JP2020094162A - Resin composition - Google Patents

Abstract

To provide a plastic molding with a high proportion of biomass material and good quality.SOLUTION: The present invention provides a resin composition containing a plasticized starch material and a thermoplastic resin. The plasticized starch material contains plasticized starch and polar organic compounds capable of gelatinizing or plasticizing starch. The polar organic compounds capable of gelatinizing or plasticizing starch includes at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature. The plasticized starch material has a type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less. The present invention also provides the plasticized starch material, a method for producing the resin composition, and a method for producing the plasticized starch material.SELECTED DRAWING: Figure 2

Description

The present invention relates to a resin composition containing a plasticized starch material, a film or sheet formed from the resin composition, the plasticized starch material, a method for producing the resin composition, and a method for producing the plasticized starch material. ..

Plastic molded products containing biomass materials are receiving attention. Since the plastic molded product contains a biomass material as a substitute for the petroleum-based material, CO2 emitted during combustion can be reduced. Examples of the biomass material include waste-based biomass (food waste, livestock excrement, construction waste, waste paper, etc.), unused biomass (non-edible crops, forest land remnants, etc.), and resource grains. it can.

Regarding a plastic molded article containing a biomass material, for example, in Patent Document 1 below, 50 to 70% by weight of starch, 20 to 40% by weight of a thermoplastic resin, and 0.1 to 10% by weight of a melting point of 60 to A low melting point additive of 100° C. and a high melting point additive having a melting point of 1 to 15% by weight of 100° C. to 150° C., and having a core portion of a granular body of a thermoplastic resin, and the surface of the core portion of the granular body. Starch-resin composite molding obtained by melt-extruding a resin from a starch-resin composite intermediate granule having a coating layer of the granules containing starch containing at least a low-melting point additive attached to Processing materials are disclosed.

JP, 2018-104629, A

If the proportion of the biomass material contained in the plastic molded product can be increased, it can contribute to the reduction of the amount of CO2 emitted. On the other hand, increasing the proportion of biomass material can affect the quality of the plastic molding. Therefore, an object of the present invention is to provide a new means for providing a plastic molded product having a high content ratio of a biomass material and having good quality.

The present inventors have found that a specific plasticized starch material can provide a plastic molded product having a high content of a biomass material and good quality.

That is, the present invention includes a plasticized starch material and a thermoplastic resin, wherein the plasticized starch material contains plasticized starch and a polar organic compound capable of gelatinizing or plasticizing the starch, and The polarizable or plasticizable polar organic compound includes at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature, and the plasticized starch material has a type A durometer hardness of 20 or more and a type D durometer. A resin composition having a hardness of 40 or less is provided.
The polar organic compound capable of gelatinizing or plasticizing starch at room temperature may be a compound having at least one amino group.
The plasticized starch material may have no foamed portion.
The polar organic compound contains a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, and a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, It may contain at least one compound selected from polyhydric alcohols.
The plasticized starch may be a plasticized starch or a modified starch.
The thermoplastic resin may be a polyolefin resin, a polyester resin, or a mixture of these resins.
The resin composition may further include cellulose nanofibers.

The present invention also provides a film or sheet including a layer formed from the resin composition.
The present invention also provides a film or sheet including a layer formed of the resin composition and having a surface having an average roughness (Ra) measured according to JIS B0031 of 2 μm or less.
The present invention also provides a porous film or sheet formed from the resin composition.
The present invention also provides a film or sheet formed from the above resin composition and permeable to air but impermeable to water.

The present invention comprises a plasticized starch and a polar organic compound capable of gelatinizing or plasticizing starch, wherein the polar organic compound capable of gelatinizing or plasticizing the starch is capable of gelatinizing or plasticizing starch at room temperature. Also provided is a plasticized starch material containing at least a possible polar organic compound and having a Type A durometer hardness of 20 or more and a Type D durometer hardness of 40 or less.

The present invention is a first mixing step of mixing 20 to 100 parts by mass of a polar organic compound capable of gelatinizing or plasticizing starch with 100 parts by mass of starch, wherein the polar organic compound is at room temperature. The first mixing step, which contains at least a polar organic compound capable of gelatinizing or plasticizing starch, and the mixture obtained by the first mixing step are heated to a temperature of 120° C. to 150° C. to plasticize the starch. Plasticizing step for obtaining a plasticized starch material by means of the plasticizing step, wherein the plasticized starch material has a type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less, and the plasticizing step. Also provided is a method for producing a resin composition, which includes a second mixing step of mixing a starch material and a thermoplastic resin to obtain a resin composition.

The present invention is a mixing step of mixing 20 parts by mass to 100 parts by mass of a polar organic compound capable of gelatinizing or plasticizing starch with 100 parts by mass of starch, wherein the polar organic compound forms starch at room temperature. A plasticized starch material in which the starch is plasticized by heating the mixture obtained by the mixing step and the mixture obtained by the mixing step to a temperature of 120° C. to 150° C., which contains at least a polar organic compound capable of gelatinizing or plasticizing. And a plasticizing step for obtaining a plasticized starch material having a type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less.

According to the present invention, the content ratio of the biomass material in the plastic molded product can be increased and good quality can be given to the plastic molded product.
The effects of the present invention are not necessarily limited to the effects described here, and may be any of the effects described in this specification.

It is a photograph of a plasticized starch material. It is an electron micrograph of the surface and cross section of a film. It is a graph which shows the measurement result of the average roughness (Ra) of the film surface. The unit of the vertical axis is μm. It is a graph which shows the measurement result of the maximum height (Ry) of the film surface. The unit of the vertical axis is μm. It is a figure which shows the measurement result of tensile elongation. It is a figure which shows the measurement result of tensile strength. It is a photograph of a plasticized starch material.

Hereinafter, modes for carrying out the present invention will be described in detail. The embodiments described below show examples of typical embodiments of the present invention, and the present invention is not limited to these embodiments.

1. Resin composition

The resin composition of the present invention comprises a plasticized starch material and a thermoplastic resin, wherein the plasticized starch material comprises plasticized starch and at least one polar organic compound capable of gelatinizing or plasticizing the starch. And a polar organic compound capable of gelatinizing or plasticizing starch at least including a polar organic compound capable of gelatinizing or plasticizing starch at room temperature, and having a type A durometer hardness of the plasticized starch material of 20. Above, and the type D durometer hardness is 40 or less.

The resin composition of the present invention contains the plasticized starch material and the thermoplastic resin in a ratio of, for example, 20 parts by mass: 80 parts by mass to 80 parts by mass: 20 parts by mass, preferably 30 parts by mass: 70 parts by mass. It may be included in a ratio of 80 parts by mass:20 parts by mass, more preferably 50 parts by mass:50 parts by mass to 80 parts by mass:20 parts by mass. The resin composition having the ratio has a high degree of biomass. The plasticized starch material can increase the biomass content of the resin composition in this way, and even if the biomass content is further increased, the resin composition has good quality.

In the present specification, the biomass degree is a value calculated by the following formula.
Formula: Degree of biomass (%)=“dry weight of biomass contained in resin composition”÷“dry weight of resin composition”×100
The resin composition of the present invention or a molded article (for example, a film and a sheet) formed from the resin composition has, for example, 20% or more, preferably 30% or more, more preferably 40% or more, more preferably 50% or more. , More preferably 60% or more, even more preferably 70% or more. The upper limit of the biomass degree may be, for example, 90% or less, 80% or less, or 70% or less.

The starch that constitutes the plasticized starch material is plasticized. As a result, the surface of the molded product formed from the resin composition can be made smooth. Further, for example, the physical properties of a layer formed from the resin composition or the physical properties of a film or sheet containing the layer (for example, tensile elongation) can be improved.

Further, the plasticized starch material can be manufactured so that the coloring and/or odor generated by heating the starch is suppressed. That is, the plasticized starch material may be one that does not have the color and/or odor, or few, if any, the color and/or odor. For example, the plasticized starch material can be transparent and/or odorless. Therefore, the resin composition obtained by mixing the plasticized starch material with a thermoplastic resin may not have the coloring and/or odor, or may have the coloring and/or odor. They are few.
These improvements in coloration and/or odor are mainly due to the polar organic compound capable of gelatinizing or plasticizing the starch constituting the plasticized starch material, and in particular, the polar organic compound gelatinizes the starch at room temperature. Or due to the inclusion of a plasticizable compound.

There are some compounds that can gelatinize or plasticize starch at room temperature in addition to polar organic compounds. Examples of substances capable of gelatinizing or plasticizing starch at room temperature include strong alkalis (eg sodium hydroxide), salts (eg calcium chloride), and anions or cations (eg Na ⁺ and Li ⁺ ). .. However, when the starch is gelatinized or plasticized using a strong alkali, the plasticized starch material becomes strongly alkaline and is difficult to handle. When salts are used, an exothermic reaction occurs with gelatinization and the temperature becomes high, so that the plasticized starch material has color. When the starch is gelatinized using anions and cations, the starch gelatinizes, but the plasticized starch material produced discolors.
In the present invention, a polar organic compound capable of gelatinizing or plasticizing starch is used, and the polar organic compound contains at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature. As a result, the inconveniences described above for other compounds do not occur or the degree of the inconvenience can be reduced.

Further, by using the plasticized starch material, a molded article (for example, a film and a sheet) having a high degree of biomass in the resin composition and having good quality (for example, surface smoothness, low coloring degree, and low odor) Can be manufactured. For example, since the resin composition of the present invention does not contain granular starch, the shape of the particles does not appear on the surface even when a thin film or sheet is formed from the resin composition. For example, even if the starch content of the resin composition of the present invention is increased, the film or sheet formed from the resin composition does not have the shape of particles on the surface.
Furthermore, the resin composition containing the plasticized starch material can be used to form a porous film or sheet having good quality as described above. According to the present invention, a resin composition and a molded article having such good properties can be provided.

Further, by using the plasticized starch material, the plasticized starch material and the thermoplastic resin can be mixed at a low temperature, and the resin composition can be molded at a low temperature. Thereby, coloring and/or odor of the molded product can be reduced.

When the resin composition of the present invention contains the plasticized starch material, transparency can be imparted to the resin composition and a molded article (for example, a film or sheet) formed from the resin composition. In addition, the resin composition of the present invention may include the plasticized starch material to smooth the surface of the resin composition and a molded article (for example, a film or sheet) formed from the resin composition.

The resin composition of the present invention contains the plasticized starch material and the thermoplastic resin as main components. The total content of the plasticized starch material and the thermoplastic resin in the resin composition of the present invention is, for example, 80% by mass or more, preferably 85% by mass or more, based on the mass of the resin composition. It may be more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

Hereinafter, the resin composition of the present invention will be described in more detail.

[Plasticized starch material]

By adopting the plasticized starch material as the biomass material in the resin composition, the biomass degree (content ratio of the biomass material) of the resin composition can be increased.
For example, if the content ratio of the known starch material (for example, non-gelatinized starch material) in the resin composition is 50% by mass or more, the resin composition may not be molded, or However, even if it is moldable, it may not have good quality. Specifically, when inflation molding is performed using the resin composition, the resin composition may not swell or foam may occur in the resin composition. Furthermore, even if the film is bulged, the film obtained by the molding has poor stretchability, so that the film is easily broken. Further, the resin composition may not have excellent strength.
Since the resin composition of the present invention contains the plasticized starch material, it has excellent moldability and is suitable for molding a film or sheet, for example. That is, the resin composition of the present invention can be used for forming a film or sheet. Moreover, since the resin composition of the present invention contains the plasticized starch material, it has excellent physical properties (for example, tensile elongation).

The type A durometer hardness of the plasticized starch material used in the present invention is 20 or more and the type D durometer hardness of the starch material is 40 or less. In the present invention, the durometer hardness is measured according to JIS K6253. When the type A durometer hardness is more than 90, the type D durometer hardness is used. As described above, the lower limit of the numerical range of hardness is defined by the type A durometer hardness and the upper limit is the type D durometer hardness. Specified by durometer hardness.
From the viewpoint of moldability of the resin composition, the plasticized starch material may have a type A durometer hardness of more preferably 22 or more, more preferably 25 or more, and even more preferably 28 or more. The plasticized starch material may more preferably have a Type D durometer hardness of 35 or less, more preferably a Type D durometer hardness of 30 or less.
The plasticized starch material having a hardness within the numerical range improves the moldability of the molded product (for example, ease of inflation molding) and/or the appearance of the molded product. By using the plasticized starch material, it is possible to produce, for example, a molded product free from fish eyes or foreign matter. When the type D durometer hardness of the plasticized starch material is more than 40, for example, the resin composition containing the plasticized starch material is not suitable for molding, and for example, inflation molding may not be possible.
The plasticized starch material used in the present invention does not have a foamed portion. The foaming can occur, for example, due to evaporation of volatile components in the manufacture of plasticized starch material. A resin composition produced by using a plasticized starch material having a foamed portion may have poor moldability, and the appearance of the resin composition may be deteriorated.

The plasticized starch material contained in the resin composition of the present invention may be a material containing plasticized starch as a main component. The content ratio of the plasticized starch in the plasticized starch material may be, for example, 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more with respect to the mass of the plasticized starch material. The content ratio of the plasticized starch in the plasticized starch material may be, for example, 99.5% by mass or less, 99% by mass or less, or 98% by mass or less with respect to the mass of the plasticized starch material. The content ratio of the plasticized starch may be measured by TG measurement (thermogravimetric analysis) at 150°C. Specifically, the content ratio may be determined based on the mass change amount measured using a TG measuring device (STA7200, Hitachi High-Tech Science Co., Ltd.). The mass change amount corresponds to the decrease amount of the volatile component, and the decrease amount corresponds to the amount of the polar organic compound capable of gelatinizing or plasticizing the starch. Therefore, the content ratio of the plasticized starch in the plasticized starch material is obtained by the following formula: (Content ratio of the plasticized starch in the plasticized starch material (unit: mass %)) = (Start of measurement of mass change amount) Mass after)/(mass before measurement of mass change amount)×100. The conditions for measuring the mass change amount are as follows: temperature range 25° C. to 150° C., temperature rising rate 20° C./min, under nitrogen.

In the present specification, the polar organic compound capable of gelatinizing or plasticizing the starch means a polar organic compound capable of gelatinizing or plasticizing the starch by contacting with the starch. Organic compounds known in the art may be used as the polar organic compound capable of gelatinizing or plasticizing the starch.
The polar organic compound capable of gelatinizing or plasticizing starch is a compound having an SP value of preferably 10 to 25, more preferably 12 to 22, more preferably 13 to 21, and even more preferably 14 to 20. You may. A polar organic compound having an SP value within the numerical range is suitable as a component of the plasticized starch material for achieving the effects of the present invention. For example, a compound having an SP value within the numerical range can reduce the coloring and/or odor of the plasticized starch material, and thereby reduce the coloring and/or odor of the resin composition of the present invention. it can.

The polar organic compound capable of gelatinizing or plasticizing starch is a polar organic compound which is not capable of gelatinizing or plasticizing starch at room temperature but capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, and starch at room temperature. With a polar organic compound capable of being gelatinized or plasticized. In the present specification, the former is also referred to as “polar organic compound capable of gelatinizing or plasticizing starch at high temperature”, and the latter is also referred to as “polar organic compound capable of gelatinizing or plasticizing starch at normal temperature”. The latter is a compound that can gelatinize or plasticize starch at room temperature and also gelatinize or plasticize starch at high temperature. For example, the starch does not gelatinize or plasticize even if the polar organic compound and starch are contacted at room temperature for 1 hour, but the starch is gelatinized or plasticized by contacting the polar organic compound and starch at high temperature for 1 hour. When it is converted, the polar organic compound is “capable of gelatinizing or plasticizing starch at high temperature”. The polar organic compound capable of gelatinizing or plasticizing starch is any of a polar organic compound capable of gelatinizing starch, a polar organic compound capable of plasticizing starch, and a polar organic compound capable of gelatinizing and plasticizing starch. May be
That is, in the present specification, "polar organic compound capable of gelatinizing or plasticizing starch" means "polar organic compound capable of gelatinizing or plasticizing starch at high temperature" and "gelatinizing or plasticizing starch at normal temperature". Both of which are volatile polar organic compounds.
In the present specification, a temperature higher than room temperature (also referred to as “high temperature”) refers to a temperature achieved by heat treatment. The high temperature is, for example, 50° C. or higher, preferably 60° C. or higher, preferably 80° C. or higher, more preferably 100° C. or higher.
In the present specification, normal temperature refers to a temperature when heat treatment is not performed. The normal temperature is, for example, less than 50°C, preferably 10 to 40°C, more preferably 15°C to 35°C, and even more preferably 20 to 30°C.

In the present invention, the polar organic compound capable of gelatinizing or plasticizing the starch, which constitutes the plasticized starch material, contains at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature. The polar organic compound capable of gelatinizing or plasticizing starch at room temperature imparts good quality to the resin composition, for example, reduces coloring and/or odor. Among polar organic compounds capable of gelatinizing or plasticizing starch at room temperature, polar organic compounds capable of gelatinizing starch at room temperature are particularly preferable. By gelatinizing the starch, the starch can be plasticized to form a plasticized starch.
The polar organic compound capable of gelatinizing or plasticizing starch at room temperature is preferably a compound having at least one amino group (for example, 1, 2, or 3 amino groups), for example, formamide (SP value 19). .2), N,N dimethylformamide (SP value: 12.1), and a combination of one or more selected from urea.
From the viewpoint of easiness of mixing with starch, more preferably, the polar organic compound capable of gelatinizing or plasticizing starch at room temperature is liquid at room temperature, for example, formamide or N,N dimethylformamide. For example, formamide is a compound that can gelatinize starch at room temperature. The plasticized starch material containing the polar organic compound capable of gelatinizing or plasticizing the starch at room temperature improves the moldability of the resin composition and facilitates the formation of pellets of the resin composition, for example. The resin composition containing a plasticized starch material containing a polar organic compound capable of gelatinizing or plasticizing starch at room temperature can also be applied to inflation molding.

In a preferred embodiment of the present invention, the polar organic compound capable of gelatinizing or plasticizing starch at room temperature may be formamide. By including the formamide in the plasticized starch material, the moldability of the resin composition (for example, ease of pellet formation and compatibility with inflation molding described above) is particularly improved. Further, since the plasticized starch material contains formamide, the coloring of the plasticized starch material can be further reduced, and the plasticized starch material can be made translucent, for example.

The polar organic compound capable of gelatinizing or plasticizing starch at room temperature is preferably 10 to 25, more preferably 12 to 24, more preferably 14 to 23, even more preferably 16 to 22, and particularly preferably 18 to. It may be a compound having an SP value of 22. A compound having an SP value within the numerical range is suitable as a polar organic compound capable of gelatinizing or plasticizing starch at room temperature.

Preferably, the total content of polar organic compounds capable of gelatinizing or plasticizing the starch in the plasticized starch material is, for example, 30% by mass or less, preferably 20% by mass with respect to the mass of the plasticized starch material. % Or less, more preferably 10% by mass or less. The total content of polar organic compounds capable of gelatinizing or plasticizing the starch in the plasticized starch material is, for example, 0.05% by mass or more and 0.1% by mass with respect to the mass of the plasticized starch material. Or more, or 0.2 mass% or more. The total content ratio is the sum of the content ratio of the polar organic compound capable of gelatinizing or plasticizing the starch at the high temperature and the content ratio of the polar organic compound capable of gelatinizing or plasticizing the starch at the normal temperature. The total content of the polar organic compounds capable of gelatinizing or plasticizing the starch is calculated by subtracting the content of the gelatinized starch measured by the TG measurement described above from 100% by mass.

In one embodiment of the present invention, the polar organic compound capable of gelatinizing or plasticizing starch is a polar organic compound capable of gelatinizing or plasticizing starch at room temperature and capable of gelatinizing or plasticizing starch at high temperature. Includes both polar organic compounds. That is, both of these two polar organic compounds form part of the plasticized starch material. By using these two polar organic compounds in combination, a suitable plasticized starch material can be obtained by mixing with a thermoplastic resin. The polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature is preferably a liquid at room temperature. This allows easy mixing with starch.

For example, the polar organic compound capable of gelatinizing or plasticizing starch further includes a polar organic compound capable of gelatinizing or plasticizing starch at a temperature (high temperature) higher than room temperature, and gelatinizing starch at the high temperature. Alternatively, the plasticizable polar organic compound may be one or more compounds selected from polyhydric alcohols. A combination of these compounds and the polar organic compound capable of gelatinizing or plasticizing the starch at room temperature is particularly suitable for plasticizing the starch mixed with the resin composition.

The polyhydric alcohol is preferably a polyhydric alcohol having 2 to 5 carbon atoms, and more preferably a polyhydric alcohol having 2 to 4 carbon atoms. The polyhydric alcohol preferably has 2 to 5 OH groups, more preferably 2 to 4 OH groups.
Examples of the polyhydric alcohol include glycerin (SP value: 16.5) and glycol. Examples of the glycol include ethylene glycol (SP value: 14.2), diethylene glycol (SP value: 14.6), and propylene glycol.
The polyhydric alcohol may be preferably one or a combination of two or more selected from glycerin, ethylene glycol, diethylene glycol, and propylene glycol.

The plasticized starch material may further include a polyhydric alcohol ester. The polyhydric alcohol ester may be a compound in which a fatty acid is ester-bonded to at least one OH group contained in the polyhydric alcohol. The polyhydric alcohol may be as described above. For example, the polyhydric alcohol may be a compound in which a fatty acid is ester-bonded to one, two, or three of the three OH groups of glycerin (referred to as monoglyceride, diglyceride, or triglyceride, respectively). More preferably, the polyhydric alcohol ester is a monoglyceride. The fatty acid may be, for example, a fatty acid having 14 to 22 carbon atoms, and more preferably 16 to 20 carbon atoms. For example, the polyhydric alcohol ester may be a monoglyceride in which a fatty acid having 14 to 22 carbon atoms, more preferably 16 to 20 carbon atoms, is ester-bonded to one OH group of glycerin. An example of the monoglyceride is glycerin monostearate. The plasticized starch material of the present invention contains the monoglyceride (for example, glycerin monostearate) in an amount of, for example, 0.1 parts by mass to 3 parts by mass, preferably 0.5 parts by mass to 2 parts by mass, relative to 100 parts by mass of starch. sell. By including the monoglyceride (particularly glycerin monostearate) in an amount within the numerical range, it is possible to prevent the pelletized plasticized starch materials from adhering to each other, and improve the handling property of the material.

The plasticized starch material may further include a surfactant. The surfactant may be, for example, stearic acid ester and/or sorbitan acid ester. The surfactant can function as a lubricant.

In one embodiment of the present invention, the plasticized starch material contains a polyhydric alcohol in addition to the plasticized starch and a polar organic compound capable of gelatinizing or plasticizing the starch at room temperature. The polyhydric alcohol may be, for example, glycerin alone, or a combination of glycerin and ethylene glycol.

In another embodiment of the present invention, the plasticized starch material contains a polyhydric alcohol and a polyhydric alcohol ester in addition to the plasticized starch and a polar organic compound capable of gelatinizing or plasticizing the starch at room temperature. The polyhydric alcohol may be, for example, glycerin alone or a combination of glycerin and ethylene glycol. The polyhydric alcohol ester may be a monoglyceride, in particular glycerin monostearate.

The plasticized starch constituting the plasticized starch material is a starch gelatinized or plasticized by heating the starch in the presence of a polar organic compound capable of gelatinizing or plasticizing the starch. The gelatinization or plasticization may be brought about by breaking the intermolecular bond (mainly hydrogen bond) by a polar organic compound which can be gelatinized or plasticized at room temperature, or gelatinized or plasticized at high temperature. It may be caused by cleavage of intermolecular bond (mainly hydrogen bond) by heating in the presence of a polarizable organic compound. The plasticized starch may be, for example, pregelatinized starch. It is considered that the plasticization contributes to imparting transparency and/or smoothness to the resin composition of the present invention.
It is considered that the plasticization also contributes to the improvement of the biomass content of the resin composition of the present invention. For example, in a molded product formed from a resin composition containing unplasticized starch, particles of the starch are likely to appear on the surface of the molded product. The starch particles have a particle size of, for example, about 20 μm. Therefore, for example, when a film is formed using a resin composition containing unplasticized starch, in order to prevent the particle shape of the starch from appearing on the surface of the film, the starch in the resin composition is The content ratio is limited to, for example, about 30 mass% at the maximum with respect to the resin composition substance amount. Further, when the film thickness is about 20 μm or less, the starch particles remarkably appear on the film surface. On the other hand, since the starch contained in the resin composition of the present invention is plasticized, the shape of the starch is less likely to appear on the surface of the resin composition. Therefore, the content ratio of starch in the resin composition of the present invention may be more than 30% by mass with respect to the mass of the resin composition, and may be, for example, not less than 60%, more preferably not less than 60%. May be 70% or more. Even if the content ratio of the starch is high, the surface of the resin composition or the molded product is smooth.

Examples of the starch used in the present invention include underground starch and above-ground starch.
Subterranean starch is starch accumulated underground, for example, starch accumulated in rhizomes or roots. Examples of the underground starch include, but are not limited to, tapioca starch (cassava starch), potato starch, sweet potato starch, kudzu starch, and bracken starch.
The above-ground starch is a starch accumulated on the ground, for example, a starch accumulated in seeds and the like. Examples of above-ground starches include, but are not limited to, corn starch, wheat starch, and rice starch.
In the present invention, underground starch is preferably used. By producing the resin composition of the present invention using underground starch, the odor of the resin composition can be further reduced.
The starch used in the present invention may be a modified product of starch (that is, modified starch), particularly a modified product of underground starch. The modified product can be plasticized at a lower temperature as compared with the unmodified starch. Therefore, it is possible to suppress odor and/or coloration due to heating during the production of plasticized starch.

The starch used in the present invention may preferably contain equilibrium water. The amount of equilibrium water is, for example, 10% by mass to 15% by mass, preferably 10% by mass to 14% by mass, more preferably 10% by mass to 13% by mass, and even more preferably 11% by mass to 13% by mass of starch. It can be% by weight. It is preferable to use a starch or a modified starch having an equilibrium water content within the above numerical range for producing the plasticized starch material according to the present invention. When starch without equilibrium water is used, the starch may not be plasticized.

According to one embodiment of the invention, the plasticized starch is a plasticized starch or a modified starch. For example, the starch can be, for example, corn starch or tapioca starch.
More preferably, the plasticized starch is, for example, one starch selected from tapioca starch (cassava starch), potato starch, sweet potato starch, kudzu starch, and bracken starch, or a plasticized product of starch in a combination of two or more, or It may be a plasticized product of the one modified starch or the modified combination of two or more starches. Even more preferably, the plasticized starch is a plasticized product of tapioca starch or a modified plasticized product of tapioca starch. These plasticized products are particularly preferable from the viewpoint of reducing the odor of the plasticized starch material and reducing the odor of the resin composition of the present invention.

According to one embodiment of the present invention, the plasticized starch material may include cellulose nanofibers (hereinafter also referred to as CNF). Dispersing CNF in a thermoplastic resin is often difficult. In the plasticized starch material, CNF can be easily dispersed in the material, and further, the plasticized starch material containing CNF and the thermoplastic resin can be easily mixed. Therefore, CNF can be easily dispersed in the thermoplastic resin by the plasticized starch material. When the resin composition of the present invention contains CNF, the rigidity of the molded product formed from the resin composition can be increased. In the embodiment in which the plasticized starch material contains CNF, CNF may not be directly added to the thermoplastic resin, but CNF may be further added to the thermoplastic resin.

The advantages of including CNF in the plasticized starch material are described in more detail below.
CNF is hydrophilic. CNF is dispersed in water because it is generally produced by crushing a cellulosic material with water to make it nano.
CNF is used, for example, to increase the strength of a thermoplastic resin. However, since thermoplastics are often hydrophobic, mixing CNFs that are hydrophilic with thermoplastics can be difficult. Therefore, for example, CNF modified (hydrophobicized CNF, in particular, powdered CNF) is mixed with a thermoplastic resin. For the hydrophobicization, for example, the TENPO oxidation method can be used. It is also practiced to mix a CNF dispersion obtained by substituting the solvent in which water disperses CNF with a liquid resin (for example, an epoxy resin or a vinyl chloride resin). It is also practiced that the cellulosic material is not crushed with water but crushed directly with an extruder, and the CNF obtained as a result of the crushing is mixed with a thermoplastic resin. Such mixing techniques can be costly (eg labor, cost, or time). Therefore, it is preferable to use the CNF dispersed in water as it is.
Further, as described above, it is difficult to disperse CNF in the thermoplastic resin. If the dispersion is poor, only one of the tensile elongation and the tensile strength of the resulting CNF-containing thermoplastic resin can be improved.
Further, CNF is generally in a state of being dispersed in water. For example, the CNF content in the CNF water dispersion is about several mass %, and the CNF water dispersion has a high water content. Therefore, it is often difficult to mix an aqueous dispersion of CNF with a thermoplastic resin.
As described above, in the plasticized starch material used in the present invention, CNF can be easily dispersed in the material, and further, the plasticized starch material containing CNF and the thermoplastic resin are easily mixed. It is possible.
As the CNF, CNF dispersed in water can be used. Even if an aqueous dispersion of CNF is used, by using the aqueous dispersion of CNF in the production of the plasticized starch material, the CNF can be easily incorporated into a thermoplastic resin without using the mixing technique described above. It can be dispersed.
Also, when the plasticized starch material containing CNF is mixed with a thermoplastic resin, CNF is well dispersed in the thermoplastic resin. Therefore, both the tensile elongation and the tensile strength of the thermoplastic resin can be improved.
Further, when the biomass content rate or the biodegradable resin content rate in the resin composition increases, the tensile strength of the resin composition may decrease. By mixing the plasticized starch material containing CNF with the thermoplastic resin as described above, the problem of reduction in tensile strength due to the high content of biomass or biodegradable resin in the resin composition is solved. be able to. Furthermore, other effects brought about by CNF can be exhibited in the resin composition.
As the CNF contained in the plasticized starch material, for example, CNF dispersed in water manufactured by the above general manufacturing method can be mentioned. In addition to the CNF dispersed in the water, a modified CNF such as the above-mentioned hydrophobized CNF may be contained in the plasticized starch material. The powdered CNF can also be dispersed in the plasticized starch material if it is dispersed in water. Thus, the plasticized starch material can have various CNFs dispersed therein. In addition, CNF dispersed in water is preferable as CNF dispersed in the plasticized starch material from the viewpoints of cost and ease of handling. CNF dispersed in water is particularly easy to put into the production facility for the plasticized starch material.
Also, CNF dispersed in a hydrophilic liquid other than water may be used. The CNF dispersed in the plasticized starch material may be dispersed in one hydrophilic liquid or may be dispersed in a mixture of two or more hydrophilic liquids. That is, the liquid in which CNFs dispersed in the plasticized starch material are dispersed may be one or a combination of two or more selected from water, glycerin, ethylene glycol, formamide, and urea water. The liquid may be one or a combination of two or more of the polyhydric alcohols mentioned above.

In the present invention, commercially available CNF may be used.
In the present invention, CNF may mean fibrous cellulose having an average fiber diameter of 10 nm to 3000 nm, which is hardly soluble in a solvent, unlike molecular cellulose. The average fiber diameter may be more preferably 10 nm to 1000 nm, more preferably 10 nm to 500 nm, even more preferably 10 nm to 300 nm, and particularly preferably 10 nm to 100 nm. The aspect ratio of CNF can be, for example, 30 to 10,000, preferably 50 to 5,000, and more preferably 50 to 1,000. The aspect ratio is a numerical value obtained by dividing the average fiber length by the average fiber diameter. The average fiber length and the average fiber diameter are average values of 10 arbitrary cellulose fibers observed with an electron microscope.

The plasticized starch material may be manufactured by the manufacturing method described below.

[Thermoplastic resin]

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

A polyolefin resin is a polymer obtained by polymerization using olefins (for example, α-olefins) as a main monomer. The polyolefin resin may be, for example, polyethylene (PE) or polypropylene (PP) or a combination thereof.
More specifically, polyethylene is low density polyethylene (LDPE: Low Density Polyethylene), high density polyethylene (HDPE: High Density Polyethylene), ultra low density polyethylene (VLDPE: Very Low Density Polyethylene), linear low density polyethylene ( It may be LLDPE: Linear Low Density Polyethylene), or ultra high molecular weight polyethylene (UHMW-PE).
The polypropylene may more specifically be a homopolymer polypropylene or a random or block copolymer polypropylene (eg ethylene-propylene copolymer etc.).
The polyolefin-based resin may be preferably a biomass-derived polyolefin-based resin (for example, biomass-derived polyethylene), and may be, for example, biomass polyethylene. The biomass polyethylene can be, for example, LDPE, LLDPE, or HDPE. As a result, the CO2 emission amount can be reduced.
The polyolefin resin may be a polyolefin resin manufactured using a metallocene catalyst. That is, the thermoplastic resin may be, for example, a metallocene catalyst-based polyethylene or polypropylene, or a combination thereof.
The polystyrene-based resin may also be a metallocene catalyst-based polystyrene-based resin.

The polyester resin is a polymer in which a monomer is polymerized by an ester bond. The polyester resin is, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polylactic acid (PLA), or polycarbonate (PC), polybutylene adipate terephthalate (PBAT), polybutylene succinate. Nate (PBS), polyhydroxyalkanoate (PHA), or a combination of two or more thereof.

The type of thermoplastic resin constituting the resin composition of the present invention may be appropriately selected by those skilled in the art depending on, for example, the type of molded article formed from the resin composition, but a thermoplastic resin having a low processing temperature is preferable. For example, when forming a film or sheet from the resin composition, the thermoplastic resin may be, for example, a polyolefin resin, preferably polyethylene or polypropylene, and more preferably LLDPE or LDPE. Even if the resin composition of the present invention is heated to the melting point of these resins, odor or coloring due to heating of the plasticized starch material is unlikely to occur. Therefore, it is possible to suppress the generation of odor or coloring when the resin composition is heated to produce a molded article.

The thermoplastic resin contained in the resin composition of the present invention is preferably 90°C to 180°C, more preferably 95°C to 170°C, more preferably 95°C to 160°C, and even more preferably 95°C to 140°C. And particularly preferably those having a melting point of 95°C to 130°C. By adopting a thermoplastic resin having a lower melting point, the temperature at the time of molding can be lowered and the odor or coloration due to the heating of the plasticized starch material can be further suppressed.

The resin composition of the present invention contains a plasticized starch material and a thermoplastic resin in a ratio of, for example, 20 parts by mass: 80 parts by mass to 80 parts by mass: 20 parts by mass, preferably 30 parts by mass: 70 parts by mass to 80 parts by mass. Part: 20 parts by mass, more preferably 40 parts by mass: 60 parts by mass to 80 parts by mass: contained at a ratio of 20 parts by mass, even more preferably 50 parts by mass: 50 parts by mass to 80 parts by mass: 20. It may be included in a ratio of parts by mass. By using the plasticized starch material, a molded product having good quality can be produced from the resin composition even if the biomass content of the resin composition of the present invention is increased within the above numerical range. ..

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

[Other ingredients]

The resin composition of the present invention may contain other components in addition to the plasticized starch material and the thermoplastic resin. Examples of the other components include a compatibilizer, an oxidative decomposition accelerator, a colorant, and an antioxidant.

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

The oxidative decomposition accelerator may be used to accelerate the decomposition of the thermoplastic resin. The oxidative degradation accelerator may accelerate the oxidative degradation of the thermoplastic resin, and may reduce the molecular weight of the thermoplastic resin to such an extent that microorganisms in soil or compost can be biodegraded.
The oxidative decomposition accelerator may include, for example, at least one compound selected from the group consisting of carboxylic acid metal salts, hydroxycarboxylic acids, transition metal compounds, rare earth compounds, and aromatic ketones. More preferably, the oxidative degradation accelerator may be a combination of a carboxylate salt and a rare earth compound. A commercially available oxidative decomposition accelerator may be used, and examples thereof include P-Life (manufactured by P-Life Japan Inc.). The oxidative decomposition accelerator, particularly the combination of the carboxylate and the rare earth compound is suitable for promoting the decomposition of the polyolefin resin.
In one embodiment of the present invention, the thermoplastic resin contained in the resin composition is a polyolefin resin (for example, polyethylene or polypropylene), and the resin composition may contain the oxidative decomposition accelerator. By adopting this embodiment, not only the plasticized starch material but also the thermoplastic resin is biodegraded. Therefore, the resin composition has a high degree of biomass and is more environmentally friendly.

The carboxylic acid salt contained in the oxidative decomposition accelerator may be, for example, a metal salt of an aliphatic carboxylic acid having 10 to 20 carbon atoms, and more preferably a stearic acid metal salt. Examples of the metal atom forming the metal salt with the aliphatic carboxylic acid include cobalt, cerium, iron, aluminum, antimony, barium, bismuth, chromium, copper, gallium, lanthanum, lithium, magnesium, molybdenum, nickel, calcium, silver. , One or more selected from sodium, tin, tungsten, vanadium, yttrium, zinc, and zirconium, and more preferably selected from calcium, magnesium, zinc, cobalt, cerium, iron, and copper. It may be one or a combination of two or more. For example, the metal salt may be iron stearate. As the carboxylic acid salt, one kind of carboxylic acid salt may be used alone, or a combination of two or more kinds of carboxylic acid salt may be used.

The rare earth compound contained in the oxidation decomposition accelerator is, for example, a rare earth oxide, a rare earth hydroxide, a rare earth sulfate, a rare earth nitrate, a rare earth acetate, a rare earth chloride, or a rare earth carboxylate. It may be an acid salt. More specifically, the rare earth compound is cerium oxide, ceric sulfate, ceric ammonium sulfate, ceric ammonium nitrate, cerium acetate, lanthanum nitrate, cerium chloride, cerium nitrate, cerium hydroxide, cerium octylate. , A lanthanum oxide, a yttrium oxide, and a scandium oxide. As the rare earth compound, one kind of rare earth compound may be used alone, or a combination of two or more kinds of rare earth compounds may be used.

Titanium oxide and/or carbon black may be used as an example of the colorant. Further, a phenolic antioxidant may be used as an example of the antioxidant, but the antioxidant is not limited thereto.

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

According to one embodiment of the present invention, the thermoplastic resin composition may include the plasticized starch material, the thermoplastic resin, and the compatibilizer. The composition ratio of the plasticized starch material and the thermoplastic resin may be, for example, 20 parts by mass: 80 parts by mass to 80 parts by mass: 20 parts by mass, and preferably 30 parts by mass: 70 parts by mass, as described above. 80 parts by mass: 20 parts by mass, more preferably 50 parts by mass: 50 parts by mass to 80 parts by mass: 20 parts by mass. The compatibilizer may be, for example, 1 part by mass to 10 parts by mass, more preferably 2 parts by mass to 9 parts by mass, based on 100 parts by mass of the total amount of the plasticized starch material and the thermoplastic resin.
In this embodiment, the thermoplastic resin may be, for example, a polyolefin resin, preferably polyethylene, and more preferably LLPDE. In this embodiment, the compatibilizer may be, for example, a carboxylic anhydride modified polyolefin, preferably a maleic anhydride modified polyethylene.
The thermoplastic resin composition according to this embodiment can be used for producing a film or sheet by a molding method such as inflation molding or T-die extrusion. The thickness of the film may be, for example, less than 200 μm, in particular 10 μm or more and less than 200 μm. The thickness of the sheet may be, for example, 200 μm or more, and particularly 200 μm or more and 1 mm or less.
In this embodiment, the thermoplastic resin may be, for example, a biomass-derived thermoplastic resin, especially a biomass-derived polyethylene.

According to another embodiment of the present invention, the thermoplastic resin composition may include the plasticized starch material, the thermoplastic resin, the compatibilizer, and the oxidative decomposition accelerator. The composition ratio of the plasticized starch material and the thermoplastic resin may be, for example, 20 parts by mass: 80 parts by mass to 80 parts by mass: 20 parts by mass, and preferably 30 parts by mass: 70 parts by mass, as described above. 80 parts by mass: 20 parts by mass, more preferably 50 parts by mass: 50 parts by mass to 80 parts by mass: 20 parts by mass. The compatibilizer may be, for example, 1 part by mass to 10 parts by mass, more preferably 2 parts by mass to 9 parts by mass, based on 100 parts by mass of the total amount of the plasticized starch material and the thermoplastic resin. The oxidative decomposition accelerator is, for example, 0.01 parts by mass to 5 parts by mass, preferably 0.05 parts by mass to 3 parts by mass, relative to 100 parts by mass of the total amount of the plasticized starch material and the thermoplastic resin. It may be more preferably 0.1 part by mass to 0.5 part by mass.
In this embodiment, the thermoplastic resin may be, for example, a polyolefin resin, preferably polyethylene, and more preferably LLPDE. In this embodiment, the compatibilizer may be, for example, a carboxylic anhydride modified polyolefin, preferably a maleic anhydride modified polyethylene. The oxidative decomposition accelerator may be a combination of a carboxylic acid salt and a rare earth compound.
The thermoplastic resin composition according to this embodiment can be used for producing a film or sheet by a molding method such as inflation molding or T-die extrusion. The thickness of the film may be, for example, less than 200 μm, in particular 10 μm or more and less than 200 μm. The thickness of the sheet may be, for example, 200 μm or more, and particularly 200 μm or more and 1 mm or less.
In this embodiment, the thermoplastic resin may be, for example, a biomass-derived thermoplastic resin, especially a biomass-derived polyethylene.
The thermoplastic resin composition according to this embodiment has a high degree of biomass, and the thermoplastic resin contained in the composition can be biodegraded.

The resin composition of the present invention may be used for producing molded articles other than films and sheets. Examples of the other molded article include, but are not limited to, a container (for example, a bottle container), a bottle cap, a plastic cardboard, a nonwoven fabric, and a monofilament. For example, the resin composition of the present invention may be used for blow molding, injection molding, profile extrusion molding, spinning (for example, melt spinning). By the blow molding, for example, a bottle container can be molded. By the injection molding, for example, a bottle cap or a container can be manufactured. By the profile extrusion molding, for example, a plastic cardboard can be molded. By the spinning (for example, melt spinning), for example, a monofilament can be formed.

The resin composition of the present invention may be manufactured by the manufacturing method described below.

[Film or sheet]

The present invention also provides a film or sheet comprising a layer formed from the resin composition according to the present invention. The film or sheet may be a single-layer film or sheet composed only of layers formed from the resin composition according to the present invention, or at least one layer formed from the resin composition according to the present invention. It may be a multilayer film or sheet in which at least one layer formed from another composition (particularly a resin composition) is laminated. The film may have a thickness of, for example, less than 200 μm, in particular 10 μm or more and less than 200 μm. The sheet may have a thickness of, for example, 200 μm or more, and particularly 200 μm or more and 1 mm or less.

According to one embodiment of the present invention, the film or sheet has an average roughness (Ra) measured according to JIS B0031 of 2 μm or less, more preferably 1.8 μm or less, and even more preferably 1.5 μm or less. On the surface, and the surface is the surface of the layer formed from the resin composition according to the present invention. The average roughness may be measured by a surface roughness meter according to JIS B0031. The resin composition of the present invention can provide a film or sheet having such a smooth surface.

The present invention also provides a porous film or sheet formed from the resin composition of the present invention. The porous film or sheet is, for example, uniaxially or biaxially, preferably by stretching the resin composition of the present invention formed in the shape of a film or sheet (particularly a monolayer film or sheet). Can be produced by stretching in a uniaxial direction. The draw ratio may be, for example, 1.05 times to 5 times, preferably 1.05 times to 3.5 times. By such stretching, holes can be formed in the film. The stretching results in interfacial delamination, which can form pores. The porous film or sheet may be permeable to air but impermeable to water, for example, as described below.

The present invention also provides a film or sheet formed from the resin composition of the present invention and permeable to air but impermeable to water. An air-permeable and water-impermeable film or sheet can be produced by subjecting the resin composition of the present invention formed in the shape of a single layer film or sheet to the stretching treatment described above. The air-permeable and water-impermeable film or sheet may be used, for example, as a back sheet of a diaper (particularly a paper diaper). In the present specification, the backsheet of the diaper is disposed outside the absorbent material of the diaper (that is, at a position farther from the body surface) so that the liquid (for example, urine) absorbed by the absorbent material is outside the diaper. Means a tarpaulin to prevent leaks. The present invention also provides a diaper including the air-permeable and water-impermeable film or sheet as a back sheet.

In the present invention, whether the film or sheet is air permeable may be determined as follows. That is, the film or sheet has a water vapor transmission rate of, for example, 200 g/m ² ·day or more, preferably 250 g/m ² ·day or more, more preferably 300 g/m ² ·day or more, even more preferably 350 g/m ² ·day or more. By having a degree, the film or sheet may be determined to be air permeable. The water vapor permeability is measured according to JIS Z 0208. If the film or sheet does not have the water vapor permeability, it may be determined that it is not air permeable.

The water vapor permeability of the film or sheet before the stretching treatment is, for example, 50 g/m ² ·day or more and less than 200 g/m ² ·day, and particularly 70 g/m ² ·day or more and 150 g/m ² ·day or less. Can be The water vapor permeability of general polyethylene is, for example, 5 to 15 g/m ² ·day. Therefore, the film or sheet according to the present invention has a higher water vapor permeability than general polyethylene even before the stretching treatment.

In the present invention, whether the film or sheet is water impermeable can be determined as follows. First, a film or sheet is placed on a paper that absorbs water (for example, newspaper), water at room temperature is placed on the film or sheet, and the sheet is left for 10 minutes. After the standing, the film or sheet is moved so that the water does not drop from the film or sheet onto the paper. Then, after the movement, if no evidence that the water is absorbed in the paper is visually confirmed, it may be determined that the paper is water impermeable. When the trace of absorption of the water in the paper is visually confirmed after the movement, it may be determined that the paper is not water-impermeable.

2. Plasticized starch material

The plasticized starch material of the present invention comprises plasticized starch and a polar organic compound capable of gelatinizing or plasticizing starch, wherein the polar organic compound capable of gelatinizing or plasticizing starch is starch at room temperature. It contains at least a polar organic compound capable of being gelatinized or plasticized, and the plasticized starch material has a type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less.
All the explanations regarding the plasticized starch material in the above “1. Resin composition” (for example, the details of the composition and each component, etc.) also apply to the plasticized starch material of the present invention. Therefore, the description of the plasticized starch material of the present invention is omitted.
The plasticized starch material has the effects as described in "1. Resin composition" above. For example, the plasticized starch material can increase the degree of biomass of the resin composition and impart good quality to the resin composition.

3. Method for producing resin composition

The method for producing a resin composition according to the present invention is a first mixing step of mixing 20 parts by mass to 100 parts by mass of a polar organic compound capable of gelatinizing or plasticizing starch with 100 parts by mass of starch, The polar organic compound contains at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature, and the first mixing step and the mixture obtained by the first mixing step are heated to a temperature of 120°C to 150°C. A plasticizing step for plasticizing the starch to obtain a plasticized starch material, wherein the plasticized starch material has a type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less. And a second mixing step of mixing the plasticized starch material and the thermoplastic resin in a ratio of 20 parts by mass: 80 parts by mass to 80 parts by mass: 20 parts by mass to obtain a resin composition.
The resin composition of the present invention described in the above “1. Resin composition” can be produced by the production method of the present invention.

The manufacturing method will be described below for each step.

(1) First mixing step

In the first mixing step, 20 to 100 parts by mass of a polar organic compound capable of gelatinizing or plasticizing starch is mixed with 100 parts by mass of starch. The starch and the polar organic compound capable of gelatinizing or plasticizing the starch are as described in the above “1. Resin composition”, and the description is also applicable to the present production method. When the amount of the polar organic compound capable of gelatinizing or plasticizing starch is 20 parts by mass or less, the plasticized starch material according to the present invention may not be manufactured. Further, when the amount of the polar organic compound capable of gelatinizing or plasticizing the starch is 100 parts by mass or more, the amount is excessive with respect to the amount of the starch, which is for producing the plasticized starch material according to the present invention. Can require extra effort and time.

The polar organic compound capable of gelatinizing or plasticizing the starch used in the first mixing step includes at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature. The polar organic compound capable of gelatinizing or plasticizing starch at room temperature is preferably 0.1 parts by mass to 100 parts by mass, more preferably 0.5 parts by mass to 75 parts by mass with respect to 100 parts by mass of the starch. Parts by weight, even more preferably 1 to 50 parts by weight, are mixed with the starch. The polar organic compound capable of gelatinizing or plasticizing starch at room temperature is preferably one or a combination of two or more selected from formamide, N,N dimethylformamide, and urea, more preferably formamide. The urea is mixed with starch, preferably as aqueous urea (aqueous urea solution).

The polar organic compound capable of gelatinizing or plasticizing the starch used in the first mixing step may include a polar organic compound capable of gelatinizing or plasticizing starch at high temperature. That is, in one embodiment of the present invention, the polar organic compound capable of gelatinizing or plasticizing starch is a polar organic compound capable of gelatinizing or plasticizing starch at room temperature and gelatinizing or plasticizing starch at high temperature. Includes both possible polar organic compounds. The polar organic compound capable of gelatinizing or plasticizing starch at high temperatures may be one or more compounds selected from polyhydric alcohols. A combination of these compounds and the polar organic compound capable of gelatinizing or plasticizing the starch at room temperature is particularly suitable for plasticizing the starch mixed with the resin composition. In the first mixing step, a polyhydric alcohol ester may be mixed in addition to the starch and the polar organic compound.

In one embodiment of the present invention, in the first mixing step, a polyhydric alcohol is mixed with the starch and the polar organic compound capable of gelatinizing or plasticizing the starch at room temperature. The polyhydric alcohol may be, for example, glycerin alone, or a combination of glycerin and ethylene glycol.

In another embodiment of the present invention, in the first mixing step, a polyhydric alcohol and a polyhydric alcohol ester are mixed in addition to the starch and the polar organic compound capable of plasticizing the starch at room temperature. The polyhydric alcohol may be, for example, glycerin alone, or a combination of glycerin and ethylene glycol. The polyhydric alcohol ester may be a monoglyceride.

Examples of the starch used in the first mixing step include underground starch and above-ground starch, and for example, corn starch or tapioca starch may be used. In the present invention, underground starch is preferably used. By producing the resin composition of the present invention using underground starch, the odor of the resin composition can be further reduced. The starch used in the first mixing step may be a modified starch (that is, modified starch).

The starch used in the first mixing step may preferably contain equilibrium water. The amount of equilibrium water is, for example, 10% by mass to 15% by mass, preferably 10% by mass to 14% by mass, more preferably 10% by mass to 13% by mass, and even more preferably 11% by mass to 13% by mass of starch. It can be% by weight. It is preferable to use a starch or a modified starch having an equilibrium water content within the above numerical range for producing the plasticized starch material according to the present invention. When starch without equilibrium water is used, the starch may not be plasticized.

The first mixing step may be performed using, for example, a stirrer. As the agitator, a commercially available device may be used. The first premixing step is preferably performed at room temperature. By performing the first mixing step at room temperature and then performing the following plasticizing step, it is possible to suppress the generation of coloring and/or odor due to heating of starch.

The starch, for example, occupies, for example, 40% by mass to 85% by mass, preferably 45% by mass to 80% by mass, more preferably, of the total amount of raw materials used for producing the plasticized starch material. It can account for 50% to 75% by weight.

In the first mixing step, the polar organic compound capable of gelatinizing or plasticizing the starch is, for example, 30 parts by mass to 120 parts by mass, preferably 35 parts by mass to 100 parts by mass with respect to 100 parts by mass of starch. Amounts, more preferably amounts of 40 to 100 parts by weight may be mixed.

In the first mixing step, the polar organic compound capable of gelatinizing or plasticizing starch at room temperature is, for example, 1 part by mass to 60 parts by mass, more preferably 1 part by mass to 100 parts by mass of starch. It may be mixed in an amount of 50 parts by mass, even more preferably 1 part by mass to 40 parts by mass, particularly preferably 1 part by mass to 30 parts by mass.
The polar organic compound capable of gelatinizing or plasticizing starch at room temperature preferably contains formamide, and more preferably only formamide.

In the first mixing step, the polar organic compound capable of gelatinizing or plasticizing starch may include a polar organic compound capable of gelatinizing or plasticizing starch at high temperature. In the first mixing step, the polar organic compound capable of gelatinizing or plasticizing the starch at the high temperature is, for example, capable of plasticizing the starch at the normal temperature from the amount of the polar organic compound capable of gelatinizing or plasticizing the starch. The remaining amount less the amount of polar organic compound may be mixed.
The polar organic compound capable of gelatinizing or plasticizing starch at high temperatures may preferably include glycerin and/or ethylene glycol. In the first mixing step, the weight ratio of glycerin to ethylene glycol is, for example, 5:1 to 0.5:1, preferably 4:1 to 1:1 and more preferably 3:1 to 1:1. And ethylene glycol can be used.
According to one embodiment of the present invention, the polar organic compound capable of gelatinizing or plasticizing starch at high temperature may include only glycerin and ethylene glycol.
In the first mixing step, monoglyceride may be further mixed with the starch. In the first mixing step, the monoglyceride is, for example, 0 parts by mass to 5 parts by mass, preferably 0.1 parts by mass to 4 parts by mass, more preferably 0.5 parts by mass to 3 parts by mass with respect to 100 parts by mass of starch. It can be mixed in parts.

(2) Plasticization process

The plasticizing step includes heating the mixture obtained in the first mixing step in an extruder. The heating plasticizes the starch to obtain a plasticized starch material. The heating is performed at a temperature of 120°C to 150°C. The extruder may be, for example, a twin screw extruder or a single screw extruder, and a commercially available one may be used. The plasticized starch material extruded from the extruder can have, for example, a cylindrical or pellet shape.

The plasticized starch material is as described in “1. Resin composition” above, and the description also applies to the plasticized starch material in the present production method. For example, the plasticized starch material has a type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less.

(3) Second mixing step

In the second mixing step, the plasticized starch material produced in the starch material producing step and the thermoplastic resin are mixed in the above ratio. By the mixing, the resin composition according to the present invention is manufactured. The mixing may be done, for example, using an extruder, preferably a twin screw extruder. In the mixing step, a compatibilizer may be mixed in addition to the plasticized starch material and the thermoplastic resin. The compatibilizing agent is as described in “1. Resin composition” above, and thus the description thereof is omitted.

In the mixing step, the components to be mixed (eg, the plasticized starch material and the thermoplastic resin, and optionally the compatibilizer) are heated. The heating can be performed so that the thermoplastic resin melts. The components to be mixed may be heated, for example, to a temperature at which the thermoplastic resin melts. The temperature may be appropriately selected by those skilled in the art depending on the type of thermoplastic resin. For example, when the thermoplastic resin is polyethylene, the temperature may be, for example, 105°C to 120°C. For example, when the thermoplastic resin is polypropylene, the temperature may be 120°C to 170°C, for example.

The manufacturing method may further include a molding step of molding the resin composition obtained in the mixing step. By the molding step, a molded product having a desired shape is manufactured. The molding can be inflation molding or T-die molding, for example. A resin composition molded into a film or sheet shape can be produced by such a molding method. The molding temperature may be appropriately selected by those skilled in the art according to the type of thermoplastic resin. For example, when the thermoplastic resin is polyethylene, the temperature may be, for example, 160°C to 185°C. For example, even when the thermoplastic resin is polypropylene, the temperature may be, for example, 160°C to 185°C.

The manufacturing method may further include a stretching step of stretching the resin composition molded into a film or sheet shape in the molding step. By the stretching step, the film- or sheet-shaped resin composition can be made porous. The stretching conditions for making the material porous are the same as those described in “1. Resin composition” above, and thus the description thereof is omitted.

4. Method for producing plasticized starch material

The present invention also provides a method of making a plasticized starch material. The manufacturing method is a mixing step of mixing 20 to 100 parts by mass of a polar organic compound capable of gelatinizing or plasticizing starch with 100 parts by mass of starch, wherein the polar organic compound is starch at room temperature. Containing at least a polar organic compound capable of being gelatinized or plasticized, and heating the mixture obtained by the mixing step and the mixing step to a temperature of 120° C. to 150° C. to plasticize the starch to plasticize the starch. It includes a plasticizing step to obtain the material.
By the manufacturing method, the plasticized starch material used for manufacturing the resin composition of the present invention is manufactured.

The mixing step and the plasticizing step included in the manufacturing method are the same as the first mixing step and the plasticizing step described in “3. Method for manufacturing resin composition”. Therefore, the description of these steps in “3. Method for producing resin composition” above also applies to the above two steps in the method for producing a plasticized starch material of the present invention.

Hereinafter, the present invention will be described in more detail based on examples. The examples described below are examples of typical examples of the present invention, and the scope of the present invention is not limited to these examples.

Test Example 1: Production and molding of resin composition (example using formamide)

(Example 1)

As shown in Table 1 below, 70 parts by mass of starch (Showa corn starch, Showa Sangyo Co., Ltd.), 32 parts by mass of glycerin, 16 parts by mass of ethylene glycol, and 4 parts by mass of formamide were prepared. These four ingredients were mixed in a mixer. The mixing was performed at room temperature. The glycerin, the ethylene glycol, and the formamide were premixed before being added to the mixer.
In addition, Table 2 below shows parts by mass of other components for producing a starch material when the amount of starch is 100 parts by mass.

The mixture obtained by the mixing was a powdery mixture. The stickiness of the powdery mixture was evaluated according to the following criteria.
A: No stickiness and easy to handle.
B: Slightly sticky, but easy to handle.
C: Sticky and difficult to handle.

The evaluation results are shown in Table 1 below, and the mixture was not sticky and was easy to handle.

The mixture obtained by the mixing was fed into a single-screw extruder (VSK50, Nakatani Kikai Co., Ltd.), and the mixture was subjected to a kneading treatment. In the feeding, the ease of feeding the mixture from the feeder to the extruder was evaluated. The evaluation criteria are as follows.
A: It easily fell from the feeder into the extruder and was easy to supply.
B: It fell from the feeder into the extruder, but some adhered to the inner surface of the feeder.
C: It was difficult to fall from the feeder into the extruder.

The evaluation results are shown in Table 1 below, and the mixture easily fell from the feeder into the extruder and was easy to supply.

The cylinder temperature in the kneading process was 130°C. In the kneading process, the vent was open. No suction was done from the vent. After the kneading process, the mixture was extruded through the extruder die and an elongated, generally cylindrical, plasticized starch material was obtained.

The plasticized starch material was evaluated for physical properties, presence of bubbles, and stickiness according to the following criteria.
<Physical properties>
A: A type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less.
C: Type D durometer hardness of more than 40, or bubbles were generated (expanded) throughout the plasticized starch material, and the hardness could not be measured.
<Presence of bubbles>
A: No bubbles were generated throughout the plasticized starch material.
B: Bubbles were generated in a part of the plasticized starch material.
C: Bubbles were generated throughout the plasticized starch material.
<Stickiness>
A: There was no stickiness.
B: Slightly sticky.
C: It was sticky.

The evaluation results are shown in Table 1 below, and the plasticized starch material had a type A durometer hardness of 20. The plasticized starch material had elasticity.
A photograph of the plasticized starch material is shown in FIG. As shown in FIG. 1( a ), no bubbles were formed throughout the plasticized starch material.
Further, the plasticized starch material was not sticky.

60 parts by mass of the plasticized starch material, 35 parts by mass of polyethylene (LLDPE, product name SP2540, Prime Polymer Co., Ltd.), and 5 parts by mass of a compatibilizing agent (maleic acid-modified polyethylene, manufactured by DuPont Co., Ltd.) were twin-screw extruder ( PCM30, Ikegai Co., Ltd.), and these components were subjected to kneading treatment. The screw temperature in the kneading process was 120° C., and the resin pressure was 4.3 MPa. In the kneading process, suction was performed from the vent. A resin composition (hereinafter, also referred to as “resin composition of Example 1”) was obtained by the kneading treatment.

The resin composition of Example 1 was supplied to an inflation molding machine (Placo Co., Ltd., die Φ65, extruder diameter 55 mm, temperature 150° C.), and inflation molding was performed. The inflation molding was performed at 150°C to 160°C. A film having a thickness of 40 μm was obtained by the inflation molding.

The moldability in the inflation molding and the appearance of the obtained film were evaluated according to the following criteria.
<Moldability>
A: The resin composition was easily stretched and satisfactorily blown up.
B: The resin composition was slightly hard to grow, but was blown up.
C: The resin composition was broken before being blown up.
<Film appearance>
A: It has a smooth surface, and no fish eyes or foreign matters were observed in the film.
B: Slight fish eyes or foreign matters were observed in the film.
C: Many fish eyes or foreign substances were observed.

The evaluation results are shown in Table 1 below, and the resin composition of Example 1 was easily stretched and satisfactorily blown up. Further, the obtained film had a smooth surface, and no fish eyes or foreign matters (such as starch particles) were observed in the film.

(Example 2)

As shown in Table 1 above, except that 70 parts by mass of starch, 16 parts by mass of glycerin, 8 parts by mass of ethylene glycol, 2 parts by mass of formamide, and 0.5 parts by mass of glycerin monostearate were mixed in the mixer. A plasticized starch material was obtained in the same manner as in Example 1. The glycerin, the ethylene glycol, the formamide, and the monoglyceride were premixed before being added to the mixer.
A resin composition (also referred to as "resin composition of Example 2") was obtained in the same manner as in Example 1 using the plasticized starch material.
Inflation molding was performed by the same method as in Example 1 using the resin composition of Example 2 to obtain a film.

Also in Example 2, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1 above. As shown in Table 1, the same evaluation results as in Example 1 were obtained.
More specifically, the plasticized starch material produced in Example 2 had a Type A durometer hardness of 65. The plasticized starch material had elasticity. A photograph of the plasticized starch material is shown in Fig. 1(b). As shown in FIG. 1( b ), no bubbles were formed throughout the plasticized starch material. Further, the plasticized starch material was not sticky.
The resin composition of Example 2 was easily stretched and swelled well. Further, the obtained film had a smooth surface, and no fish eyes or foreign matter was observed in the film.

(Example 3)

As shown in Table 1 above, except that 70 parts by weight of starch, 16 parts by weight of glycerin, 8 parts by weight of ethylene glycol, 1 part by weight of formamide, and 0.5 part by weight of monoglyceride were mixed in the mixer. A plasticized starch material was obtained in the same manner as 1.
Using the plasticized starch material, a resin composition (also referred to as “resin composition of Example 3”) was obtained in the same manner as in Example 1.
Using the resin composition of Example 3, inflation molding was carried out in the same manner as in Example 1 to obtain a film.

Also in Example 3, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1 above. As shown in Table 1, the same evaluation results as in Example 1 were obtained.

(Example 4)

As shown in Table 1 above, except that 70 parts by mass of starch, 16 parts by mass of glycerin, 8 parts by mass of ethylene glycol, 2 parts by mass of formamide, and 1 part by mass of monoglyceride were mixed in the mixer, In the same way, a plasticized starch material was obtained.
A resin composition (also referred to as "resin composition of Example 4") was obtained in the same manner as in Example 1 using the plasticized starch material.
Using the resin composition of Example 4, inflation molding was performed in the same manner as in Example 1 to obtain a film.

The same evaluation as in Example 1 was performed in Example 4. The evaluation results are shown in Table 1 above. As shown in Table 1, the same evaluation results as in Example 1 were obtained.

(Example 5)

As shown in Table 1 above, except that 70 parts by mass of starch, 16 parts by mass of glycerin, 8 parts by mass of ethylene glycol, 2 parts by mass of formamide, and 2 parts by mass of monoglyceride were mixed in the mixer, In the same way, a plasticized starch material was obtained.
A resin composition (also referred to as "resin composition of Example 5") was obtained in the same manner as in Example 1 using the plasticized starch material.
Using the resin composition of Example 5, inflation molding was performed in the same manner as in Example 1 to obtain a film.

Also in Example 5, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1 above. As shown in Table 1, the same evaluation results as in Example 1 were obtained.

(Example 6)

As shown in Table 1 above, a plasticized starch material was obtained in the same manner as in Example 1 except that 50 parts by mass of starch, 25 parts by mass of glycerin, and 25 parts by mass of formamide were mixed in the mixer. .. The glycerin and the formamide were mixed in advance before being added to the mixer.
A resin composition (also referred to as "resin composition of Example 6") was obtained in the same manner as in Example 1 using the plasticized starch material.
Inflation molding was performed by the same method as in Example 1 using the resin composition of Example 6 to obtain a film.

In Example 6, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1 above. As shown in Table 1, the same evaluation results as in Example 1 were obtained.

(Comparative Example 1)

As shown in Table 1 above, in the same manner as in Example 1 except that 70 parts by mass of starch, 16 parts by mass of glycerin, 8 parts by mass of ethylene glycol, and 0.5 part by mass of monoglyceride were mixed in the mixer. , Tried to obtain plasticized starch material. However, no plasticized starch material was obtained because the material was sticky and did not fall into the extruder.
Also in Comparative Example 1, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1 above. As shown in Table 1, the mixture for obtaining the starch material was sticky and thus difficult to handle. Also, the mixture was difficult to fall from the feeder into the extruder.

(Comparative example 2)

As shown in Table 1 above, except that 70 parts by mass of starch, 4 parts by mass of glycerin, 2 parts by mass of ethylene glycol, 0.5 parts by mass of formamide, and 0.5 parts by mass of monoglyceride were mixed in the mixer. A plasticized starch material was obtained in the same manner as in Example 1. The glycerin, the ethylene glycol, the formamide, and the monoglyceride were premixed before being added to the mixer.

The mixture obtained by mixing with the mixer was a powdery mixture. The powdery mixture was not sticky and was easy to handle.
Further, the supply of the mixture to the twin-screw extruder could be easily performed because the mixture did not have tackiness.
However, as shown in FIG. 1(d), the plasticized starch material produced in Comparative Example 2 had bubbles formed (expanded) throughout. Therefore, neither durometer hardness of type A nor E could be measured.
Since the plasticized starch material could not be formed into uniform pellets due to foaming, it could not be mixed with the thermoplastic resin.

(Comparative example 3)
As shown in Table 1 above, except that 70 parts by weight of starch, 8 parts by weight of glycerin, 4 parts by weight of ethylene glycol, 1 part by weight of formamide, and 0.5 part by weight of monoglyceride were mixed in the mixer. A plasticized starch material was obtained in the same manner as 1. The glycerin, the ethylene glycol, the formamide, and the monoglyceride were premixed before being added to the mixer.

The mixture obtained by mixing with the mixer was a powdery mixture. The powdery mixture was not sticky and was easy to handle.
Further, the supply of the mixture to the twin-screw extruder could be easily performed because the mixture did not have tackiness.
However, the plasticized starch material had a Type D durometer hardness of 50. Moreover, as shown in FIG. 1C, bubbles were formed in a part of the plasticized starch material. The durometer hardness was measured in a portion where no bubbles were formed. In addition, the plasticized starch material was not sticky.

A resin composition (also referred to as “resin composition of Comparative Example 3”) was obtained in the same manner as in Example 1 using the plasticized starch material.

The resin composition of Comparative Example 3 was used to perform inflation molding in the same manner as in Example 1 to try to obtain a film. However, the film formed from the resin composition was torn during inflation molding. In addition, fish eyes or foreign matters were observed in the torn film.

(Summary of evaluation results)

As described above, in Examples 1 to 6 using formamide, the mixture obtained by mixing with the mixer was a powdery mixture, was not sticky, and was easy to handle. Further, it was possible to easily supply these mixtures to the extruder.
Further, the plasticized starch materials produced in Examples 1 to 6 were easy to handle because they were not sticky or were slightly sticky, if any. No bubbles were formed in any of the plasticized starch materials produced in Examples 1 to 6. The moldability and appearance of the resin compositions of Examples 1 to 6 were also good.
From these results, it can be seen that the plasticized starch material according to the present invention can be more easily produced than the starch material containing no polar organic compound capable of plasticizing starch at room temperature. Furthermore, the plasticized starch material according to the present invention makes it possible to produce a resin composition having excellent moldability. Furthermore, the plasticized starch material can be formed into a film or sheet by, for example, inflation molding, even if it is blended in a high proportion with respect to the thermoplastic resin. Furthermore, the films or sheets produced do not have fish eyes or foreign matter due to starch.

Test Example 2: Evaluation of film surface

The surface and cross section of the film produced in Example 4 were observed with a scanning electron microscope. A photograph of the surface and the cross section is shown in FIG. As shown in FIG. 2( a ), no starch particles were confirmed on the surface or cross section.
On the other hand, the surface and cross-section of the film produced with the unplasticized starch material is shown in Figure 2(b). The said film was manufactured using the inflation molding machine (Placo Co., Ltd., die Φ65, extruder diameter 55 mm, temperature 160° C.). The resin composition used to produce the film was composed of 30 parts by weight of unplasticized starch, 5 parts by weight of metal soap, 65 parts by weight of polyethylene, and 5 parts by weight of compatibilizer. It was As shown in FIG. 2( b ), the film containing the unplasticized starch material has a large number of protrusions due to the starch particles formed on the surface, and the starch particles can be confirmed in the cross section.

The average roughness (Ra) of the above two films was measured according to JIS B0031 using a surface roughness meter (surface roughness profile measuring machine HANDYSURF E-40A, Tokyo Seimitsu Co., Ltd.). The measurement results are shown in FIG. As shown in FIG. 3, the average roughness of the film surface produced using the plasticized starch material in Example 4 was about 1.2 μm.
On the other hand, the average roughness of the film surface produced by using the unplasticized starch material was about 2.8 μm when measured by the same measuring method.

The maximum heights (Ry) of the two films were measured according to JIS B0061 using a surface roughness meter (surface roughness profile measuring machine HANDYSURF E-40A, Tokyo Seimitsu Co., Ltd.). The measurement results are shown in FIG. As shown in FIG. 4, the maximum height of the film surface produced in Example 4 was about 8 μm.
On the other hand, the maximum height of the film surface produced by using the unplasticized starch material was about 17 μm when measured by the same measuring method.

From the above evaluation results of the film surface, it is understood that the film formed from the resin composition containing the plasticized starch material according to the present invention has a smooth surface.

Test Example 3: Evaluation of physical properties of film

The tensile elongation and tensile strength of the film produced in Example 4 were measured according to JIS Z 1702. The same measurements were also made on films made with unplasticized starch material. The film was the same as that produced in Test Example 2. The measurement results of these tensile elongation and tensile strength are shown in FIGS. 5 and 6, respectively.

As shown in FIG. 5, the film produced in Example 4 had a higher tensile elongation compared to the film produced with the unplasticized starch material. Therefore, it can be seen that the tensile elongation can be increased by plasticizing the starch in the resin composition. Further, as shown in FIG. 6, the tensile strengths of both films were about the same.
Further, a film having a tensile elongation of a horizontal line (150%) or more other than the scale shown in FIG. 5 and a tensile strength of a horizontal line (11.8 MPa) or more other than the scale shown in FIG. Satisfies the quality requirement of Class A (relatively flexible) specified in JIS Z 1702. As shown in FIGS. 5 and 6, the film produced in Example 4 meets these quality requirements and is therefore a film with good quality.

From the above evaluation results of the physical properties of the film, it can be seen that a film having good quality can be produced by the resin composition containing the plasticized starch material according to the present invention.

Test Example 4: Preparation and evaluation of stretched film

The film produced in Example 4 was supplied to a uniaxial stretching device (manufactured by Toray Engineering Co., Ltd.) to produce a uniaxially stretched film. The draw ratio was 2.5 times.

The water vapor permeability of the stretched film was measured according to JIS Z 0208 and found to be 370 g/m ² ·day. For example, polyethylene has a water vapor transmission rate of 5 to 15 g/m ² ·day. Therefore, it can be seen that the stretched film has a high water vapor permeability.

Test Example 5: Mixing ratio of polar organic compound and starch

The state of the mixture when the materials for producing the plasticized starch material were mixed was evaluated. The composition of the evaluated mixture is as shown in Table 3 below. From the viewpoint of easy supply to the extruder, the evaluation criteria are as follows. The evaluation results of the mixture are also shown in the same table.
A: It is powdery.
B: Powdery but moist and sticky.
C: Gel or liquid.

As shown in Table 3, the mixture of Production Examples 2-1 and 2-2 was powdery but had a dampness and was sticky. The mixture of Production Examples 2-3 and 2-4 was in the form of gel or liquid. Therefore, the mixture obtained by mixing only glycerin with starch is not suitable for feeding to the extruder.
On the other hand, the mixtures of Production Examples 2-5 to 2-8 were powdery. In addition, the mixture of Production Examples 2-5 to 2-8 was easily solidified when compressed, and the lump obtained by the compression was easily broken, and easily powdered. Therefore, the mixture obtained by mixing only formamide with starch was suitable for feeding to the extruder.
The mixtures of Production Examples 2-9 to 2-12 were also powdery. In addition, the mixture of Production Examples 2-9 to 2-12 was easily solidified when compressed, and the lump obtained by the compression was easily broken, and easily became a powder. Therefore, it is understood that a powdery mixture can be obtained even when the mixture of glycerin and formamide is mixed with starch.
From the mixing ratio of the production example which was evaluated as A, it is considered that a mixture suitable for supply to the extruder can be easily obtained by setting the amount of formamide to 10 parts by mass to 70 parts by mass with respect to 100 parts by mass of starch. ..
Further, from the comparison between Production Examples 2-1 to 2-4 and Production Examples 2-9 and 2-12, when glycerin alone was mixed with starch, a powdery mixture which was not easy to handle was obtained, but formamide was added to glycerin. It can be seen that the addition results in a powdery mixture that is easy to handle despite the same amount of glycerin and the addition of the formamide liquid.

Test Example 6: Production and molding of resin composition containing CNF

(Example 2-1)

In addition to 70 parts by mass of starch (Showa corn starch, Showa Sangyo Co., Ltd.), 32 parts by mass of glycerin, 16 parts by mass of ethylene glycol, and 4 parts by mass of formamide, 0.05 parts by mass of CNF was prepared. A mixture was obtained by mixing in the mixer in the same manner as in Example 1. The mixture was kneaded in the same manner as in Example 1 to produce a CNF-containing plasticized starch material.
The plasticized starch material and polyethylene were kneaded by a twin-screw extruder to obtain a resin composition (referred to as the resin composition of Example 2-1). A film having a thickness of 40 μm (hereinafter, referred to as “film of Example 2-1”) was obtained by inflation molding using the resin composition.

Using the resin composition of Example 1, a film having a thickness of 40 μm (hereinafter, referred to as “film of Example 1”) was obtained by the above molding method.

When the tensile strength and tensile elongation of the film of Example 2-1 and the film of Example 1 were measured, the former film had higher tensile strength and tensile elongation than the latter film. Therefore, it is understood that the inclusion of CNF can improve the tensile strength and the tensile elongation.
Further, CNF was not easily dispersed in a thermoplastic resin such as polyethylene, but CNF was well dispersed in the resin composition of Example 2-1. Therefore, it is also found that CNF can be well dispersed in the thermoplastic resin by mixing the plasticized starch material mixed with CNF with the thermoplastic resin.

(Example 2-2)

Three types of plasticized starch materials were produced in the same manner as in Example 2-1, except that the amount of CNF was changed to 0.1 parts by mass, 0.5 parts by mass, or 1 part by mass. Then, in the same manner as in Example 2-1, three resin compositions were obtained using each of the three plasticized starch materials. Three sheets were manufactured in the same manner as in Example 2-1 using each of the three resin compositions. All of the three sheets obtained had higher tensile strength and tensile elongation than the sheet of Example 1. Further, CNF was well dispersed in the three resin compositions.

Test Example 7: Production and molding of resin composition (example using urea water)

(Example 3-1)

As shown in Table 4 below, in the mixer, 50 parts by mass of starch, 20 parts by mass of glycerin, 20 parts by mass of urea water (urea aqueous solution having a urea concentration of 32.5% by mass based on the mass of the aqueous solution), and glycerin mono A plasticized starch material was obtained in the same manner as in Example 1, except that 0.5 part by mass of stearate was mixed. In addition, Table 5 below shows the amounts of other components when the starch is 100 parts by mass.
Using the plasticized starch material, a resin composition (also referred to as “resin composition of Example 3-1”) was obtained in the same manner as in Example 1.
Using the resin composition of Example 3-1, inflation molding was performed in the same manner as in Example 1 to obtain a film.

Also in Example 3-1, the same evaluation as in Example 1 was performed. The evaluation results are also shown in Table 4 below. As shown in Table 4, the tackiness of the mixture for obtaining the plasticized starch material and the easiness of feeding from the feeder to the extruder were both A-rated. The plasticized starch material produced in Example 3-1 was rated A for both the durometer hardness and the presence or absence of bubbles. The plasticized starch material had a Type A durometer hardness of 30. The moldability and the film appearance of the resin composition of Example 3-1 were both evaluated as A.

(Example 3-2)

As shown in Table 4 above, 50 parts by mass of starch, 15 parts by mass of glycerin, 15 parts by mass of urea water (a urea aqueous solution having a urea concentration of 32.5% by mass with respect to the mass of the aqueous solution), and glycerin mono are prepared in the mixer. A plasticized starch material was obtained in the same manner as in Example 3-1, except that 0.5 part by mass of stearate was mixed.
A resin composition (also referred to as "resin composition of Example 3-2") was obtained in the same manner as in Example 1 using the plasticized starch material.
Inflation molding was performed in the same manner as in Example 1 using the resin composition of Example 3-2 to obtain a film.

Also in Example 3-2, the same evaluation as in Example 1 was performed. The evaluation results are also shown in Table 4 above. As shown in Table 4, the tackiness of the mixture for obtaining the plasticized starch material and the easiness of feeding from the feeder to the extruder were both A-rated. Further, the durometer hardness, the presence or absence of air bubbles, and the stickiness of the produced plasticized starch material were all rated A. The plasticized starch material had a Type A durometer hardness of 48. A photograph of the plasticized starch material is shown in (7-a) of FIG. 7. As shown in the photograph, no bubbles were generated. Further, the moldability and the film appearance of the resin composition of Example 3-2 were all evaluated as A.

(Example 3-3)

As shown in Table 4 above, 70 parts by mass of starch, 32 parts by mass of glycerin, 16 parts by mass of ethylene glycol, 4 parts by mass of urea water (urea having a urea concentration of 32.5% by mass relative to the mass of the aqueous solution) are prepared in the mixer. Aqueous solution) and 0.5 parts by mass of glycerin monostearate were mixed, and a plasticized starch material was obtained in the same manner as in Example 3-1.
A resin composition (also referred to as "resin composition of Example 3-3") was obtained in the same manner as in Example 1 using the plasticized starch material.
Inflation molding was carried out in the same manner as in Example 1 using the resin composition of Example 3-3 to obtain a film.

In Example 3-3, the same evaluation as that in Example 1 was performed. The evaluation results are also shown in Table 4 above. As shown in Table 4, the tackiness of the mixture for obtaining the plasticized starch material and the easiness of feeding from the feeder to the extruder were both A-rated. Further, the durometer hardness, the presence or absence of air bubbles, and the stickiness of the produced plasticized starch material were all rated A. The type A durometer hardness of the plasticized starch material was 30. Moreover, the moldability and the film appearance of the resin composition of Example 3-3 were both A evaluations.

(Example 3-4)

As shown in Table 4 above, 70 parts by mass of starch, 16 parts by mass of glycerin, 8 parts by mass of ethylene glycol, 2 parts by mass of urea water (urea having a urea concentration of 32.5% by mass with respect to the mass of the aqueous solution) are prepared in the mixer. Aqueous solution) and 0.5 parts by mass of glycerin monostearate were mixed, and a plasticized starch material was obtained in the same manner as in Example 3-1.
A resin composition (also referred to as “resin composition of Example 3-4”) was obtained in the same manner as in Example 1 using the plasticized starch material.
Using the resin composition of Example 3-4, inflation molding was performed in the same manner as in Example 1 to obtain a film.

The same evaluations as in Example 1 were performed in Examples 3-4. The evaluation results are also shown in Table 4 above. As shown in Table 4, the tackiness of the mixture for obtaining the plasticized starch material and the easiness of feeding from the feeder to the extruder were both A-rated. Further, the durometer hardness, the presence or absence of air bubbles, and the stickiness of the produced plasticized starch material were all rated A. The type D durometer hardness of the plasticized starch material was 30. A photograph of the plasticized starch material is shown in (7-b) of FIG. As shown in the photograph, no bubbles were generated. Moreover, the moldability and the film appearance of the resin composition of Example 3-4 were both A evaluations.

(Comparative Example 3-1)

As shown in Table 4, 50 parts by mass of starch, 6 parts by mass of glycerin, 6 parts by mass of urea water (urea aqueous solution having a urea concentration of 32.5% by mass with respect to the mass of the aqueous solution), and monoglyceride 0 in the mixer. A plasticized starch material was obtained in the same manner as in Example 1 except that 0.5 part by mass was mixed.

Also in Comparative Example 3-1, the same evaluation as in Example 1 was performed. The evaluation results are also shown in Table 4 above. As shown in Table 4, the tackiness of the mixture for obtaining the plasticized starch material and the easiness of feeding from the feeder to the extruder were both A-rated. The mixture was foaming. Further, the durometer hardness of the produced plasticized starch material was rated C, and the presence or absence of bubbles was rated B. The stickiness of the plasticized starch material was rated A. The type D durometer hardness of the plasticized starch material was 55. A photograph of the plasticized starch material is shown in (7-c) of FIG. 7. As shown in the photograph, bubbles were observed on the surface of the plasticized starch material. The moldability and the film appearance of the resin composition of Comparative Example 3-1 were both C evaluation.

(Comparative Example 3-2)

As shown in the above Table 4, 70 parts by mass of starch, 8 parts by mass of glycerin, 4 parts by mass of ethylene glycol, aqueous urea (a urea aqueous solution having a urea concentration of 32.5% by mass based on the mass of the aqueous solution) in the mixer 1 A plasticized starch material was obtained in the same manner as in Example 1 except that 1 part by weight and 0.5 part by weight of monoglyceride were mixed.

Also in Comparative Example 3-2, the same evaluation as in Example 1 was performed. The evaluation results are also shown in Table 4 above. As shown in Table 4, the tackiness of the mixture for obtaining the plasticized starch material and the easiness of feeding from the feeder to the extruder were both A-rated. The mixture was foaming. Further, the durometer hardness of the produced plasticized starch material was rated C, and the presence or absence of bubbles was rated B. The stickiness of the plasticized starch material was rated A. The type D durometer hardness of the plasticized starch material was 60. The moldability and the film appearance of the resin composition of Comparative Example 3-1 were both C evaluation.

From the above results and the results of Test Example 1, even when urea water was used instead of formamide, the obtained resin composition was excellent in moldability and a film excellent in appearance from the resin composition. It turns out that can be manufactured.

Test Example 8: Production and molding of resin composition (example using polypropylene)

(Example 4-1)

A plasticized starch material was obtained as described in Example 1. Using the plasticized starch material, except that 35 parts by mass of polypropylene (Nippon Polypro Co., Wintech WFX4TA) was used in place of 35 parts by mass of polyethylene, the resin composition (“ (Also referred to as "resin composition of Example 4-1").
Using the resin composition of Example 4-1, inflation molding was performed in the same manner as in Example 1 to obtain a film.

The evaluation described in Example 1 was performed on the resin composition of Example 4-1. As a result of the evaluation, the resin composition of Example 4-1 was easily stretched and satisfactorily blown up. Further, the obtained film had a smooth surface, and no fish eyes or foreign matter due to starch were observed in the film.

From these results, it is found that even when polypropylene is used instead of polyethylene, the resin composition obtained is excellent in moldability, and a film having an excellent appearance can be produced from the resin composition.

Claims (14)

Including a plasticized starch material and a thermoplastic resin,
The plasticized starch material comprises plasticized starch and a polar organic compound capable of gelatinizing or plasticizing starch,
The polar organic compound capable of gelatinizing or plasticizing starch includes at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature, and the plasticized starch material has a type A durometer hardness of 20 or more. And, the type D durometer hardness is 40 or less,
Resin composition. The resin composition according to claim 1, wherein the polar organic compound capable of gelatinizing or plasticizing starch at room temperature is a compound having at least one amino group. The resin composition according to claim 1 or 2, wherein the plasticized starch material does not have a foamed portion. The polar organic compound contains a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, and a polar organic compound capable of gelatinizing or plasticizing starch at a temperature higher than room temperature, The resin composition according to claim 1, comprising at least one compound selected from polyhydric alcohols. The resin composition according to any one of claims 1 to 4, wherein the plasticized starch is a plasticized product of starch or a modified plasticized product of starch. The resin composition according to claim 1, wherein the thermoplastic resin is a polyolefin resin, a polyester resin, or a mixture of these resins. The resin composition according to claim 1, further comprising cellulose nanofibers. A film or sheet comprising a layer formed of the resin composition according to claim 1. A film having a surface having a layer formed from the resin composition according to any one of claims 1 to 7 and having a surface having an average roughness (Ra) measured according to JIS B0031 of 2 µm or less, or Sheet. A porous film or sheet formed from the resin composition according to claim 1. A film or sheet formed from the resin composition according to any one of claims 1 to 7 and permeable to air but impermeable to water. Comprising a plasticized starch and a polar organic compound capable of gelatinizing or plasticizing the starch,
The polar organic compound capable of gelatinizing or plasticizing starch includes at least a polar organic compound capable of gelatinizing or plasticizing starch at room temperature, and has a type A durometer hardness of 20 or more and a type D durometer hardness. Is 40 or less. A plasticized starch material. A first mixing step of mixing 20 to 100 parts by mass of a polar organic compound capable of gelatinizing or plasticizing starch with 100 parts by mass of starch, wherein the polar organic compound gelatinizes the starch at room temperature. Or at least containing a plasticizable polar organic compound, the first mixing step,
A plasticizing step of heating the mixture obtained by the first mixing step to a temperature of 120° C. to 150° C. to plasticize the starch to obtain a plasticized starch material, wherein the plasticized starch material type A A plasticizing step having a durometer hardness of 20 or more and a type D durometer hardness of 40 or less; and a second mixing step of mixing the plasticized starch material and a thermoplastic resin to obtain a resin composition, A method for producing a resin composition. A mixing step of mixing 20 to 100 parts by mass of a polar organic compound capable of gelatinizing or plasticizing starch with 100 parts by mass of starch, wherein the polar organic compound gelatinizes or plasticizes starch at room temperature. Plasticizing to obtain a plasticized starch material by heating the mixture obtained by the mixing step and the mixture obtained by the mixing step to a temperature of 120° C. to 150° C. to obtain a plasticized starch material. Process,
including,
A method for producing a plasticized starch material having a type A durometer hardness of 20 or more and a type D durometer hardness of 40 or less.