Poly butadiene production

As can be seen from Table 9 an increase in the ( i/ Nd-ralio from 0.5 to 3.0 results in an increase of the cis- 1,4-content. A further increase of the ci/ Nd-ratio to 4.0 and 10.0 decreases the cis- 1,4-content. BR which is obtained without halide donor (at a very low catalyst activity) exhibits a unique mi-crostructural composition 71.9% czs-1,4, 21.2% trans-1,4 and 6.9% 1,2. This observation corroborates the fact that high-czs-l,4-poly(butadiene) products only can be obtained in the presence of halide donors. 

Many random copolymers have found commercial use as elastomers and plastics. For example, SBR (62), poly(butadiene- (9-styrene) [9003-55-8] has become the largest volume synthetic mbber. It can be prepared ia emulsion by use of free-radical initiators, such as K2S20g or Fe /ROOH (eq. 18), or in solution by use of alkyl lithium initiators. Emulsion SBR copolymers are produced under trade names by such companies as American Synthetic Rubber (ASPC), Armtek, B. F. Goodrich (Ameripool), and Goodyear (PHoflex) solution SBR is manufactured by Firestone (Stereon). The total U.S. production of SBR in 1990 was 581,000 t (63). 

Poly(butadiene- (9-acrylonitrile) [9008-18-3] NBR (64), is another commercially significant random copolymer. This mbber is manufactured by free-radical emulsion polymerization. Important producers include Copolymer Rubber and Chemical (Nysyn), B. F. Goodrich (Hycar), Goodyear (Chemigum), and Uninoyal (Paracdl). The total U.S. production of nitrile mbber (NBR) in 1990 was 95.6 t (65). The most important property of NBR mbber is its oil resistance. It is used in oil well parts, fuels, oil, and solvents (64) (see Elastomers, synthetic— nitrile rubber). 

The specialty class of polyols includes poly(butadiene) and polycarbonate polyols. The poly(butadiene) polyols most commonly used in urethane adhesives have functionalities from 1.8 to 2.3 and contain the three isomers (x, y and z) shown in Table 2. Newer variants of poly(butadiene) polyols include a 90% 1,2 product, as well as hydrogenated versions, which produce a saturated hydrocarbon chain [28]. Poly(butadiene) polyols have an all-hydrocarbon backbone, producing a relatively low surface energy material, outstanding moisture resistance, and low vapor transmission values. Aromatic polycarbonate polyols are solids at room temperature. Aliphatic polycarbonate polyols are viscous liquids and are used to obtain adhesion to polar substrates, yet these polyols have better hydrolysis properties than do most polyesters. 

Bis(nitrile oxides) obtained from dialkylbenzenes have been claimed as low-temperature rubber vulcanization agents (517). Curing of poly(butadiene-co-acrylonitrile) with 2,4,6-trimethylisophthalodinitrile N-oxide produces rubbery material of good quality, however, curing of (polybutadiene) was unsuccessful (518). The solubility of dinitrile oxides and stability of their ketone solutions has been studied for their application as vulcanizing agents in the production of mbberized materials (519). 

Second, the conversion of one of the blocks into another type of structure by a suitable quantitative chemical reaction, allows a broad diversification of the properties of the available block copolymers. The best example of such an opportunity is probably the hydrogenation of poly(butadiene-b-styrene) copolymers, which yields a product close to a low density poly(ethylene-b-styrene) when starting from an anionically prepared diblock (including a certain amount, ca. 10 %, of 1.2 units), while a high density poly(ethy1ene-b-styrene)... 

When irradiating a 1 1 blend of polychloroprene and poly(butadiene-acry-lonitrile) (NBR) reinforced by 50 phr furnace black and containing 5-15 phr of tetramethacrylate of bisglycerol phtalate, the product exhibited a tensile strength of 20 MPa (2,900 psi) at a dose of 15 Mrad (150 kGy) with values of elongation at break in the range of 420-480%. These values are equal to or better than those obtained from similar compounds cured chemically. ... 

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. 

High cis- 1,4-poly butadiene is manufactured on a large industrial scale and occupies a well-defined position in the elastomers market. It is employed mainly in the tyre industry, where it is blended with natural rubber and/or with styrene-butadiene rubber and applied in either sidewalls, threads or rims of tyres. It should be noted in this connection that natural rubber, in contrast to its synthetic counterpart, displays some physical properties that appear to be useful in the manufacture of tyres for heavy-duty machines. The fact is that some non-hydrocarbon substances appearing in natural rubber in small amounts (such as polypeptides) protect the high-dimensional tyre formed against collapsing prior to the vulcanisation process and thus enable a high-quality product to be obtained. 

The mechanism is complicated by the possibility of anti-syn-isomerization and by n - a-rearrangements (it - r 3-allyl Act - r 1 -allyl). In the case of C2-unsubstituted dienes such as BD the syn-form is thermodynamically favored [646,647] whereas the anti-isomer is kinetically favored [648]. If monomer insertion is faster than the anti-syn-rearrangement the formation of the czs- 1,4-polymer is favored. A higher trans- 1,4-content is obtained if monomer insertion is slow compared to anti-syn-isomerization. Thus, the microstructure of the polymer (czs-1,4- and frazzs-1,4-structures) is a result of the ratio of the relative rates of monomer insertion and anti-syn-isomerization. As a consequence of these considerations an influence of monomer concentration on cis/trans-content of BR can be predicted as demonstrated by Sabirov et al. [649]. A reduction of monomer concentration results in a lower rate of monomer insertion and yields a higher trans-1,4-content. On the other hand the czs-1,4-content increases with increasing monomer concentration. These theoretical considerations were experimentally verified by Dolgoplosk et al. and Iovu et al. [133,650,651]. Furthermore, an increase of the polymerization temperature favors the formation of the kinetically controlled product and results in a higher cis- 1,4-content [486]. l,2-poly(butadiene) can be formed from the anti- as well as from the syn-isomer. In both cases 2,1-insertion occurs [486]. By the addition of electron donors the number of vacant coordination sites at the metal center is reduced. The reduction of coordination sites for BD results in the formation of the 1,2-polymer. In summary, the microstructure of poly(diene) depends on steric factors on the metal site, monomer concentration and temperature. 

A double-side adhesive tape was prepared using a mixture of a hydroxylterminated poly butadiene, a polyol, and an isocyanate compound containing an oxadiazinetrione ring 241 A compound suitable for sealing spaced glass panels comprises a reaction product of an unsaturated polymer with functional end groups with HTPB, a decane thiol adduct, and tolylene diisocyanate 242). 

Predominantly di-end-functional polymers may be prepared by conducting polymerizations with high concentrations of a functional initiator. Some of the first commercial products of this class, carboxy and hydroxy-terminated poly butadienes, were produced by this route. 

The pyrolysis products of 1,3-diene-sulfur dioxide copolymers were analyzed in a field-ion mass spectrometer and the fragmentation results suggest an alternating 1 1 copolymer for poly(butadiene sulfone), poly(isoprene sulfone) and poly(2,3-dimethylbutadiene sulfone) [48]. 

Commercial poly(butadiene), which is mainly the 1,4 isomer, is also used to improve the impact resistance of polystyrene (Chapter 1). Polydienes also increase the rate of physical disintegration of polyblend containing them. The addition of a styrene-butadiene block copolymer e.g. SBS, page 9 et seq.) to polyethylene also accelerates the peroxidation of the latter. However, this system also requires a polymer-soluble transition metal ion catalyst e.g. an iron or manganese carboxylate) to increase the rate of photooxidation in the environment by the reactions shown in Scheme 5.3. The products formed by breakdown of alkoxyl radicals (PO ) (Scheme 3.4) are then rapidly biodegradable in compost (page 107 et seq.). 

Negative ions FAB mass spectrum of poly(butadiene) ozonolysis products. (Reprinted with permission from Ref. 76, Copyright 1999, American Chemical Society.)... 

The prefix g describes graft copolymers and the prefix b describes block copolymers. In this system of nomenclature, the first polymer segment corresponds to the homopolymer or copolymer that was formed during the first stage of the synthesis. Should this be a graft copolymer then this will represent the backbone polymer. For instance, if polystyrene is graft copolymerized with polyethylene, the product is called poly(ethylene-g-styrene). A more complex example can be poly (butadiene-co-styrene-g-acrylonitrile-co-vinylidine chloride). Similarly, examples of block copolymers would be poly(acrylonitrile- -methyl methacrylate) or poly(methyl methacry late- -acry lonitrile). 

Various metal complex systems of Ziegler type are widely applied within industry for the production of high-density polyethylene, isotactic polypropylene, 1,4-c/s-and 1,4- rans-polymers of isoprene and 1,2-poly butadiene, and many other types of copolymers, such as ones based on ethylene and propylene, which could not be produced earlier based on traditional methods of synthesis. 

Such free radicals X are produced by irradiating organobromides, organo-sulfides, mercaptans, or Br2 by the action of uv light. Alternatively, the isomerization can proceed via charge transfer complexes with sulfur or selenium. In this way, cw-l,4-poly(butadiene) is isomerized at 25 C to an equilibrium product containing 77% trans bonds. Thus, with = 77/23 = 3.35, Equation (23-8) gives AG so = "3.0 kJ/mol. 

Considerable quantities of styrene are used in producing copolymerisates and blends, as, for example, in the production of copolymers with acrylonitrile (SAN), terpolymers from styrene/acrylonitrile/butadiene (ABS polymers) or acrylonitrile/styrene/acrylic ester (ASA), etc. The glass transition temperature of poly (styrene), 100 C, can be increased by copolymerization with a-methyl styrene. What are known as high impact poly (styrenes) are incompatible blends with poly(butadiene) or EPDM, which are consequently not transparent, but translucent. For this reason, pure poly (styrenes) are occasionally called crystal poly (styrenes). 

If dianions are used and the polymerization is terminated by carbon dioxide, then poly(butadienes) with carboxyl end groups are produced. Such products with molar masses of about 10,000 g/mol are liquid rubbers that can be cross-linked with poly isocyanates (see also Section 37.3.2). 

Low-molar-mass poly(butadiene) oils with 80%-97% cw-1,4 contents are produced with other Ziegler catalysts (for example, cobalt compounds with alkyl aluminum chlorides or nickel compounds with trialkyl aluminum and boron trifluoride-etherate). The products have few cross-links and dry as fast as wood oil and faster than linseed oil. Conversion of the poly (butadiene) oils with 20% maleic anhydride gives air-drying (air-hardening) alkyd resins. Modified poly (butadiene) oils stabilize erosion-endangered soils. Because of its low viscosity, the aqueous emulsion penetrates the surface soil layers. The surface crust is reinforced by an oxidative bonding process. Since no skin is formed on the soil crust, the aqueous absorption characteristics of the soil are retained. 

Figure 35-9. Multiphase systems in the in situ production of high-impact poly(styrene) by the free radical polymerization of a styrene>c/5-poly(butadiene) solution. (After S. L. Aggarwal and R. A. Livigni.)...

We use poly sty rene-f>-poly butadiene block copolymers as the starting material with preformed polymer architecture. These polymers are comparatively cheap and easily accessible. For the present problems a series of narrowly distributed polystyrene-Zr-polybutadiene block copolymers with rather different molecular weights were synthesized via anionic polymerization (Figure 10.4, Table 10.1). As a test for the modification of technological products, a commercial triblock copolymer was also used. 

The molecular mass of the wax-like compounds, which are volatile at the decomposition temperatures and comprise the basic mass (82-97%) of the products of the thermal degradation of polybutadiene is 739. The average yield of monomer on degradation of poly butadiene does not exceed 1.5% mass of the total quantity of volatile compounds, a result which may be associated with both the partial polymerisation of the monomer produced, which is kept at room temperature, and the formation of vinylcyclohexane ... 

Brominations of polybutadienes with N-bromosuccinimide yield a-brominated poly butadienes [46,47] that may also contain butane diylidene units. The products act as typical alkyl halides and can undergo Grignard-Wurz reactions ... 

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