JPS6360731A - Preparation of biaxially oriented polyethylene-2,6-naphthalate film having high strength in longitudinal direction - Google Patents

Abstract

PURPOSE:To obtain a film having high strength in a longitudinal direction and very little thickness unevenness in the longitudinal and transverse directions, by utilizing a specific drawing and film manufacturing conditions for drawing a polyethylene-2,6-naphthalate. CONSTITUTION:A substantially unoriented polyethylene-2,6-naphthalate undrawn film is drawn in a longitudinal direction at a temp. which is 10 deg.C higher than the secondary transition temp. or more and the sticking temp. with a roll or lower in such an extent that the rate of orientation becomes 10% or more and 40% or less and then moreover drawn in the longitudinal direction at a temp. which is the preceding drawing temp. or more and the sticking temp. with the roll or lower in such an extent that the rate of orientation becomes 40% ore more and 60% or less. The film is then drawn in a transverse direction 3.5 times to make the reflective index in the transverse direction higher than that in the longitudinal direction. The film is heat-set at a temp. which is the temp. for drawing in the transverse direction of more and 230 deg.C or less, relaxed 3 to 30% in the width direction and finally redrawn in the longitudinal direction at the heat-setting temp. or more. A film is thereby obtained whose Young's modulus in the longitudinal direction, reflective index in the longitudinal direction, reflective index in the thickness direction and thickness deviations in the longitudinal and transverse directions are 1,100kg/mm<2> or more, 1,800 or more, 1,500 or less and 8% or less respectively.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a door with extremely high strength in the longitudinal direction / The present invention relates to a method for producing a 6-7 tallate film made of strong crab-axis oriented polyethylene film with very little thickness unevenness.

[Prior art and problems to be solved by the invention] As is well known, in recent years polyethylene terephthalate films have become mainstream as films for industrial materials. This polyethylene terephthalate is desired to be made into a thin film in various fields of use, and a longitudinally reinforced film is used.
For production on an industrial scale, the Young's modulus must be at most 100~
The Young's modulus is about 900 Kg/1 m' and cannot reach the currently desired Young's modulus of /100 Kv- or more. On the other hand, polyethylene co, 6-s7 talate,
High-strength films with a ylooKyy value of 2 or more are known (% Kaisho!
(Refer to Publication No. 10/30J).

Polyethylene-2,6-naphthalate has an extremely slow crystallization rate compared to polyethylene terephthalate, and can achieve a much higher area magnification than polyethylene terephthalate while suppressing oriented crystallization due to stretching as much as possible. It is known to be an extremely suitable material for producing high strength longitudinal films.

However, although the property of having a slow crystallization rate is advantageous in producing a high-strength film, it has the disadvantage that it is difficult to make the thickness uniform. Therefore, the Young's modulus in the longitudinal direction becomes /10θ9/! When producing a film with extremely small thickness unevenness in both length and width, it is impossible to simply increase the stretching ratio, and it is possible only by adopting an extremely strictly controlled manufacturing process. There are many things.

The present invention has been studied to satisfy the above-mentioned requirements, and its purpose is to have a Young's modulus in the longitudinal direction of / / 0
It is an object of the present invention to provide a method for producing a film which has a film thickness of 0 K4/wa" or more and has very little variation in thickness in the vertical and horizontal directions.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors of the present invention found that
The present invention was achieved by discovering that the above object can be achieved by employing certain stretching film forming conditions when stretching polyethylene co-6-naphthalate.

That is, the gist of the present invention is to first heat an unstretched film of substantially unoriented polyethylene co-6-7 tallate in the longitudinal direction at a temperature higher than the secondary transition point by 10°C and lower than the adhesion temperature with a roll. And after stretching so that the orientation ratio is 10% or more and 40% or less, the film is further stretched in the longitudinal direction at a temperature higher than the stretching temperature and lower than the roll adhesion temperature, and the orientation ratio is UO.
% or more and 60% or less, and then transversely stretched 3.5 times or more in the transverse direction so that the refractive index in the transverse direction is higher than the refractive index in the longitudinal direction to form a biaxially oriented film, and further The biaxially oriented film is heat set at a temperature higher than or equal to the transverse stretching temperature and lower than 230°C, and relaxed by 3 to 30% in the width direction, and then longitudinally stretched again at the above heat setting temperature, and then stretched as necessary. Heat set according to the longitudinal Young's modulus / /
00 Ky/wn2 or more, a longitudinal refractive index of 7300 or more, a thickness direction refractive index of /JOO or less, and a thickness unevenness in the longitudinal direction and loss of f% or less. Directional hypertonic crab-axis oriented polyethylene - a method for producing a 6-7 tallate film.

Polyethylene 11,6-naphthalate as used in the present invention refers to a polymer whose constituent units are substantially composed of ethylene-,2,A-7-thale units, but in small amounts, for example, 10 mole or less. Preferably less than 5 molt.
Also included are ethylene m=6-7 tallate polymers modified by components.

Polyethylene 11,6-naphthalate is generally produced by condensing naphthalene, 6-dicarboxylic acid, or a functional derivative thereof, such as methyl naphthalene or 6-dicarboxylate, with ethylene glycol in the presence of a catalyst under appropriate reaction conditions. Manufactured by In that case, as a third component other than naphthalene, 6-dicarboxylic acid and ethylene glycol, dicarboxylic acids such as adipine acid, oxalic acid, di-7thalic acid, terephthalic acid, naphthalene, 7-dicarboxylic acid, diphenyl ether dicarboxylic acid, or lower alkyl thereof. Esters; oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid or lower alkyl esters thereof; or globylene glycol, trimethylene glycol.

Tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, diethylene glycol,
/, covalent alcohols such as t-cyclohexanedimethanol; polyalkylene glycols such as polyethylene glycol and polytetramethylene glycol; and during polymerization, matting agents such as titanium dioxide, light shielding agents such as carbon black, etc. agent, phosphoric acid.

Stabilizers such as phosphorous acid and their esters, antioxidants such as hindered phenols, polymerization regulators, crystallization regulators, plasticizers, etc. may be added.

Furthermore, if the degree of polymerization of the polyethylene naphthalate used in the present invention is too low, the mechanical properties will deteriorate, so the intrinsic viscosity thereof is 0.1IO or more, preferably 0.6 to 0.0.

The film of the present invention can be used for various purposes such as magnetic tape use,
It can be used for a variety of purposes such as thermal transfer and capacitor applications, but for any purpose, it is necessary to contain a fine inert compound to impart slipperiness in order to provide runnability. . One such method is to precipitate fine particles by causing a phosphorus compound to act on a metal compound dissolved in the reaction system during the production of polyethylene naphthalate, such as a metal compound dissolved in the system after transesterification. There is a method called the precipitated particle method. This method is particularly preferable since it produces fewer coarse particles, but as a simpler method, another method, the so-called additive particle method, is more preferably used.

Here, the additive particle method is a method in which inert fine particles are blended into the polyethylene naphthalate polymer raw material at any step from the polyethylene naphthalate production process to the extrusion process before film formation. Examples of inert fine particles include kaolin, talc, magnesium carbonate, calcium carbonate, barium carbonate, calcium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, lithium fluoride, and calcium oxalate. and (!a, Ba, Zn, Mn
Examples include nine or more metal compounds selected from terephthalates such as, carbon black, and the like.

The shape of this inert compound may be spherical, lumpy, or flat, and its hardness may vary.

There is no particular restriction on the nine specific gravity colors, etc. The average particle size of the inert compound is usually an equivalent spherical diameter of 0. /~70μ, preferably from 0.3~3μ. The amount of the film to be blended is preferably o, oi to 10% by weight,
0.02 to o3 weight - more preferably 0.02 to o3 weight. OJ～O1
S is selected from a range of % by weight.

In the present invention, a substantially non-oriented unstretched film of polyethylene, 6-naphthalate, which is dried by a known method, melt-extruded, and then cast on a cooling drum, is first stretched in the longitudinal direction. One of the important aspects in the longitudinal stretching of polyethylene co-6-naphthalate is the material of the stretching rolls.

Normally, when polyethylene terephthalate is stretched, mirror-finished rolls plated with hard chrome are used to prevent scratches on the film and maintain smoothness. However, in the stretching of polyethylene-2,A-naphthalate, which will be described later, with a hard chrome-plated mirror roll, at a stretching temperature that can improve the unevenness of the film thickness,
This is unsuitable because it causes adhesion to the film. On the other hand, rolls and rolls lined with elastomers such as shite, Teflon, and silicone are known to prevent adhesion to the film, but when used in industrial scale production, they have poor durability, especially wear resistance. Have difficulty. Therefore, it is preferable to use a ceramic-coated roll, which has better non-adhesiveness and better durability than a hard chrome-plated roll, as a longitudinal stretching roll for polyester resin and 6-7 tallate. As the material of the ceramic coat roll, known materials such as At, O, etc. can be used. Also, the surface roughness varies depending on the application, but it is 0. It is preferable to use between /B and yoS.

Thus, when performing longitudinal stretching using a ceramic coated roll as a longitudinal stretching roll, multistage stretching is essential in the present invention. - Although it is possible to stretch in stages,
- The thickness unevenness in the vertical direction is reduced by stepwise stretching to the same level as commercially available polyethylene terephthalate film (R/x - about 3 inches)
In order to achieve this, it is necessary to set the stretching temperature to an extremely high temperature, but this is unsuitable because it causes adhesion to the rolls and thus loses its commercial value. In the present invention, when longitudinal stretching is carried out in multiple stages, the unstretched film is heated at a temperature higher than 70°C higher than the secondary transition point (approx. It is necessary to first stretch the film in 7 stages or in multiple stages using a roll at a temperature of about 7≠θ°C or lower so that the orientation ratio is 10% or more and 160% or less. This stretching process will be referred to as "pre-stage stretching" hereinafter. Here, the maximum axial orientation birefringence Hrm (Δn) of borie terenco and 6-naphthalate is approximately θ, 3, although it varies depending on the degree of copolymerization and the like. If the stretching temperature is below the secondary transition point, the film will become thick and thin during cold stretching, and the thickness unevenness will not be improved by subsequent stretching, which is unsuitable. On the other hand, the higher the stretching temperature, the better; however, if it exceeds the temperature at which the film sticks to the roll, surface defects will occur in the film, which is unsuitable. Furthermore, if the orientation ratio in the first stage stretching is less than 10%, it is difficult to increase the subsequent stretching temperature because the orientation of the film is low, making it difficult to improve thickness unevenness, which is unsuitable. On the other hand, if the orientation ratio in the first stage stretching exceeds tI0, it is impossible to obtain a high stretching ratio in the second stage, and in this case as well, it is difficult to improve thickness unevenness and is therefore unsuitable. Preferably JO% or less, more preferably 2! less than or equal to

The pre-stretched film thus obtained is further stretched in the longitudinal direction at a temperature above the pre-stretching temperature and below the roll adhesion temperature to obtain a longitudinally stretched film with an orientation ratio of 0% to 60 cm.

This stretching process is hereinafter referred to as "second-stage stretching".The second-stage stretching may be carried out in multiple stages as long as the orientation ratio is within the range of 60 cm or more, but it is preferably performed in stages.The second-stage stretching temperature is the same as the first-stage stretching temperature. If the temperature is lower than the first-stage stretching temperature, the thickness unevenness will not be improved.On the other hand, the adhesion temperature with the rolls in the second-stage stretching is extremely high compared to the first-stage stretching. The increase in adhesion temperature depends on the orientation ratio of the first-stage stretching, and increases as the orientation ratio after the first-stage stretching increases.It is preferable to make the orientation ratio of the first-stage stretching as high as possible.Orientation after the second-stage stretching The rate is yo%
60% or less. If the orientation ratio after the post-stretching is lower than the Da θ coefficient, no improvement in thickness unevenness in the longitudinal direction is observed, which is unsuitable. On the other hand, if it exceeds 60%, breakage occurs frequently in the subsequent transverse stretching and re-stretching steps, making it difficult to form a film, making it unsuitable.

As mentioned above, after the first-stage stretching, it is possible to proceed directly to the second-stage stretching, but in the present invention, it is also a preferable method for improving thickness unevenness to include a thermal relaxation step for orientation relaxation before the second-stage stretching. . Orientation relaxation may be performed using a roll, or may be performed using an external heating method such as an infrared heater. Heat treatment for orientation relaxation is carried out at a temperature higher than the longitudinal stretching temperature immediately before treatment and lower than the adhesion temperature with the roll for 0.5 to 3.0 seconds, /,0
It is preferable to keep the stretching ratio from 7 times to 7 times. In addition to hard chrome plated rolls and ceramic coated rolls, it is also possible to use elastomer rolls such as Teflon rolls and silicone rolls as rolls for thermal relaxation, since stretching is hardly performed.

The longitudinally-axially stretched film thus obtained is sent to a transverse stretching step, which generally consists of a tenter, at temperatures ranging from /20°C to /20°C.
The film is stretched in the transverse direction at a temperature of 3.3 times or more at a temperature of preferably /3θ°C to /60°C. At that time, it is essential to stretch so that the refractive index in the transverse direction is higher than the refractive index in the longitudinal direction. If the film in this step is oriented vertically, it will be extremely difficult to even out the thickness unevenness in the lateral direction after re-stretching, which is unsuitable.

Next, the biaxially oriented film is subjected to heat setting at a temperature above the transverse stretching temperature and below 230°C. The heat fixation in this process is
This is an essential step in order to prevent the film from breaking due to shrinkage in the width direction in the next re-stretching step, and to promote an increase in strength in the re-stretching step. Furthermore, it is essential to relax the film in the width direction by 7% to 30% before this step or the post-fire re-stretching step of the step. If the next re-stretching is performed without this width relaxing step, the orientation in the width direction is too large, which is unsuitable because breakage occurs frequently before the strength in the machine direction reaches a predetermined value. Therefore, the mountain relaxation needs to be 3% or more, preferably 3% or more. - If the width relaxation exceeds 30%, it is not preferable because the thickness unevenness of the film in the lateral direction becomes extremely worse. It is preferably -1% or less, more preferably 20% or less.

The film thus obtained is further stretched again in the machine direction.

For the re-stretching, longitudinal-stage stretching is most preferable, but if necessary, longitudinal two-stage stretching, longitudinal-re-transverse-re-longitudinal stretching, re-transverse-re-longitudinal stretching, or longitudinal stretching.

There is no problem with simultaneous transverse stretching.

Afterwards, it is heat-set and manufactured into a product depending on the purpose.
The Young's modulus of this film in the longitudinal direction is / / 00 Kt
It is essential that the refractive index in the vertical direction is /,100 or more, the refractive index in the thickness direction is /,!00 or less, and the vertical and horizontal thickness unevenness is less than or equal to 100.

If the Young's modulus in the longitudinal direction is lower than / / 00 Kg/ras2, it can be achieved with polyethylene terephthalate, and there is no advantage of using reed, polyethylene, or 6-naphthalate, which is not preferred. More preferably / J 00
K4/m" or more, more preferably / 300 K9/r
If the refractive index in the longitudinal direction is lower than /, 00, or the refractive index in the thickness direction exceeds /, !;00, the Young's modulus in the longitudinal direction is
Although it is possible to obtain a film with a thickness of 100 mm or more, the strength in the direction of lateral force is low and it is unsuitable in this case.

As described above, according to the method of the present invention, it is possible to obtain a film of polyethylene co-6-naphthalate that has less unevenness in thickness both vertically and horizontally and has extremely excellent strength in the vertical direction. The method of the present invention has extremely excellent industrial value because it can be applied to various high-quality, high-performance film applications that have previously been impossible.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The method for measuring the physical properties of the film is as follows:
This is the following circular.

(1) Thickness The thickness was measured along the longitudinal and lateral directions of the biaxially stretched film using a continuous film thickness measuring device (using an electronic micrometer) manufactured by Madarasu Ritsu Electric Co., Ltd., and υ was calculated for a length of 3 m using the following formula.

The longitudinally stretched film adhesive tarpsion was measured using a polarizing microscope manufactured by Carl Zeiss, and the birefringence Δn was determined using the following formula.

1 m-R/d R: Retardation d: Film thickness 3) Refractive index The refractive index in the longitudinal direction and the thickness direction was measured at 3° C. using an Atsube refractometer manufactured by Atago Co., Ltd. by a conventional method.

(4) Film temperature The temperature of the film at the stretched portion was measured using an infrared radiation thermometer manufactured by Burns.

(5) Film surface defects due to adhesion The surface of the aluminum evaporated film was observed using a Carl Zeiss differential interference microscope. A film with J/- or more vertical scratches forming convex portions on the film surface was marked as a defective film, and a film with less than S scratches/- was marked as a film with no film defects.

Comparative Example/, λ Example/, λ Polyethyleneco, 6-naphthalate ((n) = 0.
63) was dried by a conventional method, melt-extruded, and cast onto a cooling drum by an electrostatic adhesion method to obtain a substantially non-oriented unstretched film.

The unstretched film was first stretched in the longitudinal direction using a ceramic-coated stretching roll with a roughness of 8, but the adhesion temperature with the roll was 40°C when stretched 0 times. , at 131°C below the adhesion temperature /, - times (comparative example / ), /, 1 times (Example 1), Yu,! I times (Example,
2), ,7. ．． 2 times (Comparative Example 2) Perform the first-stage stretching, and further stretch the ISO so that the total magnification is J, 1 times
After stretching at °C, /&, 9.0 times horizontal stretching at MC to 760
Heat set at 753°C while relaxing 70% in the width direction.
After longitudinal stretching again by 53 times, the film was heat-set at θ0° C. to obtain a 7 μm film. Table 7 shows the evaluation results of this film.

Comparative Example 3 In Example--, when the overall magnification for horizontal stretching was set to 7.3 times, the film could not be formed into a film due to frequent breaks during horizontal stretching.

Comparative Example Hiroshi Example - except that the lateral stretch ratio was 3.0 times,
A film of 7μ was obtained by forming a film in the same manner as in Example 2.

Comparative Example In Example C, stretching was attempted in the same manner as in Example C except that the relaxation in the width direction was set to 0%, but when the re-longitudinal stretching ratio was increased to 3 times or more, breakage occurred frequently.Comparative Example 6 Example A film of 7μ was obtained with a relaxation rate of 3% at -.

In Comparative Example 7, Example 3, and Example 3, when stretching was performed without heat setting after transverse stretching, the edges of the film ran out and broke frequently during longitudinal stretching. On the other hand, in Example λ, films were formed at heat setting temperatures of 710° C. and 200° C. after transverse stretching.

These results are shown in Table 7.

〔Effect of the invention〕

As is clear from the results in Table 7, according to the method of the present invention, even in polyethylene 11,6-naphthalate films, films with uniform thickness unevenness comparable to polyethylene terephthalate and high strength in the longitudinal direction can be obtained. This makes it possible to obtain a film that is extremely suitable as an industrial film.

Sender: Diafoil Co., Ltd. Representative Patent Attorney Naga Kagawa - Others/names

Claims (1)

[Claims] (1) A substantially unoriented unstretched film of polyethylene-2,6-naphthalate is first heated in the longitudinal direction at a temperature that is 10°C higher than the secondary transition point and lower than the adhesive temperature with the roll, and at an orientation rate of 10°C. % or more and 40% or less, and then further stretched in the longitudinal direction at a temperature not less than the stretching temperature and not more than the roll adhesion temperature and with an orientation rate of 40% or more and 60% or less, and then in the transverse direction. 3. in the horizontal direction so that the refractive index is higher than the refractive index in the vertical direction.
After transversely stretching 5 times or more to obtain a biaxially oriented film, and further heat-setting the biaxially oriented film at a temperature above the transverse stretching temperature and below 230°C and relaxing it by 3% to 30% in the width direction, the above-mentioned Re-stretch longitudinally at a temperature below the heat-setting temperature, then heat-set if necessary, until the Young's modulus in the longitudinal direction is 1,100K.
g/mm^2 or more, longitudinal refractive index 1,800 or more,
A biaxially oriented polyethylene-2,6-naphthalate film with high strength in the longitudinal direction, which has a refractive index in the thickness direction of 1,500 or less and a thickness unevenness in both the longitudinal and lateral directions of 8% or less. manufacturing method.