TWI729604B - Polyester resin composition, polyester film, and preparation method thereof - Google Patents

Abstract

A polyester resin composition, a polyester film, and a method for producing the same of the present embodiment are provided. By applying one or more lubricant having a low melting point or a softening point, and the like, it can efficiently produce a polyester film having excellent calendering properties and excellent optical properties.

Description

Polyester resin composition, polyester film and preparation method thereof

The invention relates to a polyester resin composition, a polyester film, and a manufacturing method thereof.

The calendering process is a process of forming films and sheets using a calender, that is, a rolling mill equipped with multiple heating rollers. Because its production speed is faster than the extrusion process and easy to process thin thickness, and the calendering process is mainly used to make films and sheets.

In the past, polyvinyl chloride (PVC) resin, which was mainly used in the calendering process, had excellent processability, but was difficult to recycle and caused environmental problems. Moreover, polypropylene (PP) resin also has excellent calendering processability, but it is not environmentally friendly, and it is difficult to print and laminate without corona and primer treatment.

On the other hand, polyethylene terephthalate (PET) resin, which is a typical polyester resin, has excellent physical properties in price comparison, but has poor calendering processability. Therefore, it is known to use a polyethylene terephthalate (PETG) resin modified with a glycol having properties suitable for a calendering process to manufacture a polyester film.

[Prior Art Literature] [Patent Literature] Korea Authorized Patent Bulletin No. 2014-0109506 Korea Authorized Patent Bulletin No. 2014-0180844

[technical problem] The object of the present invention is to provide a calendered polyester resin composition, a polyester film, a method for manufacturing the same, and the like, which have few spots on the surface and excellent light transmittance.

[Technical Solution] In order to achieve the above objective, a method for preparing a polyester film provided in an embodiment disclosed in this specification includes: The preparation step is to prepare a calendered polyester resin composition containing 0.1 to 10 parts by weight of a lubricant based on 100 parts by weight of a polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit, In the kneading step, the calendered polyester resin composition is kneaded in a compounding machine to obtain a kneaded composition, In the rolling step, the kneaded composition is placed in a calender roll having two or more rolls that roll in opposite directions for rolling, and the kneaded composition is passed through a predetermined position between the calender rolls By rolling and forming into a sheet to prepare a polyester film, and The steps are completed to prepare a calendered polyester film, including a cooling process to cool the polyester film.

The lubricant may include a first lubricant having a melting point or softening point below 100°C.

The preparation method can prepare a polyester film with a spot area of 30% or less.

The lubricant may further include a second lubricant having a melting point or softening point higher than 100°C and below 160°C.

In the rolling step, the roll speed of the calender roll may be 15 m/min or more.

The lubricant may further include a second lubricant.

The melting point or softening point of the second lubricant may differ from the melting point or softening point of the first lubricant by more than 10°C.

The mixing composition may include a first lubricant and a second lubricant in a weight ratio of 1:0.1 to 2.

The lubricant may further include two or more first lubricants.

The melting point or softening point of the two first lubricants may differ by more than 10°C.

Based on the entire diol compound constituting the polymer chain of the polyester resin, the polyester resin may include 20 mol% to 90 mol% of aliphatic or cycloaliphatic diol repeating units.

The polyester resin may be derived from a compound having, as a diol repeating unit, a repeating unit of a diol residue having a linear or branched form of 2 to 10 carbon atoms.

The neopentyl glycol repeating unit may be included as the diol repeating unit.

The haze value of the polyester film may be 15% or less.

The total light transmittance (Total Transmittance) of the polyester film may be more than 80%.

In order to achieve the above purpose, another embodiment disclosed in the specification provides a calendered polyester film comprising, based on 100 parts by weight of a polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit, 0.1 to 10 parts by weight of lubricating The lubricant includes a first lubricant having a melting point or softening point of 100° C. or less, and the spot area observed on one surface is 30% or less.

The lubricant may further include a second lubricant.

The melting point or softening point of the second lubricant may differ from the melting point or softening point of the first lubricant by more than 10°C.

The total light transmittance (Total Transmittance) of the polyester film may be more than 80%.

Based on the entire diol compound constituting the polymer chain of the polyester resin, the polyester resin may include 20 mol% to 90 mol% of aliphatic or cycloaliphatic diol repeating units.

In order to achieve the above object, another embodiment disclosed in the specification provides a calendered polyester resin composition comprising, based on 100 parts by weight of a polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit, 0.1 to 10 parts by weight The lubricant includes a first lubricant having a melting point or softening point below 100°C.

The viscosity (Viscosity) of the first lubricant measured at 120° C. may be 20 mPa·s or less.

The lubricant may just contain a second lubricant.

The melting point or softening point of the second lubricant may differ from the melting point or softening point of the first lubricant by more than 10°C.

The lubricant may further include a second lubricant having a melting point or softening point higher than 100°C and below 160°C.

The lubricant may include a first lubricant and a second lubricant in a weight ratio of 1:0.1 to 2.

Based on the entire diol repeating unit, the polyester resin contains 20 mol% to 90 mol% of any selected from the group consisting of neopentyl glycol repeating units, cyclohexanedimethanol repeating units, and combinations thereof. The repeating unit serves as a diol repeating unit.

[Beneficial effect] By using the calendered polyester resin composition, polyester film, and manufacturing method of the present invention, a polyester film can be effectively prepared, and at the same time, a polyester film that is substantially free of spots or inconspicuous and has excellent light transmittance can be prepared . Moreover, an effective calendering method can be used to produce a polyester film that is recyclable and environmentally friendly and can have excellent physical properties.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art to which the present invention belongs can easily implement the present invention. The present invention can be implemented through a variety of different embodiments, and is not limited to the embodiments described in this specification. Throughout the specification, similar parts are marked with the same reference numerals.

In this specification, unless otherwise specified, a configuration "includes" another configuration, which means that other configurations may be included without excluding other configurations.

In this specification, when one configuration is "connected" to another configuration, this includes not only "direct connection" but also "connection with other components in between".

In this specification, B is located on A means that B is in direct contact with A or B is located on A when another layer is provided between B and A, and cannot be construed as being in contact with the surface of B and A in a limited manner.

In this specification, the term "their combination" included in the expression of the Markussi form means a mixture or combination of one or more selected from the group consisting of a plurality of structural elements described in the expression of the Markussi form, and means It includes one or more selected from the group consisting of the plurality of structural elements.

In this manual, the description of "A and/or B" means "A, B or A and B".

In this manual, terms such as "first", "second" or "A", "B" are used to distinguish the same terms.

In this specification, unless a different meaning is clearly expressed in a sentence, the expression of the singular number includes the expression of the plural number.

The inventors recognized that when a polyester film is manufactured through a calendering method, there is a decrease in optical properties (transparency, haze value, etc.) of the film or spots may be formed on the surface. In exploring a method to solve this problem, it was confirmed that by controlling the type and content of the lubricant applied to the polyester resin composition for calendering, the calendering method can be used to produce a polymer with high light transmittance with excellent production efficiency. The ester film has no bubble marks and surface spots, thus completing the present invention.

Hereinafter, the present invention will be explained in more detail with reference to the conceptual diagram of the film manufacturing apparatus of FIG. 1. In order to achieve the above-mentioned purpose, a method for preparing a polyester film according to an embodiment includes a preparation step, a kneading step, a rolling step, and a finishing step, and the polyester film 1b with a spot area of 30% or less is manufactured.

In the preparation step, a calendered polyester resin composition 1a containing 0.1 to 10 parts by weight of a lubricant based on 100 parts by weight of the polyester resin containing the dicarboxylic acid repeating unit and the diol repeating unit is prepared.

Based on 100 parts by weight of polyester resin, the calendered polyester resin composition 1a may include 0.1 to 10 parts by weight, or 0.5 to 6 parts by weight of lubricant. When a lubricant within the content range is used, a polyester resin composition suitable for a calendering process can be provided.

Although it is good to obtain the desired physical properties by applying one type of lubricant alone, it is easier to obtain the desired physical properties by applying two or more types of lubricants together to the composition.

The calendering process includes a process of forming a sheet or film while allowing resin to penetrate between at least two calendering rolls. In this calendering process, if the lubricant cannot sufficiently move to the surface of the resin, the external activity may be insufficient, making it difficult to release the resin from the roll easily and the film manufacturing itself may be difficult. Also, if the lubricant moves to the surface of the resin too much, a film may be manufactured, but the optical characteristics of the film may be deteriorated. In the examples, in consideration of these characteristics, two or more types of lubricants are applied to the composition to obtain better physical properties relatively easily.

Specifically, the lubricant may include a first lubricant, and the melting point or softening point of the first lubricant is 100°C or less. Specifically, the first lubricant may include one or more types of 1-1 lubricants having a melting point or softening point below 85°C or 1-2 lubricants having a melting point or softening point higher than 85°C. It is possible to further improve the release properties and bank characteristics that are difficult to improve at the same time.

The first lubricant may include a 1a lubricant having a melting point or softening point below 75°C or a 1b lubricant having a melting point or softening point higher than 75°C together. When two or more kinds of first lubricants having different melting points or softening points are mixed and used, release properties and transparency, which are difficult to improve at the same time, can be further improved.

The lubricant may include compounds, such as fatty acids and/or polymer materials, such as polyethylene and the like. Compounds such as fatty acids and metal salts of fatty acids have a melting or freezing point called titer. However, in the case of a polymer material in which solid liquid gas cannot be clearly distinguished, the melting point is not clear, so that the softening point is used as a measure of the temperature at which the lubricant (softening) melts similar to the melting point. Therefore, in the examples, the term "melting point or softening point" is used as a term for softening and melting point. However, in this specification, even if it is expressed as "melting point" or "softening point" depending on the context, the expression is interpreted as expressing the "melting point or softening point" suitable for the type of lubricant of the present invention.

When the first lubricant having a lower melting point (or softening point) is applied to the lubricant, the spot phenomenon formed on the surface of the manufactured film can be further reduced. This is considered to be because the first lubricant has a lower melting point (or softening point), so it is first softened in the film forming process, and helps to release the air bubbles of the calendered polyester resin composition in the calendering bank, and at the same time It helps the remaining lubricant on the calender roll not to remain on the surface of the film.

The viscosity (Viscosity) of the first lubricant measured at 120° C. may be 20 mPa·s or less. This means that the first lubricant has lower viscosity characteristics in the calendering environment, and this means that the first lubricant can impart sufficient plasticity and release properties to the composition from a lower temperature. When the polyester resin composition for calendering having excellent bank characteristics is used, it is possible to manufacture a calendered sheet or film that has good air bubbles in the bank and has more excellent surface quality. Also, in conjunction with the above-mentioned characteristics, it is believed that the interaction of the first lubricant with the remaining slip agent that is applied to the calender roll and may cause spots helps to improve the surface properties of the film.

The lubricant may further include a second lubricant.

The melting point (or softening point) of the second lubricant may differ from the melting point (or softening point) of the first lubricant by more than 10°C. When two or more lubricants with different melting points are applied to the calendered polyester composition together, the lubricant is softened at different temperatures and lost during the process of manufacturing the film through calendering according to the controlled process temperature. Part of it. Through the above process, the composition can have an appropriate viscosity during the kneading process and the rolling process.

Here, according to the rolling process, the difference between the melting point or softening point of the first lubricant and the second lubricant includes the case where the melting point (or softening point) of the first lubricant is higher than that of the second lubricant and the melting point of the first lubricant (Or softening point) is lower than the second lubricant. It is preferable that the melting point (or softening point) of the second lubricant is higher than that of the first lubricant.

The melting point or softening point of the second lubricant may be higher than 100°C, or may be higher than 100°C and below 160°C. Specifically, the melting point or softening point of the second lubricant may be higher than 100°C and 140°C or lower, or may be higher than 100°C and 120°C or lower. When a lubricant having such a melting point or softening point is used for the second lubricant, the elution rate of the lubricant or the softening degree of the composition can be finely controlled during the rolling process, and the resin and the first lubricant can be further improved Compatibility, and calendering method can be used to produce polyester film with excellent bank characteristics, optical characteristics and surface characteristics.

The viscosity (Viscosity) of the second lubricant measured at 140°C may be 150 mPa.s or more, 150 mPa.s to 1200 mPa.s, 150 mPa.s to 800 mPa.s, 150 mPa.s To 550 mPa.s. This means that the second lubricant has higher viscosity characteristics in the calendering environment. The first lubricant imparts sufficient plasticity and releasability to the composition from a lower temperature. On the other hand, the second lubricant contributes to the proper softening degree of the resin composition at the rolling temperature and the first lubricant and the second lubrication Improvement of compatibility between agents. Moreover, the composition containing the second resin having such characteristics allows the calendering process to be performed more efficiently by appropriately softening the resin and helping to introduce the remaining slip agent into the polymer resin, and can produce more excellent banks. Characteristics and surface characteristics of the film.

The lubricant may include the first lubricant and the second lubricant in a weight ratio of 1:0.1 to 2, 1:0.2 to 1.6, or 1:0.8 to 1.5. When the first lubricant and the second lubricant are mixed in such a weight ratio and applied to the composition, a polyester film having excellent releasability, productivity, etc., and excellent optical characteristics can be produced.

The lubricant includes a polar lubricant that contains a polar functional group in the molecule and a non-polar lubricant that does not contain a polar functional group in the molecule or the polar functional group is hardly exposed to the surface of the lubricant and thus exhibits a non-polarity as a whole.

Specifically, the polar lubricant may have any one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an ester group, and a combination thereof in the molecule. A polar lubricant may be used as the first lubricant. More specifically, the first lubricant may include a polar portion in the same molecule by including at least one of a hydroxyl group, a carboxyl group, and an ester group in the molecule, And it may include a polar part and a non-polar part, and the non-polar part includes an alkyl or alkenyl group having 12 or more carbon atoms. Specifically, the first lubricant may include at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an ester group, and a combination thereof in the molecule, and may have 12 to 66 carbon atoms.

When a lubricant with this characteristic is used as the first lubricant, it has similar properties to polyester resins with polar and non-polar parts, so the gaps between the polymer chains will open, helping to mix the lubricant into To help soften the polymer resin, and also improve compatibility with other lubricants, and help to mix the composition more easily.

The lubricant may include any one or more selected from the group consisting of the following lubricants, i) a fatty acid lubricant containing fatty acids, fatty acid salts, and fatty acid lubricants as fatty acid esters, and ii) as a fatty acid lubricant containing polyethylene, Low-density polyethylene, ultra-low-density polyethylene, oxidized polyethylene, or low-density polyethylene oxide polymer lubricants are polyethylene lubricants.

The polyester resin contains a dicarboxylic acid compound and a diol compound as monomers. That is, the polyester resin may have repeating units derived from polymerized dicarboxylic acid compounds and diol compounds.

Based on 1 mol of the dicarboxylic acid compound, the polyester resin can be polymerized by mixing the diol compound at a ratio of 1.05 to 3 mol. When mixed in the above ratio, the esterification reaction proceeds stably, which is advantageous for the formation of sufficient ester oligomers.

The dicarboxylic acid compound may comprise selected from the group consisting of terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, succinic acid, glutaric acid, orthophthalic acid, adipic acid, azelaic acid , Sebacic acid, sebacic acid, 2,5-furandicarboxylic acid, 2,5-thiophenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-bibenzoic acid, and combinations thereof any type. Specifically, the dicarboxylic acid compound may be any one selected from the group consisting of terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and combinations thereof.

The diol compound may include linear or branched aliphatic diols, alicyclic diols, and aromatic diols. Specifically, the linear or branched aliphatic diol may be selected from ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,2-octanediol, 1,3-octanediol , 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2 ,2-Diethyl-1,5-pentanediol, 2,4-Diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,1-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, Any one of the group consisting of 8-octanediol, 1,9-nonanediol, 1,10-decanediol, and combinations thereof.

Specifically, the cycloaliphatic diol may include those selected from cyclohexanedimethanol, isosorbide, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and combinations thereof. Any kind of group.

When the polyester resin containing the alicyclic diol is calendered to prepare a film or sheet, it can be chemically bonded firmly, so that a polyester film with improved impact strength, heat resistance, etc. can be produced. Moreover, when a film or sheet is manufactured by calendering a composition containing a linear or branched aliphatic diol, it can be sealed well, so that a polyamide with improved chemical resistance and surface strength of the film or sheet can be produced. Ester film.

Specifically, the diol component may include any one selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, cyclohexane dimethanol, and combinations thereof. More specifically, the diol compound may include neopentyl glycol as a diol component.

Based on the entire diol compound, the diol compound may include 20 mol% to 90 mol% neopentyl glycol, may include 30 mol% to 80 mol% neopentyl glycol, and may include 30 mol% to 80 mol%. Mole% to 60 mole% neopentyl glycol. When the diol compound contains neopentyl glycol in the above range, the specific viscosity of the resin is set in an appropriate range, so that the calendering processability can be further improved, and the color, mechanical properties and physical properties of the manufactured film can be further improved. Wait.

When the aforementioned lubricant is applied to a diol containing 20 mol% to 90 mol%, specifically 30 mol% to 80 mol%, more specifically 30 mol% to 60 mol% of aliphatic diols When it is a component of polyester resin, better processability can be obtained.

Specifically, during the calendering process, the lubricant must meet the following standards: release properties, by interacting with the polyester resin without sticking to the calender roll and release good bank characteristics, sufficient in the calendering bank Mix and eliminate bubbles, etc., transparency, and control the transparency and turbidity of the manufactured sheet.

In order to make the polyester resin composition meet all the characteristics required by the calendering process above a certain level, during the calendering process, the lubricant should quickly form a lubricant film on the surface of the polyester resin so as to have a gap between it and the calender roll. Adequate mold release. However, if the lubricant moves to the resin surface too much, the sheet or film manufactured through the calendering process may appear turbid, which may adversely affect the optical characteristics. Therefore, during the calendering process, in order to quickly form a lubricant film on the surface of the resin while preventing the lubricant from excessively moving to the surface, the space between the polymer chains in the polyester resin is opened to make the lubricant Disperse appropriately between resins. Therefore, by appropriately softening the polyester resin, the elimination of air bubbles on the bank can be performed above a certain level.

The polyester resin is, due to the influence of the linear structure of the aliphatic diol component forming the polyester, it is easier to incorporate the lubricant into the polyester resin than in the case of having a coarse chain structure such as aromatic In addition, the space between the polymer chains can be opened quickly, so that it is considered to have better calendering processability.

Moreover, when one or more types of the first lubricant and the second lubricant are used together, that is, two or more types in total are used together, the calendering characteristics and the physical properties of the film of the polyester resin of the examples can be further improved. Specifically, the polyester resin composition of the example having such characteristics was evaluated, and it has excellent characteristics in all of the releasability, bank characteristics, roll speed, spot area, and the like.

Due to the characteristics of the lubricant (first lubricant) itself, lubricants with different melting points or softening points ensure the required releasability in the resin during the calendering process, and then penetrate and have the same characteristics as the lubricant (first lubricant). Lubricants) other lubricants (second lubricants) with different melting points or softening points interact to move the remaining lubricant into the resin more easily. At this time, the interaction with the polyester resin component containing the repeating unit derived from the aliphatic diol makes it easier to perform the movement of this lubricant.

In addition to the polyester resin and lubricant, the polyester resin composition may further contain components such as a polymerization catalyst, a stabilizer, and a coloring agent.

Such a polymerization catalyst, stabilizer, and colorant can be added to the product of the esterification reaction or the transesterification reaction before the polymerization reaction is started, and can be added to the mixed slurry containing the dicarboxylic acid and the diol compound before the esterification reaction It can be added in the middle of the esterification reaction step.

As the polymerization catalyst, an antimony compound, a titanium compound, a germanium compound, an aluminum compound, or a mixture of these compounds can be used. As the antimony compound, antimony trioxide, antimony acetate, antimony glycolate, etc. can be used, and as the titanium compound, tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, titanium dioxide, titanium dioxide/silicon dioxide copolymer can be used As the germanium compound, germanium dioxide, germanium acetate, germanium glycolate, etc. can be used.

As the stabilizer, phosphorus compounds such as phosphoric acid, trimethyl phosphate, and triethyl phosphate can be used, and the addition amount based on the quality of phosphorus (P) can be 10 ppm to 100 ppm relative to the weight of the final polymer .

The colorant is added to improve the color of the polymer. Cobalt acetate, cobalt propionate metal salt colorants and coloring agents as dye components can be used. The addition amount can be 0 ppm to 100 relative to the weight of the final polymer. ppm.

The specific viscosity (IV) of the polyester resin may be 0.6 dl/g to 3.0 dl/g. Specifically, the specific viscosity (IV) of the polyester resin is 0.6 dl/g to 2.5 dl/g, 0.6 dl/g to 2.0 dl/g, 0.6 dl/g to 1.5 dl/g, 0.6 dl/g to 1.0 dl /g, 0.62 dl/g to 1.5 dl/g, 0.64 dl/g to 1.2 dl/g, or 0.6 dl/g 6 to 0.85 dl/g. When the specific viscosity of the polyester resin is within the above range, a polyester film having excellent calenderability and excellent sheet and film thickness uniformity can be produced.

The calendered polyester resin composition 1a prepared through the preparation step is applied to the film manufacturing apparatus 10 from the kneading step.

The kneading step includes a kneading process of kneading the calendered polyester resin composition in the compounding machine 100 to prepare a kneading composition.

Specifically, the mixing process can be performed by applying a high-speed mixer (for example, a Henshell mixer). More specifically, it can be performed by granulating the polyester resin composition, putting the granulated polyester resin into a high-speed mixer and mixing at a temperature of 20°C to 40°C for 30 seconds to 300 seconds. The mixing process.

The mixing step may include the above-mentioned mixing process and gelation process.

The gelation process is a process of mixing and gelling the composition, which may include i) a process of gelling using a streamlined extruder or a Banbury mixer, ii) a process of homogenization using a mixing roller The process, or iii) at least one selected from the process of homogenization using a heated roller, or is performed by sequentially applying the above three processes.

The gelled calendered polyester resin composition is then moved as a kneaded composition to be applied to a rolling step subsequently performed by a calendering method. At this time, the calendered polyester resin composition 1a can be moved onto the calender roll 200 through the transport part 120.

In the rolling step, the kneaded composition is put into a calender roll 200 having two or more rolls rolling in opposite directions to perform rolling, and the kneaded composition is passed through the calender roll 200 A predetermined position between 200 is rolled and formed into a sheet shape to prepare a polyester film 1b.

In the rolling step, a plurality of calender rolls 200 are used to form a polyester film through a calendering method. In FIG. 1, four calender rolls 200 are shown, but the number and arrangement of the calender rolls can be changed.

In the rolling step, the temperature of the calender roll 200 may be 110°C to 230°C, and may be 145°C to 210°C. When the calendering step is performed under such temperature conditions, the polyester film can be manufactured more efficiently.

Furthermore, the roll speed of the calender roll 200 may be 15 m/min or more. When using a lubricant with the above characteristics, a calender roll speed of 15 m/min or more can be used to satisfy the release and bank characteristics. This means that films with excellent production efficiency and high quality can be produced.

The polyester resin contains a repeating unit having a diol residue having 2 to 10 carbon atoms in a linear or branched form as a diol repeating unit. Specifically, the polyester resin contains a repeating unit of a diol compound having a diol residue of 2 to 10 carbon atoms in a linear or branched form as the diol repeating unit, and may include neopentyl glycol The repeating unit serves as a diol repeating unit.

This polyester resin is characterized in that in the following kneading and rolling processes, the non-polar functional group is located on the surface of the polyester film, and the polar functional group is located in the center, and interacts with the above-mentioned lubricant. Specifically, due to the interaction with the aforementioned lubricant during the calendering process, that is, due to the influence of the linear structure formed by the aliphatic diol component, the lubricant can be more easily incorporated into the polyester having such a diol repeating unit. In the resin. This can increase the roll speed, bank characteristics, etc., so that a calendered polyester film with excellent surface characteristics and optical characteristics can be manufactured.

The calendering step may further include a peeling process of peeling the polyester film from the calendering roll 200 using take off rolls (take off rolls, not shown) and adjusting the thickness and smoothness of the polyester film to manufacture the polyester film 1b. This peeling process can be performed at a temperature of 120 to 170°C.

The calendering step may further include an embossing step as required. The embossing step is to use an embossing roller or the like to form an embossing pattern on the polyester film 1b. The embossing step can be performed at a temperature of 30°C to 130°C by using an embossing roll (not shown). The polyester film 1b having an embossed pattern formed on its surface through the above-mentioned embossing step may have further improved windability.

The completion step includes a cooling process of cooling the polyester film 1b.

The completion step may include: a cooling step, cooling the polyester film produced in the rolling step; a cutting process, cutting the cooled polyester film; and a winding step, winding the cut film.

The cooling process may be performed through the cooler 300, and the winding step may be performed through the winder 400.

In the cooling process, a cooling roll (not shown) may be used to cool the polyester film 1b, and the temperature of the cooling roll may be maintained at -5°C to 50°C.

The polyester film 1b may be wound after cutting the width of the film using a side trimming device and measuring the thickness of the film using a thickness gauge.

The polyester film 1b thus produced has excellent processability and particularly excellent optical properties.

The spot area of the polyester film 1b may be 30% or less or 20% or less. The spot area of the polyester film 1b may be 10% or less, or may be 0.001% to 10%. Such a calendered polyester film with a small spot area can be efficiently manufactured through a calendering process, and at the same time has excellent optical properties. Specifically, it is considered that the spots observed on the surface of the polyester film produced by the calendering method are generated under the influence of the lubricant. However, if you want to produce polyester film with a high-efficiency calendering method and improve processing efficiency, you must use a lubricant. In this embodiment, by using the above-mentioned lubricant, it is possible to efficiently manufacture the polyester film while reducing the area of spots generated on the surface of the polyester film.

The haze value of the polyester film 1b may be 15% or less, 13% or less, 11% or less, or 0.001% to 9%.

The total light transmittance (Total Transmittance) of the polyester film 1b may be 80% or more or 88% or more.

The polyester film having the above-mentioned haze value and light transmittance refers to a film having fairly good optical properties that can be efficiently manufactured through a calendering method.

The calendered polyester film 1b according to another embodiment contains 0.1 to 10 parts by weight of a lubricant based on 100 parts by weight of a polyester resin including a dicarboxylic acid repeating unit and a diol repeating unit, and is observed in one surface thereof The spot area is less than 30%.

The detailed descriptions of the polyester resin, polyester film, lubricant, first lubricant, second lubricant, etc., are repeated with the above, so detailed descriptions thereof will be omitted.

The calendered polyester resin composition according to another embodiment contains 0.1 to 10 parts by weight of a lubricant based on 100 parts by weight of the polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit, the lubricant including a melting point Or the first lubricant whose softening point is below 100°C.

The detailed descriptions of the polyester resin, polyester film, lubricant, first lubricant, second lubricant, etc., are repeated with the above, so detailed descriptions thereof will be omitted.

When the polyester resin composition 1a of the example and a suitable lubricant are used, during the calendering process, it can be manufactured with excellent properties regarding workability (such as adhesion and release to the calender roll, and good air bubbles). , And excellent film characteristics (such as high transparency, low haze and no orange peel) polyester film 1b.

Hereinafter, the present invention will be explained more specifically. The following description is merely an illustration to help understand the present invention, and the scope of the present invention is not limited thereto.

Production of samples of Examples and Comparative Examples

1) Preparation of polyester resin chips

In order to manufacture the polyester resin, the diol component and the dicarboxylic acid component were put into a 2500 L reaction vessel with a stirrer and an outflow condenser so that the final polymer amount was 2,000 kg. The internal pressure of the reaction vessel was increased to 2.0 kg/cm ² using nitrogen gas, and the reaction was performed while increasing the temperature of the reaction vessel to 265°C. At this time, the produced water is esterified while flowing out, and then the reaction product is transferred to a polycondensation reaction vessel equipped with a stirrer, a cooling condenser and a vacuum system.

For the obtained esterification product, add antimony triglycolate as a metal polycondensation catalyst to 300 ppm based on the amount of antimony element, and add triglycolate (TEP) as a phosphorus stabilizer to 500 ppm based on the amount of phosphorus element . Thereafter, the low vacuum reaction was performed for 40 minutes while raising the internal temperature and pressure of the reaction vessel to 285°C to 290°C and 50 mmHg. After that, the glycol component was discharged to the outside, and the pressure was gradually reduced to 0.1 mmHg to perform the reaction under high vacuum to the maximum power value.

The polyester resin obtained in the polycondensation reaction is discharged and cut into pieces to prepare polyester chips.

Terephthalic acid (TPA) is used as the dicarboxylic acid compound, and diethylene glycol (DEG), neopentyl glycol (NPG) and/or cyclohexane dimethanol (CHDM) are used as the diol compound. The molar ratio of dicarboxylic acid: diol is 1:1.05 to 3.0, but the ratio of neopentyl glycol is 30 mol% to 90 mol% based on all diol compounds.

2) Preparation of polyester film

The lubricant was blended with the polyester resin to prepare the composition according to Table 1 and Table 2 below. The composition was extruded, kneaded, gelled and calendered at an average of 200°C to produce a 0.2 mm thick film. The types and characteristics of lubricants used are shown below.

Lubricant 1: Stearic acid type lubricant. Melting point 68℃, viscosity 9.87 mPas at 70℃, density 0.94 g/cm ²

Lubricant 2: Montan wax type lubricant. Melting point 82.5 (80 to 85)°C, viscosity below 20 mPas at 120°C, density 1.00 g/cm ² to 1.02 g/cm ²

Lubricant 3: Oxidized polyethylene-based lubricant. The softening point is 98°C, the viscosity is about 180 mPas at 140°C, and the density is 0.92 g/cm ² to 0.94 g/cm ²

Lubricant 4: Polyethylene lubricant. The softening point is 103°C, the viscosity is about 180 mPas at 140°C, and the density is 0.91 g/cm ² to 0.93 g/cm ²

Lubricant 5: Polyethylene lubricant. The softening point is 108℃, the viscosity is about 750 mPas at 140℃, and the density is 0.91 g/cm ² to 0.93 g/cm ²

Lubricant 6: Polyethylene lubricant. The softening point is 109℃, the viscosity is about 1100 mPas at 140℃, and the density is 0.91 g/cm ² to 0.93 g/cm ²

Evaluation of physical properties of samples of Examples and Comparative Examples

1) Processing evaluation

When calendering is performed using the polyester resin composition, the following items are evaluated.

-Releasability: Evaluate the following criteria to determine whether the sheet is released well during processing without sticking to the processing roller. O: Excellent release; △: Moderate release; X: Poor release

-Bank characteristics: Whether bubbles are generated in the calendered bank or the bubbles are released well. O: When driving at a high speed of 15 m/min or more, fewer bubbles are generated in the bank; △: Bubbles are released slightly slowly; X: Bubbles are often generated and the bubbles are released slowly.

-Transparency: Visually confirm the transparency and turbidity of the sheet produced through the calendering process. O: High transparency and no turbidity observed; △: Good transparency, but some turbidity or no turbidity is observed, but the transparency is poor; X: The transparency is poor or the turbidity is severe.

-Roller speed: During the calendering process, the roller speed is related to production efficiency and film quality. X: When the roller speed is less than 15 m/min; 0: When the roller speed is 15 m/min or more.

2) Transmittance (TT, Total Transmittance, total transmittance)

A haze meter (model: SEP-H) of Nihon Seimitsu Kogaku (Nihon Seimitsu Kogaku) was used to measure, and the total light transmittance (%) was measured using a C light source.

3) Haze evaluation

The haze meter (model: SEP-H) of Nihon Seimitsu Kogaku was used for measurement, and the haze (%) was measured with C light source.

4) Spot area

The sheet prepared through the calendering process was placed in an oven at 80°C for 24 hours, and then reflected under a fluorescent lamp to evaluate whether spots were generated in the observation area (evaluation 21 * 29.7 cm ² * average after 3 standards).

O: The spot area is less than 10%; Δ: The spot area is more than 10% and less than 50%; X: The spot area is more than 50%

The evaluation results are shown in Table 1 and Table 2, respectively.

Hereinafter, the content of the lubricant in Table 1 and Table 2 refers to the weight of the lubricant (phr, per hundred resin) based on 100 parts by weight of the polyester resin.

[Table 1] Lubricant (melting point, ℃) Composition 1 Composition 2 Composition 3 Composition 4 Composition 5 Composition 6 Lubricant 1 (68) 0.5 - 0.4 4 - - Lubricant 2 (82.5) - 0.5 0.2 - - - Lubricant 3 (98) - - - - 4 - Lubricant 5 (108) - - - - - 4 Lubricant total 0.5 0.5 0.6 4.0 4.0 4.0 Release X O O O O O embankment O ∆ ∆ X X X Transparency O O O ∆ X X Roll speed X ∆ O O O O Spot area O O O X X X

[Table 2] Lubricant (melting point, ℃) Composition 7 Composition 8 Composition 9 Composition 10 Composition 11 Composition 12 Composition 13 Composition 14 Composition 15 Lubricant 1 (68) - - - - - - - - 0.36 Lubricant 2 (82.5) - - - - - - - 0.16 - Lubricant 3 (98) 0.5 - - - 0.4 0.4 0.4 - 0.36 Lubricant 4 (103) - 0.5 - - 0.4 - - 0.24 0.27 Lubricant 5 (108) - - 0.5 - - 0.4 - - - Lubricant 6 (109) - - - 0.5 - - 0.4 - - Lubricant total 0.5 0.5 0.5 0.5 0.8 0.8 0.8 0.40 1.01 Release O X ∆ ∆ O O O O O embankment ∆ O O O O O O O O TT 90.2 89.9 89.5 89.7 90.0 89.0 89.2 89.5 89.5 Hz 11.2 13.1 12.0 12.7 13.4 12.8 15.0 6.2 10.8 Roll speed O X X X O O O O O Spot area O O O O O O O O O

Refer to Table 1 and Table 2 to confirm that it is not easy to control various characteristics such as release, bank characteristics, transparency, roll speed (processing speed), etc. through only one type of lubricant applied to the polyester resin composition. Above level.

It was confirmed that when two or more kinds of lubricants were simultaneously applied to the polyester resin composition, physical properties corresponding to ordinary or excellent can be obtained for each item. In particular, when among two or more lubricants, the first lubricant whose melting point or softening point is 100°C or less is used, and the second lubricant whose melting point or softening point is higher than 100°C and 160°C or less, even if the amount of lubricant is increased, The occurrence of spots on the surface of the sheet is also rare or inconspicuous, which is advantageous for the production of polyester resin through a calendering process.

Above, the preferred embodiments of the present invention have been described in detail, but the scope of rights of the present invention is not limited to this. Those skilled in the art to which the present invention belongs use the basic concept of the present invention defined by the claims to implement various modifications and The improved form also falls within the scope of the rights of the present invention.

1a: Polyester resin composition 1b: Polyester film 10: Film manufacturing device 100: Matching machine 200: Calender roll 300: cooler 400: Winder

Fig. 1 is a conceptual diagram briefly explaining a film manufacturing apparatus to which an embodiment can be applied.

1a: Polyester resin composition

1b: Polyester film

10: Film manufacturing device

100: Matching machine

200: Calender roll

300: cooler

400: Winder

Claims (14)

A method for preparing a polyester film, comprising: a preparation step of preparing a calendered polyester resin combination containing 0.1 to 10 parts by weight of a lubricant based on 100 parts by weight of a polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit Mixing step, kneading the calendered polyester resin composition in a blending machine to obtain a mixed composition; rolling step, put the mixed composition into two or more rolling in opposite directions And in the calender roll of the rolling roll, and by passing the kneaded composition through a predetermined position between the calender rolls to roll, and shape it into a sheet to prepare a polyester film; and completing the step, The preparation of a calendered polyester film includes a cooling process to cool the polyester film, and the lubricant includes a first lubricant having a melting point or softening point below 100°C, and a melting point or a melting point above 100°C and below 160°C. Softening point of the second lubricant to prepare the polyester film with a spot area of 30% or less, wherein the kneaded composition contains the first lubricant and the first lubricant in a weight ratio of 1:0.1 to 2 Two lubricants. The method for producing a polyester film according to claim 1, wherein the melting point or softening point of the second lubricant is different from the melting point or softening point of the first lubricant by more than 10°C. The method for producing a polyester film according to claim 1, wherein in the rolling step, the roll speed of the calender roll is 15 m/min or more. The method for preparing a polyester film according to claim 1, wherein the lubricant further comprises two or more kinds of the first lubricant, and the melting points or softening points of the two or more kinds of the first lubricants are different Above 10°C. The method for producing a polyester film according to claim 1, wherein the polyester resin contains 20 mol% to 90 mol% of aliphatic based on the entire diol compound constituting the polymer chain of the polyester resin Or alicyclic diol repeating unit. The method for producing a polyester film according to claim 1, which contains a neopentyl glycol repeating unit as the diol repeating unit. The method for producing a polyester film according to claim 1, wherein the haze value of the polyester film is 15% or less. The method for producing a polyester film according to claim 1, wherein the total light transmittance of the polyester film is 80% or more. A calendered polyester film, comprising a polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit based on 100 parts by weight, containing 0.1 to 10 parts by weight of a lubricant, and the lubricant has a melting point below 100°C Or a first lubricant with a softening point, a second lubricant whose melting point or softening point is more than 10°C different from the melting point or softening point of the first lubricant, and the spot area observed on one surface is 30% or less, wherein The weight ratio of the first lubricant and the second lubricant is 1:0.1 to 2. The calendered polyester film according to claim 9, wherein the total light transmittance of the polyester film is 80% or more. A calendered polyester resin composition comprising a polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit based on 100 parts by weight, containing 0.1 to 10 parts by weight of a lubricant, and the lubricant containing The melting point or softening point of the first lubricant, and the melting point or softening point of the first lubricant and the melting point or softening point of the second lubricant more than 10 ℃, wherein the first lubricant and the second lubricant The weight ratio of the lubricant is 1:0.1 to 2. The calendered polyester resin composition according to claim 11, wherein the viscosity of the first lubricant measured at 120°C is 20 mPa·s or less. The calendered polyester resin composition according to claim 11, wherein based on the entire diol repeating unit, the polyester resin contains 20 mol% to 90 mol% of repeating units selected from neopentyl glycol, ring The repeating unit of hexanedimethanol and any repeating unit of the group consisting of a combination thereof are used as the repeating unit of the diol. A calendered polyester resin composition comprising a polyester resin containing a dicarboxylic acid repeating unit and a diol repeating unit based on 100 parts by weight, containing 0.1 to 10 parts by weight of a lubricant, and the lubricant containing A first lubricant having a melting point or softening point, and a second lubricant having a melting point or softening point higher than 100°C and below 160°C, wherein the weight ratio of the first lubricant and the second lubricant is 1: 0.1 to 2.

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