Screw apparatus and method for supplying reinforcing fiber-containing molten resin using the apparatus
A screw apparatus comprises a melting extruder for melting a resin; a screw unit for kneading molten resin and reinforcing fibers to obtain a reinforcing fiber-containing molten resin and supplying it; and a mixer in which at least a part of the reinforcing fibers attach to the molten resin which is extruded from the melting extruder and flows down owing to gravity in an open space, and then the reinforcing fibers and the molten resin are fed into the screw unit.
| Inventors: | Matsumoto; Masahito (Ibaraki, JP), Kitayama; Takeo (Takatsuki, JP) |
| Assignee: | Sumitomo Chemical Company, Limited (Osaka, JP) |
| Appl. No.: | 08/541,456 |
| Filed: | October 10, 1995 |
| Oct 12, 1994 [JP] | 6-246590 | |||
| Nov 29, 1994 [JP] | 6-295249 | |||
| Nov 29, 1994 [JP] | 6-295250 | |||
| Jan 23, 1995 [JP] | 7-008270 | |||
| Current U.S. Class: | 366/76.1 ; 366/76.3; 366/76.6; 366/76.7; 366/76.9; 366/78; 366/91 |
| Current International Class: | B29C 45/18 (20060101); B29C 45/60 (20060101); B29C 47/00 (20060101); B29C 45/58 (20060101); B29C 47/10 (20060101); B29C 47/50 (20060101); B29C 47/60 (20060101); B29C 47/38 (20060101); B29C 47/64 (20060101); B27N 003/04 (); B28C 007/16 (); B28C 007/10 () |
| Field of Search: | 366/69,76.1,76.3,76.4,76.5,76.6,76.7,76.9,76.91,76.92,78,91,97,98,99 264/328.18,328.5 425/205 |
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| 1-286824 | Nov., 1989 | JP |
| 2-153714 | Jun., 1990 | JP |
| 2-235613 | Sep., 1990 | JP |
| 3-93510 | Apr., 1991 | JP |
| 4-286617 | Oct., 1992 | JP |
| 6-8278 | Jan., 1994 | JP |
| 491 731 | Jul., 1970 | CH |
Patent Abstracts of Japan, vol. 009, No. 303 (M-434) (Nov. 1985) & JP-A-60 141519. . Patent Abstracts of Japan, vol. 008, No. 050 (M-281) (Mar. 1984) & JP-A-58 203030. . Patent Abstracts of Japan, vol. 95, No. 002 & JP-A-07 052185 (Feb. 1995). . Patent Abstracts of Japan, JP-A-7001449, (Jan. 1995).. |
Primary Examiner: Jenkins; Robert W. Attorney, Agent or Firm: Cushman Darby & Cushman IP Group of Pillsbury Madison & Sutro, LLP
What is claimed is:
1. A screw apparatus comprising:
a melting extruder comprising a barrel which has a resin material inlet provided on a first end portion side thereof and a molten resin outlet provided on a second end portion side thereof, said second end portion being opposite to the first end portion, an extruding means positioned in the barrel, a driving means connected to the extruding means and a barrel heater for heating the barrel;
a screw unit comprising a cylinder having a feed opening provided on a first end portion side thereof and positioned under the molten resin outlet and an outlet provided on a second end portion side thereof, said second end portion being opposite to the first end portion, a screw inserted in the cylinder, a driving unit connected to the screw, and a cylinder heater for keeping the cylinder at a given temperature; and
a mixer which is positioned between the molten resin outlet and the feed opening, which has a reinforcing fiber inlet, which defines a space through which reinforcing fibers fed from the reinforcing fiber inlet flow down owing to gravity together with molten resin extruded from the molten resin outlet and then the reinforcing fibers and the molten resin are fed to the feed opening, and in which at least a part of the reinforcing fibers attach to the molten resin flowing down owing to gravity in an open space.
2. A screw apparatus according to claim 1, wherein a compression ratio in the screw unit is 4 or less and an apparent shear rate in the screw unit is 100 sec.sup.-1 or less.
3. A screw apparatus according to claim 1, wherein an apparent shear rate and a compression ratio in the screw unit are smaller than an apparent shear rate and a compression ratio in the melting extruder, respectively.
4. A screw apparatus according to claim 1, wherein the screw has a feed zone having a first screw channel depth, a compression zone connecting to the feed zone and having a screw channel depth which changes from the first screw channel depth to a second screw channel depth smaller than the first screw channel depth and a metering zone connecting to the compression zone and having the second screw channel depth, ratio of length of the feed zone, that of the compression zone and that of the metering zone being in a range of 1.5-2.5:0.8-1.5:1, and ratio (L/D) of length (L) of the screw and diameter (D) of the screw being 20 or more.
5. A screw apparatus according to claim 1, wherein the screw has a flight having a flight pitch of 1 to 1.3 times as large as diameter (D) of the screw.
6. A screw apparatus according to claim 1, wherein the screw has a mixing head at a tip thereof.
7. A screw apparatus according to claim 1, wherein the screw unit is a single screw injection machine having a single reciprocating-screw and the driving unit has a motor for rotating the screw and a pressing unit for pushing the screw in longitudinal direction thereof toward the second end portion.
8. A screw apparatus according to claim 1, wherein the screw unit is a single screw extruder having a single screw and the driving unit has a motor for rotating the screw.
9. A screw apparatus according to claim 1, wherein the mixer further comprises:
a nozzle provided with a first opening connected to the molten resin outlet, and a second opening provided at a bottom or side face thereof and communicating with the first opening through a resin passage, said second opening being at least one opening selected from a rectangular hole, a ring-shaped hole and a group of small holes; and
a chute for guiding the reinforcing fibers fed from the reinforcing fiber inlet to around the molten resin extruded from the nozzle and flowing down.
10. A screw apparatus according to claim 1, wherein the mixer further comprises a nozzle provided with a first opening connected to the molten resin outlet, a second opening provided at a bottom thereof and communicating with the first opening through a resin passage, said second opening being a ring-shaped hole, a third opening functioning as the reinforcing fiber inlet, and a fourth opening provided inside the second opening and communicating with the reinforcing fiber inlet through a fiber passage.
11. A screw apparatus according to claim 1, wherein the mixer further comprises:
a nozzle provided with a first opening connected to the molten resin outlet, a second opening provided at a bottom thereof and communicating with the first opening through a resin passage, said second opening being a ring-shaped hole, a third opening functioning as the reinforcing fiber inlet, and a fourth opening provided inside the second opening and communicating with the reinforcing fiber inlet through a fiber passage;
a nozzle heater for keeping the nozzle at a given temperature; and
a pair of rollers which is positioned under the second and fourth openings and presses a ring-shaped molten resin extruded and flowing down from the nozzle together with reinforcing fibers being inside the ring-shaped molten resin to obtain a sheet-like molten resin having the reinforcing fibers sandwiched therebetween.
12. A screw apparatus according to claim 11, wherein the mixer further comprises:
a resin cutter positioned between the nozzle and the rollers for cutting the ring-shaped molten resin extruded and flowing down from the nozzle;
a hopper for guiding the reinforcing fibers to the reinforcing fiber inlet; and
a valve for adjusting a pressure of molten resin passing through the resin passage in the nozzle.
13. A screw apparatus according to claim 1, wherein the mixer further comprises a fiber cutter for cutting reinforcing long fibers to obtain reinforcing fibers having a given length and then introducing the reinforcing fibers in scattered state into the reinforcing fiber inlet, said fiber cutter being positioned above the reinforcing fiber inlet.
14. A screw apparatus according to claim 1, wherein the melting extruder is a single screw extruder having a single extrusion screw, and the driving means has a motor for rotating the extrusion screw.
15. A screw apparatus according to claim 1, which further comprises an accumulator provided between the melting extruder and the mixer and having an accumulator inlet connected to the molten resin outlet and an accumulator outlet connected to the mixer.
16. A screw apparatus according to claim 1, wherein the feed opening has an opening width being equal to or more than an inner diameter of the cylinder, said opening width being a length of the feed opening in a direction perpendicular to longitudinal direction of the cylinder; and
an introduction space which extends to below a horizontal plane passing a central axis of the screw is formed between an outer peripheral face of the screw and a cylinder internal face continuing to a cylinder side wall which defines the feed opening, said side wall being on a side where an outer peripheral part of the screw which has temporarily left from a cylinder internal face at the feed opening again approaches to the cylinder internal face while the screw is rotating.
17. A screw apparatus according to claim 1, which further comprises:
a pushing rod positioned along a cylinder side wall which defines the feed opening, said side wall being parallel to longitudinal direction of the cylinder, and having a face facing to an outer peripheral face of the screw; and
a rod driving mechanism which reciprocates the pushing rod up and down.
18. A mixing unit comprising: a melting extruder comprising a barrel which has a resin material inlet provided on a first end portion side thereof and a molten resin outlet provided on a second end portion side thereof, said second end portion being opposite to the first end portion, an extruding means positioned in the barrel, a driving means connected to the extruding means and a barrel heater for heating the barrel; and
a mixer which is connected to the molten resin outlet, which has a reinforcing fiber inlet, which defines a space through which reinforcing fibers fed from the reinforcing fiber inlet flow down owing to gravity together with molten resin extruded from the molten resin outlet, and in which at least a part of the reinforcing fibers attach to the molten resin flowing down owing to gravity in an open space.
19. A mixing unit according to claim 18, wherein the mixer further comprises:
a nozzle provided with a first opening connected to the molten resin outlet, and a second opening provided at a bottom or side face thereof and communicating with the first opening through a resin passage, said second opening being at least one opening selected from a rectangular hole, a ring-shaped hole and a group of small holes; and
a chute for guiding the reinforcing fibers fed from the reinforcing fiber inlet to around the molten resin extruded from the nozzle and flowing down.
20. A mixing unit according to claim 18, wherein the mixer further comprises a nozzle provided with a first opening connected to the molten resin outlet, a second opening provided at a bottom thereof and communicating with the first opening through a resin passage, said second opening being a ring-shaped hole, a third opening functioning as the reinforcing fiber inlet, and a fourth opening provided inside the second opening and communicating with the reinforcing fiber inlet through a fiber passage.
21. A mixing unit according to claim 18, wherein the mixer further comprises:
a nozzle provided with a first opening connected to the molten resin outlet, a second opening provided at a bottom thereof and communicating with the first opening through a resin passage, said second opening being a ring-shaped hole, a third opening functioning as the reinforcing fiber inlet, and a fourth opening provided inside the second opening and communicating with the reinforcing fiber inlet through a fiber passage;
a nozzle heater for keeping the nozzle at a given temperature; and
a pair of rollers which is positioned under the second and fourth openings and presses a ring-shaped molten resin extruded and flowing down from the nozzle together with reinforcing fibers being inside the ring-shaped molten resin to obtain a sheet-like molten resin having the reinforcing fibers sandwiched therebetween.
22. A mixing unit according to claim 21, wherein the mixer further comprises:
a resin cutter positioned between the nozzle and the rollers for cutting the ring-shaped molten resin extruded and flowing down from the nozzle;
a hopper for guiding the reinforcing fibers to the reinforcing fiber inlet; and
a valve for adjusting a pressure of molten resin passing through the resin passage in the nozzle.
23. A mixing unit according to claim 18, wherein the mixer further comprises a fiber cutter for cutting reinforcing long fibers to obtain reinforcing fibers having a given length and then introducing the reinforcing fibers in scattered state into the reinforcing fiber inlet, said fiber cutter being positioned above the reinforcing fiber inlet.
24. A mixing unit according to claim 18, wherein the melting extruder is a single screw extruder having a single extrusion screw, and the driving means has a motor for rotating the extrusion screw.
25. A mixing unit according to claim 18, which further comprises an accumulator provided between the melting extruder and the mixer and having an accumulator inlet connected to the molten resin outlet and an accumulator outlet connected to the mixer.
26. A screw unit comprising a cylinder having a feed opening provided on a first end portion side thereof and an outlet provided on a second end portion side thereof, said second end portion being opposite to the first end portion, a screw inserted in the cylinder, a driving unit connected to the screw, and a cylinder heater for keeping the cylinder at a given temperature, in which a compression ratio is 4 or less, and an apparent shear rate is 100 sec.sup.-1 or less.
27. A screw unit according to claim 26, wherein the screw has a feed zone having a first screw channel depth, a compression zone connecting to the feed zone and having a screw channel depth which changes from the first screw channel depth to a second screw channel depth smaller than the first screw channel depth and a metering zone connecting to the compression zone and having the second screw channel depth, ratio of length of the feed zone, that of the compression zone and that of the metering zone being in a range of 1.5-2.5:0.8-1.5:1, and ratio (L/D) of length (L) of the screw and diameter (D) of the screw being 20 or more.
28. A screw unit according to claim 26, wherein the screw has a flight having a flight pitch of 1 to 1.3 times as large as diameter (D) of the screw.
29. A screw unit according to claim 26, wherein the screw has a mixing head at a tip thereof.
30. A screw unit according to claim 26, wherein the screw unit is a single screw injection machine having a single reciprocating-screw and the driving unit has a motor for rotating the screw and a pressing unit for pushing the screw in longitudinal direction thereof toward the second end portion.
31. A screw unit according to claim 26, wherein the screw unit is a single screw extruder having a single screw and the driving unit has a motor for rotating the screw.
32. A screw unit according to claim 26, wherein the screw unit further comprises a mixer which is positioned above the feed opening, which has a molten resin inlet and a reinforcing fiber inlet, which defines a space through which reinforcing fibers fed from the reinforcing fiber inlet flow down owing to gravity together with molten resin fed from the molten resin inlet and then the reinforcing fibers and the molten resin are fed to the feed opening, and in which at least a part of the reinforcing fibers attach to the molten resin flowing down owing to gravity in an open space.
33. A screw unit according to claim 32, wherein the mixer further comprises:
a nozzle provided with a first opening functioning as the molten resin inlet, and a second opening provided at a bottom or side face thereof and communicating with the first opening through a resin passage, said second opening being at least one opening selected from a rectangular hole, a ring-shaped hole and a group of small holes; and
a chute for guiding the reinforcing fibers fed from the reinforcing fiber inlet to around the molten resin extruded from the nozzle and flowing down.
34. A screw unit according to claim 32, wherein the mixer further comprises a nozzle provided with a first opening functioning as the molten resin inlet, a second opening provided at a bottom thereof and communicating with the first opening through a resin passage, said second opening being a ring-shaped hole, a third opening functioning as the reinforcing fiber inlet, and a fourth opening provided inside the second opening and communicating with the reinforcing fiber inlet through a fiber passage.
35. A screw unit according to claim 32, wherein the mixer further comprises:
a nozzle provided with a first opening functioning as the molten resin inlet, a second opening provided at a bottom thereof and communicating with the first opening through a resin passage, said second opening being a ring-shaped hole, a third opening functioning as the reinforcing fiber inlet, and a fourth opening provided inside the second opening and communicating with the reinforcing fiber inlet through a fiber passage;
a nozzle heater for keeping the nozzle at a given temperature; and
a pair of rollers which is positioned under the second and fourth openings and presses a ring-shaped molten resin extruded and flowing down from the nozzle together with reinforcing fibers being inside the ring-shaped molten resin to obtain a sheet-like molten resin having the reinforcing fibers sandwiched therebetween.
36. A screw unit according to claim 35, wherein the mixer further comprises:
a resin cutter positioned between the nozzle and the rollers for cutting the ring-shaped molten resin extruded and flowing down from the nozzle;
a hopper for guiding the reinforcing fibers to the reinforcing fiber inlet; and
a valve for adjusting a pressure of molten resin passing through the resin passage in the nozzle.
37. A screw unit according to claim 32, wherein the mixer further comprises a fiber cutter for cutting reinforcing long fibers to obtain reinforcing fibers having a given length and then introducing the reinforcing fibers in scattered state into the reinforcing fiber inlet, said fiber cutter being positioned above the reinforcing fiber inlet.
38. A screw unit according to claim 26, wherein the feed opening has an opening width being equal to or more than an inner diameter of the cylinder, said opening width being a length of the feed opening in a direction perpendicular to longitudinal direction of the cylinder; and
an introduction space which extends to below a horizontal plane passing a central axis of the screw is formed between an outer peripheral face of the screw and a cylinder internal face continuing to a cylinder side wall which defines the feed opening, said side wall being on a side where an outer peripheral part of the screw which has temporarily left from a cylinder internal face at the feed opening again approaches to the cylinder internal face while the screw is rotating.
39. A screw unit according to claim 26, which further comprises:
a pushing rod positioned along a cylinder side wall which defines the feed opening, said side wall being parallel to longitudinal direction of the cylinder, and having a face facing to an outer peripheral face of the screw; and
a rod driving mechanism which reciprocates the pushing rod up and down.
40. A method for supplying a reinforcing fiber-containing molten resin, which comprises:
a step of attaching at least a part of reinforcing fibers to molten resin flowing down owing to gravity in an open space outside a screw unit;
a step of feeding the reinforcing fibers and the molten resin to which at least a part of the reinforcing fibers attach to a feed opening of the screw unit; and
a step of kneading the molten resin and the reinforcing fibers by a screw of the screw unit and supplying the resulting reinforcing fiber-containing molten resin from an outlet of the screw unit.
41. A method according to claim 40, wherein the screw unit is a screw injection machine and which further comprises a step of storing in around the outlet of the screw injection machine the reinforcing fiber-containing molten resin obtained by kneading with the screw of the screw injection machine and a step of injecting the reinforcing fiber-containing molten resin from the outlet into a molding cavity of a molding machine.
42. A method according to claim 40, wherein the screw unit is a screw extruder.
43. A method according to claim 40, wherein the molten resin and the reinforcing fibers are kneaded by the screw at a compression ratio of 4 or less and an apparent shear rate of 100 sec.sup.-1 or less.
44. A method according to claim 40, which further comprises a step of extruding the molten resin from a molten resin outlet of a melting extruder and wherein the molten resin and the reinforcing fibers are kneaded by the screw at a compression ratio and an apparent shear rate which are smaller than those in the melting extruder, respectively.
45. A method according to claim 40, which further comprises a step of cutting reinforcing long fibers to obtain reinforcing fibers having a given length by means of a fiber cutter and directly feeding the reinforcing fibers in a scattered state from the fiber cutter.
46. A method according to claim 40, wherein the molten resin is allowed to flow down in a form of a strip and at least a part of the reinforcing fibers are attached to the molten resin in an area of its flowing down.
47. A method according to claim 40, wherein the molten resin is allowed to flow down in a form of a group of lines or rods having a space therebetween and at least a part of the reinforcing fibers are attached to the molten resin in an area of its flowing down.
48. A method according to claim 40, wherein the molten resin is allowed to flow down in a form of a tube and at least a part of the reinforcing fibers are attached to the molten resin while the reinforcing fibers are dropped owing to gravity inside the tubular molten resin.
49. A method according to claim 40, wherein the molten resin is allowed to flow down in a form of a tube, the reinforcing fibers are dropped owing to gravity inside the tubular molten resin, the tubular molten resin is pressed together with the reinforcing fibers being inside the tubular molten resin to obtain a sheet-like molten resin having the reinforcing fibers sandwiched between the molten resin sheets, and the resulting sheet-like molten resin is fed to the feed opening of the screw unit.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a screw apparatus for supplying a reinforcing fiber-containing molten resin and a method for supplying a reinforcing fiber-containing molten resin by means the apparatus.
2. Related Background Art
As conventional methods for injection molding of a fiber-reinforced resin, methods in which reinforcing fibers are introduced into molten resin in a screw injection machine has been proposed (Japanese Patent Laid-Open (Kokai) Nos. 153714/1990 and 286617/1992).
However, according to the above conventional methods, the reinforcing fibers which can be fed uniformly have limit in their length and length of the reinforcing fibers after molded is still insufficient. Moreover, the state of dispersion of the reinforcing fibers in the resin is also insufficient to cause fluctuation in filling of the reinforcing fibers in the articles.
As another conventional method, a method in which fibers and a resin material (non-molten state) are respectively and directly introduced into an injection machine is known (Japanese Patent Laid-Open (Kokai) No. 8278/1994).
However, according to this conventional method, it is also difficult to keep the fibers in a long size, and the fiber length can be kept only at about 400-500 .mu.m which is still insufficient.
SUMMARY OF THE INVENTION
The object of the present invention to provide a screw apparatus (screw injection apparatus, screw extrusion apparatus) and a method (injection method, extrusion method) for supplying of the reinforcing fiber-containing thermoplastic resin using the apparatus is to make it possible to obtain fiber-reinforced resin articles and fiber-reinforced resin pellets containing long reinforcing fibers which have not been able to be attained by conventional methods and further to make it possible to highly uniform the dispersion state of the reinforcing fibers in these articles or pellets.
The screw apparatus of the present invention comprises:
a melting extruder comprising a barrel which has a resin material inlet provided on the side of a first end portion thereof and a molten resin outlet provided on the side of a second end portion thereof (the second end portion is opposite to the first end portion), an extruding means positioned in the barrel, a driving means connected to the extruding means and a barrel heater for heating the barrel;
a screw unit comprising a cylinder having a feed opening provided on the side of a first end portion thereof and positioned under the molten resin outlet and an outlet provided on the side of a second end portion thereof (the second end portion is opposite to the first end portion), a screw inserted in the cylinder, a driving unit connected to the screw, and a cylinder heater for keeping the cylinder at a given temperature; and
a mixer which is positioned between the molten resin outlet and the feed opening, which has a reinforcing fiber inlet, which defines a space through which reinforcing fibers fed from the reinforcing fiber inlet flow down owing to gravity together with molten resin extruded from the molten resin outlet and then the reinforcing fibers and the molten resin are fed to the feed opening, and in which at least a part of the reinforcing fibers attach to the molten resin flowing down owing to gravity in an open space.
The screw in the screw unit according to the screw apparatus of the present invention may have a mixing head at the tip.
In the screw apparatus of the present invention, it is preferred that the compression ratio is 4 or less and the apparent shear rate is 100 sec.sup.-1 or less in the screw unit. It is further preferred that the apparent shear rate and the compression ratio in the screw unit are smaller than those in the melting extruder, respectively.
In the screw apparatus of the present invention, said mixer may further comprise a fiber cutter for cutting reinforcing long fibers to obtain reinforcing fibers having a given length and then introducing the fibers in scattered state into the reinforcing fiber inlet (the fiber cutter is positioned above the reinforcing fiber inlet).
The screw apparatus of the present invention may further comprise an accumulator positioned between the melting extruder and the mixer and having an accumulator inlet connected to the molten resin outlet and an accumulator outlet connected to the mixer.
Furthermore, in the screw apparatus of the present invention, it is preferred that an opening width of the feed opening (the opening width is a length in a direction perpendicular to the longitudinal direction of the cylinder) is equal to or more than an inner diameter of the cylinder; and an introduction space which extends to underneath a horizontal plane passing the central axis of the screw is formed between an outer peripheral face of the screw and a cylinder internal face continuing to a cylinder side wall which defines the feed opening (the side wall is on the side where an outer peripheral part of the screw which has temporarily left from a cylinder internal face at the feed opening again approaches to the cylinder internal face while the screw is rotating).
Moreover, the screw apparatus of the present invention may further comprise a pushing rod positioned along a cylinder side wall which defines the feed opening (the side wall is parallel to the longitudinal direction of the cylinder) and having a face facing to the outer peripheral face of the screw; and a rod driving mechanism which reciprocates the pushing rod up and down.
When the molten resin and the reinforcing fibers are fed to the screw unit in such a state that at least a part of the reinforcing fibers attach to the molten resin flowing down owing to gravity in an open space, separation of the resin and the reinforcing fibers in the vicinity of the feed opening does not occur which would occur when the reinforcing fibers are merely introduced into the molten resin in the screw unit or when the reinforcing fibers and the resin material are merely introduced from the feed opening of the screw unit. Especially, even when reinforcing fibers of high bulk specific gravity are fed, according to the present invention, the reinforcing fibers are uniformly bitten between the cylinder and the screw channel near the feed opening and, thus, the reinforcing fibers are stably fed to the screw unit.
Further, since the reinforcing fibers are attached (distributed) to the molten resin in the route of introduction of the molten resin, namely, in the route of the molten resin being sagged and flowing down by the gravity from the outlet of the melting extruder, too much external force hardly acts on the reinforcing fibers when the reinforcing fibers are distributed to the molten resin, and, as a result, the reinforcing fibers hardly break at the subsequent kneading step.
Therefore, according to the screw apparatus of the present invention, very long reinforcing fibers (for example those of about 5-30 mm) which have hitherto been difficult to use can be used, and, in addition, breakage (cutting) of the reinforcing fibers at the time of kneading in the screw unit can be inhibited.
Moreover, according to the present invention, since at least a part of the reinforcing fibers are previously attached to the molten resin outside the screw unit and they are introduced in this state into the screw unit, the reinforcing fibers are already distributed in the molten resin to some extent at the point of time when the molten resin and the reinforcing fibers have reached to the screw unit. Therefore, a good dispersion state of the reinforcing fibers in the molten resin can be readily attained by the subsequent kneading without exerting a strong shearing force. Moreover, dispersion ratio of the resin component and the reinforcing fiber component can be uniform through the molten kneaded product.
In addition, since plasticization of the resin in the screw unit is not needed, it is not necessary to exert a strong shearing force for melting the resin, and shear rate and compression ratio for the kneading in the screw unit can be set independently from those in the melting extruder. Therefore, by setting the shear rate and the compression ratio at very low levels, the chance of breakage of the reinforcing fibers in the screw unit can be reduced and the reinforcing fibers can be kept at the further longer length.
Thus, according to the screw apparatus of the present invention, there can be obtained fiber-reinforced resin articles and fiber-reinforced resin pellets containing long reinforcing fibers (for example those of about 1.5-3.5 mm) and highly uniformed in the dispersion state of the reinforcing fibers, which have not hitherto been able to be obtained. Since the dispersion state of the reinforcing fibers in the molten kneaded product obtained by the present invention is satisfactory and, besides, the reinforcing fibers are long, the fiber-reinforced resin articles obtained by molding the molten kneaded product have superior mechanical strengths such as impact strength and flexural strength.
The melting extruder and the mixer in the screw apparatus of the present invention may be used as a mixing unit.
The mixing unit of the present invention comprises:
a melting extruder comprising a barrel which has a resin material inlet provided on the side of a first end portion thereof and a molten resin outlet provided on the side of a second end portion (the second end portion is opposite to the first end portion), an extruding means provided in the barrel, a driving means connected to the extruding means and a barrel heater for heating the barrel; and
a mixer which is connected to the molten resin outlet, which has a reinforcing fiber inlet, which defines a space through which reinforcing fibers fed from the reinforcing fiber inlet flow down owing to gravity together with molten resin extruded from the molten resin outlet, and in which at least a part of the reinforcing fibers attach to the molten resin flowing down owing to gravity in an open space.
According to the mixing unit of the present invention, at least a part of the reinforcing fibers are efficiently attached to the molten resin flowing down by the gravity in an open space. Additionally, when the molten resin and the reinforcing fibers are introduced in this state into a screw unit or the like, breakage (cutting) of the reinforcing fibers in the unit can be inhibited, and, in addition, very long reinforcing fibers can be used. Therefore, by using the mixing unit of the present invention, there can be obtained simply and efficiently fiber-reinforced resin articles and fiber-reinforced resin pellets containing long reinforcing fibers which have not hitherto been able to be attained.
Further, the screw unit in the screw apparatus of the present invention may be used as an independent screw unit.
The screw unit of the present invention comprises a cylinder having a feed opening provided on the side of a first end portion thereof and an outlet provided on the side of a second end portion thereof (the second end portion is opposite to the first end portion), a screw inserted in the cylinder, a driving unit connected to the screw, and a cylinder heater for keeping the cylinder at a given temperature, in which a compression ratio is 4 or less, and an apparent shear rate is 100 sec.sup.-1 or less.
Since in the screw unit of the present invention, the compression ratio is set at 4 or less and the apparent shear rate is set at the very low range of 100 se.sup.-1 or less, the chance of the reinforcing fibers being cut at kneading is very small and the degree of the reinforcing fibers cut short in the resulting kneaded product is very low. Therefore, according to the screw unit of the present invention, there are obtained fiber-reinforced resin articles and fiber-reinforced resin pellets having a highly uniformed dispersion state of the reinforcing fibers while keeping fiber length of the reinforcing fibers longer than that in conventional methods. A compression ratio of 4 or less and an apparent shear rate of 100 sec.sup.-1 or less are the conditions under which it has been considered to be difficult to efficiently melt the fiber-reinforced resin pellets or resin materials and to highly uniformly disperse the reinforcing fibers into the molten resin, since conventionally it has been considered to be especially important to increase kneading speed.
The method for supplying a reinforcing fiber-containing molten resin of the present invention comprises:
a step of attaching at least a part of reinforcing fibers to molten resin flowing down owing to the gravity in an open space outside a screw unit;
a step of feeding the molten resin and the reinforcing fibers to a feed opening of the screw unit in such a state as at least a part of the reinforcing fibers attaching to the molten resin; and
a step of kneading the molten resin and the reinforcing fibers by a screw of the screw unit and supplying the resulting reinforcing fiber-containing molten resin from an outlet of the screw unit.
In the method of the present invention, it is preferred that the molten resin and the reinforcing fibers are kneaded by the screw at a compression ratio of 4 or less and an apparent shear rate of 100 sec.sup.-1 or less. Furthermore, the method of the present invention may further comprise a step of extruding the molten resin from a molten resin outlet of a melting extruder.
The method of the present invention may further comprise a step of cutting reinforcing long fibers to obtain reinforcing fibers having a given length by means of a fiber cutter and directly feeding the reinforcing fibers in a scattered state from the fiber cutter.
When the molten resin and the reinforcing fibers are fed to the screw unit in such a state as at least a part of the reinforcing fibers being attached to the molten resin flowing down owing to the gravity in an open space as mentioned above; no separation occurs between the resin and the reinforcing fibers at around the feed opening and the reinforcing fibers can be stably fed as explained before. Furthermore, excessively great external force is hardly applied to the reinforcing fibers at the time of distribution of the reinforcing fibers into the molten resin, and, thus, the reinforcing fibers are hardly broken at this step. Moreover, according to the method of the present invention, it can be easy to attain a good dispersion state of the reinforcing fibers in the molten resin by kneading, and, besides, the dispersion ratio of the resin component and the reinforcing fiber component can be uniform through the whole molten kneaded product.
Therefore, according to the method of the present invention, use of very long reinforcing fibers (for example those of about 5-30 mm) which have hitherto been difficult to use becomes possible and, in addition, breakage of the reinforcing fibers during kneading in the screw unit can be inhibited. As a result, there can be obtained fiber-reinforced resin articles and fiber-reinforced resin pellets containing long reinforcing fibers (for example those of about 1.5-3.5 mm) and having a highly uniformed dispersion state of the reinforcing fibers which have not been able to be obtained up to now.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional view of one example of the screw apparatus of the present invention.
FIG. 2 is a schematic sectional view of another example of the screw apparatus of the present invention.
FIG. 3 is a schematic sectional view of one example of the mixer according to the present invention.
FIG. 4 is a schematic sectional view of still another example of the screw apparatus of the present invention.
FIG. 5 is a front sectional view which shows a relation between the molten resin outlet of the melting extruder and the roving cutter in FIG. 2.
FIG. 6 is a schematic sectional view of another example of the mixer according to the present invention.
FIG. 7 is a sectional view of the mixer shown in FIG. 6, taken along line X--X of FIG. 6.
FIG. 8 is a schematic sectional view of still another example of the mixer according to the present invention.
FIG. 9 is a sectional view of the mixer shown in FIG. 8, taken along line Y--Y of FIG. 8.
FIG. 10 is a schematic sectional view of further another example of the mixer according to the present invention.
FIG. 11 is an oblique view of one example of the mixing head according to the present invention, shown partly cut away.
FIG. 12 is a sectional view of one example of the feed opening of the screw unit in the screw apparatus of the present invention.
FIG. 13 is a sectional view of another example of the feed opening of the screw unit in the screw apparatus of the present invention.
FIG. 14 is a flow chart which shows one example of operation of the screw apparatus of the present invention.
FIG. 15 is a schematic sectional view of still another example of the screw apparatus of the present invention.
FIG. 16 is a schematic sectional view of one example of the screw unit of the present invention.
FIG. 17 is a schematic sectional view of another example of the screw unit of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be explained in connection with the accompanying drawings. These drawings shown one example of the present invention and the present invention is never limited to the embodiments shown in these drawings. In the drawings, the same portions or the corresponding portions are indicated by the same reference numerals.
First, the screw apparatus of the present invention as well as the method for supplying the reinforcing fiber-containing molten resin of the present invention will be explained below.
FIG. 1 is a whole schematic view of one example of the screw apparatus of the present invention. The screw apparatus shown in FIG. 1 has screw unit 1, melting extruder 2, accumulator 3 and mixer 4. The molten resin extruded from the melting extruder 2 is introduced into the mixer 4 through the accumulator 3. In the mixer 4, at least a part of the reinforcing fibers attach to the molten resin which flows down owing to the gravity in the open space, and the molten resin and the reinforcing fibers in this state are introduced from feed opening 102 of the screw unit 1.
Each part of the screw apparatus of the present invention will be explained in detail below.
(Melting Extruder 2)
The melting extruder 2 has barrel (heating cylinder) 200, extrusion screw 210 inserted in chamber 201 formed in the barrel 200 in the longitudinal direction, driving means 220 connected to the extrusion screw 210, and barrel heater 230 positioned on the outer peripheral surface of the barrel 200. The barrel 200 has resin material inlet (feed opening) 202 provided on the side of a first end portion 200a and molten resin outlet 203 provided on the side of a second end portion 200b (the second end portion 200b is opposite to the first end portion 200a), and the resin material inlet 202 and the molten resin inlet 203 communicate with each other through the chamber 201. The resin material inlet 202 opens upwardly and hopper 204 is fitted to the resin material inlet 202. Pellet or powder thermoplastic resin material 240 is introduced from resin material inlet 202.
The melting extruder 2 shown in FIG. 1 is a single screw extruder provided with a single screw 210, and driving means 220 has motor (rotation driving unit) 221 for rotating the extrusion screw 210. Therefore, the extrusion screw 210 is rotated by the motor 221 through gear 222 provided on the side of the base end portion 210a.
The barrel heater 230 heats the barrel 200 so that the barrel reaches a given temperature (optionally selected depending on the desired resin viscosity, etc. and not so as to cause deterioration of the resin with oxidation in the temperature range of the melting point or higher of the resin used).
Therefore, the extrusion screw 210 is rotated by motor 221 and carries the resin material 240 introduced from resin material inlet 202 towards the side of the tip 200b of the melting extruder 2. During this period, the introduced resin material 240 is melted (plasticized) by the heating with barrel heater 230 and the generation of heat (frictional heat) owing to shearing action, and is discharged from the molten resin outlet 203 as molten resin 241.
The discharging amount (per unit time) of molten resin 241 discharged from the molten resin outlet 203 is determined by the speed of rotation of screw 210. The total discharging amount is determined by the total number of rotation of screw 210.
(Accumulator 3)
In FIG. 1, accumulator 3 is connected to the melting extruder 2. The accumulator 3 has accumulator barrel 300, piston 310 inserted in accumulator chamber 301 formed in the barrel 300 in the longitudinal direction thereof, piston driving means 320 connected to the piston 310, and accumulator barrel heater 330 positioned on the outer peripheral surface of the barrel 300. The accumulator barrel 300 has accumulator inlet 302 connected to the molten resin outlet 203, and accumulator outlet 303. The inlet 302 and the outlet 303 communicate with each other through the chamber 301.
The accumulator barrel heater 330 keeps the temperature of the accumulator barrel 300 at a given temperature (optionally selected depending on the desired resin viscosity, etc. and not so as to cause deterioration of the resin with oxidation in the temperature range of the melting point or higher of the resin used).
In a case where the screw apparatus of the present invention comprises the accumulator 3, the melting extruder 2 can continuously work irrespective of the operation of screw unit 1, and the molten resin 241 continuously extruded from the melting extruder 2 is temporarily stored in accumulator 3. When the amount of the stored molten resin 241 reaches a given amount, the molten resin 241 in an amount very close to the given amount is extruded from accumulator outlet 303 by the forward movement of piston 310.
When the accumulator 3 is connected to the outlet 203 of the melting extruder 2 in this way, the feeding rate of molten resin 241 can be made considerably uniform. In the screw apparatus of the present invention, the accumulator 3 may not be used as shown in FIG. 2, but, in this case, it is preferred to provide a shut-off valve 250 movable in the direction of the double end arrow 251 at the molten resin outlet 203. The shut-off valve 250 is opened or closed when discharging or stopping of the molten resin 241, respectively.
(Mixer)
FIG. 3 shows one example of the mixer of the present invention suitably used in the screw apparatus of the present invention.
The mixer 4 shown in FIG. 3 has nozzle 400 connected to the accumulator 3, nozzle heater 410 positioned on the outer periphery of the nozzle 400 and a pair of rollers 420 positioned under the nozzle 400. The nozzle 400 has a first opening 401 functioning as the molten resin inlet, a second opening 402 provided at the bottom of thereof and communicating with the first opening 401 through resin passage 403 (the second opening 402 is a ring hole), a third opening 404 functioning as the reinforcing fiber inlet, and a fourth opening 405 provided inside the second opening 402 and communicating with the third opening 404 through fiber passage 406.
The nozzle heater 410 keeps the temperature of the nozzle 400 at a given temperature (optionally selected depending on the desired resin viscosity, etc. and not so as to cause deterioration of the resin with oxidation in the temperature range of the melting point or higher of the resin used). Furthermore, a motor 421 for rotation of rollers is connected to the rollers 420 and cooling water pipe 422 for cooling the rollers is provided to the rollers 420.
Moreover, the mixer 4 has resin cutter 430 for cutting the ring-shaped molten resin 241 extruded from nozzle 400 and flows down (the resin cutter 430 is positioned between the under surface of nozzle 400 and rollers 420), hopper 440 for guiding reinforcing fibers 450 to reinforcing fiber inlet 404, and valve 460 for adjusting the pressure of the molten resin 241 which passes the resin passage 403.
In the mixer 4 shown in FIG. 3, the molten resin 241 fed from accumulator 3 through the first opening 401 is extruded in the ring-shaped (tubular) form and flow down from the second opening 402. On the other hand, the reinforcing fibers 450 fed through the third opening 404 pass through the fourth opening 405 and drop inside the ring-shaped molten resin 241. Therefore, at least a part of the reinforcing fibers 450 attach to the inner surface of the ring-shaped molten resin 241 flowing down by the gravity in an open space. Further, the ring-shaped molten resin 241 is slightly pressed by a pair of rollers 420 together with the reinforcing fibers 450 present inside the ring-shaped molten resin 241 to obtain a sheet-like molten resins 242 between which the reinforcing fibers are sandwiched.
According to this way, the reinforcing fibers 450 are more surely distributed (attached) to the molten resin 241. Thus, even if the reinforcing fibers 450 are long, separation of the resin and the reinforcing fibers at around the feed opening 102 is prevented, and the reinforcing fibers are uniformly and stably fed to the screw unit 1. Therefore, it becomes possible to use long reinforcing fibers which have hitherto been difficult to use and, furthermore, breakage of the reinforcing fibers in the course of kneading in the screw unit 1 is inhibited, and a uniform dispersion state of the reinforcing fibers can be easily attained.
Furthermore, when the reinforcing fibers 450 and the molten resin 241 are fed to the screw unit 1 as sheet-like molten resins 242 between which the reinforcing fibers are sandwiched as mentioned above, inclusion of air in the molten resin 241 in the screw unit 1 can be sufficiently inhibited, and articles free from voids and having further improved properties can be obtained.
Moreover, as shown in FIG. 1, the mixer 4 in this example is further provided with fiber cutter (roving cutter) 5 for cutting the reinforcing long fibers to obtain reinforcing fibers having a given length and then introducing the reinforcing fibers in scattered state into the reinforcing fiber inlet 404 (the fiber cutter 5 is positioned above hopper 440).
(Roving Cutter 5)
Roving cutter 5 has a pair of feed rolls 500 for delivering many continuous length reinforcing fibers (reinforcing long fibers) 451 wound on reel 452 in the flatly spread state, and cutting roll 501 provided on the outlet side of the feed rolls 500 and having a width wider than the feeding width of the reinforcing fibers 451. The cutting roll 501 has a plurality of blades 502 which instantaneously and rotatively contact with the lower feed roll 500, and the reinforcing long fibers 451 are cut to reinforcing fibers 450 having a constant length by the blades 502 and the feed roll 500. Therefore, the reinforcing fibers 450 are dispersed in the range of feeding width of the reinforcing long fibers 451 by the feed rolls 500 (somewhat wider range than the feeding width) and are dropped.
The position and rotating direction of cutting roll 501 are set so that the dropping direction of reinforcing fibers 450 is toward the hopper 440 and the reinforcing fiber inlet 404.
The length of reinforcing fibers 450 is determined by the arranging pitch of blades 502 fixed on cutting roll 501 and set usually in the range of 3-30 mm. In this connection, length of the commercially available reinforcing fibers (chips) is usually 3 mm, and reinforcing fibers 450 having various lengths other than those of commercially available fibers can be simply and efficiently obtained by using the above roving cutter 5. In addition, when the reinforcing fibers 450 are directly fed to the mixer 4 from the roving cutter 5, agglomeration of the reinforcing fibers 450 can be inhibited. Therefore, the reinforcing fibers 450 cut to a constant length by the roving cutter 5 are distributed in the scattered state to the molten resin 241 which flows down, and the degree of distribution (uniforming) of the reinforcing fibers to the molten resin is further improved.
In the screw apparatus of the present invention, it is possible to use very long reinforcing fibers which have hitherto been difficult to use as mentioned before, and, besides, when the longer reinforcing fibers are used, the length of the reinforcing fibers in the resulting fibers tends to be longer. Therefore; the length of the reinforcing fibers 450 used in the present invention is preferably 5-30 mm, especially preferably 13-25 mm.
For example, using roving glass fibers of 1100 tex (g/m) as reinforcing long fibers 451, nine of the fibers are fed between a pair of feed rolls 500 and cut by the cutting roll 501, and, thus, reinforcing fibers 450 having a length of 15 mm can be obtained. The feeding speed of reinforcing fibers 450 from cutting roll 501 is set, for example, at 3 kg/min.
In the above example, the reinforcing fibers 450 dropping from roving cutter 5 are directly contacted with molten resin 241 discharged from molten resin outlet 203 through nozzle 400, but previously cut reinforcing fibers 450 may be distributed (fed) to the flowing passage of the molten resin 241 by a vibrating feeder 6 or the like as shown in FIG. 4.
Furthermore, in either case of directly feeding the reinforcing fibers 450 cut by the roving cutter 5 or feeding them using a vibrating feeder 6, etc., mixers as shown in FIGS. 2 and 5, FIGS. 6 and 7, FIGS. 8 and 9, and FIG. 10 may be employed for attaching (distributing) at least a part of reinforcing fibers 450 to molten resin 241.
In the mixer 4 shown in FIGS. 2 and 5, nozzle 400 is not connected to molten resin outlet 203 which directly functions as the molten resin inlet of the mixer, and a strip-like molten resin 241 is directly extruded from a horizontally long and flat rectangular outlet 203 and drops by the gravity.
Furthermore, a cylindrical protective pipe 106 is provided between the outlet 203 and the inlet 102 of the screw unit 1, and a funnel-shaped hopper 440 (functioning as the reinforcing fiber inlet of the mixer) is formed at the upper end of the protective pipe 106. Roving cutter 5 is positioned above the hopper 440. The size of horizontal section of the protective pipe 106 is set to be larger than the section of the molten resin 241 discharged from inlet 203, and the protective pipe 106 is positioned in such a manner that the inner surface does not contacts with the molten resin 241.
The position of the roving cutter 5 is set so that the dropping passage of reinforcing fibers 450 joins with the upper stream portion (in the vicinity of outlet 203) of the passage of the molten resin 241 which is discharged from outlet 203 and hangs and flows down (hereinafter referred to as merely "flow-down passage"). Furthermore, it is set so that the range of dropping of the reinforcing fibers 450 nearly meets with the width of the molten resin 241 which is discharged from outlet 203 and flows down.
In the mixer 4 shown in FIGS. 2 and 5, an openable and closable shutter 470 for temporarily stopping the feeding of molten resin 241 and reinforcing fibers 450 is provided midway of the protective pipe 106. Such shutter 470 may be provided near the outlet 203, and when nozzle 400 is provided, the shutter 470 may be provided in the nozzle.
When attaching of reinforcing fibers 450 to molten resin 241 is carried out in such a manner that the reinforcing fibers 450 are distributed to the molten resin 241 in the vicinity of the outlet 203 of melting extruder 2 as shown above, also the chance of contacting of the reinforcing fibers 450 with molten resin 241 during the molten resin 241 flowing down from outlet 203 and being introduced into feed opening 102 of the screw unit 1 increases, and, therefore, distribution (attaching) of reinforcing fibers 450 to the molten resin 241 in this flow-down passage is accelerated, and, accordingly, uniform dispersion of reinforcing fibers 450 is accelerated.
In the mixer 4 shown in FIGS. 6 and 7, nozzle 400 is provided to be connected to outlet 203 of melting extruder 2, and a ring-shaped outlet port (opening) 402 is formed on the bottom of the nozzle 400. Specifically, the nozzle 400 has a first opening 401 functioning as the molten resin in
