Propylene with zinc oxide

Until they are vulcanized, elastic, amorphous ethylene-olefinic copolymers have very little possible utility except as components of caulks or sealants. However, grafting MA on the copolymers, using peroxide initiators, and compounding the modified materials with zinc oxide provides improved rubbers. A typical recipe would consist of 100 parts ethylene-propylene copolymer, 20 parts zinc oxide, 7 parts MA, and 2 parts BPO. Curing is carried out at 160°C for 30-45 min. Previously grafted copolymers, containing 2-5 MA residues, can also be cured with N-phenyl-B-naphthylamine initiator, steric acid modifier, and zinc oxide crosslinker. 

Results with butene are not as extensive as those with propylene. Nevertheless, on the basis of the ground work laid by the more extensive propylene studies, we are able to apply similar criteria to the more limited data for butene and conclude that a x-allyl species forms. Some preliminary studies suggest that two x-allyl species form from 1-butene (65), corresponding to the syn and anti forms. The results for propylene, the fact that x-allyl species form from butene, and the fact that zinc oxide is an effective catalyst for butene isomerization strongly suggest that these x-allyls are intermediates in the isomerization reaction. 

Table III. Bulk Polymerization of Propylene Oxide with Zinc Hexacyanocobaltate-Glyme-Zinc Chloride Catalyst at 30° C...

Practical interest in high-molecular-weight poly (propylene oxide) centers in its potential use as an elastomer (19). Copolymerization of propylene oxide with allyl glycidyl ether gives a copolymer with double bonds suitable for sulfur vulcanization. Table IV shows the properties of elastomers made with a copolymer prepared with a zinc hexacyano-ferrate-acetone-zinc chloride complex. Also shown are the properties of elastomers made from partially crystalline copolymers prepared with zinc diethyl-water catalyst. Of particular interest are the lower room-... 

Preparation of Poly (propylene ether) Polyols. The polymerization of propylene oxide with zinc hexacyanocobaltate complexes in the presence of proton donors results in the production of low-molecular-weight polymers. Table V shows the variety of types of compounds that have been found to act this way. Since these compounds end up in the polymer chains, it seems reasonable to call them chain initiators. Thus, in essence, each of these compounds is activated by the catalyst to react with propylene oxide to form a hydroxylpropyl derivative. Thereafter, the reaction continues on the same basis, with the proton of the hydroxyl group reacting with further propylene oxide. This sequence is shown here with 1,5-pentanediol as the initiator. The hydroxyl... 

The mechanism of stereoregulation in the stereoselective polymerisation of propylene oxide with zinc dialkoxide and related zinc dialkoxide-ethylzinc alkoxide complexes has been satisfactorily explained by the enantiomorphic catalyst sites model prepared by Tsuruta et al. [52,75], According to this model, the presence of chiral sites with a central octahedral zinc atom, bearing the polymer chain and coordinating the monomer, was assumed to be the origin of the stereoregulation mechanism. 

Figure 15.2 Reactions of bis(diisopropyI)-thiophosphoryI disulfide (DIPDIS) with ethylene-propylene-diene rubber (EPDM) and zinc oxide. (From Reference 32 with permission from John Wiley Sons.)...

Glycerol 85 % is a less potent preservative than propylene glycol. It acts as a preservative above 30 %. In lower concentrations it is less effective. Microbiological challenge tests of a zinc oxide cutaneous suspension for example showed an insufficient effect in a concentration of 110 mg/g Glycerol 85 %. Therefore it was replaced with propylene... 

SCHEME 24.10 Polymerization of racemic propylene oxide with zinc alkoxide cluster catalysts 7-9. 

Examples of stereoelective copolymerization have been reported. Matsuura, Tsuruta, Terada, and Inoue (156) prepared a polyester from 3-phenyl-A -tetrahydrophthalic acid anhydride and propylene oxide using diethyl zinc-(+)borneol as an optically active catalyst and obtained an optically active polyester. The authors reported that the stereoelective copolymerization of 3-phenyl-tetrahydrophthalic acid anhydride had occurred, but that of propylene oxide was not observed. Kximata, Furukawa, and Saegusa (157) copolymerized racemic propylene oxide with ethylene oxide using the ZnEt2/(+)-borneol system, and found that stereoelectivity of propylene oxide was not hindered by the occurrence of an ethylene oxide unit at the end of the growing chain. 

The role of the solvent may be important in anionic-coordinated polymerizations. Firstly it can play a role in the preparation of the initiator. It is known that alcoholysis reactions are solvent dependant. Secondly, it can interfere by its coordination strength on the initiator. In the case of the polymerization of propylene oxide with zinc alcoholates Ishimori etal [27] have shown that a retardation effect was observed when weakly basic solvents such as tetrahydrofuran, diethyl ether or dioxane are used. Triethylamine inhibits the polymerization almost completely. 

Fluorescent-dye-labeled PPO was synthesized with exactly one fluorophore in the polymer backbone. This was achieved by initiating the polymerization of propylene oxide with the dye 4-diethanolamino-7-nitrobenzofurazan with zinc hexacyanocobaltate as catalyst in tetrahydrofuran. A fraction of this dye-labeled polymer having molecular weight Mff = 33 600 and a narrow molecular weight distribution, = 1.1, was selected by... 

FIG U RE 11.1 Typical contour plot to abbreviate compounding data (Vistalon 3708/Ethylene-Propylene Terpolymer, Enjay Chemical Company, 1968). Note that a compound with 200 parts each of oil and filler per 100 parts of rubber by weight (phr) still has a strength of about 1000 psi (7 MPa), quite acceptable for many mechanical applications. The compound, based on a high-molecular-weight ethylene-propylene terpolymer, also contains 5 parts zinc oxide, 1 part stearic acid, 1.5 parts sulfur, 1.5 parts tetramethylthiuram disulfide, and 0.5 parts of benzothiazyl disulfide. Cross-linking takes place at 160°C for 20 min. SRF, Semi-reinforcing furnace. 

Cationic complexes, such as 55 and 56, catalyze the polymerization of propylene oxide, cyclohexene oxide, and of e-caprolactone with substantially higher activities than neutral zinc complexes. 

It is commonly known that lipids, carbohydrates, and glycolipids are present in the Golgi apparatus (27). The determination of the components that react with the ZIO mixture was carried out by removing each component from tissues before incubation in the ZIO mixture. After lipid extraction by acetone (14), chloroform-methanol (15), or propylene oxide (27), no osmium-zinc precipitates could be detected in structures that normally reacted with ZIO. Blumcke et al. (15) summarized the nature of the lipids that react with the ZIO mixture as follows lipids and lipoproteins of cell membranes, neutral fat droplets (41), and lipid globules of type II pneumocytes and alveolar macrophages were, however, not as electron dense as the normally reactive lamellae containing highly unsaturated fatty acids. 

Carbon dioxide can itself be used as a feedstock as well as a solvent for the synthesis of aliphatic polycarbonates by precipitation polymerization. Propylene oxide [39] and 1,2-cyclohexene oxide [40] can both be polymerized with CO2 using a heterogeneous zinc catalyst (Scheme 10.21). 

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