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LAMINATION OF APERTURED OR NONAPERTURED THREE-DIMENSIONAL FILMS TO APERTURED OR NON-APERTURED THREE-DIMENSIONAL AND/OR FLAT FILMS
This is a divisional of application Ser. No. 08/467,837 filed on Jun. 6.1995. now U.S. Pat. No. 5.698.054 which is a divisional of application Ser. No. 08/286.475 filed on Aug. 5. 1994. now U.S. Pat No. 5.635.275.
TECHNICAL FIELD
The present invention relates to the application or lamination of a first film material onto a second material utilizing the heat generated by extrusion of the first and/or second film materials. The present invention is especially useful in laminating an apertured film to a non-apertured threedimensional or formed film. The present invention is also especially useful for laminating a three-dimensional nonapertured film to another three-dimensional non-apertured film.
BACKGROUND OF THE INVENTION
Many types of substrates including paper, non-woven laminates, foils, films, sheeting wood and other materials have been coated using an extrusion coating method. The extrusion coating process generally includes an extruder slot (cast) die mounted in a position above the substrate to be coated.
In the processes where nip rolls are utilized to apply a coating material to a substrate, the nip rolls add pressure to the substrate and coating material at the interface. However, the nip pressure used in extrusion coating technology causes distortion of the coating material and the substrate at the nip interface.
Previous attempts to laminate a three-dimensional material onto thin film materials which are particularly sensitive to excessive thermal loads have not met with success. In particular, the application of a three-dimensional apertured or non-apertured material to another three-dimensional apertured or non-apertured material has been especially difficult to achieve. In such cases, there must be sufficient thermal energy to cause the first three-dimensional non-apertured film material and the second three-dimensional nonapertured film material to melt and fuse together. Often these materials do not have sufficient mass to resist distortion under the required thermal load necessary to achieve a good bond between the film materials.
It is therefore an object of the present invention to provide an improved method for laminating a three-dimensional apertured or non-apertured film material to a flat or threedimensional apertured or non-apertured film material.
It is another object of the present invention to provide an improved composite laminated film comprising a threedimensional apertured or non-apertured film material laminated to a flat or three-dimensional apertured or nonapertured film material.
It is still another object of the present invention to provide an article suitable for use as a disposable absorbent product such as diapers, catamenial pads, surgical dressings and the like.
DISCLOSURE OF THE INVENTION
The present invention relates, in part, to a method for producing a laminated film having at least one three
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dimensional apertured or non-apertured film material laminated to at least one flat or three-dimensional apertured or non-apertured film material and the films produced thereby. In order to have a thermoplastic material adhere or bond 5 to another material, at least one of the materials must be supplied at a sufficiently elevated temperature at a point of interface. The interface is the point at which the two materials come into contact with each other. The temperature must be sufficiently elevated so that there is sufficient 10 thermal energy supplied at the point of interface. The elevated temperature causes at least one of the following: melting and fusing of each of the materials together to form a bond, a chemical reaction of one material with the other material to form a bond, or melting of one material on the 15 other material (non-melted) to form a cohesive bond.
It is important to understand that since the viscosity of fluids correlates to the temperature of the fluids, the higher the temperature, the less viscous the fluid. Therefore, maintaining a high temperature (i.e., low viscosity) as one 20 material contacts the other material is important. This maintenance of thermal energy as. and after, the materials contact each other is controlled by two parameters of thermal dynamics, i.e.. temperature and mass. At least one material must be supplied at a sufficiently elevated temperature and 25 at a sufficient mass in order to achieve a good bond. The materials being laminated together must be maintained at that sufficiently elevated temperature for a sufficient time for the bond to form. Polymers, and in particular thermoplastic polymers useful 30 for laminating to other thermoplastic or non-thermoplastic materials, have well-defined upper limits of temperature which can be manipulated before degradation of the polymer occurs. The well-defined thermal degradation limit of the polymer necessarily controls the amount of heat supplied to 35 the lamination process. The other parameter which can be controlled is the mass of the materials being laminated together. Generally, the mass is controlled by regulating the thicknesses of the materials. In various extrusion applications, it is desired to laminate a thin material to 40 another material. However, if too thin a layer is laminated, the layer quickly loses heat and cools too quickly. Without sufficient heat, the low mass of the laminating material does not bond to the other material. Therefore, the lamination of one material to another material is limited by the parameters 45 of mass and temperature of the materials and by the length of time at which the materials are maintained at the proper temperature.
The thermal requirements of the lamination process are further affected if both materials are thermally sensitive
50 materials. The amount of thermal energy applied to the thermally sensitive materials is necessarily limited by the amount of thermal energy the materials substrate can tolerate without being damaged. This is especially true for a material which is a three-dimensional polymeric film having
55 microscopic protuberances (either open or closed). In applications where the microscopic protuberances have been opened or exploded such that there are apertures in the film, the thickness (and mass) of the film at the open ends of the protuberances is further reduced. The thinness of the open
60 ends of the protuberances results in a film material having a cloth-like or silky tactile effect which is desired in many film applications. However, these microscopic film protuberances (either open or closed) are sensitive to temperature and have the lowest mass point of the polymeric film and. as
65 such, are the most critical to protect. While it would be desirable to laminate another thermoplastic or nonthermoplastic material to such type of three-dimensional
thermoplastic film material, various difficulties occur when using the currently known coating technologies. In particular, both the thermal energy of the known extrusion coating systems and the compressive energy of the nip roll systems have, until the present invention, made it virtually impossible to achieve good bonding strength between the microscopic protuberance-filled three-dimensional material and any material laminated thereto without causing the destruction of the microscopic protuberances.
It is important that the microprotuberances not be crushed or destroyed during lamination of the three-dimensional film material to another film material. It is also important that any temperatures and/or pressures applied during the lamination process not cause the film materials being laminated together to be destroyed.
According to one embodiment of the present invention, a first thermoplastic material is extruded onto a film forming screen having a top surface and a bottom surface and having a plurality of perforations extending through the screen. A pressure differential is applied to a portion of the bottom surface of the film forming screen such that portions of the extruded film material are drawn into the perforations in the screen. The pressure differential pulls the portions of film material into the perforations in die screen and a plurality of three-dimensional microprotuberances are formed. If the pressure differential is sufficiently great, the microprotuberances are ruptured such that apertures are formed in the film. In other embodiments, the pressure differential is controlled such that no apertures are formed. The microprotuberances can have any combination of shapes; for example, the microprotuberances can be circular, hexagonal, quadrangular and the like. Likewise, the depth and width of the apertures can greatly vary, depending on the thickness by weight of the film material.
A second material is laminated to the first thermoplastic film. In certain embodiments, the second material comprises a three-dimensional apertured material wherein the second material is laminated to the first material at a point prior to the formation of the microprotuberances in the first material. In other embodiments, the second thermoplastic material comprises a non-apertured flat or three-dimensional formed film wherein the second material is laminated to the first material at a point after formation of the microprotuberances in the first film material.
According to (he present invention, various thermoplastic films are suitable for use as either first material and/or the second material. Useful films include such films as polyethylene, polypropylene, ethylene vinyl acetate and other such polymeric materials. It is to be understood that the second material can also be a non-thermoplastic material such as paper, tissue or foil. It is to be understood that either or both of the films to be laminated can include other ingredients such as surfactants to modify the film's surface energy. In such embodiments, these surfactants allow control of fluid flow onto or through the laminate material. It is further to be understood that the first and/or second materials can comprise more than one layer. In particular, the film materials can be coextruded materials. Each layer of the coextruded material can have different properties which enhance lamination of the first material to the second material and/or provide other advantages to the laminate film.
It is to be understood that each three-dimensional film has a planar surface and a three-dimensional surface. According to the present invention, either the planar surface or the three-dimensional surface of the first material can be lami
nated to either the planar surface or the three-dimensional surface of the second material. In one preferred embodiment, a thermally sensitive three-dimensional apertured film can be laminated to a thermally sensitive three
5 dimensional non-apertured film such that there is good bond strength between the apertured film and the non-apertured film without causing thermal distortion or damage to the microprotuberances of either film.
It is also to be understood that the first film material and
10 the second film material can comprise more than one layer of material. In a particularly preferred embodiment, a composite laminate film comprises a first non-apertured threedimensional film having a planar side and a threedimensional side and a second non-apertured three
15 dimensional film having a planar side and a threedimensional side, wherein the three-dimensional side of the second non-apertured film is laminated to the planar side of the first non-apertured film The composite film further has a nonwoven layer comprised of a substantially liquid per
20 vious fibrous materials adjacent the planar side of the second non-apertured film.
Thus, composite articles of the present invention provide highly desirable liquid impervious or liquid pervious characteristics and also provide the advantage of the desired
25 tactile suede or cloth-like properties to the article produced with such films.
BRIEF DESCRIPTION OF THE FIGURES
30 FIG. 1 is a simplified cross-sectional schematic illustration of one process for laminating a material B onto one side of a material A.
FIG. 1A is a greatly enlarged cross-sectional illustration of the gap area shown in FIG. 1. 35 FIG. 2 is a simplified cross-sectional schematic illustration of another process for laminating a material B onto one side of a material A.
FIG. 2A is a greatly enlarged cross-sectional illustration of the gap area shown in FIG. 2.
FIG. 3 is a simplified, greatly enlarged cross-sectional illustration of one embodiment of a composite film material comprising a three-dimensional apertured film having a planar side and a three-dimensional side, wherein the threedimensional side of the apertured film is laminated to a 45 planar side of a three-dimensional non-apertured film and a nonwoven material is laminated to the planar side of the apertured film.
FIG. 4 is a simplified greatly enlarged cross-sectional illustration of another embodiment of a composite film material comprising a three-dimensional apertured film having a planar side and a three-dimensional side, wherein the planar side of the apertured film is laminated to a planar side of a three-dimensional non-apertured film. 55 FIG. 5 is a simplified greatly enlarged cross-sectional illustration of another embodiment of a composite film material comprising a first three-dimensional non-apertured film having a planar side of the first film and a threedimensional side, wherein the planar side of the first film is gg laminated to a planar side of a second three-dimensional non-apertured film.
FIG. 6 is a simplified greatly enlarged cross-sectional illustration of another embodiment of a composite film material comprising a flat or planar material laminated to a 65 planar side of a triree-dimensional non-apertured film.
FIG. 7 is a simplified greatly enlarged cross-sectional illustration of another embodiment of a composite film
material comprising a flat or planar thermoplastic film laminated to a planar side of a three-dimensional apertured film.
FIG. 8 is a simplified greatly enlarged cross-sectional illustration of another embodiment of a composite film 5 material comprising a first three-dimensional apertured film having a planar side and a three-dimensional side, wherein the three dimensional side of the first film is laminated to a planar side of a second three-dimensional apertured film.
FIG. 9 is a simplified greatly enlarged cross-sectional 10 illustration of another embodiment of a composite film material comprising a first three-dimensional apertured film having a planar side and a three-dimensional side, wherein the three dimensional side of the first film is laminated to a planar side of a second three-dimensional apertured film. 15
FIG. 10 is a simplified greatly enlarged cross-sectional illustration of another embodiment of a composite film material comprising a first three-dimensional apertured film having a planar side and a three-dimensional side, wherein the planar side of the first film is laminated to a planar side of a three-dimensional apertured film.
FIG. 11 is a simplified greatly enlarged cross-sectional illustration of another embodiment of a composite film material comprising a three-dimensional non-apertured film 25 having a planar side and a three-dimensional side, wherein the three-dimensional side of the non-apertured film is laminated to a planar side of a coextruded three-dimensional non-apertured film.
FIG. 12 is a simplified greatly enlarged cross-sectional 30 illustration of another embodiment of a composite film material comprising a first three-dimensional non-apertured film material having a planar side and a three-dimensional side, wherein the three-dimensional side of the first film is laminated to a three-dimensional side of a second three- 35 dimensional non-apertured film and wherein a nonwoven material is laminated to the planar side of the second material.
BEST MODE OF CARRYING OUT INVENTION
One embodiment of the present invention is generally shown in FIGS. 1 and 1A. A first material A is dispensed from a slot die 10 having an aperture 12 onto a moving member 20. It is to be understood that the moving member can be a cylindrical screen or a conveyor belt type apparatus 45 or other moving member. For ease of illustration, the moving member is depicted herein as a cylindrical screen. In preferred embodiments of the present invention, the aperture 12 is spaced at a predetermined distance from the screen 20. The screen 20 has a surface 22 which is highly perforated 50 with perforations 24 (seen in FIG. 1A) shown in a greatly enlarged manner for ease of illustration. The perforations 24 extend through the surface 22 to allow fluid such as air to pass through the surface 22 of the screen 20. A vacuum chamber 26, preferably located within the screen 20, is 55 utilized to create a pressure differential.
The material A, being dispensed onto the screen 20. has a top surface 16 and a bottom surface 18. The vacuum chamber 26 creates a pressure differential between the top surface 16 and the bottom surface 18 of the material A. The 60 pressure differential causes portions of the material A to be pulled into the perforations 24 in the screen 20. The pressure differential is sufficient to produce three-dimensional microprotuberances 19 on the bottom surface 18 of the material A, as best seen in FIG. 1A. In various embodiments, the 65 pressure differential is sufficient to cause the microprotuberances 19 to rupture, thus forming an apertured material A. In
other embodiments, the pressure differential is regulated such that microprotuberances 19 are formed extending from the bottom surface 18 of material A without any rupturing of the microprotuberances 19.
The vacuum chamber 26 generally comprises a leading edge 28 and a trailing edge 29. The microprotuberances 19 are generally formed in an area adjacent the leading edge 28 of the vacuum chamber 26. As the film A moves towards the trailing edge 29, the vacuum pressure differential cools and sets the microprotuberances 19 in the film A. The width between the leading edge 28 and trailing edge 29 can be varied such that the film spends greater or less time under the pressure differential. The length of time also helps hold the microprotuberance formation such that the film cools and "sets" or embosses the microprotuberances in the film.
A second material B is laminated onto the top surface 16 of the film A. The material B generally has a top surface 32 and a bottom surface 34. In the embodiment shown, the material B is generally dispensed from a roll 35. It should be understood that the material B can be supplied in other methods, including directly from a film forming process (not shown). The material B shown in FIGS. 1 and 1A is an apertured three-dimensional thermoplastic material having a plurality of ruptured microprotuberances 37 extending from the bottom surface 34 of the material B. However, it should be understood that the material B can be a flat or nonapertured three-dimensional thermoplastic or nonthermoplastic film.
In the embodiment shown in FIGS. 1 and 1A. the material B is laminated onto the top surface 16 of the film A at a point prior to the formation of microprotuberances of the material A. The material B is passed over at least one roll 36 and brought into close proximity to the material A. The proximity of the roll 36 to the film material A can be varied. The placement of the roll 36 can be as close to the die 10 as shown in phantom as roll 36'. Alternatively, the roll 36 can be placed further downstream as shown in phantom as roll 36". The film material B can be brought into contact with film A anywhere along the surface of film A. In certain preferred embodiments of the present invention, the roll 36 is spaced at a predetermined distance from the surface 22 of the screen 20. A gap 38 generally defines the distance between the roll 36 and the screen 20. The preferred gap 38 between the roll 36 and screen 22 is determined by the effective thicknesses of each of the materials A and B being laminated together. In certain embodiments, the length of the gap 38 is much greater than the effective thicknesses of each material A and B. In certain other embodiments, the length of the gap 38 is slightly less than the effective thicknesses of each material A and material B. As materials A and B pass through the gap 38, the effective thicknesses of the materials A and B are reduced somewhat In certain embodiments, the length of the gap 38 can range from about 50% to about 99% of the effective thicknesses of the material A and material B being laminated together. In various embodiments, the gap 38 is about 75% to about 95% of the effective thicknesses of each material A and material B.
As the microprotuberances 37 of material B are brought into contact with the top surface 16 of material A. significant bonding occurs between material A and material B. In the embodiment shown in FIG. 1, the material B is laminated to the top surface 16 of the material A at an interface point 40 just prior to applying the pressure differential to the material A in order to form the microprotuberances in the material A. It is to be understood that the point of interface between material A and material B is dependent upon a number of factors including the temperatures of materials A and B, the
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