Method for producing composite resin particle, and composite resin particle
阅读说明：本技术 复合树脂粒子的制造方法及复合树脂粒子 (Method for producing composite resin particle, and composite resin particle ) 是由 幸田祥人 高田克则 五十岚弘 于 2019-07-25 设计创作，主要内容包括：本发明的目的是提供一种复合树脂粒子的制造方法,该复合树脂粒子具有氟树脂和碳纳米材料,并且保持导电性的同时成型性优异。本发明为具有氟树脂和碳纳米材料的复合树脂粒子的制造方法,具备以下工序：在分散介质的存在下对氟树脂进行粉碎；使氟树脂和碳纳米材料在分散介质中分散,而得到包含氟树脂、碳纳米材料和分散介质的分散液；将所述分散液储存到具有底面的干燥容器中,在利用下式(1)计算的干燥面积为20～100[cm～2/g]的条件下,对所述分散液进行干燥,而去除所述分散介质,干燥面积＝(S/W-1)···(1)其中,S为干燥容器的底面的面积[cm～2],W-1为分散液中的复合树脂粒子的质量[g]。(The purpose of the present invention is to provide a method for producing composite resin particles which have a fluororesin and a carbon nanomaterial and which have excellent moldability while maintaining electrical conductivity. The present invention is a method for producing composite resin particles comprising a fluororesin and a carbon nanomaterial, comprising the steps of: pulverizing a fluororesin in the presence of a dispersion medium; dispersing a fluororesin and a carbon nanomaterial in a dispersion medium to obtain a dispersion liquid containing the fluororesin, the carbon nanomaterial, and the dispersion medium; storing the dispersion in a drying vessel having a bottom surface,the dry area is 20 to 100[ cm ] calculated by the following formula (1) 2 /g]Under the conditions of (1), drying the dispersion to remove the dispersion medium, wherein the drying area is (S/W) 1 ) 1 wherein S is the area [ cm ] of the bottom surface of the drying container 2 ]，W 1 The mass [ g ] of the composite resin particles in the dispersion]。)
1. A method for producing composite resin particles, wherein the composite resin particles comprise a fluororesin and a carbon nanomaterial, the method comprising:
pulverizing the fluororesin in the presence of a dispersion medium;
dispersing the fluororesin and the carbon nanomaterial in the dispersion medium to obtain a dispersion liquid containing the fluororesin, the carbon nanomaterial, and the dispersion medium;
storing the dispersion in a drying vessel having a bottom surface, drying the dispersion under a condition that a drying area calculated by the following formula (1) is 20 to 100, and removing the dispersion medium,
dry area ═ S/W1)···(1)
Wherein the unit of dry area is cm2(ii)/g, S is the area of the bottom surface of the drying container and is expressed in cm2，W1The unit is the mass of the composite resin particles in the dispersion, and is g.
2. The method for producing composite resin particles according to claim 1,
in the step of removing the dispersion medium, the drying container is shaken before the dispersion liquid is dried.
3. The manufacturing method according to claim 1 or 2,
the composite resin particle has a bulk density of 300 or more and less than 600 as calculated by the following formula 2,
bulk density ═ W2/V1) ···(2)
Wherein the unit of bulk density is g/L, W2To a volume of V1The first measuring vessel of (5) is filled with the required mass of the composite resin particles, V1In units of L and of mass in units of g.
4. The manufacturing method according to any one of claims 1 to 3,
the composite resin particle has a porosity of less than 0.6 as calculated by the following formula (3),
void ratio of (V)3/V2) ···(3)
Wherein, V3In a volume of V2The volume V of the liquid required when the second measurement vessel is filled with the composite resin particles2And the volume of the desired liquid is in units of L.
5. A composite resin particle having a fluororesin and a carbon nanomaterial, having a bulk density of 300 or more and less than 600 as calculated by the following formula (2),
bulk density ═ W2/V1) ···(2)
Wherein the unit of bulk density is g/L, W2To a volume of V1The first measuring vessel of (5) is filled with the required mass of the composite resin particles, V1In units of L and of mass in units of g.
6. The composite resin particle according to claim 5,
the composite resin particle has a porosity of less than 0.6 as calculated by the following formula (3),
void ratio of (V)3/V2) ···(3)
Wherein, V3In a volume of V2The volume V of the liquid required when the second measurement vessel is filled with the composite resin particles2And the volume of the desired liquid is in units of L.
Technical Field
The present invention relates to a method for producing composite resin particles and composite resin particles.
Background
A technique for imparting conductivity to a resin material such as polytetrafluoroethylene is known. As an example, composite resin particles having a carbon material such as graphite or carbon nanotubes and a resin material are known (patent documents 1 and 2).
Patent document 1 describes a production method in which polytetrafluoroethylene agglomerated powder, filler powder and dry ice are simultaneously charged into a mill mixer, and these are milled and mixed. In the example described in patent document 1, graphite is used as the filler powder.
Patent document 2 describes a method of obtaining composite resin particles by drying a composite resin particle dispersion liquid containing resin material particles, a carbon nanomaterial, a ketone solvent, and a dispersant.
However, the production method described in patent document 1 realizes the composite of the carbon material and the resin material by so-called dry mixing. Therefore, in the case of using a carbon nanomaterial such as carbon nanotubes as a carbon material, it is difficult to combine the carbon nanomaterial and polytetrafluoroethylene by the production method described in patent document 1. As a result, when the carbon nanomaterial is used in the production method described in patent document 1, the resin material cannot be provided with electrical conductivity.
In the method for producing composite resin particles described in patent document 2, many composite resin particles obtained by drying aggregate, and the shape and size of the aggregate of the composite resin particles tend to be uneven. Therefore, in the case of producing an extrusion molded article such as a conductive pipe, it is necessary to reduce the voids between the powders in a state of being filled in a molding machine by pulverizing an aggregate of composite resin particles into a fine powder.
However, fluororesin particles such as polytetrafluoroethylene produced by emulsion polymerization are easily fiberized if they are subjected to a shearing force during pulverization. If the fluororesin particles are sieved and pulverized, the particles are also fibrillated. Therefore, the composite resin particles are difficult to be pulverized into a powder. Further, if the fluororesin is fiberized, the moldability inherent in the fluororesin may be lowered. Further, the conductivity imparted to the composite resin particles may also decrease.
As described above, in the conventional method for producing composite resin particles, it is difficult to produce composite resin particles having excellent moldability while maintaining electrical conductivity.
Patent document 1: japanese patent laid-open publication No. 2015-151543
Patent document 2: japanese patent laid-open publication No. 2015-30821
Disclosure of Invention
The present invention addresses the problem of providing a method for producing composite resin particles that contain a fluororesin and a carbon nanomaterial and have excellent moldability while maintaining electrical conductivity.
In order to solve the above-described problems, the present invention has the following features.
[1] A method for producing composite resin particles containing a fluororesin and a carbon nanomaterial, comprising:
pulverizing the fluororesin in the presence of a dispersion medium (first dispersion medium);
dispersing the fluororesin and the carbon nanomaterial in the dispersion medium to obtain a dispersion liquid containing the fluororesin, the carbon nanomaterial, and the dispersion medium;
storing the dispersion in a drying vessel having a bottom surface, wherein the drying area calculated by the following formula (1) is 20 to 100[ cm ]2/g]Drying the dispersion liquid under the condition of (1) to remove the dispersion medium,
dry area ═ S/W1)···(1)
Wherein S is the area [ cm ] of the bottom surface of the drying container2]，W1The mass [ g ] of the composite resin particles in the dispersion]。
[2] The method for producing composite resin particles according to [1], wherein in the step of removing the dispersion medium, the drying vessel is oscillated before the dispersion liquid is dried.
[3] The method for producing composite resin particles according to [1] or [2], wherein the composite resin particles have a bulk density of 300g/L or more and less than 600g/L as calculated by the following formula 2,
bulk density ═ W2/V1)···(2)
Wherein, W2To make the volume V1[L]The mass [ g ] of the composite resin particles required for filling the first measuring container]。
[4] The method for producing composite resin particles according to any one of [1] to [3], wherein the porosity of the composite resin particles calculated by the following formula (3) is less than 0.6,
void ratio of (V)3/V2)···(3)
Wherein, V3In a volume of V2[L]The volume [ L ] of the liquid required when the second measurement vessel is filled with the composite resin particles in the second measurement vessel [ L ]]。
[5] Composite resin particles having a fluororesin and a carbon nanomaterial, the composite resin particles having a bulk density of 300g/L or more and less than 600g/L as calculated by the following formula (2),
bulk density ═ W2/V1)···(2)
Wherein, W2To a volume of V1[L]The mass [ g ] of the composite resin particles required for filling the first measuring container]。
[6] The composite resin particle according to [5], which has a porosity of less than 0.6 as calculated by the following formula (3),
void ratio of (V)3/V2)···(3)
Wherein, V3In a volume of V2[L]The volume [ L ] of the liquid required when the second measurement vessel is filled with the composite resin particles in the second measurement vessel [ L ]]。
According to the present invention, composite resin particles having a fluororesin and a carbon nanomaterial and having excellent moldability while maintaining electrical conductivity can be produced.
Drawings
FIG. 1 is a photograph showing the appearance of the composite resin particle powder of example 2.
Fig. 2 is a photograph of a compression molding machine when the composite resin particle powder of example 2 was charged.
FIG. 3 is a photograph showing the appearance of a compression-molded article of composite resin particles of example 2.
Fig. 4 is a photograph showing the appearance of the composite resin particles of comparative example 2.
Fig. 5 is a photograph of a compression molding machine when the composite resin particles of comparative example 2 were charged.
Fig. 6 is a photograph showing the appearance of a compressed molded article of composite resin particles of comparative example 2.
FIG. 7 is a photograph showing a state in which the composite resin particles of comparative example 2 were pulverized with a sieve.
Detailed Description
In the present specification, the following terms have the following meanings.
The "average particle diameter" is a value measured by using a particle size distribution meter, and is a mode diameter in a frequency distribution.
The "volume resistivity" is a value measured by a four-terminal method using a resistivity meter (for example, "LorestaGP" manufactured by mitsubishi chemical analysis technology ltd).
"to" indicating a numerical range means that the numerical values recited before and after the range are included as a lower limit value and an upper limit value.
< method for producing composite resin particles >
Next, a method for producing composite resin particles to which an embodiment of the present invention is applied will be described in detail. In the present embodiment, the composite resin particles are composite particles containing a fluororesin and a carbon nanomaterial.
Specific examples of the fluororesin include Polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), ethylene tetrafluoroethylene copolymer (ETFE), 4-fluoroethylene-6-fluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), and the like.
Among them, as the fluororesin, polytetrafluoroethylene is preferable, polytetrafluoroethylene obtained by emulsion polymerization is more preferable, and fine powder (fine powder) containing polytetrafluoroethylene obtained by emulsion polymerization is more preferable.
The fine powder is a powder containing polytetrafluoroethylene obtained by emulsion polymerization. As the fine powder, a synthetic product may be used, and a commercially available product may also be used. As a commercially available product of the fine powder, for example, PTFE fine powder grade F-104 (average particle size: about 500 μm, manufactured by Daiki Kogyo Co., Ltd.) can be given.
The method for synthesizing the fine powder is not particularly limited. For example, tetrafluoroethylene may be emulsion-polymerized using a stabilizer and an emulsifier, and the particles in the reaction solution after emulsion polymerization may be aggregated to dry the resin particles to obtain fine powder.
From the viewpoint of workability in grinding, the fluororesin used as a raw material preferably has an average particle diameter of 400 to 500 μm. When the average particle diameter of the fluororesin is about 400 to 500. mu.m, it is not necessary to impart an excessive amount of energy to the fluororesin during pulverization, and the composite resin particles are more excellent in moldability.
The carbon nano material is a material with a carbon six-membered ring structure.
Specific examples of the carbon nanomaterial include carbon nanofibers, carbon nanohorns, carbon nanocoils, graphene, fullerene, acetylene black, ketjen black, carbon black, and carbon fibers. Among them, carbon nanotubes are also particularly preferable.
The average length of the carbon nanomaterial is not particularly limited. The average length of the carbon nanomaterial may be, for example, 10 to 600 μm. If the average length of the carbon nanomaterial is 10 μm or more, the composite resin particle is more excellent in electrical conductivity. If the average length of the carbon nanomaterial is 600 μm or less, the carbon nanomaterial is easily uniformly adhered to the fluororesin.
For example, the average length of the carbon nanomaterial can be measured by observation with a scanning electron microscope.
First, in the method for producing composite resin particles according to the present embodiment (hereinafter, referred to as "the present production method"), a fluororesin is pulverized in the presence of a first dispersion medium (pulverization process).
As the first dispersion medium, a ketone solvent is preferable. Specific examples of the ketone solvent include methyl ethyl ketone, acetone, diethyl ketone, methyl propyl ketone, and cyclohexanone. However, the ketone solvent is not limited to these examples.
Among them, methyl ethyl ketone is also preferable as the ketone solvent because composite resin particles tend to be excellent in conductivity and moldability.
When the fluororesin is pulverized in the presence of the first dispersion medium, the fluororesin preferably has an average particle diameter of 5 to 50 μm or less.
If the average particle diameter of the fluororesin is pulverized to 5 μm or more, the specific surface area of the fluororesin does not increase so much, and the amount of the carbon nanomaterial with respect to the fluororesin is sufficient. Therefore, it is difficult to form a distribution of the region where the carbon nanomaterial is adsorbed and the region where the carbon nanomaterial is not adsorbed on the region on the surface of the fluororesin, and the composite resin particles have further excellent conductivity.
When the average particle diameter of the fluororesin is pulverized to 50 μm or less, the surface roughness of the fluororesin particles becomes large, and the specific surface area increases. This makes it easy to uniformly adsorb the carbon nanomaterial on the surface of the fluororesin and to reduce the amount of aggregates of the carbon nanomaterial. As a result, the carbon nanomaterial can be uniformly adhered to the surface of the fluororesin, and the molded article of the composite resin particles has more excellent appearance uniformity.
When the fluororesin is pulverized in the presence of the first dispersion medium, the temperature of the first dispersion medium is preferably 20 ℃ or less, more preferably 10 ℃ or less. When the fluororesin is pulverized in the presence of the first dispersion medium, if the temperature of the first dispersion medium is 20 ℃ or lower, composite resin particles in which the carbon nanomaterial is uniformly adhered to the fluororesin can be easily produced while maintaining the moldability and mechanical and physical properties of the fluororesin. As a result, the composite resin particles have more excellent moldability.
As a method of pulverizing the fluororesin, a method capable of suppressing shear force applied to the fluororesin particles is preferable. Specific examples of the pulverization method include stirring with a stirrer, pulverization with ultrasonic waves, and pulverization with a pulverizer such as a food processor. However, the pulverization method is not limited to these examples.
Next, in the present production method, a fluororesin and a carbon nanomaterial are dispersed in a first dispersion medium to obtain a dispersion liquid containing the fluororesin, the carbon nanomaterial, and the dispersion medium (step of obtaining a dispersion liquid).
In the present embodiment, it is also possible to mix a first dispersion medium containing a fluororesin that is pulverized in the presence of the first dispersion medium and disperse a carbon nanomaterial in the first dispersion medium, and a carbon nanomaterial.
As a method of dispersing the fluororesin and the carbon nanomaterial in the first dispersion medium, a method capable of suppressing shear force applied to fluororesin particles is preferable. As a specific example, stirring with a stirrer is preferably used.
When the fluororesin and the carbon nanomaterial are dispersed in the first dispersion medium, the temperature of the first dispersion medium is preferably 20 ℃ or less, more preferably 10 ℃ or less. When the temperature of the first dispersion medium is 20 ℃ or lower during dispersion, composite resin particles in which the carbon nanomaterial is uniformly adhered to the fluororesin can be easily produced while maintaining the moldability and mechanical and physical properties of the fluororesin. As a result, the composite resin particles have more excellent moldability.
In this way, the fluororesin and the carbon nanomaterial are dispersed in the first dispersion medium, whereby the fluororesin and the carbon nanomaterial are combined, and composite resin particles are produced in the first dispersion medium. In the dispersed composite resin particles, the carbon nanomaterial is attached and fixed to at least a part of the surface of the fluororesin in a dispersed state.
As a result, a first dispersion liquid containing the fluororesin, the carbon nanomaterial, and the first dispersion medium can be obtained. The first dispersion liquid contains composite resin particles and a first dispersion medium. The composite resin particles are dispersed in the first dispersion medium.
When the fluororesin and the carbon nanomaterial are dispersed in the first dispersion medium, the amount of the carbon nanomaterial used is preferably 0.01 to 2 mass%, more preferably 0.01 to 0.5 mass%, relative to 100% of the total of the fluororesin and the carbon nanomaterial.
When the amount of the carbon nanomaterial used is 0.01% by mass or more, the composite resin particles have further excellent conductivity. When the amount of the carbon nanomaterial used is 2% by mass or less, the moldability and mechanical and physical properties of the composite resin particle are further excellent.
There is a strong demand in the semiconductor field to reduce the dust and out gas (out gas) of the packing. If the amount of the carbon nanomaterial used is 0.5 mass% or more, the risk of contamination due to the carbon nanomaterial in the production process can be reduced because the amount of the carbon nanomaterial used is small.
When the fluororesin and the carbon nanomaterial are dispersed in the first dispersion medium, a dispersant may also be used. Specific examples of the dispersant include acrylic dispersants. However, the dispersant is not limited thereto.
When the fluororesin and the carbon nanomaterial are dispersed in the first dispersion medium, the second dispersion liquid may also be used as the carbon nanomaterial. The second dispersion liquid is a dispersion liquid in which a carbon nanomaterial is dispersed in a second dispersion medium.
Specific examples of the second dispersion medium include the same compounds as those of the first dispersion medium. The second dispersion medium may be the same as the first dispersion medium, or may be different from the first dispersion medium. However, since the composite resin particles tend to be excellent in conductivity and moldability, the same compound as that used for the first dispersion medium is preferably used for the second dispersion medium.
In the case of using the second dispersion liquid, the composite resin particles are dispersed in a mixed medium of the first dispersion medium and the second dispersion medium.
When the second dispersion liquid is used, the content of the carbon nanomaterial is preferably 0.01 to 2 mass%, more preferably 0.01 to 1 mass%, based on 100 mass% of the second dispersion liquid. If the content of the carbon nanomaterial is 0.01 mass% or more relative to 100 mass% of the second dispersion liquid, the composite resin particles are more excellent in electrical conductivity. If the content of the carbon nanomaterial is 2 mass% or less with respect to 100 mass% of the second dispersion liquid, the moldability and mechanical and physical properties of the composite resin particle are further excellent.
Next, in the present production method, a first dispersion liquid containing a fluororesin, a carbon nanomaterial, and a first dispersion medium is stored in a drying container, and the dispersion liquid is dried under predetermined conditions to remove the dispersion medium (a step of removing the dispersion medium).
First, a first dispersion liquid containing a fluororesin, a carbon nanomaterial, and a first dispersion medium is stored in a drying container. The drying container is a container with a bottom surface.
In the present production method, the drying area is 20cm2/g～100cm2The first dispersion liquid is dried under the condition of/g to remove the dispersion medium (which means a single medium of the first dispersion medium or the second dispersion medium, or a mixed medium of the first dispersion medium and the second dispersion medium). Here, the dry area is calculated by the following formula (1).
Dry area ═ S/W1)···(1)
Wherein S is the area [ cm ] of the bottom surface of the drying container2]，W1The mass [ g ] of the composite resin particles in the first dispersion]。
In the manufacturing method, the drying area is 20-100 cm2Preferably 50 to 100 cm/g2(ii) in terms of/g. Passing through a drying area of 20cm2(ii)/g or more, the composite resin particles become uniform particles, the bulk density of the composite resin particles becomes high, and the composite resinThe moldability of the particles is improved. Since the dry area is 100cm2The workability in drying is improved because of the ratio of the component (A)/g or less.
When the first dispersion is dried, the first dispersion may be heated within a range not to impair the effects of the present invention. However, when the first dispersion is dried, it is preferably left to stand at room temperature under atmospheric pressure by natural drying.
The drying time is not particularly limited. For example, it may be 1 to 24 hours.
The pressure at the time of drying is not particularly limited. For example, it may be 1kPa to 0.2MPa, and it may be about atmospheric pressure.
Before the first dispersion is dried, the drying vessel is preferably shaken. This makes the thickness of the composite resin particles deposited on the bottom surface of the drying container uniform, and the composite resin particles after drying are likely to be uniform particles. As a result, the composite resin particles have more excellent moldability.
For vibration, a large-scale vibration device such as "double shaker NR-150" (manufactured by TITEC) can be used.
The thickness (height from the bottom surface) of the layer of the composite resin particles deposited in the drying container is preferably 0.4mm to 2mm, more preferably 0.4mm to 1mm, and still more preferably 0.4 to 0.8 mm.
The composite resin particles obtained by the present production method are preferably in a powder form at room temperature.
Bulk Density (W) of composite resin particles obtained by the present production method2the/V) is preferably 300g/L or more and less than 600g/L, more preferably 300 to 500 g/L. If the bulk density (W) of the composite resin particles2When the ratio/V) is 300g/L or more and less than 600g/L, the composite resin particles can be easily and uniformly filled in the extrusion molding machine. Here, the bulk density is calculated by the following formula (2).
Bulk density ═ W2/V1)···(2)
Wherein, W2To a volume of V1[L]The mass [ g ] of the composite resin particles required for filling the first measuring container]。W2[g]To pair dryThe mass of the composite resin particles in the state was measured.
The porosity of the composite resin particles obtained by the present production method is preferably 0.4 or more and less than 0.6, more preferably 0.4 to 0.55, and still more preferably 0.4 to 0.5. If the porosity is less than 0.6 or less, the coarse density of the compressed molded article of the composite resin particles is increased, and therefore, the decrease in the volume resistivity of the molded article is easily suppressed. Here, the porosity is calculated by the following formula (3).
Wherein, V3In a volume of V2[L]The volume [ L ] of the liquid required when the second measurement vessel is filled with the composite resin particles in the second measurement vessel [ L ]]。
V3[L]The volume [ L ] of the gap between the composite resin particles generated when the composite resin particles are filled in the second measurement vessel]. For example, V3[L]Calculated by the following method: that is, the density [ g/L ] was charged into the second measuring vessel filled with the composite resin particles]A known standard liquid, and filling the gaps between the composite resin particles with the standard liquid, and measuring the mass [ g ] of the standard liquid required for filling the inside of the second measurement vessel]。
(Effect)
According to the above-described production method, the bulk density of the composite resin particles can be easily controlled. In addition, according to the present manufacturing method, the porosity of the composite resin particles when filled into a container such as a molding machine can be controlled to be relatively small. Therefore, the composite resin particles can be uniformly filled in the compression molding machine. As a result, the composite resin particles are stably supplied to the extrusion molding machine, variation in extrusion amount is reduced, and moldability is good.
In the present production method, since the fluororesin and the carbon nanomaterial are combined by wet mixing, as in the case of pulverizing the fluororesin in the presence of the first dispersion medium, the carbon nanomaterial is easily adsorbed on the surface of the fluororesin. As a result, the composite resin particles have excellent conductivity.
As described above, according to the present production method, even if the composite resin particles after drying are not subjected to secondary processing, the bulk density or particle size of the composite resin particles can be controlled when the first dispersion liquid is dried, and composite resin particles having a bulk density equivalent to that of the fluororesin used as a raw material can be produced. Further, according to the present production method, the amount of aggregates of the composite resin particles generated is also reduced, and there is no need to crush the composite resin particles, so that composite resin particles having a small average particle size can be obtained without fiberizing the fluororesin.
Further, composite resin particles having a bulk density equivalent to that of the fluororesin as a raw material can be produced, and the porosity of the composite resin particles when filled into a container such as a molding machine can be reduced. Therefore, when a molded article such as a pipe is produced by extrusion molding using the composite resin particles, the appearance of the molded article becomes uniform.
< composite resin particles >
The composite resin particle of the present invention comprises a fluororesin and a carbon nanomaterial. In the composite resin particle, the carbon nanomaterial is attached and fixed to at least a part of the surface of the fluororesin in a dispersed state. The composite resin particles of the present invention may contain components (e.g., a dispersant) other than the fluorine resin and the carbon nanomaterial within a range in which the effects of the present invention are not impaired.
The details, specific examples, and preferred embodiments of the fluororesin are the same as those described in the above-described present production method.
The details, specific examples, and preferred embodiments of the carbon nanomaterial are the same as those described in the above-described present production method.
The composite resin particle of the present invention has a bulk density of 300g/L or more and less than 600g/L, more preferably 300g/L to 500 g/L. Here, the bulk density is calculated by the following formula (2).
Bulk density ═ W2/V1)···(2)
Wherein, W2To a volume of V1[L]The mass [ g ] of the composite resin particles required for filling the first measuring container]。
The composite resin particles of the present invention preferably have a porosity of less than 0.6, more preferably 0.4 or more and less than 0.6, and still more preferablyIs 0.4 to 0.55, and particularly preferably 0.4 to 0.5. If the void ratio (V)3/V2) When the content is less than 0.6, the coarse density of the compressed molded product of the composite resin particles is increased, and thus the decrease in the volume resistivity of the molded product is easily suppressed. Here, the porosity is calculated by the following formula (3).
Void ratio of (V)3/V2) ···(3)
Wherein, V3In a volume of V2[L]The volume [ L ] of the liquid required when the second measurement vessel is filled with the composite resin particles in the second measurement vessel [ L ]]。
V3[L]The volume [ L ] of the gap between the composite resin particles generated when the composite resin particles are filled in the second measurement vessel]. For example, V3[L]Calculated by the following method: that is, the density [ g/L ] was charged into the second measuring vessel filled with the composite resin particles]A known standard liquid, and filling the gaps between the composite resin particles with the standard liquid, and measuring the mass [ g ] of the standard liquid required for filling the second measurement vessel]。
(Effect)
The composite resin particles of the present invention have a bulk density of 300g/L or more and less than 600g/L, and therefore can be uniformly filled in a compression molding machine. As a result, the composite resin particles are stably supplied to the extrusion molding machine, variation in extrusion amount is reduced, and moldability is excellent.
< example >
The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.
(bulk Density)
The bulk density was calculated by the following formula (2).
Bulk density ═ W2/V1) ···(2)
Wherein, V1Is the volume [ L ] of the first measuring vessel]. Specifically, a sample (composite resin particles) is filled in a first measuring vessel, and the mass [ g ] of the sample necessary for the filling is measured]And is set to W2。
(void fraction)
The porosity was calculated by the following formula (3).
Void ratio of (V)3/V2) ···(3)
Wherein, V2For the volume [ L ] of the second measuring vessel]. Specifically, a sample (composite resin particles) is filled in a second measurement vessel, and the volume [ L ] of the gap formed between the particles of the sample is measured]And is set to V3。
V3[L]Calculated by the following method: that is, a standard liquid having a known density is charged into a second measurement vessel filled with a sample, and gaps between particles of the sample are filled with the standard liquid, and the mass [ g ] of the standard liquid required for filling the second measurement vessel is measured]From the known density of the standard liquid [ g/L]Calculate V3[L]。
(volume resistivity)
A compression molded article (φ 30 mm. times.t 3mm) of composite resin particles was prepared as a sample. The volume resistivity of the sample was measured in accordance with JIS K7194 using a resistivity meter ("LorestaGP" manufactured by mitsubishi chemical analysis technology ltd).
(sieving Rate)
The composite resin particles were sieved with a sieve having 1.7mm openings, the mass of the composite resin particles passing through the sieve was measured, and the sieving rate was calculated from the following formula (2).
The sieving ratio was 100 × (mass of composite resin particles passing through the sieve)/(total mass of composite resin particles sieved)
···(2)
(example 1)
First, grade F-104 (average particle size: about 500 μm, manufactured by Daiki industries Co., Ltd., hereinafter referred to as "PTFE fine powder") was prepared by mixing PTFE fine powder: 5g and methyl ethyl ketone: 20g were added to a 100mL beaker, and the beaker was cooled to maintain the temperature of the liquid in the beaker below 20 ℃. Next, a stirrer was placed in the beaker, and the liquid in the beaker was stirred. Next, an ultrasonic irradiator was placed in a beaker, and further stirred with ultrasonic waves, thereby pulverizing the PTFE fine powder in the presence of methyl ethyl ketone.
Next, a CNT dispersion containing carbon nanotubes (average length: 100 to 400 μm) and methyl ethyl ketone was prepared as a second dispersion. The content of the carbon nanotubes in the CNT dispersion was 0.2 mass%. Mixing the CNT dispersion liquid: 7.5g of the mixture was charged into a beaker, and the temperature of the liquid in the beaker was kept at 20 ℃ or lower, and the mixture was stirred in the beaker by a stirrer, whereby the pulverized PTFE fine powder and carbon nanotubes were dispersed in methyl ethyl ketone.
Next, the stirred dispersion liquid of the composite resin particles was stored in a drying container so that the mass of the composite resin particles was 1g, and the container was shaken so that the resin deposited on the bottom surface of the drying container was dispersed to have a uniform thickness. Here, the area of the bottom surface used was 20cm2The container (2) was used as a drying container, and a large shaker "double shaker NR-150" (manufactured by TITEC) was used as a shaking device in shaking. The thickness of the composite resin particles in the drying container is 1 to 2 mm.
The dispersion of the composite resin particles was naturally dried in a drying vessel at 20 ℃ under atmospheric pressure for 3 hours to produce a powder of the composite resin particles of example 1. The composite resin particles of example 1 were measured for sieving rate, bulk density and void ratio. Then, the powder of the composite resin particles of example 1 was put into a compression molding machine, and the compression molded article of example 1 was produced under conditions of 20 ℃ and 40 MPa. The compression molded body of example 1 was measured for volume resistivity. The results are shown in Table 1.
Examples 2 and 3 and comparative example 1
Composite resin particles and compression-molded articles of examples 2 and 3 and comparative example 1 were produced in the same manner as in example 1, except that the area of the bottom surface of the drying container was changed to the values shown in table 1. At the time of drying, the layer thickness of the composite resin particles in the drying container was recorded.
The composite resin particles of examples 2 and 3 and comparative example 1 were measured for their sieving ratio, bulk density, porosity and volume resistivity of the compression-molded article. The results are shown in Table 1.
Comparative example 2
As described in patent document 2, a dispersion of composite resin particles is obtained by mixing PTFE fine powder, carbon nanotubes, a ketone solvent, and a dispersant. Next, the composite resin particles of comparative example 2 were produced by drying the dispersion of the composite resin particles. Next, the composite resin particles of comparative example 2 were put into a compression molding machine, and a compression molded article of comparative example 2 was produced under conditions of 20 ℃ and atmospheric pressure.
[ Table 1]
About a dry area of 20 to 100cm2The bulk density of the composite resin particles of examples 1 to 3 obtained by drying under the conditions of/g was controlled to be 300g/L or more and less than 600 g/L. Thus, the bulk density of the composite resin particles of examples 1 to 3 was equal to that of the PTFE fine powder used as a raw material. From these results, it is predicted that the composite resin particles of examples 1 to 3 are excellent in moldability.
The composite resin particles of examples 1 to 3 all had a porosity of less than 0.6. From these results, it is predicted that the composite resin particles of examples 1 to 3 are excellent in moldability.
The sieving rates of the composite resin particles of examples 1 to 3 were all 50% or more, and the sieving rates of the composite resin particles of examples 2 and 3 were 90% or more. In contrast, the sieving ratio of the composite resin particles of comparative example 1 was 25%, and it was difficult to produce powdery composite resin particles.
The volume resistivity of the compression-molded articles of examples 1 to 3 and comparative example 1 was 4 to 10. omega. cm. From the results, it was confirmed that the composite resin particles obtained by the production methods of examples 1 to 3 can maintain conductivity.
FIG. 1 is a photograph showing the appearance of the composite resin particle powder of example 2. The composite resin particles of example 2 are expected to be fine powder, have small variations in particle size, have uniform particle sizes, and have excellent moldability.
Fig. 2 is a photograph of a compression molding machine when the composite resin particle powder of example 2 was charged. The composite resin particles of example 2 were expected to fill the inside of the compression molding machine densely and to have less variation in the extrusion amount.
FIG. 3 is a photograph showing the appearance of a compression-molded article of composite resin particles of example 2. The appearance of the compressed molded article of the composite resin particles of example 2 was uniform.
Fig. 4 is a photograph showing the appearance of the composite resin particles of comparative example 2. The composite resin particles of comparative example 2 were obtained as aggregates of composite resin particles, and included a mass in which the composite resin particles were aggregated. Therefore, in order to obtain a compression molded product having a uniform appearance, it may be necessary to pulverize the composite resin particles in a lump.
Fig. 5 is a photograph of a compression molding machine when the composite resin particles of comparative example 2 were charged. It is predicted that the composite resin particles of comparative example 2 are not densely packed in the compression molding machine and have a large variation in extrusion amount. Therefore, in order to reduce the variation in the extrusion amount, it is considered necessary to pulverize the massive composite resin particles into fine particles.
Fig. 6 is a photograph showing the appearance of a compressed molded article of composite resin particles of comparative example 2. The composite resin particles of comparative example 2 had an uneven appearance of the compression-molded article, and had many uneven spots of aggregation of carbon nanotubes and of aggregation of PTFE fine powder.
FIG. 7 is a photograph showing a state in which the composite resin particles of comparative example 2 were pulverized with a sieve. As shown in fig. 4, the composite resin particles of comparative example 2 are aggregates of the composite resin particles. As shown in fig. 7, if the lump composite resin particles are crushed by a sieve, the composite resin particles are fiberized. The fiberized composite resin particles cannot be used for the production of a compression-molded article.
As described above, it was confirmed that the composite resin particles of examples 1 to 3 are excellent in conductivity, and the moldability of the composite resin particles of examples 1 to 3 is excellent.
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