Colour-stable curing compositions containing polyisocyanates of (cyclo)aliphatic diisocyanates

Abstract

The present invention relates to a novel process for preparing isocyanurate-comprising polyisocyanates of (cyclo)aliphatic diisocyanates that are especially stable to color drift in solvents.

Claims

1. A polyisocyanate composition, comprising: (A) at least one polyisocyanate obtainable by reacting at least one monomeric isocyanate, (B) at least one salt in an amount of 10 to 300 ppm by weight, based on component (A), consisting of (B1) a phosphorus-containing acidic compound and (B2) an open-chain trisubstituted amine, (C) at least one sterically hindered phenol, (D) optionally at least one further antioxidant, (E) at least one Lewis-acidic organic metal compound capable of accelerating the reaction of isocyanate groups with isocyanate-reactive groups, (F) at least one solvent, and (G) optionally other coatings additives.

2. The polyisocyanate composition according to claim 1, wherein the monomeric isocyanate is a diisocyanate selected from the group consisting of hexamethylene 1,6-diisocyanate, pentamethylene 1,5-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 4,4-di(isocyanatocyclohexyl)methane and 2,4-di(isocyanatocyclohexyl)methane.

3. The polyisocyanate composition according to claim 1, wherein the polyisocyanate (A) comprises isocyanurate groups, biuret groups, urethane groups, allophanate groups and/or iminooxadiazinedione groups.

4. The polyisocyanate composition according to claim 1, wherein the polyisocyanate (A) comprises isocyanurate, allophanate and/or urethane groups that have been prepared using an ammonium carboxylate, ammonium hydroxide or ammonium -hydroxycarboxylate catalyst.

5. The polyisocyanate composition according to claim 1, wherein the polyisocyanate (A) is a polyisocyanate comprising primarily isocyanurate groups and having a viscosity of 500-4000 mPa*s and/or a low-viscosity allophanate optionally comprising isocyanurate and/or urethane and having a viscosity of 150-1600 mPa*s.

6. The polyisocyanate composition according to claim 1, wherein the phosphorus-containing acidic compound (B1) is selected from the group consisting of alkyl phosphates (B1a), phosphonates (B1b) and mono-O-alkyl phosphonites (B1c).

7. The polyisocyanate composition according to claim 1, wherein the phosphorus-containing acidic compound (B1) has one of the general formulae (I) to (V) ##STR00007## wherein R1 to R9 is in each case independently alkyl.

8. The polyisocyanate composition according to claim 1, wherein the open-chain trisubstituted amine (B2) is a trialkylamine.

9. The polyisocyanate composition according to claim 1, wherein the open-chain trisubstituted amine (B2) comprises a first corresponding acid having a pKa in aqueous solution between 5 and 14 at 25 C.

10. The polyisocyanate composition according to claim 1, wherein the phosphorus-containing acidic compound (B1) and the open-chain trisubstituted amine (B2) are used in a molar ratio of 1.2:0.8 to 0.5:1.

11. The polyisocyanate composition according to claim 1, wherein compound (C) has exactly one phenolic hydroxyl group per aromatic ring and in which at least one ortho position, based on the phenolic hydroxyl group, bear(s) bears an optionally substituted tert-butyl group.

12. The polyisocyanate composition according to claim 1, wherein compound (C) is selected from the group consisting of 2,6-bis(tert-butyl)-4-methylphenol (BHT), an alkyl 3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate, 3,3,3,5,5,5-hexa(tert-butyl)-,,-(mesitylene-2,4,6-triyl)tri-p-cresol, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, octyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, C7-C9-alkyl 3 -(3,5 -di-tert-butyl-4-hydroxyphenyl)propionate and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

13. The polyisocyanate composition according to claim 1, wherein the further antioxidant (D) is selected from the group of the phosphites, phosphonites, phosphonates and thioethers.

14. The polyisocyanate composition according to any claim 1, wherein the Lewis-acidic organic metal compound (E) comprises a metal selected from the group consisting of tin, zinc, titanium, zirconium and bismuth, and mixtures thereof.

15. The polyisocyanate composition according to claim 1, wherein the solvent (F) is selected from the group consisting of aromatic hydrocarbons, (cyclo)aliphatic hydrocarbons, ketones, esters, ethers, ether esters and carbonates.

16. A process for stabilizing a polyisocyanate composition, comprising adding to a polyisocyanate (A): at least one Lewis-acidic organic metal compound (E) capable of accelerating the reaction of isocyanate groups with isocyanate-reactive groups, at least one salt (B) in an amount of 10 to 300 ppm by weight based on the polyisocyanate (A), consisting of a phosphorus-containing acidic compound (B1) and an open-chain trisubstituted amine (B2), at least one sterically hindered phenol (C), optionally at least one further antioxidant (D), at least one solvent (F), and optionally at least one coating additive (G).

17. A process for producing polyurethane coatings, which comprises reacting a polyisocyanate composition according to claim 1 with at least one binder comprising isocyanate-reactive groups.

18. A process for producing polyurethane coatings, which comprises reacting a polyisocyanate composition according to claim 1 with at least one binder selected from the group consisting of polyacrylate polyols, polyester polyols, polyether polyols, polyurethane polyols, polyurea polyols, polyetherols, polycarbonates, polyester polyacrylate polyols, polyester polyurethane polyols, polyurethane polyacrylate polyols, polyurethane-modified alkyd resins, fatty acid-modified polyester polyurethane polyols, copolymers with allyl ethers and copolymers or graft polymers thereof.

19. A process, comprising employing the polyisocyanate composition according to claim 1 as a curing agent in at least one selected from the group consisting of coating materials in primers, primer surfacers, pigmented topcoats, basecoats and clearcoats in the sectors of refinishing, automotive refinishing, large vehicle finishing and wood, plastic and OEM finishing, in utility vehicles in the agricultural and construction sector and as curing agent in adhesives and sealants.

Description

EXAMPLES

(1) Feedstocks:

(2) Polyisocyanates (A): isocyanurate based on hexamethylene diisocyanate

(3) Polyisocyanate (A1): Basonat HI 100; polyisocyanurate from BASF SE. NCO content of the product: 22.0%, viscosity: 2900 mPa*s.

(4) Polyisocyanate (A2): Basonat HI 2000; low-viscosity polyisocyanurate from BASF SE. NCO content of the product: 23.2%, viscosity: 1214 mPa*s

(5) Polyisocyanate (A3), polyisocyanurate:

(6) Hexamethylene diisocyanate HDI was converted in the presence of 70 ppm by weight of benzyltrimethylammonium hydroxyisobutyrate as catalyst, based on hexamethylene diisocyanate, 60% in ethylene glycol, in a three-reactor cascade at 110, 120 and 130 C. Hexamethylene diisocyanate was distilled off in a multistage process. NCO content of the product: 22.2%, viscosity: 2900 mPa*s

(7) Polyisocyanate (A4), low-viscosity polyisocyanurate:

(8) Hexamethylene diisocyanate HDI was converted in the presence of 34 ppm by weight of benzyltrimethylammonium hydroxyisobutyrate as catalyst, based on hexamethylene diisocyanate, 60% in ethylene glycol, in a three-reactor cascade at 100/120/140 C.

(9) Hexamethylene diisocyanate was distilled off in a multistage process. Addition of 200 ppm by weight of Irganox 1135 and 200 ppm by weight of Irgafos OPH. NCO content of the product: 23.1%, viscosity: 1320 mPa*s. In the examples, the additives are included in the list of stabilizers.

(10) Polyisocyanate (A5), polyisocyanurate corresponding to example A1 of WO 2013060614:

(11) Hexamethylene diisocyanate HDI was converted in the presence of 32 ppm by weight of benzyltrimethylammonium hydroxyisobutyrate as catalyst, based on hexamethylene diisocyanate, 5% in ethylhexanol, in a multistage reactor cascade at 120 C. with an average throughput time per reactor of 20 min. The reaction was stopped chemically with 12 ppm by weight of di(2-ethylhexyl) phosphate, based on hexamethylene diisocyanate, in a 10% solution in methylglycol. Hexamethylene diisocyanate was distilled off under reduced pressure. Addition of 300 ppm by weight of methoxyacetic acid and 100 ppm by weight of BHT. NCO content of the product: 22.2%, color number 21: Hz; viscosity: 2620 mPa*s.

(12) Salt B

(13) Phosphorus-containing acidic compounds (B1)

(14) di(2-ethylhexyl) phosphate: DEHP; product from Lanxess

(15) TABLE-US-00002 dibutyl phosphate DBP; product from Lanxess Hordaphos MDB butyl phosphate (80%; 1-10% n-butanol) from Clariant Hordaphos MOB butyl phosphate (80%; 10% phosphoric acid) from Clariant Rhodafac PA 80 mixture of dibutyl and butyl phosphate, 0-1% phosphoric acid, 0-4% butanol from Solvay

(16) Equivalent ratios were calculated from the stoichiometry. The following are roughly equivalent: 50 ppm by weight of DEHP, 38 ppm by weight of DBP, 28 ppm by weight of Hordaphos MDB, 28 ppm by weight of Hordaphos MOB, 33 ppm by weight of Rhodafac PA 80. Nacure 4167 was typically computed at 200 ppm by weight with 25% active components such as 50 ppm by weight of DEHP, even though, according to manufacturer data, it partly comprises monophosphoric acid, and there is a mixture of C6 to C10 and not C8.

(17) TABLE-US-00003 Open-chain trisubstituted amines (B2) triethylamine product from Aldrich N,N-dimethylcyclohexylamine product from Aldrich N,N-dimethylethanolamine product from Aldrich

(18) Noninventive Amines:

(19) Tinuvin 770: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate

(20) ##STR00005##

(21) Tinuvin 292: mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and 1-methyl-8-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate

(22) ##STR00006##

(23) Salt B: Nacure 4167: amine-neutralized phosphate from King Industries/Worle in 30-40% propan-2-ol, 20-30% 2-methylpropan-1-ol. 30-40% reaction product of phosphoric acid, mono- or di(C6-C10)alkyl ester and an alkylamine. 25% active component in relation to catalysis of melamine resins (phosphoric esters).

(24) Sterically Hindered Phenols (C):

(25) TABLE-US-00004 BHT 2,6-bis(tert-butyl)-4- methylphenol from Sigma-Aldrich pentaerythritol tetrakis(3-(3,5-di-tert- Irganox 1010 (I. 1010) butyl-4-hydroxyphenyl)propionate) from BASF SE octadecyl 3-(3,5-di-tert-butyl-4- Irganox 1076 (I. 1076) hydroxyphenyl)propionate from BASF SE isooctyl 3-(3,5-di-tert-butyl-4- Irganox 1135 (I. 1135) hydroxyphenyl)propionate from BASF SE

(26) Antioxidants(D):

(27) TABLE-US-00005 triphenyl phosphite Tppt, from Aldrich tributyl phosphite TBP, from Aldrich dioctyl phosphonate Irgafos OPH (OPH) from BASF SE

(28) Catalysts (E):

(29) Catalyst: dibutyltin dilaurate (DBTL, DBTDL) from Sigma-Aldrich

(30) Solvent (F):

(31) TABLE-US-00006 Solvent Naphtha (boiling range Solvesso 100 about 170-180 C.): from Aldrich amyl ketone methyl

(32) Further Acid Additive:

(33) TABLE-US-00007 N. 5076 Nacure 5076 (King Industries); dodecylbenzenesulfonic acid

(34) The polyisocyanates (A) were stored under nitrogen in

(35) Formulation 1: 50% polyisocyanate, 50% Solvesso 100. 1000 ppm by weight of DBTL/Solvesso 100

(36) Formulation 2: 50% polyisocyanate, 50% methyl amyl ketone. 1000 ppm by weight of

(37) DBTL/methyl amyl ketone

(38) with the concentrations of components (B)-(D) specified in the experiments in 25 mL in tightly sealed screwtop vessels with a volume of 30 mL at 50 C. in an air circulation oven for exclusion of air. Traces of air cannot be ruled out. After one measurement, the measurement solution was poured back into the screwtop vessel, the solution was blanketed with nitrogen and the screwtop vessel was carefully closed.

(39) The percentages by weight of components (A) and (F) relate to 100% total weight based on polyisocyanate (A) and solvent (F). The concentrations of the compounds (B) to (E) in ppm by weight, in the respectively undiluted state of compounds (B) to (E), are based on the total amount of polyisocyanate (A). The tables state the amounts of the additives in ppm by weight.

(40) The color number is measured in APHA to DIN EN 1557 on a Lico 150 from Lange in a 5 cm measurement cuvette with a volume of 5 mL. Error tolerances are for the target value 20 Hz (+/5, actual value 18 Hz); target value 102 Hz (+/10, actual value 99 Hz); target value 202 Hz (+/20, actual value 197 Hz). Color numbers are measured directly (immediately before commencement of storage) and after storage over different periods of time.

(41) Examples B (not component B here) were compared directly against references R.

(42) Interaction of Lewis Acid DBTL with Additives:

(43) A mixture of 5% by weight of DBTL and 5% by weight of DEHP without amine in butyl acetate immediately gave a very large amount of white precipitate (almost 100% of the fill height). Even with 5% DBTL and 0.5% DEHP or with 0.5% DBTL and 0.05% DEHP, there was a precipitate in the interim that dissolved only after a few hours. There can be assumed to be a disadvantageous interaction of DEHP with DBTL, possibly also with coating haze.

(44) A mixture of 5% by weight of DBTL and 5% by weight of DEHP and 1.8% triethylamine as inventive ammonium phosphate in butyl acetate gave about a quarter of the precipitate with DBTL/DEHP. In the lower concentrations with 5% DBTL, 0.5% DEHP and 0.18% triethylamine, or with 0.5% DBTL, 0.05% DEHP and 0.018% triethylamine, any precipitate dissolved much more quickly after the combination. There is assumed to be no adverse interaction, or at least a distinctly lesser interaction, of inventive ammonium phosphate with DBTL.

(45) Storage Tests:

(46) TABLE-US-00008 TABLE 1 Polyisocyanate (A5) with stabilizers in formulation 1 (Solvesso 100) Stabilizers (ppm/A5) Storage time (d) B Acid C 0 7 28 70 R1 10 N. 5076*1 100 BHT 9 15 55 84 B1 200 Nacure 4167 100 BHT 9 15 16 21 *1ex. 2, PIC A1 of WO 2013060614 On addition of inventive salts (B) compared to prior art with free acids, better color drifts are obtained.

(47) TABLE-US-00009 TABLE 2 Polyisocyanate (A3) with stabilizers in formulation 1 (Solvesso 100) Stabilizers (ppm/A3) Storage time (d) B Acid C 0 7 28 70 R2*1 50 DEHP 100 I. 1135 15 27 35 66 B2 200 Nacure 4167 50 DEHP 100 I. 1135 15 26 28 35 *1ex. 6, PIC A2 of WO 2013060614 On addition of an inventive salt (B) compared to prior art with free acids, better color drift is observed.

(48) TABLE-US-00010 TABLE 3 Polyisocyanate (A1) with stabilizers in formulation 1 (Solvesso 100) Stabilizers (ppm/A1) Storage time (d) B C D 0 7 28 70 R3 200 I. 1010 200 Tppt 10 52 55 86 B3 200 Nacure 4167 200 I. 1010 200 Tppt 10 22 30 46 B4 300 Nacure 4167 200 I. 1010 200 Tppt 10 24 28 38 R4 200 I. 1010 200 OPH 8 63 130 X B5 200 Nacure 4167 200 I. 1010 200 OPH 8 30 40 57 R5 200 I. 1076 200 Tppt 8 43 63 94 B6 200 Nacure 4167 200 I. 1076 200 Tppt 8 21 30 54 B7 300 Nacure 4167 200 I. 1076 200 Tppt 8 21 28 41 R6 200 I. 1135 200 Tppt 8 46 51 100 B8 200 Nacure 4167 200 I. 1135 200 Tppt 8 22 29 42 B9 300 Nacure 4167 200 I. 1135 200 Tppt 8 21 23 39 R7 200 I. 1135 200 TBP 9 49 52 89 B10 200 Nacure 4167 200 I. 1135 200 TBP 9 21 29 47 B11 300 Nacure 4167 200 I. 1135 200 TBP 9 29 27 37 Nacure 4167 improves color drift compared to specimens without Nacure 4167

(49) TABLE-US-00011 TABLE 4 Polyisocyanate (A2) in formulation 1 (Solvesso 100) Stabilizers (ppm/A2) Storage time (d) Phosphate/ammonium phosphate C D 0 7 28 70 R8 200 I. 1135 200 OPH 12 66 135 100 R9 38 DBP 200 I. 1135 200 OPH 12 50 143 166 B12 200 Nacure 4167 200 I. 1135 200 OPH 12 22 43 46 Nacure 4167 improves color drift compared to a specimen without salt (B) and compared to a specimen with an acid rather than the salt (B).

(50) TABLE-US-00012 TABLE 5 Polyisocyanate (A1) with addition of acids (reference) and acids + amines (example) in formulation 1 (Solvesso 100) Stabilizers (ppm/A1) Storage time (d) Phosphate/ammonium phosphate C D 0 7 28 70 R10 50 DEHP 200 I. 1135 200 OPH 8 32 90 135 R11 50 DEHP + 50 Tinuvin 292* 200 I. 1135 200 OPH 8 32 90 134 R12 50 DEHP + 44 Tinuvin 770* 200 I. 1135 200 OPH 8 31 92 140 B13 50 DEHP + 18 triethylamine* 200 I. 1135 200 OPH 8 26 35 42 B14 57 DEHP + 18 triethylamine 200 I. 1135 200 OPH 11 21 34 45 B15 50 DEHP + 23 dimethylcyclohexylamine* 200 I. 1135 200 OPH 8 23 31 48 B16 57 DEHP + 16 dimethylethanolamine 200 I. 1135 200 OPH 11 25 42 51 R13 28 Hordaphos MOB 200 I. 1135 200 OPH 8 25 63 127 R14 28 Hordaphos MOB + 50 Tinuvin 292 200 I. 1135 200 OPH 9 25 62 119 R15 28 Hordaphos MOB + 44 Tinuvin 770 200 I. 1135 200 OPH 9 25 62 126 B17 28 Hordaphos MOB + 18 triethylamine 200 I. 1135 200 OPH 9 23 30 39 B18 28 Hordaphos MOB + 23 dimethylcyclohexylamine 200 I. 1135 200 OPH 9 20 28 38 R16 33 Rhodafac PA80 200 I. 1135 200 OPH 8 36 111 213 R17 33 Rhodafac PA80 + 50 Tinuvin 292 200 I. 1135 200 OPH 9 29 84 154 R18 33 Rhodafac PA80 + 44 Tinuvin 770 200 I. 1135 200 OPH 9 34 87 160 B19 33 Rhodafac PA80 + 18 triethylamine 200 I. 1135 200 OPH 9 23 33 37 B20 33 Rhodafac PA80 + 23 dimethylcyclohexylamine 200 I. 1135 200 OPH 9 22 32 40 *about a 14% stoichiometric excess of amine. Otherwise, acids and amines are equimolar.

(51) The addition of amine (B2) to acids (B1) improves color drift.

(52) TABLE-US-00013 TABLE 6 Polyisocyanate (A3) with addition of ammonium phosphate in formulation 1 (Solvesso 100) Stabilizers (ppm/A3) Storage time (d) B C D 0 7 28 70 R19 200 I. 1010 200 OPH 11 83 63 359 B21 300 Nacure 4167 200 I. 1010 200 OPH 11 21 27 58 R20 200 I. 1135 200 Tppt 12 51 69 242 B22 300 Nacure 4167 200 I. 1135 200 Tppt 12 25 36 63

(53) The examples with salt (B) are better than those without.

(54) TABLE-US-00014 TABLE 7 Polyisocyanate (A4) with addition of ammonium phosphate in formulation 1 (Solvesso 100) Stabilizers (ppm/A4) Storage time (d) B C D 0 7 28 70 R21 200 I. 1135 200 OPH 13 75 103 173 B23 300 Nacure 4167 200 I. 1135 200 OPH 13 18 20 18

(55) The example with salt (B) is better than that without.

(56) TABLE-US-00015 TABLE 8 Polyisocyanate (A1) with addition of ammonium phosphate in formulation 2 (methyl amyl ketone) Stabilizers (ppm/A1) Storage time (d) Phosphate/ammonium phosphate C D 0 7 28 70 R22 200 I. 1010 200 Tppt 11 26 41 86 B24 200 Nacure 4167 200 I. 1010 200 Tppt 11 18 20 44 B25 300 Nacure 4167 200 I. 1010 200 Tppt 11 18 21 33 R23 200 I. 1010 200 I. OPH 10 21 31 54 B26 200 Nacure 4167 200 I. 1010 200 I. OPH 10 20 23 34 B27 300 Nacure 4167 200 I. 1010 200 I. OPH 10 21 22 37 R24 200 I. 1076 200 I. OPH 9 21 33 72 B28 200 Nacure 4167 200 I. 1076 200 I. OPH 9 21 24 38 B29 300 Nacure 4167 200 I. 1076 200 I. OPH 9 22 24 49 R25 200 I. 1076 200 Tppt 9 23 34 84 B30 200 Nacure 4167 200 I. 1076 200 Tppt 9 17 19 34 B31 300 Nacure 4167 200 I. 1076 200 Tppt 9 24 16 37 R26 200 I. 1135 200 I. OPH 12 28 39 70 R27 200 DEHP 200 I. 1135 200 I. OPH 11 20 32 70 B32 300 Nacure 4167 200 I. 1135 200 I. OPH 11 20 28 36 R28 200 I. 1135 200 Tppt 10 26 42 87 B33 200 Nacure 4167 200 I. 1135 200 Tppt 10 19 22 35 B34 300 Nacure 4167 200 I. 1135 200 Tppt 10 19 20 38 R29 200 I. 1135 200 TBP 10 25 43 88 B35 200 Nacure 4167 200 I. 1135 200 TBP 10 19 21 30 B36 300 Nacure 4167 200 I. 1135 200 TBP 10 18 16 29

(57) The examples with salt (B) are better than those without.

(58) TABLE-US-00016 TABLE 9 Polyisocyanate (A3) with addition of ammonium phosphate in formulation 2 (methyl amyl ketone) Stabilizers (ppm/A3) Storage time (d) B C D 0 7 28 70 R30 200 I. 1135 200 Tppt 17 19 56 112 B37 300 Nacure 4167 200 I. 1135 200 Tppt 17 16 25 50 R31 200 I. 1135 200 TBP 17 27 66 141 B38 300 Nacure 4167 200 I. 1135 200 TBP 18 16 20 38 R32 200 I. 1010 200 Tppt 20 15 58 108 B39 300 Nacure 4167 200 I. 1010 200 Tppt 20 24 22 39 R33 200 I. 1010 200 OPH 20 19 43 111 B40 300 Nacure 4167 200 I. 1010 200 OPH 20 24 31 44 R34 200 I. 1076 200 OPH 20 22 51 95 B41 300 Nacure 4167 200 I. 1076 200 OPH 20 22 25 39 R35 200 I. 1076 200 Tppt 19 21 62 112 B42 300 Nacure 4167 200 I. 1076 200 Tppt 19 18 25 45

(59) The examples with salt (B) are better than those without.

(60) In performance tests, no disadvantages of coatings, for example of polyisocyanate/polyacrylate or polyisocyanate/polyacrylate/polyester, were found, for example in drying, evolution of pendulum hardness, scratch resistance, etch resistances, cross-cutting, Erichsen cupping or weathering.