WO2007029924A1

WO2007029924A1 - Composition for manufacturing radiation cross-linking thermoplastic olefin elastomer foam and method for manufacturing radiation cross-linking thermoplastic olefin elastomer foam using the same

Info

Publication number: WO2007029924A1
Application number: PCT/KR2006/003117
Authority: WO
Inventors: Hyo-Lin Kim; Jang-Hoon Lee; Yung-Gu Ham; Wan-Yung Park; Hyun-Bae Lee
Original assignee: Youngbo Chemical Co., Ltd.
Priority date: 2005-09-06
Filing date: 2006-08-08
Publication date: 2007-03-15
Also published as: KR100676939B1; JP4907661B2; CN101253233B; CN101253233A; JP2009507123A

Abstract

Disclosed are a composition for manufacturing radiation cross-linking thermoplastic olefin elastomer foam and a method for manufacturing radiation cross-linking thermoplastic olefin elastomer foam using the same. The composition according to the present invention include base resin, a compatibilizer, a foaming agent and a co-cros slinking agent, and a heat stabilizer, an antioxidant, a kneading enhancer and the like may be further added to the composition. If the composition for manufacturing radiation cross-linking thermoplastic olefin elastomer foam according to the present invention is used to prepare products, it is possible to manufacture environment-friendly products having further improved physical properties, and a high-efficiency radiation cross-linking thermoplastic olefin elastomer foam capable of improving appearance and various mechanical characteristics of the products.

Description

COMPOSITION FOR MANUFACTURING RADIATION CROSS- LINKING THERMOPLASTIC OLEFIN ELASTOMER FOAM AND METHOD FOR MANUFACTURING RADIATION CROSS- LINKING THERMOPLASTIC OLEFIN ELASTOMER FOAM

USING THE SAME Technical Field The present invention relates to a composition for manufacturing a radiation cross- linking thermoplastic olefin elastomer foam and a method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam using the same, and more particularly to a composition for manufacturing a thermoplastic olefin elastomer foam cross-linked by a radiation cross-linking process using polyolefin resin and an elastomer as base resins, the polyolefin resin having a hardness of 35 or more as measured with a Shore type D durometer, and a method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam using the same.

Background Art One of representative general-purpose resins is polyolefin resin having a Shore D hardness of 35 or more, such as polypropylene (PP), polyethylene(PE), etc., which is an environment-friendly material that does not only has excellent physical properties such as low density, high strength, high heat resistance, etc., but also is easily re-usable. The polyolefin resin is a plastic material that has been widely used as suitable materials for the various fields spanning from daily necessaries to industrial parts and is expected to grow the most from now on. However, the polyolefin resin has disadvantages that it has a poor low-temperature impact resistance or coatability due to its physical properties such as relatively high glass transition temperature, high crystallinity and inherent non-polarity, etc. Thus, in order to solve the problems presented in the polyolefin resin and improve its application in the related art, there have been attempts to search for combinations of various methods including copolymerization, rubbery introduction, FRP, etc. Thermoplastic olefin elastomer (also referred to as TPO) resin does not only have various physical properties due to phase separation handling, etc., for example including flexibility of the thermosetting rubber at room temperature, but also the same processability as in thermoplastics. Also, the TPO resin is a polymer blend that attracts attention as a substitute of rubber products or impact-resistant reinforced materials that has been used in the art due to its easy reusability. Commercialized TPO resin is classified into two groups: hard segment and soft segment. The hard segment of the TPO resin is composed of polyolefin resin having a high hardness, such as PP, PE, etc., and the soft segment of the TPO resin is composed of olefin elastomer such as EPDM, EPR, EVA, ethylene octene copolymer, ethylene butene copolymer, etc. Recently, there have been attempts to develop a thermoplastc oilefin elastomer resin having various compositions depending on its desired physical properties, for example blending NBR, butyl rubber, natural rubber, etc. with the TPO resin. As described above, the composition has been used to manufacture a foam capable of satisfying the desired physical properties by selecting and blending suitable materials for the radiation cross-linking thermoplastic olefin elastomer resin, followed by being subject to extrusion and foaming processes, wherein the composition further includes additional components such as a compatibilizer for enhancing blending efficiency, a foaming agent for foaming an elastomer, a co-crosslinking agent for efficiently carrying out a cross-linking process, etc. However, if the foaming agent is previously added in preparation of a composition, the composition may not be foamed since the foaming agent is already dissolved in the composition prior to a foaming process. Furthermore, it is not easy to determine and control the suitable addition time and method of the foaming agent if a conventional single screw extruder, generally used in the art, is used in the foaming process. Meanwhile, physical properties of the foaming agent in the composition may be changed according to conditions of an extruder if the foaming agent-containing composition is added to the extruder. Also, a chemical crosslinking method, most often used in the art, has a problem that environmental pollution sources may be generated during its process. Also, there has been required a novel foaming technique which is different to the conventional process used in a final foaming procedure of the processes. In the process for manufacturing a foam using the thermoplastic olefin elastomer composition, there have been steady attempts to improve physical properties of a final product of a thermoplastic olefin elastomer foam by modifying components and contents of the initially prepared composition as well as improving various process conditions and specific procedures required during the manufacturing process, and the present invention was designed based on the above-mentioned facts.

Disclosure of Invention Technical Problem Accordingly, the present invention is designed to solve the problems of the prior art, and therefore it is an object of the present invention to manufacture a good-quality product by listing suitable components and contents of the composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam, preparing the materials capable of manufacturing a good-quality product, and providing optimal conditions required in every steps of the process for manufacturing a foam using the prepared materials.

[11] In order to solve the above problem, the present invention provides a composition for manufacturing radiation cross-linking thermoplastic olefin elastomer foam and a method for manufacturing radiation cross-linking thermoplastic olefin elastomer foam using the same.

[12]

Technical Solution

[13] In order to accomplish the above object of the present invention, the composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to the present invention includes a base resin, a compatibilizer, a foaming agent and a co-crosslinking agent.

[14] The base resin is preferably a polyolefin resin composed of 10 to 80 % by weight of high-dardness polyolefin resin (a hard segement) having a hardness of 35 or more as measured with a Shore type D durometer; and 20 to 90 % by weight of elastomer.

[15] The high-hardness polyolefin resin blended with the base resin is composed of the hard segment, and the elastomer blended with the base resin is composed of the soft segment. Mechanical properties of a product are changed according to content ratios of the hard segment and the soft segment constituting the base resin. In particular, heat- resistant and mechanical properties as well as extrusion and foaming processabilities are improved with the increase in content of the polyolefin resin constituting the hard segment, while the content of the polyolefin resin should be carefully adjusted since performances of the elastomer may be deteriorated due to reduction in the flexibility in the method for manufacturing a thermoplastic olefin elastomer foam using a radiation cross-linking process. That is to say, heat-resistant and mechanical properties and processabilities are deteriorated if the content of the high-hardness (a hardness of 35 or more as measured with a Shore type D durometer) polyolefin resin constituting the hard segment is less than the lower numerical limit, while flexibility of the elastomer may be reduced if the content exceeds the upper numerical limit. At this time, it is difficult to ensure flexibility of the elastomer if the elastomer constituting the soft segment is less than the lower numerical limit, while mechanical properties and processabilities are deteriorated if the content exceeds the upper numerical limit.

[16] In the composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam, the high-hardness polyolefin resin(a hard segment) included as the base resin is preferably one selected from the group consisting of polypropylene (PP) and polyethylene (PE). In the he composition for manufacturing a radiation cross- linking thermoplastic olefin elastomer foam, the elastomer included as the base resin is preferably one selected from the group consisting of olefin elastomers (EPR, EPDM, ethylene octene copolymer, ethylene butene copolymer), styrene elastomers (SBS, SIS, SEBS), butadiene rubber, and fluorocarbon elastomers (fluorine-containing hydrocarbon polymer).

[17] The compatibilizer is included at a content of 5 to 20 parts by weight, based on 100 parts by weight of the base resin, and it is preferably at least one selected from the group consisting of a styrene-ethylene-butylene-styrene block copolymer, a styrene- butadiene-styrene block copolymer, a styrene-acrylonitrile copolymer, a graphited ethylene propylene rubber (EPDM) and a functionalized polymer. At this time, it is difficult to ensure desired physical properties of a product since interfacial adhesion between the hard segment and the soft segment constituting the base resin is not affected, but week if the content of the compatibilizer is less than the lower numerical limit, while it is difficult to ensure desired physical properties of a product since interfacial adhesion between the hard segment and the soft segment constituting the base resin is excessively affected, as well as economical efficiency is declined since an addition effect is not improved in proportion to an increasing amount of the added compatibilizer but a manufacturing cost is increased due to an excessive amount of the compatibilizer if the content exceeds the upper numerical limit.

[18] Meanwhile, the functionalized polymer selected and used as the compatibilizer is preferably one selected from the group consisting of polypropylene-grafted-maleic anhydride (so-called, referred to as 'PP-g-MAH'), ethylene ethyl acrylate- grafted-maleic anhydride (so-called, referred to as 'EEA-g-MAH'), ethylene vinyl acetate-grafted-maleic anhydride (so-called, referred to as 'EVA-g-MAH'), styrene ethylene butadiene styrene-grafted-maleic anhydride (so-called, referred to as 'SEBS- g-MAH'), maleic anhydride-copolymerized polystyrene

[PS(polystyrene)-co-MAH(Maleic anhydride)], polyethylene-grafted-maleic anhydride [PE(polyethylene)-GMA(Grafted maleic anhydride)], and ethylene ethyl acetate- grafted maleic anhydride [EEA-GMA(grafted maleic anhydride)].

[19] The foaming agent is included at a content of 1 to 30 parts by weight, based on 100 parts by weight of the base resin, and it is preferably one selected from the group consisting of inorganic foaming agents including ammonium bicarbonate, sodium bicarbonate and sodium borohydrate, or one selected from the group consisting of organic foaming agents including azodicarbonamide (ADCA), dinitrosopen- tamethylenetetramine (DPT), benzenesulfonyl hydrazide, toluenesulfonyl hydrazide (TSH) and p-toluenesulfonyl semicarbazide (PTSS). At this time, the composition is not sufficiently foamed to a desired extent if the content of the foaming agent is less than the lower numerical limit, while he composition is excessively foamed, as well as physical properties of a product are deteriorated due to the excessive foamed composition if the content exceeds the upper numerical limit.

[20] The co-crosslinking agent in the composition for manufacturing a radiation cross- linking thermoplastic olefin elastomer foam is included at a content of 0.2 to 5.0 parts by weight, based on 100 parts by weight of the base resin, and it is peferably one selected from the group consisting of organic peroxides, an unsaturated resin crosslinking agent and a polyurethane crosslinking agent. The co-crosslinking agent is added for purpose of maintaining an optimal resin viscosity in foaming the composition. At this time, it is difficult to ensure an optimal resin viscosity in foaming the composition if the content of the co-crosslinking agent is less than the lower numerical limit or exceeds the upper numerical limit. Meanwhile, the organic peroxide selected and used as the co-crosslinking agent is preferably one selected from the group consisting of hydroperoxide, dialkyl-arylperoxide(dicumyl peroxide), diacyl peroxide, peroxy ketal, peroxy ester, peroxycarbonate and ketone peroxide, and the unsaturated resin crosslinking agent selected and used as the co-crosslinking agent is preferably one selected from the group consisting of a vinyl monomer, an acrylic compound, a methacrylic compound and an epoxy compound.

[21] Meanwhile, the composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam further includes at least one additive selected from the group consisting of an antioxidant, a heat stabilizer and a kneading enhancer of mixed resin.

[22] The selected antioxidant is preferably included at a content of 0.2 to 2.0 parts by weight, based on 100 parts by weight of the base resin. At this time, processability in the extrusion and foaming processes is deteriorated if the content of the antioxidant is less than the lower numerical limit, while economical efficiency is declined and mechanical properties may be deteriorated due to an excessive amount of the added antioxidant if the content exceeds the upper numerical limit.

[23] The selected heat stabilizer is preferably included at a content of 0.2 to 5.0 parts by weight, based on 100 parts by weight of the base resin. At this time, processability in the extrusion and foaming processes is deteriorated and physical properties of a product are also deteriorated due to the degraded resin if the content of the antioxidant is less than the lower numerical limit, while economical efficiency is declined and mechanical properties may be deteriorated due to an excessive amount of the added antioxidant if the content exceeds the upper numerical limit.

[24] The selected kneading enhancer of mixed resin is preferably included at a content of 2 to 20 parts by weight, based on 100 parts by weight of the base resin, and it is preferably one selected from the group consisting of talc, calcium carbonate, bentonite and zeolite. At this time, an addition effect of the kneading enhancer of mixed resin may not be accomplished since its kneading property is not enhanced if the content of the kneading enhancer of mixed resin is less than the lower numerical limit, while an addition effect is not improved in proportion to an increasing amount of the added kneading enhancer, and process stability and physical properties of a product are deteriorated due to an excessive amount of the added kneading enhancer if the content exceeds the upper numerical limit.

[25] Hereinafter, the method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam will be described with reference to the accompanying drawings, as follows.

[26] FIG. 1 is a flowchart illustrating one embodiment of a process for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to the present invention, and FIG. 2 is a flowchart illustrating anther embodiment of a process for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to the present invention.

[27] As shown in FIG. 1, it is seen that the manufacturing process is carried out with 4 steps (SI l to S 14), as follows.

[28] Firstly, all component of the composition for manufacturing a radiation cross- linking thermoplastic olefin elastomer foam were prepared and mixed (Sl 1). Then, the foaming agent-containing composition, prepared in the step (Sl 1), was added to a twin screw extruder and extruded therein (S 12). Subsequently, the extruded product in the step (S 12) was cross-linked by irradiation with accelerated radiation (S 13). Finally, the cross-linked product in the step (S 13) was foamed (S 14).

[29] In the case of the extruder used in the extrusion step (S 12), the foaming agent- containing composition for manufacturing a thermoplastic olefin elastomer foam according to the present invention is not sufficiently foamed due to technical problems caused when a conventional single screw extruder is used to foam the foaming agent- containing composition, and therefore a twin screw extruder is preferably used in the present invention. Meanwhile, counter-rotation type and co-rotation type twin screw extruders may be all used herein, but the latter co-rotation type twin screw extruder is preferably used to ensure a more desirable extrusion efficiency.

[30] As shown in FIG. 2, it is revealed that the manufacturing process is carried out with

4 steps (S21 to S24) unlike in FIG. 1, as follows.

[31] As described above, except for the foaming agent, all components of the composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to the present invention were prepared and mixed (S21). Then, the prepared composition was extruded while adding the foaming agent, excluded in the step (S21), to a twin screw extruder through a central end of the twin screw extruder on a side feeding pattern (S22). In the above-mentioned composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam, the composition composed of the other components except for the foaming agent is prepared separately in order to add the foaming agent to the extruder on an interim side feeding pattern in the subsequent process (S22). As described above, the initial composition except for the foaming agent was added to the extruder so that efficiency of the foaming agent can be maximally improved by means of process conditions inside the extruder, and therefore, in the extrusion step (S22), a kneading property of the composition and efficiency of the foaming agent are preferably maximally improved if the foaming agent is added to the twin screw extruder on a side feeding pattern, namely through a central region of a cylinder of the twin screw extruder.

[32] The cylinder of the twin screw extruder used in the present invention is preferably maintained in a temperature of 120 to 200 ⁰C. The added composition is not suitably kneaded if the temperature of the cylinder of the twin screw extruder is less than the lower numerical limit, while a foaming property of the foaming agent, added through the central region of the cylinder of the twin screw extruder, may be deteriorated if the temperature exceeds the upper numerical limit. Also, the number of kneading blocks in screws, existing inside the cylinder of the twin screw extruder, is adjusted to a range from about 10 to 40 %. A foaming property of the added resin composition is deteriorated if the number of kneading blocks is less than the lower numerical limit, while performances of the foaming agent is deteriorated if the number of kneading blocks exceeds the upper numerical limit. Meanwhile, the screws of the twin screw extruder is preferably maintained in a temperature of 50 to 120 ⁰C. It is difficult to mold the resin composition into a mother sheet since the resin composition is abruptly solidified, and it is impossible to obtain normal products due to the phase separation in the hard and soft segments if the temperature of the screws in the twin screw extruder is less than the lower numerical limit, while the subsequent foaming process (S 14 or S24) is not effectively carried out since a foaming property of the foaming agent and physical properties of the composition are deteriorated, and therefore performances of products are deteriorated if the temperature of the screws exceeds the upper numerical limit. As described above, productivity and yields of the product may be prevented from being decreased by introducing a cooling system to reduce a temperature of the screws in the twin screw extruder to a suitable temperature range.

[33] The cross-linking process, used in the cross-linking step (S 14 or S24) used in the method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam, is a cross-linking process by irradiation with radiation, and it is preferably en- vironment-friendly and excellent in economical efficiency, and may ensure a process stability. The cross-linking step (S 13 or S23) is preferably carried out so that the extruded product can be irradiated with accelerated radiation having a voltage of 100 to 1,000 kV and a radiation dose of 0.5 to 10 Mrad, and the cross-linking voltage is preferably suitably adjusted according to thickness of the extruded sheet obtained in the extrusion step(S12 or S22), and the crosslinking radiation dose is preferably suitably adjusted according to density and physical properties of the previously added foaming agent.

[34] The extruded product obtained in the step (S 12 or S22) is not cross-linked to the sufficient depth if the cross-linking voltage is less than the lower numerical limit, while serious problems are caused in foaming the composition since excessive cross-linking appears in an overlapped region of radiation if the radiation is irradiated to the very deep extent, and economical efficiency is also declined if the cross-linking voltage exceeds the upper numerical limit. Also, it is problematic to carry out the subsequent foaming process (S 14 or S24) since the extruded product obtained in the step (S 12 or S22) is not cross-linked to the sufficient depth if the crosslinking radiation dose is less than the lower numerical limit, while serious problems are caused in foaming the composition since the cross-linking level is supersaturated due to the excessive crosslinking radiation dose, and economical efficiency is also declined if the crosslinking radiation dose exceeds the upper numerical limit.

[35] In the cross-linking method using the irradiation with radiation under the conditions as described above, the extruded sheet, which is the resultant product in the previous step (S 12 or S22) as a material to be cross-linked, is irradiated with the accelerated radiation to remove oxygen included in the olefin resin in the extruded sheet, and therefore radicals are generated in the olefin resin. The radicals generated thus is characterized by the fact that the radicals have a high reactivity, which facilitates a cross- liking reaction in the olefin resin.

[36] In the method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam, the foaming step (S 14 or S24) is preferably carried out through one process selected from the group consisting of a horizontal foaming process for installing a foaming furnace in a horizontal direction, a vertical foaming process for installing a foaming furnace in a vertical direction, and a salt foaming process using liquid salt as a heat transfer medium.

[37] At this time, the three foaming methods are all carried out under ambient pressure, and suitably divided according to installation of the foaming furnace and heat transfer media. First, the horizontal foaming process is a process in which a foam is produced in a horizontal direction since the foaming furnace is horizontally installed, and therefore its entire steps are carried out in a horizontal direction. The horizontal foaming process has an advantage that changes in physical properties in length and width directions are small due to a small expansion ratio in the length direction in foaming the composition since the gravity hardly affects the arrangement of the foaming furnace and the progress of the process. Second, the vertical foaming process is a process in which the composition is foamed while a mother sheet falls down since a foaming furnace is vertically installed. The composition is foamed in the air in the vertical foaming process, and therefore the foamed product has an excellent appearance, and also it is produced in an excellent yield due to a small deviation in the width direction. Third, the salt foaming process is very different to the two above- mentioned foaming processes in that liquid salt is used as the heat transfer medium, and has an advantage that a heat transfer efficiency is excellent and the composition is uniformly foamed on a sheet since the liquid salt other than the air is used as the heat transfer medium contrary to the vertical foaming process. In particular, the salt foaming process has a merit that the foamed product obtained by the salt foaming process has an excellent physical properties due to a very small deviation in the length or width direction, compared to the foamed product obtained by the above-mentioned horizontal or vertical foaming process.

Brief Description of the Drawings FIG. 1 is a flowchart illustrating one embodiment of a process for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to the present invention. FIG. 2 is a flowchart illustrating another embodiment of a process for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to the present invention.

Best Mode for Carrying Out the Invention Hereinafter, preferred embodiments of the present invention will be described in detail referring to the accompanying drawings. However, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention. As listed in the following Table 1, each of the compositions was classified into Embodiments 1 to 3 and Comparative examples 1 to 3, considering contents of the compositions, kinds of used extruders, use of a screw cooling system in the extruders, cross-linking processes, foaming processes, etc.

In Table 1, a polypropylene resin was used as the high-hardness polyolefin resin which is a hard segment constituting the base resin, EPDM was used as the elastomer which is a soft segment constituting the base resin, EPDM grafted with 0.9 % maleic anhydride (commercially available from DuPont) was used as the compatibilizer, ADCA was used as the foaming agent, an acrylic compound was used as the co- crosslinking agent, tetrakismethylene methane was used as the stabilizer, and talc was used as the kneading enhancer. In the kinds of the extruders, the expression "Twin" means a twin screw extruder and the expression "Single" means a single screw extruder. In particular, a co-rotation type twin screw extruder was used in Embodiment 1, and a counter-rotation type twin screw extruder was used in Embodiments 2 and 3. In the case of the cooling system, the term "Applied" is indicated if the twin screw extruder is provided with a cooling system for reducing temperature of an extruder screw, and the "Not applied" is indicated if the twin screw extruder is otherwise. The radiation dose was 3.0 Mrad in the case of Embodiments 1 to 3 in which a radiation system is used as the cross-linking process, and the radiation dose was 3.0 Mrad in the case of all the Comparative examples except for the Comparative example 5 in which the radiation dose is 11.0 Mrad. Finally, the vertical foaming process was used in the Embodiment 1 and the Comparative examples 1, 2 and 4 to 6, the horizontal foaming process was used in the Embodiment 2 and the Comparative example 3, and the salt foaming process was used in the Embodiment 3.

Table 2

[47] As seen in the Table 2, it was revealed that the compositions according to the present invention have the various good properties required in the manufacturing process, for example extrudability, foaming property, productivity, etc., in the case of the Embodiments 1 to 3, compared to the compositions of the Comparative examples 1 to 6, and therefore the extruded products also have superior physical properties. From the results, it was seen that the compositions of the present invention are proven to be excellent in technical effects.

[48] In the Table 2, the uniformity of the physical properties and the expansion ratio are in proportion to each other, and therefore the uniformity of the physical properties was determined by measuring tensile strengths in a length direction and a width direction and comparing the tensile strengths, the tensile strengths being one of the typical mechanical properties. It was revealed that the tensile strength in the length direction is 7.2 kgf/D and the tensile strength in the width direction is 5.0 kgf/D in the case of Embodiment 1. It was revealed that the tensile strengths in the length direction and the width direction are similar to each other, for example 6.8 kgf/D and 6.5 kgf/D in the Embodiment 2, respectively, and 7.2 kgf/D and 7.0 kgf/D in the Embodiment 3, respectively, since the horizontal and vertical foaming processes are used in the Embodiments 2 and 3, respectively. At this time, A measurement method for tensile strength was carried out according to KS M 3014 standard (a testing method for polyethylene foams). Meanwhile, in order to determine cell sizes of the foams after the foaming, the foams were measured using SEM. As listed in Table 2, it was revealed that the foams have the smallest cell sizes in the case of Embodiment 1 in which a counter-rotation type twin screw extruder is used, and also have the biggest cell sizes in the case of Comparative example 6. This results from the difference between the chemical cross-linking process and the radiation cross-linking process. Finally, in order to measure flexibility and heat resistance of the radiation cross-linking thermoplastic olefin elastomer foam, a pressure strength was measured for the flexibility when the foam was pressed at a pressure range of 25 %, and the heat resistance was measured by keeping the foams at 120 ⁰C for 1 hour and measuring changes in the foams. Similar to the measurement method for tensile strength, the pressure strength and the heat shrinkage were measured according to KS M 3014 standard. It was revealed that the foams have a heat shrinkage of -1 % and a pressure strength of 0.85 kgf/D in the Comparative example 1, and a heat shrinkage of -25 % and a pressure strength of 0.21 kgf/D in the Comparative example 2. Contrary to the Comparative examples 1 and 2, It was revealed that the foams have a heat shrinkage from -2.2 % to -2.5 % and a pressure strength from 0.43 kgf/D to 0.44 kgf/D, indicating that the foams have an excellent physical properties such as heat resistance and flexibility. As described above, the preferred embodiments of the present invention has been described in detail. it should be understood that the terms used in the specification and appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation.

Industrial Applicability If the composition for manufacturing radiation cross-linking thermoplastic olefin elastomer foam according to the present invention is used to prepare products, it is possible to manufacture environment-friendly products having further improved physical properties, and a high-efficiency radiation cross-linking thermoplastic olefin elastomer foam capable of improving appearance and various mechanical characteristics of the products. In recent years, an application field of TPO foam is mainly classified into two groups: materials for automobiles and for sundry goods and electronics. The biggest attention has been attracted to the TPO foam in the field of automotive interior materials in Korea and abroad. Automotive interior parts are largely classified into two groups: a pad type (soft) and a non-pad type (hard). The pad type parts are parts having a hard surface and include an instrument panel, a door trim, a console box, a garnish, etc. However, sensitive modern persons tend to prefer soft parts over hard parts in visual and feeling aspects. As a result, the pad type interior parts have been used for a door trim, an instrument panel, a head liner, a side filler, etc. At this time, materials used in the pad type interior parts have a three-layer (skin/foam/core) sandwich structure, unlike materialsused in the non-pad type interior parts. A PVC skin/PU foam/ ABS core structure has been used in recent years but is not easy to re-use, and PVC is a material expected to restrict its use as one of the environmentally toxic substances. Accordingly, there have been active and ardent attempts to substitute the conventional structure with a TPO skin/TPO foam/PP core structure, which has been, in part, applicable to some car models.

[54] Also, there have been continuous attempts to apply to materials for sundry goods and electronics, and the fields to which the materials is expected to be the most applicable are tapes and non-slip mats. A typical target of the tapes is Norton tapes, and the whole quantity of the Norton tapes has been imported and applied to construction markets. The Norton tapes has a low foaming magnitude and an excellent flexibility to the hardness, and they have been used as a spacer for maintaining shapes of silicon sealants. These tapes has an excellent adhesion and a superior shape retention. In recent years, there have been interesting but insufficient attempts to substitute the tapes with polyurethane, PVC foam, etc. in other related fields. In addition, the non-slip mats, obtained by conferring a non-slip property on the TPO foam, are applicable to various fields such as general household mats, mouse pads, packing materials of electronics, etc. In particular, the whole quantity of poron foams, used as a sealant of electronics, have been imported and used, and there have been active but insufficient attempts to substitute the imported products in Korea. These poron foams provide a possibility for the wide market to be opened if the sealing property of the TPO foam is conferred on the poron foams.

Claims

Claims A composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam comprising base resin, a compatibilizer, a foaming agent and a co-crosslinking agent, wherein the base resin is a poly olefin elastomer composed of 10 to 80 % by weight of polyolefin resin having a high Shore type D hardness of 35 or more and 20 to 90 % by weight of an elastomer, wherein the compatibilizer is included in a content of 5 to 20 parts by weight, based on 100 parts by weight of the base resin, and is at least one material selected from the group consisting of styrene-ethylene-butylene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-acrylonitrile copolymer, graphited ethylene propylene rubber and functionalized polymer, wherein the foaming agent is included in a content of 1 to 30 parts by weight, based on 100 parts by weight of the base resin, and is one selected from the group consisting of inorganic foaming agents including ammonium bicarbonate, sodium bicarbonate and sodium borohydrate, or one selected from the group consisting of organic foaming agents including azodicarbonamide, dinitrosopen- tamethylenetetramine, benzenesulfonyl hydrazide, toluenesulfonyl hydrazide and p-toluenesulfonyl semicarbazide, and wherein the co-crosslinking agent is included in a content of 0.2 to 5.0 parts by weight, based on 100 parts by weight of the base resin, and is one material selected from the group consisting of organic peroxide, an unsaturated resin crosslinking agent and a polyurethane crosslinking agent. The composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 1, wherein the high-hardness polyolefin resin included as the base resin is one material selected from the group consisting of polypropylene and polyethylene. The composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 1, wherein the elastomer included as the base resin is one selected from the group consisting of: one selected from the group consisting of olefin materials including EPR, EPDM, ethylene octene copolymer and ethylene butene copolymer; one selected from the group consisting of styrene materials including SBS, SIS and SEBS; a butadiene rubber material; and a fluorinated organic material which is a fluorine-containing hydrocarbon polymer. The composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 1, wherein the functionalized polymer selected as the compatibilizer is one selected from the group consisting of polypropylene-grafted-maleic anhydride, ethylene ethyl acrylate-grafted-maleic anhydride, ethylene vinyl acetate-grafted-maleic anhydride, styrene ethylene butadiene styrene-grafted-maleic anhydride, maleic anhydride-copolymerized polystyrene, polyethylene-grafted-maleic anhydride, and ethylene ethyl acetate-grafted maleic anhydride. The composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 1, wherein the organic peroxide selected as the co-crosslinking agent is one selected from the group consisting of hydroperoxide, dialkyl-arylperoxide(dicumyl peroxide), diacyl peroxide, peroxy ketal, peroxy ester, peroxycarbonate and ketone peroxide. The composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 1, wherein the unsaturated resin crosslinking agent selected as the co-crosslinking agent is one selected from the group consisting of a vinyl monomer, an acrylic compound, a methacrylic compound and an epoxy compound. The composition for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 1, further comprising at least additive selected from the group consisting of an antioxidant, a heat stabilizer and a kneading enhancer of mixed resin, wherein the selected antioxidant is included in a content of 0.2 to 2.0 parts by weight, based on 100 parts by weight of the base resin, and is one selected from the group consisting of phenol, amino, phosphorus and sulfur antioxidants, wherein the selected heat stabilizer is included in a content of 0.2 to 5.0 parts by weight, based on 100 parts by weight of the base resin, and is one selected from the group consisting of Cd/Ba/Zn, Cd/Ba, Ba/Zn, Ca/Zn, Na/Zn, Sn, Pb, Cd and Zn heat stabilizers, and wherein the selected mixed resinD kneading enhancer is included in a content of 2 to 20 parts by weight, based on 100 parts by weight of the base resin, and is one selected from the group consisting of talc, calcium carbonate, bentonite and zeolite. A method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam, the method comprising: (Sl 1) preparing and mixing all components of the composition as defined in any of claims 1 to 7;

(S 12) adding the resultant composition including a foaming agent to a twin screw extruder and extruding the foaming agent-containing composition;

(S 13) cross-linking the extruded product by irradiating it with accelerated radiation; and

(S 14) foaming the cross-linked product.

[9] The method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 8, wherein the extrusion step (S 12) is carried out by extng the composition prepared in the step (Sl 1) while adding it to the twin screw extruder, wherein a cylinder of the twin screw extruder is maintained at a temperature of 120 to 200 ⁰C, and a screw of the twin screw extruder is maintained at a temperature of 50 to 120 ⁰C.

[10] A method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam, the method comprising:

(521) preparing and mixing all components, except for a foaming agent, of the composition as defined in any of claims 1 to 7;

(522) extruding the resultant composition while adding the foaming agent, excluded in the step (S21), to a twin screw extruder on a side feeding pattern;

(523) cross-linking the extruded product by irradiating it with accelerated radiation; and

(524) foaming the cross-linked product.

[11] The method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 10, wherein the extrusion step (S22) is carried out by adding the composition prepared in the step (S21) to the twin screw extruder, followed by adding the foaming agent, excluded from the composition, to a twin screw extruder on a side feeding pattern, wherein a cylinder of the twin screw extruder is maintained at a temperature of 120 to 200 ⁰C, and a screw of the twin screw extruder is maintained at a temperature of 50 to 120 ⁰C.

[12] The method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 8 or 10, wherein the cross-linking step is carried out by irradiating the extruded product with accelerated radiation having a voltage of 100 to 1,000 kV and a radiation dose of 0.5 to l0 Mrad.

[13] The method for manufacturing a radiation cross-linking thermoplastic olefin elastomer foam according to claim 8 or 10, wherein the foaming step is carried out through one process selected from the group consisting of a horizontal foaming process for installing a foaming furnace in a horizontal direction, a vertical foaming process for installing a foaming furnace in a vertical direction, and a salt foaming process using liquid salt as a heat transfer medium.