JP3494249B2 - Method for producing vinyl polymer particles - Google Patents
Method for producing vinyl polymer particlesInfo
- Publication number
- JP3494249B2 JP3494249B2 JP04008195A JP4008195A JP3494249B2 JP 3494249 B2 JP3494249 B2 JP 3494249B2 JP 04008195 A JP04008195 A JP 04008195A JP 4008195 A JP4008195 A JP 4008195A JP 3494249 B2 JP3494249 B2 JP 3494249B2
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- polymerization
- polymer particles
- polymerization conversion
- particles
- ion concentration
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Description
【発明の詳細な説明】
【0001】
【産業上の利用分野】本発明は、ビニル系単量体の懸濁
重合法において、得られる重合体粒子の粒径分布が狭
く、かつこの重合体粒子を用いて発泡性ビニル系重合体
粒子とし、これを発泡成形して得られる成形品の強度に
優れるビニル系重合体粒子の製造法に関する。
【0002】
【従来の技術】懸濁重合法で得られるスチレンを主体と
するビニル系重合体粒子は、ブタン、ペンタンなどの炭
化水素類を発泡剤として含浸させることによって、発泡
性ビニル系重合体粒子が得られる。発泡性ビニル系重合
体粒子は、その粒子径によりおよそ次の三つの用途分野
に分類される。すなわち、粒子径300〜600μm
のものはインスタント食品のカップや発泡コンクリート
等に、600〜l500μmのものは各種梱包材及び
魚箱等に、またl500〜3000μmのものは建ボ
ード等に用いられる。このように、粒子径によって用途
が異なることから、用途に準じた粒径分布を有する合成
法が求められる。すなわち、ある特定の粒径の粒子が用
途量よりも過剰に合成されると、それは余剰となり経済
的にマイナスとなる。このことから目的の粒子径のもの
を効率よく得るためには、粒径分布の狭い合成法の確立
が重要となる。
【0003】一般にビニル系単量体の懸濁重合方法は、
難溶性リン酸塩、陰イオン界面活性剤、水媒体中で酸性
または中性を示す水溶性金属塩等からなる懸濁分散剤を
用い、これらの種類、濃度、添加時間等の化学的要因と
撹拌等の機械的要因を組み合わせることにより、その粒
子径及ぴ粒径分布が制御されている。しかし、従来、本
発明が目的とする粒径分布の狭い重合体粒子は得られて
いない。
【0004】このため、次のような方法が提案されてい
る。
(l)水相中の水素イオン濃度を10-7〜10-5グラム
イオンの範囲に保ち懸濁重合する方法(特開昭62−1
69801号公報)
(2)懸濁分散剤として酢酸カルシウム塩あるいはプロ
ピオン酸カルシウム塩を使用する方法(特開昭58−6
3702号公報)
(3)重合途中でリン酸三ナトリウムを加え、重合系内
でリン酸カルシウムを生成させ引き続き重合を行う方法
(特公昭59−19136号公報)
(4)ビニル系単量体の重合転化率が0〜30%の間
に、水相中の水素イオン濃度を10-10〜10-13グラム
イオンとする方法(特開平2−189302号公報)な
どである。
【0005】
【発明が解決しようとする課題】上記(l)〜(3)の
懸濁重合法では、重合体粒子の粒子径は0.l〜3.0
mmの広範囲にわたり、その粒度分布は幅広いものであ
る。また、(4)の方法は、水系の水素イオン濃度をス
チレン系単量体の重合転化率が0〜30%の間に10
-10〜10-13グラムイオンとすることを特徴とする方法
であるが、粒度分布を十分狭くできず、しかもこの重合
体粒子を用いた発泡性ポリスチレン系樹脂は、そのセル
数は少なくなり成形品とした時の強度が小さくなる等の
欠点がある。本発明は、上記課題を解決するために成さ
れたものであって、発泡性重合体粒子としたときに優れ
た品質を持つ、粒度分布のせまいスチレン系重合体粒子
を製造することを目的としてる。
【0006】
【課題を解決するための手段】本発明におけるビニル系
重合体粒子の製造法は、ビニル系単量体を難溶性リン酸
塩及び陰イオン界面活性剤の存在下に水性媒体中で懸濁
重合する際に、懸濁重合系をビニル系単量体の重合転化
率が10%を越えない範囲で60〜80℃の間の一定温
度に30分〜4時間保温処理し、次いで昇温して重合す
ると共に、ビニル系単量体の重合転化率が0〜5%の間
は水性媒体中の水素イオン濃度を10−5〜l0−8グ
ラムイオンとし、重合転化率が5%を越え10%以下の
時点で水性媒体中の水素イオン濃度を10−10〜10
−12グラムイオンに調整して重合することを特徴とす
る。
【0007】本発明におけるビニル系単量体としては、
スチレン、α−メチルスチレン、ビルトルエン、パラク
ロルスチレン等のスチレン誘導体、アクリロニトリル、
メタクリロニトリル等のシアン化ビニル、アクリル酸メ
チル、アクリル酸エチル、アクリル酸プロピル、アクリ
ル酸ブチル等のアクリル酸エステル、同様のメタクリル
酸エステル、ビニルピリジン、ビニルカルバゾール、ブ
タジエンなどがあり、ビニル系重合体粒子を発泡性スチ
レン系樹脂粒子として使用する本発明では、スチレン、
またはスチレン誘導体を50重量%以上使用することが
好ましい。
【0008】 これらビニル系単量体を水性媒体中で懸
濁重合する際の重合触媒としては、過酸化ベンゾイル、
過安息香酸ブチル等の有機過酸化物、ターシヤリーブチ
ル−2エチルヘキサノエート等の高級脂肪族系有機過酸
化物、アゾビスイソブチロニトリル等のアゾ化合物など
の一般にビニル系単量体のラジカル重合に用いられる重
合触媒が使用できる。これらは、好ましくは単量体成分
に対して0.05〜0.5重量%使用される。
【0009】 重合に際し、連鎖移動剤として、メチル
メルカプタン、ブチルメルカプタンなどの脂肪族系メル
カプタン類、トリエチルアルミニウムなどのアルミニウ
ム化合物、トリニトロベンゼンなどのニトロ化合物、四
塩化炭素、四臭化炭素などのハロゲン化炭素、α一メチ
ルスチレンダイマなどを使用してもよく、これらは、ビ
ニル系単量体に添加して使用されることが好ましい。重
合体粒子を発泡性スチレン系樹脂粒子として使用する場
合には、使用上の安全性、臭気などの問題を考慮する
と、α−メチルスチレンダイマーの使用が特に好まし
い。
【0010】重合に際し、可塑剤として、トルエン、エ
チルベンゼンなどの芳香族系有機溶剤、2エチルヘキシ
ルアジペート、2エチルヘキシルフタレートなどの二価
アコールのジエステル類、ブチルステアレート、ブチル
アセテート等の脂肪酸エステル類などを使用してもよ
く、これらは単量体成分に対して0.05〜3.0重量
%使用されることが好ましい。
【0011】重合に際し、水性媒体中で分散相を安定に
存在させるために使用される主懸濁剤としては、リン酸
三カルシウム、リン酸マグネシウム等の難溶性リン酸塩
が使用でき、これらは好ましくは水性媒体に対して0.
05〜10重量%使用される。
【0012】陰イオン界面活性剤には、ドデシルベンゼ
ンスルホン酸などのアルキルベンゼンスルホン酸塩やア
ルキルスルホン酸ナトリウム塩、オレイン酸ナトリウム
塩等の高級脂肪酸塩などが使用でき、これらは水性媒体
に対して好ましくは、0.00l〜0.05重量%使用
される。
【0013】本発明においては、懸濁重合する際に、ビ
ニル系単量体の重合転化率が0〜5%の間では重合系内
の水素イオン濃度を10-5〜10-8グラムイオンとす
る。重合転化率が0〜5%の間に重合系内の水素イオン
濃度を10-5グラムイオンを越えると、主懸濁剤である
難溶性リン酸塩が水系に溶解し始めるので好ましくな
く、逆に10-8グラムイオン未満になると重合触媒のイ
オン分解が促進され、触媒としての効果が減少する。こ
のことによって重合体粒子の重量平均分子量の増大や、
重合時間の延長を招き、製造上好ましくない。
【0014】本発明においては、重合転化率が5%を越
え10%以下のある時点で重合系内の水素イオン濃度を
10-10〜10-12グラムイオンに調整する。このとき、
水素イオン濃度が10-10グラムイオンを越えると徴小
重合体粒子生成の抑制効果が不十分となり、10-12グ
ラムイオン未満では、重合体粒子の生長が促進され、粒
度分布は幅の広いものになってしまう。
【0015】本発明においては、以上のように、重合進
行と共に水素イオン濃度を調整すると、重合転化率が1
0%を越え40%以下の間は水素イオン濃度を10-10
〜10-8グラムイオンに、重合転化率が40%を越えた
時点では水素イオン濃度を10-8〜l0-5グラムイオン
になりやすく、このように監視していることが重合体粒
子の合一を抑制し、結果として粒度分布の狭い重合体粒
子を得る上で好ましい。
【0016】 水素イオン濃度を調整する方法としては
次の方法がある。水素イオン濃度を低くくする方法とし
ては、水溶性塩基性塩を添加する方法が有効であり、逆
に水素イオン濃度を高くしていく方法としては、酸の添
加が有効である。水溶性塩基性塩としては、水溶炭酸
塩、水酸化化合物等が好ましい。また、酸性成分として
は、ビニル系単量体に重合初期から添加するものと、水
溶性塩基性塩の添加後に添加するものに分けられる。ビ
ニル系単量体に添加するものとしては、安息香酸やアジ
ピン酸などの有機酸、水酸基イオンとイオン反応するペ
ンゾイルパーオキサイドやラウロイルパーオキサイドな
どの有機過酸化物等がある。水溶性塩基性塩の添加後に
添加するものとしては、塩酸、リン酸、硫酸、酢酸、蓚
酸、亜硫酸水素ナトリウムなど一般にその水溶液が酸性
を示すものが使用できる。中でもリン酸、酢酸、亜硫酸
水素ナトリウムなどが好ましい。
【0017】このように重合転化率に応じ、重合系内の
水素イオン濃度を適宜変えることによって粒度分布の狭
い重合体粒子を得ることができる。しかし、いくつかの
問題も含む。それは、重合系内の水素イオン濃度を小さ
くすると重量平均分子量が70×104〜150×1
04、大きさ0.1〜1μmの高分子量の乳化重合物が
生成する。この乳化重合物は重合の進行とともに他のビ
ニル系重合体粒子内に取り込まれたり、粒子表面に付着
したりする。この様子は、重合の進行とともに分散系の
濁りが増大し、やがて透明性が増すという現象をもって
みることができる。超高分子量の乳化重合物を取り込ん
だり、あるいは粒子表面に付着したビニル系重合体粒子
に、プロパン、ブタン、ペンタン等の発泡剤を含浸する
ことによって得られる発泡性ビニル系重合体粒子を予備
発泡、熟成後スチーム成形した場合、得られる成形品の
セル数は少なくなり、かつ強度が小さいものとなる。つ
まり、商品価値の低いものとなる。
【0018】そこで、鋭意検討した結果、本発明におい
て、ビニル系単量体の重合転化率0〜10%の間に懸濁
重合系を60〜80℃に調節し、30分以上4時間以下
(より好ましくは2時間以下)処理することによりセル
数が多く強度に優れる成形品が得られる発泡性ビニル系
重合体粒子が得られる事を見いだしたものである。
【0019】以上のような方法により、一般に400〜
1500μmの平均粒子径を有し、粒度分布が狭いビニ
ル系重合体粒子を得ることができ、かつその発泡性重合
体粒子は、それを発泡成形して得られる成形品に綺麗な
外観を与えることができる。
【0020】なお、本発明により得られるビニル系重合
体粒子を発泡性重合体粒子とするときプロパン、ブタ
ン、ペンタン等の発泡剤を公知の方法により含浸させる
が、ビニル系重合体粒子の製造時における重合途中、好
ましくは重合率75〜98%の時に重合系内に発泡剤を
存在せしめて当該粒子に発泡剤を含浸させて発泡性重合
体粒子とすることが好ましい。
【0021】
【実施例】次に、本発明の実施例を示す。以下、重合体
粒子の粒度分布と平均粒子径の表示は、それぞれ偏差係
数(Cv)、メディアン径で表している。偏差係数(C
v)は、累積重量分布の曲線をもとに、累積重量が、1
5%、50%、85%となる粒子径をそれぞれd15、
d50、d85としたとき下記数1により算出される。
Cvの値が大きいほど粒度分布は広く、小さいほどその
分布は狭いことを意味する。また、平均径は前述のd
50で代表されるメデイアン径を採用している。
【数1】
【0022】ビニル系単量体粒子の重合転化率は、合成
中の油滴を比重液に入れて比重を求め、その値から下記
数2によリ、算出した。
【数2】【0023】モノマーとしてスチレンを用いた場合、ポ
リスチレンの比重=1.06、スチレンモノマーの比量
0.91であることから,重合転化率は、下記数3によ
り求められる。
【数3】
【0024】成形品のセル数は次の方法により求めた。
成形品を鋭利なカッターナイフ等で切り取り、その断面
の顕微鏡写真を撮影し、得られた写真より、l平方ミリ
メートル当たりの個数を求めた。成形品の強度は、JI
S A−9511に準じて、測定し求めた。
【0025】実施例1
内径140φmm、高さ210mmの3リットルオートクレ
ーブを用い、第三リン酸カルシウム24g、ドデシルベ
ンゼンスルホン酸ソーダ0.06gをイオン交換水12
00gに分散し、溶解させた。このときの重合系内の水
素イオン濃度はl0 −7.5 グラムイオンであった。こ
れに過酸化ベンゾイル3.12g(対モノマー0.26
重量%)、2−エチルヘキシルアジペート(DOA)
7.2g(対モノマー0.6重量%)を溶解したスチレ
ン1200gを撹拌しながら加え、昇温速度1℃/分で
60℃まで昇温し、1時間保温処理した後、90℃まで
昇温して重合を実施した。60℃で1時間の保温処理を
完了した時点でのビニル系単量体の重合転化率は3%で
あった。
【0026】撹拌翼としては、羽根部分が長方形で、羽
根部外周半径45mm、羽根部内周半径35mm、翼面積3
00mm2、連結部面積175mm2となる羽根部を2枚有す
るH形撹拌翼を仕込面高さの半分の高さより下側であっ
て、オートクレーブ底部より62mmの高さに設置して用
いた。邪魔板は、輻14mm、その中心組と回転軸心の距
離が53mm、先端が静止液面下40mmの位置となるよう
に対向させて2枚設置した。また回転数は270rpmに
調整した。
【0027】重合転化率が8%に達した時点で、炭酸ナ
トリウム0.24gをイオン交換水9.36gに溶解し
て加えた。このときの重合系内の水素イオン濃度は10
-10.6グラムイオンであった。重合を進め重合転化率が
5%、25%、40%、60%に達した時点で水素イオ
ン濃度を測定したところ、それぞれ10-7.5グラムイオ
ン、10-8.5グラムイオン、10-7.6グラムイオン、1
0-7.5グラムイオンであった。なお、重合転化率が高ま
るにつれて水系の濁りが強くなり、重合転化率が15%
の時にもっとも濃度が大きくなっていた。この時650
nmにおける光線透過率は50%である。これを境に光線
透過率は上昇し、重合転化率が50%の時、光線透過率
は95%となった。
【0028】重合転化率が95%に達した時点でさらに
第三リン酸カルシウム6gを加えた後、110℃に1時
間を要して昇温し、同温度に3時間保った。こののち、
95℃に30分かけて降温した。この時点でポリスチレ
ンビーズ約5gを採取した。
【0029】次に同温度でシクロヘキサン24g及ぴブ
タン84gを1時間を要して圧入した。その後、100
℃のまま3時間保持したのち、冷却速度0.5℃/分で
室温まで冷却し目的とする発泡性ポリスチレン樹脂粒子
を得た。
【0030】 得られた発泡性ポリスチレン樹脂粒子を
篩い分けした結果、平均粒子径(d50)は0.95m
m、偏差係数Cvは0.30であった。
【0031】得られた発泡性ポリスチレン樹脂粒子を5
0ml/gに予備発泡し、24時間熟成後、加熱発泡成形し
た。得られた成型品のセル数は、57ケ/mm2で、成形品
の強度は、3.18kgf/cm2であった。
【0032】実施例2
保温処理温度を70℃としたこと以外は、実施例lと同
様に行い発泡性ポリスチレン樹脂粒子を得た。重合転化
率が5%、8%、25%、40%、60%の時の水素イ
オン濃度はそれぞれ、10-7.5グラムイオン、10
-10.6グラムイオン、10-8.5グラムイオン、10-7.6
グラムイオン、10-7.5グラムイオンであった。得られ
た発泡性ポリスチレン樹脂粒子を篩い分けした結果、平
均粒子径(d50)は0.94mm、偏差係数Cvは0.3
3であった。70℃で1時間保温処理を完了した時点で
のビニル系単量体の重合転化率は5%であった。また、
得られた発泡性ポリスチレン樹脂粒子を50ml/gに予備
発泡し、24時間熟成後、加熱発泡成形した。得られ成
形品のセル数は、l02ケ/mm2で、成形品の強度は3.
20kgf/cm2であった。
【0033】実施例3
保温処理温度を80℃としたこと以外は、上記実施例l
と同様に行い発泡性ポリスチレン樹脂粒子を得た。重合
転化率が5%、8%、25%、40%、60%での水素
イオン濃度はそれぞれ、10−7.5グラムイオン、1
0−10.6グラムイオン、10−8.3グラムイオ
ン、10−7.5グラムイオン、10−7.3グラムイ
オンであった。80℃でl時間保温処理を完了した時点
でのビニル系単量体の重合転化率は、8%であった。得
られた重合体粒子を篩い分けした結果、平均粒子径(d
50)は0.85mm、偏差係数Cvは0.34であっ
た。得られた発泡性ポリスチレン樹脂粒子に50ml/gに
予備発泡し、24時間熟成後、加熱発泡成形した。得ら
れた成形品のセル数は、188ケ/mm2で、成形品の強
度は3.30kgf/cm2であった。
【0034】実施例4
保温処理時間を2時間としたこと以外は、上記実施例l
と同様に行い発泡性ポリスチレン樹脂粒子を得た。重合
転化率が5%、8%、25%、40%、60%での水素
イオン濃度はそれぞれ、10−7.5グラムイオン、1
0−10.6グラムイオン、10−8.3グラムイオ
ン、10−7.5グラムイオン、10−7.3グラムイ
オンであった。60℃で2時間保温処理を完了した時点
でのビニル系単量体の重合転化率は、5%であった。得
られた重合体粒子を篩い分けした結果、平均粒子径(d
50)は0.99mm、偏差係数Cvは0.34であっ
た。得られた発泡性ポリスチレン樹脂粒子を50ml/gに
予備発泡し、24時間熟成後、加熱発泡成形した。得ら
れた成形品のセル数は、102ケ/mm2で、成形品の強
度は3.20kgf/cm2であった。
【0035】比較例1
保温処理を行わなず、90℃まで昇温こと以外は、上記
実施例lと同様に行い発泡性ポリスチレン樹脂粒子を得
た。重合転化率が5%、8%、25%、40%、60%
での水素イオン濃度はそれぞれ、10−7.5グラムイ
オン、10−10.5グラムイオン、10−8.4グラ
ムイオン、10−7.6グラムイオン、10−7.4グ
ラムイオンであった。得られた重合体粒子を篩い分けし
た結果、平均粒子径(d50)は0.91mm、偏差係数
Cvは0.35であった。得られた発泡性ポリスチレン
樹脂粒子を50ml/gに予備発泡し、24時間熟成後、加
熱発泡成形した。得られた成形品のセル数は、44ケ/m
m2で、成形品の強度は3.10kgf/cm2であった。
【0036】比較例2
保温処理温度を50℃としたこと以外は、上記実施例l
と同様に行い発泡性ポリスチレン樹脂粒子を得た。重合
転化率が5%、8%、25%、40%、60%での水素
イオン濃度はそれぞれ、10−7.5グラムイオン、1
0−10.4グラムイオン、10−8.4グラムイオ
ン、10−7.5グラムイオン、10−7.3グラムイ
オンであった。得られた重合体粒子を篩い分けした結
果、平均粒子径(d50)は0.90mm、偏差係数Cv
は0.34であった。得られた発泡性ポリスチレン樹脂
粒子を50ml/gに予備発泡し、24時間熟成後、加熱発
泡成形した。得られた成形品のセル数は、45ケ/mm2
で、成形品の強度は3.04kgf/cm2であった。
【0037】比較例3
保温処理時間を15分としたこと以外は、上記実施例l
と同様に行い発泡性ポリスチレン樹脂粒子を得た。重合
転化率が5%、8%、25%、40%、60%での水素
イオン濃度はそれぞれ、10−7.5グラムイオン、1
0−10.5グラムイオン、10−8.5グラムイオ
ン、10−7.5グラムイオン、10−7.4グラムイ
オンであった。得られた重合体粒子を篩い分けした結
果、平均粒子径(d50)は1.05mm、偏差係数Cv
は0.63であった。得られた発泡性ポリスチレン樹脂
粒子を50ml/gに予備発泡し、24時間熟成後、加熱発
泡成形した。得られた成形品のセル数は、46ケ/mm2
で、成形品の強度は3.12kgf/cm2であった。
【0038】 上記の実施例及び比較例で得られた発泡
性ポリスチレン樹脂粒子の製造及び成形品における諸特
性をまとめて表lに示した。
【表1】
【0039】
【発明の効果】請求項1におけるビニル系重合体粒子の
製造法により、粒度分布が狭く、特に微小粒子の発生が
少なくしてビニル系重合体粒子を製造することができ
る。このため、目標粒径範囲にある高品質の粒子の収率
が上がり、さらに微小粒子が少ないことから生産時の作
業性が向上し、生産性及び収益に寄与することができ
る。このビニル系重合体粒子を発泡性重合体粒子とし、
発泡成形して得られる成形品はセル数が多く、強度に優
れる。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suspension polymerization of vinyl monomers, wherein the polymer particles obtained have a narrow particle size distribution and The present invention relates to a method for producing a vinyl polymer particle having excellent strength, which is obtained by forming a foamable vinyl polymer particle using the above method, and forming a molded article obtained by foaming the same. [0002] A vinyl polymer particle mainly composed of styrene obtained by a suspension polymerization method is impregnated with a hydrocarbon such as butane, pentane or the like as a blowing agent to form a foamable vinyl polymer particle. Particles are obtained. The expandable vinyl polymer particles are roughly classified into the following three application fields according to the particle diameter. That is, a particle diameter of 300 to 600 μm
Is used for instant food cups and foamed concrete, 600 to 1500 μm is used for various packing materials and fish boxes, and 1500 to 3000 μm is used for building boards. As described above, since the application differs depending on the particle size, a synthesis method having a particle size distribution according to the application is required. That is, if particles having a specific particle size are synthesized in excess of the usage amount, it becomes redundant and becomes economically negative. From this fact, it is important to establish a synthesis method with a narrow particle size distribution in order to efficiently obtain a target particle size. [0003] In general, a suspension polymerization method of a vinyl monomer is as follows.
Using a sparingly dispersing agent consisting of a sparingly soluble phosphate, an anionic surfactant, a water-soluble metal salt that is acidic or neutral in an aqueous medium, and the chemical factors such as their type, concentration, and addition time. By combining mechanical factors such as stirring, the particle size and the particle size distribution are controlled. However, heretofore, polymer particles having a narrow particle size distribution aimed at by the present invention have not been obtained. For this reason, the following method has been proposed. (L) A method of carrying out suspension polymerization while maintaining the hydrogen ion concentration in the aqueous phase in the range of 10 -7 to 10 -5 gram ions (Japanese Patent Laid-Open No. 62-1
(2) A method using calcium acetate or calcium propionate as a suspending and dispersing agent (JP-A-58-6).
(3702) (3) A method in which trisodium phosphate is added during polymerization to generate calcium phosphate in the polymerization system and the polymerization is continued (Japanese Patent Publication No. 59-19136) (4) Polymerization conversion of vinyl monomer A method in which the concentration of hydrogen ions in the aqueous phase is set to 10 -10 to 10 -13 gram ions while the rate is 0 to 30% (JP-A-2-189302). [0005] In the suspension polymerization methods (1) to (3), the polymer particles have a particle diameter of 0.1. 1 to 3.0
Over a wide range of mm, the particle size distribution is broad. In the method (4), the water-based hydrogen ion concentration is set to 10 when the polymerization conversion of the styrene monomer is 0 to 30%.
The method is characterized by -10 to 10 -13 gram ions, but the particle size distribution cannot be narrowed sufficiently, and the expandable polystyrene resin using the polymer particles has a reduced number of cells and is molded. There are drawbacks such as reduced strength when the product is used. The present invention has been made in order to solve the above-mentioned problems, and has an excellent quality as an expandable polymer particle, with the object of producing a narrow styrene-based polymer particle having a particle size distribution. You. [0006] preparation of the vinyl polymer particles in the present invention SUMMARY OF THE INVENTION, the aqueous medium in a vinyl monomer in the presence of insoluble phosphorus Sanshio及beauty anionic surfactant When the suspension polymerization is carried out at a constant temperature between 60 and 80 ° C. , the polymerization conversion of the vinyl monomer does not exceed 10%.
Temperature for 30 minutes to 4 hours , then raise the temperature to polymerize
In addition, while the polymerization conversion of the vinyl monomer is 0 to 5%, the hydrogen ion concentration in the aqueous medium is 10-5 to 10-8 gram ions, and the polymerization conversion is more than 5% and 10% or less. At a time point when the hydrogen ion concentration in the aqueous medium is 10 −10 to 10
It is characterized by adjusting to −12 gram ions and polymerizing. In the present invention, the vinyl monomers include:
Styrene, α-methylstyrene, virtoluene, styrene derivatives such as parachlorostyrene, acrylonitrile,
There are vinyl cyanide such as methacrylonitrile, acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate and butyl acrylate, similar methacrylates, vinyl pyridine, vinyl carbazole, butadiene and the like. In the present invention using the coalesced particles as expandable styrene resin particles, styrene,
Alternatively, it is preferable to use a styrene derivative in an amount of 50% by weight or more. [0008] As a polymerization catalyst for suspension polymerization of these vinyl monomers in an aqueous medium, benzoyl peroxide ,
Generally, vinyl monomers such as organic peroxides such as butyl perbenzoate, higher aliphatic organic peroxides such as tertiary butyl-2-ethylhexanoate, and azo compounds such as azobisisobutyronitrile. A polymerization catalyst used for radical polymerization can be used. These are preferably used in an amount of 0.05 to 0.5% by weight based on the monomer components. In the polymerization, aliphatic mercaptans such as methyl mercaptan and butyl mercaptan, aluminum compounds such as triethylaluminum, nitro compounds such as trinitrobenzene, and halogenation such as carbon tetrachloride and carbon tetrabromide are used as chain transfer agents. carbon, may be used such as α one methylstyrene da timer, it is preferably used by adding a vinyl monomer. When using polymer particles as the expandable styrene resin particles, safety in use, taking into account the problem of odor, the use of α- methyl styrene dimers are particularly preferred. In the polymerization, aromatic plastic solvents such as toluene and ethylbenzene, diesters of divalent alcohol such as 2-ethylhexyl adipate and 2-ethylhexyl phthalate, and fatty acid esters such as butyl stearate and butyl acetate are used as plasticizers. These may be used, and these are preferably used in an amount of 0.05 to 3.0% by weight based on the monomer components. In the polymerization, as a main suspending agent used for stably presenting a dispersed phase in an aqueous medium, sparingly soluble phosphates such as tricalcium phosphate and magnesium phosphate can be used. Preferably, the aqueous medium is 0.1%.
05 to 10% by weight is used. As the anionic surfactant, an alkylbenzene sulfonate such as dodecylbenzenesulfonic acid or a higher fatty acid salt such as sodium alkylsulfonate or sodium oleate can be used. Is used in an amount of 0.001 to 0.05% by weight. In the present invention, during the suspension polymerization, when the polymerization conversion of the vinyl monomer is between 0 and 5%, the hydrogen ion concentration in the polymerization system is 10 -5 to 10 -8 gram ions. I do. If the hydrogen ion concentration in the polymerization system exceeds 10 -5 gram ions while the polymerization conversion is 0 to 5%, the poorly soluble phosphate as the main suspending agent starts to dissolve in the aqueous system, which is not preferable. If it is less than 10 -8 gram ions, the ionic decomposition of the polymerization catalyst is promoted, and the effect as a catalyst decreases. This increases the weight average molecular weight of the polymer particles,
The polymerization time is prolonged, which is not preferable in production. In the present invention, the hydrogen ion concentration in the polymerization system is adjusted to 10 -10 to 10 -12 gram ions at a certain point in time when the polymerization conversion is more than 5% and not more than 10%. At this time,
When the hydrogen ion concentration exceeds 10 -10 gram ions, the effect of suppressing the formation of small polymer particles becomes insufficient, and when the hydrogen ion concentration is less than 10 -12 gram ions, the growth of the polymer particles is promoted and the particle size distribution is wide. Become. In the present invention, as described above, when the hydrogen ion concentration is adjusted along with the progress of polymerization, the polymerization conversion rate becomes 1
When the concentration is more than 0% and 40% or less, the hydrogen ion concentration is 10 −10.
10-8 gram ion, easy polymerization conversion is the hydrogen ion concentration in the 10 -8 ~l0 -5 gram ions at the time of exceeding 40%, if the it is polymer particles thus monitors This is preferred in terms of suppressing the number of particles and obtaining polymer particles having a narrow particle size distribution as a result. As a method for adjusting the hydrogen ion concentration, there is the following method. As a method of lowering the hydrogen ion concentration, a method of adding a water-soluble basic salt is effective, and conversely, as a method of increasing the hydrogen ion concentration, addition of an acid is effective. As the water-soluble basic salt, a water-soluble carbonate, a hydroxide compound and the like are preferable. The acidic components are classified into those added to the vinyl monomer from the beginning of polymerization and those added after the addition of the water-soluble basic salt. As those to be added to the vinyl monomer include organic peroxides such as such as organic acids, Bae <br/> Nzoi Le peroxide and lauroyl peroxide to hydroxyl ion and ion reactions such as benzoic acid and adipic acid . As a compound to be added after the addition of the water-soluble basic salt, a compound whose aqueous solution generally shows acidity such as hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, oxalic acid, and sodium hydrogen sulfite can be used. Among them, phosphoric acid, acetic acid, sodium hydrogen sulfite and the like are preferable. Thus, polymer particles having a narrow particle size distribution can be obtained by appropriately changing the hydrogen ion concentration in the polymerization system according to the polymerization conversion. However, there are some problems. When the hydrogen ion concentration in the polymerization system is reduced, the weight average molecular weight becomes 70 × 10 4 to 150 × 1.
0 4, emulsion polymerization of high molecular weight sizes 0.1~1μm is produced. This emulsion polymer is taken into other vinyl polymer particles or adheres to the particle surface as the polymerization proceeds. This can be seen from the phenomenon that the turbidity of the dispersion system increases with the progress of polymerization, and the transparency eventually increases. Pre-expanding expandable vinyl polymer particles obtained by taking in an ultrahigh molecular weight emulsion polymer or impregnating a vinyl polymer particle attached to the particle surface with a blowing agent such as propane, butane, or pentane In the case of steam molding after aging, the number of cells of the molded article obtained is small and the strength is small. That is, the commercial value is low. Therefore, as a result of intensive studies, in the present invention, the suspension polymerization system was adjusted to 60 to 80 ° C. while the polymerization conversion of the vinyl monomer was 0 to 10%, and was controlled for 30 minutes to 4 hours ( More preferably, the treatment is carried out for 2 hours or less) to obtain expandable vinyl polymer particles from which a molded article having a large number of cells and excellent strength can be obtained. According to the above method, generally 400 to
A vinyl polymer particle having an average particle diameter of 1500 μm and a narrow particle size distribution can be obtained, and the expandable polymer particle gives a molded product obtained by foam molding a beautiful appearance. Can be. When the vinyl polymer particles obtained by the present invention are used as foamable polymer particles, a foaming agent such as propane, butane or pentane is impregnated by a known method. It is preferred that a foaming agent is present in the polymerization system during the polymerization, preferably at a polymerization rate of 75 to 98%, and the particles are impregnated with the foaming agent to obtain foamable polymer particles. Next, examples of the present invention will be described. Below, polymer
Viewing the average particle size and particle size distribution of particles child each deviation coefficient (Cv), it is expressed in median diameter. Deviation coefficient (C
v) is based on the curve of the cumulative weight distribution, and the cumulative weight is 1
The particle diameters of 5%, 50%, and 85% are d 15 ,
When d 50 and d 85 are set, it is calculated by the following equation 1.
The larger the value of Cv, the wider the particle size distribution, and the smaller the value, the narrower the distribution. The average diameter is d
The median diameter represented by 50 is adopted. (Equation 1) The polymerization conversion of the vinyl-based monomer particles was calculated by placing the oil droplets being synthesized in a specific gravity solution to determine the specific gravity, and calculating the specific gravity from the value according to the following equation (2). (Equation 2) When styrene is used as the monomer, since the specific gravity of polystyrene is 1.06 and the specific amount of styrene monomer is 0.91, the polymerization conversion can be obtained by the following equation (3). [Equation 3] The number of cells of the molded article was determined by the following method.
The molded product was cut with a sharp cutter knife or the like, and a micrograph of the cross section was taken. The number of pieces per square millimeter was determined from the obtained photograph. The strength of the molded product is JI
It was measured and determined according to SA-9511. Example 1 Using a 3 liter autoclave having an inner diameter of 140 mm and a height of 210 mm, 24 g of tribasic calcium phosphate and 0.06 g of sodium dodecylbenzenesulfonate were ion-exchanged with 12 water.
And dispersed therein. Hydrogen ion concentration in the polymerization system at this time was l0 -7.5 grams ions. To this, 3.12 g of benzoyl peroxide (based on 0.26 of monomer)
Wt%), 2-ethylhexyl adipate (DOA)
1200 g of styrene in which 7.2 g (0.6% by weight of the monomer) was dissolved was added with stirring, the temperature was raised to 60 ° C. at a rate of 1 ° C./min, the temperature was kept for 1 hour, and the temperature was raised to 90 ° C. To carry out polymerization. The polymerization conversion of the vinyl monomer at the time when the heat treatment at 60 ° C. for 1 hour was completed was 3%. As the stirring blade, the blade portion is rectangular, the outer radius of the blade portion is 45 mm, the inner radius of the blade portion is 35 mm, and the blade area is 3 mm.
An H-shaped stirring blade having two blades having a connection area of 175 mm 2 and a thickness of 00 mm 2 was used at a height of less than half the height of the charging surface and at a height of 62 mm from the bottom of the autoclave. The two baffle plates were installed facing each other so that the baffle was 14 mm, the distance between the center set and the rotation axis was 53 mm, and the tip was 40 mm below the stationary liquid level. The rotation speed was adjusted to 270 rpm. When the polymerization conversion reached 8%, 0.24 g of sodium carbonate was dissolved in 9.36 g of ion-exchanged water and added. At this time, the hydrogen ion concentration in the polymerization system was 10
It was -10.6 gram ions. When the polymerization was proceeded and the polymerization conversion reached 5%, 25%, 40%, and 60%, the hydrogen ion concentration was measured to be 10 -7.5 g ion, 10 -8.5 g ion, 10 -7.6 g ion, 1
It was 0-7.5 gram ions. As the polymerization conversion rate increases, the aqueous turbidity increases, and the polymerization conversion rate becomes 15%.
The density was the highest at the time. At this time 650
The light transmittance in nm is 50%. At this point, the light transmittance increased, and when the polymerization conversion rate was 50%, the light transmittance became 95%. When the polymerization conversion reached 95%, 6 g of tribasic calcium phosphate was further added, and the temperature was raised to 110 ° C. over 1 hour, and kept at the same temperature for 3 hours. After this,
The temperature was lowered to 95 ° C. over 30 minutes. At this time, about 5 g of polystyrene beads were collected. Next, at the same temperature, 24 g of cyclohexane and 84 g of butane were injected under pressure over 1 hour. Then 100
After maintaining the temperature at 3 ° C. for 3 hours, the mixture was cooled to room temperature at a cooling rate of 0.5 ° C./min to obtain target expandable polystyrene resin particles. The obtained expandable polystyrene resin particles
Sieves have divided a result, the average particle diameter (d 50) is 0.95m
m and the deviation coefficient Cv were 0.30. The obtained expandable polystyrene resin particles were mixed with 5
It was prefoamed to 0 ml / g, aged for 24 hours, and then heat foamed. The number of cells of the obtained molded article was 57 / mm 2 , and the strength of the molded article was 3.18 kgf / cm 2 . Example 2 Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that the temperature of the heat treatment was changed to 70 ° C. When the polymerization conversion is 5%, 8%, 25%, 40%, and 60%, the hydrogen ion concentration is 10 −7.5 g ion,
-10.6 g ion, 10 -8.5 g ion, 10 -7.6
Gram ions and 10-7.5 gram ions. As a result of sieving the obtained expandable polystyrene resin particles, the average particle diameter (d 50 ) was 0.94 mm, and the deviation coefficient Cv was 0.3.
It was 3. The polymerization conversion of the vinyl monomer at the time when the heat treatment was completed at 70 ° C. for 1 hour was 5%. Also,
The obtained expandable polystyrene resin particles were pre-expanded to 50 ml / g, aged for 24 hours, and then heat-expanded. The number of cells of the obtained molded product is 102 / mm 2 , and the strength of the molded product is 3.
It was 20 kgf / cm 2 . Example 3 Example 1 was repeated except that the temperature of the heat treatment was 80 ° C.
In the same manner as described above, expandable polystyrene resin particles were obtained. When the polymerization conversion was 5%, 8%, 25%, 40%, and 60%, the hydrogen ion concentration was 10-7.5 g ion, 1
0 -10.6 grams ion, 10 -8.3 grams ion, 10 -7.5 grams ions was 10 -7.3 grams ions. The polymerization conversion of the vinyl monomer at the time when the heat treatment was completed at 80 ° C. for 1 hour was 8%. As a result of sieving the obtained polymer particles, the average particle size (d
50 ) was 0.85 mm, and the deviation coefficient Cv was 0.34. The obtained expandable polystyrene resin particles were pre-expanded at 50 ml / g, aged for 24 hours, and then heat-expanded. The number of cells of the obtained molded product was 188 cells / mm 2 , and the strength of the molded product was 3.30 kgf / cm 2 . Example 4 Example 1 was repeated except that the heat retention time was set to 2 hours.
In the same manner as described above, expandable polystyrene resin particles were obtained. When the polymerization conversion was 5%, 8%, 25%, 40%, and 60%, the hydrogen ion concentration was 10-7.5 g ion, 1
0 -10.6 grams ion, 10 -8.3 grams ion, 10 -7.5 grams ions was 10 -7.3 grams ions. The polymerization conversion of the vinyl monomer at the time when the heat treatment at 60 ° C. was completed for 2 hours was 5%. As a result of sieving the obtained polymer particles, the average particle size (d
50 ) was 0.99 mm, and the deviation coefficient Cv was 0.34. The resulting expandable polystyrene resin particles children and pre-expanded to 50 ml / g, after 24 hours aging was heated foam molding. The number of cells of the obtained molded article was 102 / mm 2 , and the strength of the molded article was 3.20 kgf / cm 2 . Comparative Example 1 Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that the temperature was raised to 90 ° C. without performing the heat retaining treatment. 5%, 8%, 25%, 40%, 60% polymerization conversion
Hydrogen ions are concentration is 10 -7.5 grams ion at 10 -10.5 grams ion, 10 -8.4 grams ion, 10 -7.6 grams ions was 10 -7.4 grams ion . As a result of sieving the obtained polymer particles, the average particle diameter (d 50 ) was 0.91 mm, and the deviation coefficient Cv was 0.35. The resulting expandable polystyrene resin particles children and pre-expanded to 50 ml / g, after 24 hours aging was heated foam molding. The number of cells of the obtained molded article is 44 / m
m 2, and the strength of the molded article was 3.10kgf / cm 2. Comparative Example 2 The above Example 1 was repeated except that the temperature of the heat treatment was 50 ° C.
In the same manner as described above, expandable polystyrene resin particles were obtained. When the polymerization conversion was 5%, 8%, 25%, 40%, and 60%, the hydrogen ion concentration was 10-7.5 g ion, 1
It was 0-10.4 gram ion, 10-8.4 gram ion, 10-7.5 gram ion, and 10-7.3 gram ion . As a result of sieving the obtained polymer particles, the average particle diameter (d 50 ) was 0.90 mm, and the deviation coefficient Cv
Was 0.34. The resulting expandable polystyrene resin <br/> particles children and pre-expanded to 50 ml / g, after 24 hours aging was heated foam molding. The number of cells of the obtained molded product is 45 cells / mm 2
The strength of the molded product was 3.04 kgf / cm 2 . Comparative Example 3 The above Example 1 was repeated except that the heat retention time was changed to 15 minutes.
In the same manner as described above, expandable polystyrene resin particles were obtained. When the polymerization conversion was 5%, 8%, 25%, 40%, and 60%, the hydrogen ion concentration was 10-7.5 g ion, 1
0 -10.5 grams ion, 10 -8.5 grams ion, 10 -7.5 grams ions was 10 -7.4 grams ions. As a result of sieving the obtained polymer particles, the average particle size (d 50 ) was 1.05 mm, and the deviation coefficient Cv
Was 0.63. The resulting expandable polystyrene resin <br/> particles children and pre-expanded to 50 ml / g, after 24 hours aging was heated foam molding. The number of cells of the obtained molded product is 46 cells / mm 2
The strength of the molded product was 3.12 kgf / cm 2 . The production of the expandable polystyrene resin particles obtained in the above Examples and Comparative Examples and various properties of the molded products are summarized in Table 1. [Table 1] According to the method for producing vinyl polymer particles according to the first aspect, it is possible to produce vinyl polymer particles with a narrow particle size distribution, in particular, with less generation of fine particles. For this reason, the yield of high-quality particles in the target particle size range is increased, and since the number of fine particles is small, workability during production is improved, which can contribute to productivity and profit. This vinyl polymer particles as expandable polymer particles,
A molded product obtained by foam molding has a large number of cells and is excellent in strength.
フロントページの続き (56)参考文献 特開 平5−214152(JP,A) 特開 平5−214153(JP,A) (58)調査した分野(Int.Cl.7,DB名) C08F 2/00 - 2/60 Continuation of front page (56) References JP-A-5-214152 (JP, A) JP-A-5-214153 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) C08F 2 / 00-2/60
Claims (1)
イオン界面活性剤の存在下に水性媒体中で懸濁重合する
際に、懸濁重合系をビニル系単量体の重合転化率が10
%を越えない範囲で60〜80℃の間の一定温度に30
分〜4時間保温処理し、次いで昇温して重合すると共
に、ビニル系単量体の重合転化率が0〜5%の間は水性
媒体中の水素イオン濃度を10−5〜l0−8グラムイ
オンとし、重合転化率が5%を越え10%以下の時点で
水性媒体中の水素イオン濃度を10−10〜10−12
グラムイオンに調整して重合することを特徴とするビニ
ル系重合体粒子の製造法。(57) [Claims 1] When a vinyl monomer is subjected to suspension polymerization in an aqueous medium in the presence of a sparingly soluble phosphate and an anionic surfactant, suspension polymerization is carried out. When the polymerization conversion of vinyl monomer is 10
% To a constant temperature between 60 and 80 ° C within a range not exceeding 30 %.
Incubate for a minute to 4 hours , then raise the temperature and polymerize.
When the polymerization conversion of the vinyl monomer is 0 to 5%, the hydrogen ion concentration in the aqueous medium is 10-5 to 10-8 gram ions, and the polymerization conversion is more than 5% and 10% or less. At this time, the hydrogen ion concentration in the aqueous medium is increased to 10 −10 to 10 −12.
A method for producing vinyl-based polymer particles, wherein the polymerization is performed by adjusting to gram ions.
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JP04008195A JP3494249B2 (en) | 1995-02-28 | 1995-02-28 | Method for producing vinyl polymer particles |
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JP (1) | JP3494249B2 (en) |
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1995
- 1995-02-28 JP JP04008195A patent/JP3494249B2/en not_active Expired - Fee Related
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JPH08231611A (en) | 1996-09-10 |
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