Method for preparing optical lenses

Abstract

The present invention relates to a composition comprising 10 to less than 50 wt.-% of at least one oligomeric polyisocyanate a-1) based on hexamethylene diisocyanate and more than 50 to 90 wt.-% of at least one polyisocyanate a-2) based on isophorone diisocyanate, comprising monomeric isophorone diisocyanate and at least one oligomeric isophorone diisocyanate, and an isocyanate-reactive component selected from the group consisting of polyester polyol, polyether polyol and mixtures thereof. 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 comprising providing a composition including component A) which comprises 10 to 30 wt.-% of at least one oligomeric polyisocyanate a-1) based on hexamethylene diisocyanate, and 70 to 90 wt.-% of at least one polyisocyanate a-2) based on isophorone diisocyanate containing monomeric isophorone diisocyanate and at least one oligomeric polyisocyanate based on isophorone diisocyanate, wherein the %-data relate to the sum of components a-1) and a-2), at least one isocyanate-reactive component, selected from the group consisting of polyester polyol, polyether polyol and mixtures thereof, and one or more auxiliaries and/or additives, wherein the amount of isocyanate groups of component A) is in the range of 25 to 34 wt.-%, based on the total weight of component A).

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

3. The method according to claim 1, wherein the isocyanate-reactive component is free of aromatic structures.

4. The method according to claim 1, wherein the isocyanate-reactive component comprises either polyester polyols or polyether polyols.

5. The method according to claim 1, wherein the at least one auxiliary and/or additive C) 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 oligomeric polyisocyanate of a-1) is obtained by reacting only hexamethylene diisocyanate as diisocyanate unit and the 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 polyisocyanate a-1) is present from 15 to 35 wt-%, and the at least one polyisocyanate a-2) is present from 85 to 65 wt-%.

8. The method according to claim 7, wherein the component A) has a viscosity of 550 to 2200 mPas at 23° C.

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

10. The method according to claim 1, further comprising adding the composition at room temperature into a non-heated mold.

11. The method according to claim 1, wherein the optical lens has a glass transition temperature of from 93° C. to 117° C.

12. The method according to claim 1, wherein the optical lens has a refractive index of 1.5015 to 1.5092, and a transmission of 93% to 93.4%.

13. The method according to claim 12, wherein the optical lens has a shore hardness of 86 to 88.

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) 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.

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

(8) 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.

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

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

(11) 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%).

(12) Component A)

(13) Polyisocyanate a1-I)

(14) 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.

(15) NCO content: 22.9%

(16) NCO functionality: 3.2

(17) monomeric HDI: 0.1%

(18) viscosity (23° C.) 1200 mPa.Math.s

(19) Polyisocyanate a1-II)

(20) 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.

(21) NCO functionality: 3.2

(22) monomeric HDI: 0.2%

(23) viscosity (23° C.) 700 mPa.Math.s

(24) Polyisocyanate a2-I)

(25) 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.

(26) NCO-content: 30.5%

(27) monomeric IPDI: 64.5%

(28) viscosity (23° C.): 540 mPa.Math.s

(29) Polyisocyanate a2-II)

(30) 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.

(31) monomeric IPDI: 61.6%

(32) viscosity (23° C.) 2600 mPa.Math.s

(33) Polyisocyanate a2-III)

(34) 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:

(35) NCO-content: 17.0%

(36) monomeric IPDI: 0.3%

(37) Tg: 65° C.

(38) Mixtures of Components a-1) and a-2)

(39) The HDI-polyisocyanate type a-1) was mixed together with a solution of a-2) (oligomeric IPDI mixed with monomeric IPDI) in a reaction vessel at room temperature (in case of polyisocyanate A-VII at 60° C.) under N2-atmosphere until a clear solution was present in each case.

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

(41) TABLE-US-00001 TABLE 1 Compositions of component A) A-VIII polyisocyanate A-I A-II A-III A-IV A-V A-VI A-VII (comp.) polyisocyanate 20 30 40 45 — 20 20 55 a1-I) polyisocyanate — — — — 30 — — — a1-II) polyisocyanate 80 70 60 55 70 — 46 45 a2-I) polyisocyanate — — — — — 80 — — a2-II) polyisocyanate — — — — — — 34 — a2-III) NCO-content 29.0 28.2 27.5 27.1 28.4 28.6 24.4 26.3 [%] viscosity (23° C.) 660 720 800 825 550 2200 41100 950 [mPa .Math. s] viscosity (60° C.) n.n. n.n. n.n. n.n. n.n. n.n. 960 n.n. [mPa .Math. s]
Component B)—Polyester Polyoles
Polyester Polyol B1)

(42) 7.4 parts by weight neopentylglycol, 12.4 parts by weight 1,3-butanediol, 18.2 parts by weight 2,2,4-trimethyl-1,3-pentanediol, 16.2 parts by weight 2-butyl-2-ethyl-1,3-propanediol, 18.9 parts by weight 1,1,1-trimethylolpropane, 26.9 parts by weight adipic acid were weight in a flask and slowly heated to 200° C. with stirring at atmospheric pressure, whereby approximately 5 parts by weight water were distilled. After cleavage of the water vacuum (15 mbar) was slowly applied over a period of approximately 4 hours and the reaction was completed under these conditions within further approximately 15 hours. The polyester polyol thus obtained had the following characteristic data:

(43) OH-number: 512 mg KOH/g

(44) acid number: 1.8 mg KOH/g

(45) viscosity (25° C.): 1900 mPa.Math.s

(46) OH-functionality: 2.36

(47) Polyester Polyol B2)

(48) A polyester polyol has been prepared according to the method described for B1) using 7.2 parts by weight neopentylglycol, 12.3 parts by weight 1,3-butanediol, 44.8 parts by weight 1,1,1-trimethylolpropane, 20.8 parts by weight succinic acid and 14.8 parts by weight ε-caprolacton and the following characteristic data have been obtained:

(49) OH-number: 635 mg KOH/g

(50) acid-number: 0.16 mg KOH/g

(51) viscosity (25° C.): 2120 mPa.Math.s

(52) OH-functionality: 2.92

(53) free ε-caprolacton: 0.04%

(54) Polyester Polyol B3)

(55) 5.1 parts by weight neopentylglycol, 8.5 parts by weight 1,3-butanediol, 34.1 parts by weight 1,1,1-trimethylolpropane, 18.4 parts by weight succinic acid and 11.5 parts by weight ε-caprolacton were weight in a flask and slowly heated to 200° C. under atmospheric pressure while stirring, whereby approximately 5 parts by weight water were distilled. After cleavage of the water was completed, vacuum (15 mbar) was slowly applied over a period of approximately 4 hours thus completing the reaction under these conditions within a further period of approximately 15 hours. After cooling to room temperature additional 8.4 parts by weight neopentylglycol and 14.0 parts by weight 1,3-butanediol were admixed. the thus obtained polyester polyol had the following characteristic data:

(56) OH-number: 659 mg KOH/g

(57) acid-number: 1.30 mg KOH/g

(58) viscosity (25° C.): 2410 mPa.Math.s

(59) OH-functionality: 2.53

(60) free ε-caprolacton: 0.05%

(61) Polyester Polyol B4)

(62) A polyester polyol was prepared according to the method as described for B1) using 9.6 parts by weight neopentylglycol, 16.0 parts by weight 1,3-butanediol, 30.6 parts by weight glycerin, 30.1 parts by weight adipic acid and 13.7 parts by weight ε-caprolacton and the following characteristic data have been obtained:

(63) OH-number: 663 mg KOH/g

(64) acid number: 0.18 mg KOH/g

(65) viscosity (25° C.): 1290 mPa.Math.s

(66) OH-functionality:

(67) free ε-caprolacton: 0.06%

(68) Polyester Polyol B5)

(69) A polyester polyol was prepared according to the method as described for B2) using 10.3 parts by weight 1,3-butanediol, 6.3 parts by weight diethyleneglycol, 43.6 parts by weight 1,1,1-trimethylolpropane, 18.6 parts by weight succinic acid and 13.2 parts by weight ε-caprolacton and additional 4.9 parts by weight 1,3-butanediol and 3.0 parts by weight diethyleneglycol to achieve the following characteristic data:

(70) OH-number: 658 mg KOH/g

(71) acid number: 1.40 mg KOH/g

(72) viscosity (25° C.): 2540 mPa.Math.s

(73) OH-functionality: 2.76

(74) free ε-caprolacton: 0.05%

(75) Preparation of Transparent Materials (Wherein Component B) is a Polyester Polyol)

Examples 1 to 8, Comparative Examples 1 and 2

(76) For preparing transparent materials component A) and component B), which is a polyester polyol, 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 hydroxyl groups of 1:1, using a speed-mixer DAC 150 FVZ (company Hauschild, Del.) 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-VII 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 130° C. in a drying cabinet the test plates (length×width×height: 200 mm×100 mm×4 mm) were demoled.

(77) 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.

(78) TABLE-US-00002 TABLE 2 optical and mechanical properties of the prepared test plates (component B) is polyester polyol) comp. comp. example a-1):a-2) 1 2 3 4 5 6 7 8 1 2 polyisocyanate 20:80 57.0 — 63.0 63.1 — — — — — — A-1 polyisocyanate 30:70 — 62.8 — — — — — — — — A-II polyisocyanate 40:60 — — — — 64.2 — — — — — A-III polyisocyanate 30:70 — — — — — 63.5 — — — — A-V polyisocyanate 20:80 — — — — — — 62.5 — — — A-VI polyisocyanate 20:80 — — — — — — — 61.1 — — A-VII polyisocyanate 55:45 — — — — — — — — — 59.3 A-VIII polyisocyanate  0:100 — — — — — — — — 56.1 — a)-I) polyester polyol 43.0 — — — — — 37.5 38.9 43.9 40.7 B1) polyester polyol — 37.2 — — — — — — — B2) polyester polyol — — 37.0 — — — — — — — B3) polyester polyol — — — 36.9 35.8 — — — — — B4) polyester polyol — — — — — 36.5 — — — — B5) density [g/cm.sup.3] 1.140 1.162 1.149 1.167 1.178 1.156 1.147 1.149 1.151 1.145 shore hardness D 83 88 86 87 84 82 87 87 88 85 Tg [° C.] 93 111 115 124 109 117 103 118 133 70 HDT [° C.] 79 95 96 101 92 97 88 n.n. n.n. n.n. refractive index 1.5073 1.5080 1.5085 1.5015 1.5110 1.5110 1.5015 1.5092 1.5125 1.5105 Abbe-number 54 56 46 56 51 56 52 54 56 51 transmission [%] 93.2 93.4 93.2 93.0 93.9 92.6 93.2 93.3 93.0 93.0

(79) As examples 1 to 8 show, the compositions according to the present invention provide hard, highly transparent plastics which have a high glass transition temperature and heat resistance. The test plates which have been prepared for comparison by using only component a-2) based on the IPDI (comp. 1) were extremely brittle and broke by deforming. Thus, the obtained material is less suitable for preparing spectacle lenses. The test plate which has been prepared for comparison by using an polyisocyanate component with a higher amount of HDI-polyisocyanate a-1) than claimed in the present invention (comp. 2) is not suitable as eye glass material due to the insufficient glass transition temperature and heat resistance.

(80) The direct comparison of the product characteristics of the materials of examples 1 to 7 prepared according to the present invention with those of polyallyldiglycol carbonate, the standard material for preparing plastic spectacle glasses until today (table 3) shows the clear advantages of the new materials relating to mechanical and thermal stability in combination with the outstanding optical properties. Furthermore, the lower density of the polyurethane according to the present invention allows the preparation of glasses which are more than 10% lighter than those made of PADC.

(81) TABLE-US-00003 TABLE 3 product characteristics of polyallyldiglycol carbonate density [g/cm.sup.3] 1.31 Tg [° C.] 85 HDT [° C.] 55-65 refractive index 1.498 Abbe-number 59.3 transmission [%] 89-91
(Source: CR-39® product bulletin, company PPG Industries Inc., edition Apr. 20, 2006)
Preparation of an Eye Glass Blank

(82) Polyisocyanate A-I was mixed with 1.0% 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. Polyester polyol B4) was degassed in the same manner.

(83) After cooling to room temperature 63.4 parts by weight of the pretreated and additive treated polyisocyanate A-I were mixed in a stirring vessel with 36.6 parts by weight of the degassed and to 40° C. preheated polyester polyol B4), corresponding to an equivalent ratio of isocyanate groups to hydroxyl groups of 1:1, and the mixture was stirred for 30 minutes at 40° C. 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.

(84) 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 4. The transmission at a wavelength of 390 nm was <1%, at 400 nm 2%, at 410 nm 45% and in the range above 450 nm 93%.

(85) Component B)—Polyether Polyols

(86) Polyether Polyol B1)

(87) Polypropyleneoxid polyether with an OH-number of 550 mg KOH/g and a viscosity (23° C.) of 2000 mPa.Math.s started on trimethylolpropane.

(88) Polyether Polyol B2)

(89) Polypropyleneoxid polyether with an OH-number of 525 mg KOH/g and a viscosity (23° C.) of 2600 mPa.Math.s started on pentaerythrith.

(90) Polyether Polyol B3)

(91) Polypropyleneoxid polyester with an OH-number of 470 mg KOH/g and a viscosity (23° C.) of 5400 mPa.Math.s started on ethylene diamine.

(92) Preparation of Transparent Materials (Wherein Component B) is a Polyether Polyol)

Examples 9 to 15; Comparative Example 3

(93) For preparing transparent materials component A) and component B), which is a polyether polyol, optionally by using DBTL as catalyst, were homogenized in the combinations and amount ratios (parts by weight) as shown in table 4, each corresponding to an equivalent ratio of isocyanate groups to hydroxyl groups of 1:1, using a speed mixer DAC 150 FVZ (Firma Hauschild, Del.) for 1 minute at 3500 rpm and subsequently poured by hand into open, non-heated polypropylene molds. 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 demolded.

(94) After a pre-curing time of 24 hours at room temperature the test plates were tested with respect to their optical and mechanical properties. The test results are shown in table 4.

(95) TABLE-US-00004 TABLE 4 optical and mechanical properties of the prepared test plates (component B) is polyether polyol example a-1):a-2) 9 10 11 12 13 14 15 comp. 3 polyisocyanate 20:80 58.7 — — — — 57.5 54.9 — A-I polyisocyanate 40:60 — 60.0 — — — — — — A-III polyisocyanate 45:55 — — 60.4 — — — — — A-IV polyisocyanate 30:70 — — — 59.2 — — — — A-V polyisocyanate 20:80 — — — — 57.9 — — — A-VI polyisocyanate  0:100 — — — — — — — 57.5 a2-I) polyether polyol 41.3 40.0 39.6 40.8 — — — 42.5 B1) polyether polyol — — — — 42.1 42.5 — — B2) polyether polyol — — — — — — 45.1 — B3) DBTL — — — — 0.1 0.1 — — density [g/cm.sup.3] 1.121 1.127 1.122 1.126 1.128 1.122 1.103 1.121 shore-hardness D 87 85 86 86 85 88 86 84 Tg [° C.] 103 98 93 98 92 116 97 119 HDT [° C.] 89 83 82 82 79 92 83 n.n. refractive index 1.500 1.502 1.493 1.501 1.499 1.500 1.504 1.505 Abbe-number 51 47 48 51 51 47 46 51 transmission [%] 93.6 93.3 93.3 93.5 93.2 93.3 92.4 93.1

(96) As examples 9 to 15 show, the compositions of the present invention provide hard, highly transparent materials with high glass transition temperatures and heat resistance. A test plate which has been prepared for comparison (comp. 3) by using only a component A) based on component a-2) based on IPDI was extremely brittle and broke during demolding. Accordingly, the prepared material is particularly less suitable as eyeglass material.

(97) The direct comparison of the product characteristics of materials according to examples 9 to 15, prepared according to the present invention, with those of polyallyldiglycol carbonate, which is the standard material for preparing plastic eyeglasses until today (table 3) shows the clear advantages of the new materials regarding mechanical and thermal stability besides the outstanding optical properties. Furthermore the lower density of the polyurethanes according to the present invention allows the preparation of glasses which are more than 15% lighter than those from PADC.

(98) Preparation of an Eyeglass Blank

(99) Polyisocyanate A-I was mixed with 1.0% Zelec® UN (acid phosphate ester release agent, Stepan Company, Northfield, Ill., USA) and 0.5% 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. Polyether polyol B1) was degassed in the same manner.

(100) After cooling to room temperature 59.3 parts by weight of the thus pretreated and additive treated polyisocyanate A-I were mixed in a stirring vessel with 40.7 parts by weight of the degassed and to 45° C. preheated polyether polyol B1), corresponding to an equivalent ratio of isocyanate groups to hydroxyl groups of 1:1, and the mixture was stirred for 30 minutes at 40° C. 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.

(101) 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 8. A transmission at a wavelength of 390 nm was <1%, at 400 nm 2%, at 410 nm 48% and in the range above 450 nm 93%.