JPH0196902A - Thermosensible element - Google Patents

Abstract

PURPOSE:To improve a critical temperature where the impedance value of a thermosensible element does not vary with the elapse of the time, by forming the thermosensible element with materials where trimellitic and pyromellitic acid system plasticizers and further, tribasic lead sulfate and quaternary ammonium salt are kneaded with a PVC material which is a principal composition of a negative characteristic macromolecular temperature sensing element. CONSTITUTION:A negative characteristic macromolecular temperature sensing element 3 which composes a thermosensible element is made of a thermosensible resin which has PVC as a principal composition. Its element 3 is composed of materials which are made by kneading either one of plasticizers of trimellitic and pyromellitic acid systems at least as well as tribasic lead surface and quaternary ammonium salt with the above PVC material as the principal composition. As a trimellitic system plasticizer, for example, a trimellitic acid ester plasticizer (TOTM) and as a pyromellitic acid system plasticizer, a pyromellitic acid ester plasticizer (TOPM) are used respectively. It is preferable for this element to choose the plasticizers having their compositions which not only hardly develop a bleed-out phenomenon but also lessen cracking of the plasticizers. And further, it is desirable for the amount of addition of the plasticizers to be within a range 15-40wt.%. And then, tribasic lead sulfate acts as a stabilizer and quaternary ammonium set acts as a modifier.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a heat-sensitive element, and in particular to a heat-sensitive element with excellent impedance characteristics that integrates a heat-sensitive element part and a heat-generating part, and is used in electric carpets and the like. It is related to.

(Background Art) Conventionally, in electric carpets, heat-sensitive wires have been used in combination with heat-generating wires, as shown in FIG.

That is, a tubular negative polymer thermosensitive material (thermosensitive resin material) 3 whose impedance changes according to temperature changes, an outer electrical conductor wire 4 wound around the outer surface of the tubular electrical conductor wire 4, and a conductor wire 4 wound around the core material 1, A heat-sensitive element was used that was composed of a wound electric conductor wire 2 arranged on the inner surface of a negative characteristic polymer temperature sensor 3 and an insulating layer 5 provided on the outer surface of the outer wound electric conductor wire 4. .

Further, FIG. 5 shows another example, in which 3 is a negative characteristic polymer temperature sensitive body, 12, 14, 16 are electric conductor wires, and 5 is an insulating layer.

By the way, this type of heat-sensitive element has a negative characteristic polymer thermosensor 3.
A material obtained by kneading a PVC material with a plasticizer, an ionic additive, etc. is used as the material, and a heat-resistant PVC material is also used for the insulating layer 5 on the outer surface. The reason for this is that it has lower hygroscopicity and less change in impedance over time than polyamide materials, which are known as other practical negative polymer thermosensitive materials.

However, in recent years, the surface material for electric carpets has changed from the conventional needle punch type, which is thin and has low heat insulating properties, to thick, soft surface materials such as tufted weave, which have high heat insulating properties, and have improved the life of the carpet. They are becoming more popular with the growing desire for authenticity, and in order to accommodate this trend, it has become necessary to raise the temperature of the internal heater to a higher temperature than before. Correspondingly, the temperature of heat-sensitive wires also tends to increase.

In addition, in the past, a so-called two-wire system was used in which a pair of heat-generating wires was used in addition to the heat-sensitive wire, but a so-called two-wire system in which one electrode of the heat-sensitive wire was used as a heat-generating wire was also adopted.
The f1 type is also being studied due to demands for cost reduction and improved safety. In this case as well, as described above, the temperature of the negative polymer temperature sensitive body tends to be higher than the conventional temperature because it is in contact with the heating wire.

In this way, as the temperature of the negative polymer thermosensitive material increases, P
In thermosensitive elements made of VC material, the bleed-out phenomenon of plasticizer becomes a non-negligible value, and the impedance changes over time in the direction of increasing. In the worst case, the temperature detection ability decreases and the temperature may reach a dangerous level. there were.

(Objective of the Invention) The present invention has been proposed in view of the above points, and its purpose is to increase the limit temperature at which the impedance value of the heat-sensitive element does not change over time, and to prevent abnormal use beyond this limit temperature. When this occurs, the thermosensitive resin material decomposes and deteriorates in the direction of decreasing impedance, which can maintain safety and create a heat-sensitive element with a heat-generating function that integrates a heat-sensitive wire and a heat-generating wire. It is about providing.

(Disclosure of the Invention) The present invention provides a negative characteristic polymer thermosensitive material constituting a thermosensitive element.
It is formed from a thermosensitive resin whose main component is VC, and at least one of a trimellitic acid-based plasticizer and a pyromellitic acid-based plasticizer, tribasic lead sulfate, and a quaternary ammonium salt are kneaded into this PVC material whose main component is PVC material. It is characterized by being made of materials.

PVC material is generally used as a negative characteristic polymer temperature-sensitive bar material for this type of heat-sensitive element, and addition of a plasticizer is an essential condition to maintain plasticity.

As the plasticizer, it is preferable to add at least one of a trimellitic acid-based plasticizer and a pyromellitic acid-based plasticizer.

Examples of the trimellitic acid-based plasticizer include trimellitic acid ester plasticizer (TOTM), and the structural formula of its composition is as follows.

On the other hand, examples of the pyromellitic acid plasticizer include pyromellitic acid ester plasticizer (TOPM). Its structural formula is as follows.

C00CJ+- and C00CsH+ are plasticizers that are difficult to cause bleed-out phenomenon, focusing on the fact that when the plasticity of the thermosensitive resin made of PVC material decreases, the volume-specific impedance increases, which causes changes in impedance over time. It is preferable to select a composition that reduces decomposition of the plasticizer.

The reason why the amount of plasticizer added is set in the range of 15 to 40% by weight is that below 15% by weight, the effect of increasing the thermistor constant sufficiently is small;
This is because the corresponding solubility limit in C is exceeded and a bleed-out phenomenon occurs.

Tribasic lead sulfate is a stabilizer that reduces free CI of PVC materials.
-It captures ions and produces stable substances, and mainly contributes to ion conduction.

The quaternary ammonium salt is a modifier, and the one that has ion conductivity is selected as the mechanism of the negative polymer thermosensor, and the size of the thermistor constant (B constant) is determined by the amount added, and the bleed-out phenomenon Since a decrease in the B constant causes a change in impedance over time, the amount of quaternary ammonium salt added should be set to a supersaturated state, and since quaternary ammonium salts are effective in producing a large surfactant effect, it is necessary to maintain a supersaturated state. However, the molding processability of the thermosensitive resin is not extremely deteriorated.

Therefore, the amount of quaternary ammonium salt added is 3 to 10
A range of % by weight is preferred.

Further, the quaternary ammonium salt is a salt containing perchloric acid (C10m-) or phosphoric acid (POn-) as a negative ion.

Here, the ionic conductive quaternary ammonium salt as a modifier is an effective component for stabilizing impedance over time, but as the amount of the modifier added increases, the B constant also tends to gradually increase. However, it is preferable to add the modifier in a supersaturated state than the amount at which the B constant reaches its maximum value. Even if the modifier in the thermosensitive resin decreases over time, the constant It does not appear as a change in

However, if the amount of modifier added is excessively increased, the heat-sensitive resin becomes surface activated and gelation is not promoted when extruding the heat-sensitive resin, making extrusion molding difficult. Furthermore, it becomes necessary to reduce the extrusion molding speed, which poses a problem in terms of production costs, while extrusion molding tends to cause bleed-out of plasticizers and modifiers or decomposition of PVC, which causes variations in the quality of heat-sensitive elements.

Furthermore, due to the poor flowability of the resin, the resin remains on the inner surface of the extruder during extrusion molding, and this residue carbonizes to form a carbide, and this carbide is contained in the thermosensitive resin material of the negative polymer thermosensor. This may cause a short circuit between the inner and outer electrical conductor wires.

Therefore, the amount of quaternary ammonium salt added is limited to twice the saturated amount of solution, taking extrusion processability into consideration.

Bisphenol A has the effect of suppressing the decomposition of the plasticizer in the thermosensitive resin at high temperatures, and can improve the change in impedance over time.

This bisphenol A has the following structural formula.

C.I.

Acrylic processing aids are additives added to improve the processability of PVC materials, and are mainly composed of methyl methacrylate, a copolymer of polymethyl methacrylate (MMA) and alkyl acrylate. It is.

When a small amount of acrylic processing aid is added to the resin, gelation of the resin progresses in a short period of time, and extrusion moldability can be improved.

Furthermore, this acrylic processing aid does not have any adverse effect on impedance characteristics or changes in impedance over time.

Next, embodiments of the present invention will be described with reference to the drawings.

The thermosensitive resin of the PVC material that is the material of the negative characteristic polymer thermosensitive body was prepared by changing the type and amount of plasticizer, the type and amount of stabilizer and modifier, and the Nal and Na2 of the present invention, and the conventional example Nal. and Na2, as well as Comparative Example N111. Samples of Na2 and N113 were fabricated.

The composition of each thermosensitive resin is as shown in Table 1.

The structural formula of the plasticizer used in the conventional example (Nal, Nn2) shown in Table 1 is as follows.

Phthalate ester plasticizer DTDP Phthalate ester plasticizer DDP Negative characteristic polymer thermosensitive bodies were molded using each of the thermosensitive resins shown in Table 1, and thermosensitive elements were assembled and subjected to each test.

As shown in FIG. 1, this heat-sensitive element consists of a core material 1, an inner-wound electric conductor wire 2 wound around the outer surface of the core material 1, and a negative characteristic polymer temperature-sensitive material 3 of a tube rod arranged on the outer surface of the core material 1. , an external air conductor wire 4 wound around its outer surface, and a separation layer 7 disposed on its outer surface. It is composed of an insulating layer 5.

In addition, the dimensions of each part were as follows.

Core material 1... 0.5mmφ polyester thread wrapped inside electrical conductor wire 2... 0.08vw x 0.8ml 11 copper with N
i-plated foil wound at a pitch of 0.75m Negative polymer thermosensitive body 3...Thermosensitive resin extruded to a thickness of 0.3mm and externally wound electrical conductor wire 4...0.08III x 0.811m
Separation layer 7: Wrap Ni-plated foil on copper at 1.05m5 pitch Separation layer 7: Polyester cheese 12μ2/3 lap wrap Insulation layer 5: Extrude the insulator to a thickness of 0.4a++m Figure 2 shows the impedance of each heat-sensitive element. This is a graph showing changes over time, with the horizontal axis representing elapsed time and the vertical axis representing impedance change rate (χ).

Regarding the stability of impedance over time, we tested the AC 100V 60Hz voltage at 0N-OF in an atmosphere of 120℃.
The impedance change of each sample was measured using the voltage drop method with F cycles applied, and the change in impedance of each sample was measured every elapsed time, and the extent to which the impedance value changed compared to the initial value was compared.

The present invention kl, 2 is as shown in FIG.
, it can be seen that the change in impedance over time is significantly improved compared to 2. In particular, in Comparative Example Nαl, as shown in Table 1, the amount of quaternary ammonium salt added as a denaturing agent was small, causing a bleed-out phenomenon or trapping free MCl- ions from the PVC. This is thought to be because tribasic lead sulfate, a stabilizer that creates a stable substance, also captures the negative ions of the quaternary ammonium salt, which mainly contributes to ion conduction, resulting in a shortage of ion carriers. In Comparative Example 2, since bisphenol A was not added, the plasticizer decomposed at high temperatures, the plasticizing effect decreased, and the impedance changed over time.

On the other hand, the inventor 1. In N[L2, the change in impedance over time has been significantly improved compared to the conventional example 15th floor 2. Furthermore, although not shown, the impedance change at a temperature of 100°C is even smaller than in the conventional example, and 20 d
The limit temperature at which it can be used above eg can be increased. The cause of this is due to the increase in the molecular weight of the plasticizer, but the number of bound alcohols is higher than that of trimellitic acid ester (TOTM) or pyromellitic acid ester (TOPM).
By choosing , the bleed-out speed was significantly reduced.

Note that the molecular weight of trimellitic acid ester (TOTM) is slightly smaller than that of phthalic acid ester (DTDP).

Figure 3 shows the relationship between the elapsed time and the partial insulation maximum temperature of the abnormal temperature setting for each heat-sensitive element.
Temperature control operations were repeated with the FF, and the speed at which the OFF point rose over time was compared with the temperature at which a short-circuit operation occurred due to decomposition and deterioration of the thermosensitive resin.

In addition, in the process in which the OFF point increases with the passage of time, the volume specific impedance of the thermosensitive resin also changes in the direction of increasing.

Each line in the diagram indicates that when a heat-sensitive element is used in a temperature range exceeding the impedance stability limit temperature, the impedance value stabilizes over time due to heat received from other heaters used in conjunction with it, for example. Assuming that the impedance value starts to change over time after exceeding the limit temperature, the initial value is set to 13.
This shows how the temperature control operation is repeated at 0''COFF and the OFF point increases over time.
In Inventive Example No. 1 and Na2, the heat-sensitive resin decomposes and deteriorates (carbonization phenomenon) at about 150°C, causing a short circuit and allowing safe operation, whereas in Comparative Example No. 3, Short circuit does not occur up to about 200°C.

In Comparative Example 3, a large amount (20 parts) of stabilizer is added, so the speed at which PVC deteriorates is slowed down, and the bleed-out phenomenon due to plasticizers and modifiers is more likely to occur, resulting in an increase in impedance rather than carbonization. This is because it progresses faster. In contrast, the present invention k1. In the case of Na2, the amount of stabilizer (10 parts) is not very large, and the modifier added to supersaturation also promotes the deterioration of PVC, so carbonization progresses relatively quickly compared to the increase in impedance. by.

Although the heat-sensitive element of the present invention has been described as having a tubular or cable-like structure as shown in FIG. Needless to say, this method can also be applied to a structure of .

(Effects of the Invention) Since it is made of a material kneaded with at least one of lift acid-based and pyromellitic acid-based plasticizers, tribasic lead sulfate, and quaternary ammonium salt, it has the following effects.

(a) If the impedance stability limit temperature of the heat-sensitive element is significantly improved and is used in electric carpets, it will be possible to set the surface temperature to a sufficiently warm temperature even if a surface material with good cushioning properties is used. - (b) It becomes possible to realize a one-wire system in which one electrode of the heat-sensitive element is used as a heating wire.

(c) It becomes possible to stably manufacture a heat-sensitive element with large thermistor characteristics (B constant) without changes in characteristics over time.

(d) If the impedance value of the negative characteristic thermosensitive resin material begins to change due to abnormal use exceeding the limit temperature at which the impedance does not change over time, the impedance will decrease below a relatively safe temperature. Since it decomposes and deteriorates in the direction in which it occurs, safety is improved and a one-wire system that does not require any other overheating prevention device is possible.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view showing an example of the heat-sensitive element of the present invention, Fig. 2 is a comparison graph showing the change in impedance over time of the heat-sensitive element of the present invention, and Fig. 3 is the maximum adiabatic temperature of the heat-sensitive element of the present invention. Comparison graphs showing the relationship with elapsed time, and FIGS. 4 and 5 are explanatory diagrams showing conventional heat-sensitive elements. ■...Core material, 2...Inner-wound electrical conductor wire, 3...Negative characteristic polymer exothermic body, 4...Outer-wound electrical conductor wire, 5.
... Insulating layer, 7... Separation layer Figure 1 Figure 4 Figure 5 Figure 2 Figure 1 → Kei l Prayer Procedures Master Fu Seisho (self-proposal) September 28, 1988 1988 Patent layer No. No. 254448 Co. 6 Name of the invention Thermal element, Relationship with the person making the amendment Name of IM person for patent (583) Matsushita Electric Works Co., Ltd., Agent 160 Address No. 2, 7-5-10 Nishi-Shinjuku, Shinjuku-ku, Tokyo Mizota Building 7th floor Telephone number (03) 365-1982 1.I4'゛. l'I...1 ゛Name (610B) Patent attorney Satoshi Takayama ゛・'husband,
. 6. Contents of the amendment (1) In item 71, line 11 of the specification, 1, ``...does'' is corrected to ``no deru''. (2) The 5th line of the same page of the same book is corrected to read ``1 is valid.'' (3) In the same book, page 8, line 1, replace [...no, 1 with "...
・It is necessary to make sure that there is no such thing. ” he corrected. (4) Delete "[therefore...preferable]" from the second and third lines of the same book. (5) In the same book, same page, line 5, replace r (POa-) J with “(
POa-) etc.” (6) "Formation" in the first line of No. 9 of the same book is corrected to "Formation time 1." (7) "Trimellitic acid ester J" on page 14, line 19 of the same book is corrected as [3 trimellitic acid ester J].
"pyromellitic acid ester" is corrected to "pyromellitic acid ester of 4". (9) In the same book, page 15, line 2, line 3: “In addition,...
·small. Delete J.

Claims (6)

[Claims] (1) A tubular negative polymer temperature sensitive body whose impedance changes in response to temperature changes, an outer electric conductor wire wound around the outer surface of the negative polymer temperature sensitive body, and a negative polymer temperature sensitive body wrapped around a core material. In a heat-sensitive element consisting of an inner-wound electrical conductor wire arranged on the inner surface and an insulating layer arranged on the outer surface of the outer-wound electrical conductor wire, the negative characteristic polymer temperature sensor is made of a PVC material as a main component. A heat-sensitive element comprising a material kneaded with at least one of a mellitic acid-based plasticizer and a pyromellitic acid-based plasticizer, tribasic lead sulfate, and a quaternary ammonium salt. (2) A patent characterized in that 15 to 40% by weight of plasticizer, 3 to 10% by weight of tribasic lead sulfate, and bisphenol A of 0.1 to 0.5% by weight of the amount of plasticizer are added. A heat-sensitive element according to claim 1. (3) The heat-sensitive element according to claim 1, wherein the quaternary ammonium salt is added in an amount of 1 to 2 times the limit amount at which thermistor characteristics (B constant) are maximized. (4) The heat-sensitive element according to claim 1, further comprising 1 to 5% by weight of an acrylic processing aid. (5) The heat-sensitive element according to claim 1, wherein either one of the electric conductor wires also serves as a heating wire. (6) The heat-sensitive element according to claim 1, wherein the electric conductor wire is a copper material whose surface is plated for corrosion resistance.