JPH0328452B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature-sensitive polymer material used in a temperature sensing device for controlling the temperature of a heating element such as an electric blanket or an electric carpet.

Temperature-sensitive polymer materials used for such temperature sensing must: (i) have a large rate of change in electrical properties, i.e., DC resistance, impedance, or capacitance due to temperature changes;

(ii) Variation in electrical characteristics due to usage environment, especially temperature, is small.

(iii) Must have a clear melting point to cope with abnormal temperature rises.

(iv) Mechanical strength and electrical properties do not deteriorate within the normal operating temperature range.

etc. is desired.

Hitherto, resins such as polyvinyl chloride, polyamide, and polyolefin have been proposed as temperature-sensitive polymer materials used for this type of purpose. Among these resins, polyvinyl chloride and polyamide are particularly used, but polyvinyl chloride has inferior heat resistance to polyamide and does not have a clear melting point like polyamide, so the heating element may rise abnormally. When heated, it does not have the fuse characteristic of melting within a narrow temperature range and interrupting the heater circuit. For this reason, polyamides are used, particularly high-grade nylons such as so-called nylon 11 and nylon 12, which have little variation in electrical properties due to moisture absorption.

However, the rate of change of its electrical characteristics is not necessarily a satisfactory value; for example, the thermistor B constant of impedance from 30°C to 60°C is at most 2000°C.
It only shows a value of about 〓. For this reason, it has been proposed to improve electrical properties by adding various additives such as surfactants, but these additives not only cause changes in electrical properties over time due to migration phenomena, but also often cause Since it is an ionic substance, direct current polarization occurs when a direct current component is applied, making it unsuitable as a heat-sensitive material. That is, in order to prevent changes in electrical characteristics over time, it is necessary to modify the heat-sensitive polymer material itself.

From this point of view, copolyamide has been proposed as a material with excellent heat sensitivity (Tokuko Showa).
51-10355) The temperature fuse function is lost because the melting behavior is broad.

The present invention has been arrived at as a result of intensive studies to overcome these problems. %
and (However, R ₁ is hydrogen or has 1 to 30 carbon atoms.
a straight-chain or branched alkyl group, n is a positive integer of 5 to 13) (2) A mixture or salt consisting of equimolar moles of a diamine represented by the formula and a dicarboxylic acid represented by the formula 50
or 5% by weight HOOC-A-COOH (However, R ₂ and R ₃ are hydrogen or a straight chain or branched alkyl group having 1 to 12 carbon atoms, and R ₂ and R ₃ may be the same or different. may also be used. m is a positive integer from 1 to 10. A has 4 carbon atoms.
to 20 straight-chain or branched divalent saturated hydrocarbon residues. ) The present invention provides a temperature-sensitive polymer material whose main component is a copolyamide obtained from

That is, as a lactam represented by formula a or an ω-aminocarboxylic acid represented by formula b,
Examples include caprolactam, enantholactam, capryllactam, ω-decyl lactam, ω-undecyl lactam, lauryllactam, and the corresponding ω-aminocarboxylic acids. Further, compounds in which the nitrogen of these lactams or ω-aminocarboxylic acids is substituted with an alkyl group having 1 to 30 carbon atoms, preferably 5 to 30 carbon atoms, can also be effectively used in the present invention, but the specific examples of the alkyl group Examples include n-butyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, lauryl, cetyl, stearyl, and the like. These N-substituted lactams or ω-aminocarboxylic acids can also be used in combination with unsubstituted lactams or ω-aminocarboxylic acids. These compounds are 50
It is used in an amount of from 70 to 95% by weight, preferably from 70 to 90% by weight.

Examples of dicarboxylic acids represented by the formula include adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These dicarboxylic acids are used in the form of an equimolar mixture or salt with the dipiperidyl alkane represented by the formula in an amount of 50 to 5% by weight, preferably 30 to 10% by weight. This is 5
If it is less than 50% by weight, the effect of the present invention will not be sufficiently exhibited, and if it is more than 50% by weight, the melting point of the copolyamide obtained will be low, making it unsuitable for electric blankets and electric carpets, which are the objects of the present invention. .

The relative viscosity of the m-cresol solution of the copolyamide of the present invention at a concentration of 0.5 g/100 ml is preferably in the range of 1.4 to 2.5, more preferably 1.5 to 2.5.
It is within the range of 2.3. This relative viscosity is 1.4
If it is lower than 2.5, the product cannot maintain sufficient mechanical strength, and if it is 2.5 or higher, the melt viscosity becomes too high, making it difficult to mold the product.

As specifically shown in the examples, the copolyamide obtained by the present invention has a large rate of change in volume specific impedance with temperature change, small variation in volume specific impedance due to humidity, and has a sharp change despite being a copolyamide. Because the copolyamide exhibits excellent electrical properties and exhibits excellent melting behavior, there is no change in electrical properties over time unlike when improved with additives, resulting in excellent performance as a temperature-sensitive polymer material. have.

Needless to say, the copolyamide obtained by the present invention may contain other additives, such as plasticizers, weathering stabilizers, heat stabilizers, fillers, flame retardants, colorants, etc., to the extent that they do not interfere with the electrical properties. These additives may be used in combination, or other resins may be blended.

In addition, an application example of a thermal heater using a temperature-sensitive polymer material, which is the object of the present invention, is shown in FIGS. 1A and 1B.
Shown below. A is a partially cutaway perspective view showing an example of a heat-sensitive temperature control line, which essentially includes an insulating material 1, a core wire 2,
It is composed of 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. With this configuration, the temperature can be controlled along the heat-sensitive temperature control line or control surface by utilizing the fact that the electrical characteristics of the polymer temperature-sensitive body 3, that is, the resistance value, impedance, or capacitance, change with temperature. It is something that is detected and controlled.

The present invention will be specifically explained below with reference to Examples.

Example 1 First, dodecanedicarboxylic acid HOOC
92 g of (CH ₂ ) ₁₀ COOH was placed in a 1-volume separable flask, 300 g of isopropyl alcohol was added, and the mixture was heated and stirred at 65 to 70° C. to completely dissolve. Add 1,3-di-(4-piperidyl)-propane to this heated solution. Prepare 86g of isopropyl alcohol at room temperature.
When 210 g of the solution was added through the dropping funnel while stirring, the dicarboxylic acid and diamine salt (hereinafter abbreviated as DP salt) precipitated out in a crystalline state. After completion of the dropwise addition, the mixture was left at room temperature overnight, washed with cold isopropyl alcohol, air-dried, and vacuum-dried to obtain about 176 g of DP salt.

70 g of ω-aminododecanoic acid and 30 g of the above DP salt were placed in a 500 ml separable flask equipped with a stirrer and a gas inlet tube, and heated at 220° C. for 14 hours while flowing nitrogen at a flow rate of about 200 ml/min. After the reaction was completed, the product was quickly taken out of the flask in a molten state under a nitrogen stream. The methanol extract of the obtained polymer (Soxhlet extraction for 24 hours) is
The relative viscosity at 25° C. of a metacresol solution with a concentration of 0.60% and 0.5 g/100 ml was 1.72.
Further, the melt flow index at 230°C was 35.0g/10min. Press sheets with thicknesses of 0.5 mm and 1.0 mm were made from this polymer.

Measurement of volume specific impedance: A 5 micron thick tin foil was pasted as an electrode on a 0.5 mm thick press sheet, using a model manufactured by Yokogawa Heuretsu Patscard Co., Ltd.
Using the 4247A multi-frequency LCR meter,
The volume specific impedance at 100 Hz was measured from 20°C to 90°C under an electric field strength of 100V/cm. The measurement results are shown as curve B in FIG. Note that curve A shown in the figure is the measurement result for nylon 12 homopolymer, and curve B clearly shows an improvement in the rate of change of impedance with temperature.

Additionally, differential scanning calorimetry (DSC) of this polymer
The melting curve according to the method is shown as curve b in FIG. Since it melts within a narrow temperature range, it has a fuse effect that shuts off the heater circuit in the event of abnormal temperature rise.

Measurement of tensile strength and elongation; JIS No. 2 dumbbell test pieces were punched out from a 1.0 mm thick press sheet and pulled at a tensile speed of 50.
Breaking strength and elongation were measured in mm/min. The tensile strength at break was 544 Kg/cm ² and the tensile elongation at break was 369%, while the comparative sample of nylon 12 homopolymer had a tensile strength at break of 500 Kg/cm ² and a tensile elongation at break of 290%.
Regarding mechanical properties, no inferiority was observed compared to nylon 12 homopolymer.

Example 2 In a 3-volume stainless steel autoclave, 473 g (2.396 mol) of lauryl lactam monomer, 247 g (0.799 mol) of N-n-octyl lauryl lactam, and DP salt (salt of dodecanedicarboxylic acid and 1,3-di-(4-piperidyl)propane) were placed. ) 180g (0.408mol), pure water 57g
After charging 1.4 g of orthophosphoric acid as a catalyst and completely replacing the inside of the reaction system with nitrogen, the internal pressure was reduced by applying nitrogen pressure.
It was maintained at 20Kg/cm ² G and heated at 290°C for 6 hours. Next, the pressure and temperature in the system were gradually lowered to 250°C and atmospheric pressure over about 1 hour, and stirring was continued at 250°C for 10 hours while flowing nitrogen at a flow rate of 150ml/min. After the reaction was completed, the contents were extruded into strands by applying nitrogen pressure, cooled in a water tank, and pelletized using a pelletizer. The methanol extraction content of the obtained polymer (Soxhlet extraction for 24 hours) was 0.5%.
The relative viscosity of the m-cresol solution at a concentration of 0.5 g/100 ml was 1.71, and the melt flow index at 230°C was 30.0 g/10 min.

Figure 2 shows the volume specific impedance values measured in the same manner as in Example 1 using a 0.5 mm thick pressed sheet of this polymer at 100 Hz under an electric field strength of 100 V/cm over a temperature range of 20°C to 90°C. It is shown by curve C. The temperature change rate of impedance is considerably improved compared to nylon 12 homopolymer (curve A).

Further, the melting curve of this polymer determined by DSC is shown as curve c in FIG. Since it melts within a narrow temperature range, it has a fuse effect that shuts off the heater circuit in the event of abnormal temperature rise.

Furthermore, the tensile strength at break measured in the same manner as in Example 1 was 450 Kg/cm ² and the tensile elongation at break was 405%.

Example 3 In the same manner as in Example 2, 148.0 g (0.75 mol) of lauryl lactam monomer, 15.5 g (0.05 mol) of N-n-octyl lauryl lactam and DP salt (octadecanedicarboxylic acid and 1,3-di-(4 A copolyamide polymer was produced from 110.6 g (0.20 mol) of a salt of -piperidyl)-propane.The methanol extract of the obtained polymer (Soxhlet extraction 24
The m-cresol solution with a concentration of 0.45% and 0.5 g/100 ml had a relative viscosity of 1.75 and a melt flow index of 28.0 g/10 min at 230°C.

Using a 0.5 mm thick press sheet of this polymer, the volume specific impedance was measured under an electric field strength of 100 V/cm over a temperature range of 20°C to 90°C at 100 Hz, and the second It is shown by curve D in the figure. The temperature change rate of impedance is considerably improved compared to nylon 12 homopolymer (curve A).

The melting curve of this polymer measured by DSC is shown as curve d in FIG. Since it melts within a narrow temperature range, it has a fuse effect that shuts off the heater circuit in the event of abnormal temperature rise.

Example 4 In the same manner as in Example 2, 157.8 g (0.8 mol) of lauryl lactam monomer, 44.9 g (0.1 mol) of N-n-stearyl lauryllactam and DP salt (azelaic acid and 1,5-di-(4- A copolyamide polymer was produced from 44.1 g (0.1 mol) of piperidyl)-pentane salt. The methanol extraction content of the obtained polymer (Soxhlet extraction for 24 hours) was 0.60%.
The relative viscosity of the m-cresol solution at a concentration of 0.5 g/100 ml was 1.68, and the melt flow index at 230°C was 35.0 g/10 min.

Using a 0.5 mm thick press sheet of this polymer, the volume specific impedance was measured under an electric field strength of 100 V/cm at 100 Hz from 20°C to 90°C in the same manner as in Example 1. It is shown by curve E in the figure. Nylon 12 homopolymer (curve A)
The rate of change of impedance with temperature is improved considerably.

The melting curve of this polymer measured by DSC is shown as curve e in FIG. Since it melts within a narrow temperature range, it has a fuse effect that shuts off the heater circuit in the event of abnormal temperature rise.

[Brief explanation of drawings]

FIG. 1A is a partially cutaway perspective view showing an example of a heat-sensitive temperature control line. FIG. 1B is a sectional view showing an example of a heat-sensitive temperature control surface. In the figure, 1 is an insulated wire, 2 is a core wire, 3 is a polymer temperature sensitive body, 4 is a signal wire, and 5 is a heater wire. FIG. 2 is a graph plotting the specific volume impedance of a polymer versus temperature. FIG. 3 is a graph in which the melting curve (endothermic peak) measured by differential scanning calorimetry (DSC) is plotted against temperature.

Claims (1)

[Scope of Claims] 1 (1) 50 to 95% by weight of a lactam represented by formula a or an ω-aminocarboxylic acid represented by formula b
and (However, R ₁ is hydrogen or has 1 to 30 carbon atoms.
a straight-chain or branched alkyl group, n is a positive integer of 5 to 13) (2) A mixture or salt consisting of equimolar amounts of a diamine represented by the formula and a dicarboxylic acid represented by the formula 50
or 5% by weight HOOC-A-COOH (However, R ₂ and R ₃ are hydrogen or a straight chain or branched alkyl group having 1 to 12 carbon atoms, and R ₂ and R ₃ may be the same or different. (m is a positive integer from 1 to 10. A is a divalent saturated hydrocarbon residue with a straight or branched chain having 4 to 20 carbon atoms) at a concentration of 0.5 g/100 ml. A temperature-sensitive polymer material made of copolyamide with a relative viscosity of 1.4 to 2.5.