Foam molded body and partition plate

Abstract

To provide a foam molded body that has total light transmittance and diffuse reflectance set in a balanced manner and can be reduced in weight.SOLUTION: A foam molded body 1 includes: a core layer 2 made of a foaming resin; a skin layer 3 laminated on one of principal surfaces of the core layer 2 and made of a non-foaming resin; and a skin layer 4 laminated on the other principal surface. The foam molded body 1 has a specific gravity reduced by 1-30% from a specific gravity in a state where a resin material of the foam molded body 1 is non-foaming (specific gravity reduction ratio). Air bubbles 21 contained in the core layer have an average air bubble diameter of 30-70 μm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a foam molded article obtained by foam molding a thermoplastic resin, and a partition board using the foam molded article, which is used for partitions and the like. [Background technology]

[0002] In recent years, plastic partitions (dividers) have become popular for dividing relatively large rooms. In a room divided by a partition, sunlight and other light enters the area of ​​the room facing the window. However, sunlight and other light may not enter directly into the area blocked from the window. Furthermore, when separating adjacent desks using a light-transmitting partition, if too much light passes through, the desk can be seen from the desk next to it, while if too little light passes through, the desk becomes dark. To solve this problem, a partition is needed that allows some light to pass through but makes it difficult for adjacent desks to be clearly seen from each other.

[0003] Japanese Patent Laid-Open Publication No. 2023-35789 (Patent Document 1) discloses a partition using a transparent laminate film. The transparent laminate film has a light reflectance of 3.0% or less and a total light transmittance of 90% or more to suppress light reflection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-35789 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a foam molded article that can be set with a well-balanced total light transmittance and diffuse reflectance and that can be made lighter. [Means for solving the problem]

[0006] In order to solve the above problems, the present disclosure provides the following solution. Specifically, the foam molded article according to the present disclosure is a foam molded article containing a thermoplastic resin, and includes a core layer made of a foamed resin, a first skin layer made of a non-foamed resin and laminated on one main surface of the core layer, and a second skin layer made of a non-foamed resin and laminated on the other main surface of the core layer. The foam molded article has a specific gravity reduction rate of 1 to 30%. The bubbles contained in the core layer have an average bubble diameter of 30 to 70 μm. [Effects of the Invention]

[0007] According to the foam molded article according to the present disclosure, the total light transmittance and diffuse reflectance of the foam molded article can be set in a well-balanced manner, and the weight can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a foam molded article according to this embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the foam molded article shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing the transmission and reflection of light through a foam molded article. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present inventors first considered that it was essential to reduce the weight of the partition from the viewpoint of reducing the transportation and installation costs of the partition. Patent Document 1 does not consider reducing the weight of the partition. The present inventors then considered using a foam-molded resin partition to reduce the weight of the partition. This would enable the weight of the partition to be reduced. However, foam-molded bodies typically exhibit variations in total light transmittance and diffuse reflectance depending on the bubble diameter, number of bubbles, and expansion ratio of the bubbles contained in the foam-molded body. For example, as shown in FIG. 3, when the number of bubbles 21 contained in the foam-molded body 1 is large and the bubble diameter is small, the diffuse reflectance increases and the total light transmittance decreases, resulting in a darkened side of the foam-molded body 1 opposite to the light source (e.g., sunlight or a lighting fixture). (Note that in FIG. 3, arrow A indicates the entrance hole, arrow B indicates reflected light, and arrow C indicates transmitted light. Furthermore, reference numeral 2 indicates a core layer, which will be described later, and reference numerals 3 and 4 indicate skin layers, which will be described later.) Furthermore, although a high expansion ratio and a large bubble diameter can further reduce the weight of the foamed molded article, the total light transmittance increases, resulting in visibility from the opposite side of the foamed molded article. From this perspective, the present inventors have conducted extensive research and found that in order to transmit a certain amount of light from a light source while suppressing visibility from the opposite side of the foamed molded article, it is important to set a good balance between the "specific gravity reduction rate" of the foamed molded article and the "average bubble diameter" of the bubbles contained in the foamed molded article, and have completed the present invention as described below.

[0010] In the present disclosure, the "specific gravity reduction rate" of a foam molded body indicates the degree to which the specific gravity (X) of the foam molded body has been reduced from the specific gravity (Y) of the resin that is the material of the foam molded body in an unfoamed state, and is calculated using the following formula: (1-X / Y)×100 The specific gravity (X) of the foamed molded article and the specific gravity (Y) of the non-foamed resin can be determined by the underwater displacement method using a hydrometer ("DSG-1" manufactured by Toyo Seiki Co., Ltd.).

[0011] The "average bubble diameter" of bubbles contained in a foam molded article is the arithmetic mean of the diameters of circles having an area corresponding to the cross-sectional area of ​​each bubble in the cross section of the foam molded article, and can be calculated as follows. First, a cross section of the foam molded article is formed along the thickness direction, and the cross section is observed. The cross section of the foam molded article can be formed, for example, by cutting the foam molded article along the thickness direction, or by freezing the foam molded article and processing it with a microtome or the like. The cross section of the foam molded article can be observed using a tabletop microscope (Hitachi High-Tech Corporation's "TM4000Plus"). The observation conditions can be set as follows: observation mode: 15 kV, mode 2, vacuum mode: charge reduction, detector: backscattered electron, observation magnification: 30x, imaging mode (scan: slow, image size: 1280 × 960, speed / accumulated number: 32, magnification number setting: checked), and save: JPEG. In addition, in the "auto brightness" setting, brightness can be set to 0 and contrast to 1, and the brightness / contrast and focus can be adjusted automatically before shooting. The brightness and focus can be adjusted by setting the magnification for cross-section observation to 100x, and then returning it to 30x after the above settings are used for shooting. Cross-sectional images obtained under these conditions are processed using, for example, image processing software ("ImageJ" manufactured by the National Institutes of Health, USA). More specifically, the cross-sectional images are binarized using the image processing software to clarify the outlines of the bubbles and the resin parts other than the bubbles, and the cross-sectional area of ​​the bubbles is then calculated. The diameter of a circle having an area equivalent to the cross-sectional area of ​​the bubbles is calculated. The diameter of this circle can be used as the bubble diameter, and the average bubble diameter of the bubbles contained in the foamed molded product can be calculated.

[0012] Next, the total light transmittance and diffuse reflectance of the foamed molded article can be measured using a spectrophotometer ("V570" manufactured by JASCO Corporation). In measuring the diffuse reflectance, "Spectralon" manufactured by Love Square Corporation can be used as a standard reflector.

[0013] (Configuration 1) A foam molded article according to an embodiment of the present disclosure is a foam molded article containing a thermoplastic resin, and includes a core layer made of a foamed resin, a first skin layer made of a non-foamed resin and laminated on one main surface of the core layer, and a second skin layer made of a non-foamed resin and laminated on the other main surface of the core layer. The foam molded article has a specific gravity reduction rate of 1 to 30%. The bubbles contained in the core layer have an average bubble diameter of 30 to 70 μm.

[0014] This allows the total light transmittance and diffuse reflectance of the foamed molded article to be set in a well-balanced manner, and also allows for weight reduction.

[0015] (Configuration 2) In the foam molded article of Configuration 1, the thermoplastic resin may be a polycarbonate resin.

[0016] (Configuration 3) The foam molded article of Configuration 1 or 2 may have a total light transmittance of 40 to 60% and a diffuse reflectance of 40 to 60%.

[0017] (Configuration 4) A partition plate according to an embodiment of the present disclosure may be formed from any one of the foam molded articles of Configurations 1 to 3. This ensures brightness on the side of the partition plate, for example, a partition opposite the light source, reduces mutual visibility between areas separated by the partition, and further reduces the weight of the partition.

[0018] An embodiment of a foam molded article 1 according to the present disclosure will be specifically described below with reference to Fig. 1. Note that identical or corresponding components in the figure are denoted by the same reference numerals, and the same description will not be repeated. Note that, for ease of understanding, the drawings referred to below show simplified or schematic configurations, and some components are omitted.

[0019] Here, the foam molded article 1 will be described as a partition, which is a dividing plate. However, the foam molded article 1 is not limited to partitions and can be used, for example, as a privacy sheet or roller blind attached to a window. By setting the total light transmittance and diffuse reflectance in a well-balanced manner, it is possible to achieve both good lighting and reduced visibility in these applications.

[0020] The foam molded product 1 usually has a sheet shape. However, the foam molded product 1 may also be shaped by vacuum forming or the like. From the viewpoint of facilitating shaping by vacuum forming or the like, the foam molded product 1 preferably has a thickness of 1 to 5 mm. Alternatively, the foam molded product 1 may be molded using other resin molding methods such as injection molding.

[0021] The foam molded article 1 is made of a thermoplastic resin. The thermoplastic resin is not particularly limited, but a transparent amorphous resin is preferred from the viewpoint of transparency. Examples include general-purpose plastics such as polystyrene and acrylic, engineering plastics such as polycarbonate having a deflection temperature under load of 100°C or higher, and super-engineering plastics such as polyarylate having a deflection temperature under load of 150°C or higher. While the foam molded article 1 may contain at least one selected from the group consisting of general-purpose plastics, engineering plastics, and super-engineering plastics, it is preferable that the foam molded article 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 (1.81 MPa load).

[0022] As shown in Figures 1 and 2, the foamed molded product 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.

[0023] 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.

[0024] As shown in Fig. 2, 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.

[0025] The skin layer 3 may be made of a thermoplastic resin that can adhere well to the core layer 2. More specifically, it is particularly preferable that the resin material of the skin layer 3 is the same as that of the core layer 2. In order to strengthen the skin layer 3, the skin layer 3 may be made of a reinforced resin containing an inorganic filler to an extent that does not impair the effects of the present disclosure, or a resin containing additives such as a flame retardant or a foam nucleating agent. By providing the skin layer 3, it is possible to efficiently improve the strength while reducing the weight and improving the strength. The amount of additive added can be appropriately selected within a range that does not impair the formation of bubbles 21, and the amount added used in molding a typical thermoplastic resin can be used.

[0026] 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.

[0027] Next, an example of a method for producing a foamed molded article 1 will be described (not shown). First, resin pellets serving as the resin material are loaded into the screw cylinder of the main extruder. The resin pellets are made of at least one material selected from the aforementioned general-purpose plastics, engineering plastics, and super-engineering plastics, such as polycarbonate resin. The resin pellets are heated in the screw cylinder to produce a molten 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. In this way, a mixed molten resin is produced. The mixed molten resin is discharged from the die outlet to form the core layer 2. Simultaneously, resin pellets serving as the resin material are loaded into each of the screw cylinders of the two sub-extruders and heated and melted to produce two molten resins. One of the two molten resins is discharged from the die outlet to form skin layer 3, and the other is discharged from the die outlet to form skin layer 4. The mixed molten resin and the two molten resins are merged in a die from each extruder and discharged from the die outlet so that a skin layer 3 is laminated on one main surface of the core layer 2 and a skin layer 4 is laminated on the other main surface of the core layer 2. The mixed molten resin foams as it is extruded from the die outlet into the atmosphere. In this manner, a foamed molded article 1 is produced. The foaming method is a physical foaming method using an inert gas such as nitrogen or carbon dioxide as a foaming agent. The extruded foamed molded article 1 is transported by a take-up machine to a cutting machine. The cutting machine cuts the foamed molded article 1 into the desired shape. The method for producing the foamed molded article 1 is not limited to this. 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. Alternatively, the resin material for the skin layers 3 and 4 may be printed on each of the one and the other main surfaces of the core layer 2.

[0028] The foam molded product 1 can have a specific gravity reduction rate of 1 to 30%. The specific gravity reduction rate can be calculated by the method described above. If the specific gravity reduction rate is too large, the weight can be reduced, but the strength of the foam molded product 1 decreases, and it becomes difficult to set a good balance between the total light transmittance and the diffuse reflectance of the foam molded product 1. That is, the diffuse reflectance of the foam molded product 1 increases and the total light transmittance decreases. In other words, more light rays are reflected by the foam molded product 1 and less light rays are transmitted. This makes it difficult to ensure brightness on the side of the foam molded product 1 opposite the light source. On the other hand, if the specific gravity reduction rate is too small, it becomes difficult to reduce the weight and it becomes difficult to set a good balance between the total light transmittance and the diffuse reflectance of the foam molded product 1. That is, the total light reflectance of the foam molded product 1 decreases. In other words, fewer light rays are reflected by the foam molded product 1 and more light rays are transmitted. This makes it difficult to suppress the visibility of the areas partitioned by the foam molded product 1 (partition). From this viewpoint, the specific gravity reduction rate of the foamed molded product 1 is preferably 1 to 30%, more preferably 15 to 25%, and even more preferably 22 to 24%. Alternatively, the specific gravity reduction rate of the foamed molded product 1 is preferably 1% or more, more preferably 15% or more, and even more preferably 22% or more, and is preferably 30% or less, more preferably 25% or less, and even more preferably 24% or less.

[0029] The bubbles 21 contained in the core layer 2 can have an average bubble diameter of 30 to 70 μm. The average bubble diameter can be calculated by the method described above. If the average bubble diameter of the bubbles 21 contained in the core layer 2 is too large, the weight can be reduced, but the strength of the foam molded product 1 decreases and it becomes difficult to set a good balance between the total light transmittance and diffuse reflectance of the foam molded product 1. That is, the diffuse reflectance of the foam molded product 1 increases and the total light transmittance decreases. As a result, it becomes difficult to ensure brightness on the side of the foam molded product 1 opposite the light source. On the other hand, if the average bubble diameter of the bubbles 21 contained in the core layer 2 is too small, it becomes difficult to reduce the weight and it becomes difficult to set a good balance between the total light transmittance and diffuse reflectance of the foam molded product 1. That is, the total light transmittance of the foam molded product 1 increases, making it difficult to suppress mutual visibility between the regions partitioned by the foam molded product 1 (partition). From this viewpoint, the average diameter of the bubbles 21 contained in the core layer 2 is 30 to 70 μm, preferably 40 to 60 μm, and more preferably 45 to 55 μm. Alternatively, the average diameter of the bubbles 21 contained in the core layer 2 is 30 μm or more, preferably 40 μm or more, and more preferably 45 μm or more, and is 70 μm or less, preferably 60 μm or less, and more preferably 55 μm or less.

[0030] The foam molded article 1 can have a total light transmittance of 40 to 60%. The foam molded article 1 can also have a diffuse reflectance of 40 to 60%. From the viewpoint of achieving a good balance between the total light transmittance and the diffuse reflectance of the foam molded article 1, each of the total light transmittance and the diffuse reflectance is 40 to 60%, preferably 45 to 55%, more preferably 49 to 51%, and particularly preferably 50%. Alternatively, each of the total light transmittance and the diffuse reflectance is 40% or more, preferably 45% or more, more preferably 49% or more, and 60% or less, preferably 55% or less, and more preferably 51%. In other words, each of the total light transmittance and the diffuse reflectance is preferably close to 50%.

[0031] By setting the specific gravity reduction rate of the foamed molded body 1 and the average cell diameter of the bubbles 21 contained in the core layer 2 as described above, it is possible to reduce the weight of the foamed molded body 1 and to set a good balance between the total light transmittance and the diffuse reflectance of the foamed molded body 1. As a result, when the foamed molded body 1 is used as a partition, it is possible to ensure brightness on the side opposite the light source of the partition while reducing the visibility of the areas separated by the partition.

[0032] The core layer 2 may have an expansion ratio of 1.6 to 3.3. The expansion ratio of the core layer 2 is calculated by the following method. That is, when the expansion ratio of the core layer 2 calculated by the following method is in the range of 1.6 to 3.3, the total light transmittance and diffuse reflectance of the foam molded article 1 can be set in a well-balanced manner.

[0033] The expansion ratio of the core layer 2 can be calculated as follows. First, the foamed molded article 1 is cut to obtain a sheet piece of an arbitrary size. The weight of the sheet piece is measured, and the weight per unit area W (kg / m 2 ) is calculated. In the same manner as in the cross-section observation method using a microscope described above, the thicknesses (t1 + t2) of the skin layers 3 and 4 are measured. The density ρ1 (kg / m 3 ) and the thickness of the skin layer 3 and the skin layer 4, the weight W1 (kg / m) per unit area of ​​the skin layer 3 and the skin layer 4 is calculated. 2 )<W1=ρ1×(t1+t2)> Next, the weight W2 (kg / m 2 ) is calculated. The thickness of the core layer {T-(t1+t2)} is measured using the cross-section observation method described above. The density ρ2 of the core layer 2 is calculated from the weight and thickness of the core layer 2 <ρ2=W2 / {T-(t1+t2)}>. The density ρ of the resin material of the core layer 2 before foaming is calculated. 2f Calculate the expansion ratio using the formula: <Expansion ratio = ρ 2f / ρ2>.

[0034] Because the foam molded article 1 is foam-molded, it is possible to reduce the amount of resin used. As a result, the foam molded article 1 can contribute to improving resource utilization efficiency, easing transportation burdens, reducing energy consumption, and reducing CO2 emissions. By providing the foam molded article 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 foam molded article 1 according to this embodiment can be melted and reused, it can contribute to the achievement of Goal 12 (Responsible Consumption and Production).

[0035] 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.

[0036] [Example] In Examples 1 to 3 and Comparative Examples 1 to 5, resin molded bodies were produced under the conditions shown in Table 1 below, and the total light transmittance and diffuse reflectance of each resin molded body were measured to evaluate the brightness on the side opposite the light source of the resin molded body and the mutual visibility of the areas partitioned by the resin molded body. Cases where sufficient brightness was ensured and visibility was suppressed were rated "A." Cases where visibility was suppressed with a slight decrease in brightness, or cases where sufficient brightness was ensured but visibility was slightly improved were rated "B." Cases where sufficient brightness was ensured but clear visibility was possible, or cases where visibility was sufficiently suppressed but sufficient brightness was not ensured were rated "C."

[0037] In Table 1 below, Comparative Examples 1 and 2 are non-foamed resin molded articles, while the others are resin molded articles containing a foamed core layer. The resin "PC" refers to polycarbonate resin, and the transmittance refers to total light transmittance. The additive used was Metablen.

[0038] [Table 1]

[0039] Examples 1 to 4 In the resin moldings of Examples 1 to 4, the average bubble diameter contained in the core layer was set to 30 to 70 μm, and the specific gravity reduction rate was set to 1 to 30%, thereby achieving a well-balanced total light transmittance and diffuse reflectance of 40 to 60%. In particular, Example 1 was evaluated as "A," indicating that a well-balanced total light transmittance and diffuse reflectance could be achieved. Furthermore, as shown in the "specific gravity" of Examples 1 to 4 in Table 1, a relatively light weight was achieved.

[0040] Comparing the resin molded articles of Examples 1 to 4, when the average cell diameter was 45 to 55 μm and the specific gravity reduction rate was 22 to 24%, the evaluation was "A." This shows that it is preferable to set the average cell diameter to 40 to 60 μm and the specific gravity reduction rate to 15 to 25%, it is more preferable to set the average cell diameter to 40 to 60 μm and the specific gravity reduction rate to 15 to 25%, and it is even more preferable to set the average cell diameter to 45 to 55 μm and the specific gravity reduction rate to 22 to 24%.

[0041] Furthermore, the resin molded articles of Examples 1 to 3 were evaluated using PC (polycarbonate resin) as the resin material, while the resin molded article of Example 4 was evaluated using PMMA (acrylic resin) as the resin material. That is, it is believed that the same evaluations would be obtained even if a thermoplastic resin other than PC was used in the evaluations of this example.

[0042] On the other hand, the resin molding of Comparative Example 1 was a non-foamed resin molding, and therefore the diffuse reflectance was extremely low, and the areas separated by the resin molding were clearly visible to each other, resulting in a rating of "C." In addition, weight reduction was not achieved.

[0043] The resin molding of Comparative Example 2 was a non-foamed resin molding, and due to the addition of an additive to improve diffuse reflectance, the total light transmittance was significantly low, and sufficient brightness could not be ensured, resulting in a rating of "C." Furthermore, weight reduction was not achieved.

[0044] Although the resin molding of Comparative Example 3 was lightweight due to foam molding, the specific gravity reduction rate was too large, resulting in a significantly high diffuse reflectance. As a result, sufficient brightness could not be ensured, and the product was rated "C."

[0045] The resin molding of Comparative Example 4 had a relatively large specific gravity reduction rate and a high diffuse reflectance due to the absence of a skin layer. As a result, sufficient brightness could not be ensured, and the product was rated "C."

[0046] The resin molding of Comparative Example 5 had a high total light transmittance because the specific gravity reduction rate was too small. The areas separated by the resin molding were clearly visible, so it was rated "C."

[0047] The resin molding of Comparative Example 6 had a small average bubble diameter, resulting in a high total light transmittance. The areas separated by the resin molding were clearly visible, resulting in a rating of "C."

[0048] The resin molding of Comparative Example 7 had a relatively large average bubble diameter, resulting in a high diffuse reflectance. As a result, sufficient brightness could not be ensured, resulting in a rating of "C." [Explanation of symbols]

[0049] 1 resin molding, 2 core layer, 3 skin layer, 4 skin layer, 21 air bubble

Claims

1. A foamed molded article containing a thermoplastic resin, a core layer made of a foamed resin; a first skin layer made of a non-foaming resin and laminated on one main surface of the core layer; a second skin layer laminated on the other main surface of the core layer, The foamed molded article has a specific gravity reduction rate of 1 to 30%, A foamed molded article, wherein the cells contained in the core layer have an average cell diameter of 30 to 70 μm.

2. The foamed molded article according to claim 1, The foam-molded article, wherein the thermoplastic resin is a polycarbonate resin.

3. The foamed molded article according to claim 1, The foam molded article has a total light transmittance of 40 to 60% and a diffuse reflectance of 40 to 60%.

4. A partition plate, A partition plate comprising the foam molded article according to any one of claims 1 to 3.

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