Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-03-03
2001-04-17
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S309000, C525S285000, C525S263000, C525S273000
Reexamination Certificate
active
06218476
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to novel functionalized polypropylenes having a unique combination of viscosity and yellowness index properties. This invention also relates to a novel polypropylene functionalization process.
BACKGROUND OF THE INVENTION
Grafting of monomers onto polyolefins is well known (see ‘Polymer Chemistry’ by M. P. Stevens, (Addison-Wesley), 1975, pp. 196-202). Maleation for example, is a type of grafting wherein maleic anhydride is grafted onto the backbone chain of a polymer. Maleation of polyolefins falls into at least three subgroups: maleation of polyethylene, maleation of polypropylene, and maleation of copolymers of propylene and ethylene or other monomers.
Maleation of polyethylene provides higher molecular weight products with a noticeable decrease in melt index due to cross-linking, unless special provisions are made, (see for example “Journal of Applied Polymer Science”, 44, 1941, N. G. Gaylord et al (1992); and U.S. Pat. Nos. 4,026,967; 4,028,436; 4,031,062; 4,071,494; 4,218,263; 4,315,863; 4,347,341; 4,358,564; 4,376,855; 4,506,056; 4,632,962; 4,780,228; 4,987,190; and 5,021,510). Maleation of polypropylene follows an opposite trend and yields lower molecular weight products with a sharp increase in flow rate due to fragmentation during the maleation process (see for example U.S. Pat. Nos. 3,414,551; 3,480,580; 3,481,910; 3,642,722; 3,862,265; 3,932,368; 4,003,874; 4,548,993; and 4,613,679). Some references in the literature fail to note the difference between maleation of polyethylene and polyproplyene, and claim maleation of polyolefins with conditions which are useful only for either polyethylene or polypropylene, respectively. In general, conditions which maleate polypropylene are not ideal for maleation of polyethylene due to the opposite nature of the respective maleation chemistries: fragmentation to lower molecular weights for polypropylene and cross-linking to higher molecular weights for polyethylene. This is shown in U.S. Pat. No. 4,404,312. Maleation of copolymers of propylene and ethylene or other monomers follow the pattern of the majority component.
Maleations of polypropylene can also be further subdivided into batch or continuous processes. In batch processes generally all of the reactants and products are maintained in the reaction for the entire batch preparation time. In general, batch maleation processes are difficult to use competitively in commerce due to high cost. Batch processes are inherently more expensive due to startup and cleanup costs.
The maleated polypropylenes that are reported in the previous literature can also be divided into two product types as a function of whether or not solvent is involved, either as a solvent during reaction or in workup of the maleated products. In U.S. Pat. Nos. 3,414,551; 4,506,056; and 5,001,197 the workup of the product involved dissolving the maleated polypropylene product in a solvent followed by precipitation, or washing with a solvent. This treatment removes soluble components and thus varies both the ‘apparent’ molecular weight and the acid number. Processes using an extruder produce a product in which solvent soluble components remain. In addition, extruder processes often incorporate a vacuum system during the latter stages of the process to remove volatile lower molecular weight components. Thus, different compositions are necessarily present in products produced in an extruder in contrast to those products from solvent processes or those which use a solvent in product workup.
Another subdivision of maleation of polyolefins concerns the state of the reaction process. Solvent processes, or processes where solvent is added to swell the polypropylene (see U.S. Pat. No. 4,370,450), are often carried out at lower temperatures than molten polyolefin (solvent free) processes. Such processes involve surface maleation only, with substantial amounts of polypropylene below the surface being maleation free. Processes using molten polypropylene involve random maleation of all of the polypropylene. Solvent processes are also more expensive in that solvent recovery/purification is necessary. Solvent purification is even more expensive if the process inherently produces volatile by-products, as in maleation. Note that if water is the ‘solvent’ polypropylene is not soluble and reaction must occur only on the surface of the polypropylene solid phase. Further, in aqueous processes maleic anhydride reacts with the water to become maleic acid. In these two ways processes containing water are necessarily different from non-aqueous processes. In a molten process no solvent or water remains at the end of the process to be purified or re-used. Thus a molten process would be environmentally ‘greener’ and less expensive.
SUMMARY OF THE INVENTION
The composition according to the present invention comprises a functionalized polypropylene having a yellowness index color of at least 77, and a Brookfield Thermosel viscosity of greater than 7000 cP at 190° C. Preferably, the functionalized polypropylene is further characterized by having an acid number greater than 6 milligrams of KOH per gram of polymer.
The novel process according to the present invention for the production of functionalized polypropylenes, including the novel functionalized polypropylenes of the present invention, is comprised as follows. A polypropylene is introduced into an apparatus, either in premolten form or as solid particulates (for example, pellets or powder) which are then melted; into the molten polypropylene is introduced a portion of the required amount of a free radical initiator, and the molten polypropylene and free radical initiator are mixed; into the resultant mixture is then introduced the entire amount of a functionalizing agent which is mixed therewith such that the functionalizing agent, the initial portion of initiator and the polypropylene are reacted; into the resultant reaction mixture is then introduced the remainder of the required amount of the free radical initiator to thereby form the desired functionalized polypropylene; and recovering the resultant functionalized polypropylene.
The remaining portion of the free radical initiator added after the functionalizing agent addition may be carried out in a plurality of zones. In each case the portion of the remaining free radical initiator added is mixed to form an intermediate reaction product into which additional free radical initiator is added. The percent of the remaining free radical initiator that may be added in each of the plurality of zones is between 1% and 99% by weight of the remaining free radical initiator added after the functionalizing agent addition. Preferably, the number of additional free radical initiator injection zones is between 2 and 10.
The polypropylene utilized herein has a melt flow rate of preferably about 0.1 to about 50 at 230° C. Moreover, the process described herein may be practiced in a continuous or batch manner.
DETAILED DESCRIPTION OF THE INVENTION
The applicant has unexpectedly discovered a novel batch or continuous process to functionalize polypropylenes. The process may be used to prepare a wide variety of functionalized polypropylenes, some of which are novel functionalized polypropylenes.
The novel functionalized polypropylenes according to the present invention have a yellowness index color of at least 77. The yellowness index color analysis is illustrated in the examples. The functionalized polypropylenes according to the present invention preferably have a yellowness index color ranging from at least 77 to about 200, more preferably from at least 77 to about 150, with a yellowness index color from at least 77 to about 120 being most preferred. A still further preferred yellowness index color ranges from 81 to about 120.
The functionalized polypropylene of the present invention has a Brookfield Thermosel viscosity of at least 7,000 cP at 190° C. The Brookfield Thermosel viscosity is preferably at least 7,000 to about 100,000 cP at 190° C., with a Brookfield Thermosel viscosity at 190° C. of about
Asinovsky Olga
Boshears B. J.
Eastman Chemical Company
Gwinnell Harry J.
Seidleck James J.
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