Starch-containing resin composition, pellets, flakes, resin molding, method of producing starch-containing resin composition, method of producing pellets or flakes, and method of producing resin molding

Abstract

To provide a starch-containing resin composition capable of stably forming strands.SOLUTION: The starch-containing resin composition of the present invention contains starch and a thermoplastic resin, and has a tensile modulus less than or equal to 2500 MPa after film formation. Pellets of the present invention contain the starch-containing resin composition of the present invention. Flakes of the present invention contain the starch-containing resin composition of the present invention. The method of producing the starch-containing resin composition of the present invention includes a mixing step in which raw materials including the starch and the thermoplastic resin are mixed.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a starch-containing resin composition, pellets, flakes, a resin molded product, a method for producing a starch-containing resin composition, a method for producing pellets or flakes, and a method for producing a resin molded product. [Background technology]

[0002] Recently, from the viewpoint of carbon circulation such as the use of renewable materials and reduction of carbon dioxide emissions, and from the viewpoint of protecting the global environment through the spread of biodegradable resins, there is a demand to switch from conventional petroleum-derived resins to biomass-derived resins. Against this background, a method of blending starch into resins has been developed (Patent Documents 1 and 2).

[0003] Here, it is difficult to handle powdered starch in existing resin processing or resin molding processes. Therefore, it is desirable to blend starch with a thermoplastic resin, mold it into pellets or flakes, and supply it in the form of a master batch. For example, a method of molding into pellets is to pull strands discharged from a twin-screw extruder with a pelletizer, cool them, and then cut them. For example, a method of molding into flakes is to cut strands discharged from a twin-screw extruder by hot cutting. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-026538 A [Patent Document 2] Patent No. 7121428 Summary of the Invention [Problem to be solved by the invention]

[0005] However, strands containing a high content of starch tend to become brittle, and it is difficult to stably obtain strands extruded from an extruder, for example.

[0006] Therefore, an object of the present invention is to provide a starch-containing resin composition which can stably obtain strands, a method for producing a starch-containing resin composition, pellets containing the starch-containing resin composition of the present invention, flakes containing the starch-containing resin composition of the present invention, a resin molding, a method for producing pellets or flakes, and a method for producing a resin molding. [Means for solving the problem]

[0007] In order to achieve the above object, the starch-containing resin composition of the present invention comprises: Starch and a thermoplastic resin, The tensile modulus of elasticity after film formation is 2500 MPa or less.

[0008] The pellets of the present invention comprise the starch-containing resin composition of the present invention.

[0009] The flakes of the present invention comprise the starch-containing resin composition of the present invention.

[0010] The molded resin article of the present invention contains the starch-containing resin composition of the present invention.

[0011] The method for producing the starch-containing resin composition of the present invention comprises the steps of: A mixing step of mixing a raw material containing the starch and the thermoplastic resin, The present invention relates to a method for producing the starch-containing resin composition.

[0012] The method for producing pellets or flakes of the present invention comprises the steps of: a strand forming step of extruding the starch-containing resin composition to form strands; and a strand cutting step of cutting the strands to form pellets or flakes, The starch-containing resin composition is the starch-containing resin composition of the present invention.

[0013] The method for producing a resin molded product of the present invention comprises the steps of: A resin molding process is included in which a raw material including pellets or flakes is resin molded to produce a resin molded product, The pellets are pellets of the present invention, The flakes are the flakes of the present invention. Effect of the Invention

[0014] According to the present invention, strands can be obtained stably. [Brief description of the drawings]

[0015] [Figure 1A] FIG. 1A is an electron microscope image showing a fracture cross section and the major axis of a starch grain of a starch-containing resin composition produced in an example. [Figure 1B] FIG. 1B is an electron microscope image showing the major axis of the starch granules used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Next, preferred embodiments of the present invention will be disclosed. However, the following embodiments disclose typical embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0017] In the present invention, unless otherwise specified, "mass %" and "weight %" may be read interchangeably, and "parts by mass" and "parts by weight" may be read interchangeably.

[0018] In the present invention, "starch is not substantially plasticized" means, for example, that the change in the properties of starch due to the plasticization of starch is kept within a range that allows strands with good physical properties to be obtained.

[0019] In the present invention, unless otherwise specified, the term "strand" refers to a general term for a starch-containing resin composition extruded from various extruders, and the shape such as length is not particularly limited. For example, it includes any shape extruded from various extruders, such as a long string-like one or a short plate-like one.

[0020] <Starch-containing resin composition> First, the starch-containing resin composition of the present invention will be described.

[0021] [Tensile modulus] The tensile modulus of the starch-containing resin composition of the present invention after the film molding is 2500 MPa or less. The lower limit of the tensile modulus is, for example, 500 MPa or more, 1000 MPa or more, or 1500 MPa or more, and the upper limit is, for example, 2400 MPa or less, 2200 MPa or less, or 2000 MPa or less. The tensile modulus can be measured by the measurement method described in the examples below. The tensile modulus can be adjusted, for example, by adjusting the compounding ratio of starch and thermoplastic resin, etc., described below, or the tensile modulus of thermoplastic resin, etc.

[0022] The film molding is carried out using a heat press at a temperature of 150°C to 200°C, a pressure of 0.6t to 0.9t, and a range of 1 to 10 minutes to mold a film having a thickness of 0.1 mm to 1.5 mm. The raw material to be molded may be sandwiched between iron plates or PET films and pressed to make it easier to remove the film. For example, molding is carried out under the conditions described in the examples below. The resin-containing composition to be molded is kneaded in a Banbury mixer at 150°C to 200°C and 20 to 40 rpm for 20 minutes in order to make the kneading state uniform and reduce the measurement deviation of the elastic modulus, and then used as the raw material for film molding.

[0023] When the tensile modulus of the starch-containing resin composition of the present invention after the film molding is 2500 MPa or less, a strand can be stably obtained. For example, when the strand discharged from the extruder in a long and stretched form is cut by cold cutting to obtain pellets, the frequency of breakage of the formed strand is reduced, and productivity is improved. In addition, when the strand discharged from the extruder is cut by hot cutting to obtain pellets or flakes, the strand is not brittle, so the amount of residue that is not pelletized or flakeized is reduced, and the yield is improved, and therefore productivity is also improved. In addition, a starch-containing resin composition that shows physical properties that are easily broken when a strand in a long and stretched form is produced is very brittle, so that there may be cases where subsequent processing or molding defects occur. Therefore, for example, the present invention is useful in a composition with a high starch content and in which it is desired not to substantially plasticize the starch.

[0024] [starch] The starch is not particularly limited, and examples thereof include unmodified starches obtained from corn, potato, sweet potato, tapioca, sago palm, rice, wheat, etc. That is, examples thereof include corn starch, waxy corn starch, high amylose corn starch, potato starch, sweet potato starch, tapioca starch, sago starch, rice starch, wheat starch, etc. In addition, examples thereof include processed starches obtained by etherifying or esterifying unmodified starch, or by subjecting the starch to crosslinking, oxidation, acid treatment, etc. The starch may be used alone or in combination of two or more kinds.

[0025] The starch is preferably, for example, corn starch or tapioca starch from the viewpoint of production cost, more preferably corn starch. From the viewpoint of dispersibility, the average particle size of the starch is preferably 25 μm or less, and from the viewpoint of the average particle size, unprocessed starch obtained from corn or tapioca, or processed starch made from corn or tapioca is preferable.

[0026] The content of the starch is not particularly limited, but for example, in consideration of improving the biomass ratio, it is 55% by weight or more, more preferably 60% by weight or more, and most preferably 65% ​​by weight or more, based on 100% by weight of the total weight of the starch-containing resin composition, and in consideration of dispersing the starch by mixing with a thermoplastic resin, it is 95% by weight or less, more preferably 90% by weight or less, even more preferably 80% by weight or less, and most preferably 75% by weight or less, based on 100% by weight of the total weight of the starch-containing resin composition, and the range is, for example, 55 to 95% by weight, more preferably 55 to 90% by weight, even more preferably 60 to 80% by weight, and most preferably 65 to 75% by weight. In the present invention, even if the starch content is as high as 55% by weight or more, the formed strand is unlikely to break, so long as the tensile modulus is 2500 MPa or less, the strand can be stably obtained.

[0027] The starch-containing resin composition of the present invention is, for example, a starch-containing resin composition having a structure in which starch granules are dispersed in a thermoplastic resin. For example, the starch particles (hereinafter sometimes referred to as "starch granules") can be adjusted to a certain size range by adjusting the moisture content of the starch, the moisture content of the entire starch-containing resin composition, and the amount of starch plasticizer to be described later, or by not using the starch plasticizer, as necessary. In other words, the starch can be substantially not plasticized.

[0028] Here, the strands containing a high amount of starch tend to be brittle, and for example, the strands may break during stranding, making it difficult to obtain strands stably. In order to solve this problem, for example, there is a method of adding a starch plasticizer (for example, glycerin, etc.) that plasticizes starch. On the other hand, it is known that when a starch plasticizer is used, the particle size of the starch added to the thermoplastic resin becomes smaller than the particle size of the raw starch granules. For example, Patent Document 1 discloses a form in which the average particle size is 1 μm or less. It is presumed that this is due to partial or total collapse of the starch granules due to plasticization. In other words, it is presumed that adjusting the particle size of the starch granules to a certain range of sizes leads to the starch not being substantially plasticized. However, this is merely a hypothesis, and the present invention is not limited thereto.

[0029] The average particle diameter of the starch granules is, for example, 3 μm or more. In view of the characteristic of not substantially plasticizing starch, it may be 5 μm or more, and more preferably 7 μm or more. The upper limit of the average particle diameter is not particularly limited, but is, for example, 25 μm or less, more preferably 20 μm or less, from the viewpoint of dispersibility. The average particle diameter of the starch granules can be, for example, observed using a scanning electron microscope (SEM), the magnification and field of view are adjusted so that there are 10 to 20 starch granules whose major diameters can be measured, and the average value of the major diameters of each starch granule measured from the obtained SEM image can be used as the average particle diameter. For example, when the form of the starch-containing resin composition is a pellet of the present invention described later, the measurement of the average particle diameter can basically be performed on one pellet taken out at random, but when the numerical value varies greatly for each pellet, the average value of 10 pellets taken at random can be used as the average particle diameter. Furthermore, when the above average particle diameter is satisfied at any one point in an SEM image captured at the above magnification and in the above field of view, it is deemed to satisfy the above average particle diameter in the present invention.

[0030] The water content in the starch is not particularly limited, but is preferably, for example, an amount that does not substantially plasticize the starch. The amount that does not substantially plasticize the starch is, for example, 0% by weight. In addition, when the starch contains water, the amount that does not substantially plasticize the starch should be, for example, a proportion that does not significantly change the properties of the starch, considering that water can plasticize the starch, and for example, the lower limit exceeds 0% by weight, and the upper limit is 15% by weight or less, preferably 12% by weight or less, more preferably 10% by weight or less, even more preferably 7% by weight or less, and most preferably 3% by weight or less, and the range is, for example, 0 to 15% by weight, preferably 0 to 12% by weight, more preferably 0 to 10% by weight, even more preferably 0 to 7% by weight, and most preferably 0 to 3% by weight.

[0031] The moisture content can be measured, for example, by a dry weight method using a moisture meter. In this case, the drying conditions are, for example, 130° C. and 20 minutes. The moisture content may also be measured, for example, by the Karl Fischer method.

[0032] [Thermoplastic resin] The thermoplastic resin is not particularly limited, and for example, a general known thermoplastic resin can be used. In addition, for example, a biodegradable thermoplastic resin may be used. For example, polyolefin-based resins, which are polymers of olefins having 2 to 20 carbon atoms, such as polypropylene, polybutene, polypentene, and polyethylene; polycyclic olefin-based resins such as polynorbornene; polystyrene-based resins such as polystyrene and ABS resin; polyester-based resins such as polylactic acid, polyethylene terephthalate, polybutylene terephthalate, and polybutylene succinate, and mixtures thereof may be used. Examples of the polyethylene include linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, and high-density polyethylene. In addition, the polyethylene may be a copolymer, and examples thereof include ethylene-propylene (block and random) copolymers, ethylene-α-olefin (α-olefins having 4 to 20 carbon atoms) copolymers, propylene-α-olefin (α-olefins having 4 to 20 carbon atoms) copolymers, ethylene-vinyl acetate copolymers, and ethylene-acrylic acid copolymers. The thermoplastic resin may be acid-modified, for example, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, etc. The thermoplastic resin may be grafted, for example, maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, etc. The thermoplastic resin may be used alone or in combination of two or more kinds.

[0033] The thermoplastic resin is preferably, for example, polyethylene or polypropylene from the viewpoint of versatility, and more preferably polypropylene.

[0034] The tensile modulus of the thermoplastic resin is, for example, preferably 100 MPa or more, more preferably 500 MPa or more, and preferably 1500 MPa or less, more preferably 1000 MPa or less, from the viewpoint of stable production, and the range is, for example, preferably 100 to 1500 MPa, more preferably 500 to 1000 MPa. The tensile modulus can be measured, for example, using a conventionally known tensile tester. The tensile modulus may be determined, for example, by a measurement method described in the examples below, or may be data described in literature.

[0035] The melt flow rate of the thermoplastic resin is, for example, from the viewpoint of production speed, 0.1 g / 10 min or more, 2 g / 10 min or more, 5 g / 10 min or more, and 70 g / 10 min or less, 60 g / 10 min or less, 40 g / 10 min or less, and the range is, for example, preferably 0.1 to 70 g / 10 min, 2 to 70 g / 10 min, 5 to 60 g / 10 min, and more preferably 5 to 40 g / 10 min. The melt flow rate may be determined, for example, by a method described in JIS K 7210 using a melt indexer, or may be data described in literature, etc.

[0036] The content of the thermoplastic resin is not particularly limited, but for example, in order to increase the starch content in consideration of improving the biomass ratio, the content is 5 wt % or more, 7 wt % or more, 10 wt % or more, or 15 wt % or more, and 45 wt % or less, 40 wt % or less, or 35 wt % or less, relative to the total weight of the starch-containing resin composition being 100 wt %, and the range is, for example, 5 to 45 wt %, more preferably 7 to 45 wt %, even more preferably 10 to 40 wt %, and most preferably 15 to 35 wt %.

[0037] [Elastomer] In the starch-containing resin composition of the present invention, the elastomer is an optional component. That is, the starch-containing resin composition of the present invention may or may not further contain the elastomer. The elastomer is not particularly limited, and may be added, for example, for the purpose of adjusting the physical properties of the strand. That is, it may be added for the purpose of making the starch-containing resin composition of the present invention have a preferable tensile modulus. Examples of the elastomer include resins such as olefin-based elastomers, unsaturated aliphatic elastomers, hydrogenated unsaturated aliphatic elastomers, amide-based elastomers, ester-based elastomers, styrene-based elastomers, and urethane-based elastomers, and also copolymers thereof. The copolymer may have a polar group introduced into the molecule by adding, for example, an acid anhydride, and examples of the acid anhydride that introduces the polar group into the molecule include maleic anhydride. These may be used alone or in combination of two or more types. Moreover, these substances may be contained in at least one of the starch and the thermoplastic resin in advance, for example, or may be contained at any timing when the starch-containing resin composition of the present invention is obtained.

[0038] From the viewpoint of production costs, the elastomer is preferably an olefin-based elastomer or a styrene-based elastomer, and more preferably an olefin-based elastomer.

[0039] When the starch-containing resin composition of the present invention contains the elastomer, the content of the elastomer is not particularly limited, but is, for example, blended according to the content of the starch and the properties of the thermoplastic resin, and is more than 0% by weight and less than 10% by weight, more preferably more than 0% by weight and less than 7% by weight, even more preferably more than 0% by weight and less than 5% by weight, and most preferably more than 0% by weight and less than 3% by weight, based on the total weight of the starch-containing resin composition being 100% by weight. In the starch-containing resin composition of the present invention, when the content of the elastomer is 10% by weight or less, for example, the effect on the physical properties such as mechanical properties of a molded product containing the starch-containing resin composition is small. In addition, since the elastomer is expensive, it is also advantageous from an economical point of view to set the content of the elastomer to 10% by weight or less.

[0040] [Emulsifier (surfactant)] The starch-containing resin composition of the present invention may or may not further contain an emulsifier (surfactant). The emulsifier is not particularly limited, and may be used, for example, for the purpose of facilitating mixing of the thermoplastic resin and the starch. Examples of the emulsifier include propylene glycol monostearate, glycerol monooleate, glycerol trioleate, glycerol monostearate, glycerol distearate, acetylated monoglyceride (stearate), sorbitan monooleate, propylene glycol monolaurate, sorbitan monostearate, calcium stearoyl-2-lactylate, glycerol monolaurate, sorbitan monopalmitate, soybean lecithin, diacetylated tartaric acid ester of monoglyceride, sodium stearoyl lactylate, and sorbitan monolaurate. These may be used alone or in combination of two or more. These substances may be incorporated in at least one of the starch and the thermoplastic resin in advance, or may be incorporated at any timing when obtaining the starch-containing resin composition of the present invention. As described below, the emulsifier is not included in the starch plasticizer of the present invention as long as it does not substantially plasticize the starch, i.e., does not significantly change the properties of the starch.

[0041] The emulsifier (surfactant) is preferably, for example, glycerol monostearate, glycerol distearate, or a mixture thereof, from the viewpoint of production costs, and more preferably glycerol monostearate.

[0042] The content of the emulsifier is not particularly limited, but is blended, for example, in accordance with the amount of starch and the properties of the thermoplastic resin, and is more than 0 wt % and not more than 10 wt %, more preferably more than 0 wt % and not more than 7 wt %, even more preferably more than 0 wt % and not more than 4 wt %, and most preferably more than 0 wt % and not more than 2 wt %, based on the total weight of the starch-containing resin composition being 100 wt %.

[0043] [Starch plasticizer] The starch-containing resin composition of the present invention is preferably, for example, substantially free of a starch plasticizer. In addition, in the present invention, the term "starch plasticizer" means a plasticizer used to plasticize starch, unless otherwise specified. In other words, it does not mean a plasticizer for adjusting the physical properties of a thermoplastic resin that is generally used by those skilled in the art in a form that does not contain starch. In addition, in the present invention, water is not included in the "starch plasticizer". In addition, the additive used as the emulsifier described above is not considered to be a starch plasticizer in the present invention unless it substantially plasticizes the starch, that is, does not significantly change the properties of the starch. Furthermore, the term "substantially free" means, for example, an amount that does not substantially plasticize the starch, that is, a content that does not significantly change the properties of the starch.

[0044] As described in Patent Document 1, when the starch plasticizer is used, for example, there may be a limit to the adjustment of the tensile modulus of the obtained composition. In addition, since the starch plasticizer is easily volatile, the heat resistance may decrease or the composition may be easily discolored. In other words, the physical properties and quality of the obtained resin composition are limited, and the use applications may be inevitably limited.

[0045] In addition, as a result of the inventors' study on the plasticization of starch, it was found that, for example, when glycerin or the like is used as the starch plasticizer, the content of the starch needs to be reduced by the content of the starch plasticizer. On the other hand, as described in Patent Document 1, when the blending amount of the starch plasticizer is reduced, the starch is not sufficiently plasticized. In addition, according to the results of the experiments conducted by the inventors, when the blending amount of the starch plasticizer is reduced, a hard rubber-like substance in which the starches are bonded together is formed, making it difficult to knead with a thermoplastic resin. As described above, the inventors have confirmed that when the starch content is made higher than in the past, adding an inappropriate amount of starch plasticizer adversely affects kneading with a thermoplastic resin.

[0046] Therefore, the content of the starch plasticizer is preferably 0% by weight, for example, when the weight of the entire starch-containing resin composition is 100% by weight. Even when the starch plasticizer is contained, it should be added in an amount that does not substantially plasticize the starch, that is, in a proportion that does not significantly change the properties of the starch, and is more than 0% by weight and not more than 5% by weight, more preferably more than 0% by weight and not more than 3% by weight, and even more preferably more than 0% by weight and not more than 0.5% by weight.

[0047] The starch plasticizer is not particularly limited as long as it is a substance that substantially plasticizes the starch, except for water, and examples thereof include organic compounds such as polyhydric alcohols.Specific examples thereof include sorbitol, maltitol, glycerol (glycerin), mannitol, erythritol, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-heptanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nanonediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and diglycerol.These may be used alone or in combination of two or more. Moreover, these substances may be contained in at least one of the starch and the thermoplastic resin in advance, for example, or may be contained at any timing when the starch-containing resin composition of the present invention is obtained.

[0048] [Other additives] The starch-containing resin composition of the present invention may or may not further contain various additives known in the art. Examples of the additives include inorganic fillers, heat stabilizers, light resistance agents, ultraviolet absorbers, antistatic agents, etc. These may be used alone or in combination of two or more. These substances may be incorporated in advance into at least one of the starch and the thermoplastic resin, or may be incorporated at any timing when the starch-containing resin composition of the present invention is obtained.

[0049] [Moisture in raw materials] The weight ratio of water (i.e., moisture) to the total weight of the raw materials of the starch-containing resin composition is not particularly limited, but is preferably, for example, 0% by weight, i.e., the raw materials do not contain any moisture. In addition, when the raw materials of the starch-containing resin composition contain moisture, the ratio should be such that the properties of the starch are not significantly changed, considering that the present invention has a feature of not substantially plasticizing starch and that moisture can plasticize starch. For example, the lower limit is more than 0% by weight, and the upper limit is 15% by weight or less, more preferably 10% by weight or less, even more preferably 5% by weight or less, and most preferably 3% by weight or less.

[0050] The moisture content can be measured, for example, by a dry weight method using a moisture meter. In this case, the drying conditions are, for example, 130°C and 20 minutes. The moisture content may also be measured, for example, by the Karl Fischer method. Furthermore, the moisture content may be calculated from the moisture content contained in the raw material and the composition ratio (usage weight ratio) of the raw material. For example, the moisture content in the raw material may be calculated from the moisture content contained in the starch, thermoplastic resin, elastomer, and other additives including an emulsifier used as the raw material and the composition ratio (usage weight ratio) of the raw material.

[0051] The starch-containing resin composition provided in the present invention is not limited in its final form, and may be in the form of, for example, pellets as described below, a starch-containing resin composition obtained by further mixing the pellets with another thermoplastic resin, or a molded product as described below obtained by molding the pellets or the like.

[0052] <Pellets, flakes, and resin molded products> Next, the pellets, flakes, and resin molded products of the present invention will be described.

[0053] As described above, the pellets and flakes of the present invention include the starch-containing resin composition of the present invention. In the present invention, the pellets refer to, for example, the starch-containing resin composition molded into a granular shape, and more specifically, the molded product obtained by cutting the starch-containing resin composition in the form of strands. The pellet shape refers to the shape or form of the product obtained when the starch-containing resin composition in the form of strands is cut into granular shapes. In the present invention, the flakes refer to, for example, the starch-containing resin composition molded into a plate, cube, rectangular parallelepiped, polygonal prism, polygonal pyramid, and more specifically, the molded product obtained by cutting the starch-containing resin composition in the form of strands. The flake shape refers to the shape or form of the product obtained when the starch-containing resin composition in the form of strands is cut into a plate, cube, rectangular parallelepiped, polygonal prism, polygonal pyramid, and more specifically.

[0054] As described above, the resin molded product of the present invention contains the starch-containing resin composition of the present invention. The resin molded product of the present invention is obtained, for example, by molding pellets or flakes containing the starch-containing resin composition. The resin molded product of the present invention may further contain, for example, another thermoplastic resin. The other thermoplastic resin is not particularly limited, and may be, for example, the same as the thermoplastic resin described in the above-mentioned starch-containing resin composition of the present invention.

[0055] The tensile modulus of the resin molded product is, for example, 200 to 10,000 MPa. That is, it is 200 MPa or more and 10,000 MPa or less. As shown in the examples described later, in consideration of the physical properties of the strand, for example, it is preferably 500 MPa or more, more preferably 1,000 MPa or more, and preferably 6,000 MPa or less, and more preferably 4,000 MPa or less, and the range is, for example, more preferably 500 to 6,000 MPa, and more preferably 1,000 to 4,000 MPa. The tensile modulus can be measured, for example, using a conventionally known tensile tester. The tensile modulus can be determined, for example, by a measurement method described in the examples described later.

[0056] <Method for producing starch-containing resin composition, method for producing pellets, flakes, etc., and method for producing resin molded product> Next, a method for producing the starch-containing resin composition of the present invention, a method for producing pellets or flakes, and a method for producing a molded resin product will be described.

[0057] [Method of producing starch-containing resin composition] As described above, the method for producing the starch-containing resin composition of the present invention includes a step of mixing raw materials including the starch and the thermoplastic resin (hereinafter, may be referred to as a "mixing step"), and may or may not further include a step of mixing the elastomer. In addition, the raw materials may include, for example, an emulsifier, a plasticizer for starch, and other additives in the starch-containing resin composition of the present invention.

[0058] The mixing step will be specifically described with reference to an example. In the mixing step, for example, the starch and the thermoplastic resin are kneaded while being heated. By the kneading, the starch-containing resin composition of the present invention can be obtained.

[0059] Examples of the equipment for kneading include a kneader, a Banbury mixer, a roll, a single-screw or multi-screw extruder having two or more screws, a continuous kneader, etc. A plurality of these kneaders may be combined, for example, a 1.5-screw extruder combining a single-screw and a twin-screw extruder, etc. In the present invention, there is no particular limitation, but for example, from the viewpoint of production speed, a multi-screw extruder and a combination thereof are preferred, and a twin-screw extruder is more preferred.

[0060] The kneading temperature is not particularly limited, but from the viewpoint of suppressing coloration, it is, for example, 120°C or higher, preferably 140°C or higher, more preferably 150°C or higher, and 220°C or lower, preferably 200°C or lower, more preferably 190°C or lower. The range is, for example, 120°C to 220°C, preferably 140°C to 200°C, more preferably 150°C to 190°C.

[0061] The pressure during the kneading is not particularly limited, but from the viewpoint of stable production, it is, for example, 0 MPa or more and 15 MPa or less, 10 MPa or less, 5 MPa or less, or 3 MPa or less, and the range is, for example, preferably 0 to 15 MPa, 0 to 10 MPa, or 0 to 5 MPa, and more preferably 0 to 3 MPa.

[0062] The method for producing the starch-containing resin composition of the present invention may further include, for example, a drying step. The drying step is, for example, a drying step in which the water content of the starch is adjusted to 0% by weight, and when water remains in the starch, the water content is adjusted to, for example, more than 0% by weight and 10% by weight or less, more preferably 7% by weight or less, even more preferably 5% by weight or less, and most preferably 3% by weight or less, and the range is, for example, 0 to 10% by weight, more preferably 0 to 7% by weight, even more preferably 0 to 5% by weight, and most preferably 0 to 3% by weight. The pre-drying step is, for example, a drying step in which the starch and the elastomer are heated and mixed to adjust the water content to 0% by weight, and when water remains in the starch, the water content is adjusted to, for example, more than 0% by weight and 10% by weight or less, more preferably 7% by weight or less, even more preferably 5% by weight or less, and most preferably 3% by weight or less, and the range is, for example, 0 to 10% by weight, more preferably 0 to 7% by weight, even more preferably 0 to 5% by weight, and most preferably 0 to 3% by weight. The drying step may be, for example, heat drying, vacuum drying, air drying, infrared drying, freeze drying, or drying using a desiccant such as silica gel.

[0063] In the case of the heat drying, examples of the equipment include a ribbon blender, a drum tumbler, a Henschel mixer, a super mixer, a paddle dryer, a flash dryer, a band dryer, a shelf dryer, a conveyor dryer, a fluidized bed dryer, a vibration dryer, a stirring dryer, a rotary dryer, etc. In the present invention, there are no particular limitations, but from the viewpoint of continuous production, a band dryer or a flash dryer is preferred, and a flash dryer is more preferred.

[0064] [Manufacturing methods for pellets, flakes, etc.] After the kneading, for example, the starch-containing resin composition discharged from a heated discharge portion may be molded into an appropriate shape. The shape after molding is not particularly limited, and examples thereof include pellets, flakes, crumbs, powder, sheets, and chips. After kneading, the mixture may be directly molded into a molded product. In this specification, molded products in the form of pellets, flakes, or sheets may be simply referred to as "pellets," "flakes," or "sheets."

[0065] When the starch-containing resin composition is in the form of pellets or flakes, the pellets or flakes of the present invention can be produced, for example, as follows: As described above, the method for producing the pellets or flakes of the present invention includes a strand forming step of extruding the starch-containing resin composition of the present invention to form strands, and a strand cutting step of cutting the strands to form pellets or flakes.

[0066] The strand forming step includes, for example, a step of extruding the starch-containing resin composition mixed in the mixing step (extrusion step). The extrusion step can be carried out, for example, by using a conventionally known extruder. The extruder is not particularly limited, but for example, a twin-screw extruder can be used. Both the mixing step and the extrusion step may be carried out by an extruder. The composition obtained in the mixing step may be recovered and supplied to the extruder in the extrusion step to form strands.

[0067] The strand cutting step is, for example, a step of cutting the starch-containing resin composition in the form of a strand discharged from an extrusion outlet in the extrusion step. Methods for making the starch-containing resin composition in the form of a strand into pellets or flakes include, for example, a cold cut method in which the strand is air-cooled or water-cooled and then cut with a strand cutter, a hot cut method in which the strand is cut with a rotary cutter attached to the outlet of an extruder, an underwater cut method, etc., and from the viewpoint of quality stability, for example, the cold cut method and the hot cut method are preferred, and the cold cut method is more preferred.

[0068] For example, when the physical properties of the strands are not good, the production speed can be set extremely slow to make the strands less likely to break, which allows stable production of the pellets and flakes, but the productivity is extremely reduced. In addition, when the physical properties of the strands are not good, the physical properties after molding may be poor as described above. In the present invention, since the strand physical properties of the starch-containing resin composition are improved, the production speed can be set to the same as when producing other thermoplastic resins, but for example, in the twin-screw extruder described in the examples, from the viewpoint of increasing productivity, the production speed is 0.5 kg / h or more, 1 kg / h or more, 2 kg / h or more, and 10 kg / h or less, 8 kg / h or less, or 6 kg / h or less, and the range is, for example, 0.5 to 10 kg / h, 1 to 8 kg / h, or 1 to 6 kg / h, and more preferably 2 to 6 kg / h.

[0069] [Method of manufacturing resin molded products] As described above, the method for producing a resin molded product containing the starch-containing resin composition of the present invention includes a resin molding step of resin molding a raw material containing the pellets of the present invention or the flakes of the present invention to produce a resin molded product. The raw material includes, for example, the other thermoplastic resin and the other additives. The starch-containing resin composition of the present invention further includes, for example, a kneading step of kneading the pellets or the flakes with a raw material containing the other thermoplastic resin. The resin molding step is, for example, a step of resin molding the kneaded product obtained in the kneading step to produce a resin molded product.

[0070] The resin molding step can be carried out by a conventional method, such as calendar molding, thermoforming, extrusion blow molding, inflation molding, vacuum molding, cast molding, foam molding, extrusion molding, injection molding, and melt spinning. Examples of molded products include containers, packaging materials, cushioning materials, daily necessities, machine parts, building materials, and automobile parts. EXAMPLES

[0071] Next, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0072] In this example and the above-described embodiment, the tensile modulus, average particle size, manufacturability, and water content were measured by the following procedures.

[0073] (tensile modulus) The pellets of the starch-containing resin composition were kneaded for 20 minutes at 180°C and 40 rpm in a Banbury mixer (Ms type pressure kneader DS1-3MHB-E, manufactured by Nihon Spindle Mfg. Co., Ltd.), and the kneaded mixture was sandwiched between PET films and molded for 4 minutes at 180°C and 0.9t in a heat press machine (H300-1, manufactured by AS ONE Co., Ltd.), and the PET film was removed and cooled to room temperature to produce a film with a thickness of 0.1 to 1.5 mm. The obtained film was left to stand at 23°C and 50% RH for one day, and then molded into a dumbbell test piece (JIS K 7127 Type 5) using a lever-type sample cutter (SDL-100, manufactured by Dumbbell Co., Ltd.). The eight prepared dumbbell test pieces were measured in an environment of 23°C and 50% RH using a universal material testing machine (RTG-1210, manufactured by A&D Co., Ltd.) with a chuck distance of 70 mm and a tensile speed of 100 mm / min, and the tensile modulus was calculated from the slope of the regression line of the stress / strain curve in a strain range of 0.05% including the contact point where the tangent slope is maximum between strains of 0.4% and 1.2%. The thickness of the test piece was set to the average thickness of the eight samples. A calibration curve of film thickness and tensile modulus was created from the obtained results, and the tensile modulus of the average thickness calculated from the calibration curve was taken as the tensile modulus of the starch-containing resin composition.

[0074] (Average particle size of starch granules) The average particle size of starch granules was measured by heating and molding (180°C) the starch-containing resin composition (in pellet form) into a coin shape, cooling the resulting molded body to -80°C, and then breaking the molded body, and observing the fractured surface with an electron microscope (SEM). The magnification and field of view were set so that 10 to 20 starch granules whose major diameters could be measured were included in the observation field, and the major diameters of all particles in the obtained SEM image were measured and the average value was calculated. In this example, the fractured surface of the molded coin shape was observed, but the shape of the starch-containing resin composition to be observed does not matter as long as the particles can be confirmed by SEM observation. For example, the starch-containing resin composition may be molded into a film shape and stretched to observe the broken part, or the pellet may be cooled and crushed, and the crushed surface may be observed. In addition, when almost no starch granules are confirmed in the starch-containing resin composition, the average particle size of the starch granules is considered to be less than 3 μm. An example of such a case is when starch granules are broken down due to the use of a plasticizer, resulting in fine particles with an average particle size of less than 3 μm. The "major axis" of each starch granule was calculated by considering all starch granules in the SEM image as ellipses, visually setting the part corresponding to the major axis of the ellipse, and then measuring and calculating the length of the major axis by comparing it with a scale. As an example of measuring the average particle size, Figs. 1A and 1B show SEM images of the following test plots 1-1, 2-1, 3-2, 3-3, and 4-1, as well as the raw materials corn starch, tapioca starch, and phosphate cross-linked starch when the average particle size was calculated. The double arrows shown in Figs. 1A and 1B are added to indicate the major axis of the starch granules for which the average particle size is to be measured. In Fig. 1A, the holes present on the fracture surface (holes in which starch granules were originally filled) were not measured. In this embodiment, the major axis was determined by visual observation, but the major axis of the starch granule may be extracted by a known image processing technique and the length of the major axis may be measured.

[0075] (Manufacturability) As mentioned above, the existing technology had a problem that the strands discharged from the extruder during production were brittle, making it impossible to perform stable continuous production. The manufacturability was evaluated by the time from when the strands were introduced into the pelletizer to when they were broken when the strands discharged from the extruder at 4 kg / h were water-cooled and pelletized in a pelletizer using the twin-screw extruder described in the examples. The evaluation criteria were as follows.

[0076] Manufacturability Evaluation Criteria ◎: The strand did not break even after 8 minutes or more. ◯: The strand did not break even after 4 minutes or more but less than 8 minutes. ×: Strand broke in less than 4 minutes.

[0077] (moisture content) The moisture content of starch was measured using a moisture meter (product name: MT-C, manufactured by Brabender) by the dry weight method at 130° C. for 20 minutes. The moisture content of thermoplastic resins and elastomers can also be measured by the Karl Fischer method.

[0078] When measuring the moisture content of raw materials, the moisture content in the raw materials can be calculated from the moisture content contained in the starch, thermoplastic resin, elastomer, and other additives including emulsifiers used as raw materials and the composition ratio (weight ratio used) of the raw materials.

[0079] <Production of Starch-Containing Resin Composition> (Materials used) In this example, the starches used were "corn starch (product name: Nisshoku Corn Starch Y, manufactured by Nihon Shokuhin Kako Co., Ltd.)", "tapioca starch (product name: NATIVE TAPIOCA STARCH, manufactured by ASIA MODIFIED STARCH)" and "phosphate cross-linked starch (product name: Nisshoku Neovis T-100, manufactured by Nihon Shokuhin Kako Co., Ltd.)". The average particle diameters of the respective starches are as follows. The average particle diameter of the raw material starch was measured in the same manner as described above, except that the starch to be measured was fixed to the SEM measurement stage with double-sided tape. Cornstarch 12.8μm Tapioca starch 12.2μm Phosphate cross-linked starch 11.5μm

[0080] The thermoplastic resins (hereinafter sometimes simply referred to as "resins") used were those listed in Table 1 below. As the elastomer, "Product name: Vistamax (registered trademark) 6102 (manufactured by ExxonMobil)" was used. As the emulsifier, "Product name: Rimakeal (registered trademark) S-200 (manufactured by Riken Vitamin Co., Ltd.)" was used. In this example, the above-mentioned thermoplastic resins, elastomers, and emulsifiers were used that had been sufficiently dried (water content was 1% by weight or less).

[0081] [Table 1]

[0082] [Example 1] The starch-containing resin composition of this example was prepared according to the following procedure. In this example, the relationship between the tensile modulus and manufacturability was confirmed. Also, the improvement of manufacturability by the elastomer was confirmed.

[0083] (Production of pellets containing starch-containing resin composition) Starch (cornstarch, shown as "cornstarch" in Tables 2 to 5) was dried at 130°C for 1 hour in a shelf-type air-blowing dryer. Under the conditions shown in Table 2 below, starch, thermoplastic resin, and elastomer were placed in a polyethylene bag, the mouth of the bag was tied, and the bag was shaken up and down and left and right to mix thoroughly. The entire amount was fed from a feeder installed on the top of C1 of a twin-screw extruder (φ20 mm, L / D=45, number of dies 9 (C1 to C9), Technobel Co., Ltd.). The kneading temperatures were 90°C for C1, 100°C for C2, 120°C for C3, 140°C for C4, and 160°C for C5 to 9, and the shaft rotation speed was set to 150 rpm. The discharged strand of starch-containing resin composition was held by hand, cooled with water in a water tank (product name: SCB150-1500, manufactured by Technobel Co., Ltd.), and fed to the inlet of a pelletizer (product name: SCP-203-2MT, manufactured by Technobel Co., Ltd.). The strand pulled by the pelletizer was cut in the pelletizer to produce pellets containing the starch-containing resin composition of each test plot of Example 1 (test plots 1-1 and 1-2). The tensile modulus of the starch-containing resin composition was measured by the method described above. The results are shown in Table 2.

[0084] [Comparative Example 1] In addition, pellets containing the starch-containing resin composition of Comparative Example 1 were produced in the same manner, except that no elastomer was added and the tensile modulus was not adjusted to 2500 MPa or less (Test Area 1-3). The results are shown in Table 2.

[0085] [Example 2] In this example, the type of thermoplastic resin was changed and the difference in manufacturability was confirmed.

[0086] Starch and a thermoplastic resin were mixed under the conditions shown in Table 3 below in the same manner as in Example 1 to produce pellets containing the starch-containing resin composition of Example 2 (Test Areas 2-1 to 2-3). The results are shown in Table 3.

[0087] [Comparative Example 2] In addition, pellets containing the starch-containing resin composition of Comparative Example 2 were produced in the same manner as above, except that the thermoplastic resin used had a tensile modulus of elasticity of not less than 2500 MPa (Test Area 2-4). The results are shown in Table 3.

[0088] [Example 3] In this example, the type and amount of starch added were changed to confirm manufacturability.

[0089] Starch and a thermoplastic resin were mixed under the conditions shown in Table 4 below in the same manner as in Example 1 to produce pellets containing the starch-containing resin composition of Example 3 (Test Areas 3-1 to 3-3). The results are shown in Table 4.

[0090] [Example 4] In this example, an emulsifier was added and the manufacturability was confirmed.

[0091] Starch, a thermoplastic resin, and an emulsifier were mixed under the conditions shown in Table 5 below in the same manner as in Example 1 to produce pellets containing the starch-containing resin composition of Example 4 (Test Area 4-1). The results are shown in Table 5.

[0092] [Example 5] In this example, the water content in starch was changed and the manufacturability was confirmed.

[0093] Starch and a thermoplastic resin were blended under the conditions shown in Table 6 below in the same manner as in Example 1, except that the starch dried in the same manner as in Example 1 was left to stand at room temperature until the water content of the starch reached 5.5%, to produce pellets containing the starch-containing resin composition of Example 5 (Test Area 5-1). The results are shown in Table 6.

[0094] [Table 2]

[0095] [Table 3]

[0096] [Table 4]

[0097] [Table 5]

[0098] [Table 6]

[0099] As shown in Table 2, the working examples (test plots 1-1 and 1-2) in which the tensile modulus was 2500 MPa or less had good manufacturability, even though the starch contents were high at 70 and 60% by weight. On the other hand, the comparative example 1 (test plot 1-3) in which the tensile modulus exceeded 2500 MPa had poor manufacturability. It was also found that even when the tensile modulus exceeded 2500 MPa, manufacturability was improved by setting the tensile modulus to 2500 MPa or less by adding an elastomer (test plot 1-1). Furthermore, it was also found that the starch was not substantially plasticized, since the average particle size was almost unchanged from the particle size of the original starch granules.

[0100] As shown in Table 3, the working examples (test plots 2-1 to 2-3) in which the tensile modulus was 2500 MPa or less had good manufacturability, while the comparative examples 1 and 2 (test plots 1-3 and 2-4) in which the tensile modulus was more than 2500 MPa had poor manufacturability. This shows that even when the type of starch is kept constant, manufacturability can be improved by appropriately changing the thermoplastic resin and setting the tensile modulus to 2500 MPa or less.

[0101] As shown in Table 4, as long as the tensile modulus is 2500 MPa or less, increasing the amount of starch does not affect manufacturability (Test Areas 2-2 and 3-1). In addition, even when various starches are used, as long as the tensile modulus is 2500 MPa or less, manufacturability is not affected (Test Areas 3-2 and 3-3).

[0102] As shown in Table 5, even when an emulsifier was added, it was found that there was no effect on manufacturability as long as the tensile modulus was 2500 MPa or less (Test Areas 2-1 and 4-1).

[0103] As shown in Table 6, even if starch contains a small amount of moisture, the starch granules are not plasticized, and it was found that this does not affect manufacturability (Test Areas 2-1 and 5-1).

[0104] <Additional Notes> A part or all of the above-described embodiments and examples may be described as follows, but is not limited to the following. (Appendix 1) Starch and a thermoplastic resin, A starch-containing resin composition having a tensile modulus of elasticity of 2500 MPa or less after being formed into a film. (Appendix 2) The weight of the entire starch-containing resin composition is taken as 100% by weight, The starch content is 55 to 95% by weight, The content of the thermoplastic resin is 5 to 45% by weight. 2. The starch-containing resin composition according to claim 1. (Appendix 3) The average particle size of starch granules contained in the starch-containing resin composition is 3 μm or more and 25 μm or less, The average particle size is an average particle size calculated from the average major axis of the starch granules. 3. The starch-containing resin composition according to claim 1 or 2. (Appendix 4) 4. The starch-containing resin composition according to any one of claims 1 to 3, wherein the thermoplastic resin is a polyolefin. (Appendix 5) 5. The starch-containing resin composition according to claim 4, wherein the polyolefin is at least one of polypropylene and polyethylene. (Appendix 6) Further, the elastomer 6. A starch-containing resin composition according to any one of claims 1 to 5. (Appendix 7) A pellet comprising the starch-containing resin composition according to any one of claims 1 to 6. (Appendix 8) A flake comprising the starch-containing resin composition according to any one of claims 1 to 6. (Appendix 9) A resin molded product comprising the starch-containing resin composition according to any one of claims 1 to 6. (Appendix 10) A mixing step of mixing a raw material containing the starch and the thermoplastic resin, A method for producing the starch-containing resin composition according to any one of claims 1 to 6. (Appendix 11) The mixing step further includes a step of mixing the elastomer as a raw material. The manufacturing method according to claim 10. (Appendix 12) a strand forming step of extruding the starch-containing resin composition to form strands; and a strand cutting step of cutting the strands to form pellets or flakes, The starch-containing resin composition is a starch-containing resin composition according to any one of appendixes 1 to 6. A method for producing pellets or flakes. (Appendix 13) A resin molding process is included in which a raw material including pellets or flakes is resin molded to produce a resin molded product, The pellets are as described in Appendix 7, The method for producing a resin molded product, wherein the flakes are the flakes described in appendix 8. (Appendix 14) Further, the method includes a kneading step of kneading the pellets or flakes with a raw material containing another thermoplastic resin, The resin molding step is a step of producing a resin molded product by resin molding the kneaded product obtained in the kneading step. The manufacturing method according to claim 13. [Industrial Applicability]

[0105] As described above, the present invention aims to provide a starch-containing resin composition capable of stably obtaining strands, a method for producing a starch-containing resin composition, a pellet containing the starch-containing resin composition of the present invention, a flake containing the starch-containing resin composition of the present invention, a resin molded product, a method for producing pellets or flakes, and a method for producing a resin molded product. The present invention, for example, can efficiently mass-produce a starch-containing resin composition having a high starch content. Furthermore, by improving the physical properties of the strands, the physical properties such as mechanical properties and surface appearance of a resin molded product obtained by subsequent processing or molding, such as a film or sheet, can be improved. The use of the present invention is not particularly limited. For example, the use of the starch-containing resin composition of the present invention is not limited to the pellets, flakes, and resin molded product of the present invention, but is optional, and can be used in a wide range of applications.

Claims

1. A starch-containing resin composition, The starch-containing resin composition comprises starch, and a thermoplastic resin, The tensile modulus after film formation is 2500 MPa or less, The tensile modulus is measured using the film, which is a test piece conforming to JIS K 7127 Type 5, under an environment of 23°C and 50% RH, with a chuck distance of 70 mm and a pulling speed of 100 mm / min, and is calculated from the slope of the regression line of the stress / strain curve in a strain range of 0.05% including the contact point where the slope of the tangent is maximum between strains of 0.4% and 1.2%, The weight of the total weight of the starch-containing resin composition is taken as 100% by weight, The starch content is 55 to 95% by weight, The content of the thermoplastic resin is 5 to 45% by weight. pellet.

2. 2. The pellet of claim 1, wherein the thermoplastic resin is a polyolefin.

3. 3. The pellets of claim 2, wherein the polyolefin is at least one of polypropylene and polyethylene.

4. Further, the present invention includes an elastomer. The pellets according to claim 1.

5. A resin molded product comprising the pellets according to any one of claims 1 to 4.

6. a mixing step of mixing raw materials containing the starch and the thermoplastic resin to produce a starch-containing resin composition; a strand forming step of extruding the starch-containing resin composition to form strands; and a strand cutting step of cutting the strands to form pellets. A method for producing the pellets according to any one of claims 1 to 3.

7. A mixing step of mixing raw materials containing the starch and the thermoplastic resin to produce a starch-containing resin composition; a strand forming step of extruding the starch-containing resin composition to form strands; a strand cutting step of cutting the strands to form pellets, The mixing step further includes a step of mixing the elastomer as a raw material. A method for producing the pellets according to claim 4.

8. a strand forming step of extruding the starch-containing resin composition to form strands; a strand cutting step of cutting the strands to form pellets, The starch-containing resin composition comprises starch, and a thermoplastic resin, The tensile modulus after film formation is 2500 MPa or less, The tensile modulus is measured using the film, which is a test piece conforming to JIS K 7127 Type 5, under an environment of 23°C and 50% RH, with a chuck distance of 70 mm and a pulling speed of 100 mm / min, and is calculated from the slope of the regression line of the stress / strain curve in a strain range of 0.05% including the contact point where the slope of the tangent is maximum between strains of 0.4% and 1.2%, The weight of the total weight of the starch-containing resin composition is taken as 100% by weight, The starch content is 55 to 95% by weight, The starch-containing resin composition has a content of the thermoplastic resin of 5 to 45% by weight. Pellets manufacturing method.

9. A resin molding step of resin-molding a raw material including pellets to produce a resin molded product, The method for producing a resin molded product, wherein the pellet is the pellet according to any one of claims 1 to 4.

10. The method further includes a kneading step of kneading the pellets with a raw material containing another thermoplastic resin, The resin molding step is a step of resin molding the kneaded mixture obtained in the kneading step to produce a resin molded product. The method for producing the resin molded product according to claim 9.

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