Additive for dialdehyde starch-containing thermoplastic resin, thermoplastic resin composition containing additive for dialdehyde starch-containing thermoplastic resin, and resin molding

Abstract

To provide a resin additive which is excellent in compatibility with a resin and dispersibility, when being used in a thermoplastic resin.SOLUTION: There are provided an additive for a thermoplastic resin which contains at least dialdehyde starch polyhydric alcohol adduct, wherein an aldehyde degree as an oxidation degree of the dialdehyde starch polyhydric alcohol adduct, which is a ratio of a repeating unit of a polymer having an aldehyde group in the dialdehyde starch polyhydric alcohol adduct, is 5 mol% to 30 mol%; a thermoplastic resin composition containing the additive for the dialdehyde starch-containing thermoplastic resin; and a resin molding.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an additive for thermoplastic resins that contains at least a dialdehyde starch polyhydric alcohol adduct. More specifically, the present invention relates to a resin composition in which the additive contains at least a dialdehyde starch polyhydric alcohol adduct that has a specific degree of aldehyde conversion and is excellent in compatibility, thereby imparting excellent physical properties to the thermoplastic resin, and further to a resin molded product obtained by molding the additive. [Background technology]

[0002] Thermoplastic resins, with their various physical properties such as moldability and low specific gravity, are widely used in a variety of molded articles, including building materials, automotive materials, home appliance and electronic materials, textile materials, packaging materials, agricultural materials, housing materials for home appliances, household goods, films, sheets, and structural parts. Resins such as polyester resin, polyethylene resin, and polypropylene resin are used for a variety of purposes, and additives are used to improve their mechanical properties and heat resistance.

[0003] However, if humans use plastics as described above and they end up in the environment without being burned or otherwise treated, the plastic waste generally does not decompose and eventually flows into the ocean, causing adverse effects on the environment and ecosystem. Furthermore, plastic waste that flows into the ocean turns into microplastics due to the impact of waves and ultraviolet rays from sunlight, further adversely affecting the environment and ecosystem. To reduce the environmental impact of plastic waste that ends up in the environment, biodegradable plastics, particularly bioplastics (a collective term for plastics made from biomass and biodegradable plastics), have been developed.

[0004] Known examples of the above-mentioned bioplastics include thermoplastic mixtures whose main raw material is starch or a starch derivative as a thermoplastic resin, as disclosed in Patent Documents 1 and 2. Also known are resin molded products whose biodegradability is enhanced by incorporating starch or a starch derivative into a thermoplastic resin such as polyethylene, as disclosed in Patent Documents 3 and 4. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2001-509525 [Patent Document 2] Special Publication No. 2001-509527 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-210824 [Patent Document 4] Japanese Patent Application Publication No. 2023-122968 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Documents 1 and 2, bioplastics are made primarily from starch or starch derivatives as thermoplastic resins. However, starch or starch derivatives are prone to discoloration to (light) brown or (light) yellow or become cloudy when heated during production (molding).

[0007] In Patent Documents 3 and 4, starch or a starch derivative is incorporated into a thermoplastic resin. However, during production, poor compatibility and dispersibility are observed when the starch or starch derivative is mixed with the thermoplastic resin, resulting in reduced mechanical strength of the resulting molded resin product. In particular, when dialdehyde starch is used as the starch derivative to produce a molded resin product, dialdehyde starch tends to aggregate and form clumps due to intermolecular and intramolecular acetals, resulting in the retention of starch granules in the thermoplastic resin and the presence of white spots in the molded resin product. In Patent Documents 3 and 4, additives are added to improve the compatibility and dispersibility of the starch or starch derivative with the solvent. Although the additives improve the compatibility and dispersibility of the starch or starch derivative with the thermoplastic resin, thereby improving the mechanical strength of the resulting molded resin product, further improvements are desired.

[0008] Furthermore, similar to the thermoplastic mixture, the produced resin molded product has the problem that it is prone to discoloration to (light) brown or (light) yellow or become cloudy when heated during production.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a resin additive that has excellent compatibility and dispersibility with thermoplastic resins when used in the resin. It is also an object of the present invention to provide a biomass-derived resin additive that can enhance the biodegradability of the produced resin molded products. It is also an object of the present invention to provide a resin additive that enhances the transparency of the produced resin molded products and also has excellent mechanical strength. [Means for solving the problem]

[0010] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a dialdehyde starch-polyalcohol adduct obtained by adding a polyhydric alcohol to a dialdehyde starch, the dialdehyde starch-polyalcohol adduct having a specific degree of aldehyde conversion, and adding the adduct to a thermoplastic resin, and have thus completed the present invention. That is, the present invention has been completed as follows.

[0011] [1] An additive for thermoplastic resins, comprising at least a dialdehyde starch polyhydric alcohol adduct, wherein the degree of oxidation of the dialdehyde starch polyhydric alcohol adduct is measured using the degree of aldehyde conversion, which is the proportion of repeating units of polymers having aldehyde groups in the dialdehyde starch polyhydric alcohol adduct, and the degree of aldehyde conversion is 5 mol% to 30 mol%. [2] The additive for thermoplastic resins according to [1], wherein the water content of the dialdehyde starch polyhydric alcohol adduct is 0.01% by mass to 10% by mass. [3] The additive for thermoplastic resins according to [1], characterized in that the polyhydric alcohol is at least one selected from the group consisting of glycerin, propylene glycol, 1,3-butylene glycol, polyethylene glycol, sorbitol, and xylitol. [4] A thermoplastic resin composition, characterized in that the additive for thermoplastic resins according to any one of [1] to [3] is mixed into a thermoplastic resin. [5] The thermoplastic resin composition according to [4], wherein the amount of the additive for thermoplastic resin added is 0.1% by mass to 10% by mass. [6] The thermoplastic resin composition according to [4], wherein the thermoplastic resin is at least one resin selected from the group consisting of polyolefin resin, polyvinyl chloride resin, and cellulose acetate resin. [7] A resin molded product obtained by molding the thermoplastic resin composition according to [4]. [8] The resin molded product according to [7], which is melt-molded at a temperature of 160°C to 250°C. [Effects of the Invention]

[0012] According to the present invention, instead of adding dialdehyde starch and a polyhydric alcohol to a thermoplastic resin, a dialdehyde starch-polyhydric alcohol adduct having a specific degree of aldehyde conversion is synthesized by first adding a polyhydric alcohol to dialdehyde starch. This allows the average particle size to be smaller than that of dialdehyde starch, and adding this to a thermoplastic resin results in an additive for a thermoplastic resin and a thermoplastic resin composition that have improved dispersibility and compatibility with the thermoplastic resin. Furthermore, since the additive for a thermoplastic resin of the present invention is derived from biomass, it is biodegradable, which enhances the biodegradability of resin molded products molded from the thermoplastic resin composition and reduces the environmental impact. Furthermore, the molded resin molded products have excellent mechanical strength, low haze, and high transparency. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a scanning electron microscope image (SEM image, magnification: 50x) of dialdehyde starch (Synthesis Example 1), which is the raw material for the dialdehyde starch polyhydric alcohol adduct. [Figure 2] FIG. 2 is a scanning electron microscope image (SEM image, 50x magnification) of a dialdehyde starch polyhydric alcohol adduct (Synthesis Example 3), which is an additive for thermoplastic resins in the present invention. [Figure 3] FIG. 3 is a scanning electron microscope image (SEM image, 250x magnification) of a dialdehyde starch polyhydric alcohol adduct (Synthesis Example 3), which is an additive for thermoplastic resins in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The dialdehyde starch-containing additive for thermoplastic resins according to the present invention, and the thermoplastic resin composition and molded resin product containing the dialdehyde starch-containing additive for thermoplastic resins will be described below.

[0015] (Additive for dialdehyde starch-containing thermoplastic resins) The thermoplastic resin additive of the present invention contains at least a dialdehyde starch-polyhydric alcohol adduct in which a polyhydric alcohol is added to dialdehyde starch, and the degree of oxidation of the dialdehyde starch-polyhydric alcohol adduct is measured using the degree of aldehyde addition, which is the proportion of repeating units of polymers having aldehyde groups in the dialdehyde starch-polyhydric alcohol adduct, and the degree of aldehyde addition is 5 mol% to 30 mol%.

[0016] Dialdehyde starch, the raw material for dialdehyde starch polyhydric alcohol adducts, is a polyaldehyde containing aldehyde groups and is generally represented by a polymer structure in which the following formula (1) or (2) is randomly bonded: In the following formula, n represents an arbitrary number. [ka] [ka]

[0017] Dialdehyde starch is obtained by dissolving starch in an aqueous solution, adding periodate solution, and then oxidizing it. After filtering, washing, and drying, dialdehyde starch powder is obtained.

[0018] Dialdehyde starch may contain not only the repeating units of formula (1) above, but also some unreacted glucose units as shown in formula (2). Therefore, the degree of aldehyde conversion is used as the oxidation degree to indicate the proportion of repeating units of formula (1) above. The degree of aldehyde conversion of dialdehyde starch is expressed as the percentage of glucose having cleaved aldehyde groups after the reaction relative to the total glucose units in the starch before the reaction, and the higher the degree of aldehyde conversion, the greater the proportion of repeating units of formula (1) above.

[0019] The degree of aldehyde conversion of the dialdehyde starch used in synthesizing the dialdehyde starch polyhydric alcohol adduct is preferably 25 mol% to 95 mol%. The degree of aldehyde conversion of the dialdehyde starch can be confirmed using an alkali consumption method or the like. If the degree of aldehyde conversion is high, the particles become coarse due to acetal bonds between the repeating units of formula (1), making it difficult to synthesize the dialdehyde starch polyhydric alcohol adduct. If the degree of aldehyde conversion is low, when the dialdehyde starch is used as a resin additive and mixed with a thermoplastic resin, the function of improving dispersibility and compatibility with the resin is not exhibited, resulting in fluctuations in flowability and deterioration in the physical properties of the produced resin molded product.

[0020] The coarsening of particles can be confirmed using the average particle size, which can be confirmed using a scanning electron microscope or the like. The larger the average particle size, the more coarse the particles become, making it more difficult to synthesize a dialdehyde starch polyhydric alcohol adduct.

[0021] A dialdehyde starch polyhydric alcohol adduct can be obtained by reacting dialdehyde starch with a polyhydric alcohol in an aqueous solution, filtering, washing, and then drying or concentrating to dryness. Furthermore, by reacting with a polyhydric alcohol before drying, a dialdehyde starch polyhydric alcohol adduct with a small average particle size can be obtained after drying. The oxidation degree of the dialdehyde starch polyhydric alcohol adduct used in the present invention is measured using the aldehyde degree, which is the proportion of repeating units of polymers having aldehyde groups in the dialdehyde starch polyhydric alcohol adduct. This value is 5 mol% to 30 mol%, and more preferably 5 mol% to 20 mol%. It is believed that the aldehyde groups of the dialdehyde starch, which is the raw material for the dialdehyde starch polyhydric alcohol adduct, react with the polyhydric alcohol to undergo hemiacetalization, acetalization, etc. Furthermore, since the dialdehyde starch polyhydric alcohol adduct uses the dialdehyde starch described above, it also contains unreacted glucose units. The degree of aldehyde conversion of the dialdehyde starch polyhydric alcohol adduct can be confirmed using an alkali consumption method or the like. If the degree of aldehyde conversion of the dialdehyde starch polyhydric alcohol adduct is higher than the above range, dispersibility and compatibility will be poor when mixed with a thermoplastic resin. Conversely, if the degree of aldehyde conversion is lower than the above range, fluctuations in fluidity and deterioration of physical properties will occur when mixed with a thermoplastic resin.

[0022] Examples of polyhydric alcohols used in the synthesis of dialdehyde starch polyhydric alcohol adducts include glycerin (glycerol, Gly), propylene glycol (PG), 1,3-butylene glycol (BG), polyethylene glycol (PEG), sorbitol, and xylitol (Xyl), with glycerin, propylene glycol, 1,3-butylene glycol, and xylitol being more preferred.

[0023] The water content of the dried dialdehyde starch polyhydric alcohol adduct is preferably 0.01% by mass to 10% by mass. The water content can be calculated using the weight loss rate of the resin additive before and after drying, and if the water content is high, hydrolysis of the thermoplastic resin and generation of bubbles will occur when the adduct is mixed with a thermoplastic resin.

[0024] The thermoplastic resin additive of the present invention may contain at least the above-mentioned dialdehyde starch polyhydric alcohol adduct having an aldehyde content of 5 mol% to 30 mol%, and may optionally contain, for example, colorants such as dyes or pigments, antibacterial agents, fillers, heat stabilizers, lubricants, mold release agents, nucleating agents, photodegradation agents, biodegradation accelerators, antioxidants, UV stabilizers, antistatic agents, flame retardants, deodorizers, etc. However, in consideration of environmental impact, biomass-derived additives are more preferred. The thermoplastic resin additive of the present invention is preferably composed solely of the above-mentioned dialdehyde starch polyhydric alcohol adduct having an aldehyde content of 5 mol% to 30 mol%.

[0025] (Thermoplastic resin composition) Next, a thermoplastic resin composition obtained by mixing an additive for a thermoplastic resin into a thermoplastic resin will be described.

[0026] The thermoplastic resin is not particularly limited, and examples thereof include general polyolefin resins, polyvinyl chloride (PVC) resins, cellulose acetate (TAC) resins, etc. When a polyolefin resin is used, examples of the polyolefin include polyethylene (PE), polypropylene (PP), etc. Among the thermoplastic resins, polyethylene resins and cellulose acetate resins are preferred.

[0027] The thermoplastic resin composition may contain the above-mentioned thermoplastic resin additive, preferably in an amount of 0.1 to 10% by mass, more preferably 0.5 to 1.5% by mass. If the amount of the dialdehyde starch-containing resin additive in the thermoplastic resin composition is too small, the effects of improving the mechanical strength of the produced resin molded product and improving transparency by reducing the haze value may not be achieved, while if the amount is too large, the mechanical strength of the resin molded product may be reduced.

[0028] The method for mixing the thermoplastic resin additive into the thermoplastic resin is not particularly limited, but examples thereof include a method in which the thermoplastic resin additive is melt-kneaded into the heated and melted thermoplastic resin.

[0029] (Resin molding) A resin molded product can be obtained by molding a thermoplastic resin composition obtained by mixing a thermoplastic resin additive into a thermoplastic resin. The method for obtaining a resin molded product is not particularly limited, but examples include a method in which a melt-kneaded thermoplastic resin composition is fed into an extrusion molding device, extruded, cut, and then melt-molded, such as by injection molding, to produce resin composition pellets. The heating temperature generally used for melt molding is within the range of 160°C to 250°C to improve the fluidity of the thermoplastic resin. If the heating temperature is too high, decomposition of the dialdehyde starch polyhydric alcohol adduct occurs when the thermoplastic resin additive is added, resulting in poor compatibility and dispersibility with the resin.

[0030] The resin molded product obtained by the present invention has excellent mechanical strength, improved transparency, and reduced haze. Specifically, the resin molded product preferably has a tensile strength that is 10% or more higher than that of a product not containing the additive for thermoplastic resins of the present invention, and a haze value that is lower than that of a product not containing the additive for thermoplastic resins of the present invention. The tensile strength is measured using a tensile tester, and the haze value is measured using a haze meter. [Example]

[0031] Specific examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0032] [Synthesis of additives for thermoplastic resins] The thermoplastic resin additive of the present invention was produced as follows.

[0033] (Synthesis Example 1) <Synthesis of dialdehyde starch (A1)> 10.0 parts of starch (dry weight) was added to 300 parts of water, and sulfuric acid was added with stirring to adjust the pH to 4.0. 13.2 parts of sodium periodate was added to this solution, and the mixture was reacted at 60°C for 5 hours. After the reaction, the solution was neutralized, filtered, and washed with water to remove inorganic salts. The resulting slurry was dried to obtain dialdehyde starch.

[0034] (Synthesis Example 2) <Synthesis of dialdehyde starch (A2)> Dialdehyde starch was obtained in the same manner as in Synthesis Example 1, except that 4.4 parts of sodium periodate was used instead.

[0035] (Synthesis Example 3) <Synthesis of dialdehyde starch glycerin adduct (B1)> To 300 parts of water, 10.0 parts of starch (dry weight) was added, and sulfuric acid was added while stirring to adjust the pH to 4.0. 13.2 parts of sodium periodate was added to this solution, and the mixture was allowed to react at 60°C for 5 hours. After the reaction, the solution was neutralized, filtered, and washed with water to remove inorganic salts. 8.4 parts of glycerin and 18.0 parts of water were added to the resulting slurry, and the mixture was stirred for 1 hour. The solution after stirring was concentrated under reduced pressure to remove water, and the resulting powder was dried under reduced pressure at 60°C to obtain a dialdehyde starch glycerin adduct.

[0036] (Synthesis Example 4) <Synthesis of dialdehyde starch glycerin adduct (B2)> A dialdehyde starch glycerin adduct was obtained in the same manner as in Synthesis Example 3, except that 7.0 parts of glycerin was used.

[0037] (Synthesis Example 5) <Synthesis of dialdehyde starch glycerin adduct (B3)> A dialdehyde starch glycerin adduct was obtained in the same manner as in Synthesis Example 3, except that 6.2 parts of glycerin was used.

[0038] (Synthesis Example 6) <Synthesis of dialdehyde starch glycerin adduct (B4)> A dialdehyde starch glycerin adduct was obtained in the same manner as in Synthesis Example 3, except that 8.6 parts of glycerin was used.

[0039] (Synthesis Example 7) <Synthesis of dialdehyde starch glycerin adduct (B5)> A dialdehyde starch glycerin adduct was obtained in the same manner as in Synthesis Example 3, except that 4.8 parts of glycerin was used.

[0040] (Synthesis Example 8) <Synthesis of dialdehyde starch xylitol adduct (C1)> A dialdehyde starch xylitol adduct was obtained in the same manner as in Synthesis Example 3, except that 8.4 parts of glycerin was replaced with 13.8 parts of xylitol.

[0041] (Synthesis Example 9) <Synthesis of dialdehyde starch propylene glycol adduct (D1)> A dialdehyde starch propylene glycol adduct was obtained in the same manner as in Synthesis Example 3, except that 8.4 parts of glycerin was changed to 6.9 parts of propylene glycol.

[0042] (Synthesis Example 10) <Synthesis of dialdehyde starch butylene glycol adduct (E1)> A dialdehyde starch butylene glycol adduct was obtained in the same manner as in Synthesis Example 3, except that 8.4 parts of glycerin was replaced with 8.2 parts of 1,3-butylene glycol.

[0043] [Measurement of aldehyde conversion degree] The degree of aldehyde conversion was measured by the alkali consumption method using the Cannizzaro reaction. The dialdehyde starches and dialdehyde starch polyhydric alcohol adducts of Synthesis Examples 1 to 9 were dispersed in water, and then sodium hydroxide was added and the reaction was carried out at 90°C for 5 minutes. After cooling, an amount of hydrochloric acid equivalent to the amount of added sodium hydroxide was added, and the solution was titrated to pH 7 with an aqueous sodium hydroxide solution. The amount of alkali consumption was calculated from the titration amount, and the degree of aldehyde conversion was determined from the aldehyde content.

[0044] [Moisture value measurement] The dialdehyde starch and dialdehyde starch polyhydric alcohol adduct of Synthesis Examples 1 to 9 were dried in a thermostatic bath at 105° C. for 2 hours, and then the water content was determined from the weight loss rate.

[0045] [Measuring average particle size] The average particle size was measured for the dialdehyde starch of Synthesis Example 1 and the dialdehyde starch polyhydric alcohol adduct of Synthesis Example 3. The average particle size was determined by analyzing 20 particles present in an SEM image at 50 to 300x magnification using a scanning electron microscope (JEOL, device name JEM-IT300LV) and image analysis software (Mountec Co., Ltd., product name Macview 4.0). In this case, the average particle size was determined as the equivalent circle diameter, which is the diameter of a circle having the same area as the particle, and the average particle size was calculated from the number of particles and their particle diameters.

[0046] The measurement results of Synthesis Examples 1 to 9 are shown in Table 1, and SEM images of the dialdehyde starch of Synthesis Example 1 and the dialdehyde starch polyhydric alcohol adduct of Synthesis Example 3 are shown in FIGS.

[0047] [Table 1]

[0048] [Synthesis of thermoplastic resin compositions, molding of resin molded products] Next, a thermoplastic resin composition and a resin molded product were obtained by mixing the additive for thermoplastic resin prepared above with a thermoplastic resin as follows.

[0049] [Example 1] Ten parts of the PE resin "ULTZEX LLDPE" and one part of the dialdehyde starch glycerin adduct (B1) were placed in a kneading machine (Labo Plastomill, manufactured by Toyo Seiki Seisakusho, Ltd.) and kneaded for 5 minutes at a rotation speed of 20 rpm and a temperature of 170° C. The resulting kneaded product was removed from the kneading machine and cut into approximately 5 mm square pieces using a cutter to obtain resin composition pellets.

[0050] [Example 2] Resin composition pellets were obtained in the same manner as in Example 1, except that the amount of dialdehyde starch glycerin adduct (B1) was changed to 0.1 parts.

[0051] [Example 3] Resin composition pellets were obtained in the same manner as in Example 1, except that the amount of dialdehyde starch glycerin adduct (B1) was changed to 0.01 parts.

[0052] [Example 4] Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with the dialdehyde starch glycerin adduct (B2).

[0053] [Example 5] Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with the dialdehyde starch glycerin adduct (B3).

[0054] [Example 6] Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) was replaced with the dialdehyde starch xylitol adduct (C1).

[0055] [Example 7] Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with the dialdehyde starch propylene glycol adduct (D1).

[0056] [Example 8] Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with the dialdehyde starch butylene glycol adduct (E1).

[0057] [Example 9] 10 parts of TAC resin "Celbrene ECP E001-26" and 0.1 parts of dialdehyde starch glycerin adduct (B1) were placed in a kneading machine (Laboplastomill, manufactured by Toyo Seiki Seisakusho, Ltd.) and kneaded for 5 minutes at a rotation speed of 20 rpm and a temperature of 180° C. The resulting kneaded product was removed from the kneading machine and cut into approximately 5 mm square pieces using a cutter to obtain resin composition pellets.

[0058] [Example 10] Resin composition pellets were obtained in the same manner as in Example 9, except that the dialdehyde starch glycerin adduct (B1) was replaced with the dialdehyde starch xylitol adduct (C1).

[0059] [Example 11] Resin composition pellets were obtained in the same manner as in Example 9, except that the dialdehyde starch glycerin adduct (B1) was replaced with the dialdehyde starch propylene glycol adduct (D1).

[0060] [Example 12] Resin composition pellets were obtained in the same manner as in Example 9, except that the dialdehyde starch glycerin adduct (B1) was replaced with the dialdehyde starch butylene glycol adduct (E1).

[0061] [Comparative Example 1] Ten parts of PE resin "ULTZEX LLDPE" were placed in a kneading machine (Labo Plastomill, manufactured by Toyo Seiki Seisakusho, Ltd.) and kneaded for 5 minutes at a rotation speed of 20 rpm and a temperature of 170° C. The resulting kneaded product was removed from the kneading machine and cut into approximately 5 mm square pieces using a cutter to obtain resin composition pellets.

[0062] Comparative Example 2 Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with the dialdehyde starch glycerin adduct (B4).

[0063] Comparative Example 3 Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with the dialdehyde starch glycerin adduct (B5).

[0064] Comparative Example 4 Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with dialdehyde starch (A1).

[0065] Comparative Example 5 Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with dialdehyde starch (A2).

[0066] Comparative Example 6 Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with 0.05 parts of dialdehyde starch (A1) and 0.05 parts of glycerin.

[0067] Comparative Example 7 Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with 0.05 parts of dialdehyde starch (A1) and 0.08 parts of xylitol.

[0068] [Comparative Example 8] Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with 0.05 parts of dialdehyde starch (A1) and 0.04 parts of propylene glycol.

[0069] Comparative Example 9 Resin composition pellets were obtained in the same manner as in Example 2, except that the dialdehyde starch glycerin adduct (B1) in Example 2 was replaced with 0.05 parts of dialdehyde starch (A1) and 0.05 parts of 1,3-butylene glycol.

[0070] [Comparative Example 10] Ten parts of TAC resin "Celbrene ECP E001-26" were placed in a kneading machine (Labo Plastomill, manufactured by Toyo Seiki Seisakusho, Ltd.) and kneaded for 5 minutes at a rotation speed of 20 rpm and a temperature of 180° C. The resulting kneaded product was removed from the kneading machine and cut into approximately 5 mm square pieces using a cutter to obtain resin composition pellets.

[0071] [Comparative Example 11] Resin composition pellets were obtained in the same manner as in Example 9, except that the dialdehyde starch glycerin adduct (B1) in Example 9 was replaced with dialdehyde starch (A1).

[0072] (Evaluation of optical properties) The pellets of Examples 1 to 12 and Comparative Examples 1 to 11 were hot pressed at 190° C. to form sheets with a thickness of 1.0 mm, and the haze was measured using a haze meter (NDH8000 manufactured by Nippon Denshoku Industries Co., Ltd.).

[0073] (Mechanical strength evaluation) In accordance with JIS K 7161, the pellets of Examples 1 to 12 and Comparative Examples 1 to 11 were injection molded into a mold, and the tensile strength was measured using a tensile tester (Shimadzu Corporation: Autograph AGS-X).

[0074] The names and blending ratios of the components used in producing the resin molded products are shown in Table 2. The results of the physical property evaluations are shown in Table 3.

[0075] [Table 2]

[0076] [Table 3]

[0077] As described above, in Tables 1 to 3, in comparison between Examples 1 to 8 and Comparative Example 1 (when no additive for thermoplastic resins was added), Examples 1 to 8 all showed a 10% increase in tensile strength and a decrease in haze value. In Comparative Example 2, in which the dialdehyde starch polyhydric alcohol adduct had a low degree of aldehyde conversion, no increase in tensile strength was observed, and in Comparative Example 3, in which the degree of aldehyde conversion was high, no decrease in haze value was observed. From these results, it is believed that there is an appropriate range for the degree of aldehyde conversion of the dialdehyde starch polyhydric alcohol adduct in the resin additive of the present invention.

[0078] In particular, when dialdehyde starch was added instead of the additive for thermoplastic resins of the present invention during resin kneading, as in Comparative Examples 4 and 5, the tensile strength decreased and the haze value increased. Furthermore, when dialdehyde starch and polyhydric alcohol were added separately without synthesizing a dialdehyde starch-polyhydric alcohol adduct in advance, as in Comparative Examples 6 to 9, the tensile strength also decreased and the haze value increased. This is thought to be because, based on the average particle size results in Synthesis Examples 1 and 3 and the SEM images in Figures 1 to 3, converting dialdehyde starch into a dialdehyde starch-polyhydric alcohol adduct reduces the average particle size and improves dispersibility and compatibility with the resin, leading to improved mechanical strength and a reduced haze value in the resin molded product of the present invention.

[0079] Furthermore, even when the thermoplastic resin was changed from polyethylene resin to cellulose acetate resin as in Examples 9 to 12, the tensile strength improved by 10% and the haze value decreased compared to when no additive for thermoplastic resins was added (Comparative Example 10) in all of Examples 9 to 12. Furthermore, when dialdehyde starch was added instead of the additive for thermoplastic resins of the present invention during resin kneading (Comparative Example 11), the tensile strength decreased and the haze value increased, showing the same tendency as when the thermoplastic resin was changed to polyethylene resin. [Industrial Applicability]

[0080] The thermoplastic resin additive of the present invention, when added to a thermoplastic resin, improves compatibility and dispersibility with the resin, and can be used to improve the mechanical strength and optical properties of resin molded products. Furthermore, since it is derived from biomass, it can provide resin molded products with low environmental impact.

Claims

1. An additive for thermoplastic resins, comprising at least a dialdehyde starch polyhydric alcohol adduct, wherein the degree of oxidation of the dialdehyde starch polyhydric alcohol adduct is measured using a degree of aldehyde conversion, which is the proportion of repeating units of polymers having aldehyde groups in the dialdehyde starch polyhydric alcohol adduct, and the degree of aldehyde conversion is 5 mol % to 30 mol %.

2. 2. The additive for thermoplastic resins according to claim 1, wherein the water content of the dialdehyde starch polyhydric alcohol adduct is 0.01% by mass to 10% by mass.

3. 2. The thermoplastic resin additive according to claim 1, wherein the polyhydric alcohol is at least one selected from the group consisting of glycerin, propylene glycol, 1,3-butylene glycol, polyethylene glycol, sorbitol, and xylitol.

4. A thermoplastic resin composition comprising a thermoplastic resin and the additive for thermoplastic resins according to any one of claims 1 to 3 mixed therein.

5. 5. The thermoplastic resin composition according to claim 4, wherein the amount of the additive for thermoplastic resins added is 0.1% by mass to 10% by mass.

6. 5. The thermoplastic resin composition according to claim 4, wherein the thermoplastic resin is at least one resin selected from the group consisting of polyolefin resins, polyvinyl chloride resins, and cellulose acetate resins.

7. A resin molded product obtained by molding the thermoplastic resin composition according to claim 4.

8. 8. The resin molded product according to claim 7, which is melt molded at a temperature of 160°C to 250°C.

Images