RESIN COMPOSITION
TECHNICAL FIELD
The present invention relates to a resin composition containing a resin containing, as a main component, a water-soluble monomer and having autocatalysis (component A) and a hydrolysis regulator (component B).
BACKGROUND ART
In recent years, from the purpose of global environmental protection, resins which are easily decomposed under the natural environment are watched and studied in the world. As the resins which are easily decomposed under the natural environment, biodegradable polymers represented by aliphatic polyesters, such as polylactic acid, polyglycolic acid, poly(3-hydroxybutyrate), polycaprolactone, etc., are known.
Above all, polylactic acid is a polymer material that is high in biological safety and environmentally friendly because it is made of, as a raw material, from lactic acid obtained from a plant-derived raw material, or a derivative thereof. For that reason, utilization as a general-purpose polymer is investigated, and utilization as films, fibers,
1

injection molded articles, and the like is investigated.
Recently, paying attention to easy decomposability of those resins and water solubility of decomposed monomers, practical use for excavation technology in the oil field is investigated (Patent Literatures 1 to 3) . In this application, it is required that after keeping the weight and shape of a resin in hot water for a fixed period of time, the resin is quickly decomposed (see Fig. 1) . However, in general, since aliphatic polyesters and the like are inferior in hydrolysis resistance, though they are usable up to a medium temperature of about 120°C, there is involved such a problem that they are immediately decomposed in high-temperature hot water (see Fig. 2), so that a desired performance cannot be exhibited.
Slowly decomposable resins, such as aromatic polyesters, etc., are not quickly decomposed even in hot water (see Fig. 3), and furthermore, there is involved such a problem that monomers generated by decomposition react with other components of the foregoing application and are deposited in water (Patent Literature 4) . With respect to the high temperature, there are various definitions, such as "127°C to 193°C" described in the report: U.S. Shale Gas, published in 2008 by Halliburton Company, "14 9°C or higher" described in Oil and Gas Review, 2002.5, published by Japan Oil, Gas and Metals National Corporation, etc., and in general, the high temperature is considered to be higher than "125°C to 150°C".
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Incidentally, in the present invention, a temperature higher than 135°C is referred to as "high temperature".
Meanwhile, in order to enhance the hydrolysis resistance of aliphatic polyesters and the like, there is already proposed a method in which a hydrolysis regulator, such as a carbodiimide compound, etc., is used, and an acidic group generated at the early stage and by decomposition in the resin is sealed, thereby inhibiting the hydrolysis (Patent Literatures 4 to 6).
The acidic group generated by hydrolysis of the aliphatic polyester, such as a carboxyl group, etc., becomes an autocatalyst to promote the hydrolysis, and therefore, it is confirmed that by immediately sealing this by a carbodiimide compound or the like, the hydrolysis resistance under the moist heat environment at about 50 to 120°C is enhanced.
However, with respect to the hydrolysis inhibition in
hot water at a higher temperature than 135°C, there are not made sufficient investigations from the viewpoints of resin or hydrolysis regulator.
In the light of the above, it is the actual situation that a resin composition exhibiting a desired performance as shown in Fig. 1 in hot water at a higher temperature than 135°C has not been obtained yet in the excavation technology in the oil field.
In addition, in the application of the excavation technology in the oil field, it is required that after keeping
3

the weight and shape of a resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., for a fixed period of time, the resin is quickly decomposed (see Fig. 5). However, in general, since aliphatic polyesters and the like are inferior in hydrolysis resistance, though they are usable in approximately neutral hot water, they are quickly decomposed in strongly acidic or basic hot water (see Fig. 6) , so that there is involved such a problem that a desired performance cannot be exhibited.
In addition, slowly decomposable resins, such as aromatic polyesters, etc., are not quickly decomposed even in strongly acidic or basic hot water (see Fig. 3), and furthermore, there is involved such a problem that monomers generated by decomposition react with other components of the foregoing application and are deposited in water.
JP-A-2009-114448
U.S. Patent No. 7267170
U.S. Patent No. 7228904
U.S. Patent No. 7275596
JP-A-2012-012560
JP-A-2009-173582
JP-A-2002-30208
CITATION LIST PATENT LITERATURE
Patent Literature 1:
Patent Literature 2:
Patent Literature 3:
Patent Literature 4:
Patent Literature 5:
Patent Literature 6:
Patent Literature 7:
4

SUMMARY OF INVENTION TECHNICAL PROBLEM
An object of a first invention of the present application is to solve the above-described problems of the background art and to provide a resin composition which is quickly decomposed after keeping the weight and shape of the resin in hot water at a higher temperature than 135°C for a fixed period of time.
In addition, an object of a second invention of the present application is to provide a resin composition which is quickly decomposed after keeping the weight and shape of the resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., for a fixed period of time.
SOLUTION TO PROBLEM
The present inventors made extensive and intensive investigations regarding a resin composition which Is quickly decomposed after keeping the weight and shape of the resin in hot water at a higher temperature than 135°C for a fixed period of time.
As a result, it has been found that in the case where a concentration of an acidic group can be kept low by using a resin containing, as a main component, a water-soluble monomer and having autocatalysis, hydrolysis is inhibited
5

during that time, and a decrease of the molecular weight becomes gentle, so that the weight and shape are kept, and at a point of time when a concentration of the acidic group cannot be kept low, decomposition of the resin is rapidly promoted (see Fig. 4) .
As a result of making further investigations, it has been found that when a hydrolysis regulator in which not only water resistance at 120°C is 95% or more, but also reactivity with an acidic group at 190°C is 50% or more is used for sealing the acidic group, a concentration of the acidic group can be efficiently kept low in hot water at a higher temperature than 135°C, and a timing of rapid decomposition of the resin can be controlled according to its addition amount.
That is, it has been found that when a resin containing, as a main component, a water-soluble monomer and having autocatalysis and a hydrolysis regulator in which not only water resistance at 120°C is 95% or more, but also reactivity with an acidic group at 190°C is 50% or more are compounded, the resultant is quickly decomposed after keeping the weight and shape of the resin in hot water at a higher temperature than 13 5°C for a fixed period of time, leading to accomplishment of the present invention.
Specifically, according to the present invention, the following resin composition is provided. (1) A resin composition containing a resin containing, as
6

a main component, a water-soluble monomer and having autocatalysis (component A) and a hydrolysis regulator (component B) , the resin composition satisfying any one of the following Al to A3:
Al: In hot water at an arbitrary temperature of 135°C to 160°C, after 3 hours, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less; A2: In hot water at an arbitrary temperature of 160°C to 180°C, after 1 hour, not only a resin composition-derived acidic group concentration is 30 eguivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less; and A3: In hot water at an arbitrary temperature of 180°C to 220°C, after 1 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less.
The following are also included in the present invention. (2) The resin composition as set forth above in (1) , wherein the component B has water resistance at 120°C of 95% or more
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and reactivity with an acidic group at 190°C of 50% or more.
(3) The resin composition as set forth above in (1) or (2),
wherein in hot water at an arbitrary temperature of 135°C to
220°C, after 100 hours, the weight of the water-insoluble
matter of the resin composition is 10% or less.
(4) The resin composition as set forth above in any one of
(1) to (3) , wherein a heat deformation temperature of the resin
composition is 135°C to 300°C.
(5) The resin composition as set forth above in any one of
(1) to (4), wherein the component A is a polyester.
(6) The resin composition as set forth above in (5) , wherein
a main chain of the component A is composed mainly of a lactic
acid unit represented by the following formula (1):

M
CH3
(1)
(7) The resin composition as set forth above in (6), wherein the component A contains a stereocomplex phase formed of poly(L-lactic acid) and poly(D-lactic acid).
(8) The resin composition as set forth above in any one of {1} to (7) , wherein the component B is a carbodiimide compound.
(9) The resin composition as set forth above in (8) , wherein the component B is a carbodiimide compound represented by the following formula (2):
8


(2)
(In the formula, each of Rx to R4 is independently an aliphatic group having 1 to 20 carbon atoms, an aiicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; each of X and Y is independently a hydrogen atom, an aliphatic group having 1 to 20 carbon atoms, an aiicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; and the respective aromatic rings may be bonded to each other via a substituent to form a cyclic structure.)
(10) The resin composition as set forth above in (9), wherein the component B is bis(2,6-diisopropylphenyl)carbodiimide.
(11) The resin composition as set forth above in (8) , wherein the component B is a carbodiimide compound composed of a repeating unit represented by the following formula (3):

(3)
(In the formula, each of R5 to R7 is independently an aliphatic group having 1 to 20 carbon atoms, an aiicyclic group having
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3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom. )
(12) A molded article comprising the resin composition as set forth above in any one of (1) to (11).
(13) A fiber comprising the resin composition as set forth above in any one of (1) to (11).
In addition, the present inventors also made extensive and intensive investigations regarding a resin composition which is quickly decomposed after keeping the weight and shape of the resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., for a fixed period of time.
As a result, it has been found that in the case where a concentration of an acidic group in a polymer can be kept low by using an aliphatic polyester containing, as a main component, a water-soluble monomer, hydrolysis is inhibited during that time, and a decrease of the molecular weight becomes gentle, so that the weight and shape of a resin are kept to some extent during that time, and at a point of time when a concentration of the acidic group in the polymer cannot be kept low, decomposition of the resin is rapidly promoted (see Fig. 8) .
As a result of making further investigations, it has been found that when a hydrolysis regulator satisfying specified requirements is used for sealing the acidic group, a
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concentration of the acidic group can be efficiently kept low in hot water under a chemically severe condition, such as an acidic or basic condition, etc., and a timing of rapid decomposition of the resin can be controlled according to its addition amount.
Then, it has been found that when an aliphatic polyester containing, as a main component, a water-soluble monomer is compounded with a hydrolysis regulator whose reactivity with the acidic group satisfies specified requirements, the resultant is quickly decomposed after keeping the weight and shape of a resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., for a fixed period of time, leading to accomplishment of a second invention of the present application.
Specifically, according to the second invention of the present application, the following resin composition is provided.
(14) A resin composition including an aliphatic polyester
containing, as a main component, a water-soluble monomer
(component C) and a hydrolysis regulator having reactivity
with an acidic group in a 15% hydrochloric acid aqueous solution
at 100°C of 30% or more (component D) , the resin composition satisfying any one of the following Jl to J2:
Jl: In the 15% hydrochloric acid aqueous solution at 100°C, after 6 hours, a weight average molecular weight retention rate
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of the resin composition is 50% or more, and after 24 hours, a weight of a water-insoluble matter of the resin composition is 50% or less; and
J2 : In the 15% hydrochloric acid aqueous solution at 120°C, after 1 hour, a weight average molecular weight retention rate of the resin composition is 50% or more, and after 24 hours, a weight of a water-insoluble matter of the resin composition is 50% or less.
In addition, the following are also included in the second invention of the present application.
(15) The resin composition as set forth above in (14) , wherein after 72 hours, the weight of the water-insoluble matter of the resin composition is 1% or less.
(16) The resin composition as set forth above in (14) or (15), wherein a main chain of the component A is composed mainly of a lactic acid unit represented by the following formula (1) :

/HO
_L0 c—C
\ CH3
(1)
(17) The resin composition as set forth above in any one of
(14) to (16), wherein the hydrolysis regulator (component D)
is at least one member selected from a carbodiimide compound
and an epoxy compound.
(18) A molded article comprising the resin composition as set
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forth above in any one of (14) to (16).
ADVANTAGEOUS EFFECTS OF INVENTION
The resin composition of the first invention of the present invention can be quickly decomposed after keeping the weight and shape of the resin in hot water at a higher temperature than 135°C for a fixed period of time.
Furthermore, since the resin containing, as a main component, a water-soluble monomer and having autocatalysis is used, the resin composition is efficiently dissolved in high-temperature hot water after decomposition, and it is possible to significantly reduce deposition or the like to be caused due to a reaction with other component, which is considered to be problematic in a part of aromatic polyesters. By using the hydrolysis regulator in which not only water resistance at 120°C is 95% or more, but also reactivity with an acidic group at 190°C is 50% or more in order to seal the acidic group, steady decomposition inhibition can be achieved, and a timing of decomposition of the resin in high-temperature hot water can be controlled according to its addition amount.
For that reason, the resin composition of the present invention exhibits a desired performance in the excavation technology in the oil field and can be suitably used as resin molded articles of this application, especially fibers.
The resin composition of the second invention of the
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present application can be quickly decomposed after keeping the weight and shape of the resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., for a fixed period of time.
Furthermore, since the aliphatic polyester containing, as a main component, a water-soluble monomer is used, the resin composition is efficiently dissolved in water after decomposition, and it is possible to significantly reduce deposition or the like to be caused due to a reaction with other component, which is considered to be problematic in a part of aromatic polyesters. By using the hydrolysis regulator satisfying the requirement specified in the present application in order to seal the acidic group, the hydrolysis regulator continues to exhibit a decomposition inhibition performance at a fixed level so long as it exists in the resin composition, and therefore, a timing of decomposition of the resin in high-temperature hot water can be controlled according to the addition amount of the hydrolysis regulator.
For that reason, the resin composition of the present invention exhibits a desired performance in the excavation technology in the oil field and can be suitably used as resin molded articles of this application.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is an image view in which in the case of using
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a resin in hot water at a higher temperature than 135°C, the resin is quickly decomposed after keeping the weight and shape of the resin for a fixed period of time and shows a behavior which is achieved in the resin composition of the first invention of the present application.
Fig. 2 is an image view in which in the case of using a resin in hot water at a higher temperature than 135°C, decomposition is rapidly advanced from the early stage and is concerned with a behavior in a general aliphatic polyester.
Fig. 3 is an image view in which in the case of using a resin in hot water at a higher temperature than 135°C, decomposition is rapidly advanced from the early stage and is concerned with a behavior in a general aromatic polyester.
Fig. 4 is an image view in which in the case of using a resin in hot water at a higher temperature than 135°C, changes in a molecular weight (m) and an acidic group amount (g) necessary for achieving a behavior of a change of a weight (w) of the resin as in Fig. 1 are expressed and is concerned with a behavior which is achieved in the resin composition of the first invention of the present application.
Fig. 5 is an image view in which in the case of using a resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., the resin is quickly decomposed after keeping the weight and shape of the resin for a fixed period of time and is concerned with a behavior which
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is achieved in the resin composition of the second invention of the present application.
Fig. 6 is an image view in which in the case of using a resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., decomposition is rapidly advanced from the early stage and is concerned with a behavior in a general aliphatic polyester.
Fig. 7 is an image view in which in the case of using a resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc. , decomposition is rapidly advanced from the early stage and is concerned with a behavior in a general aromatic polyester.
Fig. 8 is an image view in which in the case of using a resin in hot water under a chemically severe condition, such as an acidic or basic condition, etc., changes in a molecular weight (m) and an acidic group amount (g) necessary for achieving a behavior of a change of a weight (w) of the resin as in Fig. 5 are expressed and is concerned with a behavior which is achieved in the resin composition of the second invention of the present application.
DESCRIPTION OF EMBODIMENTS
The first invention of the present application is hereunder explained in detail. 1. A resin composition containing a resin containing, as
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a main component, a water-soluble monomer and having autocatalysis (component A) and a hydrolysis regulator (component B) , the resin composition satisfying any one of the following Al to A3:
Al: In hot water at an arbitrary temperature of 135°C to 160°C, after 3 hours, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less;
A2: In hot water at an arbitrary temperature of 160°C to 180°C, after 2 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less; and
A3: In hot water at an arbitrary temperature of 180°C to 220°C, after 1 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less.
In the present invention, in the resin containing, as
17

a main component, a water-soluble monomer and having autocatalysis (component A), the monomer generated by decomposition exhibits solubility in water, and the resin in which an acidic group generated by decomposition has autocatalysis, or at least a part of ends of the resin is sealed by the component B.
The term "water-soluble" referred to herein means that the solubility in water at 25°C is 0.1 g/L or more. From the viewpoint that the resin composition to be used does not remain in water after decomposition, the solubility in water of the water-soluble monomer is preferably 1 g/L or more, more preferably 3 g/L or more, and still more preferably 5 g/L or more.
The "main component" means that it occupies 90 mol% or more of the constituent components. A proportion of the main component is preferably 95 to 100 mol%, and more preferably 98 to 100 mol%.
As the component A, at least one member selected from the group consisting of polyesters, polyamides, polyamide-imides, polyimides, polyurethanes, and polyester amides is exemplified. Preferably, polyesters are exemplified.
Examples of the polyester include polymers or copolymers obtained by polycondensing at least one member selected from a dicarboxylic acid or an ester forming derivative thereof,
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a diol or an ester forming derivative thereof, a hydroxycarboxylic acid or an ester forming derivative thereof, and a lactone. Preferably, polyesters composed of a hydroxycarboxylic acid or an ester forming derivative thereof are exemplified. More preferably, aliphatic polyesters composed of a hydroxycarboxylic acid or an ester forming derivative thereof are exemplified.
Such a thermoplastic polyester may contain a crosslinking structure generated by being treated with a radical generating source, for example, an energy active ray, an oxidizing agent, etc., from the standpoint of moldability or the like.
Examples of the dicarboxylic acid or its ester forming
derivative include aromatic dicarboxylic acids, such as
terephthalic acid, isophthalic acid, phthalic acid,
2,6-naphthalenedicarboxylic acid,
1,5-naphthalenedicarboxylic acid,
bis(p-carboxyphenyl)methane, anthracenedicarboxylic acid,
4, 4' -diphenyl ether dicarboxylic acid,
5-tetrabutylphosphonium isophthalic acid,
5-sodiumsulfoisophthalic acid, etc. Aliphatic dicarboxylic acids, such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, dimer acid, etc., are also exemplified. Alicyclic dicarboxylic acids, such as 1, 3-cyclohexanedicarboxylic acid,
19

1, 4-cyclohexanedicarboxylic acid, etc., are also exemplified . Ester forming derivatives thereof are also exemplified.
Examples of the diol or its ester forming derivative include aliphatic glycols having 2 to 20 carbon atoms, namely ethylene glycol, 1, 3-propanedio'l, propylene glycol, 1,4-butan.ediol, neopentyl glycol, 1,5-pentandiol, 1,6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, dimer diol, etc.
Long-chain glycols having a molecular weight of 200 to 100,000, namely polyethylene glycol, poly(1,3-propylene glycol), poly(1,2-propylene glycol), polytetramethylene glycol, etc., are also exemplified. Aromatic dioxy compounds, namely 4,4'-dihydroxybiphenyl, hydroquinone, tert-butylhydroquinone, bisphenol A, bisphenol S, bisphenol F, etc., are also exemplified. Ester forming derivatives thereof are also exemplified.
Examples of the hydroxycarboxylic acid include glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and ester forming derivatives thereof, and the like. Examples of the lactone include caprolactone, valerolactone, propiolactone, undecalactone, 1,5-oxepan-2-one, and the like.
Examples of the aliphatic polyester include polymers containing an aliphatic hydroxycarboxylic acid as a main
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constituent component, polymers obtained by polycondensing an aliphatic multivalent carboxylic acid or an ester forming derivative thereof and an aliphatic polyhydric alcohol as main constituent components, and copolymers thereof.
Examples of the polymer containing an aliphatic
hydroxycarboxylic acid as a main constituent component may
include polycondensates of glycolic acid, lactic acid,
hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric
acid, hydroxycaproic acid, or the like, and copolymers thereof
Above all, polyglycolic acid, polylactic acid,
poly{3-hydroxycarbonbutyric acid),
poly(4-polyhydroxybutyric acid), poly(3-hydroxyhexanoic acid) , polycaprolactone, and copolymers thereof, and the like are exemplified. In particular, poly(L-lactic acid), poly(D-lactic acid), stereocomplex polylactic acid, and racemic polylactic acid are exemplified.
Polymers containing an aliphatic multivalent carboxylic
acid and an aliphatic polyhydric alcohol as main constituent
components are exemplified. Examples of the multivalent
carboxylic acid include aliphatic dicarboxylic acids, such as
oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic
acid, dodecanedioic acid, malonic acid, glutaric acid, dimer
acid, etc.; alicyclic dicarboxylic acid units, such as
1,3-cyclohexanedicarboxylic acid,
1,4-cyclohexanedicarboxylic acid, etc.; and ester forming
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derivatives thereof. Examples of the diol component include aliphatic glycols having 2 to 20 carbon atoms, such as ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, dimer diol, etc. Long-chain glycols having a molecular weight of 200 to 100,000, namely polyethylene glycol, poly(1,3-proylene glycol), poly(1,2-propylene glycol), and polytetramethylene glycol are exemplified. Specifically, polyethylene adipate, polyethylene succinate, polybutylene adipate, polybutylene succinate, and copolymers thereof, and the like are exemplified.
The polyester can be produced by well-known methods {for example, methods described in Saturated Polyester Resin Handbook (written by Kazuo Yuki, Nikkan Kogyo Shimbun Ltd. (published on December 22, 1989)).
Furthermore, examples of the polyester include, in addition to the above-described polyesters, unsaturated polyester resins obtained by copolymer!zing an unsaturated multivalent carboxylic acid or an ester forming derivative; and polyester elastomers containing a low melting-point polymer segment.
Examples of the unsaturated multivalent carboxylic acid include maleic anhydride, tetrahydromaleic anhydride, fumaric acid, endomethylene tetrahydromaleic anhydride, and the like.
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In such an unsaturated polyester, for the purpose of controlling its curing properties, various monomers are added, and the unsaturated polyester is cured by means of thermal curing, radical curing, or curing with an active energy ray, such as light, electron beams, etc., and then molded.
Furthermore, in the present invention, the polyester may also be a polyester elastomer obtained by copolymerizing a soft component. The polyester elastomer is a block copolymer composed of a high melting-point polyester segment and a low melting-point polymer segment having a molecular weight of 400 to 6,000 as described in publicly known literatures, for example, JP-A-11-92636, or the like. In the case of forming a polymer by using only a high melting-point polyester segment,
its melting point is 150°C or higher, and such a polymer can be suitably used.
The polyester is preferably a polyester composed of a hydroxycarboxylic acid or an ester forming derivative thereof. An aliphatic polyester composed of a hydroxycarboxylic acid or an ester forming derivative thereof is more preferred. Furthermore, it is especially preferred that the aliphatic polyester is poly(L-lactic acid), poly(D-lactic acid), or stereocomplex polylactic acid.
Here, as for the polylactic acid, its main chain is composed of a lactic acid unit represented by the following formula (1) . In this specification, the term "mainly" means
23

that a proportion of the unit is preferably 90 to 100 mol%, more preferably 95 to 100 mol%, and still more preferably 98 to 100 mol%.

L l "
—ho— c—c
\ CH3
(1)
The lactic acid unit represented by the formula (1) includes an L-lactic acid unit and a D-lactic acid unit, which are an optical isomer to each other. It is preferred that a main chain of the polylactic acid is mainly an L-lactic acid unit, a D-lactic acid unit, or a combination thereof.
The polylactic acid is preferably poly(D-lactic acid) in which a main chain thereof is composed mainly of a D-lactic acid unit, or poly (L-lactic acid) in which a main chain thereof is composed mainly of an L-lactic acid unit. A proportion of other unit constituting the main chain is in the range of preferably 0 to 10 mol%, more preferably 0 to 5 mol%, and still more preferably 0 to 2 mol%.
Examples of the other unit constituting the main chain include units derived from a dicarboxylic acid, a polyhydric alcohol, a hydroxycarboxylic acid, a lactone, or the like.
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, and the like. Examples of the polyhydric
24

alcohol include aliphatic polyhydric alcohols, such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, glycerin, sorbitan, neopentyl glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, etc.; aromatic polyhydric alcohols, such as bisphenol having ethylene oxide added thereto, etc.; and the like. Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, and the like. Examples of the lactone include glycolide, s-caprolactone. P-propiolactone, 8-butyrolactone, (3- or y-butyrolactone, pivalolactone, S-valerolactone, and the like.
For the purpose of making both mechanical physical properties of a molded article and moldability compatible with each other, a weight average molecular weight of the polylactic acid is in the range of preferably 50,000 to 500,000, more preferably 80,000 to 350,000, and still more preferably 120,000 to 250,000. The weight average molecular weight is a value obtained by measurement by means of gel permeation chromatography (GPC) and conversion into standard polystyrene.
When the polylactic acid (component A) is poly (D-lactic acid) or poly(L-lactic acid) and is a homo-phase polylactic acid, it is preferred that when measured by a differential scanning calorimeter (DSC), the polylactic acid has a crystal melting peak (Tmh) at between 150 to 190°C and a crystal melting
25

heat (AHmsc) of 10 J/g or more. When the foregoing ranges of the crystal melting point and crystal melting heat are satisfied, the heat resistance can be increased.
The main chain of the polylactic acid is preferably stereocomplex polylactic acid containing a stereocomplex phase formed of a poly {L-lactic acid) unit and a poly (D-lactic acid) unit. It is preferred that when measured by a differential scanning calorimeter (DSC), the stereocomplex polylactic acid exhibits a crystal melting peak of 190°C or higher.
In the stereocomplex polylactic acid, a stereocomplex crystallization degree (S) as prescribed by the following equation (i) is preferably 90 to 100%. S = [AHms/(AHmh + AHms)] x 100 (i)
(Here, AHms represents a melting enthalpy of the stereocomplex-phase polylactic acid crystal, and AHmh represents a melting enthalpy of the polylactic acid homo-phase crystal.}
The crystallization degree of the stereocomplex polylactic acid, particularly the crystallization degree by the XRD measurement is in the range of preferably at least 5%, more preferably 5 to 60%, still more preferably 7 to 60%, and especially preferably 10 to 60%.
The crystal melting point of the stereocomplex polylactic acid is in the range of preferably 190 to 250°C,
26

and more preferably 200 to 230°C. The crystal melting enthalpy of the stereocomplex polylactic acid by the DSC measurement is in the range of preferably 20 J/g or more, more preferably 20 to 80 J/g, and still more preferably 30 to 80 J/g. When the crystal melting point of the stereocomplex polylactic acid is lower than 190°C, the heat resistance is worsened. When it is higher than 250°C, molding at a high temperature of 250°C or higher is needed, so that there may be the case where it is difficult to inhibit the heat decomposition of the resin. In consequence, it is preferred that when measured by a differential scanning calorimeter (DSC), the resin composition of the present invention exhibits a crystal melting peak of 190°C or higher.
In the stereocomplex polylactic acid, a weight ratio of poly(D-lactic acid) to poly(L-lactic acid) is in the range of preferably 90/10 to 10/90, more preferably 80/20 to 20/80, still more preferably 30/70 to 70/30, and especially preferably 40/60 to 60/40. Theoretically, it is preferred that the weight ratio is close to 1/1 as far as possible.
A weight average molecular weight of the stereocomplex polylactic acid is in the range of preferably 50, 000 to 500, 000, more preferably 80,000 to 350,000, and still more preferably 120,000 to 250,000. The weight average molecular weight is a value obtained by measurement by means of gel permeation chromatography (GPC) and conversion into standard
27

polystyrene.
The poly(L-lactic acid) and poly(D-lactic acid) can be produced by a conventionally known method. For example, the poly(L-lactic acid) and poly(D-lactic acid) can be produced by subjecting L-lactide or D-lactide to ring-opening polymerization, respectively in the presence of a metal-containing catalyst. The poly(L-lactic acid) and poly(D-lactic acid) can also be produced by subjecting a low-molecular weight polylactic acid containing a metal-containing catalyst, after being optionally crystallized or without being crystallized, to solid-phase polymerization under reduced pressure or by pressurization from atmospheric pressure in the presence or absence of an inert gas stream. Furthermore, the poly(L-lactic acid) and poly (D-lactic acid) can be produced by a direct polymerization method of subjecting lactic acid to dehydration condensation in the presence or absence of an organic solvent.
The polymerization reaction can be carried out in a conventionally known reaction vessel, and for example, in the ring-opening polymerization or direct polymerization method, a vertical reactor or horizontal reactor equipped with a high viscosity stirring blade, such as a helical ribbon blade, etc. , can be used alone or in parallel. All of a batch type, a continuous type, and a semi-batch type may be used, or these may be combined.
28

An alcohol may be used as a polymerization initiator. It is preferred that such an alcohol does not hinder the polymerization of polylactic acid and is nonvolatile, and for example, decanol, dodecanol, tetradecanol, hexadecanol, octadecanol, ethylene glycol, trimethylolpropane, pentaerythritol, or the like can be suitably used. It may be said that an embodiment in which the polylactic acid prepolymer used in the solid-phase polymerization method is previously crystallized is preferred from the standpoint of preventing the fusion of resin pellets. The prepolymer is polymerized in a state of solid at a temperature in the range of a glass transition temperature of the prepolymer or higher and lower than a melting point thereof in a fixed vertical reaction vessel or horizontal reaction vessel, or a reaction vessel (rotary kiln, etc.) in which the vessel itself rotates, such as a tumbler or a kiln.
Examples of the metal-containing catalyst include fatty acid salts, carbonates, sulfates, phosphates, oxides, hydroxides, halides, alcoholates, and like of an alkali metal, an alkaline earth metal, a rare-earth element, a transition metal, aluminum, germanium, tin, antimony, titanium, etc. Above all, fatty acid salts, carbonates, sulfates, phosphates, oxides, hydroxides, halides, and alcoholates containing at least one metal selected from tin, aluminum, zinc, calcium, titanium, germanium, manganese, magnesium, and a rare-earth
29

element are preferred.
Specifically, from the standpoints of catalytic activity and less occurrence of a side reaction, tin-containing compounds, such as stannous chloride, stannous bromide, stannous iodide, stannous sulfate, stannic oxide, tin myristate, tin octylate, tin stearate, tetraphenyltin, etc., are exemplified as a preferred catalyst. Above all, tin(II) compounds, specifically diethoxytin, dinonyloxytin, tin(II) myristate, tin(II) octylate, tin(II) stearate, tin(II) chloride, and the like, are suitably exemplified.
A use amount of the catalyst is 0.42 x 10~4 to 100 x 10~4 (mol) per kg of the lactide, and furthermore, taking into consideration the reactivity, the color tone of the obtained polylactide, and the stability, the catalyst is used in an amount of preferably 1.68 x 10"4 to 42.1 x 10~4 (mol), and especially preferably 2.53 x 10^4 to 16.8 x 10"4 (mol).
It is preferred that the metal-containing catalyst used for the polymerization of polylactic acid is inactivated with a conventionally known deactivator prior to the use for polylactic acid. Examples of such a deactivator include organic ligands consisting of a group of chelate ligands having an imino group and capable of coordinating to the polymerization metal catalyst.
Low oxidation number phosphoric acids having an acid number of 5 or less, such as dihydride oxophosphoric acid (I) ,
30

dihydride tetraoxodiphosphoric acid (II, II) , hydride trioxophosphoric acid (III) , dihydride pentaoxodiphosphoric acid (III), hydride pentaoxodiphosphoric acid (II, IV), dodecaoxohexaphosphoric acid (III), hydride octaoxotriphosphoric acid (III, IV, IV), octaoxotriphosphoric acid (IV, III, IV), hydride hexaoxodiphosphoric acid (III, V), hexaoxodiphosphoric acid (IV), decaoxotetraphosphoric acid (IV), hendecaoxotetraphosphoric acid (IV), and enneaoxotriphosphoric acid (V, IV, IV), etc., are also exemplified.
Orthophosphoric acids represented by the formula: xH20-yP205 and satisfying x/y = 3 are also exemplified. Polyphosphoric acids called "diphosphoric acid, triphosphoric acid, tetraphosphoric acid, pentaphosphoric acid, and the like" according to the degree of condensation and satisfying 2 >x/y >1, and mixtures thereof are also exemplified. Metaphosphoric acids satisfying x/y=l, especially trimetaphosphoric acid and tetrametaphosphoric acid are also exemplified. Ultraphosphoric acids having a network structure in which a part of the phosphorus pentoxide structure remains and satisfying 1 > x/y > 0 (may be collectively referred to as "metaphosphoric acid-based compounds") are also exemplified. Acidic salts of these acids are also exemplified. Partial esters or whole esters of such an acid with a monohydric or polyhydric alcohol, or a polyalkyiene glycol are also
31

exemplified. Phosphono-substituted lower aliphatic carboxylic acid derivatives of these acids, and the like are also exemplified.
From the standpoint of catalyst deactivation ability, orthophosphoric acids represented by the formula: xH20-yP205 and satisfying x/y = 3 are preferred. Polyphosphoric acids called "diphosphoric acid, triphosphoric acid, tetraphosphoric acid, pentaphosphoric acid, and the like" according to the degree of condensation and satisfying 2 >x/y >1, and mixtures thereof are also preferred. Metaphosphoric acids satisfying x/y=l, especially trimetaphosphoric acid and tetrametaphosphoric acid are also preferred. Ultraphosphoric acids having a network structure in which a part of the phosphorus pentoxide structure remains and satisfying 1 > x/y > 0 (may be collectively referred to as "metaphosphoric acid-based compounds") are also preferred. Acidic salts of these acids are also preferred. Partial esters of such an acid with a monohydric or polyhydric alcohol, or a polyalkylene glycol are also preferred.
The metaphosphoric acid-based compound which is used in the present invention includes cyclic metaphosphoric acids in which about 3 to 200 phosphoric acid units are condensed, ultra-region metaphosphoric acids having a three-dimensional network structure, and (alkali metal salts, alkaline earth metal salts, and onium salts) thereof. Above of all, cyclic
32

sodium metaphosphate, ultra-region sodium metaphosphate, dihexylphosphonoethyl acetate (hereinafter sometimes abbreviated as DHPA) of a phosphono-substituted lower aliphatic carboxylic acid derivative, and the like are suitably used.
The polylactic acid is preferably one having a lactide content of 5,000 ppm or less. The lactide contained in the polylactic acid deteriorates the resin and worsens the color tone at the time of melting processing, and as the case may be, there is a concern that it makes unusable as a product. Although the poly(L-lactic acid) and/or poly(D-lactic acid) immediately after melt ring-opening polymerization generally contains 1 to 5% by weight of the lactide, the content of lactide can be reduced to a preferred range in any stage between the end of polymerization of poly(L-lactic acid) and/or poly (D-lactic acid) and molding of polylactic acid by carrying out conventionally known lactide reduction methods, namely, a vacuum devolatilization method with a single-screw or multi-screw extruder, or a high-vacuum treatment within a polymerizer, or the like alone or in combination.
The lower the lactide content, the more enhanced the melt stability and moist heat stability of the resin. However, since the lactide has such an advantage that it reduces the melt viscosity of the resin, it is rational and economical to set the lactide content to a value suitable for a desired
33

purpose. That is, it is rational to set the lactide content to 1, 000 ppm or less so as to achieve practical melt stability. The lactide content is selected within the range of more preferably 700 ppm or less, still more preferably 500 ppm or less, and especially preferably 100 ppm or less. When the polylactic acid component has the lactide content of the foregoing range, there are brought such advantages that the stability of the resin at the time of melt molding of a molded article of the present invention is enhanced; and that the molded article can be efficiently produced, and the moist heat stability and low gas properties of the molded article can be increased.
The stereocomplex polylactic acid can be obtained by bringing poly(L-lactic acid) and poly(D-lactic acid) into contact with each other in a weight ratio in the range of 10/90 to 90/10, preferably bringing them into melt contact with each other, and more preferably melt kneading them together. A contact temperature is in the range of preferably 220 to 2 90°C, more preferably 220 to 280°C, and still more preferably 225 to 27 5°C from the viewpoints of enhancements of the stability at the time of melting of polylactic acid and the stereocomplex crystallization degree.
Although the melt kneading method is not particularly limited, a conventionally known batch type or continuous type melt mixer is preferably used. For example, a melt stirring
34

tank, a single-screw or double-screw extruder, a kneader, an anaxial basket-type stirring tank, "VIBOLAC (registered trademark) ", manufactured by Sumitomo Heavy Industries, Inc., N-SCR, manufactured by Mitsubishi Heavy Industries, Ltd., a spectacle blade, a lattice blade, or a Kenix type stirrer, manufactured by Hitachi, Ltd., or a tubular polymerizer equipped with a Sulzer SMLX type static mixer can be used. Above all, an anaxial basket type stirring tank that is a self-cleaning type polymerizer, N-SCR, a double-screw extruder, and the like are preferred from the viewpoint of productivity and quality, especially color tone of the polylactic acid.
In the present invention, the hydrolysis regulator (component B) is an agent for sealing an end group of the resin (component A) and an acidic group generated by decomposition. That is, the hydrolysis regulator (component B) is an agent having an effect for inhibiting the autocatalysis of the resin (component A) to delay the hydrolysis.
As the acidic group, at least one member selected from the group consisting of a carboxyl group, a sulfonic acid group, a sulf inic acid group, a phosphonic acid group, and a phosphinic acid group is exemplified. In the present invention, a carboxyl group is especially exemplified.
Since the requirement for use is concerned with the use
35

in hot water at a higher temperature than 135°C, it is preferred that the component B has water resistance at 120°C of 95% or more and reactivity with an acidic group at 190°C of 50% or more.
The water resistance at 120°C as referred to herein is, for example, a value expressed by the following eguation (ii) by using 1) a calculated value of an agent remaining without being changed after the 5-hour treatment, the value being calculated by means of analysis of a dissolved portion at the time after adding 2 g of water to a system having 1 g of the component B dissolved in 50 mL of dimethyl sulfoxide and stirring the resultant at 120°C for 5 hours while refluxing, or 2) in the case where the component B is not soluble in dimethyl sulfoxide, a calculated value determined by performing the same treatment as that in the foregoing 1} using a solvent capable of dissolving the component B therein and having hydrophilicity. Incidentally, in 2), when a boiling point of the solvent to be used is lower than 120°C, the solvent was mixed with dimethyl sulfoxide in a range where at least a part of the component B is soluble therein, and 50 mL of the mixed solvent was used. Although a mixing proportion may be generally chosen within the range of 1/2 to 2/1, it is not particularly limited so long as the above-described requirement is satisfied.
In general, so long as the solvent which is used in 2)
36

is selected from tetrahydrofuran, N,N-dimethylformamide, and ethyl acetate, the component B is soluble therein. Water resistance (%) = [(Amount of the agent after the 5-hour treatment) / (Initial amount of the agent)] x 100 (ii)
In the case of evaluating an instable agent for the water resistance, a part of the agent is denatured by the hydrolysis, and the sealing ability of the acidic group is lowered. In the case of using such an agent in high-temperature hot water, the agent is deactivated by the water, and the ability for sealing the target acidic group is remarkably lowered. In view of the foregoing, the water resistance at 120°C is more preferably 97% or more, still more preferably 99% or more, and especially preferably 99.9% or more. That is, when the water resistance is 99.9% or more, namely the agent is stable in high-temperature hot water, the reaction with the acidic group can be performed selectively and efficiently.
The reactivity with an acidic group at 190°C as referred to herein is, for example, a value obtained by measuring a carboxyl group concentration regarding a resin composition obtained by adding the agent in an amount such that the group of the hydrolysis regulator, reacting with the carboxyl group, is corresponding to 1.5 equivalents to the carboxyl group concentration of the polylactic acid for evaluation to 100 parts by weight of the polylactic acid for evaluation, followed by melt kneading under a nitrogen atmosphere at a resin
37

temperature of 190°C and at a rotation rate of 30 rpm for 1 minute by using a Labo Plasto mill (manufactured by Toyo Seiki Seisaku-Sho, Ltd.), the value being given according to the following equation (iii).
Reactivity (%) = [{(Carboxyl group concentration of polylactic acid for evaluation) - (Carboxyl group concentration of resin composition)} / (Carboxyl group concentration of polylactic acid for evaluation)] x 100 (iii)
The polylactic acid for evaluation is preferably one having an MW of 120,000 to 200,000 and a carboxyl group concentration of 10 to 30 equivalents/ton. As such a polylactic acid, for example, polylactic acid ^NW3001D"f manufactured by NatureWorks LLC (MW: 150,000, carboxyl group concentration: 22.1 equivalents/ton) and the like can be suitably used. In that case, a value of the reactivity can be determined by measuring a carboxyl group concentration regarding a resin composition obtained by adding the agent in an amount such that the group of the hydrolysis regulator, reacting with the carboxyl group, is 33.15 equivalents/ton, followed by melt kneading under a nitrogen atmosphere at a resin
temperature of 190°C and at a rotation rate of 30 rpm for 1 minute by using a Labo Plasto mill (manufactured by Toyo Seiki Seisaku-Sho, Ltd.).
Besides, the reactivity with an acidic group may also be given by the equivalent evaluation.
In the case of evaluating a stable agent for the
38

reactivity, even when kneading is performed under the above-described condition, the carboxyl group concentration of the resin composition does not substantially change. In the case of using such an agent in high-temperature hot water, the ability for sealing the target acidic group is not substantially exhibited, and therefore, the decomposition of the resin (component A) cannot be inhibited.
In view of the foregoing, the reactivity with an acidic group at 190°C is more preferably 60% or more, still more preferably 70% or more, and especially preferably 80% or more. That is, when the reactivity is 80% or more, namely the reactivity with an acidic group in high-temperature hot water is high, the reaction with the acidic group can be efficiently performed.
It is important that the hydrolysis regulator (component B) of the present invention has water resistance at 120°C of 95% or more and reactivity with an acidic group at 190°C of 50% or more. That is, in a very stable agent, though the water resistance is a high value, the reactivity with an acidic group is a low value, and in that case, the ability for sealing the target acidic group in high-temperature hot water is not substantially exhibited. In a very instable agent, though the reactivity with an acidic group is a high value, the water resistance is a low value, and in that case, the agent is deactivated with water in high-temperature hot water, and
39

therefore, the ability for sealing the target acidic group is remarkably lowered.
In view of the foregoing, the hydrolysis regulator having high water resistance and reactivity with an acidic group is suitably used in the present invention.
Examples of the component B include addition reaction type compounds, such as carbodiimide compounds, isocyanate compounds, epoxy compounds, oxazoline compounds, oxazine compounds, aziridine compounds, etc.
These compounds can be used in combination of two or more thereof. From the viewpoints of water resistance and reactivity with an acidic group, carbodiimide compounds are preferably exemplified.
As the carbodiimide compound, a compound having a basic structure represented by the following general formula (I) or (II) can be exemplified.
R-N=C=N-R' (I)
(In the formula, each of R and R' is independently an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; and R and R' may be bonded to each other to form a cyclic structure, and may form two or more cyclic structures through a spiro structure or the like.)
-f-N-C-N-R' ' }n (I I)
40

(In the formula, each of R and R" is independently an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; and n is an integer of 2 to 1,000.)
From the viewpoint of stability or easiness of handling, aromatic carbodiimide compounds are more preferred. Examples thereof include aromatic carbodiimide compounds represented by the following formulae (2) and (3).

(2)
(In the formula, each of Ri to R4 is independently an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; each of X and Y is independently a hydrogen atom, an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; and the respective aromatic rings may be bonded to each other via a substituent to form a cyclic structure, and may form two or more cyclic structures through a spiro structure or the like.)
41

— ^V^—N=C=NH
\ R? /n
(3)
(In the formula, each of R5 to R7 is independently an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; and n is an integer of 2 to 1,000.)
Specific examples of such an aromatic carbodiimide
compound include polycarbodiimides synthesized by subjecting
bis(2,6-diisopropylphenyl)carbodiimide or
1,3,5-triisopropylbenzene-2,4-diisocyanate to a decarboxylation condensation reaction, a combination of these two kinds, and the like.
In the present invention, from the viewpoint of using
in high-temperature hot water,
bis (2, 6-diisopropylphenyl)carbodiimide can be suitably used.
As for bis(2, 6-diisopropylphenyl)carbodiimide, from the viewpoints of water resistance and reactivity, its purity is desirably high as far as possible, and it is preferably 95% or more, more preferably 97% or more, and still more preferably 99% or more (here, the purity is determined from an area obtained by the measurement by means of HPLC as described in the working examples as described later).
42

As for bis(2,6-diisopropylphenyl)carbodiimide, from the viewpoints of water resistance and reactivity, a total sum content of compounds represented by the following formulae (4) and (5) is preferably 5% or less, more preferably 3% or less, and still more preferably 1% or less {here, the total sum content of the compounds represented by the following formulae (4) and (5) is determined by the measurement by means of 1H-NMR as described in the working examples as described later).
In the case where the total sum content of the compounds represented by the following formulae (4) and (5) is 5% or less, the effect in high-temperature hot water is more enhanced. Although this enhancement of the effect cannot be confirmed
in warm water at about 80°C, it can be confirmed that a meaningful difference in hot water at a high temperature of
at least 180°C or higher is exhibited, and from the viewpoint of water resistance of the compounds represented by the following formulae (4) and (5), it may be conjectured that a meaningful difference is exhibited in a high-temperature region of 135°C or higher.
,R8 R10
/ (4)
(In the formula, each of Rs to Rn is an aliphatic group having 3 carbon atoms, and at least one of them is a propyl
43

group, with the other group or groups being an isopropyl group. )
R12 . R
V>N=C=N ~iy
Rl3 R15
(5)
(In the formula, each of R12 to Ri5 is an aliphatic group having 3 carbon atoms, and at least one group of them is substituted on a position other than the ortho position.)
As a method of obtaining bis(2,6-diisopropylphenyl}carbodiimide having a high purity, a generally known purification method can be adopted. As a specific method thereof, distillation, recrystallization, washing, extraction, reprecipitation, column chromatography, and the like are exemplified.
In particular, in the case of purifying only bis(2,6-diisopropylphenyl)carbodiimide from a mixture of bis(2,6-diisopropylphenyl)carbodiimide and the compound represented by the foregoing formula (4) or (5) , since the both compounds have the same molecular weight and resemble each other in terms of an affinity with a solvent, purification by means of recrystallization is preferred.
As for the solvent which is used for the recrystallization, any solvent is usable so long as it does not react with bis(2, 6-diisopropylphenyl)carbodiimide, and for example, alcohols, such as methanol, ethanol, etc., and
44

alkanes, such as hexane, etc. , can be used. A combination of two or more kinds of solvents may be used.
The resin composition of the present invention satisfies any one of the following Al to A3:
Al: In hot water at an arbitrary temperature of 135°C to 160°C, after 3 hours, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, a weight of a water-insoluble matter of the resin composition is 50% or less; A2: In hot water at an arbitrary temperature of 160°C to 180°C/ after 2 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, a weight of a water-insoluble matter of the resin composition is 50% or less; and A3: In hot water at an arbitrary temperature of 180°C to 220°C, after 1 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, a weight of a water-insoluble matter of the resin composition is 50% or less.
In order that the resin composition of the present invention may exhibit the desired performance, it is important
45

to control the resin composition so as to be quickly decomposed after keeping the weight and shape of the resin in hot water at a higher temperature than 135°C for a fixed period of time. Although the fixed period of time is determined according to an application, it is preferably any of 10 minutes to 12 hours. From the viewpoint of exhibiting the desired performance, the fixed period of time is more preferably any of 30 minutes to 6 hours, and still more preferably any of 30 minutes to 4 hours.
As for the matter of keeping the weight and shape of the resin, it is preferred that the weight of the water-insoluble matter of the resin composition is 50% or more; and that the amount of volume change expressing the shape is 50% or less. For example, even when the weight of the water-insoluble matter of the resin composition is 50% or more, if it is in the completely hydrolyzed state, it may not be said that the weight and shape of the resin are kept. From the viewpoint of exhibiting the desired performance, the weight of the water-insoluble matter of the resin composition is more preferably 70% or more, and still more preferably 90% or more. The amount of volume change expressing the shape is more preferably 30% or less, and still more preferably 10% or less.
Here, the weight and the amount of volume change of the shape of the resin are, for example, values given by the following evaluations.
A closed melting crucible (manufactured by OM Lab-Tech
46

Co., Ltd. , MR-28, capacity: 28 mL) preheated at 110°C is charged with 300 mg of the resin composition and 12 mL of distilled water and hermetically sealed, and the crucible is allowed to stand within a hot air dryer (manufactured by Koyo Thermo Systems Co., Ltd., KLO-4 5M,) previously kept at a prescribed temperature.
After allowing the crucible to stand, a time at which the temperature in the interior of the crucible reaches a prescribed test temperature after the crucible is allowed to stand in the hot air dryer is defined as a point of time of starting the test, at a point of time when a certain period of time elapses from this point of time of starting the test, the crucible is taken out from the hot air dryer. The crucible taken out from the hot air dryer is air-cooled for 20 minutes and then cooled for 10 minutes by means of water cooling to ordinary temperature, and thereafter, the crucible is opened to recover the sample and water in the interior of the crucible.
The sample and water in the interior of the crucible are subjected to filtration using a filter paper (in conformity with JIS P3801:1995, class 5A); the resin composition remaining on the filter paper is dried at 60°C under a vacuum of 133.3 Pa or less for 3 hours; thereafter, the weight of the resin composition and the volume of the shape are measured; and the weight and the amount of volume change of the shape of the resin are determined according to the following
47

equations (iv) and (v).
Weight (%) = [(Weight of resin composition after treatment for a fixed period of
time) / (Weight of resin composition at the initial stage)] x 100 (iv)
Amount of volume change of shape (%) = [(Volume of resin composition after
treatment for a fixed period of time) / (Volume of resin composition at the initial
stage)] x 100 (v)
Here, the volume of the shape is a value determined by-measuring the resin composition by a stereoscopic microscope.
As the stereomicroscope, M205C, manufactured by Leica Microsystems, and the like can be used.
Incidentally, in this evaluation, with respect to the size of the resin composition, for example, so far as a pellet-like material is concerned, those close to a cube or rectangular parallelepiped of 0.5 mm to 5 mm in each side; so far as a fibrous material is concerned, fibers having a yarn thickness of 1 um to 1,000 um and a yarn length of 1 mm to 40 mm; and so far as a filmy material is concerned, films having a thickness of 50 um to 1,000 um and a length of each of the length and the width of 5 mm to 50 mm, can be generally used.
Besides, the weight and the amount of volume change of the shape of the resin may also be given by the equivalent evaluation. The matter that the resin is quickly decomposed means the state in which the hydrolysis of the component A is promoted by the autocatalysis, and the concentration of the acidic group exponentially increases . Conversely, during the
48

period when the concentration of the acidic group is kept low by the component B, the decomposition of the component A becomes gentle. For that reason, during the period when the weight and shape of the resin are kept, it is preferred that the concentration of the acidic group derived from the resin composition is 30 equivalents/ton or less.
In the case where the concentration of the acidic group is more than 30 equivalents/ton, the hydrolysis of the component A is promoted due to the autocatalysis, and the effect of the component B is not sufficiently exhibited. When the concentration of the acidic group is lower, the change of the weight of the resin composition or the shape can be inhibited. Therefore, from the viewpoint that the desired performance is exhibited, during the period when the weight and shape of the resin are kept, the concentration of the acidic group derived from the resin composition is more preferably 20 equivalents/ton or less, still more preferably 10 equivalents/ton or less, and especially preferably 3 equivalents/ton or less.
Here, the concentration of the acidic group derived from the resin composition can be, for example, determined by preparing a resin composition in the same manner as that used in the above-described evaluation for determining the weight and the amount of volume change of the shape of the resin and measuring the resulting resin composition by means of 1H-NMR.
49

The resin composition of the present invention can be suitably used in hot water at an arbitrary temperature of 135°C to 220°C. When the temperature is 135°C or lower, there may be the case where the desired performance can be exhibited by using only the component A. In addition, when even the temperature is higher than 220°C, there may be the case where even the resin composition of the present invention is immediately decomposed, so that the desired performance cannot be exhibited. For that reason, the resin composition of the present invention can be more suitably used in hot water at an arbitrary temperature of 150°C to 220°C, can be still more suitably used in hot water at an arbitrary temperature of 170°C to 210°C, and can be yet still more suitably used in hot water at an arbitrary temperature of 190°C to 210°C.
The resin composition of the present invention satisfies any one of the following Al to A3:
Al: In hot water at an arbitrary temperature of 135°C to 160°C, after 3 hours, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours , a weight of a water-insoluble matter of the resin composition is 50% or less; A2 : In hot water at an arbitrary temperature of 160°C to 180°C, after 2 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight
50

of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, a weight of a water-insoluble matter of the resin composition is 50% or less; and A3 : In hot water at an arbitrary temperature of 180°C to 220°C, after 1 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, a weight of a water-insoluble matter of the resin composition is 50% or less.
The range where the resin composition of the present invention can be suitably used varies with the temperature. In Al to A3, at a time earlier than after the prescribed fixed period of time (1 hour, 2 hours, or 3 hours), it is preferred that the resin composition-derived acidic group concentration is 30 equivalents/ton or less, and the weight of the water-insoluble matter of the resin composition is 50% or more. In Al, it is expressed that the fixed period of time is 3 hours and during that time, the weight and shape of the resin are kept. From the viewpoint of exhibiting the desired performance in the excavation technology in the oil field or the like, in hot water at an arbitrary temperature of 135°C to 160°C, after a fixed period of time longer than 2 hours as defined in the present invention, the resin composition-derived acidic group concentration may be 30 equivalents/ton or less, and the weight of the water-insoluble
51

matter of the resin composition may be 50% or more.
In A2, it is expressed that the fixed period of time is 2 hours and during that time, the weight and shape of the resin are kept. From the viewpoint of exhibiting the desired performance in the excavation technology in the oil field or the like, in hot water at an arbitrary temperature of 160°C to 180°C, after a fixed period of time longer than 2 hours as defined in the present invention, the resin composition-derived acidic group concentration may be 30 equivalents/ton or less, and the weight of the water-insoluble matter of the resin composition may be 50% or more.
In A3, it is expressed that the fixed period of time is 1 hour and during that time, the weight and shape of the resin are kept. From the viewpoint of exhibiting the desired performance in the excavation technology in the oil field or the like, in hot water at an arbitrary temperature of 180°C to 220°C, after a fixed period of time longer than 1 hour as defined in the present invention, the resin composition-derived acidic group concentration may be 30 equivalents/ton or less, and the weight of the water-insoluble matter of the resin composition may be 50% or more.
After the fixed period of time prescribed in each of Al to A3 (1 hour, 2 hours, or 3 hours), the effect for sealing the acidic group by the component B vanishes, the decomposition of the resin is promoted due to the autocatalysis of the acidic
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group, and follox-jing that, the concentration of the acidic group exponentially increases. Furthermore, as the decomposition proceeds, the resin becomes a water-soluble monomer, whereby it becomes soluble in water. The matter that the instant phenomenon occurs quickly as far as possible after the weight and shape of the resin are kept for a fixed period of time is suitable on the occasion of using the resin composition of the present invention in the excavation technology in the oil field or the like. For that reason, it is preferred that after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less. For the foregoing reason, it is more preferred that after 18 hours, the weight of the water-insoluble matter of the resin composition is 50% or less; it is still more preferred that after 12 hours, the weight of the water-insoluble matter of the resin composition is 50% or less; and it is yet still more preferred that after 6 hours, the weight of the water-insoluble matter of the resin composition is 50% or less.
As for the resin composition of the present invention, it is preferred that in hot water at an arbitrary temperature of 135°C to 220°C, after 1Q0 hours, the weight of the water-insoluble matter of the resin composition is 10% or less . For example, on the occasion of using the resin composition in the excavation technology in the oil field or the like, the resin composition is dissolved in water quickly after keeping
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the weight and shape of the resin for a fixed period of time,
whereby it can effectively work. For that reason, it is
preferred that in hot water at an arbitrary temperature of 135°C
to 220°C, after 100 hours, the weight of the water-insoluble
matter of the resin composition is 10% or less. From the
viewpoints of treatment in water after the use and exhibition
of the desired performance, the water-insoluble matter is low
as far as possible, and after 100 hours, the weight of the
water-insoluble matter of the resin composition is more
preferably 5% or less, and still more preferably 1% or less.
It is preferred that a heat deformation temperature of
the resin composition of the present invention is 135°C to 300°C
Here, the heat deformation temperature refers to a melting
point or softening point of the resin composition. Since the
resin composition is supposed to be used in hot water at a higher
temperature than 135°C, when the heat deformation temperature
of the resin composition is higher, the resin composition can
be used in a wide temperature region. Meanwhile, when the heat
deformation temperature is 300°C or less, molding of the resin
composition of the present invention is relatively easy. For
that reason, the heat deformation temperature of such a resin
composition is more preferably 150°C to 300°C, still more
preferably 165°C to 300°C, yet still more preferably 170°C to
300°C, even yet still more preferably 175°C to 285°C, and
especially preferably 180°C to 285°C.

CLAIMS
1. A resin composition containing a resin containing, as a main component, a water-soluble monomer and having autocatalysis (component A) and a hydrolysis regulator (component B) , the resin composition satisfying any one of the following Al to A3:
Al: In hot water at an arbitrary temperature of 135°C to 160°C, after 3 hours, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less; A2 : In hot water at an arbitrary temperature of 160°C to 180°C, after 2 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less; and A3: In hot water at an arbitrary temperature of 180°C to 220°C, after 1 hour, not only a resin composition-derived acidic group concentration is 30 equivalents/ton or less, but also a weight of a water-insoluble matter of the resin composition is 50% or more, and after 24 hours, the weight of the water-insoluble matter of the resin composition is 50% or less.
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2. The resin composition according to claim 1, wherein the component B has water resistance at 12 0°C of 95% or more and reactivity with an acidic group at 190°C of 50% or more.
3. The resin composition according to claim 1 or 2, wherein
in hot water at an arbitrary temperature of 135°C to 220°C, after 100 hours, the weight of the water-insoluble matter of the resin composition is 10% or less.
4. The resin composition according to any one of claims 1
to 3, wherein a heat deformation temperature of the resin
composition is 135°C to 300°C.
5. The resin composition according to any one of claims 1 to 4, wherein the component A is a polyester.
6. The resin composition according to claim 5, wherein a main chain of the component A is composed mainly of a lactic acid unit represented by the following formula (1):



(1)
7. The resin composition according to claim 6, wherein the component A contains a stereocomplex phase formed of poly(L-lactic acid) and poly(D-lactic acid).
8. The resin composition according to any one of claims 1 to 7, wherein the component B is a carbodiimide compound.
9. The resin composition according to claim 8, wherein the
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component B is a carbodiimide compound represented by the following formula (2}:


-N=c=N
t>

wherein each of Ri to R4 is independently an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; each of X and Y is independently a hydrogen atom, an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom; and the respective aromatic rings may be bonded to each other via a substituent to form a cyclic structure.
10. The resin composition according to claim 9, wherein the component B is bis(2,6-diisopropylphenyl)carbodiimide.
11. The resin composition according to claim 8, wherein the component B is a carbodiimide compound composed of a repeating unit represented by the following formula (3):
N=C=N-
(3)
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wherein each of R5 to R7 is independently an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, an aromatic group having 5 to 15 carbon atoms, or a combination thereof, and may contain a hetero atom..
12. A molded article comprising the resin composition according to any one of claims 1 to 11.
13. A fiber comprising the resin composition according to any one of claims 1 to 11.
14. A resin composition including an aliphatic polyester containing, as a main component, a water-soluble monomer (component C) and a hydrolysis regulator having reactivity
with an acidic group in a 15% hydrochloric acid aqueous solution at 100°C of 30% or more (component D) , the resin composition satisfying any one of the following Jl to J2:
Jl: In the 15% hydrochloric acid aqueous solution at 100°C,
after 6 hours, a weight average molecular weight retention rate
of the resin composition is 50% or more, and after 24 hours,
a weight of a water-insoluble matter of the resin composition
is 50% or less; and
J2: In the 15% hydrochloric acid aqueous solution at 120°C,
after 1 hour, a weight average molecular weight retention rate
of the resin composition is 50% or more, and after 24 hours,
a weight of a water-insoluble matter of the resin composition
is 50% or less.
15. The resin composition according to claim 14, wherein
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after 72 hours, the weight of the water-insoluble matter of the resin composition is 1% or less.
16. The resin composition according to claim 14 or 15, wherein a main chain of the component A is composed mainly of a lactic acid unit represented by the following formula (1) ;
17. The resin composition according to any one of claims 14 to 16, wherein the hydrolysis regulator (component D) is at least one member selected from a carbodiimide compound and an epoxy compound.
18. A molded article comprising the resin composition according to any one of claims 14 to 17.