Hairy film with increased throughput
The present invention concerns a single or multilayer material processed with a matrix surface to create a nap on the material.
It is known from DE 198 12 097 C1 to send a thermoplastic polymer material directly onto a roller, under vacuum conditions. The roller has cavities into which the thermoplastic material enters. Next the at least partially solidified material is peeled off the roller. Small hair is formed on the surface of the thermoplastic material, during the process. A hairy film generating unit is also known from DE 198 43 109 A1 , which has a first and a second roller that form a gap between them. With the pressure in the gap, thermoplastic material is pressed into the cavities of a matrix and subsequently peeled off again.
The present invention is based on the task of improving this manner of forming hair and of making a rational manufacturing procedure possible.
This task is accomplished by means of a hairy film generating unit with the features of claim 1 , with a hairy film with the features of claim 4 and with a procedure with the features of claims 10 or 11. Other advantageous refinements are indicated in the subordinate and dependent claims.
The hairy film generating unit has a first roller with a hairy film generating matrix, formed by means of cavities, and a thermoplastic material supplying unit. A second roller is arranged facing the first, with an adjustable gap, so that thermoplastic material can be pressed into the cavities under a line pressure of at least 40 N/mm. The first roller and the thermoplastic supplying unit are so adjusted to each other that the thermoplastic material can be sent to the first roller at a rate of at least 3 m/min.
Preferably the line pressure in the hairy film generating unit is of between 40 N/mm and 120 N/mm in the gap, preferably between 60 N/mm and 100 N/mm, in particular, 70
N/mm to 90 N/mm. The velocity is preferably above 5 m/min, in particular above 6 m/min.
In accordance with one further development of the hairy film generating unit for a continuous manufacturing process, this unit has a stretching unit arranged downstream of the hairy film generating matrix, with mono and/or biaxial stretching, in particular to accelerate the manufacturing process. With suitable stretching it is possible to also increase the planar throughput. Preferably stretching by a factor of at least 1.1 is applied, in particular also by a factor of 2, 3 or for instance 8 and more, depending on the thermoplastic material used.
It is possible, in the manner described above, to generate a hairy film with hair of which at least one is at least partially curved inward, in particular in a concave manner. Preferably at least 50 % of the hair on the hairy film shows an inward curvature at their top. Another refinement has a hairy film in which at least 85 %, preferably at least 95 % and in particular, at least almost all hair have inward-curved tops.
The hairy film is preferably configured in such a way that at least 5 % of a hair's length is hollow. In accordance with one refinement, the hair have a cavity that extends between 5 % and 25 % downwards from the top, inside the hair, According to another refinement, the cavity can also be longer. Preferably the hair has an external geometry that is at least partially approximately cylindrical, in particular, predominantly cylindrical. Another refinement provides for an outer geometry that at least partially broadens from top to bottom, in particular following a concave contour.
The matrix is in particular so configured that the surface has a cavity density of preferably between 500 and 5500 cavities/cm2, preferably between 1000 and 4500 cavities, in particular, between 1500 and 2500 cavities/cm2. According to one refinement, used in particular for a hairy film that comes in contact with a sensitive surface, such as skin, or a polished surface as in a car, motorcycle, bicycle, boat, replacement parts, painted surface or similar, the hairy sheet has a surface with between 200 and 900 cavities/cm2. In addition, the cavities can be arranged as regular
patterns with different cavity densities. Figures or geometrical patterns can for instance be formed. The possibility of a completely random arrangement of the cavities on the matrix surface also exists. The cavity density in an area can for instance fluctuate between 200 and 5000 cavities/m2. According to one further development the matrix is so designed that it has at least one area of the order of magnitude of at least one to several square centimeters that has no hair and simultaneously, one or two areas with a density of over 50 cavities per square centimeter. Another refinement of the matrix surface provides that it should have at least one strip without cavities. Preferably several strips are arranged next to each other. They can be parallel to the axis of rotation of the matrix roller, parallel to a plane that is perpendicular to the axis of rotation of the matrix roller, or also at an angular ratio between these, in particular also at different angles in each case, for instance in a pattern. These strips are separated from each other by arrangements of cavities. Their density can be the same or different, for instance increasing from one side to the other along the roller. The stripe or stripes can form intersecting strips or also surfaces on the hairy film that are acted upon by a medium. The medium can be gaseous, liquid or solid. In particular, it will confer to the surface a property that it did not have before.
The length of the hair and their shape is for instance affected by the cavity depth, the speed of the thermoplastic material in the calendar, the pressure in the calendar gap, the temperature of the thermoplastic material, the calendar rollers, their composition and other parameters. According to one refinement, for instance the peeling angle of the thermoplastic material during the continuous production process is changed, in particular adjusted to achieve equal length in the hair. This is accomplished, for instance, with controls, preferably with regulators. To this end the length of the hair is for instance determined on-line and then the peeling angle of the matrix is changed.
The length of the hair can be stretched mechanically, as is known for instance from DE 198 12 097 A1. The state of the art known from this document regarding the mechanical lengthening and also the roller configuration, the equipment design in general, possible cooling devices and also heating devices for the film, the thermoplastic material used, its design and the hair geometry, are included in the context of this disclosure. The same
applies also to the state of the art known from DE 195 24 076 C1 and DE 198 43 109 A1.
In another with another concept of the invention, a procedure is proposed for the manufacture of a hairy film from a thermoplastic material, where the hairy film has a majority of the hair pressed out of the thermoplastic material and preferably, almost simultaneously stretched, while the thermoplastic material travels at a rate of at least 3 m/s through a calendar with a matrix surface of cavities on a roller, with a line pressure of at least 40 N/mm pressing the thermoplastic material into the cavities and where a hairy film is generated when the thermoplastic material is peeled off the matrix surface.
It is furthermore proposed to increase the velocity by means of a negative gap between the first and the second roller. A negative gap results when a sum of one radius of the matrix roller and one radius of the pressure roller is greater than the distance between the two roller axles. The gap can for instance measure 0.1 mm, but can also be varied, for instance to 0.15 mm. Preferably the gap is adjusted to between 150 μm and 250 μm, in particular between 170 μm and 220 μm. In this manner, a minimum contact surface of the thermoplastic material is defined between the two rollers, which is larger than the minimum contact surface area for a positive gap. Preferably the minimum contact surface area has a length of at least half a centimeter in the gap. At the same time, the feed rate of thermoplastic material and the pressure at the gap can be adjusted to affect hair geometry. In addition there is the possibility of adjusting the temperature of the rollers to the thermoplastic material. According to one configuration, the surface of the pressure roller has a temperature of approximately 121 °C to approximately 138 °C. The matrix surface, or the film, is kept at a temperature at least 20 °C lower, according to one further development, preferably in the range between 60 °C and 90 °C. The film thickness is preferably of less than 100 μm, in particular around 60 μm, preferably around 50 μm. The sheet may be of a single layer or multi-layered. It is also possible for the matrix roller to be hotter than the steel roller, for instance with the matrix roller at least 20 °C hotter than the steel roller.
In accordance with another refinement, the nip roller across from the matrix roller and forming the gap with it, is for instance a heated steel roller adjusted to a temperature between 90 °C and approximately 165 °C. The heated steel roller is preferably coated with a nonstick compound. It may be chromed. The diameter of these heated roller may is of approximately 500 mm. However, the diameter can lie within a range of approximately 400 mm to 600 mm, and also above or below. In turn, the matrix roller can be adjusted to a surface temperature in the range of 20 °C to 80 °C. The diameter of the matrix roller is preferably approximately equal to that of the nip roller, but can be greater or smaller. Preferably the diameters of the nip roller and of the matrix roller are in a ratio that is an integer, for instance 1 :2 or 3: 1.
The hairy film can furthermore have certain properties, either only the hair, or the entire film and/or in each case, only parts thereof. The hairy film can for instance have antibacterial or antiviral properties, for instance either by acting against them by inhibiting their growth and/or by destroying them. It is also possible to promote bacterial and/or viral growth with appropriate properties of the hairy film. Other properties that may be present singly or in combination are for instance to be fire-retardant, temperature-stable, transparency of at least the hairy film, be optically bleaching, be odorous or odor-inhibiting, or controlling odors, radiation-resistant, antimisting, filtering, able to affect flow, electrically conducting, optically conducting, have magnetic properties as well as many others that may eventually be described below in connection with an additive, an addition agent, a coating, or similar, without being limiting. A property of the hairy film may be affected by admixing an additive to the polymer, by a master batch, by treating the hairy film with a fluid, for instance by application, spraying, diffusion or similar.
Examples of additives that can be used are fire-retardant additives such as Exolit™ AP 750 or Exolit™ RP, supplied by Clariant. The possibility also exists of stabilizing the hairy film towards solar radiation, or other radiation, for instance thermal radiation. To this end, thermal and/or ultraviolet stabilizers can be used as additives (for instance HALS - hindered amine light stabilizers - as well as Hostavin™ N 20 or Sanduvor™ PR 31 , supplied by Clariant). Another possibility is to use opalescent pigments, for instance. It is
furthermore possible to use additives ("clarifying agents") for instance from the Millad™ product series, supplied by Milliken Chemical, chemical foaming agents and/or nucleation promoters (for instance Hydrocerol™, a mixture manufactured by Clariant), antimisting agents (for instance Atmer™ of Ciba Specialty Chemicals, marketed by Uniquema), for instance against humidity condensation, optical bleaches (for instance Uvitex™ OB, marketed by Ciba Specialty Chemicals), scents, like perfumes, for instance, aromatic additives such as those from spices like vanilla, or odor control additives (such as zeolites).
Additives that have an antimicrobial effect are for instance biostatic or biocidal additives, depending on the desired use of the invention. Some examples of substances with antimicrobial activity are for instance Irgaguard™ B 1000 of Ciba Specialty Chemicals, or numerous commercially available products that contain silver ions (for instance AlphaSan™ RC 5000 of Milliken Chemical).
Surface-active additives can also be used, such as additives with hydrophobic or hydrophilic properties.
A biodegradable material can also be used as material for hairy films and/or components in connection with the hairy film, such as bonded fabrics, laminates, tissues, films or coatings. For instance, a polymer based on starch can be used, such as Novament, Mazin® and Polytriticum® 2000, both of Midwest Grain Products Inc., biodegradable polyesters, for instance obtainable from DuPont, Eastman, Bayer and BASF, and/or polyhydroxy-alkanoates, for instance obtainable from Metabolix, alone, as mixtures or also separately, in each case in different locations. It is also possible for instance, to select a different biodegradability by the purposive utilization of different materials for the hairy film. For instance, a first layer of the hairy sheet may be biodegradable, while a neighboring second layer is not degradable, or only very slowly degradable.
Hairy films are used domestically, for instance as cloth, packaging material, for instance also to package delicate goods.
Furthermore, shielding or screening packaging can be achieved by means of the hairy film, for instance, screening against heat or cold, impact, electric and/or magnetic effects, humidity, acids, bases, abrasive media, etc. The hairy film is for instance suitable for the safe packaging of electronically sensitive components. Certain additives make available electric conductivity, optical conductivity and/or magnetic properties to the film, a layer, or a coating of the hairy film, for instance carbon black or graphite.
Reactive additives (for instance, crosslinking additives or photo-initiators, such as Irgacure™ 1700 supplied by Ciba Specialty Chemicals) can be admixed to achieve chemical and/or physical modifications of the hairy film during its formation.
In addition, the ratio of the hair's length to diameter can be of less than one, in particular in a range that lies between approximately 0.5 and approximately 0.8.
Preferably the hair is so arranged that at the center the distance between them is of approximately 140 μm to 220 μm.
Especially preferred is a calendar in which the rollers have a diameter of between 10 and 15 cm. For better heating, for instance as a function of the angle of contact and of the residence time as a function of the heat flow transferred from the roller to the film and vice versa, it is also possible to use roller diameters of over 20 cm, preferably between 30 and 50 cm.
After its manufacture, the hairy film may be further texturized, for instance with an additional microstructure and/or a macrostructure, by stamping, calendaring or similar processes, possibly in the form of a laminate that is waved, stretched, perforated, etc. In accordance with a further refinement, the length of the hair can be calibrated, i.e., in particular brought at least partially to a uniform size, either in length or in thickness, for instance, possibly by stamping, grinding, cutting, tempering, etc.
ln accordance, with another refinement, the side of the hairy film opposite to the hairy side has a structure, in particular due to the pulling the hair out of the surface, even when the pressure-exerting roller is smooth and does not have a regular structure.
In accordance with another refinement, the film and/or the thermoplastic material is preheated by means of radiation and/or convection, for instance by means of a thermal fluid such as a hot air stream, or a hot liquid. The hot liquid can be used to coat the film, to at least change one surface property of the film.
Furthermore, a crack pressure can be applied in the calendar, which can amount to a maximum of for instance over six MPa, in particular, over eight MPa.
According to one theory, the molten thermoplastic material that is pressed into the cavities escapes at the sides of the cavities and thereby returns to a solid condition sooner than other constituents of the film in contact with the surface of the matrix roller. Depending on the matrix' surface properties, the thermoplastic material adheres there and can then peeled off, with lengthening of at least part of the material inside the cavity. Preferably a concave area is generated in this manner in the cavity of a hair of the hairy film.
In a further refinement a so-called chill roller is used that is directly in contact with the film. Before the film is removed from the surface of the matrix roll, the film is preferably already cooled on a surface. This cooling can be reinforced with a chill roller that may for instance be structured, for example like a pressure roller and which is provided with a cooling medium - such as a cooling liquid - that is sent along the structuring. The cooling liquid has a temperature that is sufficient to cool the thermoplastic material, to improve the removal or peeling off of the thermoplastic material from the matrix surface. Preferably the liquid evaporates during the cooling step. The cooling step can also be used to arrange a substance on the surface, using the cooling liquid, for instance. In addition, a so-called "kiss" roller can be used, in which only a portion of the surface is wetted.
In accordance with another refinement of the hairy film generating unit, the latter can have a matrix roller and a pressure roller, in which the matrix roller is arranged at least partially beneath the pressure roller. The matrix roller is preferably arranged in such a way that the film passing through the calendar gap can be at least in part passed through a liquid. The latter is for instance arranged in the form of a bath. The liquid makes contact with at least part of the hairy film, for instance only with the hair and/or only with this surface, or with the entire film area.
In a preliminary step or a follow-up step following the manufacture of the hair, the mono or multi-layer film can be embossed, bonded, laminated and/or mechanically treated, in particular connected to another material by physical or chemical means, by friction- or form-fitting, for instance by thermal and/or ultrasonic bonding, as is known for example from US 4,374,888, to which we specifically make reference in the context of this disclosure of the invention, using adhesive, etc.; with SMS material as known from US 5,178,931 and US 5,188,885; with spunbond material as disclosed in US 4,340,563, US 4,405,297, US 4,434,204 and US 5,545,371, and/or with meltblown material as known from US 3,704,198 and US 3,849,241 ; with multi-layers as they are known from WO 96/19346, where in each case we refer to these documents in the context of this disclosure of the invention, with respect to materials, the manufacturing process and/or the applications. The same applies to bicomponent materials such as Bico fibers as they are known from US 5,336,552, US 5,382,400, US 5,759,926 and 5,783,503 and the documents mentioned in them; co-formed fibers as known from US 4,100,324, US 4,818,464 and the references mentioned there; staple fibers; "crimped", i.e. curved fibers; "carded" fibers, and tissues, to all of which we make reference in the context of this disclosure, in terms of materials; all of them can be connected to form a mono or multi-layer construction with the hairy film, for instance partially bonded in an offline or inline process. Bonding is possible with known methods and devices, for instance as known from US Design Patent No. 239,566, US Design Patent No. 264,512, US 3,855,046, US 5,770,531 , US 3,855,046 and US 4,100,319, to all of which we refer hereby in the context of this disclosure in relation to bonding.
According to another refinement of the invention, the hairy film can be stretched when it has been pulled off the matrix roller. A stretching force can for instance be directed in CD and/or MD. Methods and parameters for stretching are for instance known from EP 0 259 128 B1 , US 5,296,184, EP 0 309 073 and US 5,770,531 , which are hereby referenced regarding this invention, in terms of materials and applications, and the devices described. It is also known to stretch films together with bonded fiber fabrics or other materials, for instance as described in EP 0 259 128 B1 and EP 0 309 073 B1 , both hereby made reference to in the context of this disclosure, in terms of materials and the parameters and applications as described. The same applies also to US 4,116,892, also referred to here in the context of this disclosure, regarding stretching. Similar devices can also be used. Stretching is in particular used to increase the speed of hairy film manufacture, in particular at speeds above 5 m/min, preferably above 15 m/min. It is also possible, in this manner, to increase the planar throughput by for instance at least 20 %, in particular, over 30 %, preferably by at least 50 %. Stretching is furthermore used to change properties of the film, such as permeability to air and steam, filtering effect, etc. According to one further development, it is possible to adjust the speed of hairy film manufacture to well above 10 m/min, in particular to up to 100 m/min, when a suitable choice is made of roller diameters, roller material, cavities, thermoplastic material, gap pressure, heating and cooling rates, temperature, peeling off device, stretching device, and when they are coordinated with each other.
Because of its configuration, the hairy film can be used in different applications, which here are mentioned only as examples, without claiming to be exhaustive:
In the medical field, for ladies' and baby hygiene articles, for instance as back sheet, or as top sheet, whichever is steam-permeable, bandages, incontinence articles, as hairy film with nonstick properties, for instance as release paper, for envelopes, as adhesion promoter for plastic materials that are placed atop of each other, as printing film, as writing surface, as packaging material, as separators of cans or tins with antisliding properties, as bags for foods such as sandwiches, meat or vegetables, as printable labels, as waterproof and in particular, also steam-permeable material, for instance for printable bags, as adhesive material, used for instance for microstraps and hooking
agents, as fasteners in fastening systems, hairy film as contact surface with or without the use of an adhesive, where the hair preferably forms a barrier for the adhesive, as adhesive reservoir with adhesive on the bottom of the hairy film and/or on the hair, as friction enhancer, as adhesive in sanitary towels and slip inserts, as contact agent between two surfaces, for instance a bed and a bed cover, as wall hanging or wallpaper, as flooring material, in particular with dirt-repelling properties, as antisliding material for mats, as cleaning or polishing surface, as protective covering, for instance as overall, for instance suitable for painting or for wetting surfaces, where the material to be applied does not run off the clothing, or also as antisliding layer inside of protective clothing, as oil and/or lubricant catcher and/or cleaning agent, as adhesive side of adhesive booklets, as non-slipping tablecloth, in sports clothing, sports accessories and/or sport equipment, for instance for adhesion improvement as is for instance necessary in climbing, as part of a glove, for instance to improve the hand sliding out of the glove by non-adhesion of the skin to the hairy film surface, as barrier, for instance as viral barrier in accordance with ASTM 1671 , as medicinal implant that preferably is also biodegradable, for instance in wound healing of lesions inside the body, shoe protectors, the packaging of bottles, in CD covers, in Tetrapack packaging, as shrink-wrap, as pad, as decoration for instance in the automobile area, in the armature area, as lining material to envelop an article, as coating, as insect trap, roofing material for instance on or under roofing tiles, as sound and/or thermal insulation, in intimate articles such as toys, as surface, as filter, as sedimentation agent, as membrane, for instance as osmosis membrane, as refinement in a cyclotron, as a means of identification, for instance by the shape or the material of the hair, in the cosmetic area for instance as a cloth for cream application, as storage material for substances that later, during use, are slowly or instantly released, for instance by diffusion, or by a rupture occurring upon bending, releasing a substance, where a hair may have a predetermined breaking point, for instance as microstructure, as dirt repellant, for instance using a lotus flower effect on the surface, as lens-polishing fabric, as charging material for grains and/or powders that are for instance retained by the hair, as intermediate layer in a hygiene article, in the sanitary area, for instance in a towel, a bathing cap, as drainage agent, as leather substitute, as sea marker, as signal markers, as light sink, as protective cover for instance for a head-rest cover, as wound-covering material, as elastic bandage, as
silver-polishing cloth, as cigarette filter, as raincoat, as surface material in a disposable article, as covering material for painting, coating and similar work, to grow cell cultures, as optical switch, as electrostatically loaded agent, as binding, book spine, as velvet inset, as deep-draw sheet, as sealer, as deep cooling bag, ice-cooling bag, as contact surface for skin, as pillow, as air mattress, etc.
The hairy film can have a microstructure, in addition to the hair, that can be smaller than that of the hair. The microstructure can be an elevation or depression in the film material.
In particular, the film can be used as breathing film, for instance in filters, where the film can be arranged perpendicular to the direction of flow, parallel to it, or at an angle. The hair in particular can affect the flow, flow direction, turbulence, etc. For instance, a hairy film can be used as outer skin of rapidly moving bodies.
The film can also have a microstructure that also applies to the hair. It can be two to ten times smaller, in particular 4 to six times smaller, than the hair itself.
Some advantageous refinements and features are indicated in the description of the drawings that follows. They can also be combined into further developments together with the characteristics mentioned above. They show:
Figure 1 A first hairy film generating device and Figure 2 a second hairy film generating device
Figure 1 shows a first hairy film generating device 1 with an unrolling device 2 as thermoplastic material feeding device. From the unrolling device 2 a single or multi-layer film 3 of at least partially thermoplastic material is unwound and sent to a first deflection roller 4. Upstream of the first deflection roller there is a processing station 5. Processing station 5 for instance makes possible heating and/or coating the film 3. From the first deflection roller 4, the film 3 goes to a calendar 6. Between the calendar 6 and the first deflection roller, a second processing station 7 is arranged in this refinement. The
second processing station 7 serves preferably for heating and/or further coating, or similar. The film 3 so treated is for instance sent first to a first roller, the pressure roller 8, which is heated, before the film 3 is at least partially pressed - in a gap between the pressure roller 8 and a second roller, the matrix roller 10 of the calendar 6 - into cavities 11 in matrix roller 10. The line pressure existing in gap 9 can be adjusted via the position of the pressure roller in calendar 6. The pressure build-up and the pressure gradient can be influenced by the choice of diameter for the pressure roll 8 and the matrix roller 10. Removing the film 3 from the matrix roller 10 can be simplified by using a cooling device 12. For instance, the cooling device 12 can blow a fluid stream onto one side of film 3, to the remove the heat contained in the film. Furthermore device 1 shows an additional mechanism 13, placed between the film 3 and the matrix roller 10. It helps in peeling off the film 3 by introducing a separating flow, for instance air. The latter may be temperature-conditioned, to either cool or at least maintain at a certain temperature one side 14 of the hairy film 3, if not to heat it briefly.
The film 3 peeled off the matrix roller 10 has now become a hairy film 3a. The film 3 is now sent to a third processing station 16 via a second deflection roller 15. Here the film 3 is coated for instance with a fluid and/or for instance processed with a tool, such as a cutting device, to ready the film 3 as necessary for a subsequent use. The processing may also be stretching the film 3 in machining direction (MD) or crosswise to it (CD). In this manner it is possible to increase a throughput in terms of planar throughput. Subsequently the film 3 is prepared for further transport by means of a take-up device 17.
Figure 2 shows a second hairy film generating device 20 with an unwinder 21 and a take-up roller 22. Between them the film 23 goes through a calendar 24. This calendar 24 also has a matrix roller 25 and a pressure roller 26. However, here the film follows a considerably shorter path between unwinder 21 and take-up roller 22. It is possible to arrange a fourth processing station 27 and a fifth processing station 28 upstream and downstream, respectively, of calendar 24. As shown, the processing stations 27 and 28 can heat the film 23 or, in accordance with different implementations, can apply a coating and provide mechanical processing, such as lengthening, stretching, brushing or
other. Just as for an arrangement in accordance with the preceding figure, the processing stations 27 and 28 can also de arranged in such a way that the hairy film's 23 upper side 29 is also processed.