JPH0716908A - Double layer corrugated tube - Google Patents

Abstract

PURPOSE:To provide a double layer corrugated tube made of synthetic resin wherein it is flame retardant, strong in tensile strength, free from occurrence of needless elongation and flexure, strong in an adhesive property between resin layers, and occurrence of inferior goods in manufacture of the tube and in processing can be restrained to improve its workability in addition thereto. CONSTITUTION:The double layer corrugated tube made of synthetic resin is constructed by extrusion molding a mixed resin of 90-30 pts.wt. of vinyl chloride resin and 10-70 pts.wt. of ethylene vinylacetate copolymer or chlorinated polyethylene resin as a flame retardant external layer 1 of 0.1-0.5mm wall thickness and olefin resin as an internal layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-layer corrugated tube made of synthetic resin used for wiring electrical equipment in buildings, factories and the like.

[0002]

2. Description of the Related Art Conventionally, wiring for electric equipment in buildings, factories, etc. is generally housed in an iron pipe for wiring. Although the iron pipe has an advantage that it is satisfactory in strength, it has disadvantages that it is heavy and inconvenient to handle, corrosive, and it requires a lot of labor and time for processing such as bending and cutting. Therefore, in recent years, tubes made of synthetic resin such as vinyl chloride resin have been used in place of the tubes made of iron.
Synthetic resin pipes are lightweight and have excellent corrosion resistance, which improves on the disadvantages of iron pipes. In addition, the corrugated pipes allow flexibility, so they can be carried on-site as long products. There are advantages. However, on the other hand, synthetic resin pipes have weak tensile strength, which causes unnecessary elongation and flexure, and when concrete is poured, the pressure causes the pipes to be displaced at the embedding position, impairing the retractability of electric wires. There is.

As a countermeasure against this, Japanese Utility Model Publication No. 55-43704 discloses that an inner pipe is a corrugated pipe and an outer pipe provided outside thereof is
An inner corrugated tube made of a synthetic resin material that is softer than the inner tube, with a corrugated portion that is smooth on the outer peripheral surface and that corresponds to the outer surface shape of the inner tube. There is disclosed a flexible conduit tube made of a synthetic resin fitted so as not to completely fill the valley portion of the. On the other hand, an electric wire tube for indoor wiring may be heated to about 50 to 60 ° C due to heat generation due to energization, and a material having a low Young's modulus is required from the necessity of maintaining the initial strength even at this temperature. In addition to the heat generated on the inner surface, flame resistance is required to protect the wires from heat such as fire. In order to meet such requirements, there has been proposed a product using hard polyethylene for the inner pipe and soft vinyl chloride for the outer pipe.

[0004]

However, since adhesion between olefin resin such as polyethylene and vinyl chloride resin is poor, it is difficult to solve the problem between the outer tube and the inner tube when making a conduit by coextrusion. Distortion may occur, and the outer tube may be peeled off or bent during the cutting of the conduit or the connection with the connector, which makes it unusable. In particular, when the vinyl chloride resin used for the outer tube contains a large amount of a liquid substance such as a plasticizer, bleeding, blooming or the like may significantly impair the adhesiveness and may not be able to withstand long-term use. Therefore, the object of the present invention is flame retardant, strong tensile strength and without the occurrence of unnecessary elongation and bending,
It is an object of the present invention to provide a two-layer synthetic resin corrugated pipe which has a strong adhesiveness between resin layers and which can suppress the generation of defective products during the production and construction of the pipe and improve workability.

[0005]

A two-layer corrugated tube made of synthetic resin according to the present invention comprises 90 to 30 parts by weight of vinyl chloride resin and ethylene-vinyl acetate copolymer or chlorinated polyethylene resin.
A resin mixture with 10 to 70 parts by weight is used as a flame-retardant outer layer having a thickness of 0.1 to 0.5 mm, and an olefin resin is extruded as an inner layer.

The present invention will be described in detail below. FIG. 1 shows one embodiment of the two-layer corrugated pipe made of synthetic resin of the present invention, in which 1 is a mixed resin layer of a vinyl chloride resin as an outer layer and an ethylene-vinyl acetate copolymer or a chlorinated polyethylene resin, Reference numeral 2 is an olefin resin layer as an inner layer. The vinyl chloride resin used for forming the mixed resin layer includes, in addition to vinyl chloride homopolymer, a copolymer of vinyl chloride containing 50% by weight or more of vinyl chloride and a copolymerizable vinyl monomer. , Graft polymers of vinyl chloride and various polymers or polyvinyl chloride and vinyl monomers, post-chlorinated vinyl chloride polymers and mixtures thereof, including bulk polymerization, suspension polymerization, emulsion polymerization, It is manufactured by either solution polymerization or the like. Vinyl-based monomers used in this copolymerization or graft polymerization include olefins such as ethylene and propylene;
Halogenated olefins other than vinyl chloride such as vinylidene chloride and vinyl fluoride; vinyl esters such as vinyl acetate and vinyl laurate; alkyl vinyl ethers such as 2-ethylhexyl vinyl ether and dodecyl vinyl ether; acrylic acid, methyl acrylate , Acrylic acid such as ethyl acrylate or esters thereof; methacrylic acid such as methacrylic acid, methyl methacrylate, 2-ethylhexyl methacrylate or esters thereof;
Maleic acid or its esters; fumaric acid or its esters; acrylic derivatives such as maleic anhydride, acrylonitrile and styrene; N-substituted maleimides such as Nt-butylmaleimide and N-cyclohexylmaleimide. Are used alone or in combination of two or more. The polymer that can be graft-polymerized with vinyl chloride or the polymer that is used as a mixture with the vinyl chloride-based polymer is a common polymer that is well miscible with the vinyl chloride-based polymer. Vinylidene chloride,
Examples thereof include ethylene-vinyl acetate copolymer, ABS resin, MBS resin, chlorinated polyethylene, and synthetic rubber such as NBR and SBR.

The plasticizer to be added to the vinyl chloride resin is not particularly limited as long as it is usually used in the production of soft molded articles, and examples thereof include dioctyl phthalate, dibutyl phthalate and butyl benzyl phthalate. Phthalates such as; dioctyl adipate,
Aliphatic dibasic acid esters such as di-n-butyl adipate and dibutyl sebacate; glycol esters such as pentaerythritol ester and diethylene glycol benzoate; phosphate esters such as tricresyl phosphate and triphenyl phosphate; epoxidation Epoxidized oils such as soybean oil and epoxidized linseed oil; citrate esters such as acetyltributyl citrate, acetyltrioctyl citrate, tri-n-butyl citrate; trialkyl trimellitate, tetra-n
-Octylpyromellitate, polypropylene adipate, other polyester-based plasticizers, NBR-based plasticizers, and the like are used, and these are used alone or in combination of two or more. Also, this vinyl chloride resin,
Further, if necessary, various additives such as stabilizers, stabilizing aids, fillers, colorants, lubricants, colorants, antistatic agents, processability improvers, antioxidants, UV inhibitors and flame retardants. You may mix | blend.

The mixing ratio of the vinyl chloride resin as the outer layer of the synthetic resin double-layer corrugated pipe of the present invention and the ethylene-vinyl acetate copolymer or the chlorinated polyethylene resin is 90 to 30 parts by weight of the vinyl chloride resin. On the other hand, it is 10 to 70 parts by weight of ethylene-vinyl acetate copolymer or chlorinated polyethylene resin. If the vinyl chloride resin exceeds 90 parts by weight, the adhesion to the olefin resin as the inner layer is not improved,
On the other hand, if the amount is less than 30 parts by weight, heat generation during extrusion molding, resin sticking to the die, burning, etc. are remarkable, the long-run property is lost, and in severe cases even extrusion may not be possible. The thickness of this outer layer is 0.1 to 0.5 mm.If it is less than 0.1 mm, it is too thin to burn when exposed to a flame, and even if the flame is released, it will not disappear and lack flame retardance. If it exceeds, thermal deformation under heating, tensile strength,
It is not preferable because impact strength and the like are reduced.

On the other hand, as the olefin resin used for forming the inner layer 2 of the two-layer corrugated pipe made of synthetic resin of the present invention,
Polyethylene, polypropylene, polybutene, polypentene, ethylene-propylene copolymers, ethylene-lower α-olefin copolymers, polyolefins such as cross-linked polyethylene, and copolymers of olefins and acrylic acid can be used. The thickness of the polyolefin-based resin as the inner layer may be adjusted in consideration of the relationship with the overall thickness within a range that does not reduce the mechanical strength.

[0010]

EXAMPLES Next, the present invention will be described more specifically by way of Examples and Comparative Examples. Examples 1-6, Comparative Examples 1-7. Polyvinyl chloride having an average degree of polymerization of 1310 shown in Table 1 (manufactured by Shin-Etsu Chemical Co., Ltd., P in the table)
Abbreviated as VC), ethylene-vinyl acetate copolymer: Soabrene CH (manufactured by Nippon Synthetic Chemical Company, trade name, abbreviated as EVA in the table) and chlorinated polyethylene: Eraslen 301A (manufactured by Showa Denko, trade name, CPE in the table) And tin-based stabilizer
Add 0.8 parts by weight, 0.5 parts by weight of stearic acid and 50 parts by weight of DOP (adjusted to have a hardness of 70 in the outer layer), heat to 120 ° C with a Henschel mixer, and dry up completely. It was cooled to ℃ and discharged outside the machine to obtain a resin for the outer layer. Using a high-density polyethylene (MI = 0.4, density = 0.96) for the inner layer, a two-layer pipe is extruded and blown along the mold surface while being sandwiched by the mold rotating in the extrusion direction. A long corrugated tube was continuously obtained by molding. The thickness of the double-layer corrugated tube was set to 1.0 mm as shown in Table 1, including the inner layer and the outer layer. Tensile strength, thermal deformation rate, impact strength, flammability and adhesiveness of the obtained double-layer corrugated pipe were measured by the following methods, and the results are also shown in Table 1.

(Test method) Tensile strength: During extrusion molding of a double-layer corrugated pipe, the thickness is passed through a sizing die so that the pipe is divided into two and the thickness does not change.
A 1.0 mm plate was created. Five No. 1 test pieces were prepared using this plate based on the tensile test method of JIS K-7113, and the tensile tester: Tensilon (trade name, manufactured by Orientec Co., Ltd.) was used for measurement.・ Heat deformation rate: After keeping the double-layer corrugated tube at 60 ± 2 ℃ for 4 hours,
A steel rod with a diameter of 6 mm was placed in the center of the pipe in a direction perpendicular to the pipe axis. Then add 2.0 kg weight on it and keep it for 24 hours,
The outer diameter of the double-layer corrugated pipe after removing the load was measured, and the rate of change from the initial outer diameter was taken as the thermal deformation rate.

Impact strength: 12 double-layer corrugated tubes at 60 ± 2 ° C
It was allowed to stand for 10 days at -25 ° C ± 2 ° C for 2 hours.
A 2.0 kg weight was dropped from a height of 100 ± 1 mm, and the damage condition of the double-layer corrugated pipe was observed and evaluated according to the following criteria. ○: No cracks, etc. Δ: No cracks, etc., but 10% or more of deformation or whitening is observed. ×: A crack or the like occurred.・ Combustibility: Holds a two-layer corrugated tube with a length of about 600 mm vertically.
Position 100 mm from the bottom of this sample at 45 ° to the horizontal plane.
Burn it for 55 seconds at the tip of the reducing flame of a tilted Bunsen burner (with an oxidizing flame length of about 100 mm and a reducing flame length of about 50 mm), and it will disappear naturally within 30 seconds when the flame is removed. Those that did not extinguish were designated as "self-extinguishing" and those that did not extinguish were designated as "continuation of combustion." -Adhesiveness: The peeling condition when peeled by hand along the laminated interface of the extruded double-layer corrugated tube was observed and evaluated according to the following criteria. ○ It cannot be peeled by hand. Δ: Peeling off by applying force. ×: Easy peeling.

[0013]

[Table 1]

[0014]

EFFECT OF THE INVENTION The synthetic resin double-layer corrugated pipe of the present invention is flame-retardant, has high tensile strength and impact strength, does not cause unnecessary elongation and bending, and has strong adhesiveness between resin layers. Since it is possible to suppress the generation of defective products during manufacturing and construction and improve workability, it is extremely useful for wiring for electrical equipment in buildings, factories and the like.

[Brief description of drawings]

FIG. 1 is a partial cutaway vertical sectional view showing one embodiment of a synthetic resin double-layer corrugated pipe of the present invention.

[Explanation of symbols]

1. A mixed resin layer of a vinyl chloride resin as an outer layer and an ethylene-vinyl acetate copolymer or a chlorinated polyethylene resin, 2. An olefin resin layer as an inner layer.

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Claims (1)

[Claims] 1. 90 to 30 parts by weight of vinyl chloride resin and ethylene-vinyl acetate copolymer or chlorinated polyethylene resin 10
A two-layer corrugated pipe made of synthetic resin, which is formed by extrusion-molding an olefin resin as an inner layer and a flame-retardant outer layer having a wall thickness of 0.1 to 0.5 mm with a mixed resin of up to 70 parts by weight.