JPH07256717A - Single plasticizing screw and plasticizing method using the same - Google Patents

Abstract

PURPOSE:To provide a single plasticizing screw capable of achieving both of excellent mixing properties and low temp. extrusion properties. CONSTITUTION:In a weighing part 14, a plurality of eccentric flights A, B, C mutually arranged in parallel so that respective flight heights repeat a gradual decrease and a gradual increase over definite length along the longitudinal direction thereof and the phase of the gradual decrease and that of the gradual increase are shifted are provided between flights 16 constant in flight height. A mixing part 5 is connected to the leading end of the weighing part 14 to be inserted in a hollow barrel 2 and consists of a rotor 22 having a plurality of cavities 3 provided to the outer peripheral surface thereof and the ring inserted in the rotor 22 in a freely rotatable manner so as to be slidable in the axial direction of the rotor 22 and having a plurality of cavities provided to the inner peripheral surface thereof. A check valve 6 consists of the valve seat part 25 provided to the leading end of a weighing part 12 and a ring 23 having the valve disc part 26 corresponding thereto formed thereto.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plastic resin such as a polymer blend resin whose dispersibility is desired to be improved, or a resin such as PET (polyethylene terephthalate) or PAN (polyacrylonitrile) which is required to have low temperature extrudability. TECHNICAL FIELD The present invention relates to a uniaxial plasticizing screw suitable for plasticization and a plasticizing method.

[0002]

2. Description of the Related Art In injection molding or extrusion molding, a uniaxial plasticizing screw is widely used as a device for melting and mixing resins. This uniaxial plasticizing screw is rotatably inserted into a hollow barrel and has a material supply section, a compression section, and a measuring section in which spiral flights are continuously provided. In particular, a uniaxial plasticizing screw for injection molding is inserted into a hollow barrel so as to be rotatable and axially slidable, and has a material supply unit, a compression unit, and a measuring unit in which spiral flights are continuously provided. It has a mixing part and a check valve at the tip.

With such a uniaxial plasticizing screw,
If the polymer blend resin is plasticized, the mixture may be insufficient and the desired molded product may not be obtained. Since the polymer blend resin is a heterogeneous system in which two or more polymers (synthetic resin, synthetic rubber, etc.) are mixed, the properties vary depending on the mixed state. If the mixing is insufficient, the desired mechanical strength and surface properties cannot be obtained.

Further, when molding PET bottles, it is necessary to set the barrel temperature as low as possible to keep the acetaldehyde concentration low, but the low temperature extrudability of the above-mentioned uniaxial plasticizing screw is limited and insufficient. Also, P
AN has a high softening point, discolors at 250 ° C to 360 ° C, and
Since it decomposes at 50 ° C. or higher, it is necessary to set the barrel temperature as low as possible in a narrow range, but the above-mentioned uniaxial plasticizing screw is insufficient because of its low temperature extrudability.

Therefore, instead of a simple full-flight uniaxial plasticizing screw, a screw having improved mixing performance has been proposed. Increasing the mixing performance allows the desired mechanical strength to be obtained and the temperature uniformity allows for low temperature extrusion.

In order to improve such kneading performance, a mixing portion is provided at the tip of the screw. There are various types of this mixing section, but as a means for efficiently mixing without applying excessive shear, JP-A-2-
There are some which perform distributive mixing of 63538. This mixing unit is connected to the tip of the measuring unit of the full flight screw, and has a rotor having a plurality of cavities on the outer peripheral surface,
A ring rotatably inserted into the rotor and having a plurality of cavities on the inner peripheral surface.

Further, in order to improve the kneading performance, the flight shape of the screw may be made special.
There are various types of special flights, but there is one that uses a multi-eccentric flight of Japanese Utility Model Publication No. 3-478459 as one that collapses a solid bed that floats between flights to promote resin melting. This multi-eccentric flight is such that during a concentric flight with a constant flight height, each flight height repeats a gradual decrease and an increase along its length over a constant length and the phase of the gradual decrease and the gradual increase. It is provided with a plurality of eccentric flights that are staggered and arranged in parallel with each other.

[0008]

When the above-mentioned polymer blend resin, PET, and PAN are plasticized by a screw having such a distribution type mixing section or a screw having multi-eccentric flight, the mixing property is better than that of the full flight screw. Although the low temperature extrudability is improved, the improvement effect is not sufficient, and a uniaxial plasticizing screw having more excellent properties has been desired.

The present invention has been made in view of such demands in the prior art, and an object thereof is to plasticize a special resin such as a polymer blend resin, PET or PAN. It is an object of the present invention to provide a uniaxial plasticizing screw and a plasticizing method capable of achieving both excellent mixability and low temperature extrudability.

[0010]

Means for Solving the Problems A uniaxial plasticizing screw which achieves the above object is a uniaxial plasticizing screw having a material supplying section, a compressing section and a measuring section, wherein a mixing section is provided at the tip. , During a concentric flight with a constant flight height, each flight height repeats a taper and a ramp along its length over a constant length and shifts the phase of the ramp and ramp parallel to each other. A plurality of eccentric flights arranged in a row are provided up to the tip of the measuring section, and the mixing section is connected to the tip of the measuring section.
It comprises a rotor having a plurality of cavities on its outer peripheral surface and a ring rotatably inserted into the rotor and having a plurality of cavities on its inner peripheral surface. Especially for injection molding, injection molding is inserted into a hollow barrel so as to be rotatable and axially slidable, has a material supply section, a compression section, and a metering section, and is provided with a mixing section and a check valve at the tip. In the uniaxial plasticizing screw for use, the measuring unit repeats gradually decreasing and gradually increasing each flight height along a length thereof during a concentric flight where the flight height is constant, and A plurality of eccentric flights arranged in parallel to each other with a phase of gradually decreasing and gradually increasing are provided up to the tip of the measuring section, and the mixing section is connected to the tip of the measuring section and inserted into the hollow barrel. And a rotor having a plurality of cavities on its outer peripheral surface and a ring rotatably inserted in the rotor and slidable in the rotor axial direction and having a plurality of cavities on its inner peripheral surface. Check valve includes a valve seat provided in the metering tip, is made of said ring valve body portion is formed with respect to the valve seat portion.

A method of plasticizing a polymer blend resin having excellent dispersibility, for example, a high crystalline high fluidity rubber modified resin, is as follows. The polymer blend resin is stirred by the eccentric flight using the above-mentioned screw for injection molding. This is a method of causing a partial flow in the mixing section. In addition, the plasticizing method of PET excellent in low-temperature extrudability uses the above-mentioned screw for injection molding and polyethylene terephthalate (PE
It is a method in which T) is agitated by the eccentric flight and then flow-divided by the mixing section. Further, it is a method of plasticizing PAN which is excellent in low-temperature extrudability, and a method of using the above-mentioned screw for injection molding, stirring polyacrylonitrile (PAN) by the eccentric flight, and then causing a partial flow in the mixing section.

[0012]

In the multi-eccentric flight portion of the screw, the resin flow in the flight is agitated and the low temperature homogenization of the molten resin is promoted. Furthermore, the mixing and mixing flow is repeated while alternately passing through the cavities of the rotor and the ring in the mixing section, which causes a complicated motion to increase the mixing degree exponentially. Due to the synergistic effect of the melting accompanied by the low temperature homogenization and the series-wise mixing, both the low temperature extrudability and the improvement of the kneading degree are realized.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a uniaxial plasticizing screw for injection molding of the present invention. FIG. 2 is a sectional view taken along line XX of FIG.

In FIG. 1, a screw 1 is a hollow barrel 2
It is inserted inside and is rotatable in the direction of arrow a and is also movable in the axial direction of arrow b. A head 3 is connected to the tip of the barrel 2 with a bolt 4. The head 3 has a conical hole 3a continuous with the hole 2a of the barrel 2 and a center passage 3b.

The screw 1 has a root portion 11, a material supply portion 12, a compression portion 13, and a measuring portion 14 arranged in a straight line. The root part 11 is connected to a hydraulic motor (not shown) to be rotatable, and is also connected to a hydraulic actuator (not shown) to be movable in the axial direction. The material supply unit 12 includes a single small diameter shaft 15 and a single spiral flight 16
And a deep groove 17 is formed. Compression unit 13
Is provided with a spiral flight 16 continuing from the small diameter shaft 15 to the large diameter shaft 18, and the groove 20 becomes gradually shallower. The measuring portion 14 is provided with a spiral flight 16 continuous with a large-diameter shaft 18, and a shallow groove 21 is formed. The spiral flight 16 is concentric with the axial center, and the flight heights of the weighing unit 14 are the same. This flight 16
To send the resin forward. Further, the resin is melted and mixed by internal heat generation due to the shearing force between the inner surface of the barrel 2 and the groove bottom and heating from the barrel 2.

Between the concentric flights 16 of the measuring section 14, three eccentric flights A, B and C are provided at equal pitches. The eccentric flights A, B, and C exist over the entire length of the weighing unit 14, and the starting points As, Bs, and Cs of the eccentric flights A, B, and C start near the end of the compression unit 13. The shapes of the eccentric flights A, B and C will be described with reference to FIG. As in the X1-X1 cross section, the eccentric flight A is projected so that the flight height gradually increases from 0 ° to 90 ° and the flight height gradually decreases from 90 ° to 180 °. As in the X2-X2 cross section, the eccentric flight B is 120 ° out of phase with the eccentric flight A and is 120 °.
It is projected so that the flight height gradually increases from 210 ° to 210 ° and the flight height gradually decreases from 210 ° to 300 °. Eccentric flight C is 120 with respect to eccentric flight B
The phases are shifted so that the flight height gradually increases from 240 ° to 330 ° and the flight height gradually decreases from 330 ° to 420 °. The material supply section →
The flight 16 extending from the compression unit to the metering unit is a concentric flight like the X3-X3 cross section and has a constant flight height.

In FIG. 1, the mixing section 5 comprises a rotor 22, a ring 23, and a torpedo 24. Further, the check valve 6 includes the valve seat portion 25 and the ring 2
3 and a valve portion 26 at the end. The rotor 22 and the torpedo 24 are integrated, and a right-angled step portion 27 is formed between them. A screw 28, a positioning shaft 29, and a flange 30 are formed on the opposite side of the rotor 22 from the torpedo 24. The valve seat portion 25 includes the conical seat 31 and the flange 3
The valve seat portion 25 has a step portion to which 0 hits and a shaft having the same diameter as the measuring portion 14, and when the rotor 22 is screwed into the end of the measuring portion 14, the valve seat portion 25 is fastened together. The valve portion 26 of the ring 23 is a conical receiver, and a gap ε is formed between the valve portion 26 and the conical seat 31 described above.
When the ring 23 is pushed by the back pressure of the resin and the gap ε becomes zero, the reverse flow of the resin is blocked.

The ring 23 is inserted into the hole 2a of the barrel 2 and is slidable in the axial direction. Further, the ring 23 is rotatably fitted to the rotor 23 and is allowed to slide in the axial direction to the extent that the clearance ε becomes zero. The inlet of the rotor 23 has a small diameter to form a resin passage 32, and the resin passage 32 communicates with the cavity 33 in the first row. The cavities 33 in the shaft portion of the rotor 23 are dish-shaped depressions and are arranged in a zigzag pattern. The cavities 3 in the second to fourth rows are formed.
3 are independent. The cavity 33 in the fourth row communicates with the cutout groove 35 of the torpedo 24 through the resin passage 34. The ring 23 has an inner circumference along the outer circumference of the rotor 22 and has a pitch 1 / of the row pitch with the cavity 33 of the rotor 22.
The cavity 36 of the through hole displaced by 2 is the ring 23.
Is provided on the inner peripheral surface of the. Cavity 3 of rotor 22
7 are provided in the circumferential direction, and the cavity 3 of the ring 23 is provided.
Six 6 are provided in the circumferential direction, and the circumferential pitch is also shifted. Furthermore, the hole diameters of the cavity 33 and the cavity 36 are also different. The rotor 22 also rotates as the screw rotates, but the gap between the ring 23 and the barrel 2 and the ring 2
By properly setting the clearance between the rotor 3 and the rotor 22, the rotor 3 rotates at a considerably slower speed than the rotor 22, and the relative rotation between the ring 23 and the rotor 22 is ensured. Then, a complicated distribution operation is performed due to the axial and circumferential deviations in the arrangement of the cavities 33 and 36 and the difference in hole diameter.

Next, the operations of the multi-eccentric flights A, B, C of the screw and the mixing section 5 will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing a mixture of multi-eccentric flights A, B, and C, and the time passes from (a) to (f). In the groove between the flights 16, a multi-eccentric flight A,
B and C are protruding and retracting in order. Therefore, the resin flow is divided, the resin flow in the flight is agitated, and low temperature homogenization of the molten resin is promoted. Further, the resin passing over the eccentric flights A, B, and C is locally sheared, and the melting of the unmelted resin is promoted. Therefore, the unmelted resin begins to drift in the molten resin due to the break-up phenomenon that occurs in the plasticization process, and in the screw for injection molding, the cross channel is generated when the screw rotation is stopped or when the pressure in the screw groove drops and the gas is ejected or injected. Even if the break-up phenomenon is promoted by the flow, it is effectively plasticized by the eccentric flights A, B, and C and is stirred at the same time.

The resin thus plasticized while being stirred reaches the mixing 5. The axial flow of FIG.
As shown in the (b) circumferential flow, a shearing action due to the rotation of the rotor 22, a combination of axial division and orientation between the cavities 33, 36, and a circumferential division between the cavities 33, 36. Depending on the combination of orientations, the resin has a complicated flow. The cavities 33 and 36 are arranged perpendicularly to the shearing direction to ensure efficient mixing,
The mixing degree increases exponentially in accordance with the number of rows of the cavities 33 and 36.

As described above, the agitation action of the multi-eccentric flights A, B, C of the measuring unit 14 and the distribution and orientation actions of the distribution-type mixing unit 5 connected to the measuring unit 14 have a synergistic effect, so that the resin temperature is homogenized. And a high degree of mixing is achieved.

Although the above-described embodiment of FIG. 1 is for the case of the uniaxial plasticizing screw for injection molding, in the case of extrusion molding, the axial movement of the screw itself is unnecessary, and the check valve is also used. A uniaxial plasticizing screw of the same construction is used except that it is unnecessary.

Next, an example of performance confirmation experiment of the above-mentioned uniaxial plasticizing screw for injection molding will be described. Table 1 shows the dimensions of the screw of the present invention used and the dimensions of the full flight screw used for comparison.
The groove depth is the same and the conditions are adjusted.

[0024]

[Table 1]

The resin used in the experiment is TSOP which is a PP / EPR polymer blend resin used for bumpers.
(Mitsubishi Petrochemical Co., Ltd. TSOP YK1) and PAN
(PAN manufactured by Mitsubishi Kasei Co., Ltd.). Table 2 shows the molding conditions of each resin.

[0026]

[Table 2]

First, the result of electron microscope observation of TSOP, which is a resin that is difficult to disperse, will be described with reference to FIG. The black particles in the drawing are rubber particles, and the rubber particles of the screw of the present invention in FIG. 5 (a) are much smaller and finely dispersed than the rubber particles of the full flight screw in FIG. 5 (b). You can clearly see what you are doing.

As the properties required for the bumper material, the elongation at break and the Izod impact value were compared. Figure 6
(A) is a graph showing increase / decrease when the breaking elongation at full flight 100 RPM / 0 MPa is 100,
The screw of the present invention has a larger breaking elongation. Figure 6 (a) shows full flight 100 RPM / 0MP
It is a graph showing increase and decrease when the Izod impact value at a is 100, and the impact value is improved in the case of the screw of the present invention. As a result, it was confirmed that the elongation was improved by 20 to 50% and the impact value was improved by 3 to 8%.

The full flight screw showed brittle fracture in the final fracture, but the screw of the present invention showed ductile fracture until the end. In addition, molecular weight analysis was also performed, but the weight average molecular weight (MV) and molecular weight distribution (Q
No significant difference was observed in the value).

Further, in order to check the mixing degree of the TSOP recycled material which has been treated by coating the TSOP coating bumper and crushed, a full flight screw, an eccentric flight screw,
The surface gloss of the plasticized product of the screw of the present invention was examined.
As shown in FIG. 7, the full flight screw, the eccentric flight screw, and the screw of the present invention have improved surface gloss.

From the above results, in the case of a highly crystalline and highly fluid resin, the shearing effect cannot be sufficiently transmitted because the viscosity of the resin in the measuring section of the full flight screw decreases.
Dispersion and mixing efficiency decreases. However, if the interface is positively increased like the screw of the present invention, it can be efficiently dispersed without being affected by a change in viscosity, and a large shearing force is not applied, which adversely affects the molecular weight. Nor.

Next, as an application example of the effect of equalizing the resin temperature by the low shear and high mixing function, the experimental results of PAN injection molding will be described below. The tensile yield elongation and the Izod impact value when molded with the full flight screw and the screw of the present invention were measured, and the results are shown in FIG. The elongation is more than doubled, and the impact value is improved by 10% on average.
It is presumed that this is also due to the fact that the high dispersion effect of the screw of the present invention allowed the barrel temperature to be set to a lower temperature than that during normal production.

Next, the experimental results of PET parison injection molding will be described below as another application example of the effect of equalizing the resin temperature by the low shear high mixing function. In the injection molding of PET parison, if the molding temperature is low and the unmelted portion remains in the molten resin, the parison becomes cloudy and the transparency decreases. On the other hand, when the molten resin is too high, the resin is decomposed, the IV value is remarkably lowered, and acetaldehyde is produced. So, in the experiment, PET parison injection molding 3
Using a two-cavity mold, a 130 mm diameter full flight screw and a 130 mm diameter screw of the present invention were compared. In addition, the barrel temperature settings for the 6 zones from under the hopper of the full flight screw to the nozzle are set to 280 ° C, 290 ° C.
C, 310 ° C., 310 ° C., 310 ° C., and 300 ° C.
On the other hand, in the screw of the present invention, the barrel temperature is set in 6 zones from below the hopper to the nozzle at 280 ° C, 280 ° C, 288 ° C.
C., 285.degree. C., 285.degree. C., 280.degree. C., and the barrel temperature was lowered by 20.degree. FIG. 8 shows the results of measuring the acetaldehyde concentration by the air space method after the parison molded with both screws was blow molded.

In the case of the screw of the present invention, the acetaldehyde generation concentration is 6 at the maximum while maintaining the transparency of the parison.
The average value was reduced by 0% and the average value was reduced by 50%. At the same time, the retention rate of the IV value was also improved to 93 to 94% (conventional 85% to 90%). The kneading dispersion of the ultraviolet absorber was also good.

As a result, the high dispersion effect of the screw of the present invention positively agitates the molten resin in the barrel, which promotes the melting of the unmelted resin and at the same time reduces the temperature unevenness of the molten resin. Due to this, it became possible to set the barrel temperature to a lower temperature than during normal production.

The low shear and high mixing function of the screw of the present invention is not limited to PET and PAN, but when it is applied to dilute dispersion of master batch / liquid color, the dispersibility can be improved to save the material cost. Further, the barrel temperature can be set to a low temperature by applying it to a resin generally required to prevent thermal deterioration and making the melting temperature uniform.

[0037]

The uniaxial plasticizing screw of the present invention is a combination of a measuring unit for multi-eccentric flight and a dispersion-type mixing screw, and is for a multi-eccentric flight that effectively stirs unmelted resin while stirring the resin. By the action and the synergistic effect of the series distribution action and the orientation action, the low shear high mixing function is achieved, and the low temperature extrusion is possible.

Therefore, when the screw of the present invention is applied to the polymer blend resin, high dispersibility is obtained. Further, when the screw of the present invention is applied to PET or PAN, low temperature extrusion becomes possible and various characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a uniaxial plasticizing screw for injection molding of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a diagram showing a mixed operation of multi-eccentric flights.

FIG. 4 is a diagram showing a distribution operation of distribution-type mixing.

FIG. 5 is a diagram showing microdispersion of TSOP.

FIG. 6 is a graph showing improvement in elongation at break and Izod impact value of TSOP.

FIG. 7 is a graph showing improvement in surface gloss of TSOP recycled material.

FIG. 8 is a graph showing improvement in acetaldehyde concentration of PET.

FIG. 9 is a graph showing improvement in tensile yield elongation and Izod impact value of PAN.

[Explanation of symbols]

1 screw, 2 barrel, 5 mixing part, 6 check valve, 12 material supply part, 13 compression part, 14 metering part, 16 concentric flight, A, B, C eccentric flight, 22 rotor, 23 ring, 25 valve seat part ,
26 valve bodies, 33, 36 cavities

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29K 67:00

Claims (6)

[Claims] 1. A material supply unit, a compression unit, and a measuring unit,
In the uniaxial plasticizing screw provided with a mixing section at the tip, the measuring section is configured such that during concentric flight where the flight height is constant, each flight height gradually decreases and gradually increases along its length. A plurality of eccentric flights that are arranged in parallel with each other while shifting the phases of the gradually decreasing and gradually increasing with repeating over are provided up to the tip of the measuring section, and the mixing section is connected to the tip of the measuring section, A uniaxial plasticizing screw comprising a rotor having a plurality of cavities on its outer peripheral surface and a ring rotatably inserted into the rotor and having a plurality of cavities on its inner peripheral surface. 2. A uniaxial plastic for injection molding, which is rotatably and axially slidably inserted into a hollow barrel, has a material supply section, a compression section, and a metering section, and is provided with a mixing section and a check valve at its tip. In the chemical screw, the metering unit repeats a gradual decrease and a gradual increase of each flight height along a length thereof during a concentric flight with a constant flight height, and a gradual decrease and a gradual increase of the flight height. A plurality of eccentric flights arranged in parallel with each other by shifting the phase of the measuring section up to the tip of the measuring section, the mixing section being connected to the measuring section tip and inserted into the hollow barrel, The check valve includes a rotor having a plurality of cavities on its surface, and a ring rotatably inserted into the rotor and slidable in the rotor axial direction and having a plurality of cavities on an inner peripheral surface. , A uniaxial plasticizing screw for injection molding, comprising: a valve seat portion provided at the tip of the metering portion; and the ring having a valve body portion formed for the valve seat portion. 3. A plastic blend of a polymer blend resin having excellent dispersibility, which comprises using the screw according to claim 2 to stir the polymer blend resin in the eccentric flight, and then to flow the fraction in the mixing section. Method. 4. The method of plasticizing a polymer blend resin according to claim 3, wherein the polymer blend resin is a highly crystalline and highly fluid rubber modified resin for bumpers. 5. A plasticizer for PET excellent in low-temperature extrudability, which comprises using the screw according to claim 2 and stirring polyethylene terephthalate (PET) in the eccentric flight and then causing a partial flow in the mixing section. Method. 6. A plastic for PAN excellent in low-temperature extrudability, which comprises using the screw according to claim 2 to stir polyacrylonitrile (PAN) in the eccentric flight, and then flow a fractional flow in the mixing section. Method.