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Chap 13. Zieglar-Natta Catalyst

Chap 13. Zieglar-Natta Catalyst. Zieglar-Natta Catalyst. - Z-N 촉매 발명이전에 PP 는 atactic form 만 형성 - 그 후 isotactic PP of extraordinary MW(>10 6 ) 이 형성. - PP 의 characteristic condition

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Chap 13. Zieglar-Natta Catalyst

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  1. Chap 13. Zieglar-Natta Catalyst Zieglar-Natta Catalyst - Z-N 촉매 발명이전에 PP 는 atactic form 만 형성 - 그 후 isotactic PP of extraordinary MW(>106) 이 형성 - PP의 characteristic condition Condition 50~90℃ pressure 5 atm 이하 Solid catalyst와 함께 넣고 반응후 H2O 이나 ROH 로 정지한 후 catalyst 제거하기 위해 세척. MW은 chain transfer agent 에 의해 control 예) CO2, O2, H2, H2O, …

  2. Karl Ziegler (1898-1973) Giulio Natta (1903-1979) Discovered the synthesis of stereoregular polymers in 1954 Discovered that a combination of certain transition metal compounds and organometallic compounds polymerize ethylene in 1953 Both earned the Nobel Prize in 1963

  3. Zieglar-Natta Catalyst Monometallic Bimetallic mechanism assumption: equal site reactivity - Monometallic Corsee mechanism

  4. Zieglar-Natta Catalyst Bimetallic α-TiCl3 β-TiCl3 TiCl 2 vacancy sites => atactic 1 vacancy site => isotactic 1 vacancy site => isotactic

  5. A B E C D Polyethylene Polymerization

  6. Zieglar-Natta Catalyst PP 경우 α-TiCl3를 β-TiCl3 보다 많이 사용. Efficiency of catalyst , , or  TiCl3 > TiCl2 > TiCl4 -TiCl3 Kinetics the fraction of the sites that have monomer coordinated with them Conc. of growing chain Bimetallic Conc. of catalyst

  7. Zieglar-Natta Catalyst General considerations in Rxn Media Selection Homogeneous Polymzn ◎ Bulk Advantage ① Minimum contamination ② Cheap ③ Chain transfer to solvent elimination Disadvantage ① Dienes – crosslink (cannot make dienes) ② Monomer removal difficult (if monomer toxin, cannot use) ◎ Solution Advantage efficiency Disadvantage ① Diene crosslink ② monomer + solvent, removal is difficult ③ chain transfer to solvent hint Mn

  8. Disadvantage • Diene X-link ② Particle coalescence 합체,연합,합착 ⓐ 100℃ ③ Contamination by solvent Zieglar-Natta Catalyst Heterogeneous Polymzn ◎ Suspension Advantages ① Control runaways ② Monomer removal is fair easy

  9. Zieglar-Natta Catalyst ex) 5μ case 0.003㎝(30μ) case ◎ Emulsion Polymerization: colloidal dispersion SBR 생산키 위해 40년대 도입. latex 제조 Advantage ① Excellent control of runaways ② Diene can be polymerized cheaply ③ Monomer removal is easy ④ Much high M.W. ⑤ A stable emulsion exists for ? in paint formulation Disadvantage ①Contamination of product by emulsifier

  10. Zieglar-Natta Catalyst Typical Recipe ; ① 104 micelles/cm3 1010 polymer droplets/cm3 ② 103 radicals/cm3·sec Typical Initiator ; aqueous phase soluble Ferrous persulfate

  11. Zieglar-Natta Catalyst Initiator primary attacking centering some of the originally present micelles Spontaneous particles initiation & growth “Smith-Ewart Kinetics” Can count MW Rexnt↓, initiator conc.↓ => ↑

  12. Zieglar-Natta Catalyst 즉 a micelle turned on 1/2 time & turned off 1/2 time 1/2 means 1/2 off 1/2 on rate of radical generate and capture Surfing to the internet For further details about Zieglar-Natta Vinyl Polymzn Click next homepage. http://www.pslc.ws/macrog/ziegler.htm

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