JP5103723B2 - Method for producing methacrylic resin containing inorganic particles - Google Patents

Description

The present invention relates to a method for producing an inorganic particle-containing methacrylic resin.

Methacrylic resin is excellent in transparency, surface gloss, weather resistance, mechanical properties, etc., so it is widely used in various applications such as lighting equipment, automotive parts, signboards, building materials, display parts, etc., and has excellent surface hardness. As methacrylic resins, inorganic particle-containing methacrylic resins containing fine inorganic particles are also known.

However, the inorganic particle-containing methacrylic resin produced by a conventional method has a problem that transparency is not always sufficient.

Japanese Patent Laid-Open No. 2004-161895

Therefore, the present inventors have intensively studied to develop a method capable of producing an inorganic particle-containing methacrylic resin having both high surface hardness and high transparency, resulting in the present invention.

That is, the present invention provides a monomer (A) mainly composed of methyl methacrylate,
Radical polymerization initiator (B) and inorganic particles (C) having a primary particle size of 1 nm to 100 nm and a ζ potential of −10 mV or more at a hydrogen ion concentration of pH 7
The present invention provides a method for producing an inorganic particle-containing methacrylic resin characterized by emulsion polymerization in water in the presence of

The inorganic particle-containing methacrylic resin produced by the production method of the present invention is excellent not only in surface hardness but also in transparency.

The monomer (A) containing methyl methacrylate as a main component is a monomer containing methyl methacrylate with a content of usually 50% by mass or more, preferably 70% by mass or more, and more preferably 90% or more. Independently, the content may be 100% by mass, and is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and other copolymerizable with methyl methacrylate. The monomer may be included.

The other monomer copolymerizable with methyl methacrylate may be a monofunctional monomer having one double bond capable of radical polymerization in one molecule, or two monomers capable of radical polymerization in one molecule. A polyfunctional monomer having two or more heavy bonds may be used.

Monofunctional monomers copolymerizable with methyl methacrylate include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, benzyl acrylate, cyclohexyl Esters of acrylic acid with aliphatic alcohols, aromatic alcohols or alicyclic alcohols, such as acrylates,

Methacrylic acid and aliphatic alcohol, aromatic alcohol or alicyclic alcohol, such as propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, etc. Ester of

Esters of acrylic acid and hydroxy alcohol, such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, etc.

Esters of methacrylic acid and hydroxy alcohol, such as hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, etc.
Unsaturated acids such as acrylic acid and methacrylic acid,

Styrene monomers such as styrene and α-methylstyrene,
And monofunctional unsaturated monomers such as acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide, and vinyl acetate.

Examples of the polyfunctional unsaturated monomer include allyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1, 6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, tetramethylolmethane tetraacrylate,

Allyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol di Methacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane trimethacrylate, tetramethylolmethane tetramethacrylate,
Examples thereof include divinylbenzene and diallyl phthalate.

Other monomers are used alone or in combination of two or more. Moreover, a part of the monomer (A) containing methyl methacrylate as a main component may be polymerized.

As the radical polymerization initiator (B), water-soluble ones are preferably used. For example, inorganic peroxides such as sodium persulfate, potassium persulfate and ammonium persulfate, azo compounds such as sodium azobiscyanovalerate, 2, 2 Azoamidine compounds such as' -azobis (2-methylpropionamide) hydrochloride, cyclic azoamidine compounds such as 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl)] propane hydrochloride, 2 , 2′-azobis [2-methyl-N- [1,1′-bis (hydroxymethyl) -2-hydroxyethyl] propionamide] and the like, each of which may be used alone or in combination of two or more. Used in combination. Of these, inorganic peroxides can be preferably used.

The amount of the radical polymerization initiator (B) used is usually 0.1 parts by mass or more in terms of being able to quickly polymerize per 100 parts by mass of the monomer, and can suppress rapid heat generation due to polymerization. In terms of economy, it is usually 5 parts by mass or less.

Examples of the inorganic particles (C) include silica, alumina, aluminum hydroxide, titanium oxide and the like, and they can be used alone or in combination of two or more. Silica is preferable in that an inorganic particle-containing methacrylic resin having better transparency can be obtained.

The primary particle diameter of the inorganic particles is 1 nm to 100 nm. If it is less than 1 nm, it is easy to aggregate, and if it exceeds 100 nm, transparency tends to decrease.

The ζ potential of the inorganic particles (C) is −10 mV or more, usually +40 mV or less at a hydrogen ion concentration of pH 7. When the ζ potential is less than −10 mV, the transparency of the resulting inorganic particle-containing methacrylic resin is low.

The amount of the inorganic particles (C) used is usually 5 parts by mass or more in terms of easy surface hardness per 100 parts by mass of the monomer, and the resulting inorganic particle-containing methacrylic resin is heated and melted. In terms of fluidity, the amount is usually 50 parts by mass or less.

When the monomer (A) is emulsion-polymerized, a known additive such as an antioxidant, an ultraviolet absorber, a chain transfer agent, a release agent, a dye, or a pigment may be allowed to coexist.

In order to emulsion-polymerize the monomer (A) having methyl methacrylate as a main component, for example, the monomer (A) is mixed with water together with the radical polymerization initiator (B) and the inorganic particles (C), What is necessary is just to heat to the temperature more than the thermal decomposition temperature of a radical polymerization initiator, stirring. The usage-amount of water is 0.5 mass times-6 mass times normally with respect to the said monomer (A). By stirring, the monomer (A) is uniformly dispersed in water and emulsified, and in this state, polymerization is initiated by the radical polymerization initiator and proceeds.

The radical polymerization initiator (B) may be mixed in its entirety before the polymerization starts, or a part thereof is mixed before the polymerization starts, and after the polymerization starts, the remainder is divided into several times, Or you may add continuously.

In the production method of the present invention, a surfactant may be used, but it is preferable to disperse and polymerize the monomer (A) without using a surfactant.

In the polymerization, it is preferable to remove oxygen in advance. For example, oxygen in water is preferably removed beforehand by bubbling an inert gas such as nitrogen. Furthermore, it is preferable to polymerize in an inert gas atmosphere.

The heating temperature is usually in the range of 50 ° C. to 90 ° C., and the time required for the polymerization is usually in the range of 1 to 10 hours.

After the polymerization, the temperature may be raised to about 90 ° C. to 120 ° C. for the purpose of completing the polymerization of the unpolymerized monomer (A).

Thus, a monomer mainly composed of methyl methacrylate is polymerized to form a methacrylic resin, and a desired inorganic particle-containing methacrylic resin containing inorganic particles (D) can be obtained in a latex form.

The target inorganic particle-containing methacrylic resin can be obtained as a solid content from the polymerization mixture after polymerization by a solid-liquid separation method such as a centrifugal separation method or a drying method.

In solid-liquid separation, it is preferable to add a salting-out agent to the polymerized mixture after polymerization to salt out the solid content. As the salting-out agent, a method of adding a polyelectrolyte can be preferably used. The addition amount of the salting-out agent may be an amount sufficient to neutralize the charge of the surfactant to be used, but is usually selected appropriately in view of the state of the aggregated particles after the salting-out.

When salting out the solid content, the temperature at which the salting-out agent is added is usually less than 80 ° C. After the addition, it is possible to increase the temperature to 80 ° C. or more, usually 120 ° C. or less. The containing methacrylic resin can be obtained as a solid content, which is preferable.

The obtained inorganic particle-containing methacrylic resin is useful as a molding material. For example, a molded article having a desired shape can be obtained by a normal thermoplastic resin molding method such as a compression molding method, an extrusion molding method, or an injection molding method. Can be processed.

The molding conditions are appropriately selected depending on the molding method, but are usually molded at a temperature not lower than the melting temperature of the inorganic particle-containing methacrylic resin and not higher than the thermal decomposition temperature, specifically in the range of 180 ° C to 300 ° C. If it exceeds 300 ° C, it may be yellow or brown due to thermal decomposition.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example.

The obtained inorganic particle-containing methacrylic resin was evaluated by the following method.
(1) Surface hardness It calculated | required as pencil hardness based on JIS-D0202.
(2) Transparency Based on JIS-K7361, the total light transmittance and haze were determined by a haze meter and used as a transparency index.
(3) Inorganic particle content The inorganic particle-containing methacrylic resin having an initial mass (A) is heated from room temperature to 500 ° C. by a TGA (thermogravimetric analyzer) at a rate of temperature increase of 20 ° C./min. The mass (B) of the residue was determined and the formula (3)
Inorganic particle content (%) = B / A × 100 (%) (3)
Calculated by
(4) Primary particle diameter The primary particle diameter was determined by a dynamic light scattering method using a particle size measuring device “N4” manufactured by Coulter, USA.
(5) ζ-potential inorganic particles are dispersed in a 0.01 N potassium chloride buffer solution, and hydrochloric acid or potassium hydroxide is added to adjust the hydrogen ion concentration to pH 7.0. The ζ potential was measured using a Coulter DELSA 440SX (Coulter).

Example 1
A dispersion of 240 g of methyl methacrylate and silica particles (primary particle size of 76 nm) dispersed in water in a 2 L separable flask equipped with a cooling tube, stirring blade, nitrogen introducing tube, dropping funnel and thermometer [“Snowtex AK ”, Nissan Chemical Industries, Ltd., silica content 17.7 mass%, ζ potential at hydrogen ion concentration pH 7 was 34 mV], 136 g (silica content was 24 g) and 1064 g of pure water were added and stirred at 200 rpm. While continuing the stirring, nitrogen gas was circulated below the liquid level from the nitrogen introduction tube, and nitrogen substitution was performed by bubbling for 15 minutes. Thereafter, the temperature of the flask contents was raised by immersing the separable flask in the oil bath and raising the temperature of the oil while pulling up the nitrogen introduction tube from the liquid level and continuing to flow through the gas phase portion. When the internal temperature reached 70 ° C., an aqueous solution in which 0.96 g of sodium persulfate (polymerization initiator) was dissolved in 60 ml of pure water was added from the dropping funnel. The internal temperature was raised to 83 ° C. while stirring was continued, and a polymerization reaction was carried out for 1 hour. Thereafter, the internal temperature was raised to 98 ° C., held for 30 minutes, and cooled to room temperature to obtain a latex.

The latex was salted out by adding a sulfuric acid band as a salting-out agent, filtered, washed and dried to obtain a powdered inorganic particle-containing methacrylic resin.

The inorganic particle-containing methacrylic resin obtained above was placed in a mold having a length of 15 cm, a width of 15 cm, and a depth of 2 mm, pressed at 200 ° C., and then cooled to obtain a flat molded product. The resulting molded product had a pencil hardness of 5H, a total light transmittance of 85.2%, a haze of 6.9%, and an inorganic content of 11.9%.

Example 2
Calcium carbonate was added to a dispersion (“Snowtex O”, manufactured by Nissan Chemical Industries, Ltd., silica content 20 mass%) in which silica particles (primary particle size 13 nm) were dispersed in water. The primary particle diameter of the silica particles in the dispersion after the addition was 22 nm, and the ζ potential was −5 mV. The amount added was 0.2 g per 100 parts by mass of silica in the dispersion.
Instead of the dispersion [Snowtex AK] used in Example 1, 117 g (23.4 g of silica) after the addition of calcium carbonate as described above was used, except that the amount of pure water used was 1083 g. In the same manner as in Example 1, a methacrylic resin containing inorganic particles was obtained, and a flat molded product was obtained. The resulting molded product had a pencil hardness of 5H, a total light transmittance of 87.2%, a haze of 9.9%, and an inorganic content of 18.3%.

Comparative Example 1
Instead of the dispersion [Snowtex AK] used in Example 1, a dispersion in which silica particles (primary particle size 13 nm) are dispersed in water [“Snowtex O”, manufactured by Nissan Chemical Industries, Ltd., containing silica 20 mass%] 120 g (24 g of silica content) was used, except that the amount of pure water used was 1080 g, and in the same manner as in Example 1, an inorganic particle-containing methacrylic resin was obtained, and a flat molded product was obtained. The resulting molded article had a pencil hardness of 5H, a total light transmittance of 83.3%, a haze of 9.9%, and an inorganic content of 2.7%.

Comparative Example 2
L-aspartic acid was added to the same dispersion ["Snowtex O"] used in Example 2. The amount of L-aspartic acid added was 0.1 parts by mass per 100 parts by mass of silica. The primary particle diameter of the silica particles contained in the dispersion after addition was 23 nm, and the ζ potential was −36 mV.

Instead of the dispersion liquid [Snowtex AK] used in Example 1, 117 g of the dispersion liquid after addition of L-aspartic acid (silica content 23.4 g) was used, and the amount of pure water used was 1083 g. Except that, in the same manner as in Example 1, an inorganic particle-containing methacrylic resin was obtained, and a flat molded product was obtained. The resulting molded product had a pencil hardness of 5H, a total light transmittance of 81.1%, a haze of 25.6%, and an inorganic content of 6.2%.

Claims (1)

A monomer (A) containing methyl methacrylate at a content of 50% by mass or more ,
Radical polymerization initiator (B) and inorganic particles (C) having a primary particle diameter of 1 nm to 100 nm and a ζ potential of −10 mV to +40 mV at a hydrogen ion concentration of pH 7
Of the coexistence, a method of manufacturing a non-machine dispersoids containing methacrylic resin Ru by emulsion polymerization in water, the per monomer (A) 100 parts by mass of the use amount of the radical polymerization initiator (B) is The manufacturing method of the inorganic particle containing methacryl resin whose usage-amount of 0.1 mass part-5 mass parts and the said inorganic particle (C) is 5 mass parts-50 mass parts.