Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1987-04-17
1988-12-20
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...
525268, C08L 2304, C08L 2306
Patent
active
047925884
DESCRIPTION:
BRIEF SUMMARY
TECHNOLOGICAL FIELD
This invention relates to a polyethylene composition, and more specifically, to a polyethylene composition having excellent melt moldability which substantially comprises ultrahigh-molecular-weight polyethylene having a molecular weight of, for example, at least about 1,650,000 and low-molecular-weight to high-molecular-weight polyethylene having a molecular weight of, for example, about 1,500 to about 360,000.
BACKGROUND TECHNOLOGY
Ultrahigh-molecular-weight polyethylene has better impact strength, abrasion resistance, chemical resistance and tensile strength than general high-molecular-weight polyethylenes, and its utility as engineering plastics has been on an increase. However, the ultrahigh-molecular-weight polyethyene has a much higher melt viscosity and lower flowability than the general-purpose polyethylenes. Hence, it has the defect of poor moldability and is extremely difficult to mold by extrusion or injection molding.
Accordingly, in most cases, articles from the ultrahigh-molecular-weight polyethylene are presently produced by compression molding. Some articles, such as rods, are produced only at very low speeds by extrusion molding.
Previously, as a method of improving the melt moldability of ultrahigh-molecular-weight polyethylene, the mixing of the ultrahigh-molecular-weight polyethylene with low-molecular-weight or high-molecular-weight polyethylene was proposed.
Japanese patent publication No. 27064/1971 discloses an abrasion-resistant polyethylene resin composition comprising polyethylene having an average molecular weight of at least 500,000 and 20 to 50% by weight of polyethylene having a density of at least 0.940 and an average molecular weight of 30,000 to 120,000.
Japanese Patent Publication No. 41,309/1983 discloses a polyethylene composition comprising 85 to 50 parts by weight of polyethylene having a viscosity average molecular weight of 500,000 to 1,500,000 and 15 to 50 parts by weight of particulate ultrahigh-molecular-weight polyethylene having a viscosity average molecular weight of at least 1,000,000 and a particle size smaller than 10 mesh.
Japanese Laid-Open Patent Publication No. 177,036/1982 discloses an ultrahigh-molecular-weight polyethylene composition having improved moldability comprising 100 parts by weight of ultrahigh-molecular-weight polyethylene having a molecular weight of at least 1,000,000 and 10 to 60 parts by weight of low-molecular-weight polyethylene having a molecular weight of 5,000 to 20,000. The specification of this Laid-Open Publication states that the moldability of the ultrahigh-molecular-weight polyethylene composition is such that in the production of a slab having a thickness of 50 mm by compression molding, it required a molding cycle of 200.degree. C..times.2 hours whereas the ultrahigh-molecular-weight polyethylene alone required a molding cycle of 200.degree. C..times.3 hours; and in ram extrusion molding method, the pipe extrusion speed likewise increased to 10 cm/min. from 5 cm/min.
The moldability of the above ultrahigh-molecular-weight polyethylene composition is improved as stated above, but should be further improved.
Japanese Laid-Open Patent Publication No. 126,446/1984 discloses an ultrahigh-molecular-weight polyethylene resin composition comprising 95 to 50 parts by wight of an ultrahigh-molecular-weight polyethylene resin and 5 to 50 parts by weight of a general-purpose polyolefin resin. The specification of this patent publication discloses a composition comprising a silane-modified polyethylene resin having a melt index of 2.5 or 5.0 g/l0 min. as an actual example of the general-purpose polyolefinic resin. The moldability of the composition is described in Table 1 of this specification, but it is not that the moldability is sufficiently good with regard to all compositions
The above polyethylene resin compositions are all prepared by mixing ultrahigh-molecular-weight polyethylene with polyethylene or a polyolefin having a lower molecular weight.
On the other hand, Japanese Laid-Open patent publication N
REFERENCES:
patent: 4311752 (1982-01-01), Diedrich et al.
patent: 4336352 (1982-06-01), Sakurai et al.
Akana Yoshinori
Ishikawa Hideo
Kondoh Masayuki
Suga Michiharu
Yoshitake Junichi
Mitsui Petrochemical Industries Ltd.
Seccuro Carman J.
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