JPH0316384B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polymer temperature-sensitive 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, electrical properties, etc. do not deteriorate within the normal operating temperature range. It is desirable to have the following properties. Conventionally, resins such as polyvinyl chloride, polyamide, and polyolefin, especially polyvinyl chloride and polyamine, have been widely used as polymeric temperature-sensitive materials for this type of purpose, but polyvinyl chloride has a higher heat resistance than polyamide. Moreover, since it does not have a clear melting point like polyamide, it does not have fuse characteristics that will melt within a narrow temperature range and interrupt the heater circuit if the heating element becomes abnormally heated.
For this reason, polyamides, especially so-called high-grade nylons such as nylon 11 and nylon 12, whose electrical properties change little due to moisture absorption, are used, but the rate of change in electrical properties due to temperature changes is not always satisfactory, and It is also desired that fluctuations in electrical characteristics be further reduced. For example, the impedance thermistor B constant of these high-grade nylons from 30°C to 60° shows a value of about 2000 at most. For this reason, it has been proposed to improve the electrical properties by adding various additives such as surfactants. However, improvements made by these additives not only cause changes in electrical properties over time due to additive migration phenomena, but also changes in electrical properties due to hygroscopicity since they are more or less ionic substances or substances with polar groups. is observed, making it undesirable as a temperature-sensitive material. That is, in order to prevent changes in electrical properties over time and to reduce fluctuations in electrical properties due to moisture absorption, it is necessary to modify the polymer material itself. The present invention was arrived at as a result of intensive studies to overcome these problems. That is, (1) in the presence of 5 to 40 parts by weight of a polyolefin resin containing a carboxyl group, (2) (a) an N-alkyl-substituted lactam represented by formula a or an N-alkyl-substituted ω represented by formula b; -5 to 50% by weight of amino carboxylic acid; (However, R is a linear or branched alkyl group having 4 to 30 carbon atoms, and n is a positive integer of 5 to 13.) (b) A lactam represented by the formula a or an ω-amino compound represented by the formula b. Carboxylic acid 95 to 50
weight%

[Formula] Copolyamide obtained by polycondensing 95 to 60 parts by weight of a mixture consisting of H ₂ N (CH ₂ ) _o - COOH (b) (where n is a positive integer of 5 to 13) The present invention provides a polymer temperature-sensitive material consisting of: Examples of polyolefin resins containing carboxyl groups include polyethylene, polypropylene, poly-1-butene, poly-1-pentene, and poly-1-pentene.
- Polyolefins such as hexene, poly5-methyl-hexene - Homopolymers or ethylene and α-
A resin in which a carboxylic acid having a polymerizable unsaturated bond such as non-maleic acid is grafted to an olefin copolymer using a radical initiator, or an olefin monomer such as ethylene, propylene, butene-1 and acrylic acid or methacrylic acid. It is a resin obtained by copolymerization with a carboxylic acid having a polymerizable unsaturated bond such as. Further, the carboxyl groups contained in these polyolefin resins may be so-called ionomer resins in which part or all of the carboxyl groups have an ionic bond with a metal such as sodium or zinc. Next, the N-alkyl substituted lactams represented by formula a include caprolactam, enantholactam, capryllactam, ω-decyl lactam, ω
- A compound in which the nitrogen of the amide bond of a lactam having 5 to 13 linearly bonded methylene groups, such as undecyl lactam and lauryllactam, is substituted with a linear or branched alkyl group having 4 to 30 carbon atoms,
The corresponding lactams are sodified with sodium metal or sodium hydride to form alkyl chlorides, alkyl bromides, etc.
It is easily obtained by reacting with a halide. A specific method of operation is described, for example, in CS Marvel et al., Journal of Organic Chemistry, Vol. 22, pp. 1065-1067 (1957). The polymerizability of these N-alkyl-substituted lactams is facilitated by the substituents, and the equilibrium tends to shift toward the monomer side. is more advantageous. In addition, large lactams having 14 or more methylene groups constituting the lactam ring are not practical from an industrial standpoint from the viewpoint of raw materials. The alkyl group attached to the nitrogen atom of the amide bond is n-butyl, n-amyl, n-hexyl, n-
Straight chain saturated alkyl groups such as heptyl, n-octyl, n-decyl, n-cetyl, n-stearyl,
Includes partially branched saturated alkyls such as isoamyl and 2-ethylhexyl. methyl, ethyl,
A short-chain alkyl group such as propyl increases the hygroscopicity of the resulting copolyamide, and when used as a temperature-sensitive material, it is undesirable because it causes large fluctuations in electrical properties due to changes in humidity. 4 carbon atoms as nitrogen substituent
When the above-mentioned alkyl groups are used, the hygroscopicity of the resulting copolyamide is lowered, and fluctuations in electrical properties due to changes in humidity are reduced, providing a preferable temperature-sensitive material. On the other hand, if the number of carbon atoms in the substituted alkyl group is 30 or more, the concentration of amide bonds contained in the polymer becomes too low and the characteristics of the polyamide resin are lost, which is not preferable. In addition, N-alkyl substituted ω- represented by formula b
The amino carboxylic acid is ω-amino carboxylic acid corresponding to the above-mentioned N-alkyl substituted lactam. Lactams expressed by formula a include caprolactam, enantlactam, capryllactam, and ω-
decyl lactam, ω-undecyl lactam, lauryl lactam, etc., and the ω-aminocarboxylic acid represented by formula b is the ω-aminocarboxylic acid relative to the lactam of formula a.
It is an aminocarboxylic acid. These N-alkyl substituted lactams or N-
The copolymerization condensation of an alkyl-substituted ω-aminocarboxylic acid and an unsubstituted lactam or ω-aminocarboxylic acid is carried out by a known method in the presence of the aforementioned polyolefin resin containing a carboxyl group. Since the polyolefin resin and the copolymerized polyamide are partially grafted through carboxyl groups, both resins create a stable dispersion mixture system and are not a mere mechanical blend, as will be shown later in the examples. Unlike other materials, it provides the repeated bending resistance necessary for application to electronic blankets, and provides a temperature-sensitive material with low moisture absorption. Additionally, known electrical property improvers such as potassium iodide and copper iodide may be added to these materials, or other additives may be added to the extent that they do not interfere with the electrical properties, such as Additives such as plasticizers, light stabilizers, heat stabilizers, fillers, flame retardants, and colorants may be used in combination. Note that FIG. 1A shows an example of the heat-sensitive temperature control line that is the object of the present invention as a partially cutaway perspective view.
An example of a heat-sensitive temperature control surface is shown in FIG. 1B as a cross-sectional view. That is, in FIG. 1A, the heater wire 5 wound around the heat-resistant core wire 2 also serves as the inner sensing wire, and catches signals between it and the signal wire, that is, the outer sensing wire. 3 is a polymer temperature sensitive body interposed between the signal line 4 and the heater line 5. 1 is an insulator and serves as an outer covering. Similarly, in FIG. 1B, a polymer temperature sensitive body is interposed between the heater wire 5 and the signal wire 4, and a temperature signal is obtained by applying an alternating current voltage between the two wires. The outer sheath is insulator 1
It is covered with Next, examples of the present invention will be described. Example 1 In a 3-volume stainless steel autoclave, 394 g (1.997 mol) of lauryl lactam monomer, N-n-
Octyl lauryl lactam 206g (0.666mol),
Prepare 48g of pure water and 1.2g of orthophosphoric acid as a catalyst,
After the inside of the reaction system was completely replaced with nitrogen, the internal pressure was maintained at 20 kg/cm ² G by nitrogen pressurization, and the mixture was heated at 290° C. for 2 hours. Next, the pressure in the system was gradually lowered, and at the same time, the temperature was lowered to 250°C and atmospheric pressure after 1 hour. Here, under stirring, polyethylene containing maleic anhydride (carboxyl group content 13 mg equivalent/Kg, melt flow index at 220°C 0.3 g/10 min) was added.
206 g of low density polyethylene) was gradually added in the form of pellets. After melting, a nitrogen stream is applied under strong stirring.
The reaction was carried out by heating at 250° C. for 7 hours while flowing at a rate of 150 ml/min. After the reaction was completed, the contents were taken out in the form of strands, cooled in a water bath, and made into pellets using a pelletizer. The methanol extraction content of the obtained polymer (Soxhlet extraction for 24 hours) was 1.0%.
The melt flow index measured at 230℃ is
It was 2.44g/10min. Using this pellet, a press sheet with a thickness of 0.5 mm was made, and a sample was heated and dried in a vacuum dryer at 80°C for 10 hours to obtain a dried sample.A sample was also obtained by immersing the above press sheet in hot water at 40°C for 10 days or more. was used as a wet sample for the following measurements. Moisture content of sample: Measured by Karl-Fitscher method. Volume specific impedance: A 5 micron thick tin foil was pasted as an electrode, and the volume specific impedance was measured at 100 Hz under an electric field strength of 100 V/cm using a model 4247A multi-frequency LCR meter manufactured by Yokogawa Heuretsu Patscard Co., Ltd. . Tensile strength and elongation characteristics: A press sheet with a thickness of 1.0 mm was created, and the tensile speed was measured using a dumbbell punched test piece.
Measured at 50mm/min. The measurement results are shown in Table 1. Comparative Example A shown in the same table for reference is nylon 12 homopolymer (0.5g
The relative viscosity at 25°C of the polymer/100ml m-cresol solution was 1.90, and the melt flow index at 190°C was 4 g/10min. A polymer obtained by polymerizing 394 g (1997 mol) of lactam monomer and 206 g (0.666 mol) of N-octyl lauryl lactam by adding water and orthophosphoric acid without adding only maleic anhydride-containing polyethylene (methanol extraction) min 0.8%, 0.5g polymer/
The relative viscosity at 25℃ of 100ml m-cresol solution was 1.95, and the melt flow index at 230℃ was 15.3g/10min.
Melt flow index at 220℃ 0.3g/
This value was measured using a press sheet of a sample obtained by adding 206 g of low-density polyethylene for 10 minutes and melt-blending it in a kneader.

【table】

【represent.
The results of Example 1 show that compared to Comparative Example A, the wet sample moisture, ie water absorption, is significantly improved. Furthermore, as can be seen from the results of Example 1 and Comparative Example B, when the polyamide resin was obtained in the presence of the polyolefin resin, the mechanical properties of the sample were lower than when the polyamide resin was obtained simply by melt blending.
It has particularly excellent toughness. Example 2 Similarly to Example 1, 446 g (2.26 g) of lauryl lactam monomer was placed in a 3-volume stainless steel autoclave.
mol), N-n-stearyl lauryl lactam 252
(0.56 mol), 50 g of pure water, and 1.2 g of orthophosphoric acid, completely purged the reaction system with nitrogen, kept the internal pressure at 20 Kg/cm ² G by pressurizing nitrogen, and heated at 290°C for 5 hours. did. Next, the pressure and temperature in the system were gradually lowered to bring the atmospheric pressure to 250°C after 1 hour.
Now, while stirring, gradually add 175 g of Himilan 1652 (polyethylene ionomer resin manufactured by Mitsui Polychemicals) pellets and melt, then add nitrogen at 150 ml/min.
The mixture was heated and stirred at 250°C for 10 hours while flowing at a flow rate of .
After the reaction was completed, the reaction product was extruded in the form of a strand under nitrogen pressure, cooled in a water bath, and pelletized using a pelletizer. Methanol extraction of the obtained polymer (Soxhlet extraction, 24 hours)
was 0.9%, and the melt flow index measured at 230°C was 15.0 g/10 min. Table 2 shows the characteristic values measured by the method described in Example 1.

【table】

[Table] Compared to Comparative Example A in Table 1, the water absorption was considerably improved to 0.65%, and the thermistor B constant also showed a considerably large value. Furthermore, the strength and elongation at break of the sample, especially the elongation at break, was comparable to that of the homopolymer of Comparative Example A, indicating excellent toughness.

[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 wire.

Claims (1)

[Claims] 1. In the presence of 5 to 40 parts by weight of a polyolefin resin containing carboxyl groups. 2 (a) N-alkyl substituted lactam represented by formula a or alkyl substituted ω- represented by formula b
5 to 50% by weight of amino carboxylic acid (However, R is a linear or branched alkyl group having 4 to 30 carbon atoms, and n is a positive integer of 5 to 13.) (b) A lactam represented by the formula a or an ω-amino compound represented by the formula b. Polycondensation of 95 to 60 parts by weight of a mixture consisting of 95 to 50% by weight of carboxylic acid [Formula] H ₂ N-(CH ₂ ) _o - COOH (b) (where n is a positive integer from 5 to 13) A polymeric temperature-sensitive material made of copolymerized polyamide obtained by.