TDI based low-viscosity polyisocyanates with isocyanurate groups

Abstract

The invention relates to a polyisocyanate which is based on tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate or a mixture of tolylene 2,4- and 2,6-diisocyanate and has isocyanurate groups, wherein the polyisocyanate has a) a weight average molecular weight of from 350 to 800 g/mol, determined by means of gel permeation chromatography using a polystyrene standard and tetrahydrofuran as eluent in accordance with DIN 55672-1:2016-03, b) a polydispersity D of from >1 to 1.5, where the polydispersity D is the ratio of weight average and number average molecular weight of the polyisocyanate and the weight average and number average molecular weight are 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, and c) a content of monomeric tolylene diisocyanate of 1% by weight, based on the total weight of the polyisocyanate.

Claims

1. Polyisocyanate which is based on tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate or a mixture of tolylene 2,4- and 2,6-diisocyanate and has isocyanurate groups, wherein the polyisocyanate has a) a weight average molecular weight of from 350 to 800 g/mol, determined by means of gel permeation chromatography using a polystyrene standard and tetrahydrofuran as eluent in accordance with DIN 55672-1:2016-03, b) a polydispersity D of from >1 to 1.5, where the polydispersity D is the ratio of weight average and number average molecular weight of the polyisocyanate and the weight average and number average molecular weight are 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, and c) a content of monomeric tolylene diisocyanate of 1% by weight, based on the total weight of the polyisocyanate.

2. Polyisocyanate according to claim 1, wherein the weight average molecular weight is from 500 to 750 g/mol.

3. Polyisocyanate according to claim 1, wherein the polydispersity D is from 1.0005 to 1.3.

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

5. Polyisocyanate according to claim 1, wherein the polyisocyanate has d) a content of allophanate and urethane groups of from 0 to 0.5% by weight, based on the total weight of the polyisocyanate.

6. Polyisocyanate according to claim 1, wherein the mixture of tolylene 2,4- and 2,6-diisocyanate has a weight ratio of from 3:2 to 9.5:0.5.

7. Polyisocyanate according to claim 1, wherein the polyisocyanate has a content of isocyanate groups of from 20 to 25% by weight, based on the total weight of the polyisocyanate.

8. Mixture which has isocyanate groups and contains from 15 to 40% by weight, of at least one polyisocyanate according to claim 1, from 5 to 20% by weight, of at least one polyisocyanate based on tolylene diisocyanate and from 40 to 75% by weight, of at least one solvent, where the sum of the % by weight, even in the case of the optional presence of further compounds, is not greater than 100%.

9. Mixture according to claim 8, wherein the mixture has a viscosity of from 1 to <500 mPas at 23 C., measured in accordance with DIN EN ISO 3219:1994-10 using a cone/plate measuring instrument.

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 55672-1:2016-03 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 I (Inventive)

(9) 2040 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, 0.42 parts by weight of a Mannich base (phenol/formaldehyde/dimethylamine, 77% in xylene) was added during one hour. As soon as the free isocyanate group content was 47.4%, 0.96 parts, by weight, of methyl p-toluene sulfonate were 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 0.11 mbar and a temperature of 145 C. (short path distillation) and 200 C. (for thin film evaporator). 214 parts of solid transparent product with glassy consistency were obtained after the distillation. The resin isolated contained 0.28%, by weight, of free monomeric tolylene diisocyanate and 85.3%, by weight, of tris-(isocyanatotoluene)-isocyanurate, a number average of molecular weight of 527 g/mol and a polydispersity D of 1.08.

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

(12) Isocyanate group content: 15.0%

(13) Non volatile content: 65.2%

(14) Viscosity: 179 mPas

(15) Polyisocyanate 2 (Inventive)

(16) 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 211 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.

(17) 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.

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

(19) Isocyanate group content: 15.1%

(20) Non volatile content: 64.6%

(21) Viscosity 291 mPas

(22) Polyisocyanate 3 (Inventive)

(23) 1700 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 100 C. Then, 0.64 parts, by weight of a Mannich base catalyst (based on phenol/formaldehyde/dimethylamine, 77% in Xylene) were added in 2.5 hours. When the free isocyanate group content was 34.6%, 1.2 parts, by weight, of methyl p-toluenesulfonate were added to stop the reaction.

(24) The excess monomeric isocyanate was then removed by a thin-film evaporator at a pressure of 0.05 mbar using a short path evaporator (160 C.) and consecutively, a thin film evaporator (214 C.). 542 parts of solid transparent product with glassy consistency were obtained after distillation. The resin isolated contained 0.12%, by weight, of free monomeric tolylene diisocyanate and 60.8%, by weight, of tris-(isocyanatotoluene)-isocyanurate, a number average molecular weight of 596 g/mol and a polydispersity D of 1.20.

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

(26) Isocyanate group content: 13.7%

(27) Non volatile content: 64.8%

(28) Viscosity: 444 mPas

(29) Polyisocyanate 4 (Comparison)

(30) 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-dodecanot, were added in 55 minutes. As soon as the mixture reached a content of free isocyanate groups of 28.97%, by weight, 1055 parts of butyl acetate were added. Temperature was decreased to 45 C. Then, 17.5 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 isocyanate group content had reached 7.56%, 10.6 parts, by weight, of methyl p-toluenesulfonate were added to stop the reaction.

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

(32) The solution containing the resin had the following characteristics:

(33) Isocyanate group content: 7.6%

(34) Non volatile content: 49.8%

(35) Viscosity: 164 mPas

(36) Polyisocyanate 5 (Comparison)

(37) 1700 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 85 C. Then, 170 parts, by weight, of polyol (1,1,1-Tris(hydroxymethyD propane/diethylene glycol=65:35 by weight) were added in 49 minutes. After 55 minutes, the free isocyanate group content reached 35.86%, indicating full conversion of the isocyanatepolyol reaction.

(38) 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 consistency were 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. The resin was dissolved in ethyl acetate to a solution with the following characteristics:

(39) Isocyanate group content: 14.1%

(40) Non volatile content: 74.4%

(41) Viscosity: 772 mPas

Example 1

Drying Speed Test

(42) In these application testings, Desmophen 1300 X (Covestro), a fatty acid modified polyester polyol with an OH content of 3.2%, by weight, and a non volatile content of approx. 75%, was used in the formulations. The ratio of isocyanate groups to hydroxyl groups was 0.8 and the solid content was 40%, by weight, for all formulations.

(43) Ingredients were mixed together homogenously. Then each mixture was immediately applied onto transparent glass plates using a film applicator (thickness of wet film was 120 pn) and was allowed to dry at ambient temperature (23.5 C.) and a humidity of 50%. All testing were based on DIN 53 150:2002-09.

(44) Formulation 1

(45) TABLE-US-00001 Ingredient By weight % Polyisocyanate 2 16.5 Desmophen 1300 X 39.1 Butyl Acetate 44.4

(46) Formulation 2 (comparison)

(47) TABLE-US-00002 Ingredient By weight % Polyisocyanate 5 16.9 Desmophen 1300 X 36.4 Butyl Acetate 46.7

(48) The results are shown in the following table 1:

(49) TABLE-US-00003 TABLE 1 Formulation Viscosity T1 T4 Formulation (T4 cup) (dust dry) T3 (full cure) 1 13.1 s 7 min 19 s 22 min 32 s 30 min 50 s 2 12.8 s 10 min 21 s 3 h 47 min 5 h 1 min

(50) These drying speed tests reveal that the inventive Polyisocyanates can be used in low viscosity formulations, similar to known Urethane-polyisocyanates (comparative Polyisocyanate 5). When using inventive Polyisocyanate 2 (Formulation 1), drying is significantly faster, leading e. g. to productivity gain in industrial coatings processes.

Example 2

Drying Speed Test

(51) The drying speed test are carried out in the same way as Example 1, except that the solid content is set to 50% by weight for following formulations:

(52) Formulation 3

(53) TABLE-US-00004 Ingredient By weight % Polyisocyanate 2 20.6 Desmophen 1300 X 48.9 Butyl Acetate 30.5

(54) Formulation 4

(55) TABLE-US-00005 Ingredient By weight % Blend of Polyisocyanate 2 and Polyisocyanate 4 24.4 (2/1, by weight) Desmophen 1300 X 47.2 Butyl Acetate 28.4

(56) Formulation 5 (Comparison)

(57) TABLE-US-00006 Ingredient By weight % Polyisocyanate 4 36.2 Desmophen 1300 X 42.1 Butyl Acetate 21.7

(58) The results are shown in the following table 2:

(59) TABLE-US-00007 TABLE 2 Formulation Viscosity T1 T4 Formulation (T4 cup) (dust dry) T3 (full cure) 3 18.8 s 6 min 47 s 21 min 28 s 29 min 12 s 4 20.4 s 6 min 15 s 20 min 35 s 26 min 1 s 5 31.3 s 6 min 15 s 13 min 37 s 17 min

(60) The results show that the polyisocyanates according to this invention reveal the most efficient properties, combining low viscosity and short drying cycles.