JP3330126B2 - Rubber composite extrusion apparatus and unvulcanized rubber extrusion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composite extruder comprising a screw extruder and a gear pump, and is suitable for use by being connected to a rubber extrusion die head. The present invention also relates to a method for extruding unvulcanized rubber using the composite extruder.

[0002]

2. Description of the Related Art As a method of manufacturing a rubber extruded product such as an automobile tire tread, a weather strip, a door seal, a hose, etc., a raw rubber is prepared by adding a reinforcing agent, a filler, a plasticizer, a vulcanizing agent and a vulcanization accelerator. The additive is added, the vulcanizable rubber composition obtained by kneading is supplied to an extruder, extruded from the extruder into a desired shape via a die head, and processed such as lamination like a tire tread. After vulcanization with a vulcanizer, or a method of extruding such as a weather strip, followed by a vulcanizer followed by vulcanization, and then cutting to a desired length to produce a product. ing.

[0003] A screw extruder is generally used for the above extrusion. In this screw extruder, rubber is conveyed in a barrel by a screw, friction, shear, and compression of the rubber are performed between the inner surface of the barrel and the outer surface of the screw, and the rubber is self-heated and plasticized to be molded. It becomes viscosity. In a conventional extruder in which a die head is directly connected to a screw via a filter, it is necessary to secure a predetermined molding pressure to the die head after passing through the filter.
It was considered that the longer the length L of the screw, the better. In other words, the screw requires a supply unit, a compression unit, and a metering discharge unit. Therefore, the ratio L / D of the length L of the screw to the outer diameter D is set to 12 to 16 with respect to the rubber at room temperature. It had been.

However, if the screw is lengthened,
Such a large power is required, and temperature control of heating / cooling corresponding to each of the supply unit, the compression unit, and the metering / discharge unit is required, and the temperature control mechanism is complicated. Moreover, even if the screw length is increased as described above, a plasticizing effect comparable to that of a Banbury mixer cannot be obtained. To increase the degree of plasticization using a conventional extruder, it is necessary to increase the rotation of the screw. In this case, the temperature of the discharged rubber becomes too high, and the rubber burns, so that molding becomes impossible and the discharge amount is reduced. In addition, increasing the length of the screw also causes problems such as an increase in the amount of accumulated material when changing lots.

On the other hand, it has been known that a gear pump is connected to the tip of a screw extruder to maintain a constant rubber supply pressure to a die head to enable precision molding (Japanese Patent Laid-Open No. 5-116200). (USP
5,156,781))). This known technique is
The metering and discharging part of the screw feeding part, the compression part and the metering and discharging part is transferred to the gear pump, and the two functional areas of the feeding heating part and the compressing part are left in the screw, and the filter between the screw extruder and the gear pump and its filter. The pressure loss of the rubber generated in the breaker plate as a support is formed to be minimized. Therefore, the total length of the screw was limited to 4.5 to 8.5 in the above L / D, and the shape of the rubber passage before and after the filter and the breaker plate was complicated.

[0006]

SUMMARY OF THE INVENTION In the present invention, the L / D is further reduced and the screw length is shortened while maintaining the same screw diameter as compared with a known composite type extrusion device using a gear pump. The present invention provides an apparatus for extruding a composite rubber having a reduced amount of rubber. The present invention also provides a composite extruder capable of increasing the discharge amount while maintaining the same screw diameter and reducing the screw power. The present invention further provides a composite extruder capable of easily controlling the temperature, preventing burning of the rubber, and extruding the vulcanizable rubber composition at a low temperature. The present invention provides a compound extrusion device that can simplify the shape of a rubber passage before and after a filter. Another aspect of the present invention provides a method for extruding an unvulcanized rubber using the above extruder.

A rubber compound extrusion device according to the present invention is a rubber compound extrusion device in which a gear pump is connected to the tip of a screw extruder via a filter with a breaker plate, and a die head is connected to the discharge side of the gear pump. In the above screw extruder, the supplied rubber composition is plasticized mainly by friction between the inside of the barrel and heating from the outside, and is extruded from the filter to the space on the inlet side of the gear pump, Is to stabilize and stabilize the rubber composition passing through the filter and heading to the gear pump while stirring and plasticizing by friction and shearing.The gear pump is configured to shear and compress the rubber composition filled in the inlet side space. In addition, it stirs and plasticizes and gives a pressing pressure to the die head. The length L and outer diameter D of the serial screw
Is not less than 1 and less than 3.
Preferably, the screw extruder functions as a rubber supply unit, and the gear pump functions as a rubber compression unit and a metering discharge unit.

That is, the screw extruder used in the present invention only needs to be provided with almost only the supply section among the supply section, the compression section and the metering / discharge section required in the conventional type. Does not require a discharge unit. Therefore, the length of the screw can be greatly reduced while maintaining the thickness (D), and the temperature control mechanism is simplified accordingly.

For example, the screw length L and the outer diameter D
If the ratio L / D of the rubber composition is less than 1,
Insufficient plasticization, conversely, if it exceeds 4, the length is too large
However, there is a problem that it is not economical.
According to the configuration described above, since L / D is set to 1 to 4,
The above problem can be avoided. The ratio L / D of the length L of the screw to the outer diameter D is preferably set to 1 to 4, particularly 2 to 3. The screw extruder needs only to be capable of plasticizing the rubber composition by heating and supplying the gear composition to the gear pump against the resistance of the filter by the rotation of the screw, and requires an extrusion pressure necessary for passing through the die head. do not do. Therefore, the drive motor of the screw is smaller than that of the conventional type.

Further, the filter with a breaker of the present invention straightens the rubber composition passing through the filter and its supporting breaker plate toward the gear pump while stirring and plasticizing by friction and shear.
That is, the torsion-shaped rubber composition discharged from the screw extruder is sequentially passed through the holes of the filter and the breaker plate, and the rubber composition is stirred while accompanied by pressure loss due to shearing and friction at that time, and plasticization is performed. It is something to go further. Therefore, the rubber passages before and after the filter may have a straight cylindrical shape, and the diameter thereof can be made equal to the discharge port of the screw extruder, so that the structure is simplified accordingly.

The gear pump connected to the outlet side of the filter with a breaker performs shearing and compression on the supplied rubber composition by meshing gears to further promote agitation and plasticization, and sends the rubber composition to a die head at a predetermined pressure. Compression section and metering discharge section in a conventional screw extruder
It fulfills its function. As this gear pump, a general high-viscosity gear pump can be used, but a thread groove is provided in the bearing portion so that burnt rubber generated on the end face of the gear is automatically discharged with rotation of the gear shaft. Preferably, it is

In the above-described rubber compound extrusion apparatus, when the rubber composition is supplied to the screw extruder, the rubber composition is sent to the outlet side of the barrel with the rotation of the screw. , And heated by the action of the heat medium flowing through the barrel and the screw shaft, and plasticization proceeds. Then, the rubber composition that has reached the discharge port of the screw extruder is extruded toward a filter and a breaker plate, passes through the filter and the breaker plate, and undergoes shearing and friction at that time, whereby plasticization proceeds. Then, the mixture is stirred at the same time, and is charged into the supply side space of the gear pump in a state where the pressure is reduced by the passage resistance of the filter or the like. Then, the rubber composition supplied to the gear pump is subjected to shearing and compression with the rotation of the gear pump, further plasticization and stirring are advanced, sent to a die head at a predetermined pressure and speed, enabling precision molding. . That is, in the apparatus of the present invention, the plasticization of the vulcanizable rubber composition is mainly performed by the action of the barrel and screw of the screw extruder and the action of the filter and the breaker plate, and the second plasticization in the gear pump. This allows the vulcanizable rubber composition to be molded. The stirring of the rubber composition is performed in a screw, a filter, a breaker plate, and a gear pump.

In the rubber composite extruder of the present invention,
It is preferable that the height (flight depth) of the peak formed on the screw be (1/5) D to (1/15) D, and (1/7) D to (1/12). D is more preferred.

[0014] Compared to the height of the conventional screw crest,
By adopting a screw having a peak height of 0 to 20% lower, even when extruding a high-viscosity unvulcanized rubber, the torque applied to the screw can be reduced, and the power consumption associated with extrusion can be reduced. . In addition, the screw can be rotated at a high speed, plasticizing can be effectively performed, and the extrusion speed can be increased.

In the rubber composite extrusion apparatus of the present invention, the screw preferably has a plurality of ridges.

[0016] Compared with one or two screws conventionally used, the above structure can improve the stirring efficiency, rotate the screw at a high speed, and increase the extrusion speed. It has become possible.

The method for extruding an unvulcanized rubber according to the present invention comprises:
It is characterized in that the composite extrusion device for rubber described in any one of 1 to 5 is used.

Since the screw length is short, material accumulation is small, and hence the amount of waste generated is small. In addition, extrusion of a vulcanizable rubber composition in which the occurrence of rubber scorch is suppressed because of low power consumption, large discharge rate, and easy temperature control can be performed at a low temperature.

In the method for extruding an unvulcanized rubber according to the present invention, the rotation speed of the screw is set to 10 rpm to 120 rpm.
m.

The extruder used in the method for extruding unvulcanized rubber of the present invention has a short screw length and can prevent scorch due to local heat generation as compared with a conventional extruder. High speed rotation is possible,
Therefore, extrusion molding can be performed at high speed. In the extrusion method of the present invention, the compression ratio is 1: 1.
It is preferably 1: 1.1 to 1: 1.3, which is smaller than that of No. 6.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 10 is a screw extruder, 11 is an extrusion screw, 11a is a drive shaft, 12 is a barrel, 12a is a discharge port, 13 is a hopper for charging a vulcanizable rubber composition, and the screw 11
Has a length L and an outer diameter D having a ratio L / D of 2 to 4. The screw 11 and the barrel 12 are provided with medium passages 11b and 12b for temperature control in a conventional manner. The end face on the discharge side (left end face in the figure) of the barrel 12 is slightly inclined with respect to the vertical plane.

On the discharge side of the screw extruder 10,
A filter 14 for removing foreign matter and a breaker plate 15 for supporting the filter are arranged. The filter 14 and the breaker plate 15 are held in a stacker support block 16 in a state where both are overlapped, and connected to the discharge side of the screw extruder 10. The breaker support block 16 is composed of a support plate 17 on the front side (key pump side) and a pressing plate 18 on the rear side (screw extruder side). The filter 14 and the breaker are provided in a concave portion 17a provided in the support plate 17. The plate 15 is fitted and fixed by the holding plate 18. The support plate 17 is provided with a rubber passage 17b having the same diameter as the rubber passage 21a of the gear pump 20 described later, and the holding plate 18 is provided with a rubber passage 18b having the same diameter as the discharge port of the screw extruder 10. The back surface (the surface on the screw extruder side) of the holding plate 18 is formed in a wedge-shaped cross section of an inclined surface parallel to the discharge-side end surface of the barrel 12, and a gear pump 20 described later as the discharge-side end surface of the barrel 12. Are connected by press-fitting from above.

The gear pump 20 comprises a body 21 and a pair of upper and lower gears 22 and 23. On the supply side and the opposite discharge side of the gears 22 and 23, rubber passages 21a have the same diameter as the rubber passages 17b of the support plate 17, respectively. When the breaker support block 16 is press-fitted and connected between the gear pump 20 and the screw extruder 10 from above, a rubber passage 2 in the body 21 is formed.
1a is a rubber passage 17 in the breaker support block 16.
b, 18b through the outlet 12 of the screw extruder 10.
Communicates with a. The die head 24 is connected to the discharge side of the gear pump 20.

In the above structure, the screw extruder 1
The gear 0 and the gear pump 20 are fixed on a support frame (not shown) at predetermined intervals. Between the screw extruder 10 and the gear pump 20, a breaker support block 16 in which a filter 14 and a breaker plate 15 are set in advance is fixed by press-fitting, and the screw 11 and the barrel 12 of the screw extruder 10 are heated to a predetermined temperature. When the screw 11 and the gear pump 20 are rotated at a predetermined speed and a vulcanizable rubber composition having a predetermined viscosity is charged into the hopper 13, the rubber composition G is sent forward by the screw 11, and the shaft of the screw 11 is rotated. It is heated and plasticized by heat transfer from the surface and the inner surface of the barrel 12 and friction with the inner surface of the barrel 12, and heads toward the discharge port 12a with almost no compression in a conventional screw extruder.

The rubber composition G which has been subjected to the first plasticization treatment by heating in the screw extruder 10 enters the rubber passage 18b of the breaker block 16 in a twisted state with little stirring. Then, it passes through the filter 14 and the plater plate 15, and at that time, undergoes shearing and compression, whereby plasticization by self-heating is promoted and agitated, and is passed through the rubber passage 17 b to the supply-side rubber passage 21 a of the gear pump 20. enter in. The rubber composition G that fills the supply-side rubber passage 21a undergoes a second plasticization process by shearing and compression by the engagement of a pair of upper and lower gears 22 and 23, and is plasticized into a moldable state. At the same time, the mixture is stirred and sent to the die head 24 via the rubber passage 21a on the discharge side at a predetermined discharge speed, and is formed into a desired sectional shape and extruded.

FIG. 2 shows an example of the shape of the tip of a screw suitable for the extrusion apparatus of the present invention. The screw 11 has a peak 33 formed therein, and the height (flight depth) of the peak formed by the valley 31 is H. In the present invention, as described above, (1/15) D ≦ H ≦ D (1 /
5) It is preferably D.

The ridge 33 of the screw shown in FIG. 2 is a single thread and is formed spirally and continuously on the outer periphery of the screw. In the extrusion apparatus of the present invention, it is also a preferable embodiment that the ridge is formed in a plurality of rows. The two-row type can be obtained, for example, by forming peaks of the same shape between the peaks 33 of the screw in FIG.

The compound extruder of the present invention is characterized in that the installation of the gear pump 20 hardly causes a decrease in the rubber discharge amount. For example, when an extruder having a screw 11 diameter of 60 mm is used, the discharge rate when the extruder tip is open is 70 to 100 kg / hr. However, when the die head 24 and the die are mounted, the type of rubber and the shape of the die , But the discharge rate drops to 40 to 60 kg / hr.
According to the composite extrusion device of the present invention, 70 to 90 kg / hr
Discharge amount can be realized.

The flight depth H and the flight angle θ are appropriately set in consideration of processing characteristics such as the type and viscosity of the rubber to be extruded. Flight angle θ ranges from 45 ° to 75 °,
Although set according to the flight depth H, H = (1/1)
0) In the case of D to (1/11) D, it is preferable that θ = 50 to 55 °, and in the case of H = (1/8) D to (1/9) D, θ = 65 to 70 ° Preferably, there is.

In the composite extruder of the present invention, the compression ratio can be reduced. The compression ratio of the conventional extruder is about 1.6, while that of the conventional extruder is around 1.6, preferably 1 or less. 0.3 or less, more preferably 1.2 or less.

Since the compression ratio can be set smaller than that of the conventional extruder, heat generation of the rubber in the extruder can be suppressed. As a result, scorch (burn) can be effectively prevented, the drive motor of the extruder can be reduced in size, and power consumption can be reduced. Can also be done.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a screw extruder 10, a screw 1 was used.
The length L of one is 240 mm, the outer diameter D is 60 mm, the L / D is 4, the compression ratio is 1.23, and the diameter of the discharge port 12a is 60 mm.
Prototype was made. Filter 14, breaker plate 15, gear pump 20
(“Extruder type” manufactured by Marg, Switzerland) and the die head 24 are connected, and the SBR and NR vulcanizable rubber compositions G (Mooney viscosity ML1 + 4 = 90 to 30) are supplied to form a tire tread. did.

On the other hand, as a comparative example, a conventional screw extruder (screw length: 720 mm, outer diameter D: 60 m)
m, L / D: 12, compression ratio: 1.6, discharge port diameter: 6
0 mm), and a die head 24 was connected to the same via the same filter 14 and breaker plate 15 as described above, and a tire tread similar to the above was molded.

When the performance of the above example and the comparative example were compared, the amount of rubber supplied until the discharge of the screw extruder was stable at the start of operation and the amount of material accumulated in the screw extruder when the operation was stopped were compared with the comparative example. The amount of rubber loss decreased to 1/3 to 1/5 or less, the temperature of the rubber discharged from the screw extruder decreased by at least 5 ° C, and the power consumption of the screw extruder decreased by 30% or more.

[0035]

As described above, according to the present invention, the screw extruder functions as a supply unit in the conventional screw extruder, and the gear pump operates as the compression unit and the metering discharge unit in the conventional screw extruder. As the screw is shortened, the material pool is reduced, the discharge rate is increased, the screw power is reduced, the temperature control becomes easy, and the extrusion of the vulcanizable rubber composition is performed. This can be performed at a low temperature, thereby preventing rubber scorch and further simplifying the shape of the rubber passage before and after the filter.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an extrusion apparatus of the present invention.

FIG. 2 is a side view showing a part of an example of a screw;

[Explanation of symbols]

 10: Extruder 11: Extrusion screw 11a: Drive shaft 12: Barrel 12a: Discharge port 13: Input hopper 14: Filter 15: Breaker plate 16: Breaker support block 17: Support plate 18: Holder plate 17b, 18b, 21a: Rubber passage 20: Gear pump 21: Body 22, 23: Gear 24: Die head L: Length of screw D: Outer diameter of screw G: Rubber composition θ: Screw flight angle

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 47/00-47/96

Claims (6)

(57) [Claims] 1. A gear pump is connected to the tip of a screw extruder via a filter with a breaker plate,
In a rubber compound extruder in which a die head is connected to the discharge side of the gear pump, the screw extruder plasticizes the supplied rubber composition mainly by friction between the barrel inner surface and external heating. The filter is extruded from the above-mentioned filter to the space on the inlet side of the gear pump, wherein the filter straightens the rubber composition passing through the filter and heading toward the gear pump while plasticizing by friction and shearing. The rubber composition supplied to the inlet side space is further agitated and plasticized by shearing and compressing, and provides a pressing pressure on the die head,
The ratio L / D of the length L and the outer diameter D of the screw is 1
A composite extrusion device for rubber, wherein the number is not less than 3. 2. The apparatus according to claim 1, wherein the screw extruder functions as a rubber supply unit, and the gear pump functions as a rubber compression unit and a measurement discharge unit. 3. The height of a ridge formed on the screw is (1/5) D to (1/15) D.
A composite extrusion device for rubber according to item 1. 4. The composite extrusion device for rubber according to claim 1, wherein a plurality of ridges are formed on the screw. 5. A method for extruding an unvulcanized rubber using the rubber composite extrusion device according to claim 1. Description: 6. The rotation speed of the screw is set to 10 rpm or more.
The method for extruding an unvulcanized rubber according to claim 5, which is performed at 120 rpm.