Lightfast polyurethane compositions

Abstract

The present invention relates to a composition comprising 10 to 50 wt.-% of at least one polyisocyanate a-1) based on hexamethylene diisocyanate, comprising at least one oligomeric polyisocyanate based on hexamethylene diisocyanate and optionally monomeric hexamethylene diisocyanate and 50 to 90 wt.-% of at least one polyisocyanate a-2) based on isophorone diisocyanate, comprising at least one oligomeric polyisocyanate based on isophorone diisocyanate and optionally monomeric isophorone diisocyanate, with the proviso that at least one of the components a-1) and a-2) additionally comprises monomeric isocyanate of the named kind, as well as at least one sulfur-containing component. It has been shown that the above mentioned mixture of the specific isocyanate group containing components improves the thermal and mechanical properties of a cured composition. Thus prepared molded articles are particularly suitable for the preparation of spectacle lenses, inter alia due to these properties.

Claims

1. A method for preparing an optical lens, the method comprising providing a composition, comprising component A) 10 to 30 wt.-% of at least one polyisocyanate a-1) based on hexamethylene diisocyanate, comprising at least one oligomeric polyisocyante based on hexamethylene diisocyanate and optionally monomeric hexamethylene diisocyanate, and 70 to 90 wt.-% of at least one polyisocyanate a-2) based on isophorone diisocyanate, comprising at least one oligomeric polyisocyanate based on isophorone diisocyanate and optionally monomeric isophorone diisocyanate, and the amount of isocyanate groups of component A) is in a range from 25 to 34 wt-%, based on the total weight of component A), with the proviso that, the polyisocyanate a-1) comprises monomeric hexamethylene diisocyanate, or the polyisocyanate a-2) comprises monomeric isophorone diisocyanate, or the polyisocyanate a-1) comprises monomeric hexamethylene diisocyanate and the polyisocyanate a-2) comprises monomeric isophorone diisocyanate, wherein the %-data relate to the sum of components a-1) and a-2), component B) at least one sulfur-containing component; and optionally component C) one or more auxiliaries and/or additives; pouring the composition into a mold; and allowing the poured composition of isocyanate groups of component A) with the isocyanate-reactive groups of component B), and optionally component C to cure, and thereby, form the optical lens.

2. The method according to claim 1, wherein the optical lens is a spectacle lens.

3. The method according to claim 1, wherein the sulfur-containing component is selected from the group consisting of polythiols, sulfur containing hydroxy compounds, and mixtures thereof.

4. The method according to claim 1, wherein the sulfur-containing component has a molecular weight of 78 to 1000 g/mol.

5. The method according to claim 1, wherein the at least one auxiliary and/or additive is selected from the group consisting of UV-stabilizers, catalysts, antioxidants, mold release agents, dyes, and mixtures thereof.

6. The method according to claim 1, wherein the at least one oligomeric polyisocyanate of a-1) is obtained by reacting only hexamethylene diisocyanate as diisocyanate unit, and the at least one oligomeric polyisocyanate of a-2) is obtained by reacting only isophorone diisocyanate as diisocyanate unit.

7. The method according to claim 1, wherein the at least one sulfur-containing component is selected from the group consisting of polythiols, sulfur containing hydroxy compounds, and mixtures thereof, and has a molecular weight of 140 to 800 g/mol.

8. The method according to claim 7, wherein the sulfur-containing component has at least two thiol-groups per molecule.

9. The method according to claim 1, wherein the component A) has a viscosity of 100 to 3000 mPas at 23° C.

10. The method according to claim 1, wherein the amount of isocyanate groups of component A) is in a range from 26 to 30 wt-%.

11. The method according to claim 7, wherein the amount of isocyanate groups of component A) is in a range from 26 to 30 wt-%.

12. The method according to claim 1, wherein the pouring of the composition includes pouring into a non-heated mold at room temperature.

13. The method according to claim 1, wherein the optical lens has a thickness of at least 1 mm.

14. A method for preparing an optical lens, the method comprising: providing a composition comprising a component A), and a component B), wherein component A) comprises 10 to 30 wt.-% of at least one polyisocyanate a-1) based on hexamethylene diisocyanate, and comprising at least one oligomeric polyisocyante that is obtained by reacting only hexamethylene diisocyanate as diisocyanate unit, and 90 to 70 wt.-% of at least one polyisocyanate a-2) based on isophorone diisocyanate, and comprising at least one oligomeric polyisocyanate that is obtained by reacting only isophorone diisocyanate as diisocyanate unit, wherein the %-data are based on the sum of components a-1) and a-2), and the amount of isocyanate groups of component A) is in a range from 25 to 34 wt-%, based on the total weight of component A), with the proviso that the polyisocyanate a-1) comprises monomeric hexamethylene diisocyanate, or the polyisocyanate a-2) comprises monomeric isophorone diisocyanate, or the polyisocyanate a-1) comprises monomeric hexamethylene diisocyanate and the polyisocyanate a-2) comprises monomeric isophorone diisocyanate, and component B) comprises one sulfur-containing component selected from the group consisting of polythiols, sulfur containing hydroxy compounds, and mixtures thereof, and the sulfur-containing component has a molecular weight of 78 to 1000 g/mol; pouring the composition into a mold; and allowing the poured composition of isocyanate groups of component A) with the isocyanate-reactive groups of component B), and optionally component C to cure, and thereby, form the optical lens with a refractive index in a range of 1.541 to 1.587.

15. The method according to claim 14, wherein the at least one sulfur-containing component has a molecular weight of 140 to 800 g/mol, and at least two thiol groups.

16. The method according to claim 14, wherein the optical lens has a low optical dispersion characterized by high Abbe-numbers of from 40 to 49.

17. The method according to claim 14, wherein the amount of isocyanate groups of component A) is in a range from 26 to 30 wt-%.

18. The method according to claim 1, wherein the optical lens has a refractive index in a range of 1.541 to 1.587, and a low optical dispersion characterized by high Abbe-numbers of from 40 to 49.

Description

EXAMPLES

(1) All percentages relate to the weight, unless stated otherwise.

(2) According to the present invention the determination of the NCO contents is carried out by titration according to DIN EN ISO 11909.

(3) NCO functionalities are calculated from the gel permeation chromatogram (GPC).

(4) According to the present invention OH-numbers are determined by titration according to DIN 53240-2: 2007-11, according to the invention acid numbers are determined according to DIN 3682.

(5) The residual monomer contents have been measured by gas chromatography with internal standard according to DIN EN ISO 10283.

(6) The g/val SH-values have been adopted from the manufacturer or have been calculated.

(7) All viscosity measurements have been carried out with a physical MCR 51 rheometer of the company Anton Paar Germany GmbH (DE) according to DIN EN ISO 3219 at the shown temperatures.

(8) The glass transition temperature Tg has been measured using DSC (Differential Scanning calorimetrie) with a Mettler DCS 12E (Mettler Toledo GmbH, Giessen, DE) at a heating rate of 10° C./min.

(9) The determination of the heat resistance HDT has been carried out according to DIN EN ISO 75-2, procedure B, by using a bending stress of 0.45 MPa.

(10) Shore hardness has been measured according to DIN 53505 by using a shore hardness tester Zwick 3100 (company Zwick, DE).

(11) Measurement of the refractive indices and Abbe-numbers has been carried out using an Abbe refractometer model B of company Zeiss.

(12) Transmission measurements according to ASTM D 1003 have been carried out using a Haze-Gard Plus of the company Byk. The wavelength dependent transmission has been determined by using a dual beam spectrophotometer type Lambda 900 with integrated sphere (150 mm) of the company Perkin-Elmer, USA (0°/diffuse, reference: air T=100%).

(13) Component A)

(14) Polyisocyanate a1-I)

(15) The preparation of a isocyanurate group containing HDI polyisocyanate was carried according to example 11 of EP-A 330 966 with the modification that 2-ethylhexanol was used as catalyst solvent instead of 2-ethyl-1,3-hexanediol.

(16) TABLE-US-00001 NCO content: 22.9% NCO functionality: 3.2 monomeric HDI: 0.1% viscosity (23° C.) 1200 mPa .Math. s
Polyisocyanate a1-II)

(17) The preparation of an isocyanurate- and iminoxadiazindion group containing HDI polyisocyanate was carried out according to example 4 of EP A 0 962 455, by trimerisation of HDI by using a 50% solution of tetrabutylphosphonium hydrogen difluorid in isopropanol/methanol (2:1) as catalyst. The reaction was stopped at an NCO content in the crude mixture of 43% by adding dibutylphosphate. Subsequently removal of the unreacted HDIs using thin film distillation at a temperature of 130° C. and a pressure of 0.2 mbar was carried out.

(18) TABLE-US-00002 NCO content: 23.4% NCO functionality: 3.2 monomeric HDI: 0.2% viscosity (23° C.) 700 mPa .Math. s
Polyisocyanate a2-I)

(19) Isophorone diisocyanate (IPDI) was trimerized to an NCO-content of 30.1% according to example 2 of EP-A 0 003 765. The catalyst was deactivated by adding an equimolar amount of dibutylphosphate, relating to the used catalyst amount, and stirring for 30 minutes by 80° C. The separation of unreacted excess IPDI by thin film distillation was omitted. A solution of IPDI-isocyanurate polyisocyanate (35.5 wt-%) in monomeric IPDI (64.5 wt.-%) was present.

(20) TABLE-US-00003 NCO-content: 30.5% monomeric IPDI: 64.5% viscosity (23° C.): 540 mPa .Math. s
Polyisocyanate a2-II)

(21) 18 g (1.0 mol) water were added continuously to a mixture of 1554 g (7 mol) IPDI and 0.5 g (0.002 mol) dibutylphosphate under nitrogen environment and stirring at a temperature of 80° C. for a period of 5 hours. A short time after the addition of water a steady CO.sub.2-development occurred which was completed after stirring for 3 hours at 90° C. A colorless solution of IPDI-biuret polyisocyanate (38.4 wt.-%) in excess monomeric diisocyanate (61.6 wt.-%) was present.

(22) TABLE-US-00004 NCO-content: 30.0% viscosity (23° C.) 2600 mPa .Math. s
Polyisocyanate a2-III)

(23) The monomeric IPDI was separated from the afore mentioned polyisocyanate a2-I) by thin film distillation at a temperature of 170° C. and a pressure of 0.1 mbar. Solid IPDI-isocyanurate polyisocyanate with the following characteristic data was achieved:

(24) TABLE-US-00005 NCO-content: 17.0% monomeric IPDI: 0.3% Tg: 65° C.
Mixtures of Components a-1) and a-2)

(25) The HDI-polyisocyanate type a-1) was mixed together with a solution of a-2) of IPDI polyisocyanate in excess monomeric IPDI, monomeric HDI and/or IPDI in a reaction vessel at room temperature (in case of polyisocyanate A-VI at 60° C.) under N.sub.2-atmosphere until a clear solution was present in each case.

(26) The following table 1 shows compositions (parts by weight) and characteristic data of the so produced polyisocyanates.

(27) TABLE-US-00006 TABLE 1 Compositions of component A) A-VII A-VIII A-XI A-X polyisocyanate A-I A-II A-III A-IV A-V A-VI (comp.) (comp.) (comp.) (comp.) polyisocyanate 20 30 50 — 20 20 55 15 — — a1-I) polyisocyanate — — — 30 — — — — — — a1-II) polyisocyanate 80 70 50 70 — 46 45 — 85 — a2-I) polyisocyanate — — — — 80 — — — — — a2-II) polyisocyanate — — — — — 34 — — — — a2-III) Hexamethylene — — — — — — — — 15 15 diisocyanate Isophorone — — — — — — — 85 — 85 diisocyanate NCO-content   29.0   28.2   26.7   28.4   28.6   24.4   26.3   35.6   33.4   39.6 (%) viscosity (23° C.) 660  720  860  550  2200  41100   890  180  450  15 [mPa .Math. s] viscosity (60° C.) n.b. n.b. n.b. n.b. n.b. 960  n.b. n.b. n.b. n.b. [mPa .Math. s]
Component B)
Polythiol B1)
4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane

(28) TABLE-US-00007 equivalent weight: 88 g/val SH functionality: 3.0 viscosity (23° C.): 40 mPa .Math. s n.sub.D: 1.6304
Polythiol B2)
pentaerythrit-tetrakis(3-mercaptopropionate)

(29) TABLE-US-00008 equivalent weight: 122 g/val SH functionality: 4.0 viscosity (23° C.): 400 mPa .Math. s n.sub.D: 1.5312
Polythiol B3)
Trimethylolpropan-tris(3-mercaptopropionat)

(30) TABLE-US-00009 equivalent weight: 133 g/val SH functionality: 3.0 viscosity (23° C.): 150 mPa .Math. s n.sub.D: 1.5290
Polythiol B4)
trimethylolpropane-tris(2-mercaptoacetate)

(31) TABLE-US-00010 equivalent weight: 119 g/val SH functionality: 3.0 viscosity (23° C.): 120 mPa .Math. s n.sub.D: 1.5303

Examples 1 to 7 and Comparative Examples 1 (Comp. 1) to 7 (Comp. 7) (Preparation of Transparent Materials)

(32) For preparing transparent materials components A) and B), if applicable by using DBTL as a catalyst, were homogenized in the combinations and amount ratios (parts by weight) as shown in table 2, each according to an equivalent ratio of isocyanate groups to isocyanate-reactive groups of 1:1, using a speed-mixer DAC 150 FVZ (company Hauschild, DE) within 1 minute at 3500 U/min and subsequently poured by hand at room temperature into open non-heated polypropylene molds. Due to the high viscosity of the polyisocyanate component A-VI at room temperature this was heated to a temperature of 60° C. to facilitate the processability before weighing (all other polyisocyanate components were processed at room temperature). After a curing time of 8 hours at 100° C. in a drying cabinet the test plates (length×width×height: 200 mm×100 mm×4 mm) were demoled.

(33) After a post-curing time of 24 hours at room temperature the test plates were tested with regard to their optical and mechanical properties. The results are shown in table 2, too.

(34) TABLE-US-00011 TABLE 2 optical and mechanical properties of the prepared test plates example a-1):a-2) 1 2 3 4 5 6 7 polyisocyanate A-I 20:80 62.2 — 54.3 — — — — polyisocyanate A-II 30:70 — 62.9 — — — — — polyisocyanate A-III 50:50 — — — 53.4 — — — polyisocyanate A-IV 30:70 — — — — 55.4 — — polyisocyanate A-V 20:80 — — — — — 62.5 — polyisocyanate A-VI 20:80 — — — — — — 58.5 polyisocyanate A-VII 55:45 — — — — — — — polyisocyanate a2-I)  0:100 — — — — — — — polyisocyanate A-VIII — — — — — — — polyisocyanate A-IX — — — — — — — polyisocyanate A-X — — — — — — — m-xylylene — — — — — — — diisocyanate polythiol B1) 37.8 37.1 — — — 37.5 — polythiol B2) — — 45.7 — — — 41.5 polythiol B3) — — — 46.6 — — — polythiol B4) — — — — 44.6 — — density [g/cm.sup.3] 1,234 1,239 1,247 1,243 1,220 1,204 1,246 Shore-hardness D 86 84 85 85 87 83 88 Tg [° C.] 136 136 139 108 115 133 140 HDT [° C.] 102 101 97 91 95 97 n.b. refractive index 1,587 1,586 1,549 1,541 1,548 1,549 1,552 Abbe-number 41 42 40 42 49 49 42 transmission [%] 92.4 91.1 92.6 91.3 91.2 92.4 91.9 example comp. 1 comp. 2 comp. 3 comp. 4 comp. 5 comp. 6 comp. 7 polyisocyanate A-I — — — — — — — polyisocyanate A-II — — — — — — — polyisocyanate A-III — — — — — — — polyisocyanate A-IV — — — — — — — polyisocyanate A-V — — — — — — — polyisocyanate A-VI — — — — — — — polyisocyanate A-VII 64.2 — — — — — — polyisocyanate a2-I) — 61.0 58.2 — — — — polyisocyanate A-VIII — — — — 57.3 — — polyisocyanate A-IX — — — — — 58.9 — polyisocyanate A-X — — — — — — 54.6 m-xylylene — — — 43.6 — — — diisocyanate polythiol B1) 35.8 39.0 25.1 — 42.7 41.1 45.7 polythiol B2) — — 16.7 56.4 — — — polythiol B3) — — — — — — — polythiol B4) — — — — — — — density [g/cm.sup.3] 1,247 1,240 1,233 1,370 1,242 1,237 1,245 Shore-hardness D 79 87 86 78 82 87 n.b. Tg [° C.] 97 144 120 90 96 113 80 HDT [° C.] 55 n.b. n.b. 74 71 n.b. n.b. refractive index 1,583 1,586 1,573 1,597 1,591 1,586 1,598 Abbe-number 42 39 38 36 42 42 37 transmission [%] 91.8 91.1 91.3 92.3 92.1 91.1 92.8

(35) As the examples show, the polythiourethane systems according to the present invention provide hard, highly transparent plastics which have a high refractive index, and high Abbe-numbers besides high glass transition temperatures and heat resistance. The test plates which have been prepared for comparison by using a component a-1) with a higher amount of HDI-polyisocyanate than claimed in the present invention (comp. 1) shows an insufficient glass transition temperature and heat resistance. Thus, the obtained material is less suitable for preparing spectacle lenses. The test plates which have been prepared for comparison by using only component a-2) based on IPDI (comp. 2 and 3) were extremely brittle and broke by deforming. The use of an araliphatic diisocyanate (mSDI) as crosslinker component (comp. 4) leads to a high refractive polythiourethane, which besides a comparably low heat resistance particularly has a strong optical dispersion (low Abbe-number).

(36) The use of a polyisocyanate component, which exclusively contains monomeric IPDI besides an oligomeric HDI-polyisocyanate (comp. 5) leads to an polythiourethane with insufficient glass transition temperature and heat resistance.

(37) The materials which have been prepared by using exclusively monomeric HDI (comp. 6 and 7) were not sufficiently elastic but brittle and broke by deforming. Therein, the test sample (comp. 7) was slightly sticky at the surface after the selected curing time (8 hours/100° C.), which is a sign of incomplete crosslinking.

(38) Accordingly, these comparative materials of experiments comp. 1 to comp. 7 are less suitable for the preparation of spectacle lenses.

Example 8 (Preparation of an Eye Glass Blank)

(39) Polyisocyanate A-I was mixed with 0.16% Zelec® UN (acid phosphate ester release agents, Stepan Company, Northfield, Ill., USA) and 0.5% of Tinuvin® 326 (UV protector, BASF Schweiz AG, Basel) and stirred at 60° C. and 40 mbar for appr. 3 hours for degassing until the end of the visible foam formation. Polythiol B1) was degassed in the same manner.

(40) After cooling to room temperature 62.6 parts by weight of the pretreated and additive treated polyisocyanate A-I were mixed in a stirring vessel with 37.4 parts by weight of the degassed polythiol B1), corresponding to an equivalent ratio of isocyanate groups to isocyanate-reactive groups of 1:1, and the mixture was stirred for 30 minutes under vacuum (approximately 150 mbar). Subsequently the reaction mixture was conveyed via a valve equipped pipeline through a 0.5 μm PTFE-filter into a purified mold consisting of two glass molds and a polymeric sealing ring for spectacle glass blanks (diameter 75 mm, thickness 10 mm, −2 diopters) by applying a positive pressure of nitrogen to the stirring vessel. The casting mold was kept in an oven at 60° C. for 2 hours, then continuously heated up to 115° C. within 3 hours and finally kept at this temperature for further 2 hours. After cooling to room temperature the cured molded article was removed from the molds and for reducing stresses in the material post-annealed for 3 hours at 130° C.

(41) In this way a totally clear, transparent eyeglass blank which was free of streaks was obtained and which exhibited the optical and mechanical properties as shown in example 1. The transmission at a wavelength of 390 nm was <1%, at 400 nm 3%, at 410 nm 53% and in the range above 450 nm 92%.