Film manufacturing method

Abstract

To provide a film manufacturing method capable of suppressing a generation of a wrinkle caused by a roll and a foreign matter caused by adhesion of water droplet even when a film-forming speed is increased to 16 m / min or more.SOLUTION: A film manufacturing method includes: a step 1 of obtaining a gel-like sheet from a polymer solution extruded in sheet form from a die; a step 2 of removing a solvent in the gel-like sheet with water while stretching the sheet in a longitudinal direction to obtain an uniaxially stretched film; a step 3 of removing water droplets adhering to the surface of the uniaxially stretched film with a water absorbing roll; and a step 4 of winding up the film, in this order. In the step 3, a nip roll is provided in front of the water absorbing roll, and the nip roll can remove the water droplets adhering to the surface of the uniaxially stretched film. A speed difference relation V2 / V1, where a speed of the water absorbing roll is V2 m / min and the speed on the nip roll is V1 m / min, is 1.001 or more and 1.030 or less, and a speed V3 of winding a film onto the film roll in the step 4 is 16 m / min or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a film manufacturing method that suppresses the generation of foreign matter caused by adhesion of water droplets even when the film-forming speed is increased to 16 m / min or more. [Background technology]

[0002] Aromatic polyamide films have excellent heat resistance and rigidity, and therefore have been suitably used as magnetic recording materials and interlayer insulation for circuit boards. They are also attracting attention as thermal transfer media, dielectrics for capacitors, and general industrial materials that require heat resistance. The aromatic polyamide film is produced by a solution casting method, and is preferably produced by any of the wet, dry, and semi-dry semi-wet solution casting methods, but is generally produced by the so-called dry and wet film casting method. (Patent Document 1) The film is produced by casting a polymer solution onto a support such as a drum or an endless belt from a die to form a film, and a dryer is used to dry the solvent from the film, and a solvent extraction treatment device is used to extract and remove the solvent contained in the film by passing the dried film (film body) through a liquid, and a transverse stretching machine is used to spread the film (film body) from which the solvent has been completely removed or the solvent concentration has been reduced in the width direction by the solvent extraction treatment device, and a winding machine is used to wind up the film obtained by the transverse stretching machine into a roll. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-112328 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the film is subjected to the above-mentioned wet process, which is a general method for producing aromatic polyamide, water droplets remain on the surface of the film. When inorganic compounds or organic compounds such as calcium ions or sodium ions dissolved in the water droplets are precipitated by evaporation of water, they become adhesion spots called water stains. There is a concern that such adhesion spots may cause dropouts, which are an important electromagnetic conversion characteristic, when the film is used as a magnetic recording medium such as a magnetic tape, and therefore improvement is required.

[0005] Patent Document 1 describes a manufacturing process in which the nip pressure of the nip roll before the water-absorbing roll is controlled at a film-forming speed of 15 m / min, and a film is formed using a water-absorbing roll, thereby reducing adhesion unevenness due to remaining water droplets. However, the above technology has a problem that when a film is formed at a film-forming speed of 16 m / min or more, water droplets remain and adhesion unevenness cannot be reduced.

[0006] In view of the above, an object of the present invention is to provide a method for producing a film that suppresses the generation of foreign matter caused by adhesion of water droplets even when the film production speed is increased to 16 m / min or more. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention is characterized as follows. [I] A method for producing a film, comprising the steps of: obtaining a gel-like sheet from a polymer solution extruded into a sheet form from a die (step 1); obtaining a uniaxially stretched film by stretching the gel-like sheet in the longitudinal direction while removing the solvent in the gel-like sheet with water (step 2); removing water droplets adhering to the surface of the uniaxially stretched film with a water-absorbing roll (step 3); and winding up the film (step 4), The method includes the steps 1 to 4 in this order, and in the step 3, a nip roll is provided in front of the water absorbing roll, and the nip roll can remove water droplets attached to the surface of the uniaxially stretched film, and the speed of the water absorbing roll is V 2 m / min, the speed on the nip roll is V 1 The relation between the speed difference and m / min is V 2 / V 1is 1.001 or more and 1.030 or less, and the speed V 3 A method for producing a film having a speed of 16 m / min or more. [II] After passing through the step 3, the area of ​​the water droplets attached to the uniaxially stretched film is 0.3 mm 2 or less, and the number is 0 pieces / m 2 More than 1 piece / m 2 The method for producing a film according to the following [I] [III] The method for producing a film according to [I] or [II], wherein the water-absorbing roll has a suction capacity adjustment mechanism on its rotation shaft. [IV] The method for producing a film according to any one of [I] to [III], wherein the film is a film containing an aromatic polyamide as a main component. [V] The method for producing a film according to any one of [I] to [IV], wherein the nip roll is a hard rubber roll. [VI] The method for producing a film according to any one of [I] to [V], wherein the contact pressure of the nip rolls in the step 3 is 450 kg / cm or more and 600 kg / cm or less. [VII] The method for producing a film according to any one of [I] to [VI], further comprising, between the step 3 and the step 5, a step of subjecting the film to a heat treatment for heat setting. [VIII] The method for producing a film according to any one of [I] to [VII], wherein in step 5, an edge of the film is trimmed by 1 to 15% and then the film is wound up. [IX] The method for producing a film according to any one of [I] to [VIII], wherein the film is used for a magnetic recording medium. Effect of the Invention

[0008] The film manufacturing method of the present invention has the following effects. That is, as described below, by controlling the water absorption capacity of the water absorbing roll in the solvent removal step and controlling the tension by controlling the speed between the rolls, it is possible to control the state in which the solvent can be removed accurately even in an environment where the film production speed is 16 m / min or more, and it is possible to prevent adhesion of foreign matter due to deterioration of the liquid absorption capacity and to stably produce a film while suppressing adhesion defects. In addition, by controlling and managing the liquid absorption capacity of the water absorbing roll and the speed between the rolls, it is possible to prevent adhesion of water droplets due to deterioration of the liquid absorption capacity and wrinkles and meandering due to deterioration of conveyability due to a decrease in tension. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram illustrating a method for producing a film of the present invention. [Diagram 2] FIG. 2 is a schematic diagram for explaining a mechanism for grasping the water absorption capacity in the film production method of the present invention. [Diagram 3] FIG. 3 is an enlarged schematic view of a portion of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An example of the film production method of the present invention and a film production apparatus for implementing this method will be described below with reference to the drawings, but the present invention is not limited to this example.

[0011] The film manufacturing method of the present invention includes a step (step 1) of obtaining a gel-like sheet from a polymer solution extruded into a sheet form from a die, a step (step 2) of obtaining a uniaxially stretched film by stretching the gel-like sheet in the longitudinal direction while removing the solvent in the gel-like sheet with water, a step (step 3) of removing water droplets adhering to the surface of the uniaxially stretched film with a water-absorbing roll, and a step (step 4) of winding up the film, in which steps 1 to 4 are performed in this order.

[0012] First, in step 1, the film-forming solution (polymer solution) discharged in a sheet form from a die 1 is cast onto a support 2 such as an endless belt or drum to obtain a gel-like sheet. After that, it is dried in a dryer 3 and peeled off from the support to obtain a film body A (film body forming step). Next, it is subjected to a solvent removal step 4 to remove the solvent contained in the film body A (film body). This solvent removal step is carried out by conveying the film body by a conveying roller, stretching it in the longitudinal direction, and immersing it in water 5 to extract the solvent. Then, in step 3, before the film body enters the next tank, a nip roll scrapes off the solvent attached to the surface, and then a water absorbing roll absorbs and removes the remaining solvent. At this time, the nip roll and the water absorbing roll control the speed to adjust the tension applied to the film, thereby suppressing the meandering and wrinkles of the film body. The film body A that has undergone the solvent removal step is subjected to a heat treatment to become a film. Heat treatment includes stretching by a transverse stretching machine (stretching by heating) and heat setting treatment without stretching. The obtained film is then transported, inspected for foreign bodies using a defect detector, and then its thickness is measured, and it is wound into a roll using a winding device (winding process). Note that it is preferable to trim the edge of the film by 1 to 15% before winding.

[0013] In the above-mentioned manufacturing method, the contact pressure of the nip rolls is preferably 400 kg / cm or more and 1000 kg / cm or less, because even if the film production speed is 16 m / min or more, the occurrence of creases during transport can be suppressed and the effect of reducing the occurrence of adhesion spots can be sufficiently obtained.More preferably, the contact pressure is 450 kg / cm or more and 600 kg / cm or less.

[0014] An example of a method for removing the solvent for carrying out the present invention will now be described. As shown in Fig. 1, a nip roll 6 and a water-absorbing roll 7 are installed near the transport roll attached to the solvent removal process 4, and each roll is equipped with a mechanism for adjusting its rotation. As shown in Fig. 2, the water-absorbing roll 7 is equipped with a water tank for injecting water via a pump to a location other than the film contact area, and the water absorption time can be calculated by measuring the time it takes for a certain amount of water in this mechanism to decrease. The liquid absorption capacity of the water-absorbing roll is calculated and understood from (amount of water decreased in 1 second / area of ​​the water tank at the roll contact area). As shown in Fig. 3, a sealant with a structure similar to that of an oil seal is used at the contact area of ​​the water-absorbing roll to prevent water leakage.

[0015] The film produced by the film production method of the present invention is preferably a film mainly composed of aromatic polyamide. A film mainly composed of aromatic polyamide has a high Young's modulus in both directions of the film, and therefore has properties suitable for controlling the tension of the nip roll and the water-absorbing roll to remove water. If either film has a low Young's modulus, too much force is applied to the MD direction of the film between the nip roll and the water-absorbing roll, causing the film to be stretched unevenly and slip, resulting in clip detachment, and the effects of the present invention may not be fully obtained. The film produced by the film production method of the present invention is preferably a Young's modulus in the MD direction of 8.0 GPa or more.

[0016] In step 3 of the film manufacturing method of the present invention, the speed of the water absorbing roll is V 2 m / min, the speed on the nip roll is V 1 The relation between the speed difference and m / min is V 2 / V 1 must be 1.001 or more and 1.030 or less. If it is less than 1.001, when the film is produced at a film production speed of 16 m / min or more, meandering and wrinkles will occur due to a decrease in tension caused by the water-absorbing roll, making it difficult to obtain the effect of reducing adhesion spots. Also, if it exceeds 1.030, water will accumulate in the wrinkles formed in the TD compression direction due to excessive tension, and it may become impossible to remove the water. 2 / V1 is preferably 1.002 or more and 1.020 or less, more preferably 1.002 or more and 1.010 or less, and further preferably 1.003 or more and 1.006 or less.

[0017] In the film manufacturing method of the present invention, after the step 3, the area of ​​the water droplets attached to the uniaxially stretched film is 0.3 mm 2 or less, and the number is 0 pieces / m 2 More than 1.0 pieces / m 2 It is preferable that the thickness of the film is less than 0.3 mm. 2 In order to reduce the adhesion of water droplets of this size or larger, a method of using a water-absorbing roll having a mechanism for measuring the water-absorbing capacity of the water-absorbing roll can be mentioned. As a mechanism for measuring the water-absorbing capacity of the water-absorbing roll, a mechanism for injecting water into the water-absorbing roll and measuring the time it takes for the water to be absorbed by the water-absorbing roll can be mentioned. In this mechanism, the amount of water injected into the roll is preferably 25 g or less every 12 hours.

[0018] In the film manufacturing method of the present invention, the water-absorbing roll preferably has a suction capacity adjustment mechanism on the rotation shaft. By having the suction capacity adjustment mechanism, it is possible to grasp the change in the liquid-absorbing capacity of the water-absorbing roll, and when the liquid-absorbing capacity decreases, the liquid-absorbing capacity can be maintained by increasing the suction pressure, and the occurrence of adhesion spots can be suppressed even during long-term continuous film production. The suction pressure by the suction mechanism is preferably 0.1 kPa or more and 1.5 kPa or less, and more preferably 0.3 kPa or more and 0.7 kPa or less. By setting the suction pressure in the above range, In the film manufacturing method of the present invention, the material of the nip roll is preferably a hard rubber roll. If the material is softer than hard rubber, when pressure is applied due to the speed difference between the water absorbing roll and the nip roll during high-speed film production such as 16 m / min, the film may be subjected to uneven force, causing meandering and wrinkles, and the occurrence of adhesion spots may not be suppressed. On the other hand, if the material is harder than hard rubber, the film may be torn when pressure is applied due to the speed difference between the water absorbing roll and the nip roll during high-speed film production such as 16 m / min. In addition, if the material is other than rubber, it may deteriorate and deform due to the influence of moisture, making it impossible to drain water or causing meandering wrinkles, making it impossible to suppress the occurrence of adhesion spots.

[0019] In the present invention, it is preferable that a guide roll is provided after the water absorbing roll, since tension is not applied to the film being transported after the water absorbing roll, and thus occurrence of clip detachment due to wrinkles or meandering can be suppressed, and occurrence of adhesion spots can be efficiently suppressed.

[0020] The film produced by the film production method of the present invention is preferably an aromatic polyamide film. The aromatic polyamide film is synthesized by solution polymerization of an acid chloride and a diamine in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), or dimethylformamide (DMF), or by interfacial polymerization using an aqueous medium.

[0021] The film manufacturing method of the present invention can provide a film manufacturing method that suppresses the generation of wrinkles caused by rolls and foreign matter caused by water droplet adhesion, even when the film production speed is increased to 16 m / min or more, and can therefore be suitably used as a method for manufacturing films used for magnetic recording media, particularly data storage applications. EXAMPLES

[0022] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0023] The characteristic values ​​and effects of the present invention are evaluated according to the following measurement methods and evaluation criteria. (1) Number of adhesion spots on the film The obtained film was passed through a transmission type defect detector, and the number of water droplet defects detected was counted per 1 m of film. 2 The maximum diameter R of the adhesion spot was defined as the maximum distance from one end of the adhesion spot to the other end, and was obtained from the defect inspection results.

[0024] Example 1 A reaction solution was prepared by dissolving 2-chloro-p-phenylenediamine (hereinafter referred to as CPA) equivalent to 85 mol% and 4,4'-diaminodiphenyl ether (hereinafter referred to as DPE) equivalent to 15 mol% as aromatic diamine components in NMP so that the production amount of aromatic polyamide was 8800 kg. Next, colloidal silica was added to the reaction solution, and then 2-chloroterephthalic acid dichloride (hereinafter referred to as CTPC) equivalent to 98.4 mol% was added to the reaction solution, and the polymerization reaction was started while maintaining the polymerization tank jacket temperature at -25 ° C. As the solution temperature increased, the stirring speed was gradually reduced so that the temperature inside the polymerization tank could be kept below 35 ° C., and the polymerization reaction was completed by stirring for 2 hours, and then the hydrogen chloride by-produced in the polymerization reaction was neutralized with lithium carbonate, completing the entire process of aromatic polyamide production, and then the jacket temperature was maintained at 70 ° C. while discharging for 300 minutes to obtain 8800 kg of aromatic polyamide solution.

[0025] Using the polymer solution discharged from the die, a film was formed in a film-forming chamber with a cleanliness level of class 1000. First, the polymer solution was filtered through a filter with a filtration accuracy of 4 μm, then cast onto a belt, and heated with hot air at 180° C. for 2 minutes to evaporate the solvent, and the self-supporting film was continuously peeled off from the belt. Next, the film was introduced into a water tank filled with water with an evaporation residue amount of 150 mg / l, and the remaining solvent and inorganic salts generated by neutralization were extracted with water. At this time, the film was stretched 1.2 times in the longitudinal direction. After the completion of the water extraction, in the process of removing water droplets attached to the surface of the uniaxially stretched film with a water-absorbing roll, a nip roll was installed in front of the water-absorbing roll, and the water droplets attached to the surface of the uniaxially stretched film were removed with the nip roll. At this time, the contact pressure of the nip roll was set to 500 kg / cm, and the speed of the water-absorbing roll was set to V 2 m / min, the speed on the nip roll is V 1 m / min, V 2 / V 1 The moisture adhering to the film surface was removed with a value of 1.003, and the remaining moisture on both sides of the film was removed using a "Mas Roll" made by Masuda Seisakusho Co., Ltd. as a water absorbing roll. Next, after drying with a stenter at 280°C, the film was stretched 1.5 times in the width direction and heat-treated for 29 seconds, and then slowly cooled at a temperature of 40°C for 5 seconds, after which the film was wound up on a roll. The speed at which the film was wound up on the roll (film-forming speed) V 3 The speed was 22 m / min. Finally, an aromatic polyamide film with a thickness of 3 μm and a length of 4,300 m was obtained. The area of ​​the water droplets attached to the film was 0.26 mm2. 2 / m 2 , the number of water droplets attached is 0.35 / m 2 The number of adhesion spots was 0.58 / m 2 The results were good.

[0026] Example 2 V 2 / V 1 The same procedure as in Example 1 was carried out except that the meandering caused some folds on the water absorbing roll, and water droplets adhered between the folds, resulting in an area of ​​0.34 mm 2 / m 2The number of water droplets was 1.1 / m because they occurred between the wrinkles. 2 The number of adhesion spots increased slightly to 0.69 / m 2 It was a bit much.

[0027] Example 3 V 2 / V 1 The same procedure as in Example 1 was carried out except that the suction pressure was changed to 1.006. No meandering wrinkles were observed on the water absorbing roll, and the surface area of ​​the adhering water droplets was 0.23 mm 2 / m 2 The number of water droplets adhering to the surface was 0.24 / m 2 The number of adhesion spots was 0.61 / m 2 It was.

[0028] Example 4 V 2 / V 1 The same procedure as in Example 1 was carried out except that the suction pressure was changed to 1.010. The water absorbing roll was in a good condition with no meandering wrinkles, and the area of ​​the adhering water droplets was 0.24 mm 2 / m 2 The number of water droplets adhering to the surface was 0.26 / m 2 The number of adhesion spots was 0.64 / m 2 It was.

[0029] Example 5 V 2 / V 1 The same procedure as in Example 1 was carried out except that the suction pressure was changed to 1.012. Some meandering wrinkles were formed on the water absorbing roll, and water droplets were attached between the wrinkles, so the area of ​​the attached water droplets was 0.36 mm 2 / m 2 The number of water droplets attached to the surface increased to 1.1 droplets / m 2 The number of adhesion spots was 0.71 / m 2 It was.

[0030] Comparative Example 1 V 2 / V 1The same procedure as in Example 1 was carried out except that the strain rate was changed to 1.037, and it was confirmed that the film broke in the transverse direction.

[0031] Example 6 The same procedure as in Example 1 was carried out except that no pressure was applied to the nip rolls. Within 24 hours after the start of film formation, the area of ​​the attached water droplets was 0.26 mm 2 / m 2 The number of water droplets adhering to the surface is 0.4 droplets / m 2 The number of adhesion spots was 0.73 / m 2 After 24 hours from the start of film formation, the liquid absorption capacity rapidly decreased, and the area of ​​the adhering water droplets was 0.6 mm 2 / m 2 , the number of water droplets attached is 3.0 / m 2 The number of adhesion spots was 0.81 / m 2 Was Example 7 V 2 / V 1 The same procedure as in Example 6 was carried out except that the β-direction coefficient was changed to 1.002. During the start of film formation, some folds and wrinkles were observed, and within 24 hours after the start of film formation, the area of ​​the adhering water droplets was 0.29 mm 2 / m 2 The number of water droplets attached is 0.82 / m 2 The number of adhesion spots was 0.67 / m 2 After 24 hours from the start of film formation, the liquid absorption capacity rapidly decreased, and the area of ​​the adhering water droplets was 0.71 mm 2 / m 2 , the number of water droplets attached is 3.6 / m 2 The number of adhesion spots was 0.81 / m 2 It was.

[0032] Comparative Example 2 When the same nip roll pressure conditions as those described in JP 2003-112328 A were used, and the same V2 / V1 = 1.003 as in Example 1 was used, slight folds due to meandering occurred on the nip rolls, water droplets adhered between the folds, and the area of ​​the adhered water droplets was 0.32 mm 2 / m 2 The number of droplets is 1.17 / m2 The number of adhesion spots was 0.74 / m 2 , which was greater than those in Examples 1 to 5.

[0033] [Table 1] [Explanation of symbols]

[0034] 1: Die 2:Support 3: Dryer 4: Solvent removal process 5:Water 6: Nip roll 7: Water-absorbing roll 8: Guide roll 9: Heat treatment equipment 10: Winding device 11: Time measuring device 12: Water injection device 13: Water supply pump 14: Side seal for injection device

Claims

1. A step (step 1) of obtaining a gel-like sheet from a polymer solution extruded in sheet form from a die; a step (step 2) of stretching the gel-like sheet in a longitudinal direction while removing the solvent in the gel-like sheet with water to obtain a uniaxially stretched film; A step (step 3) of removing water droplets adhering to the surface of the uniaxially stretched film with a water absorbing roll; A method for producing a film, comprising a step (step 4) of winding the film, The method includes the steps 1 to 4 in this order. In the step 3, a nip roll is provided before the water absorbing roll, and water droplets adhering to the surface of the uniaxially stretched film can be removed by the nip roll. The speed of the water absorbing roll is V ２ m / min, the speed on the nip roll is V １ The speed difference relationship V when m / min ２ / V １ is equal to or greater than 1.001 and equal to or less than 1.030, The speed V of winding the film onto the film roll in step 4 ３ A method for producing a film, in which the film speed is 16 m / min or more.

2. After passing through the step 3, the area of ​​the water droplets adhering to the uniaxially stretched film is 0.3 mm ２ or less, and the number is 0 / m ２ 1 piece / m or more ２ The method for producing the film according to claim 1, wherein the

3. The method for producing a film according to claim 1 or 2, wherein the water absorbing roll has a suction capacity adjustment mechanism on a rotation shaft thereof.

4. The method for producing a film according to claim 1 or 2, wherein the film is a film containing an aromatic polyamide as a main component.

5. The method for producing a film according to claim 1 or 2, wherein the nip roll is a hard rubber roll.

6. The method for producing a film according to claim 1 or 2, wherein the contact pressure of the nip rolls in the step 3 is from 450 kg / cm to 600 kg / cm.

7. The method for producing a film according to claim 1 or 2, further comprising a step between the step 3 and the step 5, of subjecting the film to a heat treatment for heat setting.

8. The method for producing a film according to claim 1 or 2, wherein in step 4, the edge portions of the film are trimmed by 1 to 15% and then the film is wound up.

9. The method for producing a film according to claim 1 or 2, wherein the film is used for a magnetic recording medium.

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