JP2002127342A - Biodegradable conductive composite sheet, and mold and carrying tape using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive composite sheet which possesses a sufficient surface conductivity by using a small amount of a conductive filler, and a carrying tape which is made of a lactic acid polymer and not deformed under conditions that temperature is not controlled in summer or the like when the tape is transported and stored in a warehouse or the like. SOLUTION: A biodegradable conductive composite sheet is composed of plural layers of which an outer layer is made of a polylactic acid polymer and a conductive filler sharing 3-15% in weight, and an inner layer is made of a polylactic acid polymer. A storage modulus E' of the composite sheet is equal to or larger than 100 MPa at 120 deg.C by a testing method relating to temperature dependency of dynamic viscoelasticity specified by JIS K7198.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conductive composite sheet made of a biodegradable resin, a molded article using the same, and a carrier tape.

[0002]

2. Description of the Related Art Conventionally, as a carrier tape, a conductive sheet obtained by integrally laminating a styrene-based resin composition kneaded with a large amount of a conductive filler by co-extrusion on the front and back of a base layer made of a styrene-based resin, vinyl chloride A conductive sheet molded from a vinyl chloride resin composition obtained by kneading a conductive filler such as carbon black into a resin based resin, or at least one surface of a sheet made of a thermoplastic resin such as a styrene resin or an ethylene terephthalate resin. A sheet obtained by subjecting a conductive sheet provided with a conductive layer to secondary molding by press molding, vacuum molding, or the like has been used.

[0003] However, the carrier tape made of the conductive sheet has environmental problems, and therefore has physical properties suitable for the carrier tape during use, and biodegrades in a short period of time in a natural environment after use. Carrier tape is required.

[0004] Such a biodegradable resin used as a carrier tape is disclosed in JP-A-11-39945.
There is known a biodegradable conductive carrier tape formed from a biodegradable conductive sheet obtained by adding a conductive filler or the like to a polylactic acid-based resin and a polyalkylalkanoate-based resin disclosed in Japanese Patent Application Laid-Open Publication No. H11-139,878.

[0005] Japanese Patent Application Laid-Open No. 2000-85837 proposes a carrier tape characterized by providing a base layer made of a biodegradable resin with a coating layer containing a conductive material.

[0006]

However, a biodegradable conductive carrier tape requires a large amount of conductive filler in order to obtain a desired surface resistance. For this reason, fillers are liable to agglomerate and generate lumps,
In addition, a cost problem arises.

Further, since the heat resistance of the biodegradable carrier tape is not taken into consideration, for example, when the tape is exposed to an environment of 50 ° C. or more, such as during storage in a storage container during transportation in a shipping container, deformation or the like occurs. Occasionally, it may not be possible to use the product.

Accordingly, the present invention is to obtain a conductive composite sheet having a sufficient surface conductivity even if the amount of the conductive filler used is small, and to control the temperature during transportation and storage in a warehouse or the like. An object of the present invention is to obtain a carrier tape made of a lactic acid-based polymer which does not deform even under conditions such as summertime if it is not present.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a biodegradable conductive composite sheet comprising a plurality of layers.
The storage modulus E ′ at 120 ° C. in the test method for temperature dependence of dynamic viscoelasticity based on JIS is 100 MPa or more, and a polylactic acid-based polymer and 3
The above problems have been solved by including a conductive agent of about 15% by weight and using a polylactic acid-based polymer as the inner layer of the composite sheet.

[0010] The storage modulus E 'under predetermined conditions is 100 M
Since the pressure is set to Pa or more, a carrier tape having improved heat resistance can be manufactured, and even if a temperature rise occurs during transportation in a transportation container or storage in a warehouse or the like, deformation can be suppressed.

Further, since the conductive filler is disposed on the outer layer of the biodegradable conductive composite sheet, the amount of the conductive filler used can be reduced, and sufficient surface conductivity can be obtained even if the amount used is small. Can be.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The biodegradable conductive composite sheet according to the present invention is a laminate formed from a plurality of layers. The biodegradable conductive composite sheet has a predetermined storage modulus E ′, and the outer layer of the biodegradable conductive sheet contains a polylactic acid-based polymer and 3 to 15% by weight of a conductive agent, The inner layer of the biodegradable conductive sheet is a composite sheet made of a polylactic acid-based polymer.

The number of layers in the laminate is at least three, and may be four or more. In the case of three layers,
The intermediate layer constitutes an inner layer that satisfies the above conditions, and when there are four or more layers, at least one of the layers other than the outer layer may constitute the inner layer that satisfies the above conditions.

The storage elastic modulus E 'is defined by JIS K71.
98 refers to the storage modulus at 120 ° C. in the test method for temperature dependence of dynamic viscoelasticity based on 98. The storage modulus E ′ is preferably 100 MPa or more, and is 100 to 500 M.
Pa is preferred. If it is less than 100 MPa, heat resistance may be poor. Further, when the pressure is in the range of 100 to 500 MPa, characteristics of moldability and heat resistance can be further exhibited.

The lactic acid-based polymer constituting the outer layer and the inner layer of the biodegradable conductive sheet includes poly (L-lactic acid) having a structural unit of L-lactic acid and poly (D-lactic acid) having a structural unit of D-lactic acid. -Lactic acid), poly (DL-lactic acid) whose structural units are L-lactic acid and D-lactic acid, and a mixture thereof, and further may be a copolymer with a hydroxycarboxylic acid unit described below.

As the polymerization method of the lactic acid-based polymer, any known method such as a condensation polymerization method and a ring-opening polymerization method can be employed. For example, in the polycondensation method, L-lactic acid or D-lactic acid or a mixture thereof can be directly dehydrated and polycondensed to obtain a polylactic acid-based polymer having an arbitrary composition.

In the ring-opening polymerization method, lactide, which is a cyclic dimer of lactic acid, can be obtained by using a selected catalyst and a polylactic acid-based polymer while using a polymerization regulator and the like as necessary. it can. Lactide includes L-lactic acid dimer L-
Lactide, D-lactide which is a dimer of D-lactic acid, and DL-lactide further comprising L-lactic acid and D-lactic acid,
Polylactic acid having any composition and crystallinity can be obtained by mixing and polymerizing these as necessary.

Further, if necessary, a non-aliphatic carboxylic acid such as terephthalic acid and / or a non-aliphatic diol such as an ethylene oxide adduct of bisphenol A may be used as a small copolymerization component.

Further, a small amount of a chain extender, for example, a diisocyanate compound, an epoxy compound, an acid anhydride or the like can be used for the purpose of increasing the molecular weight. The preferred range of the weight average molecular weight of the polymer is from 60,000 to 1,000,000. If the weight average molecular weight is below this range, practical physical properties are hardly exhibited, and if it exceeds this range, the melt viscosity is too high and molding processability is poor.

The other hydroxycarboxylic acid units copolymerized with polylactic acid include optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycol Acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid Such as bifunctional aliphatic hydroxycarboxylic acids and caprolactone,
Lactones such as butyrolactone and valerolactone are exemplified.

Examples of the biodegradable aliphatic polyester include a polyhydroxycarboxylic acid excluding polylactic acid, an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, and an aliphatic polyester obtained by ring-opening polymerization of a cyclic lactone. Examples include polyester, synthetic aliphatic polyester, and aliphatic polyester biosynthesized in cells.

Examples of the polyhydroxycarboxylic acids other than the above polylactic acid include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, and 2-hydroxybutyric acid.
Examples include homopolymers and copolymers of hydroxycarboxylic acids such as 3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid.

Examples of the aliphatic diol include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. In addition, typical examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecane diacid. As the aliphatic polyester obtained by condensing these aliphatic diols and aliphatic dicarboxylic acids, one or more of each of the above-mentioned compounds are each subjected to condensation polymerization, or if necessary, jump-up with an isocyanate compound or the like. To obtain the desired polymer.

The aliphatic polyester obtained by ring-opening polymerization of the above-mentioned cyclic lactones is polymerized as a cyclic monomer by one or more of ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like. It is manufactured by

Examples of the above-mentioned synthetic aliphatic polyester include cyclic anhydrides and oxiranes, such as copolymers of succinic anhydride with ethylene oxide, propion oxide and the like.

As the aliphatic polyester biosynthesized in the above-mentioned cells, acetyl coenzyme A (acetyl-Co) is used in cells such as alkaligenes eutrophas.
Aliphatic polyesters biosynthesized according to A) are known. This aliphatic polyester is mainly poly-β-hydroxybutyric acid (poly 3HB), but in order to improve practical properties as a plastic, a valeric acid unit (HV) is copolymerized to obtain a poly (3HB-co-3HV). It is industrially advantageous to use the copolymer of (1). The HV copolymerization ratio is generally from 0 to 40%. Further, a long-chain hydroxyalkanoate may be copolymerized.

The weight average molecular weight of the polylactic acid polymer used in the present invention is preferably from 60,000 to 700,000. If the weight-average molecular weight is less than 60,000, the molten polymer drawn during sheet molding flows before it solidifies, and it may be difficult to obtain a sheet having a uniform thickness. Further, the obtained sheet is brittle, and may be easily broken or cracked by a slight stress or deformation.

On the other hand, when the weight average molecular weight exceeds 700,000, the screw rotation speed is not constant due to high load during sheet molding, and the pressure of the molten polymer (resin pressure) inside the die increases, so that extrusion by melt fracture or the like occurs. May lead to failure. In addition, there arises a problem that high shear is applied to the molten polymer at the outlet of the die, which adversely affects the appearance of the sheet. It should be noted that by increasing the extrusion temperature, the melt viscosity of the resin can be reduced, but polylactic acid is not a preferred method because it is easily decomposed by heat.

Examples of the conductive agent used for the outer layer of the biodegradable conductive composite sheet include conductive carbon, tin oxide, antimony oxide, and indium oxide. These may be used alone or in combination of two or more. Among these, conductive carbon is preferred in terms of moldability, resistivity after molding, and the like. Examples of the conductive carbon include Ketjen Black E
C, furnace black, channel black, acetylene black, etc., but Ketjen Black EC can be obtained because a high conductivity can be obtained with a small amount of addition.
Is more preferred. When Ketjen Black EC is used, a small amount of Ketjen Black EC is used, so that the mechanical properties of the biodegradable conductive composite sheet are less likely to decrease.

The conductive agent has an average particle size of 0.01 to 1
0 μm is preferable, and 0.05 to 5 μm is particularly preferable.
If it is less than 0.01 μm, dispersion in the raw material resin is poor, and
If it exceeds 0 μm, the rigidity of the obtained biodegradable conductive composite sheet will be high, and the characteristics desired as a carrier tape may be lost.

The amount of the conductive agent in the outer layer is preferably set so that the surface resistivity of the biodegradable conductive composite sheet described later falls within a predetermined range. It is preferably from 3 to 15% by weight, more preferably from 3 to 10% by weight. When it is more than 3% by weight, sufficient conductivity of the surface of the obtained biodegradable conductive composite sheet can be obtained,
When the amount is less than 15% by weight, it is possible to reduce the cost of the obtained biodegradable conductive composite sheet, to make it softer, and to suppress the occurrence of bumps.

The above outer layer and inner layer contain, in addition to the above components, lubricants, plasticizers, various surfactants, dyes, pigments, other additives and polymers, as long as the effects of the present invention are not impaired. be able to. Examples of the lubricant include behenic acid, stearic acid, pentaerythritol monoester, pentaerythritol diester, pentaerythritol tetrastearate, pentaerythritol-adipate-stearate complex ester, dipentaerythritol-adipate-stearate complex ester, diester Pentaerythritol hexstearate and the like. Examples of the plasticizer include dioctyl phthalate. Examples of the surfactant include acetylene glycol, acetylene alcohol, glycerin fatty acid ester, and polyglycerin aliphatic ester.

As a method for producing the biodegradable conductive composite sheet according to the present invention, a commonly used laminating method such as a coextrusion method or a heat compression method can be used. The coextrusion method is a method in which a plurality of extruders are connected to a single die in a feed block type or a multi-manifold type. Examples of the die include a T die, an I die, and a round die. A sheet-like material or a cylindrical material that has been melt-extruded from these bases or the like is cooled with a cast roll or water,
After being quenched by compressed air and solidified in a state close to amorphous,
It is obtained by stretching uniaxially or biaxially by a roll method, a tenter method, a tubular method or the like.

The stretching conditions for the unstretched lactic acid-based polymer sheet are as follows: a stretching temperature of 50 to 100 ° C., and a stretching ratio of 1.5 to 5 times.
The stretching speed is preferably 100% / min to 10,000% / min. Since the stretching conditions vary depending on the composition of the polymer and the thermal history of the unstretched sheet, the stretching conditions are appropriately determined while observing the value of the storage elastic modulus E ′ at 120 ° C. of the molded article. Further, after the stretching, the storage elastic modulus E 'is improved by re-heat treatment within a range from -20 ° C to the melting point (Tm) of the lactic acid-based polymer from the crystallization temperature (Tc) of the lactic acid-based polymer. Can be done.

End materials (edges, defective products, etc.) of the biodegradable conductive composite sheet generated during production can be used as a middle layer which does not satisfy the above requirements for the inner layer, which is a layer inside the laminate. . As a result, it becomes possible to add the conductive agent in the middle layer.

The surface resistivity of the biodegradable conductive composite sheet thus obtained is preferably in the range of 10 ³ to 10 ⁸ Ω. When the surface resistivity is 10 ³ Ω or more, there is no danger that the terminals of the electronic components become conductive and a short circuit occurs. When the surface resistivity is 10 ⁸ Ω or less, sufficient conductivity can be obtained, and generation of static electricity can be suppressed. it can.

In order to obtain a molded body from the obtained biodegradable conductive composite sheet by thermoforming, the biodegradable conductive composite sheet is preheated to a molding temperature by an infrared heater, a hot plate heater, hot air or the like, and is thermoformed. I do. The preheating temperature is from the glass transition point (Tg) of the lactic acid-based polymer to the melting point (Tm) of the lactic acid-based polymer.
Preheat within the range. If the preheating temperature is lower than Tg, the sheet is not softened and molding is difficult. If the preheating temperature is higher than Tm, it is difficult to obtain a uniform molded body due to the drawdown (hanging down by its own weight) of the sheet during preheating.

Examples of the thermoforming method include a vacuum forming method, a press forming method, a male and female mold forming method, a method of expanding a formed male mold after deforming a sheet along the formed male mold, and the like.

Examples of the molded body include a carrier tape and the like. When using the molded body of the biodegradable conductive composite sheet as a carrier tape, the thickness of the biodegradable conductive composite sheet may be any thickness that can be practically used as a normal carrier tape, Usually 100-1
000 μm.

[0041]

The present invention is not limited by the following examples.

[Measurement Method] A surface resistivity test piece was allowed to stand at 23 ° C. and 50% RH for 90 hours.
According to SK-6911, the surface resistivity of the obtained laminated film is measured using a surface resistance meter with a surface resistivity comparator (MCP-TESTER (trade name, manufactured by Mitsubishi Chemical Corporation)).

Grains are visually observed to evaluate the degree of the grains in the obtained laminated film.

Glass transition point, crystallization temperature, melting point Differential scanning calorimeter DSC-7 (manufactured by PerkinElmer) was used to obtain 10 mg of a film sample according to JIS-K7122.
When the temperature is raised at a rate of 10 ° C./min.
From the gram, the glass transition point, crystallization temperature and melting point are determined.

Storage elastic modulus E at 120 ° C. Using a dynamic viscoelasticity measuring apparatus VES-F type manufactured by Iwamoto Seisakusho, based on JIS K7198, in the range of room temperature to melting temperature, heating rate 1 ° C./min, frequency The measurement is performed at 10 Hz.
From the obtained viscoelastic curve, the storage elastic modulus E ′ at 120 ° C.
Ask for.

Evaluation of Heat Resistance The molded carrier tape is stored in a hot-air dryer at 50 ° C. for 150 hours, and the appearance change is visually observed.

(Example 1) Lactic acid polymer (EcoPLA4030D (glass transition point 58 ° C, melting point 175 ° C, weight average molecular weight 240,000), manufactured by Cargill), and conductive agent (Ketjen Black EC, manufactured by International)
Is mixed at a weight ratio of polylactic acid polymer / conductive agent = 95/5, supplied to a 40 mmφ co-axial twin screw extruder, melt-kneaded and extruded into strands, and then cut on pellets with a pelletizer. Thus, an outer layer pellet was obtained.

The pellets for the outer layer and the pellets for the inner layer were supplied to the co-axial twin screw extruders and extruded from a multi-manifold die, and the thickness of the outer layer / inner layer / outer layer = 150/1950 / An unstretched sheet having a total thickness of 150 (μm) and a total thickness of 2.25 mm was obtained.

The unstretched sheet is roll-stretched 2.5 times at 70 ° C. in the longitudinal direction, and then stretched by a tenter in the width direction.
The film was stretched 3.0 times at 0 ° C. Subsequently, a heat treatment was performed in a heat treatment zone of a tenter at a temperature of 120 ° C. for a treatment time of 25 seconds to obtain a 0.3 mm-thick stretched lactic acid-based conductive polymer sheet.

The storage elastic modulus E ′ at 120 ° C. of the obtained sheet was 205 MPa. The surface resistivity of the obtained laminated sheet was 3 × 10 ⁷ Ω, and there were no bumps.

Using the obtained stretched lactic acid-based polymer conductive sheet, with a hot plate contact heating type air pressure molding machine manufactured by CKD, at a molding temperature of 140 ° C. and a molding pressure of 1 MPa, a length of 20 mm was used.
A carrier tape having a pocket shape with a width of 15 mm and a depth of 3 mm was formed.

After the obtained carrier tape was stored in a hot-air dryer at 50 ° C. for 150 hours, changes in appearance were visually observed, and no abnormality such as deformation was observed.

Example 2 Lactic acid polymer (EcoPLA (D% = 3.2%, glass transition point 54, manufactured by Cargill Co., Ltd.)
, A melting point of 151 ° C, a crystallization temperature of 125 ° C, and a weight-average molecular weight of 240,000)).

The storage elastic modulus E ′ at 120 ° C. of the obtained sheet was 190 MPa. The surface resistivity of the obtained laminated sheet was 3 × 10 ⁷ Ω, and there were no bumps.

Using the obtained stretched lactic acid-based polymer conductive sheet, using a hot plate contact heating type air pressure molding machine manufactured by CKD, at a molding temperature of 140 ° C. and a molding pressure of 1 MPa, a length of 20 mm,
A carrier tape having a pocket shape with a width of 15 mm and a depth of 3 mm was formed.

After the obtained carrier tape was stored in a hot-air dryer at 50 ° C. for 150 hours, changes in appearance were visually observed, and no abnormality such as deformation was observed.

Example 3 Lactic acid polymer (EcoPLA (D% = 5.1%, glass transition point 58, manufactured by Cargill Co.)
, A melting point of 145 ° C, a crystallization temperature of 121 ° C, and a weight average molecular weight of 200,000)).

The obtained sheet had a storage modulus E ′ at 120 ° C. of 155 MPa. The surface resistivity of the obtained laminated sheet was 2 × 10 ⁷ Ω, and there were no bumps.

The obtained carrier tape was heated at 50 ° C.
After 150 hours of storage in a hot air dryer, changes in appearance were visually observed, and no abnormality such as deformation was observed.

Comparative Example 1 Lactic acid polymer (EcoPLA (D% = 8.5%, glass transition point 58, manufactured by Cargill Co.)
, A melting point of 140 ° C, a crystallization temperature of 120 ° C, and a weight average molecular weight of 200,000)).

The storage elastic modulus E ′ of the obtained sheet at 120 ° C. was 95 MPa. Further, the surface resistivity of the obtained laminated sheet was 5 × 10 ⁷ Ω, and there were no bumps.

The obtained carrier tape was heated at 50 ° C.
After 150 hours of storage in a hot-air dryer, the appearance change was visually observed. The molded part was shrunk and greatly deformed.

Comparative Example 2 The same procedure as in Example 1 was conducted except that the structure of the outer layer of Example 1 was changed to polylactic acid-based polymer / conductive agent = 98/2. As a result, the surface resistivity was 1 × 10
⁹ ohms. There were no bumps. The storage elastic modulus E ′ at 120 ° C. of the obtained sheet was 200 MPa.

[0064]

According to the present invention, a biodegradable conductive composite sheet having a predetermined storage modulus E 'is used.
A carrier tape with improved heat resistance can be manufactured, and even if a temperature rise occurs during transportation in a transportation container or storage in a warehouse or the like, deformation can be suppressed.

In addition, since the outer layer and the inner layer of the biodegradable conductive composite sheet have a predetermined structure, sufficient surface conductivity can be obtained even if the amount of the conductive filler used is small.

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Claims (3)

[Claims] 1. A biodegradable conductive composite sheet comprising a plurality of layers, wherein the composite sheet has a storage elastic modulus E ′ at 120 ° C. in a test method for temperature dependence of dynamic viscoelasticity based on JIS K7198. 100 MPa or more, the outer layer of the composite sheet contains a polylactic acid-based polymer and 3 to 15% by weight of a conductive agent, and the inner layer of the composite sheet has a biodegradable conductive composite of a polylactic acid-based polymer. Sheet. 2. A molded article using the biodegradable conductive composite sheet according to claim 1. 3. A carrier tape using the biodegradable conductive composite sheet according to claim 1.