DESCRIPTION

METHOD AND APPARATUS FOR FORMING STRANDS

Technical Field

The present invention relates to a strand forming method for extruding strands from a compound extruded from a mixer and a strand forming apparatus which includes a mixer.

Background Art

JP-A-2003-112317 discloses a pellet manufacturing technique in which strands are extruded from holes in a die which is attached to a cylinder head of a mixer via a nozzle portion, and the strands are cut to a predetermined length with a rotary cutter at the same time as the strands are so extruded into pellets. According to the disclosed technique, a casing is attached integrally to the die on a side thereof from which strands are extruded. The casing is formed in such a manner that an interior space of the casing can be filled with an inactive gas.

In the related art that has been described above, the pellets so formed are made to pass through the casing which is filled with the inactive gas, and therefore, it means that the forming method and apparatus are adopted in which the pellets are prevented from being exposed to oxygen in the air until they get out of the casing. Although the forming method and apparatus are those which take apply consideration to preventing the reduction in physical properties, the forming method and apparatus have a problem that the apparatus becomes large in size or a large space has to be provided for installation thereof because

the casing which is filled with the inactive gas has to be provided or the casing has to be integrated with the die. In addition, the forming method and apparatus also have a problem that replacement of dies or maintenance work of the apparatus becomes difficult. As countermeasures against the problems described above, in the event that no casing is provided or no inactive gas is provided which would otherwise fill the casing, compound or resin deposits produced on the peripheries of the holes in the die are oxidized to be discolored. The inventor of the invention is concerned that in case these oxidized resin deposits adhere to strands extruded, there is caused a fear that the a reduction in physical properties or inclusion of foreign matters in resulting pellets will occur.

In addition to what has been described above, the inventor of the invention has found that any improving methods that have been made to aim at increasing fluidity by improving die materials or changing configurations of holes in a die in order to prevent the generation of resin deposits cannot constitute permanent countermeasures due to the aging of a die used or alteration in the configuration of holes in the die.

Disclosure of Invention The invention has been made in view of these situations, and an object of the invention is to provide a method and apparatus for forming strands which can ensure the quality of resulting pellets sufficiently even though the configuration of the forming apparatus is simplified.

With a view to achieve the object, according to a first aspect of the invention, there is provided a strand forming method including extruding to form

strands from holes arranged in a die or dies while spraying an inactive gas towards the holes.

According to the first aspect of the invention, the peripheries of the holes in the die or dies are filled with the inactive gas. Even though resin deposits are produced, there occurs a state in which the portions where the resin deposits are so produced are prevented from being exposed to oxygen in the air by spray of the inactive gas.

According to a second aspect of the invention, there is provided a strand forming method as set forth in the first aspect of the invention, wherein the inactive gas is heated and is sprayed while a gas flow of the inactive gas is being regulated.

According to the second aspect of the invention, even though resin deposits are produced, solidification of the resin deposits produced on the peripheries of the holes in the die or dies is prevented by the inactive gas which is heated and regulated with respect to the gas flow thereof.

According to a third aspect of the invention, there is provided a strand forming apparatus including: a die having holes; and a gas spraying unit which is provided in the vicinity of the holes to spray an inactive gas towards the holes.

According to the third aspect of the invention, even though resin deposits are produced, there occurs a state in which portions where the resin deposits are produced are prevented from being exposed to oxygen in the air by the inactive gas sprayed from the spraying unit. The inactive gas is made to fill the portions in a pinpoint fashion by the gas spraying unit. Thus, the forming apparatus is made to have a configuration which needs neither apparatus which is large in size nor a large space in the vicinity of the die or dies.

According to a fourth aspect of the invention, there is provided a strand forming apparatus as set forth in the third aspect of the invention, including a heater which heats the inactive gas, and a gas flow regulator which regulates a gas flow of the inactive gas, wherein the heater and the gas flow regulator are provided upstream of the gas spraying unit.

According to the fourth aspect of the invention, the inactive gas is heated and regulated with respect to the gas flow thereof by the heater and the gas flow regulator, respectively, and since the inactive gas which is high in temperature and uniform in gas flow is sprayed from the gas spraying unit in this state, solidification of resin deposits produced on the peripheries of the holes in the die or dies is prevented.

According to a fifth aspect of the invention, there is provided a strand forming apparatus as set forth in the third aspect of the invention, including a movable arm which moves the gas spraying unit towards and away from the holes, and an angle adjusting mechanism which changes a mount angle of the gas spraying unit which is mounted on the movable arm.

According to the fifth aspect of the invention, the gas spraying unit is made to approach the die or dies for use by moving the movable arm in forming strands. In contrast to this, in performing maintenance work, for example, the movable arm is moved in a reverse direction so as to move the gas spraying unit away from the holes in the die or dies. The gas spraying unit is adjusted to an optimum spraying angle in the vicinity of the holes in the die or dies for use. In addition, it is effective to adopt a configuration in which a carriage or the like is used to move the gas spraying unit or the movable arm. According to a sixth aspect of the invention, there is provided a strand

forming apparatus as set forth in the third aspect of the invention, wherein the gas spraying unit includes a pair of gas spraying units for facing each other.

According to the sixth aspect of the invention, the inactive gas is sprayed uniformly from the pair of the gas spraying units towards the holes of the die. Thus, oxidization of resin deposits produced on the peripheries of the holes in the die or dies is prevented.

According to a seventh aspect of the invention, there is provided a strand forming apparatus as set forth in the third aspect of the invention, wherein the gas spraying unit has spraying-holes, each spraying the inactive gas towards respective one of the holes of the die.

According to the seventh aspect of the invention, each of the spraying-holes sprays the inactive gas uniformly towards respective one of the holes of the die. Thus, oxidization of resin deposits produced on the peripheries of the holes in the die or dies is prevented. According to an eighth aspect of the invention, there is provided a strand forming apparatus as set forth in the fourth aspect of the invention, wherein the heater includes a body, a heat transfer medium and a spiral passage into which the inactive gas flows.

According to the eighth aspect of the invention, the inactive gas which flows into the heater is sufficiently heated to be high temperature. Thus, solidification of resin deposits produced on the peripheries of the holes in the die or dies is prevented.

According to the above-mentioned configurations, the oxidization of resin deposits produced in the peripheries of the holes in the die or dies can be prevented by spraying the inactive gas towards the holes. Consequently,

should the resin deposits grown in the peripheries of the holes come to adhere to the extruded strands, the physical properties of the strands are decreased in no case. As a result, there is provided an advantage that cutting the strands to a predetermined length can produce pellets having a higher quality than that of pellets produced according to the related art.

According to the above-mentioned configurations, the solidification of resin deposits produced in the peripheries of the holes in the die or dies can be prevented. Consequently, there is provided an advantage that in the event that there is produced no portion which is solidified, the mixing of such solidified products can be prevented.

According to the above-mentioned configurations, there is provided an advantage that working efficiency related to, for example, replacement of dies or maintenance of the forming apparatus can be increased remarkably compared with the related art.

Brief Description of Drawings

Figs. 1A and 1 B are exemplary diagrams showing the configuration of a high-temperature inactive gas spraying device which illustrates an embodiment of a strand forming method and apparatus of the invention. Fig. 2 is an exemplary diagram showing an example of a way in which the high-temperature inactive gas spraying device is used.

Fig. 3 is an exemplary perspective view of a gas spraying unit.

Fig. 4 is an exemplary diagram showing the configuration of a heater.

Fig. 5 is an explanatory diagram which illustrates an exemplary state in the vicinity of holes in a die.

Fig. 6 is an exemplary perspective view of pellets which are not regarded as being deteriorated in quality.

Best Mode for Carrying Out the Invention Hereinafter, an embodiment of the invention will be described by reference to the accompanying drawings. Figs. 1 A and 1 B show an exemplary configuration of a high-temperature inactive gas spraying device which illustrates an embodiment of a strand forming method and apparatus of the invention. In addition, Fig. 2 is an exemplary diagram showing an example of a way in which the high-temperature inactive gas spraying device is used, Fig. 3 is an exemplary perspective view of a gas spraying unit, Fig. 4 is an exemplary diagram showing the configuration of a heater, Fig. 5 is an explanatory diagram which shows an exemplary state in the vicinity of holes in a die, and Fig. 6 is an exemplary perspective view of pellets which are not regarded as being deteriorated in quality.

In Figs. 1A and 1 B, a strand forming apparatus is configured in such a manner as to include a mixer in which a compound which is mixed is extruded as strands 2 via a die 1 and a high-temperature inactive gas spraying device 4 for spraying a nitrogen gas (although the nitrogen gas is adopted as an inactive gas in this embodiment, other inactive gases than the nitrogen gas may be adopted) to a plurality of holes 3 arranged in the die 1 so as to fill the peripheries of the holes 3 with the nitrogen gas. Although not shown in particular, a rotary cutter is provided on a downstream side of the strand forming apparatus for cutting strands 2 extruded from the holes 3 to a predetermined length so as to produce pellets.

The plurality of holes 3 are formed in the die 1. The plurality of holes 3 are formed in such a manner as to be aligned at predetermined intervals in a horizontal line. In this embodiment, ten circular holes 3 are formed (as an example). The high-temperature inactive gas spraying device 4 is configured so that a high-temperature nitrogen gas can be sprayed towards the respective holes 3 in the die at a uniform gas flow. As a specific example, the high-temperature inactive gas spraying device 4 includes a pair of gas spraying units 5, a gas flow regulator 6 and a heater 7. In addition, as is shown in Fig. 2, the high-temperature inactive gas spraying device 4 includes a movable arm 9 having an angle adjusting mechanism 8 and a moving carriage 10.

In Figs. 1A, 1 B and 3, the pair of gas spraying units 5 are each formed into a cylindrical shape which is elongated in a direction in which the holes 3 are aligned in the die 1. The pair of gas spraying units 5 are closed at one ends of the cylinders and are linked respectively with corresponding connecting pipes 11 at the other ends of the cylinders. A plurality of gas-spraying holes 12 in a predetermined size are formed at predetermined intervals in each of the pair of gas spraying units 5. The pluralities of gas-spraying holes 12 are formed to be opened in positions which match the respective holes 3 in the die 1. One end of a gas-supply pipe 13 is connected to the connecting pipes 11. The pair of gas spraying units 5 of the embodiment are formed to have heat resistance.

The pair of gas spraying units 5 are attached to the angle adjusting mechanism 8 mounted at a distal end of the movable arm 9. The pair of gas spraying units ^' 5 are adjusted to an optimum spraying angle relative to the plurality of holes 3 in the die 1.

The high-temperature inactive gas spraying device 4 of the embodiment is made not only to be disposed in the vicinity of the die 1 when forming strands 2 but also to move away from the die 1 as is shown in Fig. 2 when performing work related to replacement of dies 1 or maintenance of the strand forming apparatus. The high-temperature gas spraying device 4 of the embodiment has a construction in which working efficiency is taken into consideration. The high-temperature inactive gas spraying device 4 is formed into a movable device by the use of the moving carriage 10.

In Fig. 1 B, the other end of the gas-supply pipe 13 is connected to the gas flow regulator 6. The gas flow regulator 6 includes a gas flow regulator valve for regulating a gas flow of nitrogen gas. The gas flow regulator valve may be made to be used solely. In addition, the gas flow regulator valve may be made to electrically control the flow rate of nitrogen gay by the use of a control unit. In Figs. 1 B and 4, the heater 7 is provided for heating, for example, a nitrogen gas at normal temperatures which is supplied via a gas-supply pipe 14. A high-temperature nitrogen gas that is heated at the heater 7 is made to be supplied to the gas flow regulator 6 via a gas-supply pipe 15. To describe a specific example of a heater 7, as is shown in Fig. 4, the heater 7 includes a gas heater 16, a temperature regulator 17 and wirings 18.

The gas heater 16 includes a tubular portion (a body) 19 which is substantially tubular, a spiral gas passage 20 which is formed in the tubular portion 19, a band heater (a heat transfer medium) 21 which is provided on an outer circumference of the tubular portion 19, and rod heaters (a heat transfer medium) 22 which are provided further inside the tubular portion 19 than the

spiral gas passage 20. The spiral gas passage 20 is a passage for heating the nitrogen gas, and in the embodiment, although not limited particularly, the passage is formed into the spiral shape so as to extend over as long a distance as possible. The nitrogen gas at normal temperatures which is supplied via the gas-supply pipe 14 is made first to be heated to a high temperature by the band heater 21 and the rod heaters 22 while the nitrogen gas passes through the spiral gas passage 20 and then to be supplied to the gas flow regulator 6. In addition, the temperature to which the nitrogen gas is heated is preferably be a temperature at which resin deposits 23 (refer to Fig. 5) which are produced on the peripheries of the holes 3 in the die 1 are not solidified.

The temperature regulator 17 is provided as a device for regulating the temperatures of the band heater 21 and the rod heaters 22. In this embodiment, commercially available components are used as the temperature regulator 17, wirings 18, the band heater 21 and the rod heaters 22.

In the configuration that has been described above, the nitrogen gas at normal temperatures is heated to a high temperature by the heater 7, and the nitrogen gas so heated is passed through the gas flow regulator 6, whereby the high-temperature nitrogen gas is provided which is regulated in terms of gas flow and temperature. Then, the nitrogen gas so provided is sent to the pair of gas spraying units 5, so as to thereafter be sprayed therefrom towards the respective holes 3 (towards the peripheries of outlet side openings of the holes 3) in the die 1 , as is shown in Fig. 5. By the use of this method, the peripheries of the holes 3 in the die 1 are filled with the high-temperature nitrogen gas, and strands 2 are formed by being extruded from the respective holes 3 while preventing the

discoloration of the resin deposits 23 that would otherwise be caused due to the resin deposits 23 being oxidized.

Since the high-temperature nitrogen gas is filled on the peripheries of the holes 3, the resin deposits 23 are neither oxidized nor solidified in any case. In contrast to the related art strand forming apparatus in which tailings or residues of a resin compound used stick to the peripheries of the holes in the die and grow to resin deposits which are oxidized progressively, the invention is such that resin deposits are prevented from being discolored and therefore, an increase in quality of resulting pellets can be realized. In addition, as is seen from what has been described above, since the strand forming apparatus of the invention needs neither a casing which is filled with an inactive gas nor a large space, the strand forming apparatus is realized whose configuration is made simpler than that of the related art strand forming apparatus.

In addition, the invention may be configured in such a manner that the nitrogen gas at normal temperatures is supplied to the pair of gas spraying units 5. As this occurs, no heater 7 is used. In the event that no heater 7 is used, there exists a possibility that the resin deposits produced on the peripheries of the holes 3 in the die are solidified. However, even though the resin deposits are solidified, since the resin deposits so solidified are nothing like those oxidized, should the resin deposits so solidified be mixed into resulting strands, there occurs no such situation that a quality failure is induced by the resin deposits so mixed into the strands. Fig. 6 shows pellets 25 which are manufactured with the resin deposits 24 sticking thereto. However, since the resin deposits 24 are not oxidized and hence are not discolored, the resulting pellets 25 naturally remain the same color as the compound, and they are free

Il

from the aforesaid quality problem.

In addition, the invention can, of course, be modified variously without departing from the spirit and scope of the invention.

Industrial Applicability

According to the present invention, it is useful to provide a method and apparatus for forming strands which ensures the quality of resulting pellets sufficiently and needs to provide neither a casing for filling with an inactive gas nor a large space.