JPH0768374B2 - Polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is useful in the fields of magnetic tapes, capacitors, packaging, etc., and has a uniformly controlled surface roughness and is highly productive. The present invention relates to a property improving film.

[Conventional technology]

Polyester films, especially biaxially oriented films of polyethylene terephthalate, are excellent in various properties such as mechanical properties, optical properties, chemical resistance, and heat resistance.
It is well known that it is widely used in many fields such as magnetic tapes, capacitors, electrical insulation materials, transfer, packaging, etc., and its slipperiness is the operability in the film manufacturing process and subsequent processing steps. It is also well known that the quality of the product is greatly affected.

In general, as a method of improving the slip property of the film, a means for reducing the contact area with the contact object of the film comrades or the other by making unevenness on the surface of the film is adopted,
Mainly internal particle method or precipitation method, that is, a method of precipitating fine inorganic particles from the catalyst residue during polyester synthesis into the system, or addition method, that is, a method of adding inorganic fine particles from outside the reaction system during polyester synthesis Depends on. However, these methods have problems that it is difficult to control the amount of precipitated particles and the particle size, or the inorganic particles are not uniformly dispersed in the organic polyester and agglomerate to form coarse particles. The presence of coarse particles causes a dropout in a magnetic tape for video, which is a fatal defect. Further, when the unstretched film comprising the inorganic particle-containing polyester is stretched and oriented, a void is generated at the boundary between the particles and the polyester, and a phenomenon in which the particles fall off from the film due to contact with another substrate during processing or use, a so-called Shavings are easily generated.

On the other hand, it is said that the organic synthetic resin particles are superior in affinity and dispersibility to the above-mentioned inorganic particles. Typical examples thereof are JP-A-55-155029 and JP-A-63-1781.
Although it is a dispersion of crosslinked acrylic resin particles described in Japanese Patent Publication No. 44 etc. into polyester, when actually tried,
Is it because the state of the contact interface between the polyester main chain and the ester bond of the acrylic side chain changes slightly during melt mixing or melt film formation? It is pointed out that it is difficult to control the surface irregularities of the resulting film.
In addition, in such an organic synthetic particle addition method, it is generally necessary to go through a particle preparation step such as crushing, crushing and classification before compounding with polyester, which is disadvantageous since it complicates the step.

[Problems to be Solved by the Invention]

The present invention has been made to solve the above-mentioned problems particularly in a polyester film having a good slip property by an organic synthetic resin addition method.

[Means for Solving the Problems]

As a result of repeated studies on a polyester film having improved slip properties by the method of adding an organic synthetic resin, the inventors have found that a thermoplastic polyamide having a high glass transition temperature can be blended in a specific amount with respect to the polyester forming the film. The inventors have reached the present invention knowing that they are suitable for solving the above problems.

That is, according to the present invention, 0.001 to 3.0% by weight of a thermoplastic polyamide (B) having a glass transition temperature higher than that of the thermoplastic polyester (A) is contained in the thermoplastic polyester (A).
A film made of a composition that is dispersed in a spherical shape or an ellipsoidal shape so as to occupy, or a film in which the composition is laminated so as to form a surface layer, the center surface average roughness of the film surface and ten points. Average roughness of 0.003 each
In the case of adding acrylic resin particles, a polyester film having a thickness of 0.07 μm and 0.03 to 1.5 μm is a gist, and an ester-amide exchange reaction hardly occurs between the polyester (A) and the polyamide (B). It is advantageous that the above-mentioned problems are unlikely to occur.

Typical examples of the thermoplastic polyester (A) in the present invention are polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), poly-1,4-cyclohexylene dimethylene terephthalate (PCT). ) Or poly-p-ethyleneoxybenzoate (PEOB), which sufficiently satisfies the requirements such as performance and price as a polyester for films. Here, the glass transition temperature (hereinafter referred to as Tg) of the thermoplastic polyester (A) is the same as that of the thermoplastic polyamide (B).
It plays an important role in the relationship with Tg, but it can be measured by the DSC method. The Tg of PET is 70 ° C and the Tg of PBT is 50.
℃, PEN Tg is 120 ℃, PCT Tg is 95 ℃, PEOB Tg is 60
C is a common value. Further, other components may be introduced as a copolymerization component to the extent that the film forming ability is not impaired in these thermoplastic polyesters, and the polyester may be formed from a mixed polyester of PET and PBT, for example. Needless to say.

Next, the thermoplastic polyamide (B) used in the present invention is a thermoplastic polyamide having a higher Tg than the thermoplastic polyester (A), and the requirement for the Tg value is as follows.

That is, the thermoplastic polyester (A) and the thermoplastic polyamide (B) are melt-mixed so that the thermoplastic polyester (A) serves as a sea component and the thermoplastic polyamide (B) forms a spherical or elliptic spherical island component, It is extruded into a film and then stretched to form a film with fine protrusions. If the Tg of the thermoplastic polyamide (B) is low, it will stretch together with the thermoplastic polyester (A) during stretching, and This is because the polyamide (B) cannot serve as a nucleus and the projections on the film surface, which are essential, are less likely to appear. The difference in Tg between the thermoplastic polyester (A) and the thermoplastic polyamide (B) is preferably 20 ° C. or higher, more preferably 30 ° C. or higher.

Examples of such a high Tg polyamide include 5-tert.butylisophthalic acid, 1,1,3-trimethyl-3-phenylindane-3 ′, 5-dicarboxylic acid and 3-aminomethyl-3,5,5.
-Trimethyl-cyclohexylamine, 1,3-diaminocyclohexane, metaxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 2,4,4-trimethylhexanemethylenediamine, bis (4-aminocyclohexyl) methane, bis A polyamide containing a component such as (3-methyl-4-aminocyclohexyl) methane as a copolymerization component is preferable, and ethylenediamine, tetramethylenediamine, hexamethylenediamine, phenylenediamine, adipic acid, sebacic acid, cyclohexanedicarboxylic acid, Obtained by polycondensation by a commonly known method in combination with a polyamide-forming component such as isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, ε-aminocaproic acid, ω-aminododecanoic acid, aminobenzoic acid, and ε-caprolactam. The higher the Tg of the thermoplastic polyamide (B), the easier the roughening effect is, but
The temperature is preferably 200 ° C. or lower in consideration of workability during polycondensation or melt molding.

In the polyester film with improved slipperiness of the present invention, the thermoplastic polyamide (B) is dispersed as an island component in the thermoplastic polyester (A) as a sea component in a spherical or elliptic spherical shape. , It is preferable that the particles are as spherical as possible, and it is preferable that the particles exist in a particle size of submicron to micron order. In the case of elliptical spherical dispersion, the ratio of the major axis to the minor axis is 2.0 or less, and more preferably 1.5 or less. Be good. Further, the amount of the thermoplastic polyamide (B) is required to be 0.001 to 3.0% by weight in order to satisfy the following required numerical range for the degree of roughness of the film surface. If the amount is less than 0.001% by weight, the surface unevenness effect and slip property are insufficient, and if it exceeds 3.0% by weight, the film surface becomes too rough.

In the film of the present invention, the thermoplastic polyamide (B) serves as a nucleus to form fine protrusions on the film surface, and the larger the amount of the thermoplastic polyamide (B) and the larger the particle size, the more the film is formed. The unevenness of the surface becomes noticeable, but from the practical point of view, the center surface average roughness (SRa)
And ten-point average roughness (SRz) of 0.003 to 0.7 μm
And 0.03 to 1.5 μm are required. SRa represents the average distance of the peaks and valleys from the center plane, with the plane where the sum of the peak area and the sum of the valley areas on the film surface is the same. SRz represents the difference between the average height of 5 points of high peaks on the film surface and the average depth of 5 points of deep valleys in the film of the present invention. SRz is higher than SRa in the film of the present invention. Is small enough. That is, it has a uniformly controlled surface roughness. These can be measured by, for example, a three-dimensional surface roughness meter manufactured by Kosaka Laboratory.

The film of the present invention may be composed of the composition of the thermoplastic polyester (A) and the thermoplastic polyamide (B) alone, or may be in the form of multiple layers. The latter is a film in which a layer made of the composition is laminated with another polymer layer so as to form a surface layer on one side or both sides of the film, which leads to improvement in mechanical properties, cost reduction and the like. As this "other polymer", because of its mechanical properties and ease of manufacture,
Polyesters such as PET, PBT, PEN, PCT and PEOB are preferably used.

The film of the present invention can be produced by a generally known method. That is, the thermoplastic polyester (A) and the thermoplastic polyamide (B) are melt-mixed by a uniaxial or biaxial extruder to finely disperse the thermoplastic polyamide (B) in the thermoplastic polyester (A) to obtain Uniaxially or biaxially stretched the unstretched film obtained by melt-extruding the obtained mixture alone or together with other polymers into a film form from a T die or a circular die and cooling it with a casting roller or gas or liquid. It is a method of stretching. The surface of the unstretched film is relatively smooth, but when it is stretched, the surface becomes rough. At this time, the stretching temperature is preferably an intermediate temperature between the Tg's of the thermoplastic polyester (A) and the thermoplastic polyamide (B). This is because the stretchability is poor at a temperature lower than the Tg of the thermoplastic polyester (A), and good surface irregularities are difficult to develop at a temperature higher than the Tg of the thermoplastic polyamide (B). In the case of uniaxial stretching, the stretching ratio is preferably 1.5 times or more. Further, a more favorable film can be obtained by biaxially stretching in the longitudinal and lateral directions.
Also in this case, it is preferable to stretch the film in the length and width by 1.5 times or more.

The stretching method of the film is not particularly limited, but uniaxial stretching,
Sequential biaxial stretching, simultaneous biaxial stretching and the like can be applied. Further, as a stretching device used therefor, a two-roll type uniaxial stretching machine, a tenter type transverse stretching machine, a tenter type or tubular type simultaneous biaxial stretching machine or the like can be applied.

Further, the film of the present invention, silica, titanium oxide, calcium carbonate, alumina, in the range not impairing the effects of the present invention,
It is also possible to add inorganic additives such as kaolin, mica and talc.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Reference Example Synthesis of High Tg Polyamide 45 mol% isophthalic acid, 5 mol% terephthalic acid, 45 mol% hexamethylenediamine, bis- (4-amino-3-)
Methylcyclohexyl) methane 5 mol% and acetic acid 0.015 mol% 10 kg of raw materials were charged into the reaction vessel together with 8 kg of pure water, and the air in the reaction vessel was purged with nitrogen several times. Temperature 90
After the temperature was raised to 0 ° C. and the reaction was carried out for about 5 hours, the reaction temperature was gradually raised to 280 ° C. over 10 hours under pressure (18 bar) with stirring in the tank.

Then, the pressure was released and the pressure was reduced to atmospheric pressure, and then polymerization was carried out at the same temperature for 6 hours. After the completion of the reaction, the product was discharged from the reaction tank and cut to obtain pellets. M of this polyamide
The relative viscosity measured at 20 ° C. at a concentration of 1 g / dl in cresol was 1.50 and the Tg was 150 ° C.

(Examples 1 to 7, Comparative Examples 1 and 2) PET (A-1) pellets and polyamide (B-1) pellets obtained in Reference Example were blended in various proportions as shown in Table 1. 280 with an extruder type melt extruder
The mixture was melt-mixed at 0 ° C. and extruded from a T-die to form a film having a thickness of about 200 μ. The obtained unstretched film was simultaneously biaxially stretched at 100 ° C. in a lengthwise and transverse direction of 3.3 times and heat set at 230 ° C.

The effects of the present invention were confirmed as shown in Table 1 together with the mixing ratio and the surface roughness, static friction coefficient and mechanical properties of the obtained film. After cooling the stretched film with liquid nitrogen, split it in the length direction (MD direction) and width direction (TD direction) and take a 3,000 times scanning electron micrograph of the cross section. It was also observed that the polyamide (B-1) was dispersed in the shape of an ellipsoidal sphere having a 0.5-1 μm order and a major axis / minor axis ratio of 1.0-1.5.

(Comparative Example 3) Under the same conditions as in Example 3, using pellets of PET (A-1) and pellets of polyamide (B-2) whose main component is polyhexamethylene adipamide having Tg of 65 ° C. When the experiment was conducted, SRa of the obtained stretched film was 0.002 μm, SR
z was 0.060 μm. Further, when the cross section of the film was observed with an electron microscope, it was shown that the polyamide (B-2) was dispersed in the form of fine lines in the length direction of the film.

[Effects of the Invention] The polyester film of the present invention has been made possible by the use of an organic synthetic resin blend, which has been considered difficult in the past, to realize a film having uniformly controlled surface roughness and improved slip properties. . It has extremely high industrial value in terms of productivity, mechanical properties, and unevenness performance.

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Claims (1)

[Claims] 1. A thermoplastic polyamide (B) having a glass transition temperature higher than that of the thermoplastic polyester (A) is dispersed in a spherical or elliptic sphere so as to occupy 0.001 to 3.0% by weight. A film composed of the composition, or a film in which the composition is laminated so as to form a surface layer, wherein the center surface average roughness and ten-point average roughness of the film surface are each 0.003 to 0.07 μm.
and a polyester film having a thickness of 0.03 to 1.5 μm.