JPS5946977B2 - heat sensitive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a heat-sensitive element made of a novel organic polymer material,
More specifically, the present invention relates to a heat-sensitive element made of polyesteramide, which exhibits a remarkable change in specific volume impedance with respect to temperature.

Conventionally, it has been possible to utilize the temperature dependence of the electrical properties of organic polymer materials to use them as heat-sensitive elements.
This is well known, for example, in the case of temperature control elements for electric blankets and electric carpets. Among them, heat-sensitive elements made of a composition in which a small amount of surfactant is added to polyvinyl chloride (Japanese Patent Publication No. 35-14179), and a composition made of a composition in which a small amount of surfactant or metal ion salt is added to polyamide resin. Heat-sensitive element
No. 978 and Japanese Unexamined Patent Publication No. 51-4597) are cited as representative examples. This type of heat-sensitive element is used, for example, in an electric blanket, as shown in FIG.
A signal line 4 is further wound spirally around the outer surface of L, the outer surface of which is covered with a heat-sensitive element 3 made of an organic polymer, and the outer surface is covered with an insulating material 5 to provide flexibility. A certain thermal heater wire 1 is configured L. This thermal heater wire 1 is used in the form of being wired in a serpentine shape or the like inside the electric blanket body.
Temperature control is generally performed by detecting a temperature change in the heating element wire 2 as a change in impedance of the heat sensitive element 3 using a signal line 4, and controlling the current to the heating element wire 2 based on this. For the polyamide resin-based heat-sensitive element, a low hygroscopic material containing polydodecanamide or polyundecaneamide as a main component is particularly preferably used. In this heat-sensitive element, when the heater wire locally overheats and reaches an abnormally high temperature, reaching the melting point of the element material (170-190°C), it melts and short-circuits the heating element wire 2 and the signal wire 4. It also has the function of cutting off the power supply circuit by blowing out the fuse, so it is used more preferably than elements made of polyvinyl chloride. However, conventional polyvinyl chloride-based and polyamide resin-based heat-sensitive elements are still not fully satisfactory in electrical characteristics as temperature control elements. In other words, additives added for the purpose of increasing the temperature dependence of electrical properties generally do not have sufficient heat resistance and are not compatible with resins, resulting in exudation of the additives and other problems over long periods of time. The electrical characteristics of the device tend to change with use. On the other hand, an element containing a metal ion salt has a relatively small amount of additive and the change in the electrical properties is small, but when a direct current is applied to the element, polarization occurs and the electrical properties change. In addition, in polyamide resin-based heat-sensitive elements, polydodecanamide or polyundecaneamide, which has particularly low hygroscopicity among polyamide resins, is used as the main component, but in high-humidity surroundings, moisture absorption cannot be ignored and electrical characteristics change. However, it lacks stability as a temperature control element. In view of the current situation, an object of the present invention is to provide a novel heat-sensitive element having excellent characteristics that cannot be achieved with conventional organic polymer materials.

In other words, the main objective of the present invention is to provide a heat-resistant material with excellent electrical properties without using additives to improve electrical properties, which have many problems in terms of heat resistance, compatibility with resins, DC polarization, etc. Our goal is to provide a thermal sensing element that also has a temperature fuse function and has the excellent flexibility and processability that are characteristic of organic polymer elements, as well as the adhesion to heat-generating wires, signal lines, etc. An object of the present invention is to provide a sensitive element. The object of the present invention is to produce a polyester amide containing (4) 5 to 95% by weight of butylene terephthalate and/or butylene isophthalate units and (6) 5 to 95% by weight of dodecanamide units and/or undecane amide units. This is achieved by using a heat-sensitive element.

Butylene terephthalate and/or butylene isophthalate that form the ester component, which is one component of the polyesteramide in the present invention, are terephthalic acid and/or isophthalic acid and 1,4-butanediol,
and ester-forming derivatives thereof by a condensation reaction, and is represented by the general formula (M.n is an integer of 0 or 1 or more, provided that m and n are not both 0).

Here, when n=0, butylene terephthalate, when m=0, butylene isophthalate, NlxO. When n is O, it becomes a butylene terephthalate/butylene isophthalate copolymer. The m:n ratio can be freely selected depending on the required physical properties, and generally, when the ester component is a butylene terephthalate unit alone, it has high crystallinity and a high melting point.
As the butylene isophthalate units are used in admixture, flexibility and adhesion properties increase and relatively low melting points result.

The dodecane amide units and/or undecane amide units constituting the amide component, which is another component of the polyester amide in the present invention, are derived from 12-aminododecanoic acid units and/or 11-aminoundecanoic acids and their amide-forming derivatives. is formed and is represented by the general formula.

In the polyesteramide of the present invention, the dodecanamide unit and the undecanamide unit can be used individually or in the form of a copolymer without much difference in electrical properties, but the melting point,
They may be selected and used as appropriate for the purpose of controlling processability and the like. It is important to use a selective combination of butylene terephthalate and/or butylene isophthalate as the ester structural unit and dodecanamide and/or undecaneamide as the amide structural unit in the polyester amide of the present invention. For the first time in this copolymer-based polyester amide, polymerization progresses uniformly without phase separation over the entire copolymer composition range, and not only is a colorless polymer with a high degree of polymerization obtained, but also a novel polyester amide obtained. has excellent electrical properties and good mechanical properties. The copolymerization composition ratio of the polyester amide of the present invention is 5 to 95% by weight of butylene terephthalate units and/or butylene isophthalate units constituting the ester component (4), dodecane amide units constituting the amide component 8, and/or dodecane amide units constituting the amide component 8. Alternatively, it is necessary that the undecane amide unit is in the range of 5 to 95% by weight, more preferably the ester component (4) is in the range of 20 to 80% by weight, and the amide component (B) is in the range of 20 to 80% by weight. With copolymer compositions other than those listed above, it is impossible to obtain a heat-sensitive element having the desired properties including electrical properties.

Polyesteramides having this copolymerization composition have been found to exhibit excellent electrical properties that could not be expected from polyesters such as polybutylene terephthalate and polybutylene isophthalate, and polyamides such as polydodecaneamide and polyundecaneamide. Ta.

Polyamide has relatively excellent electrical properties, but in order to put it into practical use as a heat-sensitive element, it is essential to use electrical property improvers such as surfactants and metal ion salts.On the other hand, polyester has relatively excellent electrical properties. In terms of properties, it is inferior to polyamide as a material for heat-sensitive elements, and the present invention claims that copolymerization of units constituting both polymers will yield a new polymer with dramatically superior electrical properties. The facts are truly astonishing. The polyesteramide of the present invention contains (a) a dicarboxylic acid consisting of terephthalic acid and/or isophthalic acid, (b) 1,4-butanediol, and (c) 12-aminododecanoic acid and/or 11-aminoundecanoic acid. This is achieved by melt polymerization.

An example of a suitable polymerization method is terephthalic acid and/or
Or an aromatic dicarboxylic acid consisting of isophthalic acid,
1.05 to 2.0 times the mole of aromatic dicarboxylic acid
, 4-butanediol and 12-aminododecanoic acid and/or 11-aminoundecanoic acid, first in the presence of a conventional esterification catalyst, from about 150 to 26
The reaction is carried out by heating at a temperature of 0° C. under normal pressure. Within this time series is N2
Being sealed gives favorable results. Next is 10TW! NHg or less preferably 1wr! By carrying out heating polycondensation at 200 to 270° C. under reduced pressure below FLHg, a polyester amide with a high degree of polymerization that is transparent when melted can be obtained. In addition, aromatic dicarboxylic acid and 1,4
- from both butanediol, normal pressure, 150-260°C
First, a polyester prepolymer with an average degree of polymerization of 3 to 8 is prepared under the esterification conditions, and this prepolymer and 12-aminododecanoic acid and/or 11-aminoundecanoic acid are fed into a polymerization vessel, and the polymerization degree is 200 to 270% under reduced pressure. A uniform polyesteramide with a high degree of polymerization can be similarly obtained by carrying out heating polycondensation at .degree. When polymerizing this polyester prepolymer and an aminocarboxylic acid, a lower alkyl ester of terephthalic acid and/or isophthalic acid may be used when preparing the polyester prepolymer in advance. Furthermore, instead of 12-aminododecanoic acid or 11-aminoundecanoic acid, which is the raw material for the polyamide structural unit of the present invention, a polyamide oligomer having a relatively low degree of polymerization obtained by polymerizing these raw materials may be used for part or all of it. You can also do it.

Furthermore, 12-
Although it is preferable to use aminododecanoic acid alone, it can also be used in the form of laurolactam, which is partially or completely dehydrated and ring-closed, and when the polyamide component is small, polyesteramide can be similarly obtained with a slight delay in the reaction time. .

The polyesteramide of the present invention may also be used by copolymerizing a small amount of monomer components other than terephthalic acid, isophthalic acid, 1,4-butanediol, 12-aminododecanoic acid, and 11-aminoundecanoic acid.

For example, dicarboxylic acids such as adipic acid, sebacic acid, dodecane, naphthalene dicarboxylic acid, and cyclohexane dicarboxylic acid, and diols such as ethylene glycol, pentanediol, neopentyl glycol, 1,6-hexanediol, and cyclohexanedimethanol are used. In addition, amide-forming compounds such as hexamethylene diamine-sebacate, hexamethylene diamine-isophthalate, hexamethylene diamine dodecanoate, ε-caprolactam, and ε-aminocaproic acid may also be copolymerized in small amounts. It can be used in Titanium-based catalysts give good results in the production of polyesteramides. Particularly preferred are tetraalkyl titanates such as tetrabutyl titanate and tetramethyl titanate, and metal salts of titanium oxalate such as potassium titanium oxalate. Other catalysts include tin compounds such as dibutyltin oxide and dibutyltin laurate, and lead compounds such as lead acetate. In the above-mentioned method for producing polyester amide of the present invention, the average segment length of the polyester units and polyamide units is generally determined by the copolymerization composition ratio, but it can also be controlled by reaction conditions. In a polymer obtained by adding 12-aminododecanoic acid and/or 11-aminoundecanoic acid to a polymer, the average segment length of each unit is longer than in a polymer obtained by reacting all monomers at once. As a result, the melting point is several degrees Celsius to 20 degrees Celsius.
It becomes a high-quality polymer.

The excellent electrical properties aimed at by the present invention can be achieved with polyesteramide produced by any method. Therefore, the production conditions for polyesteramide can be selected depending on the aimed melting temperature. The melting temperature of the polyesteramide of the present invention is preferably 110°C or higher.

If the melting temperature is too low, the device will melt in a relatively low temperature range, thus limiting the usable temperature range. A suitable melting temperature for the polyesteramide comprising the copolymer composition of the present invention can be arbitrarily selected from the processing characteristics of the intended device and the temperature fuse function characteristics, but is usually 130 to 19
Particularly preferred is a temperature range of 0°C. Here, the melting temperature of polyesteramide is measured using a differential calorimeter (PerkinEl).
It is expressed as the melting peak temperature measured using a Mer Co., Ltd. DSC-1B) at a heating rate of 1'C/min.

In addition, in the case of polyester amide whose crystallinity is small and a clear melting peak cannot be observed with a differential calorimeter, a micro low-load thermal dilatometer (Rigaku Denki TMA) is used to measure the temperature of the polyester amide with a pin diameter of 1 mφ.
It was found that the softening temperature measured at a temperature increase rate of 10° C./min under a load of 2 g can be used as a substitute. The polyester amide of the present invention can be used by adding an antioxidant, a thermal decomposition stabilizer, or an electrical property improver as necessary during polymerization or processing.

The polyester amide thus obtained is usually melted using an extruder and molded into the shape of a heating wire or sheet to produce a heat-sensitive element. The present invention will be explained below with reference to Examples, in which all parts expressed as "parts" or "%" are expressed as weight ratios.

The relative viscosity in orthochlorophenol at 25°C is 0.
This value was measured under the condition of 5% concentration. Example 1 Terephthalic acid 166 Enemy 1,4-butanediol 135
A flask was charged with 0.22 parts of titanium tetrabutoxide, and after purging with N2, it was heated to 22°C with stirring, and the water and tetrahydrofuran produced were distilled out of the reaction system, resulting in esterification in 3 hours and 30 minutes. The reaction was completed.

Next, the entire amount of the polyester prepolymer was transferred to a polymerization vessel equipped with a stainless steel helical ribbon stirring blade, and 240.5 parts of 12-aminododecanoic acid, 0.10 parts of titanium tetrabutoxide, and Irganox 21010 as a stabilizer were added.
Added 0.44 parts and heated to 245℃ and 0.1Tm in about 1 hour.
Brought to Hg conditions. If you continue stirring under these conditions, 3
The reaction system became a clear viscous liquid in 10 minutes. The obtained polymer was discharged into water from a polymerization container in the form of cuts, and passed through a cutter to form pellets. The resulting polymer had a 50:5 ratio of polybutylene terephthalate triporidodecaneamide.
It has a composition ratio of 0 (weight ratio), and a relative viscosity (ηr)
1.50 Polymer It was a crystalline polymer with a melting temperature of 178°C.

A sheet-like heat-sensitive element with a thickness of 200μ was created using the polyesteramide pellets by a melt pressing method.
The volume specific impedance of the obtained element at a frequency of 120 c/s was measured in a temperature range of 50 to 110 DEG C., and the results shown in curve A in FIG. 2 were obtained. The volume specific impedance ratio Z5O/ZIlO at 50°C and 110°C of this heat-sensitive element made of polyesteramide is 3
It was 60. Comparative Examples 1 and 2 A heat-sensitive element was prepared in the same manner as in Example 1 using polydodecaneamide obtained by melt polymerizing ω-laurolactam by a conventional method, and the results of measuring the volume-specific impedance are as follows. It is shown in curve B in Figure 2.

Z5O of this heat-sensitive element made of polydodecanamide
/ZllO was 13 (Comparative Example 1). Polybutylene terephthalate having a relative viscosity (ηr) of 1.52 was obtained by polymerizing in exactly the same manner as in Example 1 except that 12-aminododecanoic acid was not used.

Example 1 of a heat-sensitive element made from this polymer
The volume specific impedance was measured using the same method as above, and the results are shown in curve C in Figure 2. Z5O/ZllO of this thermosensitive element made of polybutylene terephthalate is 11
(Comparative Example 2). It is clear from Example 1 and Comparative Examples 1 and 2 that the heat-sensitive element made of the polyesteramide of the present invention has significantly excellent heat-sensitive properties.

Examples 2 to 6 Polybutylene terephthalate (PBT) units and polydodecanamide (N
-12) Polyesteramide 3 with different composition ratio of units
The properties (solution viscosity (ηr),
The melting temperature and electrical properties were measured.

The results are shown in Table 1. Example 7 Terephthalic acid 16
6 parts of titanium tetrabutoxide, 135 parts of 1,4-butanediol, and 240.5 parts of 12-aminododecanoic acid.
12 parts, and after purging with N2, heated and reacted at 230°C for 3 hours and 30 minutes with stirring.
A mixture of tetrahydrofuran and 1,4-butanediol was distilled out of the system.

Next, the reaction mixture was transferred to a polymerization reaction vessel, and after adding 0520 parts of titanium tetrabutoxide, the temperature was increased to 245°C for about 1 hour.
When the reaction conditions were brought to 0.1 mnHg or less and the polymerization reaction was continued for an additional 2 hours, a transparent viscous polymer was obtained. A sheet-like heat-sensitive element was made from this polyesteramide in the same manner as in Example 1, and its properties were measured. As a result, ηRl. 65, melting temperature 141°C, Z5O/Zl
lO was 160. Examples 8-10 In a similar manner to Example 1, using isophthalic acid in addition to terephthalic acid and 11 in place of 12-aminododecanoic acid.
-Aminoundecanoic acid was used to polymerize polyesteramides having the composition ratios shown in Table 2.

Each of the polyesteramides obtained was a uniform transparent melt upon polymerization, and sheet-like heat-sensitive elements made from them had excellent electrical properties as summarized in Table 2.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an example of a thermal heater wire using a thermally sensitive element made of an organic polymer material. Figure 2 shows Example 1 (A) of the present invention and Comparative Example 103)2.
It is a graph which shows the change of the volume specific impedance with respect to the temperature of the heat sensitive element obtained in C). 1: Heat sensitive heater wire, 2: Heat generating wire, 3: Heat sensitive element, 4: Signal line, 5
: Insulating material, 6: Core wire.

Claims (1)

[Claims] 1 (A) 5 to 95% by weight of butylene terephthalate and/or butylene isophthalate units and (B)
1. A heat-sensitive element comprising a polyesteramide containing 5 to 95% by weight of dodecanamide and/or undecaneamide units as a main component.