JPH1158498A - Method for casting thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to realize adhesive properties across the entire width of a thermoplastic resin sheet and a high-speed casting process and further, stabilize stretching properties and coat formation by applying a static charge across a width which is larger than the entire width of the thermoplastic resin sheet to bring the resin sheet into contact tightly with a mobile cooling medium so that the melt sheet is cooled. SOLUTION: In a casting method by which a static charge is applied to a thermoplastic resin melt sheet to bring the melt sheet into contact tightly with a mobile cooling medium so that the melt sheet is cooled, the static charge is applied across a width which is larger than the entire width of the thermoplastic sheet. For this purpose, an electrode for bringing the center part of the sheet into contact tightly with the mobile cooling medium and an electrode for bringing the end part of the sheet into contact tightly with the medium are used. In addition, the applied voltage which is applied to the end part of the sheet is as low as about 5-15 kV so that discharge to the cooling medium is prevented from occurring, while the voltage to be applied to the center part of the sheet is as high as about 8-35 kV. Besides, the applied voltage which is applied to the end part of the sheet is lower than the voltage to be applied to the center part of the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for casting a thermoplastic resin sheet, and more particularly, to a method for producing a thermoplastic resin sheet that achieves superior casting.

[0002]

2. Description of the Related Art As a method of casting a thermoplastic resin melt sheet, a method of applying an electrostatic charge to the melt to improve the adhesiveness to a cooling medium has been widely used.

[0003]

In the casting method for applying an electrostatic charge as described above, the application electrodes are arranged in parallel with the width direction of the melt sheet, but the application width is smaller than the width of the sheet. Can only be installed and applied to This is because when an electrode wider than the sheet width is used, an electric discharge occurs between the electrode and the cooling medium, so that no improvement in the adhesive strength of the melt is recognized. For this reason, strong adhesion is obtained at the center of the sheet due to electrostatic charge, but adhesion to the cooling medium is weak at the end of the sheet, which causes the thermoplastic resin to crystallize and turn up at the cooling process. (Curl)
This was the cause of uneven stretching and tearing in the subsequent stretching step. Of course, it was impossible to cast at a high speed by such a casting method.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a casting method in which an electrostatic charge is applied to a thermoplastic resin melt sheet so as to adhere to a moving cooling medium and cool, and the static electricity is applied over the entire width of the thermoplastic resin sheet. A method for casting a thermoplastic resin sheet, characterized by applying a charge.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. In the present invention, the thermoplastic resin is a resin that exhibits fluidity when heated, and is typically a resin selected from polyester, polyamide, polyolefin, vinyl polymer, and a mixture or modified product thereof. Particularly, in the case of the present invention, polyester resins and polyamide resins are preferred. Polyester resin is a polymer compound having an ester bond in the molecular main chain, and is usually often synthesized by a polycondensation reaction between a diol and a dicarboxylic acid. A compound that self-condenses, such as a carboxylic acid, may be used. Representative diol compounds include ethylene glycol, propylene glycol, butylene glycol, hexene glycol represented by HO (CH ₂ ) nOH, diethylene glycol, polyethylene glycol, ethylene oxide adduct, propylene oxide adduct and the like. And diols such as ether-containing diols, and the like, alone or in combination. Representative dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, maleic acid, fumaric acid , And mixtures thereof. In the case of the present invention, in particular, polyethylene terephthalate (PET) and its copolymer, polybutylene naphthalate (PBN) and its copolymer, polybutylene terephthalate (PBT) and its copolymer, polyethylene naphthalate (PEN) and its Copolymers, polyethylene terephthalate / adipate (PET / A), polyethylene terephthalate / sebacate (PET / S), and polybutylene terephthalate / isophthalate (PBT /
I), polyethylene terephthalate-polyethylene glycol copolymer (PET-PEG), polyhexamethylene terephthalate (PHT), and mixtures and copolymers thereof are preferred. The number of repeating units of these polymer compounds is 100 or more, preferably 150 or more. As the intrinsic viscosity, orthochlorophenol (O
The measured value in CP) is 0.5 (dl / g) or more, and preferably 0.6 (dl / g) or more. Of course, various additives to these polymer compounds, for example, a sliding agent, a stabilizer, an antioxidant, a viscosity modifier, an antistatic agent,
Coloring agents, pigments and the like can be used in combination.

The polyamide resin is a polymer compound having an amide bond in the main chain, and typical examples thereof include nylon 6, nylon 66, nylon 610, nylon 12, nylon 11, nylon 7, and polymeta. / Paraxylylene adipamide, polyhexamethylene terephthalamide / isophthalamide, and polyamide compounds selected from copolymers and mixtures thereof. Of course, these may be a polyamide ether obtained by copolymerizing a polyether compound such as polyethylene glycol, polypropylene glycol or polytetramethylene glycol, or a polyester amide compound obtained by copolymerizing with a polyester. Particularly excellent effects are exhibited on polymers and amorphous polyamide resins having many or large substituents in side chains.

In a casting method in which an electrostatic charge is applied to a thermoplastic resin melt sheet to adhere to a moving cooling medium and then cooled, in a conventional casting method in which an electrostatic charge is not applied to an end, the end is closely attached to a cooling medium. Insufficient force causes crystallization or curling of the end, which causes uneven stretching and tearing in the subsequent stretching process. Of course, such a casting method Then it was impossible to cast at high speed. Therefore, for the first time, by applying an electrostatic charge over the entire width from the center to the end of the thermoplastic resin sheet, crystallization not only at the sheet center but also at the sheet end can be suppressed. Not only can a sheet having excellent thickness uniformity be obtained, but also stable stretching can be performed, and the casting speed can be increased. Of course, if the width of the applied electrode is simply increased in the conventional casting method, discharge occurs on the cooling medium due to the absence of the molten resin sheet outside the end portion of the sheet, so that such an electrode cannot be used as it is.

Therefore, in order to apply an electrostatic charge over the entire width of the thermoplastic resin sheet according to the present invention, it is necessary to use a special electrode, a method using an insulator as a cooling medium, or the like.

As such a special electrode, for example,
Representatively, the function is divided using two or more electrodes, such as an electrode for making the central portion of the sheet adhere and an electrode for making the end portion of the sheet adhere. The relative position of the plurality of electrodes is set such that the electrode for sheet edge contact is located at the position closest to the extrusion die, the sheet edge is first brought into close contact with the cooling medium by the electrode for edge, and then the center The central part is preferably brought into close contact with the part electrode. In addition, very strong adhesion is required at the center to prevent crystallization and impart properties such as surface smoothness and flatness, but at the end of the sheet, only a function to prevent crystallization is required. No strong adhesion is required. For this purpose, the applied voltage Ve applied to the end of the sheet is reduced to about 5 to 15 KV to prevent discharge to the cooling medium, while the applied voltage Vc to the center of the sheet is about 8 to 35 KV. It is important that the voltage Ve applied to the end of the sheet be lower than the voltage Vc applied to the center of the sheet. Further, it is important to make the shortest distance He at the sheet end longer than the shortest distance Hc at the sheet center from the application electrode to the melt sheet surface, and the shortest distance Hc at the center is 5 to 50 mm, The shortest distance He at the end of the sheet is 15 to 10
It is better to set it to about 0 mm. As the electrode shape, an arbitrary electrode such as a wire electrode, a blade electrode, or a needle electrode can be used.However, the shape of the application electrode for bringing the sheet end into close contact with each other may be a needle shape, or the needle electrode may be a wire. When used in combination with the electrodes, the electric charge can be concentrated only on the edge of the sheet, so that discharge to the cooling medium can be prevented, which is preferable. Further, it is preferable that a liquid film such as water having a thickness of about 0.1 to 0.5 μm is interposed only at the end of the film because the adhesion to the drum can be further improved. Of course, the electrode shape can be arbitrarily selected among a plurality of electrodes. There is also a method in which an electrode for imparting an electrostatic charge to the molten material is performed by using a moving cooling medium. In this case, only one electrode is required, and the apparatus is relatively simple and has excellent operability. An electrostatic charge can be applied over the above width, and the adhesive force can be improved at both the end and the center of the sheet, which is a more preferable method.

Next, as a method of using an insulator as a cooling medium, a surface resistance of a surface material of a moving cooling medium is set to 10 ¹¹ Ω.
/ □ or more, preferably 10 ¹³ Ω / □ or more.

Specifically, the surface material of the cooling medium is aluminum oxide Al ₂ O ₃ , titanium oxide TiO ₂ , zirconium oxide ZrO ₂ , beryllia BeO, magnesia MgO, boron nitride BN, silicon nitride Si ₃ N ₄ , spinel MgO. A
Insulating ceramic material represented by l ₂ O ₃ , mullite 3Al ₂ O ₃ .2SiO ₂ , cordierite 2MgO.2Al ₂ O ₃ .5SiO ₂ , and mixtures thereof, and fluorine represented by tetrafluoroethylene This can be achieved by using a compound and a silicone rubber material. A plurality of these insulators may be combined to form a multilayer.
It is important for the smoothness and the like of the sheet that the surface roughness of these media is 0.6 μm or less, preferably 0.2 μm or less. The moving cooling medium surface temperature is equal to or higher than the glass transition temperature Tg-50 ° C of the thermoplastic resin, and equal to or lower than Tm.
Preferably, by maintaining the temperature at Tg−25 ° C. or higher and Tg + 60 ° C. or lower, not only the sheet edge but also the center of the sheet significantly improves the adhesiveness to the cooling medium. preferable. Of course, due to the increase in the temperature of the cooling medium, the adhesiveness between the medium and the molten sheet is improved, and when the crystallization of the edge and center of the molten thermoplastic sheet progresses more strongly, the stretchability is extremely deteriorated. Therefore, at this time, the temperature of the cooling medium cannot be increased. Therefore, in order to reduce the crystallization rate of the thermoplastic resin and improve the adhesion to the cooling medium, the glass transition temperature of the thermoplastic resin is lower than the glass transition temperature Tg of the thermoplastic resin. Preferably, the resin having a temperature (Tg) is less than 20% by weight, more preferably less than 10% by weight, and most preferably less than 3% by weight.
% By weight. Examples of the resin having a low glass transition temperature (Tg) include polyethylene terephthalate / adipate (PET / A), polyethylene terephthalate / sebacate (PET / S), polybutylene terephthalate (PBT), and polyethylene terephthalate-polyethylene glycol copolymer. Merging (PET
-PEG), polyhexamethylene terephthalate (PH
T), and mixtures and copolymers thereof. By making the molecular weight of the resin used at the end of the thermoplastic resin sheet higher than the molecular weight of the resin used at the center, stable stretching can be achieved even if the adhesiveness of the sheet end to the cooling medium is slightly reduced. And a stable casting method for the thermoplastic resin sheet. Specifically, the intrinsic viscosity [ηe] of the end of the thermoplastic resin sheet
By using a resin which is higher than the intrinsic viscosity [ηc] of the thermoplastic resin at the center by 0.1 or more, preferably 0.2 or more, stable stretching and heat treatment can be performed.

Next, a method for producing a thermoplastic resin sheet according to the present invention will be described.

As the thermoplastic resin raw material used for melt extrusion, a raw material obtained by blending a raw material such as polyester or polyamide and, if necessary, adding and blending another compound, for example,
Liquid crystal polymers and other polyester resins, as well as silicon oxide, magnesium oxide, calcium carbonate, titanium oxide,
Raw materials to which inorganic compounds such as aluminum oxide, crosslinked polyester, crosslinked polystyrene, mica, talc, kaolin, etc., organic compounds such as ethylenebisstearylamide, ionic polymer compound ionomer, etc. are added, raw materials once melted, and the present invention A raw material obtained by mixing the collected raw materials of the film is prepared, dried and dehydrated, and then supplied to a melt extruder such as a single-screw extruder, a twin-screw extruder, a vent extruder, a tandem extruder, and the like. For example, melt extrusion is performed under a nitrogen stream or under vacuum so as not to lower the intrinsic viscosity [η]. Of course, the melting temperature is usually higher than the melting point of the thermoplastic resin, but once
So-called supercooled extrusion may be performed in which the resin is melted at a temperature equal to or higher than the melting point of the resin, and then cooled to a temperature equal to or lower than the melting point and equal to or higher than the melt crystallization temperature Tmc. Such supercooled extrusion not only has the effect of reducing thermal decomposition and gelation of the resin, but also reduces the production of low molecular weight oligomers. is there. At this time, in order to remove foreign matter,
It is preferable to use an appropriate filter, for example, a sintered metal, a porous ceramic, a sand, a wire mesh, or the like. The draft ratio when extruding from the die (= lip lip interval / thickness of the extruded film) is preferably 7 or more, more preferably 10 or more, so that a film with small thickness unevenness and good transparency can be easily obtained. .

The thus melted thermoplastic resin sheet is applied with an electrostatic charge, is brought into close contact with a cooling medium, is rapidly cooled, and is cast. However, it is necessary to apply the electrostatic charge over the entire width of the thermoplastic resin sheet. is there. To do this,
It is preferable that the function is divided using two or more electrodes, such as an electrode for making the center portion of the sheet adhere to and an electrode for making the end portion of the sheet adhere. The relative position of the plurality of electrodes is set such that the electrode for sheet edge contact is located at the position closest to the extrusion die, the sheet edge is first brought into close contact with the cooling medium by the electrode for edge, and then the center The central part is brought into close contact with the part electrode. The applied voltage Ve applied to the end of the sheet is as low as about 5 to 15 KV to prevent discharge to the cooling medium, while the applied voltage Ve is applied to the center of the sheet.
c is set to be as high as about 8 to 35 KV. Further, the shortest distance He at the sheet end is longer than the shortest distance He at the sheet center from the application electrode to the melt sheet surface, and the shortest distance Hc at the center is 5 to 50 mm, and the shortest distance at the sheet end. It is preferable to set He to about 15 to 100 mm. The sheet thus obtained has good adhesion to the cooling medium not only at the center but also at the ends, so that the sheet has excellent surface smoothness and crystallization prevention.

The cast film is subsequently stretched,
Specifically, for example, stretching is performed in accordance with a stretching method such as longitudinal uniaxial stretching, horizontal uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching, but in any case of stretching, crystallization of the sheet edge is suppressed. It can be stretched stably without any problems such as tearing. The stretching temperature is not particularly limited, but may be any temperature as long as it is equal to or higher than the glass transition temperature Tg of the resin, and an arbitrary temperature can be selected as needed. The stretching ratio in one direction is
2 to 8 times, preferably about 3 to 6 times. After stretching, heat setting may be performed as necessary.

The thermoplastic resin sheet thus obtained according to the present invention can be used for packaging applications, magnetic recording applications, electrical applications such as capacitors and electrical insulation, graphics applications, receiving paper applications, etc., which have been conventionally used as film applications. Of course, it is also effective for a new film application excellent in thermal dimensional stability, moldability, shape stability, and toughness.

[0017]

[Measurement method of physical properties] Next, the method of measuring physical properties used in the present invention will be described below.

1. Intrinsic viscosity [η] of polyester: 25
At ゜ C, the value was determined by the following formula using o-chlorophenol as a solvent.

[Η] = lm [ηsp / c] The specific viscosity ηsp is obtained by subtracting 1 from the relative viscosity ηr. c is the concentration. The unit is expressed in dl / g.

2. Surface roughness Rt (μm): JIS B0
Measured at room temperature with a cutoff of 0.25 mm according to 601-1976.

3. Surface resistance value (Ω / □): JIS K6
It was measured at 25 ° C. and 65 RH% according to 911.

4. Glass transition temperature Tg (° C.), cold crystallization temperature Tcc (° C.) Using a DSC-II type measuring device manufactured by PerkinElmer, sample weight 10 mg, heating rate 20 ° C. /
The temperature at which the baseline starts to be shifted is defined as Tg, and the exothermic peak when the temperature is further increased is defined as Tcc.

5. Castability: The melt is brought into close contact with a cast drum as a cooling medium at a speed of 100 m / min,
Judgment was made based on the state of adhesion, the shape and crystal state of the sheet edge, and the like. The criteria are shown in Table 1 below.

[0024]

[Table 1] 6. Stretchability: A 6-μm-thick biaxially stretched film is continuously film-formed for three days, and the sheet is broken due to longitudinal stretching, and the trouble is caused by cutting off the edge of the sheet after stretching (edge cutting). It was judged from the state. The criteria are shown in Table 2 below.

[0025]

[Table 2]

[0026]

EXAMPLES Examples and comparative examples are described below to make the present invention easier to understand.

Example 1 As a thermoplastic resin, polyethylene terephthalate (P
ET) (intrinsic viscosity [η] = 0.65, glass transition temperature 70)
C., containing 0.1 wt.% Of spherical silica having an average particle size of 0.2 μm as an additive).
After being fed to a 50 mm melt extruder and melted, after passing through a filter for removing foreign substances of 5 μm or less, 1500 m
A 1200 mm diameter drum formed into a sheet from a m-width T-die die and kept at 63 ° C. while applying an electrostatic charge (the drum surface is a chrome-plated roll mirror-finished to a maximum roughness Rt = 0.1 μm) 100 m /
The contact and cooling were performed at a speed of min. As the application electrodes used at this time, two electrodes consisting of a tungsten wire electrode having a diameter of 0.1 mm for closely contacting the center of the sheet and a tungsten wire electrode having a diameter of 0.15 mm for closely contacting the end of the sheet were used. A voltage of 15 kv was applied to the electrode that brought the sheet center into close contact, and a voltage of 7 kv was applied to the electrode that brought the sheet into close contact. The shortest distance Hc from the sheet central electrode to the melt sheet central surface is 18 mm, and the shortest distance He from the sheet edge electrode to the sheet edge is 26.
mm, and an electrostatic charge was applied over the entire width of a sheet having a width of 1350 mm or more extruded in the above-described manner.

The cast sheet thus obtained has a thickness of 1
00 μm, small thickness unevenness, excellent flatness,
The sheet was an amorphous sheet having no surface defects such as craters, and was transparent and amorphous with no fluctuations in edges or width. Subsequently, the extruded film is stretched at a stretching temperature of 105 ° C. by 5 times in multiple stages with a roll-type longitudinal multi-stage stretching machine, cooled once to Tg or less, and then the tenter is gripped while holding both ends of the longitudinally stretched film with clips. After stretching 4.1 times in the width direction in a hot air atmosphere heated to a stretching temperature of 100 ° C., heat-fixing at 220 ° C. at a fixed length, and 3% relaxing heat fixing at 150 ° C. in the width direction. The part was cut, and a biaxially oriented laminated polyester film having a thickness of 6 μm was wound up at a high speed of about 500 m / min in a stable state without breaking, and edge-treated to form a film.

The film thus obtained was a film having excellent flatness without surface defects.

Example 2 At the time of melt extrusion in Example 1, a polyethylene terephthalate / sebacate (80/20 molar ratio) copolymer (intrinsic viscosity: 0.8) was used as an adhesion promoter and a crystallization inhibitor. Weight% addition and cast drum temperature 53 ° C
A biaxially stretched polyethylene terephthalate film having a thickness of 6 μm was stabilized in the same manner as in Example 1 except that the film thickness was lowered, and a film having excellent surface flatness without surface defects could be formed. It can be seen that the inclusion of the special additive makes it possible to perform high-speed and stable casting even with low-temperature casting.

Example 3 In place of the wire electrode for contacting the end used in Example 1, an electrode having 12 pin electrodes having a diameter of 0.4 mm arranged in series along the end was used, and the casting speed was 120 m / m. mi
thickness of 6 μm in exactly the same manner as in Example 1 except that the speed was increased to n.
m, the biaxially stretched polyethylene terephthalate film was stabilized, and a film having excellent flatness without surface defects could be formed.

Thus, it can be seen that even when the casting speed was increased, a stable film could be formed because the pin electrode was used at the end.

Example 4 In the method of Example 1, a pin electrode having a diameter of 0.4 mm for further improving adhesion was arranged along the edge at the sheet edge.
Moreover, a biaxially stretched polyethylene terephthalate film having a thickness of 6 μm was stabilized in the same manner as in Example 1 except that the casting speed was increased to 140 m / min, and a film having excellent surface flatness without surface defects was formed. We were able to. Thus, it can be seen that even when the casting speed was extremely high, the pin electrode and the wire electrode were used in combination at the ends, so that stable film formation became possible.

Example 5 The procedure of Example 1 was repeated except that the PET was placed and laminated in the width direction so that PET having a high molecular weight (intrinsic viscosity 0.78) was located at both ends of the sheet, and the temperature of the cast drum was raised to 75 ° C. In the same manner as in Example 1, a biaxially stretched polyethylene terephthalate film having a thickness of 6 μm was stabilized, and a film having excellent surface flatness without surface defects could be formed.

By increasing the molecular weight at the end in this way, it can be seen that high-speed casting can be performed at high speed and stable.

Comparative Example 1 A biaxially stretched polyethylene terephthalate film having a thickness of 6 μm was formed in the same manner as in Example 1 except that the sheet end contact electrode was not used in Example 1. The film properties were not good, and there were problems such as film breakage and discharge to the drum. In all cases, stable film formation was not possible, and high-speed castability, stretchability, and film-formability were poor.

Example 6 The same procedure as in Example 1 was carried out except that the cast drum used in Comparative Example 1 was made of chrome plating and a zirconia-coated drum having a surface resistance of 10 ¹⁵ Ω / □ was coated (surface roughness Rt 0.1 μm). Similarly, a biaxially stretched polyethylene terephthalate film having a thickness of 6 μm was stabilized, and a film having excellent surface flatness without surface defects could be formed.
By using a special material for the drum as described above, high-speed castability, stretchability, and film-forming properties were excellent.

[0038]

According to the casting method in which an electrostatic charge is applied to a thermoplastic resin melt sheet and is adhered to a moving cooling medium and cooled, the electrostatic charge is applied over the entire width of the thermoplastic resin sheet to achieve high speed. Not only casting became possible, but also stretchability was stabilized, achieving significant cost reduction and stable film formation.

Claims (15)

[Claims] 1. A casting method in which an electrostatic charge is applied to a thermoplastic resin melt sheet to make it adhere to a moving cooling medium and is cooled, wherein the electrostatic charge is applied over the entire width of the thermoplastic resin sheet. Method of casting a thermoplastic resin sheet. 2. An apparatus according to claim 1, wherein said application electrode for applying an electrostatic charge comprises an electrode for bringing the central portion of the molten sheet into close contact and an electrode for bringing the sheet end into close contact. Casting method for thermoplastic resin sheet. 3. An electrostatic applied voltage Vc for bringing a central portion of a molten sheet into close contact and an electrostatic applied voltage Ve for bringing an end portion of the sheet into close contact are in a relationship of Vc> Ve. The method for casting a thermoplastic resin sheet according to claim 2, wherein 4. The shortest distance H from the applied electrode to the surface of the molten sheet is in a relationship of Hc ≦ He between the shortest distance Hc at the center of the sheet and the shortest distance He at the end of the sheet. The method for casting a thermoplastic resin sheet according to claim 2 or 3. 5. The method for casting a thermoplastic resin sheet according to claim 1, wherein the shape of the application electrode for bringing at least the edge of the melt sheet into close contact is acicular. 6. The surface material of the moving cooling medium at least at the portion where the end of the melt sheet is in close contact with the surface of the moving cooling medium has a surface resistance value of 10 ^11.
6. The method for casting a thermoplastic resin sheet according to claim 1, wherein the sheet is made of an insulating material of Ω / □ or more. 7. The method according to claim 1, wherein the electrode for imparting an electrostatic charge to the melt is a moving cooling medium.
7. The method for casting a thermoplastic resin sheet according to 5 or 6. 8. The method according to claim 1, wherein the surface temperature of the moving cooling medium is maintained at a temperature not lower than the glass transition temperature Tg−50 ° C. and not higher than Tm of the thermoplastic resin. Or a method for casting a thermoplastic resin sheet according to 7 above. 9. The thermoplastic resin sheet according to claim 1, wherein a resin having a molecular weight higher than the molecular weight of the thermoplastic resin at the central portion is used at an end portion of the thermoplastic resin sheet. Casting method of thermoplastic resin sheet. 10. A thermoplastic resin sheet comprising a resin having an intrinsic viscosity [ηe] at the end of the sheet which is higher than the intrinsic viscosity [ηc] of the thermoplastic resin at the center by 0.1 or more. Claims 1, 2, 3, 4, 5, 6,
10. The method for casting a thermoplastic resin sheet according to 7, 8, or 9. 11. Only in the vicinity of the end of the thermoplastic resin sheet,
5. The method according to claim 1, wherein a means for improving the adhesion of the molten sheet to the moving cooling medium is used in combination.
The method for casting a thermoplastic resin sheet according to 5, 6, 7, 8, 9 or 10. 12. The method for casting a thermoplastic resin sheet according to claim 11, wherein a needle electrode is used as a means for improving the adhesion. 13. A thermoplastic resin, wherein a resin having a glass transition temperature lower than the glass transition temperature Tg of the thermoplastic resin is added to the thermoplastic resin, and the surface to which the resin is added is brought into close contact with a cooling medium. 1, 2, 3, 4, 5, 6,
The method for casting a thermoplastic resin sheet according to 7, 8, 9, 10, 11 or 12. 14. The resin having a glass transition temperature lower than the glass transition temperature Tg of the thermoplastic resin is polyethylene terephthalate / adipate PET / A, polyethylene terephthalate / sebacate PET / S, polybutylene terephthalate PBT, polyethylene terephthalate-polyethylene glycol. 14. The method for casting a thermoplastic resin sheet according to claim 13, wherein the thermoplastic resin sheet is at least one selected from copolymer PET-PEG, polyhexamethylene terephthalate PHT, and a mixture or copolymer thereof. . 15. The method of claim 1, 2, 3, 4, 5, 6, 7,
A method for producing a thermoplastic resin sheet, comprising casting using the method for casting a thermoplastic resin melt sheet described in 8, 9, 10, 11, 12, 13 or 14 to produce a thermoplastic resin sheet.