Patent Description:
Blends of all-acrylic polymer particles and siloxane-based polymer particles, on the other hand, suffer from phase separation upon drying, which is manifested by the formation of optically hazy films as well as macrophase separation and substrate de-wetting. Accordingly, it would be advantageous to prepare aqueous dispersions of siloxane-acrylate hybrid copolymer particles at high solid levels with an acceptably low levels of gel formation and unreacted monomer and a high incorporation of silicon.

The present invention, as defined by the appending claims, addresses a need in the art by providing, in one aspect, a composition comprising an aqueous dispersion of polymer particles having a z-average particle size in the range of from <NUM> to <NUM> and comprising, based on the weight of the polymer particles, a) from <NUM> to <NUM> weight percent structural units of an acrylate monomer; b) from <NUM> to <NUM> weight percent structural units of an acid monomer; and c) from <NUM> to <NUM> weight percent structural units of a siloxane acrylate monomer having the following formula I:
<CHM>.

In a second aspect, the present invention is a method of preparing an aqueous dispersion of acrylate-siloxane copolymer particles comprising the steps of:.

The composition of the present invention addresses a need by providing a dispersion of siloxane-acrylate hybrid copolymer particles with a) a relatively high degree of silicon incorporation; b) a high solids content; and c) low residual monomer.

In a first aspect, the present invention is a composition comprising an aqueous dispersion of polymer particles having a z-average particle size in the range of from <NUM> to <NUM> and comprising, based on the weight of the polymer particles, a) from <NUM> to <NUM> weight percent structural units of an acrylate monomer; b) from <NUM> to <NUM> weight percent structural units of an acid monomer; and c) from <NUM> to <NUM> weight percent structural units of a siloxane acrylate monomer having the following formula I:
<CHM>.

As used herein, the term "structural unit" of a recited monomer refers to the remnant of the monomer after polymerization. For example, a structural unit of methyl methacrylate (MMA) is as illustrated:
<CHM>
structural unit of methyl methacrylate
where the dotted lines represent the points of attachment of the structural unit to the polymer backbone.

As used herein, the term "acrylate monomer" refers to one or more acrylate and/or methacrylate monomers. Examples of suitable acrylate monomers including MMA, n-butyl methacrylate (BMA), ethyl acrylate (EA), n-butyl acrylate (BA), and <NUM>-ethylhexyl acrylate (<NUM>-EHA). Preferably, at least <NUM>, and more preferably at least <NUM> weight percent of the acrylate monomer is a combination of MMA and BA.

The copolymer preferably also comprises from <NUM> to <NUM> weight percent, based on the weight of the copolymer, structural units of an acid monomer such as a carboxylic acid monomer, a phosphorus acid monomer, or a sulfur acid monomer. Examples of carboxylic acid monomers include acrylic acid (AA), methacrylic acid (MAA), and itaconic acid (IA), and salts thereof.

Suitable phosphorus acid monomers including phosphonates and dihydrogen phosphate esters of an alcohol in which the alcohol contains or is substituted with a polymerizable vinyl or olefinic group. Preferred dihydrogen phosphate esters are phosphates of hydroxyalkyl acrylates or methacrylates, including phosphoethyl methacrylate (PEM) and phosphopropyl methacrylates.

Examples of suitable sulfur acid monomers include sulfoethyl methacrylate, sulfopropyl methacrylate, styrene sulfonic acid, vinyl sulfonic acid, and <NUM>-acrylamido-<NUM>-methyl propanesulfonic acid (AMPS), and salts thereof.

Preferably, the copolymer comprises structural units of MMA, BA, MAA, and the siloxane acrylate monomer of formula I.

In one aspect, the weight-to-weight ratio of structural units of BA to structural units of MMA is in the range of from <NUM>:<NUM> to <NUM>:<NUM>; in another aspect, the weight-to-weight ratio of structural units of total acrylate monomer, preferably BA and MMA, to acid monomer, preferably MAA, is in the range of from <NUM>:<NUM> to <NUM>:<NUM>. In another aspect, the weight percent of structural units of the siloxane acrylate monomer, based on the weight of the polymer particles, is in the range of from <NUM> to <NUM> percent.

In another aspect, the polymer particles comprise, based on the weight of the polymer particles, preferably from <NUM>, more preferably from <NUM>, and most preferably from <NUM> weight percent of the siloxane monomer, to preferably <NUM>, more preferably to <NUM>, more preferably to <NUM>, and most preferably to <NUM> weight percent structural units of the siloxane acrylate monomer.

Preferably, the polymer particles comprise, from <NUM>, and more preferably from <NUM> weight percent silicon, to <NUM>, and preferably to <NUM> weight percent silicon, based on the weight of the polymer particles.

Preferably, the weight-to-weight ratio of structural units of the siloxane acrylate monomer to the siloxane acrylate monomer in the composition is at least <NUM>:<NUM>; more preferably <NUM>:<NUM>; and most preferably at least <NUM>:<NUM>, as determined by <NUM>H NMR spectroscopy as described herein.

Examples of monomers of formula I include:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

In another aspect the present invention is a method of preparing an aqueous dispersion of acrylate-siloxane copolymer particles preferably comprising the steps of:.

Preferably, after step <NUM>), a redox initiator package is added to the vessel; it is also preferred after step <NUM>) to neutralize the aqueous dispersion to a pH in the range of from <NUM> to <NUM>. More preferably, it is preferred after step <NUM>) to add the redox initiator package followed by neutralization.

In a more particularly preferred method, the composition of the present invention is prepared by emulsion polymerization wherein a monomer emulsion comprising the acrylate monomer, preferably a combination of BA and MMA; the acid monomer, preferably MAA; and the siloxane acrylate monomer dispersed in water are homogenized in the presence of a surfactant and preferably a chain transfer agent to produce a monomer emulsion having an average particle size in the range of from <NUM> to <NUM> as determined by optical microscopy.

The monomer emulsion and an initiator such as ammonium persulfate are then fed over a period of from <NUM> minutes to <NUM> hours into a heated reactor (typically in the range of from <NUM>° C to <NUM>) containing water and a surfactant. The reactor is held for a sufficient time to substantially complete polymerization, generally from <NUM> minutes to <NUM> hours, after which time the reactor is cooled to around <NUM>. The contents are then preferably treated with a redox pairing agent (also known as a redox initiator package) such as t-amyl hydroperoxide/isoascorbic acid and then neutralized. The polymer particles prepared by this method preferably have a z-average particle size in the range of from <NUM> to <NUM>, more preferably to <NUM>.

It has been discovered that an aqueous dispersion of polymer particles comprising structural units of an acrylate monomer and the siloxane-acrylate monomer of formula I can be achieved at a solids content in the range of from <NUM>, preferably from <NUM>, and most preferably from <NUM> weight percent, to <NUM>, preferably to <NUM>, and most preferably to <NUM> weight percent, with at least <NUM> mole percent, preferably at least <NUM> mole percent, more preferably at least <NUM> mole percent, and most preferably quantitative incorporation, as determined using <NUM>H NMR spectroscopy as described herein, of the siloxane acrylate monomer into the latex polymer particles. Consequently, the dispersion preferably comprises not greater than <NUM> ppm, more preferably not greater than <NUM> ppm, more preferably not greater than <NUM> ppm, and most preferably not greater than <NUM> ppm of residual unreacted monomer. It is also preferred that the amount of coagulum (gel) generated is not greater than <NUM> ppm, more preferably not greater than <NUM> ppm, and most preferably not greater than <NUM> ppm. Preferably, the amount of residual monomer is not greater than <NUM> ppm and the amount of gel generated is not greater than <NUM> ppm. Coagulum concentration is determined by isolating the residuum by filtration of the composition through successive stainless steel mesh screens of pore sizes <NUM> and <NUM>; thus, by inference, the coagulum has a particle size of > <NUM>.

Particle sizes were measured using a Malvern Zetasizer Nano ZS90, which measures Z-average particle size (Dz) using dynamic light scattering (DLS) at a scattering angle of <NUM>° using Zetasizer software version <NUM>. A drop of the sample dispersion was diluted using an aqueous solution of MilliQ water (<NUM> MΩ. cm at <NUM>) to achieve a particle count in the range of <NUM>-<NUM> thousand counts/s (Kcps). Particle size measurements were carried using instrument's particle sizing method and Dz was computed by the software. Dz is also known as the intensity-based harmonic mean average particle size and expressed as; <MAT>.

Here, Si is scattered intensity from particle i with diameter Di. Detailed Dz calculations are described in ISO <NUM>:<NUM> (Particle size analysis - Dynamic light scattering (DLS)).

The process to determine % incorporation of silicone monomer is as follows. A sample was diluted in water ~10X with a known mass of deionized water, placed into an LDPE centrifuge tube and spun at <NUM> for <NUM>. The supernatant was removed from the tube and the solid polymer at the bottom of the tube was rinsed copiously with deionized water. The spun-down polymer sample remaining in the centrifuge tube was dried at room temperature for <NUM>. A known mass of polymer sample was dissolved in ~<NUM>-<NUM> of CHCl<NUM> and <NUM>H NMR spectroscopy was performed using a Bruker <NUM> NMR. Spectra acquired were an average of <NUM> scans with a relaxation delay of <NUM>. The ratio of the integration value of the siloxane peak (∼<NUM>-<NUM> ppm) and the integration values of the butyl acrylate (<NUM> -<NUM> ppm, -(C=O)-CH<NUM>-) and methyl methacrylate sidechain peaks (<NUM>-<NUM> ppm, -CH<NUM>) was used to compute the composition of the sample (all chemical shifts relative to the residual protons of CDCl<NUM> at <NUM> ppm), and these values were compared to the monomer emulsion (ME) composition in order to estimate the overall % incorporation of silicone-containing monomer.

UPHLC-MS performed on a Waters Acquity® Ultra Performance Liquid Chromatography (UPLC) system equipped with a Waters Acquity® UPLC BEH-C18 (<NUM> × <NUM>) column coupled to a Waters Acquity photodiode array (PDA) detector operating over the wavelength range <NUM>-<NUM>. Standards were prepared by serial dilution of a stock solution of known concentration of monomer (~<NUM> wt%) in acetonitrile. Samples were prepared in duplicate, by the dilution of a known mass of sample in ~30X in acetonitrile, followed by agitation for ~<NUM>. Samples were then centrifuged for <NUM> at <NUM> RPM. The supernatant was removed by pipette and filtered using a <NUM> PTFE syringe filter for injection into the instrument. The injection volume of sample was <NUM>µL and the injection mode was partial-loop with a needle overfill of <NUM>µL. The instrument operated at a flow rate of <NUM>/min and column temperature of <NUM> using mobile phase (A): <NUM> wt% formic acid in H<NUM>O and mobile phase (B): <NUM> wt% formic acid in acetonitrile. The solvent gradient was programmed as follows: <NUM>/<NUM> (v/v) (A)/(B) for <NUM>, up to <NUM>/<NUM> (A)/(B) over <NUM>, held at <NUM>/<NUM> (A)/(B) for <NUM>, down to <NUM>/<NUM> (A)/(B) over <NUM>, and then held at <NUM>/<NUM> (A)/(B) for <NUM>. The LOD of the method was <NUM> ppm.

Isoprenol (<NUM>) was charged into a <NUM>-neck <NUM>-L round bottom flask equipped with a mechanical stirrer, a thermocouple, and a water-cooled condenser adapted to a N<NUM> bubbler. The unfilled space of the flask was purged with N<NUM> for <NUM>. The flask was heated and <NUM> ppm of Pt was added to the flask. <NUM>, <NUM>, <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-Heptamethyltrisiloxane (MD'M, <NUM>) was added into the flask over <NUM> to control the pot temperature in the range of <NUM>-<NUM>. The mixture was stirred for another <NUM> at <NUM>-<NUM>. FTIR spectroscopy indicated that the Si-H vibrational peak (~<NUM>-<NUM>) had completely disappeared. Volatiles were removed in vacuo at <NUM> for <NUM> at <<NUM> Hg. The crude product (<NUM>) was a brown colored liquid. Activated carbon (<NUM>) was added and the mixture was stirred for <NUM> before it was filtered through a <NUM>-µm filter membrane. A clear colorless final product (<NUM>) was collected (yield <NUM>%). <NUM>H, <NUM>C, and <NUM>Si NMR spectroscopy as well as GC-FID were used to characterize the product.

Isoprenyl MD'M alcohol (<NUM>), MMA (<NUM>) and Zr(acac)<NUM> (<NUM>) were charged into a <NUM>-L <NUM>-neck round bottom flask, fitted with an overhead stirrer, a temperature controller with over temperature protection, an overhead temperature monitor, a gas inlet tube, and a <NUM>-plate Oldershaw distillation column/distillation head with an automated reflux splitter/controller. Hydroquinone monomethyl ether (<NUM>) and <NUM>-hydroxy-TEMPO (<NUM>) were then added to the reaction mixture to achieve <NUM> ppm and <NUM> ppm, respectively, in the final product. A gas purge (<NUM>% O<NUM> in N<NUM>) was initiated, and stirring was commenced. A sample of pot contents was taken for NMR spectroscopic analysis. The flask pressure was reduced to <NUM> Hg and the pot contents were heated slowly to between <NUM> -<NUM> and refluxed for about <NUM>. The vapor temperature stabilized between <NUM> - <NUM>. An MMA-methanol azeotrope was distilled off at a vapor temperature of <NUM>° C using a reflux ratio of <NUM>:<NUM>. The distillation was continued until the vapor temperature reached <NUM>. The contents of the flask were allowed to cool to <NUM>, whereupon an aliquot was removed for <NUM>H NMR spectroscopic analysis. Excess MMA was removed from the final monomer via distillation at pot temperature of <NUM> and <NUM> Hg. The final product was an amber colored low viscosity liquid (<NUM>).

Deionized water (<NUM>) and Polystep B-<NUM>-N sodium lauryl sulfate (SLS, <NUM>, <NUM>% in water) were added to a <NUM>-mL, <NUM>-neck round bottom flask outfitted with a condenser, overhead stirrer, and thermocouple. The contents of the reactor were stirred at <NUM> rpm and heated to <NUM> under N<NUM>. In a separate vessel, a monomer emulsion (ME) containing deionized water (<NUM>), SLS (<NUM>, <NUM>% in water), BA (<NUM>), MMA (<NUM>), MAA (<NUM>), MM'-ALMA (<NUM>), n-dodecyl mercaptan (n-DDM, <NUM>), ammonium hydroxide solution (<NUM>, <NUM>% active in water), and sodium acetate (<NUM>) was prepared using an overhead mixer followed by treatment with a handheld homogenizer (Tissue Tearor, Model <NUM>, Biospec Products Inc. ) for <NUM> to produce an ME with average droplet size of ~<NUM>-<NUM>, as determined by optical microscopy. A portion of the ME (<NUM>) was added to the reactor with rinsing (<NUM> water), followed by the addition of ammonium persulfate (<NUM>) with rinsing (<NUM> water). The remainder of the ME and a solution of ammonium persulfate (<NUM> in <NUM> water) were fed simultaneously into the reactor over <NUM>, at a temperature of <NUM>-<NUM>° C. Upon completion of the feeds, the reactor was then held for an additional <NUM> at <NUM>-<NUM>° C. The reactor was then cooled to <NUM>° C and separate solutions of (i) Luperox TAH <NUM> tert-amyl hydroperoxide (t-AHP, <NUM> wt% active in water), SLS (<NUM>, <NUM>% active in water), and deionized water (<NUM>) and (ii) isoascorbic acid (IAA, <NUM>), VERSENE™ (EDTA, A Trademark of Dow, Inc. or its Affiliates; <NUM>, <NUM>% active in water), and iron (II) sulfate solution (<NUM>, <NUM>% active in water) were added to the reactor. The reactor was then cooled to room temperature, whereupon ammonium hydroxide solution (<NUM>% active in water) was added dropwise to adjust the pH to ~<NUM>. The aqueous dispersion was filtered successively through stainless steel mesh screens of pore sizes <NUM> and <NUM>. The final aqueous particle dispersion had a solids of <NUM>%, a z-average particle size of <NUM>, <NUM> ppm of coagulum, and quantitative incorporation of MM'-ALMA monomer as determined <NUM>H NMR spectroscopy. The level of residual MM'-ALMA in the sample was <<NUM> ppm as determined by UHPLC.

Example <NUM> was repeated, except that the monomer emulsion was prepared by combining deionized water (<NUM>), SLS (<NUM>, <NUM>% active in water), BA (<NUM>), MMA (<NUM>), MAA (<NUM>), MM'-1EO-ALMA (<NUM>), n-DDM (<NUM>), ammonium hydroxide solution (<NUM>, <NUM>% active in water), and sodium acetate (<NUM>). The final aqueous particle dispersion had a solids of <NUM>%, z-average particle size of <NUM>, <NUM> ppm of coagulum, and quantitative incorporation of MM'-1EO-ALMA monomer as determined by <NUM>H NMR spectroscopy. The level of residual MM'-1EO-ALMA in the sample was found to be <<NUM> ppm by UHPLC.

Example <NUM> was repeated, but the monomer emulsion was prepared by combining deionized water (<NUM>), SLS (<NUM>, <NUM>% active in water), BA (<NUM>), MMA (<NUM>), MAA (<NUM>), MD'M-ALMA (<NUM>), n-DDM (<NUM>), ammonium hydroxide solution (<NUM>, <NUM>% active in water), and sodium acetate (<NUM>). The final aqueous particle dispersion had a solids of <NUM>%, z-average particle size of <NUM>, <NUM> ppm of coagulum, and quantitative incorporation of MD'M-ALMA monomer as determined by <NUM>H NMR spectroscopy. The level of residual MD'M-ALMA in the sample was found to be <<NUM> ppm by UHPLC.

Example <NUM> was repeated, but the monomer emulsion was prepared by combining deionized water (<NUM>), SLS (<NUM>, <NUM>% active in water), BA (<NUM>), MMA(<NUM>), MAA (<NUM>), MD'M-IPMA (<NUM>), n-DDM (<NUM>), ammonium hydroxide solution (<NUM>, <NUM>% active in water), and sodium acetate (<NUM>). The final aqueous particle dispersion had a solids of <NUM>%, z-average particle size of <NUM>, <NUM> ppm of coagulum, and quantitative incorporation of MD'M-IPMA monomer as determined by <NUM>H NMR spectroscopy. The level of residual MD'M-IPMA in the sample was found to be <<NUM> ppm by UHPLC.

Example <NUM> was repeated, but the monomer emulsion was prepared by combining deionized water (<NUM>), SLS (<NUM>, <NUM>% active in water), BA (<NUM>), MMA (<NUM>), MAA (<NUM>), M3T'-ALMA (<NUM>), n-DDM (<NUM>), ammonium hydroxide solution (<NUM>, <NUM>% active in water), and sodium acetate (<NUM>). The final aqueous particle dispersion had a solids of <NUM>%, z-average particle size of <NUM>, <NUM> ppm of coagulum, and <NUM>% incorporation of M3T'-ALMA monomer as determined by <NUM>H NMR spectroscopy. The level of residual M3T'-ALMA in the sample was <<NUM> ppm as determined by UHPLC.

Example <NUM> was repeated, but the monomer emulsion was prepared by combining deionized water (<NUM>), SLS (<NUM>, <NUM>% active in water), BA (<NUM>), MMA (<NUM>), MAA (<NUM>), Butyl-MD5M'-ALMA (<NUM>), n-DDM (<NUM>), ammonium hydroxide solution (<NUM>, <NUM>% active in water), and sodium acetate (<NUM>). The final aqueous particle dispersion had a solids of <NUM>%, z-average particle size of <NUM> <NUM>,<NUM> ppm of coagulum, and <NUM>% incorporation of butyl- Butyl-MD5M'-ALMA monomer as determined by <NUM>H NMR spectroscopy. The level of residual Butyl-MD5M'-ALMA in the sample was <NUM> ppm as determined by UHPLC.

The process to prepare an aqueous dispersion of hybrid particles as described in <NPL> was reproduced. The synthesis was carried out using a <NUM>-mL, <NUM>-neck round bottom flask outfitted with a condenser, overhead stirrer, and thermocouple. Deionized water (<NUM>) and SLS (<NUM>, <NUM>% in water), TRITON™ X-<NUM> Polyethylene glycol t-octylphenyl ether (A Trademark of Dow, Inc. or its affiliates, <NUM>), and sodium bicarbonate (NaHCO<NUM>; <NUM>) were added to the flask. The contents of the reactor were stirred at <NUM> rpm and heated to <NUM> under N<NUM>. In a separate vessel, an ME containing deionized water (<NUM>), SLS (<NUM>, <NUM>% in water), X-<NUM> (<NUM>), BA (BA; <NUM>), MMA (<NUM>), styrene (<NUM>), and AA (<NUM>) was prepared using an overhead mixer. A portion of the ME (<NUM>) was added to the reactor, followed by the addition of ammonium persulfate (<NUM>) in deionized water (<NUM>), and the reactor temperature was increased to <NUM> over <NUM>. The remainder of the ME and a solution of ammonium persulfate (<NUM> in <NUM> water) were fed simultaneously into the reactor over <NUM> and <NUM>, respectively, at a temperature of <NUM>-<NUM> (i.e., the ammonium persulfate feed continued for <NUM> past the completion of the ME feed). At the <NUM>-h mark of feeds, MD'M-ALMA was added to the reactor (<NUM>). Upon completion of the ammonium persulfate feed, the reactor was then held for an additional <NUM> at <NUM>. The reactor was then cooled to room temperature and ammonium hydroxide solution (<NUM>% active in water) was added dropwise to raise the pH to ~<NUM>. The aqueous dispersion was filtered successively through stainless steel mesh screens of pore sizes of <NUM>. The final aqueous particle dispersion had a solids of <NUM>% (theoretical = <NUM>%), z-average particle size of <NUM>, <NUM> ppm of coagulum, and <NUM>% incorporation of MD'M-ALMA monomer as determined by <NUM>H NMR spectroscopy. The level of residual MD'M-ALMA in the serum phase was <NUM>,<NUM> ppm as determined by UHPLC.

The process to prepare an aqueous dispersion of hybrid particles as described in <NPL> was reproduced. Deionized water (<NUM>), sodium dodecylbenzene sulfonic acid (<NUM>), and sorbitani monolaurate (<NUM>) were added to a <NUM>-mL glass reactor equipped with a condenser, overhead stirrer, and thermocouple. The reactor contents were stirred at <NUM> rpm, heated to <NUM>, and sparged with N<NUM> for <NUM>. In a separate vessel, a monomer mixture composed of MMA (<NUM>), BA (<NUM>), and MD'M-ALMA (<NUM>) was prepared. The monomer mixture and a solution of ammonium persulfate (<NUM> in <NUM> water) were fed simultaneously into the reactor over <NUM>, at a temperature of <NUM>-<NUM>. Upon completion of the feeds, the reactor was then held for an additional <NUM> at <NUM>-<NUM>. The reactor was then cooled to room temperature, whereupon ammonium hydroxide solution (<NUM>% active in water) was added dropwise to raise the pH to ~<NUM>. The aqueous dispersion was filtered successively through stainless steel mesh screens of pore sizes <NUM> and <NUM>. The final aqueous particle dispersion had a solids of <NUM>% (theoretical = <NUM>%), a z-average particle size of <NUM>, <NUM>,<NUM> ppm of coagulum, and <NUM>% incorporation of MD'M-ALMA monomer as determined by <NUM>H NMR spectroscopy. The level of residual MD'M-ALMA in the serum phase was <NUM> ppm (<NUM>% unreacted monomer, based on the weight of the monomer and the structural units of MD'M-ALMA in the polymer particles) as determined by UHPLC.

Table <NUM> illustrates the solids content, the residual monomer, and the coagulum generated for each sample.

The Examples of the present inventions all were prepared with high solids content and undetected residual monomer and/or high solids content and low generation of coagulum. Table <NUM> illustrates the percent incorporation of Si atoms into the polymer particles:.

Claim 1:
A composition comprising an aqueous dispersion of polymer particles having a z-average particle size in the range of from <NUM> to <NUM>, as determined by dynamic light scattering using the method disclosed in the description, and comprising, based on the weight of the polymer particles, a) from <NUM> to <NUM> weight percent structural units of an acrylate monomer; b) from <NUM> to <NUM> weight percent structural units of an acid monomer; and c) from <NUM> to <NUM> weight percent structural units of a siloxane acrylate monomer having the following formula I:
<CHM>
where R is H or CH<NUM>;
R<NUM> is H or CH<NUM>;
each R<NUM> is independently CH<NUM> or O-Si(CH<NUM>)<NUM>;
Y is -CH<NUM>- or -CH<NUM>CH<NUM>-; and
x is <NUM> or <NUM>;
with the proviso that when x is <NUM>, R<NUM> is H; when Y is -CH<NUM>-, R<NUM> is H; and when Y is - CH<NUM>CH<NUM>-, R<NUM> is CH<NUM> and x is <NUM>;
wherein the solids content of the polymer particles in the aqueous dispersion is in the range of <NUM> to <NUM> weight percent and a) the aqueous phase of the aqueous dispersion comprises not greater than <NUM> ppm of monomer of formula I; or b) the aqueous phase of the aqueous dispersion comprises not greater than <NUM> ppm of coagulum, wherein the amount of coagulum is determined by the method disclosed in the description.