JP5656174B2 - Antistatic agent for polymer composite material and antistatic member - Google Patents

Description

  The present invention relates to an antistatic agent for polymer composite materials and an antistatic member using the antistatic agent for polymer composite materials.

There is a growing concern about the depletion of fossil resources, and the demand for biomass, a renewable resource, is increasing.
Plant-derived biomass has cellulose fibers as the main component of the tissue structure, and the strength of the cellulose fibers is extremely high, and it can be used not only in conventional fields such as fibers and ropes but also as general industrial materials. Is sufficiently hidden (see Non-Patent Document 1).
Using this cellulose fiber as a fiber reinforced material for polymer materials, efforts to improve not only the strength of polymer materials but also the utilization rate of biomass are being applied in the automobile industry, home appliances and IT equipment industries, etc. Progressing. Many molded products and members used in these industries are required to have antistatic performance in order to avoid troubles caused by static electricity.

  Many techniques have been disclosed for the prevention of electrostatic charge of polymer materials. Charging is a phenomenon in which an object is charged with electricity. When electrons are taken from another object, it is negatively charged, and in the opposite case, it is positively charged. Electricity that remains charged and does not move is called static electricity. Static electricity has a lot of negative effects such as dust adsorption, damage to textiles and hair, damage to electronic equipment due to electrical discharge, danger of fire and explosion, so it must be actively removed.

  An article having low electrical conductivity generates static electricity when charged, but can eliminate the static state if discharged immediately. Therefore, it is possible to prevent the member from being charged with static electricity by increasing the conductivity.

  It is possible to prevent troubles due to static electricity by imparting antistatic properties to various molded articles and members, but new troubles may be caused if the direction of flowing static electricity due to the conductive material is wrong. In the case of a plastic bag containing electronic device parts, the bag surface layer is required to have antistatic performance, but the plastic inner layer is required to have insulation, which is the original function of the plastic. By satisfying these two requirements at the same time, it is possible to prevent damage due to the inflow of electricity to the electronic device components in the bag.

  As a technique for imparting antistatic properties to the surface of a polymer material, an antistatic agent is used, 1) a method of mixing a conductive substance such as metal powder or carbon black, and 2) a kind of surfactant. There is a method of applying or mixing a certain antistatic agent, and as a method not using the antistatic agent, there is a method of 3) hydrophilizing the surface by plasma treatment or the like.

  For synthetic resin moldings that are easily charged, the method 1) or 2) that is inexpensive and relatively highly effective is often used. For example, as a method combining 1) and 2), a technique is disclosed in which a quaternary ammonium salt antistatic agent and an alkali metal halide salt are kneaded into a synthetic resin member mainly composed of a thermoplastic resin ( Patent Document 1). In addition, a technique of kneading conductive zinc oxide and a cationic antistatic agent in synthetic rubber has been disclosed (see Patent Document 2).

Here, in the method 1), since the conductive substances need to be in contact with each other in the polymer material, it is necessary to add a large amount of the conductive substance in the form of powder, which not only increases the cost. The original mechanical and chemical properties of the synthetic resin molding may be impaired. Furthermore, it is difficult to make the conductive material unevenly distributed only in the surface layer.
The method 2) is based on the principle that the diffusion and leakage of charges is accelerated by adsorbing moisture in the air, but when applied to the surface of a polymer material, it is effective to wipe or wash the surface. May disappear. In addition, when mixed into a polymer material, it may not be uniformly mixed if the compatibility with the polymer material is poor, and conversely, if the compatibility is good, it may be difficult to leach onto the surface and the moisture adsorption force may not be exhibited.

  As for the method 3), a method is disclosed in which the surface of the synthetic resin plate is subjected to glow discharge plasma treatment, and then a conductive coating is applied, dried and cured to form a conductive layer (see Patent Document 3). However, the method 3) requires complicated processing using a special processing apparatus and is difficult to use for general purposes.

Technologies for improving antistatic properties and conductivity have also been developed for biomass composites in which biomass is introduced into a polymer material.
For example, a method for producing a wood fiber resin composite board in which natural fibers and wood grains are mixed is disclosed by utilizing the characteristics of natural fibers that can exhibit an antistatic effect due to its high water content compared to synthetic fibers. (See Patent Document 4). However, it is indispensable to use natural fibers having a high water content, and it requires laborious steps such as penetration of process oil, blending with resin, and deoiling.
In addition, for example, a technique for providing conductivity by forming a thin film of a metal or a conductive inorganic compound on the surface of a wood-based filler such as wood powder by a vacuum deposition method or a sputtering method in advance is disclosed. (Patent Document 5). However, the methods such as vacuum deposition and sputtering require a complicated process using a special apparatus and have a problem in versatility.
In addition, for example, a technique is disclosed in which biomass raw materials such as wood and bamboo are heat-treated, the oily solution is removed and dried, and then fired at a high temperature at a graphite structure forming treatment temperature (see Patent Document 6). It is said that conductivity can be obtained by graphitizing the biomass material. Although this technology is excellent in that it does not require the addition or coating of a conductive third component, the high-temperature firing process is complicated, and the loss of biomass raw materials during production is also large. It is.

JP-A-6-2419 Japanese Patent Laid-Open No. 10-330543 JP-A-10-101824 JP 2008-194998 A JP-A-2005-75883 JP 2009-19080 A

T. Nishino, I. Matsuda, K. Hirao, Macromolecules, 37, 7683-7687 (2004)

  The problem to be solved by the present invention is that an antistatic agent for a polymer composite material excellent in antistatic property and having high insulation performance as compared with a surface layer therein while reducing surface resistance and the polymer An object of the present invention is to provide an antistatic member using an antistatic agent for composite materials.

The antistatic agent for polymer composite material according to the present invention comprises bamboo powder and polymer material having an average aspect ratio of 5 to 100 and a water content of 5% or less, and bamboo powder: polymer material = 10 by mass ratio. The mixture is melt-molded by mixing in the range of 90-80: 20, and the ratio of volume resistivity (unit: Ω · cm) to surface resistivity (unit: Ω / □) (volume resistivity / surface resistivity) is 10 ² or more.

Moreover, the antistatic agent for polymer composite materials according to the present invention is characterized in that the surface resistivity is 10 ¹⁰ to 10 ¹³ (unit: Ω / □).

  The antistatic member according to the present invention is formed by molding a polymer composite material containing the above-described antistatic agent for polymer composite materials.

The antistatic agent for polymer composite materials according to the present invention has a volume resistivity (unit: Ω · cm) to surface resistivity (unit: Ω / □) ratio (volume resistivity / surface resistivity) of 10 ² or more. Therefore, while the surface resistance is reduced, high insulation performance is maintained in comparison with the surface layer inside, in other words, the charge flows through the surface layer and diffuses and passes through the inside of the molded body to be opposite. It can be used for the production of a polymer composite material having good antistatic properties capable of preventing diffusion to the side.

  In addition, since the antistatic member according to the present invention forms a polymer composite material containing the above-mentioned antistatic agent for polymer composite materials, it is suitable for electronic parts packaging materials, vehicle members that are required to avoid charging, etc. It can be used suitably.

FIG. 1: shows the optical microscope photograph of the component between 235-140 meshes after classifying the bamboo powder manufactured by the bamboo powder manufacture example. FIG. 2 shows the major axis diameter distribution of the 235 mesh pass component after the bamboo powder produced in the bamboo powder production example is classified. FIG. 3 shows a photomicrograph (x400) of a fractured section of a molded product produced in a masterbatch-like antistatic agent production example for polymer composite material. FIG. 4 shows an enlarged view (x1000) of bamboo-derived short fibers that can be seen in the split section of the molded body produced in the master batch-like antistatic agent production example for polymer composite material.

  Embodiments of the present invention (hereinafter referred to as “embodiments of the present embodiment”) will be described below with reference to the drawings, taking as an example a blend of biomass powder derived from bamboo with a polymer material.

The antistatic agent for polymer composite materials according to this embodiment has a ratio (volume resistivity / surface resistivity) of volume resistivity (unit: Ω · cm) and surface resistivity (unit: Ω / □). 10 ² or more.
The antistatic agent for polymer composite materials according to this embodiment is a masterbatch-like antistatic agent for polymer composite materials containing, for example, bamboo-derived biomass powder (hereinafter referred to as bamboo powder). .

Bamboo powder is obtained by pulverizing bamboo.
In a broad sense, bamboo is a general term for a species of woody stems such as Kimoto, from the family Gramineae. It is said that there are 600 kinds of bamboo grown in Japan. Typical examples include bamboo shoots, mosouchiku, and honeybees. The type of bamboo used in the present embodiment is not limited. Further, in the present embodiment, bamboo means an overall body composed of trunks, branches, leaves, and roots, and in particular, trunks that contain a large amount of vascular sheaths rich in cellulose fiber components are suitable. .
Bamboo consists of cellulose, hemicellulose and lignin as its main constituents. Hemicellulose plays the role of an adhesive that binds cellulose and lignin or cellulose.

Bamboo powder can be used without any problems as long as it contains at least 30% of a component having a major axis diameter in the range of 100 to 1000 μm. Preferably, in order to perform melt mixing with a polymer material, The water content of the bamboo powder is preferably 5% or less. In order to remove excess moisture from biomass, a method of heating for several hours while applying hot air using a dryer is usually used. However, it is hydrophobic to reduce moisture to 5% or less from hydrophilic biomass. Time and energy are required compared to polymer materials.
As a suitable method for obtaining dried bamboo powder, there is a method using superheated steam. Superheated steam in the temperature range from the reversal temperature of 170 ° C. to 300 ° C. supplies heat to the bamboo more rapidly than dry air to remove moisture. At the same time, in order to decompose the hemicellulose component that decomposes at the lowest temperature, bamboo that has been superheated and steamed in this temperature range is easily crushed and crushed to obtain bamboo powder with a major axis diameter of 100 to 1000 μm used in the present invention. be able to.
Here, the major axis diameter means the maximum diameter of the bamboo powder particles, that is, the length when any two points on the outer contour line of the grain are selected so that the length between them becomes the maximum, and the fiber shape In the case of particles, the length in the major axis direction, that is, the fiber length. The mass ratio of the powder whose major axis diameter is within a predetermined range is directly measured for fibers in a 1 cm × 1 cm image obtained by microscopic observation with adjustable magnification, and the fiber length and mass are in a substantially proportional relationship. It is obtained by measuring the cumulative frequency% of the fiber length on the basis of something and replacing it with mass%.
In addition, the approximate value of the mass ratio of the powder whose major axis diameter is within a predetermined range can be easily obtained by a sieving method.

The bamboo powder preferably has an average aspect ratio in the range of 5 to 100, and more preferably in the range of 10 to 80. When the average aspect ratio of the bamboo powder exceeds 100, the melt fluidity may be hindered during melt molding with the polymer material. Moreover, when the average aspect ratio is less than 5, not only the fiber reinforcement of the resulting molded product does not appear, but also the antistatic performance may not be high.
Here, the aspect ratio is expressed as a ratio of major axis diameter / minor axis diameter. The ratio of major axis diameter / minor axis diameter may be referred to as the ratio of fiber length / fiber diameter. A large aspect ratio means a more elongated fibrous form. The mass ratio of the powder having an average aspect ratio within a predetermined range is measured according to the above-described method for measuring the mass ratio of a powder having a major axis diameter within the predetermined range.

  In general, the cellulose component contained in a large amount in the vascular sheath of bamboo takes a fibrous form. For this reason, the biomass powder having a large major axis diameter obtained by classification operation contains more fibrous components derived from cellulose and has a large aspect ratio. Bamboo powder, which is a biomass powder having a large aspect ratio, can exhibit a function as a reinforcing fiber when melt-molded together with a polymer material. Furthermore, contact between fibers tends to occur, and as a result, the antistatic performance can be further improved.

Here, the manufacturing method of bamboo powder is demonstrated.
The method for producing bamboo powder is carried out by heat-treating bamboo using heated steam at 170 to 250 ° C. and then pulverizing it until the desired major axis diameter distribution is obtained.

  Heated steam treatment is to bring steam heated to 170 to 250 ° C. into contact with bamboo. If it is less than 170 degreeC, the water-vapor treatment effect of a bamboo is small, and processing requires a long time. Furthermore, as will be described later, 170 ° C. is a reverse transition temperature, and therefore, a drying treatment can be simultaneously performed above that temperature. On the other hand, when the temperature exceeds 250 ° C., the decomposition of the bamboo tends to progress more than necessary, and the carbonization of the cellulose component tends to occur, leading to the strength of the molded body when the bamboo powder is blended with the polymer material and molded. This is not preferable because the contribution of is reduced. As heating steam processing temperature, More preferably, it is 190-240 degreeC, More preferably, it is the range of 200-230 degreeC.

  Here, the water vapor heated to 170 to 250 ° C. is water vapor in the range of saturation pressure to normal pressure. Such heated steam includes pressurized saturated steam and atmospheric superheated steam. Normal pressure superheated steam is different from pressurized saturated steam obtained by heating in a constant volume state, and refers to steam at 100 ° C. or higher under standard pressure obtained by further heating 100 ° C. steam in a state where it can expand. .

  Bamboo-derived biomass after heat treatment is preferentially decomposed by the readily degradable hemicellulose component and partially volatilized and removed. Can be easily pulverized. The crushing and crushing can be appropriately performed using a generally known crushing / crushing apparatus. At this time, a two-stage pulverization process in which fine pulverization is performed after coarse pulverization may be performed. Examples of suitable crushing and crushing apparatuses include, for example, a hammer mill, a cutter mill, a pin mill, a crusher mill, a ball mill, a rod mill, a bar mill, a disk mill, a blade mill, a vibration mill, and a combination of two or more of these methods. This is a composite grinding method.

  Although the pulverized bamboo powder can be used as it is, in order to develop a higher level of antistatic properties, it is also preferable to control the particle size distribution by classification operation. As a method used for the classification operation, a generally known classification method can be used without any limitation. Examples of suitable classification methods include, for example, sieving classification, airflow classification, vortex centrifugal classification, electrostatic separation classification, and the like, and various combinations of loads such as ultrasonic waves and longitudinal and transverse vibrations. There are different classification methods. Specifically, a vibration sieving device, a cyclone, an air classifier, a rotary drum electrostatic separator, and the like are suitable classifiers. Using these apparatuses, bamboo powder as the main ingredient of the antistatic agent is produced.

  The performance of the antistatic agent can be generally evaluated by the conductivity. For example, in the case of a metal powder or an inorganic powder, the conductivity can be easily measured by heat compression as long as it has some malleability and plasticity. However, for example, bamboo powder does not have plasticity, so it is very difficult to measure the conductivity appropriately and with good reproducibility. For this reason, antistatic performance can be evaluated by measuring the surface resistivity and volume resistivity of a molded product obtained by blending bamboo powder with a polymer material.

Bamboo powder itself has antistatic properties, but it can be used as a so-called masterbatch-type colorant when producing a polymer material product by blending with a polymer material to form a molded body. Can be preferred.
The masterbatch-like antistatic agent for polymer composite materials according to the present embodiment is, for example, a composition in which bamboo powder is mixed with a polymer material and a curing agent as necessary, and the decomposition reaction does not proceed. It can be obtained by melt molding under conditions, or after melt molding, and curing by heating, steam, light irradiation or the like.

  The polymer material blended in the antistatic agent for the polymer composite material can be used without any limitation as long as it can be combined. In particular, the thermoplastic resin can be more suitably used because it can produce an industrial product member with higher designability by melt molding.

  As the thermoplastic resin, any resin that can be combined with bamboo powder can be used without any limitation. Examples of suitable thermoplastic resins include polyolefins such as polyethylene and polypropylene; polystyrene, acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, and methyl methacrylate-butadiene-styrene (MBS) resin. Styrenic resins such as: Polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); Polylactic acid, polycaprolactone, poly (3-hydroxybutyric acid), polytetramethylglycolide, polyglycolic acid, etc. Examples include aliphatic polyesters. Among these thermoplastic resins, polyolefins are particularly preferable from the viewpoint of ease of moldability. These thermoplastic resins may be used alone or in combination of two or more.

  In addition to the thermoplastic resin, a thermoplastic prepolymer of a thermosetting resin can be used. Typical prepolymers of thermosetting resins include prepolymers such as epoxy resins, unsaturated polyester resins, silane-crosslinked polyethylene, alkyd resins, melamine resins, polyurethane, and crosslinked rubber. Among these prepolymers of thermosetting resins, prepolymers such as epoxy resins, polyurethanes, and unsaturated polyester resins are preferable because they can be easily combined with the bamboo powder according to the present invention.

The mass ratio of bamboo powder and polymer material (bamboo powder: polymer material) is preferably 10:90 to 80:20, more preferably 10:90 to 60:40, 20:80 to 55:45 is more preferable.
If the mass ratio of the bamboo powder is less than 10%, the antistatic performance may not be effectively exhibited. On the other hand, if it exceeds 80%, the mechanical strength of the antistatic member described later may be lowered.

As a method of blending and molding bamboo powder and a thermoplastic resin, a known method can be used without any limitation as long as the bamboo powder can be uniformly dispersed in the thermoplastic resin.
For example, a melt kneading method in which a thermoplastic resin is melted by heat and kneaded while applying shear stress to the bamboo powder, a solution in which the thermoplastic resin is dissolved in a solvent, the bamboo powder is added and dispersed, and then the solvent is vaporized and removed. There are a mixing method, a calender molding method in which a thermoplastic resin is softened on a heated roll, bamboo powder is added thereon, and kneaded while being pressed by a hot roll. Among these compounding methods, the melt-kneading method is most preferable in terms of efficiency and versatility.

  Specific examples of the melt-kneading method include an injection molding method using an injection molding machine, an extrusion molding method using an extrusion molding machine, and a blow molding method using a blow molding machine. Using the sheet-like molded body as a raw material, deep drawing by a vacuum molding method using a vacuum molding machine or a compression molding method using a compression molding machine is preferably used. Among these molding methods, the injection molding method and the extrusion molding method are more preferably used from the viewpoints of versatility and expandability.

  Injection molding is a method to obtain a molded product by injecting and injecting heat-melted material into a mold cavity, and cooling and solidifying it. Through the parts called sprue and runner, The mold cavity is filled with a molten bamboo powder-containing resin melt. Here, since bamboo powder does not melt, a thermoplastic resin excellent in fluidity is selected when performing injection molding that requires melt fluidity.

  Extrusion molding is a molding method in which a material melted and mixed by shearing stress and heat generated by the rotation of a screw in a heated cylinder is cooled and solidified while being extruded from a die extrusion port at a constant speed. Since high fluidity like injection molding is not required, a high-molecular weight thermoplastic resin having a high viscosity so as not to be deformed after being extruded from the extrusion port is selected. Furthermore, in extrusion molding, kneading with a screw is effectively performed. There are various screw shapes and directions of rotation, which can be selected according to the purpose of use. In the production of a molded body, in order to further increase the degree of kneading, kneading with a biaxial co-rotating screw is a more preferable method.

  For example, when molding an antistatic agent for a polymer composite material like a masterbatch according to this embodiment using an injection molding machine, high melt fluidity is required, and before filling into a mold In order to filter out large infusibilities through the screen, it is more effective for formability that the bamboo powder is distributed more in the direction where the major axis diameter is relatively small. On the other hand, when the masterbatch-like antistatic agent for polymer composite materials according to the present embodiment is molded using an extruder, bamboo powder containing long fibrous components is contained in the molten thermoplastic resin. Oriented and fluidized. Therefore, as a result, a composite containing an oriented fibrous bamboo powder is obtained, and an improvement in mechanical properties due to fiber reinforcement is easily manifested, and this is a preferred embodiment of the production method.

In obtaining a masterbatch-like polymer composite antistatic agent according to the present embodiment containing the above-described oriented fibrous bamboo powder, the melt fluidity of the polymer material is important, and It is a preferred embodiment that the melt flow rate of the molecular material is in the range of 1 to 60 g / 10 min. When the melt flow rate is less than 1 g / 10 min, the viscosity is too high, for example, there is a risk that complicated molding may be difficult. In the range exceeding 60 g / 10 min, the melt viscosity is too low, and the volume resistivity and surface resistivity are low. The ratio of
The above-described method for producing an antistatic agent for a polymer composite material according to the present embodiment according to this embodiment can also be applied to the method for producing an antistatic member according to this embodiment described later. .

As described above, the antistatic agent for polymer composite materials according to the present embodiment has a ratio of volume resistivity (unit: Ω · cm) to surface resistivity (unit: Ω / □) of 10 ² or more. is there.

The antistatic performance is usually evaluated by two types: volume resistivity and surface resistivity, which are indicators of the ease of conducting electricity, and half-life, which indicates the time during which the amount of charged electricity is halved. The lower the volume resistivity and surface resistivity, the higher the antistatic property, and the shorter the half-life, the higher the antistatic property. The volume resistivity is a resistance per unit volume and is a physical quantity inherent to a substance. On the other hand, the surface resistivity is a resistance per unit area and is also called a sheet resistance or simply a surface resistance.
The surface resistance and volume resistivity are measured according to JIS-K-6911-5.13.

As the amount of bamboo powder blended into the polymer material is increased, the surface resistivity of the molded body is reduced.
On the other hand, the volume resistivity decreases as the amount of bamboo powder blended into the polymer material is increased as in the surface resistivity, but the reduction rate is smaller than the surface resistivity.

  Such a difference in behavior between the surface resistivity and the volume resistivity is considered to result from the uneven distribution of bamboo powder in the surface layer of the molded body. Due to the uneven distribution of the bamboo powder, the surface layer of the molded body exhibits high conductivity, and the inner layer forms a layer having insulating properties. Such a multilayer structure is considered to be due to the occurrence of a layer distribution in the thermal fluidity during melt molding.

The advantages are, volume resistivity (unit: Ω · cm) and the surface resistivity (unit: Ω / □) when the ratio of is 10 ² or more, it is preferably expressed. The ratio between the volume resistivity (unit: Ω · cm) and the surface resistivity (unit: Ω / □) is more preferably 10 ³ or more.
In addition, when the antistatic agent for a polymer composite material has a surface resistivity of 10 ¹⁰ to 10 ¹³ (unit: Ω / □), the above-described effects can be preferably obtained, and 5 × 10 ¹² (unit). : Ω / □) or less, the above-mentioned effects can be more preferably obtained.
In addition, the biomass powder added to the antistatic agent for polymer composite materials is not limited to bamboo powder.

Next, the antistatic member according to the present embodiment will be described.
The antistatic member according to the present embodiment is formed by molding a polymer composite material containing the above-described antistatic agent for polymer composite materials.

  The antistatic member broadly refers to a member used for applications where it is desirable to have antistatic properties. It can be said that the container for the electronic component is an antistatic member. However, the present invention is not limited to this, and various parts of home appliances and IT equipment, automobile interior parts, and the like are preferably antistatic members. An antistatic member can be suitably obtained by molding the above-mentioned masterbatch-like antistatic agent for polymer composite materials as it is, or by adding a polymer material if necessary and molding it. it can.

The antistatic member according to the present embodiment can be manufactured by the same method as the master batch-like antistatic agent for polymer composite material described above.
At this time, the mass ratio (bamboo powder: polymer material) of the bamboo powder and the polymer material is preferably 10:90 to 80:20, and more preferably 10:90 to 60:40. More preferably, the ratio is 20:80 to 55:45.
If the mass ratio of the bamboo powder is less than 10%, the antistatic performance may not be effectively exhibited. On the other hand, if the ratio exceeds 80%, the mechanical strength of the antistatic member may be lowered.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, these examples do not limit the scope of the present invention.

(Production example of bamboo powder)
Miso bamboo (diameter: about 12 cm, length: about 40 cm, weight: about 1 kg) was placed in a superheated steam treatment apparatus manufactured by Naomoto Kogyo Co., Ltd. having the following specifications and subjected to superheated steam treatment at 220 ° C. for 120 minutes. For comparison, a crushing and fine crushing test was also performed on the Somune bamboo (above dimensions) not subjected to superheated steam treatment using the same apparatus.
The treated Sosou bamboo was taken out and crushed at 7000 rpm using the following coarse pulverizer, and then pulverized at 7000 rpm using a fine pulverizer. Furthermore, a bamboo powder having a component between 235 and 140 mesh was prepared by classification using a sieve of 140 mesh (aperture 106 μm) and 235 mesh (aperture 63 μm) using the following sieve device.
Specification of superheated steam treatment equipment:
Steam generating part: Heater capacity 6.3kW
Equivalent evaporation 9.45kg / h
Maximum working pressure 0.11 MPa
Treatment tank: Heater capacity 8kW
Inside dimensions W590xD385xH555 mm
Crusher specifications:
Coarse crushing: HM-5 type manufactured by Nara Machinery Co., Ltd. Fine grinding: Free crusher M-2 type manufactured by Nara Machinery Co., Ltd. Specifications of moisture measuring device: Moisture meter MOC-120H manufactured by Shimadzu Corporation
Specification of sieving device: MVS-I mini sieve shaker manufactured by AS ONE Co., Ltd.

<Measurement of long axis diameter distribution and average aspect ratio of bamboo powder>
The major axis diameter and the average aspect ratio were measured using the following optical microscope. The magnification of the optical microscope was changed in accordance with the size of the major axis diameter of the bamboo powder.
Optical microscope: VH-5000 type manufactured by Keyence Corporation From the photomicrograph of FIG. 1, it was found that most of the components between 235 (aperture 63 μm) to 140 mesh (aperture 106 μm) were whisker-like short fibers. From the major axis diameter distribution observation result shown in FIG. 2, the component between 235 and 140 meshes is 1.6% by mass when the major axis diameter is 100 μm or less, and the component whose major axis diameter is 100 to 1000 μm is It was 98.4 mass%.
The average aspect ratio of the component between 235 and 140 mesh measured by observation with an optical microscope was 12.3.

(Manufacturing Examples 1 to 3 of Antistatic Agent for Polymer Composite Material Like Masterbatch)
Bamboo powder (component between 235-140 mesh, aspect ratio 12.3) obtained from the bamboo powder production example and polypropylene (indicated as PP in Table 1) Novatec PP FY-6 manufactured by Nippon Polypropylene Co., Ltd., melt flow rate 2 .5 g / 10 min) is mixed with bamboo powder: polypropylene = 10: 90, 30:70, 50:50 (mass ratio), and this is a biaxial kneading extruder 160B with a vent manufactured by Imoto Seisakusho (rotating in the same direction) A biaxial screw, screw diameter: 15 mm, L / D: 25, vent port number: 1) was melt-kneaded to produce a strand-like bamboo powder composite. The melt-kneading conditions for compounding with polypropylene were as follows: a hopper temperature of 80 ° C., a barrel temperature of 190 ° C., a die temperature of 190 ° C., and a screw speed of 15 rpm.

  The master batch-like antistatic agent for polymer composites manufactured using an extruder was pre-heated at 190 ° C for 3 minutes using a heat press IMC-180C manufactured by Imoto Seisakusho, and then pressure of 12 MPa Pressurized for 5 minutes. A sheet sample of 100 mm × 100 mm was cut out from the obtained sheet having a thickness of about 0.6 mm, and used as a surface resistivity and volume resistivity measurement sample.

<Measurement of surface resistivity and volume resistivity of anti-static agent for polymer composite material like masterbatch>
For surface resistivity and volume resistivity measurement, HI-100 (main electrode φ50mm, guard inner diameter φ53) is used as a probe in accordance with JIS-K-6911 using Mitsubishi Chemical's Hirestar UP (model number MCP-HT450). 0.2 mm), an applied voltage of 1000 v, an application time of 60 seconds, and a test temperature of 23 ° C. The measurement was performed three times or more for each sample, and the average value was obtained.

As is apparent from the results in Table 1, the master batch-like antistatic agents for polymer composite materials of Production Examples 1 to 3 have a volume resistivity / surface resistivity of more than 10 ³ and a surface resistivity. Is 10 ¹³ Ω / □ or less, and it can be seen that the antistatic performance is remarkably improved as compared with polypropylene.

3 and FIG. 4 show a master batch-like antistatic agent for polymer composite material production example 1 after sufficiently cooling the sheet sample with liquid nitrogen, and then splitting the cut section with a digital micromanufactured by Keyence Corporation. This is a result of observation in a shape measurement mode (laser wavelength: 658 mm, output: 0.95 mW, pulse width: 1 ns) using a scope VK-100 / X200. FIG. 3 is an overall view of the sheet cross section (x400), and FIG. 4 is an enlarged view of the vicinity of the surface layer (x1000). As a result of microscopic observation, it is clear that the fiber component of bamboo powder is unevenly distributed near the surface layer of the sheet.

Claims (3)

Bamboo powder and polymer material having an average aspect ratio of 5 to 100 and a water content of 5% or less are mixed and melt-molded in a mass ratio of bamboo powder: polymer material = 10: 90 to 80:20. And a ratio of the volume resistivity (unit: Ω · cm) to the surface resistivity (unit: Ω / □) (volume resistivity / surface resistivity) is 10 ² or more. Antistatic agent for use. 2. The antistatic agent for polymer composite materials according to claim 1, wherein the surface resistivity is 10 ¹⁰ to 10 ¹³ (unit: Ω / □).   The antistatic member formed by shape | molding the polymer composite material containing the antistatic agent for polymer composite materials of any one of Claim 1 or 2.