Method of manufacture of thermoplastic elastomer compounds

Details Method of manufacture of thermoplastic elastomer compounds Method of manufacture of thermoplastic elastomer compounds

1987-11-02

1989-01-31

Seccuro, Carman J.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

525 88, 525194, 525196, 525197, 525192, 525211, 525232, 525237, 525 74, 524525, 524526, C08L 2326, C08L 2316, C08L 1502, C08L 900

Patent

active

048016519

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention is concerned with a method of manufacture of a partially crosslinked olefinic thermoplastic elastomer (TPE) compositions.
Although compounds comprising a polyolefin and a partially crosslinked rubber possess good properties as TPEs such as heat resistance, mechanical strength, flexibility, and elasticity, their flow properties are inferior to those of common plastics, and this has limited their use in large molded parts owing to problems such as "flow marks." To improve these problems, for example, Japanese Pat. No. 54-23702 teaches the use of compounds consisting of polyolefin and two types of rubber, partially crosslinked, and Japanese Pat. No. 56-15743 teaches a compound in which a polyolefin is blended with a polyolefin/rubber blend that has been treated with organic peroxides. Also Japanese Pat. No. 56-15740 teaches the methods of manufacture of such compounds.
Japanese Application No. 60-188419 discloses compositions in which the rubber phase includes a halobutyl rubber, which is vulcanized with metal oxides (MOx) and/or Metal Chlorides (MCl) and partially crosslinked in the presence of a polyolefin, and then additional polyolefin is added.
Although such TPE compounds have excellent properties such as processability, low temperature impact, paintability, flexibility, and mechanical strength, their stiffness at elevated temperatures was less than adequate compared to polyurethane elastomers. It is one object of the present invention to improve high temperature stiffness of this type of TPE, without loss in the characteristics of olefinic TPEs.


SUMMARY OF THE INVENTION

A method of manufacture of compositions in which polyolefin and a rubber phase comprising halobutyl rubber is partially crosslinked using MOx and/or MCl and are compounded further with a vulcanizable olefinic rubber, which is then crosslinked using organic peroxides.
Thus, a blend of (A) polypropylene 10-90 weight parts (pts.), (B) halobutyl rubber 90-10 pts. (wherein (A)+(B)=100 pts.), (C) olefinic rubber 10-120 pts., and (D) mineral oil softening agent 5-120 pts. are thermally treated with (E) MOx and/or MCl to crosslink the halobutyl rubber, to which blend of 100 pts. are then added, (F) polyolefin 100-600 pts., and (G) vulcanizable olefinic rubber 50-500 pts., which is then thermally treated with (H) an organic peroxide to crosslink the olefinic rubber.


DETAILED DESCRIPTION



(A) Polypropylene (PP)

PP suitable for use in this invention includes homopolymer or copolymer with ethylene, 1-butene, 1-pentene, 1-hexene or 4-methylpentene or other alpha-olefins with propylene as the main component, including random or block copolymers. Melt flow rate (MFR) is about 0.3-60 g/10 min, preferably 1-40, most preferably 3-30. Component A of the composition has the highest melting point of polyolefins, and imparts heat resistance and improved mechanical properties to the compound.


(B) Halobutyl Rubber

For purposes of this invention halobutyl rubber means halogenated butyl rubber. The halogen can be chlorine or bromine, usual content is 0.5-4.0 wt %. It is preferable that this component has a Mooney Viscosity, ML 1+8 (100.degree. C.) of about 30-100 and 0.5-4.0 mol % unsaturation. Halobutyl rubber can be crosslinked using MOx and/or MCl, and exists as a dispersed crosslinked rubber phase, imparting abrasion resistance, impermeability and "anti-slip properties" to the compound.


(C) Olefinic Rubber

Rubber in which two or more of: ethylene, propylene, butene, 1-hexene, 4-methyl-1-pentene, etc. are copolymerized (e.g., ethylene propylene rubber, EPR) or rubber in which two of the above monomers (preferably ethylene and propylene) are polymerized with dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene-norbornene or ethylidenenorbornene (ENB) or conjugated dienes such as butadiene or isoprene. The preferred olefinic rubber has Mooney Viscosity, ML 1+8 (127.degree.), of 5-300, Iodine Value up to 30, and 35-85 wt % ethylene content. Such olefinic rubber may be polyisobutylene, butyl rubber,

REFERENCES:
patent: 4130534 (1978-12-01), Coran et al.
patent: 4247652 (1981-01-01), Matsuda et al.
patent: 4593062 (1986-06-01), Puydak et al.
patent: 4607074 (1986-08-01), Hazelton et al.
patent: 4639487 (1987-01-01), Hazelton et al.
patent: 4728692 (1988-03-01), Sezaki et al.

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