Cleaning and liquid contact with solids – Processes – Work handled in bulk or groups
Reexamination Certificate
2001-08-15
2003-09-23
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Work handled in bulk or groups
C134S025100, C134S025400, C134S042000, C510S220000, C510S224000, C510S232000, C510S233000
Reexamination Certificate
active
06622736
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a new type of use for a water-soluble glass to protect glassware from corrosion during washing and/or rinsing cycles of a dishwashing machine, compositions intended for use in a dishwashing machine for the aforesaid purpose and a method of inhibiting the corrosion of glassware during washing and/or rinsing cycles of a dishwashing machine.
The problem of glassware corroding during washing and/or rinsing cycles of a dishwashing machine has long been known. Current opinion is that the problem of corrosion in glassware is the result of two separate phenomena. On the one hand, the corrosion is clearly due to minerals escaping from the glass composition accompanied by hydrolysis of the silicate network. On the other hand, silicate material is released from the glass. After several washes in a dishwashing machine, both phenomena can cause damage to glassware such as cloudiness, scratches, streaks and similar.
Silicate compounds are known to be effective in preventing minerals from being released from the glass composition but on the other hand can tend to increase the separation of silicate material at the surface of the glass.
Various proposals have been put forward as a means of dealing with the problems described above.
One approach is to use zinc, either in metallic form (U.S. Pat. No. 3,677,820) or in the form of zinc compounds. The use of soluble zinc salts as a means of preventing the corrosion of glassware in dishwasher detergents is described in U.S. Pat. No. 3,255,117, for example.
Because of a number of disadvantages inherent in using soluble zinc salts (in particular the formation of a precipitate of insoluble zinc salts with other ions in the washing or rinsing water), European patent applications EP 0 383 480, EP 0 383 482 and EP 0 387 997 propose the use of insoluble zinc compounds as a means of inhibiting the corrosion of glassware in automatic dishwashing machines. Specifically, the insoluble zinc salts proposed are zinc silicate, zinc carbonate, zinc oxide, basic zinc carbonate (approximately: Zn
2
(OH)
2
CO
3
), zinc hydroxide, zinc oxalate, zinc monophosphate (Zn
3
(PO
4
)
2
) and zinc pyrophosphate (Zn
2
(P
2
O7)). When using zinc salts of this type in granular cleansing compounds, the insoluble zinc compound is specified as having a maximum particle size of less than 1.7 mm (EP 0 383 482), whilst a mean particle size of less than 250 &mgr;m is specified for the insoluble zinc compound used in a liquid dishwasher compound (EP 0 383 480 and EP 0 387 997).
The disadvantage of this prior art essentially resides in the fact that, because the zinc compounds are not readily soluble or are insoluble, it is difficult to ensure that a sufficient quantity of active agent will always be present in the washing or rinsing liquid to protect glassware from corrosion. Furthermore, in view of the high specific density of the insoluble zinc compounds listed, problems of separation arise with powdered mixtures or settlement in the case of liquid mixtures.
Finally, all of the known compositions are intended to be active during only one specific stage of the washing cycle, i.e. if admixed with a granular detergent composition during the washing cycle or if admixed with a liquid rinsing composition with the rinsing cycle. None of the known compositions has the capacity to become and remain active starting from the pre-wash cycle and/or one of the intermediate rinsing cycles onwards.
The underlying objective of the present invention is to resolve at least one, but preferably all of the existing problems outlined above.
SUMMARY OF THE INVENTION
This objective is achieved by the invention due to the use of a water-soluble glass to protect glassware from corrosion, the water-soluble glass being made from at least one compound which releases an active anti-corrosion agent during the washing and/or rinsing cycles of a dishwashing machine, each of these compounds accounting for no more than 85 molar % of the glass and the solubility of the water-soluble glass being defined by a mass loss of at least 0.5 mg under the conditions specified in DIN ISO 719.
By preference, the solubility of the water-soluble glass is such that the mass loss under the specified conditions is at least 10 mg, more preferably at least 50 mg.
The invention additionally proposes that the compound(s). which release(s) an active agent to protect glassware from corrosion during the washing and/or rinsing cycles of a dishwashing machine should be from the group consisting of the oxides of zinc, aluminium, tin, magnesium, calcium, strontium, titanium, zirconium, manganese and/or lanthanum and/or precursors thereof.
In one particular embodiment, the invention proposes that at least one of the compounds used should be zinc oxide and/or a precursor thereof.
By preference, at least one of the glass-forming components of the water-soluble glass is phosphorus pentoxide and/or a precursor thereof.
Also particularly preferred as a glass component(s) is (are) one or more alkali metal oxides and/or precursors thereof.
In one especially preferred embodiment, the invention proposes using the water-soluble glass in the form of a tablet, the tablet preferably being made by casting or drawing the water-soluble glass.
Alternatively, the water-soluble glass is used in crushed form, either in the form of glass platelets or in around form.
In ground form, the mean particle size is preferably at most 500 &mgr;m.
The invention additionally relates to a composition for use in a dishwashing machine, containing an active quantity of a water-soluble glass in crushed form to protect glassware from corrosion, the water-soluble glass being made from at least one compound which releases an active agent to protect glassware from corrosion during washing and/or rinsing cycles of a dishwashing machine, each of these compounds accounting for at most 85 molar % of the glass and the solubility of the water-soluble glass being defined by a mass loss of at least 0.5 mg under the conditions specified in DIN ISO 719.
The water-soluble glass is preferably used either in the form of thin glass platelets or in ground form, most preferably with a mean particle size of at most 500 &mgr;m.
The composition proposed by the invention contains the water-soluble glass in a quantity of from 0.1 to 10.0% by weight, more preferably from 0.5 to 5.0% by weight.
In an alternative embodiment, the invention proposes a composition for use in a dishwashing machine, characterized in that it contains an active quantity of a water-soluble glass tablet form to protect glassware from corrosion, the water-soluble glass being made from at least one compound which releases an active agent to protect glassware from corrosion during washing and/or rinsing cycles of a dishwashing machine, each of these compounds accounting for at most 85 molar % of the glass and the solubility of the water-soluble glass being defined by a mass loss of at least 0.5 mg under the conditions specified in DIN ISO 719.
The tablet proposed by the invention is preferably made by casting or drawing the water-soluble glass.
With both the composition in which the water-soluble glass is present in crushed form and in the embodiment where the water-soluble glass is provided as a tablet, the solubility of the water-soluble glass is such that the mass loss under the specified conditions is preferably at least 10 mg, more preferably at least 50 mg.
In both cases, the compound(s) which release(s) an active agent to protect glassware from corrosion during washing and/or rinsing cycles of a dishwashing machine is (are) from the group consisting of the oxides of zinc, aluminium, tin, magnesium, calcium, strontium, titanium, zirconium, manganese and/or lanthanum and/or precursors thereof.
In one particular embodiment, the invention proposes that at least one of the compounds should be zinc oxide and/or a precursor thereof.
Preferably, at least one of the glass-forming components of the water-soluble glass is phosphorus pentoxide and/or a precursor thereof.
One or more alkali met
Akin Gump Strauss Hauer & Feld L.L.P.
Gulakowski Randy
Kornakov M.
Reckitt Benckiser N.V.
LandOfFree
Water-soluble glass as corrosion protection for glassware in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Water-soluble glass as corrosion protection for glassware in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Water-soluble glass as corrosion protection for glassware in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3039842