Method for producing foamed molded article

Abstract

To easily expand a foamed resin sheet to a desired thickness in an expansion process.SOLUTION: A method of manufacturing a foam molding body includes: a process of extruding a foam resin in a molten state through a slit and stretching the extruded foam resin between a pair of rollers, thereby causing a foam resin sheet to hang between first and second molds; and an expansion process to expand the foamed resin sheet to a thickness of a gap by vacuuming the foamed resin sheet under reduced pressure by both the first and second molds while the first and second molds are brought closer to each other so that the gap larger than the thickness of the foamed resin sheet is provided between the first and second molds.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a foamed molded article and the foamed molded article. [Background technology]

[0002] Patent Document 1 discloses a technique for adjusting the thickness of a foamed resin sheet extruded from a T-die by stretching the sheet with a roller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5410139 Summary of the Invention [Problem to be solved by the invention]

[0004] Some manufacturing methods for foamed molded articles involve an expansion step. In this step, a foamed resin sheet is expanded by vacuum suction to the thickness of the gap between the molds. The inventors of the present application attempted to apply the expansion step to a foamed resin sheet after it had been stretched by rollers. As a result, an unexpected technical result was obtained: the ease of manufacturing thick-walled molded articles was improved.

[0005] The present invention has been made in consideration of the above circumstances, and provides a method for producing a foamed molded article and a foamed molded article that are improved to make it easier to expand a foamed resin sheet to a desired thickness in the expansion process. [Means for solving the problem]

[0006] According to the present invention, there is provided a method for manufacturing a foamed molded article, comprising the steps of: extruding molten foamed resin through a slit and stretching the extruded foamed resin between a pair of rollers to form a foamed resin sheet hanging down between first and second molds; and expanding the foamed resin sheet to the thickness of the gap by vacuum-suctioning the foamed resin sheet with both the first and second molds while the first and second molds are brought close together so that a gap larger than the thickness of the foamed resin sheet is formed between the first and second molds.

[0007] According to the findings of the present inventors, it is believed that the surface conditions of both the front and back sides of the foamed resin sheet are improved by roller stretching, and that the foamed resin sheet with the improved surface condition is subjected to reduced pressure suction, which makes it easier to achieve good expansion.

[0008] Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other. Preferably, a fibrous filler is blended with the foamed resin in the molten state extruded through the slit. Preferably, the amount of fibrous filler contained in the foamed resin is 30% by mass or more. Preferably, the foamed molded article has a basis weight of 900 g / m 2 The foamed resin is extruded from the slit so as to be as described above.

[0009] According to another aspect of the present invention, there is provided a foamed molded article, which is obtained by stretching a foamed resin sheet having a fibrous filler content of 30% by mass or more between a pair of rollers, and then expanding the foamed resin sheet to an expansion ratio of 3 times or more by vacuum suction. [Brief explanation of the drawings]

[0010] [Figure 1] An example of a foam molding machine 1 that can be used in the method for producing a foam molded article according to one embodiment of the present invention is shown. [Figure 2] 2 is an enlarged cross-sectional view of the first and second molds 21 and 22 and the foamed resin sheet 23 in FIG. 1. FIG. [Figure 3] 2. FIG. 4 is a cross-sectional view showing a state in which foamed resin sheet 23 is suctioned by first mold 21 under reduced pressure to form foamed resin sheet 23 in a shape that conforms to cavity 21b of first mold 21. [Figure 4] FIG. 4 is a diagram showing a state in which the molds 21 and 22 are moved closer to each other from the state shown in FIG. [Figure 5] 5 is a diagram showing a state in which the foamed resin sheet 23 is decompressed and suctioned by the second mold 22 from the state of FIG. 4, so that the foamed resin sheet 23 is expanded to the thickness of the gap G between the molds 21 and 22. FIG. [Figure 6] FIG. 5 shows a foamed molded article 24 with flash 23b obtained in the process. [Figure 7] This shows the state after burrs 23b have been removed from the state shown in FIG. [Figure 8] 1 is a cross-sectional photograph of Sample 2 (basis weight 800 g / m 2 ) of the embodiment. [Figure 9] 1 is an enlarged cross-sectional photograph of Sample 2 (basis weight 800 g / m 2 ) of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0012] 1. Configuration of foam molding machine 1 First, a foam molding machine 1 that can be used to carry out a method for producing a foam molded article according to one embodiment of the present invention will be described with reference to Figures 1 to 5. The foam molding machine 1 includes a resin supplying device 2, a T-die 18, molds 21 and 22, and a pair of rollers 32. The resin supplying device 2 includes a hopper 12, an extruder 13, an injector 16, and an accumulator 17. The extruder 13 and the accumulator 17 are connected via a connecting pipe 25. The accumulator 17 and the T-die 18 are connected via a connecting pipe 27. Each component will be described in detail below.

[0013] <Hopper 12, Extruder 13> The hopper 12 is used to feed the raw material resin 11 into the cylinder 13a of the extruder 13. After being fed from the hopper 12 into the cylinder 13a, the raw material resin 11 is heated and melted in the cylinder 13a to become a molten resin. The molten resin is transported toward the tip of the cylinder 13a by the rotation of a screw disposed in the cylinder 13a. The screw is disposed in the cylinder 13a, and by its rotation, the molten resin is transported while being kneaded. A gear device is provided at the base end of the screw, and the screw is rotationally driven by the gear device. The number of screws disposed in the cylinder 13a may be one or two or more.

[0014] In this embodiment, a fibrous filler is blended into the raw material resin 11. In this embodiment, as an example, the fibrous filler is glass fiber, specifically long fiber, i.e., glass fiber. Details of the material blend, including the fibrous filler, will be described later.

[0015] <Injector 16> The cylinder 13a is provided with an injector 16 for injecting a foaming agent into the cylinder 13a. The foaming agent will be described in detail later.

[0016] <Accumulator 17, T-die 18> A foamed resin obtained by melt-kneading raw material resin 11, a foaming agent, and a fibrous filler is extruded from a resin extrusion port of cylinder 13a and injected into accumulator 17 through connecting pipe 25. Accumulator 17 includes cylinder 17a and piston 17b that can slide inside thereof, and foamed resin 11a can be stored in cylinder 17a. Then, by moving piston 17b after a predetermined amount of foamed resin 11a has been stored in cylinder 17a, foamed resin 11a is extruded through connecting pipe 27 from a slit provided in T-die 18 and hangs down to form foamed resin sheet 23.

[0017] <First and second molds 21, 22> The foamed resin sheet 23 is guided between the first and second molds 21, 22. As shown in FIGS. 1 to 5, the first mold 21 is provided with a number of vacuum suction holes 21a, which allows the foamed resin sheet 23 to be suctioned under reduced pressure and shaped into a shape that conforms to the cavity 21b of the first mold 21. The cavity 21b has a shape that includes a recess 21c, and a pinch-off portion 21d is provided to surround the recess 21c. The second mold 22 is provided with a number of vacuum suction holes 22a, which allows the foamed resin sheet 23 to be suctioned under reduced pressure and shaped into a shape that conforms to the cavity 22b of the second mold 22. The cavity 22b has a shape that includes a protrusion 22c that fits into the recess 21c, and a pinch-off portion 22d is provided to surround the protrusion 22c. Note that the cavity 22b of the second mold 22 may have a shape that includes a recess, and the cavity 21b of the first mold 21 may have a shape that includes a protrusion that fits into the recess.

[0018] <Pair of rollers 32> As shown in FIG. 1, the pair of rollers 32 are disposed below the T-die 18. A gap is formed between the pair of rollers 32 through which the foamed resin sheet 23 passes. The pair of rollers 32 may be provided together with, for example, a frame, a gear mechanism, a power mechanism, a movement mechanism, and a gap adjustment mechanism. The frame and gear mechanism rotatably support the pair of rollers 32.

[0019] The pair of rollers 32 are rotated by a power mechanism (not shown). The power mechanism is, for example, a motor. A gear mechanism transmits the power of the power mechanism to each of the pair of rollers 32, thereby synchronizing the rotation of the pair of rollers 32. The movement mechanism has the function of moving the pair of rollers 32 in the forward and backward directions together with the frame body. There are no limitations on the structure of the movement mechanism, but among electric cylinders, hydraulic cylinders, and air cylinders, electric cylinders have the highest movement accuracy, followed by hydraulic cylinders, so it is preferable to select a movement mechanism according to the required accuracy. The relative distance between the pair of rollers 32 (i.e., the size of the gap between them) can be changed by controlling the gap adjustment mechanism.

[0020] 2. Manufacturing method of foam molded body Here, a method for producing a foamed molded article according to one embodiment of the present invention will be described with reference to Figures 2 to 7. The method according to this embodiment comprises an extrusion step, a stretching step, a placement step, an expansion step, and a finishing step. These steps will be described in detail below.

[0021] 2.1 Extrusion and stretching processes The foaming resin 11a stored in the accumulator 17 is extruded at a constant extrusion speed through the slit of the T-die 18. During extrusion, the foamed molded body 24 (see FIG. 7) after the finishing process described below has a basis weight of, for example, 900 g / m 2 The foamed resin 11a may be extruded through the slit of the T-die 18 so as to have the above weight. Specifically, the weight per unit area of ​​the foamed molded body 24 may be, for example, 800, 850, 900, 950, 1000, 1050, 1100, 1200, 1300, 1400, 1500, or 2000 g / m 2 It may be any one or more of the numerical values ​​exemplified herein, or may be in a range between any two of the numerical values ​​exemplified herein.

[0022] In this case, the influence of drawdown may be minimized by varying the slit gap of the T-die 18 in accordance with the extrusion of the foamed resin sheet 23. In other words, in response to the drawdown phenomenon in which the foamed resin sheet 23 is stretched by its own weight and becomes thinner toward the top, the slit gap can be gradually widened from the start of extrusion to extrude the foamed resin sheet 23 so that the thickness is thicker toward the top, thereby adjusting the foamed resin sheet 23 to a uniform thickness from top to bottom.

[0023] Furthermore, the rotation speed of the pair of rollers 32 is adjusted in accordance with the extrusion speed of the foamed resin sheet 23 extruded from the T-die 18. Specifically, by varying the rotation speed, a difference is created between the extrusion speed of the foamed resin sheet 23 from the T-die 18 and the feed speed of the pair of rollers 32. This speed difference allows the foamed resin sheet 23 to be stretched between the T-die 18 and the pair of rollers 32, thereby adjusting the thickness of the sheet to be thin. In the following description, for simplicity, stretching the foamed resin sheet 23 with the pair of rollers 32 may be simply referred to as "roller stretching" or "longitudinal stretching."

[0024] In this embodiment, stretching by the pair of rollers 32 allows the foamed resin sheet 23 to expand to a desired thickness in the expansion process described below. Specifically, the inventors attempted to apply the expansion process to the foamed resin sheet 23 after roller stretching, resulting in a technical result that facilitates the production of thick-walled molded articles. According to the inventors' findings, the surface condition of both the front and back surfaces of the foamed resin sheet 23 is believed to be improved by roller stretching. The improvement in the surface condition is believed to include at least one of improvement by pressing and improvement by cooling. The improvement by pressing refers to the smoothing of the surface layer by pressing air bubbles on both the front and back surfaces of the foamed resin sheet 23 during roller stretching. Furthermore, the improvement by cooling is believed to create a good surface layer. That is, when the rollers 32 are at a lower temperature than the foamed resin sheet 23, the rollers 32 contact both the front and back surfaces of the foamed resin sheet 23, thereby creating a surface layer by cooling. By subjecting the foamed resin sheet 23 with such an improved surface condition to reduced pressure and suction, good expansion is likely to be achieved.

[0025] FIG. 2 shows a schematic diagram of the thickness T0 just before the roller 32 and the reduced thickness T1 just after the stretching by the roller 32. These thickness values ​​have a relationship of T0>T1. As an example, 2 In this case, the sheet may be stretched so that T0=2.0 mm becomes T1=1.6. 2In this case, the sheet may be stretched so that T0=2.5 ​​mm becomes T1=2.0. For example, the thickness T1 after roller stretching may be 1.5 to 2.0 mm, and the amount of squashing due to stretching (i.e., the difference between T0 and T1) may be 1 mm or less. The "thickness immediately after the roller / thickness immediately before the roller" may be expressed as the sheet thickness ratio T1 / T0. For example, the sheet may have a basis weight of 800 g / m 2 In this case, the sheet thickness ratio may be T1 / T0=1.6 / 2.0=0.8. 2 In this case, the sheet thickness ratio T1 / T0 may be set to 2.0 / 2.5=0.8. In the embodiment, the sheet thickness ratio T1 / T0 may be, for example, 0.8, 0.75 to 0.85, or 0.7 to 0.95. Specifically, the sheet thickness ratio T1 / T0 may be, for example, 0.7, 0.75, 0.8, 0.85, 0.9, or 0.95, or may be within a range between any two of the values ​​exemplified here. The amount of compression by roller stretching may be small or extremely small, and in this case, the sheet thickness ratio T1 / T0 may be set to 0.95 to 0.99. In this case, the amount of compression may be suppressed to emphasize cooling of the sheet surface by contact of the roller 32 with the foam resin sheet 32. "Roller stretching" in the embodiment includes the various aspects exemplified here.

[0026] The roller 32 may be cooled to a constant temperature using a roller cooling device (not shown). The temperature of the cooled roller 32 is lower than the temperature of the foam resin sheet 23 immediately before the roller 32. The temperature of the cooled roller 32 is, for example, 80°C. However, this is not limited thereto and may be 75 to 85°C or 70 to 90°C. The refrigerant used in the roller cooling device is not limited thereto. However, if the cooling device is water-cooled, for example, controlling the cooling of the roller 32 in a relatively high temperature range exceeding 100°C would be complicated, requiring the cooling water to be pressurized. Therefore, the roller 32 may be cooled to a constant cooling temperature range set below 100°C.

[0027] 2.2 Placement process In this process, as shown in FIGS. 1 and 2 , a single foamed resin sheet 23 formed by extruding molten foamed resin through a slit in a T-die 18 and letting it hang down is placed between molds 21 and 22. In this embodiment, direct vacuum molding is performed using the foamed resin sheet 23 extruded from the T-die 18 as is. Therefore, the foamed resin sheet 23 is not cooled to room temperature and solidified before molding, and the solidified foamed resin sheet 23 is not heated before molding. The foamed resin sheet 23 of this embodiment has a substantially uniform temperature throughout immediately after being extruded through the slit and is gradually cooled by the atmosphere from the surface while hanging down. Furthermore, the foamed resin sheet 23 of this embodiment is less susceptible to cooling by the atmosphere toward the center in the thickness direction. Therefore, the foamed resin sheet 23 of this embodiment has the property of increasing in temperature and decreasing in viscosity toward the center in the thickness direction. The thickness of the foamed resin sheet 23 is not particularly limited, but is, for example, 0.5 to 5 mm, preferably 1 to 3 mm. Specifically, the thickness is, for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 mm, and may be within a range between any two of the values ​​exemplified here.

[0028] 2.3 Expansion process In this process, as shown in Figures 3 to 5, the molds 21 and 22 are brought close together so that a gap G larger than the thickness of the foamed resin sheet 23 is formed between them, and the foamed resin sheet 23 is then decompressed and sucked by both the molds 21 and 22, thereby expanding the foamed resin sheet 23 to the thickness of the gap G.

[0029] In this embodiment, pinch-off portions 21d, 22d are provided on molds 21, 22, and when molds 21, 22 are brought close to each other until pinch-off portions 21d, 22d come into contact with each other, the space surrounded by pinch-off portions 21d, 22d becomes sealed space S (see FIG. 4). A portion 23a of foamed resin sheet 23 that is within sealed space S becomes foamed molded body 24 (see FIG. 5). On the other hand, a portion of foamed resin sheet 23 that is outside sealed space S becomes flash 23b.

[0030] The cavities 21b, 22b of the molds 21, 22 are configured so that the gap G between the molds 21, 22 is substantially constant over the entire portion of the foamed resin sheet 23 that will become the foamed molded body 24 (i.e., the portion within the sealed space S). When the foamed resin sheet 23 is suctioned under reduced pressure by the molds 21, 22 in this state, the foamed resin sheet 23 expands to the thickness of the gap G, forming the foamed molded body 24. Note that the pinch-off portions 21d, 22d are not essential components, and the molds 21, 22 may be brought close to each other without contacting each other so that the gap G is formed between them. However, when the molds 21, 22 are suctioned under reduced pressure with the pinch-off portions 21d, 22d abutting against each other to form the sealed space S, the pressure within the sealed space S is likely to decrease, which has the advantage of facilitating the expansion of the foamed resin sheet 23.

[0031] The thickness of the gap G is not particularly limited, but may be 1.1 to 3.0 times the thickness of the foamed resin sheet 23. Specifically, (thickness of the gap G) / (thickness of the foamed resin sheet 23) is, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0, and may be within a range between any two of the numerical values ​​exemplified here.

[0032] In the decompression and suction using the molds 21 and 22, the decompression and suction using the first mold 21 may be started first, or the decompression and suction using the second mold 22 may be started first, or the decompression and suction using the molds 21 and 22 may be started simultaneously. Also, the decompression and suction using the first mold 21 may be stopped first, or the decompression and suction using the second mold 22 may be stopped first, or the decompression and suction using the molds 21 and 22 may be stopped simultaneously. The decompression and suction using the molds 21 and 22 may be started before the molds 21 and 22 are brought close to each other, or may be started after they are brought close to each other.

[0033] When the foamed resin sheet 23 is vacuum-suctioned by both the molds 21 and 22, foaming of the foamed resin sheet 23 is promoted, causing the foamed resin sheet 23 to expand. Since the viscosity of the foamed resin sheet 23 is lowest (fluidity is highest) near the center in the thickness direction, foaming is particularly promoted near the center in the thickness direction, causing the foamed resin sheet 23 to expand. As a result, a foamed molded product 24 is obtained in which bubbles with an average large diameter are present in the layer near the center in the thickness direction (center layer), and bubbles with an average small diameter are present in the surface layers near the front and back surfaces. Such a foamed molded product 24 has a sandwich structure in which the center layer containing bubbles with an average large diameter is sandwiched between surface layers composed of bubbles with an average small diameter, and is therefore lightweight and highly rigid.

[0034] The expansion step is preferably performed by performing a first suction step, a mold approaching step, and a second suction step in this order. In the first suction step, as shown in Fig. 3, the foamed resin sheet 23 is suctioned under reduced pressure by the first mold 21, thereby forming the foamed resin sheet 23 into a shape that conforms to the cavity 21b of the first mold 21. In the mold approaching step, as shown in Fig. 4, the molds 21 and 22 are brought close to each other so that a gap G is formed between them. In the second suction step, as shown in Fig. 5, the foamed resin sheet 23 is suctioned under reduced pressure by the molds 21 and 22, thereby expanding the foamed resin sheet 23 to the thickness of the gap G.

[0035] If vacuum suction by the molds 21, 22 is started after the molds 21, 22 are brought close to each other, the foamed resin sheet 23 will come into contact with the protrusions 22c of the mold 22 before it is shaped. Normally, the temperatures of the molds 21, 22 are lower than the temperature of the foamed resin sheet 23. Therefore, when the foamed resin sheet 23 comes into contact with the protrusions 22c of the mold 22, the foamed resin sheet 23 is cooled and its viscosity increases, resulting in poor conformability to the cavities 21b, 22b of the molds 21, 22. On the other hand, if the expansion step is performed by performing the first suction step, the mold approach step, and the second suction step in this order, contact of the foamed resin sheet 23 with the molds 21, 22 before it is shaped into a shape that conforms to the cavity 21b of the first mold 21 is minimized, thereby suppressing an increase in the viscosity of the foamed resin sheet 23 and enabling the foamed resin sheet 23 to conform to the cavities of the molds 21, 22 with high precision.

[0036] 2.4 Finishing process After the expansion step, the molds 21 and 22 are opened, and the foam molded article 24 with the flash 23b is taken out as shown in FIG. 6, and the flash 23b is cut off to obtain the foam molded article 24 shown in FIG.

[0037] As described above, according to the manufacturing method of this embodiment, even if the foamed resin sheet 23 has a large wall thickness, the foamed resin sheet 23 can be made to conform to the mold cavity with high precision, and a lightweight, highly rigid foamed molded article 24 can be manufactured. Additionally, in this embodiment, the foamed resin sheet 23 is stretched by a pair of rollers 32 to facilitate expanding the foamed resin sheet 23 to a desired thickness in the expansion process. The stretching by the pair of rollers 32 improves the surface condition of the front and back sides of the foamed resin sheet 23, and the application of reduced pressure to the front and back sides of the foamed resin sheet 23 with improved surface condition is believed to result in favorable expansion. Because the foamed resin sheet 23 can be expanded to a desired thickness and expansion ratio in the expansion process, a lightweight, highly rigid foamed molded article 24 can be manufactured.

[0038] Furthermore, in the embodiment, the foamed resin 11a contains a fibrous filler, which improves the rigidity of the foamed molded body 24. Additionally, the manufacturing method of the embodiment also has the advantage of allowing for a larger amount of fibrous filler to be incorporated. As will be described in detail later in the Examples, the inventors of the present application conducted comparative experiments in which the foamed resin sheet 23 containing fibrous filler was held and laterally stretched using an expander to undergo an expansion process. The comparative experiments revealed that when an expander was used, increasing the amount of glass fiber incorporated made it impossible to mold at a certain point (Example Sample 8). This was because the sheet fell during drawdown. On the other hand, when stretching was performed using a pair of rollers 32, it was found that the expansion process could be performed successfully even with an increased amount of glass fiber incorporated (Example Samples 1 and 2). In other words, performing the expansion process after roller stretching, as in the embodiment, offers the advantage of allowing for a larger amount of fibrous filler to be incorporated.

[0039] Furthermore, in the embodiment, roller stretching has the advantage of ensuring the expansion ratio even when the amount of fibrous filler added is increased beyond a certain level. As will be explained in more detail in the Examples below, Sample 7 of the Example (using an expander) achieved an expansion ratio of only about 2 when the glass fiber content was 30% by mass. In contrast, Samples 1 and 2 of the Example achieved an expansion ratio of about 3 even when the glass fiber content was about 30%. In other words, performing the expansion step after performing roller stretching as in the embodiment has the advantage of achieving both an increase in the amount of fibrous filler added and ensuring the expansion ratio.

[0040] 3.Material composition etc. (resin material) 1 is not particularly limited, it is usually in the form of pellets. The raw material resin 11 is a thermoplastic resin such as polyolefin, and the polyolefin may be low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, an ethylene-propylene copolymer, or a mixture thereof.

[0041] (foaming agent) In FIG. 1, the blowing agent injected through the injector 16 can be a physical blowing agent, a chemical blowing agent, or a mixture thereof. Physical blowing agents include inorganic blowing agents such as air, carbon dioxide, nitrogen gas, and water, as well as organic blowing agents such as butane, pentane, hexane, dichloromethane, and dichloroethane, and even supercritical fluids of these. Supercritical fluids are preferably produced using carbon dioxide, nitrogen, or the like. Nitrogen can be obtained by adjusting the critical temperature to -149.1°C and the critical pressure to 3.4 MPa or higher, while carbon dioxide can be obtained by adjusting the critical temperature to 31°C and the critical pressure to 7.4 MPa or higher. Chemical blowing agents include those that generate carbon dioxide gas through a chemical reaction between an acid (e.g., citric acid or its salt) and a base (e.g., baking soda). Instead of injecting the chemical blowing agent through the injector 16, the chemical blowing agent can be introduced through the hopper 12.

[0042] (fibrous filler) In this embodiment, glass fiber, an example of a fibrous filler, is blended into raw resin 11. One of the purposes of blending the fibrous filler in this embodiment is to increase the rigidity of foam molded body 24. From this perspective, the fibrous filler can be an "insoluble fiber" of any material and any length. Insoluble fiber is a fiber that does not melt and disappear during the foam molding process, and is preferably an inorganic fiber, more preferably glass fiber or carbon fiber. For example, the fibrous filler may be glass wool, which is a short fiber, or carbon fiber, or any composite material fiber.

[0043] The fibrous filler may be added as is, or may be added in the form of a masterbatch containing the fibrous filler for ease of handling. The blending amount of the fibrous filler may be 30% by mass or more. In this case, the rigidity of the foamed molded article 24 is significantly improved. Specific examples of the blending amount of the fibrous filler include 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40% by mass. The blending amount of the fibrous filler may be any amount in 1% increments from 41% by mass or more, as long as the amount does not impair the degree of foaming or moldability. The blending amount of the fibrous filler may be within a range between any two of the values ​​exemplified here.

[0044] The average length of the fibrous filler in the foam molded article is, for example, 50 to 500 μm, and may be 70 to 120 μm. Specifically, it is, for example, 50, 70, 100, 120, 150, 200, 250, 300, 350, 400, 450, or 500 μm, and may be within a range between any two of the values ​​exemplified here. The average diameter of the fibrous filler in the foam molded article is, for example, 1 to 30 μm, and specifically, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 μm, and may be within a range between any two of the values ​​exemplified here. The average aspect ratio of the fibrous filler in the foamed molded article is, for example, 3 to 100, preferably 5 to 25, and specifically, for example, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100, and may be within a range between any two of the numerical values ​​exemplified here.

[0045] The average length, average diameter, and average aspect ratio of the fibrous filler in the foam molded product can be calculated by cutting out an image consisting of (thickness of the foam molded product) x (twice the thickness of the foam molded product) from the cross section of the foam molded product, selecting all fibers with lengths of 30 to 1000 μm that are visible in the image, measuring the length, diameter, and aspect ratio (length / diameter) of each fiber, and calculating and averaging the measured values.

[0046] The average length of the fibrous filler in pellet form is, for example, 1 to 10 mm, preferably 2 to 5 mm, and specifically, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm, and may be within a range between any two of the values ​​exemplified herein. The average diameter of the fibrous filler in pellet form is the same as the average diameter of the fibrous filler in the foamed molded article. The average aspect ratio of the fibrous filler in pellet form is, for example, 100 to 2000, and specifically, for example, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000, and may be within a range between any two of the values ​​exemplified herein. The average length, average diameter, and average aspect ratio of the fibrous filler in the pellet state can be calculated by randomly extracting 10 fibrous fillers observed on the surface of the pellet, measuring the length, diameter, and aspect ratio of each fiber, and calculating and averaging the measured values.

[0047] 4.Applications The foam molded article 24 is lightweight and highly rigid, and therefore can be used in a variety of applications where such physical properties are suitable. For example, the foam molded article 24 may be suitably used for relatively long and large parts such as floor undercovers for automobiles.

[0048] A skin material made of a breathable material such as a nonwoven fabric may be provided on one or both sides of foam molded article 24. The skin material can be integrally molded onto one or both sides of foam molded article 24 by placing the skin material between foam resin sheet 23 and mold 21 or between foam resin sheet 23 and mold 22 in the state shown in Fig. 2 and then performing reduced pressure suction on foam resin sheet 23 using molds 21 and 22 in the same manner as described above.

[0049] The foam molded article 24 may also be used for other applications, such as automotive interior components such as door trim and ceiling materials, boards such as luggage floor boards, ducts, engine undercovers, etc. When the foam molded article 24 is used as an automotive interior component, it is preferable to integrally mold a skin material onto one side of the foam molded article 24. For example, in conventional technology, ceiling materials are made by attaching a skin material to a polyurethane sheet with an adhesive or the like. However, according to the present invention, the skin material can be integrally molded onto the foam molded article 24, which eliminates the need for attaching the skin material, and also allows a display material to be fixed to the foam molded article 24 by an anchor effect (the effect in which the skin material is fixed to the resin as the resin seeps into the skin material) without using an adhesive.

[0050] 5. Variations Although a fibrous filler is blended in the embodiment, the present invention is not limited to this. As a variant, the raw material resin 11 may not contain a fibrous filler, or the blended amount of fibrous filler may be small. This is because even if no or only a small amount of fibrous filler is blended, the pair of rollers 32 can improve the surface condition of the foamed resin sheet 23, and the improvement in the surface condition contributes to the expansion step (see FIGS. 3 to 5). From this perspective, the blended amount of fibrous filler may be 0% by mass, or may be, for example, 1 to 10% by mass, or 2 to 5% by mass. [Example]

[0051] Using the foam molding machine 1 shown in Fig. 1, foam molded product samples Nos. 1 to 8 in Table 1 (hereinafter also referred to as Samples 1 to 8) were produced through the steps shown in Figs. 2 to 7. Samples 1 to 8 include Samples 1 and 2, which are working examples, and Samples 3 to 8, which are comparative examples. Samples 1 and 2 were subjected to roller stretching, and the roller 32 was set to a lower temperature than the foamed resin sheet 32 ​​during production. Table 1 shows the results of evaluating the elasticity gradient (bending elasticity gradient) of each sample. Fig. 8 shows the results of Sample 1 (basis weight 800 g / m 2 ) is a cross-sectional photograph. Figure 9 is an enlarged view of area A in Figure 8.

[0052] [Table 1]

[0053] The materials used are as follows: Polypropylene resin: Borealis AG, product name "Daploy WB140" Polypropylene resin: AW564 manufactured by Sumitomo Chemical Co., Ltd. Glass fiber: Asahi Fiber Glass Co., Ltd., GFPP-MG60 Chemical foaming agent: Product name Hydrocerol CF40E-J Highly concentrated carbon masterbatch: PEX999018

[0054] Samples 1, 2, 7, and 8 in Table 1 are "PP+GF (GF content 30%)," which means that 30% by mass of glass fiber (GF) is blended out of a total of 100% by mass of the entire molded body material, including resin and glass fiber. Specifically, Samples 1, 2, 7, and 8 are blended with each material in the ratio of "WB140 / GFPP-MG60 / CF40E-J / PEX999018=50 / 50 / 1 / 1." GFPP-MG60 contains approximately 60% by mass of glass fiber.

[0055] Samples 3 and 4 in Table 1 are "neat PP." Neat PP was made by blending the materials in the ratio of "WB140 / AW564 / CF40E-J / PEX999018=60 / 40 / 1 / 1." Neat PP does not contain glass fiber.

[0056] Samples 5 and 6 in Table 1 are "PP+GF (GF content 20%)," which means that 20% by mass of glass fiber (GF) is blended with a total of 100% by mass of the entire molded body material, including resin and glass fiber. Specifically, Samples 5 and 6 are blended with the following materials in a ratio of "WB140 / AW564 / GFPP-MG60 / CF40E-J / PEX999018=60 / 10 / 30 / 1 / 1." Note that 20% GF content means "approximately 20% by mass," which is actually about 18% by mass.

[0057] The evaluation of the elastic gradient was performed in accordance with JIS K 7171. The MD elastic gradient is the elastic gradient in the MD direction. The MD direction is the extrusion direction of the foamed resin sheet 23, and is also called the longitudinal direction. The TD elastic gradient is the elastic gradient in the TD direction. The TD direction is the horizontal direction intersecting with the MD direction.

[0058] Looking at Samples 1 and 2, which were roller-stretched as in the embodiment, Sample 1 had a wall thickness of 2.4 mm and an expansion ratio of 3.3, while Sample 2 had a wall thickness of 2.8 mm and an expansion ratio of 3.1. Thus, even with the fibrous filler blended, the foamed resin sheet 23 could be expanded to an expansion ratio of 3 or more. On the other hand, Samples 7 and 8 were transversely stretched with an expander, but Sample 7 did not achieve a high expansion ratio and did not have a sufficient wall thickness, and Sample 8 was unable to be molded because the foamed resin sheet 23 fell during drawdown.

[0059] Comparing Samples 3 and 4 (neat PP) with Samples 1, 2, 5, and 6 (containing glass fiber as a fibrous filler) in Table 1, the MD elasticity gradient was improved by adding fibrous fillers.

[0060] To improve rigidity, it is desirable to increase the amount of fibrous filler to a certain level (for example, 30% by mass or more). In this regard, using an expander did not work well for Samples 7 and 8, but it was not until Samples 1 and 2, which used stretching with roller 32, that samples with a 30% by mass amount were produced.

[0061] Sample 1 has a basis weight of 800 g / m 2 The foamed resin 11a was extruded from the slit of the T-die 18 so that the weight of the sample 2 was 1000 g / m 2 The foamed resin 11a was extruded from the slit of the T-die 18 so that the MD elasticity gradient was increased. Comparing Samples 1 and 2, a significant improvement in rigidity was observed in the MD elasticity gradient as the basis weight increased. The technical knowledge was obtained that by combining roller stretching, an expansion process, and fibrous filler blending, and extruding the foamed resin so that a certain basis weight or more is obtained, a foamed molded article with a significantly improved MD elasticity gradient can be obtained. From the viewpoint of increasing the basis weight compared to Sample 1, for example, a foamed molded article with a basis weight of 900 g / m 2 It is believed that by extruding the foamed resin 11a in the above manner, the MD elasticity gradient is significantly improved. [Explanation of symbols]

[0062] 1: Foam molding machine 2:Resin supply device 11: Raw resin 11a: Foam resin 12: Hopper 13: Extruder 13a: Cylinder 16: Injector 17: Accumulator 17a: Cylinder 17b: Piston 18: T-die 21: Mold (first mold) 21a: Decompression suction hole 21b: Cavity 21c: Recess 21d: Pinch-off section 22: Mold (second mold) 22a: Decompression suction hole 22b: Cavity 22c: Convex part 22d: Pinch-off section 23: Foam resin sheet 23a: Part 23b: Bali 24: Foam molding 25,27: Connecting pipe 32: Roller G: Gap S: Closed space

Claims

1. A method for producing a foamed molded article, comprising: a step of extruding a molten foamed resin obtained by melt-kneading a raw material resin, a foaming agent, and a fibrous filler through a slit to form a foamed resin sheet, sandwiching the foamed resin sheet between a pair of rollers having a temperature lower than that of the foamed resin sheet, stretching the foamed resin sheet, and causing it to hang down between first and second molds; an expansion step in which the first and second molds are brought close to each other so that a gap larger than the thickness of the foamed resin sheet is formed between them, and the foamed resin sheet is expanded to the thickness of the gap by suctioning the foamed resin sheet with both the first and second molds; Equipped with The foamed resin has a blending amount of the fibrous filler of 30% by mass or more and 40% by mass or less, The method wherein the raw resin is a polyolefin.

2. 10. The method of claim 1, The expansion is carried out so that the expansion ratio of the foamed molded article is 3 times or more and 3.3 times or less.

3. 3. The method of claim 1 or claim 2, The weight of the foamed molded body is 900 g / m ２ More than 2000g / m ２ The foamed resin is extruded through the slit so as to:

4. A method according to any one of claims 1 to 3, The method wherein the polyolefin is polypropylene.

5. A method according to any one of claims 1 to 4, The method wherein the blowing agent is a chemical blowing agent.

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