Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Patent
1988-01-29
1989-07-11
Foelak, Morton
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
264 53, 264DIG5, 264DIG18, 521 79, 521 81, 521 96, 521134, 521139, 521140, 521143, 521146, 521149, 525 80, 525 96, 525 98, 525222, C08J 900
Patent
active
048471500
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an improved foams obtained by mixing polyolefin resins and polystyrene resins in the presence of a hydrogenated styrene/butadiene block copolymer, and then expanding the resultant by use of a blowing agent.
BACKGROUND ART
When plate-like foams of synthetic resins are used as cushioning materials for cushioning packages, there are two principles for achieving the cushioning performances thereof; namely, one of which is based on the buckling destruction of a foam, and the other of which is based on the elastic deformation of a foam, thereby absorbing impact stress to achieve the cushioning ability.
Since said principles utilize the foam properties that are contrary to each other, they have advantages and disadvantages that are contrary to each other, having their own technical fields for cushioning design, and are selectively used depending on what contents are to be cushioned.
Specifically, in the former case where rigid forms typified, for example, by polystyrene resin foams, there is an advantage such that a large load (i.e., a large stress) can be cushioned with relatively smaller supporting area (i.e., with a foam of a small volume), but, on the other hand, there is involved a disadvantage such that the foam cannot endure repeated impacts, or a space formed between contents and foams (i.e. cushioning materials) subjected to buckling deformation may cause "load dislocation", whereby the contents are frictionally damaged. Accordingly, such foams are frequently used for cushioning packages placed under good control during the course of the freight handling, and containing middle class heavy goods having the surface of high hardness.
In contrast, foams having the closed-cell structure, typically foams of polyethylene resins, are suited for use in the field utilizing flexibility and the repeated elastic recovery inherent in the foams of this sort, but are not suitable for cushioning of a large load. If, for example, the density of foams is increased in order to cope with such a difficulty, flexibility will be lost, and moreover, if they are used with increased supporting areas, the packaging style must be made to be of a large scale, resulting in losing economical merits in the various phases accompanied therewith to a great extent. Accordingly, foams of this sort are frequently used for cushioning packages in which only a high cushioning performance for light weight contents is required.
In designing the cushioning for such cushioning packages, improvement of foams which are cushioning materials has been sought after.
For example, if, in the field of the soft foams in which the above elastic deformation is desirably utilized, it be possible to provide foams having higher compression, strength (i.e., compression stress) than the conventional polyethylene foams, while sufficiently keeping the flexible recovery property (i.e., a low density or highly foamed product), it would be expected to widen the field of utilization of elastic cushioning for a larger load (i.e., heavier contents). Accordingly, to accomplish such foams, developments have been made for a long time for foams of resin compositions comprising a mixture of polyolefin resin and polystyrene resin, and also a number of means for mixing them has been proposed.
Since both of these resins are poor in compatibility with each other, it was impossible to obtain foams having good quality. Accordingly, there have been a large number of proposals for improvement of mixing conditions or improvement in how to copolymerize them in order to attain homogeneous dispersion of them.
Of the proposals, what should be noted is a technique disclosed in the specification of European Patent No. 55,460. This discusses how to physically disperse polyolefin resins and polystyrene resins, and mainly discloses a production method showing a mixing condition in which the character of combination of the resins to be mixed is governed by the relation between the ratio (R) of mutual rheological characteristics and the proportion (Y) o
REFERENCES:
patent: 4020025 (1977-04-01), Zeitler et al.
Search Report From PCT/JP 87/00303.
Asahi Kasei Kogyo Kabushiki Kaisha
Foelak Morton
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