KR100515092B1 - the Bi-axial oriented Polyester Film and the Method of Manufacturing the Same - Google Patents

Abstract

In the biaxially stretched polyester film composed of ethylene terephthalate and ethylene 2,6-naphthalate in main repeating units and stretched in the longitudinal and transverse directions, when the film is stretched in the longitudinal direction with respect to the initial length of five. When the film strength is defined as σ _L and the film is stretched in the same manner as described above, when the film strength in the transverse direction is defined as σ _T , the stretching rupture generated during stretching is controlled by adjusting the combination of σ _L and σ _T to an appropriate range. It provides a polyester film which can be significantly reduced and which is excellent in breaking strength of the film.

Description

The bi-axial oriented polyester film and the method of manufacturing the same

The present invention relates to a polyester film, and more particularly to a polyester film having a high film strength, such as various high-density magnetic recording media, high-definition industrial substrates.

Currently, polyester film is used as a base material for magnetic recording media, and paper and plastic films are generally used as base materials for packaging materials and industrial materials. Polyvinyl chloride, polyolefin, polystyrene, etc. It is used.

In the case of paper, it has the advantages of excellent processability, convenient disposal and recycling, but it is expensive to manufacture and there are problems in use such as discoloration or mold caused by temperature difference or moisture when used for a long time. Although it has the advantage of being excellent in processability and good workability, not only heat resistance is weak, but also due to environmental problems in the disposal process, there is a tendency to limit the use in some developed countries.

Unlike the general polymer resins listed above, polyester resins are chemically and physically stable, have high mechanical strength, are excellent in heat resistance, durability, chemical resistance, electrical insulation, and the like, and are widely used in medical and various industrial products. Terephthalate films have excellent properties such as elastic modulus, dimensional stability, planarization, etc. and are widely used in magnetic recording media, capacitors, packaging, photographic films, labels, and other graphic arts products.

Polyethylene terephthalate is prepared by polycondensation of ethylene terephthalate produced by the transesterification reaction of dicarboxylic acid and diol.

At this time, specific examples of the dicarboxylic acid used as a raw material for imparting ethylene terephthalate as a repeating unit are dimethyl terephthalate. Terephthalic acid, dimethylisophthalate, cyclohexanedicarboxylic acid, diphenoxyethanedicarboxylate, diphenylcarboxylic acid, anstagendicarboxyl, beta-bis (chlorophenoxy) ethane-4,4 ' -Dicarboxylic acid, and the like.

On the other hand, specific examples of the diol component include ethylene glycol, polyethylene glycol, 1,3-fluoropropylene glycol, 1,2-fluoro propylene glycol, 2,2-diethyl 1,3-propanediol, 2,2-dimethyl-1 , 3 propanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentylglycol, p-xylene glycol, 1,3-cyclohexanedimethanol, 1,4-cyclohexane Dimethanol, and the like.

At this time, the apparatus and method for mixing or copolymerizing each resin are not limited. In general, a method of manufacturing a film is ejected in the form of a melt through an extruder, and then an amorphous non-oriented solidified sheet is formed in the longitudinal direction and the transverse direction. A film is manufactured by extending | stretching.

However, as the industrial sector is diversified and high performance is required, the strength of the film is required to be used for high quality or high concentration printing.

Films made of thermoplastic resins, such as polyester films, exhibit linear deformation like metal materials in sections extending from 1 to 5 with respect to the initial length when the resin is stretched due to the inherent viscoelastic characteristics of the resin. In addition, plastic deformation is shown.

The point of change from the linear deformation to the plastic deformation is defined as the yield point. In order to give a stable elastic modulus or dimensional stability of the material, methods for increasing the strength at the yield point have been developed.

In the most typical method, the sheet is molded into a sheet shape and then stretched properly in the longitudinal and transverse directions with respect to the film direction. However, such stretching in the longitudinal and transverse directions causes the film to break during the manufacturing process. As a result, both the longitudinal stretching ratio and the stretching ratio were limited to 3.00 to 4.00, and two or more multi-stretchings were performed.

However, since the stretching of polyethylene terephthalate is limited, another method has been developed to improve the strength by mixing a resin having excellent stretchability with a polyethylene terephthalate resin or copolymerizing the raw material of the resin in the polymerization step of polyethylene terephthalate. .

For example, in Korean Patent Application No. 98-30219 and Japanese Patent Laid-Open No. Hei 7-148840, a resin having ethylene 2,6-naphthalate as a repeating unit is mixed with a resin having ethylene terephthalate as the main repeating unit or in a polymerization step. The raw material having the repeating unit is copolymerized to propose a film having improved strength.

The components for having ethylene 2,6-naphthalate repeating units include dimethyl 2,6-naphthalate, dimethyl 1,2-naphthalate, dimethyl 1,5-naphthalate, dimethyl 1,6-naphthalate. Dimethyl 1,7-naphthalate, dimethyl1,8-naphthalate, dimethyl 2,7-naphthalate and the like.

In the above application, in order to produce a high strength film using a polyester resin, ethylene terephthalate and ethylene 2,6-naphthalate are the main repeating units, and the components of ethylene 2,6-naphthalate are ethylene terephthalate and ethylene. A method of increasing the strength of the film by mixing the resin or preparing a copolymerized resin so as to contain 5 to 20 mol in the total of 2,6-naphthalate components was used.

In this case, the strength of the film can be increased by introducing ethylene-2,6-naphthalate, which has a relatively rigid structure in the repeating unit molecular chain, but mixing ethylene terephthalate and ethylene2,6-naphthalate Since the increase in film strength is determined by the copolymerization ratio, it is inevitable to increase the strength within the range without breaking due to the stretching of the film.

It is an object of the present invention to provide a polyester film and a method for producing the same to increase the strength through the high magnification and reduce the number of breakages occurring during stretching in order to improve the problems of the prior art as described above.

The present invention for achieving the above object is a biaxially stretched polyester film composed of ethylene terephthalate and ethylene 2,6-naphthalate in the main repeating unit, stretched in the longitudinal direction and transverse direction, the film is the first length Equation 1 below is satisfied when the film strength when the film is elongated by 5 in the longitudinal direction is defined as σ _L , and the film strength when the film is elongated by 5 times in the lateral direction with respect to the initial length is defined as σ _T. Characterized in that.

As a result of extensive studies, the inventors found that when the combination of σ _L and σ _T is in an appropriate range, excellent strength can be maintained without stretching fracture in the film manufacturing process.

However, since σ _L and σ _T change non-independently, the above object cannot be achieved by making only one of σ _L and σ _T too high.

First of all, the sum of σ _L and σ _T is preferably 34 to 37.5 kg / mm 2, but when it is less than 34 kg / mm 2, there is a problem that the strength of the film is lowered and the physical properties are lowered. This causes a problem that increases the number of breaks.

Although the sum of σ _L and σ _T is in the range of 34 to 37.5 kg / mm 2, when the ratio of σ _L and σ _T does not satisfy the range of 1.00 to 1.20, the anisotropy of the physical property becomes large and the strength is not high. There is a problem that increases the breakage.

On the other hand, the value of σ _L should be maintained at 17.5 kg / mm 2 or more to maintain the strength meeting the above object.

There may be a variety of methods for producing a polyester film to satisfy the above Equation 1, in particular, the main ethylene terephthalate repeating unit and the ethylene 2,6-na constituting the resin mixture or copolymer constituting the film Preference is given to a method of adjusting the ratio of phthalate main repeating units and a method of controlling the stretching process.

The preferable manufacturing method of the high strength film meeting the above objective is as follows.

The resin mixture or copolymer used in the present invention is composed of a component having ethylene terephthalate as the main repeating unit and a component having ethylene 2,6-naphthalate as the main repeating unit.

Ethylene 2,6-naphthalate has a very solid structure due to its molecular structure, and since the repeating unit is added to the structure having ethylene terephthalate as the main repeating unit, a film made using such a resin is used for ethylene terephthalate only. It has a relatively high strength compared to the film produced using.

First, the resin is dried in a dryer for 4 to 7 hours in the range of 115 to 200 ℃ discharged in a melt form through an extruder.

Melt melt-extruded through an extruder is solidified and adhered to the rotating cooling drum discharged from the die. The amorphous unoriented solidified sheet thus produced is preheated and longitudinally stretched in the range of 3.00 to 4.00 magnification in the range of 80 to 140 ° C. and laterally stretched in the range of 3.00 to 4.00 magnification in the range of 120 to 150 ° C.

However, there is a limit to improving the strength of the film using this method, it is impossible to improve the strength of the film beyond a certain level.

Therefore, the present inventors have attempted to achieve high strength of the film by introducing a grade drawing to improve the properties of the resin itself and increase the strength through mixing or copolymerizing the resin.

In other words, resins are mixed or copolymerized to have ethylene terephthalate and ethylene 2,6-naphthalate as main repeating units, melt extruded using an extruder, discharged through a die, cooled, and then the sheet is longitudinally stretched, transversely stretched and graded. Stretching was performed sequentially to polarize the orientation strength of the molecules in the longitudinal direction to improve the strength of the film.

To this end, in the present invention, a film extension process for stretching the film, in which the transverse stretching is completed, is again at 1.01 to 2.00 magnification in the longitudinal direction in the range of 120 to 150 ° C.

This is to have ethylene terephthalate and ethylene 2,6-naphthalate as the main repeating unit to re-stretch again in a state where the strength of the film is improved to a certain level or more to increase the molecular orientation in the longitudinal direction, thereby increasing the strength of the film. It can be improved.

However, when the grade stretching temperature is less than 120 ℃ there is a problem that can not supply the heat as necessary for stretching, if the grade draw ratio is less than 1.01 it is difficult to give the effect of re-stretching, if it exceeds 2.00 There is a problem that cannot be continuous production.

Although the raw material and structural ratio which comprise resin used by this invention are not limited, It is preferable that ratio of ethylene terephthalate main repeating unit and ethylene 2,6-naphthalate main repeating unit is 85-95 mol: 3-15 mol.

This is because the ethylene 2,6-naphthalate having excellent stretchability is contained in a certain ratio, so that the breakage at the time of stretching can be significantly reduced.

However, when the ratio of ethylene 2,6-naphthalate is less than 3 moles, the effect of improving the strength is less. If the amount exceeds 15 moles, the physical properties are deteriorated due to the formation of irregular chains during the production cost increase and mixing. have.

In addition, the raw material of ethylene terephthalate is more preferably dicarboxylic acid, dimethyl phthalate, diol, ethylene glycol is more preferred, ethylene 2,6- naphthalate 90 dimethyl dimethyl 2-, 6- naphthalate and the remaining 10 dimethyl 1, 2-naphthalate, dimethyl 1,5-naphthalate, dimethyl 1,6-naphthalate. It is preferred to select and mix one or more of dimethyl 1,7-naphthalate, dimethyl1,8-naphthalate or dimethyl 2,7-naphthalate.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by the examples described below.

Example 1

A lip gap of 2.00 mm and a width of 780 mm in a die of dimethyl terephthalate and dimethyl 2,6-naphthalate in a ratio of 90:10, melt-discharged and cast a copolymer having an intrinsic viscosity of 0.62 dl / g, A film was prepared. And longitudinally stretched at 130 times 3.0 times and lateral stretched at 135 times 3.5 times at 135 ℃, and finally stretched at 1.145 times at 145 ℃ to produce a high strength film, F5 value, breaking strength and the number of break breaking according to the following experimental method The measurement is shown in Table 1.

Example 2

 Using the same apparatus and method as in Example 1, the high tensile film was prepared by stretching the grade 1.10 times, and the F5 value, the breaking strength and the number of breaking times were measured according to the following experimental method, and are shown in Table 1 together with Example 1. .

Example 3

 Using the same apparatus and method as in Example 1, the high strength film was prepared by stretching the grade by 1.80 times. The F5 value, the breaking strength and the number of breaking times were measured according to the following experimental method, and are shown in Table 1 together with Example 1. .

Example 4

Using the same apparatus and method as in Example 1, but prepared a high-strength film with a ratio of dimethyl terephthalate and dimethyl 2,6-naphthalate to 85:15, F5 value, breaking strength and elongation break according to the following experimental method The number of times was measured and shown in Table 1 together with Example 1.

Example 5

Using the same apparatus and method as in Example 4, the film was stretched 2.0 times to prepare a high strength film. The F5 value, the breaking strength, and the number of breaking times were measured according to the following experimental method, and are shown in Table 1 together with Example 1. .

Comparative Example 1

Using the same apparatus and method as in Example 1, but was not prepared to stretch the film was prepared, F5 value, breaking strength and the number of times of breaking were measured according to the following experimental method is shown in Table 1 together with Example 1.

Comparative Example 2

Using the same apparatus and method as in Example 4, but was not produced a film stretched, the F5 value, the breaking strength and the number of times of breaking were measured according to the following experimental method is shown in Table 1 together with Example 1.

Comparative Example 3

Using the same apparatus and method as in Example 1, but a high strength film was prepared by stretching the grade 2.10 times, F5 value, breaking strength and the number of times of breaking were measured according to the following experimental method is shown in Table 1 together with Example 1. .

Experimental Method

-F5 value measurement

Tensile strength at the time of elongation of 5 was measured according to the ASTM 882 tensile strength test method using the Instron tensile tester, it was set to F5 value.

-Breaking strength

Tensile strength at the time of fracture | rupture of the specimen was made into the breaking strength value using the tensile tester of the film by ASTM 882 using the Instron tensile tester.

-Elongation at break

The number of breaks in the course of 72 hours in the grade drawing process of the polyester film was measured.

Raw material mixing ratio Grade extension ratio F5 (kg / mm2) Breaking Strength (㎏ / ㎠) Elongation at break Raw material (A) Raw material (B) σ _L σ _T Example 1 90 10 1.30 17.8 16.4 45.2 3 Example 2 90 10 1.10 17.5 16.6 41.2 2 Example 3 90 10 1.80 18.3 16.7 49.8 6 Example 4 85 15 1.30 18.0 16.7 47.2 2 Example 5 85 15 2.00 20.2 17.1 50.8 8 Comparative Example 1 90 10 0.00 17.0 16.2 37.4 One Comparative Example 2 85 15 0.00 17.3 16.5 38.7 One Comparative Example 3 90 10 2.10 20.8 16.9 51.2 15

In Table 1, the raw material (A) shows dimethyl terephthalate as the main repeating unit, and the raw material (B) shows dimethyl 2,6-naphthalate as the main repeating unit.

Prepared by the same apparatus and method as Examples 1 to 5 and Comparative Examples 1 to 2, and the results measured by the above test method are the same as the contents of Table 1, in the longitudinal direction according to the present invention Sheets of Examples 1 and 5 manufactured so that the sum of the F5 values in the transverse direction was 34 to 37.5 kg / mm 2, the ratio was 1.00 to 1.20 kg / mm 2, and the F5 value in the longitudinal direction was 17.5 kg / mm 2 or more. It was found that the breakage strength of the film is excellent without the stretching breakage through the manufacturing process.

As described above, the present invention is a useful invention for providing a polyester film having excellent breaking strength of the film which can significantly reduce the elongation caused by stretching by adjusting the combination of σ _L and σ _T to an appropriate range.

Although the present invention has been described with reference to one embodiment, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible.

Claims (4)

delete delete delete A resin mixture or copolymer having a ratio of ethylene terephthalate main repeating unit and ethylene 2,6-naphthalate main repeating unit in an amount of 85 to 95 mol%: 3 to 15 mol% was melt-extruded to prepare a sheet, and then In the biaxially stretched polyester film produced by stretching in the transverse direction, the stretching temperature is 120 to 150 캜, the stretching ratio is 1.01 to 2.00, and then cooled at room temperature, the ethylene 2,6-naphthalate is dimethyl 90 mol% of 2,6-naphthalates and the remaining 10% are dimethyl 1,2-naphthalate, dimethyl 1,5-naphthalate, dimethyl 1,6-naphthalate. A method for producing a biaxially stretched polyester film, wherein at least one selected from dimethyl 1,7-naphthalate, dimethyl 1,8-naphthalate, and dimethyl 2,7-naphthalate is selected and mixed.