JP2000218619A - Part for kneading/dispersing for extruder, and screw therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an increase in the temperature of resin due to shear heating and extrude the resin under a highly dispersed homogeneous state by arranging intermediate grooves, overflow flights and sluice flights in a multistep fashion, halfway through a barrier-type part for kneading, when this part is manufactured. SOLUTION: In the barrier-type part for kneading 9 having plural inflow grooves 1, overflow flights 2, sluice flights 3 and outflow grooves 4 provided on the circumference, intermediate grooves 5, the overflow flights 2 and the sluice flights 3 are arranged halfway through the part 9. In addition, during the passage of resin from the inflow grooves 1 to the outflow grooves 4, the resin is mashed plural times by narrow gaps formed between the overflow flights 2 and a barrel to achieve the sufficient kneading and dispersion of the resin so that it is well homogenized. In this case, the optimal number of times of passage of the resin through the gaps is 2-4. The optimal length of the screw for an extruder in the axial direction from the inlet of the inflow groove 1 to the outlet of the outflow groove 4 is 2-4 times the diameter of the screw for the extruder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kneading / dispersing component and a screw for an extruder used for plasticizing melt extrusion of a thermoplastic plastic.

[0002]

2. Description of the Related Art When extruding a thermoplastic resin, it is extremely important to extrude the resin in a homogeneous molten state by sufficiently melting and kneading in an extruder in order to obtain a high quality resin molded product. It is. In particular, if the kneading and dispersing in the extruder is not sufficient depending on the raw material resin, an unmelted material that cannot be completely melted, or a high molecular weight component is extruded as fine gel-like particles (material), resulting in non-homogeneous Molded as it is, the physical properties of the molded article become inferior.

[0003] In the case of a transparent molded product, these inhomogeneities are conspicuous as foreign matters or uneven patterns with respect to light transmission, and have a disadvantage that they have no commercial value.

To cope with these problems, a plurality of inflow grooves 1, overflow flights 2, damping flights 3, and outflow grooves formed on a circumference as shown in FIG. 4, a mixing type mixing part for kneading, etc. of the barrier type has been proposed and actually used. The mechanism of kneading and dispersing is to force the resin to pass through the gap between the overflow flight 2 and the barrel, thereby applying shear stress to the resin to grind and disperse the unmelted material and the like.

[0005] When these kneading and dispersing parts are used in combination with a melting promoting part comprising a main flight and a subflight in a compression part, or when used in combination with a pin mixing part for distribution and mixing, etc. There is also.

[0006]

In the prior art, when the rotation speed of the screw for the extruder increases, the shearing stress acting on the resin also increases and the crushing effect is exhibited. Causes the resin temperature to increase. In injection molding and film casting molding, high resin temperature is not a particular problem, but in direct blow molding, the drawdown of the parison becomes large and the molding cycle becomes long when the resin temperature becomes high. Problem. Also, a high resin temperature can cause the generation of thermal degradation products.

[0007] In order to avoid these problems, it is usual to operate at a relatively low rotational speed. However, in this case, there is a problem that kneading and dispersion become insufficient and gel-like bumps and uneven patterns are generated. there were.

The present invention breaks through a problem which can be said to be a common wisdom that the resin temperature increases due to shear heat when the kneading dispersion is improved in the prior art. For kneading and dispersing components that can exhibit high performance, suppress the rise in resin temperature due to shear heat generation, and extrude resin with good dispersion homogeneity for kneading and dispersing components and extruders equipped with it It is intended to provide a screw.

[0009]

In order to achieve the above-mentioned object, as a result of various studies, even if the resin is passed through the narrow gap between the overflow flight and the barrel, only one pass is required.
It was found that the unmelted material and the like deformed and passed through the narrow gap and was not completely ground, but was still in a somewhat unmelted state.

As a countermeasure, a component for kneading and dispersing has been developed in which the resin is repeatedly passed through a narrow gap several times to give the resin a grinding effect repeatedly to eliminate non-uniformity such as unmelted material or high molecular weight gel.

More specifically, as shown in FIG. 1, a barrier-type kneading component 9 composed of a plurality of inflow grooves 1, overflow flights 2, damming flights 3, and outflow grooves 4 on a circumference. By arranging the intermediate groove 5, the overflow flight 2 and the blocking flight 3 in the middle thereof, the resin flowing from the inflow groove 1 overflows several times before exiting from the outflow groove 4. By passing while being crushed in a narrow gap formed between the flight 2 and the barrel, the mixture is sufficiently kneaded and dispersed to become a homogeneous state.

As the number of passes through the overflow flight 2 increases, kneading and dispersion are performed. However, the pressure loss at that portion also increases, and the extrusion rate decreases.
Two to four times is optimal.

If the axial length of the screw for the extruder from the inlet of the inflow groove 1 to the outlet of the outflow groove 4 is short, the length of each overflow flight 2 becomes short and the pressure loss becomes large. Since the extrusion amount is reduced, the length in the axial direction is suitably 2 to 4 times the diameter of the screw for the extruder.

Further, as illustrated in FIG. 2, the inflow groove 1, the outflow groove 4 and the intermediate groove 5 are formed as spiral grooves, so that the grooves themselves have a function of transferring resin, thereby reducing pressure loss. Can be reduced.

When extruding a resin having a high viscosity or a resin having a low non-Newtonian property whose viscosity does not decrease even at a high shear rate, the pressure loss should be reduced as much as possible in order to avoid an increase in the resin temperature due to heat generation. Care must be taken not to reduce the amount of extrusion, and it is necessary to consider the kneading and dispersing part of the present invention to have an optimum shape in terms of the number of grooves, the angle of the spiral, the length, and the like.

For example, when the number of grooves is four, the helix angle with a small pressure loss is in the range of 40 to 60 degrees, and particularly preferably 45 to 50 degrees. Also, if the number of grooves is 5
In the case of a book, the angle is preferably from 50 to 70 degrees, and particularly preferably from 54 to 58 degrees.

This relationship can be expressed by the following equation when the number of grooves is Nc.

10 × Nc ≧ φ ≧ 14 × Nc Also, the kneading and dispersing parts 9, 9a
It is preferable to arrange in the first half of the measuring section C after the 0 compression section.

This is because the unmelted or gelled high molecular weight component is first ground by kneading and dispersing in the first half of the measuring section C, and then in the middle to the second half of the measuring section C, the ground and the former are mixed. By distributing and mixing what has already been melted, it is possible to make the whole homogeneous.

Furthermore, a melting promoting section composed of a main flight and a subflight, and / or a measuring section C for distributive mixing, which is conventionally used in the compression section for improving the melting function of the extruder. The extruder screw combined with the kneading and dispersing part of the present invention is provided with a distributing / mixing unit in which protrusions such as pins are arranged in the groove portion in the latter half of the extruder, thereby further improving extrusion stability and homogeneity. Excellent extrusion becomes possible.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given of an example of the structure of a kneading / dispersing component and a screw for an extruder incorporating the component according to the present invention with reference to the drawings. 1 and 2 show an embodiment of a kneading / dispersing component according to the present invention.

FIG. 1 is a cross-sectional view of an extruder 5 parallel to the axis of the screw.
Overflow flight 2 consisting of a set of grooves for kneading and dispersion
Is shown three times. FIG. 2 shows a kneading / dispersing component 9a composed of four sets of grooves having a helical angle of 45 degrees and passing through the overflow flight 2 three times.

The kneading / dispersing component 9 shown in FIG. 1 comprises a plurality of inflow grooves 1, intermediate grooves 5, outflow grooves 4, overflow flights 2 and damming flights 3, and in the downstream direction of the inflow grooves 1. The wall on the rotation direction side of the extruder screw and the wall of the extruder screw are constituted by a damming flight 3, and the wall on the side opposite to the rotation direction is constituted by an overflow flight 2. In the intermediate groove 5, the upstream and downstream walls, the wall on the opposite side to the rotation direction in the first half, and the wall in the rotation direction in the second half are the blocking flight 3,
A wall in the rotation direction in the first half and a wall opposite to the rotation direction in the second half are formed by the overflow flight 2. Further, in the outflow groove 4, the upstream wall and the wall on the side opposite to the rotation direction are configured by the blocking flight 3, and the wall in the rotation direction is configured by the overflow flight 2.

The gap (not shown) between the overflow flight 2 and the barrel is selected according to the caliber of the extruder, and is usually preferably 1/50 to 1/200 of the caliber. The gap between the damming flight 3 and the barrel is usually 1/10
0 mm to 2/100 mm is preferred. The number of steps of the intermediate groove 4 is shown in FIG.
In the example, there are two stages, but this is not a limitation.
It suffices if it is 2 or more. However, when the number of stages is increased, adverse effects such as an increase in pressure loss and a decrease in the amount of extrusion appear, so that the number of stages is preferably two to four.

The configuration of the kneading / dispersing component 9a shown in FIG.
By forming each groove and flight in a spiral shape, a function of transporting the resin in the groove to the downstream side is provided. The effect of this transport function makes it possible to reduce pressure loss.

Next, an embodiment of an extruder screw in which the kneading and dispersing parts 9, 9a are combined with the conventionally used melting promoting parts and distributing mixing parts is shown in FIG.
It will be described based on.

In the extruder screw 10 composed of the feed section E, the compression section D and the measuring section C, the sub section obliquely crossing the groove constituted by the main flight 6 continuing from the feed section E in the compression section D. A kneading / dispersing section A having a kneading / dispersing component 9 or 9a provided in the first half of the measuring section C is provided in the melting promoting section provided with the flight 7, and a main flight 6 is provided in the latter half of the measuring section C. And a distributing / mixing section B in which a flow is agitated by providing a projection 8 such as a pin in the groove formed by the above.

The length of each part constituting the extruder screw 10 is 7 to 10 mm in the feed part E with respect to the barrel diameter d.
14d, preferably in the range of 9 to 11d, and the compression part D is 7 to
14d, preferably in the range of 9 to 11d, the measuring section C is 4 to
10d, preferably in the range of 6-8d.

The kneading and dispersing parts 9 or 9a provided in the first half of the measuring section C are 1-4d, preferably 2-3d.
The length of the distributing / mixing section B provided in the latter half is 1 to 3d, preferably 1 to 2d.

The incorporation of the kneading / dispersing component 9 or 9a is not limited to this example, and it can be used alone in the measuring section C of a usual screw for an extruder.

The operation of the kneading and dispersing section A will be described with reference to the example of FIG. As shown by the broken line in the figure, the resin flowing into the inflow groove 1 flows through the narrow gap between the first overflow flight 2 and the barrel, flows into the first intermediate groove 5, and then flows into the intermediate groove 5. 5 flows downstream. Then, it flows into the second intermediate groove 5 through the gap of the second overflow flight 2, and then flows downstream in the second intermediate groove 5, and further flows through the gap of the third overflow flight 2. It passes and flows into the outflow groove 4, and finally exits from the outflow groove 4.

As described above, while all the resin passes through the kneading and dispersing section A, high shear stress generated by rotation of the extruder screw 10 in the narrow gap between the overflow flight 2 and the barrel is applied several times (this example). In this case, the mixture is sufficiently kneaded and dispersed by receiving it three times.

Even if the resin is passed while applying shear stress in the gap between the overflow flight 2 and the barrel, the gel material such as the unmelted material and the high molecular weight component is softened at the temperature only once, because the resin is softened at the temperature. In fact, it is not possible to sufficiently disperse and pass through this gap and disperse sufficiently. By applying a shear stress to such a material several times, it is possible to more uniformly disperse and knead the material.

On the other hand, in order to allow the resin to pass through such a narrow gap, a large pressure loss occurs, which may cause a problem of a decrease in the throughput. In such a case,
As shown in FIG. 2, pressure loss can be effectively prevented by arranging the grooves and flights in a spiral shape in order to impart the function of transporting the resin downstream to the grooves themselves.

Next, in the extruder screw combined with the compression section D having the kneading / dispersing section A, the melting promoting section and the distribution mixing section B, first, the solid resin transferred from the feed section E to the compression section D Is melted by heating from the barrel and shearing heat generated by friction with the barrel, but is separated into the molten resin part and the solid-phase resin part by the subflight 7 of the compression part D. , The melting ability is improved, and the melting is stabilized and promoted.

The resin that has passed over the subflight 7 contains a small unmelted substance, a high molecular weight gel, and the like, and is not in a homogeneous state. Those transferred to the measuring section C flow into the kneading / dispersing section A, and are ground and kneaded and dispersed by shearing stress under the above-described action. Next, the flow of the resin is agitated in the distributing / mixing section B provided in the latter half of the measuring section C, so that the whole is homogenized and extruded.

In order to confirm the effects of the present invention, there are the following: 1: an extruder screw S ₁ , in which the kneading / dispersing part 9a (FIG. 2) of the present invention is incorporated into a usual full-flight type extruder screw. An extruder screw S ₂ in which the kneading and dispersing part 9a (FIG. 2) of the present invention is combined with a subflight type melting accelerating section and a pin type distributing / mixing section, and, for comparison, melting of the subflight 7 Extrusion experiments were carried out on an extruder screw S _{3 having} an accelerating section and a pin-type distributing / mixing section B but not having the kneading / dispersing parts 9 or 9a.

In the experiments, the diameter d was 55 mm and the length was L /
An extruder with d = 28 was used. The resin used is MFR
3.0 soft polypropylene random copolymer.

A round die was attached to the tip of the extruder to form a sheet having a thickness of 0.5 mm, and the results of observation of the occurrence of gel-like non-uniform bumps contained in the sheet are shown in Table 1.

As can be seen from Table 1, the kneading and dispersing parts 9,
The extrusion screw incorporating 9a has surprisingly reduced occurrence of bumps and has an excellent kneading and dispersing effect.

[0041]

[Table 1]

[0042]

According to the present invention described above, according to the kneading and dispersing component and the extruder screw using the same,
The occurrence of dust is greatly reduced, and an excellent kneading and dispersing effect is exhibited.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of a kneading / dispersing component according to the present invention.

FIG. 2 is a plan view of another embodiment of the kneading / dispersing component according to the present invention.

FIG. 3 is a plan view of one embodiment of an extruder screw incorporating the kneading / dispersing component according to the present invention.

FIG. 4 is a schematic view showing a flow of a resin in the kneading / dispersing component according to the present invention.

FIG. 5 is a schematic view of a conventional kneading / dispersing component and a flow of resin.

[Explanation of symbols]

 A: Kneading / dispersing section B: Distributing / mixing section C: Measuring section D: Compression section E: Feed section 1 ... Inflow groove 2 ... Overflow flight 3 ... Damage flight 4 ... Outflow groove 5 ... Intermediate groove 6 ... Main flight 7 ... Subflight 8 ... Pin-shaped protrusion 9 ... Parts for kneading and dispersing 10 ... Screw for extruder

Continued on the front page F term (reference) 4F201 AM32 BA01 BC02 BC12 BD05 BK13 BK46 BK47 BK48 BK50 BK51 4F207 AM32 KA01 KK12 KL04 KL05 KL06 KL07 KL24 KL26

Claims (4)

[Claims] 1. A barrier-type kneading part comprising a plurality of inflow grooves (1), overflow flights (2), damming flights (3) and outflow grooves (4) on a circumference.
A kneading / dispersing component for an extruder, comprising an intermediate groove (5), an overflow flight (2) and a damming flight (3) arranged in multiple stages along the way. 2. A shape in which each groove and flight are twisted at an angle of helical angle ψ10 × Nc ≧ ψ ≧ 14 × Nc (where Nc is the number of inflow grooves) satisfying the following conditions. The kneading / dispersing component for an extruder according to claim 1, wherein 3. An extruder screw comprising a feed section (E), a compression section (D), and a metering section (C),
3. A screw for an extruder, wherein the kneading and dispersing component according to claim 1 is arranged in a part of a measuring section. 4. A screw for an extruder used for plasticizing melt extrusion of a thermoplastic plastic, wherein a main flight (6) continuing from a feed section (E) and a subflight (7) dividing a groove formed by the main flight. ), And a screw for an extruder having a distributing / mixing section (B) having a projection such as a pin in a part of a groove of the measuring section (C). 2
A screw for an extruder, wherein the kneading and dispersing parts described above are combined.