Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1990-10-22
1992-05-05
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 505, 521 94, 521 95, 521140, 521915, 523217, 525192, 525193, 525194, 525221, 525222, 525227, 525232, 525240, C08J 914
Patent
active
051108429
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a foam, and more particularly to a sheet-type foam which is cured by an electron beam.
BACKGROUND ART
Electron-beam cured foams have been used as cushioning materials in automobile interiors, and a heat-resisting and heat-insulating materials.
Japanese Patent Laying-Open No. 265935/1988 discloses a cured foam consisting of an olefin resin comprising linear very-low-density polyethylene of more than 10 wt. %. The linear very-low-density polyethylene is made by copolymerizing ethylene with an .alpha.-olefin having more than 4 carbons. According to the disclosure, the olefin resin may be a polymer made from olefin monomers, such as polypropylene, or a copolymer mixture of ethylene/ethylacrylate. The linear very-low-density polyethylene may be composed by a process in which ethylene is copolymerized with an .alpha.-olefin having more than 4 carbons, such as butene-1, hexene-1, octene-1, 4-methylpentene-1, in order to add an appropriate number of short branches to the main linear chains, whereby the density is decreased.
The above document further discloses the following example. Ethylene/propylene random copolymer of 35 parts by weight having density of 0.89 g/cm.sup.3, Melt Index of 7.0 g/10 min, and melting point of 145.degree. C.; high-density polyethylene of 30 parts by weight having density of 0.957 g/cm.sup.3 and MI of 6.5 g/10 min; linear very-low-density ethylene/4-methylpentene-1 copolymer of 35 parts by weight having density of 0.905 g/cm.sup.3 and MI of 0.0 g/10 min; azodicarbonamide, as a foaming agent, of 15 parts by weight; trimethylpropane-trimethacrylate of 3.0 parts by weight; and a heat stabilizer of 0.5 parts by weight were mixed. The mixture was formed into a sheet of 1.5 mm thickness by an extruder. In order to cross-link the sheet, both surfaces were irradiated by an electron beam of 2.0 Mrad in an electron-beam irradiation apparatus. The sheet was then uniformly transported through a hot air stove at 250.degree. C. for heat foaming, whereby a sheet-type foam of about 4 mm in thickness was obtained.
The obtained cross-linked foam is of inferior tensile strength and dimensional stability, although it has good flexibility. That is, a foam produced in direct accordance with the technology disclosed in Japanese Patent Laying-Open No. 265935/1988 results in insufficient tensile strength and insufficient dimensional stability, due to inappropriateness in the selection of resins and the mixing ratio.
Additionally, Japanese Patent Laying-Open No. 155232/1981 and Japanese Patent Laying-Open No. 157839/1983 disclose a resin made of a copolymer of ethylene of which melting point ranges from 117.degree. C. to 123.degree. C. and density ranges from 0.890 g/cm.sup.3 to 0.910 g/cm.sup.3, and an .alpha.-olefin having 4 to 8 carbons. However, this resin is not comprised of 3 components, as in the above example from the prior art.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electro-beam cured sheet-type foam of improved tensile strength and dimensional stability.
It is another object of the present invention to provide an electron-beam cured sheet-type foam of improved tensile strength, dimensional stability and flexibility.
It is yet another object of the present invention to provide an electron-beam cured sheet-type foam of improved tensile strength at high temperatures and increased processability in molding wherein the foam is used in a composite material.
It is a further object of the present invention to provide an electron-beam cured sheet-type foam of improved dimensional stability whereby it may be more suitably used as a cushioning material in the automobile interiors.
It is yet another object of the present invention to provide an electron-beam cured sheet-type foam of improved tensile strength at high temperatures whereby it may be more suitably used as a heat-resisting and heat-insulating foamed material.
According to one aspect of the present invention, an electron-beam cured sheet-type foam comprises
Takeda Masashi
Uejikkoku Nario
Foelak Morton
Toray Industries Inc.
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