{
  "timeline": [
    {
      "date": "1933/4",
      "category": "会社設立",
      "region": "",
      "importance": 3,
      "event": "東洋高圧工業設立",
      "detail": "福岡県大牟田市で硫安工場を操業開始。三井化学の淵源",
      "significance": "三井化学グループの源流の一つ。後の三井東圧化学につながる肥料事業の起点",
      "source": "有価証券報告書"
    },
    {
      "date": "1941/4",
      "category": "会社設立",
      "region": "",
      "importance": 2,
      "event": "三井化学工業設立",
      "detail": "現在の大牟田工場で操業開始",
      "significance": "旧三井東圧化学のもう一つのルーツ。三井系化学事業の基盤形成",
      "source": "有価証券報告書"
    },
    {
      "date": "1951/1",
      "category": "設備投資",
      "region": "",
      "importance": 1,
      "event": "三井化学工業が名古屋工場操業開始",
      "detail": "",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "1955/7",
      "category": "会社設立",
      "region": "",
      "importance": 4,
      "event": "三井石油化学工業を設立",
      "detail": "三井系7社と興亜石油の共同出資。三井グループ主導の石油化学進出",
      "significance": "日本の石油化学工業元年を象徴する設立。当社の直接的な起源",
      "source": "有価証券報告書",
      "amount": "出資8社"
    },
    {
      "date": "1958/4",
      "category": "設備投資",
      "region": "",
      "importance": 3,
      "event": "岩国工場操業開始",
      "detail": "旧陸軍燃料廠跡地約32万㎡。エチレン年産2万トン規模の総合石油化学工場が完成",
      "significance": "日本最初期のエチレン中心石油化学コンビナートの稼働",
      "source": "有価証券報告書",
      "amount": "エチレン年産2万トン"
    },
    {
      "date": "1962/5",
      "category": "設備投資",
      "region": "",
      "importance": 2,
      "event": "岩国大竹工場へ拡張",
      "detail": "大竹地区を加え石油化学コンビナート完成",
      "significance": "西日本石油化学集積地としての地位を確立",
      "source": "",
      "amount": "エチレン年産6万トン規模の第2号プラント"
    },
    {
      "date": "1962/10",
      "category": "株式上場",
      "region": "",
      "importance": 2,
      "event": "東証・大証2部に上場",
      "detail": "",
      "significance": "株式市場からの資金調達基盤を獲得",
      "source": "有価証券報告書"
    },
    {
      "date": "1964/11",
      "category": "設備投資",
      "region": "",
      "importance": 1,
      "event": "東洋高圧工業が大阪工場操業開始",
      "detail": "",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "1965/2",
      "category": "株式上場",
      "region": "",
      "importance": 2,
      "event": "東証・大証1部に指定替え",
      "detail": "",
      "significance": "主要企業としての地位確立",
      "source": "有価証券報告書"
    },
    {
      "date": "1967/3",
      "category": "設備投資",
      "region": "",
      "importance": 3,
      "event": "千葉工場操業開始",
      "detail": "東京湾岸の五井姉崎埋立地。エチレン年産12万トンと当時日本最大・世界的規模",
      "significance": "東西2極供給体制の確立。日本石油化学産業の中核拠点",
      "source": "有価証券報告書",
      "amount": "エチレン年産12万トン"
    },
    {
      "date": "1967/11",
      "category": "組織再編",
      "region": "",
      "importance": 2,
      "event": "浮島石油化学を設立",
      "detail": "日本石油化学との折半出資。設備投資競争を避ける協調路線",
      "significance": "業界再編の先駆け。エチレン能力増強を共同で担う独自モデル",
      "source": ""
    },
    {
      "date": "1968/10",
      "category": "組織再編",
      "region": "",
      "importance": 2,
      "event": "東洋高圧工業が三井化学工業を吸収合併し三井東圧化学に商号変更",
      "detail": "",
      "significance": "後の三井化学合併の片翼となる三井東圧化学の成立",
      "source": "有価証券報告書"
    },
    {
      "date": "1971/7",
      "category": "組織再編",
      "region": "",
      "importance": 1,
      "event": "東京セロファン紙(現アールエム東セロ)に資本参加",
      "detail": "",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "1976",
      "category": "研究開発",
      "region": "",
      "importance": 3,
      "event": "独自触媒技術によるポリオレフィン技術を確立",
      "detail": "ライセンスビジネスとして海外展開",
      "significance": "ポリオレフィン分野で世界的評価。技術型企業への転換点",
      "source": "",
      "amount": "技術供与累計140件超"
    },
    {
      "date": "1984/3",
      "category": "組織再編",
      "region": "",
      "importance": 3,
      "event": "構造改革によりエチレン設備を大幅縮小",
      "detail": "産構法に基づく過剰設備処理。岩国大竹8.7万t・千葉14.3万t廃棄",
      "significance": "二度の石油危機後の業界再編の典型事例。エチレン浮島集約の起点",
      "source": "",
      "amount": "廃棄合計23万t超"
    },
    {
      "date": "1985/3",
      "category": "組織再編",
      "region": "",
      "importance": 3,
      "event": "エチレン生産を浮島石油化学に集約完了",
      "detail": "千葉は基礎化学品、岩国大竹は特殊化学品の中核拠点に再構築",
      "significance": "日本石油化学発祥の地・岩国大竹からエチレンの火が消えた象徴的転換",
      "source": ""
    },
    {
      "date": "1985/10",
      "category": "経営計画",
      "region": "",
      "importance": 3,
      "event": "「超石油化学」中期ビジョンを発表",
      "detail": "事業多角化・高付加価値化・国際化を加速",
      "significance": "汎用品依存から脱却する戦略転換の宣言",
      "source": ""
    },
    {
      "date": "1987/10",
      "category": "設備投資",
      "region": "",
      "importance": 1,
      "event": "新技術研究開発センター設置",
      "detail": "2024年にVISION HUB® SODEGAURAに改称",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "1987/12",
      "category": "海外進出",
      "region": "",
      "importance": 1,
      "event": "Mitsui Toatsu Chemicals (Asia) Pte.Ltd.設立",
      "detail": "現Mitsui Chemicals Asia Pacific",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "1988/10",
      "category": "海外進出",
      "region": "",
      "importance": 1,
      "event": "MTC Industries Inc.設立",
      "detail": "現Mitsui Chemicals America",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "1990/7",
      "category": "海外進出",
      "region": "",
      "importance": 1,
      "event": "Mitsui Petrochemical Industries Europe GmbH設立",
      "detail": "現Mitsui Chemicals Europe",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "1995/10",
      "category": "組織再編",
      "region": "",
      "importance": 3,
      "event": "宇部興産との折半出資でグランドポリマーを設立",
      "detail": "ポリプロピレン事業を一体化",
      "significance": "業界再編の先進事例。ポリオレフィン国際競争力強化策",
      "source": ""
    },
    {
      "date": "1997/10",
      "category": "組織再編",
      "region": "",
      "importance": 5,
      "event": "三井東圧化学と合併し三井化学に商号変更",
      "detail": "対等合併。三井系化学事業の集約",
      "significance": "日本化学業界最大級の合併。総合化学メーカー三井化学の誕生",
      "source": "有価証券報告書"
    },
    {
      "date": "1999/1",
      "category": "海外進出",
      "region": "中国",
      "importance": 1,
      "event": "三井化学(上海)有限公司設立",
      "detail": "現三井化学(中国)管理有限公司",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "2001/4",
      "category": "企業買収",
      "region": "",
      "importance": 2,
      "event": "武田薬品工業のポリウレタン材料事業を統合し三井武田ケミカル設立",
      "detail": "2006年に三井化学ポリウレタンに商号変更",
      "significance": "ポリウレタン事業の基盤強化",
      "source": "有価証券報告書"
    },
    {
      "date": "2003/1",
      "category": "海外進出",
      "region": "",
      "importance": 1,
      "event": "Advanced Composites Inc.発足",
      "detail": "",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "2003/12",
      "category": "株式上場",
      "region": "",
      "importance": 1,
      "event": "大証1部上場廃止（東証1部上場は継続）",
      "detail": "",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "2005/4",
      "category": "企業買収",
      "region": "",
      "importance": 3,
      "event": "出光興産とのJVプライムポリマーを設立",
      "detail": "ポリオレフィン事業統合",
      "significance": "業界再編加速の象徴的事例。後の千葉クラッカー集約の伏線",
      "source": "有価証券報告書"
    },
    {
      "date": "2009/4",
      "category": "組織再編",
      "region": "",
      "importance": 1,
      "event": "三井化学ポリウレタンを吸収合併",
      "detail": "",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "2010/4",
      "category": "社長交代",
      "region": "",
      "importance": 2,
      "event": "田中稔一が代表取締役社長に就任",
      "detail": "",
      "significance": "リーマンショック後の経営再建期を担う体制発足",
      "source": "有価証券報告書"
    },
    {
      "date": "2010/10",
      "category": "企業買収",
      "region": "",
      "importance": 2,
      "event": "三共アグロの農業化学品事業を統合し三井化学アグロ設立",
      "detail": "現三井化学クロップ&ライフソリューション。同時にフィルム・シート事業を統合し三井化学東セロ発足",
      "significance": "後のライフ＆ヘルスケア戦略の中核となる農薬事業の基盤形成",
      "source": "有価証券報告書"
    },
    {
      "date": "2012/3",
      "category": "",
      "region": "",
      "importance": 3,
      "event": "初の連結純損失計上",
      "detail": "JGAAPベース",
      "significance": "リーマン後の業績悪化が顕在化。構造改革の引き金",
      "source": "有価証券報告書",
      "amount": "純損失▲10億円"
    },
    {
      "date": "2014/3",
      "category": "",
      "region": "",
      "importance": 3,
      "event": "連結純損失が拡大",
      "detail": "3期連続の純損失",
      "significance": "構造改革の必要性が決定的に。淡輪体制発足の背景",
      "source": "有価証券報告書",
      "amount": "純損失▲251億円"
    },
    {
      "date": "2014/6",
      "category": "社長交代",
      "region": "",
      "importance": 2,
      "event": "淡輪敏が代表取締役社長に就任",
      "detail": "",
      "significance": "構造改革と成長領域シフトを主導する体制発足",
      "source": "有価証券報告書"
    },
    {
      "date": "2017/3",
      "category": "",
      "region": "",
      "importance": 3,
      "event": "収益力大幅回復",
      "detail": "構造改革効果と成長領域伸長",
      "significance": "構造改革の成果が顕在化。ポートフォリオ転換の正当性が証明された",
      "source": "有価証券報告書",
      "amount": "営業利益1021億円"
    },
    {
      "date": "2018/1",
      "category": "企業買収",
      "region": "欧州",
      "importance": 3,
      "event": "Heraeus Kulzerの歯科材料事業を買収",
      "detail": "ドイツHeraeus Holding GmbHから取得",
      "significance": "オーラルケア事業の一気のグローバル化。ライフ＆ヘルスケアの中核形成",
      "source": "有価証券報告書"
    },
    {
      "date": "2019/6",
      "category": "社長交代",
      "region": "",
      "importance": 2,
      "event": "橋本修が代表取締役社長に就任",
      "detail": "三池炭鉱出身",
      "significance": "二軸経営への転換を担う体制発足",
      "source": "有価証券報告書"
    },
    {
      "date": "2020/8",
      "category": "企業買収",
      "region": "",
      "importance": 2,
      "event": "SKC Co. Ltd.とのポリウレタン材料事業統合JV(Mitsui Chemicals & SKC Polyurethanes)設立",
      "detail": "",
      "significance": "ポリウレタンのグローバル展開強化(後に解消)",
      "source": "有価証券報告書"
    },
    {
      "date": "2021/9",
      "category": "企業買収",
      "region": "",
      "importance": 3,
      "event": "アーク・本州化学工業を連結子会社化",
      "detail": "アークは公開買付・株式交換による完全子会社化、本州化学工業は三井物産との共同公開買付により非公開化",
      "significance": "モビリティ・ICTソリューション両面の強化。ソリューションビジネス拡大の起点",
      "source": "有価証券報告書"
    },
    {
      "date": "2022/4",
      "category": "株式上場",
      "region": "",
      "importance": 1,
      "event": "プライム市場へ移行",
      "detail": "東証市場区分見直し",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "2022/7",
      "category": "組織再編",
      "region": "",
      "importance": 2,
      "event": "SKCとのポリウレタンJVを解消",
      "detail": "Mitsui Chemicals & SKC Polyurethanes合弁解消",
      "significance": "海外JV戦略の見直し",
      "source": "有価証券報告書"
    },
    {
      "date": "2023/7",
      "category": "企業買収",
      "region": "",
      "importance": 3,
      "event": "旭化成のペリクル事業を承継",
      "detail": "吸収分割により三井化学EMSが発足",
      "significance": "EUVペリクル事業の独占的地位を一段強化。ICTソリューションの戦略商品化",
      "source": "有価証券報告書"
    },
    {
      "date": "2023/8",
      "category": "構造改革",
      "region": "",
      "importance": 2,
      "event": "PTAプラント生産停止",
      "detail": "B&GM構造改革第一幕",
      "significance": "構造改革の具体的実行。減損済み資産の整理",
      "source": "IR"
    },
    {
      "date": "2023/10",
      "category": "組織再編",
      "region": "",
      "importance": 2,
      "event": "旭化成と不織布事業統合",
      "detail": "共同新設分割によりエム・エーライフマテリアルズ発足",
      "significance": "衛生材料事業の合理化と高機能シフトの起点",
      "source": "有価証券報告書"
    },
    {
      "date": "2024/3",
      "category": "組織再編",
      "region": "",
      "importance": 2,
      "event": "市原フェノールプラント生産停止を意思決定",
      "detail": "B&GM構造改革第二幕の柱",
      "significance": "フェノール市況悪化への構造的対応。クラッカー再編への布石",
      "source": "IR"
    },
    {
      "date": "2024/4",
      "category": "組織再編",
      "region": "",
      "importance": 1,
      "event": "三井化学ICTマテリアが発足",
      "detail": "アールエム東セロのICT事業を吸収分割",
      "significance": "",
      "source": "有価証券報告書"
    },
    {
      "date": "2024/8",
      "category": "設備投資",
      "region": "",
      "importance": 3,
      "event": "大阪エチレンプラントで蒸気系トラブル",
      "detail": "定修立ち上げ中に発覚",
      "significance": "B&GM構造的脆弱性と設備老朽化を顕在化。クラッカー再編の必要性を一段押し上げた",
      "source": "IR",
      "amount": "影響額△110億円"
    },
    {
      "date": "2024/10",
      "category": "設備投資",
      "region": "",
      "importance": 2,
      "event": "錦湖三井化学MDI20万トン能力増強完了",
      "detail": "",
      "significance": "ウレタン事業のグローバル供給力強化",
      "source": "IR",
      "amount": "増強後20万トン"
    },
    {
      "date": "2025/4",
      "category": "",
      "region": "",
      "importance": 2,
      "event": "𠮷田修が常務執行役員CFOに就任",
      "detail": "中島一の後任",
      "significance": "資本効率改善・PBR1倍超を経営目標の中心に据える新体制",
      "source": "IR"
    },
    {
      "date": "2025/11",
      "category": "経営計画",
      "region": "",
      "importance": 4,
      "event": "二軸経営ビジョンを発表",
      "detail": "グローバルスペシャリティカンパニー＋強靭なB&GM。28年度コア営業利益2000億円目標",
      "significance": "石油化学業界再編を主導する明確な意志表明。研究開発体制改革を伴う成長戦略の本格化",
      "source": "IR",
      "amount": "還元1500億円(4年)"
    },
    {
      "date": "2025/11",
      "category": "組織再編",
      "region": "",
      "importance": 4,
      "event": "千葉地区クラッカー集約を協議",
      "detail": "出光興産との27年度集約。住友化学のポリオレフィン事業もプライムポリマーに加わる方向",
      "significance": "日本石油化学業界再編の先行モデル。長年の課題への突破口",
      "source": "IR",
      "amount": "集約年27年度"
    },
    {
      "date": "2026/2",
      "category": "組織再編",
      "region": "",
      "importance": 2,
      "event": "自己株式取得を意思決定",
      "detail": "PBR安定的1倍超を目指す資本効率改善策",
      "significance": "還元手段を増配から自社株買いへ転換",
      "source": "IR"
    },
    {
      "date": "2026/4",
      "category": "社長交代",
      "region": "",
      "importance": 2,
      "event": "市村聡が代表取締役社長に就任予定",
      "detail": "15代社長",
      "significance": "二軸経営の実行責任者",
      "source": ""
    }
  ]
}