CZ390199A3 - Process for producing permeable film - Google Patents

Abstract

Film (12), which is a blend of thermoplastic polymer a an inorganic filler is inserted between the first disk (52) and an adjacent second disc (54). At least one (52) first disc has several axially spaced portions (56), separated by a single groove (58). Parts (56) are provided with teeth (57) that fit between the teeth (61) individual parts 60) of the second disc 54. A movie that passed the groove (58) on the first disc (52) and the teeth (61) to the second disc (54) remains flat and forms the first strip (64) the film (12) while the belt that passed between the teeth (57) to the first disc (52) and the teeth (61) on the second disc (54) have wavy character with bulging ribs and forming a second belt (66).

Description

Technical field

The present invention relates to a method for forming a breathable film, in particular a film comprising a mixture of a thermoplastic polymer and an inorganic material. This breathable film is particularly useful as a backsheet on a disposable, disposable article.

BACKGROUND OF THE INVENTION

Young children and individuals suffering from incontinence wear absorbent (absorbent) products, such as diapers, to collect urine and other body exudates (exudates). Absorbent articles serve not only to retain excreted fabrics, but also to isolate these fabrics from the wearer's body and from the wearer's clothing and bedding. Absorbent disposable articles having different shapes are known in the art. It is also known that the outer surface of a disposable diaper may be protected by a flexible, impervious liquid and vapor layer that prevents the absorbed liquid from flowing through the diaper and soiling clothing, bedding and the like. These outer surfaces, generally referred to as backsheets, are often formed from liquid-impermeable films such as polyethylene. Although these backsheets effectively prevent fluid from leaking through the diaper, they can make the diaper feel hot and uncomfortable to wear due to their air impermeability and / or moisture.

The vapor-permeable backsheets are commonly known as breathable backsheets and are described in the art. In general, these backsheets are intended to allow the passage of vapor while retarding the passage of fluid. For example, U.S. Patent No. 3,156,342, issued November 10, 1964 to Crowe, Jr., discloses the use of a microporous film as a breathable backsheet. U.S. Patent No. 3,881,489, issued May 6, 1975 to Hartwell, discloses a breathable backsheet comprising two layers, the first forming a perforated thermoplastic film and the other forming a porous hydrophobic material. U.S. Patent No. 3,989,886, issued November 2, 1976 to Sisson, discloses a breathable backsheet provided with conical hollow bumps that prevent fluid passage while allowing vapor to pass easily.

Microporous films are most often used on the breathable back layers. The microporous films comprise a mixture of a thermoplastic polymer and an inorganic filler, such as a carbonate, such as carbonate.

-2calcium. This mixture can withstand the formation of vents upon stretching when the inorganic filler separates from the polymer due to the pressure concentration. The formation of micro-vents allows the film to be breathable and allows vapor to pass through the micro-vents while slowing the passage of fluids.

It is an object of the present invention to provide an entirely novel method for forming a breathable film from a mixture of a thermoplastic polymer and an inorganic material.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a method for forming a breathable film. The film consists of a mixture of a thermoplastic polymer and an inorganic material selected from the group consisting of calcium carbonate, clay and titanium dioxide, the inorganic filler preferably being calcium carbonate. This mixed film is inserted between a pair of opposing rolls. The first disk comprises a plurality of toothed parts separated from each other by a plurality of grooved parts, wherein the toothed parts comprise a plurality of teeth. The second disc includes a plurality of teeth that engage the teeth of the first disc. When the film is inserted between the first and second reels, the film section passing between the grooved portions on the first reel and the teeth on the second reel remains two-dimensional, forming the first part in the film, while the film section extending between the teeth on the first reel and the teeth on the second reel the discs, forming a second portion having the character of convex ribs.

Brief overview of the drawings

While the specification ends with the claims particularly referring to the present invention, we hope that the present invention will be better understood from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate like elements and wherein:

Giant. 1 is a schematic illustration of an exemplary method for forming a breathable film of the present invention.

Giant. 2 is an enlarged view of the opposite pair of disks of the method of FIG. 1.

Giant. 3 is a plan view of a preferred embodiment of a breathable polymeric film having a first portion and a second portion, wherein the second portion has the shape of convex ribs.

Giant. 3A is a perspective view of a portion of the breathable film of FIG.

Giant. 4 is an enlarged photograph of a breathable film of the present invention.

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-3Fig. 4Α and 4Β are enlarged cross-sectional photographs of a breathable film showing the formation of microventures in the portions of the film that have been stretched.

Giant. 5 is an illustration of an alternate embodiment of the opposite pair of disks of the method of FIG. 1.

Giant. 6 is an illustration of another embodiment of the opposite pair of disks of the method of FIG. 1.

Giant. 7 is a schematic illustration of an alternative method for forming a breathable film of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Although the present invention will now be described in the context of a breathable film forming method particularly suitable for use as a backsheet on a disposable absorbent article such as a diaper, sanitary napkin or bandage, the present invention is by no means limited to such an application. . A detailed description of the method will enable those skilled in the art to readily adapt the present invention to other applications.

Figure 1 schematically illustrates the process of forming the breathable material of the present invention under number 10. According to the present invention, the film 12 is unwound from the supply reel 11 and moves in the direction indicated by the arrows. This film 12 comprises a mixture of a thermoplastic polymer and an inorganic material. Suitable thermoplastic polymers include polyolefins such as polyethylenes, including linear low density polyethylene, low density polyethylene, ultra low density polyethylene, high density polyethylene, or polypropylene, and mixtures thereof with the aforementioned materials and other materials. Other suitable thermoplastic polymers that can also be used are polyester, polyurethanes, compostable or biodegradable (microorganism) polymers, heat-shrinkable polymers, thermoplastic elastomers, and metallocene catalyst based polymers.

The inorganic filler or filler is selected from the group consisting of calcium carbonate, clay and titanium dioxide, the inorganic filler preferably being calcium carbonate. The inorganic fillers have a particle size of 1 to 5 microns and constitute 5 to 70% by weight of the composition, preferably 20 to 60% by weight of the composition. The inorganic filler may be provided with an ester containing a fatty acid to achieve a higher value in the polymer.

The inorganic filler and thermoplastic polymer are mixed together to form a homogeneous mixture in a suitable extruder or in a different preparatory mixing operation. This mixture is then poured into a film.

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From the supply spool 11, film 12 is inserted between the grip 51 of the two opposing disks 52 and 54 of the apparatus 50. The apparatus 50 is more clearly shown in FIG. 2. The disk 52 comprises a plurality of toothed portions 56 and grooved portions 58 extending around the periphery of the disk. The toothed portions 56 comprise a plurality of teeth 57. The teeth 57 are parallel to the axis of the disc 52. The disc 54 comprises a plurality of toothed portions 60 and grooved portions 62 extending around the periphery of the disc. The toothed portions 60 comprise a plurality of teeth 61. The teeth 61 are parallel to the axis of the disc 54. The spline portions 58 of the disc 52 form a line with the spline portions 62 of the disc 54. Similarly, the toothed portions 56 of the disc 52 are in line with the toothed portions 60 of the disc 54 the teeth of the disc 52 fit into the teeth 61 of the disc 54. The sections of the film 12 extending between the grooved portions 58 and 62 will not be formed, i.e. the film 12 will not be formed or stretched and will remain two-dimensional while those sections of the film extending between the toothed portions 56 and 60, will be formed and / or stretched to form a surface in the film having the appearance of convex ribs.

Conventional drive means and other devices that can be used in conjunction with the apparatus of Fig. 1 are well known and are therefore not shown schematically in Fig. 1.

The above process can be repeated as long as desired until the desired properties are achieved. It is even possible to select the degree of engagement of the opposite toothed wheels, the size, shape and distance of the teeth on the opposite wheels, and the size of the wheels to achieve the desired properties.

FIG. 3 shows a preferred embodiment of the breathable film 12 after having passed between a pair of opposing disks 52 and 54 of the apparatus 50. The breathable film 12 is shown in FIG. 3 in an unstretched state. The breathable film 12 is particularly suitable for use as a backside on an absorbent article, such as a sanitary napkin or disposable diaper. Film 12 has two central lines; a longitudinal line, hereinafter also referred to as axis, line or direction "1", and a transverse or lateral central line, hereinafter also referred to as axis, line or direction "t". This transverse central line "t" is usually perpendicular to the longitudinal central line "1".

In Figures 3 and 3A, the film 12 comprises a network of different sections. The network comprises at least a first section 64 and a second section 66. The film 12 comprises a transition section 65 that is at the interface between the first section 64 and the second section 66. The film 12 has a first surface 52a and an opposite second surface 52b. In the embodiment shown in FIGS. 3 and 3A, the film comprises a plurality of first sections 64 and a plurality of second sections 66. These first sections 64 have a first axis 68 and a second axis 69, wherein the first axis 68 is

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Preferably longer than the second axis 69. The first axis 68 of the first section 64 is parallel to the longitudinal axis of the film 12, while the second axis 69 is parallel to the transverse axis of the film 12. The second sections 66 have a first axis 70 and a second axis 71. parallel to the longitudinal axis of the film 12, while the second axis 71 is parallel to the transverse axis of the film 12. In the preferred embodiment of Fig. 3, the first sections 64 and second sections 66 are linear extending continuously in a direction parallel to the longitudinal axis of the film 12.

The film 12 comprises at least a first section and a second section, wherein the first section is visibly different from the second section. The term "visibly different" refers to those features of a film that are readily discernible to the naked eye when the film or articles containing the film are put to normal use.

In the preferred embodiment shown in Figures 3 and 3A, the first sections 64 are two-dimensional. That is, the forming operation through which the film 12 passes will leave the material in the first section 64 in the same condition as before. The second sections 66 comprise a plurality of elements having the character of convex ribs 74. These rib elements 74 have a first or large axis 76 that is parallel to the transverse axis of the film 12 and a second or small axis 77 that is parallel to the longitudinal axis of the film 12, the axis 76 of the rib-like elements 74 is at least equal to the second axis 77, and preferably longer than it. Preferably, the ratio of the first axis 76 to the second axis 77 is at least 1: 1 or greater, and optimally at least 2: 1 or greater.

The rib-like elements 74 in the second section 66 may be separated by unformed surfaces. Preferably, the rib-like elements 74 are adjacent to each other and are separated by an unformed area of less than 0.1 inches, measured perpendicular to the large axis 76 of the rib-like elements 74, and optimally the rib-like elements 74 are adjacent and have no unformed area between them. The size of the rib-like elements may also be varied. A more detailed description of the film having the first and second sections as shown in FIG.

and 3A, can be found in U.S. Patent No. 5,518,801, issued May 21, 1996 (Chappell), which is only mentioned herein.

FIG. 4 is an enlarged photograph of the film 12 after it has passed between two opposing rolls of the present invention, such as opposing rolls 52 and 54 of the apparatus 50. As seen in FIG. 4, the film 12 comprises two-dimensional first sections 64 and second sections 66 The film sections 12 forming the rib elements 74 of the second section 66 have been stretched or thinned, in contrast to the thick first sections 64 that were not

-6loaded or thinned. The stretching or thinning is not necessarily uniform in the second sections 66.

Giant. 4A and 4B are enlarged photographs of portions of a cross-section of a film. The film section of FIG. 4A is stretched to a greater extent than the film section of FIG. 4B, and hence has a smaller thickness than the film section of FIG. 4B. Compared to the film of FIG. 4B, the film of FIG. 4A has an increased number of vents in addition to the reduced thickness. By stretching the film, the inorganic filler is separated from the polymer, whereby the pressure concentration creates vents in the film. The formation of micro-vents allows the film to be breathable and to allow vapor to pass through, while the passage of the fluid is slowed.

One breathability measurement is a measure of the moisture vapor permeability through the material. In order to reduce humidity and temperature within the diaper calculated that, when used with the breathable film as a backsheet for the diaper, should have a transmission rate of wet vapor of 500 g / m ^2/24 hrs. To 5000 g / m ^2/24 h ., in the best case 1000 g / m ^2/24 hrs. to 5000 g / m ^2/24 hr., and optimally 2,000 g / ^m2 / 24h to 5000 g / m ^2/24 hr.

The moisture vapor permeability rate is measured by the method described below. A certain amount of Ca Cl ² is placed in a flask. The test material is placed on top of the flask and securely held by the retaining ring and the gasket. This grouping is then weighed and recorded as the initial weight. The array is placed in a chamber (confined spaces) at a constant temperature (40 °)

C) and humidity (75% relative humidity) for five hours. The array is then removed from the chamber and left for at least 30 minutes to cope with the room temperature where the weight is placed. The grouping is then weighed and recorded as the final weight. Wet vapor transmission rate (MPW) is calculated and expressed in g / m ^2/24 hr. Using the following formula:

MPW - (final weight - initial weight) x 24.0 sample area in meters x 5.0 (chamber time)

Another measure of breathability is the oxygen penetration rate (MPK) of the material. In order to reduce humidity and temperature within the diaper, calculated that the breathable film when used as a backsheet for the diaper, should have a degree of oxygen permeation 3 m ³ / m ^2/24 h to 20 m ³ / m ^2/24 throw.

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The oxygen penetration rate is measured by the method described below. The rate of oxygen penetration through the material is measured by using a glass chamber with an oxygen monitor and test. The sample is cut approximately equal in diameter to an aluminum aluminum disc having a diameter of 12 cm. The sample is placed on top of the disc. A glass chamber is placed on the disk and a circle is indicated. This circle is cut in the sample. Once ready, the sample disc (aluminum side down) is pressed between the glass chamber containing the test and the middle glass portion. A circular piece of rubber is placed between the middle glass portion and the open mouth of the glass chamber and is sealed by a second press. The chamber is filled to the brim with nitrogen at a concentration of 0.1% oxygen on both sides of the film. One side is then exposed to air (20.9% oxygen), and the time required to reach predetermined oxygen concentrations on the opposite side of the film is recorded. The oxygen penetration rate through the sample is then calculated using the following formula:

MPK = (5.57 * 10 ⁴ ) (volume (ml)) (mean time (t)) where:

(5.57 * 10 ⁴ ) = Constant value including slope of the curve (time in minutes versus% change in oxygen level (0.5%)), 1% oxygen level, seconds to minutes adjustment, minutes to days adjustment, and sample area content (0.775 in ² );

Volume = Measured volume of the glass chamber containing the oxygen test;

Time Mean = The average value of the time interval associated with a 0.5% increase in oxygen concentration.

Prior to completing this process, the mixed film MPW is less than 100 g / m ^2/24 hr and an oxygen permeation rate of less than 0.5 m ³ / m ^2/24 hrs. Thus blended film does not provide the desired breathability achieved until after it passes through the process of the present invention.

As shown in Figs. 3A and 4, the method of the present invention extends the film out of the x-y plane, i.e., in the z direction, to provide the film with increased scaling over the convex rib elements. Conversely, a traditional additional tensioner, such as described in U.S. Patent No. 4,116,892, issued September 26, 1978 (Schwarz), extends the film in the x y plane, in the longitudinal or transverse directions, or both. Hence the traditional additional tension • φ · · φ φ φ φ φ · · · · φ φ φ φ φ φ

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The apparatus produces a film of larger two-dimensional dimensions, eg a film having a greater width and / or length. The formation of a larger-dimensional film may be undesirable in certain circumstances where it may require modification of an existing manufacturing facility to handle the larger film.

In addition to providing a breathable film, the process also provides a film having the appearance of a fabric. This is particularly important if the film is to be used as a backing layer on a diaper. In addition, the present invention may also provide a breathable film with elastic properties that allow the film to be stretched under relatively low pressure. The ability to stretch under normal wear pressure can be very useful for disposable diapers since it provides increased wearer comfort and adaptability.

In contrast, when the film is unwound from the supply reel, as shown in FIG. 1, the film 12 may be inserted between the grip 51 of the two opposing disks 52 and 54 without first being deposited on the supply reel. For example, the film 12 may be inserted between the push 51 directly from the extruder.

After the film 12 has been inserted between the grip 51 of the opposing disks 52 and 54, the film 12 can be wound onto a take-up reel. Alternatively, the film may be delivered directly to the absorbent article to form its backsheet.

Examples of disposable absorbent articles are described in U.S. Patent No. 4,950,264, issued August 21, 1990 (Osborne), U.S. Patent No. 4,425,130, issued January 10, 1984 (Des Marais), U.S. Patent No. 4, U.S. Pat. No. 321,924, issued March 30, 1982 (Ahr), U.S. Patent No. 4,589,876, issued August 18, 1987 (Van Tilburg), U.S. Patent No. 3,860,003, issued January 14, 1975 (Kenneth B. Buell) ), and U.S. Patent No. 5,151,092, issued August 29, 1992 to Kenneth B. Buell.

While the entire film may be exposed to the forming operation, the present invention may also be practiced such that only a portion of the film is exposed to the forming. For example, it may be desirable to provide certain portions of the diaper backsheet with breathability, such as a side portion, while leaving other portions, e.g.

After being formed, the breathable film may be attached to other materials to form a laminate. Preferably, the breathable film is attached to the nonwoven fiber. The nonwoven fiber may comprise natural fibers (e.g., cotton or wood fibers), or may comprise synthetic fibers, such as polyethylene, polypropylene, polyester, or any combination of these fibers. The nonwoven fiber may be combed (carded), spun, hot-blown or air-blown, or may have other properties or may be produced by any of the following:

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In a manner known in the art. Nonwoven fibers are preferred when the laminate is to be used as the backsheet of the diaper, wherein the nonwoven fiber forms the outermost coating of the diaper, giving the diaper the look and feel of the fabric. In addition, the outer coating of the nonwoven fiber may provide the diaper with a band capable of joining the hooks and tabs on the fixture. Other embodiments are contemplated in which the breathable film is bonded to other materials such as wood fibers, foams, thin, coarse woven cotton cloths, films, or any other materials or combinations that provide the appearance and feel of the diaper. fabric.

These laminates can be made by any of a number of methods known to those skilled in the art. Such bonding methods include thermal bonding, adhesive bonding (using any of a variety of adhesives including spray adhesives, hot melt adhesives, latex-based adhesives, and the like), pressure bonding, ultrasonic bonding, dynamic mechanical bonding, acoustic bonding, or any other bonding agent. a suitable joining technique or a combination of such joining techniques known in the art.

Alternatively, the blended film may be first bonded to another material to form a laminate before being formed according to the method of the invention described above. The laminate may comprise any of the above structures. In a particularly preferred embodiment, the laminate is formed by extruding the breathable composition into a nonwoven fiber. The blended film is extruded directly into the nonwoven fiber in a still partially liquid state, thereby joining the blended film to one side of the nonwoven fiber. The laminate may then be subjected to the process of the invention. Alternatively, the laminate may be formed by vacuum laminating the nonwoven fiber into a breathable composition. The laminate may then be subjected to the process of the invention.

FIG. 5 is an illustration of an alternate embodiment of the opposed pair of disks of the process of FIG. 1. From the supply reel, film 12 is inserted between a grip 151 of two opposing disks 152 and 154 of the apparatus 150. The reel 152 includes a plurality of toothed portions 156 and grooved portions 158 around the circumference of the disc. The toothed parts 156 comprise a plurality of teeth 157. These teeth 157 are parallel to the axis of the disc 152. The disc 154 comprises a plurality of teeth 161 extending around the periphery of the disc. The teeth 161 are parallel to the axis of the disc 154, the teeth 157 of the disc 152 fit into the teeth 161 of the disc 154. The sections of the film 12 passing between the grooved portions 158 of the disc 152 and the teeth 161 of the disc 154 will not be formed. stays two-dimensional while sections * * · ·

The film 10 extending between the toothed parts 156 comprising the teeth 157 and the teeth 161 of the disc 154 will be formed and / or stretched to form rib-like elements in the film.

FIG. 6 is an illustration of an alternate embodiment of the opposed pair of disks of the process of FIG. 1. From the supply reel, film 12 is inserted between a grip 251 of two opposing disks 252 and 254 of the apparatus 250. parallel to the axis of the disc 252. These toothed portions 256 comprise a plurality of teeth 257. The teeth 257 are perpendicular to the axis of the disc 252. The disc 254 comprises a plurality of teeth 261 extending around the periphery of the disc. The teeth 261 are perpendicular to the axis of the disc 254. The teeth 257 of the disc 252 fit into the teeth 261 of the disc 254. The sections of the film 12 extending between the grooved portions 258 of the disc 252 and the teeth 261 of the disc 254 will not be formed. and will remain two-dimensional while sections of the film extending between the toothed portions 256 containing the teeth 257 and the teeth 261 of the disc 254 will be formed and / or stretched to form rib-like elements in the film.

Giant. 7 is a schematic illustration of an alternative method for forming a breathable film of the present invention. The film 312 is unwound from the supply reel 311 and extends in the direction indicated by the arrows. Film 312 comprises a mixture of a thermoplastic polymer and an inorganic material. From the supply reel 311, film 312 is inserted between the grip 351 of the two opposing disks 352 and 354 of the apparatus 350. The opposing disks 352 and 354 may be any of those shown in Figures 2, 5, or 6. After being formed by the apparatus 350 the film 312 is inserted between the grip of the two opposing disks 452 and 454 of the apparatus 450. The opposing disks 452 and 454 may be any of those shown in any of Figs. 2, 5 or 6.

The above process can be repeated until the desired properties are achieved. In addition, the degree of engagement of the toothed opposing discs, the size, shape and distance of the teeth on the opposing discs, and the size of the discs, may be selected to produce the desired properties.

In an alternative embodiment, the method of the invention may be performed in combination with the additional stretching operation described in the aforementioned U.S. Patent No. 4,116,892, issued September 26, 1978 to Schwarz. For example, the film may be stretched and then inserted between opposing rolls of the present invention. The above process may be reversed and / or repeated to produce the desired properties in the film.

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Various embodiments of the present invention have been illustrated and described herein, and it should be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and spirit of the invention. It is therefore intended to cover all such changes and modifications in the appended claims.

Claims (9)

PATENT CLAIMS A method for forming a breathable film, a film comprising a mixture of a thermoplastic polymer and an inorganic material, characterized in that; a) the film is inserted between the first roll and the second roll, the first roll comprising a plurality of toothed parts separated by a plurality of grooved parts, the toothed parts comprising a plurality of teeth, the second roll comprising a plurality of teeth which fit into the teeth on the first roll; when the film is inserted between the first disc and the second disc, the film section passing between the grooved portions on the first disc and the teeth on the second disc remains two-dimensional and forms first sections in the film, while the film section extending between the teeth on the first disc and the teeth on the second The disc is formed into second sections having the appearance of convex ribs. The method of claim 1, wherein the first section and the second section are visibly different from each other. Method according to claim 1 or claim 2, wherein the first section is not rib-like (does not have rib-like elements). The method of any one of the preceding claims, wherein the film forms a backsheet on the absorbent disposable article. The method of any one of the preceding claims, wherein the film forms part of the backsheet on the disposable absorbent article. Method according to any one of the preceding claims, further comprising the following step: b) bonding the film to the nonwoven fiber. The method of claim 1, wherein the film is bonded to the nonwoven fiber to form a laminate prior to step a). * 9 9 9 9 9 9 9 9 ·· «···· The method of claim 7, wherein the film is bonded to the nonwoven fiber by extruding the film into the nonwoven fiber. The method of any preceding claim, wherein the inorganic material comprises calcium carbonate. The method of claim 1, further comprising the following step: b) inserting a film between the third disc and the fourth disc, the third disc comprising a plurality of toothed parts separated by a plurality of grooved parts, the toothed parts comprising a plurality of teeth parallel to the axis of the third disc; the teeth of the fourth disc are parallel to the axis of the fourth disc.