JPS62252405A - Transparent shielding material and its production - Google Patents

Abstract

PURPOSE:To obtain a transparent shielding material excellent in mechanical strength, moisture resistance, heat resistance and damage resistance, by pouring a specified radical-polymerizable composition into a mold in the cavity of which a gauzelike electromagnetic shielding material is fixed and cured by polymerization. CONSTITUTION:A radical-polymerizable composition comprising at least one polyfunctional monomer (a) selected from a polyol polyacrylate and a polyol methacrylate, at least one lead-containing monomer (b) selected from lead acrylate and lead methacrylate and a lead salt of an organic acid is poured into a mold in the cavity of which a gauzelike electromagnetic shielding material is fixed, and this composition is cured by polymerization in this mold. The reason why the shielding material obtained by the above process can shown an excellent electromagnetic shielding performance is presumably that the lead component present in the cured polymer present in the gauze openings of the electromagnetic shielding material shows a property of shielding electromagnetic waves by its own characteristics or its ionic conduction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a shielding material that has excellent transparency, has the property of blocking radiation and electromagnetic waves, and is useful as a filter for cathode ray tubes, etc. , more specifically, the molded product has excellent optical transparency and mechanical strength, as well as moisture resistance.
This invention relates to radiation and electromagnetic wave shielding materials with excellent heat resistance and scratch resistance.

(Prior Art) In recent years, radioactive materials have been used in various fields such as medicine, energy, schools, and research institutes. This radiation is not only harmful to the human body, but also has an adverse effect on surrounding equipment and materials. Against this background, it is necessary to shield radiation when using radioactive materials.

In addition, cathode ray tubes (which are used in office automation such as various computers and word processors)
CRTs are known to emit trace amounts of X-rays and electromagnetic waves, and various filters are being developed to block these and protect the human body.

For example, a method in which an organic acid lead such as lead methacrylate is polymerized together with a vinyl monomer (#Kaikai No. 53-9996), a method in which a specific polyfunctional monomer is used as a part of the above vinyl monomer. (Japanese Unexamined Patent Publication No. 54-1797) etc. have been proposed.

(Problems to be Solved by the Invention) However, these known plastic materials include vinyl-based polymers 1, specifically methyl methacrylate (MMA), styrene (ST),
Due to the use of hydroxyalkyl methacrylate, etc., (1) the polymerization shrinkage rate is high (for example, about 20% for MMA,
ST: about 17%) (a) When hydroxyalkyl methacrylate is used, it has a hydrophilic group, so it has a high affinity for water and has poor moisture resistance. Furthermore, during molding, there is a problem of poor mold releasability due to high adhesion to glass plates and stainless steel plates that are generally used as molds.

(1) Since the boiling point of the monomer is low, there is a risk of foaming if the temperature is not adequately controlled in the case of thick-walled products.

These problems remain, and as a result, molding is extremely difficult.

Furthermore, the mechanical strength of the molded product itself is still not sufficient, and the scratch resistance of the surface is also poor.

Therefore, the present invention solves the above-mentioned drawbacks without impairing the material's transparency, radiation shielding ability, and electromagnetic wave shielding ability, and provides a shielding material with excellent mechanical strength, moisture resistance, heat resistance, and scratch resistance. The purpose is to

(Means for solving the problems) According to the present invention, in order to provide a shielding material having the above characteristics,
(A) at least one polyfunctional monomer selected from the group consisting of polyol polyacrylate and polyol methacrylate; (B) at least one lead-containing monomer selected from the group consisting of lead acrylate and lead methacrylate; C) A net-like electromagnetic wave shielding material is embedded in a polymerized and cured product of a composition made of organic acid lead.

This shielding material is produced by injecting the above radically polymerizable compositions (A) to (C) into a mold in which a net-like electromagnetic wave shielding material is fixed in the inner space, and polymerizing and curing the composition.

(Function) The shielding material of the present invention contains a radiation blocking substance in the form of a lead salt or a radiation blocking substance generally in the form of a porous body such as a net. An important feature is that a reticular radiation-blocking material is embedded within it.

That is, the component (B) used in the present invention binds the lead component in the form of an ion to the polymer chain, and the component (C) compatibilizes the lead component in the form of a salt in the polymer. The polyfunctional monomer (A) used in the present invention imparts a radiation shielding effect to the polymer molded product while maintaining excellent transparency. The feature is that a crosslinked structure can be introduced while maintaining these characteristics.

In the transparent shielding material of the present invention, the electromagnetic wave shielding material is contained in the crosslinked polymer in an embedded state so that the transparency of the molded product is not substantially impaired, thereby imparting electromagnetic wave shielding properties. However, according to the present invention, the above (A), (
By embedding the net-like electromagnetic wave shielding material in the polymerized cured product made of the compositions B) and (C), electromagnetic wave shielding performance is superior to that of a structure in which the electromagnetic wave shielding material is embedded in a normal polymer molded product. is obtained. The reason for this has not yet been elucidated, but the lead component present in the polymerized hardened material present in the mesh opening of the electromagnetic wave shielding material has the property of blocking electromagnetic waves due to its own properties or due to its ionic conductivity. This is thought to be to show that

Moreover, according to the present invention, the matrix in the molded product is made into a monopolymerized crosslinked product, which improves the mechanical strength of the material itself compared to a molded product obtained by a conventional polymer made of a single monomer or a polymer blend. This can contribute to improving heat resistance.

Moreover, since the constituent component forming the basic skeleton of the crosslinked polymer of the present invention is the polyfunctional monomer (A), various excellent advantages can be achieved. In other words, polyfunctional 7-mer (A) itself has a much lower polymerization shrinkage rate than MMA or ST, so highly accurate casting molding is possible.
Further, it is possible to prevent optical distortion from occurring due to residual stress or distortion after polymerization and curing. In addition, this polyfunctional monomer (
Since A) has a very high boiling point, it can solve the problem of foaming and improve transparency.

(Operations and Effects of the Invention) According to the present invention, transparency, radiation shielding properties and electromagnetic wave shielding properties can be achieved by a simple operation of casting the above-mentioned three-component composition into a mold in which a net-like electromagnetic wave shielding material is fixed and polymerizing and curing it. A transparent molded product with excellent barrier properties and improved heat resistance and mechanical strength is obtained, and this product is made of inexpensive C.
It is useful for applications such as RT filters, observation windows or transparent shielding materials for experimental equipment or industrial equipment that generate radiation and/or ultraviolet rays.

(Description of Preferred Embodiments of the Invention) Todoroki Nanatsuma In the present invention, at least one type selected from the group consisting of polyol polyacrylate and polyol polymethacrylate is used as the polyfunctional monomer.

A typical example of this is the following general formula % formula % where R1 is a hydrogen atom or a methyl group, X is an alkylene group,
and diester diacrylate or diester dimethacrylate, which represent a droxy-substituted alkylene group, an alkyleneoxyalkylene group, or a poly(alkyleneoxy)alkylene group.

Specific examples of such polyfunctional monomers (A) include, but are not limited to, polyethylene glycol di(meth)acrylate, polypropylene gelyl di(meth)acrylate, and polypropylene glycol di(meth)acrylate.
meth)acrylate, neobentyl glycol di(meth)acrylate, l,8-hexanediol di(meth)
Acrylate, 1゜3-butylene gelicoldi (meth)
Examples include acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate. In this specific example, when polyethylene glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate are selected, the group X in the above formula is a poly(ethyleneoxy)ethylene group and a poly(propyleneoxy)propylene group, respectively. It is preferable to select an alkyleneoxy repeating unit by adding an oxygen atom bonded to the terminal fullkylene, i.e., ÷0-CH2-CH2ya or CH3-f0-CH-CH2i, where n is 4 to 23. By making such a selection, it becomes possible to obtain a molded product with excellent transparency and mechanical strength from the crosslinked polymer.

Among the above-mentioned polyfunctional monomers (A), it is particularly effective to select polyethylene glycol di(meth)acrylate and neopentyl glycol dimethacrylate having 9 to 23 repeating ethyleneoxy units. The reason for this is that the two polyfunctional heptamers (A) mentioned above have a boiling point,
It has particularly excellent physical properties in terms of curability, compatibility, and polymerization shrinkage rate, and is extremely easy to mold, and the resulting molded product also has excellent transparency, mechanical strength, moisture resistance, and scratch resistance. This is because

(B) Boat platform Monomer 1 The lead-containing upper monomer used in the present invention is at least one type of material selected from the group consisting of lead acrylate and lead methacrylate.

These lead-containing materials themselves are conventionally known as materials that have transparent radiation-shielding ability when polymerized at a temperature above their melting point. However, the polymers obtained in this way are generally brittle and cannot withstand practical use in molding, processing, and use, and even when copolymerized with other monomers such as MMA, it is difficult to obtain strength that can be used in practical use. This seven-point solution solves the problem that the transparency of the resulting polymer is lost when the copolymerization ratio is adjusted.
had.

In the present invention, lead-containing tops having such properties are used.
By using it as an element of a crosslinked polymer in combination with other specific components, it was possible to ensure radiation shielding ability without impairing the transparency of the polymer.

In the present invention, at least one monomer selected from the group consisting of lead acrylate and lead methacrylate described above can be used, but lead methacrylate is preferably used from the viewpoint of transparency and mechanical strength.

Packaging and direct delivery amount 1 In the present invention, organic acid lead is used in combination with the lead-containing monomer (B) as the lead-containing component.

A typical example of this organic acid lead is the following general formula (% formula %), where a is an integer equal to the valence of lead, and R is the number of carbon atoms of 5.
It is a lead salt of a monobasic organic fatty acid with ~20 saturated or unsaturated hydrocarbon residues.

If the number of carbon atoms is 4 or less or 21 or more, the resulting crosslinked polymer will be unsatisfactory in terms of transparency and mechanical strength.

Specific examples of this organic lead acid include lead hexanoate, lead octylate, lead octylbenzoate, lead stearate, lead palmitate, lead palmitolate, lead lyluate, and lead naphthenate.

Gravity 11 is b1 1 In addition, during polymerization, it is desirable to use the following proportions in view of the total balance of various physical properties such as radiation shielding ability, strength, and transparency as a radiation shielding material, that is, (A) ,
Based on the three components of (B) and (C), polyfunctional heptamer (
A) is 15 to 60% by weight, preferably 20 to 45% by weight, lead-containing monomer (B) is 25 to 50% by weight, preferably 30 to 50% by weight, and organic acid lead (G) is 15 to 35% by weight. , preferably at a ratio of 25 to 35% by weight.

A catalytic amount of a radical initiator is added to this composition. As the radical initiator, t-butyl hydroperoxide,
Peroxides such as cumene hydroperoxide, di-7-butyl peroxide, 1-butyl peroxybenzoate, lauroyl peroxide, diisopropyl peroxydicarbonate, methyl ethyl ketone peroxide, azobisisobutyronitrile, azobismethyliso Azo compounds such as valeronitrile are used. These radical initiators are desirably present in an amount of 0.1 to 5% by weight, particularly 1 to 4% by weight, based on the monomer content. It can also be used in conjunction with accelerators.

This polymerizable composition may optionally contain an ultraviolet absorber and the like.

As the ultraviolet blocking substance, any ultraviolet absorber can be used, but it is preferable that the polymerized and cured molded product of the above components has a wavelength of 2
Since it absorbs or reflects ultraviolet rays of 70 nm (nanometers) or more, substances that have the ability to absorb ultraviolet rays of longer wavelengths, that is, ultraviolet rays with wavelengths in the range of 270 to 400 nm, especially be/siphenon-based substances. Alternatively, it is preferable to use a benzotriazole-based ultraviolet absorbing substance.

Suitable examples of benzophenone-based and benzotriazole-based ultraviolet absorbing substances include, but are not limited to, the following.

2.2'-dihydroxy-4-methoxybenzophenone, 2.2'-dihydroxy-4,4'-dimethoxybenzophenone.

2,2',4.4'-tetrahydroxybenzophenone, 2(2'-hydroxy-5'-methylphenyl)benzotriazole, 2(2'-hydroxy-3'-tertbutyl-5'-
methylphenyl)-5-glolobenzotriazole, 2(2'-hydroxy-4'-octoxyphenyl)benzotriazole.

2(2'-Hydroxy-3', 5'-di-tertbutyl)benzotriazole.

Important: A conductive net is used as the electromagnetic wave shielding material. In this case, the opening degree of the conductive mesh is generally 80 to 250 meshes, particularly 80 to 250 meshes, expressed as a Tyler standard mesh.
It is preferable that the mesh number be in the range of 00 meshes, that is, if the mesh number is smaller than the above range, the electromagnetic wave shielding effect will be inferior to that in the above range.

On the other hand, if it is larger than the above range, transparency will be impaired.

As the conductive mesh, a wire mesh, especially a wire mesh with a copper-plated layer, is used, but metal-plated synthetic fiber gauze is most preferably used. Metal-plated synthetic fiber gauze is obtained by weaving or knitting monofilament, multifilament yarn or spun yarn of polyester, nylon, vinylon, acrylic, etc. into a coarse weave, and adding copper, nickel, cobalt, and chromium to the gauze fabric obtained by weaving or knitting monofilament, multifilament yarn, or spun yarn of polyester, nylon, vinylon, acrylic, etc. into a coarse weave. A plated layer of metal such as , silver, or aluminum is used. The plating layer is formed by electroless plating (chemical plating), vacuum deposition, or a combination of these and electroplating. The plating layer may be formed to the extent that these surfaces become sufficiently conductive but do not cause clogging.The plating layer may be a single metal layer or a layer of multiple metals. The metal-plated synthetic fiber gauze used in the present invention may be composed of layers, for example, a combination of an electroless plating layer and an electrolytic plating layer. The aperture ratio is generally 10 to 90%, especially 30 to 80%.
It is desirable that it be within the range of %.

According to the present invention, by using a metal-plated synthetic fiber gauze as the conductive mesh, significant advantages are achieved in relation to molding shrinkage of the resin, etc. That is, when using metal nets, punched metal, etc., the resin shrinks in the area where the conductive net is provided, and the resin contracts in other areas, causing internal strain or internal stress. 0 For example.

In the part where this conductive network deviates from the center of the resin molded body,
Therefore, deformations such as warping and bending easily occur. Also,
During use or when exposed to heat, cracks are likely to occur and transparency is likely to be impaired.In contrast, according to the present invention, even when producing a relatively large molded product, the conductive network Because the synthetic fibers that serve as the base material are flexible and easily deformable, they have good ability to follow shrinkage during resin curing, and prevent deformations such as warping and bending during molding, as well as the generation of internal stress and strain. This will effectively prevent the occurrence of cutthroat and the like.

Moreover, with 1 synthetic fam, monofilaments with small diameters can be easily obtained, and the strands of the conductive network themselves can be extremely fine. You can get something that doesn't cause an eyesore. Further, this metal-plated synthetic fiber gauze itself has good workability such as cuttability, and the molded body in which it is embedded also has good workability. Furthermore, this material also has the advantage of good followability when bending is performed.

In the electromagnetic shielding material of the present invention, since the metal-plated synthetic fiber gauze has good shrinkage followability, the position where it is buried is not particularly limited; for example, it may be located in the center of the molded body, or it may be placed in any Alternatively, two or more metal-plated synthetic fiber gauze may be provided as desired. The metal plating layer may be colored as desired.Furthermore, in order to improve adhesion with the resin,
The surface of the metal-plated synthetic resin gauze may be previously treated with a coupling agent such as triethoxyaminoprobisilane, or may be dyed black for the purpose of removing metallic color.

In FIG. 1 showing the cross-sectional structure of an example of the shielding material of the present invention, the shielding plate 1 is integrally molded with the resin 2 described above, and has one surface 3 and the other surface 4. A metal-plated synthetic fiber gauze 5 is buried between them.

The two resins partitioned by this metal-plated synthetic fiber gauze are connected through the openings in the gauze 5 and are completely integrated.

That is, the cured resin 2 and the metal-plated synthetic fiber gauze 5 are completely adhered and integrated, and there are no or almost no voids in the resin matrix or the interface between the resin and the metal-plated layer.

When forming a laminate structure between a conductive porous member and a resin, the conductive porous member is sandwiched between two pre-formed resin plates, and the conductive porous member is sandwiched between the conductive porous member and the resin, and the conductive porous member is sandwiched between the conductive porous member and the resin, and the conductive porous member is sandwiched between the conductive porous member and the resin plate. It is conceivable to integrate both resin plates, but in this case, fine voids inevitably remain between the conductive member and the resin, making complete integration difficult, and the interface between the two is difficult to achieve. Peeling may occur or image distortion may occur at the interface.

According to the present invention, all of the above-mentioned drawbacks are solved by using the above-mentioned resin composition, embedding metal-plated synthetic fibers therein, and polymerizing and integrating them.

That is, as shown in FIG. 2, the shielding material 1 of the present invention has an electromagnetic wave shielding material 5 made of metal-plated synthetic fiber gauze placed in the center of two glass plates 6 and 7, and a soft vinyl chloride tube or a polymer-cured material. The molding composition is injected into the space 9 of the glass plate 6.7, which is fixed and sealed by a flexible spacer part 8.8 that can follow the shrinkage, and is polymerized and cured under the following temperature conditions: Manufacture shielding materials.

Polymerization can be carried out by any method known per se,
For example, it may be a one-stage polymerization method or a two-stage polymerization method.0For example, in the latter two-stage polymerization, the first stage is a combination of polymerization at a relatively low temperature and the second stage at a higher temperature. A method consisting of:

Further, for the purpose of removing internal strain caused by monopolymerization shrinkage, heat treatment can be performed at a temperature higher than the glass transition temperature (Tg) of the resin.

(Example) Next, examples of the present invention will be shown.

Example 1 Polyethylene glycol dimethacrylate (n = 14) 20% by weight neopentyl glycol dimethacrylate (n = 14) 15 // Lead methacrylate 35 Lead octylate
30% by weight mixture of the above proportions 70°C, 10
After heating and stirring for a minute to obtain a uniform solution, the solution was once cooled to 40° C., and 0.1% by weight of t-butyl perbenzoate was added to obtain a casting composition.

This composition was molded into a radiation and electromagnetic wave shielding plate using a mold shown in FIG. An electromagnetic wave shielding net made of 200 mesh polyester fiber monofilament gauze coated with copper to prevent clogging is applied with uniform tension.
Next, a gasket was placed on each peripheral edge of two 400 m/square glass plates.

The electromagnetic wave shielding net was inserted and clipped to provide a gap of 3 m/intestine.

The above composition was injected into this mold and heated at 80°C for 3 hours for 1
Polymerization was carried out at 20°C for 2 hours. The resulting molded plate is lead 30
wt%, and not only had radiation shielding ability, electromagnetic wave shielding ability, and ultraviolet shielding ability, but also excellent transparency, scratch resistance, mechanical strength, and moisture resistance.

Example 2 Polyethylene glycol dimethacrylate (n=23) 20% by weight 1.3 Butylene glycol dimethacrylate 15 // Lead methacrylate 35 Lead octylate
30// was polymerized and cured in the same manner as in Example 1.

The moldability was as good as in Example 1, and the physical properties of the obtained molded plate were also sufficient as in Example 1.

Comparative Example 1 MMA 35% by weight lead methacrylate 35 lead octylate 30 was polymerized and cured in the same manner as in Example 1. The obtained molded plate had excellent transparency, but was inferior in scratch resistance and mechanical strength.

Comparative Example 2゜MMA 20% by weight ST 10/1 Lead methacrylate 35 l/Lead octylate
30// Polymerized and cured in the same manner as in Example 1.

It adhered closely to the tempered glass plate and could not be released from the mold.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a transparent radiation shielding material according to the present invention. FIG. 2 is an explanatory diagram for explaining the production of the radiation and electromagnetic wave shielding material of the present invention. 1 is an electromagnetic wave shielding material, 2 is a lead-containing cured resin, 3.4 is a surface, 5 is a metal-plated synthetic fiber gauze, 6.7 is a mold, and 8 is a gasket. Figure 1 Figure 2

Claims (3)

[Claims] (1) (A) At least one polyfunctional monomer selected from the group consisting of polyol polyacrylate and polyol methacrylate; (B) At least one lead-containing monomer selected from the group consisting of lead acrylate and lead methacrylate. and (C) a transparent shielding material comprising a polymerized crosslinked composition containing a lead organic acid and a reticulated electromagnetic wave shielding material embedded therein so as not to substantially impair the transparency of the molded article. (2) The material according to claim 1, wherein the net-like electromagnetic wave shielding material is a metal-coated synthetic fiber gauze. (3) In a mold in which a net-like electromagnetic wave shielding material is fixed in the inner space, (A) at least one polyfunctional monomer selected from the group consisting of polyol polyacrylate and polyol methacrylate, (B) lead acrylate and methacrylate. A radically polymerizable composition comprising at least one lead-containing monomer selected from the group consisting of lead acid and (C) organic lead acid is injected, and the composition is polymerized and hardened in the mold. A method for producing a transparent shielding material.