200831585 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種具有多峰性分子質量分布之聚乙烯模 製組合物且尤其適合於製造具有增大之直徑及壁厚的管 線。本發明亦係關於在包含齊格勒觸媒（Ziegler eatalys〇 及輔觸媒之催化糸統存在下借助於包含連續聚合步驟之多 級反應序列來製備該模製組合物之方法。 【先前技術】 ’’具有多峰性分子質量分布之聚乙烯模製組合物"或簡稱 夕峰性聚乙烯11之表達係指具有多峰性組態之分子質量分 布曲線之聚乙烯模製組合物或聚乙烯，亦即包含複數個乙 烯聚合物片段（其每一者具有相異或不同之分子量）之聚乙 烯。舉例而S，根據本發明之一較佳實施例，可經由包含 在預疋之不同反應條件下在串聯排列之各別反應器内進行 的連續聚合步驟之多級反應序列而製備多峰性聚乙烯，以 獲得具有不同分子量之各別聚乙烯片段。該類型之方法可 在懸洋液介質中進行：在該情況下，首先在懸浮液介質及 較佳為齊格勒觸媒之合適觸媒存在下，使單體及莫耳質量 調即劑（較佳為氫）在第一反應條件下在第一反應器中聚 合，接著轉移至第二反應器且在第二反應條件下進一步加 以聚。，且若欲製備之聚乙烯例如為三峰的（tHm〇dal)，則 進步轉移至第三反應器中且在第三反應條件下進一步加 以聚合，其中第一反應條件與第二及第三反應條件不同從 而獲得具有不同分子量之三種聚乙稀片段。不同乙烤聚合 125642.doc 200831585 物片段間之分子量差異通常經由重量平均分子量Mw來評 估0 儘管齊格勒觸媒尤其適合於本發明之較佳應用，但亦可 能使用其他觸媒，例如具有均勻觸媒中心之觸媒(或"單位 點’’觸媒），例如茂金屬觸媒。 聚乙稀大規模地用於其中需要具有較高機械強度、較低 進行蠕變之傾向&較高環+竟應力破裂抗性之材料的管線BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene molding composition having a multimodal molecular mass distribution and is particularly suitable for producing a pipe having an increased diameter and wall thickness. The present invention is also directed to a method of preparing the molding composition by means of a multistage reaction sequence comprising a continuous polymerization step in the presence of a catalytic catalyst comprising Ziegler eatalys and a secondary catalyst. ''Polyethylene molding composition having a multimodal molecular mass distribution" or simply the expression of Xifeng polyethylene 11 refers to a polyethylene molding composition having a molecular mass distribution curve of a multimodal configuration or Polyethylene, that is, polyethylene comprising a plurality of ethylene polymer segments, each having a different or different molecular weight. For example, S, according to a preferred embodiment of the present invention, may be included in the pre-existing The multimodal polyethylene is prepared by a multistage reaction sequence of successive polymerization steps carried out in separate reactors arranged in series under different reaction conditions to obtain individual polyethylene fragments having different molecular weights. The method of this type can be suspended. In an aqueous medium: in this case, firstly, in the presence of a suspension medium and a suitable catalyst, preferably a Ziegler catalyst, the monomer and the molar mass tone agent are Hydrogen) is polymerized in the first reactor under the first reaction conditions, then transferred to the second reactor and further polymerized under the second reaction conditions, and if the polyethylene to be prepared is, for example, trimodal (tHm〇) Dal), progressing to the third reactor and further polymerizing under the third reaction conditions, wherein the first reaction conditions are different from the second and third reaction conditions to obtain three polyethylene fragments having different molecular weights. B-bake polymerization 125642.doc 200831585 The difference in molecular weight between fragments is usually evaluated via the weight average molecular weight Mw. Although Ziegler catalysts are particularly suitable for the preferred application of the invention, it is also possible to use other catalysts, for example with uniform touch. Media center catalyst (or "unit point ''catalyst), such as metallocene catalyst. Polyethylene is used on a large scale for the tendency to have higher mechanical strength and lower creep. & higher Ring + material stress-ruptured material pipeline
中。同時’該材料必須能夠易於加卫來製備管線，即使該 等管線經製備而具有增大之直徑及增加之壁厚亦應如此。 具有單峰性（Unimodal/mon〇m〇dal)分子質量分布，亦即 包含具有預定分子量之單—乙稀聚合物片段之聚乙稀模製 組合物具有其加：^性能或由於其環境應力破裂抗性或其機 械韌性方面之缺點。 相比而言’具有雙峰性分子質量分布之模製組合物代表 技術進步其可更易於加工且在與單峰性組合物相同密度 下具有更好的環境應力破裂抗性及較高的機械強度。 EP 739 937描述包含該模製組合物之管線，該組合物基 於聚乙烯，具有雙峰性分子f量分布，可易於加工且仍秋 具有良好之機械性f。然而，在製備具有大於50 em之增 大之直徑及大於1.5 em之增加之壁厚的管線中，通常出現 所謂的”垂曲問題”，因為平人捣 U為鬈合物熔體一旦擠壓成管線形狀 就在其凝固之前開始在重力影響下向下流動，導致管線壁 厚之相當大之差異（若在管線之整個圓周上量測）。該垂: 問題亦於EP 1 320 570中較詳細地闡明。 125642.doc 200831585 【發明内容】 本發明之-目的在於提供基於聚乙稀之模製組合物，其 由於不出現垂曲效應所以具有改良之加工性能，尤复在； 模製組合物㈣具有增大之直徑及增加之壁厚之管線的原: 料的情況下。在其相結合’由此所得之管線應尤其在很長 時期中具有在環境應力&裂抗性及機械強度方面更好之‘ 性組合。 該目的意外地由具有多峰性分子質量分布之聚乙稀模製 組合物達成，該組合物包含：45重量％至55重量％第一乙 烯均聚物A、含有乙稀及另一具有4至8個碳原子之烯烴之 20重量％至40重量％第二共聚物B，及15重量％至3〇重量％ 第三乙稀共聚物C，其中所有百分比係以該模製組合物之 總重量計，其另外包含以模製組合物之總重量計〇〇1重量 %至0.5重量％之具有以下通用化學式之有機聚氧基化合 物： R - [(CH2)n.〇]m - Η 其中η為1至10範圍内之整數， m為3至500範圍内之整數，且 R為氫原子或OH基團或具有1至1〇個碳原子且可帶有諸如 -OH、-COOH、-COOR、-〇CH3 或-〇C2H5 之其他取代基的 烷基， 或具有以下通用化學式之有機聚羥基化合物： ro_ch2_c_(ch2-or)3 其中R可為氫原子或具有1至5個碳原子且可帶有諸如 125642.doc 200831585 OH、-COOH、-COOR、_〇CH3 或-OC2H5 之其他取代基的 烷基， 或該兩種化合物之組合。 表達”第一乙烯均聚物A”、"第二乙烯共聚物B”及"第三 乙烯共聚物C”係指乙烯均聚物A、乙烯共聚物b及乙烯共 聚物C，其分別具有不同的，較佳遞增之分子量。 本發明進一步係關於以串聯懸浮聚合法製備該模製組合 物之方法’及具有等於或大於50 cm之增大之直徑及等於 或大於1.5 cm之增加之壁厚的包含該模製組合物且具有與 較高硬度組合之相當顯著之機械強度性質之管線。 本發明之聚乙稀模製組合物具有在23。〇之溫度下在0.945 g/cm3 至 0.957 g/cm3，較佳 〇,945 g/cm3 至 〇,955 g/cm3，更佳 〇,948 g/Cm3至0,955 g/cm3之範圍内之密度及三峰性分子質 量分布。第二共聚物B包含以按高分子量共聚物B之重量 計1重量％至8重量％之量的具有4至8個碳原子之其他烯烴 單體單元之部分。該等共聚單體之實例為丨·丁烯、1戊 烯、1-己烯、1-辛烯及4-甲基-1-戊烯。第三乙稀共聚物c 亦包含以超高分子量乙烯共聚物C之重量計1重量％至8重 量％範圍内之上述共聚單體之一或多者。 該等較佳量之共聚單體使達成改良之環境應力破裂抗性 成為可處。在該等較佳範圍内，聚乙烯模製組合物有利地 具有另一改良之機械性質組合。 此外’本發明之模製組合物具有根據ISO 1133之表示為 MFIl9〇/5的介於 0·1 dg/min至 0·8 dg/min，尤其 0.1 dg/min至 125642.doc 200831585 0.5 dg/min範圍内的熔融流動指數，及根據ISO/R 1191在 135°C溫度下於十氫萘中量測之介於200 cm3/g至600 cm3/g，尤其 250 cm3/g 至 550 cm3/g，尤其較佳 350 cm3/g 至 490 cmVg範圍内的黏度值VNtQt。 作為三個個別莫耳質量分布之重心位置之量度的三峰性 可借助於在連續聚合階段中形成之聚合物的根據IS〇/R 119 1之黏度值VN來描述。此處應注意在個別反應階段中 形成之聚合物的以下帶寬（bandwidth): 對第一聚合階段後之聚合物所量測之黏度值係與低 分子量聚乙烯A之黏度值VNA相同，且根據本發明係介於 50 cm3/g至 120 cm3/g，尤其 60 cm3/gS 1〇〇 cm3/g範圍内。 對第二聚合階段後之聚合物所量測之黏度值VN〗並不對 應於在第二聚合階段中形成之相對較高分子量之第二聚乙 烯B之VNB，而是聚合物A與聚合物B之混合物之黏度值。 根據本發明，VN2係介於200 cm3/g至4〇〇 cm3/g，尤其25〇 cm3/g至 350 cm3/g範圍内。 對第二聚合階段後之聚合物所量測之黏度值vn〆亦僅可 數學地確定）並不對應於在第三聚合階段中形成之超高分 子量之第三共聚物C之VNc，而是聚合物A、聚合物B鱼聚 合物c之混合物之黏度值。根據本發明，VN3係介於2〇〇 cmVg至600 cmVg，尤其25〇 em3/gjL55〇 cm3/g，尤其較佳 350 cm3/g至 490 cm3/g範圍内。 已發現聚乙二醇、甲氧基聚乙二醇及聚丙二醇為另外存 在之尤其有用的有機聚氧基化合物。較佳制具有介於 125642.doc 200831585 400 g/mol至9000 g/mol範圍内之平均莫耳質量的聚氧基化 合物。該等聚氧基化合物之較佳使用量係介於〇〇2重量％ 至〇·4重量％，尤其較佳Gli4%^3重量％範圍内。 已發現異戊四醇、三羥甲基丙烷、甘油、甘露糖醇及山 梨糖醇為另外存在之尤其有用的有機聚經基化合物。該等 聚羥基化合物之較佳使用量係介於〇〇2重量％至〇4重量 0/〇，尤其較佳0·1重量％至0.3重量％範圍内。 可藉由使單體在懸浮液中於7〇。〇至1〇〇。〇，較佳乃它至 9〇°C範圍内之溫度下在2巴至1〇巴範圍内之壓力下在由過 渡金屬化合物及有機鋁化合物組成之高活性齊格勒觸媒存 在下進行聚合來獲得聚乙烯。聚合反應可以三個階段亦即 以二個連續階段進行，由此在每一步驟中借助於莫耳質量 調節劑，較佳藉由氳的存在來調節分子質量。 詳言之，較佳在將第一反應器中之氫濃度設定為最高之 情形下進行聚合過程。在隨後其他反應器中，氫濃度較佳 有所降低，使得與第二反應器中所使用的氫濃度相比，第 二反應器中所使用的氫濃度較低。較佳在第二反應器及第 三反應器中使用預定共聚單體濃度，較佳地自第二反應器 至第二反應器遞増。如上所述，在較佳在第二反應器及第 三反應器中製備共聚物片段之階段中，因此乙烯用作單體 且具有4至8個碳原子之烯烴較佳用作共聚單體。 本發明之聚乙浠模製組合物之分子質量分布較佳為三峰 的。以此方式’在不使製造製程過度複雜化的情況下藉由 提供串聯的三個反應器可能獲得上述有利之性質組合，由 125642.doc -11· 200831585 此有利地將没備保持在某種限制之規模中。因此，為製備 三峰性聚乙烯模製組合物，乙烯之聚合較佳以在三個以串 聯方式連接之反應器中執行的連續製程進行，其中於三個 反應器中分別設定不同反應條件。聚合反應較佳於懸浮液 中進行：在第一反應器中，較佳將例如齊格勒觸媒之合適 觸媒與懸浮液介質、辅觸媒、乙烯及氫一起饋入。 車父佳’不將任何共聚單體引入第一反應器中。隨後將來 自第一反應器之懸浮液轉移至其中添加乙烯、氫且較佳亦 添加預定量之共聚單體（例如1-丁烯）的第二反應器中。與 饋入第一反應器中之氫之量相比，饋入第二反應器中之氮 之量較佳減少。將來自第二反應器之懸浮液轉移至第三反 應器。在第二反應器中，引入乙烯、氫且較佳以高於第二 反應器中所使用之共聚單體之量引入較佳預定量之共聚單 體，例如1-丁烯。與第二反應器中之氫之量相比，第三反 應器中之氫之量減少。自離開第三反應器之聚合物懸浮液 分離懸浮液介質，且將所得聚合物粉末與所要量之另一有 機聚氧基化合物或有機聚羥基化合物或另一不飽和脂肪烴 化合物混合，此後使其乾燥且隨後較佳進行製粒。 車乂佳一峰性（亦即分子質量分布曲線之較佳三峰性組態） 可根據三個個別分子質量分布之重心位置借助於在每一聚 合階段後獲得的聚合物之根據IS〇/R 1191之黏度值龍加以 描述。 第均聚物A較佳作為低分子f乙烯士句聚物a在第一聚 口反應y驟中形成·在該較佳實施例中，肖第—聚合步鱗 125642.doc -12 - 200831585 後獲得之聚合物所量測之黏度值VNi為低分子量乙稀均聚 物A之黏度值，且較佳介於5〇 〇1113仏至15〇 ，更佳6〇 cmVgiUOcn^，尤其65cm3/01〇〇cm3/g之範圍内。 根據替代實施例，第二高分子量乙烯共聚物3或第三超 面分子畺共聚物C可形成於第一聚合步驟中。 第一共聚物B較佳作為高分子量乙烯於第二聚合反應步 驟中形成。 根據一尤佳實施例，其中低分子量乙烯均聚物A係於第 一聚合反應步驟中形成且高分子量乙烯共聚物B係於第二 聚合反應步驟中形成，對第二聚合反應步驟後獲得之聚合 物所量測之黏度值VN2為低分子量乙烯均聚物a與高分子 罝乙烯共聚物B之混合物之黏度值。VN2較佳係介於7〇 cm3/g至 180 cm3/g，更佳9〇 cm3/gs17〇 cm3/g，尤其 1〇〇 cm3/g至 160 cm3/g範圍内。 在該較佳實施例中，自該等所量測的VNi&VN2之值開 始，高分子量乙烯共聚物B之黏度值VNb可例如由如下經 驗式計鼻： γ^Β = VN2-wj-VN1 1-Wj 其中，Wl為以於前兩步驟中形成之具有雙峰性分子量分布 之聚乙烯之總重量計，以重量％量測的於第一聚合步驟中 形成之低分子量乙烯均聚物之重量比例。 第三共聚物C係較佳在第三聚合反應步驟中經形成為超 高分子量乙烯：在該較佳實施例中，以及在提供不同聚合 125642.doc •13- 200831585 反應次序之替代性實施例中’對第三聚合反應步驟後獲得 之聚合物所量測之黏度值VN3為第—低分子量乙烯均聚物 A、第二高分子量乙烯共聚物B與第三超高分子量乙烯共 聚物C之混合物之黏度值。VA較佳係處於以上已界定之 較佳範圍内’亦即15〇 cmVg至300 cm3/g，較佳15〇 cm3/g 至280 cm3/g’更佳介於180 cm3/g至26〇啦3仏之範圍内， 尤其介於1 80 cm3/g至240 cm3/g之範圍内。 在該較佳實施例中，自該等所量測的VN2及VN3之值開 始，形成於第三聚合步驟中之超高分子量共聚物C之黏度 值VNc可例如由如下經驗式計算： ! 一 w2 其中，W2為以形成於所有三個步驟中之具有三峰性分子量 分布之聚乙烯之總重量計以重量％量測的形成於前兩個步 驟中之具有雙峰性分子量分布之聚乙稀之重量比例。 儘管已參考其中低分子量乙烯均聚物A、冑分子量乙烤 八聚物B及超回为子1共聚物c分別以此順序獲得之較佳 情況給出計算聚乙稀模製組合物之每一乙歸聚合物片段之 黏^值的方式，但該計算方法亦可應用於不同聚合次序。 事實上，在任何情況中，與三種乙烯聚合物片段之生產次 序無：，第-乙烯聚合物片段之黏度值與對第一聚合步驟 後獲得的乙烯聚合物所量測之黏度值VNi相等，第二乙烯 聚合物片段之黏度值可根據以形成於前兩個聚合步驟中之 ’、有又峰f生刀子里分布之聚乙烯之總重量計以重量％量測 125642.doc -14- 200831585 的形成於第—聚合步驟之第—乙烯聚合物片段之重量比例 旦1根據對刀別在第二及第二聚合步驟後獲得的聚合物所 量測之黏度值叫及謂2開始計算，而第三乙烯聚合物片 段之黏度值可根據以形成於所有三個聚合步驟中之具有三 峰=刀子里分布之聚乙烯之總重量計以重量％量測的形成 於前兩個步驟之具有雙峰性分子量分布的聚乙烯之重量比 例且根據對分別在第二及第三聚合步驟後獲得的聚合物 所量測之黏度值vn2及vn3開始計算。 除聚乙烯之外，本發明之聚乙烯模製組合物還可另外包 含其他添加劑。舉例而言，以混合物之總重量計，該等添 加劑為0重量％至10重量％、較佳0重量％至5重量％之量的 熱穩定劑、抗氧化劑、UV吸收劑、光穩定劑、金屬減活 劑、過氧化物破壞化合物、基本共同穩定劑，但亦可為總 量為〇重量❶/。至50重量％之碳黑、填充劑、顏料、阻燃劑或 其組合。 本發明之模製組合物可包含酚系抗氧化劑，尤其為自 Ciba Specialities(Gennaiiy)獲得之具有商標名 irgan〇X2 異戊四醇基（3,5·二-第三丁基-4-羥基苯基）丙酸酯，以作為 熱穩定劑。 本發明之模製組合物尤其適合於製備具有大於5〇 em， 較佳大於70 cm之增大之直徑及大於l5 cm，較佳大於2 cm 之增加之壁厚的管線。 本發明之模製組合物可藉由擠壓製程尤佳地進行加工以 製造管線，且具有介於8 kJ/m2至14 kJ/m2範圍内之缺口衝 125642.doc -15- 200831585 擊勒性（IS0)及大於500 h之環境應力破裂抗性（ESCR)。 缺口衝擊韌性iso係根據ISO 179-1/leA/DIN 53453在 -30 C下里’則。減片之尺寸為x 4 X go mm，其中在試片 中製造具有45。角度、2 mm深度及0.25 mm之缺口底面半徑 的V形缺口。 本發明之模製組合物之環境應力破裂抗性（ESCR)係藉由 内部量測方法加以測定且以h為單位敍述。該實驗室法係 由 M· Fleifiner 描述於 Kunstst〇ffe 77 (1987)，ρ· 45及以下 中’且對應於自那時起生效iIS〇/CD 1677〇。該公開案展 不蹲變測試中周邊有缺口的測試桿上的緩慢裂紋生長之測 疋值與根據ISO Π67的長期加壓測試之脆性分枝（briule branch)之間存在聯繫。借助於在8〇艺之溫度下及4 乂以之 張應力下在作為環境應力破裂促進介質的2%濃度Arkopal 水溶液中之缺口（1·6 mm/刀片）來縮短破裂開始時間以達成 失放夺間之縮短。藉由自具有1 〇 mm厚度之經壓製之板鑛 切一個具有1〇xl〇x9〇 mm之尺寸的測試試片來製造試片。 用於開缺口目的的構建在室内的開缺口裝置中借助於刀 片圍繞周邊在中部對該等測試試片開缺口 (見該公開案之 圖5)。缺口深度為16mm。 【實施方式】 實例1 、乙烯之聚合係以在三個串聯連接之反應器中之連續製程 進仃將已藉由W0 91/18934之實例2方法製備得且在該 文獻中具有操作號2.2之齊格勒觸媒以156 mmoi/h之量 125642.doc -16- 200831585 與足量懸浮液介質（己烧）、作為辅觸媒的具有240 mmol/h 之量之三乙基銘、乙浠及氫一起引入第一反應器中。設定 乙稀之量（=68.9 kg/h)及氫之量（=62 g/h)，使得在第一反應 器之氣體空間中量測到24體積％之乙烯含量及66 5體積〇/〇 之氫含量；剩餘物為氮氣與汽化懸浮液介質之混合物。 第一反應器中的聚合反應係在84°C之溫度下進行。 • 隨後將來自第一反應器中之懸浮液轉移至第二反應器 _ 中’弟一反應器中氣體空間中之氫含量減少至〇·7體積％， 且將43.2 kg/h之量的乙烯與1470 g/h之1-丁烯一起饋入第 二反應器中。氫之量之減少係借助於中間％減壓而達成。 在第二反應器之氣體空間中量測到73·5體積。/〇之乙烯、〇 7 體積％之氫及4.8體積。/。之1-丁烯，剩餘物為氮與汽化懸浮 液介質之混合物。 第二反應器中的聚合反應係在85它之溫度下進行。 經由另一中間&減壓（藉此將第三反應器之氣體空間中 Φ 之氫之里没定為0體積％)，將來自第二反應器中的懸浮液 轉移至第三反應器中。 • 外將24·3 kg/h之量的乙烯與475 g/h之量的1-丁烯一起饋入 ‘ 第二反應器中。在第三反應器之氣體空間中量測到72體積 之乙烯含置、〇體積％之氫含量及5·3體積％之“ 丁烯含 置；剩餘物為氮與汽化懸浮液介質之混合物。 第三反應器中的聚合反應係在84。(：之溫度下進行。 如上所述之串聯操作模式所需之聚合觸媒之長期活性係 借助於特別開發之具有在開頭提及之w〇文獻中表明之組 125642.doc • 17 - 200831585 合物的齊格勒觸媒而達成。該觸媒之可用性之量度為其對 氫之極高之反應及其在1小時至8小時之長時段中保持恆定 之高活性。 將懸浮液介質自離開第三反應器之聚合物懸浮液分離， 使粉末與0.2重量％的具有400 g/mol之莫耳質量的聚乙二醇 混合，此後使混合物乾燥且將粉末進行製粒。 黏度值及如實例1中所述之用於所製備之聚乙烯模製組 合物之聚合物A、B及C的比例wA、wB及wc係於以下表1中 敍述。 表1 實例 1 WA [重量％] 50 WB [重量％] 32 Wc [重量％] 18 VN! [cm3/g] 80 VN2『cm3/gl 305 VNt〇t [cm3/g] 450 FNCT [h] 3100 MFR [g/10 min] 0.32 密度[g/cm3] 0.947 拉伸螺變測試 1.72 (5 MPa/23〇C)， 伸長率[%] AZN [kJ/m2] 13.7 表1及表2中之用於物理性質之縮寫具有以下意義： -FNCT=以由M· FleiBner描述之内部量測方法量測之以 [h]為單位的環境應力破裂抗性（完整缺口蠕變測試）， 條件：80°C，2.5 MPa，2% Arkopal水溶液。 - AZN=根據 ISO 179-1/leA/DIN 53453，在-30^ 下，以 125642.doc -18- 200831585 單位kJ/m2敍述之缺口衝擊韌性IS0。 - 拉伸蠕變測試根據DIN EN ISO 899，在23 °C下及5 MPa 之張應力下；所敍述之數字為96 h後以％為單位之伸長 率。 於Battenfeld之管線擠壓單元上自經製粒材料以於以下 表2中呈現之輸出量且亦於以下表2中呈現之熔融溫度下製 造具有尺寸60 X 8 cm之管線。以此方式所製造之管線具 有完全平滑之表面，而其之其他性質係描述於以下表2 中〇 表2 單位 無PEG之比較實例 包含0.2 % PEG之組合物 輸出量 Kg/h 400 400 熔融溫度 °c 200 195 壓力 Bar 197 222 線速度 m/min 0,053 0,053 管線之外徑 mm 561 561 頂部壁厚 mm 72 74 底部壁厚 mm 125 89 如由表2所表明，自本發明之僅包含0.2重量％ PEG之組 合物所製造之管線與由不包含任何PEG之相同三峰性PE組 合物所製造之管線相比受垂曲影響顯著較小。 125642.doc -19·in. At the same time, the material must be easily configurable to prepare the pipeline, even if the pipeline is prepared to have an increased diameter and an increased wall thickness. Unimodal/mon〇m〇dal molecular mass distribution, that is, a polyethylene molding composition comprising a mono-ethylene polymer segment having a predetermined molecular weight, has its additive properties or due to its environmental stress Disadvantages in fracture resistance or its mechanical toughness. In contrast, a molding composition having a bimodal molecular mass distribution represents a technological advancement that is easier to process and has better environmental stress crack resistance and higher mechanical properties at the same density as the unimodal composition. strength. EP 739 937 describes a line comprising the moulding composition, which is based on polyethylene, has a bimodal molecular f-distribution profile, is easy to process and still has good mechanical properties f in autumn. However, in the preparation of a pipeline having an increased diameter of more than 50 em and an increased wall thickness of more than 1.5 em, a so-called "dip problem" usually occurs because the flat 捣U is a chelating melt once extruded The shape of the pipeline begins to flow downward under the influence of gravity before it solidifies, resulting in a considerable difference in the wall thickness of the pipeline (if measured over the entire circumference of the pipeline). The sag: The problem is also explained in more detail in EP 1 320 570. SUMMARY OF THE INVENTION The present invention is directed to providing a polyethylene-based molding composition which has improved processability due to no sag effect, in particular; molding composition (four) has an increase The original diameter of the pipeline with large diameter and increased wall thickness: in the case of materials. In combination, the resulting line should have a better combination of environmental stress & crack resistance and mechanical strength, especially over a long period of time. This object was unexpectedly achieved by a polyethylene molding composition having a multimodal molecular mass distribution comprising: 45% to 55% by weight of the first ethylene homopolymer A, containing ethylene and another having 4 20% to 40% by weight of the second copolymer B of the olefin of 8 carbon atoms, and 15% by weight to 3% by weight of the third ethylene copolymer C, wherein all percentages are based on the total of the molding composition Further, the weight further comprises from 1% by weight to 0.5% by weight, based on the total weight of the molding composition, of an organopolyoxy compound having the following general formula: R - [(CH2)n.〇]m - Η η is an integer in the range of 1 to 10, m is an integer in the range of 3 to 500, and R is a hydrogen atom or an OH group or has 1 to 1 carbon atom and may carry such as -OH, -COOH, - An alkyl group having another substituent of COOR, -〇CH3 or -〇C2H5, or an organic polyhydroxy compound having the following general formula: ro_ch2_c_(ch2-or)3 wherein R may be a hydrogen atom or have 1 to 5 carbon atoms and An alkane which may carry other substituents such as 125642.doc 200831585 OH, -COOH, -COOR, _〇CH3 or -OC2H5 Base, or a combination of the two compounds. The expression "first ethylene homopolymer A", "second ethylene copolymer B" and "third ethylene copolymer C" means ethylene homopolymer A, ethylene copolymer b and ethylene copolymer C, respectively There are different, preferably increasing molecular weights. The present invention further relates to a method of preparing the molding composition by a series suspension polymerization method and a molding composition having an increased diameter equal to or greater than 50 cm and an increased wall thickness equal to or greater than 1.5 cm and A pipeline having quite significant mechanical strength properties combined with higher hardness. The polyethylene molding composition of the present invention has at 23. Density in the range of 0.945 g/cm3 to 0.957 g/cm3, preferably 〇, 945 g/cm3 to 〇, 955 g/cm3, more preferably 948 g/cm3 to 0,955 g/cm3 Trimodal molecular mass distribution. The second copolymer B contains a portion of other olefin monomer units having 4 to 8 carbon atoms in an amount of 1% by weight to 8% by weight based on the weight of the high molecular weight copolymer B. Examples of such comonomers are oxime butene, 1-pentene, 1-hexene, 1-octene and 4-methyl-1-pentene. The third ethylene copolymer c also contains one or more of the above comonomers in the range of from 1% by weight to 8% by weight based on the weight of the ultrahigh molecular weight ethylene copolymer C. These preferred amounts of comonomers make it possible to achieve improved environmental stress crack resistance. Within such preferred ranges, the polyethylene molding composition advantageously has another improved combination of mechanical properties. Further, the molding composition of the present invention has a MFIl9〇/5 expressed in accordance with ISO 1133 of from 0.1 dg/min to 0.88 dg/min, especially from 0.1 dg/min to 125642.doc 200831585 0.5 dg/ The melt flow index in the range of min, and measured in decalin according to ISO/R 1191 at 135 ° C, between 200 cm 3 /g and 600 cm 3 /g, especially 250 cm 3 /g to 550 cm 3 /g Particularly preferred is a viscosity value VNtQt in the range of 350 cm3/g to 490 cmVg. The trimodality as a measure of the position of the center of gravity of the three individual molar mass distributions can be described by means of the viscosity value VN according to IS〇/R 119 1 of the polymer formed in the continuous polymerization stage. Note here that the following bandwidths of the polymer formed in the individual reaction stages: The viscosity value measured for the polymer after the first polymerization stage is the same as the viscosity value VNA of the low molecular weight polyethylene A, and The invention is in the range of from 50 cm3/g to 120 cm3/g, especially 60 cm3/gS 1〇〇cm3/g. The viscosity value VN measured for the polymer after the second polymerization stage does not correspond to the relatively high molecular weight second polyethylene B VNB formed in the second polymerization stage, but the polymer A and the polymer The viscosity value of the mixture of B. According to the invention, the VN2 system is in the range of from 200 cm 3 /g to 4 〇〇 cm 3 /g, especially from 25 〇 cm 3 /g to 350 cm 3 /g. The viscosity value vn〆 measured for the polymer after the second polymerization stage is also mathematically determined only) and does not correspond to the VNc of the ultrahigh molecular weight third copolymer C formed in the third polymerization stage, but Viscosity value of a mixture of polymer A, polymer B, fish polymer c. According to the invention, the VN3 system is between 2 〇〇 cmVg and 600 cmVg, especially 25 〇 em3/gjL 55 〇 cm 3 /g, particularly preferably in the range of 350 cm 3 /g to 490 cm 3 /g. Polyethylene glycol, methoxypolyethylene glycol and polypropylene glycol have been found to be particularly useful organic polyoxyl compounds. Preference is given to polyoxyl compounds having an average molar mass in the range from 125642.doc 200831585 400 g/mol to 9000 g/mol. The preferred amounts of such polyoxyl compounds are in the range of from 2% by weight to 4% by weight, particularly preferably from 4% by weight of Gli. Pentaerythritol, trimethylolpropane, glycerol, mannitol, and sorbitol have been found to be additional useful organic poly-based compounds. The polyhydroxy compound is preferably used in an amount ranging from 〇〇2% by weight to 〇4% by weight, particularly preferably from 0.1% by weight to 0.3% by weight. The monomer can be brought to a suspension at 7 Torr. 〇 to 1〇〇. 〇, preferably, it is polymerized in the presence of a highly active Ziegler catalyst consisting of a transition metal compound and an organoaluminum compound at a temperature in the range of from 9 bar to 1 bar at a temperature in the range of from 9 bar to 1 bar. Polyethylene is obtained. The polymerization can be carried out in three stages, i.e., in two successive stages, whereby the molecular mass is adjusted in each step by means of a molar mass regulator, preferably by the presence of rhodium. In particular, it is preferred to carry out the polymerization process in the case where the hydrogen concentration in the first reactor is set to the highest. In subsequent reactors, the hydrogen concentration is preferably reduced such that the concentration of hydrogen used in the second reactor is lower compared to the concentration of hydrogen used in the second reactor. Preferably, the predetermined comonomer concentration is used in the second reactor and the third reactor, preferably from the second reactor to the second reactor. As described above, in the stage of preparing the copolymer fragment preferably in the second reactor and the third reactor, an olefin having ethylene as a monomer and having 4 to 8 carbon atoms is preferably used as a comonomer. The molecular weight distribution of the polyethyl hydrazine molding composition of the present invention is preferably trimodal. In this way, it is possible to obtain the above-mentioned advantageous combination of properties by providing three reactors connected in series without excessively complicating the manufacturing process, which is advantageously kept in some kind by 125642.doc -11· 200831585 In the scale of the restrictions. Thus, to prepare a trimodal polyethylene molding composition, the polymerization of ethylene is preferably carried out in a continuous process carried out in three reactors connected in series, wherein different reaction conditions are set in each of the three reactors. The polymerization is preferably carried out in a suspension: in the first reactor, a suitable catalyst such as a Ziegler catalyst is preferably fed together with a suspension medium, a secondary catalyst, ethylene and hydrogen. The car father did not introduce any comonomer into the first reactor. The suspension from the first reactor is then transferred to a second reactor to which ethylene, hydrogen and preferably a predetermined amount of comonomer (e.g., 1-butene) is added. The amount of nitrogen fed into the second reactor is preferably reduced as compared to the amount of hydrogen fed to the first reactor. The suspension from the second reactor is transferred to a third reactor. In the second reactor, ethylene, hydrogen is introduced and preferably a higher predetermined amount of comonomer, such as 1-butene, is introduced in an amount higher than the amount of comonomer used in the second reactor. The amount of hydrogen in the third reactor is reduced as compared to the amount of hydrogen in the second reactor. Separating the suspension medium from the polymer suspension leaving the third reactor, and mixing the resulting polymer powder with a desired amount of another organic polyoxyl compound or an organic polyhydroxy compound or another unsaturated aliphatic hydrocarbon compound, thereby It is dried and then preferably granulated. Che Yijia Yifeng (that is, the preferred trimodal configuration of the molecular mass distribution curve) can be based on the position of the center of gravity of the three individual molecular mass distributions by means of the polymer obtained after each polymerization stage according to IS〇/R 1191 The viscosity value is described by the dragon. The first homopolymer A is preferably formed as a low molecular weight f-vinyl polymer a in the first poly-reaction y. In the preferred embodiment, the Schwarz-aggregation step is 125642.doc -12 - 200831585 The viscosity value VNi measured by the obtained polymer is the viscosity value of the low molecular weight ethylene homopolymer A, and is preferably between 5 and 1113 仏 to 15 〇, more preferably 6 〇 cm VgiUOcn^, especially 65 cm 3 〇〇 Within the range of cm3/g. According to an alternative embodiment, the second high molecular weight ethylene copolymer 3 or the third superplanar molecular ruthenium copolymer C may be formed in the first polymerization step. The first copolymer B is preferably formed as a high molecular weight ethylene in the second polymerization step. According to a particularly preferred embodiment, wherein the low molecular weight ethylene homopolymer A is formed in the first polymerization step and the high molecular weight ethylene copolymer B is formed in the second polymerization step, obtained after the second polymerization step The viscosity value VN2 measured by the polymer is the viscosity value of the mixture of the low molecular weight ethylene homopolymer a and the polymer styrene ethylene copolymer B. VN2 is preferably in the range of from 7 〇 cm 3 /g to 180 cm 3 /g, more preferably 9 〇 cm 3 / gs 17 〇 cm 3 /g, especially from 1 〇〇 cm 3 /g to 160 cm 3 /g. In the preferred embodiment, the viscosity value VNb of the high molecular weight ethylene copolymer B can be measured, for example, by the following empirical formula starting from the values of VNi & VN2 measured: γ^Β = VN2-wj-VN1 1-Wj wherein, W1 is a low molecular weight ethylene homopolymer formed in the first polymerization step, measured by weight% based on the total weight of the polyethylene having a bimodal molecular weight distribution formed in the first two steps. Weight ratio. The third copolymer C is preferably formed into an ultrahigh molecular weight ethylene in a third polymerization step: in the preferred embodiment, and in an alternative embodiment providing a different polymerization 125642.doc • 13-200831585 reaction sequence The viscosity value VN3 measured by the polymer obtained after the third polymerization step is the first low molecular weight ethylene homopolymer A, the second high molecular weight ethylene copolymer B and the third ultrahigh molecular weight ethylene copolymer C. The viscosity of the mixture. Preferably, the VA is within the preferred range defined above, i.e., 15 〇cmVg to 300 cm3/g, preferably 15 〇cm3/g to 280 cm3/g', preferably between 180 cm3/g and 26 〇3 Within the range of 仏, especially between 1 80 cm3/g and 240 cm3/g. In the preferred embodiment, the viscosity value VNc of the ultrahigh molecular weight copolymer C formed in the third polymerization step can be calculated, for example, from the following empirical formula, starting from the values of VN2 and VN3 measured: W2 where W2 is a polyethylene having a bimodal molecular weight distribution formed in the first two steps, measured by weight %, based on the total weight of the polyethylene having a trimodal molecular weight distribution formed in all three steps The weight ratio. Although reference has been made to the calculation of the low molecular weight ethylene homopolymer A, the fluorene molecular weight B-bake octamer B and the super-return to the sub-copolymer c, respectively, in this order, the calculation of each of the polyethylene molding compositions is given. The way in which the B is the viscosity of the polymer fragment, but the calculation method can also be applied to different polymerization orders. In fact, in any case, the production order of the three ethylene polymer fragments is absent: the viscosity value of the first ethylene polymer segment is equal to the viscosity value VNi measured for the ethylene polymer obtained after the first polymerization step, The viscosity value of the second ethylene polymer segment can be measured by weight % based on the total weight of the polyethylene formed in the first two polymerization steps, and the peak distribution is 125642.doc -14- 200831585 The weight ratio of the ethylene polymer segment formed in the first polymerization step is calculated according to the viscosity value measured by the polymer obtained after the second and second polymerization steps, and the viscosity is called 2, and The viscosity value of the third ethylene polymer segment may be double peaks formed in the first two steps, measured by weight %, based on the total weight of the polyethylene having a three-peak = knife distribution formed in all three polymerization steps. The weight ratio of the polyethylene having a molecular weight distribution is calculated based on the viscosity values vn2 and vn3 measured for the polymers obtained after the second and third polymerization steps, respectively. In addition to polyethylene, the polyethylene molding compositions of the present invention may additionally contain other additives. For example, the additives are from 0% by weight to 10% by weight, preferably from 0% by weight to 5% by weight, based on the total weight of the mixture, of a heat stabilizer, an antioxidant, a UV absorber, a light stabilizer, A metal deactivator, a peroxide destructive compound, a substantially co-stabilizer, but may also be in a total amount of 〇/❶. Up to 50% by weight of carbon black, filler, pigment, flame retardant or a combination thereof. The molding composition of the present invention may comprise a phenolic antioxidant, especially the one obtained from Ciba Specialities (Gennaiiy) under the trade name irgan〇X2 isopentitol (3,5·di-t-butyl-4-hydroxyl) Phenyl) propionate as a heat stabilizer. The molding compositions of the present invention are particularly suitable for the preparation of lines having an increased diameter greater than 5 〇 em, preferably greater than 70 cm, and an increased wall thickness greater than 15 cm, preferably greater than 2 cm. The molding composition of the present invention can be processed particularly well by an extrusion process to produce a pipeline having a notch in the range of 8 kJ/m2 to 14 kJ/m2. 125642.doc -15-200831585 (IS0) and environmental stress crack resistance (ESCR) greater than 500 h. The notched impact toughness iso is based on ISO 179-1/leA/DIN 53453 at -30 C. The size of the smear is x 4 X go mm, which is manufactured in the test piece with 45. V-notch with angle, 2 mm depth and 0.25 mm notch bottom radius. The environmental stress crack resistance (ESCR) of the molding composition of the present invention is determined by an internal measurement method and is described in units of h. This laboratory method is described by M. Fleifiner in Kunstst〇ffe 77 (1987), ρ·45 and below and corresponds to iIS〇/CD 1677〇 since then. The disclosure shows a correlation between the measured value of the slow crack growth on the test pole with a gap in the test and the brittle branch of the long-term pressure test according to ISO Π67. Shorten the crack initiation time to achieve loss of release by means of a notch (1.6 mm/blade) in a 2% strength Arkopal aqueous solution as an environmental stress cracking promoting medium at a temperature of 8 〇 and a tensile stress of 4 乂The shortening of the capture. A test piece was produced by cutting a test piece having a size of 1 〇 x l 〇 x 9 〇 mm from a pressed slab having a thickness of 1 〇 mm. The open-notch device constructed for the purpose of opening the gap is notched in the middle of the test piece by means of a blade around the periphery (see Figure 5 of the publication). The gap depth is 16 mm. [Examples] Example 1, the polymerization of ethylene was carried out in a continuous process in three reactors connected in series, which was prepared by the method of Example 2 of WO 91/18934 and having the operation number 2.2 in the literature. Ziegler catalyst with a volume of 156 mmoi / h 125642.doc -16- 200831585 with a sufficient amount of suspension medium (hexane), as a secondary catalyst with a volume of 240 mmol / h of triethylamine, acetamidine Hydrogen is introduced into the first reactor together. The amount of ethylene (=68.9 kg/h) and the amount of hydrogen (=62 g/h) were set so that 24% by volume of ethylene and 66 5 〇/〇 were measured in the gas space of the first reactor. The hydrogen content; the remainder is a mixture of nitrogen and a vaporized suspension medium. The polymerization in the first reactor was carried out at a temperature of 84 °C. • The suspension from the first reactor is then transferred to the second reactor. The hydrogen content in the gas space in the reactor is reduced to 〇·7 vol%, and the ethylene in an amount of 43.2 kg/h is It was fed into the second reactor together with 1470 g/h of 1-butene. The reduction in the amount of hydrogen is achieved by means of an intermediate % decompression. A volume of 73. 5 was measured in the gas space of the second reactor. / 〇 ethylene, 〇 7 vol% hydrogen and 4.8 volume. /. 1-butene, the remainder being a mixture of nitrogen and vaporized suspension medium. The polymerization in the second reactor was carried out at a temperature of 85 °C. The suspension from the second reactor is transferred to the third reactor via another intermediate & decompression (by which the Φ of the hydrogen in the gas space of the third reactor is not set to 0% by volume) . • The ethylene in an amount of 24.3 kg/h is fed into the second reactor together with 1-butene in an amount of 475 g/h. In the gas space of the third reactor, 72 volumes of ethylene, 〇 volume % of hydrogen, and 5.3 vol% of "butene were measured; the remainder was a mixture of nitrogen and vaporized suspension medium. The polymerization in the third reactor is carried out at a temperature of 84. The long-term activity of the polymerization catalyst required for the series operation mode as described above is by means of a specially developed The group of 125642.doc • 17 - 200831585 is achieved by the Ziegler catalyst. The measure of the availability of the catalyst is its extremely high reaction to hydrogen and its duration of 1 hour to 8 hours. Maintaining a constant high activity. Separating the suspension medium from the polymer suspension leaving the third reactor, mixing the powder with 0.2% by weight of polyethylene glycol having a molar mass of 400 g/mol, after which the mixture is dried. And the powder was granulated. The viscosity values and the ratios wA, wB and wc of the polymers A, B and C used in the prepared polyethylene molding composition as described in Example 1 are as described in Table 1 below. Table 1 Example 1 WA [% by weight] 50 WB [ Amount %] 32 Wc [% by weight] 18 VN! [cm3/g] 80 VN2『cm3/gl 305 VNt〇t [cm3/g] 450 FNCT [h] 3100 MFR [g/10 min] 0.32 Density [g/ Cm3] 0.947 Tensile screw test 1.72 (5 MPa/23〇C), Elongation [%] AZN [kJ/m2] 13.7 The abbreviations for physical properties in Tables 1 and 2 have the following meanings: -FNCT= Environmental stress crack resistance in [h] as measured by the internal measurement method described by M. FleiBner (complete notch creep test), conditions: 80 ° C, 2.5 MPa, 2% Arkopal aqueous solution - AZN = notched impact toughness IS0 according to ISO 179-1/leA/DIN 53453, at -30^, with 125642.doc -18- 200831585 units kJ/m2. - Tensile creep test according to DIN EN ISO 899 At 23 ° C and a tensile stress of 5 MPa; the stated number is the elongation in % after 96 h. The granulated material on the pipeline extrusion unit of Battenfeld for the output presented in Table 2 below And a line having a size of 60 x 8 cm is also produced at the melting temperature presented in Table 2 below. The line produced in this way has a completely smooth surface while the other The system is described in Table 2 below. Table 2 Comparison of units without PEG Example of composition containing 0.2% PEG Output Kg/h 400 400 Melting temperature °c 200 195 Pressure Bar 197 222 Line speed m/min 0,053 0,053 Pipeline Outer diameter mm 561 561 Top wall thickness mm 72 74 Bottom wall thickness mm 125 89 As indicated by Table 2, the line made from the composition containing only 0.2% by weight of PEG of the present invention is identical to the three peaks which do not contain any PEG. The pipelines produced by the PE compositions are significantly less affected by the deflection. 125642.doc -19·