JPH1034731A - Biaxial extruder, kneading extrusion method for pet resin using the extruder and manufacture of pet product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce to a large extent the lowering rate of IV of a material to be kneaded compared with the conventional lowering rate without the necessity of an expensive vacuum device when the material to be kneaded is dried and kneaded and extruded continuously without the predrying of a raw material and the after-treatment of kneaded resin. SOLUTION: In a biaxial kneading extruder in which a pair of screws 5, left and right, for feeding the material to be kneaded to the discharge opening 3 side on the downstream side are inserted rotatably into a cylinder 4 provided with a feed opening 3 and the discharge opening 3 for a material to be kneaded, and an internal space of the cylinder 4 positioned on the downstream side of a kneading section 10 is provided in the middle of the screw 5 as a vacuum zone VZ for removing the water content from the material to be kneaded, the length of the screen 5 in the vacuum zone VZ is set as ten times or more as long as the cylinder inner diameter D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-screw kneading extruder for extruding a polymer resin material such as plastic, a method for kneading and extruding a PET resin using the same, and a method for producing a PET product.

[0002]

2. Description of the Related Art Polymer resin materials extruded by a twin-screw kneading extruder of this type include polyethylene resins and polyethylene terephthalate (PET) resins.
It is diverse. Among them, particularly when the PET resin is kneaded, if the raw material is kneaded while containing water, the intrinsic viscosity (hereinafter referred to as IV) of the PET resin is reduced due to hydrolysis, and the molecular weight of the resin is reduced. The final product may not be usable. For this reason,
By feeding the PET material which has been dehumidified and dried in advance to a twin-screw kneading extruder, a hydrolysis reaction of the PET resin at the time of kneading is prevented (for example, Japanese Patent Application Laid-Open No.
No. 108446, JP-A-4-275125).

However, this method requires a drying facility for pre-drying the PET raw material, and requires a long time and a large amount of heat energy to dry the PET raw material, so that running costs are increased and production efficiency cannot be improved. There is. Therefore, assuming that the PET raw material can be kneaded without pre-drying, the inner space of the cylinder located downstream of the kneading segment provided in the middle of the screw is defined as a vacuum zone, and immediately after melting in this vacuum zone. A twin-screw kneading extruder has been developed which removes water from PET resin to prevent hydrolysis of the resin (for example, JP-A-6-15369, JP-A-7-90550). reference).

[0004]

Among the above-mentioned prior arts, the invention described in Japanese Patent Application Laid-Open No. 6-15369 discloses a method of removing water by post-treating a PET resin in a mixing vessel connected to a discharge port of a cylinder. PE
Although the IV of the T resin has the advantage of being improved rather than being lowered, the residence time of the PET resin in the mixing vessel requires a long time of 5 to 60 minutes, and thus the same as in the case of pre-drying the PET raw material. However, there is a drawback that the running cost increases and the production efficiency cannot be improved so much.

On the other hand, the invention described in Japanese Patent Application Laid-Open No. 7-90550 does not have such a mixing container and thus does not have the above-mentioned disadvantages, but the reduction rate of the IV of the PET resin is about 5% or less. Can only be achieved until. In the present invention, the degree of vacuum in the vacuum zone is set to 10 Torr.
Therefore, expensive vacuum equipment is required, and in this respect, the equipment cost must be increased.

The present invention has been made in view of the above circumstances, and does not require expensive vacuum equipment for continuously drying and kneading and extruding a material to be kneaded without performing pre-drying of raw materials or post-treatment of kneading resin. It is another object of the present invention to reduce the IV reduction rate of the material to be kneaded much more than before.

[0007]

The inventors of the present invention conducted various experiments in order to pursue the cause of the fact that the reduction in IV could not be suppressed so much in the conventional method (Japanese Patent Laid-Open No. 7-90550). Screw length in the zone is IV
Has been found to have a significant effect on the rate of decline. The reason for this is that the length of the screw in the vacuum zone corresponds to the residence time of the PET resin in the vacuum zone, and thus the rate of water removal in PET, which leads to a reduction in IV, depends on the length of the screw in the vacuum zone. It is because it is considered to be decided.

In the apparatus of the present invention, based on the above findings, the inner space of the cylinder located downstream of the kneading section provided in the middle of the screw is formed as a vacuum zone for removing moisture from the material to be kneaded. In the twin screw kneading extruder, the length of the screw in the vacuum zone is set to be 10 times or more the inner diameter of the cylinder (claim 1). In this case, as will be clarified in an example described later, in the case of kneading and extruding without performing pre-drying of the raw material or post-treatment of the kneading resin, even if the degree of vacuum in the vacuum zone is 10 Torr or more, the IV Can be reduced to 1.5% or less.

On the other hand, in order to carry out the apparatus of the present invention more suitably, the meshing ratio of the screw (d ₁ / d ₂ in FIG. ₂ ).
Is preferably set to 1.55 or more (claim 2). As a result, an increase in the amount of heat generated by shearing due to the shallow groove effect of the screw is prevented, and a decrease in IV is more reliably suppressed. In the apparatus of the present invention, it is preferable that the screw located in the vacuum zone is provided only with a screw flight for feeding the material to be kneaded to the downstream outlet side. In this case, the shear energy given to the molten resin can be minimized, and the residence time of the resin in the vacuum zone can be minimized, so that the IV can be more reliably prevented from lowering.

Further, in order to effectively secure the degree of sealing of the vacuum zone downstream of the kneading segment, a reverse flight for pushing out the material to be kneaded to the upstream supply port side is provided immediately adjacent to the downstream side of the kneading segment, The inside of the cylinder located downstream of the reverse flight may be set as a vacuum zone (claim 4). The device of the present invention can be applied to both cases where the kneading section is a kneading segment and a rotor segment (claims 5 and 6). However, as shown in the examples below, if the tip clearance and the length of the kneading portion are appropriately set, the use of the rotor segment at the same screw rotation speed can reduce the IV drop more than the kneading segment. Can be reliably suppressed.

The method of the present invention relates to a method for kneading and extruding a PET resin using the above-described twin-screw kneading extruder, wherein the partial pressure of water in a vacuum zone is not less than 10 Torr and not more than 80 Torr.
Torr or less, and PE inside this vacuum zone
The material to be kneaded made of T resin is passed through and extruded downstream (claim 7). In this case, the partial pressure of water in the vacuum zone is 10 Torr or more and 80 Torr.
The reason is as follows. When the pressure is less than 10 Torr, the degassing capacity of the vacuum pump exceeds the amount of generated steam.
Is exceeded, on the contrary, the amount of generated steam exceeds the degassing capacity of the vacuum pump.

The PET resin obtained by this method can be made into a final PET product by sheeting, fiberizing, pelletizing or the like according to a conventional method (claim 8).

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment of the present invention. In this figure, a twin-screw kneading extruder 1 of the first embodiment is designed as a dedicated PET resin machine, and includes a cylinder 4 having a supply port 2 and a discharge port 3 for a material to be kneaded, and a cylinder 4 having the same. And a pair of left and right screws 5, 5 rotatably inserted so as to mesh with each other. The two screws 5, 5 feed the kneaded material such as PET resin supplied from the supply port 2 into the cylinder 4 in the downstream. It is kneaded and conveyed to the discharge port 3 side.

A molding device 16 for molding the kneaded and molten PET resin into a final PET product is connected to the outlet 3 of the cylinder 4. As the molding device 16,
For example, a roller die is used to obtain a sheet-shaped PET product, an extruder and a wire drawing machine are used to obtain a fibrous PET product, and an underwater cut granulator is used to obtain a pellet-shaped PET product. Adopted.

As shown in FIG. 2, in the cylinder 4, kneading chambers 6, 6 each having a substantially eyeglass-shaped cross section are formed. The screws 5, 5 are arranged in the cylinder 4 in parallel with each other, and the screw flight 7 is connected to both kneading chambers 6, 5.
6 are arranged close to each other so as to mesh with each other at the communicating portion 6. In FIG. 2, the screws 5 and 5 rotate in the same direction, but may rotate in different directions.

Slight discharge port 3 in the middle of cylinder 4
More specifically, a vent port (degas port) 8 for degassing the inside of the kneading chambers 6, 6 in a fixed section in the axial direction of the cylinder 4 is provided. Further, the cylinder 4 is provided with a heat medium jacket (not shown) for heating or cooling the material to be kneaded in the kneading chambers 6, 6. The cylinder 4 is of a block type in which a plurality of segments 4A, 4B can be connected in an arbitrary order in the axial direction.
The structure and length of the device can be arbitrarily adjusted by changing the arrangement order and the number of connections of 4B. In the cylinder 4 of the present embodiment illustrated in FIG. 1, in order from the downstream side,
Next to the segment 4A having the supply port 2, two normal segments 4B having no supply port 2 are connected, then the segment 4A having the vent port 7 is connected, and then the normal segment 4B is connected. It is configured by connecting two.

In correspondence with the cylinder 4, the screw 5 also employs a block system in which various segments can be connected in an arbitrary order, whereby the axial length of the screw 5 can be adjusted. A kneading segment 10A or a rotor segment 10B having a torsion blade described later can be inserted into the screw 5 at an intermediate portion in the axial center direction by spline fitting.

The screw 5 of the present embodiment comprises a kneading section 1 comprising a first feed section 9 and a kneading segment 10A.
0, the reverse feed section 11 and the second feed section 12 are connected in order from the downstream side. Among them, the first feed section 9 is arranged in the most downstream (first) cylinder segment 4A having the supply port 2, and the kneading segment 10A and the reverse feed section 11 are arranged in the second cylinder segment 4B. I have. Also,
The second feed portion 12 is formed to be the longest among the components of the screw 5, and is disposed in the third and subsequent cylinder segments 4A and 4B.

The kneading segment 10A constituting the kneading section 10 does not itself have the ability to feed the material to be kneaded, but imparts a strong mixing or mixing action to the material, and has the same cross section as the screw 5. Finite thickness kneading disk 1 with an infinite screw lead
3 is formed by laminating a plurality of sheets. The kneading segment 10A is connected to the screw 5
The kneading disk 13 may have a polygonal shape other than the same cross section.

In this embodiment, the kneading chamber 6 located downstream of the kneading segment 10A is a vacuum zone VZ for removing moisture from the material to be kneaded.
That is, the vent port 8 is provided with a deaerator (vacuum pump) 1 for reducing the pressure inside the cylinder 4 to almost a vacuum.
The deaerator 14 is capable of reducing the pressure of the kneading chamber 6 to at least 80 Torr.

The second feed portion 12 of the screw 5 has such a feed capability that the resin kneaded and melted in the kneading segment 10A is not filled in the kneading chamber 6. Since the spirally continuous space formed by the groove of the second feed portion 12 communicates with the vent port 8, the molten resin in the groove is dehydrated at a preset uniform degree of vacuum. .

Since the purpose of the vacuum zone VZ is to remove water in the resin to prevent hydrolysis, even if the degree of vacuum in the kneading chamber 6 is 80 Torr or more, the partial pressure of water is reduced. 80 Torr or less is sufficient. Further, in order to improve the uniformity of the degree of vacuum in the vacuum zone VZ, the vent ports 8 may be provided at a plurality of positions separated in the axial direction.

In the present embodiment, the length of the second feed portion 12 of the screw 5 disposed in the vacuum zone VZ is set to be at least 10 times the cylinder inner diameter D. As shown in the figure, even if the degree of vacuum in the vacuum zone VZ is 10 Torr or more, the final IV reduction rate can be 1.5% or less. The reverse feed section 11 connected immediately downstream of the kneading segment 10A includes first and second feed sections 9 and 1.
A reverse flight 15 is provided in the opposite direction to the second screw flight 7, and pushes the material to be kneaded back to the upstream supply port 2 side. Therefore, the kneading segment 10A
The kneaded material kneaded and melted in the reverse feed section 11
The inside of the kneading chambers 6 and 6 is filled, thereby ensuring the airtightness of the vacuum zone VZ located downstream from the reverse feed section 11.

On the other hand, as shown in FIG. 2, when the ratio d ₁ / d ₂ between the maximum diameter and the minimum diameter in the cross section of the screw 5 is defined as the “engagement ratio”, the second feed portion 12 in the vacuum zone VZ If the meshing ratio d ₁ / d ₂ is less than 1.55, the shear heat generation may increase due to the shallow groove effect of the screw, and the decrease in IV may be accelerated in some cases. -90550).

Therefore, in the present embodiment, the meshing ratio d ₁ / d ₂ in the second feed section 12 is set to 1.55 or more. Further, by setting the engagement ratio d ₁ / d ₂ to a relatively large value as described above, there is an advantage that the amount of extrusion can be increased and even a material having a small bulk specific gravity such as a film scrap can be conveyed in a large amount. Thus, the area where the molten resin comes into contact with the vacuum is increased, so that there is an advantage that the dewatering efficiency is improved.

Further, in this embodiment, only the screw flight 7 for feeding the material to be kneaded to the discharge port 3 downstream is formed in the second feed section 12 in the vacuum zone VZ. In this case, since there is no member in the vacuum zone VZ that hinders the flow of the resin, the shear energy given to the molten resin can be minimized, and the residence time of the resin in the vacuum zone VZ can be minimized.

FIGS. 6 and 7 show a second embodiment of the present invention. This embodiment differs from the first embodiment in that a rotor segment 10B composed of a feed wing portion 17 and a return wing portion 18 is employed as the kneading portion 10 of the material to be kneaded. The rotor segment 10B self-generates heat by high shear stress generated when the material to be mixed passes through the tip clearances of the wing portions 17, 18, and plasticizes and melts the material to be kneaded by the self-heating.

Incidentally, other structures other than the kneading section 10 are as follows.
Since the structure is the same as that of the first embodiment, the same members as those of the first embodiment are denoted by the same reference numerals in FIG. 6 as those in FIG. 1, and the detailed description of the structure is omitted. . Although the rotor segment 10B having both the feed wing portion 17 and the return wing portion 18 is shown in FIG.
A rotor segment having only one of the feed wing portion 17 and the return wing portion 18 may be employed.

[0029]

【Example】

(First Experimental Example) As described above, the conventional method (Japanese Unexamined Patent Application Publication No.
No. 0550), in order to pursue the reason why the decrease in IV cannot be suppressed so much, the twin-screw kneading extruder for testing according to the first embodiment (KTX-46 manufactured by Kobe Steel Co., Ltd., cylinder inner diameter D) = 46 mm), and the test resin kneading was performed by changing the segments of the screw 5 in various ways.

In KTX-46, the kneading section is constituted by a kneading segment or a rotor segment having a kneading action, and the vacuum zone VZ is constituted by a screw. In the kneading segment 10A used in the first experimental example, five kneading disks 13 each having a thickness of about 10 mm and a chip clearance δ / D of 5.0 × 10 ⁻³ are laminated in the screw axis direction. Thus, a kneading unit 10 having an L / D of about 1.0 was employed.

As a result of the test kneading, the present inventors found that the screw 5 (the second feed unit 1) in the vacuum zone VZ was used.
2) It has been found that the length (L / D) greatly affects the IV reduction rate. That is, FIG. 3 to FIG.
(Kg / h) and a three-dimensional graph showing the relationship between the screw rotation speed N (rpm) and the amount of change in IV (ΔIV). In this case, the resin temperature T and the degree of vacuum in the vacuum zone VZ are kept constant ( (T = 260 degrees, vacuum degree = 20 Torr)
Only L / D is changed, and in FIG. 3, L / D = 3.6, FIG.
In FIG. 5, L / D = 10.8, and in FIG. 5, L / D = 18.0.

As is apparent from FIGS. 3 to 5, L /
It can be seen that as D increases, the IV change amount can be suppressed as much as possible, and in particular, the IV change amount in the range where the production amount Q is large becomes extremely small. Then, this time, L /
In order to investigate how much D can be increased to make the IV change amount smaller than before, the L / D length is variously varied when the degree of vacuum in the vacuum zone VZ is 20, 50 and 80 Torr, respectively. The test kneading of the PET resin was carried out in a different manner. Table 1 below summarizes the results.

[0033]

[Table 1]

As can be seen from Table 1, in the case of Experiment Nos. 1 to 5 in which the L / D is 10 or more, the reduction rate of IV is 1.3 in all cases where the degree of vacuum is 20, 50 and 80 Torr. % Or less, which is much lower than in the past.
On the other hand, in the case of Experiment Nos. 6 to 8 in which the L / D is 7.2, the reduction rate of the IV is 2.0% or more in all cases of the vacuum degree of 20, 50 and 80 Torr. ,
This is not much different from the conventional method.

From the above, if L / D is set to about 10 or more, the degree of vacuum in the vacuum zone VZ does not need to be reduced to 10 Torr or less unlike the conventional method (Japanese Patent Application Laid-Open No. 7-90550). , IV can be suppressed to 1.5% or less. (Second Experimental Example) Next, whether the kneading section 10 is the kneading segment 10A or the kneading section 10 is the rotor segment 10B, which is used to verify which one can further suppress the reduction of IV. The test kneading was performed by matching the structure of the apparatus other than the kneading section 10 with the operating conditions. The results are shown in the following [Table 2].

The structure of the kneading segment 10A in the second experimental example is the same as that in the first experimental example, and the structure of the rotor segment 10B is as follows. Number of rotor stirring blades 3 Chip clearance δ / D = about 0.1 Length of feed blade L1 / D = 1.3 Length of return blade L2 / D = 1.3 Twist angle θ = 60 degrees

[0037]

[Table 2]

As can be seen from Table 2, in the case of Experiment Nos. 9 to 11 employing the rotor segment 10B,
Increase the number of revolutions to 500 rpm or increase the production volume to 50 kg /
h, the IV reduction rate is 1.5%
% Or less, whereas in the case of Experiment Nos. 12 to 14 employing the kneading segment 10A, the rotational speed was set to 400 rpm (Experiment No. 13).
Shows that the rate of decrease in IV is 1.5% or less, but in other cases (Experiment Nos. 12 and 14), it exceeds 1.5%.

As described above, the use of the rotor segment 10B in the kneading section 10 reduces the IV reduction rate by 1.5%.
The operating conditions that can be suppressed below can be further expanded.

[0040]

As described above, according to the present invention,
In extruding while continuously kneading and vacuum drying the material to be kneaded without performing pre-drying of the raw material or post-processing of the kneading resin,
Even when the degree of vacuum in the vacuum zone is 10 Torr or more, the rate of decrease in IV can be effectively suppressed. For this reason, the rate of decrease in the IV of the material to be kneaded can be significantly reduced as compared with the related art without requiring expensive vacuum equipment.

Further, by employing the rotor segment in the kneading section, the operating conditions for effectively suppressing the IV reduction rate can be made wider as compared with the case where the kneading segment is employed.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a twin-screw kneading extruder according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIGS. 1 and 6;

FIG. 3 Production volume Q (kg / h) and screw rotation speed N
6 is a three-dimensional graph showing the relationship between (rpm) and the amount of change in IV (ΔIV) (provided that L / D = 3.6).

FIG. 4 Production volume Q (kg / h) and screw rotation speed N
6 is a three-dimensional graph showing the relationship between (rpm) and the amount of change in IV (ΔIV) (however, L / D = 10.8).

FIG. 5 Production volume Q (kg / h) and screw rotation speed N
6 is a three-dimensional graph showing the relationship between (rpm) and the amount of change in IV (ΔIV) (however, L / D = 18.0).

FIG. 6 is a side sectional view of a twin-screw kneading extruder according to a second embodiment of the present invention.

FIG. 7 is a sectional view taken along the line BB of FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 twin-screw kneading extruder 2 supply port 3 discharge port 4 cylinder 5 screw 7 screw flight 10 kneading section 10A kneading segment 10B rotor segment 13 kneading disc 15 reverse flight VZ vacuum zone

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29C 47/76 B29C 47/76 // B29K 105: 06 (72) Inventor Nobuyuki Yamagaki Takasago City, Hyogo Prefecture 2-3-1 Shinhama, Arai-cho Kobe Steel, Ltd. Takasago Works (72) Inventor Shinichi Nagae 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Kazuko Nakura 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel, Ltd.

Claims (8)

[Claims] 1. A pair of left and right screws (5) for feeding a material to be kneaded to a discharge port (3) downstream in a cylinder (4) having a supply port (2) and a discharge port (3) for the material to be kneaded. ) Is rotatably inserted, and the inner space of the cylinder (4) located downstream of the kneading section (10) provided in the middle of the screw (5) removes moisture from the material to be kneaded. In the twin-screw kneading extruder defined as a vacuum zone (VZ), the screw (5) in the vacuum zone (VZ)
Characterized in that the length of the extruder is set to be at least 10 times the inner diameter (D) of the cylinder. 2. The engagement ratio (d ₁ / d) of the screw (5)
_2. The twin-screw kneading extruder according to claim 1, wherein ₂ ) is set to 1.55 or more. 3. The screw (5) located in the vacuum zone (VZ) is provided with only a screw flight (7) for feeding the material to be kneaded to a downstream discharge port (3). 2. The twin-screw kneading extruder according to 2. 4. A reverse flight (15) is provided immediately adjacent to the downstream side of the kneading section (10) to push back the material to be kneaded to the upstream supply port (2) side.
The twin-screw kneading extruder according to any one of claims 1 to 3, wherein the inner space of the cylinder (4) located downstream of (5) is a vacuum zone (VZ). 5. The twin-screw kneading extruder according to claim 1, wherein the kneading section (10) comprises a kneading segment (10A). 6. The kneading section (10) includes a rotor segment (1).
The twin-screw kneading extruder according to any one of claims 1 to 4, comprising OB). 7. A partial pressure of water in a vacuum zone (VZ) is set to 10 Torr or more and 80 Torr or less, and a material to be kneaded made of PET resin is passed through the vacuum zone (VZ) to a downstream side. A method for kneading and extruding a PET resin using the twin-screw kneading extruder according to any one of claims 1 to 6, wherein the extruding is performed. 8. A method for producing a PET product, comprising molding the PET resin obtained by the kneading and extrusion method according to claim 7 into a final PET product.