JP2001162671A - Twin-screw extruder for recycled resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extrusion-mold a resin, even when it is a scrap raw material which is high in water absorbency and easily hydrolyzed, by prompt deaeration from vent holes. SOLUTION: At least on one side of the barrel 12 of a one-way rotation type twin-screw extruder, the first-third side vent holes 4A-4C are formed diagonally above, a suction box 23 covering the holes 4A-4C is installed, a vacuum pump is connected with the box 23 through a duct 25, and a slanted bottom plate 23a which faces a roof 23b and is slanted downward toward the outside is installed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-screw extruder for a recycled resin such as a polyester resin such as a PET resin or a polyamide resin having a high water absorption and causing a hydrolysis reaction in a high temperature range.

[0002]

2. Description of the Related Art Crystalline resins having high water absorption and causing a hydrolysis reaction in a high temperature range include, for example, polyethylene terephthalate resin (hereinafter referred to as PET resin) and polyamide resin. For example, PET resin is terephthalic acid + ethylene It is obtained by the reversible condensation reaction of glycol @ PET resin + water,
It has a water content of about 0.6%. When the PET resin is directly extruded with a single-screw extruder, the product extruded from the die becomes a foam having a large number of air bubbles due to vaporization of the contained moisture. Further, when the PET resin has a crystal melting temperature Tm = or higher during extrusion molding, a hydrolysis reaction occurs due to the contained water, and the viscosity decreases, that is, the intrinsic viscosity (IV value) which is a measure of the average molecular weight, the impact strength and the tensile strength. , Etc. suddenly decrease in physical properties. This causes unstable melting behavior, causing extrusion instability,
In extreme cases, the PET resin may be wound around the extrusion screw and the PET resin may not flow out of the die.

For this reason, the present inventors have proposed a technique disclosed in Japanese Utility Model Laid-Open No. 4-87.
In JP-A-228, even if the resin is easy to swell,
We have proposed a twin-screw extruder with vents in multiple stages for good extrusion.

[0004]

However, the above-described conventional twin-screw extruder employs an upper vent port 51 shown in FIG. In the barrel 52 of this twin-screw extruder, as shown in FIG. 7, the resin P flows in a helical eight-shape along the inner peripheral surface of the screw space 52 a according to the rotation of the two screws 53. The resin P is turned back at the upper and lower merging portions 54, and the flow changes into a V-shape. As a result of this reversal, the swollen resin may be caught on the downstream end of the vent port 51, and the resin piece P 'may grow little by little and gradually vent up. Unlike the vent-up in which the filling rate of the resin P is increased and the back-flow occurs, the vent-up occurs gently and grows while solidifying, so that the vent port 51 may be blocked, and the degassing efficiency may be reduced. This was the cause of a significant decrease.

The present invention solves the above-mentioned problems, and has a high water absorption, and is a crystalline regenerated resin which is easily hydrolyzed in a high temperature range.
To provide a twin-screw extruder for reclaimed resin that can extrude satisfactorily by preventing clogging from a vent port without deteriorating the IV value even when the scrap raw material contains 100% scrap. With the goal.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 comprises a barrel containing two screws which are engaged with each other in a screw space and are rotated in the same direction, and A plurality of vent ports formed between a raw material supply port and a discharge port, a resistor provided on the vent port upstream side of the screw to seal and seal the resin transported by the screw, and A heating device for holding the resin within a predetermined temperature range, and a twin-screw extruder for reclaimed resin provided with a suction device for sucking and removing moisture from the resin in the screw space at the vent port. At least one of both sides is configured as a side vent formed obliquely upward, a suction box is provided to cover the vent port, and suction means is connected to the suction box. Both is provided with a tilting bottom plate which is inclined downward and outward vent hole facing the top plate.

According to the above configuration, the vent port for discharging moisture and oligomers from the resin in the screw space is a side vent port opened at a side position shifted from a junction where the resin is turned back at an acute angle. Moisture and oligomers can be suctioned and discharged at places where the resin flow is smooth,
The resin can be prevented from being caught due to swelling to a minimum, and vent up due to the growth of the resin can be prevented. In addition, since the inclined bottom plate is provided in the vent box, it is possible to prevent the resin overflowing from the side vent and the backflow of the liquid condensed in the vent box, and to mold a uniform and high-quality resin.

According to a second aspect of the present invention, in the above structure, a tongue portion is formed on the barrel side opening of the vent hole on the upstream side along the barrel inner surface, and a chamfered portion is formed on the downstream side. . According to the above configuration, the gap between the screw and the tongue portion is reduced by the tongue portion, so that the stagnation of the resin is reduced. In addition, the chamfered portion can prevent the resin from being caught due to swelling, and can prevent the occurrence of product defects due to vent-up due to its growth and solidification or backflow of the carbonized resin.

Further, according to a third aspect of the present invention, in the above structure, an opening / closing lid capable of removing the resin on the bottom plate is provided on the suction box so as to be freely opened and closed. According to the above configuration, the resin overflowing from the side vent port can be easily removed only by scraping the resin from the bottom plate of the vent box, and the maintenance performance can be further improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an embodiment of a sheet forming equipment equipped with a twin screw extruder for a recycled resin, for example, a PET resin according to the present invention will be described with reference to FIGS. As shown in FIG. 3, the sheet forming equipment includes a fixed-quantity feeder 1 that supplies a scrap pulverized raw material from a raw material hopper 2, a twin-screw extruder 3 that plasticizes, melts and kneads the raw material from the fixed-quantity feeder 1, and Vacuum pumps 5A to 5C, which are suction devices for degassing and removing water and other volatile components in the resin (PET resin) through three side vent ports 4A to 4C of the twin screw extruder 3, and twin screw extrusion A screen changer 6 in which the screen for removing impurities disposed at the discharge port of the extruder 3 is exchangeably disposed; a gear pump 7 for discharging a fixed amount of resin at a constant pressure on the discharge side of the twin-screw extruder 3; T to form the molded resin into a sheet
A die 8 and a roll unit 9 having a chill roll or a polishing roll for cooling and solidifying a molten sheet are provided.

The twin-screw extruder 3 has a completely meshing type and co-rotating type 2 in a screw space 12 of a barrel 12.
Strip full flight screws 11A to 11D and resistor 16
A to 16C are rotatably arranged by the rotation drive device 10. 2 full flight screw 11A
Nos. 11D to 11D are shapes shown in FIG. 3, which are small in shear heat generation, easy to control the temperature of the resin, can increase the surface renewability of the resin, and are suitable for melting and kneading the PET resin. In the fully meshing co-rotating type, as the number of flights increases, the melting property and the surface renewability increase, and the deaeration effect is improved. However, since the screw grooves become shallow, the heat generated by shearing increases. For example, in a single flight, the screw groove is deep and generates little shear heat, but the surface renewability of the molten PET resin is small and the degassing effect is low. In addition, since the groove is deep, deterioration due to resin retention is likely to occur at the corner between the flight and the valley. In the case of the Sanjo flight, the surface renewability is sufficient, but since the screw groove is shallow, the shear heat is large and PE
It is difficult to control the temperature of the T resin. For this reason, two full flight screws are employed here.

These full flight screws 11A-1A
The barrel 12 that accommodates 1D in the screw space 12a is
Non-dimensional length from the material supply port 13 to the discharge port 14; L / D = 3
It is set to about 6 to 40. And the twin screw extruder 3
Are provided with first to third kneading units A to C and a metering unit D. A temperature adjusting member (heating device) 15 for cooling and heating is attached to an outer peripheral portion of the barrel 12, and the temperature adjusting member 15 includes, for example, a temperature adjusting member and a cooling water passage.

Further, first to third side vent ports 4A to 4C according to the present invention, which are opened on the side surface of the barrel 12, are formed at three places, and are respectively connected to conduits 22A to 22C in which filters 21A to 21C are interposed. The vacuum pumps 5A to 5A
It is connected to C. These side vent ports 4A-4C
As a result, moisture adhering to the recycled PET resin (PET pulverized product), moisture in the PET resin, and oligomers (deteriorated products and impurities) generated in the melting process are removed.

The side vent ports 4A to 4C are provided with the first
First side vent 4 formed at the downstream end of kneading section A
A, a second side vent 4B formed at the downstream end of the second kneading section B, and a third side vent 4B formed at the downstream end of the third kneading section C.
It consists of a side vent port 4C and is configured identically. That is, these side vent ports 4A to 4C
Is tilted obliquely upward on one side of the barrel 12 at an angle θ = 0 °
It is formed in a range of 60 °. Here, if the angle is 0 ° or less, venting easily occurs due to the weight of the resin, and it is difficult to visually check the vent hole by an operator.If the angle exceeds 60 °, it becomes difficult to provide an inclined bottom plate described later, This is because the backflow of the vent-up resin into the barrel 12 is likely to occur. Also side vent 4
A to 4C are formed only on one side, but the barrel 12
Since the resin filling ratio is 1 or less, the degassing effect is not different from that of the conventional upper vent even if it is on one side. On the contrary, the flow of the resin in the barrel 12 is more stable in the side vents 4A to 4C than in the upper vents, so that the swollen resin grows by being caught on the downstream ends of the side vents 4A to 4C. Is very low, and there is almost no vent up.

The side vent ports 4A to 4C have openings facing the screw space 12a of the barrel 12, and at the upstream end in the screw rotation direction, the gap with the screw is made as small as possible so that the resin can be cut more easily. Is attached to the tongue 21. At the downstream end of the opening, side vent ports 4A to 4C and screw space 12a are provided in order to prevent the resin from being caught and growing due to swelling of the molten resin.
A chamfered portion (undercut portion) 22 is formed by notching the connecting portion at approximately 20 ° to 60 °.

A vent box 23 is attached to and covered by the barrel 12 at the side vent ports 4A to 4C.
In a box shape having 3a, conduits 22A to 22C are connected to ports 24 of a top plate 23b, respectively. The inclined bottom plate 23a is inclined so that the outside is inclined downward from the horizontal,
The resin vented from the side vent port 4 is configured not to return. The front and rear surfaces of the vent box 23 are closed by an end plate 23c, and an openable and closable lid 23d is attached to the outer surface. The openable and closable lid 23d is opened, and a spatula or the like is used to open and close the side vent port 4. It is configured so that the overflowed resin can be easily scraped out. Furthermore, since the liquid condensed on the inner surface of the vent box 23 can flow down onto the bottom plate 23a, it does not return to the screw space 12a again unlike the upper vent type.

In the first kneading section A, a material supply feeder 1 for supplying a fixed amount of pulverized resin material from a material hopper 2 is arranged, and a discharge port of the material supply feeder 1 is connected to an upstream end of a barrel 12. . The pulverized raw material such as a bottle is thin and has a large surface area, has a high heat transfer effect from the temperature control member 15, and has a transparent amorphous state and a softening point of 70.
It is easily softened because it is as low as around ℃. This first kneading section A
In the screw space 12a from the upstream side to the downstream side,
A first full flight screw 11A and a first resistor 16A constituting a first mixing section are arranged, and a first side opposed to an upstream end of a second full flight screw 11B downstream of the first resistor 16A. A vent port 4A is formed. First and second full flight screws 11A, 1
1B can suppress the plasticization and melting of the resin due to mechanical shear energy, and is suitable for melt-kneading a PET resin having a high surface renewal property and a high dehydration effect.

As the first resistor 16A, as shown in FIG. 5, a mixing segment having a stirring effect and a staying effect and having a small shearing heat action is used. For example, L / D =
1.0-1.5D, the number of pins in the length direction is 4-6,
It is appropriate that the number of pins on the circumference is about 8 to 12. If the number of pins increases more, the stirring effect and the retention effect increase, but at the same time, the plasticizing and melting ability also increases, and the resin temperature is kept below the crystal melting temperature to remove only moisture adhering to the surface of the pulverized material. It is difficult. Conversely, if the number of pins in the length direction and the circumferential direction is reduced below this, the stirring effect and the retention effect are weak, and a part of the pulverized raw material may be sucked.

In the vicinity of the first side vent 4A, the moisture adhering to the surface of the pulverized raw material is reduced to the crystal melting temperature (about 255).
° C) or lower, preferably a crystallization temperature (about 185 at elevated temperature).
℃) or lower, no hydrolysis reaction occurs, and dehydration and degassing are performed quickly. Here, the temperature of the barrel 12 by the temperature control member 15 and the shape of the full flight screws 11A and 11B control the resin at a resin temperature equal to or higher than the softening point and equal to or lower than the crystal melting temperature. They are fused and welded to each other to form a so-called porous semi-molten state. At the first side vent port 4A, a low vacuum state of about 200 to 600 Torr (560 to 160 mmHg) is set, and even with this degree, moisture can be sufficiently removed, and steam does not flow back to the feed side. Also, a stable extruded state can be obtained without inhaling the semi-molten pulverized raw material.

In the second kneading section B, the temperature of the barrel 12 is adjusted so that the temperature of the core portion of the pulverized raw material is near the melting point, but the latent heat of evaporation is taken from the first side vent port 4A and the temperature of the resin is reduced. Therefore, the temperature of the barrel 12 by the temperature adjusting member 15 is set to be higher than the melting point of the resin. In the second kneading section B, the resin in which the surface of the pulverized raw material is molten and the core portion is in a semi-molten state is uniformly kneaded, and the resin temperature is controlled so as not to become much higher than the melting point.

The screw space 12a of the second kneading section B
Inside, a second full flight screw 11B and a second resistor 1 forming a second mixing part are arranged from the upstream side to the downstream side.
6B and a third full flight screw 11C. As shown in FIG. 4, the second resistor 16 </ b> B
By using a kneading disc with a creative effect, the resin is weakly kneaded and the sealing effect is enhanced to enhance the deaeration effect. Oligomer contained in the resin is discharged as gas from the resin surface to the outside by the second resistor 16B, and is discharged from the second side vent port 4B to the second vacuum pump 5B.
Is sucked. Here, the ultimate vacuum degree by the second vacuum pump 5B is set to 5 Torr or less.
It is better to be less than rr.

In the resistor 16B of the second kneading section B and the resistor 16C of the next third kneading section C, the resin filling ratio = 1.
(Completely filled) (screw design), so that the screw space 12a facing the second side vent port 4B is sealed, and the degree of vacuum is maintained without leakage. Become. Although the moisture of the resin is almost completely removed up to the second kneading section B, the removal of the oligomer is still incomplete by degassing from the first side vent port 4A and the second side vent port 4B.

The third kneading section C is provided with a third full flight screw 11 from the upstream side to the downstream side in the screw space 12a.
C, a third resistor 16C serving as a third mixing unit, and a fourth full flight screw 11D.
In the third kneading section C, the resin is in a completely molten state,
In order to increase the deaeration effect from the third side vent port 4C without giving excessive mixing, the surface renewal effect is obtained by using a plurality of short kneading disks (third resistor 16C) having no propulsive force. The emphasis is on increasing the degassing effect by increasing the air quality.

And the fourth full flight screw 11D
In the third side vent port 4C formed facing the upstream end of the nozzle, residual moisture and oligomers in the resin are gasified from the surface and fill the screw space 12a, and the third vacuum is supplied from the third side vent port 4C. It is sucked and removed by the pump 5C. The ultimate vacuum degree by the third vacuum pump 5C is 5 Torr or less, but preferably 1 Torr or less.

In the metering portion D, it is effective if the resin that has passed through the third side vent port 4C is directly introduced into the screen and passed therethrough, but the pressure loss of the twin-screw extruder near the third side vent port 4C is effective. If the pressure is increased and the resin is filled, and the resin is supplied to the screen as it is, there is a possibility that the resin filling length is extended due to the pressure loss of the screen and venting occurs. For this reason, it is configured to have a predetermined resin filling length L in order to have a pressure gradient that reduces the resin pressure. In this metering portion D, a fourth full flight screw 11D is incorporated in the screw space 12a, and is configured to keep the resin temperature low (high viscosity) so that the resin is not solidified by the temperature adjusting member 15. .

At the tip of the twin-screw extruder 3, a screen changer 6 having a replaceable screen 6a for removing impurities is provided, and the resin is supplied to a T-die 8 via a gear pump 7. The gear pump 7 is driven at a constant rotation to perform constant-rate extrusion by a T die 8.
The constant supply is performed by keeping the inlet pressure constant. In the above embodiment, a 100% scrap pulverized raw material (for example, bottle pulverized) having a high water content of 2 to 3% from the raw material hopper 2 is supplied to the first extruder 3 of the twin-screw extruder 3 via the quantitative feeder 1.
It is supplied to the kneading section A. The pulverized raw material is heated by the temperature adjusting member 15, and at the same time, the first full-flight screw 11A suppresses mechanical shearing to promote plasticization. First
The mixing and agitation of the resistor 16A suppresses the heat generated by shearing while mixing and agitating the plasticizer to further promote plasticization and melting, thereby leading to semi-melting. And the first side vent port 4
In A, the resin is quickly dewatered and degassed by the first vacuum pump 5A without causing a hydrolysis reaction of the resin and without inhaling the semi-molten pulverized raw material.

Next, in the second kneading section B, the transportation is promoted by the second full flight screw 11B, and further, the kneading disk as the second resistor 16B imparts a weak kneading to the resin and enhances the sealing effect to improve the second side. The degassing effect at the vent 4B is enhanced, and the oligomer contained in the resin is discharged from the resin surface as a gas to the outside,
Further, a second vacuum pump 5B is connected through the second side vent port 4B.
Is removed by suction.

Further, in the third kneading section C, the resin is in a completely molten state, is advanced by the third full flight screw 11C, and is not kneaded unnecessarily by the kneading disk of the third resistor 16C. Surface renewal and stagnation, residual moisture and oligomers in the resin are discharged from the surface as gas to the screw space 12a,
This is effectively degassed from the third side vent port 4C.

In the metering section D, the resin is sent out while being reduced in pressure by the fourth full flight screw 11D, and is supplied from the screen 6a of the screen changer 6 to the T die 8 via the gear pump 7 to form a resin sheet. . And the resin sheet is roll unit 9
Is cooled and solidified. According to the above-described embodiment, the twin-screw extruder 3 is used, and the first to third side vent ports 4A to 4C are respectively formed in the first to third kneading units A to C in three stages in the flow direction.
To remove the moisture and oligomers contained in the resin by suction, so that even if it is a 100% scrap pulverized raw material having a water content of 2 to 3%, it is possible to prevent the intrinsic viscosity (IV value) and the strength physical property values from lowering. It can be extruded well.

Further, the first to third side vents 4A to 4C formed diagonally above the barrel 12 allow the side vents 4A to 4C to be respectively opened while facing the smooth flow of the resin. It is possible to prevent adhesion of the resin and solidification and growth of the resin, thereby preventing vent-up, and satisfactorily deaerate and extrude. In addition, by providing the tongue 21 at the upstream end at the opening facing the screw space 12a of the side vent ports 4A to 4C, the gap between the full flight screws 11B to 11D and the inner surface of the screw space 12a can be reduced as much as possible. Cutting can be improved. Further, since the chamfered portion 22 is formed at the downstream end of the opening, it is possible to prevent the molten resin from being caught and growing due to swelling, and to prevent the occurrence of product defects.

Further, the inclined bottom plate 2 is provided in these side vents 4.
Since each of the vent boxes 23 having the 3a is provided, the resin coming out of the side vent port 4 can be prevented from returning, and the resin on the inclined bottom plate 23a can be easily scraped out from the opening / closing lid 23d using a spatula or the like. be able to. Furthermore, the liquid condensed on the inner surface of the vent box 23 can be retained on the bottom plate 23a, and the screw space 12
a is prevented from occurring, and the occurrence of product defects can be prevented.

[0032]

As described above, according to the first aspect of the present invention, the side vent is provided at a position deviated from the junction where the resin is turned back into the screw accommodating hole at an acute angle. Suction can be performed at a place where the flow is smooth, the resin can be prevented from being caught by swelling to a minimum, and vent up due to the growth of the resin can be prevented. In addition, since the inclined bottom plate is provided in the vent box, it is possible to prevent the resin overflowing from the side vent port and the backflow of the liquid condensed in the vent box,
A uniform and high quality resin can be molded.

According to the second aspect of the present invention, the gap between the screw and the tongue is reduced by the tongue, so that the stagnation of the resin is reduced. In addition, the chamfered portion can prevent the resin from being caught due to swelling, and can prevent the occurrence of product defects due to vent-up due to its growth and solidification or backflow of the carbonized resin.

Further, according to the third aspect of the present invention, the resin overflowing from the side vent can be easily removed only by scraping the resin from the bottom plate of the vent box, and the maintenance performance can be further improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a side bend port showing an embodiment of a twin-screw extruder for a recycled resin according to the present invention.

FIG. 2 is an overall configuration diagram showing the twin-screw extruder.

3A and 3B show a full flight screw of the twin-screw extruder, wherein FIG. 3A is a partial side view and FIG. 3B is a front view.

4A and 4B show a kneading disk of the twin-screw extruder, wherein FIG. 4A is a partial side view and FIG. 4B is a front view.

FIGS. 5A and 5B show a mixing segment of the twin-screw extruder, wherein FIG. 5A is a partial side view and FIG. 5B is a front view.

6 (a) and 6 (b) are cross-sectional views each showing a vent of a conventional twin-screw extruder.

FIG. 7 is an explanatory diagram showing a flow of resin in a conventional twin-screw extruder.

[Explanation of symbols]

 A first kneading section B second kneading section C third kneading section D metering section 1 fixed-quantity feeder 2 raw material hopper 3 twin-screw extruder 4A-4C side vent port 4A-5C vacuum pump 6 screen changer 7 gear pump 8 T die 10 rotation Drive device 11A to 11D Full flight screw 12 Barrel 12a Screw space 13 Raw material supply port 14 Discharge port 15 Temperature control member 16A to 16C Resistor 21 Tongue 22 Chamfer 23 Vent box 23a Inclined bottom plate 23d Opening / closing lid

Continued on the front page (72) Inventor Sadao Sumigaki 1-7-89 Minami Kohoku, Suminoe-ku, Osaka-shi, Osaka F-term (reference) 4F207 AA24 AA29 AA50 AG01 AL16 KA01 KK13 KK64 KL01 KL43 KL45 KL47 KL49 KL84 KL94

Claims (3)

[Claims] A barrel accommodating two screws meshed with each other and rotated in the same direction in a screw space; a plurality of vent ports formed between a material supply port and a discharge port of the barrel; A resistor provided at the vent port upstream of the screw to seal and seal the resin transported by the screw, and a heating device to maintain the resin in the screw space within a predetermined temperature range, wherein the screw is provided at the vent port. In a twin-screw extruder for reclaimed resin provided with a suction device for sucking and removing moisture from a resin in a space, the vent port is formed as a side vent formed obliquely upward on at least one of right and left sides of a barrel; A suction box that covers the mouth is provided, and the suction means is connected to the suction box, and the inclination is inclined downward toward the outside of the vent hole so as to face the top plate. Twin-screw extruder for recycled resin, characterized in that a plate. 2. A tongue for reducing a gap between the screw and a screw is formed at an opening of the vent hole facing the screw accommodating hole on an upstream side in a screw rotating direction, and a chamfer is formed on a downstream side. The twin-screw extruder for recycled resin according to claim 1. 3. The twin-screw extruder for reclaimed resin according to claim 1, wherein said suction box is provided with an openable and closable lid capable of removing the resin on the bottom plate.