JPS6087036A - Manufacturing method of biaxially oriented poly-epsilon-capro amide film - Google Patents

Abstract

PURPOSE:To improve flattness by a method wherein a film which has been finished transverse elongation, after being gradually cooled the heat fixed temperature to the temperature of 150-165 deg.C, the temperature is gradually lowered starting from the end part of the width direction to the center part and next it is rapidly cooled and pulled out at the specially determined speed. CONSTITUTION:A transverse elongated film of poly-epsilon-capro amide is held by tenter clips on both selvage parts in a heat fixed furnace 21 and is fixed by heating for 2sec at the 196 deg.C temperature and furthermore for 2sec at 196 deg.C at the condition the space of tenter clips is narrowed 5% and the film is given slackness to the width direction. The film is gradually cooled to the temperature of 150-165 deg.C which being transported in the system at the speed of 24m per minute after finishing of heat fixation, and after that the product film 30 and its selvages are separated by cutting the selvages with cutting blades 28 just before the film is released from tenter clips, and the product film is wouned to a hauling winder loaded with drawing tension 45-145kg/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a biaxially oriented poly-ε-caproamide film. More specifically, it is an improvement of the method of manufacturing a biaxially stretched poly-ε-caproamide film by first stretching it in the longitudinal direction, then holding it with tenter clips and stretching it laterally, and which has excellent flatness. The present invention relates to a method of manufacturing a film.

Biaxially oriented poly-ε-caproamide has excellent toughness, heat resistance, cold resistance, transparency, printability, chemical resistance, etc.
In addition, it is widely used as a base material film for packaging foods and other products because it has characteristics such as being resistant to pinholes. For example, to make food packaging bags, printing, lamination, bag making, food filling, and heat sealing are usually performed. In this case, the quality of the flatness of the base film depends on the production speed in printing, laminating, bag making processes, etc.
It has a big impact on yield etc. In other words, if there was slack in the base film, pitch misalignment occurred during printing.)
Wrinkles occur during the , laminating and bag making processes, making it difficult to increase production speed. Therefore, there is an extremely strong demand for improving the flatness of the base film, especially the "edge sagging phenomenon."

The "edge sagging phenomenon" is caused by the phenomenon that the edges of the film are longer than the center of the film in the longitudinal direction. This phenomenon is observed and confirmed by the difference in the way the film stretches when a constant tension is applied to the biaxially stretched film and the load is removed.

For example, the "edge sagging phenomenon" will be explained with reference to FIG. In Figure 4, / is a flat table,
3 is the base line drawn on the table, G is the adhesive tape, J is the cutting line, and O is the marked line on the film.

Baseline on a flat table/! , 3 intervals (e.g. 2
Place a film cut lengthwise (for example, 3 meters) and fix one end of it on the table with adhesive tape.

At the other end of the film, apply a certain load, e.g. width/mouthfeel 20
Tension the film by applying a load of gram, and draw a marked line O on the film corresponding to base line 3. Then apply a load and cut the film along the length! When cut into strips with a constant width (for example, 3 crn),
Since the marked lines are shifted for each strip, it is observed that the edges are longer than the center in the width direction of the film.

The difference in length between the center and the edge of the film in the width direction is thought to be due to the bowing phenomenon that occurs during the heat setting process performed after the biaxial stretching process of the film.

That is, while the biaxially stretched film is held and restrained by tenter clips at both ends in the width direction, the central part of the film in the 11] direction is not restrained in the width direction, and the influence of the tenter clips is extremely weak. Therefore, when the film is exposed to high temperatures in the heat setting process after the biaxial stretching process, the central part in the width direction will be The film temperature is taken at the transverse stretching zone where there is a portion that is still sufficiently heated to the heat setting temperature and is difficult to deform, that is, on the upstream side of the film, and lags behind the edges in the clJ direction.

Even in the film cooling step (1) following the above heat setting step, the center portion of the film in the width direction still lags, and as a result, the length of the center portion of the film in the width direction is short and the edges are not long. It is believed that this difference in length causes the "edge walnut phenomenon."

Many proposals have been made regarding methods for improving the "edge smudge phenomenon" of stretched films and producing films with excellent flatness.

For example, Japanese Patent Publication No. Sho Tag-20000 proposes a method of slowly cooling a biaxially stretched film while making the temperature uniform in the width direction when the film is heat-set and cooled. According to the experiments of the present inventors, when using this method,
An improvement effect is observed for walnuts caused by local temperature irregularities in the film or by abnormal strain that occurs during film cooling, but no improvement effect is observed for walnuts caused by the bowing phenomenon. understood.

In addition, Japanese Patent Application Laid-open No. 9-99-76 discloses that when cooling a heat-set film after biaxial stretching, the temperature of the central part of the film is maintained within a specific range;
A method has been proposed to improve the walnuts in the central portion of the film in the width direction. According to the experiments of the present inventors,
Even when this method for preventing sagging in the inside was applied to improve sagging on edges, the improvement effect was not significant.

Furthermore, Japanese Patent Application Laid-open No. 22/2003 discloses that in order to completely improve the flatness of a heat-set film after biaxial stretching, the film is heated in steam at a temperature range of 90 to 3θ°C. A method has been proposed in which a certain tension is applied. However, this method requires a separate device for steam-treating the film and a drying process for the film after steam treatment.
It has the disadvantage of high cost.

Furthermore, JP-A-Sho-f2-/21. The Guarantei υ bulletin states:
A method has been proposed to improve the flatness of the film by applying high tension to the film during stretching in the longitudinal and transverse directions, or after a heat-setting step following stretching in the transverse direction. . However, simply applying high tension to the film according to this method is not sufficient to improve the flatness; the improvement effect is only achieved when the film is combined with a thermal relaxation process after applying tension. However, it is not economical since a heat relaxation device is required.

Under such circumstances, the present inventors conducted extensive studies with the aim of providing an industrially advantageous method for producing a biaxially oriented poly-ε-caproamide film with excellent flatness. As a result, the present invention has been completed.

Therefore, the gist of the present invention is to first stretch a poly-ε-caproamide film in the longitudinal direction, then hold it with tenter clips and stretch it transversely to form a biaxially stretched poly-ε-caproamide film. To manufacture the film, the temperature of the film after lateral stretching is maintained at a uniform temperature in the width direction of the film, and from the heat setting temperature / θ ~ / 4 j
The first step is to gradually cool the film to a temperature within the range of 70°C to In the second step, the central part of the film in the width direction is slowly cooled to the range of ¥,t-SO℃ while keeping the film temperature within the range of K j ℃.
After rapidly cooling the film as follows, the film is cut at both ends immediately before it is released from the tenter clips, and the third step is to take it off while applying a take-up tension of 731<g/cr/I to the product film. The present invention relates to a method for producing a biaxially oriented poly-ε-kaprofamide film having improved flatness, the method comprising the following steps.

The present invention will be explained in detail below.

In the present invention, poly-ε-caproamide is a homopolymer of ε-caglolactam, which is generally referred to as nylon. This polymer contains lubricants, antistatic agents, antiblocking agents, and stabilizers. , various resin additives such as dyes, pigments, and inorganic fine particles may be blended.

When using the method of the present invention, a poly-ε-caproamide film is first stretched in the longitudinal direction, and then stretched in the transverse direction while holding both ear flaps of the film with tenter clips. Biaxially stretched.

In order to stretch the film in the longitudinal direction, it is preferable to use a roll longitudinal stretching method using a roll longitudinal stretching machine. Tenter clips are preferably used to stretch the film in the transverse direction. (For details on the method of sequentially biaxially stretching a poly-ε-caproamide film, see Japanese Patent Application Shojdo-7331,
See No. 1. ) Poly-ε stretched laterally using tenter clips
- In order to impart dimensional stability to the caproamide film, it is then heat-set at a temperature below the melting point, usually above /90°C, while holding both ends with tenter clips. In this heat setting process, 3
% or more relaxation is often given. Therefore, it is an object of the present invention to provide a film manufacturing method that allows the final film to have excellent flatness even after the main fixing step.
This is the object of the present invention.

When using the method of the present invention, the temperature of the film after the transverse stretching process is kept uniform in the width direction of the film in the first stage without being shredded, and is raised from the heat setting temperature to a range of /3-0 to /20"C. Cool slowly. Here, "uniformly" means at least ±3
Means to be kept within a range of °C. If this condition is not satisfied, not only the edge smudge phenomenon will occur in the final film, but also local sagging may occur in the direction of the film IIJ, so it is preferable. However, if the film temperature is set within the range of /3θ to /3°C and the process proceeds to the next second stage without slow cooling, the desired edge sagging improvement effect cannot be achieved.

When using the method of the present invention, in the second step, the film temperature is set to a profile that gradually decreases from the edge of the film in the rl direction to the center, and the temperature difference between the edge and the center is set to 7θ~ While keeping the temperature within the range of 30℃, press the center part in the direction of film transport! Slowly cool to a temperature of ~jθ°C. The temperature profile at this stage is determined by the shape and degree of the edge sag that will eventually be formed (1), and is often parabolic,
Selected from curved profiles that approximate an inverted trapezoid, etc.

In order to create a profile in which the film temperature gradually decreases from the edge to the center in the film transport direction, multiple long infrared heaters are installed parallel to the film transport direction.
The overall method is to arrange the film in a line perpendicular to the film transport direction and adjust the temperature.(b) Cold air blowing nozzles are installed along the film width direction and at an angle close to parallel to the film surface. A method of selectively cooling the central part in the width direction, (c) a method of using a number of hot air nozzles that blow out a number of controlled hot air arranged in a line perpendicular to the film width direction, and (b) - A method of using e9 together, etc. can be selected and adopted. Among them,
A method in which (a) and (b) are used in combination is preferred.

In the process of cooling the film temperature, the film temperature profile can be appropriately selected as necessary so that the temperature difference between the edge and the center in the width direction of the film is within the range of 10 to 3θ°C. However, if the temperature difference is outside this range, for example, if it is as small as 10°C, the effect of improving the edge sagging of the final film will be small, and if it is larger than 30°C, the edge in the width direction of the film will be This is undesirable because it causes a so-called "curling" phenomenon in which it curls toward the side.

In this second stage, while maintaining the film temperature at the above-mentioned profile, the central part of the film in the width direction is heated to Δ~! Cool with 0゛0 temperature agent. If the temperature at the center 771'I in the width direction of the film is not cooled to a range of gt to jθ°C, the flatness of the final product film will be improved even if an appropriate tension is applied to the film as described later. This is not desirable because it is not possible.

In addition, the cooling rates of the first stage and second stage are as follows:
Although not particularly limited, 20°C/sec to s t°C
/sec, preferably in the range of θ°C/sec to 3j′C
It is best to choose within the range of / seconds.

According to the present invention, furthermore, in the third step, after the film temperature is rapidly cooled to below Schiff s 'a over the entire film 111, both edges of the film are cut immediately before the film is released from the tenter clip, and the product film is NirijN
Take it off while applying a take-up tension of /J-kg/C1d.

Do not cool at this stage below 1°C.

Loading the product film with the above-mentioned take-up tension is not preferable because the edge walnut improvement effect is small and the accuracy of the thickness of the final product film is likely to be impaired. After the film temperature is suddenly cooled to below J'Q, just before the film is released from the tenter crimp force of 1, cut both edges of the film and apply 4j~/ltsKg/c to the product film.
Apply a pulling tension of rd.

Cutting both ends of the film must be carried out while holding both ends of the film with tenter clips, otherwise wrinkles will occur in the product film, which is not preferable.

When the above tension is applied to a film that does not cut both edges of the film, the tension is not effectively transmitted to the entire product film because the thickness of both edges is much larger than the thickness of the product film. Also, wrinkles tend to occur on the take-up nip roll, which is undesirable. Film take-up tension is Y j
When the ratio is small, the effect of improving the edge sag of the final product film is small, and the ratio becomes Δ, which tends to impair dimensional stability, which is not preferable. ``The take-up tension applied to the film can be adjusted by adjusting the rotational speed of the sample roll, the movement of the dancer roll, etc.

The present invention has been described in detail above, and according to the present invention, a film that has been biaxially stretched and then heat set can be processed without the need for a special heat relaxation device, steam treatment, drying device, etc. With the film post-processing equipment used,
It is possible to improve the film to have excellent flatness, and the industrial utility value of the present invention is extremely large.

Next, the present invention will be explained in more detail based on examples, but the present invention is not limited to the following nine examples as long as the gist thereof is not exceeded.

Example/~λ Poly-ε-caproamide with a relative viscosity of 3j was
Using a φ extruder, knead the cylinder at a temperature of -2 to 0℃, extrude it into a film using a T-die, and quickly cool it on a casting roll with a diameter of ≦000000 that has been cooled to 30'O. Approximately 0 microns, width approximately 3! An unstretched film of θ thickness was obtained.

This film-q, 1so-φ, medium 700. The film was stretched 3°0 times in the longitudinal direction using a longitudinal stretching machine consisting of a plurality of rolls. Subsequently, the film was stretched 3.2 times in the transverse direction using a tenter-equipped transverse stretching machine.

After completing the horizontal stretching, the film is placed in a heat setting furnace shown in Figure 2, holding both edges of the film with tenter clips.
Heat setting was performed at a temperature of /99 gC for 2 seconds under tension, and then for 2 seconds at a temperature of /94 °C while the tenter clip interval was narrowed by a total j% and the film was relaxed in the width direction.

After the heat setting process, the film was introduced into the apparatus shown as a schematic plan view in FIG. 1 and subjected to post-processing operations.

In Figure 1, -〇 is the film immediately after heat setting, 2 is the heat setting furnace, 22, 23, and 2 are infrared panel heaters, respectively, 2j is the cold air nozzle for cooling the center of the film, 2g
1.27 is the tenter rail, 2. is the edge cutting blade 1.29 is the film edge, 3θ
3 indicates the product film, 3/ is a dancer roll for detecting take-up tension, 3+2 indicates a nip roll, and arrow U indicates the film transport direction.

The film was transferred at a speed of 2 gm/min through the apparatus shown in Figure 2 under the temperature profile shown in Table 1 and Figure 3 (the horizontal axis is the direction in the film, the vertical axis is the film temperature). After cooling the film at a temperature of 1000 ml (meaning the set value), just before the film is released from the tenter clips.
The product film 30 and the film edges are separated by cutting the edges with a cutting blade 2 of 9, and the product film is transferred to a take-off shim winder (not shown) while applying the take-off tension shown in Table 1. It was rolled into a product with a thickness of about 75 microns and a width of 200 mm.

The properties of the obtained product film were evaluated by the methods described below. The results are shown in Table 1.

(1) Flatness of the film As shown in Figure 7, on a flat table, draw a straight line: Fix one end of the film (cut in the width direction) with adhesive tape on the table Z. Apply a load of width direction / 6n weight - θ grams to the other end of the film to tension the film, and place it on the base line 3. Draw a marked line on the corresponding film. Then, apply a load and cut the film into strips at 3°C m intervals along the length direction. Next, draw a θ graph on the free end of each strip. Apply a load of do.

If this index is 2 or less, there is no practical problem with the product film, and more preferably /, j++
Im or less is better.

(2) Film thickness unevenness (%) The thickness of a product film is measured at intervals of K 3 cm in the width direction, and the value is calculated using the following formula.

This thickness unevenness is desirably 70% or less.

(3) Hot water shrinkage rate (%) A square sample with a side length of 100 mm is prepared from the product film, and this sample is 2! The temperature was controlled in an atmosphere of 0° relative humidity and θ%, and marked lines were marked at intervals of ♂0. This sample was immersed in boiling water for S minutes and then taken out for 2 hours.
It was left in an atmosphere with relative humidity of 0% for Jg hours, and the change (Δ2+) between the gauge lines was measured and calculated using the following formula.

Hot water shrinkage rate = 10゜♂0 Examples 3 to Z Using the same type of poly-ε-cabroamide as used in Example/, an unstretched film was prepared in the same manner as on the same side, and then , ipsilaterally, followed by 3.2x stretching in the transverse direction.

After the transverse stretching, the film was held in a heat setting furnace 2/ with tenter clips at both ends of the film, and held under tension at a temperature of 793°C for 2 seconds, with the tenter clip interval being 3%. In a state where the film was narrowed and relaxed in the width direction of the film, heat setting treatment was performed at a temperature of /93°0 for 2 seconds.

While transporting the film at a speed of 2 Z meters per minute through the apparatus shown in Figure 2, After cooling under the same temperature profile conditions, it was wound up with a winder while applying the pulling tension shown in Table 1 to a thickness of approximately 71 microns and a width of approximately 71 microns. A product film at 0θ was obtained.

The properties of the obtained product film were evaluated in accordance with the method described in Example 1. The results are shown in Table 1.

[: Note: l *1 Corresponds to immediately after the film is heated and 2.2 gold is released.

*2 Corresponds to immediately after the film leaves the heater 23.

*3 Corresponds to immediately after the film leaves the heater 2g.

*4 All films are 11j cold air nozzles for cooling =
This corresponds to immediately after passing 2≦.

Comparative Examples 7 to 9 An unstretched film was prepared using the same type of poly-ε-caproamide as used in Example/in the same procedure as in the same example, and then processed in the same equipment as in the same example. The film was stretched 3°0 times in the machine direction, and then 3.2 times in the cross direction.

After the transverse stretching, the film was held in a heat setting furnace 2 with tenter clips, and held under tension at a temperature of /9°C for 2 seconds, and the tenter clip interval was further narrowed by 3%. With relaxation in the film width direction, /
A heat setting process was performed for 2 seconds at a temperature of 9j'Q.

While transporting the film at a speed of 2 gm/min through the apparatus shown in Figure 2, and applying the temperature profile and take-up tension listed in Table 2, the film was wound up with a wine goose to a thickness of approximately 73 microns. , the width of the product is 0θ.

Various properties of the obtained product film were evaluated according to the methods described in Examples. The results are shown in Table 2.

From Table 7 and Table 2, the following is clear.

(1) When the method of the present invention was used, the film had few edge walnuts, excellent flatness, little thickness disease, and a low hot water shrinkage rate.

(2) On the other hand, in the case of the comparative example that does not meet the requirements of the present invention, the film has large edge cracks, poor flatness, and large thickness spots, which is a practical problem. A film was obtained.

[Brief explanation of drawings]

Figure 1 is a perspective view for explaining the edge walnut phenomenon;
The figure is a schematic plan view of the main parts of the device used in the method of the present invention.
Figure 3 shows the temperature profile of the films of Examples 7--;
Figure 7 shows the temperature profile of the films of Examples 3 to 3.
fH73<S. In the figure, / is the table, -13 is the baseline, and Z
is the adhesive tape, Y is the cutting line, B is the marked line, λθ is the film immediately after heat setting, =27 is the heat setting furnace, 22, 23. ．． 2
', l are respectively infrared panel heaters, 2j is a cold air 22 for cooling the center of the film, is a tenter rail, 2 is an edge cutting blade, 29 is a film edge, 30 is a product film,
3/ is a dancer roll for detecting take-up tension, 32 is a nip roll, and the arrow indicates the film transport direction. Applicant: Mitsubishi Motors Corporation/Santo Kasei Co., Ltd. Agent: Patent attorney: Yo Hase - (7 others) Figure 1. Ryo 2 drawing flashes @ side do N start mocking ε procedure amendment M1゛ 1st printing part 11j9 勺 - Otsuki / 2nd Patent Office Commissioner Wakasugi Kazuo Tono Teigen / Incident display and dismissal! Patent Application No. 19-729-3 of Year I Relationship with the case of the person making the amendment Patent Applicant Address No. 2, 5-1, 2-1 Marunouchi, Chiyoda-ku, Tokyo Name (10g) Agent for Mitsubishi Monsanto Chemical Co., Ltd. 〒1
00 Address: 2-3-3, Marunouchi, Chiyoda-ku, Tokyo Subject of amendment: Patent application and specification 0) Contents of amendment: (1) Patent review attached. Replace with (Correcting the furigana of the inventor Tsuguo Okumura from "Okamuraguo" to "Okumurasoguo J.") (2) On page 70 of the specification, from line 20 to line 1/bege/, it is written as ``At least Shij'C. "means that the temperature difference in the width direction of the film is kept within a range of S°C" is corrected to "means that the temperature difference in the width direction of the film is kept within a range of S°C." The phrase "was arranged in a row in a direction perpendicular to the film transport direction," is corrected to "arranged in a row in a direction perpendicular to the film transport direction." (4) Specification No. 1! "to graph" on the 72nd line of the page
I corrected it to "Otsu O Gram". (5) Letter of Specification, page 1, line 77, “There is no practical problem,” is amended to “There is no practical problem,” (6) Letter of Specification, page 2j, line 1 Delete the line ``Enlarge the thickness unevenness''. that's all

Claims (1)

[Claims] (1) To produce a biaxially stretched poly-ε-caproamide film, a poly-ε-caproamide film is first stretched in the longitudinal direction, then held by tenter clips and stretched laterally. The temperature of the film after the horizontal stretching process is
While maintaining uniformity in the direction of the film, from the heat setting temperature /j
The first step is to slowly cool the film to a range of O~/4j 'O, then the film temperature is set to a profile that gradually decreases from the edge to the center in the width direction of the film, and the temperature difference between the edge and the center is reduced. While keeping the temperature within the range of 7θ to 30℃, press the center part in the width direction of the film! ~! In the second step, the film temperature is slowly cooled to a temperature of θ°C. After the film temperature is rapidly cooled to below g t °C during the film consumption, both edges of the film are cut just before the film is released from the tenter clips, and the product film is to Stj~/lxrvg/cdl
A method for producing a biaxially oriented poly-ε-caproamide film with improved flatness, the method comprising the following steps: a third step of drawing while applying a drawing tension of .