JPS60106103A - Polymer temperature sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive material made of a specific polyamide resin composition, and particularly to a heat-sensitive material having a capacitance component as one of the control factors. It concerns a material with improved drawer behavior.

2. Description of the Related Art The use of organic polymeric materials whose electrical properties change significantly depending on temperature, such as polyvinyl chloride and polyamide, as heat-sensitive elements has been known from the past, for example in electric blankets and electric carpets. Control factors for the thermosensitive element include direct current volume resistivity, dielectric constant, and volume specific impedance, and a combination of one or more of these may be used to operate the control circuit. Therefore, the characteristics required for a heat-sensitive element are: large changes in electrical properties due to temperature, small changes in electrical properties due to moisture absorption, and stability with no change in electrical properties over time due to heat cycles. There are some things that can be mentioned.

Up until now, in order to meet this type of purpose, ion conductive substances such as surfactants have been added to the above organic polymer materials as additives, and
, copper halide, which is easily ionically dissociated, was added (Japanese Patent Application Laid-Open No. 56-3904).

However, since the conductive carriers in these compositions are naturally ionic substances, applying a DC electric field causes polarization, causing a large change in impedance over time.
In addition, the former in particular has poor heat resistance, so it could not be used as a temperature sensor for a thermal heater as described below.

Therefore, as a result of intensive studies to solve the above-mentioned practical problems, the present invention has been developed to create a heat-sensitive material that satisfies the above-mentioned performance requirements by combining a specific polyamide resin and a specific additive. The present invention was achieved based on the discovery that the present invention can be obtained.

That is, the present invention provides a heat-sensitive material comprising a polyamide composition containing 0.1 to 10.0 parts by weight of thiocyanate to a polyamide resin having 14 or less amide groups per 100 carbon atoms. be.

According to the heat-sensitive element made of the heat-sensitive material of the present invention, the rate of change in electrical properties with respect to temperature is extremely large, and unlike surfactants, it may bleed out or deteriorate over time. It has excellent stability in electrical properties because it does not contain any metal, and it also does not corrode metal wires or metal foils such as aluminum and copper used for signal conductors, and has excellent heat resistance. This provides advantages such as ease of crosstalk with other devices.

The polyamide resin used in the present invention is a polyamide with a low amide group concentration, such as polyaminoundecamide (nylon 11) or polyω-laurolactam (nylon 12), and more specifically, a polyamide with a carbon atom number of 10I.
It is a homopolyamide or copolyamide in which the number of amide groups per O is 14 or less.

The amount of lithium thiocyanide added, which is an additive component of the polyamide composition for heat-sensitive elements in the present invention, is 0.1
~10 parts by weight, preferably 0.5 to 5.0 parts by weight, is appropriate; if it is less than 0.1 parts by weight, the electrical properties will not change sufficiently with respect to temperature, and if it is more than 1000 parts by weight, the mechanical properties of the polyamide resin will deteriorate. This is not preferable because the properties deteriorate.

The method of adding lithium thiocyanide to the polyamide resin is not particularly limited, and may include a method of adding it during the polyamide polymerization step, a method of mechanically mixing polyamide powder and lithium thiocyanide, or a method of mixing polyamide pellets and lithium thiocyanide. Any method can be used, such as melt-kneading using a post-extruder.

The polyamide composition containing lithium thiocyanide is
Usually, it is further molded into a wire or sheet shape using an extruder or the like, and then made into a heat-sensitive element.

The effects of the present invention will be explained below using examples.

Example 1 After tri-blending 1 part by weight of lithium thiocyanide to 100 parts by weight of nylon 12 pellets ("Tiamide L1901J" manufactured by Daicel Huls), they were melt-kneaded using an extruder and pelletized using a pelletizer. This pellet was compression molded at 220° to create a sheet with a thickness of approximately 0.5 m.
The temperature dependence of volume specific impedance at 0 Hz was measured. As a result, a very large slope was obtained as shown by curve A in FIG.

Example 2 After completely dissolving lithium thiocyanide in water, nylon 6.12 powder ("Diamid D1" manufactured by Taisselhüls)
700j) 100 parts by weight and 5 parts by weight of lithium thiocyanide were mixed in a Henschel mixer, and then the water was completely evaporated.

This powder was compression-molded at 220° to form a sheet with a thickness of about 0.5 mm, and the specific volume impedance was measured in the same manner as in Example 1. As shown by curve B in FIG. 1, the results showed a good temperature gradient similar to Example 1.

Comparative Example 1 A sheet with a thickness of approximately 0.5 mm was made in the same manner as in Example 1 except that lithium thiocyanide was not mixed into the nylon 12 pellets, and the temperature and impedance characteristics were examined. As shown by curve C in Figure 1, it can be seen that the slope is gentler than that of the present invention.

Comparative Example 2 In Example 1, using nylon 6.12 pellets,
Example except that lithium thiocyanide is not mixed.
1 (!: In exactly the same way, sheets with a thickness of about 0.5 mm were made and the temperature/impedance characteristics were examined, and the curve was as shown in Figure 1, and the slope was gentler than that of the present invention. I understand that.

As can be seen from these results, the temperature sensing element of the present invention has a significantly improved temperature detection function, that is, the rate of change in impedance with respect to temperature, compared to nylon 12 or nylon 6/12 alone. It has excellent electrical properties.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between volume specific impedance and temperature of polymer thermosensitive bodies obtained in Examples and Comparative Examples of the present invention. Patent applicant: Daicel-Hüls K.K. 2o-<o
60 so 100 120 1.40 Temperature (℃)

Claims (1)

[Claims] Lithium thiocyanide is added to a polyamide resin having 14 or less amide groups per 100 carbon atoms.
Polymer temperature sensitive body made of polyamide composition containing 0.0 part by weight