JP2007204745A - Resin composition for corrugated cable conduit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrugated cable conduit having sufficient mechanical properties and flame resistance, requiring the use of no or minimum amount of a halogen based flame retardant and phosphorus based flame retardant. <P>SOLUTION: The resin composition for a corrugated cable conduit molded into a tubular shape having a rough surface and made for protecting a conduit inserted therein comprises 100 parts by wt. of a resin component containing 75-99 wt.% of high density polyethylene and 25-1 wt.% of at least one type of copolymer selected from ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-(meth)acrylic acid copolymer, and 3-39 parts by wt. of metal hydroxide that is surface-treated by a fatty acid, a fatty acid salt or a silane or titanate coupling agent as a surface treatment agent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin composition for corrugated conduits molded from a flame retardant resin composition mainly composed of high density polyethylene.

  For example, a communication cable or the like is installed in a state of being protected by being inserted from a corrugated electric conduit that is molded from a resin composition and has irregularities on its surface. In such a corrugated conduit, in recent years, in addition to mechanical strength such as compression recovery and resistance to buckling, flame retardance has become particularly important.

  Halogen-based flame retardants are used in conventional flame resistant conduits, which may cause harmful dioxins and the like during combustion and incineration. Therefore, flame retardant resin compositions using phosphorus flame retardants as an alternative to halogen flame retardants have been proposed, but some phosphorus flame retardants are highly toxic. In addition, red phosphorus has a risk of explosion if it is a simple substance before being blended with the resin.

  On the other hand, a non-halogen resin composition in which a metal hydroxide or a phosphorus flame retardant is blended with low density polyethylene or an ethylene copolymer has been proposed. However, when conduits are molded from these non-halogen resin compositions, the mechanical strength such as compression resilience and resistance to buckling becomes insufficient reflecting the characteristics of the base resin component. Is not preferable.

  Therefore, it is considered advantageous to use high-density polyethylene as the base resin component in order to obtain mechanical strength as a conduit. However, simply replacing the base resin component with high-density polyethylene has a problem in that the uniform dispersibility of the flame retardant deteriorates, leading to a significant decrease in mechanical strength.

  It is an object of the present invention to provide a corrugated conduit having sufficient mechanical properties and flame resistance with minimal or no use of halogen-based and phosphorus-based flame retardants. .

  According to one aspect of the present invention, there is provided a resin composition for a corrugated conduit that is formed into a tubular shape having an uneven surface and protects an electric wire that is inserted into the tube, wherein the resin composition comprises high-density polyethylene. 75 to 99% by weight, and at least one selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, 25 to 1% by weight Containing 100 parts by weight of a resin component, and 3 to 39 parts by weight of a metal hydroxide surface-treated with a fatty acid, a fatty acid salt, or a silane or titanate coupling agent as a surface treatment agent. A resin composition for corrugated conduits is provided.

  According to the present invention, it is possible to provide a corrugated conduit having sufficient mechanical properties and flame resistance without minimizing or using halogen-based and phosphorus-based flame retardants. .

  An example of a corrugated conduit according to the present invention is shown in FIG. As shown in FIG. 1, a crest 2 and a trough 3 are formed on the tube wall 1 of the corrugated conduit. With these structures, the surface of the tube is corrugated. In addition, although the peak part 2 and the trough part 3 are helically formed in the corrugated conduit of FIG. 1, you may form many independent peak parts 2 and trough parts 3 which make a round of the outer periphery of a pipe | tube. .

  The present inventors made corrugated electric pipes with various compositions using resin compositions containing high-density polyethylene, vinyl acetate-ethylene copolymer, and magnesium hydroxide, and evaluated the combustion characteristics and mechanical characteristics. As a result, it has been found that when the blending amount of magnesium hydroxide with respect to 100 parts by weight of the resin component is set to around 25 parts by weight, relatively excellent results are obtained in both combustion characteristics and mechanical characteristics. Moreover, when producing a corrugated conduit using the same resin composition, it discovered that combustion resistance changed with the thickness of a conduit. The present invention has been made paying attention to these points.

  In the present invention, at least 75 to 99% by weight of high-density polyethylene and at least selected from the group consisting of an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, and an ethylene- (meth) acrylic acid ester copolymer. A resin composition containing 100 parts by weight of a resin component composed of 25 to 1% by weight of one type and 3 to 39 parts by weight of a surface-treated metal hydroxide is used.

  If the blending amount of the high density polyethylene in the resin component is less than 75% by weight, sufficient mechanical properties cannot be obtained. When the blending amount of the high density polyethylene in the resin component exceeds 99% by weight, the flame resistance becomes insufficient. The density of the high density polyethylene is desirably 0.945 to 0.970. If the density of polyethylene is less than 0.945, the mechanical properties of the conduit will be insufficient. Polyethylene having a density exceeding 0.970 is not practical because there is no mass-market product with low cost. The MFR of the high density polyethylene is preferably 0.01 to 5 g / 10 minutes.

  The blending amount of at least one selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene- (meth) acrylic acid ester copolymer in the resin component is less than 1% by weight. If it exists, the flame resistance deteriorates. The blending amount of at least one selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene- (meth) acrylic acid ester copolymer in the resin component exceeds 17 parts by weight. And mechanical properties become insufficient. Of these resins, ethylene-vinyl acetate copolymer is preferred. The VA of the ethylene-vinyl acetate copolymer is preferably from 3 to 45, and the MFR is preferably from 0.2 to 80 g / 10 minutes.

  Magnesium hydroxide is used as the surface-treated metal hydroxide. When aluminum hydroxide is used, the kneading / extrusion temperature is set in consideration of its low thermal decomposition dehydration temperature. In order to increase the extrusion temperature in order to increase the extrusion speed, aluminum hydroxide from which adhering moisture has been removed by baking is used. Magnesium hydroxide has a high thermal decomposition dehydration temperature, and therefore, it is not necessary to perform a special treatment as in the case of aluminum hydroxide. As the surface treatment agent, fatty acid, fatty acid salt, or silane or titanate coupling agent is used. In addition, you may use together the metal hydroxide which is not surface-treated within the range which does not impair a mechanical characteristic.

  The compounding quantity of a metal hydroxide is set to 3-39 weight part with respect to 100 weight part of resin components. If the compounding amount of the metal hydroxide is less than 3 parts by weight, sufficient flame resistance cannot be obtained. If the compounding amount of the metal hydroxide exceeds 39 parts by weight, sufficient mechanical properties cannot be obtained. Moreover, when the compounding quantity of a metal hydroxide exceeds 39 weight part, since the frictional resistance of a surface becomes large and it becomes difficult to route a cable, it is not preferable. Furthermore, when adopting a construction method in which a plurality of conduits are passed through a larger-diameter plastic pipe, if the compounding amount of the metal hydroxide exceeds 39 parts by weight, the inner diameter of the large-diameter plastic pipe is also increased due to frictional resistance. It is not preferable because it is difficult to pass the electric pipe through.

  The corrugated conduit of the present invention preferably has a thickness of 0.75 to 1.20 mm. If the wall thickness is less than 0.75 mm, the flame resistance and mechanical properties deteriorate. If the thickness exceeds 1.20 mm, the basis weight increases, the cost increases, and the flexibility deteriorates, which is not preferable. In order to pass the flame resistance specified in JIS C8411, it is preferable to change the wall thickness within the above range according to the amount of the metal hydroxide. In particular, it is preferable to increase the wall thickness as the amount of the metal hydroxide is reduced.

  As described above, according to the present invention, a corrugated conduit having excellent mechanical properties and heat resistance and excellent manufacturability can be obtained only within a relatively limited composition range.

  In addition, the corrugated conduit of the present invention includes pigments, antioxidants, weathering agents, silicone-based or nitrogen-containing flame retardants, surface-treated or untreated calcium carbonate, as long as the mechanical properties are not deteriorated. You may mix | blend suitably inorganic fillers, such as clay and a talc, the metal hydroxide of the surface untreated, and other resin components.

Examples 1-15, 17 and Comparative Examples 1-8
The following raw materials were used.
High density polyethylene (HDPE-1): Idemitsu Petrochemical, density 0.962, melt index (MI) 0.11
High density polyethylene (HDPE-2): Idemitsu Petrochemical, density 0.957, MI 0.04
Ethylene-vinyl acetate copolymer (EVA): manufactured by Mitsui DuPont, MI 4.0, VA28
Ethylene-ethyl acrylate copolymer (EEA): manufactured by Nihon Unicar, MI 1.6, EA content 24%
Magnesium hydroxide-1: surface treatment available, manufactured by Kyowa Chemical Co., Ltd.
Magnesium hydroxide-2: With surface treatment, manufactured by Kamishima Chemical Co., Ltd.

  Each said component was mix | blended in the predetermined | prescribed ratio shown in Table 1, Table 2, and Table 3, and it extruded and manufactured the corrugated electric wire pipe | tube with an internal diameter of about 16 mm which has the thickness shown in each table | surface.

The following test was done about the obtained corrugated conduit.
Compression test: Conforms to the compression restoration test of JIS C8411. Those with a compression reduction rate of less than 7% that passed, ◯, those with a compression reduction rate of 7% or more and 10% or less, △, those with a compression reduction rate of over 10%, and failure Is indicated by x.

  Flame resistance test: Complies with JIS C8411 flame resistance test. Each of three samples was tested. Those with afterflame time of 1 second or less passed, and those with afterflame time exceeding 1 second were both, but those that passed within 30 seconds were both △, failed. The result is indicated by x.

Lineability test: Cables (VVF, EEF, IV, IE) were inserted into a 10-meter conduit provided with three R100 mm bends, and the line tension was measured. The case where the line tension is less than twice the tension when the cable is inserted into a corrugated conduit using a conventional halogen flame retardant (Comparative Example 4) is more than 2 times. △ is the case. Here, VVF: P V C insulated P V C sheathed cable F lat type; EEF: P E insulated P E sheathed cable F lat type; IV: I ndoor P V C insulated wire; IE: In I ndoor P E insulated wire is there.

  Flexibility test: Conforms to the flexibility test of JIS C8411. The following evaluation was performed at -15 ° C. A corrugated conduit having an inner diameter of 16 mm is bent and held by 90 ° along the outer periphery of a cylinder having a diameter of 138 mm (outer diameter × 6), and then returned to a linear shape. After this operation is repeated seven times, a 12.2 mm diameter (75% of the inner diameter) gauge is passed through the corrugated conduit tube while the corrugated conduit tube is bent. The case where the gauge passed smoothly was marked with ◯, and the case where the gauge was difficult to pass due to deformation was marked with △.

As is apparent from Tables 1 to 3, the corrugated conduit of each Example satisfying the composition range defined in the present invention has a small compression reduction rate, excellent flame resistance, and excellent wiring properties.

The perspective view which shows an example of the corrugated conduit tube which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pipe wall 2 ... Mountain part 3 ... Valley part

Claims (2)

A resin composition for a corrugated conduit that is molded into a tubular shape having irregularities on the surface and protects an electric wire inserted through the inside, wherein the resin composition is
High-density polyethylene 75 to 99% by weight, and at least one selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer 25-1 100 parts by weight of a resin component containing% by weight;
As a surface treatment agent, a fatty acid, a fatty acid salt, or 3-39 parts by weight of a metal hydroxide surface-treated with a silane-based or titanate-based coupling agent is used. Resin composition.   2. The resin composition for corrugated conduits according to claim 1, wherein the high density polyethylene has a density of 0.945 to 0.970 and a melt flow rate of 0.01 to 5 g / 10 min.

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