Two-component polyurethane composition with adjustable pot life

Abstract

A polyurethane composition including a first and a second component, wherein the first component is a polyol with an OH functionality in the range from 1.5 to 4 and a mean molecular weight in the range from 250 to 15,000 g/mol, a diol with two hydroxyl groups which are linked via a C2 to C0 carbon chain, and a compound that includes at least one thiol group. One of the two components also additionally contains at least one metal catalyst for the reaction of hydroxyl groups and isocyanate groups which can form thio complexes, and the second component contains enough polyisocyanate that at least 5% by weight of isocyanate groups, in relation to the total polyurethane composition, are contained, and the molar ratio of all thiol groups of the mentioned compound to all metal atoms of the metal catalyst is between 1:1 and 250:1.

Claims

1. A polyurethane composition consisting of a first and a second component; wherein the first component A comprises at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and a number average molecular weight M.sub.n in the range from 250 to 15,000 g/mol, and at least one diol A2 having two hydroxyl groups that are linked via a C2 to C9 carbon chain, and at least one compound T that has at least one thiol group; and the second component B comprises at least one polyisocyanate I; wherein the composition comprises less than 0.1% by weight of carboxylic acids, based on the overall composition, one of the two components additionally comprises at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes and the second component contains sufficient polyisocyanate I for it to comprise at least 7.5% by weight of isocyanate groups based on the overall polyurethane composition, and the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 1:1 and 250:1.

2. The polyurethane composition as claimed in claim 1, wherein the metal catalyst K comprises a bismuth(III) compound.

3. The polyurethane composition as claimed in claim 2, wherein the bismuth(III) compound additionally contains an 8-hydroxyquinoline ligand or a 1,3-ketoamide ligand.

4. The polyurethane composition as claimed in claim 1, wherein the diol A2 is a linear aliphatic diol having two primary hydroxyl groups that are linked via a C4 to C9 carbon chain.

5. The polyurethane composition as claimed in claim 1, wherein the at least one compound T comprises a polythiol compound having 2 to 6 thiol groups, or a mercaptosilane.

6. The polyurethane composition as claimed in claim 5, wherein the at least one compound T is selected from the group consisting of ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), and 3-mercaptopropyltrimethoxysilane.

7. The polyurethane composition as claimed in claim 1, wherein the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 5:1 and 100:1.

8. The polyurethane composition as claimed in claim 1, wherein the metal catalyst K is present in the first component A.

9. The polyurethane composition as claimed in claim 1, wherein the polyol A1 comprises a polyether polyol.

10. The polyurethane composition as claimed in claim 1, wherein the polyisocyanate I is a form of diphenylmethane 4,4′-, 2,4′- or 2,2′-diisocyanate that is liquid at room temperature and any mixtures of these isomers (MDI) in the form of polymeric MDI or MDI containing proportions of oligomers or derivatives.

11. The polyurethane composition as claimed in claim 1, wherein the second component B comprises a polyurethane polymer containing isocyanate groups.

12. A process for bonding a first substrate to a second substrate, comprising the steps of: mixing the first and second components of a polyurethane composition as claimed in claim 1, applying the mixed polyurethane composition to at least one of the substrate surfaces to be bonded, joining the substrates to be bonded within the open time, curing the polyurethane composition.

13. An article resulting from the bonding process as claimed in claim claim 12.

14. The polyurethane composition as claimed in claim 1, wherein the second component contains sufficient polyisocyanate I for it to comprise at least 8.1% by weight of isocyanate groups based on the overall polyurethane composition.

15. A composite material comprising a structural adhesive and at least one substrate, wherein the structural adhesive is formed from the polyurethane composition as claimed in claim 1 by mixing the first and second components of the polyurethane composition and applying the mixture to a surface of the at least one substrate.

16. A composite material that comprises a matrix and at least one material held together via the matrix, wherein the matrix is formed from the polyurethane composition as claimed in claim 1 by mixing the first and second components of the polyurethane composition and applying the mixture to a surface of the at least one material.

17. A polyurethane composition consisting of a first and a second component; wherein the first component A comprises at least one polyol A1 selected from the group consisting of polyoxyethylene diol, polyoxypropylene diol, polyoxyethylene triol, polyoxypropylene triol, polyoxypropylene polyoxyethylene diol, and polyoxypropylene polyoxyethylene triol and a number average molecular weight M.sub.n in the range from 1,000 to 8,000 g/mol, and at least one diol A2 selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,9-nonanediol, and at least one compound T selected from the group consisting of ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate); and the second component B comprises at least one polyisocyanate I the polyisocyanate I being a form of diphenylmethane 4,4′-, 2,4′- or 2,2′-diisocyanate that is liquid at room temperature and any mixtures of these isomers (MDI) in the form of polymeric MDI or MDI containing proportions of oligomers or derivatives; wherein the composition comprises less than 0.1% by weight of carboxylic acids, based on the overall composition, one of the two components additionally comprises at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes and the second component contains sufficient polyisocyanate I for it to comprise at least 7.5% by weight of isocyanate groups based on the overall polyurethane composition, and the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 5:1 and 100:1.

18. The polyurethane composition as claimed in claim 17, wherein the second component contains the polyisocyanate I in an amount sufficient for it to comprise at least 8.1% by weight of isocyanate groups based on the overall polyurethane composition.

Description

EXAMPLES

(1) Substances Used:

(2) TABLE-US-00001 Voranol CP 4755 Voranol ® CP 4755 (Dow Chemical); polyether triol, CAS No. 9082-00-2; MW: 5000 g/mol; OH value: 35 mg KOH/g 1,4-Butanediol (Sigma Aldrich) 1,5-Pentanediol (Sigma Aldrich) Silquest A-189 Silquest ® A-189 (Momentive) 3-mercaptopropyltrimethoxysilane Thiocure GDMA Thiocure ® GDMA (Bruno Bock Thiochemicals); glycol dimercaptoacetate Thiocure Di- Thiocure ® Di-PETMP (Bruno Bock Thiochemicals); PETMP dipentaerythritol hexa(3-mercaptopropionate) Thiocure GDMP Thiocure ® GDMP (Bruno Bock Thiochemicals); glycol di(3- mercaptopropionate) Polymer 1 NCO-functional polyether polyurethane (preparation see below); 2.3% by weight NCO Desmodur CD-L Desmodur ® CD-L (Covestro); modified diphenylmethane 4,4′- diisocyanate (MDI); NCO content: 29.5% by weight Desmodur 44 MC Desmodur ® 44 MC liquid (Covestro); monomeric diphenylmethane liquid 4,4′-diisocyanate (MDI); NCO content: 33.6% by weight Monarch 570 Monarch ® 570 (Cabot Corp.); carbon black (filler) Whitetex White Tex ® (BASF); calcined aluminum silicate (filler) Bi cat. (2.68 mmol 35% by weight Coscat 83 (organobismuth catalyst; Coscat ® 83 Bi/g) (Vertellus Specialties Inc.)) in plasticizer containing 1 molar equivalent of 8-hydroxyquinoline (based on Bi)

(3) Preparation of Polymer 1

(4) 1300 g of polyoxypropylene diol (Acclaim® 4200 N, Covestro; OH value 28.5 mg KOH/g), 2600 g of polyoxypropylenepolyoxyethylene triol (Voranol® CP 4755, Dow Chemical Company; OH value 34.0 mg KOH/g), 600 g of 4,4′-methylene diphenyl diisocyanate (4,4′-MDI; Desmodur® 44 MC L, Covestro), and 500 g of diisodecyl phthalate (DIDP; Palatinol® Z, BASF SE, Germany) were reacted at 80° C. by a known method to give an NCO-terminated polyurethane polymer having a content of isocyanate groups of 2.3% by weight.

(5) Preparation of Polyurethane Compositions

(6) For each composition, the ingredients of the first component A specified in the tables were processed in the amounts specified (in parts by weight or wt.-%), by means of a vacuum dissolver with the exclusion of moisture, into a homogeneous paste and stored. The ingredients of the second component B specified in the tables were processed in similar manner and stored. The two components were then processed for 30 seconds, by means of a SpeedMixer® (DAC 150 FV, Hauschild), into a homogeneous paste, which was immediately tested as follows:

(7) To determine the mechanical properties, the adhesive was fashioned into a dumbbell shape according to ISO 527, Part 2, 1B and cured/stored at 23° C. and 50% RH (relative humidity) for the time specified in the tables (1 day and 7 days) and then at 90° C. for 7 days. After a conditioning period of 24 h at 23° C. and 50% RH, the modulus of elasticity in the region from 0.05 to 0.25% elongation, the tensile strength, and the elongation at break of the test specimens thus produced were measured according to DIN EN ISO 527 on a Zwick Z020 tensile tester at 23° C. and 50% RH and a testing speed of 10 mm/min.

(8) The tear propagation resistance was determined according to DIN ISO 34-1. To measure the tensile shear strength, various test specimens were produced, in each case by applying the adhesive 1 minute after the end of the mixing time between two heptane-degreased cathodically-electrocoated steel plates in a layer thickness of 2 mm and over an overlapping bonding area of 15×45 mm. The test specimens were stored/cured for 24 h at 23° C. and then for 3 h at 80° C. After a conditioning period of 24 h at 23° C. and 50% RH, the tensile shear strength was determined according to DIN EN 1465.

(9) The Tg values (glass transition temperatures) were determined using a Mettler DMA/SDTA 861e instrument on the basis of DMTA measurements on disk-shaped samples (thickness 2-3 mm, diameter 10 mm), which were cured for 7 days under standard climatic conditions (“SC”; 23° C., 50% relative humidity “RH”). The measurement conditions were: measurement in shear mode, excitation frequency 10 Hz, and heating rate of 5 K/min. The samples were cooled to −60° C. and heated to 200° C. with determination of the complex shear modulus G* [MPa], with a maximum in the curve for the loss angle “tan δ” being read off as Tg value.

(10) The pot life was measured in a viscometer as the time until the viscosity began to rise steeply after mixing the two components. Specifically, the intercept of the slope of the viscosity (y axis) with the time (x axis) was defined as the pot life. The viscosity was measured on an MCR 302 parallel-plate rheometer (Anton Paar) with a plate diameter of 25 mm and a plate distance of 1 mm at a frequency of 10 s.sup.−1 and a temperature of 20° C. This was done by first mixing the two components for 30 sec in a SpeedMixer (Hauschild) and immediately applying them to the plates for the measurement.

(11) The results of the measurements are given in the tables.

(12) Tables 1 to 6 show experiments to demonstrate the influence on the pot life of the amount of compound T, which has at least one thiol group.

(13) Tables 7 to 10 show adhesive compositions tested in respect of pot life, cure profile, and mechanics. Here, compositions according to the invention are identified as “I” (I-1 to I-4) and non-inventive reference compositions as “R” (R-1 to R-6).

(14) TABLE-US-00002 TABLE 1 Preliminary experiments V-1a to V-1f. Example V-1a V-1b V-1c V-1d V-1e V-1f First component A (amounts in parts by weight) Voranol CP 4755 97.5 97.5 97.5 97.5 97.5 97.5 1,4-Butanediol 2.5 2.5 2.5 2.5 2.5 2.5 Silquest A-189 0 0.32 0.64 1.28 3.19 6.39 Second component B (amounts in parts by weight) Polymer 1 89 89 89 89 89 89 Desmodur CD-L 10 10 10 10 10 10 Bi cat. (2.68 mmol Bi/g) 1 1 1 1 1 1 Properties of the mixture of the two components A and B Molar ratio SH:Bi 0 5:1 10:1 20:1 50:1 100:1 Pot life [min] 0 0 0 1 8 23

(15) TABLE-US-00003 TABLE 2 Preliminary experiments V-2a to V-2f. Example V-2a V-2b V-2c V-2d V-2e V-2f First component A (amounts in parts by weight) Voranol CP 4755 95 95 95 95 95 95 1,4-Butanediol 5 5 5 5 5 5 Silquest A-189 0 0.32 0.64 1.28 3.19 6.39 Second component B (amounts in parts by weight) Polymer 1 79.5 79.5 79.5 79.5 79.5 79.5 Desmodur CD-L 20 20 20 20 20 20 Bi cat. (2.68 mmol Bi/g) 0.5 0.5 0.5 0.5 0.5 0.5 Properties of the mixture of the two components A and B Molar ratio SH:Bi 0 5:1 10:1 20:1 50:1 100:1 Pot life [min] 0 0 0 0 4 16

(16) TABLE-US-00004 TABLE 3 Preliminary experiments V-3a to V-3f. Example V-3a V-3b V-3c V-3d V-3e V-3f First component A (amounts in parts by weight) Voranol CP 4755 97.5 97.5 97.5 97.5 97.5 97.5 1,4-Butanediol 2.5 2.5 2.5 2.5 2.5 2.5 Thiocure GDMA 0 0.14 0.28 0.56 1.41 2.82 Second component B (amounts in parts by weight) Polymer 1 89 89 89 89 89 89 Desmodur CD-L 10 10 10 10 10 10 Bi cat. (2.68 mmol Bi/g) 1 1 1 1 1 1 Properties of the mixture of the two components A and B Molar ratio SH:Bi 0 5:1 10:1 20:1 50:1 100:1 Pot life [min] 0 15 41 60 110 210

(17) TABLE-US-00005 TABLE 4 Preliminary experiments V-4a to V-4f. Example V-4a V-4b V-4c V-4d V-4e V-4f First component A (amounts in parts by weight) Voranol CP 4755 95 95 95 95 95 95 1,4-Butanediol 5 5 5 5 5 5 Thiocure GDMA 0 0.14 0.28 0.56 1.41 2.82 Second component B (amounts in parts by weight) Polymer 1 79.5 79.5 79.5 79.5 79.5 79.5 Desmodur CD-L 20 20 20 20 20 20 Bi cat. (2.68 mmol Bi/g) 0.5 0.5 0.5 0.5 0.5 0.5 Properties of the mixture of the two components A and B Molar ratio SH:Bi 0 5:1 10:1 20:1 50:1 100:1 Pot life [min] 0 0 4 7 19 42

(18) TABLE-US-00006 TABLE 5 Preliminary experiments V-5a to V-5f. Example V-5a V-5b V-5c V-5d V-5e V-5f First component A (amounts in parts by weight) Voranol CP 4755 97.5 97.5 97.5 97.5 97.5 97.5 1,4-Butanediol 2.5 2.5 2.5 2.5 2.5 2.5 Thiocure Di-PETMP 0 0.32 0.64 1.28 3.19 6.39 Second component B (amounts in parts by weight) Polymer 1 89 89 89 89 89 89 Desmodur CD-L 10 10 10 10 10 10 Bi cat. (2.68 mmol Bi/g) 1 1 1 1 1 1 Properties of the mixture of the two components A and B Molar ratio SH:Bi 0 5:1 10:1 20:1 50:1 100:1 Pot life [min] 0 200 400 850 >1000 >1000

(19) TABLE-US-00007 TABLE 6 Preliminary experiments V-6a to V-6f. Example V-6a V-6b V-6c V-6d V-6e V-6f First component A (amounts in parts by weight) Voranol CP 4755 95 95 95 95 95 95 1,4-Butanediol 5 5 5 5 5 5 Thiocure Di-PETMP 0 0.32 0.64 1.28 3.19 6.39 Second component B (amounts in parts by weight) Polymer 1 79.5 79.5 79.5 79.5 79.5 79.5 Desmodur CD-L 20 20 20 20 20 20 Bi cat. (2.68 mmol Bi/g) 0.5 0.5 0.5 0.5 0.5 0.5 Properties of the mixture of the two components A and B Molar ratio SH:Bi 0 5:1 10:1 20:1 50:1 100:1 Pot life [min] 0 40 200 400 1200 >2000

(20) The preliminary experiments V1a to V6f show experiments demonstrating the influence on the pot life of various compounds T having at least one thiol group and also the possibility of being able to adjust the pot life within certain limits.

(21) The results show clearly that the pot life in two-component polyurethane compositions that could not be processed at all in the absence of compound T can be adjusted through the use of compounds T via the molar ratio of thiol groups to metal atoms in the catalyst.

(22) TABLE-US-00008 TABLE 7 Example I-1 R-1 R-2 R-3 I-2 First component A (amounts in wt.-%, based on first component A) Voranol CP 4755 60 60.5 63 62.5 61.25 1,5-Pentanediol 12 12 12 12 12 Monarch 570 10 10 10 10 10 Whitex 15 15 15 15 15 Thiocure GDMP 2.5 2.5 — — 1.25 Bi cat. 0.5 — — 0.5 0.5 TOTAL 100 100 100 100 100 Second component B (amounts in wt.-%, based on first component B) Desmodur CD-L 44 44 44 44 44 Voranol CP-4755 32 32 32 32 32 Whitex 15 15 15 15 15 Monarch 570 10 10 10 10 10 TOTAL 100 100 100 100 100 Mixing ratio A:B (v/v) 1:1 1:1 1:1 1:1 1:1 NCO content [%] * 6.1 * NCO content in wt.-% of isocyanate groups based on the overall polyurethane composition.

(23) TABLE-US-00009 TABLE 8 Example I-3 R-4 R-5 R-6 I-4 First component A (amounts in wt.-%, based on first component A) Voranol CP 4755 56 56.5 59.5 59 57.5 1,5-Pentanediol 18 18 18 18 18 Monarch 570 12.5 12.5 12.5 12.5 12.5 Whitetex 10 10 10 10 10 Thiocure GDMP 3 3 — — 1.5 Bi cat. 0.5 — — 0.5 0.5 TOTAL 100 100 100 100 100 Second component B (amounts in wt.-%, based on first component B) Desmodur CD-L 30 30 30 30 30 Desmodur 44 MC liquid 25 25 25 25 25 Voranol CP-4755 22.5 22.5 22.5 22.5 22.5 Monarch 570 12.5 12.5 12.5 12.5 12.5 Whitetex 10 10 10 10 10 TOTAL 100 100 100 100 100 Mixing ratio A:B (v/v) 1:1 1:1 1:1 1:1 1:1 NCO content [%] * 8.1 * NCO content in wt.-% of isocyanate groups based on the overall polyurethane composition.

(24) The results in tables 9 and 10 show clearly that the compositions according to the invention very rapidly build up strength, in particular tensile strength and tensile shear strength, and are significantly superior to the non-inventive compositions with regard to mechanical properties, curing rate, and even adhesion profile.

(25) TABLE-US-00010 TABLE 9 Example I-1 R-1 R-2 R-3 I-2 Pot life [min] 62 85 75 18 32 Tensile shear 1 h SC 2.2 (0)  n.d. n.d. 0.84 (0)  4.3 (60) strength [MPa] 2 h SC 12.3 (100) 0.1 (0)  0.1 (0) 1.7 (0)   8.7 (100) (Proportion of 4 h SC 13.5 (100) 0.2 (0)  0.2 (0) 3.4 (30) 10.5 (100) cohesive break 1 d SC 14.6 (100) 1.1 (0)  2.0 (0)  9.1 (100) 12.4 (100) [%]) 7 d SC 12.8 (100) 8.7 (100)  11.4 (100) 13.6 (100) 11.9 (100) Tensile strength 1 d SC  16.2 (76.7) 4.1 (130)  5.5 (160) 12.9 (125) 13.8 (100) [MPa] 7 d SC  14.2 (83.2) 9.2 (159)  9.33 (154) 12.5 (151) 10.3 (101) (Modulus of elasticity [MPa]) 7 d NC + 20.5 (96)  12.7 (178)   14.2 (177) 14.2 (139) 15.0 (107) 7 d 90° C. Elongation at 1 d SC 264 18.4 34.1 213.6 218.5 break [%] 7 d SC 195.5 97.6 131.8 139.2 107.3 7 d NC + 352.6 170.6 224.5 172.1 233.4 7 d 90° C. Tear propagation 7 d SC 26.4 36.3 34.5 32.4 26.9 resistance [MPa] Tg [° C.] 7 d SC −25.5 −49.7 −52.1 −46.6 −42.1 n.d. = not determined

(26) TABLE-US-00011 TABLE 10 Example I-3 R-4 R-5 R-6 I-4 Pot life [min] 30  33  32  4  19   Tensile shear 1 h SC 5.5 (10) 0.2 (0)  0.3 (0)  1.9 (0)  3.4 (0)  strength [MPa] 2 h SC 7.3 (40) 0.8 (0)  1.1 (0)  2.5 (0)  4.8 (0)  (Proportion of 4 h SC  7.9 (100) 1.1 (0)  1.2 (0)  5.4 (0)  7.0 (10) cohesive break 1 d SC 14.1 (100) 4.2 (50) 4.7 (50) 8.1 (80) 13.0 (100) [%]) 7 d SC 14.7 (100)  8.9 (100) 11.5 (100) 12.5 (100) 13.0 (100) Tensile strength 1 d SC .sup. 14.7 (341.6)  7.2 (349)  7.4 (360) 12.8 (347) 14.1 (361) [MPa] 7 d SC 20.1 (338) 14.1 (456) 15.2 (483) 18.4 (391) 13.7 (450) (Modulus of 7 d NC + 21.5 (353) 21.3 (479) 17.3 (450) 16.3 (394) 18.4 (369) elasticity [MPa]) 7 d 90° C. Elongation at 1 d SC 132.1  4.4  4.4 94.5 93.6 break [%] 7 d SC 266.7 175.3 177.5 231.8  52.3 7 d NC + 237.3 314.3 132.1 99.8 191.3  7 d 90° C. Tear propagation 7 d SC  58.8  66.0  70.8 63.3 59.3 resistance [MPa] Tg [° C.] 7 d SC −45.8 −52.8 −52.2 −49.0  −48.6