Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-10-05
2002-08-20
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
Reexamination Certificate
active
06437086
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of compounds useful in catalyzing oxygen scavenging by oxygen scavenging polymers. Particularly, it concerns polymeric metal salts, especially polymeric cobalt salts.
2. Description of Related Art
It is well known that limiting the exposure of oxygen-sensitive products to oxygen maintains and enhances the quality and shelf-life of the product. For instance, by limiting the oxygen exposure of oxygen sensitive food products in a packaging system, the quality of the food product is maintained, and food spoilage is avoided. In addition such packaging also keeps the product in inventory longer, thereby reducing costs incurred from waste and restocking. In the food packaging industry, several means for limiting oxygen exposure have already been developed, including modified atmosphere packaging (MAP), vacuum packaging and oxygen barrier film packaging. In the first two instances, reduced oxygen environments are employed in the packaging, while in the latter instance, oxygen is physically prevented from entering the packaging environment.
Another, more recent, technique for limiting oxygen exposure involves incorporating an oxygen scavenger into the packaging structure. Incorporation of a scavenger in the package can scavenge oxygen present inside the package. The oxygen thus scavenged either can be present in the interior when product is filled into the package, or can migrate into the package after product is filled. In addition, such incorporation can provide a means of intercepting and scavenging oxygen as it passes through the walls of the package (herein referred to as an “active oxygen barrier”), thereby maintaining the lowest possible oxygen level throughout the package.
In many cases, however, the onset of oxygen scavenging in this system may not occur for days or weeks. The delay before the onset of useful oxygen scavenging is hereinafter referred to as the induction period. In addition, the rate of oxygen scavenging may also be relatively low. Much work has been done both to minimize the induction period and increase the scavenging rate. One common approach that is useful in both areas is the use of metal salts with organic counterions, such as cobalt oleate, as catalysts for oxygen scavenging in a packaging article. These metal salts can be used in multilayer-film packaging applications, wherein the layer containing the metal salts (either an oxygen scavenging layer or a layer adjacent to an oxygen scavenging layer) is not in direct contact with food.
However, these low molecular weight metal salts with organic counterions, if used in single-layer-film packaging applications wherein the film is in direct contact with food, may on occasion pose a problem with extractability in some situations. Some organic counterions are not on the U.S. Food and Drug Administration (FDA) generally regarded as safe (GRAS) list. Therefore, it is desirable to have metal salts that are substantially nonextractable in standard tests of a single-layer-film packaging application.
SUMMARY OF THE INVENTION
In one embodiment, the present invention is directed to a polymeric metal salt, preferably one comprising structure I:
wherein R is selected from C
1
-C
20
alkyl, C
5
-C
20
cycloalkyl, C
2
-C
40
branched alkyl, C
2
-C
40
branched alkyl acid or diacid, C
2
-C
12
alkenyl, C
5
-C
12
cycloalkenyl, C
2
-C
40
branched alkenyl, or C
2
-C
40
branched alkenyl acid or diacid; and M is selected from manganese, iron, cobalt, nickel, copper, rhodium, or ruthenium.
In a related embodiment, the present invention relates to a composition comprising the polymeric metal salt and an oxygen scavenging polymer. Preferably, the oxygen scavenging polymer comprises an ethylenic backbone and at least one cyclic olefinic pendant group comprising structure (III):
wherein X is —(CH
2
)
n
—, wherein n is an integer from 0 to 4, inclusive; Y is —(CRR′)
a
—, wherein a is 0, 1, or 2; and Z is —(CRR′)
b
—, wherein b is 0, 1, or 2, provided that a+b 3; and q
1
, q
2
, q
3
, q
4
, r, R, and R′ are independently selected from hydrogen; linear, branched, cyclic, or polycyclic C
1
-C
20
alkyl; aromatic groups; halogens; amines; or sulfur-containing substituents, provided that at least one of q
1
, q
2
, q
3
, or q
4
is hydrogen.
In another embodiment, the present invention relates to a packaging article comprising at least one layer comprising the composition of the present invention.
The present invention provides the advantage of providing a substantially non-extractable metal salt for use in catalyzing oxygen scavenging by an oxygen scavenging layer of a packaging article.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
In one embodiment, the present invention is directed to a polymeric metal salt. By “polymeric metal salt” is meant a metal salt comprising at least two metal counterions and having a molecular weight greater than about 500. Any metal salt comprising an organic counterion can be used. Preferably, the polymeric metal salt comprises structure I:
wherein R is selected from C
1
-C
20
alkyl, C
5
-C
20
cycloalkyl, C
2
-C
40
branched alkyl, C
2
-C
40
branched alkyl acid or diacid, C
2
-C
12
alkenyl, C
5
-C
12
cycloalkenyl, C
2
-C
40
branched alkenyl, or C
2
-C
40
branched alkenyl acid or diacid; and M is selected from manganese, iron, cobalt, nickel, copper, rhodium, or ruthenium.
The metal component of the metal salt is preferably one capable of catalyzing oxygen scavenging by an oxygen scavenging polymer, as will be described in more detail below. Preferably, M is selected from manganese, copper, or cobalt. More preferably, M is cobalt.
In reference to the R group of the organic counterion, “alkyl” is defined as being a hydrocarbon chain comprising carbon-carbon single bonds and no carbon-carbon double bonds or triple bonds. “Branched alkyl” means that the hydrocarbon chain comprises at least one carbon which bonds with three other carbon atoms (except when such carbon is a component of a cyclic group). A “cycloalkyl” is defined as an alkyl chain comprising at least one ring. An alkyl can be both a branched alkyl and a cycloalkyl. “Alkenyl” refers to a hydrocarbon chain comprising at least one carbon-carbon double bond. “Branched alkenyl” and “cycloalkenyl” are defined analogously to branched alkyl and cycloalkyl, above. A “branched alkyl [or alkenyl] acid [or diacid]” is a branched hydrocarbon chain wherein at least one branch (in the case of the acid) or at least two branches (in the case of the diacid) terminate with a —COOH moiety.
The organic counterion of the metal salt can be selected based on the intended use of the metal salt and the structural properties desired for the metal salt or a polymer composition blended with the metal salt. For example, if R is an alkyl, a cycloalkyl, a branched alkyl, an alkenyl, a cycloalkenyl, or a branched alkenyl, the resulting polymer will generally have a linear geometry. If R is a branched alkyl or alkenyl acid or diacid, the resulting polymer can sometimes have a three-dimensional geometry. If R is an alkenyl, it will typically be capable of consuming oxygen; however, such consumption may result in disruption of the carbon-carbon double bond and degradation of the polymer. If R is a cycloalkenyl, wherein the ring comprises a carbon-carbon double bond, consumption of oxygen will typically not lead to degradation of the polymer.
Preferably, if some concentration of R groups are branched alkyl or alkenyl acid or diacid, the concentration is relatively low, preferably less than about 10% of all R groups. This low concentration is sufficient to make a branched polymeric metal salt, but the polymeric metal salt retains enough monoacid character to inhibit excessive crosslinking.
Preferably, R is selected from C
1
-C
12
alkyl, C
5
-C
12
cycloalkyl, C
2
-C
40
branched alkyl, or C
5
-C
12
cycloalkenyl.
In addition, the metal salt can further comprise a capping group, wherein the capping group is at a terminus of the mo
Cai Gangfeng
Ching Ta Yen
Yang Hu
Chevron Phillips Chemical Company LP
Michl Paul R.
Williams Morgan & Amerson P.C.
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