COMB POLYMERS AS BLOCKING ADDITIVES FOR SWELLING CLAYS

Abstract

A comb polymer, in particular for use as a clay-inerting agent, including: a) at least one poly(alkylene oxide) side chain-bearing monomer unit M1 without ionic groups, b) optionally at least one cationic monomer unit MC, c) optionally at least one anionic monomer unit MA, d) optionally, at least one non-ionic monomer unit M3, wherein the molar ratio of the cationic monomer units MC to the side chain-bearing monomer units M1 is equal to or less than 10, the molar ratio of the anionic monomer units MA to the side chain-bearing monomer units M1 is less than 1, preferably equal to or less than 0.5, and the molar ratio of the non-ionic monomer units M3 to the side chain-bearing monomer units M1 is less than 5.

Claims

1. A comb polymer, in particular for use as a clay-inerting agent, comprising: a) at least one poly(alkylene oxide) side chain-bearing monomer unit M1 without ionic groups, b) optionally at least one cationic monomer unit MC, c) optionally at least one anionic monomer unit MA, d) optionally, at least one non-ionic monomer unit M3, wherein the molar ratio of the cationic monomer units MC to the side chain-bearing monomer units M1 is equal to or less than 10, the molar ratio of the anionic monomer units MA to the side chain-bearing monomer units M1 is less than 1, and the molar ratio of the non-ionic monomer units M3 to the side chain-bearing monomer units M1 is less than 5.

2. A comb polymer according to claim 1, wherein the side chain-bearing monomer unit M1 includes a structure of the formula I ##STR00010## wherein R.sup.1, and R.sup.2, in each case independently, are H or an alkyl group having 1 to 5 carbon atoms, R.sup.3, in each case independently, is H, an alkyl group having 1 to 5 carbon atoms, or a group with formula —(CH.sub.2).sub.m—[C═O].sub.p—X—R.sub.4, 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 the 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.

3. A comb polymer according to claim 1, wherein the cationic monomer unit MC in the polymer includes or consists a monomer which has a structure of the formula II, ##STR00011## wherein R.sup.5, in each case independently, is -[D].sub.d-[E].sub.e—F, with D=—(COO)— and/or —(CONH)—, E=an alkylene group having 1 to 5 carbon atoms, F=—N.sup.+R.sup.10R.sup.11R.sup.12, —S.sup.+R.sup.10R.sub.11R.sup.12 and/or —P.sup.+R.sup.10R.sup.11R.sup.12, wherein R.sup.10, R.sup.11 and R.sup.12 are independently of one another H, an aliphatic hydrocarbon moiety having 1 to 20 C atoms, a cycloaliphatic hydrocarbon moiety having 5 to 8 C atoms and/or an aryl moiety having 6 to 14 C atoms; whereby d=0 or 1, e=0 or 1, R.sup.6, R.sup.7 and R.sup.8, in each case independently, are H or an alkyl group having 1 to 5 carbon atoms.

4. A comb polymer according to claim 1, wherein the anionic monomer unit MA in the polymer includes or consists of a monomer which has a structure of the formula III, ##STR00012## wherein R.sup.13, in each case independently, is —COOM, —SO.sub.2—OM, —O—PO(OM).sub.2 and/or —PO(OM).sub.2, R.sup.14 and R.sup.15, in each case independently, are H or an alkyl group having 1 to 5 carbon atoms, R.sup.16, in each case independently, are H, —COOM or an alkyl group having 1 to 5 carbon atoms, or where R.sup.13 forms a ring together with R.sup.16 to give —CO—O—CO—, M independently from each other is H.sup.+, an alkali metal ion, an alkaline earth metal ion, a di- or trivalent metal ion, an ammonium ion and an organic ammonium group.

5. A comb polymer according to claim 1, wherein the non-ionic monomer M3 has a structure of the formula IV, ##STR00013## wherein R.sup.5′, R.sup.6′, R.sup.7′ are the same as defined for R.sup.6, R.sup.7 and R.sup.8, and m′ and p′ are the same as defined for m and p as described above in the context of the copolymer, Y, in each case independently, is a chemical bond or —O—, Z, in each case independently, is a chemical bond, —O— or —NH—, R.sup.20, 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. A comb polymer according to claim 1, wherein the comb polymer, with respect to the total number of monomer units present in the comb polymer, comprises: a) 95-100 mol-%, of the at least one poly(alkylene oxide) side chain-bearing monomer unit M.sup.1, b) 0-1 mol-%, of the at least one cationic monomer unit MC, c) 0-1 mol-%, of the at least one anionic monomer unit MA, d) 0-1 mol-%, of the at least one non-ionic monomer unit M3.

7. A comb polymer according to claim 1, wherein the comb polymer, with respect to the total number of monomer units present in the comb polymer, comprises: a) 30-70 mol-%, of of the at least one poly(alkylene oxide) side chain-bearing monomer unit M.sup.1, and b) 0-1 mol-%, of the at least one cationic monomer unit MC, c) 0-1 mol-%, of the at least one anionic monomer unit MA, d) 30-70%, of the at least one non-ionic monomer unit M3.

8. A comb polymer according to claim 1, wherein the comb polymer, with respect to the total number of monomer units present in the comb polymer, comprises: a) 10-99 mol-%, of the at least one poly(alkylene oxide) side chain-bearing monomer unit M.sup.1, and b) 1-90 mol-%, of the at least one cationic monomer unit MC, c) 0-1 mol-%, of the at least one anionic monomer unit MA, d) 0-75 mol-% or 0 mol-%, of the at least one non-ionic monomer unit M3.

9. A comb polymer according to claim 1, wherein the comb polymer consists of the at least one poly(alkylene oxide) side chain-bearing monomer unit M1 and, optionally, the non-ionic monomer unit M3.

10. A comb polymer according to claim 1, wherein the comb polymer consists of the at least one poly(alkylene oxide) side chain-bearing monomer unit M1 and the at least one cationic monomer unit MC.

11. A comb polymer according to claim 1, wherein the comb polymer is a block polymer, whereby, at least 75 mol-%, of the total number of the at least one side chain-bearing monomer units M1 are arranged in a first block of the block copolymer and wherein the block copolymer comprises a second block in which at least 75 mol-%, of the total number of the at least one cationic monomer units MC are arranged.

12. A kit of parts comprising a comb polymer according to claim 1 and a plasticizer for mineral binder compositions.

13. A composition comprising a comb polymer according to claim 1 and further comprising a mineral binder, aggregates and/or swellable clays.

14. A method comprising the steps of adding to a composition comprising swellable clays (i) a comb polymer according to claim 1 and (ii) a plasticizer for mineral binder compositions.

15. A method for inerting a swellable clay and/or for reducing or inhibiting adverse effects of swellable clays on the effectiveness of dispersants in mineral binder compositions, comprising adding the comb polymer according to claim 1 to a mineral binder composition.

Description

EXEMPLARY EMBODIMENTS

[0233] 1. Preparation Examples of Comb Polymers

[0234] 1.1 Comb Polymer P1 (Non-Ionic Homopolymer)

[0235] For the preparation of a non-ionic homopolymer by means of controlled free polymerization, a round-bottom flask equipped with a reflux condenser, stirrer system, thermometer and a gas inlet tube was initially charged with 57.4 g of 50% methoxy polyethylene glycol.sub.1000 methacrylate (0.027 mol; average molecular weight: 1′000 g/mol; ˜20 ethylene oxide units per molecule) and 18 g of deionized water. The reaction mixture was heated to 80° C. with vigorous stirring. A gentle inert N.sub.2 gas stream is passed through the solution during the whole reaction time. 378 mg of 4-cyano-4-(thiobenzoylthio)pentanoic acid (1.35 mmol) were then added to the mixture. Once the substance had fully dissolved, 67 mg of AIBN (0.41 mmol) were added. From then on, the conversion was regularly checked by means of HPLC.

[0236] When the conversion, based on methoxy polyethylene glycol methacrylate, had reached 90%, the reaction was stopped. A clear, reddish, aqueous solution was obtained having a solids content of around 40 wt. % which was diluted with water to obtain a solids content of around 30 wt. %.

[0237] The comb polymer thus obtained is a homopolymer comprising about 20 side chain-nearing monomeric units and is referred to as comb polymer P1.

[0238] 1.2 Comb Polymer P2 (Non-Ionic Homopolymer)

[0239] For the preparation of a non-ionic homopolymer by conventional free radical polymerization, a round-bottom flask equipped with a reflux condenser, stirrer system, thermometer and a gas inlet tube was initially charged with 186 g of deionized water. At a temperature of 100° C., 796 g of 50% methoxy polyethylene glycol.sub.1000 methacrylate (0.37 mol, average molecular weight: 1′000 g/mol; ˜20 ethylene oxide units per molecule) was added within 180 minutes. Additionally a solution of 4.5 g sodium hypophosphite and 6.7 g of water was added within 175 minutes and a solution of 0.93 g sodium persulfate and 5.0 g water was added within 190 minutes. Once all the solutions were added, the reaction mixture was cooled down. A clear, colorless solution was obtained having a solids content of around 40 wt. % which was diluted with water to obtain a solids content of around 30 wt. %.

[0240] This polymer is referred to as comb polymer P2.

[0241] 1.3 Comb Polymer P3 (Cationic Block Copolymer)

[0242] For the preparation of a cationic copolymer by means of controlled free radical polymerization, a round-bottom flask equipped with a reflux condenser, stirrer system, thermometer and a gas inlet tube was initially charged with 57.4 g of 50% methoxy polyethylene glycol.sub.1000 methacrylate (0.027 mol; average molecular weight: 1′000 g/mol; ˜20 ethylene oxide units per molecule) and 28.3 g of deionized water. The reaction mixture was heated to 80° C. with vigorous stirring. A gentle inert N.sub.2 gas stream was passed through the solution during the whole reaction time. 378 mg of 4-cyano-4-(thiobenzoylthio)pentanoic acid (1.35 mmol) were then added to the mixture. Once the substance had fully dissolved, 67 mg of AIBN (0.41 mmol) were added. From then on, the conversion was regularly checked by means of HPLC.

[0243] When the conversion, based on methoxy polyethylene glycol methacrylate, had reached 80%, 14.81 g of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (0.054 mol) were added. The mixture was left to react for a further 2 h and then to cool. A clear, reddish, aqueous solution was obtained having a solids content of around 40 wt. % which was diluted with water to obtain a solids content of around 30 wt. %.

[0244] The comb polymer thus obtained is a block copolymer comprising a first bock with about 20 side chain-nearing monomeric units, and a second block with about 40 cationic monomer units. This polymer is referred to as comb polymer P3.

[0245] 1.4 Further Comb Polymers

[0246] Further comb polymers were produced in a similar manner. Thereby, the methoxy polyethylene glycol.sub.1000 methacrylate was replaced by methoxy polyethylene glycol methacrylate with different chain lengths (average molecular weight of 500 g/mol, 2′000 g/mol, 3′000 g/mol and 5′000 g/mol) and/or the [2-(methacryloyloxy)ethyl]trimethylammonium chloride (cationic monomer unit) was replaced by methacrylic acid (anionic monomer unit).

[0247] The following chapter gives an overview about the comb polymers produced and their properties.

[0248] 1.5 Overview of Comb Polymers

TABLE-US-00001 TABLE 1 Comb polymers Weight of Ionic No. MPEG-MA monomer Ratio P1 1′000 g/mol none 0 P2* 1′000 g/mol none 0 P3 1′000 g/mol C 2 P4 2′000 g/mol none 0 P5 1′000 g/mol C 0.2 P6 2′000 g/mol C 0.2 P7 500 g/mol none 0 V1 none C — MPEG-MA = methoxy polyethylene glycol methacrylate C = [2-(methacryloyloxy)ethyl]trimethylammonium chloride Ratio = number of ionic monomers/number of MPEG-MA monomers *= Produced by conventional free radical polymerization

[0249] 2. Mineral Binder Compositions

[0250] 2.1 Mortar Mixtures

[0251] The mortar mixture used for test purposes had 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; available 750 g from Holcim Schweiz) Limestone filler 141 g Sand 0-1 mm 738 g Sand 1-4 mm 1107 g Sand 4-8 mm 1154 g Bentonite (swelling clay) For proportions see results section

[0252] To make a mortar mixture, the sands, the limestone filler, the cement and bentonite (if added) were dry-mixed in a Hobart mixer for 1 minute. Within 30 seconds, the mixing water (ratio of water to cement w/c=0.49) was added and the mixture was mixed for a further 2.5 minutes. The total wet mixing time was 3 minutes in each case.

[0253] Prior to the addition to the mortar mixture, the respective comb polymer (clay blocker) and plasticizer (Sika® ViscoCrete® 3082; available from Sika, Schweiz) were mixed into the mixing water (for proportions see results section). Sika® ViscoCrete® 3082 is a standard polycarboxylate ether-based superplasticizer corresponding to a polymer P as described above.

[0254] These mortar compositions are referred to as MC.

[0255] 2.2 Cement Pastes

[0256] The cement pastes used for test purposes were based on 100 g cement (CEM I 42.5 N; Normo 4; available from Holcim Schweiz), 5 g limestone filler with a grain size below 0.125 mm, bentonite (for proportions see results section) and water.

[0257] To make a cement paste, the cement/filler/bentonite mix was added to a beaker and, in another beaker, the mixing water into which the respective comb polymer (clay blocker) and plasticizer (Sika® ViscoCrete® 3082; available form Sika, Schweiz) had been mixed beforehand (for proportions see results section), was added. Afterwards the cement/filler/bentonite mix was carefully poured into the beaker containing the water, and the wet mix was mixed for 1 minute with a propeller IKA stirrer at 1000 rpm. As a reference the water to cement ratio of the cement/filler paste including the PCE was adjusted to a flow of 10-12 cm.

[0258] These cement pastes are referred to as CP.

[0259] 3. Testing Procedures

[0260] To determine the effectiveness of the clay-blocking comb polymers in the mortar mixture, the dispersing effect of the plasticizer was determined by measuring the flow table spread (ABM) of a series of mortar mixtures was measured in accordance with EN 1015-3 at different times.

[0261] The effectiveness of the clay-blocking comb polymers in the cement pastes was determined similarly. However, in this case a mini slump conus on a dry glass plate was used instead of the standard equipment defined in EN 1015-3.

[0262] The test for determining compressive strength (in MPa) was carried out on prisms (40×40×160 mm) in accordance with standard EN 12390-1 to 12390-4.

[0263] Also, the temperature curve of the mineral binder compositions (mortar mixtures, cement pastes) was recorded as control of hydration and setting behavior, respectively, after mixing. Thereby, the time to onset of the global temperature maximum was determined as a measure of the setting time.

[0264] The air content was measured according to EN 12350-7.

[0265] In the tests, all of the admixtures (clay blocker, plasticizer) have been added as aqueous solutions or dispersions with a content of active ingredients of 30 wt.-%. Bentonite was added as a powder.

[0266] 4. Results

[0267] Table 3 gives an overview of a first series of tests conducted and the results achieved. Experiments R1 to R5 are experiments conducted for comparative purposes without the addition of a comb polymer according to the invention.

TABLE-US-00003 TABLE 3 (all wt.-% are given with respect to the cement content in the mineral binder composition) Experiment Components R1 R2 R3 R4 R5 E1 E2 E3 E4 E5 Mineral binder MC MC MC MC MC MC MC MC MC MC composition Bentonite [wt. %] 0 1 1 1 1 1 1 1 1 1 Clay blocker — — B1 B2 V1 P1 P3 P4 P5 P6 Proportion [wt.-%] 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Plasticizer [wt.-%] 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 w/c 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 FTS.sup.# [mm] after  0 min 178 121 152 148 153 177 183 154 166 155 30 min 151 115 137 145 135 157 167 142 145 140 60 min 149 110 124 132 125 149 139 130 144 136 Air content [%] 3.5 3.2 3.3 2.9 2.3 2.5 3.5 3.1 3.2 3.0 Setting time [h] 12.3 10.5 12.3 11.3 11.7 12.2 11.2 10.8 11.0 10.5 Plasticizer = Sika ® ViscoCrete ® 3082 B1 = MasterSuna SBS 3890 (BASF) B2 = Floerger Floquat FL 2250 (SNF sas, France) .sup.#= flow table spread according to EN 1015-3. The time “0 min” corresponds to the first measurement immediately after the mixing of the mortar sample.

[0268] The data in Table 3 clearly shows that the inventive comb polymers are highly effective clay blockers which are at least as effective as known clay blockers. Additionally, with the inventive comb polymers the clay-blocking activity can be maintained for a long time on a rather high level. Especially advantageous are the comb polymers P1 and P3, i.e. homopolymers of side chain-bearing monomers or block copolymers of side chain-bearing monomers with cationic monomers. Thereby, comb polymer P3 with cationic monomer units is the most effective.

[0269] Table 4 shows the results of a second set of experiments with comb polymers differing in side chain length.

TABLE-US-00004 TABLE 4 (all wt.-% are given with respect to the cement content in the mineral binder composition) Experiment Components R6 R7 E6 E7 E8 Mineral binder MC MC MC MC MC composition Bentonite [wt. %] 0 1 1 1 1 Clay blocker — — P1 P4 P7 Proportion [wt.-%] 0.27 0.27 0.27 Plasticizer [wt.-%] 0.5 0.5 0.5 0.5 0.5 w/c 0.48 0.48 0.48 0.48 0.48 FTS.sup.# [mm] after  0 min 187 148 188 186 170 30 min 173 137 173 167 155 60 min 168 — 162 156 145 Air content [%] 2.4 2.4 2.6 2.5 2.6 Setting time [h] 16.0 13.3 13.2 12.8 15.3 Strength [MPa] after  1 day 19.3 20.0 18.3 19.8 19.0 28 days 45.7 44.5 48.3 49.1 44.8 Plasticizer = Sika ® ViscoCrete ® 3082 .sup.#= flow table spread according to EN 1015-3. The time “0 min” corresponds to the first measurement immediately after the making-up of the mortar sample.

[0270] As can be deduced from the results given in Table 4, comb polymers with a length of the side chains of at least 1′000 g/mol or higher are most efficient when compared with comb polymers having different chain lengths.

[0271] Table 5 shows the results of a third set of experiments in which comb polymers are compared to single MPEG side chain molecules.

TABLE-US-00005 TABLE 5 (all wt.-% are given with respect to the cement content in the mineral binder composition) Experiment Components R8 R9 R10 R11 R12 E9 Mineral binder MC MC MC MC MC MC composition Bentonite [wt. %] 0 1 1 1 1 1 Clay blocker — — B3 B4 B5 P1 Proportion [wt.-%] 0.27 0.27 0.27 0.27 Plasticizer [wt.-%] 0.5 0.5 0.5 0.5 0.5 0.5 w/c 0.48 0.48 0.48 0.48 0.48 0.48 FTS.sup.# [mm] after  0 min 190 151 156 163 177 184 30 min 163 132 140 143 147 156 60 min 153 — — — — 152 Air content [%] 2.5 2.2 2.2 2.3 2.2 2.3 Setting time [h] 13.5 12.7 13.3 12.8 13.0 13.3 Strength [MPa] after  1 day 22.1 21.6 21.7 22.0 21.2 22.5 Plasticizer = Sika ® ViscoCrete ® 3082 B3 = methoxy polyethylene glycol.sub.1000 (average molecular weight: 1′000 g/mol) B4 = methoxy polyethylene glycol.sub.3000 (average molecular weight: 3′000 g/mol) B5 = methoxy polyethylene glycol.sub.5000 (average molecular weight: 5′000 g/mol) .sup.#= flow table spread according to EN 1015-3. The time “0 min” corresponds to the first measurement immediately after the making-up of the mortar sample.

[0272] As evident from Table 5, single MPEG side chains are less effective when compared with the inventive comb polymer P1.

[0273] Table 6 shows the results of a fourth set of experiments in which the dispersing effect of the inventive clay-blocking comb polymers is compared to a standard PCE in cement pastes without swelling clays.

TABLE-US-00006 TABLE 6 (all wt.-% are given with respect to the cement content in the mineral binder composition) Experiment Components R13 R14 E10 E11 Mineral binder CP CP CP CP composition Bentonite [wt. %] — — — — Clay blocker — — P1 P3 Proportion [wt.-%] 0.5 0.5 Plasticizer [wt.-%] — 0.5 — — w/c 0.36 0.36 0.36 0.36 FTS.sup.# [mm] after 0 min 65 113 67 67 Plasticizer = Sika ® ViscoCrete ® 3082 .sup.#= flow table spread according to EN 1015-3 with mini slump conus (see above). The time “0 min” corresponds to the first measurement immediately after the mixing of the mortar sample.

[0274] Thus, the clay-blocking comb polymers according to the present invention do not have any significant plasticizing effect. Similar results have been obtained in mortar mixtures MC.

[0275] Table 7 shows the results of a fifth set of experiments whereby different clay blockers have been tested in mortar compositions with varying clay contents. Thereby, all of the experiments VC1-VC14 have been performed with mortar mixture MC, a water to cement ratio (w/c) of 0.44, 0.5 wt. % plasticizer (Sika® ViscoCrete® 3082) and (if added) 0.25 wt. % of clay blocker as depicted in the second column of Table 7. In experiments VC13-VC14, the plasticizer has been omitted, so that only the water-reducing capability of P1 could be compared directly to B1 in the absence of clay.

TABLE-US-00007 TABLE 7 (all wt.-% are given with respect to the cement content in the mineral binder composition) Clay Bentonite FTS.sup.# [mm] FTS Experiment blocker [wt. %] after 0 min. increase.sup.@ VC1 — 1.00 148 +29.7% VC2 0.66 160 VC3 0.33 178 VC4 — 192 VC5 B1 1.00 190 +30.5% VC6 0.66 220 VC7 0.33 244 VC8 — 248 (bleeding observed) VC9 P1 1.00 190 +11.6% VC10 0.66 198 VC12 0.33 209 VC12 — 212 VC13.sup.+ P1 — 133 VC14.sup.+ B1 — 222 B1 = MasterSuna SBS 3890 (BASF) .sup.#= flow table spread according to EN 1015-3. The time “0 min” corresponds to the first measurement immediately after the making-up of the mortar sample. .sup.@= relative increase of FTS with respect to FTS with 1 wt. % Bentonite for a given clay blocker .sup.+= without plasticizer

[0276] The data given in Table 7 show that the inventive comb polymers are highly robust, i.e. the sensitivity to varying swelling clay contents is rather low. Specifically, when decreasing the clay content from 1 wt. % to 0 wt. %, with the inventive comb polymer P1 as clay blocker, the FTS increases only by 11.6%. With all of the other tested clay blocker B1, the increase in FTS is >30% and, thus, much higher in this range of swelling clay contents. The much stronger increase of B1 (experiment VC14) can be explained by the significant stronger plasticizing effect of B1 itself (experiment VC14) compared to the inventive comb polymer P1 (experiment VC13).

[0277] Table 8 compares the effectiveness of the inventive comb polymer P1, which was produced via a controlled free radical polymerization, and the inventive comb polymer P2, which was produced via conventional free-radical polymerization.

TABLE-US-00008 TABLE 8 (all wt.-% are given with respect to the cement content in the mineral binder composition) Experiment Components R15 R16 E12 E13 Mineral binder MC MC MC MC composition Bentonite [wt. %] 0 1 1 1 Clay blocker — — P1 P2 Proportion [wt.-%] 0.27 0.27 Plasticizer [wt.-%] 0.5 0.5 0.5 0.5 w/c 0.48 0.48 0.48 0.48 FTS.sup.# [mm] after  0 min 190 151 184 188 30 min 163 132 156 152 60 min 153 — 152 147 Air content [%] 2.5 2.2 2.3 2.4 Setting time [h] 13.5 12.7 13.3 12.5 Strength [MPa] after  1 day 22.1 21.6 22.5 22.1 Plasticizer = Sika ® ViscoCrete ® 3082 .sup.#= flow table spread according to EN 1015-3. The time “0 min” corresponds to the first measurement immediately after the making-up of the mortar sample.

[0278] It is evident that both inventive polymers P1 and P2 having a similar side chain length of 1′000 g/mol show a similar clay-blocking effectiveness, although they were produced with different polymerization processes.

[0279] It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricting.