Injection molding machine

Abstract

To provide an injection molding machine for thermosetting resin composition that suppresses variation in quality of a molded product of a thermosetting resin composition.SOLUTION: An injection molding machine 1 for a thermosetting resin composition, which includes a heating cylinder 10, a nozzle 20 provided at a tip of the heating cylinder 10, and a screw 50 provided inside the heating cylinder 10 so as to be movable forward and backward, includes a nozzle temperature adjustment section 40 that is provided in the nozzle 20 and adjusts a temperature of the nozzle 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an injection molding machine for a thermosetting resin composition.

Background Art

[0002] In the injection molding of thermosetting resins, in order to produce molded articles of appropriate quality, it is important to control the amount of heat applied so that the temperature of the thermosetting resin is within an appropriate range. That is, it is necessary to make the thermosetting resin have a viscosity that is easy to flow and a temperature at which curing hardly progresses. For example, there is disclosed an injection molding machine for thermosetting resins having a first flow path and a second flow path provided in a heating cylinder and arranged in order from the nozzle side, a first switching device for switching the flow of each medium so that any one of a high-temperature medium, a medium-temperature medium, and a low-temperature medium flows through the first flow path, a temperature controller for the high-temperature medium for adjusting the temperature of the high-temperature medium, and a control device (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, in large resin molded articles, molded articles of thermosetting resins have come to be used. For this purpose, a large injection molding machine is required. In a large injection molding machine, the heating cylinder also becomes large, and the conventional temperature adjustment technology for thermosetting resins cannot meet the required quality of the molded article, and new technology has been demanded. In particular, the requirements for the quality of the molded article have become stricter, and technology for suppressing quality variations during manufacturing has been demanded.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide an injection molding machine for a thermosetting resin composition that suppresses quality variations in molded products of the thermosetting resin composition.

Means for Solving the Problems

[0006] According to the present invention, the following techniques are provided. [1] An injection molding machine for a thermosetting resin composition, having a heating cylinder, a nozzle provided at the tip of the heating cylinder, and a screw provided to be movable forward and backward inside the heating cylinder, a temperature adjustment unit provided in the nozzle for adjusting the temperature of the nozzle, and an injection molding machine having the same. [2] The injection molding machine according to [1], wherein the temperature adjustment unit has a flow path for circulating a heat medium, and adjusts the temperature of the nozzle by circulating the heat medium. [3] The injection molding machine according to [1] or [2], wherein the ratio L / D of the effective length L of the screw to the screw diameter D of the screw is 12.5 or more and 17.5 or less. [4] The injection molding machine according to any one of [1] to [3], wherein the thermosetting resin composition in the heating cylinder is injected from the nozzle into a mold by the screw advancing in the direction of the nozzle. [5] The injection molding machine according to any one of [1] to [4], wherein the temperature of the thermosetting resin composition injected from the nozzle is adjusted to 80°C or more and 130°C or less. [6] The injection molding machine according to any one of [1] to [5], wherein when the distance from the temperature adjustment unit to the resin flow path in the nozzle is d1, and the distance from the heater in the heating cylinder to the resin flow path in the resin kneading part of the heating cylinder is d2, d1 < d2. [7] The injection molding machine according to any one of [1] to [6], wherein the injection molding machine is a single-screw extruder. [8] The injection molding machine according to any one of [1] to [7], wherein the compression ratio of the screw is zero.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide an injection molding machine for a thermosetting resin composition that suppresses variations in the quality of molded products of the thermosetting resin composition.

Brief Description of the Drawings

[0008] [Figure 1] It is a cross-sectional view showing a schematic configuration of an injection molding machine according to an embodiment. [Figure 2] It is a front view of an injection molding machine according to an embodiment. [Figure 3] It is a cross-sectional view of a heating cylinder according to an embodiment. [Figure 4] It is an enlarged view of region A1 in FIG. 1 according to an embodiment. [Figure 5] It is an enlarged view of region A2 in FIG. 3 according to an embodiment. [Figure 6] It is a view showing a screw according to an embodiment. [Figure 7] It is a view for explaining molded products of a comparative example and a molded product of an example according to an example of an embodiment. [Figure 8] It is a view showing an evaluation result of molded product stability (continuous molding of 30 shots) according to an example of an embodiment. [Figure 9] It is a view showing an evaluation result of molding stability after holding for 3 minutes according to an example of an embodiment. [Figure 10] It is a view showing an evaluation result of stability comparison between a large-sized molding machine and a 100t molding machine according to an example of an embodiment. [Figure 11] It is a view showing an evaluation result of spiral flow according to an example of an embodiment.

Modes for Carrying Out the Invention

[0009] <Overview> The injection molding machine 1 of the present embodiment will be described with reference to FIGS. 1 to 6. FIG. 1 is a cross-sectional view showing a schematic configuration of an injection molding machine 1, which is a cross-sectional view taken along the line X1-X1 of FIG. 2. FIG. 2 is a front view of the injection molding machine 1, which is a view taken in the direction of the X arrow of FIG. 1. FIG. 3 is a cross-sectional view of the injection molding machine 1, which is a view with the screw 50, the hopper 80, and the mold 90 removed from FIG. 1. FIG. 4 is an enlarged view of the region A1 in FIG. 1, which is an enlarged view of the tip side of the nozzle 20. FIG. 5 is an enlarged view of the region A2 in FIG. 3, which is an enlarged view of the tip side of the nozzle 20 with the screw 50 removed. FIG. 6 is a side view of the screw 50.

[0010] The injection molding machine 1 is an injection molding machine 1 for a thermosetting resin composition having a heating cylinder 10, a nozzle 20 provided at the tip of the heating cylinder 10, and a screw 50 provided in the heating cylinder 10 so as to be able to advance and retreat, and has a nozzle temperature adjustment unit 40 provided in the nozzle 20 for adjusting the temperature of the nozzle 20. With the injection molding machine 1 having this configuration, not only the heating cylinder 10 but also the temperature of the thermosetting resin composition up to the tip of the nozzle 20 is appropriately controlled, variations during molding are suppressed, and stable molding is achieved. This will be described in detail below.

[0011] <Overview of Injection Molding Machine 1> The injection molding machine 1 injects a molten thermosetting resin composition into a mold 90 to produce a resin molded product. The injection molding machine 1 has a heating cylinder 10, a nozzle 20, a heating cylinder heater 30, a nozzle temperature adjustment unit 40, and a screw 50. In this embodiment, a single-screw extruder is exemplified as the injection molding machine 1, and a straight and full-flight screw is exemplified as the screw 50, but other configurations may be applied as long as the gist of the present invention is not deviated from. The injection molding machine 1 has, as configurations not shown other than the above configuration, for example, a control device for controlling the injection molding machine 1, a drive device for the screw 50, a pressure sensor, a metering device, and the like.

[0012] <Heating Cylinder 10> The heating cylinder 10 is a longitudinally long cylindrical member that is long in the left-right direction in a visual view. Inside the heating cylinder 10, a resin kneading portion 13 (resin path) through which the screw 50 is inserted is provided. A nozzle 20 is provided at the tip of the heating cylinder 10 (the left end in the diagram). A hopper 80 (see Figure 1) is attached to a resin supply port 25, which is an opening located at the upper rear side, for supplying the thermosetting resin composition, which is the molding material, into the heating cylinder 10. The heating cylinder 10 is conveniently divided into three zones, from the base side (right side in Figure 1) to the tip side (left side in Figure 1): the supply section 19a, the compression section 19b, and the metering section 19c. The supply unit 19a is located in the area from the resin supply port 25 in the horizontal direction to the heater rear section (heater rear section (1) 33a, heater rear section (2) 33b), and continuously supplies the molding material (thermosetting resin composition) introduced from the hopper 80 to the compression unit 19b. The compression section 19b is located in the horizontal direction, for example, in the area where the heater intermediate section (heater intermediate section (1) 32a, heater intermediate section (2) 32b) is provided, and plasticizes the supplied molding material before supplying it to the metering section 19c. The weighing unit 19c weighs the plasticized molding material in the horizontal direction within the range where the heater front portion 31 is provided.

[0013] <Heating cylinder heater 30> The heating cylinder heater 30 is a device for heating the heating cylinder 10 and adding heat to the thermosetting resin composition, and is attached to the outer surface 16 of the cylinder body 11 so as to wrap around it in the circumferential direction. In this embodiment, the heating cylinder heater 30 is provided with, from the tip side (left side in the diagram), a heater front section 31, a heater middle section (heater middle section (1) 32a, heater middle section (2) 32b), and a heater rear section (heater rear section (1) 33a, heater rear section (2) 33b).

[0014] Each heater may be, for example, a heat transfer medium heater in which a heat transfer medium such as water or oil flows inside, an electric heater, or a heater that combines both. In the case of a heat transfer medium heater, the heating cylinder heater 30 has a flow path for circulating the heat transfer medium, and by circulating the heat transfer medium through the flow path, it heats the cylindrical body 11 of the heating cylinder 10. The heating cylinder heater 30 may also include other components such as an insulating jacket.

[0015] <Nozzle 20> The nozzle 20 is located at the tip of the heating cylinder 10 and has an opening at its tip 21 that connects the inside and outside of the heating cylinder 10 for injecting the thermosetting resin composition molten in the heating cylinder 10 into the mold 90. The outer shape of the nozzle 20 is such that it continuously or gradually narrows in diameter towards the tip.

[0016] The resin channel 23 within the nozzle 20 is formed in continuity with the resin mixing section 13 within the heating cylinder 10. The resin channel 23 has a shape that narrows in diameter towards the nozzle tip 21, and is shaped and sized to accommodate the screw tip 52 of the screw 50 (see, for example, Figures 4 and 5).

[0017] The nozzle 20 is provided with a nozzle temperature adjustment unit 40. In this embodiment, the nozzle temperature adjustment unit 40 has a nozzle temperature adjustment unit body 41 and a connecting pipe 42. The nozzle temperature adjustment unit body 41 is attached to the outer circumferential surface 18 of the nozzle 20, which has a predetermined width and whose outer diameter is constant approximately in the front-to-back direction (left-to-right direction in the illustration). Inside the nozzle temperature adjustment unit body 41, a flow path is formed through which a heat transfer medium circulates, and the heat transfer medium is supplied and circulated from the connecting pipe 42. This adjusts the temperature of the nozzle 20 to a predetermined range. In this embodiment, the method of temperature adjustment is to supply and circulate a heat transfer medium controlled to a constant temperature through the flow path. Alternatively, a temperature sensor may be provided to measure the temperature of the nozzle 20, and feedback control may be performed. The nozzle temperature adjustment unit 40 adjusts the temperature of the thermosetting resin composition injected from the nozzle 20 to between 80°C and 130°C.

[0018] <Screw 50> The screw 50 is a longitudinal member inserted into the resin mixing section 13 inside the heating cylinder 10. In this embodiment, the screw 50 is a straight and full-flight type and has a screw body 51, a screw tip 52 provided at one end of the screw body 51 (the left end in this diagram) which has a tapered tip, and a screw base 53 provided at the other end (the right end in this diagram). A measuring device (not shown in the diagram) for rotating the screw 50 and a drive device (not shown in the diagram) for moving it forward and backward are attached to the screw base 53.

[0019] On the surface of the screw body portion 51, screw grooves 54, which are demarcated by the flights 55 (screw blades), are formed in a spiral shape to a predetermined depth.

[0020] The screw 50 is inserted into the resin mixing section 13 such that its central axis coincides with the central axis of the heating cylinder 10 (more specifically, the resin mixing section 13).

[0021] The screw 50 is rotated by the weighing device, causing the thermosetting resin composition supplied from the hopper 80 into the heating cylinder 10 (i.e., the resin mixing section 13) to be sent to the tip of the heating cylinder 10, i.e., the resin flow path 23 of the nozzle 20. Furthermore, the screw 50 is advanced by the injection motor, causing the thermosetting resin composition accumulated in the resin flow path 23 of the nozzle 20 to be injected into the mold 90 through the opening at the nozzle tip 21.

[0022] <Dimensions of Screw 50> The dimensions of screw 50 have the following characteristics: The ratio L / D of the effective screw length L to the screw diameter D (outer diameter) of the screw 50 is 12.5 or more and 17.5 or less. The effective screw length L refers to the axial length of the region in which the screw groove 54 is formed. Also, in the present embodiment, as can be seen from FIG. 6, the depth and pitch of the screw groove 54 are constant throughout the entire effective length L of the screw. That is, since the screw 50 is of the straight type, it does not have a region where the groove depth becomes shallower toward the tip side, and exhibits a shape with a compression ratio of zero.

[0023] The main factors causing variations in the temperature of the thermosetting resin composition are mainly (1) to (3). (1) Shear heat by the screw 50 (2) Heat transfer due to the contact between the nozzle 20 and the mold 90 (3) Heat dissipation to air when the nozzle 20 is separated from the mold 90 during setup When the ratio L / D is large, the kneading time of the thermosetting resin composition becomes long, and there is an increasing concern that curing is promoted by shear heat. On the other hand, when the ratio L / D is small, the kneading time of the thermosetting resin composition becomes short, and there is a concern that kneading is insufficient and unevenness in kneading of the thermosetting resin composition occurs. Therefore, by appropriately setting the ratio L / D, the thermal stability can be improved. As a result, the molten state of the thermosetting resin composition is stabilized, and metering and continuous molding are stabilized. Also, from the viewpoint that the screw 50 has a straight type configuration with a compression ratio of 0, the molten state of the thermosetting resin composition can be stabilized.

[0024] <The thickness (d1) of the nozzle 20 and the thickness (d2) of the heating cylinder 10> The distance from the nozzle temperature adjustment unit 40 to the resin flow path 23 in the nozzle 20 (that is, the thickness of the nozzle 20 at the portion where the nozzle temperature adjustment unit 40 is provided) is defined as d1. Also, the distance from the heating cylinder heater 30 in the heating cylinder 10 to the resin kneading unit 13 of the heating cylinder 10 (that is, the thickness of the heating cylinder 10 at the portion where the heating cylinder heater 30 is provided (the distance from the inner surface 15 to the outer peripheral surface 16)) is defined as d2. At this time, d1 < d2. When the distances d1 and d2 are not constant, for example, the average value can be adopted.

[0025] Since the distance d1 is shorter than the distance d2, and a constant temperature of heat transfer fluid is always flowing through the nozzle temperature adjustment unit 40, the temperature of the heat transfer fluid in the nozzle temperature adjustment unit 40 can be quickly reflected in the thermosetting resin composition temporarily stored in the resin flow path 23 of the nozzle 20.

[0026] <Summary> The features of this embodiment can be summarized as follows: [1] An injection molding machine 1 for a thermosetting resin composition, comprising a heating cylinder 10, a nozzle 20 provided at the tip of the heating cylinder 10, and a screw 50 provided inside the heating cylinder 10 so as to be able to move back and forth, A nozzle temperature adjustment unit 40 (temperature adjustment unit) is provided in the nozzle 20 and adjusts the temperature of the nozzle 20. An injection molding machine 1 having [a specific feature / feature]. [2] The injection molding machine 1 according to [1], wherein the nozzle temperature adjustment unit 40 has a flow path for circulating a heat transfer medium, and adjusts the temperature of the nozzle 20 by circulating the heat transfer medium. [3] The injection molding machine 1 according to [1] or [2], wherein the ratio L / D of the effective screw length L (axial length of the region in which the screw groove 54 is formed) to the screw diameter D (outer diameter) of the screw 50 is 12.5 or more and 17.5 or less. [4] The injection molding machine 1 according to any one of [1] to [3], wherein the screw 50 advances in the direction of the nozzle 20, thereby injecting the thermosetting resin composition in the heating cylinder 10 from the nozzle 20 into the mold 90. [5] The injection molding machine 1 according to any one of [1] to [4], wherein the temperature of the thermosetting resin composition injected from the nozzle 20 is adjusted to 80°C or more and 130°C or less. [6] Let the distance from the nozzle temperature adjuster 40 (temperature adjuster) to the resin flow path 23 in the nozzle 20 be d1, and the distance from the heater 30 (heater) in the heating cylinder 10 to the resin flow path in the resin kneading section 13 of the heating cylinder 10 be d2. When d1 < d2, the injection molding machine 1 according to any one of [1] to [5]. [7] The injection molding machine 1 according to any one of [1] to [6], wherein the injection molding machine 1 is a single-screw extruder. [8] The injection molding machine according to any one of [1] to [7], wherein the compression ratio of the screw 50 is zero.

Example

[0027] Hereinafter, this embodiment will be described in detail with reference to examples. Note that this embodiment is not limited to the descriptions of these examples. In the following examples, evaluations were performed on the following items (A) to (D). (A) Molded product stability (continuous molding of 30 shots) (B) Molding stability after holding for 3 minutes (C) Comparison of stability between a large-sized molding machine and a 100t molding machine 1 (variation coefficients of "metering time", "maximum injection pressure", and "product weight") (D) Spiral flow (fluidity of thermosetting resin compositions injected from a blank material, molding machine (1), and molding machine (2))

[0028] As injection molding machines, molding machine (1) (large-sized / 280t molding machine) and molding machine (2) (100t molding machine) described below were used. Fig. 7 shows the shape of the molded product used for evaluation. Fig. 7(a) is the molded product obtained by molding machine (1), and Fig. 7(b) is the molded product obtained by molding machine (2). [Thermosetting resin composition] A phenolic resin was used. [Molding machine] Molding machine (1): Single-screw injection molding machine 280t Effective length of screw L = 800 cm, 1200 cm, 1600 cm Screw diameter D 80cm Ratio L / D: 10, 15, 20 Screw root diameter: 60.4 cm Molded product size: 300 x 300 mm, 890 g (see Figure 7(a)) Heating cylinder temperature: 75℃ 50℃ 45℃ 40℃ 35℃ Nozzle temperature (temperature of heat transfer medium): 85℃ Mold temperature: 160℃ Molding machine (2): Single axis injection molding machine 100t Effective screw length L = 360cm, 540cm, 720cm Screw diameter D 36cm Ratio L / D: 10, 15, 20 Screw root diameter: 9.7cm Molded product size: 70 x 50 mm, 54 g (see Figure 7(b)) Heating cylinder temperature: 90℃ 60℃ 30℃ Nozzle temperature (temperature of heat transfer medium): Not set Mold temperature: 175℃

[0029] <Item (A): Molded product stability (30 continuous shots)> For thermosetting resin compositions, the variation (coefficient of variation in this case) of "mass," "injection peak pressure," "plasticization time," and "average pressure of the metering circuit" was evaluated when molded products were obtained by performing 30 consecutive shots using a molding machine (1) under three conditions: ratio L / D of 10, 15, and 20. The molded product had the following shape. Size: 120 x 80 mm 5mm thickness Molded product weight 111g [Evaluation Results] Figure 8 shows a graph of the evaluation results. The effect of the L / D ratio was significant, and it was confirmed that the smaller the L / D ratio, the more stable the molding. As shown here, in large molding machines exceeding the 280t class, the amount of heat in the heating cylinder becomes large, and it is thought that the heat has a significant effect on the thermosetting resin composition used as the molding material. Therefore, it was confirmed that properly controlling the nozzle temperature by providing a nozzle temperature adjustment unit in the nozzle is effective in improving stability.

[0030] <Item (B): Molding stability after holding for 3 minutes> When a molded product (see Figure 7) was obtained using molding machine (1) with L / D ratios of 10, 15, and 20, the coefficients of variation of "mass," "injection peak pressure," "plasticization time," and "metering circuit average pressure" were evaluated for the molding stability after holding for 3 minutes. The molding stability after holding for 3 minutes was evaluated by allowing a 3-minute waiting period after material plasticization (after weighing), and then injecting the material into the mold. Otherwise, the molding process was the same as usual.

[0031] [Evaluation Results] Figure 9 shows a graph of the evaluation results. The effect of the L / D ratio was significant, and it was confirmed that the smaller the L / D ratio, the more stable the molding process.

[0032] <Item (C): Stability comparison between large molding machines and 100t molding machines 1> The molding stability of molded products obtained using molding machine (1) (large / 280t molding machine) and molding machine (2) (100t molding machine) was evaluated by assessing the coefficients of variation of "plasticization time" and "injection peak pressure". The ratio L / D in the screw was set to 15. The evaluation procedure is as follows: In both molding machine (1) and molding machine (2) (100t molding machine), the weight of the product removed after weighing and kneading (plasticization time), injection molding (injection peak pressure), and curing (120 seconds) of the molding material (phenol resin) under the above conditions was measured. In this section (C), the variability of plasticization time and injection peak pressure was evaluated.

[0033] [Evaluation Results] Figure 10 shows a graph of the evaluation results. Figure 10(a) shows the rate of change of "plasticization time," and Figure 10(b) shows the rate of change of "injection peak pressure." As shown in the figure, it was confirmed that even large molding machines such as a 280t molding machine can perform molding as stably as or more stably than a 100t molding machine.

[0034] <Item (D): Spiral Flow> The spiral flow of three types of molded materials—blank material, a thermosetting resin composition injected from molding machine (1) (large / 280t molding machine), and molding machine (2) (100t molding machine)—was measured and their fluidity was evaluated. The ratio L / D in the screw was set to 15. The procedure for measuring spiral flow is as follows: Tablets measuring 30 mm in diameter and 20 mm in height were produced using three types of molding materials by pressure alone. The thermosetting resin compositions injected from molding machines (1) and (2) were crushed and made into tablets. Using a mold with a spiral groove having a cross-section of 5 mm on the top, 4 mm on the bottom, and 4 mm in height, the molding material was injected under the following conditions, and the fluidity was evaluated by the length of the spiral section filled before the molding material hardened, with the blank material as the baseline (100%). • Tablet preheating temperature: 95~100℃ • Mold temperature: 150±2℃ • Injection pressure: 460±10 kg / cm² 2 • Plunger speed: 40±5mm / sec • Curing time: 60 seconds [Evaluation Results] Figure 11 shows a graph of the evaluation results. It was confirmed that there was almost no difference in fluidity depending on the molding machine. [Explanation of Symbols]

[0035] 1 injection molding machine 10 Heating cylinder 11. Main body of the cylinder 12 Injection molding machine 13 Resin mixing section 20 nozzles 21 Nozzle tip 23 Resin channel 30 Heating cylinder heater 31 Front of heater 32a Heater intermediate section (1) 32b Heater intermediate section (2) 33a Rear of heater (1) 33b Rear of heater (2) 40. Nozzle temperature adjustment unit (temperature adjustment unit) 41 Nozzle temperature adjustment unit body 42 connecting pipes 50 Screw 51 Screw body 52 Screw tip 54 Screw groove 55 Flight (Screw Blade) 80 hoppers 90 molds

Claims

1. An injection molding machine for a thermosetting resin composition, comprising: a heating cylinder having a heater; a nozzle provided at the tip of the heating cylinder; and a screw provided inside the heating cylinder so as to be movable back and forth, The nozzle has a temperature adjustment unit provided in the nozzle for adjusting the temperature of the nozzle, An injection molding machine in which, when d1 is the distance from the temperature control unit to the resin flow path in the nozzle, and d2 is the distance from the heater in the heating cylinder to the resin flow path in the resin mixing unit of the heating cylinder, d1 < d2, and the depth and pitch of the screw groove are constant over the entire effective length of the screw.

2. The injection molding machine according to claim 1, wherein the temperature adjustment unit has a flow path for circulating a heat transfer medium, and the temperature of the nozzle is adjusted by circulating the heat transfer medium.

3. The injection molding machine according to claim 1 or 2, wherein the ratio L / D of the effective screw length L to the screw diameter D of the screw is 12.5 or more and 17.5 or less.

4. The injection molding machine according to claim 1 or 2, wherein the screw advances in the direction of the nozzle, causing the thermosetting resin composition in the heating cylinder to be injected from the nozzle into the mold.

5. The injection molding machine according to claim 1 or 2, wherein the temperature of the thermosetting resin composition injected from the nozzle is adjusted to 80°C or more and 130°C or less.

6. The injection molding machine according to claim 1 or 2, wherein the injection molding machine is a single-screw extruder.

7. The injection molding machine according to claim 1 or 2, wherein the temperature control unit is attached so as to wrap around the outer surface of the nozzle.

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