MXPA06007118A - Ultrasonic bonding and embossing of an absorbent product - Google Patents

Abstract

Ultrasonically bonded laminated absorbent products comprising a liquid permeable top sheet, a liquid impermeable back sheet, an absorbent core positioned between the liquid permeable top sheet and the liquid impermeable back sheet, and an adhesive composition are disclosed. The laminated structure further comprising an embossed pattern stamped onto the liquid permeable topsheet, the liquid impermeable backsheet, the absorbent core, or any combination thereof. The adhesive composition comprises a mixture of atactic and isotactic polymers such that it has melt and flow characteristics similar to those of the topsheet and backsheet.

Description

UNION AND ULTRASONIC ENGRAVING OF AN ABSORBENT PRODUCT BACKGROUND OF THE INVENTION The present invention is directed to laminated products such as diapers, incontinence garments and the like. More specifically, the present invention is directed to laminated absorbent products comprising a liquid-permeable upper sheet, a liquid-impermeable lower sheet, an absorbent core positioned between the liquid-permeable upper sheet and the liquid-impermeable lower sheet, and a composition adhesive or bonding The top sheet, the bottom sheet and the absorbent core are joined together ultrasonically. The laminated structure further comprises an engraved pattern. The adhesive composition further comprises specific mixtures of atactic and isotactic polymers so that the composition is suitable for use with the thermoplastic materials that are to be etched and ultrasonically bonded.People rely on disposable absorbent articles to make their lives easier. When the disposable article is used, the liquid-permeable upper sheet is placed next to the user's body.The upper sheet allows the passage of body fluids into the absorbent core.The lower and liquid-impervious sheet helps to prevent spillage of the liquid. The fluids maintained in the absorbent core The absorbent core is generally designed to have desirable physical properties, such as a high absorbent capacity and a high absorption rate, so that body fluids can be transported from the user's skin inside the body. Disposable absorbent article.

Frequently, one or more components of a disposable absorbent article are first adhesively bonded and then ultrasonically bonded together to ensure adequate strength of the resulting joint. For example, hot melt adhesives have been used to first join the individual components of the absorbent article, such as the top sheet (also known, such as, for example, as the side-to-body liner) and the bottom sheet (also known, for example, as the outer cover) together. Conventional hot melt adhesives can also be used to join discrete parts, such as fasteners and leg elastics to the article. In many cases, the joining of the two components together (either by a permanent type joint or simply by support components in place during the manufacturing process) forms a laminated structure in which the adhesive is placed in the form of a sandwich between the materials (such as the polymer film components and / or the components of woven or non-woven fabrics) that constitute the components that are being joined together. Once the laminated structure is formed, the laminate will typically undergo an ultrasonic bonding process to impart an increased strength in the bonded area of the laminate.

The conventional hot-melt adhesives generally used in the bonding of adhesives of the thermoplastic materials in the laminated absorbent products generally comprise several components including: (1) one or more polymers to provide a cohesive strength (2) a resin or analogous material for provide an adhesive strength; (3) waxes, plasticizers, or other materials to modify the viscosity; and (4) other additives such as antioxidants and other stabilizers. Conventional hot melt adhesives are well known in the industry by those skilled in the art.

Ultrasonic bonding is a conventional bonding technique where thermoplastic materials are exposed to high frequency vibration as they result in heating, melting and fluidizing the thermoplastic materials one inside the other to form a mechanical and / or chemical bond. Even when it was commonly used in the production of laminated absorbent products, ultrasonic bonding can be problematic in the presence of hot melt and conventional adhesive materials. For example, during the ultrasonic bonding the adhesive composition can result in bleeding of the adhesive through one or both of the thermoplastic materials. This bleeding can result in at least three significant problems. First, such bleeding can result in a discolored final product. Such discoloration, even though it typically does not affect the performance of the product, is not desirable by consumers who prefer white, non-discolored products that look clean. Secondly, bleeding on the final product can result in a sticky product which sticks to the skin with use, which is not desirable for consumers. Third, bleeding can result in an accumulation of adhesive residue on the ultrasonic bonding equipment as well as other equipment used in the manufacturing process. Such adhesive buildup can result in the need for frequent cleaning and / or replacement of machinery, which increases costs. Additionally, the buildup of adhesives on the machinery may result in the adhesive composition being deposited on the absorbent products in unintended areas, and may weaken any resulting ultrasonic bonds.

Additionally, conventional hot melt adhesive compositions are generally much more amorphous than most typical thermoplastic materials used in the construction of the absorbent article and typically have a softening point lower than that of such materials. These characteristics can result in the creation of a heat melt during the ultrasonic bonding. When heat sinking is created, a high percentage of the ultrasonic energy of the system is used to remelter the adhesive in the bonded area and less ultrasonic energy remains to melt the thermoplastic materials and carry out the ultrasonic bonding between the materials. The remelting of the adhesive is not an optimal use of ultrasonic energy as an adhesively bonded joint which is typically not as strong as an ultrasonically bonded joint since the bond strength is limited to the cohesive strength of the adhesive. Also, cohesive strength can vary significantly with temperature, and in the case of absorbent care products, body heat may be insufficient to weaken the strength of the adhesive bond to the point of failure.

Many laminated products are subjected to a process of engraving to improve the performance of a product in general, and integrity through the introduction of a pattern on the surface of the same. The engraving may include patterning of only the liquid permeable top layer, or may include pattern formation of the liquid permeable top layer together with the absorbent core. Additionally, some incorporations, the lower liquid impermeable layer can be etched in combination with the top layer and the absorbent core.

Although etching is a desired way to improve product performance, many of the fibers and synthetic absorbers used in absorbent articles, and specifically in the absorbent core of absorbent articles, are difficult to etch because these materials do not. they have sufficient bonding properties to hold and maintain the engraved pattern once it has been applied. Without these bonding properties the absorbent article will lose its structural integrity and shape and the etched pattern will deteriorate. This results in a less desirable product.

Based on the foregoing, there is a need for a hot-melt adhesive composition that can be used as an adhesive between the thermoplastic and other materials of an absorbent article, but which will not significantly interfere with the ultrasonic bonding and the etching processes brought to out on the absorbent article. It should also be desirable if the adhesive composition can strengthen the ultrasonic bond between the materials and improve the quality of the resulting ultrasonically etched pattern on the absorbent article.

SYNTHESIS OF THE INVENTION The present invention is directed to disposable products, such as to disposable products comprising ultrasonically bonded laminated structures. Laminated structures generally comprise a liquid-permeable upper sheet, a liquid-impermeable lower sheet, an absorbent core positioned between the liquid-permeable upper sheet and the liquid-impermeable lower sheet, and an adhesive composition located on at least one of the liquid permeable upper sheet, liquid impervious bottom sheet, or absorbent core. The laminated structures further comprise an engraved pattern. The etched pattern can be stamped or otherwise introduced onto at least one of the liquid permeable top sheet, the liquid impervious bottom sheet, or the absorbent core. The adhesive composition comprises selected proportions of crystalline and amorphous polymers. When such an adhesive composition is used, the laminated structures, the strong ultrasonic bonds can be easily and effectively made between two or more layers without the adverse effects generally associated with the use of conventional adhesive compositions. Additionally, when such an adhesive composition is used on a laminated structure, the bonding properties of the structure are substantially improved and the integrity of the etched pattern is improved, which also allows the improved structural integrity and performance of the absorbent article. In addition, these engraved patterns will allow an aesthetically more desirable product.

Therefore, the present invention is directed to an article comprising an ultrasonically bonded laminated structure. The laminated structure comprises a liquid permeable top sheet, an absorbent core, and an adhesive composition. The adhesive composition comprises an atactic polymer and an isotactic polymer wherein the atactic polymer has a degree of crystallinity of less than about 20% and a number average molecular weight of from 1,000 to about 300,000, and the isotactic polymer has a degree of of crystallinity of at least about 40% and a number average molecular weight of from about 3,000 to about 200,000. The liquid permeable upper sheet and the absorbent core comprise an etched pattern and are ultrasonically bonded together.

The present invention is further directed to an article comprising an ultrasonically bonded laminated structure. The laminated structure comprises a liquid-permeable upper sheet, a liquid-impermeable lower sheet, an absorbent core positioned between the liquid-permeable upper sheet and the liquid-impermeable lower sheet, and an adhesive composition. The adhesive composition comprises an atactic polymer and an isotactic polymer wherein the atactic polymer has a degree of crystallinity of less than about 20% and a number average molecular weight of from about 1,000 to about 300,000 and the isotactic polymer has a degree of crystallinity of about 40% and a number average molecular weight of from about 3,000 to about 200,000. The liquid permeable top sheet, the liquid permeable bottom sheet, and the absorbent core comprise an etched pattern and are ultrasonically bonded together.

The present invention is further directed to an article comprising an ultrasonically bonded laminated structure. The laminated structure comprises a liquid-permeable upper sheet, a liquid-impermeable lower sheet, an absorbent core positioned between the liquid-permeable upper sheet and the liquid-impermeable lower sheet, and an adhesive composition. The adhesive composition comprises an atactic polymer and an isotactic polymer wherein the atactic polymer has a degree of crystallinity of less than about 20% and a number average molecular weight of from about 1,000 to about 300,000 and the isotactic polymer has a degree of crystallinity of at least about 40% and a number average molecular weight of from about 3,000 to about 200,000. The absorbent core comprises an etched pattern and the upper sheet permeable to liquid. The lower sheet impervious to the liquid and the absorbent core are ultrasonically bonded together.

The present invention is further directed to a process for manufacturing a pattern etched onto an article comprising an ultrasonically bonded laminated structure. The process comprises providing an absorbent core and a liquid permeable top sheet comprising an adhesive composition. The adhesive composition comprises an atactic polymer and an isotactic polymer. The atactic polymer has a degree of crystallinity of less than about 20% and a number average molecular weight of from about 1,000 to about 300,000 and the isotactic polymer has a degree of crystallinity of at least about 40% and an average molecular weight of number from about 3,000 to about 200,000. A pattern is ultrasonically etched onto the liquid permeable upper sheet and the absorbent core during the ultrasonic bonding of the liquid permeable upper sheet and the absorbent core.

The present invention is further directed to a process for manufacturing a pattern etched onto an article comprising an ultrasonically bonded laminated structure. The process comprises providing a liquid-permeable top sheet, a lower sheet impervious to liquid, and an absorbent core placed between the liquid permeable upper sheet and the liquid impermeable lower sheet. The lower sheet impervious to liquid comprises an adhesive composition comprising an atactic polymer and an isotactic polymer. The atactic polymer has a degree of crystallinity of less than about 20% and a number average molecular weight of from about 1,000 to about 300,000 and the isotactic polymer has a degree of crystallinity of at least about 40% and an average molecular weight of number from about 3,000 to about 200,000. A pattern is ultrasonically bonded onto the liquid-impermeable bottom sheet, the liquid-permeable sheet and an absorbent core during the ultrasonic bonding of the liquid-permeable top sheet, the liquid-impermeable bottom sheet, and the absorbent core together.

DETAILED DESCRIPTION OF THE INCORPORATIONS CURRENTLY PREFERRED The present invention is generally directed to disposable products comprising a laminated structure. The laminated structure comprises a liquid-permeable upper sheet, a liquid-impermeable lower sheet, an absorbent core positioned between the liquid-permeable upper sheet and the liquid-impermeable lower sheet, and an adhesive composition. The liquid permeable upper sheet, the liquid impermeable lower sheet, and the absorbent core are ultrasonically joined together, and comprise an etched pattern. The etched pattern can be stamped or otherwise inserted into the liquid-permeable topsheet, the liquid-permeable bottomsheet, the absorbent core or any combination thereof. The adhesive composition comprises selected proportions of crystalline and amorphous polymers to improve the performance of an adhesive in the ultrasonic and etch bonding processes. For example, the present invention encompasses adhesive compositions comprising selected amounts of polymers having different configurations (e.g., a combination of polypropylene and isotactic polypropylene).

According to an embodiment of the present invention, the ultrasonic bonding can be used in conjunction with the adhesive composition described herein to form an ultrasonic bond for the various materials of the product in combination with the introduction of a pattern etched into the product. Ultrasonic bonding is a conventional process where polymeric materials and specifically thermoplastic materials are exposed to a high frequency vibration which results in the heating, melting and flow of the materials to form a mechanical and / or chemical bond. As used herein "thermoplastic" is meant to include polymeric materials which can be reheated and melted again several times without significant material degradation.

The process is referred to as an "ultrasonic" process because the frequencies of the vibrations used are generally above what is considered the upper limit of the human ear (greater than about 18 ilohertz). A typical ultrasonic system used for the ultrasonic bonding of thermoplastic materials includes an ultrasonic energy supply. The ultrasonic battery, which consists of a converter, a combination of waveguides and a termination waveguide that typically refers to a horn or sonotrode, an actuator and an anvil.

High frequency vibration is typically created through the application of a piezoelectric converter and an appropriate power supply. Piezoelectric materials exhibit a property such that when a voltage is applied to them, the same changes in dimensions. At the ultrasonic junction, an energy supply applies an alternating voltage at an ultrasonic frequency to the piezoelectric converter. The converter generates a continuous mechanical vibration mentioned as a longitudinal compression wave. This compression wave is transmitted from the converter to the ultrasonic stack through one or more waveguides, which are designed to efficiently transmit a vibration of a given frequency. These waveguides can also facilitate to amplify the wave vibration that is the output of the converter to achieve a desired level for the joining process.

At this point, the vibration is coupled into the final component of the stack, the horn. The horn is a type of waveguide designed to be a working tool of the ultrasonic system and is where the vibration energy is applied to the materials that are being joined. Because this is also a waveguide, it is designed to efficiently transmit a vibration of a given frequency and can in some circumstances also simplify the vibration wave.

The ultrasonic battery is typically mounted in an actuator mechanism which has three functions: (1) it mounts the ultrasonic battery in a manner that does not constrain the vibration of the components; (2) this drives the system to bring the vibration horn to a working contact with the anvil; and (3) this applies a static force. The anvil is designed to make a rigid surface for the ultrasonic horn to work against it. The materials to be joined are placed between the horn and the anvil. The horn is driven to apply a static force on the materials. The anvil can be placed to drive a fixed stop which creates a small gap (typically smaller than the thickness of the materials) between the horn and the anvil or directly loaded against the horn. In any case, a static force is developed on the materials by the ultrasonic horn and the anvil thus creating a recorded union.

When the ultrasonic system is hooked, the vibration produced on the horn surface creates an alternate compression and relaxation of the materials to be joined. The alternating high-frequency voltage field created in the materials is of varying degrees, (1) dissipated as heat in the materials (through viscous / hysteretic moisture losses); (2) stored in the material, elastic energy which is recoverable by the horn; and / or (3) absorbed and dissipated as heat and vibration in the anvil (typically insignificant). A joint is produced when the heat that is dissipated in the materials reaches the melting temperature of one or more of the materials and these flow together under the static force provided by the actuator to produce a mechanical and / or chemical bond.

According to the present invention, the ultrasonically bonded laminated structure comprises a liquid-permeable upper sheet, a liquid-impermeable lower sheet, an absorbent core placed between the liquid-permeable upper sheet and the liquid-impermeable lower sheet together with an adhesive composition .

The top sheet layer of the absorbent article has a body facing surface, which is flexible, feels soft and non-irritating to the wearer's skin. In addition, the topsheet may include sheets of hydrophobic or hydrophilic filaments and the like, and is sufficiently porous to be permeable to liquid, allowing the liquid to easily penetrate through its thickness to reach the absorbent core. It is preferred that the top sheet be hydrophilic so that liquids will transfer through the top sheet faster than if it were not hydrophilic, which will decrease the possibility that body exudates will flow out of the top sheet rather than being absorbed by the absorbent core. To obtain the desired hydrophilic effect, the fibers can be surface treated with an operative amount of surfactant, such as about 0.28% TRITON X-102 surfactant. Other types and quantities of operative surfactants can be used alternatively. The surfactant can be applied by any conventional means, such as spraying, printing, brush coatings or the like.

A suitable top sheet layer can be manufactured from a wide selection of thermoplastic materials, such as porous foams, cross-linked foams, thermoplastic materials, perforated plastic films, natural fibers (e.g., wood or cotton fibers). ), synthetic fibers, or a combination of natural and synthetic fibers. Suitable synthetic fibers include polyethylene, polypropylene, polyester, Kraton polymers, polyurethane, nylon or combinations thereof. The top sheet layer is typically employed to help isolate the user's skin from liquids maintained in the absorbent article. Various woven and non-woven fabrics can be used for the top sheet layer. The top sheet layer can be composed of a meltblown or spin-bonded fabric of the desired fibers, and it can also be a carded and bonded fabric. The various fabrics can be composed of natural fibers, synthetic fibers or combinations thereof. For the purposes of the present description, the term "non-woven fabric" means a fabric of fibrous material that is formed without the aid of a knitting or textile weaving process. The term "fabric" is used to refer to all woven, knitted and non-woven fibrous fabrics.

In the particular embodiment of the invention, the top sheet layer is a non-woven, spin-bonded polypropylene fabric composed of about 2.8-3.2 denier grams per square meter and a density of about 0.06 gm / cc.

Additionally, the absorbent article comprises a lower sheet layer. The lower sheet layer is located along an outer surface of the absorbent article and desirably comprises a thermoplastic material which is configured to be essentially impermeable to liquids. For example, a typical top sheet layer can be made of a thin plastic film, or of another material essentially liquid impervious and flexible.

As used in the present description, the term "flexible" refers to materials which are docile and which readily conform to the general shape and contours of the user's body. The lower sheet layer can prevent the exudates contained in the absorbent core from moistening the articles, such as the bed sheets and the overbeds, which are in contact with the absorbent article. Suitable thermoplastic materials for the lower layer may include polyethylene, polypropylene or combinations thereof. In particular embodiments of the invention, the lower sheet layer may include a film, such as a polyethylene film, having a thickness of from about 0.012 mm (0.5 mil) to about 0.05 1 millimeter to about 0.051. millimeters (2.0 thousandths of an inch). For example, the lower sheet film may have a thickness of about 0.32 millimeters (1.25 mils).

The alternate constructions of the lower sheet layer may comprise a woven or nonwoven fibrous fabric which has been treated or constructed in whole or in part to impart desired levels of liquid impermeability to selected regions that are adjacent to or close to the absorbent core. For example, the lower sheet layer may include a non-woven fabric permeable to the laminated gas to a designated coating surface of a polymer film material that may or may not be gas permeable. Ordinarily, the cloth material is fastened to an outward facing surface of the polymer film material. Other examples of fibrous cloth type bottom sheet layer materials are stretched and thinned laminate or stretched and thermal laminate composed of a 0.015 (0.6 mil) thick polypropylene blown film and a material bonded to polypropylene yarn of 23.8 grams per square meter (0.7 ounces per square yard) (2 denier fibers).

In particular embodiments, a lower vapor permeable sheet layer essentially impermeable to liquid may be a composite material which includes a vapor permeable film adhesively laminated to a spin-bonded material. The vapor permeable film can be obtained from Exxon Chemical Products, Incorporated under the trade name EXXAIRE. The film can include 48-60 percent by weight (% by weight) of linear low density polyethylene and 38-50% by weight of calcium carbonate particles that can be dispersed and extruded uniformly in the film. The stretched film may have a thickness of about 0.018 millimeters (0.7 mils) and a basis weight of 16-22 grams per square meter (g / m2).

The spunbonded material can be laminated adhesively to the film, and it can have a basis weight of 27 grams per square meter. The yarn-bonded material can be made using a conventional spin-bonding technology and can include polypropylene filaments having a fiber denier of 1.5-3 denier per fiber. The vapor permeable film can be adhered to the spunbonded material using a pressure sensitive hot melt adhesive at an aggregate rate of 1.6 grams per square meter and the adhesive can be deposited in the form of a swirl pattern of adhesive or of random fine fiber swirls. Another example of a suitable microporous film may be a PMP-1 material which is available from Mitsui Toatsu Chemicals, Inc., a company that has offices in Tokyo Japan or a polyolefin film XKO-8044 available from 3M Company of Minneapolis, Minnesota.

The lower vapor permeable sheet sheet and furthermore liquid impervious may alternatively include a stretched thermal laminate with high breathability (HBSTL). The stretched, high breathable thermal laminate material may include a material bonded with polypropylene yarn thermally attached to a stretched breathable film. For example, stretched thermal laminate material with high breathability may include a material bonded with polypropylene yarn of 20.4 grams per square meter (0.6 ounces per square yard) thermally attached to a breathable film of 18.7 grams per meter square. The breathable film can include two skin components with each skin component composed of 1-3% by weight of EVA / cataloy. The breathable film can also include 55-60% by weight of calcium carbonate particles, linear low density polyethylene and up to 4.8% low density polyethylene. The stretched breathable film can include a thickness of 0.011-0.013 mm (0.45-0.50 thousandths of an inch and a basis weight of 18-7 grams per square meter.) The material bonded with spinning can be thermally bonded to the film with a capacity for breathe and can have a basis weight of about 20.4 grams per square meter.The yarn-bonded material can have a denier fiber of 1.5-3 denier per fiber, and the film with stretched breathing capacity can be thermally bonded to the bonded material with spinning using a "C-star" pattern that provides an overall bound area of 15-20%.

The absorbent article further comprises an absorbent core positioned between the liquid permeable upper sheet and the liquid impermeable lower sheet. The absorbent core may include a combination of hydrophilic fibers and high absorbency material. More specifically, the high-absorbency material in the absorbent core can be selected from polymers and natural, synthetic materials and modified materials. Suitable absorbent materials include cellulosic material, rayon, glass fibers, wood pulp fibers, polyester fibers, polyamide fibers, superabsorbent materials, polypropylene fibers, or combinations thereof. The absorbent core can also be slightly etched in selected areas.

The absorbent core can have any number of shapes. For example, when the absorbent article is a diaper, the absorbent core may be rectangular, I-shaped or T-shaped and essentially narrower in the crotch region than in the front or back regions of the diaper. The size and absorbent capacity of the absorbent core can be selected according to the size of the intended use and the liquid load imparted by the intended use of the diaper. In addition, the size and absorbent capacity of the absorbent core can be varied to accommodate users of various sizes.

"The adhesive compositions for use in combination with the materials of the product, such as the absorbent product, which are ultrasonically etched and bonded together, can be introduced into the liquid-permeable top sheet of the absorbent core in the lower sheet impervious to the liquid. or in any combination thereof before or during the manufacture of the product.The adhesive composition can be applied to one or more of the materials constituting the product during the formation of the product, this can be applied to an existing formed structure or this it can be applied to discrete components before manufacturing.In a specific embodiment, the adhesive composition is introduced into the absorbent core and / or the materials facing outwards during the manufacture of the product before joining and ultrasonic etching.

The adhesive compositions described herein for use with the thermoplastic materials to be ultrasonically etched and bonded can be used in a conventional heat fusion adhesive processing equipment without modification. As such, the adhesive compositions described herein can be used in the existing equipment installed for the purpose of processing and applying the conventional hot melt adhesives in the manufacturing process. In addition, the adhesive compositions described herein can be applied during the in-line manufacturing process for immediate use or can be applied to one or more off-line thermoplastic materials at a distant location, and then sent to the manufacturing process line for use at a later date. Additionally, it should be understood that the atactic and isotactic polymers comprising the adhesive compositions described herein can be heated and mixed at a site other than the site where the laminated absorbent product is being manufactured. For example, atactic and isotactic polymers can be mixed using a heat fusion processing equipment or extruder in a first geographic location. The mixed polymers can then be allowed to cool and be processed to be a solid form such as, for example, pellets. The polymer mixture can then be sent from the first geographic site to a site where the rolled products are made. The polymer mixture simply heated to essentially liquefy the adhesive composition before being used to make a laminate comprising an etched pattern.

The adhesive compositions described herein can be shown in numerous ways according to the present invention, for example, the atactic polymer can be heated in a first container and the isotactic polymer can be heated in a second container before, after or concurrently with heating of the atactic polymer and then the two polymers when mixed liquefied together in the first container, in the second container or in the third container. Alternatively, one of any of the atactic or isotactic polymers can be heated in a vessel until it liquefies at which time the second polymer can be added to the molten and melted first polymer. Additionally, both solid polymers can be added in a single container and melted simultaneously to produce a hot melt adhesive. Based on the description given herein, one skilled in the art will recognize that other additional components as discussed herein may also be added to the adhesive compositions. It is noted that the above discussion assumes that atactic and isotactic polymers are in an essentially solid form at room temperature or at temperatures that are typically present in the working environment suitable for humans. To the extent that either or both of the polymers are available in an essentially liquid form then those steps that provide heating and melting of the polymer can be omitted from the methods for making the adhesive composition.

In accordance with the present invention, the adhesive composition can be formulated with various degrees of crystallinity which brings its melting temperature to a range similar to many of the thermoplastic materials that are being ultrasonically bonded together and etched. The adhesive composition disclosed herein does not act as a substantial heat sink in the bonding zone and therefore leaves the substantial vibration energy carrying out the ultrasonic bonding through the melting of the materials as described above. Additionally, the adhesive compositions described herein improve the chemical compatibility with many of the thermoplastic materials of interest for ultrasonic bonding. By providing improved material compatibility, the adhesive composition improves the strength of the resulting ultrasonic bond; and also the article may have a pattern engraved for a longer period of time. As described herein, the etched pattern allows for additional improved structural integrity and performance of the absorbent article.

Along with the benefits indicated above, the adhesive compositions described herein do not have the propensity to contaminate the processing equipment and adversely affect the equipment like traditional hot melt adhesives. Also, for thermoplastic materials that are not significantly affected by the ultrasonic vibration energy, the hot melt adhesive described herein makes a highly efficient binding agent to provide an interconnection in the bonding zone that may be affected by the ultrasonic energy.

The adhesive composition useful for use in combination with the liquid-permeable upper sheet, a liquid-impermeable lower sheet and an absorbent sheet placed between the liquid-permeable upper sheet and the liquid-impermeable lower sheet, which are ultrasonically etched and bonded together , comprises an atactic polymer and an isotactic polymer. As used herein the term "isotactic polymer" refers to a polymer that is at least about 60% isotactic and suitably at least about 70% isotactic and more suitably at least about 80% isotactic. As used herein, the term "atactic polymer" refers to a polymer that is at least about 80% atactic, suitably at least about 90% atactic.

The atactic polymer comprises from about 40% (by weight) to about 90% by weight of the adhesive composition and has a degree of crystallinity of about 20% or less, suitably a crystallinity of about 15% or less and an average molecular weight d number from about 1,000 to about 300,000 suitably from about 3,000 to about 100,000. The isotactic polymer comprises from about 5% (by weight) to about 30% (by weight) of the adhesive composition having a degree of crystallinity of about 40% or more suitably of about 60% or more, and more suitably about 80% (by weight) or more and a number average molecular weight of from about 3,000 to about 200,000, suitably from about 10,000 to about 100,000.

The adhesive composition is processable with melting and heat at a temperature of about 450 ° F or less, suitably 400 ° F or less, suitably 375 ° F or less, and even more adequately about 250 ° F or less. Additionally, the adhesive composition has a melt index of from about 100 to about 2,000 g / 10 minutes, suitably from about 200 to about 1,800 grams per 10 minutes, suitably from about 500 to about 1,500 grams / 10 minutes as determined by ASTM D1238. The rate of melting will depend on the crystallinity, the molecular weight and the molecular weight distribution in the polymers included in the adhesive composition.

The atactic polymer may be the same polymer as the isotactic polymer or this may be a polymer other than an isotactic polymer. Suitable polymeric materials for the preparation of the adhesive composition include, for example, polypropylene, polybutene, polyethylene, polystyrene and combinations thereof. In one embodiment, high density polyethylene (HDPE) which is essentially isotactic and low density polyethylene (LDPE), which is essentially atactic, can be used as two polymers. High density polyethylene generally has a density in the range of from 0.935 to about 0.980 grams per cubic centimeter while low density polyethylene generally has a density in the range of about 0.910 to about 0.935 grams per cubic centimeter.

As used herein, the percent by weight means the mass of a type of polymer (eg, atactic) in the adhesive composition divided by the sum of the masses of the other types of polymer, for example, the mass of any components additional that could be present in the adhesive composition, with this value being multiplied by 100. For example, if the adhesive composition comprises 40 grams of atactic polypropylene with 60 grams of isotactic polypropylene, the combination includes 40% by weight of atactic polypropylene.

In addition to the atactic and isotactic polymer components in the adhesive composition described therein, the composition may additionally comprise up to about 50% or about 60% (by weight) of a combination of additives such as a glutinizer, an antioxidant, pigments of color, fillers and / or a polymeric compalizer. Suitable examples of the glutinizing agents include PICCOLYTE® resins, REGALITE® series and STAYBELITE® esters each available from Hercules Incorporated of ilmington Delaware. Also, a suitable glutinizer is ESCOREZ, available from Exxon Chemical. The adhesive composition can suitably include from about 10% (by weight) to about 20% (by weight) of glutinizer. Examples of suitable antioxidants include IRGANOX® 565, available from Ciba-Geigy, POLYGARD®, available from Uniroyal Chemical, Co. and the ANTIOXIDANT® series available from Cytec Industries. The adhesive composition can suitably include from about 0.15% (by weight) to about 1.0% (by weight) of antioxidant. Examples of suitable color pigments and fillers include titanium dioxide, carbon black and calcium carbonate. The adhesive composition can suitably include from about 1% (by weight) to about 10% (by weight) of color pigments and fillers. Examples of suitable polymer compatibilizers include polypropylene-B-polyethylene, and diblock copolymers of polypropylene-B-polybutene. The adhesive composition can suitably include from about 2% by weight to about 10% (by weight) of polymer compatibilizer and up to about 15% of the viscosity modifier, such as mineral oil.

The adhesive compositions described herein suitably have an open time of from about 2 minutes when applied to a thermoplastic material. The adhesive composition can have an open time of up to about 30 seconds, or up to about 2 seconds, or as short as up to about 1 second depending on the desired application. As used herein, the term "open time" refers to the length of time during which an adhesive composition remains tacky on the surface of the substrate prior to solidification. The open time is affected by the crystallinity of a polymer. So the higher the level of crystallinity the shorter the open time. Desirably, the adhesive compositions described herein have typically shorter open times than conventional hot adhesives.

The adhesive compositions described herein can be used in the process of manufacturing disposable absorbent products laminated in multiple areas where an adhesive is required and wherein the ultrasonic bonding and etching will take place between two thermoplastic materials. Conventional hot melt adhesives, when located in the ultrasonic bonding area together with two thermoplastic materials, simply melt and flow into each other or both of the thermoplastic materials being joined together with the application of vibration energy to produce only an adhesive bond which is susceptible to failure with use. Because conventional hot melt adhesives have different melting and flow characteristics compared to thermoplastic materials, both thermoplastic materials have limited reactions to ultrasonic energy, as such they do not have sufficient flow together in the ultrasonic bonding process to form a stable and strong ultrasonic union. In contrast, the hot melt adhesives described herein have melting characteristics similar to those of the thermoplastic materials that are being ultrasonically bonded such that with the application of a vibration energy used in the ultrasonic bonding process, the thermoplastic materials melt together with the adhesive composition and flow together to form a reliable and strong ultrasonic bond without a significant risk of bleeding or failure.

In another embodiment of the present invention, the adhesive composition described herein for use with the ultrasonic bonds can be used to reinforce or thicken a thermoplastic material in an ultrasonic bond and etch zone. Typically it is very difficult to obtain a high strength ultrasonic bonding of thermoplastic materials having a low basis weight (thin thermoplastic materials having a smaller amount of polymer mass) since the materials tend to break or disintegrate during the process of ultrasonic union. Similarly, it is typically difficult to obtain a suitable etched pattern on low basis weight materials. The adhesive compositions described herein can be used as a material weight-increasing material to increase the basis weight of the material and improve the strength and overall durability of one or more of the components of a disposable laminated absorbent garment subjected to the ultrasonic bonding and to the engraving without the deterioration of the resulting union. That is, the adhesive compositions can be used to increase the basis weight of the material of one or more specific thermoplastic components of a laminated product to provide the increased material strength of the resulting product as opposed to using a thicker starting material. As such, the adhesive compositions described herein may also serve a dual function of acting as a binding agent and a weight-increasing agent of the material without adversely affecting the ultrasonic bonding.

As is evident from the above discussion and as known to those skilled in the art, it is typically desirable to use thin thermoplastic materials as components when manufacturing the laminated absorbent products such as when a thin disposable product is produced; that is, it is typically desirable to use small base weight thermoplastics, generally from about 0.2 ounces per square yard to about 0.8 ounces per square yard and desirably from about 0.2 ounces per square yard to about 0.6 ounces per square yard. Square yard. The reasons for this are several, with the primary reason being the cost considerations. When thinner thermoplastic materials are used to build the laminated absorbent products, significant cost savings can be had on the raw materials. Additionally, thinner materials generally result in improved flexibility of the resulting product, and in an improved notch on the user. This improved flexibility and notch can result in a more comfortable product with a reduced risk of spillage, and therefore, a more suitable product for the consumer.

Along with cost and flexibility, thinner materials also typically allow an improved breathing capacity of the resulting product. The products with a high degree of capacity to breathe are desirable since the humid and hot air contained inside the product after the soiling of the product can be exchanged with the outside air of the product allowing the cold and fresh air of the product. This results in a product more comfortable for the user, and can improve the health of the user's general skin by reducing the overhydration of the skin.

Additionally, thinner materials will typically allow better waist leg elastics to be formed so that spillage from the product is minimized. This occurs due to the fact that with thinner materials, the waist and leg band parts do not have to move as much material and function more efficiently.

In addition, the thinner materials allow an improved packaging since the resulting package containing the product is thinner and easier to handle and cheaper to transport. This is a direct result of an improvement in the folding and in the characteristics of the folding of the absorbent products when the thinner materials are used to build the product. Also thinner packages have a significant consumer appeal since they are easier to transport and do not look as bulky as conventionally packaged absorbent products.

While it is generally desirable to use the thin materials during the manufacture of the laminated disposable absorbent products as discussed above, such thin materials can lead to numerous problems during the ultrasonic bonding of such materials. An ultrasonic union as it causes the material to fail during manufacture due to the hammer / anvil combination that pushes through or perforates the material causing it to tear, fracture and / or break so that the joint fails and the product It can not be used. This is typically a direct result of the material being too thin to allow the formation of the joint. Similar problems can arise with other types of joints and fasteners. Also, as mentioned earlier, bleeding can be a problem. The short open times of the adhesive compositions described herein reduce the negative effects of adhesive bleed.

According to an embodiment of the present invention, the adhesive compositions described herein can be used on a specific thermoplastic material of a disposable laminated absorbent product to increase the basis weight of the material and therefore the strength of the treated component so that this is much less likely to fail during manufacturing when the bonding is carried out in the area containing the adhesive composition, or during use by the consumer. In this embodiment, the adhesive composition is selectively added to a specific region of a thermoplastic material, or the entire thermoplastic material to increase the base weight of the material of that region so that strength and durability are improved and the material is more resistant to effort and shear forces imparted thereon during fabrication of the ultrasonic joint. The adhesive composition used to increase the base weight of the material in the strength of the material can be applied online, that is during the manufacturing process, it can be applied off-line in a separate process before the introduction of the material treated in the process of manufacture. The adhesive compositions of the present invention act to increase the strength of the treated area by allowing a distribution of force along the entire treated area so that the strength of the area is increased. This embodiment of the present invention allows an increase in the strength of the material where it is required to improve product performance without the need to use a thicker starting material which can significantly increase costs, and also allows a Ultrasonic bonding of quality between materials.

The adhesive compositions described herein can be applied to the thermoplastic materials by a conventional hot melt adhesive equipment as indicated above. During the application of the adhesive composition to the materials, the adhesive composition can be applied in any suitable pattern or configuration to achieve the desired objective. Specifically, the adhesive composition can be applied in a bead configuration, in a swirl configuration, or it can be slotted or blown over the materials.

As noted herein, the adhesive composition for use in combination with the layers of the absorbent article which are etched and ultrasonically bonded together, comprise an amorphous atactic polymer and an isotactic polymer. An atactic polymer is generally less feasible to assume a crystalline structure, while an isotactic polymer is generally more feasible to assume a crystalline structure. Without being bound by any particular theory, it is believed that an adhesive composition comprising a specific combination of atactic and isotactic polymers, such as atactic and isotactic polypropylene, possess regions, and / or characteristics of both, an effectively crystalline material and an amorphous material By changing the relative amounts of the atactic and isotactic polymer, or for that matter the relative amounts having different degrees of crystallinity, one can change the performance characteristics of the resulting adhesive composition. The adhesive compositions of the present invention generally perform better and cost less than conventional hot melt adhesives. It should be understood, however, that the present invention encompasses adhesive compositions comprising suitable polymer compositions having different degrees of crystallinity, such as an adhesive composition comprising atactic and isotactic polypropylene, whether or not the composition possesses all the advantages herein. discussed.

As noted herein, the liquid permeable top sheet, the liquid impermeable bottom sheet, and the absorbent core any or all of which may comprise the adhesive composition described herein and may be etched to provide a specific pattern on one or more of the materials . As will be recognized by an expert in the art based on the description given herein, the engraving may be made on one or more of the materials comprising the product. For example, the engraving can be done on a sheet permeable liquid alone. In this embodiment, the liquid permeable topsheet may comprise the adhesive composition to aid in the etching process. In another embodiment, the etching can be done on the liquid permeable top sheet in combination with the absorbent core. In this embodiment, either or both of the absorbent core and the liquid impermeable top sheet may comprise an adhesive composition. In this embodiment it may be desirable to introduce the adhesive composition directly onto the absorbent core to increase the binding properties for the fibers comprising the core. In still other embodiments, the engraving can be done on the liquid-permeable upper sheet, the absorbent core and the lower sheet impervious to the liquid. In this embodiment, any one, two or all three of the components may comprise the adhesive composition. In yet another embodiment, the engraving can be done on only the absorbent core. In this embodiment, the absorbent core can comprise the adhesive composition.

Engraving is essentially the stamping or rolling of a pattern on a structure to the substrate. In one embodiment, the increased temperature is the result of an application of ultrasonic energy. The combination of heat and pressure, provided by a pattern or pattern roller, reshapes the surface of the material to create the image. The recorded materials will contain a pattern of compressed areas and uncompressed areas. The compression can be essentially applied uniformly or non-uniformly across the surface of the material. The ultrasonic bonding system discussed here can be used to compress the etched patterns or designs onto the liquid-permeable top sheet layer, the liquid-impermeable lower sheet layer, the absorbent core or any combination thereof. When used in combination with the adhesive compositions described herein, ultrasonic etching can produce high quality etched patterns, which are often judged by the clarity or fine-tuning of the artistic pattern on the product, its uniformity of pattern and by the feel of the product. .

The engraving may be a more commercially-laminated absorbent product by providing an aesthetically pleasing decorative attribute. In addition to the more aesthetically pleasing decorative attribute, the engraving allows for functional characteristics such as performance and absorbent article as well. For example, an area of compressed material will provide faster transmission and channeling of fluid, compared to uncompressed areas.

In one embodiment of the present invention, at least one of the layers of the product being etched comprises a thermoplastic polymer composed of the same material as at least one component of the adhesive composition. For example, if the adhesive composition comprises atactic and isotactic polypropylene, at least one component of the product, such as the liquid permeable top layer, for example, that is being etched will comprise polypropylene. In this case, with the application of the ultrasonic energy during the etching process, the thermoplastic polymer melts and flows together with the adhesive composition forming the material to surround a highly stable etching pattern. In a specific example, a product may comprise a liquid permeable top sheet composed of polypropylene and an absorbent core composed of cellulosic fibers. An adhesive composition comprising atactic and isotactic polypropylene can be introduced into the liquid permeable topsheet so that with the application of the ultrasonic energy during etching, the materials melt together to form a stable etched pattern.

It will be appreciated that the details of the above embodiments given for purposes of illustration should not be considered as limiting the scope of this invention. Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without departing materially from the novel techniques and advantages of this invention. Therefore, all such modifications are intended to be included within the scope of this invention, which is defined in the following claims and in all equivalents thereof. Furthermore, it is recognized that many incorporations can be conceived which do not achieve all the advantages of some incorporations, particularly of the preferred incorporations but that the absence of a particular advantage should not be considered as necessarily meaning that such incorporation is beyond the scope of the present invention.

Claims (20)

R E I V I N D I C A C I O N S

1. An article comprising an ultrasonically bonded laminated structure, the laminated structure comprising a liquid permeable top sheet, an absorbent core, and an adhesive composition, the adhesive composition comprising an atactic polymer and an isotactic polymer, the atactic polymer having a degree of crystallinity less than about 20% and a number average molecular weight of from about 1,000 to about 300,000 and the isotactic polymer has a degree of crystallinity of at least about 40% and a number average molecular weight of about 3,000 to about 200,000 where the liquid permeable upper sheet and the upper core comprise an etched pattern which is ultrasonically bonded together.

2. The article as claimed in clause 1, characterized in that it is processable with melting and heat at less than about 400 degrees Fahrenheit.

3. The article as claimed in clause 1, characterized in that the adhesive composition has a melt index of from 100 to about 2,000 grams per 10 minutes.

4. The article as claimed in clause 1, characterized in that the atactic polymer is selected from the group consisting of atactic polypropylene, low density polyethylene, atactic polystyrene, atactic polybutene, amorphous polyolefin copolymer and combinations thereof.

5. The article as claimed in clause 1, characterized in that the isotactic polymer is selected from the group consisting of isotactic polypropylene, high density polyethylene, polystyrene, isotactic polybutene and combinations thereof.

6. The article as claimed in clause 1, characterized in that the liquid permeable upper sheet comprises a material selected from the group consisting of porous foams, cross-linked foams, perforated plastic films, thermoplastic materials, natural fibers, synthetic fibers, a mixture of natural and synthetic fibers, and combinations thereof.

7. The article as claimed in clause 6, characterized in that the synthetic fibers are selected from the group consisting of polyethylene, polypropylene, polyester, Kraton polymers, polyurethane, nylon or combinations thereof.

8. The article as claimed in clause 1, characterized in that the absorbent core comprises a material selected from the group consisting of cellulosic materials, rayon, glass fibers, wood pulp fibers, polyester fibers, superabsorbent materials, fibers of polyamide, polypropylene fibers or combinations thereof.

9. The article as claimed in clause 1, characterized in that the adhesive composition additionally comprises an additional component consisting of glutinizing agents, antioxidants, viscosity modifiers, color pigments, fillers and polymeric compatibilizers.

10. An article comprising an ultrasonically bonded laminated structure, the laminated structure comprising a liquid permeable upper sheet, a liquid impervious sheet, an absorbent core positioned between the liquid permeable upper sheet and the liquid impermeable lower sheet, and an adhesive composition . The adhesive composition comprises an atactic polymer and an isotactic polymer, the atactic polymer has a degree of crystallinity of less than about 20% and a number average molecular weight of from about 1,000 to about 300,000 and the isotactic polymer has a degree of of crystallinity of at least about 40% and an average number-average molecular weight of from 1,000 to about 200,000, wherein the liquid-permeable upper sheet, the liquid-impermeable lower sheet, and the absorbent core comprise an etched pattern which is united ultrasonically together.

11. The article as claimed in clause 10, characterized in that the adhesive composition is processable with heat and fusion to less than about 400 degrees Fahrenheit.

12. The article as claimed in clause 10, characterized in that the adhesive composition has a melt index of from about 100 to about 2,000 grams per 10 minutes.

13. The article as claimed in clause 10, characterized in that the adhesive composition comprises from about 40 to about 90 percent by weight of the atactic polymer and from about 5 to about 30 percent by weight of the polymer isotactic

14. The article as claimed in clause 10, characterized in that the atactic polymer is selected from the group consisting of atactic polypropylene, low density polyethylene, atactic polystyrene, atactic polybutene, amorphous polyolefin copolymer and combinations thereof.

15. The article as claimed in clause 10, characterized in that the isotactic polymer is selected from the group consisting of isotactic polypropylene, high density polyethylene, isotactic polystyrene, isotactic polybutene and combinations thereof.

16. The article as claimed in clause 10, characterized in that the liquid-permeable upper sheet is selected from the group consisting of porous foams, thermoplastic materials, cross-linked foams, perforated plastic films, natural fibers, synthetic fibers, a mixture of natural and synthetic fibers and combinations thereof.

17. The article as claimed in clause 16, characterized in that the synthetic fibers are selected from the group consisting of polyethylene, polypropylene, polyester, Kraton polymers, polyurethane, nylon and combinations thereof.

18. The article as claimed in clause 10, characterized in that the lower sheet impervious to liquid comprises a material selected from the group consisting of polyethylene, polypropylene, and combinations thereof.

19. The article as claimed in clause 10, characterized in that the absorbent core comprises a material selected from the group consisting of cellulosic material, superabsorbent materials, rayon, glass fibers, wood pulp fibers, polyester fibers, polyamide, polypropylene fibers, and combinations thereof.

20. The article as claimed in clause 10, characterized in that the adhesive composition additionally comprises an additional component selected from the group consisting of glutinizers, antioxidants, viscosity modifiers, color pigments, fillers and polymeric compatibilizers. E S U M E N Ultrasonically bonded laminated absorbent products are disclosed which comprise a liquid permeable top sheet, a liquid impervious bottom sheet, an absorbent core positioned between the liquid permeable top sheet and the liquid impermeable bottom sheet, and an adhesive composition. The laminated structure further comprises a patterned embossed pattern on the liquid permeable upper sheet, the liquid impermeable lower sheet, the absorbent core or any combination thereof. The adhesive composition comprises a mixture of atactic and isotactic polymers such that it has melting and flow characteristics similar to those of the upper sheet and the lower sheet.