JPS58177316A - Method of forming polyester film - Google Patents

Abstract

PURPOSE:To obtain highly efficiently a polyester film without surface defect, by mixing 100pts.wt. thermoplastic polyester, 0.01 to 2pts.wt. inorganic fine powder, and 0.0001 to 0.0025pt.wt. of alkali metal compound soluble in ethylene glycol, the amount of the alkali metal compound being calculated in terms of the metal, and melting the mixture followed by extruding. CONSTITUTION:In forming a film by melting and extruding a thermoplastic polyester, 0.01 to 2pts.wt. of inorganic fine powder and 0.0001 to 0.0025pt.wt. alkali metal compound soluble in ethylene glycol, which amount of the alkali metal compound is calculated in terms of the metal, are added to 100pts.wt. said polyester. Thus without changing the physical properties of the polyester itself, the adherence of the melted and extruded sheet-like body with a rotating cooling body surface can be improved to porduce highly efficiently a polyester stretched film without surface defect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing a stretched polyester film with no surface defects at high efficiency. When rapidly cooling on the surface of a cooling body such as a drum, a wire-shaped electrode is installed between the extrusion die and the surface of the rotating cooling body to deposit electrostatic charges on the top surface of the unsolidified sheet-like material, thereby cooling the sheet-like material. The electrostatic casting method, in which a uniform film is obtained by rapidly cooling the material in close contact with the body surface, is known from VC and Niri, such as the 4I Society No. 37-6142 bulletin.

However, even in such electrostatic casting method,
As the circumferential speed of the rotary cooling body is increased to improve the film forming speed, the adhesion of the sheet to the surface of the cooling body decreases, making it difficult to obtain a uniform film, and the possibility that the sheet and rotating Inclusion of air between the film and the cooling body causes defects on the film surface.

In film production [70] Reducing production costs by increasing the permeability is an important issue as well as improving quality, so K increases the peripheral speed of the rotary cooling body to increase the film production rate. An effective method is to improve

In the electrostatic casting method, in order to increase the film forming speed, the circumferential speed of the rotary cooling body (increasingly, the amount of electrostatic charge per unit area on the surface of the sheet-like material that is in close contact with the surface of the cooling body) is reduced. However, the adhesion between the sheet material and the rotary cooling body decreases, causing defects on the film surface.For this reason, in order to increase the adhesion between the sheet material and the rotary cooling body, an extrusion die and A possible method is to increase the voltage applied to the electrode installed between the surface of the rotary cooling body and increase the amount of electrostatic charge deposited on the surface of the sheet-like object.

If the applied voltage is too high, arc discharge will occur between the electrode and the surface of the cooling body, destroying the sheet-like material on the surface of the cooling body and damaging the surface of the cooling body. Therefore, it is virtually impossible to increase the voltage applied to the electrodes above a certain level, and conventional electrostatic casting methods have limitations in increasing the film forming speed and obtaining a uniform film.

In order to overcome the limitations of the electrostatic casting method, improve the film forming speed, and obtain a highly efficient and uniform polyester film with no surface defects, Japanese Patent Publication No. 53-40231 discloses the use of alkali metals and alkaline earth metals. Or control the specific resistance of the molten polymer by containing these compounds,
A method has been proposed for producing Boris arele film with high efficiency. However, this method does not allow the alkali metal or ;l''/I/potassium earth metal compound to be
s ~ 1% by weight, preferably 0.0) ~ 0.3% by weight, &t%
The inclusion of such metals improves the adhesion between the polyester sheet and the rotary cooling body, and when such a large amount of alkali metals and alkaline earth metals are included, 11 km of the polyester will precipitate, resulting in a film. When formed, the coarsened Takeda particles cause pinholes, etc., which can induce arc discharge during film formation, and seriously worsen the color tone of the polyester itself, resulting in a polyester film with a strong color tone. This is not desirable.

The inventors of the present invention have made extensive studies in order to eliminate such drawbacks, and have not changed the physical properties of the polyester film itself.
The inventors have discovered a method for forming a polyester film with high efficiency by improving the adhesion between the melt-extruded sheet material and the surface of a rotary cooling body, and this method has been incorporated into the present invention.

That is, in the present invention, when forming a film by melt-extruding thermoplastic polynisdel, the underarm polyester 100
A polyester film forming method characterized in that 0.01 to 2 parts by weight of an inorganic fine powder and an ethylene glycol-soluble alkali metal compound are blended in Q, OOQ 1 to 0.0026 parts by weight in terms of metal. be.

The present invention will be explained in detail below.

The thermoplastic polyester in the present invention mainly refers to polyethylene terephthalate, but some of them include dibasic acids such as inphthalic acid and adipic acid, dihydric alcohols such as triethylene glyfur and 194-butanediol, polyethylene glycol, and polyethylene terephthalate. The stabilizer may be a polyester copolymerized with polyoxyalkylene glycol such as butylene glycol.

It may also contain additives such as colorants.

This polyester is usually produced by a melt polymerization method. For example, terephthalic acid or its lower alkyl ester is esterified or transesterified with ethylene glyfur to form a polymer or prepolymer, which is then heated at a temperature above its melting point under vacuum or under an inert gas. The intrinsic viscosity is 0.45 while stirring under flowing conditions.
The polycondensation reaction is carried out until it reaches about 0.75. In addition to this, additives such as catalysts can be used as desired.

Preferable examples of the ethylene glycol-soluble alkali metal compound used in the present invention include sodium hydroxide and aliphatic carboxylate, and particularly preferred examples include sodium hydroxide and sodium acetate.

Compounds that are not soluble in ethylene glyfur are difficult to uniformly disperse in polyester, and if they are present as coarse foreign matter in polyester due to agglomeration, they may cause defects such as pinholes, which is not preferable.

Further, examples of the inorganic fine powder used in the present invention include clay, kaolin, talc, silica, alumina, calcium phosphorus, etc., and these are usually used for the purpose of improving the slipperiness of polyester films. Merely containing these inorganic fine powders does not provide much hope for increasing the degree of film formation due to improved adhesion to the surface of the cooling body of the sheet-like material, and even if there is an increase, the increase is minimal. Also,
When only an alkali metal compound is contained, a slight increase in film forming speed is expected, but when it is combined with an inorganic fine powder, the effect increases dramatically compared to K.

These inorganic fine powders and ethylene glycol-soluble alkali metal compounds may be added at any time as long as they are uniformly dispersed in the polyester.[However, if the polycondensation reaction progresses and the intrinsic viscosity exceeds 0.2. It is preferable to add it while it is still in use.

Further, the inorganic fine powder and the alkali metal compound may be mixed in advance and added outside the system, and the effect remains the same even if each is added independently. Furthermore, there is no problem in adding the mono-ethylene glycol-soluble alkali metal compound simultaneously with catalysts and additives commonly used in polyester production.

In the present invention, the inorganic fine powder contained in the polyester is 0.01 to 2 parts by weight per 100 parts by weight of the polyester.
Parts by weight, more preferably 0.03 to 1.5 parts by weight. If the amount is less than 0.01 part by weight, no synergistic effect with the alkali metal compound coexisting in the polyester is expected, and rather the state is equivalent to adding the alkali metal compound alone, resulting in an increase in film forming speed due to improved adhesion. It becomes K<. Furthermore, if the content of the inorganic fine powder exceeds 2 parts by weight, the content of the inorganic fine powder in the polyester film may become too large, which may impair the original transparency and uniformity of the polyester film. Furthermore, the inclusion of a large amount of inorganic fine particles causes agglomeration of trout, making it difficult to obtain a high-quality polyester film.

In addition, the ethylene glycol soluble alkali metal compound coexisting with the inorganic fine powder in the polyester is 0.0001 to 0.0001 o, oo in terms of metal in 100 parts by weight of the polyester.
It is necessary that the amount is zsllL parts, and more preferably 0.0003 to 0.0020 parts by weight. Content is 0
．． If the amount is less than 0,001 parts by weight, the effect of increasing the film forming rate due to the synergistic effect with the inorganic fine powder in the present invention is not expected.
If the amount exceeds 0,0025 parts by weight, the color tone of the polyester film may deteriorate, resulting in a yellowish polyester film, which is not preferable. Also, 0.
The effect of increasing the film forming speed by containing more than 0.025 parts by weight of an alkali metal has almost reached saturation, but rather increases the frequency of arc discharge, making it unsuitable for obtaining a polyester film with high efficiency. .

Normally, when obtaining a polyester film containing inorganic fine powder, a polyester containing high degree of inorganic fine powder is produced in the polycondensation reaction process. In the process of obtaining a film by rWi extrusion, a method is used in which fine inorganic powder is diluted with non-singling polyester to obtain a polyester film having the desired composition. Appropriate dilution of the polyester does not interfere with the effects of the present invention. When producing and diluting a polyester with a high concentration of this inorganic fine powder and alkali metal compound, it is effective to make the inorganic fine powder and the alkali metal compound coexist in the same polyester to effectively express the inventive effect. I like it. Producing a polyester containing an alkali metal compound and a polyester containing an inorganic fine powder separately and then mixing the inorganic fine powder and the alkali metal compound in the film forming process tends to reduce the effects of the present invention by half. Although the reason for this is not clear, it suggests that there is a synergistic effect between the inorganic fine particles of the present invention and the alkali metal compound, and the adhesion between the polyester sheet and the surface of the rotary cooling body is improved for the first time. .

The present invention will be described in detail below based on Examples.

Describe the evaluation method.

(Surface defect evaluation method) The surface of the formed film is observed under a polarized lens and ranked as follows.

Rank-1 Uniform surface with no visible surface defects.

Rank-2 Minor surface imperfections are present.

Rank-3 There are relatively many minute surface defects.

Rack-4 There are relatively many large surface defects.

Rank-5 Large surface defects are present all over. Example-1 Polyethylene terephthalate was polymerized according to a conventional method using manganese acetate as a transesterification catalyst, antimony dioxide as a polymerization catalyst, and trimethyl phosphate as a heat stabilizer. At this time, before the transesterification reaction is completed,
0.0% per 100 parts by weight of polyethylene phthalate.
25 parts by weight of clay and o, o o o s parts by weight (metal equivalent) of sodium acetate were added.

The obtained polyethylene terephthalate having an intrinsic viscosity of 0.620 was dried and formed into a film under the following conditions.

Extrusion temperature: 2.85°C Electrostatic casting conditions: Electrode 0.21-f BUS applied voltage aIsoov Cooling drum temperature: zlt Longitudinal stretch ratio = 3.6 times Transverse stretch ratio = 3.9 times Heat setting temperature = 225°C Film speed: t s Om/11 of the biaxially stretched film after shoe formation! There were no surface defects, the rank was 1, and a uniform film was obtained.

Comparative Example-1 Example-1 except that sodium acetate was not added.
Polyethylene terephthalate was obtained under the same conditions, and a biaxially stretched film was obtained under the same conditions. In this case, 3! ! The surface defects were ranked -5, and no film that could be used as a product was obtained.

Example-2 In Example-1, K was substituted for sodium acetate.

0.0006 parts by weight (metal equivalent) of sodium hydroxide was added to obtain polyethylene terephthalate, and a film was further formed under exactly the same conditions as Example 1E.

The surface of the obtained film was ranked -1, and a uniform film was obtained.

Examples 3, 4, and 5 and Comparative Examples 2 and 3 Polyethylene terephthalate obtained by changing the type of inorganic fine powder and the type of alkali metal compound to 5 as shown in Table 1 was used in Example-
Table 1 shows the results obtained by changing only the film forming speed under the film forming conditions of No. 1.

Table 1 In Comparative Example 3, the polymer color tone was yellowish, and furthermore, it was Kokuden that obtained an M-grade film by arc discharge.

Examples 6 and 7 When obtaining a polyethylene terephthalate film containing an inorganic fine powder and an alkali metal compound. Table 2 shows an example of a case where a polyester containing inorganic fine powder and a polyester containing an alkali metal compound with high melting strength were made and optionally diluted in the film forming stage.

Example 6 contains the same polyethylene terephthalate (K) containing an inorganic fine powder and an alkali metal compound, and Example 6 contains polyethylene terephthalate (K) containing an inorganic fine powder and an alkali metal compound separately. It is a mixture.

1) Metal equivalent amount

Claims (1)

[Scope of Claims] l) When forming a film by melt extruding thermoplastic polyester, 0.01 to 2 parts by weight of inorganic fine powder and ethylene/glycol soluble alkali are added to 1 part of 1 part of L1. The metal compound is converted to metal equivalent to 0.
0001 to 0.0025 parts by weight of 41
11 Polyester membrane method. 2) The alkali metal compound is selected from sodium hydroxide and aliphatic carboxylate; 3) The inorganic fine powder is clay, kaolin, or talc. 4) The polyester is a polyester containing ethylene terephthalate as the main repeating unit. Patent claims! ! The method for forming a Boriesubq film according to any one of Items III to 3.