KR101450840B1 - White porous polyester film and preparing method therefof - Google Patents

Abstract

More particularly, the present invention relates to a polyester resin (A), a polyester resin (B) containing a naphthalene group in its main chain, and a polyester (C) Wherein the film has a degree of whiteness of 99.5% or more, an average reflectance of 94% or more in a wavelength range of 450 to 700 nm, and a reflectance And heat resistance and the like, and thus can be usefully used for various printing materials, labels, electronic materials, and materials for displays, and a method for producing the white porous polyester film.

A white porous polyester film, a polyester resin, a resin which is incompatible with a polyester,

Description

WHITE POROUS POLYESTER FILM AND PREPARING METHOD THEREFOF Technical Field [1] The present invention relates to a white porous polyester film,

The present invention relates to a white porous polyester film and a method for producing the same.

Various methods are known for producing a white porous polyester film. Japanese Patent Application Laid-Open No. 58-50625 discloses a method of producing a polyester film by blending a foaming agent in a polyester, and Japanese Patent Laid-Open No. 57-49648 discloses a method of blending a polyolefin resin to form micropores on the surface and inside of the film Is disclosed.

In the above prior art, the uniformity of the pores formed due to incompatibility in the process of extrusion molding, drawing, and processing after the polyolefin resin is mixed with the polyester resin causes problems such as breakage in the drawing process, And the reflectivity is insufficient to limit the application of the product. In order to solve this problem, a method of adding various compatibilizing agents has been disclosed. However, in this case, there is a limit to industrial application due to problems such as lack of thermal stability of the compatibilizing agent and transition to the surface.

In order to solve this problem, a polyolefin resin (B) such as polymethylpentene is mixed with a polyester resin (A) as described in Japanese Patent Laid-Open Publication No. 3-20328 and Korean Patent Registration No. 215496, and the porosity and pore size Two types of inorganic materials with particle size of 0.5 ~ 2 ㎛ and 2 ~ 10 ㎛ were added to form sufficiently. However, when melt extrusion and stretching are performed as a single layer at this time, the stretching magnification can not be sufficiently increased due to the inorganic and organic particles having a large diameter and no compatibility, so that sufficient characteristics in reflectance and hiding power can not be obtained. When the stretching magnification is increased, production of the film is hardly possible due to breakage or the like, and polymethylpentene has a problem of poor stability against ultraviolet rays. Therefore, in this case, a polyester film made of A / B / A or A / B co-extruded is produced to produce a multilayered polyester film, while a relatively low incompatible inorganic or organic material is injected into one or both surface layers A It was possible to increase the draw ratio. Commercial products that have been commercialized as a result of this invention include E60L, E6SL, and E6SV from Toray, Japan, and UX Type from TDF.

However, the multilayered polyester film can not be used with a reclaimed chip, and thus has a high manufacturing cost and is problematic in a manufacturing process due to co-extrusion.

In addition, since the polyolefin has a relatively low thermal stability, a film produced by mixing with a polyester has a disadvantage that its heat resistance is poor.

As a result, the present inventors have found that a polyester resin (A), a polyester resin (B) containing a naphthalene group in its main chain, a polyester (C) The white porous polyester film excellent in hiding power, whiteness and reflectance, and excellent in heat resistance and processability has been developed.

Accordingly, the present invention provides a white porous polyester film excellent in hiding power, whiteness and reflectance, and excellent in heat resistance and processability at the same time.

In order to achieve the above object, the present invention provides a polyester resin composition comprising a polyester resin (A), a polyester resin (B) containing a naphthalene group in its main chain, a polyester resin (C) .

Further, the present invention relates to a process for producing a polyester resin (A), a polyester resin (B) containing a naphthalene group in the main chain and a resin composed of a polyester and a resin (C) A method for producing a white porous polyester film by obtaining a sheet and biaxially stretching the sheet in the longitudinal direction and the transverse direction.

The white porous polyester film according to the present invention has excellent optical properties such as whiteness, hiding power, and reflectance as well as excellent heat resistance and processability, and thus can be usefully used for various printing materials, labels, electronic materials and display materials.

Hereinafter, the present invention will be described in detail.

The white porous polyester film according to the present invention comprises a polyester resin, a polyester resin containing a naphthalene group in its main chain and a polyester resin and a resin which is incompatible with the polyester. The inorganic porous particles having an average particle size of 0.1 to 0.7 탆, 15% by weight, the film has a whiteness of 99.5% or more, an average reflectance of 94% or more in a wavelength range of 450 to 700 nm, and excellent reflectance and heat resistance even after heat treatment.

The polyester resin (A) used in the present invention is preferably a polyester resin (A) which is an aromatic dicarboxylic acid-based acid component and an alkylene glycol-based glycol component, such as polyethylene terephthalate, polybutylene terephthalate, polytetramethylene terephthalate, Can be prepared by condensation polymerization of the components in a conventional manner. The aromatic dicarboxylic acid may be at least one selected from the group consisting of terephthalic acid, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, anthracenedicarboxylic acid and?,? (2-chlorophenoxy) ethane-4,4-dicarboxylic acid. Examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and hexylene glycol. In the present invention, the polyester resin (A) is preferably used in an amount of 35 to 80% by weight with respect to the total film composition. When the polyester resin (A) is used in an amount of less than 35% by weight, the content of the resins B and C, In particular, when the content of the incompatible resin (C) and the inorganic particles is increased, there is a problem that the processability is poor due to an increase in the breaking property of the film. When the content is more than 80 wt%, the desired reflectance and whiteness it's difficult.

As the polyester (B) containing a naphthalene group in the main chain, polyethylene 2,6-naphthalate having ethylene-2,6-naphthalate as a main repeating unit is typically produced by the following method.

First, molten dimethyl-2,6-naphthalate and ethylene glycol are mixed at a molar ratio of 1: 2 and heated and melted at a temperature of 150 to 180 ° C., and then molten metal components such as manganese, potassium, lithium, calcium, magnesium, And then the ester exchange reaction is carried out. The same functional derivative as dimethyl-2,6-naphthalate is exemplified by dimethyl-1,2-naphthalate, dimethyl-1,5-naphthalate, dimethyl-1,6-naphthalate, Dimethyl-1,8-naphthalate, dimethyl-2,3-naphthalate, dimethyl-2,7-naphthalate, and the like. Examples of diols usable in addition to ethylene glycol include polyethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 2,2-diethyl-1,3-propanediol, 2,2- , 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,3-cyclohexanedimethanol, 1,4- have.

After completion of the transesterification reaction and before the condensation polymerization reaction is started, a stabilizer and a condensation polymerization catalyst dispersed in ethylene glycol are introduced. As the stabilizer, phosphate such as trimethylene phosphate may be added. As the catalyst, a catalyst containing a metal component such as titanium, germanium, tin, antimony, zinc, cobalt, manganese and calcium may be added.

The condensation polymerization is carried out at a temperature of 260 to 300 ° C under a high vacuum of 5 to 0.1 Torr. The intrinsic viscosity of the polyethylene naphthalate resin thus prepared is preferably 0.5 dl / g or more.

The polyethylene 2,6-naphthalate has a glass transition temperature of about 50 占 폚 and a melting temperature of about 5 占 폚 or more higher than that of the polyester resin to improve the heat resistance of the final film and has an intrinsic viscosity higher than that of the polyester, (A), it has a partial compatibility with the transesterification reaction during the kneading and melt extrusion process, and it plays a role of supporting between the two resins at the time of stretching, Thereby improving the reflectance of light at the same time.

The polyethylene 2,6-naphthalate resin may be added in a state of being coated on the inorganic particles, and may be added separately in the melt extrusion process of the polyester, and may be added in an amount of 5 to 40% by weight, more preferably 10 To 30% by weight. When the amount of the polyethylene 2,6-naphthalate resin is less than 5% by weight, there is little effect of improving heat resistance. When it exceeds 40% by weight, the melt viscosity is high during the melt extrusion process, It is not desirable from the viewpoint of being ineffective.

The polyester-incompatible resin (C) preferably has a heat distortion temperature higher by 30 ° C or higher than the glass transition temperature of the polyester in order to suppress dropout and deformation from the inorganic particles at the time of stretching and improve the thermal stability of the final film, For example, a copolymer of polystyrene, norbornene and ethylene, and the average particle size of these resins is preferably in the range of 0.2 to 10 占 퐉 Do.

The polyester-incompatibility resin (C) may be added in a state coated on the inorganic particles and may be added separately in the melt extrusion process of the polyester, and the polyester-incompatibility resin may be added in an amount of 5 to 15 By weight, more preferably from 7.5 to 12% by weight. When the addition amount of the polyester-incompatibility resin is less than 5% by weight, the effect of addition is insignificant. When it exceeds 15% by weight, it is difficult to realize a sufficient stretching magnification, The pressure increase is accelerated by the clogging of the filter during the process, the life of the filter is lowered, the production efficiency is lowered, the dispersibility is deteriorated, the breakage is increased, the weatherability is lowered,

The inorganic particles are added in a compounding manner for the purpose of controlling optical properties such as light transmittance, reflectance and color, and controlling friction coefficient, surface roughness and fine tactile sensation. Examples of the inorganic particles usable in the present invention include titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc, zeolite or a mixture thereof. The particle size is preferably in the range of 0.1 to 0.7 μm, 0.35 mu m. If the size of the inorganic particles is less than 0.1 탆, the effect on the optical characteristics and the surface properties will be insignificant. If the size of the inorganic particles is more than 0.7 탆, the optical characteristics and the surface roughness of the film and the stretchability in film production will be lowered.

As shown in Korean Patent Publication No. 215496, when an average particle diameter of 0.5 to 2 μm and an inorganic matter of 2 to 10 μm are added in an amount of 7 to 15% It is difficult to form a stretched film without forming the protective layer A in multiple layers, and even if a film is formed, the stretching ratio can not be sufficiently imparted, causing problems such as lowering of physical properties such as reflectance and uneven thickness of the film. In addition, in the case of A / B / A or A / B co-extrusion, since the material composition of A and B layer are different as well as operation difficulty and manufacturing cost increase in operation of two or more extruders, There is a problem that the manufacturing cost is increased because it can not be recovered and used.

In the present invention, in order to solve the above-mentioned problems, there is a limit to the formation of voids when only the inorganic fine particles are used. Therefore, in order to solve the above problems, the polyester (B), the polyester resin (A) containing naphthalene groups having good heat resistance in the main chain, The resin (C) is added together with the inorganic particles.

Particularly, in the present invention, the inorganic particles are preferably used in an amount of 5 to 15% by weight based on the total film composition. When the inorganic particles are used in an amount of less than 5% by weight, it is difficult to achieve desired whiteness and reflectivity. The stability is poor.

On the other hand, the white porous polyester film of the present invention may be added with a brightener to improve the whiteness and reflectance of the film.

That is, when the L ^{* value} of the CIELAB system is less than 95.00, the film is not bright enough to obtain a high reflectance. When the b ^* exceeds -3.00, the film becomes yellow and reflectance is decreased. It is good to do. Addition of the whitening agent serves to act for increasing the reflectivity of whiteness increases, and the visible light region of the film up to the reflectance peak in the vicinity of 420 ~ 470 nm of the visible region, increasing the L ^* and reduce the b ^* . The brightener is preferably added in an amount of 0.01 to 0.2% by weight, more preferably 0.05 to 0.15% by weight based on the total weight of the film. The brightener is preferably 2,2 '- (1,2-etendienyl-4,1-phenylene) bisbenzoxazole or 2,2- (4,4-diphenolvinyl) dibenzoxazole desirable.

In addition to the above main components, polycondensation catalysts, dispersants, electrostatic agents, crystallization accelerators, antiblocking agents and inorganic lubricants may be further added to the polyester resin of the present invention, Are used in the usual amounts.

The polyester film according to the present invention can be produced by the following method.

First, a mixed resin is prepared by mixing a predetermined amount of a polyester resin (A), a polyester (B) containing a naphthalene group in the main chain, inorganic particles, a polyester resin and an incompatible polymer (C), and a brightener. At this time, the polymer particles may be coated on the surface of the inorganic particles in advance and mixed with the polyester resin. Alternatively, the polymer particles may be introduced through a separate feeder in the melt extrusion process of the polyester resin. The method of coating the organic polymer particles on the inorganic particles and then adding the mixture is preliminarily kneaded using a biaxial kneader to prepare chips and then mixed with the polyester resin.

The produced resin is melt-kneaded and extruded to obtain a sheet, and the sheet thus produced is stretched 3.0 to 6.0 times, preferably 3.0 to 4.5 times, for example, in the longitudinal and transverse directions, respectively. In order to increase the formation efficiency of voids during stretching and to prevent thickness and breaking at the time of stretching, it is also preferable to perform multi-stage stretching in two or more stages in the longitudinal and transverse stretching. In this case, To +30 캜, and then re-stretched at least 1.5 times.

The polyester film thus produced preferably has a density of 0.8 to 1.2 gr / cm 3 from the viewpoint of light weight, and the film thickness is preferably 50 to 250 탆.

Thus, the white porous polyester film according to the present invention has a reflectance reduction of 2% or less after heat treatment at 140 ° C for 72 hours, a whiteness of 99.5% or more, an average reflectance of 94% or more at a wavelength of 450 to 700 nm, Has excellent optical properties such as hiding power and reflectance and heat resistance and can be usefully used for various printing materials, labels, electronic materials and display materials.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Production Example: Production of polyester resin (A)

Dimethyl terephthalate and ethylene glycol were mixed in an equivalent ratio of 1: 2, and 0.03% by weight of manganese acetate was added as an ester exchange catalyst to this mixture to prepare bis-2-hydroxyethyl terephthalate as a monomer of polyethylene terephthalate Respectively. 0.2 wt% of tetrakis-3,5-di-t-butylhydroxyphenylpropanoyloxymethyl methane and 0.05 wt% of antimony oxide with a polycondensation catalyst were added and the polycondensation was completed to give an ultimate viscosity of 0.61 dl / gr and a glass transition temperature of 70 占 폚.

Reference example

The average particle size of the inorganic particles was measured by means of a centrifugal particle size analyzer of Shimadzu Corporation of Japan and the slurry of the inorganic particles dispersed in ethylene glycol was measured and expressed as volume average particle size.

Example 1

In the twin-screw extruder, 10 wt% of titanium dioxide having an average particle diameter of 0.25 탆, 15 wt% of polyethylene 2,6-naphthalate, and norbornene having a glass transition temperature of 138 캜 were added to the polyester resin (A) 10% by weight of a copolymer of ethylene and terephthalic acid (tikonase topaz) and 0.1% by weight of 2,2 '- (1,2-ethenediyldi-4,1-phenylene) bisbenzoxazole as a brightener were mixed Then, it was dried, melted and extruded according to a conventional polyester film production method to form a sheet. Then, the sheet was stretched in two stages at a temperature of 85 ° C in the longitudinal direction at 1.5 times and 2.5 times, And then stretched 2.5 times to prepare a 225 占 퐉 biaxially oriented polymer film.

Example 2

Except that the addition amount of titanium dioxide was 14 wt%, polyethylene 2,6-naphthalate was 30 wt%, and the glass transition temperature was 160 DEG C, and 7.5 wt% of a copolymer of norbornene and ethylene was added. Respectively.

Example 3

Except that the addition amount of titanium dioxide was 7.5% by weight, polyethylene 2,6-naphthalate was 25% by weight, and a copolymer of norbornene and ethylene having a glass transition temperature of 14% by weight was added in an amount of 14% Respectively.

Example 4

A copolymer of norbornene and ethylene having a glass transition temperature of 160 DEG C of an average particle diameter of 0.25 mu m and a copolymer of titanium dioxide and norbornene and ethylene in a weight ratio of 1: 1 was first dispersed through a super mixer 18 weight% of a compounding resin obtained by coating a copolymer resin of norbornene and ethylene on the surface of titanium dioxide, 10 weight% of polyethylene 2,6-naphthalate, and 2,2 '- (1 , 0.1% by weight of 2-etendiylidene-4,1-phenylene) bisbenzoxazole was mixed with 71.9% by weight of the above polyester resin (A), and melt-extruded so that the resin composition ratio of the final film was as shown in Table 1 To form a sheet. This sheet was stretched in two stages at 85 占 폚 in the longitudinal direction at 1.5 times and 2.5 times, and further stretched 1.5 占 and 2.5 times in the transverse direction at 125 占 폚 to prepare a 225 占 biaxially stretched polymer film.

Example 5

And 3.5 times in the longitudinal direction and 3.5 times in the transverse direction, respectively.

Example 6

Except that the addition amount of titanium dioxide was 12% by weight, polyethylene 2,6-naphthalate was 15% by weight, and 12% by weight of polystyrene having a glass transition temperature of 100 캜 was mixed with polyester and incompatibility resin in the same manner as in Example 1 Respectively.

Example 7

12% by weight of barium sulfate having an average particle diameter of 0.7 占 퐉 as inorganic particles and 10% by weight of polystyrene having a glass transition temperature of 100 占 폚 as an incompatibility resin were added.

Example 8

Except that 10% by weight of barium sulfate having an average particle diameter of 0.7 탆 and 30% by weight of polyethylene 2,6-naphthalate were added as inorganic particles and the single-step stretching was performed 3.5 times in the longitudinal direction and 3.5 times in the transverse direction. 1. ≪ / RTI >

Comparative Example 1

Except that 3 wt% of polyethylene 2,6-naphthalate was added.

Comparative Example 2

The same procedure as in Example 1 was conducted except that crystalline homopolypropylene having a melt index of 10 g / min and a glass transition temperature of -15 캜 was used as a polyester and an incompatible resin.

Comparative Example 3

15% by weight of titanium dioxide, 5% by weight of polyethylene 2,6-naphthalate, 15% by weight of crystalline homopolypropylene having a melt index of 10 gr / min and a glass transition temperature of -15 캜, % The same procedure as in Example 1 was carried out except for using.

Comparative Example 4

Except that no polyethylene 2,6-naphthalate was added.

Comparative Example 5

3% by weight of polyethylene 2,6-naphthalate, and polymethylpentene as a resin which is incompatible with polyester.

Comparative Example 6

Except that 10 wt% of polymethylpentene was added as a resin that was incompatible with polyester without addition of polyethylene 2,6-naphthalate, and that the polyolefin was stretched by 3.5 times in the longitudinal direction and 3.5 times in the transverse direction, Respectively.

[Table 1]

Test Example

Various performance evaluations of the films prepared in Examples 1 to 8 and Comparative Examples 1 to 6 were carried out by the following measurement methods, and the results are shown in Table 2 below.

(1) Apparent density

The mill tool piping consisting of carbon tetrachloride and n-heptane was maintained at 25 DEG C and measured by the submerged method.

(2) Whiteness

Was measured by a spectrophotometer of Minolta Co., Ltd. according to the method of ASTM E313.

(3) reflectance, L ^* , b ^* of the CIELAB system,

Were measured using a spectrophotometer of Minolta Co., Japan.

(4) Process stability

The frequency of occurrence of film breakage during 12 hours in the manufacturing process of the film was measured.

(5) Tensile strength

Using a tensile tester from Instron, a 50 mm long and 15 mm wide film was pulled at a rate of 200 mm / min to measure the stress when the specimen was broken.

(6) Heat resistance

The reflectance was measured after treatment in an oven at 140 ° C for 72 hours to compare the reflectance before and after the heat treatment.

[Table 2]

From the results shown in the above Table 2, it can be seen that the polyester film produced in the example according to the present invention has a whiteness of not less than 99.5% as a single layer, an average reflectance of not less than 94% in a wavelength range of 450 to 700 nm, Reflectance and heat resistance.

Claims (7)

48.4 to 71.9% by weight of a polyester resin (A) which is a polyethylene terephthalate, polybutylene terephthalate, polytetramethylene terephthalate or a mixture thereof; 10 to 30% by weight of a polyester resin (B) which is polyethylene 2,6-naphthalate, 7.5 to 14% by weight of a polyester (C) which is non-compatible with polyester which is a copolymer of polystyrene or norbornene with ethylene; And 7.5 to 14% by weight of inorganic particles Wherein the film has a reduction in reflectance after heat treatment at 140 占 폚 for 72 hours as compared to that before heat treatment of 2% or less. delete delete delete delete  The porous film according to claim 1, wherein the inorganic particles are at least one or more selected from the group consisting of titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc and zeolite, Polyester film. After mixing the resins (A), (B), and (C) and the inorganic particles according to the above-mentioned claim 1, the mixed resin is melt-kneaded and extruded to obtain a film sheet, and the sheet is biaxially stretched in the longitudinal direction and in the transverse direction Wherein the porous resin film has a thickness of 100 nm or less.