Halogen scavenger for olefin formulations

Details Halogen scavenger for olefin formulations Halogen scavenger for olefin formulations

2001-09-21

2004-10-12

Mulcahy, Peter D. (Department: 1713)

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

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S436000, C423S115000, C423S430000, C554S075000, C554S076000

Reexamination Certificate

active

06803401

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to hydrotalcite-like compositions useful as halogen scavengers in polymer formulations. More particularly, the invention related to the use of aluminum magnesium hydroxy carbonate solid solutions that inhibit the adverse effect of halide catalyst residues in plastics.
BACKGROUND OF THE INVENTION
In general during the preparation of various synthetic polymers the catalyst, used in the preparation or at least the residue thereof almost invariably remains in the final product. The removal of this catalyst residue substance, which may be present at levels as low as ten parts per million, is commercially impractical. However, leaving the catalyst in the polymer, even at such low concentrations, often causes problems.
The catalysts used to polymerize olefinic monomers are typically halogen-containing metallic or organometallic compounds, e.g., Ziegler-Natta catalysts containing titanium tetrachloride. It is reported that residual titanium chloride species in the polymers interfere with the functioning of stabilizers, e.g., antioxidants, that are typically compounded with the polymer. Residual catalyst may also catalyze polymer degradation reactions, and, particularly with halogen-containing catalyst residue, the halogens can promote corrosion of the equipment used to compound and process the polymer.
Polymers that have been compounded with stabilizers, particularly thermal and light, stabilizers, exhibit a discoloration, i.e., they develop a yellow or pinkish coloration. This has been attributed to the action of residual catalyst, and particularly halide ions, reacting with the stabilizers that have a phenol or a quinone functional group. The halide may react with the phenol group to generate a colored phenolate anion.
Since most residual catalysts are acidic, an approach to overcoming the problems associated with residual catalyst is to add a basic material to the polymer, to thereby neutralize the residual catalyst. Basic materials for this purpose are known in the art, and are commonly referred to as neutralizer compounds or halogen-scavenging compounds. One class of halogen-scavenging compound is hydrotalcite and hydrotalcite-like materials.
Hydrotalcite is the name given to a natural mineral having the chemical structure Al
2
Mg
6
OH
16
(CO
3
).4H
2
O, which may also be written as Al
2
O
3
.6MgO.CO
3
.12H
2
O. Natural hydrotalcite is an example of a basic magnesium alumino-carbonate hydrate. As obtained from the earth, natural hydrotalcite is generally contaminated with other minerals such as penninite and muscovite, as well as various heavy metals. The impurity levels in natural hydrotalcite, as well as its scare occurrence around the world, have limited its commercial use giving use to the preparation of purified synthetic hydrotalcite. For example, U.S. Pat. No. 5,250,279 describes a method for the preparation of high purity synthetic hydrotalcite having a small platelet morphology by reacting a mixture of a magnesium source, such as magnesium oxide, with an alkali metal bicarbonate, solid alumina trihydrate and an alkali metal aluminate under aqueous hydrothermal conditions at a temperature of about 160-200° C. Preparation of synthetic hydrotalcite said to have a composition which matches natural hydrotalcite is found in, for example, U.S. Pat. Nos. 3,650,704 and 3,539,306.
The term “hydrotalcite” refers to a class of basic aluminum magnesium carbonate compounds or complexes having various lattice structures and compositions.
U.S. Pat. No. 4,284,762 (the '762 patent) for example discloses a hydrotalcite of the formula
Mg
1-x
Al
x
(OH)
2
A
x

n−
omH
2
O
wherein x is greater than 0 but less than or equal to 0.5, m is a positive number, and A
n−
represents an anion having a valence of n, or a product resulting from the surface-coating of said hydrotalcite with an anionic surface-active agent. The hydrotalcite has a BET specific surface area of not more than 20 m
2
/g, and a crystallite size, in the <003> direction of at least 600 Å, and preferably at least 1,000 Å.
U.S. Pat. No. 4,299,759 (the '759 patent) discloses a hydrotalcite of the same composition as set forth in the '762 patent, but having a BET specific surface area of not more than 30 m
2
/g. The '759 patent discloses that the surface treatment, i.e., the addition of sodium stearate to the hydrotalcite particle, can be achieved by adding an aqueous solution of sodium stearate to a suspension of the hydrotalcite powder to cause chemical adsorption of the surface-active agent to the surface of the solid powder. The surface treatment agent is preferably present at a loading of about 1 to about 10% by weight, based on the weight of the hydrotalcite.
U.S. Pat. No. 4,560,545 relates to a process for preparing a basic aluminum magnesium carbonate of the formula
Al
2
.Mg
6
.(OH)
14
.(CO
3
)
2
.4H
2
O.
The process comprises heating an aqueous slurry of aluminum hydroxide, magnesium hydroxide and either ammonia or a water-soluble organic nitrogen-containing base, in the presence of carbon dioxide and at a temperature of between 70 and 100° C. at atmospheric pressure. The reaction time is from 1 to 12 hours, and the carbon dioxide is bubbled through the slurry during this time. The basic aluminum magnesium carbonate so produced may be used in pharmaceutical compositions.
Hungarian Patent HU 30,453 (Abstract No. 101:43635g, prepared by the Chemical Abstracts Service) discloses a composition with the formula
Al
2
.Mg
4
.(OH)
12
.(CO
3
).2H
2
O.
The composition is prepared by the reaction of MgCl
2
with Na
2
CO
3
and Na orthoaluminate or Al(OH)
3
in the presence of NaOH.
U.S. Pat. No. 4,539,195 claims a crystalline basic aluminum magnesium carbonate of the formula:
Al
2
(Mg)
6
(OH)
12
(CO
3
)
3
.x
(H
2
O)
in which x≧4, obtainable by hydrothermal reaction of aluminum hydroxide with magnesium hydroxide or magnesium oxide in the presence of carbonate ions in stoichiometric amounts under the influence of gravitational forces at a temperature of 50 to 100° C.
A basic magnesium aluminum carbonate of the formula
Al
2
O
3
.x
MgO.
y
CO
2
.z
H
2
O
is described in British Patent 1,086,779, wherein x can be 0.15 to 1.5, y can be varied from 0.3 to 2.5, and z is not less than 2.5.
U.S. Pat. No. 4,675,356 discloses a hydrotalcite solid solution represented by the following formula
[(M
1
2+
)
y1
(M
2
2+
)
y2
]
1-x
M
x
3+
(OH)
2
A
x

n−
.m
H
2
O
wherein M
1
2+
represents at least one divalent metal selected from the group consisting of Mg, Ca, Sr and Ba; M
2
2+
represents at least one divalent metal cation selected from the group consisting of Zn, Cd, Pb and Sn; M
3+
represents a trivalent metal cation, A
n−
represents an anion having a valency of n, and x, y1, y2 and m are positive numbers represented by the following expressions 0<x≦0.5, 0<y1, 0<y2, 0.5≦y1+y2<1, and 0≦m<2; and to a resin composition comprising the above agent. The hydrotalcite of the '356 patent may be surface treated with, for example, anionic surface-active agents such as sodium stearate.
Reheis, Inc., Berkeley Heights, N.J., sells an aluminum magnesium hydroxy carbonate, trademark L55-R®, having an analysis of 14-18% aluminum oxide, 25-29% magnesium oxide, 15-19% sodium stearate and 8.5-13.5% carbon dioxide. L55-R® is a white, odorless powder having a bulk density of 0.19-0.35 g/cc and a particle size of 100% through 400 mesh (37 microns) and not less than 90% through 10 microns.
While the prior art describes several hydrotalcite and hydrotalcite-like materials, there remains a need in the art for a system in which the modification of polymeric materials, results in substantially eliminating the problems associated with residual catalyst, and other halide-generating mechanisms, in the polymer.
SUMMARY OF THE INVENTION
The present invention provides a solid solution having the formula Al
2
(Mg)
a
(OH)
b
(CO
3
)
c
(G)
d
.eH
2
O wherein 3≦a≦5.5; 8≦b≦14; 1.2≦c≦3; 0≦d

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