JPS60262856A - Electrically conductive polymer composition and heater made by using the same - Google Patents

Abstract

PURPOSE:To provide the titled compsn. having a resistance which is abruptly increased according to a positive temp. coefficient when the value of the resistance reaches a specified temp. region, by adding electrically conductive carbon black and a filler to a polymer. CONSTITUTION:0.05-50pts.wt. filler such as talc is blended with 100pts.wt. electrically conductive polymer obtd. by blending 3-50pts.wt. electrically conductive carbon black with 100pts.wt. polymer such as PE, to obtain an electrically conductive polymer compsn. 2 having a positive temp. coefficient. The compsn. 2 is crosslinked, if desired, and molded into the desired shape. At least two electrodes 1a, 1b are fixed to the molding, and the molding is coated with an insulating layer 3 such as rubber or latex to obtain a heater.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention provides a conductive polymer composition whose resistance value rapidly increases according to a positive temperature coefficient when it reaches a certain temperature range, and a conductive polymer composition that exhibits stiffness. [Problems with conventional technology] Conventional plants have used nichrome wire or inorganic insulated wire (between the conductor and external conductor) as a heater to prevent freezing in cold regions and to keep the transferred fluid warm. Structures filled with insulating powder such as magnesium oxide) have been used, but these maintain a constant output as long as the voltage is constant, and have the disadvantage of consuming a large amount of energy.

Therefore, as a solution to the above-mentioned drawbacks, a heater with a characteristic that the output changes depending on the temperature, that is, a heater with a self-temperature control function has been proposed, but among these, heaters that use ceramics or semiconductors are expensive and cannot be used for special purposes. Although used, it is not suitable for general use VCl'i. A heater with a self-temperature control function based on a polymer material has a property (hereinafter referred to as PTC property) that its resistance increases according to a positive temperature coefficient when it reaches a certain temperature range. (C, conductive carbon black or metal powder is added,
The method of adding conductive carbon black has the fatal disadvantage of being susceptible to resistance changes depending on manufacturing conditions, and the method of adding metal powder accelerates thermal deterioration of the polymer and corrodes due to water intrusion. There are difficulties such as 0
Furthermore, it has been difficult to stabilize preferable PTC characteristics over a long period of time.

[Structure of the invention]

In view of the above, the present invention aims to solve the above-mentioned drawbacks and provide a conductive polymer composition having good PTC Iff properties and a heater using the same. The term "polymer" here refers to a polymeric material that is generally widely used, and includes polyethylene, bivalent copolymer, polyester, and fluororesin. , fluororubber, acrylic rubber, polyvinyl chloride, etc., and these are examples and are not limited to these.These polymers may be used alone or in combination of two or more. As conductive carbon black, acetylene black and furnace black with a large surface area5
For example, Palcan XC-72, C, SC (all manufactured by Gearpot), Ketjen Black EC (manufactured by Akzo), H8-500 (manufactured by Asahi Carbon), etc. can be used.

As fillers, the amount of clay, talc, silicon dioxide, diatomaceous earth, pumice powder, mica powder, and disulfide conductive carbon blank is important because it varies depending on the type of polymer and the type of conductive carbon black. Although it is difficult to make a specific decision, taking these points into consideration, Polymer 1
It is desirable to use a range of 3 to 50 parts by weight. This is because the structure changes due to the surface area and particle morphology of the conductive carbon black.
ll t is acetylene black (surface area 70η6) is 2
When adding 0 to 50 parts by weight, PTC% properties can be obtained, and in the case of Ketchig Black EC (surface fJ 11000), a similar effect was observed in the range of 5 to 30 parts by weight. This is because the amount of carbon black added differs depending on the active groups on the surface and the shape. e. In the case of conductive carbon black, if the amount added is too small, the resistance value will be too high and no heat will be generated. On the contrary, if the amount is too large, the resistance will be As soon as the resistance value becomes low, the temperature dependence of the resistance value disappears and PTC characteristics are no longer exhibited.

The added amount of the shredded filler is 0.05 to 50 parts by weight per 100 parts by weight of the polymer blended with conductive carbon black.
It is preferable to use the filler in an amount of 0.5 to 10 parts by weight, preferably in the range of 0.5 to 10 parts by weight.The reason why the filler is used in the present invention is that the filler has a resistance reducing effect on the conductive carbon black. There is very little resistance change in comparison, and there is also very little resistance change due to changes in processing conditions, etc.
Furthermore, if the amount added is less than 0.05 parts by weight, the resistance stabilizing effect will not be sufficiently effective, and if it exceeds 50 parts by weight, the physical properties of the polymer will increase. C and processability are significantly reduced (o), so C is within the above range. In addition, as other additives, antioxidants,
Rust inhibitors, stabilizers, plasticizers, lubricants, metal deactivators (for example, copper inhibitors), etc. may be added. In addition, the polymer may be used as is, or in order to prevent heat deformation,
It may be crosslinked by an appropriate method, such as electron beam irradiation, chemical crosslinking with organic peroxide or sulfur, or silane craft water crosslinking method. Such a composition is a polymer composition that exhibits PTC characteristics, such as a heater that is formed into a predetermined shape by melt molding, usually with two or nine or more electrodes arranged therein. is also used in that IT, but for safety reasons, an insulator or sheath made of rubber or plastic, such as fluororesin, may be used as the outer layer, and a metal braid or the like may also be used to provide mechanical protection.

[Example] Example 1 To 100 parts by weight of low density polyethylene (MI 6), 20 parts by weight of acetylene black and 5 parts by weight of clay were added, and tetrakis-[methylene-(3,5 Ditarsia 11 butyl 4 hydroxyhydrocinnamate)] 0.2 parts by weight of methane was added to this composition 2. Using a 40+w+ extruder, the structure was as shown in Fig. 1, that is, the electrode conductors 1a and 1b having two cores arranged in parallel were used in common. After extrusion molding into a coated form and further extruding an insulating layer 3 made of polyethylene on top of the extrusion molding, the membrane was cross-linked by irradiation of 30 Mra d, f using an electron beam as shown in the second factor. As a result of connecting the power supply 4 between the two electrode conductors 1a and 1b and applying a voltage of 100V, a heat generation temperature of 45C was obtained, and the range of the highest and lowest values of this heat generation temperature was within the IOC of 01. C Example 2 Ethylene-vinyl acetate copolymer (vinyl acetate amount 14%,
To 100 parts by weight of MI=15), 35 parts by weight of acetylene black and 10 parts by weight of tartar were added, and 4.4'-thiobis(6-tertiary-m-
A composition containing 0.2 parts by weight of (cresol) and 1 part by weight of dicumyl oxide as a crosslinking agent was prepared by placing two cows in a 40 m extruder in the structure shown in Figure 1, that is, in parallel arrangement. The electrode conductors 1a and 1b were extruded into a common coated shape and cross-linked at a water vapor pressure of 15''/7.There was little variation even when processing conditions such as extrusion temperature and extrusion pressure were changed.C Example 3 To 100 parts of polyethylene (MI=5), 7 parts of Ketjenblack ECj and 5 parts of clay were added, and as antioxidants Bo-172,214 and trimethyl-
After adding 1 part by weight of 1,2-dihydroxy + 1 N to the first blow 1 shape 4 (fs) using an extruder, it was irradiated and cross-linked using an electron beam at 730 Mrad. was obtained, and the variation due to processing conditions was within 10C.

Example 4 To 100 parts by weight of polyvinylidene fluoride, 20 parts by weight of acetylene black and 5 parts by weight of silica were added. Then, after molding into the shape shown in Figure 1 using an extruder,
When V is applied, it is 100C. In addition, the current life in a 140C oven was extremely good.

Comparative Example 1 A constant exothermic temperature of 45 C was obtained when 0.100 V was applied in Example 1, without adding clay, and the other conditions were the same as in Example 1. However, the dimensional variation was poor and the change in current life was also large. C Comparative Example 2 The same procedure as in Example 1 was carried out except that 60 parts by weight of clay was added in Example 1. When 100V was applied, an exothermic temperature of 45tZ' was obtained and the dimensional stability was very good, but the life of the current was shortened. C The change was large. If the above results are ignored, the result is C as shown in Figure 3. [Effects of the Invention] As described above, the composition of the present invention has PTC characteristics, so it operates as a heater that exhibits a self-temperature control effect. do.

Because it has PTC4 properties and exhibits a self-temperature control effect,
Compared to conventional heaters using nichrome wires or inorganic feeder wires, energy loss is extremely low, and electricity costs can be significantly reduced.

Moreover, the long-term stability of dimensions, workability, etc. can be maintained by adding fillers.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an embodiment of the heater of the present invention, Figure 2 is an explanatory diagram showing a method for testing the heat generation characteristics of the heater of Figure 1, and Figure 3 is a diagram showing the stability of the heat generating element of the present invention. 01a, 1b are graphs showing the rate of change in temperature over time when a voltage is applied to the heating element in order to investigate... Electrode conductor 3... Insulating layer 4... Power supply 2... PTC characteristics. The conductive polymer composition shown in FIG. b Figure 3 Normal day & r day)

Claims (2)

[Claims] (1) Add 0.0 part of filler to 100 parts by weight of a conductive polymer in which conductive carbon black is added to the polymer.
Conductive polymer composition with positive temperature coefficient characteristics added in 5 to 50 parts by weight 0 (2) Add 0.05 parts of filler to 100 parts by weight of a conductive polymer in which conductive carbon black is added to the polymer.
Heater C consisting of a conductive polymer composition having a positive temperature coefficient characteristic to which ~50 heavy parts have been added and an electrode provided integrally therewith.