CROSSLINKED POLYURETHANE

Abstract

A crosslinked polyurethane obtainable by a process is disclosed wherein polyisocyanates are mixed with polymeric compounds having at least two hydrogen atoms reactive toward isocyanate groups and comprising at least one diene block copolymer which has at least two hydrogen atoms reactive toward isocyanate and has a polydiene main chain and at least one side chain or terminal chain composed of a polyether and/or a polyester, where the proportion by weight of the polydiene main chain is, based on the total weight of the diene block copolymer, from 25 to 95% by weight, to give a reaction mixture that is cured. Composites and blends composed of crosslinked polyurethane and rubber are also disclosed, as well as the use of crosslinked polyurethane in the production of tires or parts of tires, cable sheathing, shoe sole, roller or hose.

Claims

1. A crosslinked polyurethane obtainable by a process wherein a) polyisocyanates are mixed with b) polymeric compounds having on average at least 1.5 hydrogen atoms which are reactive toward isocyanate groups and comprising b1) at least one diene block copolymer which has on average at least 1.5 hydrogen atoms which are reactive toward isocyanate and has a polydiene main chain and at least one side chain or terminal chain composed of a polyether and/or a polyester, where the proportion by weight of the polydiene main chain is, based on a total weight of the diene block copolymer b1), from 25 to 95% by weight and b2) optionally further polymeric compounds having at least two hydrogen atoms which are reactive toward isocyanate, c) optionally catalyst, d) vulcanizing agents, e) optionally chain extenders, chain transfer agents and/or crosslinkers, f) optionally blowing agent and g) optionally auxiliaries and/or additives, h) optionally rubber to give a reaction mixture and the mixture is cured to give crosslinkable polyurethane and double bonds of the diene block copolymer b1) are crosslinked, wherein the crosslinking of the double bonds of the diene block copolymer b1) is effected by means of a sulfur-comprising vulcanizing agent or by means of a peroxide-comprising vulcanizing agent (d).

2. The crosslinked polyurethane according to claim 1, wherein the crosslinking of the double bonds of the diene block copolymer b1) is effected by means of a sulfur-comprising vulcanizing agent or by means of a peroxide-comprising vulcanizing agent and the vulcanizing agent is added only after production of the polyurethane.

3. The crosslinked polyurethane according to claim 1, wherein symmetric diisocyanates are used as polyisocyanates.

4. The crosslinked polyurethane according to claim 1, wherein a reaction product of polybutadienol and a cyclic ester is used as diene block copolymer b1) having at least two hydrogen atoms which are reactive toward isocyanate.

5. The crosslinked polyurethane according to claim 1, wherein the diene block copolymer b1) having at least two hydrogen atoms which are reactive toward isocyanate has a number average molecular weight of from 500 to 20 000 g/mol and an average OH functionality of from 1.8 to 5.0.

6. The crosslinked polyurethane according to claim 1, wherein the diene block copolymer b1) having at least two hydrogen atoms which are reactive toward isocyanate has at least 50% of primary OH groups, based on a content of OH groups in the diene block copolymer.

7. The crosslinked polyurethane according to claim 1, wherein chain extender and/or crosslinker e) is selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, glycerol, trimethlyolpropane, ethoxylated and/or propoxylated glycerol, ethoxylated and/or propoxylated trimethylolpropane, dipropylene glycol, bis(2-hydroxyethyl)hydroquinone and mixtures of two or more components from among these.

8. The crosslinked polyurethane according to claim 1, wherein the auxiliaries and additives g) comprise silicates which can be surface-modified.

9. The crosslinked polyurethane according to claim 1, wherein the production of the polyurethane is carried out at an isocyanate index of from 90 to 110.

10. A composite comprising a crosslinked polyurethane according to claim 1 and rubber.

11. A blend of a crosslinked polyurethane according to claim 1 and rubber.

12. A process for producing a composite according to claim 10, wherein crosslinkable polyurethane and rubber are brought into contact and crosslinked.

13. A method of using the crosslinked polyurethane according to claim 1, the method comprising using said crosslinked polyurethanes for producing tires or parts of tires, cable sheathing, shoe sole, roller or hose.

14. A method of using the crosslinked polyurethane according to claim 1, the method comprising using said crosslinked polyurethanes for producing foamed films, foamed moldings or foamed particles and the particle foams obtainable therefrom.

Description

1. PRODUCTION EXAMPLE

[0071] The following starting materials were used: [0072] Polyol 1: polybutadiene polyol prepared by means of anionic polymerization and having a functionality of 1.9, with exclusively primary OH groups and an OH number of 53.8 [0073] Polyol 2: polybutadiene polyol prepared by means of free-radical polymerization and having a functionality of 2.4, with exclusively primary OH groups and an OH number of 52.5 [0074] Polyol 3: polyol prepared from polyol 1, capped with 30% by weight of polycaprolactone [0075] Polyol 4: polyol prepared from polyol 2, capped with 30% by weight of polycaprolactone [0076] Polyol 5: polyether polyol having an OH number of 55.8 and exclusively primary OH groups (based on tetramethylene oxide, functionality: 2) [0077] Isocyanate 1: aromatic isocyanate (diphenylmethane 4,4-diisocyanate) [0078] Isocyanate 2: mixture of aromatic isocyanate prepolymer based on MDI and polypropylene glycol and carbodiimide-modified MDI, NCO content approx. 26% by weight [0079] Chain extender 1 (KV 1): 1,4-butanediol [0080] Chain extender 2 (KV 2): 1,5-pentanediol [0081] Chain extender 3 (KV 3): 1,6-hexanediol [0082] Chain extender 4 (KV 4): glycerol [0083] Chain transfer agent 1 (KR 1): 1-octanol [0084] Antifoam: Xiameter antifoam from Dow Corning [0085] Catalyst: metal catalyst [0086] Rubber 1: natural rubber (Neorub 340 P, commercially available from Weber & Schaer) [0087] Rubber 2: nitrile-butadiene rubber (Perbunan NT 3445, commercially available from Lanxess) [0088] Rubber 3: styrene-butadiene rubber (Buna SBR 1500, commercially available from Trinseo) [0089] Filler 1: precipitated silica modified with sulfur-comprising organosilane [0090] Additive 1: sterically hindered phenol [0091] Additive 2: sterically hindered phenol [0092] Vulcanizing composition 1 (VZ1): sulfur [0093] Vulcanizing composition 2 (VZ2): N-cyclohexyl-2-benzothiazylsulfenamide (80%) [0094] Vulcanizing composition 3 (VZ3): zinc oxide [0095] Rubber formulation 1 (KF1): typical rubber formulation based on styrene-butadiene rubber, natural rubber, carbon black, silicates, sulfur-comprising organosilanes, VZ1, VZ2, VZ3

[0096] -Caprolactone was dried over CaH.sub.2 and subsequently distilled at 130 C. under reduced pressure, stored at 30 C. under argon and used within 14 days. Titanium tetrabutoxide was dissolved in dry toluene to give a 50% strength by volume solution and the solution was stored under argon.

Preparation of Polyol 3

[0097] 2733 g (1.242 mol) of polyol 1 were dried for three hours at 100 C. under reduced pressure in a 5 l steel reactor and 1179 g (10.35 mol) of distilled -caprolactone were added under nitrogen. The components were homogeneously mixed by stirring at 250 rpm and 120 C., before 430 l of a titanium tetrabutoxide solution (15 ppm of titanium, 50% by volume in toluene) was added and the reactor was closed. After stirring for 4 hours at 120 C., the product was drained.

Preparation of Polyol 4

[0098] 1367 g (506.4 mmol) of polyol 2 were dried for three hours at 100 C. under reduced pressure in a 5 l steel reactor and 462.7 g (4.059 mol) of distilled -caprolactone were added under nitrogen. The components were homogeneously mixed by stirring at 250 rpm and 150 C., before 840 l of titanium tetrabutoxide solution (15 ppm of titanium, 10% by volume in toluene) was added and the reactor was closed. After stirring for 4 hours at 150 C., the product was drained.

Determination of the Hydroxyl Number (OH Number)

[0099] The hydroxyl number of the polyols 3 and 4 (OH number) was determined in accordance with DIN 53240 2 and is shown in Table 1. The slightly different values for the OH number for polyols result from different reaction batches of polyol 1 or 2 with -caprolactone.

Example of TPU Synthesis:

[0100] A thermoplastic polyurethane was synthesized from diphenylmethane 4,4-diisocyanate, chain extender 1,6-hexanediol with a polycaprolactone-capped polybutadienediol corresponding to the data in Table 1 by stirring in a reaction vessel. After a reaction temperature of 80 C. had been reached, the solution was poured onto a heated hot plate at 125 C. and the TPU plate obtained was granulated after heat treatment (80 C., 15 hours).

[0101] The combination of polyols 3 and 5 enable the TPU to be poured out at a higher temperature. In the case of TPU 8, the temperature was 110 C. during casting. The granular material was processed further either on a calender or kneader or subsequently processed further by injection molding to give test specimens.

Formulations

[0102]

TABLE-US-00001 TABLE 1 Synthesis examples TPU comparison 1 TPU comparison 2 TPU 1 TPU 2 TPU 3 TPU 4 TPU 5 TPU 6 TPU 7 OH 53.70 53.70 34.20 polyol 34.20 34.80 33.60 33.60 polyol number 3: 34.20, 3: 33.65, of the polyol polyol polyol 4: 37.78 5: 56.00 Polyol 1000.0 1000.0 1 [g] Polyol 1000.0 833.3 1000.0 1000.0 1086.3 1049.5 600.0 3 [g] Polyol 166.7 4 [g] Polyol 400.0 5 [g] Isocyanate 1 204.3 209.3 157.5 158.9 162.5 261.5 309.8 350.1 211.5 [g] KV 1 92.0 [g] KV 2 95.2 [g] KV 3 39.9 39.6 38.4 38.4 38.0 82.3 55.0 [g] KV 4 0.2 0.2 [g] KR 1 1.0 1.0 [g] Additive 1 8.00 8.00 8.00 8.69 8.39 6.40 [g] Additive 2 6.40 [g] Index 100 100 100 100 100 100 100 100 100 Melting 40 to 60 C. 40 to 60 C. >100 C. >100 C. >100 C. >100 C. >100 C. >100 C. >100 C. point* [ C.] *The melting behavior was evaluated on a calender. The TPU comparisons 1 and 2 based on polyol 1 melted at very low temperatures, which indicates a very low molecular weight. The material adhered so strongly to the metallic surface of the calender that no rolled sheet could be obtained. In contrast, the TPUs based on polyol 3 displayed a higher melting point and rolled sheets could be obtained. Owing to the incompatibility of the monomers, no satisfactorily high molecular weight was obtained in Comparative Examples 1 and 2. Furthermore, 5 parts by weight of the TPUs 1 to 7 were dissolved in 95% by weight of DMF. Visual inspection of the solutions indicated that the polymer had dissolved completely.

Crosslinking by Means of Dicumyl Peroxide

[0103] As indicated in table 3, the starting materials for the polyol component were heated and mixed at 50 C. for about 30 minutes, dicumyl peroxide was subsequently added to the polyol component in the examples according to the invention and was mixed with the isocyanate for 1 minute. The mixture was poured into a step mold which had depths of 2, 6 and 10 mm and was heated to 50 C. and struck flat by means of a plastic bar. After 30 minutes, the elastomer which was already solid was removed from the mold. After storage at room temperature for about 18 hours, the plate was stored at 160 C. for 30 minutes. The plate was subsequently heated at 80 C. for another 2 hours. Before characterization, the polyurethane elastomer was stored at 23 C. at 50% atmospheric humidity for at least 7 days.

TABLE-US-00002 Comp. Ex. Ex. Comp. Ex. Ex. 1 1 2 2 3 4 Cat [g] 0.15 0.15 0.15 0.15 0.15 0.15 Antifoam [g] 0.3 0.3 0.3 0.3 0.3 0.3 KV1 [g] 4.0 4.0 4.0 4.0 4.0 4.0 Polyol 3 [g] 95 95 95 Polyol 4 [g] 95 95 95 Dicumyl 0.2 0.3 0.2 1.0 peroxide [g] Iso 2 x x x x x x Index 100 100 100 100 100 100 Shore A 69 71 70 69 68 78 Tensile 10 10 11 6 5 6 strength Elongation at 380 170 130 220 140 70 break CS (24 h/ 54 30 21 25 17 17 70 C./ 30 min) [%] CS (24 h/ 98 55 41 57 45 25 70 C./ 30 min) [%]

[0104] Table 3 shows, compared to purely thermal crosslinking as per the comparative examples, a significantly improved compression set at similar hardness and tensile strength and also a lower elongation at break due to the crosslinking for crosslinking carried out using peroxide.

Examples of Blends of Rubber and TPU

Production

[0105] The respective TPU together with the rubber corresponding to the composition from Table 3 was mixed in a 200 g laboratory kneader at 180 C. and 50 revolutions per minute for 10 minutes. The blends were subsequently stored at room temperature for at least 24 hours.

Formulations

[0106]

TABLE-US-00003 TABLE 3 Examples of synthesis of the blends Blend 1 Blend 2 Blend 3 Blend 4 Blend 5 TPU TPU 4 TPU 5 TPU 5 TPU 5 TPU 6 Rubber 1 30% 25% 50% Rubber 2 33% Rubber 3 33%

Example of TPV or TPV-Rubber Blend Synthesis

Production Example on a Laboratory Roll Mill

[0107] The TPU 3 was rolled out at 130 C. on a laboratory roll mill to give a mat. The vulcanizing additives corresponding to the data in Table 4 (ex. 7) were subsequently added. The roll sheet obtained was subsequently stored at room temperature for from 3 to 12 hours.

Vulcanization

[0108] In a steam-heated vulcanization press, the TPV or TPV/rubber is placed in a 15 cm15 cm steel frame having a thickness of from 1.8 to 2 mm and vulcanized at 100 bar, 150 to 170 C. for from 10 to 25 minutes according to the vulcanization behavior determined by means of a vulcameter.

Examples of Vulcanization Conditions

[0109]

TABLE-US-00004 TABLE 4 Vulcanization conditions for producing TPV Comp. 3 Com. 4 Comp. 5 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 TPU/blend Comparison 1 Comparison 2 Comparison 2 TPU 1 TPU 2 TPU 3 TPU 3 TPU 7 VZ 1 [phr] 2 2 2 2 2 2 2 2 VZ 2 [phr] 1 1 1 1 1 1 1 1 VZ 3 [phr] 2 2 2 2 2 2 2 2 Filler 1 0 0 2 0 0 0 2 0 [phr] Pressure 100 100 100 100 100 100 100 100 [bar] Temperature 170 170 170 170 170 170 170 170 [ C.] Time 25 25 25 25 25 25 25 25 [min.]

TABLE-US-00005 TABLE 5 Vulcanization conditions for the production of TPV/rubber blends Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 TPU/blend Blend 1 Blend 3 Blend 4 Blend 5 Blend 2 VZ 1 [phr] 2 2 2 2 2 VZ 2 [phr] 1 1 1 1 1 VZ 3 [phr] 2 2 2 2 2 Pressure [bar] 100 100 100 100 100 Temperature [ C.] 170 170 170 150 170 Time [min.] 25 25 25 30 25

Examples of Mechanical Properties

[0110]

TABLE-US-00006 TABLE 6 Examples of properties of the vulcanizates Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 TPU 1 TPU 2 TPU 3 TPU 3 TPU 5 Blend 1 Blend 3 Blend 4 Blend 5 Blend 2 Density 1.033 1.029 1.033 1.035 1.054 1.035 1.044 1.030 1.002 1.042 [g/cm3] Shore A 61 60 67 69 66 66 69 64 57 67 Tensile 7 6 7 9 10 10 11 7 16 10 strength [MPa] Elongation at 400 360 340 350 500 420 380 330 540 400 break [%] Tear 13 12 14 12 15 15 13 16 11 15 propagation resistance [kN/m] E modulus 5 6 4 6 5 6 4 7 [MPa] TMA Onset 210 219 227 214 221 197 398 425 208 224 temperature [ C.] * In the case of comparative examples 1, 2 and 3, there was very severe bubble formation during vulcanization. As a result, no mechanical properties of the plates could be measured.

Example for TPV/Rubber Composites

[0111] On a laboratory roll mill, the TPU or the TPU/rubber blend was admixed at from 80 to 130 C. with the vulcanization accelerator system according to the data in Tables 4 to 9 and rolled out to give 3-4 mm thick mats.

[0112] Firstly the rubber formulation (KF1) with the vulcanization additives and subsequently the TPU formulation were placed in a stainless steel frame (dimensions 71319 mm), so that the material to be pressed was at least 1 mm thicker than the stainless steel frame. A 2 cm wide strip of Mylar film was placed between the rubber formulation and TPU formulation at the periphery to enable the clamps for the peel-off test to be fastened later in this region.

TABLE-US-00007 TABLE 7 Examples of the production of TPV or TPV/rubber on rubber Com. 3 Com. 4 Com. 5 Com. 6 Additives in the TPU TPU [phr] 100 of 100 of 100 of 100 of TPU 3 TPU 3 TPU 7 blend 2 VZ 1 [phr] 2 2 2 2 VZ 2 [phr] 1 1 1 1 VZ 3 [phr] 2 2 2 2 Filler 1 [phr] 0 2 0 2 Rubber formulation used KF1 KF1 KF1 KF1 Vulcanization conditions Presssure [bar] 100 100 100 100 Temperature [ C.] 170 170 170 170 Time [min.] 25 25 25 25

Determination of the Adhesion

[0113] The two individual layers, consisting of PU and rubber, were vulcanized over the entire length of their flat side in a press (corresponds to the test plate). 2 cm Mylar film was placed between the two layers along the longitudinal side so that the specimens part at the place where they are later to be pulled by the machine. The test plate is sawn into 20 mm wide pieces to give a total of 5 test specimens.

[0114] The lower tensioning chuck is firstly disassembled so that the strain gauge can be removed from the test section (direction lower traverse). The roller bearing is then clamped in the upper tensioning chuck and the lower tensioning chuck is reassembled with clamp.

[0115] The test specimen is placed on the rollers and a layer (preferably the rubber layer) is pulled on the side of the Mylar film by means of a pincette through the two rollers and fixed in the lower clamp. The tensioning chuck then moves down and pulls the one layer from the other.

[0116] The maximum force F.sub.max in N and the strain in mm to rupture are reported as means from 5 tests.

[0117] The results of the 90 C. peel-off test are listed in Table 11. The bottom line shows the maximum force which the machine was able to measure without rupture occurring at the phase boundary or in one of the two materials.

TABLE-US-00008 TABLE 8 Examples for adhesion (90 C. peel-off test) Com. 3 Com. 4 Com. 5 Com. 6 Force maximum at rupture at the phase boundary [N] Force maximum at 367 364 failure of the material [N] Force maximum with 449 469 no failure of the material [N]

Measurement Methods:

[0118] The following measurement methods, inter alia, can be utilized for the characterization of the materials: DSC, DMA, TMA, NMR, FT-IR, GPC.

TABLE-US-00009 Shore hardness A DIN 7619-1, Tensile strength DIN 53 504, Elongation at break DIN 53 504, Tear propagation resistance DIN 53 515, Compression set (CS) DIN ISO 815, E modulus DIN 53 504 (S1 tensile bar), Abrasion DIN 4649