LINEAR ISOCYANATE GROUP-CONTAINING POLYMER

Abstract

A linear polymer containing isocyanate groups and having an NCO content in the range from 0.3% to 1.5% by weight and a monomeric diisocyanate content of not more than 0.5% by weight, wherein it is obtained from the reaction of at least one monomeric aromatic diisocyanate and a polyether diol having an OH number in the range from 5 to 21 mg KOH/g in an NCO/OH ratio of at least 5/1 and subsequent removal of a majority of the monomeric aromatic diisocyanate by means of a suitable separation method, and to moisture-curing polyurethane compositions having a monomeric diisocyanate content of less than 0.1% by weight, comprising said polymer. The polymer of the invention enables elastic adhesives having high elongation, surprisingly high strength and surprisingly good adhesion to plastic substrates.

Claims

1. A linear polymer containing isocyanate groups and having an NCO content in the range from 0.3% to 1.5% by weight and a monomeric diisocyanate content of not more than 0.5% by weight, wherein it is obtained from the reaction of at least one monomeric aromatic diisocyanate and a polyether diol having an OH number in the range from 5 to 21 mg KOH/g in an NCO/OH ratio of at least 5/1 and subsequent removal of a majority of the monomeric aromatic diisocyanate by means of a suitable separation method.

2. The polymer as claimed in claim 1, wherein the monomeric aromatic diisocyanate is diphenylmethane 4,4'-diisocyanate.

3. The polymer as claimed in claim 1, wherein the polyether diol contains 80% to 100% by weight of 1,2-propyleneoxy groups and 0% to 20% by weight of 1,2-ethyleneoxy groups.

4. The polymer as claimed in claim 1, wherein the polyether diol has an OH number in the range from 6 to 19 mg KOH/g and an average OH functionality of at least 1.9.

5. The polymer as claimed in claim 1, wherein the excess monomeric diisocyanate is removed by means of a distillative method.

6. The polymer as claimed in claim 1, wherein it has an NCO content in the range from 0.5% to 1.3% by weight and a monomeric diisocyanate content of not more than 0.3% by weight.

7. The polymer as claimed in claim 1, wherein the NCO content is at least 90% of the theoretical NCO content which is calculated from the addition of one mole of monomeric diisocyanate per mole of OH groups of the polyether diol.

8. A moisture-curing polyurethane composition having a monomeric diisocyanate content of less than 0.1% by weight, comprising the polymer as claimed in claim 1.

9. The moisture-curing polyurethane composition as claimed in claim 8, wherein it has a content of polymer containing isocyanate groups and having an NCO content in the range from 0.3% to 1.5% by weight and a monomeric diisocyanate content of not more than 0.5% by weight, wherein it is obtained from the reaction of at least one monomeric aromatic diisocyanate and a polyether diol having an OH number in the range from 5 to 21 mg KOH/g in an NCO/OH ratio of at least 5/1 and subsequent removal of a majority of the monomeric aromatic diisocyanate by means of a suitable separation method, based on the overall composition, in the range from 5% to 80% by weight.

10. The moisture-curing polyurethane composition as claimed in claim 8, wherein it has a content of polymer containing isocyanate groups and having an NCO content in the range from 0.3% to 1.5% by weight and a monomeric diisocyanate content of not more than 0.5% by weight, wherein it is obtained from the reaction of at least one monomeric aromatic diisocyanate and a polyether diol having an OH number in the range from 5 to 21 mg KOH/g in an NCO/OH ratio of at least 5/1 and subsequent removal of a majority of the monomeric aromatic diisocyanate by means of a suitable separation method, based on the total amount of polymers containing isocyanate groups in the composition, of at least 25% by weight.

11. The moisture-curing polyurethane composition as claimed in claim 8, wherein it additionally comprises at least one constituent containing isocyanate groups and having an average NCO functionality of more than 2.

12. A method of bonding, sealing or coating, comprising: obtaining a moisture-curing polyurethane composition as claimed in claim 8; applying it to at least one plastic substrate.

13. The method as claimed in claim 12, wherein the plastic substrate is selected from the group consisting of rigid PVC, flexible PVC, polycarbonate, polystyrene, polyester, polyamide, PMMA, ABS, SAN, epoxy resins, phenolic resins, PUR, POM, TPO, PE, PP, EPM, EPDM, and blends of polycarbonate with further plastics .

14. A cured composition obtained from the moisture-curing polyurethane composition as claimed in claim 8 after contact thereof with moisture.

15. A bonded composite comprising at least one plastic substrate and the polyurethane composition as claimed in claim 8 that has been cured by contact with moisture.

Description

EXAMPLES

[0172] Working examples are adduced hereinafter, which are intended to further elucidate the invention described. The invention is of course not limited to these described working examples.

[0173] "Standard climatic conditions" ("SCC") refer to a temperature of 23 ± 1° C. and a relative air humidity of 50 ± 5%.

[0174] Unless stated otherwise, the chemicals used were from Sigma-Aldrich.

[0175] Viscosity was measured with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 25 mm, cone angle 1°, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.-1).

[0176] Monomeric diisocyanate content was determined by means of HPLC (detection via photodiode array; 0.04 M sodium acetate / acetonitrile as mobile phase) after prior derivatization by means of N-propyl-4-nitrobenzylamine.

[0177] Polyols used: [0178] Acclaim® 4200: polyoxypropylene diol, OH number 28 mg KOH/g (from Covestro) [0179] Acclaim® 8200N: polyoxypropylene diol, OH number 14 mg KOH/g (from Covestro) [0180] Acclaim® 12200N: polyoxypropylene diol, OH number 10 mg KOH/g (from Covestro) [0181] Desmophen® 5031 BT: ethylene oxide-terminated polyoxypropylene triol, OH number 28 mg KOH/g (from Covestro)

[0182] Monomeric diisocyanates used: [0183] Desmodur.sup.® 44 MC L: diphenylmethane 4,4'-diisocyanate having an NCO content of 33.6% by weight (from Covestro)

Preparation of Polymers Containing Isocyanate Groups

Polymer L1 (Linear)

[0184] 757.7 g (0.19 eq OH) of Acclaim® 8200N and 242.3 g (1.9 eq NCO) of Desmodur® 44 MC L were reacted by a known method at 80° C. to give a polymer having an NCO content of 7.2% by weight, a viscosity of 6.8 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of about 20% by weight. Subsequently, the volatile constituents, especially a majority of the monomeric diphenylmethane 4,4'-diisocyanate, were removed by distillation in a short-path evaporator (jacket temperature 180° C., pressure 0.1 to 0.005 mbar, condensation temperature 47° C.). The linear polymer thus obtained had an NCO content of 1.0% by weight, a viscosity of 25.0 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of 0.06% by weight.

Polymer L2 (Linear)

[0185] 812.0 g (0.15 eq OH) of Acclaim® 12200 N and 188.0 g (1.5 eq NCO) of Desmodur® 44 MC L were reacted by a known method at 80° C. to give a polymer having an NCO content of 5.6% by weight, a viscosity of 13.9 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of about 14% by weight. Subsequently, the volatile constituents, especially a majority of the monomeric diphenylmethane 4,4'-diisocyanate, were removed by distillation in a short-path evaporator (jacket temperature 180° C., pressure 0.1 to 0.005 mbar, condensation temperature 47° C.). The linear polymer thus obtained had an NCO content of 0.7% by weight, a viscosity of 29.4 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of 0.04% by weight.

Polymer Ref-1 (Linear, Comparison)

[0186] 727.0 g of Acclaim® 4200 and 273.0 g of Desmodur® 44 MC L were reacted by a known method at 80° C. to give a polymer having an NCO content of 7.4% by weight, a viscosity of 5.2 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of about 17% by weight.

[0187] Subsequently, the volatile constituents, especially a majority of the monomeric diphenylmethane 4,4'-diisocyanate, were removed by distillation in a short-path evaporator (jacket temperature 180° C., pressure 0.1 to 0.005 mbar, condensation temperature 47° C.). The linear polymer thus obtained had an NCO content of 1.8% by weight, a viscosity of 13.3 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of 0.08% by weight.

Polymer C-1 (Branched)

[0188] 725.0 g of Desmophen® 5031 BT and 275 g of Desmodur.sup.® 44 MC L were reacted by a known method at 80° C. to give a polymer having an NCO content of 7.6% by weight, a viscosity of 6.5 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of about 20% by weight.

[0189] Subsequently, the volatile constituents, especially a majority of the monomeric diphenylmethane 4,4'-diisocyanate, were removed by distillation in a short-path evaporator (jacket temperature 180° C., pressure 0.1 to 0.005 mbar, condensation temperature 47° C.). The polymer thus obtained had an NCO content of 1.7% by weight, a viscosity of 19 Pa.Math.s at 20° C. and a monomeric diphenylmethane 4,4'-diisocyanate content of 0.04% by weight.

Moisture-Curing Polyurethane Compositions

Compositions Z1 to Z7

[0190] For each composition, the ingredients specified in table 1 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer

[0191] (SpeedMixer™ DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute and stored with exclusion of moisture. Each composition was tested as follows:

[0192] Shore A hardness was determined to DIN 53505 on test specimens cured under standard climatic conditions for 14 days.

[0193] To determine the mechanical properties, the composition was applied to a silicone-coated release paper to give a film of thickness 2 mm, which was stored under standard climatic conditions for 14 days, and a few dumbbells having a length of 75 mm with a bar length of 30 mm and a bar width of 4 mm were punched out of the film and these were tested in accordance with DIN EN 53504 at a strain rate of 200 mm/min for tensile strength (breaking force), elongation at break, and 5% modulus of elasticity (at 0.5-5% elongation).

[0194] Adhesion to plastic substrates was determined by applying the composition in the form of four parallel beads of width about 10 mm, height 5 mm and length 15 mm to the respective substrate, and curing under standard climatic conditions for 7 days. Subsequently, the adhesion of the cured composition was tested for a first time by making an incision into the first bead at the narrow end just above the bonding surface, holding the cut end of the bead with rounded tweezers and trying to pull the bead away from the substrate. Then the bead was incised again down to the substrate, the part that had been cut away was rolled up with the rounded tweezers and another attempt was made to pull the bead away from the substrate. In this way, the whole bead was cut away from the substrate by pulling. Subsequently, adhesion was assessed from the failure profile and was reported in table 1 under “7d SCC". Some of the test specimens were then stored immersed in deionized water for 7 days, then stored under standard climatic conditions for 2 hours, and then the second bead was cut away from the substrate by pulling with the rounded tweezers and adhesion was assessed from the failure profile and reported in table 1 under “7d H.sub.2O”. Then the test specimens were stored at 80° C. in an air circulation oven for 24 hours, followed by 2 hours under standard climatic conditions, and then the third bead was tested for adhesion as described, and adhesion was assessed from the failure profile and reported in table 1 under “1d 80° C.”. Finally, the test specimens were stored at 70° C. and 100% relative humidity for 7 days, followed by 2 hours under standard climatic conditions, and the fourth bead was tested for adhesion as described, and adhesion was assessed from the failure profile and reported in table 1 under "7d 70° C./100%RH".

[0195] The plastic substrates used were the following plastic sheets (300 × 200 × 2 mm): [0196] PMMA: Plexiglas® XT 0A000 (from Evonik Röhm) [0197] PC: Makrolon® GP clear 099 (uncoated polycarbonate, from Covestro) [0198] ABS: Metzoplast ABS/G (from Metzeler Plastics GmbH) [0199] PVC: KömaDur® ES (from Kömmerling Kunststoffe)

[0200] Adhesion was assessed under the following scale:

[0201] 100 represents more than 95% cohesive failure and means very good adhesion.

[0202] 40 represents 40% cohesive failure and means moderate adhesion.

[0203] 5 represents 5% cohesive failure and means inadequate adhesion.

[0204] 0 represents 0% cohesive failure (100% adhesive failure) and means poor adhesion.

[0205] The results are reported in table 1.

[0206] Comparative examples are identified by (Ref.).

TABLE-US-00001 Composition (in parts by weight) and properties of Z1 to Z7 Composition Z1 (Ref.) Z2 Z3 Z4 Z5 Z6 Z7 Polymer Ref-1 41.4 – - - - - Polymer L1 - 41.4 47.4 49.4 - - - Polymer L2 - - - - 41.4 47.4 49.4 Polymer C-1 14.0 14.0 8.0 6.0 14.0 8.0 6.0 pTSI.sup.1 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Carbon black 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Chalk.sup.2 32.0 32.0 32.0 32.0 32.0 32.0 32.0 Silica.sup.3 2.0 2.0 2.0 2.0 2.0 2.0 2.0 DMDEE.sup.4 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Shore A 44 49 45 45 49 44 40 Tensile strength [MPa] 6.3 6.7 3.8 2.4 5.8 4.7 1.8 Elongation at break [%] 900 1040 1170 1135 950 1200 971 Modulus of elasticity 5% [MPa] 4.3 3.9 3.8 3.8 3.8 3.3 3.3 PMMA adhesion 7 d SCC 0 100 100 100 100 100 100 7d H.sub.2O 0 100 100 100 100 100 100 1d 80° C. 0 80 100 100 100 100 100 7d 70° C./100%RH 0 100 100 100 100 100 100 PC adhesion 7 d SCC 100 100 100 100 100 100 100 7d H.sub.2O 100 100 100 100 100 100 100 1d 80° C. 100 100 100 100 100 100 100 7d 70° C./100%RH 0 0 100 100 0 100 100 ABS adhesion 7 d SCC 0 0 5 100 0 100 100 7d H.sub.2O 0 0 5 100 0 100 100 1d 80° C. 0 0 5 100 0 100 100 7d 70° C./100%RH 0 0 5 100 0 100 100 PVC adhesion 7 d SCC 0 0 5 100 0 100 100 7d H.sub.2O 0 0 5 100 0 100 100 1d 80° C. 0 0 40 100 0 100 100 7d 70° C./100%RH 0 0 100 100 100 100 100 .sup.1 p-toluenesulfonyl isocyanate .sup.2 Omyacarb® 5 GU (from Omya) .sup.3 Aerosil® R 972 (from Evonik) .sup.4 2,2'-dimorpholinodiethyl ether