POLYURETHANE COMPOSITION WITH GOOD ADHESION TO PLASTICS

Abstract

A moisture-curing polyurethane composition including (i) at least one linear polymer P1 containing isocyanate groups and having an NCO content in range from 0.3%-3.3% by weight, obtained from reaction of at least one monomeric aromatic diisocyanate and polyether diol having an OH number in range from 5-37 mg KOH/g, (ii) at least one branched polymer P2 containing isocyanate groups and having an NCO content in range from 1%-10% by weight, obtained from reaction of at least one monomeric aromatic diisocyanate and at least one polyether triol having an average OH functionality of at least 2.2 and OH number in range from 16-380 mg KOH/g, (iii) and a content of plasticizers of not more than 15% by weight, based on overall composition, wherein polymers P1 and P2 are present in weight ratio in range from 80/20-95/5, and to the use of composition as elastic adhesive or elastic sealant or elastic coating.

Claims

1. A moisture-curing polyurethane composition comprising (i) at least one linear polymer P1 containing isocyanate groups and having an NCO content in the range from 0.3% to 3.3% by weight, 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 37 mg KOH/g, (ii) at least one branched polymer P2 containing isocyanate groups and having an NCO content in the range from 1% to 10% by weight, obtained from the reaction of at least one monomeric aromatic diisocyanate and at least one polyether triol having an average OH functionality in the region of at least 2.2 and an OH number in the range from 16 to 380 mg KOH/g, (iii) and a content of plasticizers of not more than 15% by weight, based on the overall composition, wherein polymer P1 and polymer P2 are present in a weight ratio in the range from 80/20 to 95/5.

2. The moisture-curing polyurethane composition as claimed in claim 1, wherein polymer P1 has an NCO content in the range from 0.5% to 2.6% by weight.

3. The moisture-curing polyurethane composition as claimed in claim 1, wherein polymer P1 is prepared in such a way that the NCO/OH ratio in the reaction is at least 4/1, and a majority of the monomeric aromatic diisocyanate is subsequently removed by means of a suitable separation process, such that the resultant polymer P1 containing isocyanate groups, after distillation, contains not more than 0.5% by weight of monomeric diisocyanate.

4. The moisture-curing polyurethane composition as claimed in claim 1, wherein the polyether diol has an OH number in the range from 6 to 33 mg KOH/g and an average OH functionality of at least 1.9.

5. The moisture-curing polyurethane composition as claimed in claim 1, wherein the monomeric aromatic diisocyanate for both polymers P1 and P2 is diphenylmethane 4,4′-diisocyanate.

6. The moisture-curing polyurethane composition as claimed in claim 1, wherein the content of the sum total of polymer P1 and polymer P2, based on the overall composition, is in the range from 20% to 80% by weight.

7. The moisture-curing polyurethane composition as claimed in claim 1, wherein the content of monomeric diisocyanates in the composition is less than 0.1% by weight in total.

8. The moisture-curing polyurethane composition as claimed in claim 1, wherein at least one further constituent selected from the group consisting of fillers, oligomeric diisocyanates, blocked amines, catalysts and stabilizers is present.

9. (canceled)

10. A method comprising a step of bonding, sealing, or coating at least one plastic substrate with the moisture-curing polyurethane composition of claim 1.

11. The method of claim 10, 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.

12. A method of bonding or sealing, comprising the steps of (i) applying the moisture-curing polyurethane composition as claimed in claim 1 to a first substrate and contacting the composition with a second substrate within the open time of the composition, or to a first and to a second substrate and joining the two substrates within the open time of the composition, or between two substrates, and (ii) curing the composition by contact with moisture.

13. A method of coating or sealing, comprising the steps of (i) applying the moisture-curing polyurethane composition as claimed in claim 1 to a substrate, and (ii) curing the composition by contact with moisture.

14. A cured composition obtained from the moisture-curing polyurethane composition as claimed in claim 1 after contact thereof with moisture.

15. A bonded composite comprising at least one plastic substrate and the polyurethane composition as claimed in claim 1 that has been cured by contact with moisture.

Description

EXAMPLES

[0177] 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.

[0178] “Standard climatic conditions” (“SCC”) refer to a temperature of 23±1° C. and a relative air humidity of 50±5%.

[0179] Unless stated otherwise, the chemicals used were from Sigma-Aldrich.

[0180] 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).

[0181] 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.

Polyols Used:

[0182] Acclaim® 4200: polyoxypropylene diol, OH number 28 mg KOH/g (from Covestro) [0183] Acclaim® 8200N: polyoxypropylene diol, OH number 14 mg KOH/g (from Covestro) [0184] Acclaim® 12200: polyoxypropylene diol, OH number 10 mg KOH/g (from Covestro) [0185] Desmophen® 5031 BT: ethylene oxide-terminated polyoxypropylene triol, OH number 28 mg KOH/g (from Covestro) [0186] Voranol® CP 4755: ethylene oxide-terminated polyoxypropylene triol, OH number 35.0 mg KOH/g (from Dow)

Monomeric Diisocyanates Used:

[0187] Desmodur® 44 MC L: diphenylmethane 44,4′-diisocyanate having an NCO content of 33.6% by weight (from Covestro)

Preparation of Polymers Containing Isocyanate Groups:

Polymer L1 (Linear):

[0188] 727 g (0.36 eq OH) of Acclaim® 4200 and 273 g (2.18 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 7.4% by weight, a viscosity of 5.2 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of about 17% 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 linear polymer thus obtained had an NCO content of 1.8% by weight, a viscosity of 13.3 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of 0.08% by weight.

Polymer L2 (Linear):

[0190] 400 g (0.20 eq OH) of Acclaim® 4200 and 52 g (0.41 eq NCO) of Desmodur® 44 MC L were converted by a known method at 80° C. to an NCO-terminated polymer. The linear polymer thus obtained had an NCO content of 1.8% by weight, a viscosity of 33 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of about 2.5% by weight.

Polymer L3 (Linear):

[0191] 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 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of about 20% by weight.

[0192] 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 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of 0.06% by weight.

Polymer L4 (Linear):

[0193] 812.0 g (0.15 eq OH) of Acclaim® 12200N 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 Pas 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 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of 0.04% by weight.

Polymer C1 (Branched):

[0194] 725.0 g (0.36 eq OH) of Desmophen® 5031 BT and 275 g (2.2 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 7.6% by weight, a viscosity of 6.5 Pas 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 polymer thus obtained had an NCO content of 1.7% by weight, a viscosity of 19 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of 0.04% by weight.

Polymer C2 (Branched):

[0195] 685 g of Voranol® CP 4755, 115 g of Desmodur® 44 MC L and 200 g of diisodecyl phthalate were reacted by a known method at 80° C. to give a polymer having an NCO content of 2.0% by weight, a viscosity of 55 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of about 2.5% by weight.

Moisture-Curing Polyurethane Compositions:

Compositions Z1 to Z15:

[0196] For each composition, the ingredients specified in tables 1 to 4 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute and stored with exclusion of moisture. The compositions were tested as follows:

[0197] As a measure of the open time, skin time (ST) was determined. For this purpose, a few grams of the composition was applied to cardboard in a layer thickness of about 2 mm and, under standard climatic conditions, the period of time after which no residues remained any longer on an LDPE pipette used to gently tap the surface of the composition was determined.

[0198] Shore A hardness was determined to DIN 53505 on test specimens cured under standard climatic conditions for 14 days.

[0199] 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).

[0200] 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, 2 or 3 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, 2 or 3 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, 2 or 3 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, 2 or 3 under “7d 70° C./100% RH”.

[0201] The plastic substrates used were the following plastic sheets (300×200×2 mm):

[0202] PMMA: Plexiglas® XT 0A000 (from Evonik Rohm)

[0203] PC: Makrolon® GP clear 099 (uncoated polycarbonate, from Covestro)

[0204] ABS: Metzoplast ABS/G (from Metzeler Plastics GmbH)

[0205] PVC: KömaDur® ES (from Kömmerling Kunststoffe)

[0206] Adhesion was assessed under the following scale:

[0207] 100 represents more than 95% cohesive failure and means very good adhesion.

[0208] 70 to 90 represents 70% to 90% cohesive failure and means good adhesion. [0209] 5 represents 5% cohesive failure and means inadequate adhesion. [0210] 0 represents 0% cohesive failure (100% adhesive failure) and means poor adhesion.

[0211] The results are reported in tables 1 to 4.

[0212] Comparative examples are identified by (Ref.).

TABLE-US-00001 TABLE 1 Composition (in parts by weight) and properties of Z1 to Z7. Z1 Z7 Composition (Ref.) Z2 Z3 Z4 Z5 Z6 (Ref.) Polymer L1 41.4 47.4 48.7 49.4 50.4 51.4 53.4 Polymer C1 14.0 8.0 6.7 6.0 5.0 4.0 2.0 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 Polymer ratio.sup.5 75/25 86/14 88/12 89/11 91/9 93/7 96/4 Shore A 44 48 48 47 38 41 36 Tensile strength 6.3 4.9 6.5 6.3 5.5 2.3 0.9 [MPa] Elongation at break 900 1230 1060 1130 1100 1000 890 [%] Modulus of 4.3 4.4 4.9 5.0 4.9 4.5 3.4 elasticity 5% [MPa] PC adhesion 7 d SCC 100 100 100 100 100 100 100 7 d H.sub.2O 100 100 100 100 100 100 100 1 d 80° C. 100 100 100 100 100 100 100 7 d 70° C./100% RH 0 5 5 85 90 100 100 PMMA adhesion 7 d SCC 0 70 90 100 100 100 100 .sup.1p-toluenesulfonyl isocyanate .sup.2Omyacarb ® 5 GU (from Omya). .sup.3Aerosil ® R 972 (from Evonik) .sup.42,2′-dimorpholinodiethyl ether .sup.5weight ratio between linear and branched polymer

TABLE-US-00002 TABLE 2 Composition (in parts by weight) and properties of Z4 and Z8 to Z10. Composition Z4 Z8 Z9 Z10 Polymer L1 49.4 — 49.4 — Polymer L2 — 49.4 — 49.4 Polymer C1 6.0 6.0 — — Polymer C2 — — 7.5 7.5 pTSI.sup.1 0.4 0.4 0.4 0.4 Carbon black 10.0 10.0 10.0 10.0 Chalk.sup.2 32.0 32.0 30.5 30.5 Silica.sup.3 2.0 2.0 2.0 2.0 DMDEE.sup.4 0.2 0.2 0.2 0.2 Polymer ratio.sup.5 89/11 89/11 89/11 89/11 ST [min.] 70 70 70 65 Shore A 47 53 48 61 Tensile strength 6.3 6.8 7.2 6.1 [MPa] Elongation at break 1130 862 1135 745 [%] Modulus of 5.0 8.4 4.9 8.8 elasticity 5% [MPa] PC adhesion 7 d SCC 100 100 100 100 7 d H.sub.2O 100 100 100 100 1 d 80° C. 100 100 100 100 7 d 70° C./100% RH 85 90 90 80 PMMA adhesion 7 d SCC 100 100 100 100 .sup.1p-toluenesulfonyl isocyanate .sup.2Omyacarb ® 5 GU (from Omya). .sup.3Aerosil ® R 972 (from Evonik) .sup.42,2′-dimorpholinodiethyl ether .sup.5weight ratio between linear and branched polymer (polymer C2 contains 10% by weight of plasticizer)

TABLE-US-00003 TABLE 3 Composition (in parts by weight) and properties of Z11 to Z14. Z11 Z14 Composition (Ref.) Z12 Z13 (Ref.) Polymer L3 41.4 47.4 49.4 53.4 Polymer C1 14.0 8.0 6.0 2.0 pTSI.sup.1 0.4 0.4 0.4 0.4 Carbon black 10.0 10.0 10.0 10.0 Chalk.sup.2 32.0 32.0 32.0 32.0 Silica.sup.3 2.0 2.0 2.0 2.0 DMDEE.sup.4 0.2 0.2 0.2 0.2 Polymer ratio.sup.5 75/25 86/14 89/11 96/4 Shore A 49 45 45 28 Tensile strength 6.7 3.8 2.4 0.4 [MPa] Elongation at break 1040 1170 1135 53 [%] Modulus of elasticity 3.9 3.8 3.8 2.4 5% [MPa] PC adhesion 7 d SCC 100 100 100 100 7 d H.sub.2O 100 100 100 0 1 d 80° C. 100 100 100 100 7 d 70° C./100% RH 0 100 100 0 .sup.1p-toluenesulfonyl isocyanate .sup.2Omyacarb ® 5 GU (from Omya). .sup.3Aerosil ® R 972 (from Evonik) .sup.42,2′-dimorpholinodiethyl ether .sup.5weight ratio between linear and branched polymer

TABLE-US-00004 TABLE 4 Composition (in parts by weight) and properties of Z15 to Z18. Z15 Z18 Composition (Ref.) Z16 Z17 (Ref.) Polymer L4 41.4 47.4 49.4 53.4 Polymer C1 14.0 8.0 6.0 2.0 pTSI.sup.1 0.4 0.4 0.4 0.4 Carbon black 10.0 10.0 10.0 10.0 Chalk.sup.2 32.0 32.0 32.0 32.0 Silica.sup.3 2.0 2.0 2.0 2.0 DMDEE.sup.4 0.2 0.2 0.2 0.2 Polymer ratio.sup.5 75/25 86/14 89/11 96/4 Shore A 49 44 40 33 Tensile strength 5.8 4.7 1.8 0.5 [MPa] Elongation at break 950 1200 971 425 [%] Modulus of elasticity 3.8 3.3 3.3 2.9 5% [MPa] PC adhesion 7 d SCC 100 100 100 100 7 d H.sub.2O 100 100 100 100 1 d 80° C. 100 100 100 100 7 d 70° C./100% RH 0 100 100 100 ABS adhesion 7 d SCC 0 100 100 100 7 d H.sub.2O 0 100 100 100 1 d 80° C. 0 100 100 100 7 d 70° C./100% RH 0 100 100 100 PVC adhesion 7 d SCC 0 100 100 90 7 d H.sub.2O 0 100 100 100 1 d 80° C. 0 100 100 100 7 d 70° C./100% RH 100 100 100 100 .sup.1p-toluenesulfonyl isocyanate .sup.2Omyacarb ® 5 GU (from Omya). .sup.3Aerosil ® R 972 (from Evonik) .sup.42,2′-dimorpholinodiethyl ether .sup.5weight ratio between linear and branched polymer

[0213] It is clear from tables 1 to 4 that the compositions of the invention in which the linear polymer and the branched polymer are present in the ratio of the invention show good mechanical properties and improved adhesion on the plastic substrates compared to the respective reference composition having too low a content of linear polymer (Z1/Z11/Z15), while reference compositions having too high a content of linear polymer (Z7/Z14/Z18) do show good adhesion but have such low tensile strength that they are unsuitable as adhesives for elastic bonds.