Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1997-10-01
2001-11-06
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S308000, C526S348500, C526S343000, C526S345000, C428S515000, C428S516000, C428S518000
Reexamination Certificate
active
06313241
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to novel copolymers having long chain branch configuration and to novel process for forming same.
Polyolefins have been formed by free radical polymerization which provides a polymer product having broad molecular weight distribution and a structure which includes a significant amount of short and long chain branching. The good processability of these polyolefins has been attributed to a combination of broad molecular weight and long chain branching.
It is well known to produce polyolefins using conventional Ziegler catalysts. The resultant polymers also have broad molecular weight distribution but do not have a polymer structure which has a significant amount of long chain branches and, therefore, exhibit only average processability in providing film products.
More recently, metallocene or single site polymerization catalysts have been used to provide polyolefin products. In general, metallocene catalysts provide polymer products with narrower molecular weight distribution without a significant amount of long chain branching and, thereby, also exhibit processability problems related to melt fracture, low melt tension and the like. The metallocene complexes have been broken down into several categories based on their chemical composition and their molecular structure. For example, their organic moieties may be cyclopentadienyl (Cp) or indenyl (Ind) or fluorenyl (Flu) based. The organic groups may be unbridged or may be tied together in a bridged configuration. The bridged structure may form, with the metal atom of the complex, a strained configuration (generally referred to as constrained geometry catalyst technology or CGCT) or have a substantially unstrained configuration. The metallocene complexes of the various categories have activity in certain specific polymerization processes while being substantially non-active to other polymerization efforts.
Attempts have been made to improve the processability of polyolefins by broadening the molecular weight distribution of the polymer. One approach has involved generating a polymer product having a higher degree of long chain branching as part of the polymer's structure. U.S. Pat. Nos. 5,380,810; 5,525,695; 5,272,236 and 5,278,272 describe polymerization processes which require the use of specific constrained geometry catalyst (CGCT). It is believed that metallocene catalysts having constrained geometry can be used in solution polymerization to introduce long chain branching to polymer products formed from predominantly aliphatic alpha-olefins. The resultant polymers have enhanced processability at narrow molecular weight distributions.
More recently, EP Application 0 676 421 disclosed the ability to conduct gas phase polymerization of aliphatic alpha-olefins using certain metallocene compounds to provide products having long chain branching and, thereby, enhanced processability.
The molecular weight distribution or polydispersity of polymers is a well known variable which can be defined as the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) and is normally reported as Mw/Mn. This can be measured by gel permeation chromatography techniques. It is often convenient to gauge polymer processibility by measuring the polymer's metal flow index ratio under different loads (10 Kg and 2 Kg), as described in ASTM-D-1238. It is well known that polyethylene based resins which have narrow polydispersity (e.g., 1.5 to 3) have melt flow index ratio (I
10
/I
2
) of less than about 8 do not exhibit good processibility while polymers having high melt flow index ratios contain long chain branching and provide good processibility. Thus, from the melt flow ratio, one can gauge a polymer's ability to shear thin to provide a polymer with enhanced processability, e.g., low susceptibility to melt fracture surface imperfections, even under high shear stress conditions.
Copolymers formed with units derived from certain vinyl alicylic containing monomers are highly desired materials. For example, such materials have utility as a component in forming films, such as the use of copolymers of ethylene and 4-vinylcyclohexene as a cross-linking enhancer component of a multi-layer film, as described in copending U.S. Ser. No. 08/822,529 filed Mar. 24, 1997, U.S. Pat. No. 5,993,992 the teachings of which are incorporated herein by reference in its entirety. However, these alicyclic containing copolymers are difficult to process into films because of their low polydispersity and the absence of significant long chain branches in its structure.
It is highly desired and an object of the present invention to provide copolymers of ethylene and vinyl alicyclic containing monomer which have a low polydispersity while having long side chain branches and related high value of its melt flow index ratio. Such copolymers have enhanced processability and are especially useful in film forming activities.
Further, it is an object of the present invention to provide a process for catalytic polymerization of ethylene and at least one vinyl alicyclic containing comonomer by solution polymerization to provide a polymer product having good processability characteristics.
Further, it is an object of the present invention to provide process for forming films and the resultant improved film product which comprises at least one layer having the subject copolymer therein.
SUMMARY OF THE INVENTION
The present invention is directed to certain new and novel copolymers having long side chains formed from monomers of ethylene and at least one alicyclic group containing monomer represented by the formula:
wherein
represents a (i) C
5
-C
12
saturated alicyclic group which may be unsubstituted or substituted or (ii) C
6
-C
12
alicyclic group which may be unsubstituted or substituted and contains at least one ethylenic carbon-carbon double bond (non-aromatic) within the ring structure.
The present invention is further directed to a solution polymerization process capable of forming the subject copolymers having long side chains using certain unstrained bridged metallocene catalysts.
DETAILED DESCRIPTION
The present invention is directed to new and novel long chain branched containing copolymers of ethylene and a vinyl alicyclic group containing comonomer represented by the formula:
wherein
represents an alicyclic group selected from C
5
-C
12
saturated alicyclic group or a C
6
-C
12
ethylenically unsaturated alicyclic group. These groups may further have one or more of its hydrogen atoms substituted by a C
1
-C
12
hydrocarbon, as fully described below.
The subject copolymer must have ethylene as one of its monomeric forming groups. In addition, the subject copolymer must have, as one of its monomeric forming groups, at least one monomer of formula I, above. This monomer must have (i) a vinyl group; (ii) a hydrogen atom pendent from the beta carbon and the gamma carbon of the monomer I; and (iii) an alicyclic, gamma carbon atom containing group pendent from the beta carbon. The alicyclic group can be a saturated C
5
-C
12
alicyclic group such as cyclopentyl; cyclohexyl; cyclooctyl; cyclononyl; cyclodecyl; cyclohendecyl; and cyclododecyl. These groups can be unsubstituted or can have one or more C
1
-C
20
hydrocarbon group substitution on the alicyclic ring carbons provided the gamma carbon atom has a pendent hydrogen atom. The substitution group can be an aliphatic hydrocarbon such as, for example, methyl, ethyl, isopropyl, pentyl and the like; an alkenyl group, such as 3-butenyl, 4-hexenyl and the like, a saturated or unsaturated alicyclic group which may be fused or unfused to the alicyclic ring.
The alicyclic, gamma carbon atom containing group may, alternately, be selected from an unsaturated (non-aromatic) C
6
-C
12
alicyclic group such as, for example, cyclohexenyl, cyclohexadienyl, cycloheptenyl, 5-cyclooctenyl, 3-cyclooctenyl, 4-cyclcooctenyl, cyclooctadienyl, cyclododecatrienyl and the like. The alicyclic groups can, besides having at least one ethylenic unsaturation wit
Gauthier William John
Hatfield Galen Richard
Moffitt Ronald Dean
Acquah Samuel A.
Asinovsky Olga
Cryovac Inc.
Troffkin Howard
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