EP2588545A1

EP2588545A1 - Method for producing a multi-coat colour and/or effect paint system, the colour-forming coating composition comprising a ketone for reducing the pinhole count

Info

Publication number: EP2588545A1
Application number: EP11724409.5A
Authority: EP
Inventors: Bernhard Steinmetz
Original assignee: BASF Coatings GmbH
Current assignee: BASF Coatings GmbH
Priority date: 2010-07-01
Filing date: 2011-06-01
Publication date: 2013-05-08
Also published as: US20130202805A1; DE102010025768A1; JP2013534865A; WO2012000735A1; CN102918121A

Abstract

The present invention relates to a method for producing a multi-coat colour and/or effect paint system, by (1) applying a pigmented aqueous basecoat material to a substrate, (2) forming a polymer film from the coating material applied in stage (1), (3) applying a clearcoat material to the resulting basecoat film, and subsequently (4) curing the basecoat film together with the clearcoat film. The method of the invention is characterized in that in stage (1) a pigmented aqueous basecoat material is used which comprises at least one ketone of the general formula R1-(C=O)-R2, the ketone being present in an amount of 0.1% to 5% by weight, based on the weight of the coating material, and R1 represents an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 C atoms, and R2 represents an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 C atoms, and the sum of the C atoms present in R1 and R2 is at least 5 C atoms.

Description

METHOD FOR PRODUCING A MULTILAYER PAINTING STAINING AND / OR EFFECTIVENING WHERE THE PAINT - COATING COMPOSITION CONTAINS A KETONE FOR REDUCING THE NEEDLE STITCH NUMBER

description

The invention relates to a process for the preparation of a color and / or effect multilayer coating in which

(1) a pigmented aqueous basecoat on a substrate

10 is applied,

(2) a polymer film is formed from the varnish applied in step (1),

(3) a clearcoat is applied to the basecoat so obtained and then

15 (4) the basecoat layer is cured together with the clearcoat layer.

The invention also relates to pigmented aqueous basecoats which are suitable for the production of color and / or effect multilayer coatings.

The method described above is known (cf., for example, German Patent Application DE 19948004 A1, page 17, line 37, to page 19, line 22, or German Patent DE 10043405 C1, column 3, paragraph [0018], and column 8, Paragraph [0052], to column 9, paragraph [0057], in connection with column 6, paragraph [0039], to column 8, paragraph [0050]) and is widely used, for example, both for the original painting (OEM) and for used the refinishing of automobile bodies.

With the so-called basecoat / clearcoat process in question, in the wet-on-wet process, color and / or effect multilayer coatings are obtained which, in particular with regard to the appearance of pinholes visible as the smallest holes in the clearcoat and basecoat are in need of improvement.

The task on which the present invention is based is thus to provide a method of the type described above with the color and / or effect multilayer coatings which are improved compared to the coatings of the prior art. In particular, the finishes should have no or only very few pinholes and / or an increased needlestick. The pinhole limit is the dry thickness of the basecoat layer from which pinholes occur.

This object is surprisingly achieved by using in step (1) of the above-described basecoat / clearcoat method a pigmented aqueous basecoat which contains at least one ketone of the general formula R ¹ - (C =O) -R ² in which the ketone is present in an amount of 0.1 to 5% by weight, based on the weight of the aqueous basecoat material, R ^{1 is} an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 C atoms and R ^{2 is} an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 C atoms, and the sum of the C atoms present in R ¹ and R ^{2 is} at least 5 C atoms

The invention also relates to the pigmented aqueous paints described above which can be used in stage (1) of the basecoat / clearcoat process.

In step (1) of the process according to the invention, in principle, all known aqueous basecoats can be used if they contain at least one of the above-defined ketones in an amount of from 0.1 to 5% by weight, based on the total weight of the basecoat. Basecoats are referred to as "aqueous" if they contain from 30 to 70% by weight of water, based on the total weight of the basecoat The terms "aqueous basecoat" and "waterborne basecoat" are used in this application as synonyms.

The basecoats used according to the invention contain color and / or effect pigments.

In the process according to the invention, preference is given to the use of basecoats which contain binders which are curable physically, thermally or thermally and with actinic radiation as binders. Particular preference is given to containing at least one saturated or unsaturated polyurethane resin as binder. Such polyurethane resin-containing paints can also be cured usually physically, thermally or thermally and with actinic radiation.

In the context of the present invention, the term "physical curing" means the formation of a film by the release of solvent from polymer solutions or polymer dispersions, usually without the need for crosslinking agents.

In the context of the present invention, the term "thermal curing" means the heat-initiated crosslinking of a lacquer layer, in which case it is used one after the other for the crosslinking agent and / or self-crosslinking binder This is usually referred to in the art as extraneous crosslinking: Are the complementary reactive functional groups or autoreactive functional groups, ie, groups that "react with themselves," already in the binder molecules Examples of suitable complementary reactive functional groups and autoreactive functional groups are known from German Patent Application DE 199 30 665 A1, page 7, line 28, to page 9, lines 24. In the context of the present invention, actinic radiation includes electromagnetic radiation such as near infrared (NIR), visible light, UV radiation, X-radiation or γ radiation, in particular UV radiation, and corpuscular radiation such as electron radiation, beta radiation, alpha radiation, radiation I ne or neutron radiation, in particular electron radiation to understand. Curing by UV radiation is usually initiated by free-radical or cationic photoinitiators.

When thermal curing and curing are used together with actinic light, this is called dual cure.

Basecoats which are curable thermally or thermally and with actinic radiation ie by means of "dual-cure" are preferred in the present invention, in particular those which contain a polyurethane resin as binder and an aminoplast resin or a blocked or unblocked polyisocyanate as crosslinking agent in particular melamine resins preferred.

Suitable saturated or unsaturated polyurethane resins are described, for example, in German Patent Application DE 19911 498 A1, column 1, lines 29 to 49, and column 4, line 23, to column 11, line 5, German Patent Application DE 19948004 A1, page 4, line 19, to page 13, line 48, European Patent Application EP 0228003 A1, page 3, line 24, to page 5, line 40, European Patent Application EP 0 634 431 A1, page 3, line 38, to page 8, line 9, or international patent application WO 92/15405, page 2, line 35, to page 10, line 32.

For stabilization, polyurethane resins preferably contain either functional groups which can be converted into cations by neutralizing agents and / or quaternizing agents and / or cationic groups or functional groups which can be converted into anions by neutralizing agents and / or anionic groups and / or nonionic ones hydrophilic groups.

The polyurethane resins are linear or contain branches. They can also be present as graft polymers. In this case, they are preferably grafted with acrylic glass. Acrylic groups are preferably introduced into the polymer after preparation of a polyurethane primary dispersion.

Such graft polymers are well known to the person skilled in the art and are described, for example, in DE 199 48 004 A1.

If the basecoats used are preferably used as self-crosslinking systems, the polyurethane resin content is from 50 to 100% by weight, preferably from 50 to 90% by weight and particularly preferably from 50 to 80% by weight, based on the film-forming solids of the basecoat. Under film-forming solids is the non-volatile weight fraction of the coating material without pigments and / or fillers, which remains after two hours of drying at 120 ° C as a residue to understand.

In the case of systems used more rapidly, the polyurethane resin content is between 10 and 80% by weight, preferably between 15 and 75% by weight and particularly preferably between 20 and 70% by weight, in each case based on the film-forming solid of the basecoat.

It is essential to the invention that the aqueous basecoat used in step (1) of the process according to the invention comprises at least one ketone of the general formula R ¹ - (C =O) -R ² , where the ketone or the mixture of ketones is in an amount of 0 , 1 to 5 wt .-%, preferably 0.1 to 4.5 wt.% And most preferably 0.2 to 4 wt.%, Based on the weight of the aqueous basecoat, is present, R ^{1 is} an optionally substituted is aliphatic or cycloaliphatic radical having 1 to 10 C atoms and R ^{2 is} an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 C atoms, and the sum of the C atoms present in R ¹ and R ^{2 is} at least 5, preferably at least 6, more preferably in the range of 7 to 18 carbon atoms.

If the ketone content is less than 0.1% by weight, the object underlying the invention is not solved. If the content is more than 5% by weight, it may be necessary to accept disadvantages, such as a deterioration in the liability of underbaked structures. Examples of suitable substituents on the radicals R ¹ and R ² are hydroxy radicals. When R is an alkyl radical, it may be branched or unbranched. The ketones used are particularly preferably methylamyl ketone, methyl isoamyl ketone, ethyl amyl ketone, diisobutyl ketone, 2-undecanone, 2-decanone, 2-tridecanone and dicyclohexyl ketone

In addition, the basecoats used according to the invention may still contain at least one additive. Examples of such additives are residue-free or substantially residue-free thermally decomposable salts, crosslinking agents such as the above-mentioned aminoplast resins and blocked or unblocked polyisocyanates, organic solvents, reactive diluents, transparent pigments, fillers, molecularly soluble dyes, Nanoparticles, light stabilizers, antioxidants, deaerators, emulsifiers, slip additives, polymerization inhibitors, radical polymerization initiators, primers, leveling agents, film-forming agents, sag-control agents (SCAs), flame retardants, corrosion inhibitors, waxes, siccatives, biocides, matting agents and thickeners. Suitable thickeners are inorganic thickeners from the group of layered silicates. In addition to the inorganic thickeners, however, it is also possible to use one or more organic thickeners. These are preferably selected from the group consisting of (meth) acrylic acid (meth) acrylate copolymerized thickeners, such as, for example, the commercial product Viscalex HV30 (Ciba, BASF) and polyurethane thickeners, such as, for example, the commercial product DSX® 1550 from Cognis. As (meth) acrylic acid (meth) acrylate copolymer thickener, those are mentioned which contain, in addition to acrylic acid and / or methacrylic acid, one or more acrylic acid esters (that is to say acrylates) and / or one or more methacrylic acid esters (that is to say methacrylates) in copolymerized form. The (meth) acrylic acid (meth) acrylate Copolymerisat- thickeners common is that these in alkaline medium, that is at pH> 7, in particular> 7.5 by salt formation of acrylic acid and / or methacrylic acid, ie by the Formation of carboxylate groups show a strong increase in viscosity. If (meth) acrylic acid esters are used which are formed from (meth) acrylic acid and a C 1 -C 6 -alkanol are obtained, it is obtained substantially non-associative acting (meth) acrylic acid (meth) acrylate copolymer soil thickener, such as the above-mentioned Viscalex HV30. Substantially non-associative (meth) acrylic acid (meth) acrylate copolymer thickeners are also referred to in the literature as ASE thickeners ("Alkali Soluble / Swellable Emulsion", alkaline-soluble / swellable emulsion or dispersion) as (meth) acrylic acid However, (meth) acrylate copolymer thickeners can also be employed as so-called HASE thickeners ("hydrophobically modified anionic-soluble emulsions", hydrophobically modified anionic-soluble emulsion or dispersion). These are obtained when the alkanol used in place of or in addition to the Ci-C6-alkanols are those having a greater number of carbon atoms, for example 7 to 30, or 8 to 20 carbon atoms. HASE thickeners have an essentially thickening associative effect. The usable (meth) acrylic acid (meth) acrylate copolymer thickeners are not suitable as binder resins because of their thickening properties, they therefore do not fall under the binder called physically, thermally or thermally and actinically curable binders and are therefore explicitly different to the poly (meth) acrylate-based binders which can be used in the basecoat compositions according to the invention. Polyurethane thickeners are the associative thickeners referred to in the literature as HEUR ("Hydrophobically Modified Ethylene Oxide Urethane Rheology Modifiers", hydrophobically modified ethylene oxide-urethane-rheology additives), which are chemically non-ionic branched or unbranched block copolymers of polyethylene oxide. Chains (sometimes also polypropylene oxide chains) which are linked together via urethane bonds and which carry terminal long-chain alkyl or alkenyl groups having 8 to 30 carbon atoms Typical alkyl groups are for example dodecyl or stearyl groups, a typical alkenyl group is for example an oleyl group, a typical Aryl group is the phenyl group and is a typical alkylated aryl group for example, a nonylphenyl group. Due to their thickening properties and structure, the polyurethane thickeners are not suitable as physically, thermally or thermally and physically curable binder resins. They are thus explicitly different from the polyurethanes which can be used as binders in the basecoat compositions according to the invention.

Suitable additives of the abovementioned type are known, for example, from German Patent Application DE 19948004 A1, page 14, line 4, to page 17, line 5, German Patent DE 10043405 C1, column 5, paragraphs [0031] to [0033]. They are used in the usual and known quantities.

The solids content of the basecoats used according to the invention may vary depending on the requirements of the individual case. In the first place, the solids content depends on the viscosity required for application, in particular spray application, so that it can be adjusted by the person skilled in the art on the basis of his general knowledge, if appropriate with the aid of less orienting tests.

The solids content of the basecoats is preferably from 5 to 70% by weight, more preferably from 10 to 65% by weight and particularly preferably from 15 to 60% by weight. The term "solids content" is to be understood as meaning the proportion by weight which remains under evaporation as a residue under defined conditions. In the present application, the solid was determined according to DIN EN ISO 3251. The measurement duration was 60 min at 125 ° C. The preparation of the basecoats used according to the invention can be carried out using the customary and known for the production of basecoats mixing methods and mixing units.

The basecoats of the invention can be used both as one-component (IK), two-component (2K) or

Multi-component (3K, 4K) systems are used.

In one-component (1K) systems, binders and crosslinkers are juxtaposed, i. in a component, before. The prerequisite for this is that the two constituents crosslink together only at higher temperatures and / or when exposed to actinic radiation.

In two-component (2K) systems, binders and crosslinking agents are present separately in at least two components, which are combined only shortly before application. This form is chosen when the binder and crosslinking agent react with each other already at room temperature. Paints of this type are mainly used for coating thermally sensitive substrates, in particular in automotive refinish.

With the aid of the method according to the invention, it is possible to coat metallic and non-metallic substrates, in particular plastic substrates, preferably automobile bodies or parts thereof.

The invention also relates to the use of the ketones used in the basecoats according to the invention for increasing the needlestick limit and / or for reducing the number of needlestickings in aqueous pigmented paints.

In the following, the invention will be explained by way of examples. Examples

1. Preparation of a Silver Waterborne Basecoat 1

The components listed under "aqueous phase" in Table A are stirred together in the stated sequence to form an aqueous mixture, and in the next step, an organic mixture is prepared from the components listed under "organic phase". The organic mixture is added to the aqueous mixture. The mixture is then stirred for 10 minutes and with the aid of deionized water and Dimethylethanolami n to a pH of 8 and a spray viscosity of 58 mPas at a shear stress of 1000 / sec, as measured by a rotary viscometer (Rheomat RM 180 from Mettler Toledo) at 23 ° C, set.

Table A

component

parts by weight

Aqueous phase

3% Na-Mg layered silicate solution 26

Deionized water 3

Butyl glycol 1, 75

polyurethane; prepared according to page 7, Z. 55-4.5

P.8, Z. 23 of DE-A-4437535

20.5% by weight solution DSX 1550 (Cognis) 0.6

rheological

Polyester; prepared according to Example D, column 16, Z. 3.2

37-59 of DE-A-4009858

Surfactant S (BASF) 0.3

Butyl glycol 0.55

Cymel 203; Melamine-formaldehyde resin, available from 4.1

Cytec

10% dimethylethanolamine in water 0.3 Deionized water 6

polyurethane; prepared according to p. 19, Z. 44-S. 20.4 20, Z. 7 of DE-A-1998004

Surfactant Surfynol® 104 from Air Products (52%) 1, 6

Butyl glycol 0.5

3% by weight aqueous Viscalex HV 30 solution; 3.9

Rheology agent, available from BASF, in water

Organic phase

Mixture of two commercially available aluminum pigments 6.2 available from Altana-Eckart

Butyl glycol 7.5

Polyester; prepared according to Example D, column 16, Z. 5

37-59 of DE-A-4009858

Water-based paint E2:

To prepare the water-based coating E2 according to the invention, the water-based paint 1 was admixed with 1.5 parts by weight of 2-decanone.

5

Water-based paint E3:

To prepare the aqueous basecoat E3 of the invention, the aqueous basecoat 1 was admixed with 1.5 parts by weight of 2-undecanone. i o Waterborne basecoat E4:

To prepare the water-based lacquer E4 according to the invention, the aqueous base lacquer 1 was mixed with 1.5 parts by weight of 2-tridecanone.

Water-based paint E5:

15 To prepare the water-based paint E5 according to the invention, the water-based paint 1 was admixed with 1.5 parts by weight dicyclohexyl ketone.

Water-based paint E6: To prepare the aqueous basecoat E6 according to the invention, the aqueous basecoat 1 was admixed with 1.5 parts by weight of methyl / isobutyl ketone.

Water-based paint E7:

5 To prepare the water-based paint E7 of the invention, the water-based paint 1 was mixed with 1, 5 parts by weight of diisobutyl ketone.

Water-based paint E8:

For the preparation of the water-based coating material E8 according to the invention, the waterborne paint 1 o was admixed with 1.5 parts by weight of methyl / so-amyl ketone.

Water-based paint E9:

To prepare the water-based paint E9 according to the invention, the water-based paint 1 was admixed with 1.5 parts by weight of methyl amyl ketone.

15

Water-based paint E10:

To prepare the water-based paint E10 according to the invention, the water-based paint 1 was mixed with 1.5 parts by weight of ethylamyl ketone.

20

Table 1: Compositions of Waterborne Base Coatings (WBL) 1 and E2 - E10

WBL [wt%] ketone

E2 1, 5 2-decanone

E3 1, 5 2-undecanone

E4 1, 5 2-tridecanone

E5 1, 5 dicyclohexyl ketone

E6 1, 5 methyl / so-butyl ketone

E7 1, 5 diisobutyl ketone

E8 1, 5 methyl / so-amyl ketone

E9 1, 5 methyl amyl ketone

E10 1, 5 ethyl amyl ketone

The percentages by weight in Table 1 relate to the proportion of ketone in the respective aqueous basecoat. Comparative tests between waterborne basecoat 1 and waterborne basecoats E2 to E10

To determine the needle-stick limit and the number of pin-pricks, the multicoat paint systems were prepared according to the following general procedure:

A 30 x 50 cm sheet steel coated with a surfacer coating was provided with an adhesive strip on one longitudinal edge in order to be able to determine the layer thickness differences after the coating. The aqueous basecoat was applied wedge-shaped electrostatically. The resulting aqueous basecoat film was flashed off for one minute at room temperature and then dried for 10 minutes at room temperature in the oven. On the dried

15 waterborne basecoat, a conventional two-component clearcoat was applied. The resulting clearcoat layer was flashed off at room temperature for 20 minutes. Subsequently, the aqueous basecoat film and the clearcoat film were cured in a circulating air oven at 140 ° C for 20 minutes. After the visual evaluation

20 of the pinholes in the resulting wedge-shaped multi-layer coating, the layer thickness of the pinhole limit was determined. The results are shown in Table 2.

Table 2: Needle-stitch limit and number of pinholes of waterborne basecoat 1 and waterborne basecoats E2 to E10

WBL needle point limit (μιτι)

Needlestick number

11 75 E2 18 10

E3 20

E4 20

E5 16

E6 15 44 E7 24

E8 18

E9 14

E10 20

The results support the fact that the use according to the invention of ketones significantly increases the needlestick limit in comparison to water-based lacquer 1 and at the same time significantly reduces the number of pinpricks.

Claims

claims

1. A process for the production of a color and / or effect multilayer coating in which

5

(1) a pigmented aqueous basecoat is applied to a substrate,

(2) a polymer film is formed from the varnish applied in stage (1),

(3) a clearcoat is applied to the basecoat so obtained and then

15 (4) the basecoat film is cured together with the clearcoat film, characterized in that in step (1) a pigmented aqueous basecoat comprising at least one ketone of the general one is used

20 formula R ¹ - (C = O) -R ² contains, wherein the ketone in an amount of 0.1 to 5 wt .-%, based on the weight of the aqueous basecoat, is present, R ^{1 is} an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 carbon atoms and R ^{2 is} an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 carbon atoms, and the sum of

25 C atoms present in R ¹ and R ^{2 is} at least 5 C atoms.

2. The method according to claim 1, characterized in that the sum of the C atoms present in R ¹ and R ^{2 is} at least 6, preferably at least 7, more preferably at least 8 C-atoms

30

3. The method according to claim 1 or 2, characterized in that the ketone Diisobutylketon ethylamyl ketone, 2-U ndeca non, 2-tridecanone, Methyl amyl ketone, methyl isoamyl ketone, 2-decanone, and / or dicyclohexyl ketone.

4. The method according to one or more of claims 1 to 3, characterized 5 geken nzeichnet that the ketone content of the used in step (1)

Basecoat at 0, 1 to 4.5 wt.%, Based on the total weight of the basecoat is.

5. The method according to one or more of claims 1 to 4, characterized i o characterized in that the ketone content of the used in step (1)

Basecoats at 0.2 to 4 wt.%, Based on the total weight of the basecoat is.

6. The method according to one or more of claims 1 to 5, characterized in that in step (1) a pigmented aqueous basecoat is used which contains as binder at least one saturated or unsaturated polyurethane resin.

7. The method according to one or more of claims 1 to 6, characterized 20 in that in step (1) a pigmented aqueous basecoat, which is curable thermally or thermally and with actinic radiation, is used.

8. The method according to claim 7, characterized in that in step (1) 25 a pigmented aqueous basecoat is used, the one

Aminoplast resin and / or a blocked or unblocked polyisocyanate as a crosslinking agent.

9.. Pigmented aqueous paints, characterized in that they contain at least one ketone of the general formula R ¹ - (C = O) -R ² , wherein the ketone is present in an amount of 0, 1 to 5 wt .-% based on the weight of aqueous paint is present, R ^{1 is} an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 carbon atoms and R ² represents an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 C atoms, and the sum of the C atoms present in R ¹ and R ^{2 is} at least 5 C atoms.

10. Use of ketones of the general formula R ¹ - (C = O) -R ² , where R ^{1 is} an optionally substituted aliphatic or cycloaliphatic radical having 1 to 10 carbon atoms and R ^{2 is} an optionally substituted aliphatic or cycloaliphatic Residual having 1 to 10 carbon atoms, and the sum of the C atoms present in R ¹ and R ² at least 5 C-atoms is to increase the needle stick limit and / or to reduce the number of pinholes in aqueous pigmented paints.