JPH03181549A - Polyester composition for insulation film - Google Patents

Abstract

PURPOSE:To provide a polyester composition for insulation film having extremely low content of cyclic ethylene terephthalate trimer and produced in such a manner as to get a copolymer component content and a ratio of a specific metal to phosphorus satisfying respective specific requirements. CONSTITUTION:The objective polyester composition for insulation film is a polyester having an intrinsic viscosity [eta] of 0.5-1 (preferably 0.7-0.9), composed of ethylene terephthalate as main recurring unit and containing (A) 1-10mol% of at least one kind of a dibasic acid other than terephthalic acid and a diol other than ethylene glycol as a copolymerized component, (B) a metal (M) selected from alkali metal, alkaline-earth metal, iron-group metal, Mn, Sn, Pb, Zn and Cd and phosphorus (P) at ratios to satisfy the formula (M/P is equivalent ratio; phosphorus is regarded as bivalent and (C) <=0.4mol% of cyclic ethylene terephthalate trimer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an insulating film containing less ethylene terephthalate cyclic trimer.

[Prior Art] Polyethylene terephthalate is widely used in industrial applications due to its excellent mechanical, thermal, and electrical properties, and its demand is increasing. However, as applications and demand expand, the properties required of polyethylene terephthalate are becoming increasingly strict in each application field.

One of these required properties is polyethylene terephthalate molded products with a low content of low molecular weight substances.

Usually, polyethylene terephthalate or polyethylene terephthalate molded products contain 1.3 to 7% by weight of a low molecular weight substance whose main component is ethylene terephthalate cyclic trimer (hereinafter abbreviated as cyclic trimer). It is. When a polyethylene terephthalate film containing such a low molecular weight substance is used for electrical insulation of a closed-type motor for a refrigerator, for example, polyethylene terephthalate
Low molecular weight substances are extracted from the film by the refrigerating machine oil and Freon in the motor, and the cyclic trimers therein precipitate in various parts of the refrigerating machine, causing trouble. Therefore, 1.
Although it varies depending on the refrigerator model, the amount of cyclic trimer is 0.
．． There is a need for films with less than 5% by weight, preferably less than 0.4% by weight.

Conventionally, in order to eliminate such drawbacks, for example, Japanese Patent Publications No. 43-23348 and Japanese Patent Publication No. 44-2120 have proposed methods of extracting and removing low molecular weight substances from the film using various solvents. . It is true that by selecting a special solvent for extraction, low molecular weight substances can be removed in a short time.

However, increased film thickness increases the required extraction time and reduces efficiency.

Furthermore, since a solvent is used, not only is the cost high, but there is also a risk of fire, and the process requires a drying process, which reduces workability.

The present inventors have studied a polyester composition for an insulating film that eliminates such conventional drawbacks and has a low content of cyclic trimers, and have arrived at the present invention.

[Problems to be Solved by the Invention] An object of the present invention is to provide a polyester composition for an insulating film that has a low content of cyclic trimers.

[Means for Solving the Problems] The object of the present invention is to provide a polyester whose main repeating unit is polyethylene terephthalate,
The polyester contains 1 to 10 mol% of at least one of (1) dibasic acids other than terephthalic acid and diols other than ethylene glycol as a copolymerized fraction;
2) At least one metal selected from alkali metals, alkaline earth metals, iron group, manganese, tin, lead, zinc and cadmium (hereinafter referred to as specific metals) and It can be closely related to a polyester composition for an insulating film that contains phosphorus and (3) 0.4% or less of ethylene terephthalate cyclic trimer.

0.5≦M/P<1.4...■ (Here, M/P
represents the equivalent ratio of metal and phosphorus in <2). Phosphorus is calculated as divalent. ) The cyclic trimer of the present invention is a low molecular weight substance contained in polyethylene terephthalate, that is, one type of oligoester. These oligoesters are described in various literature [eg, S., D., Rose.

et, al., J. Polemer Sci.
13406 (1954), I.

Goodman, B.F., Ncsbitt, Pol.
Ymer, 1334 (1960)], it is mainly a cyclic oligomer, and about 50% or more of the cyclic oligomers are said to be cyclic trimers.

In general, polymer substances produced by polycondensation or addition polymerization always have a certain range of molecular weight distribution from low molecular weight substances to high molecular weight substances, so it is said that the presence of low molecular weight substances is unavoidable. However, because these low molecular weight substances are present in polymers, for example in electrical insulation applications,
This causes the problems mentioned above.

An important feature of the present invention is a polyester whose main repeating unit is ethylene terephthalate, wherein the polyester contains at least one dibasic acid other than terephthalic acid and a diol other than ethylene glycol.
It is included as a copolymerization component of ~10 mol%.

If the amount of copolymerization is less than 1 mol %, when forming a film using the polyester composition of the present invention, the effect of suppressing the increase of cyclic trimers during the film forming process will not be sufficient. Also,
If the amount of copolymerization exceeds 10 mol %, the effect of suppressing cyclic trimers will not increase and the melting point of the film will decrease, which is not preferable.

Examples of the copolymerized dibasic acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, and diphenic acid, and aliphatic dicarboxylic acids such as succinic acid, adipic acid, and sepatic acid. ,1,4
-cyclohexanedicarboxylic acid and the like.

Examples of copolymer diol components include polyoxyalkylene glycols such as triethylene glycol, polyethylene glycol, and polyoxytetramethylene glycol; aliphatic diols such as 1,4-butanediol and 1,6-hexanediol; Examples include alicyclic diols such as 4-cyclohexanediol and 1°3-cyclohexanediol, as well as spiroglycol and bisphenol S/ethylene oxide adducts.

Another important feature of the present invention is that the M/P in the polyester is in the range from 0.5 to less than 1.4. That is, when the equivalent ratio of the specific metal to phosphorus is 1. - If it is 4 or more, it is not good because the number of cyclic trimers increases significantly in the film forming process. Furthermore, if the equivalent ratio of the specific metal to phosphorus is less than 0.5, no further effect can be found in suppressing the formation of cyclic trimers. Further, it is not preferable because it lowers the melting point of the polyester.

Specific metals in the present invention include alkali metals such as lithium, sodium, and kali rum, alkaline earth metals such as magnesium, calcium, and strontium, iron group metals, manganese, tin, lead, zinc, and cadmium. These metals are added in the form of hydrides, alcoholades, chlorides and glycol-soluble salts of monocarboxylic acids, mainly to catalyze esterification or transesterification reactions or to form precipitated particles.

Phosphorus in the present invention is added in the form of one or more phosphorus compounds selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, or their methyl esters, ethyl esters, phenyl esters, and even half esters. . Particularly preferred are phosphoric acid, phosphorous acid, and methyl ester, ethyl ester, and phenyl ester of phosphoric acid.

Further, the intrinsic viscosity [η] of the polyester of the present invention is preferably in the range of 0.5 to 1°01, preferably 0.7 to 0.69, considering the intended use of the final product.

Next, the ease of manufacturing the polyester of the present invention will be described.

Terephthalic acid or its ester derivative, ethylene glycol, and a copolymerization component are heated and dissolved in the presence of an esterification or transesterification catalyst, and then subjected to an esterification or transesterification reaction by a conventional method. After the esterification or transesterification reaction is completed, the metal compound or phosphorus compound is added so that the ratio of the metal compound to the phosphorus compound becomes a predetermined value.

The timing of addition of the copolymerization component is not limited to the above, and can be selected at any stage from before the start of the esterification or transesterification reaction until the completion of the polycondensation reaction.

Next, a polycondensation reaction is carried out by raising the temperature and reducing the pressure in a conventional manner to obtain a polyester having an intrinsic viscosity [η] of about 0.5. The obtained polyester is solid-phase polymerized in the form of chips under reduced pressure. When performing solid phase polymerization, pre-crystallization is performed at a temperature of 180'C or lower, and then 1
Solid phase polymerization is carried out under reduced pressure of approximately torr for 10 to 30 hours to obtain chips having an intrinsic viscosity [η] of approximately 0°8.

As the polymerization catalyst in the polycondensation reaction, compounds commonly used as polyester polycondensation catalysts can be used as appropriate.

As described in detail above, according to the present invention, it is possible to obtain a polyester composition for an insulating film in which the content of cyclic trimers is significantly reduced.

[Examples] Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

Incidentally, each characteristic value of the obtained polyester was measured according to the following method.

0 Intrinsic viscosity [η] at 25°C at a concentration of 0.1 g/ml in orthochlorophenol
This is the value measured at

The element Li contained in the polymer was measured using an atomic absorption method [type AA630-13 (manufactured by Toko Seisakusho)]. Other elements were measured by a fluorescent X-ray method [TFK3064 model (manufactured by Geigerflex)].

oTm Differential scanning calorimeter [PERKIN-ELMER (DS
C)].

Dissolve 100 μl of the 0-cyclic trimer polymer in 1 ml of orthochlorophenol and apply it to a liquid chromatograph (model 8500 manufactured by Varian).
It was measured and expressed as a proportion (wt%) to the polymer.

Example 1 A mixture of 95 parts of dimethyl terephthalate, 5 parts of dimethyl isophthalate, and 60 parts of ethylene glycol was
0.09% by weight of calcium acetate and 0.03% by weight of antimony dioxide were added to the total amount of dimethyl terephthalate and dimethyl isophthalate, and transesterification was carried out by heating and raising the temperature in a conventional manner. Next, 0.07% of phosphoric acid was added to the transesterification product based on the total amount of dimethyl terephthalate and dimethyl isophthalate.
After adding % by weight, transfer to the polymerization reactor.

Next, the pressure of the reaction system was gradually reduced while heating and temperature was increased to 1.
Polymerized by a conventional method at 290°C under reduced pressure of n++aHg,
A polyester having an intrinsic viscosity [η of 0.52] was obtained.

The polymer was cut into cubes with a diameter of 3 mm, and heated at 225° C. for 25 hours under a reduced pressure of 1 mmf (g) using a rotary vacuum polymerization apparatus to obtain a polyester with an intrinsic viscosity [η] of 0.74. As a result of elemental analysis of the polyester, Ca=200ppm SP=153ppm, M
/P=1.0. Furthermore, the Tm of the polyester is 249°C, and the content of cyclic trimer is 0.31% by weight.
Met. Next, an unoriented film of 1.2 mm was obtained using a 40 mmφ melt extruder at a temperature of 290° C. and a residence time of 8 minutes.

This was biaxially stretched under normal conditions to obtain a 120 μm biaxially oriented polyester film. The content of cyclic trimer in the film was 0.36 weight.

Examples 2 to 6, Comparative Examples 1 to 4 Each polyester was obtained in the same manner as in Example 1, except that the metal compound used, the type of copolymer component, and the amount added were carried out under the conditions shown in Table 1. Ta. The M/P, cyclic trimer content, and other properties of the obtained polyester are summarized in Table-1.

Table 1 shows that when the content of copolymer components and M/P are within the range of the present invention, the content of cyclic trimers in the polyester and the obtained polyester film is low.

The following margin [Effects of the Invention] The polyester composition of the present invention, which has a reduced content of cyclic trimers, can be formed into a film and used for insulation, and even when used in contact with a refrigerant, etc. Since low molecular weight substances do not precipitate, the quality of the refrigerant can be maintained well, and troubles caused by extracted low molecular weight substances can be prevented.

For example, when regular polyethylene terephthalate film is used for electrical insulation in a sealed motor for a refrigerator,
Low molecular weight substances are extracted from the polyethylene terephthalate film by the refrigerating machine oil and Freon in the motor, and the cyclic trimers therein precipitate in various parts of the refrigerating machine, causing trouble. However, by using a film using the polyester composition of the present invention, such troubles can be prevented.

Claims (1)

[Scope of Claims] A polyester whose main repeating unit is ethylene terephthalate, wherein the polyester contains at least one of (1) a dibasic acid other than terephthalic acid and a diol other than ethylene glycol.
At least one element selected from alkali metals, alkaline earth metals, iron group, manganese, tin, lead, zinc and cadmium, which is contained as a 0 mol% copolymer component and satisfies formula [1] (2) A polyester composition for an insulating film, characterized in that it contains metal and phosphorus, and (3) 0.4% or less of an ethylene terephthalate cyclic trimer. 0.5≦M/P<1.4...[1] (Here, M
/P indicates the equivalent ratio of the metal in (2) to phosphorus. Rin is 2
Calculate as value. )