JPH0788354A - Composite microballoon - Google Patents

Abstract

PURPOSE:To easily disperse inorg. microballoons in resin, to make them lightweight and to improve the heat retaining property and strength by coating the microballoon with a film of fine-grain org. polymer carrying an inorg. fine grain on the surface. CONSTITUTION:An inorg. microballoon is added into a dispersion of a coagulant to coagulate a fine-grain org. polymer, especially of an inorg. sol such as a positively charged alumina sol, then an emulsion of an org. polymer carrying an inorg. fine grain on the surface is added in small amts. under strong agitation, and the polymer is coagulated on the surface of the microballoon to form a gel-like film. The film is densified by drying such a slurry dispersion in a spray drier, and a fine-powder composite microballoon is obtained. The microballoon is not easily broken even with a high shearing force, and the heat resistance is improved. Consequently, the microballoon is mixed in paint or adhesive to make it lightweight and to improve the heat retaining property and strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microballoon having a composite film made of an inorganic substance and an organic polymer. The microballoon of the present invention is a resin or a mixture of a resin and an inorganic substance (hereinafter, simply referred to as an admixture. It can be easily dispersed in the resin, etc.) to reduce the weight thereof and improve the heat retention and strength.

[0002]

2. Description of the Related Art Microballoons, also called microhollow spheres, are composed mainly of glass or natural glassy materials or organic polymers, and contain microbubbles generated from components that are foamed by heating, or have characteristics of raw materials. Can be obtained by incorporating fine bubbles.

However, even if these microballoons are dispersed in a resin or the like, they have a drawback that they are easily broken by a slight shearing force at the time of dispersion and are easily deformed by heating. Therefore, even if these microballoons are dispersed in a resin or the like, it is not possible to contribute to the weight reduction and the heat retention or strength of the obtained composition.

[0004]

The conventional microballoons are easily deformed or destroyed when dispersed in resin or by heating, and this is a problem to be solved.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems, and as a result, formed a microballoon made of an inorganic substance with a film formed by an aggregate of finely divided organic polymers carrying inorganic fine particles on the surface. By coating
The inventors have found that the above problems can be solved and completed the present invention.

The elements of the composite microballoon of the present invention are described below. (1) Inorganic Micro Balloons There are natural and synthetic micro balloons, but glass micro balloons are preferable because they are inexpensive and versatile. Examples of inorganic microballoons include natural shirasu balloons, borosilicate glass microballoons containing sodium borate and sodium silicate as main components, glass microballoons containing sodium silicate as main components, and silica and alumina. Examples include ceramic microballoons, which are the main components. Of these, microballoons containing silica as a main component, which are obtained by a wet method or a dry method, are preferable because they have high strength and are relatively inexpensive. Further, organic polymer microballoons cannot be used for the purpose of the present invention because they have low heat resistance, solvent resistance or elastic modulus.

The particle size of the inorganic microballoons used in the present invention is preferably in the range of 1 μm to 3 mm because it can be easily obtained commercially. When the composition obtained by blending the composite microballoon of the present invention with a resin is used for a circuit board etc.,
A smaller particle size is preferable because uniform dispersion in the composition is required. The true specific gravity is 0.10 to 1.0 g / cm ³
Is preferred. If it is less than 0.10 g / cm ³ , the microballoon film is too thin and the strength is reduced.
If it exceeds g / cm ³ , the film is too thick and the characteristics of the microballoon are not exhibited, which is not preferable.

(2) Organic Polymer As the organic polymer used in the present invention, conventionally known thermoplastic resins and thermosetting resins can be used, but those which are easily emulsified in water are preferred. Examples of such an organic polymer include acrylonitrile-butadiene rubber, acrylic rubber, styrene-butadiene rubber or ethylene-vinyl acetate rubber; or vinyl chloride resin, vinylidene chloride resin, fluorine resin, silicone polymer or styrene-acryl. Examples thereof include acid copolymers.

The fine particle organic polymer having the fine inorganic particles supported on the surface thereof is obtained by, for example, emulsion-polymerizing the monomers constituting the above organic polymer by a usual method, and the fine inorganic particles on the surface of the fine particle organic polymer. Can be carried to obtain.
At this time, it is preferable that the surface of the fine particle polymer and the inorganic fine particles have a sufficient affinity. For example, in order to support colloidal silica as inorganic fine particles on the surface of the fine particle polymer, it is preferable to modify the surface by allowing silanol groups to be present on the surface of the fine particle polymer.
There are various methods for producing a finely divided organic polymer having a surface modified as described above, but those obtained by the core-shell type emulsion polymerization method have high stability in an emulsified state, and when encapsulated. The film-forming property is good, which is preferable.

In the core-shell type emulsion polymerization method, an emulsion of an organic polymer serving as a core is formed in advance, and then a monomer which is a raw material of a polymer serving as a shell is added to the emulsion to perform copolymerization. You can get it. As a surfactant used for forming an emulsion of an organic polymer serving as a core, an anionic surfactant, particularly a derivative of sodium sulfonate or sodium sulfate can be used to obtain an organic polymer having a large molecular weight. It is possible and preferable. The particle size of the core organic polymer is 0.05
˜1.0 μm is preferable. The organic polymer component serving as the core is 10 to 90 out of the resulting core-shell type polymer.
It is preferably contained by weight%, more preferably 50 to
90% by weight. When it is less than 10% by weight, the characteristics of the organic polymer itself are not sufficiently exhibited when it is formed into a film of microballoons, which is not preferable.

Monomers which are raw materials for the shell polymer include acrylonitrile, methacrylonitrile and N.
-Vinylpyrrolidone or N-vinylcaprolactam;
Used in combination with three components of an alkoxysilane having an acryloxy group, a methacryloxy group or a vinyloxy group; and another monomer having a vinyl group such as styrene, vinyltoluene, methyl (meth) acrylate or ethyl (meth) acrylate. It is preferable that a stable emulsion of polymer particles is easily formed.

Specific examples of the alkoxysilane having an acryloxy group, a methacryloxy group or a vinyloxy group include γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and γ- (meth) acryloxypropyltris. (Trimethylsiloxy) silane, vinyltrimethoxysilane,
Examples thereof include vinyltris (methoxyethoxy) silane and vinyltrichlorosilane.

Another method for producing a surface-modified fine particle organic polymer is to produce an emulsion of an organic polymer, and add a silane coupling agent, titanate coupling agent or aluminum silane coupling agent to the emulsion. There is a method of adding and reacting.

(3) Inorganic Fine Particles The inorganic fine particles used in the present invention preferably have a diameter of 50 mμ or less, and the surface is modified to be a colloidal form in which ultrafine powder is dispersed in water. It is more preferable because it can be easily carried on the surface of the fine particle organic polymer. Examples of such inorganic fine particles include colloidal silica, alumina sol, zirconia sol, antimony oxide sol, tin oxide sol, silica or alumina powder having a diameter of 50 mμ or less.

The method of supporting the inorganic fine particles on the surface of the fine particle organic polymer is, for example, an emulsion of the organic polymer in which the inorganic fine particles are dispersed directly or in an aqueous medium, and the surface is modified as described above. A method of gradually adding it with stirring is preferred. At this time, the system is 40 ~
It is preferable to heat to 60 ° C. because loading is easily performed.

The combined ratio of the organic polymer emulsion and the inorganic fine particles is adjusted according to the properties required for the final composite microballoon film, but it is 2 in the total amount of the organic polymer component and the inorganic component in the emulsion. ~ 98% by weight
Is generally an organic polymer component, preferably 20 to 90% by weight. If it is less than 2% by weight, the performance of the organic polymer in the film does not appear, and if it exceeds 98% by weight, the dispersibility of the particulate organic polymer is deteriorated during the production of the composite microballoons, which is not preferable.

The fact that the inorganic fine particles are carried on the surface of the fine particle organic polymer means that, for example, in the case of an organic polymer having high adhesiveness, a film is formed from an organic polymer emulsion before and after carrying the inorganic fine particles, and It can be confirmed by measuring the presence or absence of a significant decrease in the tackiness of.

(4) Method of coating microballoons An inorganic microballoon is added to a dispersion liquid of an aggregating agent for aggregating the fine particle organic polymer, particularly preferably a positively charged inorganic sol such as alumina sol, and the like. When an emulsion of an organic polymer carrying inorganic fine particles on the surface is added little by little under high agitation, a gel-like film is formed by aggregation on the surface of the inorganic microballoons.

For 100 parts by weight of inorganic microballoons, the number of organic polymers having inorganic fine particles on the surface is 1
A range of 0 to 500 parts by weight is preferable. If it is less than 10 parts by weight, the impact resistance tends to be low, and conversely if it exceeds 500 parts by weight, the thickness of the film increases and the function as a microballoon deteriorates.

When the slurry-like dispersion thus obtained is subjected to a spray dryer, the coating becomes dense and fine powder-like composite microballoons are obtained. At this time, by collecting using a cyclone, the composite microballoons can be classified according to particle size.

[0021]

The composite microballoon of the present invention does not easily break even when subjected to a large shearing force, and has good heat resistance. The reason for this is not clear, but it is presumed that the above-mentioned characteristics are exhibited by the interaction between the surface of the inorganic microballoon, the fine particle organic polymer and the inorganic fine particles carried by the organic polymer.

[0022]

EXAMPLES The present invention will be described in more detail with reference to examples. Example 1 (Synthesis of core-shell type emulsion having silanol group) 1000 cc of pure water and Lebenol WZ (26 of sodium polyoxyethylene alkylphenyl ether sulfate) were placed in a stainless steel autoclave having an internal volume of 2 liters.
Wt% aqueous solution, manufactured by Kao Corporation) 19.2 g, potassium persulfate 2.5 g, tertiary dodecyl mercaptan 1.0 g,
Butyl acrylate 250 g and butadiene 250 g
Was charged with stirring with a propeller type stirring blade at 350 rpm,
The reaction is carried out at 50 ° C for 15 hours, and then Lebenol WZ
19.2 g, potassium persulfate 0.5 g, styrene 60
g, 30 g of acrylonitrile and 10 g of NUC silane monomer A-171 (vinyltrimethoxysilane, manufactured by Nippon Unicar Co., Ltd.) were added, and emulsion polymerization was continued at 70 ° C. for 5 hours.

The resulting emulsion was a styrene / acrylonitrile copolymer having silanol groups in the shell portion, with butyl acrylate / butadiene copolymer rubber particles as the core, and the solid content was 36% by weight. .

(Support of Inorganic Fine Particles) 1100 g of an organic polymer emulsion having a silanol group on the surface was charged into a 2 liter beaker, and a propeller-type stirring blade was used for 20 minutes.
With stirring at 0 rpm, 3 g of 2,4,7,9-tetramethyl-5-decyne-4,7 diol was added as a defoaming agent, and then Snowtex UP (solid content 20% by weight, diameter 5
An aqueous sol of elongated colloidal silica having a length of ˜20 mμ and a length of 40 to 300 μm. NISSAN CHEMICAL INDUSTRIES, LTD.) 38
0 g was gradually added, and stirring was continued at 40 to 45 ° C. for 1 hour to obtain a preparation liquid.

(Preparation of dispersion liquid of borosilicate glass microballoon) Borosilicate glass microballoon (average particle diameter 45 μm, true specific gravity 0.40 g / cm ³ , H-40 manufactured by Fuji Davison Chemical Co., Ltd.) 230 g, alumina sol 2
00 (positively charged alumina sol having a particle size of 30 to 100 mμ, concentration 10% by weight, manufactured by Nissan Chemical Industries, Ltd.) 320
g and 8 liters of pure water were placed in a stainless steel container having an internal volume of 12 liters, and 40 minutes for 10 minutes with a propeller type stirring blade.
The dispersion was obtained by stirring at 0 rpm.

(Synthesis of composite microballoon) While stirring with a propeller-type stirring blade for 10 minutes at 400 rpm, the total amount of the prepared organic polymer prepared by supporting the above-mentioned inorganic fine particles in the above microballoon dispersion was gradually added over 1 hour. Was added to. The obtained slurry-like mixture was passed through a 40-mesh filter cloth to remove coarse particles, and then passed through a disc-type spray dryer to be dried, whereby an average particle diameter of 50 μm was obtained.
Thus, a fine powdery composite microballoon having an average of 68% by weight of a composite coating film of a butadiene copolymer, silica and alumina was obtained. Attached is a 500 × scanning electron micrograph of the particle structure of this composite microballoon.

Example 2 As an inorganic microballoon, a ceramic microballoon (average particle diameter 45 μm, true specific gravity 0.69 g / cm 3) was used.
³ , silica content 59.7% by weight and alumina content 38.3
% By weight, Onoda Cement Co., Ltd. Microcells SL
75) Produced under the same conditions as in Example 1 except that 504 g was used, the average particle size was 47 μm, and a composite film consisting of a butadiene copolymer, silica, and alumina was 50% by weight on average.
A fine powdery composite microballoon having the above was obtained. Attached is a 1000 × scanning electron micrograph of the particle structure of this composite microballoon.

[0028]

INDUSTRIAL APPLICABILITY The composite microballoons of the present invention have excellent dispersibility in resins, are not easily broken even when subjected to a large shearing force, and have high heat resistance. Utilizing the above features, the composite microballoon of the present invention is blended with a paint, an adhesive or a molding material to improve the weight reduction, heat retention and strength thereof.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph (× 500) of the particle structure of the composite microballoon obtained in Example 1.

FIG. 2 is a scanning electron micrograph (× 1000) of the particle structure of the composite microballoon obtained in Example 2.

Claims (1)

[Claims] 1. A composite microballoon obtained by coating an inorganic microballoon with a film made of a particulate organic polymer having inorganic particles supported on the surface thereof.