JPH02292305A - Production of polymer-coated inorganic filler particle - Google Patents

Abstract

PURPOSE:To obtain an inorganic filler particle uniformly surface-coated with a polymer by performing the aqueous emulsion polymerization of an ethylenically unsaturated monomer in the presence of a specified colloidally dispersed inorganic filler powder. CONSTITUTION:Emulsion polymerization of a radical-emulsion-polymerizable, at least monoethylenically unsaturated monomer under agitation in water in the presence of an emulsifier and a radical initiator is performed in the presence of a colloidal dispersion of a fine inorganic filler powder which is colloidally dispersible in water and has a charge opposite to that of the emulsion polymer formed. After excess water is remove, if desirable, from the polymerization system after the polymerization, fine filler powders each of which is surface- coated with an emulsion polymer is obtained in a slurry or pasty form. If required, this slurry or paste is dehydrated and dried to obtain separate polymer- coated particles.

Description

[Detailed Description of the Invention] The present invention relates to a method for producing an inorganic filler coated with a polymer, and more specifically, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer, and more particularly, the present invention relates to a method for producing an inorganic filler coated with a polymer. An inorganic filler with a charge opposite to ms
Production of inorganic filler particles coated with an emulsion polymer consisting of radical emulsion polymerization of a radically polymerizable monomer having at least one ethylenically unsaturated bond in the molecule in water in the presence of a polymer. Regarding the law. These polymer-coated inorganic filler particles are particularly useful as a slurry or paste in the production of inorganic filler-containing foamed polymers, and in the dry state can be used as a molding material for compression molding, etc., or as a reinforcing material for other resins. Ru. Ryogogo and 1 As a method of coating fine inorganic fillers with a polymer, the method disclosed in JP-A-61-16936 is known. That is, in this Japanese Patent Application Laid-Open No. 61-16'136,
Aspect ratio 5-10 as filler for reinforcing thermoplastic resin
Modify the surface properties (hydrophilicity) of mineral fibers of 0 to hydrophobicity,
Disclosed is a method of suspension polymerizing such mineral fibers in order to improve their affinity with a thermoplastic resin as a matrix resin. According to the description in this publication, in the suspension polymerization, the vinyl monomer is graft-polymerized onto the surface of the mineral fiber, and as the polymerization progresses, the fiber surface is finally coated with the vinyl polymer. Therefore, this method can be said to be a method for coating animal fibers with fine inorganic material t by a simple method of graft polymerization of a vinyl monomer. The present invention is based on a physical mechanism, more specifically, based on electrical interaction, which is different from the scientific means described in Japanese Patent Application Laid-Open No. 31-16'll36. It is an object of the present invention to provide a novel method for coating an inorganic material with a polymer with a small amount of atom, which can cover the surface uniformly.According to the present invention, radicals 1, (P, A method of emulsion polymerizing a monomer having at least 1f[!] of ethylenically unsaturated bonds in its polymerizable molecule in water in the presence of an emulsifier and a radical initiator, in which the emulsion polymerization can be colloidally dispersed in water. and in the presence of a colloidal dispersion of inorganic filler fine powder having a charge opposite to that of the emulsion polymer to be produced, and after the polymerization, excess water is removed from the polymerization system or not, and the surface is characterized by obtaining clear inorganic filler fine powder particles coated with an emulsion polymer in the form of a slurry or paste, and optionally dehydrating and drying the slurry or paste to obtain individually separated polymer-coated particles. A method for producing polymer-coated inorganic filler particles is provided.In the present invention, the monomer to be subjected to polymerization has at least one monomer in the molecule that can be polymerized with a radical initiator. Typical examples of such monomers are vinyl monomers, including, for example, ethylene, propylene, vinyl chloride, etc. , vinyl bromide, vinylidene chloride, vinyl acetate, acrylonitrile, styrene, α-methylstyrene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, acrylamide, N~methylolacrylamide, 4-vinylpyridine, N-vinylpyrrolidone etc. Also,
Coincident diene monomers are also one of the typical monomers that can be used in the emulsion polymerization of the present invention. Examples of diene monomers include butadiene, isoprene, chloroprene, and biverylene. These monomers may be used alone in the method of the present invention, or two or more monomers may be used and copolymerized. In the polymerization according to the present invention, the concentration of monomers that can be used in the polymerization system is within the concentration range used in ordinary emulsion polymerization.
Generally, concentrations of about 5-80% are used. During polymerization, the monomers are milked in water at a predetermined concentration using an emulsifier. Regular milk preparations can be used. Examples of emulsifiers commonly used in the method of the present invention include anionic surfactants such as sodium lauryl sulfate and sodium alkylbenzene sulfonate, alkylammonium halides such as dodecyltrimethylammonium furomide, and There are cationic surfactants such as cetyltrimethylammonium bromide and nonionic surfactants such as polyoxydiethylene alkyl ether. Such emulsifiers are generally used in amounts ranging from about 0.01 to 2% by weight based on the aqueous medium, but may be more or less than that, as long as it is possible and as long as it is not harmful. The aqueous monomer emulsion of a predetermined concentration prepared as described above is then mixed with an inorganic filler. In the present invention, the filler mixed with the aqueous monomer emulsion is a fine powder of an inorganic filler that has a charge opposite to that of the polymer formed in the aqueous emulsion and is colloidally dispersible in water. Here, the term "inorganic filler that has a charge opposite to that of its polymer in an aqueous emulsion" refers to not only one that itself is charged in an aqueous medium, but also one that does not have a charge in an aqueous medium as it is. However, by treating the dispersion in water in an appropriate manner, it is possible to form, for example, acids, bases or salts, such as AICI3,
Fe 2 (Son > 3 or Ce(N O
3) It also includes those that can be charged by adding a salt such as 3.6H20. The typical and presently most preferred inorganic filler used in the present invention is a hydrous aluminosilicate clay mineral. Examples of hydrated aluminosilicate clay minerals include sericites, karyonites, octosites,
There are bentonites and ololites, and sericites and oleolinites are preferred, with sericite being especially preferred. In addition to these hydrated aluminosilicate clay minerals, various inorganic mineral materials can be used as long as they satisfy the above conditions, such as red red iron and whitebait. These inorganic fillers generally have the property of being well wetted by water, and therefore their fine powders are well dispersed in the aqueous medium, facilitating the achievement of a colloidal state. In the present invention, the inorganic filler is used after being ground to a particle size that allows it to be colloidally dispersed in an aqueous emulsion. The particle size is most suitable for the purpose of the present invention if it is on the order of submicrons or microns, but it is also possible to use a larger particle size if colloidal dispersion is possible. Such filler fine powder can be easily produced using a conventional pulverizer and can be used for classification. The aqueous monomer emulsion and the above inorganic filler fine powder can be mixed by adding the inorganic filler fine powder or its aqueous dispersion to the aqueous monomer emulsion and stirring, or conversely, by adding the inorganic filler fine powder or its water dispersion to the aqueous monomer emulsion, or by stirring the inorganic filler fine powder or its water dispersion. By adding the aqueous monomer emulsion to the dispersion and stirring,
Alternatively, it can be easily achieved by adding monomers and emulsifiers to an aqueous dispersion of fine inorganic powder and stirring. When an aqueous dispersion of fine filler powder is used for mixing, the filler concentration is preferably selected within a range such that the aqueous dispersion forms a suspension, and usually a concentration of about 5 to 80% by weight is used. However, the filler concentration itself is not a particularly important factor, and even if the filler is not uniformly suspended, it can be dispersed by stirring appropriately, and in this state, the filler can be maintained in its dispersed state under stirring. The monomer emulsion can be added to the monomer emulsion, or conversely, the monomer and emulsifier, or a preformed monomer emulsion, can be added to the aqueous dispersion. The concentration of the inorganic filler in the aqueous monomer emulsion subjected to polymerization is basically such that its dispersed state can be maintained under stirring polymerization conditions. This depends on the desired amount of polymer coating on the fine powder particles of the inorganic filler, the ease of stirring during polymerization, etc. Filler concentrations commonly used are about 5-80%, preferably about 10-60% by weight based on the weight of the mixed system. The inorganic filler-containing aqueous monomer emulsion obtained as described above is then subjected to a polymerization reaction after a radical initiator is added thereto. As the radical initiator, those commonly used in the emulsion polymerization of the unsaturated monomers mentioned above can be used.
Typical examples of such initiators are peroxides such as benzoyl peroxide, lauroyl peroxide, t-butylhydroberoxide, cumene hydroperoxide, potassium persulfate,
PerWR salts such as ammonium persulfate and azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylbaretonitrile), and 2,2'-azobis(2-amidinopropane) hydrochloride It is.

Commonly used redox initiators can also be suitably used as radical initiators. Such a dox-based initiator typically includes the above-mentioned peroxide and iron (II
) compounds, chromium ions, or combinations with sulfites, hydroxylamine, etc. These radical initiators are usually used in an amount of about 0.05 to 2.0% by weight based on the monomer.
, more commonly in a proportion of about 0.1 to 1.0% by weight, and most commonly in a proportion of about 0.4 to 0.6% by weight. Polymerization can be carried out at a temperature range above room temperature and below 100°C, that is, below the boiling point of water. The polymerization temperature naturally depends on the type of monomer. Usually a temperature in the range of about 30 to 70°C is employed. Since this radical polymerization is generally an exothermic reaction, the temperature should be controlled to prevent the reaction from proceeding excessively. Polymerization can be carried out statically on a laboratory scale, or it is usually carried out under stirring. In stationary polymerization, it is normally observed that after the polymerization reaction has progressed to a certain extent, the inorganic filler coated with the generated polymer settles to the bottom of the polymerization vessel. In polymerization under stirring, the polymer-coated filler particles usually settle when the stirring is stopped after the polymerization reaction is complete. The completion of the polymerization reaction can be determined by confirming that even if the temperature of the external heating system is increased, the temperature of the polymerization system no longer exceeds the temperature of the external heating system, and that no reaction heat is generated. In the case of the above-mentioned exemplified monomers, the polymerization reaction is generally completed in approximately several hours to several tens of hours. Polymers or copolymers of the monomers generally have a positive or negative charge in water. It is known that the terminal charge of the polymer molecular chain caused by a radical initiator or the polarization of polar groups in the polymer molecular chain contribute to the charge of this polymer or copolymer. As is well known, this charge is also affected by the emulsifier used. The electrical charge of such polymers or copolymers in water can be determined by measuring the so-called sweater potential.

Therefore, preliminary experiments were conducted to determine whether the monomers subjected to polymerization would produce polymers with positive or negative charges through emulsion polymerization, and what charge state the filler fine powder would take in water containing the same emulsifier. If you check in advance, you can easily know which filler to combine with a certain monomer. According to the present invention, the inorganic filler fine powder is coated with the produced polymer by the above-mentioned emulsion polymerization.

In this way, the filler particles are coated with the polymer R
The ellipse is a cm ellipse in which growing polymer radicals, which are oppositely charged on the filler particle surface, are captured by electrostatic attraction and polymerization proceeds on the filler particle surface. It is conceivable that both particles cause agglomeration between particles due to electrical interaction. In the present invention, it has not been confirmed which of the above mechanisms achieves the production of polymer-coated filler particles, or whether either of the two mechanisms is dominant, but in any case, the formation of polymer-coated filler particles is not confirmed. If the charging state specified by It seems certain that the coating of the filler particles with the filler particles is due to the electrical interaction between the two.

Coating of inorganic fillers with such polymers is not satisfactorily achieved by suspension polymerization.

This is thought to be because the particle size of the resulting polymer in suspension polymerization is too large to uniformly and densely cover the colloidal particles of the filler. When stirring is stopped after emulsion polymerization is completed, the resulting polymer-coated inorganic filler generally settles to the bottom of the polymerization vessel.

The precipitated polymer-coated inorganic filler can be obtained in the form of a slurry or paste by removing excess water from the polymerization vessel, for example, by centrifugation or simple decantation. However, depending on the filler concentration and polymer concentration, the polymer may remain in the form of a slurry at the end of polymerization.

The aqueous slurry or paste made of the polymer-coated inorganic filler particles of the present invention thus obtained may be further dehydrated, or without dehydration, or conversely, if it is too thick for the purpose of use, it may be hydrated. It can be put to use. The most important use of such slurries or pastes is the production of inorganic filler-containing resin foams by ejecting such slurries or pastes from a sealed container under heat and pressure into a low temperature, low pressure environment.

The polymer-coated inorganic filler particles formed by the method of the present invention described above can be obtained by removing water from the slurry or paste, applying vacuum, e.g. It can be converted into coalesced coated filler particles. This means that the polymer particles and filler particles do not simply exist in a mixed state in the slurry or paste, but that the filler particles are coated with the polymer and the coated filler particles are present in the slurry or paste. This means that it is dispersed in The coating layer of coated filler particles formed in this way is very uniform. This can be seen from the fact that the filler is very finely and uniformly distributed in the resin foam produced from the slurry or paste formed by the method outlined above. This has also been confirmed by microscopic photographs. As can be seen from the above explanation, according to the present invention, polymer-coated inorganic filler particles whose surfaces are uniformly coated with a polymer are prepared by a very simple method of emulsion polymerization in the presence of fine inorganic filler powder, and then the polymer-coated inorganic filler particles are processed into slurry or paste. It can be manufactured as The slurry or paste is particularly useful as a raw material for producing filler-containing resin foams, and the polymer-coated filler particles obtained by dehydrating and drying this slurry or paste can be used as fillers for blending and reinforcing matrix resins. Alternatively, it can be used as a raw material for compression molding, etc. The present invention has been described in detail above. Next, the present invention will be specifically described with reference to Examples. However, these Examples merely illustrate the present invention, and the present invention is not limited by these Examples. 100 g of sericite with a micron-sized particle size (produced by Kosaka Mine, trade name Microclean) in a 1 fJ four-necked round-bottomed flask equipped with a mercury jet stirrer, a thermometer, a pH 1 lobe, and a nitrogen gas blowing tube. , add 500 g of water which has been deoxygenated by boiling it while blowing nitrogen gas and cooling it, and boil it to about 30 O ra.
The sericite was dispersed in the water by stirring at n. The pH of the sericite dispersion was approximately 4. To this sericite dispersion, 100 g of styrene and 0.5 g of sodium lauryl sulfate were added.
g was added and stirred vigorously while blowing nitrogen gas to form a styrene water emulsion containing dispersed sericite fine powder. 1 g of potassium pervRate was added to the obtained styrene-water emulsion, the flask was sealed with mercury, and then the flask was heated to 80° C. in a hot bath and polymerized with stirring under a nitrogen atmosphere. When a small sample was taken after 3 hours of polymerization and examined using a scanning electron microscope as described below, it was observed that the filler particles were already uniformly coated with the polymer. Polymerization was carried out for a total of 5 hours. The polymerization rate at that time was approximately 95%. After polymerization, some water was removed from the polymerization mixture by centrifugation to obtain a homogeneous paste. This vest was useful in the production of foams that are ejected from high temperature, high pressure conditions into low temperature, low pressure environments. A small sample was taken from the above paste, thoroughly suctioned, dehydrated, and vacuum dried at f&80°C for 5 hours to obtain individually separated sericite particles whose surfaces were coated with boristyrene (Ps). This P
20 by scanning electron microscopy from s-coated sericite particles.
When a photograph was taken at a magnification of 1,000 times, it was observed that the entire surface of the sericite particles was uniformly coated with Ps along its complex unevenness and layered structure. I was added to the sericite aqueous dispersion prepared in the same manner as in Example 1.
After dropping an aqueous N-NaOH solution until the pH of the dispersion became 6 to 7, styrene, sodium lauryl sulfate and potassium persulfate were added in the same manner as in Example 1, and polymerization was carried out at 80°C. When stirring was stopped after 5 hours of polymerization, sericite particles were observed to settle, so 2 g of hydroquinone as a polymerization inhibitor was added to the polymerization system to stop the polymerization reaction. After stopping the polymerization, when the mixture was allowed to stand still, sericite particles were found to settle in the lower layer, and boristyrene was observed to exist as latex in the aqueous phase. The precipitated sericite was taken out, dehydrated, dried, and observed using a scanning electron microscope (SEM), but the presence of a boristyrene layer on the surface of the sericite particles was not substantially observed. Is this because the addition of alkali to the sericite aqueous dispersion causes sericite to lose its surface charge and electrically interact with boristyrene? This seems to be because it is no longer possible.辷l1Iλ The initiator of Example 1, potassium perkate, was added to the same amount of 2.2'-
Polymerization was carried out in the same manner as in Example 1 except that azobis(2-amidinopropane) hydrochloride was used. After polymerization, a polymerization sample was collected, dehydrated and dried in the same manner as in Example 1, and then treated with S
When observed by EM, it was observed that the material was uniformly coated with seriside or Ps. Polymerization was carried out in the same manner as in Example 1, except that the emulsifier of Example 1, sodium lauryl sulfate, was replaced with the same amount of sodium alkylbenzenesulfonate. After heating, a polymerized sample was collected, dehydrated and dried in the same manner as in Example 1, and then observed by SEM. It was observed that the sample was uniformly coated with cericide or Ps. Polymerization was carried out in the same manner as in Example 1, except that 100 g of styrene in Example 1 was replaced with 100 g of a 50/'50 mol% mixture of styrene and acrylic acid. After polymerization, a polymerized sample was collected, dehydrated and dried in the same manner as in Example 1. S
Observation by EM revealed that sericite was uniformly coated with styrene 7' acrylic acid copolymer. Arashi 1 100 g of the styrene of Example 1 was mixed with 100 g of a mixture of 50 y'50 mol% of styrene and methyl methacrylate.
Polymerization was carried out in the same manner as in Example 1, except that g was replaced. After polymerization, a polymerized sample was collected and dehydrated in the same manner as in Example 1.
After drying, SEM observation revealed that the sericite was uniformly coated with styrene and methyl methacrylate copolymer. Methyl methacrylate was emulsified in an aqueous sericite dispersion prepared in the same manner as in Example 1 at a concentration of 0.5 mol/AH20. The emulsifier was dodecyltrimethylammonium bromide, used at a concentration of 1 x 10-4 mol/1·H2o. 2,2'-azobis(2-
5. amidinopropane) hydrochloride. OX10” 3 mol, /
jH20 concentration and stirred under nitrogen atmosphere for 6 hours.
Polymerization was carried out at 0°C for 6 hours. The polymerization rate was about 85%. After polymerization, when stirring is stopped, polymethyl methacrylate (I-
The sericite coated with lMMA) spontaneously precipitated. When the supernatant is removed by decantation, P M M
A-coated sericite particles were obtained in the form of a slurry or paste. A small amount of the sample was sufficiently suctioned and dehydrated, and then dried at 80°C for 5 hours to obtain finely separated sericite particles whose surfaces were coated with PMMA. This PM
2 from MA-coated sericite particles by scanning electron microscopy.
When a photograph was taken at 0,000x magnification, it was observed that the entire surface of the sericite particles was uniformly coated with PMMA along its complex unevenness and layered structure. 160 g of acrylonitrile and 4 ml of sodium lauryl sulfate were added to a sericite aqueous dispersion prepared in the same manner as in Example 1.
g was added and stirred to form an emulsion. To the resulting emulsion was added 0.2 g of potassium persulfate and 0.2 g of sodium bisulfite. eg was added, and polymerization was carried out at 35°C for 8 hours with stirring under a nitrogen atmosphere. The polymerization rate is essentially 10
It was 0%. After polymerization, when stirring is stopped, polyacrylonitrile (PAN
) coated with sericite or naturally precipitated. When the supernatant was removed by decantation, PAN-coated sericite particles were obtained in the form of a slurry or paste. A small amount of the sample was thoroughly aspirated and dehydrated in the same manner as in Example 1, and then dried under vacuum to obtain clearly separated resin-coated sericite whose entire surface was uniformly coated with PAN. K-tane ■1 200 g of vinyl acetate and 6 g of sodium lauryl sulfate were added to an aqueous sericite dispersion prepared in the same manner as in Example 1, and stirred to form an emulsion. ? 0.5 g of benzoyl peroxide in a fresh emulsion. [Add 1.4 g of ferrous acid hexahydrate and 6,0 g of sodium pyrophosphate,
Polymerization was carried out at 40°C for 4 hours with stirring under a nitrogen atmosphere.

Claims (1)

[Claims] A method in which a monomer capable of radical emulsion polymerization and having at least one ethylenically unsaturated bond in the molecule is subjected to emulsion polymerization in water while stirring in the presence of an emulsifier and a radical initiator, wherein the emulsion polymerization is carried out in water. The polymerization is carried out in the presence of a colloidally dispersed inorganic filler fine powder which is colloidally dispersible and has a charge opposite to that of the emulsion polymer to be formed, and after the polymerization, excess water is removed or removed from the polymerization system. The surface of each inorganic filler fine powder particle is coated with an emulsion polymer and then obtained in the form of a slurry or paste, and if necessary, the slurry or paste is dehydrated and dried to separate individual polymer-coated particles. 1. A method for producing polymer-coated inorganic filler particles, characterized by obtaining