EP3353126A1

EP3353126A1 - Dispersant for calcium sulphate-based compositions

Info

Publication number: EP3353126A1
Application number: EP16775577.6A
Authority: EP
Inventors: Jürg WEIDMANN; Christina Hampel; Jörg ZIMMERMANN
Original assignee: Sika Technology AG
Current assignee: Sika Technology AG
Priority date: 2015-09-24
Filing date: 2016-09-22
Publication date: 2018-08-01
Also published as: CN108025973B; JP2018529616A; US10988415B2; WO2017050896A1; CN108025973A; JP6867374B2; US20190300431A1

Abstract

The present invention relates to the use of a copolymer as a dispersant for binder compositions based on calcium sulfate, the copolymer having a polymer backbone and sidechains bound thereto, and at least one ionizable monomeric unit M1 and at least one sidechain-carrying monomeric unit M2, characterized in that the copolymer has, in a direction along the polymer backbone, a non-random distribution of the monomeric units M1 and/or of the monomeric units M2.

Description

Dispersants for calcium sulfate-based compositions

Technical area

The invention relates to the use of a copolymer as a dispersant for binder compositions based on calcium sulfate, wherein the copolymer comprises a polymer backbone and side chains attached thereto and at least one ionizable monomer M1 and at least one side chain-carrying monomer M2 are present. Further, the invention relates to a binder composition with a copolymer and to a molded article obtainable therefrom.

State of the art

Dispersants or flow agents are used in the construction industry as plasticizers or water-reducing agents for mineral binder compositions, e.g. Concrete, mortar, cements, plaster and lime, used. The dispersants are generally organic polymers which are added to the make-up water or added as a solid to the binder compositions. As a result, both the consistency of the binder composition during processing and the properties in the cured state can be advantageously changed.

Polycarboxylate-based comb polymers (PCE), for example, are known as particularly effective dispersants. Such comb polymers have a polymer backbone and side chains attached thereto. Corresponding polymers are e.g. in EP 1 138 697 A1 (Sika AG).

Also known as concrete admixtures are copolymer blends as mentioned, for example, in EP 1 1 10 981 A2 (Kao). The copolymer blends are prepared by reacting ethylenically unsaturated monomers in a free radical polymerization reaction, wherein the molar ratio of the two monomers is changed at least once during the polymerization process.

However, it has been found that the known concrete dispersants can only be used to a limited extent for calcium sulfate-based compositions or gypsum compositions. The known concrete dispersants often delay so much in such compositions that they are difficult to set and / or the desired liquefaction performance is not achieved. Particularly in the production of gypsum boards and screeds, high demands are placed on the dispersants.

In this context, WO 2012/028668 A1 (Sika Technology AG) describes, for example, a polymer mixture of two polymers which differ with regard to the acid content and are particularly suitable for gypsum compositions. Although such dispersants are quite effective, but require a lot of effort, especially in the production.

There is therefore still a need for improved dispersants for calcium sulfate-based compositions which do not have the disadvantages mentioned. Presentation of the invention

The object of the invention is therefore to overcome the disadvantages mentioned above. In particular, a dispersant should enable effective liquefaction and good processing of calcium sulfate-based binder compositions. In particular, the dispersant should impair the setting behavior of the calcium sulfate-based binder compositions as little as possible. In particular, the dispersants used should as little as possible or not at all delay the setting of the calcium sulfate-based binder compositions. It is further desirable to provide a dispersing agent which can be produced flexibly and in a controlled manner. Surprisingly, it has been found that this object can be achieved by the features of independent claim 1.

The core of the invention is therefore the use of a copolymer as a dispersant for binder compositions based on calcium sulfate, wherein the copolymer comprises a polymer backbone and side chains attached thereto and at least one ionizable monomer M1 and at least one side chain-carrying monomer M2 are present, characterized in that the copolymer has a non-random distribution of monomer units M1 and / or monomer units M2 in one direction along the polymer backbone.

As has surprisingly been found, good co-liquefaction effects and at the same time relatively short setting times in binder compositions based on calcium sulfate can be achieved with copolymers of this type. In addition, the copolymers used according to the invention can be prepared in an efficient manner in a wide variety of modifications in a reliable manner.

Further aspects of the invention are the subject of further independent claims. Particularly preferred embodiments of the invention are the subject of the dependent claims. Ways to carry out the invention

A first aspect of the present invention relates to the use of a copolymer as a dispersant for calcium sulfate based binder compositions, said copolymer comprising a polymer backbone and side chains attached thereto and having at least one ionizable monomer unit M1 and at least one side chain-bearing monomer unit M2 in that the copolymer has a non-random distribution of the monomer units M1 and / or the monomer units M2 in one direction along the polymer backbone.

copolymer By the terms "ionizable monomers" and "ionizable monomer units" is meant in particular monomers or polymerized monomers which are present at a pH> 10, in particular at a pH> 12, in anionic form or negatively charged. These are in particular H-donor groups or acid groups. The ionizable groups are particularly preferably acid groups, such as, for example, carboxylic acid, sulfonic acid, phosphoric acid and / or phosphonic acid groups. Preferred are carboxylic acid groups. The acid groups may also be present as anions in deprotonated form or as a salt with a counterion or cation. In this case, a "non-random distribution" is understood to mean a non-statistical distribution of the monomer units M1 and / or the monomer units M2. This means that the ionizable monomer units M1 and / or the side chain-carrying monomer units M2 in the copolymer are arranged, for example, in at least one section in an alternating, block-like manner and / or in a gradient structure. The copolymer preferably has at least one section with a gradient structure and / or a block structure.

The structure of the copolymers can be analyzed and determined, for example, by nuclear magnetic resonance spectroscopy (NMR spectroscopy). In particular, by ¹³ C NMR spectroscopy can be determined in a conventional manner due to adjacent group effects in the copolymer and based on statistical evaluations, the sequence of the monomer units in the copolymer.

The ionizable monomer units M1 preferably comprise acid groups, in particular carboxylic acid, sulfonic acid, phosphoric acid and / or phosphonic acid groups.

The side chain-carrying monomer unit M2 contains in particular polyalkylene oxide side chains, in particular polyethylene oxide and / or polypropylene oxide side chains.

In particular, the ionizable monomer units M1 have a structure according to the formula I:

The side chain-carrying monomer units M2 preferably have a structure according to the formula II:

in which

R ¹ , each independently of one another, is -COOM, -SO 2 -OM, -O-PO (OM) ₂ and / or -PO (OM) ₂ ,

R ² , R ³ , R ⁵ and R ⁶ , each independently of one another, are H or an alkyl group having 1 to 5 carbon atoms, R ⁴ and R ^{7 are} each independently H, -COOM or an alkyl group with 1 to 5 carbon atoms, or where R ¹ forms a ring with R ⁴ to CO-O-CO-,

M independently represents H ⁺ , an alkali metal ion, an alkaline earth metal ion, a divalent or trivalent metal ion, an ammonium ion or an organic ammonium group; m = 0, 1 or 2, p = 0 or 1,

X, in each case independently of one another, represents -O- or -NH-,

R ^{8 is} a group of the formula - [AO] _n -R ^a , where A = C ₂ - to C ₄ -alkylene, R ^{a is} H, a C 1 - to C 20 -alkyl group,

Cycloalkyl group or alkylaryl group, and n = 2-250, especially 10-200.

A molar ratio of the monomer units M1 to the monomer units M2 is advantageously in the range from 0.5 to 16, in particular 1 to 12, preferably 1 to 2 to 8, more preferably 1 to 5 to 5 or 2 to 4

In particular, R ¹ = COOM, R ² = H or CH ₃ , R ³ = R ⁴ = H Thus, the copolymer can be prepared on the basis of acrylic or methacrylic acid monomers, which is interesting from an economic point of view. In addition, such copolymers have a particularly good dispersing effect in the present context.

Also advantageous are R ¹ = COOM, R ² = H, R ³ = H and R ⁴ = COOM. Corresponding copolymers can be prepared on the basis of maleic acid monomers.

The group X of the ionizable monomer units M2 is advantageously at least 75 mol%, in particular at least 90 mol%, especially at least 95 mol% or at least 99 mol% of all monomer units M2 for -O- (= oxygen atom ).

Advantageously, R ⁵ = H or CH ₃ , R ⁶ = R ⁷ = H and X = -O-. Thus, the copolymers can be prepared, for example, starting from (meth) acrylic esters, vinyl, (meth) allyl or isoprenol ethers.

In a particularly advantageous embodiment, R ² and R ^{5 are} each mixtures of 40-60 mol% H and 40-60 mol% -CH ₃ .

According to a further advantageous embodiment, R ¹ = COOM, R ² = H, R ⁵ = -CH ³ and R ³ = R ⁴ = R ⁶ = R ⁷ = H. In another advantageous embodiment, R ¹ = COOM, R ² = R ⁵ = H or -CH ₃ and R ³ = R ⁴ = R ⁶ = R ⁷ = H.

Especially suitable are copolymers in which R ¹ = COOM; R ² and R ⁵ each independently represent H, -CH ₃ or mixtures thereof; R ³ and R ^{6 are} each independently H or -CH ₃ , preferably H; R ⁴ and R ^{7 are} each independently H or -COOM, preferably H.

The radical R ⁸ in the side chain-carrying monomer units M2 consists, based on all the radicals R ^{8 of} the monomer units, in particular at least 50 mol%, in particular at least 75 mol%, preferably at least 95 mol% or at least 99 mol% %, from a polyethylene oxide.

A proportion of ethylene oxide units based on all alkylene oxide units in the copolymer is in particular more than 75 mol%, in particular more than 90 mol%, preferably more than 95 mol% and in particular 100 mol%. In particular R ⁸ has substantially no hydrophobic groups, especially no alkylene oxides having three or more carbon atoms. This means in particular that a proportion of alkylene oxides having three or more carbon atoms, based on all alkylene oxides, is less than 5 mol%, in particular less than 2 mol%, preferably less than 1 mol% or less than 0.1 mol% is. In particular, there are no alkylene oxides having three or more carbon atoms or their proportion is 0 mol%.

R ^a is advantageously H and / or a methyl group. Particularly advantageous is A = C2-alkylene and R ^a is H or a methyl group.

In particular, the parameter n = 10-150, in particular n = 15-100, preferably n = 17-70, in particular n = 19-45 or n = 20-25. In particular, in the preferred ranges mentioned, excellent dis - achieved pergierwirkungen.

Particularly preferred are copolymers wherein R ¹ = COOM; R ² and R ⁵ , independently of one another, are H, -CH ₃ or mixtures thereof; R ³ and R ⁶ , independently of one another, are H or -CH ₃ , preferably H; R ⁴ and R ⁷ , independently of one another, are H or -COOM, preferably H; and wherein X is at least 75 mol%, in particular at least 90 mol%, especially at least 99 mol% of all monomer units M2 is -O-.

Furthermore, it may be advantageous if the copolymer comprises at least one further monomer unit MS, which differs in particular chemically from the monomer units M1 and M2. In particular, several different further monomer units MS can be present. As a result, the properties of the copolymer can be further modified and adapted, for example, with regard to specific applications.

Particularly advantageously, the at least one further monomer unit MS is a monomer unit of the formula III:

wherein R ⁵ , R ⁶ , R ⁷ , m 'and p' are the same as R ⁵ , R ⁶ , R ⁷ , m and p as described above;

Y, each independently, is a chemical bond or -O-; Z, each independently, is a chemical bond, -O- or -NH-;

R ⁹ , in each case independently of one another, represents an alkyl group, cycloalkyl group, alkylaryl group, aryl group, hydroxyalkyl group or an acetoxyalkyl group, each having 1 to 20 C atoms. For example, further monomer units MS are advantageous in which m '= 0, p' = 0, Z and Y represent a chemical bond and R ^{9 represents} an alkylaryl group having 6 to 10 C atoms.

Also suitable are, in particular, further monomer units MS in which m '= 0, p' = 1, Y represents -O-, Z represents a chemical bond and R ^{9 represents} an alkyl group having 1-4 C atoms.

Further suitable are further monomer units MS where m '= 0, p' = 1, Y is a chemical bond, Z is -O- and R ^{9 is} an alkyl group and / or a hydroxyalkyl group having 1-6 C atoms , Particularly advantageously, the at least one further monomer unit MS consists of copolymerized vinyl acetate, styrene and / or hydroxyalkyl (meth) acrylate, in particular hydroxyethyl acrylate.

In particular, the polydispersity (= weight average molecular weight M _w / number average molecular weight M _n ) of the copolymer is <1 .5, in particular in the range of 1 .0 - 1 .4, especially 1 .1 - 1 .3.

A weight average molecular weight M _{w of} the entire copolymer is in particular in the range of 10Ό00 - 150Ό00 g / mol, advantageously 12Ό00 - 80Ό00 g / mol, especially 12Ό00 - 50Ό00 g / mol. In the present context are molecular weights as the weight average molecular weight M _w, or the number average molecular weight M _n, by gel permeation chromatography (GPC) with polyethylene glycol (PEG) as a standard. This technique is known per se to the person skilled in the art.

In particular, the copolymer is a polymer of substantially linear structure. This means in particular that all monomer units of the copolymer are arranged in a single and / or unbranched polymer chain. In particular, the copolymer does not have a star-shaped structure and / or the copolymer is not part of a branched polymer. In particular, the copolymer is not part of a polymer in which a plurality of, in particular three or more, extending in different directions polymer chains are attached to a central molecule. Copolymers with gradient structure

According to a preferred embodiment, the copolymer has a gradient structure in at least one section AA in a direction along the polymer backbone with respect to the ionizable monomer unit M1 and / or with respect to the side chain-carrying monomer unit M2.

In other words, the copolymer according to the invention has a concentration gradient in at least one section AA in one direction along the polymer backbone with respect to the ionizable monomer unit M1 and / or with respect to the side chain-carrying monomer unit M2. The term "gradient structure" or "concentration gradient" in the present case stands in particular for a continuous change of the local concentration of a monomer unit in at least one section in a direction along the backbone of the copolymer. Another term for "concentration gradient" is "concentration gradient". The concentration gradient may e.g. be essentially constant. This corresponds to a linear decrease or increase in the local concentration of the respective monomer unit in at least a portion AA along the direction of the backbone of the copolymer. It is possible, however, for the concentration gradient to change along the direction of the backbone of the copolymer. In this case, there is a non-linear decrease or increase in the local concentration of the respective monomer unit. The concentration gradient extends in particular over at least 10, in particular at least 14, preferably at least 20 or at least 40, monomer units of the copolymer. In contrast, abrupt changes in the concentration of monomers, e.g. occur in block copolymers, not referred to as concentration gradient.

The term "local concentration" as used herein refers to the concentration of a particular monomer at a given site of the polymer backbone. In practice, the local concentration or mean value of the local concentration can be determined, for example, by determining the nomerumsätze during the production of the copolymer. In this case, the monomers reacted in a certain period of time can be determined. The average local concentration corresponds in particular to the ratio of the molar fraction of a certain monomer converted over the period under consideration to the total molar amount of monomers reacted in the period considered.

The conversions of the monomers can be determined, for example, by means of liquid chromatography, in particular high-performance liquid chromatography (HPLC), and taking into account the amounts of monomers used, in a manner known per se. The structure of the copolymers can also set forth above are determined by ¹³ C and ¹ H-NMR spectroscopy.

The copolymer may also have more than one section AA with a gradient structure, in particular two, three, four or even more sections AA, which may be e.g. arranged one behind the other. If present, different gradient structures or concentration gradients may exist in each of the different sections AA.

Preferably, in the at least one section AA, a local concentration of the at least one ionizable monomer unit M1 along the polymer backbone continuously increases while a local concentration of the at least one side chain-bearing monomer unit M2 continuously decreases along the polymer backbone, or vice versa.

In particular, a local concentration of ionizable monomer unit M1 at the first end of the at least one portion AA is less than at the second end of portion AA, while a local concentration of side chain carrying monomer unit M2 at the first end of portion AA is greater than at the second end of the portion AA, or vice versa.

In particular, when dividing the at least one section AA into 10 equally long subsections, the average local concentration of the at least one ionizable monomer unit M1 in the respective subsections along the polymer backbone in at least 3, in particular at least 5 or 8 consecutive subsections increases as the average local concentration of the at least one sidechain-bearing monomer unit M2 in the respective subsections along the polymer backbone decreases in at least 3, in particular at least 5 or 8, successive subsections, or vice versa.

Specifically, an increase or decrease in the averaged local concentration of the at least one ionizable monomer unit M1 in the successive subsections is substantially constant while, advantageously, a decrease or increase in the averaged local concentration of the at least one sidechain bearing monomer unit M2 in the successive subsections in FIG Is also essentially constant.

According to an advantageous embodiment, the at least one section AA with the gradient structure, based on a total length of the polymer backbone, has a length of at least 30%, in particular at least 50%, preferably at least 75% or 90%.

Advantageously, the at least one section AA, based on a total number of monomer units in the polymer backbone, a proportion of at least 30%, in particular at least 50%, preferably at least 75% or 90% of monomer units. In particular, the at least one section AA, based on the weight-average molecular weight of the entire copolymer, has a weight fraction of at least 30%, in particular at least 50%, preferably at least 75% or 90%.

Thus, the section AA with the concentration gradient or the gradient structure in particular mass comes into play.

The at least one concentration gradient section AA advantageously comprises 5 to 70, in particular 7 to 40, preferably 10 to 25 monomer units M1 and 5 to 70, in particular 7 to 40, preferably 10 to 25, monomer units M2. In particular, the copolymer consists of at least 50 mol%, in particular at least 75 mol%, especially at least 90 mol% or 95 mol%, of ionic acid. sible monomer units M1 and side-chain-carrying monomer units M2.

It is advantageous if at least 30 mol%, in particular at least 50 mol%, preferably at least 75 mol%, in particular at least 90 mol% or at least 95 mol% of the ionizable monomer M1 in at least one section AA, which has a gradient structure present.

Also advantageously at least 30 mol%, in particular at least 50 mol%, preferably at least 75 mol%, in particular at least 90 mol% or at least 95 mol%, of the side chain-carrying monomer units M2 in the at least one section, which is a Gradient structure, before.

Especially preferably, the last two aforementioned conditions apply simultaneously.

In another advantageous embodiment, the copolymer has, in addition to the at least one section AA, which has a gradient structure, over a further section AB, wherein over the entire section AB substantially a constant local concentration of the monomers and / or a random or random distribution the monomers are present. Section AB may e.g. consist of monomers of a single variety or of several different monomers, which are randomly distributed. In section AB, however, in particular there is no gradient structure or no concentration gradient along the polymer backbone.

The copolymer may also have more than one further portion AB, e.g. two, three, four or more sections AB, which may differ chemically and / or structurally. Preferably, the at least one section AA connects directly to the further section AB.

It has surprisingly been found that such copolymers may be even more advantageous over time with respect to the liquefaction effect and maintenance thereof. In particular, the further section AB comprises ionizable monomer units M1 and / or side chain-carrying monomer units M2. Based on all the monomer units contained therein, the further section AB in one embodiment of the invention advantageously comprises at least 30 mol%, in particular at least 50 mol%, preferably at least 75 mol%, in particular at least 90 mol% or at least 95 mol %, ionizable monomer units M1. A possibly existing proportion of side-chain-carrying monomer units M2 in the further section AB is in particular less than 25 mol%, especially less than 10 mol% or less than 5 mol%, based on all monomer units M1 in the further section. In particular, there are no side chain-carrying monomer units M2 in the further section AB.

According to a further and particularly advantageous implementation of the invention, the further section AB comprises, based on all the monomer units contained therein, at least 30 mol%, in particular at least 50 mol%, preferably at least 75 mol%, in particular at least 90 mol% or at least 95 mole percent, side chain bearing monomer units M2. In this case, a possibly present proportion of ionizable monomer units M1 in the further section AB is in particular less than 25 mol%, in particular less than 10 mol% or less than 5 mol%, based on all monomer units M2 in the further section AB. In particular, no ionizable monomer units M1 are present in the further section AB.

It has proven to be expedient that the further section AB comprises a total of 5 to 70, in particular 7 to 40, preferably 10 to 25 monomer units. These are in particular ionizable monomer units M1 and / or side chain-carrying monomer units M2. A ratio of the number of monomer units in the at least one section AA with gradient structure to the number of monomer units in the at least one further section AB with the substantially constant local concentration is advantageously in the range from 99: 1 to 1:99, in particular 10:90 to 90:10 , preferably 80:20 - 20:80, especially 70:30 - 30:70. If present, the at least one further monomer unit MS may be part of the at least one section AA and / or the further section AB. It is also possible that the at least one further mo- unit MS is part of an additional section of the copolymer. In particular, different further monomer units MS can be present in the different sections.

If present in at least one section AA, the at least one further monomer unit MS in the at least one section AA advantageously has a proportion of 0.001-80 mol%, preferably 20-75 mol%, especially 30-70 mol%, based on all monomer units in the first section AA, on.

If present in the further section AB, the at least one further monomer unit MS in the further section AB has in particular a proportion of 0.001-80 mol%, preferably 20-75 mol%, especially 30-70 mol% or 50-70 mol% , based on all monomer units in the further section AB, on.

According to an advantageous embodiment, in the at least one section AA and / or in the further section AB, the at least one further monomer unit MS has a content of 20-75 mol%, especially 30-70 mol%, based on all monomer units in each section, available.

According to an advantageous embodiment, the copolymer consists of the at least one section AA. In another advantageous embodiment, the copolymer consists of the at least one section AA and the further section AB. Especially in the latter case, very good and long-lasting liquefaction effects result.

However, it is also possible for example for the copolymer to contain at least two different sections AA and / or at least two different further sections AB.

A particularly advantageous copolymer has at least one or more of the following characteristics: i) The copolymer consists of at least 75 mol%, especially at least 90 mol% or 95 mol%, of ionizable monomer units M1 and side chain-carrying monomer units M2 ; ii) the copolymer comprises or consists of at least a section AA and a further section AB; iii) The further section AB comprises side chain-carrying monomer units M2, in particular at least 50 mol%, preferably at least 75 mol%, in particular at least 90 mol% or at least 95 mol%, based on all the monomer units contained in section AB , A possibly existing proportion of ionizable monomer units M1 in the further section AB is less than 25 mol%, in particular less than 10 mol% or less than 5 mol%, based on all monomer units M2 in the further section AB. iv) A molar ratio of the monomer units M1 to the monomer units M2 in the copolymer is in the range of 0.5-6, preferably 0.8-3.5; v) R ¹ is COOM; vi) R ² and R ⁵ are H or CH ₃ , preferably CH ₃ ; vii) R ³ = R ⁴ = R ⁶ = R ⁷ = H; viii) m = 0 and p = 1; ix) X = -O- x) A = C ₂ -alkylene and n = 10-150, preferably 15-50; xi) R ^a = H or -CH ₃ , preferably CH ₃ ; Particularly preferred is a Copoplymer, consisting of sections AA and AB, which has at least all the features (i) - (iv). Further preferred is a copolymer which has all the features (i) - (xi). Even more preferred is a copolymer which realizes all features (i) - (xi) in the respectively preferred embodiments. Copolymer with block structure

Also advantageous is a copolymer comprising at least a first block A and at least one second block B, wherein the first block A has an ionizable monomer M1 of the formula I and the second block B has a side chain-carrying monomer unit M2 of formula II. In particular, an optional fraction of monomer units M2 in the first block A is less than 25 mol%, in particular less than or equal to 10 mol%, based on all monomer units M1 in the first block A and a possibly existing fraction of monomer units M1 in the second Block B is less than 25 mol%, in particular less than or equal to 10 mol%, based on all monomer units M2 in the second block B.

Several different monomer units M1 of the formula I and / or several different monomer units M2 of the formula II can be present in the copolymer according to the invention. The monomer units M1 and any further monomer units in the first block A are distributed in particular statistically or randomly. Likewise, the monomer units M2 and any further monomer units are present in the second block B in particular statistically or randomly distributed.

In other words, the at least one block A and / or the at least one block B is preferably present in each case as a partial polymer with random monomer distribution.

The at least one first block A advantageously comprises 5 to 70, in particular 7 to 40, preferably 10 to 25, monomer units M1 and / or the at least one second block B comprises 5 to 70, in particular 7 to 50, preferably 20 to 40, Monomer units M2.

Preferably, any fraction of monomer units M2 present in the first block A is less than 15 mol%, in particular less than 10 mol%, especially less than 5 mol% or less than 1 mol%, based on all monomer units M1 in the first Block A. In addition, any existing proportion of monomer units M1 in the second block B is advantageously less than 15 mol%, in particular less than 10 mol%, especially less than 5 mol% or less than 1 mol%, based on all monomer units M2 in the second block B. Advantageously, both conditions are fulfilled at the same time.

For example, a possibly present fraction of monomer units M2 in the first block A is particularly advantageously less than 15 mol% (based on all monomer units M1 in the first block A) and one which may be present Proportion of monomer units M1 in the second block B is less than 10 mol% (based on all monomer units M2 in the second block B).

Thus, the monomer units M1 and M2 are substantially spatially separated, which benefits the dispersing effect of the copolymer and is advantageous in terms of the delay problem.

The first block A is based on all monomer units in the first block A in particular at least 20 mol%, in particular at least 50 mol%, especially at least 75 mol% or at least 90 mol%, of monomer units M1 of formula I. Der second block B, based on all the monomer units in the second block B, advantageously comprises at least 20 mol%, in particular at least 50 mol%, especially at least 75 mol% or at least 90 mol%, of monomer units M2 of the formula II ,

A molar ratio of the monomer units M1 to the monomer units M2 in the copolymer is in particular in the range from 0.5 to 6, in particular 0.7 to 4, preferably 0.9 to 3.8, more preferably 1 .0 to 3.7 or 2 to 3.5. This achieves an optimum dispersing effect in mineral binder compositions.

Furthermore, it may be advantageous if the copolymer comprises at least one further monomer unit MS as described above. In particular, several different further monomer units MS can be present. As a result, the properties of the copolymer can be further modified and adapted, for example, with regard to specific applications.

The at least one further monomer unit MS may be part of the first block A and / or the second block B. It is also possible that the at least one further monomer unit MS is part of an additional block of the block copolymer. In particular, different monomer units MS can be present in the various blocks.

If present in the first block A, the at least one further monomer unit MS in the first block A advantageously has a proportion of 0.001-80 mol%, preferably 20-75 mol%, especially 30-70 mol%, based on all monomer units in the first block A, up. If present in the second block B, the at least one further monomer unit MS in the second block B has in particular a proportion of 0.001-80 mol%, preferably 20-75 mol%, especially 30-70 mol% or 50-70 mol% , based on all monomer units in the second block B, on. According to an advantageous embodiment, in the first block A and / or in the second block B, the at least one further monomer unit MS has a proportion of 20-75 mol%, especially 30-70 mol%, based on all monomer units in the respective block , available.

According to a further advantageous embodiment, between the first block A and the second block B at least one further block C is arranged, which differs chemically and / or structurally from the first and from the second block.

Advantageously, the at least one further block C comprises monomer units MS as described above or consists thereof. However, in addition to or instead of the monomer units MS, it is also possible for further monomer units to be present.

In particular, the at least one further block C comprises at least 50 mol%, in particular at least 75 mol%, preferably at least 90 mol% or at least 95 mol% of monomer units MS as described above.

According to a particularly advantageous embodiment, the block copolymer according to the invention is a diblock copolymer consisting of a block A and a block B.

Also suitable are block copolymers containing at least two blocks of the first block A and / or at least two blocks of the second block B. In particular, these are block copolymers which contain the first block A twice and the second block B once or block copolymers which contain the first block A once and the second block B twice. Such block copolymers are in particular triblock copolymers, tetrablock copolymers or pentablock copolymers, preferably triblock copolymers. In the tetrablock copolymers and the pentablockcopo One or two further blocks are present, for example Block C blocks as described above.

A particularly advantageous block copolymer has at least one or more of the following characteristics: i) Block A has 7 - 40, in particular 10 - 25, monomer units M1 and block B has 7 - 50, in particular 20 - 40, monomer units M2. ii) The first block A is based on all monomer units in the first block A to at least 75 mol%, preferably at least 90 mol%, of monomer units M1 of formula I; iii) The second block B is based on all monomer units in the second block B to at least 75 mol%, preferably at least 90 mol%, of monomer units M2 of the formula II; iv) A molar ratio of the monomer units M1 to the monomer units M2 in the block copolymer is in the range from 0.5 to 6, preferably 0.8 to 3.5; v) R ¹ is COOM; vi) R ² and R ⁵ are H or CH ₃ , preferably CH ₃ ; vii) R ³ = R ⁴ = R ⁶ = R ⁷ = H; viii) m = 0 and p = 1; ix) X = -O- x) A = C ₂ -alkylene and n = 10-150, preferably 15-50; xi) R ^a = H or -CH ₃ , preferably CH ₃ ;

Especially preferred is a diblock copolymer, consisting of blocks A and B, which has at least all features (i) - (iv). Further preferred is a diblock copolymer which has all the features (i) - (xi). Even more preferred is a diblock copolymer which realizes all features (i) - (xi) in the respectively preferred embodiments.

Also advantageous is a triblock copolymer consisting of the blocks A, B and C, in particular in the sequence ACB, wherein the triblock copolymer at least all features (i) - (iv). Further preferred is a triblock copolymer which has all the features (i) - (xi). Even more preferred is a triblock copolymer which realizes all the features (i) - (xi) in the respectively preferred embodiments. Block C advantageously comprises monomer units MS as described above or block C consists thereof.

In a specific embodiment, in these diblock copolymers or triblock copolymers, in addition, in block A and B additionally contain a further monomer unit MS as described above, in particular a further monomer unit MS of the formula III.

Preparation of copolymers

Another aspect of the present invention relates to a process for preparing a copolymer, in particular a copolymer as described above, wherein ionizable monomers m1 and side chain-carrying monomers m2 chain to form a non-random distribution of the ionizable monomers m1 and / or the sides carrying monomers m2 are polymerized together.

The ionizable monomers m1 correspond after polymerization to the abovementioned ionizable monomer units M1 of the copolymer. Likewise, the side-chain-carrying monomers m2 correspond after polymerization to the side-chain-carrying monomer units M2 described above.

The side-chain-carrying monomers m2 include in particular polyalkylene oxide side chains, preferably polyethylene oxide and / or polypropylene oxide side chains.

The ionizable monomers m1 preferably comprise acid groups, in particular carboxylic acid, sulfonic acid, phosphoric acid and / or phosphonic acid groups.

In particular, the ionizable monomers m1 have a structure according to the formula IV:

The side chain-carrying monomers m2 preferably have a structure according to the formula V:

wherein the groups R ¹ - R ⁸ , X and the parameters m and p are as described above in connection with the copolymer defined.

According to a further advantageous embodiment, at least one further monomer ms is present during the polymerization, which is polymerized, which is in particular a monomer of the formula VI:

wherein R ⁵ , R ⁶ , R ⁷ , R ⁹ Y, Z, m 'and p' are as defined above defined.

The preparation of the copolymer takes place in particular by a living free radical polymerization. Radical polymerization can basically be divided into three steps: initiation, growth, and termination.

The term "living free radical polymerization" is also referred to as "controlled free radical polymerization" and is known per se to those skilled in the art in other contexts. The term is used for chain growth processes in which essentially no chain termination reactions (transfer and termination) take place. The living free radical polymerization thus takes place essentially in the absence of irreversible transfer or termination reactions. These criteria can be met, for example, if the polymerization initiator is consumed very early in the polymerization and there is an exchange between the different reactive species that proceeds at least as fast as the chain propagation itself. The number of active chain ends remains during the polymerization especially substantially constant. This allows a substantially contemporaneous growth of the chains throughout the polymerization process. This results in a corresponding narrow molecular weight distribution or polydispersity. In other words, controlled radical polymerization or living-radical polymerization is characterized in particular by reversible or even absent termination or transfer reactions. After initiation, the active sites are thus retained throughout the reaction. All polymer chains are formed (initiated) simultaneously and grow continuously over the entire time. The radical functionality of the active center is ideally retained even after complete conversion of the monomers to be polymerized. This special property of controlled polymerizations makes it possible to produce well-defined structures such as gradient or block copolymers by the sequential addition of various monomers.

In contrast, in the conventional free radical polymerization such as e.g. in EP 1 1 10 981 A2 (Kao), all three steps (initiation, growth and termination) in parallel from. The lifetime of the active, growing chains is very low and the monomer concentration during the chain growth of a chain remains essentially constant. The polymer chains thus formed have no active centers which are suitable for addition of further monomers. Thus, this mechanism does not allow control over the structure of the polymers. The representation of gradient or block structures by means of conventional free radical polymerization is therefore usually not possible (see, for example, "Polymers: Synthesis, Synthesis, and Properties"; authors: Koltzenburg, Maskos, Nuyken; publisher: Springer Spektrum; ISBN: 97-3 -642-34772-6 and "Fundamentals of Controlled / Living Radical Polymerization", publisher: Royal Society of Chemistry editors: Tsarevsky, Sumerlin; ISBN: 978-1 -84973-425-7).

Thus, the "living free radical polymerization" clearly differs from the conventional "free radical polymerization" or the non-living or uncontrolled carried out free polymerization. Preferably, the polymerization is carried out by reversible addition-fragmentation chain transfer polymerization (RAFT), nitroxide mediated polymerization (NMP) and / or atom transfer radical polymerization (ATRP).

In the reversible addition-fragmentation chain transfer polymerization, the control of the polymerization is achieved by a reversible chain transfer reaction. Specifically, a growing radical chain adds a so-called RAFT agent, resulting in the formation of an intermediate radical. The RAFT agent then fragments, re-forming a RAFT agent and a radical available for propagation. In this way, the propagation probability is distributed equally over all chains. The average chain length of the polymer formed is proportional to the RAFT agent concentration as well as the reaction conversion. In particular, organic sulfur compounds are used as RAFT agents. Particularly suitable are dithioesters, dithiocarbamates, trithiocarbonates and / or xanthates. The initiation of the polymerization can be carried out conventionally by means of initiators or thermal self-initiation.

In nitroxide-mediated polymerization, nitroxides react reversibly with the active chain end to form a so-called dormant species. The equilibrium between active and inactive chain ends is strongly on the side of the dormant species, whereby the concentration of active species is very low. The probability that two active chains meet and cancel is thus minimized. Suitable as NMP agent is e.g. 2,2,6,6-tetramethylpiperidine N-oxide (TEMPO).

In the atom transfer radical polymerization (ATRP), the free radical concentration is reduced by the addition of a transition metal complex and a controlling agent (halogen-based) to the extent that chain termination reactions, such as disproportionation or recombination, are largely suppressed.

In the present context, the reversible addition fragmentation chain transfer polymerization (RAFT) has been found to be particularly preferred. The initiator used for the polymerization is particularly preferably an azo compound and / or a peroxide radical initiator, which is at least one member selected from the group consisting of dibenzoyl peroxide (DBPO), di-tert-butyl peroxide, diacetyl peroxide and azobisisobutyronitrile (AIBN), α, α'-azodiisobutyramidine dihydrochloride (AAPH) and / or azo-bis-isobutyramidine (AIBA).

If the polymerization is carried out in an aqueous solution or in water, α, α'-azodiisobutyramidine dihydrochloride (AAPH) is advantageously used as the initiator. To control the polymerization, in particular one or more representatives from the group consisting of dithioester, dithiocarbamates, trithiocarbonates and / or xanthates can be used.

It has also proven to be advantageous if the polymerization takes place at least partially, preferably completely, in an aqueous solution. In particular, a molar ratio of free ionizable monomers m1 to free side chain-carrying monomers m2 is changed at least temporarily during the polymerization.

Specifically, the change in the molar ratio includes stepwise and / or continuous change. In this way, a block structure and / or a concentration gradient or a gradient structure can be formed in a manner which is easy to control.

Optionally, during the polymerization both a continuous change and a stepwise change in the molar ratio of the free ionizable monomers m1 to the free side chain-carrying monomers m2 occurs. This stepwise change takes place in particular in time before the continuous change is carried out. Thereby, e.g. a copolymer comprises two or more sections of different structure.

To form copolymers with block and / or gradient structures, the ionizable monomers m1 and the side chain-carrying monomers m2 are preferably added at least partially offset in time. According to a further preferred embodiment, during the polymerization in a first step a) a part of the ionizable monomers m1 is reacted or polymerized and, after reaching a predetermined conversion in a second step b), the unreacted ionizable monomers m1 together with the side chains bearing monomers m2 polymerized. Step a) takes place in this case in particular essentially in the absence of side-chain-carrying monomers m2.

As a result, a copolymer having a section which consists essentially of polymerized ionizable monomers m1 and a subsequent section having a gradient structure can be produced in a simple and cost-effective manner.

According to a very particularly preferred embodiment, in the polymerization in a first step a) a part of the side chain-carrying monomers m2 reacted or polymerized and after reaching a predetermined conversion in a second step b) the unreacted side chain-bearing monomers m2 together with the ionizable monomers m1 polymerized. Step a) is carried out in particular substantially in the absence of ionizable monomers m1.

Thereby, e.g. in a simple and cost-effective manner, a copolymer having a section which consists essentially of polymerized side chain-carrying monomers m2 and a subsequent section with gradient structure can be produced.

It is advantageous to carry out steps a) and b) directly following one another. As a result, the polymerization reaction in steps a) and b) can be maintained as best as possible.

The polymerization in step a) is carried out in particular until 0.1-100 mol%, in particular 1-95 mol%, preferably 10-90 mol%, in particular 25-85 mol%, of the ionizable monomers m1 or the side chain-carrying monomers m2 are reacted or polymerized. The conversion of the monomers m1 and m2 or the progress of the polymerization can be carried out, for example, with the aid of liquid chromatography, in particular high-performance liquid chromatography (HPLC), are controlled in a conventional manner.

In particular, the copolymer is at least 50 mole%, especially at least 75 mole%, especially at least 90 mole% or 95 mole%, of polymerized ionizable monomers m1 and polymerized side chain bearing monomers m2.

The copolymer can be prepared in liquid or solid form. The copolymer is particularly preferably present as a constituent of a solution or dispersion, with a proportion of the copolymer being in particular 10 to 90% by weight, preferably 25 to 65% by weight. As a result, for example, the copolymer can be added very well to binder compositions. If the copolymer is prepared in solution, in particular in aqueous solution, it is also possible to dispense with further preparation.

According to another advantageous embodiment, a copolymer is prepared in a solid state, in particular in the form of a powder, in the form of pellets and / or plates. As a result, in particular the transport of Coplymere is simplified. Solutions or dispersions of the copolymers may e.g. be converted by spray drying in the solid state. Depending on the reaction procedure, polymers with a predetermined or well-defined structure can be prepared in a controlled manner with the process according to the invention. In particular, e.g. Block structure copolymers and / or graded-structure copolymers are available.

Preparation of Copolymers with Gradient Structure The following procedure has proven to be particularly preferred for the preparation of copolymers comprising a gradient structure: In a first step a) at least a portion of the side chain-carrying monomers m2 are reacted or polymerized and after reaching a predetermined conversion in a second step b) the ionizable monomers m1 together with not yet reacted side chain-carrying monomers m2, polymerized. Step a) takes place in particular in the absence of ionizable monomers m1.

It is also possible in a first step a) to react or polymerize at least a portion of the ionizable monomers m1 and after reaching a predetermined conversion in a second step b) the side chain-bearing monomers m2, optionally together with possibly not yet reacted ionizable monomers m1, to polymerize. Step a) takes place in particular in the absence of ionizable monomers m2.

In particular, according to the first-mentioned method, copolymers having a gate consisting essentially of polymerized side-chain-carrying monomers m2 and having a subsequent gradient-type section can be produced in an efficient and cost-effective manner.

In this case, the polymerization in step a) is carried out in particular until 1-74 mol%, preferably 10-70 mol%, in particular 25-70 mol%, especially 28-50 mol% or 30-45 mol% % of the side chain-bearing monomers m2 or the ionizable monomers m1 are reacted or polymerized.

According to a further advantageous embodiment, in step a) and / or in step b) at least one further polymerisable monomer ms of the formula VI as described above is present. The at least one further polymerizable monomer ms is polymerized in this case, in particular together with the monomer m1 and / or the monomer m2.

However, it is also possible, in addition to step a) and step b), to provide a further step c) of the polymerization of the at least one further polymerizable monomer ms. Thereby, a copolymer having an additional portion C can be prepared. In particular, step c) can be performed in time between step a) and step b). Thus, the additional section C is spatially located between sections AA and AB. However, it is also possible to carry out step c) before or after the steps a) and b). Thus, the additional section C can be arranged after section AA or before section AB.

Advantageous proportions, ratios and configurations of the monomers m1, m2, ms and of any further monomers correspond to the abovementioned proportions, ratios and embodiments which have been described in connection with the monomer units M1, M2 and MS.

Preparation of a block-structured copolymer

The following procedure has proven to be particularly preferred for the preparation of copolymers comprising a block structure: In a first step a) at least a portion of the side chain-carrying monomers m2 are reacted or polymerized and after reaching a predetermined conversion in a second step b) the ionizable monomers m1, optionally together with possibly not yet reacted side chain-bearing monomers m2, polymerized. Step a) takes place in particular in the absence of ionizable monomers m1.

The polymerization in step a) is carried out in particular until 75-95 mol%, preferably 85-95 mol%, in particular 86-92 mol%, of the initially charged monomers m2 have been reacted or polymerized. In particular, the polymerization in step b) is carried out correspondingly until 75 to 95 mol%, in particular 80 to 92 mol%, of the originally introduced monomers m1 are reacted or polymerized.

The sequence of steps a) and b) can, however, in principle also be exchanged. However, it is also possible, in addition to step a) and step b), to provide a further step c) of the polymerization of the at least one further polymerizable monomer ms. As a result, a block copolymer having an additional block C can be produced. In particular, step c) is performed temporally between step a) and step b). Thus, the additional block C is spatially arranged between the blocks A and B. Advantageous proportions, ratios and configurations of the monomers m1, m2, ms and of any further monomers correspond to the abovementioned proportions, ratios and embodiments which have been described in connection with the monomer units M1, M2 and MS. Uses of the copolymer

The novel copolymers are particularly advantageous when used as dispersants for binder compositions based on calcium sulfate.

The novel copolymers can be used in particular as plasticizers, as water reducers or to improve the processability and flowability of the calcium sulfate-based binder compositions prepared therewith.

It is likewise possible to use the copolymer for controlling and / or controlling the setting behavior of calcium sulfate-based binder compositions. By this is meant in particular that the copolymer can be used to adjust the stiffening onset and / or the stiffening end of calcium sulfate based binder compositions.

A "binder compositions based on calcium sulfate" is understood herein to mean a composition which contains at least one mineral binder and wherein a proportion of calcium sulfate in the mineral binder, based on the total weight of the mineral binder, at least 30 wt .-%, preferably at least 50 wt more preferably at least 70% by weight, in particular at least 90% by weight or 100% by weight.

The calcium sulfate can be present in any known form, in particular in the form of calcium sulfate dihydrate, calcium sulfate a-hemihydrate, calcium bisulfate hemihydrate, calcium sulfate anhydrite or mixtures thereof. Particularly preferred is calcium sulfate a-hemihydrate and / or calcium sulfate-B hemihydrate. By the term "mineral binder" is meant in particular a binder which reacts in the presence of water in a hydration reaction to solid hydrates or hydrate phases. This may be, for example, a hydraulic binder (eg cement or hydraulic lime), a latent hydraulic binder (eg slag), a pozzolanic binder (eg fly ash) or a non-hydraulic binder (gypsum or white lime).

In a preferred use, the mineral binder contains less than 20 wt%, more preferably less than 10 wt%, preferably less than 5 wt%, especially less than 1 wt%, cement. In particular, the calcium sulfate based binder compositions are cementless.

In particular, the copolymer is used in the production of gypsum boards. Gypsum boards, for example, gypsum plasterboard, in which a gypsum core is enclosed between two cardboard plates, gypsum fiber boards, which additionally contain fibers, and gypsum wall panels, which are usually poured into a mold understood. Particularly suitable are the plaster compositions according to the invention for plasterboard panels in which a gypsum core comprising or consisting of calcium sulfate β-hemihydrate and a copolymer according to the invention is enclosed between cardboard panels.

The term "gypsum" includes any known form of gypsum, in particular calcium sulphate dihydrate, calcium sulphate a hemihydrate, calcium sulphate beta hemihydrate, calcium sulphate anhydrite or mixtures thereof.

In a particularly preferred embodiment, the calcium sulfate based binder compositions comprise a calcium sulfate β-hemihydrate and the binder compositions are used to make gypsum boards. The binder compositions based on calcium sulfate preferably comprise at least 70% by weight of calcium sulfate β-hemihydrate, more preferably at least 90% by weight, of calcium sulfate β-hemihydrate, based on the total weight of the mineral binder in the binder composition. The copolymer is advantageously used in a proportion of 0.01-10% by weight, in particular 0.1-7% by weight or 0.2-5% by weight, based on the binder content.

Another aspect of the present invention relates to a binder composition comprising calcium sulfate and a copolymer as described above. The binder composition contains, based on the total mineral binder, in particular at least 30 wt .-%, preferably at least 50 wt .-%, more preferably at least 70 wt.%, In particular at least 90 wt .-% or 100 wt. %, Calcium sulphate. The calcium sulfate is defined as described above.

A weight ratio of water to binder in the binder composition is preferably in the range from 0.25 to 0.7, in particular 0.26 to 0.65, preferably 0.27 to 0.60, in particular 0.28 to 0.55.

In particular, the binder composition is a gypsum plaster, a floor covering and / or a screed.

In particular, the binder composition is a processable and / or waterborne binder composition.

An additional aspect of the present invention relates to a molded article, in particular a component of a building material or a building, obtainable by curing a binder composition as described above comprising a copolymer after addition of water. A building can e.g. a bridge, a building, a tunnel, a lane, or a runway.

However, the shaped body can also be a filling and / or a coating, for example a gypsum plaster, a floor covering or a screed.

Also, the molded article may be a product that results from the distribution and curing of filler, for example, a filling of a cavity or a joint.

According to a particularly preferred embodiment, the molding is a plasterboard or a sculpture. From the following embodiments, further advantageous embodiments of the invention result.

Short description of the drawing

The figures used to explain the exemplary embodiments show: FIG. 1: the time course of the monomer conversions in the preparation of a copolymer (CP4) according to the invention;

Fig. 2: A schematic representation of a possible structure of a

Copolymer, which can be derived from the sales according to FIG. 1. embodiments

1 . Copolvmere

1 .1 Copolmer CP1 (Blockcopolmer)

To produce the copolymer, 57.4 g of 50% strength methoxy-polyethylene glycol H 000 methacrylate (0.03 mol) and 21 g of deionized water are initially introduced into a round bottom flask equipped with a reflux condenser, stirrer, thermometer and an inert gas inlet tube. The reaction mixture is heated to 80 ° C with vigorous stirring. A slight stream of inert gas is passed through the solution during the warm-up and throughout the remaining reaction time. 378 mg of 4-cyano-4- (thiobenzoyl) pentanoic acid (1 .4 mmol) are now added to the mixture. After the substance has completely dissolved, 67 mg of AIBN (0.41 mmol) are added. From now on, the turnover is determined regularly by HPLC.

As soon as the reaction, based on methoxy-polyethylene glycol methacrylate, is more than 90%, 3.9 g of acrylic acid (0.05 mol) are added to the reaction mixture. The mixture is allowed to react for a further 4 h and then allowed to cool. What remains is a clear, slightly reddish, aqueous solution with a solids content of around 40%. Due to the nearly complete conversion (90%) of the methoxy-polyethyleneglycol-M-O-methacrylate prior to the addition of the acrylic acid, the copolymer CP1 has a block structure.

1 .2 Copolymer CP2 (block copolymer) To produce the copolymer, in a round bottom flask equipped with a reflux condenser, stirrer, thermometer and an inert gas inlet tube, 57.4 g of 50% methoxy-polyethylene glycol M, OOO-methacrylate (0.03 mol) and 21 g deionized Submitted water. The reaction mixture is heated to 80 ° C with vigorous stirring. A slight stream of inert gas is passed through the solution during the warm-up and throughout the remaining reaction time. To the mixture are then added 504 mg of 4-cyano-4- (thiobenzoyl) pentanoic acid (1 .8 mmol). After the substance has completely dissolved, 90 mg of AIBN (0.55 mmol) are added. From now on, the turnover is determined regularly by HPLC. As soon as the reaction, based on methoxy-polyethylene glycol methacrylate, is more than 90%, 3.9 g of acrylic acid (0.05 mol) are added to the reaction mixture. The mixture is allowed to react for a further 4 h and then allowed to cool. What remains is a clear, slightly reddish, aqueous solution with a solids content of around 40%. 1 .3 Copolmer CP3 (Blockcopolmer)

To prepare the copolymer, 57.4 g of 50% methoxy-polyethylene glycol O-methacrylate (0.03 mol) and 23 g of deionized water are placed in a round bottom flask equipped with a reflux condenser, stirrer, thermometer and an inert gas inlet tube. The reaction mixture is heated to 80 ° C. with vigorous stirring. A slight stream of inert gas is passed through the solution during the warm-up and the entire remaining reaction time. To the mixture are then added 504 mg of 4-cyano-4- (thiobenzoyl) pentanoic acid (1 .8 mmol). After the substance has completely dissolved, 90 mg of AIBN (0.55 mmol) are added. From now on, the turnover is determined regularly by HPLC. As soon as the reaction, based on methoxy-polyethylene glycol methacrylate, is more than 90%, 5.2 g of acrylic acid (0.07 mol) are added to the reaction mixture. The mixture is allowed to react for a further 4 h and then allowed to cool. What remains is a clear, slightly reddish, aqueous solution with a solids content of around 40%.

1 .4 copolymer CP4 (gradient polymer)

To prepare the gradient polymer by means of RAFT polymerization, 57.4 g of 50% strength methoxy-polyethylene glycol M 000 methacrylate (0.03 mol) and 22 g of deionized water are placed in a round bottom flask equipped with a reflux condenser, stirrer, thermometer and a gas inlet tube. The reaction mixture is heated to 80 ° C with vigorous stirring. A light N2 inert gas stream is passed through the solution during the warm-up and the entire remaining reaction time. 378 mg of 4-cyano-4- (thiobenzoyl) pentanoic acid (1.35 mmol) are now added to the mixture. After the substance has completely dissolved, 67 mg of AIBN (0.41 mmol) are added. From now on, the turnover is determined regularly by HPLC.

As soon as the reaction, based on methoxy-polyethylene glycol methacrylate, is 65 mol%, 4.66 g of methacrylic acid (0.05 mol) dissolved in 20 g of H ₂ O are added dropwise within 20 min. After completion, the mixture is allowed to react for a further 4 h and then allowed to cool. What remains is a clear, slightly reddish, aqueous solution with a solids content of around 35%. The gradient-gradient copolymer thus obtained is referred to as copolymer CP4. FIG. 1 shows the time course of the monomer conversions in the preparation of the copolymer CP4. The monomer conversions were determined by high performance liquid chromatography (HPLC) in a manner known per se at the times indicated in Figure 1 during the preparation of the copolymer. The upper dotted curve, which begins at the origin at the time t = 0 minutes, represents the percentage conversion of the methoxy-polyethylene glycol-methacrylate monomers (= side chain-carrying monomers m2) (scale on the right). The lower dotted curve, which at the time t = 25 minutes, represents the percentage conversion of methacrylic acid monomers (= ionizable monomers m1) (scale on the right). The solid line with the diamond-shaped points indicates the number of side chain-carrying monomers m2 that have been polymerized since the previous measurement point (= n (M2), left scale). Similarly, the solid line with the triangular points represents the number of ionizable monomers m1 that have been polymerized since the previous measurement point (= n (M1), left scale).

If the ratio n (M2) / [n (M1) + n (M2)] and n (M1) / [n (M1...) Are calculated from the information in FIG. 1 for the period from 0 to 55 minutes at the respective time ) + n (M2)], the following values result:

Table 1: Monomer ratios during the preparation of the copolymer CP4.

It can be seen from Table 1 that in the preparation of the copolymer CP4, a section consisting of 100% side chain-carrying monomer units M2 is formed during the first 25 minutes, followed by a section in which the proportion of side-chain-bearing monomer units M2 decreases continuously Proportion of ionizable monomer units M1 continuously increases. In Fig. 2 also a possible structure of the copolymer CP4 is shown schematically. This can be derived directly from the conversions mentioned in FIG. The side-chain-carrying monomer units M2 (= polymerized methoxy-polyethylene glycol-methacrylate monomers) are shown as a circle with a coiled extension. The ionizable monomer units M1 are shown as dumbbell-shaped symbols.

It can be seen from FIG. 2 that copolymer CP4 comprises a first section AA with a gradient structure and a further section AB, consisting essentially of side chain-carrying monomer units. 1 .5 Comparative polymer PR1 (random copolymer)

For comparative purposes, a commercially available dispersant of the type "Sika® ViscoCrete® G-2" (available from Sika Deutschland GmbH) was used. This is a comb polymer having a polycarboxylate backbone and polyether side chains, which is prepared by a polymer-analogous reaction of a polycarboxylic acid with unilaterally hydroxy- and amine-terminated polyether side chains. The sequence of monomer units in the comparative polymer is purely random or purely statistical. Otherwise, however, the comparative polymer is comparable to the copolymers described above.

2. Tests in Calcium Sulphate Binder Compositions 2.1 Preparation of Binder Compositions

To produce a gypsum slurry, 140 g of water were initially charged, each with 1 g of a 40% copolymer solution (corresponding to 0.2% by weight of plasticizer, based on the total weight of the calcium sulfate β-hemihydrate). Then 200 g of calcium sulfate ß-hemihydrate, 0.2 g (0.1 wt .-% based on the total weight of calcium sulfate ß-hemihydrate) of an accelerator in the form of calcium sulfate dihydrate, (available from Fluka Switzerland) within 15 seconds in sprinkled the water and allowed the gypsum slurry to sump for 15 seconds. Subsequently, the mixture was stirred thoroughly by hand for 30 seconds. 2.2 test methods To test the flow and setting behavior, a miniconus with a diameter of 50 mm and a height of 51 mm was filled with the gypsum slurry prepared in each case and after 75 seconds the slump (ABM) was determined in millimeters (based on EN 1015-3). The diameter of the forming gypsum cake was measured as soon as no flow was observed. The diameter in mm is referred to as slump.

The stiffening beginning and the stiffening end were determined with the knife cutting method according to DIN EN 13279-2 and the thumb pressure method. The beginning of stiffening (VB) is reached when, after a knife cut through the plaster cake, the cut edges no longer converge. The end of the stiffening has occurred (VE), if at a finger pressure with a pressure of about 5 kg no more water escapes from the gypsum cake.

2.3 Test results

Table 2 gives an overview of the experiments carried out and the results obtained. Experiment V1 is a comparative experiment carried out without addition of a polymer.

Table 2: Results

The experiments show that the inventive Copolypmere (Experiments V3 to V5) compared to the conventional dispersant (Experiment V2) at the same dosage comparable or even better sludge yield, but at the same time clearly less retarded or allow faster setting.

However, the embodiments described above are to be understood merely as illustrative examples, which may be modified as desired within the scope of the invention.

Claims

claims

Use of a copolymer as a dispersant for calcium sulfate-based binder compositions, the copolymer comprising a polymer backbone and side chains attached thereto and having at least one ionizable monomer unit M1 and at least one side chain-bearing monomer unit M2, characterized in that the copolymer is in a direction along the Polymer backbone has a non-random distribution of the monomer units M1 and / or the monomer units M2.

Use according to claim 1, characterized in that the copolymer has a gradient structure and / or a block structure in at least one section.

Use according to at least one of the preceding claims, wherein in the copolymer the ionisable monomer unit M1 has a structure of the formula I,

and the side chain-carrying monomer unit M2 includes a structure of Formula II

in which

R ¹ , each independently, is -COOM, -SO ₂ -OM,

-O-PO (OM) ₂ and / or -PO (OM) ₂ ,

R ² , R ³ , R ⁵ and R ⁶ , each independently of one another, are H or an alkyl group having 1 to 5 carbon atoms,

R ⁴ and R ⁷ , each independently of one another, are H, -COOM or an alkyl group having 1 to 5 carbon atoms, or where R ¹ forms a ring with R ⁴ to -CO-O-CO-,

X, in each case independently of one another, represents -O- or -NH-,

R ⁸ is a group of formula - [AO] _n -R ^a, where A = C ₂ - to C ₄ alkylene, R ^a is H, a C to C ₂ o alkyl group, cycloalkyl group, or alkylaryl group is , and n = 2-250, especially 10-200.

4. Use according to at least one of the preceding claims, characterized in that the copolymer comprises at least one further monomer unit MS of the formula III:

wherein R ⁵ , R ^{6 '} , R ^7' , m 'and p' are defined as R ⁵ , R ⁶ , R ⁷ , m and p in claim 3;

Y, each independently, is a chemical bond or -O-;

Z, each independently, is a chemical bond, -O- or -NH-;

R ⁹ , in each case independently of one another, is an alkyl group, cycloalkyl group, alkylaryl group, aryl group, hydroxyalkyl group or an acetoxyalkyl group, each having 1 to 20 C atoms.

Use according to at least one of the preceding claims, characterized in that the copolymer is a block copolymer, wherein the ionizable monomer unit M1 substantially in at least a first block A and the side chain-carrying monomer unit M2 substantially in at least one second block B, are present.

Use according to at least one of claims 1-4, characterized in that the copolymer in at least one section AA in a direction along the polymer backbone with respect to the ionizable Monomer unit M1 and / or with respect to the side chain-carrying monomer unit M2 has a gradient structure.

7. Use according to claim 6, characterized in that the copolymer in addition to the at least one section AA, which has a gradient structure, has a further section AB, wherein over the entire section AB is substantially a constant local concentration of the monomers and / or a random or random distribution of the monomers is present.

8. Use according to at least one of the preceding claims, wherein the polydispersity of the copolymer is <1 .5, and in particular in

Range from 1 .0 - 1 .4, especially 1 .1 - 1 .3.

9. Use according to at least one of the preceding claims, characterized in that a molar ratio of the monomer units M1 to the monomer units M2 in the copolymer in the range of 0.5 - 6, in particular 0.7 - 4, preferably 0.9 - 3.8, more preferably 1 .0 - 3.7 o - the 2 - 3.5, lies.

10. Use according to any one of claims 3-9, characterized in that R ¹ = COOM; R ² and R ⁵ , independently of one another, are H, -CH ₃ or mixtures thereof; R ³ and R ⁶ , independently of one another, are H or -CH ₃ , preferably H; R ⁴ and R ^7, independently of one another, H or -COOM, preferably H, stand; and wherein X is at least 75 mol%, in particular at least 90 mol%, especially at least 99 mol% of all monomer units M2 is -O-. 1 1. Use according to at least one of the preceding claims, characterized in that the copolymer is obtainable or prepared by a controlled free radical polymerization and / or a living free radical polymerization, in particular by reversible addition fragmentation chain transfer polymerization (RAFT).

12. Use according to at least one of the claims wherein the copolymer is used for controlling and / or controlling the setting behavior of the binder compositions based on calcium sulfate.

13. A binder composition comprising calcium sulfate and at least one as described in any one of the preceding claims Copolymer.

14. A binder composition according to claim 13, containing at least 30 wt .-%, preferably at least 50 wt .-%, more preferably at least 70 wt.%, In particular at least 90 wt .-% or 100 wt .-%, calcium sulfate, based on all mineral binder in the binder composition.

15. Shaped body, in particular a component of a building material or a building, obtainable by curing a mineral binder composition according to at least one of claims 13 - 14 after addition of water.