Process for Preparing Aqueous Polymer Dispersions

Abstract

A process for preparing an aqueous polymer dispersion, wherein the process comprising free-radically initiated emulsion polymerization in an aqueous medium, in the presence of at least one vinyl polymer A, to obtain a polymer B comprising a vinyl polymer phase B1 with a glass transition temperature of from −20 to +15° C. and a vinyl polymer phase B2 with a glass transition temperature of from +50 to +110° C., with the proviso that the difference in glass transition temperature between polymer B1 and polymer B2 is at least 40° C., wherein the weight ratio of polymer B1 to polymer B2 is from 80:10 to 10:20, wherein the at least one polymer A is obtained by a process comprising: free-radically initiated bulk or solution polymerizing of: from 5 to 25 wt. % of at least one carboxylic acid functional ethylenically unsaturated monomer A1, and from 75 to 95 wt. % of at least one ethylenically unsaturated monomer A2 different than monomer A1, where the amounts are given relative to the total weight of monomers charged in the polymerization to prepare the vinyl polymer A, wherein the weight average molecular weight of the polymer A is lower than the weight average molecular weight of the polymer B, and wherein the weight ratio of polymer A to polymer B is from 10:90 to 40:60.

Claims

1. A process for preparing an aqueous polymer dispersion, wherein the process comprises: a free-radically initiated emulsion polymerization in an aqueous medium, in the presence of at least one vinyl polymer A, to obtain a polymer B comprising a vinyl polymer phase B1 with a glass transition temperature of from −20 to +15° C. and a vinyl polymer phase B2 with a glass transition temperature of from +50 to +110° C., with the proviso that the difference in glass transition temperature between polymer B1 and polymer B2 is at least 40° C., wherein; the weight ratio of polymer B1 to polymer B2 is from 80:10 to 10:20, the at least one polymer A is obtained by a process comprising: free-radically initiated bulk or solution polymerizing of: from 5 to 25 wt. % of at least one carboxylic acid functional ethylenically unsaturated monomer A1, and from 75 to 95 wt. % of at least one ethylenically unsaturated monomer A2 different than monomer A1, where the amounts are given relative to the total weight of monomers charged in the polymerization to prepare the vinyl polymer A, the glass transition temperature of the at least one vinyl polymer A is from 40 to 150° C., the weight average molecular weight of the at least one polymer A is from 1000 to 70000 g/mol, the weight average molecular weight of the polymer A is lower than the weight average molecular weight of the polymer B, and the weight ratio of polymer A to polymer B is from 10:90 to 40:60.

2. The process according to claim 1, wherein the process for preparing the at least one polymer A further comprises deprotonating at least part of the carboxylic acid groups to obtain polymer A.

3. The process according to claim 1, wherein the process further comprises, prior to the free-radically initiated emulsion polymerization to obtain polymer B, dispersing the at least one polymer A in water.

4. The process according to claim 1, wherein from 10 to 22.5 wt. % of monomers A1 and from 77.5 to 90 wt. % of monomers A2 are used, where the amounts are given relative to the total weight of monomers charged in the polymerization to prepare the vinyl polymer A.

5. The process according to claim 1, wherein the amounts of monomers A1 and A2 add up to 100 wt. %.

6. The process according to claim 1, wherein the monomer A1 is methacrylic acid and/or acrylic acid.

7. The process according to claim 1, wherein the monomer A2 is styrene and/or α-methylstyrene.

8. The process according to claim 1, wherein the weight average molecular weight of the at least one polymer A is from 5000 to 60000 g/mol.

9. The process according to claim 1, wherein the glass transition temperature of the at least one vinyl polymer A is from 60 to 140° C.

10. The process according to claim 1, wherein the monomers A1 and A2 are chosen such that the at least one polymer A has a Hansch parameter higher than 1.35.

11. The process according to claim 1, wherein the difference in glass transition temperature between polymer B1 and polymer B2 is at least 50° C.

12. The process according to claim 1, wherein the monomers of polymer B1 and polymer B2 are independently selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, α-methyl styrene and any mixture thereof.

13. The process according to claim 1, wherein the weight ratio of polymer B1 to polymer B2 is from 80:10 to 10:20.

14. The process according to claim 1, wherein the polymer B1 and B2 independently have a Hansch parameter higher than 1.20.

15. The process according to claim 1, wherein preparing the polymer phase B1 is effected prior to preparing the polymer phase B2, or vice versa.

16. The process according to claim 1, wherein the weight average molecular weight of polymer B1 is at least 100000 g/mol and the weight average molecular weight of polymer B2 is lower than 100000 g/mol.

17. The process according to y wherein the weight average molecular weight of polymer B1 and polymer B2 is at least 100000 g/mol.

18. The process according to claim 1, wherein the polymer B consists of the two polymer phases B1 and B2.

19. The process according to a claim 1, wherein the weight ratio of polymer A to polymer B is from 15:85 to 35:65.

20. An aqueous polymer dispersion obtained by or obtainable by the process according to claim 1.

21. The aqueous polymer dispersion according to claim 20, wherein the amount of polymer A, polymer B1 and polymer B2 together in the aqueous polymer dispersion is more than 60 wt %, based on the solids content of the aqueous polymer dispersion.

22. An aqueous coating formulation comprising the aqueous polymer dispersion according to claim 20.

23. The aqueous coating formulation according to claim 22, wherein an amount of coalescent present in the aqueous coating formulation is less than 130 g/l.

24. The aqueous coating formulation according to claim 22, wherein the aqueous coating formulation comprises at least one pigment and/or at least one matting agent.

25. The aqueous coating formulation according to claim 22, wherein aqueous coating formulation is a one-component coating system.

26. A coated furniture obtained by applying the aqueous coating formulation according to claim 22 onto furniture, to form a coating thereon, and drying the coating.

Description

[0197] FIGS. 1 and 2

[0198] Of Example 1-Additional formulation with VOC of 128 g/L (FIG. 1) and Comparative Experiment C2-Additional formulation with VOC of 128 g/L (FIG. 2), photos of coated Leneta charts have been taken. The clear satin formulation was casted as a 150 m wet film onto a Leneta chart which was allowed to dry for 24 hours at 22° C. (+/−2° C.) and relatively humidity of 50%+/−5%. FIG. 1 shows a crack-free coating. FIG. 2 shows a coating with high amount of cracks.

[0199]

TABLE-US-00010 TABLE 9 Test data mechanical properties clear satin coatings. Ex 1 Ex 2 C1 Gloss (%) 20° 3 3 2 60° 20 21 15 85° 32 36 31 König hardness 77 78 70 (24 h at RT) (sec) König hardness 109 115 102 (24 h at RT + 16 h at 50° C.) (sec) Pencil hardness B B B Blocking (1 kg /cm.sup.2) 5 5 5 Blocking (3 kg /cm.sup.2) 5 5 5

TABLE-US-00011 TABLE 10 Test data chemical resistances clear satin coatings as tested according to DIN 68861-1B norm and IKEA R2. Ex 1 Ex 2 C1 IKEAR2 Water 24 hours 5 5 5 EtOH (48%) 1 hour 5 5 2 Coffee 1 hour 5 5 5 Total 15 15 12 DIN 68861-1B EtOH (48%) 1 hour 5 5 2 Red wine 6 hours 5 5 5 Coffee 16 hours 5 5 5 Water 16 hours 5 5 5 Mustard 6 hours 5 5 5 Onions 6 hours 5 5 5 Total 30 30 27

[0200] Comparative Experiment 1 C1 shows that in clear satin coatings the binder prepared with an oligomer with a higher acid value has poor EtOH resistance.

[0201] Pigmented glossy formulations were prepared using the ingredients and amounts (in grams) as listed in Table 11. In Tables 12 and 13 the test data on the pigmented glossy formulations is presented.

TABLE-US-00012 TABLE 11 Pigmented glossy formulations. Formulation Additional formulation for 3 Ex 1 - Formulation 4 Binder 55.0 55.0 Demineralized water 6.9 11.8 Tego Airex 902W 0.6 0.6 BG/DPnB/water 3/2/1 12.0 8.4 Demineralized water 3.3 3.3 Disperbyk 2015 1.2 1.2 Rheovis PU1190/DPM 0.02 0.02 1:1 Tioxide TR92 18.8 18.8 Tego Foamex 810 0.2 0.2 Rheovis PU1190/DPM 2.0 0.7 1:1 VOC (g/l) 121 84

[0202] For C2, pigmented glossy, a defect-free coating could be obtained with a VOC level of 121 g/L. Although the VOC level of the clear satin formulation is higher than of the pigmented glossy formulation, the pigmented glossy formulation has a higher coalescent/binder weight ratio.

TABLE-US-00013 TABLE 12 Test data mechanical properties pigmented glossy coatings. Ex 1- Ex 2- C1- C2- Ex 1- Form 3 Form 3 Form 3 Form 3 Form 4 Gloss (%) 20° 47 42 34 65 47 60° 83 83 76 92 83 85° 97 95 95 98 97 König hardness 73 67 60 35 64 (24 h at RT) (sec) König hardness 115 125 112 134 113 (24 h at RT + 16 h at 50° C.) (sec) Pencil hardness B B B B B Blocking (1 kg /cm.sup.2) 5 5 5 1 5 Blocking (3 kg /cm.sup.2) 4 4 4 1 4

TABLE-US-00014 TABLE 13 Test data chemical resistances pigmented glossy coatings as tested according to DIN 68861-1B norm and IKEA R2. Ex 1- Ex 2- C1- C2- Ex 1- Form 3 Form 3 Form 3 Form 3 Form 4 IKEAR2 Water 24 hours 5 5 5 5 5 EtOH (48%) 1 hour 5 5 2 5 5 Coffee 1 hour 5 5 5 5 5 Total 15 15 13 15 15 DIN 68861-1B EtOH (48%) 1 hour 5 5 2 5 5 Red wine 6 hours 5 5 5 5 5 Coffee 16 hours 5 5 5 5 5 Water 16 hours 5 5 5 5 5 Mustard 6 hours 5 5 5 5 5 Onions 6 hours 5 5 5 5 5 Total 30 30 27 30 30

[0203] Example 1—Formulation 4 shows that lowering the VOC level from 121 g/L to a VOC level of even 84 g/L still resulted in good performance. The results show that in pigmented glossy coatings the binder with a single Tg 49° C. polymer phase shows poor anti-blocking (Comparative Experiment C2) and the binder prepared with an oligomer with a higher acid value (Comparative Experiment C1) has poor EtOH resistance.

[0204] Pigmented satin formulations were prepared using the ingredients and amounts (in grams) as listed in Table 14. In Tables 15-18 the test data on the pigmented satin formulations is presented.

TABLE-US-00015 TABLE 14 Pigmented satin formulations. Formulation Additional formulation for 5 Ex 1- Formulation 6 Binder 55.0 55.0 Demineralized water 4.0 8.0 Tego Airex 902W 0.6 0.6 BG/DPnB/water 3/2/1 12.0 8.4 Demineralized water 3.3 3.3 Disperbyk 2015 1.2 1.2 Rheovis PU1190/DPM 1:1 0.02 0.02 Tioxide TR92 18.8 18.8 Tego Foamex 810 0.2 0.2 Ceridust 9615 4.0 4.0 Rheovis PU1190/DPM 1:1 0.9 0.5 VOC (g/l) 120.0 84.0

[0205] For C2, a crack-free coating could not be obtained. Therefore, the gloss values, the mechanical properties and chemical resistances have not been assessed.

[0206] All the binders of the examples according to the invention are tested in the pigmented satin formulation, which is the most challenging formulation.

TABLE-US-00016 TABLE 15 Test data mechanical properties pigmented satin coatings. Ex 1- Ex 2- Ex 3- Ex 4- Ex 5- Ex 6- Ex 7- Ex 8- Ex 1- Form 5 Form 5 Form 5 Form 5 Form 5 Form 5 Form 5 Form 5 Form 6 Gloss (%) 20° 3 3 4 4 4 3 3 5 4 60° 20 19 22 24 21 15 20 26 21 85° 47 48 59 57 52 40 58 58 38 König hardness 69 64 68 57 62 36 82 67 80 (24 h at RT) (sec) König hardness 116 113 110 112 98 85 123 112 111 (24 h at RT + 16 h at 50° C.) (sec) Pencil hardness B B B B B B B 2B B Blocking 5 5 5 5 5 5 5 5 5 (1 kg/cm.sup.2) Blocking 5 5 5 5 5 5 5 5 5 (3 kg/cm.sup.2)

TABLE-US-00017 TABLE 16 Test data chemical resistances pigmented satin coatings as tested according to DIN 68861-1B norm and IKEA R2. Ex 1- Ex 2- Ex 3- Ex 4- Ex 5- Ex 6- Ex 7- Ex 8- Ex 1- Form 5 Form 5 Form 5 Form 5 Form 5 Form 5 Form 5 Form 5 Form 6 IKEAR2 Water 24 hours 5 5 5 5 5 5 5 5 5 EtOH (48%) 1 5 5 5 5 5 5 5 5 5 hour Coffee 1 hour 5 5 5 5 5 5 5 5 5 Total 15 15 15 15 15 15 15 15 15 DIN 68861-1B EtOH (48%) 1 5 5 5 5 5 5 5 5 5 hour Red wine 6 5 5 5 5 5 5 5 5 5 hours Coffee 16 hours 4 4 4 4 3 5 4 4 5 Water 16 hours 5 5 5 5 5 5 5 5 5 Mustard 6 hours 5 5 5 5 5 5 5 5 5 Onions 6 hours 5 5 5 5 5 5 5 5 5 Total 29 29 29 29 28 30 29 29 30

TABLE-US-00018 TABLE 17 Test data mechanical properties pigmented satin coatings. C1- C7- C8- C9- Formulation 5 Formulation 5 Formulation 5 Formulation 5 Gloss (%) 20° 5 3  3 3 60° 27 18 19 14 85° 64 51 54 39 König hardness 66 45 28 30 (24 h at RT) (sec) König hardness 94 70 32 95 (24 h at RT + 16 h at 50° C.) (sec) Pencil hardness B 5B 3B 3B Blocking 5 5  5 5 (1 kg/cm.sup.2) Blocking 5 5 4-5 5 (3 kg/cm.sup.2)

TABLE-US-00019 TABLE 18 Test data chemical resistances pigmented satin coatings as tested according to DIN 68861-1B norm and IKEA R2. C1- C7- C8- C9- Formulation 5 Formulation 5 Formulation 5 Formulation 5 IKEAR2 Water 24 hours 5 5 5 5 EtOH (48%) 1 hour 2 5 5 4 Coffee 1 hour 5 4 4 5 Total 12 14 14 14 DIN 68861-1B EtOH (48%) 1 hour 2 5 5 4 Red wine 6 hours 5 5 5 5 Coffee 16 hours 4 2 2 4 Water 16 hours 5 5 5 5 Mustard 6 hours 5 4 3 5 Onions 6 hours 5 4 4 5 Total 26 25 24 28

[0207] Example 1—Formulation 6 shows that lowering the VOC level from 120 g/L to a VOC level of even 84 g/L still resulted in good performance.

[0208] Comparative Experiment 1 C1 shows that in pigmented satin coatings the binder prepared with an oligomer with a higher acid value has poor EtOH resistance.

[0209] Comparative Experiment C7, in which the T.sub.g of polymer B1 is too low, showed poor stain resistance (DIN 68861-1B: coffee 16 hrs) and low pencil/König hardness.

[0210] Comparative Experiment C8, in which the T.sub.g of polymer B1 and B2 are too low, showed poor stain resistance (DIN 68861-1B coffee 16 hrs) and low pencil/König hardness.

[0211] Comparative Experiment C9, in which the T.sub.g of polymer B2 is too low, showed low pencil hardness.