Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Patent
1996-09-23
1999-08-17
Raimund, Christopher
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
264 454, B32B 326
Patent
active
059391804
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a thermoplastic resin foam and a method of preparing the same.
BACKGROUND TECHNIQUE
A thermoplastic resin foam, which is light and excellent in heat insulation, flexibility and formability etc., is widely employed in various heat insulators such as a roof insulator or a floor insulator, a cushioning material, and various interior materials such as an interior material for a vehicle.
In general, a method carrying out a step of pre-expanding thermoplastic resins for obtaining expandable beads and then carrying out a step of charging the expandable beads in a mold for secondarily expanding the same and fusing the beads with each other thereby obtaining a molding is known as a method of preparing the aforementioned thermoplastic resin foam.
In the foam molding which is obtained by the aforementioned method of preparing a thermoplastic resin foam, however, strength, particularly bending strength is disadvantageously insufficient. In the bead foam molding which is obtained from the aforementioned expandable beads, for example, a non-expandable thin film is formed on the surface of each bead. Therefore, high compressive strength can be expected in the foam molding which is obtained by this method. In the bead foam molding, however, the aforementioned expandable beads are charged in a mold and thereafter secondarily expanded and fused with each other to be formed, and hence fusion power between the beads is low. When a bending load is applied to the foam molding, therefore, separation and/or breakage are readily caused in the fusion interfaces between the beads, leading to insufficient bending strength.
Japanese Patent Laid-Open No. 4-16330 discloses a method of improving the bending strength of a foam molding which is obtained by the aforementioned bead expanding method. In the method disclosed in this prior art, expandable beads which are obtained by pre-expanding thermoplastic resins are compressively charged in a mold and thereafter degassing steam having a pressure which is higher by at least 0.2 kg/cm.sup.2 than that in the mold is introduced into the mold for secondarily expanding/fusing the same, thereby improving fusion power between the beads. In the method described in this prior art, however, the foam molding obtained by forming is pressurized by the degassing steam. In order to prevent reduction of steam flows between the expandable beads resulting from excess compression, therefore, the pressure of the degassing steam cannot be much increased. Thus, the fusion power between the beads cannot be sufficiently increased, and hence it has been still difficult to obtain a foam molding having sufficient bending strength.
Also in the method described in the aforementioned prior art, in addition, two steps including that of pre-expanding the expandable beads and secondarily expanding and fusing the pre-expanded expandable beads in the mold must be executed, leading to a problem of low productivity.
OBJECTS OF THE INVENTION
A principal object of the present invention is to provide a thermoplastic resin foam which is light, excellent in bending strength, and excellent in balance between compressive strength and compression permanent strain, and a method of preparing the same.
Another object of the present invention is to provide a method of preparing a thermoplastic resin foam having homogeneous and fine cells therein.
DISCLOSURE OF THE INVENTION
According to a wide aspect of the present invention, provided is a foam which is characterized in that high expanded foams consisting of thermoplastic resins whose overall outer surfaces are covered with low-expanded-foam thin layers consisting of thermoplastic resins are thermally fused through the low-expanded-foam thin layers.
In the foam according to the present invention, expandable thermoplastic resin pellets or annular substances are expanded and thermally fused with each other, as described later. At this time, voids may be formed between the low-expanded-foam thin layers, or holes may be formed as the
REFERENCES:
patent: 2983692 (1961-05-01), D'Alelio
patent: 2983962 (1961-05-01), Merz et al.
patent: 3914359 (1975-10-01), Bevan
Kobayashi Tomoyuki
Miyazaki Kenji
Sasayama Michiaki
Raimund Christopher
Sekisui Kagaku Kogyo Kabushiki Kaisha
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