JP4857727B2 - 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 [Patent Document 1: Japanese Patent Application Laid-Open No. 2004-161795].

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 JP 2002-80506 A

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.

〔式中、Ａは炭素数３〜１８の直鎖もしくは分岐鎖アルキレン基、式（１）

（式中、Ｒは炭素数４〜１８の直鎖または分岐鎖アルキル基を示す。）
で示される２価の残基または式（２）

（式中、Ｒは前記と同じ意味を示す。）
で示される２価の残基を示し、ＥＯはオキシエチレン基を示す。ａは０〜５０の整数を示
し、ｂは０〜２００の整数を示す。ただし、ａとｂとが同時に０であることはない。Ｍは
カチオンを示す。〕
または式（II）

〔式中、Ａ、ＥＯ、ａ、ｂおよびＭは前記と同じ意味を示す。〕
で示される界面活性剤（Ｂ）、
ラジカル重合開始剤（Ｃ）および
一次粒子径１ｎｍ〜５０ｎｍの無機物粒子（Ｄ）の共存下に水中で乳化重合させることを
特徴とする無機物粒子含有メタクリル樹脂の製造方法を提供するものである。 That is, the present invention provides a monomer (A) mainly composed of methyl methacrylate,
Formula (I)

[In the formula, A is a linear or branched alkylene group having 3 to 18 carbon atoms, Formula (1)

(In the formula, R represents a linear or branched alkyl group having 4 to 18 carbon atoms.)
Or a divalent residue represented by formula (2)

(In the formula, R has the same meaning as described above.)
And EO represents an oxyethylene group. a represents an integer of 0 to 50, and b represents an integer of 0 to 200. However, a and b are not 0 at the same time. M represents a cation. ]
Or formula (II)

[Wherein, A, EO, a, b and M have the same meaning as described above. ]
A surfactant (B) represented by:
An object of the present invention is to provide a method for producing an inorganic particle-containing methacrylic resin comprising emulsion polymerization in water in the presence of a radical polymerization initiator (C) and an inorganic particle (D) having a primary particle diameter of 1 nm to 50 nm.

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,

Propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate,
Esters of methacrylic acid with aliphatic alcohols, aromatic alcohols or alicyclic alcohols, such as lauryl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, etc.

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,
Tetramethylol methane triacrylate, tetramethylol methane 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.

The surfactant (B) is represented by the formula (I) or the formula (II). In formula (I) and formula (II), examples of the linear or branched alkylene group having 3 to 18 carbon atoms represented by A include propylene, ethylethylene, dimethylethylene, butylethylene, octylethylene, decylethylene, dodecyl. Examples include ethylene, tetradecylethylene, hexadecylethylene and the like.

Examples of the linear or branched alkyl group having 4 to 18 carbon atoms represented by R in the formulas (1) and (2) include a butyl group, a pentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, and a nonyl group. Decyl group, undecyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group and the like.

a shows the average addition mole number of the bivalent residue shown by -AO-, and is an integer of 0-50, Preferably it is an integer of 0-20. When a is 2 or more, the residues represented by A in the divalent residue represented by -AO- may be the same as or different from each other.

b shows the average addition mole number of the oxyethylene group shown by -EO-, and is an integer of 0-200, Preferably it is an integer of 1-50. Note that a and b are not 0 at the same time.

When the divalent residue represented by -AO- and the divalent residue represented by -EO- may be block-bonded, randomly-bonded or randomly-bonded The sequence of the divalent residue represented by -AO- and the divalent residue represented by -EO- is not particularly limited.

Examples of the cation represented by M include alkali metal ions such as sodium ions and potassium ions, calcium ions, alkaline earth metal ions of magnesium ions, ammonium ions, and ammonium ions substituted with alkyl groups having 1 to 4 carbon atoms. Etc.

A method for producing such a surfactant (B) is disclosed, for example, in Patent Document 2 (Japanese Patent Laid-Open No. 2002-80506). The surfactant (B) is commercially available, for example, as “Latemul PD-104” from Kao Corporation.

The usage-amount of surfactant (B) is 0.05 mass part-2 mass parts normally per 100 mass parts of said monomers (A). When the amount of the surfactant (B) used is less than 0.05 parts by mass, problems such as aggregation may occur during emulsion polymerization. When the amount exceeds 2 parts by mass, it is contained in the resulting methacrylic resin containing inorganic particles. May cause the coloring.

As the radical polymerization initiator (C), water-soluble ones are preferably used. For example, inorganic peroxides such as sodium persulfate, potassium persulfate and ammonium persulfate, azo compounds such as azobiscyanovaleric acid sodium salt, 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 usage-amount of a radical polymerization initiator (C) is 0.1 mass part-5 mass parts normally per 100 mass parts of said monomers. If it is less than 0.1 part by mass, it takes a long time for the polymerization, and if it exceeds 5 parts by mass, the heat generated by the polymerization tends to be abrupt, and a part of the radical polymerization initiator remains unreacted. It is uneconomical.

Examples of the inorganic particles (D) 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 (D) is 1 nm to 50 nm. If it is less than 1 nm, it is easy to aggregate, and if it exceeds 50 nm, transparency tends to decrease.

The usage-amount of an inorganic particle is 5 mass parts-50 mass parts normally per 100 mass parts of said monomers. If it is less than 5 parts by mass, it is difficult to make the surface hardness sufficient, and if it exceeds 50 parts by mass, the fluidity when the resulting inorganic particle-containing methacrylic resin is melted by heating is lowered, making it difficult to mold.

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 the surfactant (B), the radical polymerization initiator (C), and the inorganic particles ( What is necessary is just to heat to the temperature more than the thermal decomposition temperature of a radical polymerization initiator, mixing with water with D) and 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.

Surfactant (B) and radical polymerization initiator (C) may be mixed in their entirety before the polymerization starts, or a part of them may be mixed before the polymerization starts, and the remainder after the polymerization starts. It may be added in several portions or continuously.

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 The total light transmittance was determined based on JIS-K7361-1, and the haze was determined based on JIS-K7136, which was used as an index of transparency.
(3) Inorganic particle content An inorganic particle-containing methacrylic resin having an initial mass (A) of 20 by TGA (thermogravimetric analyzer).
The residue mass (B) when the temperature is raised from room temperature to 500 ° C. at a rate of temperature increase of 500 ° C./min, and reaches 500 ° C.
To obtain 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.

Example 1
A dispersion of 240 g of methyl methacrylate and silica particles (primary particle size of about 13 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 O ”, manufactured by Nissan Chemical Industries, Ltd., silica content 20 mass%] 12
0 g (silica content is 24 g), pure water 1080 g and surfactant ["Latemul PD-104
], Kao Co., Ltd., concentration 20% by mass], 3.6 g (0.72 g of active ingredient) is added, 200 rp
Stir at m. While continuing stirring, nitrogen gas was circulated below the liquid level from the nitrogen introduction tube, 15
Nitrogen substitution was performed by bubbling for a minute. Then, pull up the nitrogen inlet tube from the liquid level,
The separable flask was immersed in an oil bath while flowing through the gas phase portion, and the temperature of the flask content was raised by raising the temperature of the oil. 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 obtained molded product was transparent, its surface hardness was 5H, total light transmittance was 86.8%, and haze was 3.1.
%, The inorganic content was 9.7%.

Example 2
An inorganic particle-containing methacrylic resin was obtained in the same manner as in Example 1 except that the amount of silica particle dispersion (Snowtex O) used was 240 g (silica content 48 g) and the amount of pure water used was 960 g. A plate-shaped molded product was obtained. The obtained molded product is transparent and its pencil hardness is 5
H, total light transmittance was 80.0%, haze was 9.1%, and inorganic content was 15.0%.

Comparative Example 1
Sodium dodecylbenzenesulfonate 2 instead of surfactant [Latemul PD-104]
Except having used g, it operated similarly to Example 1 and obtained the inorganic particle containing methacryl resin, and obtained the flat molded article. The resulting molded product had a pencil hardness of 5H, a total light transmittance of 15.1%, a haze of 98.4%, and an inorganic content of 6.7%.

Comparative Example 2
The same operation as in Example 1 was conducted except that the surfactant [Latemul PD-104] was not used.
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 83.3%, a haze of 20.0%, and an inorganic content of 2.7%.

Claims (2)

A monomer (A) containing methyl methacrylate at a content of 50% by mass or more ,
Formula (I)

[In the formula, A is a linear or branched alkylene group having 3 to 18 carbon atoms, Formula (1)

(In the formula, R represents a linear or branched alkyl group having 4 to 18 carbon atoms.)
Or a divalent residue represented by formula (2)

(In the formula, R has the same meaning as described above.)
And EO represents an oxyethylene group. a represents an integer of 0 to 50, and b represents an integer of 0 to 200. However, a and b are not 0 at the same time. M represents a cation. ]
Or formula (II)

[Wherein, A, EO, a, b and M have the same meaning as described above. ]
A surfactant (B) represented by:
A method for producing an inorganic particle-containing methacrylic resin, comprising emulsion polymerization in water in the presence of a radical polymerization initiator (C) and an inorganic particle (D) having a primary particle diameter of 1 nm to 50 nm. The amount of the surfactant (B) used per 100 parts by weight of the monomer (A) is 0.05 to 2 parts by weight, and the amount of the radical polymerization initiator (C) used is 0.1 parts by weight. The production method according to claim 1, wherein the amount of the inorganic particles used is 5 parts by mass to 50 parts by mass.