JP2001288275A - Method for highly dispersing filler in synthetic resin and its composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite material that comprises a synthetic resin as a matrix and a filler which is highly dispersed in the synthetic resin without deteriorating the synthetic resin and the filler. SOLUTION: The composite material can be produced by dispersing a filler in a solution obtained by dissolving a synthetic resin in a solvent to form a uniform suspension and adding the suspension to another solvent with which the solvent in the suspension is mixed without dissolving the synthetic resin to precipitate a composite material comprising the filler highly dispersed in the synthetic resin. In another alternative, if a synthetic resin is not dissolved in a solvent at ordinary temperature but dissolved in the heated solvent, the composite material can be produced by dissolving the synthetic resin in the heated solvent and dispersing a filler therein to form a uniform suspension, and then cooling the suspension to precipitate a composite material comprising the filler highly dispersed in the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for dissolving a synthetic resin in a solvent, a homogeneous suspension in which a filler is dispersed in a solution obtained by dissolving the filler, and mixing the solvent without dissolving the synthetic resin. The present invention relates to a method for depositing a composite material in which a filler is uniformly dispersed by adding it to a solvent or cooling, and a composite material obtained by the method.

[0002]

2. Description of the Related Art A method of using a synthetic resin as a matrix and dispersing various fillers to impart new performance is widely used at present. Examples include pigments for coloring, fine powders and fibers such as carbon black and metal for imparting conductive performance, and glass fibers and mica for obtaining mechanical strength.
However, when a filler is dispersed in a molten synthetic resin using a kneading machine as in the related art, unevenness occurs because it is difficult to uniformly disperse the filler. Furthermore, if kneading is continued for a long time to achieve higher dispersion, there is a problem that the matrix resin and the filler are deteriorated by high temperature and strong shearing force.

For example, a conductive composite material using carbon black having a developed structure (a fibrous structure having a high aspect ratio in which primary particles are connected) as a filler and a synthetic resin as a matrix includes a conductive sheet, an antistatic container, It is widely used as an electromagnetic wave shielding material, but it is known that it is difficult to find the optimal kneading conditions to obtain higher conductive performance (Plastics,
Vol. 38, no. 3 (1987), pp17-6
3, Industrial Research Committee). In order to obtain a composite material with high conductivity using carbon black, it is necessary that the filler is well dispersed and the structure is developed. This is to destroy the black structure.

Similarly, for a conductive composite material using metal flakes as a conductive filler, kneading for a long time makes the filler highly dispersed and improves the conductive performance, but on the other hand, the aspect ratio of the conductive filler is improved. To lower the conductive performance. In addition, since heating is performed at a high temperature, the metal surface is oxidized, and the conductive performance is reduced.

[0005]

Accordingly, the present invention proposes a method of dispersing a filler in a matrix resin without deteriorating the matrix resin or the filler.

[0006]

[Means for Solving the Problems] As a method for purifying a synthetic resin, a synthetic resin is dissolved in a solvent and then added to another solvent in which the solvent is mixed without dissolving the synthetic resin.
A method of reprecipitating a synthetic resin to elute impurities is known (Takayuki Otsu, Masayoshi Kinoshita, "Experimental Method for Polymer Synthesis", Kagaku Dojin (1972), pp110-112).
By utilizing this method, the filler is dispersed in a solution obtained by dissolving the synthetic resin in a solvent, and then added to another solvent in which the solvent is mixed, whereby a composite material in which the filler is highly dispersed can be obtained. .

If the synthetic resin does not dissolve at room temperature but dissolves in a heated solvent, the synthetic resin is dissolved in the heated solvent,
Then, by cooling the solution in which the filler is dispersed, a composite material in which the filler is highly dispersed can be obtained.

A matrix resin and a solvent for dissolving the matrix resin,
Examples of the combination with another solvent (precipitant) that mixes with the solvent and precipitates the matrix resin include the following. Decalin, tetralin, toluene, p-xylene in the solvent that dissolves the polyethylene resin, and n in the precipitant
-Propanol, acetone, methanol. Cyclohexane, decalin, tetralin, benzene, toluene, xylene as a solvent for dissolving the polypropylene resin, and methanol as a precipitant. Hydrocarbons and chlorinated hydrocarbons as solvents to dissolve polyisoprene resin, alcohol and acetone as precipitants.
Benzene, toluene, chloroform, methanol, carbon tetrachloride, dioxane, acetone in the solvent that dissolves polyvinyl acetate resin, aliphatic hydrocarbon, ethanol in the precipitant,
Ether, carbon disulfide. Tetrahydrofuran, methyl ethyl ketone, acetone-disulfide mixed solution as solvent for dissolving polyvinyl chloride resin, aliphatic hydrocarbon and alcohol as precipitant. Hot tetrahydroxyfuran as a solvent for dissolving polyvinylidene chloride resin, and hydrocarbons and alcohols as precipitants. Benzene, toluene, tetrahydrofuran, methyl ethyl ketone, dioxane, carbon disulfide in solvents that dissolve polystyrene resin, saturated hydrocarbons, alcohols and ethers in precipitants. Benzene, toluene, chloroform, acetone, a solvent that dissolves polymethyl methacrylate resin
Dioxane, methylene chloride, aliphatic hydrocarbons in precipitants,
Ether, methanol, ethanol. Dimethylformamide and dimethylsulfoxide in solvents that dissolve polyacrylonitrile resin, and hydrocarbons, alcohols, ethers, and ketones as precipitants. Phenol, chlorophenol, nitrobenzene, phenol-tetrachloroethane mixed solution in a solvent that dissolves polyethylene terephthalate resin, and hydrocarbon and alcohol as a precipitant. Pyridine, dimethylformamide, dimethylsulfoxide, m-cresol, chlorophenol, formic acid in a solvent that dissolves nylon-6 resin, chloroform, alcohol, hydrocarbon, ether as a precipitant. Phenol, m-cresol, formic acid, sulfuric acid as solvent for dissolving polyurethane resin, saturated hydrocarbon, alcohol, ether as precipitant. Benzene and toluene are used as solvents to dissolve natural rubber, and alcohol and acetone are used as precipitants.

The filler dispersed in the synthetic resin includes silica, mica, talc, stone powder, clay, graphite, carbon black, calcium carbonate, titanium oxide, alumina, aluminum hydroxide, ferrite, molybdenum disulfide, wood powder, Powders and flakes of metals (gold, silver, platinum, palladium, copper, aluminum, iron, lead, tin, zinc, nickel, molybdenum, chromium and their alloys), carbon fibers, aramid fibers, alumina fibers, Examples include potassium titanate whiskers, glass fibers, synthetic fibers, and various pigments. Further, a mixture thereof may be used.

In the present invention, in order to obtain a highly dispersed composite material, a solution obtained by dissolving a synthetic resin in a solvent includes:
A uniform suspension of the filler is added to another solvent (precipitant) in which the solvent is mixed without dissolving the synthetic resin to precipitate a composite material in which the filler is uniformly dispersed, or to heat. A composite material in which a uniform suspension obtained by dispersing a filler in a solution obtained by dissolving a synthetic resin that is dissolved only in a heated solvent in a heated solvent is cooled, and the filler is uniformly dispersed. The above method will be specifically described below.

The synthetic resin is dissolved in a solvent. The choice of the solvent is arbitrary, but it is assumed that the synthetic resin is dissolved and the filler is not dissolved. For example, a polystyrene resin is soluble in toluene, and a polyethylene resin is soluble in heated xylene. The concentration of the synthetic resin is not so high because the solvent is less likely to be eluted during subsequent precipitation. The filler is added to the resulting solution and stirred well to form a uniform suspension. While stirring the suspension so that the filler is uniformly dispersed without settling or floating, the mixture is added to another solvent (precipitant) in which the solvent is mixed without dissolving the synthetic resin. Precipitate. The choice of the solvent is arbitrary, but it is assumed that the filler does not dissolve.
In the case of a toluene solution of a polystyrene resin, it can be precipitated with an alcohol or a saturated hydrocarbon, and in the case of a xylene solution of a polyethylene resin, it can be precipitated with methanol or acetone. When the suspension is added to the precipitant, if the precipitant is stirred at a high speed, the solvent is easily eluted from the composite material, and a fine precipitate is obtained. At this time, if the concentration of the solvent in the precipitant is too high, the deposited synthetic resin is re-dissolved, so care is taken.

When a synthetic resin that does not dissolve at room temperature is dissolved by heating, a highly dispersed composite material can be precipitated by stirring the suspension containing the filler and cooling while keeping the suspension uniform. . When the composite material is precipitated by cooling, the solvent can be used repeatedly. The precipitated composite material is separated by filtration and dried to remove the solvent.

As a method for obtaining a composite material in which a filler is uniformly dispersed by using the present invention, there is an apparatus through the following steps. In the process as shown in FIG. 1, the matrix resin 1, the filler 2 and the solvent 3 are mixed, the obtained suspension 4 is added to the precipitant 5, and the highly dispersed composite material 6 is precipitated. The deposited composite material 6 is separated by filtration and dried.
The mixed solution 7 of the solvent and the precipitant, which is the filtrate, is separated by distillation and reused.

When the matrix resin is dissolved by heating, the matrix resin 1 and the filler 2 are added to the heated solvent 3 in a process as shown in FIG.
Is cooled to precipitate the composite material 6. The deposited composite material 6 is separated by filtration and dried. Solvent 3, which is a filtrate, is reused as it is.

[0015]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1) High density polyethylene resin (manufactured by Mitsui Chemicals, Inc., Hizex, 100 cm ³ xylene)
-2100JP, melt index: 7.4g / 10
min (210 ° C., load: 21.18 N)) 5.4 g,
Carbon black powder (made by Asahi Carbon Co., Ltd., Asahi HS-5
00, average particle size: 38 nm, DBP oil absorption: 500 m
g / g) of 0.6 g (the ratio of carbon black to polyethylene resin is 12% by weight), and the mixture was heated to 90 ° C. with stirring to dissolve the synthetic resin. The resulting suspension is added to 2 dm ³ of stirring methanol,
The composite was deposited. The precipitated composite material was separated by filtration and dried in vacuo to remove the solvent. The dried composite material was processed into a plate-shaped piece having a length and width of 20 mm and a thickness of 1 mm.

In order to evaluate the dispersion of the carbon black in the polyethylene resin and the degree of destruction of the structure of the carbon black, the electric resistance of the obtained plate-like piece was measured. If the carbon black is highly dispersed and the structure is not easily broken, the carbon black shows a small resistance value.

When the electric resistance of the obtained plate-like piece in the thickness direction was measured, it was found to be 25 Ω (electrical conductivity: 1.0 × 10 4
^-1 S / m).

Comparative Example 1 High-density polyethylene resin (Hizex-2100JP, manufactured by Mitsui Chemicals, Inc., melt index: 7.4 g / 10 min (210 ° C., load:
21.18N)) 5.4 g, carbon black powder (manufactured by Asahi Carbon Co., Ltd., Asahi HS-500, average particle size: 38)
0.6 g (nm, DBP oil absorption: 500 mg / g) was kneaded using a melt indexer (semi-automatic melt indexer 2A manufactured by Toyo Seiki Seisaku-sho, Ltd.).
Is). The temperature at the time of kneading is 210 ° C, and the extrusion load is 9
8.07N. The mixed composite material is 20 mm in length and width,
It was processed into a plate-like small piece having a thickness of 1 mm.

When the electric resistance in the thickness direction of the obtained plate-like piece was measured, it was found to be 260 Ω (electric conductivity: 9.6 × 10 ⁻³ S / k) when kneaded twice with a melt indexer.
m) 34 Ω after kneading four times (electric conductivity: 7.4)
(× 10 ⁻² S / m), and the mixture kneaded six times had 480 Ω (electric conductivity: 5.2 × 10 ⁻³ S / m).

The high conductivity in Example 1 was attributable to the fact that carbon black was highly dispersed and the structure was maintained. From the above, the synthetic resin is dissolved in the solvent, the filler is dispersed, and the synthetic resin is dissolved and the solvent is mixed without being dissolved. It has been found that a composite material is obtained.

Example 2 The same operation as in Example 1 was carried out except that the obtained suspension was not added to methanol, but was left to cool at room temperature with stirring to precipitate a composite material.

When the electric resistance in the thickness direction of the obtained plate-like piece was measured, it was found to be 10Ω (electric conductivity: 2.5 × 10
^-1 S / m).

As described above, in the case where the synthetic resin is dissolved by heating, the synthetic resin is not dissolved but added to another solvent in which the solvent is mixed. It was found that a composite material having a small degree of was obtained.

(Example 3) Polystyrene resin (manufactured by Mitsubishi Chemical Co., Ltd., Dialex) was added to 100 cm ³ of toluene.
HF-77, melt index: 7.5 g / 10 mi
n (200 ° C., load: 49.03 N)) 5.49, carbon black powder (Asahi Carbon-50, Asahi HS-50)
0, average particle size: 38 nm, DBP oil absorption: 500 mg
/ G) was added (the ratio of carbon black to polystyrene resin was 12% by weight) to dissolve the synthetic resin. The resulting suspension is stirred with 2 dm ³
To precipitate a composite material. The precipitated composite material was separated by filtration and dried in vacuo to remove the solvent. The dried composite material was processed into a plate-shaped piece having a length and width of 20 mm and a thickness of 1 mm.

When the electric resistance of the obtained plate-shaped piece in the thickness direction was measured, it was found to be 13 Ω (electric conductivity: 1.9 × 10 4).
^-1 S / m).

Comparative Example 2 A polystyrene resin was used as a matrix resin (Dialex HF-7, manufactured by Mitsubishi Chemical Corporation).
7, melt index: 7.5 g / 10 min (20
Comparative Example 1 except that 0 ° C., load: 49.03 N))
The same operation as described above was performed.

When the electric resistance in the thickness direction of the obtained plate-like piece was measured, the kneaded twice with a melt indexer was 120 kΩ (electric conductivity: 2.1 × 10 ⁻⁵ S /
m), kneaded four times, 22 kΩ (electric conductivity: 1.
1 × 10 ⁻⁴ S / m), kneaded 6 times is 11 kΩ
(Electric conductivity: 2.3 × 10 ⁻⁴ S / m).

As described above, even for synthetic resins other than polyethylene resin, the synthetic resin is dissolved in a solvent, the filler is dispersed, and added to another solvent in which the solvent is mixed without dissolving the synthetic resin to precipitate. Thus, it was found that a composite material having high dispersion and a small degree of destruction of the filler was obtained.

[0030]

As described above, according to the present invention, it is possible to obtain a composite material comprising a synthetic resin and a filler and having a high degree of dispersion of the filler. Due to the wet dispersion, the resulting composite material has less unevenness. Further, since no heating and no excessive shearing force are applied, the deterioration of the synthetic resin and the filler can be suppressed, so that a composite material with stable performance can be supplied.

[Brief description of the drawings]

FIG. 1 shows a process in which a matrix resin and a filler are added to a solvent and stirred, and the obtained suspension is added to a precipitant to precipitate a highly dispersed composite material. The deposited composite material is filtered off and dried. The mixed solution of the solvent and the precipitant, which is the filtrate, is separated by distillation and reused.

FIG. 2 is a step of adding a matrix resin and a filler to a heated solvent and stirring the mixture when the matrix resin is dissolved by heating, and cooling the obtained suspension to precipitate a highly dispersed composite material. . The deposited composite material is filtered off and dried. The filtrate is reused as a solvent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Matrix resin 2 Filler 3 Solvent 4 Suspension 5 Precipitant 6 Composite material 7 Mixture

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshihisa Otsuka 1-112-27 Kita, Kuki-shi, Saitama Pref. Employee 301 (Ref.) DE236 DG026 DJ006 DJ016 DJ036 DJ046 DJ056 DL006 FA036 GQ00

Claims (3)

[Claims] (1) A homogeneous suspension in which a filler is dispersed in a solution obtained by dissolving a synthetic resin in a solvent is added to another solvent in which the solvent is mixed without dissolving the synthetic resin. A method in which a composite material in which materials are uniformly dispersed is precipitated, filtered, and dried. 2. A uniform suspension in which a filler is dispersed in a solution obtained by dissolving a synthetic resin that does not dissolve at room temperature but dissolves in a heated solvent in a heated solvent is cooled and filled. A method in which a composite material in which materials are uniformly dispersed is precipitated, filtered, and dried. 3. A composite material obtained by the method according to claim 1.