KR0157092B1 - Process for making biaxially oriented polyester film and film thereof - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester film and a method for producing the same. At least one alumina selected from the group consisting of gamma, delta, and theta alumina having an average particle diameter of 0.005 to 3 µm and a Mohs hardness of 6 or more based on the weight of the polyester in the polyester having 80% or more of the main repeating units 0.01 to 4% by weight, 0.01 to 4% by weight of spherical silica having an average particle diameter of 0.1 to 1㎛ and at least one silane coupling agent selected from the group represented by the following formula 0.05 to 5% by weight based on alumina Biaxially oriented polyester film, characterized in that it contains excellent surface smoothness and transparency and is particularly suitable for use in labels, solar control, glass protection, photo protection and the like.

Provided that RI in the silane compound is an alkyl group.

Description

Biaxially Oriented Polyester Film And Method Of Making The Same

The present invention relates to a biaxially oriented polyester film and a method for producing the same, and more particularly, to a biaxially oriented polyester film and a method for producing the same having improved surface properties and transparency.

Polyester, which is represented by polyethylene terephalate, has a high mechanical strength because of its stable chemical structure, and is excellent in heat resistance, durability, chemical resistance, etc., and is suitable for condenser, medical, industrial, packaging, photo film, label, etc. It is widely used in various fields, such as the base material of magnetic recording media as well as a dragon.

Particularly, when used for film, the slip and wear resistance become a big factor in determining the quality of each film and the quality of the manufacturing process. Therefore, the characteristics such as wear resistance and slippage are improved for the production of high quality products. Needs to be.

In order to impart runability, processability and surface properties to such a polyester film, a method of forming irregularities on the surface of a polyester film by adding inorganic materials such as calcium carbonate, silica and kaolin as a lubricant is used. Among these inorganic lubricants, calcium carbonate, silica, and the like have an excellent effect on the surface characteristics of the polyester film, and act to reduce the transparency of the polyester film.

That is, since calcium carbonate has a higher density than polyester, the refractive index difference with polyester is large. This causes the light through the polyester film containing calcium carbonate to be refracted, dispersed and scattered, making the film opaque.

Since silica is smaller than the density of calcium carbonate, the refractive index is small, but there is a problem in that haze is raised due to generation of aggregated particles due to poor dispersibility.

As such, lubricants used to impart surface properties to the polyester film may degrade the transparency of the polyester film, preventing it from being used for labels, solar controls, safety windows, and photo resists. There is a problem.

Accordingly, an object of the present invention is to provide a polyester film having improved surface properties and transparency by improving dispersibility of an inorganic lubricant.

In order to achieve the above object, in the present invention, at least 80% of the main repeating units in the polyester made of ethylene terephthalate are gamma, delta and theta alumina having an average particle diameter of 0.005 to 3 μm and a Mohs hardness of 6 or more based on the weight of the polyester. 0.01 to 4% by weight of at least one alumina selected from the group consisting of, 0.01 to 4% by weight of the spherical silica having an average particle diameter of 0.1 to 1㎛ and at least one silane coupling agent selected from the group represented by the following formula It provides a biaxially oriented polyester film comprising 0.05 to 5% by weight based on alumina.

Provided that RI in the silane compound is an alkyl group.

Another object of the present invention is to provide a polyester film having improved surface properties and transparency by improving dispersibility of an inorganic lubricant.

In order to achieve the above object, in the present invention, at least one selected from the group consisting of gamma, delta, and theta alumina having an average particle diameter of 0.005 to 3 μm and a Mohs hardness of 6 or more is dispersed in an ethylene glycol slurry. Adding at least one silane coupling agent selected from the group represented by the formula to 0.05 to 5% by weight based on the weight of the alumina to surface-treat the alumina, and the surface-treated ethylene glycol slurry during the polyester condensation polymerization reaction. And 0.01 to 4% by weight based on the spherical silica polyester polymer having an average particle diameter of 0.1 to 1 μm to obtain a polyester polymer, and biaxially stretching the polyester polymer obtained by the polycondensation reaction. However, the addition amount of the alumina It provides a method of producing a biaxially oriented polyester film to be 0.01 to 4% by weight, based on the polyester polymers.

Provided that RI in the silane compound is an alkyl group.

In the polyester of the present invention, at least 80 mol% of the repeating units are made of ethylene terephthalate, and preferably polyesters are polyethylene terephthalates obtained by polycondensation reaction of dimethyl terephthalate and ethylene glycol.

Also usable copolymerization components are isophthalic acid, p-betaoxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxylbenzophenone, bis Dicarboxylic acid components such as (4-carboxydiphenyl) ethane, adipic acid, sephasinic acid, 5-sodium sulfoisophthalic acid, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimethanol, etc. Diol components and oxycarboxylic acid components such as paraoxybenzoic acid.

The polyester of the present invention can be applied to any of the transesterification method and the direct polymerization method.

In addition, either batch or continuous may be employed.

In the case of the transesterification method, there is no particular limitation on the transesterification catalyst, and any conventionally known one can be used.

For example, alkali earth metal compounds, such as sodium compounds, potassium compounds, magnesium compounds, calcium compounds, barium compounds, etc., and alkaline earth metal compounds such as zirconium compounds, cobalt compounds, zinc compounds, manganese compounds can be used if soluble in the reaction system. Do.

The polymerization catalyst is also not limited, but it is preferable to use an appropriately selected from antimony compounds, germanium compounds, and titanium compounds.

The average particle diameter of the lubricants gamma, delta and theta alumina used in the present invention is 0.005 to 3㎛, which is less than 0.005㎛ size of the lubricant, the surface roughness in the film is lowered to increase the coefficient of friction and poor running performance, It is because when it exceeds 3 micrometers, surface property will become poor at the time of manufacturing a film. Preferably it is 0.01-1.5 micrometers.

In addition, the amount of the lubricant is preferably 0.01 to 4% by weight based on polyester, which is poor in workability when the addition amount is less than 0.01% by weight. This is because the physical properties of the film are deteriorated because of deterioration. More preferably, 0.05 to 2 weight% is good.

The amount of the silane coupling agent used in the present invention is 0.05 to 5% by weight based on the weight of the alumina lubricant, which is less effective than the surface treatment at less than 0.05% by weight of ethylene glycol This is because the viscosity increases, the lubricant dispersibility is poor and the physical properties of the film is greatly reduced.

In the present invention, the timing of the addition of the silane coupling agent in the ethylene glycol slurry should be after mixing and stirring the lubricant, and the reaction temperature is controlled to be adjusted within the range of 30 to 160 ° C, which is when the reaction temperature is less than 30 ° C. This is because the surface treatment effect is lowered, and when the temperature exceeds 160 ° C, aggregation of lubricant is generated. Preferably 30-120 degreeC is good.

The average particle diameter of another lubricant, spherical silica, is 0.1 to 1 µm. If the size of the lubricant is less than 0.1 µm, the roughness in the film is lowered and the friction coefficient is increased, resulting in poor runability. It is because the haze of a film will increase and it is difficult to obtain a high transparency film. Preferably 0.15-0.7 micrometers is good.

In addition, the addition amount of the silica is 0.01 to 4% by weight based on the polyester, which is less than 0.01% by weight of the running friction coefficient is high processability is poor, when more than 4% by weight is poor dispersibility of the film This is because physical properties are degraded. Preferably from 0.05 to 2% by weight.

The production method of the polyester film in the present invention is not particularly limited, but biaxially oriented by biaxially stretching a polyester having a molecular weight of about 20,000 including the above additives by melt-extrusion by a tee-tie method or the like. The polyester film of the present invention is produced.

The stretching method is the same as that of ordinary polyester, and there is no change of the process by the above additive.

The stretching temperature is 60 to 150 ° C, and the stretching ratio is preferably 2.5 to 6.0 times in the longitudinal direction and the transverse direction, respectively.

The polyester film produced according to the present invention can be designed in a suitable thickness depending on the application, but is typically a film in the range of 2.0 to 200㎛ thickness.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not necessarily limited thereto.

The following methods were used for the various performance evaluation of the film manufactured in the Example and comparative example of this invention.

1) Average particle diameter

It is the volume average particle diameter which measured the ethylene glycol slurry using the centrifugal particle size measuring device of Shimadzu Corporation (Japan).

2) viscosity

The viscosity of the slurry was measured at 60 rpm using a Brookfield B viscometer.

3) molecular weight

Meta-cresol was used as a mobile phase using Waters' molecular weight measuring apparatus, the flow rate was 1 ml / min, and the column temperature was 100 degreeC, and the molecular weight of the polymer was measured.

4) smoothness of surface

Surface roughness of 30 mm in length and 50 mm in thickness of 20 mm in width was measured by the contact method using the surface roughness meter of Kosaka Research Institute (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.

Centerline maximum height (Rt): The distance between the maximum height and the minimum depth in the measurement section.

The lower the average roughness and the maximum height, the better the smoothness and the better the cohesiveness.

5) Runability

Using a tape running tester of Yokohama Systems Research Institute (Japan), the tape is run at a temperature of 1/2 inch at 20 ° C. and a relative humidity of 60%, and then the initial μk is obtained by the following equation.

However, Tin is the inlet tension and Tout is the outlet tension.

A) High speed driving

After rotating the guide pin in the film traveling direction or the reverse direction, the angle of the winding portion is measured at a traveling speed of 180 degrees and 50 cm / sec and a running tension of 300 grams.

6) transparency

Using a haze meter (L-211) of the Gardner Laboratories (USA), the scanning light and scattered light of the film cut to 5cm × 5cm was measured and evaluated by the following formula and criteria.

◎: haze value ≤ 1.0

○: 1.0 haze value ≤ 1.2

△: 1.2 haze value ≤ 1.4

×: 1.4 haze value

Example 1

Gamma alumina prepared an ethylene glycol slurry containing 20% by weight based on the total weight of ethylene glycol to determine the average particle diameter thereof. Based on the weight of gamma alumina, 0.3% by weight of H ₂ N (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ was added to surface-treat the gamma alumina. The viscosity of the obtained slurry was measured.

The dimethyl terephthalate and ethylene glycol were subjected to a transesterification reaction in a conventional manner with a molar ratio of 1 to 2. Here, the prepared ethylene glycol slurry and spherical silica were added thereto, followed by a polycondensation reaction in a conventional manner to produce a polyester having a molecular weight of about 20,000.

Thereafter, the film was dried, melted, and extruded by a conventional polyester film manufacturing method to make an unstretched sheet, and stretched 3.0 times in the longitudinal and transverse directions at 90 ° C., respectively, to make a 12 탆 thick biaxially stretched polyester film to evaluate performance. It was.

As can be seen from Table 1, the film obtained by the above method has good surface smoothness, transparency and the like.

Example 2-5

A polyester film was prepared in the same manner as in Example 1, but the input amount and average particle diameter of alumina (gamma, delta, theta) were varied within the scope of the present invention.

As can be seen from Table 1, the film made by the above method was excellent in various properties.

[Comparative Example 1-9]

A polyester film was prepared by the same method as Example 1 except for the type of inorganic lubricant or the method of adding the inorganic lubricant.

That is, in Comparative Example 1-3, hard calcium carbonate was added instead of adding alumina and spherical silica surface-treated with a silane coupling agent as the inorganic lubricant.

In Comparative Example 4-6, silica was added instead of adding alumina and spherical silica surface-treated with a silane coupling agent as the inorganic lubricant.

In Comparative Example 7-9, only the alumina surface-treated with the silane coupling agent was added instead of the alumina and the spherical silica surface-treated with the silane coupling agent as the inorganic lubricant.

The polyester film obtained by the above method had poor surface smoothness and transparency as shown in Table 1.

As can be seen from the above, the polyester film prepared using alumina (gamma, delta and theta) and silica surface-treated using a silane coupling agent according to the present invention has excellent surface smoothness and transparency, etc. Especially suitable for solar control, glass protection and photo protection.

Claims (1)

Preparing an ethylene glycol slurry by dispersing at least one alumina selected from the group consisting of gamma, delta, and theta alumina having an average particle diameter of 0.005 to 3 μm and a Mohs hardness of 6 or more; Surface treating the alumina at a temperature of 30 to 160 ° C. by adding 0.05 to 5 wt% of the at least one silane coupling agent selected from the group represented by the following formula on the ethylene glycol slurry based on the weight of the alumina; Provided that RI in the silane compound is an alkyl group. During the polyester polycondensation reaction, adding the surface-treated ethylene glycol slurry and spherical silica having an average particle diameter of 0.1 to 1 µm to 0.01 to 4% by weight based on the polyester polymer to obtain a polyester polymer; And biaxially stretching the polyester polymer obtained by the polycondensation reaction, wherein the amount of the alumina is 0.01 to 4% by weight based on the polyester polymer. Manufacturing method.