JP2010116482A - Polyoxalate and biodegradable resin composition containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable resin composition not reactive with environmental moisture even at around room temperature. <P>SOLUTION: The polyoxalate includes structural units represented by formulas (1) and (2) arranged at a molar ratio of 50:50 to 99:1 and has a weight-average molecular weight of 3,000-1,000,000, wherein R is a bivalent group selected from a group consisting of an aromatic cyclic hydrocarbon and an alicyclic hydrocarbon. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyoxalate and a biodegradable resin composition containing the polyoxalate.

Biodegradable polylactic acid resin compositions and the like have been proposed as packaging materials (see Patent Documents 1 and 2). However, the decomposition of packaging containers using these biodegradable resin compositions has occurred sequentially from the surface of the container, and it took a considerable amount of time to completely decompose the entire container. Furthermore, the degradation rate is affected by the internal structure of the resin such as the crystallinity and molecular orientation of the resin, and there is a problem that there are some areas that are easily decomposed and difficult to decompose.
In order to solve the above problem, a biodegradable resin composition containing polyethylene oxalate or the like and improved in degradability has been proposed (see Patent Document 3).

JP-A-11-116788 JP-A-9-316181 International Publication No. 2008/38648 Pamphlet

However, the glass transition temperature of polyethylene oxalate is reported to be 25 ° C. to 36 ° C., depending on the molecular weight. Therefore, it reacts with surrounding moisture even at a temperature of about room temperature to cause hydrolysis and release oxalic acid and / or oxalic acid oligomer.
Therefore, an object of the present invention is to provide a biodegradable resin composition that does not react with surrounding moisture even at a temperature of about room temperature.

  The present invention relates to a polyoxa compound having a weight average molecular weight of 3000 to 1000000 in which a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2) are arranged in a molar ratio of 50:50 to 99: 1. Provide rate.

（式中、Ｒは芳香族環炭化水素及び脂環炭化水素からなる群より選ばれるものから誘導される２価の基を表す。）

(In the formula, R represents a divalent group derived from a group selected from the group consisting of aromatic ring hydrocarbons and alicyclic hydrocarbons.)

  Moreover, this invention is 0.1-20 wt. A biodegradable resin composition containing 1% of the polyoxalate is provided.

  According to the present invention, a biodegradable resin composition that does not react with surrounding moisture even at a temperature of about room temperature can be provided.

  The polyoxalate of the present invention is a polyoxalate arranged in a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2).

R represents a divalent group derived from a group selected from the group consisting of aromatic ring hydrocarbons and alicyclic hydrocarbons, and the aromatic ring hydrocarbons and alicyclic hydrocarbons may be substituted. R preferably represents a divalent group derived from a group selected from the group consisting of a benzene ring, a cyclohexane ring and a naphthalene ring, more preferably a p-phenylene group.
The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) is 50:50 to 99: 1, preferably 70:20 to 98: 2, more preferably 70: 20-95: 5.
The weight average molecular weight of the polyoxalate of this invention is 3000-1 million, Preferably it is 5000-1 million, More preferably, it is 5000-500000.

The polyoxalate of the present invention has a larger amount of oxalic acid eluted at the time of enzymatic decomposition under a temperature condition of 37 ° C. than the amount of oxalic acid eluted at the time of hydrolysis. By including such a polyoxalate of the present invention in a biodegradable resin composition, a biodegradable resin composition excellent in biodegradability can be obtained.
The polyoxalate of the present invention preferably has a glass transition temperature of 40 ° C. or higher. Such a polyoxalate of the present invention does not react with surrounding moisture even at a temperature of about room temperature, and becomes a stable biodegradable resin that does not release oxalic acid. The glass transition temperature of the polyoxalate of the present invention is more preferably 42 ° C. or higher, and further preferably 45 ° C. or higher.

The biodegradable resin may be any resin having biodegradability, and examples thereof include chemically synthesized resins, microbial resins, and natural product-based resins. Specific examples include aliphatic polyesters, polyvinyl alcohol (PVA), and celluloses. Examples of the aliphatic polyester include polylactic acid (PLA) resin and derivatives thereof, polybutylene succinate (PBS) resin and derivatives thereof, polycaprolactone (PCL), polyhydroxybutyrate (PHB) and derivatives thereof, polyethylene adipate (PEA) ), Polyglycolic acid (PGA), polytetramethylene adipate, condensates of diol and dicarboxylic acid, and the like. Examples of celluloses include methyl cellulose, ethyl cellulose, and acetyl cellulose. These may be used alone, in a copolymer, or in combination of two or more. Examples of the component that forms the copolymer include polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, octanediol, dodecanediol, neopentyl glycol, glycerin, pentaerythritol, sorbitan, bisphenol A, and polyethylene glycol; succinic acid , Adipic acid, sebacic acid, glutaric acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, anthracene dicarboxylic acid and other dicarboxylic acids; glycolic acid, L-lactic acid, D-lactic acid, hydroxypropionic acid, hydroxybutyric acid , Hydroxycarboxylic acids such as hydroxyvaleric acid, hydroxycaproic acid, mandelic acid, hydroxybenzoic acid; glycolide, caprolactone, butyrolactone, valerolactone, poropi Examples include lactones such as olactone and undecalactone.
The biodegradable resin is preferably a polylactic acid resin. The polylactic acid resin is not particularly limited as long as it is a polyester resin obtained by polymerizing lactic acid, and may be a polylactic acid homopolymer, copolymer, blend polymer, or the like. In addition, the lactic acid used for the polymerization when using polylactic acid may be either L-form or D-form, or a mixture of L-form and D-form.

In the biodegradable resin composition of the present invention, the polyoxalate content in the biodegradable resin is preferably 0.1 to 20 wt. %, More preferably 1 to 20 wt. %.
In the biodegradable resin composition of the present invention, a known plasticizer, heat stabilizer, light stabilizer, antioxidant, ultraviolet absorber, flame retardant, colorant, pigment, filler, filler is optionally added. Additives such as mold release agents, antistatic agents, fragrances, lubricants, foaming agents, antibacterial / antifungal agents, and nucleating agents may be blended. Moreover, you may mix | blend resin other than the said biodegradable resin or the said polyoxalate with the biodegradable resin composition of this invention in the range which does not impair the effect of this invention. For example, in addition to water-soluble resins such as polyethylene glycol and polyvinyl alcohol, polyethylene, polypropylene, ethylene-propylene copolymer, acid-modified polyolefin, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, ionomer resin, polyethylene Terephthalate, polybutylene terephthalate, polyvinyl acetate, polyvinyl chloride, polystyrene, polyester rubber, polyamide rubber, styrene-butadiene-styrene copolymer, and the like can be blended. Further, for the purpose of improving the dispersibility of the polyoxalate, a copolymer of the biodegradable resin and the polyoxalate may be blended.

  The polyoxalate of the present invention can be produced from an acid component and an alcohol component by a well-known polycondensation reaction. For example, when polymerizing oxalate, it can be produced by filling a flask with a dicarboxylic acid source to be copolymerized with an oxalic acid source and ethylene glycol together with a catalyst and polycondensing under appropriate polymerization conditions. As the catalyst, compounds such as P, Ti, Ge, Zn, Fe, Sn, Mn, Co, Zr, V, Ir, La, Ce, Li, Ca, and Hf are preferable. In particular, an organic titanium compound and an organic tin compound are preferable. For example, titanium alkoxide, dibutyltin dilaurate, butyltin hydroxide oxide hydrate, and the like are preferable because of high activity. In the polycondensation reaction, a heat-resistant agent may be added if necessary to prevent thermal degradation. Further, a catalyst deactivator may be added when the polymerization is stopped.

For producing a container using the biodegradable resin composition of the present invention, a molding method known per se can be used.
For example, a multilayer film, a multilayer sheet, a multilayer parison, a multilayer pipe, or the like can be formed by performing extrusion molding using a multilayer multiple die using the number of extruders corresponding to the type of resin. In addition, a multilayer preform for bottle molding can be manufactured by co-injection molding such as a simultaneous injection method or a sequential injection method using the number of injection molding machines corresponding to the type of resin. By further processing such a multilayer film, parison, and preform, a container using the biodegradable resin composition of the present invention can be obtained.
Packaging materials such as films can be used as pouches in various forms and as lid materials for tray cups. Examples of the pouch include three- or four-side sealed flat pouches, gusseted pouches, standing pouches, pillow packaging bags, and the like. Bag making can be performed by a known bag making method. Moreover, a cup or tray-shaped packaging container can be obtained by subjecting the film or sheet to means such as vacuum forming, pressure forming, bulging forming, or plug assist forming.

For the production of a multilayer film or a multilayer sheet, an extrusion coating method or sandwich lamination can be used. Moreover, the single layer and multilayer film which were formed previously can also be laminated | stacked by dry lamination. For example, two layers of polylactic acid / polyglycolic acid laminated by dry lamination, laminating a transparent vapor deposition biodegradable film by dry lamination on a two-layer coextruded film comprising a biodegradable resin composition / polylactic acid (sealant) layer Examples of the method include, but are not limited to, a method in which two layers of biodegradable resin composition / polylactic acid (sealant) are extrusion coated on a film via an anchor agent.
Moreover, a parison, a pipe, or a preform is pinched off by a pair of split molds, and a bottle or a tube can be easily formed by blowing a fluid into the inside. Moreover, after cooling a pipe and a preform, it is heated to a stretching temperature, stretched in the axial direction, and blow stretched in the circumferential direction by fluid pressure to obtain a stretch blow bottle or the like.

  The hydrolase used in the present invention is not particularly limited as long as it generally decomposes a biodegradable resin, and those skilled in the art can use any hydrolase. Examples of such enzymes include protease, cellulase, cutinase, lipase and the like. For example, it is possible to use protease K manufactured by Wako Pure Chemical Industries, Ltd. and lipase CS2 from the independent alcoholic beverage research institute.

The buffer solution used in the present invention is not particularly limited as long as it is a buffer solution generally used for the purpose of stabilizing pH. Such buffers include glycine-HCl buffer, phosphate buffer, Tris-HCl buffer, acetate buffer, citrate buffer, citrate-phosphate buffer, borate buffer, tartrate buffer, Examples thereof include glycine-sodium hydroxide buffer. Moreover, a solid neutralizing agent may be used, and examples thereof include calcium carbonate, chitosan, and deprotonated ion exchange resin.
Examples of the present invention will be described below, but the present invention is not limited thereto.

(CLE enzyme solution)
A Cryptococcus sp. S-2-derived lipase CS2 (Japanese Patent Laid-Open No. 2004-73123, provided by the National Research Institute for Liquors) showing a lipase activity of 653 U / mL was used. The lipase activity was measured using paranitrophenyl laurate as a substrate. Here, 1 U of lipase activity is defined as the amount of enzyme when 1 μmol / min of paranitrophenol is released from paranitrophenyl laurate.

(Measurement of glass transition temperature)
The glass transition temperature (Tg) was measured using DSC 6220 (differential scanning calorimetry) manufactured by Seiko Instruments Inc. The measurement conditions were from 0 to 200 ° C. at a temperature increase rate of 10 ° C./min in a nitrogen atmosphere. The sample was a film to be described later, and the sample amount was 5 to 10 mg.

(HPLC measurement conditions)
JASCO GULLIVER series was used for the HPLC system. The analytical conditions were as follows. The column was used in a column oven in which Waters Atlantis dC ₁₈ 5 μm, 4.6 × 250 mm was maintained at 40 ° C., and 0.5% phosphoric acid and acetonitrile were used at a flow rate of 1 mL / min. Gradient was applied as described above, and 50 μl of sample was injected using this as a mobile phase. For detection, UV absorption at 210 nm was used, and purified L-lactic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a standard sample.

(Synthesis of polyoxalate (PEOx))
Into a 300 mL separable flask equipped with a mantle heater, a stirrer, a nitrogen inlet tube, and a condenser tube, 354 g (3.0 mol) of dimethyl oxalate, 223.5 g (3.6 mol) of ethylene glycol, and 0.30 g of tetrabutyl titanate are placed. The temperature in the flask was heated from 170 ° C. to 170 ° C. while distilling off methanol under a nitrogen stream, and reacted for 9 hours. Finally, 210 ml of methanol was distilled off. Thereafter, the mixture was stirred at an internal temperature of 150 ° C. under a reduced pressure of 0.1 to 0.5 mmHg for 1 hour.
The weight average molecular weight (Mw) was 30000 by GPC measurement. For GPC, Tosoh Corporation was used, and HFIP-605 was used as a column. The temperature of the column oven was 40 ° C., HFIP (hexafluoroisopropanol) was used as the eluent, and the flow rate was 0.5 ml / min. The sample injection volume was 15 μl. As the standard, polymethyl methacrylate was dissolved in HFIP. For sample preparation, HFIP was used as a solvent to a concentration of 2 mg / ml and filtered.

(Synthesis of polyoxalate (PEOx10))
Except for using dimethyl oxalate (354 g, 3.0 mol) instead of dimethyl oxalate (106.8 g, 0.9 mol) and dimethyl terephthalate (19.4 g, 0.1 mol), the same method as the synthesis of PEOx was used. Synthesized.
The weight average molecular weight (Mw) was 10,000 by GPC measurement. For GPC, HLC-8120 manufactured by Tosoh Corporation was used, TSKgel SuperHM-H × 2 was used as a column, and TSKguard column SuperH-H was used as a guard column. The temperature of the column oven was 40 ° C., chloroform was used as the eluent, and the flow rate was 0.5 ml / min. The sample injection volume was 15 μl. The standard used was chloroform dissolved in chloroform. For sample preparation, chloroform was used as a solvent to a concentration of 5 mg / ml, and filtered.

(Synthesis of polyoxalate (PEOx20))
Except for using dimethyl oxalate 354 g (3.0 mol) instead of dimethyl oxalate 94.5 g (0.8 mol) and dimethyl terephthalate 38.8 g (0.2 mol), the same method as the synthesis of PEOx described above was used. Synthesized.
The weight average molecular weight (Mw) was 20000 by GPC measurement. For GPC, HLC-8120 manufactured by Tosoh Corporation was used, TSKgel SuperHM-H × 2 was used as a column, and TSKguard column SuperH-H was used as a guard column. The temperature of the column oven was 40 ° C., chloroform was used as the eluent, and the flow rate was 0.5 ml / min. The sample injection volume was 15 μl. The standard used was chloroform dissolved in chloroform. For sample preparation, chloroform was used as a solvent to a concentration of 5 mg / ml, and filtered.

(Film production method)
The three kinds of polyoxalate obtained by synthesis were each pelletized, melted at 200 ° C. for 5 minutes, and then heated and pressed (hot pressed) at a pressure of 40 kgf / cm ² to prepare a biodegradable resin film.

(Hydrolysis test and enzymatic degradation test of polyoxalate simple substance film)
(Experimental example 1)
Hydrolysis test A PEOx film was cut into 1 cm × 1 cm (weight 10 mg), put into a 25 ml vial, and 10 ml of a 60 mmol / l phosphate buffer having a pH of 7 was added to the vial. The reaction was conducted at a reaction temperature of 4 ° C. and 30 ° C., and the reaction temperature was 37 ° C. and 45 ° C. with shaking at 100 rpm. One day later, the film was taken out. The residual liquid from which the film was taken out was quantified for the amount of oxalic acid eluted using HPLC.

Enzymatic Degradation Test A PEOx film was cut into 1 cm × 1 cm (weight 10 mg), put into a 25 ml vial, and 10 ml of 60 mmol / l phosphate buffer at pH 7 and 48 μl of CLE enzyme solution were added to the vial. The reaction was carried out at 37 ° C. and 45 ° C. with shaking at 100 rpm, and the film was taken out after 1 day. The residual liquid from which the film was taken out was quantified for the amount of oxalic acid eluted using HPLC.

(Experimental example 2)
It carried out similarly to Experimental example 1 except having replaced with the PEOx film and using the PEOx10 film.

(Experimental example 3)
It carried out similarly to Experimental example 1 except having replaced with the PEOx film and using the PEOx20 film.
The results are summarized in Table 2 below. Moreover, the hydrolysis result of the oxalic acid elution amount is shown in FIG. From these results, it was found that PEOx10 and PEOx20 are more stable in the range of 4 ° C to 45 ° C than PEOx.
The eluted oxalic acid has a concentration of 0.005 g / ml and a pH of 1.6, and PEOx, PEOx10 and PEOx20 elute oxalic acid or oxalic acid oligomers by hydrolysis in an aqueous solution.
The enzymatic degradability is evaluated as ◯ when the amount of oxalic acid eluted at the time of enzymatic degradation is larger than the amount of oxalic acid eluted at the time of hydrolysis at 37 ° C. and 45 ° C., and x It is said.

Example 1
5 wt. Of PEOx10 was added to polylactic acid (4032D manufactured by Natureworks). % Dry blended and kneaded with a microkneader (manufactured by Toyo Seiki Co., Ltd.) at a molding temperature of 200 ° C. and a screw rotation speed of 50 rpm to produce pellets. The pellet was melted at 200 ° C. for 5 minutes and then heated and pressurized (hot pressed) at a pressure of 40-50 kgf / cm ² to prepare a biodegradable resin film.
To a 25 ml vial, 10 ml of 60 mM phosphate buffer adjusted to pH 7 and 48 μl of CLE enzyme solution were added to obtain a decomposition solution. PEOx10 cut into 2 cm × 2 cm (weight 60 mg) was added to the decomposition solution at 5 wt. % Polylactic acid film was soaked and shaken at 45 ° C. and 100 rpm for 7 days. In order to avoid an extreme decrease in pH, 7 days were divided into 2 days, 2 days, and 3 days, and the decomposition solution was exchanged.

(Example 2)
The same procedure as in Example 1 was performed except that PEOx20 was used instead of PEOx10.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that PEOx was used instead of PEOx10.

(Comparative Example 2)
The same operation as in Example 1 was carried out except that PEOx10 was not contained.

(Decomposition rate)
The degradation rate was calculated by the following formula by measuring the initial weight of the biodegradable resin film, measuring the weight of the biodegradable resin film that had been degraded for one week.
((Initial weight of biodegradable resin film−weight of film after decomposition) / initial weight of biodegradable resin film) × 100 = decomposition rate (%)

It is a graph which shows the measurement conditions of HPLC. It is a graph which shows the hydrolysis result of the oxalic acid elution amount.

Claims (7)

A polyoxalate having a weight average molecular weight of 3000 to 1000000 in which a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2) are arranged in a molar ratio of 50:50 to 99: 1.

(In the formula, R represents a divalent group derived from a group selected from the group consisting of aromatic ring hydrocarbons and alicyclic hydrocarbons.)   The polyoxalate according to claim 1, wherein R is a p-phenylene group.   The polyoxalate according to claim 1 or 2, wherein the oxalic acid elution amount by enzymatic decomposition at 37 ° C is larger than the oxalic acid elution amount by the hydrolysis rate.   The polyoxalate according to any one of claims 1 to 3, which has a glass transition temperature of 40 ° C or higher.   0.1 to 20 wt. % Biodegradable resin composition containing the polyoxalate according to any one of claims 1 to 4.   The biodegradable resin composition according to claim 5, wherein the biodegradable resin is polylactic acid.   A biodegradable container comprising the biodegradable resin composition according to claim 5.

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