Rinse aid compositions containing scale inhibiting polymers

Details Rinse aid compositions containing scale inhibiting polymers Rinse aid compositions containing scale inhibiting polymers

1997-07-25

2001-04-03

Medley, Margaret (Department: 1714)

Compositions

Water-softening or purifying or scale-inhibiting agents

Plant or organic material containing

C134S025200, C510S475000, C510S476000

Reexamination Certificate

active

06210600

ABSTRACT:

FIELD OF THE INVENTION
This invention pertains to rinse aid compositions for machine dishwashing containing scale inhibiting polymers to control calcium phosphate scale.
BACKGROUND OF THE INVENTION
The machine dishwashing process comprises washing articles in a main wash cycle and rinsing them in one or more rinse cycles. A rinse aid composition is designed for use in the final rinse step of the machine dishwashing operation, separately from the detergent composition used in the main wash cycle. The rinse aid's performance is judged particularly by its ability to prevent spot and film formation on washed articles. Rinse aid compositions usually comprise an aqueous liquid containing a low-foaming nonionic surfactant, hydrotropes and an ingredient such as citric acid that can act as a builder and a pH control agent.
For many years, sodium tripolyphosphate (STP) has been used in the main wash product for machine dishwashing operation as the primary detergency builder to sequester water hardness ions (Ca
2+
, Mg
2+
). However, precipitation of STP by hardness ions can occur under underbuilt conditions which arise when an insufficient amount of STP is present in high hardness water. This situation can result in calcium phosphate deposition (scaling) on washed article surfaces. The tendency of scaling with some slow-dissolving tablet main wash products is even higher because, during the course of tablet dissolution, the wash liquor can be underbuilt if relatively high levels of hardness ions are present. The dissolution profile of the tablet is such that, in the initial stages of the wash, only part of the available phosphate will be delivered to the wash water. In addition, underdosage of other forms of product, such as liquids, powders, granulates and gels, can also cause a comparable scaling problem.
A separate problem arises from wash liquor containing STP being carried over from the main wash cycle into the rinse cycle. This carry-over results in an underbuilt or supersaturated rinse water under hard water conditions, and can lead to further scale deposition on the articles or to a reduction in the ability of the rinse water to remove previous deposition. Usually, there is a build up of scale and this deposition causes an objectionable filming, especially on glassware surfaces. Increasing temperature and water hardness increases scaling dramatically.
Regarding inhibiting scaling, U.S. Pat. No. 5,420,211 describes acid functional copolymers grafted to a polyethylene glycol backbone as detergent additives which have the property of inhibiting film formation in the main wash of machine dishwashing. However, the control of calcium phosphate scale related to underbuilt machine dishwashing conditions with an STP-built main wash product is not taught or suggested.
WO 95/32271 describes terpolymers containing carboxlic acid, 2-alkylallyl sulfonic acid and a carbohydrate derived from sugar for use in rinsing agents for dishwashing machines to prevent the formation of spots on washed articles.
DE4415804 describes terpolymers containing acrylic acid, maleic acid and vinyl alcohol and/or vinyl acetate for use in rinsing agents for dishwashing machines to prevent the formation of spots on dried crockery, glassware and cutlery.
U.S. Pat. No. 5,306,429 describes copolymers of polyamino acids as scale inhibiting agents which are said to be useful in preventing calcium phosphate scale formation when formulated in products designed for the main wash.
EP 561464 describes polyamino compounds, including polyaspartic acid and its salts, in rinse aid compositions to prevent scaling during the rinse step. However, it teaches that this rinse aid composition is particularly useful with phosphate-free main wash compositions. This qualification means that the polymer described is for inhibition of calcium carbonate scale, related to the hard water used, rather than for inhibition of calcium phosphate scale, related to underbuilt wash conditions with STP-built machine dishwashing compositions. The nature and the formation mechanism of these two types of scale are different.
EP 659873 describes an organo diphosphonic acid compound in rinse aid compositions to prevent calcium carbonate scale. Again, the control of calcium phosphate scale related to underbuilt wash conditions is not taught or suggested.
Biodegradable copolymers of itaconic acid and vinyl alcohol or vinyl acetate have been described in WO 94/17170 for incorporation in machine dishwashing and rinse aid compositions to prevent lime scale. Again, the control of calcium phosphate scale related to underbuilt wash conditions is not taught or suggested.
The prior art has not considered the calcium phosphate scale problem, especially as related to underbuilt machine dishwashing conditions arising under high water hardness. Therefore, the objectives of the present invention are the identification of scale inhibitors that are effective for inhibiting calcium/STP scale in underbuilt conditions, and particularly, the methods of their use for superior scale-inhibiting performance in machine dishwashing under underbuilt conditions.
SUMMARY OF THE INVENTION
The present invention provides rinse aid compositions containing scale inhibiting polymers for machine dishwashing to control calcium phosphate scale. The preferred polymer consists of about 50 to about 99% by wt., preferably from about 70 to about 98%, most preferably from about 75 to about 95% by wt. of an olefinically unsaturated carboxylic acid and about 1% to about 50%, preferably from 2 to 30%, most preferably from about 5 to about 25% by wt. of one or more monomer units selected from
(a) copolymerizable sulfonated monomers,
(b) copolymerizable nonionic monomers or
(c) mixtures of (a) and (b).
The average molecular weight of the polymers ranges from about 1500 to about 250,000, preferably from about 5,000 to about 100,000.
The invention is also directed to a method of using the polymers in machine dishwashing for superior scale-inhibition performance.
DETAILED DESCRIPTION OF THE INVENTION
The compositions of the invention can be formulated in any desired form such as tablets, powders, granulates, pastes, liquids and gels. Liquid compositions are most preferred.
Scale Inhibitors
An essential component of the compositions in accordance with the invention is a scale-inhibiting copolymer. It comprises 50 to 99% by wt., preferably from 70 to 98%, most preferably from about 75 to about 95% by wt. of an olefinically unsaturated carboxylic acid monomer and 1% to 50%, preferably from 2 to 30%, most preferably from about 5 to about 25% by wt. of one or more monomer units selected from
(a) copolymerizable sulfonated monomers,
(b) copolymerizable nonionic monomers or
(c) mixtures of (a) and (b).
The olefinically unsaturated carboxylic acid monomer for use herein is intended to include aliphatic, branched or cyclic, mono- or dicarboxylic acids, the alkali or alkaline earth metal or ammonium salts thereof, and the anhydrides thereof. Useful olefinically unsaturated acids of this class include acrylic acid comonomers typified by acrylic acid itself, methacrylic acid, ethacrylic acid, alpha-chloro-acrylic acid, alpha-cyano acrylic acid, beta methyl-acrylic acid (crotonic acid), alpha-phenylacrylic acid, beta-acryloxy propionic acid, sorbic acid, alpha-chloro sorbic acid, angelic acid, cinnamic acid, p-chloro cinnamic acid, beta-styryl acrylic acid (1-carboxy-4-phenyl butadiene-1,3), itaconic acid, maleic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid,fumaric acid, and tricarboxyethylene.
For the polycarboxylic acid monomers, an anhydride group is formed by the elimination of one molecule of water from two carboxyl groups located on the same polycarboxylic acid molecule. Preferred carboxylic monomers for use in this invention are the monoolefinic acrylic acids having a substituent selected from the class consisting of hydrogen, halogen and hydroxyl groups, monovalent alkyl radicals, monovalent aryl radicals, monovalent aralkyl radicals, monovalent alkaryl radicals and monovalen

Affiliated with

Also associated with

Rating

Rinse aid compositions containing scale inhibiting polymers does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rinse aid compositions containing scale inhibiting polymers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rinse aid compositions containing scale inhibiting polymers will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2531959