Resin molded product and method for manufacturing resin molded product

Abstract

To provide a bioplastic-containing resin molded article which can be manufactured at low cost.SOLUTION: A resin molded article includes a first phase containing a first thermoplastic resin as a main component, a second phase containing thermoplastic starch, and a third phase which includes the second phase and contains a second thermoplastic resin as a main component.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a resin molded product and a method for manufacturing a resin molded product. [Background technology]

[0002] Plastics (resin materials) are used in a wide range of applications. In recent years, bioplastics (a general term for plastics made from biomass and biodegradable plastics) have been developed to reduce the impact of plastic waste on the environment.

[0003] For example, Patent Document 1 describes a resin film formed using a resin composition containing at least four components in a predetermined weight ratio: a biodegradable polylactic acid resin, an aliphatic polyester resin, starch, and a plasticizer that plasticizes the starch. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-167370 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable to use bioplastics to produce resin molded products other than films. Furthermore, since bioplastics are generally expensive, it is desirable to produce bioplastic molded products at lower cost.

[0006] Therefore, the present invention provides a bioplastic-containing resin molded product that can be produced at low cost, and a method for producing the same. [Means for solving the problem]

[0007] According to a first aspect of the present invention, a first phase comprising a first thermoplastic resin as a major component; a second phase comprising thermoplastic starch; a third phase containing the second phase and containing a second thermoplastic resin as a main component; A resin molded article is provided, comprising:

[0008] According to a second aspect of the present invention, a first phase comprising a first thermoplastic resin as a major component; a second phase comprising thermoplastic starch as a major component; A resin molded article is provided, comprising:

[0009] According to a third aspect of the present invention, A method for producing a resin molded product, comprising: performing injection molding using pellets comprising thermoplastic starch; The resin molded product is a first phase comprising a first thermoplastic resin as a major component; a second phase comprising the thermoplastic starch as a major component; A method is provided, comprising: [Effects of the Invention]

[0010] The resin molded product of the present disclosure can be produced at low cost. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of an example of an injection molding apparatus used to manufacture a resin molded product according to an embodiment. [Figure 2] FIG. 2 is a scanning electron microscope (SEM) image of a cross section of the resin molded product of Reference Example 4. [Figure 3] FIG. 3 is a cross-sectional SEM image of the resin molded product of Comparative Example 2. [Figure 4] FIG. 4 is a cross-sectional SEM image of the resin molded product of Example 6. [Figure 5] FIG. 5 is a graph showing the tensile strength of the resin molded articles of Reference Example 4, Example 6, and Comparative Examples 1 and 2. [Figure 6]FIG. 6 is a graph showing the bending strength of the resin molded articles of Reference Example 4, Example 6, and Comparative Examples 1 and 2. [Figure 7] FIG. 7 is a graph showing the impact strength of the resin molded articles of Reference Example 4, Examples 2, 6, and 7, and Comparative Examples 1 to 4. [Figure 8] FIG. 8 is a graph showing the impact strength of the resin molded products of Examples 2 to 7 and Comparative Examples 3 and 4, and showing the relationship between the ratio of the TPS content to the PBS content and the impact strength. [Figure 9] FIG. 9 is a photograph showing the appearance of the resin molded product of Example 6. [Figure 10] FIG. 10 is a photograph showing the appearance of the resin molded product of Example 8. [Figure 11] FIG. 11 is a photograph showing the appearance of the resin molded articles of Examples 9 to 11. [Figure 12] FIG. 12 is a photograph showing the appearance of the resin molded articles of Examples 12 to 14. [Figure 13] FIG. 13 is a photograph showing the appearance of the resin molded articles of Reference Examples 1 to 3. [Figure 14] FIG. 14 is a cross-sectional SEM image of the resin molded product of Comparative Example 4. [Figure 15] FIG. 15 is a graph showing the impact strength of the resin molded articles of Examples 9 to 11. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments will be described with reference to the drawings as appropriate. In the drawings referred to in the following description, identical components or components having similar functions are designated by the same reference numerals, and repeated description may be omitted. Furthermore, the dimensional ratios of the drawings may differ from the actual ratios for convenience of explanation, and some components may be omitted from the drawings. In this application, a numerical range expressed using the symbol "to" includes the numerical values ​​before and after the symbol "to" as the lower and upper limits, respectively. Note that the present invention is not limited to the following embodiments, and various design modifications may be made without departing from the spirit of the present invention as set forth in the claims.

[0013] [First embodiment] The resin molded article according to the first embodiment comprises a first phase containing a first thermoplastic resin as a primary component, a second phase containing thermoplastic starch (hereinafter referred to as TPS), and a third phase containing the second thermoplastic resin as a primary component. The second phase is encapsulated within the third phase. Hereinafter, the second phase will be referred to as an embedded phase and the third phase as a coated phase, as appropriate. The first, second, and third phases constitute a microphase-separated structure. The first and third phases may form a microphase-separated structure such as an island-in-the-sea structure, a cylindrical structure, a bicontinuous structure, or a layered structure. For example, one of the first and third phases may be a matrix phase (continuous phase), and the other may be a dispersed phase. In particular, the first phase may be a matrix phase, and the third phase may be a dispersed phase. The second phase preferably contains TPS as a primary component, and more preferably consists of TPS. In this application, the term "comprises" means that additional components may be included, and encompasses "comprises as a primary component" and "consists of." "Containing as a main component" means that the content of the component in question is 50% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more of the total weight. "Consisting of" means that the product contains only the component listed, but does not exclude the inclusion of unavoidable impurities.

[0014] The TPS may comprise starch and a plasticizer. The TPS can be obtained by mixing starch and a plasticizer.

[0015] The starch may be derived from plants, for example, from grains such as corn, wheat, and rice; beans such as broad beans, mung beans, and adzuki beans; tubers such as potato, sweet potato, and tapioca; wild plants such as dogtooth violets, bracken, and kudzu; and palm trees such as sago palm.

[0016] Plasticizer can be a compound having a functional group, such as hydroxyl group, amino group, carboxyl group, that can form hydrogen bond with the functional group of starch.Examples of plasticizer include glycols such as glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, butylene glycol, polyglycerin, thiodiglycol, sugars such as glucose, fructose, sucrose, galactose, maltose, lactose, trehalose, sugar alcohols such as sorbitol, maltitol, xylitol, erythritol, mannitol, lactitol, sugar derivatives such as sucralose, hydroxy acids such as tartaric acid, polyvinyl alcohol, trehalose, polyhydroxy (meth) acrylate, polyhydric alcohols such as urea, thiourea, polyvalent amines such as hyaluronic acid, polyvinylpyrrolidone, and mixtures thereof.

[0017] TPS is derived from biomass, is biodegradable, and is inexpensive. Therefore, the resin molded product according to this embodiment can contribute to carbon neutrality, at least a portion of which is biodegradable, and can be produced at low cost. Furthermore, although TPS is generally a highly water-absorbent material, in the resin molded product according to this embodiment, the TPS is embedded in the second thermoplastic resin, so the resin molded product can have high moisture resistance.

[0018] Granular starch that has not been thermoplasticized may clog the screw during compounding or when used in an injection molding machine as described below, but pelletized TPS does not pose such a risk, and therefore the resin molded article according to this embodiment containing TPS can be produced by injection molding as described below.

[0019] The first thermoplastic resin and the second thermoplastic resin may each be, for example, polypropylene (PP), polyethylene (PE), polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS), polymethyl methacrylate (PMMA), polylactic acid (PLA), polybutylene succinate (PBS), hydroxybutyrate hydroxyhexanoate (PHBH), polyhydroxyalkanoic acid (PHA), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), or polyvinyl alcohol (PVA).

[0020] At least one of the first thermoplastic resin and the second thermoplastic resin may be biodegradable. This allows all or part of the resin molded product to be biodegradable. Examples of biodegradable resins include PLA, PBS, PHBH, PHA, PVA, PBSA, and PBAT. At least one of the first thermoplastic resin and the second thermoplastic resin may be a polyester such as PLA, PBS, PHBH, PHA, PBSA, and PBAT. At least one of the first thermoplastic resin and the second thermoplastic resin may be a biodegradable polyester.

[0021] At least one of the first thermoplastic resin and the second thermoplastic resin may be a mixture of a non-biodegradable thermoplastic resin and a biodegradation promoter. The biodegradation promoter may be, for example, a microorganism involved in biodegradation, an enzyme, a substance that attracts microorganisms, or a substance that promotes hydrolysis of the resin. This allows all or part of the resin molded article to be biodegradable.

[0022] At least one of the first thermoplastic resin and the second thermoplastic resin may be derived from biomass, thereby enhancing carbon neutrality. Examples of biomass-derived resins include biomass-derived PLA, PBS, PHBH, PHA, PE, PP, and PS.

[0023] The first thermoplastic resin and the second thermoplastic resin may each be a crystalline resin or an amorphous resin. When the first thermoplastic resin and the second thermoplastic resin are crystalline resins, it is preferable that both the first thermoplastic resin and the second thermoplastic resin have a melting point of 210°C or less. When the first thermoplastic resin and the second thermoplastic resin are amorphous resins, it is preferable that both the first thermoplastic resin and the second thermoplastic resin have a glass transition point of 150°C or less and exhibit a fluidity sufficient for molding at 210°C or less, i.e., a melt flow rate of 0.5 g / 10 min or more at 210°C or less. This makes it possible to produce molded resin products at molding temperatures of 210°C or less, thereby preventing or reducing discoloration of the molded resin products due to yellowing of the thermoplastic starch. In this application, the melting point refers to the temperature at the apex of the melting peak in the DSC curve obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012. In this application, the glass transition temperature refers to either the midpoint glass transition temperature (Tmg), the extrapolated glass transition onset temperature (Tig), or the extrapolated glass transition finish temperature (Teg) measured in accordance with JIS K7121:2012. In this application, the melt flow rate is the amount of resin extruded from a die per 10 minutes measured in accordance with JIS K7210, JIS K7390, ISO 1133, or ASTM D1238.

[0024] The elastic modulus of the second thermoplastic resin is preferably smaller than the elastic modulus of the first thermoplastic resin, which allows the resin molded product to have high impact strength.

[0025] The third phase may further comprise one or more thermoplastic resins in addition to the second thermoplastic resin. Examples of the one or more thermoplastic resins are the same as the examples of the first thermoplastic resin and the second thermoplastic resin described above.

[0026] The solubility parameter value (SP value) sp1 of the first thermoplastic resin, the SP value sp2 of the second thermoplastic resin, and the SP value (sp3) of the TPS may satisfy sp1 < sp2 < sp3 or sp3 < sp2 < sp1. Thereby, it becomes possible to easily form a structure including a coating phase and an embedding phase. Also, since the first phase and the third phase are mixed with good dispersibility with each other, the difference between sp1 and sp2 may be 1.0 (J / cm 3 ) 0.5 or less. In addition or alternatively, the resin molded article may contain a compatibilizer. Examples of the compatibilizer include compounds having a carbodiimide group (such as "Carbodilite" manufactured by Nisshinbo Chemical Inc.).

[0027] For example, when the first thermoplastic resin is PLA and the second thermoplastic resin is PBS, PBSA, or PBAT, sp1, sp2, and sp3 satisfy the above conditions.

[0028] Note that the SP value in the present invention may be determined by a method of estimating from the molecular structure of the compound or a method of estimating from the physical property values of the compound. Examples of the method of estimating from the molecular structure of the compound include the calculation method of Small, the calculation method of Rheineck and Lin, the calculation method of Krevelen and Hoftyzer, the calculation method of Fedors (R.F. Fedors, Polym. Eng. Sci., 14(2), 147(1974)), the calculation method of Hansen (C.M. Hansen, J. Paint Technol., 39., (505), 104(1967)), and the calculation method of Hoy (H.L. Hoy, J. Paint Technol., 42(540), 76(1970)). Examples of the method of estimating from the physical property values of the compound include the method of obtaining from the latent heat of vaporization, the method according to Hildebrand Rule (J. Hildebrand and R. Scott, "The Solubility of Non-electrolytes", 3rd Ed., pp. 119-133, Reinhold Publishing Corp. (1949)), the method by surface tension, the method of obtaining from the value of solubility, the method of obtaining from the refractive index, and the method of obtaining from other physical property values.

[0029] The molded resin product according to this embodiment may contain TPS in an amount greater than 0 weight percent and less than 50 weight percent, preferably 5 to 40 weight percent, and more preferably 8 to 40 weight percent, based on the total weight of the first thermoplastic resin, the second thermoplastic resin, and the TPS. The molded resin product according to this embodiment may also contain the second thermoplastic resin and the TPS in a weight ratio greater than 0 and less than 3.33, preferably 0.17 to 2.3, and more preferably 0.18 to 2.22. This amount of the first thermoplastic resin, the second thermoplastic resin, and the TPS makes it possible to easily form a structure including a coating phase and an embedded phase.

[0030] The resin molded article according to this embodiment may further contain an additive. The additive is preferably a material that does not promote yellowing of the TPS or react with the TPS to form a gel. The additive is preferably a material that is not derived from petroleum, such as an inorganic substance.

[0031] An example of an additive is a colorant. For example, inorganic particles such as calcium carbonate and titanium oxide can be used as a colorant to whiten the resin molded product. The inorganic particles may have a particle size of 1 μm or less, which can increase the crystallization rate of the first thermoplastic resin (e.g., PLA).

[0032] Another example of an additive is an antibacterial agent. A resin molded product containing an antibacterial agent can be used in food-related applications (e.g., food containers) because it prevents or reduces microbial contamination in the environment in which it is used. Examples of antibacterial agents suitable for food-related applications include antibacterial agents primarily composed of silver-based inorganic compounds or zinc oxide-based compounds. The content of the antibacterial agent may be appropriately determined depending on the mechanical properties of the resin molded product, and may be, for example, 0.1 to 1.0 parts by weight per 100 parts by weight of the total weight of the first thermoplastic resin, the second thermoplastic resin, and the TPS.

[0033] Further examples of additives include fillers, heat stabilizers, lubricants, mold release agents, nucleating agents, photodegradation agents, biodegradation accelerators, antioxidants, ultraviolet stabilizers, antistatic agents, flame retardants, and deodorizing agents.

[0034] The resin molded product according to this embodiment has a resistance of 3 kJ / m 2 More than 4kJ / m, preferably 2 The resin molded article according to this embodiment may have an impact strength of 30 MPa or more, preferably 40 MPa or more, and a flexural strength of 40 MPa or more, preferably 50 MPa or more. The resin molded article having such excellent mechanical properties can be used in a variety of applications as an interchangeable material for PP, ABS resin, etc.

[0035] The resin molded product according to this embodiment may have any shape and dimensions. For example, the resin molded product according to this embodiment may have a thickness of 0.5 mm or more, and such a resin molded product can be suitably produced by the injection molding process described below. The injection molded product can have any shape, including complex shapes. Furthermore, the resin molded product according to this embodiment may be in the form of a film with a thickness of less than 0.5 mm, and such a resin molded product can be suitably produced by an inflation molding process, an extrusion molding process, a compression molding process, or the like.

[0036] A method for producing a resin molded product according to this embodiment will be described. The method for producing a resin molded product includes injection molding using pellets containing TPS. As an example of the production method, a method for producing a resin molded product using an injection molding apparatus shown in FIG. 1 will be described below.

[0037] First, raw material pellets 104 are supplied to a hopper 103 of an injection molding apparatus 100. The raw material pellets 104 include pellets containing TPS. The pellets containing TPS may be pellets containing TPS as a main component, or may be compound pellets containing TPS and at least one of a first thermoplastic resin or a second thermoplastic resin. Pellets containing TPS as a main component can be produced by supplying starch and a plasticizer to an extrusion molding apparatus, mixing, extruding, and cutting. Commercially available TPS pellets can also be used. Compound pellets containing TPS and at least one of a first thermoplastic resin or a second thermoplastic resin can be produced by supplying TPS pellets and at least one of a first thermoplastic resin or a second thermoplastic resin to an extrusion molding apparatus, mixing, extruding, and cutting.

[0038] In addition to the pellets containing TPS, the raw material pellets 104 may further contain at least one of pellets of a first thermoplastic resin, pellets of a second thermoplastic resin, or compound pellets containing the first thermoplastic resin and the second thermoplastic resin. Furthermore, additives may be supplied to the hopper 103 as needed.

[0039] The screw 102 is retracted by the motor 101, and raw material pellets 104 are introduced from the hopper 103 into the cylinder 106. While the screw 102 is rotating, the raw material pellets 104 are heated by the heater 105 to melt the raw material pellets 104. The temperature (molding temperature) of the heater 105 is preferably 230°C or lower, and more preferably 210°C or lower. This can prevent or reduce thermal degradation and yellowing of the TPS. If necessary, a supercritical fluid such as nitrogen or carbon dioxide can be further introduced into the cylinder 106 and mixed with the melted raw material pellets 104. This facilitates the production of resin molded products with small thicknesses and resin molded products with complex shapes.

[0040] Next, the screw 102 is advanced by a motor 107, and the molten material in the cylinder 106 is injected into a mold 109 through a nozzle 108. After the mold 109 is filled with the molten material, more molten material is supplied to the mold 109 under a predetermined pressure to compensate for volume shrinkage due to subsequent solidification of the molten material.

[0041] By maintaining the mold 109 at a predetermined temperature, the molten material is cooled below the solidification temperature and solidified.

[0042] The mold clamping mechanism 111 is driven by the motor 110 to open the mold 109. Next, the ejector mechanism 113 is driven by the motor 112 to remove the solidified product (resin molded product) from the mold 109. Finally, the mold 109 is closed in preparation for the next injection molding. In this way, the resin molded product according to the first embodiment is manufactured.

[0043] [Second embodiment] The resin molded article according to the second embodiment includes a first phase containing a first thermoplastic resin as a main component and a second phase containing TPS as a main component. One of the first phase and the second phase is a matrix phase (continuous phase), and the other is a dispersed phase. The resin molded article according to the second embodiment may further include an additive.

[0044] The resin molded article according to the second embodiment contains TPS, which is biomass-derived, biodegradable, and inexpensive, and therefore the resin molded article can contribute to carbon neutrality, at least a portion of which is biodegradable, and can be produced at low cost.

[0045] The first thermoplastic resin, TPS, and additive may be the same as those used in the first embodiment, and therefore detailed description thereof will be omitted here. In particular, the first thermoplastic resin may be a polyolefin.

[0046] The resin molded product according to this embodiment may have any shape and size. For example, the resin molded product according to this embodiment may have a thickness of 0.5 mm or more, and such a resin molded product can be suitably manufactured by an injection molding process. The resin molded product according to this embodiment can be manufactured by a method similar to that of the first embodiment, except that the raw material pellets 104 do not contain the second thermoplastic resin. [Example]

[0047] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0048] (1) Preparation of resin molded products Comparative Example 1 PLA pellets ("L105" manufactured by TOTAL) were fed into an injection molding machine equipped with multiple heaters and injection molded to obtain a resin molded product. The heater temperatures were set to 180 to 200°C, with higher temperatures nearer the injection nozzle.

[0049] Comparative Example 2 The amounts of PLA pellets, PBS pellets ("FZ71PB" manufactured by Mitsubishi Chemical Corporation), and a compatibilizer ("Carbodilite" manufactured by Nisshinbo Chemical Inc.) listed in Table 1 were fed into an extruder and extrusion-molded at a temperature of 160 to 180°C to obtain compound pellets. The compound pellets were fed into an injection molding machine and injection-molded to obtain a resin molded product. The temperatures of the multiple heaters in the injection molding machine were set to 180 to 200°C, with higher temperatures being obtained closer to the injection nozzle.

[0050] Reference example 4, Example 2 ~7, and Comparative Examples 3 and 4 The amounts of PLA pellets, PBS pellets, TPS pellets, and Carbodilite listed in Table 1 were fed into an extruder and extrusion-molded at a temperature of 160 to 180°C to obtain compound pellets. The compound pellets were fed into an injection molding machine and injection-molded to obtain a resin molded product. The temperatures of the multiple heaters in the injection molding machine were set to 180 to 200°C, with higher temperatures being closer to the injection nozzle.

[0051] Example 8 A resin molded product was produced in the same manner as in Example 6, except that titanium oxide in the amount shown in Table 1 was fed to the injection molding machine in addition to the compound pellets.

[0052] [Table 1]

[0053] Examples 9 to 11 A resin molded product was produced in the same manner as in Example 6, except that the temperatures of the multiple heaters of the injection molding machine (molding temperatures) were set to the temperatures shown in Table 2.

[0054] [Table 2]

[0055] Examples 12 to 14 The amounts of PP pellets, TPS pellets, and compatibilizer (maleic anhydride-modified PP) listed in Table 3 were fed to an extruder and extrusion-molded at a temperature of 160 to 180°C to obtain compound pellets. The compound pellets were fed to an injection molding machine and injection-molded to obtain a resin molded product. The temperatures of the multiple heaters in the injection molding machine (molding temperatures) were set to the temperatures listed in Table 3.

[0056] [Table 3]

[0057] Reference examples 1 and 2 The PLA pellets were fed into an injection molding machine and injection molding was performed to obtain a resin molded product. The temperature of the multiple heaters in the injection molding machine was set to 180 to 200°C, with the temperature higher the closer to the injection nozzle. The injection molding pressure was low in Reference Example 1 and high in Reference Example 2.

[0058] Reference example 3 A resin molded product was produced in the same manner as in Reference Example 2, except that the molten PLA pellets were mixed with CO2 in a supercritical state and injection-molded in an injection molding machine.

[0059] (2) Structural observation Reference example 4 Scanning electron microscope (SEM) images of the cross sections of the resin molded products of Comparative Example 2, Example 6, and Comparative Example 4 are shown in Figures 2, 3, 4, and 14, respectively. Reference example 4 The molded resin product of Example 1 had a sea phase (continuous phase) containing PLA and an island phase (dispersed phase) containing TPS dispersed in the sea phase. As shown in Figure 3, the molded resin product of Comparative Example 2 had a sea phase containing PLA and an island phase containing PBS dispersed in the sea phase. As shown in Figure 4, the molded resin product of Example 6 had a sea phase containing PLA and an island phase dispersed in the sea phase, and the island phase had a coating phase containing PBS and a fine embedded phase containing TPS embedded in the coating phase. As shown in Figure 14, the molded resin product of Comparative Example 4 had a mottled dispersion of a phase containing PLA, a phase containing TPS, and a phase containing PBS.

[0060] (3) Mechanical property evaluation Reference example 4, implementation Example 6 The tensile strength of the resin molded articles of Comparative Examples 1 and 2 was measured in accordance with ISO 527. The results are shown in FIG. Reference example 4, implementation Example 6 Although the resin molded article of Example 1 had a lower tensile strength than the resin molded articles of Comparative Examples 1 and 2, both had a sufficiently high tensile strength of 40 MPa or more.

[0061] Reference example 4, implementation Example 6 The bending strength of the resin molded articles of Comparative Examples 1 and 2 was measured in accordance with ISO 178. The results are shown in FIG. Reference Example 4 and implementation Example 6 Although the resin molded article of Example 1 had a lower bending strength than the resin molded articles of Comparative Examples 1 and 2, both had a sufficiently high bending strength of 50 MPa or more.

[0062] Reference example 4, Example 2The impact strength of the resin molded articles of Examples 9 to 11 was measured in accordance with ISO 180. The results are shown in Figures 7 and 8. The impact strength of the resin molded articles of Examples 9 to 11 was also measured in accordance with ISO 180. The results are shown in Figure 15.

[0063] As shown in Figure 7, PLA and TPS Reference example 4 The resin molded articles of Examples 1, 2, 3, and 4, which contained PLA, PBS, and TPS and had a TPS content of 5 to 40 weight percent, exhibited impact strengths of 4 kJ / m 2 On the other hand, the resin molded products of Comparative Examples 3 and 4, in which the TPS content was 50 weight percent or more, exhibited significantly lower impact strength than the resin molded products of Examples 2, 6 and 7.

[0064] 8, the resin molded products of Examples 2 to 7, which contained PLA, PBS, and TPS and had a ratio (weight ratio) of the TPS content to the PBS content of 0.18 to 2.22, exhibited high impact strength. On the other hand, the resin molded products of Comparative Examples 3 and 4, which had a ratio (weight ratio) of the TPS content to the PBS content of 3.33 or more, exhibited significantly lower impact strength than the resin molded products of Examples 2, 6, and 7.

[0065] The resin molded articles of Examples 2 to 7 had high impact strength, likely due to the presence of a sea phase containing PLA, a coating phase containing PBS, and an island phase containing an embedded phase containing TPS, as shown in Figure 4. The resin molded articles of Comparative Examples 3 and 4, which had a TPS content of 50 weight percent or more and a ratio of the TPS content to the PBS content of 3.33 or more, did not contain a sufficient amount of PBS to coat the TPS, as shown in Figure 14. Therefore, a coating phase and an embedded phase were not formed, and the TPS phase became coarse and did not form a dispersed structure. As a result, it is likely that they exhibited significantly lower impact strength.

[0066] As shown in FIG. 15, the impact strength of the resin molded products of Examples 9 and 10 was 5 kJ / m 2 and 5.1 kJ / m 2The impact strength of the resin molded product of Example 11 was 4.2 kJ / m 2 It was.

[0067] (4) Appearance evaluation Photographs of the appearance of the molded resin products of Examples 6 and 8 are shown in Figures 9 and 10, respectively. The molded resin product of Example 6 was light brown, while the molded resin product of Example 8, to which titanium oxide was added, was white. Therefore, discoloration of the molded resin product caused by the addition of starch can be sufficiently suppressed by coloring it with titanium oxide.

[0068] Photographs of the appearance of the resin molded products of Examples 9 to 11 are shown in Figure 11. The resin molded products of Examples 9 and 10, which were molded at a temperature of 210°C or less, were white to light brown, while the resin molded product of Example 11, which was molded at a temperature of 230°C, was brown. From these appearance evaluation results and the impact strength measurement results of Examples 9 to 11 described above, it is believed that the resin molded products molded at 230°C suffered thermal degradation, and therefore molding at 210°C or less is considered preferable.

[0069] Photographs of the appearance of the resin molded products of Examples 12 to 14 are shown in Fig. 12. The resin molded products of Examples 12 and 13, which were molded at a temperature of 210°C or less, were white to light brown, but the resin molded product of Example 14, which was molded at a temperature of 230°C, was brown. Since the resin molded product molded at 230°C is thought to have undergone thermal degradation, molding at 210°C or less is considered preferable.

[0070] Photographs of the appearance of the resin molded products of Reference Examples 1 to 3 are shown in Fig. 13. In Reference Example 1, the resin did not fill all the way to the edge of the mold. In Reference Example 2, the injection pressure was increased, so the resin filled all the way to the edge of the mold, but unevenness (sink marks) occurred on the surface of the resin molded product. In Reference Example 3, the injection pressure was increased and a supercritical fluid was used, so the resin filled all the way to the edge of the mold, and no unevenness occurred on the surface of the resin molded product. [Explanation of symbols]

[0071] 100 injection molding device, 101, 107, 110, 112 motor, 102 screw, 103 hopper, 104 raw material pellets, 105 heater, 106 cylinder, 108 nozzle, 109 mold, 111 mold clamping mechanism, 113 ejector mechanism

Claims

1. a first phase comprising a first thermoplastic resin as a major component; a second phase comprising thermoplastic starch; a third phase containing the second phase and containing a second thermoplastic resin as a main component; A resin molded product having a microphase separation structure composed of the first thermoplastic resin is polylactic acid; the second thermoplastic resin is polybutylene succinate; In the resin molded product, the ratio of the content of the thermoplastic starch to the content of the second thermoplastic resin is within the range of 0.17 to 2.3 in weight ratio.

2. The resin molded article according to claim 1, which is an injection molded article.

3. The resin molded product according to claim 1 , wherein the second thermoplastic resin has a modulus of elasticity that is smaller than the modulus of elasticity of the first thermoplastic resin.

4. 2. The resin molded product according to claim 1, wherein the solubility parameter value sp1 of the first thermoplastic resin, the solubility parameter value sp2 of the second thermoplastic resin, and the solubility parameter value sp3 of the thermoplastic starch satisfy sp1 < sp2 < sp3 or sp3 < sp2 < sp1.

5. 2. The resin molded product according to claim 1, wherein the first thermoplastic resin and the second thermoplastic resin both have melting points of 210°C or less, or both have glass transition temperatures of 150°C or less and melt flow rates at 210°C or less of 0.5 g / 10 min or more.

6. 2. The resin molded article according to claim 1, wherein the resin molded article comprises the thermoplastic starch in an amount of less than 50 weight percent based on the total weight of the first thermoplastic resin, the second thermoplastic resin, and the thermoplastic starch.

7. The resin molded product according to claim 1 , further comprising an antibacterial agent containing a silver-based inorganic compound as a main component.

8. A method for producing a resin molded product, comprising: performing injection molding using pellets comprising thermoplastic starch; The resin molded product is a first phase comprising a first thermoplastic resin as a major component; a second phase comprising the thermoplastic starch as a major component; a third phase containing the second phase and containing a second thermoplastic resin as a main component; It has a microphase separation structure composed of the first thermoplastic resin is polylactic acid; the second thermoplastic resin is polybutylene succinate; The method, wherein in the molded resin product, the ratio of the content of the thermoplastic starch to the content of the second thermoplastic resin is within the range of 0.17 to 2.3 by weight.

9. 9. The method of claim 8, wherein the injection molding is performed using a supercritical fluid.

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