Thermoplastic Elastomer Composition and a Process for its Production

Abstract

An elastomer composition is provided, the composition comprising a polyolefin; crumb rubber; a peroxide; and a polyolefin grafted maleic anhydride. A method of forming the composition is also provided.

Claims

1-58. (canceled)

59. An elastomer composition comprising: a polyolefin; crumb rubber; a peroxide; and a polyolefin grafted maleic anhydride.

60. The elastomer composition according to claim 59, wherein the polyolefin comprises polypropylene.

61. The elastomer composition according to claim 59, wherein the polyolefin is a homopolymer.

62. The elastomer composition according to claim 59, wherein the polyolefin is present in an amount of at least 60% by weight.

63. The elastomer composition according to claim 59, wherein the crumb rubber is prepared from waste or used vehicle tyres.

64. The elastomer composition according to claim 59, wherein the crumb rubber has a particle size of from 10 to 250 microns.

65. The elastomer composition according to claim 59, wherein the crumb rubber is present in an amount of from 10 to 75% by weight.

66. The elastomer composition according to claim 59, wherein the peroxide comprises dicumyl peroxide (DCP).

67. The elastomer composition according to claim 59, wherein the peroxide is present in an amount of at least 0.05 parts per hundred of rubber by weight.

68. The elastomer composition according to claim 59, wherein the polyolefin grafted maleic anhydride comprises a polyolefin the same as the polyolefin.

69. The elastomer composition according to claim 68, wherein the polyolefin of the polyolefin grafted maleic anhydride is polypropylene.

70. The elastomer composition according to claim 59, wherein the polyolefin grafted maleic anhydride is present in an amount of at least 0.5 parts per hundred of rubber by weight.

71. A method for producing an elastomer composition, the method comprising: combining a polyolefin; crumb rubber; a peroxide; and a polyolefin grafted maleic anhydride; and mixing the aforementioned components with heating to a temperature above the melting point of the polyolefin.

72. The method according to claim 71, wherein the polyolefin comprises polypropylene.

73. The method according to claim 71, wherein the polyolefin is present in an amount of at least 60% by weight.

74. The method according to claim 71, wherein the crumb rubber is prepared from waste or used vehicle tyres.

75. The method according to claim 71, wherein the crumb rubber has a particle size of from 10 to 250 microns.

76. The method according to claim 71, wherein the crumb rubber is present in an amount of from 10 to 75% by weight.

77. The method according to claim 71, wherein the peroxide comprises dicumyl peroxide (DCP).

78. The method according to claim 71, wherein the polyolefin of the polyolefin grafted maleic anhydride is polypropylene.

79. The method according to claim 71, wherein the polyolefin grafted maleic anhydride is present in an amount of at least 0.5 parts per hundred of rubber by weight.

Description

EXAMPLES

Example 1

Preparation of Crumb Rubber/polypropylene Elastomer

[0058] A crumb rubber/polypropylene elastomer composition was prepared from the components set out in Table 1.

TABLE-US-00001 TABLE 1 Amount Component (% wt. of total composition) Polypropylene 69.24 (relative density 0.91 g/cm.sup.3) Crumb Rubber 30.10 Polypropylene grafted maleic anhydride 0.60 (Polyram Bondyram pellets) (equivalent to 2 phr) Dicumyl peroxide 0.06 (98% purity; ex. Sigma Aldrich) (equivalent to 0.2 phr)

[0059] The components set out in Table 1 were combined and charged together to the feed hopper of a co-kneading extruder (ex. Buss).

[0060] The extruder was operated at a barrel temperature of from 175 to 185 C. and a die temperature about 10 C. higher than the barrel temperature. The operating temperature was controlled using a thermal infra red camera. The product was allowed to cool to ambient temperature and was granulated.

[0061] An elastomer composition having a density of 0.96 g/cm.sup.3 was obtained.

[0062] For comparison purposes, the experiment was repeated using the same equipment and operating conditions, with the exception that the polypropylene grafted maleic anhydride and dicumyl peroxide were omitted. This composition is hereafter designated Comparison A.

Example 2

Compression Moulding

[0063] The mechanical strength of the elastomer composition of Example 1 and Comparison A was tested using the following procedure.

[0064] The samples were subject to compression moulding using a Bipel/Bytec 40 tonne hydraulic press with hot platens having a temperature range of up to 400 C. The samples were pressed into sheets under a vacuum following a four stage process in accordance with ISO standard 293 Plastics-Compression Moulding Test Specimens of Thermoplastic Materials.

[0065] In a first stage, each sample was pre-heated on the press for 5 minutes at 190 C. with contact pressure. Thereafter, each sample was subjected to a series of compression sequences. In each sequence, the material was compressed at 190 C. for 1 min at 240 kN, after which the pressure was relieved for 1 minute in order to ensure that gas bubbles were removed. This sequence was repeated three times. Thereafter, each sample was compressed for 3 to 5 minutes at 190 C. and 240 kN. Finally, each sample was cooled down slowly at room temperature.

[0066] After cooling, the sheets were removed from the mould and conditioned for at least one day.

[0067] Dumb-bell test specimens were made from each sample, using a test specimen cutter, and were tested according to the procedures of ISO standard 527:2012.

[0068] The above procedure was followed for a sample of 100% virgin polypropylene. The differences in the tensile stress at break, the tensile strain at break and the impact strength between the samples of each of Example 1 and Comparison A and the sample of polypropylene were determined.

[0069] The results of the tests are set out in Table 2 below. The results in Table 2 indicate the percentage change of the indicated property compared to the same property of pure polypropylene (taking the value of the relevant property of polypropylene as 0%).

TABLE-US-00002 TABLE 2 Tensile Stress Tensile Strain Impact at Break at Break Strength Comparison A 30% 3% 23% Example 1 33% +57% 11%

[0070] As can be seen from Table 2, the composition of the present invention exhibited a significantly increased tensile strain at break, compared with the sample of Comparison A and the pure polypropylene. In addition, the composition of the present invention exhibited a significantly higher impact strength than the sample of Comparison A.

Example 3

Injection Moulding

[0071] The mechanical strength of the elastomer composition of Example 1 and Comparison A was tested using the following procedure.

[0072] The materials were moulded using a Battenfeld HM40/130 injection moulding machine, with the barrel and nozzle temperatures set at 195 C. The processing conditions used are summarised in Table 3.

TABLE-US-00003 TABLE 3 Injection pressure: 500 bar Injection speed: 50 ccm/s Holding pressure: 800 bar/10 sec Screw back 100 mm/s Injection volume 13 ccm Back pressure 5 bar Cooling time 10 sec Mould temp 40 C. Melt cushion 2-3 ccm

[0073] The tensile stress and tensile strain of the moulded samples was measured. The results are set out in Table 4 below.

TABLE-US-00004 TABLE 4 Tensile Stress at Tensile Strain at Break Break (MPa) (%) Comparison A 12 43 Example 1 13 64

[0074] As can be seen from Table 4, the composition of the present invention exhibited an increased tensile stress and a significantly increased tensile strain, compared with the sample of Comparison A.

Examples 4 to 7

Varying Dicumyl Peroxide Content

[0075] The procedures of Examples 1 and 2 were repeated to prepare and test the compositions of the present invention with a range of different dicumyl peroxide contents. The compositions of the samples prepared are summarised in Table 5 below. As with Example 1, a comparison composition was prepared, designated Comparison B.

TABLE-US-00005 TABLE 5 Example 4 Example 5 Example 6 Example 7 Comparison B Polypropylene 70% 70% 70% 70% 70% (relative density 0.91 g/cm.sup.3) Crumb Rubber 30% 30% 30% 30% 30% Polypropylene 2 phr 2 phr 2 phr 2 phr grafted maleic anhydride (Polyram Bondyram pellets) Dicumyl 0.1 phr 0.2 phr 0.3 phr 1 phr peroxide (98% purity; ex. Sigma Aldrich)

[0076] The results of the tensile tests for Examples 4 to 7 and Comparison B are summarised in Table 6 below. For each property measured, the actual value of the property is indicated as a percentage change with respect to the comparison sample.

TABLE-US-00006 TABLE 6 Tensile Stress at Tensile Strain at Break Break Comparison B 0% 0% Example 4 18% +46% Example 5 5% +63% Example 6 9% +28% Example 7 12% 7%

[0077] As can be seen from Table 6, the compositions of the present invention exhibited a significantly increased tensile strain at break, compared with the sample of Comparison B.

Examples 8 and 9

Varying Polyolefin Grafted Maleic Anhydride Content

[0078] The procedures of Examples 1 and 2 were repeated to prepare and test the compositions of the present invention with a range of different polyolefin grafted maleic anhydride contents. The compositions of the samples prepared are summarised in Table 7 below. As with Example 1, a comparison composition was prepared, designated Comparison C.

TABLE-US-00007 TABLE 7 Example 8 Example 9 Comparison C Polypropylene 70% 70% 70% (relative density 0.91 g/cm.sup.3) Crumb Rubber 30% 30% 30% Polypropylene 2 phr 4 phr grafted maleic anhydride (Polyram Bondyram pellets) Dicumyl 0.2 phr 0.2 phr peroxide (98% purity; ex. Sigma Aldrich)

[0079] The results of the tests to measure tensile stress and tensile strain are summarised in Table 8 below. For each property measured, the actual value of the property is indicated as a percentage change with respect to the comparison sample.

TABLE-US-00008 TABLE 8 Tensile Stress at Tensile Strain at Break Break Comparison C 0% 0% Example 8 5% +63% Example 9 16% +70%

[0080] As can be seen from Table 8, the compositions of the present invention exhibited a significantly increased tensile strain at break, compared with the sample of Comparison C.

Examples 10 and 11

Varying Crumb Rubber Particle Size

[0081] The procedures of Examples 1 and 2 were repeated to prepare and test the compositions of the present invention with a range of different particle sizes of crumb rubber. The compositions of the samples prepared are summarised in Table 9 below.

TABLE-US-00009 TABLE 9 Example 9 Example 10 Polypropylene 70% 70% (relative density 0.91 g/cm.sup.3) Crumb Rubber 30% 30% Crumb Rubber 40 mesh 80 mesh particle size Polypropylene 2 phr 2 phr grafted maleic anhydride (Polyram Bondyram pellets) Dicumyl 0.2 phr 0.2 phr peroxide (98% purity; ex. Sigma Aldrich)

[0082] The results of the tests to measure tensile stress and tensile strain are summarised in Table 10 below.

TABLE-US-00010 TABLE 10 Tensile Stress Tensile Strain (MPa) (%) Example 9 12 11 Example 10 14 10

Example 12

Cyclic Testing

[0083] Samples of the material prepared in Example 1 and of Comparison A were moulded as described in Example 3 and subjected to cyclic compression testing. The samples were subjected to repeated cycles of compression, with each cycle comprising compressing the sample to 720 N and then decompression to 0 N. The rate of compression and decompression was varied.

[0084] The results are set out in Table 11 below.

TABLE-US-00011 TABLE 11 Number of cycles Cycle rate (kN/s) Comparison A Example 1 0.2 43 100* 0.4 100* 100* 0.6 103 190 1 360 783 *Indicates a test that was stopped after 100 cycles.

[0085] As can be seen from the results in Table 11, the sample of Example 1 performed significantly better than the sample of Comparison A, in particular exhibiting a significantly better tolerance to compression cycles before failure.