JPH0361581B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves injecting and foaming a specific resin mixture into the honeycomb-like internal structure, with metal plates on both sides, and flame-retardant
Regarding flame-retardant lightweight panels made by laminating FRP boards or inorganic boards.

In recent years, as energy prices have increased, transportation equipment has become lighter. For aircraft in particular, it is absolutely necessary to significantly reduce fuel costs by reducing weight, and this is a factor that has a major impact on the profits of air transport companies. For this reason, the 767 aircraft recently developed by the Boeing Company in the United States incorporates extensive use of composite materials to reduce weight, thereby extending its range and increasing the number of passengers it can accommodate compared to conventional aircraft.

In view of this situation, the present inventors have developed a field that requires lightweight, flame-retardant, and heat-insulating materials for use in transportation equipment, mainly aircraft, and walls of high-rise buildings. The research was carried out with the aim of developing a panel that could be provided to

That is, various types of sanderch panels using foam for the inner core have been known, and some of them are commercially available. Polyurethane foam, phenol foam, various vinyl foams, etc. have been used as the foam for the inner core, and have been used for a variety of purposes. However, while phenol foam has flame retardancy and heat insulation properties, it has problems with its "brittleness" and strength. Polyurethane foam also has a problem with flame retardancy, and vinyl foam also has a problem with gas generation during combustion.

The present inventors focused on the flame retardancy and heat insulating properties of phenol foam, and took advantage of the properties thereof, while also addressing the drawbacks of phenol foam. We have discovered a method that can sufficiently compensate for "brittleness" and strength, and have completed the present invention.

That is, in the present invention, in a panel using a honeycomb, a material having a density of 0.03 to 30 parts by weight consisting of 90 to 30 parts by weight of a phenol resin and 10 to 70 parts by weight of an epoxy resin or polyurethane resin is used as an inner core in the voids within the honeycomb.
Filled with 0.7 foam, metal plates on both sides of the honeycomb,
The present invention provides a flame-retardant lightweight panel comprising a flame-retardant FRP board or an inorganic board.

In the present invention, in order to eliminate the "brittleness" of the phenolic resin foam as the core material inside the panel, a specific reinforcing resin having other flexibility is mixed.
This constitutes one of the features of the present invention. The reinforcing resin is preferably an epoxy resin or a polyurethane resin, and one that melts at 150° C. or lower is preferable. In addition to these, thermoplastic resins that melt at temperatures below 150°C can be used as reinforcing resins. These can be used in either liquid or solid form.

Phenol resin foams are roughly classified into two types depending on the foaming method. One is liquid foaming, which is mainly based on resol foam, in which two or more liquids are mixed and foamed at room temperature. teeth
It is mainly a novolak type foam that is heated to 120 to 150°C to melt and generate volatile gas to foam.

Powdered novolak type phenolic resin foam is
Alcohols such as methanol, due to the necessity of work,
Powdered novolac type phenolic resin is dissolved or dispersed at a concentration of 20 to 90% in a low boiling point solvent such as ketones such as acetone and methyl ethyl ketone, and halogen-containing solvents such as methylene chloride and chloroform, and further applied to the required surface, It is obtained by drying at room temperature to about 60°C and then heating to 100 to 200°C to foam. Of course, these can be used when mixing the reinforcing resin of the present invention.

In the case of liquid foaming, the most common foaming is a three-component mixed system of resol type phenolic resin liquid, blowing agent liquid, and catalyst, or a two-component system in which the blowing agent liquid is mixed with one of the other components. There is no particular restriction on the number of components.

The reinforcing resin may be mixed by adding the reinforcing resin to a phenolic resin liquid or a phenolic resin liquid and a blowing agent liquid, and mixing the reinforcing resin. If a homogeneous liquid is not obtained, forced stirring can be used in a uniformly dispersed state.

When a solid resin is used as a reinforcing resin, it may be pulverized and mixed with a phenol resin liquid, or a phenol resin and a blowing agent liquid, and stirred to form a uniform dispersion. If it is difficult to finely powder a solid resin, it can be used by dissolving it in a solvent if there is a solvent that can dissolve it.
Hereinafter, it is preferable to use a solvent having a temperature of 40° C. or lower, and it is necessary that the solvent is vaporized by the reaction heat during foaming and acts as a part of the foaming agent. The use of a solvent does not vaporize during foaming and may remain as an unreacted solvent in the foam, resulting in a decrease in the strength of the foam, and if the amount is too large, it may hinder the increase in the molecular weight of the phenolic resin. is not desirable.

When foaming is performed using a solid foaming material, ie, a novolak type phenolic resin, a reinforcing resin can be used in the same manner as described above. Furthermore, in this case, since foaming is carried out by heating to 100 to 200°C, a solvent with a boiling point of up to about 100°C can be used.

Examples of reinforcing resins include liquid epoxy resins, liquid polyurethane resins, and solutions of the following solid reinforcing resins, as well as semi-cured epoxy resins, solid polyurethane resins, and various solid thermoplastic resins.

In the case of liquid reinforcing resins, those that are rapidly polymerized by the catalyst liquid in liquid foaming, or those that leave resin after the solvent evaporates due to the heat during liquid foaming, and those that are It is best to use a material that becomes polymeric when heated to ~200°C, or a material that leaves a resin after the solvent evaporates.

As the blowing agent, any foaming agent can be used as long as it generates gas when heated during curing of the compound. For example, alcohols, ketones, halogenated hydrocarbons, and hydrocarbons that volatilize at the temperature during curing, and inorganic salts such as ammonium carbonate and sodium bicarbonate that decompose at that temperature to generate gas, and dinitrosopenta. Examples include nitroso compounds such as methylenetetramine, azo compounds such as azocarbonamide and azobisisobutyronitrile, hydrazides such as benzenesulfonylhydrazide, and azides such as paratertiary butylbenzonyl azide. It is added in an amount of 1 to 50 parts by weight per 100 parts by weight of the formulation.

As the liquid epoxy resin, various commercially available epoxy resins can be used, including, for example, an epoxy resin obtained from "Epiclon 850" manufactured by Dainippon Ink and Chemicals Co., Ltd. and a curing agent such as dicyandiamide.

As the liquid polyurethane resin, it is preferable to use a so-called prepolymer in which 5 to 25% by weight of isocyanate groups remain.

The solid epoxy resin is preferably one in a semi-cured state; for example, "Epicron 850" manufactured by Dainippon Ink and Chemicals Co., Ltd. is mixed with dicyandiamide as a curing agent and dimethylbenzylamine as a curing accelerator, and the mixture is heated at 130°C for 10 minutes. A typical example is a reacted semi-cured resin. Suitable solid polyurethane resins include so-called oligomers with a low degree of polymerization, and in which 5 to 25% by weight of unreacted isocyanate groups remain.

In the case of thermoplastic resins, it is necessary to add the already polymerized compound to the phenol foam and then melt it with the heat generated during foaming. However, in the case of powder foaming, it is heated to 100 to 200°C, so it is better to utilize that heat.

In the above two foaming methods, since a strong acidic catalyst is used to turn the liquid mixture into a foam, there is a problem of metal corrosion even after foaming. Also, since foaming is completed within a few minutes after mixing the necessary ingredients, it is necessary to use it according to the conditions.

When a powdered compound is made into a foam, this problem does not occur, but it requires heating to 100 to 200° C. to foam, so these points can be taken into account and the foam can be used depending on the purpose. The amount of reinforcing resin added to the foam is determined by the degree to which it is necessary to overcome its "brittleness," the required physical property values, or the degree of flame retardancy required, but it can range from 10 to 10%.
It is necessary to mix 70 parts by weight, preferably
The optimum amount is 30 to 50 parts by weight. This usage is
If it is used in an amount less than 10 parts by weight, there is almost no effect, and if it is used in an amount exceeding 70 parts by weight, the flame retardance will be significantly reduced, which is not preferable.

Moreover, the flame retardancy of the foam produced as described above decreases as the blending ratio of the reinforcing resin increases. Therefore, it is desirable to mix 0 to 10 parts by weight of various flame retardants with the aim of improving flame retardant performance. Commercially available flame retardants containing phosphorus atoms or halogen atoms may be mixed as flame retardants, but inorganic salts such as antimony trioxide and boric acid compounds are more effective, and flame retardants containing halogen atoms and inorganic salts are more effective. The flame retardant effect can be further increased by using in combination.

The density of the obtained foam is 0.03-0.7;
If it is smaller than 0.7, the foam becomes very brittle, and if it is larger than 0.7, the weight reduction effect is not sufficient and it is not practical.

Various honeycomb materials can be used to increase the strength of the foam, including aluminum metal, paper, and organic materials such as Nomex, but paper honeycomb is the most economical. Furthermore, a flame-retardant paper honeycomb obtained by impregnating and curing a paper honeycomb with a phenol resin is most suitable.

However, metal honeycombs and various organic honeycombs can also be used depending on the strength, weight reduction, and required degree of use.

Further, the size of the honeycomb structure is preferably large in order to facilitate foaming, and although the size is not particularly limited, it is usually about 2 to 50 mm.
Materials for the surface plates attached to both sides of the honeycomb-containing foam core include metal plates such as aluminum, iron, stainless steel, magnesium, and titanium, and various metal plates such as alloys thereof, gypsum, calcium silicate, ceramic plates, Various inorganic boards such as rock wool boards, glass fiber boards, glass boards, other wood-based alloy boards, plastic boards, FRP boards, etc. can be used, but when considering their flame retardancy, light weight, and economic efficiency, , metal plates, and flame-retardant FRP plates are suitable, and FRP plates with phenolic resin as the matrix resin are particularly suitable.

Furthermore, various inorganic fibers and organic fibers such as glass fiber, carbon fiber, and aramid fiber can be used as reinforcing fibers for the FRP board, but glass fiber is the most advantageous from an economic point of view. Regarding the usage form of reinforcing fibers, there are also ways to use fibers arranged in one direction, and
Although it may be used by cutting it into short pieces of about 60 mm and dispersing it in a matrix resin, it is most preferable to use it in the form of a woven fabric for handling purposes.

It is also possible to use a so-called prepreg in a semi-cured state as the surface plate, and in that case, the surface plate is formed by being pressurized and cured by heating in a press during panel production. The thickness of this plate is approximately 0.1 to 2 mm.

The panel of the present invention is made by the following method.

How to cut out the core from a foam-filled block.

Foaming material (phenol resin foaming material + reinforcing resin + flame retardant) is uniformly dispersed in the bottom of a box that has a surface with mold releasability in advance, and the honeycomb is placed on top of it and foamed. When foaming starts, the honeycomb is sequentially filled with foam from the bottom. Approximately 60 minutes after foaming is complete, a core board of the required thickness is cut from the resulting block.

Place the top plate on top and bottom of the cut out core plate.
Unless the top plate is a semi-hardened prepreg, use an adhesive between the top plate and the core board, or an adhesive made by pre-impregnating paper, cheesecloth, or glass cloth with a phenol resin or epoxy resin to a semi-hardened state. It is made by narrowing the sheet and hardening it under pressure at 100 to 200℃.

Integral molding method Place the resin compound to be foamed on top of the surface plate, place the honeycomb and then the top plate on top, and heat and pressurize the honeycomb in a press. In this case, the upper and lower surface plates are bonded simultaneously during foam curing.

If even greater adhesive strength is required, insert the adhesive sheet between the surface material and the honeycomb,
It is also possible to increase adhesive strength.

Examples will be described below, where "parts" and "%" are based on weight.

Example 1 Glass cloth K-285 with a density of 200 g/m ²
(manufactured by Asahi Fiber Glass Co., Ltd.) with ply oven
A B-staged prepreg impregnated with 5010 (Dainippon Ink Chemical Co., Ltd., a phenolic resin product) in an amount of 220 g/m ² was prepared. This prepreg 2
The sheets were put together and a surface material with a thickness of 0.3 m/m was made using a hot press.

Cut this surface material to a size of 10 cm x 10 cm, place it on the bottom of the hot press, place the above prepreg on top as an adhesive sheet, and place the ply oven TD-
A mixture of 9 g of 2030H (Dainippon Ink Chemical Co., Ltd., phenolic resin product), 5 g of Epiclon 850 (Dainippon Ink Chemical Co., Ltd., epoxy resin product) as a reinforcing resin, 0.5 g of dicyandiamide, and 1 g of antimony trioxide as a flame retardant was used. Evenly dispersed. 10mm thickness with 8mm cell size on it
Place 5g of paper honeycomb, then prepreg and the above surface plate, and heat at 150℃ and pressure 1Kg/cm ²
Pressure molded.

The resulting panel had an overall density of 0.2 g/cm ³ , a bending strength of 39 Kg/cm ² and a strain of 0.99 m/m under maximum load.

This value is a bending strength of 23Kg/cm ² and strain of 0.83m/m for a panel without foam inside, and a bending strength of 33Kg/cm ² and 0.80 for a panel filled with only phenol foam inside. It was confirmed that it exhibited superior strength and toughness compared to m/m.

Claims (1)

[Claims] 1 In a panel using honeycomb, phenolic resin 90~
Filled with foam with a density of 0.03 to 0.7 consisting of 30 parts by weight and 10 to 70 parts by weight of epoxy resin or polyurethane resin, metal plates on both sides of the honeycomb, flame retardant
A flame-retardant lightweight panel made of FRP board or inorganic board.