KR19990053829A - White porous polyester film and its manufacturing method - Google Patents

Abstract

The present invention is a white porous polyester film of a polyester resin and a polyolefin resin, 0.1 to 1.0% by weight of an organic lubricant for increasing the incompatibility between the polyester resin and polyolefin resin based on the total weight of the resin It relates to a white porous polyester film comprising and a method for producing the same. In the present invention, the organic lubricant plays a role of allowing the polyolefin to form pores while properly distributed in the polyester resin, thereby obtaining a white porous film having excellent light weight and a paper-like texture. . Such a white porous polyester film can be used in various fields such as calendars, advertising papers, high-quality wrapping papers, printing papers, wallpaper as a substitute for paper.

Description

White porous polyester film and its manufacturing method

The present invention relates to a polyester film and a method for manufacturing the same, and more particularly, to a white porous polyester film and a method for manufacturing the same, which can be used as a substitute for paper because of its excellent light weight and texture and good antistatic and printing properties.

White polyester film retains polyester's inherent properties in terms of mechanical properties, heat resistance and dimensional stability while providing excellent light blocking, whiteness, and color and texture similar to paper, so calendars, flyers, high-quality packaging, printing paper, wallpaper It has been used as a substitute for paper. On the other hand, polyolefin-based films containing a large amount of inorganic particles have also been widely used as a substitute for paper in packaging materials and printing materials because of the advantages of light weight and excellent surface properties.

However, the white polyester film has the above-mentioned advantages, but has a disadvantage in that the stiffness and the touch on contact are too smooth, so that the texture is poor compared to the paper, and in the case of the polyolefin-based film used as a substitute for paper, mechanical and thermal There is a disadvantage of falling characteristics.

In order to overcome these disadvantages, a method has been developed that can exhibit a paper-like texture while maintaining the excellent properties of the polyester film, and can reduce the mass per unit area to about the weight of a polyolefin-based film.

As an example of such a method, Japanese Patent Laid-Open Nos. 62-243210 and Pyeong 2-206622 disclose methods for adding inorganic fine particles to polyester, and Japanese Patent Laid-Open No. 58-50625 discloses a method for adding polyester to polyester. A method of blending and reducing the weight of a blowing agent is disclosed, and Japanese Laid-Open Patent Publication No. 57-49648 improves the surface properties of a film by forming fine pores on the surface and inside of the film by blending and stretching a polyolefin resin in polyester. And lightening the film itself is disclosed.

When the polyolefin resin is mixed with the polyester resin and subjected to extrusion, molding, and stretching, fine pores are formed on the surface and inside of the film due to poor compatibility between the two resins. Therefore, using the above properties, the surface properties of the film can be improved and the weight can be realized. However, the polyolefin resin is used in combination with the polyester resin. However, the pores are limited and the pores themselves are uneven. There is a problem that the printing is uneven because there are many partially exposed or recessed parts. Therefore, in order to solve such a problem, the compatibility between the two resins needs to be maintained at an appropriate level.

In general, paper-like texture and surface characteristics can be changed very sensitively depending on the shape and distribution of pores present in the film.If the pore distribution is not designed correctly when forming the pores, the desired paper texture can not be obtained and the weight is reduced. It also adversely affects fairness. In fact, if the size of the pores present in the film is small, the specific gravity is high and heavy, while if the pores are too large, there is a problem in the processability due to breakage. Therefore, in order to obtain a film which is not insufficient for use as a paper substitute, matters concerning the distribution of pores in the film and the like must be appropriately designed.

Accordingly, an object of the present invention is to provide a white porous polyester film having excellent whiteness and texture because the size, shape and distribution of pores present in the film are properly formed.

In addition, an object of the present invention is to provide a method for producing a white porous polyester film having the above characteristics.

In order to achieve the above object, in the present invention, in the white porous polyester film made of a polyester resin and a polyolefin resin, an organic lubricant for increasing the incompatibility between the polyester resin and the polyolefin resin based on the total weight of the resin Provided is a white porous polyester film comprising 0.1 to 1.0% by weight.

According to one embodiment of the white porous polyester film of the present invention, the polyester resin is preferably at least one selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), the hindered phenolic compound 0.005 It is more preferable to contain 0.5 weight%. In addition, preferably, the polyester resin contains 0.1 to 10% by weight of inorganic fine particles having a diameter of 0.1 to 10㎛. Such inorganic fine particles are preferably any one or a mixture of two or more of titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc or zeolite.

Preferably, the content of the polyolefin-based resin is 5 to 35% by weight based on the total amount of the resin, the melt index is 1 to 25gr / min. In addition, the polyolefin resin is preferably polymerized or copolymerized from at least one monomer selected from ethylene, propylene, butene, pentene, hexene or octene.

In the present invention, the organic lubricant is preferably any one or a mixture of two or more of ethylene bis stemide wax, liquid paraffin, paraffin wax, process oil or stearyl alcohol.

Another object of the present invention is to prepare a white porous polyester film of a polyester resin and a polyolefin resin, the polyester resin and polyolefin resin by mixing in a weight ratio of 95: 5 to 65:35 Forming a first mixed resin, forming a second mixed resin by adding 0.1 to 1.0% by weight of an organic lubricant based on the first mixed resin to the first mixed resin, melting and extruding the second mixed resin It is achieved by a method for producing a white porous polyester film comprising the step of forming a film sheet and biaxially stretching the film sheet.

In the step of forming the film sheet, the average diameter of the polyolefin in the film sheet is preferably 20 µm or less, and the average number of polyolefins in the film sheet 25,000 µm ² is preferably 50 or more.

In the biaxial stretching step, the stretching is preferably made of a stretching ratio of 2 to 5 times in both the longitudinal and transverse directions.

Hereinafter, the manufacturing method of the white porous film of the present invention and the principle of the present invention will be described in detail.

First, a polyester-based resin is prepared, and the polyester-based resin used in the present invention is polyethylene terephthalate, polyethylene naphthalate or a mixture thereof, and a glycol having a main component of an acidic component and an alkylene glycol having an aromatic dicarboxylic acid as a main component. It is manufactured by polycondensing a component.

At this time, as aromatic dicarboxylic acid, dimethyl terephthalate, terephthalic acid, isophthalic acid, dimethyl-2,5-naphthalenedicarboxylate, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyldicarboxylic acid, di Phenyletherdicarboxylic acid, anthracenedicarboxylic acid or α, β-bis (2-chlorophenoxy) ethane-4,4-dicarboxylic acid and the like can be used, among which dimethyl terephthalate, terephthalic acid or dimethyl-2,5-naphthalene Dicarboxylate is particularly preferred.

In addition, examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and hexylene glycol, and among these, ethylene glycol is particularly preferable.

The polyester resin of the present invention is prepared according to a conventional polyester synthesis method, 70% by weight or more is composed of a homopolyester of polyethylene terephthalate or polyethylene naphthalate as described above, copolymerization within a range of 30% by weight As a specific example of such copolymerization components, diols such as diethylene glycol, propylene glycol, neopentylene glycol, polyethylene glycol, p-xylene glycol, 1,4-cyclohexanedimethanol, and 5-sodium sulforezocin And polyfunctional dicarboxylic acids such as dicarboxylic acids such as adipic acid and 5-sodium sulfoisophthalic acid, trimethyl acid and pyromethyl acid.

In preparing the polyester resin of the present invention, a hindered phenol compound and an inorganic particle may be added.

The hindered phenolic compound acts as a radical chain inhibitor for the thermal oxidation of polyolefin, and is added at a ratio of 0.005 to 0.5% by weight relative to the polyester resin. If the amount is less than 0.005% by weight, the effect of improving the heat resistance of the polyolefin is extremely minimal, and if it exceeds 0.5% by weight, only the manufacturing cost is increased without further improving the thermal stability effect. As a hindered phenol type compound, tetrakis 3, 5- di- t-butyl hydroxy phenyl propanoyl oxymethyl methane, an octadecyl 3, 3, 5- di- t- butyl- 4-hydroxyphenyl propanoate , 2-hydroxy-4-n-octacybenzophenone, 2,4-di-t-butylphenyl or 3,5-di-t-butyl-4-hydroxybenzoate can be selected and used alone. Of course, you may mix and use 2 or more types.

In addition, the inorganic fine particles are added to the polyester-based resin for the purpose of adjusting optical properties such as light transmittance or color, and control of friction coefficient, surface roughness and fine touch, the particle diameter is preferably in the range of 0.1 to 10㎛, The addition amount is 0.1 to 10 weight% with respect to polyester resin, Preferably it is 0.1 to 5 weight%. If the particle size is less than 0.1㎛ the effect on the optical properties and surface properties is insignificant, and when the particle size exceeds 10㎛ the surface roughness of the film is excessively increased to give a rough feeling. In addition, when the addition amount is less than 0.1% by weight, the effect of addition is insignificant, and when the addition amount is more than 10% by weight, the optical or surface properties are inferior to obtain a paper-like texture. As a result, the pressure increase is accelerated and the life of the filter is reduced, the production efficiency is lowered, the dispersibility is worsened, the fracture is increased, and the weight is also reduced.

Examples of inorganic fine particles that can be used include titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc, zeolite and the like.

In addition, polycondensation catalysts, dispersants, electrostatic agents, crystallization accelerators, antiblocking agents and inorganic lubricants may be further added as additives in addition to the main components in the preparation of the polyester resin of the present invention. Typically, materials used for this purpose are used.

The polyolefin resin mixed with the polyester resin is preferably polymerized from one or more monomers in ethylene, propylene, butene, pentene, hexene, and octene, and in particular, polymerized with propylene as a main component and other monomers as an auxiliary component. More preferred. In addition, a melt index of 1 to 25 gr / min is effective for pore formation, and preferably 5 to 35% by weight based on the total amount of resin. When it is less than 5% by weight, the formation of pores is generally nonuniform and occupies the entire pore. If the ratio is small, the film becomes stiff, and if it exceeds 35% by weight, the formation of pores is sufficient, but the heat resistance and mechanical properties of the polyolefin is poor because the amount of the polyolefin is low, the heat resistance and mechanical properties of the resulting film is poor and the processability is also poor.

The core of the present invention is to add an organic lubricant in order to maximize the pores generated between the polyester resin and the polyolefin resin by increasing the incompatibility between them after mixing the polyester resin and polyolefin resin. The organic lubricant is added 0.1 to 1.0% by weight, more preferably 0.3 to 0.7% by weight based on the total weight of the resin. If the added amount of the organic lubricant is less than 0.1% by weight, the effect of improving the compatibility is insignificant, and there is a limit in the formation of pores, and the pores themselves are uneven, so that the pores are partially exposed or recessed in the surface, resulting in poor printability. In the case where the addition ratio of the compatibilizer is more than 1.0% by weight, the polypropylene and the polyester are similar to the continuous phase form, and almost no pores are produced.

That is, the organic lubricant used in the present invention serves to control the compatibility between the polyester resin and the polyolefin resin. In more detail, the addition of an organic lubricant increases the polyolefin resin in a small and uniformly large amount in the polyester resin and increases the contact area of the polyolefin in contact with the polyester resin, thereby increasing the total porosity and uniformly distributing these pores. . As a result, the resulting film has a lower density, resulting in lighter weight, increased flexibility of the film, and improved printability since the surface of the film is embossed.

Examples of those used as organic lubricants having such a function include ethylenebissteamide-based waxes, liquid paraffin, process oils or stearyl alcohols, which are mixed well with each other due to compatibility with polyolefin-based resins during mixing. At the time of stretching, the incompatible with the polyester resin is increased to maximize the formation of pores.

On the other hand, the organic lubricating agent of the present invention is somewhat inferior in compatibility improvement but relatively inexpensive to use a large amount can avoid the complexity of the process due to the addition of the organic lubricant. In other words, in the case of organic lubricant having high compatibility improvement effect, the desired density and flexibility can be secured even in a small amount, but the process is much more complicated for uniform compounding due to the use in a small amount. In the case of the organic lubricant of the present invention, it is possible to achieve uniform compounding even through a simple process, and it is advantageous in terms of price.

As described above, when the polyester resin, the polyolefin resin, and the organic lubricant are mixed, a mixed resin is obtained. The mixed resin is dried, melted, and extruded in the same manner as in the conventional polyester manufacturing method to obtain a film. After the sheet is obtained, the sheet is stretched 2 to 5 times, preferably 3 to 4.5 times in the longitudinal and transverse directions, respectively. If the draw ratio is smaller than this, the formation of pores is poor, the density is high, the mechanical properties and the whiteness is also reduced, while the draw ratio is larger than this, the breakage of the film increases.

The dispersion state of the polyolefin resin in the mixed resin, especially the film sheet before stretching, has a significant influence on the properties of the film finally obtained. The dispersion state of the polyolefin resin can be known by observing a compounding chip or a sheet made after remelting with an electron microscope. That is, the compounding chip or the remelted sheet can be observed using an electron microscope, and the dispersion state can be evaluated by measuring the average diameter and the number of particles of the polyolefin particles dispersed in the sheet. The number of polyolefin particles varies depending on the amount of polyolefin resin added. However, when 10 parts by weight of polyolefin resin was added, the average number of polyolefin particles in the film sheet 2500 μm ² was about 90 or more. As the average number of polyolefin particles dropped to 60-65, the improvement in flexibility was apparent with a sharp decrease in density. In addition, the average diameter of the polyolefin particles (in the case of an ellipse, the average of the long axis and the short axis) also showed an average of 10 μm or less when the amount of the polyolefin-based resin was 10 parts by weight, while an average of 20 μm was added by adding 0.3 wt% of the organic lubricant. As it grows below, the texture is improved.

As a result, when the average diameter of the polyolefin particles is 20㎛ or less, the effect of improving the uniform dispersibility and film properties is apparent. When the average number of polyolefins is ² or more in 25,000㎛ ² , the decrease in density and the improvement in flexibility are apparent.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to the following Examples. Performance evaluation of the film produced in the following Examples was carried out in the following manner.

(1) the size and number of pores

The cross section was observed using an electron scanning microscope manufactured by Jeol of Japan, and then measured using an image analyzer.

(2) Average particle diameter of inorganic fine particles

The slurry of the inorganic fine particles disperse | distributed to ethylene glycol was measured using the centrifugal particle size analyzer of Shimadzu Corporation, Japan, and is shown as a volume average particle diameter.

(3) apparent density

The density gradient tube consisting of carbon tetrachloride and n-heptane was kept at 25 ° C. and measured by the ups and downs method.

(4) breaking strength

Tensile strength of the film is measured using an Instron tensile tester (ASTM D 882).

(5) Process stability

Relative evaluation was made by measuring the frequency of breakage of the film for 12 hours during the film forming process and the discharge state and chip cutting conditions under the same process / cooling conditions during the compounding process.

Compounding Fairness:

A: Both discharge / chip cutting are good

B: One of the discharge / chip cutting conditions is bad

C: Bad discharge / chip cutting

Production Process Fairness:

A: One break occurs, B: Two to three breaks occur, C: Four or more breaks occur

(6) product grade

Overall appearance, color, glossiness, state of depression pores, size, uniformity, etc. are comprehensively evaluated and represented as "good" or "bad".

<Example 1>

Dimethyl terephthalate and ethylene glycol were mixed in a 1: 2 equivalent ratio, and then a transesterification catalyst was added to the mixture to form bis-2-hydroxyethyl terephthalate as a monomer of polyethylene terephthalate. Here, polycondensation of a titanium dioxide having a cubic crystal structure having an average particle diameter of 0.5 µm with 5 wt% of polyester, 0.05 wt% of tetrakis-3,5-di-t-butylhydroxyphenylpropanoyloxymethylmethane, and polycondensation The catalyst was added and the polycondensation was completed to prepare a polyester resin having an ultimate viscosity of 0.610 dl / gr.

90 wt% of the polyester resin thus prepared and 10 wt% of the random polypropylene-ethylene copolymer having a melt index of 4.0 were mixed, and then ethylene-bis-steamide wax (N, N'-Ethylene) was used as the organic lubricant. 0.30% by weight of Bis-Stearamide) was added to compound resin by compounding method, and dried, melted, and extruded according to the conventional polyester film production method to form a sheet, followed by longitudinal draw ratio and transverse draw ratio. The biaxially stretched polymer film having a thickness of 38 μm was prepared by stretching the vessel. The film was evaluated for properties according to the method described above for this film, and the results are shown in Table 1 below.

As shown in Table 1, the film prepared in this example had excellent processability, good texture and appearance, and good breaking strength.

<Example 2>

The same method as in Example 1 was carried out, except that polyethylenenaphthalate resin having an ultimate viscosity of 0.59 dl / gr was obtained using dimethyl-2,5-naphthalenedicarboxylate instead of dimethyl terephthalate. Polyolefin was added and 0.3 wt% of ethylene-bis-steamide wax was added as the organic lubricant, followed by the same method as Example 1 to obtain a biaxially stretched polymer film having a thickness of 38 μm. Various properties were evaluated in the same manner as described above for this film, and the results are shown in Table 1 below.

<Examples 3 and 4>

Except for changing the addition amount of the polyolefin and various additives as shown in Table 1, to obtain a polymer film in the same manner as in Example 1, and then to evaluate the properties of the film in the same manner as shown in the following table 1 is shown.

As shown in Table 1, the distribution of pores is maintained at a desirable level as long as the addition amount of various additives is maintained in a limited range in the present invention, so that both the texture and appearance of the film are good, and the weight is made to some extent and fairness It can also be seen that excellent.

<Comparative Examples 1 to 7>

A polymer film was obtained by the same method as Example 1 except that the amount of polyolefin and various additives was changed as shown in Table 1, and then the properties thereof were evaluated in the same manner. 1 is shown.

As can be seen from Table 1 below, unlike the case of the examples, when the amount of the various additives is out of the preferred range defined in the present invention, the obtained film was found to be poor in at least one or more of the various properties evaluated.

Basic resin additive Olefin Resin pore Fairness Physical properties of the final film Inorganic particles Stabilizer ¹ Lubricants ² type content Average number Average diameter Compounding Production density Product grade Breaking strength unit Kinds weight% weight% weight% Copolymerization weight% 2500 μm ² Μm - - g / cm ³ - kg / mm ² Example One PET TiO ₂ 5 0.05 0.3 PP-PE 10 60 16 A A 1.020 Good 17.5 2 PEN TiO ₂ 5 0.05 0.3 PP-PE 10 64 18 A A 0.980 Good 16.5 3 PET TiO ₂ 5 0.05 0.5 PP-PE 10 58 19 A A 0.920 Good 19.0 4 PET TiO ₂ 5 0.04 0.7 PP-PE 10 56 19 A A 0.920 Good 18.3 5 PET BaSO ₄ 5 0.05 0.9 PP-PE 10 55 18 A A 0.920 Good 17.7 Comparative example One PET TiO ₂ 5 0.05 0 PP-PE 10 89 8.2 B B 1.330 Good 22.0 2 PET TiO ₂ 5 0.05 1.5 PP-PE 10 58 19 B C 0.980 Good 17.1 3 PET TiO ₂ 5 0.05 1.5 PP 10 64 22 B B 0.920 Good 18.0 4 PET TiO ₂ 5 0.10 1.5 PE 30 54 23 C C 0.975 Bad 18.3 5 PET BaSO ₄ 15 0 0.5 PP-PE 10 55 20 B B 0.920 Bad 19.0 6 PET BaSO ₄ 15 1.0 0.5 PP 10 56 21 B B 0.900 Bad 19.5 7 PEN TiO ₂ 15 0.05 0.5 PP 10 58 18 B B 0.900 Bad 18.8

1. Stabilizer: Tetrakis-3,5-di-t-butylhydroxyphenylpropanoyloxymethylmethane

2. Lubricant: Ethylene Bissteamide Wax

As can be seen from the above, according to the present invention, by adding an organic lubricating agent that can increase the incompatibility between the polyester resin and the polyolefin resin, it is possible to obtain a white porous polyester film of light and paper-like texture, in the process The degree of process can be improved. Therefore, such a white porous polyester film can be used in various fields such as calendars, flyers, high-quality packaging, printing decorative paper, wallpaper as a substitute for paper.

Claims (12)

In a white porous polyester film made of a polyester resin and a polyolefin resin, a white containing an organic lubricant for increasing the incompatibility between the polyester resin and the polyolefin resin based on the total weight of the resin 0.1 to 1.0% by weight Porous polyester film. The method of claim 1, wherein the polyester resin is at least one selected from polyethylene terephthalate and polyethylene naphthalate, and based on the polyester resin of 0.005 to 0.5% by weight of the hindered phenolic compound and 0.1 to 10% by weight of White porous polyester film comprising inorganic fine particles. The method of claim 2, wherein the inorganic fine particles are at least one selected from the group consisting of titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc and zeolite, white porous poly, characterized in that the diameter of 0.1 to 10㎛ Ester film. According to claim 1, wherein the polyolefin-based resin is polymerized or copolymerized from at least one monomer selected from the group consisting of ethylene, propylene, butene, pentene, hexene and octene, the content is 5 to 35 weight based on the total amount of the resin % And a melt index of 1 to 25 gr / min, white porous polyester film. The white porous polyester film of claim 1, wherein the organic lubricant is at least one selected from the group consisting of ethylenebissteamide-based wax, liquid paraffin, paraffin wax, process oil, and stearyl alcohol. In the method for producing a white porous polyester film of a polyester resin and a polyolefin resin, Mixing a polyester resin and a polyolefin resin in a weight ratio of 95: 5 to 65:35 to form a first mixed resin; Forming a second mixed resin by adding 0.1 to 1.0% by weight of an organic lubricant based on the first mixed resin to the first mixed resin; Melting and extruding the second mixed resin to form a film sheet; And Biaxially stretching the film sheet, characterized in that it comprises a white porous polyester film. The method of claim 6, wherein the polyester resin is at least one selected from polyethylene terephthalate and polyethylene naphthalate, and based on the polyester resin of 0.005 to 0.5% by weight of the hindered phenolic compound and 0.1 to 10% by weight of Method for producing a white porous polyester film comprising inorganic fine particles. The method of claim 6, wherein the inorganic fine particles are at least one selected from the group consisting of titanium dioxide, barium sulfate, calcium carbonate, silica, kaolin, talc and zeolite, white porous poly, characterized in that the diameter of 0.1 to 10㎛ Method for producing an ester film. According to claim 6, wherein the polyolefin resin is polymerized or copolymerized from at least one monomer selected from the group consisting of ethylene, propylene, butene, pentene, hexene and octene, the content is 5 to 35 weight based on the total amount of the resin % And a melt index of 1 to 25 gr / min method for producing a white porous polyester film. The method of claim 6, wherein the organic lubricant is at least one selected from the group consisting of ethylene bissteamide wax, liquid paraffin, paraffin wax, process oil and stearyl alcohol. . 7. The white porous polyester according to claim 6, wherein in the forming of the film sheet, the average diameter of the polyolefin in the film sheet is 20 µm or less, and the average number of polyolefins in the film sheet 25,000 µm ² is 50 or more. Method for producing a film. The method of claim 6, wherein the biaxial stretching step is performed at a draw ratio of 2 to 5 times in both longitudinal and transverse stretching.