Polymerization excess

After polymerization, excess monomer is stripped and recycled. The residual monomer content of the stripped emulsion does not represent an acute hazard. Worker exposure to monomer is monitored, and sources of exposure identified and corrected. 

Polymerization. A weighed mixture of monomer and solvent in a 30-ml ampoule was cooled in a dry ice bath and flushed with nitrogen, sealed and set without stirring in a bath. After polymerization, excess petroleum ether was added to precipitate the copolymer, which was dried under reduced pressure. 

The DIPP tantalacyclobutane complex, 32a, has been shown to polymerize excess norbornene at 50 °C to yield polynorbornene with a molecular weight... 

With polycondensation being exothermic, heat must be withdrawn during the reaction proper to maintain a constant temperature. After completion of the polymerization, excess water (water introduced by diluted reactants and water liberated by the process) is simply removed by vacuum distillation. 

Poly(tetramethylene adipamide) or nylon-4,6 is prepared from tetramethylene diamine and adipic acid by polymerization in an organic solvent or by melt polymerization followed by solid-state polymerization [79,80]. The polymer melts at 295°C, about 30°C above nylon-6,6. It is more sensitive to degradation and branching. The volatility of tetramethylene diamine also makes it difficult to control the balance of end groups during polymerization. Excess diamine is added to compensate the losses. Values of M as high as 32,900 have been reported. 

I. I-dichli)rt)ethene, I. l-dichloroethylene, asymmetric dichloroethene, CH2=CCl2, colourless liquid, b.p. 37 C. Prepared by heating 1,1,1- or 1,1,2-trichloroethene with excess lime at 70-80 C. Polymerizes readily to an insoluble solid. 

Lead ll) oxide, PbO, exists in two forms as orange-red litharge and yellow massicot. Made by oxidation of Pb followed by rapid cooling (to avoid formation of Pb304). Used in accumulators and also in ceramics, pigments and insecticides. A normal hydroxide is not known but hydrolysis of lead(II) oxyacid salts gives polymeric cationic species, e.g. [Pb OfOH) ] and plumbates are formed with excess base. 

Polysulphide rubbers. Ethylene dichloride and excess of sodium tetrasulphide when heated together give a polymeric polysulphide, Thiokol A, with properties resembling those of rubber ... 

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. 

Dimethyl acetylenedicarboxylate (DMAD) (125) is a very special alkyne and undergoes interesting cyclotrimerization and co-cyclization reactions of its own using the poorly soluble polymeric palladacyclopentadiene complex (TCPC) 75 and its diazadiene stabilized complex 123 as precursors of Pd(0) catalysts, Cyclotrimerization of DMAD is catalyzed by 123[60], In addition to the hexa-substituted benzene 126, the cyclooctatetraene derivative 127 was obtained by the co-cyclization of trimethylsilylpropargyl alcohol with an excess of DMAD (125)[6l], Co-cyclization is possible with various alkenes. The naphthalene-tetracarboxylate 129 was obtained by the reaction of methoxyallene (128) with an excess of DMAD using the catalyst 123[62],... 

When [A] [B], both ends of the growing chain tend to be terminated by the group which is present in excess. Subsequent reaction of such a molecule involves reaction with the limiting group. The effect is a decrease in the maximum attainable degree of polymerization. 

The ethylene glycol liberated by reaction (5.L) is removed by lowering the pressure or purging with an inert gas. Because the ethylene glycol produced by reaction (5.L) is removed, proper stoichiometry is assured by proceeding via the intermediate, bis(2-hydroxyethyl) terephthalate otherwise the excess glycol used initially would have a deleterious effect on the degree of polymerization. Poly(ethylene terephthalate) is more familiar by some of its trade names Mylar as a film and Dacron, Kodel, or Terylene as fibers it is also known by the acronym PET. 

We define the problem by assuming the polymerization involves AA and BB monomers and that the B groups are present in excess. We define and to be the numbers of A and B functional groups, respectively. The number of either of these quantities in the initial reaction mixture is indicated by a superscript 0 the numbers at various stages of reaction have no superscript. The stoichiometric imbalance is defined by the ratio r, where... 

What we seek next is a quantitative relationship between the extent of the polymerization reaction, the composition of the monomer mixture, and the point of gelation. We shall base our discussion on the system described by reaction (5.U) other cases are derived by similar methods. To further specify the system we assume that A groups limit the reaction and that B groups are present in excess. Two parameters are necessary to characterize the reaction mixture ... 

Fig. 13. Polymerization chemistry of phenol—formaldehyde condensation synthesis of novolac resia. The phenol monomer(s) are used ia stoichiometric excess to avoid geUation, although branching iavariably occurs due to the multiple reactive sites on the aromatic ring.

Rea.ctlons, The chemistry of butanediol is deterrnined by the two primary hydroxyls. Esterification is normal. It is advisable to use nonacidic catalysts for esterification and transesterification (122) to avoid cycHc dehydration. When carbonate esters are prepared at high dilutions, some cycHc ester is formed more concentrated solutions give a polymeric product (123). With excess phosgene the usefiil bischloroformate can be prepared (124). 

Acrylate and methacrylate polymerizations are accompanied by the Hberation of a considerable amount of heat and a substantial decrease in volume. Both of these factors strongly influence most manufacturing processes. Excess heat must be dissipated to avoid uncontrolled exothermic polymerizations. In general, the percentage of shrinkage decreases as the size of the alcohol substituent increases on a molar basis, the shrinkage is relatively constant (77). 

HydroxyethyUiydrazine (11) is a plant growth regulator. It is also used to make a coccidiostat, furazoHdone, and has been proposed, as has (14), as a stabilizer in the polymerization of acrylonitrile (72,73). With excess epoxide, polysubstitution occurs and polyol chains can form to give poly(hydroxyaLkyl) hydrazines which have been patented for the preparation of cellular polyurethanes (74) and as corrosion inhibitors for hydrauHc fluids (qv) (75). DialkyUiydrazines, R2NNH2, and alkylene oxides form the very reactive amineimines (15) which react further with esters to yield aminimides (16) ... 

Polymerizations are typically quenched with water, alcohol, or base. The resulting polymerizates are then distilled and steam and/or vacuum stripped to yield hard resin. Hydrocarbon resins may also be precipitated by the addition of the quenched reaction mixture to an excess of an appropriate poor solvent. As an example, aUphatic C-5 resins are readily precipitated in acetone, while a more polar solvent such as methanol is better suited for aromatic C-9 resins. 

Tris(2,4-pentanedionato)iron(III) [14024-18-1], Fe(C H202)3 or Fe(acac)3, forms mby red rhombic crystals that melt at 184°C. This high spin complex is obtained by reaction of iron(III) hydroxide and excess ligand. It is only slightly soluble in water, but is soluble in alcohol, acetone, chloroform, or benzene. The stmcture has a near-octahedral arrangement of the six oxygen atoms. Related complexes can be formed with other P-diketones by either direct synthesis or exchange of the diketone into Fe(acac)3. The complex is used as a catalyst in oxidation and polymerization reactions. 

Commercial-grade nitroparaftins are shipped and stored ia ordinary carbon steel. However, wet nitroparaftins containing more than 0.1—0.2% water may become discolored when stored ia steel for long periods, even though corrosion is not excessive. Aluminum and stainless steel are completely resistant to corrosion by wet nitroparaftins. Storage ia contact with lead (qv), copper, or alloys containing these metals should be avoided. Polymeric materials for gaskets, hoses, and connections should be tested for thek suitabiHty before exposure to nitroparaftins. 

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