JP2022189839A - Fire-resistant resin molding, fire-resistant structure of structural member, method for constructing fire-resistant structural member, and method for manufacturing fire-resistant resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire-resistant resin molding which can achieve both sufficient fire-resistant performance and easy manufacturability.

SOLUTION: A fire-resistant resin molding is composed of a binding agent composed of a synthetic resin, and a non-binding agent that is a component other than the binding agent, wherein the non-binding agent contains ammonium polyphosphate, polyhydric alcohol and titanium oxide, and the non-binding agent is 240 pts.mass or more and 365 pts.mass or less with respect to 100 pts.mass of the binding agent. Such a structure enables the fire-resistant resin molding to be molded into a desired shape (pellet, sheet and the like), so that it can be used easily at a construction site. Both fire-resistant performance and easiness of kneading at the time of manufacture can be achieved.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2023,JPO&INPIT

Description

The technology disclosed by this specification relates to a fire-resistant resin molding, a fire-resistant structure of a structural member, and a construction method for a fire-resistant structural member.

As a refractory coating material for coating building materials such as steel frames, a sheet-like coating material obtained by kneading a binder, a flame retardant, a foaming agent, a carbonizing material, a filler, etc. has been proposed (Patent Document 1. reference). When exposed to high temperatures in a building fire, the covering material foams and carbonizes to form a heat insulating layer, which protects the building materials.

International Publication No. 2013/008819

However, in the covering material as described above, if the content of fillers, etc. is increased in order to withstand the flames of a fire and maintain the shape of the heat insulating layer, the content of the binder becomes relatively low. Therefore, the fluidity of the mixture becomes low, and kneading becomes difficult. Therefore, there is room for improvement in order to achieve both sufficient fire resistance and ease of production.

The refractory resin molding disclosed by the present specification is composed of a binder made of a synthetic resin and a non-binder that is a component other than the binder, and the non-binder comprises ammonium polyphosphate and polyvalent It contains alcohol and titanium oxide, and the non-binder is 240 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder.

The refractory resin molded article having the composition as described above can be used after being molded into a desired shape (pellet, sheet, etc.), and is easy to construct. In addition, in order to form a sufficiently thick heat insulating layer in the event of a fire and increase the effect of delaying the conduction of combustion heat through an endothermic reaction, the content of ammonium polyphosphate and polyhydric alcohol should be large, and the heat insulating layer In order to suppress dripping and maintain strength, the content of titanium oxide should be high, but if the content of these components is increased, the content of the binder will be relatively small, kneading becomes difficult. If the amount of the non-binder is 240 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder, both fire resistance and ease of kneading during production can be achieved.

In the refractory resin molding described above, the titanium oxide may have an oil absorption of 15 g/100 g or more and 25 g/100 g or less.

If the specific surface area of the titanium oxide used is too small, the effect of preventing the heat insulating layer from dripping down from the structural member in the event of a fire and maintaining the strength of the heat insulating layer may not be sufficiently obtained. On the other hand, if the specific surface area of the titanium oxide used is too large, kneading becomes difficult. If the oil absorption of titanium oxide is 15 g/100 g or more and 25 g/100 g or less, both the strength maintenance of the heat insulating layer and the ease of kneading can be achieved. As used herein, the term "oil absorption" means that measured according to JIS K5101-13.

Further, the fire-resistant structure of the structural member disclosed by this specification includes a structural member having an insertion hole through which another member can be inserted, and a fire-resistant resin layer disposed on the inner peripheral surface of the insertion hole, The fire-resistant resin layer is composed of a binder made of a synthetic resin and a non-binder that is a component other than the binder, and the non-binder contains ammonium polyphosphate, a polyhydric alcohol, and titanium oxide. The content of the non-binder is 240 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder.

In the fire-resistant structure of the structural member described above, the structural member includes a steel beam having a through hole, and a reinforcing member attached to the steel beam, the reinforcing member having a screw thread on an outer peripheral surface, and the through hole an insertion member inserted through the hole; and a ring member having a threaded hole, fixed to the insertion member by screwing, and arranged along a peripheral edge portion of the through hole in the steel frame beam, The insertion member may have the insertion hole.

Further, the construction method for a fireproof structural member disclosed by the present specification includes a kneading step of kneading a binder made of a synthetic resin and a non-binder that is a component other than the binder, and A molding step of molding the kneaded material into a sheet, and a fireproofing by attaching the molded product obtained in the molding step to the inner peripheral surface of the insertion hole in a structural member having an insertion hole through which other members can be inserted. forming a flexible resin layer, and in the kneading step, the non-binder contains ammonium polyphosphate, polyhydric alcohol, and titanium oxide, and with respect to 100 parts by mass of the binder , the non-binder is 240 parts by mass or more and 365 parts by mass or less.

According to the fire-resistant structure of the structural member and the construction method of the fire-resistant structural member configured as described above, when a fire occurs, the fire-resistant resin layer foams, expands, and carbonizes to form a heat insulating layer. The heat insulating layer fills the gap between the rim of the insertion hole and other members, thereby suppressing the transfer of heat to the structural member and suppressing the spread of flame and heat through the insertion hole.

Here, in order to avoid difficulty in inserting other members, the thickness of the refractory resin layer is reduced to some extent, and a sufficient gap is provided between the other member to be inserted and the refractory resin layer during construction. is preferably ensured. On the other hand, in order to suppress the transfer of heat to structural members in the event of a fire, and to fill the gap between the inner peripheral surface of the insertion hole and other members to some extent, the heat insulating layer must be thick enough to exhibit sufficient fire resistance performance. It is desirable to form a heat insulating layer of thickness. The refractory resin layer having the above composition has a sufficiently large expansion ratio (the ratio of the thickness after foaming to the thickness before foaming). It is possible to achieve both of ensuring the performance.

According to the fire-resistant resin molding, the fire-resistant structure of the structural member, and the construction method of the fire-resistant structural member disclosed by the present specification, both sufficient fire resistance and ease of manufacture can be achieved.

1 is a partially enlarged perspective view of a structural member according to an embodiment; FIG. 1 is a partially enlarged exploded perspective view of a structural member according to an embodiment; FIG. Sectional drawing of the fire-resistant structure of a structural member in embodiment A partially enlarged exploded perspective view of a structural member in a modified example Sectional view of the fireproof structure of the structural member in the modified example

Embodiments will be described with reference to FIGS. 1 to 3. FIG. The refractory resin molding of the present embodiment is produced by kneading a binder made of a synthetic resin and a non-binder that is a component other than the binder and molding it into an arbitrary shape. It is suitably used as a fire-resistant covering material for covering a construction object that requires fire resistance. Non-binders include ammonium polyphosphate as a flame retardant, polyhydric alcohol as a carbonizing agent, and titanium oxide as a thickening agent. This fire-resistant resin composition is foamed and carbonized by combustion heat during a fire to form a heat-insulating layer.

The type of synthetic resin as a binder is not particularly limited, but ethylene copolymer resins such as EVA (ethylene-vinyl acetate copolymer) and EEA (ethylene-ethyl acetate copolymer), vinyl chloride, vinyl chloride- Vinyl chloride resins such as vinyl acetate copolymers, synthetic rubbers such as butyl rubbers and styrene-butadiene rubbers, and the like can be used. In particular, it is preferable to use an ethylene copolymer resin that has excellent kneading properties. When EVA is used as the binder, the VA ratio (vinyl acetate content) is preferably 10 to 20% in order to obtain a sufficient expansion ratio.

Among the non-binders, ammonium polyphosphate is a flame retardant and undergoes dehydration condensation and foaming due to combustion heat during a fire. This dehydration-condensation is an endothermic reaction, and this endothermic reaction can delay the conduction of combustion heat during a fire to a covered object such as a steel frame. The endothermic reaction is the deammonification reaction of ammonium polyphosphate.

A polyhydric alcohol is a carbonizing agent, and, like ammonium polyphosphate, undergoes dehydration condensation due to combustion heat during a fire and foams. The type of polyhydric alcohol is not particularly limited, but pentaerythritol can be preferably used.

Titanium oxide is a thickening agent that prevents the heat insulation layer formed in the event of a fire from dripping from the construction target, thereby maintaining the strength of the heat insulation layer. The larger the specific surface area of the titanium oxide used, the greater the effect of suppressing dripping, but the kneading during production becomes difficult. Therefore, it is preferable that the oil absorption of titanium oxide measured according to JIS K5101-13 is 15 g/100 g or more and 25 g/100 g or less.

In addition to the above, the non-binder may contain inorganic fibers (ceramic fibers, rock wool, etc.), release agents (fatty acid esters), lubricants, processing aids (polycarbodiimide, etc.), and the like.

In order to form a sufficiently thick insulating layer in the event of a fire and increase the effect of retarding the conduction of combustion heat through an endothermic reaction, it is better to have a large content of ammonium polyphosphate and polyhydric alcohol. In order to increase the drop-suppressing effect, the content of titanium oxide should be large. However, if the content of these components is increased, the content of the binder becomes relatively small, making kneading during production difficult. If the amount of the non-binder is 240 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder, both fire resistance and ease of kneading during production can be achieved.

It is preferable that the fire-resistant resin molding of the present embodiment does not contain a foaming agent such as melamine. Since the decomposition temperature of these blowing agents is generally higher than that of ammonium polyphosphate and polyhydric alcohol, the heat insulation layer once formed by the foaming of ammonium polyphosphate and polyhydric alcohol is weakened by the foaming of the blowing agent. Because.

The refractory resin molded product of the present embodiment is obtained by melt-kneading the above materials using, for example, a single-screw extruder or a twin-screw extruder, and extruding the resulting kneaded product into a string or rod shape. It may be a pellet obtained by pelletizing, the above material is melted and kneaded using, for example, a Banbury mixer or a kneader mixer, and the resulting kneaded product is formed into a plate shape with a stretching roll or the like and formed into a rod. It may be a pellet obtained by cutting and pelletizing, or a molded product obtained by molding the pellet obtained by these methods into an arbitrary shape by a known molding method such as press molding, extrusion molding, or injection molding. Alternatively, it may be a molded article molded into an arbitrary shape by a known molding method without pelletizing the melt-kneaded material.
In particular, a configuration in which the non-binder containing ammonium polyphosphate, polyhydric alcohol, and titanium oxide is 240 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder is a refractory resin composition In the case of pellets, it is preferable because it is possible to avoid difficulties in kneading the materials and breakage of the strands. Moreover, it is more suitable when producing pellets using a twin-screw extruder.

An example in which the fire-resistant resin molding of the present embodiment is suitably applied to a fire-resistant structure of a structural member will be described below.

The structural member 10 includes a steel beam 11 having a through hole 12 and a reinforcing member 21 attached to the steel beam 11 to reinforce the peripheral portion of the through hole 12, as shown in FIGS. The steel beams 11 are H-beams and are placed under the concrete slab S as shown in FIG. The reinforcing member 21 includes a sleeve tube 22 (corresponding to an insertion member) passed through the through-hole 12 and two ring steel members 25 (ring members) joined to the sleeve tube 22 and welded to the steel beam 11 (corresponding to ) and As shown in FIG. 2, the sleeve tube 22 is a short cylindrical member having an outer diameter substantially equal to or slightly smaller than the hole diameter of the through hole 12, and the inner space of the tube corresponds to the through hole 23. A thread 24 is provided on the outer peripheral surface of the sleeve tube 22 . Each of the two ring steel members 25 is a ring-shaped plate member having a screw hole 26, as shown in FIG. 2, and can be fixed to the sleeve tube 22 by screwing. Each ring steel member 25 has a plurality of weld holes 27 arranged so as to surround the threaded hole 26 . The welding hole 27 is a hole for plug welding.

The sleeve tube 22 is passed through the through-hole 12 so that both ends thereof protrude from the plate surface of the steel beam 11 . The two ring steel members 25 are arranged so as to sandwich the steel beam 11, fixed by being screwed to the sleeve pipe 22, respectively, and further joined to the steel beam 11 by plug welding. As shown in FIG. 3, a fire-resistant resin layer 30 is arranged over the entire circumference of the inner peripheral surface of the insertion hole 23 . The fire-resistant resin layer 30 is a layer formed by attaching the sheet-shaped fire-resistant resin molding having the above-described configuration to the inner peripheral surface of the insertion hole 23 . One end of the sleeve tube 22 slightly protrudes outward from the surface of one of the ring steel members 25 (the surface opposite to the steel beam 11), and one end of the refractory resin layer 30 protrudes further outward than that. Protruding. The same is true for the other end.

An example of a construction method for the fire resistant structural member as described above will be described below.

First, the materials for the refractory resin molding described above are kneaded using a twin-screw extruder (kneading step). Pellets are obtained by extruding the resulting kneaded material into a string or rod shape, and then water-cooling and pelletizing the strand. The pellets are put into a single-screw extruder and molded into a sheet having a width of 60 to 120 mm and a thickness of 3 mm (molding step). The melt-kneaded product can be formed into a sheet without being pelletized, but from the viewpoint of simplifying production equipment and processes, it is preferable to form the melt-kneaded product into a sheet through pellets.
The obtained sheet-like molding is adhered to the inner peripheral surface of the insertion hole 23 of the sleeve tube 22 in the structural member 10 having the above configuration to form the fire-resistant resin layer 30 (construction step).
After that, as shown in FIG. 3, a fireproof coating R may be formed on the surface of the steel beam 11 by spraying rock wool.

As shown in FIG. 3, a pipe P for passing electrical wiring or the like is inserted through the insertion hole 23 provided with the fire-resistant resin layer 30 . There is a certain amount of gap between the inner peripheral surface of the fire-resistant resin layer 30 and the outer peripheral surface of the pipe P during normal times when there is no fire.

When a fire occurs, the fire-resistant resin layer 30 foams, expands, and carbonizes to form a heat insulating layer. This heat insulating layer suppresses the transfer of heat to the structural member, and fills the gap between the inner peripheral surface of the insertion hole 23 and the pipe P to some extent, thereby suppressing the spread of flame and heat through the insertion hole 23. .

In order to avoid the difficulty of inserting the pipe P, the thickness of the fire-resistant resin layer 30 is reduced to some extent (for example, 4 mm or less) at the time of construction, and there is sufficient space between the pipe P to be inserted and the fire-resistant resin layer 30. It is preferable that a sufficient clearance be secured. On the other hand, in order for the heat insulating layer to suppress the transfer of heat to the structural members in the event of a fire, fill the gap between the inner peripheral surface of the insertion hole 23 and the pipe P to some extent, and exhibit sufficient fireproof performance, it is necessary to have a sufficient thickness. It is desirable to form a heat insulating layer with a thickness (for example, 20 mm or more). Since the refractory resin molded product of the present embodiment has a sufficiently large expansion ratio (the ratio of the thickness after foaming to the thickness before foaming), it is possible to avoid difficulty in inserting the pipe P and It is possible to achieve both of ensuring the performance.

<Test example>
[Equipment used, materials used]
"HYPERKTX" manufactured by Kobe Steel, Ltd. was used as a twin-screw kneading extruder. As a single-screw extruder, "SE" manufactured by Toshiba Machine Co., Ltd. was used.
EVA (ethylene-vinyl acetate copolymer) resin, PP (polypropylene) resin, EEA (ethylene-ethyl acetate copolymer) resin, or vinyl chloride resin was used as a binder.
Among the non-binders, ammonium polyphosphate was used as a flame retardant, pentaerythritol as a carbonizing agent, titanium oxide as a thickener, melamine as a foaming agent, fatty acid ester as a processing aid, and adipic acid-based polyester as a plasticizer.

[Test method]
1) Test Examples 1, 3 to 9
Each component shown in Table 1 was melt-kneaded using a twin-screw kneading extruder, and the molten resin extruded into strands was cooled with water and cut into 5 mm length pellets with a pelletizer. The temperature setting of the extruder was 160°C. Pellet moldability was evaluated as ◯ when pellets could be molded without problems, Δ when continuous production was impossible due to broken strands, and x when pellets could not be molded because they could not be extruded from the extruder.

Next, the obtained pellets were melted and extruded using a single-screw extruder to form a sheet having a thickness of 2 mm and a width of 20 mm. The extruder had a cylinder temperature of 120°C and a mold temperature of 140°C.

Subsequently, the obtained sheet was attached to a steel plate with a double-sided tape to form a test specimen, which was placed vertically in an electric furnace and heated at 800° C. for 2 hours to form a heat insulating layer. The shape retainability of the heat insulating layer was evaluated as ◯ when the heat insulating layer did not collapse unless force was applied, and x when easily crushed. The expansion ratio was also measured. Furthermore, it was evaluated whether or not the heat insulating layer was dripping after the heating was finished. A sample that remained in almost the same position as before heating was rated as ◯, a sample that was not in the same position but was slightly dislocated at the top end was rated as Δ, and a sample that was dripping down in the electric furnace was rated as x. Table 1 shows the results.

2) Test Examples 2 and 10
Each component shown in Table 1 was kneaded with a pressure kneader, processed into a sheet with a thickness of 5 mm with an open roll, and then cut into pellets. Others are the same as in 1) above.

3) Test Examples 11 to 20
After each component shown in Table 2 was kneaded with an open kneader, the mixture was hot-pressed (manually) at 150° C. to form a sheet. The obtained sheet was attached to a steel plate with a double-faced tape to prepare a test specimen, and the shape retention of the heat insulating layer and dripping were evaluated in the same manner as in 1) above. The expansion ratio was also measured. Table 2 shows the results.

In addition, the unit of the numerical value which shows the compounding ratio of each component in Table 1 and Table 2 is a mass part.

[Results and discussion]
In Test Examples 1 to 6, in which the amount of the non-binder was 240 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder, the kneaded material could be formed into pellets satisfactorily. In addition, the heat insulating layer retained its shape well, and no dripping was observed. The foaming ratio is 5 times to 12 times. It was enough to be compatible.

In Test Examples 7 and 10, in which the amount of the non-binder was more than 365 parts by mass, it was difficult to knead the materials, and pellets could not be obtained. Moreover, in Test Examples 8 and 9, in which the amount of the non-binder was less than 240 parts by mass, the foaming ratio was not sufficient, and dripping of the heat insulating layer was observed.

In order to maintain the shape of the heat insulating layer, achieve a sufficient expansion ratio, and prevent dripping of the heat insulating layer in a well-balanced manner, 120 to 185 parts by mass of ammonium polyphosphate and 40 parts by mass of pentaerythritol are added to 100 parts by mass of the binder. 100 parts by mass and 60 to 95 parts by mass of titanium oxide were considered preferable.

<Modification>
As with the structural member 40 shown in FIGS. 4 and 5 , the reinforcing member 41 may be composed of two flanged tubes 42 . Each flanged tube 42 has an inner diameter approximately equal to the inner diameter of the through hole 12, and has a cylindrical tube portion 43 with both ends opened, and a flange portion projecting outward from the opening edge of one opening of the tube portion 43. 44. Each flanged tube 42 is fixed to the steel beam 11 by placing the flange portion 44 in contact with the peripheral edge portion of the through hole 12 in the steel beam 11 and welding.

A fire-resistant resin layer 45 similar to that of the above-described embodiment is arranged over the entire circumference of the cylinder portions 43 of the two flanged cylinders 42 and the inner peripheral surface of the through hole 12 . One end of the fire-resistant resin layer 45 slightly protrudes outward from one end of one cylindrical portion 43 (the edge opposite to the flange portion 44). The same is true for the other end.

<Other embodiments>
The technology disclosed in this specification is not limited to the embodiments described by the above description and drawings, and includes, for example, the following various aspects.
(1) In the above embodiment, the reinforcing member 21 includes the sleeve tube 22 and the ring steel material 25, but the configuration of the reinforcing member is not limited to the above embodiment. Alternatively, the two ring steel members may be joined to the steel beam only by welding. Alternatively, the reinforcing member may comprise only one ring steel welded to one side of the steel beam. Alternatively, the reinforcing member may be a steel plate having a hole through which the pipe can be inserted and joined to the steel frame beam by welding. In these cases, a refractory resin layer may be arranged on the through-hole of the steel frame beam and the inner peripheral surface of the hole of the ring steel material or iron plate.
Further, the reinforcing member may be a steel pipe through which the pipe can be inserted, and may be welded to the inner peripheral surface of the through-hole of the steel frame beam. In this case, a refractory resin layer may be arranged on the inner peripheral surface of the steel pipe.
Also, the steel frame beam may not be provided with a reinforcing member. In that case, a refractory resin layer may be arranged on the inner peripheral surface of the through-hole of the steel beam.

(2) The fire-resistant resin composition can be used for various purposes by being molded into a desired shape. For example, it can be molded into a sheet and used as a fireproof coating material for steel structures. In addition, it can be molded into a tape shape and placed in the gaps of window frames, door frames, etc. In the event of a fire, it expands and fills the gaps to prevent flames from penetrating the back side, or the outer surface of resin or wooden window frames. It can be used as a fireproof coating tape for preventing chucking to a resin frame or a wooden frame from combustion heat in the event of a fire. It can also be molded into a plate shape and used as a lightweight fireproof shutter. It can also be molded into a film and used as a film that suppresses combustion when a storage battery such as a lithium ion battery catches fire, or as a sheet that protects against sparks during welding. In addition, it is molded into an appropriate shape and installed on the outer surface of hydrogen tanks and gasoline tanks to suppress ignition due to temperature rise in the event of a fire. It can also be used as a component to protect the interior of the living room.

(3) In the above embodiment, the end of the fire-resistant resin layer 30 protrudes from the sleeve tube 22, but the end face of the fire-resistant resin layer may be flush with the end face of the sleeve tube. Similarly, in the modified example, the end face of the fire-resistant resin layer may be flush with the end face of the cylindrical portion.

Reference Signs List 10, 40 Structural member 11 Steel beam 12 Through holes 21, 41 Reinforcement member 22 Sleeve tube (insertion member)
23... Insertion hole 24... Thread 25... Ring steel material (ring member)
26... screw holes 30, 45... refractory resin layer

Claims (6)

A refractory resin molding formed by melt-kneading,
Composed of a binder made of synthetic resin and a non-binder that is a component other than the binder,
the non-binder comprises ammonium polyphosphate, a polyhydric alcohol, and titanium oxide;
The binder is an ethylene copolymer resin,
The non-binder is 230 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder,
The titanium oxide is 60 parts by mass or more and 95 parts by mass or less with respect to 100 parts by mass of the binder,
The ammonium polyphosphate is 120 parts by mass or more and 185 parts by mass or less with respect to 100 parts by mass of the binder,
A refractory resin molding having an expansion ratio of 5 to 12 after heating at 800° C. for 2 hours. 2. The fire-resistant resin molding according to claim 1, wherein said titanium oxide has an oil absorption of 15 g/100 g or more and 25 g/100 g or less. a structural member having an insertion hole through which another member can be inserted;
A fire-resistant resin layer arranged on the inner peripheral surface of the insertion hole,
The fire-resistant resin layer is
Composed of a binder made of synthetic resin and a non-binder that is a component other than the binder,
the non-binder comprises ammonium polyphosphate, a polyhydric alcohol, and titanium oxide;
The binder is an ethylene copolymer resin,
The non-binder is 230 parts by mass or more and 365 parts by mass or less with respect to 100 parts by mass of the binder,
The titanium oxide is 60 parts by mass or more and 95 parts by mass or less with respect to 100 parts by mass of the binder,
The ammonium polyphosphate is 120 parts by mass or more and 185 parts by mass or less with respect to 100 parts by mass of the binder,
A fire-resistant structure for a structural member, wherein the fire-resistant resin layer has an expansion ratio of 5 to 12 after being heated at 800° C. for 2 hours. The structural member comprises a steel beam having a through hole and a reinforcing member attached to the steel beam,
The reinforcing member has a screw thread on its outer peripheral surface and has an insertion member that is inserted into the through hole, and a threaded hole that is fixed to the insertion member by screwing. a ring member disposed along a peripheral portion of the hole;
4. The fire-resistant structure of a structural member according to claim 3, wherein said insertion member has said insertion hole. a kneading step of kneading a binder made of a synthetic resin and a non-binder that is a component other than the binder;
A molding step of molding the kneaded product obtained in the kneading step into a sheet;
A construction step of attaching the molded product obtained in the molding step to the inner peripheral surface of the insertion hole in a structural member having an insertion hole through which other members can be inserted to form a fire-resistant resin layer;
In the kneading step, the non-binder contains ammonium polyphosphate, a polyhydric alcohol, and titanium oxide, the binder is an ethylene copolymer resin, and relative to 100 parts by mass of the binder The non-binder is 230 parts by mass or more and 365 parts by mass or less, the titanium oxide is 60 parts by mass or more and 95 parts by mass or less per 100 parts by mass of the binder, and and the ammonium polyphosphate is 120 parts by mass or more and 185 parts by mass or less, and the fire resistant resin layer after heating at 800° C. for 2 hours has an expansion ratio of 5 to 12 times. a kneading step of kneading a binder made of a synthetic resin and a non-binder that is a component other than the binder;
and a molding step of molding the kneaded product obtained in the kneading step,
In the kneading step, the non-binder contains ammonium polyphosphate, a polyhydric alcohol, and titanium oxide, the binder is an ethylene copolymer resin, and relative to 100 parts by mass of the binder The non-binder is 230 parts by mass or more and 365 parts by mass or less, the titanium oxide is 60 parts by mass or more and 95 parts by mass or less per 100 parts by mass of the binder, and and the ammonium polyphosphate is 120 parts by mass or more and 185 parts by mass or less, and the expansion ratio after heating at 800° C. for 2 hours is 5 to 12 times.

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