JP2007119564A - Method for producing polyhydroxyalkanoate resin extrusion foam and extrusion foam obtained by the production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extrusion foam which has excellent environmental compatibility and biodegradability, and to provide a method for stably producing the same. <P>SOLUTION: This method for producing the P3HA resin extrusion foam is characterized by melt-kneading a copolymer (P3HA) comprising one or more kinds of units represented by formula (1): [-O-CHR-CH<SB>2</SB>-CO-] (1) [R is an alkyl group represented by C<SB>n</SB>H<SB>2n+1</SB>; (n) is an integer of 1 to 15], an isocyanate compound, an evaporable foaming agent, and a fatty acid amide-based compound to produce the mixture, and then extruding the mixture in a low pressure region through a molding die. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a polyhydroxyalkanoate resin extruded foam derived from a plant and having biodegradability, and an extruded foam obtained from the production method.

  Sheets, films, fibers, injection-molded products, etc. using plastic are commercialized both in Japan and overseas. Among plastic waste, foam plastics used in large quantities for packaging containers, cushioning materials, cushioning materials, etc. Since it is bulky, it has become a big social problem, and its solution is desired. In this way, while the environmental problems caused by waste plastics are highlighted, biodegradable plastics that are decomposed into water and carbon dioxide by the action of microorganisms after use are attracting attention. For this reason, research on biodegradable plastic foams has been actively conducted, and so far, investigation of extruded foams such as aliphatic polyester resins and mixed resins of starch and plastic, and foamed particles obtained in batch mode. Has been made. In general, biodegradable plastics are (1) microbially-produced aliphatic polyesters such as polyhydroxyalkanoate (in the present invention, particularly poly (3-hydroxyalkanoate), hereinafter referred to as P3HA), and (2) polylactic acid or poly (polylactic acid). It is roughly classified into three types: chemically synthesized aliphatic polyesters such as caprolactone, and (3) natural polymers such as starch and cellulose acetate.

  Regarding the biodegradable extruded foam, the content that has been studied in the past is that a biodegradable aliphatic polyester resin obtained by synthesizing from petroleum-derived raw materials is reacted with a diisocyanate to improve foamability. Extruded foam obtained by molecular weight (Patent Document 1), Polylactic acid resin extruded foam characterized by having a specific melt viscosity by adding a thickener or the like (Patent Documents 2 to 4), foaming There are extruded foams (Patent Documents 5 to 10) obtained by adjusting a polylactic acid resin or an aliphatic-aromatic polyester resin to an appropriate viscosity depending on the type of agent. On the other hand, the P3HA resin extruded foam produced from microorganisms has not been studied heretofore, but the present inventors have studied the P3HA resin extruded foam (Patent Document 11).

  Patent Document 11 describes that an extruded foam is prepared by using a specific melt viscosity and non-halogen-based foaming agent even in P3HA resin. Poly (3-hydroxybutyrate) which is a kind of P3HA -Co-3-hydroxyhexanoate) (hereinafter may be referred to as PHBH), carbon dioxide gas, dimethyl ether, and hydrocarbons are used as the foaming agent, and a foam with an expansion ratio of 8 times or less can be obtained. Is disclosed. Once P3HA is melted, it slowly crystallizes, so that the film once foamed and swollen does not solidify, shrinks, and becomes a low-magnification foam. In order to obtain a P3HA extruded foam with a high magnification, especially exceeding 8 times, it is necessary to adjust the resin temperature to the crystallization temperature of P3HA to promote the solidification of the resin, but the foaming temperature is adjusted to such a low temperature. Since there was no method that could be used, a high-magnification foam was not obtained. Furthermore, thermal decomposition is a characteristic of the P3HA resin. At temperatures above the melting point, thermal decomposition may occur, which is a problem in extrusion stability. Thus, in order to obtain a foam, a method for stably obtaining a P3HA extruded foam having a further high expansion ratio has been desired.

On the other hand, the development of an extruded foam having a high open cell ratio is also desired due to the variety of applications. For example, an extruded foam with a high open cell ratio cut to a certain length is filled into a bag-like product (preferably a biodegradable bag) with or without breathability so that the shape can be freely set. It can be a rose cushioning material that can be changed. The rose cushioning material is a cushioning material, a cushioning material that can be inserted into the gaps freely, and on the other hand, it can exhibit excellent performance with a sound absorbing material, etc. Therefore, development of such particles is desired.
Japanese Patent Laid-Open No. 10-152572 JP 2000-7815 A Japanese Patent Laid-Open No. 2000-7816 JP 2003-20355 A JP 2003-35924 A JP 2003-103595 A JP 2003-261704 A Japanese Patent Laid-Open No. 2003-301066 JP 2004-58352 A Japanese Patent Laid-Open No. 2004-307661 JP 2003-327737 A

  The subject of this invention is providing the stable manufacturing method of the biodegradable resin extrusion foam excellent in the environmental compatibility derived from a plant with the high open cell ratio and high open cell ratio with a high magnification.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors slowed the temperature dependence of the melt viscosity of P3HA by mixing an isocyanate compound with P3HA, and the viscosity required for extrusion foaming even when the melt temperature is high. Furthermore, it has been found that by using a fatty acid amide compound, stable productivity can be obtained by further suppressing crystallization in the extruder. In addition, when a volatile foaming agent having high plasticity with respect to P3HA, for example, ethers, is used as the foaming agent, when the P3HA resin foam is cooled to near the maximum crystallization temperature, particularly when the P3HA resin foam is cooled, It was found that this problem was improved and the expansion ratio was increased, and the present invention was completed.

That is, the first of the present invention is a formula (1) produced from a microorganism.
[—O—CHR—CH ₂ —CO—] (1)
(Here, R is an alkyl group represented by C _n H _{2n + 1} , and n = 1 or more and 15 or less.)
A volatile foamed resin composition comprising a copolymer of at least one unit represented by the following (hereinafter referred to as poly (3-hydroxyalkanoate): abbreviated as P3HA), an isocyanate compound and an aliphatic amide compound. The present invention relates to a method for producing a P3HA resin extruded foam, which comprises melting and kneading an agent to produce a mixture, and extruding the mixture to a low pressure region through a molding die.

As a preferred embodiment,
(1) The melt viscosity η of the resin composition is larger than the melt viscosity η0 of a resin composition to which no isocyanate is added in the resin composition,
(2) The temperature T1 at which a mixture of a resin composition obtained by mixing P3HA, an isocyanate compound, and an aliphatic amide compound and a volatile foaming agent is melted by an extruder is not higher than the melting point of P3HA + 20 ° C. The resin temperature To at the time of extrusion is not less than the glass transition temperature (Tg) of P3HA and not more than the melting point (Tm),
(3) The temperature To when the mixture of a resin composition obtained by mixing P3HA, an isocyanate compound, and a fatty acid amide compound and a volatile foaming agent is extruded from the extruder is in the range represented by the formula (2). It is characterized by
Tc-20 ≦ To (° C.) ≦ Tc + 40 (2)
Here, Tc = (Tg + Tm) / 2
(4) P3HA is poly (3-hydroxybutyrate-co-3-hydroxyhexanoate),
(5) P3HA is poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), and the composition of the copolymer component is such that 3-hydroxyhexanoate is 1 mol% or more and 20 mol% or less. Characterized by the
(6) The volatile blowing agent is at least one selected from the group consisting of dimethyl ether, diethyl ether, and methyl ethyl ether.
(7) The volatile blowing agent is dimethyl ether,
The present invention relates to a method for producing the P3HA resin extruded foam described above.

  The second of the present invention relates to a P3HA resin extruded foam characterized by being obtained by the production method described above. As a preferred embodiment, the P3HA resin extruded foam described above is characterized in that the expansion ratio is larger than 8 times. Another preferred embodiment is characterized in that the open cell ratio is 80% or more. It relates to the P3HA resin extruded foam described above.

  By the production method of the present invention, a P3HA resin extruded foam having a high open cell ratio and a high magnification exceeding 8 times can be stably obtained. Furthermore, since P3HA is adopted as the resin for extrusion foaming, a resin extruded foam having excellent heat resistance and water resistance and excellent environmental compatibility derived from plants can be obtained.

  Hereinafter, the present invention will be described in more detail.

  The poly (3-hydroxyalkanoate) used in the present invention is a copolymer composed of one or more units of 3-hydroxyalkanoate represented by the formula (1).

[—O—CHR—CH ₂ —CO—] (1)
Here, R is an alkyl group represented by C _n H _{2n + 1} , and n is an integer of 1 to 15.

  As P3HA in the present invention, a homopolymer of 3-hydroxyalkanoate, or a copolymer composed of a combination of two or more types, that is, a di-copolymer, a tri-copolymer, a tetra-copolymer, etc., or a blend of two or more thereof N = 1 3-hydroxybutyrate, n = 2 3-hydroxyvalerate, n = 3 3-hydroxyhexanoate, n = 5 3-hydroxyoctanoate, n = 15 homopolymers of 3-hydroxyoctadecanoate, and copolymers such as di-copolymers and tri-copolymers composed of combinations of two or more of these 3-hydroxyalkanoate units, and blends thereof can be preferably used. . Furthermore, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), which is a copolymer of n = 1 3-hydroxybutyrate and n = 3 3-hydroxyhexanoate, is preferred. As a composition of a copolymerization component, it is especially preferable that 3-hydroxyhexanoate is 1 mol% or more and 20 mol% or less. If 3-hydroxyhexanoate is within the above range, it can be processed without heating at high temperature, so that a decrease in molecular weight due to thermal decomposition during heat processing tends to be suppressed.

  The P3HA of the present invention is produced from microorganisms. For example, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), one of P3HA, uses Alcaligenes eutrophus AC32 in which a PHA synthase gene derived from Aeromonas caviae is introduced into Alcaligenes eutrophus as a microorganism. It can be obtained by the method described in J. Bacteriol., 179, 4821 (1997) or the like by appropriately adjusting the raw materials and culture conditions.

  The lower limit of the weight average molecular weight (Mw) of the P3HA is preferably 50,000. When the weight average molecular weight is less than 50,000, the viscosity change during heat processing is abrupt, and the melt viscosity necessary for foaming cannot be sufficiently secured, so that a foam cannot be stably obtained. However, when a thickening effect sufficient to obtain a foam is obtained by adding an isocyanate compound, a suitable foam can be obtained regardless of the molecular weight range.

  The said weight average molecular weight says the weight average molecular weight (Mw) obtained from the polystyrene conversion molecular weight distribution measurement by the gel permeation chromatography (GPC) measurement using chloroform eluent.

  In the present invention, a volatile foaming agent is melt-kneaded into a resin composition obtained by mixing P3HA, an isocyanate compound, and an aliphatic amide compound.

  The isocyanate compound used in the present invention has two or more isocyanate groups in one molecule, and examples thereof include aromatic isocyanate, alicyclic isocyanate, and aliphatic isocyanate. For example, aromatic isocyanates include tolylene, diphenylmethane, naphthylene, tolidine, xylene, triphenylmethane as an isocyanate compound, and alicyclic isocyanates include isophorone, hydrogenated diphenylmethane as an isocyanate compound, aliphatic isocyanate As such, there are isocyanate compounds having skeletons of hexamethylene and lysine. Furthermore, it is possible to use a combination of two or more of these isocyanate compounds. However, it is preferable to use an aromatic isocyanate from the viewpoint of versatility, handleability, weather resistance, etc. Among them, polyisocyanate of tolylene, diphenylmethane, particularly diphenylmethane is preferable. used.

  Further, the amount of the isocyanate compound used is preferably 0.1 parts by weight or more with respect to 100 parts by weight of P3HA. If the amount is less than this, there is no effect in preventing a decrease in viscosity at the time of extrusion, and the cell membrane is formed at the time of foaming at a high temperature. In some cases, the strength cannot be tolerated, the foam cell breaks, and the effect of suppressing shrinkage may not be obtained. On the other hand, the upper limit is preferably 10 parts by weight, and if it exceeds 10 parts by weight, the thickening effect by the isocyanate compound is remarkable, and the shear heat generation during extrusion becomes intense, which may reduce the production stability during extrusion. Contrary to thickening, an excessive isocyanate compound may act as a plasticizer to lower the melt viscosity. More preferably, 0.3 to 8 parts by weight is a preferable use amount in terms of quality and practical use.

  A fatty acid amide compound is added to the resin composition in the present invention because it does not affect or accelerates the solidification of the crystal inside the extruder and the solidification after foaming.

As the classification of fatty acid amide compounds, mono-amides (R-CONH ₂ ) of saturated fatty acids and unsaturated fatty acids, substituted amides (R-CONH-R ′), bisamides (R-CONH-... -NHCO-R ′) ), Methylolamide (R—CONHCH ₂ OH), ester amide (R—CONH—... —OCO—), fatty acid amide ethylene oxide compound (R—CONH— (CH ₂ O) _n —H), specific Specifically, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, N-oleyl palmitamide, N-stearyl erucamide, etc. Although it is mentioned, it is not limited to this. The reason why the fatty acid amide compound improves the extrusion stability and does not inhibit or accelerate the solidification after foaming is not clear, but it acts like an internal and external lubricant inside the extruder, and also exhibits a crystal nucleating effect. This is probably because of this. In extrusion foaming extruders, there is a cooling cylinder and a die part for promoting proper viscosity and crystallization after the addition of a foaming agent, but fatty acid amide compounds are considered to be easily generated here. By preventing adhesion (external lubricant action), it is considered that crystal growth (enlargement) inside the extruder is suppressed and the extrusion stability is improved. Further, a resin composition comprising an isocyanate compound in P3HA tends to slow crystallization once melted at a high temperature. When a fatty acid amide compound is added, it is considered that shear exotherm between polymers is suppressed (internal lubricant action) and does not inhibit solidification during foaming, and further acts as a crystal nucleating agent to promote solidification. Although the amount of the fatty acid amide compound added depends on the type of the fatty acid amide compound used, it is usually preferable to add 0.01 to 50 parts by weight with respect to 100 parts by weight of P3HA. If the addition amount is less than 0.01 parts by weight, the extrusion stability effect may not be clear. If the addition amount is more than 50 parts by weight, a dispersion into the resin may be poor and a uniform extruded foam may not be obtained.

  As the volatile foaming agent used in the present invention, it is preferable to use a volatile foaming agent having strong plasticity. Among them, those having environmental compatibility, solubility in polyhydroxyalkanoate, and showing a gaseous state at room temperature or at the temperature of the molding die at the time of extrusion are preferable. Specific examples of the volatile foaming agent include inorganic gases such as carbon dioxide, nitrogen and air, aliphatic saturated hydrocarbons, and other foaming agents not containing halogen. These may be used singly or in combination of two or more, but volatile foam having strong plasticity capable of adjusting the extrusion temperature To from the glass transition temperature (Tg) to the melting point (Tm). It is preferable that it is an agent.

  In general, inorganic gas is generally considered to have a weak plasticizing ability to P3HA. However, for example, an extruder capable of controlling high pressure of carbon dioxide or the like can also plasticize a resin. It also acts as a bubble size adjusting agent.

  Examples of the aliphatic saturated hydrocarbon include saturated hydrocarbons having 3 to 4 carbon atoms such as propane, normal butane, and isobutane, and saturated hydrocarbons having 5 carbon atoms such as normal pentane, isopentane, and neopentane.

  Examples of other halogen-free blowing agents include, for example, dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, diisopropyl ether, furan, furfural, 2-methyl furan, tetrahydrofuran, tetrahydropyran, and other ethers, Ketones such as dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, methyl i-butyl ketone, methyl n-amyl ketone, methyl n-hexyl ketone, ethyl n-propyl ketone, ethyl n-butyl ketone, Alcohols such as methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol, t-butyl alcohol, methyl formate Ester, ethyl formate ester, formate, propyl ester, butyl formate ester formate, amyl esters, methyl propionate, and the like can be used carboxylic acid esters such as propionic acid ethyl ester. Chemical foaming agents such as azo compounds can also be used as foaming aids and cell size adjusting agents.

Among these volatile foaming agents, ethers can be suitably used from the viewpoint of foamability, foam moldability, etc. Among them, dimethyl ether, diethyl ether, and methyl ethyl ether can be preferably used, and dimethyl ether is particularly preferred. preferable. Dimethyl ether has a low environmental impact and is beginning to be used as a highly environmentally compatible material that can be used in a wide range of applications such as diesel automobile fuel, power generation fuel, and LP gas alternative fuel.
Since ethers have strong plastic performance and foaming power, when ethers are used as volatile foaming agents, the foaming temperature at which high-strength extruded foams are obtained is lowered by several tens of degrees Celsius due to their high plasticity. In addition, foaming near the low crystallization temperature becomes possible. The amount of the volatile foaming agent to be added varies depending on the plasticizing ability of the volatile foaming agent to be used, and thus it is not possible to define the range in general. However, it is preferably about 1 part by weight or more and 100 parts by weight or less with respect to 100 parts by weight of P3HA. . For example, dimethyl ether is preferably in the range of 10 to 30 parts by weight with respect to 100 parts by weight of P3HA. When the amount is less than 10 parts by weight, the plasticizing ability is insufficient, the temperature of the extruder may not be lowered to the crystallization temperature of P3HA, and the foaming agent may escape from the mixture and hardly foam. If the amount is more than 30 parts by weight, the plasticity is sufficient, but the amount of gas used is excessive, which is not economical, and gas may be ejected from the die port.

  In addition to the isocyanate compound, the volatile foaming agent, and the fatty acid amide compound, various additives may be added to P3HA in the present invention as long as the required performance of the obtained extruded foam is not impaired. Here, additives can be used according to purposes such as antioxidants, UV absorbers, dyes, pigments and other colorants, plasticizers, lubricants, crystallization nucleating agents, inorganic fillers, etc. The compounding agent which has property is preferable. Additives include inorganic compounds such as silica, talc, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, titanium oxide, silicon oxide, sodium stearate, magnesium stearate, calcium stearate and stearic acid. Although fatty acid metal salts, such as barium, etc. are mentioned, it is not a thing limited to these. Moreover, when it is necessary to adjust the bubble diameter of a foam, a bubble regulator is added. Inorganic nucleating agents include talc, silica, calcium silicate, calcium carbonate, aluminum oxide, titanium oxide, diatomaceous earth, clay, baking soda, alumina, barium sulfate, aluminum oxide, bentonite, etc. The amount is preferably 0.005 to 10 parts by weight.

The melt viscosity η of the resin composition obtained by mixing P3HA, an isocyanate compound, and an aliphatic amide compound in the present invention is preferably larger than the melt viscosity η0 of the resin composition to which no isocyanate is added in the resin composition. . When η0 ≧ η, it is suggested that there is no thickening effect by isocyanate, and the expected effects such as prevention of shrinkage immediately after foaming (improvement of strength of foamed cell film) may not be exhibited. Here, the melt viscosity is a resin composition having a predetermined shear rate of 10 s ^{−1 to} 1500 s ⁻¹ at a predetermined temperature of melting point of P3HA to 180 ° C. with a resin composition in which an isocyanate compound is mixed or not mixed. Measured by giving to the melt of the composition.

In the P3HA resin extruded foam of the present invention, a resin composition composed of P3HA, an isocyanate compound and an aliphatic amide is mixed and melted by heating with an extruder (heating melting temperature: T1), and a volatile foaming agent is added to the molten resin. The temperature To suitable for extrusion foaming is equal to or higher than the glass transition temperature (Tg) of the P3HA and lower than the melting point (Tm).
Tc-20 ≦ To (° C.) ≦ Tc + 40 (2)
(Where Tc = (Tg + Tm) / 2)
After cooling to a high pressure mixture, the mixture is produced by extrusion foaming through a die into a low pressure region. The melting temperature (T1) when a resin composition comprising P3HA and an isocyanate compound is heated and melted is Tm + 20 ° C. or less based on the melting temperature (melting point: Tm) obtained by differential scanning calorimetry of P3HA. Is preferred. When an isocyanate compound is not added, if T1 exceeds Tm + 20 ° C., low molecular weight is promoted by thermal decomposition even if the melting time is short, and it tends to be difficult to obtain a viscosity having foamability. is there. In addition, the closer the melting temperature is to the melting point, the better the solidification at the time of extrusion foaming due to the self-crystallization promoting effect of P3HA, and it becomes easier to obtain an extruded foam having a high expansion ratio. The melting time varies depending on the amount of extrusion per unit time, the melting means, etc., and thus cannot be determined unconditionally. However, the polyhydroxyalkanoate, blowing agent, and additive are uniformly dispersed and mixed, resulting in low molecular weight due to thermal decomposition. The time is selected so that it is not significantly affected. Further, as a melting means, for example, a melting and kneading apparatus used in normal extrusion foaming, such as a screw type extruder, may be appropriately selected and is not particularly limited.

  The foaming agent of the present invention can be pressed into the extruder by a known method. The pressure when injecting the foaming agent is not particularly limited, and may be any pressure that is higher than the internal pressure of the extruder in order to press-fit into the extruder.

  The P3HA extruded foam of the present invention is formed by extruding the mixture into a low-pressure region, and the temperature and pressure of the atmosphere in the low-pressure region are not particularly limited, but for example, normal temperature, atmospheric pressure atmosphere, A gas phase or a liquid phase adjusted to a higher or lower temperature, a reduced-pressure atmosphere less than atmospheric pressure, or a slightly pressurized atmosphere can be selected.

  The P3HA resin extruded foam produced in this way has an expansion ratio of preferably more than 8 times, more preferably 10 times or more. By adding an isocyanate compound, the cell membrane is strengthened and slightly contracted, but at least a P3HA resin extruded foam having a foaming ratio larger than 8 times tends to be obtained. Further, the open cell ratio is preferably 80% or more, and more preferably 90% or more. Such a foaming ratio is preferable in terms of light weight and economy, and an open cell ratio of 80% or more is preferable in terms of cushioning properties and a high degree of freedom in shape.

In the present invention, the expansion ratio is determined by submerging an extruded foam (weight W (g)) that was allowed to stand for 7 days in a graduated cylinder containing ethanol at 23 ° C. under conditions of 50% relative humidity, 23 ° C. and 1 atm. From the rise in the water level, it is given by the following formula from the foam volume V (cm ³ ) and the P3HA resin density ρ (g / cm ³ ).

Foaming ratio = V / (W / ρ)
The open cell ratio can be obtained, for example, using a multi-pynometer (manufactured by Beckman Japan Co., Ltd.) according to ASTM D-2856.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Substances used in the present invention were abbreviated as follows.
PHBH: poly (3-hydroxybutyrate-co-3-hydroxyhexanoate)
HH ratio: mole fraction of hydroxyhexanoate in PHBH (mol%)
In the examples, “parts” are based on weight unless otherwise specified.
The physical properties of the P3HA resin expanded particles in each example were measured as follows.

<Melting point Tm of P3HA resin, glass transition temperature Tg>
Differential scanning calorimetry was performed according to JIS K-7121. About 5 mg of P3HA resin used for extrusion foaming is precisely weighed, and the temperature is raised from −20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min with a differential scanning calorimeter (Seiko Electronics Co., Ltd., SSC5200). The DSC curve is obtained, the temperature at the peak top where the absolute value of the endothermic curve is the maximum is the melting point Tm, and the base line is equidistant from the extended straight line of the baseline before and after the change in the stepwise change of the baseline. The temperature at the point where the straight line and the curve of the step-like change part of the glass transition intersect was defined as Tg.

<Melt viscosity (η0, η)>
Using a capillograph (manufactured by Toyo Seiki Seisakusho), melted in the temperature range of Tm to Tm + 40 ° C. based on the Tm measured by the above method using a 1 mmφ × 10 mm die, and at a shear rate of 122 sec ⁻¹ , isocyanate The melt viscosity η0 of the mixed resin composition of additive and P3HA excluding the additive, and the melt viscosity η of the mixed resin composition of P3HA, isocyanate compound and additive were measured. Evaluation of melt viscosity was judged as follows.
○: η0 <η
×: η0 ≧ η

<Foaming ratio of P3HA resin extruded foam>
Prepare a graduated cylinder containing ethanol at 23 ° C. Use an extruded foam (weight W (g)) left in the graduated cylinder for 7 days under conditions of 50% relative humidity, 23 ° C and 1 atm using a wire mesh or the like. Then, when the volume V (cm ³ ) of the expanded particle group is read from the ethanol water level rise, it is given by the following equation from the P3HA resin density ρ (g / cm ³ ).
Foaming ratio = V / (W / ρ)

<Open cell ratio of P3HA resin extruded foam>
It measured according to ASTM D-2856 using a multi-pynometer (manufactured by Beckman Japan Co., Ltd.).
<Biodegradability of P3HA resin extruded foam>
A P3HA resin extruded foam 20 mm × 20 mm was buried in 10 cm deep soil, and after 6 months, the shape change was observed and the degradability was evaluated according to the following criteria.
○: Decomposed so that a considerable part is decomposed and the change in shape can be confirmed. ×: Extruded foam is observed with almost no change in shape, and is not decomposed.

Example 1
PHBH produced by using Alcaligenes eutrophus AC32 (J. Bacteriol., 179, 4821 (1997)) in which a PHA synthase gene derived from Aeromonas caviae was introduced into Alcaligenes eutrophus as a microorganism, with appropriate adjustment of raw materials and culture conditions ( HH ratio 10 mol%, Mw = 530,000) 100 parts by weight and polyisocyanate compound 2 parts by weight (manufactured by Nippon Polyurethane, Millionate MR-200 (2.7 to 2.8 equivalents / mol of isocyanate group)) and fatty acid amide compound 3 parts by weight of behenic acid amide was melt kneaded at a cylinder temperature of 135 ° C. with a φ35 mm single screw extruder equipped with a kneader, and the strand extruded from a 3 mmφ small hole die attached to the tip of the extruder was cut with a pelletizer. A PHBH pellet (Tg = 1 ° C., Tm = 135 ° C., Tc = 68 ° C.) having a particle weight of 5 mg was prepared. When the melt viscosity of the pellet was measured, it was higher than the melt viscosity of the pellet not added with the isocyanate described in Comparative Example 1. The pellets were fed at a rate of about 40 kg / hr to a two-stage extruder having a diameter of 65 mm and a diameter of 90 mm connected in series. The resin mixture supplied to the 65 mm diameter extruder is melted and kneaded by heating to T1 = 145 ° C., a foaming agent is added, and the resin temperature To is 80 ° C. (To is It is between Tg and Tm and satisfies the relationship of formula (2), and is cooled to 68-20 ≦ To = 80 ≦ 68 + 40), and the thickness direction is 1 mm and the width direction is 50 mm provided at the tip of an extruder having a diameter of 90 mm. A plate-like extruded foam having a thickness of about 12 mm and a width of about 68 mm was obtained by extrusion into the atmosphere from a base having a rectangular cross section.

  As a blowing agent added at this time, 16 parts of dimethyl ether with respect to 100 parts by weight of the pellets, near the tip of the 65 mm diameter extruder (on the side connected to the end opposite to the die of the 90 mm diameter extruder) The resin was press-fitted into the resin from the end). The obtained foam had an expansion ratio of 13 times and an open cell ratio of 93%. In addition, the state of the extruder was stable during operation. Moreover, the biodegradability of the obtained foam was favorable. The results are shown in Table 1.

(Example 2)
A resin mixture using 6 parts by weight of a polyisocyanate compound and fed to an extruder with a diameter of 65 mm is heated to 150 ° C. and melt-kneaded, and a resin temperature To is 90 ° C. (To is between Tg and Tm, Except that 68−20 ≦ To = 90 ≦ 68 + 40) satisfying the relationship 2), it was extruded into the atmosphere from a base having a rectangular cross section in the same manner as in Example 1. Although the foam was slightly shrunk, a plate-like extruded foam having a thickness of about 12 mm and a width of about 73 mm was obtained. The obtained foam had an expansion ratio of 15 times and an open cell ratio of 95%. In addition, the state of the extruder was stable during operation. Moreover, the biodegradability of the obtained foam was favorable. The results are shown in Table 1.

(Comparative Example 1)
Except that the isocyanate compound was not added, the resin mixture was extruded to the atmosphere from a rectangular cross-section die in the same manner as in Example 2 except that the resin mixture was heated to 170 ° C. and melt-kneaded. The foam was very shrunk, and a plate-like extruded foam having a thickness of about 3 mm and a width of about 76 mm was obtained. The obtained foam had an expansion ratio of 5 times and an open cell ratio of 59%.

Claims (11)

Formula (1) produced from microorganisms
[—O—CHR—CH ₂ —CO—] (1)
(Here, R is an alkyl group represented by C _n H _{2n + 1} , and n = 1 or more and 15 or less.)
A volatile foamed resin composition comprising a copolymer of at least one unit represented by the following (hereinafter referred to as poly (3-hydroxyalkanoate): abbreviated as P3HA), an isocyanate compound and an aliphatic amide compound. A method for producing a P3HA resin extruded foam, comprising melting and kneading an agent to produce a mixture, and extruding the mixture through a molding die to a low pressure region.   The method for producing a P3HA resin extruded foam according to claim 1, wherein a melt viscosity η of the resin composition is larger than a melt viscosity η0 of a resin composition to which no isocyanate is added in the resin composition.   When the temperature T1 at which a mixture of a resin composition obtained by mixing P3HA, an isocyanate compound and an aliphatic amide compound and a volatile foaming agent is melted by an extruder is equal to or lower than the melting point of P3HA + 20 ° C. and is extruded from a die. The method for producing a P3HA resin extruded foam according to claim 1 or 2, wherein the resin temperature To is a glass transition temperature (Tg) or higher and a melting point (Tm) or lower of P3HA. A temperature To when a mixture of a resin composition obtained by mixing P3HA, an isocyanate compound and a fatty acid amide compound and a volatile foaming agent is extruded from an extruder is in the range represented by the formula (2). The method for producing a P3HA resin extruded foam according to any one of claims 1 to 3.
Tc-20 ≦ To (° C.) ≦ Tc + 40 (2)
Here, Tc = (Tg + Tm) / 2   The method for producing a P3HA resin extruded foam according to any one of claims 1 to 4, wherein P3HA is poly (3-hydroxybutyrate-co-3-hydroxyhexanoate).   P3HA is poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), and the composition of the copolymer component is characterized in that 3-hydroxyhexanoate is 1 mol% or more and 20 mol% or less. The method for producing a P3HA resin extruded foam according to any one of claims 1 to 5.   The method for producing an extruded foam of P3HA resin according to any one of claims 1 to 6, wherein the volatile foaming agent is at least one selected from the group consisting of dimethyl ether, diethyl ether, and methyl ethyl ether.   The method for producing a P3HA resin extruded foam according to any one of claims 1 to 7, wherein the volatile foaming agent is dimethyl ether.   A P3HA resin extruded foam obtained by the production method according to any one of claims 1 to 8.   The P3HA resin extruded foam according to claim 9, wherein the expansion ratio is larger than 8 times.   The P3HA resin extruded foam according to claim 9 or 10, wherein the open cell ratio is 80% or more.