Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-02-21
1995-11-07
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
5253338, 525386, 525387, C08F 800
Patent
active
054649072
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the modification of .alpha.olefins to introduce branching therein. More particularly, the present invention relates to a process of branching .alpha.-olefins by contacting said .alpha.-olefins with a peroxide compound containing an activated unsaturated group at a temperature above 120.degree. C.
Typical commercially available polypropylene is a normally solid, predominantly isotactic, thermoplastic polymer mixture formed by the polymerization of propylene monomers in the presence of a Ziegler-Natta catalyst. This type of polypropylene generally has a linear structure. Although commercial polypropyl has many beneficial properties, it is unsatisfactory in melt strength and strain hardening. Therefore, it exhibits a number of shortcomings when melt-processed. As a result, its use has been limited in applications such as extrusion coating, blow moulding, profile extrusi on and thermoforming.
Low molecular weight, amorphous (predominantly atactic) polypropylene with a branched molecular structure is known from Fontana, et al., Ind. & Eng. Chem., 44(7), 1688-1695 (1952) and U.S. Pat. No. 2,525,787. However, the average molecular weight of this material is generally below 20,000 making it unacceptable for many applications.
Numerous patent publications disclose the treatment of linear polypropylene with ionizing radiation to either degrade or cross-link the linear polymer chains. A typical example of such a patent publication is European patent application 0 190 889 which describes a high molecular weight, long chain, branched polypropylene made by irradiating linear polypropylene with high-energy ionizing radiation. The free-end branched polymer is gel-free and has strain-hardening elongational viscosity.
Further there are a number of publications describing the treatment of polypropylene with peroxides. Such references generally refer to a degradation or cross-linking of the polypropylene and degradation normally predominates. Generally, such peroxide treatments lead to a polypropylene with a narrow molecular weight distribution and having both lower number average and weight average molecular weights. A typical example of such publications is, "Degradation of Polyolefins during Melt Processing," Hinsken et al., Polymer Degradation and Stability, 34, pp. 279-293 (1991).
Canadian patent 999,698 discloses the degradation of polypropylene in a nitrogen atmosphere at 150.degree.-220.degree. C. by using organic peroxides such as t-butyl peroxymaleic acid and 2,5-bis (t-butylperoxy)-2,5-dimethyl hexane, among others. This modification process leads to a controlled reduction of at least 50% in the viscosity (an increase in the melt flow index (MFI)) of the polypropylene.
Chodak. I. and Lazar, M.; "Effect of the Type of Radical Initiator on Crosslinking of Polypropylene," suggests that there are some possibilities to achieve a certain amount of crosslinked polypropylene by, for example, using a high content of peroxide initiator or a high irradiation dose. However, these data are characterized as sporadic and no conclusion can be drawn about the effect of reaction conditions and type of initiator on the efficiency of crosslinking.
Netherlands patent application 6,808,574 discloses the modification of rubbers, including ethylene/propylene rubbers, by contacting the rubbers with a peroxide such as-t-butylperoxy crotonate or di-t-butyl-di-peroxy fumarate at a temperature of 140.degree.-160.degree. C. in order to crosslink the rubber composition.
In addition, the following patent publications disclose the modification of polypropylene with unsaturated peroxides: World patent applications WO 91/00301, WO 91/00300, European patent applications 0 208 353, 0 273 990, and 0 322 945. In each case, the polypropylene is degraded resulting in a lower final weight average molecular weight, although, with the addition of unsaturated co-crosslinking agents, a cross-linked polypropylene with a higher molecular weight can be obtained.
Finally, European patent application 0 384 431 disclose
REFERENCES:
patent: 2525787 (1950-10-01), Fontana et al.
"Catalyzed Polymerization of Monoalkylethylenes: Promoted Aluminum Bromide Catalyst", Fontana, et al., Industrial and Engineering Chemistry, vol. 44, No. 7 pp. 1688-1695 (Jul. 1952).
"Degradation of Polyolefins during Melt Processing", Hisken, et al., Polymer Degradation and Stability 34 pp. 279-293 (1991).
"On-Line Viscoelastic Measurements For Polymer Melt Processes", Zeichner and Macosko, Proceeding of the SPE 40th ANTEC Meeting, San Francisco, pp. 79-81 (May 1982).
"Crosslinking Agents in Ethylene-Propylene Rubbers", Hofmann, Progress in Rubber and Plastics Technology, vol. 1, No. 2, pp. 18-50 (Mar. 1985).
"Rubber Chemistry and Technology", vol. 61, pp. 242-254.
"Melt Flow Index Values and Molecular Weight Distributions of Commercial Thermoplastics", Bremner et al., Journal of Applied Polymer Science, vol. 41, pp. 1617-1627 (1990).
International Search Report prepared by the European Patent Office dated Sep. 22, 1993.
"Effect of the Type of Radical Initiator on Crosslinking of Polypropylene", Chodak, et al., Die Angewandte Makromolekulare Chemie 106, pp. 153-161 (1982).
Hope Peter
Jelenic Jernej
Meijer John
Akzo Nobel N.V.
Lipman Bernard
Mancini Ralph J.
Morris Louis A.
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