Aqueous Primary Dispersions, Process Of Their Production And Use Thereof

Abstract

The invention relates to aqueous, cationically stabilized primary dispersions comprising dispersed polymer particles having a Z-average particle diameter of 5 to 500 nm and which are obtainable by emulsion polymerization of at least one olefinically unsaturated monomer (A). The emulsion polymerization takes place in the presence of one or more emulsifiers (EQ) having the following general formula: R.sup.1N.sup.(R.sup.2)(R.sup.3)(R.sup.4)X.sup., where R.sup.1 is a moiety with 15 to 40 carbon atoms which contains at least one aromatic group and at least one aliphatic group, and which contains at least one functional group selected from hydroxyl groups, thiol groups, and primary or secondary amino groups, and/or has at least one carbon-carbon multiple bond, R.sup.2, R.sup.3, and R.sup.4, independently of one another, are the same or different aliphatic moieties containing 1 to 14 carbon atoms, and X stands for the acid anion of an organic or inorganic acid. The invention further relates to a method for producing the primary dispersions, and to coating agents which include the primary dispersions, and to the use of the primary dispersions for producing electrodeposition coatings, and also to conductive substrates coated with the coating compositions. The invention further relates to emulsifiers which are used for producing the primary dispersions according to the invention.

Claims

1. An aqueous, cationically stabilized primary dispersion comprising: (1) dispersed polymer particles which i. have a Z-average particle diameter of 5 to 500 nm, and ii. are the reaction products of an emulsion polymerization of at least one olefinically unsaturated monomer (A), the emulsion polymerization of monomer (A) taking place in the presence of one or more emulsifiers (EQ) having the following formula:
R.sup.1N.sup.(R.sup.2)(R.sup.3)(R.sup.4)X.sup., wherein, R.sup.1 is a moiety with 15 to 40 carbon atoms which contains at least one aromatic group and at least one aliphatic group, and which contains at least one functional group selected from the group consisting of hydroxyl groups, thiol groups, primary amino groups, secondary amino groups, at least one carbon-carbon multiple bond, and mixtures thereof, R.sup.2, R.sup.3, and R.sup.4, independently of one another, are the same or different aliphatic moieties containing 1 to 14 carbon atoms, and X.sup. stands for the acid anion of an organic or inorganic acid HX.

2. The aqueous, cationically stabilized primary dispersion according to claim 1, wherein the moiety R.sup.1 has the structure Gr.sub.ali1-Gr.sub.arom-Gr.sub.ali2-, where Gr.sub.arom stands for an aromatic group, Gr.sub.ali1 stands for a first aliphatic group, and Gr.sub.ali2 stands for a second aliphatic group.

3. The aqueous, cationically stabilized primary dispersion according to claim 2, wherein the moiety R.sup.1 in the aliphatic group Gr.sub.ali1 has at least one carbon-carbon multiple bond.

4. The aqueous, cationically stabilized primary dispersion according to claim 2, wherein the moiety R.sup.1 in the aliphatic group Gr.sub.ali2 has at least one functional group selected from the group consisting of hydroxyl groups, thiol groups, primary amino groups, and secondary amino groups.

5. The aqueous, cationically stabilized primary dispersion according to claim 4, wherein the moiety R.sup.1 in the aliphatic group Gr.sub.ali2 has a functional group selected from the group consisting of hydroxyl groups, thiol groups, primary amino groups, and secondary amino groups in the beta-position with respect to the nitrogen atom in the general formula of the emulsifier according to claim 1.

6. The aqueous, cationically stabilized primary dispersion according to claim 2, wherein: Gr.sub.ali1 is linear, unsubstituted, and free of heteroatoms and has one to three carbon-carbon double bonds, Gr.sub.arom is a phenylene or naphthylene group, and Gr.sub.ali2 is linear, contains a hydroxyl group in the beta-position with respect to the nitrogen atom in the general formula of the emulsifier (EQ), and additionally contains O in the form of an ether group as a heteroatom.

7. The aqueous, cationically stabilized primary dispersion according to claim 1, wherein at least two of the moieties R.sup.1, R.sup.2, R.sup.3, and R.sup.4 bear a functional group selected from the group consisting of hydroxyl groups, thiol groups, primary amino groups, secondary amino groups, and mixtures thereof.

8. The aqueous, cationically stabilized primary dispersion according to claim 7, wherein in addition to bearing a functional group selected from the groups consisting of hydroxyl groups, thiol groups, primary amino groups and secondary amino groups, the at least two moieties R.sup.2, R.sup.3, and R.sup.4 bear at least one additional functional group selected from ether groups, ester groups, and amide groups.

9. The aqueous, cationically stabilized primary dispersion according to claim 1, wherein a mixture of emulsifiers (EQ) is used in which more than 50 mol-% of the moieties R.sup.1 in the emulsifiers (EQ) have carbon-carbon multiple bonds.

10. The aqueous, cationically stabilized primary dispersion according to claim 1, wherein the olefinically unsaturated monomer (A) is selected from the group consisting of: a1) (meth)acrylic acid esters which are free of acid groups; a2) monomers which bear at least one hydroxyl group, one primary amino group, one secondary amino group, one tertiary amino group, one quaternary amino group, one alkoxymethylamino group or one imino group per molecule, which are free of acid groups and which are different from the emulsifiers (EQ); a3) monomers which bear at least one acid group per molecule which may be converted to the corresponding acid anion group; a4) vinyl esters of monocarboxylic acids, branched in the alpha-position, containing 5 to 18 carbon atoms in the molecule; a5) reaction products of acrylic acid and/or methacrylic acid with the glycidyl ester of a monocarboxylic acid branched in the alpha-position and containing 5 to 18 carbon atoms per molecule; a6) cyclic or acyclic olefins; a7) (meth)acrylic acid amides; a8) monomers containing epoxy groups; a9) vinyl aromatic hydrocarbons; a10) acrylonitrile or methacrylonitrile; a11) vinyl compounds selected from the group of vinyl halides, vinylidene dihalides, N-vinyl amides, vinyl ethers, and vinyl esters that are different from the monomers a4); a12) allyl compounds; a13) polysiloxane macromonomers having a number average molecular weight M.sub.n of 1000 to 40,000 and an average of 0.5 to 2.5 ethylenically unsaturated double bonds per molecule; a14) acryloxysilane-containing vinyl monomers; and mixtures thereof.

11. The aqueous, cationically stabilized primary dispersion according to claim 10, wherein the olefinically unsaturated monomer (A) is selected from the group consisting of monomers a1), a2), a9) and mixtures thereof.

12. The aqueous, cationically stabilized primary dispersion according to claim 10, wherein a mixture of olefinically unsaturated monomers (A) is used which comprises: monomers a1) selected from the group of (meth)acrylic acid alkyl esters or (meth)acrylic acid cycloalkyl esters containing up to 20 carbon atoms in the alkyl or cycloalkyl moiety, monomers a2) selected from the group comprising monomers which bear at least one hydroxyl group, one primary amino group, one secondary amino group, one tertiary amino group or one quaternary amino group, and styrene as monomers a9).

13. A method for producing an aqueous cationically stabilized primary dispersion according to claim 1 comprising the steps of: (1) introducing the olefinically unsaturated monomer(s) (A) and the emulsifier(s) (EQ) and optionally a crosslinking agent and/or further binders into an aqueous medium, (2) converting the components of step (1) to a mini-emulsion by use of the action of shear forces, and (3) then carrying out an emulsion polymerization.

14. The method according to claim 13, wherein in step (1) one or more crosslinking agents are selected from the group consisting of blocked polyisocyanates, tris(alkoxycarbonylamino)triazines, and completely etherified aminoplast resins.

15. The method according to claim 13, wherein in step (1) an epoxy amine adduct is used as a further binder.

16. The method according to claim 13, wherein the emulsion polymerization is carried out at a temperature of 25 to 95 C. and/or a pressure of 1.5 to 3000 bar.

17. The method according to claim 13, wherein the emulsion polymerization is initiated by at least one water-soluble initiator selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, tert-butyl hydroperoxide, and mixtures thereof.

18. A coating composition comprising an aqueous, cationically stabilized primary dispersion according to claim 1.

19. The coating composition according to claim 18, wherein it is an electrodeposition coating composition.

20. An electrodeposition coating composition comprising an aqueous, cationically stabilized primary dispersion according to claim 1.

21. The electrodeposition coating composition according to claim 20, wherein the electrodeposition coating composition is cathodically depositable.

22. An electrically conductive substrate that is coated with a coating composition according to claim 18.

23. The electrically conductive substrate according to claim 22, wherein it is a metallic substrate.

24. The electrically conductive substrate according to claim 22, wherein said substrate is an automotive body or a part thereof.

25. An emulsifier (EQ) having the following general formula:
R.sup.1N.sup.(R.sup.2)(R.sup.3)(R.sup.4)X.sup., where R.sup.1 is a moiety with 15 to 40 carbon atoms which contains at least one aromatic group and at least one aliphatic group, and which contains at least one functional group selected from the group consisting of hydroxyl groups, thiol groups, primary amino groups, secondary amino groups, at least one carbon-carbon multiple bond, and mixtures thereof; R.sup.2, R.sup.3, and R.sup.4, independently of one another, are the same or different aliphatic moieties containing 1 to 14 carbon atoms; and X.sup. stands for the acid anion of an organic or inorganic acid.

Description

EXEMPLARY EMBODIMENTS

Production of Emulsifier EQ1 According to the Invention

[0128] Dimethylethanolamine lactate was initially prepared. For this purpose, 511.90 parts dimethylethanolamine, 711.9 parts 80% lactic acid, 644.2 parts butyl glycol, and 74.8 parts deionized water were stirred for 24 hours in a reaction vessel equipped with a stirrer and a reflux cooler.

[0129] 3057.2 parts Cardolite NC 513 (EEW 532 g/eq) were heated to 60 C., with stirring, in a reaction vessel equipped with a stirrer, reflux cooler, temperature probe, nitrogen inlet, and dropping funnel. 1942.8 parts of the above dimethylethanolamine lactate were slowly added dropwise over a period of 30 min. The reaction mixture was subsequently stirred until a milliequivalent (MEQ) acid value of 0.116 mmol/g was attained.

[0130] Production of a Mini-Emulsion M1 and In Situ Polymerization Thereof:

[0131] Production of the Monomer Mixture:

[0132] 33.7 parts isobornyl methacrylate, 180.8 parts methyl methacrylate, 155.9 parts butyl acrylate, 21.6 parts hydroxyethyl methacrylate, 186.2 parts styrene, 471.4 parts Araldite GY 2600 (EEW 186 g/eq), 299.0 parts of a crosslinker based on a diphenylmethane diisocyanate oligomer that had been capped with propylene glycol and butyl diglycol, and present in a 90% 1/1 (w/w) mixture composed of butoxypropanol and phenoxypropanol (CathoGuard 500 crosslinker, commercial product of BASF Coatings GmbH), 3.5 parts tert-dodecyl mercaptan, and 290.0 parts of the emulsifier EQ were stirred until a solution was present. 2104.4 parts deionized water were then added slowly, with vigorous stirring. The coarse emulsion which formed was subsequently stirred at least for an additional 5 minutes.

[0133] Production of the Mini-Emulsion:

[0134] The coarse emulsion was transferred to an apparatus for introducing high shear forces, and was subsequently homogenized in two passes at 600 bar with a high-pressure homogenizer (Model 110Y from Microfluidics, equipped with one H230Z and one H210Z homogenization chamber).

[0135] In Situ Polymerization of the Mini-Emulsion for Producing a Primary Dispersion According to the Invention:

[0136] The mini-emulsion was subsequently heated to 75 C., with stirring, in a reaction vessel equipped with a stirrer, reflux cooler, temperature probe, nitrogen inlet, and dosing unit. At a temperature of 75 C., 0.8 parts of a 1% iron(II) sulfate solution were added, and a solution of 4.4 parts sodium formaldehyde sulfoxylate dihydrate in 129.3 parts deionized water was uniformly added dropwise, concurrently with a solution of 6.1 parts of a 70% tert-butyl hydroperoxide solution in 113.1 parts deionized water, over a period of one and one-half hours. Stirring was continued for an additional hour at 75 C., and the mini-emulsion polymerized in situ was then cooled to room temperature and filtered (Nylon filter bag with an 80 m cutoff).

Particle size (Z-average): 98 nm
Particle distribution index (PDI): 0.10
Solids (after drying for 30 minutes at 180 C.): 32.8% by weight

[0137] In all examples, the particle size distribution was determined by dynamic light scattering, using a Zetasizer Nano S from Malvern. The PDI value was also derived from this measurement.

[0138] Property Testing of the Mini-Emulsion:

[0139] Production of a Coating Agent Bath from the Mini-Emulsion M1:

[0140] Production of an aqueous preparation for testing the dispersion stability: 1829.3 parts of the mini-emulsion M1 were mixed with 1978.7 parts deionized water. 192.0 parts of an aqueous pigment preparation (CathoGuard 520 pigment paste, commercial product of BASF Coatings GmbH) were then added, with stirring. The finished bath was stirred for at least 24 additional hours before being tested.

[0141] Pump Test:

[0142] The pumpability of the bath produced above was tested at 32 C. by pumping in a circuit for 24 hours, using a Little Giant MD 4 magnetic drive centrifugal pump. The sieve residue (25 m mesh size) was subsequently determined after burning in at 180 C. for 30 minutes. The pumpability was assumed to be adequate with a sieve residue <200 mg/L.

[0143] A sieve residue of 16 mg/L was determined after the test was completed.

[0144] Ultrafiltration Test:

[0145] The ultrafiltration of the bath produced above was carried out via a plate module with PVDF membranes having a total surface area of 880 cm.sup.2 (150 kDa cutoff, commercial product from Microdyn-Nadir GmbH). For assessing the ultrafiltration capability, the flux performance as well as the inlet pressure and outlet pressure were determined over a period of at least one week. The ultrafiltration capability was assumed to be adequate when the flux performance, at a minimum performance of 10 L/hm.sup.2, decreased by less than 20% over the entire test period, with no continuous decrease. The following characteristic data for the above bath were determined during the test:

TABLE-US-00001 TABLE Ultrafiltration characteristic data Change Flux compared Inlet Outlet Duration performance to start pressure pressure Temperature [h] [L/hm.sup.2] [%] [bar] [bar] [ C.] 0 18.6 0.0 1.1 0.1 26.5 51 21.4 15 1.1 0.1 28.4 121.5 21.5 15 1.1 0.1 29.4 146 21.3 15 1.2 0.1 29.5 168 21.3 15 1.2 0.1 28.6

[0146] At the end of the test, the flux performance had increased by 15% compared to the start of the test.