JPH11217448A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester film which has rigidity and tear resistance suitable for a thin magnetic tape, is made from a polyester mainly consisting of ethylene-2,6-naphthalate units and a thermoplastic polymer, and has a specified resistance to tear propagation in either direction. SOLUTION: The polyester mainly consisting of ethylene-2,6-naphthalate units contains at least 70 mol.% naphthalenedicarboxylic acid and has a glycol component based on ethylene glycol. A thermoplastic resin is added to this polyester and is dispersed in a film in the form of particles having a means particle diameter of 5 μm or below, desirably, 1 μm or below and an aspect ratio of 1-100. This film has a resistance to tear propagation of 3-20 N/mm in either of the longer and width direction and a high Young's modulus. The thermoplastic polymer is exemplified by a polybutylene terephthalate/polyether copolymer or polyether imide and is used in an amount of 0.1-50 wt.%, desirably, 5-20 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film having improved film quality and productivity. More specifically, the present invention relates to a film having excellent tear resistance and rigidity, for magnetic tape applications, photographic applications, The present invention relates to a polyester film useful as a film for use in insulation and the like.

[0002]

2. Description of the Related Art Polyethylene terephthalate films are widely used in various fields such as base films for magnetic tapes, electric insulating films, printer ribbons, and heat sensitive stencils. However, in recent years, there has been a growing demand for higher densities for miniaturization, high sound quality and high image quality in magnetic tape applications, and thinner tapes such as computer data storage tapes. Is demanded, so that higher rigidity of the film is expected, and polyethylene-2,6-naphthalate film has attracted attention.

[0003] Polyethylene-2,6-naphthalate film is superior to polyethylene terephthalate film in various properties such as rigidity, heat resistance, chemical resistance, and gas barrier properties, and has a high quality such as heat shrinkage and oligomer amount. Is also superior to polyethylene terephthalate, but there is a problem in the tear resistance of the film. Poor tear resistance not only causes film breakage in the stretching and slitting processes and causes a decrease in management yield, but also breaks in the post-processing and processing steps of the film, as well as scratches on the end face of the magnetic tape. This is because it is a major factor in the occurrence of many troubles such as tape cutting due to the problem. If the draw ratio is increased for the purpose of making the film thinner and increasing the rigidity, the tear resistance becomes more remarkable and the film tears frequently.

[0004] Investigations have been made to improve the tear resistance of polyethylene-2,6-naphthalate film. For example, Japanese Patent No. 2585494 discloses a polyethylene-2,6-naphthalate film having improved tear resistance. The patent publication discloses that if the film is stretched at a high temperature and a low magnification, a film having excellent tear resistance can be obtained. However, a high Young's modulus as intended in the present invention is obtained. And a film having excellent tear resistance have not been obtained.

Further, as another method for improving the tear resistance,
A method of increasing the intrinsic viscosity of a polymer is generally known. However, compared to polyethylene terephthalate, polyethylene-2,6-naphthalate has a higher melt viscosity and a large amount of heat generated by shearing during extrusion, so that thermal decomposition is promoted and the intrinsic viscosity tends to decrease. Is difficult to obtain. Also, in this case, the quality of the film is significantly reduced due to an increase in oligomers / pyrolyzed gelation products.

As described above, polyethylene-2,6
-Naphthalate film is superior to polyethylene terephthalate film in various characteristics, but has drawbacks such as poor tear resistance, and it is necessary to obtain a film having high rigidity and excellent tear resistance. At present, it is not easy and a new method is required for improving the tear resistance of the polyethylene-2,6-naphthalate film.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to improve the tear resistance, which is a drawback of the above-mentioned polyethylene-2,6-naphthalate film, to provide high productivity and workability, high rigidity and high quality. To provide a polyester film containing polyethylene-2,6-naphthalate as a main component.

[0008]

Means for Solving the Problems In order to solve the above problems, the present inventors have made at least polyethylene-2,6-
Polyester containing naphthalate unit as main component (A)
Then, a thermoplastic polymer (B) was added thereto, and the relationship between the tear resistance and mechanical strength of the film and the composition and amount of the thermoplastic polymer (B) to be added was studied diligently. as a result,
When the specific thermoplastic polymer (B) is added, it is dispersed in at least the polyester (A) containing polyethylene-2,6-naphthalate unit as a main component, and the tear resistance of the film is improved, and the film is broken during film formation. Found that polyester films having a high Young's modulus can be obtained, thereby completing the present invention. That is, the polyester film of the present invention comprises at least ethylene-2,
A film comprising a polyester (A) containing a 6-naphthalate unit as a main component and a thermoplastic polymer (B), wherein a tear propagation resistance in at least one direction selected from a longitudinal direction and a width direction of the film is 3 to 20 N / mm. It is characterized by being.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester (A) containing at least ethylene-2,6-naphthalate unit as a main component in the present invention is a polymer containing at least 70 mol% of naphthalenedicarboxylic acid as an acid component. As for the acid component, a small amount of another dicarboxylic acid component may be copolymerized, and ethylene glycol is used as a main glycol component, but another glycol component may be added as a copolymer component. Examples of dicarboxylic acids other than naphthalenedicarboxylic acid include terephthalic acid, isophthalic acid, diphenylsulfonedicarboxylic acid, benzophenonedicarboxylic acid, 4,4′-diphenyldicarboxylic acid,
Aromatic dicarboxylic acids such as 3,3′-diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, succinic acid, azelaic acid, sebacic acid and dodecandioic acid;
Alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid can be used. Examples of glycol components other than ethylene glycol include chlorohydroquinone, methylhydroquinone, 4,4'-dihydroxybiphenyl, 4,4
Aromatic diols such as' -dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, 4,4'-dihydroxybenzophenone, p-xylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6 Aliphatic and alicyclic diols such as 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol such as -hexanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol can be used. Further, in addition to the acid component and the glycol component, p-hydroxybenzoic acid, m-hydroxybenzoic acid, aromatic hydroxycarboxylic acids such as 2,6-hydroxynaphthoic acid and p-aminophenol, p-aminobenzoic acid, etc. If the amount is small enough not to impair the effects of the present invention, copolymerization can be further performed.

The polyester film of the present invention needs to have a tear propagation resistance in at least one direction selected from the longitudinal direction and the width direction of the film, of 3 to 20 N / mm. The tear propagation resistance is more preferably 4 to 12 N / mm for stabilizing the film forming process, and 5 to 10 N / mm stabilizes the film forming.
Most preferred for increasing the Young's modulus. If the tear propagation resistance is less than 3 N / mm, the film is likely to be broken at the time of film formation, and it tends to be a problem in the workability of the film such as slitting. It is not preferable because it is difficult to increase.

The thermoplastic polymer (B) is dispersed in the film, the average dispersion diameter is 5 μm or less, and the aspect ratio (major axis / minor axis) representing the domain shape of the thermoplastic polymer is 1 to 100. Is preferred. The average dispersion diameter is more preferably 3 μm or less, and most preferably 1 μm or less because film breakage hardly occurs. If the average dispersion diameter exceeds 5 μm, the film is likely to be broken at the time of film formation, and the smoothness of the film is also unfavorable. The aspect ratio (major axis / minor axis) representing the domain shape of the thermoplastic polymer is 1 to 100.
It is preferred that When the aspect ratio exceeds 100, the tear resistance in the major axis direction is extremely deteriorated, which is not preferable.

It is preferable that the thermoplastic polymer (B) is compatible with the polyester (A). The compatibility here can be determined by the fact that the obtained polyester film has a single glass transition temperature (Tg). Also,
The Tg of the obtained polyester film refers to the one existing between the Tg of the polyester (A) and the Tg of the thermoplastic polymer (B), and further, the gap of the heat flux is determined by the heat flux of the polyester (A). Those not exceeding 1/10 of the gap are not included.

The thermoplastic polymer (B) used in the present invention includes polybutylene terephthalate / polyether copolymer, polybutylene isophthalate / polyether copolymer, styrene / ethylene / butadiene / styrene block copolymer, styrene / Butadiene / styrene block copolymer, styrene / isoprene / styrene block copolymer, acrylonitrile / (ethylene propylene diene telepolymer) / styrene block copolymer, acrylonitrile butadiene copolymer, ethylene /
Propylene copolymer, ethylene / butadiene copolymer,
Ethylene / propylene / diene copolymer, ethylene / vinyl acetate copolymer, styrene / acrylonitrile copolymer, methyl methacrylate / styrene copolymer, methyl methacrylate / butadiene / styrene copolymer, styrene / acrylonitrile / butadiene copolymer It is possible to use polymers, polyvinyl chloride, polyurethane, polybutadiene, chlorinated butyl rubber, methyl methacrylate, polyamide, polyphenylene ether, polyarylate, polyoxymethylene, polyacetal, polyphenylene sulfide, polycarbonate, polyetherimide, polystyrene, polysulfone, etc. it can. Among them, polybutylene terephthalate / polyether copolymer and polyetherimide are preferable.

Further, as a compatibilizer, polystyrene / polymethyl methacrylate / styrene-methacrylic acid block copolymer, polystyrene-polyethylene, polyethylene-2,6-naphthalate-polystyrene block copolymer, polyethylene-2,6 A naphthalate-polybutylene terephthalate block copolymer, a polyethylene-2,6-naphthalate-polyether block copolymer, or the like may be added.

The amount of the thermoplastic polymer (B) is preferably from 0.1% by weight to 50% by weight.
If the amount is less than 0.1% by weight, the film is frequently broken during film formation, and if it exceeds 50% by weight, the excellent rigidity of the polyester film of the present invention may be lost, which is not preferable. Further, the amount is more preferably from 1% by weight to 30% by weight, and most preferably from 5% by weight to 20% by weight.

When two or more thermoplastic polymers (B) are used, it is preferable to use a master obtained by melt-kneading two or more thermoplastic polymers.

The intrinsic viscosity of the film of the present invention is not particularly limited, but is preferably 0.4 to 1.4 dl / g, more preferably 0.62 to 1 dl / g, and most preferably 0.65 to 0.1 dl / g. 8 dl / g. 0.6d intrinsic viscosity
If the amount is less than 1 / g, the film is frequently broken, whereas if it exceeds 1.4, the shear heat generation in the extrusion process increases,
As a result, the amount of oligomers in the film and the amount of thermally decomposed gel are increased, which not only deteriorates the quality of the film but also greatly increases the heat shrinkage of the film, which is not preferable.

The polyester film of the present invention preferably has a Young's modulus in at least one direction selected from the longitudinal direction and the width direction of 6 to 20 GPa. Young's modulus is more preferably 6.5 to 15 GPa, and 7 to 13 GPa.
a is most preferred. If the Young's modulus is less than 6 GPa, it is not preferable for development to various film applications, and if it exceeds 20 GPa, the tear resistance in that direction is extremely deteriorated, which is not preferable.

The polyester film of the present invention may be an unstretched or unoriented film. However, since the film is uniaxially or biaxially oriented, the effects such as high elasticity, toughness, heat resistance and electric properties are more remarkable. It is preferable because it is exhibited in

Further, the polyester film of the present invention comprises:
Although not particularly limited, those having a film thickness of 100 μm or less are preferable because the effects of the present invention are remarkably exhibited, and more preferably 75 μm or less. Further, in order to meet the needs of the market for the miniaturization of hardware and the thinning of recording media for long-time recording as a base film for magnetic recording, the film thickness is preferably 25 μm or less, and 12 μm or less.
m or less, more preferably a film having a thickness of 2 to 12 μm.

The polyester film of the present invention contains a copolymerized polyester having a mesogen group in the main chain, a plasticizer, a weathering agent, an antioxidant, and a heat stabilizer as long as the effects of the present invention are not impaired. , A lubricant, an antistatic agent, a whitening agent, a coloring agent, a conductive agent and the like may be added.

The polyester film of the present invention containing polyethylene-2,6-naphthalate as a main component may be a single film, but may be further provided with another polymer layer such as polyester, polyolefin, polyamide, polyvinylidene chloride, acrylic polymer. And the like may be laminated. In particular, when the polyester layer is laminated thinly on the surface layer, the thickness (M) of the laminated portion is set to be smaller than the average diameter (N) of the particles contained in the laminated portion (M <N). Is 1/1000 to 1/2 of M, more preferably 1/100 to 1/10, whereby a film having excellent running properties, slipperiness and smoothness can be obtained. It is preferable as a base film for magnetic recording in which emphasis is put on. Further, in the case of a laminated film of three or more layers made of polyester, productivity and quality can be improved by mixing a recovered material and the like in the central layer. Examples of such particles include, but are not limited to, silicon oxide, magnesium oxide, calcium carbonate, titanium oxide, aluminum oxide, crosslinked polyester, crosslinked polystyrene, mica, talc, and kaolin.

Next, a preferred example of using the thermoplastic polymer polybutylene terephthalate / polyether copolymer as the thermoplastic polymer (B) in the method for producing a polyester film of the present invention will be described.
It is not limited to this.

First, a polyethylene-2,6-naphthalate master chip containing 5% by weight of a thermoplastic polymer polybutylene terephthalate / polyether copolymer was added to and mixed with a raw material chip of polyethylene-2,6-naphthalate. The raw material is pre-dried at 165 ° C. for 4 hours, and then vacuum dried at 180 ° C. for 2 hours or more. Next, the film is supplied to a single-screw or twin-screw extruder heated to 280 ° C. under a nitrogen stream or vacuum so as not to lower the intrinsic viscosity. At this time, the thermoplastic polymer (B) may be directly charged into the extruder, but when a small amount of the thermoplastic polymer (B) is added to polyethylene-2,6-naphthalate as in the present invention, the master It is preferable that a chip is prepared in advance. The mixing of the raw material chips may be a dry blend, but a metering type sub hopper may be used.

Then, after being plasticized by an extruder, it is extruded into a sheet by a T-die while applying static electricity by a T-die.
The unstretched film is cooled and solidified to obtain an unstretched film. Subsequently, the unstretched film is stretched in a longitudinal direction (longitudinal direction) or a width direction (transverse direction) of the film at a temperature of 110 to 190 ° C. to a predetermined magnification, and Cool with a group of cooling rolls at ５０50 ° C. Thereafter, the film is guided to a tenter and heated to a temperature of 120 to 190 ° C. in a hot air atmosphere while holding both ends of the film with clips, and stretched at a predetermined magnification in a direction perpendicular to the stretching direction. As described above, heat treatment is performed at a temperature lower than the melting point to obtain a biaxially stretched film. Stretching temperature, stretching ratio,
The heat treatment temperature conditions and the like are determined based on the characteristics of the film to be obtained. The area magnification by stretching in the longitudinal and transverse directions is preferably 12 to 45 times, and more preferably 14 to 38 times.
It is twice. The heat setting temperature is more preferably 200 ° C. or higher and lower than the melting point, and the heat treatment time is preferably in the range of 1 to 30 seconds. The heat setting may be performed under tension, and in order to further improve the thermal dimensional stability, it is also preferable to relax in the longitudinal or / and transverse direction.

In addition to the sequential stretching method, a simultaneous biaxial stretching method can be used. In the sequential biaxial stretching method, the number of stretching in the longitudinal direction and the transverse direction is not necessarily limited to one step, and it is also preferable to perform the stretching in the longitudinal and transverse directions by dividing it into several or more steps. Can be.
Further, it is preferable to perform re-longitudinal stretching and / or re-lateral stretching before performing heat setting in order to obtain a film having a high Young's modulus. Stretching in multiple stages while gradually increasing the temperature to the side is also preferably performed.

[0027]

[Measurement method of physical properties and evaluation method of effect] (1) Tear propagation resistance: Using a light-load type tear tester manufactured by Toyo Seiki, A
It was measured according to STM-D-1922. The sample size was 51 x 64 mm, a 13 mm cut was made, and the indicated value when torn was read. In the examples, the values were determined in the MD direction (longitudinal direction) and the TD direction (width direction).

(2) Average dispersion diameter, aspect ratio: After penetrating the film into liquid nitrogen and cooling it sufficiently, split the film in the longitudinal direction in air, and observe the cross section with a scanning electron microscope (SEM). Then, measurements were taken at 10 or more visual fields at different locations. The minor axis of the major axis / minor axis of the thermoplastic polymer in the observed visual field was taken as the dispersion diameter, and the average was taken as the average dispersion diameter. The unit is expressed in μm. The ratio of the major axis / minor axis of the thermoplastic polymer was defined as the aspect ratio.

(3) Young's modulus: A sample was set in a Tensilon type tensile test (manufactured by Orientec) so as to have a width of 10 mm and a chuck-to-chuck length of 100 mm.
A tensile test was performed at a tensile speed of 200 mm / min in an atmosphere of 65% RH.

(4) Fisheye (FE): A 10 cm ² film is placed under crossed Nicols polarization, and the long axis of the glittering portion of the surrounding image having different colors is 10%.
Those having a size of not less than μm were counted. The unit is piece / c
It is shown by m ^2.

(5) Intrinsic viscosity: measured at 25 ° C. at a concentration of 0.1 g / ml in orthochlorophenol. The unit is represented by dl / g.

(6) Glass transition temperature (Tg) Measured according to JIS K7121.

Apparatus: “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. Data analysis— “Disk session SSC / 5200” Sample mass: 5 mg Heating rate: 20 ° C./min

[0034]

EXAMPLES The present invention will be described based on examples and comparative examples.

Example 1 Polyethylene-2,6 having an intrinsic viscosity of 0.65 (dl / g)
The naphthalate may be a thermoplastic polymer polybutylene terephthalate / polyether copolymer ("Hytrel 55
A master chip (intrinsic viscosity: 0.64 (dl / g)) of polyethylene-2,6-naphthalate containing 10% by weight of 57 ″ (registered trademark of Du Pont-Toray Co., Ltd.) was prepared. Using a PEN chip, the polybutylene terephthalate / polyether copolymer was weighed and mixed such that the amount thereof became 5% by weight, preliminarily dried at 165 ° C for 2 hours, and then dried at 180 ° C for 2 hours. The dried raw material chips are supplied to a 150 mm single screw extruder, melt-mixed and weighed, then passed through a fiber sintered stainless steel metal filter (5 μm cut), extruded into a sheet shape from a T-die die, and heated to 25 ° C. While applying an electrostatic charge to the kept cooling drum, it was tightly cooled and solidified (film intrinsic viscosity: 0.63 dl / g). The compression section and the measuring section were set at 310 ° C. and the residence time was 7 minutes, and then the cast film was stretched 4.5 times at 135 ° C. with a roll stretching machine in the longitudinal direction. Introduced, transversely stretched 5.3 times at 140 ° C., cooled once to 50 ° C., heat-set at 200 ° C., and biaxially oriented polyethylene-2, 6 μm thick.
A 6-naphthalate film was obtained. Table 1 shows the characteristics thus obtained. The film of the present invention was a high quality film having a high Young's modulus, excellent tear resistance, and few fish eyes. Further, the production of the above-mentioned strengthened film was extremely stable, and no troubles such as film breakage occurred during the production.

Examples 2 and 3 A biaxially oriented film was obtained in the same manner as in Example 1 except that the amount of the thermoplastic polymer (B) was changed. When the addition amount was 0.3%, the effect of the thermoplastic polymer (B) was more remarkable. This is a thermoplastic polymer (B)
Is controlled to 1 μm or less and the aspect ratio to 100 or less. As shown in Example 3, even when the addition amount of the thermoplastic polymer was 18%, the tear resistance was good.

Example 4 A film was formed in the same manner as in Example 1 except that a polycarbonate ("Iupilon S-2000" (registered trademark of Mitsubishi Gas Chemical Co., Ltd.)) was used as a thermoplastic polymer. Obtained. Even when polycarbonate is used as the thermoplastic polymer, the "Hytrel 5557" of Example 1 is used.
A high-strength film having excellent tear resistance was obtained in the same manner as in the case where was added.

Example 5 Polyetherimide ("") was used as the thermoplastic polymer (B).
A film was formed in the same manner as in Example 1 except that Ultem 1010 ″ (registered trademark of GE Plastics Co., Ltd.) was used.
A biaxially stretched film was obtained. The polyetherimide was compatible in the polyester (A), and no dispersion diameter was observed.
When polyetherimide was used as the thermoplastic polymer, a high-strength film having excellent tear resistance was obtained.

Comparative Example 1 A film was formed in the same manner as in Example 1 except that the thermoplastic polymer (B) was not added. As shown in Table 1, when the thermoplastic polymer was not added, the tear resistance of the film was poor.

Comparative Examples 2 and 3 Films were formed in the same manner as in Example 1 except that the amount of the thermoplastic polymer (B) was changed. As shown in Table 1, when only 0.05 wt% of the thermoplastic polymer (B) was added, the tear resistance of the film was poor (Comparative Example 2).
When the addition amount of the thermoplastic polymer (B) increases at 25%, the tear propagation resistance exceeds 20 N / mm and the Young's modulus becomes 5
Only films lower than GPa were obtained. In addition, fish eyes increased and the film quality tended to decrease (Comparative Example 3).

[0041]

[Table 1]

[0042]

According to the present invention, at least ethylene-2,6
-By adding a small amount of a thermoplastic polymer to a polyester containing a naphthalate unit as a main component, a film having both a high Young's modulus and excellent tear resistance can be obtained. Therefore, it is possible to increase productivity by reducing film breakage during film formation, and to improve film rigidity, processability, and quality, and widely used in various film applications such as magnetic recording, photography, and electrical insulation. It can be used.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 67:00 B29L 7:00

Claims (9)

[Claims] 1. A film comprising a polyester (A) containing at least ethylene-2,6-naphthalate unit as a main component and a thermoplastic polymer (B), in at least one direction selected from the longitudinal direction and the width direction of the film. Polyester film having a tear propagation resistance of 3 to 20 N / mm. 2. The thermoplastic polymer (B) is dispersed in a film, the average dispersion diameter of which is 5 μm or less, and the aspect ratio representing the domain shape of the thermoplastic polymer (B) is 1
The polyester film according to claim 1, wherein the number is from 100 to 100. 3. The thermoplastic polymer (B) has an average dispersion diameter of 1
The polyester film according to claim 1 or 2, wherein the thermoplastic polymer (B) has an aspect ratio of 1 to 100 or less. 4. The polyester film according to claim 1, wherein the thermoplastic polymer (B) is compatible with the polyester (A). 5. The thermoplastic polymer (B) is a polybutylene terephthalate / polyether copolymer, styrene-ethylene-butadiene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene. Block copolymer, acrylonitrile- (ethylene propylene diene telepolymer) -styrene block copolymer, ethylene propylene rubber, ethylene butadiene rubber, polycarbonate,
5. The method according to claim 1, wherein at least one selected from polyetherimide, polystyrene, styrene / acrylonitrile copolymer, methyl methacrylate / styrene copolymer, and styrene / acrylonitrile / butadiene copolymer. The polyester film according to any one of the above. 6. The polyester film according to claim 1, wherein the polyester (A) contains the thermoplastic polymer (B) in an amount of 0.1 to 50% by weight. 7. The polyester film according to claim 1, wherein the Young's modulus in at least one direction selected from the longitudinal direction and the width direction of the film is 6 to 20 GPa. 8. The polyester film according to claim 1, wherein the polyester film is a uniaxially or biaxially oriented film.
The polyester film according to claim 7. 9. A magnetic recording medium using the polyester film according to claim 1.