US 3491495 A
Description (OCR text may contain errors)
Jan. 27, 1970 L. M. PRlNCE 3,491
' CLEANING TOWEL Original Filed Oct. 15, 1964 ABRASIVE PARTICLES I2 -----PAPER 10 VENTOR. LE M. PRINCE his ATTORNEYS United States Patent Office 3,491,495 Patented Jan. 27, 1970 3,491,495 CLEANING TOWEL Leon M. Prince, Westfield, N.J., assignor to Lever Brothers Company, New York, N.Y., a corporation of Maine Continuation of application Ser. No. 404,050, Oct. 15, 1964. This application Sept. 20, 1968, Ser. No. 768,597 Int. Cl. B24d 11/00; 1524b 1/00 U.S. Cl. 51-394 9 Claims ABSTRACT OF THE DISCLOSURE A cleaning towel comprising a highly absorbent substrate coated with a dry cleaning composition which includes a binder, a porous low bulk density cleaning powder and a high bulk density carrier powder in pro portions of from about one part to about six parts by weight carrier powder to about one part by weight cleaning powder. Substantially all of the particles have particle sizes less than about 40 microns and at least 40% by weight have particle sizes greater than about 10 microns. The cleaning towels are particularly well suited for cleaning glass surfaces and are preferably used by first wetting the glass and then rubbing the wetted surface with the cleaning towel.
This application is a continuation of conending application Ser. No. 404,050, filed Oct. 15, 1964, which is now abandoned.
This invention relates to cleaning towels and, more particularly, to novel and improved cleaning towels particularly adapted for cleaning glass or similar surfaces by first moistening the glass with water and then Wiping the wetted surface with the cleaning towel.
Cleaning glass surfaces, such as windows and mirrors, as well as other surfaces, has always been a distasteful and difiicult task. In recent years a number of products have been developed for reducing the time and effort involved and for providing improved cleaning. Among them are specifically formulated liquid or semi-liquid cleaners which are sprayed or wiped on the glass surface and then removed with a cloth or paper towel. These products have the disadvantage of being susceptible of spilling and leaving stains on carpets or furniture. In addition, some types of liquid cleaners must be allowed to dry on the glass surface before being wiped away, thus slowing down the cleaning job considerably.
Another suggested form of glass cleaning device is a paper substrate coated with a dry or wet cleaning composition. Such cleaning papers have the advantage of being more convenient to use, inasmuch as they are used alone or require only water to wet the surface before use.
All of the various known glass cleaners have one or more properties or characteristics rendering them somewhat ineifective or inconvenient. For example, some of the liquid products are first dried on the surface and then wiped off. The cleaner comes oif as a dust, some of which inevitably falls onto the Window sill, floor or furniture, for example, thereby necessitating separate cleaning up of the dust from the environs of the glass cleaning operation. This is also the case with previously suggested forms of dry-coated cleaning papers, which leave dust on the glass surface, on objects in the area of the cleaning and on the users person and clothes.
Another difliculty with some types of known glass cleaners is that they leave streaks or lint on the glass surface, thereby necessitating extra wiping, such as with a moistened, lint-free cloth or a chamois to do a thorough job. Additionally, some of the cleaners leave an oily film which tends to collect dust. Others leave a water-resistant film which makes it difiicult to remoisten the glass when it is cleaned again, or in the case of car Windshields, forms vision distorting beads of water, even when the wipers are operated.
These and other disadvantages of present forms of glass cleaners are overcome, in accordance with the invention, by providing a novel and improved cleaning towel comprising an absorbent web, such as a suitable paper or cloth of natural or synthetic material, coated with a cleaning composition including porous, low bulk density cleaning powders, which provide optimum cleaning characteristics, and high bulk density carrier powders, which have good coating properties and facilitate application of the cleaning composition to the web. The powders are adhered to the webs by a binder in an amount sufficient to furnish a good bond without excessively reducing the absorbency of the web or inhibiting the cleaning properties of the powders. The cleaning towel may also include a surfactant to complement the abrading action of the powders in cleaning the surface.
The cleaning composition is preferably coated onto the web in the form of an aqueous slurry. Substances which may be included in the slurry to facilitate forming a uniform coating having the desired coating properties are, for example, a dispersant to deflocculate the cleaning and carrier powders, and a thickener. It is also desirable from a commercial standpoint to include a colorant and an odorant in the coating composition.
The cleaning towel, in accordance with the invention, has, among its advantages, a highly effective cleaning action and a relatively insignificant tendency to dust or lint. It is in completely dried form and requires only plain water, which is applied to the glass, for its use. Accordin gly, there is no danger of staining carpets and upholstery as when the liquid type cleaners are spilled. Further, the coating paper leaves no oily, dust-catching film, depositing instead a beneficial water-wettable film, which facilitates wetting the glass the next time it is cleaned. The cleaning towels can be made at low cost, sold at a very modest price and are, of course, disposable.
In use, the user simply wets the glass or other surface with water and then wipes the water and soil from the glass with the cleaning towel. The principal cleaning of the glass is accomplished by the abrasive action of the powders rather than by a chemical action. The dirt which is abraded from the surface is absorbed together with the water into the absorbent paper, the surfactant aiding the removal of dirt particles and oil film and absorption into and adsorption onto the towel.
In conjunction with the following detailed description of exemplary embodiments of the cleaning towel, reference may be made to the figures of the accompanying drawing, in which:
FIGURE 1 is a view in cross-section on a greatly enlarged scale of a small piece of cleaning towel; and
FIG. 2 is a schematic diagram of a method of making the cleaning towel.
Referring to FIG. 1, the cleaning towel comprises a highly absorbent web 10, preferably paper or other low cost material, having abrasive particles 12 adhered to it by a binder. Microscopic examination indicates that the particles of powder are adhered to the surface fibers of the paper, there being just enough binder to make the powder stick. There is no discrete layer of binder, and
under the microscope, the surface of the paper is quite rough, consisting of holes and loosely interlocked fibers.
surfaces, thereby being placed in direct contact with the surfaces to be cleaned when the paper is used.
The desirable properties of a cleaning towel, in accordance with the invention, are obtained by a careful selection of both the absorbent web and the constituents of the coating composition. Additionally, the process of making the cleaning towels should be carefully controlled, in order to obtain an optimum finished product.
As previously stated, the cleaning ability of the cleaning towels appears to be principally a result of the physical properties rather than the chemical composition of the cleaning composition. Accordingly, the size, hardness, density and geometric form of the abrasive particles are important. First of all, it has been determined that, preferably, at least 40% by weight of the particles should be in the to 40' micron size range, inasmuch as particles smaller than 10 microns do not provide very significant abrasive action. Particles greater than 40 microns may scratch the glass surface being cleaned, although particles having smooth rounded edges, such as those ground in a ball mill or those of certain materials, may be somewhat larger without harming the glass. Further, particles of relatively low hardness, say less than 3 Moh hardness generally are too soft to effectively abrade dirt from the surface of the glass. Particles harder than glass can scratch glass and thus are to be avoided, unless they are free of sharp edges. The particulate materials used for the cleaning towels are, of course, water insoluble.
It has been found that particulate materials having the above characteristics are usually of low bulk density and high porosity. The preferred low bulk density materials are suitably prepared diatomaceous earths and the pumices, the diatomaceous earths being sintered at high tem-v peratures to increase their hardness, and both, of course, being ground to the proper particle size range, as described above. Sand, insoluble phosphates and carbonates, ground glass, garnet, emery, silicon dioxide and tripoli powders have also been found to be suitable as cleaning powders. It is believed that such low bulk density powders act as cleaners by (1) abrading the soil from the glass and (2) absorbing the loosened soil onto their surfaces which are of relatively large area. However, low bulk density powders generally possess poor coating properties, that is, they tend to dry up a coating slurry prematurely, thereby causing a build-up of powder on the surface of the paper which subsequently results in dusting.
Accordingly, the low bulk density cleaning powders constitute only a portion of the abrasive particles in the cleaning paper. The balance of the abrasive particles in the coating composition are relatively high bulk density materials which possess good coating properties, for example, feldspars or feldspathoids, inasmuch as they are relatively non-porous and non-absorbent and therefore do not dry out the coating slurry. While the high bulk density powders, of course, provide a degree of cleaning action, they serve generally as carriers for the low bulk density powders. Accordingly, they may best be termed carrier powders, whereas the porous, low bulk density particles may be termed cleaning powders. Generally, the proportions of the cleaning powders to the carrier powders should be between 1 to 6 and 1 to 1 by weight. A greater proportion of cleaning powders tends to adversely affect the coating properties, whereas a lower proportion tends to excessively reduce the cleaning power of the cleaning towels.
Of equal importance in the cleaning towels is the web to which the cleaning composition is adhered. Because the cleaning action is, it is thought, principally a result of physical rather than chemical action, and more particularly, a result of abrasion, absorption and adsorption, the web should have high absorbency and a relatively smooth surface. Embossed or highly creped paper gives generally unsatisfactory results, since only a relatively small part of the surface area of the paper and coating actually contacts the surface being cleaned.- However, a
4 number of desirable properties for the cleaning paper are present in slightly creped or semi-creped paper. Satisfactory grades are bleached, semi-creped, medium wetstrength, lint-free stock in the 25 to 60 pound basis weight range.
Set forth in the table below are the specifications of a paper found to provide excellent results in the cleaning towel. Particularly noteworthy are the high absorption properties and wet strength of this paper stock.
TABLE Basis weight, lbs., 24 x 36/500 33.25 Mullen, pts. 7.2 Caliper, in 0.009 Absorption,-secs. 0.1 cc. water 3 Total absorption, water, percent 193.5 Tensile, dry, oz.machine direction 75.5 Tensile, wet, oz.machine direction 32.5 Stretch, percent 9.4
A number of binders to adhere the abrasive particles to the paper substrate have been found to be suitable. Among them are proteins, starches, natural and synthetic gums, cellulose, rubber latexes, vinyl acetate latexes and acrylic polymer latexes. Inasmuch as the coating is applied to the paper in the form of a slurry, water soluble or water dispersible binders are preferred, in view of their relative ease of processing and handling, but they should have a low tendency to redissolve, which can often be provided by cross-linking or denaturation. The binder in the composition is present in a minimal amount sufiicient to provide good binding, to sinter the particles together, and thus to provide a minimum of dusting of the powders and yet to prevent excessively reducing the absorbency of the cleaning paper. Only a small fraction of the surface areas of the particles in the composition are coated with the binder. It should be noted that the presence of the carrier powders enables a significant reduction in the amount of binder necessary to obtain good adherence of the abrasive materials over the amount that would be required if only the cleaning powders were used. Therefore, the absorbency of the finished paper is substantially higher.
Soft acrylic copolymer latexes, particularly Rhoplex B-5 (Rohm and Haas), a copolymer of ethyl acrylate and methylmethacrylate with a small percentage of either methacrylic acid or acrylic acid to supply pendant carboxyl groups, provide excellent binding power and do not significantly effect the flexibility and handle of the paper or excessively reduce its absorbency. Additionally, these binders have a low rewetting tendency, thereby limiting the extent to which the binder redissolves and reforms a slurry with the powders when the cleaning towels are used. Therefore, the abrasive particles remain bound to the web for a longer period during use and provide improved abrasive action. The optimum content of Rhoplex B-5 (46% solids content) in the coating slurry is from about 2.6% to about 3.0% by weight of the slurry.
The addition of a plasticizer to polymeric binders may improve the application versatility of the slurry formula by aiding in the wetting of the powders and the fibers of the paper by the binder. For example, about 3% tributoxyethyl phosphate added to the acrylic latex improves the bond, and the finished cleaning paper has a lower tendency to dust and a faster absorbency time.
The amount of abrasive material in the cleaning towels is, of course, a significant factor in determining their properties and characteristics. An unduly larger amount of powder requires a larger amount of binder, and the powder and binder together may reduce the cleaning power by lowering the absorbency of the Web. Further, excessive powder may cause dusting. On the other hand, too little powder provides poor cleaning. It has been found that the best results are obtained with a coating of about 10% to 35% by weight.
As described hereinafter, the preferred method of making the cleaning towels is by forming a slurry of the coating composition which is then coated onto the substrate by roller coating or by immersion of the web in the slurry. In order to obtain a proper level of coating, that is, the proper pick-upof solids in the slurry onto the finished towels, it is necessary to control the rheological behavior of the slurry. Therefore, a thickener is preferably added to improve the flow properties so that a uniform coating and impregnation of the paper substrate is obtained. Additionally, thickeners inhibit the settling of the suspended powders in the slurry. A number of thickeners, some of which also may serve 'as binders, are suitable, for example, natural orv synthetic gums and cellulosic materials. Hydroxyethylcellulose has several desirable properties as a thickener for the coating slurry, such as not requiring special handling techniques, and its ability to be dispersed in water by normal agitation at room temperature. It can be mixed in powdered form with the abrasive powders. p
Another slurry additive which enhances even coating of the cleaning composition onto the paper substrate is a dispersant to assist the retaining of the .solids in suspension and also to defiocculate the cleaning and carrier powders. For example, atrace of tetrasodium. pyro phosphate provides improved coating properties in the slurry.
It is also desirable to include a surfactant in the cleaning composition coated onto the paper. A small amount of a surfactant causes a transitory foam to develop. on the wetted glass surface which aids in the absorption. of water and soil onto the cleaning paper. It also appears that some surfactants, particularly sodium lauryl sulfate, leave a film on the glass surface which inhibits the spreading of oily soil, an important type of glass-soiling substance carried in the air, on the glass. Further, sodium lauryl sulfate renders the glass more wettable by water; that is, water tends to spread more readily on glass having an adsorbed film of sodium lauryl sulfate. The optimum level of surfactant in the cleaningcomposition on the cleaning paper is an amount which provides a relatively slight transitory foam on the wetted glass. At low levels there is little effect on absorbency of the cleaning paper, -while at high levels the foaming action may be excessive, thereby inhibiting the pick-up of the water and soil from the glass, making it difficult to remove the foam itself, and tending to leave streaks. I
The commercial attractiveness of the cleaning paper may be enhanced by the addition of a suitable colorant and odorant to the coating slurry. 1
As previously stated, the preferred method of making the cleaning paper is to form an aqueous slurry of the cleaning composition and coat it onto the paper substrate. Referring to FIG. 2 of the drawings, the paper stock in roll form is fed from a supply roll 20* through a coating bath 22 containing the slurry. The excess slurry is then removed from the paper web by squeeze rolls 24. The coated paper is then dried, such as by passing it around a series of heated rolls 26. It is desirable to remove marginally bound and unbound abrasive powders from the paper, such as by brushing it with soft brushes or by passing it through a pair of soft polymeric foam sponges 28. With some types of stiff papers, brushing tendsto improve the drape and handle of the cleaning paper as well as remove the loosely bound powder. The cleaning paper can then be cut into convenient sized sheets or perforated at intervals so that sheets can be torn from a roll by the user.
In the method there are several variables which are adjusted to provide the desired pick-up of cleaning composition onto the paper substrate. The important ones are the composition and coating properties of the slurry and the pressure of the squeeze rolls. Those skilled in the coating art can readily provide the optimum conditions in the method to obtain the desired pick-up.
In use, the glass or other surface to be cleaned is first moistened by spraying or wiping water onto it, and the wetted surface is then rubbed with a cleaning paper, which simultaneously abrades the soil from the surface and absorbs the soil and the water. When one side of the sheet becomes soiled, the sheet may be turned over and the other side used, and when it becomes saturated or completely soiled, it may thrown away.
Representative compositions for the cleaning paper, and an exemplary method of making the paper, in accordance with the invention, are set forth below.
The water was placed in a mixing vessel and the tetrasodium pyrophosphate added under vigorous agitation. The thickener, cleaning powder and carrier powder were then added rapidly to the liquid, also with agitation. When a homogeneous dispersion was obtained, the agitation was reduced and the surfactant solution and other ingerdients added in the order set forth.
A continuous roll of the paper substrate was passed through a bath of the slurry and the excess slurry squeezed from theweb by passing it between rollers. After the coated paper was dried, the surfaces were brushed with a soft sponge to remove the marginally adhered powders. The cleaning paper was then cut into sheets.
EXAMPLE II A coating composition was prepared according to the formula set forth in Example I except that a polyvinyl chloride latex plasticized with dibutyl phthalate was substituted, at the same concentration, for the plasticized Rhoplex B-5 binder. The composition was applied to a paper substrate in the same manner as in Example I and produced a comparable product.
EXAMPLE HI Ingredients: Parts by weight Water, tap 60.18 Carbopol 934 1% solution 15.00 Obsidian pumice (Celite Z-6) (cleaning powder) 8.00 Nepheline syenite, peak grade (carrier powder) 8.00 Sodium lauryl sulfate, 10% solution (surfactant) 2.00 Rhoplex B-S (binder) 2.80 Colorant 10% solution 4.00 Odorant 0.02
EXAMPLE IV Ingredients: Parts by Weight Water, tap 83.03 Tetrasodium pyrophosphate (dispersant) 0.03 Hydroxyethylcellulose (thickener) 0.32 Flux calcined diatomite (Hyfio Super Cel) (cleaning powder) 1.20 Feldspar (Clinchfield 202) (carrier powder) 7.20 Sodium lauryl sulfate, 10% solution (surfactant 3.00 Rhoplex B-5, 3% plasticizer (binder) 2.00
7 Ingredients: Parts by weight Colorant, l% solution 3.20 Odorant 0.02
The coating compositions of both Examples III and IV were prepared and applied to paper webs in the same way as those of Examples I and II.
Samples of the cleaning papers were distributed to a group of housewives who used them for cleaning windows and mirrors. They were found by most users to be convenient and easy to use, to leave no lint or dust, to be effective cleaners, and to leave no streaks or film. Laboratory tests confirmed these results.
Many modifications and variations of the invention as specifically described herein will occur to those skilled in the art. Such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
1. A cleaning towel comprising a highly absorbent web coated with a dry cleaning composition including a binder, a relatively'porous and absorbent low bulk density cleaning powder and a relatively non-porous and non-absorbent high bulk density carrier powder, the carrier powder being present in an amount suflicient to inhibit the tendency of the cleaning powder to dry out a coating slurry of the cleaning powder and carrier powder in a liquid vehicle and substantially all of the powders having particle sizes less than about 40 microns and at least 40% by weight having particle sizes greater than about microns.
2. A cleaning towel as claimed in claim 1, wherein there are from about 1 part to about 6 parts by weight carrier powder to 1 part by weight cleaning powder.
3. A cleaning towel as claimed in claim 1 wherein the carrier powder is a member selected from the group consisting of feldspathoids and feldspars.
4. A cleaning towel as claimed in claim 1 wherein the cleaning powder is a member selected from the group consisting of diatc-maceous earths and pumices.
5. A cleaning towel comprising (a) a highly absorbent web and (b) a cleaning composition coated onto the web, the
cleaning composition including (i) a cleaning powder selected from the group consisting of diatomaceous earths and pumices, (ii) a carrier powder selected from th group consisting of feldspathoids and feldspars, the
ratio by weight of carrier powder 'to cleaning powder being in the range of from about 1:1 to about 6: 1, (iii) a dispersant in an amount sufficient to deflocculate the powders,
(iv) a binder in an amount sufiicient to sinter the powders to the web without excessively reducing the absorbency thereof, and
(v) a surfactant in an amount sufiicient to provide a slight transient foaming of the dried cleaning composition when it is rewet in use.
6. A cleaning paper comprising (a) a highly absorbent paper substrate and (b) about 10% to about 35% by weight cleaning composition coated onto the substrate, the cleaning composition including (i) an obsidian pumice cleaning powder,
(ii) a feldspathoid carried powder, the ratio by weight of carrier powder to cleaning powder being in the range of from about 1:1 to about 6:1,
(iii) a dispersant in an amount sufficient to deflocculate the powders,
(iv) a plasticized acrylic polymer latex binder in an amount sufiicient to sinter the cleaning and carrier powders to the paper substrate without excessively reducing the absorbency of the substrate.
(v) a small amount of thickener, and
(vi)- a small amount of sodium lauryl sulfate to provide slight transient foaming of the cleaning position when it is rewet in use.
7. A cleaning paper as claimed in claim 6, wherein the carrier powder is nepheline syenite.
8. A cleaning composition for coating onto a web of absorbent material, comprising a relatively porous and absorbent low bulk density cleaning powder and a relatively non-porous and non-absorbent high bulk density carrier powder, the carrier powder being present in an amount sufficient to inhibit the tendency of the cleaning powder to dry out coating slurry which includes the cleaning powderand carrier powder in a liquid vehicle and in particular the ratio by weight of the carrier powder to the cleaning powder being in the range of from about 1:1 to about 6:1, and a binder in an amount of sulficient to sinter the powder to the web of material without excessively reducing the absorbency of the web of absorbent material.
9. A cleaning composition for coating a paper substrate, comprising (i) a cleaning powder selected from the group consisting of diatomaceous earths and pumices,
(ii) a carrier powder selected from the group consisting of feldspathoids and feldspars, the ratio by weight of carrier powder to cleaning powder being in the range of from about 1:1 to about 6:1,
(iii) a dispersant in an amount sufiicient to deflocculate the powders,
(iv) a binder in an amount suflicient to adhere the powders to the paper substrate without excessively reducing the absorbency thereof, and
(v) a surfactant in an amount sufficient to provide a slight transient foaming of the dried cleaning composition when it is rewet in use.
References Cited UNITED STATES PATENTS 1,868,862 7/ 1932 Washburn 252-91 1,969,900 8/1934 Pickett 25291 2,395,054 2/1946 Levine 5 l400 2,627,145 2/ 1953* Frigstad -1 5 l396 2,665,528 1/ 1954 Sternfield 5 l-402 3,121,249 2/ 1964 Afileck 15506 3,121,249 2/1964 Aflleck l5506 OTHELL M. SIMPSON, Primary Examiner US. Cl. X.R. 51-295 PC4050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 1 7 95 Dated January 27, 1970 Inventorcsk L. M. Prince It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
1-- Column 5, line 54 "drawings" should be I drawing Column 8, line 2 "carried" should be carrier Column 8, line 16, "position" should be composition Column 8, line 29 delete "of" before the word "sufficient";
Column 8, line 59 (references), "2,980,9 4/1961 Miller l5-506" should be inserted befo: "3,121 ,249 2/1964 Affleck -l5506";
Column 8, line 60 (references) "3,121,249 2/1964 Affleck '----l5506" is repeated and shot be deleted.
SIGNED AND SEALED JUL? 1970 (SEAL) Attest:
Edward M. Fletch, 1:. WILLIAM E mm .1
O m Attestmg Officcr Commissions-r of Patents