JPH02305827A - Fabricable polyester film - Google Patents

Abstract

PURPOSE:To obtain the title film excellent in pinhole resistance, deep drawability, bending processability, etc., by constituting it from a copolyester having a specified melting point and containing a lubricant so as to give thereto a specified surface orientation factor. CONSTITUTION:This film is prepared from a copolyester of an m.p. of 210-245 deg.C containing a lubricant (e.g. silica) of a mean particle diameter <=2.5mum (e.g. copolyethylene terephthalate containing 12mol% copolymerized isophthalic acid) so that it may have a surface orientation factor of 0.060-0.110.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polyester film for forming processing, and more specifically to deep drawing formability and pinhole resistance.

The present invention relates to a polyester film for molding that has excellent bendability and is particularly useful for molding into containers and the like either alone or after being laminated with other materials.

<Prior art and its problems> It has been known for a long time to manufacture containers and the like by subjecting plastic films to deep drawing processing such as vacuum forming and pressure forming. As this film, polyolefin film, polystyrene film, polyvinyl chloride film, unstretched polyethylene derephthalate film, etc. are usually used. However, the biggest drawback of polyolefin, polystyrene, and polyvinyl chloride is that they lack heat resistance, and many cannot be used at temperatures above 100°C. In addition, unstretched polyethylene terephthalate film has 1
At temperatures above 00°C, crystallization occurs, resulting in loss of transparency and brittleness. Furthermore, many of the plastic materials that have been used in the past are being mass-produced due to their gas barrier properties.

<Means for Solving the Problem> As a result of intensive study to solve the problem, the inventor of the tree arrived at the present invention.

That is, the present invention is characterized in that it contains a lubricant with an average particle size of 2.5 μm or less, is made of a copolymerized polyester with a melting point of 210 to 245°C, and has a planar orientation coefficient of 0.060 to 0.110. This is a polyester film for molding.

A representative example of the copolymerized polynisdel in the present invention is copolymerized polyethylene terephthalate.

This copolymerization component may be an acid component or a mucoalcohol component.

The acid component includes aromatic dibasic acids such as isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sepacic acid, and decane dicarboxylic acid; and alicyclic acids such as cyclohexane dicarboxylic acid. Examples of the alcohol component include aliphatic diols such as butanediol, hexanediol, neopentyl glycol, and hexanediol, and alicyclic diols such as cyclohexanedimetatool.

These can be used alone or in combination of two or more.

The proportion of copolymerized components depends on the type, but as a result, the polymer melting point is 210-245°C, preferably 215-245°C.
This is the ratio that results in a temperature range of 40°C. If the melting point is less than 210°C, crazing (cracking) will occur during molding, which is not preferable. Furthermore, since molded products are often printed, it is necessary to have a melting point of 210°C or higher in order to withstand the heat during printing. On the other hand, if the melting point exceeds 245° C., for example, even if the planar orientation coefficient described below is within a predetermined range, moldability will be insufficient, which is undesirable. Here, the melting point of polyester is measured using Seiko Electronics (Kiku M
Using DSC-8SC/580, heating rate 10℃/'
Depends on the method of determining the melting peak in minutes.

The copolymerized polyester in the present invention has an average particle size of 2.5
Contains a lubricant of µm or less. This lubricant can be either inorganic or tangible, but inorganic lubricants are preferred.
Examples of such lubricants include silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate, and examples of organic lubricants include silicone particles. Both have an average particle size of 2.5 μm.
The following must be true. Average particle size of lubricant is 2.5μm
If it exceeds this value, the lubricant in the deep-drawn part by vacuum forming etc. will become a starting point and cause pinholes or breakage in some cases, which is not preferable.

The quality of the lubricant in the copolyester may be determined by the winding properties in the film manufacturing process.

In general, it is preferable to add 9 particles if the particle size is large, and a large amount if the particle size is small. For example, in the case of silica with an average particle size of 2.3 μm, it is preferable to add 0.05% by weight, and in the case of titanium dioxide with an average particle size of 0.3 μm, it is preferable to add about 1% by weight. It is also possible to make the film opaque by intentionally adjusting the lubricant content. For example, titanium dioxide
By adding up to 151 m%, a white film can be obtained.

The copolymerized polyester in the present invention is not limited by its manufacturing method. For example, by esterifying terephthalic acid, ethylene glycol, and a copolymer component,
Next, the resulting reaction product is subjected to a polycondensation reaction to obtain a copolymerized polynisdel, and dimethyl terephthalate, ethylene glycol, and a copolymer component are transesterified, and the resulting reaction product is then subjected to a polycondensation reaction to form a copolymerized polyester. A method is preferably used.

Alternatively, a method may be adopted in which a polyester consisting of a copolymerized component is blended with polyethylene terephthalate, then melted, and copolymerized by a partition reaction. Other additives such as antioxidants, heat stabilizers, and ultraviolet absorbers may be added as necessary in the production of copolyester.

Antistatic agents and the like can also be added.

The polyester film of the present invention is produced by melting the above-mentioned copolyester and extruding it from a die to form a film.
The film is two-wheel stretched and heat-set, and the plane orientation coefficient of the film is o, oeo or more and 0.110 or less, preferably 0.
．． It is required that the value is 070 or more and 0.100 or less. If the plane orientation coefficient is less than 0.060, it becomes weak against bending.
For example, if the container is bent (also called curling) for edging after being formed, the bent portion will turn white and become brittle, which is not preferable. If the one-plane orientation coefficient exceeds 0.110, deep drawing becomes insufficient, which is not preferable. Here, the planar orientation coefficient is defined by the following formula.

"-[(几x+nV)/2]-nl In the above formula, f: plane orientation ratio, nx, ny.

nl: refractive index in the horizontal, vertical, and thickness directions of the film, respectively. Note that the refractive index is measured as follows.

A polarizing plate analyzer is attached to the eyepiece side of Atsube's refractometer, and each refractive index is measured using a monochromatic NaD ray.

The mounting solution used was methylene iodide, and the measured mt* was 25
It is ℃.

In order to obtain the above plane orientation coefficient, in the sequential secondary stretching, the longitudinal stretch ratio is 2.7 to 3.5 times, and the transverse stretch ratio is 3.0 to 3.
It is preferable to carry out stretching heat treatment at a heat setting temperature of 180 to 220°C. More preferably, the conditions under which the plane orientation coefficient is 0.060 or more and 0.110 or less are found, and the two-wheel stretching and heat setting treatments are performed.

The object of the present invention is achieved only when all three conditions of the above-mentioned melting point, lubricant, and planar orientation coefficient are satisfied.

For example, even if the lubricant conditions and the dihedral orientation coefficient conditions are achieved with polyethylene terephthalate homopolymer, sufficient deep drawability cannot be obtained, and if the average particle size of the lubricant exceeds 2.5μ, the other two Even if the conditions are met, pinholes will occur,
It may cause trouble.

The polyester film of the present invention has a thickness of 6 to 100μ
It is more preferable that m1 is 12 to 38 μm.

<Example> The present invention will be further explained below with reference to Examples.

Example 1 and Comparative Examples 1 and 2 912 mol% isophthalic copolymerized polyethylene terephthalate (melting point 229°C, intrinsic viscosity 0.60) containing 0.07 wt 8% silica with an average particle size of 2.0 μm (melting point 229°C, intrinsic viscosity 0.60)
It was melt-extruded at 10° C. and rapidly solidified to obtain an unstretched film with a thickness of 700 μm. Next, this unstretched film is
Under the conditions shown in Table 1, the film was longitudinally stretched, transversely stretched, and then heat-set to obtain a biaxially oriented film.

The properties of this film are shown in Table 4.

Table 1 Example 2 and Comparative Examples 3 to 6 Copolymerized polyethylene terephthalate containing 0.05% by weight of silica with an average particle size of 2.3 μm and copolymerized with the components shown in Table 2 (intrinsic viscosity 0. 60) was melt-extruded at the temperature shown in Table 2 and rapidly solidified to obtain an unstretched film (thickness: 2,800 μm). Next, this unstretched film was longitudinally stretched and transversely stretched under the conditions shown in Table 2, followed by heat setting treatment to obtain a biaxially oriented film.

The properties of this film are shown in Table 4.

Table 2 Example 3.4 and Comparative Example 7 Polyethylene terephthalate copolymerized with 12 mol % of isophthalic acid (intrinsic viscosity: 0.5%) containing the lubricant shown in Table 3.
60) was melt-extruded at 270°C, rapidly cooled and solidified to form an unstretched film, and then the unstretched film was longitudinally stretched at a temperature of 8.
Two-wheel stretching was carried out successively at 0° C., ii. draw ratio: 3.3 times, transverse drawing temperature: 110° C., and transverse drawing ratio: 3.5 times, followed by heat setting at 210° C.

Table 4 shows the properties of the biaxially oriented film (thickness = 50 μm).

Table 3 Examples 1 to 4. A total of 11 types of films obtained in Comparative Examples 1 to 7 were heated with an IR heater for 10 seconds to bring the temperature of the film to 130°C. It was placed on a metal mold with a depth of 80 mm, and air pressure molded at a pressure of 5 K9/cd. Next, the edges of the cup-shaped article were cut off, and the edges were curled to form a cup.

In this molding, ○: no cracks were formed in the film during pressure forming; ×: cracks were formed in the film; and during curling processing, O: no cracks were formed at the edges; Table 4 shows the results of evaluating the two points that occurred.

From the results shown in Table 4, it can be seen that the films of Examples are excellent in deep drawing properties, edge curling properties, etc.

<Effects of the Invention> The polyester film of the present invention has excellent pinhole resistance, deep drawing formability, bending workability, etc., and is suitable for molding, especially alone or laminated with other materials such as plastics, metal plates, etc. It is excellent for later deep drawing of containers, etc.

Claims (1)

[Claims] Contains a lubricant with an average particle size of 2.5 μm or less and has a melting point of 210
A polyester film for molding, which is made of a copolymerized polyester at a temperature of ~245°C and has a planar orientation coefficient of 0.060 to 0.110.