JP4309151B2 - Injection molding method and injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding how to exit by kneading a plurality of types of synthetic resin material.
[0002]
[Prior art]
Conventionally, as this type of injection molding machine, one having the following configuration is known. First, in one conventional configuration, a mixer is directly connected to the inlet of the barrel of the screw feeder so that a plurality of types of granular or pellet-shaped synthetic resin materials are fed into the barrel while being stirred and mixed by the mixer. It has become. In the screw feeder, the synthetic resin material is heated, softened and melted, kneaded, weighed, and injected into the mold. In another conventional configuration, a mixer is provided in the vicinity of the screw feeder, and a plurality of types of synthetic resin materials are premixed in the mixer and supplied from the hopper into the barrel via the conveyor. In the same manner as described above, it is injected through kneading.
[0003]
[Problems to be solved by the invention]
By the way, a synthetic resin material (hereinafter referred to as a filler compounded resin) such as polypropylene (hereinafter referred to as PP) in which an inorganic filler is blended at a high density, and a synthetic resin material (hereinafter referred to as a non-blended resin) that is not blended. In comparison, there is no difference in the numerical values of the melting point and the viscosity lowering point. However, the viscosity in the molten state (for example, MI value, that is, melt index; hereinafter referred to as melt viscosity) is greatly different, and the filler-blended resin has a higher viscosity than the unblended resin. Thus, when kneading a plurality of synthetic resin materials having vastly different viscosities, a synthetic resin material having a low viscosity acts like a lubricant, and a high-viscosity synthetic resin material has a shearing force due to a screw. I can hardly tell. Accordingly, even if the melting start temperatures of the two synthetic resin materials are equal, the high viscosity synthetic resin material maintains a state close to a solid, and thus it becomes difficult to knead a plurality of synthetic resin materials satisfactorily. Therefore, for example, when different colors are applied to a plurality of synthetic resin materials, there is a possibility that color unevenness may occur after kneading.
[0004]
FIG. 5 shows the transition of the viscosity change between the filler compounded resin and the non-compounded resin in the barrel of the screw feeder. As is apparent from FIG. 5, the non-blended resin is heated as it proceeds through the screw feeder and decreases in viscosity when reaching the melting temperature, but the viscosity decrease of the filler-blended resin is slight and the state is maintained. The
[0005]
In order to cope with such a problem, for example, the screw of the screw feeder is made into a special shape (for example, a shape having a kneading disk), and even a synthetic resin material having a high melt viscosity has a mechanical shearing force. It is also known in the art to be configured to be transmitted. However, in the case of such a configuration, irregularities are formed on the screw, the screw shape becomes complicated, and the manufacturing cost increases. In addition, the synthetic resin material tends to remain in the concave and convex portions of the screw, the self-cleaning function is deteriorated, so-called discoloration is deteriorated, and the possibility of uneven color and the like occurs as described above.
[0006]
The present invention has been made paying attention to such problems existing in the prior art. Its purpose is a simple configuration, it is possible to knead a plurality of types of synthetic resin material into a uniform state, is to provide an injection molding how the color unevenness can be suppressed at the time of such color change of the synthetic resin material .
[0007]
[Means for Solving the Problems]
To achieve the above object, an invention according to claim 1, comprising a barrel and line screw, the injection molding process by the injection machine for injection by melt-kneading the plural types of synthetic resin material, prior Symbol plurality Among the synthetic resin materials, at least a synthetic resin material having a high melt viscosity is transferred while being preheated at a temperature within the range of the melting point minus 20 ° C. to the melting point minus 60 ° C. In the barrel, and in the barrel, the viscosity decrease of the synthetic resin material having a high melt viscosity is started simultaneously with or earlier than the viscosity decrease of the other synthetic resin material, And a melt-kneading step for advancing the viscosity reduction of the synthetic resin material .
[0008]
Therefore, according to the first aspect of the present invention, when a plurality of synthetic resin materials are kneaded, the synthetic resin material having a high melt viscosity is preheated, so that the synthetic resin material having a high melt viscosity has a melt viscosity. Viscosity starts earlier or almost simultaneously with lower synthetic resin materials. Therefore, before a synthetic resin material having a low melt viscosity decreases, the difference in viscosity between the plurality of synthetic resin materials can be eliminated, and as a result, a plurality of synthetic resin materials having different melt viscosities can be uniformly mixed. can do. Moreover, since it is not necessary to make the screw of a screw feeder into a special shape, the self-cleaning function can be exhibited and color unevenness at the time of color change can be prevented.
Furthermore, a plurality of synthetic resin materials having different melt viscosities can be effectively kneaded in a uniform state by preheating the synthetic resin material having a high melt viscosity at an appropriate temperature.
[0009]
The invention according to claim 2 is the invention according to claim 1, wherein the plurality of types of synthetic resin materials have different viscosities at the start of melting.
The invention according to claim 3 is the invention according to claim 1, wherein the plurality of types of synthetic resin materials have different melting start temperatures.
[0010]
The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein in the melt-kneading step, after starting the viscosity reduction of the synthetic resin material having a high melt viscosity, each synthetic resin material The viscosity of each synthetic resin material is allowed to decrease in a state where the viscosities are matched and the viscosities are matched .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Below, 1st Embodiment of this invention is described based on FIG.
[0018]
As shown in FIG. 1, the injection molding machine of this embodiment is equipped with a screw feeder 11. The screw feeder 11 includes a barrel 12 and an in-line screw (hereinafter referred to as a screw) 13 that is rotatably supported in the barrel 12. An inlet 14 is formed on the outer periphery of one end of the barrel 12, a nozzle 15 is formed on the other end (tip), and a hopper 16 is attached to the inlet 14. Then, two types of synthetic resin materials M1 and M2 having different melt viscosities are supplied from the hopper 16 into the barrel 12 and transferred forward by the rotation of the screw 13 while being sheared and kneaded in a molten state. Injected from a nozzle 15 into a mold (not shown). In addition, as a plurality of types of the synthetic resin materials M1 and M2 having different melt viscosities, different types of synthetic resin materials such as polypropylene (PP) and polyethylene (PE) may be targeted. Moreover, even if the kind of synthetic resin material is the same, various combinations are included, such as a case where the molecular weight is different, or an inorganic filler or the like is blended only in one. Here, although it is the same kind of synthetic resin material (PP), it demonstrates taking the case of the filler compounded resin M1 with which the filler was mix | blended, and the non-mixed resin M2 which is not mix | blended.
[0019]
A weighing feeder 17 is connected to the hopper 16. The measuring feeder 17 includes a pipe 18 and a conveying screw 19 that is rotatably supported in the pipe 18. An inlet 20 is formed on the outer periphery of one end of the pipe 18, and a hopper 21 is attached to the inlet 20. And among the two kinds of synthetic resin materials M1 and M2, the filler blended resin M1 having a high melt viscosity is supplied from the hopper 21 into the measuring feeder 17, and while being measured by a predetermined amount by the rotation of the conveying screw 19, It is fed into a hopper 16 on the screw feeder 11. That is, the metering feeder 17 is appropriately controlled in the number of rotations and the rotation time of the conveying screw 19, and a required amount of filler-containing resin M <b> 1 is supplied into the metering feeder 17.
[0020]
A preheating heater 22 as a preheating means is embedded in the pipe 18 of the measuring feeder 17 so as to surround the conveyance area of the conveyance screw 19. When the filler blended resin M1 having a high melt viscosity is metered and transferred with the rotation of the conveying screw 19, the preheating heater 22 preliminarily heats the filler blended resin M1. It has become. In this case, the temperature of the preheated filler-containing resin M1 is set within the range from the melting point of the filler-containing resin M1 to the melting point minus 80 ° C., preferably within the range from the melting point minus 20 ° C. to the melting point minus 60 ° C. ing.
[0021]
Thus, in this injection molding machine, when the two types of synthetic resin materials M1 and M2 are kneaded in the screw feeder 11, the filler-containing resin M1 having a high melt viscosity is preheated to the measuring feeder 17 prior to the kneading. Preheated by the heater 22. For this reason, when the synthetic resin materials M1 and M2 are kneaded, the filler blended resin M1 having a high melt viscosity starts to decrease in viscosity earlier than the non-blended resin M2 having a low melt viscosity. Or the viscosity reduction of both M1 and M2 is started simultaneously. Therefore, there is no difference in viscosity between the two types of synthetic resin materials M1 and M2, and a shearing force is equally applied to these synthetic resin materials M1 and M2. For example, as shown in FIG. 4, in the screw feeder 11, the filler compounded resin M <b> 1 starts to decrease in viscosity earlier than the non-compounded resin M <b> 2, and later, the non-compounded resin M <b> 2 rapidly decreases in viscosity. Start. For this reason, in the vicinity of the point P where the viscosities of both M1 and M2 match, both M1 and M2 are in a state where uniform kneading is possible, and thereafter, uniform kneading is continued in a state where the viscosities of both M1 and M2 match. Even when the lowering of the viscosity of both M1 and M2 is started at the same time, the uniform kneading is continued in a state in which their viscosities coincide.
[0022]
As a result, two types of synthetic resin materials M1 and M2 having different melt viscosities can be uniformly kneaded without causing uneven kneading, and the kneaded synthetic resin materials are injected from the nozzle 15 for molding. The
[0023]
Further, in this injection molding machine, since uniform kneading is possible as described above, it is not necessary to make the screw head of the screw 13 into a special shape so as to improve kneading. For this reason, when changing the color of the synthetic resin materials M1 and M2, there is no possibility of causing a lot of synthetic resin materials to adhere to the screw 13 having a complicated shape, and a high self-cleaning function is maintained. The color change of the synthetic resin material can be performed without unevenness.
[0024]
Incidentally, each MFR value (measurement of fluidity when the synthetic resin is melted) m1 and m2 of the synthetic resin materials M1 and M2 is
m1: m2 = 3: 1 to 200: 1
In this case, the injection molding machine of this embodiment is effective. That is, when the ratio between m1 and m2 is less than m1: m2 = 3: 1, the problem of non-uniform kneading does not occur much. When the ratio between m1 and m2 exceeds m1: m2 = 200: 1, it is difficult to knead with an injection molding machine.
[0025]
Examples of synthetic resins having different MFR values include the following.
Straight PP (non-compounded resin) m1 = 27
M2 = 0.4 of PP (filler compound resin) containing 60% talc
Therefore, the ratio of MFR values is as follows.
[0026]
Straight PP: PP with 60% talc = 1: 6.75
Further, when the melting points of the synthetic resin materials M1 and M2 are Tm1 and Tm2, the difference between the melting points Tm1 and Tm2 is
5 <Tm1-Tm2 <70 degrees Celsius
In this case, the injection molding machine of this embodiment is effective. That is, when the difference in melting point is less than 5 degrees (Celsius), a normal injection molding machine may be used, and when the difference in melting point exceeds 70 degrees (Celsius), it becomes difficult to mix the synthetic resin materials M1 and M2.
[0027]
Examples of synthetic resins having different melting points include the following.
Block (copolymer) PP: Melting point 165 degrees Celsius (homo PP part)
Random (copolymer) PP: melting point 140 degrees Celsius Therefore, the difference in melting points is 25 degrees.
[0028]
Therefore, according to this embodiment, the following effects can be obtained.
(1) In the injection molding method in this embodiment, prior to kneading a plurality of synthetic resin materials M1 and M2 having different melt viscosities, a filler having a high melt viscosity is provided by the metering feeder 17 provided with the preheating heater 22. Preheating is performed on the compounded resin M1.
[0029]
For this reason, the filler blended resin M1 having a high melt viscosity starts to decrease in viscosity earlier than the non-blended resin M2 having a low melt viscosity or almost simultaneously with the non-blended resin M2 having a low melt viscosity. Therefore, when the non-blended resin M2 having a low melt viscosity starts to decrease in viscosity, the difference in viscosity between the plurality of synthetic resin materials M1 and M2 can be eliminated, and equal to those synthetic resin materials M1 and M2. Can be subjected to shearing force. As a result, a plurality of synthetic resin materials M1 and M2 having different melt viscosities can be kneaded in a uniform state. Moreover, since it is not necessary to make the screw 13 of the screw feeder 11 into a special shape, it is possible to suppress uneven color when the synthetic resin materials M1 and M2 are changed in color, and to simplify the structure and reduce the manufacturing cost of the injection molding machine. it can.
[0030]
(2) In this injection molding method, the preheating temperature is within the range from the melting point of the filler-containing resin M1 having a high melt viscosity to the melting point minus 80 ° C, preferably from the melting point minus 20 ° C to the melting point minus 60 ° C. It is set within the range. For this reason, a plurality of synthetic resin materials M1 and M2 having different melt viscosities can be effectively kneaded in a uniform state by preheating the filler-containing resin M1 having a high melt viscosity at an appropriate temperature. .
[0031]
(Second Embodiment)
Next, a second embodiment of the present invention will be described with a focus on differences from the first embodiment.
[0032]
In the second embodiment, a weighing feeder 25 is connected to the hopper 16 on the screw feeder 11 as shown in FIG. The measuring feeder 25 includes a pipe 26 and a conveying screw 27 that is rotatably supported in the pipe 26. An inlet 28 is formed on the outer periphery of one end of the pipe 26, and a hopper 29 is attached to the inlet 28. Of the two types of synthetic resin materials M1 and M2 to be kneaded, the non-blended resin M2 having a low melt viscosity is supplied from the hopper 29 into the measuring feeder 25 and is measured by a predetermined amount by the rotation of the conveying screw 27. The hopper 16 on the screw feeder 11 is fed. The hopper 16 is connected to a weighing feeder 17 similar to that of the first embodiment.
[0033]
Therefore, according to the second embodiment, in addition to the effects described in (1) and (2) in the first embodiment, the following effects can be obtained.
(3) In this injection molding method, the filler blended resin M1 having a high melt viscosity is metered and preheated by the metering feeder 17, and the non-compound resin M2 having a low melt viscosity is metered by the metering feeder 25, and the screw feeder. 11 is sent. For this reason, when it is desired to change the kneading ratio between the filler compounded resin M1 having a high melt viscosity and the low non-compounded resin M2, it is possible to easily and accurately change the setting ratio of the synthetic resin materials M1 and M2. .
[0034]
(Third embodiment)
Next, a third embodiment of the present invention will be described with a focus on differences from the first embodiment.
[0035]
In the third embodiment, as shown in FIG. 3, a second weighing feeder 17 </ b> A is connected to the hopper 16 on the screw feeder 11 in addition to the weighing feeder 17 in the first embodiment. The second measuring feeder 17A is configured in the same manner as the measuring feeder 17, and a preheating heater 22 is embedded in the peripheral wall of the pipe 18.
[0036]
Of the three types of synthetic resin materials M1, M2, and M3 having different melt viscosities, the filler blended resin M1 having a high melt viscosity is preheated by the metering feeder 17, and the synthetic resin material M3 having a slightly high melt viscosity is used. Is preheated by the second weighing feeder 17A. In this case, the preheating temperatures of the synthetic resin materials M1 and M3 are within the range of the melting point minus 80 ° C. based on the melting points of the synthetic resin materials M1 and M3 as in the case of the first embodiment. The melting point is preferably set within the range from the melting point minus 20 ° C. to the melting point minus 60 ° C. As a result, the preheating temperature of the filler compounded resin M1 having a high melt viscosity is set to be higher than the preheating temperature of the synthetic resin material M3 having a slightly high melt viscosity.
[0037]
Further, the relationship between the MFR values m1 and m2 between the synthetic resin materials M1 and M2 having the greatest difference in melt viscosity and the relationship between the melting points Tm1 and Tm2 between the synthetic resin materials M1 and M2 having the largest melting point difference are as described above. This is the same as in the first embodiment.
[0038]
Therefore, also in the third embodiment, the same effects as the effects described in (1) and (2) in the first embodiment can be obtained.
(Example of change)
In addition, this embodiment can also be changed and embodied as follows.
[0039]
In each of the above-described embodiments, the preheating heaters 22 of the weighing feeder 17 and the second weighing feeder 17A are disposed at different positions, such as in the shaft of the conveying screw 19 or in the peripheral wall of the hopper 21.
[0040]
In each of the above embodiments, the synthetic resin materials M1, M2, and M3 handled by the weighing feeders 17, 25, and 17A are appropriately changed. For example, in the said 3rd Embodiment, it is comprised so that unblended resin M2 with low melt viscosity may be measured with the measurement feeder 25 similar to 2nd Embodiment, and it may supply to the hopper 16 on the screw feeder 11. FIG.
[0041]
In the case where three or more kinds of synthetic resin materials M1 to M3 are kneaded as in the third embodiment, only the filler-containing resin M1 having the highest melt viscosity is preliminarily heated.
[0042]
In the above embodiment, the present invention is embodied in the kneading of a plurality of synthetic resin materials having the same melting start temperature and different viscosities at the start of melting, but in the kneading of a plurality of types of synthetic resin materials having different melting start temperatures. To embody this invention.
[0043]
In each of the above-described embodiments, the screw feeder 11 is a uniaxial type, but a biaxial type is used.
(Other technical ideas)
The technical ideas other than the technical ideas described in the claims will be described below from the embodiments.
[0044]
In an injection molding method in which a plurality of types of synthetic resin materials are kneaded using a shearing force and injected, in order to reduce the difference in fluidity between the synthetic resin materials at the start of kneading, prior to kneading, An injection molding method comprising preheating a synthetic resin material having low fluidity.
[0045]
【The invention's effect】
As described above in the embodiment, in the present invention, a plurality of different types of synthetic resin materials can be kneaded in a uniform state, and the self-cleaning function can be exhibited to suppress color unevenness. The structure can be simplified and the production cost of the injection molding machine can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an injection molding machine according to a first embodiment.
FIG. 2 is a cross-sectional view showing an injection molding machine according to a second embodiment.
FIG. 3 is a cross-sectional view showing an injection molding machine according to a third embodiment.
FIG. 4 is a diagram showing the operation of the injection molding method of the first embodiment.
FIG. 5 is a diagram showing the operation of a conventional injection molding method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Screw feeder, 12 ... Barrel, 13 ... Inline screw, 16 ... Hopper, 17 ... Metering feeder, 17A ... Second metering feeder, 22 ... Preheating heater as preheating means, 25 ... Metering feeder, M1 ... Melting Synthetic resin material with high viscosity (filler-blended resin), M2 ... synthetic resin material with low melt viscosity (non-blended resin), M3 ... synthetic resin material with slightly high melt viscosity.

Claims (4)

In an injection molding method using an injection machine that includes a barrel and an inline screw, and melts and kneads a plurality of types of synthetic resin materials ,
High synthetic resin material at least the melt viscosity of the pre-Symbol plurality of types of synthetic resin material, and transported while preheating at a temperature in the range of the melting point minus 60 ° C. from the melting point minus 20 ° C., to other synthetic resin material Supplying the barrel with a temperature difference; and
In the barrel, melt kneading that starts the decrease in viscosity of the synthetic resin material having a high melt viscosity at the same time as or earlier than the decrease in viscosity of the other synthetic resin material, and advances the decrease in viscosity of each synthetic resin material. injection molding method, comprising the steps.   The injection molding method according to claim 1, wherein the plurality of types of synthetic resin materials have different viscosities at the start of melting.   The injection molding method according to claim 1, wherein the plurality of types of synthetic resin materials have different melting start temperatures. In the melt-kneading step, after the viscosity reduction of the synthetic resin material having a high melt viscosity is started, the viscosity of each synthetic resin material is made to coincide with the viscosity of each synthetic resin material and the viscosity is made to coincide. injection molding method according to any one of claims 1 to 3, characterized in that cause.

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