Additive containing a superplasticizer and a copolymer

Abstract

The present invention relates to admixtures, especially a dispersant for solid particles, in particular a dispersant for mineral binder compositions, comprising: a) a superplasticizer and b) a copolymer having a polymer backbone and side chains bonded thereto, comprising at least one ionizable monomer unit M1 and at least one side chain-bearing monomer unit M2, wherein the copolymer has a nonrandom distribution of the monomer units M1 and/or the monomer units M2 in a direction along the polymer backbone, and wherein the superplasticizer and the copolymer differ from a chemical and/or structural point of view.

Claims

1. An admixture comprising: a) a superplasticizer and b) a copolymer having a polymer backbone and side chains bonded thereto, the copolymer comprising: at least one ionizable monomer unit M1 and at least one side chain-bearing monomer unit M2, wherein: the copolymer has a nonrandom distribution of the monomer units M1 and/or the monomer units M2 in a direction along the polymer backbone, the superplasticizer and the copolymer differ from a chemical and/or structural point of view, and the superplasticizer comprises the following substructure units: a) a molar parts of a substructure unit S1 of formula I ##STR00013## b) b molar parts of a substructure unit S2 of formula II ##STR00014## c) c molar parts of a substructure unit S3 of formula (III) ##STR00015## d) d molar parts of a substructure unit S4 of formula (IV) ##STR00016## where: L independently represents H.sup.+, an alkali metal ion, an alkaline earth metal ion, a di- or trivalent metal ion, an ammonium ion or an organic ammonium group, each R.sup.u independently of any other is hydrogen or a methyl group, each R.sup.v independently of any other is hydrogen or COOM, r=0, 1, or 2, t=0 or 1, G.sup.1 and G.sup.2 are each independently a C.sub.1- to C.sub.20-alkyl group, -cycloalkyl group, -alkylaryl group, or -[AO].sub.s-G.sup.4, where A=C.sub.2- to C.sub.4-alkylene, G.sup.4 is H, a C.sub.1- to C.sub.20-alkyl group, -cycloalkyl group, or -alkylaryl group, and s=2-250, G.sup.3 is independently NH.sub.2, NG.sup.5G.sup.6, or OG.sup.7NG.sup.8G.sup.9, where: G.sup.5 and G.sup.6 are each independently a C.sub.1- to C.sub.20-alkyl group, -cycloalkyl group, -alkylaryl group, or -aryl group, or are a hydroxyalkyl group, an acetoxyethyl group (CH.sub.3COOCH.sub.2CH.sub.2), a hydroxyisopropyl group (HOCH(CH.sub.3)CH.sub.2), or an acetoxyisopropyl group (CH.sub.3COOCH(CH.sub.3)CH.sub.2); or G.sup.5 and G.sup.6 together form a ring, which includes the nitrogen, in order to form a morpholine or imidazoline ring; G.sup.7 is a C.sub.2-C.sub.4-alkylene group, G.sup.8 and G.sup.9 each independently represents a C.sub.1- to C.sub.20-alkyl group, -cycloalkyl group, -alkylaryl group, -aryl group, or a hydroxyalkyl group, and a, b, c and d represent molar proportions of the respective substructure units S1, S2, S3 and S4, a/b/c/d=(0.1-0.9)/(0.1-0.9)/(0-0.8)/(0-0.8), and with the proviso that a+b+c+d=1.

2. An admixture comprising: a) a superplasticizer and b) a copolymer having a polymer backbone and side chains bonded thereto, the copolymer comprising: at least one ionizable monomer unit M1 and at least one side chain-bearing monomer unit M2, wherein: the copolymer has a nonrandom distribution of the monomer units M1 and/or the monomer units M2 in a direction along the polymer backbone, the copolymer is a block copolymer, wherein the ionizable monomer units M1 are present essentially in at least one first block A and the side chain-bearing monomer units M2 essentially in at least one second block B, and the superplasticizer and the copolymer differ from a chemical and/or structural point of view.

3. An admixture comprising: a) a superplasticizer and b) a copolymer having a polymer backbone and side chains bonded thereto, the copolymer comprising: at least one ionizable monomer unit M1 and at least one side chain-bearing monomer unit M2, wherein: the copolymer has a nonrandom distribution of the monomer units M1 and/or the monomer units M2 in a direction along the polymer backbone, 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-bearing monomer unit M2, and the superplasticizer and the copolymer differ from a chemical and/or structural point of view.

4. The admixture as claimed in claim 2, wherein the ionizable monomer unit M1 in the copolymer has a structure of formula VI ##STR00017## and the side chain-bearing monomer unit M2 includes a structure of formula VII ##STR00018## where: R.sup.1, in each case independently, is COOM, SO.sub.2OM, OPO(OM).sub.2, or PO(OM).sub.2, R.sup.2, R.sup.3, R.sup.5 and R.sup.6, in each case independently, are H or an alkyl group having 1 to 5 carbon atoms, R.sup.4 and R.sup.7, in each case independently, are H, COOM, or an alkyl group having 1 to 5 carbon atoms, or R.sup.1 forms a ring together with R.sup.4 to give COOCO, M, independently of one another, represents H.sup.+, an alkali metal ion, an alkaline earth metal ion, a di- 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, is O or NH, R.sup.8 is a group of formula -[AO].sub.n-R.sup.a, where A=C.sub.2- to C.sub.4-alkylene, R.sup.a is H, a C.sub.1- to C.sub.20-alkyl group, -cycloalkyl group, or -alkylaryl group, and n=2-250.

5. The admixture as claimed in claim 2, wherein the copolymer comprises at least one further monomer unit MS of formula VIII: ##STR00019## where: R.sup.5, R.sup.6, R.sup.7, m and p are as defined for R.sup.5, R.sup.6, R.sup.7, m and p as in claim 4; Y, in each case independently, is a chemical bond or O; Z, in each case independently, is a chemical bond, O or NH; and R.sup.9, in each case independently, is an alkyl group, cycloalkyl group, alkylaryl group, aryl group, hydroxyalkyl group, or acetoxyalkyl group, each having 1-20 carbon atoms.

6. The admixture as claimed in claim 3, wherein the copolymer, in addition to the at least one section AA having a gradient structure, has a further section AB, wherein there is essentially a constant local concentration of the monomers and/or a random distribution of the monomers over the entire section AB.

7. The admixture as claimed in claim 1, wherein a polydispersity of the copolymer is <1.5.

8. The admixture as claimed in claim 1, wherein a molar ratio of the monomer units M1 to the monomer units M2 in the copolymer is in the range of 0.5-6.

9. The admixture as claimed in claim 4, wherein: R.sup.1=COOM; R.sup.2 and R.sup.5, independently of one another, are H, CH.sub.3, or mixtures thereof; R.sup.3 and R.sup.6, independently of one another, are H or CH.sub.3, R.sup.4 and R.sup.7, independently of one another, are H or COOM; and X in at least 75 mol %, of all monomer units M2 is O.

10. A method for dispersing solid particles, comprising mixing an admixture as claimed in claim 1 with solid particles.

11. A mineral binder composition, comprising at least one admixture as claimed in claim 1.

12. A shaped body, obtained by curing a mineral binder composition as claimed in claim 11 after addition of water.

13. The admixture as claimed in claim 3, wherein the ionizable monomer unit M1 in the copolymer has a structure of formula VI ##STR00020## and the side chain-bearing monomer unit M2 includes a structure of formula VII ##STR00021## where: R.sup.1, in each case independently, is COOM, SO.sub.2OM, OPO(OM).sub.2, or PO(OM).sub.2, R.sup.2, R.sup.3, R.sup.5 and R.sup.6, in each case independently, are H or an alkyl group having 1 to 5 carbon atoms, R.sup.4 and R.sup.7, in each case independently, are H, COOM, or an alkyl group having 1 to 5 carbon atoms, or R.sup.1 forms a ring together with R.sup.4 to give COOCO, M, independently of one another, represents H.sup.+, an alkali metal ion, an alkaline earth metal ion, a di- 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, is O or NH, R.sup.8 is a group of formula -[AO].sub.n-R.sup.a, where A=C.sub.2- to C.sub.4-alkylene, R.sup.a is H, a C.sub.1- to C.sub.20-alkyl group, -cycloalkyl group, or -alkylaryl group, and n=2-250.

14. The admixture as claimed in claim 3, wherein the copolymer comprises at least one further monomer unit MS of formula VIII: ##STR00022## where: R.sup.5, R.sup.6, R.sup.7, m and p are as defined for R.sup.5, R.sup.6, R.sup.7, m and p as in claim 4; Y, in each case independently, is a chemical bond or O; Z, in each case independently, is a chemical bond, O or NH; and R.sup.9, in each case independently, is an alkyl group, cycloalkyl group, alkylaryl group, aryl group, hydroxyalkyl group, or acetoxyalkyl group, each having 1-20 carbon atoms.

15. The admixture as claimed in claim 13, wherein: R.sup.1=COOM; R.sup.2 and R.sup.5, independently of one another, are H, CH.sub.3, or mixtures thereof; R.sup.3 and R.sup.6, independently of one another, are H or CH.sub.3, R.sup.4 and R.sup.7, independently of one another, are H or COOM; and X in at least 75 mol %, of all monomer units M2 is O.

16. A method for dispersing solid particles, comprising mixing an admixture as claimed in claim 2 with solid particles.

17. A method for dispersing solid particles, comprising mixing an admixture as claimed in claim 3 with solid particles.

18. A mineral binder composition, comprising at least one admixture as claimed in claim 2.

19. A mineral binder composition, comprising at least one admixture as claimed in claim 3.

20. A shaped body, obtained by curing a mineral binder composition as claimed in claim 19 after addition of water.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The figures used to elucidate the working examples show:

(2) FIG. 1: The plot of the monomer conversions against time in the preparation of a copolymer of the invention (CP3);

(3) FIG. 2: A schematic diagram of a possible structure of a copolymer which can be derived from the conversions according to FIG. 1.

WORKING EXAMPLES

1. Preparation Examples

(4) 1.1 Superplasticizers

(5) For the experiments which follow, a superplasticizer in the form of a polymer P was prepared in a known manner per se by polymer-analogous reaction of polyacrylic acid (M.sub.W=4500 g/mol) with alcohols of the HOR.sup.1 type and amines of the H.sub.2NR.sup.2 type (conversion level greater than 97%). The raw materials used for this purpose are commercially available from various suppliers. The structure of the polymer thus prepared corresponds to the previously described polymer P having the substructure units S1, S2 and S3, where: R.sup.u and R.sup.v are hydrogen; r=0 and t=1; G.sup.1 is a mixture of a methoxy-terminated polyethylene glycol with mass M.sub.n=1000 g/mol (PEG1000-OCH.sub.3) and a methoxy-terminated polyethylene glycol with mass M.sub.n=3000 g/mol (PEG3000-OCH.sub.3). The molar ratio of PEG1000-OCH.sub.3 to PEG3000-OCH.sub.3 here is 0.205/0.153. G.sup.2 is a methoxy-terminated ethylene oxide/propylene oxide copolymer with mass M.sub.n=2000 g/mol, where the ethylene oxide and propylene oxide units are present in a molar ratio of 50:50; a/b/c/d=0.640/0.205/0.153/0.002/0, and the molecular weight of the comb polymer (M.sub.W) is about 60000 g/mol.

(6) A solution containing 40% by weight of the comb polymer in water was obtained, which is referred to hereinafter as FM.

(7) Polymers of this kind are also available commercially from Sika Schweiz AG under the Viscocrete name.

(8) 1.2 Copolymer CP1

(9) For preparation of a block copolymer by means of RAFT polymerization, a round-bottom flask equipped with a reflux condenser, stirrer system, thermometer and a gas inlet tube is initially charged with 57.4 g of 50% methoxy polyethylene glycol 1000 methacrylate (0.03 mol) and 22 g of deionized water. The reaction mixture is heated to 80 C. with vigorous stirring. A gentle inert N2 gas stream is passed through the solution during the heating and over all the remaining reaction time. 378 mg of 4-cyano-4-(thiobenzoyl)pentanoic acid (1.35 mmol) are then added to the mixture. Once the substance has fully dissolved, 67 mg of AIBN (0.41 mmol) are added. From then on, the conversion is determined regularly by means of HPLC.

(10) As soon as the conversion, based on methoxy polyethylene glycol methacrylate, is 90%, 4.66 g of methacrylic acid (0.05 mol) are added. The mixture left to react for a further 4 h and then to cool. What remains is a clear, reddish, aqueous solution having a solids content of around 40%.

(11) The copolymer thus obtained is referred to as polymer CP1 and, owing to the virtually complete conversion of the methoxy polyethylene glycol methacrylate (90 mol %), has a block structure in which the side chain-bearing monomer units (methoxy polyethylene glycol methacrylate) are present in a first block and the ionizable monomer units (methacrylic acid) essentially spatially separately in a second block.

(12) 1.3 Copolymer CP2

(13) For preparation of a copolymer by means of RAFT polymerization, a round-bottom flask equipped with a reflux condenser, stirrer system, thermometer and a gas inlet tube is initially charged with 57.4 g of 50% methoxy polyethylene glycol 1000 methacrylate (0.03 mol) and 22 g of deionized water. The reaction mixture is heated to 80 C. with vigorous stirring. A gentle N2 inert gas stream is passed through the solution during the heating and over all the remaining reaction time. 756 mg of 4-cyano-4-(thiobenzoyl)pentanoic acid (2.7 mmol) are then added to the mixture. Once the substance has fully dissolved, 135 mg of AIBN (0.8 mmol) are added. From then on, the conversion is determined regularly by means of HPLC.

(14) As soon as the conversion, based on methoxy polyethylene glycol methacrylate, is 90%, 6.99 g of methacrylic acid (0.08 mol) are added to the reaction mixture. The mixture left to react for a further 4 h and then to cool. What remains is a clear, reddish, aqueous solution having a solids content of around 40%. The copolymer thus obtained is referred to as polymer CP2.

(15) 1.4 Copolymer CP3

(16) For preparation of a gradient polymer by means of RAFT polymerization, a round-bottom flask equipped with a reflux condenser, stirrer system, thermometer and a gas inlet tube is initially charged with 57.4 g of 50% methoxy polyethylene glycol 1000 methacrylate (0.03 mol) and 22 g of deionized water. The reaction mixture is heated to 80 C. with vigorous stirring. A gentle N2 inert gas stream is passed through the solution during the heating and over all the remaining reaction time. 378 mg of 4-cyano-4-(thiobenzoyl)pentanoic acid (1.35 mmol) are then added to the mixture. Once the substance has fully dissolved, 67 mg of AIBN (0.41 mmol) are added. From then on, the conversion is determined regularly by means of HPLC.

(17) As soon as the conversion, based on methoxy polyethylene glycol methacrylate, is 65 mol %, 4.66 g of methacrylic acid (0.05 mol) dissolved in 20 g of H.sub.2O are added dropwise within 20 min. After this has ended, the mixture is left to react for a further 4 h and then to cool. What remains is a clear, pale reddish, aqueous solution having a solids content of around 35%. The copolymer with gradient structure thus obtained is referred to as copolymer CP3.

(18) FIG. 1 shows the plot of the monomer conversions against time in the preparation of the copolymer CP3. The monomer conversions were determined in a manner known per se at the times given in FIG. 1 during the preparation of the copolymer by high-performance liquid chromatography (HPLC). The upper dotted curve which begins at the origin at time t=0 minutes represents the percentage conversion of the methoxy polyethylene glycol methacrylate monomers (=side chain-bearing monomers m2) (scale to the right). The lower dotted curve which begins at time t=25 minutes represents the percentage conversion of the methacrylic acid monomers (=ionizable monomers m1) (scale to the right). The solid line with the diamond-shaped points indicates the number of side chain-bearing monomers m2 which have been polymerized since the preceding measurement point (=n(M2); left-hand scale). Correspondingly, the solid line with the triangular points indicates the number of ionizable monomers m1 which have been polymerized since the preceding measurement point (=n(M1); left-hand scale).

(19) Using the data in FIG. 1 for the period from 0 to 55 minutes at the particular time to calculate the ratio n(M2)/[n(M1)+n(M2)] and n(M1)/[n(M1)+n(M2)], the following values are found:

(20) TABLE-US-00001 TABLE 1 Monomer ratios during the preparation of the copolymer CP3. Time n(M2)/[n(M1) + n(M2)] n(M1)/[n(M1) + n(M2)] 15 100% 0% 25 100% 0% 30 33% 67% 35 29% 71% 40 25% 75% 45 17% 83% 55 10% 90%

(21) It is apparent from table 1 that, in the preparation of the copolymer CP3, during the first 25 minutes, a section consisting of 100% side chain-bearing monomer units M2 is formed, followed by a section in which the proportion of side chain-bearing monomer units M2 decreases continuously while the proportion of ionizable monomer units M1 increases continuously.

(22) FIG. 2 additionally shows a schematic of a possible structure of the copolymer CP3. This can be inferred directly from the conversions shown in FIG. 1. The side chain-bearing monomer units M2 (=polymerized methoxy polyethylene glycol methacrylate monomers) are represented as a circle with a twisted appendage. The ionizable monomer units M1 are represented as dumbbell-shaped symbols.

(23) It is apparent from FIG. 2 that copolymer CP3 comprises a first section AA with gradient structure and a further section AB consisting essentially of side chain-bearing monomer units.

2. Admixtures

(24) Various admixtures were produced by mixing the above-described superplasticizer FM and the copolymers CP1 and CP2. Table 2 gives an overview of the compositions of the admixtures produced.

(25) TABLE-US-00002 TABLE 2 Compositions of the admixtures produced Admixture Proportion of FM Copolymer/proportion ZZ1 50% by weight CP2/50% by weight ZZ2 70% by weight CP2/30% by weight ZR1 100% by weight ZR2 CP2/100% by weight

(26) The superplasticizers and copolymers prepared according to the above preparation examples were used directly for production of the admixtures without further processing. Correspondingly, the admixtures are aqueous solutions or dispersions.

3. Cement Pastes

(27) 3.1 Production

(28) The cement pastes used for test purposes are based on cement (CEM I 42.5 N; Normo 4; available from Holcim Schweiz) and water.

(29) To make up a cement paste, the cement was dry-mixed in a Hobart mixer for 1 minute. Within 30 seconds, the make-up water (ratio of water to cement w/c=0.305), into which the respective admixture composition (proportion: 0.75% by weight; based on cement content) had been mixed beforehand, was added and the mixture was mixed for a further 2.5 minutes. The total mixing time in wet form was 3 minutes in each case.

(30) 3.2 Cement Paste Tests

(31) To determine the dispersancy of the admixture compositions, the slump (ABM) of each made-up cement paste was measured at different times. The slump (ABM) of the cement pastes was determined in accordance with EN 1015-3.

(32) 3.3 Results of the Cement Paste Tests

(33) Table 3 gives an overview of the cement paste tests conducted and the results achieved. Experiment V1 is a blank experiment conducted for comparative purposes without addition of a polymer.

(34) TABLE-US-00003 TABLE 3 Results of cement paste tests ABM.sup.# [mm] after 0 30 123 180 240 300 341 No. Admixture min min min min min min min V1 <120 n.m. n.m. n.m. n.m. n.m. n.m. V2 ZR1 135 108 110 110 105 72 n.m. V3 ZR2 180 119 110 101 90 68 n.m. V4 ZZ1 162 134 135 129 125 119 111 V5 ZZ2 163 117 120 118 114 106 97 n.m. = not measureable .sup.#slump according to EN 1015-3. The time 0 min corresponds to the first measurement immediately after the cement paste has been made up.

(35) The experiments show that the admixtures of the invention (experiments V4 and V5) by comparison with a pure superplasticizer (experiment V2) or pure copolymer CP2 (experiment V3), with the same dosage, give rise not just to elevated slump but also to distinctly longer working times. The results demonstrate the functional and synergistic interaction between superplasticizer and copolymer in the admixtures of the invention.

(36) However, the above-described embodiments should be regarded merely as illustrative examples which can be modified as desired within the scope of the invention.