JP2002248664A - Injection molding machine having kneading mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine having a kneading function which does not damage a reinforcing material such as glass fibers and compounding materials, disperses additives into a resin uniformly, curtails a time required for color changing or resin changing, and is low in costs. SOLUTION: The inner wall surface of a heating cylinder is flattened, at a position beyond the metering zone of a screw, a part the peripheral surface of which is flat and the shaft diameter of which is larger than that (trough diameter) of a place right in front of the metering zone is formed, and a molten raw material, when passes through the part, receives strong shear force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for extruding or injection molding a resin or the like, particularly a thermoplastic resin and glass fiber, after melting and kneading the resin and the glass fiber.

[0002]

2. Description of the Related Art PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PP
(Polypropylene), PC (polycarbonate), PA
Injection molded products of resin (resin) mainly made of engineering plastics (abbreviated engineering plastics) such as (nylon), electrical and electronic parts, mechanical parts, parts of transportation equipment,
Widely used for building materials. In addition, when used for those applications, the mechanical strength and durability are often insufficient with only the resin, and therefore, usually a reinforcing material such as glass fiber, other pigments, a modifier, etc. are also blended. Used.

[0003] In the injection molding for producing these parts, in an injection molding apparatus equipped with a normal full-flight screw, glass fibers are produced from a blend of resin and glass fibers (chopped strands). It is difficult to obtain a molded article that is uniformly dispersed and has excellent appearance. For this reason,
A sufficiently dried resin and glass fiber are once melted and kneaded by an extruder having a melt-kneading function to form a pellet in which the glass fiber is uniformly dispersed in the resin, and the pellet is melted again by an injection molding machine. The method of injecting into a mold is adopted.

[0004] In this case, however, melting and kneading are performed twice, which is not only unfavorable in terms of energy efficiency, but also easily causes breakage and breakage of the glass fiber.

As a countermeasure, for example, Japanese Patent Publication No. Sho 56-4
There is an injection molding machine having a kneading mechanism disclosed in JP-A Nos. 7847 and 5-58888. This injection molding machine has a cylindrical heating cylinder and a multi-flight screw which rotates inside and serves as a shaft when the raw material is injected into a mold. Raw materials such as resins, especially so-called engineering plastics (engineering plastics) and, in addition, glass fibers, various pigments, and the like are mixed in a predetermined amount in the form of pellets or powders, and supplied from the upstream side of the heating cylinder. Then, the raw material supplied by rotating the screw while moving backward in the heating cylinder is sent to the downstream side in the heating cylinder, and at the same time, the resin is melted and the respective raw materials are sufficiently mixed.

[0006] In this case, firstly, there is a demand that the respective raw materials should be sufficiently uniformly mixed and dispersed, and secondly that the glass fibers and the like should not be damaged or broken as much as possible.

For this reason, for example, in an injection molding apparatus having a kneading mechanism disclosed in the above-mentioned publication, each of the screws has multiple flights formed on the outer periphery thereof, and the top of the flight and the inner surface of the cylinder are connected to each other. With a gap between them,
Further, a long groove in the axial direction and some parallel and discontinuous grooves are provided on the inner wall of the cylinder. Thus, a rub shear function accompanying the rotation of the screw is exerted, and uniform dispersion of glass fibers and the like in the resin is performed.

[0008]

However, the provision of multiple flights on the screw and the provision of grooves of a complicated shape on the inner wall surface of the elongated cylinder lead to an increase in manufacturing costs.

Further, since the raw resin is inevitably left in the groove, it takes time to change the color and the resin.

[0010] For this reason, an injection molding machine (including, but not limited to, a low production cost, does not require time for color change or resin change, and naturally has excellent kneading function of raw materials, and further has excellent mechanical strength and good appearance. Extrusion equipment) has been desired.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and to smoothen the inner peripheral surface of a heating cylinder, and at the same time, use a screw of a normal full flight type injection molding machine. The shape of this is devised. Specifically, it is as follows.

According to the first aspect of the present invention, for example, the front end of a flight type screw having a single screw thread or a compression zone (in the direction in which the raw material flows) in a heating cylinder of an injection molding machine having a kneading portion of a resin. In the downstream part, a part (also referred to as blistering in this specification) that has a shaft diameter larger than the other parts and a flat outer peripheral surface to compress the raw material is provided, and the resin in the heating cylinder always passes through this part. To do
Further, at the time of passage, a shearing force is applied between this portion and the inner surface of the heating cylinder.

[0013] With the above structure, the passing area is suddenly reduced in this portion, so that the mixture of the resin and the glass fiber sent from the upstream side (based on the flow direction of the raw material) is rapidly compressed, and the shear force is increased. Receive. At this time, mixing and dispersion of a reinforcing material such as glass fiber and a filler in the molten resin are promoted. Moreover, since there is no groove on the inner surface of the heating cylinder,
There is no stagnation of the resin material in this portion, and the presence of the resin material does not hinder color change and resin change.

According to the second aspect of the present invention, when the blister ring is formed such that the inner diameter of the heating cylinder is D, the axial length is 0.1D to 3D (preferably 0.4D).
DD. More preferably 0.4D to 0.7D. ).

The length in the axial direction is qualitatively greater as the length is longer, but the length is limited by the length of the heating cylinder and the screw.

According to the above construction, the glass fiber is 40-60.
Particularly in the case of weight%, breakage of glass fibers and the like is small, and uniform mixing and dispersion in the resin, and mixing and dispersion of each resin are promoted. In addition, the appearance of the injection-molded article becomes good.

In addition, the mixing and dispersion of each melted resin, and further, the mixing and dispersion of a reinforcing agent, a filler, a modifier and the like therein can be favorably performed.

According to the third aspect of the invention, in the blister ring portion, the radial gap between the inner surface of the heating cylinder and the outer peripheral surface of the blister ring is t, and the inner diameter of the heating cylinder is D.
Where t ≦ 0.05D, preferably t ≦ 0.04
D, more preferably, t ≦ 0.025D, and even more preferably, a relationship of 0.015D ≦ t is satisfied. Therefore, particularly preferably, 0.015D ≦ t ≦ 0.0.
The relationship of 25D is established. The preferable range of t depends on the type of the resin. Therefore, when various resins are used (in the case of high-mix low-volume production), 0.0175 is used.
It may be preferable that D ≦ t ≦ 0.0225D.

With the above structure, a preferable shearing force is generated in the melted raw material, and the mixing and dispersion of the melted resins, and the mixing and dispersion of a reinforcing agent, a filler, a modifying agent and the like therein are favorably performed. You. The reason why the gap between the inner diameter of the heating cylinder and the outer shape of the blister ring preferably satisfies 0.015D ≦ t is that if the gap is small, the effect of dispersing the glass fiber is increased. Damage,
This is in consideration of the fact that breakage or the like is likely to occur.

According to the fourth aspect of the present invention, there is provided an apparatus for melt-kneading a blend of a resin powder or pellet and a glass fiber chopped strand to perform injection molding.

With the above structure, for example, glass fibers 30 to
Although a dry blend such as PET or PA blended with 60% by weight is melted and kneaded only once, it is possible to produce an injection-molded product having good appearance and sufficient mechanical strength. In addition, since color change and resin change can be performed quickly, it is possible to sufficiently cope with home electric appliances and the like, which are often required to be produced in a variety of small quantities.

According to a fifth aspect of the present invention, there is provided an apparatus for melt-kneading a blend of a resin powder or pellets, a powdered inorganic filler and at least one of metal powders, and performs injection molding.

With the above structure, for example, a resin containing carbon powder or tungsten powder (and glass fiber depending on the case) is melted only once, and injection molding is performed by a kneading process with sufficient quality such as mechanical strength and appearance. Products can be manufactured.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

FIG. 1 shows an entire injection molding machine of the present embodiment, and FIG. 2 shows a main part thereof. In the figure, reference numeral 12 denotes a hopper of a raw material supply unit. 2 is a heating cylinder. 3
Is a single flight full flight screw. 31
Is a flight formed on the outer periphery. 35 is
The check valve 4 is a nozzle at the tip of the heating cylinder 2. Furthermore, although it is not shown for the sake of simplicity, as in the injection molding machine disclosed in the above-mentioned publications, a heater is provided on an outer peripheral portion of the heating cylinder, and a screw is provided for rotation. It is equipped with a motor.

Reference numeral 301 denotes a supply zone in the heating cylinder, 302 denotes a compression zone, and 303 denotes a measurement zone. For reference, each of these zones occupies approximately 50%, 25%, and 25% of the whole.

As in the case of the conventional injection molding machine or vent type injection molding machine, pellets of raw resin such as PET, reinforcing materials such as glass fiber, and other modifiers are mixed at a predetermined mixing ratio from the raw material supply section. Is supplied into the heating cylinder by a predetermined amount, and the supplied raw material moves from the right to the left in the drawing as the screw rotates. At this time, each raw material is compressed, the resin is melted, and the melted resin and the compound are uniformly mixed as in the injection molding machine disclosed in the above-mentioned publications. In addition, since the volume of the raw material pellets decreases (density increases) with melting, the root diameter of the screw increases toward the downstream side.

However, the screw of the injection molding machine according to the present embodiment has a flat outer periphery near the tip where the resin is melted and upstream of the check valve, and has a larger diameter than the shaft of the portion where the flight is near. A portion, a so-called blister ring 30, is provided. As a result, the mixture of the molten resin and the glass fiber, which is transferred from the compression zone in the heating cylinder to the measuring zone, is inevitably passed through the narrow gap formed between the blister ring and the inner circumference of the heating cylinder. First, it is rapidly compressed, and a large shear force is generated inside. Therefore, the mixing and dispersion of the glass fiber and the like in the molten resin are favorably performed. In addition, since the glass is melted and kneaded only once, breakage of the glass fiber and the like become very small.

The boundary between the upstream side and the downstream side (front and rear) of the blister ring is rounded as shown in FIG. Alternatively, a large-diameter compressed portion is formed that is rounded from the screw shaft root diameter portion and gradually rises in the radial direction. Therefore, the raw resin does not accumulate at the boundary between the upstream side and the downstream side of the blister ring. Further, unlike the injection molding machine disclosed in the above publication, since there is no groove in the heating cylinder, the raw material resin does not stay in that portion. As a result, the time required for changing the color of the product or changing the resin is also reduced.

Tables 1 and 2 show the results of tests and inspections of the mechanical properties and appearance of the resin mixed with the glass fiber produced by the injection molding machine of the present embodiment.

[0031]

[Table 1]

[0032]

[Table 2] Both tables show how the mechanical properties and appearance of the glass fiber reinforced resin change by changing the diameter of the blister ring while keeping the inner diameter of the heating cylinder constant at 40 mm.

Table 1 shows the test results of the mechanical strength and appearance of a composite (glass reinforced) resin composed of 45% by weight of PA6 (polyamide 6, nylon 6) and 55% by weight of glass fiber (GF). In this table, the GF fiber length indicates the length in the injection product. In Comparative Example 1, the blister ring had a diameter of 3
5 mm, which is smaller than the three embodiments. Comparative Example 2
Is manufactured by the present applicant using the composite material mixing apparatus disclosed in the above-mentioned JP-A-5-58888. In Comparative Example 3, pellets produced by a twin-screw extruder were produced by using a general-purpose injection molding machine.

Table 2 shows the test results of the mechanical strength and appearance of the composite resin of 50% by weight of PP (polypropylene) and 50% by weight of GF. Here, PP was modified with 0.14% by weight of maleic anhydride to improve interfacial adhesion with GF. In addition, Comparative Examples 1 and 2 in this table
And 3 are pellets produced by a twin-screw extruder when the diameter of each blister ring is small as in Table 1 and when the composite material mixing device disclosed in the above-mentioned JP-A-5-58888 is used. Is a case of using a general-purpose injection molding machine.

In Table 1, the blister ring diameter is 38.
mm and 38.4 mm, that is, when the gap t between the inner peripheral surface of the heating cylinder and the outer peripheral surface of the blister ring is 0.025 and 0.02 times the inner diameter D of the heating cylinder,
The fiber length is the longest. As a result, of course, various mechanical properties are extremely good, and the appearance is naturally good.

Further, as shown in Example 3, if the gap is too small, the GF fiber length seems to be short. However, the reason why the mechanical strength excluding the Izod impact value is almost the same as in the other examples is considered to be the effect of more uniform dispersion of the GF fiber. In addition, Comparative Example 3 has a low Izod impact value because the glass fiber may be short.

In Table 2, the inner diameter of the blister ring is 38.
mm and 38.8 mm, that is, when the gap between the inner peripheral surface of the heating cylinder and the outer peripheral surface of the blister ring is 0.025 and 0.015 times the inner diameter D of the heating cylinder,
The fiber length is the longest. As a result, of course, various mechanical properties are extremely good, and the appearance is naturally good.

As in the case of Table 1, if the gap t is as small as 0.01 D as in Example 3, the GF fiber length becomes shorter and the Izod impact value decreases, but the GF fiber becomes more uniform. Other mechanical strengths are about the same due to the effect of dispersion. In addition, although it is Comparative Example 3, in the case of PP, it seems that the tensile strength also decreases.

Next, when the two tables are compared, the optimum gap seems to depend on the type of the material resin.

Even if the gap is as large as 0.06D, the mechanical strength is not so reduced although the appearance is poor due to poor GF dispersion. Therefore, in applications where the appearance is not inconspicuous and the appearance is not a problem, it is considered that about 0.05D, which is slightly smaller than the gap, may be used.

The effect of dispersing the glass fibers in the resin is qualitatively proportional to the square and the length of the outer diameter of the blister ring. For this reason, in order to minimize the breakage of the glass fiber, the gap may be increased to 0.05D or 0.04D without going to that extent, while the axial length of the blister ring may be increased to 3D. . Of course, on the contrary idea, the gap t may be reduced to 0.01D and the axial length may be reduced to 0.1D.

In addition to the above, when compared with the composite material mixing apparatus disclosed in Japanese Patent Application Laid-Open No. 5-58888, there is no concave portion on the inner surface of the heating cylinder, so that qualitatively, resin change and color change are shorter. I can do it.

Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to these. That is, for example, the following may be performed.

1) Different materials, temperatures, screw rotation speeds, etc. from those tested.

2) Inert gas is supplied using a vent hole, and is discharged to the raw material charging hopper side. At this time, moisture and the like generated positively are transported out of the heating cylinder.

3) The screw is a multi-flight flight which may increase the kneading function at a slightly higher price.

4) Other equipment such as providing a suction and extraction mechanism for generated gas and moisture near the top of the measuring zone of the heating cylinder so that the raw material can be directly melted and kneaded without preliminary drying. It also has

5) In order to quickly change the color of the raw material and the resin under the high-mix low-volume production, the front end and the rear end of the blister ring have larger roundness than that shown in FIG. To protrude (project) in the radial direction from the valley of the screw. (Therefore, blistering is formed more gradually.) 6) The ratio of each zone to the entire heating cylinder is slightly different. Also, the position where the blister ring is formed is slightly upstream from FIG. 1 (note that FIG. 2 is shown at a position slightly upstream).

[0049]

As can be seen from the above description, according to the present invention, the time required for color change and resin change is small and the inexpensive kneading is performed without impairing the basic performance required of the kneading section at all. An injection molding apparatus having a function can be provided.

Therefore, it is possible to respond quickly and inexpensively even under the diversification of users' demands for colors, materials and the like.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a main part of an injection molding apparatus having a kneading function according to a first embodiment of the present invention.

FIG. 2 is a view showing a blistering section of the injection molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Hopper 2 Heating cylinder 3 Rotating screw 30 Blister ring 31 Flight 35 Check valve 301 Supply zone 302 Compression zone 303 Metering zone 4 Nozzle

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yuji Shioya 3-7-3 Fushimi-cho, Chuo-ku, Osaka-shi, Osaka Kishimoto Sangyo Co., Ltd. F term (reference) 4F206 AB25 AC01 AC04 AR18 JA07 JD03 JL02 JM01 JN03 JQ15

Claims (5)

[Claims] 1. An injection molding machine for manufacturing an injection molded product by melting and kneading a reinforcing material such as a thermoplastic resin and a glass fiber, a filler, and the like by a heating cylinder and a screw. An injection molding machine having a kneading mechanism for resin or the like, characterized in that it has a raw material compression section at a downstream position where the shaft diameter is larger than the other parts, so that the cross-sectional area of the raw material passage is reduced. 2. The resin material or the like according to claim 1, wherein the raw material compression section has an axial length of 0.1D to 3D when an inner diameter of a heating cylinder of the section is D. An injection molding machine with a kneading mechanism. 3. The raw material compression section, wherein a radial gap between the compression section and the inner surface of the heating cylinder is t,
The injection molding machine having a kneading mechanism for resin or the like according to claim 1 or 2, wherein t is 0.05D, where D is the inner diameter of the heating cylinder of the portion. 4. A resin powder or pellet,
4. An injection molding machine having a kneading mechanism for resin and the like according to claim 1, wherein the glass fiber blend is kneaded and injection-molded. 5. A resin powder or pellet,
4. A kneading mechanism for a resin or the like according to claim 1, wherein the powdery inorganic filler and at least one blend of a metal powder are kneaded and injection-molded. Injection molding machine having