JPH11291325A - Production of laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated polyester film producing method excellent in supply stability in the supply of chips of polyester and a thermoplastic resin incompatible with the polyester to an extruder and capable of realizing the production of a laminated film excellent in characteristics as a film product, film forming stability and production cost. SOLUTION: In a method for producing a laminated polyester film by coextrusion using two or more extruders, a raw material is supplied to at least one extruder and polyester and an incompatible thermoplastic resin are kneaded to be subjected to co-extrusion in a molten state. Chips based on polyester are supplied from the main hopper of the extruder and a raw material supply apparatus supplying a raw material is attached to the joining part of a main hopper and the extruder from a side surface and the chips based on the polyester and the incompatible thermoplastic resin are supplied from this apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a laminated polyester film by coextrusion using a plurality of extruders, and more particularly, to a method for stabilizing a thermoplastic resin incompatible with polyester dispersed in the polyester film. The present invention relates to a production method for supplying a stable film quality.

[0002]

2. Description of the Related Art In recent years, polyester and a thermoplastic resin (incompatible resin) incompatible with the polyester have been kneaded,
2. Description of the Related Art A low-density white polyester film containing fine bubbles inside by stretching is used in the fields of information recording and printing. Further, the white polyester film is often made into a laminated film of two or more layers according to the purpose of improving properties, imparting different properties, separating functions, and the like.

As a method for producing such a laminated film, conventionally, two or more extruders are used, and at least one extruder is mixed with a polyester chip and an immiscible resin chip. After the raw material is supplied to the extruder by a method of blending and supplying the raw material to the extruder from the hopper, or a method of supplying a compound raw material chip in which the polyester and the incompatible resin are kneaded in advance,
Production methods such as kneading, melt co-extrusion, and stretching, a production method in which two or more films are laminated after a single-layer film is formed, or a production method in which both are combined, have been used.

[0004]

By the way, when the incompatible resin is supplied in a chip blend in the raw material supply in the above-mentioned production method, the softness of the raw material chip, static electricity, surface energy, specific gravity, and Aggregation and segregation of chips occur due to differences in size, etc., or chips adhere to the inner wall of the hopper, drying dryer, and material supply line during the material supply stage to the extruder, resulting in a non-uniform mixture of the material. As a result, this has led to problems of product failure and film formation failure such as uneven film characteristics.

[0005] In addition, when compound raw material chips are used, the homogeneity of the film quality is improved, but there are problems such as a reduction in yield due to compounding and an increase in compounding cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for producing a film capable of stably supplying an incompatible resin into polyester.

[0007]

The method for producing a laminated polyester film of the present invention which achieves the above object is a method for producing a laminated polyester film by co-extrusion using two or more extruders, In a method for producing a laminated polyester film in which a raw material is supplied to at least one extruder by kneading and melt-extruding a polyester and a thermoplastic resin incompatible with the polyester, the polyester is mainly supplied from a main hopper of the extruder. A chip supplying device is provided, and a material supply device for supplying a material from a side surface is attached to a joint between the main hopper and the extruder, and a chip mainly composed of a thermoplastic resin incompatible with polyester is supplied from the device. This is a method for producing a laminated polyester film characterized by the following.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for producing a laminated polyester film by co-extrusion using two or more extruders, wherein the raw material supply to at least one extruder comprises polyester, In a method for producing a laminated polyester film in which a thermoplastic resin incompatible with the polyester is kneaded and melt-coextruded, a chip mainly composed of polyester is supplied from a main hopper of the extruder, and the main hopper and the extruder are joined. The main point is to attach a raw material supply device for supplying a raw material from the side to the part and supply chips mainly composed of a thermoplastic resin (incompatible resin) incompatible with polyester from the device.

That is, in adding the incompatible resin to the laminated polyester film, a chip mainly composed of polyester is supplied from a main hopper of at least one extruder among two or more extruders, Attaching a raw material supply device for supplying a raw material from the side surface to a junction between the main hopper and the extruder, and supplying chips mainly composed of an incompatible resin from the device, without causing the problems described above, Raw materials can be supplied stably, and product defects and film formation defects are less likely to occur, and a laminated film can be manufactured at low cost.

In the present invention, the amount of the immiscible resin supplied to the polyester is not particularly limited, but is preferably 1 to 1 of the total amount of the raw materials supplied to the extruder equipped with the raw material supply device. 30% by weight, more preferably 3 to 25% by weight, more preferably 5 to 20% by weight
Is most preferred. If the supply amount is less than 1% by weight, it becomes difficult to supply chips mainly composed of the incompatible resin, and the characteristics of the film as a product may be varied or defective. On the other hand, if the content is more than 30% by weight, the dispersion of the incompatible resin component in the film becomes non-uniform, resulting in poor film-forming properties or, in some cases, the inability to form a film.

In the present invention, a co-extrusion method is a method in which after the raw materials are melted in the extruder, the molten raw materials from different extruders are merged until the material is extruded from a die into a sheet shape. Is to join at any position between the extruder and the die and / or at the position of the die.

[0012] In the present invention, as for the supply of raw materials to at least one extruder of two or more extruders, the extruder is joined with a main hopper for supplying chips mainly composed of polyester to the extruder. When a chip mainly composed of an incompatible resin is supplied from a side surface by a raw material supply device attached to the section, the raw material supply device is used for stable supply.

The raw material supply device is not particularly limited as long as stable supply is possible. Depending on the chip supply method, (1) a device for supplying by rotation of a spiral body (screw type), and (2) a device for directly applying vibration. Supply (vibration type).

Hereinafter, a preferred example of the basic structure of the raw material supply device used in the present invention will be described.

First, the screw-type raw material supply device (1) is, for example, (A) a device in which one end is sealed and the other end is open. A cylindrical tubular body provided with a raw material supply port, and (B) a portion between the raw material supply port inside the cylindrical cylindrical body and the open end or the vicinity thereof can be rotated along the central axis of the cylindrical cylindrical body. A coil spring-shaped spiral body that is installed so that at least a portion near the raw material supply port can pass at least a chip mainly composed of an incompatible resin, or along a central axis between a sealed end and an open end. A rotating shaft arranged
A screw-shaped helical body fixed on the raw material supply port side of the rotary shaft and configured to extend and contract on the rotary shaft (representing a coil spring shape); (A) to (D) of a sub-hopper for supplying a chip mainly composed of a molten resin, and (D) a driving device connected to the spiral body from the sealing end side of the cylindrical tubular body and rotating the spiral body. It is preferable from the viewpoint of supply stability to supply at least a chip mainly containing an incompatible resin from an open end of the cylindrical body by rotation of the spiral body.

The above screw type raw material supply device is attached to the junction between the main hopper and the extruder, and is installed such that chips mainly composed of incompatible resin are supplied from the open end to the junction. The stable supply of the incompatible resin, which is the object of the invention, can be achieved.

Further, the above-mentioned sub hopper is composed of a measuring hopper for directly supplying a chip mainly composed of an incompatible resin to a raw material supply port, and a stock hopper for supplying a chip mainly composed of an incompatible resin to the measuring hopper. It consists of two types of hoppers, and when the change in the total weight of chips stored in the weighing hopper is detected by a load cell that suspends the weighing hopper, and when the amount of stored chips falls below the set lower limit, weighing is performed from the stock hopper. Chips mainly composed of incompatible resin are supplied to the hopper up to the set upper limit value, and the supply amount of chips is measured from the change in the amount of stored chips after a certain time, and the actual supply amount In the configuration controlled to automatically adjust the rotation speed of the spiral so that the difference from the set supply amount is within a certain range, the supply stability and the supply Accurately grasp, more preferably in easiness to manage.

Next, as the vibratory raw material supply device (2), for example, (a) a device in which one end is sealed and the other end is opened, and the sealed end portion or its vicinity is A trough provided with a raw material supply port, (b) a sub-hopper supplying chips mainly composed of an incompatible resin to the raw material supply port,
(C) a vibration device that is connected to a lower portion of the trough on the side of the raw material supply port and vibrates the trough. A device that transfers and supplies chips mainly composed of incompatible resin toward the open end of the trough by applying vibration in an inclined direction having a certain angle with the bottom surface of the trough is preferable in terms of supply stability. .

The cross-sectional shape of the trough may be circular, elliptical, square, rectangular, trapezoidal, or
The shape may be a rhombus, or any of polygons other than these, but in terms of supply accuracy, supply stability, etc., may be any of a square, a rectangle, and a trapezoid with the bottom side as one base. preferable.

The trough whose open end is opened downward from the bottom at right angles (the cross-sectional shape in the chip transfer direction is L-shaped) is preferable in that the supply of chips from the open end is more stabilized. . In this case, the cross-sectional shapes other than the open end and the open end may be the same or different.

The vibration generating system of the vibrating apparatus may be any of a mechanical vibration system and an electromagnetic vibration system.
It is more preferable in terms of supply stability and low noise.

The above-mentioned vibrating raw material supply device is attached to the joint between the main hopper and the extruder through a columnar cylindrical body having a specific length, and the joint from the open end is mainly made of an incompatible resin. By providing the chip so as to be supplied, stable supply of the incompatible resin can be achieved.

The above-mentioned sub hopper is composed of a measuring hopper for supplying chips mainly composed of an incompatible resin directly to a raw material supply port, and a stock hopper for supplying chips mainly composed of an incompatible resin to the measuring hopper. A weight measuring device is attached to the lower part of the vibrating device so that a change in the total weight of the chips stored in the weighing hopper can be detected. At the time of cutting, the chip mainly composed of incompatible resin is supplied from the stock hopper to the weighing hopper up to the set upper limit value. Is controlled to automatically adjust the amplitude or frequency of the vibration by the vibrator so that the difference between the actual supply amount and the set supply amount is within a certain range. What configuration, supply stability, and accurately grasp the supply amount, and more preferably in easiness to manage.

The above-mentioned raw material supply apparatus may be a screw type or a vibration type. However, when the supply of chips mainly composed of incompatible resin is performed under vacuum or reduced pressure conditions, It is more preferable to use a vibration type, and furthermore, an electromagnetic vibration type in order to prevent the device from being heated due to a decrease in heat conduction. The chips are supplied in a vacuum system or a reduced pressure system. The chips mainly consist of polyester supplied from the main hopper, and the chips mainly composed of thermoplastic resin incompatible with the polyester supplied from the raw material supply device prevent moisture absorption. Or, the main object is to prevent chip supply instability due to a pressure condition difference between the main hopper and the raw material supply device, and in the present invention, the ultimate pressure is preferably 50 kPa or less, It is preferably 40 kPa or less, and most preferably 30 kPa or less. The lower limit is not particularly limited, but is substantially about 0.1 kPa.

In the present invention, in the supply of the chip mainly composed of the incompatible resin by the above-described raw material supply device, the numerical value expressed as the supply accuracy or the supply fluctuation rate is preferably 5% or less, more preferably Most preferably, it is at most 3%, more preferably at most 2%. The supply accuracy and the supply fluctuation rate in the present invention are obtained from the following formulas based on the measurement results for a certain period.

Supply accuracy = {(Average supply amount-Set supply amount)} Set supply amount ÷ × 100 Supply fluctuation rate = (Standard deviation of supply amount ÷ Average value of supply amount) ×
100 The lower limit is not particularly limited, but the supply fluctuation rate is substantially about 0.01%.

Further, the main hopper for supplying chips mainly composed of polyester also comprises two types of hoppers, namely, a measuring hopper and a stock hopper, as in the case of the sub hopper. It is most preferable that the supply is controlled so as to be adjusted in a comprehensive manner, from the comprehensive viewpoint, from the viewpoint that the supply stability is further improved and the supply amount is more easily grasped and managed more accurately.

The control of the amount of extrusion from the extruder and the control of the amount of supply from the raw material supply device may be independent of each other or may be linked with each other. Is more preferred.

In the present invention, the main hopper and the extruder, which are the supply positions of the chips mainly composed of the incompatible resin, have a main hopper on the upper side and a lower side on the lower side. At the tip of the extruder, then the extruder, the main hopper gradually narrows and finally has a specific length that is connected to the tip input to the extruder. A columnar portion and the like correspond.

The polyester-based chip is supplied by gravity and its own weight, and the cross-sectional area of the joint (corresponding to a columnar portion) is not particularly limited. What is necessary is just to have the size necessary to supply chips mainly composed of compatible resin,
The cross-sectional shape in the plane direction may be any of a circle, an ellipse, a square, a rectangle, a trapezoid, a rhombus, and any other polygon as long as there is no problem in the supply of chips. Also, the main hopper must be located above the chip inlet to the extruder, but as long as there is no problem in chip supply, even just above the chip inlet to the extruder, It may be shifted. In other words, the columnar portion, which is the joining portion, may stand vertically or diagonally from the chip inlet to the extruder.

When the vibrating raw material supply device is used, the cross-sectional area and the cross-sectional shape of the columnar cylinder attached to the joint are the same as those of the joint. The direction of attachment to the joining portion may be horizontal or inclined at a certain angle from a horizontal plane as long as there is no problem in supplying chips mainly composed of incompatible resin.

In the present invention, the polyester of the chip mainly composed of polyester is a polymer obtained by condensation polymerization (esterification reaction) from a diol and a dicarboxylic acid. Dicarboxylic acids are represented by terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like, and diols are ethylene glycol, trimethylene glycol, tetramethylene Glycol, cyclohexanedimethanol and the like.

In the present invention, preferred examples of the polyester include polyethylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-α, β
-Bis (2-chlorophenoxy) -ethane 4,4'-dicarboxylate, polybutylene terephthalate, polybutylene-2,6-naphthalate, polyethylene-o-
Oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, or the like can be used.
Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferable in terms of quality, economy and the like such as dimensional stability, mechanical strength and workability. The polyester may be a homopolymer, a mixture of these polyesters, or a portion of another dicarboxylic acid component or diol component, preferably 20 mol% or less. Specific copolymerization components include isophthalic acid, aliphatic dicarboxylic acids having 4 to 10 carbon atoms, alicyclic dicarboxylic acids, 5-sodium sulfoisophthalic acid and esters thereof, diols having 3 to 20 carbon atoms, and cyclohexanedicarboxylic acid. Methanol or the like can be used.

Further, in the above-mentioned polyester, polyethylene glycol, as long as the effects of the present invention are not impaired,
Polyalkylene glycols such as polypropylene glycol and polytetramethylene glycol, copolymers of polyamides, polyurethanes, other polymers such as poly (meth) acrylic acid or esters thereof, or blends of copolymers thereof, , Various additives,
For example, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, surfactants, organic lubricants, pigments, dyes, organic or inorganic fine particles, fluorescent brighteners, fillers, antistatic agents, nuclei Agents and the like may be added.

The intrinsic viscosity of the above-mentioned polyester (25 ° C.
Measured in o-chlorophenol) is 0.4-1.2.
dl / g is preferable, and more preferably 0.5 to 0.8 d
Those in the range of 1 / g are suitable for practicing the present invention.

In the present invention, a chip mainly composed of polyester is defined as a polyester having a composition of 5%.
It comprises at least 5% by weight, preferably at least 70% by weight, more preferably at least 90% by weight. Further, the chip may be a mixture of two or more kinds of polyester chips having different compositions from each other as long as the effects of the present invention are not impaired.

In the present invention, preferred examples of the thermoplastic resin (incompatible resin) incompatible with the polyester include polyolefin, polyamide represented by nylon, polystyrene, poly (meth) acrylic acid, and the like. Its esters, polyurethane, polycarbonate,
At least one resin selected from polyvinyl chloride, polyvinylidene chloride, fluorine-based resin and the like can be used. Among the above incompatible resins, polyolefins are preferable from the viewpoint of the effect when the method of the present invention is employed, and particularly preferable polyolefins include polymethylpentene, polypropylene, polyethylene, ethylene-propylene copolymer and the like. These resins may be homopolymers or two or more copolymers selected from the above resins.

Further, as long as the effects of the present invention are not impaired, organic and / or inorganic fine particles, fluorescent brightener, foaming agent, filler, antioxidant, heat-resistant It may contain at least one selected from stabilizers, weather stabilizers, ultraviolet absorbers, surfactants, organic lubricants, pigments, dyes, antistatic agents, nucleating agents and the like.

In the present invention, a chip mainly composed of an incompatible resin means that the incompatible resin has a composition of 55%.
% By weight, preferably 70% by weight or more, more preferably 90% by weight or more. The chip may be a mixture of two or more kinds of incompatible resin chips having different compositions as long as the effects of the present invention are not impaired.

In the present invention, the chip means that the shape is granular, and within the range where the effect of the present invention is not impaired, specifically, the chip supply stability is poor. The size and shape of the chip are not particularly limited as long as the product failure and film formation failure do not substantially occur. The shape may be, for example, a sphere, an ellipsoid, a cube, a rectangular parallelepiped, a cylinder, an ellipsoid, or a flat or granular form thereof, or a powder. In addition, re-melting the formed film, collected raw material chips made by processing into granules, or powdery recovered flakes made by crushing the formed film, that is, the recovered raw material as it is, Alternatively, they can be used as a mixture.

Regarding the chip mainly composed of the incompatible resin, the stability of the raw material supply by the raw material supply device in the above-mentioned shape or the spiral in the raw material supply device during long-time operation using the screw type raw material supply device is reduced. A spherical body, an elliptical body, or a flattened body thereof is preferable in that the influence of the above is small.

In the present invention, when two or more kinds of chips mainly composed of the incompatible resin are used, a plurality of kinds of chips may be mixed as long as the effects of the present invention are not impaired. Alternatively, a raw material supply device capable of supplying a plurality of chips may be used, or each chip may be supplied to the extruder using a plurality of raw material supply devices.

Next, an example of the method for producing a laminated polyester film of the present invention will be described, but the present invention is not limited thereto.

As the raw material constituting the white polyester layer (A), first, a polyester chip having an intrinsic viscosity of 0.5 to 0.8 dl / g is prepared as a chip mainly composed of polyester, and sufficiently vacuum-dried. Further, a chip mainly composed of a thermoplastic resin (incompatible resin) incompatible with polyester is prepared, and vacuum dried as necessary. On the other hand, as a raw material constituting the white polyester layer (B), a mixture of a polyester chip having an intrinsic viscosity of 0.5 to 0.8 dl / g and inorganic particles of 2 to 35% by weight is prepared and sufficiently vacuum-dried. Next, chips mainly composed of polyester are supplied from the main hopper to the extruder (A), and the concentration of the immiscible resin added is determined by a raw material supply device attached to the junction between the main hopper and the extruder (A). Finally 1-30
A chip mainly composed of an incompatible resin is supplied from the side so that the weight% is obtained.

On the other hand, the raw material chips constituting the white polyester layer (B) are supplied to the extruder (B). In this way, each chip is fed to the extruder and
C. and melted in a T-die composite die so that the polymer of the extruder (B) is laminated on the surface layer (one side) or both surface layers (both sides) of the polymer of the extruder (A), and extruded into a sheet. It is wound around a mirror-surface casting drum having a surface temperature of 10 to 60 ° C. by using an electric application casting method, and cooled and solidified to form an unstretched laminated film.

The unstretched laminated film is heated at 70 to 120 ° C.
Longitudinal direction (rolling direction of film)
Then, it is stretched 2 to 5 times and cooled by a roll group at 20 to 50 ° C.

Subsequently, the longitudinally stretched film is gripped by a clip and guided to a hot air zone heated to 70 to 140 ° C. in a tenter, and is stretched in a horizontal direction (perpendicular to the vertical direction).
Stretch 5 times.

The stretching ratio is 2 to 5 times in the longitudinal and transverse directions, and the area ratio (longitudinal stretching ratio × lateral stretching ratio) is preferably 6 to 20 times. When the area magnification is less than 6 times, various properties (whiteness, concealing property, strength, etc.) of the obtained film become insufficient, and when it exceeds 20 times, the film tends to be easily broken during stretching.

In order to impart the flatness and dimensional stability of the biaxially stretched film thus obtained, the film was successively guided to a heat treatment zone in a tenter and heated at 150 to 250 ° C. for 1 to 30 minutes.
The crystal orientation is completed by performing a heat treatment for 2 seconds, and then slowly and uniformly cooled, then cooled to room temperature and wound up to produce a polyester film. During this heat treatment step, a 3 to 12% relaxation treatment may be performed in the horizontal or vertical direction as necessary. The biaxial stretching may be any of longitudinal and transverse sequential stretching or simultaneous biaxial stretching, and may be re-stretched in any of the longitudinal and transverse directions after the longitudinal and transverse stretching.

Further, after stretching in the longitudinal direction, the surface thereof may be subjected to activation treatment such as corona discharge treatment, and then subjected to coating treatment for imparting easy adhesion and antistatic function.

Such a method for producing a laminated polyester film is excellent in supply stability of a polyester and a chip mainly composed of a thermoplastic resin incompatible with the polyester to an extruder. Furthermore, it is excellent in characteristics as a film product, film formation stability, and production cost.

[0052]

[Evaluation method of effect] The film was continuously formed for 8 hours, and the laminated polyester films at 1 hour and 8 hours after the start of film formation were sampled, and the effect in the present invention was evaluated. The evaluation method is as follows. (1) Film-forming property The following evaluation was performed about the stability of film-forming. O was evaluated as good.

：: stable without any trouble such as tearing during 8 hours.

×: Troubles such as tearing increase with time. (2) Density The density of the manufactured laminated polyester film was measured by a floating / sedimentation method using a high precision electronic hydrometer SD-120L (manufactured by Mirage Trading Co., Ltd.), and 1 hour and 8 hours after the start of film formation. The following three-stage evaluation was performed on the density difference (absolute value) of the film at the point of time. Δ or more was evaluated as good.

：: less than 0.03 g / cm ³ Δ: 0.03 g / cm ³ or more and less than 0.06 g / cm ³ ×: 0.06 g / cm ³ or more (3) Whiteness According to JIS-L-1015 U, manufactured by Shimadzu Corporation
The reflectance at wavelengths of 450 nm and 550 nm was measured using V-260, and the whiteness of the laminated polyester film manufactured by the following formula was determined as B% and G%, respectively.

Whiteness (%) = 4B-3G Further, the following three-stage evaluation was performed on the whiteness difference (absolute value) of the film at 1 hour and 8 hours after the start of film formation. Δ or more was evaluated as good.

○: less than 1% △: 1% or more and less than 3% ×: 3% or more

[0058]

Next, the present invention will be described with reference to examples, but is not necessarily limited thereto. Examples 1 to 7 For the raw material constituting the white polyester layer (A), a polyester terephthalate (hereinafter abbreviated as “PET”) chip having an intrinsic viscosity of 0.63 dl / g was first used as a polyester-based chip. Polymethylpentene (hereinafter abbreviated as “PMP”) chip and polypropylene (hereinafter abbreviated as “PP”) chip are prepared as a chip mainly composed of a thermoplastic resin incompatible with PET, and only a PET chip is prepared. Vacuum dried thoroughly.
On the other hand, as for the raw material constituting the white polyester layer (B), a mixture obtained by mixing PET chips (intrinsic viscosity: 0.65 dl / g) with calcium carbonate having an average particle size of 1 μm to be 14% by weight was sufficiently vacuum-dried. Next, among the raw materials constituting the white polyester layer (A), PET chips are supplied from the main hopper to the extruder (A) under normal pressure, and the screw type attached to the junction between the main hopper and the extruder is supplied. The PMP chip and the PP chip were supplied from the side surface under normal pressure by the raw material supply device so that the PMP and PP had the concentrations (% by weight) shown in Table 1. On the other hand, chips of the raw material constituting the white polyester layer (B) were supplied to the extruder (B) under normal pressure. After the raw material thus supplied was melted at 285 ° C., a laminated molten sheet was obtained in which the white polyester layer (B) was laminated on both surface layers of the white polyester layer (A) in the T-die composite die.

The laminated melt sheet was wound around a mirror-surface casting drum having a surface temperature of 25 ° C. by an electrostatic application casting method to be cooled and solidified to prepare an unstretched laminated film. This unstretched laminated film was heated to 95 ° C., stretched 3.2 times in the machine direction, and cooled by a group of rolls at 25 ° C. to obtain a vertically stretched film.

The longitudinally stretched film is guided into a tenter while being gripped with clips, stretched 3.2 times in a transverse direction in a heating zone at 125 ° C., and further subjected to a heat treatment in a heating zone at 220 ° C. to complete the crystal orientation. A white laminated polyester film having a thickness of 75 μm (three-layer laminated structure in which the white polyester layer (A) of the inner layer is 65 μm and the white polyester layers (B) of both surfaces are each 5 μm) was obtained. Table 1 shows the evaluation results of Examples 1 to 7. Examples 8 to 10 In Example 1, polystyrene (hereinafter referred to as “P”) was used as a chip mainly composed of a thermoplastic resin incompatible with polyester.
A white laminated polyester film was produced in the same manner as in Example 1 except that chips (abbreviated as "St") were sufficiently dried in vacuum and added to the concentration (% by weight) shown in Table 1. Table 1 shows the evaluation results. Example 11 In Example 3, a vibration-type raw material supply device was used in place of the screw-type raw material supply device, and all raw materials were supplied under the condition that the ultimate pressure was about 7 kPa. Similarly, a white laminated polyester film was produced. Table 1 shows the evaluation results. Comparative Examples 1 and 2 In feeding raw materials to the extruder (A) in Example 1, a PET chip and a PMP chip were
Example 1 except that MP was mixed so as to have the concentration shown in Table 1 and supplied from the raw material supply hopper to the extruder (A).
A white laminated polyester film was produced in the same manner as described above. Table 1 shows the evaluation results.

In Examples 1 to 11, in the production method of the present invention, that is, a chip of a thermoplastic resin incompatible with polyester was supplied from the side at the joint between the main hopper and the extruder using a raw material supply device. As a result, the film production stability and the film quality uniformity were excellent, and the characteristics as a film product were excellent. On the other hand, Comparative Examples 1 and 2 were inferior in film-forming stability and uniformity of film quality due to mixing and production without using a raw material supply device.

[0062]

[Table 1]

[0063]

According to the present invention, the supply stability is excellent, and further, the characteristics as a film product, the film formation stability, and the production cost are excellent.

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Claims (6)

[Claims] 1. A method for producing a laminated polyester film by coextrusion using two or more extruders,
In a method for producing a laminated polyester film in which a raw material is supplied to at least one extruder by kneading and melt-extruding a polyester and a thermoplastic resin incompatible with the polyester, the polyester is mainly supplied from a main hopper of the extruder. A chip supplying device is provided, and a material supply device for supplying a material from a side surface is attached to a joint between the main hopper and the extruder, and a chip mainly composed of a thermoplastic resin incompatible with polyester is supplied from the device. A method for producing a laminated polyester film, which is characterized in that: 2. The method for producing a laminated polyester film according to claim 1, wherein the supply system of the raw material supply device is one of a screw system and a vibration system. 3. The method for producing a polyester film according to claim 2, wherein the supply system of the raw material supply device is a vibration type raw material supply device, and the vibration generation system of the device utilizes electromagnetic vibration. . 4. The method for producing a polyester film according to claim 1, wherein the supply of chips is performed under a pressure condition of a vacuum system or a reduced pressure system. 5. The method for producing a laminated polyester film according to claim 1, wherein the laminated polyester film is a white laminated polyester film. 6. The thermoplastic resin incompatible with the polyester is at least one selected from polyolefin, polystyrene, poly (meth) acrylic acid or its ester, polyurethane, polycarbonate, polyamide, polyvinyl chloride, polyvinylidene chloride, and fluorine resin. The method for producing a laminated polyester film according to any one of claims 1 to 5, wherein the resin is one kind of resin.