JP2611540B2 - Polyester composition for insulating film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester composition for an insulating film having a small amount of ethylene terephthalate cyclic trimer and excellent whiteness.

[Prior art] Polyethylene terephthalate has excellent mechanical properties,
Widely used in industrial applications due to its thermal and electrical properties,
Demand is also increasing. However, with the expansion of applications and demands, the properties required for polyethylene terephthalate are becoming more and more severe in each application field.

One of those required properties is a polyethylene terephthalate molded product having a low content of a low molecular weight substance.

Usually, in polyethylene terephthalate or in a molded product of polyethylene terephthalate, 1.3 to 1.7% by weight of a low-molecular-weight body mainly composed of ethylene terephthalate cyclic trimer (hereinafter abbreviated as cyclic trimer) is contained. When a polyethylene terephthalate film containing such a low molecular weight substance is used for electrical insulation of a closed motor for a refrigerator, for example, the low molecular weight substance is extracted from the polyethylene terephthalate film by a refrigerator oil or freon in the motor, and The cyclic trimer inside precipitates at various places in the refrigerator, causing trouble. For this reason, there is a demand for a film having an amount of the cyclic trimer of 0.5% by weight or less, preferably 0.4% by weight or less, depending on the type of the refrigerator.

Conventionally, in order to eliminate such defects, for example, Japanese Patent Publication No. 43-23348, Japanese Patent Publication No. 44-2120, etc.
Methods for extracting and removing low molecular weight substances from a film with various solvents have been proposed. Certainly, if a special solvent is selected and extracted, low molecular weight substances can be removed in a short time. However, the thicker the film, the longer the required extraction time and the lower the effect.

In addition, the use of the solvent not only increases the cost, but also has a risk of fire, and requires a drying step, resulting in reduced workability. Further, in the film processing step, there is a drawback that workability is deteriorated in handling properties such as color.

The present inventors, while removing such conventional disadvantages, a low content of cyclic trimers, and studied a polyester composition for an insulating film excellent in whiteness,
The present invention has been reached.

[Problems to be Solved by the Invention] An object of the present invention is to provide a polyester composition for an insulating film having a low cyclic trimer content and excellent whiteness.

[Means for Solving the Problems] The object of the present invention is to provide a polyester whose main repeating unit is polyethylene terephthalate, wherein the polyester has (1) an average particle diameter of 0.01 to 4 µm.
In addition, the inert inorganic particles having a specific surface area of 100 m ² / g or more
Alkali metal, alkaline earth metal, iron group, manganese, tin, lead,
Achieved by a polyester composition for an insulating film, which contains at least one metal selected from zinc and cadmium and phosphorus, and (3) the amount of ethylene terephthalate cyclic trimer is 0.4% by weight or less. can do.

0.5 ≦ M / P <1.4 (where M / P indicates the equivalent ratio of the metal (2) and phosphorus contained in the polyester. The phosphorus is calculated as divalent.) Cyclic trimer of the present invention The body is a low molecular weight body contained in polyethylene terephthalate, that is, one of oligoesters. These oligoesters are described in various literatures [for example, SDRose, et.al., J. Polymer Sci., 1
3 406 (1954), I. Goodman, BFNcsbitt, Polymer, 1334
(1960)], it is mainly a cyclic oligomer, and about 50% or more of the cyclic oligomer is said to be a cyclic trimer.

In general, it is said that a high molecular substance produced by polycondensation or addition polymerization always has a certain range of molecular weight distribution from a low molecular weight substance to a high molecular weight substance, so that the existence of a low molecular weight substance cannot be avoided. However, since these low molecular weight substances are present in the polymer, they cause the above-mentioned problems in, for example, electric insulation applications.

An important feature of the present invention is that the average particle size in the polyester composition is from 0.01 to 4 µ, preferably from 0.05 to 3 µ, more preferably from 0.1 to 2 µ. In addition, specific surface area of 100 m ² / g or more, preferably 200 m ² / g or more, more preferably 300 m ² / g or more of inert inorganic particles 0.5 to 10% by weight, preferably 1.0 to
The content is 5.0% by weight, more preferably 2.0 to 4.0% by weight. When the average particle size of the inert inorganic particles is smaller than 0.01 μm, the reaction system is not preferable because the viscosity of the reaction system increases, particle aggregates are generated, and whiteness cannot be imparted. On the other hand, if it is larger than 4 μm, it is not good because an increase in the number of cyclic trimers in the film forming step and an excessively roughened film cause insulation defects. Further, when the specific surface area is less than 100 m ² / g, when forming a film using the polyester composition of the present invention, such as an extrusion step, a stretching step and a heat treatment step, a cyclic trimer increases in a so-called film forming step, It is not preferable because whiteness cannot be imparted.

When the content of inert inorganic particles is less than 0.5% by weight,
When forming a film using the polyester composition of the present invention, cyclic trimers increase in a so-called film-forming step such as an extrusion step, a stretching step, and a heat treatment step, which is not preferable because whiteness cannot be imparted. In addition, the content of inert inorganic particles is
If it exceeds 10% by weight, no further effect can be found on the suppression of cyclic trimers.

As described above, the specific surface area of the particles is an indispensable factor for oligomer reduction and whiteness, which are the objects of the present invention. It is considered that oligomers are reduced by the surface activity of the particles or by adsorption to the particle surface, and whiteness is developed by irregular reflection on the particle surface.

In general, the specific surface area of the particles increases as the particle diameter decreases, but does not always match the particle diameter. The specific surface area varies depending on the surface morphology of the particles or the porous particles or the irregular particles.

As the kind of the contained inert inorganic particles, silicon dioxide, calcium phosphate, magnesium carbonate, aluminum silicate, titanium dioxide, talc, barium sulfate, calcium carbonate, obtained by a dry method or a wet method,
There are lithium fluoride, mica and the like, and silicon dioxide, titanium dioxide and calcium phosphate are preferred. Particularly, silicon dioxide is more preferable.

Another important feature of the present invention is that the M / P in the polyester is
0.5 to less than 1.4. That is, when the equivalent ratio of the specific metal to phosphorus is 1.4 or more, it is not preferable because the cyclic trimer increases remarkably in the film forming step.
On the other hand, if the equivalent ratio of the specific metal to phosphorus is less than 0.5, no further effect can be found in suppressing the cyclic trimer. Further, the melting point of the polyester is lowered, which is not preferable.

The metal (2) in the present invention includes alkali metals such as lithium, sodium and potassium, magnesium,
It indicates alkaline earth metals such as calcium and strontium, iron group, manganese, tin, lead, zinc and cadmium. These metals are mainly used as catalysts for esterification or transesterification, or to form precipitated particles.
The hydrides, alcoholates, chlorides and monocarboxylic acids are added in the form of glycol-soluble salts.

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

In addition, the intrinsic viscosity [η] of the polyester of the present invention is 0.5 to 1.5, preferably 0.
The range of 7 to 1.2 is good.

Next, an example of a method for producing the polyester of the present invention will be described.

Terephthalic acid or its ester derivative and ethylene glycol are heated and dissolved in the presence of an esterification or transesterification catalyst and subjected to esterification or transesterification by a conventional method. After completion of the esterification or transesterification reaction, the metal compound or the phosphorus compound is added so that the ratio of the metal compound to the phosphorus compound becomes a predetermined value, and the inert inorganic particles, for example, ethylene glycol is used as a slurry medium, and ethylene is added. It is added in the form of a glycol slurry or the like.

The timing of adding the inert inorganic particles is not limited to the above, and any stage from before the start of the esterification or transesterification reaction to completion of the polycondensation reaction can be selected.

Subsequently, the polycondensation reaction is carried out by raising the temperature and reducing the pressure by an ordinary method,
A polyester having an intrinsic viscosity [η] of about 0.5 is obtained. The obtained polyester is subjected to solid-state polymerization under reduced pressure in the form of chips. In the case of solid-phase polymerization, pre-crystallize at a temperature of 180 ° C or less in advance, and then perform solid-state polymerization at 190 to 250 ° C under a reduced pressure of about 1 torr for 40 to 60 hours to obtain a chip with an intrinsic viscosity [η] of about 1.0. Get.

As the polymerization catalyst in the polycondensation reaction, a compound usually used as a polyester polycondensation catalyst can be appropriately used.

As described above in detail, according to the present invention, a polyester composition for an insulating film in which the content of the cyclic trimer is significantly reduced can be obtained.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

In addition, the measurement of each characteristic value of the obtained polyester was performed according to the following method.

A. Intrinsic viscosity [η] It is a value measured at 25 ° C. at a concentration of 0.1 g / 10 ml in orthochlorophenol.

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

C.Tm This is a value measured by a differential scanning calorimeter [PERKIN-ELMER (DSC)].

D. Cyclic trimer 100 mg of the polymer was dissolved in 5 ml of orthochlorophenol, measured by liquid chromatography (Model 8500 Varian), and expressed as a percentage (% by weight) based on the polymer.

E. Average particle size It is the value measured by Horiba ultracentrifugal particle size distribution analyzer (CAPA700).

F. Specific surface area BET method surface area measuring device (Model 4200 manufactured by Nikkiso Co., Ltd.)
It is a value measured in.

G. Whiteness As an index of whiteness, film haze was measured according to ASTM-D-1003-52.

Example 1 100 parts of dimethyl terephthalate, ethylene glycol 6
In 0 parts of the mixture, based on the amount of dimethyl terephthalate,
0.09% by weight of calcium acetate and 0.03% by weight of antimony trioxide were added, and the mixture was heated and heated in a conventional manner to carry out a transesterification reaction. Next, the transesterification reaction product:
Phosphoric acid 0.07% by weight based on the amount of dimethyl terephthalate
After adding 3% by weight of silicon dioxide having a specific surface area of 380 m ² / g and an average particle size of 0.1 μm, the system is transferred to a polycondensation reaction tank. Then, while heating and raising the temperature, the reaction system was gradually decompressed to 1 mmHg.
The polymer is polymerized at 290 ° C under a reduced pressure by a conventional method, and the intrinsic viscosity [η] is obtained.
0.54 polyester was obtained. The polymer was cut into cubes having a diameter of 3 mm, and heated at 225 ° C. for 50 hours under reduced pressure of 1 mmHg using a rotary vacuum polymerization apparatus to obtain an intrinsic viscosity [η] of 0.98.
A polyester was obtained. As a result of elemental analysis in the polyester, Ca was 200 ppm, P was 153 ppm, and M / P was 1.0. The polyester had a Tm of 258 ° C. and a cyclic trimer content of 0.18% by weight. Then 40mm
With a melt extruder of φ, set temperature 290 ° C, residence time of 8 minutes, 1.2
mm of unoriented film was obtained. This was biaxially stretched under ordinary conditions to obtain a biaxially oriented polyester film having a thickness of 120 μm. The content of cyclic trimer in the film is 0.22% by weight.
And the film haze was 88%.

Examples 2 to 7, Comparative Examples 1 to 5 The same method as that of Example 1 was used, except that the metal compound and phosphorus compound used, the specific surface area of the inert inorganic particles, and the amount of addition were carried out under the conditions shown in Table 1. Each polyester was obtained. Table 1 summarizes the M / P and cyclic trimer content of the obtained polyester, and other properties.

According to Table 1, the specific surface area, content of the inert inorganic particles,
When the M / P is within the range of the present invention, the content of the cyclic trimer in the polyester and in the obtained polyester film is small.

[Effects of the Invention] The polyester composition of the present invention, which has a low content of cyclic trimers and has excellent whiteness, is formed into a film and used for insulation. Also, since low molecular weight substances do not precipitate in the refrigerant, it is possible to maintain good quality of the refrigerant, prevent troubles due to extracted low molecular weight substances, and improve workability in handling such as color classification in the film processing process. Can be expected.

For example, when a normal polyethylene terephthalate film is used for electrical insulation of a hermetic motor for a refrigerator, low molecular weight substances are extracted from the polyethylene terephthalate film by a refrigerator oil or freon in the motor, and a cyclic trimer therein is extracted. Precipitates at various places in the refrigerator, causing trouble. However, by using a film using the polyester composition of the present invention,
Such troubles can be prevented.

Claims (1)

(57) [Claims] 1. A polyester whose main repeating unit is ethylene terephthalate, wherein the polyester has (1) an average particle diameter of 0.01 to 4 μm and a specific surface area of 100 m ² /
g, containing at least 0.5 to 10% by weight of inert inorganic particles, and selected from alkali metals, alkaline earth metals, iron group, manganese, tin, lead, zinc and cadmium so as to satisfy the formula (2). A polyester composition for an insulating film, comprising at least one metal and phosphorus, and (3) an ethylene terephthalate cyclic trimer content of 0.4% by weight or less. 0.5 ≦ M / P <1.4 (where M / P indicates the equivalent ratio of the metal (2) and phosphorus contained in the polyester. The phosphorus is calculated as divalent.)