KR0164896B1 - Bi-axially oriented polyester film - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester film with improved surface properties, abrasion resistance and scratch resistance, 0.01 to 4% by weight of hard calcium carbonate having an average particle diameter of 0.01 to 3㎛ and moss (Mohs) of 6 or more ) A biaxially oriented polyester film having a hardness and 0.01 to 4% by weight of theta alumina having an average particle diameter of 0.005 to 3 μm surface-treated with a silane coupling agent can be prepared to improve surface properties, abrasion resistance, scratch resistance, and high-speed running resistance. Can be.

Description

Biaxially Oriented Polyester Film

The present invention relates to a biaxially oriented polyester film, and more specifically, to the polyester for forming a film, the addition of hard calcium carbonate and theta alumina surface treated with a silane coupling agent improves the surface properties, wear resistance and scratch resistance. A biaxially oriented polyester film.

Polyester, especially polyethylene terephthalate, is chemically and physically stable, especially high in mechanical strength during biaxial stretching, and excellent in heat resistance, durability, chemical resistance, electrical insulation, and the like for medical devices, magnetic recording media, capacitors, and photographs. It is widely used in the manufacture of various molded products as well as films, industrial products, packaging materials and labels.

In order to impart runability, processability and surface properties to a film made from such polyester, inorganic materials such as calcium carbonate, silica and kaolin are added as lubricants to form irregularities on the surface of the polyester film. However, among these inorganic lubricants, calcium carbonate, especially hard calcium carbonate, has an excellent effect on controlling the surface properties of the polyester film, but its hardness is low, causing particles to fall off due to wear during running of the film and scratches on the surface of the film. When manufactured with a magnetic tape there is a problem such as causing a drop-out (drop-out).

In addition, as a conventional polyester film production technology for improving the scratch resistance of a polyester film, Japanese Laid-Open Patent Publication No. 90-214734 uses a mixture of hard calcium carbonate and α, γ, and δ-type aluminas having low hardness. To improve the surface and wear resistance of the film and to prevent falling particles from scratching. However, the lubricant is difficult to prepare a high concentration slurry due to the central phenomenon in the production of a slurry, the viscosity has been raised a problem that the stability of the slurry is lowered.

Therefore, the present inventors have been studied to solve the above problems and to improve the surface properties, abrasion resistance and scratch resistance of the polyester film, as a result of surface-treated with a hard calcium carbonate, and a silane coupling agent to the film forming polyester By adding together theta alumina, it has been found that a film satisfying the above conditions can be produced to complete the present invention.

Accordingly, it is an object of the present invention to provide a biaxially oriented polyester film having excellent surface properties and scratch resistance when running, as well as improved wear resistance.

According to the present invention, in order to achieve the object of the present invention, 0.01 to 4% by weight of hard calcium carbonate having an average particle diameter of 0.01 to 3 μm and a Mohs hardness of 6 or more and are surface treated with a silane coupling agent of the following general formula Provided is a biaxially oriented polyester film having improved surface properties, abrasion resistance and scratch resistance, containing 0.01 to 4% by weight of theta alumina having an average particle diameter of 0.005 to 3 mu m:

In the above formula,

R ₁ is Methacryl group, formula Or an organic functional group such as an epoxy group or an amino group of formula -NH ₂ , R ₂ is an alkyl group, and OR ₃ is a hydrolyzable alkoxy group such as methoxy or ethoxy.

In the preparation of the polyester film according to the present invention, theta alumina surface-treated with a silane coupling agent is the silane in an amount of 0.05 to 5% by weight based on the weight of the lubricant added after theta alumina is dispersed in ethylene glycol. By adding a coupling agent to the surface treatment on the ethylene glycol slurry, the dispersibility of the alumina lubricant can be improved to improve the overall processability and the surface properties of the film.

The polyesters of the present invention comprise at least 80 mole% of ethylene terephthalate repeating units and the remaining amount of other copolymerized components as dicarboxylic acid components or oxycarboxylic acid components. As said dicarboxylic acid component, isophthalic acid, para-betaoxyethoxy benzoic acid, 2, 6-naphthalene dicarboxylic acid, 4, 4'- dicarboxy diphenyl, 4, 4'- dicarboxy benzophenone, bis (4-carboxyl) Diphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, and the like, and oxycarboxylic acid components include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, para And oxybenzoic acid.

The polyester is typically polyethylene terephthalate obtained by polycondensing dimethyl terephthalate and ethylene glycol. In the preparation of the polyester, either a transesterification method or a direct polymerization method may be applied, and the reactor may be either a batch type or a continuous type.

When carried out by the transesterification method, there is no restriction on the transesterification catalyst, and any conventionally known one can be used. For example, the transesterification catalyst may be selected from among alkaline earth metal compounds such as magnesium compounds, calcium compounds and barium compounds, zirconium compounds, sodium compounds, potassium compounds, cobalt compounds, zinc compounds and manganese compounds that are soluble in the reaction system. use.

The polymerization catalyst is also not limited and may be appropriately selected and used among antimony compounds, germanium compounds and titanium compounds.

The average particle diameter of the hard calcium carbonate used as the inorganic lubricant in the present invention is in the range of 0.01 to 3 µm, preferably 0.2 to 2.0 µm. If the average particle diameter of the hard calcium carbonate is less than 0.01 μm, the surface roughness of the film is lowered, so that the friction coefficient is increased, so that the running performance is lowered.

The hard calcium carbonate is added in an amount of 0.01 to 4% by weight, preferably in an amount of 0.05 to 2% by weight. If the added amount is less than 0.01% by weight, the running friction coefficient becomes high, resulting in poor workability, and when added to more than 4% by weight, coarse particles are formed due to the flocculation phenomenon of the lubricant, so that the dropout phenomenon occurs when the magnetic tape is manufactured. Not desirable

Theta alumina used as another lubricant in the present invention preferably has an average particle diameter in the range of 0.005 to 3 µm, preferably 0.01 to 1.5 µm. If the average particle size is less than 0.005㎛ the surface roughness of the film is lowered because the friction coefficient is increased, the running performance is lowered, if larger than 3㎛ the surface properties of the film is poor when produced with a magnetic tape. The lubricant is added in an amount of 0.01 to 4% by weight, preferably 0.05 to 2% by weight. When the lubricant is added in an amount of less than 0.01% by weight, the running friction coefficient is increased, resulting in poor workability. Acidity is poor and the physical properties of the film are degraded.

The theta alumina lubricant is surface treated with a silane coupling agent, theta alumina is dispersed in ethylene glycol, and then surface treated on an ethylene glycol slurry by adding a silane coupling agent of the following general formula:

In the above formula,

R ₁ is Methacryl group, formula Or an organic functional group such as an epoxy group or an amino group of formula -NH ₂ , R ₂ is an alkyl group, and OR ₃ is a hydrolyzable alkoxy group such as methoxy or ethoxy.

Preferred silane coupling agents for use in the present invention are compounds of the above general formula wherein R ₁ is a methacryl group or an epoxy group and OR ₃ is methoxy, or R ₁ is an amino group and OR ₃ is methoxy or ethoxy.

The amount of the silane coupling agent used in the present invention is in the range of 0.05 to 5% by weight, preferably 0.1 to 5% by weight based on the weight of the alumina lubricant. If the added amount is less than 0.05% by weight, the surface treatment effect is not large, and when added to more than 5% by weight, the dispersibility is poor due to the increase in viscosity of ethylene glycol and the physical properties of the film is considerably degraded. The process of adding the silane coupling agent to the ethylene glycol slurry of the lubricant is preferably carried out under stirring at 30 to 160 ° C, preferably 30 to 120 ° C after mixing and stirring the slurry of the lubricant. If the temperature is less than 30 ° C, the surface treatment effect is lowered, if higher than 160 ° C agglomeration phenomenon of the lubricant is not preferable.

The lubricants added in the preparation of the polyester film of the present invention may use a dispersant to prepare an ethylene glycol slurry. For example, soluble in ethylene glycol is selected and used among dispersants such as acryl-based compounds such as sodium polyacrylate, sodium methacrylate and ammonium acrylate, and benzenesulfonate-based compounds.

The method for producing the polyester film of the present invention is not particularly limited, and the polyester having a molecular weight of about 20,000 including the additives is melt-extruded by a conventional method by a T-die method or the like to form an unstretched sheet, and then the sheet The biaxially stretched to produce the polyester film of the present invention uniaxially oriented. The stretching process is carried out at a stretching ratio of 2.5 to 6.0 times in the longitudinal and transverse directions, respectively, at a stretching temperature of 60 to 150 ° C., in accordance with a conventional polyester film stretching process.

The polyester film prepared according to the present invention can be produced in an appropriate thickness depending on the use, but usually has a thickness of 2.0 to 200㎛.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these 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) the average particle diameter of the particles

The average particle diameter of the lubricants was measured as a weight average particle diameter of the ethylene glycol slurry using a centrifugal particle size analyzer manufactured by Shimadzu, Japan.

(2) viscosity

Using a Brookfield viscometer, the viscosity of the ethylene glycol slurry was measured at a spindle speed of 60 rpm at room temperature.

(3) molecular weight

The molecular weight of the polyester was measured using a molecular weight measuring apparatus manufactured by Waters, using meta-cresol as the mobile phase, and measured the molecular weight of the polymer at a column temperature of 100 ° C. and a flow rate of 1 ml / min.

(4) surface smoothness

The surface roughness of the film of length 30mm, width 20mm, and thickness 15micrometer was measured using the surface roughness meter at the contact of Kosaka Research Institute of Japan. Center line average roughness (Ra): When a straight line parallel to the average line of the roughness curve is drawn, it is the height of the straight line where both areas of the straight line are equal. Center line maximum height (Rt): The distance between the highest point and the lowest point in the measurement section. The lower the average roughness and the maximum height, the better the smoothness and the better the cohesiveness.

(5) wear resistance

Using a tape running tester of Yokohama System Institute, Japan, the tape with 2/1 inch width of the film was run twice at a driving speed of 3.3 cm / sec, and then the degree of powder formation on the surface of the guide pin was measured. Observation under a microscope evaluates the wear resistance according to the following criteria.

◎: When there is no powder at all on the guide pin surface.

(Circle): When powder generate | occur | produces on 20% of the guide pin surfaces.

(Triangle | delta): When white powder generate | occur | produces on 50% of the guide pin surface.

X: When white powder generate | occur | produces the whole guide pin surface.

(6) scratch resistance

Using a tape runability tester of the Yokohama Systems Research Institute, Japan, a tape with 2/1 inch width of silited tape was run twice at a running speed of 3.3 cm / sec, and the degree of scratches on the surface of the film was observed under a microscope. The scratch resistance is evaluated according to the following criteria with or without scratch lines on the film surface.

(Double-circle): When two or less scratch lines were produced | generated on the film surface.

(Circle): when 3-4 scratch lines were produced on the film surface.

Δ: when 5 to 6 scratch lines were produced on the film surface.

X: When seven or more scratch lines were produced on the film surface.

[Examples 1 to 4]

Dimethyl terephthalate and ethylene glycol were subjected to transesterification in a conventional manner in a continuous reactor in the presence of a transesterification catalyst. The obtained transesterification product, the hard calcium carbonate each having the average particle diameter and amount shown in Table 1, and the theta alumina lubricant treated with the silane coupling agent were introduced into the polycondensation reactor step by step into the polycondensation catalyst in the presence of the polycondensation catalyst. The reaction yielded a polyester polymer having a molecular weight of about 20,000.

The obtained polymer was melt-extruded and molded into a non-stretched sheet by a conventional method, and stretched at a stretch ratio of 3.0 times in the longitudinal and transverse directions at 90 ° C., respectively, to prepare a biaxially stretched film having a thickness of 15 μm. Various performance evaluations were performed.

Performance evaluation results of the film are shown in Table 1 below.

[Comparative Examples 1 to 9]

Except for using the lubricants as shown in Table 1 in the amount shown in Table 1, the polyester film was prepared in the same manner as in Examples 1 to 4 to perform a performance evaluation. The results are shown in Table 1 below.

◎: Excellent, ○: Good, △: Normal, ×: Poor

*: Gamma alumina viscosity, **: delta alumina viscosity, ***: theta alumina viscosity (based on 20% by weight of slurry)

@: Amino silane (0.3 wt%), @@: methacryl silane (@@ : 0.4 wt%, @@ : 0.2 wt%), @@@: Epoxy group silane (0.6 wt%)

As can be seen from Table 1, the biaxially oriented polyester film of the present invention containing hard calcium carbonate and theta alumina lubricant surface treated with a silane coupling agent has excellent surface properties, abrasion resistance, and scratch resistance, and thus is a magnetic recording medium. It can be useful for tape.

Claims (2)

Theta alumina having an average particle diameter of 0.01 to 3 µm 0.01 to 4% by weight of hard calcium carbonate and an Mohs hardness of 6 or more and surface treated with a silane coupling agent of the following general formula in ethylene glycol slurry: Biaxially oriented polyester film, characterized in that it contains from 4% by weight to: In the above formula, R ₁ is Methacryl group, formula Is an epoxy group or an amino group of the formula -NH ₂ , R ₂ is an alkyl group, and OR ₃ is an alkoxy group. The polyester film according to claim 1, wherein the theta alumina is surface treated by adding a silane coupling agent in an amount of 0.05 to 5% by weight based on the weight of the lubricant.