JPS6222836A - Production of electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain the titled compsn. which has excellent electrical conductivity and in which a bundle of fibers is well untwisted and can be uniformly dispersed, by impregnating a bundle of electrically conductive long fibers with an impregnant contg. a thermoplastic polymer and optionally coating it with other thermoplastic resin. CONSTITUTION:A thermoplastic polymer (e.g. PS) having a number-average MW of 200-10,000 and optionally, additives such as copper inhibitor, antioxidant, ultraviolet inhibitor, etc., are dissolved in a solvent (e.g. toluene) to obtain an impregnant. 0.5-60vol% bundle of fibers obtd. by tying up hundred to tens of thousands of electrically conductive fibers having an average diameter of 4-100mum into a bundle is immersed in said impregnant. If desired, the bundle is coated with other thermoplastic resin (e.g. PS).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a conductive 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, since synthetic resin housings do not have the ability to shield electromagnetic waves, they are susceptible to interference from interference radio waves, and there is a risk that other equipment using synthetic resin housings will be affected. For this reason, research is being carried out on conductive resin compositions that have electromagnetic wave shielding properties, and many are made by kneading conductive materials such as carbon black, carbon fiber, metal flakes, and metal fibers into thermoplastic resin. However, carbon black, carbon fiber, metal flakes, short metal fibers (
When using conductive materials such as wire diameters of 60 to 100μ, m), it is necessary to contain a large amount of these materials at 10 to 60% by volume, resulting in poor appearance of the molded product and an increase in specific gravity. was there. In addition, the wire diameter is small (wire diameter 4~
60μrIL) When a bundle of conductive long fibers is used as a conductive material, if it can be uniformly dispersed with a large aspect ratio, it will have sufficient electromagnetic wave shielding performance with a small amount of addition, and will not have poor appearance or specific gravity. Although it is known that a molded product without defects such as an increase in the number of particles can be obtained, in reality, the fibers are difficult to unravel due to entanglement and adhesion between the fibers, resulting in poor appearance, and the electromagnetic shielding performance is not sufficiently obtained. However, in order to loosen the fibers and disperse them uniformly, the current situation is that when the fibers are kneaded, the fibers break and the aspect ratio decreases, making it impossible to obtain sufficient electromagnetic shielding performance.

(Means for Solving the Problems) In view of the above-mentioned current situation, the present inventors have conducted extensive research and have found that an impregnating agent containing a thermoplastic polymer having a molecular weight of in, ooo or less is applied to conductive long fibers. If a bundle of conductive fibers is impregnated with thermoplastic resin and then coated with thermoplastic resin as necessary, the fibers will loosen even if the bundle has a small wire diameter, will be easily dispersed uniformly, and the aspect ratio will be improved. The inventors have discovered that there is little decrease in , and have completed the present invention.

That is, the present invention impregnates conductive long fibers with an impregnating agent formed by impregnating a thermoplastic polymer (El) having a molecular weight of 11 (1000 or less), and then, if necessary, impregnating a thermoplastic resin (El) other than between the polymers. The present invention provides a method for producing a conductive resin composition characterized by coating.

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, or copper, a bundle of carbon long fibers, a bundle of metal long fibers, etc. Examples include bundles of plated long glass fibers. 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 conductive long fibers are usually made into a bundle of several hundred to tens of thousands of fibers.

The thermoplastic polymer cA) having a molecular weight of 1110,000 or less used in the present invention includes ethylene polymers, propylene polymers, styrene polymers, polyamide polymers, and petroleum resins having a number average molecular weight of 10,000 or less. Any known thermoplastic polymer such as polyhydroxyolefin or polyhydroxyolefin can be used. Among them, polyethylene, polypropylene, polystyrene, polyα-methylstyrene; ethylene or propylene and vinyl acetate, methyl (meth)acrylate, (
Copolymers with ethyl meth)acrylate, (meth)acrylic acid, etc.; styrene or α-methylstyrene and acrylonitrile, methyl (meth)acrylate, ethyl (meth)acrylate, maleic anhydride, diptyl maleate, fumar A copolymer with dibutyl acid or the like is suitable for preventing fiber loosening and decrease in aspect ratio during molding.

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

As the impregnating agent used in the present invention, a thermoplastic polymer (A) with a molecular weight of 11QOOo or less is used alone or in a mixture of two or more types. It is also possible to add a molecular weight thermoplastic resin or the like.

The additives used here include higher aliphatic monocarboxylic acids and their metal salts, monoamides, condensates with alkylene diamines; esters of aromatic polyhydric carboxylic acids; higher aliphatic alcohols; phenolics, hindered phenols. , antioxidants such as Hingodamine type; ultraviolet inhibitors such as benzotriazole type, benzophenone type, and benzotriazole type; copper damage inhibitors such as hydrazine derivatives; thermoplastic polymers with a molecular weight of IQOOO or less (A ) is a method of impregnating a bundle of conductive long fibers with an impregnating agent containing:
Any method may be used as long as it penetrates between the fibers, and there are no particular limitations. For example, if the impregnant is liquid, it may be added to an impregnant liquid diluted with a solvent if necessary, and if the impregnant is solid. conductive long fibers are placed in an impregnating agent liquid in which the impregnating agent is heated and melted, or in an impregnating agent liquid in which the impregnating agent is dissolved in a solvent by heating as necessary, in the form of a bundle, preferably continuously while being loosened. After impregnating the impregnating agent between the fibers,
There is a method of adjusting the amount of impregnation using a die, roll, etc., and drying and removing the solvent as necessary.

The solvent used to dissolve and dilute the impregnating agent here varies depending on the type of impregnating agent used, but examples include aromatic solvents such as toluene and xylene; alcohols such as tetrahydrofuran, trichlorethylene, methanol, ethanol, and furohanol. ; Examples include cyclohexane.

The amount of impregnating agent is usually adjusted so that the amount of fibers occupied in the conductive long fiber after impregnation is α5 to 60% by volume. 5 to 40% by volume is preferable in terms of strength, loosening of fibers during molding, and electromagnetic wave shielding ability of the molded product.

Incidentally, the volume % 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 thus obtained bundle of conductive long fibers impregnated with the impregnating agent (hereinafter abbreviated as convergent fibers) can be cut into pellets and used as is, but then convergent fibers with a molecular weight of 1G After coating with a thermoplastic resin (B) other than thermoplastic polymerized Vermilion N having a weight of 000 or less, when pelletized,
The pellet shape (no misalignment, no stickiness on the pellet surface, etc.)
This method is more preferable because it improves workability and improves pellet appearance.

Here, as the thermoplastic resin (B) used for coating the convergent fibers as necessary, other than the above-mentioned thermoplastic polymer, preferably a known relatively high molecular weight resin used for ordinary molding, extrusion coating, etc. Any thermoplastic resin can be used; for example, olefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl alklate copolymer; polystyrene, impact-resistant polystyrene, acrylonitrile-styrene copolymer. , styrenic resins such as acrylonitrile-butadiene-styrene copolymer; acrylic resins such as polymethyl methacrylate; polyamide resins such as 6-nylon, 6-row nylon, 12-nylon, and 6012-nylon; polyethylene terephthalate, polybutylene Examples include polynisder resins such as terephthalate; polyvinyl chloride, polycarbonate, polyphenylene oxide, and mixtures thereof.

Among these, it is preferable to select and use a thermoplastic resin having 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. When an olefin resin such as polyethylene or a styrene polymer is used as an impregnating agent, it is preferable to use a styrene resin such as polystyrene or an acrylonitrile-butadiene-styrene copolymer, respectively.

Any known coating method can be used to coat the convergent fibers with the thermoplastic resin CB). For example, as in the extrusion coating of electric wires, thermoplastic resin (B) is coated by extrusion using a rad die on a convergent fiber as a core wire, and the thermoplastic resin (B) melted by heating or melted with a solvent is applied to the convergent fiber. Alternatively, a method of passing convergent fibers through said 1 [fldB), a method of sandwiching convergent fibers between sheets made of thermoplastic resin (B) and pressing, etc. A method of extrusion coating using a cross-layer rad die is preferred in that a layer can be formed.

The coating amount of the thermoplastic resin (B) is preferably relatively small when the coated conductive resin composition is used as a masterbatch, and when used as a molding material as it is, the coating amount is preferably relatively small. Although it varies greatly depending on the purpose of use, such as adjusting it to a relatively large amount of convergent fibers considering the content of convergent fibers, it is not particularly limited, but usually
~90 volume f% coated thermoplastic arbor B) 98-10
The range is i%.

The coated or uncoated convergent fibers obtained in this way may be used as they are after being cut into pellets, but they are usually mixed with thermoplastic resin as a masterbatch and used for molding. be done. 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 article is usually in the range of 13 to 5% by volume, preferably α7 to 3% by volume.

(Effects of the Invention) The conductive resin composition obtained by the manufacturing method of the present invention has good loosening of the conductive fibers, is easily and uniformly dispersed, and has little decrease in aspect ratio. It has the effect that sufficient electromagnetic wave shielding performance can be achieved by adding it, and a molded product with a good appearance can be easily obtained.

(Example) The present invention will be specifically described below with reference to Examples and Comparative Examples.

Example 1 A stainless steel long fiber bundle (19 g 7 m) consisting of 4,000 long fibers with an average diameter of 8 μm was heated to 120° C. and was heated to polyethylene wax (density [191 g ~, number average molecular weight i, so o, hereinafter referred to as PE After continuous immersion in the molten liquid (abbreviated as PE wax), the amount of impregnated PE wax is adjusted by squeezing between rubber rolls, and the amount of fiber after impregnation is 17.6% by volume (65% by weight). Fiber (I) (2
, 92g/m2) was cut into 5 lengths to produce pellets (I
). The obtained pellets (1) had little deformation and surface adhesion, and had good workability.

Heat-retardant polypropylene containing this pellet (I) and a heat retardant (31% by weight of decabromidiphenyl ether, 7% by weight of antimony trioxide) [density t 2511/cw'
, melt flow ratio (hereinafter abbreviated as MFR) 5.0
1// 10 min, hereinafter abbreviated as flame-retardant PP] and tri-blend at a ratio such that the fiber amount is 1% by volume (6.07% by weight) [9.35% by weight of pellets (I), 65in% of flame-retardant PP9CL] Then, using a 3 oz in-line screw injection molding machine set at 200°C,
A flat plate of 0x2 gate was molded.

This flat plate has an extremely good appearance and a low volume resistivity (,
It had particularly excellent electromagnetic wave shielding ability.

Comparative Example 1 The stainless steel long fibers used in Example 1 were replaced with low-density polyethylene (density Q, 915, !i'/cx"
, MFR50, 9/10m1n, hereinafter abbreviated as LDPE)
was continuously immersed in a solution of 3 times the weight of the LDPE in xylene at 160°C, then squeezed with a rubber roll to adjust the amount of LDPE impregnated, and the xylene was dried and removed. One convergent fiber (2,93117 m ) with a fiber diameter of 17.6% by volume (64.8% by weight) was obtained,
5m1! It was cut into long pieces to make pellets (■'). It should be noted that this pellet (■') was not uniformly impregnated with LDPE.

This pellet (■') and flame-retardant PP have a fiber content of 1% by volume.
(6.07% by weight) [pellets (1') 9
．． A flat plate was obtained in the same manner as in Example 1, except that tri-blending was carried out with 66% by weight of flame-retardant PP and 9164% by weight of flame-retardant PP.

This flat plate had poor fiber dispersion, poor appearance, relatively high volume resistivity, and poor electromagnetic wave shielding ability.

Example 2 The convergent fibers (I) obtained in Example 1 were coated using a 220°C extruder equipped with a rad die for resin coating cloth, so that the fiber amount after coating was 1% by volume (6.07% by weight). Coated fiber (II) (st2a, p/m) was coated with flame retardant PP so that the amount of coated resin was 4.2% by volume, and the coated fiber (II) was cut into 5 lengths to make pellets. (II). The obtained pellet (■
) had no deviation in shape, no adhesion on the surface, and was excellent in appearance, workability, etc.

A flat plate was obtained in the same manner as in Example 1 except that this Benz) (It) was used as it was.

This flat plate has an extremely good appearance, low volume resistivity,
It was superior to bamboo in its ability to shield electromagnetic waves.

Comparative Example 2 The unimpregnated stainless steel long fibers used in Example 1 were coated with flame-retardant PP so that the fiber amount after coating was 1% by volume (6.0% by weight, the amount of coated resin was 99% by volume). [Coated fiber (II') (3t67,
lil/fi) was obtained and cut into 5H lengths to obtain benz) (
n'). In addition, since the fiber bundle was not impregnated with any impregnating agent, the diameter of the fiber bundle was not constant, making it difficult to provide stable coating.

- A flat plate was obtained in the same manner as in Example 1 except that this Benz I-(III') was used as it was.

This flat plate had extremely poor fiber dispersion, a particularly poor appearance, high volume resistivity, and extremely poor magnetic wave shielding ability.

Example 3 Ethylene-vinyl acetate copolymer wax (density (
L 92 g/cy? , vinyl acetate content 14% by weight,
Number average molecular weight 3,500, hereinafter abbreviated as EVA wax)
After being continuously immersed in the bath solution, the amount of EVA wax impregnated was adjusted by squeezing between rubber rolls, and the fiber amount after impregnation was Z2 volume % (4 [10 weight %)] Convergent fiber (III)
(a759/m) was obtained and cut into 5MvL length to give Benz) (IT). Obtained Benz) (III)
There was little deformation, surface adhesion, etc., and workability was good.

This pellet (III) and high density polyethylene [density 0
．． 9617cm”, MFR41710m1n, below) (
(abbreviated as DPE) with a fiber content of 1% by volume (771% by weight)
The proportion becomes [pellets (III) 19.28% by weight,
After triblending with HDPE8 [L72% by weight],
It was molded into a 150 x 80 x 2 mW flat plate using a 3 oz in-line screw injection molding machine set at 220°C.

This flat plate has an extremely good appearance, low volume resistivity,
'It has particularly excellent electromagnetic wave shielding ability.

Comparative Example 3 Benz) (Instead of [), fibers (n
r), the ratio of fiber amount to 1 volume - 1%
II') 7.67% by weight, HDPE 92.33% by weight
A flat plate was obtained in the same manner as in Example 3 except that a triblend was used. In addition, the fiber used here (I
) was extremely easy to lose its shape and had particularly poor workability.

This flat plate had extremely poor fiber dispersion, a particularly poor appearance, high volume resistivity, and extremely poor electromagnetic wave shielding ability.

Example 4 The convergent fiber (III) obtained in Example 3 was processed using a 220°C extruder equipped with a rad die for resin coating cloth.
The amount of fiber after coating is 2.14% by volume (15.40% by weight,
Equal HDPE so that the coating resin amount is 32.855 (capacity k)
Covered fiber (IV) (22,729/rr
L) was obtained and cut into 5W lengths to obtain pellets (■). The obtained benzene (IV) had no deviation in shape, no adhesion on the surface, and was excellent in appearance, workability, etc.

The ratio of this Benz) (IV) and HDPE to a fiber content of 1% by volume (7.70% by weight) [Benz) (IV)
A flat plate was obtained in the same manner as in Example 3, except that tri-blending was carried out with 50% by weight of HDPK and 50% by weight of HDPK.

This flat plate has an extremely good appearance, low volume resistivity,
It had particularly excellent electromagnetic wave shielding ability.

Comparative Example 4 The unimpregnated stainless steel long fiber used in Example 3 had a fiber content of 2,166 volumes (15,38% by weight) after coating.
A coated fiber (IV'
) (22,817 m) was obtained and cut into sfi length to give Benz) (IV'). In addition, since the fiber bundle was not impregnated with any impregnating agent, the diameter of the fiber bundle was not constant, making it difficult to provide stable coating.

Benz) (IV') and HDPK in a ratio such that the fiber amount is 1% by volume (7.68% by weight) [pellets θv')
A flat plate was obtained in the same manner as in Example 3, except that triblending was carried out using a HDPE 50-weight device].

This flat plate had extremely poor fiber dispersion, a particularly poor appearance, high volume resistivity, and extremely poor electromagnetic wave shielding ability.

Example 5 Stainless steel long fibers (3,611/rrt) consisting of 600 long fibers with an average diameter of 20 μm were mixed with polystyrene wax [density t 0511/art? , number average molecular weight 900, hereinafter abbreviated as ps wax], the PS
After continuously immersing the wax in a solution of xylene of the same weight as the wax at 120°C, squeezing with a rubber roll to adjust the amount of PS wax impregnated, drying and removing the xylene,
A convergent fiber (V) (36,017 m ) having a fiber amount after impregnation of 14,646 (volume 100% by weight) was obtained and cut into sfl length to obtain a convergent fiber (V). Obtained Bent) (V)
There was little deformation of the surface, little surface adhesion, etc., and the workability was good.

This pellet (V) and high impact polystyrene [density t05. ! i'/i, MFR3,51/10m1n
, hereinafter abbreviated as HIPS] and zinc stearate (density t
1i7cnz ) and the amount of fiber is 1 volume f! %(7,06
weight%) [pellets (V)7α62% by weight,
HIPS 29.30% by weight, zinc stearate 0.0
8% by weight] and then molded into a flat plate measuring 150 x 80 x 2 m using a 3 oz in-line screw injection molding machine set at 200°C.

This flat plate has an extremely good appearance, low volume resistivity,
It had particularly excellent electromagnetic wave shielding ability.

Comparative Example 5 The same procedure as Example 5 was carried out except that HIPS was used instead of PS wax, and the amount of fiber after impregnation was 146% by volume (10
, 0% by weight) convergent fibers (V') (36,017 m
) was obtained and cut into 5WIL lengths to obtain pellets (V'). The pellet (V') was not uniformly impregnated with HIPS.

A flat plate was obtained in the same manner as in Example 5 except that this Benz) (V') was used instead of the pellet (V).

This flat plate had poor fiber dispersion, poor appearance, relatively high volume resistivity, and poor electromagnetic wave shielding ability.

Example 6 A stainless steel long fiber bundle (t9y/m) consisting of 4,000 long fibers with an average diameter of 8 μm was heated to 160° C. using polypropylene wax (density: 189.9/at
? , number average molecular weight 4.000, hereinafter abbreviated as pp wax) and thiobisphenol stabilizer (density t
After continuous immersion in a melt of an impregnating agent consisting of 1% by weight of O6, F, .4 volume t
% (9Q, 0 wt%) of convergent fibers (VI) (2,1,!
i'/m ) was obtained.

This convergent fiber (Vl) was coated with polypropylene (Vl) using a 230°C extruder equipped with a rad die for the resin coating cloth, so that the fiber amount after coating was 1% by volume (a07% by weight, the amount of coated resin was 98% by volume). Density [191, li'/crn'', MF
R611710m1n.

A coated fiber (Vl) (hereinafter abbreviated as pp) (23,5611/m ) was obtained by coating with ABS resin, and 3n
It was cut into long pieces to make pellets (■). Obtained Benz)
(Vf) is the shape (no misalignment, no surface adhesion, etc., appearance,
It was excellent in workability, etc.

This pellet (VI) was injection molded using a 3 ounce in-line screw type injection molding machine set at 230°C to form a flat plate of 150 x 80 x 2 itg.

This flat plate had a good appearance, low volume resistivity, and excellent electromagnetic wave shielding ability.

Test Examples The appearance of the flat plates obtained in Examples 1 to 6 and Comparative Examples 1 to 5 was visually evaluated, and the volume resistivity and electromagnetic wave shielding ability were measured. The results are shown in Table-1. The appearance evaluation criteria and measurement method are shown below.

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

5: Very good (clumps of fibers are small, number is less than 10) 4: Good
Good (small clumps of fibers, 10-19 in number) 3: Fair (some clumps of dog-like fibers, 20-39 in number) 2: Poor (large clumps of fibers, 40 in number) ~49 pieces) 1: Extremely poor (large clumps of fibers, number of 50 or more) Volume resistivity 5 Measured according to RIS (Japan Synthetic Rubber Association)-2301.

Electromagnetic shielding ability: Frequency 100 MH according to MILSTD (US military standard)-285 high impedance field measurement method
Measured in z.

Claims (1)

[Claims] Impregnating conductive long fibers with an impregnating agent containing a thermoplastic polymer (A) with a molecular weight of 10,000 or less, and then coating with a thermoplastic resin (B) other than the polymer (A) as necessary. A method for producing a conductive resin composition, characterized by: