JPH0566864B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATIONS The present invention generally relates to cover sheets for use in absorbent devices such as disposable diapers, sanitary napkins, disposable bed pads, nursing gauze, finger bandages, and incontinence diapers. BACKGROUND OF THE INVENTION Traditionally, absorbent devices consist of a cover sheet, an absorbent pad, and a barrier sheet in intimate contact with each other. Prior art cover sheets typically consist of a flexible plastic sheet with gaps in it to prevent liquids absorbed into the absorbent pads within the absorbent device from running off and staining nearby clothing. The prior art open, waterproof plastic sheets described above provide a degree of dryness. In order for the absorbent device to be acceptable to the general public, especially women, it is necessary that the liquid excreted by the human body is removed from the human body as quickly as possible through the cover sheet, which is in close contact with the human body, and absorbed. It must be able to be transferred into the sexual pad. Therefore, rapid transmission of liquid through this cover sheet is an essential requirement in the development of absorbent devices. Additionally, the prior art plastic sheets described above are not adhered to or in intimate contact with the absorbent pad. Therefore, the absorbent pad becomes misaligned within the device, thereby causing problems. In US Pat. No. 3,881,489, a disposable absorbent device is provided having an absorbent body encapsulated within a top cover sheet and an improved back sheet that is breathable but impermeable to liquids. The topsheet may be a conventional topsheet, such as those described in US Reissue Patent No. 26151. The improved backsheet is comprised of a combination of two adjacent separate hydrophobic layers forming an effective breathable portion of the backsheet. The first layer is liquid permeable and has a low open volume, while the second layer
The second layer is permeable to liquid and has a higher open volume than the first layer. The combination of the two backsheet layers prevents the passage of liquid while allowing the passage of gas. The disadvantages associated with the prior art described above are as follows.
That is, the topsheet is a typical topsheet made from plastic film and does not have any distinctive characteristics such as dryness or fluid permeability. In US Pat. No. 3,292,619 an invention relating to non-adhesive bandages is described. When such non-adhesive bandages are applied to cover a wound, only a portion of the body-side surface of the bandage is in contact with the body. Only a small portion of the total body side surface area of the bandage is in contact with the body. According to said invention, the main locations of fluid intake into the absorbent pad are located in depressions in the surface of the bandage that is in contact with the human body. The walls of the recess slope inward towards the body of the bandage and are lined with a thin film covering the surface of the body side pad of the bandage. The film lining the walls of the cavity is perforated. Each film recess includes a number of openings through which fluid enters. A disadvantage of this prior art fabric is that it is bonded by passing the fabric through a clamp between a stamped roll and a smooth-faced roll to provide indentations in the fabric. . Accordingly, depressions within the fabric reduce the total area available for absorbent material to absorb fluid. In U.S. Pat. No. 3,331,728, a film-fiber laminate is described, which laminate is made as a cover sheet for covering absorbent materials, such as those used in sanitary napkins. . The laminate is made by a continuous process in which the film is formed by a film extruder and immediately laid on an underlying web of perforated fibers. Next, suction is applied from the underside of the perforated web, leaving the freshly extruded film still sticky.
breaking the film in the region overlying the openings in the web of fibers while still in a loose flowing state, ensuring an intimate adhesion between the film and the underlying web of fibers; A complete opening is formed through the fabric. A disadvantage of the prior art is that the openings in the composite pass through the web of films and fibers. This allows fluid to pass through the composite and into the absorbent material, but also allows fluid to exit. The inclusion of fluids within products such as sanitary napkins therefore poses a problem. The drawbacks in the prior art described above do not exist in the present invention. This is because the fiber-film substrate of the present invention is a complete composite produced in one process step, with openings in the film cover and no depressions or holes in the web of fibers. It is. In addition, the invention is more economical to manufacture and has properties not found in the prior art, which will become more apparent in the remainder of the specification, drawings and claims. Will. [Means and Effects for Solving the Problems] The present invention is a fiber-film laminate used as a cover sheet for disposable articles, which comprises at least one layer of a polyethylene thermoplastic film having openings and a uniform thickness. It consists of a woven polypropylene fiber web, the film extending over and securing the surface of the web. Fixation of the film to the fibrous web is achieved when a heated, stamped roll with lands and grooves is applied to the surface of the thermoplastic film. When the heated mating surface of the roll slightly contacts the surface of the film, the individual contact surfaces of the film melt and form openings in the film, but no openings in the fibrous web. Not formed. When the film is melted to form an aperture, the molten film is in contact with the adjacent fibrous web layer at each aperture, and at least at the periphery of each aperture, the film and web are in contact with each other. Fixed. It is an object of the present invention to provide a substrate with excellent tensile strength, fluid permeation properties and rewetting properties. Another object of the invention is to provide a cover sheet with minimal fluid holding capacity. Yet another object of the invention is to provide a single sheet with two sides, one side of the sheet having a smooth, comfortable surface;
The other side has a fibrous surface with sufficient roughness to remain in intimate contact with the adjacent absorbent material. The object of the prior art is to develop substrates for use as cover sheets in disposable articles such as diapers and sanitary napkins, which have excellent tensile strength, minimal fluid retention capacity, fluid permeation properties and rewetting properties. It was to let him do it. To achieve most of these objectives, the prior art used separation layers to create disposable articles. These layers usually consist of a layer of plastic film used as a cover sheet and a layer of absorbent material wrapped in said cover sheet. When the substrate is used as a cover sheet enclosing a sanitary napkin, the outermost surface must not retain any menstrual fluid and must minimize soiling in order to be acceptable to women. Must be. Another requirement is to obtain a substrate with two sides: one side has a smooth, comfortable surface and the other side has a sanitary remains in intimate contact with the absorbent pad within the napkin and has sufficient roughness to retain said absorbent pad in places, thereby removing the absorbent pad from the perforated substrate. This facilitates the movement of fluids into the membrane. The present invention accomplishes what the prior art could not do by developing a single substrate with two sides having the properties described above.
In addition to sanitary products, the invention can be used as a substrate for tape linings, teabags, filter membranes, handkerchiefs, sponges, finger bandages, milk filters or wine, beer, oil, etc. Ru. As illustrated in FIG. 1, the substrate 10 of the present invention comprises at least one polypropylene fiber layer 1 of uniform thickness fixed to at least one layer such as a thermoplastic polyethylene film 14.
It may consist of 2. Although the above construction is a preferred embodiment, the film layer may also be comprised of any thermoplastic film such as polypropylene, polyurethane, polyester, copolyester or copolypropylene. The fibrous layer may be made of synthetic fibers such as polyolefin, rayon, polyester or acrylic, or natural fibers such as cotton, wood pulp, or a combination of synthetic and natural fibers. Additionally, the nonwoven fibrous web can be made from staple fibers, continuous filaments or microfibers. As shown in FIG. 4, the film layer 14
is arranged on the fibrous web layer 12. The film layer 14 and the fibrous web layer 12 are then fed between two mechanically driven heated rolls. Roll with stamp 18
The upper roll has mating surfaces and grooves, and the lower roll is a roll 20 with a smooth surface. The smooth roll 20 may be cooled to maintain a constant temperature. The stamped roll 18 may have various patterns depending on the opening requirements. The stamped roll 18 is placed in such a position that the protruding mating surface of the roll slightly contacts the surface of the film 14. Said roll 18
When said heated mating surface 21 of contacts the surface of said film, the respective contact surfaces of said film melt. When the film melts at the respective contact surfaces, openings 16, as shown in FIG.
is created or formed in the film 14. Further, as shown in the inset of FIG. 3, melted film 22 flows and contacts the fibers in the fibrous layer. Then, as the fiber-film layered substrate moves away from the heated roll clamp, the molten film cools and the two layers separate at the respective openings, as shown in the inset. They are fixed to each other at least at the periphery of the openings so that the openings are held in place. It is important to take care that said heated mating surface 21 of roll 18 does not in any way affect the structure or composition of said fibrous layer. The heated mating surface 21 is attached to the film 1
4, and must not penetrate beyond the point of contact. Therefore, the fibers of the fibrous web are substantially unaffected and the fibrous web maintains a uniform thickness. Moreover, since the heated roll only slightly contacts the film, the roll does not contact the fibrous web. Therefore, there are no depressions or holes in the fibrous web as seen in prior art fabrics.
As a result of fixation by this method, the substrate of the invention has two sides, one side, the surface, has a perforated film, and the other side, the fibrous layer,
As shown in FIG. 3, it does not include an opening. The shape and dimensions of the openings in the film may vary depending on the use of the substrate, but the film should have an open area of at least 1% of the total surface area. The opening area is defined as an opening. A preferred open area is 45% of the surface area. The apertures may be present over a large part of the surface of the film, and the apertures may be arranged in a plurality of bands depending on the requirements of the product in which the invention is used. The thickness of the film should be at least 2.54 μm (0.1 mil) to cover the fiber surface and at the same time produce a smooth surface. The thickness of the film is preferably at least 2.54 μm, but preferably 2.54 to 381 μm (0.1 to 381 μm).
15 mils). Although it is preferred to use an extruded and cured film, it is also possible to place the freshly extruded film, heated, softened and still tacky, directly onto the fibrous web, thereby The fixation of the film to the web is increased and improved. Depending on the final use, the fibrous layer may be
Made from various types and amounts of fibers. It is preferred to utilize a mixture of synthetic and natural, hydrophilic and hydrophobic fibers to minimize the fluid holding capacity of the substrate. The weight of the fiber web varies from 4.8 to 120 g/m ² (4.8 to 120 g/m 2 ) depending on the product design.
~100g/ ^yd2 ). The combined thickness of the two layers determines the mechanical and transverse tensile strength, fluid holding capacity, liquid permeation properties, etc.
Variations may be made depending on the required physical properties. Depending on the pressure and temperature used in the process, fibers with varying degrees of fiber-film adhesion may be used to secure the two layers together, as shown in FIG. . The surface treatment/impression is important and can be any pattern, continuous or discrete, with varying dimensions. The preferred drilling method is listed here for reference.
No. 3,507,943, which is described in commonly assigned US patents and which discloses the use of grooved rolls for gluing and opening. However, other methods such as engraving male and female rolls, engraving and smooth rolls or endless belts may also be used. In the case of an endless belt, hot air and vacuum may be used to create the openings and bond the layers together. Another method of punching holes in thermoplastic films is disclosed herein by reference and in common assignee U.S. Pat.
Described in No. 3038198. The invention described herein is particularly advantageous when used in disposable articles such as sanitary napkins. This is because the present invention provides superior flexibility and flexibility that cannot be obtained with prior art cover sheets.
This is because it provides dryness, fluid permeability properties and other physical properties. When using the cover sheet of the present invention in disposable articles, particularly sanitary napkins, having an internal absorbent core or pad, the strike-through value or fluid permeability is not as good as above the absorbent pad as was done in the prior art. The cover sheet of the present invention can be adjusted without being attached to the cover sheet. The "strike-through value" is defined as the time required for a certain amount of fluid to pass through the cover sheet and soak into the absorbent material. The less time it takes for the fluid to pass through the cover sheet, the better the strike-through value. To improve strike-through values, prior art disposable articles, such as sanitary napkins, are provided with an adhesive layer. The adhesive layer covers the entire cover sheet and is present between the cover sheet and the absorbent pad layer. This additional layer was able to ensure good contact between the cover sheet and the absorbent material. This contact is necessary because the fibers of the absorbent pad must be as close as possible to the cover sheet in order to draw in the fluid on the cover sheet. No intermediate layer is necessary in the substrate of the present invention. This is because the fibrous layer described here is an integral part of the cover sheet and therefore the distance between the cover sheet and the absorbent material cannot be made any closer.
Furthermore, the fiber layer plays an excellent role of sucking the fluid on the hydrophobic film layer. The fluid is then drawn in and transferred from the fibrous layer into the hydrophilic absorbent pad. This is a significant advance and distinct advantage over the prior art. It is also possible to adjust the strike-through value of the substrate of the present invention by varying the amount of hydrophilic fibers in the fibrous web, and by the selection of fibers used in the fibrous layer. Accordingly, the degree of fluid permeability can also be changed.
Mixtures of hydrophilic and hydrophobic fibers such as acrylic fibers and polypropylene fibers or cotton and polypropylene fibers may be mentioned by way of example. Furthermore, due to the wicking action of the hydrophilic fibers in the adjacent absorbent pad, fluid is drawn from the fibrous layer into the absorbent material. In this way, a minimum amount of fluid is retained in the cover material of the invention. Another advantage of the invention is due to the fact that the film of the invention is perforated without penetrating adjacent webs. Thus, the web layer without openings, when fixed to the film, acts as a buffer between the film layer and the absorbent pad, thereby preventing particles of absorbent material from passing through the film. and prevent contact with the wearer's skin. Since the web is composed of fibers, its surface tends to become fluffy. This surface fuzz provides yet another advantage to the present invention. The fuzzy surface adheres very easily to other fibrous surfaces, such as absorbent pads, thereby securing the pad and cover sheet together and ensuring that the pad and cover sheet do not fit inside the sanitary napkin when worn. Eliminate movement of absorbent pads. The cover sheet is therefore more stable against the absorbent pad, resulting in comfort and good pad stability. Yet another advantage of the present invention is the reduced rewetting or dryness of the cover sheet surface in products utilizing the present invention. For purposes herein, both reduced rewetting and drying are equivalent. Rewetting is defined as the amount of fluid that tends to flow back from the absorbent pad toward the outer surface of the cover sheet when the pad is saturated with fluid. Therefore, the less fluid reaches the surface of the cover sheet, the drier the surface remains. The present invention reduces rewetting in two ways. First, by using the hydrophilic fibers, as the fluid moves outward from the absorbent pad, it retards the movement of the fluid by reabsorbing the fluid from the pad. . Second, if the fluid has passed through the fibrous layer, it will come into contact with the hydrophobic film layer, and due to the fluid surface tension created against the film, a substantial amount of the fluid will remain in the film. There is no leakage to the outside through the opening. Due to the effect of the stamped roll on the film side, the base material of the present invention has a smooth surface that looks like a woven fabric. When the fiber side is fixed or glued to the film,
It provides support to the film. Due to the smoothness of the film side surface and the cushioning effect of the fiber side, the substrate also provides flexibility and comfort. Due to the large number of different shapes, depths, etc. of the apertures and embossing on the film surface used, the substrate of the present invention has a woven appearance. for example,
The embossed pattern may be pointed objects, circles, lines, etc. Further, by changing the open area percentage of the openings in the film, the ratio of the strike-through value to the degree of dryness can be changed. However, the more openings there are in the film, the better the permeability, and therefore the more opportunity for rewetting and wetting within the cover sheet to occur, which is obvious. This is a drawback. Therefore, the preferred open area is 45% of the surface area. The optimum condition when used in the present invention is to have a sufficient amount of openings in the cover sheet to provide good fluid permeability or strike-through while keeping the cover sheet surface dry. An important property of the substrates of the present invention is that by using appropriate thicknesses of fiber layers and films, said substrates can have varying degrees of dryness. The invention also has excellent tensile strength, which is due to the fact that a plastic film is incorporated within the substrate of the invention. EXAMPLES To illustrate that embodiments of the present invention have superior or substantially equal properties to various properties of the prior art, the strike-through values and A comparative test was conducted to compare rewetting values. Procter & Co. under the product name “Always”
Two identical sanitary sanitary napkins manufactured by Procter and Gamble were used here for comparison.
The cover sheet of the Procter & Gamble napkin is adhered to the absorbent material within the napkin by hydrogen bonds. For comparative testing, one napkin, hereinafter referred to as "A", was tested with the original cover sheet manufactured by Procter & Gamble, and the other napkin, hereinafter referred to as "Sample", was tested with the original cover sheet manufactured by Procter & Gamble. The cover sheet was carefully removed and the substrate of the present invention was placed in place as a cover sheet. This ensures that the same materials were used except for the cover sheet. The sanitary napkin consisted of an absorbent material encased within a plastic film cover sheet. Strike-through values were obtained by testing "A" with the original cover sheet under the following conditions. The conditions are as follows. Weigh the napkin and then place 1.5 ml of fluid onto the napkin cover sheet. The time required for the fluid to pass through the napkin's cover sheet and into the absorbent portion was measured. Then, the strike-through time was recorded. A similar test was conducted on the "sample" with the cover sheet of the present invention in place and the strike-through time was also recorded. It will be appreciated that the strike-through values for the two samples tested were both in the acceptable range for consumers. Using the moist sanitary napkin described above, place filter paper on top of the cover sheet,
Then on top of each of said film paper
Rewetability was tested by placing a 2.3 kg (5.0 lb) weight on it. The weight of the filter paper was measured before placing it on the napkin. The weight compressed the napkin, causing some of the fluid to exit the napkin and be absorbed into the filter paper. The weight is
It was left on each napkin for 2 minutes. Next, the weight and filter paper were removed. Next, the weight of the filter paper was measured and each weight was recorded. Then the difference between the initial weight and the final weight was determined. The results of the comparative test are shown in Table 1.

[Table] From the above results, it is proven that the cover sheet of the above "Sample" is approximately 50% superior in dryness to the cover sheet of "A", while the strike-through value is only 0.9 seconds higher. It was done. This is a substantial improvement over the dryness of the prior art. The dryness of the cover sheet is an important property. This is because ensuring comfort is the most important thing for women wearing sanitary napkins. As shown by the test results,
The substrates of the present invention exhibit lower dryness coefficients than the prior art, thereby exhibiting superior quality, a substantial advantage over the prior art. Embodiments of the present invention not only exhibit superior quality over the prior art, but are also economical because they are manufactured in one process step. Nothing herein is intended to limit the invention, other than as to the scope of the claims below.

[Brief explanation of the drawing]

FIG. 1 is a view of the fiber-film composite illustrating the two layers of the composite, and FIG. 2 is a view of the composite to illustrate the openings in the film. , FIG. 3 is a cross-sectional view across the opening of FIG. 2 to illustrate that the opening does not penetrate the fibrous web material, and FIG. 4 is a cross-sectional view of the film and the fibrous web material. FIG. 3 is a diagram showing a state in which the material is passed between a heated roll with a stamp and a smooth roll. 10: Fiber-film base material, 12: Polypropylene fiber layer, 14: Polyethylene film, 1
6: opening, 18: roll with stamp, 20: smooth roll, 21: mating surface, 22: molten film.

Claims (1)

Claims: 1 consisting of at least one thermoplastic film layer having openings and at least one continuous fibrous web layer having a uniform thickness, wherein the openings disposed in the film define a peripheral edge. the thermoplastic film and the continuous fibrous web are arranged face to face with each other, and the openings are arranged in the film without affecting the fibers or uniform thickness of the fibrous web. A fibrous web-film cover sheet base material for disposable articles, characterized in that the film and web are fixed to each other at the peripheral edge of the opening. 2. The cover sheet of claim 1, wherein the fibrous web is comprised of non-woven synthetic or natural fibers or a combination thereof. 3 The thickness of the thermoplastic film is at least
The cover sheet of claim 1, wherein the cover sheet is 2.54 μm (0.1 mil). 4 The opening area of the cover sheet is at least 1
%, the cover sheet according to claim 1. 5 The weight of the fibrous web is at least 4.8 g/
^2. The cover sheet of claim 1, wherein the cover sheet has a weight of at least 4 g/ ^yd2 . 6. The thermoplastic film is in a thermally softened state.
The cover sheet according to claim 1. 7. The cover sheet according to claim 1, wherein the openings are present over most of the surface of the film. 8. The openings are arranged in a plurality of strips,
The cover sheet according to claim 1. 9. The opening area of the cover sheet is 45%.
The cover sheet according to claim 1, 7 or 8.