JP2761164B2 - Conductive composition for plastic coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive composition for coating a plastic comprising an aqueous dispersion of a polyester resin.

[0002]

2. Description of the Related Art In general, plastic sheets (hereinafter abbreviated as sheets) have excellent properties such as impact resistance, easy moldability, and light weight, and are used for various purposes. However, although these sheets have the above characteristics, they are easily charged with static electricity and adhere to dust and dirt. For example, when used for packaging materials such as electronic components, the performance of the stored components may be reduced due to generation of static electricity. However, there is an inconvenience that, when used, it is contaminated by dust and dirt, and its performance is hindered.

In order to prevent these inconveniences, for the purpose of imparting conductivity to a sheet, a solution or emulsion of a resin dissolved in a solvent mixed or dispersed with a conductive substance such as an antistatic agent or conductive carbon metal powder. There is known a method of coating a sheet.

[0004]

However, when a sheet of a resin solution dissolved in a solvent is mixed or dispersed with the above-mentioned conductive material, the risk of air pollution and fire from the solvent may occur. There is a problem that it is not preferable from the viewpoint of worker health management and safety management.

Further, the residual solvent left on the coating film formed on the sheet reduces the physical properties of the sheet itself,
There is also a problem of causing blocking or the like. Also,
Emulsions using water as a medium do not have sufficient elongation of the coating film, and the coating film cannot follow the elongation of the sheet in secondary forming such as vacuum forming, pressure forming, and press forming, causing cracks or the like. However, there is 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 the coated sheet is blocked. Has the disadvantage of causing

[0006] In order to solve the above-mentioned drawbacks, the present inventors have:
First, using an aqueous solution or emulsion of a thermoplastic resin, a mixture containing a wax emulsion, and a conductivity-imparting agent, when the solid content ratio of each component is within a specific range, vacuum forming, pressure forming, press forming, etc. It has been proposed that a conductive composition for plastic coating excellent in followability, conductivity and blocking resistance of a coating film can be provided at the time of secondary forming of the sheet (Japanese Patent Application No. 4-102221).

However, as a result of further research, it has been found that when storing and transporting a sheet coated with the composition, blocking occurs under certain environmental conditions, particularly when the temperature is maintained at 50 ° C. or higher, Temperature 40 ° C,
In a high-temperature and high-humidity state with a relative humidity (RH) of about 90%, the coating film swells, and the wax contained in the composition bleeds out to the surface of the coating film, so that the coating film becomes sticky. In addition, there is a problem that the film strength is reduced and the film is easily damaged. Therefore, for example, when used for a carrier tape or the like, the strength of the seal with the cover tape is significantly reduced, and when used for a packaging bag, peeling (bag breakage) is observed at the seal portion. Had occurred. in this way,
It was very difficult to simultaneously satisfy all of the sheet secondary formability, blocking properties, and moisture resistance.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and in particular, has the following properties of the coating film during the secondary forming of the sheet, such as vacuum forming, pressure forming, and press forming, conductivity, and blocking resistance at high temperatures. It is an object of the present invention to provide a conductive composition for plastic coating which has excellent properties and durability of a coating film at high temperature and high humidity.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an aqueous dispersion of a polyester resin, a conductivity-imparting agent, a softening point of 100 ° C. or more, The inventors have found that a mixture containing an aqueous dispersion of a polyolefin resin having a size of 2 μm or more and 10 μm or less has an excellent effect when the solid content ratio of each component is within a specific range, thus completing the invention.

That is, the present invention provides: Aqueous dispersion of polyester resin, conductive carbon, softening point 100 ° C or higher, and particle size 2μm to 10μm
An aqueous dispersion of the following polyolefin resin, wherein the weight ratio of the solid content of the aqueous dispersion to the conductive carbon is 95: 5 to 50:50.
And the weight ratio of the total weight of the solid content and the conductive carbon to the solid content of the aqueous dispersion is 9
8: 2 to 75:25 , a conductive composition for plastic coating. Or 2. Aqueous dispersion of polyester resin, conductive metal compound, softening point 100 ° C or higher, and particle size 2μm to 10μm
A mixture containing the following aqueous dispersion of a polyolefin resin, wherein the weight ratio of the solid content of the aqueous dispersion to the conductive metal compound is 75:25 to 40:
60, and a weight ratio of the total content of the solid content and the conductive metal compound to the solid content of the aqueous dispersion is 98: 2 to 75:25 . It is the gist.

Hereinafter, the present invention will be described in detail. As the polyester resin constituting the conductive composition for plastic coating of the present invention, those having an ester bond between a carboxyl group and a hydroxyl group obtained by polycondensation of a polybasic acid and a polyhydric alcohol in a main chain. Yes, it may be saturated or unsaturated. Further, a copolymer with styrene, acryl, urethane or the like may be used, and an aqueous dispersion of these polyester resins can be used alone or in combination. Such an aqueous dispersion of a polyester resin may be produced by a conventionally known method.

The conductive carbon constituting the conductive composition for coating a plastic of the present invention includes Ketjen black, acetylene black, graphite, carbon whiskers and the like.

Examples of the polyolefin resin constituting the conductive composition for plastic coating of the present invention include hard polyethylene and polypropylene (excluding wax and silicone oil). These aqueous dispersions are conventionally known. It may be manufactured by a method. This polyolefin resin has a softening point of 100 ° C. or higher and a particle size of 2 μm.
m and 10 μm or less. This softening point is 100
When the temperature is lower than 0 ° C, a sufficient anti-blocking effect cannot be obtained, which is not preferable. If the particle size is less than 2 μm, the anti-blocking effect is poor, and if it exceeds 10 μm, the particles fall off the coating film, which is not preferable. Examples of commercially available products conforming to such a range include Chemipearl W300 and W308 manufactured by Mitsui Petrochemical Co., Ltd.

The above components contained in the conductive composition for plastic coating of the present invention, that is, an aqueous dispersion of a polyester resin, conductive carbon, and a polyolefin having a softening point of 100 ° C. or more and a particle size of 2 μm to 10 μm. It is a technical feature that the weight ratio of each solid content of the aqueous dispersion of the system resin is within a specific range. The weight ratio of the solid content of the aqueous dispersion of the polyester-based resin to the conductive carbon is 95: 5 to 50:50, and the total weight of the solid content of the aqueous dispersion of the polyester-based resin and the conductive carbon. And softening point 100 ° C or higher and particle size 2μm or more and 10μm
The weight ratio of the solid content of the following aqueous dispersion of polyolefin resin is 98: 2 to 75:25, particularly 98: 2 to 80:20.

It is important that the plastic coating conductive composition of the present invention satisfies both of the above two conditions. If the ratio of conductive carbon is less than 5% under the above first condition, the conductive composition becomes conductive. However, when the content exceeds 50%, the coating film becomes brittle and is unsuitable. On the other hand, if the ratio of the solid content of the aqueous dispersion of the particulate polyolefin resin is less than 2% under the above second condition, the blocking property at high temperatures becomes poor, and if it exceeds 25 %, the adhesion to the sheet becomes poor. It is not preferable.

In the present invention, a conductive metal compound may be contained in place of the conductive carbon constituting the conductive composition for coating a plastic. Examples of this conductive metal compound include white luster, titanium oxide particles coated with tin oxide, zinc oxide particles doped with aluminum, and potassium titanate whisker. In the conductive composition for coating a plastic of the present invention containing the conductive metal compound, each component, that is, an aqueous dispersion of a polyester resin, a conductive metal compound, and a softening point of 100 ° C. or more and a particle size of 2 μm or more and 10 μm or less The weight ratio of the solid content of the aqueous dispersion of the polyolefin resin is characterized by being in a specific range, similarly to the case where conductive carbon is contained. The weight ratio of the solid content of the aqueous dispersion of the polyester resin to the conductive metal compound is 75:25 to 40:60, and the solid content of the aqueous dispersion of the polyester resin and the conductive metal compound The weight ratio of the total weight to the solid content of the aqueous dispersion of the polyolefin resin is from 98: 2 to 75:25, particularly 9
8: 2 to 80:20.

It is important that the above composition of the present invention satisfies both of these two conditions. If the ratio of the conductive metal compound is less than 25% under the above first condition, the composition having good conductivity is obtained. Is not obtained, and if it exceeds 60%, the coating film becomes brittle and unsuitable. On the other hand, if the ratio of the solid content of the aqueous dispersion of the granular polyolefin resin is less than 2% under the second condition, the blocking property is deteriorated, and if it exceeds 25 %, the adhesion to the sheet is deteriorated, which is not preferable. .

The conductive composition for coating a plastic according to the present invention may further comprise, if necessary, a surfactant and a plasticizer in addition to the above-mentioned essential components within a range that does not affect the secondary moldability, the blocking property, and the conductivity. , A coalescing agent, a leveling agent, a wetting agent, an antifoaming agent, a preservative, an ultraviolet absorber, a dye, a pigment, an antioxidant, an inorganic powder, and other additives. These additives may be any known and commonly used additives.

The method for producing the conductive composition for plastic coating of the present invention includes the following: an aqueous dispersion of a polyester resin as the first component, a conductive carbon or conductive metal compound as the second component, and a third component. Aqueous dispersion of polyolefin resin is separately adjusted according to each conventional method,
It can be produced by mixing the solid content within the above-mentioned range of the weight ratio of solids and, if necessary, appropriately adding the additive as the optional component.

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

Examples of the material of the sheet to be coated include plastics such as polycarbonate, polyacrylonitrile, polydiethylene glycol bisallyl carbonate, ABS resin, polyvinyl chloride, polyester, and amorphous polyethylene terephthalate. It is a sheet used for transport trays and carrier tapes, and is useful for plastics with poor conductivity. An inorganic filler or the like may be mixed in these exemplified plastics, or an alloy of each exemplified plastic may be used.

The coated sheet is dried and solidified at a temperature equal to or lower than the heat deformation temperature of each plastic. Specifically, although it differs depending on the type of sheet, it is usually 40 to
The process is carried out at a temperature of 140 ° C., preferably 60 to 120 ° C., and the solidified coating film is solidified to an average thickness of usually 0.5 to 20 μm, preferably 1 to 10 μm.

The conductive composition for coating plastics of the present invention can be used not only as a sheet but also as a coating agent for plastic molded articles. In particular, during the secondary forming of the sheet, it is more effective to use it as a coating agent that imparts the followability, conductivity and anti-blocking properties and moisture resistance of the coating film. In addition, the composition of the present invention can be used in the field of coating production and in the field of plastic processing. Useful for products such as materials.

[0024]

The aqueous dispersion of the polyester resin constituting the conductive composition for coating plastics of the present invention serves as a conductivity imparting agent (conductive carbon or conductive metal compound) and a binder for the particulate polyolefin resin, It also functions as a binder between the sheet and the conductivity-imparting agent and the particulate polyolefin-based resin. In addition, the conductive carbon or conductive metal compound can impart good conductivity and antistatic property by being substantially uniformly dispersed in the coating film. Furthermore, the aqueous dispersion of the polyolefin-based resin is mixed with the aqueous dispersion of the polyester-based resin to impart lubricity to the surface of the coating film, and to provide blocking resistance and abrasion resistance to the sheet or coating film in contact with the coating. Can be improved. In particular, it is possible to eliminate damage to the surface of the interior electronic component due to vibration generated when an inorganic substance such as amorphous silica is used.

[0025]

EXAMPLES The present invention will be described more specifically based on Examples and Comparative Examples. However, the present invention is not limited at all by these Examples and Comparative Examples.

(Regarding each component) An aqueous dispersion of a polyester-based resin A rack skin US180 manufactured by Seiko Chemical Co., Ltd. was used. (NV. (Nonvolatile content) is 20%.)

Conductive Carbon Lion Paste W-376R manufactured by Lion Corporation was used. (NV. Is 12.5%.)

Conductive Metal Compound Lion Paste WS-520A manufactured by Lion Corporation was used. (NV. Is 41.5%.)

Softening point 100 ° C. or more, particle size 2 μm or more 1
Aqueous dispersion of polyolefin resin having a particle size of 0 μm or less Chemipearl W-308 manufactured by Mitsui Petrochemical Co., Ltd. was used.
(NV. Is 40%.)

Examples 1 to 6 and Comparative Examples 1 to 8 Using the above-described components, compositions for coating plastics having the mixing ratios shown in Table 1 were produced.

[0031]

[Table 1] Next, these compositions were applied to a thickness of 0.5 mm and a width of 300 m.
It was applied on a sheet made of amorphous polyethylene terephthalate having a length of 400 mm and a length of 400 mm using a 5 mil bar coater. Immediately in a hot air dryer, drying and solidification were performed at 60 ° C. for 5 minutes to obtain a sheet having a coating film having a thickness of 2 μm. The physical properties of the obtained sheet were evaluated by the following methods.

1. Adhesion of coating film Place the sheet on a cross-cut tester (manufactured by Toyo Seiki Seisaku-sho, Ltd.), and insert a single-edged razor to make a cross hatch.
A cellophane adhesive tape was stuck on the cross hatch, the tape was strongly pulled in a direction perpendicular to the sheet, and the state of peeling of the coating film was examined.

2. The surface resistance of the coated surface of the conductive sheet in a sheet state was measured using a surface resistance meter with a comparator (MCP-TESTER manufactured by Mitsubishi Yuka Co., Ltd.).

3. The conductive sheet after vacuum forming was vacuum formed under the condition of a drawing ratio of 25%, and the surface resistance of the coated surface at this time was measured by the same device as in the above item 2.

4. Blocking properties The coated surfaces of the sheets are overlapped with each other, a load of 1 kg / cm ² is applied in an atmosphere of 50 ° C., left for 24 hours, then left at room temperature for 2 hours, and then the two sheets are peeled off and the contact surface Was checked for blocking status.

5. Nail Scratch Property The method of scratching when the coated surface of the sheet was strongly rubbed with a nail was examined.

6. High temperature and humidity resistance Cover tape for carrier tape SP-
82 (manufactured by Shin-Etsu Polymer Co., Ltd.) at a temperature of 140 ° C.
Sealed under the conditions of a load of 4 kg / cm ² and a time of 1 second, left for 24 hours in a room temperature of 40 ° C. and a relative humidity of 90%, immediately peeled off at 180 °, examined the peeling force, and compared with the normal one. Compared.

The results of the above physical property tests are as shown in Table 2, and 〇, △ and × in the table mean the following, respectively.

1. Adhesion of coating film 〇: 100% no peeling, ×: 1% or more peeling,

2. Conductivity in sheet state 〇: 1 × 10 ⁸ Ω or less, ×: 1 × 10 ¹⁰ Ω or more,

3. Conductivity after vacuum forming 〇: 1 × 10 ⁸ Ω or less, Δ: Partially producing 1 × 10 ¹⁰ Ω or more by molding, ×: 1 × 10 ¹⁰ Ω or more

4. Blocking property 〇: No blocking, Δ: Slight blocking, ×: Blocking,

5. Nail scratching 〇: no scratch, △: slightly scratched, ×: scratched,

6. High temperature and high humidity resistance 〇: Change rate of less than 10%, Δ: Change rate of 10% or more and less than 50%, ×: Change rate of 50% or more,

[0045]

[Table 2]

(Test Results) In Examples 1, 2, 5, and Comparative Examples 1, 2, 3, 4, and 7, the weight ratio of the aqueous dispersion of the polyester resin to the conductive carbon or conductive metal compound was defined. Examples 3, 4, and 6 and Comparative Examples 5, 6, and 8 show the solid content of the aqueous dispersion of the polyester resin and the conductive carbon or the conductive metal compound. FIG. 4 shows experimental results for clarifying the effect of defining the weight ratio of the total weight and the solid content of the aqueous dispersion of a polyolefin resin having a softening point of 100 ° C. or more and a particle size of 2 μm to 10 μm.

[0047]

According to the conductive composition for coating plastics of the present invention, the composition is applied to a sheet and dried to obtain conductivity, adhesion, moldability, conductivity after molding, blocking resistance, and scratch resistance. It is excellent in all properties of high temperature and high humidity resistance, and it does not pollute the atmosphere with a solvent and has no defects. Can be provided.

Claims (2)

(57) [Claims] An aqueous dispersion of a polyester resin, conductive carbon, a softening point of 100 ° C. or more, and a particle size of 2 μm to 10 μm.
m or less, wherein the weight ratio between the solid content of the aqueous dispersion and the conductive carbon is 95: 5 to 50:50, and A conductive composition for plastic coating, wherein the weight ratio of the solid content, the total weight of the conductive carbon, and the solid content of the aqueous dispersion is 98: 2 to 75:25 . 2. An aqueous dispersion of a polyester resin, a conductive metal compound, a softening point of 100 ° C. or more, and a particle size of 2 μm to 10 μm.
m or less, wherein the weight ratio of the solid content of the aqueous dispersion to the conductive metal compound is 75:25 to 40:60, and Wherein the weight ratio of the solid content of the above, the total weight of the conductive metal compound and the solid content of the aqueous dispersion is 98: 2 to 75:25 .