JP7699799B2 - Molding machine and method for producing molded article of thermoplastic resin composition - Google Patents

Description

The present invention relates to a molding machine for molding a molded article of a thermoplastic resin composition. The present invention also relates to a method for manufacturing a molded article using a thermoplastic resin composition.

Pellets are widely used in the molding process of plastic (thermoplastic resin) molded products. Pellets are made by melt-kneading compositions containing the resin obtained by polymerization in an extruder and pelletizing them. Generally, users who process plastics either mold the pellets as is, or pelletize them again in an extruder before molding and then blend or compound them for use. The extrusion process associated with these pelletizing processes is carried out at high temperatures and high pressures, which is thought to alter the internal structure of the plastic and affect its performance.

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

Patent Document 2 relates to a resin composition molding machine that melts a thermoplastic resin composition and molds it into pellets. Patent Document 2 discloses a resin composition molding machine that has a melt-kneading section and a resin reservoir section that is tapered toward the discharge section.

Patent No. 6608306 JP 2020-128032 A

"Dependence of mechanical properties of unsorted waste container and packaging recycled plastics on molding method", Natsumi Yamazaki, Nozomi Takenaka, Aya Tominaga, Tetsuyoshi Michigami, Eiichi Takatori, Hiroshi Sekiguchi, Ryoko Nakano, Shigeru Yao, Journal of Japan Society of Material Cycles and Waste Management, 30, 122-131, (2019)

In the case of waste plastics, general pelletizing modifies the internal structure of the thermoplastic resin, resulting in lower physical properties than virgin products. The molding machines and manufacturing methods disclosed in the above-mentioned Patent Documents 1 and 2 improve the physical properties of recycled resin compositions and the like to be comparable to or even better than those of virgin products. However, the present inventors believed that the physical properties of thermoplastic resins, including virgin products, could be further improved, and further investigated molding conditions, etc. Under these circumstances, the present invention aims to provide a molding machine and manufacturing method that improve the physical properties of molded products of thermoplastic resin compositions.

The inventors conducted extensive research to solve the above problems, and discovered that the following invention meets the above objective, leading to the present invention. That is, the present invention relates to the following inventions.

<1> A molding machine for producing a molded product by melting and molding a thermoplastic resin composition,
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 portion is provided between the melt-kneading portion and the discharge portion,
a temperature difference Δt (temperature t2−temperature t1) between a temperature t1 of the melt-kneading section and a temperature t2 of the resin reservoir section is −20° C. to −80° C., and the temperature t2 is lower than the temperature t1.
<2> The molding machine according to <1>, further comprising a pelletizer for pelletizing the strand-like thermoplastic resin composition discharged from the discharge portion by chopping it into pellets.
<3> The molding machine according to <1> or <2>, wherein the resin reservoir has a volume that allows a residence time in the resin reservoir to be 5 seconds to 300 seconds.
<4> The molding machine according to any one of <1> to <3>, wherein the resin reservoir portion is elongated and has the same shape as a cross section of the melt-kneading portion, 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,
The molding machine according to any one of <1> to <4>, wherein L1/D is 40 to 80.
<6> The molding machine according to any one of <1> to <5>, wherein the thermoplastic resin composition contains a crystalline polymer.
<7> A method for producing a molded article by melting and molding a thermoplastic resin composition,
A thermoplastic resin composition is fed to a feed 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,
The thermoplastic resin composition retained in the resin reservoir is discharged from a discharge portion,
The manufacturing method is characterized in that the resin reservoir portion has a molding temperature lower than that of the melt-kneading portion, and a temperature difference Δt (t2-t1) between a temperature t1 of the melt-kneading portion and a temperature t2 of the resin reservoir portion is set to -20°C to -80°C.

According to the present invention, it is possible to improve the physical properties of molded articles made from thermoplastic resin compositions.

FIG. 1 is a schematic diagram of a molding machine according to an embodiment of the present invention. FIG. 13 is a diagram for explaining an analysis model of the effect of a resin reservoir according to the present invention. FIG. 4 is a diagram showing the relationship between the temperature distribution in a resin reservoir portion and the wall surface temperature according to the present invention. FIG. 4 is a diagram showing the relationship between the pressure distribution in a resin reservoir and the wall surface temperature according to the present invention. FIG. 2 is a diagram illustrating the shape of a test piece in an example. FIG. 2 is a diagram showing the shapes of a resin reservoir and a pelletizer in the embodiment.

The following describes in detail the embodiment of the present invention, but the description of the constituent elements described below is one example (representative example) of the embodiment of the present invention, and the present invention is not limited to the following content as long as the gist of the present invention is not changed. Note that when the expression "~" is used in this specification, it is used as an expression including the numerical values before and after it.

[Molding machine of the present invention]
The molding machine of the present invention is a molding machine for molding a molded product by melting a thermoplastic resin composition, and has 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 a temperature difference Δt (t2-t1) between a temperature t1 of the melt-kneading section and a 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 a molded product of a thermoplastic resin composition can be improved.

[Production method of the present invention]
The manufacturing method of the present invention is a manufacturing method of a molded article by melting and molding a thermoplastic resin composition, which comprises 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, allowing the thermoplastic resin composition melt-kneaded in the melt-kneading section to accumulate in a resin reservoir section, and discharging the thermoplastic resin composition accumulated in the resin reservoir section from a discharge section, characterized in that 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 a molded article of a thermoplastic resin composition can be improved.

In addition, in this application, the manufacturing method of the present invention can also be carried out using the molding machine of the present invention, and the corresponding configurations in this application can be used interchangeably.

As shown in Patent Documents 1 and 2, the present inventors have found that the physical properties of a molded product made of a composition containing recycled resins can be improved by having a resin reservoir. In general, in molding machines without a resin reservoir, the screw is arranged up to the melt-kneading section close to the discharge section. For this reason, even if the temperature of the melt-kneading section is set, the temperature is thought to be higher because shear forces also act, making it possible for the temperature to be higher. Thermoplastic resins can deteriorate if the temperature during molding is high, while it is also thought that if the temperature is low, the extrusion pressure needs to be increased, so the temperature is usually set to about the same as that of the melt-kneading section up to the vicinity of the discharge section.

The inventors further investigated the molding of thermoplastic resin compositions and found that by setting the temperature of the resin reservoir to a different temperature, preferably a lower temperature, than that of the resin that had become hot in the melt-kneading section (cylinder section), a significant improvement in the physical properties can be achieved even with virgin resin.

When polymers move at high temperatures, they move and diffuse, and it is believed that the entanglements between the polymers decrease. As a result, it is believed that the internal structure after crystallization changes to one with inferior elongation properties. Therefore, it is believed that if the decrease in entanglements can be suppressed, the physical properties of the thermoplastic resin composition can be further improved.

Figure 1 is a schematic diagram showing the structure of one embodiment of a molding machine for molding a molded product 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 section 5, and a discharge section 3. The temperature of this resin reservoir section 5 is set to a lower temperature than that of the melt-kneading section 2.

Figure 2 is a diagram for explaining an analytical model of the influence of the resin reservoir. To analyze the behavior in the melt-kneading section and the resin reservoir, a 3D analytical model of the twin-screw extruder was created with the shape shown in Figure 2. A 3D finite element model was also set for the 3D analytical model. 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. There were 1,051,099 elements and 211,230 nodes.

The main analysis conditions were as follows:
Extrusion flow rate: 10 kg/h (volume flow rate 3.6 cm ³ /sec)
Die wall temperature: 200°C, 140°C (wall transfer coefficient 100 W/ ^m2 /K)
Inlet resin temperature: 222°C (based on screw analysis results for intermediate mixing)
Screw rotation speed: 200 rpm (given peripheral speed in the same direction)
・Outlet tip pressure: 0 MPa (release condition)
Resin data: General physical properties of HDPE were used. Resin melt viscosity was determined using experimental data.

The analysis was performed using "Flow Simulator," a three-dimensional thermal flow analysis software for extrusion molding manufactured by HASL Corporation. The main analysis condition for the melt-kneading section was 200°C.

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

As shown in Figure 4, in the resin reservoir, the temperature gradually drops from the wall side toward the outlet side of the resin reservoir, and only the center part maintains high fluidity. In other words, the flow of the resin composition almost stops near the wall, and a tapered flow occurs. This tendency is particularly pronounced at 140°C.

By using a molding machine equipped with such a temperature-controlled resin reservoir to re-pelletize commercially available pellets, the elongation and other properties were improved. This makes it possible to produce high-performance thermoplastic resin composition products. Furthermore, these molded products also have excellent recyclability.

[Embodiment]
A molding machine 10 according to an embodiment of the present invention (see FIG. 1 ) has a supply port 1, a melt-kneading section 2, a resin reservoir section 5, and a discharge section 3. The molding machine 10 also has a pelletizer 4 that discharges a strand-like material from the discharge section 3 and cuts it into pellets. The molding machine 10 can melt a thermoplastic resin composition and mold it into pellets. The obtained pellets are collected in a container 6 such as a flexible container bag.

[Molding machine 10]
A 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.

The molding machine 10 in FIG. 1 has a supply port 1, a melt-kneading section 2, a resin reservoir section 5, and a discharge section 3. The thermoplastic resin composition is discharged in the form of strands from the discharge section 3 and pelletized by a pelletizer 4. The resulting pellets are collected in a container 6 such as a flexible container bag. The molding machine 10 will be described in more detail below.

[Supply port 1]
The supply port 1 is a hopper-shaped supply port. A thermoplastic resin composition in the form of a lump, powder, pellets, or the like is supplied from the upper part of the supply port 1 and transferred to the melt-kneading section 2.

[Melting and kneading section 2]
The melt-kneading section 2 melts and kneads the thermoplastic resin composition supplied from the supply port 1. This melt-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 a screw 22 connected to a motor M by a cylinder 21. In addition, when passing between the pipe and the screw 22, etc., a shear stress is applied to the thermoplastic resin composition, and the thermoplastic resin composition is kneaded.

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

[Temperature difference Δt]
The resin reservoir 5 has a lower molding temperature than the melt-kneading section 2. The temperature difference Δt (temperature t2-temperature t1) between the temperature t1 of the melt-kneading section 2 and the temperature t2 of the resin reservoir 5 is -20°C to -80°C. The temperature of the melt-kneading section 2 is the set temperature of the tip of the melt-kneading section 2, which is the connecting portion between the melt-kneading section 2 and the resin reservoir 5. The temperature of the resin reservoir 5 is the set value of the entire resin reservoir 5. In order to achieve such a temperature difference, each section can be designed to be able to set its wall surface temperature independently, or a molding machine equipped with a temperature control section that controls the temperature to achieve such a temperature difference can be used.

When the temperature of the melt-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, the temperature of the resin reservoir section 5 becomes significantly low, and the fluidity of the extruded resin decreases. This results in higher extrusion pressure and a larger load on the device. It is more preferable that the temperature difference Δt is -25°C to -70°C, or -30°C to -60°C.

[Shape, length, etc. of resin reservoir 5]
The resin reservoir 5 is preferably elongated in the same shape as the cross section of the melt-kneading section 2 and/or cylindrical. In the case of a twin-screw extruder, two screws are built in, the cross section of the cylinder part is approximately elliptical, and this elliptical cross section is elongated into a straight tube. In the case of a single-screw extruder, one screw is built in, the cross section of the cylinder part is circular, and this is elongated into a cylindrical shape.

When the length of the melt-kneading section 2 is L1 (mm), the length of the resin reservoir section 5 is L2 (mm), and the cylinder diameter of the melt-kneading section 2 is D (mm), it is preferable to set L1/L2 and L1/D as follows:

The ratio of the length L2 (mm) of the resin reservoir 5 to the length L1 (mm) of the melt-kneading section 2 is preferably 0.1 to 1.0. This ratio may be 0.2 or more, or 0.3 or more. This ratio may also be 0.9 or less, 0.8 or less, or 0.7 or less. If L2/L1 is too large, the resin reservoir 5 becomes too long, and the effect of improving elongation and the like saturates, and the low wall temperature may result in low fluidity, high extrusion pressure, and high load on the device. If L2/L1 is too small, the length of the resin reservoir 5 may be insufficient, and the effect of improving elongation and the like may not be fully achieved.

The length L1/cylinder diameter D of the melt-kneading section 2 is preferably 40 to 80. L1/D may be 45 to 75 or 50 to 70. If L1/D is too small, the resin may not be melt-kneaded sufficiently. If L1/D is too large, the resin may be excessively sheared, and it may be difficult to eliminate this shear.

The length L2 of the resin reservoir 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.

[Discharge part 3]
The discharge section 3 discharges the thermoplastic resin composition in the form of strands after passing through the resin reservoir section 5 and being melt-kneaded. The end of the discharge section 3 is adapted to the shape of the molded product. For example, in the case of pelletization, a pelletizer 4 is disposed as shown in FIG. 1 for shredding. The cut pellets are stored in a container 6. Instead of the pelletizer 4, the resin may be extruded into a mold for forming a film, pipe, tube, plate, rail, corner guard, or specially formed product that corresponds to the shape of the molded product.

[Pelletizer 4]
The pelletizer 4 chops and pelletizes the thermoplastic resin composition in a strand shape discharged from the discharge section 3. The molding machine 10 of the present invention may pelletize the thermoplastic resin composition by hot cutting or underwater cutting, which chops the composition immediately after discharge from the discharge section 3, and the strand shape also includes short strands. The molding machine 10 of the present invention may be a molding machine having a pelletizer 4 that chops and pelletizes the thermoplastic resin composition discharged from the discharge section 3.

The resin pellets obtained by pelletizing the thermoplastic resin composition using this molding machine 10 are used in the injection molding process described below.

[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 thermoplastic resin composition such as a composite resin composition or a recycled resin composition, the extrusion pressure of the molding machine, etc. Based on this extrusion amount, the volume of the resin reservoir 5 is adjusted to a size that eliminates shear stress within a predetermined range. Specifically, it is preferable that the residence time is 5 to 600 seconds to eliminate this shear stress.

The molding machine can also have a resin reservoir with a volume that achieves that residence time. This residence time is calculated by dividing the extrusion amount by the volume of the resin reservoir. Note that this residence time can also be calculated from the length of the screw that corresponds to the melt-kneading section. If the screw is short relative to the piping up to the discharge section, a large shear is applied between the cylinder and the section up to the position where the screw is installed, so this section is considered to be the melt-kneading section. On the other hand, in the resin reservoir where there is no screw, the shear applied by the screw is eliminated, so this volume portion can also be considered as a resin reservoir and its residence time, etc. can be managed.

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 shear history can be eliminated, and a resin composition can be obtained in which physical properties are better maintained or improved. On the other hand, the upper limit is preferably 300 seconds or less, or 240 seconds or less. The effect of eliminating the molding history due to shear history by extending the residence time becomes smaller from a certain point onwards, so there is little need to extend the residence time beyond a certain point in terms of equipment design.

When designing this residence time as a volume, it can be designed so that the minimum residence time can be achieved based on the maximum extrusion amount of the molding machine. Alternatively, since the residence time can be controlled by the length of the pipe attached as the resin reservoir, the length can be designed so that it can be changed appropriately according to the operating conditions. The pelletization process can be carried out by appropriately referring to the molding method for thermoplastic resin compositions in JP 2017-148997 A.

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

Among these, it is preferable to use a polyolefin resin as the first thermoplastic resin. Polyolefins are crystalline polymers obtained by polymerization of α-olefins that have a double bond at the 1-position, such as polyethylene and polypropylene.

[Thermoplastic resin composition]
The thermoplastic resin composition includes a thermoplastic resin. The thermoplastic resin composition may be substantially composed of a thermoplastic resin. In addition, the thermoplastic resin composition may include impurities generally included in a thermoplastic resin composition. In addition, the thermoplastic resin composition may include various additives that are mixed with the thermoplastic resin composition.

As additives, various property improvers can be used, such as colorants, stabilizers, UV absorbers, and plasticizers. 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. It may also 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 does not need to be specified in particular, but since it may contain additives or trace impurities, an upper limit of 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 set.

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

[Inorganic substances]
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 when molding by injection molding or the like, or is mixed in as an impurity. For example, it can be mixed as a so-called filler, and can include glass fiber, carbon fiber, calcium carbonate, talc, barium nitrate, mica, aluminum hydroxide, magnesium hydroxide, carbon black, clay, pigments, etc. 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 heat resistance can be changed, allowing the desired physical properties to be adjusted.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless the gist of the invention is changed.

[Tensile test]
(Tensile Test 1) VPP (press film), RPE (press film): A tensile test was performed using "Little Senstar LSC-02/30-2" manufactured by Tokyo Test Instruments Co., Ltd. Using the results obtained from the tensile test, a stress-strain curve (S-S curve) was prepared and the breaking elongation was obtained. 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.

(Tensile test 2) VPP (injection molding): A tensile test was performed using A&D Company. Limited "Tensilon RPF-1350". Using the results obtained from the tensile test, a stress-strain curve (S-S curve) was created and the breaking elongation was calculated. The tensile speed was 250 mm/min. The test specimen was a JIS K7161-2:2014 (ISO527-2:2012) 1B type test specimen.

(Tensile test 3) VPE (press film): A tensile test was performed using Shimadzu's "EZ-LX." Using the results obtained from the tensile test, a stress-strain curve (S-S curve) was created and the breaking elongation was calculated. The tensile speed was 100 mm/min. The test piece had the shape shown in Figure 5.

[Experimental Equipment]
Extruder: Melt kneading was carried out using a twin-screw kneading extruder manufactured by the Institute of Plastics Engineering. Each screw had a cylinder diameter of φ26 mm. The screw length (L/D) was 60.

Resin reservoir VPP, RPE: The extrusion screw-embedded portion of the extruder was used as the melt-kneading portion, and a pipe with the same shape as the cylindrical pipe cross section of the melt-kneading portion was provided between the extrusion screw and the discharge portion as the resin reservoir. It had the same cross section as the melt-kneading portion of the experimental device described above in which the twin-screw extrusion screw was embedded, length L2: 240 mm, and the volume of the pipe serving as the resin reservoir was approximately 332,480 ^mm3 (332.48 ^cm3 ).

VPE: The extrusion screw built-in portion of the extruder was used as the melt kneading portion, and a straight pipe was provided between the extrusion screw and the discharge portion as a resin reservoir. A straight pipe with a length L2 of 340 mm was provided between the melt kneading portion and the discharge portion as a resin reservoir. The volume of the pipe serving as the resin reservoir was approximately 411,140 ^mm3 (411.14 ^cm3 ).

A pelletizer was provided to chop the strands discharged from the discharge part of the extruder into pellets having a length of about 5 mm. A cross section of the resin reservoir and a schematic diagram of the tip shape of the pelletizer are shown in FIG.

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

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

[Molding of test pieces from pellets]
(1) Press film molding VPP: Temperature 210°C, press pressure 30MPa, press time 2 minutes, film thickness approximately 0.08 to 0.10mm
VPE: Temperature 200°C, press pressure 20MPa, press time 2 minutes, film thickness approximately 1.00mm
RPE: Temperature 200°C, press pressure 50MPa, press time 2 minutes, film thickness approximately 0.13-0.16mm
(2) Injection Molding Using a plastic injection molding machine "J110 AD/10H" manufactured by Japan Steel Works, Ltd., at a molding temperature of 200°C, test pieces having a thickness of 0.08 to 0.10 mm were prepared in accordance with the tensile test K7131 No. 2 (1/3) dumbbell test piece of the JIS standard.

[Reference Example 1, Test Examples 1 to 10]
The test results using a VPP press film are shown in Table 1. The test pieces used were films produced by press molding. It was confirmed that the elongation at break was improved by setting the temperature of the resin reservoir lower than that of the melt-kneading section, rather than leaving it at 200°C.

[Reference Examples 11 to 14, Test Examples 11 to 12]
The test results using injection-molded test pieces of VPP are shown in Table 2. The test pieces used were injection-molded test pieces. It was confirmed that the elongation at break was improved by setting the temperature of the resin reservoir at a lower temperature than that of the melt-kneading section, rather than leaving it at 200°C.

[Reference Example 21, Test Examples 21 to 23]
The test results using VPE are shown in Table 3. Test pieces prepared by press molding were evaluated. It was confirmed that breaking elongation was improved by setting the temperature of the resin reservoir lower than that of the melt-kneading section, rather than leaving it at 200°C. The tensile test items of Reference Example 21 and Test Example 22 are also shown in Table 3.

[Reference Example 31, Test Examples 31 to 32]
Test results using recycled polyethylene, RPE, are shown in Table 5.

The present invention can be used to mold thermoplastic resin compositions and is industrially useful.

REFERENCE SIGNS LIST 1 Supply port 10 Molding machine 2 Melt kneading section 21 Cylinder 22 Screw 3 Discharge section 4 Pelletizer 5 Resin reservoir 6 Container

Claims (7)

A molding machine for producing a molded product by melting and molding 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 portion is provided between the melt-kneading portion and the discharge portion,
A molding machine characterized in that a 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 a temperature t1 of the melt-kneading section and a temperature t2 of the resin reservoir section is -20°C to -80°C. The molding machine according to claim 1, further comprising a pelletizer that pelletizes the strand-like thermoplastic resin composition discharged from the discharge section by chopping it into pellets. The molding machine according to claim 1 or 2, wherein the resin reservoir has a volume that provides a residence time in the resin reservoir of 5 to 300 seconds. The molding machine according to any one of claims 1 to 3, wherein the resin reservoir section is elongated and has the same shape as the cross section of the melt-kneading section, and/or is cylindrical. 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,
The molding machine according to any one of claims 1 to 4, wherein L1/D is 40 to 80. The molding machine according to any one of claims 1 to 5, wherein the thermoplastic resin composition contains a crystalline polymer. A method for producing a molded article by melting and molding a thermoplastic resin composition, comprising the steps of:
A thermoplastic resin composition is fed to a feed 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,
The thermoplastic resin composition retained in the resin reservoir is discharged from a discharge portion,
The manufacturing method is characterized in that the resin reservoir portion has a molding temperature lower than that of the melt-kneading portion, and a temperature difference Δt (t2-t1) between a temperature t1 of the melt-kneading portion and a temperature t2 of the resin reservoir portion is set to -20°C to -80°C.