JPH1095042A - Manufacture of polyester sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacture of a polyester sheet which is improved so that lowering of intrinsic viscosity IV of polyester due to hydrolysis can be minimized by raising deaerating efficiency in a vent type biaxial extruder in a method for manufacture of a polyester sheet wherein the vent type biaxial extruder is used as the extruder. SOLUTION: In a method for manufacture of polyester sheet wherein the polyester sheet is extruded by melting onto a surface of a casting drum, a vent type biaxial extruder is used as an extruder. When an inner diameter (diameter) of a cylinder of the extruder is D(mm) melt extrusion is carried out under conditions wherein an extrusion amount per unit time Q(kg/hr) and a rotational frequency N(rpm) satisfy the following formula: 5.2×10<-6> ×D<2.8> <=Q/N<=15.8×10<-6> ×D<2.8> .

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 polyester sheet, and more particularly, to a method using a vent type twin screw extruder as an extruder,
By performing melt extrusion under specific conditions, the intrinsic viscosity of the polyester after melt extrusion decreases even when a substantially undried raw polyester is used or in the case of large scale with increased melt extrusion amount The present invention relates to a method for producing a polyester sheet having an extremely small content. In this specification, the intrinsic viscosity is abbreviated as IV.

[0002]

2. Description of the Related Art Polyesters represented by polyethylene terephthalate and polyethylene naphthalate are widely used as raw materials for films, bottles, fibers, and other various molded products because of their excellent chemical and physical properties. In particular, biaxially oriented polyester films represented by polyethylene terephthalate have excellent mechanical properties, electrical properties, chemical resistance, dimensional stability, etc.
Information recording materials, capacitors, packaging, plate making, electrical discharge,
It is used as a substrate in many fields such as photographic film.

[0003] Biaxially oriented polyester films are produced by stretching an extruded polyester sheet. The polyester sheet is formed by extruding a molten sheet of polyester onto the casting drum surface and cooling and solidifying it. For example, JP-A-6-91635 discloses a vented twin-screw extruder as an extruder (molding machine). The use of has been proposed. A vented twin-screw extruder is an extruder provided with a vent hole for deaeration by a depressurizing action.In the above-mentioned publication, polyester and inorganic particles are used for producing a polyester film having a slipperiness. A vented twin-screw extruder is used for mixing the organic particles with the slurry.

By the way, it can be said that the deaeration efficiency of a vent type twin-screw extruder is better when the screw rotation speed is higher for a fixed amount of extrusion. In other words, for a certain amount of extrusion, it is possible to forcibly update the polyester surface present on the screw surface by increasing the screw rotation speed,
To that extent, the efficiency of degassing from the molten polyester increases. As a result, the IV retention of the polyester is improved.

However, as a result of the present inventor's study of the relationship between the screw rotation speed and the deaeration efficiency, it has been found that, as the screw rotation speed is increased for a given amount of extrusion, the IV retention rate is improved. A phenomenon in which the retention was reduced was found. Such a phenomenon is remarkable in the case of a large vent type twin screw extruder in which the inner diameter (diameter) D of the cylinder of the extruder is 150 (mm) or more.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a polyester sheet using a vented twin-screw extruder as an extruder. An object of the present invention is to provide a method for producing a polyester sheet which is improved so as to increase the degassing efficiency in a twin-screw extruder and to minimize the decrease in the IV of the polyester due to hydrolysis.

[0007]

In order to achieve the above object, the present inventor measured the resin temperature of the molten polyester discharged from the extruder with the aim of elucidating the cause of the low IV retention ratio phenomenon. As a result, a phenomenon in which the resin temperature increases with an increase in the screw rotation speed was found. Further, as a result of further study, it was found that the cause of the decrease in IV retention from a certain region is that hydrolysis is promoted by an increase in resin temperature.

The present invention has been completed on the basis of the above findings, and the gist of the present invention is to provide a method for producing a polyester sheet by melt-extruding a polyester sheet on the surface of a casting drum. And the inner diameter (diameter) of the extruder cylinder
Where D (mm) is the extrusion rate per unit time Q (k
g / hr. ) And the number of revolutions of the screw N (rpm) satisfy the following formula (I): melt extrusion is carried out.

[0009]

## EQU2 ## 5.2 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.8 × 10 ⁻⁶ × D ^2.8 (I)

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a side view illustrating an example of a vent-type twin-screw extruder suitably used in the production method of the present invention, wherein (1) is a molding machine (extruder), and (2) is a heating cylinder. , (3) is a screw, (4) is an extrusion port,
(6) is a vent hole, (8) is a reverse screw, (9) is a polymer inlet, and M is a screw driving device.

The feature of the present invention is that when the inner diameter (diameter) of the cylinder of the extruder is D (mm), the amount of extrusion Q (kg / hr.) Per unit time and the screw rotation speed N (rpm)
m) is that the melt extrusion is carried out under the conditions satisfying the following formula (I), preferably the following formula (II), more preferably the following formula (III). By satisfying such conditions, it is possible to increase the degassing efficiency while suppressing excessive heat generation due to the shearing action of the screw, and to prevent the polyester IV from lowering.

[0012]

## EQU3 ## 5.2 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.8 × 10 ⁻⁶ × D ^2.8 (I) 6.0 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.0 × 10 ⁻⁶ × D ^2.8 (II) 6.3 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 14.7 × 10 ⁻⁶ × D ^2.8 (III)

[0013] Under the conditions shown in the following equation (IV), the number of revolutions is too high with respect to the amount of extrusion, so that excessive heat generation due to shearing of the screw tends to deteriorate the IV retention. Further, under the conditions shown in the following equation (V), the rotational speed is too low with respect to the extrusion amount, so that the degree of renewal of the molten resin surface under reduced pressure is reduced and sufficient deaeration cannot be performed, and the IV retention Tends to worsen.

[0014]

## EQU4 ## 5.2 × 10 ⁻⁶ × D ^2.8 > Q / N (IV) Q / N> 15.8 × 10 ⁻⁶ × D ^2.8 (V)

In the present invention, two or more kinds of polyesters having different bulk densities can be used as raw materials. Specifically, recycled polyester can be used as a part of the raw material. By the way, the so-called fluff in which the end of the film is crushed into small pieces in the recycled polyester,
The bulk density is in the range of 0.01 to 0.60, and there is a problem that it does not bite into the screw and stays in the supply port. In addition, in the case of a material having a low bulk density as described above, the transport efficiency of the screw in the transport section differs from the pellet, so that the pressure fluctuation at the tip of the extruder increases, and as a result, the fluctuation of the extrusion amount also increases. Therefore, the fluff having a low bulk density as described above is difficult to use in a chip production line dedicated to fluff.

However, according to the present invention, even if at least one of the polyesters has a bulk density of 0.01 to 0.60 and two or more polyesters having different bulk densities, the melt extrusion can be performed without any problem. You can do it. That is, according to the present invention, the pressure fluctuation at the extruder tip is ± 5 kg / cm ² or less, and the surface area of the polymer at the vent portion is increased, so that the degassing efficiency is improved,
Particularly, the IV retention rate is improved, and the IV reduction after melt extrusion is reduced by 10%.
% Or less.

The above-mentioned conditions of the present invention are particularly effective when the IV of the polyester having the smallest bulk density is smaller than the IV of other polyesters. The bulk density at that time is preferably 0.6 or less. When the bulk density is larger than 0.6, the effect of improving the IV retention is poor. Conversely, if the bulk density is less than 0.01, the volume of the polyester increases, making it difficult to secure a sufficient amount of raw material supplied, and also causes problems such as material blockage in the supply pipe. It will be easier. The amount of the polyester having a bulk density of 0.01 to 0.60 is usually 60% or less based on the total polyester,
It is preferably at most 55%, more preferably at most 50%.

The IV of the polyester supplied to the vented twin-screw extruder can be arbitrarily selected.
1.10 or less, preferably 0.50 to 1.00. When the polyester IV is less than 0.40,
The mechanical strength of the molded product is insufficient. Conversely, polyester I
When V exceeds 1.10, the IV reduction rate increases.
I of polyester extruded from vented twin screw extruder
The decrease in V is usually 10% or less, preferably 9%.
Or less, more preferably 8% or less.

In the present invention, the polyester refers to a polyester comprising an aromatic dicarboxylic acid component and a glycol component. In particular, 80% or more of the repeating units are ethylene terephthalate units or ethylene-2,6-naphthalate units or 1,4. Polyesters having cyclohexylene dimethylene terephthalate units are preferred. The polyester may have another third component copolymerized.

The aromatic dicarboxylic acid component includes:
Besides terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid,
Sebacic acid, 4,4'-diphenyldicarboxylic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid and the like) and the like. On the other hand, examples of the glycol component include, in addition to ethylene glycol and 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, neopentyl glycol, and the like.

In the present invention, it is not necessary to use a dry polyester as the polyester irrespective of whether or not a slurry of inorganic particles and / or organic particles described below is mixed with the polyester. Of course, there is no problem using the dried polyester, for example,
Even if a polyester dried to a water content of 50 ppm or less is used, the properties of the polyester do not deteriorate.

In the present invention, a slurry of inorganic particles and / or organic particles can be mixed with polyester in order to produce a polyester film to which lubricity is imparted. As the inorganic particles, for example, silica oxide,
In addition to calcium carbonate, titanium oxide, aluminum oxide, barium sulfate, lithium fluoride, and kaolin, inorganic pigments such as iron oxide are exemplified. Organic particles include divinylbenzene polymers, styrene-divinylbenzene copolymers, and various other pigments. In addition to the ion exchange resin, organic pigments such as anthraquinone are exemplified. The type is not particularly limited as long as the particles can be supplied as a liquid slurry.

In the present invention, the slurry medium is
Water and ethylene glycol are preferably used. The type of the liquid is not particularly limited as long as the liquid is a liquid that is vaporized when the polyester is melted or vaporized by the depressurizing action of the vent portion and does not cause a decrease in the IV of the polyester. In addition, as a method for dispersing the inorganic particles and the organic particles in the medium, a known method using ultrasonic waves or shear stress can be employed.

In the present invention, when the slurry of the inorganic particles and / or the organic particles is mixed with the polyester, it is preferable to add the slurry from the polymer inlet (9) without providing a separate addition nozzle. The supplied polyester and slurry are transferred to the extrusion port (4) by the screw (3) in the heating cylinder (2). During that time, the slurry receives heat from the heating cylinder (2) and heat generated by the shearing action and evaporates. As a result, the pressure in the heating cylinder (2) increases. Then, the medium of the slurry is vaporized before the polyester reaches the reverse screw (8) and reaches a semi-molten state, and is discharged from the polymer inlet (9). If diffusion of the vaporized medium to the surroundings poses a problem, a suction / discharge device for the vaporized medium may be provided.

The polyester is transferred from the reverse screw (8) to the vent hole (6), and is degassed by the depressurizing action of the vent hole (6). After the polyester is degassed in the vent hole (6), it is extruded from the extrusion port (4). If necessary, a vent hole is further provided between the extrusion port (4) and the vent hole (6). You may. Further, by adjusting the temperature of the heating cylinder (2) as in a usual extruder, the temperature of the extruded polyester composition can be appropriately maintained.

The temperature of the slurry supply section of the heating cylinder (2) is usually not higher than 200 ° C., preferably not higher than the boiling point of the slurry medium, more preferably not higher than the boiling point of the medium.
The temperature is set to 0 ° C. or lower. However, in order to effectively vaporize the medium from the start of slurry supply, the lower limit of the temperature of the slurry supply section of the heating cylinder (2) usually needs to be about 60 ° C.

In the present invention, since the vaporization of the slurry medium is started from the time when the raw material is supplied to the raw material supply port, it is substantially completely before the plasticization of the polyester, that is, before the reverse screw (8) is reached. The medium can be removed. Therefore, suitable water can be used as a medium for the slurry, and water up to 10% by weight relative to the polyester can be used. If the proportion of water exceeds 10% by weight, the amount of water vapor removed from the polymer inlet (9) becomes too large, making it difficult to supply new polyester and slurry.

In the present invention, the polyester is transferred to the vent hole (6) after the slurry medium is removed as described above. Then, when a substantially undried polyester is used, the moisture inside the polyester is degassed by the depressurizing action from the vent hole (6). In order to increase the degassing efficiency of water, the degree of pressure reduction of the vent hole (6)
Usually 40 mmHg or less, preferably 30 mmHg or less,
More preferably, it is 10 mmHg or less.

In the present invention, when the polyester sheet is melt-extruded on the surface of the casting drum, in order to enhance the adhesiveness of the polyester sheet to the casting drum, an electrostatic adhesion method, an air knife method, a nip roll method in which two rolls are used, and the like are used. It can be adopted as appropriate.

According to the present invention, as described above, substantially dry or undried polyester can be used. However, even when substantially undried polyester is used, the IV reduction is small. The effect of the present invention is remarkable.

That is, from the viewpoint that it is conventionally necessary to suppress the IV reduction during melting to less than 10% in order to solve the problems such as breakage of the stretching step caused by the IV reduction caused by hydrolysis. It is said that the polyester before melting must be dried until the water content becomes 50 ppm or less. However, such drying requires, for example, a condition of 80 ° C. for 3 hours, and since the dried polyester is melt-extruded after being allowed to cool, most of the heating energy in the drying step is in the melt-extrusion step. Lost without being used by Therefore, in the present invention,
The effect of using a substantially undried polyester is that not only the production efficiency but also the industrial value is remarkable from the viewpoint of energy saving.

When a substantially undried polyester is used, the regenerated polyester such as a slit film discharged from the film production process is similarly appropriately pulverized without drying, and then directly dried without drying. Together with melt extrusion.

[0033]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples and comparative examples, “%” simply means “% by weight”.

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

(2) Moisture content of polyester: Measured by a moisture measuring device (Micro moisture measuring device “CA-06” manufactured by Mitsubishi Chemical Corporation).

(3) Bulk density of polyester: JIS K
6722, using a bulk specific gravity measuring instrument,
Per unit weight W.

(4) Polyester IV retention: If the IV decrease is large, the practical strength of the film will decrease, and the film will break during biaxial stretching, making it impossible to obtain continuous production. Therefore, the IV retention was evaluated. The evaluation was ◎, 8 to 10 when the IV reduction was less than 8%.
%, And 10% was evaluated as x.

(5) Comprehensive evaluation: when the extrusion rate is 2 (t / h)
r. ) When the IV retention rate is 10% or less and good, and when the extrusion rate is 2 (t / hr.) Or more, the IV retention rate is 10% or less and ◎. And x. In addition, if melt extrusion could not be performed due to some problem, if the time from the measurement of the raw materials to the compounding was more than twice as long as when using a twin screw extruder, it was melt extruded into a sheet, When the film was frequently broken at the time of stretching, when the tip pressure fluctuation of the extruder became ± 5 kg / cm ² or more, etc., it was unsuitable and evaluated as x.

Example 1 A substantially undried polyester (PE) having an IV of 0.650 (dl / g), a water content of 0.2% and a bulk density of 0.7
T) was melt-extruded into a sheet shape using a vented twin-screw extruder, and cooled and solidified on the casting drum surface while applying an electrostatic application cooling method to obtain an unstretched sheet. Next, the film was stretched 3.5 times at 95 ° C in the longitudinal direction and 4.0 times at 110 ° C in the transverse direction, and heat-treated at 230 ° C for 2 seconds to obtain a biaxially stretched film having a thickness of 15 µm.

In the above operation, a vent type twin screw extruder having a diameter of 65 mm was used. The operating conditions were as follows: discharge rate Q: 300 (kg / hr.), Screw rotation speed N: 3
00 (rpm), the degree of vacuum at the vent portion: 2 hPa, and the resin temperature at the tip of the extruder: 295 ° C. The IV of the obtained biaxially stretched film was 0.637 (dl / g). The time required to supply the polyester to the twin-screw extruder and obtain an unstretched sheet was 15 minutes. The results are summarized in Table 1.

Example 2 In Example 1, the screw rotation speed was set to 400 (rpm).
m), the discharge amount was 600 (kg / hr.), and a polyester sheet was obtained in the same manner as in Example 1 except that biaxial stretching was not performed. The IV of the sheet is 0.627 (d
1 / g). The results are summarized in Table 1.

Example 3 70% of substantially undried polyester having an IV of 0.650 (dl / g), a water content of 0.2% and a bulk density of 0.7
And IV are 0.590 (dl / g) and water content is 0.2
%, And 30% of a substantially undried polyester having a bulk density of 0.12, were simultaneously supplied to a vented twin-screw extruder to obtain a polyester sheet. IV of the obtained sheet is 0.62
5 (dl / g). The results are summarized in Table 1.

EXAMPLE 4 A substantially undried polyester A having an IV of 0.650 (dl / g), a water content of 0.2% and a bulk density of 0.7,
V is 0.610 (dl / g), the moisture content is 0.2%, and the bulk density is 0.7. To obtain a laminated sheet of polyesters A and B. The supply rate of polyester A was 1,200 (kg / hr.), And the supply rate of polyester B was 300 (kg / hr.). The average IV of the obtained laminated polyester sheet was 0.1.
617 (dl / g). The results are summarized in Table 1.

Examples 5 to 8 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, and the conditions shown in Table 2 were used. Below, melt-extrusion was performed with a vent-type twin-screw extruder, and comprehensive evaluation was performed from the degree of IV reduction of polyester. Table 2 summarizes the results.

Comparative Example 1 In Example 1, the screw rotation speed N was set to 400 (rpm).
m), and a polyester sheet was obtained in the same manner as in Example 1 except that the discharge amount Q was changed to 200 (kg / hr.). Then, 3.5 times at 95 ° C in the longitudinal direction and 1 in the lateral direction.
An attempt was made to stretch 4.0 times at 10 ° C., but a large number of breaks occurred during transverse stretching, and a biaxially stretched film could not be obtained. Table 3 summarizes the results.

Comparative Example 2 In Example 3, the screw rotation speed N was changed to 150 (r
pm), except that the polyester was melt-extruded in the same manner as in Example 3, but the raw material supply port was filled with the polyester and clogged, so that it could not be extruded stably. Table 3 summarizes the results.

Comparative Example 3 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 prepared by adding 150
After drying at 30 ° C. for 30 minutes and subsequently at 180 ° C. for 3 hours, melt extrusion was performed into a sheet using a single screw extruder. Thereafter, a biaxially stretched film was obtained in the same manner as in Example 1. The IV of the obtained film was 0.620.
(Dl / g). The time required from the start of compounding of the material to the melt extrusion was as long as 5 hours, and it is clear that the production efficiency is extremely low as compared with the examples. Table 3 summarizes the results.

COMPARATIVE EXAMPLES 4 AND 5 A substantially undried polyester having an IV of 0.650 (dl / g), a moisture content of 0.2% and a bulk density of 0.7 is shown in Table 3 by a vented biaxial Melt extrusion was performed with an extruder, and the degree of IV reduction at that time was examined. In any case, the IV decreases greatly and cannot be adopted as a method for producing a polyester sheet. Table 3 summarizes the results.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

According to the present invention described above, the production of a polyester sheet improved so that the deaeration efficiency in a vented twin-screw extruder can be increased and the IV reduction of the polyester due to hydrolysis can be minimized. A method is provided and the industrial value of the present invention is significant.

[Brief description of the drawings]

FIG. 1 is an explanatory side view of an example of a vented twin-screw extruder suitably used in the production method of the present invention.

[Explanation of symbols]

 1: Bent type twin screw extruder 2: Heating cylinder 3: Screw 4: Extrusion port 6: Vent hole 8: Reverse screw 9: Polymer inlet M: Screw drive

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[Procedure amendment]

[Submission date] January 6, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

(5) Comprehensive evaluation: when the extrusion rate is 2 (t / h)
r. ), When the IV reduction rate is as good as 10% or less, and 押出 when the extrusion rate is 2 (t / hr.) Or more and the IV reduction rate is as good as 10% or less, and in other cases, it is practically unsuitable. And x. In addition, if melt extrusion could not be performed due to some problem, if the time from the measurement of the raw materials to the compounding was more than twice as long as when using a twin screw extruder, it was melt extruded into a sheet, When the film was frequently broken at the time of stretching, and when the tip pressure fluctuation of the extruder became ± 5 kg / cm ² or more, the film was judged to be unsuitable.

Claims (4)

[Claims] 1. A method for producing a polyester sheet by melt-extruding a polyester sheet onto the surface of a casting drum, wherein a vent-type twin-screw extruder is used as an extruder, and the inner diameter (diameter) of a cylinder of the extruder is D.
(Mm), the extrusion rate per unit time Q (kg /
hr. ) And the screw rotation speed N (rpm) are melt-extruded under the conditions satisfying the following formula (I). ## EQU1 ## 5.2 × 10 ⁻⁶ × D ^2.8 ≦ Q / N ≦ 15.8 × 10 ⁻⁶ × D ^2.8 (I) 2. The method according to claim 1, wherein the inner diameter (diameter) D of the cylinder of the extruder is 150 (mm) or more. 3. The production method according to claim 1, wherein a substantially undried raw material polyester is used. 4. The production method according to claim 1, wherein the intrinsic viscosity of the polyester after melt extrusion is reduced by 10% or less.