Aqueous polymer emulsion

Abstract

The present invention relates to an aqueous polymer emulsion comprising at least 30 wt. % of a vinyl copolymer (A), said vinyl copolymer comprising: (I) from 10 to 90 wt. % of 2-octyl acrylate monomer; (II) from 10 to 90 wt. % of at least one itaconate ester monomer according to formula (1) ##STR00001##
in which A and B may be different or the same and A and B are independently an alkyl group or an aryl group; and (III) from 0 to 80 wt. % of ethylenically unsaturated monomer other than (I) and (II); whereby the summed amount of (I), (II) and (III) is 100 wt. % and whereby the amount of vinyl copolymer (A) is given relative to the total weight amount of the polymers present in the emulsion.

Claims

1. A coating formed of a dried residue of a coating or paint composition comprised of an aqueous polymer emulsion comprising at least 70 wt. % of a vinyl copolymer (A) relative to the total weight amount of polymers present in the emulsion, wherein the vinyl copolymer (A) comprises: (I) from 25 to 55 wt. % of 2-octyl acrylate monomer; (II) from 20 to 65 wt. % of dimethyl itaconate monomer; and (III) from 0 to 55 wt. % of ethylenically unsaturated monomer other than the monomers (I) and (II), wherein the summed amount of monomers (I), (II) and (III) is 100 wt. %, and wherein the monomer (III) comprises: (IIIa) from 0.1 to 15 wt. % of carboxylic acid functional olefinically unsaturated monomer; (IIIb) from 0 to 5 wt. % of olefinically unsaturated crosslinkable monomer, different from (IIIa), (IIIc) and (IIId); (IIIc) from 0 to 5 wt. % of olefinically unsaturated wet adhesion promotor monomer, different from (IIIa), (IIIb) and (IIId); (IIId) from 0 to 54.9 wt. % of olefinically unsaturated monomer, different from (IIIa), (IIIb) and (IIIc); wherein wherein the amounts of (IIIa), (IIIb), (IIIc) and (IIId) are given relative to the total amount of (I), (II) and (III), and wherein the coating exhibits improved water resistance as compared to an identical coating where a 2-ethylhexyl acrylate monomer is employed instead of the 2-octyl acrylate monomer.

2. The coating according to claim 1, wherein the monomer (IIIa) is acrylic acid and/or methacrylic acid.

3. The coating according to claim 1, wherein the monomers (IIIb), (IIIc) and (IIId) are selected from the group consisting of acrylates, methacrylates, arylalkylenes and mixtures thereof.

4. The coating according to claim 1, wherein the monomers (IIId) are selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, styrene and combinations thereof.

5. The coating according to claim 1, wherein the vinyl copolymer (A) does not contain the monomer (IIIb) and/or the monomer (IIIc).

6. The coating according to claim 1, wherein the coating or paint composition further comprises at least one additional component selected from the group consisting of solvents, pigments, dyes, heat stabilisers, defoamers, fillers, matting agents, UV absorbers and antioxidants.

7. The coating according to claim 6, wherein the coating or paint composition is a one-component, non-crosslinkable composition.

8. A method of coating or painting a substrate comprising applying the coating of the coating or paint composition according to claim 6 to a substrate and causing or allowing an aqueous carrier medium of the emulsion to be removed.

9. The method according to claim 8, wherein the substrate is selected from the group consisting of wood optionally containing a primer and a midcoat, metal, plastic, leather, glass, paper and combinations thereof.

10. A coated or painted substrate obtained by the method of claim 9.

11. The aqueous polymer emulsion according to claim 1, wherein the vinyl copolymer comprises at least 30 wt. % of the 2-octyl acrylate monomer (I).

Description

EXAMPLES AND COMPARATIVE EXPERIMENTS

Abbreviations

(1) 2-OA 2-octyl acrylate 2-EHA 2-ethylhexyl acrylate DMI dimethyl itaconate MMA methyl methacrylate MFT minimum film formation temperature Proxel AQ 10 wt-% solution of 1,2-benzisothiazolin-3-one neutralized with KOH in water; obtained from Lonza KOH potassium hydroxide

Example 1: Copolymer Emulsion Comprising 2-OA and DMI

(2) To a round-bottomed flask equipped with a condenser, thermometer, and a stirrer were charged 400.6 parts of demineralized water which were heated to 50 C. During heat-up 4.0 parts of sodium bicarbonate and 21.2 parts of a 30 wt-% solution of sodium lauryl sulphate (surfactant) were charged.

(3) At 50 C. 0.8 parts of ammonium persulphate dissolved in 3.2 parts of demineralized water, and 10% of a pre-emulsified first monomer feed, consisting of 368.6 parts of demineralized water, 23.8 parts of methacrylic acid, 428.6 parts of dimethyl itaconate, 341.3 parts of 2-octyl acrylate, and 9.0 parts of a 30 wt-% solution of sodium lauryl sulphate, were added to the reactor and its contents were further heated to 70 C.

(4) At around 70 C. the polymerization will start causing the temperature to increase to 85 C. (if this temperature is not reached automatically, the reactor contents should be heated to 85 C.).

(5) At 85 C. the initiator feed, consisting of 89.9 parts of demineralized water, 3.2 parts of ammonium persulphate, and 1.6 parts of a 30 wt-% solution of sodium lauryl sulphate, was started. 5 minutes later feeding the remainder of the monomer feed was commenced. The initiator feed should take 135 minutes, while the monomer feed should be finished after 120 minutes. When the monomer feed was completed, the feed vessel was rinsed with 54.1 parts of demineralized water. After the initiator feed was finished, the mixture was stirred for another 20 minutes at 85 C., after which the batch was cooled to 80 C.

(6) Using a mixture of 10.1 parts of a 25 wt-)/0 solution of ammonia and 19.3 parts of demineralized water (or parts of it), the pH was increased to 7.6 (as measured at 25 C.).

(7) Over a period of 20 minutes an initiator solution was fed to the reactor in 20 minutes, consisting of 4.1 parts of demineralized water, 0.1 part of a 30 wt-% solution of sodium lauryl sulphate, and 0.2 parts of sodium persulphate. Starting 5 minutes later, a second monomer feed was added in 15 minutes, comprising 16.8 parts of demineralized water, 0.4 parts of a 30 wt-% solution of sodium lauryl sulphate, and 36.2 parts of 2-octyl acrylate. After completion of both feeds, the mixture was stirred for 60 minutes at 80 C.

(8) The emulsion was cooled to room temperature after which 5.4 parts of Proxel AQ were added. The pH was checked and when necessary adjusted to 7.5 using a 25 wt-% solution of ammonia in demineralized water. The solids content was checked and adjusted to 45% using 43 parts of demineralized water or part of it. The emulsion was made film forming by drop wise addition of 2 wt-% of butyl glycol according the general recipe shown below.

(9) TABLE-US-00001 Emulsion 98 parts Butyl glycol 2 parts Total 100 parts

Example 2: Copolymer Emulsion Comprising 2-OA and DMI/MMA

(10) Example 1 was repeated except that the 428.6 parts of dimethyl itaconate in the first monomer feed was replaced with 269.9 parts of dimethyl itaconate and 158.8 parts of methyl methacrylate.

Comparative Example A: Copolymer Emulsion Comprising 2-OA and MMA

(11) Example 1 was repeated except that the 428.6 parts of dimethyl itaconate in the first monomer feed was replaced with 428.6 parts of methyl methacrylate.

Comparative Example B: Copolymer Emulsion Comprising 2-EHA and DMI

(12) Example 1 was repeated except that the 341.3 parts of the 2-octyl acrylate in the first monomer feed was replaced with 341.3 parts of 2-ethylhexyl acrylate; and the 36.2 parts of the 2-octyl acrylate in the second monomer feed was replaced with 36.2 parts of 2-ethylhexyl acrylate.

Comparative Example C: Copolymer Emulsion Comprising 2-EHA and DMI/MMA

(13) Example 1 was repeated except that (1) the 428.6 parts of the dimethyl itaconate in the first monomer feed was replaced with 269.9 parts of dimethyl itaconate and 158.8 parts of methyl methacrylate; (2) the 341.3 parts of the 2-octyl acrylate in the first monomer feed was replaced with 341.3 parts of 2-ethylhexyl acrylate; and (3) the 36.2 parts of the 2-octyl acrylate in the second monomer feed was replaced with 36.2 parts of 2-ethylhexyl acrylate.

Comparative Example D: Copolymer Emulsion Comprising 2-EHA and MMA

(14) Example 1 was repeated except that (1) the 428.6 parts of dimethyl itaconate in the first monomer feed was replaced with 428.6 parts of methyl methacrylate; (2) the 341.3 parts of the 2-octyl acrylate in the first monomer feed was replaced with 341.3 parts of 2-ethylhexyl acrylate; and (3) the 36.2 parts of the 2-octyl acrylate in the second monomer feed was replaced with 36.2 parts of 2-ethylhexyl acrylate.

(15) Water Resistance Results

(16) With the film forming emulsions of examples 1-2 and Comparative Experiments A-D, films were cast on Leneta card with a wet film thickness of 100 m and dried to the air for 4 hours. Next, the films were aged in an oven at 50 C. for 16 hours.

(17) Water resistance was tested by putting a drop of water on the aged coating and assessing the damage done to the coating after 1 hr, 6 hrs, and 16 hrs. If no damage at all was observed the water resistance was rated a 5, while a 1 indicated complete removal of the film after removal of the water droplet. Results are shown in Table 1.

(18) TABLE-US-00002 TABLE 1 Water resistance results Water resistance after: Example No. 1 hr. 6 hrs. 16 hrs. Ex 1 5 4-5 4-5 (DMI + 2-OA) Ex 2 4-5 4-5 4-5 (DMI/MMA + 2-OA) Comp A 4-5 4-5 5 (MMA + 2-OA) Comp B 3 3-4 4 (DMI + 2-EHA) Comp C 2 2 3 (DMI/MMA + 2-EHA) Comp D 5 5 5 (MMA + 2-EHA)

(19) Comparing the results from Comparative Experiments B and C with those from Comparative Experiment D shows that use of dimethyl itaconate severely reduces the binders resistance to water. While Comparative Experiment D shows excellent water resistance for all three tests, Comparative Experiments B and C show clear marks after the water resistance test.

(20) Comparing the results from Comparative Experiments A and D shows that exchanging 2-ethylhexyl acrylate with 2-octyl acrylate in the absence of dimethyl itaconate does not influence the water resistance.

(21) Comparing the results from examples 1 and 2 with those from Comparative Experiments B and C, however, clearly shows not only a remarkable improvement in water resistance, but in some cases even a water resistance that is close to the perfect score.

(22) Surface Hardness Results

(23) With the film forming emulsions of examples 1-2 and Comparative Experiments A-D, films were cast on glass with a wet film thickness of 100 m and dried to the air for 4 hours. Next, the films were aged in an oven at 50 C. for 16 hours.

(24) Surface hardness, or Knig hardness, was determined on the aged films after they were cooled to 25 C. Results are shown in Table 2, together with the MFT's of the emulsions.

(25) TABLE-US-00003 TABLE 2 Knig hardness and MFT Knig hardness Example No. (s) MFT ( C.) Ex 1 64 <5 (DMI + 2-OA) Ex 2 55 15 (DMI/MMA + 2- OA) Comp A 91 30 (MMA + 2-OA) Comp B 43 <5 (DMI + 2-EHA) Comp C 32 12 (DMI/MMA + 2- EHA) Comp D 69 21 (MMA + 2-EHA)

(26) Comparing the results from Examples 1, 2, and Comp Ex A with those of Comp Ex B, C and D shows that surface hardness clearly improves upon use of 2-octyl acrylate instead of 2-ethylhexyl acrylate, without affecting MFT significantly. Especially for the examples comprising dimethyl itaconate MFT's are quite similar, while Knig hardness values are significantly higher for the films comprising 2-octyl acrylate instead of 2-ethylhexyl acrylate.