ADHESION PROMOTER FOR COATING COMPOSITIONS SUITABLE FOR PRODUCING SURFACER COATS

Abstract

The present invention relates to a mixture (M) which can be used as curing agent and as adhesion promoter and which comprises at least two components (M1) and (M2), which are different from one another and have in each case independently of one another free and/or blocked isocyanate groups, and which optionally comprises a further component (M3) different from (M1) and (M2); component (M1) comprises at least one aliphatic polyisocyanate, and component (M2) comprises at least one aliphatic polyisocyanate having polyether units, wherein the relative weight ratio of (M1) and (M2) in (M) to one another is in a range from 25:1 to 3:1, based in each case on the solids content of (M1) and (M2), and at least one of the components (M1), (M2), and optionally (M3) present in (M) has hydrolyzable silane groups, to a use of (M) as curing agent and adhesion promoter in a coating composition, to such a coating composition, and to methods for at least partly coating a substrate with a surfacer coat and for at least partly coating a substrate with a multicoat paint system.

Claims

1. A mixture (M) comprising at least two components (M1) and (M2), which are different from one another and comprise in each case independently of one another free and/or blocked isocyanate groups, and which mixture optionally comprises a further component (M3) different from (M1) and (M2); wherein component (M1) comprises at least one aliphatic polyisocyanate, component (M2) comprises at least one aliphatic polyisocyanate having polyether units, the relative weight ratio of components (M1) and (M2) in the mixture (M) to one another is in a range from 25:1 to 3:1, based in each case on the solids content of components (M1) and (M2), at least one of the components (M1), (M2), and optionally (M3) present in the mixture (M) has a hydrolyzable silane group, and the mixture is suitable as a curing agent and as an adhesion promoter.

2. The mixture as claimed in claim 1, wherein the relative weight ratio of components (M1) and (M2) in the mixture (M) to one another is in a range from 20:1 to 5:1, based in each case on the solids content of components (M1) and (M2).

3. The mixture as claimed in claim 1, wherein a content of component (M2) in the mixture (M) is at least 5 wt %, based on the total solids content of the mixture (M).

4. The mixture as claimed in claim 1, wherein the components (M1) and (M2) present in the mixture (M) each have a hydrolyzable silane group or (ii) the components (M1) and (M2) present in the mixture (M) each have no hydrolyzable silane groups, and the mixture (M) comprises the at least one further component (M3) which has hydrolyzable silane groups.

5. The mixture as claimed in claim 1, wherein (i) the mixture (M) is obtained by mixing components (M1) and (M2) and partly reacting the isocyanate groups of components (M1) and (M2) with at least one hydrolyzable silane compound which has at least one functional group that is reactive toward isocyanate groups, or (ii) the mixture (M) is obtained by mixing components (M1) and (M2) and adding at least one hydrolyzable silane compound as component (M3) to components (M1) and (M2).

6. The mixture as claimed in claim 1, wherein the mixture (M) is a solvent-containing dispersion at least of components (M1) and (M2) and also optionally (M3).

7. A use of method of making a coating composition, the method comprising: incorporating the mixture (M) as claimed in claim 1 as curing agent and as adhesion promoter in the coating composition, wherein the coating composition is suitable for at least partly coating a substrate, optionally at least partly coated at least with a primer coat, with a surfacer coat.

8. A coating composition comprising at least one mixture (M) as claimed in claim 1, which can be used is effective as curing agent and as adhesion promoter, at least one polymeric resin (N), different from components (M1) and (M2) and also, optionally, (M3) of the mixture (M), and at least one pigment (P), wherein the coating composition is suitable for at least partly coating a substrate, optionally coated at least partly at least with a primer coat, with a surfacer coat.

9. The coating composition as claimed in claim 8, wherein the coating composition comprises the mixture (M) in an amount in a range from 5 to 25 wt %, based on the total weight of the coating composition.

10. The coating composition as claimed in claim 8, wherein the polymeric resin (N) is selected from the group consisting of polyurethanes, polyesters, epoxy resins, poly(meth)acrylates, corresponding copolymers of these polymers, and mixtures thereof.

11. The coating composition as claimed in claim 8, wherein the coating composition comprises the at least one polymeric resin (N) in an amount in a range from 10 to 35 wt %, based on the total weight of the coating composition, and comprises the at least one pigment (P) in an amount in a range from 5 to 40 wt %, based on the total weight of the coating composition; and wherein the amounts of the components (M), (N), and (P) present in the coating composition, and also optionally at least one further component (Q) present therein, and/or optionally organic solvents present therein, add up in total to 100 wt %.

12. A method for at least partly coating a substrate, optionally at least partly coated at least with a primer coat, with a surfacer coat, the method comprising at least partly contacting the substrate with the coating composition as claimed in claim 8.

13. A method for at least partly coating a substrate with a multicoat paint system, the method comprising optionally at least partly applying a primer coat to a substrate, at least partly contacting the substrate,. optionally at least partly coated at least with the primer coat, with the coating composition as claimed in claim 8, thereby at least partly applying a surfacer coat to the substrate optionally coated at least partly at least with the primer coat, applying a basecoat film to the surfacer coat, and applying a clearcoat film to the basecoat film.

14. A surfacer coat obtained by the method as claimed in claim 12.

15. A substrate at least partly coated at least with the coating composition as claimed in claim 8.

16. A multicoat paint system obtained by the method as claimed in claim 13.

17. The method of claim 13, wherein an adhesion between the surfacer coat and the substrate is from 0 to 1.5, as measured by cross-cut testing after storage for a time of 16 hours at 40 C.

18. The method of claim 13, wherein an adhesion between the surfacer coat and the substrate is from 0.5 to 2, as measured by cross-cut testing after 3 hours after storage for 10 days under constant humidity conditions.

19. The mixture of claim 1, wherein the free and/or blocked isocyanate group is stable at a temperature of from 18 to 23 C.

Description

INVENTIVE AND COMPARATIVE EXAMPLES

[0166] Unless otherwise indicated, the amounts in parts are parts by weight, and the amounts in percent are percentages by weight in each case.

[0167] 1. Preparation of Curing Components

[0168] 1.1 Preparation of a Curing Component (B1a) (Inventive)

[0169] The reactants identified in detail in Table 1.1 below are reacted in the proportions reported in that table. First of all, xylene, n-butyl acetate (98-100% strength), 1-methoxy-2-propyl acetate, and ethyl 3-ethoxypropionate are introduced, and are mixed with Desmodur N3600, Desmodur XP2565, and Bayhydur 305. With stirring and heating under reflux, under a nitrogen atmosphere, the amount of Dynasylan 1124 specified in Table 1.1 is added dropwise at a rate such that a temperature in the range of 50-60 C. is not exceeded. The end of the addition is followed by cooling to 18-23 C.

TABLE-US-00001 TABLE 1.1 Preparation of (B1a) Item Ingredient Amount [g] 1 xylene 3.26 2 n-butyl acetate 25.75 3 1-methoxy-2-propyl 2.68 acetate 4 ethyl 3-ethoxypropionate 1.06 5 Desmodur N3600 43.17 6 Desmodur XP2565 6.87 7 Bayhydur 305 6.23 8 Dynasylan 1124 8.01

[0170] The solids content of the resulting curing component (B1a) is 58.4 wt %.

[0171] Desmodur N3600 is an aliphatic polyisocyanate based on trimerized HDI (hexamethylene diisocyanate) from Bayer, having a solids content of 100 wt % and an NCO content of about 23 wt %. Desmodur XP2565 is an aliphatic polyisocyanate based on IPDI (isophorone diisocyanate) from Bayer, having a solids content of about 80 wt % and an NCO content of about 12 wt %. Bayhydur 305 is a hydrophilic, aliphatic polyisocyanate containing polyether units and based on HDI (hexamethylene diisocyanate) from Bayer, having a solids content of 100 wt % and an NCO content of about 16.2 wt %. Dynasylan 1124 is a secondary amine, specifically bis(trimethoxysilylpropyl)amine, from Evonik.

[0172] Isocyanate group-containing reactants used in preparing the curing component (B la) are the commercially available products Desmodur N3600, Desmodur XP2565, and Bayhydur 305. Based on 100 parts by weight of these isocyanate group-containing reactants, then, 76.72 parts by weight of Desmodur N3600, 12.21 parts by weight of Desmodur XP2565, and 11.07 parts by weight of Bayhydur 305 are used, as illustrated in Table 1.2 below:

TABLE-US-00002 TABLE 1.2 Isocyanate group- containing reactants Desmodur Desmodur used in preparing B1a N3600 XP2565 Bayhydur 305 Parts by weight 76.72 12.21 11.07

[0173] 1.2 Preparation of Curing Components (B1b), (B1c), (B 1d), (B1e), and (B1f) (inventive)

[0174] The inventively employed curing components (B 1 b), (B 1 c), (B 1 d), (B1e), and (B1f) are prepared in analogy to the procedure carried out for the preparation of curing component (B1a), with the difference that, based on 100 parts by weight of the isocyanate groups-containing reactants Desmodur N3600, Desmodur XP2565, and Bayhydur 305, the respective stoichiometry of these reactants to one another that is used, i.e., their parts by weight, is varied as indicated in Table 1.3 below.

TABLE-US-00003 TABLE 1.3 Isocyanate group- containing reactants used in preparing (B1a), (B1b), (B1c), (B1d), Desmodur Desmodur Bayhydur (B1e), and (B1f) N3600 XP2565 305 Parts by weight, used in 81.96 13.14 5.0 preparing (B1b) Parts by weight, used in 80.66 11.84 7.5 preparing (B1c) Parts by weight, used in 79.46 10.54 10.0 preparing (B1d) Parts by weight, used in 76.72 12.21 11.07 preparing (B1a) (see also Tab. 1.1b) Parts by weight, used in 78.21 9.29 12.5 preparing (B1e) Parts by weight, used in 76.96 8.04 15.0 preparing (B1f)

[0175] 1.3 Preparation of a Comparative Curing Component (V1)

[0176] The comparative curing component (V1) is prepared in analogy to the procedure described for (B1a), with the difference that only the commercially available products Desmodur N3600 and Desmodur XP2565 are used as isocyanate group-containing reactants.

[0177] The comparative curing component (V1) therefore does have silane groups, but was not prepared using the isocyanate group-containing reactant Bayhydur 305.

[0178] 1.4 Preparation of curing components (B1d-1), (B1d-2), (B1d-3), and (B1d-4) (inventive)

[0179] Curing components (B1d-1), (B1d-2), (B 1d-3), and (B1d-4) are prepared in analogy to the procedure described for (B1d), with the difference that (B1 d) is admixed additionally with 2.5 wt % of glycidyloxypropyltrimethoxysilane (GLYMO) (B1d-1), 5.0 wt % of GLYMO (B1d-2), 7.5 wt % of GLYMO (B1d-3), or 10 wt % of GLYMO (B1d-4), with stirring (laboratory stirrer: 260-1820 rpm), based in each case on the total weight of (B1d).

[0180] 1.5 Preparation of a Comparative Curing Component (V2)

[0181] The reactants identified in detail in Table 1.4 below are reacted in the proportions reported in that table. Xylene, n-butyl acetate (98-100% strength), 1-methoxy-2-propyl acetate, and ethyl 3-ethoxypropionate are introduced, and are mixed with Desmodur N3600, Desmodur XP2565, and Bayhydur 305.

TABLE-US-00004 TABLE 1.4 Preparation of (V2) Item Ingredient Amount [g] 1 xylene 5.03 2 n-butyl acetate 39.71 3 1-methoxy-2-propyl acetate 4.14 4 ethyl 3-ethoxypropionate 1.64 5 Desmodur N3600 43.20 6 Desmodur XP2565 6.83 7 Bayhydur 305 6.23

[0182] The solids content of the resulting comparative curing component (V2) is 45.6 wt %.

[0183] The comparative curing component (V2) has no silane groups.

[0184] 1.6 Preparation of Curing Components (B2a), (B2b), (B2c), and (B2d) (Inventive)

[0185] Curing components (B2a), (B2b), (B2c), and (B2d) are prepared in analogy to the procedure described for (V2), with the difference that (V2) is admixed additionally with 2.5 wt % of glycidyloxypropyltrimethoxysilane (GLYMO) (B2a), 5.0 wt % of GLYMO (B2b), 7.5 wt % of GLYMO (B2c), or 10 wt % of GLYMO (B2d), with stirring (laboratory stirrer: 260-1820 rpm), based in each case on the total weight of (V2).

[0186] 2. Production of Inventive Coating Compositions

[0187] One each of the inventively employed curing components (B1c), (B1d), (B1e), (B1d-1), (B1d-2), (B1d-3), and (B1d-4), (B2a), (B2b), (B2c), or (B2d), or one of the comparative curing components (V1) or (V2), are used for producing inventive coating compositions or comparative coating compositions, which are suitable in each case for producing a surfacer coat on a substrate.

[0188] For the production of each of these coating compositions, a surfacer base varnish component and a diluent component are employed in each case.

[0189] The composition of the surfacer base varnish component is reproduced in Table 2.1.

[0190] The composition of the diluent component is reproduced in Table 2.2.

[0191] To produce the respective coating composition, surfacer base varnish component, diluent component, and in each case an inventively employed curing component or a comparative curing component, V1 or V2, are mixed with one another in a relative weight ratio of 100:13.5:17.5.

TABLE-US-00005 TABLE 2.1 Surfacer base varnish component Surfacer base varnish component Polyacrylate 18.60 Polyester 2.36 D.E.R. 671 2.20 BYK P 104 0.23 Bentone 34 0.50 n-Butyl acetate 4.00 Methoxypropyl acetate 7.30 Aerosil R972 1.45 n-Butyl acetate 1.02 Talc 8.97 Kaolin 14.90 Zinc phosphate 10.50 Titanium dioxide 9.96 Bayferrox 306 1.20 Barium sulfate 8.95 Additives 0.30 Butyl acetate 1.00 Acrylate 0.50 n-Butyl acetate 0.50 Catalyst 0.99 NC wool (solution) 2.50 n-Butyl acetate 0.50 n-Butyl acetate 0.61 Nacure 4167 1.00

[0192] The respective amount figures in Table 2.1 are parts by weight.

[0193] Employed as Additives is a mixture which contains 49.11 parts by weight of xylene, 20.26 parts by weight of ethylhexyl acrylate, 5.06 parts by weight of ethyl acrylate, 0.15 parts by weight of tert-butyl peroxy-2-ethylhexanoate, and 25.42 parts by weight of butyl glycol acetate. Employed as Catalyst is a mixture which contains 90 parts by weight of xylene and 10 parts by weight of Tinstab BL277, a commercially available product from Akcros. D.E.R. 671 is polymeric epoxy resin from Dow Chemicals. BYK P 104 is a wetting and dispersing agent from Byk. Bentone 34 is a rheological assistant from Elementis Specialties. Aerosil R972 is a hydrophobized fumed silica from Evonik. Bayferrox 306 is a black iron oxide pigment. NC wool is nitrocellulose. Nacure 4167 is a phosphorus-containing catalyst which is blocked with an amine and sold by King Industries. The polyacrylate used and the polyester used each have functional OH groups.

TABLE-US-00006 TABLE 2.2 Diluent component Diluent component n-Butyl acetate 50 Xylene 15 Solvent naphtha 160/180 13 White spirit 135/180 10 Methoxypropyl acetate 6 Butyl glycol acetate 3 Ethyl 3-ethoxypropionate 1 Dipentene 2

[0194] The respective amount figures in Table 2.2 are parts by weight.

[0195] In this way, the following inventive coating compositions and comparative coating compositions are obtained:

[0196] F1, containing (Bic),

[0197] F2, containing (Bid),

[0198] F3, containing (Ble),

[0199] F4, containing (B2a),

[0200] F5, containing (B2b),

[0201] F6, containing (B2c),

[0202] F7, containing (B2d),

[0203] F8, containing (B1d-1),

[0204] F9, containing (B1d-2),

[0205] F10, containing (B1d-3),

[0206] F11, containing (B 1 d-4),

[0207] VF1, containing (V 1), and

[0208] VF2, containing (V2).

[0209] 3. Production of Coated Substrates Using One of the Inventive or Comparative Coating Compositions

[0210] Substrates (S) used are steel panels, in each case in the form of test plaques having a size of 10200.45 cm. These substrates are first of all sanded (P180 grit) and then cleaned with a cleaning composition (SV99-0380).

[0211] A primer coat, i.e., a priming coat, is applied in a wet film thickness of 35-50 m by pneumatic spray application to the substrate pretreated as above. The resulting primer coat is subsequently dried at 18-23 C. The primer coat is produced using a primer coating composition which is prepared from a primer base varnish component, a primer diluent component, and a Glasurit component. These components are mixed with one another in a relative weight ratio of 100:8:36.

[0212] The compositions of the primer diluent component and of the Glasurit component are reproduced in Tables 3.1 and 3.2, respectively.

TABLE-US-00007 TABLE 3.1 Diluent component Methoxypropyl acetate 46.5 Butyl acetate 30.0 Xylene 20.0 Butyl glycol acetate 2.0 Ethyl 3-ethoxypropionate 1.5

TABLE-US-00008 TABLE 3.2 Glasurit component Ethanol 27.0 Isopropanol 56.0 n-Butanol 13.0 Phosphoric acid (85%) 4.0

[0213] The respective amount figures in Tables 3.1 and 3.2 are parts by weight in each case.

[0214] The composition of the primer base varnish component is reproduced in Table 3.3. The amount figures in Table 3.3 are parts by weight in each case.

TABLE-US-00009 TABLE 3.3 Primer base varnish component Mixture 1 24.70 Parosin PE 45.5 6.20 Phenodur PR263 3.30 Calcium naphthanate 0.50 (4% strength) Silica 0.65 Titanium dioxide 9.40 Talc 8.00 Zinc phosphate 5.30 Zinc oxide 2.00 Bayferrox 415 3.70 Lamp black 0.05 n-Butyl acetate 2.00 n-Butyl acetate 2.00 Mixture 2 10.90 Cellulose (solution) 3.80 n-Propanol 9.40 Plastopal FIB 0.50 n-Butanol 3.5

[0215] Bayferrox 415 is a yellow iron oxide pigment. Plastopal FIB is an isobutanol-etherified urea-formaldehyde resin from BASF. Phenodur PR263 is a phenolic resin. The silica used is the HDK T40 product from Wacker. Mixture 1 used is a mixture of 30 parts by weight n-propanol, 10.3 parts by weight n-butanol, 15.5 parts by weight isobutanol, 30 parts by weight xylene, and 14.2 parts by weight Mowital B30H, a commercially available polyvinyl butyral resin from Kuraray. Mixture 2 used is a mixture of 84 parts by weight n-propanol and 16 parts by weight Mowital B60H, a commercially available polyvinyl butyral resin from Kuraray.

[0216] With a wet film thickness of 120-180 m, one of the inventive coating compositions F1 to F11 or one of the comparative coating compositions FV1 or FV2 is applied as a surfacer coat, by means of pneumatic spray application, to the substrate pretreated and primer-coated as above. The respective surfacer coat thus applied is cured at room temperature (20-23 C.) for 10 minutes and then for a further 25 minutes at 60 C. in a forced air oven (oven temperature).

[0217] After the substrates thus coated have been cooled to 20-23 C., they are sanded using an eccentric sander and 400 grit paper, and then cleaned with the SV20-0240 cleaning composition.

[0218] Applied subsequently is a standard commercial basecoat, by pneumatic spray application, in a wet film thickness of 35-50 m. The resulting basecoat is dried at 20-23 C. for a time of 10 to 15 minutes. The basecoat is produced using a basecoat composition which is prepared from a basecoat base varnish component and a standardizer additive component. These components are mixed with one another in a relative weight ratio of 100:50.

[0219] Subsequently, a customarily employed, solvent-based clearcoat is applied to each of the resulting substrates coated with a basecoat. To produce the clearcoat, a clearcoat composition is used which is prepared from a clearcoat base varnish component, a diluent component, and a curing component. These components are mixed in a relative weight ratio of 100:8.6:50 to one another.

[0220] This is followed by drying of the resulting clearcoat for 10 minutes at 20-23 C. and then for 30 minutes at 60 C. in a forced air oven.

[0221] In the respective resulting substrate, the primer coat has a dry film thickness of 15-20 m, the surfacer coat a dry film thickness of 50-70 m, the basecoat a dry film thickness of 18-20 m, and the clearcoat a dry film thickness of about 50 m.

[0222] The following coated substrates are obtained accordingly: S-F1, S-F2, S-F3, S-F4, 5-F5, S-F6, S-F7, S-F8, S-F9, S-F10, S-F11, S-VF1, and S-VF2.

[0223] A total of 3 samples are produced of each of the different coated substrates, and each sample is investigated as described below in section 4., in each case individually. The respective average is then formed.

[0224] 4. Investigating the Adhesion Properties of the Coated Substrates

[0225] 4.1 The adhesion between a surfacer coat, obtainable by applying the inventive coating composition or a comparative coating composition to a substrate coated with a primer coat, and the substrate coated with a primer coat itself is determined and evaluated by means of the method described above.

[0226] The results are summarized in Tables 4 and 5:

[0227] As can be seen from Tables 4 and 5, a significant improvement in the adhesion to the respective primed substrate (S) can be achieved by using the inventive curing component in the coating composition used for producing a surfacer coat.

TABLE-US-00010 TABLE 4 Coated substrate Adhesion.sup.1 Adhesion.sup.2 Adhesion.sup.3 S-VF1 (comparative) 2 5 5 S-F1 0 0 0.5 S-F2 1 0 2 S-F3 0 1.5 0.5 S-F8 1.5 1.5 2 S-F9 1 0.5 0.5 S-F10 0 1 1 S-F11 0 0.5 0.5 .sup.1Evaluation of adhesion between surfacer coat and primed substrate by cross-cut testing after storage for a time of 16 hours at 40 C. .sup.2Evaluation of adhesion between surfacer coat and primed substrate by cross-cut testing after 1 h after storage for 10 days under constant humidity conditions .sup.3Evaluation of adhesion between surfacer coat and primed substrate by cross-cut testing after 3 h after storage for 10 days under constant humidity conditions

[0228] As can be seen from Table 4, a significant improvement in the adhesion to the respective substrate S can be achieved by using the inventive curing components in the coating composition used for producing a surfacer coat. In F1 to F3, the commercially available product Bayhydur 305, containing polyether units and subjected to partial silanization, is present. In F8 to F11, with GLYMO, a further compound containing silane groups is additionally present. As shown by a comparison with VF1, the presence of Bayhydur 305 is necessary in order to achieve sufficient adhesion: the use solely of the commercially available products subjected to partial silanization, Desmodur XP 2565 and Desmodur N 3600 (without Bayhydur 305) is not sufficient to achieve this.

TABLE-US-00011 TABLE 5 Coated substrate Adhesion.sup.1 Adhesion.sup.2 S-VF2 (comparative) 2.5 3 S-F4 1 1 S-F6 0.5 0 S-F7 0 0 .sup.1Evaluation of adhesion between surfacer coat and primed substrate by cross-cut testing after 1 h after storage for 10 days under constant humidity conditions .sup.2Evaluation of adhesion between surfacer coat and primed substrate by cross-cut testing after 24 h after storage for 10 days under constant humidity conditions

[0229] As can be seen from Table 5, a significant improvement in the adhesion to the respective substrate S can be achieved by using the inventive curing components in the coating composition used for producing a surfacer coat. In F4, F-6, and F7, the commercially available product Bayhydur 305, containing polyether units, is present in combination with GLYMO as a compound containing silane groups. As shown by a comparison with VF2, the presence of GLYMO is necessary in order to achieve sufficient adhesion: the use of the commercially available products Desmodur XP 2565 and Desmodur N 3600 and Bayhydur 305 alone, without the partial silanization carried out beforehand and/or the addition of a compound containing silane groups, such as GLYMO, is not sufficient to achieve this.