Hydrophilically modified polyisocyanurate plastic and process for production thereof

Abstract

The present invention relates to novel modified polyisocyanurate plastics obtainable by catalytic trimerization of a composition A), wherein the composition A) comprises oligomeric modified polyisocyanates B) that are a reaction product of an oligomeric polyisocyanate B1) and at least one functionalizing reagent B2) reactive toward isocyanate groups, where the composition A) has a content of monomeric diisocyanates of not more than 20% by weight and where the at least one functionalizing reagent B2) reactive toward isocyanate groups has at least one functional group reactive toward isocyanate groups which is not an isocyanate group. The invention further relates to the process from which the polyisocyanurate plastics of the invention are obtainable, to the use of the polyisocyanurate plastics of the invention for production of coatings, films, semifinished products, composites and moldings, and to substrates coated with such a coating.

Claims

1. A modified polyisocyanurate plastic obtained by a process comprising the steps of: (a1) providing a composition A), containing oligomeric, modified polyisocyanates B) and not more than 20% by weight of monomeric diisocyanates based on the weight of the composition A), wherein the oligomeric modified polyisocyanates B) constitute a reaction product of an oligomeric polyisocyanate B1) and at least one isocyanate-reactive functionalization reagent B2), and wherein the at least one isocyanate-reactive functionalization reagent B2) comprises at least one isocyanate-reactive functional group which is not an isocyanate group, wherein the at least one isocyanate-reactive functionalization reagent B2) is chosen such that after reaction with the polyisocyanate B1) and catalytic trimerization of the composition A) it increases the surface energy of the polyisocyanurate plastic by at least 2 mN/m; (a2) catalytic trimerization of the composition A), wherein the modified polyisocyanurate plastic is a solid, transparent and bubble-free molding.

2. The modified polyisocyanurate plastic as claimed in claim 1, wherein the at least one isocyanate-reactive functionalization reagent B2) has a surface tension of >20 mN/m and <70 mN/m.

3. The modified polyisocyanurate plastic as claimed in claim 1, wherein the at least one isocyanate-reactive functionalization reagent B2) is chosen such that after reaction with polyisocyanate B1) it increases the surface tension of B) by at least 2 mN/m.

4. The modified polyisocyanurate plastic as claimed in claim 1, wherein the at least one isocyanate-reactive functionalization reagent B2) is a polyether alcohol.

5. The modified polyisocyanurate plastic as claimed in claim 4, wherein the polyether alcohol is a polyalkylene oxide polyether alcohol having a statistical average of 5 to 50 ethylene oxide units per molecule.

6. The modified polyisocyanurate plastic as claimed in claim 5, wherein the polyalkylene oxide polyether alcohol consist of ethylene oxide units to an extent of at least 70 mol %.

7. The modified polyisocyanurate plastic as claimed in claim 5, wherein the polyalkylene oxide polyether alcohol is a polyethylene glycol monomethyl ether alcohol.

8. The modified polyisocyanurate plastic as claimed in claim 1, wherein the oligomeric polyisocyanate B1) is constructed on the basis of 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI), isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 2,4′-diisocyanatodicyclohexylmethane or 4,4′-diisocyanatodicyclohexylmethane (H12MDI) or mixtures thereof.

9. The modified polyisocyanurate plastic as claimed in claim 1, wherein the catalytic trimerization is carried out in the presence of a trimerization catalyst C), wherein the trimerization catalyst C) comprises at least one alkali metal or alkaline earth metal salt.

10. The modified polyisocyanurate plastic as claimed in claim 1, wherein it constitutes a highly converted modified polyisocyanurate plastic in which not more than 20% of the isocyanate groups originally contained in the composition A) have been preserved.

11. A process for producing a modified polyisocyanurate plastic solid, transparent and bubble-free body, comprising the steps of: (a1) providing a composition A), containing oligomeric, modified polyisocyanates B) and not more than 20% by weight of monomeric diisocyanates based on the weight of the composition A), wherein the oligomeric modified polyisocyanates B) constitute a reaction product of an oligomeric polyisocyanate B1) and at least one isocyanate-reactive functionalization reagent B2), and wherein the at least one isocyanate-reactive functionalization reagent B2) comprises at least one isocyanate-reactive functional group which is not an isocyanate group, wherein the at least one isocyanate-reactive functionalization reagent B2) is chosen such that after reaction with the polyisocyanate B1) and catalytic trimerization of the composition A) it increases the surface energy of the polyisocyanurate plastic by at least 2 mN/m; (a2) catalytic trimerization of the composition A), wherein the solid, transparent and bubble-free body is a molding.

12. The process as claimed in claim 11, wherein the catalytic trimerization is carried out in the presence of a trimerization catalyst C).

13. The process as claimed in claim 11, wherein the oligomeric polyisocyanate B1) is constructed on the basis of 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI), isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 2,4′-diisocyanatodicyclohexylmethane or 4,4′-diisocyanatodicyclohexylmethane (H12MDI) or mixtures thereof, and wherein the at least one isocyanate-reactive functionalization reagent B2) has a surface tension of >20 mN/m and <70 mN/m.

14. The process as claimed in claim 11, wherein the catalytic trimerization is continued at least up to a degree of conversion at which only not more than 20% of the isocyanate groups originally contained in the composition A) remain present, so that a highly converted modified polyisocyanurate plastic is obtained.

Description

EXAMPLES

(1) All reported percentages are based on weight unless otherwise stated.

(2) The NCO contents were determined by titrimetry in accordance with DIN EN ISO 11909.

(3) The residual monomer contents were measured in accordance with DIN EN ISO 10283 by gas chromatography with an internal standard.

(4) All the viscosity measurements were made with a Physica MCR 51 rheometer from Anton Paar Germany GmbH (Germany) to DIN EN ISO 3219.

(5) The densities of the starting polyisocyanates were determined to DIN EN ISO 2811, and those of the cured polyisocyanurate plastics to DIN EN ISO 1183-1.

(6) The contents (mol %) of the uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structures present in the starting polyisocyanates were calculated from the integrals of proton-decoupled .sup.13C NMR spectra (recorded on a Bruker DPX-400 instrument) and are each based on the sum total of uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structures present. In the case of HDI polyisocyanates, the individual structural elements have the following chemical shifts (in ppm): uretdione: 157.1; isocyanurate: 148.4; allophanate: 155.7 and 153.8, biuret: 155.5; iminooxadiazinedione: 147.8, 144.3 and 135.3; oxadiazinetrione: 147.8 and 143.9.

(7) The glass transition temperature Tg was determined by means of DSC (differential scanning calorimetry) with a Mettler DSC 12E (Mettler Toledo GmbH, Giessen, Germany) in accordance with DIN EN 61006. Calibration was effected via the melt onset temperature of indium and lead. 10 mg of substance were weighed out in standard capsules. The measurement was effected by three heating runs from −50° C. to +200° C. at a heating rate of 20 K/min with subsequent cooling at a cooling rate of 320 K/min. Cooling was effected by means of liquid nitrogen. The purge gas used was nitrogen. The values stated in the table below are based in each case on the evaluation of the 3rd heating curve. The glass transition temperature Tg determined was the temperature at half the height of a glass transition step.

(8) Shore hardnesses were measured to DIN 53505 with the aid of a Zwick 3100 Shore hardness tester (from Zwick, Germany).

(9) IR spectra were recorded on a Spectrum Two FT-IR spectrometer equipped with an ATR unit, from Perkin Elmer, Inc.

(10) Water absorption of the test specimens was determined by gravimetric means after seven-day storage in water at 23° C.

(11) Contact angle, surface tension and surface energy were determined at 23° C. with an OCA 20 contact angle measuring instrument from Dataphysics GmbH.

Starting Compounds

Oligomeric Starting Polyisocyanate B1)-1

(12) For use as polyisocyanate composition A), the starting polyisocyanate A1) prepared was an HDI polyisocyanate containing isocyanurate groups, prepared in accordance with Example 11 of EP-A 330 966. The reaction was stopped at an NCO content of the crude mixture of 40% by addition of dibutyl phosphate. Subsequently, unconverted HDI was removed by thin-film distillation at a temperature of 130° C. and a pressure of 0.2 mbar.

(13) NCO content: 21.8%

(14) NCO functionality: 3.4

(15) Monomeric HDI: 0.1%

(16) Viscosity (23° C.): 3000 mPas

(17) Density (20° C.): 1.17 g/cm.sup.3

(18) Distribution of the oligomeric structure types:

(19) Isocyanurate: 84.5 mol %

(20) Iminooxadiazinedione 5.4 mol %

(21) Uretdione 2.9 mol %

(22) Allophanate: 7.2 mol %

Oligomeric, Modified Polyisocyanate B)-1

(23) 870 g (4.51 val) of the oligomeric starting polyisocyanate B1)-1 were admixed with 130 g (0.37 val) of a methanol-started, monofunctional polyethylene oxide polyether having an average molecular weight of 350 at room temperature with stirring and subsequently heated to 100° C. for 3 h. After cooling to room temperature an oligomeric, modified polyisocyanate was obtained. The product had the following characteristic data:

(24) NCO content: 17.4%

(25) NCO functionality: 3.2

(26) Monomeric HDI: 0.1%

(27) Viscosity (23° C.): 3050 mPas

Oligomeric, Modified Polyisocyanate B)-2

(28) 900 g (4.67 val) of the oligomeric starting polyisocyanate B1)-1 were initially charged under dry nitrogen and with stirring at 100° C., over 30 min admixed with 100 g (0.20 val) of a methanol-started, monofunctional polyethylene oxide polyether having an average molecular weight of 500 and subsequently subjected to further stirring at this temperature until the NCO content of the mixture had fallen to a value of 18.8% corresponding to a complete urethanization after approximately 2 h. After addition of 0.01 g of zinc(II) 2-ethyl-1-hexanoate as allophanatization catalyst the temperature of the reaction mixture increased to 106° C. on account of the liberated heat of reaction. Once the exothermicity had died down, approximately 30 min after catalyst addition, the reaction was terminated by addition of 0.01 g of benzoyl chloride and the reaction mixture was cooled to room temperature. A practically colorless, clear polyisocyanate mixture according to the invention and having the following characteristic data was obtained:

(29) NCO content: 18.0%

(30) NCO functionality: 3.8

(31) Monomeric HDI: 0.1%

(32) Viscosity (23° C.): 4000 mPas

Oligomeric, Modified Bolyisocyanate B)-3

(33) 850 g (4.41 val) of the oligomeric starting polyisocyanate B1)-1 were initially charged under dry nitrogen and with stirring at 100° C., over 30 min admixed with 150 g (0.30 val) of a methanol-started, monofunctional polyethylene oxide polyether having an average molecular weight of 500 and subsequently subjected to further stirring at this temperature until the NCO content of the mixture had fallen to a value of 17.3% corresponding to a complete urethanization after approximately 2 h. After addition of 0.01 g of zinc(II) 2-ethyl-1-hexanoate as allophanatization catalyst the temperature of the reaction mixture increased to 108° C. on account of the liberated heat of reaction. Once the exothermicity had died down, approximately 30 min after catalyst addition, the reaction was terminated by addition of 0.01 g of benzoyl chloride and the reaction mixture was cooled to room temperature. A practically colorless, clear polyisocyanate mixture according to the invention and having the following characteristic data was obtained:

(34) NCO content: 16.0%

(35) NCO functionality: 4.0

(36) Monomeric HDI: 0.1%

(37) Viscosity (23° C.): 6500 mPas

Catalyst Mixture C)-1

(38) To produce the catalyst 159.058 g of diethylene glycol were mixed with 24.588 g of 18-crown-6 and 7.557 g of potassium acetate and stirred at room temperature until a homogeneous solution was formed.

(39) All raw materials were obtained from Sigma-Aldrich.

Production of the Inventive Examples

(40) 120 g of the starting polyisocyanate were weighed into a polypropylene cup together with 3.7 g of the catalyst mixture C)-1 and homogenized at 3500 rpm for 1 min using a DAC 150 FVZ Speed-Mixer (Hauschild, Germany). 12 g of the obtained mixture were poured into an aluminum dish having a diameter of 9.7 cm and subsequently cured at 180° C. for 15 minutes in an oven.

(41) Transparent modified polyisocyanurate plastics having the following characteristic data were obtained:

(42) TABLE-US-00001 Starting polyisocyanate B)-1 B)-2 B)-3 Appearance clear clear clear Glass transition 55.5° C. 68.0° C. 52.5° C. temperature Shore D hardness 75 76 74

(43) In all experiments, IR spectroscopy no longer detected any isocyanate groups (band at 2270 cm.sup.−1) in the reaction product.

Determination of Water Absorption

(44) Test specimens from the inventive examples B)-1 to B)-3 and a test specimen of the starting polyisocyanate B1)-1 produced in the same way were each stored in a vessel with deionized water at 23° C. for 7 days. Once the duration of storage had elapsed the test specimens were removed from the vessel, patted dry with a paper towel and subsequently weighed. Water absorption was calculated via the difference in weight before and after storage in water.

(45) TABLE-US-00002 Starting polyisocyanate B1)-1 B)-1 B)-2 B)-3 Water 0.056 0.167 0.108 0.240 absorption [g]

(46) The surface energy and the contact angle with water as a test medium were measured on the underside of the test specimens.

(47) TABLE-US-00003 Starting polyisocyanate B1)-1 B)-1 B)-2 B)-3 Contact angle [water] 61.7 47.1 51.7 50.5 Surface energy [mN/m] 45.6 50.8 49.3 51.5 Polar proportion [mN/m] 13.2 20.5 18.4 17.4

(48) Both the determination of water absorption and the measurement of surface energy and contact angle demonstrate the hydrophilic and strongly polar character of the inventive test specimens. Said specimens thus differ markedly from the unmodified starting polyisocyanate.