Method for Cleaning Plasticware

The invention relates to warewashing processes and chemicals used in washing plastic cookware, dishware and flatware. More particularly, the invention relates to primarily organic materials that can be added to water to promote a sheeting action in an aqueous rinse used after an alkaline detergent cycle. Such aqueous rinse aids promote effective sheeting to result in removal of aqueous rinse materials and solids contained therein from plastic cookware, dishware and flatware in acceptable drying time without cracking the plasticware.

Mechanical warewashing machines have been common in the institutional and household environments for many years. Such automatic warewashing machines clean dishes using two or more cycles which can include initially a wash cycle followed by a rinse cycle. Such dishwashers can also utilize soak cycle, prewash cycle, scrape cycle, second wash cycle, a rinse cycle, a sanitizing cycle and a drying cycle, if required. Such cycles can be repeated if needed and additional cycles can be used. After passing through a wash, rinse and dry cycle, dishware, cups, glasses, etc., can exhibit spotting that arises from the uneven draining of the water from the surface of the ware after the rinse step. Spotting is aesthetically unacceptable in most consumer and institutional environments.

In order to substantially prevent the formation of spotting rinse agents have commonly been added to water to form an aqueous rinse which is sprayed on the dishware after cleaning is complete. The precise mechanism through which rinse agents work is not established. One theory holds that the surfactant in the rinse aid is absorbed on the surface at temperatures at or above its cloud point, and thereby reduces the solid-liquid interfacial energy and contact angle. This leads to the formation of a continuous sheet which drains evenly from the surface and minimizes the formation of spots. Generally, high foaming surfactants have cloud points above the temperature of the rinse water, and, according to this theory, would not promote sheet formation, thereby resulting in spots. Moreover, high foaming materials are known to interfere with the operation of the warewashing machine. Common rinse aid formulas are used in an amount of less than about 1,000 parts preferably less than 500 parts, commonly 50 to 200 parts per million of active materials in the aqueous rinse. Rinse agents available in the consumer and institutional markets comprise liquid or solid forms which are typically added to, dispersed or dissolved in water to form an aqueous rinse. Such dissolution can occur from a rinse agent installed onto the dish rack. The rinse agent can be diluted and dispensed from a dispenser mounted on or in the machine or from a separate dispenser that is mounted separately but cooperatively with the dish machine.

Commonly available commercial rinse agents typically comprise a low foaming surface active agent made from homopolymers or copolymers of an alkylene oxide such as ethylene oxide or propylene oxide or mixtures thereof. Typically, the surfactants are formed by reacting an alcohol, a glycol, a carboxylic acid, an amine or a substituted phenol with various proportions and combinations of ethylene oxide and propylene oxide to form both random and block copolymer substituents.

The commonly available rinse agents have primarily focused on reducing spotting and filming on surfaces such as glass, ceramics, china and metal. However, plastic dishware is more commonly used now, especially in the institutional market. A special problem for rinse aid surfactants used for plasticware is the attack and crazing of the ware. Block copolymer surfactants do not seem to attack plastics as strongly as fatty alcohol or alkyl phenol-based nonionic surfactants. Linear alkoxylates show they do not attack plexiglass, polystyrene, or Tupperware.RTM., common utensil plastics. Nevertheless, current surfactants have not provided the desired sheeting in an acceptable drying time following the rinse cycle.

U.S. Pat. No. 5,298,289 describes the treatment and after-treatment of surfaces, especially metals, with derivatives of polyphenol compounds. These compositions are also said to be useful in treating plastic and painted surfaces to improve rinsability without water breaks. The surfactants employed are a combination of previously known anionic and nonionic surfactants.

Liquid dishwashing detergent compositions are described in U.S. Pat. No. 4,492,646 containing highly ethoxylated nonionic surfactants to reduce spotting and filming on surfaces such as glass, ceramics and metal.

European Patent Publication 0,432,836 describes the use of alkyl polyglycoside surfactants in rinse aid compositions on polycarbonate.

Fluorinated surfactants are described in U.S. Pat. No. 4,089,804 where a non-ethoxylated fluoroaliphatic sulfonamide alcohol is added to typical fluorinated hydrocarbon surfactants as a synergist. The compositions are described as useful in a wide variety of industries, e.g., household cosmetic and personal products. Rinse aid for dishwashing is mentioned.

Organosilanes are described in rinse aid compositions where the organosilane contains either a nitrogen, phosphorous or sulfur cationic group in combination with an anion, e.g. a monofunctional organic acid. U.S. Pat. No. 4,005,024 describes such compounds in a rinse aid composition to attract specific soil particles.

Aminosilanes have been described with a low foaming ethoxylated nonionic surfactant in rinse aid compositions in automatic dishwashing machines.

None of the fluorinated surfactants or silanes described in rinse aid compositions have focused on their use in plasticware.

Surprisingly, we have found that by adding a combination of a fluorinated hydrocarbon surfactant, especially an ethoxylated fluorinated aliphatic sulfonamide alcohol, with a silane surfactant, e.g. a polyalkylene oxide-modified polydimethylsiloxane, to a conventional rinse aid composition containing hydrocarbon surfactants, the resulting rinse agent provides excellent sheeting properties on plasticware without attacking or crazing the plastic and, more importantly, providing dried, non-spotted plasticware in acceptable time following the rinse cycle.

Accordingly, the present invention is a rinse aid composition for plasticware, formulated as a dilutable liquid, gel or solid concentrate and., when diluted, forming an aqueous rinse, and including in addition to conventional rinse aid surfactants, e.g. hydrocarbon surfactants, a combination of about 0.1 to 10 wt % of a fluorinated hydrocarbon nonionic surfactant and about 0.1 to 10 wt % of a polyalkylene oxide-modified polydimethylsiloxane.

A second aspect of the present invention is a method of cleaning plasticware by: (a) first contacting the ware with an alkaline aqueous cleaning agent in a warewashing machine at 100.degree.-180.degree. F. to produce cleaned plasticware, and (b) contacting the cleaned plasticware with an aqueous rinse containing a major proportion of an aqueous diluent having about 2 to 100 parts per million of hydrocarbon surfactants, and a combination of about 0.01 to 10 parts per million of a fluorinated hydrocarbon surfactant, e.g. an ethoxylated fluoroaliphatic sulfonamide alcohol, and about 0.01 to 10 parts per million of a polyalkylene oxide-modified polydimethylsiloxane.

For the purpose of this invention, the term "rinse agent" includes concentrate materials that are diluted with an aqueous stream to produce an aqueous rinse. Accordingly, an aqueous rinse agent is an aqueous material that is contacted with ware in a rinse cycle. A sheeting agent is the polymeric material used to promote the even draining of the aqueous rinse. Sheeting is defined as forming a continuous, evenly draining film, leaving virtually no spots or film upon the evaporation of water. For the purpose of this invention, the term "dish" or the term "ware" is used in the broadest sense of the term to refer to various types of articles used in the preparation, serving, consumption, and disposal of food stuffs including pots, pans, trays, pitchers, bowls, plates, saucers, cups, glasses, forks, knives, spoons, spatulas, and other glass, metal, ceramic, plastic composite articles commonly available in the institutional or household kitchen or dining room.

Since the present invention focuses on plastic articles, the term "plasticware" includes the above articles made from, e.g., polycarbonate, melamine, polypropylene, polyester resin, polysulfone, and the like.

The fluorochemical surfactant employed as an additive in the present invention in combination with a silane, defined below, is a nonionic fluorohydrocarbon, such as, for example, fluorinated alkyl polyoxyethylene ethanols, fluorinated alkyl alkoxylate and fluorinated alkyl esters. These Fluorad.TM. surfactants are available from 3M. As a fluorinated alkyl polyoxyethylene ethanol, included as a preferred surfactant is a polyoxyethylene adduct of a fluoroaliphatic sulfonamide alcohol which has excellent wetting, spreading and levelling properties. These surfactants may be described as having the formula:

wherein R.sub.f is C.sub.n F.sub.2n+1 in which n is 6-10 and x may vary from 10 to 20. Particularly valuable is the surfactant where n is 8 and x is 14. This particular surfactant identified as FC-170C is also available from 3M.

The siloxane surfactant employed as an additive in the present invention in combination with the above fluorochemical surfactant is a polyalkylene oxide-modified polydimethylsiloxane, preferably a linear polydimethylsiloxane to which polyethers have been grafted through a hydrosilation reaction. This process results in an alkyl-pendant (AP type) copolymer, in which the polyalkylene oxide groups are attached along the siloxane backbone through a series of hydrolytically stable Si--C bonds. These products have the general formula: ##STR1## wherein EO is ethyleneoxy, PO is 1,2-propyleneoxy, Z is hydrogen or alkyl of 1-6 carbon atoms, and the weight ratio in % of EO:PO may vary from 100:0 to 0-100. A broad range of surfactants have been developed varying x and y above and coefficients n and m. Preferably, n is 0 or 1 and m is at least 1. More preferred are the siloxanes where n is 0 or 1, m is 1, Z is hydrogen or methyl and the weight ratio of EO:PO is 100:0 to 20:80. Particularly valuable are the siloxanes where n is 0, Z is methyl and the weight ratio of EO:PO is 100:0 to 20:80. The siloxane surfactants herein described are known as SILWET.RTM. surfactants available from Union Carbide or ABIL.RTM. polyethersiloxanes available from Goldschmidt Chemical Corp. The particular siloxanes used in the present invention are described as having, e.g., low surface tension, high wetting ability and excellent lubricity. For example, these surfactants are said to be among the few capable of wetting polytetrafluoroethylene surfaces.

Although the fluorochemical surfactants and siloxane surfactants were known to have good wetting properties, the use of each surfactant alone with conventional rinse aid surfactants on plasticware did not perform as well as the combination and only marginally better than a conventional rinse agent without additives.

Since the use of the above additives in combination, i.e. the fluorocarbon and the siloxane, are applicable to all conventional rinse aid formulations, the following description of ingredients and rinse aid formulations is illustrative only and not limiting of the present invention.

An example of hydrocarbon surfactants in conventional rinse aid formulations are nonionic surfactants, typically a polyether compound prepared from ethylene oxide, propylene oxide, in a homopolymer or a block or heteric copolymer. Such polyether compounds are known as polyalkylene oxide polymers, polyoxyalkylene polymers, or polyalkylene glycol polymers. Such sheeting or rinse agents have a molecular weight in the range of about 500 to about 15,000. Certain types of polyoxypropylene-polyoxyethylene glycol polymer rinse aids have been found to be particularly useful. Those surfactants comprising at least one block of a polyoxypropylene and having at least one other block of polyoxyethylene attached to the polyoxypropylene block. Additional blocks of polyoxyethylene or polyoxypropylene can be present in a molecule. These materials having an average molecular weight in the range of about 500 to about 15,000 are commonly available as PLURONIC.RTM. manufactured by the BASF Corporation and available under a variety of other trademarks of their chemical suppliers. In addition, rinse aid compositions called PLURONIC.RTM. R (reverse pluronic structure) are also useful in the rinse aids of the invention. Additionally, rinse aids made by reacting ethylene oxide or propylene oxide with an alcohol anion and an alkyl phenol anion, a fatty acid anion or other such anionic material can be useful. One particularly useful rinse aid composition can comprise a capped polyalkoxylated C.sub.6-24 linear alcohol. The rinse aids can be made with polyoxyethylene or polyoxypropylene units and can be capped with common agents forming an ether end group. One particularly useful species of this rinse aid is a benzyl ether of a polyethoxylated C.sub.12-14 linear alcohol; see U.S. Pat. No. 3,444,247. Alcohol ethoxylates having EO and PO blocks can be particularly useful since the stereochemistry of these compounds can permit occlusion by urea, a feature useful in preparing solid rinse aids.

Particularly useful polyoxypropylene polyoxyethylene block polymers are those comprising a center block of polyoxypropylene units and blocks of polyoxyethylene units to each side of the center block. These copolymers have the formula shown below:

wherein m is an integer of 21 to 54; n is an integer of 7 to 128. Additional useful block copolymers are block polymers having a center block of polyoxyethylene units and blocks of polyoxypropylene units to each side of the center block. The copolymers have the formula as shown below:

wherein m is an integer of 14 to 164 and n is an integer of 9 to 22.

In the preparation of conventional rinse aid compositions, a hydrotropic agent is often employed in the formulation. Such an agent may also be used in the present invention.

Hydrotropy is a property that relates to the ability of materials to improve the solubility or miscibility of a substance in liquid phases in which the substance tends to be insoluble. Substances that provide hydrotropy are called hydrotropes and are used in relatively lower concentrations than the materials to be solubilized.

A hydrotrope modifies the solvent to increase the solubility of an insoluble substance or creates micellar or mixed micellar structures resulting in a stable suspension of the insoluble substance in the solvent. The hydrotropic mechanism is not thoroughly understood. Apparently either hydrogen bonding between primary solvent, in this case water, and the insoluble substance are improved by the hydrotrope or the hydrotrope creates a micellar structure around the insoluble composition to maintain the material in a suspension/solution. In this invention, the hydrotropes are most useful in maintaining a uniform solution of the cast rinse composition both during manufacture and when dispersed at the use location. The combination of the polyalkylene oxide materials and the casting aids tends to be partially incompatible with aqueous solution and can undergo a phase change or phase separation during storage of the solution. The hydrotrope solubilizer maintains the rinse composition in a single phase solution having the nonionic rinsing agent uniformly distributed throughout the composition.

Preferred hydrotrope solubilizers are used at about 0.1 to 20 wt % and include small molecule anionic surfactants. The most preferred hydrotrope solubilizers are used at about 1 to 10 wt % and include aromatic sulfonic acid or sulfonated hydrotropes such as C.sub.1-5 substituted benzene sulfonic acid or naphthalene sulfonic acid. Examples of such a hydrotrope are xylene sulfonic acid or naphthalene sulfonic acid or salts thereof. Such materials do not provide any pronounced surfactant or sheeting activity but significantly improve the solubility of the organic materials of the rinse aid in the aqueous rinse compositions.

Thus, a preferred embodiment of a rinse aid composition for plasticware, which is suitable for dilution to form an aqueous rinse includes: (a) about 2 to 90 wt % of one or more nonionic surfactants; (b) about 1 to 20 wt % of a hydrotrope; (c) about 0.1 to 10 wt % of an ethoxylated fluoroaliphatic sulfonamide alcohol; and (d) about 0.1 to 10 wt % of a polyalkylenoxide-modified polydimethylsiloxane.

Another embodiment of the rinse aid composition of the present invention is the combination of the above-described fluorocarbon surfactant and siloxane surfactant with a rinse aid composition containing a nonionic block copolymer and a defoamer composition. The nonionic ethylene oxide propylene oxide block copolymer in this case would not have been expected to provide effective sheeting action and low foam in an aqueous rinse due to its high cloud point and poor wetting properties. However, rinse agents diluted into an aqueous rinse providing effective sheeting and low foaming properties have been prepared from high cloud point, high foaming surfactants with an appropriate defoamer as described in copending U.S. application Ser. No. 08/049,973 of Apr. 20, 1993.

Illustrative but non-limiting examples of various suitable high cloud point nonionic surface active agents for these rinse agents include polyoxyethylenepolyoxypropylene block copolymers having the formula:

wherein x, y and z reflect the average molecular proportion of each alkylene oxide monomer in the overall block copolymer composition. x typically ranges from about 30 to 130, y typically ranges from about 30 to 70, z typically ranges from about 30 to 130, and x plus y is typically greater than about 60. The total polyoxyethylene component of the block copolymer constitutes typically at least about 40 mol-% of the block copolymer and commonly 75 mol-% or more of the block copolymer. The material preferably has a molecular weight greater than about 5,000 and more preferably greater than about 10,000.

Defoaming agents (defoamers) include a variety of different materials adapted for defoaming a variety of compositions. Defoamers can comprise an anionic or nonionic material such as polyethylene glycol, polypropylene glycol, fatty acids and fatty acid derivatives, fatty acid sulfates, phosphate esters, sulfonated materials, silicone based compositions, and others.

Preferred defoamers are food additive defoamers including silicones and other types of active anti-foam agents.

Silicone foam suppressors include polydialkylsiloxane preferably polydimethylsiloxane. Such silicone based foam suppressors can be combined with silica. Such silica materials can include silica, fumed silica, derivatized silica, silanated silica, etc. Commonly available anti-foaming agents combine a polydimethylsiloxane and silica gel. Another food additive defoaming agent comprises a fatty acid defoamer. Such defoamer compositions can comprise simple alkali metal or alkaline earth metal salts of a fatty acid or fatty acid derivatives. Examples of such derivatives include mono, di- and tri-fatty acid esters of polyhydroxy compounds such as ethylene glycol, glycerine, propylene glycol, hexylene glycol, etc. Preferably such defoaming agents comprise a fatty acid monoester of glycerol. Fatty acids useful in such defoaming compositions can include any C.sub.8-24 saturated or unsaturated, branched or unbranched mono or polymeric fatty acid and salts thereof, including for example myristic acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, palmitoleic acid, oleic acid, linoleic acid, arachidonic acid, and others commonly available. Other food additive anti-foam agents available include water insoluble waxes, preferably microcrystalline wax, petroleum wax, synthetic petroleum wax, rice base wax, beeswax having a melting point in the range from about 35.degree. to 125.degree. C. with a low saponification value, white oils, etc. Such materials are used in the rinse agents at a sufficient concentration to prevent the accumulation of any measurable stable foam within the dish machine during a rinse cycle. The defoaming composition may be present in the composition of the present invention from about 0.1-30 wt %, preferably 0.2-25 wt %.

Thus, a preferred rinse aid composition for plasticware, suitable for dilution to form an aqueous rinse also includes: (a) about 5 to 40 wt % of a nonionic block copolymer composition of ethylene oxide and propylene oxide, having a molecular weight of .gtoreq.5000 and a cloud point, measured with a 1 wt % aqueous solution, greater than 50.degree. C.; (b) about 0.2 to 25 wt % of a food additive defoamer composition; (c) about 0.1 to 10 wt % of an ethoxylated fluoroaliphatic sulfonamide alcohol; and (d) about 0.1 to 10 wt % of a polyalkylene oxide-modified polydimethylsiloxane.

Still another embodiment of the present invention is a rinse aid composition containing the combination of the above-described fluorocarbon surfactant and siloxane surfactant with a rinse aid composition containing solely food additive ingredients. The compositions include a class of nonionic surfactants, namely, the polyalkylene oxide derivatives of sorbitan fatty acid esters, which exhibit surprising levels of sheeting action, with a careful selection of defoamer compositions. These are described in copending U.S. Application Ser. No. 08/050,531 of Apr. 20, 1993, now abandoned. The effective defoamer compositions are selected from the group consisting of a silicone defoamer, an alkali metal (e.g. sodium, potassium, etc.) or alkaline earth fatty acid salt defoamer or a glycerol fatty acid monoester defoamer described above. Preferably, silicone based materials are used to defoam the sorbitan material.

Sorbitol and sorbitan can be derivatized with an alkylene oxide such as ethylene oxide or propylene oxide or derivatized with fatty acids or with both using conventional technology to produce nonionic surfactant sheeting agent materials. These sheeting agents are typically characterized by the presence of from 1 to 3 moles of a fatty acid, in ester form, per mole of surfactant and greater than 15 moles of alkylene oxide, preferably 15 to 40 moles of alkylene oxide and most preferably 15 to 25 moles of ethylene oxide per mole of surfactant. The composition of the surfactant is a mixture of a large number of compounds characterized by the molar proportion of alkylene oxide and the molar proportion of fatty acid residues on the sorbitol or sorbitan molecules. The compositions are typically characterized by average concentrations of the alkylene oxide (typically ethylene oxide) and the fatty acid on the overall compositions. Examples of preferred nonionic surfactants are Polysorbate 20.RTM., also known as Tween 20.RTM. (ICI), typically considered to be a mixture of laureate esters of sorbitol and sorbitan consisting predominantly of the mono fatty acid ester condensed with approximately 20 moles of ethylene oxide. Polysorbate 60.RTM. is a mixture of stearate esters of sorbitol and sorbitan consisting predominantly of the mono fatty acid ester condensed with approximately 20 moles of ethylene oxide. Selected polysorbate nonionic surfactant materials are approved for direct use in food intended for human consumption under specified conditions and levels of use.

Alkoxylated sorbitan or sorbitol aliphatic esters suitable for use in the rinse aid composition include any sorbitan or sorbitol aliphatic ester derivatized with an alkylene oxide capable of providing effective sheeting action or rinsing performance in cooperation with the other components of the rinse agent composition. The preferred compositions are the ethylene oxide condensates with sorbitan or sorbitol fatty acid esters. In addition to providing superior sheeting and rinsing performance, these materials are approved food additives, in the form of a liquid or waxy solid, that can be easily formulated into concentrated liquid or solid rinse agents. Alkoxylated sorbitan or sorbitol fatty acid esters suitable for use in the rinse agent include mono, di- and tri-esters and mixtures thereof. Sorbitan fatty acid esters may be derivatized by esterification of sorbitol or sorbitan with such fatty acids as lauric, myristic, palmitic, stearic, oleic, linoleic, and other well known similar saturated, unsaturated (cis or trans), branched and unbranched fatty acid. Preferred food additive or GRAS fatty acids are the sorbitan esters approved as direct food additives (e.g. sorbitan monostearate, POE 20 Sorbitan monolaurate, POE 20 Sorbitan monostearate, POE 20 Sorbitan tristearate, POE 20 Sorbitan monooleate and mixtures thereof. Based on their cost availability and ability to provide excellent sheeting action and rinsing performance, the preferred useful ethoxylated sorbitan or sorbitol fatty acid ester include monoesters derivatized with ethylene oxide.

Thus, a preferred rinse aid composition for plasticware, suitable for dilution to form an aqueous rinse, further includes: (a) about 5 to 50 wt % of a sorbitan fatty acid ester containing greater than about 15 moles of alkylene oxide per mole of sorbitan; (b) about 0.2 to 25 wt % of a defoamer composition selected from the group consisting of an alkali metal or alkaline earth metal salt of a fatty acid, a silicone, a fatty acid ester of glycerol, and mixtures thereof; (c) about 0.1 to 10 wt % of an ethoxylated fluoroaliphatic sulfonamide alcohol; and (d) about 0.1 to 10 wt % of a polyalkylene oxide-modified polydimethylsiloxane.

The rinse agents of the invention can, if desired, contain a polyvalent metal complexing or chelating agent that aids in reducing the harmful effects of hardness components in service water. Typically calcium, magnesium, iron, manganese, etc., ions present in service water can interfere with the action of either washing compositions or rinsing compositions. A chelating agent can effectively complex and remove such ions from inappropriate interaction with active ingredients increasing rinse agent performance. Both organic and inorganic chelating agents are common. Inorganic chelating agents include such compounds as sodium tripolyphosphate and higher linear and cyclic polyphosphate species. Organic chelating agents include both polymeric and small molecule chelating agents. Polymeric chelating agents commonly comprise polyanionic compositions such as polyacrylic acid compounds. Small molecule organic chelating agents include salts of ethylenediaminetetracetic acid and hydroxyethylenediaminetetracetic acid, nitrilotriacetic acid, ethylenediaminetetrapropionates, triethylenetetraminehexacetates, and the respective alkali metal ammonium and substituted ammonium salts thereof. Amino phosphates are also suitable for use as chelating agents in the composition of the invention and include ethylenediamine(tetramethylene phosphates), nitrilotrismethylenephosphonates, diethylenetriamine (pentamethylenephosphonates). These amino phosphonates commonly contain alkyl or alkyl groups with less than 8 carbon atoms. Preferred chelating agents include approved food additive chelating agents such as disodium salt of ethylenediaminetetracetic acid.

The liquid rinse agent compositions of the invention have a liquid base component which can function as a carrier with various aqueous diluents to form the aqueous rinse. Liquid bases are preferably water or a solvent compatible with water to obtain compatible mixtures thereof. Exemplary nonlimiting solvents in addition to water include low molecular weight C.sub.1-6 primary and secondary mono, di-, and trihydrate alcohol such as ethanol, isopropanol, and polyols containing from two to six carbon atoms and from two to six hydroxyl groups such as propylene glycol, glycerine, 1,3-propane diol, propylene glycol, etc.

The compositions of the invention can be formulated using conventional formulating equipment and techniques. The compositions of the invention typically can comprise proportions as set forth in Table I.

In the manufacture of the liquid rinse agent of the invention, typically the materials are manufactured in commonly available mixing equipment by charging to a mixing chamber the liquid diluent or a substantial proportion of a liquid diluent. Into a liquid diluent is added preservatives or other stabilizers. Care must be taken in agitating the rinse agent as the formulation is completed to avoid degradation of polymer molecular weight or exposure of the composition to elevated temperatures. The materials are typically agitated until uniform and then packaged in commonly available packaging and sent to storage before distribution.

The liquid materials of the invention can be adapted to a solid block rinse by incorporating into the composition a casting agent. Typically organic and inorganic solidifying materials can be used to render the composition solid. Preferably organic materials are used because inorganic compositions tend to promote spotting in a rinse cycle. The most preferred casting agents are polyethylene glycol and an inclusion complex comprising urea and a nonionic polyethylene or polypropylene oxide polymer. Polyethylene glycols (PEG) are used in melt type solidification processing by uniformly blending the sheeting agent and other components with PEG at a temperature above the melting point of the PEG and cooling the uniform mixture. An inclusion complex solidifying scheme is set forth in Morganson et al., U.S. Pat. No. 4,647,258.

The organic nature of the rinse agents of the invention can be subject to decomposition and microbial attack. Preferred stabilizers that can limit oxidative decomposition or microbial attack include food grade stabilizers, food grade antioxidants, etc. Most preferred materials for use in stabilizing the compositions of the invention include C.sub.1-10 mono, di- and tricarboxylic acid compounds. Preferred examples of such acids include acetic acid, citric acid, lactic, tartaric, malic, fumaric, sorbic, benzoic, etc.

Optional ingredients which can be included in the rinse agents of the invention in conventional levels for use include solvents, processing aids, corrosion inhibitors, dyes, fillers, optical brighteners, germicides, pH adjusting agents (monoethanol amine, sodium carbonate, sodium hydroxide, hydrochloride acid, phosphoric acid, etc.), bleaches, bleach activators, perfumes and the like.

The range of actives in the solid and liquid concentrate compositions of the invention are set forth in Table I and the ranges in the aqueous rinse in Table II.

Liquid rinse agents of the invention are typically dispensed by incorporating compatible packaging containing the liquid material into a dispenser adapted to diluting the liquid with water to a final use concentration wherein the active material is present in the aqueous rinse as shown in Table II above in parts per million parts of the aqueous rinse. Examples of dispensers for the liquid rinse agent of the invention are DRYMASTER-P sold by Ecolab Inc., St. Paul, Minn.

Solid block products may be conveniently dispensed by inserting a solid block material in a container or with no enclosure into a spray-type dispenser such as the volume SOL-ET controlled ECOTEMP Rinse Injection Cylinder system manufactured by Ecolab Inc., St. Paul, Minn. Such a dispenser cooperates with a warewashing machine in the rinse cycle. When demanded by the machine, the dispenser directs a spray of water onto the solid block of rinse agent which effectively dissolves a portion of the block creating a concentrated aqueous rinse solution which is then fed directly into the rinse water forming the aqueous rinse. The aqueous rinse is then contacted with the dishes to affect a complete rinse. This dispenser and other similar dispensers are capable of controlling the effective concentration of the active block copolymer and the additives in the aqueous rinse by measuring the volume of material dispensed, the actual concentration of the material in the rinse water (an electrolyte measured with an electrode) or by measuring the time of the spray on the solid block.

The following examples and data further illustrate the practice of the invention. These should not be taken as limiting the invention and contain the best mode.

EXAMPLE I

The following four liquid formulations were prepared by routine mixing of the ingredients.

These formulations were evaluated in a modified Champion 1 KAB dishwash machine modified to replace the front stainless panel with a glass window and to conduct rinsing tests using the machine pump and wash arms.

The test procedure is first to select appropriate test substrates to evaluate the test formulations. These substrates are typical pieces of plasticware commonly used in institutional accounts. In preparation for the sheeting test, the test substrates are conditioned with 0.2% Hotpoint soil in softened water at 160.degree. F. for three minutes in the modified Champion 1 KAB dishmachine. The test procedure is to add test rinse aid in increments of 10 ppm actives, to the machine pump, circulate the test solution at 160.degree. F. for 30 seconds, turn off the machine and observe the type of water break on each test substrate. There are three types of water break. These are:

1. No Sheeting. The test solution runs off the test substrate leaving discrete droplets behind.

2. Pinhole Sheeting. The test solution drains off of the test substrate to leave a continuous film. The film contains pinholes on the surface of the film. No droplets remain on the test substrate after the film drains and dries.

3. Complete Sheeting. The test solution drains off the test substrate to leave a continuous film with no pinholes. No droplets remain on the test substrate after the film drains and dries.

The type of water used in this test is softened well water. After each evaluation of test rinse aid per 10 ppm active increment, the results are recorded for each test substrate. The test continues until a good performance profile is obtained that allows a judgment to be made regarding the relative performance of the test formulations.

Results are given below in table form for each of the four formulations noted above.

Table 1 contains results for a commercially available rinse aid. Note that none of the plastic substrates exhibit complete sheeting until 70 ppm actives are used.

Table 2 contains results for the same set of actives containing Fluorad.TM. FC-170C. It performs marginally better at 60 ppm to complete sheet on some of the plastic substrates.

Table 3 contains results for the same set of actives containing Silwet.RTM. L-77. It also performs marginally better at 60 ppm to complete sheet on some of the plastic substrates.

Table 4 contains results for the invention. This contains both Silwet.RTM. L-77 and Fluorad.TM. FC-170C. It performs much better at 40 ppm to complete sheet on several of the plastic substrates.

The invention represented as Formulation 4 was also evaluated in four institutional test accounts relative to the commercially available rinse aid represented as Formulation 1. In each account at either the same or even at a lower concentration, there has been a significant improvement in drying results on plasticware. With the commercially available product large residual droplets of rinse water remained on the plasticware so that the dry time was much too long, i.e., the plasticware was stacked wet. With the invention, the dry time was greatly reduced and the plasticware was stacked dry.

The following three solid rinse aid formulations were prepared as previously described and compared side by side. Formula 5 contained the same active ingredients as Formula 4 of Example I. The results (Tables 5, 6 and 7) show similar effectiveness as with the Formula 4 compositions.