JPS6166749A - Polymeric thermistor material for wide-area heating - Google Patents

Abstract

PURPOSE:To provide the titled thermistor material having small impedance change between dry state and moist state, and having improved thermistor sensitivity, by kneading a low-hygroscopic polymer to nylon 12 to obtain a polymer alloy having decreased glass transition temperature, and adding an ionic substance to the polymer alloy. CONSTITUTION:Nylon 12 is kneaded with a polymer having lower hygroscopicity than nylon 12 (e.g. polyethylene glycol, acrylonitrile/butadiene copolymer rubber, etc.) to obtain a polymer alloy having a glass transition temperature of <=30 deg.C in dry state. The objective thermistor material useful for the temperature sensor of a sheet heater for electrical carpet, electrical blanket, etc. can be prepared by adding 0.5-2wt% ionic additive selected from KI, CuI and KSCN to the above polymer alloy used as a main component, and dispersing the additive homogeneously in the polymer alloy.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a thermistor material used to detect heating temperature in a sheet heating element used in electric carpets and electric blankets.

BACKGROUND OF THE INVENTION This invention relates to polymeric thermistor materials, and specifically to improved heat-sensitive polyamide compositions.

Polyvinyl chloride-based materials and polyamide-based materials, which are known as polymer thermistor materials, have been used for temperature detection in large-area heating devices such as electric carpets and electric blankets. However, the former one is 1. Since a large amount of plasticizer is added to impart flexibility, it is necessary to use it at a temperature of 80° C. or lower due to the heat-resistant properties of the plasticizer. Although quaternary ammonium 9-mhalide and the like are added to increase the thermistor characteristics (B constant), there is a limit to increasing the thermistor characteristics (B constant) t''. Polyamide-based materials are also widely used because of their excellent properties and heat resistance, as well as the ease of designing thermistor characteristics (B constant).However, this polyamide-based resin is generally Material 1 also has the disadvantage of high water absorption, and the impedance of the material varies greatly depending on the water absorption rate.To improve this disadvantage, Nylon 11 or A method of mixing nylon balls with an additive that has a plasticizing effect (Special Publication Publication No. 52-4
0439, etc.) have been proposed, but like polyvinyl chloride materials, they have the problem of being unable to be used at temperatures above 80°C due to problems with the additives' heat resistance and heat resistance (bleed-out occurs).

The inventors of the present invention investigated to overcome these drawbacks and obtain a further improved heat-sensitive polyamide resin, and as a result, they found a thermistor that can withstand continuous use at 120 degrees Celsius with little impedance fluctuation even when moisture is absorbed. We developed a material with extremely favorable properties and achieved the present invention.

In other words, the thermistor characteristics of a material made by adding ionic additives to nylon bulbs, which have the lowest hygroscopicity among polyamide resins, when air-dried at 80℃, and when absorbing moisture at a saturated water absorption amount of 90℃ at 40℃. The thermistor characteristics and the glass transition point at that time (isochronous complex dynamic stretching in a stretched deaf 51
! 1 of the loss elasticity of the modulus! As a result, for nylon bulbs, lowering the glass transition temperature causes less change in the thermistor characteristics during moisture absorption than lowering the saturated water absorption amount. I discovered that. It was also confirmed that the same relationship exists in the known method of kneading polyamide resin with JX, which acts as a plasticizer.

We also discovered that impedance fluctuations due to moisture absorption can be further reduced by adding an additive to make the thermistor characteristic sound louder on the high temperature side in order to detect partial overheating.

(Objective of the Invention) An object of the present invention is to provide a polymer thermistor material that has little change in impedance in a dry state and impedance in a hygroscopic state and has improved thermistor sensitivity.

(Disclosure of the Invention) As a result of investigating the use of polymer blends (also known as polymer alloys), which is a means of lowering the glass transition temperature of nylon 12 by a method other than the addition of plasticizers, as a thermistor material, the glass transition point is wide. If you choose a polymer alloy material whose moisture absorption is below the temperature control range of the area heating device (approximately 30 to ω℃) and whose moisture absorption is below nylon, and add an ionic substance to the i, moisture absorption will be increased. I discovered that this material has little change in the thermistor sensitivity due to heat, and there are no concerns about the heat resistance of argon plastics, making it an extremely suitable material for thermistors that can withstand continuous operation at 120 degrees Celsius.

This operation can be considered as follows.

In other words, the glass transition point when drying a nylon ball (approximately 52℃
) is 40 CX 90 SO saturated water absorption state is about 26
Since deg also decreases, ionic conduction by the ionic additive that adds Kti to increase the thermistor constant (B constant) occurs in the low temperature range, causing a large decrease in impedance. On the other hand, if the glass transition point f during drying is lowered to below 30℃ by polymer alloying in advance, the decrease in glass transition degree due to moisture absorption can be minimized, and the temperature at which ion conduction occurs can be reduced over a wide area. Since the temperature is below the practical temperature of the heating device, the thermistor constant, which increases in proportion to the amount of ionic additive added, can be increased within the temperature control range, and it is also possible to
Therefore, it is thought that the fact that the saturated water absorption amount has decreased slightly has the effect of reducing the change.

Next, examples and comparative examples will be described.

Comparative Example 1> (Conventional Example) Powerful as an ionic additive in nylon 12m fat!
J (KI) was uniformly dispersed by 0.5 layers and heated at 04℃.
A thick press sheet was prepared, and after drying at 80°C, the impedance characteristics, glass transition temperature, etc. were determined. Next, characteristics were measured after moisture absorption treatment was performed to a saturation water absorption rate of 40°C x 90cm.

Furthermore, changes in impedance characteristics after being left in a 120° C. atmosphere for 600 hours were measured. Thermistor characteristics are I
KHz characteristics were measured, and fluctuations in the thermistor characteristics were expressed by how many degrees of deviation occurred in the impedance value equivalent to 50° C. during drying.

Results: Glass transition point when dry: 52°C Glass transition point when absorbed: 26°C Saturated water absorption rate: 1.5 cm Difference in thermistor characteristics due to moisture absorption △T, = -26
Discrepancy in characteristics after 600 hours at deg120°C Tr-
+2 degrees Comparative Example 2> (Conventional example) After uniformly dispersing 0.5% of potassium iodide (KI) 't' as an ionic additive and 15% of paraoxybenzoic acid ester as a plasticizer in nylon 124111 fat. 0
．． A 5°C thick press sheet T- was made and the same test as above was carried out.90 Results: Dry glass transition point 9°C Moisture absorption 〃 3°C Saturated water absorption rate 1.3% Difference in teamister characteristics due to moisture absorption ΔT, = −16
Deg120℃X Characteristic deviation after 600 hours ΔT,
= + 13 deg <Example 1> (present invention) 3ON polyethylene glycol in nylon 12m fat
Iodizing power9 (KI
) 'i 0.5 weight 1 uniformly distributed and constant diameter 0.5■
A thick press sheet was prepared and the same test as above was conducted.

Results: Glass transition point when dry: 4℃ Moisture absorption: 18℃ Saturated water absorption rate: 1.24% Difference in thermistor characteristics due to moisture absorption ΔT, = -18
Difference in characteristics after 600 hours at deg120℃ ΔTt=
+2deg〈Example 2〉(Invention) Modified P-Pt 30% was kneaded in nylon 12 resin, and potassium iod9ide (KI) ff-0,5 was added as an ionic additive.
A press sheet having a thickness of 0.5 mm was prepared by uniformly dispersing the powder, and the same test as above was conducted.

Results: Glass transition point when dry: ℃ Moisture absorption: 1 5℃ Saturated water absorption rate: 1.13 cm Difference in thermistor characteristics due to moisture absorption ΔTs=-12 de
g12G℃×Difference in characteristics after 600 hours ΔT2+3
deg〈Example 3〉 (Invention) NBR (acrylo-nitrile-butadiene copolymer rubber) t-151F & kneaded L in nylon 12 resin, potassium iodide (KI) t-0.5t uniform as ionic additive A press sheet with a constant diameter of 0.5 m in thickness was prepared by dispersing the mixture, and the same test as above was conducted.

Results: Dry glass transition point 15℃ Moisture absorption 〃 5℃ Saturated water absorption rate 1.3chi Difference in thermistor characteristics due to moisture absorption ΔT+ = 17
．． 5 Deg 120℃ x 600R deviation of W property Δ
In addition to examples where Ts=+2 deg or more, extreme polymer alloys such as nylon elastomer, nylon prebolimer, polybutadiene, modified ethylene, etc. can be agglomerated. It can be said that a combination that can be dispersed in nylon spheres, has less hygroscopicity than nylon 12, and has a glass transition temperature of 5° C. or lower when used as a polymer alloy is effective.

Here, the glass transition point was limited to below (support) °C because
The operating temperature range of large-area heating devices such as sleepy carpets is from (to)℃ to ω℃, and it is added to improve the thermistor characteristics (increase the B constant) in order to detect localized heat generation. This is because the ionic conduction effect of the ionic additive is maintained at a temperature below the operating temperature, and because the temperature is such that fluctuations in the glass transition point due to moisture absorption are significantly reduced.

In addition, the ionic additive loincloth was selected because it is heat resistant and easy to disperse, and addition 41 includes o, o,
If it is less than os s, the B constant will not be large and the dispersion will not be uniform, but if it is added more than 2.0 ts, the hygroscopicity will increase due to the ionic additive, which is considered to be an increase in ionic polarization. This is because there is a large drop in impedance.

(Effects of the Invention) As described above, according to the present invention, there is little change in impedance in a dry state and impedance in a moisture-absorbed state, and the thermistor sensitivity is improved, making it possible to use a polymer thermistor material.

Claims (1)

[Claims] Polydodecanamide (nylon 12) and other nylon 1
In a polymer alloy whose main component is polyamide with a lower hygroscopic polymer added than 2, the main ingredient is one with a dry glass transition temperature of 30°C or less, and any of KI, CuI, and KSCN is used as an ionic additive. 0.0
A polymer thermistor material for wide area heating, which is added in a range of 5% to 2% by weight.