to the first aspect of the present invention, may be provided by reacting e.g. a polyetheramine, represented by the formula X (A0)n NH₂ where: each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X represents a hydrogen atom or C1-C4 alkyl. n may be a number in the range of 20 to 80, such as 25 to 80, typically in the range of 20 to 60, e.g. the range of 25 to 60. In case the second component is maleic acid or a second component wherein R' 15 is a COOH-group, the polyetheramine may first graft to one of the two carboxylic acid groups, and further bind to the adjacent carboxylic acid group providing a further structural element according to the fourth formula.

A further structural element according to the first formula of the resulting dispersant, being a dispersant according to the first aspect of the present invention, may be provided by grafting e.g. a polyether to the intermediate polymer. Preferred polyethers are polyethers comprising one or more terminal hydroxyl groups. Monofunctional polyethers are the most preferred for use since problems with undesirable gelling of the reaction product are thereby minimized. Suitable polyethers are represented by the following formula:

X (A0)n OH each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X represents a hydrogen atom or C1-C4 alkyl.

Polyethers corresponding to the description are well-known in the art and may be readily obtained from a number of commercial sources. Methods for their preparation include an initiator such as monoalcohol or glycol or other substances having one or more active hydrogen atoms with the base catalyzed or others, followed by the addition of oxyalkylene group to the desired molecular weight.

The number of the oxyalkylene groups in the polyether or polyetheramine are preferably from 20 to 80, such as 25 to 80, typically in the range of 20 to 60, e.g. the range of 25 to 60.

17 81720

Both ethylene oxide and propylene oxide may be used, and they may be added in any manner such as random addition, block addition, alternating addition of random, and block and others. When the number of the oxyalkylene groups constituting the oxyalkylene chain of the polyether, or polyetheramine is too large or too little, the resulting dispersing effect may be insufficient.

The resulting polymer is a dispersant according to the first aspect of the present invention. It is clear that optional and/or preferred features as set out in relation to the dispersants according to the first aspect of the present invention, apply as well to the corresponding features and components used in a process of manufacturing a dispersant according to the second aspect of the present invention.

The first component (A') will provide a first structural element in the dispersant according to the first aspect of the present invention. The second component (D') will provide a second structural element in the dispersant according to the first aspect of the present invention, and will serve as a base for providing the further structural elements, which are obtained by grafting the one or more further components to the intermediate polymer.

A further component according to a formula having a hydroxyl group will provide a further structural element according to the first formula as set out in relation to the dispersants according to the first aspect of the present invention, by being grafted on a carboxylic group of the second component D'.

A further component according to a formula having an amine group will provide a further structural element according to the third formula as set out in relation to the dispersants according to the first aspect of the present invention, by being grafted on a carboxylic group of the second component D'. 81720

The groups R6 or Rl 2 of the further structural elements in the dispersant according to the first aspect of the present invention, will be determined by the type of second component used during the polymerization of the intermediate polymer.

The group R3 of the first structural elements in the dispersant according to the first aspect of the present invention, will be determined by the type of first component used during the polymerization of the intermediate polymer, which is preferably styrene in order to provide R3 being a phenyl group.

It is understood that a plurality of different further components may be grafted, simultaneously or consecutively, in order to provide different further structural elements in the dispersant.

The amount of moles of first and second component, used to provide the intermediate polymer, are chosen in such a way that, after the further components have been grafted to the parts of the second component in the intermediate polymer, the molar ratios as provided in relation to the dispersant of the first aspect of the invention is met. In particular, the amount of moles of second component (D') is chosen to meet about the sum of second structural elements (D) and further structural elements (Bl, B2, Cl and C2) in the dispersant to be provided.

In case further components according to a formula (B') and further components according to a formula (C) are used, the number of moles of further component (B') is preferably larger than the number of moles of further component (C). The number of moles of further component (B') is preferably more than 50% of the total number of moles of further components (B' and C). The number of moles of further component (B') may represent 50% to 100% of the total number of moles of further components (B' and C). Hence only further component (B') may be used. As an alternative though, only further component (C) may be used. According to a third aspect of the present invention, a process according to the present invention comprises providing the first component (A'), and copolymerizing this component with additional components thereby providing a dispersant suitable for dispersing matter comprising gypsum.

The process comprises the steps of

• providing a first component (A'), corresponding to a formula:

R¹I R'2

HC^=C

R'3 wherein:

• providing a second component (D') being maleic acid or corresponding to the formula:

R'13 R'14

C=

R' 15 COOM wherein: R' 13 and R' 14 being a hydrogen atom or C1-C4 alkyl;

R' 15 being a hydrogen atom or a group represented by the formula -COOM; each M representing a hydrogen atom, an alkali metal atom, an alkali earth metal atom, an ammonium ion, alkylamine ion, a

20 81720

substituted alkylamine ion or the residue of an organic ammonium group; providing at least a first further component (Bl", B2", C"), wherein said first further component corresponding to one of a first formula, a second formula and a third formula, said first formula being

R"6 (CO)₁ O(AO)_nX (_{B 1}")

said second formula being

R"9 (CH₂)_pO(AO)_nH φ₂,,.j

said third formula being,

R"10 R"l l C^=C

R" 12 CONH(AO)_nX /£»\ wherein:

R"6 and R"9 and R" 12 each representing a hydrogen atom or a group represented by the formula -(CO)_rO(AO)_nX, or a group represented by the formula -(CH2)_pO(AO)_nX, or a group represented by the formula - CONH(AO)_nX; R"4, R"5, R"7, R"8, R"10 and R"l l each representing a hydrogen atom or Cl-C4 alkyl; in which each p is a number in the range of O to 3; each r is a number in the range of O to 1 ; 81720

each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X represents a hydrogen atom or C 1 -C4 alkyl; • polymerizing said first, said second and said at least first further component, providing a polymeric dispersant, wherein the amounts of moles of the first, the second and the at least a first further component being chosen such that in the dispersant provided,

• the mol ratio of a second structural element (D) originating from component (D') over the total of further structural elements (Bl , B2, Cl , C2) originating from said at least one further component (Bl", B2", C") is in the range of 1 :1 to 10:1,

• the mol ratio of a first structural element (A) originating from the first component (A') over the second structural element (D) originating from said second component (D') is in the range of 1 : 1 to 4: 1.

The first component is polymerizable aromatic or substituted aromatic component such as styrene, methyl styrene, dimethylstyrene, trimethylstyrene, ethyl styrene, isopropylstyrene, propylstyrene, 4-tertbutyl styrene, fiuorostyrene, trifluoromethylstyrene,

?? 81720

pentafluorostyrene, difluorostyrene, bromostyrene, 4-ethoxystyrene, 4-tert-butoxystyrene, vinylbenzoic acid, or styrene sulphonate. Preferably the first component is styrene.

Optionally the second component is unsaturated dicarboxylic acid or anhydride, preferably maleic acid or maleic anhydride, or a combination of such products.

The various components are thus copolymerized. In the case of such copolymerization process, the polymer can be made by batch, semi-batch and continuous polymerization process using normal aqueous or non-aqueous copolymerization. The preferred solvent is aqueous.

According to some embodiments of the present invention, providing at least a first further component (Bl", B2", C") may comprise providing at least a first and a second, mutually different, further component (B l ", B2", C"), said second further component corresponding to one of said first, said second and said third formula.

According to some embodiments of the present invention, the formula of said first further component may correspond to a first or a second formula and the formula of said second further component may correspond to a third formula.

According to some embodiments of the present invention, R"6 or R"9 of said first further structural element may represent o a hydrogen atom or o a group represented by the formula -(CO)rO(AO)n X, or o a group represented by the formula -(CH2)pO(AO)n X; and R" 12 of said second further structural element represents o a hydrogen atom or o a group represented by the formula - CONH(AO)nX 81720

It is understood that a plurality of different further structural elements may be present, each having the same or different values for p, r and/or n and/or the same or different AO groups and/or the same or different X groups.

The amount of moles of first and second component are chosen in such a way that the mol ratios as provided in relation to the dispersant of the first aspect of the invention are met.

The mol ratio of the second component (D') over the total of at least one further component (Bl ", B2", C") is typically in the range of 1 : 1 to 10: 1. The mol ratio of second structural element (D) over total amount of moles of further structural elements, i.e. the sum of moles of all further structural elements, may be in the range of 1 : 1 to 7: 1, preferably 1 : 1 to 4: 1 , preferably in the range of 1.25: 1 to 4: 1 , e.g. 2: 1 to 3: 1.

The mol ratio of the first component (A') over the second component (D') is typically in the range of 1 : 1 to 4: 1.

In case further components according to a formula Bl " and/or B2" and further components according to a formula (C") are used, the number of moles of further components (Bl " and/or B2") is preferably larger than the number of moles of further component (C"). The number of moles of further components (Bl " and/or B2") is 81720

preferably more than 50% of the total number of moles of further components (Bl " and/or B2" and C"). The number of moles of further components (Bl " and/or B2") may represent 50% to 100% of the total number of moles of further components (Bl " and/or B2" and/or C"). Hence only further components (Bl " and/or B2") may be used. As an alternative though, only further component (C") may be used.

The polymeric dispersant of the present invention, obtainable by any of the processes as set out above, may be fully or partially neutralized before or after the polymer reaction, e.g. by using alkaline substances. Example of suitable alkaline substances are metal hydroxides such as alkali metal hydroxides and alkaline earth metal hydroxides, aluminium hydroxides or oxide hydroxides, tin or zinc compounds, alkyl amines or hydroxy alkyl amines.

The resulting polymer provides a dispersant according to the first aspect of the present invention. It is clear that optional and/or preferred features as set out in relation to the dispersants according to the first aspect of the present invention, apply as well to the corresponding features and components used in a process of manufacturing a dispersant according to this third aspect of the present invention.

The first component (A') will provide a first structural element in the dispersant according to the first aspect of the present invention. The second component (D') will provide a second structural element in the dispersant according to the first aspect of the present invention.

A further component according to a first formula will provide a further structural element according to the first formula as set out in relation to the dispersants according to the first aspect of the present invention.

A further component according to a second formula will provide a further structural element according to the second formula as set out in relation to the dispersants according to the first aspect of the present invention. 81720

A further component according to a third formula will provide a further structural element according to the third formula as set out in relation to the dispersants according to the first aspect of the present invention.

The groups R6, R9 or Rl 2 of the further structural elements in the dispersant according to the first aspect of the present invention, will be determined by the groups R"6, R"9 or R" 12 of the further components used during the copolymerization.

The group R3 of the first structural elements in the dispersant according to the first aspect of the present invention, will be determined by the type of first component used during the copolymerization, which first component is preferably styrene in order to provide R3 being a phenyl group.

It is understood that a plurality of different further components may be chosen, in order to provide different further structural elements in the dispersant.

According to a further, fifth aspect of the present invention, the use of a dispersant according to any the first aspect of the present invention is provided. The dispersant according to any the first aspect of the present invention is used for dispersing matter comprising gypsum in an aqueous slurry.

According to some embodiments of the present invention, the weight of the dispersion in the slurry may be 0.01% to 3.0% of the weight of the gypsum in the slurry .

Optionally, the weight of the dispersion in the slurry is 0.05% to 1.0% of the weight of the gypsum in the slurry.

The use of a dispersant according to the present invention may thus comprise mixing of matter comprising gypsum, e.g. gypsum itself, water, the dispersant and optionally other additives, such as retarders, accelerators, air entangling agents, waterproofing agents, 81720

efflorescence resistance agents, pigments, colorants or coloring agents, fibers or any mixture of such additives.

The use of the dispersant according to the first aspect of the present invention, a high water reduction, i.e. less water use, and low set time can be achieved by incorporating the dispersant according to the present invention into the composition or slurry comprising matter which matter comprises gypsum. At the same time, the present composition or slurry comprising matter comprising gypsum, does not exhibit extensive delay in set and, therefore, does not delay the timetable for forming the desired structure of which the cured gypsum comprising matter is to become part of.

The gypsum is preferably present in the compositions or slurry comprising gypsum in an amount larger than 40 wt% of the compositions or slurry comprising gypsum. More preferably, gypsum is present in an amount larger than 45 wt% of the compositions or slurry comprising gypsum, and most preferably in an amount larger than 50 wt%. The gypsum is preferably in the hemihydrate form of gypsum.

Water is needed in processing compositions or slurry comprising gypsum to disperse and set the gypsum. The amount of water required in the compositions or slurry comprising gypsum can be defined as consistency, i.e. the volume of water (ml) required to produce lOOg of compositions or slurry comprising gypsum. The excess of water in gypsum products, such as in case gypsum plasterboards are made, is removed by heating. One advantage by the use of the dispersant according to the first aspect of the present invention, is that a reduced amount of water can be used in the compositions or slurry comprising gypsum so that less time and energy are needed to remove the excess of water.

The independent and dependent claims set out particular and preferred features of the invention. Features from the dependent claims may be combined with features of the independent or other dependent claims as appropriate. 81720

The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

The present invention will be described with respect to particular embodiments.

It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Throughout this specification, references to "one embodiment" or "an embodiment" are made. Such references indicate that a particular feature, described in relation to the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, though they could. Furthermore, the particular features or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.

The word "parts" represents "parts by weight" unless otherwise specified.

When reference is made to mol ratio, molar rate or mol rate of various structural elements, this is to be understood as the average number of repeating units of the one structural element in the polymer, over the average number of repeating units of the other structural element (or group of structural elements) in the polymer. 81720

When reference is made to mol ratio, molar rate or mol rate of various components, this is to be understood as the number of moles of the one component in the reaction mixture, over the number of moles of the other component (or group of components) in the reaction mixture.

In the following examples, the synthesis of the polymeric dispersant used in gypsum composition is either by copolymerization or by grafting. Polymer 1 was synthesized by a copolymerization method. The polymer 2, 3, 4, 5, 6 and 7 were synthesized by grafting polyether, amines orpolyetheramine, and mixture thereof to polycarboxylic acid.

Polymer dispersant 3, 4, 5, 6, 7 and 8 are examples of embodiments of a dispersant according to the present invention.

The consistency of gypsum slurry containing various dispersant was tested in accordance with ASTM C472. The test is used to determine the amount of water that is required to produce desired consistency for 10Og gypsum, which reflects the fluidity necessary to obtain proper flow of the gypsum slurry in the manufacturing process.

Consistency = ml H₂O / lOOg gypsum

A slurry comprising gypsum was prepared by swiftly adding gypsum hemihydrate (20Og) into polystyrene cup containing water or dissolved dispersant candidate (125ml), as shown in Table I. The dispersant is always used in 0.4% by weight of gypsum.

After 20 seconds, the slurry is gently hand-agitated for 30 seconds using metal spatula. The slurry is immediately poured into a cylinder tube (φ 60mm), the tube is removed and the diameter of the slurry is then measured. Set times are measured by Vicat test. The initial set time determination is followed in accordance with ASTM C266. The method involves preparing gypsum composition similar to the method for determining consistency. However, 81720

to test the initial set time, the gypsum is poured into the cup. A 30Og mass, 1mm diameter Vicat needle is then allowed to repeatedly fall freely with the force of gravity to the top surface of the gypsum slurry. The initial set time is defined as the time when the vicat needle stops penetrating the slurry.

Two examples of gypsum slurry, to which no dispersant is added, are shown in Table I. The results for various examples incorporating a gypsum dispersant are given in Table I.

Preparation Polymer Example 1 The monomer mix was prepared by mixing 0.54 parts methacrylic acid (MAA), with 0.12 parts methoxy polyethylene glycol methacrylate, average molecular weight 2000 (50% in water) under N₂ for 10 minutes in a 3 neck round bottom flask. Then, 0.03 part Merchapto propionic acid was added. The obtained mixture was stirred for 10 minutes under N₂. Water was added to a reactor vessel fitted with condenser, N₂ inlet tube, thermometer and overhead stirrer. The mixture was stirred and heated to 75 ⁰C while kept under N₂. Then, the monomer mix and 0.01 parts Na₂S₂Os (10% in water) were simultaneously added to the reactor over a 3 hours period while the temperature was kept at 75 ⁰C. The monomer mix and Na₂S₂Os solution were kept under N₂ during the addition. When the addition was complete, the resulting mixture was stirred at 75 ⁰C for an additional 3 hours, while kept under N₂ (comparative Polymer dispersant 1).

Preparation Polymer Example 2

25 parts of a 50% aqueous solution of a polyacrylic acid of 5000 molecular weight was added to 52 parts of a polyethylene-polypropylene oxide polymer of molecular weight 2000, which was terminated at one end by a primary amine group and at the other end by a methyl group. The mixture was heated and maintained at 180 ⁰C, while under flowing nitrogen gas stream for a total of 2 hours. The water solution and formed as by-product was removed in the nitrogen stream (comparative Polymer dispersant 2) 81720

Preparation Polymer Example 3

75 parts of polyethylene glycol mono methyl ether, average molecular weight of 1200, is added to an open top flange pot along with 12.5 parts styrene-maleic anhydride copolymer (SMA-3000, 3:1 molar ratio, average molecular weight 3800), and heated to 120 ⁰C with stirring for 30 to 60 minutes until most of the copolymer dissolved. Further 12.5 parts of SMA-3000 is added, and reacted for 2 to 6 hours with stirring at 170 ⁰C under nitrogen padding. The resulting copolymer is then neutralized with NaOH (Polymer dispersant 3).

Preparation Polymer Example 4

50 parts of polyethylene glycol mono methyl ether, average molecular weight of 1200, is added to an open top flange pot along with 25 parts styrene-maleic anhydride copolymer (SMA-3000, 3:1 molar ratio, number molecular weight 3800), and heated to 120 ⁰C with stirring for 30 to 60 minutes until most of the copolymer dissolved. Further 25 parts of SMA-3000 is added, and reacted for 2 to 6 hours with stirring at 170 ⁰C under nitrogen padding. The resulting copolymer is then neutralized with NaOH (Polymer dispersant 4).

Preparation Polymer Example 5

43 parts of polyethylene glycol mono methyl ether, average molecular weight of 1200, is added to an open top flange pot along with 28.5 parts styrene-maleic anhydride copolymer (SMA-2000, 2:1 molar ratio, number molecular weight 3000), and heated to 120 ⁰C with stirring for 30 to 60 minutes until most of the copolymer dissolved. Further 28.5 parts of SMA-2000 is added, and reacted for 2 to 6 hours with stirring at 170 ⁰C under nitrogen padding. The resulting copolymer is then neutralized with NaOH (Polymer dispersant 5).

Preparation Polymer Example 6

43 parts of polyethylene glycol mono methyl ether, average molecular weight of 1600, is added to an open top flange pot along with 28.5 parts styrene-maleic anhydride 81720

copolymer (SMA-3000, 3:1 molar ratio, number molecular weight 3800), and heated to 120 ⁰C with stirring for 30 to 60 minutes until most of the copolymer dissolved. Further 28.5 parts of SMA-3000 is added, and reacted for 2 to 6 hours with stirring at 170 ⁰C under nitrogen padding. The resulting copolymer is then neutralized with NaOH (Polymer dispersant 6).

Preparation Polymer Example 7

55 parts of polyethylene glycol mono methyl ether, average molecular weight of 1000, is added to an open top flange pot along with 22.5 parts styrene-maleic anhydride copolymer (SMA-3024, 3:1 molar ratio, number molecular weight 10,000), and heated to 120 ⁰C with stirring for 30 to 60 minutes until most of the copolymer dissolved. Further 22.5 parts of SMA-3024 is added, and reacted for 2 to 6 hours with stirring at 170 ⁰C under nitrogen padding. The resulting copolymer is then neutralized with NaOH (Polymer dispersant 7).

Preparation Polymer Example 8

45 parts of polyethylene glycol mono methyl ether, average molecular weight of 1000, is added to an open top flange pot along with 27.5 parts styrene-maleic anhydride copolymer (SMA-3000, 3: 1 molar ratio, number molecular weight 3800), and heated to 120 ⁰C with stirring for 30 to 60 minutes until most of the copolymer dissolved. Further 27.5 parts of SMA-3000 is added, and reacted for 2 to 6 hours with stirring at 170 ⁰C under nitrogen padding. The mixture was then added to the monoethanolamine solution and heated to about 80 ⁰C (Polymer dispersant 8).

81720

Table I

The larger the diameter of the gypsum slurry, the less consistent the slurry is. Less consistent gypsum slurry is more easy to apply.

For gypsum slurry without dispersant, it is clear that more water is needed (160ml) in order to obtain a less consistent slurry, resulting in a diameter of the slurry of about 200mm or more.

Preparation Polymer Example 9

45 parts of polyethylene glycol mono methyl ether, average molecular weight of 1000, is added to an open top flange pot along with 27.5 parts styrene-maleic anhydride copolymer (SMA-3000, 3:1 molar ratio, number molecular weight 3800), and heated to 120 ⁰C with stirring for 30 to 60 minutes until most of the copolymer dissolved. Further 27.5 parts of SMA-3000 is added, and reacted for 2 to 6 hours with stirring at 170 ⁰C under nitrogen padding. The resulting copolymer is then neutralized with NaOH (Polymer dispersant 9). 81720

Preparation Polymer Example 10

A mixture of 161.7 parts of isopropanol and 132.3 parts of water was loaded into a reaction vessel fitted with a thermometer, a stirrer, a dropping funnel and a nitrogen inlet tube, a reflux condenser, stirred while the inside of the reaction vessel was flushed with nitrogen, and then heated to 82 ⁰C. A monomer mixture solution was prepared by mixing

100 parts of methyl polyethylene glycol monomethacrylic ester (average number of addition mols of ethylene oxide of 23), 22 parts of (meth)acrylic acid, 53.4 parts of styrene and 25 parts of isopropanol. The obtained aqueous monomer mixture solution and sodium persulfate solution (4.4 parts of sodium persulfate and 32 parts of water) were each added dropwise over a period of 120 minutes.

After the dropwise addition was completed, the remaining sodium persulfate solution was further added thereto over a period of 30 minutes. The reaction vessel and the contents thereof were continuously kept at a temperature of 82 ⁰C for 60 minutes to complete the polymerization reaction. The resulting dispersant was obtained by neutralizing the reaction solution with an 30% aqueous sodium hydroxide solution. (Polymer dispersant 10).

Preparation Polymer Example 11 A mixture of 161.7 parts of isopropanol and 132.3 parts of water was loaded into a reaction vessel fitted with a thermometer, a stirrer, a dropping funnel and a nitrogen inlet tube, a reflux condenser, stirred while the inside of the reaction vessel was flushed with nitrogen, and then heated to 82 ⁰C. A monomer mixture solution was prepared by mixing 143 parts of polyethylene glycol methacrylate (contains 30% water, average number of addition mols of propylene oxide of 4 and mols of ethylene oxide of 14), 36 parts of acrylic acid, 94 parts of styrene and 45 parts of isopropanol. The obtained aqueous monomer mixture solution and sodium persulfate solution (3.6 parts of sodium persulfate and 32 parts of water) were each added dropwise over a period of 120 minutes. 81720

After the dropwise addition was completed, the remaining of sodium persulfate solution was further added thereto over a period of 30 minutes. The reaction vessel and the contents thereof were continuously kept at a temperature of 82 ⁰C for 90 minutes to complete the polymerization reaction. The resulting dispersant was obtained by neutralizing the reaction solution with a 30% aqueous sodium hydroxide solution. (Polymer dispersant 11).

Preparation Polymer Example 12

A mixture of 137.5 parts of isopropanol and 112.5 parts of water was loaded into a reaction vessel fitted with a thermometer, a stirrer, a dropping funnel and a nitrogen inlet tube, a reflux condenser, stirred while the inside of the reaction vessel was flushed with nitrogen, and then heated to 82 ⁰C. A monomer mixture solution was prepared by mixing 85 parts of methyl polyethylene glycol monomethacrylic ester (average number of addition mols of ethylene oxide of 23), 28 parts of acrylic acid, 72 parts of styrene and 25 parts of isopropanol. The obtained aqueous monomer mixture solution and sodium persulfate solution (a mixture of 1.6 parts sodium persulfate and 22 parts of water) were each added dropwise over a period of 120 minutes.

After the dropwise addition was completed, the remaining sodium persulfate solution was further added thereto over a period of 30 minutes. The reaction vessel and the contents thereof were continuously kept at a temperature of 82 ⁰C for 150 minutes to complete the polymerization reaction. The resulting dispersant was obtained by neutralizing the reaction solution with a 30% aqueous sodium hydroxide solution. (Polymer dispersant 12).

The composition of the polymer dispersants is shown in table II. 81720

Table II

Evaluation of polymer dispersant 2, 9, 10, 11, and 12

A slurry comprising gypsum was prepared by swiftly adding gypsum hemihydrate (20Og) into polystyrene cup containing water or dissolved dispersant candidate (140ml), as shown in Table II. The dosage dispersant was adjusted to obtain slurry diameter of 200mm ± 5mm.

After 20 seconds, the slurry is gently hand-agitated for 30 seconds using metal spatula. The slurry is immediately poured into a cylinder tube (φ 60mm), the tube is removed and the diameter of the slurry is then measured, giving an indication of the flow of the slurry. Set times are measured by Vicat test. The initial set time determination is followed in accordance with ASTM C266. The method involves preparing gypsum composition similar to the method for determining consistency. However, to test the initial set time, the gypsum is poured into the cup. A 300g mass, 1mm diameter Vicat needle is then allowed to 81720

repeatedly fall freely with the force of gravity to the top surface of the gypsum slurry. The initial set time is defined as the time when the vicat needle stops penetrating the slurry. The results are shown in table III.

Table III

As is clear, using a gypsum dispersant according to the present invention, i.e. dispersants 9, 10, 1 1 , and 12, a lower initial setting time is obtained as compared to the use of a dispersant being comparative examples (dispersant 2).

Preferably the amount of structural elements in the gypsum dispersant is such that the ratio (expressed as mol-ratio) of structural element A to the total of structural elements Bl, B2, Cl, C2 and D is in the range of 1 :4 to 4: 1, more preferred in the range of 1 : 1 to 3:1, such as in the range of 1 : 1 to 2: 1.

The ratio (expressed as mol-ratio) of structural element D to the total of Bl , B2, Cl and/or C2 is preferably in the range of 1 : 1 to 10:1 , more preferred in the range of 1 : 1 to 5:1. The ratio (expressed as mol-ratio) of structural element D to the total of Bl and B2, and the ratio (expressed as mol-ratio) of structural element D to the total of Cl and C2 is preferably in the range of 1 : 1 to 10: 1, more preferred in the ratio 1 : 1 to 5 : 1. 81720

The above is in particular preferred when structural element A is provided by styrene, structural element D is provided by maleic acid, the structural element Bl being of the type of maleic half esters and component Cl, if present, is a maleic amide.

Several different dispersants according to the first aspect of the present invention may be made by copolymerization of a plurality of components. As examples, component A' and component D' may be copolymerized with further components B' and/or C.

The first component corresponds to a general formula

R¹I R'2

HC^=C R'3

The first component are polymerizable aromatic components such as styrene, methylstyrene, 4-methoxystyrene, 4-methylstyrene. Styrene is preferred.

The second component corresponds to the general formula

R'13 R'14

R'15 COOM

Suitable examples are unsaturated dicarboxylic acid, including maleic acid, itaconic acid, citraconic acid and fumaric acid, and their anhydrides including maleic anhydrides, itaconic anhydride and citraconic anhydride. It is preferably to use maleic acid or maleic anhydride. The first and second components may be copolymerized with a further component (Bl") e.g maleic ester or half ester of polyalkylene glycols blocked with an alkyl group at one end such as methoxypolyethylene glycol, methoxypolyethylene-polypropylene glycol, ethoxypo lyethylene glyco l, ethoxypolyethylene -polypropylene glycol, propoxypolyethylene glycol, and propoxypolyethylene -polypropylene glycol. It is preferably to use maleic half ester of methoxypolyalkylene glycol. 81720

The first and second components may be copolymerized with a further component (B2") e.g vinyl ether or allyl ether, such as methoxypo Iy ethylene glycol monovinyl ether, polyethylene glycol monovinyl ether, methoxypolyethylene glycol mono(meth)allyl ether and polyethylene glycol mono(meth)allyl ether. The first and second components may be copolymerized with a further component (C") e.g including maleic amide or imide of polyalkylene glycols blocked with an alkyl group at one end, such as amido polyethyleneglycol methyl ether, amido polypropyleneglycol methyl ether, amido polyethylenepropyleneglycol methyl ether, amido polyethyleneglycol ethyl ether, amido polypropyleneglycol ethyl ether, amido polyethylenepropyleneglycol ethyl ether, amido polyethyleneglycol butyl ether, amido polypropyleneglycol butyl ether, amido polyethylenepropyleneglycol butyl ether. It is preferably to use maleic amide of amido polyethyleneglycol methyl ether. Two or more different components Bl" may be copolymerized with the first and second components. Similarly two or more components B2" or two or more components C" may be copolymerized with the first and second components. Optionally, combinations of one or more components Bl", one or more components B2" and/or one or more components C" may be copolymerized with the first and second components.

An other process of manufacturing a dispersant according to the present invention uses first the polymerization of two components, providing an intermediate polymer, and thereafter grafting one or more further components to the intermediate polymer.

As examples, component A' and component D' may be copolymerized forming so-to-say a backbone intermediate polymer structure.

The first component corresponds to a general formula

R¹I R'2

HC^=C R'3 81720

The second component corresponds to the general formula

R'13 R'14

R'15 COOM

Suitable examples are unsaturated dicarboxylic acid, including maleic acid, itaconic acid, citraconic acid and fumaric acid, and their anhydrides including maleic anhydrides, itaconic anhydride and citraconic anhydride. It is preferably to use maleic acid or maleic anhydride.

Onto the carboxylic acid groups, polyetheramines (compounds C) and/or polyethers (compounds B') are grafted. Two or more different polyetheramines may be grafted simultaneously or in sequence. Similarly two or more polyethers may be grafted simultaneously or in sequence. Optionally, one or more polyetheramines and one or more polyethers may be grafted simultaneously or in sequence.

It is to be understood that although preferred embodiments and/or materials have been discussed for providing embodiments according to the present invention, various modifications or changes may be made without departing from the scope and spirit of this invention.

Claims

81720CLAIMS

1.- A dispersant, suitable for dispersing matter comprising gypsum, the dispersant comprising • a first structural element (A), corresponding to the formula:

wherein:

Rl and R2 being a hydrogen atom or C1-C4 alkyl; R3 being an aromatic or substituted aromatic group; a second structural element (D) corresponding to the formula:

wherein:

Rl 3 and Rl 4 being a hydrogen atom or C1-C4 alkyl;

Rl 5 being a hydrogen atom or a group represented by the formula -COOM; each M representing a hydrogen atom, an alkali metal atom, an alkali earth metal atom, an ammonium ion, alkylamine ion, a substituted alkylamine ion or the residue of an organic ammonium group; at least a first further structural element (Bl , B2, Cl , C2), wherein said at least one further structural element corresponding to one of a first formula, a second formula, a third formula and a fourth formula, said first formula being 81720

said second formula being

said third formula being

said fourth formula being

wherein:

R6 and R9 and Rl 2 each representing a hydrogen atom or 81720

a group represented by the formula -COOX, or a group represented by the formula -(CO)₁-O(AO)_nX, or a group represented by the formula -(CH2)_pO(AO)_nX, or a group represented by the formula - CONH(AO)_nX; R4, R5, R7, R8, RlO and Rl 1 each representing a hydrogen atom or

Cl-C4 alkyl; in which each p is a number in the range of O to 3; each r is a number in the range of O to 1 ; each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X represents a hydrogen atom or C1-C4 alkyl; the mol ratio of the second structural element (D) over the total of the further structural elements (B 1 , B2, Cl , C2) is in the range of 1 : 1 to 10: 1 , the mol ratio of the first structural element (A) over the second structural element (D) is in the range of 1 : 1 to 4: 1.

2.- A dispersant according to claim 1, wherein the mol ratio of the second structural element (D) over the total of the further structural elements (Bl, B2, Cl, C2) is in the range of 1 : 1 to 4: 1 , preferably in the range of 1.25: 1 to 4: 1.

3.- A dispersant according to claim 1 or 2, wherein the mol ratio of the first structural element (A) over the second structural element (D) is in the range of 1 ,5 : 1 to 4: 1 , preferably in the range of 2: 1 to 4:1, even more preferred in the range of 2:1 to 3: 1.

4.- A dispersant according to any one of the preceding claims, wherein each n is a number in the range of 25 to 80, typically in the range of 25 to 60. 81720

5.- A dispersant according to any one of the preceding claims, wherein the dispersant comprises at least a second further structural element (Bl , B2, Cl , C2) being different from said first further structural element, said second further structural element corresponding to one of said first, second, third or fourth formula.

6.- A dispersant according to any one of the claims 1 to 5, wherein R3 is a phenyl group.

7.- A dispersant according to claim 6, wherein Rl and R2 are hydrogen atoms.

8.- A dispersant according to any one of the claims 1 to 7, wherein the weight average molecular weight of the dispersant is in a range of 5000 to 500000.

9.- A process for manufacturing a dispersant, suitable for dispersing matter comprising gypsum, the process comprises the steps of

• providing a first component (A'), corresponding to a formula:

R¹I R'2

HC^=C

R'3 wherein:

R' 1 and R'2 being a hydrogen atom or C1-C4 alkyl; R'3 being an aromatic or substituted aromatic group;

R'13 R'14

C:

R¹15 COOM wherein: R'13 and R'14 being a hydrogen atom or C1-C4 alkyl; 81720

R' 15 being a hydrogen atom or a group represented by the formula -COOM; each M representing a hydrogen atom, an alkali metal atom, an alkali earth metal atom, an ammonium ion, alkylamine ion, a substituted alkylamine ion or the residue of an organic ammonium group;

• polymerizing said first and said second component, providing an intermediate polymer structure having carboxylic acid groups;

H₃C (AO)n OH (_B>)

or a formula

H₃C (AO)n NH₂ (_C>)

wherein: each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X representing a hydrogen atom or Cl -C4 alkyl, the amounts of moles of the first, the second and the at least a first further component being chosen such that in the dispersant provided,

• the mol ratio of a second structural element (D) originating from component

(D') to which no of said further component is grafted over the total of further structural elements (Bl, B2, Cl, C2) originating from component (D') to 81720

which at least one further component (B', C) is grafted is in the range of 1 :1 to 10:1,

10.- A process for manufacturing a dispersant, suitable for dispersing matter comprising gypsum, the process comprises the steps of • providing a first component (A'), corresponding to a formula:

R¹I R'2

HC^=C

R'3 wherein:

R' 1 and R'2 being a hydrogen atom or C1-C4 alkyl; R'3 being an aromatic or substituted aromatic group; • providing a second component (D') being maleic acid or corresponding to the formula:

R'13 R'14

R¹15 COOM wherein:

R' 13 and R' 14 being a hydrogen atom or C1-C4 alkyl; R'15 being a hydrogen atom or a group represented by the formula -COOM; each M representing a hydrogen atom, an alkali metal atom, an alkali earth metal atom, an ammonium ion, alkylamine ion, a substituted alkylamine ion or the residue of an organic ammonium group; 81720

providing at least a first further component (Bl", B2", C"), wherein said first further component corresponding to one of a first formula, a second formula and a third formula, said first formula being R"4 R"5

R"6 (CO).0(AO)_nX (_{B 1}")

said second formula being

R"7 R"8

R"9 (CH₂)_p O(AO)_n H ^₂,,.)

said third formula being

R"10 R"l l C^=C

R" 12 CONH(AO)_nX /£»\ wherein:

R"6 and R"9 and R" 12 each representing a hydrogen atom or a group represented by the formula -(CO)_rO(AO)_nX, or a group represented by the formula -(CH2)_pO(AO)_nX, or a group represented by the formula - CONH(AO)_nX; R"4, R"5, R"7, R"8, R"10 and R"l l each representing a hydrogen atom or Cl-C4 alkyl; in which each p is a number in the range of O to 3; 81720

each r is a number in the range of 0 to 1 ; each n is a number in the range of 20 to 80; each AO representing an oxyalkylene group having 2 to 4 carbon atoms; each X represents a hydrogen atom or Cl -C4 alkyl;

• polymerizing said first, said second and said at least first further component, providing a polymeric dispersant, wherein the amounts of moles of the first, the second and the at least a first further component being chosen such that in the dispersant provided, the mol ratio of a second structural element (D) originating from component (D') over the total of further structural elements (Bl, B2, Cl, C2) originating from said at least one further component (Bl", B2", C") is in the range of 1 :1 to 10:1 and the mol ratio of a first structural element (A) originating from the first component (A') over the second structural element (D) originating from said second component (D') is in the range of 1: 1 to 4: 1.

11.- The use of a dispersant according to any one of the claims 1 to 8, for dispersing matter comprising gypsum in an aqueous slurry.