JPH0515369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a screw for a molding machine such as an injection molding machine or an extruder used for molding synthetic resin.

[Prior art]

In the molding of synthetic resins, in recent years, from the viewpoint of higher quality and lower costs, injection molding machines are required to have contradictory performances such as high kneading and high plasticization of resin.

For example, when using color ring molding, which involves mixing natural pellets with colorants, additives, etc. during molding, and plasticizing and coloring the material in a plasticizer, instead of using expensive colored pellets for the purpose of cost reduction, , since homogeneous distribution is extremely important,
High kneading ability is required, and high plasticizing ability is also required to improve productivity through cycle up.

In commonly used screws with only main flights, the transfer capacity can be increased by forming deep grooves in order to achieve high plasticization, but this will reduce the kneading effect, so high plasticization and high kneading For molding where both are required, a long screw or Dalmage screw is unavoidably used, or a double flight screw having a main flight and a sub-flight with a slightly smaller diameter than the main flight is used.

[Problem that the invention seeks to solve]

However, a long screw causes problems with thermal deterioration and requires a large molding machine, making it less effective in spite of the increased cost.Also, Dalmage screws are a step forward in terms of complete dispersion and cannot provide sufficient shearing action. Furthermore, double-flight screws are good for high plasticization because they allow the Merrill film to be made thinner due to the action of the secondary flights, improve external heating efficiency, and increase shearing force, but in terms of high kneading, the Meryl film is compressed by the secondary flights. The folding effect that occurs when the resin is released only promotes micro-kneading, and the kneading is better than that of screws using only the main flight, but if the coloring ratio is low and the color is light, the molded product may become discolored. There were problems such as unevenness.

The present invention was devised to solve the above-mentioned conventional problems, and aims to provide a screw that is excellent in plasticizing ability, micro-kneading, and macro-kneading. .

[Means for solving problems]

This invention for the above-mentioned purpose has a sub-flight of a required length provided between the main flights with an outer diameter smaller than that of the main flight from the opposite side of the main flight continuously formed around the shaft. The above problem is solved by increasing the lead angle and forming parallel and alternate pairs of branches.

[Effect]

In the screw having the above configuration, the resin material is plasticized and kneaded by the main flight in the same way as usual, and is also plasticized by the first sub-flight, and is released after passing over the first sub-flight and is micro-kneaded. , which is pushed towards the second sub-flight, and the one that has overcome the first sub-flight is further pushed out along the main flight by the second sub-flight, and the second sub-flight along with those that did not get over the first sub-flight, were made to cross over the second sub-flight, were kneaded micro-macroscopically, and then merged with those that were pushed out along the main flight. and then macro-kneaded.

〔Example〕

The drawing shows the metering zone part of the injection device, where 1 is a screw and 2 is a cylinder. The screw 1 performs so-called metering by rotating to plasticize and knead the resin in the hopper while accumulating it in front of the screw in the same way as an injection device with a normal configuration.As the screw 1 moves forward, the accumulated molten resin is transferred into the mold cavity. extrude and fill.

On the shaft portion 11 of the screw, a main flight 12 having an outer diameter that is approximately the same as the inner diameter of the heating cylinder is continuously formed at a predetermined lead angle across the feed zone, compression zone, and metering zone, and is located in the metering zone. In the groove 13 between the main flights 12, there are sub-flights 14.

The outer diameter of this sub-flight 14 is formed to be slightly smaller than the outer diameter of the main flight 12, and the lead angle is made larger than that of the main flight 12, so that the main flight 14
It consists of parallel first flights 14a and second flights 14b which are alternately branched out in pairs from opposite sides of the two. Also, the above flight 14a, 1
The inner corner 15 of the branch part 4b is formed into an arc shape to prevent resin from accumulating.

Note that although two sets of sub-flights 14, 14 are shown in the drawing, the number of sub-flights may be arbitrary depending on the purpose. In addition to the melting zone, the arrangement may be in the compression zone, or in both the melting zone and the compression zone.

Next, the flow of molten resin in the screw 1 will be explained with reference to FIG.

When the screw 1 rotates for measurement, the resin in the hopper is transferred forward along the groove 13 of the screw, plasticized and kneaded, as usual.
Accumulates in front of the screw.

The feed zone of the screw 1 preheats the granular resin introduced from the hopper while moving it forward, and sends it to the next compression zone.
In the compression zone, the resin is semi-molten by shearing action and external heating, generating resin pressure and sending it to the metering zone. In the metaling zone, the unmelted solid bed is completely melted due to the play-up phenomenon, etc., and the molten resin is homogenized by kneading.

At this time, since the sub-flight 14 as described above is provided in the metering zone, plasticization and kneading are performed in the metering zone in the same way as in the case of a normal full-flight screw, and the approximately molten resin is is separated into a melted part and an unmelted part by the first sub-flight 14a, and the separated unmelted part is melted by some of the first sub-flights 14, and together with the melted part, the first sub-flight 1
4a to be released and micro-kneaded, and the other to be pushed out along the first sub-flight 14a toward the second sub-flight 14b.

The resin that has crossed the first sub-flight 14a is
one pushed out along the main flight by the second sub-flight 14b, and the second sub-flight 1
It joins with the one pushed out towards 4b and
The main flight 12 is melted completely and divided into micro- and macro-kneaded parts.
The material pushed out along the direction and the material that has passed over the second sub-flight 14b are combined and macro-kneaded.

In this case, since two sets of sub-flights 14 consisting of the first sub-flight 14a and the second sub-flight 14b are provided, the same action is performed twice, and the resin is completely melted. It is also kneaded on a micro and macro level.

〔Effect of the invention〕

As described above, the present invention includes sub-flights provided in the groove between the main flights, and parallel first flights which are alternately formed in pairs with lead angles larger than the main flights from opposite sides of the main flights. It consists of a second flight, and the resin can be plasticized and kneaded by these flights, so even if the screw groove is formed deep for the purpose of high plasticization, the kneading effect will not decrease. Both high plasticization and high kneading effects can be obtained at the same time. Also, kneading is carried out in the first sub-flight and the second sub-flight.
The sub-flight is effective in both micro and macro aspects, making it possible to obtain high-quality molded products with no color unevenness even when coloring at a low ratio, and the molding cycle can be shortened, increasing productivity. This has the effect of improving

[Brief explanation of the drawing]

The drawings show one embodiment of a screw for a molding machine according to the present invention, and FIG. 1 is a sectional view of a metering zone portion of an injection device, and FIG. 2 is a developed view thereof. 1... Screw, 2... Cylinder, 11... Shaft, 12... Main flight, 13... Groove, 14...
Sub-flight, 14a...First sub-flight, 14
b...Second secondary flight.

Claims (1)

[Claims] 1. It has a main flight that is continuously formed around the shaft part with the required lead angle, and a sub-flight of the required length that is provided in the groove between the main flights with an outer diameter smaller than that of the main flight. In the screw, the sub-flights are formed from parallel first and second flights which are alternately branched into pairs with a lead angle larger than that of the main flight from the opposite side of the main flight. Screw of the machine.