Study On Preparation And Application Of Chlorinated Polymer

Chlorinated polymer is an important series of fine chemicals,of which chlorinated polypropylene and chlorosulfonated polyethylene have been widely used in ink industry.Nowadays,most of the chlorinated polyolefins in China are produced via a CTC solvent method,which uses carbon tetrachloride(CTC) as solvent.However,this method is scheduled to be stopped by December 31,2009 since CTC is an ozone depleting substance(ODS) and such applications in chemical industry are strictly controlled under the Montreal Protocol.Therefore,it is of great significance to develop a non-CTC solvent process technology for the production of chlorinated polyolefins.Till now,plenty of alternative solvents have been studied for the replecement of CTC as a process agent in the production of chlorinated polyolefins,however,various other problems are encountered.For example,some solvents like dichloromethane and chloroform can react with chlorine further giving rise to the side production of CTC,while aromatic solvents can be chlorinated gradually forming polychlorobenzenes that are toxic and difficult to be removed completely from the final products.In contrast, although water is an inert solvent for the chlorination reaction,it fails to provide a uniform condition for the chlorination of polymers,leading to the nonhomodeneous distribution of chlorine on the polymer chains.Thus, the above solvents have not been used in the commercial production of chlorinated polyolefins till now.Considering the difficulties of finding an inert solvent to chlorine like CTC,this dissertation proposed a novel concept for the first time.That is,liquid paraffin is chosen as a reactive solvent because it can dissolve polyolefin at higher temperature,and its chlorinated form,chlorinated paraffin(CP),can dissolve chlorinated polyolefin too.Therefore,the whole reactions always take place at homogeneous solution,which is similar to the CTC solvent method.More importantly,two useful products,viz.chlorinated polyolefin and chlorinated paraffin are prepared synchronously.Recently,the continuous accumulation of a large amount of waste rubber(WR) has brought about a series of global environmental problems and public health concern.Thus,the foremost significant thing currently is searching for a method to dispose of WR efficiently.In retrospect, pyrolysis/combustion techniques and polymer blend technology are the two most important approaches concerning cutting down the accumulation of WR.As far as the former is concerned,a major drawback is that a mass of oxides of sulfur(SOx),oxides of nitrogen (NOx) and other polycyclic aromatic hydrocarbons releases concomitantly.These emissions demand further treatment to conform with the strict environmental regulations requirement.In view of the economic and environmental advantages,the latter is regarded as a better available choice.However,the surface energy mismatch and incompatibility between WR and polymer usually results in performance degradation to some extent.Therefore,we prepared a series of chlorinated waste rubber(Cl-WR) by a water based chlorination method and studied the potential applications of Cl-WR.The major work and innovative results of this dissertation are as follows:(1) The structure and properties of chlorinated polyolefin products by CTC solvent method and paraffin solvent method are determined by differential scanning calorimetry(DSC),Fourier transform infrared (FTIR) spectroscopy,proton magnetic resonance(¹H-NMR) and ¹³C-NMR.The results indicate that polyolefin chain can be homogeneously chlorinated in paraffin as in CTC solvent via a radical mechanism.The present process is superior to the conventional CTC solvent method because it can reduce the solvent emission dramatically, enhance the volume efficiency of reactor and achieve a unified production of chlorinated polyolefin and CP under atmospheric pressure. Therefore,liquid paraffin is a promising solvent to replace CTC solvent to produce chlorinated polyolefin.(2) In order to extend the application of the abundant waste rubber powder,chlorinated waste rubber(Cl-WR) is prepared by a water based chlorination method using chlorine as chlorinating agent.Experimental study is carried out on the preparation of Cl-WR,and the optimum condition is found,namely,reaction temperature between 70～90℃, the flow rate of chlorine at about 0.6 g/min,and 1%of radical initiator. The properties and polarity of WR and Cl-WR are characterized by TG, ATR-FTIR,and contact angle to water.The results indicate that 1) it is feasible to prepare Cl-WR by a water based chlorination method;2) the hydrophobicity and polarity of Cl-WR are higher than those of WR. Furthermore,the excellent miscibility and compatibility of Cl-WR with PVC was demonstrated by scanning electron microscope(SEM) images of the resulting blends.All the above-mentioned analysis provide a good basis for the application development of Cl-WR.(3) The effect of blending process of PVC and Cl-WR on the mechanical properties of PVC/Cl-WR blend is studied experimentally. The results reveal that(a) the process of plasticizing PVC first and then adding Cl-WR powder is better than the process of blending the admixture of PVC and Cl-WR at the same time;(b) The mechanical properties of PVC/Cl-WR blend are better than that of PVC/WR,and the PVC/14%Cl-WR blend has the best mechanical properties;(c) The addition of crosslinking agent has a significant enhancement for the mechanical properties of PVC/WR and PVC/Cl-WR blends,and the mechanical properties of PVC/14%Cl-WR improved most.At last,the optimum recipe for the mixture of PVC,additives and Cl-WR is studied. The results indicate that when PVC blended with 60 meshes Cl-WR with chlorine content of 14%at the mass ratio of 5:2,the PVC/Cl-WR has the best mechanical properties.This observation is justified by the better compatability of PVC/Cl-WR blends over PVC/WR blends via SEM images.(4) The mechanical properties,hydrophilicity,swelling resistance, morphology and thermal properties of PVC/Cl-WR are characterized and compared with those of PVC/WR blends.The results indicate that all properties of the PVC/Cl-WR blends show noticeable improvements over PVC/WR blends due to the improved polarity of Cl-WR and better compatability between PVC and Cl-WR,which is demonstrated by scanning electron microscope(SEM) images of the resulting blends.(5) A new application of Cl-WR as a flame retardant for combustible polymers,such as low density polyethylene(LDPE),is proposed for the first time.The thermal properties of WR and Cl-WR are characterized by thermogravimetric analysis(TG).The results indicate that the char residue of Cl-WR with maximum chlorine content of about 42%is 38% which is higher than that of WR,28%,and Cl-WR is in favour of char formation at high temperature.According to a number of experiments,an optimum recipe of flame retardancy of LDPE/Cl-WR is found as follows: to 100 g of LDPE,adding 80 g of flame retardant(Cl-WR and Sb₂O₃ with their mass ratio being 1.5:1) and 3 g of Montmorillonite.At such optimum conditions,the LDPE/Cl-WR blend can pass the UL-94 V-0 rating test and the LOI value of LDPE/Cl-WR can increase to 27.2.In addition,Cl-WR can improve the thermal stability of LDPE/Cl-WR blend in the high temperature region due to the favorable char formation of Cl-WR.Based on the TG and DTG analysis of LDPE/Cl-WR blends,the char formation mechanism of Cl-WR at high temperature is proposed.(6) Two novel hydrophobic ionic liquids(IL) with partial substitution of chlorine and fluorine in the 1-butyl-3-methylimidazolium cation(noted as[BMIM]or[C₈H₁₅N₂]hereafter),viz. [C₈H_12.28Cl_0.96F_1.76N₂]Cl and[C₈H_12.75Cl_1.58F_0.67N₂][PF₆],are synthesized, which are derived from the precursors[BMIM]Cl and[BMIM][PF₆], respectively through chlorination with chlorine gas and fluorination with potassium fluoride.The ¹H-NMR analyses show that the chlorination reaction mainly take place at the hydrogen of imidazolium ring and partly at the hydrogen of methyl subgroup in butyl.Although the decomposition temperature of IL[C₈H_12.28Cl_10.96F_1.76N₂]Cl and[C₈H_12.75Cl_1.58F_0.67N₂][PF₆] is lower,and the viscosity is higher than those of the corresponding non-modified IL,these new kinds of ILs exhibit an excellent hydrophobic property.Particularly for the[C₈H_12.75Cl_1.58F_0.67N₂][PF₆],the solubility of water in it was below 0.0001%,which implied that IL [C₈H_12.75Cl_1.58F_0.67N₂][PF₆]can be used as a promising potential extractant for the extraction of organic compounds from industrial waste water.