JPH11181254A - Production of polyester composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To industrially and advantageously produce the subject composition causing a slight lowering, etc., in intrinsic viscosity of a polyester and capable of maintaining the quality at a high level by crushing a polyester and a specific polymer in an apparatus comprising a crusher and a single screw extruder while controlling the resin temperature to specific temperature conditions and carrying out the melt extrusion. SOLUTION: (A) A polyester containing preferably >=80% ethylene terephthalate unit, etc., and (B) a low-melting polymer incompatible with the component A (e.g. polypropylene) are crushed in an apparatus comprising a crusher and a single screw extruder while controlling the resin temperature in the crusher to the melting point of the component B or below and then carrying out the melt extrusion. The resultant composition has preferably <=10% lowering rate of the intrinsic viscosity of the polyester and is useful for producing a white polyester film, etc. A cylindrical crusher having a rotating disk equipped with cutting blades arranged on the base is preferred as the crusher. The extruder is preferably equipped with one or more vacuum vent part in one or more sites of the cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polyester composition.

[0002]

2. Description of the Related Art In the fields of various printing materials and image receiving papers, white polyester films which are lightweight and have cushioning properties by containing microbubbles are used. As a method for producing such a white polyester film, for example, as proposed in JP-A-63-168441, a method of stretching a polyester composition containing a polyester and a polymer incompatible with the polyester is known. Generally adopted. And, as the incompatible polymer,
An olefin polymer represented by polypropylene or the like having a lower melting point than polyester is used. Hereinafter, a polymer that is incompatible with polyester and has a low melting point is simply referred to as an “incompatible polymer”.

[0003] By the way, the scrap such as the film edge recovered from the polyester film manufacturing process is
After being pulverized, it is melted and reused. However, when the incompatible polymer is contained in such a regeneration step, the following various problems occur.

(1) To grind polyester to be regenerated, various grinders such as a cylindrical grinder having a rotating disk with a cutting blade disposed on the bottom surface are used. The immiscible polymer melts and adheres to the cutting blade, and the crushing ability is extremely reduced. Therefore, it is necessary to reduce the amount of heat generated by friction by reducing the amount of pulverization, or to frequently stop the pulverizer to remove the incompatible polymer attached to the tip of the cutting blade.

[0005] (2) In the melt extrusion step, it is necessary to plasticize polymers having different melting points, so that bubbles and the like are generated in the extruded product. That is, generally, inside the extruder,
Heat generated by the shear force between the screw and cylinder causes plasticization (melting) of the thermoplastic resin,
The low melting point resin (immiscible polymer) melted early penetrates between the high melting point resin (polyester) and the inner wall of the screw and / or cylinder and inhibits the generation of shear force. As a result, the solid bed in the extruder is broken and melt extruded while containing air bubbles.

(3) In the case where a film or the like is produced by once being regenerated into pellets and then extruded together with another polyester through a drying step again to produce a film or the like, melting or deterioration of the incompatible polymer during drying (heat degradation) Deterioration and coloration), and in particular, problems such as a reduction in the foaming ability of the incompatible polymer (thermal deterioration), which are important in the production of a foamed film, inevitably occur.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the industrial use of polyesters and polyester compositions containing incompatible and low-melting polymers. This is an advantageous production method, and maintains a high quality of the polyester composition, such as a decrease in the intrinsic viscosity (hereinafter abbreviated as "IV") of the polyester and a small thermal deterioration of a polymer incompatible with the polyester. It is an object of the present invention to provide a possible manufacturing method.

[0008]

That is, the first aspect of the present invention is as follows.
The gist of the present invention is a method for producing a polyester composition containing a polyester and a polymer having an incompatible and low melting point with respect to the polyester, using an apparatus comprising a pulverizer and a single-screw extruder,
After the polyester and the polymer are treated in a pulverizer, the melt extrusion is performed, and the method for producing a polyester composition is characterized in that the resin temperature in the pulverizer is controlled to be equal to or lower than the melting point of the polymer. .

The second gist of the present invention is that the molten polyester composition from the single-screw extruder is guided to a metering pump and then extruded from a slit die into a sheet on a rotary cooling drum. A method for producing a polyester composition, comprising forming a stretched sheet, and then stretching the obtained unstretched sheet in at least one direction.

[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 an explanatory side view of an example of an apparatus (a cylindrical crusher and a vented single-screw melt extruder) preferably used in the production method of the present invention, and FIG. 2 is a cylindrical crusher shown in FIG. It is a section explanatory view of a machine. In the figure, (1) is a cylindrical pulverizer, (2) is a raw material inlet, (3) is a heating cylinder, (4) is a screw, (5) is a vent hole, (6) is a metering pump, (7) Is a filter, (8) is a slit base, (9) is a rotary cooling drum, (10) is a take-up roll, (D) is a disk with a cutting blade, (M) is a driving device,
(A) represents a sheet.

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

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, examples of the incompatible polymer include polyolefins such as polyethylene, polypropylene, polymethylpentene and polymethylbutene. In particular, in the temperature range of the glass transition temperature of the amorphous state of the polyester or higher, a polyolefin-based polymer having a higher elastic modulus than the polyester is preferably used because it can generate many fine bubbles in the film. You. Examples of such a polyolefin polymer include polyethylene and polypropylene. The melt flow index of the polyolefin polymer is usually 0.2 to
120, preferably in the range of 0.5 to 50.

As the other incompatible polymer, a polystyrene homopolymer or a random copolymer, a block copolymer or a graft copolymer with another monomer mainly composed of styrene repeating units can be used. Specific examples thereof include general-purpose amorphous polystyrene, crystalline polystyrene having stereoregularity, impact-resistant polystyrene, acrylonitrile-styrene-based copolymer, acrylonitrile-butadiene-styrene resin, and liquid crystal polyester.

The above incompatible polymer is disclosed in, for example,
According to the method described in JP-A-3-168441, it is blended with polyester and used to produce a white polyester film.

In the present invention, the polyester may contain inorganic and / or organic particles according to a known method, or may contain fine particles based on a catalyst residue at the time of polymerization.

In the present invention, the polyester composition containing the polyester and the incompatible polymer is typically composed of a recycled polyester. For example, (1) a combination of a scrap of a white polyester film (such as a film edge recovered from the manufacturing process) and a new raw material of a normal polyester, (2) a scrap of a normal polyester and a new raw material of a white polyester ( (3) a combination of a scrap of a white polyester film and a scrap of a normal polyester. However, since the effect of the present invention is exerted on a polyester composition containing a polyester and an incompatible polymer, it is not necessarily limited to a recycled polyester. In the case of a recycled polyester, the amount of the recycled resin is usually 10 to 50% by weight based on the total amount of the resin, and the content of the incompatible polymer in the polyester composition containing the polyester and the incompatible polymer. Is usually 1 to 45% by weight.

By the way, generally, the raw material to be subjected to melt extrusion is sufficiently dried beforehand in order to prevent a reduction in molecular weight (IV reduction) due to hydrolysis. That is, the water content before melt extrusion is usually 500 ppm or less, preferably 100 pp.
m, more preferably 50 ppm or less. Then, it is dried with hot air at 150 ° C. or higher, preferably 200 ° C. or lower, more preferably 160 ° C. to 180 ° C. for about 1 to 3 hours.

However, when the drying temperature is higher than the melting point of the incompatible polymer, (1) the incompatible polymer is selectively melted and adheres to the inner wall of the dryer or to the inside of the transfer section, (2) The melted incompatible polymer may be degraded by thermal decomposition or the like and mixed into the regenerated polyester to cause problems such as generation of bumps and gels and discoloration. When the drying temperature is lower than the melting point of the incompatible polymer, not only does the drying efficiency deteriorate, but also the water content in the finally obtained polyester after drying increases, and after the melt extrusion, May decrease in molecular weight. Furthermore, since oxygen is present in ordinary hot air (dry air), the incompatible polymer is oxidized and colored yellow,
In some cases, the molecular weight is reduced and the original properties are impaired.

Accordingly, in the present invention, the starting resins (polyester and incompatible polymer) to be subjected to melt extrusion are:
Preferably, it is substantially undried without performing a drying treatment. Then, the water in the raw material resin is removed from a vent hole (5) of a single screw melt extruder described later.

In the present invention, the above-mentioned raw material resin is supplied from the raw material charging port (2) to the cylindrical crusher (1). As shown in FIG. 2, the cylindrical crusher (1) crushes the raw material resin by a disk (D) with a cutting blade disposed on the bottom surface. The rotation speed of the disk (D) depends on the size of the cylindrical crusher (1), but is usually 2,000 rpm or less, preferably 1,8 rpm.
00 rpm or less. It is preferable that the supply amount of the raw material resin is adjusted so that the rotational power of the cutting blade arranged on the bottom surface of the cylindrical crusher (1) is kept constant. The type of the cylindrical crusher (1) may be any type.

At the time of pulverization, the temperature of the raw resin in the cylindrical pulverizer (1) rises due to frictional heat generated between the raw resin and the cutting blade and the side surface of the pulverizer. In order to suppress the thermal deterioration and maintain the quality of the polyester composition at a high level, it is important to control the temperature of the raw material resin in the pulverizer to be equal to or lower than the melting point of the incompatible polymer in the raw material resin. From the viewpoint of removing as much moisture as possible from the raw material resin, the temperature of the raw material resin is preferably as high as possible. Therefore, the temperature of the raw material resin in the pulverizer is preferably as high as possible within a range satisfying the above conditions, and the lower limit is usually 90 ° C., preferably 100 ° C., and more preferably 105 ° C.

The temperature of the raw material resin in the crusher can be easily adjusted by changing the rotation speed of the cutting blade. For example, when the temperature rise of the raw resin in the pulverizer is large and may be higher than the melting point of the incompatible polymer, the rotational speed of the cutting blade may be reduced. It is preferable to control the number of rotations by detecting the temperature in the crusher and automatically performing the system.

In the present invention, the raw resin pulverized in the cylindrical pulverizer (1) is supplied to a heating cylinder (3) of a vented single-screw extruder connected to the cylindrical pulverizer (1).
Is derived. In the present invention, the vented single-screw extruder used as a preferred embodiment only has to have a vacuum vent at least at one or more locations in the cylinder. ),
(5) is not required.

The ratio (L / D) of the cylinder length (L) to the cylinder inner diameter (D, diameter) in the single screw extruder is usually 1
The range is 8 to 60, preferably 20 to 50. L /
When D is less than 18, melting tends to be insufficient, and degassing at the vent hole (5) tends to be insufficient. L / D is 6
If it exceeds 0, the residence time of the raw resin increases, the temperature of the raw resin in the extruder is unavoidable, and the degree of polymerization tends to decrease.

The degree of vacuum at the vent is usually 40 hectopascal or less, preferably 30 hectopascal or less, more preferably 20 hectopascal or less, in order to increase the degassing efficiency of the moisture by diffusing the moisture from the surface of the molten resin. It is said.

The molten resin in the single-screw extruder can be drawn out as a polyester composition from the die of the extruder by the action of the screw (4) and formed into a strand. After guiding the polyester composition to the metering pump (6), it is extruded into a sheet from a slit-shaped die (8) onto a rotary cooling drum (9) to form an unstretched sheet (A). The sheet (A) is preferably stretched in at least one direction. In this case, to prevent troubles such as film breakage,
The reduction rate of the intrinsic viscosity after melt extrusion is preferably 10% or less, more preferably 8% or less, and particularly preferably 6% or less.

In the above method, particularly in the case of regenerated polyester, the polyester from the cylindrical crusher (1) is directly formed into a film as it is. This is an extremely effective method that can maintain a high quality of polyester and incompatible polymer. In particular, when producing a white (foamed) polyester film, since the color change of the incompatible polymer is small, the color change of the obtained film is small,
Further, since the ability to form fine bubbles does not decrease, the density of the foamed film can be maintained at a high level.

Further, the recycled polyester composition can be introduced into a metering pump (6), mixed with a new polyester melted by another melt extruder, extruded into a sheet, and formed into a sheet. And before extruding from the base,
For example, foreign substances may be removed by a filter (7) such as a mesh filter or a sintered metal filter. If the pressure loss at the time of filter filtration is large and the output is reduced, a gear pump or the like is used as a fixed amount pump (6). Can be used.

[0030]

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 (dl / g):
Incompatible with the polyester, 100 g of a mixed solvent of phenol / tetrachloroethane: 50/50 (weight ratio) is added to 1 g of the polyester from which other polymer components and particles are removed.
Then, the mixture was dissolved by adding ml, and measured at 30 ° C.

(2) Whiteness (b value): color analyzer ("TC-1800MKII" manufactured by Tokyo Denshoku Co., Ltd.)
And the color tone (L, a, b) of the film was measured according to the method of JIS Z8722, and the b value was used as the whiteness. When the b value is large on the + side, it indicates that the yellow color is strong. 3
Evaluation was made based on the average of the measured values of the points.

(3) Film density (g / cm ³ ): A 10 cm × 10 cm square sample was cut out from an arbitrary portion of the film, its weight was measured, and the thickness at 9 arbitrary points was measured with a micrometer. The weight per unit volume was calculated from the average value and the weight. The number of measurements is n =
5 and the average value was taken as the density film density.

(4) Melt flow index (MF)
I) (g / 10 min): JIS K-6758-19
81 was measured. The higher this value, the lower the melt viscosity of the polymer.

(5) Comprehensive evaluation: Comprehensive evaluation was performed according to the following criteria. That is, the case where the IV decrease and the increase in the b value were small was evaluated as 更 に, the case where the density decrease of the biaxially stretched film was small was evaluated as ◎, and the case where the IV decrease or the increase in the b value was large was evaluated as x.

Reference Example 1 87% polyethylene terephthalate (PET) chip having an IV of 0.65 (dl / g) and MF10 (g / 10 mi)
13) Crystalline polypropylene (PP) chips of 13% were blended, melt-extruded into a film at 290 ° C., and cooled on a rotating cooling drum at 30 ° C. to obtain an unstretched sheet. The obtained unstretched sheet was stretched 3.3 times at 85 ° C. in the machine direction and 3.3 times at 115 ° C. in the transverse direction.
Heat treatment at 30 ° C, finally thickness 50μm, density 1.0
(G / cm ³ ) of a PP-containing PET film was obtained.

Example 1 The above-mentioned PP-containing PET was placed in a cylindrical grinder having an inner diameter of 800 mm.
The film is charged, the resin temperature in the crusher is set to 140 ° C., and the rotation speed of the disk on which the cutting blade is arranged is set to 1,000 rpm.
m, the diameter of the single screw extruder directly connected to the pulverizer is 80 mm, L
/ D was 36,000. After boosting with a gear pump,
It was melt extruded and formed into a sheet on a rotating cooling drum at 30 ° C. The characteristics evaluation results of the obtained sheet are as shown in Table 1,
It was good.

Comparative Example 1 A sheet was formed in the same manner as in Example 1 except that the resin temperature in the pulverizer was changed to 170 ° C. Table 1 shows the characteristic evaluation results of the obtained sheet. After the treatment with a crusher for 30 minutes, the cutting blade was observed. As a result, it was confirmed that a resin, which seemed to have melted polypropylene, had adhered to the upper side (inner surface) of the rotating cylinder.

Example 2 The sheet obtained in Example 1 was stretched 3.3 times in the longitudinal direction at 85 ° C., further stretched 3.3 times in the transverse direction at 115 ° C., and then heat-treated at 230 ° C. Finally, a film having a thickness of 50 μm was obtained. The density of the obtained film was 1.05 (g / g).
cm ³ ) and other properties are as shown in Table 1, and there was no change in color tone, and it was good.

Comparative Example 2 A polyester composition A was prepared in the same manner as in Example 1 except that the pressure was increased by a gear pump, melt-extruded into strands, quenched in a water bath, and pelletized with a pelletizer. I got The composition was dried at 150 ° C. for 2 hours, melt-extruded into a film with a single-screw extruder having a diameter of 50 mm, and then formed into an amorphous sheet.
The film was stretched 3 times, further stretched 3.3 times in the transverse direction at 115 ° C., and then heat-treated at 230 ° C. to finally obtain a 50 μm thick film. The density of the film is 1.20 (g / c
m ³ ). Other characteristics are as shown in Table 1. The change in color tone was large and the IV value was also reduced.

[0041]

[Table 1]

[0042]

According to the present invention described above, there is provided an industrially advantageous method for producing a polyester composition containing a polyester and a polymer having an incompatible and low melting point with the polyester,
Provided is a production method capable of maintaining the quality of the polyester composition at a high level, such as a decrease in the intrinsic viscosity (hereinafter abbreviated as "IV") of the polyester and a small thermal deterioration of a polymer incompatible with the polyester. Thus, the industrial value of the present invention is remarkable.

[Brief description of the drawings]

FIG. 1 is an explanatory side view of an example of an apparatus (a cylindrical crusher and a vented single-screw melt extruder) preferably used in the production method of the present invention.

FIG. 2 is an explanatory sectional view of the cylindrical crusher shown in FIG. 1;

[Explanation of symbols]

 1: grinding machine 2: raw material input port 3: heating cylinder 4: screw 5: vent hole 6: metering pump 7: filter 8: slit-shaped base 9: rotary cooling drum 10: take-up roll D: disk with cutting blade M: drive Apparatus A: Sheet

Claims (6)

[Claims] 1. A method for producing a polyester composition containing a polyester and a polymer having an incompatible and low melting point with respect to the polyester, wherein an apparatus comprising a pulverizer and a single screw extruder is used. A method for producing a polyester composition, comprising: controlling a resin temperature in a pulverizer at a temperature equal to or lower than a melting point of the polymer when performing melt extrusion after treating the polymer in a pulverizer. 2. The method according to claim 1, wherein a cylindrical grinding machine having a rotary disk with a cutting blade disposed on a bottom surface is used. 3. A single screw melt extruder having a vacuum vent at at least one location of a cylinder.
Or the production method according to 2. 4. The production method according to claim 1, wherein the intrinsic viscosity reduction rate of the polyester after melt extrusion is 10% or less. 5. After introducing the molten polyester composition from the single-screw extruder according to claim 1 to a metering pump, extrude it from a slit die into a sheet on a rotary cooling drum to form an unstretched sheet, A method for producing a polyester composition, comprising stretching the obtained unstretched sheet in at least one direction. 6. The production method according to claim 5, wherein the molten polyester composition is introduced into a metering pump, mixed with the polyester melted by another melt extruder, and extruded into a sheet.