JP2000086872A - Resin composition having ptc characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition which can be directly applied to the surface of a substrate to form thereon a wet film capable of easily forming a cured film having excellent adhesion by heating and can give a PTC(positive temperature coefficient) material having an arbitrary set switching temperature by using a base prepared by dissolving or dispersing a solvent-soluble polyester resin having a specified glass transition temperature and a specified amount of a conductive filler in an organic solvent and a curing agent. SOLUTION: This composition comprises a first package being a inky or pasty base prepared by dissolving and dispersing a base polymer being a solvent- soluble polyester resin having a glass transition temperature of 50 deg.C or below and 20-100 pts.vol., per 100 pts.wt. polyester resin, conductive filler (e.g. carbon powder) in an organic solvent (e.g. isophorone) and a second package being a curing agent. It is desirable that the curing agent is selected among aliphatic, aromatic, and alicyclic polyisocyanate compounds. It is desirable that the composition further contains a catalyst (e.g. tert. amine compound) which accelerates the crosslinking reaction of the polyester resin with the polyisocyanate compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a positive temperature coefficient (Positive Temperature Coe) having a positive temperature coefficient as the temperature increases when a specific temperature range is reached.
fficient, hereinafter abbreviated as “PTC”. ) (Hereinafter abbreviated as “PTC characteristics”), and a resin composition (hereinafter abbreviated as “PTC composition”).

[0002]

2. Description of the Related Art PTC compositions are useful for sheet heating elements having a self-temperature control function, circuit protection devices, polyswitch devices, temperature compensation circuits, temperature sensors, and the like.
Many PTC compositions have been proposed to date. This conventional PTC composition is obtained by dispersing a specific conductive filler in a crystalline polymer, and they conduct electricity due to volume expansion of the polymer accompanying melting of crystallites due to an increase in temperature. It is said that the breakage of the chain of the conductive filler increases the resistance value and exhibits PTC characteristics. Specific examples of conventional PTC compositions include polyethylene, polypropylene, olefins such as polyvinylidene fluoride, or crystalline polymers such as copolymers thereof with vinyl acetate or acrylates, and carbon black or metal powder. Representatively, a conductive filler is dispersed therein.
No. 338, JP-B-42-23288, JP-A-49-82735, JP-A-60-31540, JP-A-60-31548, JP-A-62-18
No. 1347, JP-A-1-304704 and the like. Conventional PTC compositions as described above are:
The crystalline polymer is heated and melted, kneaded with a conductive filler by a hot roll or a Banbury mixer or the like, and then pressed into a sheet.

[0003] The superiority and practicality of the PTC properties of the PTC composition are judged by the following items, and in order to be put to practical use, it is necessary to satisfy all of the properties (1) to (5). . (1) The ratio (Rp / Ro) of the resistance value (Rp) at the peak temperature (temperature at which the resistance becomes maximum; Tp) to the initial resistance value (resistance value at room temperature; Ro) is large, that is, the resistance Large change rate; (2) large resistance value rise gradient (α), that is, sharp change after PTC rise; (3) initial resistance value (Ro) is an appropriate value according to the intended use; (4) The switch temperature (temperature at which the resistance value rapidly changes; Ts) is an appropriate value, and the resistance value changes rapidly at an appropriate temperature according to the intended use; (5) After the peak temperature (Tp) There is no sudden drop in resistance.

[0004] However, the conventional PTC composition is difficult to uniformly disperse the filler due to the manufacturing method of kneading the conductive filler by heating and melting a crystalline polymer, particularly a polyolefin, and obtains a composition having stable characteristics. In addition, if the amount of the conductive filler is increased, the PTC characteristic is lost, or physical characteristics such as adhesion and flexibility are significantly deteriorated, so that the initial resistance (Ro) is low. Can't do things,
Further, there is a problem that the switch temperature (Ts) is determined by the melting point of the polymer to be used and cannot be adjusted according to the purpose of use.

A conventional PTC composition in which a conductive filler such as carbon is dispersed in a crystalline polymer is usually used.
2 shows a temperature-resistance characteristic curve (CL) as shown in FIG. In FIG. 1, To is the room temperature (25 ° C.), Ts is the switch temperature (the temperature at which the resistance value changes rapidly), Tp is the peak temperature (the temperature at which the resistance value becomes maximum), and Ro is the initial resistance value (room temperature (To ), Rs is the switch temperature (T
s), Rp is the resistance at peak temperature (Tp),
Α is a resistance rise gradient [times / ° C.] accompanying a temperature rise after the switch temperature (Ts). As is clear from FIG. 1, in the conventional PTC composition, after reaching the peak temperature (Tp), the resistance rapidly decreases. This is considered to be because when the temperature is raised to the melting point or more and the crystalline polymer is melted, the conductive fillers dispersed therein come into contact with each other again to conduct electricity. PT having such properties
When the C composition is heated to a temperature higher than the peak temperature (Tp) for some reason, the self-temperature control function is lost and a large current flows. As a result, the temperature is further increased, which may eventually lead to burnout. Yes, dangerous.

In order to improve the property that the resistance value suddenly drops after reaching the peak temperature (Tp) as described above,
In a conventional crystalline olefin resin-based PTC composition, after being press-formed into a sheet, irradiation with radiation such as an electron beam or γ-ray is performed to crosslink the resin. However, irradiation with such radiation, in addition to the expensive equipment, leaves active radicals in the resin depending on the conditions,
Since heat resistance and durability may be significantly deteriorated, careful condition management is required.

[0007] Most of the conventional PTC compositions are press-formed into sheets as described above, but recently, in order to enhance practicality, inks or pastes which can be directly applied to a substrate are used. A PTC composition in the form of a powder is also disclosed.
For example, JP-A-6-45105, JP-A-8-12
No. 182 discloses an amorphous polymer such as natural rubber or synthetic rubber, a crystalline polymer particle such as polyethylene or polypropylene which is incompatible with the amorphous polymer, and a conductive filler such as conductive carbon black and graphite. Consisting of PT
A composition C is disclosed.
No. 039 discloses a printing ink for a self-temperature controlling heater, comprising a copolymer of vinyl acetate and polyethylene (EVA) having a specific vinyl acetate content as a base polymer and containing conductive particles therein. Have been.

As described above, the greatest difficulty in producing an ink-like or paste-like PTC composition using a crystalline polymer such as an olefin-based polymer as a base polymer is the balance between the solvent solubility of the base polymer and the PTC properties. is there. That is, in order to form an ink-like or paste-like composition, it is essential to dissolve the base polymer in an appropriate solvent. However, if the crystallinity of the polymer is high, the PTC property is excellent, but it is difficult to dissolve in the solvent. Conversely, when the crystallinity of the polymer is low, the polymer is easily dissolved in the solvent but the PTC property is inferior. For example, both the solvent solubility and the PTC property require contradictory crystallinity. That is, Japanese Patent Laid-Open No. 6-451
No. 05 and Japanese Patent Application Laid-Open No. 8-120182 disclose a method in which a conductive filler is dispersed in an amorphous polymer such as a natural rubber or a synthetic rubber, and the amorphous filler is compatible with the amorphous polymer. No olefin-based crystalline polymer particles are dispersed, and those disclosed in the above-mentioned JP-A-10-183039 are ethylene-vinyl acetate having a vinyl acetate content in a specific range which is a minimum required amount for dissolution. A copolymer is used as a base polymer, conductive particles are dispersed in the base polymer, and then a solvent is added to form an ink. Thus, the balance between the solvent solubility of the amorphous polymer and the PTC characteristics of the crystalline polymer is obtained. However, when these properties alone are viewed individually as solvent solubility and PTC properties, none of these properties can be optimized, It can not be said that may not always satisfactory in both respects the agent soluble and PTC characteristics.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention can be applied directly to a substrate surface by a printing method or the like to form a film, and can be used for irradiation of radiation such as electron beam or γ-ray. A sheet heating element or element having excellent PTC characteristics without complicated cross-linking treatment (hereinafter referred to as “PTC material”
Collectively. ) Is to be provided.

[0010]

In order to achieve the above object, a resin composition having PTC characteristics according to the present invention comprises a solvent-soluble polyester resin having a glass transition temperature of 50 ° C. or lower as a base polymer, and a base resin comprising the same. Polyester resin 1
20 parts by volume to 100 parts by volume of a conductive filler is dissolved and dispersed in an organic solvent in the form of an ink or paste in which an organic solvent is used, and a curing agent, comprising two liquids, After mixing the two liquids of the paste-form base material and the curing agent, the mixture is applied to a substrate provided with electrodes, and heated and dried and cured to crosslink the polyester resin to produce a PTC material.

The PTC composition of the present invention will be described in more detail. Various solvent-soluble polyester resins are used as a base polymer, and granular conductive carbon is dispersed in the base polymer to form a paste. The paste is applied to a polyester film provided with electrodes and dried (see FIG. 4). When the temperature-resistance value was measured, as shown in FIG. 2, the characteristic curve (C
La), the resistance value is initially 40 to 50 as the temperature rises.
A characteristic curve (CL-b) that gradually rises up to about twice and gradually falls again, and a characteristic curve (CL-b) in which the resistance value rapidly rises to about 100 times the initial value as the temperature rises and then drops sharply again. The characteristics of the three patterns b) were obtained.
In this case, when the used polyester resin showed which characteristic curve of the three patterns, it was found that there was no particular correlation with the basic characteristics of the resin such as the glass transition temperature (Tg) of the polyester resin. The characteristic curve is also P
In view of the characteristics required as a TC material, it was not suitable for practical use. For this reason, simply using a polyester resin as the base polymer would provide an excellent P
It is clear that a resin composition having TC characteristics cannot be obtained.

Next, a small amount of a polyvalent isocyanate compound was mixed with the same carbon-dispersed paste as described above, and after stirring, the mixture was applied to a polyester film provided with electrodes in the same manner as described above, and the temperature-resistance value of the heat-cured coating film was applied. 2 is significantly different from the case of FIG. 2 in which the polyvalent isocyanate is not mixed, as shown in FIG. 3, a characteristic curve (CL-a) in which the resistance value hardly changes even when the temperature rises, As the temperature rises, the resistance value rapidly increases to 1000 times or more of the initial value, and even when the temperature is further increased, the resistance value of 1000 times or more of the initial value is maintained, and the characteristic curve (CL-
The characteristic curves of the two patterns d) were obtained. in this case,
Which of the three characteristic patterns shown in FIG. 2 when the polyvalent isocyanate compound is not mixed is completely independent of which characteristic curve is exhibited, and the glass transition temperature of the polyester resin used as the base polymer ( Tg). That is, a polyester resin having a glass transition temperature (Tg) higher than 50 ° C. as a base polymer did not show any PTC characteristics like the characteristic curve of CL-a, whereas the glass transition temperature (Tg) was low. Those using a polyester resin having a temperature of 50 ° C. or lower as a base polymer, like the characteristic curve of CL-d,
At a specific temperature, the resistance value rises extremely sharply, and the rate of change of the resistance value reaches 1000 times or more of the resistance value at room temperature (initial resistance value). Was maintained at 1000 times or more of the resistance value of the above, and substantially maintained an insulating state. That is, by using a polyester resin having a glass transition temperature (Tg) of 50 ° C. or less as a base polymer, dispersing a conductive filler in the base resin, and crosslinking with a polyvalent isocyanate compound, without requiring irradiation with radiation or the like. A PTC material having excellent PTC characteristics and having a resistance value that does not decrease again even when the temperature is further increased after the switch temperature can be obtained.

In the PTC composition of the present invention, the polyvalent isocyanate compound reacts with a carboxyl group and a hydroxyl group at the terminal of the polyester molecule to promote crosslinking.
The mechanism of why the PTC property is exhibited only for polyester resins having a glass transition temperature (Tg) of 50 ° C. or lower has not been analyzed. However, the effect was surprising as described above. Further, it was found that changing the curing temperature changed the switch temperature (Ts) (see FIG. 5). That is, the PTC composition of the present invention can provide a PTC material having an arbitrary switch temperature (Ts) by defining the curing temperature.

The solvent-soluble polyester resin which is the base polymer in the PTC composition of the present invention is a polyester resin such as polyethylene glycol terephthalate or polybutylene glycol terephthalate, which is obtained by converting a part of an acid component or a glycol component to another component (a copolymer monomer). ) Can be produced by lowering the melting point and crystallinity by imparting solubility by random polymerization. Examples of the acid component used as the copolymer monomer include orthophthalic acid; isophthalic acid;
6-naphthalenedicarboxylic acid; aromatic divalent carboxylic acid such as paraphenylenedicarboxylic acid, alicyclic divalent carboxylic acid such as 1,4-cyclohexanedicarboxylic acid, succinic acid; glutaric acid; adipic acid; suberic acid; azelaic acid Aliphatic dicarboxylic acids such as sebacic acid. Examples of the glycol component include 1,2-propylene glycol; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; aliphatic dihydric alcohols such as neopentyl glycol; diethylene glycol; Glycol; dipropylene glycol; polyglycols such as tripropylene glycol. These copolymer monomers may be used alone or in combination of two or more. Polyester resin copolymerized by the above method to impart solvent solubility,
It is commercially available from a number of manufacturers, and among them, one having a glass transition temperature (Tg) of 50 ° C. or less and suitable for the purpose of the present invention can be used. Moreover, the selection condition of the polyester resin as the base polymer is only the above-mentioned glass transition temperature (Tg), and the balance between the solvent solubility of the conventional base polymer in the form of an ink or a paste and the PTC property is not balanced. You don't need to worry about it. The polyester resin may be used as a mixture of two or more.

As the conductive filler, any of various conventionally known materials such as carbon powder, metal powder and metal plating powder can be used. However, when metal powder or metal plating powder is used, it is preferable to avoid easily oxidizable metals such as iron, copper, and aluminum. As the shape of the conductive filler, a granular or spherical powder having a structure of about 0.006 to 50 μm without development of a structure is preferable, and carbon powder such as furnace black, thermal black and carbon beads is more preferable. Further, the above-mentioned conductive fillers may be used alone or in combination of two or more. The amount of the conductive filler is related to the initial resistance value (resistance at room temperature; Ro) of the composition. The larger the amount of the filler, the lower the initial resistance value (Ro). Since the resistance value (Ro) becomes high, the compounding amount is adjusted so as to exhibit an appropriate resistance value according to the application.
It is blended in the range of 0 volume parts. When the conductive filler is carbon powder, 2 parts per 100 parts by weight of the polyester resin is used.
It is preferable that the amount is about 0 to 300 parts by weight.
The solvent-soluble polyester resin used as the base polymer of the PTC composition in the present invention has a good dispersibility of the carbon black and other fillers, and the composition according to the present invention is excellent regardless of the amount of the conductive filler. Since the PTC characteristics are exhibited, the volume resistivity is determined to be 0.1 to 1 by determining the type and amount of the conductive filler within the above range.
Even if carbon powder is used as the conductive filler, a wide range of PTC materials having a volume resistivity of 1 to 1000 Ω · cm can be produced.

As the polyvalent isocyanate compound used as a crosslinking agent, toluene diisocyanate (TD
I); diaminodiphenylmethane diisocyanate (M
DI); 1,5-naphthalenediisocyanate (ND
I); Toluidine diisocyanate (TODI); Xylylene diisocyanate (XDI); Aromatic diisocyanate such as p-phenylene diisocyanate, isophorone diisocyanate (IDPI); Hydrogenated XDI; Alicyclic diisocyanate such as hydrogenated MDI; HDI); trimethylhexamethylene diisocyanate (TMDI); 1,3,6-hexamethylene triisocyanate; lysine diisocyanate (LDI); aliphatic diisocyanates such as 1,6,11-undecane triisocyanate and aliphatic triisocyanates There are generally used polyvalent isocyanate compounds. The amount of these polyvalent isocyanate compounds to be used is preferably about 1 to 25 parts by weight, more preferably about 2.5 to 20 parts by weight, based on 100 parts by weight of the polyester resin. If the amount of the polyvalent isocyanate compound used is less than 1 part by weight, the crosslinking effect is low and sufficient PTC characteristics cannot be obtained. When the amount is more than 25 parts by weight, there is no particular problem, but there is no need to use a large amount. The polyvalent isocyanate compound can be dissolved and dispersed in an organic solvent by dissolving a solvent-soluble polyester resin and a conductive filler into an ink- or paste-based base material, mixed before application, and heat-cured after application. It is essential to achieve the effects of the present invention, for example, to prepare a conductive composition paste using a solution in which a polyester resin and a polyvalent isocyanate compound are reacted in advance, and to apply and dry this paste There is no effect of using a polyvalent isocyanate compound.

Furthermore, a catalyst can be used in the PTC composition according to the present invention in order to promote a crosslinking reaction between the polyester resin and the polyvalent isocyanate. Examples of the catalyst include trimethylamine; N, N-dimethylcyclohexylamine; N, N, N ′, N′-tetramethylethylenediamine; N, N, N ′, N′-tetramethylpropane-1,3-diamine; N, N ', N'-tetramethylhexane 1,6-diamine; N, N, N', N ", N"-pentamethyldiethylenetriamine;tetramethylguanidine;triethylenediamine; N, N-dimethylpiperazine; Methylmorpholine; tertiary amine compounds such as 1,2-dimethylimidazole, stannasoctoate; dibutyltin acetate; dibutyltin dilaurate; dibutyltin mercaptide; dibutyltin thiocarboxylate; dibutyltin dimaleate; dioctyltin mercaptide; Organic gold such as dioctyltin thiocarboxylate The compounds can be used. When the amount of the catalyst is small, the effect of promoting the curing is low, and when the amount is large, the pot life of the curable composition after mixing the polyvalent isocyanate compound is short, and the usability is poor. Therefore, the amount of the catalyst used is determined according to the activation effect of the used catalyst in consideration of both the curing acceleration effect and the pot life, but is usually about 0 to 0.5 part by weight based on 100 parts by weight of the polyester resin. Is preferred. The catalyst may be preliminarily mixed with the main component, or may be added at the same time when the polyvalent isocyanate compound is mixed with the main component.

As the solvent, those which dissolve the polyester resin to be used, other than those having a functional group which reacts with the polyvalent isocyanate compound, such as an alcohol-based solvent, are used. Specific examples include ethyl acetate; butyl acetate; methyl benzoate; ester solvents such as ethyl benzoate; cellosolve acetate; butyl cellosolve acetate;
Carbitol acetate; glycol ester solvents such as butyl carbitol acetate; dimethyl succinate; diethyl succinate; dimethyl adipate; aliphatic dibasic acid ester solvents such as diethyl adipate; acetone; methyl ethyl ketone; methyl isobutyl ketone; isophorone Ketone solvents such as dioxane; and cyclic ether solvents such as tetrahydrofuran can be used. The amount of the solvent used is not particularly limited, but the amount is such that the main agent has an appropriate viscosity according to an application method such as screen printing. Usually, it is used in an amount of 30 to 60% by weight in the main ingredient.

If necessary, additives such as a dispersant, an antifoaming agent, a thixotropic agent, and a leveling agent may be added to the PTC composition according to the present invention.

A method for producing a PTC material from the PTC composition of the present invention will be described. The main agent is a 20 to 40% polyester resin solution, a predetermined amount of conductive filler, and if necessary, a curing catalyst, and other additives are blended and kneaded well with a mixer such as a three-roll mill or a planetary mixer. If necessary, a solvent is further added to adjust the viscosity to an appropriate value. In use, first, the required amount of the main agent is measured and fractionated, and 2.5 to 2.5 parts by weight based on 100 parts by weight of the resin component in the main agent.
20 parts by weight of a polyvalent isocyanate compound (usually,
(0.5 to 5 parts by weight with respect to 00 parts by weight), and after stirring well, the mixture is applied to a substrate provided with electrodes. The application method is
Usual coating methods such as screen printing, stencil printing, roll coater, gravure coater, brush coating and the like can be employed. After the application, the coating is heated in an oven furnace to perform drying and curing. Switch temperature of cured coating (Ts)
Depends on the type of the polyester resin and the conductive filler used and the compounding ratio thereof, but varies greatly depending on the curing temperature. Therefore, in order to obtain a cured coating film having a predetermined switch temperature (Ts), the oven furnace is required to have a predetermined temperature. It is necessary to control the temperature. Drying and curing times vary depending on the curing temperature, the type and amount of the curing accelerating catalyst, but usually from 3 to 1
It takes 5 hours.

The solvent-soluble polyester resin used in the present invention has good adhesion to many organic or inorganic substrates in other fields, and is used for adhesives and coatings excellent in flexibility, weather resistance and heat stability. Widely used for. Therefore, the PTC composition according to the present invention using the same polyester resin as a base polymer is also a polyester film, a polyimide film, plastics such as polyvinyl chloride, or ceramics, inorganic materials such as glass, or wood,
It has good adhesion to fibers and the like, and these wide-ranging materials can be used as a base material. Examples of the method for forming an electrode on a base material include, but are not limited to, attaching a metal foil, etching, and printing a conductive paste.

[0022]

EXAMPLES Next, the present invention will be specifically described with reference to examples, but these examples do not limit the present invention at all.

Examples 1 to 7 and Comparative Examples 1 to 13 As shown in Table 1, 100% by weight of a 10% solvent-soluble polyester resin having a different glass transition temperature (Tg) was added to a 36% isophorone solution having a particle size of 0.09 μm. 100 parts by weight of thermal black (Asahi Carbon Co., Ltd.) and 0.10 parts by weight of dibutyltin laurate were blended and kneaded with a three-roll mill to prepare a paste. This paste
Alternatively, this paste is used as a base material, and 10 parts by weight of a polyvalent isocyanate compound (Sumitomo Bayer Co., Ltd .; Sumidur L) is mixed as a curing agent, and then a distance of 30 mm as shown in FIG. 2.5m width opposite
m, a pair of strip-shaped silver electrodes having a thickness of 10 μm and a thickness of 1
The PTC characteristics between the electrodes were measured after applying to an 88 μm polyester film (PET film) over a width of 30 mm (shaded area in the figure), heating in an oven furnace at 80 ° C. for 12 hours, and drying and curing. 1 is shown.

[0024]

[Table 1]

The meanings of the symbols in Table 1 are as follows. Ro: Initial resistance value (resistance value at room temperature). Ts: switch temperature (temperature at which the resistance value changes rapidly). Tp: peak temperature (temperature at which the resistance value becomes maximum), where the symbol “>” rises after the switch temperature (Ts) without inflection temperature of temperature-resistance value. Mc: change rate (Rp / Ro, Rp) at peak temperature (Tp)
Is the resistance value at Tp), however, when Tp is a “>” mark, Ts
The change ratio (Rs + 20 / Ro) of the resistance value (Rs + 20) at a temperature higher by 20 ° C. than that was obtained. α: Resistance value rise gradient accompanying temperature rise after the switch temperature. Dc: change rate (Rp + 50 / Ro) of the resistance value (Rp + 50) at a temperature 50 ° C. higher than the peak temperature (Tp), where Tp is 80 ° C. higher than Ts when Tp is a “>” mark The change ratio (Rs + 80 / Ro) of the resistance value (Rs + 80) at the temperature was taken. CL-a to d: characteristic curves shown in FIGS. 1 and 2.

As shown in Table 1, Comparative Examples 1 to
Those which do not contain a curing agent such as 7, 9, 11 and 13 show no PTC characteristics at all (characteristic curve CL-
a), the change of the resistance value was slow even if the PTC characteristic was exhibited (characteristic curve CL-b), or the resistance value dropped after exceeding the peak temperature was large (CL-c). On the other hand, those using a polyester resin having a glass transition temperature (Tg) of 50 ° C. or less as shown in Examples 1 to 7 showed an extremely sharp change in resistance value (characteristic curve). CL-d). However, among those containing a curing agent, those using a polyester resin having a glass transition temperature (Tg) higher than 50 ° C., such as Comparative Examples 8, 10 and 12, did not show any PTC characteristics (characteristics). Curve CL-a).

Examples 8 to 12 and Comparative Examples 14 to 16 A solvent-soluble polyester resin having a glass transition temperature (Tg) of 6 ° C. (trade name of Toyobo Co., Ltd .; Byron 300) 100
100 parts by weight of thermal black (Asahi Carbon Co., Ltd.) having a particle size of 0.09 μm and 0.10 parts by weight of dibutyltin laurate were mixed with 36 parts by weight of a 36% isophorone solution.
The paste was prepared by kneading with this roll mill. After a predetermined amount of a polyvalent isocyanate compound (Sumitomo Bayer Corp .; Sumidule L) shown in Table 2 was mixed with this paste as a curing agent, the polyester having the silver electrode shown in FIG. After coating on a film and heating and drying at 80 ° C. for 12 hours in an oven furnace, P
The TC characteristics were measured, and the results are shown in Table 4. Comparative Example 1
6 is a solution obtained by first mixing dibutyltin laurate and 2.5 parts by weight of a polyisocyanate compound with a polyester resin solution, and heating and stirring the mixture at 80 ° C. for 12 hours.
A paste was prepared by blending 00 parts by weight of thermal black, applied to a polyester film provided with silver electrodes shown in FIG. 4 in the same manner as described above, and dried by heating at 80 ° C. for 1 hour in an oven furnace. The PTC characteristics between the electrodes were measured.
The symbols in the table are the same as in Table 1.

[0028]

[Table 2]

As shown in Table 2, Comparative Example 14
When the amount of the polyvalent isocyanate compound is less than 1 part by weight as in 15, the resistance value drops again after exceeding the peak temperature (characteristic curve CL-c), and the effect of blending the polyvalent isocyanate compound is obtained. Was inadequate. On the other hand, when the polyvalent isocyanate compound is used in an amount of 1 part by weight or more as in Examples 8 to 12, the resistance value does not drop again, and the change in the resistance value becomes sharp, resulting in an excellent PTC. Characteristics were obtained (characteristic curve CL-d). However, in Comparative Example 16 using a polyester resin which had been crosslinked before being applied to a substrate by reacting with a polyvalent isocyanate compound, the effect of using the polyvalent isocyanate compound did not appear at all. This indicates that the effect of using the polyvalent isocyanate compound is exhibited only when the crosslinking of the polyester resin is performed after application to the substrate.

Example 13 The same paste as in Examples 8 to 12 was mixed with 10 parts by weight of a polyvalent isocyanate compound (trade name of Sumitomo Bayer Co., Ltd .; Sumidur N350) as a curing agent, and as shown in FIG. After being applied to a polyester film provided with a silver electrode, the temperature (curing temperature) of the oven furnace and the curing time were changed as shown in Table 3 to obtain the P between the electrodes after drying and curing.
The TC characteristics were measured, and the results are shown in Table 3. The characteristic curves 1 to 3 in the table are shown in FIG.

[0031]

[Table 3]

As shown in Table 3 and FIG. 5, the switch temperature (Ts) changes depending on the oven furnace temperature. Therefore,
By defining the oven furnace temperature, that is, the drying / curing temperature, a PTC material having a wide range of arbitrary switch temperatures (Ts) can be produced.

[0033]

As described above, the resin composition having PTC characteristics according to the present invention is a two-pack type of a base resin and a curing agent having a solvent-soluble polyester resin having a glass transition temperature of 50 ° C. or lower as a base polymer. Since it is in the form of an ink or paste, a film can be formed directly on the substrate by a general-purpose coating method such as screen printing, and cross-linking treatment by irradiation with radiation using an expensive device is not necessary. Various PTC materials such as a PTC element and a planar heating element having a self-temperature control function can be easily manufactured without requiring any special condition management. In addition, this composition can be used in a wide range of fields because the switch temperature at which the resistance value changes rapidly only by changing the curing temperature can be arbitrarily set. further,
The cured film has excellent adhesion to many organic or inorganic substrates, and also has excellent flexibility, weather resistance, and thermal stability.

[Brief description of the drawings]

FIG. 1 is a graph showing a temperature-resistance characteristic curve of a conventional PTC composition.

FIG. 2 is a graph showing a temperature-resistance characteristic curve of a resin composition in which a polyester resin is not crosslinked.

FIG. 3 is a graph showing a temperature-resistance characteristic curve of a resin composition obtained by crosslinking a polyester resin.

FIG. 4 is an explanatory view of a PTC property measurement test of the composition.

FIG. 5 is a graph showing a temperature-resistance change magnification characteristic showing a difference in switch temperature due to a difference in curing temperature of the PTC composition of the present invention.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Chiga Moriguchi 2-5-30 Nishi-Nagasu-cho, Amagasaki-shi, Hyogo F-term in Ogi Chemical Industry Co., Ltd. (Reference) DA036 DA066 EN028 EN038 EN048 ER007 EU118 EU138 EU238 EZ048 FD116 FD147 FD158 GQ00

Claims (5)

[Claims] 1. A solvent-soluble polyester resin having a glass transition temperature of 50 ° C. or lower is used as a base polymer, and this and a conductive filler in an amount of 20 to 100 parts by volume per 100 parts by volume of the polyester resin are dissolved and dispersed in an organic solvent. A resin composition having PTC characteristics, comprising two liquids of a cured ink or paste base material and a curing agent. 2. The polyisocyanate compound according to claim 1, wherein the curing agent is selected from the group consisting of a polyvalent isocyanate compound comprising an aliphatic polyvalent isocyanate, an aromatic polyvalent isocyanate and an alicyclic polyvalent isocyanate. Resin composition. 3. The resin composition according to claim 2, further comprising a catalyst for promoting a crosslinking reaction between the polyester resin and the polyvalent isocyanate. 4. The catalyst according to claim 3, wherein said catalyst is selected from the group consisting of tertiary amine compounds and organometallic compounds.
The resin composition as described in the above. 5. A solvent-soluble polyester resin having a glass transition temperature of 50 ° C. or lower is used as a base polymer, and this and 20 to 100 parts by volume of a conductive filler per 100 parts by volume of the polyester resin are dissolved and dispersed in an organic solvent. A resin composition having a PTC characteristic comprising a crosslinked cured product obtained by mixing two liquids of a cured ink or paste-based main agent and a curing agent, and then heating and curing the mixture.