Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-11-17
2002-09-10
Anthony, Joseph D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S357000, C524S396000, C524S567000, C556S040000, C556S121000, C556S122000, C556S131000, C556S133000
Reexamination Certificate
active
06448314
ABSTRACT:
The subject of the present invention is the use of zinc acetylacetonate, predominantly crystallized in the form of a monohydrate compound, as stabilizing agent for halogenated polymers.
Its subject is likewise a process for the preparation of the said zinc acetylacetonate.
Anhydrous zinc acetylacetonate is a product known in the literature, as well as its role of stabilizing halogenated polymers, and most particularly chlorinated polymers, such as poly(vinyl chloride).
However, while the importance of this compound is not under challenge, it exhibits, nevertheless, the disadvantage of having to be stored under special conditions, free of water. In the opposite case, under the effect of ambient humidity, the product cakes and can no longer be used as it is.
The aim of the present invention is to provide another type of zinc acetylacetonate which can be used as agent stabilizing halogenated polymers, not exhibiting the above disadvantage.
The first subject of the present invention is therefore the use of zinc acetylacetonate comprising at east 4.4% by weight of water, as halogenated polymer stabilizer.
It should be noted that for the sake of simplicity and of clarity of the disclosure which follows, the zinc acetylacetonate whose use constitutes one of the subjects of the invention, will be described as “monohydrate”, to distinguish it from the “anhydrous” zinc acetylacetonette used up until now.
Likewise its subject is a process for the preparation of zinc acetylacetonate monohydrate, in which a zinc oxide and/or hydroxide and acetylacetone are brought into contact, in the presence of a solvent; the said solvent being used with a quantity of between 20 and 200 parts by weight, per 100 parts by weight of acetylacetone.
It is important to specify that up until now, reference has only been made to zinc acetylacetonate in anhydrous form, as halogenated polymer stabilizer. It is indeed known in this field that the presence of water in these compositions should be as low as possible. Indeed, given the high temperatures for forming such formulations, the water is vaporized and, upon escaping, can cause the appearance of defects in the final article, which is obviously not desirable.
However, it has been found that zinc acetylacetonate monohydrate, contrary to what was expected, did not exhibit any disadvantage when it was introduced into a halogenated polymer formulation. Indeed, during the use of the composition thus additivated, the appearance of bubbles or other defects due to the evacuation of the water is not observed.
Furthermore, in the publication by E. Lippert and M. R. Truter, which appeared in Journal of Chemical Society, 1960, p. 4996-5006, it is indicated that the monohydrated form of zinc acetylacetonate is the most stable crystalline form. Persons skilled in the art would therefore have expected to have a lower stabilizing activity than the anhydrous compound. However, here again, nothing of the such was observed.
It should be noted finally that the monohydrate compound is stable over time and does not cake, even when it is stored under an ambient atmosphere, that is to say with some humidity.
However, other characteristics and advantages of the present invention will appear more clearly on reading the description which follows.
The composition used in the invention is therefore zinc acetylacetonate comprising at least 4.4% by weight of water.
More particularly, the water content is between 4.4 and 8.8% by weight. According to a particular variant of the invention, the composition used has a water content of between 4.75% and 8.15% by weight. According to an advantageous variant of the invention, the compound has a structure similar to that of zinc acetylacetonate monohydrate.
Expressed differently, the compound according to the invention corresponds to the following average formula:
[CH
3
—CO—CH
2
—CO—CH
3
]
2
Zn; x.H
2
O;
in which x is a number which is an integer or otherwise, greater than or equal to 0.65.
More particularly, the zinc acetylacetonate used in the invention is such that the abovementioned coefficient x is between 0.65 and 1.3. According to a more specific embodiment, the coefficient x is between 0.7 and 1.2.
Preferably, a compound which is predominantly crystallized in the form of a .monohydrate compound is used. In other words, the coefficient x is of the order of 1.
The crystals of zinc acetylacetonate hydrate according to the invention exhibit a limited acicular character (morphology different from that of a needle).
It should be noted that this product may exist in the form of a powder but also in a granulated or compacted form if necessary, subject to an appropriate forming step.
The zinc acetylacetonate may be obtained using conventional processes with or without solvent.
Reference may be made, for example, to the manual “Metal &bgr;-diketonates and allied derivatives” by R. C. Mehrota, R. Gaur, D. P. Gaur, which appeared in 1978, Academic Press, in which various methods for synthesizing these products are described.
A second subject of the present invention consists in another process which makes it possible to obtain zinc acetylacetonate hydrate.
This process consists in bringing a zinc oxide and/or hydroxide and acetylacetone into contact, in the presence of a solvent; the solvent being used in a quantity of between 20 and 200 parts by weight, per 100 parts by weight of acetylacetone.
Preferably, the content of solvent is less than or equal to 100 parts by weight relative to the same reference.
According to a more specific variant of the invention, the quantity of solvent used is at least 40 parts by weight relative to the same reference, and preferably at least 50 parts by weight.
Thus, one embodiment of the process according to the invention consists in using a quantity of solvent of between 20 and 100 parts by weight per 100 parts by weight of acetylacetone, more particularly between 40 and 100 parts by weight, and preferably between 50 and 100 parts by weight.
The solvent used in the reaction is more particularly a compound capable of solubilizing acetylacetone and it is preferably inert towards the constituents of the reaction mixture, under the reaction conditions.
According to a particularly advantageous variant of the present invention, the solvent is chosen from compounds whose boiling point is at most 100° C., measured at atmospheric pressure.
Among the compounds which can be used as solvents, there may be mentioned, with no limitation being intended, C
1
-C
6
aliphatic alcohols such as methanol, ethanol or propanol. Also suitable are ketones, such as acetone; compounds comprising amide functions, such as formamide or dimethylformamide; compounds which are aromatic, such as benzene, or optionally comprising one or more alkyl substituents.
Obviously, using a combination of the solvents indicated above will not depart from the scope of the present invention.
The bringing into contact takes place, in addition, in the presence of an acetylacetone/zinc oxide and/or hydroxide molar ratio of between 2/1 and 2.4/1. Preferably, the process according to the invention is carried out in the presence of a molar ratio of between 2/1 and 2.2/1. According to a particularly advantageous variant of the present invention, the bringing into contact takes place with an acetylacetone/zinc oxide and/or hydroxide molar ratio close to the stoichiometric value.
The bringing into contact takes place with stirring.
Preferably, the reaction is carried out in a turbosphere-type reactor, or any other apparatus provided with mechanical stirring means allowing good homogenization of a heterogeneous reaction mixture.
According to a specific embodiment of the invention, the bringing into contact is carried out by introducing the acetylacetone into a zinc oxide and/or hydroxide and solvent mixture.
The bringing into contact of the reagents is carried out while the temperature is preferably maintained between room temperature and about 100° C. More particularly, the bringing into contact takes place at a temperature of less than 80° C. According to a preferr
Anthony Joseph D.
Rhodia Chimie
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