Structures and high-pressure tanks

Abstract

To provide a structure that is highly durable and has good heat insulation performance when heated to high temperatures. [Solution] The structure 10 comprises a foam 11, a adherend 12, and a heat-expandable adhesive 13 placed between the adherend 12 and the foam 11.

Description

Technical Field

[0001] The present invention relates to a structure applied to a high-pressure tank or the like.

Background Art

[0002] Pressure vessels used in high-pressure hydrogen tanks and the like are used, for example, in hydrogen fuel cell vehicles. In order to reduce damage when the pressure vessel is impacted, a protective member may be attached to the outer peripheral surface thereof, as disclosed in Patent Documents 1 to 3. The protective member is generally often formed of a foam, and the foam is adhered to the outer peripheral surface of the pressure vessel via an adhesive, for example.

[0003] In order to protect the pressure vessel from flames and the like during a vehicle fire, studies have been made to improve the heat insulation property during high-temperature heating. For example, Patent Document 3 discloses that an unfoamed thermal foaming material such as thermally expandable graphite is contained in a foam protective member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when a thermal foaming material such as thermally expandable graphite is blended in a foam protective member as in Patent Document 3, in order to exhibit appropriate heat insulation performance, it is necessary to blend the thermal foaming material in a relatively large amount, which may increase the cost. In addition, the deterioration of the protective member is accelerated by the acid components and moisture contained in the expandable graphite, and there are problems with durability.

[0006] Therefore, the object of the present invention is to provide a structure that has high durability and good heat insulation performance at high temperatures, even without incorporating additional materials into the foam that constitutes protective members of high-pressure tanks. [Means for solving the problem]

[0007] As a result of diligent research, the inventors have found that the above problems can be solved by placing a heat-expandable adhesive that expands when heated between the foam and the adherend, such as the container body that constitutes the high-pressure tank, and have completed the present invention as follows. That is, the present invention provides the following [1] to [5]. [1] A structure comprising a foam, a adherend, and a heat-expandable adhesive disposed between the adherend and the foam. [2] The structure according to [1] above, wherein the thermally expandable adhesive contains an adhesive base and a thermally expandable compound. [3] The structure according to [2] above, wherein the adhesive base comprises one or more selected from the group consisting of a hot melt adhesive base, a one-component curing adhesive base, a two-component curing adhesive base, an emulsion-type adhesive base, and a solvent-based adhesive base. [4] The structure according to [2] or [3] above, wherein the thermally expandable compound comprises one or more thermally expandable graphite and a foaming flame retardant. [5] The container comprises a container body, a protective member containing foam, and a heat-expandable adhesive, A high-pressure tank in which the protective member is bonded to the surface of the container body by the heat-expandable adhesive. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a structure that is highly durable and has good heat insulation performance when heated to high temperatures, without requiring additional materials to be included in the foam that constitutes the protective member of a high-pressure tank. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing a structure relating to one embodiment of the present invention. [Figure 2] This is a partial cross-sectional view showing a high-pressure tank according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below using embodiments. <Structure> As shown in Figure 1, the structure of the present invention is a structure 10 comprising a foam 11, a substrate 12, and a heat-expandable adhesive 13 placed between the substrate 12 and the foam 11. When the structure 10 having the above configuration is heated to a high temperature, such as in the event of a fire, the heat-expandable adhesive 13 expands to form an insulating layer, resulting in good heat insulation and excellent fire resistance. Furthermore, since an insulating layer can be formed without including a heat-expandable compound such as heat-expandable graphite in the foam 11, cost increases can be suppressed, and the deterioration of the foam 11 due to the acidic components and moisture of heat-expandable graphite can be prevented, thereby improving durability. The following describes in detail each component that makes up the structure 10 of the present invention.

[0011] [Thermal expandable adhesive] The heat-expandable adhesive 13 expands when heated, and expands when heated to a high temperature (for example, 600°C), forming an insulating layer. Furthermore, the heat-expandable adhesive 13 has adhesive properties, and can bond foams 11 and other materials to the adherend 12 via the heat-expandable adhesive 13. The thermally expandable adhesive is fluid at room temperature (23°C) or at a temperature lower than the thermal expansion temperature of the thermally expandable adhesive (for example, the expansion start temperature of the thermally expandable compound described later). Because the thermally expandable adhesive is fluid at the above temperature, it can be easily applied to the adherend or foam by coating or other means. Furthermore, the thermally expandable adhesive is capable of solidification or curing. The thermally expandable adhesive is placed between the adherend 12 and the foam 11 by coating or other means while it is fluid, and then, upon solidification or curing, it loses its fluidity, allowing the foam 11 to adhere to the adherend 12.

[0012] Note that the expansion start temperature of the thermally expandable compound as mentioned here is as described later. When there are two or more thermally expandable compounds, it means the expansion start temperature of the thermally expandable compound with the lowest expansion start temperature. Further, solidification means solidifying the fluidized thermally expandable adhesive without accompanying the reaction of the components constituting the thermally expandable adhesive, and it is solidified by the volatilization of water or a solvent, the phase change from a liquid to a solid, etc. Also, curing means that the fluidity of the thermally expandable adhesive is lost and it is solidified with the accompanying reaction of the components constituting the thermally expandable adhesive. The thermally expandable adhesive of the present invention may cause both solidification and curing, and may adhere a foam or the like to the adherend.

[0013] (Thermally expandable compound) The thermally expandable adhesive of the present invention may be, for example, a thermally expandable adhesive composition containing a thermally expandable compound and an adhesive base. The thermally expandable compound is a compound that expands the thermally expandable adhesive by expanding itself upon heating or generating a gas or the like. The thermally expandable adhesive expands when heated to a temperature not lower than the expansion start temperature of the thermally expandable compound by containing the thermally expandable compound, and forms a heat insulating layer by the expansion residue.

[0014] Examples of the thermally expandable compound include thermally expandable layered inorganic substances, foaming flame retardants, thermal decomposition type foaming agents, etc. The thermally expandable compound may be used alone or in combination of two or more.

[0015] The thermally expandable layered inorganic substance is a conventionally known substance that expands upon heating, and examples thereof include vermiculite, thermally expandable graphite, etc. Among them, thermally expandable graphite is preferable. The thermally expandable layered inorganic substance may be used alone or in combination of two or more. As the thermally expandable layered inorganic substance, particulate or flaky ones may be used. The thermally expandable layered inorganic substance, particularly thermally expandable graphite, can have a high degree of expansion and can form a large volume of voids upon heating expansion. Also, thermally expandable graphite is easy to adjust the expansion start temperature within a desired temperature range, and it is easy to increase the residue hardness of the expansion residue, and the fire resistance and fire extinguishing performance of the structure can be made excellent.

[0016] Thermally expandable graphite is obtained by treating powders such as natural flake graphite, pyrolytic graphite, and kish graphite with an inorganic acid and a strong oxidizing agent to form a graphite intercalation compound, and is a kind of crystal compound that maintains the layered structure of carbon. Examples of the inorganic acid include concentrated sulfuric acid, nitric acid, and selenic acid. Examples of the strong oxidizing agent include concentrated nitric acid, persulfate, perchloric acid, perchlorate, permanganate, dichromate, dichromate, and hydrogen peroxide. The thermally expandable graphite obtained by the acid treatment as described above may be further neutralized with ammonia, aliphatic lower amines, alkali metal compounds, alkaline earth metal compounds, etc.

[0017] The particle size of the thermally expandable graphite is preferably 20 to 200 mesh. When the particle size of the thermally expandable graphite is within the above range, it is easy to expand and create a large volume of voids, so the heat insulation performance during expansion is improved. Also, the dispersibility in the resin is improved. The average aspect ratio of the thermally expandable graphite is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. The upper limit of the average aspect ratio of the thermally expandable graphite is not particularly limited, but from the viewpoint of preventing cracking of the thermally expandable graphite, it is preferably 1,000 or less. When the average aspect ratio of the thermally expandable graphite is 2 or more, it is easy to expand and create a large volume of voids, so the heat insulation performance during expansion is improved. The average aspect ratio of the thermally expandable graphite is the average value of the values obtained by measuring the maximum dimension (long diameter) and the minimum dimension (short diameter) for each of 10 thermally expandable graphites and dividing the maximum dimension (long diameter) by the minimum dimension (short diameter). The long diameter and short diameter of the thermally expandable graphite can be measured using, for example, a field emission scanning electron microscope (FE-SEM).

[0018] (Foamable flame retardant) Examples of foaming flame retardants include phosphorus-containing compounds such as ammonium phosphate, ammonium polyphosphate, aluminum phosphite, and melamine polyphosphate. While foaming flame retardants can impart flame retardancy to heat-expandable adhesives, they themselves also expand upon heating. Foaming flame retardants may be used individually or in combination of two or more. From the viewpoint of fire resistance and residue hardness, at least one foaming flame retardant selected from ammonium polyphosphate and aluminum phosphite is preferred, with ammonium polyphosphate being more preferred.

[0019] (Thermolytic foaming agent) Pyrolytic foaming agents include compounds that foam and generate gas when heated. The gas generated by the pyrolytic foaming agent causes the thermally expandable adhesive to expand. Organic or inorganic chemical foaming agents can be used as pyrolytic foaming agents. Examples of organic blowing agents include azodicarbonamide, azodicarboxylate metal salts (such as barium azodicarboxylate), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, hydrazodicarbonamide, hydrazine derivatives such as 4,4'-oxybis(benzenesulfonyl hydrazide) and toluenesulfonyl hydrazide, semicarbazide compounds such as toluenesulfonyl semicarbazide, melamine, dicyandiamide, and pentalythritol. Examples of inorganic blowing agents include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and anhydrous monosodium citrate. Among these, azo compounds and nitroso compounds are preferred from the viewpoint of obtaining fine bubbles, as well as from the viewpoints of economy and safety, azodicarbonamide, azobisisobutyronitrile, and N,N'-dinitrosopentamethylenetetramine are more preferred, and azodicarbonamide is particularly preferred. The pyrolysis foaming agent may be used alone or in combination of two or more. Furthermore, when using a thermal decomposition type blowing agent as the thermally expandable compound, it is preferable that the thermally expandable adhesive further contains at least one selected from a blowing flame retardant and a flame retardant in order to provide appropriate fire resistance.

[0020] The expansion initiation temperature of a thermally expandable compound is preferably 100 to 250°C. Setting the expansion initiation temperature above the lower limit prevents the thermally expandable adhesive from expanding unintentionally except in the event of a fire. Setting it below 250°C allows for rapid expansion in the event of a fire, thereby improving fire resistance and fire extinguishing performance. From these viewpoints, the expansion initiation temperature is more preferably 125 to 200°C, even more preferably 150 to 195°C, and even more preferably 155 to 190°C. A thermally expandable compound having the above-mentioned expansion initiation temperature is preferably thermally expandable graphite. Therefore, the expansion initiation temperature of thermally expandable graphite is preferably 100 to 250°C, more preferably 125 to 200°C, even more preferably 150 to 195°C, and even more preferably 155 to 190°C.

[0021] Furthermore, if the thermally expandable adhesive contains two or more thermally expandable compounds, it is desirable that the expansion onset temperature of at least one of the thermally expandable compounds be within the above range, but it is preferable that the thermally expandable compound with the lowest expansion onset temperature be within the above range. For example, if the thermally expandable compound contains thermally expandable graphite and a foaming flame retardant, the expansion onset temperature of the thermally expandable graphite is lower than that of the foaming flame retardant. Therefore, as described above, it is desirable that the expansion onset temperature of the thermally expandable graphite be within the above range. As described later, the expansion initiation temperature is determined by heating the thermally expandable compound using a rheometer and measuring the temperature at which the force in the normal direction begins to rise. The measured temperature is defined as the expansion initiation temperature. In the case of thermal decomposition type foaming agents, the expansion initiation temperature is generally not detectable by the above measurement method, but it is desirable that the temperature at which decomposition occurs and gas is generated (decomposition temperature) falls within the above temperature range.

[0022] The content of the thermally expandable compound is preferably 10 to 80% by mass, based on the total solid content of the thermally expandable adhesive. By including the thermally expandable compound above the lower limit, the expansion ratio during high-temperature heating becomes sufficiently high, resulting in good heat insulation and fire resistance performance of the thermally expandable adhesive during fire. Furthermore, by keeping it below the upper limit, it becomes possible to include a certain amount of adhesive base in the thermally expandable adhesive, making it easier to achieve good adhesion. In addition, after solidification or curing, the thermally expandable compound is more easily held by the adhesive base, resulting in good mechanical strength of the thermally expandable adhesive. The content of the thermally expandable compound in the thermally expandable adhesive is more preferably 15 to 70% by mass, even more preferably 20 to 60% by mass, and even more preferably 25 to 55% by mass.

[0023] Of the thermally expandable compounds mentioned above, it is preferable to use at least one of thermally expandable graphite and a foaming flame retardant. Using these makes it easier to impart flame retardancy to the thermally expandable adhesive and improve its fire resistance. Furthermore, it is more preferable to use at least thermally expandable graphite as the thermally expandable compound. Using thermally expandable graphite makes it easier to adjust the expansion start temperature within the above range, and also makes it easier to increase the expansion ratio and residue hardness.

[0024] The content of thermally expandable graphite is preferably 5 to 60% by mass, based on the total solid content of the thermally expandable adhesive. Including thermally expandable graphite above the lower limit makes it easier to increase the expansion ratio and residue hardness, resulting in good fire resistance of the thermally expandable adhesive. Conversely, keeping it below the upper limit makes it possible to include a certain amount of other components besides thermally expandable graphite, such as adhesive base and foaming flame retardant, in the thermally expandable adhesive, making it easier to improve various performance characteristics. The content of thermally expandable graphite in the thermally expandable adhesive is more preferably 7 to 50% by mass, even more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass, based on the total solid content.

[0025] Furthermore, it is preferable to use both a thermally expandable graphite and a foaming flame retardant as the thermally expandable compound. The content of thermally expandable graphite when these are used in combination is as described above. On the other hand, the content of the foaming flame retardant is preferably 5 to 63% by mass, based on the total solid content of the thermally expandable adhesive. By including the foaming flame retardant above the lower limit, it becomes easier to increase the expansion ratio and residue hardness, resulting in good fire resistance of the thermally expandable adhesive. Also, by keeping it below the upper limit, it becomes possible to include components other than the foaming flame retardant, such as the adhesive base and thermally expandable graphite, in the thermally expandable adhesive to a certain extent, resulting in good performance in various aspects. The content of the foaming flame retardant is more preferably 10 to 50% by mass, even more preferably 15 to 40% by mass, and even more preferably 20 to 35% by mass.

[0026] When using thermally expandable graphite and a foaming flame retardant in combination, the mass ratio of the foaming flame retardant to the thermally expandable graphite in the thermally expandable adhesive (foaming flame retardant / thermally expandable graphite) is preferably 0.1 to 10. By keeping the content ratio within the above range, it becomes easier to increase the expansion ratio and residue hardness, resulting in good fire resistance performance of the thermally expandable adhesive. From these viewpoints, the above content ratio is more preferably 0.2 to 5, even more preferably 0.5 to 3, and even more preferably 0.8 to 2.

[0027] <Adhesive base> The adhesive base used in thermally expandable adhesives is the adhesive component that provides the adhesive properties. Examples of adhesive bases include hot-melt adhesive bases, one-component curing adhesive bases, two-component curing adhesive bases, emulsion-type adhesive bases, and solvent-based adhesive bases.

[0028] (Hot melt adhesive base) Hot-melt adhesive bases are non-fluid at room temperature but become fluid when heated. Furthermore, heated hot-melt adhesive bases solidify again when cooled. A heat-expandable adhesive becomes a hot-melt adhesive simply by containing a hot-melt adhesive base. When using a hot-melt adhesive base as the adhesive base for a heat-expandable adhesive, it becomes easier to maintain good adhesion to the substrate not only before high-temperature heating but also after high-temperature heating. Therefore, the expansion residue after high-temperature heating can continue to adhere to the substrate, resulting in better fire resistance. In addition, by using a hot-melt adhesive base, the heat-expandable fire resistant agent can cool and solidify immediately when left at room temperature after application, resulting in improved workability. Furthermore, it becomes easier to expand the heat-expandable adhesive at a high expansion ratio when heated to high temperatures.

[0029] As a hot-melt adhesive base, resins conventionally used as the main component of hot-melt adhesives (hereinafter also referred to as "main component resin") can be used. Specifically, resins such as ethylene-vinyl acetate copolymer resin (EVA), ethylene-(meth)acrylic acid ester copolymer resin, polyolefin resin, and rubber can be used. The main component resin may be used alone or in combination of two or more types. Among these, at least one selected from ethylene-vinyl acetate copolymer resin (EVA) and ethylene-(meth)acrylic acid ester copolymer resin is preferred. Using these makes it possible to achieve good adhesion to the adherend, and it is easier to maintain good adhesion to the adherend not only before high-temperature heating but also after high-temperature heating. Among these, ethylene-vinyl acetate copolymer resin (EVA) is more preferred as the main resin of the hot-melt type adhesive base.

[0030] The ethylene-vinyl acetate copolymer resin (EVA) used in hot-melt adhesive bases is not particularly limited as long as it is a resin copolymerized with ethylene and vinyl acetate. The vinyl acetate content of the ethylene-vinyl acetate copolymer resin is not particularly limited, but from the viewpoint of suitable use as a hot-melt adhesive base, it is preferably 15 to 45% by mass, more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass. The vinyl acetate content was measured in accordance with JIS K 6924-1:1997.

[0031] Examples of (meth)acrylic acid esters that constitute the ethylene-(meth)acrylic acid ester copolymer resin include alkyl (meth)acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, methyl methacrylate, and ethyl methacrylate, as well as (meth)acrylic acid esters having functional groups such as epoxy groups and hydroxyl groups, such as 2-hydroxyethyl acrylic acid and glycidyl acrylate. These may be used alone or in combination of two or more types. Furthermore, the ethylene-(meth)acrylic acid ester copolymer resin may also be copolymerized with a third component such as carbon monoxide or maleic anhydride. The ethylene-(meth)acrylic acid ester copolymer resin is preferably ethylene-methyl methacrylate copolymer (EMMA). Furthermore, the content of constituent units derived from (meth)acrylic acid ester in the ethylene-(meth)acrylic acid ester copolymer resin is not particularly limited, but is, for example, 5 to 50% by mass, preferably 10 to 40% by mass, and more preferably 15 to 35% by mass.

[0032] Examples of polyolefin resins include at least one olefin copolymer obtained by copolymerizing ethylene with an α-olefin having 3 to 20 carbon atoms. Examples of α-olefins having 3 to 20 carbon atoms include propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Among the above olefin copolymers, copolymers of ethylene with an α-olefin having 6 to 8 carbon atoms are preferred, and copolymers of ethylene with 1-octene are more preferred. These olefin copolymers may be used individually or in combination of two or more types.

[0033] The above-mentioned olefin copolymer preferably has an α-olefin copolymerization ratio of 20 to 40 mol%. Furthermore, the above-mentioned olefin copolymer preferably has a melt flow rate (g / 10 min) of 5 to 2500, and more preferably 150 to 2500. The melt flow rate of the olefin copolymer is measured under conditions of 190°C and a load of 21.2 N in accordance with JIS K7210.

[0034] As the copolymer of ethylene and 1-octene mentioned above, commercially available products from Dow Chemical, synthesized using a single-site metallocene catalyst, such as "Affinity EG8185" (MFR=30), "Affinity EG8200" (MFR=5), "Affinity GA1900" (MFR=1000), "Affinity GA1950" (MFR=500), and "Affinity PT1409" (MFR=6), can be used. These commercially available copolymers of ethylene and 1-octene have a copolymerization ratio of 1-octene of 35-37 mol%. Furthermore, copolymers other than those of ethylene and α-olefins having 3 to 20 carbon atoms mentioned above can also be used. These may include polyethylene, polypropylene, polyhexene, polyoctene, propylene-butene copolymer, propylene-hexene copolymer, and propylene-octene copolymer. These polyolefin resins should be appropriately selected, for example, so that their melt flow rate falls within the range described above.

[0035] Rubbers used in hot-melt adhesive bases include dienes such as butadiene, styrene-butadiene, chloroprene, and butadiene-acrylonitrile; non-dienes such as isobutylene-isoprene and ethylene-propylene; and thermoplastics (also called thermoplastic elastomers) such as styrene, olefin, ester, and urethane.

[0036] The melt flow rate (MFR) of the main resin used in hot-melt adhesive bases is not particularly limited, but from the viewpoint of applicability and adhesion, it is, for example, 1 to 3000 g / 10 min, preferably 5 to 2500 g / 10 min, more preferably 10 to 1500 g / 10 min, even more preferably 100 to 1000 g / 10 min, and even more preferably 150 to 1000 g / min. The melt flow rate is measured under conditions of 190°C and a load of 21.2 N, and for ethylene-vinyl acetate copolymer resins, it is preferable to measure it in accordance with JIS K 6924-1:1997. For main resins other than ethylene-vinyl acetate copolymer resins, such as ethylene-(meth)acrylic acid ester copolymer resins, it is fine to measure them in accordance with JIS K 7210:1999.

[0037] Commercially available resins can be used as the main component of the hot-melt adhesive base. Examples include Tosoh Corporation's "UltraCen 726" as an ethylene-vinyl acetate copolymer resin, and Sumitomo Chemical's "Aclift CM5021" as an ethylene-methyl methacrylate copolymer resin.

[0038] The hot-melt adhesive base preferably contains a tackifying resin in addition to the main resin mentioned above. Examples of tackifying resins include rosin-based, terpene-based, petroleum resin-based, and coumarone resin-based resins. Examples of rosin-based tackifying resins include gum rosin, wood rosin, polymerized rosin, disproportionated rosin, hydrogenated rosin, dimerized rosin, esters of the above rosins with pentaerythritol, glycerin, diethylene glycol, etc. (rosin esters), and rosinphenol resins. Examples of the terpene-based tackifying resins mentioned above include terpene resins, copolymers of terpenes and styrene, copolymers of terpenes and α-methylstyrene, copolymers of terpenes and phenol, and hydrogenated versions thereof. Examples of the above-mentioned petroleum resin-based tackifying resins include aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, aliphatic-aromatic copolymer petroleum resins, and hydrogenated versions thereof.

[0039] Furthermore, unhydrogenated C9 petroleum resins are preferred as petroleum resin-based tackifying resins. Unhydrogenated C9 petroleum resins are resins obtained by (co)polymerizing the C9-C10 fractions, i.e., aromatic fractions, contained in the cracked oil fractions produced as by-products of steam cracking of petroleum products, and are resins that have not been hydrogenated. These unhydrogenated C9 petroleum resins may be used alone or two or more types may be used in combination. (Co)polymerization refers to either homopolymerization or copolymerization. The above-mentioned C9-C10 fractions (aromatic fractions) are not particularly limited, but examples include vinyl aromatic hydrocarbons such as vinyltoluene, indene, styrene, and α-methylstyrene. Examples of coumarone resin-based tackifying resins include coumarone resin and coumarone-indene resin. In addition to the above, xylene resin can also be used as a tackifying resin. Among the above, petroleum resin-based and rosin-based tackifying resins are preferred. The above tackifying resins may be used individually or in combination of two or more.

[0040] The softening point of the tackifying resin is not particularly limited, but is, for example, 90 to 150°C, preferably 100 to 140°C, and more preferably 110 to 130°C. Having the softening point within this range allows for a good balance of properties such as adhesion, applicability, and strength after solidification or curing of the thermally expandable adhesive. The softening temperature is the temperature measured according to the JIS K2207 ring-and-ball method.

[0041] When the adhesive base contains a main resin and a tackifying resin as a hot-melt type adhesive base, the content of the tackifying resin is, for example, 3 to 150 parts by mass per 100 parts by mass of the total of the main resin and the tackifying resin. Having 3 parts by mass or more of the tackifying resin enhances the adhesion of the heat-expandable adhesive. Having 150 parts by mass or less prevents the strength of the heat-expandable adhesive after solidification or curing from being impaired by the tackifying resin. The content of the tackifying resin is preferably 10 to 100 parts by mass, more preferably 15 to 75 parts by mass, and even more preferably 20 to 50 parts by mass.

[0042] (1-component curing adhesive base) In this invention, a heat-expandable adhesive can be made into a one-component curing adhesive by using a one-component curing adhesive base. The one-component curing adhesive base is preferably a moisture-curing adhesive base that hardens with moisture in the air. Suitable one-component curing adhesive bases include modified silicones, isocyanate group-containing polymers, and cyanoisocyanate-based adhesive bases. These may be used individually or in combination of two or more. By using a one-component curing adhesive base, it is possible to prevent the heat-expandable adhesive from sagging due to heating after application.

[0043] Among the above, modified silicone is preferred as the one-component curing adhesive base. The modified silicone is preferably a polymer containing crosslinkable silyl groups (crosslinkable silyl group-containing polymer). Specifically, the crosslinkable silyl group in the crosslinkable silyl group-containing polymer is a functional group represented by the following formula (1). In the crosslinkable silyl group-containing polymer, the number of crosslinkable silyl groups is not particularly limited as long as there is one or more, but for example, about 1 to 5 is preferred, and about 2 to 4 is more preferred.

[0044] -SR 1 a X 3-a (1) In formula (1), R 1is a hydrocarbon group, preferably an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. X represents a reactive group, and the reactive group represented by X is selected from halogen atoms, hydrogen atoms, hydroxyl groups, alkoxy groups, acyloxy groups, ketoximate groups, amide groups, acid amide groups, mercapto groups, ketoxime groups, alkenyloxy groups, and aminooxy groups. If there are multiple X groups, X may be the same group or different groups. Of these, alkoxy groups and ketoxime groups are preferred for X, and alkoxy groups are more preferred. Furthermore, methoxy groups are more preferred for alkoxy groups. a is an integer of 0, 1, or 2, and 0 or 1 is more preferred.

[0045] Furthermore, as the crosslinkable silyl group-containing polymer, at least one selected from crosslinkable silyl group-containing polyoxyalkylene polymers, crosslinkable silyl group-containing acrylic polymers, and crosslinkable silyl group-containing acrylic-modified polyoxyalkylene polymers is preferred. By using these modified silicones as a one-component curing adhesive base, a good balance between residue hardness and expansion ratio can be achieved. In addition, it has good weather resistance and can be suitably used outdoors. Moreover, it tends to provide good adhesive strength to various materials.

[0046] As the crosslinkable silyl group-containing polyoxyalkylene polymer, a polymer containing a crosslinkable silyl group within the molecule and having polyoxyalkylene in the main chain skeleton is preferred, and a polymer having polyoxyalkylene in the main chain skeleton and containing a crosslinkable silyl group at the main chain end is more preferred. Furthermore, polyoxypropylene is preferred as the polyoxyalkylene.

[0047] Furthermore, as the acrylic-modified polyoxyalkylene polymer containing a crosslinkable silyl group, a polymer containing a crosslinkable silyl group within the molecule and having (meth)acrylic-modified polyoxyalkylene in the main chain skeleton is preferred, and a polymer having (meth)acrylic-modified polyoxyalkylene in the main chain skeleton and containing a crosslinkable silyl group at the main chain end is more preferred. In addition, (meth)acrylic-modified polyoxyalkylene is preferred.

[0048] Examples of acrylic polymers containing crosslinkable silyl groups include polymers having an acrylic polymer in their main chain skeleton and having one or more crosslinkable silyl groups in the molecule. Here, the acrylic polymer can be any conventionally known polymer, and is not particularly limited as long as it is an acrylic polymer obtained by polymerizing or copolymerizing one or more acrylic monomers selected from (meth)acrylic acid, (meth)acrylic acid esters, (meth)acrylonitrile, (meth)acrylamide, etc. The acrylic polymer is preferably one in which (meth)acrylic acid ester monomers are the main component (for example, 50% by mass or more, preferably 70% by mass or more in the polymer), and examples include acrylic acid esters with 1 to 20 carbon atoms in the ester portion. Furthermore, acrylic polymers can also be copolymerized with monomers other than the acrylic monomers mentioned above. Examples of copolymerizable monomers include vinyl monomers such as fluoroolefins, α-olefins, vinyl esters, and vinyl ethers.

[0049] The number-average molecular weight of the modified silicone is not particularly limited, but is, for example, 5,000 to 100,000, preferably 10,000 to 50,000. The number-average molecular weight is a value measured in polystyrene equivalent by the GPC method. Commercially available modified silicones can also be used. For example, as crosslinkable silyl group-containing polyoxyalkylene polymers, Kaneka Corporation's "MS Polymer S203" and "MS Polymer S303" can be used.

[0050] In addition, as the crosslinkable silyl group-containing polymer, a crosslinkable silyl group-containing silicone resin may be used. A crosslinkable silyl group-containing silicone resin is a polymer that has a polyorganosiloxane in its main chain and crosslinkable silyl groups at its terminals. As an example of a crosslinkable silyl group-containing silicone resin, "Sekisui Silicone Sealant" manufactured by Sekisui Fuller Co., Ltd. can also be used.

[0051] (2-component curing adhesive base) A two-component curing adhesive base is an adhesive base that hardens when two components are mixed. In this invention, by using a two-component curing adhesive base, a heat-expandable adhesive can be made into a two-component curing type. Using a two-component curing adhesive base allows for relatively high adhesive strength. Furthermore, it makes it easier to improve adhesion to the adherend not only before combustion but also after combustion. In addition, the curing time can be easily controlled by appropriately changing the adhesive base used. Moreover, it is possible to prevent the heat-expandable adhesive from sagging due to heating after application. Two-component curing adhesive bases consist of a main component and a hardener, and it is best to store them separately until immediately before use. Therefore, when using a two-component curing adhesive base, it is best to incorporate components other than the two-component curing adhesive base into either the main component or the hardener. Then, it is best to mix the first component containing the main component and the second component containing the hardener immediately before use to obtain a heat-expandable adhesive.

[0052] As a two-component curing adhesive base, any resin commonly used in two-component curing adhesives can be used, such as polyurethane resins, epoxy resins, and acrylic resins, with epoxy resins being preferred among these. In the case of epoxy resins, an epoxy compound having epoxy groups can be used as the main component, and a curing agent that cures epoxy groups can be used as the curing agent. Known curing agents can be used, including polyamine-based, imidazole-based, polymercaptan-based, and acid anhydride-based curing agents. As for epoxy resins, commercially available products can be used; for example, "Sdine 3120" manufactured by Sekisui Fuller Co., Ltd. can be used.

[0053] (Emulsion-type adhesive base) In thermally expandable adhesives, emulsion-type adhesive bases are dispersed in a dispersion medium, preferably water. By using an emulsion-type adhesive base, the thermally expandable adhesive is made into an emulsion dispersion, thus becoming an emulsion-type adhesive. Emulsion-type thermally expandable adhesives can be solidified by volatilizing the dispersion medium. Using an emulsion type makes it easier to incorporate large amounts of thermally expandable compounds, thereby improving fire resistance. Furthermore, it helps to reduce environmental impact. Additionally, it allows for a balanced increase in both residue hardness and expansion ratio. As emulsion-type adhesive bases, vinyl acetate resin-based, ethylene-vinyl acetate resin-based, acrylic resin-based, and aqueous polymer-isocyanate-based adhesive bases can be used. Among these, ethylene-vinyl acetate resin-based adhesive bases are preferred. For ethylene-vinyl acetate resin-based adhesive bases, an ethylene-vinyl acetate copolymer resin can be used. Commercially available products can also be used as emulsion-type adhesive bases; for example, as an ethylene-vinyl acetate resin-based adhesive base, "Esdyne K-474" manufactured by Sekisui Fuller Co., Ltd. can be used.

[0054] (Solvent-based adhesive base) In the present invention, solvent-based adhesive bases are dissolved in an organic solvent in thermally expandable adhesives. By using a solvent-based adhesive base as the adhesive base, the thermally expandable adhesive becomes solvent-based, containing an organic solvent and with the solvent-based adhesive base dissolved in the organic solvent. Solvent-based thermally expandable adhesives can be solidified by volatilizing the organic solvent. Using solvent-based compounds makes it easier to incorporate large amounts of thermally expandable compounds, thereby improving fire resistance. Furthermore, it can sometimes achieve a good balance between high residue hardness and expansion ratio. Additionally, it improves adhesive performance, making it easier to maintain good adhesion to the substrate not only before combustion but also after.

[0055] Examples of solvent-based adhesive bases include vinyl acetate resin-based, chloroprene rubber-based, and acrylic resin-based adhesive bases, with chloroprene rubber-based and acrylic resin-based adhesive bases being preferred. For chloroprene rubber-based adhesive bases, chloroprene rubber conventionally used in solvent-based adhesives may be used. For acrylic resin-based adhesive bases, acrylic resin conventionally used in solvent-based adhesives may be used. In the present invention, using chloroprene rubber-based adhesive bases allows for a good balance between high residue hardness and high expansion ratio. Furthermore, using acrylic resin-based adhesive bases makes it easier to maintain good adhesion to the adherend not only before combustion but also after combustion. Commercially available solvent-based adhesive bases can also be used. For example, "Esdyne 235L" from Sekisui Fuller Co., Ltd. can be used as a chloroprene rubber base, and "Esdyne 7858" from Sekisui Fuller Co., Ltd. can be used as an acrylic resin base.

[0056] The content of the adhesive base in the heat-expandable adhesive of the present invention is preferably 10 to 80% by mass, based on solid content. By setting the content of the adhesive base to 10% by mass or more, the adhesion of the heat-expandable adhesive obtained by solidifying or curing the heat-expandable adhesive to the adherend can be improved. Furthermore, by setting it to 80% by mass or less, it is possible to include a certain amount or more of components other than the adhesive base, such as heat-expandable compounds, resulting in good performance in various aspects such as fire resistance. From these viewpoints, the content of the adhesive base in the heat-expandable adhesive is more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0057] Furthermore, the hot-melt adhesive base, one-component curing adhesive base, two-component curing adhesive base, emulsion-type adhesive base, and solvent-based adhesive base described above are each preferably used individually in thermally expandable adhesives. For example, if the adhesive base contains a hot-melt adhesive base, the hot-melt adhesive base should be used alone as the adhesive base. The same applies to the other adhesive bases.

[0058] However, two or more of the above adhesive bases may be used in combination. For example, a heat-expandable adhesive may contain an adhesive base other than a hot-melt adhesive base in addition to a hot-melt adhesive base, for example, a one-component curing adhesive base in addition to a hot-melt adhesive base. However, even in such cases, when using a heat-expandable adhesive as a hot-melt type, it is sufficient to ensure that the hot-melt adhesive base is the main component. Therefore, even if a hot-melt type heat-expandable adhesive contains other adhesive bases, it is preferable that the content of the hot-melt type adhesive base is greater than the content of the other adhesive bases, and the content is, for example, 50 to 100% by mass, preferably 75 to 100% by mass, and more preferably 85 to 100% by mass, based on the total amount of adhesive bases. Furthermore, when a hot-melt adhesive base and a one-component curing adhesive base are included, if the heat-expandable adhesive is used as a one-component curing type, the one-component curing adhesive base should be the main component. In that case, the content of the one-component curing adhesive base should be greater than the content of the other adhesive bases, and the content should be, for example, 50 to 100% by mass, preferably 60 to 100% by mass, and more preferably 70 to 100% by mass, based on the total amount of adhesive bases. Of course, other adhesive bases can be used in combination; for example, a one-component curing adhesive base and a solvent-based adhesive base can be used together.

[0059] When a hot-melt adhesive base is used as the adhesive base (however, when two or more adhesive bases are used in combination, the hot-melt adhesive base must be the main component), the thermally expandable adhesive does not need to be solid at room temperature (23°C) and not fluid, but as described above, it is sufficient if the adhesive base melts at a temperature below the expansion initiation temperature of the thermally expandable compound, and the thermally expandable adhesive becomes fluid. On the other hand, when an adhesive other than a hot-melt adhesive base is used as the adhesive base (however, when two or more adhesive bases are used in combination, the adhesive base other than a hot-melt adhesive base is included as the main component), the thermally expandable adhesive only needs to be fluid at room temperature (23°C).

[0060] As adhesive substrates, among the above, hot-melt adhesive bases, one-component curing adhesive bases, and two-component curing adhesive bases are preferred from the viewpoint of adhesion and fire resistance, and among these, hot-melt adhesive bases are more preferred from the viewpoint of having a higher expansion ratio when heated at high temperatures. Furthermore, from the viewpoint of improving adhesion, curing types such as one-component curing adhesive bases and two-component curing adhesive bases are more preferred.

[0061] (Inorganic filler) The heat-expandable adhesive (heat-expandable adhesive composition) of the present invention may contain inorganic fillers other than the heat-expandable compound described above. When heated and an insulating layer is formed, the inorganic fillers increase the heat capacity and suppress heat transfer, while acting as aggregates to improve the strength of the expanded residue. The inorganic fillers that can be used in the present invention are not particularly limited and include, for example, alumina, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, metal oxides such as ferrite, calcium carbonate, zinc carbonate, strontium carbonate, barium carbonate, metal carbonates such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, hydrotalcite, calcium sulfate, gypsum fiber, calcium silicate, silica, diatomaceous earth, dawsonite, barium sulfate, talc, clay, mica, montmorillonite, bentonite, activated clay, and sepia. Examples include olite, imogolite, sericite, glass fibers, glass beads, silica balloons, aluminum nitride, boron nitride, silicon nitride, carbon black, graphite, carbon fiber, carbon balloons, various metal powders, potassium titanate, magnesium sulfate, lead zirconate titanate, aluminum borate, molybdenum sulfide, silicon carbide, stainless steel fibers, zinc borate, various magnetic powders, slag fibers, fly ash, sodium phosphate, potassium phosphate, magnesium phosphate, metal phosphates such as aluminum phosphate, metal orthophosphates, metal metaphosphates, and metal tripolyphosphates. Among these, calcium carbonate, barium sulfate, and aluminum hydroxide are preferred from the viewpoint of improving the fire resistance of the thermally expandable adhesive, with calcium carbonate being more preferred among them. The inorganic filler may be used alone or in combination of two or more types. Furthermore, calcium carbonate is particularly preferable when used in combination with ammonium polyphosphate. Using these together makes it easier to increase the hardness of the residue. If the thermally expandable adhesive contains an inorganic filler, its content is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 8 to 30% by mass, based on the total solid content of the thermally expandable adhesive.

[0062] (Other ingredients) The heat-expandable adhesive of the present invention may contain wax. Wax is preferably included in the heat-expandable adhesive when using a hot-melt type adhesive base. By including wax, the heat-expandable adhesive of the present invention can improve the solidification rate. In addition, the inclusion of wax makes it easier to suppress dripping in long-term humid and hot environments. Furthermore, wax can also reduce the viscosity of the heat-expandable adhesive when it melts, making it easier to improve the applicability of the heat-expandable adhesive. As the wax, any wax that is crystalline and has good compatibility with the hot-melt adhesive base should be used. Specifically, examples of waxes include synthetic waxes such as Fischer-Tropsch wax and polyethylene wax, paraffin waxes such as refined paraffin wax, and natural waxes such as microcrystalline wax. Synthetic waxes are preferred, and among them, Fischer-Tropsch wax is more preferred. The wax may be used alone or in combination of two or more types. The wax content in the heat-expandable adhesive is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 10 parts by mass, per 100 parts by mass of the adhesive base.

[0063] The heat-expandable adhesive of the present invention may contain flame retardants other than the foaming flame retardants described above. Examples of such flame retardants include phosphate ester compounds. Examples of phosphate ester compounds include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, octyldiphenyl phosphate, tributoxyethyl phosphate, trichloroethyl phosphate, tris(2-chloropropyl) phosphate, tris(2,3-dichloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, tris(bromochloropropyl) phosphate, bis(2,3-dibromopropyl)-2,3-dichloropropyl phosphate, bis(chloropropyl)monooctyl phosphate, tris(2-ethylhexyl) phosphate, triphenyl phosphate, tricresyl phosphate (TCP), trixylenyl phosphate, cresyldiphenyl phosphate, xylenyldiphenyl phosphate, and the like.

[0064] The thermally expandable adhesive of the present invention may further contain a catalyst. The catalyst can be suitably used as a curing catalyst when the thermally expandable adhesive has curing properties, such as a one-component curing type or a two-component curing type. By containing a curing catalyst, the thermally expandable adhesive of the present invention can accelerate the curing reaction. As a curing catalyst, for example, when using modified silicone, titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, aluminum-based catalysts, bismuth-based catalysts, etc., can be used. The catalyst content in the thermally expandable adhesive is not particularly limited, but is about 0.1 to 15 parts by mass per 100 parts by mass of adhesive base.

[0065] Furthermore, the thermally expandable adhesive of the present invention may contain additives other than those mentioned above, as necessary, as long as the objective of the present invention is not impaired. Examples of such additives include polymerization initiators, plasticizers, lubricants, shrinkage inhibitors, nucleating agents, colorants (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, anti-aging agents, flame retardant aids, antistatic agents, surfactants, vulcanizing agents, dispersants, and surface treatment agents. Additives may be used individually or in combination of two or more. Furthermore, thermally expandable adhesives may contain an organic solvent to dissolve the adhesive base in solvent-based adhesives, or a dispersion medium such as water to disperse the adhesive base in emulsion-based adhesives.

[0066] The heat-expandable adhesive is formed by solidifying or curing between the foam and the adherend as described above, and is preferably formed in layers on the adherend. The thickness of the heat-expandable adhesive formed in layers on the adherend is not particularly limited, but is, for example, 0.1 to 15 mm, preferably 0.3 to 5 mm, and more preferably 0.5 to 3 mm.

[0067] (Method of manufacturing a thermally expandable adhesive) The thermally expandable adhesive of the present invention can be obtained by mixing an adhesive base, a thermally expandable compound, and other inorganic fillers and other components as needed. Furthermore, in the case of emulsion-type or solvent-type adhesives, it is preferable to manufacture them by adding a thermally expandable compound and other components as needed to an organic solvent in which the adhesive base has been dissolved beforehand, or a dispersion medium in which the adhesive base has been dispersed, and then mixing them. Furthermore, in the case of a two-component curing type adhesive, a main component and a curing agent are prepared as the adhesive base, and a thermally expandable compound and other components as needed are added to at least one of the main component or curing agent to prepare a one-component and a two-component adhesive. In this case, it is best to mix the one-component and two-component adhesives immediately before use to prepare the thermally expandable adhesive.

[0068] [Foam] The foam 11 has numerous fine bubbles inside and can constitute a protective member that protects the adherend 12. By having the foam 11, the structure 10 can protect the adherend 12 with the foam 11, and damage to the adherend 12 when it is subjected to impact can be reduced. The foam 11 is preferably a flammable foam. That is, the foam 11 burns when heated to a high temperature (for example, 600°C). Therefore, the foam 11 burns away when heated to a high temperature, and as a result does not hinder the thermally expandable adhesive 13 from expanding and forming an insulating layer when heated to a high temperature, so that the adherend 12 can be properly protected by the thermally expandable adhesive 13 in the event of a fire or other incident.

[0069] The foam 11 is not particularly limited as long as it is a flammable foam that can constitute a protective member, and examples include polyolefin foam, acrylic foam, and polyurethane foam, among which polyurethane foam is preferred. Since polyurethane foam can be easily manufactured by casting foam, foams of various shapes can be easily obtained. Therefore, as will be described later, even if the surface of the adherend 12 to which the foam 11 is attached is curved, such as in a high-pressure tank, the foam 11 can be easily molded into a shape that corresponds to the shape of the surface of the adherend to which it is attached.

[0070] Examples of polyolefin resins used in polyolefin foams include polyethylene resin, polypropylene resin, and ethylene-vinyl acetate copolymer resin (EVA). These may be used individually or in combination of two or more. In addition, polyolefin foams may also contain resins other than polyolefin resins, as long as the polyolefin resin constitutes the main component of the foam's resin composition (for example, 50% or more by mass, preferably 70% or more by mass of the resin composition). The polyolefin foam is not particularly limited as long as it is a foam obtained by foaming a polyolefin resin, but it is preferable that it is a foam obtained by foaming a foaming composition containing a foaming agent and a polyolefin resin. As the foaming agent, a thermal decomposition type foaming agent such as azodicarbodiamide is preferred, but it is not particularly limited.

[0071] Acrylic foam is a foam obtained by foaming a known acrylic resin. The acrylic resin is not particularly limited, but it is preferably an acrylic polymer obtained by polymerizing monomer components containing various (meth)acrylates such as alkyl (meth)acrylates.

[0072] Polyurethane foams can be obtained by foaming a foaming composition containing a polyol, a polyisocyanate, and a foaming agent. The foaming polyurethane resin composition may further contain, if necessary, a catalyst, a foam stabilizer, a flame retardant, an inorganic filler, and the like. Examples of blowing agents used in polyurethane foams include organic physicoblasting agents such as hydrocarbons, ether compounds, hydrochlorocarbons (HFCs), hydrofluoroolefins (HFOs), and mixtures thereof, and inorganic physicoblasting agents such as water, nitrogen gas, oxygen gas, argon gas, and carbon dioxide gas. Among the above, HFOs and water are preferred blowing agents, and HFOs and water may be used in combination. Examples of catalysts include resinification catalysts, foaming catalysts, and trimerization catalysts. Examples of flame retardants include flame retardants other than blowing flame retardants such as phosphate ester compounds, and examples of inorganic fillers include inorganic fillers other than thermally expandable compounds. Details of flame retardants and inorganic fillers are as described in the section on thermally expandable adhesives.

[0073] The foam preferably does not contain thermally expandable graphite, and more preferably does not contain thermally expandable compounds. By not containing thermally expandable graphite, the foam is prevented from degrading due to the acidic components and moisture contained in expandable graphite, making it easier to improve the durability of the structure. Furthermore, by not including thermally expandable compounds such as thermally expandable graphite in the foam, it is not necessary to include large amounts of thermally expandable graphite or other thermally expandable compounds in the structure, thus preventing the cost of the structure from increasing. The thickness of the foam is not particularly limited, but it is preferably greater than the thickness of the heat-expandable adhesive, for example, about 1 to 150 mm, preferably 2 to 100 mm, and more preferably 4 to 50 mm.

[0074] The foam can be molded by known methods, but it is preferably molded by casting foam. In casting foam, for example, a foaming composition can be poured into a mold having a shape that matches the adherend, and the foaming composition can be foamed inside the mold to obtain the foam.

[0075] [Adherent material] The adherend is preferably coated with a heat-expandable adhesive, and the foam is bonded to it via the heat-expandable adhesive. The surface on which the heat-expandable adhesive is coated may be metal, resin, or fiber-reinforced plastic, but fiber-reinforced plastic is preferred among these. Details of fiber-reinforced plastic are described below. Because the adherend surface is fiber-reinforced plastic, the adherend can be suitably applied to high-pressure tanks and the like. In the present invention, it is preferable that the structure is applied to a high-pressure tank, and therefore, the adherend is preferably the container body that constitutes the high-pressure tank.

[0076] <High-pressure tank> The following provides a more detailed explanation of how the structure can be applied to a high-pressure tank. The container body of a high-pressure tank is a pressure-resistant pressure vessel that can be filled with pressurized gas. The gas filled inside the container body may be a non-flammable gas such as nitrogen, carbon dioxide, oxygen, argon, or helium, but a flammable gas such as hydrogen, methane, ethane, propane, n-butane, isobutane, or LPG is preferred. As described later, the container body is protected from damage by impact by having a foam and a heat-expandable adhesive on its outer surface, and a heat insulating layer is formed when heated to high temperatures, so that even in the event of a fire, the spread of damage from flammable gas can be properly prevented. Among the gases listed above, hydrogen is preferred for filling inside the pressure vessel body. Because the gas filled is hydrogen, the pressure tank can be applied to hydrogen fuel cell vehicles and the like. Normally, the inside of the pressure vessel body is filled with high-pressure gas, and the gas may be filled in a partially liquefied state.

[0077] The container body is not particularly limited as long as it is a pressure-resistant container, and may be made of metal, resin, or fiber-reinforced plastic. However, from the viewpoint of durability, it is preferable that at least the surface of the container body constituting the surface of the adherend is made of fiber-reinforced plastic. Fiber-reinforced plastics are reinforced plastics in which fibers are compounded with resin. Thermosetting resins such as epoxy resins, polyester resins, and polyamide resins can be used as the resin in fiber-reinforced plastics. Examples of fibers in fiber-reinforced plastics include carbon fibers, glass fibers, and aramid fibers, with carbon fibers and glass fibers being preferred, and carbon fibers being particularly preferred. Therefore, CFRP (Carbon Fiber Reinforced Plastic) and GFRP (Glass Fiber Reinforced Plastic) are preferred, with CFRP being more preferred.

[0078] Furthermore, the container body may have a multilayer structure, for example, comprising a liner layer that forms the inner circumferential surface of the container and creates an internal space for sealing the fluid, and a reinforcing layer that covers the outer circumferential surface of the liner layer. Here, the liner layer can be formed from, for example, a synthetic resin such as a polyamide resin or a polyethylene resin, or a metal such as an aluminum alloy. The reinforcing layer may be made of fiber-reinforced plastic.

[0079] Figure 2 shows a specific example of the structure of the present invention being applied to a high-pressure tank. The container body 21 in the high-pressure tank 20 is not particularly limited, but as shown in Figure 2, it comprises a hollow cylindrical body 22 and dome portions 23, 23 connected to both sides of the body 22. The dome portions 23, 23 are parts whose cross-section is not a straight line along the axial direction of the body 22, and are specifically composed of curves. For example, a nozzle (not shown) is provided at the top of each of the dome portions 23, 23, and one nozzle constitutes a valve, which serves as an inlet and outlet for the gas filled inside.

[0080] In the high-pressure tank 20, the foam 11 constitutes a protective member. The foam 11 is positioned to cover a portion of the dome portion 23 of the high-pressure tank 20. Specifically, the foam 11 has a shape that is a cone with the top removed, and is positioned on the surface of the dome portion 23 so as to avoid the top of the dome portion 23 (i.e., the nozzle) and surround the top when viewed along the axial direction of the body portion 22. The foam 11 constituting the protective member is bonded to the surface of the container body 21 via a heat-expandable adhesive 13 placed between the foam 11 and the surface of the container body 21 (dome portion 23). The heat-expandable adhesive 13 may be laminated over the entire surface of the foam 11 facing the container body 21, or it may be laminated on only a portion of the surface facing the container body 21.

[0081] The high-pressure tank 20, by having a foam 11, adequately protects the container body 21 and reduces damage when the container body 21 is subjected to impact. Furthermore, by providing a heat-expandable adhesive 13 between the foam 11 and the container body 21, for example, in the event of a fire, the heat-expandable adhesive 13 forms an insulating layer, allowing the high-pressure tank 20 to be adequately protected. Note that the parts of the container body 21 other than the top of the dome portion 23 are generally thinner and have lower impact and heat resistance, but the presence of the foam 11 and heat-expandable adhesive 13 effectively protects these areas. However, the location where the foam body 11 is provided is not limited to the top of the dome portion 23, but may also be the body portion 22, or it may be positioned to straddle both the dome portion 23 and the body portion 22.

[0082] In the above description, the structure 10 is shown in which a foam 11 and a heat-expandable adhesive 13 are provided on the adherend 12, but other components besides the foam 11 and heat-expandable adhesive 13 may also be provided. Specifically, a non-foamed resin layer may be provided between the foam 11 and the heat-expandable adhesive 13, or a further non-foamed resin layer may be provided on the surface side of the foam 11. Therefore, the protective member in the high-pressure tank 20 may consist of the foam 11 alone as described above, or it may contain other members besides the foam 11. In the latter case, the protective member may consist of a composite of the foam 11 and other members (for example, a laminate of foam and non-foamed resin layers), and the composite may be bonded to the outer surface of the container body 21 via a heat-expandable adhesive 13. In other words, the foam 11 may be directly bonded to the adherend 12 (for example, the outer surface of the container body 21) via the heat-expandable adhesive 13, or it may be bonded via another component (for example, a non-foamed resin layer).

[0083] (Method of manufacturing a structure) The structure of the present invention can be manufactured by bonding a foam to a substrate via a heat-expandable adhesive. Specifically, a heat-expandable adhesive is applied to the surface of the substrate (for example, the container body in the case of a high-pressure tank), or to the surface of the foam on the substrate side, and then the foam is laminated onto the substrate surface via the heat-expandable adhesive, and the heat-expandable adhesive is solidified or cured to bond the foam to the substrate surface.

[0084] Furthermore, as described above, if the structure includes components other than foam and thermally expandable adhesive (for example, a non-foamed resin layer) on top of the adherend, it is preferable to bond a composite (for example, a laminate of foam and a non-foamed resin layer) having foam and components other than foam to the adherend via a thermally expandable adhesive. In this case as well, it is preferable to apply the thermally expandable adhesive to the surface of the adherend, or to the adherend-side surface of the composite, then laminate the composite to the surface of the adherend via the thermally expandable adhesive, and then solidify or cure the thermally expandable adhesive to bond the composite containing the foam to the surface of the adherend.

[0085] The method for applying the heat-expandable adhesive is not particularly limited, but examples include applying it with a brush or known coating device, or applying it to the object to be coated by spraying. If the heat-expandable adhesive is of the hot-melt type, it can be melted by heating and then the molten heat-expandable adhesive can be applied. When the heat-expandable adhesive is melted, it is preferable to heat it to a temperature below the expansion start temperature of the heat-expandable compound, and the heating temperature is, for example, 100 to 160°C, preferably 120 to 155°C.

[0086] In the above manufacturing method, the method for solidifying or curing the heat-expandable adhesive is not particularly limited. By containing the above-mentioned adhesive base, the heat-expandable adhesive can be solidified or cured even when left at room temperature (for example, around 0 to 40°C) in the atmosphere. However, the heat-expandable adhesive may be solidified or cured by heating or other means as necessary. For example, if the adhesive base is either an emulsion-type adhesive base or a solvent-based adhesive base, the solidification of the heat-expandable fire-resistant material composition may be accelerated by heating or other means to volatilize the organic solvent or water. Also, if the adhesive base is a two-component curing-type adhesive base, the curing of the heat-expandable fire-resistant material composition may be accelerated by heating.

[0087] In the above explanation, the structure was applied to a high-pressure tank and the adherend was the container body. However, the structure can be applied to other materials besides high-pressure tanks, such as construction materials (gypsum board, ALC), window sashes, and steel doors. [Examples]

[0088] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The evaluation method in the examples is as follows.

[0089] (Fire resistance) The structure was placed in an electric furnace preheated to 600°C, heated and burned for 10 minutes, then removed, and the expansion ratio was calculated using the following formula (1). Expansion ratio = Volume of expanded residue after combustion / Volume of thermally expandable adhesive before combustion (1)

[0090] (Fire resistance performance after durability testing) The structure was left in an environment of 80°C and 85%RH for 3000 hours. Then, the structure was placed in an electric furnace preheated to 600°C, heated and burned for 10 minutes, and then removed. The expansion ratio was calculated using the above formula (1).

[0091] (Expansion start temperature of thermally expandable graphite) 100 mg of thermally expandable graphite was taken as a sample, and using a rheometer (TA Instruments, "Discovery HR2"), the temperature was increased at a rate of 10°C / min, and the temperature at which the force in the normal direction began to rise was measured and defined as the expansion onset temperature.

[0092] The components used in the examples and comparative examples are as follows: <Adhesive base> EVA: Ethylene-vinyl acetate copolymer resin, hot-melt adhesive base, "UltraCen 726", manufactured by Tosoh Corporation, vinyl acetate content 33% by mass, melt flow rate 700g / 10min (190℃, load 21.2N) Modified silicone: One-component curing adhesive base, "MS Polymer S303", manufactured by Kaneka Corporation, a polyalkylene oxide whose main chain skeleton consists of polypropylene oxide and has propyl dimethoxysilyl groups at the ends of the main chain, number average molecular weight 20,000 Epoxy-based: A two-component curing adhesive base, "Esdyne 3120," manufactured by Sekisui Fuller Co., Ltd., consisting of a main component containing an epoxy compound and a curing agent containing a polyamine. Acrylic solvent-based: "Metal Lock Y600" manufactured by Cemedyne Co., Ltd. <Adhesive-granting resin> C9 Unhydrogenated: Unhydrogenated C9 petroleum resin (aromatic petroleum resin), "Petol 120", manufactured by Tosoh Corporation, softening point 120°C <Thermally expandable graphite 1> ADT Corporation, product name "ADT501", expansion start temperature 150℃ <Thermally expandable graphite 2> Air Water Co., Ltd., product name "CA-60N", expansion start temperature 230℃ <Foaming flame retardant> Ammonium polyphosphate: "AP422", manufactured by Clariant.

[0093] <wax> Fischer-Tropsch wax, "FT-105", manufactured by Nippon Seiro Co., Ltd. <Antioxidant> • Phenolic antioxidant, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], "Irganox 1010", manufactured by BASF.

[0094] (Example 1) [Production of foam] A polyol mix containing 50 parts by mass of polyol, 3 parts by mass of foam stabilizer, 50 parts by mass of blowing agent (HFO), and 5 parts by mass of resinification catalyst was mixed with 50 parts by mass of polyisocyanate to obtain a foamable urethane resin composition. This composition was then poured into a mold having a flat cavity, foamed, and cured to obtain a 7 mm thick flat urethane resin foam. [Preparation of thermally expandable adhesives] According to the formulations in Table 1, each component was uniformly heated, melted, and kneaded at 130°C to obtain a hot-melt, heat-expandable adhesive. [Creating structures] A thermally expandable adhesive heated to 140°C was applied to the entire surface of one side of a 98mm square plate-shaped CFRP substrate. A 98mm square, 7mm thick foam was then laminated onto the applied thermally expandable adhesive, and the foam was bonded to the substrate via the solidified thermally expandable adhesive to obtain the structure. In each example and comparative example, the thickness of the layered thermally expandable adhesive was 1mm.

[0095] [Example 2] A foam was prepared in the same manner as in Example 1. A one-component, heat-expandable adhesive was obtained by mixing each component at room temperature under a vacuum atmosphere according to the formulation shown in Table 1. The heat-expandable adhesive was applied to the entire surface of one side of a 98mm square plate-shaped CFRP substrate at room temperature (23°C). A 98mm square, 7mm thick foam was then laminated onto the applied heat-expandable adhesive. After that, it was left for 24 hours in a 23°C, 50%RH environment to bond the foam to one side of the substrate via the cured heat-expandable adhesive, thereby obtaining a structure.

[0096] [Example 3] A foam was prepared in the same manner as in Example 1. The main component of "Esdyne 3120," which contains an epoxy compound, was mixed with all components except the adhesive base to form a liquid 1, and the curing agent of "Esdyne 3120" was used as the liquid 2. The thermally expandable adhesive, obtained by mixing liquid 1 and liquid 2, was applied to the entire surface of one side of a 98 mm square plate-shaped CFRP substrate at 23°C. A 98 mm square, 7 mm thick foam was then laminated onto the applied thermally expandable adhesive. After that, it was left for 24 hours in a 23°C, 50% RH environment to bond the foam to one side of the substrate via the cured thermally expandable adhesive, thereby obtaining a structure.

[0097] [Examples 4-6] Examples 4-6 were carried out in the same manner as Examples 1-3, except that the type of thermally expandable graphite was changed.

[0098] [Example 7] The procedure was carried out in the same manner as in Example 1, except that a GFRP substrate was used instead of CFRP as the substrate.

[0099] (Comparative Example 1) A foam was prepared in the same manner as in Example 1, except that 15 parts by mass of a foaming flame retardant (ammonium polyphosphate) and 25 parts by mass of thermally expandable graphite were added to the polyol mix. A commercially available acrylic solvent-based adhesive was applied to the entire surface of one side of a 98mm square CFRP (carbon fiber reinforced polymer) plate-shaped substrate at room temperature (23°C). A 98mm square, 7mm thick foam was then laminated onto the applied heat-expandable adhesive. After that, the substrate was left for 24 hours at 23°C and 50% RH to fix the foam to one side of the substrate via the hardened heat-expandable adhesive, thereby obtaining a structure.

[0100] [Table 1] *The content in adhesives is expressed as mass % based on solid content.

[0101] The structures of Examples 1 to 7 had a foam, a substrate, and a heat-expandable adhesive placed between them. As a result, they had a high expansion ratio and good thermal insulation performance when heated at high temperatures, and even after long-term storage in a high-temperature, high-humidity environment, the high expansion ratio was maintained, resulting in excellent durability. In contrast, the structure of Comparative Example 1 contained expandable graphite, a heat-expandable compound, in the foam, resulting in a high expansion ratio and good thermal insulation performance when heated at high temperatures, but the expansion ratio decreased after long-term storage in a high-temperature, high-humidity environment, and it could not be said to have excellent durability. [Explanation of symbols]

[0102] 10 Structure 11. Foam (protective material) 12 Adherent material 13. Thermally expandable adhesives 20 High-pressure tanks 21 Container body (adherent material) 22 Torso 23 Dome section

Claims

1. A structure comprising a foam, a substrate, and a heat-expandable adhesive disposed between the substrate and the foam.

2. The structure according to claim 1, wherein the thermally expandable adhesive contains an adhesive base and a thermally expandable compound.

3. The structure according to claim 2, wherein the adhesive base comprises one or more selected from the group consisting of a hot-melt adhesive base, a one-component curing adhesive base, a two-component curing adhesive base, an emulsion-type adhesive base, and a solvent-based adhesive base.

4. The structure according to claim 2 or 3, wherein the thermally expandable compound comprises one or more thermally expandable graphite and a foaming flame retardant.

5. The container comprises a container body, a protective member containing foam, and a heat-expandable adhesive. A high-pressure tank in which the protective member is bonded to the surface of the container body by the heat-expandable adhesive.

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