WO2025035453A1

WO2025035453A1 - Polycarboxylate based dispesant

Info

Publication number: WO2025035453A1
Application number: PCT/CN2023/113542
Authority: WO
Inventors: Qing Zhang; Yalei CHEN; Jiali ZHU; Jianghong Liu
Original assignee: Sika Technology AG
Current assignee: Sika Technology AG
Priority date: 2023-08-17
Filing date: 2023-08-17
Publication date: 2025-02-20
Anticipated expiration: 2026-02-17
Also published as: WO2025037017A1; MX2025014466A; CN121419950A

Abstract

The invention relates to dispersant for mineral binder compositions, which contains a copolymer comprising or consisting of a) a mole fractions of a structural subunit S1 of the formula (I) b) b mole fractions of a structural subunit S2 of the formula (II) c) optionally, c mole fractions of a further structural subunit S3 derived from other comonomers, wherein Ru, Rv, M, R, R5, R6, R7, R8 and z, are defined as described in the description. The invention also relates to a method for producing such dispersants, a hydraulically setting binder composition comprising the same.

Description

POLYCARBOXYLATE BASED DISPESANT

Technical field

The invention relates to a dispersant containing a polycarboxylate copolymer for hydraulically setting binder compositions, and its use for improving the early strength as well as a method for producing this dispersant.

Background art

Dispersants are used as plasticizers or water-reducing agents for hydraulically setting binder compositions, such as concrete, mortars, cements, plasters, and lime, for example. The dispersants are generally organic polymers, which are added to the mixing water or admixed in solid form to the binder compositions. As a result, it is possible to advantageously modify not only the binder composition consistency during processing but also the properties in the cured state.

In this regard, lots of prior art references describe for example dispersants based on polycarboxylic acid copolymers. The copolymers include a structural unit derived from an unsaturated polyalkylene glycol ether monomer with a predetermined structure and a structural unit derived from an unsaturated carboxylic acid monomer. The unsaturated polyalkylene glycol ether monomer can e.g. comprise an alkenyl group such as a vinyl group, an allyl group, a methallyl group, and a 3-methyl-3-butenyl group. Inter alia, the unsaturated carboxylic acid monomer can be selected from unsaturated (di) carboxylic acid monomers such as e.g. (meth) acrylic acid, maleic acid, fumaric acid or itaconic acid, or the salts thereof. The copolymers can be produced by solvent or bulk copolymerization with a polymerization initiator. Typically, the copolymerization is effected using a chain transfer agent such as hypophosphites like sodium hypophosphite.

However, there are problems with such known dispersants. The first one is related to the insufficient early strength. In order to increase the early strength of such dispersants, some additional functional monomers are usually needed in the polycarboxylic acid copolymers, which makes the reaction process more complex and energy consumptive. Furthermore, such dispersants may be not very efficient in certain binder compositions.

There is thus a need to develop new and improved dispersants which reduce or overcome the aforementioned drawbacks.

Disclosure of the invention

It is an object of the present invention to provide new dispersants which do not have or reduce the above mentioned drawbacks, especially showing further improved early strength and setting time performances as well as better water reduction and slump keeping performance, even with a reduced addition amount. Such dispersants may be especially suitable for the mineral binder, in particular cement, preferably a Portland cement and the supplementary cementitious materials (SCM) such as limestone, slag, or pozzolanic binder.

Furthermore, the dispersants should be based on the polycarboxylic acid copolymers which may be prepared easily and need no additional functional monomers to enhance the early strength.

Surprisingly, it has been found that the objective of the invention can be achieved by a copolymer according to claim 1.

The present invention also provides a method for preparation of the new dispersants and the mineral binder composition containing such dispersants.

Further aspects of the invention are subjects of further independent claims. Particularly preferred embodiments of the invention are subjects of dependent claims.

Ways of carrying out the invention

A first aspect of the invention relates to a dispersant for mineral binder compositions, which contains a copolymer comprising or consisting of:

a) a mole fractions of a structural subunit S1 of the formula (I)

b) b mole fractions of a structural subunit S2 of the formula (II)

c) optionally, c mole fractions of a further structural subunit S3 derived from other comonomers

where

M independently of one another represents H⁺, an alkali metal ion, alkaline earth metal ion, a bivalent or trivalent metal ion, an ammonium ion or an organic ammonium group,

each R^u independently of one another stands for hydrogen or a methyl group,

each R^v independently of one another stands for hydrogen or COOM,

R⁵, R⁶, and R⁷, in each case independently of one another, are H or an alkyl group with 1 –5 carbon atoms, in particular H;

R⁸, in each case independently of one another, is a group of the formula - [AO] _n-R^a, where

A is independently of one another C₂-to C₄-alkylene,

R^a is H, a C₁ to C₂₀ alkyl, cycloalkyl or alkylaryl group, and

n is an integer such that the number average molecular weight (M_n) of the group - [AO] _n-R^a is more than 4'900 g/mol, especially more than 5’200 g/mol, in particular more than 5'700 g/mol;

z is 0, 1 or 2;

and where a, b, and c are mole fractions of the respective structural subunits S1, S2, an S3, where

a/b/c = (0.1 –0.99) / (0.01 –0.9) / (0 –0.8) , preferably

a/b/c = (0.76 –0.99) / (0.01 –0.24) / (0 –0.23) , and

with the proviso that a + b + c is 1 and that a/b > 3.2.

Another aspect of the invention relates to a method for producing the dispersant as described above.

A still another aspect of the invention relates to a mineral binder composition comprising a dispersant as described above and a mineral binder, in particular cement, preferably a Portland cement and the supplementary cementitious materials (SCM) such as limestone, slag, or pozzolanic binder.

Surprisingly, it is found by the inventors that the dispersant based on the copolymer as defined above may significantly improve the early strength and also result in the short setting time in the mineral binder compositions in particular containing cement, preferably a Portland cement and the supplementary cementitious materials (SCM) . Especially, it is surprisingly found that the selected number average molecular weight (M_n) of the group - [AO] _n-R^a and the ratio of a/b as required in the copolymer may be essential to the improvement of the early strength and the setting behavior.

The sequence of the structural subunits S1, S2, and S3 in the copolymer may be alternating, block-like or random. It is also possible, moreover, for there to be further structural subunits in addition to the structural subunits S1, S2, S3 and S4.

The structural subunits S1, S2, S3 and S4 together preferably have a weight fraction of at least 50 wt%, more particularly at least 90 wt%, very preferably at least 95 wt%or at least 99 wt%, of the total weight of the copolymer. Even more preferred, the structural subunits S1, S2 and S4 together have a weight fraction of at least 50 wt%, more particularly at least 90 wt%, very preferably at least 95 wt%or 99 wt. %, or even 100 wt.%of the total weight of the copolymer.

Especially preferred are copolymers with R^u and R^v being hydrogen or methyl and M being H⁺ or an alkali metal ion. Such kind of copolymers can be produced starting from (meth) acrylic acid or salts thereof.

Herein, A is independently of one another C₂-to C₄-alkylene, meaning that A may be independently any selected from C₂-, C₃-or C₄-alkylene in case of single or multiple occurrences.

With regard to structural subunit S2, R⁵ = R⁶ = R⁷ = H with R^a = H, z=0 and A = C₂-alkylene is preferred. Copolymers of these kinds can be prepared, for example, starting from ethylene glycol vinyl ethers (EPEG) . Likewise preferred are structural subunits S2 where R⁵ = R⁶ = R⁷ = H with R^a = H and z=0, and A consists of one C4-alkylene unit followed by C₂-alkylene units. Copolymers of these kinds can be prepared, for example, starting from ethylene glycol vinyloxybutyl ethers (VPEG) .

Preferably, a proportion of ethylene oxide units or C₂-alkylene oxide units in the group of the formula - [AO] _n-R^a, based on all the alkylene oxide or C₂-alkylene oxide units present in the group of the formula - [AO] _n-R^a, is more than 90 mol %, especially more than 95 mol %, preferably more than 98 mol %, in a particular 100 mol %. This is in particular advantageous if air entrainment by the copolymers shall be reduced. However, for special applications, copolymers comprising higher proportions of C₃-and or C₄-alkylene oxide units in the groups of the formula - [AO] _n-R^a might be suitable as well.

In the present invention, it is essential to select the integer of n such that the number average molecular weight (M_n) of the group - [AO] _n-R^a is more than 4'900 g/mol, especially more than 5’ 200 g/mol, in particular more than 5'700 g/mol. In a further embodiment, the integer of n may be selected such that the number average molecular weight (M_n) of the group - [AO] _n-R^a is less than 10’ 000, preferably less than 8’ 000. Therefore, in one advantageous embodiment, the integer of n may be an integer larger than 105, such as 110 or 115 or 120 or 130 and preferably less than 240, such as 235, 225, 210, 200, 190 and 185.

It has been found that the slump property could not be improved and the setting time could not be significantly shortened if M_n is less than 4’900 g/mol. Also, the mechanical property will be further improved if the number average molecular weight (M_n) is above 4’900 g/mol.

In the present context, the weight-average molecular weight (M_w) and the number-average molecular weight (M_n) are determined presently by gel permeation chromatography (GPC) using polyethylene glycol (PEG) as a standard. This technique is known per se to the person skilled in the art.

According to the instant invention, the ratio of the mole fraction a/b is required to be more than 3.2, preferably more than 3.6 or 4.0 or 4.5. As for the upper limit of a/b, it depends on the preparation and synthesis of the copolymer and may be such as below 13.0, preferably below 12.0 or such as below 11.0 or 9.5 or 8.0. It has been found that the properties in terms of slump, air content and setting time may be probably inclined to be insufficient if the ratio of a/b is less than 3.2.

Regarding the weight of the copolymer, the copolymer preferably has a mean molecular weight M_n of 500 –200'000 g/mol, especially 5'000 –70'000 g/mol, in particular 15'000 –50'000 g/mol.

In a particular embodiment, the copolymer comprises a further structural subunit S3. Thereby, the further structural units typically are units arising by polymerization of ethylenically unsaturated compounds, in particular ethylenically unsaturated carboxylic acids or derivatives thereof, particularly salts, anhydrides, esters, or amides thereof. With further structural subunit S3, the properties of the copolymer can e.g. be adapted to special applications.

Typically, if present, the further structural subunit S3 can e.g. be present with a proportion of >0 –50 mole %, especially >0 –30 mole %, in particular >0 –10 mole %, especially 0.0001 –5 mole %, in particular 0.001 –2 mole %, with respect to the sum of the structural units S1, S2, S3 and S4 of the copolymer. Especially, the further structural subunit S3 may be also absent in the copolymer.

Examples of further structural subunit S3 are units arising by polymerization of hydroxy alkyl (meth) acrylate in which alkyl may refer to C1-C8 or C2-C6 alkyl, like hydroxy ethyl (meth) acrylate, maleic acid, mesaconic acid, citraconic acid, glutaconic acid, fumaric acid, maleamic acid, itaconic acid, vinylbenzoic acid, crotonic acid, or anhydrides of the aforementioned acids or derivatives thereof, particularly the salts, anhydrides, esters, or amides thereof, preferably hydroxy alkyl (meth) acrylate like hydroxy ethyl (meth) acrylate.

Nevertheless, in a highly preferred embodiment, the copolymer has less than 2 mol %of structural subunit S3, especially less than 1 mol %structural subunit S3, particularly no structural subunit S3. Such kind of copolymers can be produced in a highly efficient and economic manner and at the same time show very good plasticizing effects in in various and different mineral binder systems.

The copolymer of the invention usually contains a subunit S4 derived from the chain transfer agent which comprises unsaturated alkyl sulfonate (S) , hypophosphite (H) , and/or mercapto-group containing aliphatic acid (M) ; preferably hypophosphite (H) ; more preferably sodium or kalium hypophosphite.

The unsaturated alkyl sulfonate includes usually a C-C unsaturated group like vinyl group in the molecule, such as allyl sulfonate or methallyl sulfonate.

The mercapto-group containing aliphatic acid may be represented by the formula HS-R’-COOH, wherein R’ denotes a divalent aliphatic group such as alkylene group having 1-8, preferably 1-6 carbon atoms. The suitable examples thereof may include mercapto propionic acid or mercapto acetic acid, preferably mercapto propionic acid.

The hypophosphite is usually used as a chain transfer agent in the free radical polymerization of a polycarboxylate polymer. It includes the hypophosphites of an alkali metal such as sodium or potassium. One preferred hypophosphite is sodium hypophosphite.

The copolymer is produced by free radical polymerization. Thereby the copolymer forms by the successive addition of free-radical building blocks. Thereby, the free-radical building blocks may be added in alternating, block-like or random manner.

In particular, the copolymer is produced in a polymerization reaction at a temperature of 10℃ to 50℃, preferably of 15℃ to 35℃. Surprisingly, such kind of copolymers can have a highly uniform distribution of structural subunits S1, S2 and if present S3.

In particular, the copolymer is obtained by a polymerization reaction which takes place in the presence of an initiator for free radical polymerization. The initiator preferably is a redox system-based initiator.

Especially, the initiator comprises a peroxide and a reducing agent. The reducing agent especially comprises a sulfinic acid derivate and/or a metal salt. In particular, the reducing agent comprises hydroxymethylsulfinate salt and/or an iron salt, preferably a sodium hydroxymethylsulfinate and an iron (II) salt, e.g. iron sulfate. The peroxide is in particular hydrogen peroxide.

According to a particular preferred embodiment, the copolymer is obtained in a polymerization reaction which takes place in absence of peroxydisulfates and/or persulfates.

A further aspect of the present invention is related to a method for producing the dispersant as described above, in particular a copolymer as described above, comprising the step of polymerizing:

a) a' mole fractions of a compound S1' of the formula (III) :

b) with b' molar fractions of a compound S2' of the formula (IV) :

c) optionally c' molar fractions of a further compound S3';

wherein R^u, R^v, M, R, R⁵, R⁶, R⁷, R⁸, and z, are defined as described above in connection with the copolymer and where a', b', and c' are mole fractions of the respective structural subunits S1', S2', an S3', where

a'/b'/c'= (0.1 –0.99) / (0.01 –0.9) / (0 –0.8) , preferably

a'/b'/c'= (0.76 –0.99) / (0.01 –0.24) / (0 –0.23) , and

with the proviso that a'+ b'+ c′ is 1 and that a’ /b’ > 3.2.

In advantageous embodiments, a compound S1' of the formula (III) may be an acrylic acid or a methacrylic acid. In other advantageous embodiments a compound S2' of the formula (IV) may be polyethylene glycol vinyl ether (EPEG) , polyethylene glycol monomethallyl ether (HPEG) , isopentenyl polyethylene glycol (TPEG) , or polyethylene glycol vinyl oxybutyl ethers (VPEG) ; preferably polyethylene glycol vinyl ether (EPEG) .

EPEG and VPEG are structurally different from polyethylene glycol monomethallyl ether (HPEG) , isopentenyl polyethylene glycol (TPEG) or isobutenyl polyethylene glycol (IPEG) which are usually used in the synthesis of polycarboxylate dispersant and may result in the better effects in terms of the slump, air content and setting time.

In one preferred embodiment, the copolymer is prepared by polymerizing (meth) acrylic acid and EPEG wherein a chain transfer agent as described above is added along with other optional additives like initiators.

Preferably, the copolymer is produced by free radical polymerization. Thereby, the copolymer forms by the successive addition of free-radical building blocks. Thereby, the free-radical building blocks may be added in alternating, block-like or random manner. In particular, the polymerization takes place at a temperature 10℃ to 50℃, preferably of 15℃ to 35℃.

In particular, the polymerization takes place in the presence of an initiator for free radical polymerization. The initiator preferably is a redox system-based initiator.

Preferably, the chain transfer agent is used in a proportion of 1 –5 wt. -%, especially 2 –3 wt. -%, with respect to the total weight of the compounds S1', S2', and S3' or the structural units S1, S2 and S3, respectively.

Another aspect of the present invention is related to a mineral binder composition comprising a copolymer as described above and a hydraulically setting binder, in particular cement.

All embodiments and preferred features as described above also apply to this aspect.

The mineral binder composition comprises at least one mineral binder. The expression "mineral binder" refers more particularly to a binder which reacts in the presence of water, in a hydration reaction, to give solid hydrates or hydrate phases. This may be, for example, a hydraulic binder (e.g., cement or hydraulic lime) , a latent hydraulic binder (e.g., slag) , a pozzolanic binder (e.g., flyash) , or a nonhydraulic binder (gypsum or white lime) .

The mineral binder or the binder composition comprises more particularly a hydraulic binder, preferably cement.

Cements are composed of main constituents, usually additionally of calcium sulfate (gypsum and/or hemihydrate and/or anhydrite) and optionally of secondary constituents and/or cement additives such as grinding aids. Main constituents are used in quantities of more than 5%by weight. The main constituents can be Portland cement clinker, also referred to as clinker, slag sand, natural or synthetic pozzolans, fly ash, for example, siliceous or calcareous fly ash, burnt shale, limestone and/or silica fume. As secondary constituent, the cements can contain up to 5%by weight of finely divided inorganic, mineral substances, which originate from the clinker production, for example, raw meal, or correspond to the other main constituents.

The cement, for the preparation of the mineral binder composition according to the invention, can be any conventional cement, for example, one in accordance with the five main cement types according to DIN EN 197-1: namely, Portland cement (CEM I) , Portland composite cements (CEM II) , blast-furnace cement (CEM III) , pozzolan cement (CEM IV) and composite cement (CEM V) . These main cement types are subdivided, depending on the amount added, into an additional 27 cement types, which are known to the person skilled in the art and listed in DIN EN 197-1.

Naturally, all other cements that are produced according to another standard are also suitable, for example, according to ASTM standard or China standard for example sulphoaluminate cement (CSA cement) .

The mineral binder or the binder composition comprises preferably cement, preferably a Portland cement and the supplementary cementitious materials (SCM) such as limestone, slag, fly ash or pozzolanic binder.

In one embodiment, the cement for which the inventive dispersant is especially suitable may be the Portland cement, for example as defined in the China standard GB 175-2020.

In one embodiment, a hydraulic binder suitable for the invention may comprise (in each case relative to the total dry weight of hydraulic binder) , in addition to the inventive copolymer as described above as the dispersant,

ai) 50 –92 w%, preferably 70 –77.55 w%of Ordinary Portland Cement,

aii) 5 –50 w%, preferably 21 –30 w%of biomass ash.

According to another embodiment, a hydraulically setting binder composition of the present invention may comprise (wt. -%are relative to the total dry weight of the composition unless otherwise indicated) , in addition to the inventive copolymer as described above as the dispersant,

a) 1 –90 wt. -%, preferably 5 –75 wt. -%, especially 6 –20 wt. -%or 25 –75 wt. -%of steel making slag,

b) a silica source in a dosage that will result in a weight ratio of steel making slag to silica source in the range of 1: 1 –25: 1, preferably 2: 1 –20: 1, more preferably 2.5: 1 –10: 1, especially 2.8: 1 –5: 1,

c) optionally a sulfate source in a dosage that will result in an amount of 0.75 –8 wt. -%of sulfate, preferably 1.5 –5 wt. -%of sulfate, in each case relative to the combined dry weight of the steel making slag and the silica source,

d) optionally an additive selected from the group consisting of alkanolamines, reducing agents, sugars, sugar acids, carboxylic acids or their salts, amino acids or their salts, mineral salts, or mixtures thereof, in a dosage that will result in an amount of 0.05 –10 wt. -%, preferably of 0.1 –5 wt. -%of the additive, relative to the dry weight of steel making slag.

According to further embodiments of the present invention, a binder composition may comprise, in addition to the inventive copolymer as described above as the dispersant, a mixture of

a) 25 –100 mass parts of Portland cement (P) ,

b) 3 –50 mass parts of calcined clay (CC) , especially of metakaolin,

c) 5 –100 mass parts of limestone (L) .

Especially, in such binder compositions, the mass ratios of calcined clay (CC) , limestone (L) , and Portland cement (P) are as follows:

P : CC is from 33 : 1 to 1 : 1, preferably from 8 : 1 to 1 : 1,

CC : L is from 10 : 1 to 1 : 33, preferably from 5 : 1 to 1 : 10, and

P : L is from 20 : 1 to 1 : 4, preferably from 5 : 1 to 1 : 1.

According to a specific embodiment of the present invention, a binder composition consists of a mixture of

a) 50 mass parts of Portland cement (P) ,

b) 20 –50 mass parts of calcined clay (CC) , especially of metakaolin,

c) 10 –50 mass parts of limestone (L) .

In another preferred embodiment, the mineral binder composition additionally contains solid aggregates, especially gravel, sand and/or aggregates. Corresponding compositions can be used, for example, as mortar mixtures or concrete mixtures.

In addition, common components such as other concrete plasticizers, for example lignosulfonates, sulfonated naphthalene-formaldehyde condensates, sulfonated melamine-formaldehyde condensates, or polycarboxylate ethers which are chemically different from the copolymers of the present invention, accelerators, corrosion inhibitors, retardants, shrinkage reducing agents, antifoaming agents, or pore formers may be present in the mineral binder composition.

In the present context, a mineral binder composition is more particularly a processable and/or aqueous mineral binder composition.

The mineral binder composition is preferably a mortar composition, a concrete composition or a gypsum composition. The mineral binder composition is more particularly a mineral binder composition which is processable and/or is mixed with water.

A weight ratio of water to binder in the mineral binder composition is preferably in the range of 0.25 –0.7, more particularly 0.26 –0.65, preferably 0.27 –0.60, especially 0.28 –0.55.

The copolymer is used advantageously with a fraction of 0.01 –10 wt%, more particularly 0.1 –7 wt%or 0.2 –5 wt%, based on the binder content.

Another aspect of the present invention is related to a molding obtainable by curing a binder composition as described above after addition of water. These moldings may in principle be shaped in any way and may be part of a construction, for example, a building, a traffic way or a bridge.

Further advantageous embodiments and combinations of features of the invention will emerge from the following exemplary embodiments and the totality of the patent claims.

Exemplary embodiments

1. Preparation of Copolymers

1.1 Copolymer P1

500 g water, 8 g sodium hypophosphite and 500 g of EPEG-6000 were placed in a reaction vessel, stirred until all monomers dissolved and then cooled down to 15 ℃.

Following this step, a first premixture (60 g water, 14 g NaOH (32%) , and 30 g acrylic acid) , a second premixture (16 g water and 2.0g hydrogen peroxide (30%) ) and a third premixture (20 g water and 1.2 g Rongalite) were slowly dropped into the reaction vessel along with 0.75g Fe (II) under agitation. Agitation continued until a peroxide test was negative.

After the end polymerization reaction, a clear, viscous solution of copolymer P1 was obtained.

1.2 Further copolymers

Further copolymers P1 to P3, P5 and PC14 have been produced similarly as copolymer P1 as described above and they are listed in the following table 1:

Table 1: Copolymers

1) AA = Acrylic acid; MA = Maleic acid

2) EPEG-6000: Mn of the group - [AO] _n-R^a in side chain of EPEG polymer is about 6000

3) HPEG-4000: Mn of the group - [AO] _n-R^a in side chain of HPEG polymer is about 4000

2. Tests

Concrete or mortar were prepared by mixing the specified amounts of Portland cement (Onoda P.O. 52.5 or Hailuo P.O 52.5) , fly ash, slag, sand and gravel (5-25 mm) and a certain amount of water to adjust the W/C ratio of 0.34. The respective copolymers were formulated to solid content of 20%and then added to the mixture in the amounts indicated in the tables below, the stated amounts being in each case relative to the weight of the cement and fly ash.

After the period as indicated in the tables, the slump flow was determined according to standard GB/T 50080-2016. The slump was measured according to standard GB/T 50080-2016.

The setting time of the concrete mixture was measured according to GB-T50080-2016.

Compressive strength was determined according to standard GB/T 50081-2019.

Claims

A dispersant for mineral binder compositions, which contains a copolymer comprising or consisting of:

a) a mole fractions of a structural subunit S1 of the formula (I)

b) b mole fractions of a structural subunit S2 of the formula (II)

c) optionally, c mole fractions of a further structural subunit S3 derived from other comonomers

where

M independently of one another represents H⁺, an alkali metal ion, alkaline earth metal ion, a bivalent or trivalent metal ion, an ammonium ion or an organic ammonium group,

each R^u independently of one another stands for hydrogen or a methyl group, each R^v independently of one another stands for hydrogen or COOM, R⁵, R⁶, and R⁷, in each case independently of one another, are H or an alkyl group with 1 –5 carbon atoms, in particular H;

R⁸, in each case independently of one another, is a group of the formula - [AO] _n-R^a, where

A is independently of one another C₂-to C₄-alkylene,

R^a is H, a C₁ to C₂₀ alkyl, cycloalkyl or alkylaryl group, and

n is an integer such that the number average molecular weight (M_n) of the group - [AO] _n-R^a is more than 4'900 g/mol, especially more than 5’200 g/mol, in particular more than 5'700 g/mol;

z is 0, 1 or 2;

and where a, b, and c are mole fractions of the respective structural subunits S1, S2, and S3, where

a/b/c = (0.1 –0.99) / (0.01 –0.9) / (0 –0.8) , preferably

a/b/c = (0.76 –0.99) / (0.01 –0.24) / (0 –0.23) , and

with the proviso that a + b + c is 1 and that a/b > 3.2.
The dispersant according to claim 1, wherein R^u and R^v are hydrogen or methyl and M is H⁺ or an alkali metal ion.
The dispersant according to at least any of claims 1 –2, wherein R⁵ = R⁶ = R⁷ = H and R^a = H.
The dispersant according to at least any of claims 1 –3, wherein a proportion of ethylene oxide units or C₂-alkylene oxide units in the group of the formula - [AO] _n-R^a, based on all the alkylene oxide or C₂-alkylene oxide units present in the group of the formula - [AO] _n-R^a, is more than 90 mol %, especially more than 95 mol %, preferably more than 98 mol %, in a particular 100 mol %.
The dispersant according to at least any of claims 1 –4, wherein the ratio of the mole fractions a/b is >3.5, preferably >4.0, in particular >4.5.
The dispersant according to at least any of claims 1 –5, wherein the ratio of the mole fractions a/b is <13.0, preferably <12.0, in particular <9.5.
The dispersant according to at least any of claims 1 –6, wherein n is an integer such that the number average molecular weight (M_n) of the group - [AO] _n-R^a is less than 10’000, preferably less than 8’000.
Method for producing the dispersant as described in claim 1, comprising the step of polymerizing:

a) a' mole fractions of a compound S1' of the formula (III) :

b) with b' molar fractions of a compound S2' of the formula (IV) :

c) optionally c' molar fractions of a further compound S3';

wherein R^u, R^v, M, R, R⁵, R⁶, R⁷, R⁸ and z, are defined as described in claim 1 and where a', b', and c' are mole fractions of the respective structural subunits S1', S2', an S3', where

a'/b'/c'= (0.1 –0.99) / (0.01 –0.9) / (0 –0.8) , preferably

a'/b'/c'= (0.76 –0.99) / (0.01 –0.24) / (0 –0.23) , and

with the proviso that a'+ b'+ c' is 1 and that a’/b’ > 3.2.
Method according to claim 8 whereby the copolymer is produced by free radical polymerization at a temperature 10℃ to 50℃, preferably of 15℃ to 35℃.
Method according to any of claims 8 –9 whereby a chain transfer agent is added which comprises unsaturated alkyl sulfonate (S) , hypophosphite (H) , and/or mercapto-group containing aliphatic acid (M) ; preferably hypophosphite (H) ; more preferably sodium or kalium hypophosphite.
Method according to any of claims 8 –10 whereby the chain transfer agent is used in a proportion of 1 –5 wt. -%, especially 2 –3 wt. -%, with respect to the total weight of the compounds S1', S2', and S3'.
Method according to any of claims 7 –10 whereby the compound S2' of the formula (IV) is polyethylene glycol vinyl ether (EPEG) , polyethylene glycol monomethallyl ether (HPEG) , isopentenyl polyethylene glycol (TPEG) , or polyethylene glycol vinyl ethers (VPEG) .
A mineral binder composition comprising a dispersant according to any of claims 1 –7 and a mineral binder, in particular cement, preferably a Portland cement and the supplementary cementitious materials (SCM) such as limestone, slag, fly ash or pozzolanic binder, preferably fly ash.
A mineral binder composition comprising a dispersant according to any of claims 1 –7 and a mineral binder, said mineral binder comprising or consisting of

a) 25 –100 mass parts of Portland cement,

b) 3 –50 mass parts of calcined clay, especially of metakaolin,

c) 5 –100 mass parts of limestone.