JP2001279014A - Dielectric expansion-molded product having improved dimensional stability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lightweight composite dielectric foam having dimensional stability as a dielectric material for an antenna, a laser reflector, etc., and having a small change of dielectric constant accompanied with a temperature change. SOLUTION: This dielectric expansion-molded product is obtained by substantially uniformly dispersing a dielectric ceramic into a foam composed of a styrenic base material preferably in an amount of 5-50 wt.% based on the total amount with the base resin, is characterized by having 1.0-2.0 dielectric constant, <=0.005 dielectric loss tangent and 0.3-0.04 g/cm3 bulk specific gravity, including a residual foaming agent therein in an amount of <=3 wt.% and having -0.5 to 0% rate of dimensional change as compared with the previous state when left in an oven at 50 deg.C for 100 days and has dimensional stability. The styrenic base resin preferably contains a polyolefin resin having a low molecular weight in an amount of 0.1-10 pts.wt. based on the total amount thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric foam molded article made of a foamed dielectric material and having improved dimensional stability. In addition, the present invention relates to a foam molded article which can be used as a dielectric, particularly a foam molded article having excellent dimensional stability which can be used as a dielectric material of each layer constituting a spherical dielectric lens utilizing the principle of a Luneberg lens. Goods.

[0002]

2. Description of the Related Art A spherical dielectric lens utilizing the principle of a Luneberg lens has been known for a long time, and has been used in radar radio reflectors, antennas, and the like because of its characteristics. Japanese Patent Publication No. 43-27061 discloses a dielectric structure of this type. In this publication, the ideal shape of the spherical dielectric lens is said to have a relative permittivity of 2.0 at the center of the sphere, and the relative permittivity decreases outward from the sphere. It is taught that the outer skin layer is a sphere whose relative dielectric constant continuously changes to 1.0. However, actually producing such a sphere having a relative dielectric constant that changes continuously involves manufacturing difficulties and a great deal of cost. Therefore, usually, a plurality of spheres (5 to 15 layers) having different relative dielectric constants are usually used. The structure in which the spherical dielectric materials are stacked in layers from the concentric center portion to the outside is defined as a spherical dielectric lens. That is, the relative permittivity of the outermost layer is made close to 1.0, and then the relative permittivity is increased toward the inner layer, and the core layer at the center has a structure having a relative permittivity of close to 2.0. Manufactured as a sphere. Although the value of the relative dielectric constant is important as a dielectric material for a spherical dielectric lens, the value of the dielectric loss tangent (tan δ) is an important characteristic that further affects its performance. This is an index indicating the dielectric loss.
Even if it is within the range of 2.0 to 2.0, if the dielectric loss tangent is large, the relative dielectric constant loss (loss) of the material will be large, and the performance as a radar reflector or antenna will be sufficiently exhibited. become unable. Therefore, the value of the dielectric loss tangent (tan δ) needs to be 0.005 or less. In addition, when the volume of the multilayer molded body made of these dielectric materials becomes large, it takes a great deal of labor and cost to transport and further install them, so that the dielectric materials are lightweight, that is, specific gravity. Is desirably small.

As a dielectric material, it is known that polystyrene is a dielectric material having a low dielectric loss tangent. Polystyrene has a relative dielectric constant of about 2.5 measured at 60 Hz in an unfoamed state, and a low dielectric tangent of about 0.0002. Therefore, by appropriately foaming this polystyrene, it is possible to prepare a foam having a dielectric constant of about 2.5 or less according to the difference in bulk specific gravity. However, the relative dielectric constant is 1.
In order to achieve a value of 0 to 2.0, in particular, to obtain a portion having a relative dielectric constant of 1.5 or more, the bulk specific gravity must be about 0.4 or more. For this reason, it is necessary to mix materials having other dielectric properties in order to reduce the weight while utilizing the dielectric properties of polystyrene.

Therefore, in order to provide an improved dielectric material utilizing the properties of polystyrene as a dielectric material,
Several proposals and attempts have been made in the prior art.
These are, for example, as follows: 1) Japanese Patent Publication No. 56-38003 discloses a composite dielectric material comprising a plastic dielectric and aluminum metal particles having an average particle size of about 0.1 mm to 1.0 mm. Have been. In the example of this publication, foamed polystyrene having a specific gravity of 0.117 g / cm ³ was used as a plastic dielectric material, and a suitable amount of high-purity aluminum particles having a diameter of about 0.5 to 1.0 mm was mixed with the polystyrene. These are formed into a molded body using a polymer as a binder.
However, in this case, it is extremely difficult to uniformly mix foamed polystyrene having a low specific gravity and aluminum particles having a high specific gravity, and when a molded body is formed, a variation in specific gravity and a variation in aluminum concentration occur inside the molded body. . In addition, vinyl acetate polymer is used as a binder, but if the amount is small, the adhesion becomes insufficient and the molded body becomes extremely brittle, and if it is large, the effect of increasing the relative dielectric constant of the molded body decreases. Therefore, it is difficult to adjust the amount of the binder. From this example, the specific gravity for obtaining a relative dielectric constant of 2 was 0.3 g / cm.
^Three or more are required. 2) Japanese Patent Publication No. 60-52528 discloses that a desired relative dielectric constant can be obtained between foamed plastic particles or inorganic hollow particles such as glass balloons and shirasu balloons and metal-coated particles whose surfaces are covered with a thin metal film. Discloses a mixed dielectric material obtained by mixing at an appropriate mixing ratio. In the example of this publication, metal foam particles in which the surface of the foamed plastic particles is covered with a thin film of a metal such as copper or aluminum by a method such as vapor deposition are appropriately mixed with the plastic particles foamed 20 to 30 times, and then thermally foamed. It is a method of molding. In this document, the above 1) Japanese Patent Publication No. 56-3800
The problem of non-uniform mixing caused by mixing derivatives having different specific gravities and the problem of increasing the specific dielectric constant, which is caused by increasing the relative dielectric constant, which is found in Japanese Patent Publication No. 3-3, has been solved, but a new problem has arisen. In other words, thermoforming is to thermally fuse resin particles in a mold to each other with heat from steam or the like, but metal-coated particles whose surface is covered with a thin metal film include:
Of course, it does not have heat-fusibility and cannot be molded. Therefore, if the mixing ratio of the metal coating particles is increased in order to increase the relative dielectric constant, the meltability of the molded article is rapidly reduced, and the molded article becomes weak in physical properties and cannot be used for practical use. Further, when the surface of the foamed plastic particles is deposited with a metal, it requires a great deal of labor and cost, and is not practical. 3) Japanese Patent Publication No. 61-21147 discloses a dielectric material obtained by mixing a metal foil flake, which has an affinity with a foamable resin and is coated on one or both sides of a metal foil with a resin containing a surfactant, in a foamable resin. A body material is disclosed. In the specific description, the metal foil flakes surface-treated under certain conditions are kneaded with expanded polystyrene in an extruder, formed into strands, and then cut into pellets. According to this method, the disadvantages of the dielectric materials described in the above two publications, that the composite material cannot be mixed homogeneously, that the specific gravity increases when the relative dielectric constant is increased, and that metal separation occurs during molding, are eliminated. However, the use of metal foil flakes increases the dielectric loss tangent. Further, as the performance of the foamable dielectric material obtained in this document, the relationship between the relative dielectric constant and the specific gravity of the foam is disclosed in Examples, but the specific gravity of any foam is 0.3 or more. Yes, it can be seen that all are high density. Therefore, the prior art could not provide a practical and sufficient dielectric material.

Further, it is necessary to assume that most of spherical dielectric lenses using the principle of a Luneberg lens used as a radar wave reflector and an antenna are used outdoors for a long period of time. Accordingly, stable performance cannot be maintained unless the change in the relative dielectric constant is small in a temperature range in which these use conditions are taken into consideration in the seasonal temperature change during the use period. For this reason, the dielectrics constituting them are required to have long-term dimensional stability performance. In addition, between 5 and 15 dielectric layers having different relative dielectric constants constituting the spherical dielectric lens must be sufficiently in close contact with each other. This is because, when a gap (air layer) is generated between the layers, an air layer having a relative dielectric constant of 1.0 enters between the layers, and the performance of the Luneberg lens itself is lost. Because. Therefore, dimensional accuracy and dimensional stability of each layer are very important for such a spherical dielectric lens, and in particular, it must be possible to stably maintain a constant size over a long period of time.

[0006] In addition, several proposals and attempts have been made with respect to the dimensional stability of foamed styrene resin products. For example, it is as shown below. 4) Japanese Patent Publication No. 61-11183 discloses that a foamed polystyrene molded article is heated at normal pressure or reduced pressure for several hours or more to equilibrate a foaming agent gas pressure in the molded article with atmospheric pressure, thereby obtaining the molded article. The present invention discloses a method for stabilizing the size of expanded polystyrene, characterized by forcibly reducing the size of the expanded polystyrene to the vicinity of a desired size. According to the contents of this publication, the molded article obtained is molded in air at 45 to 70 ° C. after molding.
It is necessary to leave the mixture at room temperature for 2 to 24 hours at room temperature or 65 ° C. under reduced pressure. However, assuming a case where this method is actually used in a production factory, in order to perform these dryings, a new drying facility must be created and molded articles must be sequentially put into the equipment, which makes the work complicated. is there. Further, as a foaming agent for foamed polystyrene, flammable gases such as butane and pentane are usually used, but since these foamed gases escape during the heating and drying, the drying equipment has a high explosion-proof property. Required. Therefore, introduction of the drying equipment requires huge equipment costs and is not practical. 5) Japanese Patent Application Laid-Open No. 61-207448 discloses that an aromatic vinyl monomer and a polyfunctional monomer copolymerizable therewith have a gel content of 30% by weight or more. A foam molded article of a copolymer (expansion ratio 3 to 15 times) is disclosed. In this publication, as the evaluation of the dimensional stability performance, the dimensional change rate on the 7th day after molding and the change rate of the molded article on the 90th day after molding are obtained, and the dimensional change rate over time is represented by the difference between the two. . Therefore, the observation period of the temporal change is 90
-7 = 83 days, and only dimensional change data at room temperature (19 to 20 ° C.) during this period is taken. However, when a foamed molded product is usually used as a spherical dielectric lens, the use period is as long as one year or more, and it is particularly important to evaluate the long-term dimensional stability of the foamed molded product over time. However, this publication does not provide evaluation data over a longer period than the above period. 6) Japanese Patent Publication No. 4-38222 discloses that foamed particles preliminarily foamed by heating a polyethylene-styrene copolymer resin containing a volatile foaming agent are left at room temperature for 2 to 14 days, and then filled in a mold. And heat molding to obtain a foam molded product.
A production method for aging the foam molded article at a temperature of 0 to 60 ° C for 4 hours or more, preferably 8 hours or more is disclosed. According to this publication, since a polyethylene-styrene copolymer resin is used, the foaming agent and the solvent remaining in the foamed molded product are easily dissipated, and the dimensions of the foamed molded product are stabilized. However, in this publication, pre-expanded particles are
A method of leaving the product for 14 days (one week in the example) is used, and the molded product needs to be aged in a drying room. Usually, the maturation period of the pre-expanded particles is about 8 hours to 1 day. However, leaving for one week (Example) after the pre-expansion is performed by using a special hopper (pre-expanded particles are put in the hopper). In this case, the pre-expanded particles are stored as they are in a breathable bag) for as long as one week, during which time the hopper cannot be used, which is extremely inefficient in production. In addition, in order to dry the molded article, the above-mentioned JP-B-61-11-11
As in the case of Japanese Patent No. 183, there is a problem that special equipment is required. Further, in the evaluation of dimensional stability described in Japanese Patent Publication No. 4-38222, data of 6 months storage at room temperature is shown, and the dimensional change rate during this period is 0.5 to 1.2. % (Example), which is relatively large, and is not suitable for a field requiring fine dimensional stability such as a spherical dielectric lens. Therefore, a dielectric material having desired properties as a dielectric material and excellent dimensional stability performance has not yet been obtained.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to achieve a high dielectric constant, a low dielectric loss tangent, a light weight, and a high dielectric constant which cannot be obtained by the above-described conventional dielectric materials. An object of the present invention is to obtain a foam molded article having dimensional stability over a long period of time. The present inventor has noted that polystyrene has an excellent relative dielectric constant and an extremely low dielectric loss tangent as a dielectric material, and its foaming performance,
Subsequently, studies were made to obtain an excellent dielectric material by utilizing the characteristics. That is, an object of the present invention is to provide a foam having a styrene-based resin as a base material, and 1) to have extremely high dimensional stability over a long period of time; 2) to have a small change in relative permittivity with temperature change; 3) Utilizing the principle of a Luneberg lens, which satisfies the condition that the dielectric loss tangent is 0.005 or less when the relative dielectric constant is in the range of 1.0 to 2.0; An object of the present invention is to obtain a dielectric material suitable for an application such as a spherical dielectric lens.

The inventor of the present invention has proposed that a dielectric material, which is a subject, is lightweight and has a relative dielectric constant of 1.0 to 2.0.
Within the range, a styrene-based resin foam having a dielectric loss tangent of 0.005 or less was studied. Here, when simply increasing the relative dielectric constant of polystyrene as a dielectric material, it is possible to use a metal powder, a metal foil (aluminum flake), or the like as a polymer material as in the above cited document. However, in this case, the value of the dielectric loss tangent is increased, which is not preferable. In addition, when a metal is used, the amount of change in the relative dielectric constant with respect to a change in temperature is large, so that it is not suitable. Therefore, the present inventor has selected a dielectric ceramic which has a unique dielectric property and has an effect of increasing the relative dielectric constant by mixing with a styrene-based foam. As a result, it was found that, when used in the dielectric foam molded article of the present invention, the conditions of the high relative dielectric constant, low dielectric loss tangent, and weight reduction described above can be satisfied by mixing dielectric ceramics.

On the other hand, in terms of dimensional stability, a molded product obtained by foaming a polystyrene resin usually contracts by -0.6 to -0.8% for one year when left at room temperature. In this regard, in the molded article of styrene resin foam,
It is vaguely known that the dimensional change rate is small when the amount of the foaming agent and the foaming aid contained in the molded article is small. It was unclear how small this would be. Also,
To evaluate the degree of dimensional change over time, a long-term test is required. Conventionally, tests have been performed only for a period of at least six months to one year. Absent. Therefore, when the foam is actually used for a long period (one year or more), it cannot be guaranteed that the dimensions do not substantially change. Therefore, the present inventor
After extensive research, 1) Correlation between the dimensional change rate of the foamed molded article made of styrene resin particles and mixed with the above dielectric ceramics, and the amounts of the foaming agent and the foaming aid remaining in the molded article. And found that it is possible to obtain a dielectric foam molded article having improved dimensional stability, and 2) also studied a method for simply measuring the dimensional change over time over a long period of time. By limiting the range of dimensional change with time of the foamed molded article based on the above, it has been found that a dielectric foamed molded article which maintains a high dimensional stability for a long time, which has not been achieved in the past, can be obtained. That is, the present inventor has found that the dimensional change rate of the dielectric foam molded article obtained from the expandable styrene resin particles and the amount of the foaming agent and the foaming auxiliary remaining in the molded article are close. The relationship is as follows. In a foamed styrene resin product having a bulk specific gravity of 0.3 to 0.04 g / cm ³ , the amount of the foaming agent (or foaming agent and foaming aid) remaining in the foamed molded product exceeds 3% by weight. In this case, the dimensional change (degree of dimensional shrinkage) shows a high value of -0.6 to -0.8% in one year even at room temperature, as compared to before the molded article is left. When the amount of the blowing agent is 3% by weight or less, -0.3% to 0%
% Of the dimensional change. In addition, the present inventor has found that a styrene-based resin foam molded article has an accelerated change with time, and the dimensional change rate of the dielectric foam molded article when the dielectric foam molded article is left in an oven at 50 ° C. for about one month. The value was found to be substantially equal to or equivalent to the value of the dimensional change rate of the foamed molded article when the same dielectric foamed molded article was allowed to stand at room temperature for one year (see the test example described later). The degree of time-dependent dimensional change of the dielectric foam molded article when left for 3 years is replaced with the measured value of the dimensional change rate when the dielectric foam molded article is left in an oven at 50 ° C. for 100 days. The conclusion that it can be evaluated was obtained. Therefore, in order to obtain the desired foam molded article in the present invention, the dimensional change rate when left in an oven at 50 ° C. for 100 days due to a reduction in the content of the foaming agent or the like is −0. Any material having dimensional stability of 5% to 0% may be used. According to this accelerated test, shrinkage of -1.2% or more was observed when the amount of the foaming agent in the molded product exceeded 3% by weight, whereas -0.4% or less when the amount was 3% by weight or less. Only the following slight shrinkage was observed. Based on the above study, the present inventor adjusted the amount of the blowing agent to a specific range, and obtained a dimensionally stable dielectric foamed molded product comprising a base resin based on a styrene-based resin. A new dielectric foam molded product suitable for use as a spherical dielectric lens by selecting ceramics as a high dielectric material to be mixed with the resin material and mixing it with the above resin at a specific ratio to produce a composite material Invented.

[0010]

Accordingly, the present invention provides a dielectric foam molded article in which dielectric ceramics are substantially uniformly dispersed in a foam made of a styrenic base resin,
The foamed article has a relative dielectric constant of 1.0 to 2.0, a dielectric loss tangent of 0.005 or less, and a bulk specific gravity of 0.3 to 0.04 g / cm ^3. And the amount of the foaming agent (or foaming agent and foaming aid) remaining in the foamed molded product is 3% by weight or less, and the foamed molded product is placed in an oven at 50 ° C. for 100%. The present invention relates to a dielectric foam molded article having dimensional stability, wherein a dimensional change rate of the foam molded article when left for a day is -0.5% to 0% as compared with that before leaving. The preferred blowing agent here is pentane or butane. Furthermore, the present invention is preferably the above-mentioned dielectric foam molded article, characterized by containing a low-molecular-weight polyolefin resin in an amount of 0.1 to 10 parts by weight based on the total amount of the styrene-based base resin. The low molecular weight polyolefin resin has a weight average molecular weight of 50.
It is preferably a low molecular weight polyethylene having a molecular weight of 0 to 10,000 and a melting point of 100 to 130 ° C. The dielectric ceramic dispersed in the foam is preferably mainly composed of a powder or whisker, and the content of the dielectric ceramic is the total of the styrene-based base resin and the dielectric ceramic. 5 to 50% by weight based on the amount. In this specification, not only the main resin component (base resin) such as a styrene-based resin and a styrene-based resin blend or copolymer, but also other various additives other than the foaming agent, a modifier, Those containing an auxiliary as necessary as components are described as "styrene-based base resin".

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Dielectric ceramics used in the dielectric foam molded article of the present invention include barium titanate, calcium titanate, magnesium titanate, strontium titanate, lead titanate and the like. Alternatively, they can be used by appropriately mixing. These ceramics are added in the form of powder or whiskers. Usually, it is preferable to use ceramic powder having an average particle size of 10 μm or less in consideration of dispersibility and ease of handling during granulation. In whiskers, the fiber diameter is 0.1-10μ.
m and a length in the range of about 1 to 100 μm can be used. This dielectric ceramic is present in an amount of 5 to 50% by weight, preferably 20 to 4% by weight, based on the total amount of the styrene base resin and the dielectric ceramic in the dielectric foam molded article.
It is desirably 0% by weight. If the ceramic is added in an amount exceeding 50% by weight based on the total amount of the styrene-based base resin and the dielectric ceramic in the dielectric foam molded article, foaming becomes difficult, and the obtained foam has a desired density. In addition to this, the physical properties of the foam become brittle, so that it cannot be used. Conversely, if the addition to the ceramics is 5% by weight or less, there is not much effect of improving the relative dielectric constant of the foam, and therefore the bulk specific gravity cannot be reduced. Therefore, in a preferred embodiment of the present invention, the dielectric ceramic dispersed in the foam is preferably mainly composed of a powder or a whisker, and the content of the dielectric ceramic is the styrene-based base resin. And 5 to 50% by weight based on the total amount of the dielectric ceramics.

As the (volatile) blowing agent used in the present invention, for example, an aliphatic hydrocarbon such as propane, butane, n-pentane, isopentane, hexane, or a halogenated hydrocarbon such as methyl chloride or Freon is used. Is done. These volatile foaming agents may be used alone or in combination of two or more. However, aliphatic hydrocarbons that do not easily cause environmental destruction are preferably used. In addition, butane or pentane is more preferably used, and pentane is most preferably used, from the viewpoint that the amount of the foaming agent remaining in the case of a foamed molded product is small. When aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, and isomers thereof are used alone or in combination, an aromatic hydrocarbon such as toluene, xylene or ethylbenzene, or butyl acetate or the like is used. Known and commonly used solvents such as esters may be used in combination as a foaming auxiliary in a small amount. The total amount of a foaming agent and a foaming auxiliary added to a styrene-based base resin which is a raw material of a dielectric foam molded article having dimensional stability of the present invention (hereinafter, referred to as
The amount of the foaming agent may be abbreviated) to reduce the amount of the foaming agent remaining in the dielectric foam molded article to 3% by weight or less.
It is desirable that the amount is smaller than the amount added to the base resin of a conventional general foam molded article. Therefore, the amount is usually 1 to the weight of the styrene base resin particles.
To 6 parts by weight. From the viewpoint that a smaller amount is suitable, the amount of the blowing agent is preferably about 1 to 4.5 parts by weight, and more preferably about 1 to 3.5 parts by weight. When the aging time after the pre-expansion of the expandable styrenic resin particles is set in a normal range (8 hours to 1 day), and when the general expandable styrenic resin particles are used, the expanded molded article In order to suppress the amount of the foaming agent or the total amount of the foaming agent and the foaming auxiliary therein to 3% by weight or less, the amount of the foaming agent added is generally 3.5% by weight based on the weight of the expandable styrene resin particles. The following settings are usually required: However, when using an amount of the foaming agent of 3.5% by weight or less, when obtaining a foamed molded product having a desired bulk specific gravity of 0.3 to 0.04 g / cm ³ at a relatively high foaming ratio, The foaming time becomes very long and is not practical.
Therefore, in an attempt, a low-molecular-weight polyolefin resin was mixed into a styrene-based resin as a base material. As a result, the low-molecular-weight polyolefin resin has an effect of enabling to obtain a foam molded article having a desired expansion ratio even with a low foaming agent amount, and at the same time, an effect of efficiently dissipating the foaming agent from the foamed resin particles. Has been found to significantly contribute to the improvement of dimensional stability. When 0.1 to 10 parts by weight of the low molecular weight polyolefin resin is added based on the total amount of the styrene base resin, a desired expansion ratio can be obtained even with a foaming styrene resin having a low foaming agent amount of 3.5 wt% or less. In addition, the blowing agent quickly escapes from the pre-expanded particles after the pre-expansion, so that the amount of the blowing agent is 3.0% by weight or less within a general aging time. A certain foam molded article is obtained. As this low molecular weight polyolefin resin,
Low molecular weight polypropylene, polyethylene or a mixture thereof can be used, but low molecular weight polyethylene having a weight average molecular weight of 500 to 10,000 and a melting point of 100 to 130 ° C. is particularly preferable. The addition amount of the low molecular weight polyolefin resin is 0.1 to 10 parts by weight, for example, 0.5 to 10 parts by weight, preferably 0.3 part by weight based on the total amount of the styrene-based base resin. To 3 parts by weight. If the amount is less than 0.1 part by weight, the effect of mixing the low-molecular-weight polyolefin resin cannot be obtained as expected, and if it exceeds 10 parts by weight, the fusion of the molded article is extremely reduced. This is not preferred. Therefore, a preferred embodiment of the present invention is a low molecular weight polyolefin resin, preferably having a weight average molecular weight of 500 to 10
000, and a low-molecular-weight polyethylene resin having a melting point of 100 to 130 ° C., comprising 0.1 to 10 parts by weight based on the total amount of the styrene base resin. is there.

The styrenic resin serving as the base resin in the dimensionally stable dielectric foam molded article of the present invention is not limited to a homopolymer of a styrenic monomer, but may be a copolymer with another monomer. (Made by using a styrene monomer in a proportion of 50% by weight or more). Styrene monomers include
In addition to styrene alone, substituted styrenes such as α-methylstyrene, ethylstyrene, p-chlorostyrene and the like are included. The other monomer of the copolymer includes (meth) acrylates such as methyl methacrylate, methyl acrylate, butyl methacrylate, and butyl acrylate, and vinyl monomers such as acrylonitrile, vinyl toluene, and vinyl carbazole. No. These may be used alone or in combination of two or more. Therefore, as the styrene resin used in the present invention,
Other than polystyrene, poly α-methylstyrene, poly p-
In addition to polysubstituted styrene such as chlorostyrene, a copolymer of styrene and substituted styrene (for example, α-methylstyrene), a copolymer of styrene and a vinyl monomer (for example, acrylonitrile), and the like can be given. . More preferred styrene resins include polystyrene, polystyrene-butadiene copolymer, polystyrene-maleic anhydride copolymer, polystyrene-acrylonitrile copolymer, styrene graft copolymer, and the like.
Further, it may be selected from a copolymer with a styrene-maleimide derivative, a styrene-acrylate copolymer, a styrene-methacrylate copolymer, and a styrene copolymer such as a styrene-acryl or methacrylic acid copolymer. It is possible. More preferred are α-methylstyrene-styrene copolymer, α-methylstyrene-acrylonitrile copolymer and styrene-α-methylstyrene-acrylonitrile terpolymer. Where α
-Methylstyrene or the total amount of styrene and α-methylstyrene must be at least 50 parts by weight based on 100 parts by weight of the total resin. Also, as the styrene resin,
Usually, a weight average molecular weight of 150,000 to 500,000
0, more preferably 200,0 weight average molecular weight
High molecular weight styrenic resins having from 00 to 300,000 are used, but it is also possible to partially blend lower molecular weight styrenic resins. In particular, when a low-molecular-weight styrene resin is added to the styrene-based base resin in addition to the addition of the low-molecular-weight polyolefin, an action of synergistically improving the expansion ratio with the addition of the low-molecular-weight polyolefin, a blowing agent from the expanded particles. It has been found that it has a dissipating effect. Further, the addition of the low molecular weight styrene resin may be replaced by the addition of the low molecular weight polyolefin. By using a low-molecular-weight styrene resin, a foamed molded article having a desired expansion ratio can be obtained even with expanded styrene-based resin particles having a low foaming agent amount of 3.5% by weight or less. Since the blowing agent quickly escapes from the particles, the amount of the blowing agent becomes 3.0% by weight or less within a general aging time. The low-molecular-weight styrene resin has a weight average molecular weight of 500 to 100,000, preferably 5 to 100,000.
000 to 100,000 are used. The amount of the low molecular weight styrene resin is 1 to 30 parts by weight, preferably 3 to 30 parts by weight, based on the total amount of the styrene resin as the base resin.
To 10 parts by weight. If the amount is less than 1 part by weight, the effect of the above-mentioned addition is hardly observed. If the amount exceeds 30 parts by weight, the strength of the foamed molded article is extremely lowered, which is not preferable. The styrene-based resin includes, in addition to the above-mentioned polyolefin resin, a resin in which another resin such as a polyphenylene ether-based resin is blended in an amount of 50% by weight or less.

The styrene resin is not limited to a styrene resin newly synthesized by suspension polymerization.
A styrene-based resin regenerated by recycling (recycling) a styrene-based resin foam or the like is used. It is preferable to use the regenerated styrene resin as a raw material for the expandable styrene resin particles from the viewpoint of resource reuse and environmental protection. Therefore, in recent years, the use of recycled styrenic resins is rapidly advancing. In the regenerated styrenic resin, the styrenic resin and the styrenic resin foam which were distributed and used in the market were recovered, and then the foam was reduced in volume by melting or the like, and then recovered. The styrene-based resin is finely pulverized by cutting, and the pulverized material is put into an extruder and extruded to obtain pelletized styrene-based resin particles (so-called regenerated pellets). In a production plant for expandable styrene resin particles,
Off-grade expandable styrenic resin particles produced during the production process, that is, having a particle size of less than 0.5 mm or a particle size of 2
recover foamable styrene-based resin particles outside the required quality that are not suitable for general use of styrene-based resin foam exceeding
By extruding this, the regenerated pellets obtained are also regenerated styrene resin,
It can be used for the styrene base resin in the present invention.

The styrenic base resin used in the dielectric foam molded article having dimensional stability of the present invention may contain, if necessary,
Various other additives, modifiers and auxiliaries can be incorporated in appropriate amounts. These include, for example, a plasticizer (for example, DOP, DOA, DBP, coconut oil, palm oil, stearic acid, etc.) for improving the expansion ratio, and an inorganic or organic nucleating agent (for example, talc, bentonite, ethylene bisstearic acid) Amide, zinc stearate, etc.), and a cell forming agent, a coloring agent, a lubricant, an antistatic agent, a flame retardant (for example, hexabromocyclododecane, tetrabromobisphenol A, pentabromomonochlorocyclohexane, etc.). These chemicals are appropriately selected and used from those conventionally used in expandable styrene resin particles, and are added in the step of extruding the styrene base resin or the step of impregnating the blowing agent.

The above-mentioned styrenic base resin is generally produced by suspension polymerization of a styrenic monomer or the like in an aqueous medium. These suspension polymerizations are carried out in an aqueous suspension system containing a radical polymerization initiator, a dispersant and a dispersing aid. Examples of the radical polymerization initiator include polymerization initiators used in general radical polymerization, for example, organic peroxides such as benzoyl peroxide, butyl perbenzoate, t-butyl peroxybenzoate, and azobisisobutyro. An azo compound such as nitrile is exemplified. In addition, examples of the dispersant to be used include poorly water-soluble inorganic salts such as tricalcium phosphate, magnesium phosphate, and hydroxyapatite, and organic polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose. Further, as the dispersing aid used in combination with the above dispersant, dodecyl phenyl oxide disulfonate, sodium dodecyl benzene sulfonate, anionic surfactants such as sodium α-olefin sulfonate, polyoxyethylene alkyl ether, Nonionic surfactants such as polyoxyethylene octyl phenol ether are exemplified.

Except for the case where off-grade expandable styrene resin particles already containing a blowing agent are used as a raw material, the styrene resin particles are usually impregnated with a blowing agent. Therefore, the above-mentioned suspension-polymerized styrene-based base resin is formed into a particle form or a pellet form by extrusion molding, and an expandable styrene-based resin particle is produced by impregnating it with a foaming agent.

However, in the present invention, the styrene base resin must contain dielectric ceramics uniformly. For this reason, it is conceivable to add a large amount of dielectric ceramic to the suspension polymerization system of the styrene-based base resin. However, since this polymerization system becomes extremely unstable, the dielectric ceramic is mixed in an extruder. It is desirable. Therefore, the method is as follows: (A) A styrene-based base resin, and, if desired, a low-molecular-weight polyolefin and a high-dielectric ceramic are kneaded with an extruder to obtain a ceramic-containing styrene-based resin pellet in which these are uniformly mixed. A method of transferring the base resin pellets to a suspension system and dispersing them, and then impregnating a foaming agent to obtain expandable styrene resin particles uniformly containing high dielectric ceramics; (B) expandable styrene base material A method of kneading and extruding resin particles and high dielectric ceramic in an extruder to obtain an expandable styrene resin pellet in which the high dielectric ceramic is uniformly contained; a method of obtaining expandable styrene base resin particles here is as follows. For example, 1) a styrene-based base resin particle (optionally containing a low-molecular-weight polyolefin) obtained by suspension polymerization or a styrene-based base resin pellet (optionally containing a low-molecular-weight polyolefin) obtained from an extruder,
A method of impregnating a foaming agent in a suspension system, or 2) adding a foaming agent into the extruder after kneading with a styrene-based base resin (containing a low-molecular-weight polyolefin if desired) in the extruder. This is a method of impregnating a styrene-based base resin to obtain foamable pellets; (C) after kneading a styrene-based base resin (containing a low-molecular-weight polyolefin if desired) and a high dielectric ceramic in an extruder. A method in which a foaming agent is added into an extruder, impregnated into a styrene-based base resin, and extruded to obtain foamable styrene-based resin pellets uniformly containing high dielectric ceramics.

The expandable styrene resin particles or pellets in which the produced high dielectric ceramics are uniformly contained are usually sufficiently dried by using a drier or the like and then sieved by a sieving machine. Of particle size
Next, a blending agent such as a lubricant and an antistatic agent is mixed with the separated expandable styrene resin particles or pellets, and then sealed and packed in a drum or the like. Thus, the stored expandable styrenic resin particles or pellets are pre-expanded to any apparent specific gravity as necessary, and then, according to a conventional method, the pre-expanded particles are filled into a mold such as a mold, and The pre-expanded particles are fused to each other by heating and foaming using steam, whereby a foam molded article (foam) having dimensional stability of a desired shape (dimension) can be produced.

The dielectric foam molded article of the present invention in which the dielectric ceramic is substantially uniformly dispersed in the foam made of the styrenic base resin is an object of the above-mentioned problem, namely, "excellent dimensional stability over a long period of time." In addition, the temperature dependence of the relative dielectric constant is small, and the dielectric tangent is 0.005 or less when the relative dielectric constant is in the range of 1.0 to 2.0;
04G / cm ³ and an extremely satisfying all lightweight is condition as the dielectric material "excellent molded foam. Therefore,
The dielectric foam molded article of the present invention is used as a dielectric material for a radar radio wave reflector or an antenna provided with a spherical dielectric lens in which the above conditions are required, for example, a lens utilizing the principle of a Luneberg lens. it can. In addition, the present invention, as further inferred from the following examples,
Even at a bulk specific gravity of about 0.25 g / cm ³ , a dielectric material having a relative dielectric constant of 2.0 or more and a dielectric loss tangent of 0.005 or less can be provided. As a dielectric material for antennas, radar radio reflectors, etc., and as a dielectric material in other applications requiring a relative dielectric constant exceeding 2.0. The values of the relative permittivity and the dielectric loss tangent described in this specification can be measured by a cavity resonance method using a plate-like sample. That is, a sample having a thickness d is inserted into the cavity resonator, tuning is performed by the axial length change method, the sample to be measured is removed, and tuning is performed again by the axial length change method. Is measured. The relative permittivity and the dielectric loss tangent are calculated by applying the obtained s value and d value to predetermined formulas (Keiji Suzuki, “Microwave Measurement”, High Frequency Measurement Complete Book No. 4, published by Corona Co., Ltd.) , Third Edition, 19
61, 180-205).

[0021]

The present invention will be described in more detail with reference to the following examples, but these examples are not intended to limit the present invention.

First, in order to create a standard for evaluating the dimensional change rate over time, the following test was performed on a styrene resin foam molded article. An ion-exchanged water was placed in an autoclave having a content of 5 L with a Faddler-type stirrer. 1800 gr was added, 5.4 gr of tricalcium phosphate and 0.05 gr of sodium dodecylbenzenesulfonate were added, and the mixture was thoroughly mixed and stirred. To the system, 1800 gr (100 parts by weight) of a styrene monomer, 5.4 gr of benzoyl peroxide and 1.8 gr of t-butylperoxybenzoate as a polymerization initiator were added, and the temperature was raised to 90 ° C. while stirring. The polymerization was allowed to proceed for a period of time to produce polystyrene particles. After completion of the polymerization, n-pentane as a blowing agent was press-fitted into the autoclave in an amount shown in Table 1 below, and the system was heated to 120 ° C. and maintained for 6 hours to convert the blowing agent into polystyrene. The particles were impregnated. After this treatment, the polymerization reaction system was cooled to room temperature, and the formed expandable styrene resin particles were taken out of the vessel, and trilime phosphate adhering to the particle surfaces was removed by acid washing. Thereafter, water adhering to the particle surface was removed through a centrifugal separation or drying step, and particles having a particle diameter of 0.7 to 1.0 mm were separated by sieving. After aging these particles at room temperature for 5 days, they were prefoamed with steam at 101 ° C. to a bulk magnification of 10 times (bulk specific gravity of 0.1). After the obtained pre-expanded particles were aged at room temperature for 24 hours, they were charged into a molding die of an automatic molding machine and heated at a pressure (gauge pressure) of 0.7 kg / cm ^{2 for} 8 seconds.
A 30 × 30 × 5 cm foam molded product produced by water-cooling and allowing the mold to cool was taken out and used as a sample for dimension measurement.

The amount of the foaming agent contained in the molded article is 1
A part of the foamed molded product on the day is taken, its weight is measured, it is kept in an oven at 150 ° C. for 1 hour, and then its weight is measured again. ]. Similarly, the amount of the foaming agent contained in the expandable styrene-based resin particles before molding was also measured by taking a part of the expandable styrene-based resin particles before prefoaming and measuring the weight by 150. The temperature was kept in an oven at a temperature of 1 ° C. for 1 hour, and then the weight was measured again.

(Equation 1) The results are shown in Table 1.

[Table 1] Next, in order to evaluate the dimensional stability performance of the foam molded article, the relationship between the amount of the foaming agent contained in the foam molded article and the dimensional change rate of the molded article with time was examined. As described below, the rate of dimensional change over time of the foamed molded product is expressed by the following [Formula-2] or
It was determined according to [Equation-4]. Regarding the foamed molded article, first, the dimensional change rate of the molded article on the first day after molding was calculated based on the following [Equation-2], and this value was used as a reference value before leaving. The dimensional change rate of the foamed molded article at room temperature was determined from the difference between the dimensional change rate with respect to the mold at the time when the molded article was left at room temperature for a predetermined number of days and the above-mentioned reference value, according to the following [Equation 3]. The dimensional change rate of the foamed molded article when left in an oven at 50 ° C. is calculated according to the following [Equation-4].
It was determined from the difference between the dimensional change rate with respect to the mold at the time when it was left for a predetermined number of days in a 50 ° C. oven and the reference value.

(Equation 2)

(Equation 3)

(Equation 4)

The dimensional change rate of the foamed molded article over time when the samples of Test Examples 1 and 2 were left at room temperature and the dimensional change rate over time of the foamed molded article when left in an oven at 50 ° C. Graphs are shown in FIGS. 1 and 2, respectively. In the graph shown in FIG. 1, Test Example-1 in which the amount of the foaming agent contained in the foamed molded product is 1.2% by weight.
In the test sample in which the dimensional change of the foamed molded article after one year at room temperature was less than -0.2%, the amount of the foaming agent contained in the foamed molded article was 3.5% by weight. In the sample of -2, it can be seen that the dimensional change rate of the foam molded article is as large as about -0.7%. In the graph shown in FIG. 2, in the sample of Test Example 1 in which the amount of the foaming agent contained in the foam molded article is 1.2% by weight, the foam molding on the 100th day when left in an oven at 50 ° C. The dimensional change of the product is about -0.2
%, But the amount of the foaming agent contained in the foam molded article is 3.
In the sample of Test Example 2 which is 5% by weight, a remarkable dimensional shrinkage of about -1% was observed in the dimensional change of the foam molded article.
Also, from the graph shown in FIG. 1 and the graph shown in FIG.
It is apparent that the value of the dimensional change of the foamed molded product for about one month when left in the oven at 0 ° C. substantially corresponds to or corresponds to the dimensional change of the foamed molded product for about one year when left at room temperature. It is. Therefore, it is estimated that leaving the foamed molded article in the oven at 50 ° C. for 100 days is equivalent to leaving the foamed molded article at room temperature for about 3 years. With the measured value of the dimensional change of
It is possible to evaluate the degree of dimensional change over time of the foamed molded article when left for a year.

Example 1 100 parts by weight of a polystyrene resin and 25 parts by weight (20% by weight) of barium titanate having an average particle diameter of 10 μm or less as a high dielectric substance were put into an extruder, which was melted by heating and mixed by a screw. Following kneading, it was extruded in the form of a strand, after which the strand was cut in a rotary pelletizer and pelletized. 1500 gr of polystyrene resin pellet containing the obtained dielectric
In a 5 L autoclave, furthermore, 2500 g of ion-exchanged water, 15 gr of tricalcium phosphate as a dispersant and 0.15 g of sodium dodecylbenzenesulfonate
r into an autoclave, and then, while stirring the mixture, 45 g of a volatile blowing agent n-pentane.
(3% by weight based on resin pellets). Next, the temperature of the aqueous suspension in the autoclave was raised to 130 ° C., and this state was maintained for 8 hours, thereby impregnating the resin pellets with n-pentane. After this treatment, the aqueous suspension was cooled to room temperature, and the formed composite dielectric foamed resin particles were washed with water, dehydrated by a centrifugal separator, dried by a drier, and then aged at 20 ° C. room temperature for 5 days. The composite dielectric foamed resin particles thus obtained were prefoamed with steam to have a bulk specific gravity shown in Table-2. After the pre-expanded particles are aged, they are put into a molding die of an automatic molding machine and molded, and are then molded into a 30 ×
A foam molded product of 30 × 5 cm was obtained. A part of this foam molded product was cut out to 50 × 50 × 1.0 mm, and the relative permittivity at 12 GHz was determined by the cavity resonance method using the plate-like sample.
The dielectric loss tangent (tan δ) was measured. The results are shown in Table-2. The amount of the foaming agent in the foamed resin particles in this example was determined by a gas chromatography using the gas chromatography according to a standard method. In addition, the amount of the foaming agent contained in the molded article was similarly determined by taking a part of the molded article on the first day after molding. Table 2 shows these results.
It was shown to. The dimensional change of the molded article on the first day after molding and the dimensional change on the 100th day after standing in a 50 ° C. oven were examined according to [Equation-2] to [Equation-4].

Example 2 In Example 1, the amount of the blowing agent n-pentane was changed to 60 g.
The same operation as in Example 1 was carried out except that r (4% by weight based on the resin pellets) was used. Example 3 In Example 1, the weight average molecular weight was 100 at the time of extrusion.
0, and the same procedure as in Example 1 was carried out except that 1 part by weight of polyethylene wax having a melting point of 111 ° C. was added. Example 4 In Example 2, the weight average molecular weight was 300 at the time of extrusion.
0 and the same procedure as in Example 1 except that 2 parts by weight of polyethylene wax having a melting point of 128 ° C. was added. Example-5 100 parts by weight of styrene resin particles already containing 5% by weight of n-pentane as a blowing agent, and barium titanate 67
Part (40% by weight) was put into an extruder, which was melted by heating, kneaded with a screw, and then extruded in the form of a strand. Thereafter, the strand was cut with a rotary type pelletizer to remove the foaming agent. The resulting composite dielectric foamed resin pellets were obtained. The pellets were prefoamed or molded in the same manner as in Example 1 and evaluated.

Comparative Example 1 In Example 1, barium titanate was not added as a high dielectric substance, and the amount of the volatile blowing agent n-pentane was 7
The same operation as in Example 1 was performed except that the amount was 5 gr (5% by weight based on the resin pellets). Comparative Example 2 The procedure of Example 1 was repeated, except that the amount of the volatile blowing agent n-pentane was changed to 75 gr (resin pellets 5% by weight). Comparative Example-3 In Example-5, except that styrene resin particles already containing 7% by weight of n-pentane as a foaming agent were used.
It carried out similarly to Example-5.

The results are summarized in Table 2.

[Table 2] Even if the dimensional change rate of the foamed molded product on the first day after molding is large, it is not a problem since the change rate may be considered in advance in the mold design stage. On the other hand, the dimensional change rate with time is desirably as small as possible. 1) In Example 1, although the amount of the foaming agent in the molded product was 1.7% to 1.8% by weight, the dimensional change measured on the first day after molding was slightly large, After leaving in the oven 1
The dimensional change on day 00 was as small as -0.3% or less. The relative dielectric constant is a bulk specific gravity of 0.23 g / cm ^3.
, A value of approximately 2.0 was obtained, and the dielectric loss tangent was also a small value. 2) In Example 2, the amount of the foaming agent in the molded product was 2.7% by weight.
2.8% by weight, the dimensional change measured on the first day after molding is somewhat large,
The dimensional change on day 0 was as small as -0.4% or less. The relative dielectric constant was approximately 2.0 at a bulk specific gravity of 0.22 g / cm ³ , and the dielectric loss tangent was also a small value. 3) Example-3 is a system in which a low molecular weight polyethylene wax was added at the time of extrusion. The amount of the foaming agent of the foamed resin particles was 2.2% by weight, which is the same as in Example-1, whereas the molded product was The amount of the foaming agent therein was reduced to 1.3% by weight. This indicates that the blowing agent was efficiently dissipated during the prefoaming or molding due to the addition of the low molecular weight polyethylene wax. The dimensional change rate measured on the first day after molding was somewhat large, but the dimensional change rate on day 100 after standing in the 50 ° C. oven was as small as −0.2% or less. The relative dielectric constant was approximately 2.0 at a bulk specific gravity of 0.23 g / cm ³ , and the dielectric loss tangent was also a small value. 4) Example-4 is a system in which a low molecular weight polyethylene wax was added at the time of extrusion. The amount of the blowing agent in the expanded resin particles was 3.1% by weight, which is almost the same as in Example-2. The amount of the foaming agent in the molded product was as small as 2.0% by weight. This indicates that the blowing agent was efficiently dissipated during the prefoaming or molding due to the addition of the low molecular weight polyethylene wax. Although the dimensional change measured on the first day after molding is slightly large,
The dimensional change rate on day 0 was as small as -0.3% or less. The relative dielectric constant was approximately 2.0 at a bulk specific gravity of 0.22 g / cm ³ , and the dielectric loss tangent was also a small value. 5) Example-5 is an example in which the amount of the high dielectric substance was increased, but the relative dielectric constant was approximately 2.0 at a bulk specific gravity of 0.16 g / cm ³ , and the dielectric loss tangent was also small. It was a small value. The amount of the foaming agent in the molded article is from 2.2% by weight to 2.3% by weight.
In terms of weight%, the dimensional change measured on the first day after molding was somewhat large, but the dimensional change on day 100 after standing in a 50 ° C. oven was as small as −0.3% or less. 6) Comparative Example 1 is an example in which a high dielectric material was not added and a large amount of a foaming agent was impregnated. The amount of the foaming agent in the molded product was 3.9% by weight to 4.0% by weight. Although the dimensional change measured on the first day after molding was small, the dimensional change on 100 days after standing in a 50 ° C. oven was a large value exceeding -1.2% in all cases. The relative dielectric constant is a bulk specific gravity of 0.42.
g / cm ³ , which is a small value of 1.51;
A value of 1.6 or higher could not be obtained at low density. 7) Comparative Example-2 is an example in which a larger amount of the foaming agent was impregnated with respect to Example-1, but the relative dielectric constant was bulk specific gravity 0.22 g / cm.
^{In 3} , the value of about 2.0 could be obtained, but the amount of the foaming agent in the molded article was as high as 3.6 to 3.7% by weight, so the dimensional change measured on the first day after molding was obtained. Although the ratio was small, the dimensional change on the 100th day after standing in the 50 ° C. oven was a large value exceeding −1.1% in all cases. 8) Comparative Example-3, is an example extruded foamed styrene resin containing a large amount of blowing agent to Example -5, the dielectric constant in the bulk specific gravity 0.17 g / cm ^3, approximately 2.0
Was obtained, but since the amount of the foaming agent in the molded article was as high as 3.5% by weight, the dimensional change measured on the first day after molding was small, but 100 days after standing in an oven at 50 ° C. Of all were large values exceeding -1.0%.

[0029]

As described above, according to the present invention, extremely high dimensional stability with time can be achieved for a dielectric foam molded article, and therefore, the amount of change in relative permittivity with respect to temperature change over a long period of time is small. It is possible to provide a lightweight and very excellent dielectric foam molded article having a dielectric loss tangent of 0.005 or less in a ratio of 1.0 to 2.0 and a bulk specific gravity of 0.3 to 0.04 g / cm ^3. it can. The dielectric foam molded article of the present invention is a molded article having extremely high dimensional stability with a dimensional change rate of -0.5% to 0% when left at room temperature for 3 years. Therefore, this dielectric foam is particularly suitable for a dielectric material used outdoors such as a spherical dielectric lens utilizing the principle of the Luneberg lens. In addition, the present invention has a high dielectric constant of 2.0 or more and a dielectric loss tangent of about 0.25 even at a bulk specific gravity of about 0.25 g / cm ³ while maintaining high dimensional stability that is stable for a long period of time. 005 or less dielectric material can be provided. By utilizing this property, it can be used as a dielectric material for antennas other than spherical dielectric lenses, radar radio wave reflectors, etc. It can be used in various applications commonly used as a dielectric material in applications where a rate is required.

[Brief description of the drawings]

FIG. 1 shows Test Example-1 when left at room temperature for one year.
7 is a graph showing the relationship between the number of days at room temperature and the dimensional change rate of each of the foam molded products of Test Example 2 and Test Example-2.

FIG. 2 is a graph showing the relationship between the number of days aged at 50 ° C. and the dimensional change of each of the foamed molded products of Test Example-1 and Test Example-2 when left in an oven at 50 ° C. for 100 days. It is.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 3/44 H01B 3/44 PF term (Reference) 4F074 AA16 AA17 AA24 AA32 AC22 AC23 BA36 BA37 BA39 BA40 BA44 BA53 CA21 CA23 CA31 CA34 CA38 CA49 DA02 DA22 DA47 DA59 4J002 BB022 BB122 BC021 DE186 FD320 5G303 AA04 AA10 AB06 AB07 AB20 BA11 CA01 CA09 CB03 CB06 CB17 CB25 CB32 CB35 5G305 AA09 AA20 AB09 AB10 CC27 CB28

Claims (4)

[Claims] 1. A dielectric foam molded article in which dielectric ceramics are substantially uniformly dispersed in a foam made of a styrenic base resin, and the foam molded article has a relative dielectric constant of 1.0.
Having a value in the range of 0.005 to 2.0, a dielectric loss tangent of less than 0.005, and a bulk specific gravity of 0.3 to 0.04 g /
cm ³ , the amount of the foaming agent remaining in the foamed molded article is 3% by weight or less, and the foaming when the foamed molded article is left in an oven at 50 ° C. for 100 days. The dimensional change rate of the molded product is -0.5% compared to before leaving
A dielectric foam molded article having dimensional stability, characterized in that the content is from 0 to 0%. 2. The dielectric foam molded article according to claim 1, wherein the low-molecular-weight polyolefin resin is contained in an amount of 0.1 to 10 parts by weight based on the total amount of the styrene-based base resin. 3. The low molecular weight polyolefin resin,
The dielectric foam molded article according to claim 2, wherein the molded article is a low molecular weight polyethylene having a weight average molecular weight of 500 to 10,000 and a melting point of 100 to 130 ° C. 4. The dielectric ceramic dispersed in a foam is mainly composed of a powder or a whisker, and the content of the dielectric ceramic is based on the styrene base resin and the dielectric ceramic. The dielectric foam molded article according to claim 1, wherein the content is 5 to 50% by weight based on the total amount of the above.