JPH0350792B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition with excellent antistatic performance. More specifically, the volume resistivity is 10 ⁸ to 10 ¹⁰ Ωcm
This invention relates to a resin composition that can be controlled within the range of . Since polymer materials are inherently insulating, they are widely used as insulators in electrical and electronic components.
However, in recent years, as the methods of using polymeric materials have become more sophisticated, the required performance has also become more sophisticated, and it has become difficult to realize these demands.
One such problem is that electronic parts are damaged by static electricity generated in polymeric materials when they are handled.
In dry conditions, potentials of tens of thousands of volts are generated in polymeric materials, easily damaging semiconductors and other materials. In order to prevent such troubles, the volume resistivity must be 10 ¹⁰ Ωcm or less. On the other hand, when the volume resistivity is less than 10 ⁸ Ωcm, the insulating properties of the polymer material are lost, causing problems such as electric shock, leakage, or sudden discharge and damage when electrically charged electronic components come into contact. Become. In order to protect such electronic components from static electricity, it is necessary to control the volume resistivity within an extremely narrow range of 10 ⁸ to ^{10 10} Ωcm. For this purpose, there is a method of applying an antistatic agent to the surface of the molded product, but although it exhibits its function in a short period of time, it changes significantly over time, is greatly affected by humidity, and furthermore, the resistance value varies greatly. This is not something we should be very satisfied with. It is also known to mix conductive carbon, such as Ketschien Black EC and acetylene black, with polymer materials, but these conductive carbons have a low resistance value of about 10 ^-1 Ωcm. Although it is easy to obtain a resistance value of about 10 ² - ^{10 6} Ωcm when compounded into a compound, it is extremely difficult to control the resistance value around 10 ⁸ - 10 ¹⁰ Ωcm, and it varies widely depending on the kneading and molding conditions, making it difficult to put into practical use. It is impossible. As described above, there has been no known method for accurately controlling the resistance value within the range of 10 ⁸ to ^{10 10} Ωcm, and the development of such a method has been strongly desired. The inventors of the present application focused on this point and, as a result of intensive study, discovered that the purpose could be achieved by using a specific graphite, and arrived at the present invention. The present invention will be explained in detail below. The graphite used in the present invention is natural earthy graphite, and its fixed carbon content is preferably in the range of 50% to 90%. Graphite includes natural conductive earth-like graphite, natural flake graphite, and artificial graphite, but these graphites are flat and have a high particle aspect ratio, making it difficult to control the resistance value and also making it difficult to control the resin. It has the disadvantage that the resistance value varies greatly depending on the direction of measurement because it tends to be oriented in the direction of flow.
It cannot be applied to the present invention. If the fixed carbon content is less than 50%, the amount of graphite added to obtain the desired resistance value will be large, and the fluidity will be poor, making it difficult to obtain a satisfactory molded product. Furthermore, if the resistance value exceeds 90%, the resistance value of the molded product will vary greatly, making it difficult to control the resistance value to 10 ⁸ to ^{10 10} Ωcm. The fixed carbon content referred to here is the residue obtained by subtracting the volatile content and ash content according to JIS K-6221, and is expressed by the following formula. Fixed carbon content = 100 - (ash content + volatile content)% The average particle size of graphite is preferably 100μ or less. If it exceeds 100μ, the resistance value will vary widely and the strength will be low. The amount of graphite added varies depending on the fixed carbon content, but is selected in the range of 5 to 50% by weight. Organic polymer materials used in the present invention include polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polystyrene,
Thermoplastic resins such as ABS resin, polyamide, polyacetal, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether sulfone, phenolic resin, unsaturated polyester, epoxy resin, etc. Examples include heat curing. As a method for mixing graphite and these polymeric materials, methods such as a method using a kneading machine such as a roll, a Banbury, or a kneader, and a method such as continuous kneading and extrusion using a single-screw or twin-screw extruder are employed. During kneading, additives such as lubricants, stabilizers, flame retardants, and plasticizers, reinforcing materials such as glass fiber and whiskers, calcium carbonate, clay, silica, mica,
An inorganic filler such as talc may be added as necessary. The composition thus obtained can be processed into a film or sheet by conventional processing methods such as calendering or inflation, or
It can also be molded into various molded products by injection molding, compression molding, etc., such as IC carriers, IC test jigs,
Used as trays, transport cases, etc. When the composition of the present invention using natural earthy graphite is used, there is little variation in resistance value depending on molding conditions, and it is 10 ⁸ to ^{10 10} Ω.
It is possible to stably produce cm products. There is considerable damage to semiconductors due to static electricity, and the economic effects of the present invention are extremely large. The present invention will be specifically explained below using Examples. Example 1 4.15Kg of polybutylene terephthalate and 0.85Kg of natural earthy graphite (fixed carbon content 85%, average particle size 6.5μ)
was placed in a V-blender and mixed at 40 rpm for 10 minutes.
This was kneaded into pellets using a 40 mm single screw extruder. The resulting pellets were molded into test strips measuring 120 x 25 x 3 mm using a 1 oz injection molding machine. Five specimens were randomly selected from among the test specimens, and the volume resistivity of each specimen was measured at an applied voltage of 100 VDC. The results are shown in Table-1.

[Table] As is clear from the results, the composition of the present invention was able to control the resistance within an extremely narrow range of (8.0±1.1)×10 ⁸ Ωcm. Comparative Example 1 Example 1 except that the natural earthy graphite was replaced with conductive carbon, Ketschien Black EC (manufactured by Lion Akzo Co., Ltd.), and the amount added was 0.31 kg so that the resistance value was within 10 ⁸ - ^{10 10} Ωcm. A similar test was conducted. The results are shown in Table-2.

[Table] In this way, the values vary over a wide range from 9.3×10 ⁷ Ωcm to 1.6×10 ¹² Ωcm, and the desired 10 ⁸
It was impossible to control the resistance within the range of ~10 ¹⁰ Ωcm. Comparative Example 2 Natural earthy graphite was replaced with acetylene black (Denka Black), which is conductive carbon, and the resistance value was
The same test as in Example 1 was conducted except that the amount added was changed to 0.51 kg so that the resistance was 10 ⁸ to ^{10 10} Ωcm. Display the results -
Shown in 3.

[Table] As shown, it varies in a wide range from 6.4 × 10 ⁷ Ωcm to 1.9 × 10 ¹¹ Ωcm, and the
It was impossible to control the resistance within the range of 10 ⁸ to ^{10 10} Ωcm. Example 2 Natural earthy graphite with fixed carbon content of 80% and average particle size of 6.5μ
The same operation as in Example 1 was performed except that the amount added was 0.90 kg so that the resistance value was in the range of 10 ⁸ to ^{10 10} Ωcm. The results are shown in Table-4.

[Table] From this result, it was possible to control the resistance within an extremely narrow range of (5.9±1.0)×10 ⁸ Ωcm. Example 3 2.25Kg of polyphenylene sulfide resin, 2.00Kg of glass fiber (3mm chopped strand) and natural earthy graphite (fixed carbon content 85%, average particle size 6.5μ)
0.75 kg was kneaded into pellets in the same manner as in Example 1, and the same test was conducted. The results are shown in Table-5.

[Table] From this result, it was possible to control the resistance within an extremely narrow range of (7.1±1.0)×10 ⁸ Ωcm. Comparative Example 3 Natural flaky graphite with a fixed carbon content of 97% and an average particle size of 6.5 μm was used instead of natural earthy graphite, and the resistance value was 10 ⁸
The same operation as in Example 3 was carried out with the amount added being 0.65 kg so as to fall within ~10 ¹⁰ Ωcm. The results are shown in Table-6.

[Table] As shown, the resistance varied within the range of 9.2×10 ⁷ Ωcm to 1.8×10 ¹¹ Ωcm, and it was impossible to control it to 10 ⁸ to ^{10 10} Ωcm.

Claims (1)

[Claims] 1. An antistatic resin composition comprising 50 to 90% fixed carbon, 5 to 50% by weight of natural earthy graphite with an average particle diameter of 100 microns or less, and 95 to 50% by weight of an organic polymer material.