JPH0593184A - Antistatic coating agent, treatment of molding therewith and molding treated therewith - Google Patents

Abstract

PURPOSE:To obtain the title agent which can easily impart antistatic properties to an instrument or apparatus made of a fluororesin irrespsectively of its shape or structure by adding a specified powder to a solution of an amorphous fluoropolymer in a fluorinated solvent. CONSTITUTION:The title agent is prepared by adding a carbon powder to a solution prepared by dissolving an amorphous fluoropolymer, desirably one represented by the formula (wherein m and n are integers, and n/(m+n)=0.2-1.0) in a fluorinated solvent (e.g. Fluorinate FC-75, a product of 3M Company of U.S.A.).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating agent used for antistatic treatment of a molded article made of a fluororesin or various articles having a coating layer made of a fluororesin, and an antistatic agent using the same. Regarding processing method.

[0002]

2. Description of the Related Art Fluorine-based resins are widely used as molding materials and lining materials for various articles because of their excellent chemical resistance, heat resistance, non-adhesiveness, water resistance, electrical characteristics, etc. However, since it has a high insulating property, there is a drawback that charging is likely to occur. Therefore, when applied to equipment that comes into contact with flammable liquids or flammable gases such as organic solvents, there is a risk of ignition and explosion due to discharge due to the equipment itself and the contact fluid being charged. The adhesion of dust to the surface may be a serious problem, and the prevention of static charge is a major problem.

As a means for preventing this electrification, it is conceivable that carbon powder such as carbon black is mixed into the fluororesin to impart conductivity, but in order to obtain sufficient conductivity, the amount of carbon powder blended However, the mechanical properties such as strength and the original performance of the fluororesin are deteriorated, and the large amount of expensive carbon powder causes a very high material cost, resulting in poor practicability. Therefore, in the chemical resistant tube made of a fluororesin produced by the paste extrusion method or the melt extrusion method, the carbon powder is blended on the inner layer side as a two-layer structure to improve the mechanical properties and the original characteristics of the fluororesin. Some have been made to have conductivity, while ensuring a certain level of performance and using a small amount of carbon powder as a whole.

[0004]

However, the chemical resistance tube having the above-mentioned two-layer structure is limited to the pipe for piping and the pipe interior material from the manufacturing method, and the elbow, cheese, reducer, Since it cannot be applied to non-linear parts such as various valves, and requires special manufacturing equipment, the equipment cost is high and the conductivity is not sufficient.

However, in the field where fluorocarbon resins are used, those requiring antistatic properties are used in addition to the above-mentioned piping system, in addition to mixing,
There are a wide variety of tower tanks and tanks used for reactions, storage, etc., various internal equipment such as stirrers, strainers, distributors, etc. installed inside these, fluid containers, etc. The current situation is that there is no effective antistatic means. Further, there has been found no means for secondarily providing antistatic protection to existing equipment and devices using a fluororesin.

In view of the above situation, the present invention is simple and inexpensive, regardless of the shape and structure of equipment and devices using a fluororesin and without impairing the characteristics and performance of the fluororesin. An antistatic coating agent and antistatic treatment that can impart an excellent antistatic function and that can also secondarily prevent the static charge on various equipment and devices that use existing fluorocarbon resins. It is intended to provide a way.

[0007]

In order to achieve the above object, the antistatic coating composition of the present invention has a constitution in which carbon powder is mixed in a solution in which an amorphous fluoropolymer is dissolved in a fluorine-based solvent. It is what

Further, in the present invention, an amorphous fluoropolymer represented by the general formula: [Wherein, m and n are integers, and the ratio of n / (m + n) is in the range of 0.2 to 1.0], and the blending amount of carbon powder is amorphous fluoro. A preferred embodiment is a composition in the range of 10 to 100 parts by weight with respect to 100 parts by weight of the polymer.

On the other hand, for the same purpose, the antistatic treatment method of the present invention is characterized in that the above antistatic coating agent is applied to the surface of the article to be treated, which is made of a fluororesin, and then heat treatment is applied. The configuration is adopted. Also,
For the same purpose, the antistatically treated molded article of the present invention has at least a part of the surface of the fluororesin molded article.
The antistatic coating agent according to any one of 1 to 4 is adopted.

[0010]

Detailed Structure and Function of the Invention Since the antistatic coating material of the present invention is a solution in which amorphous fluoropolymer is dissolved in a fluorine-based solvent, carbon powder is blended,
This is applied and dried to form a conductive coating in which carbon powder is dispersed in the fluoropolymer. Therefore, various molded articles and linings made of fluorocarbon resin are produced or constructed using only fluorocarbon resin in the same manner as in the past, and then the coating agent is applied to the surface requiring antistatic, A good antistatic function is imparted by the conductive coating formed.

Since this conductive coating is formed by volatilizing the solvent from a solution in which the amorphous fluoropolymer is completely dissolved, for example, an insoluble fluorine resin powder and carbon powder are dispersed and contained in an oil agent. Compared to a coating film formed using a suspension, it is dense and excellent in strength, retains sufficient properties as a fluororesin layer, and has good binding properties of carbon powder by the polymer, and high speed. Even if it comes into contact with the fluid, there is no risk that it will fall out of the coating layer and mix into the fluid, and even if it comes into contact with the surface, it will not be contaminated by the carbon powder and it will be easy to carry and handle. Since they are well connected, they exhibit very good conductivity even when they are thin and the blending ratio of carbon powder is small. On the other hand, in the carbon powder-containing layer formed by paste extrusion or melt extrusion like the inner layer of the chemical resistant tube, since the connection of the carbon powder is easily broken by kneading during production,
Even if the thickness and the blending ratio of the carbon powder are set to be large, sufficient conductivity cannot be obtained.

As the amorphous fluoropolymer used in such an antistatic coating agent, any amorphous fluoropolymer which can be dissolved in a fluorine-based solvent to form a solution can be used without particular limitation. General formula of;

[0013] [In the formula, m and n are integers, and the ratio of n / (m + n) is in the range of 0.2 to 1.0].

That is, the amorphous fluoropolymer represented by the above general formula is polytetrafluoro, which is known as a fluorine-based resin which is soluble in a specific fluorine-based solvent and insoluble in various solvents but is very excellent. It has almost the same performance as ethylene resin and perfluoroalkoxy ethylene resin. Commercial products of such amorphous fluoropolymers include, for example, US E.I.
There are Teflon AF1600 and Teflon AF2400 manufactured by DuPont.

The fluorine-based solvent used for the antistatic coating agent may be any solvent that can dissolve the amorphous fluoropolymer used. Therefore, as the fluorine-based solvent for the amorphous fluoropolymer represented by the above general formula, a fluorine-inert liquid is suitable, and a commercially available product thereof is, for example, a product name Fluorinert FC manufactured by 3M USA.
-75, Fluorinert FC-77, Fluorinert F
There is C-40 etc.

As the carbon powder, any of various carbon blacks known as antistatic compounding agents for synthetic resins can be used, but fibrous powder such as Ketjen black is particularly preferable.

The amount of carbon powder blended with the amorphous fluoropolymer is 10 to 100 parts by weight of the former.
A range of about 100 parts by weight is preferable, and if it is too small, sufficient conductivity cannot be imparted, and conversely, if it is too large, the binding property of the carbon powder by the polymer and the mechanical properties of the formed film are deteriorated. The solid content concentration of the coating material is preferably about 5 to 10% by weight.

As means for applying the coating agent of the present invention, various methods such as dip coating, spray coating, brush, roll, and blade coating, and other various methods can be adopted. It may be selected as appropriate. The coating thickness is usually in the range of about 5 to 10 μm as a dry coating film thickness.

When an antistatic treatment is applied to the surface of a fluorine resin to be treated using the above coating agent, the coating agent may be simply applied to form a conductive coating. It is desirable to perform heat treatment after the formation of. That is, by this heat treatment, the conductive coating film and the underlying fluororesin are strongly integrated to form a substantially continuous layer, so that delamination or the like can be prevented.

Here, the heat treatment temperature is preferably at least not lower than the glass transition point of the amorphous fluoropolymer used in the coating agent. The heating means is not particularly limited, but heating by infrared rays or far infrared rays is preferable. That is, according to this infrared or far-infrared heating, since the conductive coating that exhibits a black color due to the inclusion of carbon powder has high heat absorption, the melting point of the underlying fluororesin is the glass transition point of the amorphous fluoropolymer of the coating. In both cases of higher and lower cases, the coating side is in a molten state first, and then the underlayer in contact with the coating is melted and fused with the coating. Therefore, there is an advantage that the thermal adverse effect and the shape change of the underlayer hardly occur.

The object to be coated is not limited to various shapes made of fluorocarbon resin, but also those having a coating layer made of fluorocarbon resin such as a lining, etc., as long as it requires antistatic properties, and the shape and structure are particularly limited. Alternatively, existing equipment may be used.
Further, although there is no particular limitation on the fluorine-based resin as a base for coating, it is desirable that the heat treatment temperature be higher than the melting point of the base layer. Incidentally, a coating agent using the above-mentioned general formula as an amorphous fluoropolymer was applied to the surface of a molded article made of perfluoroalkoxyethylene resin (melting point 300 to 310 ° C.), and heat-treated at a temperature not lower than the melting point of the resin. However, the coating layer is firmly fused to the surface of the underlying molded article,
A molded product having an excellent antistatic effect was obtained.

[0022]

【Example】

Example 1 2 g of an amorphous fluoropolymer (Teflon AF1600, trade name, manufactured by E.I.DuPont, USA) was added to a fluorine-based solvent (Fluorinert FC-7, trade name, manufactured by 3M, USA).
5) 1 g of Ketjen Black was mixed and dispersed in a solution dissolved in 30 cc to prepare an antistatic coating agent. Then, the above coating agent is applied by brush coating on the surface of a perfluoroalkoxyethylene resin chemically resistant tube (diameter 22 mm, thickness 1.5 mm), and dried at room temperature to give a conductive layer having a thickness of about 5 μm. A coating film was formed, and then heat treatment was performed for 3 minutes by setting the temperature on the surface of the coating film to 320 ° C. by an infrared heating device. When the electric resistance of the treated tube for 1 cm was measured, it was 3 to
It was 50 KΩ.

Example 2 An antistatic coating agent was prepared in the same manner as in Example 1 except that the amount of Ketjen black used was changed to 0.7 g. Then, in the same manner as in Example 1, the above coating agent was applied to the surface of the chemical resistant tube and dried to form a conductive coating film having a thickness of about 3 μm. Then, in the same manner as in Example 1, an infrared heating device was used. The heat resistance of the tube after the heat treatment was 3 to 100K under the same conditions as in Example 1.
It was Ω.

Example 3 An antistatic coating agent was prepared in the same manner as in Example 1 except that the same amount of Teflon AF2400 (trade name, manufactured by EI DuPont, USA) was used as the amorphous fluoropolymer. Then, in the same manner as in Example 1, the above coating agent was applied to the surface of the chemical resistant tube and dried to form a conductive coating film having a thickness of about 5 μm. Then, in the same manner as in Example 1, an infrared heating device was used. When subjected to a heat treatment with, the electric resistance of the treated tube under the same conditions as in Example 1 was 10 to 70.
It was KΩ.

Example 4 An iron cylindrical tank (inner diameter 20c) having a lining made of perfluoroalkoxyethylene resin (resin layer thickness 3 mm) through a glass fiber cloth having a thickness of about 0.5 mm.
m, height 30 cm), an antistatic coating agent prepared in the same manner as in Example 1 was applied by brush coating, and dried at room temperature to form a conductive coating having a thickness of about 5 μm. Heat treatment was performed while moving the surface of the coating film by a high temperature hot air device (about 600 ° C.). 1c of the inner surface of the tank after processing
When the electric resistance between m lengths was measured, it was 100 to 500.
It was KΩ.

Example 5 A paddle type made of stainless steel in which an antistatic coating agent prepared in the same composition ratio as in Example 1 was lined with a perfluoroalkoxyethylene resin having a thickness of about 3 mm on the entire surface. When the stirring blade (equipped in a small reaction tank for experiments, two blades with a width of 3 cm and a length of 10 cm) was dipped and dried three times, the surface was uniformly conductive with a thickness of about 10 μm. A film was formed. Next, the stirring blade was loaded in an infrared heating furnace, and heat treatment was performed at 340 for 10 minutes. When the electrical resistance of the surface of the stirring blade after the treatment for 1 cm was measured, it was 20 to 30 KΩ.

[Chargeability Comparison Test] A chemical resistant tube made of perfluoroalkoxyethylene resin having a diameter of 22 mm and a thickness of 1.5 mm, which was divided into three along the axial direction (10 cm in length), was used on the inner surface side. In the method in which the same antistatic coating material as in Example 1 is applied with a brush, dried at room temperature, and then heat-treated under the same conditions as in Example 1, the thickness of the conductive coating is changed by changing the number of times the coating material is applied. Different test pieces (described in Table 1) were prepared.

Next, an untreated test piece A, antistatic test pieces C1 to C4, and 2 made of perfluoroalkoxyethylene resin having an inner layer containing carbon powder produced by two-layer tubular extrusion molding were used. A test piece B obtained by dividing a layer tube (having the same diameter and wall thickness as the above-mentioned chemical resistant tube, the inner layer having a thickness of 0.1 mm and containing 10% by weight of Ketjenblack) in the same manner as above was made of silk cloth on the inner surface side. After rubbing twice, the amount of charge on the inner surface of
n System Inc. The results shown in Table 1 below were obtained by measurement with a Model-75 manufactured by Mfg. Co., Ltd. The outer surface of each test piece was covered with aluminum foil in order to avoid the influence of the outer surface charge on the measured value. The test was done with the sides facing each other.

[0029]

[Table 1]

From the above table, it can be seen that the antistatic coating agent of the present invention can achieve a sufficient antistatic effect with about three application times. It should be noted that the charge amount is larger than that of the two-layer tube, but considering that the coating film thickness is much thinner than that of the inner layer of the two-layer tube, the efficiency is high, and it is much easier as an antistatic means. It can be said that it is highly practical.

[0031]

EFFECTS OF THE INVENTION According to the antistatic coating agent of the present invention, a tough conductive coating film can be formed only by applying it to various antistatic surfaces such as various moldings and linings made of fluororesin. , An excellent antistatic function can be easily and inexpensively provided regardless of the shape and structure of equipment and devices using fluorocarbon resin, and without impairing the characteristics and performance of the fluorocarbon resin. It also becomes possible to secondarily prevent static electricity from existing equipment and devices that use resin. However, this conductive coating shows high conductivity even in a state where the film thickness is thin and the mixing ratio of carbon powder is low, the amount of carbon powder required for antistatic can be reduced accordingly, and the film forming component is amorphous fluorocarbon. Since it is a polymer, it has excellent film characteristics peculiar to fluorocarbon resin, has good affinity with the fluorocarbon resin of the base, and also has high binding strength of carbon powder and is mixed into the contact fluid due to falling of the powder. There is no risk of contamination during handling or handling.

According to the structure of claim 2 in which an amorphous fluoropolymer having a specific structure is used, and in the structure of claim 2 in which the amount of carbon powder to be mixed with the amorphous fluoropolymer is within a specific range, the above-mentioned charging There is an advantage that the prevention function can be exhibited more efficiently, and a conductive film having particularly excellent film characteristics is formed.

On the other hand, according to the antistatic treatment method of the present invention, the above-mentioned conductive film can be reliably formed, and at the same time, the film and the underlying fluororesin are strongly integrated so that delamination does not occur. ..

Further, since the antistatic-treated molded article of the present invention has the above-mentioned antistatic coating agent applied on at least a part of the surface of the fluororesin molded article, it is excellent in the physical properties of the fluororesin as a whole. And retains chemical properties and has good antistatic performance.

Claims (5)

[Claims] 1. An antistatic coating agent comprising carbon powder mixed in a solution obtained by dissolving an amorphous fluoropolymer in a fluorine-based solvent. 2. An amorphous fluoropolymer having the general formula; The antistatic coating agent according to claim 1, wherein m and n are integers and the ratio of n / (m + n) is in the range of 0.2 to 1.0. 3. The antistatic coating agent according to claim 1, wherein the compounding amount of the carbon powder is in the range of 10 to 100 parts by weight with respect to 100 parts by weight of the amorphous fluoropolymer. 4. An antistatic treatment method, which comprises applying the antistatic coating agent according to any one of claims 1 to 3 to a surface of an object to be treated made of a fluororesin, and then performing heat treatment. .. 5. An antistatic-treated molded article obtained by applying the antistatic coating agent according to claim 1 on at least a part of the surface of a fluororesin molded article.