Method of making shaped foam implements

What is claimed is:

1. A method of producing a molded, foam implement having a three dimensional shape, the method comprising the steps of:

a) providing a water phase, said water phase comprising a polymerization initiator;

b) providing an oil phase, said oil phase comprising:

(i) from about 80% to about 98% by weight of a monomer component capable of forming a copolymer having a Tg value of from about -40.degree. C. to about 90.degree. C., said monomer component comprising:

1) from about 10% to about 80% by weight of a substantially water-insoluble, monofunctional monomer capable of forming a homopolymer having a Tg of about 35.degree. C. or less;

2) from about 10% to about 70% by weight of a substantially water-insoluble, monofunctional comonomer capable of imparting toughness about equivalent to that provided by styrene;

3) from about 2% to about 50% of a substantially water-insoluble, polyfunctional crosslinking agent selected from the group consisting of divinyl benzene, analogs of divinyl benzene, diacrylates of diols, analogs of diacrylates of diols, and mixtures thereof; and

(ii) from about 2% to about 20% by weight of an emulsifier component which is soluble in said oil phase and which is suitable for forming a stable water-in-oil emulsion;

wherein said oil phase is substantially immiscible with said water phase and the ratio of said water phase to said oil phase (water:oil ratio) is between about 15:1 and about 125:1;

c) delivering both of said phases to a mixing means, wherein said water phase is delivered at a first flow rate and said oil phase is delivered at a second flow rate, wherein said flow rates are in a relationship defined by said water:oil ratio;

d) processing said water and oil phases using said mixing means, wherein said mixing means provides sufficient shear so as to emulsify said water phase in said oil phase so as to provide a continuous flow of a high internal phase emulsion (HIPE) having an internal phase size distribution;

e) providing a sequence of mold cavities, each of said mold cavities having a predetermined three dimensional configuration defined by a cavity wall wherein said three dimensional configuration is defined by said shape of said implement;

f) depositing said HIPE in one of said sequence of mold cavities using a HIPE delivery means;

g) curing said HIPE in said mold cavity so as to produce a molded HIPE foam having a cell size distribution that substantially conforms to said internal phase size distribution;

h) removing said molded HIPE foam from said mold; and

i) repeating steps f through h until one of said oil phase and said water phase becomes depleted such that step c can no longer be accomplished, wherein said steps are repeated at a rate that is high enough that said HIPE is deposited into said mold cavity before said HIPE reaches a gel point.

2. A method according to claim 1 wherein steps e through i are accomplished by an injection molding process.

3. A method according to claim 1 wherein step f is accomplished by providing a pair of converging belts each of said belts having a plurality of mold cavity halves thereon wherein said mold cavity halves mate as said belts converge to form said mold cavity.

4. A method according to claim 1 wherein:

the HIPE provided by step c comprises a first HIPE having a first internal phase size distribution;

the mold cavities of step e comprise an assembly of first mold cavity segments that are mated to form first mold cavities;

step f comprises depositing said first HIPE into one of said first mold cavities;

step g comprises curing said first HIPE in said first mold cavity to form a pre-molded HIPE foam;

and steps h and i are replaced by the following steps:

h) processing a second water phase and a second oil phase, provided according to steps a, b and c, using a second mixing means according to steps a, b and c, wherein said second mixing means provides sufficient shear so as to emulsify said second water phase in said second oil phase so as to provide a continuous flow of a second high internal phase emulsion (HIPE) having a second internal phase size distribution that differs from said first internal phase size distribution, said water and oil phases being provided according to steps a through c;

i) removing one or more of said mold first cavity segments from said first mold cavity to expose said pre-molded HIPE foam, said pre-molded HIPE foam being carried by a remaining portion of said mold cavity segments;

j) providing a sequence of one or more second mold cavity segments and mating said segments with said residual portion of said first mold cavity segments to form a sequence of second mold cavities;

k) depositing said second HIPE in one of said sequence of second mold cavities using a second HIPE delivery means;

l) curing said second HIPE in said second mold cavity so as to produce a second molded HIPE foam having a second cell size distribution that substantially conforms to said second internal phase size distribution so as to form a molded foam implement;

m) removing said molded foam implement from said mold; and

n) repeating steps e through m until one of said oil phase and said water phase becomes depleted such that step k can no longer be accomplished, wherein said steps are repeated at a rate that is high enough such that both of said HIPEs are deposited into said mold cavities before either of said HIPE reaches a gel point.

5. A method according to claim 1 wherein said three-dimensional, molded, foam implement comprises a component of an absorbent article.

6. A method according to claim 5 wherein said component comprises an absorbent component.

7. A method according to claim 5 wherein said component has a predetermined shape designed to substantially conform to at least a portion of a wearer's body.

8. A method according to claim 1 wherein said three-dimensional, molded, foam implement comprises a toy.

9. A method according to claim 1 wherein said three-dimensional, molded, foam implement comprises a filter element.

10. A method according to claim 1 wherein said three-dimensional, molded, foam implement comprises an insulating material.

11. A method according to claim 1 wherein said monomer component is capable of forming a copolymer having a Tg value of from about -40.degree. C. to about 30.degree. C.

12. A method according to claim 11 wherein said monomer component is capable of forming a copolymer having a Tg value of from about -20.degree. C. to about 30.degree. C.

13. A method according to claim 1 wherein said monomer component comprises from about 40% to about 80% by weight of a substantially water-insoluble, monofunctional monomer capable of forming a homopolymer having a Tg of about 35.degree. C. or less.

14. A method, according to claim 13 wherein said monomer component comprises from about 50% to about 70% by weight of a substantially water-insoluble, monofunctional monomer capable of forming a homopolymer having a Tg of about 35.degree. C. or less.

15. A method according to claim 1 wherein said monomer component comprises from about 20% to about 50% by weight of a substantially water-insoluble, monofunctional comonomer capable of imparting toughness about equivalent to that provided by styrene.

16. A method according to claim 15 wherein said substantially water-insoluble, monofunctional comonomer capable of imparting toughness about equivalent to that provided by styrene is selected from the group consisting of styrene, methyl methacrylate, isoprene, piperylene, dimethylbutadiene, and mixtures thereof.

17. A method according to claim 1 wherein each of said cavities in said sequence is connected to cavities lying adjacent thereto by an isthmus.

18. A method according to claim 4 wherein each of said cavities in said sequence is connected to cavities lying adjacent thereto by an isthmus.

19. A method according to claim 1 wherein a substantially liquid impermeable membrane is interposed between said HIPE and at least a portion of said cavity wall so that said HIPE is cured while in contact with said membrane.

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FIELD OF THE INVENTION

The present invention relates to tridimensional shaped foam implements and methods of making such implements. More particularly, the present invention relates to tridimensional absorbent components useful in absorbent articles such as sanitary napkins, panty liners, tampons, and the like and methods of making such shaped absorbent components.

BACKGROUND OF THE INVENTION

Absorbent articles such as sanitary napkins, pantiliners, and incontinence pads are devices that are typically worn in the crotch region of an undergarment. These devices are designed to absorb and retain liquid and other discharges from the human body and to prevent body and clothing soiling. Sanitary napkins are a type of absorbent article worn by women in a pair of panties that is normally positioned between the wearer's legs, adjacent to the perineum. Sanitary napkins of a wide variety of shapes and dimensions are currently used by women for the collection of menses and other bodily discharges.

In the past, a number of efforts have been directed at providing sanitary napkins that maintain contact with the wearer's body. One attempt to provide such body contact is disclosed in U.S. Pat. No. 2,747,575 issued May 29, 1956 to Mercer. The Mercer patent discloses a catamenial bandage having a longitudinal hump which bulges towards and may contact the body of the wearer. The catamenial bandage described in the Mercer patent suffers from several disadvantages, however. For instance, the size and shape of the absorbent pad and hump in the Mercer bandage appear to limit the conditions under which the bandage is able to maintain contact with (and conform to) the body of the wearer. The portions of the bandage that lie laterally to the sides of the hump are not thin and flexible. In addition, the hump of the Mercer bandage is made of a cellulosic material, and, as a result, may tend to collapse and become permanently distorted during use.

U.S. Pat. No. 4,425,130 issued to DesMarais on Jan. 10, 1984, discloses a compound sanitary napkin that comprises a primary menstrual pad and a panty protector joined to one another at their corresponding ends in such a manner that the two constituents are free to move relative to one another along essentially their entire common length. The primary menstrual pad is intended to absorb the bulk of the bodily fluids discharged by the user, while the panty protector is intended to protect the user's garments from soiling. In use, the relative freedom of movement between the primary menstrual pad and the panty protector serves to maintain the primary menstrual pad adjacent the user's crotch region while the panty protector remains associated with the user's undergarment.

The current tendency has been to develop sanitary napkins that are increasingly thinner, and thus more comfortable and less obtrusive than prior sanitary napkins. Recently, efforts have been directed at developing thin sanitary napkins which have the capacity to absorb and contain medium to high menstrual discharges. Previously, such discharges could only be handled by relatively thick sanitary napkins. Examples of thin sanitary napkins having capacities great enough to handle medium to high menstrual flows are disclosed in U.S. Pat. Nos. 4,950,264 and 5,009,653, issued to Osborn, III, on Aug. 21, 1990 and Apr. 23, 1991, respectively.

It is also desirable that sanitary napkins, not only maintain contact with, but conform as closely as possible to the wearer's body. Such a body-conforming capability increases the effectiveness of the sanitary napkin by reducing the possibility that menses will travel beyond the perimeter of the sanitary napkin and leak. There have been a number of recent efforts to provide sanitary napkins and other absorbent articles with improved body-conforming characteristics. In addition to serving as examples of thin sanitary napkins, the sanitary napkins disclosed in the above-mentioned Osborn patents also serve as examples of anatomically-conforming sanitary napkins. While the sanitary napkins disclosed in the Osborn patents work quite well, the search for improved sanitary napkins has continued.

For example, published PCT Application Serial No. WO 94/16658, published on Aug. 4, 1994, discloses a generally thin, flexible sanitary napkin which has a central absorbent hump, and is capable of handling medium to high menstrual flows. The hump is particularly useful in fitting into the space between the wearer's labia to more readily intercept menses and other bodily discharges when they leave the wearer's body. The search, however, has continued for Improved sanitary napkins, particularly sanitary napkins that will achieve even better fit within the space between the wearer's labia majora, and which are more adept at absorbing blood-based liquids, such as menses.

Three dimensional absorbent articles designed for absorbing blood-based liquids are also known. Typically such articles are intended to enable intralabial interception of such fluids with extralabial storage of the absorbed fluids. One attempt to increase the body fitting capability of sanitary napkin has been to combine both a cupped and a humped shape in the same article, typically achieving a sanitary napkin having a flattened front portion combined with a raised rear portion, in order to better fit the variations in the anatomy in longitudinal direction. One such structure is described in U.S. Pat. No. 4,804,380, issued to Lassen, et al. on Feb. 14, 1989 which describes an article that has a substantially flat or concave front portion intended to cover area of the mons pubis, and a longitudinally oriented raised peak in the rear portion that is said to adjust and mold into the inverted-V shape of the rear portion of the labia. Although this type of structure does provide a sanitary napkin with a certain degree of three dimensionality, such structures still cannot actually fit the various complex body shapes of the female anatomy that comprise nonlinear grooves and nonplanar surfaces. The sanitary napkin of the '380 reference is provided with its three dimensionality by mechanically shaping an initially flat structure. This means, for example, that the raised peak in the rear portion thereof has a rectilinear profile when seen in side view, and therefore it fails to conform properly to the corresponding non-linear profile of a wearer's anatomy as seen in a longitudinal direction.

Another example of an absorbent article having three dimensionality is described in published PCT application Ser. No. WO 99/01095 ('095 application), published in the name of the Procter & Gamble Company on Jan. 14, 1999. The devices described therein have a profile along the longitudinal centerline that provides improved conformity to human female anatomical features allowing improved bodily fit. However, improvements are still needed because the complex set of fold lines and planar surfaces is difficult to fabricate. Further, the contours of the device are substantially linear and planar compared to the nonlinear nature of anatomical surfaces (See, for example, FIG. 4 thereof).

The development of highly absorbent articles for blood and blood-based liquids such as catamenial pads (e.g., sanitary napkins), tampons, wound dressings, bandages and surgical drapes can be challenging. Compared to water and urine, blood and blood based liquids such as menses are relatively complex mixtures of dissolved and undissolved components (e.g., erythrocytes or red blood cells). In particular, blood-based liquids such as menses are much more viscous than water and urine. This higher viscosity hampers the ability of conventional absorbent materials to efficiently and rapidly transport these blood-based liquids to regions remote from the point of initial discharge. Undissolved elements in these blood-based liquids can also potentially clog the capillaries of these absorbent materials. This makes the design of appropriate absorbent systems for blood-based liquids such as menses particularly difficult.

Foams of various types have been suggested for use in tampons, sanitary napkins and other articles that absorb blood and blood-based liquids. See for example U.S. Pat. No. 4,110,276 (DesMarais), issued Aug. 29, 1978 (soft, flexible, open celled foams made from polyurethanes, cellulose, or styrene/butadiene rubber that can be used in tampons and sanitary pads); U.S. Pat. No. 4,752,349 (Gebel), issued Jun. 21, 1988 (foams of "medium cell size" hydrophilized by surfactant treatment and having a density within the range of 0.1 to 0.8 g/cc); U.S. Pat. No. 4,613,543 (Dabi), issued Sep. 28, 1986 (hydrophilic cellular polymers used in catamenial products); U.S. Pat. No. 3,903,232 (Wood et al.), issued Sep. 2, 1975 (compressed hydrophilic polyurethane foams useful in biomedical applications, including catamenial devices); U.S. Pat. No. 4,049,592 (Marans et al.) issued Sep. 20, 1977 (biodegradable hydrophilic polyurethane foams highly absorptive upon contact with liquids or bodily liquids having utility in sanitary napkins and the like). Prior foams used in these products have tended to have relatively large cell sizes. As a result, these prior foams do not exert sufficient fluid capillary pressure for blood and blood-based liquids to acquire discharged menstrual liquids quickly from and through the topsheet of catamenial products such as sanitary napkins. This results in undesirable wetness since the surface in immediate contact with the body retains some of the fluid that is not absorbed into the core and is available to be transferred back onto the body of the wearer.

Suitable absorbent foams for absorbent products have also been made from a High Internal Phase Emulsion (hereafter referred to as a "HIPE"). HIPE foams can provide the fluid capillary pressure necessary to remove most of the menstrual fluid from the body, or topsheet adjacent to the body, thus minimizing wetness. However, it has been found that the residual hydratable salts such as calcium chloride typically present in prior HIPE foams can impair the rapid acquisition blood and blood-based liquids by these foams, and especially the wicking of such liquids within these foams. As noted above, blood and blood-based liquids such as menses are more highly viscous than water and especially urine