JPH06179839A - Conductive composition for coating plastics - Google Patents

Abstract

PURPOSE:To provide a conductive composition for surface coating which can give a coating film excellent in contour following properties, conductivity and blocking resistance. CONSTITUTION:The conductive composition comprises a mixture of an aqueous solution or emulsion of a thermoplastic resin (1), a wax emulsion (2) and a conductive carbon (3), wherein the weight ratio of the solid matter of (1) to that of (2) is 98:2-50:50, and the weight ratio of the total of the solid matters of (1) and (2) to that of (3) is 95:5-50:50, or wherein component (3) is a conductive metal compound, and the weight ratio of the total of the solid matters of (1) and (2) to that of (3) is 75:25-40:60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic coating conductive composition comprising an aqueous solution or emulsion of a thermoplastic resin.

[0002]

2. Description of the Related Art Generally, a plastic sheet (hereinafter abbreviated as a sheet) has excellent properties such as impact resistance, easy moldability and light weight, and is used for various purposes. But,
While these sheets have the above-mentioned characteristics, they are easily charged with static electricity, and dust and dirt adhere to them, so when they are used for packaging materials such as electronic components, the performance of the stored components may deteriorate due to the generation of static electricity. However, there is a disadvantage that it is contaminated with dust and dirt during use, and its performance is impaired.

To prevent these disadvantages, a conductive material such as an antistatic agent, conductive carbon or metal powder is mixed or dispersed in a resin solution or emulsion dissolved in a solvent for the purpose of imparting conductivity to the sheet. A method of coating a sheet with an object is known.

[0004]

However, when the sheet is coated with a mixture or dispersion of the above-mentioned conductive material in a solution of a resin dissolved in a solvent, there is a risk of air pollution and fire caused by the solvent. However, there is a problem that it is not preferable in terms of worker health management and safety management.

Further, there is a problem that the residual solvent left in the coating film formed by coating on the sheet causes deterioration of the physical properties of the sheet itself, blocking, and the like. Also,
Emulsion using water as a medium does not have sufficient elongation of the coating film, so the coating film may not follow the elongation of the sheet during secondary molding of the sheet such as vacuum forming, pressure forming, press forming, etc. However, there arises a problem that the conductivity is impaired. Therefore, a plasticizer or a soft polymer is used to improve the elongation of the coating film, but in this case, the coating film becomes soft and blocking occurs in the coated sheet. As described above, it was difficult to satisfy both the sheet secondary moldability and the blocking property at the same time.

Therefore, in view of the above-mentioned conventional problems, the present invention is excellent in the followability of the coating film, the conductivity and the blocking resistance, especially in the secondary forming of the sheet such as vacuum forming, pressure forming and press forming. Another object of the present invention is to provide a conductive composition for plastic coating.

[Means for Solving the Problems]

As a result of intensive studies to solve the above problems, the present inventors have found that the solid content ratio of each component in a mixture containing an aqueous solution or emulsion of a thermoplastic resin, a wax emulsion, and a conductivity-imparting agent. It was found that the compound has an excellent effect when is within a specific range, and the invention was completed.

That is, the present invention is as follows: A mixture containing an aqueous solution or emulsion of a thermoplastic resin, a wax emulsion, and conductive carbon, wherein the weight ratio of the aqueous solution or emulsion solid content to the emulsion solid content is 98: 2 to 50:50, A conductive composition for plastic coating, wherein the weight ratio of the solid content, the total weight of the solid content and the conductive carbon powder is 95: 5 to 50:50. And 2. A mixture containing an aqueous solution or emulsion of a thermoplastic resin, a wax emulsion, and a conductive metal compound, wherein the weight ratio of the aqueous solution or emulsion solid content to the emulsion solid content is 98: 2 to 50:50. And a plastic coating conductive composition in which the weight ratio of the solid content, the total weight of the solid content and the conductive metal compound is 75:25 to 40:60. Is the gist.

The present invention will be described in detail below. The thermoplastic resin constituting the conductive composition for plastic coating of the present invention, vinyl acetate resin, styrene resin, acrylic resin, methacrylic resin, ethylene resin, vinyl chloride resin, vinylidene chloride resin, Examples thereof include polyester-based resins, polyurethane-based resins, polyvinyl alcohol-based resins and epoxy-based resins, and aqueous solutions or emulsions of these thermoplastic resins can be used alone or in combination. The aqueous solution or emulsion of the thermoplastic resin may be produced by a conventionally known method.

As the wax for forming the wax emulsion which constitutes the conductive resin composition for plastic coating of the present invention, natural wax, synthetic hydrocarbon wax or modified products thereof can be used. Examples of natural waxes include beef tallow, hydrogenated hardened pork tallow, animal waxes such as lanolin, beeswax and whale wax, waxes obtained by hydrogenating soybean oil, waxes obtained by hydrogenating castor oil and carnauba wax. , Candelilla wax, tree wax, vegetable wax such as nuka wax, montan wax,
Mineral waxes such as ceresin wax, paraffin wax, microcrystalline wax are mentioned.

Further, as the synthetic hydrocarbon wax,
Examples thereof include polyethylene waxes having a molecular weight of about 500 to 5,000, polypropylene waxes, waxes by the Fischer-Tropsch method, and oxides and acid-modified products of these synthetic waxes. The wax emulsion can be produced by adding an emulsifier to the above wax and emulsifying it using various emulsifiers by a known method.

Examples of the conductive carbon constituting the conductive resin composition for plastic coating of the present invention include Ketjen black, acetylene black, graphite and carbon whiskers.

The weight ratio of each of the above-mentioned components contained in the plastic coating conductive composition of the present invention, that is, an aqueous solution or emulsion of a thermoplastic resin, a wax emulsion, and a solid of conductive carbon is within a specific range. There is a technical feature in that. The range is such that the weight ratio of the solid content of the aqueous solution or emulsion of the thermoplastic resin to the solid content of the wax emulsion is 98: 2 to 50:50.
In addition, the weight ratio of the total weight of the solid content of the aqueous solution or emulsion of the thermoplastic resin and the solid content of the wax emulsion to the conductive carbon is 95: 5 to 50:
50.

It is important for the conductive composition for plastic coating of the present invention to satisfy both of the above two conditions, and the solid content ratio of the wax emulsion is less than 2% under the first condition. And the blocking performance deteriorates,
If it exceeds 50%, the adhesion to the sheet becomes poor, which is not preferable. Further, in the second condition, if the ratio of the conductive carbon is less than 5%, good conductivity cannot be obtained, and if it exceeds 50%, the coating film becomes brittle, which is not suitable.

In the present invention, a conductive metal compound may be contained in place of the conductive carbon constituting the plastic coating conductive composition. Examples of the conductive metal compound include white sinter, titanium oxide particles coated with tin oxide, zinc oxide particles doped with aluminum, and potassium titanate whiskers.

In the conductive composition for plastic coating of the present invention containing the conductive metal compound, the weight ratio of each component, that is, an aqueous solution or emulsion of a thermoplastic resin, a wax emulsion, and a solid content of the conductive metal compound is The feature is that it is within a specific range as in the case of containing conductive carbon. The range is such that the weight ratio of the aqueous solution or emulsion solid content of the thermoplastic resin to the emulsion solid content of the wax emulsion is 98: 2 to 50:50, and the solid content of the aqueous solution or emulsion of the thermoplastic resin and the solid content of the wax emulsion. The total weight of the components and the weight ratio of the conductive metal compound are 75: 2.
5 to 40:60.

It is important that the composition of the present invention satisfies both of these two conditions, and if the solid content ratio of the wax emulsion is less than 2% under the first condition, the blocking property is reduced. If it exceeds 50%, the adhesion to the sheet deteriorates, which is not preferable. In the second condition, if the ratio of the conductive metal compound is less than 25%, good conductivity cannot be obtained, and if it exceeds 60%, the coating film becomes brittle and unsuitable. Absent.

The conductive composition for coating plastics of the present invention comprises, in addition to the above essential components, a surfactant, a plasticizer, a coalescing agent, a leveling agent, a wetting agent, an antifoaming agent, an antiseptic agent, an ultraviolet absorber, Dyes, pigments, antioxidants, inorganic powders and other additives can be added as required. These additives may be any conventionally known additives.

The method for producing the conductive composition for plastic coating of the present invention is as follows: an aqueous solution or emulsion of a thermoplastic resin as the first component, a wax emulsion as the second component, conductive carbon as the third component or Conductive metal compounds are separately prepared according to a conventional method, and those in the range of the solid content weight ratio shown above are mixed, and if necessary, an additive as an optional component is added to the conductive and blocking properties. It can be manufactured by adding appropriately within the range that does not reach.

The composition of the present invention obtained by the above method is applied to a sheet, and the coating method includes dipping method, spray method, flow coating method, gravure method, roll coating method and the like. Then, a smooth surface solidified coating film can be obtained.

The material of the sheet to be coated is, for example, polymethyl methacrylate, polycarbonate, polystyrene, acrylonitrile styrene copolymer, methyl methacrylate styrene copolymer, polydiethylene glycol bisallyl carbonate, ABS.
Resins, rubber-reinforced methacrylic resins, cellulose acetate, cellulose acetate butyrate, polyvinyl chloride, polyethylene, polypropylene, polyester, amorphous polyethylene terephthalate, polyvinylidene chloride, and other plastics are useful, especially useful for plastics with poor conductivity. Is. An inorganic filler or the like may be mixed in these exemplified plastics, or alloys of the exemplified plastics may be used.

The above-mentioned coated sheet is dried and solidified at a temperature not higher than the heat distortion temperature of the molded product. In particular,
Normally 40 to 140, although it depends on the type of seat
C., preferably in the range of 60 to 120.degree.

In the composition of the present invention coated on the above-mentioned sheet, the average film thickness of the solidified coating film varies depending on the use, but is usually 0.5 to 20 μm, preferably 1
It is in the range of 10 μm.

The conductive composition for plastic coating of the present invention can be used in the field of coating production and plastic processing, but especially troubles due to static electricity such as trays for electronic parts, carrier tapes, reels for carrier tapes, etc. It is useful for products such as packaging materials that should be prevented.

[0025]

The aqueous solution or emulsion of the thermoplastic resin constituting the conductive composition for coating plastics of the present invention acts as a binder for the conductive carbon or the conductive metal compound, and serves as a binder for the plastic sheet and the conductive carbon or the conductive metal compound. Also functions as a binder. When the wax emulsion is mixed with an aqueous solution or emulsion of a thermoplastic resin, it imparts lubricity to the surface of the coating film and improves blocking resistance and scratch resistance of the sheet or coating film in contact therewith. Further, the conductive carbon or the conductive metal compound can impart good conductivity and antistatic property by being dispersed almost uniformly in the coating film.

The electrically conductive composition for plastic coating of the present invention can be used not only as a plastic sheet but also as a coating agent for plastic molded articles. It is effective to use it as a coating agent that imparts conformability, conductivity and blocking resistance.

[0027]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples and Comparative Examples.

(Preparation of Each Component) Emulsion of Thermoplastic Resin An emulsion containing the raw materials shown in Table 1 was prepared. To the pure water, the total amount of the emulsifier and the polymerization initiator was added, and a mixture of two kinds of monomers was added dropwise over 3 hours while stirring at 70 ° C.
Further, the mixture was continuously stirred at the same temperature for 30 minutes for polymerization to obtain a copolymer having a degree of polymerization of about 10,000, and an acrylic copolymer emulsion having a solid content of 30% and a minimum film forming temperature of 70 ± 2 ° C. was obtained.

[0029]

[Table 1]

Wax Emulsion An emulsion of oxidized polyethylene wax, which was the raw material of Table 2, was prepared.

[0031]

[Table 2]

A conductive carbon Ketjen Black EC dispersed in water (Lion Paste W-310A, manufactured by Lion Corporation) was used.
(NV (nonvolatile content) is 17.5%.)

A conductive metal compound, white luster, dispersed in water (Lion Paste WS-520A, manufactured by Lion Corporation) was used. (NV is 4
It is 1.5%. )

Other Components Dibutyl phthalate was used as a plasticizer and diethylene glycol monoethyl ether was used as a fusing agent.

Examples 1 to 6 and Comparative Examples 1 to 8 Using the above raw materials, surface coating compositions having the mixing ratios shown in Table 3 were produced.

[0036]

[Table 3]

Next, these compositions were applied to a thickness of 0.5 m.
A sheet made of amorphous polyethylene terephthalate having a size of m, a width of 300 mm and a length of 400 mm was formed and applied to a coating film having a thickness of 2 μm using a bar coater. And
Immediately, it was put in a hot air drier, dried and solidified at 60 ° C. for 5 minutes to obtain a coating sheet. The physical properties of the obtained coating sheet were evaluated by the following methods.

1. Adhesion of coating film Place the sheet on a cross-cut tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and insert a single-edged razor to make a cross hatch. Stick cellophane adhesive tape on the crosshatch, pull the tape strongly in the direction perpendicular to the sheet,
The peeling state of the coating film was examined. 2. The surface resistance of the coated surface of the conductive sheet in a sheet state was measured by a surface resistance meter with a comparator (MCP-TESTER manufactured by Mitsubishi Petrochemical Co., Ltd.). 3. The conductive sheet after vacuum forming was vacuum formed under the condition that the drawing ratio was 25%, and the surface resistance of the coated surface at this time was measured by the same device as in the above 2. 4. Blocking property The coated surfaces of the sheets are placed on top of each other, and in a 35 ° C atmosphere,
Apply a load of 5 kg / cm ² and leave it for 24 hours, then let it stand at room temperature for 2 hours.
After standing for a time, the two sheets were peeled off and the blocking state of the contact surface was examined. 5. Nail Scratch Property The method of scratching when the coated surface of the sheet was strongly rubbed with a nail was examined.

The results of the above physical property tests are as shown in Table 4, and ◯, Δ, and × mean the following, respectively.

1. Adhesion of coating film ◯: No peeling of 100%, ×: Peeling of 1% or more, 1. Conductivity in sheet state ◯: 1 × 10 ⁸ Ω or less, ×: 1 × 10 ¹⁰ Ω or more, 3. 3. Electrical conductivity after vacuum forming ◯: 1 × 10 ⁸ Ω or less, Δ: What partially causes 1 × 10 ¹⁰ Ω or more by molding, ×: 1 × 10 ¹⁰ Ω or more, 4. Blocking property ◯: No blocking, Δ: little blocking, ×: blocking, 5. Scratchability of nails ◯: No scratch, Δ: Slight scratch, ×: Scratch,

(Test Results) Examples 1, 2, 5 and Comparative Examples 1, 2, 3, 4, 7 clearly show the effect of defining the ratio of the aqueous solution or emulsion of the thermoplastic resin to the wax emulsion. Examples 3 and 4 and Comparative Examples 5, 6 and 8 show the total weight of the solid content of the aqueous solution or emulsion of the thermoplastic resin and the wax emulsion, and the conductive carbon and the conductive metal compound. It shows the experimental results that clarify the effect of defining the ratio with the weight.

[0042]

[Table 4]

[0043]

EFFECTS OF THE INVENTION According to the conductive composition for plastic coating of the present invention, by applying it to a sheet and drying it, the conductivity, adhesion, moldability, conductivity after molding, blocking resistance and scratch resistance are obtained. Since it is excellent in all performances and has no drawbacks, it is possible to provide a very good conductive composition for plastic coating in place of the conventional conductive surface coating agent.

Claims (2)

[Claims] 1. A mixture containing an aqueous solution or emulsion of a thermoplastic resin, a wax emulsion, and conductive carbon, wherein the weight ratio of the aqueous solution or emulsion solid content to the emulsion solid content is 98: 2 to 50. : 50, and the weight ratio of the total weight of the solid content, the solid content, and the conductive carbon is 95: 5 to 50:50, the conductive composition for plastic coating. 2. A mixture containing an aqueous solution or emulsion of a thermoplastic resin, a wax emulsion, and a conductive metal compound, wherein the weight ratio of the aqueous solution or emulsion solid content to the emulsion solid content is 98: 2 or more. 50:50, and the weight ratio of the solid content, the total weight of the solid content and the conductive metal compound is 75:25 to 40:60, and the conductive composition for plastic coating. object.