JP2003170484A - Polymer filter and method for producing thermoplastic polymer film using the filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer filter which can make a film excellent in surface smoothness and optical properties in film melting-extrusion by a T die, and to provide a method for producing a film using the filter. <P>SOLUTION: In a polymer filter, an angle between a line segment and a core hole central axis is 3-55°. The line segment passes through the center of a core hole inlet, is drawn on a plane vertical to a core central axis, and connects the center of the core hole inlet and the core central axis. In another polymer filter, the core hole central axis crosses the core central axis, and the angle between the central axes is 25-65°. In further another polymer filter, angle between the line segment which passes through the center of the core hole inlet, and connects the center of the core hole inlet and the core central axis on a projected plan on a plane vertical to the core central axis and the core hole central axis is 3-55. In an alternative polymer filter, the angle between the core hole central axis and the core central axis on a projected plan which passes through the center of the core hole inlet and includes the core central axis is 25-65°. The method for producing the thermoplastic polymer film uses the filter. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer filter and a method for producing a film using the same. More specifically, the present invention relates to a polymer filter capable of forming an optically excellent film having no die line and having excellent surface smoothness and having no fish eye or silver streak in the film melt extrusion using a T-die, and the polymer. The present invention relates to a method for producing a film having excellent surface smoothness and optical properties using a filter.

[0002]

2. Description of the Related Art In recent years, an attempt has been made to replace a glass substrate with a plastic film in order to make a liquid crystal display (LCD) lighter, thinner and have a larger screen. Also,
A super-twisted nematic (STN) uses a retardation film and a polarizing film to form a thin film transistor (TFT).
A polarizing film is used for. These films used as a liquid crystal material are required to have a high degree of surface smoothness and optical characteristics, and a film free from die lines, fish eyes, silver streaks, foreign matters, etc. is required. For this reason, the development of plastic materials having excellent optical properties has been promoted, and various improvements have been attempted in film forming technology. For example, JP-A-9-17466
No. 4, as a melt extrusion filter for producing an optical film having no die line and having excellent surface smoothness, the total number of core holes is 0.
It has been proposed that the filter is 5 to 1 times and the positions of the core holes of the filters do not overlap each other. But,
In the case of a polymer whose film-forming property cannot be said to be good, the occurrence of die lines and the like could not be completely prevented even when the filter was used, and therefore it is possible to form a film having excellent surface smoothness and optical performance. There has been a demand for a polymer filter and a method for producing a film using the polymer filter.

[0003]

DISCLOSURE OF THE INVENTION The present invention can form an optically excellent film having no die line and excellent surface smoothness, and no fish eye or silver streak in the film melt extrusion by T die. The object of the present invention is to provide a polymer filter and a method for producing a film having excellent surface smoothness and optical properties using the polymer filter.

[0004]

As a result of intensive studies to solve the above problems, the present inventor has found that in a polymer filter used for film melt extrusion by a T-die, the central axis of the core hole is oriented toward the central axis of the core. Whether the core hole has a constant angle with the core radial direction, or the center axis of the core hole is not orthogonal to the center axis of the core and forms a constant angle with the center axis of the core. By using a filter that makes a constant angle with the core central axis, the molten polymer flowing in the core is homogenized, partial retention of the molten polymer in the core is eliminated, die line,
It was found that a good film free from fish eyes, silver streaks, and foreign matter can be formed, and the present invention has been completed based on this finding. That is, the present invention is: 1) A filter comprising a tubular core (A) having one end closed and the other end open, a filter (B) attached to the core (A), and a housing (C) for housing these. ,
(1) The tubular core (A) has one end closed inside the housing, extends through the wall surface of the housing to the outside of the housing, and has the other end opened to the outside of the housing,
The tubular portion existing inside the housing has at least one core hole penetrating its wall surface, and (2) the filter.
(B) is a bag-like shape and covers the core hole so as to isolate it from the inner space of the housing, and after the substance to be filtered introduced into the housing through the housing hole is filtered by the filter, it passes through the core hole. (3) The housing (C) is a container opened to the outside only through the housing hole for introducing the substance to be filtered, and (4) the core hole is perpendicular to the central axis of the core. A polymer characterized in that an angle formed by a core hole center axis and a line segment connecting the center of the core hole entrance and the core center axis projected onto a plane including the center of the entrance is 3 to 55 °. A filter, 2) a filter comprising a cylindrical core (A) having one end closed and the other end open, a filter (B) attached to the core (A), and a housing (C) for accommodating them,
(1) The tubular core (A) has one end closed inside the housing, extends through the wall surface of the housing to the outside of the housing, and has the other end opened to the outside of the housing,
The tubular portion existing inside the housing has at least one core hole penetrating its wall surface, and (2) the filter.
(B) is a bag-like shape and covers the core hole so as to isolate it from the inner space of the housing, and after the substance to be filtered introduced into the housing through the housing hole is filtered by the filter, it passes through the core hole. (3) The housing (C) is a container opened to the outside only through the housing hole for introducing the substance to be filtered, and (4) the center of the core hole inlet and the core center axis are The angle between the center axis of the core hole and the center axis of the core projected on the plane including
A polymer filter characterized by being ゜. 3) A filter comprising a cylindrical core (A) having one end closed and the other end open, a filter (B) attached to this, and a housing (C) for housing these,
(1) The tubular core (A) has one end closed inside the housing, extends through the wall surface of the housing to the outside of the housing, and has the other end opened to the outside of the housing,
The tubular portion existing inside the housing has at least one core hole penetrating its wall surface, and (2) the filter.
(B) is a bag-like shape and covers the core hole so as to isolate it from the inner space of the housing, and after the substance to be filtered introduced into the housing through the housing hole is filtered by the filter, it passes through the core hole. (3) The housing (C) is a container opened to the outside only through the housing hole for introducing the substance to be filtered, and (4) the core hole is perpendicular to the central axis of the core. The angle between the core hole center axis and the line segment connecting the center of the core hole entrance and the core center axis projected onto the plane including the center of the entrance is 3 to 55 °, and the center of the core hole entrance is And a polymer filter characterized in that the angle between the center axis of the core hole and the center axis of the core is 25 to 65 ° projected onto a plane including the center axis of the core, and 4) a heating cylinder having a screw. Thermoplastic polymer The step (1) of heating and melting, the step (2) of filling the molten polymer into the inside of the polymer filter of the present invention through a pipe composed of a polymer outlet of a heating cylinder, and filtering the molten polymer with a filter, the filtered molten polymer Transfer from the core open part to T die through piping etc.
A step (3) of extruding from a die, a step (4) of solidifying the molten polymer extruded from a T die by passing through a cooling roll,
A method for producing a thermoplastic polymer film, comprising:

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer filter of the present invention comprises:
It is composed of a cylindrical core (A) having one end closed and the other end open, a filter (B) attached thereto, and a housing (C) for housing them. (1) The tubular core (A) has one end closed inside the housing, extends through the wall surface of the housing to the outside of the housing, and has the other end opened to the outside of the housing,
At least one core hole penetrating the wall surface is provided in a tubular portion existing inside the housing. It is preferable that there are a plurality of core holes from the viewpoint of filtration rate and the like. (2) The filter (B) has a bag shape and covers the core hole so as to isolate the core hole from the inside of the housing, and after the substance to be filtered introduced into the housing through the housing hole is filtered by the filter, the core It is configured to go through a hole. The filter (B) is made of a material through which molten polymer can pass. Examples of such a material include a wire net, a sheet having pores, a filter cloth, and the like, and the wire net is preferable from the viewpoint of strength and the like. (3) The housing (C) is a container opened to the outside only by a housing hole for introducing the substance to be filtered. It is preferable that a pipe or the like from the outside of the housing is directly connected to the housing hole. In the polymer filter, the substance to be filtered which has flown into the housing can be filtered through the filter (B) and then passed through the core hole. The filter (B) preferably projects from the core wall surface in order to increase the area while covering the core hole. The substance to be filtered is filled into the inside of the housing from the housing hole through piping and the like, is pressurized and filtered while passing through the filter (B), and flows into the core from the core hole,
It flows from the open end to the outside of the housing. In order to improve the efficiency of filtration, it is preferable to have a plurality of core holes. Each of the plurality of core holes may be covered with the filter (B) one by one, all of them may be covered with one filter, or several of them may be covered with one filter. . In the polymer filter of the present invention, a plurality of core holes are preferably formed so as to make one round in the circumferential direction of the core tube. In addition, it is preferable that the plurality of core holes that go around the core as one set be provided at regular intervals in the core central axis direction. It is preferable that the filter (B) covers a plurality of core holes of the above-mentioned one circumference, and that a plurality of filters are provided in the core central axis direction. Specifically, it is preferable to project from the core wall surface in a radial disk shape.

FIG. 1 is a cross-sectional view of the above preferred embodiment of the polymer filter of the present invention, taken along a plane passing through the core central axis. The molten polymer flows into the filter through the housing hole (c ′), passes through the filter (B), flows into the core (A) through the core hole (a), and flows out of the filter through the core opening. The core center axis is an axis passing through the center point of a cross section obtained by cutting the core along a plane perpendicular to the length direction of the cylinder. The core hole inlet is an inlet through which the molten polymer filtered by the filter (B) flows into the core,
In the outer surface layer of the tubular core (A), the core is missing. The center of the core hole is the center of gravity of the shape of the core hole inlet, and is the center when the core hole inlet is circular. FIG. 2 is a cross-sectional view of the core of one embodiment of the above-described preferred embodiment of the polymer filter of the present invention, which is cut by a plane A which is perpendicular to the central axis of the core and includes the center of at least one core hole inlet. In the polymer filter of this aspect, the angle α formed by the projected central axis b of the core hole 1 and the line segment a connecting the center of the inlet of the core hole 1 and the central axis of the core is projected on the plane A, respectively. It is 3 to 55 °, more preferably 5 to 50 °. In the present invention, the center of the core hole inlet is the center of gravity of the shape of the core hole, for example, the center of the circle when the core hole is circular, the intersection of the major axis and the minor axis when the core hole is elliptical. If the core hole is rectangular, it is the intersection of the diagonal lines. In conventional polymer filters,
All of the plurality of core holes were oriented in the direction of the central axis of the core, and the central axis of the core hole intersected with the central axis of the core.Therefore, the molten polymer fed from the multiple core holes into the core was Since they collide with each other in the vicinity of the central axis, pass through the core as a bundle without being sufficiently mixed, and are extruded from the opening to the outside of the filter and pass through the die, a die line is generated. In the polymer filter of this embodiment, the core hole central axis b is inclined with respect to the straight line a connecting the center of the core hole inlet and the core central axis, and the molten polymer extruded from the plurality of core holes to the core is ,
It is possible to prevent the occurrence of die lines because the molten polymer is extruded from the die while rotating in a spiral and mixed with each other to form a uniform molten polymer. If the angle α is less than 3 °, the extruded molten polymer may not be sufficiently mixed with each other, and a die line may occur. If the angle α exceeds 55 °, the wall surface of the core becomes thin, and the strength of the core may be insufficient.

FIG. 3 is a sectional view of a core of another embodiment of the polymer filter of the present invention, taken along a plane B including the center of at least one core hole inlet and the center axis of the core. In the polymer filter of this embodiment, on the plane B,
The projected angle β between the core hole central axis b and the core central axis c is 25 to 65 °, and more preferably 30 to 45 °. In the conventional polymer filter, the center axis of the core hole and the center axis of the core are orthogonal to each other, so that the molten polymer is likely to stay near the outlet of the core hole, and the staying polymer is thermally decomposed to generate gel or gas. However, as a result, fish eyes and silver streaks were generated in the extruded film. In the polymer filter of the present embodiment, the molten polymer is extruded into the core along the polymer flow direction, so that the molten polymer does not stay in the vicinity of the core hole outlet, and the gel is formed by thermal decomposition of the polymer. Since there is no generation of gas or gas, it is possible to prevent the generation of fish eyes and silver streaks. If the angle β is less than 25 °, it may be difficult to process the core hole. If the angle β exceeds 65 °, the molten polymer may be retained, and fish eyes and silver streaks may occur. FIG. 4 (a) is a cross-sectional view of a core of another embodiment of the polymer filter of the present invention, taken along a plane A ′ that is perpendicular to the core central axis and includes the center of at least one core hole inlet. Four
(b) is a cross-sectional view of the core of the same embodiment taken along a plane B ′ including the center of at least one core hole inlet and the center axis of the core. In the polymer filter of the present embodiment, the central axis b of the core hole 1 projected onto the plane A ′,
The angle γ formed by the line segment a connecting the center of the inlet of the core hole 1 and the center axis of the core is 3 to 55 °, more preferably 5 to 50 °, and the core is projected onto the plane B ′. The angle δ formed by the hole center axis b and the core center axis c is 25 to 65 °, more preferably 30 to 45 °. The polymer filter of this embodiment is a polymer filter in which the polymer filter of the embodiment shown in FIG. 2 and the polymer filter of the embodiment shown in FIG. 3 are combined.

The method for producing a film of the present invention comprises a step (1) of heating and melting a thermoplastic polymer by a heating cylinder having a screw, in which the molten polymer is introduced into the inside of the polymer filter of the present invention from a polymer outlet of the heating cylinder through a pipe or the like. Step (2) of filling and filtering the molten polymer with a filter, step (3) of transferring the filtered molten polymer from the core opening portion to a T die through a pipe or the like, and extruding from the T die, extruding from the T die The step (4) of passing the molten polymer through a cooling roll to solidify the molten polymer. FIG. 5 is an explanatory view of the method for producing a film of the present invention. The thermoplastic polymer is melted by the heating cylinder of the extruder 3 and filtered by the filter 4,
The sheet is extruded from the T-die 5 onto the cooling roll 6.
FIG. 6A is a schematic view of the filter, and FIG. 6B is an assembly view of the filter. The molten polymer is filtered by the filter 4 and extruded from the T die 5 into a sheet. In the step (1), the cylinder temperature is (Tg + 1
0 ° C) to 350 ° C, preferably (Tg + 10 ° C) to 30
It is 0 ° C. In the step (2), the molten polymer is extruded from the outlet of the heating cylinder, flows into the inside of the filter from the inlet of the polymer filter, is filled outside the core and the leaves, and is extruded from the screw of the heating cylinder. By this, it passes through the filter of the leaf and moves into the inside of the leaf, and further flows into the inside of the core through the core hole and flows out of the filter through the inside of the core. During this period, the temperature of the polymer is preferably maintained at the temperature when extruded from the cylinder. In the step (3), the molten polymer flowing out from the filter is extruded as it is from the T die in the form of a molten sheet. In step (4),
When the molten sheet passes through a cooling roll, it is cooled to a temperature not higher than the glass transition temperature of the thermoplastic polymer to be solidified, but it is stretched to a certain thickness until it is solidified into a film. As a method of stretching the sheet, the sheet traveling direction, a method of stretching the sheet at a speed faster than the rotation speed of the cooling roll by installing a take-up roll after the cooling roll, pressing the molten polymer passing through the cooling roll with a pressure roll The method of doing is mentioned.

Examples of the thermoplastic polymer to which the method of the present invention can be applied include vinyl aromatic polymers, chain polyolefins, polyamides, polyesters, polycarbonates and polymers having an alicyclic structure. The method of the invention is particularly suitable for use with polymers having an alicyclic structure. Examples of vinyl aromatic polymers include polystyrene, poly-α-methylstyrene, polyvinyltoluene, polyvinylnaphthalene, and styrene-acrylonitrile copolymers. Examples of the polyolefin used in the present invention include low density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, poly-
4-methyl-1-pentene and the like can be mentioned.
Examples of polyamides include nylon 3, nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, and nylon 612. Examples of polyesters include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. Examples of the polycarbonate include bisphenol A polycarbonate,
Branched bisphenol A polycarbonate, o, o, o ',
Examples thereof include o'-tetramethylbisphenol A polycarbonate. Examples of the polymer having an alicyclic structure include a norbornene-based polymer, a monocyclic cycloolefin-based polymer, a cyclic conjugated diene-based polymer, a vinyl alicyclic hydrocarbon-based polymer and hydrides thereof. Among these, the norbornene-based polymer and its hydride and the vinyl alicyclic hydrocarbon-based polymer and its hydride have good heat resistance and mechanical strength, and can be preferably used. In the method of the present invention, the thermoplastic polymers may be used alone or in combination of two or more. Among the above thermoplastic polymers, a polymer having an alicyclic structure can be particularly preferably used.

In the method for producing a film of the present invention,
A polymer filter that melts a thermoplastic polymer and the central axis of the core hole does not face the central axis of the core and forms a certain angle with the radial direction of the core. Angled polymer filter, or
The molten polymer flowing through the core is homogenized by filtering the molten polymer with a polymer filter in which the central axis of the core hole forms a constant angle with the radial direction of the core and the central axis of the core. Can be extruded through a T-die to produce a good film free from die lines, fish eyes, silver streaks, foreign matters, and the like. In particular, the polymer film having an alicyclic structure produced by the method of the present invention has small birefringence, high mechanical strength, good transparency and heat resistance, and low water absorption, and thus is suitable as an optical material. Can be used for.

[0011]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, a 50 mmφ extruder and a leaf disk type polymer filter having an opening of 15 μm were used to extrude a ring-opening polymer hydride into a film form from a coat hanger die to give an outer diameter of 4 mm.
Adhering to a 50mm cooling roll, width 650mm, thickness 40
A μm film was formed at a speed of 25 m / min. After continuing film formation for 6 hours, cut out an evaluation film with a width of 650 mm and a length of 300 mm, and install it between the projection light source and the screen at an angle of 45 ° with respect to the optical axis, and a film of a film image enlarged and projected. The number of die lines in the width direction was visually counted, and burned foreign matters, fish eyes, and silver streaks on the film were observed. Production Example 1 500 parts by weight of cyclohexane, 0.82 parts by weight of 1-hexene, 0.15 part by weight of dibutyl ether and 0.30 part by weight of triisobutylaluminum were placed in a reactor and kept at 45 ° C. under a nitrogen atmosphere while - methyl tetracyclo ^{[. 4.4.0.1 2, 5 .1 7,10} ] dodeca-3-ene (also known as M
200 parts by weight of TD) and 40 parts by weight of a 0.7 wt% toluene solution of tungsten hexachloride were continuously added over 2 hours for polymerization. Then, 1.06 parts by weight of butyl glycidyl ether and 0.52 parts by weight of isopropyl alcohol were added to inactivate the polymerization catalyst and terminate the polymerization reaction. To 100 parts by weight of the solution containing the obtained ring-opening polymer, 30 parts by weight of cyclohexane and 5 parts by weight of nickel-alumina catalyst [JGC Chemical Co., Ltd.] as a hydrogenation catalyst were added, and pressurized to 5 MPa with hydrogen, The reaction was carried out at 200 ° C. for 4 hours to obtain a solution containing 20% by weight of a hydride of the MTD ring-opening polymer. After removing the hydrogenation catalyst from this solution by filtration, a soft polymer [Kuraray Co., Ltd., Septon 200
2] 0.03 parts by weight and an antioxidant [Ciba Specialty Chemicals Co., Irganox 1010] 0.03 parts by weight were added, and cyclohexane as a solvent and other volatile components were added to a cylindrical concentrating dryer [(shares ) Hitachi, Ltd.], and the hydride of the ring-opening polymer was extruded in a molten state into a strand form from an extruder, cooled, and then pelletized. The weight average molecular weight of the obtained hydrogenated ring-opening polymer was 35.0.
00, the hydrogenation rate was 99.9%, and the glass transition temperature was 134 ° C. Example 1 A film of the ring-opened polymer hydride obtained in Production Example 1 was formed using a polymer filter having a shape A shown in FIG. 7 and an angle γ of 45 ° and an angle δ of 45 °. Neither die line, burnt foreign matter, fish eye nor silver streak was observed. Examples 2 to 11 The ring-opened polymer hydride obtained in Production Example 1 was formed into a film and evaluated in the same manner as in Example 1 except that the polymer filter having the shape shown in Table 1 was used. Comparative Examples 1 to 4 The ring-opened polymer hydride obtained in Production Example 1 was formed into a film and evaluated in the same manner as in Example 1 except that the polymer filter having the shape shown in Table 1 was used. The results of Examples 1 to 11 and Comparative Examples 1 to 4 are shown in Table 1.

[0012]

[Table 1]

As can be seen from Table 1, the core hole of the shape A having an inclination of 3 to 55 ° with respect to the radial direction of the core and also having an inclination of 25 to 65 ° with respect to the central axis of the core. In Examples 1, 4, 5, 6, and 7 using the polymer filter,
No die line, or less than 2
A film having excellent surface smoothness is obtained. Examples 2, 8, 9 using the polymer filter of the shape B in which the core hole has an inclination of 3 to 55 ° only with respect to the radial direction of the core.
Then, the number of die lines was 4 or less, and a film having good surface smoothness was obtained. In Examples 3, 10 and 11 using the polymer filter of shape C in which the core hole has an inclination of 25 to 65 ° only with respect to the central axis of the core, the number of die lines is 5 or less, and the film has good surface smoothness. Has been obtained. On the other hand, the shape D in which the core hole has neither inclination in the radial direction of the core nor in the center axis of the core
Comparative Example 1 using the polymer filter described in 1., the core hole has an inclination with respect to the radial direction of the core, the central axis of the core, or both, but a large number of die lines are generated in Comparative Examples 2, 3, and 4 in which the inclination is small. is doing.

[0014]

EFFECTS OF THE INVENTION By using the polymer filter of the present invention, a film having no die line which could not be formed by the conventional melt extrusion method and having excellent surface smoothness, and having no surface defects such as fish eyes and silver streaks. Can be formed into a film. The polymer film having an alicyclic structure produced by the method of the present invention has a small birefringence, a large mechanical strength, good transparency and heat resistance, and a small water absorption property, and thus is suitable as an optical material. Can be used.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a preferred embodiment of a polymer filter of the present invention, taken along a plane passing through a core central axis.

FIG. 2 is a cross-sectional view of one embodiment of the polymer filter of the present invention.

FIG. 3 is a cross-sectional view of another embodiment of the polymer filter of the present invention.

FIG. 4 is a cross-sectional view of another embodiment of the polymer filter of the present invention.

FIG. 5 is an explanatory diagram of a method for producing a film of the present invention.

FIG. 6 is a schematic view and assembly drawing of a filter.

FIG. 7 is a schematic view of a polymer filter used in Examples.

[Explanation of symbols]

1 core hole 2 cores 3 extruder 4 filters 5 T die 6 cooling rolls

Claims (4)

[Claims] 1. A filter comprising a cylindrical core (A) having one end closed and the other end open, a filter (B) attached to the core, and a housing (C) for accommodating them (1) ) The tubular core (A) has one closed end inside the housing, extends through the wall surface of the housing to the outside of the housing, and has the other end open to the outside of the housing, and is inside the housing. The tubular portion has at least one core hole penetrating its wall surface, and (2) the filter (B) is bag-shaped and covers the core hole so as to isolate the core hole from the housing internal space. The substance to be filtered introduced into the housing from the hole is configured to pass through the core hole after being filtered by the filter. (3) The housing (C) is for introducing the substance to be filtered. A container opened to the outside only through a housing hole. (4) The core hole center axis and the center of the core hole entrance projected onto a plane that is perpendicular to the core center axis and includes the center of the core hole entrance. A polymer filter characterized in that an angle formed by a line connecting the central axis of the core is 3 to 55 °. 2. A filter comprising a tubular core (A) having one end closed and the other end open, a filter (B) attached to the core (A), and a housing (C) for housing them (1) ) The tubular core (A) has one closed end inside the housing, extends through the wall surface of the housing to the outside of the housing, and has the other end open to the outside of the housing, and is inside the housing. The tubular portion has at least one core hole penetrating its wall surface, and (2) the filter (B) is bag-shaped and covers the core hole so as to isolate the core hole from the housing internal space. The substance to be filtered introduced into the housing from the hole is configured to pass through the core hole after being filtered by the filter. (3) The housing (C) is for introducing the substance to be filtered. It is a container opened to the outside only through a housing hole, and (4) the angle between the core hole central axis and the core central axis projected on a plane including the center of the core hole inlet and the core central axis is 25 to 65 °. A polymer filter characterized in that 3. A filter comprising a cylindrical core (A) having one end closed and the other end open, a filter (B) attached to the core (A), and a housing (C) for accommodating them (1) ) The tubular core (A) has one closed end inside the housing, extends through the wall surface of the housing to the outside of the housing, and has the other end open to the outside of the housing, and is inside the housing. The tubular portion has at least one core hole penetrating its wall surface, and (2) the filter (B) is bag-shaped and covers the core hole so as to isolate the core hole from the housing internal space. The substance to be filtered introduced into the housing from the hole is configured to pass through the core hole after being filtered by the filter. (3) The housing (C) is for introducing the substance to be filtered. A container opened to the outside only through a housing hole. (4) The core hole center axis and the center of the core hole entrance projected onto a plane that is perpendicular to the core center axis and includes the center of the core hole entrance. The angle formed by the line segment connecting the core center axis is 3 to 55 °, and the angle formed by the core hole center axis and the core center axis is projected on a plane including the center of the core hole inlet and the core center axis. Is 25 to 65 °. A polymer filter. 4. The step (1) of heating and melting a thermoplastic polymer with a heating cylinder having a screw, the molten polymer through a pipe comprising a polymer outlet of the heating cylinder, or the like, according to claim 1. A step (2) of filling the inside of the polymer filter and filtering the molten polymer with the filter, a step of transferring the filtered molten polymer from a core opening portion to a T die through a pipe or the like, and extruding from the T die (3), T A method for producing a thermoplastic polymer film, comprising the step (4) of passing a molten polymer extruded from a die through a cooling roll to solidify the molten polymer.