CA1153541A

CA1153541A - Absorbent article with improved pad

Info

Publication number: CA1153541A
Application number: CA000365982A
Authority: CA
Inventors: Hamzeh Karami
Original assignee: Colgate Palmolive Co
Current assignee: Colgate Palmolive Co
Priority date: 1979-12-03
Filing date: 1980-12-02
Publication date: 1983-09-13
Also published as: DE3044449A1; AU6466580A; GR72829B; CH651185A5; AR240232A1; JPH0451181B2; IT8050223A0; DK154045C; PT72110B; ZA806694B; AU536507B2; IE802505L; DK154045B; PT72110A; FR2470590A1; NL8006293A; PH17624A; DK477680A; MX153968A; JPS5685401A

Abstract

ABSORBENT ARTICLE WITH IMPROVED PAD

ABSTRACT OF THE DISCLOSURE

An absorbent article comprising, a backing sheet of fluid impervious material, a fluid previous cover sheet, and a first pad adjacent the cover sheet comprising a loosely formed fibrous mass. The article has a separate second pad intermediate the first pad and the backing sheet, with the second pad comprising a mass of fibers having compressed regions extending throughout a substantial part of the second pad. The average interfiber spacings in the second pad are substantially less than the average interfiber spacings in the first pad, such that the second pad rapidly transmits body fluids to remote locations of the second pad for retention in the areas at a location spaced from the cover sheet.

Description

~53541 BACKGROUND OF THE INVENTION

The present invention relates to disposable ahsorbent articles.
A varlous assortment o~ disposable absorbent articles have been proposed for use in receiving and retaining body fluids.
Such articlesJ e.g., disposable diapers, sanitary napkins and the like, have normally b~en constructed with a fluid impervious backing sheet, a f`luid pervious cover or top sheet, an absorbent pad intermediate the backing and cover sheets, such as comminuted wood pulp termed in the art as fluff. Although increasingly popular due to disposabilityJ certain problems remain associated with the absorbent pads which prevent the articles ~rom being totally satisfactory. I
First, it is necessary that the pads rapidly spread body fluids ~rom the point of application toward remote locations of` the pads in order to minimize pad saturation in localized areas and make maximum use of the full pad capacity. Second, it is desirable that the pads preferentially retain the body fluids at locations spaced from the cover sheet in order to minimize back wetting through the cover sheet with attendant discom~ort to the wearer. Third, the pads should be soft and ~53541 conformable to the shape of the wearer in order to provide a proper fit of the articles and maximum comfort. Finally, the pads should be made in accordance with simplified manufacturing techniques in order to reduce the cost of the disposable articles to the consumer.
In the applicant's earlier filed application No. 248,289 filed August 8, 1977, there is disclosed, in a disposable absorbent article, having a fluid impervious back sheet and a fluid pervious top sheet, a pad assembly comprised of a loosely formed bat adjacent the cover sheet and a second bat or pad between the first one and the backing sheet and having compressed regions throughout a substantial part of the second pad and also having uncompressed areas adjacent said compressed regions. Such a pad is functionally superior to a conventional single pad type disposable product.
In United States patent 3,612,055 there is disclosed a single pad diaper construction wherein the one surface not in contact with the top sheet is processed to form a paper-like skin to effect fluid spread to the backside of the diaper.
SUMMARY OF THE INVENTION
The aim of the present invention is the provision of an absorbent article of simplified construction having improved fluid dispersing and retention capabilities.
The present invention provides a disposable absorbent article comprising a backing sheet of fluid impervious material, a fluid pervious cover sheet, a first absorbent pad adjacent said cover sheet comprising a loosely formed fibrous mass of wood fluff, and a separate second absorbent pad intermediate said first pad and backing sheet, said second pad comprising a mass of fibers of wood fluff which are more dense than said first pad throughout said second pad with interfiber spacings in said second pad being substantially less than interfiber spacings ~53541 in said first pad, said second pad thereby having its compressed regions extending throughout at least said second pad, said compressed regions rapidly transmitting body fluids to remote locations of the second pad for retention in said compressed regions at a location spaced from the cover sheet.
Thus, the pads minimize back wetting of the body fluids through the cover sheet and maintain the cover sheet in a relatively dry condition during use of the article.
The pads may be made in a simplified manner and at a reduced cost.
DESCRIPTION OF THE DRAWINGS
In the drawings:
Figure l is a fragmentary front plan view of an absorbent article of the present invention being illustrated in the form of a disposable diaper.
Figure 2 is a fragmentary sectional view taken substantially as indicated along the line 2-2 of Figure 1.
Figure 3 is a perspective view of the article of Figure 1 as folded into a box-pleat configuration.
Figure 4 is a top plan view partly broken away for clarity of another form of a disposable diaper.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figures 1 and 2, there is shown a disposable absorbent article generally designated 20 which is illustrated in the form of a disposable diaper. Although for convenience the article described will be a disposable diaper, it will be understood that the principles of the invention are equally applicable to other disposable absorbent articles, such as sanitary napkins and underpads. As shown, the article or diaper 20 has an absorbent pad assembly 21 having a fluid impervious backing sheet 22, such as polyethylene, defining a back surface 23 of the pad assembly, which covers the back - 3 ~

~S3S41 surface 28 of pad 26, a fluid pervious top or cover sheet 24, such as nonwoven material, defining a substantial portion of a front surface 25 of the - 3a -~53541 pad assembly, and an absorbent pad generally designated 26 intermediate the backing sheet 22 and cover sheet 24. With reference to Fig. 1, the diaper 20 may have a pair of tape fasteners 38 for securing the diaper about an infant during placement, and the backing sheet 22 may have lateral side margins 32 folded over and secured to the cover sheet 24 such that the margins 32 cover side portions of the pad 26.
As sho~n in Figs. 1 and 2~ the absorbent pad 26 has a first absorbent pad or layer 40 located adjacent the cover sheet 24 and a second absorbent pad or layer 42 located inter-mediate the first pad 40 and the backing sheet 22. The pad 26 may have a top wadding sheet 34 covering a front surface 30 of the upper first pad 40 and a back wadding sheet 36 covering a back surface 28 of the lower second pad 42. In one form, as shown, a back surface 41 of the first pad 40 may be placed against a front surface 43 of the second pad 42, or, in an alternative form, a fluid pervious sheet, such as a wadding sheet, may be interposed between the first and second pads 40 and 42, respectively.
The first pad 40 is made from a loosely formed mass of fibers, such as comminuted wood pulp termed in the art as fluff. Although the first pad may be compacted, if desired, the first pad 40 may have minimal compression in order to obtain a soft, fluffy front pad 40 with relative~y large interfiber spacings.

~S354~

The density of top pad 40 should be between about 0.03g/cm3 and about 0.07g/cm3 ~ preferably between about 0~04g/
cm3 and about 0.07g/cm3 and more preferably between about 0.06g/cm and about 0.07g/cm3 . The second lower pad 42 is also made from a mass o~ fibers, such as comminuted wood pulp, similar to pad 40 but this pad is prepared as by compression or any other suitable conventional means, to a density of between about 0.14g/cm3 and about 0.22 g/cm3, preferably from about 0 16g/cm3 and 0.20 g/cm3 , and more preferably from about 0.18g/cm3 and 0.20g/cm3 . Within the aforedescribed parameters of densities, lt is desirable that the ratlo of the density of the lower pad 42 to that o~ the top pad 40 be ~rom about 1.5:1 to about 7:1, preferably about '2:1 to about 5:1 and more preferably ~rom about 2:1 to 4:1. The densitles are, of course, simply determined from a given weight of a measured volume (length x width x thickness with the latter measured as described below).
The thicknesses of the pads may vary widely but, in general, they are combined to give an overall thickness of about 40 mils to 1500 mils (about lmm to about 40 mm) with ratios of thicknesses of top to bottom pad ranging from about 50:1 to 1:1, preferably 20:1 to 2:1, and more preferably 10:1 to 4:1. All thicknesses are based upon measurements with a load of 4.1g/cm on the pad since without such an applied load the loftiness and resiliency of the fluff pad would give varying values. Density 11535~1 parameters are then based on such thickness determinations.
For infant diapers total pad thickness will, obvious-ly, generally be lower than for adult incontinence pads and diapers and for feminine sanitary napkins ! Typical newborn infant diapers may have total pad thickness of about lmm to about 6 mm or about 2mm to about lOmm depending on the diaper style. For larger babies, pad thickness totals may range from about 2mm to about 8mm or about 3mm to about 12mm.
Sanitary napkin pad totals typically may range from about 3mm to about lOmm, or about 4mm to about 20mm or more, e.g. about 6mm to about 40 mm, again, depending on the particular style of the sanitary napkin.
Further, it may be desirable to point out that total pad fluff weights will, of course, vary considerably as do the thicknesses and sizes of the pads. ~s a guide, such weights may vary from about 10 to 20 grams up to about 100 grams.
Again, generally, the ratio of the weights of the top to bottom pads may vary from about 2:1 to 1:2 but preferably will be about the same, particularly as this permits the greatest facility in manufacture. Thus, for example, a single web of fluff can be formed in any of the conventional ways, then split and the one for the bottom layer compressed as desired in accordance with the present invention.
In use, the dlaper 20 is secured about an infant by the tape fasteners 38. During voiding, urine passes through ~53S~l the cover sheet 24 into a localized portion of the first pad 40, and due to the relatively small interfiber spacings in the compressed second pad 42, the fluids are rapidly absorbed from the first pad 40 by the second pad 42. Also, the compressed pad 42 rapidly transmits the fluids to pad portions which are remote the point of urine application to the diaper. Although a relatively large amount of fluff material has been compressed in producing the pad 42 and thu~ it has a smaller fluid holding capacity than the pad 40 due to the relative size of their interfiber spacings, the rapid spreading of the fluid through-out pad 42 permits the overall pad composite 26 to retain sub-stantially as much fluid as an equivalent weight uncompressed pad assembly much like reservoirs which retain the body fluids in localities but due to the more rapid and efficient spreading of the urine there is much less leakage after each urination and also a marked reduction in back wetting thereby maintaining the top sheet 24 in a relatively dry condition. In this manner, the first and second pads 40 and 42, respectively, cooperate to rapidly disperse fluids throughout the second pad 42 while making maximum use of the pad material and maintaining the top sheet 18 in a relatively dry state.
As previously indicated, the first pad 40 is relative-ly soft and conformable since it is relatively uncompressed.
Accordingly, the first and second pads 40 and 42 respectively, provide a pad structure for the diaper which is soft and conform-able to the shape of the wearer in order to maximize comfort and provide an excellent fit of the diaper. In addition~ the pad 26 ~S3541 o~ the present invention may be made in a simplified manner by compressing the second pad 42 and by then placing the first pad 40 against the second pad 42 during manufacture of the diaper. Thus, the diaper is made without the necessity of wetting and drying the compressed regions which would otherwise add to the complexity and cost o~ manufacture.
Referring to Fig. 3, the pad assembly 21 of Fig. 1 may be ~olded along a plurality of longitudinally extending fold lines to define a box-pleat configuration of the diaper. Thus, the diaper is folded along a pair of first fold lines 50 to de~ine a longitudinally extending central panel 52 and along a pair o~ s~econd fold lines 54 to define a pair of longitudin-ally extending first panels 56 intermediate the ~old lines 50 and ~4 and a pair of outermost panels 58 extending from the second fold lines 54.
Re~erring to Fig. 4, the diaper 60 is of an hour-glass configuration having a crotch area 62 and four portlons of greater width defining ears 64, 66, 68 and 70. The diaper includes a backing sheet 72 of polyethylene or the like and a top sheet 74, similarly as the box-pleated diaper. An absorbent pad assembly 75 similar to pads 26, 40 and 42 of the box-pleated diaper is disposed between the top and backsheets.
Waddings 77 similar to 34 and 36 of the box-pleated diaper may be provided similarly as in the box-pleated diaper. The pad assembly including wadding sheets are of lesser dimensions, as ~5354~

indicated than the top and backsheets which are o~ similar dimensions.
In a product blind test of 106 users comprising a first standard pad diaper (pad of 36 grams wood fluff of iniform density of 0.1 g/cc - pad size 300mm x 409mm) with a second

2-layer pad diaper of the present invention of similar dimenslons and weight as the first diaper but wherein the top pad of the second diaper has a density of o~06g/cc and the second bottom pad a density of 0.2g/cc, it was found as ~ollows :

prefer prefer no pre- ratio double std. ference flu~f Layer _____ ______ _______ ______ B B B
- o~rerall preference 41 21 38 + 1.49 - drier bottom 35 20 45 ~ 1.36 - strength 34 9 57 + 1.65 - absorption 37 21 42 ~ 1.38 - overall fit + 1.02 - fit at thighs - 1. o8 - thickness 33 15 52 ~ 1.44 Leakage occurence diaper could absorb if needed.

~LS3S4~

The overall preference ratio o~ + 1.49 is statistically equivalent to a ~2 sigma preference for the 2-layer pad diaper and indicates at a 95~ confidence level that a majority would prefer the 2~1ayer pad di~per to the conventional single pad diaper.

Claims

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

1. A disposable absorbent article comprising a backing sheet of fluid impervious material, a fluid previous cover sheet, a first absorbent pad adjacent said cover sheet compris-ing a loosely formed fibrous mass of wood fluff, and a separate second absorbent pad intermediate said first pad and backing sheet, said second pad comprising a mass of fibers of wood fluff which are more dense than said first pad throughout said second pad with interfiber spacings in said second pad being substantially less than interfiber spacings in said first pad, said second pad thereby having its compressed regions extending throughout at least said second pad, said compressed regions rapidly transmitting body fluids to remote locations of the second pad for retention in said compressed regions at a location spaced from the cover sheet.

2. The article of claim 1 wherein the ratio of the densities of the second pad to the first pad is between about 1.5:1 and about 7:1.

3. The article of claim 2 wherein the ratio of densities is between about 2:1 and 4:1.

4. The article of claim 1 wherein said more dense part of the second pad extends to side and end edges of the second pad.

5. The article of claim 1 including a top wadding sheet covering a front surface of the first pad.

6. The article of claim 1 including a back wadding sheet covering a back surface of the second pad.

7. The article of claim 6 wherein said back wadding sheet is compressed.

8. The article of claim 2 wherein the first pad has a density between about 0.03 and about 0.07 g/cm and the second pad has a density between about 0.14 and 0.22 g/cm.

9. The article of claim 8 wherein the ratio of the first to second pad thicknesses is between about 20:1 and about 2:1.