Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-02-01
2002-08-27
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S216000, C525S232000, C525S240000
Reexamination Certificate
active
06441093
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoplastic elastomer composition for calender-molding and a sheet prepared therefrom. More particularly, the invention relates to a thermoplastic elastomer composition containing an olefin copolymer rubber and a polypropylene resin, said composition being excellent in calender moldability and being capable of producing a calendered sheet superior in appearance, and to a sheet obtained by subjecting the thermoplastic elastomer composition to calender-molding.
2. Description of Related Arts
Thermoplastic elastomers containing an olefin copolymer rubber and a polypropylene resin have found use in widespread fields, including automobile parts, electric home appliances, sundry goods and so on, making a good use of the characteristics thereof that they need not the vulcanization step and they can be processed with a molding machine for ordinary thermoplastic resins.
One example of methods for molding thermoplastic elastomers into a sheet is a calender molding. It is known that this method is superior in productivity compared to other molding methods, for example, extrusion molding with T-die or the like, the method had a problem, however, that the appearance of the obtained sheet was deteriorated by winding and adhesion of a thermoplastic elastomer around rollers when the thermoplastic elastomer was subjected to the calender molding. In order to overcome this problem, there is proposed a composition improved by adding an ethylene-based polymer resin and a higher fatty acid amide and the like to a thermoplastic elastomer (JP-A-7-166012). The addition resulted in problems, however, that the composition and hence use to be applied were limited or the appearance was deteriorated by bleeding of the higher fatty acid amide on the sheet surface.
SUMMARY OF THE INVENTION
Under these circumstances, an object of the present invention is to provide a thermoplastic elastomer composition having an excellent calender processability, which is capable of providing a calendered sheet having a good appearance, by selecting a specified polypropylene resin constituting the composition, without troublesome steps in which an ethylene polymer resin described above or the like are additionally mixed, and a sheet.
That is, the present invention relates to a thermoplastic elastomer composition for calender-molding obtained by dynamically heat-treating a mixture comprising 40 to 95% by weight of the component (A) and 60 to 5% by weight of the component (B) respectively described below:
(A) an oil-extended olefin copolymer rubber containing 100 parts by weight of an olefin copolymer rubber having a Mooney viscosity (ML
1+4
100° C.) of 120 to 350 and 20 to 150 parts by weight of a mineral oil softening agent, and
(B) a polypropylene resin composed of a propylene homopolymer as a first segment and a propylene-ethylene random copolymer having an intrinsic viscosity of tetralin solution at a temperature of 135° C. of 0.5 to 6.0 dl/g and a weight ratio of ethylene to propylene of 10/90 to 60/40 as a second segment, wherein the weight ratio of the first segment to the second segment is 95/5 to 50/50.
Additionally, the present invention provides a sheet obtained by calender-molding the thermoplastic elastomer composition as above.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below in detail.
The component (A) used in the present invention is an oil-extended olefin copolymer rubber containing 100 parts by weight of an olefin copolymer rubber having a Mooney viscosity (ML
1+4
100° C.) of 120 to 350 and 20 to 150 parts by weight of mineral oil softening agent.
The olefin copolymer rubber is a rubber containing olefin units as a major component. Examples of the olefin copolymer rubber include, ethylene-&agr;-olefin (e.g. propylene, 1-butene, 1-hexene, 1-octene) copolymer rubbers and ethylene-&agr;-olefin (e.g. propylene, 1-butene, 1-hexene, 1-octene)-non-conjugated diene copolymer rubbers such as, for example, ethylene-propylene copolymer rubber (EPM), ethylene-propylene-non-conjugated diene copolymer rubber (EPDM), ethylene-1-butene-non-conjugated diene copolymer rubber and &agr;-olefin-conjugated diene copolymer rubbers such as propylene-butadiene copolymer rubber. Among them, ethylene-propylene-non-conjugated diene copolymer rubber is particularly preferred from the viewpoint of a balance among various physical properties of molded products. The non-conjugated diene includes dicyclopentadiene, 1,4-hexadiene, 1,5-cyclooctadiene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene and the like, and 5-ethylidene-2-norbornene is particularly preferred.
A preferred specific example is ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber in which the content of propylene is 10 to 55% by weight, preferably 20 to 40% by weight, and the content of non-conjugated diene such as 5-ethylidene-2-norbornene or the like is 1 to 30% by weight, preferably 3 to 20% by weight. When the content of propylene is less than 10% by weight, the flexibility may be lost, and when it is more than 55% by weight, the mechanical property may be lowered. When the content of non-conjugated diene represented by 5-ethylidene-2-norbornene is less than 1% by weight, the mechanical property may be lowered, and when it is more than 30% by weight, the durability such as light resistance, heat ageing property or the like may be lowered. The Mooney viscosity (ML
1+4
100° C.) of the olefin copolymer rubber is 120 to 350 and preferably 140 to 300. When the Mooney viscosity is too low, the mechanical strength is deteriorated, and when the Mooney viscosity is top nigh, the production of good sheet becomes difficult by the reason that the surface of molded sheet becomes rough or others.
As the mineral oil softening agent, higher boiling petroleum fractions are used, and examples thereof include paraffin-based oil, naphthene-based oil, aromatic oil or the like, and paraffin-based oil is preferable because it provide a thermoplastic elastomer composition excellent in stain resistance and durability such as light resistance, and articles of clear or light-color of the composition. The content of the mineral oil softening agent is 20 to 150 parts by weight, preferably 30 to 120 parts by weight, more preferably 35 to 80 parts by weight based on 100 parts by weight of the olefin copolymer rubber. When the content of the mineral oil softening agent is less than 20 parts by weight, the flowability of the thermoplastic elastomer composition is lowered and the processability in calender-molding is deteriorated. On the other hand, when the content is more than 150 parts by weight, the plasticity is so increased that the adhesiveness to calender rolls becomes extremely high, the processability becomes bad and, in addition, performances such as physical properties of the molded article are lowered.
The Mooney viscosity (ML
1+4
100° C.) of the oil-extended olefin copolymer rubber as the component (A) is preferably 30 to 100 and more preferably 40 to 90. When the Mooney viscosity is less than 30, the adhesiveness to calender rolls may be increased or the mechanical properties become low. On the other hand, when it is more than 100, the production of smooth sheet may become difficult because the surface of sheet obtained by calendar-molding becomes rough.
Use of an olefin copolymer rubber with a Mooney viscosity of 120 to 350 as described above and addition of the mineral oil softening agent in the above-described amount enable production of an olefin thermoplastic elastomer composition which is capable of simultaneously satisfying both requirements, i.e., improvement in processability and improvement in mechanical properties by gift of flexibility and increase of flowability. In general, mineral oil softening agents are used as agents for increasing flowability in olefin thermoplastic elastomer composition. According to studies of the inventors, however, when an oil-extended rubber is not used, addition of 40 parts by weight or
Hamanaka Tatsuo
Makino Makoto
Natsuyama Nobuhiro
Shigematsu Hironobu
Tominaga Takeshi
Nutter Nathan M.
Sughrue & Mion, PLLC
Sumitomo Chemical Company Limited
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