KR100242958B1 - Manufacturing process of functional polyester film - Google Patents

Abstract

The present invention is applied to the polyester film surface to produce a polyester film imparted functionality by applying a functional resin aqueous solution capable of imparting a two-printing function, easy adhesion function, heat sealing function, antistatic function, gas permeability, or release function A method of manufacturing an amorphous polyester film sheet according to a conventional method, and applying the functional resin solution thereon, irradiating electromagnetic waves having a predetermined frequency range in which water molecule motion can be excited. It is a method of longitudinally extending | stretching and transversely stretching an aqueous layer.

The method for producing a polyester film imparted with the functionality of the present invention can prevent contamination in the tenter by applying electromagnetic waves in the frequency range that can excite water molecules during drying, and the number of breakages during the film forming process. By reducing the manufacturing efficiency and to distribute the functional resin aqueous solution more evenly, there is an effect that can produce a polyester film having a uniform thickness and physical properties.

Description

Manufacturing method of polyester film which gave functionality

The present invention relates to a method for producing a polyester film imparted with functionality, and more particularly, to the surface of the polyester film imparting a printing function, an adhesive function, a heat sealing function, an antistatic function, a gas permeation inhibitory function or a release function. A functional resin solution is applied to a polyester resin which is useful as an OHP film, a graphic film for laser printers or inkjet printers, a film for diazos, a film for protecting electronic materials, or a packaging material by coating a functional resin solution that can be used. It relates to a method for manufacturing to have a uniform physical properties using electromagnetic waves while more evenly distributed.

Polyester is a polymer having excellent mechanical, physical, and chemical properties, and is widely used in fibers, films, and other molding products. In particular, the film sector is widely used in various packaging materials, photographic materials, electrical materials, and metallizations.

When polyester film is used as graphic material and various post-processing material, general polyester film is made of copolyester film, corona treatment on the surface of film, or chemical coating is applied to give new functionality. I'm using.

Among these methods, a method of applying a chemical to a polyester film to give a new function to the surface of the film is the most widely used industrially. First, a function to be provided is to improve the printability between the ink and the polyester film. Adhesiveness to two-printing and second-processing products with various special functions, such as OHP films, or films applied for making graphics or diazo films for laser or inkjet printers. Third, heat-sealing function for lamination of various packages, fourth antistatic function, which is an essential function of polyester film for protecting various graphic films and electronic materials, and fifth, oxygen and gas as packaging materials. Reducing the permeability and other chemicals applied on the polyester film There is a release function to facilitate the peeling of.

Generally, a polyester film is obtained by carrying out biaxial stretching after melt-extruding a polyester chip. More specifically, the step of extruding the polyester chip at a high temperature of 300 ℃ or more, the step of producing an amorphous sheet by cooling to room temperature by using a casting drum (cooling drum circulating the cooling water therein), Stretching the sheet three times or more in the same direction as the sheet moving direction using the rolls arranged vertically or horizontally, and stretching the sheet thus drawn three times or more perpendicularly to the traveling direction of the sheet in a tenter preheated with hot air. It is produced through a process consisting of a step of producing a stretched polyester film.

By the way, while such a method is suitable for producing a conventional biaxially stretched polyester film, there are many problems in applying to the production of a polyester film coated with a chemical substance having the above-mentioned functionalities, which is recently increasing in demand. It implies

In other words, in the case of producing a polyester film imparted with functionality according to the conventional method, the polymer in an emulsion state for imparting two-printing, easy-adhesion, heat-sealing, antistatic or release function after longitudinal stretching and before entering transverse stretching, After applying the water-soluble or water-dispersible chemicals, the coating layer is dried in the tenter and preheated by heating to a temperature suitable for transverse stretching in the direction perpendicular to the sheet traveling direction, and then transversely stretched to apply the chemicals. It is made of a polyester film.

At this time, in order to stretch about 3 times in the transverse direction in the tenter, the aqueous solution applied to the sheet should be dried, and at the same time, the sheet should be preheated and heated above the glass transition temperature (Tg) suitable for stretching. As such, the drying of the functional chemical solution applied to the sheet during the drying and preheating processes must be uniform, and the sheet must be uniformly heated to achieve uniform stretching to produce a high quality polyester film. If the drying and stretching are not uniform, firstly, the thickness of the product is uneven, the thickness of the coating layer is uneven, so that the desired physical properties are not uniformly obtained. Second, the decrease in stress at break of the final film and thermal shrinkage ( It may cause an increase in heat shrinkage.

However, when the drying of the aqueous solution and the preheating of the sheet at the same time with the hot air in the tenter as described above, the hot air is in direct contact with the coating layer of the aqueous functional chemical solution before the functional chemical solution is completely dried. No drying In addition, since the sheet is not preheated uniformly, there is a considerable problem in producing a polyester film having a uniform physical property since the lateral stretching is not uniform. In addition, since the vapor evaporated from the functional chemical solution and the hot air supplied from the outside coexist in the tenter, there is a problem that a temperature gradient occurs, thereby preventing preheating and stretching uniformly. Furthermore, in the conventional polyester film manufacturing method, drying and preheating must be performed simultaneously in a tenter having a short heating zone in which only the sheet is heated. Therefore, an excessive amount of hot air must be supplied at a high temperature to supply sufficient heat. At this time, the breakage occurs frequently during film formation due to the difference in specific heat and draw ratio between the portions coated with the chemical aqueous solution and the uncoated portions on the sheet surface, resulting in a decrease in productivity.

In order to improve this, there may be a method of extending the heating zone by lengthening the inlet of the tenter, or installing a dryer after coating the chemical, and laterally stretching it after drying. There is a problem in that the cost of equipment modification is high, and the method of drying by heating or hot air causes various problems such as poor physical properties of the final film due to uneven stretching.

On the other hand, if the functional resin solution is applied to the amorphous sheet, longitudinal stretching and drying are performed, not only the undried resin solution becomes the main cause of contamination in the tenter but also the functional resin solution is not uniformly dispersed. There is a problem of not exhibiting functionality.

The present invention is to solve the problem in applying the conventional method of manufacturing a polyester film as described above to apply a chemical to the surface of the film to give a functional polyester film, and functionalized by drying using electromagnetic waves It is an object of the present invention to provide a method for producing a polyester film that has a uniform thickness and uniform physical properties by uniformly distributing an aqueous resin solution and imparts functionality capable of improving manufacturing operability.

Method for producing a polyester film imparted with the functionality for achieving the object of the present invention comprises the steps of producing an amorphous polyester sheet by melting and extruding a polyester chip, applying a functional resin aqueous solution to the surface of the sheet Irradiating electromagnetic waves having a frequency range of 0.1 to 10 GHz, drying the sheet, and longitudinally stretching the dried sheet.

The production method of the present invention will be described in more detail as follows.

First, an amorphous polyester sheet is prepared as in the conventional polyester film production method. Specifically, a polyester chip is melt-extruded at a high temperature of 300 ° C. or higher and a casting drum in which cooling water is circulated therein is used. Cooling to room temperature produces an amorphous polyester sheet.

The functional resin aqueous solution is applied to the surface of the sheet thus prepared, and in the present invention, the functional resin aqueous solution may be a resin that can impart functionality such that a conventional polyester film is used as a graphic material or various post-processing materials. More specifically, at least one resin can be selected and used from an acrylic resin, a polyethylene resin, a polyurethane resin, a polyvinyl chloride resin, and a copolymer thereof. This functional resin is mixed with water and applied to the surface of the amorphous polyester sheet in the form of an aqueous solution, the thickness of which may vary depending on the intended use.

Then, as a drying step characteristically performed in the present invention, the aqueous solution is dried by irradiating electromagnetic waves having a predetermined frequency range on the surface of the sheet on which the functional resin aqueous solution is applied in the same manner as described above. At this time, the frequency range of the electromagnetic wave is preferably 0.1 ~ 10GHz bar, when having a frequency in such a range, the water molecule motion can be in an excited state (excited state) it is possible to dry.

As such, when the functional resin aqueous solution coating layer is dried using electromagnetic waves, the drying may be uniformly performed, and preheating may be uniformly performed in the post process, so that uniform stretching may be performed in the stretching process performed in the tenter. In addition, the productivity can be improved by reducing the occurrence of frequent breakage during film formation due to simultaneous drying and preheating of the functional resin aqueous solution coating layer inside the tenter.

At this time, the irradiation of electromagnetic waves consists of a combination of a general reflecting plate and an absorption plate, the electromagnetic wave irradiated to the drying chamber and outflowed to the outside is invented and used by the device absorbed by the absorption plate, there is no harm caused by the leakage of electromagnetic waves, installed in a small space There is no difficulty in actual field application.

In addition, since the functional resin aqueous solution layer is formed directly on the surface of the sheet before the stretching process is performed as described above, the functional resin aqueous solution can be evenly distributed to produce a film of uniform physical properties. Further, by completely drying the functional resin aqueous solution layer before the stretching in the tenter proceeds, contamination inside the tenter due to the aqueous functional resin solution can be prevented.

The sheet thus uniformly dried is longitudinally stretched in the advancing direction, and the method is longitudinally stretched three times or more in the same direction as the moving direction of the sheet.

Finally, after drying according to the method described above to produce a polyester film having a predetermined thickness by transverse stretching.

Hereinafter, the present invention will be described in detail with reference to Examples. The present invention is not limited by the Examples.

EXAMPLE

The polyester chip was melt-extruded at a high temperature of 300 ° C. or higher, and then cooled to room temperature using a casting drum in which cooling water was circulated to prepare an amorphous polyester sheet. After the application of an easily-adhesive functional resin solution prepared by mixing 3% by weight of acrylic resin and pure water to 97% by weight on the surface of the sheet, the electromagnetic wave having a frequency range of 0.1 to 10 GHz was irradiated and dried. Then, the prepared sheet was stretched four times or more in the same direction as the moving direction of the sheet using rolls arranged vertically or horizontally, and then the dried sheet was transversely stretched to prepare a polyester film having a thickness of 100 μm.

[Comparative Example]

In the same manner as in the above embodiment, an amorphous polyester sheet was prepared, longitudinally stretched, and then coated with a functional resin aqueous solution. Then, hot air was applied at a temperature of 250 ° C. in a tenter to dry the functional resin aqueous coating layer while simultaneously transverse stretching. Polyester film was prepared.

Experimental Example

The polyester films prepared according to the above Examples and Comparative Examples were measured for the heat shrinkage, thickness, elongation, surface, operability and distribution of the functional resin aqueous solution, and the results are shown in Table 1 below.

Here, the heat shrinkage is cut into two samples of two sides of the polyester film and the center portion of the prepared polyester film 30cm × 30cm in length, and then made into three samples, all of which draw a line of a certain length in the transverse direction of the film and in a 150 ℃ oven After standing for 30 minutes, the line length of the sample was measured and the percentage of (reduced length / circle length) was calculated as (the value of the central sample-the value of the edge portion sample) and expressed as its absolute value.

The thickness measurement is made by cutting two pieces of both sides and the center part of the film so that it is 30cm in width x 30cm in length and making three samples, and then superimposing two pieces of each sample and measuring the thickness (using ONO SOKKI's ST-022 product). ), The value was calculated as (value of the central sample-the value of the edge sample) and expressed as the absolute value.

Elongation was measured according to ASTM D 882-91 method using the universal testing machine to the breaking strength, elongation and F-5 value. In this case, the breaking strength refers to the strength when the sample ruptures during the tensile test, the tensile rate refers to the degree of increase until the sample ruptures, and the F-5 value refers to the tensile strength at 5% elongation. At this time, the measurement conditions were the crosshead speed of 500mm / min, the width of the sample was 15mm, the length of the sample was 50mm, divided into a central portion and the edge portion was carried out by taking three samples. The value measured in this way was calculated as (the value of the central part sample-the value of the edge part sample), and represented as the absolute value.

Observation of the surface of the polyester film coated with a functional resin solution was carried out by cutting the sample into 2 mm width x 10 mm length, placing it on the slide glass, coating the sample with gold under vacuum of 0.1 torr, and then preparing the sample. The surface was observed at a magnification of 200 times using a reflection microscope.

The operability was measured by measuring the number of breaks generated during film formation for 5 days.

In addition, the measuring method of the uniform distribution of the functional resin aqueous solution using a polarizing microscope to cut each of the films coated with the functional resin aqueous solution of 200mm × 200mm size each 5 to observe while rotating the analyzer, at this time If there is no difference in contrast, it can be seen that the coating layer is uniformly applied, indicating that the path difference [Γ] is the same for each part of the film, and the difference in contrast due to the path difference appears in the film coated with the aqueous functional resin solution. If the difference in the surface tension value is measured by taking the respective portions of the surface tension value difference occurs according to the contrast portion, it can be determined that the coating layer is unevenly applied on the film. In addition, if a sample in which the difference in contrast appears on a polarizing microscope is taken and observed with a DIC, the difference between a portion where the coating is uniform and a portion where the coating is uneven can be observed.

In the case of the polyester film produced according to the method of the present invention from the results of Table 1, the thickness is good, the surface is good, the physical properties are also uniform, as well as the shrinkage due to heat and the number of breaks is excellent, the operation is excellent, It can be seen that the distribution of the functional resin is also uniform. However, the polyester film prepared according to the conventional method has a nonuniform thickness, poor surface, nonuniform physical properties, high shrinkage ratio due to heat, and frequent breakage, resulting in poor operability and uneven distribution of the applied functional resin. It can be seen.

As described above, the method for producing a polyester film imparted with the functionality of the present invention is to prepare an amorphous polyester sheet, and to print on the surface thereof, a printing function, an easily bonding function, a heat sealing function, an antistatic function, and a gas permeation inhibiting function. Alternatively, after coating a functional resin solution which can impart a release function, the coating layer is dried using an electromagnetic wave having a frequency range in which water molecule motion can be excited, followed by longitudinal stretching and uniform stretching It can not only produce polyester film with physical properties and uniform thickness, but also improve the physical properties by uniformly applying functional resin aqueous solution, prevent contamination of tenter, and reduce breakage rate during film formation. There are many effects such as to improve.

Claims (2)

Melting and extruding a polyester chip to prepare an amorphous polyester sheet, applying a functional resin aqueous solution to the surface of the sheet, irradiating electromagnetic waves having a frequency range of 0.1 to 10 GHz, and drying the dried sheet. A method for producing a polyester film imparted with the functionality consisting of the step of longitudinal stretching, and the step of transverse stretching. According to claim 1, wherein the functional resin is selected from one or more selected from acrylic resins, polyethylene resins, polyurethane resins, polyvinyl chloride resins, and copolymers thereof. Method for producing an ester film.