阅读说明：本技术 用于压延的聚酯树脂组合物及制备聚酯膜的方法 (Polyester resin composition for calendering and method for producing polyester film ) 是由 卢一镐 吴美玉 李得永 崔常勋 于 2018-12-27 设计创作，主要内容包括：根据一个实施方案的用于压延的聚酯树脂组合物包括具有热性能可调的润滑剂,因此可以增强压延加工性并且抑制残留组分导致的最终膜的物理性能劣化。另外,使用用于压延的聚酯树脂组合物制备的聚酯膜环保并且具有优异的耐热性和表面强度,因此可以用于各种环保材料,例如装饰片材。(The polyester resin composition for calendering according to an embodiment includes a lubricant having adjustable thermal properties, and thus it is possible to enhance calendering workability and suppress deterioration of physical properties of a final film due to residual components. In addition, the polyester film prepared using the polyester resin composition for calendering is environmentally friendly and has excellent heat resistance and surface strength, and thus can be used for various environmentally friendly materials such as decorative sheets.)

1. A polyester resin composition for calendering, comprising a polyester resin obtained by polymerization of a dicarboxylic acid component and a diol component, and 0.1 to 10 parts by weight of a lubricant, based on 100 parts by weight of the polyester resin;

wherein the lubricant has a weight loss ratio of 1 to 20% from its initial weight at 150 ℃ for 100 minutes and a weight loss ratio of 20 to 65% from its initial weight at 200 ℃ for 100 minutes.

2. The polyester resin composition for calendering of claim 1, wherein the lubricant has a weight reduction rate of 2 to 15% with respect to its initial weight at 150 ℃ for 100 minutes and a weight reduction rate of 25 to 65% with respect to its initial weight at 200 ℃ for 100 minutes.

3. The polyester resin composition for calendering of claim 1, wherein the lubricant is heated from 30 ℃ to 350 ℃ at a rate of 20 ℃/min at a weight reduction rate of 30 to 70% with respect to its initial weight.

4. The polyester resin composition for calendering of claim 1, wherein the content of the lubricant is 0.1 to 5 parts by weight based on 100 parts by weight of the polyester resin.

5. The polyester resin composition for calendering of claim 1, wherein the lubricant comprises a combination of a first lubricant and a second lubricant, the weight ratio of the first lubricant to the second lubricant being 1: 2 to 2: 1.

6. the polyester resin composition for calendering of claim 5, wherein the first lubricant has a weight reduction rate of 1 to 12% with respect to its initial weight at 150 ℃ for 100 minutes, and the second lubricant has a weight reduction rate of 10 to 25% with respect to its initial weight at 150 ℃ for 100 minutes.

7. The polyester resin composition for calendering of claim 6, wherein the first lubricant has a weight reduction rate of 20 to 45% with respect to its initial weight at 200 ℃ for 100 minutes, and the second lubricant has a weight reduction rate of 40 to 80% with respect to its initial weight at 200 ℃ for 100 minutes.

8. The polyester resin composition for calendering of claim 1, wherein the dicarboxylic acid component comprises terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, or a combination thereof; the glycol component includes ethylene glycol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, or combinations thereof.

9. The polyester resin composition for calendering of claim 8, wherein the glycol component comprises 30 to 90 mole% of at least one of neopentyl glycol and cyclohexanedimethanol.

10. The polyester resin composition for calendering of claim 1, wherein the Intrinsic Viscosity (IV) of the polyester resin is 0.6 to 1.0 dl/g.

11. A method of making a polyester film comprising:

(1) adding a lubricant to a polyester resin to prepare a polyester resin composition;

(2) kneading the composition to gelatinize it; and

(3) calendering the gelled composition to form a film;

wherein the polyester resin is obtained by polymerization of a dicarboxylic acid component and a diol component; the lubricant is used in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the polyester resin; the lubricant has a weight loss ratio of 1 to 20% from its initial weight at 150 ℃ for 100 minutes and a weight loss ratio of 20 to 65% from its initial weight at 200 ℃ for 100 minutes.

12. The method of producing the polyester film according to claim 11, wherein the lubricant is heated from 30 ℃ to 350 ℃ at a rate of 20 ℃/min at a weight loss rate of 30 to 70% relative to its initial weight.

13. The method of manufacturing the polyester film according to claim 12, wherein the lubricant comprises at least one of fatty acid, fatty acid salt, metal salt of organic acid, fatty acid ester, amide, hydrocarbon wax, ester wax, phosphate ester, polyolefin wax, modified polyolefin wax, talc, and acrylic copolymer.

14. The method of producing the polyester film of claim 13, wherein the lubricant comprises a combination of a first lubricant and a second lubricant; the weight ratio of the first lubricant to the second lubricant is 1: 2 to 2: 1; the first lubricant has a weight reduction ratio of 1 to 12% relative to its initial weight when kept at 150 ℃ for 100 minutes, and the second lubricant has a weight reduction ratio of 10 to 25% relative to its initial weight when kept at 150 ℃ for 100 minutes.

15. The method of preparing a polyester film according to claim 11, wherein the dicarboxylic acid component comprises terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, or a combination thereof;

the glycol component comprises ethylene glycol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, or combinations thereof;

the diol component includes 30 to 90 mole percent of at least one of neopentyl glycol and cyclohexanedimethanol.

Technical Field

The following embodiments relate to a polyester resin composition applied to a calendering process and a method of preparing a polyester film therefrom. More particularly, embodiments relate to a polyester resin composition mixed with additives to improve calendering processability, and a method of preparing a polyester film used as an environmentally friendly material therefrom.

Background

The calendering process is a process of molding a film, a sheet, or the like using a calender, i.e., a rolling mill provided with a plurality of heating rollers. The calendering process is mainly used for preparing films, sheets, and the like because the calendering process is faster in production speed and can be more conveniently processed to a thinner thickness than a die casting process.

Polyvinyl chloride (PVC) resins, which have been conventionally used in calendering processes, have excellent processability, but are neither easily recycled nor environmentally friendly after treatment. In addition, although polypropylene (PP) resins are excellent in calendering processability, they are not environmentally friendly and have problems in printing and lamination without corona and primer treatment.

Meanwhile, as a representative polyester resin, a polyethylene terephthalate (PET) resin is inexpensive and inexpensive, but is poor in calendering processability. Therefore, it is known to prepare a polyester film from a polyethylene terephthalate glycol (PETG) resin modified with ethylene glycol to impart properties suitable for a calendering process thereto (see korean patent publication No. 2014-0109506).

Disclosure of Invention

Technical problem

In order to apply the polyester resin to the calendering process, it is known to prevent the polyester resin from adhering to a metal roll and to improve its fluidity at high temperature by blending additives in addition to further introducing a diol component such as 1, 4-cyclohexanedimethanol.

However, although such additives increase processability during the calendering process, they remain upon completion of the calendering process, thereby degrading the physical properties of the final film or sheet.

The research result of the inventor finds that: if the thermal properties of the additive for increasing the calendering processability are adjusted, the calendering processability can be improved by the additive and the decrease in the physical properties of the final film can be suppressed.

Accordingly, the following embodiments are directed to providing a polyester resin composition mixed with an additive that enhances material processability in a calendering process and does not impair physical properties of a final product.

In addition, the following embodiments are directed to providing a method of preparing a polyester film that is environmentally friendly and has excellent physical properties from a polyester resin composition at a relatively low cost.

Solution to the problem

According to an embodiment for achieving the above object, there is provided a polyester resin composition for calendering, which comprises a polyester resin obtained by polymerization of a dicarboxylic acid component and a diol component, and 0.1 to 10 parts by weight of a lubricant, based on 100 parts by weight of the polyester resin; wherein the lubricant has a weight loss ratio of 1 to 20% from its initial weight at 150 ℃ for 100 minutes and a weight loss ratio of 20 to 65% from its initial weight at 200 ℃ for 100 minutes.

According to another embodiment, there is provided a method of preparing a polyester film, including: (1) adding a lubricant to a polyester resin to prepare a polyester resin composition; (2) kneading the composition to gelatinize it; (3) calendering the gelled composition to form a film; wherein the polyester resin is obtained by polymerization of a dicarboxylic acid component and a diol component; the lubricant is used in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the polyester resin; the lubricant has a weight loss ratio of 1 to 20% from its initial weight at 150 ℃ for 100 minutes and a weight loss ratio of 20 to 65% from its initial weight at 200 ℃ for 100 minutes.

The invention has the advantages of

Since the polyester resin composition for calendering of the present embodiment includes the lubricant whose thermal properties are controlled, the calendering processability can be improved, and the decrease in physical properties of the final film caused by the residual component can be suppressed.

In particular, the lubricant has a specific weight reduction ratio range with respect to the temperature conditions applied to the calendering process. Therefore, the composition has appropriate adhesion and mold release properties to a metal roll, as well as plasticity and high-temperature fluidity, in a calendering process, and a lubricant does not unnecessarily remain in the calendering process, and thus physical properties of the polyester film, such as heat resistance and surface strength, are not impaired.

Accordingly, the polyester resin composition according to the embodiment may be applied to a calendering process to provide a polyester film having excellent physical properties at a relatively low cost.

In addition, the polyester film thus prepared is environmentally friendly and has excellent heat resistance and surface strength, and thus it can be used as various environmentally friendly materials, such as decorative sheets.

Best Mode for Carrying Out The Invention

The following embodiments provide a polyester resin composition for calendering and a method of preparing a polyester film therefrom.

The following embodiments may be modified into various forms as long as the gist of the present invention is not changed.

Throughout the description of the embodiments, the term "comprising" means that other elements may be included, unless otherwise specified.

Throughout the specification, the terms first, second, etc. are used to describe various components. But the composition should not be limited by the terminology. The term is used only to distinguish one component from another.

Polyester resin composition for calendering

According to one embodiment, the polyester resin composition for calendering includes a polyester resin and a lubricant.

According to one embodiment, the polyester resin composition for calendering includes a lubricant that is eluted (or decomposed) at a processing temperature when the resin passes through a heated roll, thereby improving processability.

Specifically, the lubricant can improve the melt fluidity of the resin inside the resin, and can prevent adhesion to devices outside the resin, such as rollers used in the process.

Therefore, the lubricant functions to impart moldability and high-temperature fluidity to the polyester resin composition and appropriate adhesion to and releasability from a metal roll in a calendering process.

In this case, if the amount of the lubricant eluted at the processing temperature is too small, the molding process cannot be smoothly performed due to adhesion of the resin, and the resin will remain on the roll for a long time, causing a problem of thermal degradation.

On the other hand, if the amount of the lubricant eluted at the processing temperature is too large, the lubricant is consumed before the entire process is completed, so that the lubricant is insufficient at the final stage of the process, resulting in breakage due to a decrease in releasability from the roller; bubbles are generated due to excessive elution of the lubricant at the temperature-increasing stage, resulting in poor surface appearance of the product.

Typically, in a calendering process, the chips are gelled and then fed into the processing rolls at a temperature above the glass transition temperature. Thereafter, it was subjected to warming and calendering treatment, and then quenched at room temperature and treated using an emboss roller according to the use.

In the calendering process, the lubricant should act uniformly from gelation to the final stage. For this reason, it is necessary to adjust the elution (or decomposition) amount of the lubricant in each stage according to the process temperature.

That is, in the calendering process, the thermal properties of the lubricant can be adjusted according to the temperature rather than the type and content of the lubricant to significantly improve the effectiveness of the lubricant.

According to the above embodiment, the lubricant has a specific range of the weight reduction rate depending on the temperature condition.

As an example, the lubricant has a weight loss ratio of 1 to 20% relative to its initial weight when held at 150 ℃ for 100 minutes. Specifically, the lubricant may have a weight loss rate of 2 to 15%, or 2 to 10%, relative to its initial weight, when held at 150 ℃ for 100 minutes. Within the above preferred range, it may be advantageous to improve the fluidity of the resin without melt-adhering to the surface of the processing roll.

As another example, the lubricant has a weight loss ratio of 20 to 65% relative to its initial weight when held at 200 ℃ for 100 minutes. Specifically, the lubricant may have a weight loss rate of 25 to 65%, or 35 to 65%, relative to its initial weight, when held at 200 ℃ for 100 minutes. Within the above preferred ranges, it may be advantageous to reduce friction between the sheet and the roll and release properties therefrom without carbonizing on the surface of the processing roll.

As yet another example, the lubricant may be heated from 30 ℃ to 350 ℃ at a rate of 20 ℃/min at a rate of weight loss from its initial weight of 30 to 70%. Specifically, the lubricant may be heated from 30 ℃ to 350 ℃ at a rate of 20 ℃/min at a rate of weight loss from its initial weight of 35 to 65%, or 40 to 65%. Within the above-described range of the weight reduction ratio, it is possible to contribute to releasability of the sheet and prevention of generation of bubbles.

As yet another example, the lubricant may be heated from 30 ℃ to 300 ℃ at a rate of 20 ℃/min at a rate of weight loss from its initial weight of 30 to 70%, 35 to 65%, or 40 to 65%.

The type of the lubricant is not particularly limited as long as the above thermal properties are satisfied.

Specifically, any lubricant may be used regardless of its chemical structure and type, so long as it satisfies a weight reduction rate of 1 to 20% under the condition of being maintained at 150 ℃ for 100 minutes and a weight reduction rate of 20 to 65% under the condition of being maintained at 200 ℃ for 100 minutes by isothermal thermogravimetric analysis.

In addition, in the isothermal thermogravimetric analysis, the lubricant can be used if it satisfies a weight loss rate of 30 to 70% by heating from 30 ℃ to 350 ℃ at a rate of 20 ℃/min.

The content of the lubricant is 0.1 to 10 parts by weight based on 100 parts by weight of the polyester resin.

Specifically, the lubricant may be contained in an amount of 0.1 to 5 parts by weight, 1 to 5 parts by weight, 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, 3 to 5 parts by weight, or 5 to 10 parts by weight, based on 100 parts by weight of the polyester resin, but is not limited thereto.

If the content of the lubricant is within the above range, it is possible to prevent the excessive lubricant from deteriorating physical properties while maximizing the rolling workability.

As still another example, in the case where two or more types of lubricants are used in combination, it may be more advantageous to satisfy both the fluidity inside the resin and the mold release property outside the resin.

Meanwhile, in the case where two or more types of lubricants are used in combination, the thermal properties of each lubricant are prioritized according to the process temperature.

The lubricant may consist of two or more lubricants having different thermal properties.

In particular, the lubricant may comprise a combination of a first lubricant and a second lubricant.

In this case, the weight ratio of the first lubricant to the second lubricant may be in the range of 1: 2 to 2: 1, in the above range. More specifically, the weight ratio of the first lubricant to the second lubricant may be in the range of 1: 1.6 to 1.8: 1, in the above range.

The first lubricant and the second lubricant may have different thermal properties.

For example, the first lubricant may have a weight loss ratio of 1 to 12% relative to its initial weight when held at 150 ℃ for 100 minutes, and the second lubricant may have a weight loss ratio of 10 to 25% relative to its initial weight when held at 150 ℃ for 100 minutes.

As another example, the first lubricant may have a weight loss rate of 20 to 45% relative to its initial weight when held at 200 ℃ for 100 minutes. The second lubricant may have a weight loss rate of 40 to 80% with respect to its initial weight when maintained at 200 ℃ for 100 minutes.

There is no particular limitation on the types of the first lubricant and the second lubricant as long as their combination satisfies the above-described thermal properties. In addition, the first lubricant may be in the form of a combination of two or more lubricants as long as the above thermal properties are satisfied. Also, the second lubricant may be in the form of a combination of two or more lubricants as long as the above thermal properties are satisfied.

In addition, the first lubricant and the second lubricant may perform different functions in the calendering process. Although their functions are not particularly limited, for example, the first lubricant may enhance the fluidity of the resin composition in the calendering process, and the second lubricant may enhance the releasability from the metal roll.

The polyester resin is obtained by polymerization of a dicarboxylic acid component and a diol component.

That is, the polyester resin includes a dicarboxylic acid component and a diol component as monomers.

Specifically, since the polyester resin is obtained by polymerization of a dicarboxylic acid component and a diol component, it may have repeating units derived therefrom.

The dicarboxylic acid component may include terephthalic acid (TPA), isophthalic acid (IPA), naphthalene dicarboxylic acid (NDC), cyclohexane dicarboxylic acid (CHDA), succinic acid, glutaric acid, phthalic acid, adipic acid, azelaic acid, sebacic acid (sebasic), sebacic acid sister-in-law carboxylic acid (decanodicarboxylic acid), 2, 5-furandicarboxylic acid, 2, 5-thiophthalic acid, 2, 7-naphthalenedicarboxylic acid, 4' -biphenyldicarboxylic acid, derivatives thereof, or combinations thereof.

Specifically, the dicarboxylic acid component may include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, or a combination thereof, but is not limited thereto. More specifically, the dicarboxylic acid component may include terephthalic acid and/or isophthalic acid, but is not limited thereto.

That is, the diol component may include a linear or branched aliphatic diol, a cycloaliphatic diol, an aromatic diol, and the like.

For example, the linear or branched aliphatic diol may include Ethylene Glycol (EG), diethylene glycol (DEG), neopentyl glycol, 1, 3-propanediol, 1, 2-octanediol, 1, 3-octanediol, 2, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 2-butyl-2-ethyl-1, 3-propanediol, 2-diethyl-1, 5-pentanediol, 2, 4-diethyl-1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 1-dimethyl-1, 5-pentanediol, 1, 6-hexanediol, 2-ethyl-3-methyl-1, 5-hexanediol, 2-ethyl-3-ethyl-1, 5-hexanediol, 1, 7-heptanediol, 2-ethyl-3-methyl-1, 5-heptanediol, 2-ethyl-3-ethyl-1, 6-heptanediol, 1, 8-octanediol, 1, 9-nonanediol, 1, 10-decanediol, or a combination thereof, but is not limited thereto.

In addition, the alicyclic diol may include Cyclohexanedimethanol (CHDM), isosorbide (isosorbide), 2,4, 4-tetramethyl-1, 3-Cyclobutanediol (CBDO), etc., but is not limited thereto.

Specifically, the glycol component may include ethylene glycol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, or a combination thereof, but is not limited thereto.

In the case of preparing a film or sheet by calendering a polyester resin including a linear or branched aliphatic diol, it may have excellent chemical resistance and surface strength since wrapping is good.

In the case of producing a film or sheet by calendering a polyester resin including an alicyclic diol or an aromatic diol as a diol component, since the chemical structure thereof is strongly bonded, impact resistance and heat resistance can be improved.

As one example, the diol component may include 10 to 90 mole%, 20 to 90 mole%, 30 to 90 mole%, 20 to 85 mole%, 23 to 84 mole%, or 24 to 83 mole% neopentyl glycol or cyclohexanedimethanol, based on the total moles of the diol component.

In addition, the polyester resin is obtained by polymerization of a dicarboxylic acid component, which may include an aromatic dicarboxylic acid, and a diol component, which may include (i) a branched aliphatic diol or an alicyclic diol and (ii) a linear aliphatic diol.

Specifically, the dicarboxylic acid component may include at least one of terephthalic acid and isophthalic acid, and the diol component may include (i) at least one of neopentyl glycol and cyclohexanedimethanol and (ii) ethylene glycol.

In addition to the polyester resin and the lubricant, according to one embodiment, the polyester resin composition may further include components such as a polymerization catalyst, a stabilizer, and a colorant.

The polymerization catalyst, stabilizer and colorant may be added to the product of the esterification reaction or transesterification reaction before the initiation of the polymerization reaction, and the polymerization catalyst, stabilizer and colorant may be added to the mixed slurry containing the dicarboxylic acid and the diol compound before and during the esterification reaction.

The polymerization catalyst may be antimony compounds, titanium compounds, germanium compounds, aluminum compounds or a mixture thereof. Examples of the antimony-based compound include antimony trioxide, antimony acetate, and ethylene glycol antimony. Examples of the titanium-based compound include tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, titanium dioxide, and a titanium dioxide/silica copolymer. Examples of the germanium-based compound include germanium dioxide, germanium acetate, and germanium ethylene glycol.

As the stabilizer, phosphorus compounds such as phosphoric acid, trimethyl phosphate, triethyl phosphate and the like can be used. The amount added may be 10 to 100ppm based on the weight of the phosphorus (P) element based on the weight of the final polymer. If the amount of the stabilizer added is less than 10ppm, the stabilizing effect is insignificant and the final polymer may be yellowed. If the amount of the stabilizer added exceeds 100ppm, the activity of the polymerization catalyst is inhibited, which is disadvantageous in obtaining a polymer having a high polymerization degree.

The colorant is used to enhance the color of the polymer. The colorant may include metal salt colorants such as cobalt acetate and cobalt propionate, as well as dyes-based colorants. The colorant may be added in an amount of 0 to 100ppm based on the weight of the final polymer.

The Intrinsic Viscosity (IV) of the polyester resin may be 0.6 to 3.0 dl/g. Specifically, the Intrinsic Viscosity (IV) of the polyester resin may be 0.6 to 2.5dl/g, 0.6 to 2.0dl/g, 0.6 to 1.5dl/g, 0.6 to 1.0dl/g, 0.62 to 1.5dl/g, 0.64 to 1.2dl/g, or 0.66 to 0.85dl/g, but is not limited thereto.

If the intrinsic viscosity of the polyester resin is within the above range, the calendering processability, the kinematic viscosity retention rate in the calendering process, and the thickness uniformity of the sheet or film are excellent.

Method for preparing polyester resin composition

The method for preparing the polyester resin composition comprises: (1a) mixing a dicarboxylic acid component and a diol component and carrying out an esterification reaction; (1b) carrying out polycondensation on the obtained esterification reaction product to obtain polyester resin; (1c) adding a lubricant to the polyester resin to prepare the polyester resin composition.

The dicarboxylic acid component and the diol component used in the esterification reaction in step (1a) are as described above.

Here, it is preferable to mix 1.05 to 3.0 moles, 1.05 to 2.0 moles, or 1.05 to 1.5 moles of the diol component with 1 mole of the dicarboxylic acid component. If mixed in a ratio within the above range, the esterification reaction can be stably performed, so that sufficient ester oligomer can be favorably formed.

Meanwhile, it is not preferable to use an acrylic compound as a raw material of the polyester resin because it generates a non-melted gel.

The polycondensation in step (1b) may be at a temperature of 230 to 270 ℃ and 0.1 to 3.0kg/cm²Under pressure of (c). More specifically, the polycondensation may be at a temperature of 240 to 295 ℃ and 0.2 to 2.9kg/cm²Under the pressure of (3).

The polycondensation reaction may be carried out in the presence of a polycondensation catalyst, stabilizer, colorant, dispersant, antiblocking agent, electrostatic agent, antistatic agent, antioxidant, heat stabilizer, ultraviolet blocking agent, photoinitiator, or any combination known to those skilled in the art. These additives may be used within a range not impairing the effects of the resin composition.

As an example, the polycondensation may be carried out in the presence of a polycondensation catalyst.

The polycondensation catalyst may include, but is not limited to, alkali metals, alkaline earth metals, antimony, titanium, manganese, cobalt, cerium, germanium, or any combination thereof. The polycondensation catalyst is preferably an antimony compound.

The polycondensation catalyst can be used in an amount of 50 to 1000ppm, 50 to 500ppm, or 50 to 400ppm based on the total weight of the polyester resin. If the amount of the polycondensation catalyst is within the above range, the polycondensation reaction rate is accelerated and side reactions are suppressed, so that the transparency can be advantageously improved.

As another example, the polycondensation may be conducted in the presence of a stabilizer.

The stabilizer may include a phosphorus-based stabilizer. The phosphorus-based stabilizer may include phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triethyl phosphonoacetate, hindered phenols, or any combination thereof, but is not limited thereto. The stabilizer may be used in an amount of 3000ppm or less, 1 to 2,500ppm, 1 to 1500ppm, or 1 to 1000ppm, based on the total weight of the polyester resin.

As yet another example, the polycondensation may be conducted in the presence of a colorant.

The colorant may include an organic colorant, an inorganic colorant, a dye, or a combination thereof, but is not limited thereto. Specifically, the colorant may be cobalt acetate, cobalt propionate, an inorganic colorant, or a combination thereof. The colorant may be used in an amount of 1 to 500ppm, or 1 to 200ppm, based on the total weight of the polyester resin.

Thereafter, the polyester resin and the lubricant are mixed to prepare a polyester resin composition.

In this case, the type and content of the lubricant added are as described above.

Method for producing polyester film

A method of preparing a polyester film according to one embodiment includes:

(1) adding a lubricant to a polyester resin to prepare a polyester resin composition;

(2) (ii) gelling the composition; and

(3) calendering the gelled composition to form a film.

Hereinafter, each step will be described in detail.

In step (1), a lubricant is added to a polyester resin to prepare a polyester resin composition.

The polyester resin used herein is obtained by polymerization of the dicarboxylic acid component and the diol component as described above.

Specifically, the dicarboxylic acid component may include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, or a combination thereof. The glycol component may include ethylene glycol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, or combinations thereof. Further, in this case, the diol component may include 30 to 90 mole% of at least one of neopentyl glycol and cyclohexanedimethanol.

In addition, the lubricant may be added in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the polyester resin.

As described above, the weight reduction rate of the lubricant with respect to its initial weight at 150 ℃ for 100 minutes may be 1 to 20%, and the weight reduction rate with respect to its initial weight at 200 ℃ for 100 minutes may be 20 to 65%.

In addition, the lubricant may be heated from 30 ℃ to 350 ℃ at a rate of 20 ℃/min at a weight reduction rate of 30 to 70% relative to its initial weight.

In addition, the lubricant may be heated from 350 ℃ to 500 ℃ at a rate of 20 ℃/min at a weight reduction rate of 30 to 70% relative to its initial weight.

The type of the lubricant is not particularly limited as long as the above thermal properties are satisfied.

For example, the lubricant includes at least one, more preferably, at least two, but not limited to, fatty acids, fatty acid salts, metal salts of organic acids, fatty acid esters, amides, hydrocarbon waxes, ester waxes, phosphate esters, polyolefin waxes, modified polyolefin waxes, talc, and acrylic copolymers.

Specifically, the lubricant may be selected from at least one of stearic acid, palmitic acid, montan wax, Loxiol, PE wax, paraffin wax, cetyl ester, glyceryl distearate and modified compounds thereof.

In addition, the lubricant may be composed of at least two types. For example, it may comprise a combination of a first lubricant and a second lubricant. In this case, the weight ratio of the first lubricant to the second lubricant may be in the range of 1: 2 to 2: 1, in the above range.

In addition, the first lubricant may have a weight reduction rate of 1 to 12% with respect to its initial weight when kept at 150 ℃ for 100 minutes, and the second lubricant may have a weight reduction rate of 10 to 25% with respect to its initial weight when kept at 150 ℃ for 100 minutes.

The polyester resin and the additive may be mixed using a high speed mixer, such as a henschel mixer. For example, the polyester resin composition may be pelletized, and the pelletized polyester resin composition may be put into a high-speed mixer and mixed at a temperature ranging from 20 to 40 ℃ for 30 to 300 seconds.

In the step (2), the thus obtained polyester resin composition is kneaded and gelled.

The step of kneading the composition to gel it may include at least one selected from the group consisting of: (2a) gelatinizing it using a planetary extruder or a banbury intensive mixer; (2b) homogenizing it using a mixing roller; and (2c) homogenizing it using heated rollers.

As yet another example, steps (2a), (2b) and (2c) may be performed sequentially in the gelation step.

The temperature conditions in the above step may be in the range of 180 to 230 ℃ for step (2a), 90 to 130 ℃ for step (2b), and 90 to 130 ℃ for step (2c), but are not limited thereto.

In step (3), the thus gelled composition is calendered to form a film.

The calendering step may be performed at a speed of 10 to 120m/min in a temperature range of 145 to 210 ℃ using a plurality of calendering rolls, but is not limited thereto.

In addition, the step may further include the steps of: the film was released from the calendering rolls using a take-off roll and the thickness and smoothness of the film were adjusted during calendering. The detachment of the film and the adjustment of the thickness and smoothness of the film may be performed at a speed of 30 to 120m/min within a temperature range of 120 to 170 ℃, but is not limited thereto.

The calendered film may be further subjected to a surface treatment step.

For example, the surface treatment may be performed by a method such as an embossing treatment.

The embossing treatment refers to a process of applying heat and pressure to the surface of the film to form a concave or convex shape.

For example, the embossing process may be performed at a temperature range of 30 to 90 ℃ using an embossing apparatus. In this case, the surface treatment speed of the film may be 30 to 120m/min, but is not limited thereto.

The surface treatment step may enhance the windability of the film and impart matte properties to the film.

Subsequently, the rolled film is cooled.

If the step of embossing processing has been performed, a step of detaching the film from the embossing device using the annealing roller is performed in advance.

The detachment of the film may be performed at a speed of 40 to 130m/min in a temperature range of 5 to 80 ℃, but is not limited thereto.

The cooling of the rolled film may be performed at a speed of 30 to 120m/min using a cooling roll in a temperature range of-5 to 50 ℃.

Subsequently, the width of the film thus prepared was cut using a side finishing device, and the thickness of the film thus prepared was measured using a thickness gauge.

The cooled film can then be rolled up. For example, the cooled film may be wound at a speed of 55 to 95m/min using a winder, but is not limited thereto.

Polyester film

The polyester film manufactured according to the method of the embodiment as described above is environmentally friendly and excellent in surface hardness, optical properties, and heat resistance.

The surface hardness of the film may be B to HB.

Surface hardness can be measured by the electronic pencil hardness tester method. For example, pencils (6B to 9H) supplied by mitsubishi corporation may be used and measured at 45 ° at the same load (200g) and the same speed.

In addition, the transparency of the polyester film may be 30 to 75%, more specifically 32 to 73%, 33 to 70%, 35 to 68%, or 40 to 65%, but is not limited thereto.

In addition, the haze of the polyester film may be 0 to 20%, more specifically 0 to 15%, 2 to 15%, or 2 to 13%, but is not limited thereto.

The haze is a measure of the transparency and visibility of the film. If the haze of the film satisfies the above range, it means that the optical properties of the film hardly deteriorate even if additional lamination such as a printed layer is formed, and thus the product practicality is excellent.