Extruded foam article

Abstract

To provide an extruded foam article capable of enhancing strength.SOLUTION: An extruded foam article 1 comprises a core layer 2 made of a foamable resin, and a skin layer 3 made of a non-foamable resin, and laminated on a main surface of the core layer 2. Each of the core layer 2 and the skin layer 3 contains a polycarbonate resin. At least one of the core layer 2 and the skin layer 3 contains a liquid crystal polymer having a melting temperature lower than that of the polycarbonate resin (a low melting point liquid crystal polymer). The extruded foam article 1 is formed into a fibrous shape so that the low melting point liquid crystal polymer contained in the molten resin extends in an extrusion direction particularly in the skin layer when extrusion-formed by an extruder. This enhances a flexural modulus particularly in the extrusion direction, and as a result, strength of the extruded foam article is enhanced.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to extruded foam molded articles. [Background technology]

[0002] In recent years, foamed resins have been attracting attention because they can improve convenience by reducing the weight of resin molded articles and reduce carbon dioxide emissions. There are two methods for molding foamed resins: extrusion molding and injection molding.

[0003] Injection molding can produce foamed molded articles with complex shapes. However, the surface layer of the molten resin flows within the mold while cooling and solidifying. During this process, a relatively thin, non-foamed skin layer is formed on the surface of the foamed molded article. On the other hand, extrusion molding has fewer restrictions on mold size and load than injection molding, and is therefore suitable for continuously producing foamed molded articles of a single shape and thickness. Furthermore, sheet-like foamed molded articles obtained by extrusion molding can be shaped into somewhat complex shapes or relatively large sizes by vacuum molding or other processes.

[0004] Japanese Patent Laid-Open Publication No. 2003-103556 (Patent Document 1) discloses a foam injection-molded article obtained by impregnating a resin with an inert fluid such as supercritical carbon dioxide as a blowing agent and then injection-molding the resulting resin. The foam injection-molded article is made of a resin with high gas permeability (such as polycarbonate) and a resin with low gas permeability (such as a liquid crystalline polymer). The gas permeability of the resin with high gas permeability is at least 50 times that of the resin with low gas permeability. The resin with low gas permeability has foam cells, with at least a portion of the molded article near the center of the wall thickness having foam cells with an aspect ratio in the range of 1 to 2. This results in a foam injection-molded article with fine cells and well-balanced physical properties.

[0005] Japanese Patent Laid-Open Publication No. 11-12381 (Patent Document 2) discloses a foam having a structure in which a surface layer is formed on at least one side of an internal layer, and which is made by mixing a liquid crystal resin into a thermoplastic resin such as polycarbonate. In the foam, the liquid crystal resin content in the surface layer is higher than the liquid crystal resin content in the internal layer. This results in a foam with excellent mechanical strength and dimensional stability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-103556 [Patent Document 2] Japanese Patent Application Publication No. 11-12381 Summary of the Invention [Problem to be solved by the invention]

[0007] The foam injection-molded article in Patent Document 1 is obtained by injection molding. Therefore, Patent Document 1 does not consider extrusion molding. Furthermore, the foam injection-molded article obtained by injection molding is considered to include a core layer, which is a foamed layer, and a skin layer, which is a non-foamed layer formed on the main surface of the core layer. However, the liquid crystalline polymer contents in the core layer and the skin layer are not considered.

[0008] In the foam of Patent Document 2, the liquid crystal resin content in the surface layer is higher than that in the inner layer because the liquid crystal resin has higher fluidity than the thermoplastic resin, causing the liquid crystal resin to migrate toward the surface layer (see paragraph "0036" in the specification of Patent Document 2). That is, in the foam of Patent Document 2, the layer with a higher liquid crystal resin content as a result of the migration of the liquid crystal resin is defined as the surface layer, and the layer with a lower crystalline resin content is defined as the inner layer. In addition, the surface layer is foam-molded (see paragraph "0032" in the specification of Patent Document 2). Thus, Patent Document 2 does not disclose a foam in which a non-foamed skin layer is formed on one side of the foam layer.

[0009] An object of the present disclosure is to provide an extruded foam molded product that can achieve improved strength. [Means for solving the problem]

[0010] In order to solve the above problems, the present disclosure provides the following solution. Specifically, the extruded foam according to the present disclosure comprises a core layer made of a foamed resin and a skin layer made of a non-foamed resin and laminated on a main surface of the core layer. The core layer and the skin layer each contain a polycarbonate resin. At least one of the core layer and the skin layer contains a liquid crystal polymer having a melting temperature lower than that of the polycarbonate resin (hereinafter referred to as a low-melting-point liquid crystal polymer). [Effects of the Invention]

[0011] The extruded foam according to the present disclosure can improve strength. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an extruded foam according to this embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional photograph of the core layer of the extruded foam shown in FIG. [Figure 3] FIG. 3 is an enlarged cross-sectional photograph of the skin layer of the extruded foam shown in FIG. [Figure 4] FIG. 4 is a graph showing the melting temperatures of polycarbonate resin and low-melting-point liquid crystal polymer. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Configuration 1) An extruded foam according to an embodiment of the present disclosure comprises a core layer made of a foamed resin and a skin layer made of a non-foamed resin laminated on a main surface of the core layer. Each of the core layer and the skin layer comprises at least one resin selected from the group consisting of super engineering resins and engineering resins. At least one of the core layer and the skin layer comprises a low-melting-point liquid crystal polymer having a melting temperature lower than that of the at least one resin selected from the group consisting of super engineering resins and engineering resins.

[0014] This makes it easier for the liquid crystal polymer with a relatively low melting point to be oriented so as to extend along the extrusion direction during extrusion molding, thereby particularly improving the flexural modulus of the extruded foam in the extrusion direction, and as a result, improving the strength of the extruded foam.

[0015] (Configuration 2) In the extruded foam molded product of Configuration 1, at least one resin selected from the group consisting of super engineering resins and engineering resins may be a polycarbonate resin, thereby particularly improving the flexural modulus in the extrusion direction of the extruded foam molded product, and further improving the strength of the extruded foam molded product.

[0016] (Configuration 3) In the extruded foam molded product of Configuration 1 or 2, the low-melting liquid crystal polymer may be contained in a skin layer, which can more effectively improve the flexural modulus of the extruded foam molded product, particularly in the extrusion direction, and can further improve the strength of the extruded foam molded product.

[0017] (Configuration 4) In the extruded foam molded product of any one of Configurations 1 to 3, the low-melting liquid crystal polymer may be fibrous, thereby particularly improving the flexural modulus of the extruded foam molded product in the extrusion direction, and as a result, improving the strength of the extruded foam molded product.

[0018] (Configuration 5) In the extruded foam molded product of any one of Configurations 1 to 4, the low-melting liquid crystalline polymer may be contained in the core layer and the skin layer, and the content of the low-melting liquid crystalline polymer in the skin layer may be equal to or greater than the content of the low-melting liquid crystalline polymer in the core layer.

[0019] (Configuration 6) In the extruded foam molded product of any one of Configurations 1 to 5, the low-melting liquid crystal polymer may have a melting temperature lower than the temperature at which the melt viscosity of at least one resin selected from the group consisting of super engineering resins and engineering resins becomes 4000 to 8000 Pa s, thereby further improving the strength of the extruded foam molded product and allowing bubbles to be appropriately formed inside the core layer.

[0020] (Configuration 7) In the extruded foam of any one of Configurations 1 to 6, the skin layer may contain less than 10% by weight of the low-melting liquid crystal polymer, which can reduce the size of the cells formed in the core layer and make the surface of the extruded foam uniform.

[0021] (Configuration 8) The extruded foam molded product of any one of Configurations 1 to 7 may have a flexural modulus of elasticity of 1500 MPa or more in the extrusion direction. The ratio (M2 / M1) of the flexural modulus of elasticity M2 in the extrusion direction to the flexural modulus of elasticity M1 in the width direction of the extruded foam molded product may be 1.2 or more. This can improve the strength of the extruded foam molded product.

[0022] Hereinafter, an embodiment of the extruded foam molded product 1 of the present disclosure will be specifically described with reference to Figures 1 to 3. Note that the same or corresponding components in the figures are denoted by the same reference numerals, and the same description will not be repeated. Note that, to make the description easier to understand, the drawings referred to below show simplified or schematic configurations, and some components are omitted.

[0023] The extruded foam 1 contains a polycarbonate resin. The resin material of the extruded foam 1 may contain at least one of a super engineering resin and an engineering resin. The super engineering resin is a thermoplastic resin having a deflection temperature under load of 150°C or higher, such as polyphenylsulfone (PPSU), polysulfone (PSU), polyarylate (PAR), polyetherimide (PEI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyethersulfone (PES), polyamideimide (PAI), polyvinylidene fluoride (PVDF), tetrafluoroethylene perfluoroalkylvinyl copolymer (PFA), etc. The engineering resin is a thermoplastic resin having a deflection temperature under load of 100°C or higher, such as polycarbonate resin (PC), modified polyphenylene ether (m-PPE), syndiotactic polystyrene (SPS), etc. However, the thermoplastic resin contained in the extruded foam 1 preferably has a deflection temperature under load of 90°C or higher. The extruded foam 1 may contain at least one resin selected from the group consisting of super engineering resins and engineering resins. Preferably, the extruded foam 1 primarily contains polycarbonate resin, for example, at a concentration of 50% by weight or more. Polycarbonate resins not only have excellent heat processability, but also have excellent appearance design and mechanical strength. In the present disclosure, the deflection temperature under load can be determined in accordance with ISO 75-2B (load 1.81 MPa). The resin material of the extruded foam 1 is not particularly limited as long as it is a thermoplastic resin, but the present embodiment will be described using polycarbonate resin.

[0024] The extruded foam 1 has a foamed layer (hereinafter referred to as a core layer) 2, a non-foamed layer (hereinafter referred to as a skin layer) 3 laminated on one main surface of the core layer 2, and a skin layer 4 laminated on the other main surface of the core layer 2. The extruded foam 1 of this embodiment has the skin layer 3 and the skin layer 4 on one and the other main surfaces of the core layer 2, but the core layer 2 may have the skin layer 3 or the skin layer 4 on either one or the other main surface.

[0025] The core layer 2 is made of a foamed resin. The core layer 2 can be formed by physical or chemical foam molding of a molten resin material. The core layer 2 of the present disclosure is preferably foam molded using a physical foaming agent such as nitrogen or carbon dioxide at a relatively low pressure, with nitrogen being more preferred. Examples of physical foaming agents include inert gases such as nitrogen, carbon dioxide, air, and argon.

[0026] The skin layer 3 is made of a non-foaming resin. That is, the skin layer 3 is not foamed. The skin layer 3 may be extruded from a die outlet in a non-foamed state by co-extrusion molding and laminated integrally with the core layer 2. Alternatively, after the core layer 2 is formed, the skin layer 3 may be fixed to one main surface of the core layer 2 by adhesion, welding, or the like.

[0027] The skin layer 3 may be made of a thermoplastic resin that can adhere well to the core layer 2. More specifically, the resin material of the skin layer 3 is preferably the same as that of the core layer 2. The skin layer 3 may contain additives to an extent that does not significantly impair the effects of the present disclosure. The types of additives are not particularly limited, but examples include bubble nucleating agents, crystal nucleating agents, lubricants, surfactants, tension modifiers, shrinkage inhibitors, flow modifiers, impact modifiers, fillers, reinforcing agents, antioxidants, heat stabilizers, light stabilizers, UV absorbers, plasticizers, lubricants, mold release agents, antistatic agents, colorants (pigments, dyes, etc.), surface effect additives, infrared absorbers, radiation stabilizers, flame retardants, drip-proofing agents, and antioxidants. The amount of additive added can be appropriately selected within a range that does not impair bubble formation, and the amount used in molding conventional thermoplastic resins can be used.

[0028] The skin layer 4 is the same as the skin layer 3, except that it is laminated on the other main surface of the core layer 2. Therefore, a detailed description of the skin layer 4 will be omitted.

[0029] At least one of the core layer 2, skin layer 3, and skin layer 4 contains a low-melting point liquid crystal polymer (low-melting point LCP (Liquid Crystal Polymer)). In this embodiment, the skin layer 3 and the skin layer 4 are laminated on one and the other main surfaces of the core layer 2, but the skin layer 3 or the skin layer 4 may be laminated on only one or the other main surface of the core layer 2.

[0030] The low-melting liquid crystal polymer has a melting temperature lower than that of the polycarbonate resin constituting the core layer 2, the skin layers 3, and the skin layers 4. As a result, when the extruded foam molded product 1 is extrusion foam molded, the low-melting liquid crystal polymer stretches in the extrusion direction within the polycarbonate resin, and is oriented in the extrusion direction to form a fibrous shape. This allows the extruded foam molded product 1 to have an improved flexural modulus, particularly in the extrusion direction, and as a result, the strength of the extruded foam molded product 1 can be improved.

[0031] On the other hand, if the melting temperature of the liquid crystal polymer is higher than that of the polycarbonate resin, the liquid crystal polymer does not melt at the temperature at which the polycarbonate resin melts, and so the low-melting-point liquid crystal polymer does not stretch in the extrusion direction within the polycarbonate resin, but disperses in a granular form. As a result, it becomes difficult to orient in the extrusion direction and form fibers. Furthermore, if the melting temperature of the liquid crystal polymer is higher than that of the polycarbonate resin, when the liquid crystal polymer is heated to melt it in the method for producing the extruded foam 1 described below, the melt viscosity of the polycarbonate resin decreases too much, so the polycarbonate resin and the liquid crystal polymer are not mixed properly, and the liquid crystal polymer is difficult to stretch and orient in the extrusion direction.

[0032] In terms of the melt viscosity of the polycarbonate resin and the low-melting-point liquid crystal polymer, the melt viscosity of the low-melting-point liquid crystal polymer is lower than that of the polycarbonate resin during extrusion molding. The greater the difference in melt viscosity between them, the easier it is for the low-melting-point liquid crystal polymer to be formed into fibers oriented in the extrusion direction. The difference in melt viscosity between the polycarbonate resin and the low-melting-point liquid crystal polymer is preferably 10 to 30 times. If the difference in melt viscosity is less than 10 times, it becomes difficult for the low-melting-point liquid crystal polymer to be formed into fibers oriented in the extrusion direction, and the effect of improving the flexural modulus may be reduced. If the difference in melt viscosity is more than 30 times, the low-melting-point liquid crystal polymer can be sufficiently formed into fibers oriented in the extrusion direction, but the melt viscosity of the polycarbonate resin becomes too high, resulting in poor moldability.

[0033] Regarding the above-mentioned melt viscosity, the case of a low-melting liquid crystal polymer and a polycarbonate resin is described as an example. However, this phenomenon is determined by the relationship between the melting temperature of the super engineering resin or engineering resin and the melting temperature of the low-melting liquid crystal polymer. That is, it is important that the melting temperature of the low-melting liquid crystal polymer is lower than the melting temperature of the super engineering resin or engineering resin.

[0034] Here, an example of a method for producing the extruded foam 1 will be described (not shown). First, resin pellets, which serve as the resin material, are loaded into the screw cylinder of the main extruder. The resin pellets are made of at least one thermoplastic resin selected from the above-mentioned thermoplastic resins, such as polycarbonate resin. Granular low-melting-point crystalline polymer is then loaded into the screw cylinder. The resin pellets and the low-melting-point crystalline polymer are heated in the screw cylinder to produce a molten resin. The low-melting-point crystalline polymer melts at a temperature higher than its melting point, melting together with the polycarbonate resin. Next, a blowing agent is injected into the molten resin from a blowing agent injection cylinder attached to the screw cylinder of the main extruder. The blowing agent is dissolved in the molten resin by the screw cylinder, kneaded, and uniformly dispersed. This produces a mixed molten resin. The mixed molten resin is then discharged from the die outlet to form the core layer 2. Simultaneously, resin pellets and a low-melting-point liquid crystalline polymer, which serve as the resin material, are loaded into each of the screw cylinders of the two sub-extruders and heated to melt them, producing two molten resins. One of the two molten resins is extruded from the die outlet to form skin layer 3, and the other is extruded from the die outlet to form skin layer 4. The mixed molten resin and the two molten resins flow into the die from their respective extruders, merge within the die, and are extruded from the die outlet so that skin layer 3 is laminated on one main surface of core layer 2 and skin layer 4 is laminated on the other main surface of core layer 2. The mixed molten resin foams as it is extruded from the die outlet into the atmosphere. The extruded foam 1 is cooled and then transported to a cutting machine by a take-up machine. The cutting machine cuts the extruded foam 1 into the desired shape. The extruded foam 1 can be produced in this manner. The foaming method is a physical foaming method using an inert gas such as nitrogen or carbon dioxide as a foaming agent.

[0035] When extruded through the die, the low-melting-point liquid crystalline polymer contained in each of the molten resin mixture forming the core layer 2 and the mixed resin mixture forming the skin layers 3 and 4 is extruded from the die outlet in a molten state together with the polycarbonate resin, and therefore easily stretches along the extrusion direction. By including a crystalline polymer having a melting temperature lower than that of the polycarbonate resin, a fibrous low-melting-point liquid crystalline polymer can be formed inside the extruded foam 1, thereby particularly improving the flexural modulus of the extruded foam 1 in the extrusion direction. As a result, the strength of the extruded foam 1 can be improved. However, the method for producing the extruded foam 1 is not limited to this. For example, the core layer 2 and the skin layers 3 and 4 may be separately molded, and then the skin layers 3 and 4 may be bonded to one and the other main surfaces of the core layer 2, respectively.

[0036] The low-melting-point liquid crystalline polymer is particularly susceptible to fibrous formation in the skin layer 3 or 4. That is, in the above-described production method, the two molten resins are more susceptible to shear stress generated between the two molten resins and the inner wall of the die near the die outlet than the mixed molten resin located between the two molten resins. Furthermore, because the skin layers 3 and 4 are made of non-foaming resins, they are less susceptible to bubbles than the core layer 2, in which bubbles are formed. Therefore, the low-melting-point liquid crystalline polymer contained in the skin layers 3 and 4 is more likely to form fibers extending in the extrusion direction than the low-melting-point liquid crystalline polymer contained in the core layer 2. Thus, the low-melting-point liquid crystalline polymer is preferably contained in the skin layer 3 or 4 from the viewpoint of orienting the low-melting-point liquid crystalline polymer in a fibrous form along the extrusion direction and improving the strength of the extruded foam 1, which can more effectively improve the strength of the extruded foam 1.

[0037] As shown in FIG. 2, the fiberized low-melting-point liquid crystal polymer L is oriented along the extrusion direction inside the core layer 2. The photograph in FIG. 2 is a 1000x magnification image of the cross section of the core layer 2 taken using a scanning electron microscope after freeze-fracturing. Also, as shown in FIG. 3, the fiberized low-melting-point liquid crystal polymer L is oriented along the extrusion direction inside the skin layer 3. The photograph in FIG. 3 is a 3000x magnification image of the cross section of the skin layer 3 taken using a scanning electron microscope after freeze-fracturing. As shown in FIGS. 2 and 3, the low-melting-point liquid crystal polymer L contained in the skin layer 3 is fiberized more finely than the low-melting-point liquid crystal polymer L contained in the core layer 2. The same applies to the skin layer 4.

[0038] Next, the content of the low-melting point liquid crystalline polymer in the core layer 2, skin layer 3, and skin layer 4 will be described. The content of the low-melting point liquid crystalline polymer in the skin layer 3 and skin layer 4 is preferably equal to or greater than the content of the low-melting point liquid crystalline polymer in the core layer 2. That is, as described above, the low-melting point liquid crystalline polymer is likely to be formed into a fibrous form in the skin layer 3 and skin layer 4. Therefore, by making the content of the low-melting point liquid crystalline polymer in the skin layer 3 and skin layer 4 equal to or greater than that in the core layer 2, the strength of the extruded foam 1 can be further improved.

[0039] The low-melting-point liquid crystal polymer has a melting temperature lower than the temperature at which the melt viscosity of the polycarbonate resin is 4000 to 8000 Pa·s. As described above, the core layer 2 is made of a foamed resin. In order to properly form bubbles inside the core layer 2 during foam molding of the core layer 2, i.e., to prevent bubble breakage, etc., it is preferable to heat the mixed molten resin in the screw cylinder in the above-mentioned manufacturing method so that the melt viscosity of the mixed molten resin is 4000 to 8000 Pa·s. When the resin material forming the core layer 2 is a polycarbonate resin, the melt viscosity of the polycarbonate resin is preferably such that the shear rate of the polycarbonate resin is in the range of 90 to 200 sec-1, and in this case, the melt viscosity is preferably in the range of 4000 to 8000 Pa·s. For example, when the shear rate of the polycarbonate resin is 100 sec-1, the melt viscosity of the polycarbonate resin is 5000 to 6000 Pa·s. The heating temperature at which the melt viscosity of the polycarbonate resin reaches 4000 to 8000 Pa s can be 220 to 230° C. In order to form the low-melting liquid crystal polymer into a fibrous form and to properly form bubbles in the core layer 2, it is preferable that the melting temperature of the low-melting liquid crystal polymer be lower than the temperature at which the melt viscosity of the polycarbonate resin reaches 4000 to 8000 Pa s.

[0040] Each of the skin layers 3 and 4 preferably contains less than 10% by weight of a low-melting-point liquid crystalline polymer relative to the skin layer 3 and the skin layer 4. By laminating the skin layers 3 and 4 to the core layer 2, they suppress bubble growth in the core layer 2 during extrusion foam molding, thereby forming fine bubbles and contributing to a uniform surface of the extruded foam 1. Typically, the melt viscosity of a liquid crystalline polymer is significantly lower than that of a polycarbonate resin. Therefore, when a polycarbonate resin is mixed with a liquid crystalline polymer, the melt viscosity decreases. A decrease in melt viscosity promotes bubble growth, making it difficult to form fine bubbles and to uniform the surface of the extruded foam 1. Therefore, adding less than 10% by weight of a low-melting-point liquid crystalline polymer to each of the skin layers 3 and 4 suppresses a decrease in the melt viscosity of the molten resin in the above-mentioned production method, facilitating the formation of fine bubbles and the uniform surface of the extruded foam 1. On the other hand, from the viewpoint of improving the strength of the extruded foam 1, the low-melting point liquid crystalline polymer is preferably contained in each of the skin layers 3 and 4 at 1% by weight or more. That is, from the viewpoint of improving the strength of the extruded foam 1 and making the surface uniform, the content of the low-melting point liquid crystalline polymer in each of the skin layers 3 and 4 is preferably 1% by weight or more and less than 10% by weight, more preferably 2.5% by weight or more and less than 7% by weight, and more preferably 5% by weight or more and less than 7% by weight. In other words, the content is preferably 1% by weight or more, preferably 2.5% by weight or more, more preferably 5% by weight or more, and less than 10% by weight, preferably 7% by weight or less.

[0041] By including a low-melting-point liquid crystalline polymer, the extruded foam 1 can have a flexural modulus in the extrusion direction of 1500 MPa or more, preferably 1700 MPa or more. The ratio (M2 / M1) of the flexural modulus M2 in the extrusion direction to the flexural modulus M1 in the width direction of the extruded foam 1 can be 1.2 or more, preferably 1.5 or more. This can improve the strength of the extruded foam 1. The flexural modulus in the extrusion direction of the extruded foam 1 can be 2500 MPa or less. The ratio (M2 / M1) can be 2.0 or less. The width direction is the direction perpendicular to the extrusion direction in a plan view. The ratio (M2 / M1) is preferably 1.2 or more and 2.0 or less, more preferably 1.5 or more and 2.0 or less. The flexural modulus in the extrusion direction is preferably 1500 MPa or more and 2500 MPa or less, more preferably 1700 MPa or more and 2500 MPa or less. However, the flexural modulus in the extrusion direction of the extruded foam molded product 1 can be set appropriately depending on the application.

[0042] By including a low-melting-point liquid crystal polymer in the skin layers 3 and 4, it is possible to reduce the permeability of oxygen, moisture, etc. Furthermore, the low-melting-point liquid crystal polymer has flame retardancy, which allows the extruded foam 1 to have flame retardancy.

[0043] Because the extruded foam molded product 1 is foam-molded, it is possible to reduce the amount of resin used. As a result, the extruded foam molded product 1 can contribute to improving resource utilization efficiency, easing transportation burdens, reducing energy consumption, and reducing CO2 emissions. By providing the extruded foam molded product 1 to society, it is possible to contribute to the achievement of Goal 7 (Affordable and Clean Energy), Goal 9 (Industry, Innovation and Infrastructure), and Goal 11 (Sustainable Cities and Communities) of the 17 Sustainable Development Goals (SDGs) established by the United Nations. Furthermore, because the extruded foam molded product 1 according to this embodiment can be melted and reused, it can contribute to the achievement of Goal 12 (Responsible Consumption and Production).

[0044] Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0045] [Example] In Examples 1 to 5 and Comparative Examples 1 and 2, extruded foams were produced by coextrusion molding under the conditions shown in Table 1 below, and the maximum stress, yield strain, and flexural modulus of each extruded foam were measured. In Table 1, "%" indicates weight percent, "PC" indicates polycarbonate resin, "LCP" indicates liquid crystal polymer, "MD" indicates the extrusion direction, and "TD" indicates the width direction (the direction perpendicular to the extrusion direction in a plan view). The polycarbonate resin constituting the skin and core layers was "Panlite (registered trademark), L1225L" manufactured by Teijin Limited. The low-melting-point LCPs used were "A8100" and "AL7000" manufactured by Ueno Pharmaceutical Co., Ltd., and the high-melting-point LCP (LCP with a melting temperature higher than that of polycarbonate resin) was "A5000" manufactured by Ueno Pharmaceutical Co., Ltd. Skin layers were formed on both main surfaces of the core layer.

[0046] [Table 1]

[0047] Examples 1 and 4 The extruded foams of Examples 1 and 4, which contained a low-melting point LCP in the skin layer, were able to improve the flexural modulus, particularly in the extrusion direction, compared to Comparative Example 1, which contained no LCP in either the core layer or the skin layer, and Comparative Example 2, which contained a high-melting point LCP in the skin layer.

[0048] (Examples 2, 3 and 5) Furthermore, when comparing Examples 2, 3, and 5, in which both the core layer and the skin layer contain a low-melting-point LCP, it was confirmed that when the content of low-melting-point LCP in the skin layer and the core layer is the same (Example 2), or when the content of low-melting-point LCP in the skin layer is greater than that in the core layer (Example 3), the ratio (M2 / M1) is 1.5 or greater, and the flexural modulus in the extrusion direction is more effectively improved.

[0049] Next, as shown in Figure 4, we compared the melt viscosity of polycarbonate resin, low-melting point liquid crystal polymer, and polycarbonate resin containing low-melting point liquid crystal polymer. Under each condition, the PC and LCP were as described above. "5%" means that 5 wt% of LCP was added to PC, and "10%" means that 10 wt% of LCP was added to PC. Furthermore, "230°C" indicates the melt viscosity when heated to 230°C.

[0050] According to the graph in Figure 4, when 5 wt% of LCP was added to PC, the melt viscosity was hardly reduced compared to PC. On the other hand, when 10 wt% of LCP was added to PC, the melt viscosity was significantly reduced. Thus, it was confirmed that adding 10 wt% or more of LCP significantly reduces the melt viscosity. As a result, it is thought that the growth of bubbles contained in the core layer is promoted, preventing the formation of fine bubbles and making it difficult to achieve a uniform surface for the extruded foam. [Explanation of symbols]

[0051] 1 extruded foam molding, 2 core layer, 3 skin layer, 4 skin layer, L low melting point liquid crystal polymer

Claims

1. An extruded foam molded article, a core layer made of a foamed resin; a skin layer made of a non-foaming resin and laminated on a main surface of the core layer; the core layer and the skin layer each contain at least one resin selected from the group consisting of super engineering resins and engineering resins, At least one of the core layer and the skin layer comprises a liquid crystal polymer (hereinafter referred to as a low-melting point liquid crystal polymer) having a melting temperature lower than that of at least one selected from the group consisting of the super engineering resin and the engineering resin.

2. The extruded foam according to claim 1, The extruded foam, wherein the at least one resin selected from the group consisting of super engineering resins and engineering resins is a polycarbonate resin.

3. The extruded foam according to claim 1, The extruded foam, wherein the low melting point liquid crystal polymer is contained in the skin layer.

4. The extruded foam according to claim 1, The extruded foam molded article, wherein the liquid crystal polymer is fibrous.

5. The extruded foam according to claim 1, the low-melting-point liquid crystal polymer is contained in the core layer and the skin layer; an extruded foam, wherein the content of the low-melting point liquid crystal polymer in the skin layer is equal to or greater than the content of the low-melting point liquid crystal polymer in the core layer;

6. The extruded foam according to claim 1, The extruded foam molded product, wherein the low-melting point liquid crystal polymer has a melting temperature lower than the temperature at which the melt viscosity of at least one resin selected from the group consisting of the super engineering resin and the engineering resin becomes 4000 to 8000 Pa·s.

7. The extruded foam according to claim 1, The extruded foam molded article, wherein the skin layer contains the low-melting point liquid crystal polymer in an amount of less than 10% by weight based on the weight of the skin layer.

8. The extruded foam according to any one of claims 1 to 7, The extruded foam has a flexural modulus of 1500 MPa or more in the extrusion direction, The extruded foam has a ratio (M2 / M1) of a bending modulus M2 in the extrusion direction to a bending modulus M1 in the width direction of the extruded foam of 1.2 or more.

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