Method for producing aqueous dispersions

Abstract

The present invention relates to a process for preparing an aqueous dispersion of polymer particles by radical aqueous emulsion polymerization and also to the use thereof in paints, paper coatings, foams, crop protection compositions, cosmetic compositions, liquid inks, or thermoplastic molding compounds.

Claims

1. A process for preparing an aqueous dispersion of polymer particles by radical aqueous emulsion polymerization, the process comprising: i) preparing an aqueous dispersion of a seed polymer by radical aqueous emulsion polymerization of an aqueous monomer emulsion comprising: a) 25.0 to 99.9 wt % of at least one nonionic, monoethylenically unsaturated monomer M1 having a water-solubility ≤50 g/L at 20° C., b) 0 to 15.0 wt % of one or more monoethylenically unsaturated monomers M2 selected from the group consisting of a monomer M2a which comprises at least one anionic or anionogenic group and a neutral monomer M2b which has a water-solubility of >50 g/L at 20° C., and a mixture thereof, c) 0.1 to 60.0 wt % of at least one polyalkylene oxide-containing substance, based on a total weight of the monomers used in said preparing i) and of the polyalkylene oxide-containing substance; ii) preparing an aqueous dispersion of a swell-seed by radical aqueous emulsion polymerization of an aqueous suspoemulsion comprising: d) 5 to 99.9 wt % of at least one nonionic, monoethylenically unsaturated monomer M3 having a water-solubility ≤50 g/L at 20° C., e) 0 to 75.0 wt % of one or more monoethylenically unsaturated monomers M4 selected from the group consisting of a monomer M4a which comprises at least one anionic or anionogenic group and a neutral monomer M4b which has a water-solubility of >50 g/L at 20° C., and a mixture thereof, and f) 0.1 to 20.0 wt % of the seed polymer obtained in said preparing i), based on a total weight of the monomers used in said preparing ii) and of the seed polymer; iii) subsequently forming at least one polymer shell by radical aqueous emulsion polymerization of at least one shell-forming monomer M5 in the presence of the swell-seed obtained in said preparing ii), to form an aqueous dispersion of emulsion polymer particles; and iv) subsequently neutralizing the aqueous dispersion obtained in said forming iii) to a pH of at least 7.5 with at least one base; wherein the polyalkylene oxide-containing substance is a polysiloxane-polyalkylene oxide copolymer, and wherein the aqueous dispersion of polymer particles has a whiteness after storing at 50° C. for 6 weeks of greater than 79.

2. The process according to claim 1, wherein a volume median of particle size of the seed polymer, determined by hydrodynamic fractionation, in an unswollen state ranges from 10 to 100 nm.

3. The process according to claim 1, wherein a volume median of particle size of the swell-seed, determined by hydrodynamic fractionation, in an unswollen state ranges from 50 to 300 nm.

4. The process according to claim 1, wherein the polysiloxane-polyalkylene oxide copolymer is at least one selected from the group consisting of a polysiloxane-polyalkylene oxide graft copolymer, and a polysiloxane-polyalkylene oxide graft copolymer with α-ω structure.

5. The process according to claim 1, wherein the polysiloxane-polyalkylene oxide copolymer is a polysiloxane-polyalkylene oxide copolymer, which is a polysiloxane-polyalkylene oxide graft copolymer of formula (I): ##STR00025## where R, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9 independently of one another are H or alkyl, OH, O-alkyl, allyl, O-allyl, phenyl or alkyl ester; n is 0 to 1000; m is 1 to 100; and X has the following structure of formula (Ia): ##STR00026## where R.sup.10 is OH, O-alkyl, O-allyl, O-phenyl or an alkyl ester; R.sup.11, R.sup.12, R.sup.13, R.sup.14, R.sup.15, R.sup.16 independently of one another are H, alkyl or phenyl; o is 0-100; p is 1-100; t is 0 or 2; u is 0-10; v is 0-10; and w, x, y, z independently of one another are 1-10.

6. The process according to claim 1, wherein said neutralizing iv) takes place in the presence of at least one polymerizable plasticizer monomer which is subsequently polymerized in a radical aqueous emulsion polymerization, optionally with addition of the further shell-forming monomer M5.

7. The process according to claim 6, wherein the at least one polymerizable plasticizer monomer is selected from the group consisting of a styrene, α-methylstyrene, methyl 2-tert-butylacrylate, 2-methyl-2-butene, 2,3-dimethyl-2-butene, 1,1-diphenylethene, an ester of 2-phenylacrylic acid, and an ester of atropic acid.

8. The process according to claim 1, further comprising v) forming at least one further shell by radical aqueous emulsion polymerization of the shell-forming monomer M5 in the presence of the emulsion polymer particles obtained in said forming iii).

9. The process according to claim 1, wherein the monomer M1 is selected from the group consisting of an ester of monoethylenically unsaturated C.sub.3-C.sub.8 monocarboxylic acid with C.sub.1-C.sub.10 alkanol, an ester of monoethylenically unsaturated C.sub.4-C.sub.8 dicarboxylic acid with C.sub.1-C.sub.10 alkanol and a mixture thereof.

10. The process according to claim 1, wherein the monomer M2 is selected from the group consisting of a monoethylenically unsaturated C.sub.3-C.sub.8 monocarboxylic acid, a salt and an anhydride thereof, and a mixture thereof.

11. The process according to claim 1, wherein the monomer M3 is selected from the group consisting of an ester of monoethylenically unsaturated C.sub.3-C.sub.8 monocarboxylic acid with C.sub.10-C.sub.10 alkanol, an ester of monoethylenically unsaturated C.sub.4-C.sub.8 dicarboxylic acid with C.sub.1-C.sub.10 alkanol and a mixture thereof.

12. The process according to claim 1, wherein the monomer M4 is selected from the group consisting of a monoethylenically unsaturated C.sub.3-C.sub.8 monocarboxylic acid, a salt and an anhydride thereof, and a mixture thereof.

13. The process according to claim 1, wherein the shell-forming monomer M5 in said forming iii) is selected from the group consisting of a nonionic ethylenically unsaturated monomer M5-1 having a water-solubility ≤50 g/L at 20° C., a mixture thereof, and an ethylenically unsaturated monomer M5-2 selected from the group consisting of a monomer M5-2a which comprises at least one anionic or anionogenic group, a neutral monomer M5-2b which have a water-solubility of >50 g/L at 20° C., and a mixture thereof.

14. The process according to claim 13, wherein the monomers M5 comprise: g) 25 to 100.0 wt % of at least one monomer M5-1, and h) 0 to 75.0 wt % of at least one monomer M5-2, based on a total weight of the monomers M5.

15. The process according to claim 13, wherein the monomer M5 is the monomer M5-1, which is at least one selected from the group consisting of an ester of monoethylenically unsaturated C.sub.3-C.sub.8 monocarboxylic acid with C.sub.1-C.sub.10 alkanol, an ester of monoethylenically unsaturated C.sub.4-C.sub.8 dicarboxylic acid with C.sub.1-C.sub.10 alkanol, a vinylaromatic, and an ester of vinyl alcohol or allyl alcohol with aliphatic C.sub.1-C.sub.10 monocarboxylic acid.

16. The process according to claim 13, wherein the monomer M5 is the monomer M5-2, which is at least one selected from the group consisting of a monoethylenically unsaturated C.sub.3-C.sub.8 monocarboxylic acid, a salt and an anhydride thereof, and an unsaturated fatty acid.

17. An aqueous polymer dispersion, obtained by the process according to claim 1.

18. The aqueous polymer dispersion according to claim 17, having an internal water content of 20% to 40%, based on a total water content of the dispersion.

19. A paint, comprising the aqueous polymer dispersion according to claim 17.

Description

EXAMPLES

(1) Starting Material:

(2) Emulsifier 1: Alkyl polyglycol ether sulfates (30% form), Disponil® FES 993 Emulsifier 2: Alkylbenzenesulfonate, Disponil® LDBS 20 Polysiloxane 1: Polysiloxane-polyalkylene oxide graft copolymers, EFKA@ 3031 (solvent-free, BASF SE) Polysiloxane 2: Polysiloxane-polyalkylene oxide graft copolymers, EFKA® 3288 Polysiloxane 3: Polyether-modified polysiloxane, PulpSil® 955S Biocide: Acticid® MV (Thor) Sodium hydroxymethanesulfinate: Rongalit-C
Preparing the Core-Shell Particles:

Example 1

(3) Seed Dispersion A1:

(4) The initial charge, consisting of 778.75 g of water and 35 g of emulsifier 1 (30%), was heated under a nitrogen atmosphere to a temperature of 80° C. in a polymerization vessel equipped with anchor stirrer, reflux condenser, and two feed vessels. When the temperature was reached, a solution of 402.5 g of water, 5.83 g of emulsifier 1 (30%), and 105 g of polysiloxane 1 was metered into the initial charge over 10 minutes. After the end of the feed, the feed vessel was rinsed with 17.5 g of water into the initial charge. Then 67.2 g of a 2.5 wt % aqueous sodium peroxodisulfate solution were added. After 5 minutes a preliminary emulsion, consisting of 123.94 g of water, 11.67 g of emulsifier 1 (30%), 240.45 g of methyl methacrylate, and 4.55 g of methacrylic acid, were metered together with 2.8 g of a 25 wt % aqueous ammonia solution, at 80° C. over 1 hour. After the end of the feed, the feed vessel was rinsed with 17.5 g of water into the initial charge. This was followed by a further 45 minutes of polymerization. After cooling to room temperature had taken place, 6 g of biocide and 22.5 g of rinsing water were added.

(5) Solids content: 20.0%

(6) Particle size (PSDA, median): 52 nm

(7) pH: 6.5

Example 2

(8) Dispersion (Swell-Core) B1

(9) The initial charge, consisting of 619.4 g of water, was heated under a nitrogen atmosphere to a temperature of 85° C. in a polymerization vessel equipped with anchor stirrer, reflux condenser, and two feed vessels. When the temperature was reached, 12.21 g of a 7 wt % sodium peroxodisulfate solution were added over 2 minutes, followed by 118.13 g of seed dispersion A1. After the end of the feed, the feed vessel was rinsed with 11.25 g of water into the initial charge. Thereafter a preliminary emulsion, consisting of 159.75 g of water, 19.5 g of emulsifier 1 (30%), 324 g of methyl methacrylate, and 126 g of methacrylic acid, was metered in over the course of 120 minutes at 85° C. Lastly, the feed vessel was rinsed with 22.5 g of water and polymerization was continued for 30 minutes.

(10) Solids content: 33.6%

(11) pH: 3.1

(12) Particle size (PSDA, volume median): 157 nm

Example 3

(13) Hollow Particle Dispersion C.sub.1

(14) The initial charge, consisting of 421.12 g of water and 107.69 g of dispersion B1, was heated under a nitrogen atmosphere to a temperature of 81° C. in a polymerization vessel equipped with anchor stirrer, reflux condenser, and two feed vessels. Following addition of 25.2 g of a 1.4 wt % sodium peroxodisulfate solution, the preliminary emulsion 1, consisting of 22 g of water, 2.2 g of emulsifier 2, 29.79 g of methyl methacrylate, 5.37 g of n-butyl methacrylate, and 0.77 g of methacrylic acid, was metered in over the course of 60 minutes. Thereafter the preliminary emulsion 2, consisting of 112.2 g of water, 14.96 g of emulsifier 2, 2.2 g of linseed oil fatty acids, 3.74 g of allyl methacrylate, and 252.3 g of styrene, together with 26.75 g of a 2.5 wt % sodium peroxodisulfate solution, was metered in over the course of 120 minutes. After the end of the feeds, 3.36 g of a 2.5 wt % sodium peroxodisulfate solution were added and the internal temperature was increased over 40 minutes to 92° C. Subsequently, over 10 minutes, 26.14 g of α-methylstyrene were added. After a further 20 minutes of stirring, 243 g of a 2.5 wt % sodium hydroxide solution were metered in over 20 minutes and incorporated by stirring for 20 minutes. Subsequently, over 15 minutes, preliminary emulsion 3, consisting of 44 g of water, 7 g of emulsifier 2, 0.31 g of methacrylic acid, and 79.8 g of styrene, was metered in. Five minutes after the end of the feed, 5.64 g of a 10 wt % aqueous solution of tert-butyl hydroperoxide were added, and 31 g of a 3 wt % aqueous sodium hydroxymethanesulfinate solution were metered in over 20 minutes. 30 minutes after the end of the feed, a further 9.16 g of a 10 wt % aqueous solution of tert-butyl hydroperoxide and 8.52 g of a 5.1 wt % aqueous sodium hydroxymethanesulfinate solution were metered in in parallel over 60 minutes.

(15) Solids content: 31.3%

(16) pH: 9.0

(17) Particle size (PSDA, volume median): 413 nm

(18) Whiteness: 81.5

Examples 4-8

(19) Further seed dispersions were prepared in the same way as for example 1, with the additive used and the amounts of emulsifier being varied. The changes can be seen from the following table:

(20) TABLE-US-00001 Amount of emulsifier 1/pphm Particle size Initial Additive (PSDA, Ex. Additives/pphm* charge solution median)/nm pH 4 Polysiloxane 1 30 3.00 0.10 88 6.5 5 Polysiloxane 1 30 3.00 1.00 42 6.4 6 Polysiloxane 1 30 3.00 2.00 38 6.4 7 Polysiloxane 2 30 3.00 0.50 41 7.1 8 Polysiloxane 3 30 3.00 0.50 65 6.3 *parts per hundred monomers (the additive used is treated as a monomer)

Examples 9-21

(21) Further swell-core dispersions were prepared in the same way as for example 2. As well as the amount and particle size of the seed used, the amount of initiator was varied and additional emulsifier was included in the initial charge.

(22) TABLE-US-00002 Emulsifier 1 Particle size in initial (PSDA, Ex. Seed/pphm NaPS.sup.a)/pphm charge/pphm median)/nm 9 Ex. 1 4.5 0.19 — 168 10 Ex. 1 5.0 0.19 — 162 11 Ex. 1 5.5 0.19 — 159 12 Ex. 1 6.0 0.19 — 155 13 Ex. 6 1.5 0.19 — 179 14 Ex. 6 2.0 0.19 — 162 15 Ex. 6 2.5 0.19 — 149 16 Ex. 6 3.0 0.19 — 139 17 Ex. 1 5.5 0.40 — 159 18 Ex. 1 5.5 0.05/0.1.sup.b) — 159 19 Ex. 1 5.5 0.19 0.05 159 20 Ex. 1 5.5 0.19.sup.c) — 159 21 Ex. 1.sup.d) 5.5 0.19 — 165 .sup.a)sodium peroxodisulfate .sup.b)0.05 pphm NaPS initial, 0.1 pphm metered parallel to the feed .sup.c)added after seed .sup.d)stored at 50° C. for 6 weeks

Comparative Example 1

(23) Dispersion (Swell-Core) BC1

(24) The initial charge, consisting of 477.7 g of water, 1.51 g of emulsifier 1, and 12.16 g of polysiloxane 1, was heated under a nitrogen atmosphere to a temperature of 82° C. in a polymerization vessel equipped with anchor stirrer, reflux condenser, and two feed vessels. Thereafter preliminary emulsion 1, consisting of 73.92 g of water, 0.25 g of emulsifier 1, 25.54 g of methyl methacrylate, and 0.34 g of methacrylic acid, and 14.55 g of a 7 wt % sodium peroxodisulfate solution, was added and polymerization took place for 30 minutes, the temperature within the polymerization vessel being adjusted to 85° C. Subsequently, preliminary emulsion 2, consisting of 555.01 g of water, 24.93 g of emulsifier 1, 332.32 g of methyl methacrylate, and 153.34 g of methacrylic acid, was metered in at 85° C. over the course of 120 minutes. Lastly, the feed vessel was rinsed with 10 g of water and polymerization was continued for 15 minutes.

(25) Solids content: 33.3%

(26) pH: 3.1

(27) Particle size (PSDA, volume median): 140 nm

Comparative Examples 2 to 6

(28) Further swell-core dispersions were prepared in the same way as for comparative example 1, with variations not only in the additive but also in the amount of initiator and emulsifier in the initial charge.

(29) TABLE-US-00003 Emulsifier 1 Particle size Comp. in initial (PSDA, ex. Additive/pphm NaPS/pphm charge/pphm median)/nm 2 Polysiloxane 2 2.21 0.19 0.08 110 3 Polysiloxane 3 2.21 0.19 0.08 175 4 Polysiloxane 1 2.21 0.19 0.09 131 5 Polysiloxane 1 2.21 0.09/0.2.sup.a) 0.08 123 6 Polysiloxane 1 2.21 0.40 0.08 178 .sup.a)0.09 pphm NaPS initial, 0.2 pphm metered parallel to the feed

Example 22 and Comparative Example 7

(30) Two further hollow particle dispersions were prepared in the same way as for example 3, the seed used and the swell-core used, respectively, having been stored at 50° C. for six weeks.

(31) TABLE-US-00004 Swell-core Particle size (PSDA, dispersion median)/nm pH Whiteness Ex. 22 Ex. 21 425 9.2 81.7 Comp. ex. 7 Comp. ex.1 406 (multimodal) 8.3 75.0