JPH0450170B2 - - Google Patents

Description

[Detailed description of the invention]

[Objective of the Invention] (Industrial Application Field) This invention relates to a screw for injection molding, and relates to improving the dispersibility of pigments in dry colors, hard colors, masterbatches, etc. (Prior art) In order to melt plastic materials and improve their kneading and dispersion, a Japanese Patent Publication No. 43-24493 as shown in Fig. 5 was used.
As shown in No. 1, a plunger 2 with a small gap between the screw 1 and the cylinder is provided, and grooves 3 and 4, which do not penetrate through the outer peripheral surface of the plunger 2, are arranged alternately in opposite directions so that they do not communicate with each other. A screwdriver 1 having a feed zone F, a compression zone C, and a metering zone M as shown in Fig.
1, a mixing flight 12 of one or more threads is provided over a predetermined range of at least one of the compression zone C or the metering zone M, and the top surface of this flight 12 is provided with a mixing flight 12 in the axial direction of the screw. A screw is formed by providing a plurality of grooves 13 whose depths change parallel to each other, and the depth changes of adjacent grooves in the axial direction are opposite to each other. As shown in No. 1810, there is a screw in which a sub-flight 22 branching off from a main flight 21 is connected to the main flight 21 on the downstream side. (Problems to be Solved by the Invention) In the above-mentioned conventional screw, it was necessary to apply a high back pressure of 20 Kgf/cm ^{2 or} more to obtain sufficient color dispersion. As a result, the plasticizing ability decreases and the resin temperature increases, resulting in a decrease in productivity and a deterioration in the quality of molded products. It is an object of the present invention to provide a screw that can obtain high dispersibility due to low back pressure due to high kneading properties. [Structure of the invention] (Means for solving the problems) In order to achieve the above-mentioned objectives, high kneading performance and melting functions are performed by a sub-flight screw, and high dispersion ability is provided in the mixing section. A screw for plastic molding, which forms a feed zone, a compression zone, and a metering zone from the material supply side to the material discharge side, has a cylinder and a cylinder at the tip of the metering zone. On the outer circumferential surface of the plunger having a small gap between them, mixing sections are provided which are alternately arranged in opposite directions so that the non-penetrating first stop grooves do not communicate with each other. In one or both zones, at least one sub-flight has a sub-flight that is slightly lower than the main flight and has a lead angle larger than that of the main flight, and the starting and ending ends of the sub-flight are aligned with the axis. A weir parallel to the direction is connected to the main flight, and the weir is on the downstream and upstream sides of the
This high dispersion screw for plastic injection molding is characterized in that it is continuously and smoothly connected to the bottom surface of the screw groove by a straight line or a curve, and has a height slightly lower than the sub-flight. (Function) In order to improve the kneading and dispersion of plastic materials, a mixing section is provided to improve color dispersion, and a sub-flight is provided to compensate for the reduction in plasticizing ability caused by the mixing section. That is, according to the present invention, the material resin in the groove formed by the main flight is reduced by making the height of the sub-flight slightly lower than the main flight, so that the molten material that accumulates in the rear part of the groove (the part in contact with the entire surface of the main flight) is reduced. The material easily overcomes the sub-flight and enters the groove formed by the back surface of the sub-flight and the front surface of the main flight, separating the molten material from the unmelted material, with the unmelted material directly contacting the inner surface of the barrel and melting progresses. On the other hand, since the molten material is sent to the mixing section and easily dispersed, good dispersion and kneading can be achieved with low back pressure. (Embodiment) To explain one embodiment of the present invention with reference to FIGS. 1, 2, and 3, plastic material supplied from the material supply port 31 is transferred to a field zone F, a compression zone C, and a metering zone. The objects are transferred in the order of M in the direction of arrow X. 32 is the main flight, which is continuously provided from the feed zone F to the metering zone M at equal pitches. 33
In the mixing section, a plurality of plunger-shaped grooves 34 and 35 with a small gap between them and the cylinder, which do not penetrate through the outer circumferential surface, are provided, and are alternately arranged in opposite directions so that they do not communicate with each other. FIG. 2 is an enlarged view of section Y in FIG. 1, which forms the main part of the screw of the present invention, and is provided with a sub-flight 36 that is slightly lower in height than the main flight 32 and has a larger lead angle, and its starting and terminal ends. A weir 37 parallel to the axis connects the main flight 32 at a portion. Therefore, in order to prevent material from passing through unmelted as in the conventional open type, the unmelted material is always melted when it crosses the weir 37. Therefore, it is designed to have properties intermediate between an open type and a closed type so that the material does not stagnate and melts. Furthermore, in order to ensure that heat is transferred well from the pallet that covers the outer peripheral surface of the screw, the starting and ending ends of the weir 37 are continuously smooth in straight or curved lines that gradually become shallower from the depth of the screw groove, as shown in Figure 3. is connected to. Therefore, this part has the effect of high kneading performance, and on the other hand, since the mixing part, which has the characteristic of high dispersion, is provided at the tip of the metering zone M of this screw, high dispersion due to low back pressure is achieved. It has the effect that can be obtained. Next, a comparison test was conducted between the screw according to the present invention in FIG. 1 and the conventional screws in FIGS. 8, 9, and 10. Molded product: Tarai (shown in Figure 4) weight 315g, resin: PP and dry color blending ratio 0.1%, 0.4
%, 0.8% mixed molding conditions Screw rotation speed: 175 rpm (MAX) Back pressure: 0, 10, 20 Kgf/cm ² cycles: injection 5 seconds, cooling 15 seconds, 1 cycle 34
Seconds Barrel temperature: 225℃ Molding machine: IS-550E (manufactured by Toshiba Machine) Mold clamping force
550 tons, Screw diameter φ75 As a result of comparing the color dispersion status using a color difference meter under the above-mentioned molding conditions, the results shown in the table below were obtained.

[Table] In the table ×: Defective
△: Fairly good
○: Good As described above, the screw of the present invention has a low back pressure of 20 kg.
It has high dispersibility even at f/cm ² or less.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment according to the present invention. Second
The figure is an enlarged view of section Y in Figure 1. Figure 3 is Figure 2-
Cross-sectional view. FIG. 4 is a diagram of a test product for comparison between the present invention and a conventional example. FIG. 5 is a diagram of a screw having a conventional mixing section. FIG. 6 is a diagram of another conventional example having a mixing section. FIG. 7 is a diagram showing still another conventional screw having sub-flights. FIGS. 8, 9, and 10 are diagrams of conventional screws, and FIG. 8 is a diagram of a screw having short subflights in the compression zone where both the groove start and end are open. Figure 9 is a diagram of a screwdriver with a mixing section in full flight. FIG. 10 is a diagram of a screw having short sub-flights in the compression zone with openings at both the groove start and end, and a mixing section at the tip. 31...Material supply port, 32...Main flight, 3
3...Mixing section, 34, 35...First stop groove, 36...Sub flight, 37...Weir, F...
Feed zone, C...Compression zone, M...Metering zone.

Claims (1)

[Scope of Claims] 1. In a plastic material molding screw that forms a feed zone, compression zone, and metering zone from the material supply side to the material discharge side, there is a screw between the cylinder and the tip of the mailing zone. A mixing section is provided on the outer circumferential surface of the plunger having a booth, in which non-penetrating first-stop grooves are arranged alternately in opposite directions so as not to communicate with each other, and either the compression zone or the metering zone, or both. At least one subflight across the zone has a subflight that is slightly lower than the main flight and has a lead angle larger than the lead angle of the main flight, and is parallel to the axial direction at the starting and trailing ends of the subflight. A high dispersion screw for injection molding connects to the main flight as a weir. 2. On the downstream and upstream sides of the weir,
The screw according to claim 1, characterized in that the screw is continuously and smoothly connected to the bottom surface of the screw groove by a straight line or a curve. 3. The screw according to claims 1 and 2, wherein the height of the weir is slightly lower than the subflight.