JP7704711B2 - Fireproof composite material and its manufacturing method - Google Patents

Description

The present invention relates to a fire-resistant composite material containing reinforcing fibers and a method for producing the same.

Composite materials containing reinforcing fibers and resins are lightweight yet strong, and are therefore widely used in fields such as railroad cars, automobiles, civil engineering and construction, and sporting goods. For example, the following Patent Document 1 discloses a fiber-reinforced composite material in which reinforcing fibers are contained in a thermosetting resin such as vinyl ester resin.

JP 2017-132932 A

The fiber-reinforced composite material described in Patent Document 1, particularly the fiber-reinforced composite material using vinyl ester resin as the base material (matrix resin), may release flammable gas from the vinyl ester resin when placed in a high-temperature environment caused by a fire or the like. This makes it difficult to ensure sufficient fire resistance.

The present invention was made in consideration of the above circumstances, and aims to provide a fireproof composite material with excellent fireproofing properties and a method for producing the same.

In order to solve the above-mentioned problems, a fire-resistant composite material according to one aspect of the present invention is a fire-resistant composite material comprising a base material made of a vinyl ester resin and reinforcing fibers contained in the base material, and characterized in that the concentration of styrene gas generated from the vinyl ester resin in the composite material is 287 ppm or more and 550 ppm or less when measured by gas chromatographic analysis at 300°C (claim 1).

In this specification, fireproofing is a broad concept that refers to the property of being difficult to burn, and includes non-combustible, flame-retardant, and fire-resistant.

The fireproof composite material of the present invention has the property that, when subjected to gas chromatographic analysis, the concentration of styrene gas generated from the vinyl ester resin constituting the base material is 550 ppm or less. This means that even in a high-temperature environment caused by a fire or the like, flammable gases, mainly styrene gas, are unlikely to be released from the fireproof composite material. Therefore, even if the fireproof composite material approaches a fire, it will not ignite, and the fireproofing properties of the fireproof composite material can be well ensured.

Specifically, the fireproof composite material can be evaluated as non-flammable by Test Method I for Non-metallic Materials for Railway Vehicles, which complies with Article 83 of Section 5, Chapter 8, "Fire Prevention Measures for Vehicles, etc." of Ordinance of the Ministry of Land, Infrastructure, Transport and Tourism No. 151 (Claim 2).

Furthermore, the fireproof composite material can have a bending strength according to JIS K7074 of 1200 MPa or more (Claim 3).

In other words, by producing a fireproof composite material using the manufacturing method described below, it is possible to keep the concentration of the styrene gas to 550 ppm or less, imparting fireproofing equivalent to non-combustibility, while still ensuring a bending strength of 1200 MPa or more. This makes it possible to realize a fireproof composite material that combines high fireproofing and strength.

A method for producing a fire-retardant composite material according to another aspect of the present invention includes the steps of: molding a prepreg material in which reinforcing fibers are impregnated with vinyl ester resin; introducing the molded prepreg material into a mold and pultrusion molding the molded body; and heating the molded body obtained by the pultrusion molding in a heating furnace at 290°C to 320°C for 5 to 20 minutes (Claim 4).

According to the manufacturing method of the present invention, by heating the molded body after pultrusion molding under specific temperature (290-320°C) and time (5-20 minutes) conditions, the concentration of styrene gas generated from the vinyl ester resin can be reduced to 550 ppm or less when measured by gas chromatography analysis at 300°C. This makes it possible to improve the fire resistance of the molded body after the heat treatment, i.e., the fireproof composite material. Furthermore, according to the above-mentioned heat treatment conditions, the degree of decrease in strength of the vinyl ester resin that may occur due to the heat treatment can be kept to a minimum. If the decrease in strength due to the heat treatment is small, the increase in strength due to the reinforcing effect of the reinforcing fibers will exceed the amount of the decrease in strength, and the strength of the fireproof composite material can be increased overall.

As described above, the present invention can provide a fireproof composite material with excellent fireproofing properties.

FIG. 1 is a perspective view showing a fire-retardant composite material according to an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a pultrusion device for producing the above fire-retardant composite material. 1 is a table showing characteristics of examples and comparative examples. 1 is a table showing analytical conditions when gas chromatographic analysis was performed on Examples and Comparative Examples.

[Fireproof composite material structure]
Fig. 1 is a perspective view showing a fireproof composite material 1 according to one embodiment of the present invention. As shown in this figure, the fireproof composite material 1 includes a base material 2 and reinforcing fibers 3 contained in the base material 2. In this embodiment, the fireproof composite material 1 is a plate-shaped member having a certain thickness t and width W.

The base material 2 is a resin member shaped into a plate by pultrusion molding, which will be described later. The base material 2 is made of vinyl ester resin, that is, a thermosetting resin in which acrylic or methacrylic groups are added to epoxy resin.

The reinforcing fibers 3 are numerous filaments contained in the base material 2 to reinforce the base material 2, and are arranged inside the base material 2 in a state oriented in a certain direction along the longitudinal direction X of the fireproof composite material 1. As the reinforcing fibers 3, carbon fibers, glass fibers, aramid fibers, ceramic fibers, etc. can be used. Among them, carbon fibers are advantageous in improving the strength and corrosion resistance of the molded product. As the carbon fibers, it is preferable to use PAN (polyacrylonitrile)-based carbon fibers, which have particularly high strength.

The content of reinforcing fibers 3 in the fireproof composite material 1 is preferably set such that the fiber weight content (Wf) is 65% or more and 85% or less, and the fiber volume content (Vf) is 50% or more and 80% or less.

[Method of manufacturing fireproof composite material]
Fig. 2 is a diagram showing a schematic configuration of a pultrusion device 20 for manufacturing the above-mentioned fireproof composite material 1. As shown in this figure, the pultrusion device 20 includes a fiber feeder 21, a resin impregnation tank 22, a molding die 23, a heating furnace 24, a take-up machine 25, and a cutter 26. The fiber feeder 21, the resin impregnation tank 22, the molding die 23, the heating furnace 24, the take-up machine 25, and the cutter 26 are arranged in this order from the upstream side in the drawing direction (the left side in Fig. 2).

The fiber delivery machine 21 is a device that delivers the reinforcing fibers 3 downstream toward the resin impregnation tank 22. The fiber delivery machine 21 includes a plurality of delivery rollers 31 around which the reinforcing fibers 3 are wound, and a plurality of guide rollers 32 that guide the reinforcing fibers 3 delivered from the delivery rollers 31 to the downstream side. The reinforcing fibers 3 are wound around the delivery rollers 31 in a bundled sheet shape, and are delivered downstream according to the rotation of the delivery rollers 31. In other words, what is delivered from the delivery roller 61 is a sheet-like body in which continuous reinforcing fibers 3 extending along the delivery direction are bundled into a sheet shape. Hereinafter, this is referred to as a fiber sheet 3A. As the fiber sheet 3A, a sheet-like unopened fiber bundle may be used as it is, or the fiber bundle may be opened and spread out. Alternatively, the unopened fiber bundles may be combined by a means such as sewing, and used as the fiber sheet 3A. Each fiber sheet 3A sent out from the multiple delivery rollers 31 is guided by a guide roller 32 and led downstream toward the resin impregnation tank 22.

The resin impregnation tank 22 is a tank for impregnating the fiber sheet 3A with resin. Liquid impregnation resin 12 is stored inside the resin impregnation tank 22. The impregnation resin 12 is the resin that constitutes the base material 2 (Figure 1) after molding. In other words, the impregnation resin 12 is a liquid vinyl ester resin. The impregnation resin 12 can contain additives such as a flame retardant.

Each fiber sheet 3A sent out from the fiber feeder 21 is individually introduced into the impregnation resin 12, so that each fiber sheet 3A is impregnated with the impregnation resin 12. The fiber sheet 3A impregnated with the impregnation resin 12 is led out of the resin impregnation tank 22 via a guide roller 33 or the like.

The fiber sheet 3A discharged from the resin impregnation tank 22 is a sheet-like body made of reinforcing fibers 3 impregnated with the impregnation resin 12, and is hereinafter referred to as a prepreg sheet 3B. The prepreg sheet 3B contains reinforcing fibers 3 that are continuous in the drawing direction and impregnation resin 12 (vinyl ester resin) that has impregnated the reinforcing fibers 3, and corresponds to the "prepreg material" in this invention. The multiple prepreg sheets 3B discharged from the resin impregnation tank 22 are stacked and shaped in the thickness direction by multiple guides 34, while being guided downstream and sent to the molding die 23.

The forming die 23 is a metal mold that receives and heats the laminated prepreg sheets 3B supplied from the resin impregnation tank 22 through the guide 34. The forming die 23 has an internal cavity that penetrates in the drawing direction. That is, the forming die 23 receives the laminated prepreg sheets 3B into the cavity, and heats the received prepreg sheets 3B to shape the prepreg sheets 3B into a cross-sectional shape that corresponds to the cavity. In this embodiment, the forming die 23 has a cavity with a rectangular cross-sectional shape that corresponds to the fireproof composite material 1 (Figure 1). The prepreg sheets 3B are shaped in such a cavity and discharged downstream as a molded body 11 with a rectangular cross-sectional shape.

The molding die 23 has a built-in heating device (not shown). This heating device heats the prepreg sheet 3B at least downstream of the molding die 23 until the temperature of the impregnated resin 12 exceeds the curing temperature of the material (vinyl ester resin). In other words, the molded body 11 discharged from the molding die 23 is a molded body with a rectangular cross section that contains the cured impregnated resin 12 (vinyl ester resin) and the reinforcing fibers 3.

The heating furnace 24 is a furnace for heating the molded body 11. The heating furnace 24 includes a heating chamber through which the molded body 11 discharged from the molding die 23 passes, and a heat source for maintaining the inside of the heating chamber at a predetermined high temperature range (both are not shown). In this embodiment, the temperature of the heating chamber, i.e., the internal temperature of the heating furnace 24, is set to 290°C or higher and 320°C or lower. The length of the heating furnace 24 is set so that the time required for the molded body 11 to pass through the heating furnace 24 is 5 minutes or higher and 20 minutes or lower. That is, in this embodiment, the molded body 11 is heat-treated at a heating temperature of 290 to 320°C for 5 to 20 minutes. This heat treatment causes flammable gas to be released from the vinyl ester resin contained in the molded body 11.

From the heating furnace 24, the molded body 11 that has been subjected to the above-mentioned heat treatment is discharged as the fireproof composite material 1. That is, the fireproof composite material 1 comprises a base material 2 made of vinyl ester resin from which flammable gas is released when heated, and reinforcing fibers 3 arranged inside the base material 2 in a state where they are drawn in the same direction (pulling direction) (see FIG. 1).

The take-up machine 25 is a device that takes up the fireproof composite material 1 discharged from the molding die 23 and sends it further downstream. In this embodiment, the take-up machine 25 is equipped with multiple pairs of rollers 35 and a pair of endless belts 36 that are arranged in the vertical direction and wrapped around the rollers 35. However, the take-up machine is not limited to one that uses such endless belts 36, and any type of take-up machine suitable for the shape of the molded body 11, such as a clamp type, can be used.

The cutter 26 is a device including a saw blade 37 that cuts the fireproof composite material 1 sent from the take-up machine 25 to a predetermined length. After the fireproof composite material 1 is cut to a predetermined length by the saw blade 37, it is transported downstream by a transport section not shown.

[Action and Effect]
As described above, in this embodiment, the prepreg sheet 3B in which the reinforcing fibers 3 are impregnated with the vinyl ester resin (impregnation resin 12) is introduced into the molding die 23 and pultrusion molded, and the molded body 11 obtained by this is heated in the heating furnace 24 at 290 to 320° C. for 5 to 20 minutes to produce the fireproof composite material 1. The fireproof composite material 1 produced by this method has excellent properties in terms of both fireproofness and strength, as will be apparent from the evaluation of each example described later.

That is, in this embodiment, the molded body 11 is heated by the heating furnace 24 at a specific temperature (290 to 320°C) and time (5 to 20 minutes), so that the heat treatment can release a significant amount of flammable gas from the vinyl ester resin. This means that the components that can volatilize as flammable gas are reduced from the vinyl ester resin. Therefore, the fireproof composite material 1 obtained through the above heat treatment has the property that even if it is placed in a high-temperature environment due to a fire or the like, less flammable gas can volatilize from its base material 2 (vinyl ester resin). In other words, since the fireproof composite material 1 is unlikely to release flammable gas even in a high-temperature environment, it does not ignite even when it approaches a fire and has excellent fire resistance. Moreover, the above-mentioned heat treatment conditions are necessary and sufficient conditions to ensure fire resistance, and the vinyl ester resin is not heated at an excessive temperature or time. Therefore, the degree of decrease in strength of the vinyl ester resin that may occur due to the heat treatment can be kept to a minimum. If the loss in strength due to heat treatment is small, the increase in strength due to the reinforcing effect of the reinforcing fiber 3 will exceed the loss in strength, and the overall strength of the fireproof composite material 1 can be increased.

[Example]
The results obtained by actually manufacturing the fireproof composite material 1 by the method of the embodiment described above are shown in Fig. 3 as Examples 1 to 9. That is, the temperature and time of the heat treatment in the heating furnace 24 were variously changed within the range of the conditions of the above embodiment (290 to 320°C/5 to 20 minutes), and the flat-plate-shaped fireproof composite material 1 was manufactured according to the manufacturing method shown in Fig. 2, and the obtained results are respectively referred to as Examples 1 to 9. The fiber weight content (Wf) of Examples 1 to 9, that is, the weight ratio of the reinforcing fiber 3 in the fireproof composite material 1, was 66% in all cases.

The manufacturing conditions other than the heat treatment in Examples 1 to 9 are as follows.
(Manufacturing conditions)
Dimensions: Thickness (t) x width (W) = 2 mm x 30 mm
- Matrix resin: Lipoxy (Showa Denko)
・Reinforced fiber: Carbon fiber T-700 (manufactured by Toray)
Mold temperature: 160°C
・Line speed: 0.2m/min

In the above manufacturing conditions, the matrix resin refers to the resin (vinyl ester resin) that constitutes the base material 2, the mold temperature refers to the heating temperature in the molding die 23, and the linear speed refers to the speed at which the fireproof composite material 1 is taken up by the take-up machine 25, in other words, the drawing speed through the molding die 23.

Figure 3 also shows Comparative Examples 1 to 3. Comparative Examples 1 to 3 differ from the above embodiment in the conditions of the heat treatment in the heating furnace 24. Specifically, Comparative Examples 1 and 2 are those in which the heat treatment was performed at a temperature different from the temperature conditions of the above embodiment (290 to 320°C), and Comparative Example 3 is one in which the heat treatment was omitted altogether. The other manufacturing conditions are the same as those of Examples 1 to 9.

The fire resistance and strength of the above examples and comparative examples were evaluated using the following methods.

(i) Gas Chromatography Analysis For the above-mentioned Examples and Comparative Examples, a gas chromatographic analysis was performed at 300°C using a thermal desorption-gas chromatograph mass spectrometer (TG-GC/MS device). Gas chromatographic analysis is an analysis method in which a sample is heated to a specific temperature (here, 300°C) and the components volatilized from the sample due to the heating are measured. The analysis conditions (measurement conditions) are as shown in Figures 4(a) and 4(b). The combustible gas recognized as a volatile component in this gas chromatographic analysis at 300°C was mainly styrene gas. Therefore, an analysis was performed to measure the concentration (ppm) of styrene gas for the Examples and Comparative Examples. The results are shown in Figure 3 as styrene gas concentration. The styrene gas concentration in Figure 3 refers to the initial detection concentration of styrene gas.

(ii) Bending Strength Measurement Bending strength measurement, i.e., bending test, was performed on the above-mentioned Examples and Comparative Examples. The test conditions were in accordance with JIS K7074. The test piece used in this bending test had a size of 2 mm x 15 mm x 100 mm in thickness x width x length. A bending test was performed on the test piece of this size by JIS K7074 A method (three-point bending) to measure the stress (MPa) at which the test piece broke. The results are shown in FIG. 3 as bending strength. In addition, the strength ratio (%) when the bending strength in the case where the heat treatment was omitted (Comparative Example 3) was set to 100 is also shown in FIG. 3.

(iii) Fireproofing Evaluation The above-mentioned examples and comparative examples were subjected to a fireproofing evaluation by the test method I for non-metallic materials for railway vehicles in accordance with Article 83 of the Ministry of Land, Infrastructure, Transport and Tourism Ordinance No. 151 of 2001, Chapter 8, Section 5, "Fire Prevention Measures for Vehicles, etc." The test method I for non-metallic materials for railway vehicles in accordance with the same law is a test method prescribed in the interpretation criteria established for the above-mentioned ministerial ordinance, that is, the "Interpretation Criteria of the Ministerial Ordinance Prescribing Technical Standards for Railways," and is roughly based on the following method. That is, an alcohol container is placed under the center of a test piece (182 mm x 257 mm) held in a 45-degree tilted position, and 0.5 cc of pure ethyl alcohol in the alcohol container is burned until it is completely burned. Then, the ignition, flame, smoke generation, and flame state of the test piece during alcohol combustion are investigated, and the residual flame, residual dust, carbonization, and deformation state of the test piece after alcohol combustion are investigated. Based on these investigation results, it is judged whether the product falls into one of the categories of "non-flammable", "extremely flame-retardant", or "flame-retardant" (or whether it falls into none of the categories). The results of evaluating the fire retardancy of the Examples and Comparative Examples using this test method are shown in Figure 3. In Figure 3, "o" for non-flammability indicates that the evaluation result using the above test method was "non-flammable", which has the best fire retardancy, and "x" for non-flammability indicates that the evaluation result was not "non-flammable", i.e., the fire retardancy is relatively poor.

As can be seen from Figure 3, the conditions of the heat treatment when producing Examples 1 to 9 are all within the temperature range of 290 to 320°C and the time range of 5 to 20 minutes. The styrene gas concentration of Examples 1 to 9 obtained under such conditions, that is, the concentration of styrene gas generated from the vinyl ester resin in the composite material measured by gas chromatography analysis at 300°C, was 287 ppm in the lowest case (Example 9) and 550 ppm in the highest case (Example 1). In other words, it was confirmed that the concentration of styrene gas generated from the vinyl ester resin in the composite material for Examples 1 to 9 was 550 ppm or less. And, because the concentration of styrene gas was 550 ppm or less, the fire resistance evaluation of Examples 1 to 9 was "non-flammable".

In contrast, in Comparative Example 1, in which the heat treatment temperature was set at 280°C, lower than in Examples 1 to 9, the styrene gas concentration was high at 600 ppm, resulting in a fire resistance rating below "non-flammable." In Comparative Example 3, in which no heat treatment was performed, the styrene gas concentration rose to 1,300 ppm, naturally resulting in an evaluation below "non-flammable." Meanwhile, in Comparative Example 2, in which the heat treatment temperature was set at 330°C, higher than in Examples 1 to 9, the styrene gas concentration dropped to 248 ppm, but it was found that excessive heating caused the resin to deteriorate and crack, making it unusable as a product (defective molding).

In terms of bending strength, Comparative Example 3, which did not undergo heat treatment, had the highest bending strength of 1479 MPa. In Examples 1 to 9, which did undergo heat treatment, bending strength was lower than Comparative Example 3, but even in the lowest case (Example 9), the bending strength only decreased to 1218 MPa, and it was found that a strength ratio of 82% of Comparative Example 3 was ensured. In Example 1, which had the highest bending strength among the examples, a bending strength of 1409 MPa (95% strength ratio) was ensured. In other words, it was found that Examples 1 to 9, which were heated at temperatures of 290 to 320°C for 5 to 20 minutes, ensured a bending strength of 1200 MPa or more according to JIS K7074.

From the above, Examples 1 to 9 have a relatively high bending strength of 1200 MPa or more according to JIS K7074, while being rated "non-flammable" for fire resistance according to Test Method I for Nonmetallic Materials for Railway Vehicles in accordance with Article 83 of Chapter 8, Section 5 "Fire Prevention Measures for Vehicles, etc." of Ordinance of the Ministry of Land, Infrastructure, Transport and Tourism No. 151 of 2001, and can be said to be excellent composite materials that combine high fire resistance and strength.

[Modification]
In the above embodiment, a plate-shaped fireproof composite material 1 (FIG. 1) having a rectangular cross section is formed, but the shape of the fireproof composite material is not limited to this, and it is possible to form fireproof composite materials having various cross-sectional shapes.

In the above embodiment, continuous fibers extending in the same direction along the longitudinal direction X of the fireproof composite material 1 are used as the reinforcing fibers 3 contained in the fireproof composite material 1, but the reinforcing fibers that can be contained in the fireproof composite material do not have to be continuous fibers and may be long or short fibers. In addition, the reinforcing fibers may be oriented in two or more directions. For example, to form a fireproof composite material containing reinforcing fibers oriented in two or more directions using the drawing device 20 shown in FIG. 2, the directions of the reinforcing fibers 3 of each fiber sheet 3A sent out from the multiple feed rollers 31 may be staggered. That is, the fiber direction of the fiber sheet 3A sent out from some of the feed rollers 31 is set to the same direction as the feed direction, while the fiber direction of the fiber sheet 3A sent out from the other feed rollers 31 is set to a direction different from the feed direction. To make the direction of the reinforcing fibers in the fiber sheet 3A different from the feed direction as in the latter case, for example, a fiber sheet 3A can be prepared in which bundles of reinforcing fibers (fiber bundles) extending in a direction different from the feed direction (for example, a direction perpendicular to the feed direction) are combined by a means such as sewing.

Furthermore, the direction of the reinforcing fibers contained in each of the fiber sheets 3A sent out from the multiple delivery rollers 31 may be set to two or more. That is, the fiber sheet used as the material before pulling on the upstream side of the pulling device 20 may be a multiaxial fiber sheet containing reinforcing fibers oriented in two or more directions. Also, a woven fabric in which reinforcing fibers are woven together may be used as the fiber sheet. Furthermore, a tape-like roving material containing reinforcing fibers may be used as the material before pulling.

In the above embodiment, the process of introducing the fiber sheet 3A sent from the fiber delivery machine 21 into the resin impregnation tank 22 to form the prepreg sheet 3B, the process of introducing the molded prepreg sheet 3B into the molding die 23 to perform pultrusion molding, and the process of heating the molded body 11 obtained by the pultrusion molding in the heating furnace 24 were performed continuously in one production line, but at least one process may be separated from the production line and multiple processes may be performed independently. For example, instead of the method of the above embodiment in which the molded body 11 discharged from the molding die 23 is directly fed into the heating furnace 24 (inline type), a fireproof composite material similar to that of the above embodiment can also be produced by an offline type in which the molded body 11 discharged from the molding die 23 is first cut to a predetermined length by a cutter and then fed into the heating furnace.

1 Fireproof composite material 2 Base material 3 Reinforced fiber 3C Prepreg sheet (prepreg material)
23 Molding die (mold)
24 Heating furnace

Claims (4)

A composite material having fire retardant properties,
A base material made of vinyl ester resin;
Reinforcing fibers contained in the base material;
A fireproof composite material, characterized in that the concentration of styrene gas generated from a vinyl ester resin in the composite material is 287 ppm or more and 550 ppm or less, as measured by gas chromatography analysis at 300°C. 2. The fire-retardant composite material according to claim 1,
A fireproof composite material that is non-combustible when evaluated according to Test Method I for Non-metallic Materials for Railway Vehicles in accordance with Article 83 of Section 5, Chapter 8, "Fire Prevention Measures for Vehicles, etc." of Ordinance of the Ministry of Land, Infrastructure, Transport and Tourism No. 151. The fire retardant composite material according to claim 1 or 2,
A fireproof composite material having a bending strength according to JIS K7074 of 1200 MPa or more. A step of molding a prepreg material in which reinforcing fibers are impregnated with vinyl ester resin;
A step of introducing the molded prepreg material into a mold and pultrusion molding;
and heating the molded body obtained by the pultrusion molding in a heating furnace at 290°C or higher and 320°C or lower for 5 minutes or longer and 20 minutes or shorter.