JPH09263690A - Conductive plastic composition and molded article - Google Patents

Abstract

(57) Abstract: Provided are a plastic composition which has electrical conductivity and biodegradability, and which can give a molded article excellent in mechanical strength, and a plastic molded article such as this. SOLUTION: A conductive material containing polylactic acid, cellulose acetate or aliphatic polyester or a mixture thereof and carbon powder, having a surface resistivity of 10 ⁸ Ω □ or less and a carbon powder content of 15% by volume or less. Resin composition,
Also, by kneading a resin composition containing polylactic acid, cellulose acetate or aliphatic polyester or a mixture thereof and carbon powder, the surface resistivity is 10 ⁸ Ω □ or less, and the carbon powder content is 15 volume. % Of the conductive resin composition, the method includes the step of kneading the resin composition so that the water content is 2.0% or less based on the total weight of the composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive plastic composition and a molded product thereof. The present invention particularly relates to a conductive biodegradable plastic composition and a molded product thereof.

[0002]

2. Description of the Related Art As the social situation surrounding the global environment and the growing interest in the environment, biodegradable plastics that are completely decomposed and digested by microorganisms in the soil have attracted attention as a measure for waste disposal. Several patent applications have already been filed for molded articles using such plastics (JP-A-62-124083, JP-A-2-92816, JP-A-1-295765, etc.). As products for biodegradable use,
There are many agricultural films, fishing gear, packaging materials, etc., but conductive materials have not been known so far.

In the tray for transporting electronic parts, the tray is provided with conductivity in order to prevent the LSI chip from being charged. As the antistatic method, a general-purpose resin such as polystyrene or polypropylene mixed with a conductive filler such as carbon black, or a method in which a surfactant is applied or kneaded is mainly used. Kaisho 51-21
336, JP-A-59-90994, JP-A-61-235138, etc.).

However, various kinds of biodegradable plastics are kneaded with conductive carbon so as not to impair biodegradability, and
Further, it was difficult to knead and mold the polyester while maintaining sufficient strength without breaking the ester bond of polyester, which is the main composition of the biodegradable plastic.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and is a plastic which has electrical conductivity and biodegradability, and which can give a molded product excellent in mechanical strength. It is intended to provide compositions and such plastic moldings.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that biodegradable plastics (aliphatic polyester, polylactic acid, cellulose acetate, etc.) containing 15 vol. %, It has been found that a conductive biodegradable plastic having a surface resistivity of 10 ⁸ Ω □ or less and a biodegradability not impaired can be obtained by mixing at a ratio of not more than%. is there.

The present inventor also suppresses the hydrolysis of the ester bond constituting the resin by suppressing the water content of the resin and the carbon black to be kneaded to 2.0% or less during kneading, and It has been found that the strength can be made sufficiently equal to that of the raw material resin. Therefore, the present invention comprises polylactic acid, cellulose acetate or aliphatic polyester or a mixture thereof and carbon powder, the surface resistivity is 10 ⁸ Ω □ or less, and the carbon powder content is 15% by volume or less. The present invention provides a conductive resin composition.

The present invention also kneads a resin composition containing polylactic acid, cellulose acetate or an aliphatic polyester or a mixture thereof and carbon powder, and has a surface resistivity of 10 ⁸ Ω □ or less, and Carbon powder content is 15
Provided is a method for producing a conductive resin composition having a volume percentage of not more than 2.0, which comprises, when kneading the resin composition, setting the water content to 2.0% or less based on the total weight of the composition.

The present invention further provides a molded article made of the above-mentioned conductive resin composition, particularly a molded article for carrying electronic parts and a grounding part for automobiles for removing static electricity. Known biodegradable plastic moldings are mainly those that are excellent in biodegradability, and application development as a durable material used for housings and structures of electronic devices has become popular,
There was no known electrically conductive material. As mentioned above, a method for imparting conductivity to a resin is already known, but no countermeasure for a resin susceptible to hydrolysis such as biodegradable plastic is described.

However, according to the present invention, it is possible to provide a biodegradable molded article having various conductivity properties such as low-power equipment. Particularly, in the packaging material of electronic material, it can be recovered after being transported. Alternatively, it is expected that the molded article of the present invention will be biodegraded after landfill disposal and the load on the environment can be reduced. Regarding the embossed tape and reel, JP-A-6-171666 and JP-A-6-
Although proposed in 171667, nothing is mentioned about conductivity.

Further, the grounding component for releasing the static electricity of the vehicle has a risk of causing dust pollution due to abrasion because it comes into contact with the road, but by using the resin composition of the present invention, it is washed by rainwater, Biodegraded in soil and rivers,
It is expected that the load on the environment can be reduced.

[0012]

EXAMPLES The present invention will be further described with reference to the following examples. Example 1 Aliphatic polyester (Showa High Polymer: Bionole # 1020)
Knead carbon black into the pellets of the following conditions,
Injection molded.

Carbon black used (CB): CABOT company 1. BLACK PEARLS2000 2. VALCAN-XC72 3. Since the degree of chaining of carbon black particles is large in the order of VALCAN-P 1>2> 3, conductivity can be imparted to the resin with a small amount. Drying and kneading conditions Kneading machine: Labo Plastomill manufactured by Toyo Seiki Nozzle temperature: 115-120 ° C Torque: 4-6kgm CB (VULCAN-XC72) Mixing ratio of powder: 0-50% by weight (a) Drying of resin and CB powder Water content 2.0 without treatment
% Or more. (B) When the resin and CB powder are dried at 80 ° C. for 3 hours and the water content is 1.0 to 2.0%. (C) When the resin and the CB powder are introduced at 80 ° C. for 3 hours while being forcibly dried so that the water content is 1.0% or less.

Injection conditions Injection molding machine: JC-25SS manufactured by Japan Steel Works Injection time: 7 seconds (injection temperature: 134-144 ° C) Cooling time: 15-20 seconds (cooling temperature: 20-40 ° C) Injection pressure: 300 〜450kgf / cm ² Molded test piece: 60 × 20 × 2mm Measurement of various physical properties (1) The surface resistance of the obtained test piece was measured, and as a result, 5 to 20% by weight (3.6 to 15% by volume) of carbon black was added. By doing so, the surface resistivity could be suppressed to 10 ⁸ Ω □ or less (Fig. 1).

(2) River water was collected, and various test pieces with a thickness of 2 mm (molded under the condition of (c)) were allowed to stand in an environment circulated in a water tank, and biodegradability by blending carbon black As a result, when the carbon black content was 15% by volume or less, the biodegradability was halved compared to that without CB, but the biodegradability was not lost (Fig. 2). .

On the other hand, it was found that the biodegradability was extremely deteriorated when the content was more than 15% by volume (FIG. 3). (3) Molding by controlling the water content in the resin by the above method, cutting a 20 mg section from the test piece, 2
After dissolving with ml of chloroform, the molecular weight was measured by chromatography. As a result, when the water content was 1.0% or less, the decrease in the molecular weight of the resin could be prevented. This is probably because hydrolysis could be suppressed during melt-kneading (FIG. 4).

(4) As a result of measuring the tensile strength of the test piece,
It was found that the tensile strength after drying was higher than that without drying (FIG. 5). From these facts, the carbon black content is 5 to 20% by weight.
(3.6 to 15% by volume), by sufficiently performing a drying treatment and suppressing the water content to 2.0% or less, a desired molded product can be obtained without impairing the physical properties and biodegradability of the raw material resin. Do you get it.

Example 2 Molding of LSI tray and physical properties and dimension change material (1) Aliphatic polyester (Showa High Polymer: Bionole #
1020 × 15) [Containing 15% by weight of talc] (2) VALCAN-XC72 (carbon black) The above materials were sufficiently dried to a water content of 0.5% or less.

The kneading-screw extruder: Berstorff ZE40A Dice: .phi.5 × 5 millimeter Strand cooling: the position of the introduction of bulk structure of the water-cooled kneader and a resin and carbon black: 6 molded cylinder heater temperature: 160 to 170 ° C. Mold temperature: 20-30 ° C Injection time: 6 seconds Cooling time: 18 seconds Injection pressure, holding pressure, etc .: Appropriate optimum conditions Dimensional change after molding Resin itself without carbon black (n) and carbon black (c) The LSI tray was left in an environment of 40 ° C and 70% rh for 70 days to measure the short side of the LSI tray. The changes were compared (Fig. 8, 10-point measurement error bar shows quasi-deviation σ).
Although both n and c have been changing at a relative dimensional change rate of 0.2%, the width of σ of n is large, which shows that the dimensions vary.

Bending strength change after molding Resin itself containing no carbon black (n) and carbon black (c) The LSI tray was left in an environment of 40 ° C. and 70% rh for 70 days. A part of the short side was cut out and changes in bending strength were compared (FIG. 9). The bending strength of n is 30% higher than that of c, and it can be seen that the physical properties are vulnerable to impact.

Biodegradability test with river water 5 g of test piece cut out from LSI tray was left standing in an environment in which river water was collected and circulated in a water tank, and left for 150 days. It was measured. The results are shown in Table 1 below (unit: g).

[0022]

[Table 1]

From the above table, LS containing carbon black
It can be confirmed that the I tray is definitely biodegradable, although it is slightly inferior in biodegradability to the one not containing carbon black. Example 3 Embossed tape material (1) Aliphatic polyester (Showa High Polymer: Bionole #
1020 × 15) [Containing 15% by weight of talc] (2) VALCAN-XC72 (carbon black) The above materials were sufficiently dried to a water content of 0.5% or less.

Sheet forming single-screw extruder: φ30 mm (Likua RY-30 used) Sheet size: thickness 0.5 mm, width 60 mm Take-up conditions: roll temperature 30 ° C., take-up speed 80 cm / min embossing 10 × 20 × 5 mm The embossing was continuously molded on a sheet as shown in FIG. 10, and the seal was also made of the same composition.

As a result, it is possible to mount electric parts on the reel similar to the conventional one, and the biodegradability test is also conducted in the second embodiment.
Similarly to the above, although it was halved compared to the resin containing no carbon black, biodegradation was ensured. Example 4 Material for Parts for Automotive Grounding (1) Aliphatic polyester (Showa High Polymer: Bionole #
1020 × 15) [Containing 15% by weight of talc] (2) VALCAN-XC72 (carbon black) The above materials were sufficiently dried to a water content of 0.5% or less.

Kneading twin-screw extruder: Bellstorf ZE40A Die: φ5 × 5 mm Strand cooling: Water-cooled molding 15 (width) × 3 (thickness) × 1000 mm (length) Cut out from a molded product or sheet and cut to any length The cut pieces were hung on the rear part of the automobile and attached to the ground by contacting them with a length of 5 to 10 mm.

As a result, a static electricity removing effect equivalent to that of a grounding part made of a metal chain was exhibited, and static electricity did not fly even if the knob was touched for opening and closing the door. When the resin, which became dust in the abrasion test, was left to stand in river water, it was digested by microorganisms within 30 days.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the carbon black compounding ratio and the surface resistivity with respect to the polyester resins obtained in Examples.

FIG. 2 is a photograph showing the biodegradability of the polyester resin molded product obtained in the example.

FIG. 3 is a graph showing the relationship between the blending ratio of carbon black and the biodegradability of the polyester resins obtained in the examples.

FIG. 4 is a graph showing the relationship between the water content of the resin composition at the time of kneading obtained in the example and the molecular weight of the resin in the obtained molded product.

FIG. 5 is a graph showing the relationship between the water content of the resin composition during kneading obtained in the examples and the tensile strength of the obtained molded product.

FIG. 6 is a schematic diagram showing the bulk structure of the kneading machine used in the examples and the introduction positions of the resin and carbon black.

FIG. 7 is a schematic plan view showing the structure of an LSI tray obtained in an example.

FIG. 8 is a graph showing relative changes with time of the dimensions of the LSI tray obtained in the example.

FIG. 9 is a graph showing relative changes with time of bending strength of LSI trays obtained in Examples.

FIG. 10 is a schematic diagram showing the shape of embossing used in the examples.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C08L 67/02 C08L 67/02 // B65D 85/86 0333-3E B65D 85/38 S

Claims (4)

[Claims] 1. A polylactic acid, a cellulose acetate, or an aliphatic polyester, or a mixture thereof and carbon powder, which has a surface resistivity of 10 ⁸ Ω □ or less and a carbon powder content of 15% by volume or less. Conductive resin composition. 2. A resin composition containing polylactic acid, cellulose acetate, an aliphatic polyester, or a mixture thereof and carbon powder is kneaded to have a surface resistivity of 10 ⁸ Ω □.
The following, and in producing a conductive resin composition having a carbon powder content of 15% by volume or less, when kneading the resin composition, the water content relative to the total weight of the composition 2.0
% Or less. 3. A molded article for carrying electronic parts, comprising the conductive resin composition according to claim 1. 4. A grounding component for an automobile for removing static electricity, which comprises the conductive resin composition according to claim 1.