Compositions: coating or plastic – Coating or plastic compositions – Carbohydrate or derivative containing
Reexamination Certificate
2002-09-13
2003-12-30
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Carbohydrate or derivative containing
C106S015050, C106S016000, C106S162100, C106S205010, C264S330000, C264S331110, C424S078090, C523S122000, C524S027000, C524S055000, C524S056000
Reexamination Certificate
active
06669771
ABSTRACT:
TECHNICAL FIELD
The present invention relates to biodegradable resin compositions. More specifically, the present invention relates to a biodegradable resin composition that can be produced at reduced cost while maintaining the strength and physical properties of the biodegradable resin; a biodegradable resin composition with improved biodegradability; and a resin composition having an additional useful function.
BACKGROUND ART
Plastics have conventionally been used in a wide variety of fields because they are lightweight, durable and excellent in molding processability. On the other hand, however, plastics decompose very little under natural environmental conditions. Therefore, if disposed of by underground burial, plastics remain almost permanently. If plastics are disposed of by incineration, problems arise such as the generation of toxic gas or damage to the incinerator. The disposal of plastics has been focused on as an environmental problem.
Therefore, with the purpose of protecting the global environment, there have been active attempts to develop biodegradable resins. Biodegradable resins are currently classified into the following groups:
chemically synthesized resins such as polycaprolactone, polylactic acid, polyvinyl alcohol, polybutylene succinate and copolymers thereof;
microbially produced resins such as polyhydroxybutyrate/valerate copolymers; and
natural product-derived resins such as acetyl cellulose.
Further, there is a proposal to add starch or processed starch to these resins in order to reduce the cost and improve biodegradability (Japanese Unexamined Patent Publications Nos. 14228/1990, 31333/1991, 248851/1992, 331315/1993 and 207047/1994).
The addition of starch, etc. to biodegradable resin improves biodegradability but severely reduces strength, elongation (%) and like mechanical properties required of the resin composition and moldings thereof, thus causing the problem that the resulting products become fragile. Therefore, in reality, there is a limitation on the proportion of starch to resin and the desired cost reduction has not yet been achieved.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a biodegradable resin composition with improved biodegradability while substantially maintaining the mechanical properties of the biodegradable resin. Another object of the invention is to provide a biodegradable resin composition that can be produced at reduced cost while substantially maintaining the mechanical properties of the biodegradable resin. A further object of the invention is to provide a biodegradable resin composition with an additional useful function while substantially maintaining the mechanical properties of the biodegradable resin.
The present inventors carried out intensive research day and night to achieve the above objects and found that the addition of a mannan digestion product to a biodegradable resin can provide a resin composition with improved biodegradability and furthermore can produce the resin composition and moldings thereof at a lower cost than the single use of biodegradable resin while the mechanical properties of the resin composition and moldings thereof are substantially equivalent to those of the biodegradable resin and moldings thereof. The inventors further found the following specific effect of the resin composition comprising a biodegradable resin and a mannan digestion product: the resin composition can adsorb bacteria to different degrees depending on the mannan digestion product content of the resin composition. The inventors confirmed that various products with antimicrobial barrier properties can be produced by using the above-mentioned resin composition. The bacterial adsorption or adhesion peculiar to the resin composition of the invention is presumably one of the causes of the excellent biodegradability of the resin composition of the invention. The present invention has been developed based on these novel findings. More specifically, the invention provides the following biodegradable resin compositions:
Item 1. A biodegradable resin composition comprising a biodegradable resin and a mannan digestion product.
Item 2. The biodegradable resin composition according to item 1 wherein the biodegradable resin is an aliphatic polyester.
Item 3. The biodegradable resin composition according to item 1 wherein the biodegradable resin is at least one member selected from the group consisting of polyhydroxybutyrate, polylactic acid, polycaprolactone, polybutylene succinate, polybutylene succinate/adipate, polybutylene succinate carbonate, polyvinyl alcohol and cellulose acetate.
Item 4. The biodegradable resin composition according to item 1 wherein the biodegradable resin is a polylactic acid polymer.
Item 5. The biodegradable resin composition according to item 4 wherein the polylactic acid polymer is a a homopolymer or copolymer of lactic acid (polylactic acid), or at least one copolymer of lactic acid and at least one member selected from the group consisting of cyclic lactone, glycolic acid, &agr;-hydroxybutyric acid, &agr;-hydroxyisobutyric acid, &agr;-hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid, hydroxyoctanoic acid, ethylene glycol, polyethylene glycol, 1,4-butanediol, succinic acid and sebacic acid.
Item 6. The biodegradable resin composition according to item 1 wherein the biodegradable resin is a polylactic acid.
Item 7. The biodegradable resin composition according to item 1 wherein the biodegradable resin has a number average molecular weight of 20,000 or more and a melting point of 70° C. or higher.
Item 8. The biodegradable resin composition according to item 1 wherein the mannan digestion product is at least one member selected from the group consisting of mannooligosaccharides, galactomannan digestion products and glucomannan digestion products.
Item 9. The biodegradable resin composition according to item 1 wherein the proportion of the mannan digestion product is 0.05 to 40 wt. % relative to 100 wt. % of the biodegradable resin.
Item 10. The biodegradable resin composition according to item 1 wherein the proportion of the mannan digestion product is 1 to 40 wt. % relative to 100 wt. % of the biodegradable resin.
Item 11. The biodegradable resin composition according to item 1 which further comprises a crystal nucleating agent.
Item 12. The biodegradable resin composition according to item 11 wherein the crystal nucleating agent is at least one member selected from the group consisting of talc, boron nitride, calcium carbonate, magnesium carbonate and titanium oxide.
The present invention further provides moldings produced by molding the above biodegradable resin compositions. Such moldings include, for example, biodegradable products and products with antimicrobial barrier properties.
BEST MODE FOR CARRYING OUT THE INVENTION
The mannan digestion product used in the present invention is a compound formed by the digestion of mannan and comprising mannose.
Mannans are polysaccharides mainly consisting of mannose and include those classified into the following classes:
(1) Plant-derived mannans: such mannans include copra meal and flakes from coconut palms, Heacra Palm (a plant of the palm family originating in South Africa), tsukuneimo (a type of yam) mannan, and yamaimo (Japanese yam) mannan.
(2) Glucomannans: polysaccharides comprising glucose and mannose. Such mannans include, for example, mannans from konjac tubers, lily, narcissus and the subterranean stem of Lycoris radiata.
(3) Galactomannans: polysaccharides comprising galactose and mannose. Such mannans include, for example, mannans from locust bean gum, soybean hulls derived from soybean seed coat, tamson gum, tara gum, guar gum, etc.
(4) Other mannans: mannans composed of mannose and at least two other sugars. Such mannans include D-galacto-D-gluco-D-mannan contained in the wood of conifers, and mannan from xanthan gum, etc.
The mannan digestion product used in the present invention can be obtained by digesting various mannans, including those exemplified above, using a suita
Tokiwa Yutaka
Tsuchiya Akihito
Green Anthony J.
Knobbe Martens Olson & Bear LLP
National Institute of Advanced Industrial Science and Technology
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