KR20190078121A - Polyester film for molding and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a polyester film for molding and a method for producing the same. More specifically, the present invention relates to a polyester film for molding, which has excellent moldability and heat resistance by controlling elongation and thermal shrinkage and expansion rate after hairline processing, by using a copolymer polyester component and through the optimization of a film manufacturing process using the same. The present invention provides a polyester film for molding, which has a thermal expansion coefficient of 500 ppm/°C or less in a machine direction (MD) at an initial load of 1.2 N and a temperature region of 30-120°C, has a thermal expansion coefficient of 200 ppm/°C or less in a transverse direction (TD) at an initial load of 0.01 N and a temperature region of 120-130°C, and has an elongation at break of 50% or more in all directions of the film after hairline processing.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for molding,

The present invention relates to a polyester film for molding and a method of manufacturing the same, and more particularly, to a polyester film for molding and a method of manufacturing the polyester film, and more particularly to a polyester film for molding which is excellent in moldability and heat resistance by controlling an elongation after hairline processing, And a method for producing the same.

Recently, the importance of design is increasing in household appliances such as TVs, washing machines, refrigerators, and the like, and various methods are applied to the iron plates used in household appliances.

Conventionally, as a method of decorating an iron plate, PCM (Pre-coated Metal), which is a method of directly painting, is used. In this method, paint, pigment, resin, etc. are coated directly on a steel plate and dried, and environmental pollution caused by the use of solvent and a large amount of water are consumed in each coating process, thereby increasing the processing cost.

In recent years, VCM (Vinyl Coated Metal) method, which is a method of bonding a film designed by vapor deposition and printing to a steel plate, is in the limelight. It is advantageous in that it is eco-friendly and processing cost is low because no solvent or water is used.

Although various films such as PVC, PE, PC, and PET are used for such VCM process, polyester film is mainly used for VCM because of its excellent mechanical and chemical properties and low price.

Furthermore, in recent years, in order to increase the design value of household appliances, the shape of home appliances is becoming more complicated.

In this connection, Patent Document 1 and Patent Document 2 provide a biaxially oriented polyester film with a co-polyester component. However, in the VCM process, a 'hairline' process is required to physically scratch the surface of the film in order to give a metal feel, which causes the elongation of the film to drop sharply, which hinders formability. In addition, Curling or wrinkling of the film occurs in the laminating process with PVC or steel plate, which is caused by the thermal expansion of the film, and it is necessary to control the thermal expansion rate of the film.

Therefore, it is required to develop a film material that can satisfy the formability in the film for VCM use. In addition, since the VCM process may cause curl or wrinkle problem due to film deformation when it is laminated with PVC or steel plate, Material development is urgently needed.

Korean Patent No. 10-0757771 Korean Patent Publication No. 10-2015-0118047

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a polyester film for molding which is excellent in moldability and heat resistance and a method for producing the same.

These and other objects and advantages of the present invention will become more apparent from the following description of a preferred embodiment thereof.

The object of the present invention is to provide a thermoplastic resin composition which has an initial load of 1.2 N and a thermal expansion coefficient in a machine direction of not more than 500 ppm / (TD, Transverse Direction) is 200 ppm / DEG C or less, and the elongation at break in all directions of the film after hair line processing is 50% or more.

Here, the fracture elongation may be the elongation at break when the hairline depth is 10% or less of the maximum film thickness and MD (length) (MD) is 100 or less.

Preferably, the film has a heat shrinkage ratio of -3 to + 3% and 0 to +3% at 150 ° C in the MD and TD directions, respectively, and a melting point (Tm) measured by DSC of 230 ° C or more .

Preferably, the film has a crystallization degree deviation of not more than 30% by using an X-ray diffraction analyzer in the MD, TD, +45, and -45 directions of the film at a wavelength of 5 to 40? .

Preferably, the film has an LDH (Limit Dome Height) of 20 mm or more in an evaluation of deep drawing of a film on which a hair line has been processed.

Preferably, the polyester film is a copolyester formed from a diol component comprising terephthalic acid or an ester forming derivative thereof and ethylene glycol, wherein the diol component is selected from neopentyl glycol other than ethylene glycol, 1,4-cyclohexanedimethanol , Diethyl glycol, propanediol, and butanediol. The polyester film according to the present invention is characterized in that it is at least one selected from the group consisting of diethyl glycol, propanediol and butanediol.

Preferably, the diol component containing ethylene glycol is a mixture of ethylene glycol and neopentyl glycol, and the neopentyl glycol component is not less than 0.1 mol% and not more than 5 mol%.

Further, the above object can be achieved by a method of stretching a film in a running direction by 2 to 4 times and by 3 to 5 times in a width direction, wherein stretching in a width direction is stretched in a tenter in 3 to 6 steps, Wherein the stretching ratio of the next step to the previous stage stretching is increased by 10 to 58% within the range of the temperature of the step of 100 to 130 캜 and the final stage of the temperature of 130 to 160 캜. Lt; / RTI >

Here, the stretching in the width direction in the tenter is performed in three steps.

Preferably, the substrate is heat-treated at 210 to 250 ° C for about 10 seconds while being soaked to 1 to 5% in the tenter.

Preferably, the difference between the stretching zone temperature of the final stage in the tenter and the initial temperature of the heat fixing zone is 50 ° C to 100 ° C.

Preferably, the film has a thermal expansion coefficient in the machine direction (MD) of 500 ppm / ° C or less in an initial load of 1.2 N, a temperature range of 30 to 120 ° C, an initial load of 0.01 N, a temperature of 120 to 130 ° C The thermal expansion coefficient of the transverse direction (TD) in the region is 200 ppm / ° C or less, and the elongation at break in the film longitudinal direction after the hairline processing is 50% or more.

Preferably, the film has a heat shrinkage ratio of -3 to + 3% and 0 to +3% at 150 ° C in the MD and TD directions, respectively, and a melting point (Tm) measured by DSC of 230 ° C or more .

Preferably, the film has a crystallization degree deviation of not more than 30% by using an X-ray diffraction analyzer in the MD, TD, +45, and -45 directions of the film at a wavelength of 5 to 40? .

Preferably, the film has an LDH (Limit Dome Height) of 20 mm or more in an evaluation of deep drawing of a film on which a hair line has been processed.

Preferably, the film is a copolymerized polyester formed from a terephthalic acid or its ester-forming derivative and a diol component comprising ethylene glycol, wherein the diol component comprising ethylene glycol is a mixture of ethylene glycol and neopentyl glycol, And the content of pentyl glycol is 0.1 mol% or more and 5 mol% or less.

According to the present invention, it is possible to provide a polyester film for molding which is excellent in moldability and heat resistance by adjusting the thermal property of the polyester film and the elongation after fracture of the hairline.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

Hereinafter, the present invention will be described in detail with reference to examples of the present invention. It will be apparent to those skilled in the art that these embodiments are provided by way of illustration only for the purpose of more particularly illustrating the present invention and that the scope of the present invention is not limited by these embodiments .

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Also, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

In describing and / or claiming the present invention, the term "copolymer" is used to refer to a polymer formed by copolymerization of two or more monomers. Such copolymers include binary copolymers, terpolymers, or higher order copolymers.

According to the present invention, there is provided a polyester film for molding which is excellent in moldability and heat resistance at the same time by controlling the breaking elongation after hairline processing and the thermal expansion coefficient, shrinkage and melting point of the film by adding a copolymerization component and optimizing the production conditions.

The polyester film for molding according to one embodiment of the present invention is a polyester film having a thermal expansion coefficient in the longitudinal direction (MD, Machine Direction) of 500 ppm / 占 폚 or less at an initial load of 1.2 N and a temperature range of 30 to 120 占 폚, The thermal expansion coefficient in the transverse direction (TD) is 200 ppm / ° C or less in the initial temperature range of 0.01 N and 120 to 130 ° C, and the elongation at break in the film longitudinal direction after hair line processing is 50% or more .

More preferably, the fracture elongation is a fracture elongation at the time when the hairline depth is 10% or less of the maximum film thickness and the length (MD) is 100 pieces / cm or less.

The laminating process of the polyester film and the PVC film is carried out at about 120 ° C. In this case, the tensile force is applied to the polyester film in the MD direction. When the expansion rate is high, the film is subjected to heat wrinkling or curling . Further, the lapping process between the polyester film and the steel plate is performed at about 230 DEG C, at which time film distortion may occur due to heat shrinkage due to heat shrinkage or expansion in the TD direction and a low melting point of the film. The polyester film for molding according to the present invention can solve all of these problems.

The polyester film for molding according to the present invention satisfies the requirement that the elongation at break in the forward direction of the film (360 ° all directions including MD and TD) is 50% or more after hairline processing, .

That is, the polyester film exhibits anisotropy depending on the position of the product, which causes a deviation in the elongation according to the direction, and the elongation is also lowered by the hairline processing. Therefore, in the VCM film, it is important to prevent the film from breaking By satisfying the above-described elongation at break, a polyester film for molding having excellent moldability can be provided.

To this end, the polyester film for molding according to the present invention can improve the elongation at break of the film through various copolymerization reforming such as neopentyl glycol, 1,4-cyclohexane dimethanol, diethyl glycol, propanediol and butanediol. When the polyester film is copolymerized and modified, the degree of crystallinity can be lowered, thereby increasing the flexibility of the film and improving the moldability. Further, by optimizing the conditions of the stretching zone and the heat-setting zone under film production conditions, it is possible to provide a polyester film excellent in moldability and heat resistance.

The polyester film for molding according to the present invention has a heat shrinkage ratio of -3 to + 3% and 0 to +3% at 150 ° C in the MD and TD directions, and a melting point (Tm) measured by DSC of 230 Lt; / RTI >

Further, the polyester film for molding according to the present invention has a crystallization degree deviation of 30 (nm) by using an X-ray diffraction analyzer in the MD, TD, +45, %, And the LDH (Limit Dome Height) in the deep drawing evaluation of the hair-line-processed film may be 20 mm or more.

The polyester film for molding according to the present invention is a copolymer polyester formed from a terephthalic acid or an ester-forming derivative thereof and a diol component containing ethylene glycol, and the diol component is selected from neopentyl glycol other than ethylene glycol, 1,4-cyclohexane Dimethanol, diethyl glycol, propanediol, and butanediol.

Preferably, the diol component containing ethylene glycol is a mixture of ethylene glycol and neopentyl glycol, and the neopentyl glycol component may be not less than 0.1 mol% and not more than 5 mol%. When the content of the diethylene glycol-containing diol component is less than 0.1 mol%, the effect of fracture elongation due to the copolymerization modification is insufficient. When the content of the diethylene glycol component exceeds 5 mol%, the degree of crystallization is lowered and the CTE value and the heat shrinkage value Which causes heat wrinkles or curl problems when PVC and steel sheets are laminated.

The method for producing a polyester film for molding according to another embodiment of the present invention is characterized in that the stretching in the transverse direction is carried out at a stretching speed of 3 to 5 times in the width direction, And stretching was carried out in six steps. The stretching in each step was carried out by increasing the stretching magnifications of the next step for the previous step by 10 to 58% within the range of the initial stage temperature of 100 to 130 캜 and the final stage of 130 to 160 캜 .

The polyester film produces a polyester resin obtained by polycondensation reaction of a terephthalic acid or ester-forming derivative and a diol component or copolymer including ethylene glycol in the presence of a catalyst and a heat stabilizer. According to the present invention, in addition to ethylene glycol, the neopentylol component is preferably contained in an amount of 0.1 mol% or more and 5 mol% or less.

In order to prepare the resin, first, a diol component containing terephthalic acid or its ester-forming derivative and ethylene glycol is heated to a temperature of 260 to 300 ° C to form bishydroxyethylene terephthalate or its oligomer, Step reaction and subsequent reaction of bishydroxyethylene terephthalate or its oligomer with at least one catalyst selected from among antimony compounds, titanium compounds and germanium compounds and various additives such as phosphoric acid-based heat stabilizers and silica particles dispersed in ethylene glycol And a second stage reaction for producing a liquid PET having a predetermined viscosity by a satisfactory polycondensation reaction at a temperature of generally 280 to 310 ° C.

As the polycondensation catalyst to be used in the present invention, a glycol-soluble antimony compound such as antimony oxide, antimony acetate or the like is suitable, and its content is suitably 150 to 350 ppm with respect to the resin.

If the addition amount of the polycondensation catalyst is less than 150 ppm, the polymerization time is prolonged and the rate of IV increase is remarkably decreased. Thus, it is difficult to obtain a polymer having a desired molecular weight. To overcome this problem, the polycondensation temperature must be maintained at a high temperature. And haze is improved in the production of the film. However, the coefficient of friction between the film and the roll at the time of producing the film is lowered, which deteriorates the running property of the film, which is not preferable. If the addition amount of the catalyst is more than 350 ppm, the polycondensation reaction time is shortened but the molecular weight is not uniform, and there is a closed end to obtain a colored polymer, and haze is deteriorated during the preparation of the film and coarse particles are formed not.

The heat stabilizer used in the present invention includes phosphorus compounds such as trimethyl phosphate, triethyl phosphonoacetate, phosphoric acid and the like, and the content thereof is preferably 100 to 300 ppm based on the resin. If the addition amount of the heat stabilizer is less than 100 ppm, the product due to the side reaction is increased to color the polymer and deteriorate the heat resistance. On the other hand, when the amount exceeds 300 ppm, the polycondensation reaction is delayed, And shorten the LIP cleaning cycle in the life recycling and film production process of the polymer filter.

Further, in order to secure the running property of the film, it is preferable that the content of the particles is 2 to 20 wt% based on the weight of the polyester resin. When the content of the particles is less than 2 wt%, it is difficult to exhibit sufficient matt characteristics and at the same time, it is difficult to secure film running properties. On the other hand, when the content of the particles exceeds 20 wt%, the surface of the film becomes very rough, so that it is difficult to secure the appearance of the molded article, and film breakage due to the particles may occur during stretching of the film.

In addition, the average diameter of the particles is preferably 1 to 10 mu m. When the average diameter of the particles is less than 1 mu m, the particles easily aggregate and it is difficult to obtain uniform particles and it is difficult to secure the running property of the film. On the other hand, when the average diameter of the particles exceeds 10 탆, the surface roughness of the film becomes large, and it is difficult to secure the appearance of the molded article.

The thus-produced polyester resin was vacuum-dried, melted by a compressor, extruded into a sheet through a T-die (DIE), adhered to a casting drum by electrostatic application (pinning) A polyester film is obtained, and uniaxial stretching of 2 to 4 times by a difference in peripheral speed between a roll and a roll is performed on a roll heated to a temperature not lower than the glass transition temperature of the polyester resin.

Thereafter, the uniaxially stretched polyester film is re-stretched to produce a biaxially stretched polyester film. At this time, the stretching is performed in the direction perpendicular to the uniaxial stretching direction, and the preferred stretching ratio is 3 to 5 times. Such stretching in the width direction may be performed in three to six steps, and will be described with reference to three steps in this specification.

In this case, the stretching temperature is preferably 100 to 130 ° C in the initial stage of the stretching zone, and 130 to 160 ° C in the final stage based on the tenter, and the stretching magnification of the next step for the previous stretching is preferably 10 to 58%.

This is because in the initial stage of the tenter, the force is concentrated at the central portion of the film to cause the stretching first, and at the end of the tenter, the stretching of the edge portion of the film occurs largely. By increasing the temperature and stretching width at the final stage of stretching, So that the elongation at break can be improved. When the temperature at the final stage is lower than 130 占 폚, the elongation at break of the edge portion of the film is not increased. When the temperature is higher than 160 占 폚, the film thickness controllability is inferior.

If the increase in the stretching width is less than 10%, the stretching magnification of the film edge lowers at the end of the tenter and the breaking elongation becomes low. If the stretching width exceeds 58%, it is difficult to realize the tenter structure. And the draw ratio at the end becomes too high, so that the posterior control property deteriorates and the risk of breakage increases.

The method for producing a polyester film for molding according to the present invention may be a heat treatment in a tenter at 210 to 250 ° C. for about 10 seconds while the polyester film is toe-in at 1 to 5%.

It is also preferable that the difference between the stretching zone temperature of the final stage in the tenter and the initial temperature of the heat fixing zone is 50 占 폚 to 100 占 폚. If the temperature difference is less than 50 캜, sufficient crystallization can not be performed in the heat-setting zone and the thermal expansion rate increases. If the temperature difference exceeds 100 캜, the temperature of the heat-setting zone is high, The thermal expansion rate is increased.

The thickness of the biaxially stretched polyester film produced by the method for producing a polyester film for molding according to the present invention is 5 to 300 탆, preferably 10 to 250 탆.

Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. However, this embodiment is intended to explain the present invention more specifically, and the scope of the present invention is not limited to these embodiments.

[Example 1]

100 mol% of terephthalic acid and a diol component containing 97 mol% of ethylene glycol and 3 mol% of neopentyl glycol as a diol component containing ethylene glycol were heated to 270 DEG C to prepare bis-hydroxyethylene terephthalate or its oligomer And the resultant bishydroxyethylene terephthalate or its oligomer is reacted with the antimony compound catalyst and the heat stabilizer at 290 占 폚 in the presence of silica particles dispersed in trimethyl phosphate and ethylene glycol at a constant viscosity To produce a liquid phase PET.

The chips were sufficiently dried at 160 ° C. for 7 hours using a vacuum drier, melted by an extruder, and adhered to the cooling drum through a feed block and a tie rod by electrostatic application to form an amorphous unstretched polyester sheet. The film was stretched 3.0 times in the film advancing direction at 95 캜 by heating, then stretched 4.0 times in the direction perpendicular to the film advancing direction while heating at 110 캜, 125 캜 and 140 캜 in three stretching zones, (Stretching magnification = (rear stage tenter width - front stage tenter width) / back stage tenter width * 100) is 17%, 33%, and 55%. Then, the film was heat-treated for 10 seconds at 210 ° C (initial) to 240 ° C (final) with 3% Toe-in to prepare a film. At this time, the thickness of the final film was set to 30 μm, thereby finally producing a polyester film.

Here, the stretching magnifications of the respective zones in Example 1 were (1200-1000) / 1200 * 100 = 16.6%, (1800-1200) / 1800 * 100 = 33.3% and (4000-1800) / 4000 * And the decimal point was rounded off. The stretching zone width, elongation zone temperature and heat fixing zone temperature for three stretched zones are shown in Table 1, respectively. The same applies hereinafter.

[Example 2]

A polyester film was produced in the same manner as in Example 1, except that the three stretching zones were heated at 100 캜, 115 캜 and 130 캜, respectively.

[Example 3]

A polyester film was produced in the same manner as in Example 1, except that it was heated at 130 ° C, 145 ° C and 160 ° C in three stretching zones.

[Example 4]

A polyester film was produced in the same manner as in Example 1, except that stretching magnifications of the respective zones in the three stretching zones were 29%, 33%, and 48%, respectively.

[Example 5]

A polyester film was produced in the same manner as in Example 1 except that stretching magnifications of the respective zones in the three stretching zones were 29%, 38%, and 44%, respectively.

[Example 6]

A polyester film was produced in the same manner as in Example 1, except that the stretching magnifications of the respective zones in the stretched three zones were elongated to 17%, 28%, and 58%, respectively.

[Example 7]

A polyester film was produced in the same manner as in Example 1, except that the heat treatment temperature in the tenter was changed from 190 캜 (initial) to 240 캜 (final).

 [Comparative Example 1]

A polyester film was produced in the same manner as in Example 1, except that it was heated at 90 ° C, 105 ° C and 120 ° C in three stretching zones.

[Comparative Example 2]

A polyester film was produced in the same manner as in Example 1, except that it was heated at 140 占 폚, 155 占 폚 and 170 占 폚 in three stretching zones.

[Comparative Example 3]

A polyester film was produced in the same manner as in Example 1 except that the stretching ratio in each zone was elongated to 50%, 33%, and 25% in three stretching zones.

[Comparative Example 4]

A polyester film was produced in the same manner as in Example 1 except that the stretching ratio in each zone was elongated to 60%, 29%, and 13% in three stretching zones.

[Comparative Example 5]

A polyester film was produced in the same manner as in Example 1, except that the stretching magnifications of the respective zones were elongated to 17%, 20%, and 63% in three elongation zones.

[Comparative Example 6]

A polyester film was produced in the same manner as in Example 1, except that the heat treatment temperature in the tenter was changed from 180 캜 (initial) to 240 캜 (final).

[Comparative Example 7]

A polyester film was produced in the same manner as in Example 1, except that the heat treatment temperature in the tenter was changed from 245 캜 (initial) to 250 캜 (final).

[Comparative Example 8]

A polyester film was produced in the same manner as in Example 1, except that 20 mol% of neopentyl glycol and 80 mol% of ethylene glycol were used in the production of the resin.

The properties of the polyester films for molding according to Examples 1 to 7 and Comparative Examples 1 to 8 were measured through the following experimental examples and the results are shown in Table 2 below.

[Experimental Example]

1. Rupture elongation

The film was transferred to an A4 size film with # 2,000 sandpaper under a load of 2 kg, and the surface was subjected to hairline processing. The film was then cut into a width of 12.65 mm in the direction to be measured, and then subjected to tensile strength Ltd., model SSTM-5KN) was used to measure the elongation at break. The elongation at break shown in Table 2 was the elongation in all the directions of the film, and showed the lowest value of the elongation at break in the film full width (total width of the film wound in the tenter). Here, the film forward direction means 360 占 forward direction including MD and TD directions.

2. Moldability

The film was transferred to an A4 size film with a load of 2KG with # 1000 sandpaper, and the surface was hairline processed. The film was cut into 90 × 90 mm, and the height of the tip was increased to 30 mm through Ericsson equipment. And evaluated by the following criteria.

○: No burst, crack, or cloudiness of the film

X: Any one of film break, crack, and cloudiness

3. Heat resistance

(1) Heat resistance of PVC joint

The acrylic urethane resin composition was coated on one side of the polyester film using a gravure coater to a thickness of 1 탆 and passed through a drying oven at 120 캜 for about 1 minute, followed by laminating with a PVC film having a thickness of 90 탆. At this time, a tensile force of about 10 to 30 kgf was applied to the polyester film in the MD direction. The appearance of the final laminated sheet was checked and evaluated according to the following criteria.

○: No wrinkles or curls on sheet

X: Wrinkles or curls on sheet

(2) Heat resistance of iron plate joint

An adhesive (BN-4000) was applied on the steel plate to a thickness of about 5 탆, heated to 240 캜, and after laminating, the film state was checked and evaluated according to the following criteria.

○: No deformation or wrinkle of film

X: Film distortion or wrinkling

The heat resistance test showed the same results in all Examples and Comparative Examples (1) heat resistance at the time of PVC lamination and (2) heat resistance at the time of lamination.

4. Crystallinity deviation

The crystallinity of the film MD and TD in the range of 5 to 40 [theta] in the direction of left and right 45 degrees was measured through an X-ray diffractometer (Rigaku, D / Max-2500) The deviation was calculated. The crystallization degree deviation shown in Table 2 is a value obtained by measuring the position where the elongation at break is lowest.

Crystallinity Deviation = (Peak - Peak) / Peak * 100

Maximum Peak: MD, TD, maximum crystallinity in 45 ° left and right direction

Minimum Peak: MD, TD, Minimum Crystallinity in 45 ° Direction

5. Thermal Expansion Coefficient (CTE)

The samples in the MD and TD directions were subjected to dynamic mechanical analysis (DMA, Hitachi, Japan) at an initial load of 1.2 N and 30 to 120 ° C, and samples in the TD direction at an initial load of 0.01 N and 120 to 130 ° C, DMA-7000), and the thermal expansion coefficient was calculated using the following equation.

Thermal expansion coefficient (ppm / 占 폚) = film length change (占 퐉) / temperature change amount (占 폚)

6. Heat shrinkage

The film was cut into a size of 10 * 10 cm, and then stored in an oven at 150 ° C for 30 minutes. Then, a change in length before and after being placed in an oven was calculated using the following equation.

Heat shrinkage rate = (length before oven-length after oven) / length before oven * 100

7. DSC

The DSC was measured using a differential scanning calorimeter (DSC, Hitachi, DSC-7020) and the melting temperature was confirmed.

8. Film thickness variation

The thickness was measured using a film thickness meter (Hilldebrand Gmbh, Model: 219081) in the entire width of the product (TD direction / direction perpendicular to the running direction), and the thickness range value was calculated using the following equation.

Thickness Range = Thickness Max - Thickness Min

9. Limit Dome Heigh

The height (LDH) at which the hairline processed film was blown out was measured in a circular deep drawing (punch diameter 50 cm) mode using a sheet material testing machine (RB316FT, R & B).

Note 1) The width of the zone just before the stretching zone is 1000mm

(Note 1) The breaking elongation is the lowest breaking elongation value in the full width of the film (total width of the film wound in the tenter)

(Note 2) The crystallinity deviation is the value obtained by measuring the position where the elongation at break is lowest

As can be seen from Table 2, when the stretching zone temperature of the polyester film, the stretch ratio of each stretching zone, and the heat fixing temperature were both within the range of Examples, it was found that both the moldability and the heat resistance were satisfied.

However, in Comparative Example 1, it was confirmed that orientation crystallization was increased due to a low elongation zone temperature, resulting in a decrease in elongation at break. In Comparative Example 2, the elongation zone temperature was high and the moldability was good, Wrinkles occurred during processing.

Further, in Comparative Examples 3 and 4, the elongation was made early in the stretching zone and the stretching magnification was decreased at the end of the stretching zone. As a result, in the stretching zone end, sufficient heat quantity was not received at the edge portion in the film full width, . On the contrary, in Comparative Example 5, due to excessive stretching in the final stretching zone, the moldability and heat resistance are good, but the film thickness can not be controlled.

In Comparative Example 6, the thermal fixation temperature was low and the crystallinity of the film was lowered to increase the thermal expansion coefficient, resulting in poor heat resistance. On the contrary, in Comparative Example 7, since the heat fixing temperature was too high, orientation crystallization was reversely reversed, so that the degree of crystallization was lowered and the coefficient of thermal expansion was increased.

Finally, in Comparative Example 8, it was confirmed that the content of neopentyl glycol was too high to lower the Tm, resulting in film deformation during lamination of the steel sheet, increased amorphousness, and a high coefficient of thermal expansion, resulting in poor heat resistance.

As described above, according to the present invention, by optimizing the copolymerization content and the production conditions of the polyester film, it is possible to control the breaking elongation and thermal properties after hairline processing, thereby providing a polyester film excellent in moldability and heat resistance can do.

It is to be understood that the present invention is not limited to the above embodiments and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims (16)

As a polyester film,
(MD, Machine Direction) is 500ppm / ° C or less in the initial temperature range of 1.2N and 30 to 120 ° C and the initial load is 0.01N and the temperature range is 120 to 130 ° C. Direction) has a thermal expansion coefficient of 200 ppm / ° C or less,
Wherein the elongation at break in all directions of the film after hairline processing is 50% or more. Wherein the breaking elongation is a breaking elongation at the time when the depth of the hairline is 10% or less of the maximum film thickness and the length (MD) is 100 or less of the bow. The method according to claim 1,
The film had heat shrinkage rates of -3 to +3% and 0 to +3% at 150 DEG C in the MD and TD directions, respectively,
And a melting point (Tm) measured by DSC is 230 占 폚 or higher. The method according to claim 1,
Wherein the film has a crystallization degree deviation of 30% or less by using an X-ray diffraction analyzer in the MD, TD, +45, and -45 directions of the film at 5 to 40? Wavelength band. Polyester film. The method according to claim 1,
Wherein the film has a LDH (Limit Dome Height) of 20 mm or more in a deep drawing evaluation of a film on which a hairline has been processed. 6. The method according to any one of claims 1 to 5,
Wherein the polyester film is a copolymerized polyester formed from a terephthalic acid or an ester-forming derivative thereof and a diol component comprising ethylene glycol, wherein the diol component is selected from neopentyl glycol other than ethylene glycol, 1,4-cyclohexanedimethanol, diethylglycol , Propanediol, and butanediol. The polyester film for molding according to claim 1, wherein the polyester film is a polyester film. The method according to claim 6,
Wherein the diol component comprising ethylene glycol is a mixture of ethylene glycol and neopentyl glycol, and the neopentyl glycol component is not less than 0.1 mol% and not more than 5 mol%. A method for producing a polyester film for molding,
Stretching 2 to 4 times in the running direction of the film and 3 to 5 times in the width direction,
The stretching in the transverse direction is carried out in the tenter in 3 to 6 stages and the stretching in each stage is carried out in the initial stage of 100 to 130 캜 and in the final stage of 130 to 160 캜 at the stretching magnification By 10 to 58%, respectively, based on the total weight of the polyester film. 9. The method of claim 8,
Wherein the stretching in the transverse direction in the tenter is performed in three steps. 9. The method of claim 8,
Treated at 210 to 250 ° C for about 10 seconds while being soaked in the tenter at a rate of 1 to 5%. 9. The method of claim 8,
Wherein the difference between the stretching zone temperature of the final stage in the tenter and the initial temperature of the heat fixing zone is 50 占 폚 to 100 占 폚. 11. The method according to any one of claims 8 to 10,
The film had a thermal expansion coefficient of 500 ppm / ° C or less in the longitudinal direction (MD, Machine Direction) at an initial load of 1.2 N and a temperature range of 30 to 120 ° C, and an initial load of 0.01 N at a temperature range of 120 to 130 ° C. (TD), the thermal expansion coefficient of the transverse direction (TD) is 200ppm / ° C or less, and the film line length when the hairline is processed in the longitudinal direction (MD) at a hairline depth of 10% Wherein the elongation at break of the polyester film is 50% or more. 11. The method according to any one of claims 8 to 10,
Wherein said film has a heat shrinkage ratio of -3 to + 3% and 0 to +3% at 150 DEG C in MD and TD directions, respectively, and a melting point (Tm) measured by DSC is 230 DEG C or more. Wherein the polyester film is a polyester film. 11. The method according to any one of claims 8 to 10,
Wherein the film has a crystallization degree deviation of 30% or less by using an X-ray diffraction analyzer in the MD, TD, +45, and -45 directions of the film at 5 to 40? Wavelength band. Wherein the polyester film is a polyester film. 11. The method according to any one of claims 8 to 10,
Wherein the film has an LDH (Limit Dome Height) of 20 mm or more in a deep drawing evaluation of a film on which a hair line has been processed. 11. The method according to any one of claims 8 to 10,
The film is a co-polyester formed from a diol component comprising terephthalic acid or an ester-forming derivative thereof and ethylene glycol,
Wherein the diol component comprising ethylene glycol is a mixture of ethylene glycol and neopentyl glycol, and the neopentyl glycol component is not less than 0.1 mol% and not more than 5 mol%.