Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2000-05-04
2003-04-22
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C558S424000, C564S442000, C568S425000, C568S631000, C523S122000
Reexamination Certificate
active
06552214
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antimicrobial compound having improved resistance to conversion to a toxic compound or a dioxin-related compound.
2. Discussion of Related Art
Model et al., U.S. Pat. No. 3,800,048 and Model et al., U.S. Pat. No. 3,904,696 disclose halogenated hydroxydiphenyl ethers for controlling microorganisms. Of these, IRGASAN® DP 300 2,4,4′-dichloro-2′-hydroxydiphenyl ether produced by Ciba-Geigy Corporation, Ardsley, N.Y., is a well-known bacteriostat for industrial use. However at a temperature above about 200° C., IRGASAN® DP 300 ether converts to a chlorinated dioxin, 2,8-dichlorodibenxo-p-dioxin (DCDD), which is structurally similar to compositions suspected of causing a variety of adverse health effects including cancer.
Hence, in certain applications, it may be preferable to avoid use of IRGASAN® ether such as in plastic fabrications, which may involve high temperature. As such, there is a long-felt yet unsolved need for an antimicrobial compound that can be used in higher temperature fabrications without converting to a dioxin related compound.
SUMMARY OF THE INVENTION
Accordingly, a halogenated hydroxydiphenyl ether can be reacted with a compound that imparts a functional blocking moiety to prevent the conversion of the halogenated hydroxydiphenyl ether to dioxin related compounds at the higher temperatures typically used in plastic fabrication. In one embodiment, the compound comprises a blocked halogenated hydroxydiphenyl ether of the formula:
where X
1
is a halogen, X
2
is chlorine or bromine, X
3
is hydrogen, chlorine or bromine, X
4
is chlorine, bromine, alkyl having 1 to 3 carbon atoms, —CHO, —CN or —NH
2
, X
5
is chlorine, bromine, methyl, trichloromethyl, —CHO, —CN or —NH
2
, n is 1 or 2, and R is an ether linkage inhibiting group.
The invention also relates to a process for the preparation of a blocked halogenated hydroxydiphenyl ether comprising reacting a halogenated hydroxydiphenyl ether of the formula (II):
with a blocking functionality providing compound.
In another embodiment, the invention relates to an antimicrobial composition comprising a plastic and a blocked halogenated hydroxydiphenyl ether of the formula (I) and to a process for the preparation of a plastic comprising incorporating an effective amount of an antimicrobial blocked halogenated hydroxydiphenyl ether of the formula (I) into the plastic.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In a preferred embodiment, an antimicrobial compound comprises a blocked halogenated hydroxydiphenyl ether of the formula:
wherein X
1
is a halogen, X
2
is chlorine or bromine, X
3
is hydrogen, chlorine or bromine, X
4
is chlorine, bromine, alkyl having 1 to 3 carbon atoms, —CHO, —CN or —NH
2
, X
5
is chlorine, bromine, methyl, trichloromethyl, —CHO, —CN or —NH
2
, n is 1 or 2, and R is an ether linkage inhibiting group such as trimethylsilyl, butyldimethylsilyl, tert-butyldimethylsilyl, trifluoroacetyl, pentafluoropropionyl and heptafluorobutyryl. Other examples of R include methoxy, methyl, amino and nitro groups that inhibit the formation of an ether linkage in reaction with X
3
.
A preferred compound of formula (I) is 2,4,4′-trichloro-2′-trimethylsilyloxy diphenyl ether according to the following formula (III):
The compounds of formula (I) can be produced by reacting a halogenated hydroxydiphenyl ether of the formula:
with a blocking functionality providing compound. In formula (II), X
1
can be a halogen, X
2
is chlorine or bromine, X
3
is hydrogen, chlorine or bromine, X
4
is chlorine, bromine, alkyl having 1 to 3 carbon atoms, —CHO, —CN or —NH
2
, X
5
is chlorine, bromine, methyl, trichloromethyl, —CHO, —CN or —NH
2
, and n is 1 or 2.
The blocking functionality providing compound can be any compound that will react with the hydroxyl (—OH) of formula (II) to provide a functionality that will not react with X
3
to result in an ether linkage between the 2,2′ positions. The reaction that provides the blocking functionality can be any suitable reaction, such as silylation, acylation, or alkylation.
Suitable blocking groups include silyl groups such as trimethylsilyl, butyldimethylsilyl and tert-butyldimethylsilyl. Preferred reagents for conducting the silylation reaction include bis(trimethylsilyl) trifluoroacetamide (BSTFA), N- or O-bis (trimethylsilyl) acetamide (BSA), hexamethyldisilazane (HDMS), N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) and N-trimethylsilylimidazole.
The silyl reaction can be carried out in an organic solvent such as hexane, benzene, ether or the like in the absence of water. The reaction can be conducted at a suitable temperature, for example at a temperature between about 15° and about 55° C., preferably at room temperature. Generally, the reaction is completed within about 5 minutes to about 2 hours. Desirably, the reaction is completed within about 20 minutes and preferably within about 5 minutes. The concentration of silylation reagent to starting material can be in excess of 1.0:1.0 on a per mole basis, preferably in excess of 3.0:1.0.
Additionally, an acylation reaction can be used to provide a blocking functionality. The acylation can convert the 2′ hydroxyl group of the halogenated hydroxydiphenyl ether into an ester through the action of a carboxylic acid or carboxylic acid derivative. Preferred acylating agents include perfluoroacylimidazoles such as trifluoroacetylimidazole (TFAI), pentafluoropropionylimidazone (PFPI) and heptafluorobutyrylimidazole (HFBI).
The acylation reaction can be conducted in an organic solvent such as hexane or benzene at a temperature, for example, between about 15° and about 55° C., preferably at room temperature. Typically, the reaction is completed within 5 minutes but the reaction time can be extended to 1 hour. Concentration of acylation reagent to starting material can be in excess of 1.0:1.0 on a per mole basis, preferably in excess of 3.0:1.0.
Another suitable blocking providing reaction is alkylation wherein the hydrogen of the 2′ hydroxyl group of the halogenated hydroxydiphenyl ether is replaced with an aliphatic or aliphatic-aromatic group. Pentafluorobenzylbromide (PFBBr) is an example of a suitable alkylating compound.
The alkylation reaction can be carried out in a suitable organic solvent such as methylene chloride with tetrabutylammonium as a counter ion. The reaction can be conducted at a temperature for example between about 15° and about 55° C., preferably at room temperature. Typically, the reaction is completed within 5 minutes but the reaction time can be extended to 24 hours. Concentration of alkylating reagent to starting material can be in excess of 1.0:1.0 on a per mole basis, preferably in excess of 3.0:1.0.
The diphenyl ethers can be used in combination with other antimicrobially active substances. For example, the compound can be used with halogenated salicylic acid alkyl amides and anilides, with halogenated diphenyl ureas, with halogenated benzoxazoles or benzoxazolones, with polychlorohydroxydiphenyl methanes, with halogendihydroxydiphenyl sulfides, with bactericidal 2-imino-imidazolidines or tetrahydropyrimidines or with biocidal quaternary compounds or with certain dithiocarbamic acid derivatives such as tetramethyl thiuram disulphide. Various additional antimicrobial substances alone or in combination can be used with the diphenyl ethers to broaden the range of antimicrobial action and/or to provide a synergistic effect.
The diphenyl ether according to formula (I) can be incorporated into a plastic composition by addition into a polymer prior to the formation of pellets or by the addition of the ether in powder form immediately prior to or during a melt stage of a molding process. The diphenyl ether can be provided in a powder form, as pellets or as a blend of ether-containing pellets and non-ether-containing pellets.
The antimicrobial compound can be incorporated into a wide variety of plastics
May Ralph Joseph
Mondello Frank John
Caruso Andrew J.
General Electric Company
Johnson Noreen C.
Shaver Paul F.
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