WO2000069423A1

WO2000069423A1 - Inverse phase emulsions having a preservative system with low evaporative water loss

Info

Publication number: WO2000069423A1
Application number: PCT/US2000/013848
Authority: WO
Inventors: Ronald Wayne Berg; Steven Lee Barnholtz; Larry Neil Mackey
Original assignee: The Procter & Gamble Company
Priority date: 1999-05-19
Filing date: 2000-05-19
Publication date: 2000-11-23
Also published as: AR022641A1; PE20001501A1; AU5033200A

Abstract

A preservative system. The preservative system may be used with a high internal phase inverse emulsion. The emulsion, in turn, may be used in conjunction with and disposed on a wipe, or similar substrate used to clean the skin, a hard surface, etc. The emulsion locally expresses water in use upon application of pressure. The water is usable for cleaning the selected surface. The preservative system described herein provides efficacious antimicrobial activity without a deleterious effect on evaporative water loss.

Description

INVERSE PHASE EMULSIONS HAVING A PRESERVATIVE SYSTEM WITH LOW EVAPORATIVE WATER LOSS

FIELD OF THE INVENTION The present invention is related to cleaning articles, particularly high internal phase inverse emulsions disposable on a substrate.

BACKGROUND OF THE INVENTION

Substrates having lotions and other coatings are well known in the art.

Lotions are often used in conjunction with substrates to soften the substrate. Lotions can also be used to soothe the skin when the substrate is used, for example, as a facial tissue. Examples of substrates having lotion and useful in the facial tissue art are found in U.S. Patent 4,426,418, issued Jan. 17, 1984 to

Coleman et al. and commonly assigned U.S. Patent 4,481 ,243, issued Nov. 6,

1984 to Allen, the disclosure of which Allen patent is incorporated herein by reference.

However, these attempts in the art do not solve the problem of how to use the lotion to improve cleaning of the skin with the tissue. Nor do these attempts show how to clean other surfaces using a substrate treated with a lotion.

Products, such as wipes, have been developed. Certain wipes have a significant advantage over earlier prior art cleaning products for removing soiling, particularly from the perianal region. Such wipes comprise a substrate (e.g., a nonwoven or tissue) treated with a water-in-lipid emulsion. Such wipes are particularly advantageous for cleaning, especially when provided in the form of wet-like cleansing wipes used to remove perianal soils. Examples of such wipes and their manufacture are found in commonly assigned World Patent Applications WO 96/14835, published May 23, 1996, in the names of Mackey et al.; and WO 96/21505, published July 18, 1996, in the name of DesMarais, the disclosures of which are incorporated herein by reference. These wipes release significant quantities of water during use for comfortable, more effective cleaning. The lipid phase of the emulsion found in these wipes is sufficiently brittle so as to be easily disrupted by low shear contact or compression (e.g., during the wiping of the skin) to readily release this internal water phase, but sufficiently tough at elevated temperatures where the lipid is melted to avoid premature release of the water phase during the rigors of processing. The continuous lipid phase of these articles is also sufficiently stable during storage so as to prevent significant evaporation of the internal water phase. The normal tensile strength and flushability properties of these articles are not adversely affected when treated with the high internal phase inverse emulsions of the present invention. As a result, users of these articles get comfortable, efficient, moist cleaning without having to change their normal cleaning habits. This technology is readily useful for other purposes, such as cleaning hard surfaces, etc.

During cleaning, water is released from the emulsion to remove dirt from the skin. The area of the skin wetted by the water and from which dirt is removed is then wiped dry with the regions of the substrate free of the emulsion. Similar benefits occur when the wipe is used to clean other surfaces, such as window glass, countertops, sinks, porcelain and metal fixtures, walls and the like, and from other surfaces, such as carpeting or furniture. The mechanism to transfer the water from the emulsion to the surface to be cleaned involves several steps. First, the water is released or expressed from the emulsion due to pressure imparted by the user. The pressure ruptures the emulsion, freeing the water. The water then saturates the substrate. Upon saturation, the water penetrates the substrate in the Z-direction. Excess water, which is that water in excess of the local absorbent capacity of the substrate then is transferred from the wipe to the surface. It has been found that incorporating a preservative system into the emulsion inhibits microbial growth, minimizing sanitation problems. However, it has been found that many preservative systems have a deleterious effect on naturally occurring water loss associated with the emulsion. Over time, evaporative losses cause the emulsion to lose so much water that efficacious cleaning is no longer provided. However, it has been unexpectedly found that with the preservative systems of the claimed invention both antimicrobial efficacy and low evaporative water losses can be attained.

SUMMARY OF THE INVENTION The invention comprises a high internal phase inverse emulsion. The emulsion is disposable on a wipe. The emulsion has a preservative system to prevent microbial growth. The emulsion further has a low evaporative water loss relative to emulsions free of said preservative system. The emulsion is preferably disposed on a substrate and usable as a wipe.

DETAILED DESCRIPTION OF THE INVENTION The emulsion, and any wipe disclosed herein, may be used for several purposes. For example, the emulsion and wipe may be used as a facial tissue, bath tissue, paper towel, a baby wipe, an adult wipe, a hard surface cleaner, etc. The intended use of the emulsion and wipe does not limit the final product. The Preservative System The Preservative System usable herein may be generally comprised of selected known antimicrobial agents. However, the specific preservative system described and claimed herein overcomes the prior art problems of increasing evaporative losses known to occur in an inverse phase emulsion. Preferably, the inverse phase emulsion having the preservative system described hereinbelow has an evaporative water loss, when compared to an inverse phase emulsion free of a preservative system but otherwise identical to that claimed herein, of not more than 20% greater than a like emulsion free of said preservative system, preferably not more than 15% greater, more preferably not more than 10% greater, and most preferably not more than 5% greater.

Two emulsions may be considered to be "like" if the emulsions are generally identical in composition except that one emulsion has a preservative system according to the present invention and the other emulsion is free of such a preservative system. As used herein, a preservative system is any substance, or combination of components, which provide microbial stability to the emulsion, and thereby inhibit microbial growth.

This evaporative water loss improvement, in combination with a preservative system which has efficacy against microbial activity, may be accomplished by providing a preservative system which generally, but not necessarily, has a pH less than 5.5, and/or a partition coefficient of less than approximately 0.1 . However, it is to be recognized that other preservatives not meeting the above criteria and having the evaporative water loss properties described and claimed hereinbelow will be suitable for use with the present invention. More particularly, the preservative system usable with the present invention may have a water solubility of at least 0.03 grams per gram of deionized water, preferably of at least 0.05 grams per gram of deionized water, more preferably of at least 0.1 grams per gram of deionized water, and most preferably of at least 0.5 grams per gram of deionized water. Water solubility is taken as the maximum concentration of the substance under consideration, which forms a stable, optically transparent single phase solution. Preferably, the water solubility of the preservative system does not exceed 3 grams per gram of deionized water and may even be as low as 1 gram per gram of deionized water. The water solubility of various compounds may be found in the Merck Index, 10^th edition, published by Merck & Co.; Cosmetic And Drug Preservation Principles and Practice, edited by Kabara, published by Marcel Dekker; and Cosmetic Microbiology, A Practical Handbook, edited by Brannan, published by CRC Press, which are incorporated herein by reference.

Suitable preservatives for use either in combination or alone, in the preservative system of the present invention, include sodium hydroxy methyl glycinate, Chemical Abstract Services Number 70161-44-3, sold under the trade name Suttocide A by ISP Sutton Laboratories of Chatham, New Jersey; Formaldehyde releasers such as; Dimethyloldimethylhydantoin, Chemical Abstract Services Number 6440-58-0, sold under the name Glydant; imidazolidinyl urea, Chemical Abstract Services Number 39236-46-9, sold under the name Germall 115; diazolidinyl urea, Chemical Abstract Services Number 78491-02-8, sold under the name Germall II; 2-Bromo-2-nitropropane-1 , 3-diol, Chemical Abstract Services Number 52-51-7, sold under the name Bronopol; and, sodium sorbate.

Evaporative water loss is measured by the following procedure. A syringe having a needle with an internal diameter of 0.040 inches is provided. The syringe is heated to 70°C. Also a substrate is provided. The substrate is cellulosic, through air dried, and has a basis weight of 26 pounds per 3,000 square feet and may be made according to commonly assigned U.S. Pat. Nos. 4,529,480; 4,637,859; 4,687,153; 5,223,096; and 5,240,562, the disclosures of which are incorporated herein by reference. A two-ply embossed Bounty paper towel substrate, sold by the instant assignee, may be used for this purpose. Beads of the emulsion are extruded at one-quarter inch intervals, over a length of 8 inches until the syringe is evacuated. Approximately 24 beads per sample may be extruded in this manner. Six samples are prepared and allowed to cool to room temperature. Each sample is weighed to the nearest one-hundredth gram using any suitable laboratory balance having a resolution of at least 0.01 grams. The samples are stored in a temperature and humidity controlled room under standard TAPPI laboratory conditions having a temperature of 73±2°F. and 50±2%RH.

The samples are stored for 168 hours in a flat, horizontal and unconstrained position and condition. After 168 hours, each sample is reweighed and the results of the samples averaged to give the evaporative water loss. The evaporative water loss is taken as the difference in weight between the final and initial weighings, divided by the amount of water phase initially provided in the emulsion, X 100%. The amount of water phase initially provided with the emulsion is known from the preparation technique. The amount of water phase initially added to the emulsion may be determined in accordance with commonly assigned U.S. Patent Application Serial No. 09/121 ,504, provisionally filed July 31 , 1997, perfected July 23, 1998, in the names of Mackey, et al. The Substrate

The wipe comprises a substrate and an emulsion disposed thereon. The substrate may be cellulosic, particularly a tissue, a nonwoven, a foam, or any combination thereof. Suitable cellulosic substrates are described in U.S. Patents 5,245,025, issued Sept. 14, 1993 to Trokhan et al.; 5,503,715, issued April 2, 1996 to Trokhan et al.; 5,534,326, issued July 9, 1996 to Trokhan et al.; 4,637,859 issued Jan. 20, 1987 to Trokhan; 4,514,345, issued April 30, 1985 to Johnson et al.; 4,529,480, issued July 16, 1985 to Trokhan; 5,328,565, issued July 12, 1994 to Rasch et al.; 4,191 ,609, issued March 4, 1980 to Trokhan; 4,300,981 , issued Nov. 17, 1981 to Carstens; 4,513,051 , issued April 23, 1985 to Lavash; 4,637,859, issued Jan. 20, 1987 to Trokhan; 5,143,776, issued Sept. 1 , 1992 to Givens; 5,637,194, issued June 10, 1997 to Ampulski et al.; 5,609,725, issued March 11 , 1997 to Phan; and 5,628,876, issued May 13, 1997 to Ayers et al., the disclosures of which patents are incorporated herein by reference.

A suitable tissue substrate has a basis weight of about 7 to 25 pounds per 3,000 square feet per ply, preferably about 8 to 10 pounds per 3,000 square feet per ply, and most preferably about 8-1/2 pounds per 3,000 square feet per ply for bath tissue applications, and about 18 to 22 pounds per 3,000 square feet per ply for hard surface cleaning applications. A multi-basis weight substrate is feasible for the claimed invention. A multi-basis weight substrate has regions of high and low basis weight juxtaposed together, and optionally intermediate basis weight regions. The high basis weight regions provide strength. The low basis weight regions provide for transfer of water released from the emulsion to the surface. In a degenerate case, the low basis weight regions may be apertures, to increase the transfer of water to the surface. If a multi-basis weight substrate is used, the macro-basis weight of the substrate, averaging both high and low basis weight regions or high, intermediate and low basis weight regions, is considered.

If a multi-basis weight substrate is desired, such a substrate may be made according to commonly assigned U.S. Patents 5,277,761 , issued Jan. 11 , 1994 to Phan et al.; 5,443,691 , issued Aug. 22, 1995 to Phan et al.; and 5,614,061 , issued March 25, 1997 to Phan et al., the disclosures of which patents are incorporated herein by reference. If a multi-basis weight substrate having radially oriented fibers is desired, such a substrate may be made according to commonly assigned U.S. Patents 5,245,025, issued Sept. 14, 1993 to Trokhan et al.; 5,503,715, issued April 2, 1996 to Trokhan et al.; 5,527,428, issued June 18, 1996 to Trokhan et al.; or 5,534,326, issued July 9, 1996 to Trokhan et al., the disclosures of which patents are incorporated herein by reference. If one desires to use a more durable or nonwoven substrate for a wipe, such a substrate may be made according to commonly owned U.S. Patents 4,097,965, issued July 4, 1978 to Gotchel et al.; 4,130,915, issued Dec. 26, 1978 to Gotchel et al.; 4,296,161 , issued Oct. 20, 1981 to Kaiser et al.; and 4,682,942, issued July 28, 1987 to Gotchel et al., the disclosures of which patents are incorporated herein by reference.

The Emulsion

The emulsion comprises: (1 ) a continuous solidified lipid phase; (2) an emulsifier that forms the emulsion when the lipid phase is fluid; and (3) an internal polar phase dispersed in the lipid phase. This emulsion ruptures when subjected to low shear during use, e.g., wiping of the skin or other surface, so as to release the internal polar phase. 1. External Lipid Phase The continuous solidified lipid phase provides the essential stabilizing structure for the high internal phase inverse emulsions of the present invention. In particular, this continuous lipid phase is what keeps the dispersed internal phase from being prematurely released prior to use of the article, such as during storage.

The continuous lipid phase can comprise from about 2 to about 60% of the emulsion of the present invention. Preferably, this continuous lipid phase will comprise from about 5 to about 30% of the emulsion. Most preferably, this lipid phase will comprise from about 6 to about 15% of the emulsion.

The major constituent of this continuous lipid phase is a waxy lipid material. This lipid material is characterized by a melting point of about 30°C or higher, i.e., is solid at ambient temperatures. Preferably, the lipid material has a melting point of about 50°C or higher. Typically, the lipid material has a melting point in the range of from about 40° to about 80°C, more typically in the range of from about 50° to about 70°C.

Although this waxy lipid material is solid at ambient temperatures, it also needs to be fluid or plastic at those temperatures at which the high internal phase inverse emulsion is applied to the carrier. Moreover, even though the lipid material is fluid or plastic at those temperatures at which the emulsion is applied to the carrier substrate, it should still desirably be somewhat stable (i.e., minimal coalescence of emulsion micro-droplets) for extended periods of time at elevated temperatures (e.g., about 50°C or higher) that are normally encountered during storage and distribution of the articles of the present invention. This lipid material also needs to be sufficiently brittle at the shear conditions of use of the article such that it ruptures and releases the dispersed internal polar phase. These lipid materials should also desirably provide a good feel to the skin when used in personal care products such as wet-like cleansing wipes and tissue used in perianal cleaning. Suitable waxy lipid materials for use in the high internal phase inverse emulsion of the present invention include natural and synthetic waxes, as well as other oil soluble materials having a waxy consistency. As used herein, the term "waxes" refers to organic mixtures or compounds that are generally water- insoluble and tend to exist as amorphous or microcrystalline or crystalline solids at ambient temperatures (e.g., at about 25°C). Suitable waxes include various types of hydrocarbons, as well as esters of certain fatty acids and fatty alcohols. They can be derived from natural sources (i.e., animal, vegetable or mineral) or they can be synthesized. Mixtures of these various waxes can also be used.

Some representative animal and vegetable waxes that can be used in the present invention include beeswax, carnauba, spermaceti, lanolin, shellac wax, candelilla, and the like. Particularly preferred animal and vegetable waxes are beeswax, lanolin and candelilla. Representative waxes from mineral sources that can be used in the present invention include petroleum-based waxes such as paraffin, petrolatum and microcrystalline wax, and fossil or earth waxes such as white ceresine wax, yellow ceresine wax, white ozokerite wax, and the like. Particularly preferred mineral waxes are petrolatum, microcrystalline wax, yellow ceresine wax, and white ozokerite wax. Representative synthetic waxes that can be used in the present invention include ethylenic polymers such as polyethylene wax, chlorinated naphthalenes such as "Halowax," hydrocarbon type waxes made by Fischer-Tropsch synthesis, and the like. Particularly preferred synthetic waxes are polyethylene waxes. Besides the waxy lipid material, the continuous lipid phase can include minor amounts of other lipophilic or lipid-miscible materials. These other lipophilic/lipid-miscible materials are typically included for the purpose of stabilizing the emulsion 12 to minimize loss of the internal polar phase or for improving the aesthetic feel of the emulsion on the skin. Suitable materials of this type that can be present in the continuous lipid phase include hot melt adhesives such as Findley 193-336 resin, long chain alcohols such as cetyl alcohol, stearyl alcohol, and cetaryl alcohol, water-insoluble soaps such as aluminum stearate, silicone polymers such as polydimethylsiloxanes, hydrophobically modified silicone polymers such as phenyl trimethicone, and the like. Other suitable lipophilic/lipid miscible materials include polyol polyesters. By "polyol polyester" is meant a polyol having at least 4 ester groups. By "polyol" is meant a polyhydric alcohol containing at least 4, preferably from 4 to 12, and, most preferably from 6 to 8, hydroxyl groups. Polyols include monosaccharides, disaccharides and trisaccharides, sugar alcohols and other sugar derivatives (e.g., alkyl glycosides), polyglycerols (e.g., diglycerol and triglycerol), pentaerythritol, and polyvinyl alcohols. Preferred polyols include xylose, arabinose, ribose, xylitol, erythritol, glucose, methyl glucoside, mannose, galactose, fructose, sorbitol, maltose, lactose, sucrose, raffinose, and maltotriose. Sucrose is an especially preferred polyol. With respect to the polyol polyesters useful herein, it is not necessary that all of the hydroxyl groups of the polyol be esterified, however disaccharide polyesters should have no more than 3, and more preferably no more than 2 unesterified hydroxyl groups. Typically, substantially all (e.g., at least about 85%) of the hydroxyl groups of the polyol are esterified. In the case of sucrose polyesters, typically from about 7 to 8 of the hydroxyl groups of the polyol are esterified.

By "liquid polyol polyester" is meant a polyol polyester from the hereinbefore described groups having a fluid consistency at or below about 37°C. By "solid polyol polyester" is meant a polyol polyester from the hereinbefore described groups having a plastic or solid consistency at or above about 37°C. Liquid polyol polyesters and solid polyol polyesters may be successfully employed as emollients and immobilizing agents, respectively, in emulsions of the present invention. In some cases, solid polyol polyesters may also provide some emolliency functionality.

2. Internal Polar Phase

Typically, the major component of the high internal phase inverse emulsions of the present invention is the dispersed internal polar phase. In preferred embodiments, the polar phase will contain a significant percentage of water, preferably at least about 60%, by weight of the emulsion, more preferably at least about 75%, by weight, still more preferably at least about 90%, by weight.

The internal polar phase can provide a number of different benefits when released. For example, in wet-like cleaning wipes for perianal cleaning where the internal polar phase is water, it is this released water that provides the primary cleansing action for these wipes.

In a preferred embodiment of the present invention, the internal polar phase (preferably comprising water as a major constituent) is a polar phase comprising an antimicrobial compound. Another advantage of the wipes according to the present invention is that besides the disinfection properties delivered, good cleaning is also provided as the polar phase may further comprise solvents. The emulsion may comprise essential oils including, but not limited to, those obtained from thyme, lemongrass, citrus, lemons, oranges, anise, clove, aniseed, cinnamon, geranium, roses, mint, lavender, citronella, eucalyptus, peppermint, camphor, sandalwood and cedar and mixtures thereof. Actives of essential oils to be used herein include, but are not limited to, thymol (present for example in thyme), eugenol (present for example in cinnamon and clove), menthol (present for example in mint), geraniol (present for example in geranium and rose), verbenone (present for example in vervain), eucalyptol and pinocarvone (present in eucalyptus), cedrol (present for example in cedar), anethol (present for example in anise), carvacrol, hinokitiol, berberine, terpineol, limonene, methyl salycilate and mixtures thereof. Preferred actives of essential oils to be used herein are thymol, eugenol, verbenone, eucalyptol, carvacrol, limonene and/or geraniol. Thymol may be commercially available for example from Aldrich, eugenol may be commercially available for example from Sigma, Systems - Bioindustries (SBI) - Manheimer Inc.

Typically, the antimicrobial preservative or mixtures thereof will be present in the internal polar phase at a level of from 0.001 % to 5%, preferably from 0.001 % to 3%, more preferably from 0.005% to 1 %, by weight of total internal polar phase. Solvents may be present in the internal polar phase according to the present invention. These solvents will, advantageously, give an enhanced cleaning to the wipes of the present invention. Suitable solvents for incorporation herein include propylene glycol derivatives such as n-butoxypropanol or n- butoxypropoxypropanol, water-soluble CARBITOL® solvents or water-soluble CELLOSOLVE® solvents. Water-soluble CARBITOL® solvents are compounds of the 2-(2-alkoxyethoxy)ethanol class wherein the alkoxy group is derived from ethyl, propyl or butyl. A preferred water-soluble carbitol is 2-(2- butoxyethoxy)ethanol also known as butyl carbitol. Water-soluble CELLOSOLVE ® solvents are compounds of the 2-alkoxyethoxyethanol class, with 2- butoxyethoxyethanol being preferred. Other suitable solvents are benzyl alcohol, methanol, ethanol, isopropyl alcohol and diols such as 2-ethyI-1 ,3-hexanediol and 2,2,4-trimethyl-1 ,3-pentanediol and mixture thereof. Preferred solvents for use herein are n-butoxypropoxypropanol, butyl carbitol® and mixtures thereof. A most preferred solvent for use herein is butyl carbitol®.

The internal polar phase herein may further comprise other optional ingredients including radical scavengers, chelating agents, thickeners, builders, buffers, stabilizers, soil suspenders, dye transfer agents, brighteners, anti dusting agents, enzymes, dispersant, dye transfer inhibitors, pigments, perfumes, and dyes and the like.

Suitable chelating agents to be used herein may be any chelating agent known to those skilled in the art such as the ones selected from the group consisting of phosphonate chelating agents, amino carboxylate chelating agents or other carboxylate chelating agents, or polyfunctionally-substituted aromatic chelating agents and mixtures thereof.

Further carboxylate chelating agents to be used herein includes malonic acid, salicylic acid, glycine, aspartic acid, glutamic acid, dipicolinic acid and derivatives thereof, or mixtures thereof.

Typically, the chelating agent, or a mixture thereof, is present in the internal polar phase at a level of from 0.001% to 5% by weight, preferably from 0.001 % to 3% by weight and more preferably from 0.001 % to 1.5%.

The wipes according to the present invention are suitable for various surfaces including animate surfaces (e.g. human skin) as well as inanimate surfaces including any hard-surfaces. Regardless of its composition, the internal polar phase will preferably comprise from about 67 to about 92% of the emulsion. Most preferably, the internal polar phase will comprise from about 82 to about 91 % of the emulsion. Where the internal polar phase comprises water as a major component, the internal phase can comprise water-soluble or dispersible materials that do not adversely affect the stability of the high internal phase inverse emulsion. One such material that is typically included in the internal water phase is a water- soluble electrolyte. The dissolved electrolyte minimizes the tendency of materials present in the lipid phase to also dissolve in the water phase. Any electrolyte capable of imparting ionic strength to the water phase can be used. Suitable electrolytes include the water soluble mono-, di-, or trivalent inorganic salts such as the water-soluble halides, e.g., chlorides, nitrates and sulfates of alkali metals and alkaline earth metals. Examples of such electrolytes include sodium chloride, calcium chloride, sodium sulfate, magnesium sulfate, and sodium bicarbonate. The electrolyte will typically be included in a concentration in the range of from about 1 to about 20% of the internal water phase.

Other water-soluble or dispersible materials that can be present in the internal polar phase include thickeners and viscosity modifiers. Suitable thickeners and viscosity modifiers include polyacrylic and hydrophobically modified polyacrylic resins such as Carbopol and Pemulen, starches such as corn starch, potato starch, tapioca, gums such as guar gum, gum arabic, cellulose ethers such as hydroxypropyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and the like. These thickeners and viscosity modifiers will typically be included in a concentration in the range of from about 0.05 to about 0.5% of the internal phase.

Again, where water is a major constituent of the internal polar phase, water- soluble or dispersible materials that can be present in the internal phase include polycationic polymers to provide steric stabilization at the polar phase-lipid phase interface and nonionic polymers that also stabilize the emulsion. Suitable polycationic polymers include Reten 201 , Kymene® 557H and Acco 711.

Suitable nonionic polymers include polyethylene glycols (PEG) such as Carbowax. These polycationic and nonionic polymers will typically be included in a concentration in the range of from about 0.1 to about 1.0% of the polar phase.

3. Emulsifier

Another key component of the high internal phase inverse emulsion of the present invention is an emulsifier. In the emulsions of the present invention, the emulsifier is included in an effective amount. What constitutes an "effective amount" will depend on a number of factors including the respective amounts of the lipid and internal polar phase components, the type of emulsifier used, the level of impurities present in the emulsifier, and like factors. Typically, the emulsifier comprises from about 1 to about 10% of the emulsion. Preferably, the emulsifier will comprise from about 3 to about 6% of the emulsion. Most preferably, the emulsifier will comprise from about 4 to about 5% of the emulsion. While the singular "emulsifier" is used to describe this component, more than one emulsifier may be used when forming the emulsion. Indeed, as discussed below, it may be desirable to utilize both a primary and a secondary emulsifier when certain materials are employed. Though not intended to limit the scope of the invention, where two emulsifiers are utilized, preferred is where the primary emulsifier comprises from about 1 to about 7%, more preferably from about 2 to about 5%, most preferably from about 2 to about 4%, by weight of the emulsion; and the secondary emulsifier comprises from about 0.5 to about 3%, more preferably from about 0.75 to about 2%, most preferably from about 0.75 to about 1.5%, by weight of the emulsion. The emulsifier needs to be substantially lipid-soluble or miscible with the lipid phase materials, especially at the temperatures at which the lipid material melts. It also should have a relatively low HLB value. Emulsifiers suitable for use in the present invention have HLB values typically in the range of from about 2 to about 5 and can include mixtures of different emulsifiers. Preferably, these emulsifiers will have HLB values in the range of from about 2.5 to about 3.5.

Preferred emulsifiers for use in the present invention include silicone polymer emulsifiers such as alkyl dimethicone copolyols (e.g., Dow Corning Q2- 5200 laurylmethicone copolyol). Such emulsifiers are described in detail in U.S. Patent Number 5,756,112, issued May 26, 1998, which is incorporated by reference herein.

Other suitable emulsifiers are described in co-pending U.S. Patent Application Serial No. 08/336,456, filed November 9, 1994 by L. Mackey et al. (Case 5478), and U.S. Patent Application Serial No. 08/761 ,097, filed Dec. 5, 1996 by L. Mackey et al. (Case 5478R), both of which are incorporated by reference herein. Emulsifiers described therein include certain sorbitan esters, preferably the sorbitan esters of C16-C22 saturated, unsaturated or branched chain fatty acids. Because of the manner in which they are typically manufactured, these sorbitan esters usually comprise mixtures of mono-, di-, tri-, etc. esters. Representative examples of suitable sorbitan esters include sorbitan monooleate (e.g., SPAN® 80), sorbitan sesquioleate (e.g., Arlacel® 83), sorbitan monoisostearate (e.g., CRILL® 6 made by Croda), sorbitan stearates (e.g., SPAN® 60), sorbitan triooleate (e.g., SPAN® 85), sorbitan tristearate (e.g., SPAN® 65) and sorbitan dipalmitates (e.g., SPAN® 40). Laurylmethicone copolyol is a particularly preferred emulsifier for use in the present invention. Other suitable emulsifiers described therein include certain glyceryl monoesters, preferably glyceryl monoesters of C16-C22 saturated, unsaturated or branched chain fatty acids such as glyceryl monostearate, glyceryl monopalmitate, and glyceryl monobehenate; certain sucrose fatty acid esters, preferably sucrose esters of the C12-C22 saturated, unsaturated, and branched chain fatty acids such as sucrose trilaurate and sucrose distearate (e.g., Crodesta® F10), and certain polyglycerol esters of C-16-C22 saturated, unsaturated or branched fatty acids such as diglycerol monooleate and tetraglycerol monooleate. In addition to these primary emulsifiers, coemulsifiers can be used to provide additional water- in-lipid emulsion stability. Suitable coemulsifiers include phosphatidyl cholines and phosphatidyl choline-containing compositions such as the lecithins; long chain C16-C22 fatty acid salts such as sodium stearate, long chain C16-C22 dialiphatic, short chain C1-C4 dialiphatic quaternary ammonium salts such as ditallow dimethyl ammonium chloride and ditallow dimethyl ammonium methylsulfate; long chain C16-C22 dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C1-C4 dialiphatic quaternary ammonium salts such as ditallowoyl-2-hydroxyethyl dimethyl ammonium chloride, the long chain C16-C22 dialiphatic imidazolinium quaternary ammonium salts such as methyl-1 -tallow amido ethyl-2-tallow imidazolinium methylsulfate and methyl-1 -oleyl amido ethyl-2-oleyl imidazolinium methylsulfate; short chain C1-C4 dialiphatic, long chain C16-C22 monoaliphatic benzyl quaternary ammonium salts such as dimethyl stearyl benzyl ammonium chloride, and synthetic phospholipids such as stearamidopropyl PG-dimonium chloride (Phospholipid PTS from Mona Industries). Interfacial tension modifiers such as cetyl and stearyl alcohol for closer packing at the water-lipid interface can also be included.

Other emulsifiers useful in making the articles of the present invention include the high viscosity emulsifiers described in co-pending U.S. Patent Application Serial No. 08/759,547, filed Dec. 5, 1996 by L. Mackey and B. Hird and allowed February 24, 1999, which is incorporated by reference herein. These emulsifiers preferably have a viscosity at 55°C of at least about 500 centipoise. (Viscosity can be measured using a Lab-Line Instruments Brookfield- type rotating disc viscometer.) That application describes specifically the use of emulsifiers such as those designated by The Lubrizol Corporation (Wickliffe, OH) as OS-122102, OS-121863, OS-121864, OS-80541J and OS-80691J, which are reaction products of (i) a hydrocarbyl-substituted carboxylic acid or anhydride (preferably a polyisobutylene-substituted succinic acid or anhydride); and (ii) an amine or alcohol, to form an ester or amide product. The materials, and methods for their manufacture, are described in U.S. Patent Number 4,708,753, issued November 24, 1987 to Forsberg [see especially Column 3, lines 32-38; and Column 8, line 10, to Column 26, line 68], and U.S. Patent Number 4,844,756, issued July 4, 1989 to Forsberg, both of which are incorporated by reference herein.

Other materials believed to be useful in the present invention include hydrocarbon-substituted succinic anhydrides such as those described in U.S. Patent 3,215,707, issued November 2, 1965 to Rense; U.S. Patent 3,231 ,587, issued January 25, 1996 to Rense; U.S. Patent Number 5,047,175, issued to Forsberg on September 10, 1991 ; and World Patent Publication Number WO 87/03613, published by Forsberg on June 18, 1987. These publications are all incorporated by reference herein.

Still other materials useful as the emulsifier, particularly as a co-emulsifier with a high viscosity primary emulsifier, are ABA block copolymers of 12- hydroxystearic acid and polyethylene oxide. Such materials are described in U.S. Patent 4,875,927, issued to T. Tadros on October 24, 1989, which is incorporated by reference herein. A representative material of this class useful as an emulsifier herein is available from Imperial Chemical Industries PLC as Arlacel P135. While all the above-described materials may be used as a single emulsifier, it may be desired to employ more than one emulsifier when forming the emulsion. In particular, where a high viscosity emulsifier is used, a certain "tacky" feel may result when the treated article is subjected to in-use shear pressures that break the emulsion. In this case, it may be desirable to use a relatively lower viscosity co-emulsifier with the primary emulsifier, to allow use of a lower amount of the main emulsifier, thereby alleviating tackiness. In one preferred embodiment of the present invention, a primary emulsifier available from Lubrizol (i.e., reaction product of polyisobutylene-substituted succinic acid and an amine) and a secondary emulsifier that is an ABA block copolymer of poly-12-hydroxystearic acid and polyethylene oxide (e.g., ICI's Arlacel P135) are used to provide an emulsion with improved water retention levels over time, as well as beneficial reduced tackiness (via reduction in level of primary emulsifier). The skilled artisan will recognize that different desired end-uses will dictate whether multiple emulsifiers are appropriate, and the appropriate relative amounts of each if appropriate. Such a determination will require only routine experimentation by the skilled artisan in view of the present disclosure.

4. Optional Emulsion Components

The high internal phase inverse emulsions of the present invention can also comprise other optional components typically present in moisture containing solutions of this type. These optional components can be present in either the continuous lipid phase or the internal polar phase and include perfumes, antimicrobial (e.g., antibacterial) actives, pharmaceutical actives, deodorants, opacifiers, astringents, skin moisturizers, and the like, as well as mixtures of these components. All of these materials are well known in the art as additives for such formulations and can be employed in effective, appropriate amounts in the emulsions of the present invention. A particularly preferred optional component that is included in the emulsions of wet-like cleansing wipes according to the present invention is glycerin as a skin conditioning agent.

The emulsion component of the articles of the present invention is described and claimed herein in terms of components, and corresponding amounts of the components, that are present after emulsion formation. That is, when the stable emulsion is formed and applied to the carrier. It is understood that the description (components and amounts) of the emulsion also encompasses emulsions formed by combining the described components and levels, regardless of the chemical identity of the components after emulsification and application to the carrier.

C. Other Optional Article Components

Besides the high internal phase inverse emulsion, there are other optional components that can be included in the articles of the present invention, typically for the purpose of improving the cleaning performance of the article when the internal polar phase of the emulsion is released. Certain of these optional components cannot be present in the emulsion at significant levels (e.g., greater than 2% of the internal phase) because they can cause premature disruption of the emulsion. These include various anionic detergent surfactants that have relatively high HLB values (e.g., HLBs of from about 10 to about 25), such as sodium linear alkylbenzene sulfonates (LAS) or alkyl ethoxy sulfates (AES), as well as nonionic detergent surfactants such as alkyl ethoxylates, alkyl amine oxides, alkyl polyglycosides, zwitterionic detergent surfactants, ampholytic detergent surfactants, and cationic detergent surfactants such as cetyl trimethyl ammonium salts, and lauryl trimethyl ammonium salts. See U.S. Patent 4,597,898 (Vander Meer), issued July 1 , 1986 (herein incorporated by reference), especially columns 12 through 16 for representative anionic, nonionic, zwitterionic, ampholytic and cationic detergent surfactants. Instead, these high HLB detergent surfactants can be applied or included in the article separately from the emulsion. For example, an aqueous solution of these high HLB detergent surfactants can be applied to the carrier either before or after application of the emulsion to the carrier. During wiping, the emulsion is disrupted, releasing the polar phase components so that they can then be combined with the high HLB detergent surfactant to provide improved hard suiface cleaning.

Though the description of the invention generally relates to applying a single water-in-lipid emulsion to the carrier, it is recognized that two or more different emulsions may be utilized in preparing a single article. In such embodiments, the emulsions may differ in a variety of ways, including but not limited to, the ratio of the internal polar phase and the external lipid phase, the emulsifiers used, the components used for either or both of the internal and lipid phases, and the like. Utilization of multiple emulsions in one article may be particularly desirable when two or more components are incompatible with each other, but can each be included in a separate emulsion. Alternatively, if a particular reaction is desired at the time of use, the reactants can be provided in separate emulsions. Upon shearing of the emulsions during use, the desired reaction will occur. For example, where foaming is desired during the wiping processes, a mild acid can be incorporated in the internal polar phase of one emulsion, while bicarbonate is incorporated in the internal polar phase of a second emulsion. Upon shearing of the emulsions during use, the reactants interact to provide the desired foam.

Suitable emulsion descriptions are also found in the aforementioned commonly assigned World Patent Applications WO 96/14835, published May 23, 1996, in the names of Mackey et al.; and WO 96/21505, published July 18, 1996, in the name of DesMarais, incorporated herein by reference.

The Pattern

As noted above, the emulsion is preferably applied to the substrate in a discontinuous pattern. As noted above, a discontinuous pattern is one in which the emulsion has distinct regions separated by regions of the substrate which are free of the emulsion. Suitable discontinuous patterns comprise discrete island regions of the emulsion, essentially continuous networks of emulsion, discrete macropattems of the emulsion, and, preferably, discrete stripes of the emulsion disposed in a semi-continuous pattern. The stripes are preferably continuous, as illustrated, but may, alternatively, comprise a pattern of discrete segments which collectively comprise a stripe. If stripes are selected, the stripes are preferably oriented in the machine direction, for ease of manufacture.

The emulsion may be applied to and disposed on the substrate by any suitable means well known in the art, such as gravure printing, flexographic printing, spraying, and preferably extruding. More preferably, the emulsion is extruded as a series of continuous cylindrically shaped beads. A continuous cylindrical shape is preferred for the emulsion because this shape reduces the suiface area to volume ratio of the emulsion.

The stripes may be straight, as shown, may be sinusoidally shaped, etc. If sinusoidally shaped stripes are selected, preferably the stripes are in phase, so that parallelism is maintained and each stripe remains equally spaced from the adjacent stripes.

It is desired that the emulsion have the minimum possible surface area to volume ratio. Minimizing the surface area to volume ratio reduces water loss from the emulsion due to evaporation. Preferably the emulsion has a surface area to volume ratio of less than or equal to 4/unit length, more preferably less than or equal to 3/unit length, and most preferably less than or equal to 2/unit length, wherein the unit length is measured in the cross section of the emulsion. Suitable surface area to volume ratios for cylindrical beads of emulsion range from 40 to 200 inches^ and preferably 75 to 125 inches^-1. However, the optimum results are not achieved, for example, by presenting a single, unitary sphere of emulsion to the user with the wipe. Such an arrangement would likely provide adequate water. However, the water distribution would be highly localized and may not adequately spread throughout the suiface area of the wipe. Preferably, the distribution of the emulsion, or, more particularly, the water released therefrom, approximates the perception of a water spray onto the skin.

It will be apparent to one skilled in the art that as the basis weight and absorbency of the substrate increase, the amount of water necessary to locally saturate the substrate will likewise increase. Therefore, as the basis weight and/or absorbency of the substrate increases, the amount of emulsion applied to the substrate should increase proportionately. Preferably, 5 to 35 percent, and more preferably 10 to 25 percent of the surface area of the wipe has emulsion disposed thereon. Upon rupture, the emulsion locally wets corresponding regions of the substrate. The wetted portion of the substrate may range from 10 to 90 percent of the surface area of the substrate, with, of course, the balance of the surface area of the substrate remaining dry due to the discontinuous pattern.

It will be apparent that in use the percentage of wetted surface area will be greater than the percentage of surface area initially coated by the emulsion. It is to be further understood that, of course, the entire wipe may be wetted as a function of the time and/or use of the wipe.

Thus, beads of emulsion are preferably applied to the substrate in an arrangement that accommodates both the diameter and pitch of the beads in a preferred geometry. The amount of water carried by the emulsion increases according to the square of the diameter of the beads. Therefore, as the diameter of the beads increases, the pitch between adjacent stripes of emulsion should likewise increase. Suitable pitches between adjacent beads of emulsion range from 0.030 to 1.500 inches, and preferably from 0.175 to 0.375 inches.

If the emulsion is to be directly exposed to the surface, i.e., disposed on the outside of the substrate as the wipe is presented to the user, the emulsion preferably comprises a level at least 25 percent, more preferably at least 50 percent, and most preferably at least 75 percent of that of the basis weight of the substrate. Alternatively, if the emulsion is disposed between two-plies of substrate in a laminate construction, for tissue applications, preferably the emulsion comprises at least 150 percent, more preferably at least 200 percent, and most preferably at least 250 percent of the combined basis weight of the two plies. In such a laminate construction for hard surface cleaning applications, preferably the emulsion comprises at least 500 percent, more preferably at least 650 percent, and most preferably at least 800 percent of the combined basis weight of the two plies.

It is to be noted that the basis weights described herein refer to the overall basis weight of the substrate, as an average of the various different basis weight regions contained within the substrate. The basis weight of the substrate may be measured according to ASTM Test Method D3776-9, which test method is incorporated herein by reference, with results reported in pounds per 3,000 square feet. The emulsion weight is gravimetrically measured once the basis weight of the substrate is known, as the tare. If desired, the regions of the substrate free of the emulsion may be slightly wider in the cross machine direction at the edges of the wipe than the corresponding regions disposed at the interior of the wipe. This arrangement accommodates processing and slitting of a wide, multi-roll position web of the wipe into narrower discrete units for transport and sale to the consumer. It will be apparent to one skilled in the art that the regions free of the substrate may form a border at the other edges of the wipe as well. Such a geometry can easily be accomplished by not applying the emulsion continuously. Instead, the emulsion may be intermittently applied in the machine direction. The substrate is then cut or perforated in the cross machine direction coincident the regions free of the emulsion in order to yield discrete or separable wipes.

The emulsion may define decorative indicia such as macropatterns. The macropattems may be used above, as shown, or may be superimposed on the discontinuous stripe pattern of emulsion. Macropatterns of emulsion provide the advantage that locally heavier loadings of water can be applied from a pattern that provides an aethetically pleasing visual cue to the user of where the emulsion is present. Macropatterns of emulsion may form decorative indicia. Such decorative indicia may be provided in the form of flowers, butterflies, clouds, tradenames, advertising, or any other planar pattern envisioned by the user.

In a preferred embodiment, the substrate comprises a multi-basis weight tissue. A multi-basis weight substrate may be made according to the aforementioned patents describing the same and incorporated by reference hereinabove. A multi-basis weight substrate provides the advantage that excess water will more easily saturate the low basis weight regions and, therefore, be more readily applied to the suiface. Preferably the multi-basis weight substrate comprises an essentially continuous high basis weight network region with discrete low basis weight regions distributed throughout the essentially continuous network.

Alternatively, a substrate having a semi-continuous pattern of high and low basis weight regions may be selected. In yet a less preferred embodiment, a substrate having an essentially continuous network of low basis weight regions with discrete high basis weight regions distributed therein may be utilized, provided, however, one is willing to accept the strength tradeoff inherent in such a substrate. Such a substrate, prophetically, provides the benefit that the essentially continuous pattern of low basis weight regions will more readily allow water expressed from the emulsion to penetrate the substrate and be transferred to the suiface.

If a substrate having an essentially continuous high basis weight region is selected, preferably the pitch of the discrete low basis weight regions is less than the pitch between adjacent stripes of the emulsion. This relative difference in pitches assures that the emulsion will intercept the low basis weight regions and be more readily transmitted therethrough, as described above.

For the embodiments described herein for tissue applications, a substrate having a basis weight of 7 to 10 pounds per 3,000 square feet per ply and 50 to 300, and more preferably 100 to 200 discrete low basis weight regions per square inch is suitable. For hard surface cleaning applications, a substrate having a basis weight of 20 pounds per 3,000 square feet and 100 to 200 discrete low basis weight regions per square inch is suitable. In a preferred embodiment, the wipe may be made according to commonly assigned U.S. Application entitled "Cleaning Articles Comprising a Cellulosic Fibrous Structure Having Discrete Basis Weight Regions Treated with A High Internal Phase Inverse Emulsion" filed July 1 , 1997, in the names of Nicholas J. Nissing et al., the disclosure of which patent is incorporated herein by reference. If a substrate having a semi-continuous basis weight pattern is selected, such a substrate may be made according to commonly assigned U.S. Pat. No. 5,628,876, issued May 13, 1997 to Ayers et al., and incorporated herein by reference. Preferably, the semi-continuous pattern is oriented in the machine direction. If such a geometry is selected, prophetically, the beads of emulsion may be applied to the semi-continuous patterned substrate such that the emulsion is juxtaposed with, and preferably coincident, the low basis weight regions of the substrate. This arrangement provides the advantage, discussed above, that the water expressed from the emulsion is more readily transmitted through the low basis weight regions of the semi-continuous patterned substrate. The low basis weight regions of the semi-continuous pattern, if parallel to the machine direction, may be disposed on a pitch less than or equal to the stripes of the emulsion.

It will be apparent to one skilled in the art that many variations are feasible and within the scope of the claimed invention. For example, a laminate construction comprising emulsion disposed between two plies of substrate may be made as described above. It is not necessary, however, that the plies be identical. One ply may be a nonwoven for strength. The other ply may be a tissue to provide for transmission of the water to the suiface. If desired, the nonwoven ply may be treated to render it hydrophobic and thereby ensure that the water released from the emulsion is transferred to the surface via the tissue ply. Alternatively, a laminate comprising two tissue plies may be selected. One of the plies may have a multi-basis weight region pattern described above. The multi-basis weight region may comprise a semi-continuous pattern. The other ply may comprise a single basis weight region for strength. This embodiment provides for greater transmission of water through one of the plies than through the other ply. Alternatively, the multi-basis weight region ply may comprise an essentially continuous network of high basis weight regions with discrete low basis weight regions distributed therein.

In yet another embodiment, a laminate having a plurality of several laminae may be provided. The laminae may comprise alternating plies of substrate and emulsion. Such a laminate may have two outwardly facing substrate laminae as described above. The emulsion may be wholly contained within the laminate. Alternatively, emulsion may be disposed on one exposed surface of such a laminate.

In yet another embodiment stripes of emulsion may be comprised of discrete spheres of emulsion. The discrete spheres of emulsion are juxtaposed to collectively form the discontinuous pattern. This arrangement provides the advantage of a suitable surface area to volume ratio, similar to the generally cylindrically shaped beads described above. One of ordinary skill will understand that discrete spheres of emulsion may be juxtaposed to form any discontinuous pattern desired.

Yet another variation, but applicable to any of the foregoing embodiments, is to vary the amount of the emulsion within the discontinuous pattern. For example, certain stripes of emulsion may have relatively more emulsion than other stripes. This arrangement allows for locally heavier loading of the water onto the surface to be cleaned, but yet still provides relatively drier edges to minimize the amount of residual water left on the suiface. It will be apparent that, depending upon the desired application, the wipes may be provided as discrete units, may be joined in seriatum by perforations, etc. The wipes may be individually dispensed , such as is commonly done for facial tissues. If individual dispensing is desired, the wipes may be provided in either a reach-in or pop up dispenser, as disclosed in commonly assigned U.S. Pats. 4,623,074 issued Nov. 8, 1986 to Dearwester; 5,520,308 issued May 28, 1996 to Berg. Jr. et al. and 5,516,001 issued May 14, 1996 to Muckenfuhs et al., the disclosures of which are incorporated herein by reference. Alternatively, the wipes may be core-wound, as disclosed in commonly assigned U.S. Pat. No. 5,318,235, issued June 7, 1994 to Sato, the disclosure of which is incorporated herein by reference. If desired, the wipes may be lightly compressed for packaging, provided care is taken not to rupture the emulsion. Such packaging may be accomplished as disclosed in commonly assigned U.S. Patent 5,664,897, issued July 8, 1997 to Young et al., the disclosure of which is incorporated herein by reference.

Claims

WHAT IS CLAIMED IS:

1. An inverse phase emulsion having a preservative system characterized in that said emulsion has an evaporative water loss not more than 120% of the evaporative water loss of a like internal phase emulsion without said preservative system.

2. An inverse phase emulsion according to Claim 1 having a water loss not more than 115% of the evaporative water loss of a like internal phase emulsion without said preservative system.

3. An inverse phase emulsion according to Claim 2 having a water loss not more than 110% of the evaporative water loss of a like internal phase emulsion without said preservative system.

4. An inverse phase emulsion comprising a preservative system, said preservative system having at least one component with a water solubility greater than 0.03 grams per gram of deionized water, characterized in that said preservative system has no component with a water solubility less than 0.03 grams per gram of deionized water.

5. An inverse phase emulsion comprising a preservative system, said preservative system having a plurality of components, characterized in that each component has a water solubility greater than 0.03 grams per gram of deionized water.

6. An inverse phase emulsion according to any of the foregoing claims and having a preservative system with at least one component, said component having a water solubility greater than 0.1 grams per gram of deionized water.

7. An inverse phase emulsion according to Claim 6 having a water solubility greater than 0.5 grams per gram of deionized water.

8. An inverse phase emulsion according to any of the foregoing claims having a pH of less than 5.5.

9. An inverse phase emulsion according to any of the foregoing claims wherein said preservative system comprises one or more components selected from the group consisting of sodium hydroxy methyl glycinate, formaldehyde releasers, imidazolidinyl urea, diazolidinyl urea, 2-Bromo-2- nitropropane-1 3-diol, sodium sorbate and combinations thereof.

10. An inverse phase emulsion according to any of the foregoing claims wherein said emulsion is disposed on a substrate, said substrate preferably comprising a nonwoven material.