Multimodal PCE copolymers and use in cementitious mixtures

Abstract

Multimodal poly(carboxylate ether) copolymers are made in an emulsion polymerization. The PCE copolymer has a multimodal molecular weight distribution. It is useful to partially or fully replace cellulose ether as a water retention aid in cementitious mixtures.

Description

[0001] MULTIMODAL PCE COPOLYMERS AND USE IN CEMENTITIOUS MIXTURES

[0002] FIELD

[0003] This application relates to the field of concrete, mortar, grout and stucco.

[0004] INTRODUCTION

[0005] Concrete, mortar, grout and stucco (called cementitious mixtures) are typically prepared in two stages. First, a dry mix that contains cement, filler and solid particulate additives (“dry components”) is blended together. Second, water is added to the dry mix to make a wet mix, which can be further formulated into the final cementitious mixture. The dry mix is stable as long as it remains sufficiently dry; it can be stored for long periods and transported easily. The wet mix starts to cure when water is added and must be used before it becomes unworkable.

[0006] The major components of the dry mix are filler and cement. The dry mix components may also include small quantities of other additives, such as water-reducing agents, water retention aids, organic binders, starch ethers, fibers, air entrainment agents, curing accelerators, curing retarders, defoamers and pigments.

[0007] The quantity of water added to make the wet mix is chosen to provide a workable viscosity. The viscosity of the wet mix should allow it to be poured into a mold or form or spread smoothly on a substrate without dripping and allow the cementitious mixture to conform and adhere to tiles or other materials pressed onto it. For example, a tiling mortar wet mix must be spread on a substrate with a trowel, remain on the substrate without running, and remain compressible enough that, when a tile is pressed into the wet mix, the wet mix will deform to fully contact and adhere to the back surface of the tile. More contact with the back surface of the tile generally leads to better tile adhesion after the mortar cures.

[0008] Water retention aids prevent water from settling out or otherwise separating from dry ingredients in the wet mix. In this way, the water retention aids improve cement hydration and curing of the wet mix, improve adhesion of the wet mix to substrates and control the open time and workable life of the wet mix. Useful water retention aids should prevent separation of the water without hurting the workability of the wet mix as previously described.

[0009] The most common water retention aid is cellulose ether. Cellulose ether is made by an energy- intensive, high-waste process. Further, the performance of cellulose ethers in cementitious mixtures can vary widely based on naturally occurring variations in the cellulose starting materials.

[0010] It would be desirable to identify alternate water retention aids that provide water retention and workability on a par with (or better than) existing water retention aids and that are made with consistent quality by a simple, low-waste process. SUMMARY

[0011] Poly(carboxylate ether) copolymers (PCE copolymers) comprise a plurality of polyethylene glycol (PEG) polymer or oligomer chains that are pendant from an acidic backbone polymer. Ester linkages connect the PEG chains to the backbone polymer. The structure is often called a “comb” structure and is illustrated with the acidic backbone polymer like the spine of a comb and the pendant PEG chains attached to the backbone like the teeth of a comb.

[0012] PCE copolymers are sometimes added to cementitious mixtures as water-reducing agents, but they are not known as water retention aids. Water-reducing agents (also known as plasticizers or superplasticizers) are different from water retention aids. The water-reducing agents allow the cementitious mixture to maintain a workable viscosity with less water, but they do not generally improve water retention.

[0013] The ester linkages in PCE copolymers can be hydrolyzed to release the pendant PEG chains and recover the acidic backbone polymer of the PCE copolymer as a poly(carboxylic acid) polymer. For the purposes of this document, the poly(carboxylic acid) polymer that is made by hydrolyzing the ester linkages of a PCE copolymer is called a “hydrolysis product polymer” or “HPP.” We hypothesize that the molecular weight profile of the HPP for a PCE copolymer is roughly equal to formula weight profile of the acidic polymer backbone in the corresponding PCE copolymer.

[0014] We have discovered that certain multimodal PCE copolymers are effective as water retention aids in a wet mix and provide workability that is roughly equal to (or better than) cellulose ethers. As used herein, “multimodal” means that the HPP of the PCE copolymer comprises a higher molecular weight (HMW) component and a lower molecular weight component (LMW). As used herein, a “higher molecular weight (HMW) component” has a weight average molecular weight (Mw) that is higher than the weight average molecular weight of the “lower molecular weight (LMW) component.” As used herein, a “lower molecular weight (LMW) component” has a weight average molecular weight (M„) that is lower than the weight average molecular weight of the “higher molecular weight (HMW) component.” We hypothesize that the presence of the HMW and LMW components in the HPP indicate that the PCE copolymer it is derived from also comprises a higher molecular weight (HMW) component with a longer acidic backbone polymer and a lower molecular weight (LMW) component with a shorter acidic backbone polymer.

[0015] The multimodal PCE copolymers can be made in consistent quality by emulsion polymerization.

[0016] One aspect of this invention is a multimodal poly(carboxylate ether) (PCE) copolymer that comprises repeating units derived from:

[0017] (a) from 10 to 60 weight percent (wt%) of (meth)acrylic acid monomers;

[0018] (b) from 30 to 70 wt% of alkyl (meth)acrylate monomers wherein the alkyl moiety comprises on average from 1 to 3.5 carbon atoms; and

[0019] (c) from 5 to 40 wt% of PEG monomers, which each independently contain:

[0020] (i) a (meth)acrylate moiety linked by an ester linkage to (ii) a polyethylene glycol moiety that contains on average more than 1 ethylene oxide unit, and

[0021] (iii) an end moiety linked to the polyethylene glycol moiety at the opposite end from the (meth) acrylate moiety, which is selected from hydrogen or an alkyl moiety; and

[0022] (d) from 0 to 20 wt% of other unsaturated monomers, wherein (i) the weight percentages are based on the total weight of the PCE copolymer, (ii) the PCE copolymer comprises an acidic polymer backbone linked by ester linkages to a plurality of pendant polyethylene glycol side chains; and (iii) hydrolysis of the ester linkages in the PCE copolymer produces a poly(carboxylic acid) polymer (called a “hydrolysis product polymer” or “HPP”) which has a multimodal molecular weight distribution.

[0023] A second aspect of the invention is a poly(carboxylate ether) (PCE) copolymer that comprises repeating units derived from:

[0024] (a) from 10 to 60 weight percent (wt%) of (meth)acrylic acid monomers;

[0025] (b) from 30 to 70 wt% of alkyl (meth)acrylate monomers wherein the alkyl moiety comprises on average from 1 to 3.5 carbon atoms; and

[0026] (c) from 5 to 40 wt% of PEG monomers, which each independently contain:

[0027] (i) a (meth)acrylate moiety linked by an ester linkage to

[0028] (ii) a polyethylene glycol moiety that contains on average more than 1 ethylene oxide unit, and

[0029] (iii) an end moiety linked to the polyethylene glycol moiety at the opposite end from the (meth) acrylate moiety, which is selected from hydrogen or an alkyl moiety; and

[0030] (d) from 0 to 20 wt% of other unsaturated monomers, wherein (i) the weight percentages are based on the total weight of the PCE copolymer, (ii) at least 50 wt% of the PCE copolymer is soluble at a concentration of ~1 mg / mL in a solution of tetrahydrofuran / formic acid (THF-FA; 100 / 5 vol / vol ratio); and (iii) the PCE copolymer has a dispersity (Mw / Mn) of at least 6.0 as measured by SEC in a solution of tetrahydrofuran / formic acid (THF-FA; 100 / 5 vol / vol ratio) according to the Test Methods.

[0031] A third aspect of this invention is a process to make a poly(carboxylate ether) (PCE) copolymer comprising performing an emulsion polymerization of:

[0032] (a) from 10 to 60 wt% of (meth)acrylic acid monomers;

[0033] (b) from 30 to 70 wt% or alkyl (meth)acrylate monomers wherein the alkyl moiety comprises on average from 1 to 3.5 carbon atoms; and

[0034] (c) from 5 to 40 wt% of PEG monomers, which each independently contain:

[0035] (i) a (meth)acrylate moiety linked by an ester linkage to

[0036] (ii) a polyethylene glycol moiety that contains on average more than 1 ethylene oxide unit, and

[0037] (iii) an end moiety linked to the polyethylene glycol moiety at the opposite end from the (meth) acrylate moiety, which is selected from hydrogen or an alkyl moiety; and

[0038] (d) from 0 to 20 wt% of other unsaturated monomers, in an aqueous medium that contains an emulsifying quantity of surfactant and a polymerization initiator, wherein (i) weight percentages are based on the total weight of monomers; (ii) the emulsion polymerization is carried out in at least two stages; and (iii) at least one stage of the polymerization is carried out in the presence of at most 0.1 wt% of a chain transfer agent, and (ii) at least one stage of the polymerization is carried out in the presence of at least 0.4 wt% of a chain transfer agent.

[0039] A fourth aspect of this invention is an aqueous dispersion comprising polymer particles suspended in an aqueous medium wherein the polymer particles comprise a PCE copolymer as described in the first or second aspect of the invention.

[0040] A fifth aspect of this invention is a cementitious mixture comprising the following dry components (a)-(c):

[0041] (a) filler;

[0042] (b) cement;

[0043] (c) at least 0.01 wt% of a PCE copolymer as described in the first or second aspect of the invention, based on the total weight of the dry components; and optionally further comprising water.

[0044] A sixth aspect of this invention is a cured cementitious mixture comprising:

[0045] (a) filler;

[0046] (b) cured cement; and

[0047] (c) a PCE copolymer as described in the first or second aspect of the invention, or its hydrolysis products.

[0048] The multimodal PCE copolymer acts as a water retention aid. It can be used alone or in combination with other water retention aids and can wholly or partially replace cellulose ether for that purpose. Some embodiments can further provide wet mixes with improved water retention and workability.

[0049] DETAILED DESCRIPTION

[0050] PCE copolymers and their Synthesis

[0051] This invention relates to a multimodal PCE copolymer. In an acidic aqueous environment, the PCE copolymer can exist as a dispersion of polymer particles suspended in an aqueous medium. In a basic aqueous environment, the carboxylic acid moieties in the PCE copolymer become charged, and the PCE copolymer swells and can dissolve into the aqueous phase. Depending on the concentration of dissolved polymer, the viscosity of the aqueous phase may increase.

[0052] The PCE copolymer comprises repeating units derived from (meth)acrylic acid monomers , alkyl (meth)acrylate monomers and PEG monomers.

[0053] As used herein “(meth)acrylic acid” refers to either acrylic acid or methacrylic acid or a mixture of both acrylic acid and methacrylic acid. In some embodiments, (meth)acrylic acid monomers consist essentially of acrylic acid. In some embodiments, (meth)acrylic acid monomers consist essentially of methacrylic acid. In some embodiments, (meth)acrylic acid monomers are a mixture comprising acrylic acid and methacrylic acid, in which methacrylic acid makes up at least 10 wt% of the mixture or at least 20 wt% or at least 30 wt% or at least 40 wt% or at least 50 wt% or at least 60 wt% or at least 70 wt% or at least 80 wt% or at least 90 wt%. In some embodiments, (meth)acrylic acid monomers are a mixture comprising acrylic acid and methacrylic acid, in which acrylic acid makes up at least 10 wt% of the mixture or at least 20 wt% or at least 30 wt% or at least 40 wt% or at least 50 wt% or at least 60 wt% or at least 70 wt% or at least 80 wt% or at least 90 wt%. In some embodiments, (meth)acrylic acid monomers may further contain small amounts of other alkyl acrylic acids ; in some embodiments, the concentration of other alkyl acrylic acids is at most 10 wt% or at most 5 wt% or at most 2 wt% or at most 1 wt% or essentially 0 wt% (no measurable concentration).

[0054] Like (meth)acrylic acid, “(meth)acrylate” refers to either an acrylate or methacrylate moiety or a mixture of both acrylate and methacrylate moieties. (Meth)acrylate moieties can have the equivalent embodiments to the embodiments stated for (meth)acrylic acid monomers.

[0055] As used herein, “polyethylene glycol” or “PEG” refers to an oligomer or polymer that contains on average more than one repeating ethylene oxide unit. Some embodiments of PEG moieties can be represented by the Formula:

[0056] -(CR3H-CH2-O-)„- wherein “n” represents a number of alkylene oxide units (CR3H-CH2-O- , and each R3is individually hydrogen or a lower alkyl group. In the PEG moiety, more than 50 mole percent of alkylene oxide units are ethylene oxide, and R3contains on average less than 0.5 carbon atoms. In some embodiments, R3contains on average at most 0.3 carbon atoms or at most 0.2 carbon atoms or at most 0.1 carbon atoms or at most 0.05 carbon atoms or at most 0.02 carbon atoms or 0.00 carbon atoms. In some embodiments, at least 70 mole percent of the alkylene oxide units in the PEG are ethylene oxide units, or at least 80 mole percent or at least 90 mole percent or at least 95 mole percent or at least 98 mole percent. In some embodiments, 100 mole percent of the alkylene oxide units in the PEG are ethylene oxide units. In some embodiments, alkylene oxide units other than ethylene oxide units are selected from propylene oxide or butylene oxide units.

[0057] In some embodiments, the PEG contains on average at least 2 alkylene oxide units or at least 4 alkylene oxide units or at least 5 alkylene oxide units or at least 7 alkylene oxide units or at least 9 alkylene oxide units or at least 10 alkylene oxide units or at least 12 alkylene oxide units or at least 13 alkylene oxide units or at least 15 alkylene oxide units or at least 17 alkylene oxide units or at least 19 alkylene oxide units. In some embodiments, the PEG contains on average at most 50 alkylene oxide units or at most 45 alkylene oxide units or at most 40 alkylene oxide units or at most 30 alkylene oxide units or at most 25 alkylene oxide units or at most 23 alkylene oxide units or at most 20 alkylene oxide units. Embodiments of the number “n” reflect these embodiments.

[0058] The PCE copolymer contains from 10 to 60 wt% of repeating units derived from (meth)acrylic acid monomers, based on the total weight of the PCE copolymer. In some embodiments, the PCE copolymer contains at least 15 wt% repeating units derived from (meth)acrylic acid monomers or at least 20 wt% or at least 22 wt% or at least 24 wt% or at least 25 wt% or at least 27 wt% or at least 28 wt% or at least 30 wt% or at least 32 wt% or at least 35 wt%. In some embodiments, the PCE copolymer contains at most 55 wt% repeating units derived from (meth)acrylic acid monomers, or at most 50 wt% or at most 45 wt% or at most 43 wt% or at most 40 wt% or at most 38 wt%. In some embodiments, the (meth)acrylic acid monomers comprise primarily (more than 50 wt%) methacrylic acid.

[0059] The PCE copolymer contains from 30 to 70 wt% repeating units derived from alkyl (meth)acrylate monomers, based on the total weight of the PCE copolymer. The alkyl (meth) acrylate monomers comprise an alkyl moiety linked by an ester moiety to a (meth) acrylate moiety. The alkyl moiety of the alkyl (meth)acrylate monomer comprises on average from 1.0 to 3.5 carbon atoms. The (meth)acrylate portion of the alkyl (meth)acrylate monomer has the description previously given.

[0060] In some embodiments, the alkyl moiety contains on average at most 3.2 carbon atoms or at most 3.0 carbon atoms or at most 2.8 carbon atoms or at most 2.6 carbon atoms or at most 2.4 carbon atoms or at most 2.2 carbon atoms or at most 2.0 carbon atoms. In some embodiments, the alkyl moiety contains on average at least 1.2 carbon atoms or at least 1.4 carbon atoms or at least 1.6 carbon atoms or at least 1.8 carbon atoms or at least 2.0 carbon atoms. In some embodiments, the alkyl moiety in at least 50 wt% of the alkyl (meth)acrylate monomers is selected from methyl and ethyl groups, or at least 60 wt% or at least 70 wt% or at least 80 wt% or at least 90 wt% or up to 100 wt%. In some embodiments, the alkyl moiety in at least 50 wt% of the alkyl (me th) acrylate monomers is an ethyl group, or at least 60 wt% or at least 70 wt% or at least 80 wt% or at least 90 wt% or up to 100 wt%. In some embodiments, alkyl moieties in a minority of the alkyl (meth)acrylate monomers may comprise 3 or more carbon atoms, such as propyl, butyl and hexyl groups. In some embodiments, the alkyl moiety in at most 50 wt% of the alkyl (meth)acrylate monomers contains 3 or more carbon atoms, or at most 40 wt% or at most 30 wt% or at most 20 wt% or at most 10 wt% or 0 wt%.

[0061] Examples of suitable alkyl (meth)acrylate monomers include methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate. In some embodiments, the alkyl (meth)acrylate monomers comprise primarily (more than 50 wt%) ethyl acrylate or at least 60 wt% or at least 70 wt% or at least 80 wt% or at least 90 wt% or up to 100 wt%. In some embodiments, the alkyl (meth) acrylate monomers may comprise a mixture of alkyl (meth)acrylate monomers, and in some embodiments the alkyl (meth)acrylate monomers consist essentially of a single monomer.

[0062] In some embodiments, the PCE copolymer contains at least 35 wt% repeating units derived from alkyl (meth)acrylate monomers, or at least 40 wt% or at least 45 wt% or at least 48 wt% or at least 50 wt%. In some embodiments, the PCE copolymer contains at most 65 wt% repeating units derived from alkyl (meth)acrylate monomers, or at most 60 wt% or at most 58 wt% or at most 56 wt% or at most 54 wt% or at most 52 wt% or at most 50 wt%.

[0063] The PCE copolymer contains from 5 to 40 wt% repeating units derived from “PEG monomers,” based on the total weight of the PCE copolymer. The PEG monomers contain (i) a (meth)acrylate moiety linked by an ester linkage to (ii) a polyethylene glycol moiety that contains on average more than 1 ethylene oxide unit and (iii) an end moiety linked to the polyethylene glycol moiety at the opposite end from the (meth)acrylate moiety, which is selected from hydrogen or an alkyl moiety. Formula 1 illustrates exemplary PEG monomers: wherein:

[0064] • each R1is independently hydrogen or an alkyl group selected such that R1comprises on average less than 2 carbon atoms;

[0065] • each R2is independently an end moiety selected from hydrogen or an alkyl group; and

[0066] • each R3is independently hydrogen or a lower alkyl group selected such that R3comprises on average less than 0.5 carbon atoms, as previously described;

[0067] • - CR3H-CH2On- is a polyethylene glycol (PEG) moiety, as described previously, comprising n repeating alkylene oxide units, wherein n is on average greater than 1.

[0068] In some embodiments, the meth(acrylate) moiety of the PEG monomer comprises primarily (more than 50 wt%) an acrylate moiety (R1= H). In some embodiments, the meth(acrylate) moiety of the PEG monomer comprises primarily (more than 50 wt%) a methacrylate moiety (R1= -CPE). In some embodiments, R1comprises on average at most 1.2 carbon atoms or at most 1.0 carbon atoms or at most 0.8 carbon atoms or at most 0.6 carbon atoms or at most 0.4 carbon atoms or at most 0.2 carbon atoms. In some embodiments, R1comprises on average at least 0.2 carbon atoms or at least 0.4 carbon atoms or at least 0.6 carbon atoms or at least 0.8 carbon atoms or at least 1.0 carbon atoms.

[0069] Embodiments of the polyethylene glycol moiety, R3and n are previously described.

[0070] The polyethylene glycol moiety of the PEG monomer is terminated by in an end moiety (R2) opposite the meth(acrylate) moiety. In some embodiments, the end moiety is a hydrogen atom (R2= H). In some embodiments, the end moiety is an alkyl group (R2= alkyl). Alkyl groups in the end moiety (R2) contain at least 1 carbon atom. In some embodiments, alkyl groups in the end moiety (R2) contain on average at most 24 carbon atoms or at most 22 carbon atoms or at most 20 carbon atoms or at most 18 carbon atoms or at most 16 carbon atoms. In some embodiments, alkyl groups in the end moiety (R2) are lower alkyl groups, meaning the alkyl groups contain on average less than 8 carbon atoms or at most 6 carbon atoms or at most 4 carbon atoms or at most 2 carbon atoms. In some embodiments, alkyl groups in the end moiety (R2) are fatty alkyl groups, meaning the alkyl groups contain on average at least 8 carbon atoms or at least 10 carbon atoms or at least 12 carbon atoms or at least 14 carbon atoms. In some embodiments, end moieties on the PEG monomers contain a mixture of lower alkyl groups and fatty alkyl groups . In some embodiments, PEG monomers are selected so that the monomer is moderately hydrophilic but also moderately lipophilic, and the monomer interacts with the oil phase during emulsion polymerization. In some embodiments, the PEG monomers are selected such that the resulting PCE copolymer is insoluble in acidic aqueous media, but is soluble in basic aqueous media. PEG chains that contain little or no propylene oxide or butylene oxide units are generally hydrophilic. When the PEG monomer contains many alkylene oxide repeating units (such as when n is on average at least 10 or at least 15 or at least 20), then in some embodiments the PEG monomer can be made more lipophilic by having a fatty end group in R2and / or by incorporating propylene oxide or butylene oxide into the PEG chain. On the other hand, when the PEG monomer contains only a small number of alkylene oxide units (such as when n is on average at most 10 or at most 15 or at most 20), then in some embodiments the PEG chain contains little or no propylene oxide or butylene oxide, and / or the end moiety (R2) comprises hydrogen or a lower alkyl group.

[0071] In some embodiments, the PEG monomer has a number average molecular weight of at least 150 g / mol or at least 200 g / mol or at least 300 g / mol or at least 400 g / mol or at least 450 g / mol or at least 500 g / mol. In some embodiments, the PEG monomer has a number average molecular weight of at most 3000 g / mol or at most 2000 g / mol or at most 1000 g / mol or at most 900 g / mol or at most 800 g / mol or at most 750 g / mol.

[0072] In some embodiments, the PCE copolymer contains at least 6 wt% repeating units derived from PEG monomer, or at least 8 wt% or at least 10 wt% or at least 12 wt% or at least 13 wt%. In some embodiments, the PCE copolymer contains at most 38 wt% repeating units derived from PEG monomer, or at most 35 wt% or at most 30 wt% or at most 25 wt% or at most 20 wt% or at most 18 wt% or at most 16 wt% or at most 14 wt%.

[0073] The PCE copolymer may optionally contain from 0 to 20 wt% repeating units derived from other ethylenically unsaturated comonomers. Examples of suitable other comonomers include maleic acid, itaconic acid, styrene, vinyl acetate, vinyl alcohol, acrylonitrile, acrylamide, alkyl acrylamides, 2- acrylamido-2-methylpropane sulfonic acid, sodium styrenesulfonate, sodium vinylsulfonate, phosphoethyl methacrylate, and vinyl chloride. In some embodiments, the PCE copolymer contains at most 15 wt% repeating units derived from other comonomers, or at most 10 wt% or at most 5 wt% or at most 3 wt% or at most 2 wt%. In some embodiments, the PCE copolymer may contain essentially no repeating units derived from other comonomers (0 wt%).

[0074] Suitable (meth)acrylic acid monomers, alkyl (meth) acrylate monomers, PEG monomers and other comonomers are commercially available. PEG monomers can also be made by known processes, such as reaction of (meth)acryloyl chloride with polyethylene glycol as described in Lin-Gibson et al., “Synthesis and Characterization of PEG Dimethacrylates and Their Hydrogels” , 5(4) Biomacromolecules 1280-1287 (2004) and Takeshita et al., “Crystallization of graft copolymers 1. Graft Chains Miscible with Main Chains” 42 Polymer Journal 482-488 (2010). In some embodiments, the PCE copolymer is a random copolymer. In some embodiments, the PCE copolymer meets Formula 2: wherein:

[0075] • each R is independently an alkyl group in a repeating unit derived from alkyl (meth)acrylate monomer, as described previously;

[0076] • each R1is independently hydrogen or an alkyl group as described previously;

[0077] • each R2is independently an end group as described previously;

[0078] • -(CR3H-CH2O)n- is a polyethylene glycol moiety, as previously described, comprising n repeating alkylene oxide units;

[0079] • each R3is independently hydrogen or a lower alkyl group as described above;

[0080] • each M is independently a substituent that is appropriate for a comonomer in an PCE copolymer, such as a hydroxyl moiety, an amide moiety, an alkyl amide moiety, a nitrile moiety, a halide, an acetate moiety, an organosulfonate moiety or an organophosphate moiety;

[0081] • x represents a number of repeating units derived from (meth)acrylic acid monomer, representing on average from 10 to 60 wt% of the polymer;

[0082] • y represents a number of repeating units derived from alkyl (meth)acrylate monomer, representing on average from 30 to 70 wt% of the polymer;

[0083] • z represents a number of repeating units derived from PEG monomer, representing on average from 5 to 40 wt% of the polymer;

[0084] • m represents a number of repeating units derived from other monomers, representing on average from 0 to 20 wt% of the polymer; and

[0085] • terminal groups on the polymer backbone are not shown.

[0086] In some embodiments of Formula 2, the illustrated repeating units are randomly distributed within the polymer. Embodiments of R, R1, R2, R3, M, x, y, z, n and m are described previously.

[0087] As illustrated in Formula 2, the PCE copolymer comprises a poly(carboxylic acid) polymer backbone (“acidic polymer backbone”). Pendant alkyl and polyethylene glycol (PEG) moieties are linked to the acidic polymer backbone by ester linkages. This structure is sometimes referred to as a “comb” structure, as described previously.

[0088] As previously described, pendant alkyl and polyethylene glycol (PEG) moieties can be removed from the acidic polymer backbone of the PCE copolymer by hydrolysis to yield a poly(carboxylic acid) polymer, called the “hydrolysis product polymer” or “HPP.” An example of the HPP is illustrated in Formula 3: wherein x, y, z, m, M and R1correspond to the values in the PCE copolymer and terminal groups on the polymer backbone are not shown. The molecular weight profile of the HPP is expected to roughly equal the formula weight profile of the acidic polymer backbone in the PCE copolymer.

[0089] The molecular weight of the acidic polymer backbone in the PCE copolymer may be conveniently measured by (1) hydrolyzing the PCE copolymer to recover the HPP and (2) performing a size exclusion chromatography (SEC) analysis on the HPP in an aqueous medium, as described in the Test Methods. The HPP is normally soluble in the aqueous medium, and the HPP is similar to commercially-available acrylic standards.

[0090] Alternatively, the molecular weight of the acidic polymer backbone in the PCE copolymer may be measured by (1 ) hydrolyzing the PCE copolymer to recover the HPP and (2) performing a SEC analysis on the HPP in a solution of tetrahydrofuran / formic acid, as described in the Test Methods. For some HPP, SEC analysis in a solution of tetrahydrofuran / formic acid may provide clearer resolution of the molecular weight peaks corresponding to the HMW and LMW components than aqueous SEC analysis.

[0091] Alternatively, the molecular weight of some embodiments of the PCE copolymer may be directly analyzed by a SEC analysis in a solution of tetrahydrofuran / formic acid, as described in the Test Methods. In some embodiments, at least 50 wt% of the PCE copolymer is soluble at a concentration of -1 mg / mL in a solution of tetrahydrofuran / formic acid (THF-FA; 100 / 5 vol / vol ratio), or at least 60 wt% or at least 70 wt% or at least 80 wt% or at least 90 wt% or at least 95 wt% or up to 100 wt%. Again, for some PCE copolymers, SEC analysis in a solution of tetrahydrofuran / formic acid may provide clearer resolution of the molecular weight peaks corresponding to the HMW and LMW components than aqueous SEC analysis.

[0092] Molecular weights in this document are determined based on the Test Methods, which provide relative molecular weight determinations based on comparisons to known standards. It is known that different test methods or different standards may determine different molecular weights for the same polymer. For absolute molecular weights, fractions that are recovered from SEC analysis may be analyzed with a multi-angle light scattering (MALS) detector according to known procedures.

[0093] As previously described, for the PCE copolymers in this invention, the HPP has a multimodal molecular weight distribution. The HPP comprises at least a higher molecular weight (HMW) component and a lower molecular weight (LMW) component. In some embodiments, an SEC analysis of the different molecular weight fractions of the HPP has two or more distinct peaks with a minimum between them, which show the existence of HMW and LMW components. In other embodiments, the SEC analysis shows a major peak with a higher or lower molecular weight shoulder or a higher or lower molecular weight tail; the shoulder or tail evidences the presence of two components, even though no minimum can be measured between their peaks. We hypothesize that the presence of HMW and LMW components in the HPP indicates that the corresponding PCE copolymer has HMW and LMW components, in which:

[0094] • the higher molecular weight (HMW) component comprises a longer chain, higher molecular weight backbone polymer; and

[0095] • the lower molecular weight (LMW) component comprises a shorter chain, lower molecular weight polymer backbone.

[0096] In some embodiments, (1) a higher molecular weight (HMW) component of the HPP has a weight average molecular weight (Mw) of more than 200 kg / mol, and (2) a lower molecular weight (LMW) component of the HPP has a weight average molecular weight (Mw) of less than 200 kg / mol. In some embodiments, the Mwof the HMW component of the HPP is at least 250 kg / mol or at least 300 kg / mol or at least 350 kg / mol or at least 400 kg / mol or at least 450 kg / mol or at least 500 kg / mol or at least 550 kg / mol. In some embodiments, the M„ of the HMW component of the HPP is at most 5000 kg / mol or at most 2000 kg / mol or at most 1500 kg / mol or at most 1200 kg / mol or at most 1000 kg / mol or at most 900 kg / mol or at most 800 kg / mol or at most 750 kg / mol.

[0097] In some embodiments, the Mwof the LMW component of the HPP is at most 180 kg / mol or at most 150 kg / mol or at most 120 kg / mol or at most 100 kg / mol or at most 80 kg / mol or at most 70 kg / mol or at most 65 kg / mol or at most 60 kg / mol or at most 55 kg / mol or at most 50 kg / mol or at most 45 kg / mol. In some embodiments, the M„ of the LMW component of the HPP is at least 10 kg / mol or at least 12 kg / mol or at least 15 kg / mol or at least 16 kg / mol or at least 17 kg / mol.

[0098] In some embodiments, the HMW component of the HPP has a dispersity (Mw / Mn, also called polydispersity index or molecular weight distribution) of at least 4.0 or at least 5.0 or at least 6.0 or at least 6.5 or at least 7.0. In some embodiments, the HMW component of HPP has a dispersity of at most 15 or at most 12 or at most 11 or at most 10. In some embodiments, the LMW component of the HPP has a dispersity of at least 1.5 or at least 1.8 or at least 2.0 or at least 2.2 or at least 2.3. In some embodiments, the LMW component of the HPP has a dispersity of at most 5.0 or at most 4.0 or at most 3.8 or at most 3.5.

[0099] In some embodiments of the HPP, a higher molecular weight (HMW) component has a weight average molecular weight (Mw) that is at least 50 kg / mol higher than the weight average molecular weight (Mw) of a lower molecular weight (LMW) component, or at least 75 kg / mol or at least 100 kg / mol or at least 125 kg / mol or at least 150 kg / mol or at least 175 kg / mol or at least 200 kg / mol or at least

[0100] 250 kg / mol or at least 300 kg / mol or at least 350 kg / mol or at least 400 kg / mol. In some embodiments of the HPP, the higher molecular weight (HMW) component has a weight average molecular weight (Mw) -l i that is at most 1000 kg / mol higher than the weight average molecular weight (Mw) of a lower molecular weight (LMW) component, or at most 900 kg / mol or at most 850 kg / mol or at most 800 kg / mol.

[0101] In some embodiments, the HPP of the complete PCE copolymer has a dispersity of at least 5.0 or at least 5.5 or at least 6.0 or at least 6.5 or at least 7.0 or at least 7.5 or at least 8.0. In some embodiments, the HPP of the complete PCE copolymer has a dispersity of at most 18 or at most 15 or at most 13 or at most 12.

[0102] In some embodiments, the PCE copolymer has a number average molecular weight (Mn) of at least 25 kg / mol or at least 30 kg / mol or at least 35 kg / mol, when measured in tetrahydrofuran / formic acid solution according to the Test Methods. In some embodiments, the PCE copolymer has a weight average molecular weight (Mw) of at least 200 kg / mol or at least 300 kg / mol or at least 400 kg / mol or at least 500 kg / mol or at least 750 kg / mol or at least 1000 kg / mol, when measured in tetrahydrofuran / formic acid solution according to the Test Methods. In some embodiments, the PCE copolymer has a dispersity (Mw / Mn) of at least 6.0 or at least 8.0 or at least 9.0 or at least 10 or at least 12 or at least 15 or at least 20 or at least 25 or at least 30, when measured in tetrahydrofuran / formic acid solution according to the Test Methods. In some embodiments, the PCE copolymer has a dispersity of at most 70 or at most 60 or at most 50, when measured in tetrahydrofuran / formic acid solution according to the Test Methods.

[0103] Note that the molecular weight data for the PCE copolymer applies only to the portion of the PCE copolymer that is soluble at a concentration of ~1 mg / mL in a solution of tetrahydrofuran / formic acid (100 / 5 vol / vol ratio). Molecular weight of insoluble species is not measured by the SEC apparatus. In some embodiments, at least 50 wt% of the PCE copolymer is soluble or at least 55 wt% or at least 60 wt% or at least 65 wt% or at least 70 wt% or at least 75 wt% or at least 80 wt%.

[0104] In some embodiments, the HPP of the PCE copolymer comprises at least 20 wt% of the HMW component based on the total weight of the HPP, or at least 30 wt% or at least 40 wt% or at least 45 wt% or at least 55 wt% or at least 60 wt% or at least 65 wt%. In some embodiments, the HPP of the PCE copolymer comprises at most 90 wt% of the HMW component based on the total weight of the HPP, or at most 85 wt% or at most 80 wt% or at most 75 wt% or at most 70 wt% or at most 65 wt% or at most 60 wt% or at most 55 wt% or at most 52 wt%. In some embodiments, the HPP of the PCE copolymer comprises at least 5 wt% of the LMW component based on the total weight of the HPP, or at least 10 wt% or at least 15 wt% or at least 20 wt% or at least 25 wt% or at least 30 wt% or at least 35 wt% or at least 40 wt% or at least 45 wt% or at least 48 wt%. In some embodiments, the HPP of the PCE copolymer comprises at most 52 wt% of the LMW component based on the total weight of the HPP, or at most 50 wt% or at most 45 wt% or at most 40 wt% or at most 35 wt%. In some embodiments, the PCE copolymer has similar ratios of HMW components and LMW components as described for the HPP.

[0105] In some embodiments, the PCE copolymer comprises an HMW component with a weight average molecular weight of at least 200 kg / mol or at least 300 kg / mol or at least 400 kg / mol or at least 500 kg / mol or at least 600 kg / mol or at least 700 kg / mol or at least 800 kg / mol or at least 900 kg / mol, when measured in tetrahydrofuran / formic acid solution according to the Test Methods. In some embodiments, this HMW component makes up at least 40 wt% of the PCE copolymer or at least 45 wt% or at least 50 wt% or at least 55 wt% or at least 60 wt% or at least 65 wt%.

[0106] In some embodiments, the HPP is bimodal, and the HMW component and the LMW component are the only molecular weight-based components of the HPP. In some embodiments, the PCE copolymer is bimodal, and the HMW component and the LMW component are the only molecular weight-based components of the PCE copolymer.

[0107] In some embodiments, the HPP of the PCE copolymer further comprises a medium molecular weight (MMW) component, which has a weight average molecular weight (Mw) greater than the LMW component but less than the HMW component. In some embodiments, the HPP of the PCE copolymer comprises at most 25 wt% of the MMW component based on the total weight of the poly(carboxylic acid), or at most 20 wt% or at most 15 wt% or at most 10 wt% or at most 5 wt% or 0 wt%. In some embodiments, the PCE copolymer has an MMW component with similar ratios as described for the HPP.

[0108] In some embodiments, the LMW component of the PCE copolymer is produced by using a chain transfer agent in the polymerization of the LMW component. In this case, at least one end of the acidic polymer backbone in LMW component may be terminated by the residue of a chain transfer agent. For example, the PCE copolymer in LMW component may comply with Formula 4: wherein A is a residue of a chain transfer agent, and all other moieties have the meaning defined for Formula 2.

[0109] In some embodiments, A is represented by the formula (-S-R4) wherein R4comprises hydrogen or an aliphatic moiety. In some embodiments, R4is hydrogen. In some embodiments, R4is a hydrocarbyl moiety, such as an alkyl moiety. In some embodiments, R4comprises oxygen, such as a ketone, a carboxylic acid or a carboxylate ester moiety. In some embodiments, R4comprises at least 2 carbon atoms or at least 3 carbon atoms. In some embodiments, R4comprises at most 24 carbon atoms or at most 20 carbon atoms or at most 18 carbon atoms or at most 16 carbon atoms or at most 14 carbon atoms or at most 12 carbon atoms or at most 10 carbon atoms or at most 8 carbon atoms or at most 6 carbon atoms or at most 4 carbon atoms. In some embodiments, A is represented by the formula (-O-R4), -R4-X or simply R4, wherein R4has the description previously provided and X is a halogen such as chlorine or iodine.

[0110] In some embodiments, the monomers are selected such that the PCE copolymer is alkali-soluble, which means soluble in water with a pH of 10, as measured according to the Test Methods. Cementitious environments are alkaline. In some embodiments, the PCE copolymer dissolves in the cementitious mixture. In some embodiments, the PCE copolymer has solubility of at least 1 g / 100 g in water with a pH of 10. In some embodiments, the PCE copolymer has solubility of at least 10 g / 100 g in water with a pH of 10, or at least 20 g / 100 g or at least 30 g / 100 g. The solubility limit of some PCE copolymers may be difficult to measure, because the viscosity of the solution increases with increasing concentration of PCE copolymer.

[0111] In some embodiments, the monomers are selected such that the resulting PCE copolymer can remain in a stable dispersion in an aqueous acidic environment, such as in water with a pH of at most 6.5 or at most 5.5 or at most 5.0 or at most 4.5 or at most 4.0 or at most 3.5 or at most 3.0. The ability to remain in a dispersion is impacted by the balance of hydrophilic and lipophilic moieties in the polymer. The selection and proportions of acid, acrylate and PEG monomers can impact the hydrophilicity and lipophilicity of the PCE copolymer as previously described and the ability of the PCE copolymer to remain in a stable dispersion.

[0112] The PCE copolymers of this invention are made by emulsion polymerization. Emulsion polymerization processes are well-known and described in numerous publications, such as Emulsion Polymerization of Acrylic Monomers, published by Rohm and Haas Company, (1966) which is available

[0113] Lovell et al, Fundamentals of Emulsion Polymerization, 21 Biomacromolecules 4396-4441 (2020); and Juaregui, Thesis: Synthesis and Optimization of Emulsion Polymers published by California Polytechnic State University, San Luis Obispo (2016).

[0114] Emulsion polymerization takes place in an aqueous medium, which contains surfactants that act as emulsifiers. The monomers and surfactant form a dispersed organic phase in the aqueous medium, and polymerization is initiated by a free radical initiator or a redox initiator. The selection and proportions of the monomers in the emulsion polymerization reflect their desired proportions in the resulting polymer, as described previously. In some embodiments, the monomer emulsion contains at least 15 wt% monomers, based on the total weight of the emulsion, or at least 20 wt% monomers or at least 30 wt% monomers or at least 40 wt% monomers or at least 50 wt% monomers or at least 60 wt% monomers. In some embodiments, the monomer emulsion contains at most 70 wt% monomers, based on the total weight of the emulsion, or at most 60 wt% monomers or at most 50 wt% monomers.

[0115] Examples of appropriate surfactants for use as emulsifiers are commercially available from The Dow Chemical Company under the DOWFAX™ and TRITON™ trademarks. See, for example “Solutions for Emulsion Polymerizations,” published by The Dow Chemical Company (2018). In some embodiments, the weight percent of emulsifiers to monomer is 0.1 wt% or at least 0.2 wt% or at least 0.5 wt% or at least 1.0 wt% or at least 1.5 wt%. In some embodiments, the weight ratio of emulsifiers to monomer is at most 3.0 wt% or at most 2.5 wt% or at most 2.0 wt%.

[0116] Initiators for emulsion polymerization are known and commercially available. In some embodiments, the initiator is a water soluble free radical initiator. Examples of free radical initiators include persulfate salts such as ammonium persulfate and sodium persulfate and water-soluble azo compounds such as 2,2'-azobis[2-methylpropionamidine] dihydrochloride and 4,4'-azobis[4- cyanovalericj acid. In some embodiments, the weight ratio of initiator to monomers is at least 0.05 wt% or at least 0.1 wt% or at least 0.15 wt%. In some embodiments, the weight ratio of initiator to monomers is at most 1.0 wt% or at most 0.5 wt%.

[0117] In many embodiments, the emulsion polymerization is carried out at a temperature of at least 50°C or at least 60°C or at least 70°C or at least 75°C. In many embodiments, the emulsion polymerization is carried out at a temperature of at most 95°C or at most 90°C. Pressure is not critical, as long as the blend of water, emulsifiers and other ingredients is stable; in most embodiments, ambient pressure is convenient. In many embodiments, the reaction mixture is agitated to provide good mixing.

[0118] In some embodiments, the polymerization is catalyzed by a redox catalyst. Redox catalysts are commercially available and their use in emulsion polymerization of acrylic monomers is known and published in numerous references, such as Emulsion Polymerization of Acrylic Monomers, published by Rohm and Haas Company, (1966) and Sarac, “Redox Polymerization,” 24 Prog. Polym. Sci. 1149-1204 (1999).

[0119] Normal emulsion polymerization generally yields PCE copolymers with a molecular weight that corresponds to the HMW component. Polymerization of the LMW component (and optionally the MMW component) is carried out under conditions suitable to limit the growth of the polymer backbone. Known means to control chain growth include: use of a chain transfer agent, atom transfer radical polymerization (ATRP), reversible addition / fragmentation chain transfer polymerization (RAFT) or nitroxide-mediated polymerization. See, for example, Cunningham, “Living / Controlled Radical Polymerizations in Dispersed Phase Systems,” 27 Pro, Poly, Sci. 1039-1067 (2002) and “Sigma -Aldrich Controlled Radical Polymerization Guide,” published by Merck KGaA (2019).

[0120] In some embodiments, the LMW component is polymerized in the presence of a chain transfer agent. Chain transfer agents and their use are well known. See for example K. Matyjaszewski & T. Davis, Handbook of Radical Polymerization, Ch. 12 “Control of Free Radical Polymerization by Chain Transfer Methods” 629-691 (2002). Examples of suitable chain transfer agents include thiols, disulfides, alcohols and halogenated alkyl compounds. In some embodiments, the chain transfer agent is represented by Formula 5:

[0121] (5) R4-SH wherein R4has the description previously given. Examples of suitable chain transfer agents are methyl mercaptopropionate, octanethiol and dodecanethiol, which are commercially available.

[0122] The quantity of chain transfer agent is suitable to limit the growth of the acidic polymer backbone as described previously. In some embodiments, the polymerization of the LMW component takes place in the presence of at least 0.4 wt % chain transfer agent, based on the total weight of monomers in the reaction mixture, or at least 0.5 wt% or at least 0.6 wt% or at least 0.7 wt% or at least 0.8 wt% or at least 0.9 wt% or at least 1.0 wt%. In some embodiments, the polymerization of the LMW component takes place in the presence of at most 5.0 wt % chain transfer agent, based on the total weight of monomers in the reaction mixture, or at most 4.0 wt% or at most 3.0 wt% or at most 2.0 wt% or at most 1.8 wt% or at most 1.6 wt% or at most 1.4 wt% or at most 1.2 wt%. In some embodiments, the polymerization of the HMW component takes place in the presence of at most 1.0 wt % chain transfer agent, based on the total weight of monomers in the reaction mixture, or at most 0.5 wt% or at most 0.3 wt% or at most 0.1 wt% or 0 wt%.

[0123] At least one HMW component and at least one LMW component may be polymerized separately, and then the HMW and LMW components may be physically blended to form the multimodal PCE copolymer. Alternatively, an HMW component and an LMW component may be polymerized sequentially in the same reaction mixture. In some embodiments, the HMW component is made first by polymerizing a first portion of monomers under conditions suitable to form the HMW component, and then the LMW portion is made by polymerizing a second portion of monomers in the product mixture from the HMW polymerization, under conditions suitable to form the LMW component. In some embodiments, the LMW component is made first by polymerizing a first portion of monomers under conditions suitable to form the LMW component, and then the HMW portion is made by polymerizing a second portion of monomers in the product mixture from the LMW reaction, under conditions suitable to form the HMW component. In some cases, it may be simpler to make the HMW component first because if the LMW component process is performed first, residual chain transfer agent could carry over into the HMW component process and negatively influence the molecular weight of the HMW component.

[0124] In some embodiments, the monomer mixtures that are used to polymerize the HMW and LMW components comprise similar monomers in similar ratios, so that the resulting HMW and LMW components have similar polymer compositions. In some embodiments, the monomer mixtures that are used to polymerize the HMW component and the LMW component comprise different monomers and / or different proportions of monomers, so that the resulting HMW and LMW components have different polymer compositions.

[0125] The product of the emulsion polymerization is an aqueous dispersion, which contains polymer particles that comprise the PCE copolymer suspended in an aqueous medium. In some embodiments, the z-average diameter of the polymer particles is at least 10 nm or at least 25 nm or at least 50 nm or at least 70 nm or at least 90 nm. In some embodiments, the z-average diameter of the polymer particle is at most 1200 nm or at most 1000 nm or at most 800 nm or at most 600 nm or at most 500 nm or at most 250 nm or at most 150 nm or at most 100 nm. In some embodiments, the aqueous dispersion is a colloidal dispersion.

[0126] In some embodiments, the aqueous dispersion that results from the polymerization may be modified, such as by adding water or other solvents, by adding dispersants or other additives, or by adding acids, bases or buffers to adjust the pH.

[0127] The aqueous medium in the aqueous dispersion comprises at least 50 wt% water, based on the weight of the aqueous medium. In some embodiments, the aqueous medium comprises at least 60 wt% water, based on the weight of the aqueous medium, or at least 70 wt% or at least 80 wt% or at least 90 wt% or at least 95 wt% or 100 wt%. Other components of the aqueous medium, if any, should be miscible with water and should not cause the PCE copolymer particles to dissolve or become colloidally unstable in the aqueous medium.

[0128] In some embodiments, the aqueous dispersion has a pH of at most 6.0 or at most 5.0 or at most 4.5 or at most 4.0 or at most 3.5 or at most 3.0. In some embodiments, the aqueous dispersion has a pH of at least 1.8 or at least 2.0 or at least 2.5. In some embodiments, the PCE copolymer becomes water- soluble at pH of at least 7 or at least 8 or at least 9 or at least 10.

[0129] In some embodiments, the aqueous dispersion is stable at 25°C for at least 1 day or at least 1 week or at least 1 month or at least 2 months or at least 3 months or at least 6 months. In this context, “stable” means that the aqueous dispersion does not show visible phase separation, coalescence or agglomeration of particles.

[0130] In some embodiments, the aqueous dispersion comprises at least 10 wt% of the polymer particles, based on the total weight of the aqueous dispersion, or at least 15 wt% or at least 20 wt% or at least 25 wt% or at least 27 wt% or at least 29 wt%. In some embodiments, the aqueous dispersion comprises at most 60 wt% of the polymer particles, based on the total weight of the aqueous dispersion, or at most 50 wt% or at most 45 wt% or at most 40 wt%.

[0131] In some embodiments, the aqueous dispersion may be stored and used without recovering the PCE copolymer.

[0132] In some embodiments, the aqueous dispersion may be spray-dried to form a powder comprising the PCE copolymer. Spray-drying equipment is commercially available with instructions for its use, and spray-drying is described in many publications such as: Santos et al., “Spray Drying - A Overview”, available at: “Spray Dry Manual” published by Bete Performance Spray Engineering at www.BETE.com; and More Swati et al, “Review on Spray Drying Technology” 4(2) IJPCBS 219-225 (2014). PCE copolymer powders may be easier to store and transport and may optionally be added to a dry mix before water is added.

[0133] Use as a Concrete Additive

[0134] Multimodal PCE copolymers of this invention perform as water retention aids in cementitious mixtures (dry mix or wet mix). Powders that contain the PCE copolymer may be added to the dry mix before water is added. Alternatively, powders or aqueous dispersions that contain the PCE copolymer may be added to the wet mix after water is added. Alternatively, powders or aqueous dispersions that contain the PCE copolymer may be added to water before the water is added to the dry mix.

[0135] The cementitious mixtures contain filler, cement and optionally other additives as dry components. (“Dry components” are any components of the cementitious mixture that are normally solid at up to 40°C and atmospheric pressure.)

[0136] Fillers for cementitious mixtures usually contain inorganic particles. The particle sizes of the filler vary depending on the intended use of the cementitious mixture. Mortar, grout and stucco fillers generally contain sand. US standards for masonry filler are listed in ASTM C144 and in AASHTO M 45-15 / ASTM C 144-11. Concrete fillers generally contain aggregate, a mixture of sand and gravel of various sizes. US standards for concrete aggregate filler are listed in ASTM C33 and AASHTO M 6 / M 80. See also, Kousmata et al., Design and Control of Concrete Mixtures, Chapter 6 “Aggregates for Concrete” (2016). In some embodiments, the filler may also contain pozzolans such as fly ash, calcined kaolin, pumices, or fumed silica; pozzolans and their use in cementitious mixtures are well-known and described in US Patent 9181131B2. In some embodiments, the filler may also contain inorganic pigments such as titanium dioxide, other metal oxides or carbon black. In some embodiments, the filler may also contain organic fibers or particles.

[0137] In some embodiments, the cementitious mixture contains at least 50 wt% filler, based on the dry components and excluding water, or at least 60 wt% or at least 65 wt% or at least 70 wt%. In some embodiments, the cementitious mixture contains at most 85 wt% of filler, based on the dry components and excluding water, or at most 80 wt%. In some embodiments, the cementitious mixture contains at least 50 volume percent filler, based on the dry components and excluding water, or at least 55 volume percent or at least 60 volume percent. In some embodiments, the cementitious mixture contains at most 85 volume percent of filler, based on the dry components and excluding water, or at most 80 volume percent or at most 75 volume percent.

[0138] The ASTM recognizes five categories of cement: Type 1 (ordinary Portland cement); Type 2 (moderate sulfate resistant cement); Type 3 (rapid hardening cement), Type 4 (low heat cement) and Type 5 (high sulfate resistant cement). Blends and variations on these five categories are also available, such as Portland limestone cement (Type IL). Any of these cements may be used in the cementitious mixtures of this invention. In some embodiments, the cement is ordinary Portland cement. In some embodiments, the cement is a variation of ordinary Portland cement, known as white cement. In some embodiments, the cement is Portland limestone cement. In some embodiments, the cement is a more specialized cement, such as a high alumina cement or a calcium sulfoaluminate cement. Suitable cements are commercially available.

[0139] The cementitious mixture should contain enough cement to effectively bind the dry components together. In some embodiments, the cementitious mixture contains at least 15 wt% cement or at least 20 wt%, based on the dry components and excluding water. In some embodiments, the cementitious mixture contains at most 50 wt% cement or at most 40 wt% or at most 35 wt% or at most 30 wt%, based on the dry components and excluding water.

[0140] Examples of other additives that may optionally be included in the cementitious mixtures include supplementary water retention aids, starch ethers, rheology modifiers, air-entraining agents, accelerators, retarders, supplementary superplasticizers and defoamers.

[0141] • Redispersible powder is an organic polymer powder that disperses in the wet mix and gives the cured cementitious mixture improved flexibility and toughness. Some embodiments of redispersible powders include one or more of ethylene / vinyl acetate copolymers, vinyl acetate / ethylene tertiary carbonate copolymers and acrylic acid copolymers. • Supplementary water retention aids, such as cellulose ethers, further slow the separation of water out of the wet mix. In some embodiments, the PCE copolymer is the only water retention aid in the cementitious mixture. In some embodiments, the cementitious mixture further comprises a supplementary water retention aid. In some embodiments, the weight ratio of PCE copolymer to supplementary water retention aid is at least 1 :4 or at least 1 :3 or at least 1 :2 or at least 1 :1. In some embodiments, the weight ratio of PCE copolymer to supplementary water retention aid is at most 9:1 or at most 4: 1 or at most 3: 1 or at most 2:1 or at most 1:1.

[0142] • Starch ethers, such as hydroxypropyl starch ether, can improve the anti-sagging and anti-slip performance of the wet mix, as well as lengthening open time and providing a smoother surface.

[0143] • Rheology modifiers, such as bentonite clay, organically-modified clay, attapulgite, fumed silica and precipitated calcium carbonate, can modify the viscosity and shear thinning behavior of the wet mix.

[0144] • Air-entraining agents cause the formation of small air-bubbles in wet mix, which can improve the resilience of the cured mixture under freeze-thaw cycles. Air-entrainment agents are frequently surfactants.

[0145] • Accelerators speed the setting of the wet mix. They may be especially useful in cold-weather environments. Examples of common accelerators include calcium nitrate, calcium nitrite, calcium formate and certain aluminum compounds.

[0146] • Retarders slow the setting time of the wet mix. Examples of common retarders include calcium, sodium and ammonium salts of lignosulfonic acid, hydroxycarboxylic acids, carbohydrates, lead oxides, zinc oxides, phosphates, borates and fluorates.

[0147] • Superplasticizers allow the production and use of wet mix with lower water content. Examples of supplementary superplasticizers include sulfonated melamine-formaldehyde condensates, sulfonated naphthalcnc-formaldchydc condensates, modified lignosulfonatcs and polycarboxylatc ethers. Superplasticizer formulations with instructions for their use are commercially available.

[0148] • Defoamers can reduce air-entrainment and voids in the wet mix. Examples of defoamers include mineral oils, polyglycols and polyethersiloxanes. In some embodiments, the wet mix contains at least 10 ppm defoamer, based on the total weight of the wet mix, or at least 25 ppm or at least 40 ppm or at least 50 ppm. In some embodiments, the wet mix contains at most 500 ppm defoamer, based on the total weight of the wet mix, or at most 200 ppm or at most 100 ppm or at most 75 ppm.

[0149] The foregoing additives are commercially available with instructions for their use.

[0150] In some embodiments, the cementitious mixture contains at most 10 wt% of the other additives or at most 5 wt% or at most 2 wt%, based on the dry components and excluding water. In some embodiments, the cementitious mixture contains no measurable content of the other additives (essentially 0 wt%) or at least 1 wt% or at least 2 wt%, based on the weight of dry components and excluding water. The cementitious mixture contains the PCE copolymer of this invention in a quantity suitable to reduce or prevent separation of water from the wet mix. In some embodiments, the cementitious mixture contains at least 0.05 wt% PCE copolymer, based on the weight of the cement, or at least 0.08 wt% or at least 0.10 wt% or at least 0.1 wt% or at least 0.15 wt% or at least 0.2 wt% or at least 0.25 wt% or at least 0.3 wt%. In some embodiments, the cementitious mixture contains at most 1.0 percent PCE copolymer, based on the total weight of the cement, or at most 0.8 wt% or most 0.6 wt% or most 0.5 wt% or most 0.4 wt% or most 0.3 wt%.

[0151] In some embodiments, the multimodal PCE copolymers function as both water retention aids and water reduction agents (superplasticizers) . We hypothesize, without intending to be bound, that the HMW component influences the water retention more strongly than the LMW component, and the LMW component influences water reduction more strongly than the HMW component. Depending on the desired performance of the multimodal PCE, it may be desirable to select blends of HMW and LMW components in proportions higher or lower than within the named range.

[0152] In some embodiments, the cementitious mixture contains at most 0.15 wt% cellulose ether, based on the weight of dry components and excluding water, or at most 0.1 wt% or at most 0.08 wt% or at most 0.05 wt% or at most 0.02 wt% or at most 0.01 wt%. In some embodiments, the cementitious mixture contains essentially no cellulose ether (0 wt%). In some embodiments, the cementitious mixture contains at least 0.01 weight percent cellulose ether.

[0153] In some embodiments, the cementitious mixture contains at most 0.15 wt% supplementary superplasticizers, based on the weight of dry components and excluding water, or at most 0.1 wt% or at most 0.08 wt% or at most 0.05 wt% or at most 0.02 wt% or at most 0.01 wt%. In some embodiments, the cementitious mixture contains essentially no supplementary superplasticizers (0 wt%).

[0154] In some embodiments, some or all of the dry components are preblended to make a dry mix before the dry components are mixed with water to form a wet mix. In some embodiments, some of the dry components, particularly additives, may be omitted from the dry mix and either may be added to the water before it is blended in to form the wet mix or may be added into the wet mix after it is formed.

[0155] To make the wet mix, water is blended with the dry components in a quantity sufficient to fully wet the dry components and provide a cementitious mixture that is homogeneous and has desirable workability and viscosity. The optimum quantity of water varies depending on the dry components and their intended use, and can be readily determined by experimentation. In some embodiments, the amount of water is at least 10 wt%, based on the total weight of the wet mix, or at least 15 wt% or at least 18 wt% or at least 20 wt%. In some embodiments, the amount of water is at most 30 wt%, based on the total weight of the wet mix, or at most 25 wt% or at most 22 wt% or at most 20 wt%.

[0156] In some embodiments, the wet mix has a water retention of at least 92 percent, when measured according to the Test Methods, or at least 94 percent or at least 95 percent or at least 96 percent or at least 97 percent or at least 98 percent. There is no maximum desired water retention, but in many cases retention over 99 percent is unnecessary. The wet mix may be used in any suitable application. For example:

[0157] • Concrete wet mix may be cured in molds or forms to make solid structures, such as pavement, pavers, floors, blocks, walls, pillars or other concrete articles.

[0158] • Mortar may hold bricks, blocks, tiles or other structural elements in place.

[0159] • Stucco may coat a wall or form a layer in an exterior insulation and finishing (EIFS) system. After it is applied, the wet mix is permitted to dry and cure. The time needed to dry and cure varies significantly depending on the selection of dry components in the wet mix (such as choice of cement, accelerators and retarders), the quantity of water, the thickness of the application, and the temperature and humidity at which the drying and curing occur. In many embodiments, the cementitious mixture dries to the touch in a few hours or less, and can be weight-bearing in a day or two. On the other hand, curing to full strength may take many days.

[0160] After curing is complete, the cured cementitious mixture reflects the contents of the wet mix used to make it. The cured cementitious mixture contains filler, cured cement, optionally additives, and residual PCE copolymer of this invention or its reaction products. In some embodiments, the alkaline environment of the wet mix hydrolyzes ester linkages in the PCE copolymer and releases the PEG side chains. As a result, some or all of the PEG side chains may be stripped from the PCE copolymer. The liberated PEG polymer may migrate to other parts of the wet mix, and may become trapped there in the cured cementitious mixture. Likewise, some or all of the acidic polymer backbone may be partially or wholly stripped of side chains and comprise a higher level of pendant acid moieties than the original PCE copolymer.

[0161] Test Methods

[0162] Unless stated otherwise, measurements listed in this application are made using the following test methods:

[0163] Hydrolysis of PCE Copolymer to obtain HPP:

[0164] Samples of PCE copolymer powder are hydrolyzed in a Parr Bomb (#4749) vessel to obtain the corresponding HPP. Hydrolysis is performed by adding -0.50 g of PCE copolymer, 1 g of potassium hydroxide pellets, 0.25 g of DI water and 10 mL of ethanol to a Teflon cup. The Teflon cup is placed inside the Parr Bomb vessel, and the vessel is sealed according to manufacturer instructions. The sealed vessel is placed in a 150°C oven for 3 days. The resulting sample is cooled to room temperature and the supernatant is decanted. The resulting solid mass of HPP in the vessel is collected and rinsed with 10 mL of ethanol and allowed to dry at room temperature.

[0165] Aqueous SEC Measurement of Molecular Weight of HPP:

[0166] Samples of HPP solution are prepared. The HPP is mixed in a concentration of 2 mg / g in an aqueous phosphate buffer solution (20 mM having a pH of 7.0). The sample is agitated on a mechanical shaker overnight at room temperature to fully dissolve the HPP. Next, the sample solution is filtered using a 0.2 p Target2 (Fisher) PVDF filter. The sample is visually inspected to ensure that no undissolved material is present.

[0167] SEC analysis is performed using a Waters UPLC system equipped with an isocratic pump, degasser, injector, column oven and differential refractive index (RI) detectors operated at 35°C. The UPLC system is equipped with a TOSOH Bioscicncc TSKgcl G2500PWxl and TSKgcl GMPWxl columns (packed with 7 pm and 13 pm particles and with internal dimensions of 7.8 mm x 300 mm. The system is calibrated using sixteen narrow-dispersity polyacrylic acid sodium salts ranging from Mp = 216 Da to Mp = 1.1 million Da obtained from American Polymer Standards Corporation. A 20 pL sample is injected and the flow rate of the mobile phase is held at a rate of 1.0 ml / min. Data is collected and processed using Version 3 of Empower software (Waters, Milford, MA). Note: This system delivers relative molecular weight data based on the standards used in calibration, rather than absolute molecular weight data.

[0168] Solubility in Organic Solvent and SEC Measurement of Molecular Weight of Organic-Soluble PCE Copolymer

[0169] Samples of PCE copolymer are dissolved at a concentration of ~1 mg / mL in a solution of tetrahydrofuran / formic acid (THF-FA; 100 / 5 vol / vol ratio) and filtered through an Acrodisc CR13mm 0.45 pm PTFE filter. The molecular weight distribution of the polymer is determined by size exclusion chromatography (SEC). Analysis is performed using an Agilent 1200 series HPLC system equipped with degasser, pump, autosampler, and UV-Vis and Wyatt T-rEX refractive index detectors operating at 35°C. The system contains is equipped with Shodex KF-805L and KF807L columns (packed with 10 pm and 18 pm particles and with ID length of 8 x 300 mm). The sample injection volume is 100 pL and the mobile phase is 100 / 5 vol / vol THF-FA at a flow rate of 1.0 mL / min. The system is calibrated using narrow-dispersity polystyrene standards ranging from Mp = 580 Da to Mp = 6.5 million Da obtained from Agilent Corporation. Data is collected using ASTRA 7 software and processed using ASTRA 8 software. The mass of polymer recovered is calculated based on polymer peak areas, using the refractive index detector response, RI detector calibration, and an estimated dn / dc = 0.084 mL / g. Insoluble polymers are not recovered, and so comparing the mass of polymer recovered to the 1 mg / mL mass of polymer that was mixed with the injected sample shows the percent of polymer that was soluble in the solvent. Note: This system delivers relative molecular weight data based on the standards used in calibration, rather than absolute molecular weight data.

[0170] Mortar Preparation for Testing

[0171] Mortars arc made for testing using the following generalized procedure.

[0172] 64.7 g sand, 35.0 g cement and additives are mixed to create a dry mix. If PCE copolymers are added, they are added to the dry-mx as spray-dried powders. Water is added to this dry mix to prepare a fresh mortar paste for application tests. The quantity of additives and water in the fluid mixture are selected so that the final wet mix contains (1) the desired amount of additives, and (2) a roughly 0.22 ratio of water to dry mix in the mortar.

[0173] A wet mix mortar is prepared as follows, except as specifically noted in specific test methods:

[0174] 1. Water is added to the dry mix:

[0175] 2. The sample is mixed for 30 to 60 seconds, until the wet mix is smooth and homogeneous with no lumps;

[0176] 3. The sample is allowed to rest for 3 minutes;

[0177] 4. The sample is mixed for 1 minute;

[0178] 5. The sample is allowed to rest for 4.5 minutes; and

[0179] 6. The sample is mixed for 30 seconds

[0180] Water Retention Test

[0181] Mortar is prepared as described previously. An aluminum ring is placed in the center of a preweighed circular filter paper circle on a flat non-absorbent surface. The ring has an inner diameter of 55 mm and a depth of 10 mm. The filter paper is Whatman grade 2294 filter paper with a diameter of 110 mm and a base weight of 556 g / m2. The ring is completely filled with a sample of the mortar; the weight of the sample is -55 to 65 g. The sample is allowed to rest for 30 minutes. The filter paper is removed and weighed to determine the water it has taken up, and the weight of water in the filter paper is subtracted from the initial amount of water in the mortar to obtain the water retention value.

[0182] Mortar Compressibility Test

[0183] Mortar is prepared as described previously, except in Step 5 the mortar is rested for 7 minutes, and Step 6 is omitted.

[0184] About 100 g of the mortar sample is applied to an acrylic glass plate using a * in. bylA in. notched trowel kept maintained at a 60° incline angle to the substrate. After trowelling twice, the mortar is let dry for 10 minutes and then covered using a 10 cm x 10 cm glass plate. A weight of 2.21 kg is immediately placed on the plate for 30 seconds. An image of compressed mortar is taken under a light box to quantify the mortar spread area and to determine compressibility.

[0185] Examples

[0186] The following examples illustrate specific embodiments of the invention, but do not limit the broadest scope of the invention.

[0187] The materials in Table 1 are used for the Examples:

[0188] Table 1

[0189] Synthesis of PCE 1 - PCE5 (High and Low Molecular Weight PCE)

[0190] The monomers listed in Table 2 are emulsion polymerized according to the following process: SLS (12.60 g of 28 wt% aqueous solution) and water (579.48 g) are charged into a 3 L, 4-neck round bottom flask equipped with a water condenser, overhead stirrer and a thermocouple, placed under nitrogen and heated to 88 °C.

[0191] A monomer emulsion is prepared by mixing together SLS (8.40 g, 28 wt% aqueous solution) and water (195 g) in a glass jar at ambient temperature. The desired monomers as shown in Table 2 arc added in the following order:

[0192] • (meth) acrylate monomer, • PEG Monomers,

[0193] • methacrylic acid monomer (MAA) containing dissolved MMP (if any).

[0194] The weight ratio of monomers for each example is selected to reflect the proportions shown in Table 2, and the total mass of monomers is selected to provide a final PCE copolymer dispersion having the solids content in Table 2. A 41.8 g portion of the monomer emulsion is added to the round bottom flask while stirring. Immediately after the monomer emulsion is added, a mixture of APS initiator (0.53 g in 11.25 g water) is added to the kettle, followed by a water rinse (3.75 g). At the exotherm peak, a solution of aqueous APS (0.23 g in 45 g of water) and the remainder of the monomer emulsions are added to the round bottom flask over 1.5 hours while the contents are maintained at 85 °C. After 1.5 hours, the monomer emulsion and APS vessels and feed lines are rinsed with water, and the reaction mixture is stirred for 5 min at 85 °C. An aqueous solution of APS (0.19 g in 48.875 g of water) is added over 15 min. The contents are cooled to 75 °C, and dilution water (15 g) was added.

[0195] Cooling is continued to 30 °C, and remaining free monomer in the round bottom flask is chased during cooling by addition of 0.15% active ferrous sulfate heptahydrate (2.74 g), followed by addition of 70% aqueous t-butyl hydroperoxide (0.3 g diluted in 9.38g water) over 15 minutes and rinsed with water (1.988 g), concurrent with addition of isoascorbic acid (0.41 g in 9.38 g water) over 15 minutes, and rinsed with additional water (1.988 g). Then the addition of t-butyl hydroperoxide and isoascorbic acid additions were repeated, as described previously.

[0196] The process yields an aqueous dispersion that contains particles of PCE copolymer suspended in an aqueous medium. The aqueous dispersion is filtered successively through 100 mesh and 325 mesh screens. The approximate solids content of the aqueous dispersion is shown in Table 2. The aqueous dispersion has a pH of 2.5 to 4.

[0197] Samples of dispersions of PCE1 to PCE5 are spray dried to produce PCE copolymer powder. The aqueous dispersions are diluted to 15-20 wt% solids. The dilute dispersion is spray-dried using a GEA Mobile Miner spray dryer equipped with a two-fluid nozzle atomizer. The inlet and outlet temperatures are set at 120-125°C and 55-65°C, respectively. The nitrogen (N?) pressure to the nozzle is set at 1 bar with 50% flow rate, equivalent to 6 kg / hr of air flow. The dilute aqueous dispersion is introduced into the spray dryer by a peristaltic pump. The water content in the atomized droplet is rapidly vaporized by contact with hot N2 flow at the inlet temperature. The dried powder is then cooled to the outlet temperature. A cyclone in the spray dryer separates the dried polymer powder from the N2 flow in the cyclone. Residual powder is filtered before ventilation.

[0198] Samples of dispersions of PCE1 to PCE5 are freeze-dried to produce PCE copolymer powder. Each dispersion is placed in a - -20°C freezer for 2 days and then placing them on a LABCONCO FreeZone 4.5L -50 °C instrument for 3 days with the vacuum set to 0.01 Torr and the condenser set to - 50°C. Samples of each PCE copolymer powder are hydrolyzed and molecular weight profile of the HPP is measured by aqueous SEC according to the method given in the Test Methods. Results are shown in Table 2.

[0199] Table 2

[0200] PCE1-PCE5 are mixed with each other and with cellulose ether (Cel Eth 1) to make the mixtures shown in Table 3. The mixtures in IE3a to IE10 are bimodal PCE copolymers.

[0201] Synthesis of PCE 6 (One-pot Bimodal Molecular Weight PCE)

[0202] SLS (8.4 g, 28 wt% aqueous solution) and water (386.25 g) are charged into a 2-L, 4-neck round bottom flask equipped with a water condenser, overhead stirrer and a thermocouple, placed under nitrogen and heated to 88°C.

[0203] SLS (5.60 g, 28 wt% aqueous solution) and water (203.875 g) are stirred together in a glass jar at ambient temperature as the aqueous carrier for the monomer emulsions. Two monomer emulsions (MEI and ME2) are prepared.

[0204] MEI is prepared by adding, in the following order:

[0205] • 50 wt% EA monomer,

[0206] • 13 wt% MPEGMA500 monomer,

[0207] • 37 wt% methacrylic acid monomer.

[0208] ME2 is prepared by adding, in the following order:

[0209] • 49 wt% EA monomer, with 1 wt% MMP CTA dissolved into the EA monomer prior to addition.

[0210] • 13 wt% MPEGMA500 monomer,

[0211] • 37 wt% methacrylic acid monomer.

[0212] The organic content of the monomer emulsions is 70 wt%. MEI makes up 70 wt% of the monomer emulsions and ME2 makes up 30 wt% of the monomer emulsions.

[0213] A portion of MEI (27.45 g) is taken from MEI and added to the kettle to seed the process. Immediately after the 27.45 g MEI is added, a mixture of APS initiator (0.38 g in 7.50 g water) is added to the kettle, followed by a water rinse (2.5 g). After the exotherm peak, a solution of aqueous APS (0.15 g in 30 g of water) and the monomer emulsions (MEI is fed to completion, then ME2 is started to feed to reactor and fed to completion) are gradually added to the round bottom flask over 1.5 hours while the contents are maintained at 85 °C. After 1.5 hours, the monomer emulsion and APS vessels and feed lines are rinsed with water, and the reaction mixture is stirred for 5 min at 85 °C. An aqueous solution of APS (0.13 g in 32.5 g of water) is added over 15 min. The contents are cooled to 75 °C, and water (10.0 g) was added.

[0214] Cooling is continued to 30 °C, and remaining free monomer in the round bottom flask is chased during cooling by addition of 0.15% active ferrous sulfate heptahydrate (1.83 g), followed by addition of 70% aqueous t-butyl hydroperoxide (0.2 g diluted in 6.2 g water) over 15 minutes and rinsed with water (1.25 g), concurrent with addition of isoascorbic acid (0.28 g in 6.25 g water) over 15 minutes, and rinsed with additional water (1.25 g). Then the addition of t-butylhydroperoxide and isoascorbic acid additions is repeated once, as described previously.

[0215] The reaction process yields an aqueous dispersion that contains particles of bimodal PCE copolymer (PCE6) suspended in an aqueous medium. The aqueous dispersion is filtered successively through 100 mesh and 325 mesh screens. The approximate solids content of the aqueous dispersion is 31 wt%. The aqueous dispersion has a pH of 2.5 to 3.5.

[0216] The aqueous dispersion is spray dried as described for PCE1-PCE5, and a powdered sample of PCE 6 is recovered. A sample of the PCE 6 powder is hydrolyzed, and the molecular weight profile of the HPP is measured by aqueous SEC according to the method given in the Test Methods. Results are shown in Table 2.

[0217] A sample of the PCE 6 powder is dissolved in a mixture of tetrahydrofuran and formic acid, and its molecular weight is measured as set out in Test Methods. The mass recovery is 79.2 wt%. The number average molecular weight for the portion recovered is 38.3 kg / mol. The weight average molecular weight for the portion recovered is 1757 kg / mol. The dispersity for the portion recovered is 46.0.

[0218] Use in Mortar

[0219] Mortars are made for testing using the procedures in the Test Methods. The additives and their proportions in each mortar sample are shown in Table 3. The mortars are tested for water retention and compressibility. The compressibility test shows the workability of the mortar. The results are shown in Table 3. Table 3

[0220] Inventive examples IE1 to IE 10 use multimodal PCE copolymer; they all have 95% or better water retention and compressibility from 68% to 100%. Comparative examples CE2 to CE 8 use unimodal PCE copolymer; they have viscosity too low or too high to be compressible, and several have water retention well below 95%. Comparative example CE1 has good water retention and adequate compressibility, but uses a full 0.3 wt% cellulose ether.

Claims

CLAIMS:

1. A multimodal poly (carboxylate ether) (“PCE”) copolymer that comprises repeating units derived from:(a) from 10 to 60 weight percent of (meth)acrylic acid monomers;(b) from 30 to 70 weight percent of alkyl (meth)acrylate monomers wherein the alkyl moiety comprises on average from 1 to 3.5 carbon atoms; and(c) from 5 to 40 weight percent of PEG monomers, which each independently contain:(i) a (meth) acrylate moiety linked by an ester linkage to(ii) a polyethylene glycol moiety that contains on average more than 1 ethylene oxide unit, and(iii) an end moiety linked to the polyethylene glycol moiety at the opposite end from the (meth)acrylate moiety, which is selected from hydrogen or an alkyl moiety; and(d) from 0 to 20 weight percent other unsaturated monomers, wherein (i) the weight percentages are based on the total weight of the PCE copolymer, (ii) the PCE copolymer comprises an acidic polymer backbone linked by ester linkages to a plurality of pendant polyethylene glycol side chains; and (iii) hydrolysis of the ester linkages in the PCE copolymer produces a poly(carboxylic acid) polymer (called a “hydrolysis product polymer” or “HPP”), which has a multimodal molecular weight distribution.

2. The PCE copolymer of Claim 1 wherein the HPP comprises (1) from 20 to 95 wt% of the HMW component which has a weight average molecular weight (Mw) above 200 kg / mol, and (2) from 5 to 80 wt% of the LMW component which has a weight average molecular weight (Mw) below 200 kg / mol.

3. The PCE copolymer of Claim 2 wherein the HPP comprises from 45 to 95 wt% of the HMW component and from 5 to 55 wt% of the LMW component.

4. The PCE copolymer of Clam 2 wherein (1) the weight average molecular weight (M„) of the wherein the HMW component of HPP is at least 300 kg / mol, and (2) the weight average molecular weight (M„) of the LMW component of HPP is at most 100 kg / mol.

5. The PCE copolymer of Clam 2 wherein (1) the weight average molecular weight (Mw) of the HMW component of the HPP is from 350 kg / mol to 1500 kg / mol, and (2) the weight average molecular weight (Mw) of the LMW component of the HPP is from 10 kg / mol to 80 kg / mol.

6. The PCE copolymer of Claim 2 wherein the dispersity (Mw / Mn) of the HPP is at least 5.0.

7. The PCE copolymer of Claim 2 wherein:(a) the weight average molecular weight (Mw) of the HMW component of the HPP is from 350 kg / mol to 1500 kg / mol, and(b) the weight average molecular weight (Mw) of the LMW component of the HPP is from10 kg / mol to 80 kg / mol; and(c) the dispersity (Mw / Mn) of the HPP is at least 5.0.

8. The PCE copolymer of any one of Claims 1 through 7 which meets Formula 2:wherein:(a) each R is independently an alkyl group comprising on average from 1 to 3.5 carbon atoms:(b) each R1is independently hydrogen or an alkyl group selected such that R1comprises on average less than 2 carbon atoms;(c) each R2is independently hydrogen or an alkyl group;(d) -(CHR3-CH2O)n- is a polyethylene glycol moiety, as previously described, comprising n repeating alkylene oxide units;(e) each R3is independently hydrogen or a lower alkyl group;(f) each M is independently a hydroxyl moiety, an amide moiety, an alkyl amide moiety, a nitrile moiety, a halide, an acetate moiety, an organosulfonate moiety or an organophosphate moiety;(g) x represents a number of repeating units derived from (mcth)acrylic acid monomer;(h) y represents a number of repeating units derived from alkyl (meth)acrylate monomer;(i) z represents a number of repeating units derived from PEG monomer;(j) m represents a number of repeating units derived from other monomers; and(k) terminal groups on the polymer backbone are not shown.

9. The PCE copolymer of Claim 8 which is a random copolymer.

10. The PCE copolymer of Claim 9 wherein:(a) each R comprises on average from 1.5 to 2.5 carbon atoms;(b) each R1comprises on average at most 1.2 carbon atoms;(c) each R3comprises on average from 0.0 to 0.2 carbon atoms;(d) x corresponds to from 25 to 45 weight percent of repeating units derived from (meth)acrylic acid monomers;(e) y corresponds to from 34 to 55 weight percent of repeating units derived from alkyl ( eth jacry late monomers;(f) z corresponds to from 10 to 38 weight percent of repeating units derived from PEG monomers;(g) m corresponds to from 0 to 2 weight percent of repeating units derived from other unsaturated monomers;(h) either (1) n is on average from 4 to 15, and R2comprises from 0 to less than 8 carbon atoms, or (2) n is on average at least 15, and R2comprises from at least 8 carbon atoms.1 1. An aqueous dispersion comprising polymer particles suspended in an aqueous medium wherein the polymer particles comprise the PCE copolymer of Claim 8.

12. The aqueous dispersion of Claim 11 wherein the pH of the aqueous dispersion is from 2 to 5.5.

13. A cementitious mixture comprising dry components (a)-(c):(a) filler;(b) cement;(c) at least 0.05 weight percent of the PCE copolymer of Claim 8, based on the weight of the cement, and optionally further containing water.

14. The cementitious mixture of Claim 13 which is a wet mix containing from 20 to 40 weight percent water, based on the weight of the dry components.

15. A process to make a poly(carboxylate ether) (PCE) copolymer comprising the step of performing an emulsion polymerization of:(a) from 10 to 60 wt% of (meth)acrylic acid monomers;(b) from 30 to 70 wt% or alkyl (meth)acrylate monomers wherein the alkyl moiety comprises on average from 1 to 3.5 carbon atoms; and(c) from 5 to 40 wt% of PEG monomers, which each independently contain:(!) a (meth) acrylate moiety linked by an ester linkage to(ii) a polyethylene glycol moiety that contains on average more than 1 ethylene oxide unit, and(iii) an end moiety linked to the polyethylene glycol moiety at the opposite end from the (meth)acrylate moiety, which is selected from hydrogen or an alkyl moiety; and(d) at most 20 wt% of other unsaturated monomers, in an aqueous medium that contains an emulsifying quantity of surfactant and a polymerization initiator, wherein (i) weight percentages are based on the total weight of monomers; (ii) the emulsion polymerization is carried out in at least two stages; and (iii) at least one stage of the polymerization is carried out in the presence of at most 0.1 wt% of a chain transfer agent, and (ii) at least one stage of the polymerization is carried out in the presence of at least 0.4 wt% of a chain transfer agent.

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