Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1993-02-12
1995-11-21
Teskin, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526160, 5263481, 528481, 528491, 528492, 528494, 528503, 524113, 524577, 2642893, 264340, 264345, C08F11212, C08J 518, C08L 2516, D01F 620
Patent
active
054688230
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to semicrystalline manufactured articles made of syndiotactic poly-p-methylstyrene (s-PpMS) exhibiting very good thermomechanical properties, and to processes for the preparation thereof.
It is known that p-methylstyrene (pMS), in comparison with styrene, is advantageously Obtained starting from toluene instead of benzene (in fact, pMS is primarily prepared by hydrodemethylation of toluene).
Recently, suitably modified zeolitic catalysts have been made available, which allow commercial production of pMS containing only small amounts of m-methylstyrene (mMS). In the past, only 65/35 mMS/pMS mixtures (known as vinyltoluene) were commercially available.
Atactic poly-p-methylstyrene (PpMS), obtained via radical polymerization, exhibits characteristics which are very similar to those of atactic polystyrene and compared to atactic polystyrene has the advantage of a lower density (4% lower), a higher Tg (113.degree. C. against 102.degree. C.) and better mold packing characteristics (lower melt viscosities).
It is also known that isotactic PpMS, obtained by conventional catalyst systems of the Ziegler-Natta type, does not crystallize and is therefore of no practical interest.
In contrast, syndiotactic PpMS obtained by the recently available syndiospecific catalyst systems is, as synthesized, a semicrystalline product having a melting point lower than 195.degree. C. However, said polymer is unable to crystallize either during molding operation or by subsequent annealing of the amorphous manufactured articles obtained therefrom.
It has now been found that it is possible to obtain semicrystalline manufactured articles (semi-finished products, formed articles, fibers, films, etc.) made of s-PpMS. In particular, manufactured articles can be obtained wherein the polymer is in a new crystalline form characterized by a melting point (225.degree. C.) which is higher than the melting point of the known crystalline forms.
The semicrystalline manufactured articles of the invention are obtained by exposure of amorphous manufactured articles to suitable organic solvents and by subsequent thermomechanical treatments.
It has, in fact, been found that amorphous s-PpMS manufactured articles are able to crystallize very rapidly when exposed to a suitable organic solvents, optionally in the form of vapour.
Solvents which are capable of inducing the crystallization of s-PpMS comprise tetrahydrofuran and o-dichlorobenzene as well as dimethylformamide, dimethylacetamide and N-methyl-2-pyrrolidone. Tetrahydrofuran and ethers which are structurally similar to tetrahydrofuran can induce very fast crystallization processes.
Various crystalline forms are obtained from said solvent treatment depending on the kind of solvent employed, in that the relevant structures usually clathrate molecules of the solvent in their crystal lattice.
BRIEF DESCRIPTION OF THE DRAWINGS
For instance, FIGS. 1A, 1B and 1C respectively show the X-ray diffraction spectra of a sample obtained by compression molding (amorphous sample), and subsequently exposed to tetrahydrofuran vapours or immersed in o-dichlorobenzene.
By annealing samples in the clathrate crystalline forms it is possible, depending on the starting clathrate form and the annealing conditions, to obtain samples in one of the four non clathrate crystalline forms, herein named as I, II, III and IV (the former three are actual crystalline forms, whereas form IV is a mesomorphic form), the X-ray diffraction spectra thereof being shown in FIGS. 2A, 2B, 2C and 2D respectively.
FIG. 3 shows the X-ray diffraction spectrum of the crystalline form IV.
FIG. 4A shows a DSC scan of an annealed film sample of semicrystalline s-PpMS exhibiting the crystalline form III.
FIG. 4B shows a DSC scan of an annealed film sample of semicrystalline s-PpMS exhibiting the crystalline form IV.
FIG. 4C shows a DSC scan of an annealed film sample of semicrystalline s-PpMS exhibiting the crystalline form II.
FIG. 5A shows an X-ray diffraction spectrum similar to the spectra of 150% drawn film having
REFERENCES:
patent: 4959435 (1990-09-01), Seitz et al.
patent: 5171834 (1992-12-01), Funaki
Gaetano Guerra et al., "Solid-state high-resolution 13C nuclear magnetic resonance spectra of syndiotactic poly(p-methyl-styrene)," Polymer Communications, vol. 32, No. 14, pp. 430-432 (1991).
Alfonso Grassi et al., "Reactivity of Some Substituted Styrenes in the Presence of a Syndiotactic Specific Polymerization catalyst," Macromolecules, vol. 22, pp. 104-108 (1989).
Patent Abstracts of Japan, vol. 14, No. 242 (C-721) May 23, 1990.
Corradini Paolo
DeRosa Claudio
Guerra Gaetano
Iuliano Mauro
Oliva Leone
Montecatini Tecnologie S.p.A.
Teskin Fred
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