JP2002160340A - Biodegradable conductive composite sheet and molding or carrier tape using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive composite sheet with which a punching quality of an obtainable molding is excellent and cracks and burs hardly occur. SOLUTION: A biodegradable conductive composite sheet is composed of plural layers. An outer layer of the composite sheet contains at least a polylactic acid polymer, a biodegradable aliphatic polyester and a conductive agent, and a mixing ratio of the polylactic acid polymer and the biodegradable aliphatic polyester is 50:50-90:10 in weight. An inner layer of the composite sheet contains at least a polylactic acid polymer and a biodegradable aliphatic polyester, and a mixing ratio of the polylactic acid polymer and the biodegradable aliphatic polyester is 50:50-90:10 in weight. A crystal melting calorie ΔHm of the biodegradable aliphatic polyester is equal to or larger than 55 J/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable conductive composite sheet, and a molded article or a carrier tape using the same.

[0002]

2. Description of the Related Art In recent years, with great progress in surface mounting technology, demand for high-performance and small-sized electronic components, particularly chip-type electronic components such as ICs, transistors, and diodes, has been increasing. These chip-type electronic components are usually housed in a carrier tape or tray obtained by secondary forming such as vacuum forming, air forming, press forming, etc., of a plastic sheet, and are transported and stored. When stored in a carrier tape, it is sealed in a top tape as a lid material and supplied as a package.

Conventionally, as a carrier tape, a conductive sheet integrally laminated by co-extrusion of a styrene resin composition kneaded with a multilayer conductive filler on the front and back of a styrene resin base material layer is used. A conductive sheet formed by molding a vinyl chloride resin composition obtained by kneading a conductive filler such as carbon black into a vinyl resin into a sheet shape,
Or, a conductive sheet having a conductive layer provided on at least one surface of a sheet made of a thermoplastic resin such as a styrene-based resin or an ethylene terephthalate-based resin is subjected to thermoforming such as press forming or vacuum forming, and further fed for automatic feeding. A punched hole has been used.

[0004] However, the carrier tape made of the above conductive sheet has environmental problems when it is discarded. Therefore, it has physical properties suitable for the carrier tape during use, and is in a natural environment after use. There is a demand for a carrier tape that is biodegradable in a short time.

[0005] As an example of using such a biodegradable resin as a carrier tape, a resin prepared by adding a conductive filler to a polylactic acid-based resin and a polyalkylalkanoate-based resin disclosed in JP-A-11-39945 is disclosed. Degradable carrier tapes are known.

[0006]

However, this biodegradable carrier tape requires a large amount of conductive filler in order to obtain a desired surface resistance. For this reason, the filler is likely to be aggregated to generate lumps, and there is a cost problem. On the other hand, studies have been made to reduce the amount of conductive filler used. However, a resin that reduces the amount of conductive filler used and maintains a desired surface resistance may have a problem in punching workability and the like. That is, if the resin is molded and punched to provide a perforation hole, the resin may not be punched cleanly, and the molded body may be broken or fine resin residue (burr) may occur. In this case, using a machine that automatically performs the punching process causes a stop of the automatic feeding.

Accordingly, an object of the present invention is to provide a conductive composite sheet which has good punching workability of the obtained molded article and is less likely to generate cracks and burrs.

[0008]

According to the present invention, there is provided a biodegradable conductive composite sheet comprising a plurality of layers, wherein the outer layer of the composite sheet comprises at least a polylactic acid-based polymer, a biodegradable aliphatic polyester and a conductive agent. Containing, the mixing ratio of the polylactic acid-based polymer and the biodegradable aliphatic polyester,
The weight ratio is 50:50 to 90:10, and the inner layer of the composite sheet contains at least a polylactic acid-based polymer and a biodegradable aliphatic polyester. And the mixing ratio is 5 by weight.
0:50 to 90:10, and the above problem was solved by being characterized in that the heat of crystal fusion ΔHm of the biodegradable aliphatic polyester was 55 J / g or more.

Since a conductive agent is contained in the outer layer of the sheet having a laminated structure, the amount of the conductive agent used in the entire sheet can be reduced, and the density of the conductive agent near the sheet surface can be increased. A sufficient surface resistance can be obtained.

Further, when the obtained sheet is punched out, cracks and burrs of the molded body are less likely to occur.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

The biodegradable conductive composite sheet according to the present invention is a laminate composed of a plurality of layers. The number of layers in this laminate may be at least three, and may have four or more layers. For this reason, this laminate has two outer layers,
It will have at least one inner layer.

The outer layer contains at least a polylactic acid-based polymer, a biodegradable aliphatic polyester and a conductive agent. The inner layer contains at least a polylactic acid-based polymer and a biodegradable aliphatic polyester.

The above-mentioned polylactic acid-based polymer has a structural unit of L
Poly (L-lactic acid) which is lactic acid, poly (D-lactic acid) whose structural unit is D-lactic acid, poly (DL-lactic acid) whose structural unit is L-lactic acid and D-lactic acid, and a mixture thereof. Good,
Further, it may be a copolymer with a hydroxycarboxylic acid unit described below.

As the polymerization method for the polylactic acid 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 as required. 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.

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 other than 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 with one or more of ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like. It is manufactured by

Examples of the above synthetic aliphatic polyester include cyclic acid 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) may be 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 heat of crystal fusion ΔHm of the biodegradable aliphatic polyester is 55 J / g or more. If it is less than 55 J / g, cracks and resin residue (hereinafter, referred to as “burrs”) are likely to occur when the obtained molded body of the biodegradable conductive composite sheet is punched.

Examples of the conductive agent 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 EC, furnace black, channel black, acetylene black, and the like.Ketjen Black EC is more preferred in that high conductivity can be obtained with a small amount of addition. preferable. 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 average particle size of the conductive agent is 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 mixing ratio of the polylactic acid-based polymer and the biodegradable aliphatic polyester in the outer layer and the inner layer is represented by a polymerization ratio of polylactic acid-based polymer / biodegradable aliphatic polyester =
90/10 to 50/50 is good, and 80/20 to 55/4
5 is preferred. When the mixing ratio is larger than 90/10, the molded body of the obtained biodegradable conductive composite sheet is liable to crack during punching. On the other hand, when the ratio is less than 50/50, burrs are likely to be generated at the time of punching of the obtained molded body of the biodegradable conductive composite sheet.

The amount of the conductive agent in the outer layer is preferably such 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 12% by weight. If the amount is less than 3% by weight, the conductivity of the surface of the obtained biodegradable conductive composite sheet may not be sufficient. If the amount is more than 15% by weight, the cost of the obtained biodegradable conductive composite sheet may increase. Connect.

The above-mentioned outer layer and inner layer contain, in addition to the above-mentioned 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 and a heat compression method can be used. The co-extrusion method is a method in which a resin extruded from a plurality of extruders is led to one die via a feed block type or a multi-manifold or the like.
An I die, a round die and the like can be mentioned. The above-mentioned thermocompression bonding method
This is a method in which another type of film is formed on the surface of the unwound mixed film using a roll or a press plate to form a laminate.

The surface resistivity of the biodegradable conductive composite sheet thus obtained is preferably in the range of 10 ³ to 10 ⁸ Ω. If the surface resistivity is less than 10 ³ Ω, the terminals of the electronic components may be conductive and short-circuited.
If it exceeds 0 ⁸ Ω, sufficient conductivity cannot be obtained, and static electricity tends to be generated. The inner layer of the present invention may contain a conductive agent as long as the object of the present invention is achieved. However, the amount is smaller than the amount of the conductive agent used for the outer layer. When a conductive agent is used for the inner layer, the conductivity increases in the thickness direction, and the electrostatic characteristics can be further improved.

The resulting biodegradable conductive composite sheet can be formed into various molded articles. As the molding method, thermoforming can be used. Thermoforming is performed by preheating the biodegradable conductive composite sheet to a forming temperature with an infrared heater, a hot plate heater, hot air or the like.
The preheating temperature is set within a range from the glass transition point (Tg) of the polylactic acid-based polymer to the melting point (Tm) of the polylactic acid-based polymer. 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.

As a method of thermoforming, there are 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. It is preferable to use a biodegradable conductive composite sheet as a carrier tape because it has sufficient conductivity.

[0037]

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.
In accordance with SK-6911, the surface resistivity of the obtained laminated film was measured using a surface resistance meter with a surface resistivity comparator (MCP-TESTER (trade name, manufactured by Mitsubishi Chemical Corporation)).

[0039] Using the crystal melting heat differential scanning calorimeter DSC-7 (manufactured by Perkin-Elmer) to determine the crystalline heat of fusion based on JIS-K7121 and 7122. That is, 10 mg of the biodegradable aliphatic polyester was weighed, the condition thereof was adjusted under standard conditions, the nitrogen gas flow rate was 25 ml / min, and the heating temperature was 10 mm.
The endothermic peak and its area were read from the DSC curve drawn while the temperature was raised to 200 ° C. at a rate of ° C./min, and the heat of crystallization (ΔHm) was calculated.

The punched laminate sheet was cut into a size of 10 cm × 10 cm and subjected to JIS-
An impact test was performed based on K7124, and burrs and cracks of the laminated sheet after the test were visually evaluated according to the following criteria. ：: No cracks or burrs ×: Cracks or burrs (Example 1) Polylactic acid-based polymer (EcoPLA4040D, manufactured by Cargill Co., Ltd.)
A ". ), Biodegradable aliphatic polyester (manufactured by Showa Polymer Co., Ltd., trade name: Bionole 1001, heat of crystal fusion: 5)
5J / g) (abbreviated as "BN" in Table 1) and a conductive agent (Ketjen Black EC, manufactured by International Corporation) were mixed with a polylactic acid-based polymer / biodegradable aliphatic polyester / conductive agent = 80 / The mixture was mixed at a weight ratio of 20/9, supplied to a twin-screw extruder, melt-kneaded, discharged in a strand shape, and then pulverized into a pellet shape with a pelletizer to obtain an outer layer pellet.

Further, a polylactic acid-based polymer alone (as described above) and a biodegradable aliphatic polyester (as described above) are combined with a polylactic acid-based polymer / biodegradable aliphatic polyester =
The resulting mixture was mixed at a weight ratio of 70/30, supplied to a twin-screw extruder, melt-kneaded, discharged into a strand, and then pulverized into a pellet with a pelletizer to obtain an inner layer pellet.

The pellets for the outer layer and the pellets for the inner layer are supplied to each single screw extruder, extruded from one T-die, and a laminated sheet having an outer layer / inner layer / outer layer = 10/280/10 (μm) is obtained. Created.

The surface resistivity and punching property of the obtained laminated sheet were measured. Table 1 shows the results. as a result,
The surface resistivity was 5 × 10 ⁶ Ω, and burrs and cracks after punching were not recognized as apparent from Table 1.

(Example 2) The weight ratio of each component of the pellets for the outer layer was set to polylactic acid-based polymer / biodegradable aliphatic polyester / conductive agent = 55/45/9, and the weight of each component of the pellets for the inner layer. A laminated sheet was prepared in the same manner as in Example 1, except that the ratio was set to polylactic acid-based polymer / biodegradable aliphatic polyester = 55/45. Table 1 shows the results.
As a result, the surface resistivity was 5 × 10 ⁶ Ω, and burrs and cracks after punching were not recognized as apparent from Table 1.

(Comparative Example 1) Biodegradable aliphatic polyester manufactured by Showa Polymer Co., Ltd., trade name: Bionole 3001
A laminated sheet was prepared in the same manner as in Example 1 except that (the heat of crystal fusion was 40 J / g). Table 1 shows the results. As a result, the surface resistivity was 5 × 10 ⁶ Ω, and burrs after punching were recognized.

(Comparative Example 2) The weight ratio of each component of the outer layer pellets was set to polylactic acid-based polymer / biodegradable aliphatic polyester / conductive agent = 55/45/9, and the weight of each component of the inner layer pellets was A laminated sheet was prepared in the same manner as in Comparative Example 1, except that the ratio was changed to polylactic acid-based polymer / biodegradable aliphatic polyester = 55/45. Table 1 shows the results.
As a result, the surface resistivity was 5 × 10 ⁶ Ω, and burrs and cracks after punching were not recognized as apparent from Table 1.

Comparative Examples 3 and 4 The weight ratio of the polylactic acid-based polymer and the biodegradable aliphatic polyester in the outer layer pellet and the inner layer pellet was as shown in Table 1, and the amount of the conductive agent in the outer layer pellet was as shown in Table 1. Was set to 9% by weight of the total amount of the polylactic acid-based polymer and the biodegradable aliphatic polyester, to produce a laminated sheet in the same manner as in Example 1. Table 1 shows the results. As a result, the surface resistivity was 5 × 10
^{It was 6} Ω, and burrs and cracks after punching were not recognized as apparent from Table 1.

(Comparative Examples 5 and 6) The weight ratio of the polylactic acid-based polymer and the biodegradable aliphatic polyester in the outer layer pellet and the inner layer pellet was as shown in Table 1, and the amount of the conductive agent in the outer layer pellet was as shown in Table 1. Was changed to 9% by weight of the total amount of the polylactic acid-based polymer and the biodegradable aliphatic polyester to prepare a laminated sheet in the same manner as in Comparative Example 1. Table 1 shows the results. As a result, the surface resistivity was 5 × 10
^{It was 6} Ω, and burrs and cracks after punching were not recognized as apparent from Table 1.

[0049]

[Table 1]

[0050]

According to the present invention, since a conductive agent is contained in the outer layer of the sheet having a laminated structure, the amount of the conductive agent used in the entire sheet can be reduced, and
Since the density of the conductive agent near the sheet surface can be increased, a sufficient surface resistance can be obtained.

Further, the heat of crystal fusion ΔHm is 55 J / g.
When the biodegradable aliphatic polyester described above is used, cracks and burrs of the molded body during punching are less likely to occur.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 67/02 C08L 67/02 67/04 ZBP 67/04 ZBP H01B 5/14 H01B 5/14 ZF term (reference) 3E067 AA11 AB41 AC04 BA10A BB14A BC07A CA21 CA30 EA32. CF18W CF18X CF19W CF19X DA036 DE096 DE126 FD116 FD170 GN00 GQ00 5G307 GA02 GB01 GC02

Claims (3)

[Claims] 1. A biodegradable conductive composite sheet comprising a plurality of layers, wherein an outer layer of the composite sheet contains at least a polylactic acid-based polymer, a biodegradable aliphatic polyester, and a conductive agent,
The mixing ratio between the polylactic acid-based polymer and the biodegradable aliphatic polyester is 50:50 to 90:10 by weight, and the inner layer of the composite sheet is formed of at least the polylactic acid-based polymer and the biodegradable fat. The mixing ratio between the polylactic acid-based polymer and the biodegradable aliphatic polyester is 50:50 to 90:10 by weight, and the heat of fusion of crystal of the biodegradable aliphatic polyester ΔHm
Is 55 J / g or more. 2. A molded article comprising the biodegradable conductive composite sheet according to claim 1. 3. A carrier tape comprising the biodegradable conductive composite sheet according to claim 1.