JP2014061671A - Production method of polyester sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a polyester sheet that is improved so that IV reduction may be suppressed to the minimum, and haze increase of a polyester sheet may be suppressed.SOLUTION: The production method of a polyester sheet is provided in which polyester is melt-extruded into a sheet-like shape on a casting drum surface. The production method of a polyester sheet is characterized in that a vent-type twin screw extruder in which an inner diameter (diameter) D of a cylinder is 140 mm or more is used as an extruder, melt extrusion is performed under the condition that an extrusion output Q (kg/hr) per unit time and the number of revolutions N (rpm) of a screw satisfy the following expression (1), a casting drum having a diameter d of 1,500 mm or more is used, and a molten sheet is cooled and cured under the condition that the number of revolutions n (rpm) and a diameter d (mm) of a casting drum satisfy the following expression (2). 5.2×10×D≤Q/N≤15.8×10×D... (1), 750≤d/n≤4000 ... (2).

Description

  The present invention relates to a method for producing a polyester sheet, and melt extrusion is performed under specific conditions, and the sheet is cooled, so that a substantially undried raw material polyester is used or the amount of melt extrusion is increased. Even in the case of a large scale, the present invention relates to a production method capable of obtaining a polyester sheet excellent in transparency with a very low decrease in intrinsic viscosity (hereinafter sometimes abbreviated as IV) of a polyester after melt extrusion. It is.

  Conventionally, polyesters typified by polyethylene terephthalate and polyethylene naphthalate are widely used as raw materials for films, bottles, fibers, and other various molded articles because of their excellent chemical and physical properties. In particular, biaxially oriented polyester film represented by polyethylene terephthalate has excellent mechanical properties and chemical resistance. Magnetic tape, ferromagnetic thin film tape, photographic film, packaging film, electronic component film, electrical It is widely used as a material for insulating films, metal laminate films, protective films for various members, and the like.

  In recent years, polyester films are often used for various optical films, such as prism sheets for LCD members, light diffusing sheets, reflectors, touch panels, and other base films, antireflection base films, and display explosion-proof base films, It is used for various applications such as PDP filter films and touch panel films. In the optical use, the IV of the polyester is preferably high from the viewpoint of productivity, and more transparent from the viewpoint of use.

  A biaxially oriented polyester film is produced by stretching an extruded polyester sheet. The polyester sheet is formed by extruding a molten polyester sheet onto the casting drum surface and solidifying by cooling. For example, Patent Document 1 proposes the use of a vented twin-screw extruder as an extruder (molding machine). The vent type twin screw extruder is an extruder having a vent hole for degassing by depressurizing action. In the above publication, in order to produce a polyester film with slipperiness, polyester and inorganic particles are used. A vented twin screw extruder is used to mix the organic particles with the slurry. Patent Document 2 and Patent Document 3 disclose a method for producing a polyester sheet using a vented twin-screw extruder under specific extrusion conditions.

  However, if the melted sheet is not sufficiently cooled and solidified even if it is extruded under a specific extrusion condition using a bent twin-screw extruder, the resulting polyester sheet and the polyester film obtained by stretching the sheet are used. Transparency deteriorates.

JP-A-6-91635 JP-A-10-95042 JP 2012-61831 A

  The present invention has been made in view of the above circumstances, and its solution is to use a vented twin-screw extruder as an extruder and minimize IV down under the conditions of a specific vented extruder. Another object of the present invention is to provide a polyester sheet manufacturing method improved so as to suppress haze-up of the polyester sheet by manufacturing under specific casting drum conditions.

As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be easily solved by adopting a specific configuration, and the present invention has been completed.
That is, the gist of the present invention is to use a vented twin-screw extruder having a cylinder inner diameter (diameter) D of 140 mm or more as an extruder in a polyester sheet manufacturing method in which polyester is melt-extruded into a sheet form on a casting drum surface. A casting drum having a diameter d of 1500 mm or more is used under the condition that the extrusion rate per unit time Q (kg / hr) and the screw rotation speed N (rpm) satisfy the following formula (1). The present invention resides in a method for producing a polyester sheet, characterized in that the molten sheet is cooled and solidified under the conditions that the rotational speed n (rpm) and diameter d (mm) of the casting drum satisfy the following formula (2).
5.2 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.8 × 10 ⁻⁶ × D ^2.8 (1)
750 ≦ d / n ≦ 4000 (2)

  According to the present invention, the degassing efficiency in the vent type twin screw extruder is increased to minimize the IV down of the polyester due to hydrolysis, and the haze up of the polyester sheet is minimized by optimizing the casting drum conditions. Thus, an improved method for producing a polyester sheet is provided, and the industrial value of the present invention is remarkable.

  The polyester sheet referred to in the present invention is a polyester sheet melt-extruded from an extrusion die onto a casting drum according to a so-called extrusion method.

  The feature of the present invention is that when the inner diameter (diameter) of the cylinder of the extruder is D (mm), the extrusion amount Q (kg / h) per unit time and the screw rotation speed N (rpm) are expressed by the following formula (1). ), Preferably melt extrusion under conditions satisfying the following formula (3), more preferably the following formula (4). By satisfying such conditions, it is possible to increase the deaeration efficiency while preventing excessive heat generation due to the shearing action of the screw, and to prevent the polyester from going down.

5.2 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.8 × 10 ⁻⁶ × D ^2.8 (1)
6.0 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.0 × 10 ⁻⁶ × D ^2.8 (3)
6.3 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 14.7 × 10 ⁻⁶ × D ^2.8 (4)

In the present invention, in the step of cooling and solidifying the molten polyester with the casting drum, the diameter of the casting drum is d (mm) when the diameter of the casting drum is d (mm) and the number of rotations of the casting drum is n (rpm). And the rotation speed n (rpm) must satisfy the following formula (2). By satisfying such conditions, it is possible to effectively cool and solidify a molten polyester sheet that has been melt-extruded under specific conditions, to suppress whitening of the sheet due to insufficient cooling, and to obtain a polyester sheet that is more excellent in transparency. it can. When d / n is less than 750, the molten polyester sheet is not sufficiently cooled by the casting drum, and when d / n is greater than 4000, the rotational speed is too slow relative to the diameter of the casting drum. Although it is sufficient, it is not preferable because productivity is remarkably deteriorated.
750 ≦ d / n ≦ 4000 (2)

  In the present invention, in order to support the cooling of the surface of the molten sheet that does not contact the casting drum, a cold air machine or a cooling roll may be used on the side opposite to the casting drum as necessary.

  The polyester used in the present invention refers to a polyester obtained by polycondensation of a dicarboxylic acid unit and a diol unit. Examples of the dicarboxylic acid unit include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the diol unit include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like.

  The polyester in the present invention is obtained by a conventionally known method, for example, a method of directly obtaining a low polymerization degree polyester by reaction of a dicarboxylic acid and a diol, or after reacting a lower alkyl ester of a dicarboxylic acid and a diol with a conventionally known transesterification catalyst. It can be obtained by a method of conducting a polymerization reaction in the presence of a polymerization catalyst. As the polymerization catalyst used in the present invention, known catalysts such as an antimony catalyst, a germanium compound, and a titanium compound may be used. Preferably, the amount of the antimony compound is zero or 100 ppm or less as antimony.

  The polyester used in the present invention may be obtained by forming a chip after melt polymerization and further subjecting it to solid phase polymerization as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The IV of the obtained polyester is usually 0.40 to 1.10 dl / g, preferably 0.50 to 1.00 dl / g.

  In the present invention, two or more kinds of polyesters having different bulk densities can also be used as raw materials. Specifically, recycled polyester can be used as part of the raw material. A so-called fluff obtained by pulverizing the end portion of a film into small pieces among recycled polyester has a problem that it has a bulk density in the range of 0.01 to 0.60 and stays in the supply port without being well bitten by the screw. In addition, in the case of a material having a low bulk density as described above, the pressure fluctuation at the tip of the extruder becomes large because the transportation efficiency with the pellet is different in the screw transportation section, and as a result, the fluctuation in the amount of extrusion also increases. Therefore, it is difficult to use a fluff having a low bulk density as described above on a chip manufacturing line dedicated to the fluff.

  You may make the polyester sheet in this invention contain particle | grains on the conditions which do not impair transparency. Examples of particles used in the present invention include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, and crosslinked polymers. Examples thereof include organic particles such as particles and calcium oxalate. Examples of the method of adding particles include a method of adding particles in a polyester as a raw material, a method of adding directly to an extruder, and the like. Two methods may be used in combination.

  The particle size of the particles used is usually 0.05 to 5.0 μm, preferably 0.1 to 4.0 μm. The particle content is usually 0.001 to 30.0 wt%, preferably 0.01 to 10.0 wt%, based on the polyester. If the particle content is high, the haze increases and the transmittance in the visible light region may be reduced. If the particle content is low, handling may be difficult.

  The method of adding particles to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester, but the polycondensation reaction may proceed preferably after the esterification stage or after the transesterification reaction. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder. It is performed by the method of blending.

  In this invention, you may add an additive other than the said particle | grain as needed. Examples of such additives include stabilizers, lubricants, cross-linking agents, anti-blocking agents, antioxidants, dyes, pigments, and ultraviolet absorbers.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. Various physical properties and characteristics are measured or defined as follows. In the examples, “%” means “% by weight”.

(1) IV of polyester
100 g of a mixed solvent of phenol / tetrachloroethane: 50/50 (weight ratio) was added to 1 g of polyester from which other polymer components and particles incompatible with polyester were removed, and measurement was performed at 30 ° C.

(2) Bulk density of polyester Based on JIS K6722, it calculated | required as the weight W per unit volume V using the bulk specific gravity measuring device.

(3) Measurement of haze The haze of a sheet | seat was measured using the Nippon Denshoku Industries Co., Ltd. haze meter.

(4) Comprehensive evaluation The sheet obtained by cooling and solidifying the melt-extruded molten polyester sheet has an acceptable IV down and haze-up, and has no problem in productivity, and the obtained sheet has an IV down and haze-up. A case where the material was very large, or could not be melt-extruded due to some problem, or a case where the film was frequently broken by subsequent stretching was evaluated as x.

Examples 1-4:
A substantially undried polyester having an IV of 0.650 (dl / g), a water content of 0.2%, and a bulk density of 0.7 was used as a raw material. Comprehensive evaluation was performed from melt extrusion and IV and haze of the obtained polyester sheet. The results are summarized in Table 1 below.

Comparative Examples 1-2:
A substantially undried polyester having an IV of 0.650 (dl / g), a water content of 0.2%, and a bulk density of 0.7 was used as a raw material. Comprehensive evaluation was performed from melt extrusion and IV and haze of the obtained polyester sheet. The obtained sheet had large IV down and haze up, and could not be adopted as a production method. The results are summarized in Table 1.

  The production method of the present invention includes, for example, a prism sheet for an LCD member, a light diffusion sheet, a reflector, a touch panel, a base film for antireflection, an anti-reflection base film, a display explosion-proof base film, a PDP filter film, and a touch panel. It can utilize suitably as a manufacturing method of the film of various uses, such as a film.

Claims (1)

In a method for producing a polyester sheet in which polyester is melt-extruded on a casting drum surface in a sheet form, a vent type twin-screw extruder having a cylinder inner diameter (diameter) D of 140 mm or more is used as an extruder, and an extrusion rate Q per unit time (Kg / hr) and screw rotation speed N (rpm) are melt-extruded under conditions satisfying the following formula (1), a casting drum having a diameter d of 1500 mm or more is used, and the rotation speed n of the casting drum is n A method for producing a polyester sheet, comprising cooling and solidifying a molten sheet under a condition that (rpm) and diameter d (mm) satisfy the following formula (2).
5.2 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.8 × 10 ⁻⁶ × D ^2.8 (1)
750 ≦ d / n ≦ 4000 (2)