JPS6375243A - Antistatic plate material and its production - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] A, 9. OBJECTS OF INDUSTRIAL APPLICATION This invention relates to an antistatic board material used for floors, walls, ceilings, etc. of semiconductor factories, etc., and a method for manufacturing the same.

Prior art The conventional plate material with antistatic effect is made of a conductive material with a specific volume resistivity of approximately 10"Ω・am or less, and is capable of dissipating the electric charge generated on the surface to a grounding point etc. was needed.

Also, in order to reduce costs and improve aesthetics, synthetic resin materials are recommended.9! It was considered beautiful.

In order to make synthetic resin, which is originally an insulator, electrically conductive, conductive materials such as metal powders such as An and Ni, carbon black, metal fibers, and carbon miscellaneous are kneaded and dispersed in the resin to increase the electrical resistivity. A common method is to lower the

In this case, in order to set the specific volume resistivity to 10'' Ω·cm or less, it is usually necessary to mix 10 to 40% of the conductive material with respect to the resin material.

However, such conductive materials are generally more expensive than resins, and from the viewpoint of manufacturing costs, it is desirable to obtain the desired antistatic effect with a conductive material that costs as little as possible, and it is also easy to manufacture. I'm glad that something happened.

5F = IJJ is the cause] The present invention uses less +, + conductive material than the conventional one, but has the same or better results. [-1] It is an object of the present invention to provide a board material that is effective against electric shocks and to provide an easy manufacturing method thereof.

R stages of the present invention to solve the structural problems of the invention; The electric protection board material is characterized by having a structure in which conductive fibers are scattered in spots densely dispersed in the plastic resin in the board material made of a thermoplastic resin.

This will be explained with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a structural model of the plate material susceptible to electrostatic disease 11 of the present invention, and FIG.
This is a cross-sectional view taken along the line XX in the figure, in which a plate material 1111 made of a hot IIr plastic resin is scattered with spots 2 in which conductive fibers are densely dispersed in the Ir plastic resin. When the thickness of the plate material is approximately 3 mm or less, each spot exists in a state where it penetrates from the front surface to the back surface of the plate material, as shown in Figure 2, and as a result, the conductive fibers in each spot penetrate the plate material. are densely distributed throughout the thickness.

In the structure described in -1-, 9 u other than spot 2 where the conductive fibers are densely dispersed in the natural plastic resin (metal powder, carbon black, metal fiber, charcoal fiber, etc. The conductive material may be loosely dispersed.

FIG. 3 is a cross-sectional view of an antistatic plate model of the present invention in such an embodiment, and FIG. 4 is a cross-sectional view taken along the line XX of FIG. 1, showing a conductive material.

For example, the conductivity ta! at spot 2! Plate material 1 made of thermoplastic resin in which conductive fibers of the same type as i are loosely dispersed
There are scattered spots 2 in which the conductive fibers are densely dispersed in the thermoplastic resin.

Figure 5 is a model showing the distribution state of conductive fibers in the cross section shown in Figure 4, and the horizontal axis is x-X in Figure 1.
The position on the line, the vertical axis is the conductivity in the area where the conductive fibers are sparsely dispersed! It represents the relative conductive fiber mixing ratio when the uniform mixing ratio of a fiber is set to 1, and the distribution curve Y shows the conductive fiber in the direction of the thickness of the plate material at the position corresponding to spot 2 in Figure 4. For example, on the order of 102, it shows that the particles are densely dispersed and mixed.

In either the structure shown in Figures 1 and 2 or the structure shown in Figures 3 and 4, the volume resistivity (Ω・cm) is inversely proportional to the mixing rate of conductive m!a. Therefore, the local specific volume resistivity in the thickness direction of the plate material becomes extremely low at the position corresponding to the spot 2 where the conductive 1a fibers are densely dispersed.

The specific volume resistivity in the thickness direction of the plate material in the spot 2 where conductive IA miscellaneous is densely dispersed depends on the spacing between the spot phases 11, but it is generally preferable to set it to 104Ωcm or less. .

Also conductive! The spacing between the spot phases 1 in which the a-fibers are densely dispersed is preferably 15 cm or less, preferably 10 cm or less.

In this way, by locally concentrating the conductive fibers and scattering spots where the specific volume resistivity of those areas is extremely small, it is possible to reduce the r +: Conductive fibers allow electric charges to easily move from the front surface to the back surface of the board.

There is no particular problem with the solid resistivity in the thickness direction of the plate material in areas other than spots where conductive fibers are densely dispersed. It is desirable that the surface resistance id of the plate material is about 10' to 10''Ω, but this level of surface resistance can be easily achieved by sparsely dispersing the conductive material or applying conductive paint to the surface using 'J cloth. be done.

If the above surface resistance value is achieved, charges generated on the surface of the plate other than spots where conductive fibers are densely dispersed will easily move along the plate surface to the spot and quickly pass through the spot. to reach the back side of the board.

The distance between spots where conductive fibers are densely distributed is 1
The reason for setting the distance to 5 cm or less, preferably 10 cm or less, is to increase the probability that the charges will be grounded and removed, and to prevent the charges from remaining on the surface of the plate material for a long time. Electric charge is mainly generated by walking on a floor material, for example, but if the distance between the spots where conductive fibers are densely distributed in the thickness direction of the board material is 15 cm or more, it will be generated when walking. This means that at least one spot marked with "-" exists for each shoe footprint, which is preferable because the probability of dissipating the generated electric charge is increased.

When using this antistatic plate material, the antistatic plate material of the present invention is laminated on a base structure made of a highly conductive material such as a metal plate or metal mesh, or a conductive Paint is applied to the back side to form the floor, wall, and ceiling of the room.The base structure or the conductive paint surface is grounded by an appropriate method.

When installed in this way, the electric charges generated on the surface (indoor side) of the board (on the indoor side), which is susceptible to electrostatic disease, move along the surface of the board and reach the surface of spot 2, where the conductive fibers are densely dispersed. , the spot 2 is moved in the thickness direction to reach the base structure made of a highly conductive material or the conductive paint surface provided on the back surface of the plate material, and is grounded and removed.

In this way, compared to the case where the conductive fibers are uniformly dispersed, the antistatic IF effect of 7 can be obtained by using a small amount of the conductive fibers, for example, less than one portion of the portion.

Note that thermoplastic resins include polyvinyl chloride, polyethylene, polypropylene, and polyester.

Polymethyl methacrylate and other arbitrary thermoplastic resins can be selected.

This has been explained in detail above. A board material with electrification disease 1F has a structure in which spots where conductive fibers are densely dispersed in the thermoplastic resin are scattered in the board material made of a thermoplastic resin.
It cannot be manufactured simply by mixing the reprinted conductive fibers with thermoplastic resin powder 1W & fiber or pellets, kneading at a temperature of 1-1 below the thermal melting temperature of the thermoplastic resin, and molding it into a plate shape.

In this case, if the kneading takes a sufficient amount of time, the conductive fibers will become uniformly dispersed in the thermoplastic resin, and if the kneading is performed unevenly, the conductive fibers will not be dispersed in the thermoplastic resin. Although the conductive am is uniformly dispersed, spots in which the conductive am is densely dispersed are not formed.

Conductive fibers are placed in a plate material made of heat 0f plastic resin.
rq! Electrification disease 1 having a structure in which spots are densely dispersed in the polymorphous resin (bimorphic board material has a bulk ratio It!
A spherical (marimo-like) bundle of conductive fibers with a diameter of 10 mm or less at o, o+ ~ 0.15 is heated to 0f plastic resin powder, am
Alternatively, the conductive 1aIIn may be mixed with pellets and heated to H+ (while remaining unevenly dispersed in the plastic resin).
(Manufactured by molding into a plate shape at a temperature of I- below the thermal melting temperature of the plastic resin.

At this time, the bulk specific gravity is 0, 04 to 0.15 and the diameter is 10 mm or more.
Conductive materials other than spherical materials, e.g.
- There is no problem even if conductive fibers or conductive powders such as metal powder or carbon black which are not bundled as described above are mixed at the same time.

Specifically, G) thermoplastic resin powder, la
Spread conductive fibers or pellets all over the hot press surface, place the conductive fiber spherical bundles in between at appropriate intervals, and hot press at a temperature higher than the melting temperature of the plastic resin. ① A mixture of thermoplastic resin powder, w&fiber, or pellets and the conductive fiber spherical bundle described in 1 above at room temperature is sprinkled all over the hot press surface, and the thermoplastic A method of hot pressing at a temperature higher than the thermal melting temperature of the resin to form a plate, using a kneading device that can mildly knead the thermoplastic resin powder, fibers, or pellets and the above conductive fiber spherical bundle, 1 (
Conductivity m! There is a method of kneading (a) to such an extent that a is not uniformly dispersed, and then forming the mixture into a plate shape.

In the case of (2), the point at which the conductive mm is formed into a plate shape before it is uniformly dispersed in the plastic resin varies depending on the nature of the kneading equipment used.

-Although it cannot be determined generally, 1 Usually, the kneading is finished when the equipment has been kneading for about 0.2 to 0.5 times the time required to uniformly disperse the conductive MAm in the thermoplastic resin. It can be formed into a plate shape.

If the kneading time is too short, the thermoplastic resin will not be completely melted, and if the kneading time is too long, the conductive fibers will be uniformly dispersed.

Therefore, for a specific kneading device, the optimum kneading time may be determined experimentally by setting the kneading time range in "-" to 11.

Methods such as extrusion molding, injection molding, and hot pressing are used to form the heated 6-kneaded material into a plate shape. Tokoro 9! After the heated kneaded material is once made into pellets, it may be formed into a plate shape.

Here, a method for forming a spherical (marimo-like) bundle of conductive fibers with a bulk specific gravity of 0.04 to 0°15 and a diameter of 10 mm or more is as follows:
I will explain carbon m using someone as an example.

Pitch-based fibers, which are difficult to produce long am, are manufactured in the form of short pieces by centrifugal spinning, so short fibers become intricately intertwined with each other and become cotton-like aggregates with low bulk specific gravity. Therefore, even if it is used as it is and an attempt is made to disperse it in a resin matrix material, the flocculent material does not completely loosen and it is difficult to uniformly disperse it.

The complicated cotton-like tangles of short fibers are loosened in advance,
In order to make a carbon fiber bundle that is compacted to increase its bulk specific gravity and disperse easily, Japanese Patent Application No. 60-253724, ``Method for manufacturing a carbon fiber bundle'', creates a swirling air flow inside. 58! A carbon fiber bundle made by mixing short am flocculent aggregates of carbon fibers in a cylindrical container and swirling them with airflow! The manufacturing method is described.

In order to generate swirling airflow inside a cylindrical container, it is sufficient to send airflow from an airflow inlet pipe provided on the side of the cylindrical container in the direction of the tangential line, and the introduced airflow flows along the inner wall of the cylindrical container. After rotating, the air is discharged to the outside through the air outlet [1] equipped with a filter.

In addition, a normal cyclone type device may be used.

Therefore, if a flocculent aggregate of short carbon fibers is mixed into a cylindrical container or sent into the cylindrical container along with airflow, the flocculent aggregate of short female fibers will flow into the cylindrical container along with the airflow. By repeating the spinning, dispersion, and focusing, a carbon fiber bundle having approximately uniform size and shape is finally formed.

The shape of the obtained carbon fiber bundle can be broadly classified depending on the operating conditions, and the diameter of the short carbon fibers aligned in one direction is 2 to 4 mm.
It becomes a cylindrical shape, or a spherical marimo-like shape made of curled carbon fiber short fibers.

In the present invention, the term "bundled material" refers to short fibers that are first disentangled and then gathered into small lumps through such a process.

To explain the operating conditions specifically, the following three parameters have a large influence.

■Ratio α between the volume (v) of the carbon fiber short fiber flocculent aggregate and the volume (V) of the cylindrical container [α= v / V] ■The number of rotations per second at which the carbon fibers rotate along the inner wall of the cylindrical container γ[
rpsl ■Time t [minutes] for rotating the carbon M&fibers In other words, by controlling these three parameters, it is possible to create charcoal, a cylindrical type with a diameter of 2 to 4 mm in which the short fibers are aligned in one direction, or When the bulk specific gravity is in the range of 0.02 to 0.20, spherical particles with a particle diameter of 10 mm or less can be obtained.

In the method of the present invention, the thus produced spherical bundle having a bulk specific gravity of 0.04 to 0.15 and a diameter of 10 mm or less is used.

Although such a spherical bundle may be used in the method (1) or (2) above, the case where the method (2) is used will be explained in detail.

Spherical shape with a bulk ratio of 0.04 to 0.15 and a diameter of 10 mm or less (
(Marimo-like) bundled conductive fibers are mixed with thermoplastic resin powder or pellets, and kneaded at a temperature higher than the thermal melting temperature of the thermoplastic resin.

If kneading is stopped before the conductive fibers are uniformly dispersed in the ffffqj resin, some of the conductive fibers on the surface layer of the spherical bundle will separate from the bundle and become loosely dispersed in the hot OT plastic resin. The center of the spherical bundle is densely dispersed in the thermoplastic resin.

When molded into a plate shape in such a state, the plate material has a structure in which the conductive fibers are sparsely dispersed and the spots where the conductive fibers are densely distributed in the thickness direction of the plate material are scattered. A preventive plate material is obtained.

Antistatic board materials that use carbon fiber as conductive fibers have a slightly grayish overall appearance, as if darker spots are scattered on the surface of the board material.

When conductive fibers are used as a spherical bundle and formed into a plate shape before being kneaded with 8 plastic resin and uniformly dispersed, L
As described above, it is possible to easily form a structure in which conductive fibers are sparsely dispersed in a plate material, and spots where conductive fibers are densely dispersed in the thickness direction of the plate material are scattered. , cutting of the conductive fibers during the kneading process with the molten thermoplastic resin is suppressed. Since carbon fibers are particularly susceptible to breakage due to mechanical stress, this effect appears in IAyt.

Using an appropriate solvent, only the resin is removed from a board made by kneading and dispersing carbon fiber into resin, and carbon! Only a fiber was extracted]-1 that m! Ir;i: The results of measuring the distribution are shown in FIG. 6 as a model.

In Fig. 6, the horizontal axis represents the fiber length when the +l average length of carbon mIn used as the raw material is taken as 100, the vertical axis represents the frequency, and the A line represents the fiber length distribution of the carbon fiber used as the raw material.
Line B shows the fiber length distribution of carbon fibers in a conventional antistatic board material in which carbon fibers are uniformly dispersed, and line C shows the fiber length distribution of carbon fibers in the antistatic board material of the present invention.

The fiber length of charcoal used as raw material 1 is 4t L with its f average length of 100 as the center (
In contrast, in conventional antistatic plate materials, the charcoal J mi is cut during the kneading process and is distributed around a fiber length of around one-tenth of the raw material (line B). In the case of unreleased IJI (1? anti-static board material,
Although some of the carbon fibers are cut, some remain uncut, showing a wide distribution (line C) centered on the fiber length before and after the raw material portion.

Such long fibers! Since the conductive fibers with length a remain, the decrease in surface electrical resistance is remarkable even in areas where the conductive fibers are sparsely dispersed.

As the thermal LTr plastic resin, the method of the present invention can be applied to polyvinyl chloride, polyethylene, polypropylene, polyester, polymethyl methacrylate, and any other 8+if q resin. These fevers
(Plastic resin is used in powder, am or pellet form.

rh@1 Sprinkle polyethylene powder all over the hot press surface 4i
L,, during which the true specific gravity is 1.6. Diameter 15g, length 3m
Bulk specific gravity 0-1 obtained by treating m pitch-based carbon m male by the method described in Japanese Patent Application No. 60-253724
0. A spherical bundle with a diameter of 4 mm is approximately 3 cm x 3 c
One piece was placed for every m area and hot pressed at 120°C to create a plate sample with a thickness of 0.7 mm. One dark color was placed in the area where the carbon fiber spherical bundle was placed.

At the location where the carbon fiber spherical bundle exists, Ag paste was applied to the front and back of the board only in a portion with an area of 0.50 cm2, and the volume resistivity was measured, and it was found to be 40.
It was 2Ω·cm.

After measuring the volume resistivity, carbon fibers were extracted from the plate material of the measurement part, and the average fiber length was measured to be 2.7 mm, which showed that there was almost no J breakage. In addition, the carbon fiber content in the measured area was 1BvO %. When the volume resistivity in the area where carbon ta fiber spherical bundles were not present was measured in the same way, it was 1014 Ω.
It was on the order of cm.

Comparative Example 1 18 VOI% of the unaggregated pitch-based carbon fibers (floc-like) used in Example 1 and 72VO1% of the polyethylene powder used in Example 1 were thoroughly kneaded with a forced kneader until the carbon fibers became uniform. Pellets were made by extrusion molding, and a 0.7 mm thick plate was prepared in the same manner as in Example 1.

The f-board was uniformly grayish.

The volume resistivity of this pull plate is 10”Ω at any part.
It is of the order of ΦCm and is carbon! The average fiber length of a fiber is 0
．． It was 19mm.

Example 2 Polyethylene pellet 70voJ1%, Ni powder-1
A mixture of 5 vou% and 15 vou% of the same carbon fiber spherical aggregates as used in Example 1 was put into a central screw extruder, the extrudate was carted to make pellets, and the pellets were hot pressed and molded. Got the board. The volume resistivity of the dark colored portions scattered on the f-plate 1- was measured in the same manner as in Example 1 and found to be 1.4×10 3 Ω·Cm.

After measuring the volume resistivity, carbon U and fibers were extracted from the plate material of the measurement part, and the fiber length was fixed, and the average length was 1.2 m.
m, the longest length was 2.4 mm, and the shortest length was 0.3 mm.

When the volume resistivity of the other parts was kept constant at 3, it was on the order of 104 to 105 Ωecm.Except that the unbound pitch carbon fiber (floc-like) used in Comparative Example 1 was used as the carbon fiber. Raw materials having the same composition as in Example 2 were sufficiently kneaded using a forced kneader in the same manner as in Comparative Example 2 until the carbon fibers became uniform.

A pellet was made by extrusion molding, and a strip having a thickness of 0.7 mm was prepared in the same manner as in Example 1. The board was uniformly gray in color.

The volume resistivity of this sample is 105Ω everywhere.
・In the order of cm, the uniform fiber M length of carbon fiber is 0.17
It was mm.

C6 Effects of the invention Compared to conventional synthetic resin-based plate materials with electrostatic disease 1F, conductive
If the male is used twice; 4 times, better electrification disease 1F sexual activity will be obtained.
? Since an anti-static moat can be obtained, it is possible to create a belt with excellent cost performance that makes effective use of expensive conductive fibers.
) - A flexible plate material is obtained, and its manufacture is easy.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the basic structural model of the antistatic plate material of the present invention, Fig. 2 is a cross-sectional view taken along the line x-X of Fig. 1,
Fig. 3 is an f-plane view of a model of a plate material susceptible to electrostatic disease IF in one of the embodiments of the present invention, Fig. 4 is a cross-sectional view taken along the FIG. 6 is a model diagram showing the distribution state of conductive ta males in a cross section, and FIG. 6 is a model diagram showing the fiber length distribution of carbon fibers in various samples.

Claims (1)

[Scope of Claims] 1. An antistatic plate material comprising a thermoplastic resin plate material having a structure in which spots in which conductive fibers are densely dispersed in the thermoplastic resin are scattered. 2. The antistatic plate material according to claim 1, wherein the conductive material is sparsely dispersed in the thermoplastic resin other than the spots where the conductive fibers are densely dispersed in the thermoplastic resin. 3 The specific volume resistivity in the thickness direction of the plate at the spot where the conductive fibers are densely dispersed in the thermoplastic resin is 10.
^4Ω・cm or less Claim 1 or 2
Antistatic plate material as described in section. 4. The antistatic plate material according to claim 1, 2, or 3, wherein the distance between the spots where the conductive fibers are densely dispersed in the thermoplastic resin is 15 cm or less. 5. The antistatic plate material according to claim 1, 2, 3, or 4, wherein the conductive fibers are carbon fibers. 6 A conductive fiber spherical bundle with a bulk specific gravity of 0.04 to 0.15 and a diameter of 10 mm or less is mixed with thermoplastic resin powder, fibers, or pellets, and the conductive fibers are nonuniformly dispersed in the thermoplastic resin. Conductive fibers are densely dispersed in a plate material made of thermoplastic resin, characterized in that it is formed into a plate shape at a temperature higher than the melting temperature of the thermoplastic resin in its original state. A method for producing an antistatic plate material having a structure in which spots are scattered. 7. The method for producing an antistatic plate material according to claim 6, wherein the conductive fibers are carbon fibers.