BLOCK COPOLYMER

Abstract

A block copolymer, in particular for use as a dispersant for mineral binder compositions, including at least one first block A and at least one second block B, wherein the first block A has a monomer unit M1 and the second block B has a monomer unit M2. To this end a proportion of monomer units M2 which is in any case present in the first block A is less than 25 mol %, in particular less than or equal to 10 mol %, based on all the monomer units M1 in the first block A and a proportion of monomer units M1 which is in any case present in the second block B is less than 25 mol %, in particular less than or equal to 10 mol %, based on all the monomer units M2 in the second block B.

Claims

1. A block copolymer comprising at least one first block A and at least one second block B, the first block A having a monomer unit M1 of the formula I, ##STR00007## and the second block B containing a monomer unit M2 of the formula II ##STR00008## where R.sup.1, in each case independently of any other, is COOM, SO.sub.2OM, OPO(OM).sub.2 and/or PO(OM).sub.2, R.sup.2, R.sup.3, R.sup.5 and R.sup.6, each independently of one another, are H or an alkyl group having 1 to 5 carbon atoms, R.sup.4 and R.sup.7, each independently of one another, are H, COOM or an alkyl group having 1 to 5 carbon atoms, or where R.sup.1 with R.sup.4 forms a ring to COOCO, M, in each case independently of any other, is 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 of any other, is O or NH, R.sup.8 is a group of the formula [AO].sub.nR.sup.a, where A=C.sub.2 to C.sub.4-alkylene, R.sup.a is H, or a C.sub.1 to C.sub.20-alkyl group, -cyclohexyl group or -alkylaryl group, and n is 2-250; and where any fraction of monomer units M2 present in the first block A is less than 25 mol % based on all the monomer units M1 in the first block A, and where any fraction of monomer units M1 present in the second block B is less than 25 mol % based on all the monomer units M2 in the second block B.

2. The block copolymer as claimed in claim 1, wherein at least one first block A comprises 5-70 monomer units M1 and/or in that the at least one second block B comprises 5-70 monomer units M2.

3. The block copolymer as claimed in claim 1, wherein the first block A comprises 25-35 monomer units M1 and/or in that the at least one second block B comprises 10-20 monomer units M2.

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

5. The block copolymer as claimed in claim 1, wherein the first block A, based on all the monomer units in the first block A, consists to an extent of at least 20 mol % of monomer units M1 of the formula I and/or in that the second block B, based on all the monomer units in the second block B, consists to an extent of at least 20 mol % of monomer units M2 of the formula II.

6. The block copolymer as claimed in claim 1, wherein the block copolymer comprises at least one further monomer unit MS: ##STR00009## where R.sup.5, R.sup.6, R.sup.7, m and p are defined like R.sup.5, R.sup.6, R.sup.7, m and p in claim 1; Y, in each case independently of any other, is a chemical bond or O; Z, in each case independently of any other, is a chemical bond, O or NH; R.sup.9, in each case independently of any other, is an alkyl group, cycloalkyl group, alkylaryl group, aryl group, hydroxyalkyl group or an acetoxyalkyl group, in each case having 1-20 C atoms.

7. The block copolymer as claimed in claim 1, 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 for at least 75 mol % of all monomer units M2, is O.

8. The block copolymer as claimed in claim 1, wherein n=10-150.

9. The block copolymer as claimed in claim 1, wherein it is a diblock copolymer, consisting of a block A and a block B.

10. A process for preparing a block copolymer as claimed in claim 1, comprising a step of a) polymerizing monomers m1 of the formula IV ##STR00010## and also a step of b) polymerizing monomers m2 of the formula V ##STR00011## where R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, m, p and X are defined as in claim 1 and where in step a) any fraction of monomer m2 present is less than 25 mol % based on the monomers m1, and in step b) any fraction of monomer m1 present is less than 25 mol % based on the monomers m2; and where the steps a) and b) are performed in temporal succession in any order.

11. The process as claimed in claim 10, wherein the polymerization is accomplished by reversible addition-fragmentation chain transfer polymerization (RAFT).

12. The process as claimed in claim 10, wherein the polymerization in step a) is carried out until 75-95 mol of the monomers m1 originally introduced have undergone reaction or polymerization, and/or wherein the polymerization in step b) is carried out until 75-95 mol % of the monomers m2 originally introduced have undergone reaction or polymerization.

13. The process as claimed in claim 10, wherein in step a) and/or in step b) there is at least one further polymerizable monomer ms ##STR00012## where R.sup.5, R.sup.6, R.sup.7, R.sup.9, m, p, Y and Z are defined like R.sup.5, R.sup.6R.sup.7, R.sup.9, m, p, Y and Z in claim 10.

14. The use of a block copolymer as claimed in claim 1 as a dispersant for a mineral binder composition for water reduction and/or for extending the workability of a mineral binder composition.

15. A mineral binder composition comprising at least one block copolymer as described in claim 1.

16. A shaped article obtainable by fully curing a mineral binder composition as claimed in claim 15 following addition of water.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0107] FIG. 1, which is used for elucidating the working examples, shows the heat profile of mortar mixtures admixed on tempering with a dispersant in the form of a diblock copolymer P1 (solid line), of a random polymer P2 prepared by radical copolymerization (dotted line), and of a random polymer P3 prepared by polymer-analogous esterification (dashed line).

WORKING EXAMPLES

1. Preparation Examples for Polymers

1.1 Diblock Copolymer P1 (n=20; M1/M2=1; RAFT)

[0108] For the preparation of a diblock copolymer P1 by RAFT polymerization, a round-bottom flask equipped with a reflux condenser, agitator, thermometer, and inert gas inlet tube was charged with 57.4 g of 50% methoxy-polyethylene glycol.sub.1000 methacrylate (0.03 mol; average molecular weight: 1000 g/mol; 20 ethylene oxide units/molecule) and 18.4 g of deionized water. The reaction mixture was heated to 80 C. with vigorous stirring. A gentle stream of inert gas (N.sub.2) was passed through the solution during heating and for the whole of the rest of the reaction time.

[0109] Added to the mixture then were 273 mg of 4-cyano-4-(thiobenzoyl)pentanoic acid (0.85 mmol; RAFT agent). When the substance had fully dissolved, 42 mg of AIBN (0.26 mmol; initiator) were added. From this point on the conversion was ascertained regularly by HPLC.

[0110] As soon as the conversion, based on methoxy-polyethylene glycol methacrylate, was more than 80 mol %, 2.33 g of methacrylic acid (0.03 mol) were added to the reaction mixture. The mixture was reacted for a further 4 h and then left to cool. This left a clear, slightly reddish, aqueous solution having a solids content of around 40 wt %. The molar ratio of methacrylic acid to methoxy-polyethylene glycol methacrylate is 1.

1.2 Random Polymer P2 (Comparative Example; n=20; M1/M2=1; RAFT)

[0111] For comparison purposes, a second polymer P2 was prepared with random or statistical monomer distribution. The procedure here was analogous to that for the preparation of polymer P1 (preceding section), but the methacrylic acid was included in the initial charge together with the methoxy-polyethylene glycol1000 methacrylate. The solids content of the polymer P2 is again around 40 wt %.

1.3 Random Polymer P3 (Comparative Example; n=20; M1/M2=1; PAE)

[0112] Likewise for comparison purposes, a further polymer P3 was prepared with random or statistical monomer distribution. In the case of polymer P3, however, preparation took place by polymer-analogous esterification (PAE). The procedure here is essentially as described in EP 1 138 697 B1 at page 7 line 20 to page 8 line 50 and also in the examples specified therein. Specifically, a polymethacrylic acid was esterified with methoxy-polyethylene glycol.sub.1000 (unilaterally methoxy-terminated polyethylene glycol having an average molecular weight of 1000 g/mol; 20 ethylene oxide units/molecule), to result in a molar ratio of methacrylic acid units to ester groups of 1 (M1/M2=1). The solids content of the polymer P3 is again around 40 wt %.

1.4 Diblock Copolymer P4 (n=9; M1/M2=1; RAFT; H.SUB.2.O

[0113] Diblock copolymer P4 was prepared in the same way as for diblock copolymer P1, but using, rather than methoxy-polyethylene glycol.sub.1000 methacrylate, the corresponding amount of methoxy-polyethylene glycol.sub.400 methacrylate (average molecular weight: 400 g/mol; 9 ethylene oxide units/molecule). The solids content of the polymer P4 is again around 40 wt %.

1.5 Diblock Copolymer P5 (n=9; M1/M2=1; RAFT; EtOH)

[0114] Diblock copolymer P5 was prepared in the same way as for diblock copolymer P4, but using, instead of water, the corresponding amount of ethanol as solvent. The solids content of the polymer P5 is again around 40 wt %.

1.6 Diblock Copolymer P6 (n=20; M1/M2=3; RAFT)

[0115] Diblock copolymer P6 was prepared in the same way as for diblock copolymer P1, but the amounts of methacrylic acid and methoxy-polyethylene glycol.sub.1000 methacrylate used were adapted such that the molar ratio of methacrylic acid to methoxy-polyethylene glycol methacrylate for the same molecular weight of the diblock copolymer is 3. The solids content of the polymer P6 is around 40 wt %.

1.7 Diblock Cool Mer P7 (n=9. M1/M2=3; RAFT; H.SUB.2.O)

[0116] Diblock copolymer P7 was prepared in the same way as for diblock copolymer P6, but using, rather than methoxy-polyethylene glycol.sub.1000 methacrylate, the corresponding methoxy-polyethylene glycol.sub.400 methacrylate (average molecular weight: 400 g/mol; 9 ethylene oxide units/molecule). The solids content of the polymer P7 is again around 40 wt %.

1.8 Diblock Copolymer P8 (n=9; M1/M2=3; RAFT; EtOH)

[0117] Diblock copolymer P8 was prepared in the same way as for diblock copolymer P7, but using, instead of water, the corresponding amount of ethanol as solvent. The solids content of the polymer P6 is likewise around 40 wt %.

1.9 Overview of Polymers

[0118] Table 1 provides an overview of the polymers prepared and used below.

TABLE-US-00001 TABLE 1 Polymers prepared Preparation No. Structure n M1/M2 Solvent method P1 Diblock 20 1 Water RAFT P2 Random 20 1 Water RAFT P3 Random 20 1 Water PAE P4 Diblock 9 1 Water RAFT P5 Diblock 9 1 Ethanol RAFT P6 Diblock 20 3 Water RAFT P7 Diblock 9 3 Water RAFT P8 Diblock 9 3 Ethanol RAFT

2. Mortar Mixtures

2.1 Preparation

[0119] The mortar mixture used for test purposes has the dry composition described in table 2:

TABLE-US-00002 TABLE 2 dry composition of mortar mixture Component Amount [g] Cement (CEM I 42.5 N; Normo 4; 750 g available from Holcim Switzerland) Limestone filler 141 g Sand 0-1 mm 738 g Sand 1-4 mm 1107 g Sand 4-8 mm 1154 g

[0120] In order to make up a mortar mixture, the sands, the limestone filler and the cement were mixed dry in a Hobart mixer for 1 minute. Over the course of 30 seconds, the tempering water (for amounts in table 3), admixed beforehand with the respective polymer (cf. table 3), was added, and mixing was continued for 2.5 minutes. The total wet mixing time lasted 3 minutes in each case.

2.2 Mortar Tests

[0121] To determine the dispersing effect of the polymers, the flow value (ABM) of fresh mortar mixtures was measured in each case at various times. The flow value (ABM) of the mortar was determined in accordance with EN 1015-3.

[0122] Further, the effect of the polymers on the hydration behavior of mineral binder compositions was ascertained by measuring the temperature profile of mortar mixtures over time, after having been made up with water. The temperature measurement took place under adiabatic conditions, using a thermocouple as temperature sensor, in a conventional way. All the samples were measured under the same conditions. The measure taken for the solidification time in the present case is the time [t(TM)] which elapses from the making-up of the mortar mixture through to the attainment of the temperature maximum occurring after the induction phase or resting phase (cf. FIG. 1).

3. Results of the Mortar Tests

[0123] Table 3 gives an overview of the mortar tests conducted (T1-T12) and the results obtained in the tests. Test R is a blank test carried out for comparative purposes, without addition of polymer.

TABLE-US-00003 TABLE 3 Mortar test results Level of addi- ABM.sup.# [mm] after tion* 30 60 90 t (TM) No. Polymer [wt %] w/c** 0 min min min min [h:min] R <120 n.m. n.m. n.m. T1 P1 0.5 0.435 179 150 146 139 8:51 T2 P2 0.5 0.435 126 116 n.m. n.m. 10:10 T3 P3 0.5 0.435 128 124 121 n.m. 10:08 T4 P1 0.6 0.450 233 226 205 193 T5 P2 0.6 0.450 132 125 123 n.m. T6 P3 0.6 0.450 136 130 130 127 T7 P1 0.5 0.450 225 148 131 n.m. T8 P4 0.5 0.450 145 129 n.m. n.m. T9 P5 0.5 0.450 131 134 n.m. n.m. T10 P6 0.5 0.450 225 224 207 179 T11 P7 0.5 0.450 150 134 n.m. n.m. T12 P8 0.5 0.450 131 124 n.m. n.m. n.m. = not measurable *= weight fraction of polymer solution based on cement content **= weight ratio of water to cement .sup.#= flow value as per EN 1015-3. The time 0 min corresponds to the first measurement immediately after the mortar sample was made up.

[0124] A comparison of tests T1-T3 shows that with polymer P1, based on a diblock structure, under identical conditions, the plasticizing effect achieved is greater and longer-lasting than with the analogous but randomly constructed polymers P2 and P3. The same pattern emerges on comparative tests T4-T6, which were carried out with a high level of addition and a high water content.

[0125] Moreover, with polymer P1, the temperature maximum occurs after just 8:51 h, whereas the maximum when using the other two polymers, P2 and P3, occur not until about 1:20 h later. In terms of the delay in the hydration profile and in the setting, therefore, polymer P1 is more advantageous.

[0126] In tests T7 and T8 it is apparent that polymer P1, with the longer side chains or a larger value of n (=number of ethylene oxide units in monomer unit M2; n=20 for P1), is more advantageous in terms of the plasticizing effect by comparison with polymer P4, which has much shorter side chains (n=9). From contrasting tests T8 and T9, moreover, it is apparent that the use of water (H.sub.2O) as solvent during the polymerization is more advantageous than the use of ethanol.

[0127] Corresponding results are also found for the polymers P6-P8 used in tests T10-T12.

[0128] From a comparison of tests T7 and T10, furthermore, it can be concluded that the initially approximately equal plasticizing effect of polymer P6, with a ratio of M1/M2=3, can be maintained more effectively over time than the polymer P1, which possesses a ratio of M1/M2=1.

[0129] From the results presented, therefore, the conclusion is that in a variety of respects the polymers of the invention are advantageous over known polymers. In particular, with the polymers of the invention, even at relatively low levels of addition, high dispersing effects and plasticizing effects can be achieved, and can also be maintained for a comparatively long time at a level which is of interest for practice. Moreover, the polymers of the invention are also very advantageous in relation to the delay problem.

[0130] The embodiments described above, however, should be understood merely as illustrative examples, which may be modified as desired within the scope of the invention.