CA1139053A

CA1139053A - Disposable diaper type garment having wetness indicator

Info

Publication number: CA1139053A
Application number: CA000354149A
Authority: CA
Inventors: Judith C. Mroz; Dennis A. Thomas
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1979-06-18
Filing date: 1980-06-17
Publication date: 1983-01-11
Also published as: JPS5643402A; EP0021492B1; JPS63177907U; DE3066261D1; US4231370A; EP0021492A1; JPH0111682Y2

Abstract

IMPROVED DISPOSABLE DIAPER TYPE
GARMENT HAVING WETNESS INDICATOR

Abstract An improved absorbent product, such as a disposable diaper type garment having a wetness indicator disposed between a translucent cover member and an absorbent member.
The improvement relates to providing a flexible pH-change/color-change wetness indicator coating on a surface portion of the product which is visible through the cover member, and which retains sharp edge definition of the coated surface portion when wetted; for instance, by urine.
The coating is preferably applied in the form of a stripe to a portion of the inwardly facing surface of a backsheet of a disposable diaper; Such a coating comprises a solid-solid mixture (eg., solution) of a pH-change/color-change type material dispersed in a matrix of adhesive material which coating is sufficiently flexible to not substantially impair the flexibility of the product, and which coating is suffi-ciently adhesive and flexible to remain on the coated surface portion through a normal period of use of the product.

Description

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IMPRO~IED DISPOSAP,LE DIAPEI~ TYPE
Ç:~RMENT ~IAVING WETNE:SS II~DICATOR
-Desc~iption .
Technical Field This invention xelates ~o absorbent products such as disposable diapers and the like whicn are provided with wetness indicators.

Back~round Art U~S. Paten~ Number 4,022~211 which issued May 10, 1977 to Terry K. Timmons et al. discloses a Wetness Indicator For Absorbent Pads which indicator comprises a water-soluble or water~dispersible coloring a~ent. The coloring agent may be ap?lied, ~or instance, in a printed pattern on the inwardly facing surace of a light-transmit~in~, fluid-imperviolls backing sheet of a disposable diaper. Then, when ~he dia~er is wet~ed, the coloring 2ge~t becomes in~isible. The coloring agent ~ay be used by itself, or with a suitable b~nder, or with a separate carxier means such as an absorbent sheet. A preLerred form of coloring ~gent is said to be a wa~er-soluble dye in a water~soluble polyvinyl alcohol binder.
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U.S. Patent ~umber 3,675,654 which issued ~uly 11, 1972

2~ ~o Joseph S, ~aker et al. discloses a Disposable ~r~icle With ~oisture-Actuated Indicating Agent. The indieating agent is stated to comprise either a small a~ount of rinely di~ided water soluble dye ~a~ing a high dye streng~'n or suc~
a dye ad~ixed with a finely di~ided diluent masking a~ent, 2S such as talcum pow~er. I~hen wett~d, the dye is dissolved, and the dye solution becomes visible through a transluc~nt bac~sheet o the article. Such a solution in combination with an absorbent member substantially obviates producing a sharply defined pattern of activated we~ness indicator.

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U.S. Pa~en~ ~lumber 3,731,685 ~7hich issued ~ay 8, 1973 ~o William ~idus discloses a Moisture Indicating Strip For Diapcrs and Surgical Dressings. Essentially, one end portion of an indicator strip is secured to such a garment 5 so that the opposi~e end extends beyond an edge of the garment, and so ~hat the attached end is disposed to beco~le wet when t~e garment is wetted in use. The strip is capable of supporting capillary action from th~. secured end to the opposite end which opposite end is impre~nated w~th a chemical which changes color when wet.

U.S. Patent Num~er 3,952,746 which issued ~pril 27, 1976 to F. Wayne Su~mers discloses a Humldity Indicating . Diaper Cover ~7hich, essentially, comprises a moisture indicator strip and means for moisture activating and viewing the indica~or -strip during the use of th~ diaper.

U S. Patent ;Number 3,063,812 which issued November 13, 1962 to Galen F. Collins discloses a De~ermination of Albumin In Liquids; in particular albumin in urine. Basically, the basis of the invention is stated to be "protein error"
- X0 exhibited by eertain indicators ~Jhereby in solutions containing ~rotein such indi.cators undergo their characteris~lc acid-~o-base color change at a lower p~ value than that at which they would chal~e color in the absence of protein~ For instance, an indicator tablet co~prising bromophenol blue is provided with an acid reacting substance to lower the pH
value of urine belo~ the acid-to-base color change point of ~he indicator. Then, if the color change occurs it indicates - the presence of albumin in the urine.

. U.S. Patent ~umber 3,004,895 which issued October 17, 1961 to S. M. Schwartz discloses a Diaper Rash Preventative ~hich, essentially; comprises a member which is readily p~rmeable by c~mmonia and means or immobilizing c~m~onia which passes therethrough. Thus, when th pexmeable member 7 ~

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- 3 is a wall por~ion o a pouch containing an ammonia immohiliz-~ng agent, the pouch can be disposed inside a diaper or diaper pail and be effective with respect tO immobilizing ammonia which contacts the pouch as, for instance, when a diaper is wetted with urine. Such a pouch may, if translucent, ~urther contain a p~l-change/color-change indicator for the purpose of visibly indicating when the effectit-eness of the ammonia in~obilizing agent has been ex~a~ d.

U.S. Patent ~umber 2,537,124 which issued January g, 1951 to Roland D. Earle et al. disclose a Latex Adhesive Containing Phenolphthalein and Method of Using Same. This patent teaches the use of a pH-change/color-ch2nge indicator in a latex-type adhesive which will undergo a visible color ch~nge as the adhesive dries. ~ user of the adhesive can 15 then infer the degree of adhesive dryness from the color of the adhesi~e and, based thereon, decide when to bring adhesive coated articles together for the purpose of adhesively ~eCuring them together. Thus, this patent discloses a degree o~ dryness indicator ~7hich is yisible prior to its 20 end use but which is not disclosed to be visible after its intended use. Neither does this patent suggest tha~ the adhesive need be 1exible when dry, nor that its color ~hange would reverse i Lewetted. Inde~d, as disclosed, the aqueous phase of the adhesive would have a pH of at least 25 nine (9) and be reduced upon drying. It i.s believed that such a high pH indicator would not, after undergoing a ~lor change upon dryir.g, reverse its color change when rewetted with urine.

As com~ared to the oregoing bac~ground art, the present 30 invention provides a visible pH-change/color-change ~etness~urine indicator coating which obviates the need ~or a discrete substrate with its attendant application complexities of cut~ing, registration, and securement; and which comprises ~eans for substantially obviating migration of colorant when 35 wetted. Thus, the resulting color indicating pattern of a .~ . .. . ~

coating embodiment o~ the presen~ 'in~ention will have a ~harp edge definition wh~n wetted rather than a quasi blurred edge defini~ion such as would result rorn high dye strength materials which are relatively highly water-soluble. Also, the present invention substantially obviates migration of colorants through an adjacent absorbent member and thereby reduces th~ likelihood of skin irritations ~Jhich might otherwise be precipitated.

Disclosure Of The Invention -In accordance with one aspect of the present inventionJ
therP is provided an improved disposable ~bsorbent product ha~ing a pH-change/color-change wetness indicator. The ~etness indicator is a coating material which comprises a solid~solid dispersion of a pH-change/color-chan~e ~aterial which coating is sufficiently flexible to not substantially impair the flexibility of the product, and ~ich coating is su~ficiently flexible and adhesive to remain on an associated coated sur~ace por~ion of the product during the normal use o the product. The coating is applied ~o a surface por~ion of the product so that it is visible from the outside to, for example, an attendant or the person using the article.
Pxeferably, the coa~ed surface is a pat~erned por~ion of the i~wardly facing surface of a translucent cover member o~ the ~x~icle; for instance, a water-impervious ~hermoplastic backsheet of a disposable diaper.

~r e~ Description Of The Drawings ~ hile the claims hereof particularly point out and ~istinctly claim the subject matter regardcd as forming the present invention, it is belie~ed the invention will be better understood from the following descrip~ion of the i~ention .aken in conjunction with the accompanying drawings i~ which corresponding features of the two views are identically ~esignated, and in which:

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F~ure 1 i~ a pcrspective view o~ a disposable dlaper ~mbodying the pr~sent w~tness indicator invention, a~ in which view a stripe of p~l-change/color-chan~e coating material is shown to be partially activated.

Figure 2 is an enlarged scale fragmentary sec~ional view taken along line 2-2 o~ Figure 1.

Figure 3 is a graph showing the relation between the pH of two color-change activators and the time to effect a subst:antial color change of a wetness indicator 10 coating o~ an embodiment of the present invention.

.~igure 4 is a graph showing the relation between the thickness o~ a color indicator coating and the time to -achie~e a prede~ermined degree of color change when the -coating is activated by urine having a pH of 6.3.

Detailed Descri tion 0~ The Invention ~ n exe~plary improved disposabl~ diaper 20 embodying th~ present invention is sho~m in perspective in Figure l, ~d in the fragmentary sectional view Figure 2. Diaper 20 comprises ~ mois~ùre imperviou~ cover member or baclcsheet 21, a moisture pervious topsheet 22, tape fas~ners 23 o which there are two but only one shown in Figure 1, and ~sture indica~or coa-ting 26 which is coated onto a portion of ~he inwardly facing surface of bac~shee~ 21.
~or~ion 28 o~ coatin~ 26 represents an unactivated portion ~5 o~ coating 26, a~d portîon 30 represents an activated . ~ portion o coating 26. Diaper 2û furthrr co~aprises aTL
a~soLbent ~.e~b~r or core 32 ~s sho~m in Figure 2.

The co~pon~nts and materials of diaper 20 are ~e~y ~lexible so that ~he diaper will be suf~iciently co~pl~ant to conform to thc sn~pe of ~he lower torsv of the wear~r ~uring the pcriod of use of the diaper. For inst~nce, ba~sh~ 21 is pr~f~r~bly a thin (eg., 1 mil~ transluce~
polycthyl~ne film; the topsheet 22 is pref~rably a thi~, ...
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3~3 1exibl~ sheet of mo~sture pervious hydrophobic m~terial;
- and the absorbent core 32 is preferably an air-laid web of absorbent fibrous material.
, Briefly, the present invention is an improved diaper type ~arment which is very flexible for the above stated reasons, and which garment includes a highly flexible p~l-change/color change wetness indicator coating so disposed that it will be activated within a rélatively short time after the wearer urinates. More specifically, the present invention pro~ide~ an acid buffered pH-change/color-change coating material which, when wetted with urine, will undergo a subs~antial color change; and which coating is so disposed . that the eolor change will be visible to, fcr instance, a percipient attendant of the wearer. Thus, while the stripe 15 of coating 26 of diaper 20 is said to be applied to the - inside surface of backsheet 21, it is not intended to thereby limit the present invention. Rather, such a coating could also be applied, for instance, to the outwardly facin~
~urface of absorbent core 32.
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Coating 26 is a solid-solid ~ixture, ~or instance, 601id-solid solution of a pH change/color-change type material dispersed in a matrix of adhesi~e material. The m~trix material is preferably sufficiently ElexibLe so that the coating 26 does not substantially impair ~he flexibility of a disposable diaper or other product in which it is incorporated. Moreover, the coating must be sufficiently adhesive and flexible to remain intact on the ~urface coated therewith through a normal period of use.
That is, coating 26 is highly 1exible with respect to the other components of diaper 20 so that the coating will not substantially impair the flexibility or corafors~abillty of the diaper.

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~3~3 An exemplary coating 26, ~s described hereinabove and as shown in Fi~ures 1 and 2, may b~ ~rmed ~roTn a coating composition comprising fou~ principa~ ~unc~ional componen~s:

a first latex composition in the amount o~ about 33%;

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a second latex composition in the amount of about 66%;

an acid buffer such as phosphoric acid in the amount of about 1%; and, . a pH-change/color-change material such as bromo-. - ph~nol blue in the amount of about .07%.

~ The ~irst latex (Late~ 1) composltion of the above described exemplary coating composition is an aqueous emu~sion copolymer o~ styrene, and 2-ethylhexyl acrylate with l~ss ~han 5~/O ~lethacrylate acid and less than 5iO Il-met~ylol acrylamide. The ratio of the styrene and 2-ethyl~
hexyl acrylate is adjusted to yield; a random copolymer with - a glass transi~ion te~perature, Tg of about -18C. The f-irs~ la~ex has an intrinsic viscosity o~ about 1.4 measured ;20 in tet~ahydroi~uran a~c 25~C:~ Distilled water exhibits a contact angle of ~rom abou~ 74 ~o about~ 80 with a dry coating of thls la~ex after about 60 seconds o~ contac~

The second 12tex (Latex 2~ composi~ion of the above described exemplary coating composition is preferably product ~5 ~ID. X695_385_04 WhiCh is a product of Findley Adhesives, - Inc~ e Milwaukee, Wisconsin. That product has thP following ...~omponents~
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30.4~%: '~irflex 405',lAir Products & Chemicals Inc., ~llento~, PA ~A non ionic surfactant stabilized, random vinyl acetate~ethylene c~polymer emulsion).

7.53%: 'Product Flx-0012',2Pearsall Chemical Corp., Houston, TX ~A li~uid chlorinated paraffin).

60.98V/o '~lyam.~l 40-140l'3Reichhold Chemical Corp., ~hite Plains, ~lew York (An alcohol stabilized, random homo-polymer polyvinyl acetate emulsion~.

0.0~%: "Colloids 681-F',4Colloids Inc., 394 Frelinghuysen Ave., ~lewark, ~IJ (~ defoamer).

0.25%: '~rexoil llO"~efoamer, Lubricants, Inc., PØ
Box 21~ Pewaulkee, WI ~A defoamer).

0~7-1~0~/o Phosphoric acid (75% by weight), Fisher Scientific Co., Fairto~n, ~J (The amount of phosphoric acid is determined by the pH Or the mixture, acid is added to make the pH ~ 1.0).

These components are mixed in the follo~ing manner. The "Airflex 405"is placed in a compounding vessel and, under high a~itation, the chlorina~ed paraffin is added and ~ixing is continued for about 45 ~inutes. After the chlorinated paraf~in has been ~horoughly dispersed,"Colloids 681-F"
defoame~ is addPd to the compounding vessel, mixed uith ~e other materials therein, and the"Drexoil llO"de~oamer is mixed thereinto. The phosphoric acid is premixed with 1/4 as m~ch water in a sep~rate vessel and after mixing, is added to the compounding vessel. This is ollowed by the additisn of the'~lyamul 40-140"with good agitation. The entire composition is stirred for 45 mi~utes until smooth.
The pH of the composition is adjusted ~o about 1.0 by addition of a premix of phosphoric acid with water. The ~iscosity o the product is adjusted to from abou~ 750 to 5 inclusive. The terms bearing the superscript numerals axe ,.
Trademarks, ~ -3~

about 1500 cps at 25C by wat~r addition, using a ~r~okfield Viscomcter Model RPT, spindle ~5 a~ 20 rpm. Dis~illed water lexhibits a contact angle of from about 5 to about 11 with a dry coating of this latex composition after about 60 seconds o contac~. .

- The compcnents of the exemplary coating mix described hereinabove are combined in the following preferred manner:

. the bromophenol blue is slowly and with mixing added to and dissolved in Latex 1 to for~ a mixture A;

the phosphoric acid is then s10~71y and with mixing . added to the mixture ~ to form a mixture B; and Latex 2 is then added to the mixture B.
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This resultant aqueous mixture can then be applied to the inside of the thermoplastic backsheet o a diaper. This lS indicator solution will adhere to the polyethylene of the backsheet and dry to a flexible coating that is light yellow ` ~n color. Distilled water exhibits a contact angle o ; 7-10 with the dry film of this example mix~ure. (Contact a~gle is measured af~er 60 seconds of cont:act). When urine migrates ~hrough the absorbent material of the diaper and wets the indicator stripe, the color of the indicator will chan~e ~rom ligh~ yellow to blue. Wi~h the above mixture - ~nd urine of a pH of 6.2 ~his color change will occur within S minutes. Lower pH urines will cause longer change times . ~5 and higher p~l urine will cause shorter change ~imes; reference l~igure 3.

Further, the color change time can be affeeted by the thi~kness of the indicator film, referenc~ Figure 4. The preferred dry film thickness for the exemplary coating 3~ material described a~ove is abou~ , 0015 inches .

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After the indicator has changed color, it will remain reasonably immobilized in the matrix, and will therefore, remain a wetness signal ~or sometime af~er color change. It ~s believed that the latex matrix p~ovides both a physical 5 barrier to the migration of the large bromophenol blue ` molecules ancl physical protection from the fluid 10w patterns within the liaper.

The above formulation can be ~aried to adjust the indicator properties. If the above ratio of Latex l, with which distilled water exhibits a contact angle of 74-80, to Latex 2, with which distilled water has a contact angle of 5~ , is varied the time required ~or indicator develop-~ents and efficiency of retaining the bromophenol blue are a~fected. For example, if t~e ratio o~ Latex l:Latex 2 lS (described above as 1:2) were changed to 1:1 the resultant indicator would change color more quic~ly, but would hold ' b~omophenol blue less strongly and bleeding of the color would occur. If the same ratio were changed to 1:4, the resulting indicator would change color moxe slowly, and ~0 would hold bromophenol blue more strongly.

The exemplary coating composition is pre~erably applied i~ a predetern~ned pattern: for instance, a one-half-inch wide s~ripe having a ~hickness of about one-and-one-half m~ls such as stripe 2G, Figure 1. Then, upon color change, ~5 th~ ed~e definition of the pattern r~mains sharp because mlgration of the bromophenol blue is substantially obviated by the acid buffered latex matrix.
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Figure 3 is a graph o actlvator pH versus c~lor-change-time data which was ~btained by wettinO a number of ex~mplary disposable diapers embodying the present in~ention, The stripe.26 of each diaper had a thickness of one-and-one-half mils; was one-half-inch wide; and extended generally ~ertically alonO the medial posterior portion o~ the inner surface of the diapers' backsheets, C~urve 41, Figure 3, was derived from samples activated by urin~, And Curve 43 was derived from samples activated by ammonia. Lines 45 and 46 represent the low and.hi~h pH values, respectively, of the noxmal range of urine as reported on page 13 in Interpretation o~ Diagnostic Tests, A ~andbook Synopsis of Laboratory Medicine, Copyrighted 1970 by Little, Brown and Company . -(Inc.), which handbook is further identified by Library Of Congress Catalog Card No. 72-1~2015, Line 47 on Figure 3 ~dentiies the pH value of normal aver~ge urine as also reported in the above identified handbook Figure 4 is a graph (Curve 51) o~ we~ness indicator coating 26 thiclcnesses versus color change times which data were obtained through the use of samp~e disposable diapers -wherein coatings 26 comprised the exemplary coatin~ composition described hereinabove, and all of the samples were act.iva~ed ~ by urine having a pH of about 6,3.
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W~ile particular embodiments of the present invention have been illustrated and describ~d, it would be obvious to those skilled in the art that var;ous other changes and modifications can be made without departing from the spirît a~d scope o~ the invention, It is int nded to eover in the - .appended claims all such ~hanges and modifications that are 3~ within the scope of this invention.

What is claimed is:

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEDGE IS CLAIMED ARE DEFINED AS FOLLOWS:
Claims

1. An improved disposable diaper type garment having a wetness indicator disposed intermediate a flexible trans-lucent cover member and a 1exible absorbent member, said improvement comprising a flexible pH-change/color-change type wetness indicator coating which is so disposed on an area of a said member that it is visible through said cover member and is in liquid communicable relation with said absorbent member, said coating comprising a solid-solid mixture of a pH-change/color-change type`material dispersed in a highly flexible matrix of adhesive material.

2. The improved disposable diaper type garment of Claim 1 wherein said pH-change/color-change material comprises bromophenol blue, said matrix of adhesive material comprises a highly flexible latex adhesive, and said coating comprises sufficient acid buffering means for providing said coating with an initial pH of less than about 3Ø

3. The improved disposable diaper type garment of Claim 2 wherein said coating comprises sufficient said acid buffering means for substantially obviating color change of said coating due to atmospheric moisture.

4. The improved disposable diaper type garment of Claim 2 wherein said mixture is a solid-solid solution>
and wherein said latex adhesive is sufficiently hydrophilic to enable some portion of said bromophenol blue to be contacted by urine contacting said coating, and said coating comprises means for sufficiently obviating migration of said bromophenol blue in said matrix that said bromophenol blue will not be substantially dispersed into contacting urine adjacent said coating whereby the as-applied edge definition of said coating will remain substantially intact when said coating undergoes a urine activated, pH change induced color change.

5. The improved disposable diaper type garment of Claim 4 further comprising sufficient said acid buffering means for providing said coating with an initial pH of from about 1.0 to about 2Ø

6. The improved disposable diaper type garment of Claim 5 wherein said acid buffering means comprises phosphoric acid.

7. The improved disposable diaper type garment of Claim 5 wherein said cover member is a sheet of translucent thermoplastic material, said coating is disposed on a portion of an inwardly facing surface of said cover member, and said coating comprises sufficient bromophenol blue and said acid buffering means that said coating will undergo a distinct color change within about five minutes or less after said garment has been wetted with urine by a wearer of said garment.