JP2002355880A - Kneading/devolatilizing extrusion molding apparatus utilizing supercritical fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To gasify a supercritical fluid from a molten molding compound impregnated with the supercritical fluid while suppressing the deterioration of a polymer and the re-flocculation of a filler to certainly devolatilize the same. SOLUTION: The kneading/devolatilizing extrusion molding apparatus is equipped with a devolatilizing twin-screw extrusion molding machine E for gasifying the supercritical fluid in the molten molding compound impregnated with the supercritical fluid discharge from a discharge pipeline 25 to separate and remove the same and subsequently extruding the molding compound. The devolatilizing twin-screw extrusion molding machine E is constituted so that a supply port 3 provided with a pressure control means 11 is provided to a cylinder 1 on the upstream side thereof, and a downstream open vent port 6a, a first forcible exhaust vent port 7a and a second forcible exhaust vent port 7b are successively provided between the supply port 3 and a die 4 from an upstream side and an upstream open vent port 6b is provided to the upstream region of the supply port 3. A first weir part 5a is provided to the screw 2 in the vicinity of the upstream region of the first forcible exhaust vent port 7a and a second weir part 5b is provided in the vicinity of the upstream region of the second forcible exhaust vent port 7b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a supercritical fluid and a molding material which are melted and kneaded to form a molten molding material impregnated with a supercritical fluid. The present invention relates to a kneading and devolatilizing extrusion molding apparatus using a supercritical fluid, which can gasify a critical fluid and efficiently separate and remove the same to form a high-quality molded product.

[0002]

2. Description of the Related Art A supercritical fluid is used as a molding method for molding materials requiring strict molding conditions, such as a polymer having a small difference between a melting temperature and a thermal decomposition temperature, a heterogeneous polymer blend, and a mixed molding material of a polymer and a filler. Attention has been paid to the melt molding method used.

Next, an example of a conventional melt molding method using a supercritical fluid will be described.

In the conventional melt molding method using a supercritical fluid, a supercritical carbon dioxide gas and a polymer are melted and kneaded by a melting and kneading device such as an autoclave or a screw extruder, and then the atmospheric side vent port is formed. Melting and kneading while suppressing shear heat generation by a devolatilizing extruder such as an intermeshing type twin-screw extruder having a (Japanese Unexamined Patent Publication No.
No. 292981).

[0005]

However, in the above-mentioned conventional technique, for example, in the case of a mixed molding material of a polymer and a filler, carbon dioxide gas is diffused and removed from an atmospheric pressure vent port and then mixed with the mixed molding material. Were found to remain, causing reagglomeration of the filler, deterioration of physical properties, generation of voids, etc., and it became necessary to forcibly devolatilize.

However, carbon dioxide in a supercritical state has the characteristic that when it changes from a supercritical state to a gaseous state due to a decrease in pressure, the solubility in a polymer rapidly decreases. In this case, the following operation is required to prevent re-aggregation of the filler.

(1) The pressure from the outlet of the melting and kneading apparatus to the extruder for devolatilization is maintained at 7.3 MPa or more,
It is necessary to maintain the supercritical state, but for that purpose, immediately before charging the molten polymer to the devolatilizing extruder, install a pressure regulating nozzle and a pressure regulating valve and reduce the resin pressure in the devolatilizing extruder at once It is desirable.

(2) It is necessary to reduce the resin temperature from the outlet of the melting and kneading apparatus to the extruder for devolatilization as much as possible to suppress reaggregation of the filler.

Therefore, when the above operations (1) and (2) are applied as they are, the pressure rapidly drops from a high pressure, so that the carbon dioxide gas expands rapidly, and the resin temperature decreases and the carbon dioxide gas is reduced. There is a loss of plasticizing effect caused by separation from the molten polymer and an increase in viscosity due to an increase in freezing point. As a result, since bubbles of carbon dioxide gas are included in the high-viscosity molten polymer, the volume is increased, and the feeding ability of the molten polymer in the devolatilizing extruder is significantly reduced, and it is necessary to increase the feeding ability. To increase the feed capacity of the devolatilizing extruder by increasing the screw rotation speed of the devolatilizer will apply more shear force than necessary to the molten polymer after devolatilization, and the polymer will increase as the resin temperature rises. However, there is a problem that deterioration of the filler and re-aggregation of the filler are caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to provide a supercritical fluid from a molten molding material impregnated with a supercritical fluid while suppressing polymer deterioration and filler reaggregation. It is an object of the present invention to realize a kneading and devolatilizing extrusion apparatus using a supercritical fluid, which can gasify a fluid and reliably devolatilize the fluid.

[0011]

In order to achieve the above object, a kneading and devolatilizing extrusion molding apparatus using a supercritical fluid according to the present invention provides a supercritical fluid for melting and kneading a supercritical fluid and a molding material. A fluid melting / kneading device, and after the supercritical fluid in a molten molding material impregnated with a supercritical fluid discharged from a discharge conduit of the supercritical fluid melting / kneading device is gasified and separated and removed. A kneading and devolatilizing extrusion molding apparatus using a supercritical fluid including a devolatilizing twin-screw extruder for extruding, wherein the devolatilizing twin-screw extruder includes a cylinder,
Two screws rotatably disposed in the cylinder, a supply port provided with a pressure regulating means provided upstream of the cylinder, and a die disposed at the downstream end of the cylinder. The cylinder has a downstream open vent port and at least one forced exhaust vent port between the supply port connected to the discharge pipe line and the die in order from the upstream side to the downstream side. Are provided at an interval from each other, and an upstream opening vent port is provided at an upstream portion of the supply port, and each of the screws has a weir at a portion near the upstream side of the forced exhaust vent port. Parts are provided.

Further, each screw in the devolatilizing twin-screw extruder is provided with a deep groove forward flight at a portion corresponding to the upstream open vent port.

Further, the weir portion in the devolatilizing twin-screw extruder is made of an inverse kneading disk or a seal ring.

In addition, each screw in the devolatilizing twin-screw extruder is provided with a combination of a forward flight and a forward kneading disc at a portion corresponding to a downstream open vent port.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of a kneading and devolatilizing extrusion molding apparatus using a supercritical fluid will be described with reference to the drawings.

As shown in FIG. 1, in the kneading and devolatilizing extrusion molding apparatus using a supercritical fluid according to the present embodiment, the supercritical fluid and the molding material are melted and kneaded to be impregnated with the supercritical fluid. A supercritical fluid melting / kneading device (not shown) for forming a melt molding material, and a supercritical fluid supplied through the discharge line 25 of the supercritical fluid melting / kneading device. And a devolatilizing twin-screw extruder E capable of forming a high-quality molded product by gasifying and removing a supercritical fluid.

Here, the melting and kneading apparatus for supercritical fluid is as follows:
As long as the supercritical fluid and the molding material are melted and kneaded, and the supercritical fluid is impregnated with the molten molding material and can be discharged from the discharge pipe while maintaining the supercritical fluid state, any type can be used.

The devolatilizing twin-screw extruder E has a cylinder 1 heated by a heating means (not shown), and two screws 2 rotatably disposed in the cylinder 1. Pressure control means 1 such as a pressure control valve and a pressure control nozzle
A supply port 3 is provided, and a die 4 is provided at the downstream end of the cylinder 1.

In the cylinder 1, a downstream open vent port 6a, a first forced exhaust vent port 7a and a second forced exhaust vent port are sequentially provided from the supply port 3 side connected to the discharge pipe line 25 to the die 4 side. 7b are provided at intervals from each other, and an upstream open vent port 6 is provided upstream of the supply port 3.
b is provided. And the first forced exhaust vent 7
a and the second forced exhaust vent 7b are connected to the branch pipes 9a, 9b.
Is connected to one end of the suction pipe 8, and the other end of the suction pipe 8 is connected to vacuum generating means such as a vacuum pump 10. The branch pipes 9a and 9b are provided with adjusting means 12a and 12b such as a flow control valve and a flow control nozzle in order to adjust the exhaust capacity of each of the forced exhaust vents 7a and 7b.
Is attached.

On the other hand, each screw 2 is provided with a first weir portion 5a near the upstream side of the first forced exhaust vent 7a, and a portion near the upstream side of the second forced exhaust vent 7b. Is provided with a second weir portion 5b.

Next, the operation of the kneading and devolatilizing extrusion molding apparatus using a supercritical fluid according to the present embodiment will be described.

A discharge pipe 25 is connected to the supply port 3 provided with the pressure regulating means 11, and a molten molding material impregnated with a supercritical fluid is supplied through the discharge pipe 25. The molten molding material impregnated with the supercritical fluid in the discharge conduit 25 is maintained at a high pressure (7.3 MPa or more in the case of carbon dioxide gas), and is rapidly reduced to a low pressure close to the atmospheric pressure by the pressure regulating means 11. The pressure is reduced and introduced into the cylinder 1.

The molten molding material impregnated with the supercritical fluid is:
When the supercritical fluid is introduced into the cylinder 1 after passing through the pressure regulating means 11, the supercritical fluid gasifies at a stretch and foams to increase the volume rapidly. At that time, a part of the air bubbles breaks and separates into a space in the cylinder 1 and a part of the air bubbles flows upstream in the cylinder 1 and is radiated to the atmosphere from the upstream open vent port 6b. Most of them are transferred to the downstream side while being contained in the molten molding material.

The molten molding material transferred from the supply port 3 to the downstream side is supplied to the first weir section 5a (gas separation section A).
The bubbles of the supercritical fluid elongated and gasified by the surface renewal function by the rotation of the screw are broken and separated, and a downstream open vent between the supply port 3 and the first weir part 5a (gas separation part A). It is released from the mouth 6a to the outside of the machine. Along with this, the volume of the molten molding material is reduced, and the resin feeding ability in the devolatilizing twin-screw extruder E is maintained at a high state.
As a result, the first weir portion 5 can be formed without increasing the screw rotation speed.
Since a can pass through, the melt-molded material after devolatilization does not needlessly exert a shearing force to increase the temperature, thereby preventing polymer deterioration and filler re-aggregation.

The molten molding material that has passed through the first weir 5a is gasified and remains from the first forced exhaust vent 7a between the first weir 5a and the second weir 5b (first decompression unit B). The supercritical fluid and the volatile components contained in the molding material are forcibly exhausted, and further remain from the second forced exhaust vent port 7b between the second weir section 5b and the die 4 (second decompression section C). The gasified supercritical fluid and the volatile components contained in the molding material are forcibly evacuated and then extruded from the die 4.

The number of forced exhaust vents is not limited to the two described above, but can be increased or decreased depending on the situation of devolatilization. However, L / D increases as the number of forced exhaust vents increases.
Becomes longer, and if it is increased more than necessary, resin degradation and filler
It is preferable to use one or two places because reagglomeration of the particles easily occurs.

In the present invention, the devolatilizing twin-screw extruder preferably has a self-cleaning property. Preferably, each screw in the devolatilizing twin-screw extruder is provided with a deep groove forward flight at a position upstream of the supply port, that is, at a position corresponding to the upstream open vent. On the other hand, the screw shape in the gas separation section A from which the gasified supercritical fluid is released from the downstream side open vent port 6a has the ability to send to the downstream side like a forward flight screw or a forward kneading disk. However, if possible, it is preferable to use a combination of a forward flight screw having a high ability to feed and stretch to form a thin film and a kneading disk having a high surface renewal ability, in order to maintain the feeding ability and avoid shear heat generation.

The weir portion may be any of seal rings, gate valves, rotary gate valves, reverse kneading disks, reverse flight disks, etc., as long as they block the flow of the molten molding material and provide a sealing function. However, an inverted kneading disc or a seal ring having a simple mechanism and low shearing force is preferable. When a kneading disk is used in the separation section, it is preferable to use a seal ring, a gate valve, or the like that is not easily sheared, in order to suppress a rise in resin temperature as much as possible.

Further, the vacuum generating means for forcibly exhausting the gas from the forced exhaust vent port is not limited to a vacuum pump, but may be any other known means such as an aspirator, a blower or the like, as long as the pressure can be adjusted so that the molten molding material does not vent up. Can be used.

Next, a kneading and devolatilizing extrusion molding apparatus using a supercritical fluid according to another embodiment will be described.

The kneading and devolatilizing forming apparatus using a supercritical fluid according to the present embodiment, as shown in FIG. 2, as devolatilization twin-screw extruder E _1, downstream open vent 6a of the cylinder 1 the used one provided a forced exhaust vent 7 at one place downstream, it is obtained by connecting the discharge line 25 of the melt for the supercritical fluid to the supply port 3 of the cylinder 1 and kneading apparatus E _2.

The devolatilizing twin-screw extruder E ₁ is the same as the devolatilizing twin-screw extruder E shown in FIG. 1 except that the forced exhaust vent port 7 is provided at one place. The same reference numerals are given to the portions and the description is omitted.

The supercritical fluid melting / kneading apparatus E ₂ has a twin-screw extruder 20 in which two screws 22 are rotatably arranged in a cylinder 21, and a blowing side connected to the tip of the cylinder 21. It has a gear pump 24 and a discharge pipe 25 having one end connected to the discharge side of the gear pump 24, and sequentially from the supply part side where the hopper 23 is provided to the gear pump side, a transport part, a melting part, a kneading / mixing part, It has a discharge unit.

A kneading disk 22a is provided at a position corresponding to the kneading / mixing section of each screw 22, and a backflow preventing means such as a seal ring or a gate valve is provided at a position near the upstream side of the kneading disk 22a. 26 are provided.

A supercritical fluid injection port 27 is provided at a position corresponding to the kneading / mixing section of the cylinder 21. The supercritical fluid injection port 27 is connected to the flow control valve 3
1. It is connected to a supercritical fluid generator 28 via a supply pipe 30 in which a flow meter and the like are interposed.

Here, the supercritical fluid generator 28 is capable of generating a supercritical fluid by making an inert gas such as carbon dioxide gas or nitrogen gas stored in a cylinder 29 higher than a critical pressure and a critical temperature. Any type is acceptable.

Incidentally, in the case of carbon dioxide gas, the critical temperature 3
It becomes a supercritical fluid at 1.1 ° C. and a critical pressure of 7.38 MPa or more. In the case of nitrogen gas, it becomes a supercritical fluid at a critical temperature of −147 ° C. and a critical pressure of 3.4 MPa or more.

Example 1 A kneading and devolatilizing extrusion molding apparatus using a supercritical fluid having the same structure as that shown in FIG. 2 was used.

A twin-screw extruder (manufactured by Nippon Steel Works, Ltd.) was prepared by mixing a molding material obtained by mixing 15% by weight of a master batch resin obtained by mixing a filler with 85% by weight of general-purpose polypropylene.
X30α, L / D42, pressure-resistant hopper) 15kg
/ H and injected at a rate of / h and melted, and then brought into a supercritical state from a supercritical fluid inlet (62 ° C, 9 MPa)
Was added so that the addition amount was 6% by weight, and the mixture was sufficiently kneaded. At this time, the resin pressure in the cylinder is 9-11MP
a, The resin temperature before the gear pump was 170 ° C to 180 ° C. The supercritical state of the molten molding material impregnated with the supercritical fluid discharged from the gear pump into the discharge line is maintained in the discharge line, and the resin temperature before the pressure regulating valve is 1.
At 65 ° C., the resin pressure was 8 MPa.

The molten molding material impregnated with the supercritical fluid is devolatilized by a twin-screw extruder (Nippon Steel Works, TEX30α, L /
D42, crevice: reverse kneading disc 0.5D installed), and operated by rotating the screw at 90 rpm. After the molten molding material came out of the die stably, the screw was rotated. The number was set to 74 rpm, and a vacuum pump (manufactured by Anlet Co., Ltd., dry system) was operated to gradually lower the pressure at the forced vent port (decompression section) so as not to vent up from the supply port, thereby releasing devolatilization. At this time, the pressure gauge at the forced vent port (decompression section) is -98.
Kpa (-760 mmHg).

After 20 minutes, when the amount of gas exhausted from the open vent port was measured by the underwater replacement method, about 100 L / h of gas was discharged from the upstream open vent port on the upstream side of the supply port to the downstream side on the downstream side of the supply port. Approx. 500L from the side vent
/ H of gas was released. The resin temperature at this time is
It was 181 ° C. at the exit of the die.

Table 1 also shows the results when supercritical carbon dioxide gas was similarly injected so that the addition amount was 3% by weight.

[0043]

[Table 1]

The MFR value of the molded article (abbreviation of Melt Flow Rate, which indicates the fluidity of the molten resin. The MFR of polypropylene is usually measured at 230 ° C. under a load of 2.16 kg under a load of 2.16 kg). Shows almost the same value as the MFR value of the filler, no decrease in viscosity due to residual gas has occurred, and bubbles were found around or around the filler by observation of the molded product using a scanning electron microscope (SEM). From this, it was confirmed that carbon dioxide in the resin was completely removed.

(Comparative Example 1) The same test as in Example 1 was performed except that the downstream open vent of the devolatilizing twin-screw extruder used in Example 1 was closed with blind metal.

However, when a molten molding material impregnated with supercritical carbon dioxide gas is flowed, the penetration of the resin downstream of the supply port in the devolatilizing twin-screw extruder is poor, so that the resin pressure in the discharge pipe increases, and Since the molten molding material began to leak from the connection between the pressure regulating valve and the devolatilizing twin-screw extruder, the screw speed of the devolatilizing twin-screw extruder was increased from 74 rpm to 111 rpm to secure the transfer capacity.

The amount of supercritical carbon dioxide added is 6% by weight.
In the case of, since a bursting sound was periodically heard from the downstream open vent, the carbon dioxide gas that had lost its escape area intermittently moved upstream along with the molten molding material toward the open vent. It was inferred that the transfer of the molten molding material became unstable. Furthermore, the metal opening of the vent port in the decompression section vented up, was gradually closed by the molten molding material, and had to be periodically cleaned.

In the same manner, the results obtained when supercritical carbon dioxide gas was injected so that the added amount became 3% by weight are shown in Table 2 together.
Shown in

[0049]

[Table 2]

From the MFR value and SEM observation of the molded product,
Although it was confirmed that carbon dioxide was removed from the molded article, the MFR value was 0.3 to 0.8 as compared with the value of Example 1.
When the molecular weight distribution was high and the molecular weight distributions were compared, broadening was confirmed, indicating that polymer degradation had occurred.

(Comparative Example 2) The same test as in Example 1 was conducted except that the upstream open vent of the devolatilizing twin-screw extruder used in Example 1 was closed with blind metal.

When the molten molding material impregnated with the supercritical carbon dioxide gas was flowed, the penetration of the resin downstream of the supply port in the devolatilizing twin-screw extruder was poor, though not as much as in Comparative Example 1.

However, since the resin pressure in the discharge pipe began to rise, the screw rotation speed of the devolatilizing twin-screw extruder was reduced to 74 rpm.
pm to 89 rpm to ensure transfer capacity.

The amount of supercritical carbon dioxide added was 6% by weight.
In the case of, a bursting sound was periodically heard from the downstream open vent, and the molten molding material began to vent little by little.
Increased to 11 rpm to avoid vent up.

Table 3 also shows the results obtained when supercritical carbon dioxide gas was injected so that the addition amount was 3% by weight.
Shown in

[0056]

[Table 3]

[0057]

Since the present invention is configured as described above, the following effects can be obtained.

From the melt molding material impregnated with the supercritical fluid, the deterioration of the polymer can be suppressed and the gasified supercritical fluid and volatile components can be completely devolatilized efficiently, and the deterioration of the polymer and the filler Without re-aggregation,
High quality molded products can be manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a devolatilizing twin-screw extruder according to an embodiment.

FIG. 2 is an explanatory diagram of a kneading / mixing extrusion molding apparatus using a supercritical fluid using a devolatilizing twin-screw extruder according to another embodiment.

[Explanation of symbols]

 1, 21 cylinder 2, 22 screw 3 supply port 4 die 5 weir 5a first weir 5b second weir 6a downstream open vent 6b upstream open vent 7 forced exhaust vent 7a first forced exhaust vent 7b Second forced exhaust vent port 8 Suction line 9a, 9b Branch line 10 Vacuum pump 11 Pressure adjusting unit 12a, 12b Adjusting unit 20 Twin screw extruder 23 Hopper 24 Gear pump 25 Discharge line 26 Backflow prevention unit 27 Supercritical Fluid inlet 28 Supercritical fluid generator 29 Cylinder 30 Supply line 31 Flow control valve 32 Flow meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuaki Yamachika 1-6-1, Funakoshi Minami, Aki-ku, Hiroshima-shi, Hiroshima Japan Steel Works Co., Ltd. (72) Inventor Toru Emi 1-chome, Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima No. 6 No. 1 F term in Japan Steel Works, Ltd. (reference) 4F201 AA11 AB11 AB16 BA01 BC02 BC12 BC33 BC37 BD05 BK02 BK13 BK27 BK36 BK40 BK49 BK75 4F207 KA01 KB21 KF03 KK13 KL05 KL22 KL47

Claims (4)

[Claims] 1. A supercritical fluid melting / kneading device (E ₂ ) for melting / kneading a supercritical fluid and a molding material, and a discharge line (25) of the supercritical fluid melting / kneading device. A supercritical fluid provided with a devolatilizing twin-screw extruder (E, E ₁ ) for gasifying, separating and removing the supercritical fluid in the molten molding material impregnated with the discharged supercritical fluid, and extruding the gas; A kneading and devolatilizing extrusion molding apparatus using a fluid, wherein the devolatilizing twin-screw extruder comprises a cylinder (1) and two screws (2) rotatably disposed in the cylinder.
And pressure regulating means (1) provided on the upstream side of the cylinder.
1) a supply port (3) attached thereto; and a die (4) disposed at a downstream end of the cylinder. The cylinder includes: a supply port connected to the discharge pipe; A downstream open vent port (6a) and at least one forced exhaust vent port (7, 7a, 7b) are sequentially provided between the die and the downstream from the upstream side to the downstream side. At the same time, an upstream open vent port (6b) is provided at an upstream portion of the supply port, and each screw has a weir portion (5, 5a, 5b) at a location near the upstream side of the forced exhaust vent port. Is a kneading and devolatilizing extrusion molding apparatus using a supercritical fluid. 2. Each of the screws (2) in the devolatilizing twin-screw extruder (E, E ₁ ) has an upstream open vent port (6b).
2. A kneading and devolatilizing extrusion molding apparatus using a supercritical fluid according to claim 1, wherein a deep groove forward flight is provided at a portion corresponding to (1). 3. The devolatilizing twin-screw extruder (E, E ₁ ), wherein the weirs (5, 5a, 5b) comprise an inverse kneading disc or a seal ring. Kneading and devolatilizing extrusion equipment using supercritical fluid. 4. Each of the screws (2) in the devolatilizing twin-screw extruder (E, E ₁ ) has a downstream open vent port (6a).
4. A kneading / mixing process using a supercritical fluid according to claim 1, wherein a combination of a forward flight and a forward kneading disc is provided at a portion corresponding to
Devolatilization extrusion molding equipment.