Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-07-09
2004-02-03
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S060000, C521S097000, C521S182000
Reexamination Certificate
active
06686400
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to foamed and expanded beads of a polyester-based resin and to a foam molding obtained therefrom.
Foamed plastic moldings are recently used in large amounts mainly as packing receptacles and cushioning materials, because of their lightness in weight, cushioning property, heat insulating property and moldability. These foamed plastic moldings, however, pose a problem of pollution of natural environment by disposal thereof. To cope with this problem, a variety of biodegradable foam moldings have been proposed. For example, Japanese Laid Open Patent Publication No. H06-248106 proposes a method for obtaining a foam molding in which biodegradable aliphatic polyester beads are impregnated with propane and pentane as a blowing agent. The beads are heated with steam to form foamed and expanded beads, which are subsequently molded by heating in a mold cavity. Japanese Laid Open Patent Publication No. H10-324766 discloses a foam molding of an aliphatic polyester having a gel fraction of at least 5% by weight.
The known foamed polyester resin moldings, however, are not fully satisfactory. The foam molding obtained with the method of Japanese publication H06-248106 undergoes considerable shrinkage during the molding step and has poor dimensional stability. While Japanese publication H10-324766 has solved the problem of shrinkage, the foam molding thereof has a problem in resistance to hydrolysis.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide foamed, expanded beads of a polyester-based resin which have excellent resistance to hydrolysis and which can afford foam moldings having excellent heat resistance and excellent resistance to hydrolysis.
Another object of the present invention is to provide foamed, expanded beads of the above-mentioned type which has a low apparent density.
In accomplishing the above objects, the present invention provides foamed and expanded beads comprising:
a base resin including a polyester-based resin containing at least 35 mole % of an aliphatic ester component, and
at least one gel accelerating agent selected from the group consisting of fatty acids having 12-25 carbon atoms, metal salts of the fatty acids, esters of the fatty acids and amides of the fatty acids in an amount of 0.15-3% by weight, said beads having a gel fraction of at least 5% by weight.
In another aspect, the present invention provides a foam molding obtained by heating the above foamed and expanded beads.
The foamed and expanded beads according to the present invention have excellent heat resistance, hydrolysis resistance and moldability as well as biodegradability and exhibit a sufficient expandability while maintaining cell wall strengths, so that there can be produced, with good reproducibility, low-density foam moldings having excellent properties such as good shape recovery by aging, good surface smoothness, strong adhesion between cells and high dimensional accuracy. The foamed and expanded beads according to the present invention permit the production of foam moldings at a lower temperature as compared with those beads which do not contain the gel accelerating agent but contain inorganic particles.
The foamed bead molding obtained using the foamed beads of the present invention is excellent in heat resistance, hydrolysis resistance (especially in hydrolysis resistance under a high temperature and humidity conditions), dimensional stability and appearance. The foam molding also has a high closed cell content and is thus excellent in mechanical strengths such as compressive creep resistance, and cushioning property. Because of these properties, the foam molding is preferably applied to a cushioning material, wrapping material and containers of various types. Also, the foamed bead molding, which has biodegradability and is thus easy to dispose of after use, has great industrial significance.
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments of the invention to follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The foamed and expanded beads including a base resin which comprises a polyester-based resin (hereinafter referred to simply as “expanded beads”) according to the present invention may be prepared by expanding unexpanded beads of the above base resin.
The polyester-based resin which is the essential component of the base resin may be any polyester-based resin containing an aliphatic ester component in the main chain thereof in an amount of at least 35 mole %, preferably 45-100 mole %, more preferably 60-100 mole %. Such a polyester-based resin has biodegradability.
Examples of the polyester-based resin include (a) aliphatic polyesters, such as polybutylene succinate, polybutylene adipate and poly(butylene succinate/adipate), obtained by polycondensation of an aliphatic polyol and an aliphatic polycarboxylic acid, (b) aliphatic-aromatic polyesters, such as poly(butylenesuccinate/terephthalate), obtained by polycondensation of an aromatic polycarboxylic acid, an aliphatic polycarboxylic acid and an aliphatic polyol, as disclosed in published Japanese translation of international patent application (JP-T-H10-505620), (c) ring open polymerization products of lactones such as polycaprolactone, and (d) polycondensation products of hydroxyacids such as hydroxybutyric acid and lactic acid.
Additionally, the polyester-based resin may be a product obtained by treating the above polyester with a coupling agent for increasing the molecular weight thereof, a blend of a plurality of the above polyesters or a copolymer of the above polyester with a carbonic diester.
Examples of the coupling agents include diisocyanates such as 2,4-tolylenediisocyanate, diphenylmethane-diisocyanate, 1,5-naphthylenediisocyanate, xylylenediisocyanate, hydrogenated xylylenediisocyanate, hexamethylenediisocyanate and isophoronediisocyanate; and aryl carbonates such as dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate and m-cresyl carbonate.
Particularly preferred polyester-based resins for use in the present invention are products obtained by polycondensing one or more aliphatic polyols having not more than 4 carbon atoms with one or more aliphatic dicarboxylic acids having not more than 4 carbon atoms.
The base resin may contain one or more additional polymers other than the polyester-based resin, if desired. Examples of such additional polymers include a styrene-butadiene copolymer, a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, a hydrogenated styrene-isoprene-styrene block copolymer, an ethylene-propylene rubber, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyamide, starch and cellulose. The amount of the additional polymer or polymers is not more than 40% by weight, preferably not more than 20% by weight, most preferably not more than 10% by weight, based on the weight of the base resin.
In the production of foamed and expanded beads (hereinafter referred to simply as “expanded beads”) according to the present invention, unexpanded beads of the above base resin are first prepared. The unexpanded beads may be produced by any conventional method. For example, the base resin containing a polyester-based resin is melted and kneaded with an extruder and then extruded into strands. The strands are cooled and then cut into a desired length or are first cut into a suitable length and then cooled to obtain unexpanded beads. The average weight of one polyester-based resin-containing bead may be 1-6 mg, preferably 1-4 mg. When the average weight of the beads is excessively large, a difficulty may be caused in controlling the expansion of the expanded beads at the time of molding in a mold cavity by control of the temperature of a heating medium. Further, too large a weight of the beads may require a long co
Sasaki Hidehiro
Shinohara Mitsuru
Tokiwa Tomoo
Foelak Morton
JSP Corporation
Lorusso, Loud & Kelly
LandOfFree
Foamed and expanded beads of polyester-based resin and foam... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Foamed and expanded beads of polyester-based resin and foam..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Foamed and expanded beads of polyester-based resin and foam... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3295908