Molded article

Abstract

To provide a molded article containing starch with excellent transparency.SOLUTION: The molded articles of the present invention are molded articles formed from a resin composition comprising a plasticized starch and a thermoplastic resin. The plasticized starch comprises: starch; a polar organic compound capable of gelatinizing or plasticizing the starch at temperatures higher than room temperature; and sugars. After leaving the molded articles in an environment at 103°C for 16 hours, impact testing was conducted using the DIRT IMPACT A method according to JIS K7124-1. A whitening effect occurs at the point of impact on the molded articles struck by the projectile and the maximum mass of the projectile exceeds 200 g.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a molded article. [Background technology]

[0002] Conventional plastic molded products are difficult to decompose in the natural environment after disposal, making them a cause of environmental pollution. In recent years, materials that decompose in the natural environment after disposal have been studied, and plastic molded products containing biomass materials have attracted attention as such materials. Because these plastic molded products contain biomass materials as an alternative to petroleum-based materials, they can reduce CO2 emissions during combustion. Examples of biomass materials include waste biomass (food waste, livestock excrement, construction waste, and waste paper), unused biomass (inedible parts of agricultural crops and forest residues), and resource grains. More specific examples of biomass materials include wood flour, rice straw, bamboo, and old rice.

[0003] Starch, which is abundant in nature and inexpensive, is widely used as a biomass material. Starch is a so-called carbon-neutral material, because the amount of carbon dioxide emitted upon combustion is equal to the amount of carbon dioxide absorbed by the original plant (starch) during its growth. However, starch itself is a high-molecular-weight material, and as it is, it has poor fluidity during molding, making it difficult to mold. Therefore, starch that has been plasticized by various methods is used. Regarding plastic molded products containing starch, for example, Patent Document 1 below discloses an article containing a polymeric component, which includes a starch-based polymer material containing a first starch and a second starch, and a polyolefin-based polymer material. The article has a biomethane potential test result at a temperature of about 52°C using an inoculum containing about 55% by weight of water and about 45% by weight of organic solids, and the amount of the polymeric component that biodegrades after 91 days is greater than the amount of the first starch and the second starch. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-521181 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a starch-based polymer material is used as a biomass material, depending on the plant species from which it is derived, there is a problem that after molding, the material may have a hazy appearance and lose transparency. An object of the present invention is to provide a molded article containing starch that has excellent transparency. [Means for solving the problem]

[0006] The present inventors have found that a specific blending composition can improve the transparency of a molded article containing starch, regardless of the plant species from which it is derived.

[0007] That is, the present invention provides: A molded article molded from a resin composition containing plasticized starch and a thermoplastic resin, the plasticized starch comprises a starch and a polar organic compound capable of gelatinizing or plasticizing the starch at a temperature higher than room temperature; A molded body in which, after being left to stand in an environment at a temperature of 103°C for 16 hours, an impact test is conducted using the Dart Impact A method in accordance with JIS K7124-1, and the body is struck by a warhead, whitening occurs at the impact point, and the maximum mass of the warhead exceeds 200g. The molded body may further contain a sugar. The starch can be tapioca starch or corn starch. The polar organic compound capable of gelatinizing or plasticizing the starch at a temperature higher than room temperature may include at least one compound selected from polyhydric alcohols. The sugar may be one or more selected from the group consisting of trehalose, erythritol, mannitol, xylitol, maltitol, sorbitol, and maltotriose. The polyhydric alcohol may be glycerin or glycol. The glycerin content may be 0% by mass or more and 10% by mass or less. The polyhydric alcohol may be at least one of ethylene glycol or propylene glycol. The molded article is molded into the shape of a film or sheet. The present invention also provides a molded article formed into the shape of a film or sheet, and the surface of the film or sheet is covered with a membrane to form a laminate. [Effects of the Invention]

[0008] According to the present invention, a molded article containing starch and having excellent transparency can be provided, regardless of the plant species from which it is derived. The effects of the present invention are not necessarily limited to the effects described herein, and may be any of the effects described in this specification. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a photograph of the testing equipment used for the dart impact test. [Figure 2] 1 is a photograph of the impact point of the sheet with the warhead in Example 1 when the warhead mass is 275 g. [Figure 3] 10 is a photograph of the impact point of the sheet with the warhead in Comparative Example 1 when the warhead mass is 275 g. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the embodiments described below are examples of typical embodiments of the present invention, and the present invention is not limited to these embodiments.

[0011] 1.Resin composition

[0012] The resin composition used in the present invention contains a plasticized starch and a thermoplastic resin. The plasticized starch contains starch and a polar organic compound capable of gelatinizing or plasticizing the starch at a temperature higher than room temperature. The plasticized starch may further contain a sugar.

[0013] The resin composition used in the present invention preferably contains the plasticized starch and the thermoplastic resin in a ratio of 5:95 to 75:25 parts by mass, more preferably 10:90 to 70:30 parts by mass, and even more preferably 15:75 to 70:30 parts by mass. The resin composition having such a ratio can reduce the size of the starch granules contained in the molded article.

[0014] The starch contained in the plasticized starch is plasticized. This makes it possible to smooth the surface of a molded article formed from the resin composition. Furthermore, it is also possible to improve the physical properties (e.g., tensile elongation) of a film or sheet formed from the resin composition.

[0015] Furthermore, by using the plasticized starch, it is possible to produce molded articles (e.g., films or sheets) having good quality (e.g., high transparency, surface smoothness, low coloration, and low odor). For example, since the particle size of the starch granules contained in the resin composition of the present invention is 2 μm or less, even if a thin film or sheet is formed from the resin composition, the shape of the starch granules does not appear on the surface. For example, even if the starch content of the resin composition of the present invention is increased, the film or sheet formed from the resin composition does not have the shape of starch granules on its surface.

[0016] Furthermore, the inclusion of the plasticized starch in the resin composition of the present invention can impart excellent transparency to a molded article (e.g., a film or a sheet) formed from the resin composition, and can also smooth the surface of a molded article (e.g., a film or a sheet) formed from the resin composition.

[0017] The resin composition of the present invention contains the plasticized starch and the thermoplastic resin as main components, and the total content of the plasticized starch and the thermoplastic resin in the resin composition of the present invention is, for example, preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 30% by mass or more, and still more preferably 50% by mass or more, based on the total amount of the resin composition.

[0018] The resin composition used in the present invention will be described in more detail below.

[0019] [Plasticized starch]

[0020] By using the plasticized starch in a resin composition, excellent moldability can be achieved when producing a molded article from the resin composition, and the transparency and physical properties of the molded article can be improved. For example, if the content of a previously known starch (e.g., ungelatinized starch) in a resin composition is 50% by mass or more, the resin composition may not be molded, or even if molded, the molded product may not be of good quality. Specifically, when the resin composition is subjected to inflation molding, the resin composition may not expand, or foaming may occur within the resin composition. Furthermore, even if the resin composition expands, the film obtained by the molding has poor stretchability, making the film prone to tearing and lacking in strength.

[0021] The resin composition used in the present invention contains the plasticized starch, and therefore has excellent moldability and is suitable for molding, for example, a film or sheet. That is, the resin composition used in the present invention can be used to mold a film or sheet. Furthermore, since the resin composition contains the plasticized starch, it has excellent physical properties (e.g., tensile elongation).

[0022] Furthermore, the plasticized starch used in the present invention does not have foamed portions. Foaming can occur, for example, due to the evaporation of volatile components during the production of the plasticized starch. Resin compositions produced using plasticized starch with foamed portions may have poor moldability, and further, the appearance of molded articles produced from the resin composition may be poor.

[0023] The plasticized starch used in the present invention may be a material containing starch as a main component. The starch content in the plasticized starch may be, for example, preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total amount of the plasticized starch. The starch content in the plasticized starch may be, for example, preferably 99.5% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on the total amount of the plasticized starch. The starch content may be measured by TG measurement (thermogravimetric analysis) at 150°C. Specifically, the content may be determined based on the mass change measured using a TG measurement device (STA7200, Hitachi High-Tech Science Corporation). The mass change corresponds to the amount of volatile components reduced, which in turn corresponds to the amount of polar organic compounds capable of gelatinizing or plasticizing the starch. Therefore, the starch content in the plasticized starch can be calculated by the following formula: (starch content in the plasticized starch (unit: mass%)) = (mass after starting to measure the amount of mass change) / (mass before starting to measure the amount of mass change) × 100. The conditions for measuring the amount of mass change are as follows: temperature range of 25°C to 150°C, heating rate of 20°C / min, under nitrogen.

[0024] Examples of starches constituting the plasticized starch used in the present invention include underground starch and aboveground starch. Subterranean starch refers to starch accumulated underground, for example, in rhizomes or roots, etc. Examples of subterranean starches include, but are not limited to, tapioca starch (cassava starch), potato starch, sweet potato starch, kudzu starch, and bracken starch. Terrestrial starch refers to starch accumulated above ground, for example, starch accumulated in seeds, etc. Examples of terrestrial starches include, but are not limited to, maize starch, wheat starch, sago starch, acorn starch, and rice starch. In the present invention, preferably, underground starch is used. By using underground starch to produce the resin composition used in the present invention, the odor of the resin composition can be further reduced. The starch used in the present invention may be a modified starch (i.e., modified starch), particularly a modified starch derived from a starch derived from a soluble starch. Examples of such modified starches include physically modified starches and chemically modified starches. Examples of physically modified starches include pregelatinized starch and heat-moisture starch. Examples of chemically modified starches include acetoacetate-esterified starch, acetate-esterified starch, hydroxymethyl-etherified starch, hydroxypropyl-etherified starch, carboxymethyl-etherified starch, allyl-etherified starch, methyl-etherified starch, succinate-esterified starch, xanthogen acetate-esterified starch, nitrate-esterified starch, urea phosphate-esterified starch, phosphate-esterified starch, phosphate-crosslinked starch, formaldehyde-crosslinked starch, acrolein-crosslinked starch, and epichlorohydrin-crosslinked starch. Modified starches can be plasticized at lower temperatures than unmodified starch. Therefore, odor and / or coloration associated with heating during the production of plasticized starch can be suppressed.

[0025] The starch used in the present invention may preferably contain equilibrium moisture. The amount of equilibrium moisture may be, for example, preferably 10% to 15% by mass, more preferably 10% to 14% by mass, even more preferably 10% to 13% by mass, and even more preferably 11% to 13% by mass, relative to the mass of the starch. It is preferable to use starch or modified starch containing an equilibrium moisture within the above numerical range, as this allows the starch to be plasticized.

[0026] According to one embodiment of the present invention, the starch in the plasticized starch is plasticized. The plasticized starch is a plasticized starch or a plasticized modified starch. For example, the starch can be plasticized corn starch or plasticized tapioca starch. The plasticized starch is more preferably a plasticized product of one starch or a combination of two or more starches selected from tapioca starch (cassava starch), potato starch, sweet potato starch, arrowroot starch, and bracken starch, or a plasticized product of a modified version of the starch or a combination of two or more modified starches. Even more preferably, the plasticized starch is a plasticized product of tapioca starch or a plasticized product of modified tapioca starch. These plasticized products are particularly preferred from the viewpoint of reducing the odor of the resin composition used in the present invention.

[0027] The polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, which constitutes the plasticized starch used in the present invention, refers to a polar organic compound that can gelatinize or plasticize starch by coming into contact with the starch at a temperature higher than room temperature. Any organic compound known in the art may be used as the polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature.

[0028] The polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature refers to a polar organic compound that is not capable of gelatinizing or plasticizing starch at room temperature but is capable of gelatinizing or plasticizing starch at a temperature higher than room temperature. In this specification, a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature is also referred to as a "polar organic compound capable of gelatinizing or plasticizing starch at a high temperature." For example, if a polar organic compound does not gelatinize or plasticize starch when contacted with the starch for one hour at room temperature, but gelatinizes or plasticizes the starch when contacted with the polar organic compound for one hour at a high temperature, the polar organic compound is "capable of gelatinizing or plasticizing starch at a high temperature." The polar organic compound capable of gelatinizing or plasticizing starch may be any of a polar organic compound capable of gelatinizing starch, a polar organic compound capable of plasticizing starch, and a polar organic compound capable of gelatinizing and plasticizing starch. In this specification, a temperature higher than room temperature (also referred to as "high temperature") refers to a temperature achieved by heat treatment. The high temperature may be, for example, a temperature of 50°C or higher, preferably a temperature of 60°C or higher, more preferably a temperature of 80°C or higher, and even more preferably a temperature of 100°C or higher. In this specification, room temperature refers to the temperature when no heat treatment is performed. Room temperature is, for example, less than 50°C, preferably 10 to 40°C, more preferably 15 to 35°C, and even more preferably 20 to 30°C.

[0029] Preferably, the total content of polar organic compounds capable of gelatinizing or plasticizing the starch at temperatures higher than room temperature in the plasticized starch is, for example, preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, relative to the total amount of the plasticized starch. The total content of polar organic compounds capable of gelatinizing or plasticizing the starch at temperatures higher than room temperature in the plasticized starch is, for example, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more, relative to the total amount of the plasticized starch. The total content of polar organic compounds capable of gelatinizing or plasticizing the starch at temperatures higher than room temperature is calculated by subtracting the content of the gelatinized starch measured by the TG measurement described above from 100% by mass.

[0030] In one embodiment of the present invention, the polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature is preferably liquid at room temperature, which allows easy mixing with starch.

[0031] The polar organic compound that constitutes the plasticized starch and that is capable of gelatinizing or plasticizing starch at a temperature (high temperature) higher than room temperature may contain at least one polyhydric alcohol.

[0032] In the present invention, the polyhydric alcohol refers to an alcohol having two or more hydroxyl groups in the molecule. Such a polyhydric alcohol is preferably a polyhydric alcohol having 2 to 5 carbon atoms, more preferably a polyhydric alcohol having 2 to 4 carbon atoms. The polyhydric alcohol preferably has 2 to 5 hydroxyl groups (OH groups), more preferably 2 to 4 hydroxyl groups (OH groups). The polyhydric alcohols may include, for example, glycerin and glycols, such as ethylene glycol and propylene glycol. The polyhydric alcohol may be preferably one or more selected from glycerin, ethylene glycol, and propylene glycol, and more specifically, may contain a combination of one or more selected from ethylene glycol and propylene glycol. The plasticized starch of the present invention may contain the polyhydric alcohol in an amount of, for example, preferably 10 to 40 parts by mass, more preferably 20 to 35 parts by mass, per 100 parts by mass of the starch. The content of the polyhydric alcohol in the resin composition may be preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.

[0033] From the viewpoint of suppressing the occurrence of bleeding under high temperature and humidity conditions, the content of glycerin in the plasticized starch is preferably 0% by mass or more and 10% by mass or less, more preferably 0% by mass or more and 9% by mass or less, and even more preferably 0% by mass or more and 7% by mass or less. The smaller the amount of glycerin, the more the occurrence of bleeding can be suppressed. Therefore, it is preferable to not use glycerin and to use other polyhydric alcohols instead of glycerin, for example, it is preferable to use ethylene glycol or propylene glycol instead of glycerin. That is, from the viewpoint of suppressing the occurrence of bleeding, it is also possible to completely eliminate glycerin and to contain, for example, only ethylene glycol or only propylene glycol.

[0034] However, a decrease in the glycerin content can result in larger starch granules. To keep the starch granules small even when the glycerin content is reduced, the plasticized starch may further contain an organic acid. An organic acid refers to an organic compound that exhibits acidity, and an organic compound refers to a compound having at least one carbon atom. Examples of organic acids include carboxylic acids, sulfonic acids, sulfinic acids, organic phosphinic acids, and organic phosphonic acids.

[0035] Examples of the carboxylic acid include monocarboxylic acids such as lactic acid, gluconic acid, acetic acid, and acetic anhydride; dicarboxylic acids such as tartaric acid, maleic acid, maleic anhydride, adipic acid, succinic acid, succinic anhydride, and malic acid; and carboxylic acids having three or more carboxyl groups such as citric acid. Examples of the sulfonic acid include benzenesulfonic acid and methanesulfonic acid. Examples of the sulfinic acid include benzenesulfinic acid and cysteinesulfonic acid. Examples of the organic phosphinic acid include diethylphosphinic acid. Examples of the organic phosphonic acid include methylphosphonic acid.

[0036] In the plasticized starch, the starch is gelatinized or plasticized by heating the starch at a temperature higher than room temperature in the presence of a polar organic compound capable of gelatinizing or plasticizing the starch. The gelatinization or plasticization of the starch may be brought about, for example, by breaking intermolecular bonds (mainly hydrogen bonds) by heating in the presence of a polar organic compound capable of gelatinizing or plasticizing the starch at high temperatures. The gelatinized or plasticized starch may be, for example, pregelatinized starch. It is believed that this plasticization contributes to imparting transparency and / or smoothness to the molded article of the present invention.

[0037] This plasticization is also thought to contribute to reducing the size of starch granules contained in molded articles formed from the resin composition used in the present invention. For example, in molded articles formed from resin compositions containing unplasticized starch, the starch particles are likely to appear on the surface of the molded articles. The starch particles have a particle size of, for example, about 20 μm. Therefore, for example, when a film is formed using a resin composition containing unplasticized starch, the content of the starch in the resin composition is limited to, for example, a maximum of about 30 mass% relative to the total amount of the resin composition in order to prevent the starch particle shape from appearing on the surface of the film. Furthermore, when the film thickness is set to about 20 μm or less, the starch particles are significantly visible on the film surface. On the other hand, since the starch contained in the resin composition used in the present invention is plasticized, the particle size of the starch granules is 2 μm or less, and the shape of the starch is unlikely to appear on the surface of the resin composition. Therefore, the content of starch in the resin composition used in the present invention can be more than 30% by mass, for example, 50% or more, particularly 60% or more, and more particularly 70% or more, based on the total amount of the resin composition. Even if the content of starch is high, the surface of the molded product is smooth.

[0038] Examples of sugars contained in the plasticized starch include powder sugars such as sucrose, trehalose, erythritol, mannitol, xylitol, and maltotriose. Examples of liquid sugars include malbit and sorbitol. Trehalose, erythritol, mannitol, xylitol, maltotriose, malbit, and sorbitol are particularly preferred from the viewpoint of suppressing coloration of the molded product. The content of the sugars is, for example, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to the total amount of the plasticized starch. The content of the sugars is, for example, preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 2.0% by mass or more, relative to the total amount of the plasticized starch.

[0039] According to one embodiment of the present invention, the plasticized starch may contain cellulose nanofibers (hereinafter also referred to as CNF). Dispersing CNF in a thermoplastic resin is often difficult. The plasticized starch can easily disperse CNF in the material, and further, the plasticized starch containing CNF can be easily mixed with a thermoplastic resin. Therefore, the plasticized starch can easily disperse CNF in a thermoplastic resin. By including CNF in the resin composition of the present invention, the tensile properties and impact strength of a molded article formed from the resin composition can be improved. In an embodiment in which the plasticized starch contains CNF, CNF may be added to the thermoplastic resin.

[0040] The benefits of including CNF in the plasticized starch are explained in more detail below. CNFs are hydrophilic and are generally produced by disintegrating cellulose materials with water to produce nano-sized particles, so they are dispersed in water. CNFs are used, for example, to increase the strength of thermoplastic resins. However, because thermoplastic resins are often hydrophobic, mixing hydrophilic CNFs with thermoplastic resins can be difficult. Therefore, for example, CNFs have been modified to hydrophobize them (especially powdered CNFs) and mixed with thermoplastic resins. For example, the TENPO oxidation method can be used for this hydrophobization. Alternatively, a CNF dispersion obtained by solvent substitution of the water in which CNFs are dispersed has been mixed with a liquid resin (e.g., epoxy resin or vinyl chloride resin). Another example involves directly crushing cellulose materials in an extruder without crushing them with water, and then mixing the resulting CNFs with a thermoplastic resin. Such mixing methods can be costly (e.g., labor, expense, or time). Therefore, a method using CNFs dispersed in water as is is desirable. Furthermore, as mentioned above, it is difficult to disperse CNF in a thermoplastic resin, and if the dispersion is poor, only one of the tensile elongation and tensile strength of the resulting CNF-containing thermoplastic resin can be improved. In addition, CNF is generally dispersed in water, and for example, the CNF content in a CNF aqueous dispersion is about several mass percent, meaning that the CNF aqueous dispersion contains a high amount of water. Therefore, it is often difficult to mix a CNF aqueous dispersion with a thermoplastic resin. As described above, the plasticized starch used in the present invention allows CNF to be easily dispersed in the material, and further allows the plasticized starch containing CNF to be easily mixed with a thermoplastic resin. The CNF may be a CNF dispersed in water. Even if an aqueous dispersion of CNF is used, by using the aqueous dispersion of CNF in the production of the plasticized starch, the CNF can be easily dispersed in the thermoplastic resin without using the mixing method described above. Furthermore, when the plasticized starch containing CNF is mixed with a thermoplastic resin, the CNF disperses well in the thermoplastic resin, thereby improving both the tensile elongation and tensile strength of the thermoplastic resin. Furthermore, increasing the starch content or biodegradable resin content in a resin composition can reduce the tensile strength of the resin composition. By blending the plasticized starch containing CNF with a thermoplastic resin as described above, the problem of reduced tensile strength due to a high starch content or biodegradable resin content in the resin composition can be resolved. Furthermore, other effects brought about by CNF can also be exhibited in the resin composition. Examples of CNF contained in the plasticized starch include CNF dispersed in water produced by the general production method described above. In addition to the CNF dispersed in water, modified CNF such as the hydrophobized CNF described above may also be contained in the plasticized starch. Powdered CNF can also be dispersed in the plasticized starch by dispersing it in water. In this way, the plasticized starch can disperse various CNFs in the material. Note that CNF dispersed in water is preferred as the CNF to be dispersed in the plasticized starch from the viewpoints of cost and ease of handling. CNF dispersed in water is particularly easy to introduce into the production equipment for the plasticized starch. CNF dispersed in a hydrophilic liquid other than water may also be used. The CNF dispersed in the plasticized starch may be dispersed in one hydrophilic liquid or in a mixture of two or more hydrophilic liquids. That is, the liquid in which the CNF dispersed in the plasticized starch is dispersed may be one or a combination of two or more selected from water, glycerin, ethylene glycol, propylene glycol, formamide, and urea water. The liquid may also be one or a combination of two or more of the polyhydric alcohols mentioned above.

[0041] Commercially available CNFs may be used in the present invention. In the present invention, CNF refers to fibrous cellulose that differs from molecular cellulose and is poorly soluble in solvents and has an average fiber diameter of 10 nm to 3,000 nm. The average fiber diameter is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm, even more preferably 10 nm to 300 nm, and even more preferably 10 nm to 100 nm. The aspect ratio of CNF is, for example, preferably 30 to 10,000, more preferably 50 to 5,000, and even more preferably 50 to 1,000. The aspect ratio is the value obtained by dividing the average fiber length by the average fiber diameter. The average fiber length and average fiber diameter are the average values ​​of 10 random cellulose fibers observed under an electron microscope.

[0042] The plasticized starch may be produced by the production method described below.

[0043] [Thermoplastic resin]

[0044] The thermoplastic resin contained in the resin composition of the present invention may be preferably a polyolefin resin, a polyester resin, or a mixture of these resins. The thermoplastic resin may also be a polystyrene resin.

[0045] Polyolefin resins are polymers obtained by polymerization of olefins (e.g., α-olefins) as the main monomers. The polyolefin resins may be, for example, polypropylene (PP) resin, polyethylene (PE) resin, or a combination thereof. The polypropylene resin may be, for example, a homopolymer polypropylene resin, or a random copolymer or block copolymer polypropylene resin (such as an ethylene-propylene copolymer), or a combination thereof. The polyethylene resin may be, for example, a low density polyethylene resin (LDPE: Low Density Polyethylene), a high density polyethylene resin (HDPE: High Density Polyethylene), a very low density polyethylene resin (VLDPE: Very Low Density Polyethylene), a linear low density polyethylene resin (LLDPE: Linear Low Density Polyethylene), or an ultra high molecular weight polyethylene resin (UHMW-PE: Ultra High Molecular Weight Polyethylene), or a combination thereof. The polyolefin resin may preferably be a biomass-derived polyolefin resin (e.g., a biomass-derived polyethylene resin), such as a biomass polyethylene resin. The biomass polyethylene resin may be, for example, LDPE, LLDPE, or HDPE. This can reduce CO2 emissions. The polyolefin resin may be a polyolefin resin produced using a metallocene catalyst, i.e., the thermoplastic resin may be, for example, a metallocene-catalyzed polyethylene resin or polypropylene resin, or a combination thereof. The polystyrene resin may also be a metallocene catalyst-based polystyrene resin.

[0046] A polyester resin is a polymer formed by polymerizing monomers via ester bonds. Examples of the polyester resin include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polylactic acid (PLA), polycarbonate (PC), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), or a combination of two or more thereof.

[0047] Polystyrene-based resins are polymers formed by polymerization of styrene-based monomers. Examples of such polystyrene-based resins include polystyrene resins, rubber-reinforced polystyrene resins (high impact polystyrene resins, HIPS), acrylonitrile-styrene copolymers (AS resins), methacrylate ester-styrene copolymers, acrylonitrile-acrylic rubber-styrene copolymers, and acrylonitrile-ethylene-propylene-styrene copolymers, or combinations of two or more of these.

[0048] The type of thermoplastic resin constituting the resin composition used in the present invention may be appropriately selected by those skilled in the art depending on, for example, the type of molded article to be formed from the resin composition. However, a thermoplastic resin with a low processing temperature is preferred. For example, when the resin composition is formed into a film or sheet, the thermoplastic resin may be, for example, preferably a polyolefin resin, more preferably a polyethylene resin or a polypropylene resin, and even more preferably LLDPE or LDPE. Even when the resin composition of the present invention is heated to the melting point of these resins, odor or discoloration due to heating of plasticized starch is unlikely to occur. Therefore, the occurrence of odor or discoloration can be suppressed when the resin composition is heated to produce a molded article.

[0049] The thermoplastic resin contained in the resin composition used in the present invention preferably has a melting point of 90° C. to 180° C., more preferably 95° C. to 170° C. By using a thermoplastic resin with a lower melting point, the molding temperature can be lowered, and odor or coloration caused by heating the plasticized starch can be further suppressed.

[0050] The thermoplastic resin may be in the form of pellets or powder, and is mixed, kneaded, and uniformly dispersed during molding using an extruder, injection molding, or the like.

[0051] The resin composition used in the present invention may contain the plasticized starch and thermoplastic resin in a ratio of, for example, preferably 20 parts by mass:80 parts by mass to 80 parts by mass:20 parts by mass, more preferably 30 parts by mass:70 parts by mass to 80 parts by mass:20 parts by mass, even more preferably 40 parts by mass:60 parts by mass to 80 parts by mass:20 parts by mass, and even more preferably 50 parts by mass:50 parts by mass to 80 parts by mass:20 parts by mass. By using the plasticized starch, molded articles of good quality can be produced from the resin composition even when the starch content in the resin composition is increased to the above-mentioned numerical range.

[0052] According to one embodiment of the present invention, the thermoplastic resin may be a biodegradable resin. In this embodiment, both the plasticized starch and the thermoplastic resin are biodegradable. Therefore, the resin composition according to this embodiment is more environmentally friendly.

[0053] [Other ingredients]

[0054] The resin composition used in the present invention may contain, in addition to the plasticized starch and the thermoplastic resin, other components such as a compatibilizer, an oxidative decomposition accelerator, a colorant, and an antioxidant.

[0055] The compatibilizer may be used to further improve the compatibility between the plasticized starch and the thermoplastic resin. Examples of the compatibilizer include carboxylic acid anhydride-modified polyolefins, olefin-based graft-modified products, and olefin-based comonomers. The carboxylic acid anhydride constituting the carboxylic acid anhydride-modified polyolefin may preferably be maleic anhydride. The compatibilizer may be, for example, one or a combination of two or more selected from the group consisting of a modified polyethylene copolymer, a modified polypropylene copolymer, and a maleic anhydride-modified ethylene-propylene copolymer. The olefin-based graft-modified product may be an acid-modified polyolefin, more specifically, a polyolefin graft-modified with an unsaturated carboxylic acid or its derivative. The (unmodified) polyolefin used for graft modification may be, for example, polyethylene, polypropylene, or an ethylene-α-olefin copolymer (ethylene-propylene copolymer), particularly polypropylene. For example, the acid-modified polyolefin described in JP 2010-095671 A may be used.

[0056] Examples of the colorant include titanium oxide and / or carbon black, and examples of the antioxidant include, but are not limited to, phenol-based antioxidants.

[0057] [Thermoplastic resin composition]

[0058] The resin composition used in the present invention may be a thermoplastic resin. Specific examples of the thermoplastic resin composition according to the present invention will be described below.

[0059] According to one embodiment of the present invention, the thermoplastic resin composition may contain the plasticized starch, the thermoplastic resin, and the compatibilizer. As described above, the ratio of the plasticized starch to the thermoplastic resin may be, for example, preferably 20 parts by mass:80 parts by mass to 80 parts by mass:20 parts by mass, more preferably 30 parts by mass:70 parts by mass to 80 parts by mass:20 parts by mass, and even more preferably 50 parts by mass:50 parts by mass to 80 parts by mass:20 parts by mass. The content of the compatibilizer may be, for example, preferably 1 part by mass to 10 parts by mass, more preferably 2 parts by mass to 9 parts by mass, per 100 parts by mass of the total amount of the plasticized starch and the thermoplastic resin. In this embodiment, the thermoplastic resin is, for example, a polyolefin-based resin, such as a polypropylene (PP) resin or a polyethylene (PE) resin, or a combination thereof. The thermoplastic resin is particularly preferably a polypropylene resin, more preferably a block copolymer polypropylene resin. In this embodiment, the compatibilizer is, for example, a carboxylic acid anhydride-modified polyolefin, preferably a modified polypropylene copolymer or a modified polyethylene copolymer. The thermoplastic resin composition according to this embodiment can be used to produce a film or sheet by a molding method such as inflation molding, T-die molding, or calendar molding. In the present invention, the term "film" refers to a thin membrane-like material, and the thickness of the film can be, for example, less than 200 μm, particularly 10 μm or more and less than 200 μm. In the present invention, the term "sheet" refers to a thin plate-like material, and the thickness of the sheet can be, for example, 200 μm or more, particularly 200 μm or more and 1 mm or less. In this embodiment, the thermoplastic resin may be, for example, a biomass-derived thermoplastic resin, in particular a biomass-derived polyethylene resin.

[0060] According to another embodiment of the present invention, the thermoplastic resin composition may contain the plasticized starch, the thermoplastic resin, the compatibilizer, and the oxidative decomposition accelerator. As described above, the ratio of the plasticized starch to the thermoplastic resin may be, for example, preferably 20 parts by mass:80 parts by mass to 80 parts by mass:20 parts by mass, more preferably 30 parts by mass:70 parts by mass to 80 parts by mass:20 parts by mass, and even more preferably 50 parts by mass:50 parts by mass to 80 parts by mass:20 parts by mass. The content of the compatibilizer may be, for example, preferably 1 part by mass to 10 parts by mass, more preferably 2 parts by mass to 9 parts by mass, per 100 parts by mass of the total amount of the plasticized starch and the thermoplastic resin. The content of the oxidative decomposition accelerator may be, for example, preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and even more preferably 0.1 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of the plasticized starch and the thermoplastic resin. In this embodiment, the thermoplastic resin is, for example, a polyolefin-based resin, such as a polypropylene (PP) resin or a polyethylene (PE) resin, or a combination thereof. The thermoplastic resin is particularly preferably a polypropylene resin, more preferably a block copolymer polypropylene resin. In this embodiment, the compatibilizer is, for example, a carboxylic acid anhydride-modified polyolefin, preferably a modified polypropylene copolymer or a modified polyethylene copolymer. The oxidative decomposition accelerator may be a combination of a carboxylate and a rare earth compound. The thermoplastic resin composition according to this embodiment can be used to produce a film or sheet by a molding method such as inflation molding or T-die extrusion. The thickness of the film can be, for example, less than 200 μm, particularly 10 μm or more and less than 200 μm. The thickness of the sheet can be, for example, 200 μm or more, particularly 200 μm or more and 1.5 mm or less. In this embodiment, the thermoplastic resin may be, for example, a biomass-derived thermoplastic resin, in particular a biomass-derived polyethylene resin. The thermoplastic resin composition according to this embodiment has a high biomass content, and the thermoplastic resin contained in the composition is biodegradable.

[0061] The resin composition used in the present invention may be used to produce molded articles other than films and sheets. Examples of such molded articles include, but are not limited to, containers (e.g., bottle containers), bottle caps, plastic cardboard, nonwoven fabrics, and monofilaments. For example, the resin composition used in the present invention may be used for blow molding, injection molding, profile extrusion molding, and spinning (e.g., melt spinning). For example, bottle containers can be molded by the blow molding. For example, bottle caps or containers can be produced by the injection molding. For example, plastic cardboard can be molded by the profile extrusion molding. For example, monofilaments can be molded by the spinning (e.g., melt spinning).

[0062] The resin composition used in the present invention may be produced by the production method described below.

[0063] 2. Molded body

[0064] The molded article of the present invention is molded from a resin composition containing plasticized starch and a thermoplastic resin. Such molded articles include films or sheets, laminates, nonwoven fabrics, etc. These will be explained below.

[0065] [Film or sheet]

[0066] The molded article of the present invention may be formed into the shape of a film or sheet. The film or sheet may be a single-layer film or sheet composed solely of a layer formed from the resin composition used in the present invention, or may be a multi-layer film or sheet in which at least one layer formed from the resin composition and at least one layer formed from another composition (particularly a resin composition) are laminated. The film may have a thickness of, for example, less than 200 μm, particularly a thickness of 10 μm or more and less than 200 μm. The sheet may have a thickness of, for example, 200 μm or more, particularly a thickness of 200 μm or more and 1.5 mm or less.

[0067] According to one embodiment of the present invention, the film or sheet has a surface having an average roughness (Ra) measured in accordance with JIS B0031 of preferably 2 μm or less, more preferably 1.8 μm or less, and even more preferably 1.5 μm or less, and this surface is the surface of a layer formed from the resin composition of the present invention. The average roughness may be measured using a surface roughness meter in accordance with JIS B0031. The resin composition used in the present invention can provide a film or sheet having such a smooth surface. The film or sheet formed from the resin composition used in the present invention can be suitably used for cards, packaging, containers, separators, covers, dividers, laminates, and bags.

[0068] The sheet or film can be produced using conventional molding techniques for petroleum-based plastics. For example, plasticized starch and thermoplastic resin may be mixed in a mixer such as a Henschel mixer, tumbler mixer, Barbary mixer, or kneader mixer, and then molded into a sheet using a T-die extruder or a calendar molding machine, or into a film using an inflation molding machine. Alternatively, the raw materials, such as plasticized starch and thermoplastic resin, may be directly kneaded, mixed, and molded. Alternatively, the raw materials may be mixed in a mixer, and then strands may be extruded using a single- or twin-screw extruder, cut into pellets, and the pellets may be used as a masterbatch to mold a sheet or film.

[0069] When producing a sheet or film, the molding temperature range employed is preferably in the range of 95 to 200°C when the raw materials are directly kneaded, mixed, and molded, from the viewpoint of suppressing the occurrence of scorching or decomposition of the raw materials and seizing inside the cylinder, and from the viewpoint of suppressing the discharge of unmelted plasticized starch, which may cause problems along with an increase in pressure.Furthermore, when master pellets are produced and molded, the range of 95 to 200°C is preferred.

[0070] In addition, from the viewpoint of preventing the raw material from burning or decomposing, the residence time in the cylinder is preferably within 10 minutes at most.

[0071] The sheet extrusion molded by the T-die extruder may be formed to a predetermined thickness by setting the temperature of the take-up roll to 60°C or less, and the sheet may be cooled, taken up, and wound up. The film extrusion molded by the inflation molding machine may be formed to a predetermined thickness by setting the temperature of the take-up roll to 90°C or less, and the film may be cooled, taken up, and wound up.

[0072] [Laminate]

[0073] The present invention also provides a laminate in which the surface of the film or sheet is coated with a membrane. The laminate may be one in which one surface of the film or sheet is coated with a membrane, or both surfaces of the film or sheet. By coating the surface of the film or sheet with a membrane, bleed-out from the coated surface can be suppressed. The membrane may be, for example, a polyolefin-based resin such as polyethylene (PE) resin, polypropylene (PP) resin, or a combination of two or more of these. It may also be, for example, a polylactic acid resin (PLA), polycarbonate resin (PC), polyethylene terephthalate resin (PET), polyethylene naphthalate resin (PEN), polybutylene terephthalate resin (PBT), polybutylene adipate terephthalate resin (PBAT), polybutylene succinate resin (PBS), polyhydroxyalkanoate resin (PHA), or a combination of two or more of these polyester-based resins. An adhesive layer may be provided between the film or sheet and the membrane. The adhesive layer may be made of a resin having a melting point lower than that of the resin composition forming the film or sheet, such as an epoxy resin or a urethane resin.

[0074] In the laminate, the film may have a thickness of, for example, less than 200 μm, particularly a thickness of 10 μm or more and less than 200 μm. The sheet may have a thickness of, for example, 200 μm or more, particularly a thickness of 200 μm or more and 1.5 mm or less. The membrane may have a thickness of, for example, less than 60 μm, particularly a thickness of 10 μm or more and less than 50 μm. The laminate provided by the resin composition used in the present invention can be suitably used for cards, covers, packaging, containers, separators, dividers, bags, and laminates.

[0075] [Nonwoven fabric]

[0076] The present invention also provides a nonwoven fabric formed from the resin composition used in the present invention. The fiber diameter of the fibers constituting the nonwoven fabric is preferably 5 to 30 μm, more preferably 5 to 25 μm, and even more preferably 5 to 20 μm. The average single fiber fineness of the fibers constituting the nonwoven fabric is preferably 0.16 dtex or more and 20 dtex or less, more preferably 0.17 dtex or more and 15 dtex or less, and even more preferably 0.17 dtex or more and 10 dtex or less. From the viewpoint of spinning stability, the average single fiber fineness is preferably 0.17 dtex or more. On the other hand, the finer the fineness, the more adhesion points there are between the threads in the nonwoven fabric, which tends to result in higher strength and better flexibility. From the viewpoint of the strength of the nonwoven fabric, the average single fiber fineness is preferably 0.2 dtex or less. The average single fiber fineness is determined by the fiber cross-sectional area A (m ) in a fiber cross-section photograph. 2 ) and polymer density ρ (g / m 3 ) can be calculated using the following formula: Single fiber fineness (dtex) = A (m 2 )×ρ(g / m 3 )×10000(m).

[0077] In the present invention, the nonwoven fabric preferably has a basis weight of 10 to 200 g / m 2 and more preferably 10 to 190 g / m 2 and more preferably 20 to 180 g / m 2 By setting the basis weight within the above range, sufficient strength can be obtained, particularly when used as a nonwoven fabric for shopping bags.

[0078] In the present invention, the apparent density of the nonwoven fabric is preferably 0.3 g / cm 3 or less, more preferably 0.2 g / cm 3 or less, and more preferably 0.15 g / cm 3 By setting the apparent density within the above range, sufficient bulkiness can be obtained, particularly when used as a nonwoven fabric for wiping. The apparent density can be calculated by dividing the basis weight by the thickness.

[0079] The nonwoven fabric of the present invention may be produced by a spunbonding method, a meltblowing method, etc. For example, the spunbonding method is a production method in which the resin composition is heated and melted, spun from a spinneret, and the cooled and solidified filaments are pulled and stretched by an ejector, collected and deposited on a moving net to form a web, and then heat-bonded by an embossing roller under heat and pressure.

[0080] The spinneret and ejector may be of various shapes, such as round or rectangular. Among them, a combination of a rectangular spinneret and a rectangular ejector is preferably used, since it uses a relatively small amount of compressed air and is less likely to cause fusion or friction between filaments. A spinneret having a round discharge shape is preferably used.

[0081] The spinning temperature during melting and spinning is preferably 200 to 300°C, more preferably 210 to 280°C, and even more preferably 220 to 260°C. By setting the spinning temperature within the above range, a stable molten state can be achieved, and excellent spinning stability can be obtained. The resin composition (raw material) is melted and metered by an extruder, supplied to a spinneret, and spun out from the nozzle holes of the spinneret.

[0082] The spun filament fibers can be cooled by any conventional method, for example, by blowing cooling air onto the filaments spun from the spinneret.

[0083] The cooled and solidified fibers are pulled and stretched by compressed air ejected from an ejector. The filaments are then collected on a moving net to form a nonwoven web, and the resulting nonwoven web is integrated by thermal bonding to obtain a nonwoven fabric.

[0084] Examples of the thermal bonding method include a thermal embossing roll, in which each of a pair of upper and lower rolls has an engraved (uneven) surface, a thermal embossing roll consisting of a combination of a roll with one flat (smooth) surface and a roll with an engraved (uneven) surface, and a thermal calender roll consisting of a combination of a pair of upper and lower flat (smooth) rolls. Alternatively, ultrasonic fusion may be used.

[0085] Among these, from the viewpoints of strength and abrasion resistance, thermal bonding using an embossed roll is preferably employed. Also, from the viewpoint of reducing the application of pressure to the entire surface, it is preferable to use a roll with engraved (concave and concave portions) on either the top or bottom.

[0086] The shapes of the engravings on the hot embossing rolls can be round, oval, square, rectangular, flat, etc. Shapes such as rectangular, rhombus, regular hexagon and regular octagon can be used.

[0087] The surface temperature of the hot embossing roll may be preferably −50 to −5° C. relative to the melting point of the resin composition. By setting the surface temperature of the hot embossing roll to be preferably −50° C. or higher, more preferably −40° C. or higher, and even more preferably −30° C. or higher relative to the melting point of the resin composition, sufficient thermal adhesion can be achieved, strength can be ensured, and the generation of fluff can be easily suppressed.

[0088] Furthermore, by setting the surface temperature of the hot embossing roll to be −5° C. or lower than the melting point of the resin composition, peeling of the resins due to melting of the fibers can be easily prevented.

[0089] The linear pressure of the hot embossing roll during thermal bonding can preferably be 5 to 50 kgf / cm. By setting the linear pressure to preferably 5 kgf / cm or more, more preferably 10 kgf / cm or more, and even more preferably 15 kgf / cm or more, sufficient thermal bonding can be achieved. On the other hand, by setting the linear pressure to preferably 50 kgf / cm or less, more preferably 40 kgf / cm or less, and even more preferably 30 kgf / cm or less, excessive stress from the roll can be prevented, thereby maintaining bulkiness. Nonwoven fabrics provided by the resin composition used in the present invention can be suitably used for covers, bags, various filters, wet sheets, masks, separators, containers, and packaging.

[0090] 3. Physical properties of the molded body

[0091] [Whitening phenomenon]

[0092] The target molded body is dried for 16 hours in an oven set at 103°C. After 16 hours, the molded body is removed and allowed to stand at room temperature for at least 2 hours. After standing at room temperature, an impact test is performed using the Dart Impact A method in accordance with JIS K7124-1. The whitening phenomenon is evaluated when, during the impact test, the bullet impacts the molded body, whitening occurs at the impact point, and the maximum mass of the bullet exceeds 200g, preferably exceeds 220g, more preferably exceeds 240g, even more preferably exceeds 250g, and even more preferably exceeds 275g.

[0093] Figures 1(A) and (B) are photographs of the testing equipment used for the dart impact test. Figure 1(A) is a photograph of the testing equipment itself. Figure 1(B) is a photograph of the dart (warhead) dropped from the testing equipment. The following explains the testing method for the whitening phenomenon of molded bodies using these figures. First, a test specimen (170 mm wide x 170 mm long x 0.5 mm thick) is clamped between the upper and lower test specimen clamps 5 and 6 of the testing equipment shown in Figure 1(A), and the specimen is clamped and fixed using the clamping cylinder 7. The electromagnet 2 is energized, and the tip 8 of the iron dart shaft shown in Figure 1(B) is inserted into the electromagnet 2, fixing the specified dart 12 vertically. The test height (the vertical distance from the surface of the fixed specimen to the bottom of the tip of the dart 12) is adjusted to 0.66 m ± 0.01 m (Method A). A spare specimen is fixed between the upper and lower test specimen clamps 5 and 6. No weight is added to the dart 12. Turn off the power to the electromagnet 2, release the dart 12 from the dart release device 3, and observe the position where the dart 12 impacts the test specimen. After the dart 12 bounces off the surface of the test specimen, grab it by hand. If necessary, perform another preliminary test and adjust the position of the electromagnet 2 so that the dart 12 reproducibly impacts the center of the test specimen fixing part. Next, select a bullet mass close to the mass at which the expected whitening phenomenon occurs. Place the required number of weights 11 on the dart shaft 9 and securely fasten the weights 11 with the weight holder 10. Place the first test specimen on the lower test specimen clamp 6, ensuring that it is uniformly flat, has no creases, and covers the entire gasket. Secure it with the upper test specimen clamp 5. Turn on the power to the electromagnet 2, and secure the dart 12 in place. Turn off the power to the electromagnet 2, release the dart 12, and allow it to fall freely. If the dart 12 bounces off the surface of the test piece, the bouncing dart 12 is grabbed by hand to prevent further impact on the test piece and to prevent damage to the hemispherical contact surface of the dart 12. After the dart 12 falls, the test piece is left for 10 minutes, and the impact point of the test piece with the dart 12 is visually inspected to check for whitening. Add weights 11 to increase the mass of the dart 12 until whitening is confirmed at the impact point.

[0094] The criteria for determining the bleaching phenomenon are as shown in Table 1 below. [Table 1]

[0095] If no bleaching occurs, add weights to increase the warhead mass, and the maximum warhead mass is the mass just before the evaluation becomes ×.

[0096] [Tensile properties]

[0097] The molded article of the present invention has a modulus of elasticity of preferably 0.2 GPa or more, more preferably 0.3 GPa or more, and even more preferably 0.4 GPa or more. The molded article of the present invention has a breaking elongation of preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more. The molded article of the present invention has a maximum stress of preferably 10 N or more, more preferably 12 N or more, and even more preferably 14 N or more. These tensile properties are measured in accordance with JIS K 7161.

[0098] 4.Method for producing resin composition

[0099] [One embodiment of the method for producing a resin composition]

[0100] One embodiment of a method for producing a resin composition used in the present invention includes a first mixing step of mixing starch with a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, a plasticized starch preparation step of heating the mixture obtained in the first mixing step to plasticize the starch and prepare plasticized starch, and a second mixing step of mixing the plasticized starch with a thermoplastic resin to obtain a resin composition. According to one embodiment of the method for producing a resin composition used in the present invention, the resin composition described above in "1. Resin composition" can be produced.

[0101] Each step of the manufacturing method will be described below.

[0102] (1) First mixing process

[0103] In the first mixing step, starch is mixed with a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature. A sugar may also be added in this step. The starch and the polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature are as described above in "1. Resin composition," and this description also applies to the present production method.

[0104] In the first mixing step, the polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature may be mixed with the starch in an amount of preferably 5 to 40 parts by mass, more preferably 10 to 40 parts by mass, and even more preferably 20 to 40 parts by mass, per 100 parts by mass of the starch. The polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature may contain at least one polyhydric alcohol. Examples of such polyhydric alcohols include one or a combination of two or more selected from ethylene glycol, propylene glycol, and glycerin, and preferably ethylene glycol and propylene glycol.

[0105] The polyhydric alcohol more preferably contains glycerin and / or ethylene glycol. In the first mixing step, glycerin and ethylene glycol may be used, for example, at a mass ratio of glycerin to ethylene glycol of preferably 1:8 to 0.5:1, more preferably 1:4 to 1:1, and even more preferably 1:3 to 1:1. The polyhydric alcohol more preferably contains glycerin and / or propylene glycol. In the first mixing step, glycerin and propylene glycol may be used, at a mass ratio of glycerin to propylene glycol of preferably 1:8 to 0.5:1, more preferably 1:4 to 1:1, and even more preferably 1:3 to 1:1. The polyhydric alcohol may consist solely of glycerin. Furthermore, the polyhydric alcohol may be solely ethylene glycol or solely propylene glycol, without containing glycerin. In order to prevent bleeding, when only glycerin is used, the glycerin is mixed with the starch in an amount of preferably 40 parts by mass or less, more preferably 38 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of the starch.

[0106] When the amount of glycerin used as the polyhydric alcohol is 25 parts by weight or less, an organic acid may be preferably contained in order to reduce the size of the starch granules in the resin composition. Examples of such organic acids include succinic acid, malic acid, maleic acid, tartaric acid, adipic acid, gluconic acid, lactic acid, etc., and their anhydrides. From the viewpoints of preventing discoloration and balancing cost and effectiveness, succinic acid, malic acid, tartaric acid, maleic acid, etc. are preferred, with succinic acid and tartaric acid being more preferred. The organic acid is mixed with the starch in an amount of preferably 0.1 to 5 parts by weight, more preferably 0.3 to 4 parts by weight, and even more preferably 0.5 to 3 parts by weight, per 100 parts by weight of the starch.

[0107] The starch used in the first mixing step may be an underground starch or a ground starch, for example, corn starch or tapioca starch. In the present invention, an underground starch is preferably used. By producing a resin composition using an underground starch, the odor of the resin composition can be further reduced. The starch used in the first mixing step may be a modified starch (i.e., a modified starch).

[0108] The starch used in the first mixing step may preferably contain equilibrium moisture. The amount of equilibrium moisture may be, for example, preferably 10% to 15% by mass, more preferably 10% to 14% by mass, even more preferably 10% to 13% by mass, and even more preferably 11% to 13% by mass, based on the mass of the starch. It is preferable to use starch or modified starch containing equilibrium moisture within the above ranges in order to produce the plasticized starch material according to the present invention. If starch that does not contain equilibrium moisture is used, the starch may not be plasticized.

[0109] In the first mixing step, the sugars can be mixed with the starch in an amount of preferably 2.0 to 4.0 parts by mass, more preferably 2.5 to 3.5 parts by mass, and even more preferably 2.8 to 3.2 parts by mass, per 100 parts by mass of the starch.

[0110] The first mixing step may be carried out using, for example, a stirrer. A commercially available device may be used as the stirrer. The first pre-mixing step is preferably carried out at room temperature. By carrying out the first mixing step at room temperature and then carrying out the following plasticized starch preparation step, it is possible to suppress the generation of coloring and / or odor due to heating of starch.

[0111] The starch may, for example, preferably account for 40% by mass to 85% by mass, more preferably 45% by mass to 80% by mass, and even more preferably 50% by mass to 75% by mass of the total amount of raw materials used to produce the plasticized starch.

[0112] (2) Plasticized starch preparation process

[0113] The plasticized starch preparation step includes heating the mixture obtained in the first mixing step in an extruder. The starch is plasticized by the heating to obtain plasticized starch. The heating is preferably carried out at a temperature of 100°C to 150°C, more preferably 100°C to 140°C, and even more preferably 100°C to 130°C. The extruder may be, for example, a twin-screw extruder or a single-screw extruder, and commercially available extruders may be used. The plasticized starch extruded from the extruder may have, for example, a cylindrical shape (strand) or a pellet shape.

[0114] (3) Second mixing step

[0115] In the second mixing step, the plasticized starch prepared in the plasticized starch preparation step is mixed with a thermoplastic resin. A resin composition is produced by this mixing. The mixing may be performed using, for example, an extruder, preferably a twin-screw extruder. In this mixing step, a compatibilizer may be mixed in addition to the plasticized starch and the thermoplastic resin. The compatibilizer is as described above in "1. Resin composition," and therefore, its description will be omitted.

[0116] In the second mixing step, the components to be mixed (e.g., the plasticized starch, the thermoplastic resin, and optionally the compatibilizer) are heated. The heating is carried out so as to melt the thermoplastic resin, and may be carried out at a temperature of preferably 100°C to 200°C, more preferably 100°C to 190°C, and even more preferably 100°C to 180°C. The components to be mixed may be heated, for example, to a temperature at which the thermoplastic resin melts. The temperature may be appropriately selected by a person skilled in the art depending on the type of thermoplastic resin.

[0117] 5. Manufacturing method of molded body

[0118] [One embodiment of a method for producing a molded body]

[0119] The molded article of the present invention is obtained by molding the resin composition obtained in the mixing step in the method for producing a resin composition. A molded article having a desired shape is produced by this molding. This molding can be, for example, inflation molding or T-die molding. A molded article molded into a film or sheet shape can be produced by such a molding method. The molding temperature can be appropriately selected by those skilled in the art depending on the type of thermoplastic resin. For example, when the thermoplastic resin is polyethylene, the temperature can be 160°C to 200°C. For example, when the thermoplastic resin is polypropylene, the temperature can be 160°C to 200°C.

[0120] Furthermore, the resulting film or sheet-shaped article may be stretched.

[0121] [Another embodiment of the method for producing a resin composition]

[0122] Another embodiment of the method for producing a resin composition according to the present invention includes a mixing step of mixing starch, a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, a sugar, and a thermoplastic resin, and a heating step of plasticizing the starch by heating the mixture obtained in the mixing step. According to another embodiment of the production method of the present invention, the resin composition of the present invention described above in "1. Resin composition" can be produced.

[0123] In another embodiment, unlike the above-described manufacturing method, the raw ingredients are directly mixed together without first preparing a plasticized starch.

[0124] Each step of the manufacturing method will be described below.

[0125] (1)Mixing process

[0126] In the mixing step, starch, a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, a saccharide, and a thermoplastic resin are mixed together. The starch, the polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, the saccharide, and the thermoplastic resin are as explained above in "1. Resin composition," and this explanation also applies to the present production method.

[0127] In the mixing step, the polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature is mixed with the starch in an amount of preferably 5 to 40 parts by mass, more preferably 10 to 40 parts by mass, and even more preferably 20 to 40 parts by mass, per 100 parts by mass of the starch.

[0128] The sugar used in the mixing step can be mixed with the starch in an amount of preferably 2.0 to 4.0 parts by mass, more preferably 2.5 to 3.5 parts by mass, and even more preferably 2.8 to 3.2 parts by mass, per 100 parts by mass of the starch.

[0129] The thermoplastic resin used in the mixing step is mixed with the starch in an amount of preferably 10 to 900 parts by mass, more preferably 10 to 800 parts by mass, and even more preferably 15 to 800 parts by mass, per 100 parts by mass of the starch.

[0130] (2)Heating process

[0131] In the heating step, the mixture obtained in the mixing step is heated. The heating can be carried out so as to melt the thermoplastic resin. The components to be mixed may be heated, for example, to a temperature at which the thermoplastic resin melts. The temperature may be appropriately selected by those skilled in the art depending on the type of thermoplastic resin. For example, when the thermoplastic resin is polyethylene, the temperature may be 100°C to 170°C. For example, when the thermoplastic resin is polypropylene, the temperature may be 150°C to 200°C. The particle size of the starch granules contained in the resin composition produced by the mixing step and the heating step is 2 μm or less. Furthermore, the obtained resin composition can be molded by the method described above in "5. Method for producing molded article" to obtain a molded article. [Example]

[0132] The present invention will be described in more detail below with reference to examples. Note that the examples described below are representative examples of the present invention, and the scope of the present invention is not limited to these examples. The evaluation methods and evaluation criteria used in the examples are as follows:

[0133] (1) Whitening phenomenon

[0134] The whitening phenomenon of the test specimens was evaluated by the method described above in "3. Physical properties of molded body."

[0135] Test Example 1: Production and molding of resin composition (example of film or sheet)

[0136] Example 1

[0137] As the plasticized starch material, 67 parts by mass of corn starch (Showa Sangyo Co., Ltd.), 12 parts by mass of glycerin, 11 parts by mass of ethylene glycol, and 3 parts by mass of trehalose (Hayashibara Co., Ltd.) as a sugar were prepared. These four components were mixed in a mixer. The mixing was carried out at room temperature. The glycerin, ethylene glycol, and sugar were mixed in advance before being added to the mixer.

[0138] The mixture obtained by this mixing was a powder mixture.

[0139] The mixture obtained by the above mixing was fed into a twin-screw extruder (PCM30, Ikegai Corporation), and the mixture was subjected to a kneading treatment.

[0140] The cylinder temperature during the kneading process was 110°C. During the kneading process, suction was applied through a vent. After the kneading process, the mixture was extruded through the die of the extruder, and an elongated, approximately cylindrical plasticized starch (masterbatch) was obtained.

[0141] 63 parts by mass of the plasticized starch, 16 parts by mass of polypropylene (trade name: FH1016, manufactured by Sumitomo Chemical Co., Ltd.), 15 parts by mass of polypropylene (trade name: Qualia, manufactured by SunAllomer Co., Ltd.), 3.0 parts by mass of modified ethylene copolymer (N525, manufactured by DuPont), and 3.0 parts by mass of metallocene plastomer (Kernel, manufactured by Japan Polyethylene Co., Ltd.) were fed into a twin-screw extruder (PCM30, manufactured by Ikegai Corporation), and these components were subjected to a kneading treatment. The screw temperature during the kneading treatment was 170°C, and the resin pressure was 4.4 MPa. During the kneading treatment, suction was performed through a vent. A resin composition (hereinafter also referred to as "the resin composition of Example 1") was obtained by the kneading treatment.

[0142] The resin composition of Example 1 was supplied to a twin-screw extruder (PCM30, Ikegai Corporation) and then molded into a sheet. The molding was carried out at 180 to 200° C. A sheet having a thickness of 0.5 mm was obtained by the molding.

[0143] The whitening phenomenon of the sheet was evaluated according to the above method. The maximum mass of the warhead in the dart test was 275g. Figure 2 shows a photograph of the impact point of the sheet with the warhead when the warhead mass was 275g. As shown in Figure 2, no whitening phenomenon was observed.

[0144] (Comparative Example 1)

[0145] A resin composition (hereinafter also referred to as "resin composition of Comparative Example 1") was obtained in the same manner as in Example 1, except that no plasticized starch was added, and instead 53 parts by mass of corn starch (Showa Sangyo Co., Ltd.), 16 parts by mass of polypropylene (trade name: FH1016, manufactured by Sumitomo Chemical Co., Ltd.), 15 parts by mass of polypropylene (trade name: Qualia, manufactured by SunAllomer Co., Ltd.), 3.0 parts by mass of modified ethylene copolymer (N525, manufactured by DuPont), and 3.0 parts by mass of metallocene plastomer (Kernel, manufactured by Japan Polyethylene Corporation) were added.

[0146] The resin composition of Comparative Example 1 was molded in the same manner as in Example 1 to obtain a sheet having a thickness of 0.5 mm.

[0147] The whitening phenomenon of the obtained sheet was evaluated in the same manner as in Example 1. The maximum mass of the warhead in the dart test was 35 g. Figure 3 shows a photograph of the impact point of the sheet with the warhead when the warhead mass was 35 g. As shown in Figure 3, the whitening phenomenon was confirmed.

[0148] (Comparative Example 2)

[0149] As the plasticized starch material, 67 parts by mass of corn starch (Showa Sangyo Co., Ltd.), 12 parts by mass of glycerin, 11 parts by mass of ethylene glycol, and 0.1 parts by mass of maleic anhydride (Nippon Shokubai Co., Ltd.) were prepared. These four components were mixed in a mixer. The mixing was carried out at room temperature. The glycerin, ethylene glycol, and acid were premixed before being added to the mixer.

[0150] The mixture obtained by this mixing was used to obtain a plasticized starch (masterbatch) in the same manner as in Example 1.

[0151] 63 parts by mass of the plasticized starch, 16 parts by mass of polypropylene (trade name: FH1016, manufactured by Sumitomo Chemical Co., Ltd.), 15 parts by mass of polypropylene (trade name: Qualia, manufactured by SunAllomer Co., Ltd.), 3.0 parts by mass of modified ethylene copolymer (N525, manufactured by DuPont), and 3.0 parts by mass of metallocene plastomer (Kernel, manufactured by Japan Polyethylene Co., Ltd.) were fed into a twin-screw extruder (PCM30, manufactured by Ikegai Corporation), and these components were subjected to a kneading treatment. The screw temperature during the kneading treatment was 180°C to 200°C, and the resin pressure was 4.4 MPa. Suction was performed through a vent during the kneading treatment. A resin composition (hereinafter also referred to as the "resin composition of Comparative Example 2") was obtained by the kneading treatment.

[0152] The resin composition of Comparative Example 2 was molded in the same manner as in Example 1 to obtain a sheet having a thickness of 0.5 mm.

[0153] The whitening phenomenon of the obtained sheet was evaluated in the same manner as in Example 1. The maximum mass of the bullet in the dart test was 180 g.

[0154] (Summary of evaluation results)

[0155] Example 1 contained sugars and the maximum mass of the bullet exceeded 275 g. On the other hand, Comparative Examples 1 and 2, which did not contain sugars, had a maximum mass of less than 200 g, and were prone to whitening and had poor transparency.

Claims

1. A molded article molded from a resin composition containing plasticized starch and a thermoplastic resin, the plasticized starch comprises a starch and a polar organic compound capable of gelatinizing or plasticizing the starch at a temperature higher than room temperature; The molded body is left to stand in an environment at a temperature of 103°C for 16 hours, and then subjected to an impact test using the Dart Impact A method in accordance with JIS K7124-1. When the molded body is hit by a warhead, whitening occurs at the impact point of the molded body, and the maximum mass of the warhead exceeds 200g.

2. The molded article according to claim 1 , further comprising a sugar.

3. The molded article according to claim 1 , wherein the starch is tapioca starch or corn starch.

4. The molded article according to claim 1 , wherein the polar organic compound capable of gelatinizing or plasticizing the starch at a temperature higher than room temperature includes at least one compound selected from polyhydric alcohols.

5. 2. The molded article according to claim 1, wherein the saccharide is at least one selected from the group consisting of trehalose, erythritol, mannitol, xylitol, maltitol, sorbitol, and maltotriose.

6. The molded article according to claim 1 , wherein the polyhydric alcohol is glycerin or glycol.

7. The molded article according to claim 6, wherein the glycerin content is 0% by mass or more and 10% by mass or less.

8. The molded article according to claim 6, wherein the polyhydric alcohol is at least one of ethylene glycol and propylene glycol.

9. The molded article according to claim 1 , which is molded into the shape of a film or sheet.

10. The molded article according to claim 1 , which is molded into the shape of a film or sheet, and the surface of the film or sheet is covered with a membrane to form a laminate.

Images