THERMOPLASTIC ELASTOMER COMPOSITION AND MOLDED PRODUCT OBTAINED THEREFROM

Abstract

This invention relates to a thermoplastic elastomer composition having a type A hardness (i.e., the momentary value) of 55 or less in accordance with JIS K6253, which comprises 35 to 65 parts by weight of an olefin-based thermoplastic elastomer (A) having a type A hardness (i.e., the momentary value) of 75 or less in accordance with JIS K6253 and 65 to 35 parts by weight of a styrene-based thermoplastic elastomer (B) having a type A hardness (i.e., the momentary value) of 60 or less in accordance with JIS K6253 (with the total amount of components (A) and (B) being 100 parts by weight) and a molded thermoplastic elastomer product obtained via molding of such composition.

Claims

1. A thermoplastic elastomer composition having a type A hardness (i.e., the momentary value) of 55 or less in accordance with JIS K6253, which comprises 35 to 65 parts by weight of an olefin-based thermoplastic elastomer (A) having a type A hardness (i.e., the momentary value) of 75 or less in accordance with JIS K6253 and 65 to 35 parts by weight of a styrene-based thermoplastic elastomer (B) having a type A hardness (i.e., the momentary value) of 60 or less in accordance with JIS K6253 (with the total amount of components (A) and (B) being 100 parts by weight).

2. A The thermoplastic elastomer composition according to claim 1, wherein a compression set measured at 70° C. 24 hours later is 95% or less in accordance with JIS K6262.

3. The thermoplastic elastomer composition according to claim 1, which is obtained by adding a foaming agent (C).

4. A molded thermoplastic elastomer product, which is obtained by molding the thermoplastic elastomer composition according to claim 1.

5. A foam-molded thermoplastic elastomer product, which is obtained by molding the thermoplastic elastomer composition according to claim 3.

6. The thermoplastic elastomer composition according to claim 2, which is obtained by adding a foaming agent (C).

7. A molded thermoplastic elastomer product, which is obtained by molding the thermoplastic elastomer composition according to claim 2.

8. A foam-molded thermoplastic elastomer product, which is obtained by molding the thermoplastic elastomer composition according to claim 6.

Description

EXAMPLES

[0119] Hereafter, the present invention is described in greater detail with reference to the examples, although the scope of the present invention is not limited to these examples.

[0120] Physical properties were measured and evaluated in the manner described below.

(1) MFR (g/10 min)

[0121] MFR was measured in accordance with ASTM D 1238 at 230° C. and a load of 2.16 kgf.

(2) Measurement of Shore Hardness

[0122] In accordance with JIS K6253, Shore hardness was measured with the use of a 6-mm-thick laminate of 2-mm-thick press sheets (a laminate of 3 sheets each with a thickness of 2 mm) using a Shore A durometer. The Shore A hardness (i.e., the momentary value) was determined immediately after the measurement.

(3) Compression Set (CS)

[0123] In accordance with JIS K 6250, the prepared sheets were laminated and then subjected to the compression set test in accordance with JIS K6262.

[0124] The test was performed using a 12-mm-thick laminate of 6 sheets (each 2 mm-thick), the laminate was compressed by 25% at 70° C. for 24 hours, and measurement was carried out 30 minutes after the strain (compression) had been eliminated.

(4) Foamed Layer Conditions

[0125] The foamed layer of the foam-molded product was cut, and the foaming conditions were observed under a stereoscopic microscope (×10).

[0126] The conditions of the foamed layer were evaluated in accordance with the following standards.

[0127] Excellent: Foaming conditions are uniform and no tearing or bursting is observed.

[0128] Good: While foaming conditions are not completely uniform, no tearing or bursting is observed.

[0129] Fair: Foaming conditions are not uniform, and tearing or bursting is observed in part.

[0130] Poor: Foam has experienced significant tearing or bursting significantly or swollen and thus are impossible to evaluate.

(5) Appearance

[0131] The exterior of the resulting foam-molded product was visually evaluated in accordance with the following standards.

[0132] Excellent: The surface is smooth without warpage, such as sink marks, pit marks, or weld lines.

[0133] Good: The surface is free of warpage, such as sink marks, pit marks, or weld lines.

[0134] Poor: The defects described above have been observed, and practical use of the product is difficult.

(6) Flexibility

[0135] The surface of the foam-molded product was pushed with a finger and evaluated in accordance with the following standards.

[0136] Excellent: Not much force is necessary to push a finger into the product, and the surface is satisfactorily soft.

[0137] Good: While some force is necessary to push a finger into the product, the surface is satisfactorily soft.

[0138] Poor: The surface is as hard as a molded resin product, a considerable amount of force is necessary to push a finger into the product, and the surface is not soft.

(7) Stickiness

[0139] The surface of the foam-molded product was touched by sliding a finger across it and evaluation was made in accordance with the following standards.

[0140] Good: The surface of the molded product does not stick to the finger when touched, and the surface is not scratchy.

[0141] Poor: The surface of the molded product sticks to the finger when touched, and the surface is scratchy.

(8) Bottoming-Out

[0142] The surface of the foam-molded product was pushed with a finger and evaluated in accordance with the following standards.

[0143] Good: An adequate degree of resilience was observed immediately after pushing, and the hardness of the bottom of the molded product is not sensed.

[0144] Poor: The molded product is too hard to push with a finger, or the finger reaches the bottom of the molded product and a sensation of hardness is experienced immediately after pushing.

Examples 1 to 8 and Comparative Examples 1 to 3

Mold Materials

(1) Olefin-Based Thermoplastic Elastomer (A)

(1-1) Olefin-Based Thermoplastic Elastomer (TPV-1)

[0145] Ethylene-propylene-diene copolymer rubber (65 parts by weight; tradename: Mitsui EPT™ 3072 EPM; manufactured by Mitsui Chemicals, Inc.) as peroxide-crosslinkable olefin-based copolymer rubber, 15 parts by weight of a propylene-ethylene block copolymer (tradename: Prime Polypro™ J707G; manufactured by Prime Polymer Co., Ltd.) as a peroxide-degradable olefin-based plastic, 20 parts by weight of butyl rubber (tradename: IIR065; manufactured by ExxonMobil Chemical; unsaturation grade: 0.8 mol %; Mooney viscosity ML.sub.1+8 (125° C.): 32) as a peroxide-uncrosslinkable rubbery material, and 10 parts by weight of paraffin-based process oil (tradename: Diana Process Oil PW-100; manufactured by Idemitsu Kosan Co., Ltd.) as a softening agent were mixed in advance using a closed mixer (Mixtron BB-16; manufactured by Kobe Steel, Ltd.), the resultant was allowed to pass through a sheet roller so as to flatten it into a sheet, and the resulting sheet was processed into horny pellets using a pelletizer (manufactured by HORAI Co., Ltd.).

[0146] Subsequently, 112 parts by weight of the resulting pellets, 0.6 parts by weight of a mixed solution of 0.3 parts by weight of a crosslinking agent (1,3-bis(tert-butylperoxyisopropyl)benzene) and 0.3 parts by weight of a crosslinking aid (divinylbenzene), and 0.1 parts by weight of a phenolic antioxidant (Irganox 1010; manufactured by BASF) were mixed using a tumble blender, and the resulting mixture was allowed to evenly adhere to pellet surfaces.

[0147] Subsequently, 112.7 parts by weight of the pellets to the surface of which the crosslinking agent, the crosslinking aid, and the antioxidant had adhered were kneaded using an extruder (Product No. LTX-46; manufactured by Kobe Steel, Ltd.) at 220° C. and at a treatment rate of 50 kg/hour, and a partially crosslinked olefin-based thermoplastic elastomer (TPV-1) was obtained. The resulting olefin-based thermoplastic elastomer (TPV-1) exhibited a Shore A hardness (i.e., the momentary value) of 51.

(1-2) Olefin-Based Thermoplastic Elastomer (TPV-2)

[0148] Ethylene-propylene-diene copolymer rubber (67 parts by weight, tradename: Mitsui EPT™ 4100 E; manufactured by Mitsui Chemicals, Inc.) as peroxide-crosslinkable olefin-based copolymer rubber, 16 parts by weight of homopropylene (tradename: Prime Polypro™ F704NP; manufactured by Prime Polymer Co., Ltd.) as a peroxide-degradable olefin-based plastic, and 17 parts by weight of paraffin-based process oil (tradename: Diana Process Oil PW-100; manufactured by Idemitsu Kosan Co., Ltd.) as a softening agent were mixed in advance using a closed mixer (Mixtron BB-16; manufactured by Kobe Steel, Ltd.), the resultant was allowed to pass through a sheet roller to prepare into the form of a sheet, and the resulting sheet was processed into horny pellets using a pelletizer (manufactured by HORAI Co., Ltd.).

[0149] Subsequently, 100 parts by weight of the resulting pellets, 1.5 parts by weight of a mixed solution of 1.0 parts by weight of a crosslinking agent (1,3-bis(tert-butylperoxyisopropyl)benzene) and 0.5 parts by weight of a crosslinking aid (divinylbenzene), and 0.1 parts by weight of a phenolic antioxidant (Irganox 1010; manufactured by BASF) were mixed using a tumble blender, and the resulting mixture was allowed to evenly adhere to the pellet surface.

[0150] Subsequently, 101.6 parts by weight of the pellets to which the crosslinking agent, the crosslinking aid, and the antioxidant had adhered on the surface and 40 parts by weight of paraffin-based process oil (tradename: Diana Process Oil PW-100; manufactured by Idemitsu Kosan Co., Ltd.) as a softening agent were kneaded using an extruder (Product No. KTX-46; manufactured by Kobe Steel, Ltd.) at 220° C. at a treatment rate of 40 kg/hour, and the partially crosslinked olefin-based thermoplastic elastomer (TPV-2) was obtained. The resulting olefin-based thermoplastic elastomer (TPV-2) exhibited the Shore A hardness (i.e., the momentary value) of 46.

(1-3) Olefin-Based Thermoplastic Elastomer (TPV-3)

[0151] Ethylene-propylene-diene copolymer rubber (70 parts by weight, tradename: Mitsui EPT™ 3072 EPM; manufactured by Mitsui Chemicals, Inc.) as peroxide-crosslinkable olefin-based copolymer rubber, 20 parts by weight of homopropylene (tradename: Prime Polypro™ J105G; manufactured by Prime Polymer Co., Ltd.) as a peroxide-degradable olefin-based plastic, 10 parts by weight of a propylene-α-olefin copolymer (tradename: Vistamaxx 6102; manufactured by Exxon Mobil Corporation) as a peroxide-uncrosslinkable rubbery material, and 20 parts by weight of paraffin-based process oil (tradename: Diana Process Oil PW-100; manufactured by Idemitsu Kosan Co., Ltd.) as a softening agent were mixed in advance using a closed mixer (Mixtron BB-16; manufactured by Kobe Steel, Ltd.), the resultant was allowed to pass through a sheet roller to prepare into the form of a sheet, and the resulting sheet was processed into horny pellets using a pelletizer (manufactured by HORAI Co., Ltd.).

[0152] Subsequently, 120 parts by weight of the resulting pellets, 0.6 parts by weight of a mixed solution of 0.4 parts by weight of a crosslinking agent (1,3-bis(tert-butylperoxyisopropyl)benzene) and 0.2 parts by weight of a crosslinking aid (divinylbenzene), and 0.1 parts by weight of a phenolic antioxidant (Irganox 1010; manufactured by BASF) were mixed using a tumble blender, and the resulting mixture was allowed to evenly adhere to the pellet surface.

[0153] Subsequently, 120.7 parts by weight of the pellets to which the crosslinking agent, the crosslinking aid, and the antioxidant had adhered on the surface were kneaded using an extruder (Product No. KTX-46; manufactured by Kobe Steel, Ltd.) at 220° C. at a treatment rate of 50 kg/hour, and the partially crosslinked olefin-based thermoplastic elastomer (TPV-3) was obtained. The resulting olefin-based thermoplastic elastomer (TPV-3) exhibited the Shore A hardness (i.e., the momentary value) of 71.

(2) Styrene-Based Thermoplastic Elastomer (B)

(2-1) Styrene-Based Thermoplastic Elastomer (St-1)

[0154] Tradename: Septon™ 2063 (manufactured by Kuraray Co., Ltd., Shore A hardness in accordance with JIS K6253: 36)

(2-2) Styrene-Based Thermoplastic Elastomer (St-2)

[0155] Tradename: EARNESTON™ JS2ON (manufactured by Kuraray Co., Ltd., Shore A hardness in accordance with JIS K6253: 1)

(2-3) Styrene-Based Thermoplastic Elastomer (St-3)

[0156] Tradename: Tuftec™ H1221 (manufactured by Asahi Kasei Corporation, Shore A hardness in accordance with JIS K6253: 42)

(2-4) Styrene-Based Thermoplastic Elastomer (St-4)

[0157] Tradename: Tuftec™ H1062 (manufactured by Asahi Kasei Corporation, Shore A hardness in accordance with JIS K6253: 67)

(3) Other Resins

(3-1) Homopolypropylene (PP-1)

[0158] Tradename: Prime Polypro™ J105G (manufactured by Prime Polymer Co., Ltd.)

(3-2) Homopolypropylene (PP-2)

[0159] Homo-type polypropylene comprising 12% by mass of high-molecular-weight components exhibiting the limiting viscosity (η) of 8.5 dl/g and the melt flow rate of 3.0 g/10 min

(3-3) Block Polypropylene (PP-3)

[0160] Block-type polypropylene exhibiting the melt flow rate (ASTM-D-1238-65T; 230° C., load 2.16 kg) of 55 g/10 min (ethylene unit content: 9 mol %)

Kneading, Molding, and Evaluation

[0161] The materials were weighed in accordance with the amounts shown in Table 1, 0.1 parts by weight of a phenolic antioxidant (Irganox 1010; manufactured by BASF) as a heat stabilizer and 0.1 parts by weight of a diazo weather resistant agent (Tinuvin 326; manufactured by BASF) as a weather resistant agent were thoroughly mixed with 100 parts by weight of the mixture of the materials using a Henschel mixer, the resultant was kneaded using an extruder (Product No. KTX-46; manufactured by Kobe Steel, Ltd.) at 200° C. and a treatment rate of 60 kg/hour, and pellets of the thermoplastic elastomer composition were obtained.

[0162] Subsequently, 2 parts by weight of a chemical foaming agent (Hydrocerol™ CF; manufactured by Clariant) as a foaming agent was added to 100 parts by weight of the thermoplastic elastomer composition, and the resultant was then subjected to molding using a core-back injection molding machine (150-ton injection molding machine; manufactured by Meiki Co., Ltd.). Injection molding was carried out at an injection temperature of 220° C. and a mold temperature of 50° C. with a gap in the mold of 2.5 mm, and the molten resin was injected into the mold. After the mold had been filled with resin, the mobile mold was allowed to move by 2 mm, so as to increase the internal volume of the gap, and the molded product was removed therefrom after the completion of cooling. The thickness of the resulting molded product was 4.5 mm, 5-cm-square (vertical and horizontal) test pieces were prepared, and the test pieces were then subjected to various evaluation tests.

[0163] The thermoplastic elastomer composition and the foam-molded products were evaluated in accordance with the method described above. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Comparative Ex. 1 Ex. 2 Example 1 Ex. 3 Ex. 4 Ex. 5 Olefin-based thermoplastic elastomer (A) (1-1) TPV-1 50 45 40 47.5 47.5 47.5 (1-2) TPV-2 (1-3) TPV-3 Styrene-based thermoplastic elastomer (B) (2-1) St-1 50 45 40 47.5 25 (2-2) St-2 47.5 22.5 (2-3) St-3 (2-4) St-4 Other resins (3-1) PP-1 10 20 (3-2) PP-2 2.5 2.5 2.5 (3-3) PP-3 2.5 2.5 2.5 MFR (g/10 min) 2.16 kgf 3.5 4.8 5.6 3.7 2.9 3.1 Shore hardness Momentary value 40 52 79 41 42 47 Compression set (CS) (%) 70° C. 24 hr 90.7 92.4 92.6 91.3 38.9 76.3 Foamability evaluation Conditions of foamed layer excellent excellent good excellent good good Appearance good excellent good excellent excellent excellent Flexibility excellent good poor excellent excellent excellent Stickiness good good good good good good Bottoming-out good good poor good good good Comparative Comparative Ex. 6 Example 2 Example 3 Ex. 7 Ex. 8 Olefin-based thermoplastic elastomer (A) (1-1) TPV-1 47.5 (1-2) TPV-2 47.5 (1-3) TPV-3 47.5 Styrene-based thermoplastic elastomer (B) (2-1) St-1 25 90 47.5 47.5 (2-2) St-2 (2-3) St-3 22.5 (2-4) St-4 95 Other resins (3-1) PP-1 (3-2) PP-2 2.5 5 2.5 2.5 2.5 (3-3) PP-3 2.5 5 2.5 2.5 2.5 MFR (g/10 min) 2.16 kgf 4.1 5.2 4.2 30.5 5.1 Shore hardness Momentary value 49 45 71 38 50 Compression set (CS) (%) 70° C. 24 hr 90 85.4 100 93.9 88.5 Foamability evaluation Conditions of foamed layer excellent good fair good good Appearance excellent poor poor excellent excellent Flexibility excellent good poor excellent good Stickiness good poor poor good good Bottoming-out good poor poor good good

[0164] As is apparent from the results shown in Table 1, the thermoplastic elastomer composition according to the present invention has both flexibility and mold processability (injection foamability). While the thermoplastic elastomer composition according to the present invention exhibited the type A hardness (i.e., the momentary value) of 55 or less, the resulting foam-molded product was not substantially subject to “bottoming-out.”

[0165] All publications, patents, and patent applications cited herein are incorporated herein by reference in their entirety.