Propene-butene copolymers

Copolymers of different monomeric units that are able to co-crystallize in the same lattice are classic examples of polymer crystals including disorder due to isomorphic substitution of monomeric units in the crystal lattices. This occurs for instance for isotactic butene-3-methylbutene [3] or styrene-o-fluorostyrene [4] copolymers and isotactic [5-8] and syndiotactic [9, 10] propene-butene copolymers, which are crystalline in the whole range of compositions. In these cases the constitutional disorder due to the presence of mono-... 

Figure 2.26 Values of the -axis of the unit cell (a) and melting temperature (b) of syndiotactic propene-butene copolymers as a function of the butene concentration [10]. (A) Reproduced from Reference [10a] with permission from American Chemical Society, Copyright 1998.

Sacchi, M.C. Fan, Z.-Q. Forlini, F. Tritto, L Locatelli, P. Use of different alkoxysilanes as external donors in MgCl2-supported Ziegler-Natta catalysts to obtain propene/1-butene copolymers with different microstructure. Macromol. Chem. Phys. 1994, 195, 2805-2816. 

Polyethylene (PE) is a family of addition polymers based on ethylene. Polyethylene can be linear or branched, homopolymer, or copolymer. In the case of a copolymer, the other comonomer can be an alkene such as propene, butene, hexene, or octene or a compound having a polar functional group such as vinyl acetate (VA), acrylic acid (AA), ethyl acrylate (EA), or methyl acrylate (MA). If the molar percent of the comonomer is less than 10%, the polymer can be classified as either a copolymer or homopolymer. Figure 4.1 presents a diagram of the family of polymers based on ethylene monomer. 

Figure 10.4 C-NMR at 25.2 MHz of (a) O-ethylene-l-propene copolymer, (b) an ethylene-butene copolymer, (c) an ethylene-l-pentene copolymer, (d) an ethylene-1-hexene copolymer, (e) an ethylene-l-heptene copolymer and (f) an ethylene-1-octene copolymer. Reproduced with permission from J.C. Randall,of Polymer Science Polymer Physics Edition, 1973,11, 275. 1973, Wiley...

Butene is used in the plastics industry to make both homopolymers and copolymers. Polybutylene (1-polybutene), polymerized from 1-butene, is a plastic with high tensile strength and other mechanical properties that makes it a tough, strong plastic. High-density polyethylenes and linear low-density polyethylenes are produced through co-polymerization by incorporating butene as a comonomer with ethene. Similarly, butene is used with propene to produce different types of polypropylenes. 

Through the addition of small amounts of propene, 1-butene, 1-hexene or 1-octene to ethylene, short side chains can be added to the main polymer chain. The word linear should be interpreted to mean the absence of chain branches. With these short side chains LLDPE has a density range from 0.900 g/cm3 for VLDPE (very LDPE) to 0.935 g/cm3 for octene-ethylene copolymer. In this field metallocene catalysts become more and more important. 

For the packaging of sensitive foods, PP films are coated with polyvinylidene chloride, polyvinyl acetate, EVAcopolymers, polyacrylates, styrene-butadiene copolymers, LDPE, poly-l-butene or random copolymers of propene with ethylene and 1-butene. By using these various coatings PP has recently sharply reduced the use of regenerated cellulose (cellophane), the previous market leader in this area. 

Butene-1 is less reactive than propene but random copolymers can be prepared. Reactivity ratios for several vanadium catalysts are given in Table 21. 

Polymer (B) Characterization Solvent (A) ethylene/propylene copolymer M /kg.mor = 0.78,M ,/kg.mor = 0.79, 50 mol% propene, alternating ethylene/propylene units from complete hydrogenation of polyisoprene 1-butene C4H8 1992CH1 106-98-9... 

The oxidation stability of poly( butylene isophthalate-co-terephthalate) copolyesters has been shown to decrease steadily with isophthalate unit content [26]. As expected, GC-MS analyses show that oxidation takes place mainly in the butylene units, through the same mechanism as before. Small-molecule products of a copolyester containing 25 mol% isophthalate included THF, butyrolactone, 3-buten-2-one, 2-propenal, and various other cyclised and carbonyl fragments, along with acetic acid. As has been observed for most polyesters, thermal and thermo-oxidative reactions occur simultaneously, and the lower stability of butylene-isophthalate units is most probably responsible for the lower overall stability of copolymers containing this structure, even under the oxidation conditions used. 

Semicrystalline polyolefin blends were prepared by mixing two different random copolymers of propene with 4-lOC alpha-olefin at a ratio from 1 3-1 1. The first copolymer contained 1-10 wt% of C4 io alpha-olefin (1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene), whereas the second 15 0 wt% of the same comonomer. The mixing was carried out in reactors, polymerizing the monomers in the presence of stereospecific catalysts supports on active magnesium dihalides, in at least two sequential stages. The resulting R-TPOs showed limited... 

Fig. 1. CO/ethene-based PK-E. Note Applied notation for perfectly alternating CO/a-olefin polyketones PK-MiM2-re, in which Mi and M2 are abbreviations for the types of a-olefins incorporated in the co- or terpolymer chain [eg M = ethene (E), propene (P), butene (B), pentene (P), hexene (H), octene (0), decene (D), dodecene (Do), tetradecene (Td), hexadecene (Hd), octadecene (Od), icosene (Ic), and styrene (S)] and n, the molar monomer index n = [100 x [M2]/([Mi] + [M2])], is the percentage of M2 (in mol%) on the total amount of a-olefin incorporated in the polymer backbone. For example, PK-E represents a copolymer build up of CO and ethene, while PK-EP-6 represents a terpolymer build up of CO, ethene, and propene in a molar ratio of 100 94 6.

The practically most important copolymer is made from ethene and propene. Titanium- and vanadium-based catalysts have been used to synthesize copolymers that have a prevailingly random, block, or alternating structure. Only with Ziegler or single site catalyst, longer-chain a-olefins can be used as comonomer (e.g., propene, 1-butene, 1-hexene, 1-octene). In contrast to this, by radical high-pressure polymerization it is also possible to incorporate functional monomers (e.g., carbon monoxide, vinyl acetate). The polymerization could be carried out in solution, slurry, or gas phase. It is generally accepted [173] that the best way to compare monomer reactivities in a particular polymerization reaction is by comparison of their reactivity ratios in copolymerization reactions. 

On a laboratory scale, single site catalysts based on metallocene/MAO are highly useful for the copolymerization of ethene with other olefins. Propene, 1-butene, 1-pentene, 1-hexene, and 1-octene have been studied in their use as comonomers, forming linear low-density polyethene (LLDPE) [188,189]. These copolymers have a great industrial potential and show a higher growth rate than the homopolymer. Due to thee short branching from... 

Allyl chloride, " propenyl chloride isomers, trichloroethylene,l,3-dichloro-2-butene, 3-chloro-2-chloromethyl-1-propene, and chloroprene are all claimed to undergo alternating copolymerization with MA. Isopropenyl chloride is essentially nonpolymeriz-able by both free-radical and ionic initiators. However, mixtures of isopropenyl chloride and MA in benzene with AIBN, at 60°C, copolymerize quite readily to give colorless materials, with relatively high viscosities. The composition of the copolymers were found to be independent of monomer feed ratio and to consist essentially of a 1 1 composition of the monomer pair. In contrast, cis- and -propenyl chloride exhibit low copolymerization rates with MA and the resultant copolymers exhibit much lower specific viscosities than the isopropenyl chloride-co-MA polymers. 

De Footer and co-workers [25] described a comprehensive C-NMR method for the analysis of composition in the most common commercial polyethylene copolymers. The method covers ethene copolymers with propene, also butene-1, hexene-1, octene-1, and 4-methyl pentene-1 in the composition range of 1-10 mol%. The chemical shift assignments and values of the resonances of the copolymers are presented... 

By NMR spectroscopy, and by comparison with copolymers containing 1-propene and 1-butene comonomer units (E/P and E/B copolymers), typical HDPE samples were shown to contain on the order of 0.5 2.5 methyl branches per thousand backbone carbon atoms longer branches were not detected and are assumed to be absent [47]. Combined NMR and IR evidence indicates that the number of methyl branches in HDPE samples does not correlate with attainable crystallinity values, which implies that the methyl branches can be largely accommodated in the crystalline domains of polyethylene [47, 48]. 

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