KR100389297B1 - White porous polyester film and its manufacturing method - Google Patents

Abstract

The present invention relates to a white porous polyester film, wherein the polyester resin has an intrinsic viscosity of 0.5 to 0.8 dL / g and 60% by weight or more of the main repeating unit is ethylene terephthalate, and a polyolefin resin having a melt index of 1.0 to 25 g / 10 minutes. And a nonionic antistatic agent, wherein the polyolefin resin is 5 to 35% by weight based on the total resin, and the antistatic agent is 0.1 to 2.5% by weight relative to the polyether resin. And a method for producing the same. The white porous polyester film of the present invention has a property different from that of a conventional polyester film in density and texture, and is useful as a substitute substrate of general pulp paper as a synthetic paper having durability.

Description

White porous polyester film and its manufacturing method

The present invention relates to a white porous polyester film and a method of manufacturing the same, and more particularly, to a white porous polyester film and a method of manufacturing the same, which are beautiful in appearance and have improved whiteness, apparent density, dispersibility, and antistatic properties.

Generally, polyolefin films containing inorganic fine particles have been used as substrates for paper substitutes. However, polyolefin films have limited mechanical strength, heat resistance, weather resistance, and numerical stability. It is a trend to use as a substitute for paper.

Polyester is widely used in the manufacture of medical and various industrial products due to its physical and chemical stability, high mechanical strength, excellent heat resistance, durability, chemical resistance, and electrical insulation. Among them, polyethylene terephthalate films are particularly widely used in magnetic recording media, capacitors, photographic films, industrial products, packaging materials, labeling products, graphic arts products, and other various applications due to their excellent properties such as elastic modulus, dimensional stability, and diactivation. In addition, as a substitute for paper, various cards (credit cards and communication cards), label supplies, printer award papers, barcode printer award papers, posters, calendars, maps, dust-free paper, display boards, white boards, photo papers, and copy papers And the proportion used for special purpose printed publications is increasing.

However, the polyester film is too stiff to be used as a substitute for paper, and the texture is different from that of paper, and it does not give a paper-like feeling in terms of transparency and color, and because the density of the polyester itself is heavy, There is a disadvantage that it is inconvenient to store and use a large amount.

Therefore, attempts have been actively made to develop a lightweight film having a soft texture such as paper while utilizing the excellent properties of the existing polyester film. For example, Japanese Patent Application Laid-Open No. 87-243120 and No. 90-206622 describes a method of adding inorganic particles to polyester, and Japanese Patent Laid-Open No. 83-50625 discloses a method for reducing the weight of polyester by blending a blowing agent to polyester. Publications 82-49648 and 88-68441 describe a method of blending and stretching a polyolefin resin in polyester to form fine pores on the surface and inside of the film to improve the surface properties of the film and at the same time reduce the weight. .

However, these conventional techniques have the following disadvantages. First, in the case of producing a film by adding a large amount of inorganic particles, the specific gravity of polyester is increased, so that the weight of the film is not easy, and when the film is prepared by mixing a blowing agent, the dispersibility of bubbles is poor and the particle size of the inorganic material to be added. It is difficult to control the physical properties of the film is difficult to control. In addition, the method of dry blending polyolefin resin to polyester has a large amount of static electricity generated due to the characteristics of polyolefin, which causes loss of information when used for high-level information recording such as magnetic cards, and difference in molding process temperature of polyester during extrusion. Is too large to cause thermal aging of the polyolefin, so the mechanical properties of the final film are very degraded, the color of the film is yellowed, and the glossiness of the film surface is too large to lose the luxury.

The technical problem to be achieved by the present invention, by maximizing the dispersibility of the polyolefin resin in the polyester resin, improved physical properties, paper-quality texture, excellent mechanical properties and excellent antistatic function, lightweight lightweight substitutes It is to provide a white porous polyester film that can be usefully used as a substrate and a method for producing the same.

In order to achieve the above technical problem, in the present invention, a polyester resin having an intrinsic viscosity of 0.5 to 0.8 dL / g and at least 60% by weight of the main repeating unit is ethylene terephthalate, a polyolefin resin having a melt index of 1.0 to 25 g / 10 minutes, and It provides a white porous polyester film comprising a nonionic antistatic agent, wherein the polyolefin resin is 5 to 35% by weight based on the total resin, and the antistatic agent is 0.1 to 2.5% by weight relative to the polyester resin. do.

In addition, in the present invention to achieve another technical problem of the present invention,

(a) a polyester resin comprising 0.1 to 2.5% by weight of an antistatic agent, based on a polyester resin, having an ultimate viscosity of 0.5 to 0.8 dL / g and at least 60% by weight of the main repeating unit consisting of ethylene terephthalate, Mixing a polyolefin resin having a melt index of 1.0 to 25 g / 10 minutes in a weight ratio of 95: 5 to 65:35 to form a mixed resin;

(b) drying the mixed resin under the following conditions;

T _m (PO)-10 〈T ₁ 〈T _m (PO) + 10

2 <t _d <4, degree of vacuum: 10mmHg

In the above formula, T _m (PO) is the melting temperature (° C.) of the polyolefin resin, T ₁ is the temperature (° C.) of the resin in the dryer, and t _d represents the drying time (hr).

(c) melt-extruding the dried resin under the following conditions to form a film sheet; And

Where T _m (PET) is the melting temperature (° C.) of the polyester resin, T ₂ is the temperature (° C.) of the molten resin in the melt extruder, and T ₃ represents the temperature (° C.) of the melt extrusion die.

(d) biaxially stretching the unstretched film sheet provides a method for producing a white porous polyester film, the method comprising:

Hereinafter, the main components and the manufacturing method of the polyester film of the present invention will be described in detail.

The polyester used for the white porous polyester film of this invention can be obtained by polycondensing a polyhydric organic acid component and a polyhydric alcohol component.

The organic acid is preferably carboxylic acid and more preferably aromatic dicarboxylic acid, and specific examples thereof are methyl terephthalic acid, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid and diphenoxy. Ethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenylether dicarboxylic acid, anthracene dicarboxylic acid and α, β-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid Of these, dimethyl terephthalic acid and terephthalic acid are preferable.

The alcohol is preferably glycol and more preferably alkylene glycol, specific examples of which are ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and hexylene glycol, with double ethylene glycol being preferred. Do.

The polyester preferably has an intrinsic viscosity of 0.5 to 0.8 dL / g.

In addition, the polyester is 60% by weight or more of the homopolyester of polyethylene terephthalate is copolymerizable within 40% by weight. The copolymer component is preferably a diol compound such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, para-xylene glycol, 1,4-cyclohexane dimethanol and the like; Dicarboxylic acids such as adipic acid, sodium 5-sulfoisophthalic acid, and the like; And polyfunctional carboxylic acids such as trimellitic acid, pyromellitic acid and the like.

The polyolefin resin used in the white porous polyester film of the present invention is polymerized or copolymerized from at least one monomer selected from olefinic compounds having a melt index of 1.0 to 25 g / 10 minutes, preferably homo polyethylene, block polypropylene, Random polymethylpentene and mixtures thereof. The monomer is also preferably at least one monomer selected from the group consisting of ethylene, propylene, butene, pentene, hexene and octene.

When the polyolefin resin is mixed with polyester and extruded and stretched, fine pores are formed on the surface and inside of the film due to incompatibility between the two resins, and thus, the surface properties of the film can be improved and lightened simultaneously using these properties. have.

The content of the polyolefin resin is preferably 5 to 35% by weight and more preferably 8 to 20% by weight based on the total resin. If the content of the polyolefin is less than 5% by weight can not be achieved, while the content of more than 35% by weight is poor dispersibility and texture of the film.

The antistatic agent used in the white porous polyester film of the present invention is added to the polyester resin to not only impart excellent antistatic properties to the film, but also increase the surface tension of the film to improve adhesion to ink and coating liquid. In recent years, there is a characteristic of removing static electricity that adversely affects the loss of recorded information in information recording applications such as magnetic cards.

The antistatic agent is preferably N, N-bis (2-hydroxyethyl) alkylamine, oleic acid monoglyceride, oleic acid diglyceride, stearic acid monoglyceride, stearic acid diglyceride, polyoxyethylene sorbitan fatty acid ester, Nonionic compounds, such as polyoxyalkylphenyl ether and polyethyleneglycol fatty acid ester, are used alone or in combination.

In the white porous polyester film of the present invention, inorganic fine particles may be added for the purpose of adjusting optical properties such as light transmittance or color, and controlling friction coefficient, surface roughness and fine touch, and the inorganic fine particles are preferably Barium sulfate, titanium dioxide, calcium carbonate, silicon dioxide, calcium carbonate, magnesium oxide, talc or mixtures thereof.

The average particle diameter and the addition amount of the inorganic fine particles may be changed depending on the thickness and the use in the final film, the average particle diameter of the inorganic fine particles is preferably 0.1 to 10㎛ and more preferably 0.1 to 3㎛. If the average particle diameter is less than 0.1㎛ the effect on the optical properties and surface properties is insignificant, while if the average particle diameter exceeds 10㎛ because the surface roughness of the film is excessively increased to give a rough feeling. In addition, the paper substitute polyester film is more preferably not more than 3㎛ because when it exceeds 3㎛ the effect of giving a texture such as paper is inferior.

The amount of the inorganic fine particles added is preferably 1.0 to 15% by weight based on the polyester resin. If the added amount exceeds 15% by weight, mechanical properties such as strength and flexibility of the film are lowered, and a large amount of inorganic material causes a problem such as an increase in the pressurization pressure of the filter and a film breaking during the polyester film manufacturing process. On the other hand, if the dose is less than 1.0% by weight, the light transmittance of the final film is increased, the shielding is poor and the whiteness is low, the color is not good.

The hindered phenolic compound may also be added to the white porous polyester film of the present invention for the purpose of inhibiting the radical chain reaction of the thermal oxidation of the polymer resin.

The amount of the hindered phenol compound added is preferably 0.005 to 0.5% by weight based on the polyester resin. If the amount is less than 0.005% by weight, the effect of improving the heat resistance of the polyolefin is very minimal, and if it exceeds 0.5% by weight, the thermal stability effect is no longer improved, but only the cost increases.

The hindered phenol compound is preferably tetrakis 3,5-di-t-butylhydroxyphenylpropanoyloxymethylmethane, octadecyl 3,3,5-di-t-butyl-4-hydroxy Phenylpropanoate, 2-hydroxy-4-n-octacybenzophenone, 2,4-di-t-butylphenyl or 3,5-di-t-butyl-4-hydroxybenzoate, the compound These are used alone or in combination of two or more.

In addition, a polycondensation catalyst, a dispersant, an electrostatic agent, a crystallization accelerator, a nucleating agent, an antiblocking agent, and the like can be added to the white porous polyester film of the present invention by an effective amount within a range that does not impair the effects of the present invention.

In order to prepare the white porous polyester film of the present invention, first, by the general polyester synthesis method, the ultimate viscosity is 0.5 to 0.8 dL / g and 60 wt% or more of the main repeating unit is made of ethylene terephthalate and is within 40 wt%. To prepare a polyester resin copolymerized in. At this time, 0.1 to 2.5% by weight of the antistatic agent on the basis of the polyester resin is mixed with the polyester resin, in addition to the above-described inorganic fine particles or hindered phenolic compound may be mixed.

The polyester resin and the polyolefin resin having a melt index of 1.0 to 25 g / 10 minutes are mixed at a weight ratio of 95: 5 to 65:35, and melt-extruded through a direct extruder to prepare a primary mixed resin by compounding.

Next, the mixed resin is sufficiently dried in the range satisfying the following conditions.

T _m (PO)-10 〈T ₁ 〈T _m (PO) + 10

2 <t _d <4, degree of vacuum: 10mmHg

In the above formula, T _m (PO) is the melting temperature (° C.) of the polyolefin resin, T ₁ is the temperature (° C.) of the resin in the dryer, and t _d represents the drying time (hr). In this step, if the drying is not sufficiently carried out, the water content in the resin is increased to cause the hydrolysis of the polyester resin to cause stretching is impossible, if the drying time is longer than necessary or the drying temperature is high deterioration of the polyolefin resin Discoloration occurs.

Next, the dried resin is melt-extruded under conditions satisfying all of the following conditions to form a film sheet.

In the above formula, T _m (PET) is the melting temperature (° C.) of the polyester resin, T ₂ is the temperature (° C.) of the molten resin in the melt extruder, and T ₃ represents the temperature (° C.) of the melt extrusion die.

As can be seen from the above formula, the temperature (T ₁ ) of the molten resin in the melt extruder should be set to 10 to 55 ℃ higher than the melting temperature of the polyester resin, and at the same time 105 to 150 ℃ higher than the melting temperature of the polyolefin resin. . Melting temperature of the conventional polyester resin is 250 to 260 ℃, if the temperature of the molten resin is not more than 10 ℃ higher than this, a large amount of cosmetic melt of the polyester resin is generated, it is impossible to obtain a uniform sheet, 55 ℃ If it is too high, the melt viscosity of the relatively high viscosity polyolefin resin does not decrease significantly with increasing temperature, whereas the melt viscosity of the relatively low viscosity polyester resin decreases greatly, so that the difference in the melt viscosity between the two resins increases. The dispersibility of the polyolefin resin in the polyester resin is extremely reduced, and a sheet having good mixing properties cannot be obtained.

Similarly, the temperature of the molten resin in the melt extruder should be set 105 to 150 ° C. higher than the melting temperature of the polyolefin resin. Therefore, for example, in the case of polypropylene having a melting temperature of 150 to 170 ° C, the temperature of the molten resin should be set to 255 to 320 ° C.

The temperature (T ₂ ) of the melt extrusion die should be set to 10 to 60 ° C. higher than the melting temperature of the polyester resin, so that the balance of the resin temperature in the melt extruder can be maintained in the die as described above. This is because the melt viscosity of the polyolefin resin and the polyester resin is different in temperature dependency.

Finally, the unstretched sheet is stretched in the longitudinal and transverse directions using a conventional biaxial stretching method to produce a white porous polyester film of the present invention. At this time, the draw ratio is preferably 2.5 to 6 times. If the draw ratio is too small, the formation of pores is poor, the specific gravity is high, the mechanical properties are insufficient, and the whiteness is decreased. On the other hand, when the draw ratio is too large, the film breakage phenomenon appears frequently. to be.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are intended to illustrate the present invention, and the present invention is not limited to the following Examples. In Examples and Comparative Examples of the present invention, various performance evaluation of the produced film was carried out by the following method.

(1) apparent density

The density gradient tube consisting of carbon tetrachloride and xylene was maintained at 25 ° C. and measured by ups and downs.

(2) breaking strength

The breaking strength of the film was measured for tensile strength of the film according to ASTM D 882 using UTM4206 from Instron.

(3) whiteness

The whiteness of the film was determined by reflecting the reflectance B% at 450 nm and the reflectance G% at 550 nm according to the method of JIS-1015, and then determining the whiteness according to the following formula.

Whiteness = 4B-3G

(4) color b value (yellowness)

The color b value was measured at a measurement angle of 2 ° using a light source color difference meter (model name: SZS-∑ 80) of Nippon Denshi Kogyo Co., Ltd. as a measurement light source.

(5) dispersibility

The dispersion state and uniformity of the pores with respect to the polyester inside the film were evaluated by observing with an electron microscope (SEM).

(6) texture

The softness of the film was observed by touch and visual observation.

(7) appearance

Thickness uniformity and color and color uniformity of the film were visually determined.

(8) Antistatic characteristics

Surface resistance (unit; Ω) was measured using Hewlett-Packard's insulation resistance meter (20 ° C, 65% relative humidity, applied voltage 500V), and then the antistatic specifications were evaluated based on the following criteria.

Good: Surface resistance is less than 10 ¹² Ω

Poor: Surface resistance over 10 ¹² Ω

(9) process stability

The frequency of breakage of the film was measured for 24 hours and classified into A, B, C and D based on the following criteria.

A: 1 time or less

B: 5 times or less

C: 10 times or less

D: more than 10 times

<Example 1>

After mixing dimethyl terephthalate and ethylene glycol in an equivalence ratio of 1: 2, by adding 0.05% by weight of manganese acetate, which is a transesterification catalyst, a polyethylene terephthalate monomer, that is, bis-2-hydroxyethylene terephthalate Was prepared. Based on 100% by weight of polyester resin, 5% by weight of titanium dioxide having a cubic crystal structure having an average particle diameter of 0.5 µm and 1.0% by weight of NN-bis (2-hydroxyethyl) alkylamine as an antistatic agent were added thereto. Next, a polycondensation reaction was carried out using 0.04% by weight of antimony trioxide as a polycondensation reaction catalyst to prepare a solidified copolymerized polyester resin having an intrinsic viscosity of 0.60 dL / g (high intrinsic viscosity of 0.630 dL / g and a melting temperature of 256 ° C.). It was.

Next, the obtained polyester resin and the homopolypropylene resin for sheet formation having a melt index of 5.0 g / 10 minutes and a melting temperature of 161 ° C. were mixed so as to have a weight ratio of 85:15. Tea mixed resin was prepared.

Next, the mixed resin was dried in a dryer at 160 ° C. for 4 hours, and a sheet was formed by adjusting the temperature of the melt resin to 285 ° C. and the temperature of the melt extrusion die to 290 ° C. using a melt extruder.

Next, a biaxially stretched polyester film having a thickness of 100 μm was prepared by longitudinal stretching and transverse stretching of the sheet at a draw ratio of 3.5: 1. The film was evaluated for physical properties according to the method described above, and the results are shown in the following [Table 1]. As can be seen in Table 1, the physical properties of the produced film were all good.

<Examples 2 to 6>

A white porous polyester film was prepared in the same manner as in Example 1, except that the final addition amount of the inorganic fine particles and the antistatic agent was changed as shown in Table 1 below, to obtain a white porous polyester film. The physical properties were evaluated and the results are shown in the following [Table 1]. As can be seen from Table 1, the physical properties of the produced film were generally good.

<Comparative Examples 1 to 12>

A white porous polyester film was prepared by the same method as in Example 1, except that the polypropylene content, the inorganic fine particles and the amount of addition of the antistatic agent were changed as shown in Table 1 below. The physical properties of the film were evaluated according to the following [Table 1]. As can be seen in Table 1, the physical properties of the produced film are poor in density, breaking strength, whiteness, color b value, dispersibility, texture, appearance, antistatic properties or process stability depending on the conditions.

TABLE 1

(A) Titanium dioxide (average particle size 0.5 mu m, cubic crystal structure)

(B) antistatic agent

As can be seen from the above, the white porous polyester film of the present invention prepared by adding a polyolefin resin, an inorganic fine particle and an antistatic agent to a polyester resin component is different from a conventional polyester film in terms of density and texture. Has different properties. Therefore, the white porous polyester film of the present invention is useful as a substitute substrate for general pulp paper as a durable synthetic paper.

Claims (3)

In the manufacturing method of the white porous polyester film containing a polyester resin and a polyolefin resin, (a) a polyester resin comprising 0.1 to 2.5% by weight of an antistatic agent based on a polyester resin, an intrinsic viscosity of 0.5 to 0.8 dL / g, and at least 60% by weight of the main repeating unit consisting of ethylene terephthalate, Mixing a polyolefin resin having a melt index of 1.0 to 25 g / 10 minutes in a weight ratio of 95: 5 to 65:35 to form a mixed resin; (b) drying the mixed resin under the following conditions; T _m (PO)-10 <T ₁ 〈T _m (PO) + 10 2 <t _d <4, degree of vacuum: 10mmHg In the above formula, T _m (PO) is the melting temperature (° C.) of the polyolefin resin, T ₁ is the temperature (° C.) of the resin in the dryer, and t _d represents the drying time (hr). (c) melt-extruding the dried resin under the following conditions to form a film sheet; And Where T _m (PET) is the melting temperature (° C.) of the polyester resin, T ₂ is the temperature (° C.) of the molten resin in the melt extruder, and T ₃ represents the temperature (° C.) of the melt extrusion die. (d) biaxially stretching the unstretched film sheet at a draw ratio of 2.5 to 6 times in the longitudinal and transverse directions, respectively. The method of claim 1, wherein the polyester resin of step (a) is 0.005 to 0.5% by weight of the hindered phenolic compound or 0.1 to 10% by weight of the average particle diameter of 0.1 to 10㎛ based on the polyester resin The manufacturing method characterized by further including an inorganic fine particle. The method according to claim 1 or 2, wherein the polyester resin is at least one selected from polyethylene terephthalate and polyethylene naphthalate, 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, Wherein said polyolefin resin is polymerized or copolymerized from at least one monomer selected from the group consisting of ethylene, propylene, butene, pentene, hexene and octene.