Patent Application
20060128245
The present invention relates to a method of manufacturing a perforated nonwoven, perforation means, particularly needles, engaging in the nonwoven. The needles are positioned on a first roller, the needles engaging through the nonwoven in a surface of a second roller. Furthermore, a roll calender for perforating a nonwoven is provided, the roll calender having a first roller and a second roller. The first roller has perforation means. A perforated nonwoven material is also. described, which is produced using a method and/or a roll calender.
Calenders which each have a needle roller and a perforated roller are described in European Patent Application 1 048 419 A1 and in European Patent Application 1 046 479 A1. The needles of the needle roller engage in the corresponding diametrically opposite openings of the perforate roller and are thus capable of perforating material guided through the gap formed by the perforated roller and the needle roller. Materials which may be perforated are to be plastic films, paper, or nonwoven materials. The latter are to be able to be up to a few millimeters thick.
The object of the present invention is to provide a method and a device which allow the technical outlay for manufacturing perforated nonwoven to be kept low, but simultaneously allow high production speed.
This object is achieved by a method of manufacturing a perforated nonwoven having the features of claim 1 and by a roll calender for perforating a nonwoven having the features of claim 10. Further advantageous embodiments are specified in the particular subclaims.
EP 0 598 970 A1 discloses a device and a method for producing a perforated web, for example, a membrane material. In the process, the web advances between two counterrotating cylinders, of which a first cylinder is smooth and a second cylinder is provided with projections. The second cylinder rotates at a greater peripheral speed than the peripheral speed of the smooth cylinder. The smooth cylinder comprises an elastically yielding covering of a rubber material or textile fibers. The different peripheral speeds of the cylinders produce a slipping action, which creates in the web holes and forms around them strands of partially detached material. These strands extend in the direction, in which the membrane material passes between the two cylinders. The function of the strands consists in allowing liquid to pass from the one side of the membrane to the other, and preventing the liquid from flowing back in the opposite direction.
EP 0 214 608 A2 describes perforated spunbonded nonwovens of polypropylene fibers and bicomponent fibers. In this connection, it discloses a method of perforating a nonwoven, wherein a positive roller mounts a plurality of perforation needles, which are brought into contact with a counter roller. The nonwoven is perforated in that the perforation needles enter the cavities of the counter roller and in so doing penetrate the nonwoven. The nonwoven has perforations with diameters ranging from 0.015 to 0.125 of an inch. However, only 20% to 55% of the entire surface is perforated.
WO9967454 discloses a method for producing from fibers a nonwoven material with a plurality of perforated hole structures extending over the cross section of the nonwoven.
The perforated hole structures are produced by laying the fibers on a screen belt to a fibrous web, by subsequently perforating the fibrous web in a perforation mechanism, and converting it into a nonwoven in a bonding unit. To this end, the perforation mechanism comprises two elements. One element possesses a plurality of spikes directing toward the fibrous web. The second element possesses openings, into which the spikes of the first element immerse in part, and displace without damage the fibers of the fibrous web while passing therethrough, thereby forming the hole structures. The openings of the second element connect to a source of overpressure and vacuum, which permits taking into the openings or blowing out therefrom fibers that are in the region of the openings. Nonwovens produced therefrom have hole structures with a diameter from 0.5 mm to 5 mm and 40 to 120 bonding points per square centimeter, with the bonding surface being 10% to 40% of the surface of the nonwoven material.
WO03004229 discloses a nonwoven fabric perforating device according to
WO03004259 discloses a perforating device, wherein a first roller with a positive structure engages a second roller with a negative structure and perforates a nonwoven in this process.
For example, a counter roller 3 shown in
The present invention relates to a method of manufacturing a perforated nonwoven, perforation means, particularly needles, engaging in the nonwoven. The needles are positioned on a first roller, the needles engaging through the nonwoven in a surface of a second roller. Furthermore, a roll calender for perforating a nonwoven is provided, the roll calender having a first roller a second roller. The first roller has perforation means. A perforated nonwoven material is also described, which is produced using a method and/or a roll calender.
Calenders which each have a needle roller and a perforated roller are described in European Patent Application 1 048 419 A1 and in European Patent Application 1 045 479 A1. The needles of the needle roller engage in the corresponding diametrically opposite openings of the perforated roller and are thus capable of perforating material guided through the gap formed by the perforated roller and the needle roller. Materials which may be perforated are to be plastic films, paper, or nonwoven materials. The latter are to be able to be up to a few millimeters thick.
The object of the present invention is to provide a method and a device which allow the technical outlay for manufacturing perforated nonwoven to be kept low, but simultaneously allow high production speed.
This object is achieved by a method of manufacturing a perforated nonwoven having the features of claim 1 and by a roll calender for perforating a nonwoven having the features of claim 10. Further advantageous embodiments are specified in the particular subclaims.
A method according to the present invention for manufacturing a perforated nonwoven provides that perforation means, particularly needles, engage in the nonwoven. The needles are positioned on a roller, the needles engaging through the nonwoven into a surface of a second roller. The needles displace fibers of the nonwoven, the needles engaging in a material. The material is selected in such a way that the needles may displace the material. In particular, the needles may displace the material in such a way that contours form in the material. The needles preferably engage reproducibly in these contours. The contours are particularly first formed by the engaging of the perforation means. The perforation means preferably at least partially engage in fibrous material which preferably forms at least apart of a surface of the second roller. The displaceable material is particularly a felt material.
According to a refinement, the perforation means are needles. The needles may have differing geometries and cross-sections. For example, the needles may be pointed or blunt, may have undercuts, and may be cylindrical or conical. The geometry and the cross-section may change over the length of the needle. In addition to needles, pyramids, stumps, particularly conical stumps, mushroom geometries, oblong geometries having heads, at least partially round heads, for example, may be used. The perforation means may be milled, etched, or even eroded from the solid. The perforation means may also be incorporated later, for example, glued, clamped, or in another form-fitting and/or frictional way.
The perforation means, particularly needles, preferably engage in felt material which forms the surface of the second roller. In this way, because the felt material is positioned on the second roller, the felt material forms a counterpart diametrically opposite the needles, which preferably may have an elastic behaviour, but also has a certain hardness. The felt material is preferably capable of stabilizing the nonwoven on the second roller, so that the roller may laterally displace nonwoven fibers as it slides into the nonwoven.
According to one embodiment, the felt material which is used on the second roller is positioned on the second roller while standing under mechanical tension. This particularly offers a certain strength of the felt material in relation to a pressure exerted by the needles and/or the first roller. Felt fibers are also capable in this way of having a certain elastic behaviour.
According to one embodiment of the method, the first roller, having the needles, is driven, while the second roller which has the felt material on the surface is not driven directly. Rather, a movement of the first roller ensures that the second roller is carried along by the engagement of the needles in the nonwoven material. In this way, the first roller and the second roller run synchronously with one another. The felt material is preferably selected in such a way that when the needles engage in the felt material, this always occurs at approximately the same points. Openings are thus formed within the felt material in which the needles always engage. In this way, wear of the felt material when it is used on the second roller is restricted.
According to a further embodiment, the needles are heated. The heating is preferably to a temperature which lies below a melting temperature of the nonwoven or a decomposition temperature of the felt material. For example, a needle surface temperature may be such that fibers of the nonwoven are melted and/or softened, without, however, the fiber structure as such being destroyed. A refinement of the method provides that the felt material is applied to the second roller as a shrinkage hose. This shrinkage hose is preferably seamless. The second roller preferably has a metal surface. It may be smooth on its surface or have a corrugation. The corrugation is, for example, applied as a spiral or in the form of grooves with their axes parallel. There is also the possibility that the surface of the second roller has screw-like grooves with a left or right pitch. The particularly metal surface of the second roller and the felt material are preferably connected in that the hose exerts a pressure on the metal surface of the second roller. Furthermore, an adhesive may also be applied between the felt material and the metal surface. This adhesive may preferably be dissolved again through the effect of alcohol or something similar, for example. In this way, the connection between the film material and the second roller may be removed again. If the felt material is too worn, it is replaced with a new felt material. The remaining parts of the second roller do not absolutely have to be replaced.
A refinement, which also represents an independent idea, provides that the felt material is applied to a carrier. The felt material having the carrier is then subsequently applied to the roller, pulled on, for example. The carrier is preferably a changeover bobbin. The changeover bobbin is preferably pushed onto the roller. The changeover bobbin and the roller are connected via typical connections, which are particularly frictional and/or form-fitting. For example, tongue and groove systems, screw connections, or something similar may be used. The felt material is preferably applied replaceably to the carrier, so that the carrier is reusable. The carrier, in particular the changeover bobbin, allows rapid felt material replacement. A standstill time of the calender is thus minimized. The felt material and the carrier are connected, for example, as was described above in the context of the connection of the felt material to the roller. A plastic material is preferably used for the changeover bobbin. A shrinkage hose only has to be pulled onto the changeover bobbin. The rollers of the calender may remain unchanged. By using multiple changeover bobbins, even shorter useful lives of the felt material may be overcome rapidly. Through a sufficient supply, replacement of the changeover bobbin may be performed simultaneously with a replacement of a roll from the unwinder.
According to a further and also independent idea of the present invention, the roll calender is constructed in such a way that the counter roller may be made accessible on one side in such a way that, for example, a changeover bobbin may be replaced. This is preferably performed while the other side remains in its position, in a bearing, for example. If the weight of the counter roller must be compensated for, a support may be provided on the calender for this purpose. The support absorbs the weight which would otherwise be produced by unclamping the now free side of the counter roller. The support is preferably at least partially movable so that there is sufficient protection as the changeover bobbin is pulled off and on. A part of the support is particularly movable along the axis of the counter roller. According to a refinement, the counter roller is supported on the free side by an attachable weight receiver. The weight receiver is screwed on, for example, and extends along the axis of the counter roller. The force receiver is particularly long enough that the sleeve may be pushed on and off.
A further, also independent idea provides that the calender has a roller changer for the counter roller. If, for example, a first felt material is worn so much that it must be replaced, the first counter roller having the first felt material is moved away from the perforation roller and a second counter roller of the calender having a second felt material is brought into contact with the perforation roller. The first counter roller may now, for example, be uninstalled in order to replace the first felt material. For example, a roller changer for a calender is disclosed in German Patent 100 05 306 C1, to which reference is made in its entirety in the scope of this disclosure, particularly in regard to the calender, the roller replacement, and the operation of the roller.
A good pressure during the use of a felt hose results, for example, if the felt hose is pulled over the cleaned surface of the second roller or the cleaned carrier and subsequently is wetted through with water heated to approximately 60-80° C. In this case, it may be advantageous to add an additional wetting agent to the water, this may be a detergent, for example. In this way, shrinkage of the felt hose is accelerated. Subsequently, the felt hose is quenched using cold water and dried on the second roller at a temperature of 30-40° C., for example. The connection between the felt material and the second roller and/or carrier achieved in this way is sufficient that there is no slip between the felt material and the second roller as the needles penetrate into the felt material.
A surface of the felt material itself may also be processed. This is necessary, for example, if the felt material surface has elevations or appearances of wear, which cause interference. There is also the possibility of either roughening the surface or processing it in such a way that its degree of roughness decreases. The latter may be performed, for example, using light singing of protruding felt material fibers and subsequent removal using a brush, for example.
A felt material which has wool as a fibrous material is preferably used. For certain applications, however, it may also be advisable to use other fibrous materials as the felt material. These may be, for example, flax or cotton, viscose, polyamide, polyacrylonitrile, polyester, polypropylene, aramid, polytetrafluoroethylene, polyamide, or polyphenylene sulfide. While wool has a long-term heat resistance of around 100° C., at a higher needle temperature, polyamide, polyester, or aramid fibers are used, for example. Special durability of the shrinkage hose used has resulted when it has a hardness of group F according to DIN 61 200. The felt material preferably has a gross density between 0.32 and 0.48 g/cm3. The felt material preferably has a felt thickness which is greater than 5 mm, particularly greater than 8 mm, preferably 10 mm and more, for example, up to 15 mm. A felt hose is preferably used which has a wool felt according to F 2 having a wall thickness of approximately 10 mm and a density of 0.36 g/cm3.
Use of a felt hose and/or a felt material has the further advantage that little consideration must be taken of temperature expansion of the needle and/or of the first roller. Particularly if the first roller carries along the second roller, the needles and the engagement points in the felt material are automatically synchronized. Furthermore, an embodiment provides that the material of the second roller has a lower elasticity than the felt material which forms the surface of the second roller. The second roller is preferably manufactured from a metal, particularly an alloyed steel. Another embodiment provides that the second roller has plastic, and preferably is made predominantly of plastic. Furthermore, the second roller may also be a hollow roller.
A gap between the first and the second roller is preferably set in such a way that the needles which penetrate into the nonwoven displace the fibers of the nonwoven and press against the felt material, the fibers being compressed and an opening in the nonwoven being stabilized. Depending on the speed of the rollers and/or the nonwoven guided through them, the pressure applied, the temperature, and other parameters, there is the possibility that the openings will assume a funnel shape, for example. Furthermore, the use of a felt material on the second roller allows the use of greatly differing needle geometries. These may be pointed, conical, blunt, or shaped in other ways. Their cross-sections may be rectangular, star-shaped, round, semicircular, figure-shaped, or even mixtures of all of these.
According to a refinement, the needles are particularly shaped in such a way that as the needles engage, fibers are at least partially displaced out of the nonwoven. In this case, the fibers form a structure which deforms corresponding to a geometry of the needles. The structure preferably arises from a nonwoven surface after the nonwoven passes through the first and the second roller. Another embodiment of the method provides that upon penetration of the needles into the felt material, fibers are at least partially also pulled into the felt material. As the nonwoven is subsequently pulled off of the second roller, this may lead to the existing texturing of the nonwoven surface becoming more pronounced. For example, by adhering in the felt, the fibers may be pulled out until the felt-fiber connection is broken.
According to a further idea of the present invention, a roll calender for perforating a nonwoven is provided, the roll calender having a first and a second roller. The first roller has perforation means which project from a surface of the first roller. The first and the second roller form a gap, through which a nonwoven to be perforated is guided. The second roller has a felt material as a surface, the gap between the first and the second roller being set in such a way that the perforation means engage in the felt material. A refinement provides that the gap between the first and second roller is changeable. In particular, it may be set in such a way that the needles used do not engage completely in the felt material and the nonwoven guided through, but only up to a certain range.
The needle roller preferably has a circular needle shape. A needle diameter preferably has a value between 1 and approximately 3 mm. A needle area is particularly between 1.5 and 5 mm2, a needle density is preferably between 8 and 25 per cm2, a needle area component preferably being between 30% to 70%. An insertion depth of the needles into the felt material is preferably between 2 mm to 6 mm. The gap between the first and the second roller is preferably set in such a way that the needles are not inserted completely into the felt material and into the nonwoven. A further embodiment provides that the gap has a size such that a nonwoven guided between them is compressed simultaneously with the perforation. For example, the nonwoven may be subjected to a pressure and/or a temperature for this purpose, which is exerted by the first roller or parts thereof on the nonwoven.
Data of an exemplary needle roller, using which various nonwovens were perforated on the second roller in interaction with a felt material, are listed in the following table.
Exemplary measurement data of various experiments which were determined using a needle roller and a felt-coated counter roller are listed in the following table:
A: polypropylene spunbonded nonwoven
B: polypropylene spunbonded nonwoven + polyethylene/polypropylene bi-component spunbonded nonwoven In the experiments shown, the screen belt speed was 95 m/minutes.
The perforation means, particularly the needles, are preferably implemented in such a way that the nonwoven is perforated so it is permeable to liquid. It has been shown to be particularly suitable in this case to use a prebonded nonwoven as the nonwoven used. A single-layer nonwoven is preferably used. For example, a spunbonded nonwoven made predominantly of polypropylene is used, which is single-layer. This spunbonded nonwoven preferably has a weight between 20 g/m2 and 40 g/m2. The basic weight is preferably around 30 g/m2. A prebonded nonwoven has, for example, a bonded area in the form of thermobonding of 14.49%. The nonwoven preferably has a bonded area between 10% and approximately 60%. Besides thermobonding, the nonwoven may also obtain its stability and strength through other bonding methods, for example, through water jet bonding, adhesive, adhesive fibers, ultrasound welding, etc. The hole sizes which were produced, for example, were 1.09 mm2 as hole area, an average length being 1.35 mm in MD and an average length in CD being 1.04 mm. The needle roller used was heated from the inside using a thermal oil for this purpose, a surface temperature of the needle roller being set between 105° C. and 130° C. Using the single-layer nonwoven, hole sizes were achieved which had an axis ratio MD to CD of approximately 1. Speeds of up to 95 m/minutes were used in this case.
Further experiments were performed, for example, on a two-layer nonwoven. A first layer was made of a spunbonded nonwoven made of polypropylene, a second layer was made of a bi-component material. The two-layer nonwoven was prebonded and had a bonding area of approximately 17%. Especially good, stable circular perforations resulted for a base weight which was between 30 and 40 g/m2.
A prebonded nonwoven which has a bonding area which is particularly between 8% and 25% is preferably used for perforation.
Besides the materials polypropylene and polyethylene cited, the nonwovens may also have other materials, for example, polyamides, polyester, glass fibers, PET, viscose, acetate, polyacrylics, polystyrene, polyvinyl chloride, their copolymers, and mixtures thereof. The use of bi-component or multicomponent nonwovens made of these materials in particular is also possible.
Further advantageous embodiment and refinements may be inferred from the following drawing. The features illustrated there may be combined with the embodiment of the present invention described above into further independent refinements, without the present invention being restricted as such in its embodiment by the drawing.
It may also be seen from
The construction and mode of operation of the schematic drawing shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10232148.5 | Jul 2002 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP03/07217 | 7/5/2003 | WO | 8/19/2005 |
