JPH10116702A - Ptc composition material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the crystalline high-molecular composition material, which has the low resistivity not found in conventional devices and has the PTC (positive temperature coefficient) characteristic with excellent resistance stability after repeating trip-cycle tests. SOLUTION: This PTC composition material is formed by compounding 550-1,000/pts.wt. of titanium carbide having an average particle diameter of 0.1-5μm into 100 pts.wt. of crystalline high molecules. In this case, by performning the surface treatment for the titanium carbide with silane-compound coupling agent the resistance of the PTC composition material after trip-cycle tests can be more stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition having a PTC characteristic (positive temperature coefficient characteristic) that increases rapidly when a resistance reaches a specific temperature range. More particularly, the present invention relates to a PTC resin composition which has a low resistance in a normal state and has excellent reproducibility of resistance during repeated switching operations.

[0002]

2. Description of the Related Art Conventionally, a resin composition having PTC characteristics in which a conductive polymer such as carbon black or metal powder is filled and dispersed in a crystalline polymer such as polyethylene or polypropylene, or a PTC element using the same is known. is there. For example, for carbon black,
No. 33707, JP-A-4-167501 and the like, and metal powders are disclosed in JP-A-5-47503.

[0003] In the PTC composition in which a conductive powder is filled and dispersed in a crystalline polymer as described above, the PTC characteristic is such that the crystalline polymer rapidly expands in volume at its melting point, so that it is dispersed in the polymer. This occurs because the distance between the conductive powders increases and the contact resistance between the powders sharply increases. In the above-mentioned known PTC composition to which such a principle is applied, there is a problem that a change in resistance becomes large while the crystal of the crystalline polymer is repeatedly melted and solidified.

In order to solve the above problems, it has been proposed to use carbon black as a conductive powder and to crosslink a crystalline polymer as a matrix resin using a silane compound crosslinker (Japanese Patent Laid-Open Publication No. HEI 9-26186). 2-14090
No. 2).

On the other hand, as a new attempt, as a conductive powder to be filled and dispersed in a crystalline polymer, conductive inorganic powders other than carbon black and metal powder, such as titanium carbide, titanium boride, zirconium boride, niobium boride, and silicide It has been reported that a PTC composition using niobium, tungsten silicide, molybdenum silicide, or the like is used (J. Mate).
real Science 26, 145 (199
1)).

[0006]

By the way, the performance required of the PTC composition requires that the PTC characteristic rapidly rises and shows a large change in resistance, and that the initial resistance in a normal state be small. Furthermore, in recent years, application stability of PTC elements for overcurrent protection, which require large switching power, requires characteristics stability after repeated switching operation (trip cycle test), particularly, no change in resistance. The specific requirements are that the specific resistance at room temperature is 0.5 Ωcm or less, the change in resistance before and after the switching temperature is 106 or more, and the resistance does not change after repeated switching operation (trip cycle test). It is. In the above-mentioned conventional example, one satisfying the above requirements at the same time has not been obtained. An object of the present invention is to provide a PTC composition satisfying the above requirements.

[0007]

According to the present invention, an average particle diameter of 0.1 to 5 μm is used for 100 parts by weight of a crystalline polymer.
m of titanium carbide powder in an amount of 550 to 1000 parts by weight.

The PTC composition of the present invention exhibits good PTC characteristics in which the change in resistance before and after the switching temperature is 10 ⁶ or more, and has a very low specific resistance at a temperature below the switching, The resistance after a trip cycle test or the like is extremely stable. Therefore, with the composition of the present invention, an overcurrent protection device or the like having stable device characteristics requiring a large switching power can be completed.

Although the reason why the resistance of the composition of the present invention has become stable and hardly increased as described above after the trip cycle test has not been sufficiently elucidated, the following phenomena are effective in combination. It is thought that it is. That is, the conventional PTC element uses titanium carbide as a matrix polymer 10
It is a composition in which 500 parts by weight or less is added to 0 parts by weight. Even if titanium carbide has a higher surface energy than carbon black or the like, when it is put in a trip state, wetting of the matrix polymer proceeds. As a result, even if the trip state is released and cooling is performed, the connection (percolation) between the titanium carbide powders progresses to a slightly incomplete state, and the resistance increases while repeating this many times. Can be On the other hand, when the concentration of titanium carbide is 550 parts by weight or more with respect to 100 parts by weight of the matrix polymer as in the present invention, the low molecular weight components and side chains in the matrix polymer participating in wetting have a finite concentration, Wetting stops progressing. If titanium carbide powder having an average particle diameter of 0.1 to 5 μm is added in an amount of 550 parts by weight or more based on 100 parts by weight of the crystalline polymer, kneading becomes extremely difficult (viscosity of the composition increases, ductility and mixing The adhesion to the metal surface of the machine is reduced), the constraint of the position of the matrix polymer around the titanium carbide is increased, and the movement of the matrix crystal at the time of trip hardly occurs. Conventionally, the resistance was increased due to the temperature history during production due to stabilization, and the original good specific resistance could not be obtained.On the other hand, the composition of the present invention showed a good It is considered that a resistor is obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The crystalline polymer used as the matrix polymer in the PTC composition of the present invention can be used not only alone but also as a mixture of a plurality of crystalline polymers. Crystalline polymers are effective. Examples of the crystalline polymer used in the present invention include high-density polyethylene, medium-density polyethylene, polyethylenes such as low-density polyethylene, or ethylene-
Examples thereof include an ethylene copolymer such as a vinyl acetate copolymer and an ethylene-ethyl acrylate copolymer, a polyolefin such as polypropylene, a thermoplastic polyamide, a thermoplastic polyester, and a polyvinylidene fluoride.

The crystalline polymer used in the present invention can be crosslinked after blending titanium carbide powder and the like. The cross-linking treatment is preferable because the PTC element can be prevented from being broken due to abnormal heating and the pressure resistance of the PTC element can be improved. The above-mentioned cross-linking may be performed by any method such as an electron beam cross-linking method, a chemical cross-linking method using an organic peroxide, and a silane cross-linking method using a silane compound cross-linking agent.

The titanium carbide powder used in the present invention may be titanium carbide generally available on the market, but its average particle size is adjusted to 0.1 to 5 μm. The reason why the average particle diameter is 0.1 to 5 μm is that those having a particle size of 0.1 μm or less are difficult to obtain and difficult to obtain. On the other hand, when the thickness is 5 μm or more, even if a large amount is added, the stability of the resistance in the trip cycle test cannot be sufficiently obtained.

The amount of the titanium carbide powder is 550 to 1000 parts by weight based on 100 parts by weight of the crystalline polymer. If the amount is less than 550 parts by weight, the stability of the resistance in the trip cycle test becomes poor, and if it exceeds 1000 parts by weight, kneading becomes extremely difficult.

Since the titanium carbide powder is a relatively fine powder having an average particle diameter of 5 μm or less, it may be added by a surface treatment to a content of 600 parts by weight or more based on 100 parts by weight of the crystalline polymer. The fluidity does not deteriorate, and the composition can be easily formed into a thin sheet. On the other hand, if the MFR of the crystalline polymer is increased, the amount of addition can be increased. However, the kneading operation becomes difficult with a resin having an excessively large MFR. Therefore, the adjustment of the MFR alone limits the amount of addition to, for example, about 850 parts by weight. It is.

In the composition of the present invention, a titanium carbide powder surface-treated with a silane compound coupling agent is blended in order to highly blend the titanium carbide powder into the crystalline polymer, or the silane compound powder is mixed with the titanium carbide powder. It is preferable to mix a predetermined amount of the ring agent. By performing the surface treatment, the amount of addition to the crystalline polymer can be increased, and the stability of the resistance in the trip cycle test can be further improved.

The silane compound coupling agent used herein has the general formula (1) (Wherein, n is an integer of 2 or 3, R is a methyl group or an ethyl group, X is an organic group having an alkyl group, a halogenated alkyl group, a vinyl group, an amino group, a mercapto group, etc.) , Methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, vinyltrimethoxysilane, vinylethoxysilane, vinyltri (ethoxymethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltri Methoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N-
β- (aminoethyl) γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane and the like.

Among the silane compound coupling agents described above, the coupling agent containing no unsaturated bond is more effective than the coupling agent containing a functional group such as a vinyl group, an acryloyl group, and a methacryloyl group containing an unsaturated bond. It is a particularly preferable coupling agent because it has a great effect of increasing the stability of resistance in a trip cycle test.

The amount of the surface treatment of the silane compound coupling agent is set to a weight ratio of 0.1 to the titanium carbide powder.
The range of 001 to 0.01 is preferred. If the amount is 0.001 or less in weight ratio, the effect of the surface treatment is not sufficient, and if it exceeds 0.01, the effect of the surface treatment is only saturated with respect to the amount added. However, since the excess part of the silane compound coupling agent volatilizes or reacts with the moisture in the air and changes to a silanol compound,
The compositions of the present invention are less likely to inhibit the PTC properties.
The use of titanium carbide powder surface-treated with a silane compound coupling agent has the advantage of improving the fluidity of the composition and facilitating molding processing as compared with the case of untreated titanium carbide powder. be able to. However, if the addition amount exceeds 1000 parts by weight with respect to 100 parts by weight of the matrix polymer, kneading becomes difficult, which is not preferable.

The method of coupling the silane compound coupling agent used in the present invention to the titanium carbide powder includes adding the silane compound coupling agent to a solvent such as alcohol, water, an organic solvent or the like. A wet treatment method of forming a slurry and drying, a dry treatment method in which the silane compound coupling agent is directly added to the titanium carbide powder without a solvent and stirred and coupled,
In addition, there is an integral blend method or the like which is simultaneously added at the time of kneading the composition of the present invention. However, the stability of the PTC element resistance in the results of the trip cycle test is best when the surface treatment is performed by a wet method. This is followed by the dry method.

The composition of the present invention may optionally contain an antioxidant, a crosslinking accelerator, an inorganic filler, a colorant, and the like.

The PTC composition of the present invention can be prepared by adding a titanium carbide powder and other additives to a crystalline polymer (matrix polymer) by applying sufficient shearing force to the polymer, for example, a Banbury mixer, a roll mill, a screw type. It is obtained by melt-kneading using a kneading device such as an extruder.

Next, a PTC element using the PTC composition will be described. The basic configuration of a PTC element is composed of a molded product obtained by molding a PTC composition into a desired shape, for example, a rod shape, a column shape, a plate shape, and the like, and at least two electrodes connected to the molded product. As an index indicating the structure of the PTC element, d /
Although the t ratio may be used (d: equivalent outer shape = 2 × ((electrode area) / π) ^1/2 , t: average thickness of the PTC composition molded body), the composition is molded into a thin film. To form electrodes on the entire upper and lower surfaces of the film, ie, d / t
In the case of an element having a large ratio, an element having a low resistance can be obtained in principle. Therefore, when an element having this structure is formed using the composition having a low resistance of the present invention, an element having an extremely low resistance can be formed.
In the case of an element having a structure in which the d / t ratio is about 1, the resistance is d
The resistance is higher than that of a conventional PTC
Although it is not so small as compared with the element, since the heat radiation rate of the element is small, when an element having a structure with a d / t ratio of about 1 is prepared using the composition having a small specific resistance of the present invention,
There is an advantage that the trip response time can be shortened as compared with a case where a device having the same resistance is made using a conventional PTC composition.

Examples of a method of forming an electrode include a method of thermocompression bonding a metal such as nickel and copper, a method of forming a metal electrode by vacuum deposition, sputtering, or thermal spraying, and a method of forming an electrode via a conductive adhesive. Etc. can be used. Above all, a method of thermocompression bonding a metal foil or the like at a temperature equal to or higher than the melting point of the resin is simple and economical. In that case, it is preferable to use a metal foil having a roughened surface such as an electrolytic foil because the peeling of the electrode can be prevented.

[0024]

The present invention will be described in detail below with reference to examples.

Examples 1 to 8 and Comparative Examples 1 to 5 Table 1 shows PTC element structures of Examples 1 to 8 and Table 2 shows PTC element structures of Comparative Examples 1 to 5. How to make it is as follows.

The mixture was kneaded with a kneader at a mixing ratio shown in Tables 1 and 2 at 150 ° C., and a sheet-like composition was obtained by a roll mill. The composition was heated at 190 ° C. and pressurized at a pressure of 100 kg / cm ² for 10 minutes, and then cooled to room temperature at the same pressure to preform the composition to a uniform thickness of 0.5 mm. Further, a PTC composition layer sheet is sandwiched between the upper and lower sides by a 25 μm-thick electrolytic nickel foil, and heated at 190 ° C. by a mold for 100 minutes for 100 minutes.
It was pressurized at a pressure of g / cm ² , then cooled to room temperature at the same pressure, and the electrode metal was laminated. Then at room temperature
Crosslinking was achieved by irradiating ⁶⁰ Co gamma rays at the doses shown in Tables 1 and 2. Then length 20mm, width 10m
Cut the laminate sheet to m size, 0.05mm
A brass terminal having a thickness of 30 mm, a length of 30 mm and a width of 10 mm is attached to the entire device electrode by cream solder, and the
The cream solder was melted and connected at ℃, the flux was washed with ethanol, and dried at 100 ℃ to produce a PTC element. The above is the PTC elements of Examples 1 to 7 and Comparative Examples 1 to 5. In Example 8, the thickness of the PTC composition layer was 3 mm, the length of the PTC element was 10 mm, and the width of the PTC element was 4 mm. Except for that, it was created in the same manner as above.

In Examples 5 to 7, the titanium carbide powder used as the conductive filler was subjected to a surface treatment with a silane compound coupling agent. The surface treatment of the titanium carbide powder was performed as follows. . 1 kg of titanium carbide powder was added to a treatment solution obtained by dissolving 20 g of a silane compound coupling agent and 2 g of acetic acid in a mixed solvent of 500 g of water and 500 g of ethanol, and stirred well to form a uniform slurry. It was removed by drying.

The titanium carbide powder (average particle diameter 20 μm) used in Comparative Examples 3 and 4 was prepared by using TiC-M (large particle grade) using a 280 mesh sieve to remove coarse particles having a particle diameter of 50 μm or more. The particle size was adjusted. In this case, the average particle diameter was measured by a laser diffraction scattering method. However, the average particle diameter of the other titanium carbide powders is the same as that of Sub S shown in ASTM B 330-88.
Performed by the ieve method.

Various characteristics of the above 13 types of PTC elements were measured by the following test methods.

Resistance: Measured at a temperature of 25 ° C. according to a conventional method.

Specific resistance: Calculated from the resistance obtained above by the following equation. Specific resistance = (resistance × surface area of PTC composition layer / thickness of PTC composition layer)

Resistance change value: As exemplified in FIG.
It was calculated by the following equation from the initial resistance (25 ° C.) of the C element and the maximum resistance after the trip state. Resistance change value = log (maximum resistance / resistance (25 ° C))

Resistance after trip cycle test: A PTC element was connected to a power supply having a sufficiently large current capacity, and a DC voltage of 14 V was applied to the PTC element. Thus, the trip state was maintained for 5 minutes. Thereafter, the power was turned off, the PTC element was cooled naturally, and one hour later, the resistance of the PTC element was measured at room temperature of 25 ° C. The resistance (25 ° C.) after repeating this trip cycle 10 times was defined as the resistance after the trip cycle test. The increase ratio with the initial resistance was defined as a resistance increase rate (%).

The above results are collectively shown in Table 1 for Examples and Table 2 for Comparative Examples.

[0035]

[Table 1]

[0036]

[Table 2]

Examples 1 to 4 and Comparative Examples 1 to 4 all use PTC using titanium carbide powder as a conductive filler.
It is a PTC element made from the composition. Examples 1 to 4 all show good initial resistance, specific resistance, and resistance change values, and that the resistance after the trip cycle test also showed little change. In Comparative Examples 1 to 4, the initial resistance, the specific resistance, and the resistance change value were good values, but the resistance after the trip cycle test was significantly increased, which proves to be a practical problem.

Comparative Example 5 is a PTC element prepared from a conventionally used PTC composition using carbon black. Despite having the same element structure as Examples 1 to 4, Examples 1 to 4 4, the initial resistance and the specific resistance are higher and the resistance change value is considerably smaller.

In Examples 5, 6, and 7, a PTC element prepared from a PTC composition using titanium carbide powder surface-treated with a silane compound coupling agent as a conductive filler and adding 750 to 900 parts by weight of the filler was used. It is about.
In Examples 5, 6, and 7, all showed good initial resistance, specific resistance, and resistance change values, and the resistance after the trip cycle test was small, but the titanium carbide powder with a silane compound coupling agent was further used. By surface treatment of
It can be seen that the resistance of the PTC element after the trip cycle test was stabilized. In addition, Embodiments 5 and 6 and Embodiment 7
Comparing the results of the above, when a silane compound coupling agent other than a silane compound coupling agent containing a reactive unsaturated group such as a vinyl group is used, the effect of improving the trip cycle test result is further increased. You can see that.

In the eighth embodiment, the initial resistance and the resistance value after the trip cycle test are larger than those of the other embodiments. This is because the structure of the PTC element is different. It can be seen that the rate of increase in resistance after the test is also at the same level as in the other examples. In the eighth embodiment, the trip cycle response time, that is, the time from when the power is turned on in the trip cycle test to when the power supply enters the trip state is measured. The obtained result was 12 seconds, and for comparison, it was 24 seconds in Comparative Example 5 made of a PTC composition using carbon black as the conductive filler. Comparative Example 5 has a flat structure, but the initial resistance is almost the same as Example 8. From this, it was clarified that Example 8 had superior responsiveness to overcurrent as compared with the conventional PTC element.

[0041]

As is clear from the above, the PT of the present invention
The C composition has an unprecedented low specific resistance and is excellent in resistance stability after repeated trip cycle tests. Therefore,
An overcurrent protection element that performs large power switching and an overcurrent protection element that has a fast trip response can be manufactured. Since the application field of the overcurrent protection element having the PTC characteristic can be expanded, the industrial use value is extremely high.

[Brief description of the drawings]

FIG. 1 is a graph showing a temperature change of PTC element resistance using a PTC composition of the present invention.

Claims (3)

[Claims] 1. A titanium carbide powder having an average particle size of 0.1 to 5 μm with respect to 100 parts by weight of a crystalline polymer.
A PTC composition comprising 0 parts by weight. 2. The PTC composition according to claim 1, wherein the crystalline polymer is cross-linked. 3. The PTC composition according to claim 1, wherein the titanium carbide powder is surface-treated with a silane compound coupling agent.