JPH10330948A - Production of silver-coated resin grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a resin grain with the surface coated with a continuous silver layer in uniform thickness. SOLUTION: The mixture of a vinyl polymerizable functional group-contg. alkoxysilane and a vinyl monomer selected from (meth)acrylic ester monomers and other copolymerizable monomers is copolymerized to obtain a silanol group- contg. resin grain, the resin grain is dipped in a soln. contg. a mercapto group- contg. silane compd. and then brought into contact with a soln. of a silver compd. to adsorb silver ion, which is then reduced, and a silver layer is formed on the resin surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing resin particles in which the surface of the resin particles is coated with a continuous silver layer having a uniform thickness.

[0002]

2. Description of the Related Art An electroless plating method is known as a method for forming a silver layer on the surface of an organic substance such as a molded article or a resin particle formed of a polymer compound. However, when trying to form a silver plating layer on the resin particle surface,
Since the plating layer does not easily grow in the circumferential direction of the particles and easily grows radially or agglomerate from the particle surface, it becomes difficult to form a uniform plating layer as the particle diameter decreases. As described above, the fine particles having the silver plating layer formed by the conventional method have a problem that the formed silver layer is not uniform. In general, when electroless plating is performed on a non-conductive substance such as an organic substance, the catalyst is catalyzed with a tin chloride-hydrochloric acid-based solution and a palladium chloride-hydrochloric acid-based solution, and then the electroless silver plating solution is used. Was used to perform metallic silver coating. In these methods, in the case of fine particles made of a synthetic resin, it is difficult to uniformly coat the silver layer on the surface of the fine particles, and there are problems in workability and economy, and furthermore, adhesion between the resin particles and the silver layer. There was also a problem with gender.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a silver layer coating which eliminates the above-mentioned drawbacks, has sufficient strength against peeling on the surface of polymer particles, and forms a continuous silver layer. It is to provide resin particles.

[0004]

[Means for Solving the Problems]

The inventors of the present invention have conducted intensive studies to improve the above-mentioned disadvantages, and as a result, have found that a vinyl polymerizable functional group-containing alkoxysilane and a (meth) acrylate monomer and other copolymerizable monomers can be used. Silanol group-containing resin particles obtained by copolymerizing a selected vinyl monomer mixture were immersed in a solution containing a mercapto group-containing silane compound, and then contacted with a solution of a silver compound to adsorb silver ions. The present inventors have found that a method of forming silver layer on the surface of the resin particles by post-reduction to precipitate silver solves the above-mentioned problem, and reached the present invention. Hereinafter, the present invention will be described in detail.

[0006] The vinyl polymerizable functional group-containing alkoxysilane used in the present invention refers to one silicon atom, three hydrolyzable groups bonded to a silicon atom, and one radical polymerizable group bonded to a silicon atom. It is a compound having a group, and the radically polymerizable group referred to in the present invention means a radically polymerizable double bond group. This double bond has a C = C bond. Preferred radically polymerizable groups are at least one selected from the group consisting of vinyl groups, acrylic groups, and methacrylic groups. Specific examples of the vinyl polymerizable functional group-containing alkoxysilane used in the present invention include the following general formulas 1 to
And at least one compound selected from the group consisting of

[0007]

Embedded image (Where R ¹ represents a hydrogen atom or a methyl group;
² represents an alkylene group having 1 to 10 carbon atoms which may have a substituent; R ³ represents an alkyl group having 1 to 6 carbon atoms. )

Specific examples of the compounds represented by the general formulas 1 to 3 include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane,
γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltriacetoxysilane, etc. Specific examples of the compound represented by the general formula 2 include vinyltrimethoxysilane and vinyltrimethoxysilane. Ethoxysilane, vinyltriacetoxysilane and the like, any one of these may be used alone or two or more may be used in combination,
In the present invention, γ-propylvinyltrimethoxysilane is particularly preferred from the viewpoint of easy copolymerizability with a vinyl monomer.

[0009] The (meth) acrylate monomer and other copolymerizable vinyl monomers used in the present invention include:
It is a component effective for setting the hardness, flexibility, and glass transition temperature of resin particles, which are basic properties for forming a core serving as a core, and can be appropriately selected according to required performance. Specific examples of these monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate,
Alkyl or cycloalkyl esters of (meth) acrylic acid such as n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethyl (hexyl) acrylate, cyclohexyl (meth) acrylate An α, β-ethylenically unsaturated carboxylic acid such as (meth) acrylic acid, maleic acid and fumaric acid; and other copolymerizable monomers such as styrene and α-methylstyrene. And styrene derivatives such as vinyl toluene; and vinyl esters such as vinyl acetate and vinyl propionate. These can be used alone or in combination of two or more.

In the present invention, a method for producing silanol group-containing resin particles obtained by copolymerizing the vinyl polymerizable functional group-containing alkoxysilane and a vinyl monomer is not particularly limited, and a known and commonly used method is used. Can be adopted, for example,
It can be produced by employing polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, and dispersion polymerization. For example, in the solution polymerization, after removing the solvent, pulverization is performed to a desired particle size, and the obtained particles are spheroidized. Further, resin particles having a predetermined particle size can be produced by employing a polymerization method such as emulsion polymerization, suspension polymerization, or dispersion polymerization. Among these polymerization methods, the suspension polymerization method and the dispersion polymerization method are also preferable in the present invention because the particle diameter can be easily controlled, and particularly, the resin particles prepared by employing the dispersion polymerization method have a particle diameter. Are narrow and very uniform, and the average particle size is usually 0.1.
It is in the range of 1 to 50 μm.

In the present invention, it is necessary to use a vinyl polymerizable functional group-containing alkoxysilane as an essential component of the copolymer resin particles. 0.5 to 20 parts by weight, preferably 2 to 5 parts by weight based on 100 parts by weight of the monomer mixture. When the amount is 0.5 parts by weight or less, the silanol-containing -OH group contained in the resin is small, so that when treated with a solution containing a silver compound described below, the formed silver layer tends to be non-uniform,
Further, the adhesion between the resin particles serving as nuclei and the silver layer tends to be poor, which is not preferable. When the amount exceeds 20 parts by weight, the content of the polysiloxane skeleton in the resin particles becomes too high, and the inherent hardness and flexibility of the resin derived from the vinyl monomer is lost, or the silanol group-containing resin is lost. It is not preferable because the particles tend to aggregate during the production of the particles.

The silane compound having a mercapto group used for adsorbing metal ions is represented by the general formula HSCH ₂ CH ₂
CH ₂ Si (OR) ₃ (R is an alkyl group having 1 to 6 carbon atoms)
Specific examples thereof include, for example, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and the like. The amount of the mercapto group-containing silane compound varies depending on the type of the silane compound to be used and the type of the core resin particles, but cannot be unconditionally specified. It is preferably used in the range of parts. If the amount is less than 1 part by weight, the silver layer formed on the surface of the resin particles tends to be non-uniform and the adhesiveness tends to be poor, so that it is not preferable. If the amount exceeds 20 parts by weight, the mercapto group-containing silane compound itself is used. This is not preferred because fine particles are also likely to be produced by the hydrolysis and condensation of

In the present invention, silanol group-containing resin particles are immersed in a processing solution containing a mercapto group-containing silane compound, and then contacted with a solution containing a silver compound to adsorb metal ions, and then reduced to reduce the metal ions. It is immobilized as metallic silver on the surface of the resin particles. As the aqueous solution of the silver compound, an aqueous solution of a salt, a complex or the like is used. Specific examples thereof include an aqueous solution of silver nitrate, an aqueous solution of silver nitrate-ammonia, an aqueous solution of silver nitrate-ethylenediamine, an aqueous solution containing silver nitrate and various water-soluble amines, an aqueous solution of silver nitrate-ammonia-citrate. Aqueous acid salt solution, silver nitrate
An aqueous solution containing silver ions (or silver complex ions) such as an aqueous solution of sodium ammonia-sodium ethylenediaminetetraacetate (EDTA) and an aqueous solution of silver cyanide is exemplified.

The concentration of silver ions or silver complex ions in the aqueous silver compound solution is preferably a concentration obtained by adding 0.1 to 30% by weight of silver or silver complex salt. Various additives can be contained in the aqueous solution of these silver compounds as needed. Examples of such additives include buffers such as ammonium chloride, lactic acid, citric acid, tartaric acid, and sodium acetate, and brighteners such as ammonium thiosulfate, methanol, and glycol ether. When complex ions are formed in an aqueous solution, complexation of anonia, amines, diamines, glycol, lactic acid, citric acid, tartaric acid, aminopropionic acid, ethylenediaminetetraacetic acid or salts thereof, potassium cyanide, sodium cyanide, etc. Agents can be used.

By immersing resin particles treated with a mercapto group-containing silane compound having a metal ion-adsorbing functional group in an aqueous solution of a silver compound, silver ions or silver complex ions are adsorbed on the functional groups of the resin particles. You. The immersion time of the resin particles in the aqueous solution varies depending on the concentration of the functional group, the concentration of silver ions (or silver complex ions), and the pH of the aqueous solution, but is usually about 1 to 20 minutes. In addition, the aqueous solution of the silver compound is preferable in terms of the adsorption rate and the amount of adsorption depending on the particle diameter of the resin particles and the concentration of the mercapto group on the surface of the resin particles.
It is preferable to use an acid or an alkali to prepare H.

[0016] The reducing agent used in the reduction after the silver ion (or silver complex ion) is adsorbed on the functional group includes:
For example, hydrazine, hydrazine salt (hydrazine sulfate,
One or a mixture of two or more of hydrazine hydrochloride), formalin, acetaldehyde, formic acid, Rochelle salt, hydroxylamine, glucose, ascorbic acid, borohydride compounds (sodium boron hydride, dimethylamine borane, etc.) can be used. The reduction step is preferably performed by adding resin particles to an aqueous solution of a silver compound to adsorb silver ions (or silver complex ions) to functional groups, and then directly adding a reducing agent to the aqueous solution. The particles may be taken out of the aqueous solution of the metal compound and may be carried out in another step.

The silver ions (or silver complex ions) adsorbed on the resin particles are reduced by the reducing action, and metallic silver precipitates to form a silver film on the surface. If the reduction temperature is too low, the reaction temperature is slow and the efficiency is poor. On the other hand, if the reduction temperature is too high, the solution boils to lower the working efficiency.
C. and silver can be precipitated by reduction at room temperature, but it is preferable to reduce while heating. The pH of the aqueous solution at the time of reduction is preferably about 3 to 13. In the initial stage of the reduction, first, silver ions (or silver complex ions) adsorbed on the resin particles precipitate to form nuclei,
It is considered that as the reaction progresses, metallic silver grows and grows continuously on the nucleus to form a silver film.

The thickness of the silver film can be adjusted by the silver ion (silver complex ion) concentration in the aqueous solution of the silver compound, the ratio of the functional groups of the resin particles, the particle diameter, the reduction time, etc., but usually 0.01 μm. About 10 to about 10 μm is preferable. When the thickness of the silver film is 0.01 μm or less, it is difficult to form a continuous dense silver layer on the surface of the resin particles, and a silver compound aqueous solution is prepared so that the silver layer becomes 10 or more on the surface of the resin particles. This is not preferable because particles of silver alone tend to be generated.

The silver-coated resin particles of the present invention can be used, for example, as a conductive filler used in a conductive paint or the like, or
It can be used as a catalyst, an antibacterial pigment used for paints and the like, and a functional filler for resin molded articles.

[0020]

Next, the present invention will be described in detail by reference examples, examples and comparative examples. However, the following is an example, and the present invention is not limited to these examples. In addition, the compounding amount of each component in the following examples is based on weight unless otherwise specified.

Example 1 In a one-liter four-necked flask, 585 g of methanol, 275 g of water, 100 g of methyl methacrylate, and γ-propylvinyltrimethoxysilane 3
g, Juliemer AC-30H [polymethacrylic acid 2
After charging 50 g of a 0% aqueous solution (manufactured by Nippon Pure Chemical Co., Ltd.) and 2 g of V-59 [polymerization initiator manufactured by Wako Pure Chemical Industries, Ltd.], the internal temperature was raised to 65 ° C. under stirring, and Hold at temperature for 6 hours. The obtained contents were filtered and washed to obtain silanol group-containing resin particles. The obtained resin particles have an average particle size of about 2 μm.
m of monodispersed particles. 100 g of the obtained monodispersed particles
Into a 1 liter flask, into which methanol 75
g, 25 g of water, 1 g of γ-mercaptopropyltrimethoxysilane, and 5 g of 25% aqueous ammonia, and dispersed well using ultrasonic vibration at a liquid temperature of 30 ° C. for 2 hours. 100 g of the particles obtained by filtration are mixed with 400 g of water and 5 g of glucose.
Was dissolved in an aqueous solution. Next, an aqueous solution comprising 240 g of water, 60 g of silver nitrate, 240 g of a 25% aqueous NaOH solution, and 200 g of 25% aqueous ammonia was added to the aqueous solution containing the resin particles treated with the silane compound under ultrasonic dispersion. After continuing stirring at room temperature for 2 hours, the contents were filtered and washed to obtain silver-coated resin particles.

Comparative Example: Resin particles were prepared in the same manner as in Example 1 except that γ-mercaptopropyltrimethoxysilane was not used, but silver fine particles were scattered on the particle surface. In this state, uniform silver-coated particles were not obtained.

[0023]

The metal-coated resin particles obtained by the method of the present invention are characterized in that silanol group-containing resin particles obtained by copolymerizing a vinyl polymerizable functional group-containing alkoxysilane and a vinyl monomer are used as nuclei. Through the treatment process using the group-containing alkoxysilane, a metal layer having a continuous and uniform thickness is formed on the surface of the resin particles, and the metal layer is not detached.

Claims (2)

[Claims] 1. A silanol obtained by copolymerizing a vinyl polymerizable functional group-containing alkoxysilane and a vinyl monomer mixture selected from (meth) acrylate monomers and other copolymerizable monomers. Group-containing resin particles,
Immerse in a solution containing a mercapto group-containing silane compound,
Then, the resin particles are brought into contact with a solution of a silver compound to adsorb silver ions and then reduced to form a silver layer on the surface of the resin particles. 2. The alkoxysilane having a vinyl polymerizable functional group has one silicon atom, three hydrolyzable groups bonded to the silicon atom, and one radical polymerizable group bonded to the silicon atom. The method for producing silver-coated resin particles according to claim 1, wherein the compound is γ-propylvinyltrimethoxysilane, and the silane compound containing a mercapto group is γ-mercaptopropyltrimethoxysilane.