JPS6380598A - Wave absorbing compound - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION 40.Objective of the Invention Industrial Application Field The present invention is directed to prevention of radio wave interference in surrounding structures (buildings, bridges, steel towers, etc.) such as airports, broadcasting and communication bases, measures against false images of ship radars, This invention relates to radio wave absorber compositions used to prevent side lobes in parabolic antennas, countermeasures against television ghosts, and prevent leakage in microwave ovens.

BACKGROUND OF THE INVENTION In order to achieve the above object, a radio wave absorber 3 having a structure in which a radio wave absorber layer 1 made of a radio wave absorber composition is sandwiched with a radio wave reflector 2 such as a metal plate is used as shown in FIG. and
As a radio wave absorber composition, one in which a ferromagnetic material such as ferrite, conductive powder such as carbon powder, or conductive fiber such as fully bent short fiber or carbon m fiber is mixed into a rubber or resin matrix is known. [Yasuo Hashimoto: Journal of the Japan Rubber Association Vol. 57, No. 4, P218 (1984)] Conductive powders such as carcalf, metal powders, carbon ta fibers and metal fibers, t
In a dielectric absorber that contains fibers and absorbs radio waves due to dielectric loss in the absorbing layer, even a slight deviation in the thickness of the absorbing layer from the no-reflection condition will cause large reflections, causing the absorption band to change. becomes very narrow. On the other hand, radio wave absorbers using ferromagnetic materials are inferior in weight, but have a relatively wide band.

'Various rubbers or resins are used as the matrix of radio wave absorber compositions. Japanese Patent Publication No. 54-110496
describes the use of chloroprene as the matrix rubber.

Further, JP-A-58-201398 describes the use of thermoplastic vinyl chloride, polystyrene, polypropylene, thermosetting unsaturated polyester, epoxy, etc. as the matrix resin.

Further, JP-A-58-188192 describes a radio wave absorber composition using 5 to 80% by weight of a phenolic resin as a matrix, and containing 10 to 80% by weight of ferrite and 2 to 70% by weight of steel fibers.

There are few examples of it being mixed with fiber as a reinforcing material, but
8-6200 describes that thermosetting resin materials such as epoxy resins containing ferrite should be reinforced with inorganic fibers or organic fibers such as glass laminated cloth to increase durability and mechanical strength. .

Since the m-point radio wave absorber to be solved by the invention is used outdoors and exposed to the surface, it must be made of flame retardant grade 2 or flame retardant grade 1 material based on JISA No. 1321, but the above-mentioned rubber However, radio wave absorber compositions using resin-based matrices do not satisfy these conditions.

In general, in resin molded products, it is difficult to make flame retardant when the matrix is a general-purpose thermosetting resin such as unsaturated polyester, epoxy, or polyurethane.
It is difficult to obtain certification as flame retardant grade 2 or flame retardant grade 1 based on the No.

Therefore, it is thought that by using a phenol resin as a matrix, an absorbent composition having excellent flame retardancy and smoke resistance can be obtained. However, if the phenolic resin content is too high, it is difficult to obtain a moat with not only first class flame retardancy but also second class flame retardancy.

Ferrite tiles made by sintering non-combustible soft ferrite without using any resin have been put into practical use as a measure to remove TV ghosts, and are installed on the exterior walls of buildings, which can cause problems. However, since this tile is expensive to manufacture, an inexpensive resin-based radio wave absorber composition has been desired.

Means for Solving the Problems The radio wave absorber composition according to the present invention comprises (1) a thermosetting phenolic resin, and (2) a ferromagnetic powder, a conductive powder, a conductive flake, and a conductive fiber. A composition containing one or more types, (3) an inorganic filler and/or an organic flame retardant, and (4) an organic male and/or inorganic fiber, and a thermosetting phenolic resin content of 5 to 30 % by weight, the content of inorganic filler and/or organic flame retardant is 1 to 40% by weight, the content of organic fiber and/or inorganic fiber is 1 to 20% by weight, and JISA1
IF equivalent to class 2 flame retardant or class 1 flame retardant specified in No. 321
It has the following.

The present inventors believe that a thermosetting resin is necessary as a matrix for the radio wave absorber composition in terms of durability and dimensional stability, and as a result of studying various thermosetting resins, they found that flame retardant 2.
It has been found that phenolic resin is extremely effective in achieving flame retardancy of 5 to 30% by weight.

If it is less than 5% by weight, there is no problem with flame retardant class 1, but when liquid phenol resin is used, it is difficult to knead and the strength of the obtained molded product becomes extremely low, so it is not practical.
If it exceeds % by weight, it will be difficult to achieve grade 2 flame retardancy, and its use as a building material will be narrowed, and it is unfavorable in terms of fire prevention and fire resistance, especially when applied to exterior walls.

Due to radio wave absorption characteristics, the ferrite content may be set to 60% by weight or less, but in that case, the phenolic resin content may be 30% by weight.
It is difficult to achieve grade 2 flame retardancy if it exceeds this.

Therefore, if the phenolic resin content is reduced to 30% by weight or less by adding an inorganic filler and/or an organic flame retardant, secondary flame retardance can be achieved at the same time.

Furthermore, by adding an inorganic filler and/or an organic flame retardant to reduce the phenolic resin content to 15% by weight or less, it can be made usable by making it flame retardant.

As the ferromagnetic powder, Ni-Zn type, M n -Zn
The type and content of the 0 ferromagnetic powder, which can use soft ferrite such as GO-Ba series, GO-Ba series, magnetite, etc., the content, and the thickness of the radio wave absorption layer are approximately determined depending on the target frequency to be absorbed. The content is usually adjusted within the range of 60 to 80% by weight, but the optimum content, composition, and thickness are ultimately determined experimentally.

Examples of conductive materials include various metal powders and flakes such as aluminum, copper, zinc, brass, nickel, iron, and stainless steel, or their fibrous materials, carbon blur, graphite, conductive potassium titanate, carbon tala male, etc. can be used.

The type and content of these components are similarly determined experimentally depending on the target frequency.

Therefore, in order to set the phenolic resin content to 5 to 30% by weight and impart properties such as secondary flame retardancy, primary flame retardance, and mechanical strength and durability, it is necessary to use ferromagnetic powder, conductive powder, and conductive powder. It is necessary to adjust with components other than flakes or conductive fibers.

Inorganic fillers include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, zinc chloride, magnesium oxide, and aluminum silicate (clay).
, magnesium silicate (talc), calcium silicate,
Examples include silica sand, diatomaceous earth, hydrated silicic oxide, titanium oxide, antimony oxide, boron oxide, red phosphorus, and mica. Alternatively, glass balloons, fly ash balloons, shirasu balloons, etc. may be used as the balloon-shaped filler.

Various compounds can be used as the organic flame retardant, but halogen compounds, phosphate ester compounds, and halogen-containing phosphate ester compounds are particularly effective.

If the content of these inorganic fillers and/or organic flame retardants exceeds 40% by weight, the phenol content will drop below 5% by weight, which is unfavorable for production and physical properties.

As reinforcing materials, organic MA miscellaneous and/or inorganic fibers such as glass fiber, Kevlar fiber, mineral mkn (asbestos,
Short fibers and long fibers such as Wallath night), zonolite, and potassium titanate, as well as woven, nonwoven, and knitted fabrics thereof, can be used.

By controlling the added amount of the inorganic filler and/or organic flame retardant and this reinforcing material, the phenol content can be adjusted to 5 to 30% by weight, and in terms of strength, it can be used for reprinted exterior wall tiles and first-class flame retardant materials. It is superior to .

Comparative Example I Adding ferrite and antimony trioxide as a flame retardant to HET acid-based unsaturated polyester resin at the following blending ratio,
Knead in a kneader for about 30 minutes, and then add glass cheese 1-/
After adding BMC and kneading for about 10 minutes, it was taken out as a BMC (bulk molding compound) r&form material. Weigh 3 kg of this material, and the blood pressure is 80 kg 10 m2.14
Cured for 7 minutes at 0℃, 10mm thick x 300
A flat plate of mm x 300 mm was molded.

Princess Seven (buttocks tX) biased criticism (maol$) HET drunken non-asthetic polyester finger 15
40 Difficult Smoke J Yohken Hiantimon
23 Ferrite 7
5 50 glass tip
55 The obtained molded plate was subjected to a surface test according to the method specified in JISA1321.

As a result, this material has a 0 calorific value (temperature x time area) and a smoke emission coefficient that are 3rd grade flame retardant, and are about three times the standard values for 2nd grade flame retardant, and are polyester resin-based and have a 2nd grade flame retardant level. could not be achieved.

Comparative Example 2 and Examples 1 to 5 A BMC molding material was obtained in the same manner as in Comparative Example 1 by adding ferrite and the like to a liquid resol type phenol resin according to the compounding ratio shown in Table 1.

Note that aluminum hydroxide (trade name: Hygilite) was used as the inorganic filler, tetrabromobisphenol A was used as the organic flame retardant, and chopped glass fiber was used as the non-ATAA.

A certain amount of this material was weighed and molded into a flat plate with a thickness of 7 to 10 mm. The surface of the obtained flat plate was coated with urethane paint twice, and a surface test and a perforation test were conducted using the method specified in JISA1321 with the painted side facing up. The test results are shown in the lower part of Table 1.

Table 1 The relationship between the phenolic resin content and the smoke generation coefficient CA is shown in Figure 1. In Figure 1, the horizontal axis represents the phenolic resin content (wt%), the vertical axis represents the smoke generation coefficient a CA, and the point El is Example 1, point E2 is example 2, point E3 is example 3
, point E4 is data corresponding to Example 4, and point C2 is data corresponding to Comparative Example 2, respectively, and the range indicated by the symbol ■ (smoke generation coefficient C
60 to 30) corresponds to class 2 flame retardancy, and the range indicated by the symbol (smoke generation coefficient C430 or less) corresponds to class 1 flame retardancy.

Figure 2 shows the relationship between the phenolic resin content and the temperature difference from the standard 10 minutes after the start of the test. In Figure 2, the horizontal axis is the phenolic resin content (wt%), and the vertical axis is the temperature difference ("0").
The range indicated by the symbol (temperature difference of 0°C or less) corresponds to class 1 flame retardancy. The symbols of each point are the same as in FIG.

As is clear from Table 1, FIG. 1, and FIG. 2, when the phenolic resin content is reduced, the exothermic temperature, calorific value, and smoke generation coefficient decrease. In Comparative Example 2 with a phenolic resin content of 35% by weight, the temperature x time area and smoke emission coefficient were within the standard values for flame retardant grade 2, but the afterflame exceeded 30 seconds, so it did not reach the flame retardant grade 2 level. . Therefore, the phenolic resin content is 3
Must be 0% by weight or less.

Examples 1, 2 and 5 had performance at the level of flame retardancy level 2, and all of the perforation test results were within the specifications.

Examples 3 and 4 were systems to which aluminum hydroxide was added, and had flame retardant performance of class 1 level.

The exothermic temperature of Example 4 was lower than that of the pearlite plate, which is a '11' quasi-plate, and the effect of reducing the phenolic resin content to 8% by weight and increasing the aluminum hydroxide as an inorganic filler to 15% by weight was manifested. It is thought that it was done.

Comparing Example 1 and Example 3, although they had almost the same phenolic resin content, Example 3 had a lower smoke generation coefficient of 30 or less, which was at the level 1 flame retardant level. This is also considered to be an effect of aluminum hydroxide.

Therefore, suppressing the content of phenolic resin provides secondary or primary flame retardancy, and aluminum hydroxide, magnesium hydroxide, etc. are preferable as fillers added in addition to ferrite.

Comparing the bending strength (JISK6911), Example 1
was approximately 4 kg f/mm 2 in Example 5, while it was approximately 6 kg f/mm 2 in Example 5, demonstrating the effect of the glass fiber chop as a reinforcing material.

Furthermore, when molding the BMC molding material of Example 1, both sides were reinforced with glass cloth, and the bending strength was approximately 8 kg.
It was found to have an intensity approximately twice that of f/mm2.

Example 6 Hexamine novolac powder was used as the phenol resin, Shirasu balloon was used as the inorganic filler, and these were mixed with ferrite and glass fiber chops in a mixer. This powder mixture was heated at 160°C and under a surface pressure of 30 Kg.
/cm2 for 15 minutes, and the obtained flat plate was coated with urethane and similarly subjected to a combustion test according to JISA1321, and was found to be flame retardant class 1. Table 1 shows the blending composition and combustion test results.

C1 Effects of the Invention Using the composition obtained by the present invention, as shown in FIG. A radio wave absorber 3 can be constructed by combining the radio wave reflectors 2. By appropriately selecting the type and content of ferrite and the thickness of the composition, radio waves in the target frequency band can be efficiently absorbed.

As a radio wave reflector, it can be directly attached to a metal body such as a bridge or a metal plate with bolts, etc., and has excellent workability. Furthermore, even without using a metal plate, it is also possible to integrally mold metal mesh, metal foil, metal wire mixed fiber glass cloth, carbon ia fiber paper, etc. in the mold during BMC molding.

The radio wave absorber obtained by the present invention is JISA1321
It has properties equivalent to class 2 flame retardant or class 1 flame retardant, and can be installed on the exterior wall of a building. It can be installed in the same way as tiles with direct adhesive or mortar, or it can be installed mechanically by opening large bolts, etc. It is easy to install, durable, and can be used as an inexpensive radio wave absorber. Can be provided.

Furthermore, as shown in FIG. 4, by forming or processing the BMC of the composition of the present invention into a pyramid-shaped radio wave absorption layer 1 and combining it with a radio wave reflector 2, it can also be used as a broadband anechoic chamber absorber 3. can.

[Brief explanation of the drawing]

Figure 1 shows the phenolic resin content and JI of the radio wave absorber composition.
Figure 2 is a diagram showing the relationship between the smoke generation coefficient and the smoke generation coefficient according to SA1321, Figure 2 is a diagram showing the relationship between the phenolic resin content and the temperature difference between the reference temperature 10 minutes after the start of the test, and Figure 3 is a diagram showing the relationship between the phenolic resin content and the temperature difference between the reference temperature and the reference temperature 10 minutes after the start of the test. Diagram 4 showing an example of the structure of the radio wave absorber used.
The figure also shows an example of the structure of a broadband anechoic chamber absorber. l: Radio wave absorbing layer made of a radio wave absorber composition 2: Radio wave reflector such as a metal plate 3: Radio wave absorber 4: Radio wave

Claims (4)

[Claims] (1) Thermosetting phenolic resin, (2) one or more of ferromagnetic powder, conductive powder, conductive flakes, and conductive fiber; (3) an inorganic filler and/or an organic flame retardant; (4) A composition containing organic fibers and/or inorganic fibers,
The thermosetting phenolic resin content is 5 to 30% by weight, the inorganic filler and/or organic flame retardant content is 1 to 40% by weight, and the organic fiber and/or inorganic fiber content is 1 to 20% by weight.
A radio wave absorber composition having performance equivalent to class 2 flame retardancy or class 1 flame retardancy specified in ISA1321.