JPS6228565B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention improves the resistance value, impedance, or capacitance behavior of a heat-sensitive material with respect to temperature in a polymer thermosensitive body made of a mixture of specific polyamide resins, particularly in a device that controls temperature using a capacitance component as one control factor. The present invention relates to a polymer thermosensitive body. Polymer thermosensitive materials are often used as constituent materials for electric wires for heating elements such as electric blankets and electric carpets. (2) small fluctuations in electrical properties depending on the environment in which the heating element is used, especially humidity; (3) mechanical strength and electrical properties within the normal operating temperature range. (4) it has a clear melting point to cope with abnormal temperature rises, etc. Polymer materials known to have been used as thermosensors include polyvinyl chloride, cellulose esters, polyamides, copolymers of acrylic esters and acrylonitrile (Japanese Patent Publication No.
Publication No. 1627, Special Publication No. 7635, Special Publication No. 1976-
(Refer to Publication No. 14179). Examples of applications of heat-sensitive temperature control lines or surfaces using these polymeric materials are shown in FIGS. 1A and 1B. A is a partially cutaway perspective view showing an example of a heat-sensitive temperature control line, which essentially consists of an insulating material 1, a core wire 2, a polymer temperature-sensitive body 3, a signal line 4, and a heater line 5. Further, B is a sectional view showing an example of a heat-sensitive temperature control surface. By adopting such a configuration, the electrical characteristics of the polymer temperature sensitive body 3,
That is, the temperature is detected and controlled along a thermosensitive temperature control line or surface by utilizing the fact that resistance value, impedance, or capacitance changes with temperature. Among the polymer materials mentioned above that are known as polymer thermosensors, polyamide resin has
It is often used as a polymer thermosensitive material because it has excellent mechanical properties, heat resistance, moldability, etc. Furthermore, polyamide resin is a crystalline polymer and has a clearer melting point than other resins, making it possible to cope with abnormal temperature rises. In other words, when polyamide resin is used for the polymer thermosensitive body 3 shown in FIGS. 1A and 1B, the melting point of the polyamide resin is around 200°C, and the temperature of the heating wire may rise above the melting point due to abnormal temperature rise. When this occurs, the polymer thermosensitive body melts, causing a short circuit between the heating wire 5 and the signal wire 4 shown in FIGS. 1A and 1B, and it becomes possible to activate the safety device. In order to make the rate of change in resistance, impedance, or capacitance due to temperature even more remarkable in the operating temperature range as a polymer thermosensor, for example, Japanese Patent Publication No. 14179/1983 describes the There is a description of producing a polymeric temperature sensitive composition in which an ionic surfactant, that is, a cationic or anionic surfactant is blended with vinyl chloride or polyamide resin. However, these ionic surfactants have poor heat resistance, and polyvinyl chloride has poorer heat resistance than polyamide resin, and unlike polyamide resin, it does not have a clear melting point and cannot cope with abnormal temperature rises. It has its drawbacks. Furthermore, when an ionic surfactant is blended with a well-known polyamide resin such as nylon 6 or nylon 66,
Due to the poor heat resistance of ionic surfactants, they cannot be blended. That is, it is possible to add surfactants such as stearyldimethylbenzylammonium chloride described in Japanese Patent Publication No. 35-14179 to polyamide resin to increase the temperature change in its electrical properties. However, its heat resistance is too poor to be kneaded into polyamide resin, so it is almost impossible to knead it into polyamide resin. In addition, nylon 6, a typical polyamide resin, as described in Japanese Patent Publication No. 26-1627,
Alternatively, in the case of nylon 66, etc., its water absorption ability is too high for a heat-sensitive material, so a film that provides moisture resistance such as polyvinyl chloride is formed on the outermost layer, as is already known as a heat-sensitive wire for electric blankets. Even so, it is difficult to obtain substantially complete moisture proofing. For this reason, nylon 6 or nylon 66
The control temperature point of a heat sensitive body using a heat sensitive body varies considerably depending on the environmental conditions in which it is placed. In other words, nylon 6 or nylon 66 has too high water-absorbing ability and its electrical properties vary significantly depending on the environmental conditions in which it is used, so it is practically impossible to use it as a heat-sensitive wire for electric blankets, electric carpets, etc. . This disadvantage increases synergistically when water-absorbing additives such as surfactants are added. Currently, the best polymer thermosensitive materials include nylon 11, nylon 12, or nylon 11, nylon 12, nylon 6, which has added electrical property improvers.
12, nylon 12, 12 and polyvinyl chloride are known. However, when using nylon 11, nylon 12, etc. alone, the temperature change in electrical properties is small and the absolute value of the electrical properties is large, creating difficulties in terms of electrical circuits (controllers). On the other hand, nylon 11 and nylon 12, which have improved electrical properties by adding additives,
Although polyvinyl chloride solves the above problems,
A major new problem arises in that DC polarization phenomena occur significantly. In addition, Japanese Patent Publication No. 10355/1988 describes the improvement of electrical properties by copolymerizing polyamide, but copolymerization increases water absorption, so it is not preferred as a polymer thermosensitive material. do not have. The inventors of the present invention solved the above problems and, as a result of intensive study on polymer thermosensitive materials whose electrical properties change less due to humidity (water absorption), found that N-substituted polyamide resin and
A mixture with polyamide resin whose equilibrium water absorption rate at 65% RH (maximum absorbed water content in an atmosphere controlled to 20°C and 65% RH) is 2.5% or less is excellent as a polymer thermosensitive material. They discovered this and arrived at the present invention. The N-substituted polyamide resin according to the present invention has a skeleton represented by the following general formula (), (), or/and (). [In the formula, X ₁ , X ₂ , X ₃ and X ₄ may be the same or different, and represent an aliphatic or aromatic hydrocarbon group, and R ₁ and R ₂ may be the same or different, respectively. may also represent an alkyl group, an arylalkyl group, an alkoxyalkyl group, a hydroxyalkyl group, or a polyoxyalkylene group. ] In the above general formulas () to (), X ₁ to _{X 4}
The hydrocarbon group represented by is preferably an alkylene group. In addition, the groups represented by R ₁ and R ₂ include an alkyl group having 1 to 20 carbon atoms,

[Formula] (n=1-20), -(CH ₂ ) _o -O-C _n H _2n+1 (n=1-20, m=1-20), -
(C _o H _{2 o} O) - _n H (n=1-20, m=1-20) is exemplified. The N-substituted polyamide resin according to the present invention can be produced by methods described in many known documents. Examples of methods for producing these include, for example, a method of copolymerizing N-substituted lactams and lactams, a method of polycondensing N-substituted aminocarboxylic acids and ω-aminocarboxylic acids, and a method of polycondensing dibasic acids with N-substituted diamines and diamines. There are a method of condensation, a method of N-substitution reaction of nylon polymer, etc. The molecular weight of the N-substituted polyamide resin according to the present invention is preferably such that the relative viscosity (ηγ) of a 0.4% m-cresol solution measured at 25°C is 1.3 or more. In addition, the polyamide resins having an equilibrium water absorption rate of 2.5% or less in an atmosphere of 20°C and 65% RH according to the present invention include nylon 11, nylon 12, nylon 6,
12, nylon 12, 12, nylon 6, 12/12 copolymer, nylon 6, 12/12, 12 copolymer, nylon
12/12, 12 copolymer, etc. are preferred. The reason why the equilibrium water absorption rate of the polyamide resin used here is limited as described above is as follows. That is, the impedance changes due to water absorption (generally, it becomes smaller when water is absorbed). In a polymer thermosensitive body, temperature is sensed from the value of impedance, so if the impedance changes due to surrounding humidity, an incorrect temperature will be sensed. Therefore, it is desirable that the equilibrium water absorption rate be as low as possible, and 2.5% is the critical point, and if it is larger than this, the accuracy of the thermosensor will be disrupted. In the present invention, N-substituted polyamide resin and 20
The mixing ratio of polyamide resin with an equilibrium saturated water absorption rate of 2.5% or less at ℃ and 65% RH is such that the ratio of N-substituted acid amide bonds to all acid amide bonds in the mixture is 3 to 70%. By this, the intended effects of the present invention can be achieved. The electrical properties can be further improved by adding to the blend of the present invention an electrical property improver that does not significantly reduce heat resistance or water absorption. below,
The present invention will be explained in more detail with reference to Examples. Example 1 N-octyl substituted nylon 12 (in general formula (), N-substitution rate 40%, X ₁ = X ₂ = (CH ₂ ) ₁₁ , R ₁ =
After blending 50 parts by weight of C ₈ H ₁₇ ) and 1250 parts by weight of nylon using a twin-screw extruder, a film of about 120 μm was obtained. 50μ aluminum foils measuring 15 cm square and 16 cm square were fused to both sides of this film by hot pressing to obtain a sample piece for measuring electrical properties. The temperature dependence of the impedance of the sample piece (dried sample) immediately after the sample piece was prepared was measured, and the thermistor B constant was calculated. After the measurement, the sample piece was saturated with moisture in a constant temperature and humidity chamber at 45℃ and 95%RH, and the impedance at 45℃ (Zwet) was measured, and the impedance of the dried sample at 45℃ (Zdry) was measured. ), the impedance fluctuation due to moisture absorption was investigated, and the results are shown in Table 1. From the results in Table 1, it can be seen that the blend obtained here has a large thermistor B constant and a significantly small variation in impedance due to moisture absorption, making it an excellent polymer thermosensitive material. Comparative Example 1 An experiment similar to Example 1 was conducted using Nylon 12, and the results are shown in Table 1. Example 2 N-methyl nylon 6/12 copolymer (in the general formula (), X ₁ = (CH ₂ ) ₁₁ , X ₂ = (CH ₂ ) ₅ , N-
Substitution rate 20%, R ₁ = CH ₃ ) 30 parts by weight and nylon 6,
Example 1 using a blend consisting of 70 parts by weight of 12
An experiment similar to that was conducted and the results shown in Table 1 were obtained. From the results in Table 1, it can be seen that the blend obtained here exhibits excellent properties as a polymer thermosensitive material. Comparative Example 2 The same procedure as in Example 1 was carried out using a blend consisting of 30 parts by weight of nylon 6/12 copolymer (a copolymer of 80 parts by weight of laurolactam and 20 parts by weight of caprolactam) and 6, 12, and 70 parts by weight of nylon. An experiment was conducted and the results shown in Table 1 were obtained. Example 3 N-heptyl substituted nylon 11 (in general formula (), N-substitution rate 30%, X ₁ = X ₂ = (CH ₂ ) ₁₀ , R ₁ =
C ₇ H ₁₅ ) 20 parts by weight and nylon 12/6, 12 copolymer
An experiment similar to that in Example 1 was conducted using a blend consisting of 80 parts by weight, and the results shown in Table 1 were obtained. From the results in Table 1, it can be seen that the blend obtained here is excellent as a polymer thermosensitive material.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1A is a partially cutaway perspective view showing an example of a heat-sensitive temperature control line, and FIG. 1B is a sectional view showing an example of a heat-sensitive temperature control surface. 1... Insulating material, 2... Core wire, 3... Polymer temperature sensitive body, 4
...signal line, 5...heater line.

Claims (1)

[Claims] 1 N-substituted polyamide resin, 20℃, 65%RH
A polymer characterized by comprising a mixture of a polyamide resin having an equilibrium water absorption of 2.5% or less such that the ratio of N-substituted amide bonds to the total acid amide bonds in the mixture is 3 to 70%. Thermosensitive body.