JP3270205B2 - Method for producing easily adhesive high strength polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an easily adhesive high-strength polyester film, and more particularly, to an easy-adhesive layer having no heat transfer and excellent adhesiveness.
In particular, the present invention relates to a method for producing a high-strength polyester film useful as a base material for a magnetic recording medium.

[0002]

2. Description of the Related Art Melt extrusion of a thermoplastic polyester, for example, polyethylene terephthalate or a copolymer thereof, polyethylene naphthalene dicarboxylate or a copolymer thereof, or a blend thereof with a small proportion of another resin to form a film. Is known. It is also known that the resulting biaxially stretched and heat-set polyester film has better heat resistance, gas barrier properties, electrical properties and chemical resistance than films made of other resins.

[0003] The above polyester film is usually produced by a simple biaxial stretching method, that is, simultaneous or sequential stretching in the machine direction and the transverse direction, followed by heat fixing at a high temperature. For polyester films, further improvement in strength is desired depending on the application. For this reason, as a method for producing a high-strength polyester film, a method in which the film is biaxially stretched in the longitudinal and transverse directions and then stretched again (re-longitudinal stretching method). Has been proposed (Japanese Patent Publication No. 34-5)
887, Japanese Patent Publication No. 36-2258, etc.). In this re-longitudinal stretching method, for example, the polyester film after biaxial stretching is re-longitudinal-stretched under the conditions of a stretching temperature of 80 to 180 ° C. and a stretching ratio of 1.2 times or more (in some cases, further transverse stretching). Re-longitudinal stretched film has the advantage that the mechanical strength in the machine direction is 1.5 times or more that of a simple biaxially stretched film. It is extremely useful as a film.

By the way, since the surface of the polyester film is highly crystallographically oriented, the surface has high cohesiveness,
For example, the adhesion of paints, adhesives, inks and the like is poor.

Therefore, as a method of improving the adhesiveness, physical treatments such as corona treatment, ultraviolet treatment, plasma treatment, EB treatment, flame treatment and the like, or chemical treatments such as alkali, amine aqueous solution, trichloroacetic acid phenols and the like are used. Is known. However, these methods have practical disadvantages such as deterioration of the adhesive force with time and contamination of the working environment due to volatilization of the chemical.

As another means, there is known a method in which a primer layer is provided by applying an easily adhesive coating solution to a film surface by a process other than the ordinary polyester film forming process. However, in this method, an organic solvent is usually used as a solvent for the coating liquid, and it is difficult to say that the coating atmosphere is sufficiently clean. There are safety and hygiene problems such as deterioration.

[0007] Therefore, if this primer treatment is carried out in the process of forming a polyester film using an aqueous coating solution, there is no adhesion of dust in a clean environment, and there is no danger of explosion or deterioration of the environment due to the aqueous solvent. However, it is advantageous in terms of film performance, economy and safety.

[0008]

SUMMARY OF THE INVENTION In order to facilitate the adhesion of a high-strength polyester film, the present inventor applied a commonly used easy-adhesive binder coating solution after the first-stage longitudinal stretching, and found that the vertical re-stretching occurred. The film has poor slipperiness when stretched,
It has been clarified that problems such as transfer of a coating film to a hot roll and adhesion of foreign matter due to generated static electricity occur because the friction coefficient increases. The present inventor further studied to solve such a trouble, and as a result, a specific filler (fine particles)
The inventors have found that when the aqueous coating liquid containing the addition type polyester resin is applied so as to have a specific thickness, the above trouble can be suppressed, and the present invention has been achieved.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the slip of a film during the manufacturing process, to suppress the transfer of a coating film when a hot roll is in contact, and to make various coatings applied to the film, such as offset ink and gravure. Inks, silk screen inks, UV inks, magnetic paints, adhesives, electrophotographic toners, chemical matte paints, diazo paints, hard coat paints, UV paints, heat-sealing compositions, inorganic film-forming substances, etc., especially magnetic paints It is an object of the present invention to provide a method for producing an easy-adhesion high-strength polyester film having an easy-adhesion layer having excellent adhesion and low tackiness, and further having low electrification.

[0010]

According to the present invention, there is provided, according to the present invention, at least one side of a longitudinally stretched polyester film comprising at least 70 mol% of an acid component comprising terephthalic acid and / or naphthalenedicarboxylic acid. Next transition point is 20
A water-based easy-adhesion coating solution containing 99 to 80% by weight of a polyester resin at 150 to 150 ° C and 1 to 20% by weight of fine particles having an average particle size of 0.01 to 0.1 μm has a final coating film thickness of 0.005 to
A coating film which is coated in an amount of 0.03 μm, then dried and stretched in the transverse direction, further stretched in the longitudinal direction, and if necessary, stretched in the transverse direction, and then heat-fixed.
Is obtained by a method for producing an easily adhesive high-strength polyester film having a coefficient of friction of 0.42 to 0.44 .

In the present invention, the polyester constituting the polyester film is a linear saturated polyester in which terephthalic acid and / or naphthalenedicarboxylic acid accounts for 70 mol% of the total acid component. Specific examples of the polyester include polyethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, terephthalic acid-2,6-naphthalenedicarboxylic acid-ethylene glycol copolymer, and the like.

The linear saturated polyester may contain an agent for improving the film properties, such as a lubricant, an antistatic agent, a coloring agent, a flame retardant, a light-shielding agent, a stabilizer, and an ultraviolet absorber. The lubricant may be either internally precipitated particles or externally added particles, or may be a combination of two or more. As the externally added particles, for example, silica, kaolin, calcium carbonate, calcium phosphate, titanium oxide,
Silicone resin particles, crosslinked polystyrene particles and the like can be mentioned, and as internal precipitation particles, for example, those precipitated during the production of polyester with a combination of an alkali (earth) metal compound, a phosphorus compound and the like can be mentioned.

The polyester in the present invention is known per se and can be produced by a known method. Inherent viscosity of polyester (O-chlorophenol, 35
C) is preferably from 0.45 to 0.9.

In the present invention, the polyester is melt-extruded by a conventional method, quenched and solidified to obtain an amorphous unstretched film, and the unstretched film is stretched first in the longitudinal direction and then in the transverse direction. These stretchings are performed by running a film. A known means can be used for the stretching means in the longitudinal direction and the transverse direction. For example, in the longitudinal stretching (longitudinal stretching), the unstretched film is heated by a heating roll group,
This is performed using the peripheral speed difference between the low-speed roll and the high-speed roll. At that time, it is preferable to provide an infrared heater between the low-speed roll and the high-speed roll to heat the film to the stretching temperature, or the low-speed roll may heat the film to the stretching temperature.
The stretching in the longitudinal direction is normally performed at a magnification of 1.5 to 5.7 times. The stretching in the transverse direction (transverse stretching) is performed using a tenter-type stretching heat treatment apparatus. When the horizontal stretching is not performed again, the horizontal stretching is performed at a predetermined magnification. When the horizontal stretching is performed again, the horizontal stretching is performed at a magnification lower than the predetermined magnification (total stretching magnification). The biaxially stretched film stretched in the transverse direction is usually subjected to a heat (fixation) treatment at a low temperature as described above.

The biaxially stretched film thus obtained is further stretched at least in the longitudinal direction, in other words, in the longitudinal direction, or in the longitudinal and transverse directions, and then subjected to a heat (fixing) treatment. This second longitudinal stretching (re-longitudinal stretching) can be performed in the same manner as the above-described first-stage longitudinal stretching means, or can be performed by another method. For example, the first-stage longitudinal stretching can be performed by an infrared heating method, and the re-longitudinal stretching can be performed by a roll heating method. As the method of re-longitudinal stretching, the infrared heating method is advantageous in terms of the process because the temperature of the hot roll in contact with the coating material is low. Further, the horizontal stretching (re-horizontal stretching) and the heat (fixation) treatment are performed again using a tenter-type stretching heat treatment apparatus. In the tenter-type stretching heat treatment apparatus, when the transverse stretching ratio is set to 1, the re-lateral stretching is not substantially performed, and only the heat setting treatment is performed.

A longitudinal stretching device, a transverse stretching device,
As can be understood from the above, a conventionally known apparatus can be used as the re-longitudinal stretching apparatus, the final heat treatment apparatus, and the like.

In the present invention, the transverse stretching ratio is preferably 2 times or more, more preferably 2.5 times or more, and particularly preferably 3 times or more. However, when re-horizontal stretching is performed, the above ratio can be determined in combination with the re-horizontal stretching ratio. The upper limit of the transverse stretching ratio depends on the film properties, but is preferably 6 times or less, more preferably 5 times or less.

The magnification of the re-longitudinal stretching depends on the mechanical strength of the film and the like, but is preferably 2.0 times or more, more preferably 2.2 times or more. The upper limit of this magnification is preferably about 4.6 times. The first-stage longitudinal stretching ratio (predetermined ratio) is 1.5.
To 3.0 times, preferably 1.5 to 2.6 times.

[0019] The temperature of the final heat treatment is preferably selected from the range of 150 to 240 ° C, more preferably 170 to 230 ° C. This time is usually several tens of seconds or less. The stretching temperature can be selected from a conventionally known temperature range.

In the present invention, an easily adhesive aqueous coating solution is applied after the first-stage longitudinal stretching, and this coating solution has a secondary transition point of 20%.
It contains a polyester resin at ~ 150 ° C and a filler (fine particles).

The polyester resin preferably has a hydrophilic group in the molecule. Examples of the hydrophilic group include a sulfonic acid group, a carboxylic acid group, and a polyether group. Specific examples of the polyester resin include terephthalic acid-isophthalic acid-5-K sulfoisophthalic acid-ethylene glycol-neopentyl glycol copolymerized polyester, 2,6-naphthalenedicarboxylic acid-isophthalic acid-5-Na sulfoisophthalic acid-ethylene Preferred are glycol-bisphenol A / alkylene oxide adduct copolymerized polyester, terephthalic acid-isophthalic acid-ethylene glycol-dimethylolpropionate amine salt-diethylene glycol copolymerized polyester, and the like.

The secondary transition point of this polyester resin is 20
To 150 ° C, preferably 40 to 130 ° C. If the secondary transition point is lower than 20 ° C., the film is likely to be blocked, while if it exceeds 150 ° C., the stretchability is poor and the surface is rough.

The fine particles may be either inorganic or organic. Fine particles of silica, calcium carbonate, calcium oxide, alumina, kaolin, titanium oxide, crosslinked acrylic resin, crosslinked polystyrene, silicone resin, carbon black, tin oxide, and the like can be preferably exemplified.

The fine particles have an average particle size of 0.01 to 0.1.
It needs to be 1 μm. The preferred average particle size is 0.01
5 to 0.05 μm. This average particle size is 0.01 μm
If it is less than 0.1 μm, the film will have poor slipperiness and process characteristics will deteriorate, while if it exceeds 0.1 μm, fine particles will fall off and the film surface will be too rough, which is not preferred.

The mixing ratio of the polyester resin and the fine particles is as follows:
The ratio is 80 to 99% by weight of polyester resin and 20 to 1% by weight of fine particles. If the ratio of the fine particles is less than 1% by weight,
Insufficient sliding of the film, resulting in poor process characteristics.
If it exceeds 0% by weight, the amount of the particles is too large and the particles easily fall off.

The aqueous coating liquid for easy adhesion in the present invention may contain a wetting agent in order to improve the wettability to the polyester film. Examples of the wetting agent include surfactants such as anionic surfactants, cationic surfactants, and nonionic surfactants, such as polyethylene oxide / polypropylene oxide block copolymers, polyoxyethylene alkylphenyl ether, and polyoxyethylene. Ethylene-fatty acid ester, sorbitan fatty acid ester,
Glycerin fatty acid ester, fatty acid metal soap, alkane sulfonate, alkyl sulfate, alkylbenzene sulfonate, alkyl sulfonate, alkyl diphenyl ether disulfonate, alkyl sulfosuccinate, quaternary ammonium chloride salt, alkylamine hydrochloride And the like. The amount of the wetting agent is preferably 2 to 30% by weight, more preferably 3 to 20% by weight of the total solids in the coating liquid.

Further, as long as the effects of the present invention are not lost, for example, an antistatic agent, an ultraviolet absorber, a pigment, an organic filler, an inorganic filler, a lubricant, a blocking inhibitor,
Other additives such as a cross-linking agent such as melamine, epoxy, and aziridine, and a single or blend of an acrylic resin, a polyurethane resin, and the like can be mixed.

The solid content of the aqueous coating solution is usually 30% by weight.
Or less, and more preferably 10% by weight or less. The amount of coating is preferably 0.5 to ²⁰ g, more preferably 1 to 10 g, per m ² of the running film.

As a coating method, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a reverse coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method, or the like may be applied alone or in combination.
This aqueous coating liquid may contain a small amount of an organic solvent for the purpose of assisting the stability of the coating liquid or the coating property of the coating liquid. The coating can be applied to one or both sides of the film.

The one-stage stretched polyester film coated with the aqueous coating solution is dried and led to processes such as transverse stretching, re-longitudinal stretching, and heat setting. For example, a vertically stretched one-stage stretched polyester film coated with an aqueous coating solution is guided to a stenter, and is horizontally stretched, re-longitudinal stretched, and thermally fixed. During this time, the coating solution dries and forms a film on the film. Drying may be performed before or during the transverse stretching.

The coefficient of friction of the coating film thus obtained is
The thickness (dry) of the coating film of the high-strength polyester film having the primer layer (easy adhesion layer) of 0.42 to 0.44 needs to be 0.005 to 0.03 μm. If the thickness is less than 0.005 μm, the adhesiveness is poor, while if it exceeds 0.03 μm, the surface is roughened, and the transfer tends to occur due to shaving in the process. In particular, when the secondary transition point of the polyester resin as the binder is high, the surface roughness increases as the film thickness increases.

The thus obtained high-hardness polyester film having an easy-adhesion layer (primer layer) has high strength and various coatings such as ink for cellophane, magnetic paint, toner composition for electrophotography, and chemical matte paint. It shows high adhesion to a very wide range of coatings such as diazo coatings, UV inks, etc., especially strong adhesion to magnetic coatings and good blocking resistance without tackiness.

[0033]

The present invention will be further described below with reference to examples. In the examples, “parts” means “parts by weight”. Each characteristic of the film was measured by the following method.

1. Adhesiveness An evaluation paint is applied to the primer-coated polyester film using a Meyer bar so that the thickness after drying becomes about 4 μm, and dried at 100 ° C. for 3 minutes. Thereafter, aging was performed at 60 ° C. for 24 hours. 600 (3
M company) (12.7 mm wide and 15 cm long) were adhered so as not to contain air bubbles, and JIS C2701 (197
5) Using a manual load roll as described above, bring the tape into close contact, and cut it out into a tape width. The strength when this is peeled 180 degrees is measured. [Evaluation paint] In terms of solid content, urethane resin Nipporan 2304 25 parts (Nippon Polyurethane) PVC / vinyl acetate resin Esrec A 50 parts (Sekisui Chemical) Dispersant Ratio P 1 part (RIKEN Vitamin) Magnetic agent CTX- 860 500 parts (manufactured by Toda Chemical Co., Ltd.) are dissolved in a mixed solvent of methyl ethyl ketone / toluene / cyclohexanone to make 40%, and 2 parts are mixed with a sand grinder.
Spread over time. Thereafter, 25 parts (in terms of solid content) of coronate L as a crosslinking agent are added, and the mixture is stirred well to obtain a magnetic paint.

2. Secondary transition point of polyester (Tg) The secondary transition point is measured using SSC / 580DS type DSC of Seiko Denshi Kogyo KK Approximately 10 mg of the sample is sealed in an aluminum bolter, melted once by DSC, then gradually cooled, and then cooled to 0 ° C. before starting the main measurement. 10 ° C / mi
A change in the amount of heat is measured while increasing the temperature at a speed of n, and Tg is determined from the change.

3. Blocking property 10 after matching the front and back of the polyester film
cm × 15 cm square, and a weight of 50 kg / cm ² was applied thereto at 50 ° C. in an atmosphere of 50% RH for 17 hours.
Then, the peel strength of this 10 cm width is measured. The peeling speed at this time is 100 mm / min.

4. Surface slipperiness (film slipper) According to ASTM D 1894-63, using a slippery measuring device manufactured by Toyo Tester Co., Ltd., the coefficient of static friction (μs)
Is measured. However, the thread plate is a glass plate and the load is 1 kg.

5. Surface roughness Ra (Center Line Average: center line average roughness) According to JIS B0601, using a high-precision surface roughness meter SE-3FAT manufactured by Kosaka Laboratory Co., Ltd., the radius of the needle is 2 μm.
m, magnification of 200,000 times at a load of 30 mg, cut-off of 0,0.
Under the condition of 08 mm, the chart is drawn, a portion of the measured length L is extracted from the film surface roughness curve in the direction of the center line, the center line of the extracted portion is set as the X axis, and the direction of the vertical magnification is set as the Y axis. When the roughness curve is represented by Y = f (x), the value given by the following equation is represented in μm.

[0039]

(Equation 1)

In this measurement, the reference length was set to 1.25 mm and 4
And the average value is shown.

Example 1 An unstretched sheet was prepared by melt-extruding polyethylene terephthalate (containing a lubricant) having an intrinsic viscosity of 0.64, and stretched 2.1 times in the machine direction. Subsequently, on one surface of the obtained vertically uniaxially stretched film, terephthalic acid-isophthalic acid-5-Na sulfoisophthalic acid-ethylene glycol-neopentyl glycol copolymerized polyester (secondary transition point 75 ° C.) 9
0% by weight, fine particles of crosslinked acrylic resin having an average particle size of 0.03 μm (Microgel E-2 manufactured by Nippon Paint Co., Ltd.)
002) 7 wt% and polyethylene oxide nonyl phenyl ether (Nonipol 85 manufactured by Sanyo Chemical Industries, Ltd.)
4.9 g / m of a 4% aqueous coating liquid having a solid content of 3 wt%
^A kiss coat method was applied with an application amount of ² . Next, after stretching 3.8 times in the horizontal direction, the film was stretched twice in the vertical direction again at 120 ° C. and heat-set at 220 ° C. The thickness of the obtained film was 9 μm, and the thickness of the coating film was 0.02 μm. Table 1 shows the characteristics of this film. In addition, the above-mentioned copolymer polyester
Is dimethyl terephthalate 155 parts, dimethyl isophthalate
29 parts of phthalate, 71 parts of ethylene glycol, neope
110 parts of ethylene glycol, 0.1 parts of zinc acetate and
0.1 part of antimony oxide was charged into a reaction vessel,
The transesterification was performed at 220 ° C. for 3 hours.
Then, 13.4 parts of sodium 5-sulfoisophthalate
Was added and an esterification reaction was performed at 220 ° C. for 1 hour.
Then, under reduced pressure at 240 to 270 ° C (10 to 0.2 mmH
g) to carry out a polycondensation reaction over 2 hours to produce.

[0042]

Comparative Example 1 A plain re-stretched film was obtained in the same manner as in Example 1 except that the aqueous coating solution was not applied. Table 1 shows the characteristics of this film.

Example 2 An unstretched sheet was prepared by melt-extruding polyethylene terephthalate having an intrinsic viscosity of 0.64, and stretched 2.3 times in the machine direction. Subsequently, on one side of the obtained longitudinally uniaxially stretched film,
Silica with terephthalic acid-isophthalic acid-5-K sulfoisophthalic acid-ethylene glycol-1,4-butanediol copolymerized polyester (secondary transition point 76 ° C.) 90 wt%, average particle size 0.03 μm (Nissan Chemical Industries, Ltd.) Made
6% by weight of Snowtex ST-50) and polyethylene oxide nonyl phenyl ether (manufactured by Sanyo Chemical Co., Ltd.)
Nonipol 85) A 4% aqueous coating solution having a solid content of 4 wt% was applied by a kiss coat method at an application amount of 4.5 g / m ² . Next, after stretching 3.7 times in the horizontal direction, it was stretched 2.2 times again in the vertical direction at 120 ° C. and heat-set at 230 ° C. The thickness of the obtained film is 10 μm, and the thickness of the coating film is 0.0 μm.
It was 17 μm. Table 1 shows the characteristics of this film.
The above-mentioned copolymerized polyester is dimethyl terephthalate.
155 parts, dimethyl isophthalate 19.4 parts,
130 parts of Tylene glycol, 1,4-butanediol 1
0 parts, zinc acetate 0.1 parts and antimony trioxide 0.1
Parts into a reaction vessel, at 140-220 ° C for 3 hours
To carry out a transesterification reaction. Then, 5-Sulhui
Add 26.8 parts of potassium sophthalate, and add
After carrying out the esterification reaction for 240 hours,
Polycondensation under reduced pressure (10-0.2 mmHg) for 2 hours
The reaction was carried out to produce.

[Examples 3 to 6, Comparative Examples 2 to 4] The amount of the aqueous coating liquid applied was 3.7 g / m ² in Example 3.
Example 4 was 6.1 g / m ² and Example 5 was 3.0 g / m ² .
Example 6 was 4.7 g / m ² , Comparative Example 2 was 18.8 g / m ² ,
Comparative Examples 3 33.0 g / m ^2, Comparative Example 4 0.25 g / m ²
The same procedure was performed as in Example 1 except that the thickness of the coating film was changed .
Table 1 shows the results obtained when the redrawing ratio in the longitudinal direction was 2.0 times as in Example 1 .

[0045]

[Table 1]

[0046]

According to the present invention, it is possible to improve the slip of the film during the manufacturing process, to suppress the transfer of the coating film when the hot roll is in contact, and to control various coatings applied to the film, for example, magnetic coatings. A method for producing a high-strength polyester film having excellent adhesiveness can be provided.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-235019 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 27/36 C08J 7/04

Claims (4)

(57) [Claims] A 99% to 80% by weight of a polyester resin having a secondary transition point of 20 to 150 ° C. on at least one side of a longitudinally stretched film of a polyester in which 70% by mole or more of an acid component is composed of terephthalic acid and / or naphthalenedicarboxylic acid. And 1 to 20% by weight of fine particles having an average particle size of 0.01 to 0.1 μm
And a final coating film thickness of 0.005.
And the amount coated becomes ～0.03Myuemu, then subjected to drying and transverse stretching consists further re-stretched in the longitudinal direction, subjected to transverse re-stretching if necessary, subjected to thereafter heat set the coating
A method for producing an easily adhesive high-strength polyester film having a coefficient of friction of 0.42 to 0.44 . 2. The method according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene 2,6-naphthalenedicarboxylate. 3. The method according to claim 1, wherein the polyester resin is a polyester resin having a sulfonic acid group or a carboxylic acid group in the molecule. 4. The adhesive strength between the coating film and the magnetic paint is 40 to 46.
2. The easy-adhesion property according to claim 1, which is in the range of g / 12.7 mm.
A method for producing a high-strength polyester film.