JP2007136693A - Extruded foam of polyhydroxyalkanoate resin and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extruded foam of a polyhydroxyalkanoate resin excellent in environmental compatibility and having biodegrability, and its stable manufacturing method. <P>SOLUTION: A volatile foaming agent is melted to be kneaded with a resin composition (A), which is based on a copolymer comprising at least one kind of a unit represented by the formula (1): [-O-CHR-CH<SB>2</SB>-CO-] (wherein R is an alkyl group represented by C<SB>n</SB>H<SB>2n+1</SB>wherein n is 1-15) [Hereinbelow, referred to as poly (3-hydroxyalkanoate) short for P3HA], to prepare a mixture. Immidiately after the mixture is extruded to a low pressure region through a molding die adjusted to a temperature from 80°C to the melting point of the mixture + 20°C and the extrudate is cooled so that the surface temperature thereof becomes below 80°C to manufacture the extruded foam of the P3HA resin. <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 by the production method.

  In recent years, plastic, sheets, films, fibers, injection-molded products, etc., have been commercialized both in Japan and overseas, but foam used in packaging containers, cushioning materials, cushioning materials, etc. in plastic waste. Since plastic is bulky, it has become a big social problem, and its solution is desired. 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.

  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.

  As for a method for producing a polyester extruded foam, a thermoplastic polyester extruded foam containing an aromatic molecule such as polyethylene terephthalate has been conventionally studied. For example, an extruded foam that rapidly cools a foam having a specific viscosity range. A method has been reported (Patent Document 11). Patent Document 11 is a method for producing a structure by rapidly cooling a polyester that has been extruded and foamed after releasing the pressure to a temperature below its glass transition temperature and suppressing crystallization.

  On the other hand, Patent Document 12 discusses an extruded foam of P3HA resin produced from microorganisms.

  Patent Document 12 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), and carbon dioxide, dimethyl ether, and hydrocarbon are used as a foaming agent, and it is disclosed that a foam can be obtained. However, once the P3HA is melted, the volatile foaming agent hardly contributes to foaming (forms almost no bubbles) because of slow crystallization, and the ejected matter has a low appearance defect slightly mixed with bubbles. Even if foamed or foamed and foamed, the swelled film did not solidify and contracted, resulting in a foam with poor appearance. 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 beautiful appearance 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. Development is desired because it may be used as a sex control particle or as a carrier for culturing cells.
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-A-6-145404 JP 2003-327737 A

  Then, 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 open-cell ratio with high appearance and a high open cell ratio.

  As a result of intensive studies to solve the above problems, the inventors of the present invention melted and kneaded a volatile foaming agent into a resin composition containing P3HA to produce a mixture, and the mixture was subjected to low pressure through a molding die. Immediately after being extruded into the region, by quenching with a refrigerant so that the surface temperature of the discharged product becomes less than 80 ° C., crystallization of the resin composition can be promoted, gas escape from the resin composition can be suppressed, and the appearance is beautiful. Discovered that a foam can be obtained, and further discovered that when a substance having a thickening effect, such as an isocyanate compound, is mixed, the appearance of the foam is significantly improved by improving the bubble film strength, and the present invention is completed. It came to do.

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 foaming agent is melt-kneaded with a resin composition (A) containing a copolymer (hereinafter, poly (3-hydroxyalkanoate): abbreviated as P3HA) composed of one or more units represented by the following formula: P3HA resin extrusion characterized in that the mixture is extruded and extruded to a low pressure region through a molding die adjusted to 80 ° C. or higher and melting point + 20 ° C. or lower, and the surface temperature of the discharged product is cooled to less than 80 ° C. The present invention relates to a method for producing a foam.
However, the resin composition (A) satisfies the relationship of the formula (2).
η> 500 Pa · s (2)
η: Melting viscosity at the melting point of the resin composition (A) + 20 ° C. and a shear rate of 122 sec ⁻¹

As a preferred embodiment,
(1) The resin composition (A) comprises P3HA and a substance showing a thickening effect,
(2) The substance showing the thickening effect is an isocyanate compound,
(3) The resin composition (A) comprises an aliphatic amide compound,
(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 one or more selected from the group consisting of carbon dioxide, propane, isobutane, normal butane, dimethyl ether, diethyl ether, and methyl ethyl ether.
The present invention relates to a method for producing the P3HA resin extruded foam described above.

  A second aspect of the present invention relates to a P3HA resin extruded foam characterized by being obtained by the method for producing an extruded foam described above, and as a preferred embodiment, the open cell ratio is 70% or more. It relates to the P3HA resin extruded foam described above.

  In the present invention, since P3HA is adopted as the extrusion foaming resin, a resin extruded foam having excellent heat resistance and water resistance and excellent environmental compatibility derived from plants is produced by the production method of the present invention. And can be obtained stably. In addition, a foam can be obtained that decomposes by the action of microorganisms and returns to the earth's carbon circulation system in both aerobic and anaerobic environments when discarded. Furthermore, it is a plant-derived foam obtained by positively fixing carbon dioxide on the earth and is expected to prevent global warming.

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

  The poly (3-hydroxyalkanoate) of the present invention is a copolymer comprising units composed of one or more 3-hydroxyalkanoates 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. . Among them, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) which is a copolymer of 3-hydroxybutyrate with n = 1 and 3-hydroxyhexanoate with n = 3 is preferable. As a composition of a polymerization component, it is especially preferable that 3-hydroxyhexanoate is 1 mol% or more and 20 mol% or less. If 3-hydroxyhexanoate is within the range, it can be processed without being heated to a 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.

In the resin composition comprising P3HA of the present invention, the melt viscosity (η) at the melting point + 20 ° C. and the shear rate of 122 sec ⁻¹ of the resin composition (A) satisfies the following formula (2).
η> 500 Pa · s (2)
A foam can be stably obtained by having such melt viscosity.

  The lower limit of the weight average molecular weight (Mw) of P3HA is preferably 50,000. When the weight average molecular weight is less than 50,000, the viscosity change during heat processing is rapid, and the melt viscosity necessary for foaming may not be sufficiently secured, so there is a tendency that a foam cannot be stably obtained. . However, there is no problem even if the average molecular weight is less than 50,000 when a thickening effect sufficient to obtain a foam can be obtained by adding a substance showing a thickening effect such as an isocyanate compound described later. 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 which used the chloroform solution.

  In the present invention, P3HA has effects such as thickening, shrinkage prevention immediately after foaming, and improvement in strength of the foamed cell membrane, and therefore a substance exhibiting a thickening effect (hereinafter sometimes referred to as a thickener) is added. It is preferable. An isocyanate compound is mentioned as a substance which shows a particularly preferable thickening effect.

  As an isocyanate compound of this invention, it has 2 or more isocyanate groups in 1 molecule, Aromatic isocyanate, alicyclic isocyanate, aliphatic isocyanate etc. are mentioned as a kind. More specifically, the aromatic isocyanate is an isocyanate compound having a skeleton of tolylene, diphenylmethane, naphthylene, tolidine, xylene, triphenylmethane, and the alicyclic isocyanate is an isocyanate compound having a skeleton of isophorone or hydrogenated diphenylmethane. Examples of the aliphatic isocyanate include an isocyanate compound having a skeleton of hexamethylene and lysine. Further, a combination of two or more of these isocyanate compounds can be used. Of these, aromatic isocyanates are preferred from the viewpoints of versatility, handleability, weather resistance, etc., and tolylene and diphenylmethane are particularly preferred, and polyisocyanates of diphenylmethane are particularly preferred.

  In addition, when the isocyanate compound is used, the amount used is preferably 0.1 parts by weight or more with respect to 100 parts by weight of P3HA. Is recognized. 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 shear heat generation at the time of extrusion becomes violent, which may deteriorate the production stability at the time of extrusion. More preferably, 0.3 to 8 parts by weight is a preferable use amount in terms of quality and practical use.

  In the present invention, it is preferable to add a fatty acid amide compound to P3HA 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 palmitoamide, N-stearyl erucamide, etc. Can be mentioned. 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. About the addition amount of a fatty acid amide type compound, although depending on the kind of fatty acid amide type compound to be used, it is usually preferable to add 0.01 weight part or more and 50 weight part or less with respect to 100 weight part of P3HA resin. 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.

  In the resin composition (A) comprising P3HA in the present invention, in addition to an isocyanate compound and a fatty acid amide compound that are added as necessary, various kinds of resins can be used as long as they do not impair the required performance of the obtained extruded foam. Additives may be added. 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 present invention is characterized by melting and kneading a volatile foaming agent to the resin composition (A) containing P3HA. Among them, a foaming agent that has environmental compatibility and is dissolved in the resin composition (A) at the temperature T0 of the molding die at the time of extrusion is 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 alone or in combination of two or more.

  In general, inorganic gas is generally considered to have low solubility in P3HA. However, for example, an extruder capable of controlling high pressure of carbon dioxide or the like can be solubilized in 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 blowing agents, propane, isobutane, normal butane, dimethyl ether, diethyl ether, and methyl ethyl ether can be preferably used from the viewpoints of foamability, foam formability, and the like, and dimethyl ether is particularly preferable. Ethers have strong solubility, plastic performance and foaming power for P3HA resins.

  The amount of the volatile foaming agent used in the present invention varies depending on the solubility of the volatile foaming agent to be used, and thus cannot be uniformly defined. However, it is generally 1 to 100 parts by weight with respect to 100 parts by weight of P3HA. Preferably there is. More preferably, it is in the range of 1 to 30 parts by weight. When the amount is less than 1 part by weight, there is a case where foaming hardly occurs even when quenched. On the other hand, when the amount is more than 30 parts by weight, the amount of gas used is excessive, which is not economical, and there is a risk that gas may be ejected from the die port.

  In the P3HA resin extruded foam of the present invention, the resin composition (A) containing P3HA is heated and melted with an extruder (heating melting temperature: T1), and a volatile foaming agent is press-fitted into the molten resin. And a volatile foaming agent are kneaded and made into a low pressure region through a molding die adjusted to 80 ° C. or higher and melting point + 20 ° C. or lower, and the surface temperature of the discharged product is a temperature lower than 80 ° C., preferably the glass transition temperature of the discharged product. Cool higher. In general, for example, a method of foaming by quenching below the glass transition point is employed as in the method described in JP-A-6-145404. However, in the present invention, the glass transition point is not required. It is possible to make it foam.

  The melting temperature (T1) when the resin composition (A) is heated and melted is preferably a melting point + 40 ° C. or lower based on the melting temperature (melting point: Tm) obtained by differential scanning calorimetry of P3HA. . When a substance exhibiting a thickening effect such as an isocyanate compound is added, the thickening effect tends to be widened until T1 reaches a melting point of about + 50 ° C., and the melting temperature range capable of stable extrusion tends to widen. Further, 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 the easier it is to obtain an extruded foam with a beautiful appearance by rapid cooling. It is as follows.

  Although the melting time varies depending on the amount of extrusion per unit time and the melting means, etc., it cannot be determined unconditionally. However, P3HA, foaming agent and additives are uniformly dispersed and mixed, and the molecular weight is significantly reduced by thermal decomposition. A range of times is chosen. 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.

  According to the foaming method of the present invention, the foamed material is foamed when the discharged material is extruded from the molding die into the low pressure region, and the surface temperature of the discharged material is rapidly cooled to less than 80 ° C. There is a feature. In the resin composition (A), the dissolved volatile foaming agent is a resin composition (except for the case where the molding die temperature can be adjusted to the temperature of resin crystallization using a highly plastic volatile foaming agent. Since the crystallization of A) is slow, it almost does not contribute to foaming (forms almost no bubbles), and the ejected matter becomes a low-foam with a poor appearance with some bubbles mixed, or solidifies even if bubbles are formed Since it is slow, it shrinks and becomes a foam having a non-uniform shape. On the other hand, by extruding the discharged material into a low pressure region and cooling it, it is characterized in that the crystallization of the resin composition is promoted, the foam formation is excellent and the appearance can be improved.

  The low pressure region in which the P3HA extruded foam is extruded from the molding die can be selected from a gas phase and a liquid phase adjusted to a reduced pressure atmosphere below atmospheric pressure or a slightly pressurized atmosphere. Immediately after being extruded, it is preferable to cool the discharge with a refrigerant of less than 80 ° C. The cooling method includes, for example, cooling with hot water or cold water, cooling with cold air, or the like.

  The P3HA resin extruded foam produced in this way forms a relatively uniform cell and has a beautiful appearance. Further, the open cell ratio is preferably 70% or more, and more preferably 90% or more. Such a foaming ratio is preferable in terms of lightness and economy, and an open cell ratio of 70% or more is preferable in terms of cushioning properties and high shape freedom.

  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 foam in each example were measured as follows.

<Melting point (Tm) and glass transition temperature (Tg) of P3HA resin>
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, and the straight line that 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 curves of the step-like change portion of the glass transition intersect was defined as Tg.

<Melt viscosity (η)>
Resin composition comprising P3HA at a melting point of + 20 ° C. and a shear rate of 122 sec ⁻¹ based on the melting point measured by the above method using a capilograph (manufactured by Toyo Seiki Seisakusho) using a 1 mmφ × 10 mm die. The melt viscosity η of (A) was measured. Evaluation of melt viscosity was judged as follows.
○: η> 500 Pa · s
×: η ≦ 500 Pa · s

<Surface temperature of discharged material of P3HA resin composition>
The temperature of the discharged material surface was measured with a non-contact thermometer (Thermo Hunter PT-7LD, manufactured by Optex).
○: Less than 80 ° C ×: 80 ° C or more

<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.).

<Appearance evaluation of P3HA resin extruded foam>
The extruded foam was visually observed.
A: Almost no unfoamed portion is observed.
X: Many unfoamed parts are confirmed, and the surface of the discharged material is rough.

<Biodegradability of P3HA resin extruded foam>
A P3HA resin extruded foam 20 mm × 20 mm × 1.5 to 2.5 mm was buried in soil having a depth of 10 cm, 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 4 parts by weight (manufactured by Nippon Polyurethane, Millionate MR-200 (2.7 to 2.8 equivalents / mol 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 resin composition (A1) pellet having a particle weight of 5 mg (melting point: 135 ° C., Tg = 1 ° C.) was prepared. When the melt viscosity of the pellet was measured, the condition of formula (2) was satisfied. 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 = 155 ° C., a foaming agent is added, and the resin temperature To is 135 ° C. (≦ melting point) with the 90 mm diameter extruder connected thereto. +20), continuously extruded from a rectangular cross-section die with a thickness of 1 mm and a width of 50 mm provided at the tip of an extruder with a diameter of 90 mm, and air at 20 ° C. was blown onto the upper and lower surfaces of the rectangular cross-section for about 20 seconds. When the discharged product was rapidly cooled, it uniformly foamed to obtain a plate-like extruded foam having a thickness of about 2 mm and a width of about 120 mm. The surface temperature of the discharged product when air was blown for about 20 seconds was less than 80 ° C.

  As a foaming agent added at this time, 10 parts of dimethyl ether with respect to 100 parts by weight of the resin composition (A1) pellets, near the tip of the 65 mm diameter extruder (the end side opposite to the die of the 90 mm diameter extruder) The resin was press-fitted into the resin from the end portion on the side connected to the resin. The obtained foam had an expansion ratio of 7 times and an open cell ratio of 82%. In addition, the state of the extruder was stable during operation. Further, the appearance and biodegradability of the obtained foam were good. The results are shown in Table 1.

(Example 2)
Extrusion was performed from the rectangular cross-section die into the atmosphere in the same manner as in Example 1 except that the resin temperature To during extrusion was 105 ° C. (≦ melting point + 20). Although the foam was slightly shrunk, a plate-like extruded foam having a thickness of about 2 mm and a width of about 180 mm was obtained. The obtained foam had an expansion ratio of 14 times and an open cell ratio of 88%. In addition, the state of the extruder was stable during operation. Further, the appearance and biodegradability of the obtained foam were good. The results are shown in Table 1.

(Example 3)
A foam was prepared in the same manner as in Example 1 except that the discharge product continuously extruded from the die having a rectangular cross section was immersed in a water bath having a water temperature of 30 ° C. for about 10 seconds. Foamed uniformly by rapid cooling. The surface temperature of the discharged material when taken out from the water tank was less than 80 ° C. The foam was a plate-like extruded foam having a thickness of about 2.5 mm and a width of about 180 mm. The obtained foam had an expansion ratio of 15 times and an open cell ratio of 90%. In addition, the state of the extruder was stable during operation. Further, the appearance and biodegradability of the obtained foam were good. The results are shown in Table 1.

Example 4
A foam was prepared in the same manner as in Example 2 except that the discharged material continuously extruded from the die having a rectangular cross section was immersed in a water bath at a water temperature of 5 ° C. for about 10 seconds. Foamed uniformly by rapid cooling. The surface temperature of the discharged material when taken out from the water tank was less than 80 ° C. The foam was a plate-like extruded foam having a thickness of about 2.5 mm and a width of about 180 mm. The obtained foam had an expansion ratio of 15 times and an open cell ratio of 80%. In addition, the state of the extruder was stable during operation. Further, the appearance and biodegradability of the obtained foam were good. The results are shown in Table 1.

(Example 5)
As a foaming agent, a foam was prepared in the same manner as in Example 1 except that 5 parts of isobutane was added to 100 parts by weight of the resin composition (A1) pellets. Foamed uniformly by rapid cooling. The surface temperature of the discharged product when air was blown for about 20 seconds was less than 80 ° C. The foam was a plate-like extruded foam having a thickness of about 1.5 mm and a width of about 120 mm. The obtained foam had a foaming ratio of 4 times and an open cell ratio of 71%. In addition, the state of the extruder was stable during operation. Further, the appearance and biodegradability of the obtained foam were good. The results are shown in Table 1.

(Comparative Example 1)
Except not performing forced cooling by air, it was extruded into the atmosphere from a base having a rectangular cross section in the same manner as in Example 1. The surface temperature of the discharged material after about 20 seconds after coming out of the die was 80 ° C. or higher. The discharged product was uneven in foaming, and foamed and unfoamed portions were generated, and a plate-like mottled foam having a thickness of about 2 mm and a width of about 75 mm was obtained. The obtained foam had a foaming ratio of 3 times and an open cell ratio of 55%.

Claims (9)

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 foaming agent is melt-kneaded with a resin composition (A) containing a copolymer (hereinafter, poly (3-hydroxyalkanoate): abbreviated as P3HA) composed of one or more units represented by the following formula: P3HA resin extrusion characterized in that the mixture is extruded and extruded to a low pressure region through a molding die adjusted to 80 ° C. or higher and melting point + 20 ° C. or lower, and the surface temperature of the discharged product is cooled to less than 80 ° C. A method for producing a foam.
However, the resin composition (A) satisfies the relationship of the formula (2).
η> 500 Pa · s (2)
η: Melting viscosity of resin composition (A) at melting point + 20 ° C. and shear rate of 122 sec ⁻¹   The method for producing a P3HA resin extruded foam according to claim 1, wherein the resin composition (A) comprises P3HA and a substance exhibiting a thickening effect.   The method for producing a P3HA resin extruded foam according to claim 2, wherein the substance exhibiting the thickening effect is an isocyanate compound.   The method for producing a P3HA resin extruded foam according to any one of claims 1 to 3, wherein the resin composition (A) comprises an aliphatic amide compound.   The method for producing an 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. A method for producing a P3HA extruded foam according to any one of claims 1 to 5.   The volatile blowing agent is at least one selected from the group consisting of carbon dioxide, propane, isobutane, normal butane, dimethyl ether, diethyl ether, and methyl ethyl ether. Manufacturing method of P3HA resin extruded foam.   A P3HA resin extruded foam obtained by the method for producing an extruded foam according to any one of claims 1 to 7.   9. The P3HA resin extruded foam according to claim 8, wherein the open cell ratio is 70% or more.