JPH02102046A - Fiber-film base material - Google Patents

Abstract

PURPOSE: To obtain a base material having an excellent tensile strength, fluid permeable characteristics and rewettable characteristics by fixing a film to a web by a roll with a heated pressing die having at least one layer of a polyethylene thermoplastic film and a mating surface from a nonwoven polypropylene fiber web and grooves. CONSTITUTION: A thermoplastic polyethylene film 14 or the like is disposed on one propylene fiber web layer 12 having a uniform thickness in a layer of a thermoplastic polyethylene film 14 or the like. An upper roll has a mating surface and grooves, and a lower roll has a roll 1 with a pressing die of a smooth surface roll 20 at a position where the mating surfaces are slightly brought into contact with the surface of the film 14, individual surfaces of the film are melted to form an opening 16 at the film 14. Further, the melted film 22 is fed, brought into contact with fibers in an insulating layer, and fixed to each other at peripheral edges of the opening. The film has an opening area of at least 1%, and its thickness is at least 2.54 μm, and a weight of the fiber web is at least 4.8 G/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention generally relates to covers for use in absorbent devices such as disposable diapers, sanitary napkins, disposable bed pads, nursing gauze, finger bandages and incontinence diapers. Regarding the seat.

[Prior art and problems to be solved by the invention] Conventionally,
The absorbent device consists 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 on the absorbent pads within the absorbent device from running off and staining nearby clothing.

The prior art open-space 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 from the human body is moved away from the human body as quickly as possible through said cover sheet that is in close contact with the human body. , must be able to be transferred into an absorbent 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 may become misaligned within the device, thereby causing problems.

In U.S. 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 above-mentioned topsheet may be a conventional topsheet, such as U.S. Reissue Patent Box 26.
．． It may be as described in No. 151.

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 permeable to liquid and has a lower open volume, while 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 distinguishing 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 padding of the bandage.

The film lining the walls of the cavity is perforated. Each of the four parts of the film contains a number of openings through which fluid enters. A disadvantage of this prior art fabric is that the clamping of the fabric between a stamped roll and a smooth surfaced roll causes the fabric to adhere by passing through a section and giving the fabric an indentation. . Accordingly, depressions within the fabric reduce the total area available for absorbent material to absorb fluid.

In U.S. Pat. No. 3,331,728, the film-
A fibrous 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, and while the freshly extruded film is still sticky and fluid, it is placed between the film and the underlying web of fibers. At the same time as ensuring a close adhesion to the web of fibers, the film is torn in the area placed over the opening, and a complete opening is formed through the fabric. A drawback of the prior art is that the openings in the composite pass through the web of film and fibers. This allows fluid to pass through the composite and into the absorbent material, but also allows fluid to exit. Therefore, the inclusion of fluid within products such as sanitary napkins creates problems.

The drawbacks in the prior art described above do not exist in the present invention. Because the fiber-film substrate of the present invention is a complete composite produced in one process step,
It has openings in the film cover and no depressions or holes in the web of fibers. 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 polyethylene thermoplastic film having openings and a non-woven material having a uniform thickness. It consists of a woven polypropylene fibrous web, the film being spread over and secured to the surface of the web. Fixing of the film to the fibrous web is achieved when a heated stamped roll with mating surfaces (1and) 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 an opening is formed in the film;
No openings are formed in the fibrous web. When the film is melted to form an aperture, the molten film is in contact with the adjacent fibrous web layer at the side apertures, and at least at the periphery of each aperture, the film and web are fixed to each other.

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 having two sides, one side of said sheet having a smooth, comfortable surface and the other side having an adjacent absorbent surface. It has a fibrous surface that is rough enough to remain in intimate contact with the 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.

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 having two sides as shown below, the two sides being:
One side has a smooth, comfortable surface and the other side is rough enough to remain in close contact with the absorbent pad within the sanitary napkin and retain said absorbent pad in places. The absorbent pad has a perforated substrate and thereby facilitates fluid migration from the perforated substrate into the absorbent pad.

The present invention accomplishes what the prior art could not do by developing a single substrate with two sides with the properties described above.

In addition to sanitary products, the invention can be used as a backing material for tape linings, tea bags, filtration membranes, handkerchiefs, sponges, finger bandages, milk filters or filters for wine, beer, oil, etc. be done.

As illustrated in FIG. 1, the base material IO of the present invention is
It may also consist of at least one layer of polypropylene fibers 12 of uniform thickness, such as a thermoplastic polyethylene film 14, both fixed in one layer. It may also consist of any thermoplastic film such as polypropylene, polyurethane, polyester, co-polyester or co-polypropylene. Said fibrous layer may be made of synthetic fibers such as polyolefin, rayon, polyester or acrylic or cotton, wood bulbs etc. The nonwoven fibrous web may be made from staple fibers, continuous filaments, or microfibers.

As shown in FIG. 4, the film layer 14 is disposed over the fibrous web layer 12. The film layer 14 and the fibrous web layer 12 are then fed between two mechanically driven heated rolls. The upper roll, which is the stamped roll 18, has a mating surface 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. When the heated mating surface 21 of the roll 18 contacts the surface of the film, the respective contact surface of the film melts. As the film melts at the respective contact surfaces, openings 1B are created or formed in the film 14, as shown in FIG. Furthermore, as shown in the inset of FIG.
flows and contacts the fibers in the fibrous layer. The fiber-film layered substrate is then heated and the molten film cools as the heated rolls move away from each other, and the two layers are inserted into the side openings. As shown in the figure, the openings are fixed to each other at the periphery of the openings.

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. Said heated mating surface 21 should only contact the surface of said film 14 and not penetrate beyond the point of contact. Therefore, the fibers of the fibrous web are essentially 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 dimples or holes in the fibrous web as found in prior art fabrics.

As a result of fixation by this method, the substrate of the invention has two sides, one side, the surface, with the perforated film and the other side, the fibrous layer, as shown in FIG. , does not include openings. The shape and dimensions of the opening of the film may be changed depending on the use of the base material,
The film should have an open area of less than 1% of the total surface area. The open area is defined as openings.

A preferred opening area is 45% of the surface area. The openings may be present over a large part of the surface of the film and may be arranged in bands depending on the requirements of the product in which the invention is used. The thickness of the film is at least 2.54 μm (2.54 μm) so as to cover the fiber surface and at the same time produce a smooth surface.
0.1 mil). The thickness of the film is preferably at least 2,654 μm, but is between 2.54 and 3 μm.
It may vary within the range of 81 μm (0.1 to 15 mils). Although it is preferred to use an extruded and cured film, a heated, softened, and still tacky, freshly extruded film may be placed directly onto the fibrous web, thereby causing a Increasing and improving the fixing properties of the film. The fibrous layer is made from different types and amounts of fibers depending on the final application. 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 fibrous web is between 4.8 and 120 g/T, depending on the product design.
d, (4 to 100 g/yd2). The combined thickness of the two layers may vary depending on the desired physical properties, such as machine and transverse tensile strength, fluid holding capacity, liquid permeation properties, etc. Depending on the pressure and temperature used in the process, fibers with varying degrees of fiber-film adhesion can be used to
As shown in the figure, the two layers may be fixed to each other.

Surface treatment/embossing is important and different dimensions (d
It can be any pattern, continuous or individually separated, with 1mensions). A preferred drilling method is described in commonly assigned U.S. Patent No. 3.507.94, incorporated herein by reference, which discloses the use of grooved rolls for gluing and opening.
This is based on the technology described in No. 3. 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 described in common assignee US Pat. No. 3,038,198, incorporated herein by reference.

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, dryness, fluid permeability properties and other physical properties not available with prior art cover sheets. When using the cover sheet of the present invention in disposable articles, particularly sanitary napkins, which have 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 adjustment can be made without attaching the cover sheet of the present invention to the cover sheet. The "strike-through value" is defined as the time required for a certain amount of liquid to pass through the cover sheet and soak into the absorbent material. The shorter the time required for the liquid to penetrate 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 is
It 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. The fibers of the absorbent pad are
Since it must be as close as possible to the cover sheet in order to suck in the fluid on said cover sheet,
Said contact is necessary. 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 fibrous layer plays an excellent role in sucking the fluid on the hydrophobic film layer. The liquid 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, the fluid permeability It is also possible to change the degree. 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. Accordingly, the web layer without openings, when fixed to the film, acts as a buffer between the film layer and the absorbent pad, allowing particles of absorbent material to pass through the film and prevent wear and tear. prevent contact with human skin. Since the web is composed of fibers, its surface tends to become fluffy. This surface fuzz provides yet another advantage of 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 absorbent pad remains within the sanitary napkin when worn. Eliminate movement. Therefore, the cover sheet is 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 it 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 fluid will be 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 substrate of the present invention has a smooth, thick surface that looks like a woven fabric. The fibrous sides provide support to the film when secured or adhered 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. Openings and microbossing on the film surface used
Due to the large number of different shapes, depths, etc., the substrates of the present invention have a woven appearance. For example, the embossed pattern may be pointed objects, circles, lines, etc. Furthermore, by changing the opening area percentage of the openings in the film,
The ratio of strike through value to dryness can be varied. 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 opening area is 45 of the surface area.
%. Optimal conditions when used in the present invention provide good fluid permeability or strike-through, while
The cover sheet has a sufficient amount of openings to keep the surface of the cover sheet dry. An important characteristic 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.

[Example] Embodiments of the present invention have the following advantages over various characteristics of the prior art:
Comparative tests were conducted comparing the strike-through and rewet values of various cover sheets to demonstrate superior or substantially equal properties. Procter and Gamble under the product name ``Always.''
Two identical sanitary sanitary napkins manufactured by the company BLE) were used here for comparison. The cover sheet of the Brocter & Gamble napkin is adhered to the absorbent material within the napkin by hydrogen bonding. To perform a comparative test, one napkin, hereinafter referred to as rAJ, was tested with the original cover sheet manufactured by Brocter & Gamble, and the other napkin, hereinafter referred to as "sample", was tested with said cover sheet. The base material of the present invention was then placed in an appropriate position 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 cover sheet of plastic film. The strike-through value is r with the original cover sheet.
It was obtained by testing AJ 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. and,
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 consumer acceptable range.

Using the moist sanitary napkins described above, place a filter paper on top of the cover sheet, then add 2.3 kg (5,
The rewetability was tested by placing a weight of 0 bond) on the surface. 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 by the filter paper. The weight was placed on each napkin for 2 minutes. The weight and filter paper were then 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 1 Properties A Sample Weight (-Durham per square yard 29.6 33.0) Thickness (mils) 15.5 12.0 Strike Through (sec) 3.9 4.8 (Cover sheet) Rewetting ( Durham) 0.042 0.02B
(Dryness of cover sheet surface) From the above results, the cover sheet of the “sample” has r
Approximately 50% better dryness than AJ's cover sheet.
On the other hand, the strike-through value was proven to be only 0.9 seconds higher. 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 substrate of the present invention exhibits a lower dryness coefficient than the prior art, thereby demonstrating 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 multiple 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. 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, 16: opening, 18: roll with stamp, 20: smooth roll, 21: mating surface, 22: molten film.

Claims (9)

[Claims] 1. the thermoplastic film comprises at least one thermoplastic film layer having an aperture and at least one continuous fibrous web layer having a uniform thickness, the aperture disposed in the film having a periphery; and said continuous fibrous web
the openings are arranged in the film, arranged face to face with each other, without any effect on the fibers or uniform thickness of the fibrous web, and the film and web are arranged at the periphery of the openings; Fibrous web-film cover sheet substrate for disposable articles, characterized in that they are fixed to each other. 2. A cover sheet according to claim 1, wherein the fibrous web comprises nonwoven synthetic or natural fibers or combinations thereof. 3. the thermoplastic film has a thickness of at least 2.54
The cover sheet according to claim 1, which is 0.1 mil. 4. The cover sheet of claim 1, wherein the open area of the cover sheet is at least 1%. 5. The weight of the fibrous web is at least 4.8 g/m^
2 (at least 4 g/yd^2). 6. The cover sheet of claim 1, wherein the thermoplastic film is in a thermosoftened state. 7. The cover sheet according to claim 1, wherein the openings are present over most of the surface of the film. 8. The cover sheet according to claim 1, wherein the openings are arranged in a plurality of strips. 9. The cover sheet according to claim 1, wherein the open area of the cover sheet is 45%.