Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...
Reexamination Certificate
1999-09-13
2001-07-17
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
With oxygen or halogen containing chemical bleach or oxidant...
C510S375000
Reexamination Certificate
active
06262008
ABSTRACT:
The invention relates to a stabilized sodium carbonate peroxyhydrate suited for use together with crystalline synthetic silicate-based detergent powders.
Sodium perborate has long been used as a bleaching agent in laundry detergents.
The principal commercial product was sodium perborate tetrahydrate (PB4). The drawback of PB4 is its poor solubility in water. When lower temperatures and the use of hydrogen peroxide activators such as TAED were adopted in the washing of laundry, a shift was made in laundry detergents to the use of sodium perborate monohydrate (PB1), which has a higher solubility. Subsequently the use of sodium perborate has also been adopted in dishwashing machine detergents instead of chlorine compounds and in stain remover salts.
Sodium perborate is a fairly economical product and relatively stable in phosphate-free detergents, which have become common especially in countries which do not have wide-scale and efficient treatment of waste waters. Perhaps the biggest drawback of sodium perborate is that it contains boron. It has been presumed that boron causes health risks and therefore, for example, maximum limits have been set for the amount of boron in drinking water, and in many places these limitations are being made stricter. For this reason there is need for a boron-free bleaching agent which is not hazardous to watercourses or to human beings. Also, the solubility of sodium perborate is not optimal for all products.
Sodium carbonate peroxyhydrate (2Na
2
CO
3
*3H
2
O
2
) would theoretically be a relatively desirable product, since environmentally non-desirable degradation products are not produced from this bleaching agent. In addition, its solubility is quite good. Sodium carbonate peroxyhydrate is commonly referred to with the erroneous name of “sodium percarbonate,” suggesting that the compound in question is a so-called per-compound or per-salt. As the formula presented above shows, sodium carbonate peroxyhydrate is merely a so-called addition product, in which the hydrogen peroxide is quite loosely bonded, and it contains no group corresponding to the structure of actual per-compounds, as do, for example, sodium perborate. sodium monopersulfate, alkali persulfates, etc. A real sodium percarbonate does exist, but it is a hazardous product which cannot be used in household products. Evidently owing partly to its addition structure, sodium carbonate peroxyhydrate is not very stable, and therefore high technical requirements are set for a process for the production of sodium carbonate peroxyhydrate.
In technochemical household products, for example, in dishwashing machine detergents and in stain removers the properties of which are increasingly beginning to approach those of actual detergents so that they contain, among other ingredients, tensides, enzymes, hydrogen peroxide activators, etc., it is desirable to protect sodium carbonate peroxyhydrate from decomposition.
Bleaching agents are used in technochemical household products mostly in laundry detergents. In laundry detergents, silicate-based products such as zeolites, in particular zeolite 4A, are being used increasingly instead of phosphates as so-called builders. It has not been possible to use sodium carbonate peroxyhydrate in zeolite-containing detergents because the product decomposes very rapidly upon coming into contact with zeolite. The reason for this is not precisely known. It must be taken into account that zeolites normally contain quite considerable amounts of water, for example zeolite 4A usually contains water approx. 20%.
In order to give a washing powder an environment-friendly image, zeolite is being used increasingly as a builder instead of phosphate. At the same time, the aim has been to shift to the use of sodium carbonate peroxyhydrate instead of sodium perborate. In this case, problems have been encountered owing to the instability of sodium carbonate peroxyhydrate. A large number of stabilization methods have been developed to solve this problem.
A considerable number of inventions relate to coatings which contain in the coating layers boric acids or boron salts, such as ortho- and metaborates. The use of additives such as silicates and magnesium sulfate have also been proposed. EP applications 459 625 (Mitsubishi Gas Chem.) and 675 851 (Solvey Interox) propose the use of boric acid and silicates as the coating; EP application 675 852 (Solvey Interox) boric acid and phosphates; EP application 487 256 (Kao Corp.) a borate; EP applications 652 809 and 523 169 (FMC Corp.) borosilicate and phosphonic acid derivatives; and U.S. Pat. No. 4,526,698 (Kao Corp.) a borate and an alkali metal silicate or a Mg compound.
All of such methods have the disadvantage that, even though the stability is relatively good, boron has not been entirely eliminated. Furthermore, the solubility of sodium carbonate peroxyhydrate is often decreased, which is not necessarily good. Combinations of sodium sulfate and sodium chloride have also been used for coating sodium carbonate peroxyhydrate, for example, in EP applications 592 969 and 624 549 (Solvey Interox). In these methods, stability may be based on the fact that sodium sulfate, sodium chloride and sodium carbonate which may form upon the degradation of sodium carbonate peroxyhydrate are known to form an addition product together with hydrogen peroxide. There is the disadvantage that chloride, as is known, causes corrosion of stainless steel appliances, such as household appliances. The amounts of coating must also be rather large. Furthermore, chlorinated products may be formed in a reaction between the organic ingredients of detergents, hydrogen peroxide or its degradation products and chloride.
The use of inorganic salts in a coating, together with special coating techniques, also seems to be the most common method of attempting to improve the stability of sodium carbonate peroxyhydrate.
Another group consists of coating methods based on the use of organic substances, either monomeric or polymeric.
The applicant's patent application WO-94/05594 describes a method by which a product quite stable as such is obtained. The product is highly suitable for, for example, stain removers in which sodium carbonate peroxyhydrate is used as such or for products in which relatively inert substances such as pure sodium carbonate and possibly only small amounts of ordinary detergent components are added to the said chemical.
JP application 61 36216 (Sunstar INC. et al.) describes a cleansing agent for dentures, which contains glauber salt 17% and a per-compound, e.g. sodium percarbonate. Glauber salt is a hydrous form of sodium sulfate, sodium sulfate decahydrate. Sodium percarbonate is first mixed with glauber salt, thereafter a polymer in an alcohol solution is atomized over the mixture, which polymer may be, for example, polyvinyl pyrrolidone, and the alcohol is evaporated. The product thus obtained is then mixed with the other components of the cleansing agent to obtain the final cleansing agent for dentures.
JP application 60 30723 (Matsamura Kagaku Kogyo) discloses a product for cleaning urine-stained textiles. Sodium carbonate peroxyhydrate and certain actual peroxy compounds, such as potassium percarbonate and certain persulfates and perborate, are coated by sprinkling water-soluble non-heavy metal salt powders, such as sulfates, chlorides and phosphates, over the said hydrogen peroxide compounds or per-compounds and by using a water-soluble adhesive such as polyvinyl pyrrolidone and other water-soluble polymers which contain, among others, maleate and acrylate groups, in order to obtain the final product. It is difficult by means of powder sprinkling to render the surface of sodium carbonate peroxyhydrate sufficiently protective in order that the product could be used in detergents and in particular detergents which contain zeolite, which very rapidly decomposes sodium carbonate peroxyhydrate. At least the amounts of material used for the powder sprinkling must be quite large. Indeed, in the invention an inorganic salt is used in an amount of 20-35
Korvela Timo
Renvall Ilkka
Greenberg & Traurig, LLP
Kemira Chemicals Oy
Manak Joseph M.
Ogden Necholus
Petruncio John M
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