BLOCK COPOLYMERS AS DISPERSANTS FOR ALKALI-ACTIVATED BINDERS

Abstract

The invention relates to a block copolymer for use as a dispersant for mineral binder compositions, containing an alkali activating agent. Said block copolymer comprises at least one first block A and at least one second block B, the first block A containing a monomeric unit M1 and the second block B containing a monomeric unit M2. A proportion of monomeric units M2, if any, in the first block A is less than 25 mol %, in particular less than or equal to 10 mol %, relative to all the monomeric units M1 in the first block A, and a proportion of monomeric units M1, if any, in the second block B is less than 25 mol %, in particular less than or equal to 10 mol %, relative to all the monomeric units M2 in the second block B.

Claims

1. A method comprising applying a block copolymer P as dispersant in a binder composition comprising at least one mineral binder and an alkaline activating agent, where the block copolymer P comprises 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 including a monomer unit M2 of the formula II ##STR00008## where R.sup.1, in each case independently of any other, is COOM, SO.sub.2-OM, OPO(OM).sub.2 and/or PO(OM).sub.2, R.sup.2, R.sup.3, R.sup.5 and R.sup.6, in each case independently of one another, are H or an alkyl group having 1 to 5 carbon atoms, R.sup.4 and R.sup.7, in each case 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 make COOCO, M, 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 is 0, 1 or 2, p is 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 is C.sub.2- to C.sub.4-alkylene, R.sup.a is H, 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 method as claimed in claim 1, wherein the at least one first block A of the block copolymer P comprises 5-70 monomer units M1 and/or wherein the at least one second block B of the block copolymer P comprises 5-70 monomer units M2.

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

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

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

6. The method as claimed in claim 1, wherein the block copolymer P comprises at least one further monomer unit MS of the formula III: ##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; 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 carbon atoms.

7. The method as claimed in claim 1, wherein in the block copolymer P, R.sup.1 is 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 where X for at least 75 mol % of all monomer units M2 is O.

8. The method as claimed in claim 1, wherein in the block copolymer P, n is 10-150.

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

10. The method as claimed in claim 1, wherein the mineral binder comprises or consists of a latent hydraulic and/or pozzolanic binder.

11. The method as claimed in claim 10, wherein the binder composition has 5-95 wt % of hydraulic binder.

12. The method as claimed in claim 1, wherein the activating agent comprises an alkali metal hydroxide, alkali metal carbonate and/or alkali metal sulfate.

13. A binder composition comprising at least one mineral binder, an alkaline activating agent and a block copolymer P as defined in claim 1.

14. A method for producing a binder composition as claimed in claim 13, by mixing a mineral binder with a block copolymer P and with an alkaline activating agent.

15. A shaped article obtainable by fully curing a binder composition as claimed in claim 14 following addition of water.

Description

WORKING EXAMPLES

1. Preparation Examples for Polymers

1.1 Diblock Copolymer P1

[0155] For the preparation of the diblock copolymer P1 by RAFT polymerization, a round-bottom flask equipped with a reflux condenser, agitator, thermometer, and inert gas inlet tube is charged with 57.4 g of 50% methoxy-polyethylene glycol 1000 methacrylate (0.03 mol) and 24.9 g of deionized water. The reaction mixture is heated to 80 C. with vigorous stirring. A gentle stream of inert gas is passed through the solution during heating and for the whole of the rest of the reaction time. Added to the mixture then are 756 mg of 4-cyano-4-(thiobenzoyl)pentanoic acid (2.7 mmol). When the substance has fully dissolved, 135 mg of AIBN (0.82 mmol) are added. From this point on the conversion is ascertained regularly by HPLC.

[0156] As soon as the conversion, based on methoxy-polyethylene glycol methacrylate, is more than 80%, 5.85 g of acrylic acid (0.08 mol) are added to the reaction mixture. The mixture is reacted for a further 4 h and then left to cool. This leaves a clear, slightly reddish, aqueous solution having a solids content of around 40%.

1.2 Diblock Copolymer P2

[0157] For the preparation of the diblock copolymer P2 by RAFT polymerization, a round-bottom flask equipped with a reflux condenser, agitator, thermometer, and inert gas inlet tube is charged with 347.21 g of 48% methoxy-polyethylene glycol 2000 methacrylate (0.08 mol) and 112.2 g of deionized water. The reaction mixture is heated to 80 C. with vigorous stirring. A gentle stream of inert gas is passed through the solution during heating and for the whole of the rest of the reaction time. Added to the mixture then are 2.27 g of 4-cyano-4-(thiobenzoyl)pentanoic acid (0.008 mol). When the substance has fully dissolved, 404 mg of AIBN (0.0024 mol) are added. From this point on the conversion is ascertained regularly by HPLC.

[0158] As soon as the conversion, based on methoxy-polyethylene glycol methacrylate, is more than 80%, 23.78 g of acrylic acid (0.33 mol) are added to the reaction mixture. The mixture is reacted for a further 4 h and then left to cool. This leaves a clear, slightly reddish, aqueous solution having a solids content of around 40%.

1.3 Statistical Polymer P3

[0159] In a reaction vessel equipped with a mechanical agitator, thermometer and reflux condenser, 234 g of water, 60 g of maleic anhydride (0.6 mol), 520 g of allyl-polyethylene glycol ether (0.47 mol; average molecular weight 1100 g/mol) were

2. Mortar Mixtures

2.1 Preparation

[0160] The mortar mixture used for test purposes has the dry composition described in table 1:

TABLE-US-00001 TABLE 1 Dry composition of mortar mixture Component Amount [g] Cement (CEM I 42.5 N; Normo 4; available 525 g from Holcim Switzerland) Slag (Lruns) 225 g Limestone filler 141 g Sand 0-1 mm 738 g Sand 1-4 mm 1107 g Sand 4-8 mm 1154 g

[0161] In order to make up a mortar mixture, the sands, the limestone filler, the cement and the slag were mixed dry in a Hobart mixer for 1 minute. Over the course of 30 seconds, the tempering water (water-to-cement ratio w/c=0.44) was added, and mixing was continued for 2.5 minutes. The total wet mixing time lasted 3 minutes in each case.

[0162] In advance, before the addition to the mortar mixture, the respective polymer (proportion: 0.32 wt %; based on solids content of the polymer and based on cement content) and also, where appropriate, a basic activating agent (NaOH; 1.25 wt % based on binder content (cement plus slag)) were admixed to the tempering water. Where both a polymer and a basic activating agent were admixed, the basic activating agent was added to the tempering water before the polymer was added.

2.2 Mortar Tests

[0163] To determine the dispersing effect of the polymers, the flow value (ABM) of made-up 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.

[0164] 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.

2.3 Results of the Mortar Tests

[0165] Table 2 gives an overview of the mortar tests conducted and the results obtained in the tests. Test T1 is a blank test carried out for comparative purposes, without addition of polymer.

TABLE-US-00002 TABLE 2 Mortar test results Activating ABM.sup.# [mm] after No. Polymer.sup.+ agent* 0 min 30 min 60 min 90 min t (TM) [h] T1 <120 n.m. n.m. n.m. T2 P3 232 187 161 142 18.0 T3 P3 NaOH 187 150 139 130 15.5 (19%) (20%) (14%) (9%) T4 P1 273 254 239 229 18.2 T5 P1 NaOH 275 258 249 234 17.0 (+1%) (+2%) (+4%) (+2%) T6 P2 263 252 249 226 14.2 T7 P2 NaOH 263 229 208 176 14.8 (0%) (9%) (17%) (22%) n.m. = not measurable .sup.+polymer content = 0.32 wt % based on solids content of polymer and cement content. *activating agent content = 1.25 wt % based on binder content. .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. The percentage figure in parentheses in the case of the tests with NaOH corresponds to the percentage change in flow value, relative to the flow value in the line above for the corresponding test without NaOH.

[0166] The tests show clearly that when using block copolymers P1-P2 (see tests T4-T7), the percentage change in the flow value from the addition of NaOH, at least at early times, turns out clearly to be lower than when using the reference polymer P3 (see tests T2 and T3). It is evident, furthermore, that when the block copolymers of the invention are added at an equal dosage, in absolute terms, they have a clearly better plasticizing performance, which, moreover, is also maintained at a relatively high level for longer times.

[0167] From the results presented, therefore, the conclusion is that in a variety of respects the block copolymers of the invention are advantageous over known polymers. In particular, with the polymers of the invention, 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 clearly less susceptible to alkaline activating agents than conventional polymers.

[0168] The embodiments described above, however, should be understood merely as illustrative examples, which may be modified as desired within the scope of the invention.