JP2002358829A - Electric insulation material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable high voltage electric insulation material with high dielectric breakdown voltage, having good shape of electric tree. SOLUTION: The electric insulation material contains polylactic acid group resin. On the basis of total repeated structure units of a molecule, polylactic acid group resin with average molecular weight of 10,000-1,000,000 (Mw) has repeated structure units originated in lactic acid (lactic acid unit) by 70-100 mol%, and glycolic acid units, and/or hydroxycapronic acid unit as a unit other than lactic acid unit by 0-30 mol%. As the results, (1) a high voltage electric insulation material with biodegradation property is provided, (2) a high voltage electric insulation material with high dielectric breakdown voltage is provided, and (3) a high voltage electric insulation material having electric tree of good shape is provided and (4) a high voltage electric insulation material combined with excellent biodegradation property, high dielectric breakdown voltage, and electric tree of good shape, are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical insulating material containing a lactic acid-based resin that can withstand a high voltage of 1 kV or more. The present invention further relates to an electric cable, an electric component, and a high-voltage power supply mold including an electric insulating material containing a polylactic acid-based resin.

[0002]

2. Description of the Related Art Conventionally, low-density polyethylene, which has been used as an insulating material for high-voltage electric cables such as power lines,
Since the insulator has a low melting point and may be deformed when the conductor generates heat when the cable is energized, the insulator may be deformed. The power cable manufacturing method that requires this cross-linking step has a problem in that the time required for the manufacturing is long in order to complete the cross-linking reaction.

[0003] Insulating materials for high voltage are required to be resistant to dielectric breakdown (high dielectric breakdown voltage) in addition to insulating properties. Electric cables are expected to have higher voltages in the future, and it is desired that the electric cables have a higher dielectric strength than the current crosslinked polyethylene. In addition, polyethylene has a problem that it is difficult to detect dielectric breakdown in advance because the electrical tree at the time of dielectric breakdown is long.

On the other hand, used electric cables are separated and metals are recycled, but cross-linked resins are difficult to reuse due to their properties. Disposal of the waste resin thus generated has become a problem in recent years, like other waste treatments. Further, when the temporary cable is buried in the soil, it takes a huge cost to recover it from the soil again. Otherwise, the resin is left in the environment semipermanently.

[0005]

One of the problems to be solved by the present invention is to provide a biodegradable high-voltage electrical insulating material. One of the problems to be solved by the present invention is to provide a high-voltage electrical insulating material having a high dielectric breakdown voltage. One of the problems to be solved by the present invention is to provide a high-voltage electric insulating material having a good electric tree shape. One of the problems to be solved by the present invention is to provide a high-voltage electrical insulating material having excellent biodegradability, high dielectric breakdown voltage, and good electrical tree shape.

[0006]

Means for Solving the Problems In view of the problems to be solved by the above-mentioned invention, the inventors of the present invention have described in the prior art polylactic acid, which has been spotlighted only by its biodegradability by those skilled in the art. As a result of intensive studies on various physicochemical properties of the resin, surprisingly, the inventors have found that the polylactic acid resin has extremely excellent insulating properties, and have completed the present invention. And
Based on this surprising knowledge, as a result of intensive studies,
The present inventors have found that the above problem can be solved by using a polylactic acid-based resin as an electrical insulating material, and have completed the present invention. That is, the present invention is specified by the matters described in the following [1] to [6].

[1] An electrical insulating material containing a polylactic acid-based resin.

[2] The polylactic acid-based resin contains 70 to 100 mol% of a repeating structural unit derived from lactic acid (lactic acid unit) based on all repeating structural units in the molecule, and a repeating structural unit other than the lactic acid unit. A repeating structural unit (glycolic acid unit) derived from glycolic acid, and / or
Having a repeating structural unit (hydroxycaproic acid unit) derived from hydroxycaproic acid of 0 to 30 mol%, and
The electrical insulating material according to [1], having a weight average molecular weight (Mw) of one million.

[3] The isomer content in the repeating structural unit (lactic acid unit) derived from lactic acid in the polylactic acid resin is as follows:
The electric insulating material according to [1] or [2], which is 0 to 10 mol%.

[4] An electric cable including at least a part of the electric insulating material according to any one of [1] to [3].

[5] An electric part comprising at least a part of the electric insulating material according to any one of [1] to [3].

[6] A high-voltage power supply mold including at least a part of the electrical insulating material according to any one of [1] to [3].

[0013]

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

[Polylactic acid-based resin] In the present invention, the polylactic acid-based resin includes polylactic acid, a copolymer of lactic acid and a copolymerizable polyfunctional compound such as hydroxycarboxylic acid, and a mixture thereof. . The polylactic acid-based resin has at least 50 mol% or more of a repeating structural unit derived from lactic acid (lactic acid unit) based on all repeating structural units in the molecule. In the case of a mixture, components other than the polylactic acid-based resin are less than 30% by weight. In the case of a mixture, a compatibilizer may be contained.

[0015] Among these polylactic acid resins, preferred are polylactic acid, which is a homopolymer, or a copolymer containing 0 to 10 mol% of a repeating structural unit other than a lactic acid unit. In the case of polylactic acid, poly-L-lactic acid or poly-D-lactic acid having an optical isomer content of 0 to 10 mol% is more preferable. That is, the number of repeating structural units (lactic acid units) derived from D-lactic acid is 0.
Poly L-lactic acid containing 10 to 10 mol% or poly D-lactic acid containing 0 to 10 mol% of a repeating structural unit (lactic acid unit) derived from L-lactic acid is particularly preferred. Poly L-lactic acid containing 1 to 8 mol% of a repeating structural unit (lactic acid unit) derived from D-lactic acid is more preferable.

When the polylactic acid-based resin is a copolymer, the arrangement of the copolymer may be any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer. Further, these may be at least partially cross-linked with a polyvalent isocyanate such as xylylene diisocyanate or 2,4-tolylene diisocyanate, or a cross-linking agent such as cellulose, a polysaccharide such as acetyl cellulose or ethyl cellulose. A part may have any structure such as a linear, annular, branched, star-like, and three-dimensional network structure, and is not limited at all.

[Lactic acid] Lactic acid as a raw material is L-lactic acid, D-lactic acid,
-Lactic acid, DL-lactic acid, or a mixture thereof. When lactide, which is a cyclic dimer of lactic acid, is used as a raw material of the resin, L-lactide, D-lactide, and meso-lactide, or And mixtures thereof.

[Copolymerizable polyfunctional compound] Examples of the copolymerizable polyfunctional compound include glycolic acid,
2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid ,
Hydroxycarboxylic acids such as 2-hydroxycaproic acid, 3-hydroxycaproic acid, 4-hydroxycaproic acid, 5-hydroxycaproic acid, 6-hydroxycaproic acid, 6-hydroxymethylcaproic acid, and mandelic acid;
Cyclic esters such as glycolide, β-methyl-δ-valerolactone, γ-valerolactone, ε-caprolactone;
Saturated aliphatic polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid,
And anhydrides thereof; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 3-methyl-
1,5-pentanediol, 2,3-butanediol,
Polyhydric alcohols such as 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, tetramethylene glycol, and 1,4-hexanedimethanol; polysaccharides such as cellulose;
Examples thereof include aminocarboxylic acids such as α-amino acids. Of these, glycolic acid and 6-hydroxycaproic acid are preferably used, and the content (copolymer composition) is 0 to 30 mol%. These copolymerizable polyfunctional compounds may be one kind or a mixture of two or more kinds, and when having an asymmetric carbon, L-form, D-form, and a mixture of any ratio thereof may be used. Good.

[Method for Producing Polylactic Acid Resin] The method for producing the polylactic acid resin used in the present invention is not particularly limited, and is described, for example, in JP-A-59-096123 and JP-A-7-033861. A method of directly dehydrating and condensing lactic acid, or US Pat. No. 4,057,3
No. 57, Polymer Bulletin, Vol. 14,
491-495 (1985), Makromol.
Chem. 187, pp. 1611-1628 (198
6)) and the method of ring-opening polymerization using lactide which is a cyclic dimer of lactic acid.

[Weight average molecular weight of polylactic acid-based resin] The weight-average molecular weight (Mw) of the polylactic acid-based resin used in the present invention is not particularly limited, but may range from 10,000 to 1
Million is preferable, 30,000 to 500,000 is more preferable, and 50,000 to 300,000 is further preferable. Weight average molecular weight (Mw) and molecular weight distribution (Mw) of the polylactic acid resin used in the present invention
/ Mn) is a desired one by appropriately selecting reaction conditions such as the type of raw materials, the type of solvent, the type and amount of catalyst, the reaction temperature, the reaction time, and the degree of dehydration of the reaction system in the production method. Can be controlled.

[Use] Polylactic acid-based resin has high insulating properties and can be widely used as an electrical insulating material. The electric insulating material of the present invention includes, for example, coating materials for electric wires and cables, consumer and industrial electronic devices, OA devices such as copiers, computers, printers, general insulating materials such as instruments, rigid printed wiring boards, flexible Printed wiring boards, high-frequency circuit boards for sanitary communication devices, etc., base materials for transparent conductive films such as liquid crystal substrates, optical memories, surface heating elements such as automobile and aircraft defrosters, various memories, transistors, ICs, LSIs, and LEDs・ Semiconductor elements such as MCM and sealing materials and parts, sealing materials for electric and electronic parts such as motors, contactors, switches, and sensors; body materials such as televisions and video cameras; parabolic antennas, flat antennas, and radar dome structures Member, interlayer insulating film between wirings inside the multi-chip module, or Enmaku include a planarization film, a surface protective film and the flexible circuit substrate or the like.

The electrical insulating material containing the polylactic acid-based resin of the present invention has a high dielectric breakdown voltage, and is therefore particularly preferably used as a high-voltage insulating material. In the present specification, a high voltage is a voltage of at least 100 V / mm or more, preferably a voltage of at least 500 V / mm or more, more preferably a voltage of at least 1 kV / mm or more, and more preferably a voltage of at least 5 kV / mm or more. More preferably at least 10 kV / mm or more, more preferably at least 50 kV / mm or more, more preferably at least 100 kV / mm or more, more preferably at least 500 kV / mm or more, more preferably at least 1000 kV. / Mm
It means the above voltage. According to the present invention, 500 kV / m is difficult to realize with the prior art materials.
Even if a high voltage of 600 kV / mm or more is applied, the insulating properties can be favorably exhibited without breaking. For example, it can be used for an electric cable used for power transmission and the like, a mold for a high-voltage power supply, and the like. A high-voltage electric cable is an electric cable in which at least a conductor is covered with an insulating layer containing a polylactic acid-based resin. A layer can be provided, or a flame-retardant resin layer can be formed outside the insulating layer. In addition, conductive carbon, or a wire made of a copper collective wire, or a resin composition to which metal powder is added to form a semiconductive layer, and a polylactic acid-based resin is coated thereon to form an insulating layer. Covered with a metal sheet, or provided with a semiconductive layer, the outermost cable coated with a flame-retardant resin or rat repellent resin, carbon single copper wire, or a resin composition with a metal powder added Cover to form a semiconductive layer, cover it with a polylactic acid-based resin to form an insulating layer, further provide a metal film layer thereon, and combine several to several tens of such copper wire coatings on the outermost Examples include a cable coated with a flame-retardant resin or a mouse repellent resin. Polylactic acid-based resins are particularly effective for high-voltage electricity, and are suitably used as large-capacity cables and DC cables.

The insulating material for an electric cable according to the present invention comprises:
It is suitably used for a power cable of 6.6 kV or more and a power cable of 66 kV or more. The electric cable of the present invention using the electric cable insulating material is formed by a known method. The structure of the cable of the present invention is formed by continuous coating on a conductor. Further, as the structure of the cable of the present invention, a conductor coated with an insulator on a single layer, a jacket, a separator with a conductor, a conductor, a semiconductor layer provided on an insulator, etc. Is mentioned.

[Additives] Additives can be added to the polylactic acid resin used in the present invention according to the purpose. Examples of additives include heat stabilizers, light stabilizers, antioxidants,
Examples include ultraviolet absorbers, pigments, colorants, various fillers, antistatic agents, release agents, fragrances, lubricants, flame retardants, foaming agents, fillers, antibacterial agents, antibacterial agents, nucleating agents, and the like.

[0025]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.

The weight average molecular weight (Mw) of the GPC polylactic acid-based resin was evaluated by gel permeation chromatography (GPC) using polystyrene as a standard under the following conditions. Apparatus: Shodex GPCsystem-11 Column: PLgel 5 μm MIXED-C (manufactured by Polymer Laboratories) Solvent: chloroform Concentration: 1% by weight Injection volume: 20 μL Flow rate: 1.0 mL / min

The dielectric constant, dielectric loss tangent, and volume specific resistance of the sample
The test method for the dielectric constant, dielectric loss tangent, and volume resistivity of a sample
ASTM D-150, D-150, D-2
57.

Evaluation of biodegradability Biodegradability was measured by using a test film piece of 5 × 5 cm (thickness: 0.2).
mm) was buried in soil at a temperature of 35 ° C. and a water content of 30%, and a decomposition test was carried out to observe changes in appearance.

Production Example 1 100 parts by weight of L-lactide, 0.01 part of stannous octoate, and 0.03 part of lauryl alcohol were charged into a thick cylindrical stainless steel polymerization vessel equipped with a stirrer. Then, after degassing under vacuum for 2 hours, the atmosphere was replaced with nitrogen gas. The mixture was heated at 200 ° C. for 3 hours with stirring under a nitrogen atmosphere. While maintaining the temperature as it was, the air was gradually degassed by a vacuum pump through an exhaust pipe and a glass receiver, and the pressure inside the reaction vessel was reduced to 3 mmHg.
One hour after the start of degassing, the distillation of the monomer and low molecular weight volatiles disappeared, so the inside of the container was replaced with nitrogen, and the polymer was extracted from the lower part of the container into a strand and pelletized.
Polylactic acid was obtained. The weight average molecular weight was 136,000.

[Production Example 2] 100 g of 90% L-lactic acid was placed in a 1 L reactor equipped with a Dien-Stark trap.
Was distilled off while stirring at 150 ° C. and 50 mmHg for 3 hours, and then 0.062 g of tin powder was added.
The mixture was stirred for another 2 hours at mmHg to oligomerize. To this oligomer, 0.288 g of tin powder and 211 g of diphenyl ether were added, azeotropic dehydration was performed at 150 ° C. and 35 mmHg, the distilled water and the solvent were separated by a water separator, and only the solvent was returned to the reactor. After 2 hours, the solvent returned to the reactor was 4
After passing through a column packed with 60 g of molecular sieves 3A and returning to the reactor, it was heated at 150 ° C. and 35 m
The reaction was performed at mHg for 40 hours to obtain a polylactic acid solution. To this solution, 440 g of dehydrated diphenyl ether was added, diluted and cooled to 40 ° C., and the precipitated crystals were filtered, washed with 100 g of n-hexane three times, and washed.
It dried at 50 degreeC and 50 mmHg. This powder was added with 120 g of 0.5N hydrochloric acid and 120 g of ethanol, stirred at 35 ° C. for 1 hour, filtered, dried at 60 ° C. and 50 mmHg,
Polylactic acid was obtained. The weight average molecular weight of this polylactic acid is 1
It was 45,000.

[Production Example 3] 90 parts by weight of L-lactide, D
10 parts by weight of L-lactide (1: 1 mixture of L-lactide and D-lactide), 0.01 part of stannous octoate, and 0.03 part of lauryl alcohol were added to a thick cylindrical form equipped with a stirrer. Preparation example 1
A heating reaction was carried out in the same manner as described above. After completion of the reaction, the polymer was drawn out from the lower part of the container in a strand shape and pelletized to obtain poly L-lactic acid containing 5 mol% of an optical isomer (a repeating structural unit (lactic acid unit) derived from D-lactic acid). The weight average molecular weight was 151,000.

[Preparation Example 4] 97 parts by weight of L-lactide, 3 parts by weight of glycolide, 0.01 part of stannous octoate, and 0.03 part of lauryl alcohol were used. Preparation Example 1
A heating reaction was carried out in the same manner as described above. After the completion of the reaction, the polymer is drawn out from the lower part of the container in a strand form and pelletized, and a repeating structural unit derived from lactic acid (lactic acid unit) 96 mol%, a repeating structural unit derived from glycolic acid (glycolic acid unit)
Lactic acid-glycolic acid copolymer containing 4 mol% of The weight average molecular weight was 145,000.

Production Example 5 97 parts by weight of L-lactide, ε
-3 parts by weight of caprolactone and stannous octoate 0.
01 parts and 0.03 part of lauryl alcohol were charged into a thick cylindrical stainless steel polymerization vessel equipped with a stirrer, and heated and reacted in the same manner as in Production Example 1. After the completion of the reaction, the polymer was withdrawn from the lower part of the vessel in the form of a strand and pelletized. % Lactic acid-hydroxycaproic acid copolymer was obtained. The weight average molecular weight was 122,000.

[Production Example 6] A catalyst-containing polyethylene (SLMB12; 23.1 g) was mixed with 300 g of low-density polyethylene (Mirason SL011 manufactured by Mitsui Chemicals) and formed into a sheet at 165 ° C (sheet thickness 0.1 m).
m). Thereafter, the sheet was immersed in water at 80 ° C. and allowed to stand overnight to perform a crosslinking reaction, and then the sheet was taken out and dried well.

Example 1 Poly-L obtained in Production Example 1
Lactic acid is pressed at 200 ° C with a hot press machine,
A molded product having a thickness of mm was obtained. This molded body is placed in a dryer for 12 hours.
Heat treatment was performed at 0 ° C. for 5 minutes. This molded body sample was divided into two 3
Sandwiched between inch SUS sphere electrodes, waveform 1.2 × 50
When a microsecond impulse voltage was applied three times at 3 kV step and the voltage when the sample was destroyed was measured,
It was 0 kV / mm. The electrical tree shape at the time of dielectric breakdown was also good. Dielectric constant is 3.0, dielectric loss tangent is 110 × 10
⁻⁴ , the volume resistivity was 1 Ω · cm × 10 ¹⁶ or more. As a result of the biodegradation test, the shape easily collapsed by external force after three months.

Example 2 Poly-L obtained in Production Example 2
Lactic acid is treated in the same manner as in Example 1, and molded to a thickness of 0.1 mm.
I got a body. This molded body sample was subjected to impeller
When measuring the loose dielectric breakdown strength, 640 kV / mm
Met. The shape of the electric tree was also good. The dielectric constant is
3.1, dielectric loss tangent 120 × 10^-4, Volume resistivity is 1
Ω · cm × 10 ¹⁶That was all. As a result of the biodegradation test,
Three months later, the shape easily collapsed due to external force.

Example 3 A poly-L-lactic acid containing 5 mol% of the optical isomer (a repeating structural unit (lactic acid unit) derived from D-lactic acid) obtained in Production Example 3 was molded in the same manner as in Example 1. Thus, a molded product having a thickness of 0.1 mm was obtained. This molded body sample is
When the impulse breakdown strength was measured in the same manner as in Example 1, it was 702 kV / mm. The shape of the electric tree was also good.

[Example 4] 96 mol% of the repeating structural unit derived from lactic acid (lactic acid unit) obtained in Production Example 4 and 4 repeating structural units derived from glycolic acid (glycolic acid unit)
Example 1 A lactic acid-glycolic acid copolymer containing mol%
To obtain a molded body having a thickness of 0.1 mm. When the impulse breakdown strength of this molded body sample was measured in the same manner as in Example 1, it was 610 kV / mm. The shape of the electric tree was also good.

[Example 5] 96 mol% of a repeating unit derived from lactic acid (lactic acid unit) obtained in Production Example 5 and 4 mol% of a repeating unit derived from 6-hydroxycaproic acid (hydroxycaproic acid unit) were contained. Lactic acid-hydroxycaproic acid copolymer was molded in the same manner as in Example 1,
A molded product having a thickness of mm was obtained. When the impulse breakdown strength of this molded sample was measured in the same manner as in Example 1, it was 59%.
It was 0 kV / mm. The shape of the electric tree was also good.

[Comparative Example 1] The molded article (0.1 mm thick) of the crosslinked polyethylene obtained in Production Example 6 was measured for impulse dielectric breakdown strength in the same manner as in Example 1, and found to be 483 k.
V / mm. There is a problem that the electrical tree at the time of dielectric breakdown is long and it is difficult to detect the dielectric breakdown in advance. Dielectric constant 2.3, dielectric loss tangent <5 × ^{10 -4,} the volume resistivity was 1Ω · cm × ^{10 1 6} or more. As a result of the biodegradability test, there was no change in appearance for 12 months or more, and no biodegradability was exhibited.

[0041]

The high-voltage electrical insulating material of the present invention has a high dielectric breakdown voltage and is excellent in electrical insulation and biodegradability, so that it can be widely used in various fields. One of the effects of the present invention is to provide a high-voltage electrically insulating material having biodegradability. One of the effects of the present invention is to provide a high-voltage electrical insulating material having a high dielectric breakdown voltage. One of the effects of the present invention is to provide a high-voltage electrical insulating material having a good electrical tree shape. One of the effects of the present invention is to provide a high-voltage electrical insulating material having excellent biodegradability, high dielectric breakdown voltage, and good electrical tree shape.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J029 AA02 AD01 AD10 AE16 EA02 EA03 EA05 KB02 5G305 AA02 AB02 AB05 AB35 BA12 CA01

Claims (6)

[Claims] 1. An electrical insulating material comprising a polylactic acid-based resin. 2. The polylactic acid-based resin contains 70 to 100 mol% of a repeating structural unit derived from lactic acid (lactic acid unit) based on all repeating structural units in the molecule, and glycol as a repeating structural unit other than the lactic acid unit. Having a repeating structural unit derived from an acid (a repeating structural unit derived from glycolic acid (glycolic acid unit)) and / or a repeating structural unit derived from hydroxycaproic acid (hydroxycaproic acid unit) of 0 to 30 mol%, and having 10,000 The electrical insulating material according to claim 1, having a weight average molecular weight (Mw) of １００1,000,000. 3. The isomer content of the repeating unit derived from lactic acid (lactic acid unit) in the polylactic acid-based resin is from 0 to 1
The electrical insulating material according to claim 1, wherein the amount is 0 mol%. 4. An electric cable comprising at least a part of the electric insulating material according to claim 1. 5. An electrical component comprising at least a part of the electrical insulating material according to claim 1. 6. A high-voltage power supply mold comprising at least a part of the electrical insulating material according to claim 1.