JPH0821486B2 - Method for producing PTC composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electric material, and more specifically,
A property in which electrical resistance rapidly increases in a relatively narrow temperature range with increasing temperature [PTC characteristics (Positive temperature coefficien
t)], that is, a method for producing a PTC composition.

[Prior Art] A PTC composition limits overcurrent to a predetermined current or less when a circuit including a heater, a positive temperature coefficient thermistor (PTC THERMISTER), a thermal sensor, a battery, etc., which stops heat generation when it rises to a certain temperature, is short-circuited. On the other hand, it can be used as a circuit protection element or the like in which the circuit is restored when the short circuit is removed.
As the PTC composition, various substances have been developed at present, and for example, there is a composition in which conductive particles such as carbon black are uniformly dispersed in at least one polymer such as polyethylene and ethylene-acrylic acid copolymer.

Conventionally, a method for producing a PTC composition is generally one in which one or more resins used as a polymer are first mixed and uniformly dispersed, and a necessary amount of carbon black is added to this mixture, followed by kneading. Being manufactured.

[Problems to be solved by the invention]

The preferred properties of the PTC composition are that it has a large resistance value (peak resistance) at high temperature and a low resistance value (room temperature resistance) of 100 mΩ or less at room temperature, that is, a high peak resistance / room temperature resistance ratio. Is.

However, in the conventional method for producing a PTC composition, a high peak resistance value is not always obtained, and sufficient peak resistance cannot be obtained even if the kneading time or the kneading temperature is changed,
The organic peroxide is added to the raw material as an additive to crosslink the polymer, and even if the peak resistance is increased, the room temperature resistance is also increased.
For example, it cannot be used as a circuit protection element.

The present invention has been made based on the above background, and an object thereof is to provide a method capable of producing a PTC composition having a low room temperature resistance of 100 mΩ or less and a high peak resistance. It is to be.

[Means for solving problems]

The present inventor, as a result of various tests and studies for achieving the above-mentioned object, once kneaded the polymer and the conductive particles, and further kneaded at the same time as crosslinking by adding a crosslinking agent to the kneaded product,
The present invention has been completed based on the finding that a composition having good PTC characteristics can be obtained by completing crosslinking during kneading.

That is, the method for producing a PTC composition of the present invention is a method for producing a PTC composition that includes kneading a polymer and conductive particles to uniformly disperse the particles in the polymer.
A cross-linking agent is added during the kneading, and the cross-linking is carried out simultaneously with the kneading to complete the cross-linking during the kneading.

In a preferred embodiment of the present invention, the kneading time can be 20 to 90 minutes. Further, the kneading temperature can be set to a melting point of the polymer and a temperature range higher than the melting point by 70 ° C., more preferably a melting point of the polymer and a temperature range higher than the melting point by 50 ° C.

 Hereinafter, the present invention will be described in more detail.

Components of PTC composition As the polymer used in the present invention, 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-acetic acid Vinyl copolymer, polypropylene, polystyrene, styrene-acrylonitrile copolymer, polyvinyl chloride,
At least 2 selected from polycarbonate, polyacetal, polyalkylene oxide, polyphenylene oxide, polysulfone, fluororesin, and the like.
There are various kinds of blend polymers. In the present invention, the type and composition ratio of the polymer can be appropriately selected depending on the desired performance, application and the like.

Further, as the conductive particles dispersed in the polymer, particles of a conductive substance such as carbon black, graphite, tin, silver, gold and copper, and silver-plated particles can be used.

The cross-linking agent used in the present invention is capable of cross-linking its components in the PTC composition, and as such a cross-linking agent, sulfur and sulfur compounds, selenium, magnesium oxide, lead monoxide, zinc oxide can be used. , Oximes, nitroso compounds, polyamines and organic peroxides. In addition, a crosslinking accelerator can be used together. Preferred crosslinking agents for this invention are organic peroxides such as hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, silyl peroxides.

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

Manufacturing Method This PTC composition is prepared by mixing and kneading the raw materials, the polymer, the conductive particles, and other additives in a predetermined ratio.

In this invention, the kneading of the polymer and the conductive particles,
It is carried out by kneading the polymer and the conductive particles in a predetermined ratio. The blending ratio of the polymer and the particles can be appropriately selected depending on the particle content of the target composition, the type of the polymer, the type of the mixer, the kneader and the like. In the present invention, pretreatment such as crushing, heating, and mixing may be performed before kneading. The temperature for kneading is in the temperature range from the melting point of the polymer to be kneaded to 70 ° C, preferably 50 ° C higher than the melting point. This is because the kneaded polymer can be gelated and the conductive particles can be uniformly dispersed in the range.

When the polymer is pretreated by heating before kneading, it is preferable to preliminarily heat the polymer to an appropriate temperature to soften it and then add conductive particles and knead.

One of the features of this invention is that a crosslinking agent is added during the kneading of the polymer and the conductive particles, and the crosslinking is carried out simultaneously with the kneading so that the crosslinking is completed during the kneading. At the time of addition of this cross-linking agent, it can be appropriately selected depending on the performance and type of the kneading device, the amount and type of the kneaded product, but preferably 2 to 30 minutes after the start of kneading the polymer and the conductive particles, and It is preferably 5 to 10 minutes after the start of kneading.

In this invention, it is desirable to appropriately select the kneading parameters in order to obtain a good PTC composition, and the kneading time is preferably 20 to 90 minutes, more preferably
30 to 60 minutes. This is because if the kneading time is deviated, the room temperature resistance increases. Regarding the kneading temperature,
The kneading is carried out in a temperature range between the melting point of the polymer and a temperature 70 ° C. higher than this melting point, preferably in the temperature range between the melting point of the polymer and a temperature 50 ° C. higher than this melting point. In the present invention, the kneading and the cross-linking reaction are completed at the same time, and therefore, the kneading and the cross-linking reaction are not performed by further heating.

When other additives are mixed in the PTC composition, these additives may be added either before or after the kneading in the first half, before or after the kneading in the second half, or simultaneously with the addition of the crosslinking agent.

The PTC composition obtained according to the present invention can be used in various applications. For example, when used for a PTC element, this PTC composition is formed into a film, and a metal foil electrode is thermocompression-bonded to the upper and lower sides of the film to form a laminate, and the laminate is cut to a predetermined size to form an electrode. Lead wires can be connected to the surface by spot welding, soldering, etc. to manufacture PTC elements.

[Work]

Since the present invention is configured as described above, it is considered that the invention operates as follows.

In theory, the mechanism is not always clear,
It is known that crosslinking the polymer of the PTC composition increases the peak resistance but also the room temperature resistance, and that kneading reduces the room temperature resistance but the peak resistance. It is considered that if these two contradictory factors are implemented at the optimum time, the room temperature resistance can be lowered and the peak resistance can be increased.

Moreover, the viscosity is increased by the crosslinking reaction during the kneading, the dispersibility of the conductive particles is improved, and the crosslinking reaction and the kneading are simultaneously advanced to complete the crosslinking reaction during the kneading, whereby the crosslinking chains are appropriately broken, It is considered that a good PTC composition having such low room temperature resistance and high peak resistance as described above can be obtained.

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

〔Example〕

 The present invention will be specifically described by way of example.

Example 1 A substance having PTC characteristics having the following composition was prepared.

% By weight Polymer ... High-density polyethylene (Toyo Soda, Nipolon Hard 5100) ... 24 Ethylene-acrylic acid copolymer (Dow Chemical, Primacor 3460) ... 36 Conductive particles ... Carbon black (Cabot, Sterling V) ... 38 Antioxidant ... (Ciba Geigy, Irganox 1010) ... 2 Crosslinking agent ... Organic peroxide (Yoshitomi Pharmaceutical, Lupasol 130) ... 1 Polymer, conductive particles, and antioxidant on the above two rolls The mixture was kneaded at 180 ° C. for 5 minutes, 5 minutes after the kneading was started, the above-mentioned crosslinking agent was added, and the kneading was continued for another 40 minutes to obtain a PTC composition. Then, the PT obtained with a nickel foil with a thickness of 65μ
The C composition was sandwiched and thermocompression bonded by a press to prepare a laminate.
The obtained laminated body was cut into a predetermined size (10.5 × 10.5 × 0.38 mm) to obtain a PTC element. Room temperature resistance of this PTC element,
The peak resistance was measured. The results are shown in Table 1.

The trade name Irganox 1010 is a white crystalline powder made of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, and the trade name Lubazole 130 is 2,5-dimethyl-
90% of 2,5-di (t-butylperoxy) hexin-3
It is the contained liquid.

Comparative Example 2 A PTC element was manufactured in the same manner as in Example 1 except that the kneading time was 5 minutes and no crosslinking agent was added, and the room temperature resistance and the peak resistance were measured. The results are shown in Table 1.

Examples 3 to 8 PTC elements were manufactured in the same manner as in Example 1 except that the kneading time shown in Table 1 was used, and the room temperature resistance and the peak resistance were measured. The results are shown in Table 1.

From this result, it can be seen that the peak resistance can be increased to a high resistance of 10000 Ω or more by adding the crosslinking agent, and the room temperature resistance of 100 mΩ or less can be reduced by continuing the kneading for a certain time even after the addition of the crosslinking agent. .

Comparative Example 9 After kneading for 30 minutes in Comparative Example 5, the cross-linking agent Lubazole 130 was added, kneading for 5 minutes, taken out, and then cross-linked for 1 hour in an oven at 180 degrees. The obtained PTC composition was press-molded to obtain a PTC element. Peak resistance exceeded 10,000 ohms but room temperature resistance was 103 milliohms.

〔The invention's effect〕

As demonstrated by the examples, the following effects can be obtained by the present invention.

While having a low room temperature resistance of 100 milliohms or less,
A PTC composition capable of producing a PTC device having high peak resistance can be provided.

Claims (6)

[Claims] 1. A method for producing a PTC composition comprising kneading a polymer and conductive particles to uniformly disperse the particles in the polymer, wherein a crosslinking agent is added during the kneading. The method for producing a PTC composition is characterized in that the crosslinking is carried out simultaneously with the kneading, and the crosslinking is completed during the kneading. 2. The method for producing a PTC composition according to claim 1, wherein the kneading time is 20 to 90 minutes. 3. The kneading temperature is a melting point of the polymer and 70 from the melting point.
The manufacturing method according to claim 1 or 2, which is a temperature range with a temperature higher by ° C. 4. The kneading temperature is a melting point of the polymer and 50 from the melting point.
The manufacturing method according to claim 3, which is in a temperature range of a temperature higher by 0 ° C. 5. The method according to any one of claims 1 to 4, wherein the crosslinking agent is added 2 to 30 minutes after the start of kneading. 6. The cross-linking agent is at least one selected from hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters and silyl peroxides.
The method according to any one of claims 1 to 5, which is a kind of organic peroxide.