JP2009096849A - Biodegradable resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable resin composition having high crystallinity, while using a polyhydroxyalkanoate (PHA) copolymer having a very slow crystallization rate as a main body, and suitably usable in molding applications. <P>SOLUTION: The biodegradable resin composition containing at least one kind of the PHA copolymers as the main body further comprises a poly(3-hydroxybutyrate) polymer and a nucleating agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biodegradable resin composition that has high crystallinity and can be suitably used in molding applications.

As a new resource that contributes to the prevention of global warming and the establishment of a recycling-oriented society, biomass, which is a resin derived from organisms such as plants, has attracted attention. When biomass is burned, carbon dioxide (CO ₂ ) is generated in the same manner as petroleum-derived resins, but plants absorb CO ₂ by photosynthesis during the growth process, and CO _{2 in the} atmosphere is seen in the entire life cycle. The balance is considered to be zero. Such a property that does not affect the increase or decrease in CO ₂ is called carbon neutral. In recent years, the idea of carbon neutral has spread and various plant-derived resins have been developed. Among these, aliphatic polyesters such as starch, glucose, poly-3-hydroxyalkanoate, and polylactic acid are known as plant-derived resins that can be melt-molded.

  Among aliphatic polyesters, poly-3-hydroxyalkanoate is highly expected as a biopolymer that can be cultivated from microorganisms among plant-derived resins that can be melt-molded. Among them, PHBH copolymer: poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer has good mechanical properties and is used as a melt molding material. Is a plant-derived resin that is expected to be developed in the future. However, the PHBH copolymer has a problem that the crystallization rate is extremely slow for use as an industrial molding material.

  In general, it is believed that the addition of a nucleating agent can accelerate the crystallization of a crystalline polymer, and the addition of an appropriate nucleating agent can improve the nucleation density and the crystallization rate. . PHB polymer, a kind of poly-3-hydroxyalkanoate: Numerous types of nucleating agents such as talc, boron nitride, saccharin and the like are effective for crystallization of poly (3-hydroxybutyrate) polymer. It is known (see Non-Patent Documents 1 and 2).

  However, there is no known method for promoting crystallization of a poly-3-hydroxyalkanoate copolymer (hereinafter also referred to as a PHA copolymer) such as a PHBH copolymer.

In Patent Document 1, polyhydroxyalkanoate (PHA-Y) having a melting point higher than that of PHA-X is added to polyhydroxyalkanoate (PHA-X), and molding is performed at a temperature lower than the melting point of PHA-Y. However, although a method of using the unmelted crystal as a nucleating agent is shown, there is a limitation on the molding processing temperature, which is not a practical molding processing method.
US Pat. No. 5,693,389 R. E. Withey, J .; N. Hay, Polymer, 1999, 40, 5147-5152 Y. He, Y. Inoue, Biomacromolecules, 2003, 4, 1865-1867

  The present inventors examined a method for promoting crystallization of a PHA copolymer such as a PHBH copolymer. As a result, a PHA copolymer such as a PHBH copolymer, particularly a PHBH copolymer having a relatively high content of 3HH units, was studied. For coalescence, it has been found that the nucleating agent described above does not function effectively, that is, the addition of the nucleating agent does not promote crystallization.

  The present invention has been made in view of the above situation, and an object thereof is to provide a biodegradable resin composition which is mainly composed of a PHA copolymer having a remarkably low crystallization rate and has high crystallinity and can be suitably used in molding applications. To do.

  As a result of intensive studies to solve the above problems, the present inventors promoted crystallization of the PHA copolymer by blending the PHA copolymer with the nucleating agent together with the PHB polymer. The present inventors have found that this can be done and have completed the present invention.

  That is, the present invention is a biodegradable resin composition mainly comprising at least one polyhydroxyalkanoate copolymer, and further contains a poly (3-hydroxybutyrate) polymer and a nucleating agent. The present invention relates to a biodegradable resin composition.

  Preferably, the polyhydroxyalkanoate copolymer is a poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer or poly [(3-hydroxybutyrate) -co- ( 3-hydroxyvalerate)] copolymer.

  Preferably, the biodegradable resin composition is mainly composed of a poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer.

  Preferably, the poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer is used in an amount of 1 to 30 with respect to 100 parts by weight of the poly (3-hydroxybutyrate) copolymer. 0.1 to 10 parts by weight of the nucleating agent and parts by weight.

  Preferably, the poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer has a content of 3-hydroxyhexanoate units of 5 to 25 mol%.

  Preferably, the nucleating agent is at least one selected from the group consisting of talc, boron nitride, and saccharin.

  In addition, the present invention provides a biodegradable resin composition molded article that is molded using the above-described biodegradable resin composition at a temperature not lower than the melting point of the poly (3-hydroxybutyrate) polymer. It also relates to the manufacturing method.

  Furthermore, the present invention relates to a processing method characterized by molding the above-described biodegradable resin composition at a temperature equal to or higher than the melting point of the poly (3-hydroxybutyrate) polymer.

  According to the present invention, it is possible to provide a biodegradable resin composition which is mainly composed of a PHA copolymer having a remarkably low crystallization rate and has high crystallinity and can be suitably used in melt molding applications.

  The present invention is described in detail below.

  The biodegradable resin composition of the present invention is mainly composed of at least one polyhydroxyalkanoate copolymer. Here, “mainly” means that at least one polyhydroxyalkanoate copolymer accounts for 50% by weight or more, preferably 60% by weight or more of the total biodegradable resin component constituting the composition. Means that

The polyhydroxyalkanoate copolymer is [—CHR—CH ₂ —CO—O—] (where R is an alkyl group represented by C _n H _{2n + 1} , and n is an integer of 1 to 15. ) Is a copolymer composed of two or more types of repeating units. This copolymer has the property of decomposing under anaerobic conditions, has excellent moisture resistance, and can have a high molecular weight.

  Representative examples of the copolymer include, for example, poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer, poly [(3-hydroxybutyrate) -co- ( 3-hydroxyvalerate)] copolymer, [(3-hydroxybutyrate) -co- (3-hydroxyoctanoate)] copolymer, [(3-hydroxybutyrate) -co- (3-hydroxy Decanoate)] copolymer and the like. Among these, [(3-hydroxybutyrate)-(3-hydroxyhexanoate)] copolymer and poly [(3-hydroxybutyrate) -co- (3-hydroxyvalerate)] copolymer are preferable. Furthermore, a [(3-hydroxybutyrate)-(3-hydroxyhexanoate)] copolymer is particularly preferred.

  The poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer (hereinafter also referred to as “PHBH copolymer”) means 3-hydroxybutyrate and 3-hydroxyhexanoate. As used herein, “main component” means 50 mol% or more, preferably 60 mol% or more of the total monomer units constituting the copolymer. It means that hydroxybutyrate and 3-hydroxyhexanoate are occupied. The copolymer may be composed of only 3-hydroxybutyrate and 3-hydroxyhexanoate as a monomer unit constituting the copolymer, or other monomers as long as these are the main components. It may contain a unit.

  Although it does not specifically limit as another monomer unit, For example, units derived from hydroxycarboxylic acid other than 3-hydroxybutyrate and 3-hydroxyhexanoate, a unit derived from a polycarboxylic acid, a unit derived from a polyhydric alcohol, a unit derived from a lactone, etc. Is mentioned. Specifically, hydroxycarboxylic acids such as glycolic acid, 4-hydroxybutyric acid, 4-hydroxyhexanoic acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, hydroxybenzoic acid; oxalic acid, malon Acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid Acids, polycarboxylic acids such as 5-tetrabutylphosphonium sulfoisophthalic acid; ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethyl Norol, Neopentyl glycol, Glycerin, Trimethylolpropane, Pentaerythritol, Bisphenol A, Aromatic polyhydric alcohol in which ethylene oxide is added to bisphenol, Diethylene glycol, Triethylene glycol, Polyethylene glycol, Polypropylene glycol, Polytetra Polyhydric alcohols such as methylene glycol; lactones such as glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone, etc. It is done. As these other monomer units, only one type may be used, or two or more types may be used in combination.

  The polymerization format of the PHBH copolymer is not particularly limited, and may be any copolymerization format such as random copolymerization, alternating copolymerization, block copolymerization, etc., but it is easy to control the physical properties of the obtained copolymer. Therefore, random copolymerization is preferable.

  The constitutional ratio of the monomer units of the PHBH copolymer is not particularly limited. For example, 3-hydroxybutyrate unit / 3-hydroxyhexanoate unit = 99/1 to 70/30 (mol / mol). Although preferable, since the effect of promoting crystallization in the present invention is more significantly exhibited while exhibiting good mechanical properties, 3-hydroxybutyrate unit / 3-hydroxyhexanoate unit = 95/5 to 75 / 25 (mol / mol) is more preferable.

  The molecular weight of the PHBH copolymer is not particularly limited, but the number average molecular weight is preferably 30,000 to 2,500,000, more preferably 50,000 to 2,000,000, and further preferably 100,000 to 1,500,000. preferable. If the number average molecular weight of the PHBH copolymer is less than 30,000, mechanical properties such as strength may be insufficient, and if it exceeds 3 million, moldability may be inferior. In addition, although the measuring method of the weight average molecular weight of PHBH copolymer is not specifically limited, As an example, chloroform is used as a mobile phase, Waters GPC system is used as a system, Showa Denko Co., Ltd. ) By using Shodex K-804 (polystyrene gel), the molecular weight in terms of polystyrene can be obtained.

  As a method for producing the PHBH copolymer, a known polymerization method can be used. Preferably, a method of producing glucose, vegetable oil or the like as a raw material in the body of the microorganism can be mentioned.

  Poly [(3-hydroxybutyrate) -co- (3-hydroxyvalerate)] copolymer (hereinafter also referred to as “PHBV copolymer”) is mainly composed of 3-hydroxybutyrate and 3-hydroxyvalerate. It refers to a copolymer as a component. Here, “main component” means that 50% by mole or more, preferably 60% by mole or more of the total monomer units constituting the copolymer is occupied by 3-hydroxybutyrate and 3-hydroxyvalerate. Means that. In the copolymer, the monomer units constituting the copolymer may be composed only of 3-hydroxybutyrate and 3-hydroxyvalerate, or other monomer units as long as they are mainly composed of these units. May be included. Other monomer units include those described above for the PHBH copolymer. The molecular weight of the PHBV copolymer is not particularly limited, and may be approximately the same as the molecular weight of the PHBH copolymer. Regarding the method for producing the PHBV copolymer, a known polymerization method can be used, and a method in which glucose, vegetable oil or the like is used as a raw material to produce it in the body of the microorganism is preferable. The biodegradable resin composition of the present invention comprises a poly (3-hydroxybutyrate) in order to promote crystallization of a PHA copolymer and facilitate its use in melt molding, while mainly comprising a PHA copolymer. Rate) polymer (hereinafter also referred to as “PHB polymer”) and a nucleating agent. As will be described later, crystallization promotion of the PHA copolymer cannot be achieved only by adding a substance generally known as a nucleating agent to the PHA copolymer. However, when the nucleating agent is added to the PHA copolymer together with the PHB polymer which is a biodegradable resin that can be accelerated in crystallization by the nucleating agent, the crystallinity of the PHA copolymer is clearly improved.

  The PHB polymer is a polymer substantially consisting of only 3-hydroxybutyrate units. The molecular weight of the PHB polymer is not particularly limited, and may be approximately the same as the molecular weight of the PHBH copolymer. A known polymerization method can also be used as a method for producing a PHB polymer, but a method of producing glucose, vegetable oil or the like as a raw material in the body of a microorganism is preferable.

  As the nucleating agent, those known as substances that improve the crystallinity by adding to the polymer can be used. Examples include higher fatty acid amides, urea derivatives, sorbitol compounds, boron nitride, higher fatty acid salts, aromatic fatty acid salts, talc, saccharin, and the like, and at least one of them can be used. Of these, talc, boron nitride, and saccharin are preferred because they are excellent in the crystallization promoting effect in the present invention.

  In the biodegradable resin composition of the present invention, the blending amount of each component is not particularly limited as long as the effects of the present invention are achieved. However, specifically, the blending amount of the PHB polymer is preferably 1 to 30 parts by weight and the blending amount of the nucleating agent is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the PHA copolymer. . More preferably, the blending amount of the PHB polymer is 1 to 20 parts by weight, and the blending amount of the nucleating agent is 0.5 to 5 parts by weight.

  When the blending amount of the PHB polymer is less than 1 part by weight or the blending amount of the nucleating agent is less than 0.1 part by weight, the effect as a nucleating agent tends to be low and the moldability tends to be lowered. On the other hand, when the blending amount of the PHB polymer exceeds 30 parts by weight or the blending amount of the nucleating agent exceeds 10 parts by weight, the effect corresponding to the content cannot be expected, which is not practical and uneconomical. is there.

  You may mix | blend the following additives with the biodegradable resin composition of this invention as needed. Examples of the additives include stabilizers, lubricants, flame retardants, pigments, inorganic fillers, organic fillers, mold release agents, antistatic agents, ultraviolet absorbers, antioxidants, antibacterial and antifungal agents, and plasticizers. What is necessary is just to select an optimal thing suitably for these additives according to the use etc. in which a composition is used.

  In molding the biodegradable resin composition of the present invention, each component may be directly put into a molding machine, but from the viewpoint of handling, uniformity of kneading, etc., it is molded after being pelletized once. Processing may be performed. For pelletization, for example, a known apparatus such as a Banbury mixer, a roll mill, a kneader, a single-screw or multi-screw extruder is used, and the mixture is mechanically kneaded while heating at an appropriate temperature to be pelletized. Can be shaped. The temperature at the time of kneading may be adjusted according to the melting temperature of the polymer to be used, and may be about 100 to 200 ° C., for example, but the effect of promoting crystallization by the combined use of the PHB polymer and the nucleating agent is further improved. In order to exhibit efficiently, it is preferable to set it as the temperature more than melting | fusing point of the PHB polymer contained in the said composition. In the molding process, any molding process method such as extrusion molding, compression molding, blow molding, calendar molding, vacuum molding, foam molding, injection molding, injection blow, or the like can be employed.

  Specific uses of the biodegradable resin composition of the present invention include, for example, food containers, sheets, bottles, transparent plates, films, stretched films, packaging materials, plastic bags, cushioning materials, agricultural multi-films, and fish nets. , Tableware, garbage bags, etc.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
1. P (3HB-co-3HH)
Microorganism-produced P (3HB-co-3HH) having a 3HH unit content of 18 mol% was used as a raw material. Since this polymer had a very wide comonomer unit composition distribution, it was fractionated at room temperature using a chloroform / n-heptane mixed solvent. A fraction (Mn = 1.15 × 10 ⁵ , Mw / Mn = 1.42) having a content of 3HH units obtained by this fractionation of 21 mol% was used below.
2. P (3HB)
As the microbial production P (3HB), one having Mn = 1.55 × 10 ⁵ and Mw / Mn = 2.56 was purified and used.
3. Boron nitride Fine powder of boron nitride obtained from Nacalai Tesque was used.
4.3 Content measurement method of 3HH unit In measuring the content of 3HH unit in the raw material and P (3HB-co-3HH) after fractionation, a ¹ H NMR spectrum of 600 MHz was measured at 30 ° C. in a CDCl ₃ solution at Bruker. Measured with a company AVANCE 600 spectrometer.
5). Polymer molecular weight measurement method The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of each polymer were measured using Tosoh HPLC- containing TSK GEL G2000Hxl and GMHxl columns (manufactured by Tosoh Corporation). Measurements were made using 8020 gel permeation chromatography. As eluent, chloroform was used at a flow rate of 1.0 mL · min ⁻¹ . When preparing a GPC elution curve, polystyrene having a narrow molecular weight distribution was used as a standard substance.
Example 1
A fine powder of boron nitride is dispersed in chloroform by sonication, and then the polymer is dissolved to obtain 88% by weight of P (3HB-co-3HH), 10% by weight of P (3HB), and boron nitride. A chloroform solution containing 2% by weight was prepared, and a film was produced therefrom by a solution casting method. The obtained film was dried at room temperature under vacuum for 1 week to remove the residual solvent, and then used for the following evaluation.
Comparative Example 1
A film consisting only of P (3HB-co-3HH) was obtained according to the method described in Example 1.
Comparative Example 2
In accordance with the method described in Example 1, a film composed of 98% by weight of P (3HB-co-3HH) and 2% by weight of boron nitride was obtained.
Comparative Example 3
According to the method described in Example 1, a film composed of 90% by weight of P (3HB-co-3HH) and 10% by weight of P (3HB) was obtained.
Reference example 1
A film consisting only of P (3HB) was obtained according to the method described in Example 1.
Reference example 2
In accordance with the method described in Example 1, a film composed of 98% by weight of P (3HB) and 2% by weight of boron nitride was obtained.
(Evaluation methods)
Each film obtained above was used as a sample, and a non-isothermal crystallization investigation was performed by a differential scanning calorimetry method (DSC: Pyris Diamond, Perkin Elmer) using nitrogen as a purge gas. In non-isothermal crystallization, the sample is first melted at 190 ° C. over 3 minutes to destroy the thermal history, and then the sample is cooled (cooling scan) from 190 ° C. to −40 ° C. at a scanning speed of 2.5 ° C./min. The crystallization behavior was observed.

  After cooling, the sample was held at −40 ° C. for 3 minutes. Finally, the sample was heated (heating scan) from −40 ° C. to 200 ° C. at a scanning speed of 10 ° C./min, and the behavior of low-temperature crystallization and melting was observed. The melting point is indicated by the melting peak temperature when heated from −40 ° C. to 200 ° C. When there are a plurality of melting peak temperatures, the temperature on the higher temperature side is taken as the melting point.

  The results are shown in FIGS.

  FIG. 1 shows a DSC cooling curve obtained by cooling from a molten state at 190 ° C. In Reference Example 1 and Reference Example 2, the crystallization peaks are at 113.6 ° C. and 118.1 ° C., respectively. Compared to Reference Example 1, Reference Example 2 has a higher crystallization temperature and a narrower crystallization temperature range. This confirmed that boron nitride is a good nucleating agent for P (3HB).

  In Comparative Example 1 where P (3HB-co-3HH) alone was not crystallized during the DSC cooling scan. Further, no exothermic peak was detected at all in Comparative Example 2 in which boron nitride coexists. This shows that boron nitride is not an effective nucleating agent for P (3HB-co-3HH). Furthermore, in Comparative Example 3, which is a binary system of P (3HB-co-3HH) and P (3HB), no exothermic peak was detected, so P (3HB) does not crystallize in this system. I understand that.

  However, in Example 1, which is a ternary system of P (3HB-co-3HH), P (3HB), and boron nitride, two exothermic peaks were observed at 115.4 ° C. and 98.9 ° C. Since the exothermic temperature 115.4 ° C. is very close to the exothermic temperatures in Reference Example 1 and Reference Example 2, it can be seen that this peak is due to the crystallization of P (3HB) in the ternary system. Therefore, the peak at 98.9 ° C. indicates that P (3HB-co-3HH) is crystallized in the ternary system.

  FIG. 2 shows a DSC heating curve obtained by scanning from a glass state at −40 ° C. In Reference Example 1 and Reference Example 2, the melting point peaks are at 170.9 ° C. and 172.7 ° C., respectively. In Example 1, there are several melting points, and the highest peak at about 169.4 ° C. corresponds to the melting point peaks in Reference Example 1 and Reference Example 2. Thus, the broad endothermic peak at 80-95 ° C. in Example 1 is due to the melting of P (3HB-co-3HH).

  In Comparative Examples 1 to 3 and Example 1, the glass transition point is in the range of −7.0 to −6.5 ° C., but in Comparative Examples 1 and 2, no exothermic (cooling crystallization) peak was detected. This also reveals that boron nitride is not an effective nucleating agent for P (3HB-co-3HH).

  In Comparative Example 3, an exothermic (cooling crystallization) peak was detected at about 80 to 90 ° C, and an endothermic (melting) peak was detected at about 170 ° C. The absolute values of the exothermic enthalpy and endothermic enthalpy in the heating scan are almost the same. Therefore, in the binary system of P (3HB-co-3HH) and P (3HB), the P (3HB) component is crystallized in the DCS heating scan. It can be seen that it is not crystallized in the cooling scan. In Reference Example 1, Reference Example 2 and Example 1, no exothermic (cooling crystallization) peak was detected in the heating scan, indicating that crystallization was almost complete in the DSC cooling scan.

  From the above results, in the ternary system of P (3HB-co-3HH), P (3HB), and boron nitride, boron nitride selectively accelerated crystallization of P (3HB), and P generated in the system It can be seen that the crystals of (3HB) boost the rapid crystallization of P (3HB-co-3HH).

DSC cooling curve obtained by cooling from the molten state at 190 ° C DSC heating curve obtained by scanning from a glass state at −40 ° C.

Claims (8)

A biodegradable resin composition mainly comprising at least one polyhydroxyalkanoate copolymer,
A poly (3-hydroxybutyrate) polymer;
A biodegradable resin composition comprising a nucleating agent.   As polyhydroxyalkanoate copolymer, poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer or poly [(3-hydroxybutyrate) -co- (3-hydroxy The biodegradable resin composition according to claim 1, further comprising a copolymer.   3. The biodegradable resin composition mainly comprising a poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer. Degradable resin composition.   1 to 30 parts by weight of the poly (3-hydroxybutyrate) polymer with respect to 100 parts by weight of the poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer, The biodegradable resin composition according to claim 3, further comprising 0.1 to 10 parts by weight of the nucleating agent.   The poly [(3-hydroxybutyrate) -co- (3-hydroxyhexanoate)] copolymer has a content of 3-hydroxyhexanoate units of 5 to 25 mol%. The biodegradable resin composition in any one of 2-4.   The biodegradable resin composition according to any one of claims 1 to 5, wherein the nucleating agent is at least one selected from the group consisting of talc, boron nitride, and saccharin.   A biodegradable resin composition, wherein the biodegradable resin composition according to any one of claims 1 to 6 is molded at a temperature equal to or higher than a melting point of a poly (3-hydroxybutyrate) polymer. A method for producing a molded article.   A processing method comprising molding the biodegradable resin composition according to any one of claims 1 to 6 at a temperature equal to or higher than a melting point of a poly (3-hydroxybutyrate) polymer.

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