JP3419964B2 - Antistatic monomer-cast nylon molded product - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antistatic monomer-cast nylon molded product, particularly various parts used in a production line of semiconductor-related products, such as a carrier pallet,
Monomer cast nylon molded products with excellent antistatic properties, which are useful for housings, rollers, etc., or for applications where static electricity is disliked, for example, industrial parts such as wheels, rollers, gears, bearings, guides, etc. Is.

[0002]

2. Description of the Related Art Generally, the following methods are known for imparting antistatic properties to resin molded products. (A) A cationic, anionic, amphoteric or nonionic surfactant is kneaded into the resin. (B) The surface active agent is applied to the surface of the resin molded product. (C) A conductive filler such as a carbon-based or metal-based substance or a metal-plated inorganic substance is added to and mixed with the resin. However, when the above method is applied to impart antistatic properties to a monomer-cast nylon molded product, there are the following disadvantages.

In the case of (a) above, since the monomer casting is a molding method involving a polymerization reaction,
When a surfactant is added in an amount sufficient to exert antistatic performance, it inhibits the polymerization reaction and makes molding impossible or extremely difficult.If the amount added does not affect the polymerization reaction, the desired antistatic property is obtained. I can not get sex. next,
In the case of the method (b), that is, the method of applying a surfactant to the surface of a molded product obtained by monomer casting, the surfactant may fall off due to external factors. There is a problem that the property is less than that of the kneading method of a surfactant, or that a part to be cut for surface treatment must be applied after the part is processed.

Next, in the case of the above method (c), when the filler is a metal-based substance or a metal-plated inorganic substance, the difference in specific gravity between the filler and the liquid raw material (monomer) is large, and after the raw material is injected. The conductive filler is not uniformly dispersed in the molding die. Further, when the filler is carbon black, the large specific surface area, which is advantageous in ordinary plastic molding, increases the absorption amount of the liquid raw material, and the liquid raw material thickens and is molded. Make it difficult. Further, when the carbon fiber is filled, if it is dispersed in the liquid raw material, the fibers are entangled with each other and it is difficult to uniformly disperse the fiber, and the viscosity is increased, which makes molding difficult.

Further, the applicant of the present invention has previously made an invention relating to an antistatic monomer-cast nylon molded product (Japanese Patent Laid-Open No. Sho 61-206, 2006).
64-29428). This invention is to obtain a monomer-cast nylon molded product by mixing carbon fine particles obtained by carbonizing and firing a spherical or granular phenol resin to obtain a monomer-cast nylon molded product, which is required as a volume resistivity value of 10 ³ to 10 ⁹ (Ω ・ c
It is possible to obtain a molded product showing a measured value of about m),
There are cases in which stable performance cannot be exhibited due to large variations among sampling sites in the material or between lots.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above problems in the prior art and has excellent antistatic performance,
Moreover, there is little variation in antistatic performance between material parts,
It is another object of the present invention to provide a monomer-cast nylon molded product having less variation in antistatic performance between lots.

[0007]

The present invention achieves the above objects, and the gist of the present invention is to obtain a true specific gravity of 2.0 to 100 parts by weight per 100 parts by weight of nylon.
2.3 and Ri name contains 5 to 30 parts by weight of flaky carbon fine particles having an average particle diameter of 1 to 30 [mu] m, and volume resistivity 1
It exists in an antistatic monomer cast nylon molded product characterized by having a value of 0 ³ to 10 ⁹ (Ω · cm) .

The present invention relates to a molded product mainly composed of monomer-cast nylon, in which specific carbon fine particles are uniformly dispersed. Monomer cast nylon, ε-caprolactam as the main raw material nylon 6, ω
-Nylon 12 containing lauryl lactam as a main raw material, and further copolymerized nylon of ε-caprolactam and ω-lauryl lactam, and the like. As the scale-like carbon fine particles (hereinafter, may be abbreviated as scale-like carbon) added to this, there is scale-like graphite. The true specific gravity of this scale-like carbon is in the range of 2.0 to 2.3, and the difference from the specific gravity (about 1.0) of lactams, which is the raw material monomer of nylon, is small, so that it settles in the monomer like metal-based fine particles. Instead, it can be uniformly dispersed in the target molded article.

The true specific gravity of the scale-like carbon must be in the range of 2.0 to 2.3. If it is less than this lower limit, it tends to float in the mold during polymerization and curing, and it is dispersed uniformly. The product cannot be obtained. When the true specific gravity exceeds the above upper limit, the degree of sedimentation of scale-like carbon becomes large.
This true specific gravity is measured by a density gradient tube according to JIS K7112.

The average particle size of the scale-like carbon to be added is 1 to 30 μm.
Must be within m. Since this average particle size is significantly larger than that of carbon black ultrafine powder of carbon black type, it is uniformly dispersed in the liquid material nylon monomer without agglomeration between the added ones. Can be made. When the average particle size is less than the lower limit of the above range, the viscosity of the liquid raw material increases, making it difficult to inject it into the mold, and the molding itself becomes difficult. On the other hand, if the average particle size exceeds the above upper limit, the degree of sedimentation of the scale-like carbon in the mold becomes large, and it becomes difficult to form a molded product having uniform performance. A particularly preferable range of the average particle size is 1
~ 20 μm. The average particle size is measured by "Shimadzu Centrifugal Sedimentation Type Particle Size Analyzer SA-CP3" manufactured by Shimadzu Corporation (based on the liquid phase sedimentation method, the particles are sedimented and the sedimentation state is detected by a light transmission means. Is an average particle diameter.).

The content ratio of the scale-like carbon in the monomer-cast nylon molded product is 5 to 30 parts by weight per 100 parts by weight of nylon in the molded product. If the content ratio of the scale-like carbon is less than the lower limit, the required performance of the volume resistivity cannot be satisfied, and preferable antistatic performance is not provided. On the other hand, when the content ratio of the scale-like carbon exceeds the above upper limit, the scale-like carbon settles within the time until the raw material is solidified in the molding die, and a portion having a high additive concentration is formed in the molded product. In some cases, this portion causes poor polymerization, and it may not be possible to obtain the specified size. Therefore, considering the molding conditions, the product appearance, and the required antistatic properties, the scale-like carbon content is suitably 5 to 30 parts by weight, and a particularly preferred range is 10 to 25 parts by weight.

Next, a method for producing the monomer-cast nylon of the present invention will be described. As the anionic polymerization catalyst used for the polymerization of the nylon raw material monomer, any catalyst conventionally known for this type of anionic polymerization can be used. Specific examples thereof include alkali metals, alkaline earth metals, hydrides of these metals, oxides, hydroxides,
Examples thereof include carbonates, alkylated products, alkoxides, Grignard compounds, and reaction products of them with ω-lactams. As the polymerization promoter, any polymerization promoter known in the anionic polymerization of nylon monomer can be used. Specific examples thereof include various isocyanate compounds, urea derivatives, acyllactams and the like.

In order to produce the molded article of the present invention, any method known as a monomer casting method using a nylon monomer as a raw material may be used. Specifically, the polymerization molding temperature is not less than the melting point of the nylon monomer used and not more than the melting point of the molded nylon, and usually in the range of 120 to 200 ° C. The time required for polymerization is usually within 3 hours. Regarding the selection of the catalyst and the co-catalyst, any combination of the above-mentioned compounds may be used, and one kind or a combination of two or more kinds may be used.

The reason why the volume resistivity of the molded article varies depending on the type of the additive for imparting antistatic property is that the difference in the resistivity of the additive itself and contact at the interface between the resin and the additive It is estimated that the difference is due to the difference in surface area. Compared with a monomer-cast nylon molded article produced by adding spherical or granular carbon fine particles obtained by carbonizing the phenol resin particles in the description of JP-A-64-29428 mentioned in the section of the prior art, The reason why the molded article of the present invention has a high volume resistivity value is not clear, but it is considered to be due to the above reason. That is, while the carbon fine particles used in the molded article described in the above publication are spherical or granular,
The carbon fine particles used in the molded article of the present invention are in the form of scales, and because the shapes are different as described above, a difference occurs in the contact area with nylon, resulting in a difference in the volume resistivity value of the molded article. It is presumed that it comes out.

The volume specific resistance value (Ω · cm) of the monomer-cast nylon molded product of the present invention is generally 10 ³ to 10 ⁹ for the applications described in the above-mentioned industrial application field. Those in the order range are preferable. However, since in the IC-related parts which may destroy the IC internal circuit, ¹⁰⁵ to
⁷ Oh - da - intended volume resistivity of are particularly preferred. The volume resistivity (Ω · cm) is measured using a 100 mm square, 5 mm thick test piece as a sample box 16008A R
Digital multimeter 3478 using ESISTIVITY CELL
It was measured by A (manufactured by Yokogawa Hulet Packer).

[0016]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Example 1 Stainless steel beaker with anhydrous ε-caprolactam 2,
Taking 500 g, heating to a temperature of 140 to 160 ° C., 20 g of hexamethylene diisocyanate as a polymerization cocatalyst and graphite preheated [graphite UFG-10 manufactured by Showa Denko KK, True specific gravity of 2.2, average particle size of 4 μm (measured by the Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-CP3)] are added and mixed. This addition amount is such that the content (parts by weight) of graphite shown in Tables 2 and 3 below per 100 parts by weight of nylon in the finally obtained monomer-cast nylon molded product.

Separately, 1,000 g of anhydrous ε-caprolactam was taken in another stainless steel beaker, and 6 g of sodium hydride (63% oily) as a polymerization cocatalyst was added to this, and 140-160 was added.
Adjust to ℃. Then, this is mixed with the above graphite mixed monomer and poured into a molding die at 150 ° C.
After being polymerized for a minute, the molded product was taken out. This molding die shall be able to obtain a square flat plate with a height of 500 mm, a width of 500 mm and a thickness of 15 mm, and the plate shall be molded so that it stands upright. The raw material mixture is injected from a gate (injection port) provided on the upper part of the. This makes it clear during the progress of the polymerization reaction whether the dispersion of the added carbon fine particles is uniform or non-uniform between the upper portion close to the sprue and the lower portion. The molded product thus obtained is viewed in an upright state and divided into three parts, an upper part, a middle part and a lower part, which are used as measurement samples. That is, the volume specific resistance value of each of these samples is measured, and the variation of the volume specific resistance value in the upper part, the middle part and the lower part of the molded product is examined. The results are shown in Table 2 below.

Comparative Example 1 The amount of graphite (UFG-10) added in Example 1 was changed so that the amount of graphite per 100 parts by weight of nylon in the nylon molded product would be the value shown in Table 3, and otherwise. In the same manner as in Example 1, a monomer-cast nylon molded product was obtained. The characteristics of the obtained molded product were measured in the same manner as in Example 1, and the results are shown in Table 3. Comparative Example 2 Instead of graphite (UFG-10) in Example 1, granular carbon obtained by carbonizing and firing the phenol resin particles described in JP-A-64-29428 mentioned in the section of the above-mentioned prior art. The characteristics were measured in the same manner as in Example 1 except that fine particles [Bellpar C-2000S manufactured by Kanebo Co., Ltd.] were added. The results are shown in Table 3.

Comprehensive evaluation of the molded articles obtained in the above Examples and Comparative Examples was carried out as follows. As described at the end of Example 1, a molded product having a height of 500 mm, a width of 500 mm and a thickness of 15 mm was divided into three equal parts, an upper part, a middle part and a lower part. ) Was measured, and the variation in the number of digits was compared for the resistance value, and the quality of the uniformity of the volume specific resistance value was determined. Next, the appearance of the molded product was examined. That is, in the molded product, a polymerization defect may partially occur, and a part which is not cured according to a predetermined mold shape may be formed. Therefore, this is visually inspected. The following three stages were evaluated according to the molding state.

(1) Good --- Good condition without causing polymerization failure. (2) Yes --- Although some polymerization defects occur, there is no problem in collecting test pieces. (3) Defective --- The test piece cannot be collected due to significant polymerization failure. Based on the above measurement and inspection, the following four-stage comprehensive evaluation was performed. This is shown in Table 1. In Table 1, "variation in the number of digits of the measured value" means that a sample of one molded product is divided into the upper, middle, and lower three stages as described above, and the volume resistivity of each is calculated. It is a numerical value obtained by finding out how many digits are different between two values.

[0021]

[Table 1]

The contents of the comprehensive evaluation in Table 1 are as follows. (1) Good --- Withstands actual use. (2) Yes --- It usually withstands actual use, but it may cause a problem depending on the purpose of use. (3) Defective --- There is a problem and it is difficult to use it in practice. Or, there are some problems in production. (4) No --- Actual use is not possible. Or there is a production problem. Table 2 shows the evaluation results of Example 1 and Table 3 shows the evaluation results of Comparative Examples 1 and 2 in accordance with the above criteria. The content in Tables 2 and 3 means the graphite content (parts by weight) per 100 parts by weight of nylon in the molded product.

[0023]

[Table 2]

[0024]

[Table 3]

In Table 3 above, in the case of the graphite content of Comparative Example 1 being 35 parts by weight, the column of the volume resistivity value and the column of the variation of the number of digits of the measured value are marked with horizontal lines. Means that the lower part of the molded product caused poor polymerization, the test piece could not be collected, and the variation value of the number of digits of the measured value could not be obtained. In Table 3, when the graphite content of Comparative Example 1 is 4 parts by weight and when the graphite content of Comparative Example 2 is 5 parts by weight, a horizontal line is added to the column of variation in the number of digits of each measured value. There is
This means that the same measurement method as the other examples exceeded the measurement limit, and therefore it was impossible to grasp the numerical value of the variation.

[0026]

The monomer-cast nylon molded article of the present invention has the additive uniformly dispersed throughout the molded article,
It has an excellent antistatic property by uniformly holding a useful volume resistivity value.

Claims (4)

(57) [Claims] 1. A nylon 100 parts by weight per Ri name contains 5 to 30 parts by weight scale-like carbon particles of the true specific gravity 2.0 to 2.3 and an average particle diameter of 1 to 30 [mu] m, and a volume specific resistance
An antistatic monomer cast nylon molded product having a resistance value of 10 ³ to 10 ⁹ (Ω · cm) . 2. The antistatic monomer cast nylon molded article according to claim 1, wherein the nylon is nylon 6, nylon 12 or a copolymerized nylon of ε-caprolactam and ω-lauryllactam. 3. The content ratio of the scale-like carbon fine particles is 10 to 25 parts by weight per 100 parts by weight of nylon.
Antistatic monomer cast nylon molded product described. 4. The average particle size of the scale-like carbon fine particles is 1 to 20.
The antistatic monomer cast nylon molded article according to claim 1, which has a thickness of μm.