Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2001-05-09
2003-04-29
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S080000, C528S083000, C528S084000, C536S047000, C536S055000, C525S450000
Reexamination Certificate
active
06555645
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel polyurethane resin of specific structure obtained by using 2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or a modification product thereof as a bonding agent, and more specifically relates to a novel polyurethane resin having decomposing ability, that is, hydrolyzability and biodegradability and a molded article prepared from the same.
TECHNICAL BACKGROUND
In recent years, environmental pollution due to plastic waste has become a global problem. The greatest cause of the problem lies in the fact that plastics such as polystyrene, polyvinyl chloride, and polypropylene which constitute most of the waste have no biodegradability and thus remain as intact in the soil even after land fill disposal.
When incinerated, plastics have generally large combustion heat and combustion gas causes environmental pollution. Thus, it is difficult to conform to the problem by usual incineration equipment alone. Although recycle has gradually become widespread, a considerably large portion of plastics application area is essentially inadequate for recycle.
On such present situations, development of biodegradable plastic which can decompose under natural environment, has been carried out. Many biodegradable resins have already been known. Representative resins are polyglycolic acid, polylactic acid, polyhydroxybutyric acid, polyhydroxyvaleric acid, polycaprolactone and other polyhydroxycarboxylic acids; and polybutylene succinate, polybutylene adipate and other aliphatic polyesters which can be obtained by polycondensation of polyhydric alcohols and polybasic acids. Other materials which are investigated for application are polysuccinimide and other polyamino acids; molasses, cellulose, modified cellulose, chitin, chitosan and other saccharides and modified materials thereof; resins derived from gelatin, sericin, lignin and other modified proteins; and natural high polymers from vegetable oils.
However, in order to substitute the above biodegradable resins for conventionally used resins in many application fields, physical, mechanical or chemical properties are still unsatisfactory. Particularly, polylactic acid is the sole colorless and transparent plastic in the biodegradable resins and is excellent in the tensile strength. On the other hand, polylactic acid has low elasticity and elongation and is disadvantageous in brittleness. Further, many of these plastics have difficulty in preparation and thus many improvements have been carried out.
One of these improvements is a process for reacting an aliphatic polyester oligomer with a polyisocyanate compound. For example, a process for preparing aliphatic polyester by reacting polylactide with polyisocyanate has been disclosed in Japanese Laid-Open Patent HEI 5-148352. Examples for using a polyisocyanate compound as a bonding agent of polyhydric alcohol and polybasic acid in the preparation of aliphatic polyester have been described in Japanese Laid-Open Patent HEI 4-189822 and 6-157703. Examples for bonding saccharides with polyisocyanate have been disclosed in Japanese Laid Open-Patent HEI 9-302061. However, the polyisocyanate compounds used in these patents generally have high toxicity and diamine which develops by decomposition of isocyanate is also hazardous to natural environments. Consequently, hexamethylene diisocyanate or isophorone diisocyanate which is not so hazardous to natural environments has been used in Japanese Laid Open Patent HEI 5-70543 and 5-50575. However, hexamethylene diisocyanate leads to operation difficulty due to high vapor pressure in preparing biodegradable resins, and the resulting resin is disadvantageous in low breaking strength and breaking strength, though excellent in elongation.
On the other hand, isophorone diisocyanate differs in the activity of the two isocyanate groups and has a very low reaction velocity which causes problems on preparing the biodegradable resin.
The subject of the present invention is to provide, in view of the problems in the conventional technology, a novel degradable resin having improved properties as compared with conventional biodegradable resin. Another subject of the invention is to provide a resin and a molded product thereof which can be safely abandoned in the natural environment as compared with conventional technology, can be obtained under mild reaction conditions and have decomposability, that is, hydrolyzability and biodegradability.
DISCLOSURE OF THE INVENTION
As a result of an intensive investigation in order to achieve the above subjects, the present inventors have found that a polyurethane resin obtained by using 2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane (hereinafter referred to simply as NBDI) which is no mutagenicity in corresponding amine as a bonding agent of the degradable resin can surprisingly enhance elongation and elasticity while maintaining or improving the strength of the known biodegradable resin and that a biodegradable polyurethane resin can be prepared under mild conditions. Thus, the present invention has been completed.
That is, the aspects of the invention can be illustrated by the following items.
(1) A degradable polyurethane resin characterized by resulting from reaction of polyol with 2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by the formula (1);
wherein the two isocyanatomethyl groups are located on 2,5-positions or 2,6-positions or a mixture thereof, and/or a modified compound thereof, wherein the polyol is a single compound or a mixture or a copolycondensate of one or more compounds selected from the group consisting of (A) polyhydroxycarboxylate polyol, (B). aliphatic polyester polyol and (C) saccharides, or (D) straight or branched polyol resulting from condensation of (A) and/or (B) with aliphatic polyhydric alcohol having functionality of three or more,
(2) A degradable polyurethane resin according to the above item (1) wherein the polyhydroxycarboxylate polyol is obtained by modification of the terminal carboxyl group to a hydroxyl group in the aliphatic polyhydroxycarboxylic acid represented by the formula (2);
wherein R
1
is an alkylene group having 1 to 4 carbon atoms in the straight chain portion and having 1 to 6 total carbon atoms which include branched alkyl groups, and m is an integer of 1 or more.
(3) A degradable polyurethane resin according to the above item (2) wherein R
1
in the formula (2) is an alkylene having 1 carbon atom, alkylene having 1 carbon atom in the straight chain portion and substituted by methyl, ethyl or propyl, or having 2 carbon atoms in the straight chain portion and substituted by methyl or ethyl, or having 3 carbon atoms in the straight chain portion and substituted by methyl, and R
1
in the formula (2) is aliphatic polyhydroxycarboxylate polyol comprising the same or different structural units,
(4) A degradable polyurethane resin according to the above item (1) wherein aliphatic polyester polyol is obtained by reacting a single compound or mixture selected from aliphatic polyhydric alcohol represented by the formula (3);
HO—R
2
—OH (3)
wherein R
2
is an unsubstituted or substituted aliphatic hydrocarbon group having 2 to 20 carbon atoms, with a single compound or mixture selected from aliphatic polybasic acid represented by the formula (4);
HOOC—R
3
—COOH (4)
wherein R
3
is an unsubstituted or substituted aliphatic hydrocarbon group having 2 to 20 carbon atoms,
(5) A degradable polyurethane resin according to the above item (1) wherein saccharides are a single compound or mixture selected from monosaccharide, molasses, cellulose or cellulose derivative.
(6) A degradable polyurethane resin according to the above item (1) wherein the aliphatic polyhydric alcohol having three or more functionality is a single compound or mixture selected from the compounds represented by the formula (5);
R
4
(OH)
n
(5)
wherein R
4
is a hydrocarbon group having 1 to 20 carbon atoms and n is an integer of 3 to 6.
(7) A degradable polyurethane resin according to the abo
Ikeda Kan
Matsuno Hiroaki
Sato Naoki
Burns Doane , Swecker, Mathis LLP
Gorr Rachel
Mitsui Chemicals Inc.
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