JPS6337142A - Production of electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain a composition having good appearance and containing dispersed fibers in well disentangled state, preventing the lowering of aspect ratio of the fiber, by impregnating a bundle of electrically conductive filaments with an impregnant produced by compounding short fibers and short particles in a thermoplastic polymer and coating the impregnated conductive filaments with other thermoplastic resin. CONSTITUTION:An impregnant containing shot fibers of an average diameter of <=1,000mum and/or particles having an average particle diameter of <=100mum and a thermoplastic polymer having a molecular weight of <=10,000 is impregnated in a bundle of electrically conductive filaments and, if necessary, the bundle is coated with a thermoplastic resin other than the above polymer. The thermoplastic polymer is preferably polyethylene, polypropylene, etc. The thermoplastic resin is an olefin resin when an ethylene polymer is used in the impregnant or a polystyrene, etc., when the polymer of the impregnant is styrene polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a mW resin composition in which conductive fibers are well dispersed and a molded article having excellent conductivity can be easily obtained.

BACKGROUND OF THE INVENTION Electronic devices and their components are increasingly using plastic housings instead of metal housings. However, synthetic resin housings do not have the ability to shield electromagnetic waves, so they are susceptible to interference from radio waves, and there is a risk that other synthetic resin housings may cause interference to other equipment. Research is being carried out on conductive resin compositions with electromagnetic wave shielding properties, and many of these compositions are made by kneading conductive materials such as Kazen black, Kagen fiber, metal flakes, and metal fibers into thermoplastic resin. However, Cargon Black, Car? fibers, metal flakes, short metal fibers (
When using conductive materials such as wires with a wire diameter of 30 to 100 μm, it is necessary to contain a high fkK content of 10 to 100 μm, which may result in poor appearance of the molded product and an increase in specific gravity.

In addition, if a bundle of conductive long fibers (with a small wire diameter of 4 to 30 μm) is used as a conductive material, and if it can be uniformly dispersed with a large aspect ratio, the electromagnetic wave will be sufficient with the addition of a small amount. It is known that it is possible to obtain molded products that have shielding performance and are free from defects such as poor appearance and increased specific gravity, but in reality, the fibers are difficult to unravel due to entanglement and adhesion between the fibers, resulting in poor appearance. There is a problem that electromagnetic wave shielding performance cannot be obtained sufficiently.As a countermeasure to this problem, if the fibers are loosened and kneaded vigorously in order to disperse them uniformly, the fibers will be cut and the aspect ratio will decrease. The current situation is that sufficient electromagnetic wave shielding performance cannot be obtained.

(Ninth Means to Solve the Problem) In view of the current situation as described above, the inventors of the present invention have conducted extensive research and found that short fibers with an average diameter of 1.000 am or less and/or particles with an average particle diameter of 100 μm or less have been developed. and the molecule t10,00
By impregnating a bundle of tetraelectric long fibers with an impregnating agent containing a thermoplastic polymer of 0 or less, and then coating the bundle with a thermoplastic resin as necessary, it is possible to form conductive fibers with a small wire diameter. Even if it is a bundle, the fibers loosen easily and are easily and uniformly dispersed.
The reduction in aspect ratio is small, and the amount of particles with an average particle diameter of 100 μm or less used here can be arbitrarily selected within a wide range by adjusting the total particle concentration in the impregnating liquid. agents, such as pigments, fillers, flame retardants'i? By using conductive long fibers,
1. We have discovered that, in addition to imparting magnetic wave shielding performance, it is possible to easily color a resin composition, reduce combustion heat, impart flame retardancy, etc. in a single treatment, and have completed the present invention.

That is, the present invention has an average wire diameter of 1.000 Jim? )
, short fibers and/or particles with an average particle size of 100 μm or less, and a thermoplastic polymer (A) with a molecular weight of 10,000 or less
A bundle of conductive long fibers is impregnated with an impregnating agent containing the following, and then, if necessary, coated with a thermoplastic resin (B) other than the polymer (A)! The present invention provides a method for producing a conductive resin composition having the following characteristics.

As the bundle of conductive long fibers used in the present invention, any conventionally known bundle of conductive long fibers can be used, such as a bundle of metal long fibers such as stainless steel, iron, steel, a bundle of Kagen long fibers, a bundle of metal long fibers, etc. Examples include bundles of long glass fibers with plating. The average diameter of the fibers is usually 4 to 100μ.
In order to obtain a more effective electromagnetic wave shielding effect with a small amount of addition, a thickness of 4 to 30 μm is preferable. Incidentally, such a bundle of conductive long fibers is usually made up of several hundred to tens of thousands of fibers.

As the short fibers with an average diameter of 1,000 Am or less used in the present invention, conventionally known short fibers can be used, such as metal short fibers such as stainless steel, iron, and copper, carzen short fibers, glass short fibers, and metal-metallic short fibers. Kagen tandanwei,
Although metal-plated short glass fibers and other inorganic short fibers can be produced, short fibers having a wire diameter of 4 to 60 μm and an aspect ratio of 10 to 70 are particularly preferred because of their excellent fiber dispersibility and workability.

Further, examples of particles having an average particle diameter of 100 μm or less include particles having higher heat resistance than the thermoplastic polymer (4) having a melting point of molecule t1o, ooo or less, such as carden black, titanium white, penguin, etc. Inorganic pigments, organic pigments such as phthalocyanine, monoazo, polyazo, and quinacridone, and fillers such as calcium carbonate, silicon dioxide, talc, mica, etc. Particles of 01 to 60 μm are preferred.

Molecules i1Q, thermoplastic polymer fA of 000 or less] used in the present invention include ethylene polymers, propylene polymers, styrene polymers, polyamide polymers, petroleum resins with number average molecular weights of IQ, 000 or less. Any known thermoplastic polymer such as , I-hydroxyolefin, etc. can be used. Among them, polyethylene, polypropylene, I-listyrene, polyα-methylstyrene: a copolymer of ethylene or propylene with vinyl acetate, methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylic acid, etc.; styrene Alternatively, copolymers of α-methylstyrene and acrylonitrile, methyl (meth)acrylate, ethyl (meth)acrylate, maleic anhydride, sibutyl maleate, diptyl fumarate, etc. may cause fiber loosening during molding, as This is suitable for preventing a decrease in the ect ratio.

As for the molecular weight, the number average molecular weight is usually 200 to 10.00.
Among them, those with a molecular weight of 600 to 6,000 are preferred in terms of impregnating workability, strength against deformation of fiber bundles after impregnation, and good loosening of fibers during molding.

The impregnating agent used in the present invention has an average wire diameter of 1,000μ.
A mixture of short fibers with a diameter of 100 μm or less and/or particles with an average particle size of 100 μm or less and a thermoplastic polymer (A) with a molecular size of −1110,000 or less is used, but various additives and the polymer may be added as necessary. A thermoplastic resin or the like having a higher molecular weight than the composite (A) may also be added.

The additives used here include higher aliphatic monocarboxylic acids and their metal salts, monoamides, condensates with alkylene diamines; esters of aromatic polyhydric carmenic acids; higher aliphatic alcohols; phenolics, hindered phenols. , hindered amine type antioxidants; ultraviolet ray inhibitors such as benzophenone type and benzotriazole type; and copper damage inhibitors such as hydranone derivatives.

The method of impregnating a bundle of conductive long fibers with an impregnating agent is as follows:
The impregnating agent may not only adhere to the surface of the fiber bundle but also penetrate between the fibers, and is not particularly limited. In some cases, the thermoplastic polymer (A) in the impregnating agent is diluted with a solvent if necessary, and if the thermoplastic polymer (A) in the impregnating agent is solid at one degree of impregnation, it is added to the impregnating agent liquid in which it is heated and melted. Conductive long fibers are continuously immersed in a bundle, preferably in an impregnating agent solution in a solvent by heating or as necessary, while being loosened, and the impregnating agent is impregnated between the fibers. After that, impregnate it using a die, roll, etc.
- There are methods such as adjusting and drying and removing the solvent as necessary.

Here, the solvent used to dissolve and dilute the impregnating agent is the same as the impregnating agent used! Examples include aromatic bath agents such as toluene and xylene; alcohols such as tetrahydrofuran, trichlorethylene, methanol, ethanol, and propatool; and dichlorohexane, although they vary depending on the type.

The amount of impregnating agent is 0.5 to 60 volumes in the four-ring long fibers after impregnation! Normally, it is adjusted to 6-chi, and in particular, it is adjusted to 5-40 yen in terms of strength such as fiber deformation after impregnation, fiber loosening during molding, and electromagnetic wave shielding ability of the molded product. is preferable.

The amount of short fibers and/or particles contained in the impregnating agent varies depending on the type of short fibers and/or particles used, the purpose of use, etc., but is usually 10
~80 capacity.

Note that the volume t% is a volume percentage calculated from the weight proportions of the fibers and the impregnating agent, based on the true densities of the fibers and the impregnating agent, and the same applies below.

The bundle of conductive long fibers (hereinafter abbreviated as convergent fibers) obtained in this manner and impregnated with the impregnating agent can be cut into pellets and used as is, but then the convergent fibers with a molecular weight of 10 ,000 or less and is coated with a thermoplastic resin (B) other than a thermoplastic polymer, and then pelletized,
There is no deformation of the pellet shape, no stickiness on the pellet surface, etc.
It is more preferable because the improvement in workability also improves the appearance.

Here, if necessary, the thermoplastic resin (Bl) used for coating the convergent fibers is preferably a known thermoplastic resin with a relatively high molecular weight used for ordinary molding, extrusion coating, etc., other than the above-mentioned thermoplastic polymer. Any plastic resin can be used; for example, olefin resins such as polyethylene, polyzolopyrene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer; shoulder styrene, impact-resistant polystyrene, acrylonitrile-styrene copolymer. , styrenic resins such as acrylonitriloptazoene-styrene copolymer; acrylic resins such as polymethyl methacrylate; polyamide resins such as 6-nylon, 66-1-ylon, 12-nylon, 6,12-fylon, etc. ; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyvinyl chloride, polycargonate, rifhenylene oxide, and mixtures thereof.

Among these, as the thermoplastic resin (B), it is preferable to select and use one that has good compatibility with the impregnating agent in the convergent fibers. For example, when an ethylene polymer or a propylene polymer is used as the impregnating agent, Polyethylene etc. olefin 7 series m
When fat or styrene polymer is used as an impregnating agent,
It is preferable to use styrenic resins such as polystyrene and acrylonitrile-butadiene-styrene copolymer.

Any known coating method can be used to coat the convergent fibers with the thermoplastic resin (B). For example, as in the extrusion coating of electric wires, thermoplastic resin (B) is extruded onto a cross using convergent fibers as a core wire using a rad die, and thermoplastic resin (B) is converted into convergent fibers by heating and melting or melting with a solvent. coating or convergence in the resin (B) q1. !
There are methods such as passing the convergent fibers through sheets of thermoplastic resin (B) and pressing them together, but extrusion using a RAD die into a cloth is preferred because it is easy to control the amount of coverage and provides stable coverage. A coating method is preferred.

The coating amount of the thermoplastic resin (B) is preferably relatively small when the conductive resin composition after coating is used as a master patch 7, and when used as a molding material as it is, it is preferable that the coating amount is relatively small. It varies greatly depending on the purpose of use, such as adjusting the conductive fiber content so that it is relatively large, but it is not particularly limited, but in general, the thermoplastic resin coating is applied to 2 to 90 capacitance fibers of convergent fibers. (B) 9
It is in the range of 8 to 10 volumes.

The coated or uncoated convergent fibers obtained in this way can be used as they are after being cut into pellets, but they are usually mixed with a thermoplastic resin as a master match and molded. used. Alternatively, it may be used for molding after being mixed with a thermoplastic resin, cross-wired, extruded, and pelletized to form a molding material. The amount of fiber contained in the molded product is usually 0.3 to 5 by volume, preferably 0.7
It is in the range of ~3 capacitance.

(Effects of the Invention) The conductive resin composition obtained by the production method of the present invention has good loosening of conductive fibers, is easily and uniformly dispersed, and has a
Since the decrease in the duct ratio is small, sufficient electromagnetic wave shielding performance can be achieved with the addition of a small amount of conductive fiber, and a molded product with a good appearance can be easily obtained.

Moreover, when known additives such as pigments, fillers, flame retardants, etc. are used as particles, in addition to imparting electromagnetic wave shielding performance as described above, coloring of the resin composition, reduction of combustion heat, and imparting flame retardancy are simultaneously achieved. It also has the advantage that it can be easily done in one treatment.

(Example) The present invention will be specifically described below with reference to Examples and Comparative Examples. All parts in the examples are based on weight.

Example 1 A stainless steel long fiber bundle (2,29 parts m) consisting of #15,000 long fibers with an average diameter of 8 μm was thoroughly loosened, and polyethylene wax (molecular jilt, 50Q, density 0.911/1x3) was prepared. 30 parts and 70 parts of heavy calcium carbonate (specific gravity 2.7) with an average particle size of IQμm,
After immersing it in an impregnating agent heated to 120°C, the amount of impregnation is adjusted without convergence, and the stainless steel length Mj
, a convergent fiber consisting of 13.75% by weight (131% by volume) of fiber, 25.88% by weight (54,12% by volume) of polyethylene wax and 60.37% by weight (42,57% by volume) of calcium carbonate ( It (161 parts m) was obtained and cut into 3 mx lengths to obtain pellets (11).

This pellet (1146.16 parts) and 153.84 parts of high-density polyethylene [density 0.961/cm3s melt flow ratio (hereinafter abbreviated as MFR) 6.0 g/l square were mixed and heated to 220°C. A flat plate of 150 x 80 x 2 m was molded using an in-line screw type injection molding machine.

This flat plate is made of stainless steel fiber 6.3s' weight
% (1,00% by volume), polyethylene wax 11.
94 wt% (16.34 liters), calcium carbonate 2
It is composed of 7.87% by weight (12.85% by volume) and 5% and 84% by weight of high-density polyethylene (69.81% by volume), and has a good appearance and low volume resistivity.
It was particularly excellent in magnetic wave shielding ability.

Comparative Example 1 Stainless steel long fiber 34.6 was prepared in the same manner as in Example 1 except that the addition of calcium carbonate to the astringent agent was omitted.
A convergent fiber (1') (6,34,!i'/m) consisting of 9 wt. Tomocho cut it and obtained pellets.

Next, this pellet was prepared in the same manner as in Example 1 except that (1) 18.29 parts and 27.87 parts of heavy calcium carbonate with an average particle size of 10 μm were mixed and B) 5184 parts of density polyethylene were used. A flat plate was formed.

This flat plate had the same composition as the flat plate of Example 1, but the dispersion of calcium carbonate was poor and the appearance was poor.
The moldability was also not good.

Comparative Example 2 6.35 parts of the long fiber bundle used in Example 1 cut into 3 mm length, 11.94 parts of polyethylene wax, and IS
27.87 parts of calcium carbonate and 53 parts of high-density polyethylene
．． After mixing with 84 parts, the temperature was set at 230°C (40)
After kneading in a vented extruder, pellets were obtained to obtain pellets (11) with a length of 3 dragons, and flat plates in the order of 150 x 80 x 2 were prepared in the same manner as in Example 1 except that this pellet (Il) was used. Molded.

This flat plate had the same composition as the flat plate of Example 1 and had a good appearance, but the volume resistivity was high because the fibers were severely cut during kneading, and the electromagnetic wave shielding ability was poor. .

Example 2 A stainless steel long fiber bundle (2, OF/m) consisting of 1,400 long fibers with an average diameter of 15 μm was thoroughly loosened and made into polypropylene wax (molecule i: 3,000° density: 0.9011/cnL”) 80 parts and average wire diameter 14μm
, 20 parts of short carbon fibers having an average length of 0.7fl and a density of 1.81/cm3 are mixed and immersed in an impregnating agent prepared by heating to 170°C.
Stainless steel long fibers 80w/f% (33,
61 capacity *), polypropylene wax 16w ff% (
59.01% by weight) and 4% by weight of carpin short fibers (7% by weight)
, 38 volume%) convergent fiber (II) (2,5#
/m> was obtained and cut into 3fi lengths to obtain Pellet) (III).

Next, 10.06 parts of this pellet (n) and polypropylene (density 0.911/crIL3. MFR6, O9
A flat plate of 150 x 80 x 2 m was molded in the same manner as in Example 1, except that 89.94 parts of the following were used.

This flat plate is stainless steel fiber 8.05% by weight C1
．． oos amount%), polypropylene wax 1.61% by weight (1,76% by volume), cardiff fiber 0.4% by weight (0
, 22% by volume) and polypropylene 89, 94% by weight
(97.02% by volume), had a good appearance, had a low volume resistivity value, and had particularly excellent magnetic wave shielding ability.

Comparative Example 3 The long fiber bundle used in Example 2 was cut into 3n length 8,
Pellets (■
was obtained, and then a flat plate of 150 x 80 x 2 mi+ was molded in the same manner.

This flat plate had the same composition as the flat plate of Example 2, and had a good appearance, but because the fibers were severely cut during kneading, the volume resistivity was high, and the electromagnetic wave shielding ability was poor. .

Example 3 A stainless steel long fiber bundle (4,211/m) consisting of 410,000 long wires with an average wire diameter of 8 μm was thoroughly loosened, and polyethylene wax (molecule II 1.500,
Density 0.9117cm”) 90 parts and average particle size 0.0
1μm carpin black (density 1.8#/CrIL3
) and immersed in an impregnating agent prepared by heating to 120°C, and adjusting the impregnating temperature after convergence.
), polyethylene wax 27% by weight (73,81% by volume) and carmen black 31t% (4,15% by volume)
) convergent fibers (III) (6, OJF/m 2 ) were obtained.

Next, high-density polyethylene (density 0.9611/crn", MFR6,
0,9/10) and coated fibers (I [I) (1
3g/m) was obtained, cut into 3 silk lengths and pelleted (III).
I got it.

Except for using a mixture of 23.76 parts of this pellet (I[I) and 76.24 parts of high-density polyenalene lol2111
! A flat plate of 150 x 80 x 2 mm was molded in the same manner as in Example 1.

This flat plate has 7.68% by weight of stainless steel fiber (1
,00% by volume), polyethylene wax 2.96% by weight
(3,35 volume i%), carbon black 0.33 weight percent (0,198 volume percent) and high density polyethylene 89.0
It was made of triple f-chi (95.46 volume i%), had a good appearance, had a volume resistivity value of 1, and was particularly excellent in magnetic wave shielding ability.

Example 4 A stainless steel long IR male 26.25 kg was prepared in the same manner as in Example 3 except that the amounts of polyethylene wax and carbon black used were changed to 40 parts and 60 parts, respectively.
% (5,51% by volume), polyethylene wax 29.5
Weight (5L 74 volume 11 and car contact black 44.
Convergent fibers (■
) (16JF/m), and then similarly coated wire a(
fV) (40 g/m) was prepared, and then cut into 3 silk lengths to obtain Ilet) (fV).

A flat plate of 150 x 80 x 2 m was molded in the same manner as in Example 1 except that 69.24 parts of this pellet (fV) and 30.76 parts of high-density polyethylene were mixed and used.

This flat plate has 7.27% by weight of stainless steel fiber (
1,00 volume 196), polyethylene wax & 17% by weight (9,76 volume i%), carden black 12.25% by weight (7,40 volume i%) and high density polyethylene 72
．． It consisted of 31% by weight (81.84% by volume), had a good appearance, a low volume resistivity value, and was particularly excellent in electromagnetic wave shielding ability.

Test Examples The appearance of the flat plates obtained in Examples 1 to 4 and Comparative Examples 1 to 3 was visually evaluated, and the volume solid resistance value and radio wave shielding ability were measured. The results are shown in Table-1. The method for determining the appearance evaluation platform is shown below.

Appearance evaluation of the flat plate The appearance was evaluated based on the size and number of undispersed fiber clusters observed on one side of the flat plate.

5: Extremely good (4#1. There is a small amount of loose fibers or particles, and the number is less than 10 (v4) 4: Good (*There is a small amount of loose fibers or particles, and the number is 10 to 19) ) 3: Normal (there are some large fibers or particles, the number is 20)
~391 hard) 2: Poor (Large clusters of fibers or particles, number 40-49) 1: Extremely poor (Large clusters of fibers or particles, number SOS or higher) Volume resistivity 5RIS (Japan Measured according to Synthetic Rubber Association)-2301.

Electromagnetic shielding ability

Claims (1)

[Claims] An impregnating agent containing short fibers with an average diameter of 1,000 μm or less and/or particles with an average particle diameter of 100 μm or less and a thermoplastic polymer (A) with a molecular weight of 10,000 or less is applied to a bundle of conductive long fibers. A method for producing a conductive resin composition, which comprises impregnating the conductive resin composition with a thermoplastic resin (B) other than the polymer (A), if necessary.