Two-component coating compositions for coating fiber-reinforced plastics materials

Abstract

The present disclosure relates to two-component coating material compositions including a paint base component A and a curing component B. The paint base component A includes one or more polyols A1 selected from the group of polyols containing ester groups and which possess a hydroxyl number of 300 to 500 mg KOH/g and have a hydroxyl group functionality of greater than 2. The curing component B includes one or more polyisocyanates B1 having on average 2.4 to 5 NCO groups. The two-component coating material composition possesses a solids content of at least 96 wt %, and the molar ratio of the NCO groups in the curing component B to the acidic hydrogen atoms in the paint base component A is from 1:1.15 to 1:0.95. The disclosure further relates to a method for coating fiber-reinforced plastics and to a method for producing coated fiber-reinforced plastics, and to coating fiber-reinforced plastics.

Claims

1. A two-component coating material composition which comprises a paint base component A and a curing component B, wherein the paint base component A comprises: i. one or more polyols A1 which are selected from the group of polyols containing ester groups and which possess a hydroxyl number of 300 to 500 mg KOH/g and have a hydroxyl group functionality of greater than 2; ii. one or more aliphatic polyols A2 free from ether groups and ester groups, of the general formula (I)
R.sup.1—(OH)p  (I) in which R.sup.1 is a p-valent branched, cyclic or linear, saturated or unsaturated, aliphatic hydrocarbon radical having 5 to 18 carbon atoms, the radical R.sup.1 optionally comprising one or more tertiary amino groups, and p is 2 to 6; iii. one or more species A3 of the general formula (II)
R.sup.2—(C═O).sub.r—O-(AO).sub.s—R.sup.3  (II) in which R.sup.2 is a saturated or unsaturated, aliphatic hydrocarbon radical having 6 to 30 carbon atoms, R.sup.3 is H, a radical PO(OH).sup.2, or the optionally partially phosphated radical of a mono-or disaccharide, or the optionally partially phosphated radical of an alditol, AO represents one or more alkylene oxide radicals selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide, r is 0 or 1, and s is 0 to 30; iv. one or more crosslinking catalysts A4 selected from the group of organo tin compounds; v. optionally one or more polyamines A5 having at least two secondary amino groups and an amine number of 120 to 280 mg KOH/g; vi. optionally one or more polyether diols A6; vii. optionally one or more polyether-modified alkylpolysiloxanes A7; viii. optionally one or more pigments A8 and/or one or more fillers A8; and ix. optionally one or more additives A9 selected from the group consisting of wetting and/or dispersing agents, rheological assistants, and flow control agents; and wherein the curing component B comprises: i. one or more polyisocyanates B1 which have on average 2.4 to 5 NCO groups; and the two-component coating material composition possesses a solids content of at least 96 wt %, based on the total weight of the two-component coating material composition according to ASTM D369 (2015), and wherein the molar ratio of the NCO groups in the curing component B to the acidic hydrogen atoms of the hydroxyl groups, primary amino groups and secondary amino groups in the paint base component A is from 1:1.15 to 1:0.95.

2. The two-component coating material composition as claimed in claim 1, in which the polyol or polyols A1 are branched polyols containing ester groups and having a hydroxyl number of from 340 to 460 mg KOH/g and a hydroxyl group functionality of 3 to 4.

3. The two-component coating material composition as claimed in claim 1, in which the aliphatic polyol or polyols A2 free from ether groups and ester groups possess the general formula (I)
R.sup.1—(OH).sub.p  (I) in which R.sup.1 is a p-valent branched, saturated, aliphatic hydrocarbon radical having 6 to 16 carbon atoms, the radical R.sup.1 optionally comprising one to three tertiary amino groups, p is 2 to 4, and 2 to 6 carbon and/or nitrogen atoms are located between two immediately adjacent hydroxyl groups.

4. The two-component coating material composition as claimed in claim 1, in which the aliphatic polyol or polyols A2 free from ether groups and ester groups have a hydroxyl number in the range from 500 to 1000 mg KOH/g.

5. The two-component coating material composition as claimed in claim 1, wherein, in the one or more species A3 of the general formula (II), R.sup.2 is a saturated or unsaturated, aliphatic hydrocarbon radical having 10 to 24 carbon atoms, R.sup.3 is H, a radical PO(OH).sub.2, or the optionally partially phosphated radical of a mono- or disaccharide, or the optionally partially phosphated radical of an alditol, more particularly of sorbitol, AO represents one or more alkylene oxide radicals selected from the group consisting of ethylene oxide and propylene oxide, r is 0 or 1, and s is 0 or 1 to 25.

6. The two-component coating material composition as claimed in claim 1, wherein, in the one or more species A3 of the general formula (II), R.sup.2 is a saturated or unsaturated, aliphatic hydrocarbon radical having 10 to 24 carbon atoms, R.sup.3 is H, a radical PO(OH).sub.2, or the optionally partially phosphated radical of a monosaccharide, or the optionally partially phosphated radical of an alditol, more particularly of sorbitol, AO represents one or more alkylene oxide radicals selected from the group consisting of ethylene oxide and propylene oxide, and the ethylene oxide fraction in the entirety of the radicals AO is at least 70 mol %, r is 0 or 1, and s is 0 or s is 6 to 20.

7. The two-component coating material composition as claimed in claim 1, in which the crosslinking catalyst or catalysts A4 are selected from the group of dialkyltin dicarboxylates and dialkyltin dimercaptides.

8. The two-component coating material composition as claimed in claim 1, in which the polyamines A5 possess the general formula (V) in which the radicals R.sup.4 independently of one another are branched or unbranched alkyl radicals having 1 to 6 carbon atoms, the radical R.sup.5 is a w-valent aliphatic and/or cycloaliphatic hydrocarbon radical having 6 to 24 carbon atoms, and w is 2 to 4.

9. The two-component coating material composition as claimed in claim 1, in which the polyether diol or diols A6 possess the general formula (VII)
HO-(AO).sub.t—H  (VII) in which the radicals AO independently of one another are alkylene oxide radicals selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide, and t is 5 to 30.

10. The two-component coating material composition as claimed in claim 1, in which the polyether-modified alkylpolysiloxane or alkylpolysiloxanes A7 are polyether-modified methylpolysiloxanes.

11. The two-component coating material composition as claimed in claim 1, in which the aliphatic polyisocyanate or polyisocyanates B1 are trimers and/or tetramers of diisocyanates, and the trimers and/or tetramers are selected from the group of iminooxadiazinediones, isocyanurates, allophanates, and biurets.

12. The two-component coating material composition as claimed in claim 1, in which the weight sum of constituents A1 to A9 and B1 within the total weight of the two-component coating material composition is at least 90 wt %; the weight sum of constituents A1, A2, and A5, based on the total weight of the paint base component A, is from 75 to 95 wt %; the weight sum of constituents A1, based on the weight sum of constituents A1 and A2, is more than 50 wt %; the weight sum of constituents A3, based on the total weight of the paint base component A, is from 1 to 7 wt %; the weight sum of constituents A4, based on the total weight of the paint base component A, is from 0.15 to 1.5 wt %; the weight sum of constituents A5, based on the weight sum of constituents A1, A2, and A5, is less than 50 wt % to 0 wt %; the weight sum of constituents A6, based on the total weight of the paint base component A, is from 0 to 10 wt %; the weight sum of constituents A7, based on the total weight of the paint base component A, is from 0 to 5 wt %; the weight sum of constituents A8, based on the total weight of the paint base component A, is from 0 to 20 wt %; the weight sum of constituents A9, based on the total weight of the paint base component A, is from 0 to 8 wt %; and the weight sum of constituents B1, based on the total weight of the curing component B, is at least 90 wt %.

13. A method for coating a fiber-reinforced plastic, wherein (1) the fiber-reinforced plastic is placed into a mold, (2) the mold is closed except for a gap between fiber-reinforced plastic and mold, to form a hollow between mold and fiber-reinforced plastic, (3) the hollow is flooded with a two-component coating material composition as claimed in claim 1, (4) the coating material composition is cured, and (5) subsequently the coated fiber-reinforced plastic is removed.

14. A method for producing a coated fiber-reinforced plastic, wherein (A) a preform of fibers or fiber assemblies which serve for fiber reinforcement of the fiber-reinforced plastic to be produced is placed into the mold, (B) the mold is closed except for a gap, and the hollow formed is evacuated, (C) subsequently a liquid plastic is injected that forms the matrix of the fiber-reinforced plastic to be produced, (D) the mold is closed, with liquid plastic being pressed through the preform and wetting the fibers or fiber assemblies, (E) the liquid plastic is cured, to form the fiber-reinforced plastic, (F) the mold, directly following step (E), is closed except for a gap between fiber-reinforced plastic and mold, so as to form a hollow between mold and fiber-reinforced plastic, (G) the hollow is flooded with a two-component coating material composition as claimed in claim 1, (H) the coating material composition is cured, and (I) subsequently the coated fiber-reinforced plastic is removed.

15. The method as claimed in claim 13, wherein the fiber-reinforced plastic is in the form of a component selected from bodywork parts of a motor vehicle.

16. The method as claimed in claim 13, wherein the width of the gap in step (2) or step (F) is such that the film thickness of the cured coating material composition is in the range from 100 to 250 μm.

17. The method as claimed in claim 13, wherein the coated fiber-reinforced plastic, without an intermediate sanding operation, is coated with one or more basecoat films and one or more clearcoat films, and the basecoat film(s) and clearcoat film(s) are cured separately or jointly.

18. A method for coating fiber-reinforced plastics, the method comprising a use of the two-component coating material composition as defined in claim 1.

19. The method as claimed in claim 14, wherein the fiber-reinforced plastic is in the form of a component selected from bodywork parts of a motor vehicle.

20. The method as claimed in claim 14, wherein the width of the gap in step (2) or step (F) is such that the film thickness of the cured coating material composition is in the range from 100 to 250 μm.

Description

EXAMPLES

2K Coating Material Compositions: Examples 1 to 4

(1) All figures in table 1 are figures in parts by weight. The constituents in paint base component A and curing component B add up in each case to 100 parts by weight. Prior to use, paint base component A and curing component B were mixed homogeneously with one another in the stated weight ratio. Unless otherwise indicated, all of the components used are solvent-free (100% solids).

(2) In the preparation of the paint base component A of examples 1 to 3, constituents A1 and A2 were introduced initially and the further constituents A3, A4, A6, and A7 were mixed in with stirring (mixing time about 30 min at a maximum temperature of 60° C.). The paint base material was subsequently filtered and discharged.

(3) In the preparation of the paint base component A of the pigment-containing example 4, a millbase was first prepared from constituents A5, A8, A9a, and A9b, with A5 being introduced initially and with constituents A8, A9a, and A9b being mixed in with stirring (mixing time: 10 min, at a maximum temperature of 60° C.). This was followed by milling in a bead mill (millbase:beads ratio=1:1.5) for 30 min at 2000 rpm with compliance with a maximum temperature of 60° C. (Hegmann fineness<5 μm). To let down the millbase, the further constituents were added with stirring, and mixing took place for 10 min at a maximum temperature. The paint base material was subsequently filtered and discharged.

(4) Paint base component A and curing component B were not homogeneously mixed until shortly before application, in the above-specified weight ratio, in the mixing head of the unit, as described below.

(5) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Paint base component A A1 57.58 57.58 57.88 35.55 A2 29.67 29.67 29.82 18.30 A3 5.00 5.00 5.00 5.00 A4 0.75 0.75 0.30 0.75 A5 — — — 30.00 A6 5.00 5.00 5.00 5.00 A7 2.00 2.00 2.00 2.00 A8 — — — 1.50 A9a — — — 1.00 A9b — — — 0.50 A9c — — — 0.40 Curing component B B1a 100 90 — — B1b — 10 — — B1c — — 100 100 Weight ratio of 100:141 100:157 100:171 100:130 paint base material A to curing agent B A1: branched, short-chain polyester polyol having a hydroxyl number of about 400 mg KOH/g and a hydroxyl group functionality of between 2.2 and 3 A2: mixture of 2,2,4-trimethylpentane-1,3-diol and 2-butyl-2-ethylpropanediol (53/47, w/w) A3: mixture of compounds of the formula R.sup.2—(C═O).sub.r—O—(AO).sub.s—R.sup.3 comprising (a) R.sup.2 = mixture of saturated and unsaturated hydrocarbon radicals having 12 to 22 carbon atoms, r = 0, AO = mixture of primarily ethylene oxide units and a few propylene oxide units, and R.sup.3 = H (M.sub.n ≈ 650 g/mol); and (b) R.sup.2 = unsaturated hydrocarbon radical having 21 carbon atoms, s = 0, and R.sup.3 = H A4 : dioctyltin dilaurate A5: secondary diamine based on a polyaspartic ester with an amine number of about 190 mg KOH/g A6: linear propylene glycol having two terminal hydroxyl groups and a number-average molar mass (via end-group determination) of about 900 g/mol A7: polyether-modified methylpolysiloxane A8: highly conductive carbon black pigment A9a: commercial wetting and dispersing agent (52% in 1:1 methoxypropyl acetate/alkyl benzene) based on a copolymer having acidic groups A9b: commercial thickener based on an organically modified bentonite clay A9c: commercial flow control agent based on polyacrylate B1a: hexamethylene diisocyanate trimer of the iminooxadiazinedione type with an NCO content of 23.5 wt % B1b: hexamethylene diisocyanate trimer of the isocyanurate type with an NCO content of 11 wt % B1c: hexamethylene diisocyanate allophanate/trimer with an NCO content of 19.5 wt %
Production of a Coated, Fiber-Reinforced Molding in the Surface RTM Process
(A) Production of the Fiber-Reinforced Molding (Minidos Epoxy-RTM/SFT Unit MX 600; Mixing Head 5/8 ULKP-2KVV)

(6) The mold was opened, an external release agent was applied and spread around, a carbon fiber preform (Chomarat) was inserted, and the mold (mold carrier type: CFT 380; closing force: 250 kN) was closed. The epoxy matrix material (resin: Baxxores ER2200 (heated to 83° C.); curing agent: Baxxodur EC2120 (heated to 30° C.)) was introduced under pressure into the mold (resin: 132 bar, nozzle in nozzle: 0.9 mm; curing agent 130 bar, nozzle: 0.4 mm) and cured for 5 min at a mold carrier temperature of between 115 and 130° C.

(7) (B) Coating of the Fiber-Reinforced Molding (Overmolding)

(8) Following the production of the fiber-reinforced molding as per step (A), the mold was opened to a gap, and the coating material composition of example 1 was introduced through two slots under pressure (paint base component A: temperature: 65° C., 0.5 mm slot, 172 bar; curing component B: temperature: 60° C.; 0.6 mm slot, 180 bar) to give a coating having a thickness of 200 μm (cured). The curing of the coating material composition took place at a mold carrier temperature of about 115 to 130° C. (150 s). The coated molding was demoldable without problems and free of residue.

(9) The moldings coated in accordance with the invention can, if need be, be recoated without a costly and inconvenient cleaning operation, let alone sanding procedures. Following transport or prolonged storage, however, it is advisable for the coated moldings to be simply wiped down using a commercial plastics cleaner. No other pretreatments are required.

(10) The fiber-reinforced molding coated in accordance with the invention was recoated with a commercial standard refinish basecoat material (BC JW62-7A52; 10 min at 23° C.; then 15 min at 80° C.) and with a clearcoat material (CC JF71-0408; EverGloss; 10 min at 23° C.; then 45 min at 80° C.) and cured (both products are available from BASF Coatings GmbH).

(11) Subsequently, a constant conditions test was carried out in accordance with DIN EN ISO 6270-2 (2005-09) (240 h at 40° C.) with subsequent evaluation for blistering (visual), by means of the cross-cut test according to DIN EN ISO 2409 (2013-06; DE) (1 h and 24 h after end of exposure) and a steam jet adhesion test according to DIN 55662 (2009-12) (1 h and 24 h after end of exposure). No blistering was observed. In the cross-cut test and steam jet test as well, no delamination of the coating films was found.