JP5071598B2 - Biodegradable resin composition - Google Patents

Description

  The present invention relates to a biodegradable resin composition containing, as a main component, a hardly hydrolyzable biodegradable resin such as polylactic acid. More specifically, the present invention has transparency along with the degradability of the biodegradable resin. The present invention relates to an enhanced biodegradable resin composition.

  Recently, biodegradable resins have attracted attention from various viewpoints in various fields. In particular, biodegradable resins such as polylactic acid are hardly hydrolysable and stable even when contacted with water, etc., so various molded products using such hardly hydrolyzable biodegradable resins are practical. It is offered to. For example, Patent Document 1 proposes a lactic acid resin composition containing polylactic acid as a main component and a molded product thereof.

  By the way, a molded body made of a biodegradable resin such as polylactic acid is hardly hydrolyzable, so it takes time to decompose due to the action of an enzyme. Since the decomposition proceeds, it takes a long time until the biodegradable resin forming the molded body is completely decomposed, and the property of biodegradability is not fully utilized.

In order to solve such a problem, the present applicant previously described a biodegradable resin composition in which an aliphatic polyester such as polyethylene oxalate is blended as an ester decomposition accelerator in a biodegradable resin such as polylactic acid. Proposed (see Patent Document 2).
Aliphatic polyesters such as polyethylene oxalate blended in this biodegradable resin composition are easily hydrolysable and easily hydrolyze to release acid when mixed with water. It functions as an agent. That is, since the released acid accelerates the hydrolysis of the biodegradable resin, the degradation of the biodegradable resin by the enzyme can be significantly accelerated. Further, when a molded body such as a container formed of this biodegradable resin composition is mixed with an enzyme aqueous solution, cracks are generated in the molded body due to hydrolysis of the aliphatic polyester. Easily penetrates into the molded body, leading to the degradation of the biodegradable resin from within the molded body. As a result, the degradation of the biodegradable resin by the enzyme is significantly accelerated even in the form of molded products. There is an advantage of being.

Patent Document 3 proposes a biodegradable polyester composition in which a small amount of polyglycolic acid is blended with polylactic acid.
Furthermore, in Patent Document 4, a block or graft copolymer having a polyamino acid as a hydrophilic segment and a degradable polymer (for example, polylactic acid) as a hydrophobic segment is mixed with a degradable resin such as polylactic acid. A resin composition is disclosed.

JP-A-11-116788 WO2008-038648 JP 2009-13352 A JP 2000-345033 A

  As disclosed in Patent Documents 2 and 3, a resin composition in which a polyester such as polyethylene oxalate or polyglycolic acid is blended with polylactic acid has improved biodegradability but has transparency. There is a disadvantage that it is lowered. Further, as disclosed in Patent Document 4, a resin composition in which polylactic acid is blended with a copolymer having a hydrophilic segment such as a polyamino acid and a hydrophobic segment of a degradable polymer has a certain amount. Although an improvement in transparency is brought about, the degree thereof is not sufficient, and further, a sufficient improvement in terms of biodegradability cannot be realized.

  Accordingly, an object of the present invention is to provide a biodegradable resin composition having excellent biodegradability and excellent transparency.

  According to the present invention, in the biodegradable resin composition containing the hardly hydrolyzable biodegradable resin (A) and the ester decomposition accelerator (B), the ester decomposition accelerator (B) is hardly hydrolyzed. The block copolymer polyester containing the segment (X) of the water-soluble polyester and the segment (Y) of the easily hydrolyzable polyester in a weight ratio of 10/90 <X / Y <75/25 is blended. A biodegradable resin composition is provided.

In the present invention, the hardly hydrolyzable means that a TOC (total amount of 10% diluted solution of a sample polymer prepared in 100 mg / 10 ml concentration and hydrolyzed at 100 rpm for 7 days at 45 ° C. Organic carbon content) is 5 ppm or less. Furthermore, water-soluble polyester is not included.
Moreover, the easily hydrolyzable means that the TOC (total organic carbon content) measured in the same manner as described above is larger than 5 ppm.

In the biodegradable resin composition of the present invention,
(1) The polyester constituting the segment (X) is polylactic acid, and the easily hydrolyzable polyester constituting the segment Y is polyglycolic acid.
(2) The block copolymer polyester is contained in an amount of 1 to 20 parts by weight as an ester decomposition accelerator (B) per 100 parts by weight of the hardly hydrolyzable biodegradable resin (A).
(3) 1 to 10% by weight of the hardly hydrolyzable biodegradable resin (A) is a low molecular weight polylactic acid having a weight average molecular weight (Mw) in the range of 50,000 or less,
Is preferred.

  In the biodegradable resin composition of the present invention, a block copolymer polyester comprising a hardly hydrolyzable polyester segment (X) and an easily hydrolyzable polyester segment (Y) as an ester degradation accelerator (B). (Hereinafter sometimes referred to as a copolyester) is used. When such a copolyester is brought into contact with moisture, the easily hydrolyzable polyester segment (Y) is hydrolyzed to release an acid acting as an ester decomposition catalyst. As a result, the decomposition of the hardly hydrolyzable biodegradable resin (A) in the composition is accelerated.

  Moreover, said copolyester has the segment (X) of the hardly hydrolyzable polyester. This segment (X) has a high affinity for the hardly hydrolyzable biodegradable resin (A). Therefore, the copolymer polyester containing the segment (X) is uniformly in the biodegradable resin (A). It can be finely dispersed. Therefore, the biodegradable resin composition of the present invention containing such a copolyester as the ester decomposition accelerator (B) has excellent transparency as well as excellent biodegradability. For example, when a 200 μm-thick film is formed using this resin composition, a film having a very low haze (cloudiness: JIS K6714) of 15% or less can be obtained.

  As described above, according to the present invention, the molded body molded from this biodegradable resin composition has excellent transparency and can be applied to various applications as well as quickly. It can be collapsed and is extremely advantageous in avoiding environmental destruction such as an increase in dust, and the used molded product can be collected to recycle and recycle the biodegradable resin.

It is a diagram which shows the relationship between a decomposition time and a TOC value about the ester decomposition accelerator used in the Example and the comparative example.

  The biodegradable resin composition of the present invention contains a hardly hydrolyzable biodegradable resin (A) and an ester decomposition accelerator (B) as main components, and in addition to this, an ester decomposition acceleration assistant (C). Such additives are appropriately blended, and these components are prepared by melt-kneading with an extruder or the like.

<Biodegradable resin (A)>
In the present invention, the biodegradable resin used is hardly hydrolyzable. For example, as described above, the TOC (total organic carbon content) measured by a predetermined method is 5 ppm or less, Contains no sex polyester. Examples of such hardly hydrolyzable biodegradable resins include polylactic acid, polyhydroxyalkanoate, polycaprolactone, polybutylene succinate, cellulose acetate and the like, which are copolymers and blends. It can also be used in the form. In the present invention, polylactic acid is particularly preferably used.

  The polylactic acid may be 100% poly-L-lactic acid or 100% poly-D-lactic acid, or may be a melt blend of poly-L-lactic acid and poly-D-lactic acid, It may be a random copolymer or block copolymer of L-lactic acid and D-lactic acid.

  Furthermore, the above-described biodegradable resin (A) has various aliphatic polyhydric alcohols and fats as long as the characteristics of the biodegradable resin are not impaired, for example, as long as the TOC value is maintained within the above-described range. It can also be used in the form of a copolymer obtained by copolymerizing an aromatic polybasic acid, hydroxycarboxylic acid, lactone or the like.

Examples of such polyhydric alcohols include ethylene glycol, propylene glycol, butanediol, octanediol, dodecanediol, neopentyl glycol, glycerin, pentaerythritol, sorbitan, and polyethylene glycol.
Examples of the polybasic acid include oxalic acid, succinic acid, adipic acid, sebacic acid, glutaric acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, and terephthalic acid.
Examples of the hydroxycarboxylic acid include glycolic acid, hydroxypropionic acid, hydroxyvaleric acid, hydroxycaproic acid, and mandelic acid.
Examples of the lactone include caprolactone, butyrolactone, valerolactone, poropiolactone, undecalactone, glycolide, and mandelide.

  In the present invention, polylactic acid can be most suitably used as the biodegradable resin (A) from the viewpoint of being suitably applied in the field of packaging materials such as containers.

  In addition, the biodegradable resin (A) described above should have a molecular weight sufficient to form a film from the viewpoint of moldability, but contains a low molecular weight component as long as the moldability is not impaired. It is preferable. For example, the biodegradable resin (A) has a low content of 1 to 10% by weight, preferably 1 to 5% by weight, and a weight average molecular weight (Mw) of 50,000 or less, preferably 500 to 2000. The inclusion of molecular weight polylactic acid is suitable for ensuring excellent biodegradability. That is, such a low molecular weight polylactic acid is rapidly degraded to the monomer (lactic acid) level by the ester degradation accelerator (B) described later, and the monomer functions as an ester degradation accelerator. Degradability can be obtained.

  The above-described biodegradable resin (A) is hardly hydrolyzable with a TOC value of 5 ppm or less, and requires a very long time for its decomposition. Therefore, the following ester decomposition accelerator (B) is blended, Improve the degradation rate.

<Ester degradation accelerator (B)>
In the present invention, a block copolymerized polyester containing a hardly hydrolyzable polyester segment (X) and an easily hydrolyzable polyester segment (Y) is used as the ester degradation accelerator (B).
That is, since this copolyester contains a segment (Y) of an easily hydrolyzable polyester, it is more easily hydrolysable than the biodegradable resin (A), and the TOC value measured by the method described above. Shows a value greater than 5 ppm, preferably in the range of 10 to 50 ppm. Accordingly, this copolyester acts as an ester decomposition accelerator (B) and releases an acid that functions as a catalyst for ester decomposition when mixed with moisture, and this acid hydrolyzes the biodegradable resin (A). Will be promoted quickly.

  Further, the copolymer polyester includes a segment (X) of a hardly hydrolyzable polyester. That is, the polyester which this segment (X) constitutes has a TOC value of 5 ppm or less, which is higher than that of the biodegradable resin (A), similarly to the above-described hardly hydrolyzable biodegradable resin (A). Shows affinity. For this reason, this copolyester can be uniformly and finely dispersed in the hardly hydrolyzable biodegradable resin (A), and therefore it is possible to ensure excellent transparency.

  In the present invention, the polyester that forms the hardly hydrolyzable segment (X) as described above is not particularly limited as long as it has a TOC value of 5 ppm or less and is hardly hydrolyzable. From the viewpoint of high affinity for A), aliphatic polyesters are preferred, and in particular, polyesters of the same type as the biodegradable resin (A), specifically, polylactic acid, polyhydroxyalkanoate, polycaprolactone, poly Butylene succinate and cellulose acetate are more preferred, and polylactic acid is most suitable.

Further, the polyester formed by the easily hydrolyzable segment (Y) has a TOC value higher than 5 ppm, preferably 10 ppm or more, particularly when mixed with water, having a concentration of 0.005 g / ml. Polyesters that readily release an acid having an aqueous solution or aqueous dispersion having a pH (25 ° C.) of 4 or less, particularly 3 or less, are preferred. Is the best.
This polyoxalate is a polyester in which oxalic acid is used as an acid component.

  In the present invention, the hardly hydrolyzable segment (X) and the easily hydrolyzable segment (Y) as described above have a weight ratio (X / Y) of 10/90 <X / Y <75/25. It contains in the ratio which becomes the range of. That is, when the content ratio of the hardly hydrolyzable segment (X) is larger than the above range, for example, the TCO value is in a range of 5 ppm or less, and the function of this copolymer polyester as an ester decomposition accelerator is obtained. It will be damaged and it will be difficult to improve biodegradability. On the other hand, when the content ratio of the easily hydrolyzable segment (Y) is larger than the above range, the function as an ester decomposition accelerator is sufficient, but the dispersibility for the biodegradable resin (A) is impaired. As a result, the transparency is lowered.

  Moreover, the copolymerization form of the copolymerized polyester mentioned above is a block copolymer. That is, in the case of a block copolymer, the affinity of the segment (X) to the biodegradable resin (A) and the ester resolution of the segment (Y) are fully exhibited, and uniform dispersion to the biodegradable resin (A) is achieved. The biodegradability can be maximized while securing the property (that is, transparency).

  Furthermore, the weight average molecular weight (Mw) of the above-mentioned copolymerized polyester is preferably in the range of 1,000 to 200,000 from the viewpoint of ensuring dispersibility in the above-mentioned hardly hydrolyzable biodegradable resin (A). It is.

  The above-mentioned copolymer polyester used in the present invention has a TOC higher than 5 ppm, and unless the affinity for the biodegradable resin (A) and the ester decomposition accelerating property are impaired, the above-mentioned segment (X) or Copolymer components other than the segment (Y) may be contained. Examples of such copolymer components include polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, octanediol, dodecanediol, neopentyl glycol, glycerin, pentaerythritol, sorbitan, bisphenol A, polyethylene glycol; oxalic acid, Dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, glutaric acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid and andracenedicarboxylic acid; glycolic acid, L-lactic acid, D-lactic acid, hydroxypropionic acid, Hydroxycarboxylic acids such as hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, mandelic acid, hydroxybenzoic acid; glycolide, caprolactone, butyllactone, valerolacto , Polo lactones, lactones, such as undecalactone; and the like can be mentioned.

  The copolyester used as the ester degradation accelerator (B) described above varies depending on the type, but generally 0.01 to 30 parts by weight per 100 parts by weight of the biodegradable resin (A). It is preferably used in an amount of 1 to 10 parts by weight. If the amount of the ester decomposition accelerator (B) used is too small, it may be difficult to promote the decomposition of the biodegradable resin (A). There is a possibility that the biodegradable resin (A) starts to be decomposed in the preparation stage or the stage where it is used as a molded body, and further, uniform dispersion becomes difficult and transparency tends to be impaired.

In addition, the above-mentioned copolymer polyester is a dibasic acid component, a diol component, a lactone, etc. for forming a polyester of segment (X) or segment (Y) according to a conventional method, and an acid or a copolymer component used as necessary. It can be obtained by polycondensation using an alcohol component. In this case, in order to produce the block copolymer, after the polyester of the segment (X) or the segment (Y) is produced, the component forming the segment (Y) or the segment (X) is added and the copolymerization is performed. Just do it.
The formation of the block polymer can be confirmed by the fact that a melting peak derived from the segment (X) and a melting peak derived from the segment (Y) are expressed by differential thermal analysis.

<Other additives>
The biodegradable resin composition of the present invention contains the above-described biodegradable resin (A) and ester decomposition accelerator (B) (copolymerized polyester) as main components, and in addition to this, the ester decomposition acceleration aid. Additives such as the agent (C) can be appropriately blended.

  The ester decomposition accelerating aid (C) is a component used for accelerating the hydrolysis of the copolymerized polyester (that is, the ester decomposition accelerator (B)). For example, an alkali metal or an alkaline earth metal is used. Typical examples include inorganic compounds such as basic compounds containing, zeolites that release alkali metal and alkaline earth metal ions, and ion-releasing fillers. That is, such inorganic particles promote hydrolysis of the ester decomposition accelerator (B) during molding and / or in the presence of water. Such inorganic particles also have a function of promoting the hydrolysis of the biodegradable resin (A) described above by itself.

  Basic compounds containing alkali metals or alkaline earth metals include sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, potassium silicate, calcium silicate, magnesium silicate , Sodium phosphate, calcium hydroxide, magnesium hydroxide and the like.

  As the above-mentioned zeolite, various natural or synthetic zeolites containing alkali metal or alkaline earth metal ions as exchangeable ions can be used.

  Examples of the ion releasing filler include oxide glasses such as aluminosilicate glass, borosilicate glass and soda lime glass containing alkali metal and alkaline earth metal, and fluoride glass such as zirconium fluoride glass. it can.

  Said ester decomposition acceleration | stimulation adjuvant (C) may be used individually, or may be mixed and used.

  In the present invention, from the viewpoint of little influence on the environment, no adverse effects on the properties of the biodegradable resin (A), and the decomposition of inorganic particles during thermoforming of the resin composition does not occur. Among the inorganic particles exemplified in the above, basic compounds containing calcium and / or sodium, zeolite capable of releasing calcium ions and / or sodium ions, calcium ion and / or sodium ion releasing fillers are preferable, and calcium carbonate is particularly preferable. Sodium carbonate is optimal.

In addition, the above-mentioned inorganic particles have an average particle size (average particle size D _{50 in} terms of volume by laser diffraction scattering method) of 10 μm or less, particularly 0.01 μm to from the viewpoint of uniformly dispersing in the resin composition. The thing in the range of 5 micrometers is preferable.

  Such inorganic particles are preferably used in an amount of 0.05 to 2 parts by weight, particularly 0.05 to 1 part by weight, per 100 parts by weight of the ester decomposition accelerator (A). If the amount of the inorganic particles is too large, the thermoformability and transparency of the resin composition are impaired, or the ester decomposition accelerator (B) or the biodegradable resin (A) in the molded body molded from the resin composition. ) Is promoted and the shape of the molded body is impaired, and the uniform dispersibility with respect to the biodegradable resin (A) is also impaired, leading to a decrease in transparency. Moreover, when the amount of the inorganic particles is less than the above range, it is insufficient to increase the decomposition rate of the biodegradable resin.

  Of the inorganic particles described above, sodium carbonate has the greatest hydrolysis promoting function for the ester decomposition accelerator (B) and the biodegradable resin (A). For this reason, when sodium carbonate is used alone. In some cases, the molecular weight of the biodegradable resin (A) is extremely lowered during thermoforming, and further, the product value may be lowered due to discoloration of the biodegradable resin (A). Therefore, when sodium carbonate is used, the amount is preferably in the range of 0.1 to 35 ppm with respect to the biodegradable resin (A), and is preferably used in combination with calcium carbonate. While promoting the degradation of polyglycolic acid, it is possible to suppress a decrease in the molecular weight of the biodegradable resin (A) and increase the enzymatic degradation rate of the resulting biodegradable resin composition. Thus, when sodium carbonate and calcium carbonate are used in combination, the total blending amount is preferably within the above-described range.

  Further, in addition to the ester decomposition acceleration aid (C) as described above, various resin additives can be appropriately blended, for example, in an amount that does not impair the moldability and biodegradation characteristics of the biodegradable resin. Plasticizers, light stabilizers, antioxidants, UV absorbers, flame retardants, colorants, pigments, fillers, mold release agents, antistatic agents, fragrances, foaming agents, antibacterial / antifungal agents, nucleating materials, etc. Further, other thermoplastic resins can be blended if necessary.

<Preparation and use of biodegradable resin composition>
The biodegradable resin composition of the present invention containing the various components described above is a mixture of the above-described (A) and (B), and various additives such as an ester decomposition accelerating aid (C) blended as appropriate, It can be prepared by melt-kneading in an extruder at a temperature at which each component does not decompose (for example, about 150 ° C. to 240 ° C.). In this case, the ester decomposition accelerator (B) (that is, the copolyester) and the biodegradable resin (A) may be directly mixed, or a master batch of the ester decomposition accelerator (B) and other components may be added. It may be produced and mixed with the biodegradable resin (A).

Such a resin composition can be used as molded bodies having various shapes by a molding method known per se, for example, extrusion molding, injection molding, compression molding or the like.
In particular, the resin composition of the present invention is excellent in transparency. For example, when a film having a thickness of 200 μm is formed, the haze is 15% or less. Therefore, the resin composition is required to have visibility of contents. It is particularly preferably used in the field of packaging materials.

That is, in the field of packaging materials, the above-described biodegradable resin composition can be used as a packaging film or sheet. In particular, the film is formed into a bag-like container (pouch) by bag making such as bonding with a three-way seal. ) Can be used.
Further, the film or sheet can be used as a cup-shaped or tray-shaped container by vacuum forming, pressure forming, stretch forming, plug assist forming, or the like. A cup-shaped container or a tray-shaped container may be directly molded by injection molding or compression molding. Furthermore, it can be used as a test tube-shaped preform by injection molding or the like, and can be used as a bottle-shaped container by blow molding using this preform.

  In the molded products of various shapes as described above, if necessary, they were laminated with other resins by molding using an extruder equipped with a multilayer multiple die or a co-injector equipped with a plurality of injection gates. It can also be used as a multilayer structure. In addition, when the film is multilayered, it is also possible to use a dry laminating method using an adhesive, an extrusion coating method, or a sandwich laminating method in which films are laminated with a molten resin.

<Disassembly method>
A molded body such as a container molded using the biodegradable resin composition of the present invention may be supplied to a decomposition tank as it is upon disposal, but this is appropriately cut into small pieces by cutting, crushing, or the like. After that, it can be supplied to the decomposition tank and decomposed.

  This decomposition treatment is performed in an aqueous medium in the presence of a catalyst. As such a catalyst, a water-containing solid acid catalyst, for example, an activated clay having a high specific surface area obtained by acid treatment of smectite clay such as acid clay or bentonite can be used, but an enzyme is used. Is preferred. That is, not only from the viewpoint of environmental impact and waste treatment, but also when an enzyme is used as a catalyst, the hydrolysis of the ester decomposition accelerator (B) is carried out from the inside of the molded body due to the penetration of moisture into the molded body. As the decomposition proceeds and the hydrolysis of the biodegradable resin (A) is promoted, the enzyme quickly penetrates into the molded body (waste). This is very advantageous in that the decomposition of (A) occurs and the molded product can be decomposed in a short time until it completely disintegrates.

  Examples of such enzymes include protease, cellulase, cutinase, lipase and the like, and these enzymes may or may not be immobilized. For example, protease K manufactured by Wako Pure Chemical Industries, Ltd. is used in the form of an aqueous solution. Moreover, microorganisms may be put in and the extracellular enzyme may be used, and the culture medium component and nutrient component which the microorganism requires may be added.

  In order to prevent the pH of the enzyme reaction solution from changing, the solvent during the decomposition treatment as described above can be performed, for example, by exchanging the reaction solution or using a buffer solution as the reaction solution. Suitable buffers include glycine-HCl buffer, phosphate buffer, Tris-HCl buffer, acetate buffer, citrate buffer, citrate-phosphate buffer, borate buffer, tartaric acid buffer, glycine- A sodium hydroxide buffer solution etc. are mentioned. Further, a solid neutralizing agent may be used in place of the buffer solution, and water may be used as the solvent. Examples thereof include calcium carbonate, chitosan, and deprotonated ion exchange resin. Neutralization can also be performed by appropriately adding an acid or alkali to the reaction solution. Moreover, you may add organic solvents, such as ethanol, as needed.

That is, it is preferable to perform the decomposition treatment by mixing and stirring the waste of the molded body of the biodegradable resin composition with the enzyme aqueous solution in the decomposition tank. At this time, the amount of the enzyme used varies depending on the activity of the enzyme used, but generally it may be an amount of about 0.01 to 10 parts by weight per 100 parts by weight of the hardly hydrolyzable biodegradable resin. The decomposition treatment is performed by putting the compact waste into the charged enzyme aqueous solution and stirring it.
In the case of using the above-described solid acid catalyst, since the solid acid catalyst contains water, the solid acid catalyst is dispersed in an appropriate organic solvent, and the compact waste is put into this dispersion. Is good.

  In such a decomposition treatment, it is preferable to heat at a temperature lower than the deactivation temperature of the enzyme (usually about 50 ° C.). By such heating, hydrolysis of polyglycolic acid (B) can be further promoted.

  As described above, when the decomposition is performed and the molded body is completely disintegrated, the biodegradable resin is decomposed into monomers or oligomers constituting the resin, and is taken out and used for microorganisms such as methane fermentation. Energy conversion may be performed, and if necessary, monomers or oligomers may be recovered by a separation operation such as distillation or extraction and reused for the synthesis of the biodegradable resin.

  In the following experimental examples, haze, TOC (elution total organic carbon content measurement) and enzyme degradability were measured by the following methods.

Haze measurement;
Measurement was performed according to JIS K6714 using a color computer [SM-4: Suga Test Instruments Co., Ltd.].

TOC (elution total organic carbon content) measurement (evaluation of hydrolyzability);
Using a JFC-300 freeze pulverizer manufactured by Nippon Analytical Industries, Ltd., the sample polymer was freeze pulverized, and 100 mg of the powdered sample polymer was poured into a 25 ml vial together with 10 ml of distilled water, It was hydrolyzed by shaking at 100 rpm. 1 ml of the supernatant of the sample solution is taken every time since the start of the test (every day), passed through a 0.45 μm filter, diluted 10-fold, and eluted with TOC-5000A manufactured by Shimadzu Corporation. The amount was measured, converted to a value at 100 mg / 10 ml, and set as a TOC value, and the hydrolysis amount was evaluated based on the TOC value.

Enzymatic degradation test;
Cryptococcus sp. 20 mg of S-2 derived lipase (Independent Administrative Institution Liquor Research Institute: JP-A-2004-73123) powder was dissolved in 1 ml of 0.05M Tris-HCl buffer (pH 8.0) containing 50 w / w% glycerin, A CLE enzyme solution was prepared.
12 μl of the above CLE enzyme solution was added to 10 ml of 60 mmol / L phosphate buffer having a pH of 7 to obtain an enzyme decomposition solution.
A film having a predetermined thickness produced using the biodegradable resin composition of the sample was placed in a 25 ml vial together with 10 ml of the enzyme decomposition solution and shaken at 45 ° C. and 100 rpm for 6 days. In addition, in order to avoid the extreme fall of pH, it divided | segmented 6 days every 2 days, and changed each decomposition solution. After 6 days, the film was taken out and dried in a 45 ° C. oven overnight, and the weight was measured.
The amount of enzymatic degradation of the film was calculated by subtracting the measured value from the initial film weight.

<Manufacture of copolyester>
1. Manufacture of block copolymer polyester A 300 mL separable flask equipped with a mantle heater, a stirrer, and a nitrogen introduction tube was charged with a predetermined amount of L-lactide (Musashino Chemical Laboratory Co., Ltd.), 2-ethylhexanoic acid tin (Wako Jun (Manufactured by Yakuhin Co., Ltd.) was added, and the temperature in the flask was heated from 100 ° C. to 200 ° C. in a nitrogen stream and reacted for 30 minutes. A predetermined amount of glycolide (manufactured by Sigma-Aldrich Japan Co., Ltd.) was added thereto and further reacted for 30 minutes. Thereafter, the mixture was stirred for 30 minutes under an internal temperature of 200 ° C. and a reduced pressure of 0.1 to 0.5 mmHg, and unreacted monomers and oligomers were removed by distillation.
When the copolymer polyester was produced as described above, the charged weight ratio of lactide and glycolide was variously changed as shown in Table 1, and four types of block copolymer polyesters B7525, B5050, B2575, and B1090 were obtained. .

It was confirmed by DSC measurement that the obtained copolyester was a block copolymer by the presence of a PLA melting peak and a PGA melting peak.
Moreover, the weight average molecular weight about the obtained copolyester was measured using Tosoh Co., Ltd. GPC, and the result was shown in Table 1.
For high molecular weight compounds, HFIP-605 was used as a column, HFIP (hexafluoroisopropanol) was used as an eluent, and polymethyl methacrylate was used as a standard substance.
For the low molecular weight, TSKgel SuperHM-H × 2 was used as a column, TSKguard column SuperH-H was used as a guard column, chloroform was used as an eluent, and polystyrene was used as a standard substance.

2. Manufacture of Random Copolymerized Polyester A predetermined amount of L-lactide, glycolide and tin 2-ethylhexanoate are placed in a 300 mL separable flask equipped with a mantle heater, a stirrer and a nitrogen inlet tube, and the temperature in the flask is set to 100 under a nitrogen stream. C. to 200.degree. C. and allowed to react for 1 hour. Thereafter, the mixture was stirred for 30 minutes under an internal temperature of 200 ° C. and a reduced pressure of 0.1 to 0.5 mmHg, and unreacted monomers and oligomers were removed by distillation.
When the copolymerized polyester was produced as described above, lactide and glycolide were charged at a weight ratio of 50/50 to obtain a random copolymerized polyester R5050.
About this random copolymer polyester, the weight average molecular weight was measured similarly to the above, and the result was shown in Table 1.
In addition, since the melting peak was single by DSC measurement, it was judged that it was a random copolymer.

3. Production of polyglycolic acid Polyglycolic acid (PGA) was produced in the same manner as in the production of the random copolymer polyester except that L-lactide was not used.
About this polyglycolic acid, the weight average molecular weight was measured similarly to the above, and the result was shown in Table 1.

<Hydrolysis test>
The TOC value was measured by the method described above for the block copolymer, random copolymer and polyglycolic acid of lactic acid and glycolic acid produced above, and the relationship between the number of days of hydrolysis and the TOC value is shown in FIG. . In addition, Table 1 shows the TOC value after 4 days of hydrolysis (holding time at 45 ° C.).

  From the above results, it was found that the greater the blending amount of glycolic acid in the copolyester, the higher the hydrolyzability. Further, from the results of B5050 and R5050, it was found that the block copolymer had higher hydrolyzability even at the same blending ratio.

<Experimental example 1>
As polylactic acid (PLA), 4032D (d-lactic acid 1.4%) manufactured by natureworks was prepared. The physical properties of this polylactic acid are as follows.
Weight average molecular weight: 160,000 TOC value (7 days of hydrolysis): 4 ppm

The previously synthesized block copolymer polyester B5050 was used as an ester decomposition accelerator, and this was melt kneaded with the above polylactic acid at a weight ratio shown in Table 2 to prepare a biodegradable resin composition.
Using an ultra-small kneader (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the obtained resin composition was kneaded at a molding temperature of 220 ° C. and a screw rotation speed of 50 rpm to produce pellets. The pellet was melted at 220 ° C. for 5 minutes and then heated and pressed (hot pressed) at a pressure of 80 to 100 kgf / cm ² to prepare a 200 μm thick film. About this film, the haze and the amount of enzymatic degradation were measured by the method described above, and the results are shown in Table 2.

<Experimental Examples 2 and 3>
A biodegradable resin composition was prepared in the same manner as in Experimental Example 1 except that random copolymer polyesters R2575 and R5050 were used as ester degradation accelerators, and the film was molded in the same manner to determine the amount of haze and enzymatic degradation. It was measured. Table 2 shows the blending amount of each component used for preparing the composition, and the measurement results of haze and enzymatic degradation amount.

<Experimental example 4>
Calcium carbonate (brilliant 1500 manufactured by Shiroishi Kogyo Co., Ltd.) was prepared as a decomposition promoting aid.
This calcium carbonate is blended with polylactic acid together with the block copolymer polyester B5050 in the blending amounts shown in Table 2, a biodegradable resin composition is prepared in the same manner as in Experimental Example 1, and a film is formed in the same manner. The haze and the amount of enzymatic degradation were measured. Table 2 shows the measurement results of the haze and the amount of enzymatic degradation together with the blending amounts of the respective components used for the preparation of the composition.

<Experimental example 5>
Low molecular weight polylactic acid (PLA) having a weight average molecular weight of 40,000 was prepared.
This low molecular weight polylactic acid was blended with high molecular weight polylactic acid in the blending amounts shown in Table 2 together with calcium carbonate (degradation accelerating aid) and block copolymer polyester B5050, and biodegraded in the same manner as in Experimental Example 4. An adhesive resin composition was prepared, and the film was molded in the same manner to measure the haze and the amount of enzymatic degradation. Table 2 shows the measurement results of the haze and the amount of enzymatic degradation together with the blending amounts of the respective components used for the preparation of the composition.

<Experimental Examples 6-8>
A biodegradable resin composition was prepared in exactly the same manner as in Experimental Example 1, except that polyglycolic acid, block copolymer polyester B7525 or block copolymer polyester B1090 was used in place of the block copolymer polyester as the ester degradation accelerator. And the film was shape | molded similarly and the haze and the enzymatic decomposition amount were measured. Table 2 shows the measurement results of the haze and the amount of enzymatic degradation together with the blending amounts of the respective components used for the preparation of the composition.

<Experimental Example 9>
Using polyglycolic acid as an ester degradation accelerator, blended in high molecular weight polylactic acid together with calcium carbonate (degradation acceleration aid) in the blending amounts shown in Table 2, and in the same manner as in Experimental Example 1, biodegradable resin A composition was prepared, and a film was molded in the same manner to measure the amount of haze and enzymatic degradation. Table 2 shows the measurement results of the haze and the amount of enzymatic degradation together with the blending amounts of the respective components used for the preparation of the composition.

<Experimental example 10>
A film was prepared using only polylactic acid in the same manner as in Experimental Example 1 without using any ester degradation accelerator, and the haze and the amount of enzymatic degradation were measured. The results are shown in Table 2.

<Experimental example 11>
A film was prepared by adding the low molecular weight polylactic acid used in Experimental Example 5 to the polylactic acid used in Experimental Example 1 in the blending amounts shown in Table 2, and the haze and enzymatic degradation amount were determined in the same manner as in Experimental Example 1. It was measured. The results are shown in Table 2.

上記表２に示された実験例１〜１１のうち、実験例１、４及び５が本発明の実施例であり、実験例２、３及び６〜１１が比較例である。

Of Experimental Examples 1 to 11 shown in Table 2 above, Experimental Examples 1, 4 and 5 are examples of the present invention, and Experimental Examples 2, 3 and 6 to 11 are comparative examples.

Claims (4)

  In the biodegradable resin composition containing the hardly hydrolyzable biodegradable resin (A) and the ester degradation accelerator (B), the segment of the hardly hydrolyzable polyester (X) as the ester degradation accelerator (B) ) And an easily hydrolyzable polyester segment (Y) in a weight ratio of 10/90 <X / Y <75/25 is blended. object.   The biodegradable resin composition according to claim 1, wherein the polyester constituting the segment (X) is polylactic acid, and the easily hydrolyzable polyester constituting the segment (Y) is polyglycolic acid.   The biodegradation according to claim 1 or 2, comprising 1 to 10 parts by weight of the block copolymerized polyester as an ester decomposition accelerator (B) per 100 parts by weight of the hardly hydrolyzable biodegradable resin (A). Resin composition.   The low molecular weight polylactic acid having 1 to 10% by weight of the hardly hydrolyzable biodegradable resin (A) having a weight average molecular weight (Mw) in the range of 50,000 or less. Biodegradable resin composition.

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