JPH0578407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to a synthetic resin extruder. In particular, the present invention relates to an extruder suitable for continuously producing synthetic resin foam having a large cross section.

(Prior Art) Synthetic resin extruders are already known. In this extruder, the outer diameter of the screw and the inner diameter of the barrel are each set to a certain size, the screw is rotatably attached to the barrel in a cantilevered manner, and a raw material inlet is provided on the side of the barrel where the screw is supported. It is something. When synthetic resin is introduced into the raw material input port, the extruder advances the resin in the barrel by rotating the screw, and discharges the resin from the tip of the barrel. Therefore, by attaching a cap to the tip of the barrel and drilling a desired hole in the cap, the resin is formed into a long body with a constant cross section and extruded within the hole of the cap. In this way, the extruder is used to produce a resin molded body with a constant cross-sectional shape.

An extruder is required to heat the synthetic resin therein and extrude it as a uniform molten state. For this reason, the outer diameter of the screw was made close to the inner diameter of the barrel, and the distance between them was made small so that the resin could be well kneaded between them. Furthermore, the outer diameter of the screw was made substantially uniform from the base to the tip, and the inner diameter of the barrel was also made to be substantially uniform accordingly.

(Problems to be Solved by the Invention) In the conventional extruder, as shown in FIG. 6, the barrel 1 has an almost uniform inner diameter D from the bottom of the hopper 3 to the tip F, and the screw 2 has The outer diameter d was assumed to be approximately uniform, and the inner diameter D was made slightly larger than the outer diameter d.

However, in the extruder described above, the outer diameter of the screw and the inner diameter of the barrel are uniform all the way to the tip of the screw, so the resin is kneaded between the barrel and the screw screw, which generates heat. . Therefore, the resin is locally heated between the screw screw and the barrel even at the screw tip, and the resin is gathered to the center of the screw shaft in a locally heated state and guided to the base. . Therefore, the resin in the mouthpiece could not be heated uniformly. For this reason, when trying to extrude a foam with a large cross section, the resin foams non-uniformly, making it impossible to obtain a uniform foam. Therefore, it is necessary to mix the resin more uniformly at the end of the extruder, and for this purpose, attempts have been made to attach something like a mixer to the end of the extruder. However, adding something like a mixer to the end of the extruder not only unnecessarily complicates the equipment, but also may cause the resin to cool and cause the temperature to become uneven. The result was that. Therefore, it was necessary to further improve this point.

JP-A-50-161552 proposes providing a small diameter section at the tip of the screw and providing a protrusion on the peripheral surface of the small diameter section in order to impart a flow pattern to the resin during the extrusion process. Since the protrusion was provided so as to extend in the axial direction only at the tip of the small diameter portion, it was not useful for uniformly mixing the resin.
Furthermore, in JP-A-56-11813, when covering a telephone line with foamed resin, a small-diameter portion is provided at the tip of the screw, and a protrusion is provided on the peripheral surface of the small-diameter portion. Since it was attached only to the tip of the section, it was not effective in uniformly mixing the resin.

(Means for Solving the Problems) This invention was created in response to the above-mentioned needs. The inventor provided a small diameter portion at the screw tip of the extruder, and also made the inner diameter of the barrel tip correspondingly small. At the same time, the inventor provided a protrusion that extends toward the inner surface of the barrel over the entire axial length on the peripheral surface of the small diameter portion of the screw, made the protrusion different from the screw screw, and made the protrusion extend in the circumferential direction. It was made discontinuous. Here, making the protrusion discontinuous in the circumferential direction means dividing the protrusion in the circumferential direction, and making one protrusion resulting from the division less than or equal to one-third of the length in the circumferential direction at the small diameter portion, and This means that the length of the notch between the protrusions in the circumferential direction is 1/20 or more and 1/3 or less of the circumference. The inventor has found that by doing so as described above, the resins can be mixed uniformly and the above-mentioned drawbacks can be eliminated. This invention was born based on such confirmation.

This invention is an extruder in which the outer diameter of the screw and the inner diameter of the barrel are approximately the same, the screw is rotatably attached to the barrel in a cantilevered manner, and a raw material inlet is provided on the side of the screw supporting the barrel. In this method, a small diameter part is provided at the tip of the screw, and the inner diameter of the tip of the barrel is also made small, a protrusion is provided over the entire length in the axial direction on the peripheral surface of the small diameter part of the screw, and the protrusion is discontinuous in the circumferential direction.
The synthetic resin is characterized in that the two protrusions are one-third or less of the circumferential length of the small diameter portion, and the circumferential length of the notch located between the protrusions is one-twentieth or more and one-third or less of the circumferential length. This invention relates to an extruder for producing resin foam.

In the extruder according to the present invention, the outer diameter of the screw and the inner diameter of the barrel are made approximately the same size along the longitudinal direction, and the screw is rotatably attached in a cantilever type inside the barrel. Since the input port is provided, when resin is put into the raw material input port, the resin is pushed forward by the screw and is well kneaded between the screw and the barrel, becoming almost uniform and being pushed to the tip of the barrel. . Further, since a small diameter portion is provided at the screw tip and the inner diameter of the barrel tip is also made small, the resin is kneaded in a cylindrical shape with a small diameter. Therefore, no dead center occurs at the center of the screw shaft. Moreover, the protrusions are provided on the circumferential surface of the small diameter part of the screw over the entire length in the axial direction, the protrusions are discontinuous in the circumferential direction, each protrusion is one-third or less of the circumferential length of the small diameter part, and the protrusions are made discontinuous in the circumferential direction. The circumferential length of the notch located between is 1/20 of the circumference.
Since the ratio is set to 1/3 or less, the resin is well kneaded by the rotation of the protrusions, resulting in a more uniform composition that is discharged from the barrel. Thus, according to the extruder according to the present invention, resin can be discharged from the barrel in a uniform state. Therefore, it is suitable for extruding a resin containing a foaming agent to make a foam with a large cross section.

(Example) An example of implementation of the extruder according to the present invention will be described below based on the drawings. 1st
The figure is a partially cutaway vertical cross-sectional view of an extruder according to the present invention. FIG. 2 is an enlarged partially cutaway perspective view of the tip of the screw in the extruder shown in FIG. 1.
FIG. 3 is a partially cutaway vertical sectional view of another extruder according to the present invention. FIG. 4 is an enlarged side view of the screw tip in the extruder shown in FIG. 3.
FIG. 5 is a side view of the small diameter portion attached to the tip of the screw in the extruder according to the present invention.

In Fig. 1, 1 is a barrel, 2 is a screw, 3 is a raw material inlet, 4 is a screw support part, and 5 is a screw.
is a screw screw, 6 is a small diameter part of the screw, 7 is a reduced inner diameter part of the barrel, 8 is a space between barrel 1 and screw 2 in the small diameter part, 9 is a protrusion, 10
11 is a breaker plate, 11 is a base, 12 is a heating device, 13 is a cooling device, and 14 is a space between the barrel 1 and the screw 2 in the large diameter portion.

In the extruder shown in Fig. 1, the inner diameter is reduced at the tip of the barrel 1, the outer diameter is reduced at the tip of the screw 2, and a discontinuous portion is formed on the circumferential surface of the reduced portion over the entire axial length. It differs from conventional extruders in that it is provided with protrusions 9. Conversely, in the extruder shown in Fig. 1, the screw 2 is rotatably attached in a cantilevered manner within the barrel 1, with the screw outside diameter and the barrel inside diameter being approximately the same size along the longitudinal direction. , has a structure in which a raw material inlet 3 is provided on the barrel 1 next to the support part 4 of the screw 2, and this structure is similar to the barrel 1 and the screw 2.
The extruder is similar to the conventional extruder shown in FIG.

To be more specific, the length of the screw 2 is 10 to 30 times longer than its outer diameter, and the screw of the extruder according to the present invention also has a large diameter portion L within that range. have. The large diameter portion L of the screw ends with an outer diameter of a constant size. Here, the outer diameter is a value measured at the protruding tip of the screw screw 5. Corresponding to the large diameter portion of the screw 2 having a constant size, the barrel 1 also has a large diameter portion with a constant inner diameter, and the inner diameter is larger than the screw outer diameter in order to accommodate the screw 2. It is slightly enlarged. Further, the large diameter portion of the barrel is made slightly longer than the length of the large diameter portion of the screw 2. A slight clearance is formed between the tip of the screw screw 5 and the barrel 1 in the large diameter portion.

The large diameter portion of the screw 2 has a screw thread like a conventional screw. A screw groove is formed between the screw screws, and the depth of the screw groove is large right below the raw material input port 3 and becomes smaller as it approaches the tip. The depth of this groove is not particularly different from the conventional one. Further, the screw screw 5 has a constant helical angle, and this helical angle is also the same as that of the conventional screw thread.

The extruder according to the present invention is significantly different from conventional extruders because, as described above, the screw 2 has a small diameter portion 6 at the tip, and also has a small diameter portion 6 on the circumferential surface of the small diameter portion 6 over the entire axial length. It has a protrusion 9,
Another point is that the barrel 1 is provided with an inner diameter reduced portion 7 at the tip. The small diameter portion 6 has an outer diameter that is 0.5 to 0.9 times the outer diameter d of the screw, particularly the outer diameter of the tip of the large diameter portion. The small diameter portion 6 has an axial length that is 1 to 3 times the screw outer diameter d.
A large number of protrusions 9 are formed on the peripheral surface of the small diameter portion 6. The inner surface of the reduced inner diameter portion 7 of the barrel is close to the tip of the projection 9, and the reduced inner diameter portion 7 extends slightly longer than the small diameter portion 6 in the screw axis direction. On average, between the small diameter part 6 of the screw and the reduced inner diameter part 7 of the barrel, the distance between the barrel 1 and the screw 2 in the large diameter part is 0.7-1.3 of 14.
There is a double gap.

The projection 9 attached to the small diameter portion 6 stands up toward the inner surface of the reduced inner diameter portion 7 of the barrel. Further, as shown in FIG. 2, the protrusions 9 are attached in large numbers, and are therefore discontinuous in the circumferential direction of the small diameter portion 6. To be more specific, protrusion 9 in Figure 1
As shown in FIG. 2, rectangular parallelepipeds are arranged in a grid. Although the protrusion 9 is shown as small in the figure, generally speaking, the protrusion 9
The length x in the circumferential direction is one-third or less of the circumference of the small diameter portion, and the length y in the screw axis direction
is less than or equal to the radius r of the small diameter portion 6.

As a result of the protrusions 9 being formed discontinuously in the circumferential direction, notches 15 are formed between adjacent protrusions 9. The notch 15 is more than half the minimum length of the protrusion 9 and less than five times the maximum length of the protrusion 9 both in the circumferential direction and in the axial direction. Also, the height z of the protrusion 9
is more than half of the above minimum length of the projection 9, and more than the depth of the groove at the tip of the large diameter part of the screw;
It is considered to be less than double. A clearance larger than the clearance between the barrel 1 and the screw screw 5 at the large diameter portion is provided between the tip of the projection 9 and the inner surface of the barrel 1.

FIGS. 3 and 4 show other examples of the extruder according to the present invention. The extruder shown in FIGS. 3 and 4 is different from the extruder shown in FIGS. 1 and 2 in that the extruder shown in FIG. The features are that the screw screw consists of two threads, that the screw screw 5 has notches 16 in some places, and that the protrusion 9 has a structure similar to the screw screw 5. Although the extruder shown in FIGS. 3 and 4 has a notch 16 formed in the screw screw 5, the notch has only a small length in the circumferential direction. Specifically, the notch is less than one-twentieth of the circumference. The screw screw may have a notch 16 of this size.

The protrusion 9 in FIGS. 3 and 4 has a similar structure to the screw screw 5, but the notch 15 thereof is larger than the notch 16. Further, the tip of the protrusion 9 forms a large clearance with the inner surface of the reduced inner diameter portion 7, and this clearance is larger than the clearance formed between the screw screw 5 and the barrel 1 in the large diameter portion. Therefore, even when the screw is rotated in the small diameter portion 6, the resin does not generate much heat, and the resin is mixed well and advances.

The small diameter part 6 of the screw may be made integrally with the large diameter part of the screw, but it is preferable to make it separately and attach it later to the tip of the large diameter part. Further, as shown in Fig. 1, the barrel 1 may be made by separately making only the inner part of the reduced inner diameter part and later attaching it to the barrel as an integral part, but as shown in Fig. 3, Alternatively, the entire reduced inner diameter portion may be made separately from the beginning and then attached.

The small diameter portion 6 of the screw is not limited to that shown in FIGS. 1 through 4. Various types as shown in A to D in FIG. 5 can be used. In the small diameter portion shown in FIG. 5A, the protrusion 9 has a rectangular parallelepiped shape, but it is large and one side spans more than half of the radius. B in FIG. 5 shows an example in which protrusions 9 slightly smaller than those in A are densely arranged in a grid pattern. C in FIG. 5 shows an example in which the projections 9 extend in the direction of the screw axis, and D in FIG. 5 shows an example in which the height of the projections 9 is increased and the projections 9 are sparsely attached. .

The shape of the protrusion 9 is not limited to the illustrated example. The protrusion 9 can have various shapes such as a cylinder, a prism, a cone, a pyramid, a truncated cone, and a truncated pyramid.

(Effects of the Invention) According to the present invention, a small diameter portion is provided at the screw tip, the inner diameter of the tip of the barrel is also made small, and a protrusion is provided on the circumferential surface of the screw small diameter portion over the entire axial length. , the protrusions are discontinuous in the circumferential direction, each protrusion is one-third or more of the circumferential length at the small diameter part, and the circumferential length of the notch located between the protrusions is one-twentieth or more and one-third of the circumferential length. With the following settings, the resin charged into the extruder is brought to the center of the screw shaft at the tip of the screw, and is well mixed by the protrusions to have a uniform composition and temperature. Therefore, when extruded as a resin mass with a large cross section, the entire resin mass is uniformly foamed and a good foamed product can be obtained.

The extruder shown in FIGS. 1 and 2 is suitable for making a foamable resin by pressurizing a blowing agent in the middle of the barrel to produce a resin foam. In addition, the extruder shown in Fig. 3 and Fig. 4 has two extruders connected in series, and the blowing agent is mixed in the first extruder, and this is transferred to the second extruder. It is suitable for use as a second extruder when foaming is made.

[Brief explanation of the drawing]

1 and 3 are partially cutaway longitudinal sectional views of an extruder according to the present invention. FIG. 2 is a partially cutaway enlarged perspective view of FIG. 1. FIG. 4 is a partially cutaway enlarged side view of FIG. 3. FIG. 5 is a side view of the small diameter portion of the screw that can be used in the present invention. FIG. 6 is a partially cutaway vertical sectional view of a conventional extruder. In the figure, 1 is the barrel, 2 is the screw, 3
is the raw material inlet, 4 is the screw support part, 5 is the screw screw, 6 is the screw small diameter part, 7 is the barrel inner diameter reduction part, 8 is the gap, 9 is the protrusion, 10 is the breaker plate, 11 is the cap, 12 is the heating tool , 13
1 is a cooling device, 14 is a spacer, and 15 and 16 are notches.

Claims (1)

[Claims] 1. The screw is rotatably attached in a cantilever manner in the barrel, with the outer diameter of the screw and the inner diameter of the barrel being approximately the same size along the longitudinal direction,
In an extruder in which a material input port is provided along the screw support of the barrel, a small diameter portion is provided at the tip of the screw, and the inner diameter of the tip of the barrel is also made small. Protrusions are provided across the protrusions, the protrusions are discontinuous in the circumferential direction, each protrusion is one-third or less of the circumferential length at the small diameter part, and the circumferential length of the notch located between the protrusions is one-twentieth of the circumferential length. An extruder for producing a synthetic resin foam, characterized in that the ratio is one-third or less. 2 The outside diameter of the small diameter part is 0.5-0.5 of the outside diameter of the remaining large diameter part.
0.9 times, and the length in the axial direction of the small diameter portion is 1 to 3 times the outer diameter of the large diameter portion, as set forth in claim 1. .