JPS63138701A - Manufacture of ptc device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an electric element, and more specifically, the present invention relates to a method for manufacturing an electric element, and more particularly, the present invention relates to a method for manufacturing an electric element, and more particularly, to CPo5t mouth veteran
The present invention relates to a method for manufacturing a device having a PTC device, that is, a PTC device.

[Conventional technology]

PTC compositions are used in heaters that stop generating heat when the temperature rises to a certain level, and positive characteristic thermistors (PTC THERMISTE).
I? ) When a circuit containing a thermal sensor, battery, etc. is short-circuited, the resistance value increases due to self-heating based on Joule heat, limiting the overcurrent to a predetermined current or less, and the circuit returns to normal when the short circuit is removed. It can be used as a circuit protection element, etc. Currently, various materials have been developed as PTC composite acids, such as those in which conductive particles such as carbon black are uniformly dispersed in at least one polymer resin such as polyethylene or ethylene-acrylic acid copolymer. be.

Conventionally, the preparation of PTC compositions is generally made by adding the required amount of carbon black to one or more resins used as polymers and kneading them, for example, in a niegu and/or two-roll mill. There is. A PTC element is manufactured from this PTC composition, for example, in the following manner. This PTC composition is formed into a film, metal foil electrodes are thermocompressed on the top and bottom of the film to form a laminate, this laminate is cut into desired dimensions, and the leads on the electrode surfaces are electrically connected. It is manufactured by

[Problems to be Solved by the Invention] Preferred characteristics for a PTC element and a PTc composition are a high resistance value (peak resistance) at high temperatures and a low resistance value of 100 mΩ or less at room temperature (room temperature resistance). ), that is, to obtain a high ratio of peak resistance/room temperature resistance.

However, the conventional method of manufacturing a PTC element does not necessarily provide a low room temperature resistance value, and furthermore, there is a problem that the room temperature resistance value varies greatly depending on the manufacturing loft.

The present invention has been made based on the above background,
The purpose is to provide a method for manufacturing a PTC element that has a low room temperature resistance of 100 mΩ or less and has no variation in room temperature resistance from manufacturing loft to manufacturing loft. ``[Means for solving the problem] In order to achieve the above-mentioned purpose, the present inventor has conducted various tests and researches to solve the problem by subjecting the mixed material obtained from kneading to a thermal history of heating and rapid cooling. The present invention was completed based on the knowledge that an element having good PTC characteristics can be obtained.

That is, the method for manufacturing a PTC element of the present invention is a method for manufacturing a PTC element comprising at least two metal electrodes and a PTC composition bonded to the electrodes,
C, [The acid compound is made by kneading at least one kind of polymer and conductive particles such as carbon black, and the particles are uniformly dispersed in the polymer, and the PTC composition is mixed with the polymer used for crosstalk. It is characterized by heating to a temperature close to the melting point of the polymer having the lower melting point among the coalesced materials, and then subjecting the heated mixture to a heating and rapid cooling step of rapidly cooling it to a temperature below zero degrees.

In a preferred embodiment of the present invention, the temperature near the melting point of the low melting point polymer can be adjusted to ±20° C. of the melting point of the low melting point polymer.

In a preferred embodiment of this invention, rapid cooling is carried out by -20
This can be carried out by cooling to ~60°C.

In a preferred embodiment of this invention, the thermal history of the heating and rapid cooling steps can be repeated.

This invention will be explained in more detail below.

Polymer The polymer used in this invention includes polyethylene,
Polyethylene oxide, t-4-polybutadiene, polyethylene acrylate, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, polyester, polyamide, polyether, polycaprolactam,
Fluorinated ethylene-propylene copolymer, chlorinated polyethylene, chlorosulfonated ethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, styrene-acrylonitrile copolymer, polyvinyl chloride, polycarbonate, polyacetal, polyalkylene oxide, polyphenylene Examples include oxides, polysulfones, fluororesins, and blend polymers of at least two selected from these. In this invention, the type of polymer, composition ratio, etc. can be appropriately selected depending on desired performance, use, etc.

Conductive Particles and Additives As the conductive particles dispersed in the polymer, particles of conductive substances such as carbon black, graphite, tin, silver, gold, copper, and silver-plated particles can be used.

In preparing the PTC composition, in addition to the above-mentioned polymer and conductive particles, various additives can be mixed as necessary. Examples of such additives include flame retardants, antioxidants, stabilizers, etc., such as antimony compounds, phosphorus compounds, chlorinated compounds, and brominated compounds.

This PTC composition is prepared by blending and kneading the raw materials, polymers, conductive particles, and other additives in predetermined proportions.

Kneading In this invention, when mixing the polymer and conductive particles, for example, the conductive particles are incorporated into the polymer using a kneader and/or two rolls, and then the conductive particles are uniformly mixed into the polymer. to be dispersed. In this invention, kneading can be carried out in one stage, but it can also be kneaded in two stages.

In this invention, when this two-stage kneading is performed separately into preliminary mixing and main mixing, at least two types of polymers are used, and the mixing between the polymer and the conductive particles is performed separately for each polymer. It is also possible to pre-knead the polymer and conductive particles, and then main-knead each pre-kneaded product in a predetermined ratio. In the present invention, preliminary kneading and main kneading are performed for each polymer by kneading the polymer and conductive particles. The blending ratio of the polymer and particles can be appropriately selected depending on the particle content of the target composition, the type of polymer, the type of mixer such as a kneader or two rolls, and the like. In this invention, pretreatments such as pulverization, heating, and mixing may be performed before preliminary kneading and main kneading.

The temperature at which the wires are mixed is in a temperature range higher than the melting point of the polymer to be kneaded. This is because within this range, the polymer to be kneaded gels and the conductive particles can be uniformly dispersed.

When the polymer is pretreated by heating before being mixed, it is preferable to heat the polymer to a temperature range higher than its melting point to soften it, and then add conductive particles and knead it.

In this invention, when kneading in one step, before mixing,
Pretreatments such as premixing, heating, and addition of additives can be performed. The equipment used for this kneading is a kneader and two
This is a kneading machine such as this roll.

The temperature during this kneading is arbitrary, but preferably,
The temperature range is higher than the melting point of the polymer used. Therefore, the temperature range varies depending on the type of polymer used. In the embodiment in which the mixture is heated and softened in advance during kneading, it is preferable to knead at a temperature higher than the highest melting point of the polymers used.

When an additive is mixed into the PTC composition, the additive may be added before or after mixing, or at the same time as kneading.

Preparation of PTC element In this invention, a PTC composition and an electrode are bonded to form a PTC element.
The C element can be manufactured by a conventional method. For example, a PTC composition is formed into a film, metal foil electrodes are thermocompression bonded to the top and bottom of the film to form a laminate, the laminate is cut to a predetermined size, and lead wires are soldered to the electrode surface. A PTC element can be manufactured by joining by a spot welding method or the like.

Thermal History A feature of this invention is that the PTC composition obtained by cross-crossing is subjected to thermal history.

In this invention, the thermal history consists of heating and rapid cooling steps, and this thermal history may be repeated once or multiple times. The heating of the thermal history is performed by heating to a temperature near the melting point of a polymer having a low melting point among the polymers used for the crosstalk. A preferable heating temperature is within a temperature range of ±20° C. of the melting point of a polymer having a low melting point among the polymers used for mixing and purification. The time for maintaining and leaving in this temperature range can be changed as appropriate depending on the type and composition of the polymer used, but for example,
-20 minutes, preferably 5-10 minutes.

The rapid cooling of the thermal history is performed by rapidly cooling to a temperature below zero degrees, preferably to -20 to 60 degrees Celsius. The time for maintaining this low temperature state can be changed as appropriate depending on the type and composition of the polymer used, but for example, 2 to 20
minutes, preferably 5 to 10 minutes. This rapid cooling
For example, liquid nitrogen, dry ice, liquid oxygen, liquid helium, etc. can be used.

In the above description, the thermal history of the present invention was carried out subsequent to the preparation of the PTC element, but in this invention, the thermal history was carried out before or during the preparation of the PTC element. You can also do a history.

[For production]

Since this invention is configured as described above, it operates as follows.

Although the mechanism of thermal history in this invention is not necessarily clear, it is thought to work as follows.

Although the PTC composition and the electrode are macroscopically bonded to some extent by thermocompression bonding, microscopically they are bonded non-uniformly at the interface between the PTC composition and the electrode. It is believed that the thermal history of this invention eliminates the non-uniformity. Furthermore, when kneaded with a kneader or two-roll kneading machine, the conductive particles are macroscopically dispersed almost uniformly in the polymer, but microscopically they overlap with conductive particles such as carbon black. It is thought that there is non-uniform contact at the interface with the coalescence. Heating softens the polymer and narrows the contact distance between the conductive particles and the polymer, and rapid cooling causes the matrix polymer to break finely, and the broken pieces enter the voids, further shortening the contact distance.

By repeating this thermal history, the conductive particles and the polymer come into even microscopic contact at the interface.

The above description is for a better understanding of the invention and is not intended to limit the scope of the invention.

〔Example〕

This invention will be specifically explained by way of example.

Comparative example A material having PTC properties having the following composition was prepared.

Weight% Polymer...High density polyethylene...26
(Manufactured by Toyo Soda, HDPE 5100) Ethylene-acrylic acid copolymer...26 (Manufactured by Exxon, EAA50
00) Conductive particles...carbon black...47
(Cabot Sterling V) Antioxidant...Irganox 1010...I
The PTCPTC composition was charged into two rolls (manufactured by Yasuda Seiki Seisakusho Co., Ltd., 191-TM) and kneaded at 180°C for 30 minutes. The obtained PTC composition was formed into a film, nickel foil electrodes with a thickness of 100 μm were placed on the top and bottom of the film, and the electrodes and the composition were brought into contact with each other by pressure bonding while heating.
A laminate was produced by cooling and bonding while applying pressure, and then cut into 10.5 a layer x 10.5 layer to a thickness of 0.4
A 5+u PTC element was manufactured.

Regarding the 1865 PTC elements obtained in this way,
Room temperature resistance was measured. As a result, the average room temperature resistance was 48.
It is 67 mΩ, and the variation is σ-4.64.

Example 1 The PTC element obtained in the comparative example was heated at 80°C for 10
The mixture was left to stand for a minute, then rapidly cooled to minus 40°C, left at that temperature for 10 minutes, further heated and left at 80°C for 5 minutes, and then returned to room temperature.

As a result of measuring the room temperature resistance of the obtained PTC element,
The average room temperature resistance decreased by 5 mΩ.

Example 2 Among the PTC elements obtained in Example 1, the room temperature resistance was 46 m
As a result of subjecting the PTC element of Ω or more to the same thermal history as in Example 1, the room temperature resistance further decreased by 3.5 mΩ. Next, the PTC element after this thermal history has a room temperature resistance of 46 m.
As a result of subjecting the PTC element of Ω or more to the same thermal history as in Example 1, the room temperature resistance was further reduced to 2. It went down by OmΩ. As a result, the average room temperature resistance of 1792 PTC elements was 43.4 mΩ, and the variation was σ-2.66.

〔Effect of the invention〕

The following effects can be obtained by this invention.

As demonstrated in the examples, PTC has lower room temperature resistance and less variation than PTC cords made by conventional methods.
element can be obtained.

Claims (1)

[Claims] 1. A method for manufacturing a PTC element comprising at least two metal electrodes and a PTC composition bonded to the electrodes, comprising:
The PTC composition is made by kneading at least one kind of polymer and conductive particles and uniformly dispersing the particles in the polymer. 1. A method for producing a PTC element, which comprises heating the polymer to a temperature near the melting point of the polymer and rapidly cooling it to a temperature below zero. 2. The method for producing a PTC element according to claim 1, wherein the temperature near the melting point of the low melting point polymer is ±20° C. of the melting point of the low melting point polymer. 3. A method for manufacturing a PTC element according to claim 1 or 2, which comprises rapid cooling to -20 to 60°C. 4. The method for manufacturing a PTC element according to any one of claims 1 to 3, wherein the thermal history of the heating step and the rapid cooling step is repeated multiple times.