β-glucan ester derivatives

Abstract

Provided is a β glucan ester derivative with which preferable water resistance and heat resistance are obtained and both rigidity and flexibility can be achieved.　This β glucan ester derivative having a C3 acyl group and a C6-C8 acyl group is a β-1,3-glucan ester derivative or a β-1,4-glucan ester derivative, and has a bending strength of at least 8 MPa at 80ºC and a bending elastic modulus of at least 250 MPa at 80ºC.

Description

[Technical field]

[0001] The present disclosure relates to beta glucan ester derivatives.

[0002] In recent years, from the viewpoint of environmental conservation, technologies related to bioplastics made from microorganisms and plants have been proposed. For example, a β-1,3-glucan ester derivative obtained by esterifying at least a portion of the hydroxyl groups in β-1,3-glucan with an acid or the like is known as a bioplastic made from microorganisms.

[0003] It has been considered to mold and process the above-mentioned β-1,3-glucan ester derivatives and β-1,4-glucan ester derivatives having a similar structure for use in various applications. Conventionally, a technique has been disclosed in which mechanical properties and thermoplasticity are obtained by introducing a long-chain component having 14 or more carbon atoms into the β-1,3-glucan ester derivative (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 013232 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology disclosed in the cited document 1 does not have sufficient water resistance and heat resistance for use in housing facilities and wet areas, and also has issues in terms of achieving both rigidity and flexibility.

[0006] The present disclosure has been made in view of the above, and aims to provide a β-glucan ester derivative that has favorable water resistance and heat resistance, and is capable of achieving both rigidity and flexibility. [Means for solving the problem]

[0007] The present disclosure relates to a β-glucan ester derivative having an acyl group having 3 carbon atoms and an acyl group having 6 to 8 carbon atoms, the β-glucan ester derivative being a β-1,3-glucan ester derivative or a β-1,4-glucan ester derivative, having a flexural strength at 80°C of 8 MPa or more and a flexural modulus at 80°C of 250 MPa or more. [Brief description of the drawings]

[0008] [Figure 1] 1 is a graph showing temperature dependence of bending strength in Examples and Comparative Examples. [Diagram 2] 1 is a graph showing the temperature dependence of flexural modulus in Examples and Comparative Examples. [Diagram 3] 1 is a graph showing the relationship between bending strength and Pr substitution degree in Examples. [Figure 4] 1 is a graph showing the relationship between the flexural modulus and the degree of Pr substitution in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The β-glucan ester derivative according to the present embodiment is a β-1,3-glucan ester derivative or a β-1,4-glucan ester derivative. The β-glucan ester derivative is a polymer in which a plurality of glucose molecules are bound by glycosidic bonds. The β-1,3-glucan ester derivative has a main chain of β-glucan formed by β-1,3 glycosidic bonds. The β-1,4-glucan ester derivative has a main chain of β-glucan formed by β-1,4 glycosidic bonds.

[0010] (β-1,3-glucan ester derivative) The β-1,3-glucan ester derivative in this embodiment is preferably a curdlan ester derivative or a paramylon ester derivative. Both curdlan and paramylon are compounds derived from microorganisms. By using ester derivatives obtained by esterifying these compounds, it becomes possible to manufacture microbial-derived plastics. Curdlan and paramylon are a type of β-1,3-glucan, which is a polysaccharide. Although the curdlan ester derivative and paramylon ester derivative according to this embodiment are derived from microorganisms, they have strength equivalent to that of polypropylene and have excellent moldability.

[0011] The structure of curdlan is represented by the following formula (1). Curdlan is a polysaccharide β-1,3-glucan contained in soil bacteria. Curdlan has a molecular weight of about 1 million, and its derivatives have high strength but poor fluidity. n1 in the following formula (1) represents an integer of 1000 to 6200. A curdlan ester derivative represented by the following formula (2) can be obtained by esterifying at least a part of the hydroxyl groups in curdlan, as described in detail later. As the esterification method, a conventionally known method can be used.

[0012] The structure of paramylon is shown in the following formula (3). Paramylon is a polysaccharide β-1,3-glucan contained in Euglena. Paramylon has a molecular weight of about 300,000, and its derivatives have the properties of low strength but good fluidity. In the following formula (3), n2 represents an integer of 300 to 2000. By esterifying at least a portion of the hydroxyl groups in paramylon, as described in detail later, a paramylon ester derivative shown in the following formula (4) can be obtained. As the esterification method, a conventionally known method can be used.

[0013] [ka] Formula (1)

[0014] [ka] Formula (2)

[0015] [ka] Formula (3)

[0016] [ka] Formula (4)

[0017] In the above formulas (2) and (4), R each independently represents a hydrogen atom, an acyl group having 3 carbon atoms (hereinafter sometimes referred to as a "short chain component"), or an acyl group having 6 to 8 carbon atoms (hereinafter sometimes referred to as a "long chain component"). However, at least one of R is an acyl group having 3 carbon atoms, and at least one of R is an acyl group having 6 to 8 carbon atoms, and all of R are not hydrogen atoms at the same time. n1 in formula (2) represents an integer of 1000 to 6200. n2 in formula (4) represents an integer of 300 to 2000. This allows synthesis in a shorter time than when only long chain components are introduced as substituents. Specifically, synthesis in a shorter time than when a component having more than 8 carbon atoms is introduced as a long chain component as a substituent. In addition, since the β-1,3-glucan ester derivative is a heteroester having short-chain and long-chain components that are different types of substituents, the crystallinity or thermal properties such as glass transition temperature and melt viscosity of the molded product can be easily controlled, and the injection moldability, rigidity and flexibility can be adjusted to a preferred range. The β-1,3-glucan ester derivative according to this embodiment preferably does not contain acyl groups having 4 and 5 carbon atoms. This can suppress the odor of the molded product, such as its peculiar odor, and the molded product can be applied to water-related areas, housing facilities, etc.

[0018] The sum of the degree of substitution DSs of the short chain component (hereinafter sometimes referred to as "degree of substitution DSs") and the degree of substitution DSl of the long chain component (hereinafter sometimes referred to as "degree of substitution DSl") in the above formula (2) is called the total degree of substitution DSs + DSl (hereinafter sometimes referred to as "DSs + DSL"). The total degree of substitution DSs + DSl is preferably 2.0 or more from the viewpoint of improving the water resistance (hydrolysis resistance) and long-term durability required for water-related and housing facilities. In this specification, the degree of substitution DSs and the degree of substitution DSl respectively mean the average number of hydrogen atoms substituted by the short chain component and the long chain component per glucose unit. If DSs + DSL is less than 2.0, the proportion of hydroxyl groups remaining in the molecule becomes high, and therefore preferable water resistance and long-term durability cannot be obtained. DSs + DSL is more preferably 2.5 or more, and even more preferably 3.0.

[0019] In the β-1,3-glucan ester derivative, the ratio of the degree of substitution DSs to the degree of substitution DSL, DSs:DSl, is preferably 2.5:0.5 to 2.8:0.2. This allows the β-1,3-glucan ester derivative to have a flexural strength at 80°C of 8 MPa or more and a flexural modulus at 80°C of 250 MPa or more. In addition, the obtained molded article can have both rigidity and flexibility. From the above viewpoints, the DSs:DSl of the β-1,3-glucan ester derivative is more preferably 2.6:0.4 to 2.8:0.2, and even more preferably 2.7:0.3 to 2.8:0.2. The degree of substitution DSs and the degree of substitution DSL can be, for example, 1 It can be measured by HNMR.

[0020] The structure of the acyl group having 3 carbon atoms and the acyl group having 6 to 8 carbon atoms is not particularly limited as long as it satisfies the condition of the number of carbon atoms. The bond between carbon atoms may be a saturated bond or may contain an unsaturated bond. In addition to the above, it may have any of a straight chain structure, a branched chain structure, and a ring structure. Examples of such saturated aliphatic acyl groups include a propanoyl group, which is a saturated aliphatic acyl group having 3 carbon atoms and a straight-chain structure, an isopropanoyl group having a branched chain structure, and a cyclopropanoyl group having a ring structure; saturated aliphatic acyl groups having 6 to 8 carbon atoms and a straight-chain structure, such as an n-hexanoyl group, an n-heptanoyl group, an n-octanoyl group, an isohexanoyl group, an isoheptanoyl group, and an isooctanoyl group having a branched chain structure, a cyclohexanoyl group, a cycloheptanoyl group, and a cyclooctanoyl group having a ring structure, a hexenoyl group, a heptenoyl group, and an octenoyl group having an unsaturated bond, and an acetylphenyl group having an aromatic ring.

[0021] The hydrogen atoms in the hydroxyl groups of β-1,3-glucan are replaced with short-chain and long-chain components by esterification as described above. The method of esterifying β-1,3-glucan according to the present disclosure is not particularly limited, but examples thereof include the TFAA method and the acid chloride method. The acid chloride method is a method in which β-glucan and an acid chloride are heated in a solvent in the presence of a chlorine scavenger component (pyridine, etc.) to dehydrochlorinate, and the hydrogen atoms in the hydroxyl groups of β-glucan are replaced with acyl groups to perform esterification. The TFAA method is a method in which β-glucan and a carboxylic acid are heated in a solvent in the presence of TFAA (trifluoroacetic anhydride) as an acid catalyst to perform dehydration condensation and esterification.

[0022] In the acid chloride method, the acid chloride used for esterification includes acid chlorides having the number of carbon atoms and structure corresponding to the short chain component and the long chain component. For example, propionyl chloride is an acid chloride used for introducing a saturated aliphatic acyl group having 3 carbon atoms. For example, hexanoyl chloride, heptanoyl chloride, and octanoyl chloride are examples of acid chlorides used for introducing a long chain component having a linear structure, which is a saturated aliphatic acyl group having 6 to 8 carbon atoms. In addition to the above, the acid chloride may have a branched chain structure, a ring structure, and an unsaturated bond. In the acid chloride method, NMP (N-methyl-2-pyrrolidone) is preferred as an esterification solvent used in esterification using the above chloride. In that case, it is preferred to use pyridine in combination for the purpose of capturing chlorine. Pyridine captures the released chlorine to form pyridine hydrochloride.

[0023] In the TFAA method, the acid used for esterification includes carboxylic acids having the number of carbon atoms and structure corresponding to the short-chain component and the long-chain component. For example, propionic acid is used as a carboxylic acid for introducing a saturated aliphatic acyl group having 3 carbon atoms. For example, n-hexanoic acid, n-heptanoic acid, and n-octanoic acid are used as a carboxylic acid for introducing a long-chain component having a linear structure, which is a saturated aliphatic acyl group having 6 to 8 carbon atoms. Similarly, isohexanoic acid, isoheptanoic acid, and isooctanoic acid having a branched chain structure, cyclohexane carboxylic acid, cycloheptane carboxylic acid, and cyclooctane carboxylic acid having a ring structure, hexenoic acid, heptenoic acid, and octenoic acid having an unsaturated bond, and benzoic acid having an aromatic ring are included. The above acid also functions as a solvent for the generated β-1,3-glucan ester derivative. In the TFAA method, trifluoroacetic anhydride is used in combination as the acid used as the solvent.

[0024] (β-1,4-glucan ester derivative) The structure of β-1,4-glucan is represented by the following formula (5), and is a polymer in which multiple glucose units are linked by β-1,4-glycosidic bonds, such as plant-derived cellulose. In the following formula (5), n3 represents an integer of 300 to 2000. The structure of a β-1,4-glucan ester derivative is represented by the following formula (6), which represents a structure in which at least a portion of the hydrogen atoms of the hydroxyl groups of β-1,4-glucan are substituted with the above-mentioned short-chain component and long-chain component. The β-1,4-glucan ester derivative can be synthesized by the same esterification as that of the β-1,3-glucan ester derivative.

[0025] [ka] Formula (5)

[0026] [ka] Formula (6)

[0027] In the above formula (6), R each independently represents a hydrogen atom, an acyl group having 3 carbon atoms (hereinafter sometimes referred to as a "short chain component"), or an acyl group having 6 to 8 carbon atoms (hereinafter sometimes referred to as a "long chain component"). However, at least one R is an acyl group having 3 carbon atoms, and at least one R is an acyl group having 6 to 8 carbon atoms, and all R are not hydrogen atoms at the same time. n3 in formula (6) represents an integer of 300 to 2000.

[0028] The β-1,4-glucan ester derivative preferably has a total degree of substitution DSs+DSl, which is defined in the same manner as the β-1,3-glucan ester derivative, of 2.0 or more. More preferably, DSs+DSl is 2.5 or more, and even more preferably 3.0. In addition, the β-1,4-glucan ester derivative preferably does not contain an acyl group having 4 or 5 carbon atoms.

[0029] In the β-1,4-glucan ester derivative, the ratio of the degree of substitution DSs to the degree of substitution DSl, DSs:DSl, is preferably 1.5:1.5 to 2.2:0.8. This allows the β-1,4-glucan ester derivative to have a flexural strength at 80°C of 8 MPa or more and a flexural modulus at 80°C of 250 MPa or more. In addition, the obtained molded article can have both rigidity and flexibility. From the above viewpoints, the DSs:DSl of the β-1,4-glucan ester derivative is more preferably 1.9:1.1 to 2.2:0.8, and even more preferably 1.9:1.1 to 2.1:0.9. The degree of substitution DSs and the degree of substitution DSl are, for example, 1 It can be measured by HNMR.

[0030] The β-glucan ester derivative according to this embodiment has a bending strength at 80°C of 8 MPa or more and a bending modulus at 80°C of 250 MPa or more. Since polypropylene has a bending strength at 80°C of about 8 MPa and a bending modulus at 80°C of about 250 MPa, the β-glucan ester derivative according to this embodiment has a heat resistance equal to or higher than that of polypropylene. Therefore, the β-glucan ester derivative can be preferably applied to housing equipment and water-related applications. The Tg (glass transition temperature) of the β-glucan ester derivative is preferably 100°C or more.

[0031] (Method for purifying β-glucan ester derivative) The purification method of the β-glucan ester derivative according to the present embodiment includes, for example, a precipitation step of mixing a synthesis reaction solution containing the β-glucan ester derivative with a reprecipitation solvent, and a cooling step of lowering the temperature of at least one of the synthesis reaction solution and the reprecipitation solvent. In addition to the above, the purification method may include a washing step of washing the precipitate in the precipitation step.

[0032] [Precipitation process] The precipitation step is a step of mixing a synthesis reaction solution containing a β-glucan ester derivative obtained by esterifying at least a portion of the hydroxyl groups in the β-glucan ester derivative with a reprecipitation solvent. The precipitation step causes the β-glucan ester derivative to precipitate (reprecipitate).

[0033] The reprecipitation solvent is, for example, a good solvent that substantially dissolves the β-glucan ester derivative, and a poor solvent that substantially does not dissolve the β-glucan ester derivative. In the precipitation step, a precipitate containing the β-glucan ester derivative is precipitated by mixing the reprecipitation solvent with the synthesis reaction solution. In the precipitation step, it is preferable to add the reprecipitation solvent to the synthesis reaction solution and mix them. Furthermore, it is preferable to add a good solvent to the synthesis reaction solution to dissolve it, and then drop the poor solvent. This can prevent precipitation from occurring at the interface between the synthesis reaction solution and the solvent, and can suppress aggregation of the precipitate. In addition to the above, the precipitation step can be performed in a single container.

[0034] The good solvent may be any solvent that can substantially dissolve the β-glucan ester derivative, and may be, for example, ketones such as acetone and methyl isobutyl ketone; ethers such as tetrahydrofuran, 1,4-dioxane, and methylal; esters such as butyl acetate and propylene glycol-1-monomethyl ether-2-acetate; aromatic compounds such as toluene, chlorobenzene, and α-dichlorobenzene; chloroform, N,N-dimethylformamide, and N-methyl-2-pyrrolidone. In addition to the above, when a washing step is provided for washing the precipitate that has been reprecipitated, it is preferable to use a good solvent that can wash the impurities used in the esterification that remain in the precipitate. The good solvent may be one type of solvent, or a mixture of multiple types of solvents may be used as the good solvent.

[0035] The poor solvent is substantially insoluble in the β-glucan ester derivative, and has a lower solubility in the β-glucan ester derivative than the good solvent. Specifically, water is preferably used as the poor solvent. The poor solvent may be one type of solvent or a mixture of multiple types of solvents.

[0036] [Cooling process] The cooling step is a step of lowering the temperature of at least one of the synthesis reaction solution and the reprecipitation solvent. For example, the cooling step may be a step of cooling at least one of the synthesis reaction solution and the reprecipitation solvent before mixing the synthesis reaction solution and the reprecipitation solvent in the precipitation step. In addition to the above, the cooling step may be a step of cooling the mixed solution after mixing the synthesis reaction solution and the reprecipitation solvent in the precipitation step. By providing the cooling step, the yield of the β-glucan ester derivative can be improved.

[0037] [Cleaning process] The washing step is a step of washing the precipitate containing the β-glucan ester derivative precipitated in the precipitation step. The washing step removes impurities contained in the precipitate. The solution used in the washing step is not particularly limited as long as it can substantially dissolve the β-glucan ester derivative. When the acid chloride method is used as the esterification method, examples of the impurities include a reaction product between chlorine and pyridine, etc. used as a chlorine catcher agent (e.g., pyridine hydrochloride and propionic acid). When the TAFF method is used as the esterification method, examples of the impurities include the acid used in the esterification. When the TAFF method is used as the esterification method, the solution used in the washing step is preferably capable of dissolving the acid used in the esterification. The washing step is not particularly limited and can be performed using a known method.

[0038] The β-glucan ester derivative purified by the purification method of the present embodiment is then molded by various molding methods. As the molding method, for example, commonly used methods such as injection molding, casting, compression, and inflation can be applied. Since the β-glucan ester derivative according to the present embodiment has a preferable melt viscosity, it is particularly preferably molded by injection molding. The molded product can be applied to various applications such as water-related products used in bathtubs and kitchens in homes, housing equipment, and exterior materials for homes.

[0039] The present disclosure is not limited to the above-described embodiments, and modifications and improvements within the scope that can achieve the object of the present disclosure are included in the present disclosure. EXAMPLES

[0040] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples. However, Example 2 is a reference example.

[0041] <Example 1> At room temperature, a predetermined amount of paramylon (weight average molecular weight: about 300,000) as β-glucan, dehydrated NMP (N-methyl-2-pyrrolidone, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) as a solvent, and dehydrated pyridine (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) as a chlorine catcher agent were placed in a reaction vessel and stirred for 5 hours. After that, the mixture was cooled to -10 ° C or less overnight while continuing to stir. Next, propionyl chloride and hexanoyl chloride (both manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) as premixed acid chlorides were slowly dropped into the paramylon solution and stirred at 90 ° C for 4 hours to carry out an esterification reaction. Next, the resulting reaction solution was cooled to 65 ° C, and methanol was dropped to stop the reaction. Next, pure water at 40 ° C was dropped into the resulting reaction solution to carry out reprecipitation. Next, the filtrate from which the reprecipitation was filtered was repeatedly washed and filtered with a washing solution until the pH became 7, and the filtrate was vacuum dried at 70 ° C to obtain the β-glucan ester derivative of Example 1.

[0042] <Example 2, Comparative Examples 1 to 4> For Example 2 and Comparative Examples 1 to 4, the β-glucan ester derivatives according to each Example and Comparative Example were obtained in the same manner as in Example 1, except that the β-glucan shown in Table 1 was used, and in Comparative Example 1, stearoyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of hexanoyl chloride, and the ratio of each acid chloride was adjusted so that the carbon chain ratio (Dss:Dsl) was the ratio shown in Table 1. The short chain component type "Pr" shown in Table 1 indicates a propanoyl group, which is a saturated aliphatic acyl group having 3 carbon atoms. The long chain component type "He" indicates an n-hexanoyl group, which is a saturated aliphatic acyl group having 6 carbon atoms, and "St" indicates a stearoyl group, which is a saturated aliphatic acyl group having 18 carbon atoms.

[0043] (Degree of substitution measurement) The substitution degrees of short-chain components and long-chain components of the β-glucan ester derivatives of the above examples and comparative examples were 1 The measurement was performed by HNMR (JNM-ECA (500 MHz, JEOL). The measurement solvent used was chloroform-d (99.8 ATOM%) manufactured by Wako Pure Chemical Industries, Ltd. The substitution degree of the short chain component and the long chain component was 1 The degree of substitution was calculated from the ratio of the peak areas of the substituents corresponding to the short-chain and long-chain components in the HNMR spectrum to the peak area of ​​the ring protons in the glucose unit. The total degree of substitution was determined as the sum of the degree of substitution of the short-chain components (DSs) and the degree of substitution of the long-chain components (DSl), assuming that the maximum degree of substitution in glucose units is 3. The results are shown in Table 1.

[0044] (Tm, Tg measurement) The melting point (Tm, ° C.) and glass transition temperature (Tg, ° C.) of the β-glucan ester derivatives of the above examples and comparative examples were measured using a DSC (EXSTAR DSC7020, manufactured by Hitachi High-Tech Science Corporation). The sample was filled into an aluminum pan, heated from 30 ° C. to 250 ° C. at a heating rate of 20 ° C. / min, and held for 1 minute after reaching 250 ° C. Then, cooled to -60 ° C. at a heating rate of 200 ° C. / min, and held for 1 minute after reaching -60 ° C. Then, heated to 250 ° C. at a heating rate of 20 ° C. / min, and the melting point (Tm, ° C.) and glass transition temperature (Tg, ° C.) were calculated. The results are shown in Table 1. In Table 1, "NA" means that it cannot be measured. Usually, when measuring the melting point Tm or glass transition point Tg with a DSC (differential scanning calorimeter), it is detected by using the inflection point of the endothermic curve or exothermic curve with respect to temperature. However, in the case of polysaccharide esters with relatively low crystallinity, the endothermic or exothermic curve with respect to temperature may not show a clear peak, making it difficult to identify the inflection point. In the present disclosure, a composition may be identified by its Tg value, but the Tm value is useful in observing the thermal properties of the composition, and even if it cannot be derived directly from the inflection point, it is possible to predict the Tm value from Tg and other parameters.

[0045] [Table 1]

[0046] The β-glucan ester derivatives of the above examples and comparative examples were injection molded to prepare samples for measuring physical properties. The injection molding machine used was MiniJet Pro (manufactured by Scientific Thermofisher). The injection pressure was 900 bar, 10 sec, and the dwell pressure was 250 bar, 10 sec. The sample mold for the Charpy test shown below was 80 mm long, 12.5 mm wide, and 2.5 mm thick (striped piece).

[0047] (Bending strength, bending modulus measurement) The samples of each of the examples and comparative examples molded as above were used to measure the bending strength at 23°C and 80°C, and the bending modulus at 23°C and 80°C. The measurements were performed in accordance with JIS K 7171, except that the thickness of the test piece was set to 2.6±0.2 mm. Measurements were performed on 3 samples, and the average value was calculated. The results are shown in Table 2.

[0048] (Temperature dependence of bending strength and bending modulus) The bending strengths of the β-glucan ester derivatives of Example 1 and Comparative Example 1 at test temperatures of 23° C., 60° C., and 80° C., respectively, are shown in Figure 1. Similarly, the bending moduli of Example 1 and Comparative Example 1 at test temperatures of 23° C., 60° C., and 80° C., respectively, are shown in Figure 2. From the results of Figures 1 and 2, it is clear that the test temperature of the β-glucan ester derivatives of Example 1 and Comparative Example 1 is approximately proportional to the bending strength and bending modulus.

[0049] (80°C bending strength and 80°C bending modulus of β-glucan ester derivatives with short chain component: C3 and long chain component: C8) 3 and 4 show the 23°C bending strength and 23°C bending modulus, respectively, when the substitution degree of the short chain component and the long chain component of the paramylon ester derivative, which is a β-glucan ester derivative, is changed. The paramylon ester derivatives in Figs. 3 and 4 were substituted with a propionyl group (Pr, C3) as the short chain component and an octanoyl group (Oc, C8) as the long chain component. The total substitution degree was set to 3. The horizontal axis of the graphs in Figs. 3 and 4 shows the substitution degree of Pr, which is a short chain component, the vertical axis of the graph in Fig. 3 shows the 23°C bending strength, and the vertical axis of the graph in Fig. 4 shows the 23°C bending modulus. From the results in Figs. 3 and 4, it is clear that the Pr substitution degree is approximately proportional to the bending strength and bending modulus.

[0050] Since the chain lengths of the long chain component C6 and C8 are close, the β-glucan ester derivative of Example 1 with short chain component C3 and long chain component C6 and the β-glucan ester derivative of short chain component C3 and long chain component C8 show similar behavior in terms of strength and thermal properties. From the results of Figures 3 and 4, it is clear that the β-glucan ester derivative of short chain component C3 and long chain component C8, which has a flexural strength and flexural modulus at 23 ° C. similar to those of the β-glucan ester derivative of Example 1 with short chain component C3 and long chain component C6, has a Pr substitution degree (total substitution degree = 3) of about 2.5. Therefore, in a β-glucan ester derivative with a short chain component of C3 and a long chain component of C8 with a Pr substitution degree of 2.5 (Dss:Dsl=2.5:0.5), the bending strength and bending modulus at 80°C for the long chain component C8 can be obtained from the relationship between temperature and mechanical properties shown in Figures 1 and 2. That is, the bending strength at 80°C for a β-glucan ester derivative with a short chain component of C3, a long chain component of C8, and Dss:Dsl=2.5:0.5 is found to be 12 MPa, since it is the value of the vertical axis (bending strength) when the horizontal axis (temperature) is 80°C on the straight line shown in Figure 1. Similarly, the bending modulus at 80°C is found to be 398 MPa, since it is the value of the vertical axis (bending modulus) when the horizontal axis (temperature) is 80°C on the straight line shown in Figure 2.

[0051] (Water absorption bending strength, water absorption bending elasticity measurement) The molded samples of each of the Examples and Comparative Examples were immersed in pure water at 80° C. for 20 hours, and then the bending strength and bending modulus were measured at 23° C. and 80° C. under the same conditions as above. Measurements were performed 3 times, and the average values ​​were calculated. The results are shown in Table 2.

[0052] (Charpy impact test) The Charpy impact value was measured using the samples of each of the above molded Examples and Comparative Examples. The measurement was performed in accordance with JIS K 7111. Edgewise impact test pieces were prepared as test pieces, and notched Charpy impact strength was measured. Measurements were performed for n=5, and the average value was calculated. The results are shown in Table 2.

[0053] (Heavy Deflection Temperature (HDT)) The deflection temperature under load was measured using the samples of each of the above molded examples and comparative examples. The measurement was performed in accordance with JIS K 7191-2. A constant bending load (1.80 MPa) was applied to the center of a test piece of 80 mm x 12 mm x 2.5 mm (flatwise direction), the temperature was raised at a constant rate (120 ° C / h), and the temperature (° C) was measured when the distortion at the center reached a specified deflection (0.55 to 0.57 mm). Measurements were performed with n = 3, and the average value was calculated. A temperature of 48 ° C or higher was considered to be acceptable. A heat distortion tester No. 148-HD-PC (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) was used for the measurement. The results are shown in Table 2.

[0054] [Table 2]

[0055] From the results of the Examples and Comparative Examples, it is clear that the β-glucan ester derivatives according to the Examples have higher flexural strength at 80° C. and flexural modulus at 80° C., and are excellent in heat resistance, compared to the β-glucan ester derivatives according to the Comparative Examples. In addition, it is clear that preferable water resistance, rigidity, and flexibility can be obtained, and that these can be achieved simultaneously.

Claims

1. A β-glucan ester derivative having an acyl group having 3 carbon atoms and an acyl group having 6 to 8 carbon atoms, The β-glucan ester derivative is a β-1,3-glucan ester derivative, The 80°C bending strength is 8 MPa or more, and the 80°C bending modulus is 250 MPa or more, the ratio of the degree of substitution DSs of the acyl group having 3 carbon atoms to the degree of substitution DSl of the acyl group having 6 to 8 carbon atoms, DSs:DSl, is 2.5:0.5 to 2.8:0.2 in the β-1,3-glucan ester derivative; In the β-1,3-glucan ester derivative, the total substitution degree DSs+DSl, which means the average number of hydrogen atoms substituted with short-chain components and long-chain components per glucose unit, is 3.

0.

2. The β-glucan ester derivative according to claim 1, having a Tg of 100° C. or higher.

3. The β-1,3-glucan ester derivative according to claim 1 or 2, wherein the ratio of the degree of substitution DSs of the acyl group having 3 carbon atoms to the degree of substitution DSl of the acyl group having 6 to 8 carbon atoms, DSs:DSl, is DSs:DSl = 2.7:0.3 to 2.8:0.2 in the β-1,3-glucan ester derivative.

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