JP3977536B2 - Resin particles and method for producing the same - Google Patents

Description

【００１２】
（メタ）アクリル系のモノマーの例としては、メチル（メタ）アクリレート、エチル（メタ）アクリレート、プロピル（メタ）アクリレート、ブチル（メタ）アクリレート、２−エチルヘキシル（メタ）アクリレート、ラウリル（メタ）アクリレート、ステアリル（メタ）アクリレート、シクロヘキシル（メタ）アクリレート、２−ヒドロキシエチル（メタ）アクリレート、２−プロピル（メタ）アクリレート、クロロ−２−ヒドロキシエチル（メタ）アクリレート、ジエチレングリコールモノ（メタ）アクリレート、メトキシエチル（メタ）アクリレート、グリシジル（メタ）アクリレート、ジシクロペンタニル（メタ）アクリレート、ジシクロペンテニル（メタ）アクリレートおよびイソボロノル（メタ）アクリレート等を挙げることができる。
【００１３】
また、上記（メタ）アクリル酸エステルの共重合体には、２官能性あるいは多官能性モノマーが共重合していることが好ましい。ただし、２官能性あるいは多官能性モノマーには適当な使用量の範囲があり少ない使用量では芯材部作成の段階で内包されているトルエンによってポリマーの膨潤、溶解などが起こり、芯材部がうまく得られず、また多く用い過ぎると、逆に粒子が潰れ易くなってしまう。従って、２官能性あるいは多官能性モノマーの使用量は、芯材部に使用される全モノマーに対して０．５〜６０重量％が適当である。２官能あるいは多官能性モノマーの例としては、エチレングリコールジ（メタ）アクリレート、トリエチレングリコール（メタ）アクリレート、テトラエチレングリコール（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールトリ（メタ）アクリレート、１，１，１・トリヒドロキシメチルエタントリアクリレート、１，１，１・トリスヒドロキシメチルメチルエタントリアクリレート、１，１，１・トリスヒドロキシメチルプロパントリアクリレートおよびビニルベンゼンを挙げることができる。
本発明の紫外線吸収性樹脂粒子において、反応性ベンゾトリアゾール系化合物は、この粒子の芯材部を形成するアクリル系化合物１００重量部に対して、通常は１〜４０重量部、好ましくは１０〜３０重量部の量で使用される。
【００１４】
また、芯材部を作成する際にトルエンを用いることにより、反応性ベンゾトリアゾール系化合物の未反応分を最小限に抑えることができる。これは、結晶性である反応性ベンゾトリアゾール系化合物がトルエンに対してたいへん溶解性が良いために、芯材部に用いられるモノマーを水性媒体中に分散させる際、モノマーとトルエン中に均一に溶解している反応性ベンゾトリアゾール系化合物の結晶析出を最小限に抑えることが出来るためである。そして、内包されているトルエンは、乾燥時に揮散して本発明の粒子中に残ることはない。ただし、トルエンを多く用いると、トルエン揮散後の芯材部の空胞が多くなるために粒子が潰れ易く、また少ない使用量では反応性ベンゾトリアゾール系化合物の未反応分を最小限に抑えるのには不十分である。従って、芯材部の１０〜７０重量％が適当である。この芯材部は、通常１〜１６μｍ、好ましくは３〜１３μｍの平均粒子径を有する球状の樹脂粒子である。
【００１５】
本発明の粒子には、上記のような芯材部の表面にメタクリレート系の樹脂からなる表層部が形成されている。
この表層部は、低級アルキルメタクリレートの重合体、または低級アルキルメタクリレートと多官能ビニル系モノマーの共重合体で形成されているものが好ましい。低級アルキルメタクリレートは、炭素数１〜４のアルキル基でエステル化されたメタクリル酸を意味し、例えばメチルメタクリレート、エチルメタクリレート、ｎ−ブチルメタクリレート、ｉ−ブチルメタクリレート等があげられる。また、これらを２種以上組合せて用いることもできる。また、表層部に用いられる多官能ビニル系モノマーとしては、例えばジビニルベンゼン等の芳香族系架橋剤、（ポリ）エチレングリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート等のアクリル系架橋剤等が挙げられ、耐候性の面からはアクリル系架橋剤が好ましい。
この表層部は、通常は０．０１〜１μｍ、好ましくは０．０５〜０．５μｍの平均層厚を有している。この表層部の平均層厚が上記範囲を逸脱して薄いと、芯材部からの未反応の反応性ベンゾトリアゾール系化合物の溶出を有効に防止できないことがあり、また上記範囲を逸脱して厚いと、製造が困難になる場合が多い。
このような層構成を有する本発明の樹脂粒子は、その平均粒子径が通常は１．０２〜１８μｍ、好ましくは３．１〜１４μｍの範囲内にある。
【００１６】
本発明の樹脂粒子は、以下に記載するように、水性媒体中で芯材部を形成するモノマーとトルエンを微粒子状に分散させて重合し、次いでこの水性媒体中にモノマーを追加して添加して表層部を形成する方法により容易に製造することができる。
【００１７】
ここで水性媒体としては、通常は水が使用されるが、この水性媒体には、アルコール等の水に可溶な有機溶媒が混合されていてもよい。
上記のようなモノマーとトルエンを水性媒体に分散させる際には、乳化剤および分散安定剤等を使用することが好ましい。従って、乳化重合、ソープフリー乳化重合、懸濁重合またはシード重合により芯材部を形成することができる。例えば乳化重合の場合に使用させる乳化剤の例としては、ドデシルベンゼンスルホン酸ナトリウムのようなアルキルベンゼンスルホン酸塩、ポリエチレングリコールノニルフェニルエーテルのようなポリエチレングリコールアルキルエーテル、ならびに、ビニル基、アクリロイル基およびアリル基のような反応性基を有する反応性乳化剤等を挙げることができ、また分散安定剤の例としては、ポリビニルアルコールおよびポリアクリル酸塩のような水溶性高分子化合物を挙げることができる。この乳化剤および分散安定剤等は、モノマーとトルエン１００重量部に対して通常は０．１〜５重量部の量で使用される。
芯材部に用いられるモノマーとトルエンは、通常はホモミキサー等の分散装置を用いて水性媒体中に分散させる。ここで使用することができる反応開始剤としては、アゾビスイソブチロニトリル等のアゾ化合物、過酸化ベンゾイル、過酸化ラウロイル等の有機過酸化物、および、過硫酸カリウム、過硫酸アンモニウム等の過硫酸塩を挙げることができる。このような反応開始剤は、モノマー１００重量部に対して通常は０．１〜５重量部の量で使用される。
【００１８】
上記のようにして水性媒体中に分散されたモノマーを重合させる際には反応容器内を窒素ガスなどの不活性ガスでパージすることが好ましい。こうして反応容器内を不活性ガスでパージした後、反応液の温度を６０〜８０℃に加熱することにより重合反応が進行する。
なお、上記のような反応条件では、この芯材部を形成するトルエンが内包されたポリマー粒子を製造するのに要する反応時間は、通常５〜８時間である。
【００１９】
本発明の方法では、上記のようにして一旦芯材部を形成するトルエンが内包されたポリマー粒子を生成させた後、この水性媒体中にモノマーを追加して添加し、生成したポリマー粒子の表面に表層部を形成する。即ち、水性媒体に追加して添加されたモノマーが反応して、前段階で生成したポリマー粒子（芯材部）の表面を被覆するように反応させることにより、表層部を形成することができる。
具体的には、芯材部を形成するために使用したモノマーとトルエンの合計量の５〜３０重量％の量の新たなモノマーを水性媒体中に追加して添加し、攪拌装置等で攪拌する。なお、通常はこの水性媒体中にさらに反応開始剤を投入する。
こうして追加添加されたモノマーは、少なくともその一部が上記工程で生成したポリマー粒子の表面に付着すると考えられる。こうしてモノマーを追加し添加した後、反応液を６０〜８０℃に加熱することにより、ポリマー粒子の表面にあるモノマーを重合させて表層部を形成する。なお、この表層部を形成する際の反応時間は通常は３〜６時間である。
【００２０】
上記のようにして表層部を形成した後、濾過、遠心分離等により生成した粒子を分離し、さらに乳化剤、分散安定剤および残留モノマー等を除去するための洗浄を行い、その後、乾燥（乾燥時に内包されたトルエンは揮散する）、粉砕工程を経て本発明の樹脂粒子粉体が得られる。
【００２１】
【実施例】
以下実施例によりこの発明を詳細に説明するが、これによりこの発明は限定されるものではない。
実施例１
化学式（１）で表される化合物３０ｇ、メチルメタクリレート８０ｇ、エチレングリコールジメタクリレート１０ｇ、トルエン３０ｇ、及びアゾビスイソブチロニトリル１ｇを混合して均一溶液とし油相を調整した。また、精製水４２０ｇにメチルセルロース１．６ｇ、ジオクチルスルホコハク酸ナトリウム０．１ｇ、及びヘキサメタリン酸ナトリウム０．１ｇを添加して溶解させ、水相を調整した。
次いで、上記の油相と水相をＴ．Ｋ．ホモミキサー（特殊機化工業製）を用いて２分間高速攪拌を行って均一な懸濁溶液とした。この後、１．５リットルオートクレーブに仕込み、反応系内をＮ₂ 置換後、２００ｒｐｍの攪拌下、６５℃で７時間重合を行った。７時間経過後、反応液を室温まで冷却した。
こうして反応させて得られた芯材部を形成するポリマー粒子の平均粒子径は９．０μｍであった。次いで、この反応液にアゾビスイソブチロニトリル０．１５ｇを含むメチルメタクリレート２０ｇとエチレングリコールジメタクリレート２．５ｇを追加添加して、２００ｒｐｍの攪拌下、再び反応液を６５℃に加熱して５時間反応させた。
反応後、反応液を室温まで冷却し、生成した粒子と分散媒とを濾過により分離した。得られた粒子について水洗・濾過を２回行った。こうして得られた粒子を乾燥し、その後、粉砕を行って本発明の化粧用微粒子粉体を得た。この粉体の平均粒子径は９．４μｍであり、この粒子には、芯材部の表面に平均厚さ０．２μｍの表層部が形成されている。
【００２２】
得られた粒子１重量部を、ベンゾトリアゾール系化合物が可溶であり、かつポリアクリレート樹脂が不溶であるエステル油、シリコン油、スクワラン油９９９重量部に３分間超音波をかけて分散させ、４０℃で２４時間静置した後、上澄み液を分取して、この中に含まれる粒子を２０００ｒｐｍで２０分間遠心分離することにより分離した。得られたオイルについて吸光度を測定し、予め２−（２′−ヒドロキシ−５′−メタクリロキシエチルフェニル）−２Ｈ−ベンゾトリアゾールを用いて作成した検量線から溶出した紫外線吸収剤の量を求め、溶出した紫外線吸収剤の量を使用した紫外線吸収剤（全内包量）に対する相対値として表した。
結果を表１に示す。
【００２３】
実施例２
実施例１において、芯材部の形成のためのモノマーとして化学式（１）で表される化合物２５ｇ、メチルメタクリレート６５ｇ、エチルメタクリレート２０ｇ、エチレングリコールジメタクリレート１０ｇ、及びトルエン３０ｇを用いた以外は同様にして行い、平均粒子径９．４μｍ、芯材部の平均粒子径９．０μｍ、表層部の平均厚さ０．２μｍである本発明の樹脂粉体を得た。得られた樹脂粒子について、実施例１と同様にして紫外線吸収剤の溶出量を測定した。
【００２４】
実施例３
実施例１において、表層部の形成のためのモノマーとしてエチルメタクリレート１７．５ｇとエチレングリコールジメタクリレート５ｇを用いた以外は同様にして行い、平均粒子径８．５μｍ、芯材部の平均粒子径８．２μｍ、表層部の平均厚さ０．１５μｍである本発明の樹脂粉体を得た。得られた樹脂粒子について、実施例１と同様にして紫外線吸収剤の溶出量を測定した。
【００２５】
比較例１
実施例１において、トルエンを使用せず、トルエンをメチルメタクリレートに置き換えた以外は同様にして行い、平均粒子径９．２μｍ、芯材部の平均粒子径８．８μｍ、表層部の平均厚さ０．２μｍである樹脂粉体を得た。得られた樹脂粒子について、実施例１と同様にして紫外線吸収剤の溶出量を測定した。
【００２６】
比較例２
実施例１において、２−（２′−ヒドロキシ−５′−メタクリロキシエチルフェニル）−２Ｈ−ベンゾトリアゾールの代わりに４−ｔｅｒｔ−ブチル−４′−メトキシジベンゾイルメタン（紫外線吸収剤）を用いた以外は同様にして行い、平均粒子径８．５μｍ、芯材部の平均粒子径８．２μｍ、表層部の平均厚さ０．１５μｍである樹脂粉体を得た。
得られた樹脂粒子を紫外線吸収剤が可溶で、かつポリアクリレート樹脂が不溶であるエステル油、シリコン油、スクワラン油９９９重量部に３分間超音波をかけて分散させ、４０℃で２４時間静置した後、上澄み液を分取して、この中に含まれる粒子を２０００ｒｐｍで２０分間遠心分離することにより分離した。得られたオイルについて吸光度を測定し、予め４−ｔｅｒｔ−ブチル−４′−メトキシジベンゾイルメタンを用いて作成した検量線から溶出した紫外線吸収剤の量を求め、溶出した紫外線吸収剤の量を使用した紫外線吸収剤（全内包量）に対する相対値として表した。
結果を表１に示す。
【００２７】
【表１】

【００２８】
実施例４
上記実施例１〜３で製造した粒子をファンデーションの全体量に対して１０重量％の量で配合して刺激性の評価試験に供したところ、紫外線吸収剤に起因すると思われる肌荒れ等は発生せず、かつ良好な日焼け止め性能を有していた。
【００２９】
【発明の効果】
上記の表１から明らかなように、本発明の粒子は、粒子を形成する樹脂自体が紫外線吸収性を有しており、芯材部作成の際にトルエンを用いたものは紫外線吸収剤の溶出が極めて少なくなり、またさらに、その樹脂の表面がベンゾトリアゾール骨格を含有しないメタクリレート系樹脂で覆われているために、ベンゾトリアゾール骨格が直接皮膚に接触することもない。従って本発明の粒子を含有する化粧料では、紫外線吸収剤の溶出、および皮膚への接触による肌荒れ等が発生しない。なお上記表１において、実施例１〜３の粒子から溶出した紫外線吸収剤は、粒子に付着していた未反応の２−（２′−ヒドロキシ−５′−メタクリロキシエチルフェニル）−２Ｈ−ベンゾトリアゾール（化学式（１）で表される化合物）であると思われ、洗浄等でほぼ完全に溶出しないようにすることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultraviolet-absorbing resin particle and a method for producing the same, and more specifically, for example, a resin particle suitable for protecting the skin by absorbing ultraviolet rays harmful to the skin when blended in cosmetics and the production thereof. Regarding the method.
[0002]
[Prior art]
Sunlight contains ultraviolet rays that cause erythema (sunburn) on human skin and cause stains and freckles. Cosmetics that contain ultraviolet absorbers to shield or absorb such ultraviolet rays Is used.
[0003]
Examples of the ultraviolet absorber include inorganic pigments such as titanium dioxide, zinc oxide, and iron oxide that shield ultraviolet rays, and organic ultraviolet absorbers that absorb ultraviolet rays. The above-mentioned inorganic pigment hides the skin and shields ultraviolet rays, and when such an inorganic pigment is applied to the skin, it is whitened or colored, so that it cannot be incorporated in a large amount in cosmetics.
[0004]
On the other hand, the organic ultraviolet absorber absorbs ultraviolet rays without hiding the skin, so that the problem of whitening or coloring does not occur. For these reasons, in recent years, organic ultraviolet absorbers are increasingly used as ultraviolet absorbers.
However, many organic ultraviolet absorbers are irritating to the skin, and may be irritating to the skin when mixed with other cosmetic base materials.
[0005]
Therefore, in order to prevent such an organic ultraviolet absorber from coming into direct contact with the skin, it has been proposed to disperse and restrain the ultraviolet absorber in the resin particles. For example, Japanese Patent Publication No. Sho 62-51931, Japanese Patent Laid-Open Publication No. Sho 62-198612, etc. disclose resin particles containing such an organic ultraviolet absorber.
By constraining the organic ultraviolet absorbent in the resin particles in this way, the ultraviolet absorbent is less likely to come into direct contact with the skin, and the irritation is reduced as compared with cosmetics directly blended with the ultraviolet absorbent. Therefore, if the resin particles with the ultraviolet absorber bound inside are used as described above, the skin irritation by the ultraviolet absorber should be eliminated. However, even if such resin particles are actually used, they are still affected by the ultraviolet absorber. The skin may be irritated.
[0006]
In other words, the organic ultraviolet absorber is only constrained by physical engagement force in the holes existing in the particles formed from the resin, separately from the resin structure forming the particles, and the cosmetics are formed in the holes. If the oily base of the material enters, the oily base moves out of the particles. When actually measured, in some cases, several percent of the used organic ultraviolet absorber may be eluted. The ultraviolet absorber thus eluted caused skin irritation.
[0007]
Japanese Patent Laid-Open No. 7-291845 discloses UV-absorbing resin particles having low elution, but even if such resin particles are actually used, the UV absorption incorporated into the resin itself. The skin may still be irritated because the acting benzotriazole skeleton is in direct contact with the skin.
[0008]
[Problems to be solved by the invention]
The present invention minimizes the unreacted portion of the reactive benzotriazole-based compound, that is, the eluted portion, without reducing the ultraviolet absorbing action, and does not cause skin irritation of the benzotriazole skeleton in the ultraviolet absorbing resin. And an object of the present invention is to provide a manufacturing method thereof.
[0009]
[Means and Actions for Solving the Problems]
The resin particles of the present invention comprise a core part having ultraviolet absorptivity obtained by dispersing a benzotriazole-based compound having polymerization activity and a (meth) acrylic monomer in an aqueous medium containing toluene and copolymerizing them, And a surface layer portion made of methacrylate resin formed on the surface of the core material portion .
Further, in the method for producing resin particles of the present invention, a benzotriazole compound having polymerization activity, a (meth) acrylic monomer, and toluene are dispersed in an aqueous medium and polymerized to encapsulate toluene as a core part. Obtain polymer particles, then add and add methacrylic monomer to the aqueous medium to polymerize the monomer that forms methacrylate resin on the surface of the polymer particles produced in the above process, and volatilize toluene during drying It is characterized by.
Furthermore, the cosmetic of the present invention is characterized in that the resin particles are blended.
[0010]
The benzotriazole-based compound having a polymerization activity used in the present invention refers to a compound having an ultraviolet absorption effect derived from a benzotriazole structure and a polymerization activity derived from a methacryloyl group, an acryloxy group, etc., hereinafter referred to as a reactive benzotriazole Sometimes referred to as a compound. As such a reactive benzotriazole-based compound, a compound represented by the chemical formula (1) is preferably used. Therefore, this compound has an excellent ultraviolet ray absorbing action and also exhibits good reactivity with an acrylic compound.
[0011]
[Chemical 1]

[0012]
Examples of (meth) acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, Stearyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-propyl (meth) acrylate, chloro-2-hydroxyethyl (meth) acrylate, diethylene glycol mono (meth) acrylate, methoxyethyl ( Mention may be made of (meth) acrylate, glycidyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate and isoboronor (meth) acrylate. Kill.
[0013]
Further, it is preferable that a bifunctional or polyfunctional monomer is copolymerized in the copolymer of the (meth) acrylic acid ester. However, difunctional or polyfunctional monomers have a range of appropriate amounts to use, and if the amount is small, the polymer contained will be swollen or dissolved by the toluene contained at the stage of preparing the core part, and the core part will be If it is not obtained well, and if it is used too much, the particles tend to collapse. Accordingly, the amount of the bifunctional or polyfunctional monomer used is suitably 0.5 to 60% by weight based on the total amount of monomers used in the core material part. Examples of bifunctional or polyfunctional monomers include ethylene glycol di (meth) acrylate, triethylene glycol (meth) acrylate, tetraethylene glycol (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) ) Acrylates, 1,1,1 · trihydroxymethylethane triacrylate, 1,1,1 · trishydroxymethylmethylethane triacrylate, 1,1,1 · trishydroxymethylpropane triacrylate and vinylbenzene. .
In the ultraviolet-absorbing resin particles of the present invention, the reactive benzotriazole-based compound is usually 1 to 40 parts by weight, preferably 10 to 30 parts per 100 parts by weight of the acrylic compound that forms the core part of the particle. Used in parts by weight.
[0014]
Moreover, the unreacted part of a reactive benzotriazole type compound can be suppressed to the minimum by using toluene when producing a core part. This is because the crystalline reactive benzotriazole compound is very soluble in toluene, so when the monomer used for the core material is dispersed in an aqueous medium, it is uniformly dissolved in the monomer and toluene. This is because crystal precipitation of the reactive benzotriazole-based compound can be minimized. The encapsulated toluene does not volatilize during drying and does not remain in the particles of the present invention. However, if a large amount of toluene is used, the number of voids in the core material after volatilization of toluene increases, so the particles tend to be crushed, and with a small amount of use, the amount of unreacted reactive benzotriazole compounds can be minimized. Is insufficient. Therefore, 10 to 70% by weight of the core part is appropriate. This core material part is a spherical resin particle which has an average particle diameter of 1-16 micrometers normally, Preferably it is 3-13 micrometers.
[0015]
In the particles of the present invention, a surface layer portion made of a methacrylate resin is formed on the surface of the core portion as described above.
The surface layer portion is preferably formed of a polymer of a lower alkyl methacrylate or a copolymer of a lower alkyl methacrylate and a polyfunctional vinyl monomer. Lower alkyl methacrylate means methacrylic acid esterified with an alkyl group having 1 to 4 carbon atoms, and examples thereof include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and i-butyl methacrylate. Moreover, these can also be used in combination of 2 or more types. The polyfunctional vinyl monomer used for the surface layer is, for example, an aromatic crosslinking agent such as divinylbenzene, or acrylic crosslinking such as (poly) ethylene glycol di (meth) acrylate or trimethylolpropane tri (meth) acrylate. An acrylic crosslinking agent is preferable from the viewpoint of weather resistance.
This surface layer portion usually has an average layer thickness of 0.01 to 1 μm, preferably 0.05 to 0.5 μm. If the average layer thickness of the surface layer portion is thin and deviates from the above range, the elution of unreacted reactive benzotriazole-based compounds from the core material portion may not be effectively prevented. In many cases, manufacturing is difficult.
The average particle diameter of the resin particles of the present invention having such a layer structure is usually in the range of 1.02 to 18 μm, preferably 3.1 to 14 μm.
[0016]
As described below, the resin particles of the present invention are polymerized by dispersing a monomer that forms a core part and toluene in a fine particle form in an aqueous medium and then adding the monomer to the aqueous medium. Thus, it can be easily manufactured by a method of forming the surface layer portion.
[0017]
Here, water is usually used as the aqueous medium, but an organic solvent soluble in water such as alcohol may be mixed in the aqueous medium.
When the above monomer and toluene are dispersed in an aqueous medium, it is preferable to use an emulsifier, a dispersion stabilizer and the like. Therefore, the core part can be formed by emulsion polymerization, soap-free emulsion polymerization, suspension polymerization or seed polymerization. Examples of emulsifiers used in the case of emulsion polymerization include alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, polyethylene glycol alkyl ethers such as polyethylene glycol nonylphenyl ether, and vinyl, acryloyl and allyl groups. Reactive emulsifiers having a reactive group such as, and examples of dispersion stabilizers include water-soluble polymer compounds such as polyvinyl alcohol and polyacrylates. These emulsifiers and dispersion stabilizers are usually used in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the monomer and toluene.
The monomer and toluene used for the core part are usually dispersed in an aqueous medium using a dispersing device such as a homomixer. Reaction initiators that can be used here include azo compounds such as azobisisobutyronitrile, organic peroxides such as benzoyl peroxide and lauroyl peroxide, and persulfates such as potassium persulfate and ammonium persulfate. Mention may be made of salts. Such a reaction initiator is usually used in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the monomer.
[0018]
When the monomer dispersed in the aqueous medium is polymerized as described above, the inside of the reaction vessel is preferably purged with an inert gas such as nitrogen gas. After purging the inside of the reaction vessel with an inert gas in this way, the polymerization reaction proceeds by heating the temperature of the reaction solution to 60 to 80 ° C.
Note that, under the reaction conditions as described above, the reaction time required for producing the polymer particles encapsulating toluene forming the core part is usually 5 to 8 hours.
[0019]
In the method of the present invention, after the polymer particles containing toluene once forming the core portion are formed as described above, a monomer is additionally added to the aqueous medium, and the surface of the generated polymer particles A surface layer portion is formed on the surface. That is, the surface layer part can be formed by reacting the monomer added in addition to the aqueous medium so as to cover the surface of the polymer particles (core material part) produced in the previous step.
Specifically, a new monomer in an amount of 5 to 30% by weight of the total amount of the monomer and toluene used for forming the core part is added to the aqueous medium and stirred with a stirrer or the like. . Usually, a reaction initiator is further added to the aqueous medium.
It is considered that at least a part of the monomer added in this way adheres to the surface of the polymer particles generated in the above-described process. After the monomer is added and added in this manner, the reaction liquid is heated to 60 to 80 ° C. to polymerize the monomer on the surface of the polymer particles to form the surface layer portion. In addition, reaction time at the time of forming this surface layer part is 3 to 6 hours normally.
[0020]
After forming the surface layer as described above, the particles generated by filtration, centrifugation, etc. are separated, and further washed to remove the emulsifier, dispersion stabilizer and residual monomer, and then dried (during drying) The encapsulated toluene is volatilized), and the resin particle powder of the present invention is obtained through a pulverization step.
[0021]
【Example】
Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereby.
Example 1
30 g of the compound represented by the chemical formula (1), 80 g of methyl methacrylate, 10 g of ethylene glycol dimethacrylate, 30 g of toluene, and 1 g of azobisisobutyronitrile were mixed to prepare a homogeneous solution to prepare an oil phase. Further, 1.6 g of methylcellulose, 0.1 g of sodium dioctylsulfosuccinate and 0.1 g of sodium hexametaphosphate were added to 420 g of purified water and dissolved to prepare an aqueous phase.
Next, the above oil phase and aqueous phase are mixed with T.W. K. Using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), high-speed stirring was performed for 2 minutes to obtain a uniform suspension solution. Thereafter, the reaction system was charged into a 1.5 liter autoclave, the inside of the reaction system was replaced with N ₂ , and polymerization was carried out at 65 ° C. for 7 hours with stirring at 200 rpm. After 7 hours, the reaction solution was cooled to room temperature.
The average particle size of the polymer particles forming the core part obtained by the reaction in this manner was 9.0 μm. Next, 20 g of methyl methacrylate containing 0.15 g of azobisisobutyronitrile and 2.5 g of ethylene glycol dimethacrylate were added to the reaction solution, and the reaction solution was again heated to 65 ° C. with stirring at 200 rpm. Reacted for hours.
After the reaction, the reaction solution was cooled to room temperature, and the produced particles and the dispersion medium were separated by filtration. The obtained particles were washed with water and filtered twice. The particles thus obtained were dried and then pulverized to obtain the cosmetic fine particle powder of the present invention. This powder has an average particle diameter of 9.4 μm, and a surface layer portion having an average thickness of 0.2 μm is formed on the surface of the core portion of the particles.
[0022]
1 part by weight of the obtained particles is dispersed in 999 parts by weight of ester oil, silicon oil, squalane oil in which the benzotriazole compound is soluble and the polyacrylate resin is insoluble by applying ultrasonic waves for 3 minutes. After leaving still at 24 degreeC, the supernatant liquid was fractionated and the particle | grains contained in this were isolate | separated by centrifuging for 20 minutes at 2000 rpm. Absorbance was measured for the obtained oil, and the amount of the ultraviolet absorber eluted from a calibration curve prepared in advance using 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole was determined. The amount of the eluted ultraviolet absorber was expressed as a relative value to the ultraviolet absorber (total inclusion amount) used.
The results are shown in Table 1.
[0023]
Example 2
In Example 1, the same procedure was performed except that 25 g of the compound represented by the chemical formula (1), 65 g of methyl methacrylate, 20 g of ethyl methacrylate, 10 g of ethylene glycol dimethacrylate, and 30 g of toluene were used as monomers for forming the core part. Thus, the resin powder of the present invention having an average particle size of 9.4 μm, an average particle size of the core material portion of 9.0 μm, and an average thickness of the surface layer portion of 0.2 μm was obtained. About the obtained resin particle, it carried out similarly to Example 1, and measured the elution amount of the ultraviolet absorber.
[0024]
Example 3
In Example 1, the same procedure was carried out except that 17.5 g of ethyl methacrylate and 5 g of ethylene glycol dimethacrylate were used as the monomers for forming the surface layer portion. The average particle size was 8.5 μm and the average particle size of the core portion was 8 The resin powder of the present invention having a thickness of 0.2 μm and an average thickness of the surface layer portion of 0.15 μm was obtained. About the obtained resin particle, it carried out similarly to Example 1, and measured the elution amount of the ultraviolet absorber.
[0025]
Comparative Example 1
In Example 1, the same procedure was performed except that toluene was not used and toluene was replaced with methyl methacrylate. The average particle size was 9.2 μm, the average particle size of the core material portion was 8.8 μm, and the average thickness of the surface layer portion was 0. A resin powder having a thickness of 2 μm was obtained. About the obtained resin particle, it carried out similarly to Example 1, and measured the elution amount of the ultraviolet absorber.
[0026]
Comparative Example 2
In Example 1, 4-tert-butyl-4'-methoxydibenzoylmethane (ultraviolet absorber) was used instead of 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole. The resin powder having an average particle size of 8.5 μm, an average particle size of the core material portion of 8.2 μm, and an average thickness of the surface layer portion of 0.15 μm was obtained.
The obtained resin particles are dispersed for 3 minutes in 999 parts by weight of ester oil, silicon oil, squalane oil in which the UV absorber is soluble and the polyacrylate resin is insoluble, and the resin particles are allowed to stand at 40 ° C. for 24 hours. After placement, the supernatant was separated and the particles contained therein were separated by centrifuging at 2000 rpm for 20 minutes. Absorbance of the obtained oil was measured, and the amount of the ultraviolet absorber eluted from the calibration curve prepared in advance using 4-tert-butyl-4'-methoxydibenzoylmethane was determined. It represented as a relative value with respect to the used ultraviolet absorber (total inclusion amount).
The results are shown in Table 1.
[0027]
[Table 1]

[0028]
Example 4
When the particles produced in Examples 1 to 3 above were blended in an amount of 10% by weight with respect to the total amount of the foundation and subjected to an evaluation test for irritation, rough skin and the like thought to be caused by the ultraviolet absorber did not occur. And had good sunscreen performance.
[0029]
【The invention's effect】
As is apparent from Table 1 above, the particles of the present invention are such that the resin itself forming the particles has ultraviolet absorption properties, and those using toluene in the preparation of the core material portion are eluted with ultraviolet absorbers. Furthermore, since the surface of the resin is covered with a methacrylate resin not containing a benzotriazole skeleton, the benzotriazole skeleton does not come into direct contact with the skin. Therefore, in the cosmetic containing the particles of the present invention, elution of the ultraviolet absorber and rough skin due to contact with the skin do not occur. In Table 1, the ultraviolet absorber eluted from the particles of Examples 1 to 3 was unreacted 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzoate adhering to the particles. It seems to be triazole (a compound represented by the chemical formula (1)), and it can be prevented from being almost completely eluted by washing or the like.

Claims (7)

  Formed on the surface of the core material portion having a UV-absorbing core material portion obtained by dispersing and copolymerizing a benzotriazole-based compound having a polymerization activity and a (meth) acrylic monomer in an aqueous medium containing toluene And a surface layer portion made of a methacrylate resin.   The resin particles according to claim 1, wherein the amount of toluene used is 10 to 70% by weight of the core part.   1 part by weight of the resin particles was dispersed in 999 parts by weight of squalane oil by applying ultrasonic waves for 3 minutes and allowed to stand at 40 ° C. for 24 hours, and then the supernatant was collected and centrifuged. The resin particles according to claim 1 or 2, wherein an elution amount of the benzotriazole-based compound is 30 ppm or less.   The resin particle according to claim 3, wherein the elution amount is 20 to 30 ppm.   A polymer particle containing toluene as a core material is obtained by dispersing a benzotriazole-based compound having polymerization activity, a (meth) acrylic monomer, and toluene in an aqueous medium, and then polymerizing the polymer particles. A method for producing resin particles, comprising adding a monomer and polymerizing a monomer that forms a methacrylate resin on the surface of the polymer particles produced in the above step, and evaporating toluene during drying. The method for producing resin particles according to claim 5 , wherein the amount of toluene used is 10 to 70% by weight of the core material part. A cosmetic comprising the resin particles according to any one of claims 1 to 4 .