Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-10-06
2003-05-27
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S087000, C524S099000, C524S107000, C524S254000, C524S255000, C524S258000, C524S284000, C524S323000, C524S349000, C524S343000, C524S350000, C524S502000, C524S508000, C524S513000, C524S537000, C524S556000
Reexamination Certificate
active
06569927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the oxidative stabilization of organic materials, especially polyolefin-based thermoplastic resins. More particularly, the present invention relates to the oxidative stabilization of thermoplastic resins with synergistic blends of (1) secondary aromatic amines and/or N,N′-substituted oxamides, (2) sterically hindered phenols, and (3) lactones having a base structure of a 3-phenylbenzofuran-2-one.
2. Description of Related Art
Manufacturers of plastic goods have experienced a long-standing problem in stabilizing plastic resins during the high temperature, high shear, blending, and extrusion processes that are common in the industry. Resins that show excellent long-term heat stability characteristics may not be sufficiently protected against the type of degradation that occurs in an extruder during long residence times or in applications where the plastic is exposed to high temperature heat fusion followed by compression molding.
U.S. Pat. No. 4,611,016 discloses a process for stabilizing organic polymeric materials comprising incorporating therein a benzofuran (2) one or indolin (2) one compound as stabilizer. Such stabilized polymeric materials are said to be stabilized against degradation during the polymer processing.
U.S. Pat. No. 4,797,511 discloses a composition stabilized against oxidative degradation comprising: a polyolefin, carbon black homogeneously incorporated in said polyolefin, a stabilizing amount of thiodiethylene bis(3,5-di-t-butyl-4-hydroxy)hydrocinnamate first stabilizer component incorporated into said polyolefin and a second stabilizer component of at least one amine antioxidant selected from the group consisting of a para-substituted aralkyl-substituted diphenylamine; a para-phenylenediamine and a polymerized dihydroquinoline incorporated into said polyolefin.
U.S. Pat. No. 4,837,259 discloses polypropylene stabilized against oxidative degradation by the presence therein of a stabilizing amount of an antioxidant composition that comprises:
(a) at least one aralkyl-substituted diarylamine; and
(b) at least one sterically hindered phenol.
U.S. Pat. No. 5,175,312 discloses compounds of the formula
in which R
1
is C
13
-C
30
alkyl, R
2
is hydrogen, C
1
-C
10
alkyl, C
5
-C
12
cycloalkyl, C
5
-C
7
cycloalkyl which is substituted by C
1
-C
4
alkyl, or is phenyl or C
7
-C
12
phenylalkyl, R
3
is hydrogen or C
1
-C
4
alkyl and Z is phenyl, phenyl which is substituted by C
1
-C
8
alkyl, C
1
-C
4
alkoxy or chlorine, a group
n which n is 1 or 2 or a group
in which the radicals A independently of one another are C
1
-C
8
alkyl, methoxy or ethoxy, that are said to be suitable for stabilizing organic material against oxidative, thermal and actinic degradation.
U.S. Pat. No. 5,516,920 discloses compounds of the formula
as stabilisers for protecting organic materials, in particular polymers and lubricants, against thermal, oxidative or light-induced degradation.
U.S. Pat. No. 5,607,624 discloses a process for the preparation of 3-arylbenzofuranones of a defined structure similar to the above.
U.S. Pat. No. 5,807,505 discloses compounds of the formula
as stabilizers for protecting organic materials against thermal, oxidative or light-induced degradation.
WO 99/03915 discloses synergistic blends of phosphites and lactones having a base structure of 3-phenylbenzofuran-2-one with or without other additives as stabilizers for polymers, particularly during melt processing as evidenced by changes in melt flow and in some instances, resistance to yellowing.
Krönke, C.,
Proceedings from Polyolefins X International Conference;
pp. 555-569 (1997) discloses, inter alia, an extremely active stabilizer for polyolefin processing based on a benzofuranone (lactone) derivative. The author states that, when used in combination with phenolic/phosphite antioxidant blends, new levels of performance are achieved.
The disclosures of the foregoing are incorporated herein by reference in their entirety.
SUMMARY OF THE INVENTION
The present invention is characterized by a polymeric material that includes a stabilizing mixture comprising at least three components. The first component is a secondary aromatic amine, the second component is a sterically hindered phenol, and the third component is a lactone having a base structure of a 3-phenylbenzofuran-2-one.
The synergistic effect of blends of secondary aromatic amines and/or N,N′-substituted oxamides and hindered phenols when used to stabilize polyolefins is known in the art. However, the use of these blends suffers from a major drawback, i.e., they have been found to a furnish sub-par performance as stabilizers during melt processing, especially when subjected to multiple pass extrusion testing, as evidenced by measuring retention of melt-flow rate and resistance to yellowing. Multiple pass extrusion is a very common test method to assess the process stabilization afforded to a polymer. Moreover, this lack of processing stabilization effect has impeded the more widespread use of secondary aromatic arnine/phenol blends in more demanding applications as far as processing stabilization is concerned.
It has now, surprisingly, been found that this impediment to the use of secondary aromatic amines and/or N,N′-substituted oxamide/phenol blends as processing stabilizers can be circumvented when a third component, chosen from the class of 2-phenylbenzofuran-2-one lactones, is included, thus giving a ternary blend. Thus, the present invention is directed to the discovery that various combinations of secondary aromatic amines and/or N,N′-substituted oxamides and sterically hindered phenols form synergistic blends with 3-phenylbenzofuran-2-one lactone with tremendously improved process stabilization, as evidenced by retention of melt flow rate and, in some cases, resistance to yellowing on multiple pass extrusion.
More particularly, the present invention is directed to a composition comprising:
(A) a thermoplastic resin; and
(B) a stabilizing amount of a blend of at least one sterically hindered phenol antioxidant, at least one secondary aromatic amine and/or N,N′-substituted oxamide antioxidant, and at least one lactone antioxidant having a 3-phenylbenzofuran-2-one structure.
In a preferred embodiment, the present invention is directed to a composition comprising:
(A) a thermoplastic resin; and
(B) a stabilizing amount of:
(1) a first stabilizer comprising at least one secondary aromatic amine and/or N,N′-substituted oxamide antioxidant selected from the group consisting of
(i) a hydrocarbon-substituted diarylamine,
(ii) a reaction product of a diarylamine and an aliphatic ketone,
(iii) an N,N′-hydrocarbon Substituted para-phenylenediamine, and
(iv) a polymerized dihydroquinoline;
(2) a second stabilizer comprising at least one sterically hindered phenol antioxidant; and
(3) a third stabilizer comprising at least one lactone antioxidant of the structure
wherein
R
1
and R
2
are independently selected from the group consisting of hydrogen, chloro, hydroxy, C
1
-C
25
alkyl, C
7
-C
9
-phenylalkyl, unsubstituted or C
1
-C
4
alkyl-substituted phenyl, unsubstituted or C
1
-C
4
alkyl-substituted C
5
-C
8
cycloalkyl; C
1
-C
18
alkoxy, C
1
-C
18
alkylthio, C
1
-C
4
alkylamino, di-(C
1
-C
4
alkyl)amino, C
1
-C
25
alkanoyloxy, C
1
-C
25
alkanoylamino, C
3
-C
25
alkenoyloxy, C
3
-C
25
alkanoyloxy which is interrupted by oxygen, sulfur or >N—R
8
; C
6
-C
9
cycloalkylcarbonyloxy, benzoyloxy or C
1
-C
12
alkyl-substituted benzoyloxy;
R
8
is hydrogen or C
1
-C
8
alkyl; and
R
3
and R
4
are independently selected from the group consisting of C
1
-C
8
alkyl, C
1
-C
4
alkoxy, halogen, a group
in which n is 1 or 2, or a group
in which the radicals A are independently selected from the group consisting of C
1
-C
8
alkyl and C
1
-C
8
alkoxy.
In another aspect, the present invention is directed to a method for stabilizing a composition comprising a thermoplastic resin comprising adding the
Dawson Robert
Dilworth Michael P.
Uniroyal Chemical Company, Inc.
Zimmer Marc S.
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