JPH06254380A - Composite microballoon - Google Patents

Abstract

PURPOSE:To provide composite microballoons which are not broken when dispersed in a resin, reduce the weight of the resin and improve the heat retaining property and strength of the resin. CONSTITUTION:Each of inorg. microballoons is coated with a coating film made of an aggregate of a fine particle-shaped org. polymer with inorg. fine particles carried on the surface. The inorg. fine particles are stuck to the coating film and the composite microballoons are obtd.

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, these microballoons are difficult to disperse in a resin or the like, and even if they are dispersed, they are easily broken by a slight shearing force at the time of dispersion,
Further, it has a drawback that it is easily melted 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. On the other hand, in recent years, artificial microballoons made of ceramic having excellent mechanical strength have been manufactured, but they are extremely expensive.

[0004]

The conventional microballoons are difficult to disperse in a resin or the like, and even if they are dispersed, they easily break or melt when heated or when heated. This is the problem to be solved. Is.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that inexpensive microballoons made of an inorganic substance that are easily broken and have a weak binding force to a resin or the like have inorganic fine particles on the surface thereof. The inventors have found that the above problems can be solved by coating with a film of an aggregate of supported fine particle organic polymers, and further by adhering inorganic particles to the film, 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 Supported on the Surface of Fine Particle Organic Polymer The inorganic fine particles supported on the surface of the fine particle organic polymer used in the present invention preferably have a particle size of 50 nm or less, and are ultrafine particles. A colloidal form in which a powdery powder is dispersed in water is more preferable because it can be easily carried on the surface of the finely divided organic polymer whose surface has been modified. Examples of such inorganic fine particles include colloidal silica, alumina sol, zirconia sol, antimony oxide sol, tin oxide sol, silica having a diameter of 50 nm or less, or alumina powder.

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) Inorganic fine particles to be adhered to the fine particle organic polymer film The inorganic fine particles used here may be the same as or different from the inorganic fine particles carried on the surface of the fine particle organic polymer. Since it is not necessary to support the organic polymer in the form of fine particles, it is possible to use an inexpensive one having a relatively large particle size. The amount of inorganic microballoon 100 used
1 to 100 parts by weight is preferable with respect to parts by weight. If the amount is less than 1 part by weight, the effect of the present invention is not sufficiently exerted, while 10
If the amount exceeds 0 parts by weight, the surface will not be a dense film, which is not preferable.

(5) Method for coating microballoon Agglomerating agent for agglomerating the particulate organic polymer, such as aluminum sulfate, aluminum lactate, methyl cellulose, polyoxyethylene / oxypropylene glycol monoether, etc., particularly preferably positively charged. In the dispersion of alumina sol, add inorganic microballoons,
Subsequently, under high agitation, an emulsion of an organic polymer carrying inorganic fine particles on the surface is added little by little, and the gelled film is formed by aggregation on the surface of the inorganic microballoons.

For 100 parts by weight of inorganic microballoons, 1 part of the organic polymer carrying the inorganic fine particles on the surface is used.
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.

Subsequent to the above step, inorganic fine particles are added to the system and stirred in the same manner, whereby the inorganic fine particles can be attached to the gel-like film.

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

[0023]

The composite microballoon of the present invention is easy to disperse in a resin or the like, 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 that the surface of the composite micro-balloon is a dense film of inorganic fine particles, and the surface of the inorganic micro-balloon, a fine particulate organic polymer, inorganic fine particles supported on the organic polymer and It is presumed that the above characteristics are exhibited by the interaction of the inorganic fine particles attached to the film of the fine particle organic polymer.

[0024]

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 obtained 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. .

(Supporting of Inorganic Fine Particles) 1100 g of an organic polymer emulsion having silanol groups 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 nm and a length of 40-300 nm. Nissan Chemical Industries, Ltd.) 95
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 Shirasu microballoon) Shirasu microballoon which is a volcanic glass balloon (average particle diameter of 23 μm, whose main component is 75.8% by weight of silica and 12.7% by weight of alumina), Specific gravity 1.0g
/ Cm ³ , Showa Chemical Industry Co., Ltd. Super Balloon # 3
00) 230 g, alumina sol 200 (positively charged alumina sol having a particle size of 30 to 100 μm, concentration 10% by weight, manufactured by Nissan Chemical Industries, Ltd.) 80 g, and 8 liters of pure water were charged into a stainless steel container having an internal volume of 12 liters,
A propeller-type stirring blade was stirred for 10 minutes at 400 rpm to obtain a dispersion liquid.

(Preparation of composite microballoon) While stirring with a propeller-type stirring blade at 400 rpm for 10 minutes, the total amount of the preparation liquid of the organic polymer carrying the above-mentioned inorganic fine particles in the above-mentioned microballoon dispersion liquid was gradually added over 1 hour. Was added to. Further, as inorganic fine particles, kaolin (average particle size of 0.
3 μm, true specific gravity 2.58 g / cm ³ , Kanaya Kosan (present)
(Manufactured by ASP-072) (57 g) was added and stirring was continued for 30 minutes.

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.
A fine powdery composite microballoon having an average of 68% by weight of a composite coating consisting of a butadiene copolymer, silica, alumina and kaolin was obtained at 5 μm.

(Evaluation of Properties of Composite Microballoon) The composite microballoon obtained above was stably dispersed in acetone without swelling or aggregation even after 30 days at room temperature.

Powdered vinyl chloride resin (average degree of polymerization 130
0, average particle size 100 μm, manufactured by Toagosei Chemical Industry Co., Ltd.
TS-1300) 100% by weight, and compounded with 20% by weight of the composite micro-balloon, 19.5 rpm and 2
Put on a 6 inch roll under 0 rpm differential rotation,
After kneading at room temperature for 5 minutes until just before the vinyl chloride resin gelled due to frictional heat, the particle structure of the composite microballoon was taken with a scanning electron micrograph at 500 times. As a result, the composite microballoons obtained in this example were hardly broken.

Comparative Example 1 Shirasu microballoons used in this example were blended into a powdery vinyl chloride resin under the same conditions as in Example 1 and kneaded with a roll. When a scanning electron micrograph of the microballoon was taken at a magnification of 500 times,
Most were destroyed.

[0033]

INDUSTRIAL APPLICABILITY The composite microballoon of the present invention is excellent in dispersibility in a resin, is not easily broken even when subjected to a large shearing force, and has large heat resistance and is inexpensive. 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 (magnification: 500) of the particle structure of a composite microballoon after roll-kneading with a vinyl chloride resin in Example 1.

FIG. 2 is a graph showing the particle structure of Shirasu microballoon 500 after roll-kneading with a vinyl chloride resin in Comparative Example 1.
It is a scanning electron micrograph at a magnification of 2.

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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 carried on its surface, and further adhering the inorganic particles to the film.