JP5752897B2 - Method for producing thermoplastic resin film - Google Patents

Description

  The present invention relates to a technique for manufacturing a film at low cost by efficiently reusing the reuse of a thermoplastic resin film.

  The thermoplastic resin film has an ear that does not become a product in the film forming process. In addition, slitting is generally performed in order to obtain a product having a predetermined width from a wide intermediate product. Even at this stage, a portion remaining on the core of the cut and wide intermediate product appears. In addition to this, the appearance of windings such as `` wrinkles '', `` uneven end faces '', `` gauge bands '', etc. generated in the slits, `` scratches '', `` dirt '', `` Defects such as “open holes” and parts that do not become products occur due to changes in product type. These may be reused in the following way.

  That is, when the film is finely pulverized or compressed, and then melted with an extruder or the like to obtain a strand, solidified (referred to as a recycled chip), and the same or similar thermoplastic resin film is produced again. It is put together with a new thermoplastic resin (hereinafter referred to as virgin raw material or virgin chip) and melted with an extruder to obtain a predetermined thermoplastic resin film.

  In order to advantageously perform this reuse, for example, Japanese Patent Application Laid-Open No. 9-39073 discloses a manufacturing apparatus and method thereof. In this document, the problem that the influence of the filler already added remains, and as a countermeasure, a detailed structure is proposed for the polymer filter in the manufacturing apparatus.

  However, a new problem has recently occurred as a problem in reuse. That is, a thermoplastic film is often provided with a coating such as easy adhesion, easy slipping, peeling and antistatic so as to be suitable for processing by a customer. Even if the coating passes through the pulverization or melt extrusion in the reuse process, the coating components are not sufficiently pulverized or dispersed, and sometimes the gelation inherent to the resin is promoted. On the other hand, in order to produce a thermoplastic resin film at a low cost, the ratio of recycled materials is increased. Then, as a result, gel-like foreign matters are generated due to these, and the quality cannot be maintained. Although it is a good number at the beginning of production, it increases over time, so it may be necessary to change filters frequently. There are devices that change the filter without stopping film formation or in a very short time, but in any case, the product does not become a product and is lost.

JP 9-39073 A

  An object of the present invention is to provide an apparatus and a method for advantageously reusing waste generated in the process of manufacturing a thermoplastic resin film. Provided a thermoplastic resin film manufacturing apparatus and a manufacturing method thereof that can reduce the manufacturing cost by reducing the ratio of the virgin raw material used in the production of a new film even if it is a scrap film having a coating with a specific function added. To do.

The above object of the present invention is achieved by the following manufacturing method. That is,
In the production of a thermoplastic resin film having a coating process, the thermoplastic resin is polyethylene terephthalate, polyethylene 2,6-naphthalate, polyphenylene sulfide, polypropylene, polystyrene, polyamide or aramid, and a filtration layer for filtering the molten thermoplastic resin is described below. A filtration layer that simultaneously satisfies the conditions (1) to (4) is used, and an unused (virgin) chip after polymerization and a recycled (recycled) chip of film waste are mixed and melt extruded. A method for producing a thermoplastic resin film.
(1) Filtration accuracy at a collection efficiency of 95% is 0.6 to 15 μm,
(2) Having at least one filtration layer made of a metal fiber nonwoven fabric, and the basis weight of the finest filtration layer among the filtration layers made of the metal fiber nonwoven fabric: w is 500 to 10,000 g / m ² , and the wire diameter of the metal fiber: d is 22 μm or less, the product w · d is 15000 or more,
(3) The number of intersections of fibers in the finest filtration layer among the filtration layers made of the metal fiber nonwoven fabric is in the range of 2.5 to 5.3 × 10 ¹¹ ,
(4) The finest filtration layer has a thickness of 200 μm or more among the filtration layers made of the metal fiber nonwoven fabric.
Here, the intersection number C (points / m ² ) of the fiber is calculated by the following equation (1):
C = 4w ² / [π ³ r ³ ρ ² (T-2r)] × 10 ¹² (1)
w: basis weight (g / m ² ), r: wire radius (μm), ρ: density (g / cm ³ ), T: filtration layer thickness (μm), filtration layer thickness T (mm) is It is calculated by the following formula (2).
T = w / ρ / (1-ε) / 1000 (2)
Here, ε represents the porosity.

  This filter is used at least in a thermoplastic resin film manufacturing process in which virgin chips and recycled chips are mixed and melt extruded. In addition, when there is a recycling chip forming process of melt extrusion after pulverization of film waste, it may be used here.

  By using this filter, foreign matter can be suppressed even when the weight ratio of recycled chips is 20 to 100%, and the same kind of products can be produced at a reduced cost.

It is a flowchart of the thermoplastic resin film manufacturing apparatus which concerns on one embodiment of this invention. It is sectional drawing of the filter used in the Example. It is sectional drawing of the filtration apparatus used in the Example. It is explanatory drawing of the usage method of the filtration apparatus used in the Example.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the thermoplastic resin film production apparatus of the present invention. This is an example of a biaxially stretched film, but the present invention is effective for both uniaxially stretched and unstretched films.

  In general, several kinds of resin pellets (chips) are weighed and mixed in one weighing process, and the thermoplastic resin film is crystallized and dried as needed in the second drying process, and is put into the third extruder. Then, the sheet is extruded through a slit die, passed through a cooling drum, and then longitudinally stretched by a uniaxial stretching machine. Then, before passing through 9 biaxial stretching machine, a coating film may be made with 8 coating apparatus. Alternatively, in the case where stretching is performed simultaneously with a biaxial stretching machine, coating may be performed before that. In either case, the effect of the present invention is not changed. After biaxial stretching, the ear 11 is cut off in 10 transport steps, and a mill roll 13 as an intermediate product is obtained with a winder 12. The mill roll is slit to a predetermined width in 14 slitting processes and delivered to the customer through 15 packing / shipping processes. In the slitting process, 16 cuttings that are ears generated for cutting out to a predetermined width and a core part 17 of a mill roll remaining after feeding a predetermined length are generated as a scrap film. 11 ear edge films and 16 cuts and 17 core films are pulverized in 18 crushing processes, stored and dried as necessary, extruded as a strand in the regenerative extruder 20, cut into recycled pellets Get (chip). This pellet is again transported to one weighing step. The coating width of the coating 7 can be determined so as to be convenient after biaxial stretching. However, if the slipperiness is different between the uncoated part and the coated part, problems such as wrinkles often occur in 10 transport processes, 12 winders, and 14 slit processes. Adjusted. Therefore, the 16 cut and 17 core films are put into the reproduction process with the coating film.

In the present invention, gel-like foreign substances are easily generated when the application process as shown in FIG. 1 is provided, and a great effect is achieved in reducing the foreign substances, but the application process is not particularly essential.
The extruder 3 in FIG. 1 may be biaxial or uniaxial, and the presence or absence of a vent is not particularly limited. However, since a tendency to break the gel shape is recognized with a high share, and as a result, the filter life may be increased, the twin screw extruder is preferable.

  The filter of 4 may be either leaf type or candle type. The arrangement of the elements may be either vertical or horizontal, but the vertical type is preferred as is generally said. Further, in order to suppress the generation of gel due to the residence deterioration of the resin itself, the leaf type with the doughnut-shaped filtration layer shown in the cross section in FIG. 2 is more suitable, and the center hub is preferably a so-called hard type.

  The filtration accuracy of the filtration layer for molten resin is set based on quality requirements. The standard is 1/5 or less of the size of the core of the foreign material, but it is in the range of 0.6 to 15 μm with 95% collection efficiency. Many thermoplastic resin films are often required to suppress the number of foreign matters of 50 μm or more. Moreover, when the foreign material more than this size increases, it will become easy to generate | occur | produce a film break at the extending process. When the collection efficiency is 0.6 or less, the molten resin filter has a high viscosity and the pressure loss becomes too high, which is often not realistic.

  The filtration layer must have at least one filtration layer made of a metal fiber nonwoven fabric in order to ensure the amount of foreign matter collected. Although the thing which sintered the metal particle is used as a filter material for molten resin, since the porosity is small, it is not suitable for the purpose of increasing the amount of collection.

  In the nonwoven fabric filter, a multilayer structure of about 2 to 5 layers is common. Also, in order to maintain strength, or to avoid creating a dead space in the resin flow, a wire mesh or a sintered particle filter medium may be combined as a support for the filter medium.

The filter traps the gel, but even with a filter having the same filtration accuracy, the gel is deformed, broken, and bonded, so the amount of foreign matter in the film varies. In addition, the pressure increase with time due to clogging, the increase in the number of foreign matters over time, and the aspect of the foreign matter size distribution are also different. As a result of testing and various studies using various filter media, the number of intersections determined by the following formula (1) is 2.5 to 5.3 × for the finest filtration layer among the filtration layers made of metal fiber nonwoven fabric. It was found that a material having a thickness in the range of 10 ¹¹ and having a thickness of 200 μm or more determined by the formula (2) is particularly good. For calculating the number of intersections, refer to Japanese Patent Application Laid-Open No. 2003-247198.

  In the present invention, the main filtration layer relates to a filtration layer made of the finest metal fiber nonwoven fabric, and the type and characteristics of the front and rear layers are not particularly limited. However, if the target gel type is limited, a metal fiber nonwoven fabric single layer structure is desirable from the viewpoint of element cost and pressure loss.

  Moreover, about the filtration layer which consists of the finest metal fiber nonwoven fabric, the wire diameter of the fiber of the nonwoven fabric is 22 micrometers or less. Above this, sufficient filtration accuracy cannot be obtained with generally acceptable resin pressure. And again, the number of intersections mentioned above cannot be obtained. The aspect ratio of the fiber is not particularly specified, and may be in a range for a general nonwoven fabric.

Basis weight of the nonwoven fabric is in the range of 500~10000g / m ^2. Below this, clogging cannot be used quickly. Above this, the pressure loss increases and cannot be used. Preferably it is the range of 1300-4800 g / m < ² >. This range is a preferable range in terms of strength and cost of the filter medium.

According to the above, the product of the wire diameter and the basis weight, w · d of 15000 or more was particularly good, and good results were obtained. The porosity is selected so as to satisfy the filtration accuracy and the above range.
The filtration accuracy mentioned here refers to a particle size (μm) at which 95% of 11 types or dust ACFTD defined in JIS-Z8901-1974 are cut.

  The material of the filter medium is preferably made of stainless steel from the viewpoint of activity with thermoplastic resins and from the viewpoint of recycling and reuse. Among stainless steels, SUS304, SUS316, SUS316L and the like are suitable, but not limited thereto.

  As the thermoplastic resin used in the present invention, polyethylene terephthalate, polyethylene 2,6-naphthalate, polyphenylene sulfide, polypropylene, polystyrene, which are thermoplastic resins having high functionality in mechanical properties, thermal properties, electrical properties, etc. Polyamide, aramid, etc. are preferred. In particular, thermoplastic resin is melt-extruded into a sheet, biaxially stretched in the longitudinal and lateral directions, and heat-treated for photoresists, magnetic materials, surface protection, and reflection, with excellent dimensional stability, mechanical and thermal stability Suitable for thermoplastic resin films used for optical applications such as prevention.

  The range of the melt viscosity of the thermoplastic resin that can be filtered through the filter in the present invention is 200 to 12000 Poise. If it is less than 200 Poise, the filtration resistance of the filter of the present invention is not increased, and it becomes difficult to effectively use the entire surface of the medium of the present invention. On the other hand, a melt viscosity exceeding 12000 Poise is not preferable because the pressure loss becomes too large when filtering through the filter of the present invention, and the risk of media deformation and media layer collapse increases. Thermoplastic resins have different viscosities depending on the molten state. That is, since the melt viscosity varies depending on the molecular weight and melt temperature of the thermoplastic resin, for example, when passing through a filter configured as in the present invention, the melt viscosity can be controlled and adjusted to 200 to 12000 Poise. is important. By doing this, the pressure loss can be abnormally high and the filter can be damaged, or the non-uniform flow of molten thermoplastic resin caused by abnormally low filtration resistance can be prevented, and homogeneous thermoplastic resin can be discharged. Thus, the filter can be used in an optimal state including the collection efficiency of the filter.

  Hereinafter, the present invention will be described in more detail with reference to examples. The measurement method was as follows.

(1) Average particle diameter of filler The area of a particle is obtained from a transmission electron micrograph, and the average value is obtained from all observed particles as the diameter of a circle having the same area.

(2) Filtration accuracy 11 types of test powder JIS-Z8901-1974 or dust ACFTD was dispersed in distilled water, the particle size distribution was measured with HIAC, and 95% compared with the particle size distribution after passing through the filter. Use the cut value as the filtration accuracy.

(3) Porosity The volume of the space is determined from the volume of the filter medium, the amount of material used and the specific gravity, and is expressed as a percentage.

(4) Weight per unit area of the filter medium The weight of the material used per unit filtration area of the filter medium (unit: g / m ² ).

(5) Material diameter of filter medium The particle diameter is measured from a micrograph and the average diameter is obtained. In the case of different diameters having a major axis and a minor axis, the minor axis is measured and taken as the average diameter.

(6) Cross section of filter media After the filter media is hardened with epoxy resin, cut along the vertical or flat cross section of the media, and after the cut surface is polished, a metal micrograph is taken and the metal fiber shaft arrangement direction, material diameter, Observe the void state.

(7) Ventilation resistance The outer periphery of a filter having an effective diameter of 40 mm is sealed at 0.5 l / min. With a pair of upper and lower hemispherical cups having holes through which air flows.・ Read the difference in air pressure in the upper and lower cups with a manometer when air of cm ² is flowed.

(8) Number of foreign substances in the film The polyester film was cut into 210 mm length × 148 mm width (area 310.8 cm ² ), and the entire range of this film was inspected by the visual inspection by the crossed Nicols method. Subsequently, the foreign matter in the detected sample film was observed with transmitted light using an optical microscope, and the maximum diameter of the portion observed as an optically abnormal range was defined as the size of the foreign matter. In addition, when the cavity (void) which exists around a foreign material nucleus is observed as an optically abnormal range, it included in the size of the foreign material. Then, the size of the foreign particles was measured by the average diameter, and the number was counted by dividing into ranks of 50 μm or more and less than 90 μm and 90 μm or more.

(9) Temporal pressure increase coefficient From the result of measuring the change in pressure loss (MPa) obtained at the pressure detection end for the resin upstream of the filter at 5 or more different filtration amounts, linear regression was performed and the slope obtained was expressed by the following equation: Standardized in (3) and used as the time-dependent pressure increase coefficient.
K = ΔP · S / Q / F / η (3)
Here, K: time-dependent pressure increase coefficient (MPa · h / m ² / Poise), ΔP: pressure increase (MPa), S: filtration area (m ² ), Q: filtration amount (m ³ ), F: flux rate (m ³ / h / m ² ) = discharge rate (m ³ / h) / S, η: melt viscosity (Poise).

(10) Intrinsic viscosity
Intrinsic viscosity ([η] dl / g) was measured with an o-chlorophenol solution at 25 ° C.

(11) Melt viscosity The viscosity of a heat-melted thermoplastic resin is measured by a Koka flow tester, and a calibration curve of a temperature-viscosity curve is created. Viscosity at the time of melting of thermoplastic resin is calculated from a calibration curve by detecting temperature.

(12) Melt density The PVT measurement of the thermoplastic resin heated and melted was performed, and the value under the pressure of the filter part was taken as the melt density.

(13) Filtration amount With respect to the number of revolutions for equipment with gear pumps, and for equipment with no gear pumps, several discharges were measured with the resin discharged from the slit die outlet against the number of revolutions of the extruder. Accumulated from the number-discharge amount relational expression was used as the filter filtration amount.

[Examples 1 to 3, Comparative Examples 5 to 7 ]
The filter material shown in Table 1 was constructed and sintered using stainless steel fibers made of SUS316L and various wire diameters as a filter.
As shown in FIG. 2, the filter device is formed into a disk shape having a diameter of 7 inches with the filter medium 31, and the two disk-shaped filter mediums are combined to withstand the filtration pressure and melt inside the two filter mediums. Stainless steel punching plate 32 made of SUS304 and wire mesh 33 are used as a support to secure a space through which the thermoplastic resin can flow, and the outer periphery is welded (welded portion 34), and the inner periphery is rounded and discharged to the center. The hub ring 36 having the holes 35 was welded (welded portion 37) to collect the molten thermoplastic resin in the central portion in the radial direction of the filter. This disk-like filter is generally called a leaf filter.
The leaf filter 40 is stacked to form an assembled filter device as shown in FIG. In FIG. 3, a plurality of leaf filters 40 are stacked and assembled using a filter shaft 41 as a support, and are housed in a filter housing 42. The molten thermoplastic resin is introduced from the thermoplastic resin introduction hole 43, filtered by each filter 40, and then discharged from the thermoplastic resin discharge hole 44.

Further, as shown in FIG. 4, a pressure detection device 51 is installed at the inlet of the filtration device 50 to measure the pressure applied to the filter, and when an abnormally high pressure is applied, the motor 53 of the gear pump 56 is stopped. The interlock was activated. Then, after the thermoplastic resin started to pass through the filter, the molten resin was passed up to an upper limit of the pressure at the inlet of the filtration device 50 to 25 MPa, and discharged onto the cooling drum 61 using a wide base 60. The surface temperature of the cooling drum 61 was 20 ° C. In addition, electrostatic pinning 62 was used to bring the thermoplastic resin sheet into close contact with the drum 61.
The biaxially stretched polyester film is obtained by stretching this unstretched film at Tg to (Tg + 60) ° C. so that the total magnification becomes 3 to 6 times once or twice in the longitudinal direction, and then Tg to (Tg + 60) ° C. Then, the film is stretched so that the magnification is 3 to 5 times in the width direction, and component A is applied on both sides thereof, or component B is applied uniformly on one side with a roll coater. Alternatively, the film is stretched simultaneously in the longitudinal direction and the width direction, further subjected to heat treatment at 180 to 230 ° C. for 1 to 60 seconds as necessary, and contracted by 0 to 20% in the width direction at a temperature 10 to 20 ° C. lower than the heat treatment temperature. It is obtained by performing reheat treatment while Tg was 78 ° C. in terms of glass transition temperature. Intrinsic viscosity was 0.64 dl / g.
Here, after extending | stretching to the vertical direction, the coating films A and B were apply | coated uniformly with the roll coater on both surfaces. Subsequently, it was supplied to a tenter and proceeded to winding and slitting processes after transverse stretching and heat setting treatment. Foreign matter was inspected with a film sampled from the product after the slit. The results are shown in Table 1.

<Film of coating A>
The polyethylene terephthalate chip was dried at 170 ° C. for 3 hours, then supplied to an extruder, melted at a melting temperature of 295 ° C., filtered through a filter device 80, stretched 3.6 times, and rapidly cooled to obtain a longitudinally stretched film. . The ratio of recycled chips was 30%.
An aqueous coating liquid having a solid content concentration of 8% was applied to both surfaces of the film after completion of the longitudinal stretching by a roll coater. The composition is a polyester copolymer (Tg = 90 mol% of terephthalic acid / 4 mol% of isophthalic acid / 5 mol of 5-sodium sulfoisophthalic acid and 90 mol% of ethylene glycol / 10 mol% of diethylene glycol). Acrylic copolymer (Tg = 40) consisting of 62% by weight of polyester and 70% by mole of methyl methacrylate / 40% by mole of ethyl acrylate / 5% by mole of N-methylolacrylamide / 2% by mole of 2-hydroxyethyl methacrylate. Of 20% by weight acrylic, 3% by weight of wax (carnauba wax), 5% by weight of silica filler (average diameter: 0.1 μm), wetting agent (polyoxyethylene (n = 7) lauryl ether) 10% by weight.
This film was subsequently dried at 95 ° C., stretched 3.8 times in the transverse direction at 120 ° C., and thermally fixed by shrinking 3% in the width direction at 220 ° C. to obtain a film having a thickness of 188 μm. The thickness of the coating film was 0.1 μm. Since the number of foreign matters tended to increase over time, comparison was made when the filtration amount (m ³ ) / filtration area (m ² ) was 40.

<Film of coating film B>
As a lubricant, porous silica particles having an average particle diameter of 1.7 μm, which are aggregated particles, were added to 0.066% by weight with respect to the polymer, and the mixed polyethylene terephthalate chips were dried at 170 ° C. for 3 hours, and then put into an extruder. It was supplied, melted at a melting temperature of 295 ° C., filtered through a filter device 80, stretched 3.6 times, and rapidly cooled to obtain a longitudinally stretched film. The ratio of recycled chips was 40%.
10% including Asahi Kasei Wacker Silicone Co., Ltd. DEHESIVE 39005VP (100 parts), DEHESIVE 39006VP (100 parts by weight), Nippon Unicar Co., Ltd. A-187 (2 parts by weight) on one side of the film after completion of the longitudinal stretching. A concentrated aqueous solution was applied with a roll coater so that the film thickness after dry transverse stretching was 0.04 μm.
After coating, it was supplied to a stenter and stretched 3.9 times in the transverse direction at 120 ° C. The obtained biaxially oriented film was heat-fixed at a temperature of 205 ° C. for 5 seconds and wound into a roll to obtain a film having a thickness of 30 μm. Since the number of foreign matters tended to increase over time, comparison was made when the filtration amount (m ³ ) / filtration area (m ² ) was 20.

[Comparative Examples 1-4]
In Table 1, the comparative examples 1-4 from which only the used leaf filter differs are described. The gel-like foreign material accumulated in the recycling chip rises and saturates after repeated recycling. The amount of foreign matter was compared after the amount of filtration was more than 5 times of circulation that was almost saturated. Compared to the examples, the amount of foreign matter was large, and the pressure increase was fast. The results are shown in Table 1.

  The present invention can produce a film with few foreign matters when producing a thermoplastic resin film. Moreover, it contributes to the life extension of the polymer filter for removing foreign substances. In the film manufacturing process for efficiently reusing the waste film, the waste utilization ratio can be increased. Regarding technology. By these, the film manufacturing cost can be reduced.

DESCRIPTION OF SYMBOLS 1 Measurement process 2 Drying process 3 Extruder 4 Polymer filter 5 Slit die 6 Cooling drum 7 Uniaxial stretching machine 8 Coater 9 Biaxial stretching machine 10 Conveying process 11 Ear part (edge film)
12 Winding machine 13 Mill roll 14 Slit process (slitter)
15 Packing process 16 Cutting 17 Core part (core film)
18 Crushing process 19 Flakes storage / drying 20 Regeneration extruder 21 Pelletizer 22 Chip (pellet)
23 Molten resin 24 Unstretched film 25 Uniaxially stretched film 26 Biaxially stretched film 27 Product 28 Flakes
29 Chip receiving / storage 31 Filter medium 32 Punching metal 33 Retainer mesh 34 Outer welded portion 35 Filter resin outlet 36 Hub ring 37 Inner welded portion 40 Leaf filter 41 Filter shaft 42 Filter housing 43 Inlet 44 Outlet 45 Filter flange 50 Filter device (Polymer filter)
51 Pressure Detection End 52 Extruder Motor 53 Gear Pump Motor 54 Pressure Detection End 55 for Gear Pump Input Pressure Extruder 56 Gear Pump 57 Feed Hopper 60 Cap (Slit Die)
61 Cooling drum 62 Electrostatic pinning wire

Claims (3)

In the production of a thermoplastic resin film having a coating process, the thermoplastic resin is polyethylene terephthalate, polyethylene 2,6-naphthalate, polyphenylene sulfide, polypropylene, polystyrene, polyamide or aramid, and a filtration layer for filtering the molten thermoplastic resin is described below. A filtration layer that simultaneously satisfies the conditions (1) to (4) is used, and an unused (virgin) chip after polymerization and a recycled (recycled) chip of film waste are mixed and melt extruded. A method for producing a thermoplastic resin film.
(1) Filtration accuracy at a collection efficiency of 95% is 0.6 to 15 μm,
(2) Having at least one filtration layer made of a metal fiber nonwoven fabric, and the basis weight of the finest filtration layer among the filtration layers made of the metal fiber nonwoven fabric: w is 500 to 10,000 g / m ² , and the wire diameter of the metal fiber: d is 22 μm or less, the product w · d is 15000 or more,
(3) The number of intersections of fibers in the finest filtration layer among the filtration layers made of the metal fiber nonwoven fabric is in the range of 2.5 to 5.3 × 10 ¹¹ ,
(4) The finest filtration layer has a thickness of 200 μm or more among the filtration layers made of the metal fiber nonwoven fabric.
Here, the intersection number C (points / m ² ) of the fiber is calculated by the following equation (1):
C = 4w ² / [π ³ r ³ ρ ² (T-2r)] × 10 ¹² (1)
w: basis weight (g / m ² ), r: wire radius (μm), ρ: density (g / cm ³ ), T: filtration layer thickness (μm), filtration layer thickness T (mm) is It is calculated by the following formula (2).
T = w / ρ / (1-ε) / 1000 (2)
Here, ε represents the porosity. Reuse of the film scraps (recycle) chips, debris film formed with a silicone release coating on the film, grinding method for producing a thermoplastic film according to claim 1, wherein the chip was regenerated by melting. Reuse of the film scraps (recycle) chips, debris film formed of an acrylic easy adhesion coating on the film, grinding method for producing a thermoplastic film according to claim 1, wherein the chip was regenerated by melting.

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