WO2024113133A1

WO2024113133A1 - Polycarboxylate based dispersant

Info

Publication number: WO2024113133A1
Application number: PCT/CN2022/134894
Authority: WO
Inventors: Yalei CHEN; Qing Zhang; Jiali ZHU
Original assignee: Sika Technology Ag
Filing date: 2022-11-29
Publication date: 2024-06-06

Abstract

The invention relates to a copolymer, in particular a dispersant for hydraulically setting binder compositions, comprising the structural subunits S1 of the formula (I), S2 of the formula (II), and optionally further structural subunit S3, in which the copolymer further contains a subunit S4 derived from the chain transfer agent comprising unsaturated alkyl sulfonate (S) and hypophosphite (H) in a weight ratio S/H of 0.6 : 1 to 3.9 : 1 or comprising mercapto-group containing aliphatic acid (M) and hypophosphite (H) in a weight ratio M/H of 0.4 : 1 to 1.2 : 1. The invention also relates to the method for producing such copolymers, a hydraulically setting binder composition comprising such copolymers and the use of specific chain transfer agent for producing the copolymer.

Description

POLYCARBOXYLATE BASED DISPESANT

Technical field

The invention relates to a polycarboxylate copolymer, in particular a dispersant based on it for hydraulically setting binder compositions, and its use as well as a method for producing such kind of copolymers. Further aspects of the invention are related to a chain transfer agent for the polycarboxylate copolymer.

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.

Among the useful chain transfer agents, hypophosphites like sodium hypophosphite is in great demand and widely used in the preparation of such polycarboxylic acid copolymers, especially for ethylene glycol vinyl ethers (EPEG) based polycarboxylic acid polymers.

However, the problems in connection with hypophosphites are (i) the shortage of hypophosphite like sodium hypophosphite and (ii) the environmental regulations on the content of phosphorus which should be strictly restrained. Therefore, there is an urgent demand to develop a new alternative chain transfer agent which may reduce or overcome the aforementioned drawbacks but still result in a polycarboxylic acid based dispersant having comparable or even better water reduction and slump keeping performances.

Disclosure of the invention

It is an object of the present invention to provide new dispersants which do not have the above mentioned drawbacks, especially have a reduced amount of hypophosphites, but provide comparable or improved properties for use in mineral binder compositions, especially in terms of the water reduction and slump keeping performance.

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

Furthermore, the present invention also provides a method for preparation of the new dispersants in which a specific chain transfer agent is added which has reduced amount of hypophosphites.

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 copolymer, in particular a dispersant for mineral binder compositions, 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,

R ⁵, R ⁶, and R ⁷, in each case independently of one another, are H or an alkyl group with 1 –5 carbon atoms, in particular H;

R ⁸, in each case independently of one another, is a group of the formula - [AO] _n-R ^a, where

A is C ₂-to C ₄-alkylene,

R ^a is H, a C ₁ to C ₂₀ alkyl, cycloalkyl or alkylaryl group, and

n is 1 –250, in particular n is 2 –200 or even 10 –120;

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 –0.9) / (0.1 –0.9) / (0 –0.8) , preferably

a/b/c = (0.4 –0.85) / (0.15 –0.5) / (0 –0.6) , and

with the proviso that a + b + c is 1;

wherein the copolymer further contains a subunit S4 derived from the chain transfer agent comprising unsaturated alkyl sulfonate (S) and hypophosphite (H) in a weight ratio S/H of 0.6 : 1 to 3.9 : 1 or comprising mercapto-group containing aliphatic acid (M) and hypophosphite (H) in a weight ratio M/H of 0.4 : 1 to 1.2 : 1.

Another aspect of the invention relates to a chain transfer agent and the use thereof. The chain transfer agent comprises unsaturated alkyl sulfonate (S) and hypophosphite (H) in a weight ratio S/H of 0.6 : 1 to 3.9 : 1 or comprises mercapto-group containing aliphatic acid (M) and hypophosphite (H) in a weight ratio M/H of 0.4 : 1 to 1.2 : 1

Surprisingly, it is found by the inventors that the copolymer as defined above which are prepared using the specific chain transfer as specified above may significantly improve the water reducing property and the slump retention ability of the cement, and also result in the short setting time in some cases.

The sequence of the structural subunits S1, S2, and S3 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.

With regard to structural subunit S2, R ⁵ = R ⁶ = R ⁷ = H with R ^a = H and A = C ₂-alkylene is preferred. Copolymers of these kinds can be prepared, for example, starting from ethylene glycol vinyl ethers (EPEG) .

Preferably, a proportion of ethylene oxide units or C ₂-alkylene oxide units in the group of the formula - [AO] _n-R ^a, based on all the alkylene oxide or C ₂-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 C ₃-and or C ₄-alkylene oxide units in the groups of the formula - [AO] _n-R ^a might be suitable as well.

Also, with highly preferred copolymers, n is 10 –120, especially 22 –80, preferably 30 –70, especially preferred 40 –60.

Preferably, a number average molecular weight (M _n) of the group - [AO] _n-R ^a is 500 –7'000 g/mol, especially 1'000 –4000 g/mol, in particular 1'500 –3'500 g/mol, particularly 2'000 –3'200 g/mol.

Such a number of [AO] units in the group of the formula - [AO] _n-R ^a and/or such number average molecular weights (M _n) of the group of the formula - [AO] _n-R ^a have turned out to be a preferred choice with regard to the overall plasticizing effect of the copolymer in different mineral binder compositions.

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 another preferred embodiment, the ratio of the mole fraction a/b is 1.7 –7. In a further preferred embodiment, the mole fraction a/b is in a range of 2.4 –4, in particular 2.5 -3.9. It has been found that the slump may be probably inclined to be insufficient if the ratio of a/b is less than 2.4 while the slump retention ability may be likely impaired if the ratio a/b is higher than 4.

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 concerns 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 has to contain a subunit S4 derived from the chain transfer agent which comprises hypophosphite in combination with unsaturated alkyl sulfonate or mercapto-group containing aliphatic acid. Surprisingly, it has been found that the resultant copolymer may show higher water reduction and slump keeping performances, if using the combination of hypophosphite with unsaturated alkyl sulfonate or mercapto-group containing aliphatic acid as a chain transfer agent in the preparation of the copolymer having the subunits S1, S2 and S3 as described above. Furthermore, it is also found that the sulfate sensitivity may be also significantly improved by using the resultant copolymer, especially when the chain transfer agent contains hypophosphite with alkyl sulfonate.

Advantageously, in the specific chain transfer agent combination, the weight ratio of unsaturated alkyl sulfonate (S) to hypophosphite (H) , i.e. ratio of S/H, is in a range of 1 : 1 to 3.6 : 1 or 1.9 : 1 to 3.1 : 1, or the weight ratio of mercapto-group containing aliphatic acid (M) to hypophosphites (H) , i.e. ratio of M/H, is in a range of 0.6 : 1 to 1 : 1.

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 a copolymer, 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, R ⁵, R ⁶, R ⁷, R ⁸, 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 –0.9) / (0.1 –0.9) / (0 –0.8) , preferably

a'/b'/c'= (0.4 –0.85) / (0.15 –0.5) / (0 –0.6) , and

with the proviso that a'+ b'+ c' is 1;

in which a chain transfer agent is added which comprises comprises unsaturated alkyl sulfonate (S) and hypophosphite (H) in a weight ratio S/H of 0.6 : 1 to 4 : 1 or comprises mercapto-group containing aliphatic acid (M) and hypophosphite (H) in a weight ratio M/H of 0.4 : 1 to 1.2 : 1

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) .

EPEG is 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 The chain transfer agent of the present invention is particularly effective when EPEG is used in the synthesis of polycarboxylate dispersant.

In one preferred embodiment, the copolymer is prepared by polymerizing (meth) acrylic acid and EPEG wherein a chain transfer agent comprising hypophosphite such as sodium hypophosphite in combination with unsaturated alkyl sulfonate such as (meth) allyl sulfonate and mercapto-group containing aliphatic acid like mercapto propionic acid is added along with other optional additives like initiators.

Advantageously, in the specific chain transfer agent combination, the weight ratio of unsaturated alkyl sulfonate (S) to hypophosphites (H) , i.e. S/H, is in a range of 1 : 1 to 3.6 : 1 or 1.9 : 1 to 3.1 : 1, or the weight ratio of mercapto-group containing aliphatic acid (M) to hypophosphites (H) , i.e. M/H, is in a range of 0.6 : 1 to 1 : 1. Thereby, the content of hypophosphite may be significantly reduced.

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 and/or gypsum.

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 which the grinding aid used according to the invention is used, 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) .

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) .

The inventors have found that the resultant polymer in which the subunit S4 derived from the inventive chain transfer agent combination is introduced may have stronger sulfate resistance (in other words: be less sensitive to sulfate) and thus more suitable for the CSA cement. Furthermore, it is also possible to add the copolymer as a dispersant into binder composition with low content of Portland cement clinker or high content of the supplementary cementitious materials (SCM) such as limestone, slag, and clay minerals.

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.

Furthermore, the present invention is concerned with the use of a composition as a chain transfer agent for the polycarboxylate ether, comprising unsaturated alkyl sulfonate and hypophosphite or comprising mercapto-group containing aliphatic acid and hypophosphite. Advantageous embodiments as described above also apply to this aspect.

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

450 g water, 3 g sodium hypophosphite and 450 g of EPEG-3000 were placed in a reaction vessel, stirred until all monomers dissolved and then cooled down to 15 ℃.

Following this step, a first premixture (90 g water, 18 g NaOH (32%) , 2.1 g mercaptopropionic acid and 39 g acrylic acid) , a second premixture (12 g water and 1.5g hydrogen peroxide (30%) ) and a third premixture (15 g water and 0.75 g Rongalite) were slowly dropped into the reaction vessel along with 1g 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

Polymer PC-11 is a market available PCE product having the composition as specified in the following table 1 which is used as a comparison in the form of an aqueous solution with the same solids content as copolymer P1 solution above. Further copolymers P1 to P14 have been produced similarly as copolymer P1 as described in the following table 1:

Table 1: Copolymers

1) AA = Acrylic acid; MA = Maleic acid

2) EPEG-3000:

3) M = mercaptopropionic acid; H = sodium hypophosphite; S = sodium methallyl sulfonate

*= Comparative example

2. Tests

Concrete or mortar were prepared by mixing the specified amounts of Portland cement (Jinfeng P. O 42.5 or Onoda P. II 52.5) , sand, optional gravel (5-25mm) , and Type II fly ash and a certain amount of water to adjust different W/C ratios as indicated in Tables 2-1 to 2-7. The respective copolymers were formulated to solid content of 20%and then added to the mixture in the amounts indicated in Table 2-1 to 2-7 below, the stated amounts being in each case relative to the weight of the cement.

In the test based on CSA cement, a cement paste was formulated by 87 g water, 300g CSA cement and the copolymers as specified in Table 2-7.

After the period as indicated in Tables 2-1 to 2-7, the slump flow was determined according to standard EN 12350-5, wherein 0 minutes refers to the test performed directly after the end of mixing. The slump was measured according to standard EN 12350-2.

The setting time of the concrete mixture was measured according to GB-T50080-2002.

Claims

Copolymer, in particular a dispersant for mineral binder compositions, 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,

R ⁵, R ⁶, and R ⁷, in each case independently of one another, are H or an alkyl group with 1 –5 carbon atoms, in particular H;

R ⁸, in each case independently of one another, is a group of the formula - [AO] _n-R ^a, where

A is C ₂-to C ₄-alkylene,

R ^a is H, a C ₁ to C ₂₀ alkyl, cycloalkyl or alkylaryl group, and

n is 1 –250, in particular n is 2 –200 or even 10 –120;

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 –0.9) / (0.1 –0.9) / (0 –0.8) , preferably

a/b/c = (0.4 –0.85) / (0.15 –0.5) / (0 –0.6) , and

with the proviso that a + b + c is 1;

in which the copolymer further contains a subunit S4 derived from the chain transfer agent comprising unsaturated alkyl sulfonate (S) and hypophosphite (H) in a weight ratio S/H of 0.6 : 1 to 3.9 : 1 or comprising mercapto-group containing aliphatic acid (M) and hypophosphite (H) in a weight ratio M/H of 0.4 : 1 to 1.2 : 1.
Copolymer according to claim 1, wherein R ^u and R ^v are hydrogen or methyl and M is H ⁺ or an alkali metal ion.
Copolymer according to at least any of claims 1 –2, wherein R ⁵ = R ⁶ = R ⁷ = H and R ^a = H.
Copolymer according to at least any of claims 1 –3, wherein a proportion of ethylene oxide units or C ₂-alkylene oxide units in the group of the formula - [AO] _n-R ^a, based on all the alkylene oxide or C ₂-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 %.
Copolymer according to at least any of claims 1 –4, wherein the ratio of the mole fractions a/b is 1.7 –7, in particular 2.4 –4.
Copolymer according to at least any of claims 1 –5, wherein the proportion of subunit S4 derived from the chain transfer agent is in a range of 1 –5 wt. -%, especially 2 –3 wt. -%, with respect to the total weight of the structural units S1, S2 and S3.
Copolymer according to at least any of claims 1 –5, wherein the weight ratio S/H is in a range of 1 : 1 to 3.6 : 1 or 1.9 : 1 to 3.1 : 1, or the weight ratio M/H is in a range of 0.5 : 1 to 1 : 1.
Method for producing a copolymer, in particular a copolymer 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, R ⁵, R ⁶, R ⁷, R ⁸ 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 –0.9) / (0.1 –0.9) / (0 –0.8) , preferably

a'/b'/c'= (0.4 –0.85) / (0.15 –0.5) / (0 –0.6) , and

with the proviso that a'+ b'+ c' is 1;

in which a chain transfer agent is added which comprises unsaturated alkyl sulfonate (S) and hypophosphite (H) in a weight ratio S/H of 0.6 : 1 to 4 : 1 or comprises mercapto-group containing aliphatic acid (M) and hypophosphite (H) in a weight ratio M/H of 0.4 : 1 to 1.2 : 1.
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 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 claim 10, whereby the weight ratio S/H is in a range of 1 : 1 to 3.6 : 1 or 1.9 : 1 to 3.1 : 1, or the weight ratio M/H is in a range of 0.5 : 1 to 1 : 1.
Method according to any of claims 7 –10 whereby the compound S2' of the formula (IV) is polyethylene glycol vinyl ether (EPEG) .
A mineral binder composition comprising a copolymer according to any of claims 1 –7 as a dispersant and a mineral binder, in particular cement, preferably a sulphoaluminate cement or cement having Portland cement and the supplementary cementitious materials (SCM) such as limestone, slag, and clay minerals, and/or gypsum.
Use of a chain transfer agent comprising unsaturated alkyl sulfonate (S) and hypophosphite (H) in a weight ratio S/H of 0.6 : 1 to 3.9 : 1 or comprising mercapto-group containing aliphatic acid (M) and hypophosphite (H) in a weight ratio M/H of 0.4 : 1 to 1.2 : 1 for the preparation of a copolymer as defined in claim 1.