Hydrolytically degradable olefin copolymers

Details Hydrolytically degradable olefin copolymers Hydrolytically degradable olefin copolymers

1999-09-29

2001-09-11

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S266000, C526S302000, C526S319000, C526S943000

Reexamination Certificate

active

06288184

ABSTRACT:

TECHNICAL FIELD
The present invention relates to olefin copolymers, such as ethylene copolymers, containing a hydrolyzable component that allows the copolymer to be broken down into dispersable fragments upon exposure to aqueous conditions. The copolymers are prepared by transition metal-catalyzed polymerization.
REFERENCES
Alikhan, M. I. et al., U.S. Pat. No. 5,817,394 (1998).
Goto, Y. et al., EP 0462588 A (12/1991).
Hajime, Y. et al., EP 0442476 A2 (8/1991).
Johnson, L. K. et al.,
J. Am. Chem. Soc
. 117:6414-5 (1995).
Johnson, L. K. et al.,
J. Am. Chem. Soc
. 118:267-8 (1996).
E. Kubo et al., U.S. Pat. No. 4,981,749 (1991).
Ouchi et al.,
J Chem. Soc. Japan
71(7):1078-82 (1968).
Killian, C. M. et al.,
Organometallics
16:2005-7 (1997).
Raley, J. M., U.S. Pat. No. 4,761,322 (1988).
Small, B. L. etal.,
J Am. Chem. Soc
. 120:4049-50 (1998).
Smorada, R. L., in
Encycl. Polym. Sci. Eng
., Vol. 10, J. I. Kroschwitz, ed., (New York: John Wiley & Sons, 1987) at pp. 227-53.
Yasuda, H. et al., EP 0799842 A1 (10/1997).
Yasuda, H. et al., U.S. Pat. No. 5,563,219 (10/1996).
BACKGROUND
Over the past several years, a great deal of research has been directed to the design of biodegradable polymers. Concern over waste disposal, particularly of packaging materials, disposable diapers, etc., motivates much of this work. Products designed to degrade after their intended use may be composed of photosensitive or hydrolytically degradable polymers. Polymers intended to degrade during use, as in controlled-release delivery systems, are nearly always hydrolytically degradable. Hydrolytically degradable polymers are frequently polyester-based, prepared by condensation or radical polymerization. Also employed are physically or chemically bonded blends of synthetic polymers with biomaterials such as starch.
For many purposes, the superior physical properties provided by polyolefins prepared by addition polymerization are desirable. To date, however, incorporation of polar groups into such polyolefins has had limited success, since many polar monomers poison, or competitively coordinate with, the organometallic polymerization catalysts that are typically used. Copolymers of olefins, such as ethylene, with polar monomers such as acrylates, were initially limited to block copolymers, formed by two-stage polymerization, e.g., by post-polymerization of an acrylate or methacylrate monomer onto a previously formed polyolefin chain (Yasuda et al., 1996, 1997; Goto et al, Hajime et al.). Masakazu et al., in JP Kokai 4-45108 (1992), described the preparation of an ethylene copolymer containing 4.7 mole % ethyl acrylate, Mn 9,100, Mw 22,500, that show improved adhesion over polyethylene homopolymer. Johnson et al. (1996) described the formation of random olefin-acrylate copolymers using Brookhart-type catalysts. None of these polymers, however, include a hydrolyzable linkage in the backbone of the polymer, and therefore they would not be hydrolytically degradable. Ouchi et al. described free radical copolymerization of diallylidene pentaerythritol with styrene; however, incorporation of the diene monomer was low, and increased incorporation significantly decreased the intrinsic viscosity of the product. The reaction conditions would also be expected to produce a non-stereoregular polymer.
Accordingly, providing olefin copolymers that have good physical properties and stability under conditions of use, at neutral or near-neutral pH, but that degrade into soluble or easily dispersable particles in an aqueous medium would be desirable.
SUMMARY OF THE INVENTION
In one aspect, the present invention is directed to a degradable olefin copolymer. The polymer backbone comprises at least two monomer units. The first monomer unit is non-hydrolyzable and of the form —R
1
CH—CHR
2
—, in which R
1
is hydrido or alkyl and R
2
is hydrido, alkyl, alkenyl, aryl, alkaryl or halogen or in which R
1
and R
2
are linked to form —Q— in which Q is substituted or unsubstituted hydrocarbylene. The second monomer unit is hydrolyzable and of the form —CHR
3
—CH—(L
1
)
m
—X—(L
2
)
n
—CH—CHR
4
— in which R
3
and R
4
are independently hydrido or alkyl, L
1
and L
2
are optionally substituted hydrocarbylene groups, m and n are independently 0 or 1, and X is a group that is hydrolytically cleavable. Preferably, X does not include a hydroxyl group, a primary or secondary amino group, a thiol group, or a group effective to oxidize a metal center of the soluble transition metal catalyst. Examples of suitable X moieties include, but are not limited to, an acetal linkage, a ketal linkage, an ester linkage, and an imide linkage. It is also preferred that there are no adjacent hydrolyzable monomer units in the copolymer. The mole percent of the second monomer unit in the copolymer generally ranges from about 0.1 mole percent to about 50 mole percent.
In a related aspect, the invention provides a method for preparing a degradable olefinic copolymer by addition polymerization, in the presence of a suitable transition metal catalyst and a suitable catalyst activator, of a first olefinic monomer of the form CH
2
R
1
═CH
2
R
2
, wherein R
1
and R
2
are as defined above, with a second olefinic monomer of the form CHR
3
═CH—(L
1
)
m
—X—(L
2
)
n
—CH═CHR
4
wherein R
3
, R
4
, L
1
, L
2
, m, n and X are as defined above.
The transition metal catalyst may be a metallocene complex of a Group IV, Group V, or Group VI transition metal, such as Ti, Hf, Zr, V, Nb, or Mo. Other effective transition metal catalysts are imine, preferably diimine, complexes of Group I or Group VIII transition metals, such as Pd, Ni, Fe, Co, Cu, Ag, and Au, and imine-containing ligands.
These and other objects and features of the invention will become more fully apparent when the following detailed description of the invention is read in conjunction with the accompanying drawings.


REFERENCES:
patent: 4761322 (1988-08-01), Raley
patent: 4981749 (1991-01-01), Kubo et al.
patent: 5280094 (1994-01-01), Mulhall
patent: 5439996 (1995-08-01), Baird et al.
patent: 5563219 (1996-10-01), Yasuda et al.
patent: 5817394 (1998-10-01), Alikhan et al.
patent: 6127482 (2000-10-01), Keogh
patent: 0442476 (1991-08-01), None
patent: 0462588 (1991-12-01), None
patent: 0799842 (1997-10-01), None
patent: 1041580 A1 (2000-04-01), None
patent: WO 92/12185 (1992-07-01), None
patent: WO 97/45465 (1997-12-01), None
patent: WO 98/37110 (1998-08-01), None
Johnson et al. (1995), “New Pd(II)- and Ni(II)-Based Catalysts for Polymerization of Ethylene and &agr;-Olefins,”J. Am. Chem. Soc.117(23):6414-6415. (no month).
Johnson et al. (1996), “Copolymerization of Ethylene and Propylene with Functionalized Vinyl Monomers by Palladium(II)-Catalysts,”J. Am. Chem Soc.118(1):267-268. (no month).
Killian et al. (1997), “Preparation of Linear &agr;-Olefins Using Cationic Nickel(II) &agr;-Diimine Catalysts,”Organometallics16(10):2005-2007. (no month).
Ouchi et al. (1968), “Copolymerization of Diallylidenepentaerythritol,”J. Chem. Soc. Japan71(7):1078-1082.
Small et al. (1998), “Highly Active Iron and Cobalt Catalysts for the Polymerization of Ethylene,”J. Am. Chem. Soc.120(16):4049-4050. (no month).
Smorada (1987),Encyclopedia of Polymer Science and Engineering10:227-253, J.I. Kroschwitz, ed., New York: John Wiley & Sons.
Smorada (1987),Encyclopedia of Polymer Science and Engineering10:227-253, J.I. Kroschwitz et al., New York: John Wiley & Sons.

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