JPH02281602A - Manufacture of polymer ptc element - Google Patents

Abstract

PURPOSE:To shorten the treating time of a polymer PTC element by a method wherein a PTC main body sheet consisting of a polymer, a conductive substance and a silane crosslinking agent is formed and this sheet is subjected to crosslinking treatment utilizing a microwave induction heating. CONSTITUTION:A raw material consisting of a polyvinylidene fluoride 1a, for example, as a polymer, a raw material consisting of a carbon black 1b as a conductive substance and a raw material consisting of a silane compound 1c as a crosslinking agent are kneaded and thereafter, the kneaded material is turned into a PTC main body sheet. This PTC main body sheet 1 is subjected to crosslinking treatment. This treatment is conducted while a microwave is irradiated using a microwave generator 10, such as a magnetron and the like, in a state that the sheet 1 is exposed in a water content-containing atmosphere on a supporting material 11. Thereby, the energy of the microwave is absorbed in water content in the sheet 1, water molecules are actively vibrated and a crosslinking reaction is promoted. Then, after the sheet is dried, electrodes are adhered on the surface and rear of the main body sheet 1 to punch in every unit sheet. Then, after leads are connected, a resin molding is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a polymer PTC element using a silane crosslinking agent as a raw material.

(Prior art) For example, when the main component is a polymer such as polyethylene, polypropylene, or polyvinylidene fluoride mixed with a conductive substance such as carbon black, its resistance suddenly decreases when the temperature is raised to a certain temperature. The so-called positive temperature coefficient (PTC) increases.

Po5ifyye Temperalure Coef
Polymer PTC elements having a ficient

To manufacture such a polymer PTC element, first, a polymer such as polyvinylidene fluoride, a conductive material such as carbon black, and a silane compound as a crosslinking agent are prepared as raw materials, and after kneading these materials, press molding is performed. Form a PTC main body sheet. Next, before drying this PTC main sheet, P is added to promote the crosslinking reaction of the silane compound contained therein.
Crosslinking treatment is performed by exposing the TC main body sheet to an atmosphere containing moisture, such as a water tank, and performing heat treatment. Such heat treatment allows oxygen in the moisture to permeate into the PTC main sheet, thereby promoting the crosslinking reaction. Conventionally, the heat treatment conditions for carrying out such a crosslinking reaction are approximately 80° C. for several hours.

After the crosslinking treatment, the polymer PTC element as shown in FIG. 3 is finally completed through steps such as drying, electrode attachment, punching, lead attachment, and resin molding. 1 is a PTC main body sheet, 2 and 3 are electrodes (conductive sheets) formed on the front and back surfaces of the main body sheet 1, 4.5 are solder 6,
Leads 8 are connected to the electrodes 2 and 3 via 7, and resin is used to cover the entire structure.

(Problems to be Solved by the Invention) However, in the conventional method for manufacturing a polymer PTC element, there is a problem in that the manufacturing efficiency is low because the crosslinking treatment is carried out over several hours.

The present invention has been made in response to the above-mentioned problems.
It is an object of the present invention to provide a method for manufacturing a polymer PTC element that reduces processing time.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a step of forming a PTC main body sheet consisting of a polymer, a conductive substance, and a silane crosslinking agent, The method is characterized by comprising a step of crosslinking the wafer by using microwave induction heating.

(Function) By crosslinking the PTC main sheet using microwave induction heating, the water in the PTC main sheet absorbs microwave energy and the oxygen molecules actively vibrate, resulting in a crosslinking reaction. promoted. As a result, the crosslinking reaction can be carried out to the same extent as conventional methods in a short period of time, so that production efficiency can be improved.

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

FIGS. 1(a) to 1(i) show an embodiment of the method for manufacturing a polymer PTC element of the present invention, which will be explained below in the order of the manufacturing steps.

First, in step (a), a polymer such as polyvinylidene fluoride (LAS), a conductive material such as carbon black LB, and a crosslinking agent such as silane compound IC
Prepare each raw material consisting of.

As the silane compound IC, well-known materials such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxysilane, vinyltriacetylsilane, etc.) can be used.

Next, in step (b), these raw materials are kneaded using a Labo Plastomill, etc., and then, in step (C), they are formed into a sheet using an extruder, etc., to produce PT as shown in Figure 2 (a).
C. Form the main body sheet 1. Next, this PTC main body sheet 1 is crosslinked as shown in (d). This crosslinking treatment
C The main body sheet 1 is exposed to an atmosphere containing moisture on the support 11, and as shown in FIG. . As a result, the microwave energy is absorbed by the water in the PTC main sheet 1, causing the water molecules to vibrate actively, thereby promoting the crosslinking reaction.

When energy is obtained using microwave induction heating in this way, the amount of heat generated by the microwave energy Q is expressed by the following equation.

Q=K f E2e tan δ Here, K: constant, f: microwave frequency, E: high frequency electric field between electrodes, ε: permittivity of dielectric, ε: Loss angle of dielectric.

As is clear from the above equation, the amount of heat generated Q can be easily varied by varying f when other parameters are held constant. As an example, by using a microwave generator 10 that generates microwaves of 915 MHI and a power of 200 to 300 W, it is possible to perform a crosslinking reaction to the same extent as in the conventional method by processing for 10 to 30 minutes. did it. With a power of 200 W, it takes about 30 minutes, but with a power of 300 W, a similar result can be obtained in about 10 minutes.

By appropriately controlling the calorific value Q, it is also possible to omit the drying step to be performed later.

By performing cross-linking treatment using microwave induction heating in this way, water molecules become actively thermally mobile, which accelerates the cross-linking reaction and achieves similar results in a shorter time compared to conventional methods. can be obtained.

Subsequently, as in step (e), the PTC main body sheet 1 is dried in a vacuum dryer, and in step (f), electrodes (conductive PT sheet) using 2.3
C. Adhere to the front and back surfaces of the main body sheet 1. As mentioned above (e
It is also possible to combine the drying step in (d) with the crosslinking step in (d). Next, in step (g), the PTC main body sheet 1 is punched out into unit sheets A, B, C, . . . as shown in FIG. 2(C) in order to manufacture individual parts. Then (h
) Each unit sheet A, B, C in the process.

After connecting the leads 4 and 5 to the electrodes (conductive sheet) 2.3 on the front and back surfaces via the solders 6 and 7, (
In step i), resin molding is performed to complete a polymer PTC element covered with resin 8 as shown in FIG.

As described above, according to this embodiment, the crosslinking treatment of the PTC main body sheet 1 in the step (d) in FIG. The same degree of crosslinking reaction can be carried out. This makes it possible to significantly shorten the crosslinking treatment time, thereby improving production efficiency.

The method of performing microwave induction heating can be easily realized by using microwave generation technology such as a magnetron used in a general microwave oven.

[Effects of the Invention] As described above, according to the present invention, the crosslinking treatment is performed using energy generated by microwave induction heating, so the treatment time is shortened and the crosslinking reaction can be performed to the same extent as in the past. can be set.

[Brief explanation of drawings]

FIGS. 1(a) to (i) are block diagrams showing an embodiment of the method for manufacturing a polymer'PTC element of the present invention, and FIG. 2(a)
to (c) are schematic diagrams of the device obtained in the main steps of this example, and FIG. 3 is a cross-sectional view showing the polymer PTC device.
FIG. 4 is an explanatory diagram of the crosslinking step of this example. 1... PTC main body sheet, 2.3... Electrode (conductive sheet), 10... Microwave generator.

Claims (1)

[Claims] PT consisting of polymer, conductive substance and silane crosslinking agent
C. A method for manufacturing a polymer PTC element, comprising the steps of forming a main body sheet and crosslinking the PTC main sheet using microwave induction heating.