HOLLOW POLYMER COMPOSITION

Abstract

Provided is method of making a hollow polymer composition, comprising the steps of (a) providing an aqueous dispersion comprising (i) hollow polymer particles, wherein the hollow polymer particles comprise polymerized units of one or more multivinyl monomer, (ii) water, and (iii) one or more organic alcohol, and (b) removing water from the aqueous dispersion to form a dry composition comprising the hollow polymer particles and the alcohol, wherein either water is absent from the dry composition or else water is present in the dry composition in an amount such that the weight ratio of water to hollow polymer particles is 0.2:1 or less.

Also provided are dry compositions that could be made by such a method, and non-aqueous dispersions of such dry compositions.

Claims

1. A method of making a hollow polymer composition, comprising the steps of (a) providing an aqueous dispersion comprising (i) 1% to 40% hollow polymer particles, by weight based on the weight of the aqueous dispersion, wherein the hollow polymer particles comprise 0.01% to 20% polymerized units of one or more multivinyl monomer, by weight based on the weight of the hollow polymer particles, (ii) 40% to 98.9% water, by weight based on the weight of the aqueous dispersion, and (iii) 0.1% to 20% one or more organic alcohol, by weight based on the weight of the aqueous dispersion, and (b) removing water from the aqueous dispersion to form a dry composition comprising the hollow polymer particles and the alcohol, wherein either water is absent from the dry composition or else water is present in the dry composition in an amount such that the weight ratio of water to hollow polymer particles is 0.2:1 or less.

2. The method of claim 1, further comprising the step (c) after step (b), forming a dispersion of the dry composition in a non-aqueous medium.

3. A hollow polymer composition comprising hollow polymer particles and one or more organic alcohol, wherein the weight ratio of the organic alcohol to the hollow polymer particles is 0.01:1 to 1:1, wherein the hollow polymer particles comprise 0.01 to 20% polymerized units of one or more multivinyl monomer, by weight based on the weight of the hollow polymer particles, wherein water is optionally present in the hollow polymer composition in an amount such that the weight ratio of the water to the hollow polymer particles is 0:1 to 0.05:1.

4. The hollow polymer composition of claim 3, wherein the polyol is selected from the group consisting of polyols having molecular weight of 200 or less, cyclodextrins, and mixtures thereof.

5. The hollow polymer composition of claim 3, wherein the polyol is glycerol.

6. The hollow polymer composition of claim 3, wherein the multivinyl monomer is divinyl benzene.

7. The hollow polymer composition of claim 3, wherein the hollow polymer particle comprises a core polymer and a shell polymer, wherein the weight ratio of the shell polymer to the core polymer is from 8:1 to 15:1.

8. A non-aqueous dispersion comprising one or more organic alcohol and hollow polymer particles dispersed in a non-aqueous medium.

9. The non-aqueous dispersion of claim 8 additionally comprising mineral pigment and binder polymer.

10. The non-aqueous dispersion of claim 8, wherein the non-aqueous medium comprises ethanol.

Description

EXAMPLE 1: SOLVENT RESISTANCE OF COATINGS

[0098] To test the ability of hollow polymer particles to perform in the presence of solvent, the following test was performed. A water-borne coating containing a hollow polymer particle was made and then applied to a substrate and dried. Then solvent was applied to the surface of the dried coating. If the coating became transparent when the solvent was applied, it was considered that the solvent caused the hollow polymer particle to collapse, thereby ruining the formerly-hollow polymer particle's ability to scatter light. That hollow polymer particle was deemed unsuitable for use with solvent. In contrast, if a dried water-borne coating containing a different hollow polymer particle remained opaque after exposure to solvent, that hollow polymer particle was deemed suitable for use with solvent.

[0099] The water-borne coatings used for this test and the results were as follows. The amounts of the ingredients are parts by weight of the latexes as supplied. The viscosity of each coating was adjusted by addition of alkali swellable emulsion to achieve viscosity of 30 to 35 seconds at 23 C. in a DIN#4 cup.

TABLE-US-00001 Example 1-1C Example 1-2 HP-1 85 HP-2C 85 Binder-1 15 15 isopropanol opaque opaque ethyl acetate transparent opaque

[0100] The coating that employs HP-2C turns transparent on exposure to ethyl acetate. Therefore HP-2C, which contains no polymerized units of multivinyl monomer, is not suitable as the hollow polymer particles of the present invention.

EXAMPLE 2: DRYING AND RE-DISPERSING

[0101] Samples of HP-1 were dried in a laboratory drier, which makes a thin layer of aqueous latex HP-1 on a substrate and then exposes the layer to heated air at 110 C. When the layer is dry, it is lightly ground with glass beads to produce powder. The powder was then mixed with ethanol and subjected to a grinding process. Grinding was conducted in a Mastersizer particle size analyzer from Malvern Instruments Limited, which has a propeller to agitate the liquid sample and apparatus to circulate some of the liquid sample through a laser light scattering device to measure the particle size distribution. Sufficient powder was added to ethanol to give 13% obscuration of the measuring laser beam at the beginning of the test, as suggested by the instrument software. The mixture thus formed was then agitated in the instrument for 20 minutes, as the instrument continued to measure the particle size distribution by laser light scattering. Typically, in samples that dispersed well in the ethanol, the obscuration at 20 minutes was greater than the 13% obscuration at the beginning of the test.

[0102] Dv50 is measured after 20 minutes of the grinding process. It is considered that large values of Dv50 shows that the powder remains agglomerated in the ethanol; that is, large Dv50 shows that the powder fails to separate into the original hollow polymer particles. Perfect re-dispersion of the hollow polymer particles would yield a Dv50 of 0.48 m. After 20 minutes of grinding, Dv50 of 5 m or lower is considered desirable. It is also desirable that the additive cause a low value of Dv50 when the additive is used in an amount such that the weight ratio of the additive to hollow polymer particles is 0.3:1 or less.

[0103] Further, it is desirable that Dv90 is low after 20 minutes of the grinding process. One possible outcome of the grinding process is a dispersion in which many particles of small diameter are present, but a few extremely large agglomerates are also present. This is an undesirable outcome, because even a small number of large agglomerates can ruin the appearance of a coating. The presence of the many small-diameter particles can cause a relatively low value of Dv50, but the presence of the large agglomerates will cause Dv90 to be relatively high.

[0104] Various compounds were added to HP-1 prior to drying. The additives and the results after drying and grinding in ethanol are shown below. Examples with suffix C are comparative examples.

TABLE-US-00002 Amount of Dv50 after Dv90 after Example Additive additive.sup.(1) 20 min (m) 20 min (m) 1C.sup.(2) none 0 33.0 63.2 2C none 0 1.8 28.6 3C none 0 5.0 49.8 4C PCC 45 12.0 65.2 5C GCC 43 26.0 158.2 6C TiO2 43 7.6 66.8 7C BaSulf 43 2.7 24.5 8C BaSulf 50 3.8 44.9 9C Kaolin 20 3.7 15.1 10 HPMC 1.5 25.7 195.0 11 D-fructose 1 70.9 198.2 12 D-fructose 5 15.6 122.5 13 D-fructose 10 39.5 158.8 14 D-glucose 1 52.5 176.7 15 D-glucose 5 88.6 208.6 16 D-glucose 10 30.2 204.3 17 PVOH 5 6.8 23.2 18 PVOH 10 4.5 33.6 19 PVOH 20 6.4 74.9 20 a-CD 0.1 3.9 18.4 21 a-CD 1 7.6 46.1 22 a-CD 3 1.0 4.3 23 a-CD 10 5.0 48.5 24 glycerol.sup.(3) 1 3.6 14.0 25 glycerol.sup.(3) 5 2.5 15.7 26 glycerol.sup.(3) 8 0.9 2.8 Note: .sup.(1)weight of additive as supplied divided by the total weight of HP-1, expressed as a percentage. Note: .sup.(2)spray dried in a laboratory-scale spray drier. All others were dried in a lab drier as described above. Note: .sup.(3)glycerol was supplied as a solution of glycerol (85% by weight) in water (15% by weight).

[0105] Glycerol performed the best: with only 1% to 8% use level, glycerol achieved low values of Dv50 and Dv90 in the samples after 20 minutes of grinding in ethanol. Also performing well was alpha-cyclodextrin, which performed almost as well at 10% use level and below. PVOH also performed well, though the use level of PVOH was somewhat higher. Glycerol, alpha-cyclodextrin, and PVOH are all polyols. Other polyols tested, D-fructose, D-glucose, and HPMC, showed some beneficial effect on particle size but not as good an effect as shown by the polyols glycerol and alpha-cyclodextrin.

[0106] Comparative additives PCC, GCC, TiO2, barium sulfate, and kaolin, showed some beneficial effect on particle size but at very high use levels. The comparative samples with no additive showed unacceptably high values of Dv90.