JPH02286208A - Biaxial extruder for dehydrate and dry molding of thermoplastic resin - Google Patents

Abstract

PURPOSE:To surely dehydrate even in the case where the moisture content of polymer is large, and enable granulating molding to be performed by providing squeezing parts on at least two positions at predetermined distances on a screw part from the material supplying port of a barrel to a vent hole, and arranging dehydration ports at intervals on the barrel corresponding thereof. CONSTITUTION:A material sent compressedly from a material supplying port 54 by means of a feed screw part 50a is squeezed the water content through a squeezing effect produced at a first squeezing part 50b1 and the water content squeezed is exhausted outside of a barrel 52 from a dehydration port 62. The material sent compressedly again by a following feed screw part 50a is squeezed of the remaining water content through a squeezing effect produced at a first squeezing part 50b2 and the remaining water content squeezed is exhausted in a state of water and steam outside of the barrel 52 from a dehydration port 64. Following this, the temperature rises; as a result, the entire of water content remaining at a vent stuffer 58 is vaporized, and thus, dehydration and dry molding of thermoplastic resin can be performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an apparatus for dehydrating and drying powdered raw materials containing a large amount of water after polymerization, such as ABS resin and MMAvfJ resin. In particular, the present invention relates to a twin-screw extruder that performs dewatering using two or more dewatering ports, and performs I & final drying in a ventilator to achieve granulation molding.

[Conventional technology]

Conventionally, ABS resin and MMAv! ! Thermoplastic resin polymers such as fats contain a large amount of water in their manufactured state. For this reason, conventionally, this type of water-containing polymer was generally dehydrated by hot air drying. However, in this case, a large amount of energy is consumed, and the polymer deteriorates due to being exposed to high temperatures for a long period of time. Further, in this case, even if dehydration was attempted using an extruder, there were problems such as insufficient penetration into the screw of the extruder, insufficient extrusion amount, and insufficient deaeration due to the high water content.

From this point of view, various extruders suitable for dehydrating, degassing, and granulating the water-containing polymer described above have been proposed in the past.

For example, as shown in FIG. 2, there is a first stage in which a feed part 10a, a rotor part 10b, and a slot part 10C are respectively formed toward the forward end of the screw shaft 10, and an intermediate stage connected thereto; The final stage is connected to form a discharge screw part 10d, and has two screw shafts that mesh with each other and rotate in opposite directions.A material supply port 12 is formed at the base end and a discharge port 14 is formed at the distal end. , and is inserted into a cylinder barrel 18 having a vent hole 16 for deaeration attached to the forward side near each slot portion 10C to constitute a twin-screw extruder, and the feed of at least the first stage of this twin-screw extruder is It has been proposed that a slit section 20 for dewatering is provided at the lower part of the cylinder barrel where the section is located (Japanese Patent Application Laid-Open No. 59-214631).

In addition, as shown in FIG. 3, a barrel 30, a screw 40
and a screw drive unit (not shown) as main components, the barrel 30 has a feed barrel 31 that receives material supply, slits 1 to 32 that have slits that allow liquids to pass through but do not allow solids to pass through, and heating Standard barrel 33 with means, pentro 34 for removing volatiles
A pent barrel 35 is provided. and,
The material supplied to the barrel 30 is fed to the feed barrel 3
1 and the forward direction screw 42 and sent forward, the mixture is further sent forward by the standard barrel 33 and the forward direction screw 42, and the mixture sent to the slit barrel 32 part is further sent to the needle provided on the forward screw 40. Back pressure is applied by the ding disk 44 and the reverse thread screw 46, and moisture is discharged from the slit portion to the outside of the thread.
A structure has also been proposed in which the dehydrated polymer is heated and melted in a standard barrel 33, and residual moisture, residual monomer, etc. are vaporized and removed from the system in a pent barrel 35 (Tokuko Sho). 59-37021).

[Problem to be solved by the invention]

However, according to the above-mentioned conventional twin-screw extruder shown in FIG. 2, the two screws are oppositely rotating screws that mesh with each other and rotate in opposite directions. In addition, in the second stage shown in the figure, since the slit section 20 for dehydration is provided at the bottom on the opposite side from the vent hole 16 that performs deaeration, dehydration and deaeration cannot be expected. Since these are carried out almost simultaneously, there are problems in actual dehydration molding, such as operational problems.

Furthermore, according to the conventional apparatus shown in FIG. 3 described above, when manufacturing thermoplastic resin, the slit barrel 32 for dewatering is concentrated in one location of the barrel 30, so when increasing the manufacturing capacity. In this case, for example, when a pent stuffer is provided in the vent hole 34 of the pent barrel 35, there is a risk that the polymer may fly out from the pent stuffer. In other words, if it is concentrated in one place such as the dewatering port, the squeezing effect will actually be in only one place, and if the extrusion amount is increased, the sufficient squeezing effect will not be exerted.
The residual moisture content increases, causing a phenomenon in which the water boils and flies out of the pento stuffer together with the polymer.

Incidentally, for ABS resin powder with a moisture content of 40% or more, the screw rotation speed N5 = 470 ρ1 m, and the extrusion amount Q = = 1
It was confirmed that when the weight was 40 kg/H, a sufficient squeezing effect was not exhibited as described above, making molding difficult.

Note that the device shown in FIG. 3 is not a fully meshing type screw, and moreover, it has two dewatering ports, each of which has a dewatering effect of only one location in the slit.
Therefore, there is a drawback that a sufficient squeezing effect for dehydration cannot be expected.

Therefore, an object of the present invention is to provide a twin-screw extruder for dehydrating and dry molding a thermoplastic resin by providing at least two dehydrating ports and two constricting portions in the barrel to increase the water content of the polymer. To provide a twin-screw extruder for dehydration and dry molding of thermoplastic resin, which can exhibit a sufficient squeezing effect even when the temperature is low, achieve reliable dehydration, and granulate and mold a high-quality resin.

[Means to solve the problem]

The twin-screw extruder for dewatering and drying molding of thermoplastic resin according to the present invention is equipped with twin-screws that mesh with each other and rotate in the same direction. In a twin-screw extruder that is inserted through a barrel without a discharge port at its tip, a screw portion between the material supply port and the vent port of the barrel is provided with at least two constrictions separated by a predetermined distance. , the barrel is characterized in that dewatering ports are spaced apart from each other in correspondence with the constricted portions of these screws.

In the above twin-screw extruder, it is preferable to provide a wedge wire type dewatering screen at each dewatering port of the barrel.

[Effect]

According to the twin screw extruder for dewatering and drying molding of thermal VR plastic resin according to the present invention, from the feed screw part that supplies material to the feed screw part that vents up the molten material, each By providing at least two constricted portions separated by a predetermined distance, and by providing dehydration ports corresponding to these constricted portions and separated by a predetermined distance from each other in the barrel, dewatering of resin powder material with a high moisture content is extremely efficient. can be achieved well.

〔Example〕

Next, embodiments of the twin-screw extruder for dehydration and dry molding of thermoplastic resin according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional side view of essential parts of a typical embodiment of a twin-screw extruder for dehydrating and drying a thermoplastic resin according to the present invention. In FIG. 1, reference numeral 50 is a twin screw;
Reference numeral 2 designates barrels through which the twin screws 50 are inserted.However, in this embodiment, the twin screws are configured to mesh with each other and rotate in the same direction. Further, the barrel 52 is provided with a material supply port 54 at its base end and a discharge port 56 at its distal end. Furthermore, a vent stuffer 58 and a vent hole 60 are provided in the distal end direction of the barrel 52, spaced apart from each other by a predetermined distance.

Therefore, in the twin screw extruder of the present invention, the barrel 5
Feed screw portion 5
Qa is the screw part 50bl with reverse thread.

50b2 are provided in at least two locations spaced apart by a predetermined distance. In addition, in the illustrated example,
Two constricted portions are provided with a predetermined distance between each other. Therefore, in this embodiment, the throttle portions provided at two locations of the twin screw 50 (reverse screw portion 5
0bl, 50b2), dewatering ports 62 and 64 are provided at a predetermined distance apart from each other slightly on the front side (material supply port 54fl!II). In this case, each of the dewatering ports 62 and 64 is equipped with a wedge wire type dewatering screen.

Next, the operation of the twin-screw extrusion (2) of this embodiment configured as described above will be explained.

First, the barrel roller 2 is heated and maintained at a required temperature, and the twin screw 50 is driven to rotate at a required rotational speed 9. Next, ABS resin powder with a water content of 40% is added to the material supply port 54.
The pellets were then molded into pellets. In this case, the material force-fed by the feed screw portion 50a from the material supply port 54 has moisture squeezed out by the throttling action (back pressure) generated at the first throttling portion (50b1) at the dewatering port 50.
2 to the outside of the barrel 52. Then, the material to be pressure-fed by the next feed screw portion 50a is transferred from the dewatering port 64 to the barrel due to the residual moisture squeezed out by the throttling action (back pressure) generated in the second throttling portion (50b2) as water and steam. It is discharged to the outside of 52. Thereafter, the material pumped by the feed screw portion 50a is melted and raised in temperature, and any remaining moisture is vaporized in the vent stuffer 58 and discharged to the outside of the barrel 52. Furthermore, gas components generated by melting of the material being pumped are discharged from the vent 60 to the outside of the barrel 52. In this way, according to the twin-screw extruder of the present invention, it is possible to simply and easily perform dehydration and dry molding of extremely good thermoplastic resins such as ABS resins.

Next, a specific example of molding a thermoplastic resin using the twin-screw extruder of the present invention having the above configuration will be shown in comparison with molding using a conventional device having the configuration shown in FIG. 3, for example. That's right.

Using a drive motor for K plate week 55, the screw was driven at a rotational speed Ns = 470 r, p, n+, and the water content was 4.
Do not mold ABS resin pellets with 0% ABS resin powder. 11 In the twin-screw extruder of the present invention, a wedge wire type dehydration screen was attached to the dehydration port. The results were as follows.

Discharge amount Q "Yuarashi" L Conventional device 140 Present invention (1) 194 Present invention (2) 217 Vent stuffer pellet Relatives from: 3 Vent up good Good good Good good Good [Effects of the invention] From the above-mentioned embodiments As is clear, according to the invention:
Between the feed screw part of the twin-screw that supplies material to the feed screw part that vents the molten material, at least two constricted parts are provided with a predetermined distance between each part, and the constricted parts are By providing the dehydration ports in the barrels at predetermined intervals, it is possible to extremely efficiently dewater resin powder material having a high moisture content.

In particular, according to the twin-screw extruder of the present invention, as is clear from the above experimental example, when molding resin pellets using ABSvfJ fat powder with a water content of 40%, the discharge amount is increased. It was also confirmed that the venting from the vent stuffer and the forming condition of the pellet were extremely good. However, according to the conventional apparatus, the discharge M 140 ktr/H is the limit for ABS resin powder with a moisture content of 40%, and if the moisture content and discharge amount exceed that, molding defects are likely to occur.

Further, according to the twin-screw extruder of the present invention, the use of the vent stuffer becomes unnecessary if water can be sufficiently dehydrated in the second constriction section. That is, if the capacity is about discharge JtQ=190 kf/H, the vent stuffer is not necessary, and the steam is discharged from the second dehydration port portion to fulfill the role of the vent stuffer. Therefore, in this case, by making the vent starrer foot part a back ventro,
Barrel length can be shortened. In addition, it has an energy-saving effect and can be configured as a labor-saving mechanical device. Furthermore, it prevents the contamination of burnt resin due to resin deterioration generated from the vent stuffer, making it possible to use high-quality thermoplastic resin. Molding can be easily realized.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various design changes can be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

Fig. 1 is a cross-sectional side view of essential parts showing an embodiment of a twin-screw extruder for dehydration and dry-brim molding of thermoplastic resin according to the present invention, and Fig. 2 is a cross-sectional side view of the main parts of a twin-screw extruder for dehydrating and dry-molding thermoplastic resin according to the present invention. FIG. 3 is a schematic diagram showing another configuration example of a conventional apparatus for molding thermoplastic resin. 0...Screw shaft 10a...Feed part ob・
...Rotor part 10C...Slot part Od...Discharge screw part 2...Material supply port 14...Discharge port 6...Vent hole 18...Cylinder barrel 0...Slit part O. ... Barrel 31 ... Feed barrel 2.
...Slit barrel 33...Standard barrel 4...Bentro 35...Bent barrel 0...Screw
42... Forward screw 4... Kneading disk 6... Reverse thread screw 0... Twin screw Oa... Feed screw portion 50b1... Reverse thread screw (first constriction part) 50
b2...Reverse thread screw (second throttle part) 52...
・Barrel 54...Material supply port 56...Discharge port 58...Vent staff r

Claims (2)

[Claims] (1) Two screws that are equipped with two screws that mesh with each other and rotate in the same direction, and that these two screws are inserted through a barrel that has a material supply port at its base end and a discharge port at its tip. In the screw extruder, at least two constrictions are provided at a predetermined interval in the screw portion between the material supply port and the vent port of the barrel, and dewatering ports are provided in the barrel corresponding to the constrictions of these screws. A twin-screw extruder for dehydration and dry molding of thermoplastic resin characterized by spaced arrangement. (2) The twin-screw extruder for dehydration and dry molding of thermoplastic resin according to claim 1, wherein a wedge wire type dehydration screen is provided at each dehydration port of the barrel.