JPH04145178A - Adhesive - Google Patents

Abstract

PURPOSE:To obtain an adhesive having high heat-resistance (>=400 deg.C) and elasticity and giving a coating film free from generation of craze and crack by using expanded graphite powder and an inorganic binder for bonding the powder particles as essential components. CONSTITUTION:The objective adhesive contains, as essential components, (A) expanded graphite powder as main component and (B) an inorganic binder to bond the particles of the powder with each other (e.g. sodium silicate, primary aluminum phosphate, ethyl silicate, organic titanate, colloidal silica and cement).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an adhesive, and more particularly, to an adhesive having high heat resistance.

[Prior Art] Conventionally, adhesives used industrially are mostly made of organic synthetic resins or synthetic rubbers.

When thermal stability is required, a thermosetting resin such as a phenol resin or an epoxy resin is generally used as the main adhesive material, with an adjuvant added thereto. However, for example, inorganic adhesives are used when they have heat resistance at high temperatures of 400° C. or higher.

In other words, when organic adhesives are exposed to high temperatures, they soften or
Since it burns and generates gas, an inorganic substance with a high thermal decomposition temperature must be used.

Examples of inorganic adhesives include those filled with ceramic fillers such as alumina and silica, glue fillers such as mica and aluminum powder, and those filled with inorganic fibers such as short glass fibers. Techniques related to these include Japanese Patent Publication No. 53-119932,
Some of them are published in Japanese Patent Publication No. 15771/1983.

These adhesives usually add additives such as a binder catalyst to an inorganic filler and dissolve it in water or an organic solvent to make it liquid, and then apply it to an adhesive base material. Then, the other solid is applied to the surface of this adhesive layer. are bonded together and solidified by drying at room temperature or heating to volatilize water or organic solvent to form an adhesive film.

[Problems to be Solved by the Invention] By the way, a member made by bonding two solid bodies together with an adhesive may receive shocks or vibrations from the outside, or may be bent. However, inorganic adhesives conventionally used at high temperatures are difficult to deform, have poor elasticity, and are brittle because the inorganic filler is physically and chemically stable. For this reason, the adhesive film often cracks or breaks, resulting in a decrease in adhesive strength.

Therefore, an object of the present invention is to provide an adhesive that is heat resistant and elastic.

[Means for Solving the Problems] The adhesive according to the present invention has as essential components graphite powder that has been subjected to foaming treatment as a main component, and an inorganic binder that binds particles of the graphite powder.

[Function] In the present invention, graphite as a main component is a crystal of carbon atoms, and a physically and chemically stable inorganic substance is used as a binder that binds particles of graphite powder. The adhesive coating can withstand high temperatures. Furthermore, the graphite powder has a sponge structure due to the foaming process, so it has elasticity, and therefore the adhesive film is resistant to impact energy, vibration energy,
Absorbs bending stress and prevents cracks and cracks from occurring.

[Example] The present invention will be explained in detail below.

First, the main component of graphite is elastic graphite (trade name: Elphite) (Kowa Oil Co., Ltd.),
(hereinafter referred to as elastic graphite) (joint research with Mitsui Mining Co., Ltd. and the Kyushu Industrial Technology Research Institute of the Agency of Industrial Science and Technology) was used. This elastic graphite is a carbon material (graphite) with elastic functions created by foaming a water-soluble carbonaceous intermediate and then graphitizing it, and has a sponge structure (the partition walls have a honeycomb structure). .

Here, the graphite will be briefly explained.

Graphite, also known as graphite, is the most stable element of carbon and can be obtained by igniting coke, pitch, anthracite, etc. in an electric furnace without air. Its crystal structure is a good match for diamonds, with regular hexagonal rings forming an infinitely expanding layer, with many such layers existing in parallel. Carbon has four valence electrons, and each carbon atom is bonded to each other in a plane in the 120' direction, but only one electron remains. This electron is in the plane C-
It assists in the bonding of C and is also involved in the weak bonding between layers. For this reason, the one electron left in each C atom acts similar to the free electrons of metals, becoming a conductor of heat and electricity, and also tends to peel off thinly between layers. It is not attacked by chemicals and does not evaporate unless it reaches extremely high temperatures (3500°C).

These properties are used to make crucibles for melting metals, and they are also used in electrodes. Also, due to its soft properties, it is used as a lubricant for machines and, mixed with clay in various proportions, for pencil lead.

Next, Table 1 shows typical characteristics of the elastic graphite obtained by foaming this graphite.

Table 1 As can be seen from Table 1, elastic graphite has properties such as high compression recovery, light weight, high heat resistance, good electrical conductivity, and good chemical resistance.

Next, the formation of the adhesive film will be explained.

First, a high viscosity liquid inorganic adhesive is created by mixing an inorganic binder with raw material powder of elastic graphite.

Next, this inorganic adhesive is applied to the adhesive base material as it is or diluted with water or an organic solvent by various application methods such as dipping, brushing, and spraying. Here, examples of adhesive base materials include metal plates such as iron, aluminum, stainless steel, galvanized steel plates, and brass, heat insulating materials mainly composed of inorganic fibers, and various heat-resistant materials such as glass and concrete. I can do it. Next, an adhesive member is bonded to the surface of the adhesive layer coated with the inorganic adhesive, and allowed to dry naturally at room temperature or forcibly dry by heating for a predetermined period of time. Examples of the adhesive member to be bonded to the adhesive base material include those of the same type as the adhesive base material, and heat-resistant members such as facing materials made of glass cloth, noncombustible paper, marble thin plates, and the like.

Drying is performed to solidify the adhesive film by volatilizing volatile components such as water and organic solvents added to the inorganic binder to impart fluidity. In forming the coating film at this time, since the surface of the elastic graphite powder has poor reactivity, the inorganic binder binds by using the pores of the elastic graphite as anchors. This forms an adhesive film.

In addition, as the inorganic binder, silicate type such as sodium silicate, phosphate type such as monobasic aluminum phosphate, alkyl silicate such as ethyl silicate, metal alcoholade such as organic titanate, colloidal silica, alumina,
Examples include low melting point glass, metals such as enamel, solder, and silver solder, and cements such as Portland cement and alumina cement.

Next, Tables 2 to 7 show examples conducted using various inorganic binders.

In addition, in all Examples, drying was carried out at room temperature (25°C
) for 48 hours.

Table 2 Table 2 Table 2 Table 2 Table 2 In each of the examples, the coating is rich in elasticity and has excellent adhesive strength and strength.

In each of the above examples, the coating was dried at room temperature (2
5° C.) for 48 hours, but the drying time can also be shortened by heating and forcing drying. However, care must be taken as rapid drying at high temperatures may cause the volatile components to evaporate in a short period of time, resulting in defects such as wrinkles in the adhesive film.

As described above, the adhesive of the above embodiment has elastic graphite, which is a foamed graphite powder as a main component, and an inorganic binder that binds particles of the graphite powder as essential components.

Therefore, according to the above embodiments, since both are made of inorganic materials, the adhesive coating can withstand high temperatures of 400° C. or higher. In addition, the graphite powder has a sponge structure due to the foaming process.
It has elasticity and absorbs impact energy, vibration energy, and bending stress.

Therefore, it is possible to prevent the coating from cracking or cracking due to impact, vibration, or bending, and furthermore, it is possible to prevent the adhesive force between the two members from decreasing.

Furthermore, since the adhesive film uses the pores of elastic graphite as anchors to bond, it does not require an expensive firing furnace and can be easily formed, unlike ceramics that are sintered at high temperatures and pressures. can.

By the way, when carrying out the present invention, it is possible to add a trace amount of an organic binder in addition to the inorganic binder, and by adding this, it is also possible to impart characteristics unique to the organic binder. For example, when an organic balloon such as a vinylidene chloride balloon (fine hollow spheres) is added and placed under high temperature, the vinylidene chloride that forms the outer shell of the hollow spheres of the balloon scatters, creating further air bubbles within the adhesive film. can be formed.

Furthermore, since inorganic adhesives do not have reactive groups, thixotropic properties can be controlled. Therefore, when applying the adhesive to an adhesive base material with a brush, it is possible to improve the quality and workability by using a low viscosity at the time of application and a high viscosity at the end of application.

The adhesive of this example can be used, for example, for adhesion between members such as metal plates, insulating materials mainly composed of inorganic fibers, and plasterboard, or for adhesion between members such as glass cloth or noncombustible paper. It can be used for bonding facing materials. These materials constitute the wall materials of buildings and are effective as fireproof materials.

Alternatively, it can be used as a structural material for drying furnaces and boilers. When the structural material is a metal plate, it can particularly follow the thermal expansion and contraction of the metal plate, absorb vibrations, prevent cracks, and extend its life.

In addition, when used as a wall material, the adhesive film absorbs the vibrational energy of sound, so it also has an effect as a sound absorbing material.

By the way, as mentioned above, graphite uses three of the four valence electrons of atoms to bond with each other, creating a regular hexagonal planar network structure, and the remaining one valence electron is mobile.
Adhesive coatings can also be used as electrically conductive coatings because they easily conduct heat and electricity.

Furthermore, since elastic graphite can also absorb electromagnetic waves, it is also possible to form an electromagnetic wave shielding adhesive film.

[Effects of the Invention] As described above, the adhesive of the present invention has as essential components a foamed graphite powder as a main component and an inorganic binder that binds particles of the graphite powder. Both are made of physically and chemically stable inorganic substances, and the adhesive coating can withstand high temperatures of, for example, 400° C. or higher. In addition, the graphite powder has a sponge structure due to the foaming process, so it has elasticity and absorbs impact energy, vibration energy, and bending stress. It is possible to prevent this from occurring and, in turn, prevent the adhesive strength between the two members from decreasing.

Patent applicant: Tokiwa Denki Co., Ltd. Agent: Patent attorney: Higuchi (1 person)

Claims (1)

[Claims] 1. An adhesive comprising, as essential components, a foamed graphite powder as a main component and an inorganic binder that binds particles of the graphite powder.