Method for manufacturing a laminate

Abstract

The present invention relates to a method for producing a laminated body, wherein the laminated body is obtained by laminating and integrating a foamed bead molded body a having interconnected voids composed of foamed particles A and a foamed bead molded body b having interconnected voids composed of foamed particles B. The void ratio (P) of the foamed bead molded body a is a ) and the porosity of the expanded particle molded body b (P b ) difference [P b ‑P a ] is 5% or more, and the expanded particles A and the expanded particles B meet the following conditions (1) to (3): (1) The average pore size d of the through-holes of the expanded particles A A The average pore diameter d of the through-holes of the expanded particles B is B The difference [d B ‑d A ] is 0.3 mm or more and 2 mm or less; (2) the average outer diameter D of the expanded particles B B 3.5 mm or more and 5 mm or less; (3) the average outer diameter D of the expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B ‑D A ] is greater than 0.3mm and less than 2mm.

Description

Technical Field

[0001] The present invention relates to a method for producing a laminate. Background Art

[0002] Conventionally, it is known to produce a laminated body by integrally molding a laminate of raw materials having different physical properties in order to obtain desired characteristics.

[0003] For example, Patent Document 1 discloses a thermoplastic resin in-mold molded body characterized by a non-uniform porosity within the molded body. Patent Document 1 states that by making the porosity within a molded body non-uniform, a molded body can be stably and economically obtained that has porosity-dependent properties such as water permeability, air permeability, and sound absorption, and that is resistant to peeling and cracking while maintaining mechanical strength.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-240286 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] However, the thermoplastic resin in-mold molded article described in Patent Document 1 uses rod-shaped pre-expanded particles with a large aspect ratio L / D, resulting in a high porosity, and thus has a technical problem of insufficient mechanical strength. Furthermore, when manufacturing a laminated body comprising multiple layers having different porosities (hereinafter also referred to as a laminated body having a porosity difference) by integral molding, there is a technical problem of difficulty in controlling the porosity of each layer.

[0009] The present invention has been made in view of the above-mentioned technical problems, and an object of the present invention is to provide a method for producing a laminated body that can easily obtain a laminated body having excellent mechanical strength and a desired porosity difference under a wide range of molding conditions.

[0010] Solutions for solving the above technical problems

[0011] The present inventors have diligently studied and found that the above-mentioned technical problems can be solved by adopting the following configuration, thereby completing the present invention.

[0012] That is, the present invention is as follows.

[0013] [1] A method for producing a laminated body, wherein the laminated body is produced by integrally molding a cylindrical thermoplastic resin foamed particle A having through holes and an aspect ratio L / D of less than 2 and a cylindrical thermoplastic resin foamed particle B having through holes and an aspect ratio L / D of less than 2, wherein the laminated body is obtained by laminating and integrating a foamed particle molded body a having interconnected voids composed of the foamed particles A and a foamed particle molded body b having interconnected voids composed of the foamed particles B, wherein the void ratio (P) of the foamed particle molded body a is less than 0. a ) and the porosity (P b ) difference [P b -P a ] is 5% or more, and the foamed particles A and the foamed particles B meet the following conditions (1) to (3).

[0014] (1) The average pore diameter d of the through-holes of the expanded particles A A The average pore size d of the through-holes of the expanded particles B is B The difference [d B -d A ] is 0.3mm or more and 2mm or less;

[0015] (2) The average outer diameter D of the expanded particles B B 3.5mm or more and 5mm or less;

[0016] (3) The average outer diameter D of the expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B -D A ] is greater than -0.3mm and less than 2mm.

[0017] [2] The method for producing a laminate according to [1] above, wherein the average pore diameter d of the through-pores of the expanded particles A is A It is not less than 0.5mm and not more than 2mm.

[0018] [3] The method for producing a laminate according to [1] or [2], wherein the average pore diameter d of the through-pores of the foamed particles B is B It is more than 2mm and less than 3mm.

[0019] [4] The method for producing a laminate according to any one of [1] to [3] above, wherein the average outer diameter D of the expanded particles A is A The average outer diameter D of the expanded particles A is 2 mm or more and 4.5 mm or less. A The average outer diameter D of the expanded particles B B The difference [D B -D A] is greater than 0.1mm and less than 2mm.

[0020] [5] The method for producing a laminate according to any one of [1] to [4] above, wherein the average pore diameter d of the through-pores of the expanded particles A is A The average pore size d of the through-holes of the expanded particles B is B The difference [d B -d A ](x), the average outer diameter D of the expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B -D A ](y) satisfies the following formula (1):

[0021] 0.6≤x+y≤2.2…Formula (1).

[0022] [6] The method for producing a laminate according to any one of [1] to [5] above, wherein the average pore size d of the expanded particles A is A Relative to the average outer diameter D of the expanded particles A A The ratio of [d A / D A ] is less than 0.3.

[0023] [7] A method for manufacturing a laminate as described in any one of [1] to [6] above, wherein the ratio of the apparent density of the foamed particles A to the volume density of the foamed particles A is greater than 1.7 and less than 2.3, and the ratio of the apparent density of the foamed particles B to the volume density of the foamed particles B is greater than 2.3 and less than 3.0.

[0024] [8] The method for producing a laminate according to any one of [1] to [7] above, wherein the expanded particles A are polyolefin resin expanded particles, and the expanded particles B are polyolefin resin expanded particles.

[0025] [9] The method for producing a laminate as described in any one of [1] to [8] above, wherein the foamed particles A are composed of a polyolefin resin foamed core layer and a polyolefin resin covering layer covering the foamed core layer.

[0026]

[10] A method for manufacturing a laminate as described in any one of [1] to [9] above, wherein the foamed particles B are composed of a polyolefin resin foam core layer and a polyolefin resin coating layer coating the foam core layer, and the bending elastic modulus of the polyolefin resin constituting the foam core layer is not less than 1000 MPa and not more than 1500 MPa.

[0027]

[11] The method for producing a laminate according to any one of [1] to

[10] , wherein the volume (Va ) and the volume of the expanded particle molded body b (V b ) ratio [V a ∶V b ] is 80:20~10:90.

[0028] Effects of the Invention

[0029] According to the present invention, a method for producing a laminated body can be provided, which can easily produce a laminated body having excellent mechanical strength and having a porosity difference of, for example, 5% or more under a wide range of molding conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram showing the appearance of an example of the cylindrical expanded beads having through-holes of the present invention.

[0031] Figure 2 This is a schematic diagram showing the appearance of an example of the cylindrical expanded beads having through-holes of the present invention. DETAILED DESCRIPTION

[0032] [Method for producing laminate]

[0033] In the method for producing a laminate of the present invention (hereinafter also referred to as the "method for producing a laminate"), the laminate is produced by integrally molding cylindrical thermoplastic resin expanded particles A (hereinafter also referred to as "expanded particles A") having through-holes and an aspect ratio L / D of less than 2, and cylindrical thermoplastic resin expanded particles B (hereinafter also referred to as "expanded particles B") having through-holes and an aspect ratio L / D of less than 2. The laminate is obtained by laminating and integrating an expanded particle molded body a having interconnected voids composed of the expanded particles A and an expanded particle molded body b having interconnected voids composed of the expanded particles B. The void ratio (P) of the expanded particle molded body a is 0.01%. a ) and the porosity (P b ) difference [P b -P a ] is 5% or more, and the foamed particles A and the foamed particles B meet the following conditions (1) to (3).

[0034] (1) The average pore diameter d of the through-holes of the expanded particles A A The average pore size d of the through-holes of the expanded particles B is B The difference [d B -d A ] is 0.3mm or more and 2mm or less;

[0035] (2) The average outer diameter D of the expanded particles B B 3.5mm or more and 5mm or less;

[0036] (3) The average outer diameter D of the expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B -D A ] is greater than -0.3mm and less than 2mm.

[0037] In this specification, “X to Y” indicating a numerical range is synonymous with “X or more and Y or less” and indicates a numerical range including X and Y as endpoints of the numerical range.

[0038] The method for producing a laminate of the present invention facilitates the production of a laminate comprising an integrated expanded bead molded article A and an integrated expanded bead molded article B having a desired porosity difference by integrally molding expanded beads A and expanded bead molded article B. Furthermore, the method for producing a laminate of the present invention utilizes expanded beads having an aspect ratio L / D of less than 2, resulting in a laminate having excellent mechanical strength, such as flexural strength.

[0039] Specifically, the method for producing a laminate of the present invention includes, for example, at least the following steps (1) to (3), wherein a laminate is produced by laminating and integrating an expanded bead molded article a and an expanded bead molded article b. The order of steps (1) and (2) is not particularly limited; step (2) may be performed after step (1), or step (1) may be performed after step (2).

[0040] Step (1): a step of filling a forming mold with the expanded particles A;

[0041] Step (2): a step of filling the forming mold with the expanded particles B; and

[0042] Step (3): A main heating step of supplying a heating medium to heat the expanded particles A and the expanded particles B integrally.

[0043] <Steps (1) and (2)>

[0044] In step (1), for example, the mold can be opened to fill the mold with expanded beads A. In step (2), the mold can also be filled with expanded beads B in the same manner as in step (1).

[0045] <Process (3)>

[0046] In step (3), for example, after closing the forming mold, a heating medium such as steam is supplied to the expanded particles A and expanded particles B filled in a layered manner, thereby heating the expanded particles A and expanded particles B integrally, causing the expanded particles A and expanded particles B to undergo secondary foaming and fuse to each other. This allows the expanded particle molded body a, in which the expanded particles A are fused to each other and have interconnected voids, and the expanded particle molded body b, in which the expanded particles B are fused to each other and have interconnected voids, to be laminated and integrated. At this time, the expanded particle molded body a and the expanded particle molded body b are shaped into the shapes of their respective forming spaces, and the expanded particles A and the expanded particles B are fused to each other at the interface between the expanded particle molded body a and the expanded particle molded body b.

[0047] In step (3), the pressure of the steam supplied (integrated molding pressure) can be appropriately varied depending on the base resin of the expanded particles A and B described later, but is preferably 0.12 MPa(G) or higher, more preferably 0.16 MPa(G) or higher, and preferably 0.24 MPa(G) or lower, more preferably 0.22 MPa(G) or lower. In this specification, the unit [MPa(G)] refers to gauge pressure. Gauge pressure is the value obtained by subtracting atmospheric pressure from absolute pressure.

[0048] <Step (4)>

[0049] From the viewpoint of making it easier to manufacture the laminate, the method for manufacturing the laminate of the present invention preferably further includes a temporary welding step (step (4)), in which, after performing either step (1) or step (2), that is, after either the expanded particles A or the expanded particles B are filled into the forming mold, a heating medium is supplied to temporarily weld the expanded particles previously filled. In step (4), the pressure of the steam supplied (first layer molding pressure) is lower than the pressure of the steam in step (3), preferably 0.08 MPa (G) or more, more preferably 0.10 MPa (G) or more, and preferably 0.16 MPa (G) or less, more preferably 0.14 MPa (G) or less. In addition, temporary welding means that the expanded particles are welded to each other in a state where there is a gap between them, taking into account the passage of the heating medium supplied later, and preferably formed into a popcorn shape.

[0050] When the method for manufacturing a laminate includes step (4), it is preferred that any one of steps (1) or (2) is performed continuously with step (4). In addition, the forming mold used at this time may also be different from the forming mold used in step (3). That is, the foamed particles A or B temporarily welded by step (4) may be separately filled into the forming mold used in step (3) to perform step (3). However, from the viewpoint of excellent productivity, the method for manufacturing a laminate of the present invention preferably includes all steps (1) to (4), and all steps are performed continuously by one forming mold.

[0051] As a method for filling the expanded particles into the forming mold in steps (1) and (2), a known method can be adopted. For example, within a range that does not excessively increase the secondary foaming force of the expanded particles, the following methods can be adopted: a method in which the expanded particles are pressurized with pressurized gas, a predetermined internal pressure is applied to the bubbles of the expanded particles, and then the particles are filled into the mold (a pressurized filling method); a method in which the expanded particles are compressed by the pressurized gas, and then the pressure in the mold is released (a compression filling method); a method in which the mold is opened before filling the expanded particles into the mold to expand the forming space, and the mold is closed after filling to mechanically compress the expanded particles (a crack filling method), etc.

[0052] Generally, when a laminated body formed by stacking different types of expanded particle molded bodies by integral molding is manufactured, the porosity of the obtained expanded particle molded body tends to be lower than that of a single-layer expanded particle molded body composed of a single expanded particle. In addition, it is not easy to manufacture a laminated body with a desired porosity difference, and the porosity difference tends to become smaller. The reason is that the total amount of heat of the heating medium supplied to the expanded particles tends to increase, or the molding pressure tends to vary. According to the manufacturing method of the present invention, by making the expanded particles A and the expanded particles B satisfy a specific relationship, a laminated body with excellent mechanical strength and a desired porosity difference can be easily obtained under a wider range of molding conditions. Specifically, the manufacturing method of the present invention can freely select the order of the above-mentioned steps (1) and (2), and can manufacture a laminated body with a desired porosity difference in a wider range of molding pressures.

[0053] <Laminate>

[0054] (Total thickness)

[0055] The total thickness of the laminate can be appropriately changed according to the use of the laminate, and is preferably 20 mm or more, more preferably 30 mm or more, and even more preferably 40 mm or more, and is preferably 500 mm or less, more preferably 450 mm or less, and even more preferably 400 mm or less.

[0056] (density)

[0057] From the viewpoint of achieving an excellent balance between lightness and mechanical strength, the density of the laminate is preferably 10 kg / m 3 More than 15 kg / m 3 More than 20 kg / m 3 Above, and preferably 150kg / m 3 Below, more preferably 100 kg / m 3Below, more preferably 50kg / m 3 The density of the laminate can be calculated by dividing the mass of the laminate by the volume of the laminate and converting the unit to [kg / m 3 ] to obtain. In addition, the volume of the stacked body can be obtained by a method of obtaining it by calculation based on its external dimensions, a method of obtaining it by 3D scanning, or the like.

[0058] <Expanded Bead Molded Body a>

[0059] The expanded bead molded article a is composed of thermoplastic resin expanded beads A and has interconnected voids.

[0060] The void ratio of the expanded particle molded body a (P a ) as long as the void ratio (P b ) is not particularly limited, but is preferably 5% or more, more preferably 7% or more, even more preferably 10% or more, particularly preferably 12% or more, and is preferably 20% or less, more preferably 17% or less. By setting the porosity of the expanded bead molded article a within the above range, the characteristics of a molded article having voids are utilized, and a laminate having an excellent appearance is obtained.

[0061] The interconnected voids in the expanded bead molded article a are composed of voids between the expanded beads constituting the expanded bead molded article a and voids formed by through-holes in the expanded beads constituting the expanded bead molded article a.

[0062] The voidage of the expanded particle molded body a can be measured, for example, by the following method. First, a rectangular parallelepiped test piece is cut out from the center portion of the expanded particle molded body a. The test piece is sunk into a graduated cylinder filled with ethanol, and the true volume Vc[L] of the test piece is obtained based on the rising portion of the liquid level of ethanol. In addition, the apparent volume Vd[L] is obtained based on the outer dimensions of the test piece. The voidage of the expanded particle molded body a can be obtained by the following formula (2) based on the true volume Vc and apparent volume Vd obtained.

[0063] Void ratio (%) = [(Vd-Vc) / Vd] × 100 (2)

[0064] The thickness of the expanded particle molded body a (H a ) can be appropriately changed according to the purpose of the laminate, but from the viewpoint of maintaining the sound absorption and other properties of the laminate and improving the mechanical strength, it is preferably 10 mm or more, more preferably 15 mm or more, further preferably 20 mm or more, further preferably 25 mm or more, and is preferably 100 mm or less, more preferably 80 mm or less, further preferably 60 mm or less, further preferably 40 mm or less.

[0065] The thickness of the expanded bead molded article a can be determined by cutting the expanded bead molded article a from the laminate to determine its volume, dividing the volume of the expanded bead molded article a by the projected area of the expanded bead molded article a when viewed from above, and converting the unit to [mm].

[0066] (Thermoplastic resin expanded particles A)

[0067] The thermoplastic resin expanded particles A have through-holes, an aspect ratio L / D of less than 2, and a cylindrical shape. If the expanded particles A do not have through-holes and / or have an aspect ratio of 2 or more, it is difficult to obtain a laminate that achieves both desired porosity and mechanical strength.

[0068] Aspect Ratio L / D

[0069] From the viewpoint of improving mechanical strength, the aspect ratio L / D of the expanded beads A is preferably 1.7 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. The lower limit thereof is not particularly limited but is generally 0.8.

[0070] The aspect ratio L / D of the foamed particle A is obtained by measuring the maximum length (L) and the maximum cross-sectional diameter (D) of the cross section of 100 randomly selected foamed particles A using a vernier caliper, etc., calculating the ratio (L / D), and taking the arithmetic average of these values.

[0071] The average pore diameter of the through hole d A 》

[0072] The average pore diameter d of the through-holes of the expanded particles A A As long as the above-mentioned condition (1) is met, there is no special limitation. From the viewpoint of more easily manufacturing a laminate having a desired porosity difference and obtaining a laminate with a better surface appearance, it is preferably 0.5 mm or more, more preferably 0.6 mm or more, and preferably 2 mm or less, more preferably less than 1.5 mm, further preferably less than 1 mm, and further preferably 0.8 mm or less.

[0073] The average pore diameter d of the through-pores of the expanded particles A was determined as follows: A . For 50 or more foamed particles A randomly selected from the foamed particle group A, cut perpendicularly to the through-hole at the position where the cut surface has the largest area. Take a photo of the cut surface, find the cross-sectional area (opening area) of the through-hole portion, calculate the diameter of an imaginary circle having the same area as the area, and calculate the arithmetic average of these values as the average pore diameter d of the through-holes of the foamed particles A. A .

[0074] Average outer diameter DA 》

[0075] Average outer diameter D of expanded particles A A As long as the above condition (3) is met, there is no special limitation. From the viewpoint of making it easier to manufacture a laminate having excellent mechanical strength and a desired porosity difference, it is preferably 2 mm or more, more preferably 2.5 mm or more, further preferably 3 mm or more, and preferably 4.5 mm or less, more preferably 4.3 mm or less, further preferably 4 mm or less.

[0076] The average outer diameter D of the expanded particles A is determined as follows: A . For more than 50 foamed particles A randomly selected from the foamed particle A group, cut them perpendicularly to the through-hole at the position where the cut surface has the largest area. Take a photo of the cut surface, find the cross-sectional area of the foamed particle A (including the cross-sectional area of the opening of the through-hole), calculate the diameter of an imaginary circle with the same area as the area, and take the value obtained by arithmetic averaging as the average outer diameter D of the foamed particle A. A .

[0077] 《 A / D A ]》

[0078] From the viewpoint of more easily producing a laminate having a desired porosity difference and obtaining a laminate having a more excellent surface appearance, the average pore diameter d of the expanded particles A is A Relative to the average outer diameter D of expanded particles A A The ratio of [d A / D A ] is preferably 0.7 or less, more preferably 0.5 or less, further preferably 0.4 or less, further preferably 0.3 or less, and particularly preferably less than 0.25, and its lower limit is not particularly limited, but can be 0.1.

[0079] Apparent Density

[0080] From the viewpoint of easier production of a laminate having excellent mechanical strength and lightness, the apparent density of the expanded particles A is preferably 30 kg / m 3 More than 35kg / m 3 More than 40kg / m 3 More than, and preferably 200kg / m 3 Below, more preferably 150kg / m 3 Below, more preferably 100 kg / m 3 Below, more preferably 80kg / m 3 the following.

[0081] The apparent density of the foamed particles A is determined as follows. First, the foamed particles A group is placed under the conditions of a relative humidity of 50%, 23°C, and 1 atm for 2 days. Next, a measuring cylinder filled with ethanol at 23°C is prepared, and an arbitrary amount of the foamed particles A group (mass W1 of the foamed particles A group) is sunk into the ethanol in the measuring cylinder using a metal mesh or other tool. Then, taking into account the volume of the metal mesh or other tool, the volume V1 [L] of the foamed particles A group read through the rising water level is measured. The unit is converted to [kg / m 3 ]Thus, the apparent density of the foamed particles A is calculated.

[0082] Volume Density

[0083] From the viewpoint of achieving a good balance between the mechanical strength and lightness of the obtained laminate, the bulk density of the expanded particles A is preferably 10 kg / m 3 More than 15 kg / m 3 More than 20 kg / m 3 Above, and preferably 150kg / m 3 Below, more preferably 100 kg / m 3 Below, more preferably 80kg / m 3 Below, more preferably 50kg / m 3 Below, particularly preferably 30kg / m 3 the following.

[0084] The bulk density of the expanded particles A is determined as follows. Randomly take expanded particles A from the group of expanded particles A and place them in a 1-liter graduated cylinder. A large number of expanded particles are placed in a naturally stacked state up to the 1-liter mark. The mass W2 [g] of the expanded particles is divided by the volume V2 (1 [L]), i.e., (W2 / V2), and the unit is converted to [kg / m 3 ], and the bulk density of the foamed particles A is calculated.

[0085] Apparent density / bulk density ratio

[0086] From the viewpoint of more easily producing a laminate having a desired porosity difference, the ratio of the apparent density of the foamed particles A to the bulk density of the foamed particles A (apparent density / bulk density) is preferably greater than 1.7 and preferably less than 2.5, more preferably less than 2.3.

[0087] Base resin

[0088] Examples of thermoplastic resins used as the base resin of the expanded particles A include polyolefin resins such as polystyrene resins, polyethylene resins, and polypropylene resins, polyester resins such as polyethylene terephthalate and polylactic acid, and polycarbonate resins. Among these, polyolefin resins are preferred, and polypropylene resins are more preferred from the perspective of mechanical strength. Specifically, the expanded particles A are preferably polyolefin resin expanded particles, and more preferably polypropylene resin expanded particles.

[0089] When the expanded particles A are formed as expanded particles of a multilayer structure as described later, the base resin of the expanded particles A refers to the resin constituting the expanded core layer.

[0090] When the base resin of the expanded particles A is a polypropylene resin, from the viewpoints of mechanical strength, etc., its flexural modulus is preferably 600 MPa or more, more preferably 800 MPa or more, and from the viewpoint of producing a good molded article even at a low molding pressure, it is preferably 1000 MPa or less. In addition, when the expanded particles A are composed of expanded particles of a multilayer structure described later, the polypropylene resin constituting the foam core layer preferably satisfies the above-mentioned flexural modulus.

[0091] The flexural modulus of a polypropylene resin can be determined by preparing a test piece (test piece dimensions: 80 mm in length, 10 mm in width, and 4 mm in thickness) in accordance with JIS K7171:2016. When the expanded particles A are configured as multilayer expanded particles described below, the polypropylene resin constituting the core layer preferably satisfies the aforementioned flexural modulus.

[0092] "constitute"

[0093] Here, Figure 1 and Figure 2 FIG. 1 is a schematic diagram showing an example of a cylindrical foamed particle having a through hole according to the present invention. Figure 1 The foamed particles 1 shown in FIG. 1 have through holes 3 that penetrate the foamed particles 1 and have a cylindrical shape. In addition, the foamed particles A may also be as follows Figure 2 The foamed particles 10 shown have through holes 3 and a multilayer structure including a cylindrical foamed core layer 5 and a covering layer 7 covering the foamed core layer 5 .

[0094] The expanded particles A are preferably Figure 2 The foamed particles 10 shown have a multilayer structure comprising a foamed polyolefin resin foam core layer 5 (hereinafter also referred to as the "foamed core layer") and a polyolefin resin covering layer 7 (hereinafter also referred to as the "covering layer") covering the foamed core layer 5.

[0095] From the viewpoint of the weldability of the expanded particles during the in-mold forming and the viewpoint of suppressing excessive secondary foaming to ensure the void ratio of the laminate, the coating layer preferably covers the substantially entire outer surface of the foaming core layer, more preferably covers the entire outer surface of the foaming core layer completely. In addition, in the scope that does not hinder the purpose effect of the present invention, the foaming core layer part that is not covered by the coating layer may also be present. From the same viewpoint, the coating layer is preferably in a non-foamed state or is in fact in a non-foamed state, more preferably in a non-foamed state. In addition, in the scope that does not hinder the purpose effect of the present invention, the coating layer may also slightly contain bubbles.

[0096] From the perspective of improving the weldability of the expanded particles and thereby facilitating the production of a laminate having excellent mechanical strength, the difference between the melting point (Tmc) of the expanded core layer and the melting point (Tms) of the covering layer [Tmc - Tms] is preferably greater than 0°C, more preferably 5°C or greater, and even more preferably 7°C or greater. Furthermore, from the perspective of suppressing delamination between the expanded core layer and the covering layer, the upper limit is preferably 20°C. The resin constituting the covering layer is preferably a polyolefin resin, more preferably a polypropylene resin.

[0097] From the viewpoint of improving the weldability of the expanded beads, the mass ratio of the cover layer to the expanded core layer (cover layer / expanded core layer) is preferably 0.5 / 99.5 to 20 / 80, more preferably 1 / 99 to 15 / 85, and even more preferably 3 / 97 to 10 / 90.

[0098] (Method for producing expanded particles A)

[0099] The expanded particles A can be produced, for example, by a method comprising the following steps (A) to (D): Here, an example of expanded particles having a multilayer structure consisting of an expanded core layer and a covering layer covering the expanded core layer will be described.

[0100] Step (A): a granulation step in which a base resin for constituting a foamed core layer and a resin for constituting a covering layer are melt-kneaded separately and co-extruded to obtain multilayered resin particles having through-pores, each comprising a non-foamed core layer and a covering layer covering the core layer;

[0101] Step (B): a dispersing step of dispersing the multilayered resin particles in a dispersion medium in a sealed container;

[0102] Step (C): an impregnation step of heating the substrate resin constituting the foamed core layer to a temperature above which the substrate resin softens, so that the multilayered resin particles are impregnated with the foaming agent;

[0103] Step (D): A foaming step in which the expandable multi-layered resin particles impregnated with a foaming agent are released from a sealed container together with a dispersion medium into an atmosphere having a pressure lower than the pressure in the sealed container, and at least the core layer is foamed to form a foamed core layer, thereby producing expanded particles.

[0104] Process (A)

[0105] In step (A), for example, an extruder having a core layer forming extruder, a coating layer forming extruder, and a multilayer wire harness forming die arranged on the outlet side of these extruders can be used. In the core layer forming extruder, a base material resin for constituting a foamed core layer and additives added as needed are melt-kneaded to form a core layer forming melt kneaded product. In the coating layer forming extruder, a resin for constituting a coating layer and additives added as needed are melt-kneaded to form a coating layer forming melt kneaded product. The core layer forming melt kneaded product and the coating layer forming melt kneaded product are introduced into a multilayer wire harness forming die so as to merge them, thereby forming a composite body having a core layer in a non-foamed state and a coating layer in a non-foamed state that covers the core layer, and a core-sheath structure. The composite is then extruded through a small hole in a die attached to the front end of the extruder into a cylindrical strand having through-holes. After cooling in water, it is cut into a predetermined mass using a pelletizer (strand cutting method). This yields multilayered resin particles comprising a cylindrical core layer having through-holes and a non-foamed state and a covering layer covering the core layer. In addition to the above methods, other methods for cutting the extruded composite include underwater cutting, where the composite is extruded in water, and thermal cutting, where the composite is extruded in air and then immediately cut.

[0106] In the multilayer resin particles composed of a core layer and a coating layer in a non-foamed state, additives such as bubble regulators, flame retardants, flame retardant aids, bubble nucleating agents, plasticizers, antistatic agents, antioxidants, UV inhibitors, light stabilizers, conductive fillers, and antibacterial agents can be added as needed. When adding additives, they can be added in step (A). Examples of bubble regulators include inorganic powders such as talc, mica, zinc borate, calcium carbonate, silica, titanium oxide, gypsum, zeolite, borax, aluminum hydroxide, and carbon; and organic powders such as phosphoric acid nucleating agents, phenol nucleating agents, amine nucleating agents, and polyvinyl fluoride resin powder. When adding a bubble regulator, the content of the bubble regulator in the multilayer resin particles is preferably 0.01 to 1 part by mass relative to 100 parts by mass of the multilayer resin particles.

[0107] Process (B)

[0108] In step (B), the multilayered resin particles can be dispersed in a dispersion medium using, for example, a stirrer in a hermetically sealable container such as an autoclave that can withstand heating and pressure.

[0109] The dispersion medium is not particularly limited as long as it does not dissolve the multilayered resin particles. Examples thereof include alcohols such as ethylene glycol, glycerin, methanol, and ethanol in addition to water, and water is preferred.

[0110] In step (B), a dispersant is preferably added to the dispersion medium to prevent fusion of the multilayered resin particles. Examples of dispersants include organic dispersants such as polyvinyl alcohol, polyvinyl pyrrolidone, and methylcellulose; and sparingly soluble inorganic salts such as aluminum oxide, zinc oxide, kaolin, mica, magnesium phosphate, and tricalcium phosphate. These can be used alone or in combination of two or more. Among these, sparingly soluble inorganic salts are preferred for ease of handling, and kaolin is more preferred.

[0111] A surfactant may be further added to the dispersion medium. Examples of the surfactant include sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium polyoxyethylene alkyl ether phosphate, sodium polyoxyethylene alkyl ether sulfate, and other anionic surfactants and nonionic surfactants commonly used in suspension polymerization.

[0112] Process (C)

[0113] In step (C), for example, the expandable multi-layered resin particles can be obtained by heating to a temperature at which the base resin constituting the foamed core layer softens or higher and impregnating the foaming agent.

[0114] The blowing agent is not particularly limited as long as it can foam the multilayered resin particles. Examples of blowing agents include inorganic physical blowing agents such as air, nitrogen, carbon dioxide, argon, helium, oxygen, and neon; aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, and n-hexane; alicyclic hydrocarbons such as cyclohexane and cyclopentane; halogenated hydrocarbons such as chlorofluoromethane, trifluoromethane, 1,1-difluoroethane, 1,1,1,2-tetrafluoroethane, chloromethane, chloroethane, and dichloromethane; and organic physical blowing agents such as dialkyl ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether. Among these, inorganic physical blowing agents that do not damage the ozone layer and are inexpensive are preferred, with nitrogen, air, and carbon dioxide being more preferred, and carbon dioxide being particularly preferred. These can be used alone or in combination of two or more.

[0115] The amount of the foaming agent blended can be determined in consideration of the desired apparent density of the foamed particles, the type of base resin, the type of foaming agent, etc., but it is generally preferred to use 5 to 50 parts by mass of an organic physical foaming agent, and preferably 0.5 to 30 parts by mass of an inorganic physical foaming agent, per 100 parts by mass of the multilayered resin particles.

[0116] The heating temperature in step (C) is preferably at least the melting point of the base resin and no more than 80°C above the melting point, specifically preferably 100°C to 230°C. The time for maintaining the heating temperature is preferably at least 1 minute, more preferably at least 20 minutes, and preferably no more than 100 minutes, more preferably no more than 60 minutes.

[0117] Furthermore, by adjusting the heating time and holding time, expanded particles having a crystal structure in which a melting peak inherent to the resin and one or more melting peaks (high temperature peaks) on the high temperature side thereof appear in the DSC curve obtained by differential scanning calorimetry (DSC) can be produced.

[0118] Process (D)

[0119] In step (D), for example, the expandable multi-layered resin particles impregnated with a foaming agent and heated in step (C) can be released from a sealed container into an atmosphere having a pressure lower than the pressure in the sealed container, and at least the core layer can be foamed to form a foamed core layer, thereby producing expanded particles.

[0120] Specifically, the pressure in the sealed container is maintained at a pressure greater than the vapor pressure of the foaming agent, and one end of the sealed container below the water surface is opened. The foamable multi-layered resin particles impregnated with the foaming agent are released from the sealed container together with the dispersion medium into an atmosphere having a pressure lower than the pressure in the sealed container, typically to atmospheric pressure, to foam at least the core layer of the foamable multi-layered resin particles to form a foamed core layer, thereby producing foamed particles. Alternatively, the foamable multi-layered resin particles after step (C) can be cooled and removed, and then heated with a heating medium such as hot air or steam to cause foaming, thereby producing foamed particles.

[0121] In step (D), the temperature during foaming is usually preferably 110° C. to 170° C. The pressure in the sealed container is preferably not less than the vapor pressure and not more than 5 MPa(G).

[0122] The above steps (B) to (D) are preferably performed as a series of steps in a single closed container. However, they can also be performed as separate steps by taking out the multilayered resin particles and the like in each step, putting them back into the closed container, and performing the next step.

[0123] In addition, especially when obtaining expanded particles with a lower apparent density, after the expanded particles are aged under atmospheric pressure as is usually done for them, the expanded particles are placed in a pressurizable sealed container, and a pressurized treatment is performed by pressing a pressurized gas such as air into the container to increase the internal pressure of the expanded particles. By heating the expanded particles in the container for a specified time using a heating medium such as steam, expanded particles with an even lower apparent density (secondary expanded particles) can be obtained.

[0124] <Expanded Bead Molded Body b>

[0125] The expanded bead molded article b is composed of expanded beads B and has interconnected voids.

[0126] The porosity of the expanded particle molded body b (P b) as long as the porosity (P a ) is not particularly limited as long as it is 5% or higher, but is preferably 10% or higher, more preferably 15% or higher, and even more preferably 20% or higher, and is preferably 50% or lower, more preferably 45% or lower, even more preferably 40% or lower, and even more preferably 35% or lower. By setting the porosity of the expanded bead molded article b within the above range, the mechanical strength of the laminate can be maintained, and the laminate can fully utilize the characteristics of the molded article having voids.

[0127] The void ratio of the expanded bead molded article b can be measured by the same method as that for measuring the void ratio of the expanded bead molded article a described above.

[0128] The interconnected voids in the expanded bead molded article b are composed of voids between the expanded beads constituting the expanded bead molded article b and voids formed by through-holes in the expanded beads constituting the expanded bead molded article b.

[0129] (Porosity of expanded bead molded article a (P a ) and the porosity of the expanded particle molded body b (P b )

[0130] The present invention relates to a method for producing a laminated body by integrally laminating and integrating expanded bead molded bodies (a) and (b) having interconnected voids. In particular, the method can easily produce a laminated body in which the porosity of expanded bead molded bodies (a) and (b) has a difference of at least a specific value. By achieving a sufficient difference between the porosity of expanded bead molded bodies (a) and (b) constituting the laminated body, the laminated body can exhibit sound absorption properties over a wide frequency range, and can easily balance properties such as air permeability and water permeability with mechanical strength, thereby promising various applications.

[0131] From the above viewpoints, the difference between the porosity of the expanded bead molded article a and the porosity of the expanded bead molded article b [porosity (P b )-Porosity (P a )] is 5% or more, preferably 6% or more, more preferably 7% or more. From the same point of view, the above difference [void ratio (P b )-Porosity (P a The upper limit of )] is preferably 30% or less, more preferably 25% or less, and further preferably 18% or less.

[0132] The thickness of the expanded particle molded body b (H b) can be appropriately changed according to the purpose of the laminate, but from the viewpoint of fully exerting the unique characteristics of the molded body with voids, such as sound absorption, it is preferably 10 mm or more, more preferably 15 mm or more, further preferably 20 mm or more, further preferably 25 mm or more, and is preferably 400 mm or less, more preferably 350 mm or less, further preferably 300 mm or less, further preferably 250 mm or less.

[0133] The thickness of the expanded bead molded article b can be measured by the same method as the thickness of the expanded bead molded article a.

[0134] In addition, from the viewpoint of balancing the properties unique to a molded article having voids, such as sound absorption, and mechanical strength, the thickness (H a ) and the thickness of the expanded particle molded body b (H b ) ratio [thickness (H a ):Thickness(H b )] is preferably 80:20 to 10:90, more preferably 70:30 to 20:80, and further preferably 60:40 to 30:70.

[0135] Similarly, from the viewpoint of the balance between the properties unique to a molded article having voids, such as sound absorption, and mechanical strength, the volume (V a ) and the volume of the expanded particle molded body b (V b ) ratio [volume (V a ):Volume(V b )] is preferably 80:20 to 10:90, more preferably 70:30 to 20:80, and further preferably 60:40 to 30:70.

[0136] The volumes of the expanded bead molded article a and the expanded bead molded article b can be obtained by cutting each of them from the laminate and calculating based on their outer dimensions, or by using 3D scanning.

[0137] (Thermoplastic resin expanded particles B)

[0138] The thermoplastic resin expanded particles B have through-holes, an aspect ratio L / D of less than 2, and a cylindrical shape. If the expanded particles B do not have through-holes and / or have an aspect ratio of 2 or more, it is difficult to obtain a laminate that achieves both desired porosity and mechanical strength.

[0139] Aspect Ratio L / D

[0140] From the viewpoint of mechanical strength, the aspect ratio L / D of the expanded beads B is preferably 1.7 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. The lower limit thereof is not particularly limited, but is 0.8.

[0141] The aspect ratio L / D of the expanded particles B is determined by the same method as the aspect ratio L / D of the expanded particles A.

[0142] The average pore diameter of the through hole d B 》

[0143] The average pore diameter d of the through-holes of the expanded particles B B There is no particular limitation as long as the above-mentioned condition (1) is met, but from the viewpoint of increasing the porosity of the foamed particle molding b and making it easier to produce a laminate having a desired porosity difference, it is preferably 2 mm or more, more preferably 2.2 mm or more, and preferably 3 mm or less, more preferably 2.8 mm or less, further preferably 2.6 mm or less, and further preferably 2.5 mm or less.

[0144] The average pore size d of the through-holes of the expanded particles A A The average pore diameter d of the through-holes of the foamed particles B was calculated in the same way. B .

[0145] The specific conditions (1) to (3) satisfied by the expanded particles A and B of the present invention are described in detail below. The present invention is a method for producing a laminated body. In a method for producing a laminated body by integrally molding, a laminated body is obtained by laminating and integrating expanded particle molded bodies a and b having interconnected voids. By integrally molding using two types of expanded particles satisfying the specific conditions (1) to (3), a laminated body having excellent mechanical strength and a desired porosity difference can be easily obtained under a wide range of molding conditions.

[0146] (1) Average pore diameter d of the through-holes of the expanded particles A A The average pore diameter d of the through-holes of the expanded particles B is B The difference [d B -d A ]》

[0147] The average pore diameter d of the through-holes of the expanded particles A A The average pore diameter d of the through-holes of the expanded particles B is B The difference [d B -d A ] is 0.3 mm or more and 2 mm or less. By making the average pore size d A and the average pore diameter d B The above-mentioned specific difference makes it possible to easily produce a laminate having a difference in porosity. In particular, by making the average pore size d of the expanded particles A A Smaller than the average pore size d of the expanded particles B B, even at a lower molding pressure, it is possible to form a foamed particle molding with low porosity. On the other hand, when using the above-mentioned difference [d B -d A ] When a laminate is manufactured by combining expanded particles with a diameter of less than 0.3 mm, there is a possibility that the laminate will have a small difference in porosity or a laminate with low mechanical strength.

[0148] From the viewpoint of more easily producing a laminate having excellent mechanical strength and a desired porosity difference, the above difference [d B -d A ] is preferably 0.5 mm or more, more preferably 0.7 mm or more, further preferably 1 mm or more, and particularly preferably 1.2 mm or more. In addition, from the viewpoint of maintaining the mechanical strength of the laminate, the above difference [d B -d A ] is preferably less than 1.8 mm.

[0149] 《(2) Average outer diameter D B 》

[0150] Average outer diameter D of expanded particles B B By making the average outer diameter D of the expanded particles B B Within the above range, the mechanical strength of the laminate can be maintained, and the decrease in the porosity of the expanded bead molded body b can be suppressed, and a laminate having a desired porosity difference can be easily produced. B It is preferably 3.7 mm or more and preferably 5 mm or less, more preferably 4.8 mm or less, further preferably 4.5 mm or less, and even more preferably 4.3 mm or less.

[0151] The average outer diameter D of the expanded particles A A Similarly, the average outer diameter D of the foamed particles B is calculated as B .

[0152] 《(3) Average outer diameter D of expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B -D A ]》

[0153] Average outer diameter D of expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B -D A] is not less than -0.3mm and not more than 2mm, preferably not less than 0.1mm, more preferably not less than 0.3mm, and preferably not more than 1.5mm, more preferably not more than 1.3mm, and further preferably not more than 1.0mm. By making the difference [D B -D A ] Within the above range, the filling properties of the expanded particles A and B into the forming mold can be controlled, and a laminate having a desired porosity difference can be easily produced.

[0154] From the viewpoint of controlling the difference in the void ratio of the laminate, it is preferred to appropriately control both the voids between the foamed particles constituting each foamed particle molded body and the voids formed by the through-holes possessed by the foamed particles constituting each foamed particle molded body. Specifically, the voids between the foamed particles constituting each foamed particle molded body can be adjusted mainly by the quality of the filling properties of the foamed particles. In addition, the voids formed by the through-holes possessed by the foamed particles constituting each foamed particle molded body can be adjusted mainly by the size of the pore size of the foamed particles. From such a viewpoint, and from the viewpoint of maintaining the mechanical strength of the laminate and more easily manufacturing a laminate having a desired void ratio difference, it is preferred that the foamed particles A and the foamed particles B satisfy the following formula (1).

[0155] 0.6≤x+y≤2.2…Formula (1)

[0156] Here, x is the difference [D B -D A ](mm), y is the difference [d B -d A ](mm).

[0157] From the viewpoint of more easily producing a laminate having a desired porosity difference, it is preferred that the average outer diameter D of the expanded particles A be A The average outer diameter D of the expanded particles A is 2 mm or more and 4.5 mm or less. A The average outer diameter D of the expanded particles B B The difference [D B -D A ] is greater than 0.1mm and less than 2mm.

[0158] 《 B / D B ]》

[0159] From the viewpoint of more easily producing a laminate having a desired porosity difference, the average pore diameter d of the expanded particles B is B Relative to the average outer diameter D of the expanded particles B B The ratio of [d B / D B] is preferably 0.3 or more, more preferably 0.5 or more, and is preferably 1.5 or less, more preferably 1.0 or less.

[0160] Apparent Density

[0161] From the viewpoint of more easily producing a laminate having a desired porosity difference, the apparent density of the expanded particles B is preferably 40 kg / m 3 More than 45kg / m 3 More than 50 kg / m 3 Above, and preferably 250kg / m 3 Below, more preferably 200kg / m 3 Below, more preferably 150kg / m 3 Below, more preferably 100kg / m 3 Below, more preferably 80kg / m 3 the following.

[0162] The apparent density of expanded particles B was determined by the same method as that for the apparent density of expanded particles A.

[0163] Volume Density

[0164] From the viewpoint of achieving a good balance between the mechanical strength and lightness of the obtained laminate, the bulk density of the expanded particles A is preferably 10 kg / m 3 More than 15 kg / m 3 More than 20 kg / m 3 More than, and preferably 200kg / m 3 Below, more preferably 150kg / m 3 Below, more preferably 100 kg / m 3 Below, more preferably 50kg / m 3 Below, more preferably 30kg / m 3 the following.

[0165] The bulk density of expanded particles B was determined by the same method as that for the bulk density of expanded particles A.

[0166] Apparent density / bulk density ratio

[0167] From the viewpoint of making it easier to produce a laminate having a desired porosity difference, the ratio of the apparent density of the foamed particles B to the bulk density of the foamed particles B (apparent density / bulk density) is preferably greater than 2.3, and preferably less than 3.0, more preferably less than 2.8, and further preferably less than 2.6.

[0168] Base resin

[0169] Examples of the base resin for expanded particles B include the same resins as for expanded particles A. Among them, the base resin for expanded particles B is preferably a polyolefin resin, more preferably a polypropylene resin. Specifically, expanded particles B are preferably polyolefin resin expanded particles, more preferably polypropylene resin expanded particles.

[0170] When the expanded particles B are formed as expanded particles of a multilayer structure as described later, the base resin of the expanded particles B refers to the resin constituting the core layer.

[0171] When the base resin of the expanded particles B is a polypropylene resin, from the perspective of improving the mechanical strength of the laminate and more easily producing a laminate having a desired porosity difference, the flexural modulus is preferably 600 MPa or greater, more preferably 800 MPa or greater, further preferably 1000 MPa or greater, particularly preferably 1200 MPa or greater, and preferably 1500 MPa or less. Furthermore, when the expanded particles B are formed into expanded particles of a multilayer structure described later, the polypropylene resin constituting the foam core layer preferably satisfies the above-mentioned flexural modulus.

[0172] In particular, if the flexural modulus of the base resin of expanded particles B is greater than that of the base resin of expanded particles A, the difference in the porosity of the resulting laminate can be increased, which is preferred. From this perspective, the flexural modulus of the base resin of expanded particles B is preferably greater than that of the base resin of expanded particles A by 100 MPa or more, more preferably by 200 MPa or more, and particularly preferably by 300 MPa or more. The upper limit of the difference in flexural modulus is approximately 800 MPa.

[0173] "constitute"

[0174] The expanded particles B may be Figure 1 The foamed particles 1 shown in FIG. 1 have through holes 3 penetrating the foamed particles 1 and have a cylindrical shape, and can also be as shown in FIG. Figure 2 The expanded particles 10 shown have through holes 3 and a multilayer structure including a cylindrical core layer 5 and a covering layer 7 covering the core layer 5 .

[0175] The expanded particles B are not particularly limited, but from the same viewpoint as the expanded particles A, they can be Figure 2 The expanded particles B are shown as consisting of a foamed core layer 5 and a covering layer 7 covering the foamed core layer 5. In this case, the expanded particles B can be produced by the same method as the expanded particles A.

[0176] Example

[0177] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0178] The following measurements or evaluations were performed on the resins, expanded beads, and expanded bead molded articles in Examples and Comparative Examples.

[0179] [Measurement method]

[0180] <Resin>

[0181] (Melt Flow Rate (MFR))

[0182] The MFR of the resin was measured in accordance with JIS K7210-1: 2014. In the case of polypropylene resin, the measurement conditions were a temperature of 230° C. and a load of 2.16 kg, and in the case of polyethylene resin, the measurement conditions were a temperature of 190° C. and a load of 2.16 kg.

[0183] (Melting Point)

[0184] The melting point of the resin is determined by adjusting the state of a test piece of approximately 3 mg using "(2) After a certain heat treatment, the melting temperature is measured" in accordance with JIS K7121:1987. The test piece is heated from 23°C to 200°C at a heating rate of 10°C / min, then cooled from 200°C to 30°C at a cooling rate of 10°C / min, and then heated from 30°C to 200°C at a heating rate of 10°C / min. A DSC curve is obtained, and the shape of the melting peak is observed. The peak temperature of the melting peak is defined as the melting point of the test piece. If multiple melting peaks appear in the DSC curve, the peak temperature of the melting peak with the largest area is defined as the melting point.

[0185] (Flexural modulus)

[0186] The flexural modulus of the resin was determined in accordance with JIS K7171:2016. A 4 mm thick sheet was prepared by hot pressing at 230°C, and a test piece measuring 80 mm in length, 10 mm in width, and 4 mm in thickness (standard test piece) was cut from the sheet. The indenter radius R1 and the support base radius R2 were both 5 mm, the distance between the fulcrums was 64 mm, and the test speed was 2 mm / min.

[0187] <Foaming Particles>

[0188] (Aspect ratio L / D)

[0189] The aspect ratio L / D of the foamed particles is obtained by measuring the maximum length (L) and the maximum cross-sectional diameter (D) of the cross section of 100 randomly selected foamed particles using a vernier caliper, etc., calculating the ratio (L / D), and taking the arithmetic average of the values.

[0190] (Average hole diameter)

[0191] The average pore diameter of the through-holes of the expanded particles is determined as follows: At least 50 expanded particles randomly selected from a group of expanded particles are cut perpendicularly to the through-holes at a position where the cut surface has the largest area. A photograph of the cut surface is taken. In the resulting cross-sectional photograph, the cross-sectional area (opening area) of the through-hole portion is determined. The diameter of a phantom circle having the same area as the calculated area is then calculated. The resulting arithmetic average of these values is used as the average pore diameter d of the through-holes of the expanded particles.

[0192] (Average outer diameter)

[0193] The average outer diameter of the expanded particles is determined as follows. At least 50 expanded particles randomly selected from the group of expanded particles are cut perpendicularly to the through-holes at the position where the cut surface has the largest area. A photograph of the cut surface is taken, and the cross-sectional area of the expanded particles A (including the cross-sectional area of the through-hole opening) is determined. The diameter of a phantom circle having the same area as this area is calculated, and the arithmetic average of these values is taken as the average outer diameter D of the expanded particles.

[0194] (Apparent density)

[0195] The apparent density of the foamed particles is determined as follows. The foamed particle group is placed under the conditions of a relative humidity of 50%, 23°C, and 1 atm for 2 days. Next, a measuring cylinder filled with ethanol at a temperature of 23°C is prepared, and an arbitrary amount of the foamed particle group (mass W1[g] of the foamed particle group) is sunk into the ethanol in the above-mentioned measuring cylinder using a metal mesh or other tool. Then, taking into account the volume of the metal mesh or other tool, the volume V1[L] of the foamed particle group read through the rising water level is measured. The unit is converted to [kg / m 3 ]Thus, the apparent density of the foamed particles is calculated.

[0196] (bulk density)

[0197] The bulk density of the expanded particles is determined as follows. Randomly take expanded particles from the expanded particle group and place them in a 1L graduated cylinder. A large number of expanded particles are placed in a naturally stacked state up to the 1L mark. The mass of the expanded particles W2 [g] is divided by the volume V2 (1 [L]), that is, (W2 / V2), and the unit is converted to [kg / m 3 ], and the volume density of the foamed particles is calculated.

[0198] (Average wall thickness)

[0199] The average wall thickness t of the expanded particles is calculated by the following formula (3).

[0200] Average wall thickness of expanded particles t = [(average outer diameter D of expanded particles) - (average pore diameter d of expanded particles)] / 2 (3)

[0201] (Heat of fusion of high temperature peak)

[0202] The heat of fusion of the high-temperature peak of the foamed particles is determined as follows. About 3 mg of foamed particles are collected and measured by a differential scanning calorimeter (DSC Q1000 manufactured by TA Instruments) at a temperature increase of 10°C / min from 23°C to 200°C to obtain a DSC curve having an endothermic peak (resin-specific peak) caused by the inherent melting of the polypropylene resin and one or more melting peaks (high-temperature peaks) appearing on its high-temperature side. In the following description, the resin-specific peak is referred to as A, and the high-temperature peak appearing on the higher-temperature side is referred to as B. Draw a straight line (α-β) connecting the point α corresponding to 80°C on the DSC curve and the point β on the DSC curve corresponding to the melting end temperature T of the foamed particles. In addition, the above-mentioned melting end temperature T refers to the intersection of the DSC curve on the high-temperature side of the high-temperature peak B and the high-temperature side baseline. Next, a straight line parallel to the vertical axis of the graph is drawn from point γ on the DSC curve corresponding to the valley between the resin-specific peak A and the high-temperature peak B. The point where this line intersects with the line (α-β) is designated as δ. The area of the high-temperature peak B is the area enclosed by the curve of the high-temperature peak B portion of the DSC curve, the line segment (δ-β), and the line segment (γ-δ), and this is taken as the heat of fusion of the high-temperature peak.

[0203] (Porosity of expanded particles (beads))

[0204] The bead void ratio was calculated by the following formula (4).

[0205] Bead void ratio (%) = open area of expanded particles / cross-sectional area of expanded particles × 100 (4)

[0206] In addition, the cross-sectional area of the expanded particles and the open area of the expanded particles are obtained together in the measurement of the average pore size of the through-holes of the expanded particles. Specifically, first, for more than 50 expanded particles randomly selected from the expanded particle group, the area of the cut surface is the largest at a position relative to the through-hole. A photo of the cut surface is taken, and the area of the cut surface of the expanded particles in the obtained cross-sectional photo (including the area of the opening portion of the through-hole) is obtained, and the value obtained by arithmetic average is used as the cross-sectional area of the expanded particles. In addition, the cross-sectional area of the through-hole portion is obtained in the obtained cross-sectional photo, and the value obtained by arithmetic average is used as the open area of the expanded particles.

[0207] <Foamed Bead Molded Article and Laminated Article>

[0208] (Thickness of Expanded Bead Molded Article a, Expanded Bead Molded Article b, and Laminated Article)

[0209] The thickness of the expanded particle molded article and the laminate was determined using the above method. Specifically, the volumes of the expanded particle molded article a, expanded particle molded article b, and the laminate were calculated based on their respective outer dimensions, and the resulting volumes were divided by their respective projected areas when viewed from above, and the thickness was converted to [mm].

[0210] (Porosity of Expanded Bead Molded Article)

[0211] The porosity of the foamed particle molded body a and the foamed particle molded body b is determined as follows. A rectangular test piece cut from the center of the foamed particle molded body a constituting the laminate is sunk into a graduated cylinder filled with ethanol, and the true volume Vc [L] of the test piece is determined based on the rising portion of the ethanol liquid level. In addition, the apparent volume Vd [L] is determined based on the outer dimensions of the test piece (length 25 mm × width 25 mm × height 100 mm). Based on the true volume Vc and the apparent volume Vd determined, the porosity of the foamed particle molded body a is determined by the following formula (2). The porosity of the foamed particle molded body b is also measured in the same manner.

[0212] Void ratio (%) = [(Vd-Vc) / Vd] × 100 (2)

[0213] (Density of laminate)

[0214] For the density of the laminate, the skin layer during molding was removed from the laminate, and three test pieces were randomly cut out in the form of a rectangular parallelepiped with a length of 25 mm, a width of 25 mm, and a thickness of 100 mm. The mass and volume of each test piece were measured, and the apparent density of the three test pieces was calculated. The arithmetic mean value was obtained as the density of the laminate.

[0215] (Maximum flexural strength of expanded bead molded article a)

[0216] The measurement was conducted in accordance with JIS K7221-2:2006, and the maximum point of the bending strength of the expanded bead molded article was measured as the maximum bending strength.

[0217] Specifically, a test piece measuring 120 mm in length, 25 mm in width, and 20 mm in thickness was cut from the center of the expanded bead molded article a in the thickness direction of the laminate, after removing the surface skin. Using this test piece, flexural strength was measured in accordance with JIS K7221-2:2006, except that the descent rate of the pressurizing wedge was set to 10 mm / min, the distance between the fulcrums was set to 100 mm, the radius of the front end of the support platform was set to 5 mm, and the radius of the front end of the pressurizing wedge was set to 5 mm.

[0218] If the maximum bending strength of the expanded bead molded article a in the laminate is low, the mechanical strength of the laminate as a whole will be reduced. In particular, when the ends of the expanded bead molded article a in the laminate are fixed, if an external force is applied from the expanded bead molded article b, there is a possibility that the expanded bead molded article a will crack.

[0219] [Evaluation method]

[0220] (Appearance of Laminated Body)

[0221] The appearance of the laminates of the Examples and Comparative Examples was evaluated as follows. Appearance was evaluated visually in a 200 mm x 200 mm area near the center of the expanded bead molded article a side of the laminate, viewed from above. Specifically, a sensory test was conducted by ten panelists skilled in the art using a five-point scale, with a score of 5 indicating sufficient transfer of the mold shape to the surface and a score of 1 indicating insufficient transfer. The scores were averaged and evaluated according to the following criteria.

[0222] A: The above average score is 3.5 points or above

[0223] B: The average score is 2.0 or higher and less than 3.5

[0224] C: The average score is less than 2.0

[0225] <Production of Expanded Beads and Expanded Bead Molded Articles>

[0226] Table 1 shows the main resins used to produce the expanded particles. The polypropylene resins PP1 and PP2 used as the base resins for the expanded particles are both ethylene-propylene random copolymers. The polypropylene resin PP3 used as the resin for forming the coating layer is an ethylene-propylene-butene random copolymer, and PE1 is a linear low-density polyethylene (LLDPE).

[0227] [Table 1]

[0228]

[0229] <Production of Expanded Beads>

[0230] Foaming particles 1~5

[0231] (Granulation process)

[0232] An extruder equipped with a core layer forming extruder, a cladding layer forming extruder, and a multilayer wire harness forming die located at the outlet of the extruder was used. The base resin constituting the foamed core layer, as listed in Table 2, was supplied to the core layer forming extruder and melt-kneaded to form a core layer forming melt-kneaded product. The resin constituting the cladding layer, as listed in Table 2 (the total of the resin constituting the core layer and the resin constituting the cladding layer was set to 100% by mass), was supplied to the cladding layer forming extruder and melt-kneaded to form a cladding layer forming melt-kneaded product. The core layer forming melt-kneaded product and the cladding layer forming melt-kneaded product were then introduced into a multilayer wire harness forming die and merged. A cylindrical wire harness having through holes (core layer: 95% by mass, cladding layer: 5% by mass) was extruded from a small hole in the die attached to the front end of the extruder. After water cooling, the pellets were cut using a pelletizer to a mass of approximately 1.5 mg and an aspect ratio (L / D) of 1. The pellets were then dried to obtain multilayer resin particles 1 having through holes. Furthermore, 1000 ppm of zinc borate as a cell control agent was added to the thermoplastic resin composition constituting the core layer based on 100 parts by mass of the multilayered resin particles.

[0233] (Dispersion process, impregnation process, foaming process)

[0234] In a 400 L sealed container equipped with a stirrer, 315 L of water as a dispersion medium, 115 kg of the obtained multilayered resin particles, 0.3 kg of kaolin as a dispersant, 0.03 kg of a surfactant (NEOGEN S-20F, sodium alkylbenzenesulfonate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 0.01 kg of aluminum sulfate as a dispersant were added. Carbon dioxide was then injected at a pressure of 0.20 MPa(G) (0.15 MPa(G) in the case of expanded beads 3) as a foaming agent. Subsequently, the temperature of the dispersion medium was raised to 148.5° C. while stirring and maintained for 6 minutes to produce expandable multilayered resin particles. Subsequently, the temperature of the dispersion medium was raised to 149° C. and maintained for 15 minutes. The sealed container was then opened while carbon dioxide was injected at a pressure of 0.32 MPa(G), and the expandable multilayered resin particles and the dispersion medium were released from the sealed container to atmospheric pressure to produce expandable particles having through-pores (primary expandable particles). The obtained expanded beads were aged at 23° C. for 24 hours under atmospheric pressure, and then their physical properties were measured. Table 2 shows the physical properties of the obtained expanded beads 1 to 5.

[0235] In the production of expanded beads 1 to 5, the outer and inner diameters of the multilayer strand forming mold were appropriately adjusted so that the physical properties of the obtained expanded beads became desired.

[0236] (Secondary foaming)

[0237] After filling the pressure-resistant container with primary expanded particles, air, acting as an inorganic gas, is injected into the pressure-resistant container, thereby impregnating the bubbles with the inorganic gas. At this point, the pressure within the bubbles of the primary expanded particles is 0.45 MPa(G). Steam is then supplied to the primary expanded particles removed from the pressure-resistant container and heated at atmospheric pressure to cause them to foam (secondary expanded particles). The steam pressure supplied during heating is 0.32 MPa(G).

[0238] Foamed particles 6

[0239] The multilayered resin particles 1 were produced by the same method as the expanded beads 1 , except that no through-holes were provided and the particles were cut with a pelletizer to a mass of about 1 mg.

[0240] <Production of Laminated Body>

[0241] Example 1

[0242] Expanded particles 1 were used as expanded particles A, and expanded particles 4 were used as expanded particles B. Expanded particles B were filled into a forming mold (mold) with the cracking amount (first crack) listed in Table 3. After the mold was closed so that the length of the forming space for expanded particles B in the thickness direction was 30 mm, steam was introduced into the forming mold and temporarily fused to the expanded particles B at a forming pressure of 0.14 MPa (G). The movable mold was then opened and expanded particles A were filled with the cracking amount (cracking during integrated molding) listed in Table 3. After the mold was closed so that the length of the forming space for expanded particles A in the thickness direction was 30 mm, steam was introduced into the forming mold and main heating was performed. Molding was performed at a forming pressure of 0.22 MPa (G) to form a stacked integrated product. The stack was then cooled and removed from the forming mold. The stack was then dried and aged in an oven at 60°C for 24 hours to obtain a flat-plate-shaped stack measuring 300 mm long, 250 mm wide, and 60 mm thick. Table 3 shows the physical properties of the obtained laminate.

[0243] Example 2

[0244] A laminate was obtained in the same manner as in Example 1 except that expanded beads 2 were used as expanded beads A. Table 3 shows the physical properties and evaluation results of the obtained laminate.

[0245] Example 3

[0246] A laminate was obtained in the same manner as in Example 2 except that the order of filling the expanded particles and the amount of cracks during the laminate production were changed as shown in Table 3. Table 3 shows the physical properties and evaluation results of the obtained laminate.

[0247] Example 4

[0248] A laminate was obtained in the same manner as in Example 1 except that expanded beads 2 were used as expanded beads A and expanded beads 5 were used as expanded beads B. Table 3 shows the physical properties and evaluation results of the obtained laminate.

[0249] Example 5

[0250] A laminate was obtained in the same manner as in Example 1 except that expanded beads 3 were used as expanded beads A. Table 3 shows the physical properties and evaluation results of the obtained laminate.

[0251] Example 6

[0252] A laminate was obtained in the same manner as in Example 1 except that the molding pressure during molding of the laminate was changed to the molding pressure described in Table 3. Table 3 shows the physical properties and evaluation results of the obtained laminate.

[0253] [Table 2]

[0254]

[0255] [Table 3]

[0256]

[0257] Comparative Example 1

[0258] A laminate was obtained in the same manner as in Example 1 except that expanded beads 6 were used as expanded beads A. Table 4 shows the physical properties and evaluation results of the obtained laminate.

[0259] Comparative Example 2

[0260] A laminate was obtained in the same manner as in Comparative Example 1 except that the molding pressure during molding of the laminate was changed to the molding pressure described in Table 4. Table 4 shows the physical properties and evaluation results of the obtained laminate.

[0261] Comparative Example 3

[0262] A laminate was obtained in the same manner as in Example 1 except that expanded beads 4 were used as expanded beads A and expanded beads B, and the amount of cracks and the molding pressure during the molding of the laminate were changed to the values shown in Table 4. Table 4 shows the physical properties and evaluation of the obtained laminate.

[0263] Comparative Example 4

[0264] A laminate was obtained in the same manner as in Comparative Example 3, except that the order of filling the expanded particles in producing the laminate was changed to the order of expanded particles A and then expanded particles B, the molding pressure during the temporary fusing of the expanded particles A was changed to the molding pressures listed in Table 4, and the amount of cracks and the molding pressure during the molding of the laminate were changed to the values listed in Table 4. The physical properties and evaluations of the obtained laminate are shown in Table 4.

[0265] Comparative Example 5

[0266] A laminate was obtained in the same manner as in Example 1 except that expanded beads 3 were used as expanded beads B. Table 4 shows the physical properties and evaluation results of the obtained laminate.

[0267] [Table 4]

[0268]

[0269] As shown in Table 3, according to the manufacturing method of the laminate of the present invention, a laminate having excellent mechanical strength and a desired void ratio difference can be easily obtained. Specifically, a laminate having a desired void ratio difference can be obtained with a wider range of molding conditions, and even with a particularly low molding pressure, a laminate having a desired void ratio difference can be obtained. In addition, there is no restriction on the order in which the expanded particles A and the expanded particles B are filled. Furthermore, the obtained laminate is also excellent in appearance. According to Example 5, as long as the expanded particles A and the expanded particles B satisfy the specific relationship of the present invention, even if the void ratio of the beads of the expanded particles A and the void ratio of the beads of the expanded particles B are the same, a laminate having a desired void ratio difference can be manufactured.

[0270] Comparative Examples 1 to 5 show that when expanded particles that do not satisfy the above conditions (1) to (3) are used, it is difficult to obtain a laminate having excellent mechanical strength and a desired porosity difference by integral molding.

[0271] Comparative Examples 1 and 2 use expanded particles without through-holes as expanded particles A. In Comparative Example 1, the voids in expanded particle molded article a are formed by the spaces between the expanded particles, but the resulting laminate exhibits significantly poor mechanical strength. On the other hand, in Comparative Example 2, the molding conditions were modified from those in Comparative Example 1 to improve mechanical strength, but the porosity of expanded particle molded articles a and b decreased, and the difference in porosity between expanded particle molded articles a and b also decreased.

[0272] Comparative Examples 3 and 4 use the same type of expanded particles. When the same type of expanded particles is used to integrally mold a laminate, even if molding conditions are adjusted, it is difficult to obtain a laminate having excellent mechanical strength and a desired porosity difference.

[0273] In Comparative Example 5, the average pore diameter d A and the average pore diameter d B The difference is within the expected range, but the average outer diameter D of the expanded particles B is B The example of the embodiment using a combination of expanded particles that does not satisfy the above conditions (2) and (3) is relatively small. The resulting laminate does not have the desired porosity difference. This is believed to be because the filling properties of the expanded particles B are too good, so the spaces between the expanded particles cannot be effectively and flexibly utilized.

[0274] Industrial Applicability

[0275] The laminate obtained by the laminate production method of the present invention has excellent mechanical strength and a desired porosity difference, and is therefore suitable for use as, for example, a sound absorbing material, a moisture permeable material, a water permeable material, and the like in automobile parts, building materials, and the like.

[0276] Description of Reference Numerals

[0277] 1.10 foam particles

[0278] 3 through holes

[0279] 5 (foaming) core layer

[0280] 7 cladding layer.

Claims

1. A method for producing a laminated body, wherein the laminated body is produced by integrally molding a cylindrical thermoplastic resin foamed particle A having through-holes and an aspect ratio L / D of less than 2 and a cylindrical thermoplastic resin foamed particle B having through-holes and an aspect ratio L / D of less than 2, wherein the laminated body is produced by integrally molding the cylindrical thermoplastic resin foamed particle A having through-holes and an aspect ratio L / D of less than 2, wherein the cylindrical thermoplastic resin foamed particle B has through-holes and an aspect ratio L / D of less than 2, wherein the cylindrical thermoplastic resin foamed particle A has ... The laminate is a laminate obtained by laminating and integrating a foamed bead molded body a having interconnected voids composed of the foamed particles A and a foamed bead molded body b having interconnected voids composed of the foamed particles B. The porosity P of the expanded particle molded body a a The porosity P of the expanded particle molded body b b The difference [P b -P a ] is more than 5%, The expanded particles A and the expanded particles B meet the following conditions (1) to (3): (1) The average pore diameter d of the through-holes of the expanded particles A A The average pore size d of the through-holes of the expanded particles B is B The difference [d B -d A ] is 0.3mm or more and 2mm or less; (2) The average outer diameter D of the expanded particles B B 3.5mm or more and 5mm or less; (3) The average outer diameter D of the expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B -D A ] is greater than -0.3mm and less than 2mm.

2. The method for producing a laminate according to claim 1, wherein: The average pore diameter d of the through-holes of the expanded particles A A It is not less than 0.5mm and not more than 2mm.

3. The method for producing a laminate according to claim 1 or 2, wherein: The average pore diameter d of the through-holes of the expanded particles B B It is more than 2mm and less than 3mm.

4. The method for producing a laminate according to any one of claims 1 to 3, wherein: The average outer diameter D of the expanded particles A A The average outer diameter D of the expanded particles A is 2 mm or more and 4.5 mm or less. A The average outer diameter D of the expanded particles B B The difference [D B -D A ] is greater than 0.1mm and less than 2mm.

5. The method for producing a laminate according to any one of claims 1 to 4, wherein: The average pore diameter d of the through-holes of the expanded particles A A The average pore size d of the through-holes of the expanded particles B is B The difference [d B -d A ] i.e. x, the average outer diameter D of the expanded particles A A The average outer diameter D of the expanded particles B B The difference [D B -D A ] That is, the relationship of y satisfies the following formula (1): 0.6≤x+y≤2.2…Formula (1).

6. The method for producing a laminate according to any one of claims 1 to 5, wherein: The average pore size d of the expanded particles A A Relative to the average outer diameter D of the expanded particles A A The ratio of [d A / D A ] is less than 0.

3.

7. The method for producing a laminate according to any one of claims 1 to 6, wherein: The ratio of the apparent density of the expanded particles A to the bulk density of the expanded particles A is 1.7 to 2.3, and the ratio of the apparent density of the expanded particles B to the bulk density of the expanded particles B is 2.3 to 3.

0.

8. The method for producing a laminate according to any one of claims 1 to 7, wherein: The foamed particles A are polyolefin resin foamed particles, and the foamed particles B are polyolefin resin foamed particles.

9. The method for producing a laminate according to any one of claims 1 to 8, wherein: The expanded particles A are composed of a polyolefin resin foam core layer and a polyolefin resin covering layer covering the foam core layer.

10. The method for producing a laminate according to any one of claims 1 to 9, wherein: The expanded particles B are composed of a polyolefin resin foam core layer and a polyolefin resin covering layer covering the foam core layer. The polyolefin resin constituting the foam core layer has a bending elastic modulus of 1000 MPa to 1500 MPa.

11. The method for producing a laminate according to any one of claims 1 to 10, wherein: The volume V of the expanded particle molded body a a The volume V of the expanded particle molded body b b The ratio [V a ∶V b ] is 80:20~10:90.

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