Resin molded body

Abstract

To provide a resin molded body capable of enhancing toughness.SOLUTION: The resin molded product 1 according to the present invention has a core layer 2 made of a foamed resin, and skin layers 3 and 4 made of a non-foamed resin laminated on the main surfaces of the core layer 2. The core layer 2 contains a polyamide resin 21 and a plurality of silicone particles 22. Each of the plurality of silicone particles 22 has a scale-like shape and is arranged on a bubble wall between adjacent bubbles 23 of the core layer 2 made of the foamed resin. When a load is applied to the resin molded body, the stress is distributed around the plurality of silicone particles, so that toughness can be improved.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a resin molded article containing a polyamide resin and silicone particles. [Background technology]

[0002] In recent years, various methods for recycling plastic products have been investigated in view of the depletion of petroleum resources and environmental protection.

[0003] Japanese Patent No. 7276731 (Patent Document 1) discloses a polyamide resin composition for material recycling of polyamide resin products such as automobile parts or office automation equipment. The polyamide resin composition is composed of 100 parts by weight of polyamide resin (A), 0.01 to 12 parts by weight of silicone resin (B), and 0.01 to 5 parts by weight of silane coupling agent (C) having at least one functional group selected from the group consisting of an isocyanate group, an epoxy group, and an acid anhydride group. As a result, even if the polyamide resin product contains silicone resin as an impurity, the polyamide resin composition inhibits the silicone resin from falling off from molded articles and adhesion of the silicone resin to the mold surface during molding, and also improves the mechanical properties of the molded articles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7276731 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, with the increasing demand for smaller and more functional resin products, attention has been focused on toughness as an ability to absorb impact. When a resin molded body is subjected to an impact and cracks occur, the destruction cannot be prevented even by removing the impact. However, if the above-mentioned toughness of the resin molded body can be improved, the impact on the resin molded body can be absorbed and the destruction of the resin molded body can be suppressed.

[0006] Therefore, an object of the present disclosure is to provide a resin molded article that can improve toughness. [Means for solving the problem]

[0007] In order to solve the above problems, the present disclosure provides the following solution. Specifically, the present disclosure provides a resin molded article having a core layer made of a foamed resin and a skin layer made of a non-foamed resin laminated on at least one of the main surfaces of the core layer. The core layer contains a polyamide resin and a plurality of silicone particles. Each of the plurality of silicone particles has a scale shape. [Effects of the Invention]

[0008] According to the resin molded article according to the present disclosure, toughness can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a resin molded body according to this embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional photograph of the resin molded body shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the resin molded body shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present inventors have conducted extensive research into improving the toughness of resin molded articles containing polyamide resin and a plurality of silicone particles, as described below. Generally, when attempting to improve the strength of a resin molded article made from polyamide resin, the inclusion of foreign matter such as silicone particles is undesirable, and a high purity of the polyamide resin is preferable. However, as described above, when recycling existing polyamide resin products, foreign matter such as silicone particles may be present. Therefore, the present inventors have conducted extensive research into resin molded articles made from polyamide resin as a base material that can achieve improved strength, i.e., improved toughness, even when containing silicone particles, which are foreign matter.

[0011] The present inventors first considered that the toughness of a resin molded body could be improved if the absorbed energy could be increased relative to the load applied to the resin molded body. To increase the absorbed energy, the present inventors considered forming the resin molded body from a foamed resin having a large number of bubbles and arranging a plurality of flaky silicone particles on the bubble walls formed between the bubbles. As a result, as is known from Griffith's theory, stress tends to concentrate around the flaky silicone particles with a high aspect ratio, dispersing the stress applied to the load point around the plurality of silicone particles, making it easier to increase the absorbed energy. However, if the resin molded body is formed only from a foamed resin, there is a risk that the resin molded body will break linearly from the load point, making it difficult to properly distribute the stress.

[0012] Therefore, the present inventors conceived the idea of ​​laminating a non-foamed resin layer (skin layer) made of a non-foamed resin on the main surface of a foamed resin layer (core layer) made of a foamed resin containing multiple scale-shaped silicone particles. The provision of a skin layer not only improves the rigidity of the resin molded body but also facilitates the dispersion of the aforementioned stress. Specifically, when a load is applied to the highly rigid skin layer, the skin layer is prevented from breaking linearly from the load point, and fracture is more likely to occur dispersedly from various locations on the cell walls in the core layer where multiple silicone particles are arranged. This allows for a relatively large fracture surface, which in turn allows the resin molded body to absorb more energy before it is completely destroyed, thereby improving its toughness. The present disclosure was completed by the present inventors based on this finding. Patent Document 1 does not propose such an improvement in the toughness of a resin molded body.

[0013] (Configuration 1) A resin molded article according to an embodiment of the present disclosure includes a core layer made of a foamed resin and a skin layer made of a non-foamed resin laminated on at least one of the main surfaces of the core layer. The core layer includes a polyamide resin and a plurality of silicone particles. Each of the plurality of silicone particles has a scale shape.

[0014] This makes it possible to disperse stress due to a load applied to the resin molding, thereby increasing the absorbed energy and improving the toughness of the resin molding.

[0015] (Configuration 2) In the resin molded article of Configuration 1, the core layer may contain less than 10.0 parts by weight of the silicone particles per 100 parts by weight of the polyamide resin contained in the core layer, thereby more effectively improving the toughness of the resin molded article.

[0016] (Configuration 3) In the resin molded article of Configuration 1 or 2, the average particle size of the plurality of silicone particles may be 1 to 500 μm, which makes it possible to more effectively improve the toughness of the resin molded article.

[0017] (Configuration 4) In the resin molded article of any one of Configurations 1 to 3, the core layer may have an expansion ratio of 1.5 to 3. This makes it possible to more effectively improve the toughness of the resin molded article.

[0018] (Configuration 5) In the resin molded product of any one of Configurations 1 to 4, the skin layer may include a first skin layer laminated on one main surface of the core layer and a second skin layer laminated on the other main surface of the core layer, thereby more effectively improving the toughness of the resin molded product.

[0019] (Configuration 6) In the resin molded article of Configuration 5, the total thickness of the first skin layer and the second skin layer may be 10% to 50% of the overall thickness of the resin molded article, thereby more effectively improving the toughness of the resin molded article.

[0020] (Configuration 7) In the resin molded article of any one of Configurations 1 to 6, the skin layer may contain a polyamide resin and a plurality of silicone particles. By using the same resin material as that of the core layer, the manufacturing efficiency of the resin molded article 1 can be improved.

[0021] Hereinafter, an embodiment of a resin molded product 1 according to the present disclosure will be described in detail 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.

[0022] 1, the resin molded product 1 has a core layer 2, 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. Although the resin molded product 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, the core layer 2 may have the skin layer 3 or the skin layer 4 on at least one of the one main surface or the other main surface.

[0023] The overall thickness of the resin molded body 1, including the core layer 2, the skin layer 3, and the skin layer 4, is preferably 2 mm or more and 15 mm or less, and more preferably 2 mm or more and 10 mm or less. By forming the resin molded body 1 with such a thickness, it becomes easier to more effectively improve the toughness.

[0024] 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.

[0025] As shown in FIG. 2, the core layer 2 contains a polyamide resin 21 and a plurality of silicone particles 22. FIG. 2 is an image of a cross section of the resin molded body 1 cut along the thickness direction, photographed at an acceleration voltage of 15 kV and a magnification of 30 times. In the figure, the relatively white parts located near the center of the image are the scaly silicone particles 22, and the relatively black parts are the bubbles 23. The polyamide resin 21 is the base material of the core layer 2 and forms the core layer 2. The core layer 2 is foam-molded as described above, and therefore has a large number of bubbles 23. The plurality of silicone particles 22 are preferably disposed inside the polyamide resin 21, which is the base material of the core layer 2, particularly in the bubble walls formed between the numerous bubbles 23.

[0026] Each of the plurality of silicone particles 22 has a scale shape. In this disclosure, "silicone particle" refers to a silicone resin that has been hardened by a crosslinking process, and "scale shape" refers to a thin, flat shape, including those referred to as plate-like, flake-like, and plate-like. More specifically, "scale shape" refers to a shape whose area in a plan view is larger than the area in a side view observed from a direction perpendicular to the observation direction in the plan view. Area S1 [μm 2 ] and the area S0 [μm 2 The ratio S1 / S0 to the total amount of silicone particles 22 is preferably 5 or more and 200 or less, more preferably 10 or more and 100 or less, and even more preferably 20 or more and 60 or less. The shape of the silicone particles 22 in a plan view is not particularly limited and may be circular, elliptical, angular, irregular, or the like. The silicone particles 22 may be either an addition reaction curing type or a peroxide curing type.

[0027] Inclusion of multiple scale-shaped silicone particles 22 in the polyamide resin 21, which is the base material of the core layer 2, facilitates stress dispersion in response to a load applied to the resin molded body 1. More specifically, the silicone particles 22 are less likely to adhere to the polyamide resin 21. That is, the silicone particles 22 can be included in the core layer 2 in a state in which they are easily peeled from the polyamide resin 21. As a result, when a load is applied to the resin molded body 1 (skin layer 3 or 4), stress tends to concentrate around the silicone particles 22, i.e., at the interface between the polyamide resin 21 and the silicone particles 22, dispersing the stress in response to the load applied to the resin molded body 1. As a result, the absorbed energy can be increased, improving the toughness of the resin molded body 1. That is, increasing the absorbed energy can prevent the resin molded body 1 from being completely destroyed by repeated bending. The non-adhesion state between the polyamide resin 21 and the silicone particles 22 can be confirmed from the state of the silicone particles 22 and the cell walls of the core layer 2 after foam molding. When the polyamide resin 21 and the silicone particles 22 are not bonded, bubbles 23 are more likely to form at the interface of the silicone particles 22, and the silicone particles 22 are more likely to be arranged so as to cross the bubble walls formed between adjacent bubbles 23.

[0028] The core layer 2 may contain less than 10.0 parts by weight of the silicone particles 22 relative to 100 parts by weight of the polyamide resin 21 contained in the core layer 2. If the content of the silicone particles 22 in the core layer 2 is too low, it becomes difficult to properly distribute stress. On the other hand, if the content of the silicone particles 22 is too high, the fracture stress required for fracture per unit fracture surface of the core layer 2 becomes small, making it difficult to increase the absorbed energy. Therefore, from the perspective of more effectively improving toughness, the content of the silicone particles 22 in the core layer 2 is preferably 0.1 parts by weight or more but less than 10.0 parts by weight, preferably 0.2 to 5.0 parts by weight, and more preferably 0.3 to 2.0 parts by weight, relative to 100 parts by weight of the polyamide resin 21. In other words, the content of the silicone particles 22 in the core layer 2 is preferably 0.1 parts by weight or more, preferably 0.2 parts by weight or more, and more preferably 0.3 parts by weight or more, relative to 100 parts by weight of the polyamide resin 21. It is advisable to keep the amount below 10.0 parts by weight, preferably 5.0 parts by weight or less, and more preferably 2.0 parts by weight or less.

[0029] The average particle diameter of the plurality of silicone particles 22 can be 1 to 500 μm. If the average particle diameter is greater than 500 μm, stress tends to concentrate more around the silicone particles 22. Although a sufficient improvement in toughness can be achieved, breakage tends to occur more easily around the silicone particles 22 than when the average particle diameter is 1 to 500 μm. On the other hand, if the average particle diameter is less than 1 μm, although a sufficient improvement in toughness can be achieved, the effect of the silicone particles 22 in dispersing stress may be reduced. Therefore, from the viewpoint of more effectively improving toughness, it is preferable that the average particle diameter of the plurality of silicone particles 22 be 1 to 500 μm. It is preferable that the particle diameter distribution of the plurality of silicone particles 22 be a normal distribution.

[0030] The average particle size of the multiple silicone particles 22 can be determined by the following method. The resin molded body 1 is dissolved in phenols, a saturated methanol solution of calcium chloride, concentrated formic acid, or the like, and then filtered to separate the silicone particles 22. A membrane filter with a maximum pore size of 0.22 μm is used for filtration. The obtained silicone particles 22 are photographed at 500x magnification using a differential scanning electron microscope, and the particle size of any multiple silicone particles 22 that can be identified is determined by enlarging the image to a magnification that allows the particle size to be measured. The average value of the particle sizes can be used as the average particle size of the multiple silicone particles 22. Here, the smallest hypothetical sphere that can completely encapsulate the scaly silicone particles 22 is considered, and the diameter of this hypothetical sphere is used as the particle size.

[0031] The silicone particles 22 have a lower hardness than the polyamide resin 21. Therefore, when a load is applied to the resin molded body 1, the silicone particles 22 deform before the base polyamide resin 21, thereby alleviating the stress on the polyamide resin. As a result, it is believed that the resin molded body 1 becomes more easily deformable, which increases the absorbed energy and improves toughness.

[0032] The core layer 2 can have an expansion ratio of 1.5 to 3 times. If the expansion ratio of the core layer 2 is too low, it becomes difficult for the silicone particles 22 to be arranged on the cell walls between adjacent cells 23, which may reduce the effect of dispersing stress. On the other hand, if the expansion ratio of the core layer 2 is too high, the cell diameter of the cells contained in the core layer 2 increases, or the number of cells increases, making the core layer 2 more susceptible to fracture. Therefore, from the perspective of more effectively improving toughness, the expansion ratio of the core layer 2 is preferably 1.5 to 3 times, more preferably 1.8 to 2.7 times, and more preferably 1.9 to 2.4 times. In other words, the expansion ratio of the core layer 2 is preferably 1.5 times or more, more preferably 1.8 times or more, and more preferably 1.9 times or more. It is preferably 3 times or less, more preferably 2.7 times or less, and more preferably 2.4 times or less.

[0033] 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 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.

[0034] The resin material contained in the skin layer 3 is not particularly limited as long as it has a predetermined rigidity that can achieve the above-mentioned dispersion of stress in the core layer 2. Furthermore, the resin material contained in the skin layer 3 is preferably a polyamide-based resin, but, for example, when the resin molded body 1 is molded by extrusion molding, the resin material of the skin layer 3 is not particularly limited as long as its viscosity at the heating temperature during molding is approximately the same as that of the core layer 2 and multilayer extrusion is possible.

[0035] Like the core layer 2, the skin layer 3 may contain a polyamide resin 21 and a plurality of silicone particles 22. Using the same resin material as the core layer 2 can improve manufacturing efficiency. Furthermore, the skin layer 3 may be made of a thermoplastic resin that can adhere well to the core layer 2. Using the same resin material as the core layer 2 can ensure particularly good adhesion between the core layer 2 and the skin layer 3.

[0036] The core layer 2 and the skin layer 3 may contain additives to the extent that they do not significantly impair the effects of the present disclosure. The types of additives are not particularly limited, but include, for example, 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, 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.

[0037] 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.

[0038] The total thickness of skin layer 3 and skin layer 4 can be 10% to 50% of the overall thickness of resin molded body 1. As shown in FIG. 3 , when the overall thickness of resin molded body 1 is T, the thickness of skin layer 3 is t1, and the thickness of skin layer 4 is t2, the ratio of the total thickness of skin layer 3 (t1) and skin layer 4 (t2) to the overall thickness of resin molded body 1 (T) can be calculated using the formula (t1 + t2) / T × 100. This can more effectively improve the toughness of the resin molded body. From the viewpoint of improving toughness, the total thickness of skin layer 3 and skin layer 4 should be 10% to 50% of the overall thickness of resin molded body 1, preferably 10% to 30%. In other words, the total thickness of skin layer 3 and skin layer 4 should be 10% or more, 50% or less, and more preferably 30% or less of the overall thickness of resin molded body 1.

[0039] Here, an example of a method for manufacturing the resin molded body 1 will be described (not shown). First, resin material (polyamide resin and flaky silicone particles) is introduced into the screw cylinder of the main extruder. The resin material can be obtained by crushing a silicone resin-coated polyamide resin film, a silicone resin-coated polyamide resin cloth, a silicone resin-coated polyamide resin molded product, or the like. Alternatively, the resin material may be a mixture of flaky silicone particles formed by crushing a silicone resin film and a polyamide resin base material. The resin material is heated in the screw cylinder to produce a molten resin containing the flaky silicone particles. 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 then discharged from the die outlet to form the core layer 2. Simultaneously, resin materials are introduced into each of the screw cylinders of the two sub-extruders, heated and melted, to produce 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. At this time, the multiple silicone particles are arranged so as to be embedded in the cell walls of the polyamide resin. The extruded resin molded body 1 is cooled and then transported to a cutting machine by a take-up machine. The cutting machine cuts the resin molded body 1 into the desired shape. The resin molded body 1 can be manufactured in this manner. A physical foaming method using an inert gas such as nitrogen or carbon dioxide as a foaming agent can be used. However, the manufacturing method of the resin molded body 1 is not limited to this. For example, the core layer 2 and the skin layers 3 and 4 may be formed separately, and then the skin layers 3 and 4 may be adhered to one and the other main surfaces of the core layer 2, respectively.Furthermore, as long as the skin layer 3 or 4 can be formed on the surface of the core layer 2, the molding method is not limited to the above-mentioned co-extrusion molding method, and injection molding or extrusion molding may also be used.

[0040] Because the resin molded body 1 includes a foam-molded core layer, the amount of resin used can be reduced. As a result, the resin molded body 1 can contribute to improving resource utilization efficiency, easing transportation burdens, reducing energy consumption, and reducing CO2 emissions. By providing the resin molded body 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 resin molded body 1 according to this embodiment can be melted and reused, it can contribute to the achievement of Goal 12 (Responsible Consumption and Production).

[0041] 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.

[0042] [Example] Resin molded articles were prepared in Examples 1 to 9 and Comparative Examples 1 to 3, and the toughness of each resin molded article was evaluated by a three-point bending test. Specifically, in Examples 1 to 9 and Comparative Examples 1 to 3, plate-shaped resin molded articles measuring 10 mm in width, 60 mm in length, and weighing 1.2 g were prepared. The resin molded articles were made of polyamide resin as the base material, and skin layers were formed on both the main surfaces of the core layer and the other main surface. A three-point bending test was performed on each resin molded article under conditions of a fulcrum distance of 30 mm and a loading rate of 10 mm / min. In a graph showing the SS curve (stress-strain curve) obtained from the bending test, toughness was calculated from the area enclosed by the SS curve, a perpendicular line from the fracture point to the horizontal axis, and the horizontal axis. Toughness was evaluated as follows: "A" for toughness greater than 2.0 N·m, "B" for toughness greater than 1.5 N·m but not greater than 2.0 N·m, and "C" for toughness less than 1.5 N·m. It should be noted that the resin molded body according to the present invention is not limited to this embodiment.

[0043] [Table 1]

[0044] In Table 1 above, the thickness of the skin layer refers to the thickness of one of the two skin layers laminated on both main surfaces of the core layer, and is approximately half the thickness of the two skin layers. The skin layer thickness ratio refers to the ratio of the total thickness of the two skin layers to the thickness of the resin molded body. The silicone particle content refers to the content of silicone particles per 100 parts by weight of polyamide resin. The "particle size" of the silicone particles refers to the average particle size of multiple silicone particles, with an average particle size of 1 to 500 μm being indicated as "within range," an average particle size greater than 500 μm being indicated as ">500," and an average particle size less than 1 μm being indicated as "<1." The expansion ratio is the specific gravity of the resin molded body after expansion divided by the specific gravity of the resin material before expansion.

[0045] (Comparison of Examples 1 to 9 with Comparative Examples 1 to 3) The resin molded articles of Examples 1 to 9 contained silicone particles, had a skin layer and a core layer, and the core layer was foam-molded. On the other hand, the resin molded article of Comparative Example 1 did not contain silicone particles, the resin molded article of Comparative Example 2 had an expansion ratio of 1 and therefore did not have a foam-molded core layer, and the resin molded article of Comparative Example 3 had spherical silicone particles. Comparing the resin molded articles of Examples 1 to 9 and Comparative Examples 1 to 3, Examples 1 to 9 were rated "B" or higher in toughness, demonstrating relatively good toughness, whereas the comparative examples were rated "C" in toughness and failed to achieve good toughness.

[0046] (Comparison of Examples 1, 2 and 5) Examples 1, 2, and 5 were compared, with the same skin layer thickness, silicone particle size and shape, and core layer expansion ratio, but different silicone particle content. Example 5, with a content of 10 phr, was rated "B" for toughness, while Examples 1 and 2, with a content of 0.5 phr or 2 phr, were rated "A" for toughness. This shows that if the content is less than 10 phr, preferably 5 phr or less, and more preferably 2 phr or less, the toughness of the resin molded article can be more effectively improved.

[0047] (Comparison of Examples 1, 8 and 9) Examples 1, 8, and 9 were compared, which had the same silicone particle content and shape, and the same core layer expansion ratio, and roughly the same conditions but different skin layer thicknesses, but different silicone particle sizes. Example 1, in which the particle size was "within range," was rated "A" for toughness, while Examples 8 and 9, in which the particle size was ">500" or "<1," were rated "B" for toughness. This demonstrates that if the particle size is "within range," the toughness of the resin molded product can be more effectively improved.

[0048] (Comparison with Examples 1, 4, and 6 and Comparative Example 2) Examples 1, 4, and 6 were compared with Comparative Example 2, which had the same skin layer thickness, silicone particle content, particle size, and shape, but differed only in the expansion ratio of the core layer. Example 6, which had an expansion ratio of 4, was rated "B" for toughness, while Examples 1 and 4, which had an expansion ratio of 2 or 3, were rated "A" for toughness. Furthermore, Comparative Example 2, which had an expansion ratio of 1, i.e., an unfoamed core layer, was rated "C" for toughness. This demonstrates that the toughness of the resin molded article can be more effectively improved if the expansion ratio of the core layer is 1.5 to 3 times, or at least 2 to 3 times.

[0049] (Comparison of Examples 1, 3 and 7) Examples 1, 3, and 7 were compared, with the same silicone particle content, particle size, and shape, and the same core layer expansion ratio, but different skin layer thickness ratios. Example 7, in which the skin layer thickness ratio was 55%, was rated "B" for toughness, while Examples 1 and 3, in which the skin layer thickness ratio was 10% or 30%, were rated "A" for toughness. This shows that the toughness of the resin molded body can be more effectively improved if the skin layer thickness ratio is 10% or more and 50% or less, preferably 10% or more and 30% or less.

[0050] In this example, a resin molded body containing silicone particles in the skin layer was used, but it is believed that if the skin layer does not contain silicone particles, which are foreign matter, the skin layer will be less likely to break, and the toughness of the resin molded body as a whole can be improved. [Explanation of symbols]

[0051] 1 resin molded body, 2 core layer, 21 polyamide resin, 22 silicone particles, 23 air bubbles, 3 skin layer, 4 skin layer

Claims

1. A resin molded product having a core layer made of a foamed resin and a skin layer made of a non-foamed resin laminated on at least one of the main surfaces of the core layer, the core layer includes a polyamide resin and a plurality of silicone particles; The resin molded article, wherein each of the plurality of silicone particles has a scale shape.

2. The resin molded article according to claim 1, The resin molded product, wherein the plurality of silicone particles are contained in the core layer in an amount of less than 10.0 parts by weight per 100 parts by weight of the polyamide resin contained in the core layer.

3. The resin molded article according to claim 1, The average particle size of the plurality of silicone particles is 1 to 500 μm.

4. The resin molded article according to claim 1, The core layer is a resin molded article having an expansion ratio of 1.5 to 3 times.

5. The resin molded article according to claim 1, The resin molded body, wherein the skin layer includes a first skin layer laminated on one main surface of the core layer and a second skin layer laminated on the other main surface of the core layer.

6. The resin molded article according to claim 5, A resin molded body, wherein the total thickness of the first skin layer and the second skin layer is 10% or more and 50% or less of the overall thickness of the resin molded body.

7. The resin molded article according to any one of claims 1 to 6, The skin layer comprises a polyamide resin and a plurality of silicone particles.

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