Patent Application
20100305543
The present invention relates to nonwoven fabric of a basis weight of 10 to 30 g/m2 prepared from endless filaments of 0.5 to 3.5 den of fineness by spun-melt technology primarily for producing hygienic products and method of production thereof.
In the manufacture of hygienic absorbent products as diapers for children, sanitary napkins and incontinence pads for patients, mostly nonwoven fabrics are used for the construction of these products prepared by spun-melt technology from endless polyolefin filaments, i.e. spunbonding and producing sheeting layers of the product. On the one hand the top-sheet, on the other the back-sheet. The basis weight of these nonwoven fabrics is usually in the range from 10 to 30 g/m2 and their thickness in the range from 0.15 to 0.25 mm. The achieved ratio of basis weight and thickness, that is the volume mass, indicates the bulk of the product and in this case it is in the range from 40 to 200 kg/m3. These processes are described for example in patents U.S. Pat. No. 5,814,349 a U.S. Pat. No. 5,814,249 (Reifenhäuser).
The nonwoven fabrics currently used for hygienic products are thermally reinforced by raster calender, making use of a raster pattern with a bonding area of 17 to 25% of the total area of the raster calender.
An often used raster for this type of nonwoven fabrics is the so-called “pyramid” pattern, available from the manufacturer of the embossed surfaces the company Ungericht under the trade designation U 2888. This known and current method of thermal reinforcement of nonwoven fabrics makes it possible to produce sufficiently durable nonwoven fabric, nevertheless, its drawback consists in the fact that such nonwoven fabrics are not sufficiently bulky, sufficiently elastic, sufficiently soft and sufficiently flexible, which manifests itself by general stiffness of the final product as diapers, hygienic napkins and incontinence pads.
The subject matter of the nonwoven fabric according to the present invention consists in the fact that it is composed of endless polyolefin filaments of a volume mass in the range from 40 to 80 g/m3, basis weight in the range from 10 to 30 g/m2 and thickness in the range from 0.15 to 0.80 mm, thermally bonded on a part of its surface in the range from 10 to 16% of its total surface area.
The polyolefin filaments are preferably monomeric or bicomponent filaments.
To achieve the required bulk, it is essential that it is thermobonded on a part of its surface, which amounts to 10 to 16% of its total surface area, the bonding area being usually equal to 14% and the whole nonwoven fabric is treated with hydrophilic lubrication, for example with a lubricating agent.
It is an advantage that the thermal bonding is accomplished in the form of longitudinal spots distributed in the shape of a raster, where each adjacent line is offset with respect to both adjacent lines by a half of the longitudinal pitch of the raster. The pitch of the individual bonding spots in the longitudinal direction is equal to 2 mm and in the transversal direction of 5.58 mm, the width of the bonding spot is 0.4 mm and its length is equal to 3.99 mm, the number of points per square cm is 9 points, the bonding spot v is 1.562 mm2, the raster depth is 0.7 mm.
The method for producing the nonwoven fabric according to the present invention consists in the fact that a basic system of endless filaments of 0.5 to 3.5 den of fineness is created by spun-melt technology, which is stochastically deposited on a moving belt, of a basis weight of 10 to g/m2 and then is passes through a calendering system consisting of a smooth roller and an embossed roller.
The temperature of the embossed roller is preferably in the range from 110 to 190° C. and the pressing force of the embossed roller on the smooth roller is in the range from 50 to 100 N/mm and the endless filaments are produced by monopolymeric polyolefin endless filaments.
The advantage consists in the fact that nonwoven fabric is used as a covering back-sheet in the final hygienic product and, at the same time, as a loop counter-fastener in the fastening system “hook-loop”.
The invention solves to a considerable extent the above-mentioned disadvantages of the prior art, namely the high stiffness, insufficient softness and compliance of the nonwoven fabric. The method according to the present invention provides a very bulky, soft, nonwoven fabric of low stiffness, loose structure, with a very good hand and good flexibility, and with high stretching capacity even in the transversal direction. A pattern with smaller bonding area and with optimal distribution of bonding points on the calender embossed roller has been applied.
The spun-melt nonwoven fabric according to the present invention is prepared from endless filaments, for example monopolymeric polyolefin filaments of required basis weight stochastically deposited on a moving belt. The filament fineness is within a range of 0.5 to 3.5 den, most frequently higher than 1.0 den, and the basis weight is within the range of 10 to 30 g/m2.
In the known process of nonwoven fabric production of spun-melt type, the polymer granules are hot melted to obtain melt and consequently extruded through melt-spinning nozzles to produce a number of fine filaments. The air nozzles provide the elongation of filaments, which are deposited on a moving belt to form a stochastically arranged flat filament configuration.
The produced flat filament configuration passes through the bonding device constituted by bonding calender rollers heated up to a temperature of 110 to 190° C. adjusted to a pressure of 50 to 100 N/mm. One of the pair of bonding rollers is provided with a bonding raster produced by a series of elevated bonding areas—bonding points.
The pattern of the embossed calender roller is constituted by a series of parallel longitudinally arranged bonding points whose bonding area is in range of 10 to 16% of the surface area of the calender roller, the preferred bonding area being 14% of the surface area of the calender roller.
We have used the pattern designated by the manufacturer of raster surfaces Ungricht by trade designation U 3343B. As illustrated in
Thermal bonding of the nonwoven fabric is in the form of longitudinal spots distributed on the latter in the shape of a raster, where each adjacent line is offset with respect to both adjacent lines by a half of the raster longitudinal pitch.
Volume mass is the function of ratio of basis weight and thickness—when the basis weight is maintained at a constant value and the thickness is less, the nonwoven fabric is bulkier and its volume mass is less and vice versa.
In the case the basis weight is 14 g/m2, the volume mass is lower by 17%, in the case the basis weight is 17 g/m2, the volume mass is lower by 27%, in the case the basis weight is 20 g/m2, the volume mass is lower by 32% than in nonwoven fabrics of comparable basis weight reinforced by a current pattern U 2888.
According to another embodiment, the nonwoven fabric is manufactured from endless filaments produced from two polymers, the polymers being polyolefins. The cross section of the filament may be in the form of core/sheath or side/side, the abundance of the individual polymers being in the range of 10 to 90%, for example polymer A 90% and polymer B 10% and vice versa.
By creating a loose structure of the nonwoven fabric, the invention enables a simplified embodiment of fasteners of hygienic products of the “hook-loop” type. In the standard hook-type fasteners, one part of the fastener comprises hooks and the other part, i.e. the counter-fastener, consists of a strip with loosened fibers serving as loop-like fastening elements into which the hooks engage. The application of nonwoven fabrics according to the present invention enables fastening without the use of a counter-fastener, which is substituted by the voluminous nonwoven fabric according to the present invention.
Specific examples of nonwoven fabric embodiments according to the present invention:
The nonwoven fabric is made from polypropylene filaments with a fineness of 1.5 den. Its basis weight is 14 g/m2 and its thickness is 0.23 mm, its volume mass thus being 60.86 kg/m3.
To reinforce it, a raster calender was used provided with a roller with pattern U 3343B described above and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 14 g/m2 and its thickness is 0.23 mm, its volume mass thus being 60.86 kg/m3.
The nonwoven fabric is treated with hydrophilic lubrication, for example with lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 17 g/m2 and its thickness is 0.28 mm, its volume mass thus being 60.71 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 17 g/m2 and its thickness is 0.28 mm, its volume mass thus being 60.71 kg/m3.
The nonwoven fabric is treated with hydrophilic lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 20 g/m2 and its thickness is 0.31 mm, its volume mass thus being 64.51 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 20 g/m2 and its thickness is 0.31 mm, its volume mass thus being 64.51 kg/m3.
The nonwoven fabric is treated with hydrophilic lubrication, for example with lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den. Its basis weight is 12 g/m2 and its thickness is 0.17 mm, its volume mass thus being 70.58 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den Its basis weight is 12 g/m2 and its thickness is 0.17 mm, its volume mass thus being 70.58 kg/m3.
The nonwoven fabric is treated with hydrophilic lubrication, for example with lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den. Its basis weight is 14 g/m2 and its thickness is 0.18 mm, its volume mass thus being 77.77 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den. Its basis weight is 14 g/m2 and its thickness is 0.18 mm, its volume mass thus being 77.77 kg/m3.
The nonwoven fabric is treated with hydrophilic lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den. Its basis weight is 17 g/m2 and its thickness is 0.18 mm, its volume mass thus being 9 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den. Its basis weight is 17 g/m2 and its thickness is 0.18 mm, its volume mass thus being 9 kg/m3.
The nonwoven fabric is treated with hydrophilic lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den Its basis weight is 20 g/m2 and its thickness is 0.25 mm, its volume mass thus being 80.00 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene and polyethylene filaments in the form of core/sheath in the ratio of 70% of polypropylene and 30% of polyethylene of a fineness of 1.5 den. Its basis weight is 20 g/m2 and its thickness is 0.25 mm, its volume mass thus being 80.00 kg/m3.
The nonwoven fabric is treated with hydrophilic lubrication, for example with lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 0.5 den. Its basis weight is 12 g/m2 and its thickness is 0.17 mm, its volume mass thus being 70.58 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 0.5 den. Its basis weight is 12 g/m2 and its thickness is 0.17 mm, its volume mass thus being 70.58 kg/m3.
The nonwoven fabric is treated with hydrophilic lubrication, for example with lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 14 g/m2 and its thickness is 0.19 mm, its volume mass thus being 73.68 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 14 g/m2 and its thickness is 0.19 mm, its volume mass thus being 73.68 kg/m3.
The nonwoven fabric is treated with hydrophilic lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 17 g/m2 and its thickness is 0.285 mm, its volume mass thus being 59.64 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 17 g/m2 and its thickness is 0.285 mm, its volume mass thus being 59.64 kg/m3.
The nonwoven fabric is treated with hydrophilic lubrication, for example with lubricating agent Silastol PHP 90 from the company Schill&Seilacher, in the amount of 0.40% by weight of the material.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 17 g/m2 and its thickness is 0.28 mm, its volume mass thus being 60.71 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
where PH designates the measuring standards by the firm Paul Hartmann
This nonwoven fabric is designed to be used in the final product, for example in diapers or incontinence pads as the back-sheet. At the same time, it is used as a loop counter-fastener for the current hook-type fastening system.
The nonwoven fabric is made from polypropylene filaments of a fineness of 1.5 den. Its basis weight is 25 g/m2 and its thickness is 0.21 mm, its volume mass thus being 119.1 kg/m3.
To reinforce it, a raster calender was used provided with a roller with U 3343B pattern and the applied technological characteristics were as follows:
At the same time as this now-woven fabric, a nonwoven fabric made of polypropylene filaments of fineness higher than 1.5 den is being produced on another production line. Its basis weight is 25 g/m2 and its thickness is 0.27 mm, its volume mass thus being 92.6 kg/m3.
To reinforce it, a raster calender was used provided with a roller with the classical U 2888 pattern and the applied technological characteristics were as follows:
Comparing the above results, namely the “tear strength”, it is evident that the values of the bulkier nonwoven fabric are in this characteristic higher, i.e. this nonwoven fabric can serve much better as a counter-fastener to the current hook-type fastening system than the nonwoven fabric reinforced by means of the classical pattern.
| Number | Date | Country | Kind |
|---|---|---|---|
| PV 2007-554 | Aug 2007 | CZ | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CZ08/00093 | 8/18/2008 | WO | 00 | 3/24/2010 |
