臥式離心氣流干燥機的設計含14張CAD圖

臥式離心氣流干燥機的設計含14張CAD圖,臥式,離心,氣流,干燥機,設計,14,cad 附錄一 外文譯文 無鈷干燥系統(tǒng)的發(fā)展過程 Johan H.bieleman Sasol Servo BV ,the Netherlands 摘要 在空氣干燥機用于干燥涂層系統(tǒng)，以催化聚合的過程，其中鈷羧酸是使用最廣泛的干燥劑。然而，化合物鈷很可能是在美國國家毒理學計劃中研究的致癌因素，例如硫酸亞鐵鈷。因此，德國已不再給含鈷油漆授予藍色天使獎。其他過渡金屬羧酸如錳 或鐵基很低的催化效果表明，鈷不能平等作為自氧化聚合反應的催化劑。干涂料的實 驗調查的各種有機螯合配體對自氧化過程中的錳催化性能的影響。錳的活動受有機配體的強烈影響。 新錳基于無鈷，顯示良好的干燥性能和改進的顏色保留干涂料的配位化合物。 1．簡介 空氣干燥醇酸涂料包含除了主要成分、 醇酸、 色素和溶劑少量的干燥劑。 在干燥加快的漆膜，在自氧化的不飽和脂肪酸含量存在的醇酸樹脂成分作為基于氧化交聯(lián)過程。 烘干機，也指在解決方案中，防水劑添加劑是有機物溶劑和粘合劑中可溶性有機金屬化合物?；瘜W，屬于金屬皂類的干燥和它們添加到吹干涂料系統(tǒng)，以加速或促進后應用固體階段在一個適當?shù)臅r間內從液膜轉化。 轉換發(fā)生的的聯(lián)編程序系統(tǒng)一個的過程將金屬陽離子的陰離子的干燥機、催化氧化交聯(lián)作為承運人聯(lián)編程序系統(tǒng)中的一部分。 鈷數(shù)十年來一直活動主要的干燥機使用中干涂料。但是最近的研究與七水合鈷硫酸事務局療效為鈷化合物會遵守重新分類程序。繼最近公布委托指令 2001 年 /59/Ecof 歐洲共同體。 氧化物分類使用以下風險提示：R 22/R 43/R 50/R 53。相關的鈷烘干機烘干機沒有更改還，因為它是尚不清楚如果像七水合鈷硫酸，水溶性化合物毒性數(shù)據(jù)作為找到的鈷的分類。 干燥機制造商已啟動幾個測試程序以收集數(shù)據(jù)的生物利用度鈷，用作涂料。還是一個干燥機、無鈷替代方案以取代鈷烘干機的壓力。在某些情況下含鈷成分不會獲得批準獲得環(huán)境獎項，如德國藍色天使獎。 2．干燥過程及干燥影響 醇酸漆的干燥過程是緩慢蒸發(fā)中揮發(fā)性的結果，在第二個步驟中化學干燥會發(fā)生。醇酸樹脂的氧化交聯(lián)過程發(fā)生的 H-原子中的自由基反應從亞油酸的雙亞甲組提取的葡萄酒，結果基采取了大氣氧和從過氧化物。在過氧化物與鈷催化劑降低到烷氧基和過氧自由基。 這些自由基窗體交聯(lián)的重組過程稱為"自氧化交聯(lián)過程"(圖 2)。 圖 1 “自氧化”反應方程式 顯然"自氧化"一詞已被定義為一個無催化氧化反應的過程。 圖 2 在自氧化交聯(lián)過程中醇酸樹脂的反應變化 但是，自氧化反應發(fā)生重大率僅在面前的一種催化劑，如過渡金屬提涂料的干燥、自氧化過程通過添加烘干機的加速。沒有這些干燥的催化劑漆層可能要幾個月后才能完成干燥。 更詳細化學干燥氧化法可以通過結合在一起的四個步驟來表示: l 步驟 1： 誘導期 l 步驟 2：過氧化物形成 l 步驟 3: 過氧化物分解自由基 l 步驟 4: 聚合 從這種涂料應用直到電影開始吸收空氣中的氧的時間測量誘導步驟。吸收的氧窗體過氧化物跨聯(lián)編程序(步驟 2) 中的共軛雙鍵。 當該過氧化物開始分解時，就形成了交聯(lián)站點。交聯(lián)在聚合過程中隨著粘度迅速增加。 第 2 和第 4 步最有效地進行樹脂含共軛的雙鍵 ；但是，非共軛樹脂顯示還有些反應。在這種情況下多個的雙鍵可能會導致激活的各種亞甲組重新排列位置的非共軛雙鍵、取決于雙鍵的原始位置。 步驟 1 和 2 使干燥的速度大大提高。 由于他們對氧化還原反應的敏感性的氧進行作為干燥機系統(tǒng)中的金屬。烘干機也激活的過氧化物形成；假定是多價金屬是以雙鍵，增加氧化易感性的關聯(lián)。鈷干燥機的增加減少了能源所需使一個不飽和樹脂氧吸收激活。 活性氧滲透傾向于過氧化物的形成。不久，過氧化被形成及其烷氧基催化反應中的分解(圖 3) 圖 3 自氧化交聯(lián)過程中的反應 基于長油醇酸樹脂的環(huán)境照顧裝飾涂料的干燥系統(tǒng)通常使用一個鈷/鋯/鈣組合干燥機。鈷是活性干燥劑, 但是，為了改善通過干燥、硬度和穩(wěn)定性，鋯和鈣的輔助干燥中正在使用鈷結合。 鈷烘干機的潛在替代產(chǎn)品的基本特征。 基本上，干燥機金屬可分為兩個組：活動烘干機和輔助干燥。這種差異應視為任意它們之間不存在大量的重疊。 在環(huán)境溫度氧攝取、過氧化形成和過氧化分解推廣活動烘干機。 輔助烘干機不顯示催化自己在周圍的溫度下，但提高活動的干燥機金屬的活動。原發(fā)性干燥機性能報告了各種過渡金屬。 但是，僅錳找到了大量的實際使用。 沒有該替代烘干機-為金屬羧酸-類似于中鈷的性能。 但是，反應以及對顏色相同的過渡金屬的影響等屬性與主要是有關化學成分的復合金屬。由于"自由金屬陽離子"并不存在于解決方案，這是可以理解的。金屬離子始終圍繞陰離子、溶劑分子或其他配體組。 純羧酸的大多是數(shù)商業(yè)烘干機。但是，對于某些應用程序錳基于強螯合配體與組成如找到了商業(yè)使用、配體將扮演重要的角色的這種化合物催化氧化干燥。強螯合配體對催化活性通過改變電子密度的復雜的離子等金屬中心及其潛在的氧化還原。 下一節(jié)將對干燥機的各種錳的成分，使用有機配體。 3．實驗性 3.1 過程和使用的材料 對涂料的各種干燥的影響已被計算，使用不同干等體系的涂料。在指定為標準漆的長油油漆組成如表 1 所示。干燥劑被添加到下階段。 這兩個商用油漆無干燥機由這次測試的廠商提供，以及準備進行系統(tǒng)"新鮮色漆和清漆用漆基"已被使用。 干燥性能已確定根據(jù) ASTM 或使用干燥的錄像機的類似過程。下面的過程使用了： 1．干燥的錄音機。干燥條件：23℃/50℃ 相對濕度。使用的儀器是直線的錄像機。后干燥階段被考慮。 階段 a：涂料流一起、 濕邊緣時間。 階段 b：一條線是可見，油漆開始聚合：無塵。階段 c：使翻錄電影：以自由或表面干。 階段 d：表面路徑： 通過干或總干。 2．干燥進一步成立的"拇指測試"，并根據(jù) ASTM D1640。 電影的 Konig 硬度被評估通過鐘擺阻尼測試根據(jù) DIN53157。一個玻璃面板是涂有 60 濕膜，在 23℃，相對濕度 50％，硬度條件下保持發(fā)展的時間與一科尼格擺監(jiān)測。振蕩時間的測量，以減少從最初的 6 °?3 °是在幾秒鐘內給出偏轉。 鈷-鋯-鈣干燥機組合已作為參考，使用金屬比率后，除非另有說明。 0.06 Co 0.3zr 0.1Ca 這種組合是基于對 10 鈷，鋯，鈣 18 10 商用級別的混合物。這兩個商業(yè)，以及 金屬配合物作為實驗已被使用。詳情將載于表和數(shù)字。 3.2 結論和討論 3.2.1 鈷與錳干燥機 在下面的表 1 中顯示演示與干燥機在白宮漆，制定根據(jù)這種標準的漆，表 1 中的錳鈷催化作用直接比較。 表 1 在白色醇酸樹脂漆中 Mn 與 Co 效果 活潑的干 燥劑 輔助干燥 劑 無塵 ( 小 時) 無軌 ( 小 時) 總共干燥 時間 白度指數(shù) 硬度(s/k) 0.08Co 0.4zr 0.2Ca 1.30 2.00 3.30 78 52 0.08Mn 0.4zr 0.2Ca 7.15 9.45 15.15 73 29 鈷與錳在同一金屬劑量對干燥機干燥性能有不利影響，白度和硬度。顯然 不宜以改變。出于實際應用的 7 個小時以上的無塵時間將導致塵埃粒子附著在干燥涂層。此外，長期粘性，無干燥時間的增加，總的賠償風險增加。 3.2.2 錳-聯(lián)吡啶配合物 錳配合物已被報告為有效干涸。錳化合物和螯合劑的化合物得到了廣泛的商業(yè)應用，在聚氨酯清漆醇酸樹脂的實例，以及在水性醇酸樹脂漆。這些錳的化合物，而不是鈷催干劑使制定的淺色聚氨酯醇酸清漆。最近，錳的復雜活動特殊性已被確定，作者對 Mn-bipy 復雜的結構，提出了投影圖 4。 圖 4 Mn-biby 的結構 在鈷催干劑與聚氨酯配合使用清晰的深色清漆醇酸樹脂和光的原因是缺乏吸引力。以 Mn - hipy 色彩，而不是在相當大的改進合作的結果。這種改善只是在液體清漆可見; 沒有在硬化涂層的差異已被發(fā)現(xiàn)。相對于錳羧酸在干燥速度顯著改善可以看到(見表 2)。該錳 hipy 復雜也適用于水性涂料的基礎上的短油醇酸樹脂乳液。 這兩種樹脂體系，聚氨酯醇酸樹脂和短油醇酸樹脂乳液，有共同的物理干燥是非常重要的，而交聯(lián)的膜的形成和硬度的貢獻是相當?shù)?，而對勞醇酸樹脂為基礎的系統(tǒng)。 表 2 Mn-bipy 在含有基醇酸聚氨酯的家具中的影響 活潑的干燥劑 輔助干燥劑 總共干燥時間(小時) 固體漆 0.06Co 0.3Zr 0.1Ca 2.00 15 0.06Mn 0.3Zr 0.1Ca 5.30 6 0.03Mn-bipy 0.3Zr 0.1Ca 1.30 6 干燥速度使用錳 hipy 已記錄在色素漆的基礎上，聚氨酯醇酸樹脂(見表 3)相似的積極影響。然而，Mn-hipy 有負面影響的白度。 表 3 在白色醇酸樹脂漆中 Mn-bipy 在聚氨酯醇酸樹脂中的影響效果 活潑的干燥劑 輔助干燥劑 總共干燥時間(小時) 白度 0.06Co 0.3Zr 0.1Ca 4.45 79 0.06Mn 0.3Zr 0.1Ca 9.30 77 0.03Mn-bipy 0.3Zr 0.1Ca 4.15 73 此外，比較數(shù)據(jù)已被記錄在一個標準的白色油漆，醇酸樹脂的基礎上 (見表 4)。盡管在干燥時間可以看到同樣的改善，但整體表現(xiàn)仍然不足，需要進一步改善。像在聚氨酯醇酸樹脂漆，一個復雜的聯(lián)吡啶上的白度產(chǎn)生負面影響已經(jīng)確定，也是在勞醇酸油漆。此外，漆膜仍太軟。 表 4 在白色醇酸樹脂漆中 Mn-bipy 在羅醇氨樹脂中的影響效果 活潑的干燥劑 輔助干燥劑 無塵(小時) 無軌(小時) 總共干燥時間 白度指數(shù) 硬度 (s/k) 0.08Co 0.3Zr 0.1Ca 2.00 2.30 4.45 80 36 0.08Mn 0.3Zr 0.1Ca 10.00 13.00 15.15 78 29 0.03 Mn-bipy 0.3Zr 0.1Ca 5.00 7.00 10.00 72 21 顯然，錳催化效率提高利用聯(lián)吡啶配體。但是，進一步的改善是必要的，以便能夠使用和錳，鈷，而不是基于干燥器。 3.2.3 錳-聚配體復合物 配體與配體成分變化大評估。聯(lián)吡啶是一種典型的強場配體，形成穩(wěn)定的復合物與錳。在干燥特性的進一以步改善將達到使用兩個或兩個以上配體組成：通常是強場配體和一個弱場配體。下一步改善干燥特性的另一個優(yōu)點是使用混合配體儲存穩(wěn)定性的改善，低粘度，使高濃度達到少雨成分，而在復雜的金屬濃度為 6％錳。 下面的測試結果證明了“聚配型錳配合物”的“錳小巴指出”起生效。對干燥，硬度以及顏色速度是積極的影響使用聚配體為基礎，而不是僅僅聯(lián)吡啶錳(表 5) 表 5 在白色醇酸樹脂漆中 Mn-Plb 在聚氨酯醇酸樹脂中的影響效果 活潑的干燥劑 輔助干燥劑 無塵(小時) 無軌(小時) 總共干燥時間 白 度 指數(shù) 硬度(s/ k) 0.06Co 0.3Zr 0.1Ca 2.00 2.30 4.45 80 36 0.06Mn 0.3Zr 0.1Ca 10.00 13.00 15.15 78 29 0.03 Mn-bipy 0.3Zr 0.1Ca 5.00 7.00 10.00 76 21 0.03 Mn-blp 0.3Zr 0.1Ca 4.20 5.45 8.00 77 24 醇酸樹脂涂料在羅湖干燥仍稍遜使用錳，鈷。進一步改善完成修改樹脂組成;利用介質油醇酸或勞混合醇酸樹脂和醇酸樹脂莫。 在密蘇里州的干燥特性醇酸樹脂涂料是為錳，鈷作為干燥器乘客聯(lián)絡小組(表中 的提法比較 6 和 7)。利用與錳乘客聯(lián)絡小組一起輔助干燥器作用是有限的使用劑量不能保證在評估這些醇酸樹脂涂料莫。因此，在干燥催化劑總額可能減少 2.4％至 0.3％ (表 6)。 表 6 白漆在中期油基醇酸 干燥機中活躍的干燥 劑 固體中活躍的干燥劑 干燥原料成本指數(shù) S．b=2 9.7% 總共干燥時間 3 月后在 23℃ 的干燥 時間 硬 度 (s/k) W-I Co-Zr- Ca 1.2%Co 0.075 100 1.86 4.30 7 63 80 Mn-plg 6%Mn 0.04 60 0.40 5 6 57 81.5 表 7 半光澤黑色漆的基礎上，連鎖停止中等油醇酸樹脂 干燥機中活躍的干燥 劑 固體中活躍的干燥劑 干燥原料成本指數(shù) S．b=29 .7% 總共干燥時間 3 月后在 23℃ 的干燥時 間 硬 度 (s/k) Co-Zr- Ca 1.2%Co 0.09 100 2.78 4 4 106 Mn-plg 6%Mn 0.09 106 1.11 9 6 113 4. 結論 有機配合物的前途在于提供錳鈷催化劑作為替代的功能。在測試的配方，新錳聚配體干燥介質提供了類似的石油總干醇酸樹脂涂料的特點，而不會造成液體或固化涂料的不利影響。新的干燥性能優(yōu)于傳統(tǒng)的錳對干燥器。 附錄二 外文原文 Progress in the Development of Cobalt-free Drier Systems Johan H.bieleman Sasol Servo BV ,the Netherlands Summary Driers are used in air-drying coating systems to catalyze the polymerization process. cobalt-carboxylates are the most widely used driers . However , cobalt cornpounds may indirectly be implicated as carcinogen suspects as aresult of studies in the U.S.A , in the national toxicology program using cobalt sulphate heptahydrate . Hence , Germany is no longer granting the Blue Angel award to cobalt-containing paints . Other transition metal carboxylates such as based on manganese or iron show much lower catalytic effects and cannot equalize cobalt as a catalyst in autoxidation polymerization reactions . The effect of various organic chelating ligands on the catalytic properties of manganese in autoxidation processes was investigated experimentally in air-drying paints . The activity of manganese is strongly effected by organic ligands . New manganese based coordination compounds enable the formulation of co-free air-drying paints , which show good drying performances and improved color retention . 1 Introduction Air drying alkyd paints contain besides the main constituents , alkyd resins(binders) , pigment and solvents small amounts of driers . The driers speed up the oxidative cross- linking process of a paint film , based on the autoxidation of the unsaturated fatty acids , which are present as constituents of alkyd resins . Driers , also referred to as siccatives when in solution , are organo-metallic compounds soluble in organic solvents and binders . Chemically , driers belong to the class of metal soaps and they are added to air-drying coating systems to accelerate or promote after application the transformation from the liquid film into the solid stage within an appropriate time . The transformation occurs by oxidative cross-linking of the binder system , a process , which is catalysed by the metallic cation of the drier .The anionic part of the drier molecule serves as the carrier , to solubilize the drier in the binder system . For deCADes cobalt has been the main active drier used in air-drying paints . However as the result of recent studies with cobalt sulphate heptahydrate , cobalt compounds are subject to reclassification procedures . Following the recently published commission Directive 2001 /59/Ecof the European Community . Cobalt oxide is classified using following risk phrases : R 22/R 43/R 50/R 53 . The classification for cobalt driers have not been changed yet , as it is still unclear if the toxicity data as found for water soluble compounds like Cobalt sulphate heptahydrate , are relevant for cobalt driers . Drier manufacturers have initiated several test-procedures in order to collect data for the bioavailability of cobalt , used as a drier in paints .Nevertheless , the pressure to replace cobalt driers with cobalt-free alternatives is growing . In some case cobalt-containing compositions will not be granted for environment awards ,like for the Blue Angel Germany . 2 The drying process and the effect of driers The drying process of alkyd paint is the result of the slow evaporation of the volatile compoments and in a second step chemical drying takes place . The oxidative cross-linking process of alkyd resins occurs vin a radical reaction in which H-atoms are abstracted from the double methylene group of linoleic acid . The resulting radicals take up atmospheric oxygen and from hydroperoxides . The hydroperoxides degrade with cobalt catalyst into alkoxy and peroxy radicals . These radicals form cross-links by recombination . This process is known as “the autoxidation cross-link process” (figure 2) . Apparently the term “ autoxidation ” has been defined as an non-catalyzed oxidation reaction of a substrate exposed to the oxygen of the air . Figure 1.General reactions for “autoxidation ” reactions . Figure 2.Schematic presenation of the autoxidation cross-linking process of alkyd resins However , autoxidation reactions occur at significant rates only in presence of a catalysts , such as a transition metal [ ref . 1 , 3 , 4 ] .The autoxidation process referring to the drying of paints is accelerated by addition of driers . Without these drying catalysts the paint layer may dry only after some months ; with driers this is accomplished within a few hours . More in a detail , chemical drying by oxidation can be through as a combination of four steps : l Step 1 : Induction period l Step 2 : Peroxide formation l Step 3 : Peroxide decomposition into free radicals l Step 4 : Polymerization The induction step is measured from the time the coating is applied until the film begins to absorb oxygen from the air . The absorbed oxygen forms peroxides across the conjugated double bonds in the binder (Step 2) . When the peroxides start to decompose , active cross-linking sites are formed . As crosslinking proceeds during the polymerisation , the viscosity increases rapidly . Step 2 and 4 proceed most effectively with resins containing conjugated double bonds ; however , non-conjugated but poly-unsaturated resins show also some reactivity . In such a case the multiple double bonds may cause the activation of the various methylene groups , to rearrange the position of the non- conjugated double bonds , depending on the original position of the double bonds . The step 1 and 2 are accelerated dramatically by the presence of driers . The mutivalent metals in the drier system act as oxygen carries because of their susceptibility to redox reactions . Driers also activate the formation of peroxides ; assumed is the multivalent metal is associated to the double bonds , increasing the oxidation susceptibility . The addition of cobalt drier reduces the energy , which is necessary for the activation of the oxygen absorption by an unsaturated resin , with a factor 10 [ ref . 1 , 5] . The penetration of activated oxygen into the film favors the peroxide formation . As soon as peroxide are formed their decomposition in a metal-catalysed reaction to alkoxy (RO · ) and peroxy radicals (ROO · ) takes palace (figure 3) . Figure 3 . Reactions during the autoxidation cross-linking process Drier systems for ambient cared decorative paints based on long oil alkyd resins are usually siccativated using a cobalt / zirconium / calcium combination drier . Cobalt is the active drier . However , in order to improve through-drying , hardness and stability , auxiliary driers , like zirconium and calcium , are being used in conjunction with cobalt . General characteristics of potential alternatives to cobalt driers . Essentially , drier metals can be divided into two groups : active driers and auxiliary driers . This difference should be considered arbitary as a considerable amount of overlap exists between them . Active driers promote at ambient temperatures oxygen uptake ,peroxide formation and peroxide decomposition . Auxiliary driers do not show catalytic themselves at ambient temperatures , but enhance the activity of the active drier metals . Next to cobalt ,various transition metals have been reported as having primary drier properties . However , only manganese has found substantial practical use . None of the alternative driers-as metal carboxylates-resemble in performance to cobalt . The limitations of the alternatives in relation to the application in paints are summarized as follows : However , the reactivity as well as properties like effect on colour of the same transition metal are largely related to the chemical composition of the metal compound [ref . 6 ] . This is understandable as “ free metallic cations ” do not exist in solution . The metal ions are always surrounded by anions , by solvent molecules or by other ligand groups . Most commercial driers are pure carboxylates . However , for some applications manganese based compositions with strong chelating ligands such as bipyridine have found commercial use .The ligand plays an important role in the catalytic oxidative drying of these compounds (ref . 7) . Strongly chelating ligands effect the catalytic reactivity by altering the electron density at the metallic center of a complex ion and so its redox potential . Next section will be addressed to the performance as a drier various manganese based compositions , using organic ligands . 3 Experimental 3.1 Procedure and used materials The effect of various driers on the drying of paints has been evaluated , using different air-drying paint systems . The composition of the long-oil paint , designated as standard paint , is shown in table 1 . The drier is added to the paint during the let-down stage . As paint systems both commercially available paints , supplied by the manufacturer for this test without drier , as well as prepared “ fresh paints and varnishes ” have been used . The drying performance was determined according to ASTM or similar procedures , using a drying recorder . Following procedures have been used : 1: the drying recorder . Drying condition : 23℃/50℃ relative humidity . The used instrument is a straight-line recorder . Following drying stage are being considered : Stage a – the paint flows together , the wet-edge time . Stage b – a line is visible , the paint begins to polymerize : dust-free . Stage c – ripped film : take-free or surface-dry . Stage d – surface path : through dry or total dry . 2: the drying was further established by the “ thumb-test ” and according to ASTM D1640 . The Konig hardness of the films was assessed by using the pendulum damping test according to DIN53157 . A glass panel was coated with a 60 mm wet film ,kept under conditions of 23℃ and 50% RH and the hardness development in time was monitored with a Konig pendulum . The oscillation time measured to reduce the deflection from initial 6°to 3°is given in seconds . A cobalt-zirconium-calcium drier combination has been used as reference , using following metal ratio , unless otherwise indicated . 0.06 Co 0.3zr 0.1Ca This combination is based on a mixture of commercially available grades of Co 10 , Zr 18 and Ca 10 . Both commercial as well as experimental metal complexes have been used . Details will be presented in the tables and figures . 3.2 Results and discussion 3.2.1 Co vs Mn drier A direct comparison demonstrating the catalytic effect of Co versus Mn drier in a white house paint , formulated according to the standard paint according to table 1 is shown in following table 1 . Replacing Co drier with Mn drier at same metal dosage has a detrimental effect on the drying performance , whiteness and hardness .Obviously Mn is unsuitable to replace Co drier . For practical application a dust-free time of over 7 hours will result in adhesion of dust particles in the dried coating . Moreover , the long tack-free and total dry time increase the risk of damages to the paint film and the appearance . 3.2.2 Manganese-bipyridine complexes Manganese complexes have been reported as effective dries [ ref . 6 ] . Compounds of Mn and chelating compounds , like 1 , 10-phenantroline and bipyridine , have found widespread commercial application , for instance in urethane alkyd varnishes as well as in waterborne alkyd paints . The application of these manganese compounds instead of cobalt driers enables the formulation of light colored urethane alkyd varnishes . Recently the active speciesc of the Mn-bipy complex has been determined as being [Mn4O2 (2ethylhexanoate)6 (bipy)2 ] [ref . 7] . A projection of the structure of the Mn-hipy complex is presented in figure 4 . Figure 4 . Structure Mn-hipy complex . The use of Co driers in conjunction with clear urethane alkyd resins in dark colored varnishes and are for optical reasons less attractive . Using Mn-hipy instead of Co results in considerable improvement in color . This improvement is just visible in the liquid varnish ; no Differences in the hardened coating have been found . Compared to the Mn carboxylate remarkable improvement in drying speed can be noticed (table 2 ) . The Mn-hipy complex is also applicable in waterborne coating , based on short-oil alkyd emulsions . Both resin systems , urethane alkyd and short-oil alkyd emulsions , have in common that the physical drying being very important and the contribution of cross-linking to the film formation and hardness is rather low , compared to systems based on LO alkyd resins . Similar positive effects on drying rate using Mn-hipy have been recorded in the pigmented paint , based on a urethane alkyd resin(table 3) . However ,the Mn-hipy has a negative effect on the whiteness . Furthermore ,comparative data have been recorded in a standard white paint , based on LO alkyd resin (table 4) .Although same improvement on the drying time could be noticed , the overall performance is still insufficient and needs further improvement . Like in the urethane alkyd paint , a negative effect of the bipy complex on the whiteness has been determined , also in the LO alkyd paint . Moreover ,the paint film remains too soft , using the Mn-hipy drier . Obviously the catalytic effectiveness of Mn is improved using bipy as ligand . However , further improvements are necessary in order to be able and use Mn-based driers instead of Co . 3.2.3 Manganese-poly-ligand complexes A large variation in ligands and compositions of ligands have been evaluated . Bipy is a typical strong field ligand and forms stable complexes with Mn . Further improvement in drying properties could be reached in using compositions of two or more ligands : typically a strong field ligand and a weak field ligand . Next to the improvement drying characteristics another advantage of using mixed ligands is the improved storage stability and low viscosity , enabling to reach high concentrated drier compositions ; the metal concentration in the complex is 6% Mn [ref . 8] . Following test results demonstrate the effect of “ poly-ligand-based Mn complexes ” (indicated as “ Mn-plb ” ) . The speed of drying , hardness as well as color are positively effected using the poly-ligand based Mn instead of just bipy (table 5) . The drying in LO alkyd paints is still slightly inferior using th