Polybutadiene monomer production

Styrene is frequently used as part of some terpolymers with large practical utilization. One such copolymer is acrylonitrile-butadiene-styrene terpolymer (ABS). Usually it is made as poly(l-butenylene-graft-l-phenylethylene-co-cyanoethylene). This form of the copolymer can be made by grafting styrene and acrylonitrile directly on to the polybutadiene latex in a batch or continuous emulsion polymerization process. Grafting is achieved by the free-radical copolymerization of styrene and acrylonitrile monomers in the presence of polybutadiene. The degree of grafting is a function of the 1,2-vinyl content of the polybutadiene, monomer concentration, extent of conversion, temperature and mercaptan concentration (used for crosslinking). The emulsion polymerization process involves two steps production of a rubber latex and subsequent polymerization of styrene and acrylonitrile in the presence of the rubber latex to produce an ABS latex. 

This combination of monomers is unique in that the two are very different chemically, and in thek character in a polymer. Polybutadiene homopolymer has a low glass-transition temperature, remaining mbbery as low as —85° C, and is a very nonpolar substance with Htde resistance to hydrocarbon fluids such as oil or gasoline. Polyacrylonitrile, on the other hand, has a glass temperature of about 110°C, and is very polar and resistant to hydrocarbon fluids (see Acrylonitrile polymers). As a result, copolymerization of the two monomers at different ratios provides a wide choice of combinations of properties. In addition to providing the mbbery nature to the copolymer, butadiene also provides residual unsaturation, both in the main chain in the case of 1,4, or in a side chain in the case of 1,2 polymerization. This residual unsaturation is useful as a cure site for vulcanization by sulfur or by peroxides, but is also a weak point for chemical attack, such as oxidation, especially at elevated temperatures. As a result, all commercial NBR products contain small amounts ( 0.5-2.5%) of antioxidant to protect the polymer during its manufacture, storage, and use. 

Commercially, anionic polymerization is limited to three monomers styrene, butadiene, and isoprene [78-79-5], therefore only two useful A—B—A block copolymers, S—B—S and S—I—S, can be produced direcdy. In both cases, the elastomer segments contain double bonds which are reactive and limit the stabhity of the product. To improve stabhity, the polybutadiene mid-segment can be polymerized as a random mixture of two stmctural forms, the 1,4 and 1,2 isomers, by addition of an inert polar material to the polymerization solvent ethers and amines have been suggested for this purpose (46). Upon hydrogenation, these isomers give a copolymer of ethylene and butylene. 

The particle size of the dispersed phase depends upon the viscosity of the elastomer-monomer solution. Preferably the molecular weight of the polybutadiene elastomer should be around 2 x 10 and should have reasonable branching to reduce cold flow. Furthermore, the microstructure of the elastomer provides an important contribution toward the low-temperature impact behavior of the final product. It should also be emphasized that the use of EPDM rubber [136] or acrylate rubber [137] may provide improved weatherability. It has been observed that with an increase in agitator speed the mean diameter of the dispersed phase (D) decreases, which subsequently levels out at high shear [138-141]. However, reagglomeration may occur in the case of bulk... 

Butadiene is by far the most important monomer for synthetic rubber production. It can be polymerized to polybutadiene or copolymerized with styrene to styrene-butadiene rubber (SBR). Butadiene is an important intermediate for the synthesis of many chemicals such as hexa-methylenediamine and adipic acid. Both are monomers for producing nylon. Chloroprene is another butadiene derivative for the synthesis of neoprene rubber. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Butadiene is a monomer used in high volume in the manufacture of a wide range of polymers, including styrene-butadiene rubber, polybutadiene, nitrile rubber, acrylonitrile-butadiene-styrene resins and st rene-butadiene latexes. It is also an intermediate in the production of various other chemicals. 

The ozonization method has been extended to the most varied polymer/monomer systems, such as polybutadiene-03 with acrylamide, methyl methacrylate or styrene, cellulose-03 with styrene or acrylonitrile (127), starch-03 with styrene (126). In this last case the formation of some homopolystyrene as side-product has been mentionned by the authors. The starch-styrene graft copolymers are claimed to be good emulsifiers for water-oil suspensions. 

For example, these workers (103) found that polybutadiene can be successfully metalated by n-BuLi-TMEDA, and the product subsequently used to graft styrene monomer to form poly(butadiene-g-styrene). This result showed that the grafting efficiency was 100%. Catalyst efficiency was found to be 75-95%. Thus, the n-BuLi-TMEDA metalating and grafting system is particularly effective for polydiene backbones. In fact, Falk and Schlatt (104) showed that poly(butadiene-g-styrene) has excellent tensile strength. 

The production of butadiene monomer is discussed below in polybutadiene section Polybutadiene. The largest volume of styrene is produced by the alkylation of benzene with ethylene to give ethyl benzene, which is then dehydrogenated to give styrene.27... 

Synthetic polymers from alkene monomers are also a major target for epoxidizers. Polyisoprenes,26 polybutenes and polybutadienes have all been epoxidized by general in situ peracid methods. In the case of liquid polybutadienes, a wide range of types is available. Products with varying contents of 1,4-cis, 1,4-trans, and 1,2-vinyl alkene groups are available (Figure 3.6). 

In the industrial production of structured AN-Bu-St (ABS) latex particles, the grafting copolymerization of AN and St on crossUnked polybutadiene (PB) seed latex is carried out in emulsion polymerization. Therefore, information on the effect of PB crosslinking density on the swelling of PB latex particles by a St-AN monomer mixture is very important for the production of ABS copolymers with desired properties. Mathew et al. [177] studied the effect of several thermodynamic parameters, such as the crosslinking density, particle size and monomer mixture composition on the swelling behavior of PB latex particles by pure St and AN, and St-AN mixtures of various compositions. They reported... 

Both the monomer and polymer are soluble in the solvent in these reactions. Fairly high polymer concentrations can be obtained by judicious choice of solvent. Solution processes are used in the production of c(5-polybutadiene with butyl lithium catalyst in hexane solvent (Section 9.2.7). The cationic polymerization of isobutene in methyl chloride (Section 9.4.4) is initiated as a homogeneous reaction, but the polymer precipitates as it is formed. Diluents are necessary in these reactions to control the ionic polymerizations. Their use is avoided where possible in free-radical chain growth or in step-growth polymerizations because of the added costs involved in handling and recovering the solvents. 

Solution polymerization. Solution polymerization involves polymerization of a monomer in a solvent in which both the monomer (reactant) and polymer (product) are soluble. Monomers are polymerized in a solution that can be homogeneous or heterogeneous. Many free radical polymerizations are conducted in solution. Ionic polymerizations are almost exclusively solution processes along with many Ziegler-Natta polymerizations. Important water-soluble polymers that can be prepared in aqueous solution include poly(acrylic acid), polyacrylamide, poly(vinyl alcohol), and poly(iV-vinylpyrrolidinone). Poly(methyl methacrylate), polystyrene, polybutadiene, poly(vinyl chloride), and poly(vinylidene fluoride) can be polymerized in organic solvents. 

For completeness it should be pointed out that many interesting morphologies of the type described above can be obtained by polymerizing a solution of AB or ABA block copolymers in styrene monomer, analogous to the process of HIPS production in which polybutadiene homopolymer is the dissolved species. This approach has been described in detail by Echte... 

The ability to proceed from a trorw-1,4-polybutadiene to a cis-l,4-polybuta-diene by changing the nature of the catalyst components implies, in accord with the proposed mechanism, either the production of more soluble catalyst compositions—e.g., as would be expected from TH4 as compared with TiCl4—inversion of the monomer in solution, ease of adsorption of the cis- monomer on the surface of the insoluble catalyst complex, or ease of hydrogen bond formation between the cis- monomer and the aluminum atom present in the complex. Alternatively, the inversion can occur in the formation of the monomer-catalyst complex without recourse to inversion in solution. 

Alcock and coworkers studied the polymerization of butadiene (as well as of monoolefins, acetylene and aromatic olefins) trapped within the tunnel clathrate system of tris((9-phenylenedioxy)cyclotriphosphazene, induced by Co-y-radiation. The host was used in order to find if the concatenation and orientation of the monomer molecules under the steric forces generated within the host crystal lattice will lead to stereospecific polymerization. The clathrate was prepared by addition of liquid butadiene to the pure host at low temperature. The irradiation was conducted at low temperatures. Irradiation of pure butadiene (unclathrated bulk monomer) leads to formation of a mixture of three addition products f,2-adduct, cis- and trons-f,4-adducts. In contrast, the radiation-induced polymerization within the tunnel system of the host yielded almost pure trans-1,4-polybutadiene. A small percentage of f, 2-addition product was observed, but no evidence for the formation of c/s-f,4-adduct was found, confirming the earlier observation by Fin ter and Wegner. The average molecular weight was about 5000,... 

Successive addition of 1,3-butadiene and isocyanide to the solution of the Ni catalyst forms a product with flexible polybutadiene blocks and rigid polyisocyanide blocks. Although the reaction of butadiene and isoprene in the presence of CoCl2/MAO causes homopolymerization of butadiene, the reaction catalyzed by CoCl2/MAO/PPh3 affords a copolymer with 1,2-butadiene and 3,4-isoprene units [94]. The monomer reactivity ratios indicate higher reactivity of butadiene than isoprene. 

However, the most interesting products could be obtained upon the radiolysis of butadiene derivatives included in a host matrix ( - ) For a number of monomers with a non-centrosymmetric molecular structure it could be demonstrated that y-irradiation leads to stereoregular, optically active polymers in a direct asymmetric induction. Especially these studies indicate that apart from polymerization in solution using optically active catalyst systems (A), the solid state polymerization represents a suitable method to obtain stereoregular polybutadienes. 

When lithium alkyls are used in anionic polymerizations, they tend to give cis products (m-polybutadiene and m-polyisoprene). There is also no termination step with these polymerizations. The rate of polymerization depends on the amounts of initiator and monomer present [13]. 

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