JP2000211953A - Admixture for electromagnetic wave-absorbing cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject admixture consisting of crushed chips of a foam essentially comprising an electromagnetic wave-absorbing material, an inorganic filler and an organic binder, and intended for affording lightweight electromagnetic wave-absorbing cement prevented from cracking when hardened. SOLUTION: This admixture intended for affording electromagnetic wave- absorbing cement consists of crushed chips of a foam essentially comprising pref. 2-30 wt.% of an electromagnetic wave-absorbing material, pref. 70-90 wt.% of an inorganic filler, and pref. 7-20 wt.%; of an organic binder; wherein the electromagnetic wave-absorbing material is e.g. an electroconductive material, magnetic material, dielectric material, being pref. carbon black; the inorganic filler which is included for imparting this admixture with nonflammability is e.g. calcium carbonate, talc, zinc oxide, aluminum hydroxide, magnesium hydroxide; and the organic binder is a thermoplastic resin because the foam is produced by expansion under heating, being pref. polyvinyl chloride, polyvinylidene chloride or the like, in particular.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an admixture for electromagnetic wave absorbing cement and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the development of electronic equipment in the highly information-oriented society has been remarkable.
The spread to factories and homes is expanding rapidly. For this reason,
There is an urgent need for measures to prevent malfunctions of devices caused by noise generated from various electronic devices. As a countermeasure for preventing such malfunction, a method of shielding or absorbing electromagnetic waves using a material having electromagnetic wave shielding performance or electromagnetic wave absorbing performance has been studied. For example, as the outer wall, inner wall, flooring of intelligent building,
Alternatively, a method of shielding or absorbing electromagnetic waves using such a material as an adhesive or a jointing agent for tiling or the like has been studied.

[0003] As a cement composition having such electromagnetic wave absorption performance and the like, a composition in which fine powdered carbon particles, carbon fibers and the like are mixed in a cement composition has been proposed (Japanese Patent Application Laid-Open No. 4-74747). ). Similarly, a cement composition in which iron powder and ferrite powder are mixed has been proposed.

[0004]

However, in a cement composition in which fine powdered carbon particles, carbon fibers, etc., iron powder, ferrite powder, etc. are mixed, when hardening,
There is a problem that cracks are caused by curing shrinkage. Further, in a cement composition in which fine powder carbon particles and carbon fibers are mixed, there is a problem that the fine powder carbon particles and carbon fibers are unevenly distributed in the composition, and stable electromagnetic wave absorption performance cannot be obtained. . Further, in a cement composition in which iron powder or ferrite powder is mixed,
Since the ferrite-based material has a high specific gravity, there is a problem that the weight of the cement composition cannot be reduced.

An object of the present invention is to solve such a conventional problem, to prevent the occurrence of cracks at the time of curing, to reduce the weight, and to exhibit stable electromagnetic wave absorption performance. It is an object of the present invention to provide an admixture for electromagnetic wave absorbing cement that can be used.

[0006]

The admixture for electromagnetic wave absorbing cement of the present invention comprises an electromagnetic wave absorbing material, an inorganic filler,
It is characterized by being composed of crushed pieces of foam using an organic binder as a main constituent material. The admixture for electromagnetic wave absorbing cement of the present invention is composed of crushed pieces of foam,
It has closed cells inside. Therefore, when mixed with the cement composition, there is no impregnation or intrusion of the matrix into the inside of the strip, and the effect of stress relaxation due to the flexibility of the strip can be ideally exhibited. In addition, since it is a crushed flake of a foam, it has irregularities on its surface, and can strongly exert an anchoring effect on a matrix. Due to such stress relaxation and anchor effect, the admixture of the present invention can effectively prevent the occurrence of cracks due to the hardening shrinkage of the cement matrix.

Further, since the admixture of the present invention is composed of crushed fragments of a foam containing an electromagnetic wave absorbing material, when mixed in a cement composition, the admixture is formed along the domain structure of the crushed particles. Can be formed continuously. For this reason, good electromagnetic wave absorption can be provided to the cement composition, and excellent electromagnetic wave absorption performance can be provided to the cement composition.

Further, since the admixture of the present invention is a flake having closed cells as described above, it does not impregnate or invade the matrix when mixed with the cement composition, thus reducing the weight of the cement composition. Can be effectively achieved.

The admixture for electromagnetic wave absorbing cement of the present invention comprises:
This is one of the methods capable of producing the admixture for electromagnetic wave absorbing cement of the present invention, wherein a paste-like compound containing an electromagnetic wave absorbing material, an inorganic filler, an organic binder, a foaming agent, and a plasticizer of an organic binder is made of gold. After filling in the mold, applying press pressure, heating in the mold to foam the foaming agent, cooling the mold, taking out the molded body from the mold,
The molded article is heated again in the open state to expand and expand, and thereafter, the plasticizer is removed to obtain a cured foam, and the foam is pulverized into small pieces.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The electromagnetic wave absorbing material used in the present invention is not particularly limited as long as it can impart an electromagnetic wave absorbing property to an admixture containing the same. For example, a conductive material, a magnetic material, and a dielectric material can be used. Body material and the like.

As the conductive material, carbon black,
Examples of commonly used conductivity-imparting materials such as Ketjen black, acetylene black, graphite compounds, ZnO-based, SnO ₂ / Sb-based, and In ₂ O ₃ / Sn-based metal oxides are given.

Examples of the magnetic material include materials having magnetic loss characteristics typified by metal oxide magnetic materials such as Mn-Zn ferrite, Ni-Zn ferrite, and Mn-Mg-Zn ferrite. .

Examples of the dielectric material include barium titanate, strontium titanate, barium / strontium titanate, and calcium titanate represented by titanate compounds.

The above-mentioned electromagnetic wave absorbing material can be used alone or in combination as an imparting material for exhibiting a desired electromagnetic wave absorbing property. Further, the electromagnetic wave absorbing material, in the molding of the foam in the present invention, as long as the shape does not destroy the cell structure, particles, flakes, fibers and various shapes can be used, There is no particular limitation.

The inorganic filler used in the present invention comprises:
It is included to give the admixture of the present invention nonflammability or quasi-nonflammability, and can be appropriately selected in consideration of the degree of nonflammability given to the admixture of the present invention, workability in a manufacturing process, and the like. Things. Representative examples of such inorganic fillers include calcium carbonate, talc, zinc oxide,
Examples thereof include aluminum hydroxide and magnesium hydroxide. In particular, when high noncombustibility is required, an inorganic substance containing metal hydroxide or water of crystallization, such as aluminum hydroxide or magnesium hydroxide, which absorbs heat by a dehydration reaction can be used. When a polyvinyl chloride resin or the like is used as an organic binder described later, it is preferable that zinc oxide serving as a gelling agent is contained as an inorganic filler in the production process.

The organic binder used in the present invention comprises:
The material is not particularly limited as long as it can bind the electromagnetic wave absorbing material and the inorganic filler. However, a thermoplastic resin is preferably used because a foam is generally formed by heating and foaming. Among thermoplastic resins, chlorine-based resins capable of imparting nonflammability or quasi-nonflammability are preferably used, and specific examples thereof include polyvinyl chloride,
Examples include polyvinylidene chloride, ethylene-vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer, and the like.

The admixture of the present invention is composed of crushed fragments of a foam mainly composed of the above-mentioned electromagnetic wave absorbing material, inorganic filler and organic binder. The content of the electromagnetic wave absorbing material in the foam is as follows. It is appropriately selected in consideration of the required degree of electromagnetic wave absorption and the type of electromagnetic wave absorbing material to be used.
Degree is preferable, and more preferably about 5 to 20% by weight. In particular, when the electromagnetic wave absorbing material is carbon black, the amount is preferably about 2 to 20% by weight, more preferably about 5 to 15% by weight. If the content of the electromagnetic wave absorbing material is small, it may not be possible to obtain sufficient electromagnetic wave absorbing performance, and if the content of the electromagnetic wave absorbing material is large,
In the manufacturing process, a foam having a uniform cell structure may be difficult to obtain due to the thickening action of the electromagnetic wave absorbing material.

The content of the inorganic filler in the foam is appropriately selected in consideration of the degree of incombustibility imparted to the admixture, workability in the production process, and the like.
It is preferably about 0% by weight, more preferably about 80 to 90% by weight.

The content of the organic binder in the foam is appropriately selected in consideration of the degree of nonflammability imparted to the admixture and the type of the organic binder to be used, but is generally about 7 to 20% by weight. Preferably, more preferably 1
It is about 0 to 15% by weight. If the content of the organic binder is small, it may be generally difficult to form a foam in the manufacturing process, and if the content of the organic binder is large, the admixture may be imparted with noncombustibility or semi-combustibility. Generally difficult.

The admixture of the present invention may contain, as the inorganic filler, one other than the above specific examples.
For example, it may contain silica, clay, bentonite, mica, wollastonite, glass fiber, potassium titanate fiber and the like. In addition, in order to impart uniformity and stability of foaming in the production process, in addition to the above zinc oxide, zinc carbonate, zinc stearate, tribasic lead sulfate, dibasic lead phosphite, lead stearate And the like. Various conventionally known additives can be added according to the type of the organic binder used.

The admixture of the present invention is composed of crushed pieces of foam. The size of the crushed pieces is not limited as long as it can be used as an admixture. A preferred range is a particle size of 0.02 to 0.5 gr / cc and a sieve residue of 5% or less with a mesh size of 5 mm.
More preferably, the bulk density is 0.05 to 0.1.
gr / cc, particle size of 1% or less of sieve residue having a mesh size of 5 mm. If the bulk density is too low, it becomes a fine powder, and when used as an admixture for cement, it does not have an appropriate viscosity, which may make construction difficult. Also, if the bulk density is too high or the sieve residue with a mesh size of 5 mm increases,
The particle size of the admixture is increased, and the finished appearance such as mortar finish may be impaired.

In the present invention, the cell diameter of the closed cells contained in the crushed flakes as the admixture is not particularly limited, but may be, for example, about 1 to 3 mm as an average diameter.

Since the admixture of the present invention is composed of crushed pieces of a foam as described above, it has closed cells, and when mixed with a cement composition such as mortar, the admixture contains particles inside the crushed pieces. No matrix penetration. For this reason, the flexibility of the foam is sufficiently exhibited, the effect of stress relaxation is sufficiently exhibited, and a high anchoring effect on the matrix is exhibited due to the unevenness of the crushed strip surface. Therefore, it is possible to effectively prevent the occurrence of cracks due to the curing shrinkage of the matrix. Moreover, since it is an admixture having elasticity, it is excellent in workability, such as exhibiting good iron spreadability during coating.

Further, since the admixture contains an electromagnetic wave absorbing material, in a cement composition such as mortar, the electromagnetic wave absorbing material is contained in a wall material forming an admixture (foam) and has a domain structure. To form Therefore, stable electromagnetic wave absorption performance can be exhibited without uneven distribution in the cement composition.

In addition, since the admixture of the present invention is composed of crushed pieces of foam having closed cells, the weight of the cement composition can be reduced and heat insulation can be imparted. Furthermore, since the inorganic filler is contained as a main constituent material, it is possible to impart flame retardancy to the cement composition, and the cement composition has good adaptability to the ground and imparts good bite to the ground to the cement composition. Can be.

The production method of the present invention is a method capable of producing the above-mentioned admixture of the present invention. First, a paste containing an electromagnetic wave absorbing material, an inorganic filler, an organic binder, a foaming agent, and a plasticizer of an organic binder is used. Prepare a compound in the form of Although the order of addition is not particularly limited, for example, an inorganic filler, an organic binder, a foaming agent, and a plasticizer are mixed and kneaded, and a compound obtained by adding an electromagnetic wave absorbing material to a paste-like compound. I do.

Next, the obtained paste-like compound is filled in a mold, press pressure is applied, and the mixture is heated in the mold to foam the foaming agent. Next, the mold is cooled, the molded body is taken out from the mold, and the molded body is heated again in an open state to expand and expand. Next, the plasticizer contained therein is removed by heating or the like to obtain a cured foam. The cured foam thus obtained is crushed into a crusher or the like and crushed into small pieces. By adjusting the degree of crushing at this time, the particle size and the like of the obtained crushed pieces can be adjusted. Due to the crushing, the bubbles in the foam are partially broken into small pieces.Since a part of the broken bubbles becomes the surface of the small pieces, the admixture having a large number of irregularities on the surface is used. can do.

As the electromagnetic wave absorbing material, the inorganic filler, and the organic binder, those described above can be used. As the foaming agent, any of an organic foaming agent and an inorganic foaming agent can be used. Organic foaming agents are used. The foaming agent is appropriately selected in consideration of the foaming temperature, solubility in an organic binder, and the like. For example, azobisisobutyronitrile (AIBN), N, N'-dinitrosopentamethylenetetramine (DPT), P-toluenesulfonyl hydrazide (TSH), P, P-oxybis (benzenesulfonyl hydrazide) (OBSH), azodicarbamide (ADCA) and the like. The amount of the foaming agent to be added is appropriately selected depending on the type of the foaming agent to be used, the desired expansion ratio, and the like. Generally, the amount is preferably about 10 to 25% by weight, more preferably 15 to 25% by weight in the paste compound. About 20% by weight.

The plasticizer of the organic binder may be any as long as it can impart plasticity to the organic binder and can be easily removed in the production process. When a vinyl chloride resin, vinylidene chloride, ethylene-vinyl chloride copolymer or the like is used, For example, a solvent such as toluene and xylene can be used.

The amount of the plasticizer to be added is not particularly limited as long as it gives plasticity to the extent that the organic binder can be foamed in the production process. 30 to 80% by weight, more preferably 40 to 60% by weight, in the paste compound.

The addition amounts of the electromagnetic wave absorbing material, the inorganic filler and the organic binder are appropriately selected so that the desired contents are obtained in the finally obtained foam. The expansion ratio in the expansion step of the production method of the present invention is appropriately selected in consideration of the particle size, bulk specific gravity and the like of the finally obtained admixture. If a general expansion ratio is given, for example, the expansion ratio in a mold is 2 to 5 times, and more preferably 3 to 5 times.
It is 4 times, and a numerical value of 8 to 11 times, more preferably 9 to 10 times is exemplified as the total expansion ratio after foaming in the open state. However, the present invention is not limited to these.

When a vinyl chloride resin is contained as an organic binder, it is preferable to add zinc oxide as an inorganic filler. Such a zinc oxide is known to act as a gelling agent for the vinyl chloride resin, and when the foaming agent is foamed by heating in a mold,
The vinyl chloride resin can react with zinc oxide to form a gel. Due to such gelling, a foam can be formed with a small amount of an organic binder, and the subsequent heating and expansion in an open state can be stably performed.
Therefore, a foam in which cells are uniformly dispersed can be obtained. In such a case, the content of zinc oxide in the final foam is preferably about 10 to 40% by weight, more preferably 20 to 30% by weight.

[0033]

EXAMPLE 1 In order to produce a foam comprising the main constituent materials shown in Table 1,
A paste-like compound comprising the main constituent materials and auxiliary materials shown in Table 1 was prepared. Specifically, calcium carbonate, talc, zinc oxide, AIBN and DPT as blowing agents, and toluene as a plasticizer were mixed with a vinyl chloride resin at the mixing ratio shown in Table 1, and kneaded with a kneader.
Carbon black as an electromagnetic wave absorbing material was added to the obtained paste compound at the mixing ratio shown in Table 1 and kneaded. The obtained paste-like compound is filled in a mold, press pressure is applied by a press machine, and while maintaining airtightness, the inside of the mold is heated to foam the foaming agent and oxidize with the vinyl chloride resin. The zinc was reacted and gelled.

While maintaining the airtight state of the mold, the mold was cooled to room temperature, the molded body was taken out of the mold, and heated again under normal pressure to expand the foam. The expansion ratio in the mold was 3.4, and the total expansion ratio after normal pressure expansion was 9.
It was 3.

Thereafter, the foam was dried to almost completely remove the plasticizer contained in the foam to obtain a cured foam. Next, the obtained foam was cut into an appropriate size in advance, and then cut by a crusher equipped with a sawtooth-shaped rotary blade, and crushed into fine pieces through a sieve.

The bulk density of the obtained crushed fragments was 0.09 g.
r / cc, and the sieve residue having a mesh size of 5 mm was 0.8%.

[0037]

[Table 1]

Application Example 1 One bag (65) of the admixture made of the crushed fragments obtained in Example 1
cm ³⁾ with respect to the cement one bag (40 kg) ratio (admixtures and cement volume ratio of: 1 were mixed in pairs 1), this was stirred with water from 20 to 22 liters, paste-like material for cement mortar And This was applied to a foundation of a building wetted with water in advance so as to have a thickness of about 10 mm according to a conventional method.

When the cured state was observed, no cracks were observed and a good finished appearance was exhibited. When the resistance value was measured using a resistance meter,
Ω and good conductivity was confirmed.

Application Example 2 Except that the volume ratio of admixture to cement was changed to 5 to 1,
A cement mortar kneaded material was prepared in the same manner as in the above-mentioned application example 1, and applied to the foundation of a building. When the state after curing was observed, small cracks were partially observed,
The resistance value was 250Ω, and it was confirmed that the film had good conductivity.

COMPARATIVE APPLICATION EXAMPLE 1 A foam was prepared in the same manner as in Example 1 except that carbon black was not used and talc was increased to 39 parts by weight instead. To obtain crushed fragments. To 85 parts by weight of the obtained crushed fragments, 15 parts by weight of carbon black were added and mixed.
The cement mortar was prepared in the same manner as in the above-mentioned application example 1 by mixing one bag (40 kg) of cement with respect to cm ³ , and applied to the foundation of a building in the same manner as in the above-mentioned application example 1.

When the cured state was observed, no cracks were observed and a good finished appearance was exhibited. However, when the resistance value was measured using a resistance meter, it was 2700 MΩ. This conductivity was considered to be due to the moisture contained in the mortar, and the conductivity due to carbon black was not obtained.

Comparative Application Example 2 An attempt was made to prepare a cement mortar by adding only carbon black to cement. However, since carbon black has a small specific gravity and has water repellency,
Cement mortar in which carbon black was uniformly mixed could not be obtained.

Example 2 An admixture of the present invention was obtained in the same manner as in Example 1 except that the main constituent materials and auxiliary materials having the composition shown in Table 2 were used.
The bulk density of the obtained admixture was 0.06 gr / cc, and the sieve residue having a mesh size of 5 mm was 0.7%.

[0045]

[Table 2]

Application Example 3 A cement mortar was prepared in the same manner as in Application Example 1 except that the admixture obtained in Example 2 was used, and applied to the foundation of a building.

When the cured state was observed, no cracks were observed and a good finished appearance was exhibited. When the resistance value was measured, it was 2500 Ω, and it was confirmed that the film had good conductivity.

As is apparent from the above results, by mixing the admixture of the present invention into the cement mortar, the cement mortar can be hardened without generating a large crack that would impair the electromagnetic wave absorption performance. Can be. Further, as is apparent from the comparison between the application example 1 and the comparative application example 1, by including carbon black in the admixture, good conductivity can be imparted to the mortar, and good electromagnetic wave absorption can be achieved. Performance can be exhibited.

Further, Embodiments 1 and 2 according to the present invention
When applying the cement mortar containing the admixture of the above, the biting property against the foundation of the building was good, and the iron spreadability was also good.

[0050]

EFFECTS OF THE INVENTION By using the admixture of the present invention, it is possible to prevent the occurrence of cracks, flame retardancy, bite to the substrate, spread iron, reduce weight, and heat insulation, which are important in cement such as mortar. Can be done. Further, since the admixture of the present invention contains an electromagnetic wave absorbing material and has electromagnetic wave absorbing properties, it is possible to impart good electromagnetic wave absorbing properties to cement, such as mortar, into which the admixture is mixed. Therefore, good and stable electromagnetic wave absorption performance can be imparted to a cement molded article such as mortar.

As is clear from the above, the admixture of the present invention is applicable to the outer wall, inner wall, floor material,
Alternatively, it is useful as an admixture for building materials requiring electromagnetic wave absorption performance, such as an adhesive for tiled or an adhesive.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 9/00 H05K 9/00 M

Claims (9)

[Claims] 1. An admixture for electromagnetic wave absorbing cement, comprising a crushed piece of a foam mainly composed of an electromagnetic wave absorbing material, an inorganic filler, and an organic binder. 2. The admixture for an electromagnetic wave absorbing cement according to claim 1, wherein the electromagnetic wave absorbing material is at least one selected from a conductive material, a magnetic material, and a dielectric material. 3. The admixture for electromagnetic wave absorbing cement according to claim 1, wherein the electromagnetic wave absorbing material is carbon black. 4. The inorganic filler according to claim 1, wherein at least one selected from the group consisting of calcium carbonate, talc, zinc oxide, aluminum hydroxide and magnesium hydroxide is contained. Admixture for electromagnetic wave absorbing cement. 5. The organic binder according to claim 1, wherein the organic binder comprises at least one selected from polyvinyl chloride, polyvinylidene chloride, and ethylene-vinyl chloride copolymer. Admixture for electromagnetic wave absorbing cement. 6. A mold compound is filled with a paste-like compound containing an electromagnetic wave absorbing material, an inorganic filler, an organic binder, a foaming agent, and a plasticizer of an organic binder, a press pressure is applied, and heating is performed in the mold. After the foaming agent is foamed, the mold is cooled, the molded body is taken out from the mold, and the molded body is heated again in an open state to expand and expand, and then the plasticizer is removed to obtain a cured foam. A method for producing an admixture for electromagnetic-wave-absorbing cement, which comprises crushing flakes into small pieces. 7. The paste-like compound contains at least a vinyl chloride resin as an organic binder and at least zinc oxide as an inorganic filler, and foams a foaming agent by heating in a mold. The method for producing an admixture for electromagnetic wave absorbing cement according to claim 6, wherein the gelation is carried out by reacting zinc oxide. 8. The method for producing an admixture for electromagnetic wave absorbing cement according to claim 6, wherein the electromagnetic wave absorbing material is at least one selected from a conductive material, a magnetic material, and a dielectric material. 9. The method for producing an admixture for electromagnetic wave absorbing cement according to claim 6, wherein the electromagnetic wave absorbing material is carbon black.