JP2000296528A - Method for producing thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a product having an excellent productivity and quality with a simple facility by insulating a conductive portion of a surface of a charged roll from a core of the roll and manufacturing a cast sheet. SOLUTION: The sheet is directly charged, efficiently brought into close contact with a cooling medium, air entraining between the sheet and the medium or an instability of a bank mold is suppressed by the sheet sandwiched between the charged roll and the medium. A conductive portion of the surface of the charged roll is insulated from the core of the roll. In order to cool the surface of the roll even without passing an insulation refrigerant, the cooling medium used for the cooling medium is branched, guided to the charged roll to simplify an apparatus constitution and to simplify apparatus maintenance. If the charged roll and the cooling medium are discharged therebetween, only the conductive layer on the surface of the charged roll is damaged, but the surface of the charged roll is not largely roughed. Adverse influence is not effected to the surface of the film, and the damage is limited only to the surface layer and the roll can easily be recycled. Thus, a casting speed can be accelerated, and the sheet of high quality can be manufactured with good productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic resin sheet which is excellent in productivity, in particular, high-speed castability, and is excellent in quality by using a simple apparatus. is there.

[0002]

2. Description of the Related Art A conventional method for producing a thermoplastic resin sheet is disclosed in, for example, Japanese Patent Publication No. 37-6142, in which a sheet melt-extruded from a die is cooled while maintaining the temperature below the glass transition temperature of the resin. A method of applying a static electricity to a medium and bringing the medium into close contact and quenching to obtain an amorphous cast sheet having a smooth surface, followed by uniaxial stretching or biaxial stretching as necessary.

On the other hand, in a sheet manufacturing method called a calendar forming method, a molten resin is sandwiched between rolls to form a resin pool called a bank, and a sheet is formed from a gap between the rolls.

However, such a method has the following disadvantages.

That is, the maximum speed at which a molten thermoplastic resin sheet is rapidly cooled in close contact with a cooling drum to obtain a transparent, smooth-surfaced sheet with low crystallinity is determined by an electrostatic application method, a vacuum suction method, a pressing method, or the like. Even if all means effective for high-speed casting are used, air entrapment cannot be prevented.
It could not be made faster than about 0 to 60 m / min, resulting in poor productivity. In addition, a plurality of rolls are used in the calendering apparatus, each of which requires a driving device and a cooling device, which is a large and expensive facility. Furthermore, in the case of a polyethylene terephthalate resin or the like in which a bank cannot be formed stably, it is difficult to increase the casting speed to 30 m / min or more, resulting in poor productivity.

[0006]

The inventors of the present invention have conducted various studies, and as a result, have found that a cast sheet in which a molten sheet is tightly cooled and solidified on a cooling medium while sandwiching a molten sheet between a charged roll and a cooling medium such as a casting drum. It has been found that the above-mentioned drawbacks of the prior art are improved by the method, and that high-speed casting, which has not been achieved before, is possible.

The method of casting while sandwiching a molten sheet between a charging roll and a cooling medium, which the present inventors have found, is an excellent high-speed casting technique that has not been achieved in the past.

However, since a roll to which a high voltage is applied is used, the cooling of the roll involves the use of an insulating refrigerant and a complicated apparatus and maintenance such as combining a cooling device corresponding to such a refrigerant. Further, when a discharge occurs between the charging roll and the cooling medium, the surface of the charging roll is greatly damaged, which may be transferred to a film and become a surface defect.

[0009] That is, an object of the present invention is to provide a production method capable of solving the above-mentioned drawbacks and obtaining a thermoplastic resin sheet excellent in both productivity and quality with simple equipment.

[0010]

Means for Solving the Problems In view of the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, have used a charging roll in which the conductive portion of the roll surface is insulated from the roll core, and cooled the molten sheet with a cooling medium. The present inventors have found that the above problem can be solved by casting while sandwiching them, and have reached the present invention.

That is, the method for producing a thermoplastic resin sheet of the present invention has the following configuration (1). (1) In a method for producing a cast sheet in which a thermoplastic resin is melted and then discharged as a molten sheet from a die, and the sheet is tightly cooled and solidified on a cooling medium while being sandwiched between the charging roll and the cooling medium, a method of producing a cast sheet is disclosed. A method of manufacturing a thermoplastic resin sheet, wherein a cast sheet is manufactured with a part insulated from a roll core.

Further, the method for producing a thermoplastic resin sheet of the present invention has the following aspects (2) to (9) as preferred specific embodiments. (2) The conductive portion of the charging roll surface and the roll core are insulated by a ceramic layer (1).
3. The method for producing a thermoplastic resin sheet according to item 1. (3) The method for producing a thermoplastic resin sheet according to (1), wherein the conductive portion of the charging roll surface and the roll core are insulated by a resin layer. (4) The conductive portion of the surface portion of the charging roll is a metal layer,
The method for producing a thermoplastic resin sheet according to any one of (1) to (3), wherein the thermoplastic resin sheet is formed by any one of plating, vapor deposition, and thermal spraying. (5) The method for producing a thermoplastic resin sheet according to any one of (1) to (4), wherein a refrigerant is circulated inside the charging roll, and the roll surface temperature is set to Tg or lower of the thermoplastic resin. (6) The method for producing a thermoplastic resin sheet according to (1), wherein the width of the conductive portion on the surface portion of the charging roll is shorter than the width of the cast sheet by 10 mm or more. (7) The thermoplastic resin sheet according to any one of (1) to (6), wherein a charge having the same polarity as that of the molten sheet is applied to the molten sheet before the molten sheet comes into contact with the charging roll. Manufacturing method. (8) The method for producing a thermoplastic resin sheet according to (1), wherein the thermoplastic resin is a polyester composition. (9) The method for producing a thermoplastic resin sheet according to any one of (1) to (8), wherein the cast sheet is stretched and / or heat-treated.

[0013]

Embodiments of the present invention will be described below.

According to the present invention, the molten thermoplastic resin is extruded into a sheet shape, and the molten sheet is tightly cooled and solidified on a cooling medium while being sandwiched between a cooling roll and a charging roll whose conductive portion on the roll surface is insulated from the roll core. This is a method for producing a thermoplastic resin sheet to be formed.

According to the method of the present invention, the sheet can be efficiently brought into close contact with the cooling medium by directly applying a charge to the sheet, and has better adhesion than the conventional electrostatic application casting method.
Furthermore, by sandwiching between the charging roll and the cooling medium, air entrainment between the sheet and the cooling medium and the instability of bank molding, which were problems in the conventional high-speed casting method, can be suppressed. 80-300m
A high-speed cast that reaches as much as 1 / min can be realized.

Further, according to the method of the present invention, the conductive portion on the surface of the charging roll and the roll core are insulated from each other, so that the roll surface can be cooled without passing the insulating refrigerant. For this reason, for example, it becomes possible to branch the cooling refrigerant used for the cooling medium and guide it to the charging roll, so that the device configuration is simplified and the device maintenance is also simplified.
Furthermore, even if a discharge occurs between the charging roll and the cooling medium, only the conductive layer on the charging roll surface is damaged, so that the charging roll surface is not greatly roughened and does not adversely affect the film surface. Further, since the damage is limited only to the surface layer portion, the roll can be easily reproduced.

The thermoplastic resin in the present invention is a resin which exhibits fluidity upon heating, and is typically a resin selected from polyester, polyamide, polyolefin, polyphenylene sulfide, vinyl polymer, and a mixture or modified product thereof. In the case of the present invention, polyester resins and polyamide resins are preferred, and polyester resins are particularly preferred. Polyester is a high molecular compound having an ester bond in the molecular main chain, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and copolymers thereof, among which polyethylene terephthalate and polyethylene naphthalate and These copolymers are preferred, and polyethylene terephthalate and its copolymers are particularly preferred. The number of repeating units of these polymer compounds is 80 or more, preferably 120 or more.
Orthochlorophenol (OCP)
It is good that the measured value is 0.4 (dl / g) or more, preferably 0.55 (dl / g) or more. Of course, these polyester resins can be used in combination with various additives such as a slipping agent, a stabilizer, an antioxidant, a viscosity modifier, an antistatic agent, a coloring agent, a pigment, and a liquid crystal polyester. The polyamide resin is a polymer compound having an amide bond in the main chain, and typical examples thereof include nylon 6, nylon 66, and nylon 61.
0, nylon 12, nylon 11, nylon 7, polymeta / para-xylylene adipamide, polyhexamethylene terephthalamide / isophthalamide, and a polyamide compound selected from the related copolymers and mixtures thereof. Further, as the polyphenylene sulfide resin, a linear compound having substantially no branched structure is preferable.

In the present invention, the charging roll is composed of a conductive portion of a surface layer, an insulating layer as an intermediate layer, and a roll core. The roll core and the roll surface layer are electrically insulated, and electricity is applied only to the roll surface layer. In this way, electricity does not flow to the roll core, and a normal cooling structure that does not particularly take into consideration insulation is adopted inside the roll core. Cooling of the charging roll is necessary to prevent the molten sheet from sticking to the roll, and it is preferable to keep the roll surface temperature at or below the Tg of the thermoplastic resin.

The insulating layer formed on the charging roll may be selected from the viewpoints of electrical insulation and heat resistance, and is preferably a ceramic material, a silicone resin, or a Teflon resin, and particularly preferably a ceramic material. As the ceramic, alumina, zirconia, titania and a mixture thereof are preferable. As the fluororesin, an ethylene tetrafluoride resin,
Preference is given to fluorinated ethylene / perfluoroalkoxy resin, tetrafluoroethylene / hexafluoropropylene resin, ethylene / tetrafluoroethylene resin, ethylene / chlorotrifluoroethylene resin and the like.

The material of the conductive layer formed on the surface of the charging roll is preferably a metal, and a metal film formed by electroless plating, vapor deposition, or thermal spraying is preferable. Further, the surface of the charging roll is preferably smooth to directly touch the molten sheet, for example, the surface roughness is preferably 1S or less,
More preferably, it is 0.5S or less. Next, the roll core of the charging roll is not particularly limited to a material or the like, but when spraying ceramic on its surface, stainless steel or carbon steel is preferable, and further for the structure, a structure through which cooling water flows, For example, a double tube structure is preferable. The double pipe has a structure in which a roll core is formed of an outer cylinder and an inner cylinder, and cooling water flows through a gap between the outer cylinder and the inner cylinder.

Next, a method for charging the roll will be described.

The role of the conductive layer formed on the surface of the charging roll is to give a charge to the molten sheet. So contact the metal brush or carbon brush on the roll surface,
A method of supplying power from a brush is preferred. The voltage applied to the roll is preferably 100 V to 10 KV, and a DC positive voltage or a negative voltage is applied to the roll. The cooling medium may be grounded. Further, an electric resistance can be inserted between the ground and the cooling medium in order to limit the value of the current flowing through the molten sheet.

In the present invention, a charge is applied to the sheet by the potential difference existing between the charging roll and the cooling medium, and the sheet is brought into close contact with the cooling medium. However, depending on the electrical characteristics of the thermoplastic resin at the time of melting, the molten sheet is applied to the roll. The surface may be roughened by being drawn. In order to prevent this, it is preferable to apply a charge of the same polarity as the roll to the sheet before the molten sheet comes into contact with the roll.

The method of applying the electric charge includes, for example, applying a wire between the base and the roll in the sheet width direction, and applying a voltage having the same polarity as the roll to the wire. The electrode for this is not particularly limited, but the above-mentioned wire-shaped electrode or tape-shaped electrode can be preferably used.

The cooling medium in the production method of the present invention is necessary for cooling the molten sheet and obtaining an amorphous sheet. The form is preferably a drum, and it is preferable to circulate cooling water or the like inside the drum to keep the drum surface temperature constant. The drum surface is preferably a metal, for example, a surface having a surface roughness of 0.5 S or less, which is hard chrome plated, is preferred.

According to the production method of the present invention, since there is a potential difference between the roll and the cooling medium, it is necessary to pay attention to electric discharge and the like. It is important that the width is also at least 10 mm.

Further, depending on post-processing (for example, stretching) of the cast sheet, it is necessary to form the sheet edge portion thicker than the sheet central portion. In this case, the surface length of the roll itself is smaller than the cast sheet width. Just do it.
However, in this case, since the film edge does not easily adhere to a cooling medium such as a drum, it is preferable to adhere the film edge portion by another method. For example, a method of selectively applying static electricity only to the edge portion, a method of blowing and pressing compressed air to the edge portion, and a method of applying water or the like only to the drum surface where the edge portion is applied can be cited.

The sheet cast by the method of the present invention can be further subjected to stretching and / or heat treatment, if necessary. Stretching can be performed by various methods such as longitudinal uniaxial stretching, horizontal uniaxial stretching, sequential biaxial stretching, simultaneous biaxial stretching, and usually, a biaxially stretched sheet can be used to obtain a mechanically balanced sheet. it can.
Stretching can be performed by a method of performing between rolls having different peripheral speeds or by a tenter method in which a sheet is gripped by a clip and the clip interval is changed.

The stretching ratio is not particularly limited, but is preferably 2 to 8 times in one direction, more preferably about 3 to 6 times. The stretching may be performed at a temperature equal to or higher than Tg. The heat treatment may be performed at a predetermined temperature as needed after the stretching, and conditions may be appropriately set according to necessary sheet characteristics.

According to the method for producing a thermoplastic resin sheet of the present invention, a high-quality sheet can be produced with high productivity by high-speed casting.

Next, the method for producing a thermoplastic resin sheet according to the present invention will be described more specifically by taking the production of a polyethylene terephthalate sheet as an example.

As a raw material, a polyethylene terephthalate resin or a raw material obtained by adding and blending another compound as required, for example, a liquid crystal polymer or another polyester resin, further, silicon oxide, magnesium oxide, calcium carbonate, titanium oxide, aluminum oxide, crosslinked polyester Raw materials to which inorganic compounds such as cross-linked polystyrene, mica, talc, and kaolin, and organic compounds such as ethylenebisstearylamide and ionic polymer compound ionomers are added;
Once the raw material has been melted, the raw material obtained by mixing the recovered material of the sheet of the present invention, etc. are prepared, and dried and dried.
After dewatering, single screw extruder, twin screw extruder, vent extruder,
It is supplied to a melt extruder such as a tandem extruder, and is melt-extruded under a nitrogen stream or under vacuum so as to minimize the molecular weight, for example, the intrinsic viscosity [η]. Of course, the melting temperature is usually equal to or higher than the melting point Tm of the polyester resin. Extrusion can be performed in a so-called supercooled state. Extrusion in such a supercooled state not only has the effect of reducing the thermal decomposition and gelation of the resin, but also has the effect of reducing the generation of low-molecular-weight oligomers, thereby reducing drum contamination and facilitating casting. There is also. In order to remove foreign substances in the raw material, it is preferable to extrude the molten resin while filtering the molten resin with an appropriate filter, for example, a sintered metal, a porous ceramic, a sand, a wire mesh, or the like.

The positional relationship between the die and the casting drum is not particularly limited, but it is preferable for stable casting to adjust the molten resin sheet so that it is extruded in the vertical direction. Further, the draft ratio when extruding the molten sheet from the die (= die lip interval / thickness of the extruded sheet) is preferably 3 or more, more preferably 7 to 20.
Within this range, a sheet with small thickness unevenness and good flatness can be easily obtained.

The polyester resin thus melted is extruded from a die.
Casting is carried out so as to be sandwiched between a roll to which a voltage of 0 KV is applied and a casting drum.

The cast sheet thus obtained is subjected to a stretching treatment as required. For example, in the case of a sequential biaxial stretching method, the cast sheet is first heated to Tg or more by a preheating roll, and then longitudinally rolled by rolls having different peripheral speeds. The sheet is stretched 2 to 8 times in the direction, and the sheet is cooled by a cooling roll. Next, the sheet stretched in the longitudinal direction is guided to a tenter-type transverse stretching machine, where both ends of the sheet are gripped by clips, and the sheet is heated to Tg or more by hot air. The sheet is stretched 2 to 8 times in the lateral direction by increasing the width of the clips at both ends, and the sheet is heat-treated by hot air if necessary.

[0036]

[Measurement method of physical properties] Next, the measurement method used in the present invention will be described below. 1. The intrinsic viscosity [η] of the polyester resin was determined at 25 ° C. using o-chlorophenol as a solvent by the following formula.

[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. Cast surface properties Light is applied to a cast sheet surface of 10 m ² or more, and the reflected light is visually observed to determine the presence or absence of surface irregularities such as craters. The criteria are as follows.

No irregularities are found on the surface at all. ○ There are irregularities on the surface, but the depth is less than 0.1 μm, which is shallow and disappears by stretching. Surface State of Charging Roll After the operation was completed, the surface state of the charging roll was observed. The mark x indicates that a scratch transferred to the film occurred on the roll surface due to discharge, and the mark ○ indicates that there was no scratch transferred to the film due to damage to the conductive layer alone.

[0039]

The present invention will be described in more detail by way of examples. Example 1 As a charging roll, a roll having a diameter of 150 mm and a surface length of 800 mm was prepared. The roll is obtained by spraying alumina ceramic on the surface of a carbon steel roll and depositing aluminum only on the surface.

As the thermoplastic resin, polyethylene terephthalate (PET) (intrinsic viscosity [η] = 0.63,
As an additive, 0.1 wt% of colloidal silica particles having an average particle size of 0.5 μm was added. After being dried so that the water content of the PET resin is 20 ppm or less, it is supplied to a melt extruder having a cylinder diameter of 250 mm, melted at 285 ° C., filtered through a 10 μm cut fiber sintered metal filter, It was introduced into a die and the melt was extruded into a sheet. The extruded molten sheet was cast at a peripheral speed of 100 m / min while being sandwiched between the above-mentioned roll and a casting drum having a surface roughness of 0.1 S and having a surface of 1.5 m in diameter and hard chrome plated. Although the charging roll surface length was smaller than the cast sheet width, the edge portion of the cast sheet was brought into close contact by applying a positive charge of 8 KV to the needle electrode.

During casting, a DC positive voltage of 3 KV was applied by bringing the carbon brush into contact with the surface of the charging roll, and the drum was grounded. Further, a tungsten wire having a diameter of 0.2 mm was stuck between the die and the charging roll in the film width direction, and a positive charge of 7 KV was applied to this wire.

Cooling water was passed from the common cooler to the drum and the charging roll, and the surface temperature of each was set to 25 ° C.

The cast sheet thus obtained is 200
It was an amorphous sheet having a thickness of 850 mm, a thickness of 850 mm, a small thickness unevenness, excellent flatness, and no surface defects.
Subsequently, the extruded sheet is stretched 4.5 times at a stretching temperature of 98 ° C. with a roll-type longitudinal multi-stage stretching machine, cooled to Tg or less,
Subsequently, the both ends of the longitudinally stretched sheet are guided to a tenter while being gripped with clips, stretched 4.5 times in the width direction in a hot air atmosphere heated to a stretching temperature of 100 ° C, and heat-fixed at 220 ° C at a fixed length, and 3% relaxed heat fixing was performed in the width direction at 150 ° C., and a biaxially oriented laminated polyester sheet having a thickness of 10 μm was wound up at a high speed of about 450 m / min in a stable state without breaking.

The film was formed for three months in this manner.
The obtained film was a film having excellent flatness with no surface defects. Although the charging roll surface was partially damaged, the surface was smooth and was not transferred to the film. Table 1 shows the results. Comparative Example 1 A roll having a diameter of 150 mm and a surface length of 800 mm was prepared as a charging roll. The roll is obtained by applying hard chrome plating to the surface of a carbon steel roll. Since the surface of the roll and the roll core are electrically connected, power was supplied to the roll surface from a roll bearing. Further, for cooling the charging roll, silicone oil at a temperature of 25 ° C. was circulated from a dedicated cooler. Except for this, a film was formed for 3 months in the same manner as in Example 1. Damage due to discharge and the like was observed on the surface of the charging roll, and scratches due to this were observed on the sheet surface. Table 1 shows the results. Example 2 A roll having a diameter of 150 mm and a surface length of 800 mm was prepared as a charging roll. The roll was obtained by spraying alumina ceramic on the surface of a carbon steel roll and plating the surface with nickel by electroless plating. A film was formed in the same manner as in Example 1 except that the charging roll was changed. Table 1 shows the results.

[0045]

[Table 1]

[0046]

According to the present invention, the casting speed can be increased by casting the molten thermoplastic resin sheet while sandwiching it between a cooling medium and a charging roll in which the conductive portion of the surface and the roll axis are insulated, so that a high quality sheet can be produced. Can be manufactured well. The sheet manufactured in this way can be preferably used as an industrial material, a magnetic material, and a packaging material.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B29L 7:00 F Term (Reference) 4F071 AA44X AA45 AA46 AA46X AA54 AA55 AA56 AA75 AF36 AG28 AH04 AH12 AH14 BA01 BB06 BB07 BB08 BC01 4F205 AA24 AA25 AE09 AG01 AJ02 AJ03 AJ06 AK02 AR06 GA07 GB02 GC02 GF23 GF24 GN18 GN24 GN30 GW06 GW21 4F207 AA24 AA25 AE09 AG01 AJ02 AJ03 AJ06 AK02 AR06 KA01 KE06 AK02 AJ02 A0602 QA03 QC06 QG01 QG18 QW07

Claims (9)

[Claims] 1. A method for manufacturing a cast sheet, comprising: melting a thermoplastic resin, discharging the molten sheet from a die as a molten sheet, and tightly cooling and solidifying the sheet on a cooling medium while sandwiching the sheet between the charging roll and the cooling medium. A method for producing a thermoplastic resin sheet, characterized in that a cast sheet is produced with a configuration in which the conductive portion is insulated from a roll core. 2. The method for producing a thermoplastic resin sheet according to claim 1, wherein the conductive portion of the charging roll surface and the roll core are insulated by a ceramic layer. 3. The method for producing a thermoplastic resin sheet according to claim 1, wherein the conductive portion on the surface of the charging roll and the roll core are insulated by a resin layer. 4. The method according to claim 1, wherein the conductive portion of the surface layer of the charging roll is a metal layer and is formed by any one of plating, vapor deposition and thermal spraying. 3. The method for producing a thermoplastic resin sheet according to item 1. 5. The thermoplastic resin sheet according to claim 1, wherein a cooling medium is circulated inside the charging roll so that the roll surface temperature is equal to or lower than Tg of the thermoplastic resin. Method. 6. The method for producing a thermoplastic resin sheet according to claim 1, wherein the width of the conductive portion in the surface portion of the charging roll is shorter than the width of the cast sheet by 10 mm or more. 7. The method according to claim 1, wherein before the molten sheet comes into contact with the charging roll,
The method for producing a thermoplastic resin sheet according to any one of claims 1 to 6, wherein a charge having the same polarity as that of the roll is applied to the molten sheet. 8. The method for producing a thermoplastic resin sheet according to claim 1, wherein the thermoplastic resin is a polyester composition. 9. The method for producing a thermoplastic resin sheet according to claim 1, wherein the cast sheet is stretched and / or heat-treated.