Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-10-02
2002-03-26
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C423S420200, C423S430000, C423S432000, C524S387000, C524S390000, C524S425000, C524S436000
Reexamination Certificate
active
06362261
ABSTRACT:
BACKGROUND OF THE INVENTION
Halogenated plastics or molding compounds produced therefrom are known to have a tendency toward degradation or decomposition reactions if they are exposed to thermal stress or come into contact with high energy radiation, for example ultraviolet light. To counteract this there are customarily incorporated into them heavy metal compounds based, for example, on lead, barium and/or cadmium. However, from the viewpoint of occupational health, there is a requirement to replace these absolutely effective stabilizers with substances which are less hazardous to health. As alternatives to the heavy metal compounds, for example calcium soaps and zinc soaps may be considered as stabilizers, but these do not achieve the efficiency of said heavy metal compounds, so that to increase their stabilizing action costabilizers are required.
German Patent DE-C-30 19 632 (Kyowa Chemical Ind.) describes the use of hydrotalcites to inhibit the thermal or UV-induced degradation of halogenated thermoplastic resins. In this patent, results of studies are reported which indicate that if hydrotalcites which are readily available on the market are incorporated, for example, into vinyl chloride resins, these hydrotalcites accelerate the dechlorination of the resins on heating or even cause a decomposition, black coloration or foam formation of the resins. In addition, it has been found that these hydrotalcites have poor dispersibility in the resins and adversely affect the rheological properties of the resins during the deformation and the appearance of the finished molded bodies. These research results are due to the small crystal size of the customary hydrotalcites and also to the high specific BET surface area of at least about 50 m
2
/g and the water coating of the hydrotalcite particles. Accordingly, it is proposed in German Patent DE-C-30 19 632 to use hydrotalcites having a large crystal size and having a specific BET surface area of no more than 30 m
2
/g. If desired, the hydrotalcites can be coated with an anionic surface-active compound such as sodium stearate.
European Patent Application EP-A-189 899 (Kyowa Chemical Ind.) also describes resin compositions which comprise hydrotalcites having specific BET surface areas less than 30 m
2
/g. This European patent application discloses that the hydrotalcites can be modified with esters of higher fatty acids, anionic surface-active compounds and coupling agents of the silane or titanium types in order to improve the compatibility of the hydrotalcite with the plastic compounds. The hydrotalcites are to be modified in accordance with EP-A-189 899 by mechanical mixing of hydrotalcites with the modifying agents in pure or dissolved form.
According to DE-C-33 06 822 (Giulini Chemie), hydrotalcites of the formula [Mg
6
Al
2
(OH)
12
] (CO
3
)
2
.xH
2
—where x≧2—are obtained by reacting aluminum hydroxide with magnesium hydroxide or magnesium oxide in the presence of basic magnesium carbonate as carbonate ion donor at a temperature of from 50° C. to 100° C. and subsequent spray-drying from the suspension. Aluminum hydroxide is used in particular in the form of “active” aluminum hydroxide.
U.S. Pat. No. 4,656,156 (Aluminum Company of America) describes a method of producing hydrotalcite, with the aluminum component used being the aluminate liquor of the Bayer process. The Bayer liquor is reacted with “active” magnesium oxide, as can be obtained, for example, by calcining magnesium carbonate. Use of this method is only economically expedient at those points where the Bayer liquor itself is produced, since otherwise in this case relatively large amounts of water would also have to be transported.
DE-A-15 92 126 (Kyowa Chemical Ind.) describes the production of hydrotalcites from various starting materials, for example from a suspension of solid aluminum hydroxide, solid magnesium hydroxide and sodium hydrogen carbonate. The reactions are carried out batchwise here and the products are separated off from the water phase by filtration or centrifugation and washed before they are dried.
According to DE-C-44 25 266 (Metallgesellschaft AG), the outlines of the topic of stabilizing halogenated plastics which is known to those skilled in the art are as follows: halogenated thermoplastic resins such as polyvinyl chloride (PVC) are converted during processing—in the course of melt forming—into polyene structures, hydrogen chloride (HCl) being eliminated. The polymer becomes discolored. To improve the thermal stability it is customary to incorporate metal carboxylates (“metal soaps”) as stabilizers into the resin. However, since the incorporation of substances of this type as sole stabilizers can lead in the case of relatively long-duration melt forming to so-called metal burning, which causes black discoloration of the polymer, it is general practice to add a costabilizer. Customary costabilizers are, for instance, polyols, organic phosphorous esters or epoxy compounds. According to the teaching of DE-C-44 25 266, specific lithium-containing layer lattice compounds may be used to stabilize, in particular, PVC. The use of similar Li-containing layer lattice compounds to stabilize halogenated plastics is also taught, furthermore, by DE-A-44 25 275 (Metallgesellschaft AG).
DE-A-196 17 138 (Henkel KGaA) discloses a method for producing cationic layer compounds and the use of these compounds as stabilizers for halogenated plastics. The compounds are produced by subjecting layer compounds of specific structure to an alkali-induced aging in an aqueous environment, the alkali metal hydroxide content of the aqueous medium being set in the range from 1 to 6 molar, the aging temperature in the range from 60 to 100° C. and the aging time in the range from 2.5 to 50 hours. Special retreatment methods for further improving the stabilizing action with respect to halogenated plastics are, however, neither disclosed nor suggested in DE-A-196 17 138.
BRIEF SUMMARY OF THE INVENTION
The present invention includes methods of preparing cationic layer compounds, and more particularly, methods wherein a modified cationic layer compound, according to general formula (I) disclosed herein, is first subjected to a crystallization step, and then, a retreatment step. The retreatment in accordance with the present invention comprises steam drying. The present invention also includes modified cationic layer compounds prepared according to such methods, and methods of stabilizing halogenated plastics therewith.
The object of the present invention was to provide stabilizers for halogenated plastics. These stabilizers should be distinguished by an improved activity profile compared with the known prior art. In particular, halogenated plastics with these stabilizers incorporated therein should have improved values in the range of the initial color under thermal stress. The stabilizers, in addition, should have the following properties: good compatibility with calcium compounds and/or zinc compounds; dispersibility in halogenated plastics without impairing their rheological properties; high ability to trap well the decomposition products of halogenated plastics; this means in particular improved properties with respect to the ability to absorb hydrogen chloride; good long-term stability of halogenated plastics, in particular PVC (polyvinyl chloride), with the stabilizers incorporated therein.
The present invention firstly relates to a method for producing cationic layer compounds, in which layer compounds of the general formula (I)
[E
e
Z
z
D
d
V
v
(OH
−
)
x
](A
n−
)
a
.qH
2
O (I)
where:
E is a monovalent cation selected from the group consisting of the alkali metals,
e is a number in the range from 0 to 2,
Z is a divalent metal cation,
z is a number in the range from 0 to 6,
D is a trivalent metal cation,
d is a number in the range from 0 to 3,
V is a tetravalent metal cation,
v is a number in the range from 0 to 1,
(A
n−
) is an acid anion of charge n−, where n is an integer from 1 to 3, and
q is a number in the range fr
Daute Peter
Foell Juergen
Klamann Joerg-Dieter
Kuepper Stefan
Lange Ilona
Cognis Deutschland GmbH
Drach John E.
Ettelman Aaron R.
Hoke Veronica P.
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