JPH061723B2 - Heat sensitive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a heat-sensitive element comprising a novel resin composition,
More specifically, the present invention relates to a high-performance heat-sensitive element which is used as a sensor material for controlling the temperature of heating appliances such as electric blankets and electric carpets and which is particularly excellent in bending fatigue resistance.

<Prior Art> It is well known in the art to utilize a temperature dependency of electrical properties of a polymer material as a temperature detector, as is seen in, for example, an electric blanket or an electric carpet. ing. In these heating appliances, one of the characteristics such as polymer dielectric constant, DC resistance, and impedance, or a combination of two or more characteristics is selected as a control factor, and these characteristics change with temperature. Is used to activate the temperature control circuit. The properties required for such a heat-sensitive element material are (1) a large change in the electrical properties of the polymer with temperature, that is, high temperature detection sensitivity, and (2) a small change in the electrical properties due to moisture absorption. , (3) little change in electrical characteristics over time, and (4)
Mechanical properties, especially excellent bending fatigue resistance, are mentioned. In general, polyamide is a material that has a large temperature dependence of electrical characteristics, and is also excellent in heat resistance, mechanical properties, and moldability. Among them, nylon 11 and nylon 1
So-called high-grade polyamides such as 2 have been put to practical use as suitable heat-sensitive element materials. However, polyamide is inherently hygroscopic, and it is inevitable that nylon 11 and nylon 12, which have relatively low hygroscopicity, will change in properties due to moisture absorption. A method using a mixture of a nylon low-polymerization degree phenol resin for the purpose of reducing the hygroscopicity of nylon and improving the temperature detection sensitivity to obtain a high-performance heat-sensitive element material (for example, JP-B-53-117). Method) and a method in which a novolac-type phenol resin is graft-copolymerized with nylon (for example, Japanese Patent Publication No. 54-3).
No. 7640) is disclosed.

<Problems to be Solved by the Invention> According to these methods, although an effect is recognized in terms of moisture resistance, introduction of a phenol resin into nylon impairs the original toughness and flex fatigue resistance of nylon. Even if the deterioration of flex fatigue resistance is relatively small by using a phenolic resin with a low degree of polymerization, it is harsh assuming that the electric blanket may be folded or wrinkled during use. It is difficult to endure various bending conditions. Further, these materials are still insufficient in temperature detection sensitivity, and there is a demand for high-performance thermosensitive element materials having high sensitivity, low moisture absorption and excellent mechanical properties such as bending fatigue resistance.

An object of the present invention is to provide a high-performance heat-sensitive element material having higher sensitivity and lower hygroscopicity than ever before and excellent mechanical properties such as flexural fatigue strength.

<Means for Solving Problems> The above-mentioned problems are (I) (a) 90 to 10% by weight of a polyamide unit represented by the following formula (1) and (b) a polyester unit 10 represented by the following formula (2). A heat-sensitive element is provided which comprises a resin composition obtained by kneading 100 parts by weight of polyester amide composed of 90% by weight and 1 to 50 parts by weight of (II) phenol formaldehyde resin. .

(Here, i represents an integer of 10 or 11.) The present invention will be described in detail below.

The polyesteramide used in the present invention is a copolymer in which the polyamide portion is composed of the undecane amide or dodecane amide unit represented by the formula (1) and the polyester portion is composed of butylene terephthalate or butylene isophthalate unit. This copolymer is obtained by polycondensing monomer raw materials such as corresponding amino acids or lactams, 1,4-butanediol, terephthalic acid and its ester, isophthalic acid and its ester,
For example, it is manufactured by the method as disclosed in JP-A-56-88428. The copolymerization ratio of the polyamide part and the polyester part needs to be in the range of 90/10 to 10/90% by weight, and if it is out of this range, the flex fatigue resistance of the copolymer is significantly deteriorated, which is not preferable.

The above-mentioned polyester amide itself can be used as a heat-sensitive element material having excellent temperature sensing ability and mechanical properties (for example, JP-A-57-206001 and 58-136624), and further moisture resistance can be obtained by combining with a phenol resin. Thus, it becomes an extremely excellent thermosensitive element material having improved electrical property stability.

The (II) phenol formaldehyde resin used in the present invention is obtained by polycondensing a phenol derivative such as phenol, alkylphenol, oxybenzoic acid ester and formaldehyde with an ordinary acid catalyst.
When phenol is polycondensed with formaldehyde, there are a total of three reaction sites at both ortho and para positions. In the case where an alkylphenol or oxybenzoic acid ester in which one of these is substituted is used as a raw material, the resulting phenol resin has a mostly linear structure, and the linear phenol resin thus obtained The average molecular weight of is usually in the range of 200 to 2000. On the other hand, when phenol is used as a raw material, the reaction site of phenol is not substituted, and a three-dimensional structure is obtained by crosslinking. In the present invention, a linear structure phenol resin can be used, of course,
Further, even a partially crosslinked phenolic resin having a three-dimensional structure can be used as long as it has a significantly high crosslinking density and is completely cured by itself. For example, a phenolic resin having a moderately controlled crosslink density, such as a granular phenolic resin marketed by Kanebo Co., Ltd. under the trade name of "Belpearl", is preferably used in the present invention.

The blending amount of the (I) polyesteramide component and the (II) phenol formaldehyde resin component must be in the range of 1 to 50 parts by weight of the (II) phenol formaldehyde resin with respect to 100 parts by weight of the (I) polyesteramide component. Yes, based on 100 parts by weight of (I) polyesteramide component
(II) The phenol formaldehyde resin is more preferably in the range of 5 to 40 parts by weight. When the content of the phenol formaldehyde resin is less than 1 part by weight, the hygroscopicity of the polymer becomes large, which is inconvenient. On the other hand, when the content of the phenol resin exceeds 50 parts by weight, the material becomes a hard and brittle material and the flex fatigue resistance is impaired. It is inconvenient.

The method for mixing the polyesteramide and the phenol resin is not particularly limited, and a generally known method can be adopted. That is, pellet amide and phenol resin pellets, powders, strips, liquids, etc. are uniformly mixed with a high-speed stirrer and then melt-kneaded with an extruder, and polyester amide and phenol resin during molding without kneading with an extruder. Any method such as a method of blending and extruding, a method of melt-kneading using a Banbury mixer or a rubber roll machine can be adopted.

To the resin composition of the present invention, an electrical property improving material such as copper halide, copper halide complex salt, alkali metal halide salt, and surfactant may be further added as long as the stability of the electrical properties is not impaired. Also, mechanical properties,
Other additives such as an antioxidant, a thermal decomposition stabilizer, a light resistance agent, a hydrolysis resistance improver, a colorant, a flame retardant, and various molding aids can be appropriately used as long as the electrical characteristics are not impaired.

A thermosensitive element can be obtained by supplying the above resin composition to an ordinary extruder or the like and molding it into a shape such as a heating wire or a sheet.

<Operation> It is extremely important to combine the polyester amide and the phenol resin as the heat-sensitive element material of the present invention.
By adopting a specific polyester amide, which is originally extremely flexible and has excellent flex fatigue resistance, it is possible to obtain a material with excellent flex fatigue resistance and durability that cannot be obtained with a combination of nylon and phenol resin. The moisture resistance of amide was effectively improved by the added phenol resin, and an extremely excellent thermosensitive element material having good electric characteristics, moisture resistance and durability was obtained.

<Examples> The present invention will be described in more detail with reference to the following examples. The evaluation of various characteristics in the following examples and comparative examples was performed as follows.

(1) Relative viscosity of solution: Relative viscosity at 25 ° C. of a solution of 0.5 g of polymer dissolved in 100 ml of orthochlorophenol.

(2) Melting point: melting peak temperature when measured using a Perkin-Elmer DSC-1B type differential differential calorimeter at a heating rate of 20 ° C./min.

(3) Moisture absorption rate: It was calculated from the weight increment when the equilibrium weight was reached by placing the polymer in an atmosphere of 25 ° C. and 65% RH.

(4) Thermistor characteristics: After drying the resin composition, a sheet having a thickness of about 0.2 mm is formed by melt pressing, and conductive coating is applied in a circle on both sides of this sheet to form an electrode.
After measuring the AC resistance at a frequency of Hz, the volume specific impedance (Zsp) was calculated from the electrode area and the sheet thickness. The Bz constant, which is a parameter of the thermistor characteristic, was calculated from the volume specific impedance at 50 ° C. and 110 ° C. according to the following formula. The larger this value, the better the sensitivity of the thermosensitive element.

(5) Flexural fatigue resistance: the resin composition is melted by a hot press,
Then, it is cooled with a cooling press to prepare a press sheet with a thickness of 1 mm, and a test piece with a width of 5 mm and a length of 80 mm is cut out from this sheet, and a load of 1 kg and a bending angle of 270 are measured using a MIT soft fatigue tester manufactured by Toyo Seiki Seisakusho. A bending test was carried out at a temperature of 120 times / minute, and the number of times of bending until the test piece was broken was measured to obtain bending fatigue resistance.

Example 1 11-aminoundecanoic acid 54.5 parts by weight, terephthalic acid 1
A mixture of 2.5 parts by weight and 12.2 parts by weight of 1,4-butanediol is heated and reacted at a temperature of 230 ° C. under N ₂ atmosphere,
Then, a polymerization catalyst was added, and after about 1 hour, 250 ° C., 1
A polyester having a weight ratio of polyamide (N-11) to polyester (PBT) of 75:25, a relative viscosity of 1.53, and a melting point of 153 ° C. is obtained by bringing the reaction conditions to Torr or lower and further performing a polymerization reaction for about 2 hours. The amide was obtained.

Next, 85 parts by weight of this polyester amide and 15 parts by weight of Bell Bell S-930 granular phenol resin manufactured by Kanebo Co., Ltd. were dry blended with a Henschel mixer and then melt-kneaded with an extruder to obtain a thickness. A 0.2 mm sheet was prepared as a sample for measuring electrical characteristics and hygroscopicity, and a 1 mm thick sheet was prepared as a sample for measuring bending fatigue resistance. The properties shown in Table 1 were obtained. It was

It was found that the heat-sensitive element obtained here had excellent sensitivity, excellent bending fatigue resistance, and extremely high performance with little influence of humidity.

Comparative Example 1 Various properties of a resin composition obtained by melt-kneading were measured in the same manner as in Example 1 except that nylon 12 was used instead of the polyesteramide resin, and the results are shown in Table 1. It was shown to. This product had low bending fatigue resistance and could not be put to practical use.

Example 2 Polyamide obtained by polymerizing in exactly the same manner as in Example 1 except that 22.9 parts by weight of 12-aminododecanoic acid, 37.0 parts by weight of terephthalic acid and 36.1 parts by weight of 1,4-butanediol were used as raw materials. (N-12) part and polyester (PB
The weight ratio of T) part is 30:70, relative viscosity is 1.52, melting point 17
70 parts by weight of polyester amide at 1 ℃ and "bell pearl"
The characteristics of the resin composition obtained by melt-kneading 30 parts by weight of S-930 were measured in the same manner as in Example 1, and the results shown in Table 1 were obtained. It was found that the heat-sensitive element obtained here was also an excellent heat-sensitive element having high bending resistance, moisture resistance, and temperature detection sensitivity.

Example 3 A resin composition obtained by melt-kneading 20 parts by weight of a phenol resin obtained by polycondensing P-nonylphenol and formalin under an acidic catalyst and 80 parts by weight of the polyesteramide prepared in Example 1. Various properties of the product were measured in the same manner as in Example 1, and the results are shown in Table 1.

Examples 4 to 5 Various characteristics of various resin compositions obtained by changing the types and mixing ratios of the polyesteramide and the phenol resin used are described below.
Shown in the table. The heat-sensitive elements obtained here were all high-performance heat-sensitive elements having high sensitivity, high humidity resistance and high durability.

<Effects of the Invention> According to the present invention, a high-performance thermosensitive element having excellent bending fatigue resistance, which is not obtained by the conventional combination of nylon and phenol resin, and having high sensitivity and low moisture absorption, was obtained.

By using such a high-performance heat-sensitive element, the durability of heating appliances such as electric blankets and electric carpets can be improved, and temperature control can be made more precise.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-61-2303 (JP, A) JP-A-61-2302 (JP, A) JP-A-61-2301 (JP, A) JP-A-61- 97904 (JP, A)

Claims (1)

[Claims] 1. A polyester amide comprising 100% by weight of 90 to 10% by weight of a polyamide unit represented by the following formula (1) and 10 to 90% by weight of a polyester unit represented by the following formula (2). Part and a resin composition obtained by kneading 1 to 50 parts by weight of (II) phenol formaldehyde resin. (Here, i represents an integer of 10 or 11.)