JP2018039860A - Polyester resin composition and nucleating agent used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin composition which contains mcl-PHA as a resin component, has a high crystallization speed, and is excellent in moldability, and to provide a nucleating agent used for the same.SOLUTION: In a polyester resin composition, 3 pts.wt. or more and 30 pts.wt. or less of pulverized cellulose fiber is added to 100 pts.wt. of poly3-hydroxyalkanoic acid derived from microorganism. It is preferable that the poly3-hydroxyalkanoic acid is a polymer of the 3-hydroxyalkanoic acid having 6 or more and 14 or less carbon atoms. It is preferable that the pulverized cellulose fiber has a fiber width of 2 μm or less and a fiber length of 80 μm or less.SELECTED DRAWING: None

Description

  In recent years, in order to combat global warming, it has been required to use materials that suppress the emission of carbon dioxide. For this reason, carbon neutral environmentally-circulating materials that are biosynthesized by animals and plants and microorganisms and decompose into water and carbon dioxide by the action of microorganisms are attracting attention. By using environmentally recyclable materials, it is possible to form a carbon dioxide circulation cycle that repeats fixation and emission of carbon dioxide in a decades cycle, thus preventing an increase in carbon dioxide that causes global warming. Can do.

  One of the environmentally circulated materials is a polyhydroxyalkanoate derived from a microorganism (hereinafter, abbreviated as “PHA” in the present specification). PHA is a natural polyester having hydroxyalkanoic acid as a structural unit, and it is an environmentally friendly plastic because it is degraded by both aerobic and anaerobic microorganisms. Moreover, since it is excellent in water resistance and gas barrier property, it attracts attention also as a functional material. Furthermore, it can be produced without competing with edible natural resources because it is biosynthesized by fermentation production of microorganisms from not only food resources such as sugar and lipids but also surplus organic waste and non-edible vegetable oils. It also has the advantage. In addition, by adjusting the supply carbon source and culture conditions, various polymerization degrees and copolymer compositions can be obtained, and various physical properties such as tensile strength, melting point, glass transition point, and flexibility can be controlled. It is.

  Among the PHAs, PHAs having a structural unit of 3-hydroxyalkanoic acid having 6 to 14 carbon atoms are classified as medium chain PHA (hereinafter referred to as “mcl-PHA”) and deposited. It is known to be efficiently biosynthesized by microorganisms of the genus Pseudomonas, to which the microorganism Pseudomonas putida (FERM P-16953) belongs.

mcl-PHA is a transparent and soft resin having a melting point of 40 to 70 ° C. and a glass transition point of −40 to −20 ° C., and has characteristics of being soft and transparent. For this reason, mcl-PHA is considered to be usable in a wide range of fields such as packaging materials, food materials, construction / civil engineering materials, agriculture / horticultural materials, medical materials, adsorption / carrier / filtration materials, etc. Establishment of is desired.
On the other hand, PHA having a structural unit of 3-hydroxyalkanoic acid having 3 to 5 carbon atoms as a structural unit is classified as a short chain PHA (hereinafter abbreviated as “scl-PHA”) and has a melting point. 150 ° C. or higher.

  mcl-PHA has a problem that crystallization is very slow, and for this reason, solidification from the molten state becomes slow at the time of molding processing, making it difficult to mold, or even if solidified, from the mold There was a drawback that the mold release speed and the like became slow, and the productivity deteriorated.

  Conventionally, inorganic compounds such as silica, talc, clay, alumina, mica, zirconia, titania, tin oxide, indium tin oxide, antimony tin oxide, calcium carbonate, and zeolite have been used as methods for improving the general polyester crystallization rate. A method of adding as a nucleating agent is disclosed (Patent Document 1). Patent Document 2 includes amides, aromatic esters, linear diesters, urethanes, sulfones, ester derivatives having a tartrate aromatic group, or mixtures thereof as PHA crystallinity improvers. Further, Patent Document 3 discloses a sugar selected from the group consisting of erythritol, D-arabitol, ribitol, xylitol, galactitol, D-mannitol, L-mannitol, myo-inositol, scyllo-inositol, maltitol, and lactitol. Alcohols are disclosed as crystallinity improvers for PHA.

JP 2014-105337 A JP 2014-65906 A Japanese Patent No. 5645176

  The present invention has been made in view of the above-described conventional circumstances, and includes a polyester resin composition containing a poly-3-hydroxyalkanoic acid derived from a microorganism as a resin component, having a high crystallization rate and excellent moldability. It is an object to provide a crystal nucleating agent used therefor.

  In order to solve the above problem, the present inventor uses cellulose fiber as a crystal nucleating agent for poly-3-hydroxyalkanoic acid, so that not only the resin component but also the crystal nucleating agent is used so that all materials are carbon neutral. A polyester resin composition made of an environmental circulation material was considered. And as a result of further earnest research, the cellulose fiber is not used as it is, but by pulverizing it as a crystal nucleating agent for poly-3-hydroxyalkanoic acid without significantly impairing transparency and biodegradability. The present inventors have found that the function can be dramatically improved and have completed the present invention.

  That is, the polyester resin composition of the present invention is characterized in that pulverized cellulose fibers are added in an amount of 3 parts by weight to 30 parts by weight with respect to 100 parts by weight of the microorganism-derived poly-3-hydroxyalkanoic acid.

  In the present specification, “pulverization” means all methods for reducing the fiber length and fiber width of cellulose fibers, and is a concept including not only mechanical pulverization but also chemical pulverization. Further, loosening cellulose fibers (in other words, reducing the fiber width) is referred to as “defibration”, but the term “pulverization” in this specification includes “defibration”.

  The poly-3-hydroxyalkanoic acid used as the resin component raw material of the polyester resin composition of the present invention can be a polymer of 3-hydroxyalkanoic acid having 6 to 14 carbon atoms. If it is like this, it can be set as a transparent and soft polyester resin composition.

  As a microorganism that efficiently produces poly-3-hydroxyalkanoic acid, a microorganism of the genus Pseudomonas can be used. Particularly preferred is Pseudomonas putida (FERM P-16953).

  The pulverized cellulose fiber preferably has a fiber width of 2 μm or less and a fiber length of 80 μm or less. In this case, crystallization of poly-3-hydroxyalkanoic acid is further improved.

  Moreover, it is also preferable to modify at least a part of the hydroxyl groups present in the pulverized cellulose with an aromatic functional group or to form a carboxylic acid ester group. According to the inventor's test results, the crystallization of poly-3-hydroxyalkanoic acid is further remarkable when at least a part of the hydroxyl groups of cellulose is modified with a functional group having an aromatic group or a carboxylic acid ester group. It will be excellent.

  The polyester resin composition of the present invention can be used in a wide range of fields such as food materials, construction / civil engineering materials, agricultural / horticultural materials, medical materials, adsorption / carrier / filtration materials and the like. In particular, a seedling sheet as a seed holding body using the polyester resin composition of the present invention is particularly preferable because it is transparent and easy to check seeds and has excellent seed holding performance.

  Since the resin composition of the present invention has thermoplasticity, it can be formed into a molded body. Further, the molded body formed by the resin composition of the present invention has good water resistance, flexibility, transparency, biodegradability, biocompatibility, etc., and is used as an agricultural material, a medical material, etc. It can be preferably used. In addition, since it is a microorganism-derived resin made from plant resources, it can be replaced with a conventional petroleum-derived resin as a material that can contribute to the suppression of global warming.

It is a FE-SEM photograph of the pulverized cellulose fiber. It is an infrared absorption spectrum of a benzoylated cellulose fiber. It is an infrared absorption spectrum of an acetylated cellulose fiber. It is a chart which shows the measurement result of DSC about Examples 5-7 and comparative example 2. FIG. It is a cross-sectional schematic diagram of a seedling sheet.

(About poly-3-hydroxyalkanoic acid)
The polyester resin composition of the present invention uses microorganism-derived poly-3-hydroxyalkanoic acid as a resin component. Since poly-3-hydroxyalkanoic acid is degraded by both aerobic and anaerobic microorganisms, it is easily degraded by these microorganisms when discarded. Moreover, since it is excellent in water resistance and gas barrier property, it can also be utilized as a functional material. For example, it can be used in a wide range of fields such as food materials, construction / civil engineering materials, agriculture / horticultural materials, medical materials, adsorption / carrier / filtration materials.

Among the poly-3-hydroxyalkanoic acids, a random copolymer containing structural units having different carbon numbers and represented by the following general formula (1) having 6 to 14 carbon atoms is preferable (wherein R is C _n. It is either an alkyl group represented by H _2n +1 or an alkenyl group represented by C _n H _2n (where n is an integer of 3 or more and 11 or less).

  This poly-3-hydroxyalkanoic acid is mcl-PHA having a structural unit of 3-hydroxyalkanoic acid having 6 to 14 carbon atoms as a structural unit, and becomes a soft and transparent functional material. It can be suitably used for materials for use, agriculture / horticultural materials and the like. mcl-PHA is polymerized in a microorganism through enzymatic addition of CoA, dehydrogenation, and water addition through a β-oxidation pathway, which is a fatty acid decomposition system, starting from sugar, alcohol, fat, fatty acid, and the like. The polymer structural unit may be an alkane structure of a saturated hydrocarbon, or may be a fatty acid structure of an alkene structure including one or more side chains having an unsaturated hydrocarbon.

  When mcl-PHA is used as the poly-3-hydroxyalkanoic acid, those containing an alkenyl group having a double bond introduced into the side chain of the monomer unit are also preferred. Poly (3-hydroxyalkanoic acid) in which a double bond is introduced into the side chain of such a monomer unit may be used as it is, but there is a problem in the strength of the resin composition due to insufficient molecular weight, for example. In addition, crosslinking may be carried out by using heat or light in the presence of a crosslinking agent, heat or photopolymerization initiator, or chain extension may be performed. In this way, it can control so that it may become a resin composition which has desired viscosity and intensity | strength. In this case, the type of the crosslinking agent and initiator used is not limited. For example, as the crosslinking agent, a monomer having a plurality of acryloyl groups or methacryloyl groups, bismaleimide, or the like can be used. In addition, since the content of the monomer unit having a double bond in the poly (3-hydroxyalkanoic acid) is too small, crosslinking or chain extension becomes difficult, so the minimum content is preferably 0.1 mol% or more. 1% or more is more preferable, and 5% or more is particularly preferable. Moreover, since it is difficult to obtain a uniform cross-linked reaction product when the amount is too large, the maximum content is preferably 30 mol% or less, more preferably 25 mol% or less, and particularly preferably 20 mol% or less. If it exists, there is no problem even if the content of the monomer unit having a double bond exceeds 30 mol%.

  As microorganisms that produce mcl-PHA, for example, microorganisms such as Pseudomonas oleovorans and Pseudomonas aeruginosa are known in addition to the deposited microorganism (FERM P-16953). In these microorganisms, mcl-PHA accumulates in the microbial cells. In particular, in order to increase the productivity of mcl-PHA, genetically modified microorganisms in which microorganisms such as Escherichia coli are introduced as genes for various PHA synthase groups may be used, or culture conditions including the types of substrates may be optimized. Good.

  Although it does not specifically limit as a monomer which comprises poly 3-hydroxy alkanoic acid, For example, 3-hydroxy hexanoic acid, 3-hydroxy heptanoic acid, 3-hydroxy octanoic acid, 3-hydroxy nonanoic acid, 3-hydroxy decanoic acid, 3 -Hydroxyundecanoic acid, 3-dodecanoic acid, 3-hydroxytridecanoic acid, 3-hydroxytetradecanoic acid, 3-hydroxynonenoic acid, 3-hydroxyoctenoic acid, 3-hydroxydecenoic acid, 3-hydroxyundecenoic acid, 3- And hydroxytridecenoic acid.

  Among these, 3-hydroxyoctanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, 3-hydroxyundecanoic acid, 3-dodecanoic acid, 3-hydroxytridecane At least one monomer selected from the group consisting of acids, 3-hydroxytetradecanoic acid, 3-hydroxynonenoic acid, 3-hydroxyoctenoic acid, 3-hydroxydecenoic acid, 3-hydroxyundecenoic acid and 3-hydroxytridecenoic acid And a copolymer are preferred.

  When mcl-PHA is used as the poly-3-hydroxyalkanoic acid, the weight average molecular weight is preferably 50,000 to 2,500,000, and more preferably 200,000 to 1,500,000. If the weight average molecular weight is less than 50,000, mechanical properties such as strength may be insufficient, and if it exceeds 2.5 million, molding processability may be inferior. In addition, the weight average molecular weight here means what was measured from the polystyrene conversion molecular weight distribution using the gel permeation chromatography (GPC) which used chloroform eluent. As a column in the GPC, a column suitable for measuring the molecular weight is used.

(About cellulose fiber)
Cellulose fibers are added as a crystal nucleating agent to the polyester resin composition of the present invention. According to the test results of the inventors, cellulose fibers are pulverized to enhance the effect as a crystal nucleating agent, increase the crystallization speed, and provide a polyester resin composition excellent in molding processability. The pulverization method is not particularly limited. For example, as a mechanical pulverization method, a homogenizer, ball mill, bead mill, colloid mill, conical mill, disc mill, edge mill, hammer mill, mortar, roller mill, jet mill, or the like is used. Can do. In combination with mechanical pulverization (or in place of mechanical pulverization), oxidative decomposition is performed using an oxidizing agent such as sodium hypochlorite, or hydrolysis is performed using an acid such as sulfuric acid. It can also be pulverized.

As a method for pulverizing cellulose fibers, for example, the following method can be used.
・ Method 1
Using natural cellulose as a raw material, an oxidation reaction is performed by using an N-oxyl compound as an oxidation catalyst in water and an oxidizing agent such as sodium hypochlorite acting on it, and then impurities are removed from the fiber of the reactant containing water. By performing a defibrating treatment with a homogenizer, cellulose fibers having a fiber width of 2 μm or less can be obtained.
・ Method 2
Cellulose fibers having a fiber width of 1 μm or less can be obtained by removing impurities from a water suspension or slurry of cellulose fibers after acid hydrolysis with sulfuric acid and performing a fibrillation treatment with a homogenizer.
・ Method 3
A method of physically pulverizing natural cellulose. That is, a device that pulverizes by introducing a cellulose raw material into a gap between two relatively moving members and applies a shearing force, such as a mortar-type pulverizer, a wet atomizer that refines with a high-pressure water flow, or other airflow pulverization Any device such as an apparatus may be used, and the method is not particularly limited.

  The pulverized cellulose fiber needs to be added in an amount of 3 to 30 parts by weight with respect to 100 parts by weight of the microorganism-derived poly-3-hydroxyalkanoic acid. When the cellulose fiber is less than 3 parts by weight, a sufficient effect as a crystal nucleating agent is not exhibited and the resin composition is inferior in moldability. Moreover, when a cellulose fiber exceeds 30 weight part, mechanical strength will fall.

  The pulverized cellulose fiber preferably has a fiber width of 2 μm or less and a fiber length of 80 μm or less. In this way, the function as a crystal nucleating agent can be improved more reliably. More preferably, the fiber width is 0.5 to 1.5 μm, and the average fiber length is 30 to 70 μm.

Moreover, it is also preferable that at least a part of the hydrogen atoms of the hydroxyl group contained in the pulverized cellulose fiber is substituted with an aromatic acyl group having 6 to 11 carbon atoms (see the following general formula (2) (here) R ² , R ³ and R ⁶ each independently represent a hydrogen atom or an aromatic acyl group having 6 to 11 carbon atoms, provided that at least one of R ² , R ³ and R ⁶ is This is an aromatic acyl group having 6 to 11 carbon atoms.) If this is the case, the effect as a crystal nucleating agent is further increased, and a resin composition having more excellent moldability can be obtained.

  In the modified cellulose represented by the general formula (2), an aromatic hydrocarbon having a specific carbon number is substituted on at least a part of the hydroxyl group of the β-glucose ring. Furthermore, since cellulose is a complete plant-derived component, it is carbon neutral and can significantly reduce the load on the environment.

  The “cellulose” referred to in the present invention is a polymer compound in which a large number of glucoses are polymerized by β-1,4-glycosidic bonds, and the carbon atoms at the 2nd, 3rd and 6th positions in the glucose ring of cellulose. Means that the hydroxyl group bonded to is unsubstituted.

  In the present invention, when using the above-described modified cellulose, it is sufficient that the aromatic acyl group having the specific carbon number is included in any part of the whole, and it may be composed of the same structural unit. It may consist of a plurality of structural units. Moreover, it is not always necessary to contain the aromatic acyl group in one structural unit. Further, different types of structural units may be included at random.

  Moreover, the resin composition of the present invention may contain a flame retardant. Thereby, the flame retarding effect such as reduction or suppression of the burning rate can be improved. The flame retardant is not particularly limited, and a conventional flame retardant can be used. For example, brominated flame retardants, chlorine-based flame retardants, phosphorus-containing flame retardants, silicon-containing flame retardants, nitrogen compound-based flame retardants, inorganic flame retardants and the like can be mentioned. Among these, hydrogen halides are not generated by thermal decomposition during resin compounding or molding, and do not corrode processing machines or molds or deteriorate the working environment. Phosphorus-containing flame retardants and silicon-containing flame retardants are preferred because they are less likely to adversely affect the environment through the generation of harmful substances such as dioxins when they are diffused or decomposed.

  In addition to cellulose fibers, the resin composition of the present invention may contain other components for the purpose of further improving various properties such as moldability and flame retardancy, as long as the object of the present invention is not impaired. . Other components include, for example, plasticizers, stabilizers (antioxidants, UV absorbers, etc.), mold release agents (fatty acids, fatty acid metal salts, oxy fatty acids, fatty acid esters, aliphatic partially saponified esters, paraffin, low molecular weight Polyolefin, fatty acid amide, alkylene bis fatty acid amide, aliphatic ketone, fatty acid lower alcohol ester, fatty acid polyhydric alcohol ester, fatty acid polyglycol ester, modified silicone), antistatic agent, flame retardant aid, processing aid, anti-drip agent , Antibacterial agents, fungicides and the like. Furthermore, a coloring agent containing a dye or a pigment can be added.

  The polyester resin composition of the present invention has excellent water resistance, flexibility, and biodegradability, and has a low environmental load, so that it can be suitably used as a component of agricultural materials and medical materials.

  As a preferred embodiment, mcl-PHA has a resin composition that takes advantage of the properties such as softness, biodegradability, water resistance, gas barrier properties, transparency, and the like. And so on.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the scope of the present invention is not limited to the examples shown below.

<Preparation of mcl-PHA>
Two types of mcl-PHA (1) and mcl-PHA (2) were prepared as microorganism-derived poly-3-hydroxyalkanoic acid by the following procedure.
(Preparation of mcl-PHA (1))
Pseudomonas putida 27N01 (FERM P-16953) was agitated and cultured with aeration using a jar fermenter containing the nutrient medium solution (1) shown below. The culture conditions were a temperature of 30 ° C., a pH of 6.9 to 7.0, and an aeration rate of 3 L / min. After culturing for 48 hours, the culture solution in the jar fermenter was centrifuged to collect microbial cells. And after drying a microbial cell, it extracted with chloroform, the solvent was distilled off by the evaporator, and the extract was obtained.

[Nutrient medium solution]
1.5 g of ammonium sulfate per liter of water 1.4 g of disodium hydrogen phosphate
Potassium dihydrogen phosphate 1.4 g Sodium hydrogen carbonate 0.5 g
Yeast extract 0.3g Magnesium sulfate 0.4g
0.05g ammonium iron citrate
Octanoic acid 5.5g

The extract obtained as described above was subjected to methyl esterification decomposition at 120 ° C. under a pressure of 90 minutes, and the temperature of the produced monomer methyl ester was analyzed by a capillary gas chromatograph equipped with a molecular weight measuring device. In addition, ¹ H-NMR and ¹³ C-NMR spectrum analysis was performed to obtain the monomer composition.

As a result, the monomer composition is 3 to 17% of the compound 3-hydroxyhexanoic acid (a) shown below, 70 to 85% of 3-hydroxyoctanoic acid (b), and 3 to 12 of 3-hydroxynonanoic acid (c). %, 3-hydroxydecanoic acid (d) is 10-25%, and they were found to be randomly copolymerized polymers.

(Preparation of mcl-PHA (2))
Of the culture conditions in Synthesis Example 1, 5.5 g of octanoic acid in the nutrient medium solution (1) was changed to 4 g of glucose, and the other culture conditions and operations were similarly performed to obtain an extract.

The extract thus obtained was subjected to methyl esterification decomposition at 120 ° C. under a pressure of 90 minutes, and the produced monomer methyl ester was subjected to temperature rise analysis using a capillary gas chromatograph equipped with a molecular weight measuring device. In addition, ¹ H-NMR and ¹³ C-NMR spectrum analysis was performed to obtain the monomer composition.

  As a result, the monomer composition is mainly composed of 3-hydroxyoctanoic acid of 60% or more, and 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid and 3-hydroxyhexanoic acid are contained in a few percent to several tens of percent, respectively. In addition, several percent of 3-hydroxyalkenoic acid having an unsaturated bond in the side chain was contained.

<Preparation of ground cellulose fiber>
Ground cellulose fibers were obtained by the following method.
Using natural cellulose (fiber length 50-800 μm Nippon Paper Industries Co., Ltd .: KC Flock WG-100) as a raw material, an oxidation reaction was performed by using sodium hypochlorite with N-oxyl compound as an oxidation catalyst in water. . At this time, the reaction was carried out by changing the concentration of sodium hypochlorite in various ways. Thereafter, impurities were removed from the fibers of the reaction product containing water, and physical defibration treatment with a homogenizer was performed at different times to obtain cellulose fibers.

  The cellulose fiber thus obtained (after oxidation catalyst treatment and homogenizer treatment for 5 hours) is dehydrated in several steps using t-butyl alcohol, and finally dispersed in 100% t-butyl alcohol. Lyophilized. It was confirmed that the completely dried fiber was pulverized by FE-SEM observation. FIG. 1 shows an FE-SEM photograph.

The length and width of the fiber were obtained by observing the fiber form with a scanning electron microscope field of view, selecting 10 representative fibers, measuring the width and length, and averaging them. As a result, as shown in Table 1, cellulose fibers having various fiber widths and fiber lengths can be obtained by changing the concentration of sodium hypochlorite, which is an oxidizing agent, or changing the defibration time with a homogenizer. I understood that.

<Preparation of modified ground cellulose fiber>
Modified cellulose fibers in which hydroxyl groups existing in cellulose were benzoylated, benzyl etherified, and acetylated with respect to cellulose fibers having various fiber widths and fiber lengths prepared as described above were prepared. The method is described below.

(Preparation of benzoylated cellulose fiber)
Cellulose fibers were swelled in an aqueous potassium hydroxide solution (concentration: 114 g / L), filtered, taken out in a fiber state, suspended in acetone, and reacted with 2 equivalents of benzoyl chloride. After the reaction, the solvent and side reaction products were removed and purification was performed. When the infrared absorption spectrum of the reaction product was measured, it was confirmed that the hydroxyl group was substituted with a benzoyl group (see FIG. 2).

(Preparation of benzyl etherified cellulose fiber)
The cellulose fiber was swollen in an aqueous potassium hydroxide solution (concentration: 114 g / L), filtered, taken out in a fiber state, suspended in acetone, and then reacted with 2 equivalents of benzyl chloride. After the reaction, the solvent and side reaction products were removed and purification was performed.

(Preparation of acetylated cellulose fiber)
Cellulose fibers were swollen in an aqueous potassium hydroxide solution (114 g / L), filtered, taken out in a fiber state, suspended in acetone, and reacted with 4 equivalents of acetyl chloride. After the reaction, the solvent and side reaction products were removed and purification was performed. When the infrared spectrum of the reaction product was measured, it was confirmed that the hydroxyl group was chemically modified with an acetyl group (see FIG. 3).

<Preparation of polyester resin composition>
(Examples 1-4 and Comparative Example 1)
The above-mentioned mcl-PHA (1) (that is, mcl-PHA prepared by growing microorganisms in a nutrient medium supplemented with octanoic acid) is a polyester resin component, and has various fiber widths and fiber lengths as crystal nucleating agents. Cellulose fibers were added and kneaded with a kneader to prepare polyester resin compositions of Examples 1 to 4. The amount of cellulose fiber added was 5 parts by weight per 100 parts by weight of mcl-PHA (1). Moreover, mcl-PHA (1) to which no cellulose fiber was added was used as Comparative Example 1.

(Evaluation)
The polyester resin compositions of Examples 1 to 4 and Comparative Example 1 prepared as described above were subjected to non-isothermal crystallization measurement. The higher the crystallinity of the crystalline polymer, the higher the heat resistance. Therefore, the crystallinity can be evaluated by non-isothermal crystallization measurement. That is, a plastic resin such as polyester has a temperature zone that is easy to crystallize, and if this temperature is passed slowly, sufficient crystallization as the material can be obtained. In addition, since the amount of heat generated at this time is proportional to the amount of crystal generated, the degree of crystallinity can be evaluated by comparing the calorific value. Details of the non-isothermal crystallization measurement are described below.

  Sufficient crystals were produced by slowly cooling the sample heated at 70 ° C. for 30 minutes above the melting point (45 ° -65 ° C.) of mcl-PHA to -10 ° C. (−1 ° C./min), The amount of crystallization generated at that time and the crystallization peak temperature were measured with a differential thermal analyzer (DSC). This was repeated twice for one sample, and the average was taken as the result.

  As a result, as shown in Table 2, Examples 1 to 4 to which cellulose fibers were added as a crystal nucleating agent had a crystallization peak temperature of 3.2 ° C. or higher and a crystallization heat amount of 23 J / g or higher. On the other hand, in Comparative Example 1 in which no cellulose fiber was added, a clear crystallization peak temperature was not observed, and the amount of crystallization heat was not measured. From the above, it was found that crystallization of mcl-PHA (1) was promoted by the addition of pulverized cellulose fibers.

(Examples 5-7 and Comparative Example 2)
The above-mentioned mcl-PHA (2) (that is, mcl-PHA prepared by growing microorganisms in a nutrient medium supplemented with glucose) is used as a polyester resin component, and benzoylated cellulose fiber as a crystal nucleating agent is used as mcl-PHA (2 ) 5 parts by weight with respect to 100 parts by weight and kneaded with a kneader to prepare polyester resin compositions of Examples 5 and 6. Further, mcl-PHA (1) was used as a polyester resin component, and cellulose fibers were added in the same amount as a crystal nucleating agent and kneaded with a kneader to prepare a polyester resin composition of Example 7. Further, mcl-PHA (2) to which no crystal nucleating agent was added was used as Comparative Example 2.

(Evaluation)
The polyester resin compositions of Examples 5 to 7 and Comparative Example 2 prepared as described above were subjected to non-isothermal crystallization measurement. As a result, as shown in Table 3 and FIG. 4, in Examples 5 to 7 in which benzoylated cellulose fibers or cellulose fibers were added as crystal nucleating agents, the crystallization peak temperature was 3.8 to 9.2 ° C., and the crystallization heat amount was 25 to It became more than 65J / g. On the other hand, in Comparative Example 1 in which no cellulose fiber was added, no clear crystallization peak temperature was observed, and no crystallization heat quantity was measured. From the above, it was found that crystallization of mcl-PHA (2) was promoted by the addition of pulverized cellulose fibers. Moreover, even if the addition amount of a benzoylated cellulose fiber is the same from Example 5 and Example 6 which used the benzoylated cellulose fiber as a crystal nucleating agent, the direction of Example 5 with smaller fiber width and fiber length is more. It has been found that the crystallization peak temperature and the amount of crystallization heat are significantly increased. Furthermore, from a comparison between Example 5 and Example 7, it was found that the benzoylated cellulose fiber was more effective as a crystal nucleating agent than cellulose that was not chemically modified.

(Examples 8 to 12)
The above-mentioned mcl-PHA (2) (that is, mcl-PHA prepared by growing microorganisms in a nutrient medium supplemented with glucose) is a polyester resin component, and benzyl etherification of various fiber widths and fiber lengths as a crystal nucleating agent Cellulose fibers were added to mcl-PHA (2) and kneaded with a kneader to prepare polyester resin compositions of Examples 8 to 11. In addition, a polyester resin composition of Example 12 was similarly prepared using acetylated cellulose fibers as a crystal nucleating agent.

(Evaluation)
The polyester resin compositions of Examples 8 to 12 prepared as described above were subjected to non-isothermal crystallization measurement. As a result, as shown in Table 4, in Examples 8 to 11 in which benzyl etherified cellulose fibers were added as a crystal nucleating agent, the crystallization peak temperature and the heat of crystallization were remarkably high as in the case of benzoylated cellulose fibers. I found out that Further, in the case of Example 12 in which acetylated cellulose fiber was added as a crystal nucleating agent, the crystallization peak temperature was 4.1 ° C. and the crystallization heat amount was 31 J / g, which was slightly inferior to benzyl etherified cellulose fiber. However, it was found to function as a crystal nucleating agent.

<Manufacture of seedling sheets>
(Example 13)
The above-mentioned mcl-PHA (1) (that is, mcl-PHA prepared by growing microorganisms in a nutrient medium supplemented with octanoic acid) is used as a polyester resin component, with a fiber length of 50 μm and a fiber width of 2 μm or less as a crystal nucleating agent. Benzyl etherified cellulose fibers were added and kneaded with a kneader to prepare a polyester resin composition. The amount of cellulose fiber added was 5 parts by weight per 100 parts by weight of mcl-PHA (1).
The polyester resin composition thus obtained was mixed with soybean seeds 3 as a carrier 1 and developed on a paper sheet 2 as shown in FIG. The paper sheet was used because it is water-soluble and biodegradable. That is, it is sufficient that the sheet for developing the mixture has a function of holding the resin composition and the seeds when used, and a material that is water-soluble after installation and does not give a load to the environment is preferable. In addition, a seedling sheet developed on a polyethylene film instead of the paper sheet was also produced.

(Example 14)
In Example 14, a cellulose fiber having a fiber length of 50 μm and a fiber width of 2 μm or less was used as a crystal nucleating agent.

(Comparative Examples 3-5)
In Comparative Example 3, calcium carbonate fine powder having a particle size of 1 to 50 μm was added as a crystal nucleating agent, and in Comparative Example 4, titanium oxide fine powder having a particle size of 1 to 50 μm was added. In Comparative Example 5, no crystal nucleating agent was added. Other production conditions were the same as in Example 13 to produce seedling sheets of Comparative Examples 3-5.

(Evaluation)
-Evaluation by non-isothermal crystallization measurement About the polyester resin composition which comprises the seedling seedling sheet | seat of Example 13 and Example 14, and Comparative Examples 3-5, the non-isothermal crystallization measurement was performed. As a result, in Comparative Example 3 in which calcium carbonate fine powder was added as a crystal nucleating agent, the exothermic peak temperature was around 3.9 ° C., whereas in Example 13 using benzyl etherified cellulose fibers, 9.3. It was found that the effect as a crystal nucleating agent was markedly superior to the calcium carbonate fine powder in the case of benzyl etherified cellulose fibers.

-Evaluation by visual test In addition, in visual observation, the films of Example 13 and Example 14 are almost colorless and transparent, whereas in Comparative Examples 3 and 5 using calcium carbonate or titanium oxide,
It turned out to be cloudy and the transparency that is an advantage of mcl-PHA was lost.

・ Evaluation by germination test

Watering the seedling seedling sheet and observing until the seeds germinate, water resistance and adhesiveness for holding the seeds, transparency of whether the seeds are visible from the outside, and molding into the seedling seedling sheets Sex was evaluated.
As a result, in Comparative Example 5 in which no crystal nucleating agent was added as shown in Table 5, the tackiness was sufficient and the seeds could be retained, but the workability such as adhering to other base materials and soil was improved. It became a problem. In Comparative Example 3 in which calcium carbonate was added as a crystal nucleating agent, the color became cloudy to white and the transparency was lost, making it difficult to visually recognize the state of seed dispersion. Further, the formability to a paper sheet was not good. On the other hand, in the seedling sheet of Example 13 using fine benzyl etherified cellulose fibers as a crystal nucleating agent and Example 14 using fine cellulose fibers as a crystal nucleating agent, the seed dispersion is clearly visible. It was easy to form into a paper sheet. On the other hand, what was shape | molded on the polyethylene film was able to be made to peel easily. Thereby, even if it used the polyethylene film as a release paper, it turned out that it can utilize.

In the present invention, by dispersing fine cellulose modified in mcl-PHA resin and allowing it to function as a crystal nucleating agent, the crystallization rate is improved, and an agricultural film or seedling sheet that utilizes biodegradability and transparency, A medical material can be obtained.

1. Holding body (resin molded body)
2 ... paper sheet 3 ... soybean seeds

Claims (9)

  A polyester resin composition in which 3 to 30 parts by weight of pulverized cellulose fibers are added to 100 parts by weight of a poly-3-hydroxyalkanoic acid derived from microorganisms.   The polyester resin composition according to claim 1, wherein the poly-3-hydroxyalkanoic acid is a polymer of 3-hydroxyalkanoic acid having 6 to 14 carbon atoms.   The polyester resin composition according to claim 1, wherein the microorganism is a genus Pseudomonas.   The polyester resin composition according to any one of claims 1 to 3, wherein the pulverized cellulose fibers have a fiber width of 2 µm or less and a fiber length of 80 µm or less.   The polyester resin according to any one of claims 1 to 4, wherein at least a part of hydroxyl groups present in the pulverized cellulose is modified with a functional group having an aromatic group or a carboxylic acid ester group. Composition.   A crystal nucleating agent for a poly-3-hydroxyalkanoic acid derived from a microorganism, comprising pulverized cellulose fibers.   The crystal nucleating agent according to claim 6, wherein the pulverized cellulose fiber has a fiber width of 2 μm or less and a fiber length of 80 μm or less.   The crystal nucleating agent according to claim 6 or 7, wherein at least a part of the hydroxyl groups present in the pulverized cellulose hydroxyl group is modified with a functional group having an aromatic group or a carboxylic acid ester group.   A seedling sheet comprising a polyester resin composition according to any one of claims 1 to 5, wherein the seed holder is a seed holder.