JPH0757852A - Waterproof heating element unit - Google Patents

Abstract

PURPOSE:To improve waterproofing property by covering a heating element unit with a waterproof insulating material consisting of an outer layer of a specified polyethylene shrink tube and an inner layer of an adhesive resin, and applying an adhesive resin to a lead wire leading hole. CONSTITUTION:This unit has a two-layer structure consisting of an outer layer 3 of a cross-linked polyethylene shrink tube and an inner layer 5 of a thermal shrink tube provided with an adhesive resin. As the adhesive resin of the layer 5, each hot melt composition such as ethylene vinyl acetate copolymer (EVA), ethylene ethyl acrylate copolymer (EEA), and ethylene methyl methacrylate copolymer (EMMA) is given, and the EVA hot melt composition is preferred from the viewpoint of working temperature and water absorptivity. Examples of an adhesive resin 2 to be filled in the leading hole of a wire 1 include hot melt compositions such as EVA, EEA, EMMA. The cover layer 7 of an electric linear heating element is polyethylene, polypropylene, or the like, the added adhesive resin is EVA, EEA, EMMA or the like, and the addition amount is preferably 3-15wt.%. Thus, reliability and waterproofing property are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric linear heating element unit used for snow melting, heating, drying equipment and the like.

[0002]

2. Description of the Related Art As a waterproofing method for electric parts and the like, there is a method in which a butyl rubber tape is spirally wound around each waterproof part without any gaps and covered with vinyl chloride tape and a shrink tube to protect the part. Disadvantages of this method are that it relies heavily on human labor, it is difficult to improve efficiency by machines, it is difficult to waterproof complex structures, especially those with large irregularities, and there are large variations in the waterproof performance of the products, resulting in poor yield. To be There is also a method of using an epoxy adhesive, but there are drawbacks such that the process is complicated because the two-liquid mixing method is the mainstream and the flexibility is lost after curing.

Although there is a waterproof insulation shrinkable tube commercially available in the past, parallel connection of lead wires (2
When the crotch drawer is applied, the insulation performance was not sufficiently secured.

[0004]

DISCLOSURE OF THE INVENTION As a result of investigations, the inventors of the present invention have found that when a waterproof coating is applied to the connection part of an electric linear heating element, insufficient adhesion between parts is caused, and a valley in the two-forked lead-out part occurs. The present invention has been made by discovering that water has invaded from a portion thereof, and the present invention provides a heating element unit which is improved in the above various drawbacks and is excellent in waterproofness.

[0005]

DISCLOSURE OF THE INVENTION The present invention is directed to an electric linear heating method in which a coating layer of a thermoplastic resin is coextruded on a core layer of a semiconductive composition in which carbon black is dispersed in a thermoplastic resin. A waterproof heating element unit having a cross-linked polyethylene shrink tube as an outer layer and a waterproof coating having an adhesive resin as an inner layer on a body connection portion and having a water insulation of 2000 MΩ or more.
The outer layer used here is a cross-linked polyethylene shrink tube, and the inner layer is made of an adhesive resin. The heat-shrinkable tube containing an adhesive resin has a two-layer structure as shown in FIG. 1, and the inner layer and the outer layer do not necessarily have to be integrated. The outer layer is a polyethylene shrink tube cross-linked with an electron beam, and is provided with flame retardancy as needed.

Examples of the adhesive resin for the inner layer include ethylene vinyl acetate copolymer (EVA), ethylene ethyl acrylate copolymer (EEA), ethylene methyl methacrylate copolymer (EMMA), polyester copolymer and nylon copolymer. There are various hot-melt compositions such as polymers, and EVA hot-melt composition compositions are preferable in terms of processing temperature and water absorption. The adhesive resin used in the present invention for filling the lead wire of the wire connecting portion, for example, a vinyl electric wire, has a hot melt composition such as EVA, EEA, EMMA, a polyester copolymer, and a nylon copolymer. Melt viscosity 2000-15000 cps
It is preferably about (180 ° C.). The adhesive resin that is the inner layer of the tube and the adhesive resin that fills the two-pronged outlet may be the same or different.

Although the above-mentioned adhesive resin has adhesiveness itself, it is preferable to use it in a hot-melt composition in order to enhance waterproofness. The hot melt has a high fluidity and fills the voids of the details. A tackifier and other additives may be used in combination with the hot melt. The hot melt filling method may be either a gun injection method or a pressure injection method using a mold. Examples of the thermoplastic resin used in the coating layer of the electric linear heating element used in the present invention include polyethylene (PE) and polypropylene (PP), and the adhesive resin added to this is EVA,
One or more of EEA, EMMA, maleic acid-modified PE and PP, and aionomer are used in combination. The amount of addition is preferably about 3 to 15% by weight in consideration of deterioration of physical properties.

FIG. 1 is a partial cross-sectional view of the insulating portion or waterproof portion of the waterproof heating element unit of the present invention.

[0009]

The present invention will be described in more detail based on the following examples. Example 1 An electric linear heating element was obtained by coextrusion molding a core layer of a semiconductive composition obtained by adding acetylene black to PP and a coating layer of PE. This heating element is cut into 2100 mm, holes are drilled at both ends with a 2 mm diameter drill, and crimp terminals are driven in.
00V vinyl insulated vinyl sheath electric wire is connected, EVA hot melt (product name Melter Ball manufactured by Konishi Co., Ltd.) is filled in the two-forked outlet of the electric wire, and the part is EVA hot melt internal heat shrink tube (Sumitomo Electric Sumitube W5C manufactured by Kogyo Co., Ltd., and heated for 2 minutes by a hot air generator (Hot air gun manufactured by Steinel), and then the waterproof part is left in water for 12 hours or more, and a battery-type insulation resistance meter (Mega Ohm manufactured by Hioki Electric Co., Ltd.) As a result of measuring the underwater insulation resistance with a high tester, a value of 2000 MΩ or more was obtained.

Example 1 In Example 1, P was used as a coating layer for the electric linear heating element.
A heating element unit was prepared in the same manner as in Example 1 except that EEA (12% by weight) was added and molded, and the underwater insulation resistance was measured to obtain a value of 2000 MΩ or more. The adhesiveness between the coating layer and the EVA-based hot melt interior heat shrink tube was also good. Comparative Example 1 An electric linear heating element was obtained by coextrusion molding a core layer of a semiconductive composition obtained by adding acetylene black to PP and a coating layer of PE. This heating element is cut into 2100 mm, holes are drilled at both ends with a 2 mm diameter drill, and crimp terminals are driven in.
Two 00V vinyl-insulated vinyl sheath electric wires are connected, and the heating element, crimp terminal, electric wire, and other parts are spirally wound with a self-bonding insulating tape (Fuco Tape No. 1 manufactured by Furukawa Electric Co., Ltd.) whose main component is butyl rubber. Winding, then spirally wrapping a self-fusing insulating tape (Fuco Tape No. 2 manufactured by Furukawa Electric Co., Ltd.) consisting of two layers of a polyethylene base material and an adhesive layer containing butyl rubber as a main component, and further protecting layer As a result of measuring the underwater insulation resistance in the same manner as in Example 1 after coating a vinyl chloride tape or a heat-shrinkable tube (Sumitube C manufactured by Sumitomo Electric Industries, Ltd.) cross-linked with an electron beam to prepare a heating element unit, 6 per 100 waterproof treatment points
Insulation failure (2000 MΩ or less) occurs at some places, resulting in poor yield.

Comparative Example 1 An electric linear heating element was obtained by coextrusion molding a core layer of a semiconductive composition made by adding acetylene black to PP and a coating layer of PE. This heating element is cut into 2100 mm, holes are drilled at both ends with a 2 mm diameter drill, and crimp terminals are driven in.
Two 00V vinyl-insulated vinyl sheath electric wires are connected, and the connection part is an EVA hot-melt interior type heat-shrinkable tube (Sumitube W5C manufactured by Sumitomo Electric Industries, Ltd.) or EVA.
After coating with one of the interior heat-shrinkable tubes (Sumitube W manufactured by Sumitomo Electric Industries, Ltd.) and heating in the same manner as in Example 1, the result of measuring the in-water insulation resistance in the same manner as in Example 1 shows which case. Also was 2000 MΩ or less, and the insulation was poor.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a wire connection portion and a waterproof portion of a heating element unit showing an embodiment of the present invention.

[Explanation of symbols]

 1: 600V vinyl insulated vinyl sheath electric wire 2: adhesive resin 3: outer layer of heat-shrinkable tube containing adhesive resin 4: crimp terminal 5: inner layer of heat-shrinkable tube containing adhesive resin 6: electrical conductive linear heating element semi-conductive layer 7 : Electric linear heating element coating layer

Claims (2)

[Claims] 1. An electric linear heating element formed by co-extruding a coating layer of a thermoplastic resin on a core layer of a semiconductive composition in which carbon black is dispersed in a thermoplastic resin. A waterproof heating element unit comprising a shrinkable tube, a coating of a waterproof insulating material whose inner layer is an adhesive resin, and an adhesive resin applied to the bifurcated outlets of the lead wires of the connection portion. 2. The waterproof heating unit according to claim 1, wherein the coating layer of the thermoplastic resin contains 3 to 50% by weight of the adhesive resin having a polar functional group.