JP2016108385A - Biodegradable resin composition and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable resin composition having excellent dimension stability at molding, the biodegradable resin composition capable of quickly decomposing a molded article, and also to provide a manufacturing method thereof.SOLUTION: In a biodegradable resin composition, an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton polymerized by an initiator containing a divalent or higher hydroxy group is three-dimensionally crosslinked with a hydrophilic polymer. The glass transition point of the hydrophilic polymer is -60°C or higher and 30°C or lower.SELECTED DRAWING: None

Description

  The present invention relates to a biodegradable resin composition and a method for producing the same.

  In recent years, biodegradable resins derived from biomass that are made from renewable resources and that have less impact on the environment at the time of disposal have become a focus of attention as environmental problems such as the depletion of petroleum resources, plastic waste disposal, and global warming become more serious. ing. Among these, polylactic acid has been attracting attention as a biodegradable resin in the plastics industry, and its research and development are actively conducted.

  Polylactic acid is obtained by polymerizing lactic acid or lactide, which is a dimer of lactic acid, obtained by fermenting corn, sugar, radish, etc. Even if it is finally biodegraded or incinerated, the total amount of carbon dioxide gas It is an environmentally low-load polymer that does not directly lead to an increase. Polylactic acid has a strength comparable to that of polyethylene and polystyrene, has high transparency compared to other biodegradable plastics, and is excellent in weather resistance, heat resistance, processability, etc. It has been put to practical use for covering materials, fibers, earth retaining nets, grass bags, etc. Since polylactic acid is decomposed in soil or compost to become water and carbon dioxide, agricultural coating materials and the like used outdoors can be left as they are after use.

  Since polylactic acid is hardly hydrolysable, its biodegradability is considerably lower than other biodegradable resins such as polycaprolactone and polyhydroxybutyric acid. The property of biodegradability is not fully utilized.

  Polylactic acid is very brittle because of its poor heat resistance, impact resistance and flexibility, and has problems in workability, so that its industrial use is limited. Although methods for obtaining molded products using polylactic acid have been studied, plastic containers such as blistered products and bottles may shrink when exposed to high temperatures, causing problems such as the contents of the containers popping out. End up. Therefore, dimensional stability may be required for the plastic container described above. That is, in order to use a molded product using polylactic acid in a wide field, it is important to impart dimensional stability.

  An object of this invention is to provide the biodegradable resin composition which has favorable dimensional stability at the time of shaping | molding, and can decompose | disassemble a molded article rapidly, and its manufacturing method.

This invention for solving the said subject concerns the biodegradable resin composition as described in following (1).
(1) A resin composition obtained by three-dimensionally crosslinking an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton polymerized by an initiator having a divalent or higher hydroxyl group and a hydrophilic polymer, wherein the hydrophilic high A biodegradable resin composition having a glass transition point of molecules of -60 ° C or higher and 30 ° C or lower.

  The polylactic acid composition of the present invention and a molded product obtained using the same have good dimensional stability when melt-molded, and can be rapidly decomposed when the molded product is discarded.

It is a general phase diagram showing the state of a substance with respect to temperature and pressure. It is a phase diagram for defining the range of compressive fluid in this embodiment.

  A mode for carrying out the present invention will be described. Note that it is easy for a person skilled in the art to make other embodiments by appropriately changing or correcting the following aspects of the present invention, and these changes and modifications are included in the present invention. The description is an example of a preferred embodiment of the invention and is not intended to limit the invention.

Although this invention concerns on the biodegradable resin composition of following (1), following (2)-(7) is also included as embodiment.
(1) A resin composition obtained by three-dimensionally crosslinking an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton polymerized by an initiator having a divalent or higher hydroxyl group and a hydrophilic polymer, wherein the hydrophilic high A biodegradable resin composition having a glass transition point of molecules of -60 ° C or higher and 30 ° C or lower.
(2) The biodegradable resin composition as described in (1) above, wherein the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton is polylactic acid or a copolymer of polylactic acid.
(3) The biodegradable resin composition as described in (1) or (2) above, wherein the content of the hydrophilic polymer in the biodegradable resin composition satisfies the following formula (1).
1% by mass ≦ [A / (A + B)] × 100 ≦ 50% by mass (1)
A: Mass of hydrophilic polymer in biodegradable resin composition B: Having polyhydroxycarboxylic acid skeleton in biodegradable resin composition
Mass of aliphatic polyester resin (4) Melting | fusing point of the aliphatic polyester resin which has the said polyhydroxycarboxylic acid frame | skeleton is 170 degreeC or more and 220 degrees C or less, Any one of said (1)-(3) characterized by the above-mentioned. The biodegradable resin composition described in 1.
(5) An aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton polymerized by an initiator having a divalent or higher hydroxyl group and a hydrophilic polymer having a glass transition point of −60 ° C. or higher and 30 ° C. or lower by a crosslinking agent. Crosslinking reaction is performed, The manufacturing method of the biodegradable resin composition as described in any one of said (1)-(4) characterized by the above-mentioned.
(6) The aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton is obtained by polymerizing a raw material monomer with an initiator having a divalent or higher hydroxyl group in a compressive fluid. The manufacturing method of the biodegradable resin composition as described in said (5).
(7) The method for producing a biodegradable resin composition according to (5) or (6), wherein the crosslinking reaction is performed in a compressive fluid.

(Biodegradable resin composition)
The biodegradable resin composition of the present invention uses an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton and a hydrophilic polymer as raw material components.
The aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton is, for example, a biodegradable resin containing a structure in which lactic acid, hydroxyalkylcarboxylic acid, or the like is polycondensed in a repeating unit. The biodegradable resin is a polyester resin having a high concentration of ester groups in the main chain and a short alkyl chain in the side chain, and having a conventional aromatic chain as the main chain. In comparison, hydrolysis and thermal decomposition are likely to occur, and when the molded product is discarded, it is decomposed in soil or compost into water and carbon dioxide.

The polyhydroxycarboxylic acid skeleton has a (co) polymerized skeleton of hydroxycarboxylic acid, a method of directly dehydrating condensation of hydroxycarboxylic acid, a method of ring-opening polymerization of a corresponding cyclic ester, an enzymatic reaction such as lipase It can form by the method of synthesize | combining using.
As the monomer for forming the polyhydroxycarboxylic acid skeleton, aliphatic hydroxycarboxylic acid and cyclic ester of hydroxycarboxylic acid can be used.
From the viewpoint of transparency and thermal properties of the biodegradable resin composition, an aliphatic hydroxycarboxylic acid is preferable, and a hydroxycarboxylic acid having 2 to 6 carbon atoms is more preferable, such as lactic acid, glycolic acid, 3-hydroxybutyric acid, and the like. And lactic acid is particularly preferable.

  From the viewpoint of increasing the molecular weight of the polyhydroxycarboxylic acid to be polymerized, it is preferable to perform ring-opening polymerization of the cyclic ester. The hydroxycarboxylic acid skeleton of the resin obtained by ring-opening polymerization is a skeleton obtained by polymerizing the hydroxycarboxylic acid constituting the cyclic ester. For example, the polyhydroxycarboxylic acid skeleton of a resin obtained using lactide is a skeleton obtained by polymerizing lactic acid. Hereinafter, a resin having a skeleton obtained by polymerizing lactic acid is referred to as polylactic acid.

  Since the polylactic acid can improve the heat distortion temperature by crystallization, it needs to have crystallinity. In order to crystallize polylactic acid, it is necessary to adjust the optical purity to a certain value or more, and the optical purity is preferably 92% or more. The melting point is preferably 170 ° C. or higher and 220 ° C. or lower, and more preferably 180 ° C. or higher and 200 ° C. or lower. When the melting point is 170 ° C. or higher, the effect of improving thermal deformability due to crystallization is sufficiently exhibited. Since it is not necessary to melt at a high temperature at the time of molding processing due to being 220 ° C. or lower, thermal decomposition does not occur at the time of molding processing.

  These polylactic acids are synthesized using, for example, a method in which a monomer such as lactic acid or other composition is mixed and subjected to dehydration polymerization directly in the presence of an appropriate catalyst and an initiator, or an enzymatic reaction such as lipase. It can obtain by polymerizing according to the well-known method suitably selected according to the objectives, such as a method to do. In particular, as a preferred embodiment of the present invention, it is preferable to obtain polylactic acid by a method of synthesizing by ring-opening polymerization of cyclic lactide because the molecular weight, the amount of residual monomers and the like can be easily controlled.

Moreover, in this invention, it is good to superpose | polymerize polylactic acid by superposing | polymerizing in the compressive fluid mentioned later.
The polylactic acid segment used in the present invention is a polymer mainly composed of L-lactic acid and / or D-lactic acid, but copolymerized with other monomer components having ester-forming ability. It may be.

  The weight average molecular weight of the polylactic acid segment in the present invention is preferably from 100,000 to 600,000, more preferably from 200,000 to 400,000. When the weight average molecular weight is 100,000 or more, the content of the low molecular weight component is not high, so that the melting point does not decrease and sufficient heat resistance can be exhibited. In addition, since the molecular weight is 600,000 or less, there are many reactive sites with the hydrophilic polymer and the crosslinking agent that are copolymerized with the polylactic acid segment to ensure impact resistance, and components that are not copolymerized are mixed. Therefore, the hydrophilic polymer that has not undergone the crosslinking reaction at the time of molding does not bleed out and the impact resistance cannot be expressed.

  Other copolymer components include aliphatic diols, aromatic diols, low molecular weights derived from aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, hydroxycarboxylic acids, and ester-forming derivatives thereof. Examples include diols derived from polyalkylene glycols, compounds containing a plurality of hydroxyl groups in the molecule, or derivatives thereof.

Examples of the aromatic dicarboxylic acid include isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyletherdicarboxylic acid, and diphenylsulfonedicarboxylic acid. Etc.
Examples of the alicyclic dicarboxylic acid include 3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and the like.

Examples of the aliphatic dicarboxylic acid include malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, and trimethyladipine. Examples include acid, pimelic acid, azelaic acid, sebacic acid, and suberic acid.
Examples of the hydroxycarboxylic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxyvaleric acid, hydroxypropionic acid, hydroxycaproic acid, hydroxybenzoic acid, and the like.

Examples of the aliphatic diol include dicarboxylic acid, ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like. .
Examples of the aromatic diol include 2,2-bis (4-β-hydroxyethoxyphenyl) propane and 2,2-bis (4-β-hydroxyethoxyphenyl) sulfone.

Examples of the diol derived from the low molecular weight polyalkylene glycol include polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol.
Examples of the compound containing a plurality of hydroxyl groups in the molecule include glycerin and pentaerythritol.

  In addition, it is preferable that the ratio for which the polymer chain derived from another polymerizable monomer occupies the polymer whole quantity of a polylactic acid segment is 50 mol% or less in conversion of a monomer. Furthermore, it is more preferable that it is 20 mol% or less. Further, the arrangement pattern of the copolymer may be any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer.

  It is important for the biodegradable resin composition of the present invention to form a three-dimensional crosslink with a hydrophilic polymer described later. In general, polylactic acid has a problem that a solidification rate after melt molding is slow and a molding cycle is long, and sinking occurs due to volume shrinkage during molding. A method of improving the crystallization rate by using a nucleating agent is known. However, in the present invention, the molecular motion is restrained by forming a three-dimensional bridge to reduce the volume shrinkage. In addition to suppressing the occurrence of ash, the effect of shortening the solidification time can be expected.

<< Initiator used for polymerization of polylactic acid >>
In the present invention, an initiator is used in the polymerization of polylactic acid. With the initiator, the molecular weight of the polymer can be controlled to a desired molecular weight.
As the initiator, known initiators can be used, but it is important to three-dimensionally crosslink an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton and a hydrophilic polymer in order to ensure impact resistance and molding shrinkage. is there. For this reason, it is necessary to use the initiator which has a bivalent or more hydroxyl group, and the initiator which has a trivalent or more hydroxyl group is preferable. When the hydroxyl group of the initiator is monovalent. Even if the crosslinking reaction with the hydrophilic polymer described later proceeds sufficiently, graft copolymerization or block copolymerization is formed, and three-dimensional crosslinking does not occur. In the graft or block copolymer, the hydrophilic polymer part is easily arranged on the surface of the pellet or molded product of the biodegradable resin composition, so that moisture in the air is absorbed and the pellet is agglomerated. End up. Further, in the molded product, there is a problem that the texture is lost due to moisture absorption due to the presence of the hydrophilic polymer on the surface. It is important to improve the impact resistance by dispersing the rubber-like hydrophilic polymer in the biodegradable resin composition by three-dimensional crosslinking at room temperature, which is superior to block and graft copolymerization. An improvement effect can be obtained.

As the initiator, a polyhydric alcohol is used. The polyhydric alcohol may be either saturated or unsaturated.
Examples of dialcohol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexanediol, nonanediol, tetramethylene glycol, and polyethylene glycol. Can be mentioned.
Examples of trihydric or higher alcohols include glycerol, sorbitol, xylitol, ribitol, erythritol, triethanolamine, and trimethylolpropane.
Further, a polymer having an alcohol residue at the terminal, such as polycaprolactone diol or polytetramethylene glycol, can be used as an initiator. Thereby, a diblock or triblock copolymer is synthesized.

<< Catalyst used for polymerization of polylactic acid >>
In the present invention, a catalyst may be used in the polymerization of polylactic acid.
As the catalyst, a known catalyst can be used. When polymerization is performed by a compressed fluid or solution polymerization described later, not only a metal catalyst but also an organic catalyst can be used.

<<< Metal catalyst >>>
The metal catalyst is preferably an organic catalyst containing a metal atom. Such a metal catalyst is not particularly limited, and tin compounds such as tin octylate and tin dibutylate, aluminum compounds such as aluminum acetylacetonate and aluminum acetate, titanium compounds such as tetraisopropyl titanate and tetrabutyl titanate Known compounds such as compounds, zirconium compounds such as zirconium isoprooxide, and antimony compounds such as antimony trioxide are used.
What is necessary is just to adjust the addition amount of the said metal catalyst suitably according to the metal catalyst seed | species and the kind of substituent. For example, when ring-opening polymerization of lactide using tin octylate, 0.005 to 0.5 parts by mass, preferably 0.01 to 0.2 parts by mass of octyl with respect to 100 parts by mass of lactide. It is preferable to use tin oxide.

<<< Organic catalyst >>>
The organic catalyst is preferably a compound that functions as a basic nucleophile, more preferably a compound containing a basic nucleophilic nitrogen atom, and even more preferably a cyclic compound having a nitrogen atom. There is no restriction | limiting in particular as said compounds, According to the objective, it can select suitably, For example, cyclic | annular monoamine, cyclic diamine (For example, cyclic diamine compound etc. which have an amidine skeleton), cyclic triamine which has a guanidine skeleton. Examples thereof include a compound, a heterocyclic aromatic organic compound containing a nitrogen atom, and N-heterocyclic carbene. The cationic organic catalyst is used in the ring-opening polymerization reaction. In this case, hydrogen is extracted from the polymer main chain (back-biting), and therefore, the molecular weight distribution is widened and it is difficult to obtain a high molecular weight product.

Examples of the cyclic amine include quinuclidine.
Examples of the cyclic diamine include 1,4-diazabicyclo- [2.2.2] octane (DABCO), 1,5-diazabicyclo (4,3,0) -5-nonene.
Examples of the cyclic diamine compound having an amidine skeleton include 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and diazabicyclononene.
Examples of the cyclic triamine compound having a guanidine skeleton include 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) and diphenylguanidine (DPG).
Examples of the heterocyclic aromatic organic compound containing a nitrogen atom include N, N-dimethyl-4-aminopyridine (DMAP), 4-pyrrolidinopyridine (PPY), pyrocholine, imidazole, pyrimidine, and purine. Can be mentioned.
Examples of the N-heterocyclic carbene include 1,3-di-tert-butylimidazol-2-ylidene (ITBU).
Among these, DABCO, DBU, DPG, TBD, DMAP, PPY, and ITBU are preferable because they are less affected by steric hindrance and have high nucleophilicity or have a boiling point that can be removed under reduced pressure.

  Among these organic catalysts, for example, DBU is liquid at room temperature and has a boiling point. When such an organic catalyst is selected, the organic catalyst can be almost quantitatively removed from the polymer by subjecting the obtained polymer to a reduced pressure treatment. In addition, the kind of organic solvent and the presence or absence of a removal process are determined according to the use purpose of a product, etc.

  The type and amount of the organic catalyst vary depending on the combination of the compressive fluid and the ring-opening polymerizable monomer described later, and thus cannot be specified unconditionally. It is preferably no greater than 1 part by mass, more preferably no less than 0.1 parts by mass and no greater than 1 part by mass, and even more preferably no less than 0.3 parts by mass and no greater than 0.5 parts by mass. If the amount used is less than 0.01 parts by mass, the organic catalyst may be deactivated before the polymerization reaction is completed, and a polymer having a target molecular weight may not be obtained. On the other hand, when the amount used exceeds 15 parts by mass, it may be difficult to control the polymerization reaction.

<<< Hydrophilic polymer >>>
Since the hydrophilic polymer is three-dimensionally cross-linked with the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton, the hydrophilic polymer has a plurality of functional groups capable of reacting with the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton, or is cross-linked. It is necessary to react with the agent. As the functional group, known groups such as a hydroxyl group, a carboxyl group, a vinyl group, an amide group, an epoxy group, and an isocyanate group can be used. However, since the chain end of the polylactic acid segment is a hydroxyl group, it is easy to react. Is preferred.

  As the hydrophilic polymer, known polymers can be used from natural polymers such as cellulose, alginic acid and pectin, and synthetic polymers such as polyacrylamide, polyethylene oxide, polyvinyl alcohol and polystyrenesulfone sodium. Further, the hydrophilic polymer may have a polyhydroxycarboxylic acid skeleton.

The hydrophilic polymer of the present invention is a water-soluble polymer having a water absorption of 2% or more measured by the method A described in JIS K7209 Plastics-Determination of water absorption.
In order to develop impact resistance, the Tg of the hydrophilic polymer is preferably −60 ° C. or more and 30 ° C. or less, that is, rubbery at room temperature, and when Tg is lower than −60 ° C., impact resistance However, the thermal properties of the polylactic acid resin composition are lowered, and the heat distortion temperature is lowered. On the contrary, when Tg is higher than 30 ° C., the effect of improving the impact resistance cannot be obtained.

It is important that the content of the hydrophilic polymer in the biodegradable resin composition satisfies the following formula (1).
1% by mass ≦ [A / (A + B)] × 100 ≦ 50% by mass (1)
A: Mass of hydrophilic polymer in biodegradable resin composition B: Having polyhydroxycarboxylic acid skeleton in biodegradable resin composition
Mass of aliphatic polyester resin
In the formula (1), the content of the hydrophilic polymer is 1% by mass or more and 50% by mass or less, and preferably 10% by mass or more and 30% by mass or less. When the amount is less than 1% by mass, the effect of modifying the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton cannot be sufficiently obtained, and impact resistance and decomposability cannot be improved. When the amount is more than 50% by mass, hydrolysis of the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton is promoted too much, so that it is difficult to maintain the shape after the molding process and may not be practically used.

<Crosslinking agent>
There is no restriction | limiting in particular as said crosslinking agent, A well-known thing can be used. For example, divalent or higher isocyanate, oxazoline, epoxy, carboxylic anhydride, acid chloride and the like can be mentioned. Among these, divalent or higher isocyanates and derivatives thereof are preferable because they can be easily reacted with the polylactic acid segment, and the urethane group is formed after the crosslinking reaction, so that the mechanical strength can be improved by the intermolecular interaction.

<Additives>
In this invention, when obtaining the said copolymer, you may add an additive as needed. Examples of additives include nucleating agents, surfactants, antioxidants, antifogging agents, ultraviolet absorbers, pigments, colorants, inorganic particles, various fillers, heat stabilizers, flame retardants, antistatic agents, and surfaces. Wetting improvers, incineration aids, lubricants, natural products, mold release agents, plasticizers, and the like. If necessary, a polymerization terminator (benzoic acid, hydrochloric acid, phosphoric acid, metaphosphoric acid, acetic acid, lactic acid, etc.) can also be used after the polymerization reaction for obtaining the copolymer.
The addition amount of the additive varies depending on the purpose of addition and the type of additive, but is preferably 0 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the copolymer.

<Nucleating agent>
The nucleating agent is not particularly limited as long as it imparts an action of promoting crystallization of the crystalline polymer, and a known nucleating agent can be used.
Examples of the organic nucleating agent include aliphatic esters, aliphatic amides, fatty acid metal salts and the like, and examples of the inorganic nucleating agent include talc, smectite, bentonite, dolomite, sericite, feldspar powder, kaolin, Examples thereof include silicates such as mica and montmorillonite. Particularly preferred is a polylactic acid composed of an optical isomer of lactic acid constituting the polylactic acid segment, which can form a stereocomplex type crystal with the polylactic acid segment, and an organic compound containing the structure of the optical isomer. It is at least one of the contained substances. Examples of the organic compound containing the structure of the optical isomer include those having a low molecular weight of polylactic acid and cannot be called a resin, and those containing other types of polymers and partially polylactic acid.
Although the addition amount of the said nucleating agent is not specifically limited, 0.1 mass part-15 mass parts are preferable with respect to 100 mass parts of polylactic acid segments, 1 mass part-12 mass parts are more preferable, and 3 mass parts- 10 parts by mass is more preferable. When the amount is less than 0.1 parts by mass, a remarkable crystallization promoting effect tends to be hardly obtained, and when the amount exceeds 15 parts by mass, the resin strength tends to decrease.

<Analysis of biodegradable resin composition>
The molecular structure of the polylactic acid resin composition can be confirmed by X-ray diffraction, GC / MS, LC / MS, IR measurement, etc. in addition to NMR measurement by solution or solid. Similarly, the formation of a crosslinked product by the polymer crosslinking agent can be confirmed by analyzing the molecular weight change before and after the reaction or analyzing the number of functional groups of the polymer crosslinking agent.

An example of the separation means for each component when analyzing the polylactic acid resin composition is shown in detail.
First, 1 g of the biodegradable resin composition is put into 100 mL of THF, and a solution in which the soluble components are dissolved is obtained while stirring for 30 minutes at 25 ° C.
This is filtered through a membrane filter having an opening of 0.2 μm to obtain a THF-soluble component of the polylactic acid resin composition.
Subsequently, this is melt | dissolved in THF, it is set as the sample for GPC measurement, and it inject | pours into GPC used for the molecular weight measurement of each above-mentioned resin.

On the other hand, a fraction collector is placed at the eluate outlet of GPC, and the eluate is collected every predetermined count, and the eluate is eluted every 5% in area ratio from the elution curve elution start (curve rise). Get.
Next, for each elution, 30 mg of sample is dissolved in 1 mL of deuterated chloroform, and 0.05% by volume of tetramethylsilane (TMS) is added as a reference substance.
The solution is filled in a 5 mm diameter glass tube for NMR measurement, and a spectrum is obtained by performing integration 128 times at a temperature of 23 ° C. to 25 ° C. using a nuclear magnetic resonance apparatus (JNM-AL400 manufactured by JEOL Ltd.). .
The composition and composition ratio of [polylactic acid segment], [hydrophilic polymer], [nucleating agent] and the like contained in the polylactic acid resin composition can be determined from the peak integration ratio of the obtained spectrum.

For example, peak assignment is performed as follows, and the component ratio of the constituent monomer is determined from each integral ratio. The attribution of the peak is, for example,
Near 8.25 ppm: derived from benzene ring of trimellitic acid (for one hydrogen)
8.07 ppm to around 8.10 ppm: derived from benzene ring of terephthalic acid (for 4 hydrogens)
7.1 ppm to 7.25 ppm vicinity: derived from benzene ring of bisphenol A (for 4 hydrogens)
Around 6.8 ppm: derived from benzene ring of bisphenol A (for 4 hydrogens) and from double bond of fumaric acid (for 2 hydrogens)
5.2 ppm to around 5.4 ppm: methine derived from bisphenol A propylene oxide adduct (one hydrogen)
4.0-4.2 ppm vicinity: Derived from methine group of lactic acid (for one hydrogen)
4.0 ppm to around 5.0 ppm: derived from methylene of aliphatic alcohol (for two hydrogens)
3.7 ppm to around 4.7 ppm: bisphenol A propylene oxide adduct derived from methylene (for 2 hydrogens) and bisphenol A ethylene oxide adduct derived from methylene (for 4 hydrogens)
2.2 ppm to around 2.6 ppm: derived from aliphatic dicarboxylic acid methylene (for two hydrogens)
Around 1.6 ppm: derived from methyl group of bisphenol A and aliphatic alcohol (for 6 hydrogens)
Near 1.2 to 1.3 ppm: It can be derived from the methyl group of lactic acid (for 3 hydrogen atoms).

Similarly, the polylactic acid resin composition can be analyzed by pyrolysis gas chromatography. An example is shown below.
A reaction pyrolysis gas chromatograph mass spectrometry (GC / MS) method using a reaction reagent is performed. The reaction reagent used in the reaction pyrolysis GC / MS method is a 10% by mass methanol solution (manufactured by Tokyo Chemical Industry Co., Ltd.) of tetramethylammonium hydroxide (TMAH). The GC-MS device uses Shimadzu QP2010 (instrument management No. 040108Z), the data analysis software uses Shimadzu GCMSsolution, and the heating device uses Frontier Labs Py2020D.

〔Analysis conditions〕
・ Reaction pyrolysis temperature: 500 ℃
Column: Ultra ALLOY-5, L = 30 m, ID = 0.25 mm,
Film = 0.25 μm
Column heating: 50 ° C. (holding 1 minute) to 10 ° C./min to 330 ° C. (holding 11 minutes)
Carrier gas pressure: 53.6 kPa constant Column flow rate: 1.0 mL / min
・ Ionization method: EI method (70 eV)
Mass range: m / z, 29-700
Injection mode: Split (1: 100)
At this time, the optical purity of the polylactic acid segment of the biodegradable resin composition can be measured by changing the column to be used to a chiral column.

<< Compressive fluid >>
In the present invention, it is preferable to perform a crosslinking reaction in a compressive fluid in the step of crosslinking the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton and the hydrophilic polymer with a crosslinking agent. Moreover, when obtaining a polylactic acid segment, it is preferable to produce an aliphatic polyester resin having a hydroxycarboxylic acid skeleton by performing a polymerization reaction in a compressive fluid.

The compressive fluid will be described with reference to FIGS. 1 and 2. FIG. 1 is a phase diagram showing the state of a substance with respect to temperature and pressure. FIG. 2 is a phase diagram for defining the range of the compressible fluid.
The compressible fluid means a fluid in a state existing in any of the regions (1), (2), and (3) shown in FIG. 2 in the phase diagram shown in FIG. To do.

  In such a region, it is known that the substance has a very high density and behaves differently from that at normal temperature and pressure. In addition, when a substance exists in the area | region of (1), it becomes a supercritical fluid. A supercritical fluid is a fluid that exists as a non-condensable high-density fluid in a temperature and pressure region that exceeds the limit (critical point) at which gas and liquid can coexist, and does not condense even when compressed. Further, when the substance is present in the region (2), it becomes a liquid, but in the present invention, it is obtained by compressing a substance that is in a gaseous state at normal temperature (25 ° C.) and normal pressure (1 atm). Represents liquefied gas. Further, when the substance is present in the region (3), it is in a gaseous state, but in the present invention, it represents a high-pressure gas whose pressure is 1/2 (1/2 Pc) or more of the critical pressure (Pc).

  Examples of the substance constituting the compressive fluid include carbon monoxide, carbon dioxide, dinitrogen monoxide, nitrogen, methane, ethane, propane, 2,3-dimethylbutane, and ethylene. Among these, carbon dioxide is preferable in that it has a critical pressure of about 7.4 MPa and a critical temperature of about 31 ° C., can easily create a supercritical state, and is nonflammable and easy to handle. These compressive fluids may be used alone or in combination of two or more.

  When polymerization is performed in a compressive fluid, the polymer produced is plasticized by the compressive fluid, and the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton used in the present invention is polymerized in the compressive fluid. In this case, since crystallization is inhibited, it can be handled as a fluid at a temperature lower than the crystallization temperature of the polymer. For general copolymerization of crystalline polylactic acid, methods of dissolving or dispersing in an organic solvent after polylactic acid polymerization or a method of carrying out in a molten state are known, but crystalline polylactic acid is chloroform, methylene chloride, etc. It dissolves only in halogen-based solvents, and these solvents have a boiling point that is too low to raise the temperature to the reaction temperature required for copolymerization. In addition, since the reaction in the molten state must be carried out at 180 ° C. or higher, polylactic acid depolymerization and main chain cleavage occur simultaneously with the copolymerization, and the mechanical strength of the copolymer may not be sufficiently developed. .

Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.
In addition, each physical property of the polymer used by an Example and a comparative example was calculated | required as follows.

<Measurement of glass transition point>
The melting point and glass transition temperature (Tg) in the present invention were measured using a DSC system (differential scanning calorimeter) (“Q-200”, manufactured by TA Instruments). Specifically, the glass transition temperature of the target sample was measured by the following procedure. First, about 5.0 mg of the target sample was placed in an aluminum sample container, and the sample container was placed on a holder unit and set in an electric furnace. Next, the sample was heated from 40 ° C. to 200 ° C. at a temperature increase rate of 10 ° C./min in a nitrogen atmosphere (first temperature increase). Thereafter, the temperature was decreased from 200 ° C. to −15 ° C. at a temperature decrease rate of 10 ° C./min, and further heated to 200 ° C. at a temperature increase rate of 10 ° C./min (second temperature increase), and the DSC curve was measured.
From the obtained DSC curve, the DSC curve at the second temperature rise was selected using the analysis program in the Q-200 system, and the value was read by adopting the midpoint method in the thermogram. Asked. The endothermic peak top temperature at the second temperature increase can be determined as the melting point.

(Synthesis of an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton)
<Polyester resin A-1>
In a 1 L four-necked flask equipped with a nitrogen introducing tube, a dehydrating tube, a stirrer, and a thermocouple, 500 parts by mass of L-lactide, 0.10 parts by mass of trimethylolpropane, and di (2-ethylhexanoic acid) tin 0 .05 parts by mass, reacted at 180 ° C. for 2 hours, and reduced in pressure to 10 torr at 175 ° C. to distill off the remaining monomer, which is an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton [polyester resin A- 1] was obtained. The weight average molecular weight (Mw) was 205,000, the melting point was 178 ° C., and the optical purity (%) was 99.7%.

<Polyester resins A-2 to A-4>
It is an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton in the same manner as in [Polyester resin A-1] except that the input amount of raw materials is changed as shown in Table 1 in the synthesis of [Polyester resin A-1]. [Polyester resin A-2] to [Polyester resin A-4] were obtained. Table 2 shows the weight average molecular weight (Mw), melting point and optical purity (%) of the obtained polyester resin.

<Synthesis of polyester resin having no polyhydroxycarboxylic acid skeleton>
In a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, 61.7 parts by mass of an ethylene oxide 2-mole adduct of bisphenol A, 3.6 parts by mass of propylene glycol, 3.1 parts by mass of trimellitic anhydride, and 0.2 parts by mass of dibutyltin oxide was added and reacted at 170 ° C. for 1 hour under normal pressure. Next, 31.5 parts by mass of adipic acid was added and reacted at 230 ° C. for 4 hours under normal pressure, and then reacted for 5 hours under reduced pressure of 10 mmHg to 15 mmHg to obtain [Polyester Resin C]. The Tg was 23.1 ° C. and the water absorption rate was 1.2%.

<Synthesis of nucleating agent>
Into a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, 100 parts by mass of D-lactide was charged, the internal temperature was gradually raised to 50 ° C., and then ring-opening polymerization was performed at 10 mmHg for 30 minutes. Next, the temperature was raised to 170 ° C. in a nitrogen atmosphere, and after confirming that the system was homogenized by visual observation, 0.2 parts by mass of tin 2-ethylhexanoate and 1.0 part by mass of ethylene glycol were added. The polymerization reaction was carried out. At this time, the internal temperature of the system was controlled so as not to exceed 190 ° C. After the reaction time of 2 hours, delactide was performed under conditions of 190 ° C. and 10 mmHg to complete the polymerization reaction, to obtain a poly D-lactic acid resin (PDLA). The weight average molecular weight was 13,700.

Example 1
85 parts by mass of [Polyester Resin A-1] in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, PEG 20000 (manufactured by Wako Pure Chemical Industries, Tg-32 ° C., water-soluble polymer) as a hydrophilic polymer 15 After adding 2 parts by mass of triphenylmethane-4, 4 ′, 4 ″ -triisocyanate and 100 parts by mass of dichlorobenzene as mass parts and a crosslinking agent, the mixture was uniformly mixed, and then reacted at 100 ° C. for 4 hours. After the reaction, the pressure was reduced at 180 ° C. to distill off dichlorobenzene, and 5 parts by mass of poly-D-lactic acid resin was added as a nucleating agent to obtain [Biodegradable resin composition B-1].

(Example 2)
85 parts by mass of [Polyester resin A-1] in a pressure vessel, 15 parts by mass of polyethylene glycol 20000 (manufactured by Wako Pure Chemical Industries, Ltd.) as a hydrophilic polymer, and triphenylmethane-4, 4 ′, 4 ″ -tri as a crosslinking agent 2 parts by mass of isocyanate was added, pressurized to 10 MPa with carbon dioxide, and reacted at 100 ° C. for 4 hours. As a nucleating agent, 5 parts by mass of a poly-D-lactic acid resin was added to obtain [Biodegradable resin composition B-2].

(Examples 3 to 6)
[Example 2] [Biodegradable resin composition B-3] to [Biodegradable] of Examples 3 to 6 were the same as Example 2 except that the amount of raw materials charged was changed as shown in Table 3. Resin composition B-6] was obtained.

(Comparative Example 1)
[Example 2] [Biodegradable resin composition B-7] to [Biodegradable resin of Comparative Examples 1 to 4 were the same as Example 2 except that the amount of raw materials was changed as shown in Table 3. Composition B-10] was obtained.

A test piece was prepared from the obtained biodegradable fat composition using an injection molding machine, and the heat distortion temperature was measured in accordance with JIS K7191-2. Furthermore, the Izod impact strength was measured according to JISK7110, the mold shrinkage was measured according to JISK7152-4, and the biodegradation period was measured according to JISK6953-1. The results are listed in Table 4.
The impact test is preferably high because it shows the impact resistance / durability of the molded product, and when it is lower than 5 kJ / cm ^2, the possibility of occurrence of a problem is high.
-Evaluation criteria-
◎: 15kJ / cm ² or more ○: 10kJ / cm ² or more 15kJ / cm less than ² △: 5kJ / cm ² or more 10kJ / cm ² less than ×: 5kJ / cm less than ²

It is preferable that the heat distortion temperature showing heat resistance is also high, and when it is lower than 70 ° C., it was determined as x because it easily deformed in a high temperature environment such as in a car in summer.
-Evaluation criteria-
◎: 100 ° C. or higher ○: 80 ° C. or higher and lower than 100 ° C. Δ: 70 ° C. or higher and lower than 80 ° C.

The molding shrinkage rate is preferably low. If 1.5% or more, sink marks or warpage may occur, it was determined as x.
-Evaluation criteria-
◎: Less than 0.5% ○: 0.5% or more and less than 1.0% △: 1.0% or more and less than 1.5% ×: 1.5% or more

The biodegradation period is preferably short.
-Evaluation criteria-
◎: Less than 120 days ○: 120 days or more and less than 240 days △: 240 days or more and less than 360 days ×: 360 days or more

JP-A-11-116788

Claims (7)

  A resin composition obtained by three-dimensionally cross-linking an aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton polymerized by an initiator having a divalent or higher hydroxyl group and a hydrophilic polymer, the glass of the hydrophilic polymer A biodegradable resin composition having a transition point of -60 ° C or higher and 30 ° C or lower.   The biodegradable resin composition according to claim 1, wherein the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton is polylactic acid or a copolymer of polylactic acid. The biodegradable resin composition according to claim 1 or 2, wherein the content of the hydrophilic polymer in the biodegradable resin composition satisfies the following formula (1).
1% by mass ≦ [A / (A + B)] × 100 ≦ 50% by mass (1)
A: Mass of hydrophilic polymer in biodegradable resin composition B: Having polyhydroxycarboxylic acid skeleton in biodegradable resin composition
Mass of aliphatic polyester resin   The biodegradable resin composition according to any one of claims 1 to 3, wherein the aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton has a melting point of 170 ° C or higher and 220 ° C or lower.   An aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton polymerized by an initiator having a divalent or higher hydroxyl group and a hydrophilic polymer having a glass transition point of −60 ° C. or higher and 30 ° C. or lower are crosslinked with a crosslinking agent. The manufacturing method of the biodegradable resin composition in any one of Claims 1-4 characterized by the above-mentioned.   6. The aliphatic polyester resin having a polyhydroxycarboxylic acid skeleton is obtained by polymerizing a raw material monomer with an initiator having a divalent or higher hydroxyl group in a compressive fluid. The manufacturing method of the biodegradable resin composition as described in any one of.   The method for producing a biodegradable resin composition according to claim 5 or 6, wherein the crosslinking reaction is performed in a compressive fluid.

Images