Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1990-12-20
1993-01-19
Ziegler, Jacob
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 86, 525316, C08L 902, C08L 906
Patent
active
051807793
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an internal box of a refrigerator which has excellent flon resistance. More specifically, the present invention relates to an internal box of a refrigerator which is endowed with anti-flon property such as high stress cracking resistance, particularly against HCFC-123 and HCFC-141b, by using a high nitrile content thermoplastic resin having a specific composition. The term "flon" is used in the same meaning as a fluorinated/chlorinated hydrocarbon.
In addition, the phraseology "an internal box of a refrigerator" includes the interior of a door of the refrigerator.
BACKGROUND ART
The housing of a refrigerator recently used is one formed as a thermal insulation housing manufactured by a method wherein a space between an internal box and an external box which has been constructed by combining the two boxes is filled with a foam produced by injecting, foaming and solidifying a rigid polyurethane foam stock within the space (referred to hereinafter as in-situ foaming method). Also in the door of the refrigerator, a rigid polyurethane foam is charged as a thermal insulator by the in-situ method between the space which has been constructed by combining the internal and external boxes.
Hitherto, an ABS resin widely used for various purposes has been primarily used as the internal box of a refrigerator. The phraseology "ABS resin widely used for various purposes" means a resin composition which is obtained polymerizing a monomer mixture of 10-40% by weight of a of a vinyl cyanide compound and 60-90% of an aromatic vinyl compound in the presence poly(conjugated diene) synthetic rubber or, in other words, by graft copolymerizing the monomer mixture; or a resin composition in which a copolymer of a vinyl cyanide compound/aromatic vinyl compound is blended with the graft copolymer so that the content of the vinyl cyanide compound is in the range of 10-40% by weight.
As the reason why an ABS resin has been used as a material of an internal box of a refrigerator, there are mentioned a high balance of physical properties such as rigidity and impact property, easy formability, excellent glossy appearance and stress cracking resistance against a flon such as CFC-11 (trichloromonofluoromethane) which is a foaming agent for a rigid polyurethane foam. The internal box of a refrigerator is produced by a heat forming method of a thermoplastic resin sheet, for example by a vacuum forming technique, so that the sheet should have easy formability, particularly vacuum formability. The internal box obtained by the vacuum forming has an average thickness of less than 1 mm, and thus it should have high modulus in order to avoid deformation. If a rigid polyurethane foam is charged into a space which is formed by combining an internal box made of the ABS resin with an external box made of a steel sheet by the in-situ method, the rigid polyurethane foam adheres to the ABS resin and the steel sheets thus causing stress attributed to the difference in the linear expansion coefficients of the steel sheet/rigid polyurethane foam/ABS resin during the operation of the refrigerator. Therefore, the internal box should have stress cracking resistance against CFC-11 as a foaming agent for the rigid polyurethane foam. As notch effect is produced by the adhesion of the rigid polyurethane foam, the internal box is required to have a high notched Izod impact value. Furthermore, excellent gloss is required in order to improve the appearance of the refrigerator.
CFC-11 as a foaming agent for a rigid polyurethane foam contains chlorine and is non-decomposable. Thus, it is suspected that it can destroy the ozone stratum in the stratosphere and there is thus a worldwide trend to the restriction of its use. As an alternative to CFC-11 for use as a foaming agent for a rigid polyurethane foam, another fluorinated/chlorinated hydrocarbon such as HCFC-123 (1-hydro-1,1-dichloro-2,2,2-trifluoroethane) is now to be used. However, HCFC-123 has by far a higher solubility of an ABS resin therein than CFC-11, and the
REFERENCES:
patent: 3819762 (1974-06-01), Howe
patent: 3963807 (1976-06-01), Howe
Database WPIL, Accession No. 83-737303, Derwent Publications Ltd., London, GB.
Database Chemical Abstracts, vol. 82, No. 24, 1975, Abstract No. 157294q.
Kamoshita Ryuji
Kashiwagi Hiroki
Takimoto Koji
Monsanto Kasei Company
Ziegler Jacob
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