Molding Machine and Manufacturing Method for Molded Products of Thermoplastic Resin Compositions

Abstract

To provide a molding machine that improves physical properties of a thermoplastic resin composition molded product.SOLUTION: A molding machine 10 for melting and molding a thermoplastic resin composition includes: a supply port 1 for supplying a thermoplastic resin composition; a melting and kneading unit 2 for melting and kneading the thermoplastic resin composition fed from the supply port 1; a discharge unit 3 for discharging the thermoplastic resin composition melted and kneaded in the melting and kneading section 2; and a resin reservoir 5 provided between the melting and kneading unit 2 and the discharge unit 3. A temperature difference Δt(t2-t1) between a temperature t1 in the melting and kneading unit 2 and a temperature t2 in the resin reservoir 5 is -20°C to -80°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a molding machine for a molded product of a thermoplastic resin composition. Further, the present invention relates to a method for manufacturing a molded product using a thermoplastic resin composition.

Background Art

[0002] Pellets are widely used in the molding process of plastic (thermoplastic resin) molded products. Pellets are obtained by melt-kneading a composition containing a resin obtained by polymerization using an extruder and then pelletized. Generally, users who perform plastic processing use the pellets as they are for molding, or, before molding, they are pelletized again using an extruder for blending or compounding before use. Since these extrusion processes associated with pelletization are carried out at high temperature and high pressure, it is considered that they change the internal structure of the plastic and affect its performance.

[0003] Patent Document 1 relates to a resin composition molding machine that melts a thermoplastic resin composition and forms it into pellets. Patent Document 1 discloses a resin composition molding machine having a resin reservoir provided between a melt-kneading section and a discharge section.

[0004] Patent Document 2 relates to a resin composition molding machine that melts a thermoplastic resin composition and forms it into pellets. Patent Document 2 discloses a resin composition molding machine having a resin reservoir with a tapered shape toward the melt-kneading section and the discharge section.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the case of waste plastics, in general pelletizing, the internal structure of the thermoplastic resin is denatured, and the physical properties are deteriorated compared to virgin products. By the molding machines and manufacturing methods disclosed in Patent Document 1 and Patent Document 2 described above, the physical properties of recycled resin compositions and the like are comparable to or better than those of virgin products. However, the present inventors considered that there is a possibility that the physical properties of thermoplastic resins including virgin products can be further improved, and further examined molding conditions and the like. Under such circumstances, an object of the present invention is to provide a molding machine and a manufacturing method for improving the physical properties of molded articles of a thermoplastic resin composition.

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the present inventors have found that the following invention meets the above object, and have arrived at the present invention. That is, the present invention relates to the following invention.

[0009] <1> A molding machine for molding a molded article by melting a thermoplastic resin composition, comprising: a supply port for supplying a thermoplastic resin composition; a melt-kneading section for melt-kneading the thermoplastic resin composition supplied from the supply port; a discharge section for discharging the thermoplastic resin composition melt-kneaded in the melt-kneading section; a resin reservoir section provided between the melt-kneading section and the discharge section; The temperature of the resin reservoir can be adjusted independently of the melt-kneading section, and the temperature difference Δt (temperature t2 - temperature t1) between the temperature t1 of the melt-kneading section and the temperature t2 of the resin reservoir is -20°C to -80°C, and the temperature t2 is lower than the temperature t1. A molding machine characterized by this. <2> The molding machine according to <1> above, having a pelletizer that pelletizes by shredding the strand-shaped thermoplastic resin composition discharged from the discharge section. <3> The molding machine according to <1> or <2> above, wherein the resin reservoir is a resin reservoir having a volume that makes the residence time in the resin reservoir 5 seconds to 300 seconds. <4> The molding machine according to any one of <1> to <3> above, wherein the resin reservoir is extended in the same shape as the cross-section of the melt-kneading section and / or is cylindrical. <5> When the length of the melt-kneading section is L1 (mm), the length of the resin reservoir is L2 (mm), and the cylinder diameter of the melt-kneading section is D (mm), L2 / L1 is 0.1 to 1.0, The molding machine according to any one of <1> to <4> above, wherein L1 / D is 40 to 80. <6> The molding machine according to any one of <1> to <5> above, wherein the thermoplastic resin composition contains a crystalline polymer. <7> A method for manufacturing a molded product by melting and molding a thermoplastic resin composition, Supplying the thermoplastic resin composition to the supply port of a resin composition molding machine, Melting and kneading the thermoplastic resin composition supplied from the supply port in a melt-kneading section, Allowing the thermoplastic resin composition melt-kneaded in the melt-kneading section to stay in a resin reservoir, Discharging the thermoplastic resin composition staying in the resin reservoir from a discharge section, The manufacturing method is characterized in that the resin reservoir has a lower molding temperature than the melt-kneading section, and the temperature difference Δt (t2 - t1) between the temperature t1 of the melt-kneading section and the temperature t2 of the resin reservoir is -20°C to -80°C.

Advantages of the Invention

[0010] According to the present invention, the physical properties of a molded article of a thermoplastic resin composition can be improved.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to the following contents unless the gist thereof is changed. In this specification, when the expression "~" is used, it is used as an expression including the numerical values before and after it.

[0013] [Molding Machine of the Present Invention] The molding machine of the present invention is a molding machine for molding a molded article by melting a thermoplastic resin composition, and includes a supply port for supplying the thermoplastic resin composition, a melt-kneading section for melt-kneading the thermoplastic resin composition supplied from the supply port, a discharge section for discharging the thermoplastic resin composition melt-kneaded in the melt-kneading section, and a resin reservoir section provided between the melt-kneading section and the discharge section. The temperature of the resin reservoir section can be adjusted independently of the melt-kneading section, and the temperature difference Δt (t2 - t1) between the temperature t1 of the melt-kneading section and the temperature t2 of the resin reservoir section is -20°C to -80°C. According to the molding machine of the present invention, the physical properties of the molded article of the thermoplastic resin composition can be improved.

[0014] [Manufacturing Method of the Present Invention] The manufacturing method of the present invention is a manufacturing method for molding a molded article by melting a thermoplastic resin composition. The thermoplastic resin composition is supplied to the supply port of a resin composition molding machine, the thermoplastic resin composition supplied from the supply port is melt-kneaded in a melt-kneading section, the thermoplastic resin composition melt-kneaded in the melt-kneading section is retained in a resin reservoir section, and the thermoplastic resin composition retained in the resin reservoir section is discharged from a discharge section. The resin reservoir section has a molding temperature lower than that of the melt-kneading section, and the temperature difference Δt (t2 - t1) between the melt-kneading section and the resin reservoir section is -20°C to -80°C. According to the manufacturing method of the present invention, the physical properties of the molded article of the thermoplastic resin composition can be improved.

[0015] In addition, in the present application, the manufacturing method of the present invention can also be carried out by the molding machine of the present invention, and the corresponding configurations in the present application can be used mutually.

[0016] As shown in Patent Documents 1 and 2, the inventors have found that by adopting a configuration having a resin reservoir, it is possible to improve the physical properties of molded articles of compositions containing recycled resin and the like. Generally, in a molding machine without a resin reservoir, a screw is arranged up to a melt-kneading section close to the discharge section. For this reason, even if the temperature of the melt-kneading section is set, shear force also acts, so it is considered that the temperature becomes higher. Thermoplastic resins may deteriorate when the temperature during molding is high. On the other hand, it is also considered that when the temperature is low, it is necessary to increase the extrusion pressure. Usually, the temperature is set to be approximately the same as that of the melt-kneading section up to the vicinity of the discharge section.

[0017] As a result of further studying the molding of thermoplastic resin compositions, the inventors have found that by setting the temperature of the resin reservoir to a temperature different from that of the resin which has become high temperature in the melt-kneading section (cylinder section), preferably a lower temperature, a significant effect of improving physical properties can be obtained even with virgin resin and the like.

[0018] When a polymer moves while remaining at a high temperature, it is considered that the polymer moves and diffuses, and the entanglement between polymers decreases. As a result, it is considered that the internal structure after crystallization has mutated to be inferior in elongation characteristics. Therefore, it is considered that if the decrease in this entanglement is suppressed, the physical properties of the thermoplastic resin composition can be further improved.

[0019] FIG. 1 is a schematic view showing the structure according to an embodiment of a molding machine for a molded article of a thermoplastic resin composition of the present invention. The molding machine 10 according to the first embodiment of the present invention has a supply port 1, a melt-kneading section 2, a resin reservoir 5, and a discharge section 3. The temperature of this resin reservoir 5 is set to be lower than that of the melt-kneading section 2.

[0020] Figure 2 is a diagram for explaining the analysis model of the influence of the resin accumulation part. When analyzing the behavior in the melt kneading part and the resin accumulation part, for the twin-screw extruder, a 3D analysis model with the shape shown in Figure 2 was created. Also, for the 3D analysis model, a 3D finite element model was set. The basic mesh size of the finite element model was 1.2 mm, and the breaker plate and the tip of the strand die were set to 0.5 mm. The number of elements was 1,051,099 elements, and the number of nodes was 211,230 points.

[0021] The main analysis conditions were set as follows. · Extrusion flow rate: 10 kg / h (volume flow rate 3.6 cm 3 / sec) · Die wall temperature: 200 °C, 140 °C (wall heat transfer coefficient 100 W / m 2 / K) · Inlet resin temperature: 222 °C (from the screw analysis result of the middle kneading) · Screw rotation speed: 200 rpm (applying the peripheral speed of co-rotating) · Outlet tip pressure: 0 MPa (release condition) · Resin data: Using general physical properties of HDPE · The resin melt viscosity was used with experimental data.

[0022] The analysis was carried out using the 3D heat flow analysis software "Flow Simulator" manufactured by HASL Co., Ltd. for extrusion molding. The main analysis condition for the melt kneading part was 200 °C.

[0023] Figure 3 is a diagram showing the relationship with the wall temperature of the resin accumulation part and the like according to the present invention. Figure 4 is a diagram showing the relationship between the pressure distribution of the resin accumulation part and the like according to the present invention and the wall temperature. Also, the upper part of Figure 4 is when the wall temperature of the die is 200 °C. The lower part of Figure 4 is when the wall temperature of the die is 140 °C. The resin pressures at each temperature in Figure 4 are displayed with the same color range.

[0024] As shown in Fig. 4, in the resin reservoir, the temperature gradually decreases from the wall surface side toward the outlet side from the inlet side of the resin reservoir, and only the central part maintains high fluidity. That is, the flow of the resin composition almost stops near the wall surface, and a tapered flow occurs. It can be seen that this tendency is particularly large at 140°C.

[0025] Then, as a result of repelletizing commercially available pellets using a molding machine provided with such a resin reservoir with temperature control, the elongation and the like were improved. Thereby, products of high-performance thermoplastic resin compositions can be produced. Further, this molded product also has excellent recycling characteristics.

[0026] [Embodiment] The molding machine 10 (see Fig. 1) according to the embodiment of the present invention has a supply port 1, a melt-kneading part 2, a resin reservoir 5, and a discharge part 3. Further, this molding machine 10 has a pelletizer 4 that discharges in a strand shape from the discharge part 3 and cuts this to form pellets. With this molding machine 10, a thermoplastic resin composition can be melted and formed into pellets. The obtained pellets are collected in a container 6 such as a flexible container bag.

[0027] [Molding Machine 10] The molding machine 10 in Fig. 1 relates to an embodiment of the molding machine of the present invention and is suitable for the molding method of the present invention.

[0028] The molding machine 10 in Fig. 1 has a supply port 1, a melt-kneading part 2, a resin reservoir 5, and a discharge part 3. The thermoplastic resin composition is discharged in a strand shape from the discharge part 3 and pelletized by the pelletizer 4. The obtained pellets are collected in a container 6 such as a flexible container bag. The molding machine 10 will be described in more detail below.

[0029] [Supply Port 1] The supply port 1 is a hopper-shaped supply port. The thermoplastic resin composition in the form of lumps, powders, pellets, etc. is supplied from the upper part of this supply port 1 and transferred to the melt-kneading part 2.

[0030] [Melt-Kneading Part 2] The melting and kneading section 2 melts and kneads the thermoplastic resin composition supplied from the supply port 1. This melting and kneading section 2 is heated to the melting temperature of the thermoplastic resin composition, and the thermoplastic resin composition is extruded toward the resin reservoir section 5 by rotating the screw 22 connected to the cylinder 21 by the motor M. Further, when passing through between this pipe and the screw 22 or the like, a shear stress is applied to the thermoplastic resin composition, and the thermoplastic resin composition is kneaded.

[0031] [Resin reservoir section 5] The resin reservoir section 5 is provided between the melting and kneading section 2 and the discharge section 3. This resin reservoir section 5 can eliminate the shear stress applied to the thermoplastic resin composition melt-kneaded in the melting and kneading section 2.

[0032] [Temperature difference Δt] The resin reservoir section 5 has a lower molding temperature than the melting and kneading section 2. Further, the temperature difference Δt (temperature t2 - temperature t1) between the temperature t1 of the melting and kneading section 2 and the temperature t2 of the resin reservoir section 5 is -20°C to -80°C. The temperature of the melting and kneading section 2 is the set temperature at the tip of the melting and kneading section 2 which is the connection portion between the melting and kneading section 2 and the resin reservoir section 5. The temperature of the resin reservoir section 5 is the set value for the entire resin reservoir section 5. In order to obtain such a temperature difference, each part can be set to have an independent wall surface temperature, or a molding machine equipped with a temperature control unit for controlling the temperature so as to obtain such a temperature difference can be used.

[0033] When the temperature of the melting and kneading section 2 is 200°C, the temperature of the resin reservoir section 5 is 120°C to 180°C. When the temperature difference Δt is small, the improvement effect may be limited. When the temperature difference Δt is large, since the temperature of the resin reservoir section 5 becomes considerably low, the fluidity of the extruded resin decreases. For this reason, the extrusion pressure becomes high and the device load becomes large. The temperature difference Δt is more preferably -25°C to -70°C or -30°C to -60°C.

[0034] [Shape, length, etc. of the resin reservoir section 5] The resin accumulation part 5 is preferably extended with the same shape as the cross-section of the melt-kneading part 2 and / or is columnar. In the case of a twin-screw extruder, two screws are built in, and the cross-section of the cylinder part is substantially elliptical, and it is assumed to be extended in a straight tubular shape with this elliptical cross-section. In the case of a single-screw extruder, one screw is built in, and the cross-section of the cylinder part is circular, and it is assumed to be an extended columnar shape.

[0035] When the length of the melt-kneading part 2 is L1 (mm), the length of the resin accumulation part 5 is L2 (mm), and the cylinder diameter of the melt-kneading part 2 is D (mm), it is preferable to set L1 / L2 and L1 / D as follows, respectively.

[0036] The ratio of the length L2 (mm) of the resin accumulation part 5 to the length L1 (mm) of the melt-kneading part 2 is preferably 0.1 to 1.0. This ratio may be 0.2 or more, or 0.3 or more. Also, this ratio may be 0.9 or less, 0.8 or less, or 0.7 or less. When L2 / L1 is too large, the resin accumulation part 5 becomes too long, and the effects such as improvement in elongation are saturated, and there are cases where the fluidity is low due to the low wall temperature, the extrusion pressure is high, and the device load is high. When L2 / L1 is too small, the length of the resin accumulation part 5 is insufficient, and there are cases where the effects such as improvement in elongation cannot be sufficiently achieved.

[0037] The ratio of the length L1 of the melt-kneading part 2 to the cylinder diameter D is preferably 40 to 80. L1 / D may be 45 to 75, or 50 to 70. When L1 / D is too small, there are cases where the resin cannot be sufficiently melt-kneaded. When L1 / D is too large, the resin is excessively sheared, and it may become difficult to eliminate this shear.

[0038] The length L2 of the resin accumulation part 5 depends on the size of the molding machine 10, the extrusion amount, the residence time, etc., but can be 10 mm or more, 30 mm or more, 50 mm or more, 80 mm or more, 100 mm or more, etc.

[0039] [Discharge part 3] The discharging section 3 passes through the resin reservoir section 5 and discharges the thermoplastic resin composition after melt-kneading in a strand shape. The tip of the discharging section 3 shall be adapted to the shape of the molded product. For example, when pelletizing, as shown in Fig. 1, a pelletizer 4 is arranged to cut it into pieces. The cut pellets are accommodated in a container 6. Instead of the pelletizer 4 or the like, it may be extruded into a mold corresponding to the shape of the molded product, such as a film, a pipe, a tube, a plate, a rail, a corner guard, or a shaped molded product.

[0040] [Pelletizer 4] The pelletizer 4 cuts the strand-shaped thermoplastic resin composition discharged from the discharging section 3 into pieces and pelletizes it. Note that the molding machine 10 of the present invention may be pelletized by a hot cut or an under-water cut that cuts it into pieces immediately after discharging from the discharging section 3. The strand shape includes those in a short state. The molding machine 10 of the present invention may be a molding machine having a pelletizer 4 that cuts the thermoplastic resin composition discharged from such a discharging section 3 into pieces and pelletizes it.

[0041] The resin pellets obtained by pelletizing the thermoplastic resin composition by this molding machine 10 are used in the injection molding process described later.

[0042] [Extrusion conditions] In the molding machine, it is preferable that the extrusion amount per unit time is controlled within a predetermined range according to the type of the thermoplastic resin composition such as a composite resin composition or a recycled resin composition and the extrusion pressure of the molding machine. Based on this extrusion amount, the volume of the resin reservoir section 5 is adjusted to a size that eliminates the shear stress within a predetermined range. Specifically, it is preferable that the residence time is 5 to 600 seconds for the size that eliminates this shear stress.

[0043] Further, the molding machine can be configured to have a resin reservoir portion with a volume that achieves the residence time. This residence time is determined from the extrusion rate / volume of the resin reservoir portion. Note that this residence time may also be determined from the length where the screw corresponding to the melt kneading portion is provided. When the screw is shortened with respect to the piping up to the discharge portion, a large shear is applied between the cylinder and the position where the screw is provided, so it is regarded as the melt kneading portion. On the other hand, in the resin reservoir portion without a screw, the shear applied by the screw is eliminated, so this volume portion can also be regarded as the resin reservoir portion and its residence time and the like can be managed.

[0044] This residence time is more preferably 10 seconds or more, 30 seconds or more, and even more preferably 60 seconds or more. The longer the residence time, the more the molding history due to the shear history can be eliminated, and a resin composition with more maintained or improved physical properties can be obtained. On the other hand, the upper limit is preferably 300 seconds or less, or 240 seconds or less. Since the effect of eliminating the molding history due to the shear history by increasing the residence time becomes less with the change amount becoming small from a certain level, there is little need to make it longer than a certain level in terms of the device design.

[0045] When designing this residence time as a volume, it can be designed to achieve the minimum residence time based on the maximum extrusion rate of the molding machine. Or, substantially, since the residence time can be controlled by the length of the piping attached as the resin reservoir portion, it may be managed as a design that can appropriately replace the length according to the operating conditions. Note that the pelletizing process can be carried out with appropriate reference to the molding method of the thermoplastic resin composition disclosed in JP-A-2017-148997.

[0046] [First thermoplastic resin] The present invention relates to a thermoplastic resin composition containing a thermoplastic resin or the like. A thermoplastic resin is a resin that softens when heated and can be injection-molded. For example, polyolefin resins, polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylic resins such as PMMA, polyvinyl chloride, polyamide resins, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polycarbonate (PC), polyetheretherketone (PEEK), polyphenyl sulfide (PPS), and the like can be mentioned.

[0047] Among these, it is preferable to use a polyolefin resin as the first thermoplastic resin. A polyolefin is a crystalline polymer obtained by polymerization of α-olefins having a double bond at the 1-position, such as polyethylene and polypropylene.

[0048] [Thermoplastic resin composition] The thermoplastic resin composition contains a thermoplastic resin. This thermoplastic resin composition may consist essentially of a thermoplastic resin. Further, it may generally contain impurities and the like contained in the thermoplastic resin composition. Further, it may contain various additives and the like used by mixing with the thermoplastic resin composition.

[0049] As the additive, various physical property improvers can be used. For example, colorants, stabilizers, UV absorbers, plasticizers, and the like can be mentioned. The first thermoplastic resin contained in the thermoplastic resin composition is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. Further, it may be 80% by mass or more, or 90% by mass or more. The upper limit of the first thermoplastic resin contained in the thermoplastic resin composition may not be particularly defined. However, since it may contain additives and trace impurities, an upper limit such as 99.9% by mass or less, 99.5% by mass or less, 99% by mass or less, 98% by mass or less, 95% by mass or less may be provided.

[0050] [Composite resin composition] The thermoplastic resin composition may use a first thermoplastic resin and a composite resin composition containing an inorganic substance and / or a polymer component different from the first thermoplastic resin. In conventional molding, the composite resin composition may have a lower elongation at break, particularly, than the first thermoplastic resin composition. According to the present invention, such a decrease in elongation at break can be suppressed.

[0051] [Inorganic substance] The composite resin composition can contain an inorganic substance. This inorganic substance is used in combination with the first thermoplastic resin and is a component that is used in combination or mixed as an impurity when molding by injection molding or the like. For example, those mixed as so-called fillers can be mentioned, such as glass fiber, carbon fiber, calcium carbonate, talc, barium nitrate, mica, aluminum hydroxide, magnesium hydroxide, carbon black, clay, pigments, and the like. By containing an inorganic substance, the elastic modulus, breaking strength, impact resistance, etc. can be improved, and the optical properties such as color and reflectance and the heat resistance can be changed to adjust to the desired physical properties.

Examples

[0052] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless the gist thereof is changed.

[0053] [Tensile test] (Tensile Test 1) A tensile test was conducted using “Little Senstar LSC-02 / 30-2” manufactured by Tokyo Testing Machine Co., Ltd. for VPP (press film) and RPE (press film). Using the results obtained by the tensile test, a stress-strain curve (S-S curve) was created to determine the elongation at break. The tensile speed was 50 mm / min for VPP and 100 mm / min for RPE. The test piece for VPP had the shape shown in FIG. 5.

[0054] (Tensile Test 2) VPP (Injection Molding): A tensile test was conducted using "Tensilon RPF-1350" from A&D Company, Limited. Using the results obtained from the tensile test, a stress-strain curve (S-S curve) was created to determine the elongation at break. The tensile speed was set at 250 mm / min. The test specimens were Type 1B test specimens according to JIS K7161-2:2014 (ISO 527-2:2012).

[0055] (Tensile Test 3) VPE (Press Film): A tensile test was conducted using "EZ-LX" manufactured by SHIMADZU. Using the results obtained from the tensile test, a stress-strain curve (S-S curve) was created to determine the elongation at break. The pulling speed was set at 100 mm / min. The test specimens had the shape shown in Figure 5.

[0056] [Experimental Equipment] · Extruder Melt kneading was carried out using a twin-screw kneading extruder manufactured by the Plastic Engineering Research Institute. It has a cylinder diameter of φ26 mm for each axis. Regarding the screw length, L / D is 60.

[0057] · Resin Reservoir For VPP and RPE: The built-in part of the extrusion screw of the above extruder was used as the melt kneading part, and between the discharge part, a pipe with the same shape as the cross-section of the cylinder pipe of the melt kneading part was provided as the resin reservoir. It has the same cross-sectional shape as the melt kneading part where the twin-screw extrusion screw of the above-described experimental equipment is built-in, with a length L2 of 240 mm. The volume of the pipe that becomes this resin reservoir is approximately 332,480 mm 3 (332.48 cm 3 )

[0058] For VPE: The built-in part of the extrusion screw of the above extruder was used as the melt kneading part, and between the discharge part, a straight pipe was provided as the resin reservoir. A straight pipe with a length L2 of 340 mm was provided as the resin reservoir between the melt kneading part and the discharge part. The volume of the pipe that becomes this resin reservoir is approximately 411,140 mm 3 (411.14 cm 3 )

[0059] · Pelletizer A pelletizer was provided to cut the strands discharged from the discharge part of the extruder into pellets about 5 mm in length. An outline diagram of the cross-section of the resin reservoir part, the tip shape of the pelletizer, etc. is shown in Fig. 6.

[0060] [Raw material] · VPP: Japan Polypropylene Co., Ltd. "BC03BSW", MFR: 30 g / 10 min, virgin polypropylene resin · VPE: Asahi Kasei Corporation "Suntech (registered trademark) 'B470'", MFR (190, 2.16): 0.30 g / 10 min, virgin polyethylene resin · RPE: Toyama Environmental Maintenance Co., "PE Hard", recycled polyethylene resin

[0061] [Experimental conditions] Using the above experimental apparatus, molding was carried out under the experimental conditions shown in Tables 1 to 4 to obtain pellets. Test molded products were molded from the obtained pellets and evaluated. The temperature of the melt kneading part was set at 200 °C.

[0062] [Molding of test molded products from pellets] (1) Press film molding VPP: Temperature 210 °C, press pressure 30 MPa, press time 2 minutes, film thickness about 0.08 - 0.10 mm VPE: Temperature 200 °C, press pressure 20 MPa, press time 2 minutes, film thickness about 1.00 mm RPE: Temperature 200 °C, press pressure 50 MPa, press time 2 minutes, film thickness about 0.13 - 0.16 mm (2) Injection molding Using a plastic injection molding machine "J110 AD / 10H" manufactured by Japan Steel Works, at a molding temperature of 200 °C, in accordance with the JIS standard tensile test K7131 2(1 / 3) type dumbbell test piece, test piece dimensions of a test piece with a thickness of 0.08 - 0.10 mm were produced.

[0063] [Reference Example 1, Test Examples 1 - 10] Table 1 shows the test results using the preform film of VPP. The test specimens used films formed by press molding. It was confirmed that the elongation at break improved by setting the temperature of the resin accumulation part lower than that of the melt-kneading part rather than keeping it at 200°C.

[0064]

Table 1

[0065] [Reference Examples 11 - 14, Test Examples 11 - 12] Table 2 shows the test results using injection-molded specimens of VPP. The test specimens used injection-molded specimens. It was confirmed that the elongation at break improved by setting the temperature of the resin accumulation part lower than that of the melt-kneading part rather than keeping it at 200°C.

[0066]

Table 2

[0067] [Reference Example 21, Test Examples 21 - 23] Table 3 shows the test results using VPE. The test specimens evaluated those produced by press molding. It was confirmed that the elongation at break improved by setting the temperature of the resin accumulation part lower than that of the melt-kneading part rather than keeping it at 200°C. Also, Table 3 shows each tensile test item of Reference Example 21 and Test Example 22.

[0068]

Table 3

[0069]

Table 4

[0070] [Reference Example 31, Test Examples 31 - 32] Table 5 shows the test results using RPE, which is recycled polyethylene.

[0071]

Table 5

Industrial Applicability

[0072] The present invention can be used for molding a thermoplastic resin composition and is industrially useful.

Explanation of Signs

[0073] 1 Supply port 10 Molding machine 2 Melting and kneading section 21 Cylinder 22 Screw 3 Discharge section 4 Pelletizer 5 Resin storage section 6 Container

Claims

1. A molding machine for molding a molded article by melting a thermoplastic resin composition, comprising: a supply port for supplying the thermoplastic resin composition; a melt-kneading section for melt-kneading the thermoplastic resin composition supplied from the supply port; a discharge section for discharging the thermoplastic resin composition melt-kneaded in the melt-kneading section; a resin reservoir section provided between the melt-kneading section and the discharge section; wherein the temperature of the resin reservoir section can be adjusted independently of the melt-kneading section, and a temperature difference Δt (temperature t2 - temperature t1) between the temperature t1 of the melt-kneading section and the temperature t2 of the resin reservoir section is -20°C to -80°C. The molding machine is characterized by this.

2. The molding machine according to claim 1, further comprising a pelletizer for pelletizing by cutting the strand-like thermoplastic resin composition discharged from the discharge section.

3. The molding machine according to claim 1 or 2, wherein the resin reservoir section has a volume such that a residence time in the resin reservoir section is 5 seconds to 300 seconds.

4. The molding machine according to any one of claims 1 to 3, wherein the resin reservoir section is extended in the same shape as a cross-section of the melt-kneading section and / or is cylindrical.

5. When the length of the melt-kneading section is L1 (mm), the length of the resin reservoir section is L2 (mm), and the cylinder diameter of the melt-kneading section is D (mm), L2 / L1 is 0.1 to 1.0, L1 / D is 40 to 80. The molding machine according to any one of claims 1 to 4 is characterized by this.

6. The molding machine according to any one of claims 1 to 5, wherein the thermoplastic resin composition contains a crystalline polymer.

7. A method for manufacturing a molded article by melting a thermoplastic resin composition, comprising: supplying the thermoplastic resin composition to a supply port of a resin composition molding machine; melt-kneading the thermoplastic resin composition supplied from the supply port in a melt-kneading section; retaining the thermoplastic resin composition melt-kneaded in the melt-kneading section in a resin reservoir section; discharging the thermoplastic resin composition retained in the resin reservoir section from a discharge section; wherein the resin reservoir section has a lower molding temperature than the melt-kneading section, and a temperature difference Δt (t2 - t1) between the temperature t1 of the melt-kneading section and the temperature t2 of the resin reservoir section is -20°C to -80°C. The manufacturing method is characterized by this.

Images