TDI based polyisocyanate mixture with a high solids content

Abstract

The invention relates to a polyisocyanate mixture comprising at least one polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups and at least one polyurethane which is based on tolylene diisocyanate and has isocyanate groups, wherein the polyisocyanate mixture has a) a solids content of from 51 to 90% by weight, based on the total weight of the polyisocyanate mixture and b) a content of monomeric tolylene diisocyanate of 0.9% by weight, based on the total weight of the polyisocyanate mixture, and the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups has a polydispersity D of from 1 to 1.5, based on the total weight of the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups, where the polydispersity D is the ratio of weight average and number average molecular weight of the polyisocyanurate and the weight average and number average molecular weight is in each case determined by means of gel permeation chromatography using a polystyrene standard and tetrahydrofuran as eluent in accordance with DIN 55672-1:2016-03.

Claims

1. Polyisocyanate mixture comprising at least one polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups and at least one polyurethane which is based on tolylene diisocyanate and has isocyanate groups, wherein the polyisocyanate mixture has a) a solids content of from 51 to 90% by weight, based on the total weight of the polyisocyanate mixture, b) a content of monomeric tolylene diisocyanate of 0.9% by weight, based on the total weight of the polyisocyanate mixture, and the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups has a polydispersity D of from 1 to 1.5, based on the total weight of the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups, where the polydispersity D is the ratio of weight average and number average molecular weight of the polyisocyanurate and the weight average and number average molecular weight is in each case determined by means of gel permeation chromatography using a polystyrene standard and tetrahydrofuran as eluent in accordance with DIN 55672-1:2016-03.

2. Polyisocyanate mixture according to claim 1, wherein the solids content is from 55 to 85% by weight.

3. Polyisocyanate mixture according to claim 1, wherein the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups has a polydispersity D of from 1.0005 to 1.3.

4. Polyisocyanate mixture according to claim 1, wherein the content of monomeric tolylene diisocyanate is 0.5% by weight.

5. Polyisocyanate mixture according to claim 1, wherein the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups and the polyurethane which is based on tolylene diisocyanate and has isocyanate groups are present in a weight ratio to one another of from 2.5:1 to 1:2.5.

6. Polyisocyanate mixture according to claim 1, wherein the polyisocyanate mixture has a viscosity of from 300 to <2000 mPas at 23 C., measured in accordance with DIN EN ISO 3219: 1994-10 using a cone/plate measuring instrument.

7. Polyisocyanate mixture according to claim 1, wherein the polyisocyanate mixture has a content of isocyanate groups of from 11.0 to 20.0% by weight, based on the total weight of the polyisocyanate mixture.

8. Polyisocyanate mixture according to an claim 1, wherein the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups has a content of allophanate and urethane groups of from 0 to 0.5% by weight, based on the total weight of the polyisocyanurate.

9. Polyisocyanate mixture according to claim 1, wherein the solids content is from 60 to 80% by weight.

10. Polyisocyanate mixture according to claim 1, wherein the solids content is from 65 to 75% by weight.

11. Polyisocyanate mixture according to claim 1, wherein the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups has a polydispersity D of from 1.005 to 1.15.

12. Polyisocyanate mixture according to claim 1, wherein the content of monomeric tolylene diisocyanate is 0.1% by weight.

13. Polyisocyanate mixture according to claim 1, wherein the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups and the polyurethane which is based on tolylene diisocyanate and has isocyanate groups are present in a weight ratio to one another of from 2.0:1 to 1.1.5.

14. Polyisocyanate mixture according to claim 1, wherein the polyisocyanate mixture has a viscosity of from 500 to <1500 mPas at 23 C., measured in accordance with DIN EN ISO 3219:1 994-10 using a cone/plate measuring instrument.

15. Polyisocyanate mixture according to claim 1, wherein the polyisocyanate mixture has a content of isocyanate groups of from 12.0 to 18.0% by weight, based on the total weight of the polyisocyanate mixture.

16. Polyisocyanate mixture according to claim 1, wherein the polyisocyanate mixture has a content of isocyanate groups of from 14.0 to 16.0% by weight, based on the total weight of the polyisocyanate mixture.

17. Polyisocyanate mixture according to an claim 1, wherein the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups has a content of allophanate and urethane groups of from 0% by weight to 0.1% by weight, based on the total weight of the polyisocyanurate.

18. Polyisocyanate mixture according to an claim 1, wherein the polyisocyanurate which is based on tolylene diisocyanate and has isocyanate groups has a content of allophanate and urethane groups of from 0 to 0.05% by weight, based on the total weight of the polyisocyanurate.

19. Process for preparing a polyisocyanate mixture according to claim 1, which comprises the steps (i) reaction of tolylene diisocyanate to form isocyanurate groups in the presence of at least one catalyst; (ii) stopping of the reaction at a content of isocyanate groups of from 30 to 48.3% by weight, by deactivation of the catalyst, (iii) removal of the unreacted tolylene diisocyanate, (iv) addition of at least one organic solvent which is inert to isocyanate groups and (v) addition of the at least one polyurethane which is based on tolylene diisocyanate and has isocyanate groups and is optionally diluted in at least one solvent and optionally further auxiliaries and additives, where the steps (iv) and (v) can be carried out in any order or simultaneously.

20. Process according to claim 19, wherein the steps (i) to (iii) are carried out in the presence of from 0 to <1% by weight, based on the total weight of the compounds used in step (i) and (ii), of liquid distillation auxiliaries which are inert under distillation conditions and have a boiling point at least 50 C. above that of the isocyanurate group-free monomeric isocyanate and/or from 0 to <1% by weight, based on the total weight of the compounds used in step (i) and (ii), of compounds which have one or more hydroxyl groups.

21. Two-component system comprising an isocyanate component A) containing at least one polyisocyanate mixture according to claim 1 and an NCO-reactive component B) containing at least one compound which is reactive towards isocyanate groups.

22. Process for producing a composite system or a coated substrate, which comprises a step in which a two-component system according to claim 21 is applied to at least one substrate and comprises at least one further step in which the two-component system applied to the substrate is cured, optionally under the action of heat.

23. Process according to claim 22, wherein the substrate comprises one or more materials selected from the group consisting of metal, plastic, glass, wood, leather, textiles and mixtures thereof.

24. Composite system or coated substrate which has been produced or can be produced by a process according to claim 22, wherein the composite system is a piece of furniture, a decorative object, a floor covering, a wooden interior installation or a shoe and the coated substrate is a piece of furniture, a decorative object, a floor covering or a wooden interior installation.

25. Process according to claim 22, wherein the substrate comprises one or more materials selected from the group consisting of a natural or synthetic fibrous material and mixtures thereof.

26. Process according to claim 22, wherein the substrate comprises one or more materials selected from the group consisting of paper, cork and wood.

Description

EXAMPLES

(1) All percentages are, unless indicated otherwise, by weight.

(2) The determination of the NCO contents was carried out titrimetrically in accordance with DIN EN ISO 11909:2007-05.

(3) The residual monomer contents were determined gas-chromatographically using an internal standard in accordance with DIN EN ISO 10283:2007-11.

(4) All viscosity measurements were carried out in accordance with DIN EN ISO 3219:1994-10 using a cone/plate measuring instrument. Unless indicated otherwise, measurements were carried out at a temperature of 23 C.

(5) The distribution of the oligomers was determined by gel permeation chromatography in accordance with DIN 55672:2016-03 using polystyrene as standard and tetrahydrofuran as eluent.

(6) The non volatile content was determined in accordance with DIN EN ISO 3251 using a drying temperature and time of 2 hours at 120 C. and a test dish diameter of 75 mm and a weighed-in quantity of 2.00 g+/0.02.

(7) The drying properties of the coating systems were determined in accordance with DIN 53 150:2002-09.

(8) Polyisocyanate 1

(9) 1500 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 2 L flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 80 C. Then, 0.52 parts, by weight, of a Mannich base catalyst (bisphenol A/formaldehyde/dimethylamine, 25% in n-butyl acetate/xylene 19:56) were added in two hours. As soon as the free isocyanate group content was 40.4%, 1.0 part, by weight, of dibutyl phosphate was added to stop the reaction.

(10) The excess monomeric isocyanate was then removed by a combination of short path distillation and thin-film evaporator at a pressure of 0.05 mbar and a temperature of 180 C. (short path distillation) and consecutively 180 C. (thin film evaporator). 370 parts of a solid transparent product with glassy consistency were obtained after the distillation. The resin isolated contained 0.18%, by weight, of free monomeric tolylene diisocyanate and 78.9%, by weight, of tris-(isocyanatotoluene)-isocyanurate, a number average of molecular weight of 533 g/mol and a polydispersity D of 1.09.

(11) The resin was dissolved in ethyl acetate to get a solution with the following characteristics:

(12) Isocyanate group content: 15.1%

(13) Non volatile content: 64.6%

(14) Viscosity: 291 mPas

(15) Polyisocyanate 2

(16) 1700 parts of a mixture of tolyluene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20% tolylene 2,6-diisocyanate, were added to a 2 L flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 85 C. Then, 170 parts, by weight, of polyol (1,1,1-Tris(hydroxymethyl) propane/diethylene glycol=65:35) were added in 49 minutes. After 55 minutes, the free isocyanate group content reached 35.9%, indicating full conversion of the isocyanate-polyol reaction.

(17) Excess monomeric isocyanate was then removed by distillation at a pressure of 0.01 mbar, using a short path evaporator (132 C.) and consecutively, a thin film evaporator (127 C.). 735 parts of solid transparent product with glassy consistency was obtained. The isolated resin had a number average molecular weight of 750 g/mol and a polydispersity D of 1.14. It contained 0.20% of free monomeric tolylene diisocyanate.

(18) The resin was dissolved in ethyl acetate to a solution with the following characteristics:

(19) Isocyanate group content: 14.1%

(20) Non volatile content: 74.4%

(21) Viscosity: 772 mPas

(22) Polyisocyanate 3

(23) 1575 parts of a mixture of tolylene diisocyanate, containing approx. 80% tolylene 2,4-diisocyanate and approx. 20%/tolylene 2,6-diisocyanate and 750 parts, by weight, of butyl acetate, were added to a 4 L flask with stirrer equipped with a reflux condenser, dropping funnel and nitrogen inlet. The mixture was heated to 88 C. Then, 168 parts, by weight, of 1-dodecanol, were added in 55 minutes. As soon as the mixture reached a content of free NCO groups of 28.97% (weight), 1055 parts of butyl acetate were added. Temperature was decreased to 45 C. Then, 17 parts, by weight, of a Mannich base catalyst (bisphenol A/formaldehyde/dimethylamine, 25% in n-butyl acetate/xylene 19:56) were added during 23.5 hours. When the NCO group content had reached 7.56%, 10.6 parts, by weight, of methyl p-toluenesulfonate were added to stop the reaction.

(24) The resin isolated contained 13.23%, by weight, of tris-(isocyanatotoluene)-isocyanurate and had a molecular weight (number average) of 1160 g/mol at a polydispersity D of 1.62.

(25) The resin was dissolved in ethyl acetate to get a solution with the following characteristics:

(26) Isocyanate group content: 7.6%

(27) Non volatile content: 49.8%

(28) Viscosity: 164 mPas

Example 1

(29) For performance testings, Desmophen 1300 X (Covestro), a fatty acid modified polyester polyol with OH content of 3.2%, by weight, and a non volatile content of approx. 75%, was used as a coreactant. The ratio of isocyanate groups to hydroxyl groups was 0.8 and the solid content of the final formulation at application was 40%, by weight.

(30) Ingredients were mixed together homogenously, as summarized for Formulation 1, 2 and 3. Then the mixture was immediately applied onto transparent glass using a film applicator (thickness of wet film 120 m) and was allowed to dry at ambient temperature (23.5 C.) and a humidity of 50%. Testings were based on the DIN 53 150:2002-09.

(31) Formulation 1 (Inventive)

(32) TABLE-US-00001 Ingredient Weight % Blend of Polyisocyanate 1 and Polyisocyanate 2 20.3 (7.5:3, by weight) Desmophen 1300 X 46.0 Butyl Acetate 33.7
Formulation 2 (Comparison)

(33) TABLE-US-00002 Ingredient Weight % Blend of Polyisocyanate 3 and Polyisocyanate 2 27.6 (16:5, by weight) Desmophen 1300 X 38.6 Butyl Acetate 33.8

(34) TABLE-US-00003 TABLE 1 Viscosity, solids content and drying times of Formulations 1 and 2 Viscosity Solids Formu- (T4 cup/ content lation 23 C.) (%) T1 T3 T4 1 15.5 s 48.2 11 min 1 s 44 min 2 s 56 min 2 15.8 s 44.4 10 min 7 s 25 min 26 s 36 min 3 s
Pendulum Hardness (Koenig):

(35) TABLE-US-00004 TABLE 2 Pendulum Hardness (Koenig) of Formulations 1 and 2 Formulation 2 d 4 d 7 d 1 170 s 177 s 173 s 2 160 s 165 s 177 s
Solvent-Resistance Testing

(36) A film was prepared as described above and dried for seven days. Then, a cotton ball, wetted by the solvent, was placed on the surface of the coating. Status of the film was observed after different times, as shown in table 3.

(37) TABLE-US-00005 TABLE 3 Solvent-resistance of Formulations 1 and 2 Acetone Butyl Acetate Xylene Ethanol Formulation 1 min 3 min 5 min 1 min 3 min 5 min 1 min 3 min 5 min 1 min 3 min 5 min 1 5 1 1 2 0 0 0 1 1 2 2 5 1 1 2 0 0 0 1 1 2 0: No traces, film complete/ 1-4: Increasing damage of the film/ 5: Film destroyed

(38) The results show, that by using a polyisocyanate mixture according to the invention, a coating can be formulated at similar viscosity during application and similar end performance, but significantly lower content of organic solvents, as compared to the prior art.