以下，對本發明進行詳細說明。本發明之懸浮聚合用分散穩定劑含有具有以下之通式(I)所表示之羰基末端及通式(II)所表示之甲醯基末端之改質乙烯醇系聚合物(改質PVA)。 [化4](式中，R表示碳數2～9之烷基) 改質PVA中之通式(I)所表示之羰基末端之含有率相對於各末端(末端二醇基、末端羥甲基、末端羧酸鹽基、通式(I)所表示之羰基末端及通式(II)所表示之甲醯基末端)之合計含量，必須為10莫耳%～40莫耳%。於通式(I)所表示之羰基末端之含有率未達10莫耳%之情形時，羰基末端所引起之不飽和雙鍵起點減少或保護膠體性降低，故而結果無法獲得具有適度之粒徑之乙烯系樹脂。因此，相對於上述各末端之合計含量，通式(I)所表示之羰基末端之含有率必須為10莫耳%以上，較佳為15莫耳%以上，更佳為20莫耳%以上。又，為了製成相對於上述各末端之合計含量，通式(I)所表示之羰基末端之含有率超過40莫耳%之改質PVA，必須利用精密聚合等控制作為異種鍵結末端之末端二醇基或自乙酸乙烯酯單體衍生之末端羥甲基，而對工業製造較為不利。因此，相對於上述各末端之合計含量，通式(I)所表示之羰基末端之含有率必須為40莫耳%以下，較佳為38莫耳%以下，更佳為35莫耳%以下。 於本發明中，末端二醇基意指1,2二醇末端(-CH2
-CH(OH)-CH(OH)- CH3
)，末端羥甲基意指-CH2
CH2
OH，末端羧酸鹽基係指-CH2
COOX(X為Na等鹼金屬等金屬原子)。 重要的是改質PVA中之通式(I)所表示之羰基末端之R為碳數2～9之烷基。存在使用式(I)所表示之羰基末端之R之碳數為1之乙醛之方法，但由於沸點較低，故而存在難以控制聚合、或於懸浮聚合法時因水溶性較高而與乙酸乙烯酯單體液滴之親和性較低而缺乏聚合穩定性之缺點，於工業上並不合適。因此，R之碳數較佳為2以上，進而較佳為3以上。又，若R之碳數超過9，則由於沸點較高，故而難以將未反應成分去除、或成為缺乏分散性能之改質PVA，而未充分地表現出要求物性。因此，R之碳數較佳為9以下，更佳為8以下，進而更佳為6以下，進而更佳為5以下。R可為直鏈狀，亦可為支鏈狀。作為較佳之R之具體例，可列舉：乙基、正丙基、異丙基、正丁基、異丁基、第二丁基、第三丁基、正戊基、異戊基、新戊基、第三戊基、己基、異己基、庚基、辛基等。 改質PVA中之通式(II)所表示之甲醯基末端之含有率相對於各末端(末端二醇基、末端羥甲基、末端羧酸鹽基、通式(I)所表示之羰基末端及通式(II)所表示之甲醯基末端)之合計含量，必須為1莫耳%～25莫耳%。於含有率未達1莫耳%之情形時，甲醯基末端所引起之不飽和雙鍵起點減少或保護膠體性降低，故而結果無法獲得具有適度之粒徑之乙烯系樹脂。因此，相對於上述各末端之合計含量，通式(II)所表示之甲醯基末端之含有率必須為1莫耳%以上，較佳為2莫耳%以上，更佳為3莫耳%以上。又，若製成相對於上述各末端之合計含量而通式(II)所表示之甲醯基末端之含有率超過25莫耳%之改質PVA，則著色變得顯著，於用作分散劑時，會對乙烯系樹脂之著色造成影響。又，存在化學不穩定、水溶液之黏度變高或凝膠化之情形。因此，相對於上述各末端之合計含量，通式(II)所表示之甲醯基末端之含有率必須為25莫耳%以下，較佳為23莫耳%以下，更佳為20莫耳%以下。 乙烯醇系聚合物之末端二醇基、末端羥甲基、末端羧酸鹽基可如網屋繁俊, 「PVA之微細結構」, 高分子加工, 38(8), P388-396, 1989年所記載般根據質子NMR(nuclear magnetic resonance，核磁共振)之波峰位置及其積分值進行鑑定及定量。通式(I)所表示之羰基末端及通式(II)所表示之甲醯基末端亦可根據質子NMR之波峰位置及其積分值而求出。 對末端二醇基、末端羥甲基、末端羧酸鹽基、通式(I)所表示之羰基末端、及通式(II)所表示之甲醯基末端之含量之測定順序進行說明。將乙烯醇系聚合物完全皂化至皂化度99.95莫耳%以上後，充分地進行甲醇洗淨，而製作分析用乙烯醇系聚合物。但是，於測定通式(II)所表示之甲醯基末端之情形時無需皂化，而直接進行分析。對應於成為測定對象之官能基，將所製作之分析用乙烯醇系聚合物溶解於表1所記載之各溶劑中，進而添加數滴NaOH重水溶液使pH＝14後，設為表1所記載之測定溫度且表1所記載之累計次數，獲得該1
H-NMR光譜。任一末端之含量均以PVA之主鏈之亞甲基(1.2～2.0 ppm)之波峰之積分值作為基準，並根據表示表1所記載之各末端之波峰之積分值而算出。具體而言，於各末端測定用1
H-NMR光譜中，若將改質PVA之主鏈之亞甲基之積分值設為b，將各末端之積分值設為a，則鑒於質子數(亞甲基為2，各末端為X(羰基末端及末端二醇基由於出現之波峰為甲基，因此X＝3，末端羧酸鹽基及末端羥甲基由於出現之波峰為亞甲基，因此X＝2，甲醯基末端為X＝1))，改質率(%)計算為(a/X)/(b/2)×100。 再者，末端羧酸鹽基與末端γ-內酯結構處於化學平衡。質子NMR之測定如上所述般於pH值14下進行，故而即便於改質PVA中存在末端γ-內酯結構之情形時，亦會全部轉化為末端羧酸鹽基。因此，於本發明中，末端羧酸鹽基之含量意指末端羧酸鹽基及末端γ-內酯結構之合計含量。 [表1]
又，於本發明之改質PVA中，相對於各末端(末端二醇基、末端羥甲基、末端羧酸鹽基、通式(I)所表示之羰基末端及通式(II)所表示之甲醯基末端)之合計含量，末端羧酸鹽基含有率較佳為2莫耳%～8莫耳%。原因在於藉由將末端羧酸鹽基之含有率設為2莫耳%以上、較理想為3莫耳%以上，可發現改質PVA對乙烯系化合物之親和性提高、空隙增加而塑化劑吸收量增加等物性面上之改善。又，藉由將末端羧酸鹽基之含有率設為8莫耳%以下、較理想為6莫耳%以下，保護膠體性變高，且分散力提高。 本發明之改質PVA之黏度平均聚合度可設為通常使用之200～3500，黏度平均聚合度較佳為500～1000。藉由使黏度平均聚合度為500以上，可獲得保護膠體性提高、二次粒子容易微細化之優勢。又，藉由將黏度平均聚合度設為1000以下，所生成之乙烯系樹脂粒子之多孔性增大，可提高塑化劑吸收性。 黏度平均聚合度係依據JIS K6726：1994而測定。即，根據於將改質PVA完全皂化並精製後於30℃之水中所測得之極限黏度[η]而求出。 就水溶性或水分散性之觀點而言，本發明之改質PVA之皂化度較佳為60莫耳%以上，更佳為65莫耳%以上，進而更佳為70莫耳%以上。又，就使生成之乙烯系樹脂粒子之多孔性增大之觀點而言，本發明之改質PVA之皂化度較佳為80莫耳%以下，更佳為75莫耳%以下。 改質PVA之皂化度係依據JIS K6726：1994而測定。即，可藉由利用氫氧化鈉對試樣中之殘留乙酸基(莫耳%)進行定量，並將其自100中減去而求出。 關於本發明之改質PVA，就促進生成之乙烯系粒子之微細化，又，容易增大生成之乙烯系粒子之多孔性之觀點而言，與聚合物(改質PVA)之雙鍵量成比例之0.2質量%水溶液於波長320 nm下之吸光度較佳為0.2以上，更佳為0.3以上，進而較佳為0.4以上。就雙鍵量增加而聚合物(改質PVA)之穩定性降低之觀點而言，本發明之改質PVA之0.2質量%水溶液於波長320 nm下之吸光度較佳為2.0以下，更佳為1.5以下。 於本發明中，改質PVA之0.2質量%水溶液於波長320 nm下之吸光度係以如下方式進行測定。將測定對象之改質PVA溶解於水中而製備25℃之0.2質量%水溶液。繼而，將該水溶液添加至槽(光路長度10 mm)中，測定波長320 nm下之吸光度。再者，於實施例中，使用島津製作所公司製造之吸光光度計「UV-1800」進行吸光度測定。 本發明之改質PVA之製造方法並無特別限制，於使乙烯酯單體進行自由基聚合時，於下述式(III)所表示之醛共存下一面導入含氧氣體(典型而言為吹入)一面進行聚合，將所獲得之聚合物溶解於醇類之後，利用氫氧化鈉或氨等鹼、或者鹽酸或對甲苯磺酸等酸進行處理而使乙烯酯聚合物皂化之方法簡便且有效率。於本發明中，「導入含氧氣體」之概念係指自反應體系外向反應體系內追加地送入氧氣，即便反應體系內原本便存在來自空氣等之氧氣，而該氧氣亦不會作為被導入之氧氣進行處理。 並不意圖根據理論而限定本發明，若於式(III)所表示之醛共存下使乙烯酯單體進行聚合，則醛之末端質子被奪去而進行鏈轉移，藉此於改質PVA中生成通式(I)所表示之羰基末端。又，認為末端羧酸鹽基係乙烯酯單體之支鏈因皂化處理被切斷而生成，因此可利用聚合率或聚合法等控制其含量(聚合率越高，支鏈越增多，而末端羧酸鹽基越增多)。 通式(III)： [化5](式中，R表示碳數2～9之烷基) R之具體例如式(I)所述。作為式(III)所表示之醛之具體例，可列舉：丙醛、丁醛、戊醛、戊醛、己醛、庚醛、辛醛、壬醛、癸醛。式(III)所表示之醛可單獨使用，亦可將複數種組合使用。 作為乙烯酯單體，除乙酸乙烯酯以外，可列舉：甲酸乙烯酯、丙酸乙烯酯、戊酸乙烯酯、癸酸乙烯酯、月桂酸乙烯酯、硬脂酸乙烯酯、苯甲酸乙烯酯、新戊酸乙烯酯、飽和支鏈脂肪酸乙烯酯及柯赫酸乙烯酯等。 本發明之改質PVA之聚合法並無特別限制，可任意地使用溶液、乳化、懸浮、塊狀聚合等公知之聚合方法，相較於使溶劑進行鏈轉移而可鍵結於末端之溶液聚合，利用乙烯酯單體濃度與作為改質種之醛濃度較高之聚合法進行製造之方法於容易將羰基導入至末端之方面而言較佳，從而較佳為懸浮聚合法。 作為用以生成甲醯基末端之方法，有藉由氧化劑使PVA之主鏈氧化裂解之方法(專利文獻：日本專利特開2000-86992號公報)或使甲醛共存而進行聚合之方法等，前者之氧化劑之處理或PVA之溶解等步驟會增加、或不易控制聚合度分佈。又，關於後者，由於甲醛為低沸點化合物，故而不易單獨進行處理，而難以控制聚合。相對於此，根據本發明者之研究結果，若使於氧氣之共存下進行聚合而獲得之聚乙酸乙烯酯皂化，則會生成甲醯基末端，故而該方法簡便且較佳。 氧氣之導入方法可任意選擇，較佳為導入以氧氣濃度成為1質量%～9質量%之方式利用如氮氣、氬氣、或氦氣之惰性氣體進行稀釋後之氣體。若氧氣濃度未達1質量%，則未將充分量之氧氣導入至反應場所而難以獲得具有甲醯基末端之目標PVA。又，若超過9質量%，則由於超過乙酸乙烯酯之爆炸極限氧氣濃度(9～10質量%)，故而會產生安全上之擔憂。 氧氣向反應體系之導入可任意選擇，一面於聚合液中直接起泡一面進行聚合之方法可增大氧氣與反應體系內之接觸面積，故而導入效率良好。 導入之氧氣量可任意選擇，相對於單體量之氧氣之物質量較佳為0.02莫耳%～20莫耳%之範圍。若超過20莫耳%以上，則會與聚合中之自由基反應而逐漸不進行聚合，於製造方面而言欠佳。又，若成為0.02莫耳%以下，則難以獲得具有充分之甲醯基末端之改質PVA。 使乙烯酯單體進行自由基聚合時之聚合起始劑並無特別限定，可將如下者單獨使用或將兩種以上組合使用：偶氮雙異丁腈、偶氮雙-2,4-二甲基戊腈、偶氮雙(4-甲氧基-2,4-二甲基戊腈)、偶氮雙二甲基戊腈、偶氮雙甲氧基戊腈等偶氮化合物；過氧化乙醯、過氧化苯甲醯、過氧化月桂醯、過氧化乙醯基環己基磺醯基、2,4,4-三甲基戊基-2-過氧化苯氧基乙酸酯等過氧化物；過氧化二碳酸二異丙酯、過氧化二碳酸二(2-乙基己酯)、過氧化二碳酸二乙氧基乙酯等過氧化碳酸酯化合物；過氧化新癸酸第三丁酯、過氧化新癸酸α-異丙苯酯、過氧化新癸酸第三丁酯等過氧化酯化合物等。又，聚合反應溫度並無特別限定，通常可於30～90℃左右之範圍內設定。 於本發明中，聚合率係指利用聚合物濃度測定法所測得之值。即，於聚合過程中對聚合液進行採樣並測定其重量，基於將單體及溶劑蒸餾去除而獲得之聚合物之重量算出聚合液之聚合物濃度，求出相對於單體之聚合物量並算出聚合率。 本發明之懸浮聚合用分散穩定劑亦可於無損本發明之主旨之範圍內，亦可使例如丙烯酸、甲基丙烯酸、丁烯酸等不飽和單羧酸或者該等不飽和單羧酸之烷基酯、順丁烯二酸、反丁烯二酸、伊康酸等不飽和二羧酸或者該等不飽和二羧酸之烷基酯、丙烯腈、甲基丙烯腈、丙烯醯胺、甲基丙烯醯胺等腈或醯胺、伸乙基磺酸、烯丙基磺酸、甲基烯丙基磺酸等烯烴磺酸或者該等之鹽、乙烯醚、乙烯基酮、α-烯烴、鹵化乙烯、偏二鹵乙烯等可與乙烯酯單體共聚合之單體進行共聚合。該單體之混合比率相對於乙烯酯單體之合計莫耳數適宜為10莫耳%以下，較佳為5莫耳%以下。 皂化可將上述所獲得之乙烯酯聚合物溶解於醇中，並於鹼觸媒或酸觸媒之存在下進行。作為醇，可列舉甲醇、乙醇、丁醇等。醇中之聚合物之濃度自20～70重量%之範圍中選擇。作為鹼觸媒，可使用氫氧化鈉、氫氧化鉀、甲醇鈉、乙醇鈉、甲醇鉀等鹼金屬之氫氧化物或醇化物之類的鹼觸媒，作為酸觸媒，可使用鹽酸、硫酸等無機酸水溶液、對甲苯磺酸等有機酸。該觸媒之使用量相對於乙烯酯單體必須設為1～100毫莫耳當量。於該情形時，皂化溫度並無特別限制，較理想為自通常為10～70℃之範圍、較佳為30～50℃之範圍中選擇。反應通常進行1～3小時。 本發明之懸浮聚合用分散穩定劑亦可於無損本發明之主旨之範圍內含有上述改質PVA以外之PVA或其他各種添加劑。作為該添加劑，例如可列舉pH值調整劑、交聯劑、防腐劑、防黴劑、抗黏連劑、消泡劑等。就明顯發揮本發明之效果之觀點而言，本發明之懸浮聚合用分散穩定劑較佳為含有10質量%以上之改質PVA，更佳為含有30質量%以上，進而更佳為含有70質量%以上。 本發明之懸浮聚合用分散穩定劑可尤佳地使用於乙烯系化合物之懸浮聚合。作為乙烯系化合物之單體，可列舉：氯乙烯等鹵化乙烯；乙酸乙烯酯、丙酸乙烯酯等乙烯酯；丙烯酸、甲基丙烯酸、該等之酯及鹽；順丁烯二酸、反丁烯二酸、該等之酯及酸酐；苯乙烯、丙烯腈、偏二氯乙烯、乙烯醚等。該等之中，本發明之懸浮聚合用分散穩定劑尤佳為於單獨使氯乙烯進行懸浮聚合或將氯乙烯與可與氯乙烯共聚合之單體一併進行懸浮聚合時使用。作為可與氯乙烯共聚合之單體，可列舉：乙酸乙烯酯、丙酸乙烯酯等乙烯酯；(甲基)丙烯酸甲酯、(甲基)丙烯酸乙酯等(甲基)丙烯酸酯；乙烯、丙烯等α-烯烴；順丁烯二酸酐、伊康酸等不飽和二羧酸類；丙烯腈、苯乙烯、偏二氯乙烯、乙烯醚等。 本發明之懸浮聚合用分散穩定劑於製造塑化劑吸收性優異之氯乙烯粒子之方面而言，適合製造軟質用氯乙烯，就粒度分佈等優異之方面而言，亦可應用於製造硬質用氯乙烯。又，可製造塑化劑吸收性優異之氯乙烯粒子意指所獲得之氯乙烯粒子之空隙較多，故而亦可期待本發明之懸浮聚合用分散穩定劑之脫單體性亦優異或所獲得之氯乙烯粒子之魚眼較少。 本發明之懸浮聚合用分散穩定劑可單獨使用，又，亦可與其他穩定劑、例如纖維素系衍生物、界面活性劑等併用。 藉由使用本發明之懸浮聚合用分散穩定劑，即便藉由高溫水添加聚合法進行懸浮聚合，亦可獲得樹脂粒子為多孔性且粒徑分佈均勻之氯乙烯樹脂。以下，舉例對乙烯系化合物之聚合法具體地進行說明，但並不限定於該等。 於製造氯乙烯樹脂粒子等樹脂粒子之情形時，相對於乙烯系化合物單體，添加上述懸浮聚合用分散穩定劑0.01質量%～0.3質量%、較佳為0.04質量%～0.15質量%。又，乙烯系化合物與水之比以質量比計可設為乙烯系化合物：水＝1：0.9～1：3，較佳為1：1～1：1.5。 聚合起始劑可使用先前用於乙烯系化合物之聚合者，其中可單獨使用或組合使用如下者：過氧化二碳酸二異丙酯、過氧化二碳酸二(2-乙基己酯)、過氧化二碳酸二乙氧基乙酯等過氧化碳酸酯化合物；過氧化新癸酸第三丁酯、過氧化新癸酸α-異丙苯酯、過氧化新癸酸第三丁酯等過氧化酯化合物；過氧化乙醯基環己基磺醯基、2,4,4-三甲基戊基-2-過氧化苯氧基乙酸酯等過氧化物；偶氮雙-2,4-二甲基過氧化腈、偶氮雙(4-甲氧基-2,4-二甲基過氧化腈)等偶氮化合物；進而過硫酸鉀、過硫酸銨、過氧化氫等。 進而，亦可任意添加適當用於乙烯系化合物之聚合之聚合調整劑、鏈轉移劑、凝膠化改良劑、抗靜電劑、PH值調整劑等。 實施乙烯系化合物之聚合時之各成分之添加比率、聚合溫度等只要依據先前於乙烯系化合物之懸浮聚合中採用之條件進行確定即可，並不存在特別限定之原因。 藉由使用本發明之懸浮聚合用分散穩定劑，可獲得微細且粒度之均勻性較高、塑化劑吸收性較高、鬆比重適當之樹脂粒子。 於一實施形態中，使用本發明之懸浮聚合用分散穩定劑而獲得之樹脂粒子可具有140 μm以下、較佳為130 μm以下、典型而言為110 μm～140 μm之平均粒徑。所謂平均粒徑，係指依據JIS Z8815：1994，使用60目(網眼250 μm)、80目(網眼180 μm)、100目(網眼150 μm)、150目(網眼106 μm)、200目(網眼75 μm)之篩網求出粒度分佈時之累積頻度50%(質量基準)之粒徑(D50)。 於一實施形態中，使用本發明之懸浮聚合用分散穩定劑而獲得之樹脂粒子利用上述方法求出粒度分佈時之累積頻度80%(質量基準)之粒徑(D80)與累積頻度20%(質量基準)之粒徑(D20)之差可成為60 μm以下，較佳為可成為55 μm以下，典型而言可成為40 μm～60 μm。 於一實施形態中，使用本發明之懸浮聚合用分散穩定劑而獲得之樹脂粒子可具有23 phr以上之塑化劑吸收量，較佳為可具有30 phr以上之塑化劑吸收量，典型而言可具有23 phr～35 phr之塑化劑吸收量。於本發明中，樹脂之塑化劑吸收量係根據以下之順序而測定。於內徑25 mm、深度85 mm之鋁合金製容器之底部鋪滿玻璃纖維，並投入樹脂10 g。向其中添加塑化劑(鄰苯二甲酸二辛酯，以下稱為DOP)15 mL，放置30分鐘使DOP充分滲透至樹脂中。其後於1500 G之加速度下對過剩之DOP進行離心分離，測定被樹脂吸收之DOP之質量，並將其換算成樹脂每100質量份之DOP質量份(phr)。 於一實施形態中，使用本發明之懸浮聚合用分散穩定劑而獲得之樹脂粒子可具有0.40 g/mL以上、較佳為0.42 g/mL以上、典型而言為0.40 g/mL～0.45 g/mL之鬆比重。鬆比重係依據JIS K6720-2：1999而測定。 [實施例] 以下，列舉實施例對本發明進而詳細地進行說明。 再者，以下只要無特別說明，則「份」及「%」意指「質量份」及「質量%」。 (實施例1) 〈分散穩定劑之製造〉 將乙酸乙烯酯(單體)100份、水120份、分散劑之聚乙烯醇0.087份、改質種之正丁醛1.5份、及0.026份之偶氮雙異丁腈添加至聚合罐中，一面將氧氣-氮氣混合氣體(氧氣濃度4%，相對於乙酸乙烯酯之氧氣總量為0.11莫耳%)吹入至聚合液正上方之氣相中，一面進行加熱使其等於60℃下聚合，於聚合率達到90%之時間點停止聚合。繼而，藉由常規方法將未聚合之乙酸乙烯酯去除，將所獲得之聚合物溶解於甲醇中，利用氫氧化鈉並藉由常規方法進行皂化，藉由過濾將甲醇分離，於90℃之吉爾老化恆溫箱內乾燥80分鐘，藉此獲得粉狀之改質乙烯醇聚合物(分散穩定劑)。藉由上述分析法分別測定所獲得之改質乙烯醇聚合物之黏度平均聚合度、皂化度、0.2質量%水溶液於波長320 nm下之吸光度、各末端(末端二醇基、末端羥甲基、末端羧酸鹽基、通式(I)所表示之羰基末端及通式(II)所表示之甲醯基末端)之合計含量中所占之末端羧酸鹽基之含有率、式(I)所表示之羰基末端之含有率、及式(II)所表示之甲醯基末端之含有率，結果黏度平均聚合度為600，皂化度為71莫耳%，吸光度為0.29，末端羧酸鹽基之含有率為3.7莫耳%，通式(I)所表示之羰基末端為26.3莫耳%，通式(II)所表示之甲醯基末端為3.7莫耳%。 〈氯乙烯之懸浮聚合〉 向具備攪拌器之容量30 L之不鏽鋼製高壓釜中於攪拌下添加30℃之水12 kg、上述獲得之分散穩定劑9.5 g、作為聚合起始劑之過氧化新癸酸第三丁酯4.6 g、過氧化新癸酸α-異丙苯酯1 g。於真空中將高壓釜脫氣後，添加氯乙烯單體5 kg，並於57℃下聚合4小時。 〈氯乙烯樹脂之評價〉 利用以下之方法對所獲得之氯乙烯樹脂之平均粒徑、粒度分佈、塑化劑吸收量、及鬆比重進行評價。將結果示於表2(表2-1及2-2)。 平均粒徑之測定係依據JIS Z8815：1994，使用60目(網眼250 μm)、80目(網眼180 μm)、100目(網眼150 μm)、150目(網眼106 μm)、200目(網眼75 μm)之篩網，將累積頻度50%(質量基準)之粒徑(D50)設為平均粒徑，將累積頻度80%(質量基準)之粒徑(D80)與累積頻度20%(質量基準)之粒徑(D20)之差設為粒度分佈。 鬆比重係依據JIS K6720-2：1999而測得。 塑化劑吸收量係根據以下之順序進行測定。於內徑25 mm、深度85 mm之鋁合金製容器之底部鋪滿玻璃纖維，並投入氯乙烯樹脂10 g。向其中添加塑化劑(鄰苯二甲酸二辛酯，以下稱為DOP)15 mL，放置30分鐘使DOP充分滲透至氯乙烯樹脂中。其後於1500 G之加速度下對過剩之DOP進行離心分離，測定氯乙烯樹脂10 g中所吸收之DOP之質量，並將其換算成氯乙烯樹脂每100質量份之DOP質量份(phr)。 (實施例2～4、6、8、9) 將改質種及其添加量、由氧氣-氮氣混合氣體供給之氧氣總量、氧氣-氮氣混合氣體之氧氣濃度、氧氣-氮氣混合氣體之吹入場所、聚合率、聚合度、皂化度變更為表2所記載之條件，除此以外，以與實施例1相同之方式獲得改質乙烯醇聚合物(分散穩定劑)。關於表2中之氧氣-氮氣混合氣體之吹入場所，有「氣相」者係與實施例1同樣地將氧氣-氮氣混合氣體之噴出口配置於聚合液正上方之氣相並吹入之方法，有「液相」者係將氧氣-氮氣混合氣體之噴出口插入至聚合液內並吹入之方法(起泡)。 繼而，使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對改質乙烯醇聚合物(分散穩定劑)及氯乙烯樹脂之特性進行評價所得之結果示於表2。 (實施例5) 針對實施例2中所獲得之改質乙酸乙烯酯聚合物，調整氫氧化鈉量並進行皂化，藉此獲得皂化度80%之改質乙烯醇聚合物。使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對分散穩定劑及氯乙烯樹脂之特性進行評價所得之結果示於表2。 (實施例7) 將實施例6中所獲得之改質乙烯醇聚合物於120℃下進行4小時熱處理，藉此獲得吸光度增加之樹脂。使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對分散穩定劑及氯乙烯樹脂之特性進行評價所得之結果示於表2。 (實施例10) 將乙酸乙烯酯100份、改質種之正丁醛1.3份及偶氮雙異丁腈0.083份添加至聚合罐中，一面將氧氣-氮氣混合氣體(氧氣濃度為3%，相對於乙酸乙烯酯之氧氣總量為0.05莫耳%)吹入至聚合液正上方之氣相中，一面加熱至65℃，於聚合率達到70%之時間點停止聚合。其後以與實施例1相同之順序進行皂化，並經過分離操作而獲得粉狀之改質乙烯醇聚合物(分散穩定劑)。使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對分散穩定劑及氯乙烯樹脂之特性進行評價所得之結果示於表2。 (比較例1) 將改質種之添加量變更為表2所記載之條件，藉由氮氣置換將反應體系設為氮氣環境下，一面自氣相導入氮氣一面進行聚合，除此以外，以與實施例1相同之方式獲得改質乙烯醇聚合物(分散穩定劑)。繼而，使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對分散穩定劑及氯乙烯樹脂之特性進行評價所得之結果示於表2。於該情形時，所獲得之氯乙烯樹脂粒子之平均粒徑較大，粒徑分佈亦寬廣，因此分散穩定劑之分散力不充分。 (比較例2) 將聚合率及皂化度變更為表2所記載之條件，於未進行氮氣置換並將反應體系液封而阻斷來自外部之空氣導入之狀態下，其他條件與實施例1相同而獲得改質乙烯醇聚合物(分散穩定劑)。繼而，使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對分散穩定劑及氯乙烯樹脂之特性進行評價所得之結果示於表2。於該情形時，所獲得之氯乙烯樹脂粒子之平均粒徑較大，粒徑分佈亦寬廣，因此分散穩定劑之分散力不充分。再者，比較例2中雖生成若干甲醯基末端，但認為其係由反應體系中原本存在之空氣產生。 (比較例3) 將乙酸乙烯酯100份、甲醇120份添加至聚合罐中，一面將氧氣-氮氣混合氣體(氧氣濃度6%，氧氣總量0.10莫耳%)吹入至聚合液正上方之氣相中，一面加熱至65℃，於聚合率達到90%之時間點停止聚合。其後以與實施例1相同之順序進行皂化，並經過分離操作而獲得粉狀之改質乙烯醇聚合物(分散穩定劑)。繼而，使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對分散穩定劑之特性進行評價所得之結果示於表2。於該情形時，氯乙烯樹脂黏連化而無法進行測定。 (比較例4) 將乙酸乙烯酯100份、甲醇68份、改質種之十二烷醛10.7份及偶氮雙異丁腈0.083份添加至聚合罐中，藉由氮氣置換將反應體系製成氮氣環境下後進行加熱並升溫至70℃，於聚合率達到85%之時間點停止聚合。其後以與實施例1相同之順序進行皂化，並經過分離操作而獲得粉狀之改質乙烯醇聚合物(分散穩定劑)。繼而，使用所獲得之分散穩定劑，除此以外，以與實施例1相同之條件實施氯乙烯之懸浮聚合。將利用與實施例1相同之方法對分散穩定劑及氯乙烯樹脂之特性進行評價所得之結果示於表2。於該情形時，所獲得之氯乙烯樹脂粒子之平均粒徑較大，粒徑分佈亦寬廣，因此分散穩定劑之分散力不充分。 [表2-1]
[表2-2] Hereinafter, the present invention will be described in detail. The dispersion stabilizer for suspension polymerization of the present invention contains a modified vinyl alcohol-based polymer (modified PVA) having a carbonyl terminal represented by the following formula (I) and a formazan terminal represented by the formula (II). [Chemical 4] (wherein R represents an alkyl group having 2 to 9 carbon atoms) The content of the carbonyl terminal represented by the formula (I) in the modified PVA is relative to each terminal (terminal diol group, terminal hydroxymethyl group, terminal carboxylic acid) The total content of the acid salt group, the carbonyl terminal represented by the formula (I) and the formazan terminal represented by the formula (II) must be 10 mol% to 40 mol%. When the content of the carbonyl terminal represented by the formula (I) is less than 10 mol%, the starting point of the unsaturated double bond caused by the carbonyl terminal is decreased or the colloidal property is lowered, so that a moderate particle size cannot be obtained as a result. A vinyl resin. Therefore, the content of the carbonyl end group represented by the formula (I) must be 10 mol% or more, preferably 15 mol% or more, and more preferably 20 mol% or more, based on the total content of the above respective terminals. In addition, in order to obtain a modified PVA having a content of a carbonyl terminal represented by the formula (I) in excess of 40 mol%, it is necessary to control the end of the heterojunction terminal by precision polymerization or the like in order to obtain a total content of the respective terminals. A diol group or a terminal hydroxymethyl group derived from a vinyl acetate monomer is disadvantageous for industrial production. Therefore, the content of the carbonyl end group represented by the formula (I) must be 40 mol% or less, preferably 38 mol% or less, and more preferably 35 mol% or less, based on the total content of the above respective terminals. In the present invention, the terminal diol group means a 1,2 diol terminal (-CH 2 -CH(OH)-CH(OH)-CH 3 ), and the terminal hydroxymethyl group means -CH 2 CH 2 OH, terminal The carboxylate group means -CH 2 COOX (X is a metal atom such as an alkali metal such as Na). It is important that the R at the carbonyl end represented by the formula (I) in the modified PVA is an alkyl group having 2 to 9 carbon atoms. There is a method of using acetaldehyde having a carbon number of 1 in R of a carbonyl terminal represented by the formula (I), but since the boiling point is low, it is difficult to control the polymerization, or in the suspension polymerization method, the water solubility is high and acetic acid The low affinity of the vinyl ester monomer droplets and the lack of polymerization stability are not industrially suitable. Therefore, the carbon number of R is preferably 2 or more, and more preferably 3 or more. Further, when the carbon number of R exceeds 9, the boiling point is high, so that it is difficult to remove the unreacted component or the modified PVA which lacks the dispersibility, and the desired physical properties are not sufficiently exhibited. Therefore, the carbon number of R is preferably 9 or less, more preferably 8 or less, still more preferably 6 or less, still more preferably 5 or less. R may be linear or branched. Specific examples of preferred R include ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, t-butyl, n-pentyl, isopentyl, and neopentyl Base, third amyl, hexyl, isohexyl, heptyl, octyl and the like. The content of the terminal group of the formazan represented by the formula (II) in the modified PVA is relative to each terminal (terminal diol group, terminal methylol group, terminal carboxylate group, carbonyl group represented by the formula (I) The total content of the terminal and the terminal group of the formazan represented by the formula (II) must be 1 mol% to 25 mol%. When the content rate is less than 1 mol%, the starting point of the unsaturated double bond caused by the end of the carbenyl group is decreased or the protective colloid property is lowered, so that a vinyl resin having a moderate particle diameter cannot be obtained as a result. Therefore, the content of the formazan group terminal represented by the formula (II) must be 1 mol% or more, preferably 2 mol% or more, more preferably 3 mol%, based on the total content of the above respective terminals. the above. In addition, when the modified PVA having a content of the formazan group terminal represented by the formula (II) exceeding 25 mol% is obtained as a total amount of the respective terminals, the coloring becomes remarkable, and it is used as a dispersing agent. This will affect the coloration of the vinyl resin. Further, there is a case where the chemical instability is unstable and the viscosity of the aqueous solution becomes high or gelatinized. Therefore, the content of the formazan terminal represented by the formula (II) must be 25 mol% or less, preferably 23 mol% or less, more preferably 20 mol%, based on the total content of the above respective terminals. the following. The terminal diol group, the terminal methylol group, and the terminal carboxylate group of the vinyl alcohol polymer can be as long as the net house, "Microstructure of PVA", Polymer Processing, 38(8), P388-396, 1989 The peak position and its integral value of proton NMR (nuclear magnetic resonance) are identified and quantified. The carbonyl terminal represented by the formula (I) and the formazan terminal represented by the formula (II) can also be determined from the peak position of the proton NMR and the integral value thereof. The order of measurement of the content of the terminal diol group, the terminal methylol group, the terminal carboxylate group, the carbonyl terminal represented by the formula (I), and the formazan terminal represented by the formula (II) will be described. After the vinyl alcohol polymer was completely saponified to a saponification degree of 99.95 mol% or more, the methanol was sufficiently washed to prepare a vinyl alcohol polymer for analysis. However, in the case of measuring the end of the formazan group represented by the formula (II), the analysis is carried out without saponification. The prepared vinyl alcohol-based polymer was dissolved in each solvent described in Table 1 in accordance with the functional group to be measured, and a few drops of a NaOH heavy aqueous solution was added thereto to adjust the pH to 14 to be described in Table 1. The 1 H-NMR spectrum was obtained by measuring the temperature and the cumulative number of times described in Table 1. The content of either end was calculated based on the integrated value of the peak of the methylene group (1.2 to 2.0 ppm) of the main chain of PVA, and was calculated based on the integrated values of the peaks at the respective ends shown in Table 1. Specifically, in the 1 H-NMR spectrum for each end measurement, when the integral value of the methylene group of the main chain of the modified PVA is b, and the integral value of each end is a, the number of protons is considered ( The methylene group is 2, and each end is X (the carbonyl terminal and the terminal diol group are methyl groups due to the occurrence of a peak, so X=3, the terminal carboxylate group and the terminal methylol group are methylene groups due to the occurrence of a peak. Therefore, X = 2, the end of the formazan group is X = 1), and the rate of change (%) is calculated as (a / X) / (b / 2) × 100. Furthermore, the terminal carboxylate group is in chemical equilibrium with the terminal γ-lactone structure. Since the measurement of proton NMR is carried out at pH 14 as described above, even in the case where the terminal γ-lactone structure is present in the modified PVA, it is completely converted into a terminal carboxylate group. Therefore, in the present invention, the content of the terminal carboxylate group means the total content of the terminal carboxylate group and the terminal γ-lactone structure. [Table 1] Further, in the modified PVA of the present invention, it is represented by the terminal (the terminal diol group, the terminal methylol group, the terminal carboxylate group, the carbonyl terminal represented by the formula (I) and the formula (II). The total content of the terminal carboxylate group is preferably from 2 mol% to 8 mol%. The reason is that the content of the terminal carboxylate group is 2 mol% or more, preferably 3 mol% or more, and it is found that the affinity of the modified PVA to the vinyl compound is improved, and the void is increased to form a plasticizer. Improvement in physical properties such as increased absorption. In addition, when the content of the terminal carboxylate group is 8 mol% or less, or preferably 6 mol% or less, the protective colloid property is increased and the dispersing power is improved. The viscosity average degree of polymerization of the modified PVA of the present invention can be set to 200 to 3,500 which is usually used, and the average degree of polymerization of the viscosity is preferably 500 to 1,000. When the average degree of polymerization of the viscosity is 500 or more, the advantage of improving the colloidal property and making the secondary particles easy to be fine can be obtained. In addition, by setting the viscosity average degree of polymerization to 1000 or less, the porosity of the produced ethylene-based resin particles is increased, and the plasticizer absorbability can be improved. The viscosity average degree of polymerization was measured in accordance with JIS K6726:1994. That is, it was determined based on the ultimate viscosity [η] measured in water at 30 ° C after the modified PVA was completely saponified and purified. The degree of saponification of the modified PVA of the present invention is preferably 60 mol% or more, more preferably 65 mol% or more, and still more preferably 70 mol% or more from the viewpoint of water solubility or water dispersibility. In addition, the degree of saponification of the modified PVA of the present invention is preferably 80 mol% or less, and more preferably 75 mol% or less, from the viewpoint of increasing the porosity of the produced ethylene resin particles. The degree of saponification of the modified PVA was measured in accordance with JIS K6726:1994. That is, the residual acetic acid group (% by mole) in the sample can be quantified by using sodium hydroxide, and it can be obtained by subtracting it from 100. In the modified PVA of the present invention, the amount of the double bond of the polymer (modified PVA) is increased from the viewpoint of facilitating the refinement of the produced ethylene-based particles and increasing the porosity of the produced ethylene-based particles. The absorbance of the 0.2% by mass aqueous solution at a wavelength of 320 nm is preferably 0.2 or more, more preferably 0.3 or more, still more preferably 0.4 or more. The absorbance of the 0.2% by mass aqueous solution of the modified PVA of the present invention at a wavelength of 320 nm is preferably 2.0 or less, more preferably 1.5, from the viewpoint of an increase in the amount of the double bond and a decrease in the stability of the polymer (modified PVA). the following. In the present invention, the absorbance of a 0.2% by mass aqueous solution of the modified PVA at a wavelength of 320 nm is measured in the following manner. The modified PVA to be measured was dissolved in water to prepare a 0.2% by mass aqueous solution at 25 °C. Then, this aqueous solution was added to a tank (optical path length: 10 mm), and the absorbance at a wavelength of 320 nm was measured. Further, in the examples, the absorbance measurement was performed using an absorbance photometer "UV-1800" manufactured by Shimadzu Corporation. The method for producing the modified PVA of the present invention is not particularly limited. When the vinyl ester monomer is subjected to radical polymerization, an oxygen-containing gas is introduced while being coexisting with the aldehyde represented by the following formula (III) (typically, blowing) After the polymerization is carried out, the obtained polymer is dissolved in an alcohol, and the method of saponifying the vinyl ester polymer by treating with an alkali such as sodium hydroxide or ammonia or an acid such as hydrochloric acid or p-toluenesulfonic acid is simple and effectiveness. In the present invention, the concept of "introduction of an oxygen-containing gas" means that oxygen is additionally supplied to the reaction system from the outside of the reaction system, and even if oxygen is derived from air or the like in the reaction system, the oxygen is not introduced as the introduction. Oxygen is processed. The present invention is not intended to be limited by theory. If the vinyl ester monomer is polymerized in the presence of an aldehyde represented by the formula (III), the terminal proton of the aldehyde is removed and chain-transferred, thereby modifying the PVA. The carbonyl terminus represented by the formula (I) is produced. In addition, it is considered that the branch of the terminal carboxylate-based vinyl ester monomer is formed by saponification treatment, so that the content can be controlled by a polymerization rate, a polymerization method, or the like (the higher the polymerization rate, the more the branch is increased, and the end The more carboxylate groups are). General formula (III): [Chemical 5] (wherein R represents an alkyl group having 2 to 9 carbon atoms) R is specifically described in the formula (I). Specific examples of the aldehyde represented by the formula (III) include propionaldehyde, butyraldehyde, valeraldehyde, valeraldehyde, hexanal, heptaldehyde, octanal, furfural, and furfural. The aldehyde represented by the formula (III) may be used singly or in combination of plural kinds. Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl valerate, vinyl phthalate, vinyl laurate, vinyl stearate, and vinyl benzoate. Vinyl pivalate, saturated branched fatty acid vinyl ester, and vinyl kocholate. The polymerization method of the modified PVA of the present invention is not particularly limited, and a known polymerization method such as solution, emulsification, suspension, or bulk polymerization can be used arbitrarily, and solution polymerization which can be bonded to the terminal is carried out as compared with a chain transfer of a solvent. The method of producing by using a polymerization method in which the concentration of the vinyl ester monomer and the aldehyde having a higher concentration of the modified species is higher is preferable in that the carbonyl group is easily introduced to the terminal, and thus the suspension polymerization method is preferred. As a method for producing a thiol end, there is a method of oxidatively cleavage of a main chain of PVA by an oxidizing agent (Patent Document: Japanese Laid-Open Patent Publication No. 2000-86992) or a method of co-preserving formaldehyde to carry out polymerization, etc. The treatment of the oxidizing agent or the dissolution of the PVA may increase or make it difficult to control the polymerization degree distribution. Further, in the latter case, since formaldehyde is a low boiling point compound, it is not easy to handle it alone, and it is difficult to control the polymerization. On the other hand, according to the findings of the present inventors, when the polyvinyl acetate obtained by the polymerization in the coexistence of oxygen is saponified, the formamyl terminal is formed, and thus the method is simple and preferable. The method of introducing oxygen can be arbitrarily selected, and it is preferable to introduce a gas diluted with an inert gas such as nitrogen, argon or helium gas so that the oxygen concentration becomes 1% by mass to 9% by mass. If the oxygen concentration is less than 1% by mass, a sufficient amount of oxygen is not introduced into the reaction site, and it is difficult to obtain a target PVA having a formazan terminal. On the other hand, when it exceeds 9% by mass, the explosion-limited oxygen concentration (9 to 10% by mass) of vinyl acetate is exceeded, which causes safety concerns. The introduction of oxygen into the reaction system can be arbitrarily selected, and the method of performing polymerization by directly foaming in the polymerization liquid can increase the contact area between oxygen and the reaction system, so that the introduction efficiency is good. The amount of oxygen introduced may be arbitrarily selected, and the mass of oxygen relative to the monomer amount is preferably in the range of 0.02 mol% to 20 mol%. When it exceeds 20 mol% or more, it will react with the radical in a polymerization, and it will not carry out a polymerization gradually, and it is unpreferable in terms of manufacture. Moreover, when it is 0.02 mol% or less, it is difficult to obtain the modified PVA which has a sufficient methyl group terminal. The polymerization initiator for radical polymerization of the vinyl ester monomer is not particularly limited, and the following may be used singly or in combination of two or more kinds: azobisisobutyronitrile, azobis-2,4-di Azo compound such as methylvaleronitrile, azobis(4-methoxy-2,4-dimethylvaleronitrile), azobisdimethylvaleronitrile, azobismethoxyvaleronitrile; peroxidation Peroxidation of acetamidine, benzammonium peroxide, laurel, hexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate a peroxycarbonate compound such as diisopropyl peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate or diethoxyethyl peroxydicarbonate; A peroxyester compound such as ester, α-isopropylphenyl peroxy neodecanoate or tert-butyl peroxy neodecanoate. Further, the polymerization reaction temperature is not particularly limited, and it can be usually set within a range of from about 30 to 90 °C. In the present invention, the polymerization rate means a value measured by a polymer concentration measurement method. That is, the polymerization liquid was sampled during the polymerization, and the weight thereof was measured. The polymer concentration of the polymerization liquid was calculated based on the weight of the polymer obtained by distilling off the monomer and the solvent, and the amount of the polymer relative to the monomer was determined and calculated. Polymerization rate. The dispersion stabilizer for suspension polymerization of the present invention may also be in the range of the gist of the present invention, and may also be an unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid or crotonic acid or an alkane of the unsaturated monocarboxylic acid. An unsaturated dicarboxylic acid such as a base ester, maleic acid, fumaric acid or itaconic acid or an alkyl ester of the unsaturated dicarboxylic acid, acrylonitrile, methacrylonitrile, acrylamide, A An olefin sulfonic acid such as a nitrile or a guanamine such as acrylamide or a decylamine, an ethyl sulfonate, an allyl sulfonic acid or a methallyl sulfonic acid; or a salt thereof, a vinyl ether, a vinyl ketone or an α-olefin; A monomer copolymerizable with a vinyl ester monomer, such as an ethylene halide or a vinylidene halide, is copolymerized. The mixing ratio of the monomers is preferably 10 mol% or less, and preferably 5 mol% or less, based on the total number of moles of the vinyl ester monomer. Saponification The vinyl ester polymer obtained above can be dissolved in an alcohol and carried out in the presence of a base catalyst or an acid catalyst. Examples of the alcohol include methanol, ethanol, butanol, and the like. The concentration of the polymer in the alcohol is selected from the range of 20 to 70% by weight. As the alkali catalyst, an alkali catalyst such as a hydroxide or an alcoholate of an alkali metal such as sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide or potassium methoxide can be used. As the acid catalyst, hydrochloric acid or sulfuric acid can be used. An organic acid such as an aqueous solution of inorganic acid or p-toluenesulfonic acid. The amount of the catalyst used must be from 1 to 100 millimolar equivalents based on the vinyl ester monomer. In this case, the saponification temperature is not particularly limited, but is preferably selected from the range of usually 10 to 70 ° C, preferably 30 to 50 ° C. The reaction is usually carried out for 1 to 3 hours. The dispersion stabilizer for suspension polymerization of the present invention may contain PVA or other various additives other than the above-described modified PVA within the scope of the gist of the present invention. Examples of the additive include a pH adjuster, a crosslinking agent, a preservative, an antifungal agent, an anti-blocking agent, and an antifoaming agent. In view of the effect of the present invention, the dispersion stabilizer for suspension polymerization of the present invention preferably contains 10% by mass or more of modified PVA, more preferably 30% by mass or more, and even more preferably 70% by mass. %the above. The dispersion stabilizer for suspension polymerization of the present invention can be preferably used for suspension polymerization of a vinyl compound. Examples of the monomer of the vinyl compound include vinyl halide such as vinyl chloride; vinyl ester such as vinyl acetate or vinyl propionate; acrylic acid, methacrylic acid, esters and salts thereof; maleic acid and antibutylic acid. Aenedioic acid, such esters and anhydrides; styrene, acrylonitrile, vinylidene chloride, vinyl ether, and the like. Among these, the dispersion stabilizer for suspension polymerization of the present invention is preferably used for suspension polymerization of vinyl chloride alone or suspension polymerization of vinyl chloride with a monomer copolymerizable with vinyl chloride. Examples of the monomer copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylates such as methyl (meth)acrylate and ethyl (meth)acrylate; and ethylene; An α-olefin such as propylene; an unsaturated dicarboxylic acid such as maleic anhydride or itaconic acid; acrylonitrile, styrene, vinylidene chloride or vinyl ether. The dispersion stabilizer for suspension polymerization of the present invention is suitable for producing soft vinyl chloride in terms of producing vinyl chloride particles having excellent plasticizer absorbability, and is also useful for manufacturing hard use in terms of excellent particle size distribution and the like. Vinyl chloride. Further, since the vinyl chloride particles having excellent plasticizer absorbability can be obtained, since the obtained vinyl chloride particles have a large number of voids, it is expected that the dispersibility of the dispersion stabilizer for suspension polymerization of the present invention is also excellent or obtained. The vinyl chloride particles have fewer fish eyes. The dispersion stabilizer for suspension polymerization of the present invention may be used singly or in combination with other stabilizers such as cellulose derivatives, surfactants and the like. By using the dispersion stabilizer for suspension polymerization of the present invention, even if suspension polymerization is carried out by a high-temperature water addition polymerization method, a vinyl chloride resin in which the resin particles are porous and has a uniform particle size distribution can be obtained. Hereinafter, the polymerization method of the vinyl compound will be specifically described, but it is not limited thereto. In the case of producing a resin particle such as a vinyl chloride resin particle, the dispersion stabilizer for suspension polymerization is added in an amount of 0.01% by mass to 0.3% by mass, preferably 0.04% by mass to 0.15% by mass, based on the ethylene compound monomer. Further, the ratio of the ethylene compound to water can be, for example, a vinyl compound: water = 1:0.9 to 1:3, preferably 1:1 to 1:1.5. As the polymerization initiator, those previously used for the polymerization of a vinyl compound may be used, and the following may be used singly or in combination: diisopropyl peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, Peroxycarbonate compounds such as diethoxyethyl oxydicarbonate; peroxidized neodecanoic acid tert-butyl ester, peroxy neodecanoic acid α-cumyl ester, peroxy neodecanoic acid tert-butyl ester, etc. Ester compound; peroxide such as etidylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; azobis-2,4-di An azo compound such as methyl peroxynitrile or azobis(4-methoxy-2,4-dimethylperoxynitrile); further potassium persulfate, ammonium persulfate, hydrogen peroxide or the like. Further, a polymerization regulator, a chain transfer agent, a gelation improver, an antistatic agent, a pH adjuster, and the like which are suitably used for polymerization of a vinyl compound may be added as needed. The addition ratio, the polymerization temperature, and the like of the respective components in the polymerization of the vinyl compound are not particularly limited as long as they are determined according to the conditions previously employed in the suspension polymerization of the vinyl compound. By using the dispersion stabilizer for suspension polymerization of the present invention, resin particles having a fine particle size uniformity, a high plasticizer absorbability, and a suitable bulk specific gravity can be obtained. In one embodiment, the resin particles obtained by using the dispersion stabilizer for suspension polymerization of the present invention may have an average particle diameter of 140 μm or less, preferably 130 μm or less, and typically 110 μm to 140 μm. The average particle diameter refers to 60 mesh (mesh 250 μm), 80 mesh (mesh 180 μm), 100 mesh (mesh 150 μm), 150 mesh (mesh 106 μm), according to JIS Z8815:1994. A mesh of 200 mesh (mesh 75 μm) was used to determine the particle size distribution (D50) of the cumulative frequency of 50% (mass basis). In one embodiment, the resin particles obtained by using the dispersion stabilizer for suspension polymerization of the present invention have a cumulative frequency of 80% (mass basis) particle diameter (D80) and a cumulative frequency of 20% when the particle size distribution is determined by the above method. The difference in particle diameter (D20) of the mass standard) may be 60 μm or less, preferably 55 μm or less, and typically 40 μm to 60 μm. In one embodiment, the resin particles obtained by using the dispersion stabilizer for suspension polymerization of the present invention may have a plasticizer absorption amount of 23 phr or more, preferably a plasticizer absorption amount of 30 phr or more, typically It can have a plasticizer absorption of 23 phr to 35 phr. In the present invention, the plasticizer absorption amount of the resin is measured in the following order. The bottom of the aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm was covered with glass fiber and charged with 10 g of resin. 15 mL of a plasticizer (dioctyl phthalate, hereinafter referred to as DOP) was added thereto, and allowed to stand for 30 minutes to sufficiently permeate the DOP into the resin. Thereafter, the excess DOP was centrifuged at an acceleration of 1500 G, and the mass of the DOP absorbed by the resin was measured and converted into DOP parts by mass (phr) per 100 parts by mass of the resin. In one embodiment, the resin particles obtained by using the dispersion stabilizer for suspension polymerization of the present invention may have a content of 0.40 g/mL or more, preferably 0.42 g/mL or more, and typically 0.40 g/mL to 0.45 g/ The specific gravity of mL. The bulk specific gravity is measured in accordance with JIS K6720-2:1999. [Examples] Hereinafter, the present invention will be described in detail with reference to examples. In addition, unless otherwise stated, "parts" and "%" mean "parts by mass" and "% by mass". (Example 1) <Production of dispersion stabilizer> 100 parts of vinyl acetate (monomer), 120 parts of water, 0.087 parts of polyvinyl alcohol of a dispersing agent, 1.5 parts of n-butyraldehyde of modified substance, and 0.026 part of Azobisisobutyronitrile was added to the polymerization tank, and an oxygen-nitrogen mixed gas (oxygen concentration of 4%, relative to the total amount of oxygen of the vinyl acetate of 0.11 mol%) was blown into the gas phase directly above the polymerization liquid. In the middle, heating was carried out at a temperature equal to 60 ° C, and the polymerization was stopped at a time when the polymerization rate reached 90%. Then, the unpolymerized vinyl acetate is removed by a conventional method, the obtained polymer is dissolved in methanol, saponified by a conventional method using sodium hydroxide, and methanol is separated by filtration at a temperature of 90 ° C. The aging oven was dried for 80 minutes, whereby a powdered modified vinyl alcohol polymer (dispersion stabilizer) was obtained. The viscosity average degree of polymerization, the degree of saponification, the absorbance of a 0.2% by mass aqueous solution at a wavelength of 320 nm, and the respective ends (end diol group, terminal hydroxymethyl group, and the like) were respectively measured by the above analysis method. The content of the terminal carboxylate group in the total content of the terminal carboxylate group, the carbonyl terminal represented by the formula (I) and the formazan terminal represented by the formula (II), and the formula (I) The content of the carbonyl end group and the content of the formazan group represented by the formula (II) showed a viscosity average degree of polymerization of 600, a degree of saponification of 71 mol%, an absorbance of 0.29, and a terminal carboxylate group. The content of the carbonyl group represented by the formula (I) was 26.3 mol%, and the end of the carbenyl group represented by the formula (II) was 3.7 mol%. <suspension polymerization of vinyl chloride> To a stainless steel autoclave having a capacity of 30 L with a stirrer, 12 kg of water at 30 ° C, 9.5 g of the dispersion stabilizer obtained above, and a new peroxidation as a polymerization initiator were added under stirring. 3-4 g of tert-butyl citrate and 1 g of α-isopropylphenyl peroxy neodecanoate. After the autoclave was degassed in a vacuum, 5 kg of vinyl chloride monomer was added, and polymerization was carried out at 57 ° C for 4 hours. <Evaluation of Vinyl Chloride Resin> The average particle diameter, particle size distribution, plasticizer absorption amount, and bulk specific gravity of the obtained vinyl chloride resin were evaluated by the following methods. The results are shown in Table 2 (Tables 2-1 and 2-2). The average particle size is determined according to JIS Z8815:1994, using 60 mesh (mesh 250 μm), 80 mesh (mesh 180 μm), 100 mesh (mesh 150 μm), 150 mesh (mesh 106 μm), 200 For the mesh (mesh 75 μm), the particle size (D50) with a cumulative frequency of 50% (mass basis) is set as the average particle diameter, and the particle size (D80) and cumulative frequency of the cumulative frequency of 80% (mass basis) are accumulated. The difference in particle diameter (D20) of 20% (mass basis) was set as the particle size distribution. The bulk specific gravity is measured in accordance with JIS K6720-2:1999. The plasticizer absorption amount was measured in the following order. The bottom of the aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm was covered with glass fiber, and 10 g of vinyl chloride resin was introduced. 15 mL of a plasticizer (dioctyl phthalate, hereinafter referred to as DOP) was added thereto, and left for 30 minutes to sufficiently permeate DOP into the vinyl chloride resin. Thereafter, the excess DOP was centrifuged at an acceleration of 1500 G, and the mass of DOP absorbed in 10 g of the vinyl chloride resin was measured and converted into DOP parts by mass (phr) per 100 parts by mass of the vinyl chloride resin. (Examples 2 to 4, 6, 8, and 9) The modified species and the amount thereof added, the total amount of oxygen supplied from the oxygen-nitrogen mixed gas, the oxygen concentration of the oxygen-nitrogen mixed gas, and the oxygen-nitrogen mixed gas were blown. A modified vinyl alcohol polymer (dispersion stabilizer) was obtained in the same manner as in Example 1 except that the conditions, the polymerization rate, the degree of polymerization, and the degree of saponification were changed to those described in Table 2. In the same manner as in the first embodiment, the oxygen-nitrogen mixed gas injection port was placed in the gas phase immediately above the polymerization liquid, and was blown into the gas-nitrogen mixed gas in the gas phase. In the method, the "liquid phase" is a method in which a discharge port of an oxygen-nitrogen mixed gas is inserted into a polymerization liquid and blown in (foaming). Then, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results of evaluation of the properties of the modified vinyl alcohol polymer (dispersion stabilizer) and the vinyl chloride resin by the same method as in Example 1 are shown in Table 2. (Example 5) With respect to the modified vinyl acetate polymer obtained in Example 2, the amount of sodium hydroxide was adjusted and saponified, whereby a modified vinyl alcohol polymer having a degree of saponification of 80% was obtained. Suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results of evaluation of the properties of the dispersion stabilizer and the vinyl chloride resin by the same method as in Example 1 are shown in Table 2. (Example 7) The modified vinyl alcohol polymer obtained in Example 6 was subjected to heat treatment at 120 ° C for 4 hours, whereby a resin having an increased absorbance was obtained. Suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results of evaluation of the properties of the dispersion stabilizer and the vinyl chloride resin by the same method as in Example 1 are shown in Table 2. (Example 10) 100 parts of vinyl acetate, 1.3 parts of modified type n-butyraldehyde, and 0.083 parts of azobisisobutyronitrile were added to a polymerization tank, and an oxygen-nitrogen mixed gas (oxygen concentration was 3%, The mixture was blown into the gas phase immediately above the polymerization liquid while being blown into the gas phase immediately above the polymerization liquid, and heated to 65 ° C to stop the polymerization at a time point when the polymerization rate reached 70%. Thereafter, saponification was carried out in the same manner as in Example 1 and subjected to a separation operation to obtain a powdery modified vinyl alcohol polymer (dispersion stabilizer). Suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results of evaluation of the properties of the dispersion stabilizer and the vinyl chloride resin by the same method as in Example 1 are shown in Table 2. (Comparative Example 1) The amount of the modified species was changed to the conditions described in Table 2, and the reaction system was placed under a nitrogen atmosphere, and the reaction was carried out while introducing nitrogen gas from the gas phase, and the mixture was polymerized. A modified vinyl alcohol polymer (dispersion stabilizer) was obtained in the same manner as in Example 1. Then, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results of evaluation of the properties of the dispersion stabilizer and the vinyl chloride resin by the same method as in Example 1 are shown in Table 2. In this case, the obtained vinyl chloride resin particles have a large average particle diameter and a wide particle size distribution, so that the dispersing power of the dispersion stabilizer is insufficient. (Comparative Example 2) The polymerization rate and the saponification degree were changed to the conditions described in Table 2, and the other conditions were the same as in Example 1 except that the nitrogen gas was not replaced and the reaction system was liquid-sealed to block the introduction of air from the outside. A modified vinyl alcohol polymer (dispersion stabilizer) was obtained. Then, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results of evaluation of the properties of the dispersion stabilizer and the vinyl chloride resin by the same method as in Example 1 are shown in Table 2. In this case, the obtained vinyl chloride resin particles have a large average particle diameter and a wide particle size distribution, so that the dispersing power of the dispersion stabilizer is insufficient. Further, in Comparative Example 2, although some of the formazan terminal was formed, it was considered to be generated by the air originally present in the reaction system. (Comparative Example 3) 100 parts of vinyl acetate and 120 parts of methanol were added to a polymerization tank, and an oxygen-nitrogen mixed gas (oxygen concentration of 6%, total amount of oxygen of 0.10 mol%) was blown directly above the polymerization liquid. In the gas phase, one side was heated to 65 ° C, and the polymerization was stopped at a time point when the polymerization rate reached 90%. Thereafter, saponification was carried out in the same manner as in Example 1 and subjected to a separation operation to obtain a powdery modified vinyl alcohol polymer (dispersion stabilizer). Then, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results obtained by evaluating the properties of the dispersion stabilizer by the same method as in Example 1 are shown in Table 2. In this case, the vinyl chloride resin was stuck and could not be measured. (Comparative Example 4) 100 parts of vinyl acetate, 68 parts of methanol, 10.7 parts of a modified species of dodecyl aldehyde, and 0.083 parts of azobisisobutyronitrile were added to a polymerization tank, and the reaction system was prepared by nitrogen substitution. After heating in a nitrogen atmosphere, the temperature was raised to 70 ° C, and the polymerization was stopped at a time when the polymerization rate reached 85%. Thereafter, saponification was carried out in the same manner as in Example 1 and subjected to a separation operation to obtain a powdery modified vinyl alcohol polymer (dispersion stabilizer). Then, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion stabilizer obtained was used. The results of evaluation of the properties of the dispersion stabilizer and the vinyl chloride resin by the same method as in Example 1 are shown in Table 2. In this case, the obtained vinyl chloride resin particles have a large average particle diameter and a wide particle size distribution, so that the dispersing power of the dispersion stabilizer is insufficient. [table 2-1] [Table 2-2]