JP2003327816A - Modified biodegradable polyester resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition solving the molding problems of a biodegradable polyester comprising the blocking trouble and the lowering of productivity and effective for preventing the draw down in blow molding, vacuum forming, etc., improving inflation film-forming property and foaming performance. <P>SOLUTION: The biodegradable polyester resin composition is produced by adding 0.5-40 wt.% catechins to an aliphatic polyester resin such as a poly-3- hydroxybutyrate, a poly-3-hydroxybutyrate-3-hydroxyvalerate copolymer, a poly-3-hydroxybutyrate-3-hydroxyhexanoate copolymer, polylactic acid and polycaprolactone. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable resin composition, which is biodegradable, that is, is easily decomposed by microorganisms, is excellent in the global environment and biological environment, and has improved strength and processability. To provide.

[0002]

2. Description of the Related Art Since the social problem that huge amounts of plastics discarded in the natural environment cause environmental damage has been highlighted, it decomposes in the natural environment and returns to carbon dioxide and water. Biodegradable plastics are being developed. Currently known biodegradable plastics are classified according to the manufacturing method, and are obtained by chemical synthesis methods (for example, polylactic acid (hereinafter referred to as PLA), polycaprolactone (hereinafter referred to as PCL), polybutylene succinate), and natural products. There are blends (eg starch and cellulose and blends of these with other degradable plastics), and microbial polyesters (eg poly-3-hydroxyalkanoates such as poly-3-hydroxybutyrate).

Among them, the microorganism-produced polyester is a storage material for accumulating microorganisms in the body, and is a polymer material used as an energy source when the microorganisms fall into a starvation state. In addition, many microorganisms that decompose microbial-produced polyesters inhabit the natural world, and even in the natural environment such as soil, rivers, lake water, seawater, activated sludge, compost (compost), etc. It has an excellent feature that it can be rapidly decomposed even by a specific treatment method.
Furthermore, the advantage of this polyester is that it has thermoplasticity similar to general-purpose plastics, and it is much more practical than natural products such as starch and cellulose in that it can be processed into various processing forms by ordinary plastic processing methods. Is a polymer.

Microorganism-produced polyester represented by polyhydroxyalkanoate is an aliphatic polyester biosynthesized by microorganisms with enzymes in the body, and its structure is limited to some extent by the specificity of enzymes possessed by microorganisms. There are various types. As well known, poly-3-hydroxybutyrate (Fig. 1, hereinafter referred to as P
(Represented as (3HB)), and poly-3-hydroxybutyrate-3-consisting of two monomer units of 3-hydroxybutyrate (hereinafter referred to as 3HB) and 3-hydroxyvalerate (hereinafter referred to as 3HV). Examples thereof include a hydroxyvalerate copolymer (FIG. 2, hereinafter referred to as P (3HB-co-3HV)). Also, from the natural world, a poly-3-hydroxybutyrate-3-hydroxyhexanoate copolymer composed of two monomer units of 3-hydroxybutyrate (3HB) and 3-hydroxyhexanoate (hereinafter referred to as 3HH) Microorganisms that biosynthesize (Fig. 3, hereinafter referred to as P (3HB-co-3HH)) have also been isolated. (Japanese Patent No. 2777757).

Regarding the polymer physical properties of P (3HB), P (3HB-co-3HV) and P (3HB-co-3HH), a research paper by Toi et al.
ecules, Vol.28, No.14, 1995 ”. P (3HB) is a homopolymer, has a single physical property, and is hard and brittle. Although the physical properties of P (3HB-co-3HV) change depending on the composition of 3HV, the crystallinity does not change significantly because the structure of 3HB and 3HV is the difference of one side chain methylene group. Even if the composition ratio is increased, the elasticity does not change significantly, and the elongation does not exceed 100%. On the other hand, the crystallinity of P (3HB-co-3HH) decreases sharply as the 3HH composition ratio increases, and the physical properties change significantly. This is because the structures of 3HB and 3HH differ by two side chain methylene groups.

As described above, even in the same microbial polyester, there are differences in the physical properties depending on the unit structure,
In addition, it has been clarified that the physical properties of the copolymer polymer change depending on the composition ratio.

Since the microbial polyester has thermoplasticity, it can be molded by various processing methods like other general-purpose plastics. For example, the P (3HB-co
-3HV) was once marketed under the trade name "BIOPOL".
However, regarding the processing of P (3HB-co-3HV), Japanese Patent Laid-Open No.
As disclosed in JP-A-143521 and JP-A-6-270368, it is necessary to devise various means to cause moldings to fuse with each other during processing and cause blocking, and to overcome the problem that productivity deteriorates. Has not reached.

Regarding the processing method of P (3HB-co-3HH), Japanese Patent Laid-Open No. 9-508424, Japanese Patent Laid-Open No. 9-508426, and Japanese Patent Laid-Open No. 10-12892.
No. 0, etc., but the blocking problem and the productivity reduction problem similar to those in the processing of P (3HB-co-3HV) have not been overcome, and their solution has been desired.

These problems are common problems of biodegradable polyester resins including not only polyhydroxyalkinoates which are microbial polyesters but also other aliphatic polyesters such as PLA and PCL.
It has a low glass transition temperature of aliphatic polyester,
This is due to the slow crystallization rate.

In order to solve such a problem, various additives have been studied so far, for example, a research paper “Journal of Polymer Science: Part B: Polymer Ph” by Inoue et al.
ysics, Vol.38, 1845-1859 (2000) ", describes that the glass transition temperature is increased by adding 4,4'-thiodiphenol to PCL. However, we have not yet found any additives that have been studied and effective, including 4,4'-thiodiphenol, for which safety has been confirmed such as application to food applications and effects on environmental hormones. It has not been.

[0011]

DISCLOSURE OF THE INVENTION The present invention provides the above-mentioned processing problems derived from biodegradable polyester resin, namely blocking and production, by adding catechin, which is a natural product of which safety has been confirmed, to an aliphatic polyester. It is an object of the present invention to provide a resin composition which solves the problem of deterioration of properties, and further prevents blowdown in blow molding, vacuum molding and the like, improves inflation film forming property, and improves foaming performance.

[0012]

The present inventor has found that the addition of catechins to an aliphatic polyester resin increases the glass transition temperature and the crystallization rate,
The present invention has been completed.

That is, the present invention relates to a biodegradable polyester resin composition obtained by adding catechins to an aliphatic polyester resin.

A preferred embodiment thereof relates to the above biodegradable polyester resin composition having a catechin content of 0.5 to 40% by weight.

In another preferred embodiment, the aliphatic polyester resin is P (3HB), P (3HB-co-3HV), P (3HB-co-
3HH), PLA, and PCL, which is one or more selected from the group consisting of PH and PCL, more preferably, the aliphatic polyester resin is P
The present invention relates to the above biodegradable polyester resin composition, which is a (3HB-co-3HH) copolymer.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The biodegradable polyester resin composition of the present invention is a resin composition obtained by adding catechins to an aliphatic polyester resin.

The aliphatic polyester used in the present invention is not particularly limited, but it is effective for those having a low glass transition temperature, a low crystallization rate in the molding process and easy blocking during processing. Specifically, P (3HB), P (3HB-co-3HV), P (3HB-co-3HH), PLA, PCL
And the like, or a mixture thereof.
Among these, P (3HB-co-3HH) is preferable in terms of physical properties. The molecular weight of these aliphatic polyesters is 100,000 to 1
It is preferably 500,000, most preferably 300,000 to 1,000,000.

The catechins used in the present invention include:
In general, catechins in a broad sense represented by 3-hydroxyflavanols can be used, and specifically, gallocatechin, epigallocatechin, epicatechin,
Examples thereof include epigallocatechin gallate, epicatechin gallate, and their derivatives. These catechins can be generally obtained by extraction from plants, especially tea leaves, but of course, those obtained by chemical synthesis may be used. Further, as long as it does not affect the physical properties of the polyester resin composition, it may contain impurities, and for example, a tea extract containing catechins as a main component may be used as it is.

The composition ratio of the aliphatic polyester resin and the catechins in the polyester resin composition of the present invention is 99.5 to 60% by weight of the aliphatic polyester and 0.5 to 40% by weight of the catechins. Is preferred. If the catechins are less than 0.5% by weight or the aliphatic polyester exceeds 99.5% by weight, the hydrogen bonding force between the catechins and the aliphatic polyester is insufficient and it is difficult to obtain the modifying effect. On the other hand, when the amount of catechins exceeds 40% by weight or the amount of aliphatic polyester is less than 60% by weight, the hydrogen bonding force becomes too strong, resulting in a hard and brittle resin composition, which is not very practical. Also, depending on the type of aliphatic polyester, phase separation may occur and a sufficiently uniform composition may not be obtained.

The biodegradable polyester resin composition of the present invention mainly comprises an aliphatic polyester and catechin, but other additives such as a plasticizer, a nucleating agent, a lubricant and a filler may be added depending on the required characteristics. Agents, anti-blocking agents, antioxidants, light stabilizers, UV absorbers, pigments and the like may be added. Further, a general polyester resin can be mixed within a range that does not affect the biodegradability.

The biodegradable polyester resin composition of the present invention is subjected to dry blending of the granular material of each component such as aliphatic polyester, or the mixture is subjected to dry blending and once pelletized. It may be subjected to a molding process after the granules. Further, it may be dissolved in a solvent and cast-molded. The catechins may be added and mixed during the initial dry blending, or may be added before the problematic molding process. The form of the molding process is not particularly limited, and examples thereof include inflation, extrusion, injection, blow, foaming of beads, foaming by extrusion, casting and the like.

In the biodegradable polyester resin composition of the present invention, hydrogen bonding between the phenolic hydroxyl group of catechins and the carbonyl carbon of the ester group of the aliphatic polyester increases the glass transition point and improves the crystal acceleration. Thought to be

The biodegradable polyester resin composition of the present invention eliminates the problems in the conventional aliphatic polyesters during processing (drawing down in blocking, blow molding, vacuum molding, etc.), and enables inflation film formation and foaming performance. Since it is excellent in various properties, it can be processed in various ways, such as mulch film and nursery pots in the agricultural field, film and containers for food packaging, laminating film with paper, water retention sheets and vegetation nets in the field of civil engineering, and compost. It can be used in various applications such as bags, trash bags, adhesives used for bookbinding, paper diapers, sanitary products, and foamed molded products for cushioning.

[0025]

(Example 1) P (3HB- having a property of 3HH composition ratio of about 10 mol%, weight average molecular weight of about 300,000, melting point of 140 ° C., glass transition temperature of about 4 ° C., maximum crystallization temperature of about 70 ° C.
co-3HH), catechin (Sigma-Aldrich Fine Chemicals
Manufactured by the company, purity 98%) 10, 20, 30, 40,
It was added so as to be 50% by weight. This and P (3HB-co-3HH) without addition of catechin were each dissolved in acetone at a concentration of 10 mg / ml, and a film with a thickness of 200 μm was prepared by a casting method. Evaporated.

The glass transition temperature of the produced film is D
It was measured by SC. In DSC measurement, the temperature was raised from −50 ° C. to 200 ° C. at 20 ° C./min, held at 200 ° C. for 1 minute, quenched with liquid nitrogen, and then again from −50 ° C. to 20 ° C./m.
The temperature was raised at in and the peak that appeared first was taken as the glass transition temperature. The results are shown in Table 1.

[0027]

[Table 1] Furthermore, it was confirmed by Fourier transform infrared spectroscopy (hereinafter referred to as FT-IR) that the phenolic hydroxyl group of catechin and the carbonyl group of polyester were hydrogen-bonded by the following method.

On the silicon wafer of the sample stand, the P (3H
An acetone solution of B-co-3HH) and catechin was applied to form a film having a thickness of about 10 μm, and naturally dried for 2 weeks. Then, the FT-IR spectrum is measured, and the peak at a wavelength of 1770 to 1670 cm ⁻¹ that represents the carbonyl stretching vibration is measured by a linear function, and a peak that represents a hydrogen bond near 1710 cm ⁻¹ , 1725.
a peak representing an aliphatic polyester crystal in the vicinity of cm ^-1 ,
The peak representing non-crystal near 1740 cm ^-1 was separated to determine the ratio of hydrogen bonds. The results are shown in Table 2.

[0029]

[Table 2] As shown in Table 2, as the amount of catechin added increases,
It was confirmed that the proportion of hydrogen bonds increased. Also, in the peak of wavelength 3050 to 3720 cm ^-1 which represents stretching vibration of phenolic hydroxyl group, the peak which qualitatively shows hydrogen bond is 3220.
It was confirmed that the peak intensity appears near cm ⁻¹ and that the peak intensity increases as the amount of catechin added increases.

Example 2 P (3HB) was used in place of the P (3HB-co-3HH) polymer of Example 1, and catechins of 15, 30, 4 were used.
A film was prepared in the same manner as in Example 1 except that 0,50% by weight was added, and its glass transition temperature was measured by DSC.
The results are shown in Table 1.

Example 3 PCL was used in place of the P (3HB-co-3HH) polymer of Example 1, and catechins of 10, 20, 30, 4 were used.
A film was prepared in the same manner as in Example 1 except that 0,50% by weight was added, and its glass transition temperature was measured by DSC.
The results are shown in Table 1.

In the same manner as in Example 1, the presence or absence of hydrogen bond was confirmed by FT-IR. The results are shown in Table 3.

[0033]

[Table 3] In addition, 1 catechin was added to PCL to measure mechanical properties.
0,20,30 wt% added and catechin not added P
CL was dissolved in dioxane as a solvent so that PCL had a concentration of 10 mg / ml, and a film having a thickness of 200 μm was prepared by a casting method. After drying, the solvent was gradually evaporated at room temperature, and the remaining residual solvent was removed by vacuum drying at 30 ° C. for 2 weeks. A dumbbell test piece was prepared using the obtained film, a tensile test was performed, and the tensile strength and elongation were measured. The results are shown in Table 4.

[0034]

[Table 4] Example 4 A film was prepared in the same manner as in Example 1 except that PLA was used instead of the P (3HB-co-3HH) polymer of Example 1 and 10, 20, 30, 40 wt% of catechin was added. , Its glass transition temperature was measured by DSC. The results are shown in Table 1.

[0035]

Industrial Applicability According to the present invention, the glass transition temperature of biodegradable aliphatic polyester is increased, the problem of blocking during processing is solved, blowdown, drawdown prevention in vacuum molding and the like, improvement of inflation film forming property, A biodegradable aliphatic polyester resin composition having improved foaming performance and mechanical properties can be provided. Further, it is expected that the hydrogen bond between catechin and the aliphatic polyester imparts rigidity to the resin and improves the mechanical properties.

[Brief description of drawings]

FIG. 1 shows the structure of P (3HB).

FIG. 2 shows the structure of P (3HB-co-3HV).

FIG. 3 shows the structure of P (3HB-co-3HH).

Claims (4)

[Claims] 1. A biodegradable polyester resin composition obtained by adding catechins to an aliphatic polyester resin. 2. The biodegradable polyester resin composition according to claim 1, wherein the content of catechins is 0.5 to 40% by weight. 3. The aliphatic polyester resin is poly-3-hydroxybutyrate, poly-3-hydroxybutyrate-
3. One or more selected from the group consisting of 3-hydroxyvalerate copolymer, poly-3-hydroxybutyrate-3-hydroxyhexanoate copolymer, polylactic acid, and polycaprolactone. 1. The biodegradable polyester resin composition according to 1. 4. The biodegradable polyester resin composition according to claim 3, wherein the aliphatic polyester resin is a poly-3-hydroxybutyrate-3-hydroxyhexanoate copolymer.