WO2022004254A1

WO2022004254A1 - Sandwich panel

Info

Publication number: WO2022004254A1
Application number: PCT/JP2021/020958
Authority: WO
Inventors: 政夫上坂
Original assignee: 住友ベークライト株式会社
Priority date: 2020-06-30
Filing date: 2021-06-02
Publication date: 2022-01-06
Also published as: JP7088424B2; JPWO2022004254A1

Abstract

A sandwich panel (100) according to the present invention is provided with a core layer (10) that has a honeycomb structure, and a cured material (resin sheets (40)) of a prepreg (20) that is provided on both surfaces of the core layer (10), wherein both the core layer (10) and the prepreg (20) contain a water-soluble phenol resin as a binder.

Description

Sandwich panel

The present invention relates to a sandwich panel.

The sandwich panel is composed of a hollow honeycomb core composed of a wall having a hexagonal cross section and a skin material such as a pair of prepregs joined to both sides of the honeycomb core. Sandwich panels, which are lightweight and highly rigid, are used, for example, in structural members for aircraft.

Various methods are disclosed as a method for manufacturing a sandwich panel. As a general method, for example, there is a technique described in Patent Document 1. According to the same document, a plurality of cloths are impregnated with a phenol resin, and two laminated plates obtained by heat and pressure molding are impregnated with a phenol resin phenol resin phenol resin composition, heated, and cured. A sandwich panel can be obtained by arranging it on both sides of the honeycomb core and forming it under heat and pressure molding.

Japanese Unexamined Patent Publication No. 2018-199267

In many of the conventional methods for producing sandwich panels as disclosed in Patent Document 1, the phenol resin is previously dissolved in an organic solvent to make it liquid, and then the honeycomb core and the base material for prepreg are impregnated with the phenol resin. Therefore, it has been pointed out that the safety of organic solvents and the impact on the working environment have become problems, and that they also contribute to global warming and air pollution.
On the other hand, in recent years, there have been increasing demands for adhesion, combustion resistance, etc. in sandwich panels for aircraft applications.

As a result of diligent studies from the viewpoint of increasing productivity without using an organic solvent while maintaining the performance obtained by the conventional sandwich panel, the present inventor has made both the core layer and the prepreg water-soluble as a binder resin. It was found that it is effective to include a phenol resin. That is, by using the water-soluble phenol resin, the phenol resin can be impregnated into the core layer and the prepreg without using an organic solvent, the impregnation property of the phenol resin becomes high, and the adhesion between the core layer and the prepreg becomes high. The following first invention was completed by finding that it is possible to obtain a high degree of combustion resistance and good combustion resistance.

According to the present invention
A sandwich panel comprising a core layer having a honeycomb structure and a cured product of a prepreg provided on both sides of the core layer.
A sandwich panel is provided in which both the core layer and the prepreg contain a water-soluble phenolic resin as a binder resin.

Further, the present inventor has found that the impregnation property can be dramatically improved by using a specific water-soluble phenol resin, and by using this for at least one of the core layer and the prepreg, the core layer and the prepreg can be used. We have found that the adhesion can be improved and good combustion resistance can be obtained, and the following second invention has been completed.

According to the present invention
A sandwich panel comprising a core layer having a honeycomb structure and a cured product of a prepreg provided on both sides of the core layer.
The core layer and / or the prepreg contains a water-soluble phenolic resin as a binder resin, and the prepreg contains a water-soluble phenol resin.
A sandwich panel is provided in which the water-soluble phenol resin is a phenol resin synthesized by using one or more selected from lignin, lignin derivatives, lignin decomposition products and modified products thereof.

According to the present invention, a sandwich panel having good adhesion and combustion resistance is provided.

It is a schematic diagram which shows an example of the sandwich panel which concerns on this embodiment. It is a process sectional view which shows an example of the manufacturing method of the sandwich panel which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by the same reference numerals, and the description thereof will be omitted as appropriate.
In the present specification, the notation "a to b" in the description of the numerical range means a or more and b or less unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass or more and 5% by mass or less".

<First Embodiment>
FIG. 1 is a schematic view showing an example of a sandwich panel according to the present embodiment.
The sandwich panel 100 of the present embodiment includes a core layer 10 having a honeycomb structure, a cured product (resin plate 40) of a prepreg 20 (prepreg 21 on the upper surface and prepreg 22 on the lower surface) provided on both sides of the core layer 10. To prepare for.

In the present embodiment, both the core layer 10 and the prepreg 20 contain a water-soluble phenol resin as a binder resin. As a result, good wettability between the water-soluble phenol resin and the core layer 10 and the prepreg 20 can be obtained, and the water-soluble phenol resin can be satisfactorily impregnated into the core layer 10 and the prepreg 20. Therefore, the generation of voids in the core layer 10 and the prepreg 20 can be effectively suppressed, and the transparency can be improved. Further, in the obtained sandwich panel 100, the adhesion between the core layer 10 and the resin plate 40 can be improved, and good combustion resistance can be obtained. Although the details of the relationship between the adhesion and the combustion resistance are not clear, when the resin plate 40 on one surface of the sandwich panel 100 is exposed to flame in the combustion resistance test, the inside of the honeycomb structure of the core layer 10 is formed. Since the air expands, if the adhesion between the core layer 10 and the resin plate 40 is not sufficient, a slight gap is formed, and it is presumed that the flame spreads from there. Therefore, it is considered that the combustion resistance can be improved by improving the adhesion between the core layer 10 and the resin plate 40.

[Water-soluble phenolic resin]
The water-soluble phenol resin of the present embodiment is a resin that can be dissolved or dispersed in water. As a result, the water solubility is increased, and the wettability with the core layer 10 and the prepreg 20 can be improved.
Examples of the water-soluble phenolic resin include lignin, lignin derivatives, lignin decomposition products, and phenolic resins using one or more selected from these modified products. For example, examples of the lignin modified product include those disclosed in Japanese Patent Publication No. 48-22340.
Above all, from the viewpoint of obtaining good adhesion, it is highly water-soluble, and it can be expected that both impregnation into the prepreg base material and good wettability with the core layer and prepreg can be expected due to the phenol formaldehyde of the lignin component. A resol-type lignin-modified phenol resin having the same thermosetting property as the phenol resin is preferable.

[Lignin-modified phenolic resin]
The lignin modification rate of the lignin-modified phenolic resin is preferably 10 to 60%, more preferably 20 to 50%. By setting the modification rate to the above lower limit value or more, good impregnation property and wettability are maintained, and by setting the modification rate to the above upper limit value or less, a suitable resin viscosity can be obtained and the thermosetting property can be improved.

The lignin-modified phenol resin is obtained by reacting lignins, which will be described later, phenols, and aldehydes in the presence of a catalyst. Further, the above-mentioned resole-type lignin-modified phenol resin can be obtained by reacting lignins, phenols and aldehydes in the presence of an alkaline catalyst.

[Lignins]
The lignins used in the lignin-modified phenolic resin include at least one selected from lignin and lignin derivatives.
Lignin, along with cellulose and hemicellulose, is a major component that forms the structure of plants and is one of the most abundant aromatic compounds in nature. Examples of lignin include alkaline lignin such as kraft lignin, soda lignin, soda-anthraquinone lignin, pulp lignin containing lignin sulfonic acid; organosolv lignin; high temperature and high pressure water treatment lignin; explosive lignin; enzyme saccharified lignin; lignophenol; phenolized lignin. ; Etc. can be mentioned.
The origin of lignin is not particularly limited, and examples thereof include woods and herbs that contain lignin and form xylem, such as conifers such as cedar, pine and hinoki, broad-leaved trees such as beech, birch, nara and zelkova, rice and wheat. Examples include grasses (herbs) such as corn and bamboo. Of these, lignin derived from coniferous trees is preferable from the viewpoint of mechanical properties of the cured prepreg product.

In the present embodiment, the "lignin derivative" refers to a compound having a unit structure constituting lignin or a structure similar to the unit structure constituting lignin. The lignin derivative has a phenol derivative as a unit structure. Since this unit structure has chemically and biologically stable carbon-carbon bonds and carbon-oxygen-carbon bonds, it is resistant to chemical deterioration and biological decomposition.

Examples of the lignin derivative include guaicylpropane (ferulic acid) represented by the following formula (A), syringylpropane (sinapinic acid) represented by the formula (B), and 4-hydroxyphenylpropane represented by the formula (C). (Cumaric acid) and the like. The composition of the lignin derivative depends on the biomass used as the raw material. Lignin derivatives containing a guaiacylpropane structure are mainly extracted from conifers. Lignin derivatives containing a guaiacyl propane structure and a syringyl propane structure are mainly extracted from hardwoods. Lignin derivatives containing a guaiacyl propane structure, a syringyl propane structure and a 4-hydroxyphenyl propane structure are mainly extracted from herbs.

The lignin derivative is preferably obtained by decomposing biomass. Biomass takes in and immobilizes carbon dioxide in the atmosphere in the process of photosynthesis, so biomass contributes to suppressing the increase in carbon dioxide in the atmosphere. It can contribute to the suppression of carbon dioxide. Examples of the biomass include lignocellulosic biomass. Examples of lignocellulosic biomass include leaves, bark, branches and wood of plants containing lignin, and processed products thereof. Examples of plants containing lignin include the above-mentioned broad-leaved trees, coniferous trees, and gramineous plants.

Biomass decomposition methods include chemical treatment methods, hydrolysis treatment methods, steam explosion methods, supercritical water treatment methods, subcritical water treatment methods, mechanical treatment methods, cresol sulfate methods, pulp production methods, etc. Can be mentioned. From the viewpoint of environmental load, steam blasting method, sub-critical water treatment method, and mechanical treatment method are preferable. From the viewpoint of cost, the pulp production method is preferable. From the viewpoint of cost, it is preferable to use by-products of biomass utilization.

Examples of the lignin derivative include those obtained by decomposing lignocellulosic, which is a combination of lignin, cellulose and hemicellulose. The lignin derivative may contain a lignin decomposition product, a cellulose decomposition product, a hemicellulose decomposition product, etc., which are mainly composed of a compound having a lignin skeleton.

The lignin derivative preferably has many reaction sites on which the curing agent acts by the electrophilic substitution reaction on the aromatic ring, and the fragrance containing a phenolic hydroxyl group is excellent in that the less steric damage near the reaction site is, the better the reactivity. It is preferable that at least one of the ortho-position and the para-position of the ring is unsubstituted, and lignin derived from coniferous trees or herbs, which contains a large amount of guaiacyl nucleus or 4-hydroxyphenyl nucleus structure as an aromatic unit of lignin, is preferable.

In addition to the above basic structure, the lignin derivative may be one having a functional group in the lignin derivative (lignin secondary derivative).

The functional group of the lignin secondary derivative is not particularly limited, but for example, two or more of the same functional groups capable of reacting with each other or those capable of reacting with other functional groups are preferable. Specific examples thereof include a vinyl group having a carbon-carbon unsaturated bond, an ethynyl group, a maleimide group, a cyanate group, an isocyanate group and the like, in addition to an epoxy group and a methylol group.

[Core layer]
As the core layer 10, for example, a sheet-like member formed by impregnating a base material for a core layer having a honeycomb structure with a binder resin can be used. The core layer 10 can have high strength and light weight due to the honeycomb structure.
The honeycomb structure is a known structure, and is intended to be a structure in which a plurality of substantially regular hexagonal through holes penetrating from the upper surface to the lower surface are formed.

In the present embodiment, the binder resin of the core layer 10 contains the above-mentioned water-soluble phenol resin, but may contain other resins other than the above-mentioned water-soluble phenol resin as long as the effect of the present invention is not impaired, for example. , Thermosetting resin and the like. Examples of the thermosetting resin include thermosetting resins such as phenol resins other than water-soluble, unsaturated polyester resins, and epoxy resins. The phenolic resin includes a compound having one or more phenolic hydroxyl groups in the molecule, for example, novolak resin such as novolak type phenol, novolak type cresol, novolak type naphthol; bisphenol resin such as bisphenol F, bisphenol A; paraxylylene. Phenolic aralkyl resins such as modified phenolic resins; resol-type phenolic resins such as dimethylene ether-type resol and methylol-type phenol; compounds obtained by further converting the above resins into methylols. Such a binder resin is dissolved in a known organic solvent and used as a binder solution by impregnating the base material for the core layer.

Examples of the base material having the honeycomb structure of the core layer 10 include those obtained by molding aramid fiber, paper, balsa wood, plastic, aluminum, titanium, glass, an alloy thereof and the like into a honeycomb shape by a known method. From the viewpoint of heat resistance, it is preferable that the base material having the honeycomb structure of the core layer 10 contains aramid fibers.

The layer thickness of the core layer 10 is not particularly limited, but may be, for example, 1 mm or more and 50 mm or less, 3 mm or more and 40 mm or less, or 5 mm or more and 30 mm or less.

The size of each core cell in the core layer 10 is not particularly limited, but can be, for example, 1 mm or more and 10 mm or less on one side.

The area of the surface (upper surface, lower surface) of the core layer 10 is not limited, but for example, it may have a surface area for one sandwich panel or a total surface area for a plurality of sandwich panels. good. This makes it possible to separate one sandwich panel 100 into individual pieces and cut out a plurality of panels to obtain the sandwich panel 100, thereby improving productivity. For example, the area of the surface (upper surface, lower surface) of the core layer 10 can be a large area, and may be, for example, 1 m ² or more.

Further, the core layer 10 may have various surface treatments on the inside and / or the outside from the viewpoint of improving corrosion resistance and heat resistance.

[Prepreg]
As the prepreg 20, for example, a sheet member in a B stage state in which a binder resin is impregnated into a prepreg base material can be used. Examples of the prepreg base material include a fiber base material.
In the B stage state, the reaction rate calculated from the measurement result of DSC (Differential Scanning Calorimeter) for the binder resin impregnated in the prepreg substrate is more than 0% and 60% or less, preferably 0. It means that it is 5% or more and 55% or less, and more preferably 1% or more and 50% or less.

In the present embodiment, the binder resin of the prepreg 20 contains the above-mentioned water-soluble phenol resin, but may contain a resin other than the above-mentioned water-soluble phenol resin as long as the effect of the present invention is not impaired. The above-mentioned water-soluble phenol resin is used.

As the fiber base material, aramid fiber, polyester fiber, polyphenylene sulfide fiber, carbon fiber, graphite fiber, glass fiber, silicon carbide fiber and the like can be used. From the viewpoint of high heat resistance, the fiber base material preferably contains glass fiber.

By containing the fiber base material, the heat resistance of the sandwich panel 100 can be further improved. Further, since the difference in linear expansion coefficient between the resin plate 40 and the core layer 10 can be reduced, the warp of the sandwich panel 100 can be suppressed.

In the present embodiment, the prepreg 20 is in a B stage state in which, for example, a binder resin is impregnated into a fiber base material. Conventionally, since the binder resin is dissolved in an organic solvent and then impregnated with the fiber base material, the organic solvent remains in the prepreg in the B stage state, and the odor due to the residual solvent is present in the sandwich panel manufacturing process. There was a problem. On the other hand, since the prepreg 20 of the present embodiment uses a water-soluble phenol resin as the binder resin, the odor caused by the conventional organic solvent can be reduced.

The upper limit of the glass transition temperature (Tg) of the cured product of the prepreg 20 is, for example, 250 ° C. or lower, preferably 220 ° C. or lower, and more preferably 200 ° C. or lower. This makes it possible to carry out the heat and pressurization treatment under low temperature conditions. On the other hand, the lower limit of the glass transition temperature (Tg) may be, for example, 110 ° C. or higher, or 120 ° C. or higher. This makes it possible to improve the thermal characteristics.

In the present embodiment, the binder resins used in the core layer 10 and the prepreg 20 may be the same or different from each other, but they can effectively improve the adhesion and the combustion resistance. It is preferably the same binder resin.

[Resin plate]
The resin plate 40 of the present embodiment is obtained by curing the prepreg 20 in the manufacturing process of the sandwich panel 100. The curing conditions are shown in the description of the manufacturing method of the sandwich panel 100.

A plurality of resin plates 40 may be laminated. Further, another functional layer may be interposed between the core layer 10 and the resin plate 40. For example, a thermoplastic sheet may be interposed to improve the adhesion.

[Use]
The sandwich panel 100 of this embodiment can be suitably used for an aircraft panel. For example, the sandwich panel 100 can be used for the interior of an aircraft such as a toilet and a partition, and the equipment inside the aircraft such as a wagon housing.

[Manufacturing method of sandwich panel]
Next, a method for manufacturing the sandwich panel 100 of the present embodiment will be described.

(Step 1) Preparation of Core Layer 10 and Prepreg 20 A base material for the core layer 10 is prepared. The base material for the core layer 10 has a honeycomb structure and is preferably formed of aramid fibers.
A base material having a honeycomb structure is prepared, and the base material is impregnated with a binder solution containing a water-soluble phenol resin. Then, the base material is dried to obtain a core layer 10 using a water-soluble phenol resin as a binder resin.

On the other hand, prepare a base material for prepreg 20. Examples of the base material for the prepreg 20 include a fiber base material. The base material for prepreg 20 is impregnated with a binder solution containing a water-soluble phenol resin. Then, the base material is dried to obtain prepreg 20 using a water-soluble phenol resin as a binder resin.

In both the core layer 10 and the prepreg 20, as the impregnation method, for example, a method of injecting and coating the base material using an injection device such as the binder solution spray nozzle, and a method of immersing the base material in the binder solution. , A method of applying the binder solution to the substrate by various coaters such as a knife coater and a comma coater, a method of transferring the binder solution to the substrate by a transfer roll, and the like. Of these, a method of immersing the base material in the binder solution is preferable.
The conditions for heating and drying are not particularly limited, but usually 100 to 220 ° C., preferably 120 to 190 ° C. for 2 to 10 minutes.

The binder solution containing the water-soluble phenol resin may contain other additives in addition to the water-soluble phenol resin. The additive is not particularly limited, and examples thereof include fillers such as inorganic fillers, rubber, and thermoplastic resins.
Further, a thermosetting resin other than the water-soluble phenol resin may be contained as long as the effect of the present invention is not impaired, and examples thereof include thermosetting resins such as phenol resin, unsaturated polyester resin and epoxy resin. Be done.
The content of the water-soluble phenol resin contained in the binder solution is not particularly limited, but is preferably 70 to 100% by mass, preferably 80% by mass or more, when the total solid content is 100% by mass. More preferred.

(Step 2) Laminating the core layer and the prepreg Next, as shown in FIG. 2A, the prepreg 20 in the B stage state (prepreg 21, 22) is placed. As a result, a laminate containing the core layer 10 and the prepreg 20 is formed. The prepreg 20 can cover the entire surface (upper surface and lower surface) of the core layer 10. In the present embodiment, the number of prepregs 20 to be laminated may be one or a plurality. Further, another functional layer may be arranged between the core layer 10 and the prepreg 20. As the other functional layer, for example, a foam layer made of a thermosetting resin can be used.

Subsequently, as shown in FIG. 2A, a metal plate 30 (the upper side is a metal plate 31 and the lower side is a metal plate 32) is arranged on the upper and lower surfaces of the laminated body.

Subsequently, as shown in FIG. 2B, the core layer 10 and the prepreg 20 are heated and pressed while the metal plate 30 is in contact with the prepreg 20. As a result, the prepreg 20 can be cured to form the resin plate 40 (the upper side is the resin plate 41 and the lower side is the resin plate 42).
For the above heating and pressurization, for example, conditions of 110 ° C. to 140 ° C., 30 minutes to 90 minutes, and 0.35 MPa to 2.0 MPa can be adopted.

Further, the above heating and pressurizing step can be performed in the atmosphere. Therefore, productivity can be improved.

Further, when the prepreg 20 is heated and pressed, a part of the resin constituting the prepreg 20 may move onto the inner wall surface of the honeycomb structure of the core layer 10. As a result, in the structure in which the resin plates 40 are joined to both surfaces of the core layer 10, the resin constituting the resin plate 40 is covered from the resin plate 40 to a part of the upper end portion or the lower end portion of the inner wall of the core layer 10. It will be formed continuously so that the adhesion can be improved. However, the structure is such that the entire inside of the core layer 10 is not filled with the resin constituting the resin plate 40. Thereby, the sandwich panel 100 having a structure excellent in strength and light weight can be obtained.

In the present embodiment, an example in which the metal plate 30 is used in the method for manufacturing the sandwich panel 100 has been described, but the present invention is not limited to this. Further, for example, a cushion layer may be arranged between the metal plate 30 and the prepreg 20 to heat and pressurize. The cushion layer may be made of, for example, a paper material, a rubber material, or a composite material thereof.

<Second Embodiment>
In the sandwich panel 100 of the first embodiment, both the core layer 10 and the prepreg 20 contain a water-soluble phenol resin, whereas in the sandwich panel 100 of the second embodiment, at least one of the core layer 10 and the prepreg 20 is a binder. Except for the fact that the resin contains a water-soluble phenol resin, and the above-mentioned water-soluble phenol resin is made by using one or more selected from lignin, a lignin derivative, a lignin decomposition product and a modified product thereof. It has the same configuration and function as the sandwich panel 100 of the first embodiment.
Hereinafter, the points different from the first embodiment will be described.

In the sandwich panel 100 of the second embodiment, the water-soluble phenol form is made of one or more selected from lignin, lignin derivatives, lignin decomposition products and modified products thereof, whereby the water-soluble phenol resin is said to be water-soluble. The impregnation property of the sex phenol resin can be dramatically improved, and as a result, by using it for at least one of the core layer 10 and the prepreg 20, the adhesion between the core layer and the prepreg can be improved and good combustion resistance can be obtained. Be done.
Further, in the second embodiment, the water-soluble phenol form using one or more selected from the above-mentioned lignin, lignin derivative, lignin decomposition product and modified product thereof has adhesion and combustion resistance. It is preferable that it is used in the prepreg 20, and it is more preferable that it is used in the core layer 10 and the prepreg 20.

In the manufacturing process of the sandwich panel 100 of the second embodiment, no water-soluble phenol resin is used as the binder solution, provided that at least one of the core layer 10 and the prepreg 20 contains the water-soluble phenol resin as the binder resin. A solution may be used.
As the binder solution that does not use the water-soluble phenol resin, a known one can be used, and a solution obtained by dissolving a thermosetting resin other than the water-soluble phenol resin in a known organic solvent can be used. Examples of the thermosetting resin include thermosetting resins such as phenol resins other than water-soluble, unsaturated polyester resins, and epoxy resins. The phenolic resin includes a compound having one or more phenolic hydroxyl groups in the molecule, for example, novolak resin such as novolak type phenol, novolak type cresol, novolak type naphthol; bisphenol resin such as bisphenol F, bisphenol A; paraxylylene. Phenolic aralkyl resins such as modified phenolic resins; resol-type phenolic resins such as dimethylene ether-type resol and methylol-type phenol; compounds obtained by further converting the above resins into methylols.

Although the embodiments of the present invention have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than the above can be adopted.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the description of these Examples.

[Preparation of lignin]
First, lignin used for the synthesis of lignin-modified phenolic resin was prepared by the following procedure.
1500 parts by mass of dried cedar wood flour with a water content of 50%, 5000 parts by mass of pure water, 180 parts by mass of sodium hydroxide, 120 parts by mass of sodium carbonate and 0.5 parts by mass of 9,10-anthraquinone as a cooking aid in a capacity of 10 L It was charged in a stainless steel autoclave facility and subjected to a cooking reaction at 170 ° C. for 3 hours with stirring. The post-reaction cooking liquor was cooled to room temperature, the pulp component was removed by a screen, and then the black liquor containing lignin was separated. The separated black liquor was concentrated to a concentration of 20% with an evaporator to obtain a concentrated black liquor. Dilute sulfuric acid was added to the concentrated black liquor to adjust the pH to 8, and the resulting precipitate was centrifuged. After washing twice with 500 parts by mass of water, the precipitate was suspended in 5 times the amount of water and readjusted to pH 2 with dilute sulfuric acid. The precipitated lignin was centrifuged again, washed with a small amount of water, suction filtered, and freeze-dried to obtain 140 parts by mass of alkaline lignin in the form of a brown powder.

[Synthesis of lignin-modified phenolic resin]
Next, using the prepared alkaline lignin, a lignin-modified phenol resin was synthesized by the following procedure.
・ Lignin-modified phenolic resin a
In a four-necked flask equipped with a stirrer, a cooling tube and a thermometer, 139 parts by mass of phenol, 32 parts by mass of a 20% sodium hydroxide aqueous solution, and 166 parts by mass of pure water were charged, and 139 parts by mass of alkaline lignin was placed in the flask while stirring. After adding to the reaction solution and uniformly dissolving at 60 ° C., 180 parts by mass of 37% formalin was added dropwise to the reaction solution over 30 minutes. After reacting at 90 ° C. for 60 minutes and 70 ° C. for 40 minutes while continuing stirring, the mixture was cooled to room temperature to obtain 653 parts by weight of the lignin-modified phenol resin a. The lignin denaturation rate based on the solid resin content was 42%, the non-volatile content was 51%, the pH was 7.5, and the viscosity of the solution resin was 0.71 Pa · s.

・ Lignin-modified phenolic resin b
The synthesis was carried out in the same manner as the lignin-modified phenol resin a except that 139 parts by mass of phenol was changed to 205 parts by mass of phenol and 139 parts by mass of alkaline lignin was changed to 67 parts by mass, and 654 parts by mass of lignin-modified phenol resin b was obtained. The lignin denaturation rate based on the solid resin content was 20%, the non-volatile content was 52%, the pH was 7.8, and the viscosity of the solution resin was 0.68 Pa · s.

[Binder solution]
The following binder solution was prepared.
-Binder solution A1
A water-soluble phenol resin (33304 manufactured by Durez) was used as the binder solution A1.
-Binder solution A2
The lignin-modified phenol resin b having a lignin modification rate of 20% obtained by the above synthesis method was used as a binder solution A2.
-Binder solution A3
The lignin-modified phenol resin a having a lignin modification rate of 42% obtained by the above synthesis method was used as a binder solution A3.
・ Binder solution B
An organic solvent (methanol) -based phenol resin (23056 manufactured by Durez) was used as the binder solution B.

<Example 1>
1) Production of core layer A honeycomb core was prepared using aramid paper (“Nomex412” manufactured by DuPont, thickness 50 μm). A series of operations such as impregnating the obtained honeycomb core with the binder solution A for 5 minutes, taking out the honeycomb core, and drying at 80 ° C. for 45 minutes was repeated twice. Then, it was cured at 190 ° C. for 30 minutes to obtain a core layer having a thickness of 10 mm and a thickness of 48.1 kg / m ^3.
2) Production of prepreg Glass fiber (# 7781, manufactured by HEXCEL) was impregnated with the binder solution A and dried at 150 ° C. for 3 minutes to obtain a sheet-shaped prepreg (thickness 250 μm). The prepreg was in the B stage state.
3) Manufacture of sandwich panel A laminated body was obtained by arranging one prepreg on each side of the core layer. Subsequently, a SUS plate (thickness: 1.5 mm, Rz: 1.0 μm) was pressed against both sides of the obtained laminate, and heated and pressed at 0.7 MPa, 127 ° C. for 60 minutes using a mechanical press. The prepreg was cured to form a resin plate. Then, the SUS plate was separated from the resin plate to obtain a sandwich panel composed of a resin plate, a honeycomb core, and a resin plate.
The glass transition temperature (Tg) of the cured product of the prepreg was 180 ° C.

<Examples 2 to 4, reference example>
Each sandwich panel was obtained in the same manner as in Example 1 except that the binder solution of the core layer and the binder solution of the prepreg were as shown in Table 1.

The following evaluations were made on the obtained core layer, prepreg, and sandwich panel. The evaluation results are shown in Table 1.

(Adhesion)
Measurements were made in accordance with ASTM D1781 (Standard Test Method for Drum Peeling for Adhesives) and evaluated according to the following criteria:
⊚: ≧ 150N / 76mm
◯: ≧ 100N / 76mm and <150N / 76mm
Δ:> 80N / 76mm and <100N / 76mm
×: ≦ 80N / 76mm

(Combustion resistance)
Measurements were made in accordance with FAR 25.853 (d) (combustion test of aircraft components; heat release) and evaluated according to the following criteria.
^{◎: ≦ 35kW / m 2 /} 35kW · min / m 2
^{○: ≦ 45kW / m 2 /} 45kW · min / m 2, ^{cutlet> 35kW / m 2 / 35kW ·} min / m 2
^{△: ≦ 65kW / m 2 /} 65kW · min / m 2, ^{cutlet> 45kW / m 2 / 45kW ·} min / m 2
^{×:> 65kW / m 2 /} 65kW · min / m 2

(Impregnability)
The core layer and prepreg before laminating were each observed under a microscope at 50 times and evaluated according to the following criteria.
⊚: No voids are confirmed in the core layer and prepreg ○: Slight voids are present in at least one of the core layer and prepreg Δ: Many voids are present in at least one of the core layer and prepreg ×: Core layer and prepreg There is a void on at least one side

(Odorous)
The prepreg before laminating was brought close to the nose to smell it, and the evaluation was made according to the following criteria.
◎: Odorless ○: Slightly odor △: Smell ×: Strong odor

This application claims priority on the basis of Japanese Application Japanese Patent Application No. 202-112637 filed on June 30, 2020, and incorporates all of its disclosures herein.

10 Core layer 20 Prepreg 21 Prepreg 22 Prepreg 30 Metal plate 31 Metal plate 32 Metal plate 40 Resin plate 41 Resin plate 42 Resin plate 100 Sandwich panel

Claims

A sandwich panel comprising a core layer having a honeycomb structure and a cured product of a prepreg provided on both sides of the core layer.
A sandwich panel in which both the core layer and the prepreg contain a water-soluble phenolic resin as a binder resin.
The sandwich panel according to claim 1, wherein the water-soluble phenol resin is a phenol resin synthesized by using one or more selected from lignin, lignin derivatives, lignin decomposition products and modified products thereof. ..
A sandwich panel comprising a core layer having a honeycomb structure and a cured product of a prepreg provided on both sides of the core layer.
The core layer and / or the prepreg contains a water-soluble phenolic resin as a binder resin, and the prepreg contains a water-soluble phenol resin.
A sandwich panel, wherein the water-soluble phenol resin is a phenol resin synthesized by using one or more selected from lignin, lignin derivatives, lignin decomposition products and modified products thereof.
The sandwich panel according to claim 3, wherein the prepreg contains the water-soluble phenol resin as a binder resin.
The sandwich panel according to any one of claims 1 to 4, wherein the prepreg is a fiber base material impregnated with the binder resin.
The sandwich panel according to any one of claims 1 to 5, wherein the core layer is a base material made of aramid fibers having a honeycomb structure impregnated with the binder resin.
The sandwich panel according to any one of claims 1 to 6, wherein the core layer has a layer thickness of 1 mm or more and 50 mm or less.
The sandwich panel according to any one of claims 1 to 7, wherein the glass transition temperature (Tg) of the cured product of the prepreg is 110 ° C. or higher and 250 ° C. or lower.
The sandwich panel according to any one of claims 1 to 8, which is used for an aircraft panel.
A method for manufacturing a sandwich panel comprising a core layer having a honeycomb structure and a cured product of a prepreg provided on both sides of the core layer.
The core layer is prepared by impregnating the base material for the core layer constituting the core layer with a binder solution containing a water-soluble phenol resin.
A step of impregnating a prepreg material constituting the prepreg with a binder solution containing a water-soluble phenol resin to prepare the prepreg, and a step of preparing the prepreg.
In no particular order,
A step of arranging the prepreg on the opening surfaces of the upper surface side and the lower surface side of the core layer impregnated with the binder solution and integrating them by heating and pressurizing.
How to make sandwich panels, including.
A method for manufacturing a sandwich panel comprising a core layer having a honeycomb structure and a cured product of a prepreg provided on both sides of the core layer.
The step of impregnating the core layer base material constituting the core layer with a binder solution containing a water-soluble phenol resin to prepare the core layer, and the binder solution containing a water-soluble phenol resin in the prepreg material constituting the prepreg. And at least one of the steps of preparing the prepreg by impregnating with
A step of arranging the prepreg on the opening surfaces of the upper surface side and the lower surface side of the core layer impregnated with the binder solution and integrating them by heating and pressurizing.
Including
A method for producing a sandwich panel, wherein the water-soluble phenol resin is a phenol resin synthesized by using one or more selected from lignin, lignin derivatives, lignin decomposition products and modified products thereof.