Flame-retardant coating film, flame-retardant coating foam film, and resin housing

Abstract

The purpose of the present disclosure is to obtain a flame-retardant coating film capable of suppressing formation of holes in a resin housing during flame contact.　A flame-retardant coating film (2) according to the present disclosure covers the surface of a resin substrate (1) molded from a resin material, the flame-retardant coating film (2) comprising: an A layer (3) disposed on the surface of the resin substrate (1); and a B layer (4) disposed on the side of the A layer (3) opposite from the resin substrate (1). The A layer (3) contains a binder resin, a flame retardant, a foaming agent, and a carbonizing agent. The B layer (4) contains aluminum hydrogen phosphite and a foaming agent (5) as expanding agents.

Description

Flame-retardant coating film, flame-retardant coating foam film, and resin housing

[0001] The present disclosure relates to a flame-retardant coating film and a flame-retardant coating foam film having flame retardancy, and a resin housing.

[0002] Resin materials are lightweight and excellent in processability, so they are used in various products and parts. For these products and parts (hereinafter collectively referred to as "resin parts"), resin materials that can withstand flames are required from the viewpoint of safety. Currently, flame-retardant resin materials containing flame retardants are widely used. However, even flame-retardant resin materials are difficult to withstand flames depending on the intensity of the flame.

[0003] In particular, in a resin housing in which electronic components are housed, when ignition occurs from the electronic components, the resin housing becomes hot and melts. As a result, holes may form in the resin housing, and the spread of fire may expand through the holes. Therefore, it is necessary to coat the surface of the resin housing with a flame-retardant material to suppress the increase in temperature of the resin housing and suppress the formation of holes in the resin housing.

[0004] For example, Patent Document 1 discloses a technique for improving the flame retardancy of a resin part by coating the surface of the resin part with a paint. Further, Patent Document 2 discloses a technique for improving the flame retardancy of a resin part by coating the surface of the resin part with a laminate.

[0005] Specifically, the paint disclosed in Patent Document 1 is a foaming refractory paint that forms a foaming layer due to an increase in temperature during flame contact, and is a foaming refractory paint that can form a coating film excellent in water resistance and fire resistance after exposure to water. The foaming refractory paint contains a vinyl acetate copolymer, a foaming agent, a charring agent, a flame retardant, and an adhesion-imparting resin. Since a charred layer formed by foaming during flame contact is formed by the foaming agent, the charring agent, and the flame retardant, the increase in temperature of the resin part can be suppressed.

[0006] Furthermore, the laminate disclosed in Patent Document 2 is a fire-resistant laminate consisting of a two-layer structure of an insulating thermal foam layer and a thermal expansion layer. The insulating thermal foam layer contains aluminum phosphite and resin, and the thermal expansion layer contains thermal expandable graphite and resin. When exposed to flame, the aluminum phosphite expands due to the crystal growth of thermally decomposed phosphoric acid, and the insulating thermal foam layer containing aluminum phosphite becomes a hard aluminum phosphite-containing sintered body (inorganic heat insulating layer) that is electrically insulating and has fine pores. On the other hand, when exposed to flame, the thermal expansion layer becomes a soft, expandable material. Therefore, even if cracks or chips occur in the insulating thermal foam layer due to the decomposition gas from the thermal expansion layer in contact with the insulating thermal foam layer and the expansion of aluminum phosphite in the insulating thermal foam layer when exposed to flame, the thermal expansion layer is designed to shield against the flame.

[0007] Japanese Patent Publication No. 2023-175249 Japanese Patent Publication No. 2019-96410

[0008] However, in the technology disclosed in Patent Document 1, the carbonized layer formed during flame contact is soft, so if the carbonized layer is exposed to flame for a long period of time, deformation and detachment of the carbonized layer occur, reducing the thermal insulation performance of the carbonized layer. As a result, if a resin housing coated with the foamed fire-resistant paint of Patent Document 1 is exposed to flame for a long period of time, the melting due to the high temperature of the resin housing cannot be suppressed, leading to the problem of holes forming in the resin housing.

[0009] Furthermore, in the technology disclosed in Patent Document 2, if cracking or chipping occurs in the insulating thermal foam layer during flame contact, the soft thermal expansion layer cannot be reinforced with the insulating thermal foam layer. Therefore, if the thermal expansion layer is exposed to flame for a long period of time, the thermal expansion layer gradually deforms and shrinks, reducing the thermal insulation performance of the thermal expansion layer. As a result, if a resin housing coated with the refractory laminate of Patent Document 2 is exposed to flame for a long period of time, the melting due to the high temperature of the resin housing cannot be suppressed, leading to the problem of holes forming in the resin housing.

[0010] This disclosure has been made in view of the above, and aims to provide a flame-retardant coating film that can suppress the formation of holes in the resin housing when exposed to flame.

[0011] To solve the above-mentioned problems and achieve the objective, the flame-retardant coating film according to this disclosure is a flame-retardant coating film that covers the surface of a resin substrate molded from a resin material, and comprises a layer A disposed on the surface of the resin substrate and a layer B disposed on the opposite side of the resin substrate with layer A in between. Layer A contains a binder resin, a flame retardant, a foaming agent and a carbonizing agent, and layer B contains aluminum hydrogen phosphite and a foaming agent as an expander.

[0012] The flame-retardant coating film described herein has the effect of suppressing the formation of holes in the resin housing when exposed to flame.

[0013] A schematic cross-sectional view showing an example of the structure of the flame-retardant coating film according to Embodiment 1. A schematic cross-sectional view showing an example of the change in the structure of the flame-retardant coating film due to flame contact with the flame-retardant coating film according to Embodiment 1. A schematic cross-sectional view showing another example of the structure of the flame-retardant coating film according to Embodiment 1. A schematic cross-sectional view showing an example of the structure of the flame-retardant foamed coating film according to Embodiment 2. A schematic cross-sectional view showing an example of the structure of the resin housing according to Embodiment 3.

[0014] The flame-retardant coating film, flame-retardant foamed coating film, and resin housing according to the embodiment will be described in detail below with reference to the drawings. Note that the shape and size of each particle shown in the drawings are schematic representations for the purpose of making the explanation easier to understand and do not represent the actual shape and size of each particle.

[0015] Embodiment 1. Figure 1 is a schematic cross-sectional view showing an example of the structure of the flame-retardant coating film 2 according to Embodiment 1. Figure 2 is a schematic cross-sectional view showing an example of the change in the structure of the flame-retardant coating film 2 due to flame contact with the flame-retardant coating film 2 according to Embodiment 1. The flame-retardant coating film 2 is a flame-retardant coating film 2 that covers the surface of a resin substrate 1 molded from a resin material. The resin substrate 1 and the flame-retardant coating film 2 constitute a resin housing 11, which will be described later. The flame-retardant coating film 2 comprises a layer A 3 arranged on the surface of the resin substrate 1 and a layer B 4 arranged on the opposite side of the resin substrate 1 with layer A 3 in between. The flame-retardant coating film 2 is a two-layer flame-retardant coating film 2 comprising layer A 3 and layer B 4. Layer A 3 contains a binder resin, a flame retardant, a foaming agent, and a carbonizing agent. Layer B 4 contains a binder resin, aluminum hydrogen phosphite as an expanding agent, and a foaming agent 5. Layer B 4 is laminated on the surface of layer A 3 that faces away from the resin substrate 1. In Figure 1, for the sake of explanation, only the foaming agent 5 of layer B 4 is shown.

[0016] The binder resin of layer A 3 contains at least one resin from among alkyd resin, urethane resin, epoxy ester resin, epoxy resin, silicone resin, acrylic resin, and polyester resin. In particular, from the viewpoint of improving the adhesion of layer A 3 to the resin substrate 1, and from the viewpoint of facilitating the dispersion of flame retardants, foaming agents, etc., in the binder resin, it is preferable that the binder resin contains at least one resin from among alkyd resin and epoxy ester resin. In addition, the binder resin may be a resin dissolved in an organic solvent, or a resin dispersed as an emulsion in an aqueous dispersion medium. In particular, from the viewpoint of environmental considerations, it is preferable that the latter be used for the binder resin. Specific examples of alkyd resins include "Watersol BC-3010", "Watersol BC-3040", and "Watersol BC-3140" manufactured by DIC Corporation. Specific examples of epoxy ester resins include DIC's "Watersol BM-1000P," "Watersol EFD-5570," and "Watersol EFD-5580."

[0017] The flame retardant in layer A 3 preferably contains at least one flame retardant from among ammonium polyphosphate and melamine polyphosphate. These flame retardants decompose when heated and, when used in combination with a foaming agent and a carbonizing agent, exhibit the function of promoting the formation of a soft carbonized layer with fine pores (organic heat insulating layer A 9, shown in Figure 2 and described later) when exposed to flame due to the gasification of the foaming agent. Ammonium polyphosphate and melamine polyphosphate may be used in which the surface is coated with melamine to enhance water resistance. In addition to the above-mentioned flame retardants, it is preferable that the flame retardant further contains at least one flame retardant from among zinc borate, guanylurea phosphate, and piperazine phosphate. This further promotes the formation of the carbonized layer. The average particle size of the flame retardant particles is preferably in the range of 1 μm or more and less than 500 μm, and more preferably in the range of 1 μm or more and 300 μm or less. If the average particle size of the flame retardant particles is less than 1 μm, the specific surface area of ​​the particles is large, and the flame retardant is more susceptible to the effects of hydrolysis. Therefore, if the flame retardant is exposed to a high-humidity environment for a long period of time, deterioration of layer A 3 may occur, potentially leading to peeling of layer A 3 from the resin substrate 1. On the other hand, if the average particle size of the flame retardant particles is 500 μm or larger, the smoothness and gloss of the surface of the resin housing 11 may be impaired when the surface of the resin substrate 1 is coated with layer A 3.

[0018] The blowing agent in layer A3 undergoes gas decomposition upon heating, promoting the expansion of the carbonized layer and enhancing its heat-insulating properties, thereby contributing to improved flame retardancy of the carbonized layer. Preferably, the blowing agent used has the property of gasifying at a rate of 60% or more by weight when heated at a temperature of 350°C or lower. Specific examples of blowing agents include melamine, urea, dicyandiamide, and guanidine. These blowing agents not only promote the expansion of the carbonized layer, but the gasified components diffuse onto the surface of the flame-retardant coating film 2, reducing the combustion temperature of the flame. Preferably, the amount of blowing agent added is 5 to 150 parts by weight per 100 parts by weight of the binder resin's solid content ratio. If the amount of blowing agent added is less than 5 parts by weight per 100 parts by weight of the binder resin's solid content ratio, the uniformity of the micropores in the carbonized layer decreases, resulting in variations in the thickness of the carbonized layer after expansion, potentially impairing the appearance of the carbonized layer. On the other hand, if the amount of foaming agent added exceeds 150 parts by weight per 100 parts by weight of solid content of the binder resin, an excessive amount of gas will be generated, the voids in the carbonized layer will increase, and the adhesion between the expanded carbonized layer and the resin substrate 1 may decrease.

[0019] The carbonizing agent in layer A3, when used in combination with the flame retardant, exhibits the function of forming carbonized components through a condensation reaction when heated by flame. In other words, the carbonized layer is formed by the synergistic action of the carbonizing agent and the flame retardant. The carbonizing agent is preferably a polysaccharide or a polyhydric alcohol. Specifically, the carbonizing agent preferably contains at least one of glucose, pentaerythritol, dipentaerythritol, triethylene glycol, sorbitol, and resorcinol. The carbonizing agent may also be a combination of the exemplified polysaccharides or polyhydric alcohols and other polysaccharides or polyhydric alcohols.

[0020] When layer A 3, which contains the above components, is heated by flame, the foaming agent gasifies, transforming it into a soft carbonized layer with fine pores. The expansion start temperature of layer A 3 is preferably 200°C to 300°C. In this way, a carbonized layer can be formed in the initial stages when layer A 3 is exposed to flame.

[0021] The leavening agent and foaming agent 5 of layer B 4 are dispersed in the binder resin. Layer B 4 can be formed by coating the surface of the dried layer A 3 with a composition containing the binder resin, leavening agent and foaming agent 5, and then drying this composition. The binder resin of layer B 4 contains at least one resin from among alkyd resin, urethane resin, epoxy ester resin, epoxy resin, silicone resin, acrylic resin, and polyester resin. The binder resin of layer B 4 may be the same resin as the binder resin of layer A 3, or it may be a different resin from the binder resin of layer A 3.

[0022] The expanding agent for layer B 4 is aluminum hydrogen phosphite (Al2(HPO3)3). When heated by flame, aluminum hydrogen phosphite expands due to the crystal growth of thermally decomposed phosphoric acid, exhibiting the function of forming a hard inorganic insulating layer (inorganic insulating layer B 10, shown in Figure 4 and described later) with fine pores. The expansion start temperature of layer B 4 is preferably higher than the expansion start temperature of layer A 3. For example, if the expansion start temperature of layer A 3 is 200°C or higher and 300°C or lower, the expansion start temperature of layer B 4 is preferably higher than 300°C. In this way, when aluminum hydrogen phosphite is heated at a temperature higher than 300°C, expansion of the aluminum hydrogen phosphite occurs, and the inorganic insulating layer B 10 can be formed. Since the inorganic insulating layer B 10 is composed of inorganic components, in addition to flame retardancy, it has excellent hydrolysis resistance and weather resistance.

[0023] The amount of leavening agent added to layer B 4 is preferably 20 parts by weight or more and 200 parts by weight or less per 100 parts by weight of the solid content ratio of the binder resin. If the amount of leavening agent added to layer B 4 is less than 20 parts by weight per 100 parts by weight of the solid content ratio of the binder resin, the inorganic insulation layer B 10 becomes thin. As a result, when the inorganic insulation layer B 10 is exposed to a high humidity environment, moisture may penetrate into the organic insulation layer A 9, potentially leading to a decrease in adhesion between the organic insulation layer A 9 and the resin substrate 1. On the other hand, if the amount of leavening agent added to layer B 4 exceeds 200 parts by weight per 100 parts by weight of the solid content ratio of the binder resin, the thickness of the inorganic insulation layer B 10 becomes thicker. Therefore, when a curved resin substrate 1 is coated with a flame-retardant coating film 2, cracks are more likely to occur in the inorganic insulation layer B 10 at the curved parts of the resin substrate 1. Although the flame retardancy of the inorganic insulation layer B 10 can be ensured, the appearance of the inorganic insulation layer B 10 may be impaired.

[0024] Here, we consider the case where the expansion start temperature of layer A 3 is between 200°C and 300°C, and the expansion start temperature of layer B 4 is higher than 300°C (i.e., the expansion start temperature of layer B 4 is higher than the expansion start temperature of layer A 3). When layer A 3 is heated by flame at a temperature between 200°C and 300°C, it expands and changes into a soft carbonized layer with fine pores due to the gasification of the foaming agent. At this time, decomposition gas is generated as layer A 3 expands, so if the expansion start temperature of layer B 4 is higher than that of layer A 3, there is a concern that cracks and chips may occur in the unexpanded layer B 4 due to the pressure of the decomposition gas generated as layer A 3 expands (the expansion pressure of layer A 3). Therefore, if layer B 4 is impregnated with a foaming agent 5 and the decomposition start temperature of this foaming agent 5 is set to 300°C or lower, when layer B 4 is heated by flame at a temperature of 300°C or lower, the foaming agent 5 in layer B 4 will gas-decompose. This gas decomposition creates holes 6 that penetrate the B layer 4 in the direction of its thickness, as shown in Figure 2. The holes 6 are foaming marks of the foaming agent 5. The decomposition gas generated as the A layer 3 expands is released outside the system (outside the A layer 3 and outside the B layer 4) through the holes 6, thereby suppressing the occurrence of cracks and chips in the B layer 4 due to the expansion pressure of the A layer 3.

[0025] Specific examples of the blowing agent 5 in layer B 4 include azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, 4,4'-oxybis(benzenesulfonylhydrazide), sodium bicarbonate, and barium azocarboxylate. Furthermore, in order to form holes 6 that penetrate layer B 4, the amount of gas generated from the blowing agent 5 in layer B 4 is preferably 100 g / ml or more. In addition, the average particle size of the blowing agent 5 particles in layer B 4 is preferably in the range of 1 μm or more and less than 100 μm. If the average particle size of the blowing agent 5 particles in layer B 4 is less than 1 μm, the amount of gas generated from each particle during the blowing of the blowing agent 5 in layer B 4 will be small, making it difficult to release the decomposition gas generated from layer A 3. As a result, although the flame retardancy of layer A 3 and layer B 4 will not be affected, voids will be generated at the interface between layer A 3 and layer B 4, and after expansion of layer A 3 and layer B 4, the carbonized layer and inorganic insulating layer B 10 may be more susceptible to damage from vibrations or other shocks. On the other hand, if the average particle size of the foaming agent 5 in layer B 4 is 100 μm or more, large holes 6 may be formed in layer B 4 when the foaming agent 5 in layer B 4 is foamed, which may impair the appearance of the inorganic insulating layer B 10 formed after heating of layer B 4.

[0026] Next, the effects of the flame-retardant coating film 2 according to Embodiment 1 will be described.

[0027] In this embodiment, as shown in Figure 1, the flame-retardant coating film 2 is a flame-retardant coating film 2 that covers the surface of a resin substrate 1 molded from a resin material, and comprises an A layer 3 disposed on the surface of the resin substrate 1 and a B layer 4 disposed on the opposite side of the resin substrate 1 with the A layer 3 in between. The A layer 3 contains a binder resin, a flame retardant, a foaming agent, and a carbonizing agent, so when the A layer 3 is heated by contact with a flame, the A layer 3 expands and changes into an organic heat insulating A layer 9, and decomposition gas is generated as a result of the expansion of the A layer 3. On the other hand, the B layer 4 contains a foaming agent 5, so when the B layer 4 is heated by contact with a flame, the gas decomposition of the foaming agent 5 forms holes 6 that penetrate the B layer 4 in the direction of its thickness. As a result, the decomposition gas associated with the expansion of the A layer 3 is released outside the system (outside the A layer 3 and B layer 4) through the holes 6, so even if the expansion of the B layer 4 starts later than the expansion of the A layer 3, the occurrence of cracks and chips in the B layer 4 due to the expansion pressure of the A layer 3 can be suppressed. Therefore, even if the inorganic heat insulating layer B 10 is exposed to flames for a long period of time, the heat insulating structure of the inorganic heat insulating layer B 10 can be maintained, and the formation of holes in the resin housing 11 during flame exposure can be suppressed.

[0028] Specifically, the expansion start temperature of layer A 3 shown in Figure 1 should be set to 200°C to 300°C, the expansion start temperature of layer B 4 should be higher than that of layer A 3, and the decomposition start temperature of the foaming agent 5 in layer B 4 should be 300°C or lower. In this way, when the flame-retardant coating film 2 is heated by flame, layer A 3 begins to expand at a relatively low temperature of 200°C to 300°C, and in the initial stages of flame contact, layer A 3 transforms into the organic insulating layer A 9 (see Figure 2), and decomposition gas is generated as layer A 3 expands. The foaming agent 5 in layer B 4 undergoes gas decomposition at a temperature of 300°C or lower, and this gas decomposition forms holes 6 that penetrate layer B 4 in the direction of its thickness. Then, as the decomposition gas generated as layer A 3 expands is released outside the system through the holes 6, even if the expansion start temperature of layer B 4 is higher than that of layer A 3, the occurrence of cracks and chips in layer B 4 due to the expansion pressure of layer A 3 can be suppressed. Therefore, even if the inorganic heat insulating layer B 10 (see Figure 4) is exposed to flames for a long period of time, the heat insulating structure of the inorganic heat insulating layer B 10 can be maintained, and the formation of holes in the resin housing 11 during flame exposure can be suppressed. Note that layer B 4 begins to expand at a temperature exceeding the expansion start temperature of layer A 3 (a temperature exceeding 300°C), and changes into a hard inorganic heat insulating layer B 10.

[0029] Because the organic insulation layer A 9 is soft, if only the organic insulation layer A 9 is exposed to flame for a long period of time, the foamed shape of the organic insulation layer A 9 collapses, and the insulation performance of the organic insulation layer A 9 deteriorates. In this embodiment, however, since layer B 4 contains aluminum hydrogen phosphite as an expander, when the flame-retardant coating film 2 is heated by flame, layer B 4 expands and changes into a hard inorganic insulation layer B 10. This reinforces the soft organic insulation layer A 9 with the hard inorganic insulation layer B 10, suppressing deformation and detachment of the organic insulation layer A 9. Therefore, even if the organic insulation layer A 9 is exposed to flame for a long period of time, the insulation structure of the organic insulation layer A 9 can be maintained, and the opening of holes in the resin housing 11 during flame exposure can be suppressed. In other words, in this embodiment, the insulation structure of the organic insulation layer A 9 and the insulation structure of the inorganic insulation layer B 10 can be maintained even with prolonged exposure to flame, and the opening of holes in the resin housing 11 during flame exposure can be suppressed.

[0030] Next, a modified example of the flame-retardant coating film 2 according to Embodiment 1 will be described.

[0031] Figure 3 is a schematic cross-sectional view showing another example of the structure of the flame-retardant coating film 2 according to Embodiment 1. To further increase the mechanical strength of the inorganic heat insulating layer B 10, it is preferable that layer B 4 contains an inorganic fibrous filler 7 as a reinforcing material. The inorganic fibrous filler 7 is a fibrous inorganic material or glass frit, and it is preferable that it has heat resistance such that its weight loss rate is 10% or less when heated at a temperature of 900°C. The fibrous inorganic material is compounded in layer B 4. When cracks occur in the inorganic heat insulating layer B 10, the fibrous inorganic material exhibits the function of improving the strength of the inorganic heat insulating layer B 10 through the composite effect of the fibers. Specific examples of fibrous inorganic materials include glass fibers, alumina fibers, carbon fibers, acicular titanium oxide, acicular alumina, magnesium sulfate inorganic fibers, and acicular zinc oxide. The glass frit melts due to the thermal energy of the flame and flows into the cracks in the inorganic heat insulating layer B 10, thereby filling the cracks and exhibiting the function of suppressing the expansion of the cracks. Preferably, the glass frit has a softening temperature of 500°C or higher and has the function of flowing into cracks in the expanded aluminum hydrogen phosphite. Such a glass frit may contain one of the following as a main component: Bi2o3-ZnO, ZnO-SiO2-b2o3, SiO2-b2o3, and SiO2-b2o3-ZrO2.

[0032] Embodiment 2. Next, the flame-retardant coated foam film 8 according to Embodiment 2 will be described with reference to Figure 4. Figure 4 is a schematic cross-sectional view showing an example of the structure of the flame-retardant coated foam film 8 according to Embodiment 2. In Embodiment 2, parts that overlap with Embodiment 1 described above are denoted by the same reference numerals and their description is omitted.

[0033] As shown in Figure 4, the flame-retardant foamed coating film 8 is a flame-retardant foamed coating film 8 that covers the surface of a resin substrate 1 molded from a resin material. The resin substrate 1 and the flame-retardant foamed coating film 8 constitute the resin housing 11, which will be described later. The flame-retardant foamed coating film 8 comprises an organic heat insulating layer A 9 placed on the surface of the resin substrate 1 and an inorganic heat insulating layer B 10 placed on the opposite side of the resin substrate 1 with the organic heat insulating layer A 9 in between. The flame-retardant foamed coating film 8 is a two-layer structure comprising the organic heat insulating layer A 9 and the inorganic heat insulating layer B 10. The organic heat insulating layer A 9 is a carbide having fine pores. The inorganic heat insulating layer B 10 contains phosphoric acid and aluminum.

[0034] The organic heat insulating layer A 9 is formed by heating layer A 3 of the above-described embodiment 1 with a flame. The organic heat insulating layer A 9 is flexible and is a heat insulating layer that conforms to the surface irregularities (not shown) of the resin substrate 1. The diameter of the micropores in the organic heat insulating layer A 9 is preferably 5 mm or less. The hardness of the organic heat insulating layer A 9, as measured with a C-type hardness tester, is preferably less than 50.

[0035] The inorganic thermal insulation layer B 10 is formed when the layer B 4 of the above-described embodiment 1 is heated by flame. The inorganic thermal insulation layer B 10 is a thermal insulation layer having fine pores. Preferably, the foam diameter of the fine pores in the inorganic thermal insulation layer B 10 is 5 mm or less. Due to the gas decomposition of the foaming agent 5 contained in the layer B 4 (see Figure 1), irregularities (not shown) are formed on the surface of the inorganic thermal insulation layer B 10. As a result, the inorganic thermal insulation layer B 10 becomes a strong thermal insulation layer, and even if the inorganic thermal insulation layer B 10 is exposed to flame for a long period of time, the thermal insulation structure of the inorganic thermal insulation layer B 10 can be maintained. The inorganic thermal insulation layer B 10 exhibits a function of reinforcing the organic thermal insulation layer A 9. As a result, even if the organic thermal insulation layer A 9 is exposed to flame for a long period of time, the thermal insulation structure of the organic thermal insulation layer A 9 can be maintained. Preferably, the hardness of the inorganic thermal insulation layer B 10 measured with a Type C hardness tester is 60 or higher. To further increase the hardness of the inorganic heat insulating layer B 10, fibrous inorganic materials or glass frit may be compounded into the inorganic heat insulating layer B 10. Specific examples of fibrous inorganic materials include glass fibers, alumina fibers, carbon fibers, acicular titanium oxide, acicular alumina, magnesium sulfate inorganic fibers, and acicular zinc oxide. Specific examples of glass frit include the components described in Embodiment 1 above.

[0036] Next, the effects of the flame-retardant coating foam film 8 according to Embodiment 2 will be described.

[0037] In this embodiment, as shown in Figure 4, the flame-retardant foam coating film 8 is a flame-retardant foam coating film 8 that covers the surface of a resin substrate 1 molded from a resin material, and comprises an organic heat insulating layer A 9 disposed on the surface of the resin substrate 1 and an inorganic heat insulating layer B 10 disposed on the opposite side of the resin substrate 1 with the organic heat insulating layer A 9 in between. Since the organic heat insulating layer A 9 is a soft carbide with fine pores, if only the organic heat insulating layer A 9 is exposed to flames and hot air for a long period of time, the foam shape of the organic heat insulating layer A 9 collapses, and the heat insulating performance of the organic heat insulating layer A 9 decreases. In this embodiment, the inorganic heat insulating layer B 10 contains phosphoric acid and aluminum, making it a hard inorganic heat insulating layer B 10. This reinforces the soft organic heat insulating layer A 9 with the hard inorganic heat insulating layer B 10, suppressing deformation and detachment of the organic heat insulating layer A 9. Therefore, even if the organic heat insulating layer A 9 is exposed to flames for a long period of time, the heat insulating structure of the organic heat insulating layer A 9 can be maintained, and the opening of holes in the resin housing 11 during flame exposure can be suppressed.

[0038] In this embodiment, the hardness of the organic insulation layer A 9, as measured by a C-type hardness tester, may be set to less than 50, while the hardness of the inorganic insulation layer B 10, as measured by a C-type hardness tester, may be set to 60 or higher. Doing so enhances the effect of reinforcing the organic insulation layer A 9 with the inorganic insulation layer B 10, thereby further suppressing deformation, detachment, cracking, and chipping of the organic insulation layer A 9. As a result, even when the organic insulation layer A 9 is exposed to flames for a long period of time, the insulation structure of the organic insulation layer A 9 can be maintained, and the formation of holes in the resin housing 11 during flame exposure can be further suppressed.

[0039] Embodiment 3. Next, the resin housing 11 according to Embodiment 3 will be described with reference to Figure 5. Figure 5 is a schematic cross-sectional view showing an example of the structure of the resin housing 11 according to Embodiment 3. In Embodiment 3, parts that overlap with Embodiments 1 and 2 described above are denoted by the same reference numerals and their description is omitted.

[0040] As shown in Figure 5, the resin housing 11 is a box-shaped resin component in which the electronic components 12 are housed. The resin housing 11 comprises a box-shaped resin substrate 1 molded from a resin material and a flame-retardant coating film 2 or a flame-retardant foamed coating film 8 covering the surface of the resin substrate 1. The resin substrate 1 forms the main body of the resin housing 11. Although the surface of the resin substrate 1 is covered by either the flame-retardant coating film 2 or the flame-retardant foamed coating film 8, for the sake of explanation, both reference numerals for the flame-retardant coating film 2 and the flame-retardant foamed coating film 8 are shown together in Figure 5. The flame-retardant coating film 2 is the same as the flame-retardant coating film 2 in Embodiment 1 described above. The flame-retardant foamed coating film 8 is the same as the flame-retardant foamed coating film 8 in Embodiment 2 described above.

[0041] Specific examples of electronic components 12 include capacitors, IC chips, and batteries such as lithium-ion batteries. These electronic components 12 are merely examples and are not intended to limit the types of electronic components 12 housed inside the resin housing 11. Figure 5 illustrates a printed circuit board 13 equipped with electronic components 12 such as capacitors and IC chips, housed inside the resin housing 11. The surface of the resin substrate 1 includes an inner surface 1a facing the inside of the resin housing 11 and an outer surface 1b facing the outside of the resin housing 11. Figure 5 illustrates an example in which both the inner surface 1a and the outer surface 1b of the resin substrate 1 are covered with a flame-retardant coating film 2 or a flame-retardant foamed coating film 8, but only one of the inner surface 1a or outer surface 1b of the resin substrate 1 may be covered with the flame-retardant coating film 2 or the flame-retardant foamed coating film 8.

[0042] Next, the effects of the resin housing 11 according to Embodiment 3 will be described.

[0043] In the present embodiment, as shown in FIG. 5, the resin housing 11 is a resin housing 11 in which the electronic component 12 is housed inside, and includes a resin base material 1 formed of a resin material and a flame-retardant coating film 2 or a flame-retardant coating foam film 8 that covers the surface of the resin base material 1. With this configuration, even when a flame is generated due to ignition of the electronic component 12 inside the resin housing 11 and the flame touches the resin housing 11, the formation of holes and thermal deformation of the resin housing 11 can be suppressed, and the spread of fire to the devices around the resin housing 11 can be suppressed. Further, even when a flame is generated outside the resin housing 11 and the flame touches the resin housing 11, the formation of holes and thermal deformation of the resin housing 11 can be suppressed, and the electronic component 12 inside the resin housing 11 can be prevented from being touched by the flame.

[0044] When the inner surface 1a of the resin base material 1 is covered with the flame-retardant coating film 2 or the flame-retardant coating foam film 8, the effect of suppressing the formation of holes and thermal deformation of the resin housing 11 due to the flame generated inside the resin housing 11 can be enhanced. On the other hand, when the outer surface 1b of the resin base material 1 is covered with the flame-retardant coating film 2 or the flame-retardant coating foam film 8, the effect of suppressing the formation of holes and thermal deformation of the resin housing 11 due to the flame generated outside the resin housing 11 can be enhanced. Further, when both the inner surface 1a and the outer surface 1b of the resin base material 1 are covered with the flame-retardant coating film 2 or the flame-retardant coating foam film 8, the effect of suppressing the formation of holes and thermal deformation of the resin housing 11 can be further enhanced as compared with the case where only one side of the resin base material 1 is covered with the flame-retardant coating film 2 or the flame-retardant coating foam film 8.

[0045] The configuration shown in the above embodiment is an example, and it is possible to combine it with another known technique, it is also possible to combine the embodiments with each other, and it is also possible to omit or change a part of the configuration without departing from the gist.

[0046] 1 resin base material, 1a inner surface, 1b outer surface, 2 flame-retardant coating film, 3 A layer, 4 B layer, 5 foaming agent, 6 hole, 7 inorganic fibrous filler, 8 flame-retardant coating foam film, 9 organic heat-insulating A layer, 10 inorganic heat-insulating B layer, 11 resin housing, 12 electronic component, 13 printed circuit board.

Claims

1. A flame-retardant coating film covering the surface of a resin substrate molded from a resin material, comprising: a layer A disposed on the surface of the resin substrate; and a layer B disposed on the opposite side of the resin substrate with layer A in between, wherein layer A contains a binder resin, a flame retardant, a foaming agent, and a carbonizing agent; and layer B contains aluminum hydrogen phosphite and a foaming agent as an expanding agent.

2. The flame-retardant coating film according to claim 1, characterized in that the expansion initiation temperature of layer A is 300°C or lower, the expansion initiation temperature of layer B is higher than the expansion initiation temperature of layer A, and the decomposition initiation temperature of the foaming agent in layer B is 300°C or lower.

3. The flame-retardant coating film according to claim 1 or 2, characterized in that the B layer contains an inorganic fibrous filler as a reinforcing material.

4. A flame-retardant foamed coating film formed by heating a flame-retardant coating film according to any one of claims 1 to 3, comprising: an organic heat insulating A layer formed by heating the A layer; and an inorganic heat insulating B layer formed by heating the B layer, wherein the organic heat insulating A layer is a carbide having fine pores, and the inorganic heat insulating B layer contains phosphoric acid and aluminum.

5. A flame-retardant foam coating film covering the surface of a resin substrate molded from a resin material, comprising: an organic heat insulating layer A disposed on the surface of the resin substrate; and an inorganic heat insulating layer B disposed on the opposite side of the resin substrate with the organic heat insulating layer A in between, wherein the organic heat insulating layer A is a carbide having fine pores, and the inorganic heat insulating layer B contains phosphoric acid and aluminum.

6. The flame-retardant foamed coating film according to claim 4 or 5, characterized in that the hardness of the organic heat insulating layer A, as measured by a Type C hardness tester, is less than 50, and the hardness of the inorganic heat insulating layer B, as measured by a Type C hardness tester, is 60 or more.

7. A resin housing for which electronic components are housed, comprising: a resin substrate molded from a resin material; and a flame-retardant coating film according to any one of claims 1 to 3 covering the surface of the resin substrate.

8. A resin housing for which electronic components are housed, comprising: a resin substrate molded from a resin material; and a flame-retardant coating foam film according to any one of claims 4 to 6 covering the surface of the resin substrate.

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