ELASTOMERIC THERMOPLASTIC PRE-EXPANSION COMPOSITION COMPRISING AN ELASTOMER AND A PHYSICAL BLOWING AGENT

Abstract

A subject matter of the invention is a pre-expansion thermoplastic elastomeric composition comprising at least 10% by weight of one or more elastomers and heat-expandable polymeric particles encapsulating a heat-expandable fluid.

Another subject matter of the invention is a process for the preparation of an expanded thermoplastic elastomeric composition comprising the following stages:

injection into a mold or addition to an extruder die of the pre-expansion elastomeric composition according to the invention, then

heating the pre-expansion elastomeric composition at a temperature greater than the temperature for expansion of the heat-expandable polymeric particles, preferably of greater than 160 C.

A subject matter of the invention is also an expanded thermoplastic elastomeric composition capable of being obtained by the process.

Finally, a subject matter of the invention is a sealing lip used in the fields of the transportation industry and in the construction industry.

Claims

1. Noncrosslinked pre-expansion thermoplastic elastomeric composition, comprising: at least 10% by weight, with respect to the total weight of the composition, of one or more multiblock elastomers comprising at least one soft block and at least one hard block, heat-expandable polymeric particles encapsulating a heat-expandable fluid.

2. Thermoplastic elastomeric composition according to claim 1, characterized in that the elastomer or elastomers are chosen from hard block/soft block diblock elastomers, hard block/soft block/hard block triblock elastomers and preferably from hard block/soft block/hard block triblock elastomers.

3. Thermoplastic elastomeric composition according to claim 1, characterized in that the elastomer or elastomers are chosen from styrene/butadiene/styrene (SBS) polymers, styrene/isoprene/styrene (SIS) polymers, styrene/ethylene-butylene/styrene (SEBS) polymers, styrene/ethylene/propylene/styrene (SEPS) polymers, styrene/ethylene/ethylene-propylene/styrene (SEEPS) polymers, styrene/ethylene-butylene/styrene polymers comprising different units from the units resulting from ethylene and butylene in the ethylene-butylene block (SOESS), styrene/ethylene-butylene/styrene polymers comprising functionalized units making possible crosslinking in the styrene block or blocks, multiblock copolymers of ethylene and of -olefins and the mixtures of these polymers, and preferably from styrene/ethylene-butylene/styrene (SEB S) polymers.

4. Thermoplastic elastomeric composition according to claim 1, characterized in that the elastomer or elastomers represent from 10% to 40% by weight, preferably from 15% to less than 40% by weight, more preferably from 15% to 37% by weight, better still from 15% to 35% by weight, with respect to the total weight of the elastomeric composition.

5. Thermoplastic elastomeric composition according to claim 1, characterized in that the heat-expandable polymeric particles are chosen from particles which can expand from 140 C., preferably from 160 C.

6. Thermoplastic elastomeric composition according to claim 1, characterized in that the heat-expandable polymeric particles are chosen from acrylonitrile particles including a hydrocarbon, such as isobutane, isopentane and haloalkanes.

7. Thermoplastic elastomeric composition according to claim 1, characterized in that it comprises from 0.1% to 7% by weight, preferably from 0.5% to 2%, with respect to the total weight of the composition, of one or more heat-expandable polymeric particles.

8. Thermoplastic elastomeric composition according to claim 1, characterized in that it additionally comprises one or more polyolefin thermoplastic polymers, preferably chosen from homopolymers and copolymers of polyethylene, of polypropylene, functionalized polyolefins, and the mixtures of these polymers.

9. Thermoplastic elastomeric composition according to claim 1, characterized in that it comprises a homopolymer and/or copolymer of polypropylene and advantageously also a homopolymer and/or copolymer of polyethylene.

10. Thermoplastic elastomeric composition according to claim 1, characterized in that it comprises one or more plasticizing agents, preferably one or more plasticizing oils, more preferably one or more hydrocarbon oils, in particular one or more paraffinic oils.

11. Thermoplastic elastomeric composition according to claim 1, characterized in that it comprises: from 10% to 40% by weight, preferably from 15% to less than 40% by weight, more preferably from 15% to 37% by weight, better still from 15% to 35% by weight, of one or more elastomers chosen from styrene/butadiene/styrene (SBS) polymers, styrene/isoprene/styrene (SIS) polymers, styrene/ethylene-butylene/styrene (SEBS) polymers, styrene/ethylene/propylene/styrene (SEPS) polymers, styrene/ethylene/ethylene-propylene/styrene (SEEPS) polymers, styrene/ethylene-butylene/styrene polymers comprising different units from the units resulting from ethylene and butylene in the ethylene-butylene block (SOESS), styrene/ethylene-butylene/styrene polymers comprising functionalized units making possible crosslinking in the styrene block or blocks, multiblock copolymers of ethylene and of -olefins and the mixtures of these polymers, and preferably from styrene/ethylene-butylene/styrene (SEBS) polymers, from 15% to 50% by weight, preferably from 20% to 40% by weight, of one or more paraffinic oils, from 5% to 40% by weight, preferably from 10% to 35% by weight, of one or more polyolefin thermoplastic polymers, preferably chosen from homopolymers and/or copolymers of polyethylene, of polypropylene, and the mixtures of these polymers, from 0.1% to 7% by weight, preferably from 0.5% to 2% by weight, of heat-expandable polymeric particles encapsulating a heat-expandable fluid, the contents being given with respect to the total weight of the composition.

12. Process for the preparation of an expanded thermoplastic elastomeric composition comprising the following stages: injection into a mold or addition to an extruder die of the pre-expansion thermoplastic elastomeric composition according to any one of the preceding claims, then heating the pre-expansion thermoplastic elastomeric composition at a temperature greater than the temperature for expansion of the heat-expandable polymeric particles, preferably of greater than 160 C.

13. Noncrosslinked expanded thermoplastic elastomeric composition capable of being obtained by the process according to claim 12.

14. Sealing lip used in the fields of the transportation industry and in the construction industry, comprising the expanded thermoplastic elastomeric composition according to claim 13.

Description

EXAMPLE

[0122] Compositions according to the invention

[0123] The contents are shown as % by weight.

TABLE-US-00001 Composition A1 A2 Copolymer having linear SEBS blocks 34 18 comprising 32% by weight of styrene units.sup.(1) Paraffinic oil 34 28 Polypropylene.sup.(2) 20 4 Medium-density polyethylene 7 8.5 (MFI = 0.1, d = 0.939) Calcium carbonate (5 m) 3.65 35.15 Phosphite 0.35 0.35 Heat-expandable polymeric microspheres.sup.(3) 1 1 Polyphenylene ether.sup.(4) 5 .sup.(1)Taipol 6151 .sup.(2)PP050G2M .sup.(3)Expancel 980DU120 .sup.(4)PX-100F MFI: melt flow index

[0124] The elastomeric composition A1 according to the invention is compared with a commercial composition B1 used for the sealing of motor vehicle windows. The compositions A1 and B1 exhibit an equivalent hardness.

TABLE-US-00002 Characteristics and standards B1 (Comp.) A1 (Inv.) Hardness (Shore A) ISO868 68 67 (15 s) Relative density ISO1183 1.13 0.69 Stress at a strain of ISO37 2.3 2.2 100% (in MPa) 23 C. - H1 - 500 mm/min Tensile strength (in ISO37 6.1 4.7 MPa) 23 C. - H1 - 500 mm/min Elongation at break (in ISO37 470 540 %) 23 C. - H1 - 500 mm/min Compression set ISO815-1, A 48 53 (in %) 22 h, 70 C. Fogging test DIN 75201-B, 5.9 1.6 (in mg) 100 C.

[0125] At equivalent hardness, the composition A1 according to the invention exhibits a lower relative density than the comparative composition B1, which reflects the expansion of the composition A1 according to the invention.

[0126] However, despite a lower density and an equivalent hardness, the composition A1 according to the invention exhibits similar elastomeric properties to the composition B1, in particular relating to the compression set, which remains low and in accordance with the requirements necessary in the motor vehicle field.

[0127] Furthermore, the fogging tests show that the composition A1 according to the invention exhibits a much lower emission of volatile organic compounds than the comparative composition B1.

[0128] The elastomeric composition A2 according to the invention is compared with a conventional commercial composition B2 used for the sealing of motor vehicle windows. The compositions A2 and B2 exhibit an identical hardness.

TABLE-US-00003 Characteristics and standards B2 (Comp.) A2 (Inv.) Hardness (Shore A) ISO868 45 45 (15 s) Relative density ISO1183 1 0.75 Stress at a strain of ISO37 1.2 1.5 100% (in MPa) 23 C. - H1 - 500 mm/min Tensile strength (in ISO37 3.3 2.9 MPa) 23 C. - H1 - 500 mm/min Elongation at break ISO37 650 351 (in %) 23 C. - H1 - 500 mm/min Compression set ISO815-1, A 43 47 (in %) 22 h, 70 C. Fogging test DIN 75201-B, 2.9 1.2 (in mg) 100 C.

[0129] At identical hardness, the composition A2 according to the invention exhibits a lower relative density than the comparative composition B2, which reflects the expansion of the composition A2 according to the invention.

[0130] However, despite a lower density and an identical hardness, the composition A2 according to the invention exhibits similar elastomeric properties to the composition B2, in particular relating to the compression set, which remains low and in accordance with the requirements necessary in the motor vehicle field. Furthermore, the fogging tests show that the composition A2 according to the invention exhibits a much lower emission of volatile organic compounds than the comparative composition B2.