Method for producing polyisocyanates of (cyclo)aliphatic diisocyanates which are flocculation-stable in solvents

Abstract

The present invention relates to a new process for preparing polyisocyanates containing isocyanurate groups and being flocculation-stable in solvents from (cyclo)aliphatic diisocyanates.

Claims

1. A method comprising: adding at least one additive into a polyisocyanate mixture comprising at least one solvent, and reducing flocculation and/or precipitation in the polyisocyanate mixture, wherein the additive comprises a salt of: (A1) at least one phosphorus-containing acidic compound selected from the group consisting of (A1a) a mono- and/or di-C.sub.1 to C.sub.18 alkyl phosphate, (A1b) a mono- and/or di-C.sub.1 to C.sub.18 alkyl phosphonate, (A1c) a mono-C.sub.1 to C.sub.12 alkyl phosphinate, and (A1d) an alkyl derivative of a phosphorus-containing diacid, and (A2) at least one open-chain trisubstituted amine; wherein the at least one additive is used in a concentration of 200 to 300 ppm by weight based on the polyisocyanate.

2. The method according to claim 1, wherein the polyisocyanate is (cyclo)aliphatic.

3. The method according to claim 1, wherein the polyisocyanate is at least one polyisocyanate made from at least one monomer selected from the group consisting of hexamethylene 1,6-diisocyanate, pentamethylene 1,5-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 4,4′-di(isocyanato-cyclo-hexyl)-methane 2,4′-di(isocyanatocyclohexyl)methane.

4. The method according to claim 1, wherein the polyisocyanate has isocyanurate, iminooxadiazinedione, biuret or allophanate optionally with urethane structures.

5. The method according to claim 1, wherein the at least one open-chain trisubstituted amine (A2) is a trialkylamine.

6. The method according to claim 1, wherein the at least one open-chain trisubstituted amine (A2) has a first corresponding acid having a pKa of between 5 and 14 at 25° C. in an aqueous solution.

7. The method according to claim 1, wherein the solvent comprises water and the additive is used substoichiometrically in relation to the amount of water present in the solvent.

8. The method according to claim 1, wherein the polyisocyanate admixed with additive further comprises at least one phenol or bridged bisphenol which has exactly one phenolic hydroxyl group on each aromatic ring and has alkyl groups in the ortho positions to the phenolic hydroxyl group.

9. The method according to claim 1, wherein the polyisocyanate admixed with additive further comprise at least one Lewis acid.

10. A method for stabilizing a polyisocyanate or a polyisocyanate mixture in solvent against flocculation during storage, the method comprising: mixing the polyisocyanate or polyisocyanate mixture with at least one additive comprising a salt of: (A1) at least one phosphorus-containing acidic compound selected from the group consisting of (A1a) a mono- and/or di-C.sub.1 to C.sub.18 alkyl phosphate, (A1b) a mono- and/or di-C.sub.1 to C.sub.18 alkyl phosphonate, (A1c) a mono-C.sub.1 to C.sub.12 alkyl phosphinate, and (A1d) an alkyl derivate of a phosphorus-containing diacid, and (A2) at least one open-chain trisubstituted amine, thereby obtaining mixture (I); and storing mixture (I), thereby stabilizing mixture (I) against flocculation during storage; wherein the at least one additive is used in a concentration of 200 to 300 ppm by weight based on the polyisocyanate.

11. The method according to claim 10, wherein the mixture (I) further comprises Lewis acids as catalysts and/or antioxidants and/or other customary coatings additives.

12. A method for coating a substrate with a polyisocyanate or a polyisocyanate mixture stabilized against flocculation during storage in solvents, the method comprising: mixing the polyisocyanate or polyisocyanate mixture with 200 to 300 ppm of at least one additive based on the polyisocyanate or polyisocyanate mixture, the at least one additive is a salt of: (A1) at least one phosphorus-containing acidic compound selected from the group consisting of (A1a) a mono- and/or di-C.sub.1 to C.sub.18 alkyl phosphate, (A1b) a mono- and/or di-C.sub.1 to C.sub.18 alkyl phosphonate, (A1c) a mono-C.sub.1 to C.sub.12 alkyl phosphinate, and (A1d) an alkyl derivate of a phosphorus-containing diacid, and (A2) at least one open-chain trisubstituted amine, thereby obtaining mixture (I); mixing the mixture (I) with a solvent and optionally other additives, thereby obtaining mixture (II); storing the mixture (II) thereby reducing flocculation in the mixture (II); subsequently mixing the mixture (II) with at least one binder-comprising component, thereby obtaining mixture (III); and subsequently applying the mixture (III) to the substrate.

13. The method according to claim 12, wherein the binder-comprising component is at least one selected from the group consisting of a polyacrylate polyol, a polyester polyol, a polyurethane polyol, a polycarbonate polyol and a polyether polyol.

14. The method according to claim 12, wherein severe flocculation is not seen in the mixture (II) until at least 126 days.

15. The method according to claim 12, wherein the at least one polyisocyanate mixture further comprises at least one antioxidant.

16. The method according to claim 15, wherein the at least one additive is added in an amount which is substoichiometric in relation to the total amount of water in the mixture.

Description

EXAMPLES

(1) Ingredients:

(2) Salt (A):

(3) Nacure® 4167: amine-neutralized phosphate from King Industries/Worlée) 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 esters and an alkylamine. 25% “active” component in relation to catalysis of melamine resins (phosphoric esters).

(4) 200 ppm by weight of Nacure® 4167 correspond to 50 ppm by weight of phosphoric ester A. If this is calculated for simplification as dioctyl phosphate, the stoichiometrically 50 ppm by weight diethylhexyl phosphate and 48 ppm by weight dioctyl phosphonate corresponds to Irgafos® OPH.

(5) 200 ppm by weight of Nacure) 4167/polyisocyanate correspond, in the case of a 50% strength solution of polyisocyanate in solvent, to 3 ppm by weight of water/solvent. On even greater dilution down to 30% polyisocyanate in solvent, this corresponds to even smaller amounts of water. The salts (A) therefore have no effect as a stoichiometric water scavenger at water contents of 400 to 800 ppm by weight of water/solvent. The mechanism of action is different from that of conventional water scavengers.

(6) Polyisocyanates:

(7) Polyisocyanate 1, polyisocyanurate:

(8) Hexamethylene diisocyanate HDI was reacted in the presence of 70 ppm by weight of benzyltrimethylammonium hydroxyisobutyrate as catalyst, based on hexamethylene diisocyanate, at 60% strength 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.

(9) Polyisocyanate 2: Basonat® HI 100; polyisocyanurate from BASF SE. NCO content of product: 22.0%, viscosity: 2900 mPa*s.

(10) Other Additives

(11) The compounds used in the tables hereinafter are abbreviated as follows: I. 1010: Irganox® 1010 (BASF SE); pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate); primary antioxidant I. 1076: Irganox® 1076 (BASF SE); octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate; primary antioxidant I. 1135: Irganox® 1135 (BASF SE); benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl ester; primary antioxidant I. OPH: Irgafos® OPH (BASF SE); di-n-octyl phosphonate; secondary antioxidant (used here accordingly. Corresponds formally also to compound type A2) TBP: tributyl phosphite; secondary antioxidant Tppt: triphenyl phosphite; secondary antioxidant DEHP: di(ethylhexyl) phosphate; acid
Test Method:

(12) For determining the flocculation stability, mixtures consisting of polyisocyanate and solvent mixtures, containing 400-800 ppm by weight of water to solvent mixture, were prepared. Water is added in order to bring about faster flocculation than with the amounts of water present in commercial solvents. Firstly, this simulates solvents of poor quality (with lots of moisture); secondly, it is an accelerated test. The higher the water concentration, the quicker, normally, the flocculation. The water content was determined by means of Karl-Fischer titration. Additives were incorporated via the solvents. 50 g of the mixture was rendered inert by the passage of nitrogen over it in 50 mL screw lid vessels without writing on the side, which were then firmly closed and stored at 23° C.±5° C./(50%±10% atmospheric humidity). The flocculation was assessed by inspection daily on weekdays in the first two weeks, after three weeks, and, from four weeks onward, at two-week intervals. The greater the number of days obtained, the better.

(13) To assess the flocculation stability, a report is made of the first day on which one of the two following flocculation stages is achieved (or the day of the end of the test): Slight flocculation: weakly apparent Severe flocculation, readily apparent, sedimentation, discontinuation of the study For better recognition of turbidity, apparently clear solutions are briefly slightly horizontally rotated in a circle. In some cases slight flocculation is then evident better than as a tail.

(14) The amounts of the additives are in ppm by weight, based on polyisocyanate.

(15) Test Method 1:

(16) Test method 1 takes place with 30% polyisocyanate in 70% xylene/butyl acetate=2:1, with addition of 400 ppm by weight of water/solvent.

(17) Test Method 2:

(18) Test method 2 takes place with 40% polyisocyanate in butyl acetate with addition of 800 ppm by weight of water/solvent.

(19) Test Method 3:

(20) Test method 3 takes place with 40% polyisocyanate in xylene/butyl acetate=3:1, with addition of 600 ppm by weight of water/solvent.

Storage Examples

(21) The examples which follow are intended to illustrate the invention, but not to confine it to these examples.

(22) The experimental series show that in the inventive examples, longer storage times without flocculation or with lower flocculation are obtained than with the reference examples without additives and with noninventive additives.

(23) It is shown by way of example, moreover, that this effect in different typical coatings solvent mixtures, albeit to different extents.

(24) TABLE-US-00001 TABLE 1 Polyisocyanate 1 with addition of salt (A) and further additives (antioxidants) in test method 1. Storage for 168 days (d) with discontinuation after flocculation of all specimens Stabilizers (ppm) Primary Secondary Flocculation (d) Salt (A) antioxidant antioxidant Slight Severe Total R1 200 I. 1010 200 Tppt 21 21 42 B1 300 Nacure 4167 200 I. 1010 200 Tppt 21 168 189 R2 200 I. 1010 200 I. OPH 42 42 84 B2 300 Nacure 4167 200 I. 1010 200 I. OPH 14 126 140 R3 200 I. 1076 200 I. OPH 28 28 56 B3 300 Nacure 4167 200 I. 1076 200 I. OPH 42 126 168 R4 200 I. 1076 200 Tppt 12 21 33 B4 300 Nacure 4167 200 I. 1076 200 Tppt 5 126 131 R5 200 I. 1135 200 Tppt 6 28 34 B5 300 Nacure 4167 200 I. 1135 200 Tppt 42 126 168 R6 200 I. 1135 200 TBP 28 28 56 B6 300 Nacure 4167 200 I. 1135 200 TBP 7 154 161

(25) The examples with salt (A) are better than those without.

(26) TABLE-US-00002 TABLE 2 Polyisocyanate 2 with addition of a salt (A) and further additives (antioxidants) in test method 1. Storage for 210 days (discontinuation of the studies) Stabilizers (ppm) Primary Secondary Flocculation (d) Salt (A) antioxidant antioxidant Slight Severe Total R7 200 I. 1010 200 Tppt 28 42 70 B7 200 N. 4167 200 I. 1010 200 Tppt 9 210 219 B8 300 N. 4167 200 I. 1010 200 Tppt 12 210 222 R8 200 I. 1076 200 Tppt 12 42 54 B9 200 N. 4167 200 I. 1076 200 Tppt 9 210 219 B10 300 N. 4167 200 I. 1076 200 Tppt 9 168 177 R9 200 I. 1135 200 Tppt 8 21 27 B11 200 N. 4167 200 I. 1135 200 Tppt 10 210 220 B12 300 N. 4167 200 I. 1135 200 Tppt 10 168 178 R10 200 I. 1135 200 TBP 21 21 42 B13 200 N. 4167 200 I. 1135 200 TBP 13 210 223 B14 300 N. 4167 200 I. 1135 200 TBP 21 210 231

(27) The examples with salt (A) are better in flocculation than those without.

(28) TABLE-US-00003 TABLE 3 Polyisocyanate 2 with addition of a salt (A) and further additives (antioxidants) in test method 1. Storage for 154 days. In this case an additive of type a4b) of WO 2013/060809 is supplemented or replaced by the salt (A) Stabilizers (ppm/PIC) Salt (A) & additive a) of Primary Flocculation (d) WO 2013/060809 antioxidant Slight Severe Total R11 7 28 35 R12 200 I. OPH 7 28 35 B15 200 N. 4167 2 154 156 B16 200 N. 4167 + 200 I. OPH 7 154 161 R13 200 I. OPH 200 I. 1135 7 28 35 B17 200 N. 4167 200 I. 1135 3 154 157 B18 760 N. 4167 200 I. 1135 2 154 156 B19 200 N. 4167 + 200 I. OPH 200 I. 1135 2 154 156

(29) The examples with salt (A) are better in flocculation than those without.

(30) Irgafos OPH (as well as its function as a secondary antioxidant) corresponds to an additive of the type of acidic phosphorus derivatives a4b) of WO 2013/060809 for improving flocculation.

(31) By adding an ammonium phosphate or by replacing one of the additives of type a) of WO 2013/060809 by salt (A), the flocculation is improved further.

(32) Nacure 4167 here is used at only 25% based on the active substance (phosphates), and in stoichiometric terms is therefore used even in a smaller amount than Irgafos OPH.

(33) TABLE-US-00004 TABLE 4 Polyisocyanate 1 with addition of a salt (A) in test method 1. In this case an additive of types a4b) and a4a) of WO 2013/060809 is supplemented or replaced by a salt (A). Storage for 154 days Stabilizers (ppm/PIC) Salt (A) & additive a) of Primary Flocculation (d) WO 2013/060809 antioxidant Slight Severe Total R14 4 7 11 R15 200 I. OPH 4 42 46 B20 200 N. 4167 2 154 156 B21 200 N. 4167 + 200 I. OPH 2 154 156 R16 50 DEHP 200 I. 1135 2 28 30 B22 200 N. 4167 200 I. 1135 2 126 128

(34) By replacing one of the additives of type a4b) of WO 2013/060809 by salt (A) the flocculation is further improved.

(35) TABLE-US-00005 TABLE 5 Polyisocyanate 2 with addition of a salt (A) and a further additive (antioxidant) in test method 2 (40% in butyl acetate, 800 ppm by weight water). In this case an additive of type a4b) of WO 2013/060809 is replaced by the salt (A). Storage lasted for 112 days. Stabilizers (ppm/PIC) Salt (A) & additive a) of Primary Flocculation (d) WO 2013/060809 antioxidant Slight Severe Total R17 200 I. 1135 4 11 15 R18 600 I. OPH 200 I. 1135 6 21 27 B23 2400 N. 4167 200 I. 1135 12 112 124

(36) By replacing one of the additives of type a4b) of WO 2013/060809 by salt A the flocculation is further improved.

(37) TABLE-US-00006 TABLE 6 Polyisocyanate 3 with addition of a salt (A) and a further additive (antioxidant) in test method 2 (40% in solvent xylene/butyl acetate = 3:1, 600 ppm by weight water). In this case an additive of type a4b) of WO 2013/060809 is replaced by the salt (A). Storage lasted for 154 days. Stabilizers (ppm/PIC) Salt (A) & additive a) of Primary Flocculation (d) WO 2013/060809 antioxidant Slight Severe Total R19 200 I. OPH 200 I. 1135 4 21 25 B24 200 I. OPH + 200 N. 4167 200 I. 1135 5 154 159

(38) The addition of salt (A) further improves the flocculation.

(39) In performance trials no disadvantages were found of coating materials, as for example of polyisocyanate/polyacrylate or polyisocyanate/polyacrylate/polyester, in terms, for example, of drying, development of pendulum hardness, scratch resistance, etch resistances, cross-cut, Erichsen cupping, or weathering.