Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-06-07
2003-02-25
Sanders, Krieellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S102000, C524S425000, C523S122000
Reexamination Certificate
active
06525117
ABSTRACT:
BACKGROUND OF THE INVENTION
A variety of microbiocides, including zinc pyrithione, are useful in vinyl chloride polymer compositions (or “PVC”). However, the use of biocides such as zinc pyrithione is largely limited to PVC plastisol formulations where the heat history is not excessive and there is little or no shear that would be likely to have an adverse effect on both the static and dynamic heat stability of the system. Attempts to overcome this negative effect on PVC heat stability by adding epoxidized soybean oil, organophosphite, barium or calcium intermediates (metal soaps) have all met with limited success.
U.S. Pat. Nos. 5,344,636 and 5,741,526 describe certain mixed metal hydroxide/oxide compositions are used in combination with an anti-microorganism agent. Mixed metal hydroxycarbonates (or hydrotalcites) are not disclosed by either patent.
Japanese Patent Publication No. 10-158452 describes PVC compositions containing a mixture of a hydrotalcite compound, a hindered amine compound, and an N-containing sulfur fungicide, such as 2-(4-thiazolyl) benzimidazole.
Japanese Patent Publication No. 10-182315 describes an antimicrobial agent comprising a magnesium/aluminum/zinc hydrocarbonate (hydrotalcite) and either 2-mercapto pyridine-N-oxide (or a derivative of it) dispersed thereon. The antimicrobial efficiency of this system at high temperatures is attributed to its increased solubility (presumably in the resin) and melting point elevation as a consequence of dispersion of the microparticle hydrotalcite. The preparation of the intended antimicrobial agent appears to be tedious since the coating of active ingredient on the surface of the hydrotalcite is achieved in an aqueous medium with a water-soluble salt of the 2-mercapto pyridine-N-oxide. Subsequently, filtration, drying and pulverization are also required before the product can be used. This Japanese patent publication also seems to suggest that zinc pyrithione (zinc bis (2-mercaptopyridine-N-oxide)) is bound to the surface of the hydrotalcite.
SUMMARY OF THE INVENTION
In the present case, a mixed metal (e.g., magnesium/aluminum) hydroxycarbonate (or “hydrotalcite”) composition is effective in improving the heat stability of biocides (such as zinc pyrithione) that are contained in such PVC formulations. Performance improvement is obtained by simply adding the hydrotalcite to the biocide-containing formulation with no prior treatment or contact between the two ingredients of the invention. In the present invention there is deemed to be no substantial chemical bonding between the hydrotalcite component and the zinc atom, which continues to be bound to the pyrthione ligand, as is the case for the composition described in Japanese Patent Publication No. 10-182315.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to the stabilization of the known PVC biocide, zinc pyrithione, which, as earlier described, has certain deficiencies in regard to its detrimental effect on the heat stability of PVC.
The mixed metal hydroxycarbonate stabilizer additive used in connection with the present invention are more commonly referred to as “hydrotalcites”. Persons of ordinary skill in the art recognize this type of material, in one embodiment, as being a hydroxycarbonate of magnesium and aluminum, having a typical formula of Mg
4
Al
2
OH
12
CO
3
×H
2
O. A commercially available material of this type is sold under the trademark HYSAFE 539 by J. M. Huber. The zinc/magnesium/aluminum hydrocarbonates are another embodiment of this type of material that may also be employed. A commercially available material of this type is sold under the trademark ALKAMIZER 4 by Kyowa K K.
As earlier mentioned, it is not necessary to pretreat these materials in aqueous media; in accordance with the present invention, they can simply be dry blended together so that the mixed metal hydroxycarbonate stabilizer will be present in effective amount for its eventual use in the PVC composition. According to this invention, the amount of zinc pyrithione biocide (expressed in terms of active ingredient) that is incorporated into PVC can range from about 100 ppm to about 5000 ppm. The amount of hydroxycarbonate used in conjunction with the zinc pyrithione biocide can range from about 0.2 phr to about 10 phr. More preferred ranges are about 200 to about 3000 ppm for the zinc pyrithione biocide and about 0.5 to about 7 phr for the hydroxycarbonate stabilizer. The most preferred ranges are about 500 to about 2000 ppm for the zinc pyrithione biocide and about 1.0 to about 5 phr for the hydroxycarbonate stabilizer. In general, the amount of hydroxycarbonate added to the PVC will increase with the quantity of zinc biocide added. In accordance with the present invention, the use of relatively low zinc pyrithione biocide levels with relatively high hydroxycarbonate level is also possible. Alternatively, relatively high zinc pyrithione biocide levels in conjunction with relatively low levels of hydroxycarbonate, while not most preferred, can also be employed. Actual levels employed during PVC processing may deviate from the most preferred range to accommodate other additives incorporated by the processor or dictated by the end application.
If the relative amounts of zinc pyrithione and mixed metal hydroxycarbonate to each other in a blend containing these two components is considered, it can range from about 20% to about 99.8%, by weight of the blend of such of zinc pyrithione and mixed metal hydroxycarbonate. Another embodiment of this invention has these two in the following amount: from about 75% to about 98%, by weight of the blend of such of zinc pyrithione and mixed metal hydroxycarbonate.
As earlier mentioned, in a preferred embodiment of the present invention, the presence of a hindered amine stabilizer is not needed in either the zinc pyrithione/stabilizer blend or in the final PVC composition containing that biocide/stabilizer blend.
The PVC formulation can contain the conventional functional additives that have traditionally been used in their normal amounts including: plasticizers; additional stabilizers (ultraviolet and/or heat); dyes; pigments; lubricants; additional biocides; and the like. U.S. Pat. No. 5,575,951 is incorporated herein by reference for showing (for example, at Col. 3, lines 9-40) some such additives that might be used.
REFERENCES:
patent: 4474760 (1984-10-01), Hill
patent: 4686239 (1987-08-01), Rei
patent: 5137569 (1992-08-01), Waldron et al.
patent: 5319000 (1994-06-01), O'Connor et al.
patent: 5344636 (1994-09-01), Miyata
patent: 5648413 (1997-07-01), Sato et al.
patent: 5741526 (1998-04-01), Miyata
patent: 5929132 (1999-07-01), Hani et al.
patent: 10-158452 (1998-06-01), None
patent: 10-182315 (1998-07-01), None
Derwent Patent Abstract 90-166626/22 (1990).
Derwent Patent Abstract 96-247036/25 (1996).
Derwent Patent Abstract 98-433658/37 (1998).
Derwent Patent Abstract 98-393600/34 (1998).
Akzo Nobel N.V.
Fennelly Richard P.
Sanders Krieellion A.
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