In-mold foam molded body and method for manufacturing in-mold foam molded body

Abstract

The present invention addresses the problem of suppressing poor fusion of a piston contact portion of a feeder due to an overfill phenomenon. This in-mold foam molded body, which is composed of thermoplastic resin foam particles, has a surface (30a) on which a circular piston trace (30P) having a diameter a is formed, and is characterized in that: the surface (30a) has, in an outer peripheral region (31) surrounded by the circumference of the piston trace (30P) and a concentric circle of the piston trace (30P) having a diameter 1.3a, a recess (32) recessed 1 mm or more deeper than the piston trace (30P); and the area of a formation region of the recess (32) accounts for 25% or more of the total area of the outer peripheral region (31).

Description

In-mold foam molded article and method for producing in-mold foam molded article

[0001] The present invention relates to an in-mold foam molded article and a method for producing an in-mold foam molded article.

[0002] As a technique for producing a thermoplastic resin foam molded article, a technique is known in which thermoplastic resin foam particles are filled into a mold via a feeder to produce an in-mold foam molded article of the thermoplastic resin foam particles. In such in-mold foam molding technology, the space near the raw material supply port of the feeder in the mold tends to be excessively filled with foam particles. As a result, a partial overfilling phenomenon occurs near the raw material supply port of the feeder, and even if heated steam is supplied through the ventilation holes, the diffusion of heated steam in the region where the overfilling phenomenon occurs becomes insufficient, which causes a problem that poor fusion bonding of the in-mold foam molded product is likely to occur.

[0003] As a technique for solving such a problem, for example, the technique disclosed in Patent Document 1 produces an in-mold foam molded article by using a mold in which a convex portion protruding toward the raw material supply port is provided in a molding space at a position facing the raw material supply port.

[0004] Japanese Unexamined Patent Application Publication No. 2020-062844

[0005] Although the above-mentioned conventional techniques are excellent, there is a demand for developing a new technique for solving poor fusion bonding of in-mold foam molded products caused by the above-mentioned overfilling phenomenon, particularly poor fusion bonding at a portion that comes into contact with the piston of the feeder.

[0006] Therefore, an object of one aspect of the present invention is to implement an in-mold foam molded article capable of suppressing poor fusion bonding at a piston contact portion of a feeder caused by an overfilling phenomenon, and a method for producing the in-mold foam molded article.

[0007] To solve the above problems, an in-molded foamed molded body according to one aspect of the present invention is an in-molded foamed molded body composed of thermoplastic resin foam particles, having a surface on which a circular piston mark of diameter a is formed, and on the surface, in the outer peripheral region surrounded by the circumference of the piston mark and the concentric circle of the piston mark with a diameter of 1.3a, there is a recess that is recessed by 1 mm or more from the piston mark, and the area of ​​the recessed region is 25% or more of the total area of ​​the outer peripheral region.

[0008] To solve the above problems, a method for manufacturing an in-mold foamed molded article according to one aspect of the present invention includes a filling step of filling a molding space with irregularly shaped thermoplastic resin foam particles using a feeder equipped with a piston and a plurality of air blowing holes that blow air toward a single point in the molding space of the mold, wherein the single point where the air converges is defined as the focal point, and the distance between the focal point and the raw material supply port of the mold is defined as the focal position, the angle of the air blowing holes is adjusted in the filling step such that the focal position is greater than 0 mm and less than or equal to 30 mm.

[0009] According to one aspect of the present invention, in a molded foamed body, poor fusion of the piston contact portion of the feeder due to overfilling can be suppressed.

[0010] This figure schematically shows the general configuration of a feeder used in a method for manufacturing an in-molded foamed molded article according to an embodiment of the present invention, where 101 is a front view and 102 is a cross-sectional view. This is a schematic top view showing the general configuration of the surface of an in-molded foamed molded article according to an embodiment of the present invention. These are a schematic top view and a cross-sectional view showing the general configuration of feeder marks formed on the surface of an in-molded foamed molded article according to an embodiment of the present invention.

[0011] One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic and patent documents mentioned herein are incorporated herein by reference. Furthermore, each drawing is shown for clarity when referred to in conjunction with the following description, and is not necessarily drawn to a fixed scale.

[0012] [Technical Concept] In the technology described in Patent Document 1, in-mold foam molding was performed using a mold in which a protrusion was provided on the part facing the raw material supply port to which the feeder is connected, with the protrusion projecting toward the said raw material supply port. According to the technology of Patent Document 1, in the molding space, the protrusion prevents the filling density of foam particles in the space near the raw material supply port from becoming excessively high, thus preventing the phenomenon of overfilling.

[0013] In this case, the in-molded foamed molded body of Patent Document 1 has a structure in which a recess originating from the convex portion is formed on the back surface of the feeder trace, which is the contact area of ​​the feeder. Therefore, depending on the shape of the in-molded foamed molded body, it may not be possible to form a recess on the back surface of the feeder trace, and in this respect, there is room for improvement in the technology of Patent Document 1.

[0014] The inventors diligently studied measures to suppress poor fusion of the piston contact portion of the feeder due to overfilling, regardless of the shape of the in-molded foamed molded body. The inventors hypothesized that by lowering the packing density in the area surrounding the piston contact portion of the foamed particle packing in the mold during the in-molded foaming process, heating vapor diffusion would be promoted at the piston contact portion where overfilling occurs, thereby improving poor fusion of the foamed particles. The inventors then focused on the fact that the surface shape of the area surrounding the piston trace, which corresponds to the piston contact portion, differs from the surface shape of other areas on the surface of the in-molded foamed molded body. The inventors found that a recess is formed in the area surrounding the piston trace on the surface of the in-molded foamed molded body after in-molded foaming, and that if the ratio of the area of ​​the recess to the total area of ​​the area surrounding the piston trace is within a specific range, poor fusion of the piston contact portion of the feeder due to overfilling can be suppressed, leading to an in-molded foamed molded body according to one embodiment of the present invention.

[0015] In other words, an in-molded foamed molded body according to one embodiment of the present invention (hereinafter sometimes referred to as "this in-molded foamed molded body") is an in-molded foamed molded body composed of thermoplastic resin foam particles, having a surface on which a circular piston mark of diameter a is formed, and on the surface, in the outer peripheral region surrounded by the circumference of the piston mark and the concentric circle of the piston mark with a diameter of 1.3a, there is a recess that is recessed by 1 mm or more from the piston mark, and the area of ​​the recessed region is 25% or more of the total area of ​​the outer peripheral region.

[0016] Furthermore, the inventors diligently studied a manufacturing method suitable for producing this in-mold foamed molded article. In the in-mold foaming process, regions with a low packing density of foam particles are considered to be recessed compared to other regions. Therefore, it is thought that the recesses in the surrounding regions are formed when the packing density of the foam particle filling in the mold becomes low in the region surrounding the piston contact portion during the in-mold foaming process, resulting in accelerated diffusion of heated steam and subsequent fusion. Accordingly, the inventors diligently studied measures to worsen the fluidity around the feeder discharge port, particularly in in-mold foaming methods using irregularly shaped foam particles. The inventors then focused on the points (focal points) where air from multiple air outlets of the feeder converges during the foam particle filling process. They found that if the distance between the air convergence point and the raw material supply port is set within a specific range, the above-mentioned recesses in the in-mold foamed molded article can be formed, leading to a method for manufacturing an in-mold foamed molded article according to one embodiment of the present invention.

[0017] In other words, a method for manufacturing an in-mold foamed molded article according to one embodiment of the present invention (hereinafter sometimes referred to as "this manufacturing method") includes a filling step of filling a molding space with irregularly shaped thermoplastic resin foam particles using a feeder equipped with a piston and a plurality of air blowing holes that blow air toward a single point in the molding space of the mold, wherein the single point where the air converges is defined as the focal point, and the distance between the focal point and the raw material supply port of the mold is defined as the focal position, the angle of the air blowing holes is adjusted in the filling step such that the focal position is greater than 0 mm and less than or equal to 30 mm.

[0018] The following provides a detailed explanation of this manufacturing method and the molded foamed product.

[0019] [Method for Manufacturing In-Mold Foamed Molded Articles] Figure 1 schematically shows the general configuration of the feeder 10 used in this manufacturing method, where 101 in Figure 1 is a front view and 102 in Figure 1 is a cross-sectional view. As shown in Figure 1, the feeder 10 is cylindrical in shape. In Figure 1, the longitudinal direction of the feeder 10 is the LD direction, and in the LD direction, one side (front side, mold 20 side) is the LDa side, and the side opposite the LDa side is the LDb side (rear side).

[0020] As shown in Figures 101 and 102, the feeder 10 comprises an outer cylinder 11, an inner cylinder 12, a ring member 13, a tip component 14, and a piston 15. In the feeder 10, the outer cylinder 11, the ring member 13, and the tip component 14 are connected in this order from the LDb side to the LDa side. In this manufacturing method, the feeder body refers to a feeder with the ring member 13 removed.

[0021] The outer cylinder 11 and the inner cylinder 12 are formed in a cylindrical shape. The inner cylinder 12 is inserted inside the outer cylinder 11. The inner cylinder 12 constitutes a flow path through which thermoplastic resin foam particles pass. A gap is formed between the outer surface of the inner cylinder 12 and the inner surface of the outer cylinder 11, and this gap becomes an air passage B through which air flows for filling the thermoplastic resin foam particles.

[0022] The ring member 13 is connected to the LDa-side ends of the outer cylinder 11 and the inner cylinder 12. The ring member 13 is provided with a plurality of air outlets 13a. These air outlets 13a are in communication with the air passage B. The plurality of air outlets 13a are formed so that their extension direction is inclined with respect to the central axis X. More specifically, the plurality of air outlets 13a are formed so that the central axis of the plurality of air outlets 13a is directed toward the focal point O in the molding space A. Therefore, the air that has passed through the air passage B is forcefully blown out from the air outlets 13a toward the focal point O in the molding space A, as shown by the dotted line C in Figure 102.

[0023] The tip component 14 is a cylindrical component having an outlet 14a at its LDa-side end. The foamed particles pass through the inner cylinder 12 and the ring member 13 and are supplied from the outlet 14a into the molding space A of the mold 20. The tip component 14 is a component that comes into contact with the in-mold foamed molded body that will become the final product. Therefore, the front end surface of the tip component 14 on the LDa side is shaped to match the shape of the mold 20 or the in-mold foamed molded body.

[0024] The piston 15 is rod-shaped and extends in the LD direction, and is capable of reciprocating back and forth within the feeder 10. The LDa-side end of the piston 15 is the part that opens and closes the discharge port 14a of the tip component 14, and is shaped to fit into the discharge port 14a. In the piston 15, the LDa-side end is the part that comes into contact with the in-mold foamed molded body that will become the product.

[0025] Furthermore, as shown in Figure 1, if the diameter of the piston 15 is a, then the diameter of the feeder 10 is 1.3 times a, i.e., 1.3a. The diameter of the piston 15 is approximately the same as the diameter of the discharge port 14a of the tip component 14. Also, the diameter of the feeder 10 is the same as the outer diameter of the tip component 14. The diameter a of the piston 15 is preferably 8 mm or more and 50 mm or less.

[0026] Here, the feeder 10 is configured to have multiple air outlets 13a located on the central axis X of the piston 15, which blow air toward a single point (focal point O) within the molding space A of the mold 20. When air is supplied toward the focal point O within the molding space A of the mold 20 in this way, the air pressure in the space E within the tip part 14 decreases, resulting in an air shortage. To compensate for this air shortage in the space E within the tip part 14, an airflow is generated inside the feeder 10 from the LDb side toward the LDa side. Along this airflow, the thermoplastic resin foam particles, which are the raw material, are guided into the molding space A. The central axis X can also be said to be the central axis of the feeder 10. The air pressure blown from the air outlets 13a is preferably 0.1 MPa or more and 0.6 MPa or less.

[0027] This manufacturing method includes a filling step in which irregularly shaped thermoplastic resin foam particles are filled into a molding space using the feeder 10 described above. More specifically, first, the feeder 10 is attached to the raw material supply port 22 of the mold 20 so that the end face of the feeder 10 on the LDa side and the molding surface 21 of the mold 20 are flush. Next, prior to filling with thermoplastic resin foam particles, the piston 15 is retracted to the LDb side by a drive mechanism (not shown). Then, air for filling with thermoplastic resin foam particles is supplied to the air passage B, thereby supplying and filling the thermoplastic resin foam particles into the molding space A in the manner described above. Once the molding space A is filled with thermoplastic resin foam particles, the piston 15 is moved to the LDa side, closing the discharge port 14a of the tip component 14 with the piston 15, and stopping the supply of thermoplastic resin foam particles to the molding space A.

[0028] This manufacturing method includes, after the filling step described above, a heating step of heating the thermoplastic resin foam particles filled in the molding space A, and a cooling step of cooling the in-mold foam molded body formed in the molding space A.

[0029] In the heating step described above, steam is supplied to the molding space A of the mold 20. This supply of steam causes the thermoplastic resin foam particles filling the molding space A to heat and fuse together, forming the in-mold foamed molded body. In the cooling step described above, cooling water is supplied to the molding space A of the mold 20. This supply of cooling water cools the in-mold foamed molded body within the molding space A.

[0030] This manufacturing method is characterized by the setting of the focal point O in the filling process. Here, in the state in which the feeder 10 is attached to the raw material supply port 22 of the mold 20, that is, the state shown in Figure 1, the angle formed by the straight line connecting the center of the end face on the LDa side of the feeder 10 and the focal point O, and the straight line connecting the focal point O and the air blow hole 13a is called the ring angle θ. The ring angle θ can also be said to be the inclination angle of the air blow hole 13a with respect to the central axis X. The distance between the focal point O and the raw material supply port 22 is called the focal position D. In the state shown in Figure 1, the focal position D can be said to be the distance between the focal point O and the end face on the LDa side of the feeder 10 (the end face on the LDa side of the piston 15).

[0031] Here, using the raw material supply port 22 (i.e., the end face on the LDa side of the feeder 10) as a reference, the focal position D is defined as a positive (+) value when the focal point O is on the LDa side, and as a negative (-) value when the focal point O is on the LDb side. In this manufacturing method, air is discharged toward the focal point O in the molding space A of the mold 20, so the focal position D is a positive value.

[0032] In the filling process of this manufacturing method, the angle of the air outlet 13a, i.e., the ring angle θ, is adjusted so that the focal position D is greater than 0 mm and less than or equal to 30 mm. In the filling process, irregularly shaped thermoplastic foam particles have poor fluidity and tend to remain on the tip component 14 due to convection. Also, in the filling process, the further the focal position D is from the raw material supply port 22, the greater the force with which the thermoplastic foam particles are discharged from the discharge port 14a tends to be. Furthermore, in the filling process, the focal position D is usually adjusted to be greater than 30 mm.

[0033] In the filling process of this manufacturing method, the focal position D is adjusted to be smaller than usual. By adjusting the focal position D to the above numerical range, according to this manufacturing method, the fluidity of the irregularly shaped thermoplastic resin foam particles in the filling process is adjusted so that no particles remain at the tip part 14, and the filling density is reduced only in the area surrounding the discharge port 14a. In other words, according to this manufacturing method, in the foam particle filling in the mold, the foam particles at the piston contact portion of the feeder are overfilled, while the foam particles around the piston contact portion have a lower filling density and are more sparse than those at the piston contact portion. The area of ​​the discharge port 14a corresponds to the piston contact portion area in the foam particle filling in the mold. The area surrounding the piston contact portion is the area in the foam particle filling in the mold that comes into contact with the tip part 14. In other words, the area surrounding the piston contact portion corresponds to the area surrounding the discharge port 14a, and is the area of ​​the raw material supply port 22 excluding the discharge port 14a. In a foamed particle-filled material, if the diameter of the piston contact area is a, then the diameter of the area surrounding the piston contact area is 1.3a.

[0034] Here, if the foam particles at the piston contact area of ​​the feeder are overfilled, and the foam particle density around the piston contact area is also high and not sparse, steam entering the molding space A from the core vent (not shown) of the mold 20 will pass through the gaps between the mold 20 and the foam particles, and the gaps between the foam particles themselves, and mainly penetrate into the overfilled area from the discharge port 14a (piston contact area) side. On the other hand, according to this manufacturing method, the foam particles around the piston contact area are sparse, so steam entering the molding space A from the core vent (not shown) of the mold 20 can easily flow into the area around the piston contact area. Therefore, according to this manufacturing method, steam penetrates into the overfilled area from the side around the piston contact area as well as from the discharge port 14a (piston contact area) side. As a result, according to this manufacturing method, steam can easily penetrate into the overfilled area, and the fusion properties of the overfilled area are improved. Thus, according to this manufacturing method, it is possible to suppress poor fusion of the piston contact area of ​​the feeder due to the overfilling phenomenon in the in-mold foamed molded body.

[0035] The focal position D is not particularly limited as long as it is within the above numerical range, but from the viewpoint of fusion properties of the piston contact portion, it is preferably 0 mm to 25 mm. The ring angle θ can be set arbitrarily as long as the focal position D can be adjusted within the above numerical range. From the viewpoint of fusion properties of the piston contact portion, the ring angle θ is preferably 14° to 24°, and more preferably 15° to 22°.

[0036] In this manufacturing method, the filling step includes attaching a ring member 13 to the feeder body and discharging air toward the focal point O in the molding space A of the mold 20. Therefore, unlike the technology described in Patent Document 1, there is no need to provide a protrusion on the molding surface of the mold structure, and the overfilling phenomenon can be prevented simply by changing the specifications of the ring member 13 of the feeder 10. Thus, since the overfilling phenomenon can be prevented without constraints on the mold structure or the shape of the foamed molded product inside the mold, this manufacturing method is highly versatile.

[0037] Furthermore, the feeder 10 used in this manufacturing method may be configured as long as it is located on the central axis X of the piston 15 and has multiple air outlets 13a that blow air toward the focal point O in the molding space A of the mold 20, and is not limited to a configuration that includes a ring member 13.

[0038] [Thermoplastic resin foam particles used in the method for manufacturing in-mold foamed articles] <Base resin> The base resin that constitutes the irregularly shaped thermoplastic resin foam particles used in this manufacturing method is not particularly limited, and examples include polyolefin resins, polystyrene resins, styrene-modified polyolefin resins (olefin-modified polystyrene resins), polyester resins, etc. Among these, polyolefin resins are preferred because they offer good crack resistance, cushioning properties, chemical resistance, heat resistance, compression recovery rate, and ease of recycling.

[0039] The polyolefin resin is not particularly limited and includes polypropylene resins, polyethylene resins, etc. Examples of polypropylene resins include propylene homopolymers, ethylene / propylene copolymers, and ethylene / propylene / 1-butene copolymers. Examples of polyethylene resins include ethylene homopolymers, high-density polyethylene resins, medium-density polyethylene resins, low-density polyethylene resins, and linear low-density polyethylene resins, and more specifically, ethylene / 1-butene copolymers and ethylene / 4-methyl-1-pentene copolymers. Furthermore, the copolymer may be a random copolymer or a block copolymer.

[0040] There are no particular limitations on the method for producing thermoplastic resin expanded particles, and conventionally known production methods can be mentioned. By way of example, when the expanded particles to be produced are polyolefin resin expanded particles, production methods disclosed in International Patent Publication WO2009 / 075208, Japanese Patent Application Laid-Open No. 2006-117842, and the like can be mentioned. Further, when the expanded particles to be produced are polystyrene-based resin expanded particles, production methods disclosed in Japanese Patent Application Laid-Open No. 2003-201360, Japanese Patent Application Laid-Open No. 2014-118474, International Patent Publication WO2015 / 137363, and the like can be mentioned (the particles are described as "pre-expanded particles" in said patent documents). Further, when the expanded particles to be produced are styrene-modified polyolefin-based resin expanded particles, production methods disclosed in Japanese Patent Application Laid-Open No. 2008-239794, International Patent Publication WO2016 / 152243, and the like can be mentioned. However, the method for producing expanded particles is not limited to these production methods.

[0041] The expanded particles obtained in this manner can appropriately contain or be coated with additives such as flame retardants, antistatic agents, and colorants by conventionally known methods. There is no particular limitation on the particle diameter of the expanded particles, and for example, the particle diameter may be 1 mm or more and 10 mm or less. From the viewpoint of fillability into the molding space of a mold, the particle diameter is preferably 1 mm or more and 5 mm or less, and more preferably 1 mm or more and 3 mm or less.

[0042] There is no particular limitation on the expansion ratio of the expanded particles, and for example, the expansion ratio may be 3 times or more and 90 times or less. From the viewpoint of mechanical strength and moldability, the expansion ratio is preferably 5 times or more and 60 times or less, and more preferably 5 times or more and 45 times or less.

[0043] Such expanded particles are commercially available, for example, as Eperan-PP and Eperan-XL manufactured by Kaneka Corporation, and are readily available.

[0044] <Physical Properties of Thermoplastic Resin Expanded Particles> (Bulk Density of Thermoplastic Resin Expanded Particles) The bulk density of the thermoplastic resin expanded particles is preferably 10.0 g / L or more and 300.0 g / L or less, more preferably 12.0 g / L or more and 100.0 g / L or less, still more preferably 14.0 g / L or more and 60.0 g / L or less, even more preferably 15.0 g / L or more and 50.0 g / L or less, and particularly preferably 16.0 g / L or more and 40.0 g / L or less. This configuration has the advantage that thermoplastic resin expanded particles with little variation in expansion ratio and good moldability can be obtained. The method for measuring the bulk density of the thermoplastic resin expanded particles will be described in detail in the Examples described later.

[0045] (Irregularity Degree of Thermoplastic Resin Expanded Particles) The thermoplastic resin expanded particles preferably have an irregularity degree represented by the following formula of 2.20 or more: Irregularity degree = True density of thermoplastic resin expanded particles / Bulk density of thermoplastic resin expanded particles.

[0046] In the present specification, the irregularity degree is an index indicating the bulkiness of the thermoplastic resin expanded particles. The irregularity degree of the thermoplastic resin expanded particles is preferably 2.20 or more, more preferably 2.40 or more, and still more preferably 2.50 or more. This configuration has the advantage that a foamed molded article of thermoplastic resin excellent in sound absorption performance and having a small amount of deformation can be obtained.

[0047] Further, the upper limit of the irregularity degree of the thermoplastic resin expanded particles is not particularly limited, but is preferably 3.00 or less, more preferably 2.90 or less, still more preferably 2.80 or less, and particularly preferably 2.70 or less. This configuration has the advantage that a foamed molded article having high mechanical properties can be obtained. Details of the method for measuring the irregularity degree of the thermoplastic resin expanded particles will be described in detail in the Examples described later.

[0048] The shape of the thermoplastic resin foam particles that satisfies the preferred numerical range of the degree of irregularity mentioned above is a shape other than the shapes (spherical and cylindrical) generally used when manufacturing foam particles. Shapes other than spherical and cylindrical are sometimes referred to as "irregular shapes." In other words, it is preferable that the thermoplastic resin foam particles are irregularly shaped particles. The shape of the thermoplastic resin foam particles is preferably one selected from the group consisting of star shape, anchor cross shape, macaroni shape, cross shape, L shape, Y shape, T shape, U shape, and polygon, more preferably one selected from the group consisting of star shape, anchor cross shape, and macaroni shape, even more preferably star shape or anchor cross shape, and even more preferably star shape. This configuration has the advantage of being able to obtain a thermoplastic resin foam molded article that has excellent sound absorption performance and a small amount of deformation.

[0049] The shape of the thermoplastic resin foam particles will be the same as or approximately the same as the shape of the thermoplastic resin particles used as raw materials. If the thermoplastic resin particles are irregularly shaped, the thermoplastic resin foam particles obtained by foaming the thermoplastic resin particles will also be irregularly shaped foam particles.

[0050] Furthermore, in one embodiment of the present invention, the polyolefin-based thermoplastic resin foam particles may or may not form hollow holes.

[0051] [In-Mold Foamed Molded Body] This in-molded foamed molded body can be molded by in-molding foam molding using the present manufacturing method, for example, and is composed of thermoplastic resin foam particles. Hereinafter, this in-molded foamed molded body will be described with reference to Figures 2 and 3, and Figure 1 which shows the present manufacturing method. Figure 2 is a schematic top view showing the general structure of the surface 30a of the in-molded foamed molded body 30 according to this embodiment. Figure 3 is a schematic top view and cross-sectional view showing the general structure of the feeder trace 30F.

[0052] As shown in Figure 2, circular feeder traces 30F are formed on the surface 30a of the in-molded foamed body 30. When thermoplastic resin foam particles filled into the mold 20 shown in Figure 1 are in-molded, the area on the surface 30a of the obtained in-molded foamed body 30 that comes into contact with the feeder 10 has a different shape from the other areas, and feeder traces 30F are formed.

[0053] As shown in the top views of Figures 2 and 3, the feeder trace 30F has a circular piston trace 30P and an outer peripheral region 31 of the piston trace 30P. The piston trace 30P corresponds to the contact area with the piston 15, and the outer peripheral region 31 corresponds to the contact area with the part of the feeder 10 other than the piston 15, i.e., the tip component 14. The outer peripheral region 31 is shown as being divided into six sections in the drawings, but these are traces of steam holes during the heating process, and the entire area is considered the outer peripheral region 31 (i.e., the entire ring area divided into six sections in the drawings is considered the outer peripheral region 31). The same applies to Figures 1 and 3.

[0054] As mentioned above, if the diameter of the piston 15 is a, then the diameter of the feeder 10 is 1.3 times a, or 1.3a. Corresponding to this relationship between the diameter of the piston 15 and the diameter of the feeder 10, if the diameter of the piston trace 30P is a, then the diameter of the feeder trace 30F is 1.3 times a, or 1.3a. Therefore, the outer peripheral region 31 can be said to be the outer peripheral region enclosed by the circumference of the piston trace 30P and the concentric circles of the piston trace 30P with a diameter of 1.3a.

[0055] Furthermore, the diameter of the piston mark 30P corresponds to the diameter of the piston 15 described above. That is, the diameter of the piston mark 30P is preferably 8 mm or more and 50 mm or less, similar to the diameter a of the piston 15 described above.

[0056] The in-molded foamed body 30 according to this embodiment is characterized by the shape of its outer peripheral region 31. Specifically, as shown in the cross-sectional view of Figure 3, the in-molded foamed body 30 has a recess 32 on its surface 30a in the outer peripheral region 31 that is recessed by 1 mm or more than the piston trace 30P.

[0057] As shown in Figure 3, in addition to the recess 32, a recess 32' is also formed in the outer peripheral region 31, which is recessed by less than 1 mm from the piston trace 30P. As described above, in this manufacturing method, the fluidity of the irregularly shaped thermoplastic foam particles during the filling process is adjusted so that they do not remain in the tip part 14 and the filling density around the discharge port 14a is low. Therefore, in the mold 20 filled with thermoplastic foam particles, the filling density around the discharge port 14a is lower than the filling density of other spaces, so that the diffusion of heated steam is promoted around the discharge port 14a and the thermoplastic foam particles fuse together. It is thought that the recess 32 formed in the outer peripheral region 31 was formed recessed from the piston trace 30P due to the fusion of thermoplastic foam particles caused by this promotion of heated steam diffusion.

[0058] In the top view of Figure 3, the formation region of the recess 32 shown in the cross-sectional view is typically indicated as a shaded area. The shape and location of the formation region of the recess 32 in the outer peripheral region 31 are not limited to the shaded area in the top view of Figure 3. As described above, the recess 32 is formed randomly in the outer peripheral region 31 because it is caused by the fusion of thermoplastic resin foam particles due to the promotion of heated steam diffusion. Furthermore, the recess 32 is an unprocessed area that has not undergone any processing treatment. Note that "processing treatment" refers to processing treatment of the in-molded foamed body in general, such as excavation and molding (stamping).

[0059] In the in-molded foamed body 30 according to this embodiment, the area of ​​the recessed region 32 is 25% or more of the total area of ​​the outer peripheral region 31. By having a ratio of 25% or more of the area of ​​the recessed region 32 to the total area of ​​the outer peripheral region 31, it is possible to realize an in-molded foamed body that can suppress fusion defects at the contact portion of the piston 15 of the feeder 10 due to overfilling.

[0060] The depth of the recess 32 relative to the piston mark 30P is not particularly limited as long as it is 1 mm or more, but is preferably 1.2 mm or more, and more preferably 1.5 mm or more. Furthermore, the upper limit of the depth of the recess 32 relative to the piston mark 30P is not particularly limited, but from the viewpoint of the aesthetic appearance of the product, it is preferably 10 mm or less, and more preferably 5 mm or less.

[0061] The ratio of the area of ​​the recess 32 to the total area of ​​the outer peripheral region 31 is not particularly limited as long as it is 25% or more, but is preferably 40% or more, and more preferably 60% or more. Furthermore, the higher the ratio of the area of ​​the recess 32 to the total area of ​​the outer peripheral region 31, the better, but is preferably 90% or less, and more preferably 100% or less. Details of the method for measuring the ratio of the area of ​​the recess 32 to the total area of ​​the outer peripheral region 31 will be explained in detail in the embodiments described later.

[0062] [Thermoplastic resin foam particles constituting the in-mold foamed molded body] The thermoplastic resin foam particles constituting this in-mold foamed molded body may be non-irregularly shaped thermoplastic resin foam particles. Even if the thermoplastic resin foam particles are not irregularly shaped, if the fluidity of the thermoplastic resin foam particles can be adjusted in the filling process by adjusting the focal position D so that they do not remain at the tip component 14 and the filling density around the discharge port 14a is reduced, this in-mold foamed molded body can be manufactured.

[0063] For ease of manufacturing the in-mold foamed molded product, the thermoplastic resin foam particles constituting the in-mold foamed molded product are preferably the thermoplastic resin foam particles described in the section "[Thermoplastic resin foam particles used in the manufacturing method of the in-mold foamed molded product]". In particular, the thermoplastic resin foam particles are preferably foam particles with a deformation degree of 2.2 or higher. Furthermore, the base resin of the thermoplastic resin foam particles is preferably a polyolefin resin.

[0064] One possible embodiment is as follows:

[0065] [1] An in-molded foamed molded body composed of thermoplastic resin foam particles, having a surface on which a circular piston mark of diameter a is formed, wherein the outer peripheral region of the surface enclosed by the circumference of the piston mark and a concentric circle of the piston mark with a diameter of 1.3a has a recess that is recessed by 1 mm or more from the piston mark, and the area of ​​the recessed region is 25% or more of the total area of ​​the outer peripheral region.

[0066] [2] The in-mold foamed molded body of [1], wherein the thermoplastic resin foamed particles are foamed particles with a degree of irregularity of 2.2 or more.

[0067] [3] The in-mold foamed molded body of [1] or [2], wherein the base resin of the thermoplastic foamed particles is a polyolefin resin.

[0068] [4] The recesses are randomly formed in the outer peripheral region of any of the in-molded foamed bodies from [1] to [3].

[0069] [5] The recess is an unprocessed part of any of the in-molded foamed molded bodies from [1] to [4], wherein the recess is an unprocessed part that has not undergone any processing treatment.

[0070] [6] A molded foamed body from any of [1] to [5], wherein the diameter a of the piston trace is 8 mm or more and 50 mm or less.

[0071] [7] A method for manufacturing an in-mold foamed molded body, comprising a filling step of filling a molding space with irregularly shaped thermoplastic resin foam particles using a feeder equipped with a piston and having a plurality of air blowing holes that blow air toward a single point in the molding space of the mold, wherein the single point where the air converges is defined as the focal point, and the distance between the focal point and the raw material supply port of the mold is defined as the focal position, the angle of the air blowing holes is adjusted in the filling step such that the focal position is greater than 0 mm and less than or equal to 30 mm.

[0072] [8] The method for manufacturing an in-mold foamed molded body according to [7], wherein the feeder comprises a feeder body and a ring member provided with a plurality of air blowing holes, and the filling step includes the step of attaching the ring member to the feeder body and discharging air toward the single point in the molding space of the mold.

[0073] [9] A method for manufacturing an in-mold foamed molded article according to [7] or [8], wherein the angle of the air blow hole is 14° or more and 24° or less.

[0074]

[10] A method for manufacturing an in-mold foamed molded article according to any of [7] to [9], wherein the air pressure discharged from the air outlet is 0.1 MPa or more and 0.6 MPa or less.

[0075]

[11] A method for manufacturing an in-mold foamed molded body according to any of [7] to

[10] , wherein the diameter of the piston is 8 mm or more and 50 mm or less.

[0076]

[12] A method for manufacturing an in-mold foamed molded article according to any of [7] to

[11] , wherein the thermoplastic resin foamed particles are foamed particles with a degree of irregularity of 2.2 or more.

[0077]

[13] A method for manufacturing an in-mold foamed molded article according to any of [7] to

[12] , wherein the base resin of the thermoplastic foamed particles is a polyolefin resin.

[0078] The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited by these examples.

[0079] [Materials] The materials used in the examples and comparative examples are shown below.

[0080] (Polyolefin resins) ・Polyolefin resin A: 1-butene / ethylene / propylene random copolymer (melting point 149°C, 1-butene content 3.8% by weight, ethylene content 0.5% by weight, and MI = 10.1 g / 10 min) ・Polyolefin resin B: Linear low-density polyethylene (melting point 122°C, MI = 2.0 g / 10 min, density 0.926 g / cm³) ３ ) (Additives) - Additive A: Purified glycerin D (manufactured by Lion Corporation) - Additive B: Tarcan powder (registered trademark) PK-S (manufactured by Hayashi Chemical Co., Ltd.) [Measurement Method] The measurement and evaluation methods for various items carried out in the examples and comparative examples are described below.

[0081] (Melting point of polypropylene resin) The melting point of polyolefin resin A or B was determined by the DSC method using a differential scanning calorimeter (DSC6200 model, manufactured by Seiko Instruments Inc.). The specific operating procedure was as follows (1) to (4): (1) The temperature of polyolefin resin A or B (weight: 5 mg to 6 mg) was increased from 40.0°C to 220.0°C at a heating rate of 10.0°C / min to melt the polyolefin resin A or B; (2) The temperature of the melted polyolefin resin A or B was then decreased from 220.0°C to 40.0°C at a cooling rate of 10.0°C / min to crystallize the polyolefin resin A or B; (3) The temperature of the peak (melting peak) of the DSC curve of the polyolefin resin A or B obtained during the second heating (i.e., at (3)) was taken as the melting point of the polyolefin resin A or B. Furthermore, if multiple peaks (melting peaks) exist in the DSC curve of polyolefin resin A or B obtained during the second heating step using the method described above, the temperature of the peak with the largest heat of fusion (melting peak) was defined as the melting point of polyolefin resin A or B.

[0082] (MI of polypropylene resin) The MI of polypropylene resin was determined using the MI measuring instrument described in JIS K7210:1999, under the following conditions: orifice diameter of 2.0959 ± 0.005 mmφ, orifice length of 8.000 ± 0.025 mm, load of 2.16 kgf, and temperature of 230°C (230 ± 0.2°C).

[0083] <Degree of Irregularity of Foamed Particles> The degree of irregularity of polyolefin resin foamed particles was calculated by dividing the "true density," measured by the method shown below, by the "bulk density," measured by the method shown below. Specifically, it was measured using the following formula: Degree of Irregularity = True density of foamed particles (g / L) / Bulk density of foamed particles (g / L).

[0084] (True density of foamed particles) The weight M1 (g) of polyolefin resin foamed particles was accurately weighed to the nearest 0.001g (rounded to the fourth decimal place). When the weighed polyolefin resin foamed particles were immersed in a graduated cylinder containing 100 mL of water at 23°C, the volume V1 (cm³) of the polyolefin resin foamed particles was determined from the rise in the scale. ３ The following formula was used to calculate the true density of the foamed particles: True density of foamed particles (g / L) = Weight of foamed particles M1 (g) / Volume of foamed particles V1 (cm³) ３ ) / 1000}.

[0085] (Bulk density of foamed particles) The method for measuring the bulk density of foamed particles was as follows (1) to (3): (1) Foamed particles were placed in a container of volume V2 (L) until the foamed particles overflowed from the container; (2) The powder surface (upper end) of the container was scraped, and the weight M2 (g) of the foamed particles in the container was measured; (3) The bulk density of the foamed particles was calculated using the following formula: Bulk density of foamed particles (g / L) = Weight of foamed particles M2 (g) / Volume of container V2 (L).

[0086] (Focal position of the feeder) As the ring member, a ring member was used in which the diameter A of the circle formed by connecting the centers of multiple air outlets in a circular shape was 27 mm. As the feeder, a feeder was used in which the distance B from the ring member to the tip of the feeder was 40 mm. In addition, in the examples and comparative examples, a ring member with a ring angle θ of 10° to 14° was used.

[0087] First, using the definition of tangent (tan) in trigonometry, the distance E from the center of the ring member to the focal point was calculated from the radius (A / 2) of the circle formed by connecting the centers of multiple air outlets in a circular shape, and the ring angle θ. Then, using the calculated distance E and the distance B from the ring member to the tip of the feeder, the focal position was calculated using the following formula: Focal position (mm) = E - B (40 mm).

[0088] (Ratio of the area of ​​the recess formed by a depression of 1 mm or more relative to the piston mark to the total area of ​​the outer perimeter) The method for measuring the ratio of the area of ​​the recess formed by a depression of 1 mm or more relative to the piston mark to the total area of ​​the outer perimeter (hereinafter referred to as the outer perimeter recess area ratio) is as follows. The recess state of the feeder mark on the surface of the in-molded foamed body was measured using a laser displacement meter (Keyence Corporation, LJ-V7200). Then, in the outer perimeter region enclosed by the outer circumference of the piston mark (diameter a) and the concentric circle of the piston mark with a diameter of 1.3a, the total area A of the outer perimeter region and the area B of the recess formed by a depression of 1 mm or more relative to the piston mark were measured, and the outer perimeter recess area ratio was calculated using the following formula: Recess area ratio [%] = B / A × 100.

[0089] (Evaluation of fusion around the piston contact area) The piston mark area on the surface of the in-molded foamed body was rubbed five times by hand. The fusion around the piston contact area was evaluated based on the degree of adhesion of the foam particles in the piston mark area after the five rubs. The evaluation was performed according to the following criteria: A (Excellent): The foam particles do not separate at all. B (Good): Some separation of the foam particles is observed, but the foam particles themselves do not detach from the in-molded foamed body. C (Poor): The foam particles detach from the in-molded foamed body.

[0090] [Example 1] (Preparation of polyolefin resin particles) Polyolefin resin A was weighed to 100 parts by weight, additive A to 0.20 parts by weight, and additive B to 0.10 parts by weight. These were dry blended using a small tumbler manufactured by ON Machinery Co., Ltd. to obtain a mixture. This mixture was then melt-kneaded at a resin temperature of 200°C using a twin-screw extruder (TEM26-SX manufactured by Toshiba Machine Co., Ltd.) and extruded in a strand shape from a five-baseline die attached to the tip of the extruder. The extruded product (strand) was water-cooled in a water tank 2 m long. After that, the water-cooled product was taken up and shredded into a star-shaped form using a shredding device [manufactured by Ishinaka Iron Works Co., Ltd.] (shredding process). Through this operation, polyolefin resin particles (weight per particle of 2.5 mg) were obtained.

[0091] (Preparation of polyolefin resin foam particles) In a 10 L pressure vessel, 100 parts by weight of the obtained foaming polyolefin resin particles, 442 parts by weight of water as an aqueous dispersion medium, 0.33 parts by weight of kaolin as a dispersant, 0.05 parts by weight of sodium dodecylbenzenesulfonate as a dispersion aid, 0.03 parts by weight of citric acid as a pH adjuster, and 3.5 to 7.5 parts by weight of carbon dioxide as a blowing agent were charged according to the foaming pressure to prepare a dispersion containing the blowing agent. While stirring the obtained dispersion, the foaming temperature (temperature inside the pressure vessel) was set to 151.0°C. After the temperature and pressure inside the pressure vessel reached the predetermined foaming temperature and pressure, the temperature and pressure inside the pressure vessel were maintained at the predetermined foaming temperature and pressure for a further 30 minutes. Next, carbon dioxide was introduced and the pressure inside the pressure vessel was maintained at the foaming pressure of 3.0 MPa. The valve at the bottom of the pressure vessel was opened, and the dispersion liquid inside the pressure vessel was released to atmospheric pressure through a 4.0 mm diameter orifice to obtain polyolefin resin foam particles. The polyolefin resin foam particles were dried at 75°C for 24 hours. The obtained single-stage foam particles showed two peaks originating from the polyolefin resin in the DSC curve obtained by measurement using the DSC method. The bulk density of the obtained polyolefin resin foam particles was evaluated. The results are shown in Table 1.

[0092] (Preparation of polyolefin resin foam molded articles) The obtained polyolefin resin foam particles were foam-molded in-mold using a polyolefin in-mold foam molding machine (manufactured by Dabo Co., Ltd.) and a mold for box-shaped molded articles.

[0093] In the filling process, a feeder was used that had a ring member with a 15 mm gap between the concave and convex molds and a focal position of +30 mm. The polyolefin resin foam particles were heated and pressed together with steam at 0.30 MPa (gauge pressure), and then 30°C cooling water was sprayed onto the mold at a pressure of 0.4 MPa for 40 seconds to cool the in-mold foamed molded body. After that, the mold was opened and the polyolefin resin in-mold foamed molded body was removed from the mold using air or a release jig. The obtained in-mold foamed molded body was left at room temperature for 30 minutes, then cured and dried in a constant temperature room at 75°C for 15 hours, and then left at room temperature for another 4 hours to obtain a polyolefin resin foamed molded body.

[0094] [Examples 2 to 7, Comparative Examples 1 and 2] Foamed particles and foamed molded articles were obtained by the same method as in Example 1, except that the type of each material, the shape of the foamed particles, and the focal length of the feeder were changed as shown in Table 1. The physical properties of the obtained foamed particles and foamed molded articles were measured and evaluated.

[0095] [Summary] In the in-molded foamed articles of Examples 1 to 7, the concave area ratio of the outer peripheral region is 25% or more, that is, the area of ​​the concave region is 25% or more of the total area of ​​the outer peripheral region. On the other hand, in the in-molded foamed articles of Comparative Examples 1 and 2, the concave area ratio of the outer peripheral region is less than 25%.

[0096] Furthermore, in Examples 1 to 7, the angle of the air outlet is adjusted during the filling process so that the focal point is greater than 0 mm and less than or equal to 30 mm. On the other hand, in Comparative Example 1, the angle of the air outlet is adjusted during the filling process so that the focal point is greater than 30 mm, using irregularly shaped foamed particles. In Comparative Example 2, the angle of the air outlet is adjusted so that the focal point is greater than 0 mm and less than or equal to 30 mm, using foamed particles with an irregularity of less than 2.2.

[0097] A comparison of the in-molded foamed molded bodies of Examples 1 to 7 with the in-molded foamed molded bodies of Comparative Examples 1 and 2 revealed that the in-molded foamed molded bodies of Examples 1 to 7 exhibited superior fusion around the piston contact area. Furthermore, a comparison of the filling process of Examples 1 to 7 with the filling process of Comparative Examples 1 and 2 revealed that the filling process of Examples 1 to 7 exhibited superior fusion around the piston contact area.

[0098] This invention can be used in all aspects of in-mold foam molding technology.

[0099] 10 Feeder 13 Ring member 13a Air outlet 15 Piston 20 Mold 22 Raw material supply port 30 Foamed molded body inside the mold 30a Surface 30P Piston trace 31 Outer peripheral region 32 Recess

Claims

1. An in-molded foamed molded body composed of thermoplastic resin foam particles, having a surface on which a circular piston mark of diameter a is formed, wherein the surface has a recess that is recessed by 1 mm or more from the piston mark in the outer peripheral region enclosed by the circumference of the piston mark and a concentric circle of the piston mark with a diameter of 1.3a, and the area of ​​the recessed region is 25% or more of the total area of ​​the outer peripheral region.

2. The in-molded foamed article according to claim 1, wherein the thermoplastic resin foamed particles are foamed particles with a degree of irregularity of 2.2 or higher.

3. The in-molded foamed article according to claim 1, wherein the base resin of the thermoplastic foamed particles is a polyolefin resin.

4. The in-molded foamed body according to claim 1, wherein the recesses are formed randomly in the outer peripheral region.

5. The in-molded foamed article according to claim 1, wherein the recess is an unprocessed section that has not undergone any processing treatment.

6. The in-molded foamed body according to claim 1, wherein the diameter a of the piston trace is 8 mm or more and 50 mm or less.

7. A method for manufacturing an in-mold foamed molded body, comprising a filling step of filling a molding space with irregularly shaped thermoplastic resin foam particles using a feeder equipped with a piston and having multiple air blowing holes that blow air toward a single point in the molding space of the mold, wherein, when the single point where the air converges is defined as the focal point and the distance between the focal point and the raw material supply port of the mold is defined as the focal position, the angle of the air blowing holes is adjusted in the filling step such that the focal position is greater than 0 mm and less than or equal to 30 mm.

8. The method for manufacturing an in-mold foamed molded article according to claim 7, wherein the feeder comprises a feeder body and a ring member provided with a plurality of air blowing holes, and the filling step includes the step of attaching the ring member to the feeder body and discharging air toward the single point in the molding space of the mold.

9. The method for manufacturing an in-molded foamed article according to claim 7, wherein the angle of the air outlet is 14° or more and 24° or less.

10. The method for manufacturing an in-molded foamed article according to claim 7, wherein the air pressure discharged from the air outlet is 0.1 MPa or more and 0.6 MPa or less.

11. The method for manufacturing an in-molded foamed article according to claim 7, wherein the diameter of the piston is 8 mm or more and 50 mm or less.

12. The method for producing an in-molded foamed article according to claim 7, wherein the thermoplastic resin foamed particles are foamed particles with a degree of irregularity of 2.2 or higher.

13. The method for producing an in-molded foamed article according to claim 7, wherein the base resin of the thermoplastic foamed particles is a polyolefin resin.

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