Method for setting in-mold molding conditions for expanded bead molding and method for manufacturing expanded bead molding

Abstract

To provide a method for setting in-mold molding condition of a foamed particle molded product capable of easily finding in-mold molding condition that allows for reducing steam quantity used in in-mold molding without impairing physical properties of the foamed particle molded product.SOLUTION: A method for setting in-mold molding conditions includes a reference condition derivation step S1, a steam reduction condition range derivation step S2, and an in-mold molding condition derivation step S3. In step S1, a reference condition is derived which is capable of producing a foamed particle molded product having a fusion ratio X1 equal to or greater than a target fusion ratio XT without carrying out a packing step. In step S2, at least a part of the reference condition is changed to derive a steam reduction condition range capable of producing a foamed particle molded product having a predetermined fusion ratio X2 with a total steam amount less than the reference condition. In step S3, a packing step is added to the steam reduction condition to derive an in-mold forming condition capable of producing a foamed particle molded product having a fusion ratio equal to or greater than the target fusion ratio XT.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for setting in-mold molding conditions for an expanded bead molding and a method for producing an expanded bead molding. [Background technology]

[0002] Polystyrene-based resin expanded bead molded bodies obtained by molding expanded polystyrene-based resin beads in a mold are lightweight and have excellent compression properties, and therefore are used in various fields such as automobile materials, construction materials, and logistics materials. For molding expanded beads in a mold, a mold is used that includes a first mold and a second mold and is configured so that a molding cavity corresponding to the shape of a desired molded body is formed between the first mold and the second mold. After filling the molding cavity of such a mold with expanded beads, steam is supplied to the first mold and the second mold in a predetermined order to heat the expanded beads in the mold, thereby obtaining a molded body having a desired shape (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-237468 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for reducing the energy required for producing expanded bead moldings. From this perspective, there is a demand for reducing the amount of steam used during in-mold molding without impairing the physical properties of the moldings.

[0005] The present invention has been made in view of the above background, and aims to provide a method for setting in-mold molding conditions for expanded bead moldings, which makes it possible to easily find in-mold molding conditions that enable a reduction in the amount of steam used during in-mold molding without impairing the physical properties of the expanded bead moldings, and a method for producing expanded bead moldings that enables a reduction in the amount of steam used during in-mold molding without impairing the physical properties of the expanded bead moldings. [Means for solving the problem]

[0006] One aspect of the present invention resides in a method for setting in-mold molding conditions for an expanded bead molding product according to the following items (1) to (6).

[0007] [1] A molding die having a first die and a second die configured to be able to form a molding space between the first die and the second die is used, and a method including a first one-way heating step of supplying steam from the first die side to the molding space to heat the expanded beads in the molding space, a second one-way heating step of supplying steam from the second die side to the molding space after the first one-way heating step to heat the expanded beads in the molding space, a main heating step of supplying steam from both the first die side and the second die side to the molding space after the second one-way heating step to heat the expanded beads in the molding space, and a pressure holding step of holding the steam supplied in the main heating step in the molding die to mold expanded polystyrene resin beads into an X-shaped mold. T A method for setting in-mold molding conditions for an expanded bead molding to obtain an expanded bead molding having a fusion rate of at least [%], The setting method includes a reference condition deriving step, a steam reduction condition range deriving step, and an in-mold molding condition deriving step, In the step of deriving the reference condition, the steam pressure and the amount of steam in the first one-way heating step, the steam pressure and the amount of steam in the second one-way heating step, and the steam pressure and the amount of steam in the main heating step are included as the steam heating conditions, and the fusion rate X1 [%] is determined to be equal to or smaller than X without substantially performing the pressure holding step. T The molding conditions under which an expanded bead molding product can be produced with a bonding strength of 0.01 to 0.01% are determined as standard conditions. In the steam reduction condition range deriving step, at least a part of the steam heating conditions of the standard conditions is changed so that a total steam amount, which is the sum of the steam amount in the first one-way heating step, the steam amount in the second one-way heating step, and the steam amount in the main heating step, is less than the total steam amount in the standard conditions, and a range of steam reduction conditions, which is a molding condition under which an expanded bead molding having a fusion rate X2 [%] of 10% or more can be produced without substantially performing a pressure holding step, is derived as the steam reduction condition range; In the in-mold molding condition derivation step, the first one-way heating step, the second one-way heating step, and the main heating step under each steam reduction condition derived in the steam reduction condition range derivation step are performed. T A pressure dwell time is added so that the pressure dwell time is longer than the pressure dwell time under the steam reduction condition, and the fusion rate is X T The method for determining in-mold molding conditions for an expanded bead molding product derives a range of molding conditions that can produce an expanded bead molding product having a relative humidity of 10% or more as the in-mold molding conditions.

[0008] [2] The steam reduction conditions are: Requirement 1: The steam pressure Pa2 [MPa (G)] in the first one-way heating step under the steam reduction condition is 0.7 to 1.3 times the steam pressure Pa1 [MPa (G)] in the first one-way heating step under the standard condition. Requirement 2: the amount of steam Wa2 [kg] in the first one-way heating step under the reduced steam condition is less than the amount of steam Wa1 [kg] in the first one-way heating step under the standard condition; Requirement 3: the steam pressure Pb2 [MPa (G)] in the second one-way heating step under the reduced steam condition is 0.7 to 1.3 times the steam pressure Pb1 [MPa (G)] in the second one-way heating step under the standard condition; and Requirement 4: The amount of steam Wb2 [kg] in the second one-way heating step under the reduced steam conditions is less than the amount of steam Wb1 [kg] in the second one-way heating step under the standard conditions.

[0009] [3] The method for setting in-mold molding conditions for an expanded bead molding product according to [1] or [2], wherein the reduced steam conditions are configured so that a difference (X1-X2) between a fusion rate (X1) [%] of an expanded bead molding product obtained by in-mold molding under the standard conditions and a fusion rate (X2) [%] of an expanded bead molding product obtained by in-mold molding under the reduced steam conditions is 5% or more and 70% or less. [4] The steam reduction conditions are: Requirement 5: The steam pressure Pm2 [MPa (G)] in the main heating step under the steam reduction conditions is 0.7 to 1.3 times the steam pressure Pm1 [MPa (G)] in the main heating step under the standard conditions; and Requirement 6: The method for setting in-mold molding conditions for an expanded bead molding product according to any one of [1] to [3], wherein the following two requirements are satisfied: the amount of steam Wm2 [kg] in the main heating step under the reduced steam conditions is 0.7 to 1.3 times the amount of steam Wm1 [kg] in the main heating step under the standard conditions.

[0010] [5] The steam reduction conditions are: Requirement 7: The method for setting in-mold molding conditions for an expanded bead molding product according to any one of [1] to [4], wherein the following requirement is satisfied: the total amount of steam [kg] under the reduced steam conditions is 0.8 times or less the total amount of steam [kg] under the standard conditions. [6] The steam reduction conditions are: Requirement 8: The method for setting in-mold molding conditions for an expanded bead molding material according to any one of [1] to [5], wherein the requirement that the amount of steam Wm2 [kg] in the main heating step under the reduced steam conditions is 0.8 to 4 times the amount of steam Wa2 [kg] in the first one-way heating step under the reduced steam conditions is satisfied.

[0011] Another aspect of the present invention is a method for producing an expanded molding of beads according to the following item [7]. [7] A method for producing an expanded bead molding, comprising in-mold molding polystyrene-based resin expanded beads under in-mold molding conditions set by using the method for setting in-mold molding conditions for an expanded bead molding according to any one of [1] to [6] to produce an expanded bead molding. Effect of the Invention

[0012] According to the above-mentioned aspect, it is possible to provide a method for setting in-mold molding conditions for an expanded bead molding, which makes it possible to easily find in-mold molding conditions that enable a reduction in the amount of steam used during in-mold molding without impairing the physical properties of the expanded bead molding (hereinafter referred to as the "molded body"); and a method for producing an expanded bead molding that enables a reduction in the amount of steam used during in-mold molding without impairing the physical properties of the molded body. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram showing a flow chart of a method for setting molding conditions in a mold for producing an expanded bead molding. [Diagram 2] FIG. 2 is a partial cross-sectional view showing a main part of a mold used for in-mold molding of expanded beads. [Diagram 3] FIG. 3 is an explanatory diagram showing a flow chart of the in-mold molding method for expanded beads. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (Method of Setting In-Mold Molding Conditions for Expanded Bead Molding) The method for setting the in-mold molding conditions includes a step S1 for deriving a reference condition, a step S2 for deriving a steam reduction condition range, and a step S3 for deriving an in-mold molding condition, as shown in Fig. 1. By carrying out these steps, the setting method can obtain a desired fusion rate X while reducing the amount of steam used in the in-mold molding of expanded polystyrene resin beads (hereinafter referred to as "expanded beads"). T The in-mold molding conditions set by the setting method can be applied to, for example, the following in-mold molding methods.

[0015] The mold used for in-mold molding comprises a first mold 2 and a second mold 3, as shown in Fig. 2, for example. At least one of the first mold 2 and the second mold 3 is configured to be movable in the opening and closing direction of the mold 1. The first mold 2 and the second mold 3 are configured to abut against each other when the mold 1 is in a completely closed state, forming a molding space 11 between them. The molding space 11 may have any shape that corresponds to the shape of the desired molded body.

[0016] The first mold 2 and the second mold 3 each have a hollow structure, and are configured so that the internal space of each mold communicates with the molding space. For example, the first mold 2 and the second mold 3 may have a plurality of core vents (not shown) on the inner wall parts 23, 33 facing the molding space 11, which communicate between the internal space of each mold and the molding space 11. This allows the steam supplied to the internal space of the first mold 2 and the second mold 3 to reach the molding space 11 through the through grooves formed in the core vents of the inner wall parts 23, 33.

[0017] As shown in FIG. 3, the in-mold molding method of the expanded beads includes a filling step P1, a first one-side heating step P3, a second one-side heating step P4, and a main heating step P5.

[0018] In the filling step P1, the molding space 11 of the mold 1 is filled with foamed particles. The foamed particles to be filled in the molding space are not particularly limited as long as they are foamed particles having a polystyrene-based resin as a base resin, and known foamed polystyrene-based resin particles can be used. Here, the above-mentioned polystyrene-based resin refers to a resin having a content of components derived from styrene-based monomers of more than 50 mol %. From the viewpoint of improving the moldability and mechanical properties of the polystyrene-based resin in a well-balanced manner, the content of components derived from styrene-based monomers in the polystyrene-based resin is preferably 80 mol % or more, and more preferably 90 mol % or more.

[0019] The expanded polystyrene resin particles can be obtained, for example, by expanding expandable polystyrene resin particles containing an organic physical blowing agent, which is made of a polystyrene resin as a base resin. Examples of the organic physical blowing agent include hydrocarbons having 3 to 6 carbon atoms.

[0020] The expandable polystyrene resin particles can be produced by a conventionally known method such as suspension polymerization. In addition, the expandable polystyrene resin particles can be expanded by a conventionally known method. For example, a heating medium such as steam is supplied to the expandable polystyrene resin particles, and the expandable polystyrene resin particles are heated to expand the expandable polystyrene resin particles. More specifically, the expandable polystyrene resin particles can be expanded by heating the expandable polystyrene resin particles with steam or the like using a cylindrical expansion machine equipped with a stirrer.

[0021] As the polystyrene-based resin, a homopolymer of a styrene-based monomer and a copolymer containing a styrene-based monomer can be used. More specifically, the polystyrene-based resin may be a styrene-acrylic acid copolymer, a styrene-methyl acrylate copolymer, a styrene-ethyl acrylate copolymer, a styrene-butyl acrylate copolymer, a styrene-methacrylic acid copolymer, a styrene-methyl methacrylate copolymer, a styrene-ethyl methacrylate copolymer, a styrene-butyl methacrylate copolymer, a styrene-maleic anhydride copolymer, a styrene-acrylonitrile copolymer, an acrylonitrile-butadiene-styrene copolymer, a styrene-methylstyrene copolymer, a styrene-dimethylstyrene copolymer, a styrene-ethylstyrene copolymer, a styrene-diethylstyrene copolymer, or the like, which is mainly composed of polystyrene (GPPS) or styrene.

[0022] In the in-mold molding method, after the filling step P1 is completed and before the first one-sided heating step P3 is performed, an exhaust step P2 (see FIG. 3) may be performed as necessary to exhaust the air within the forming mold 1 to the outside of the forming mold 1. In the exhaust step P2, for example, a method can be used in which steam is supplied to the molding space 11 from both the first mold 2 side and the second mold 3 side to replace the air within the forming mold 1 with steam.

[0023] When the exhaust step P2 is performed, for example, the pressure of the steam supplied to the first mold 2 and the second mold 3 is preferably 0.02 MPa (G) or more and 1 MPa (G) or less, and more preferably 0.03 MPa (G) or more and 0.06 MPa (G) or less. In addition, in the exhaust step P2, it is preferable to supply steam at the above-mentioned pressure for, for example, 1 to 5 seconds.

[0024] After the filling step P1 or the exhaust step P2, which is performed as required, is completed, a first one-side heating step P3 is performed in which steam is supplied from the first mold 2 side to the molding space 11 to heat the foamed beads in the molding space 11. In the first one-side heating step P3, the degree of heating of the foamed beads in the molding space 11 can be controlled by controlling the steam pressure Pa and the steam amount Wa of the steam supplied to the first mold 2. In the first one-side heating step P3, for example, as described later, the steam supply valve of the first mold 2 and the drain valve of the second mold 3 are opened, and the other steam supply valves and drain valves are closed, so that steam can be caused to flow from the first mold 2 side to the second mold 3 side. This allows the foamed beads in the molding space 11 to be heated.

[0025] After the first one-sided heating step P3 is completed, a second one-sided heating step P4 is performed in which steam is supplied from the second mold 3 side to the molding space 11 to heat the expanded beads in the molding space 11. In the second one-sided heating step P4, the degree of heating of the expanded beads in the molding space 11 can be controlled by controlling the steam pressure Pb and the steam amount Wb of the steam supplied to the second mold 3. In the second one-sided heating step P4, for example, as described later, the steam supply valve of the second mold 3 and the drain valve of the first mold 2 are opened, and the other steam supply valves and drain valves are closed, so that steam can be caused to flow from the second mold 3 side to the first mold 2 side. This allows the expanded beads in the molding space 11 to be heated.

[0026] After the second one-side heating step P4 is completed, a main heating step P5 is performed in which steam is supplied to the molding space 11 from both the first mold 2 side and the second mold 3 side to heat the foamed beads in the molding space 11. In the main heating step P5, the degree of heating of the foamed beads in the molding space 11 and the degree of pressure (surface pressure) applied to the inner wall of the mold 1 can be controlled by controlling the steam pressure Pm and the steam amount Wm of the steam supplied to the first mold 2 and the second mold 3. In the main heating step P5, for example, as described later, the steam supply valve of the first mold 2 and the steam supply valve of the second mold 3 are opened and the drain valves of each mold are closed, thereby increasing the pressure in the molding space 11. This makes it possible to increase the surface pressure applied to the mold 1 while heating the foamed beads in the molding space 11.

[0027] After the main heating step P5 is completed, a pressure-holding step P6 is performed in which the steam supplied to the mold 1 in the main heating step P5 is held in the mold 1. In the pressure-holding step P6, the degree of heating of the expanded beads in the molding space 11 can be controlled by controlling the pressure-holding time t (unit: seconds), that is, the time for which the steam supplied to the mold 1 is held. In the pressure-holding step P6, for example, as described below, the steam supplied into the molding space 11 can be held in the molding space 11 by closing the steam supply valves and drain valves of each mold. This makes it possible to gradually reduce the decrease in surface pressure applied to the mold 1 and to maintain the state in which the expanded beads in the molding space 11 are heated under a desired pressure for a long period of time without supplying steam to the mold 1.

[0028] In the in-mold molding method, the heating performed up to the pressure holding step P6 causes the foamed particles in the molding space 11 to undergo secondary expansion while fusing with each other to form a molded body. After the pressure holding step P6 is completed, a cooling step P7 may be performed as necessary to cool the molded body in the mold 1. After the shape of the molded body in the mold 1 has been stabilized to a certain extent, the mold 1 is opened to obtain the molded body.

[0029] Next, each step in the method for setting the in-mold molding conditions will be described in more detail.

[0030] [Reference condition derivation step S1] In the reference condition derivation step S1, in the above-mentioned in-mold molding method, the fusion rate X1 (unit: %) is determined to be equal to or smaller than the target fusion rate X without substantially carrying out the pressure holding step P6. T The molding conditions under which a molded body having a fusion rate of 100% or more can be produced are derived as reference conditions. Here, the molding conditions under which the above-mentioned "dwelling step P6 is not substantially performed" include molding conditions under which the dwelling step P6 is not performed (i.e., the dwelling time t is 0 seconds) and molding conditions under which the dwelling time t is greater than 0 seconds and is equal to or less than a value that does not significantly affect the improvement of the fusion rate of the molded body. More specifically, the molding conditions under which the "dwelling step P6 is not substantially performed" include molding conditions under which the dwelling time t is, for example, greater than 0 seconds and less than 5 seconds. In addition, the target fusion rate XT can be set to a value required depending on the application or shape of the molded article. For example, the target fusion rate X T It may be 80%, 85%, or 90%.

[0031] More specifically, in the reference condition derivation step S1, the steam pressures Pa, Pb, Pm and the steam amounts Wa, Wb, Wm in the in-mold molding method shown in Fig. 3 are variously changed to perform steps P1 to P5, and in-mold molding is performed without substantially performing the pressure holding step P6. In this case, the pressure holding time t may vary within the range described above, but from the viewpoint of making it easier to derive suitable reference conditions, it is preferable that it be a constant value.

[0032] The fusion rate of the molded body thus obtained is measured, and the target fusion rate X T Molding conditions that enable the production of a molded body having the above fusion rate are set as candidates for the reference conditions.

[0033] The method for measuring the fusion rate is, for example, as follows. First, the molded body is folded so as to be roughly equal parts and broken. At this time, the molded body may be cut in advance to make it easier to break. Then, 100 or more expanded beads are randomly selected from the expanded beads exposed on the fracture surface of the molded body and visually observed to determine whether the expanded beads are broken from the inside (i.e., material destruction) or at the interface between the expanded beads (i.e., interface destruction). Then, the ratio of the total number of expanded beads with material destruction to the total number of expanded beads visually observed, expressed as a percentage, is taken as the fusion rate of the molded body (unit: %).

[0034] The candidates for the standard conditions are the molding conditions under which the molding was actually produced and the fusion rate was measured, as well as the target fusion rate X T Based on the molding conditions that have been experimentally confirmed to be able to achieve a fusion rate of X or more, TThe molding conditions may include molding conditions that are estimated to achieve the fusion rate X1 or more. In other words, the candidates for the reference conditions may include molding conditions under which the fusion rate has not actually been measured. For example, the fusion rate of a molded body usually tends to increase as the amount of heat applied to the expanded beads increases. Therefore, under two molding conditions with the same steam pressure but different steam amounts, the target fusion rate X T If the above fusion rate X1 can be achieved, the target fusion rate X1 can also be achieved under the molding conditions with the intermediate steam amount between these two molding conditions. T It can be estimated that a fusion rate of X1 or more can be achieved.

[0035] One molding condition selected from the candidates for the reference condition obtained in the above manner is derived as the reference condition. The reference conditions derived in this manner include at least six steam heating conditions: steam pressure Pa1 (unit: MPa (G)) and steam amount Wa1 (unit: kg) in the first one-way heating process P3, steam pressure Pb1 (unit: MPa (G)) and steam amount Wb1 (unit: kg) in the second one-way heating process P4, and steam pressure Pm1 (unit: MPa (G)) and steam amount Wm1 (unit: kg) in the main heating process P5. There is no particular limitation on the method of selecting the reference conditions from the candidate reference conditions, but from the viewpoint of efficiently performing the subsequent steam reduction condition range derivation step S2, it is preferable to derive as the reference conditions the molding conditions having the smallest total steam amount W1 (unit: kg), that is, the sum of the steam amount Wa1 in the first one-way heating process P3, the steam amount Wb1 in the second one-way heating process P4, and the steam amount Wm1 in the main heating process P5, assuming that a predetermined fusion rate is satisfied.

[0036] [Step S2 for deriving the range of steam reduction conditions] In step S2 of deriving the range of steam reduction conditions, at least some of the steam heating conditions of the standard conditions are changed to derive a range of steam reduction conditions, which are molding conditions under which a molded body having a fusion rate X2 (unit: %) of 10% or more can be produced with a total steam amount W2 (unit: kg) less than the total steam amount W1 under the standard conditions without substantially performing the pressure holding process P6.

[0037] More specifically, in the steam reduction condition range derivation step S2, one or more steam heating conditions among the steam amount Wa1 in the first one-way heating step P3, the steam amount Wb1 in the second one-way heating step P4, and the steam amount Wm1 in the main heating step P5 under the standard conditions are changed so that the total steam amount W2 is less than the total steam amount W1 under the standard conditions, and in-mold molding is performed. Also, in the steam reduction condition range derivation step S2, in addition to the steam amounts Wa1, Wb1, and Wm1, one or more steam heating conditions among the steam pressures Pa1, Pb1, and pressure Pm1 under the standard conditions may be changed to perform in-mold molding.

[0038] The molding conditions in which the dwelling step P6 is not substantially performed include molding conditions in which the dwelling step P6 is not performed (i.e., the dwelling time t is 0 seconds). More specifically, the molding conditions in which the dwelling step P6 is not substantially performed include molding conditions in which the dwelling time t is, for example, 0 seconds or more and less than 5 seconds. Similarly to the reference condition derivation step S1, the dwelling time t in the steam reduction condition range derivation step S2 may vary within the above-mentioned range, but from the viewpoint of making it easier to derive suitable steam reduction conditions, it is preferable that the dwelling time t be a constant value.

[0039] The fusion rate of the molded product thus obtained is measured, and the range of steam reduction conditions that allows the production of a molded product having a fusion rate X2 of 10% or more is derived as the range of steam reduction conditions. TFrom the viewpoint of facilitating the introduction of in-mold molding conditions that can achieve the above, the fusion rate X2 is preferably 20% or more, more preferably 30% or more, and even more preferably 50% or more. The steam reduction condition range may include steam reduction conditions under which a molded body is actually produced and the fusion rate is measured, as well as steam reduction conditions that are estimated to be able to achieve the fusion rate in the specific range based on steam reduction conditions that have been experimentally confirmed to be able to achieve the fusion rate in the specific range. In other words, the steam reduction condition range may include steam reduction conditions under which the fusion rate has not actually been measured.

[0040] The steam reduction condition range derived in this manner is composed of one or more steam reduction conditions having at least six steam heating conditions: steam pressure Pa2 (unit: MPa (G)) and steam amount Wa2 (unit: kg) in the first one-way heating process P3, steam pressure Pb2 (unit: MPa (G)) and steam amount Wb2 (unit: kg) in the second one-way heating process P4, and steam pressure Pm2 (unit: MPa (G)) and steam amount Wm2 (unit: kg) in the main heating process P5.

[0041] The steam reduction conditions are: Requirement 1: The steam pressure Pa2 in the first one-way heating step P3 under the steam reduction condition is 0.7 to 1.3 times the steam pressure Pa1 in the first one-way heating step P3 under the standard condition. Requirement 2: The steam amount Wa2 of the first one-side heating step P3 under the steam reduction condition is less than the steam amount Wa1 of the first one-side heating step P3 under the standard condition. Requirement 3: the steam pressure Pb2 in the second one-way heating step P4 under the steam reduction conditions is 0.7 to 1.3 times the steam pressure Pb1 in the second one-way heating step P4 under the standard conditions; and Requirement 4: The amount of steam Wb2 in the second one-way heating step P4 under the reduced steam conditions is less than the amount of steam Wb1 in the second one-way heating step P4 under the standard conditions.

[0042] The steam supplied to the first mold 2 in the first one-side heating step P3 usually passes through the molding space 11 and is led from the second mold 3 to the outside of the molding die 1. Similarly, the steam supplied to the second mold 3 in the second one-side heating step P4 usually passes through the molding space 11 and is led from the first mold 2 to the outside of the molding die 1. Therefore, the in-mold molding method has a problem in that the amount of steam Wa used in the first one-side heating step P3 and the amount of steam Wb used in the second one-side heating step P4 tend to be large.

[0043] In contrast, as described above, by setting the range of the steam pressure Pa2 in the first one-sided heating step P3 and the steam pressure Pb2 in the second one-sided heating step P4 to the ranges specified in the requirements 1 and 3, it is possible to produce a molded body that satisfies a predetermined fusion rate X2, while easily deriving the range in which the steam amount Wa2 in the first one-sided heating step P3 and the steam amount Wb2 in the second one-sided heating step P4 can be reduced, and the addition of the pressure holding step P6 makes it possible to achieve the target fusion rate X2. T It is possible to more easily derive the range of conditions that can achieve the above. Furthermore, by reducing the amount of steam in the first one-way heating step P3 and the second one-way heating step P4, in which the amount of steam used tends to be relatively large, the total amount of steam W2 can be more effectively reduced.

[0044] From the viewpoint of more reliably obtaining the above-mentioned effects, in requirement 1, the steam pressure Pa2 in the first one-side heating step P3 under the reduced steam conditions is more preferably 0.8 to 1.2 times, and even more preferably 0.9 to 1.1 times, the steam pressure Pa1 in the first one-side heating step P3 under the standard conditions. Also, in requirement 3, the steam pressure Pb2 in the second one-side heating step P4 under the reduced steam conditions is more preferably 0.8 to 1.2 times, and even more preferably 0.9 to 1.1 times, the steam pressure Pb1 in the second one-side heating step P4 under the standard conditions.

[0045] The steam reduction conditions are preferably configured so that the difference X1-X2 between the fusion rate X1 of the molded body obtained by molding in the mold under the standard conditions and the fusion rate X2 of the molded body obtained by molding in the mold under the steam reduction conditions is 5% to 70%. By setting the difference X1-X2 in the fusion rates in the specific range, the total amount of steam can be reduced while the target fusion rate X T Therefore, the range of steam reduction conditions that can achieve the above can be more easily derived.

[0046] From the viewpoint of further reducing the total amount of steam, the difference in the fusion rates X1-X2 is more preferably 7% or more, even more preferably 10% or more, particularly preferably 15% or more, and most preferably 20% or more. T From the viewpoint of more easily deriving in-mold molding conditions that can achieve the above, the difference in fusion rates X1-X2 is more preferably 70% or less, even more preferably 60% or less, particularly preferably 50% or less, and most preferably 40% or less.

[0047] In determining the preferred range of the difference in fusion rates X1-X2, the upper and lower limits of the difference in fusion rates X1-X2 described above can be combined in any way. For example, the preferred range of the difference in fusion rates X1-X2 may be 7% or more and 70% or less, 10% or more and 60% or less, 15% or more and 50% or less, or 20% or more and 40% or less.

[0048] The steam reduction conditions are as follows: Requirement 5: The steam pressure Pm2 in the main heating step P5 under the steam reduction conditions is 0.7 to 1.3 times the steam pressure Pm1 in the main heating step P5 under the standard conditions; and Requirement 6: The steam amount Wm2 of the main heating step P5 under the steam reduction condition is 0.7 to 1.3 times the steam amount Wm1 of the main heating step P5 under the standard condition. In this way, by bringing the steam pressure and steam amount of the main heating step P5 under the steam reduction condition closer to the steam pressure and steam amount of the main heating step P5 under the standard condition, it becomes easier to derive suitable steam reduction conditions, and the addition of the pressure holding step P6 makes it possible to achieve the target fusion rate X T It is therefore easier to derive the range of conditions under which the above can be achieved.

[0049] From the viewpoint of more reliably obtaining the above-mentioned effects, in requirement 5, the steam pressure Pm2 in the main heating step P5 under the reduced steam conditions is more preferably 0.8 to 1.2 times, and even more preferably 0.9 to 1.1 times, the steam pressure Pm1 in the main heating step P5 under the standard conditions. Also, in requirement 6, the steam amount Wm2 in the main heating step P5 under the reduced steam conditions is more preferably 0.8 to 1.2 times, and even more preferably 0.9 to 1.1 times, the steam amount Wm1 in the main heating step P5 under the standard conditions.

[0050] The steam reduction conditions are: Requirement 7: It is preferable that the total steam amount W2 under the steam reduction condition is 0.8 times or less the total steam amount W1 under the standard condition. In this case, the total steam amount can be reduced more reliably.

[0051] The steam reduction conditions are: Requirement 8: It is preferable that the steam amount Wm2 in the main heating step P5 under the steam reduction condition is 0.8 to 4 times the steam amount Wa2 in the first one-side heating step P3 under the steam reduction condition. In this case, the target fusion rate X T Therefore, the range of steam reduction conditions that can achieve the above can be more easily derived.

[0052] [Step S3 for deriving molding conditions in mold] In the in-mold molding condition derivation step S3, the first one-side heating step P3, the second one-side heating step P4, and the main heating step P5 are determined according to the steam reduction conditions derived in the steam reduction condition range derivation step, and the pressure retention time t T A pressure dwell time P6 is added so that the pressure dwell time t2 (unit: second) under the steam reduction condition is longer than the pressure dwell time t2 (unit: second) under the steam reduction condition, and the fusion rate is X T The range of molding conditions that can produce the above-described molded body is derived as the in-mold molding conditions.

[0053] More specifically, in the in-mold molding condition derivation step S3, the steam pressures Pa2, Pb2, Pm2 and steam amounts Wa2, Wb2, Wm2 under the steam reduction condition are adopted as the steam pressures and steam amounts in each step P3 to P5, and the in-mold molding is performed by changing the pressure retention time t to a value longer than the pressure retention time t2 under the steam reduction condition. The fusion rate of the molded body obtained in this manner is measured, and the target fusion rate X T A range of molding conditions that can produce a molded body having the above fusion rate is derived as the in-mold molding conditions. From the viewpoint of stably obtaining a molded body with a high fusion rate without excessively lengthening the molding cycle of the molded body, the dwell time t of the in-mold molding conditions in the in-mold molding condition derivation step S3 is preferably 5 seconds or more and 30 seconds or less, and more preferably 8 seconds or more and 25 seconds or less.

[0054] The number of steam reduction conditions used in deriving the in-mold molding conditions may be one or more. From the viewpoint of more easily deriving the in-mold molding conditions that can obtain a good molded body with a smaller amount of steam, it is preferable to derive the in-mold molding conditions in the in-mold molding condition deriving step S3 using steam reduction conditions in which the total steam amount W2 of the steam reduction conditions is 0.8 times or less than the total steam amount W1 of the standard conditions. From the same viewpoint, the total steam amount W2 of the steam reduction conditions used in the in-mold molding condition deriving step S3 is more preferably 0.75 times or less, and even more preferably 0.7 times or less, of the total steam amount W1 of the standard conditions.

[0055] In addition, from the viewpoint of increasing the fusion rate of the obtained molded body, in the in-mold molding condition derivation step S3, the target fusion rate X T From the same viewpoint, it is preferable to derive the in-mold molding conditions using steam reduction conditions that can achieve a fusion rate X2 of 0.5 times or more. T It is more preferable that the fusion ratio X2 is 0.6 or more times the fusion ratio X2 of the sintered body 10, and it is further preferable that the fusion ratio X2 is 0.7 or more times the fusion ratio X2 of the sintered body 10.

[0056] The in-mold molding conditions derived in the in-mold molding condition derivation step S3 may include one molding condition or two or more molding conditions. In addition, the in-mold molding conditions may include the molding conditions under which the molded body was actually produced and the fusion rate was measured, as well as the target fusion rate X T Based on the molding conditions that have been experimentally confirmed to be able to achieve a fusion rate of X or more, T The molding conditions may include molding conditions that are estimated to achieve the above fusion rate. In other words, the in-mold molding conditions may include molding conditions for which the fusion rate has not actually been measured. For example, the dwell time t T Under two different molding conditions, the target fusion rate X T If the above fusion rate X1 can be achieved, the target fusion rate X1 can also be achieved under molding conditions with a pressure holding time intermediate between the pressure holding times under these two molding conditions. T It can be estimated that the above fusion rate can be achieved.

[0057] The in-mold molding conditions derived in the in-mold molding condition derivation step are the maximum value F of the surface pressure applied to the molding die 1 in the main heating step P5 in the in-mold molding condition derivation step. max is 0.09 MPa (G) or more and 0.12 MPa (G) or less, and the surface pressure applied to the forming die 1 in the pressure holding step P6 in the in-mold molding condition derivation step is F maxIt is preferable that the time during which the pressure is -0.01 MPa or more is set to 4 seconds or more and 20 seconds or less. In this case, the total amount of steam is reduced while the target fusion rate X T In addition, since the molding cycle for the molded article can be easily shortened, the productivity of the molded article can be further improved.

[0058] The surface pressure applied to the mold 1 is obtained by measuring the pressure generated during in-mold molding near the center of the molding surface (inner wall) when looking from one mold to the other along the mold clamping direction. A surface pressure gauge can be used to measure the surface pressure. The surface pressure gauge may be provided in the first mold 2 or in the second mold 3.

[0059] (Method of manufacturing foamed bead molded body) In producing a foamed bead molding, it is preferable to produce a foamed bead molding by in-mold molding the foamed beads under the in-mold molding conditions set by the in-mold molding condition setting method. As described above, the in-mold molding condition setting method can derive in-mold molding conditions that can reduce the amount of steam used compared to the standard conditions and obtain a molding having a fusion rate comparable to that of a molding obtained by in-mold molding under the standard conditions. Therefore, by performing in-mold molding using the in-mold molding conditions, a molding having good physical properties can be easily obtained while reducing the amount of steam used. In addition, the in-mold molding conditions set by the setting method can perform in-mold molding in a molding cycle equivalent to the molding cycle of the standard conditions set in the standard condition derivation step, or a molding cycle shorter than the molding cycle of the molding conditions set in the standard condition derivation step, and thus the productivity is excellent.

[0060] When the in-mold molding conditions including a plurality of molding conditions are derived in the method for setting the in-mold molding conditions, any one of the plurality of molding conditions may be used to perform in-mold molding in the manufacturing method. From the viewpoint of reducing the amount of steam used, it is preferable to perform in-mold molding by adopting the molding condition with the smallest total amount of steam among the molding conditions included in the in-mold molding conditions. EXAMPLES

[0061] Example 1 An example of the method for setting the in-mold molding conditions is described below. In this example, the in-mold molding conditions were derived for producing a plate-shaped molded body having a length of 1000 mm, a width of 600 mm, and a thickness of 50 mm using expanded polystyrene beads.

[0062] The specific configuration of the mold 1 used in this example will be described with reference to Fig. 2. As shown in Fig. 2, the mold 1 has a first mold 2 and a second mold 3. The first mold 2 is fixed, and the second mold 3 is configured so as to be able to move in the opening and closing direction of the mold 1 relative to the first mold 2. Between the first mold 2 and the second mold 3, there is provided a molding space 11 capable of molding a molded body having the above-mentioned shape.

[0063] The first die 2 has a hollow structure. The first die 2 has a first steam supply valve 21 configured to be able to supply steam from the outside of the molding die 1 to the internal space of the first die 2, and a first drain valve 22 configured to be able to lead steam from the internal space of the first die 2 to the outside of the molding die 1. Although not shown in the figure, a plurality of core vents are drilled in the inner wall portion 23 of the first die 2 facing the molding space 11, which communicate between the internal space of the first die 2 and the molding space 11.

[0064] In the internal space of the first mold 2, a first watering nozzle 24 configured to be able to spray water onto the inner wall portion 23 is provided.

[0065] In addition, a surface pressure gauge (not shown) configured to be able to measure the pressure (i.e., surface pressure) applied to the inner wall 23 is attached to the inner wall 23 of the first mold 2. The surface pressure gauge is provided near the center of the inner wall 23 when the first mold 2 is viewed from the second mold 3 along the mold clamping direction. More specifically, the surface pressure gauge is provided at a position on the inner wall 23 corresponding to the center of a surface of the molded body that is 1000 mm long and 600 mm wide. The expanded particles heated during the in-mold molding process fuse together while undergoing secondary expansion to form a molded body. Therefore, by providing the surface pressure gauge on the inner wall 33, the progress of the in-mold molding can be easily grasped through the change in surface pressure accompanying the secondary expansion of the expanded particles. The surface pressure gauge may be attached to the inner wall 33 of the second mold 3.

[0066] Although not shown in the figure, a pressure gauge configured to be able to measure the pressure of steam and a flow meter configured to be able to measure the flow rate of steam are attached to the steam piping connected to the first steam supply valve 21. This makes it possible to measure the pressure and amount of steam supplied from the first steam supply valve 21 to the first mold 2.

[0067] The second die 3 also has a hollow structure like the first die 2. The second die 3 has a second steam supply valve 31 configured to be able to supply steam from the outside of the molding die 1 to the internal space of the second die 3, and a second drain valve 32 configured to be able to lead steam from the internal space of the second die 3 to the outside of the molding die 1. Although not shown in the figure, a plurality of core vents are drilled in the inner wall portion 33 facing the molding space 11 in the second die 3 to communicate between the internal space of the second die 3 and the molding space 11.

[0068] In the internal space of the second mold 3, a second water spray nozzle 34 configured to be able to spray water onto the inner wall portion 33 is provided.

[0069] Although not shown in the figure, a pressure gauge configured to be able to measure the pressure of steam and a flow meter configured to be able to measure the flow rate of steam are attached to the steam piping connected to the second steam supply valve 31. This makes it possible to measure the pressure and amount of steam supplied from the second steam supply valve 31 to the second mold 3.

[0070] In this example, the in-mold molding of the expanded beads is carried out according to the procedure shown in Fig. 3. That is, first, a filling step P1 is carried out to fill the molding space 11 of the molding die 1 with the expanded beads (step P1). The expanded beads used in this example are polystyrene-based resin expanded beads with polystyrene as the base resin. The expanded beads have a bulk magnification of 60 times. The bulk density of the expanded beads can be measured by the following method.

[0071] First, fill a measuring cylinder with expanded particles and lightly tap the floor surface with the bottom of the measuring cylinder several times to stabilize the filling height of the expanded particles in the measuring cylinder. After that, read the bulk volume (unit: L) of the expanded particles from the graduations on the measuring cylinder. Then, divide the mass (unit: g) of the expanded particles in the measuring cylinder by the aforementioned bulk volume and convert the value into units to obtain the bulk density of the expanded particles (unit: kg / m 3 ) can be obtained.

[0072] After the filling step P1 is completed, an exhaust step P2 is performed in which the air in the forming mold 1 is swept out of the forming mold 1 by steam. In the exhaust step P2 of this example, with the first steam supply valve 21, the first drain valve 22, the second steam supply valve 31, and the second drain valve 32 shown in Fig. 2 open, steam is supplied from the first steam supply valve 21 to the first mold 2, and steam is supplied from the second steam supply valve 31 to the second mold 3. This makes it possible to replace the air that has been stagnating in the internal space of the first mold 2 and the internal space of the second mold 3 with steam.

[0073] After the exhaust step P2 is completed, as shown in FIG. 3, a first one-side heating step P3 is performed in which steam is supplied from the first mold 2 side to the molding space 11. In the first one-side heating step P3 of this example, the first steam supply valve 21 and the second drain valve 32 shown in FIG. 2 are opened, and the other valves are closed. In this state, steam is supplied from the first steam supply valve 21 to the first mold 2, thereby introducing the steam into the internal space of the first mold 2. The steam introduced into the internal space of the first mold 2 flows into the molding space 11 through a core vent provided on the inner wall portion 23 of the first mold 2. As a result, the foamed particles in the molding space 11 are heated. Thereafter, the steam in the molding space 11 is led to the internal space of the second mold 3 through a core vent provided on the inner wall portion 33 of the second mold 3, and is led out of the molding mold 1 from the second drain valve 32.

[0074] After the first one-side heating step P3 is completed, as shown in FIG. 3, the second one-side heating step P4 is performed to supply steam from the second mold 3 side to the molding space 11. In the second one-side heating step P4 of this example, the second steam supply valve 31 and the first drain valve 22 shown in FIG. 2 are opened, and the other valves are closed. In this state, steam is supplied from the second steam supply valve 31 to the second mold 3, thereby introducing the steam into the internal space of the second mold 3. The steam introduced into the internal space of the second mold 3 flows into the molding space 11 through a core vent provided on the inner wall portion 33 of the second mold 3. As a result, the foamed particles in the molding space 11 are heated. Thereafter, the steam in the molding space 11 is led to the internal space of the first mold 2 through a core vent provided on the inner wall portion 23 of the first mold 2, and is led out of the molding mold 1 from the first drain valve 22.

[0075] After the second one-side heating step P4 is completed, a main heating step P5 is carried out to supply steam to the molding space 11 from both the first mold 2 side and the second mold 3 side, as shown in FIG. 3. In the main heating step P5 of this example, the first steam supply valve 21 and the second steam supply valve 31 shown in FIG. 2 are opened, and the other valves are closed. In this state, steam is supplied from the first steam supply valve 21 to the first mold 2, and steam is supplied from the second steam supply valve 31 to the second mold 3, thereby introducing steam into the internal space of the first mold 2 and the internal space of the second mold 3. The steam introduced into the internal spaces of these molds flows into the molding space 11 through the core vents provided in the inner walls 23 and 33. This increases the pressure in the molding space 11 and heats the foamed particles.

[0076] After the main heating step P5 is completed, as shown in Fig. 3, a pressure holding step P6 is carried out in which the steam supplied to the first die 2 and the second die 3 in the main heating step P5 is held within the molding die 1. In the pressure holding step P6 of this example, all the valves shown in Fig. 2 are closed to hold the steam within the molding die 1. This makes it possible to gently reduce the decrease in pressure applied to the molding surface of the molding die 1 and to maintain for a long period of time the state in which the expanded beads within the molding space 11 are heated under the desired pressure without supplying steam to the molding die 1.

[0077] After completion of the pressure holding step P6, a cooling step P7 is performed to cool the molded body in the forming mold 1, as shown in Fig. 3. The cooling step P7 in this example includes a water cooling step of spraying water onto the inner wall portions 23, 33 from the first watering nozzle 24 and the second watering nozzle 34 shown in Fig. 2, and a vacuum cooling step of reducing the pressure in the internal spaces of the first mold 2 and the second mold 3 after the water cooling step is completed.

[0078] In the water cooling step, water is sprayed onto the inner walls 23, 33 from the first water spray nozzle 24 and the second water spray nozzle 34. This makes it possible to lower the temperature of the inner walls 23, 33 and to cool the molded body in contact with the inner walls 23, 33.

[0079] In the vacuum cooling step, a vacuum valve (not shown) provided on the mold 1 is opened, and the other valves are closed. In this state, the pressure inside the mold 1 is reduced by forcibly discharging the gas inside the mold 1 through the vacuum valve using a vacuum pump. When the pressure inside the mold 1 is reduced, the water sprayed inside the mold 1 in the water cooling step is more likely to evaporate. When the water evaporates, heat inside the mold 1 is taken away as latent heat of evaporation, so by reducing the pressure inside the mold 1, the mold 1 and the molded body can be cooled more quickly. After the vacuum cooling step is completed, the vacuum state inside the mold 1 is released by opening an exhaust valve (not shown) provided on the mold 1.

[0080] After the cooling step P7 is completed, the molding die 1 is opened to obtain a molded body.

[0081] In this example, the in-mold molding conditions applicable to the in-mold molding method having the above-mentioned steps P1 to P7 were derived using the in-mold molding condition setting method (see Figure 1) including the above-mentioned standard condition derivation step S1, steam reduction condition range derivation step S2, and in-mold molding condition derivation step S3.

[0082] First, in the reference condition derivation step S1, the filling step P1, the exhaust step P2, the first one-side heating step P3, the second one-side heating step P4, the main heating step P5 and the cooling step P7 were carried out under three molding conditions shown in the condition numbers A1 to A3 in Table 1, and a molded body was produced without carrying out the pressure holding step P6. T The "total steam amount W" shown in Table 1 is the sum of the steam amount Wa in the first one-way heating step P3, the steam amount Wb in the second one-way heating step P4, and the steam amount Wm in the main heating step P5, and the "maximum surface pressure Fmax " is the maximum surface pressure applied to the inner wall portion 33 of the second mold 3 in the main heating process P5. In the reference condition derivation step S1, since the pressure holding process P6 is not performed as described above, the symbol "-" is entered in the "Pressure Holding Process" column in Table 1.

[0083] The fusion ratios of the molded bodies obtained by performing in-mold molding under each molding condition are shown in Table 1. The method for measuring the fusion ratio is as described above. That is, first, the molded body was bent so that the molded body would break near the center in the vertical direction, and the molded body was broken into roughly equal parts. Then, 100 or more expanded beads were randomly selected from the expanded beads exposed on the fracture surface of the molded body and visually observed, and the fusion ratio of the molded body was calculated by expressing the ratio of the total number of expanded beads with material destruction to the total number of expanded beads visually observed as a percentage. As shown in Table 1, among condition numbers A1 to A3, the fusion ratio X was greater than the target fusion ratio X T The molding conditions that satisfy the above conditions are condition numbers A1 and A2. Therefore, in the reference condition derivation step S1, these two molding conditions were set as candidates for the reference conditions. Then, among condition numbers A1 and A2, condition number A2, which has the smallest total steam amount W, was set as the reference condition.

[0084] In addition, in the in-mold molding under condition number A2, the molding cycle was evaluated by measuring the time from when the mold clamping started to when the molded body was released from the mold. The mold was opened when the pressure (surface pressure) applied to the inner wall of the mold in the cooling step P7 reached a gauge pressure of 0.02 MPa (G). As a result, the time required from the start of mold clamping to mold release was 205 seconds. The shorter this time, the more efficient the in-mold molding of the foamed bead molding can be performed, which means a better molding cycle.

[0085] In the steam reduction condition range derivation step S2, at least some of the steam heating conditions of the reference conditions (condition number A2) are changed, and with the four types of molding conditions shown in condition numbers B1 to B4 in Table 1, the filling process P1, the exhaust process P2, the first one-sided heating process P3, the second one-sided heating process P4, the main heating process P5, and the cooling process P7 are performed, and a molded body is produced without performing the pressure holding process P6. In condition numbers B1 and B2, the steam amount Wa in the first one-sided heating process P3 and the steam amount Wb in the second one-sided heating process P4 are changed from the reference conditions. Also, in condition number B3, the steam amount Wa in the first one-sided heating process P3 and the steam amount Wb in the second one-sided heating process P4 are changed from the reference conditions. Further, in condition number B4, the steam amount Wa in the first one-sided heating process P3, the steam amount Wb in the second one-sided heating process P4, and the steam amount Wm in the main heating process P5 are changed from the reference conditions.

[0086] The fusion rate of the molded body obtained by performing in-mold molding under each molding condition is as shown in Table 1. In the "Fusion rate difference X1 - X2" column of Table 1, the value obtained by subtracting the fusion rate of the molded body under each molding condition from the fusion rate of the molded body under the reference conditions is described. In the "Requirement 1: Pa2 / Pa1" column, the ratio value of the steam pressure Pa2 of the steam supplied in the first one-sided heating process P3 under each of condition numbers B1 to B4 to the steam pressure Pa1 of the steam supplied in the first one-sided heating process P3 under the reference conditions is described. In the "Requirement 2: Wa2 < Wa1" column, "OK" is described when the steam amount Wa2 used in the first one-sided heating process P3 under each of condition numbers B1 to B4 is less than the steam amount Wa1 in the first one-sided heating process P3 under the reference conditions, and "NG" is described when it is Wa1 or more.

[0087] In the column of "Requirement 3: Pb2 / Pb1", the ratio values of the steam pressure Pb2 of the steam supplied in the second one-sided heating step P4 to the steam pressure Pb1 of the steam supplied in the second one-sided heating step P4 under the reference conditions for each of the condition numbers B1 to B4 were described. In the column of "Requirement 4: Wb2 < Wb1", when the steam amount Wb2 used in the second one-sided heating step P4 for each of the condition numbers B1 to B4 is less than the steam amount Wb1 used in the second one-sided heating step P4 under the reference conditions, "OK" was described, and when it is equal to or more than Wb1, "NG" was described. In the column of "Requirement 5: Pm2 / Pm1", the ratio values of the steam pressure Pm2 of the steam supplied in the main heating step P5 to the steam pressure Pm1 of the steam supplied in the main heating step P5 under the reference conditions for each of the condition numbers B1 to B4 were described.

[0088] In the column of "Requirement 6: Wm2 / Wm1", the ratio values of the steam amount Wm2 used in the main heating step P5 to the steam amount Wm1 used in the main heating step P5 under the reference conditions for each of the condition numbers B1 to B4 were described. In the column of "Requirement 7: W2 / W1", the ratio values of the total steam amount W2 to the total steam amount W1 under the reference conditions for each of the condition numbers B1 to B4 were described. In the column of "Requirement 8: Wm2 / Wa2", the ratio values of the steam amount Wm2 used in the main heating step P5 to the steam amount Wa2 used in the first one-sided heating step P3 for each of the condition numbers B1 to B4 were described.

[0089] As shown in Table 1, among the condition numbers B1 to B4, the molding conditions where the fusion rate X is 10% or more are condition number B1 and condition number B2. Therefore, in the steam reduction condition range derivation step S2, these two molding conditions were set as the steam reduction conditions, and the range including condition numbers B1 and B2 was set as the steam reduction condition range.

[0090] In the in-mold molding condition derivation step S3, among the steam reduction conditions derived in the steam reduction condition range step S2, a pressure dwell step P6 was added to condition number B2, which had the smallest total steam amount W2, to set three molding conditions shown as condition numbers C1 to C3 in Table 1. Then, under these three molding conditions, the filling step P1, the exhaust step P2, the first one-side heating step P3, the second one-side heating step P4, the main heating step P5, the pressure dwell step P6, and the cooling step P7 were performed to produce a molded body. Note that for condition numbers C1 to C3, in the pressure dwell step P6, the surface pressure was the maximum surface pressure F max The time it took for the pressure to reach -0.01 MPa (G) or more was measured and is shown in Table 1.

[0091] The fusion rate of the molded body obtained by performing molding in a mold under each molding condition is as shown in Table 1. As shown in Table 1, the condition numbers C1 to C3 are all the target fusion rate X T The molded body having the above fusion rate can be obtained. The total steam amount W under these molded molding conditions is smaller than the total steam amount W1 (i.e., 6.8 kg) under the standard conditions. Therefore, in the molded molding condition derivation step S3, condition numbers C1 to C3 were derived as the molded molding conditions.

[0092] [Table 1]

[0093] As described above, in the method for setting the in-mold molding conditions, the in-mold molding conditions are derived in three steps: in the step S1 for deriving the reference conditions, in the step S2 for deriving the range of steam-reducing conditions, a range of steam-reducing conditions that can produce a molded body with a smaller amount of steam than the reference conditions is derived, and in the step S3 for deriving the in-mold molding conditions, a pressure-holding step P6 is added to the steam-reducing conditions. By deriving the in-mold molding conditions in these three steps, it is possible to easily find in-mold molding conditions that can reduce the amount of steam used during in-mold molding while obtaining a foamed bead molding having a good fusion rate. In addition, according to the in-mold molding conditions obtained by the method for setting the in-mold molding conditions, it is possible to produce a molded body having a good fusion rate while reducing the amount of steam.

[0094] Furthermore, when the molding cycle was evaluated for in-mold molding under condition numbers C1 to C3, the times required from the start of mold clamping to demolding under these molding conditions were 152 seconds, 161 seconds, and 157 seconds, respectively. From these results, it was found that condition numbers C1 to C3, which were derived as in-mold molding conditions, can perform in-mold molding in a molding cycle that is faster than condition number A2, which was used as the reference condition, and are therefore superior in productivity.

[0095] Comparative Example 1 In this example, a method for setting in-mold molding conditions when molding conditions that do not perform the first one-side heating step P3 and the second one-side heating step P4 are derived as steam reduction conditions in the steam reduction condition derivation step S2 will be described. More specifically, in this example, the condition number B3 in Example 1, that is, the molding conditions that do not perform the first one-side heating step P3 and the second one-side heating step P4 and perform the main heating step P5, was set as the steam reduction condition. Then, in-mold molding was performed under molding conditions (Table 2, condition numbers D1 to D2) in which the pressure holding step P6 was added to the steam reduction condition in the in-mold molding condition derivation step S3, and the fusion rate of the obtained molded body was measured. Table 2 shows the fusion rates of the molded bodies obtained by in-mold molding under condition numbers D1 to D2.

[0096] [Table 2]

[0097] As shown in Table 2, when the first one-way heating process P3 and the second one-way heating process P4 were not performed, even if the pressure holding process P6 was added after the main heating process P5, a molded body having the desired fusion rate could not be obtained.

[0098] Example 2 In this example, a method for setting molding conditions in a mold when a box-shaped molded body is produced using expanded polystyrene resin particles having a styrene-butyl acrylate copolymer as a base resin will be described. The base resin of the expanded particles used in this example is a styrene-butyl acrylate copolymer containing 0.5% by mass of a butyl acrylate component. The bulk ratio of the expanded particles is 60 times. The mold 1 in this example has a molding space 11 capable of producing a box-shaped molded body having dimensions of 550 mm in length, 350 mm in width, 110 mm in height, and 25 mm in thickness, and is configured so that the inner wall part on the first mold 2 side in the mold clamping direction corresponds to the bottom surface of the box-shaped molded body (i.e., the surface with a length of 550 mm and a width of 350 mm). The surface pressure gauge is provided near the center of the inner wall part of the first mold 2 when the first mold 2 is viewed from the second mold 3 along the mold clamping direction.

[0099] Using such expanded beads and molding die 1, step S1 of deriving standard conditions and step S2 of deriving steam reduction condition range were carried out in the same manner as in Example 1. The molding conditions (condition number E1 and condition numbers F1 to F3) under which in-mold molding was carried out in these steps are shown in Table 3. The target fusion rate X T was set at 90%.

[0100] As shown in Table 3, in this example, condition number E1 was used as the reference condition, and some of the steam heating conditions in the reference condition were changed to derive a steam reduction condition range including condition numbers F1 and F2. In addition, in the in-mold molding condition deriving step S3, a pressure dwell process P6 was added to condition number F2, which had the smallest total steam amount among condition numbers F1 and F2 shown in Table 3. As a result, two in-mold molding conditions, condition numbers G1 and G2 shown in Table 3, were derived.

[0101] [Table 3]

[0102] As shown in Table 3, according to the in-mold molding conditions (condition numbers G1 to G2) derived in this example, the target fusion rate X can be achieved with a smaller total steam amount than the standard condition (condition number E1). T Molded articles having the above fusion rates could be obtained.

[0103] Furthermore, when the molding cycle was evaluated for in-mold molding under condition number E1 and condition numbers G1 to G2, the time required from the start of mold clamping to demolding under these molding conditions was 134 seconds, 141 seconds, and 115 seconds, respectively. From these results, it was found that condition numbers G1 to G2, which were derived as in-mold molding conditions, can perform in-mold molding with a molding cycle equal to or faster than condition number E1, which was used as the reference condition, and are therefore excellent in productivity.

[0104] Example 3 In this example, a method for setting molding conditions in a mold when producing a flat-plate-shaped molded body using expanded polystyrene resin beads with a styrene-acrylonitrile copolymer as the base resin is described. The base resin of the expanded beads used in this example is a styrene-acrylonitrile copolymer containing 26% by mass of an acrylonitrile component. The expanded beads have a bulk ratio of 60 times. The mold 1 has a molding space 11 capable of producing a flat-plate-shaped molded body having dimensions of 1000 mm in length, 600 mm in width, and 25 mm in thickness.

[0105] Using such expanded beads and mold 1, the reference condition derivation step S1 and the steam reduction condition range derivation step S2 were carried out in the same manner as in Example 1. The molding conditions (condition numbers H1 to H3 and condition numbers I1 to I2) under which in-mold molding was carried out in these steps are shown in Table 4. The target fusion rate X T was set at 80%.

[0106] As shown in Table 4, in this example, condition number H2 was set as the reference condition, and a steam reduction condition range including condition number I1 was derived by changing some of the steam heating conditions of the reference condition. In step S3 of deriving in-mold molding conditions in this example, a pressure dwell process P6 was added to condition number I1 shown in Table 4. As a result, condition number J1 shown in Table 4 was derived as the in-mold molding condition.

[0107] [Table 4]

[0108] As shown in Table 4, according to the in-mold molding conditions (condition number J1) derived in this example, the target fusion rate X was achieved with a smaller total steam amount than the standard condition (condition number H2). T Molded articles having the above fusion rates could be obtained.

[0109] Furthermore, when the molding cycle was evaluated for in-mold molding under condition numbers H2 and J1, the time required from the start of mold clamping to demolding was 218 seconds and 125 seconds, respectively. From these results, it was found that the in-mold molding condition under condition number J1 allows for in-mold molding with a faster molding cycle than the standard condition under condition number H2, and is therefore superior in productivity.

[0110] From the above results, it can be seen that in Examples 2 and 3 as well, by deriving the in-mold molding conditions in the three steps described above, it is possible to easily find in-mold molding conditions that enable a reduction in the amount of steam used during in-mold molding without impairing the physical properties of the foamed bead molding, as in Example 1.

[0111] Comparative Example 2 In this example, a method for setting the in-mold molding conditions when molding conditions under which the fusion between the expanded beads is insufficient are adopted as the steam-reduced conditions is described. More specifically, in this example, the steam-reduced conditions were the condition number I2 in Example 3, that is, the molding conditions under which the fusion rate of the molded body is less than 10%. Then, in the in-mold molding condition derivation step S3, in-mold molding was performed under molding conditions (Table 5, condition numbers K1 to K2) in which a pressure-holding process P6 was added to the steam-reduced conditions, and the fusion rate of the obtained molded body was measured. Table 5 shows the fusion rates of the molded bodies obtained by in-mold molding under condition numbers K1 to K2.

[0112] [Table 5]

[0113] As shown in Table 5, when molding conditions that resulted in insufficient fusion between the foamed particles were adopted as steam reduction conditions, even if the pressure holding process P6 was added to those molding conditions, a molded body having the desired fusion rate could not be obtained.

[0114] The above describes the method for setting the in-mold molding conditions for the expanded bead molding product of the present invention and the method for producing the expanded bead molding product based on Examples 1 to 3. However, the specific aspects of the method for setting the in-mold molding conditions for the expanded bead molding product of the present invention and the method for producing the expanded bead molding product are not limited to those described in the examples, and the configurations can be changed as appropriate within the scope of the present invention. [Explanation of symbols]

[0115] 1 mold 11 Molding space 2. First Type 3. Second Type

Claims

1. A molding die including a first die and a second die configured to be able to form a molding space between the first die and the second die is used, and a method including a first one-way heating step of supplying steam from the first die side to the molding space to heat the expanded beads in the molding space, a second one-way heating step of supplying steam from the second die side to the molding space after the first one-way heating step to heat the expanded beads in the molding space, a main heating step of supplying steam from both the first die side and the second die side to the molding space after the second one-way heating step to heat the expanded beads in the molding space, and a pressure holding step of holding the steam supplied in the main heating step in the molding die to mold the expanded polystyrene resin beads into an X-ray tube. Ｔ A method for setting in-mold molding conditions for an expanded bead molding product in order to obtain an expanded bead molding product having a fusion rate of [%] or more, comprising the steps of: The setting method includes a reference condition deriving step, a steam reduction condition range deriving step, and an in-mold molding condition deriving step, In the step of deriving the reference condition, the steam pressure and the amount of steam in the first one-way heating step, the steam pressure and the amount of steam in the second one-way heating step, and the steam pressure and the amount of steam in the main heating step are included as steam heating conditions, and a fusion rate X １ [%] is X Ｔ The molding conditions under which an expanded bead molding product can be produced having a particle size of 100 [%] or more are derived as reference conditions, In the steam reduction condition range derivation step, at least a part of the steam heating conditions of the standard conditions is changed so that a total steam amount, which is a sum of the steam amount in the first one-way heating step, the steam amount in the second one-way heating step, and the steam amount in the main heating step, is less than the total steam amount in the standard conditions, and a fusion rate X of 10% or more is achieved without substantially performing a pressure retention step. ２ A range of steam reduction conditions, which is a molding condition under which an expanded bead molding having the steam reduction ratio of 0.01 to 0.01, can be obtained as the steam reduction condition range. In the in-mold molding condition derivation step, the first one-way heating step, the second one-way heating step, and the main heating step under each steam reduction condition derived in the steam reduction condition range derivation step are determined. Ｔ A pressure holding step is added so that the pressure holding time is longer than the pressure holding time under the steam reduction condition, and the fusion rate is X Ｔ The method for determining in-mold molding conditions for an expanded bead molding product derives a range of molding conditions that allows the production of an expanded bead molding product having a molecular weight of 100 [%] or more as the in-mold molding conditions.

2. The steam reduction conditions are: Requirement 1: Steam pressure Pa in the first one-way heating step under the steam reduction condition ２ [MPa (G)] is the steam pressure Pa in the first one-way heating step under the reference conditions. １ [MPa (G)] is 0.7 times or more and 1.3 times or less, Requirement 2: The amount of steam Wa in the first one-way heating step under the steam reduction condition ２ [kg] is the amount of steam Wa in the first one-way heating step under the reference conditions １ Requirement 3: The steam pressure Pb in the second one-way heating step under the steam reduction condition is less than [kg]. ２ [MPa (G)] is the steam pressure Pb in the second one-way heating step under the reference conditions. １ [MPa (G)] is 0.7 times or more and 1.3 times or less; and Requirement 4: The amount of steam Wb in the second one-way heating step under the steam reduction condition ２ [kg] is the amount of steam Wb in the second one-way heating step under the reference conditions １ 2. The method for setting the in-mold molding conditions for the foamed bead molding product according to claim 1 , wherein the in-mold molding conditions satisfy the four requirements:

3. The steam reduction conditions are the fusion rate X of the foamed bead molding obtained by in-mold molding under the standard conditions. １ [%] and the fusion rate X of the foamed bead molding obtained by molding in a mold under the steam reduction condition. ２ Difference from [%] X １ -X ２3. The method for setting in-mold molding conditions for an expanded bead molding product according to claim 1 or 2, wherein the in-mold molding conditions are set so that the ratio of the in-mold molding conditions to the in-mold molding conditions is 5% or more and 70% or less.

4. The steam reduction conditions are: Requirement 5: Steam pressure Pm in the main heating step under the steam reduction conditions ２ [MPa (G)] is the steam pressure Pm of the main heating step under the reference conditions. １ [MPa (G)] is 0.7 times or more and 1.3 times or less; and Requirement 6: The amount of steam Wm in the main heating step under the steam reduction conditions ２ [kg] is the amount of steam Wm in the main heating step under the standard conditions １ 3. The method for setting the in-mold molding conditions for the foamed bead molding product according to claim 1 or 2, wherein the in-mold molding conditions satisfy two requirements:

5. The steam reduction conditions are:

3. The method for setting in-mold molding conditions for an expanded bead molding product according to claim 1 or 2, wherein the following requirement is satisfied: Requirement 7: The total steam amount [kg] under the reduced steam conditions is 0.8 times or less the total steam amount [kg] under the standard conditions.

6. The steam reduction conditions are: Requirement 8: The amount of steam Wm in the main heating step under the steam reduction condition ２ [kg] is the amount of steam Wa in the first one-way heating step under the steam reduction condition ２ 3. The method for setting the in-mold molding conditions for the foamed bead molding product according to claim 1 or 2, wherein the in-mold molding conditions satisfy the requirement that the in-mold molding conditions are 0.8 to 4 times the mass [kg] of the foamed bead molding product.

7. A method for producing an expanded bead molding, comprising molding expanded polystyrene resin beads in a mold under in-mold molding conditions set by using the method for setting in-mold molding conditions for an expanded bead molding according to claim 1 or 2 to produce an expanded bead molding.

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