KR950013688B1 - Polyester film - Google Patents

Abstract

No content.

Description

Polyester film

The present invention relates to a polyester film, and in particular, by adding an antioxidant and inert particles and limiting the content of terminal carboxyl groups and cyclic trimers, it is possible to improve not only heat resistance but also display insulation, abrasion resistance, surface properties and withstand voltage defects. It relates to a polyester film.

In general, polyester, especially polyethylene terephthalate (hereinafter referred to as PET) is chemically stable, has high physical and mechanical strength, and has excellent heat resistance, durability, chemical resistance, and electrical insulation. It is widely used for various medical and industrial molded products, in addition to the use of metals, capacitors, electrical insulation materials, and packaging materials.

However, in addition to the lack of heat resistance when used for electrical insulation, such polyester films contain low molecular weights such as ethylene terephthalate cyclic trimer, unreacted polymers, dimethyl terephthalic acid, and the like, which is a linear polyester. Extraction or precipitation in the film has the disadvantage of causing various problems. That is, when used as an insulating material in a hermetic motor such as a refrigerator, the annular trimer inside the polyester film is extracted by the refrigerant to prevent the motor from being exposed or to contaminate the refrigerant, thereby causing various abnormalities. In addition, in the use of magnetic media, the cyclic trimer inside the film is easily precipitated to the surface during the application of a high temperature magnetic layer coating or calendon, and becomes a powder or a foreign substance, which causes the performance of the final product such as dropout. In addition, low molecular weights, such as cyclic trimers, deposited on the surface during the film production process may cause projections and voltage defects, resulting in deterioration of product appearance and hardness.

For the above reasons, the lower molecular weight such as cyclic trimer in the polyester film is better, the lower the content, and the content of the cyclic trimer is preferably 1.0% by weight or less. In particular, since the oligomer of polyester is always present in an equilibrium concentration with the polymer according to the characteristics of the polymer in the manufacturing process, it is very difficult to control and lower the content.

Thus, in order to remove low molecular weights, such as cyclic trimers which are mixed or adhered to a polyester film and which adversely affects a film, from the film, the method of extracting the low molecular weights in a film was conventionally used using various solvents.

In Japanese Patent Publication No. 43-253348, a linear polyester-based film is immersed in a dimethyl formamide solution heated to a boiling point temperature to remove low molecular weight mixed in the film, and then the dimethyl formamide solution is physically or appropriately prepared. Japanese Patent Publication No. 44-2120 discloses a method of removing by using a solvent, and when a linear polyester film is immersed in a heating solution column of benzyl alcohol, the low molecular weight mixed in the film becomes about 1% or less. The method is characterized in that after the extraction and removal, the benzyl alcohol solution is substantially completely removed.

However, in the above extraction method, selecting an appropriate solvent enables efficient extraction and removal of the low molecular weight, but it takes a long time to extract and requires a separate process for using the solvent, thereby reducing workability and cost. Not only cause the rise. Since the problem that the physical property of a film falls with the solvent to be used arises, it is unpreferable.

Accordingly, in the present invention, by adding an appropriate amount of antioxidant and inert particles and appropriately controlling the production process without adding a separate process such as solvent extraction during the production of polyester film, the content of the cyclic trimer is lowered and heat resistance is achieved. It not only solves the fault which shows in a conventional film by giving. An object of the present invention is to provide a polyester film having improved electrical insulation, heat resistance, abrasion resistance, surface characteristics and withstand voltage defects.

At least one oriented polyester film of the present invention for achieving the above object is 0.01 to 3.0% by weight of the antioxidant and the average particle diameter of a film made of a polyester in which at least 70% by weight of the film constituents are polyethylene terephthalate It contains 0.01 to 5.0% by weight of inert particles of 0.01 to 5um, characterized in that the content of ethylene terephthalate cyclic trimer is 0.7% by weight or less.

In particular, it is preferable that V of this invention satisfy | fills following Formula (1) and (2) simultaneously.

[COOH] ≤-2.5 [IV] + 31.25 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (1)

[IV] ≤-0.5 [C ₃ ] + 1.0 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (2)

Where [COOH] is the terminal carboxyl group content (meq / 10 ⁶ ) of the polyester, [IV] is the ultimate viscosity of the film (dl / g), and [C ₃ ] is the ethylene terephthalate cyclic trimer contained in the film The content of (% by weight).

In the present invention, ethylene terephthalate cyclic trimer is a cyclic oligomer produced by a cyclization reaction between both ends of a molecule, and the structure is as follows:

As for the polyester film of this invention, the intrinsic viscosity measured at the density | concentration of 0.3g per 25 ml of orthochlorophenols at 35 degreeC is 0.5-1.0 dl / g, Especially 0.6-0.9 dl / g is preferable. If the intrinsic viscosity is less than 0.5 dl / g, the breakage occurs frequently during the manufacturing process of the film, not only the productivity is greatly reduced, but also the content of the cyclic trimer is high, and if the content exceeds 1.0 dl / g, the content of the cyclic trimer Since the melt viscosity is very high without significantly lowering, there are difficulties in the manufacturing process such as extrusion instability, which makes the film difficult.

The polyester of this invention as mentioned above is obtained by polycondensing the acid component which has aromatic dicarboxylic acid as a main component, and the glycol component which has alkylene glycol as a main component. Aromatic dicarboxylic acids include, for example, dimethyl terephthalic acid, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexane dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl carboxylic acid, diphenyl ether carboxyl Acid, anthracene dicarboxylic acid, α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylic acid, and the like, with dimethyl terephthalic acid and terephthalic acid being particularly preferred. Examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, hexylene glycol, and the like, and ethylene glycol is particularly preferable.

As described above, the polyester of the present invention is a homopolyester of 70 wt% or more made of PET and may be copolymerized within the remaining 30 wt%. As a copolymerization component, For example, Diol compounds, such as diethylene glycol, propylene glycol, neopentylene glycol, polyethylene glycol, p-xylene glycol, 1, 4- cyclohexane dimethanol, 5-sodium sulforesorcin, Dicarboxylic acid components such as adipic acid and 5-sodium sulfoisophthalic acid, and polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid.

The antioxidant added to the polyester film of this invention means antioxidants, such as a phenol type, phosphorus type, and a thioether type, and mixtures thereof. Phenolic compounds include, for example, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 3,9-bis [1,1-dimethyl-2- [β- (3- t-butyl-4-hydroxy-5-methylphenyl) propionylcarboxy) tetrakis [methylene-3- [3 ', 5'-di-t-butyl-4'-hydroxy tetrakis [methylene-3-3 (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) Butane, 4,4'-butylidenebis (6-t-butyl-3-methylphenol), octadecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) prop Cypionate, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di -t-butyl-4-methyl-4-hydroxyphenyl) propionate], pentaerythryl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl] propionate , 2,2'-thio-diethylenebis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis-n-octylthio) -6 -(4 -Hydroxy-3,5-di-t-butylanyl) -1,3,5-triazine, N, N'-hexamethylene (3,5-di-t-butyl-4-hydroxy-hydrocinnamin Amide), 3,5-di-t-butyl-4-hydroxy-benzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t -Butyl-4-hydroxybenzyl) benzene, bis (3,5-di-t-butyl-hydroxybenzylphosphorylethyl) kalsum and the like.

Phosphoric acid compounds include phosphoric acid, phosphorous acid, methyl phosphate, ethyl phosphate, triethyl phosphate, phenyl phosphate and the like and esters thereof. Specifically, phosphoric acid-cyclic neopenta tetraylbis (2,6-di-t-butyl) 4-methylphenyl) ester, cyclic neopentane tetrayl-bis (octadecyl-phosphite), bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, tris (2,4-di -t-butylphenyl) phosphite, 4,4'-butylidenebis (3-methyl-6-t-butylphenyl-di-tridecyl) phosphite, 1,1,3-tris (2-methyl- 4-ditridecyl-phosphite-5-t-butylphenyl) butane, diphenyl-isooctyl-phosphite, dimethyl-isodecyl-phosphite, tris-nonylphenyl-phosphite, tri (mono + dinononyl Phenyl) phosphite, 4,4'-isopropylidene-diphenol-alkyl (C ₁₂ -C ₁₅ ) phosphite, and the like. Thioether compounds include, for example, ditridecyl-thio-di-propionate, tedragis [methylene-2- (lauryl-thio) propionate] methane, bis [2-methyl-4- (3- n-alkyl (C ₁₂ or C ₁₄ ) thio-propionyloxy) -5-t-butylphenyl] sulfide and the like.

In the polyester film of the present invention, the antioxidant is added in an amount of 0.01 to 3.0% by weight, particularly preferably 0.05 to 2.0% by weight. When the added amount is less than 0.01% by weight, it is difficult to manufacture the film of the present invention because there is almost no effect of adding the antioxidant, and when the added amount is more than 3.0% by weight, there is no further low molecular weight reducing effect, but rather the heat resistance of the film is poor. You lose.

Inert particles, which are further components added to the polyester film of the present invention, mean at least one or more selected from inert inorganic particles and organic particles insoluble in polyester. Inert inorganic particles are chemically inert compounds selected from oxides or inorganic salts of elements 2, 3 and 4 of the Periodic Table of the Elements, such as wet or dry silica, synthetic or natural calcium carbonate, calcium phosphate, terephthalate, Magnesium carbonate, sodium fluoride, aluminum hydroxide, alumina. Talc, titanium dioxide and mica, and the like, and silica, potassium carbonate, calcium phosphate, sodium fluoride and titanium dioxide are particularly preferred. Organic particles insoluble in polyester include, for example, crosslinked polymers, elastomers, fluorine-based polymer fine particles, and the like, and crosslinked polystyrene and fluorine-based polymer fine particles are particularly preferable.

Inert particles added in the present invention as described above has an average particle diameter of 0.01 to 5.0um, particularly preferably 0.05 to 4.0um. If the average particle size is less than 0.01 μm, the surface roughness of the film is low, so that the winding property is greatly deteriorated, the productivity is lowered, and the regeneration amount of the cyclic trimer is increased during the manufacturing process, and the average particle size is larger than 5.0 μm. The regeneration of the cyclic trimer is no longer suppressed and the surface of the film is excessively roughened, which causes insulation defects in the film.

In the polyester film of the present invention, the inert particles are added in an amount of 0.01 to 5.0% by weight. If the added amount is less than 0.01% by weight, the regeneration amount of the cyclic trimer increases during the manufacturing process, and when the added amount is more than 5.0% by weight, the regeneration of the low molecular weight material is no longer suppressed and the flexibility, mechanical properties, and electrical properties of the final film are no longer suppressed. Its properties, such as wear resistance and powder generation, are inferior. For the above reason, the average particle diameter and the addition amount of the inert particles in the polyester film of the present invention are in the above range.

In this invention, the addition time of the inert particle of the said antioxidant is not specifically limited, It is possible at any time before completion of a polycondensation reaction. In particular, when adding during the polymerization reaction, it is preferable to add after the transesterification reaction or at the beginning of the polycondensation reaction.

In addition, the polyester film of the present invention, in addition to the antioxidant and inert particles described above, known additives, such as antistatic agents, ultraviolet absorbers, heat stabilizers, crystallization promoters, colorants, nucleating agents and antiblocking agents, etc. It can be added within an undamaged range.

A feature of the present invention is that in order to reduce the content of the cyclic trimer to 0.7% by weight or less, an appropriate amount of an antioxidant and an inert particle having a particle size in a range is added and the manufacturing process is appropriately controlled. Control methods of the manufacturing process include, for example, copolymerization method, solid phase polymerization method, polymer alloy method, polymer reaction method, crosslinking reaction method and hermetic sealing method and other methods for optimizing the time and temperature of the polymerization reaction. At least one of the methods is selected and used.

The polyester film of the present invention produced as described above is characterized by containing a cyclic trimer at 0.7% by weight or less. When the content of the cyclic trimer is more than 0.7% by weight, the cyclic trimer in the polyester precipitates on the surface in the film forming step or in a later step using the film, which causes various abnormalities in the manufacturing process and the product.

Moreover, it is preferable that the polyester film of this invention satisfy | fills following formula (1) and (2).

[COOH] ≤-2.5 [IVI] + 31.25 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (1)

[IV] ≤-0.5 [C ₃ ] + 1.0 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (2)

Where [COOH] is the terminal carboxyl group content (meq / 10 ⁶ ) of the polyester, [IV] is the ultimate viscosity of the film (dl / g), and [C ₃ ] is the ethylene terephthalate cyclic trimer contained in the film The content of (% by weight).

If [COOH] and [IV] are out of the range of said Formula (1), the heat resistance of a film will fall. Or deterioration of the physical properties of the film due to deterioration of the film production of the present invention is difficult.

In addition, when [IV] and [C ₃ ] deviate from the range of the above formula (2), the heat resistance of the polymer and the low content characteristics of the cyclic trimer cannot be satisfied at the same time, and the heat resistance is excellent but the cyclic trimer content is high, The cyclic trimer content is low, but a phenomenon such as poor heat resistance occurs, making the film of the present invention difficult.

The present invention will be described in more detail with reference to the following examples. However, the following examples are only examples of the present invention and the present invention is not limited thereto.

Various performance evaluations of the films produced in Examples and Comparative Examples of the present invention were carried out by the following method.

1) cyclic trimer content

The 100 mg of the film was dissolved in 1 ml of orthochlorphenol to separate the polymer and the oligomer, and the content of the cyclic trimer was measured using Varian's high-performance liquid chromatography. The measured values are expressed in weight percent of the initial sample.

2) terminal carboxyl groups

Makromol. Chem. 26. Measured according to the method of 226 (1958).

3) polymer melting point

It was the value (degreeC) measured using the differential scanning calorimeter by a Perkin-Elmer company, and a temperature increase rate is 20 degreeC / min.

4) heat resistance

The heat resistance of the film of thickness 250um was measured based on JISK-7217. Heat resistance was evaluated by the time taken for the film elongation before a test to fall to 50% after a test, and was represented by the following symbol.

Duration ≥300 hours: ◎ Very good

100 hours ≤ required time <300 hours: ○ Good,

Required time <100 hours: × Bad

(Example 1-2)

To a mixture of 100 parts of dimethyl terephthalate (hereinafter referred to as parts by weight) and 75 parts of ethylene glycol, 0.09 parts of calcium acetate and 0.03 parts of antimony trioxide were added and heated at atmospheric pressure to remove the produced methanol and excess ethylene glycol, thereby performing a transesterification reaction. It was. At the end of the transesterification reaction, the amount of octadecyl 3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate, a silica and phenolic antioxidant, is shown in Table 1 below. After the addition, the reaction system was gradually reduced in pressure while heating and heated to polycondensation by a conventional method at 275 ° C. while maintaining the temperature at 1 torr, thereby preparing a polymer having an intrinsic viscosity of 0.65 dl / g. This polymer was cut into 2 mm x 3 mm x 3 mm cubes, and solid-phase polymerized at 210 degreeC and 0.1 torr for 20 hours, and the polymer of ultimate viscosity 0.76 dl / g was produced. Melt extrusion is carried out to form an unstretched sheet by a conventional method, and the unstretched sheet is stretched 3.5 times in the longitudinal direction and 3.5 times in the transverse direction in the range of 60 to 150 ° C., respectively, and then 30 seconds or less at a specific temperature of 240 ° C. or less. Heat setting was performed to produce a biaxially oriented film having a thickness of 250 μm. The performance evaluation results of the produced film are shown in Table 1.

Comparative Example 1-2

The same procedure as in Example 1-2 was carried out, but as shown in Table 1, an additive was added and a polycondensation reaction was carried out at 295 ° C. to produce a polymer having an intrinsic viscosity of 0.60 dl / g. The polymer was cut into a cube of 2mm × 3mm × 3mm, solid-phase polymerized at 240 ° C and 0.1torr for 14 hours to produce a polymer having an ultimate viscosity of 0.75dl / g, and then a biaxially oriented film having a thickness of 250um was produced. Table 1 shows.

Example 3-4

The method was carried out in the same manner as in Example 1-2, but as shown in Table 1, inert particles and phosphorus antioxidant were added to prepare a polymer having an intrinsic viscosity of 0.70 dl / g. Melt extrusion is carried out to form an unstretched sheet by a conventional method, and the unstretched sheet is stretched 3.5 times in the longitudinal direction and 3.5 times in the transverse direction in the range of 60 to 150 ° C., respectively, and then 30 seconds or less at a specific temperature of 240 ° C. or less. Heat setting was performed to produce a biaxially oriented film having a thickness of 250 μm. The performance evaluation results of the produced film are shown in Table 1.

Comparative Example 3-4

Perform the same method as in Example 3-4, but as shown in the following Table 1, the additive was added and the polycondensation reaction at 295 ℃ to produce a polymer of intrinsic viscosity 0.69dl / g, then a 250um thick biaxially oriented film The performance evaluation results are shown in Table 1.

Example 5-6

In the same manner as in Example 1-2, but as shown in Table 1, inert particles and a thioether-based antioxidant was added to the polycondensation reaction at 270 ℃ to produce a polymer having an extreme viscosity of 0.60dl / g. The polymer was cut into a cube of 2mm x 3mm x 3mm, solid-phase polymerized at 205 ° C and 0.1torr for 25 hours to produce a polymer having an ultimate viscosity of 0.75 dl / g. Table 1 shows.

[Comparative Example 5-6]

Example 5-6 was carried out in the same manner as in the following Table 1, but the additive was added to the polycondensation reaction at 295 ℃ to produce a polymer of intrinsic viscosity 0.60dl / g. The polymer was cut into a 2mm × 3mm × 3mm cube, solid-phase polymerized at 240 ° C and 0.1torr for 15 hours to produce a polymer having an ultimate viscosity of 0.75 dl / g, and then a biaxially oriented film having a thickness of 250 μm was produced. Table 1 shows.

As a result of comparing the performance of the polyester film produced in the above Examples and Comparative Examples, as shown in Table 1, by adding a certain amount of antioxidant and inert particles to the polyester and controlling the manufacturing process of the terminal carboxyl group and the cyclic trimer The polyester film of the present invention produced by lowering the content was found to have excellent heat resistance as well as electrical insulation, abrasion resistance, surface characteristics, and withstand voltage defects. Therefore, the polyester film of the present invention is suitable for electrical insulation, magnetic, packaging, and the like, and can be variously used for capacitors, graphics, and general industrial fields.

TABLE 1

* A1: Octadecyl3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate

A2: triethyl phosphate

A3: bis [2-methyl-4- (3-n-alkyl (C ₁₂ or C ₁₄ ) thio-propionyloxy] -5-t-butylphenyl] sulfide

* B1: silica, B2: calcium phosphate, B3: crosslinked polystyrene fine particles

Claims (3)

A film made of polyester, wherein at least 70% by weight of the film constituents is polyethylene terephthalate, comprising 0.01 to 3.0% by weight of antioxidant and 0.01 to 5.0% by weight of inert particles having an average particle diameter of 0.01 to 5um, and comprising ethylene terephthalate At least uniaxially oriented polyester film, characterized in that the content of the cyclic trimer is 0.7% by weight or less. The polyester film according to claim 1, wherein the polyester film satisfies the following formulas (1) and (2) simultaneously. [COOH] ≤-2.5 [IV] + 31.25 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (1) [IV] ≤-0.5 [C ₃ ] + 1.0 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (2) Where [COOH] is the terminal carboxyl group content (meq / 10 ⁶ ) of the polyester, [IV] is the ultimate viscosity of the film (dl / g), and [C ₃ ] is the ethylene terephthalate cyclic trimer contained in the film The content of (% by weight). The polyester film according to claim 1 or 2, wherein the intrinsic viscosity of the polyester film is 0.5 to 1.0 dl / g.