High-strength lightweight non-woven fabric made of spunbonded non-woven, method for the production thereof and use thereof

Abstract

The invention relates to a high-strength light-weight non-woven fabric made of spunbonded non-woven, particularly for use as a reinforcement or strengthening material, comprising at least one ply of melt-spun synthetic filaments, which are bonded by means of high-energy water jets, characterized in that it includes a thermally activatable binding agent, which is applied onto the ply of melt-spun filaments in the form of at least one thin layer. The invention further relates to a method for producing such a non-woven fabric.

Claims

1. A method for producing a high-strength light-weight non-woven fabric characterized by the following steps: a) depositing at least one ply of spun-bonded melt-spun synthetic filaments by means of a spun-bonded non-woven production process; b) applying at least one thin layer of a thermally activatable binding agent to said at least one ply; c) hydroentangling the at least one ply in the presence of the thermally activatable binding agent using high-energy high-pressure water jets to form a resulting structure in which the synthetic filaments are hydroentangled, said binding agent is drawn into and distributed within said at least one ply, and said binding agent does not form a true surface layer on a surface of said at least one ply; d) drying and thermally treating the resulting structure to activate the binding agent and form said non-woven fabric, wherein: cohesive bonds are present in said non-woven fabric between said spun-bonded melt-spun synthetic filaments; at least a portion of said binding agent is thermally bonded to said spun-bonded melt-spun synthetic filaments to form adhesive bonds distributed within the non-woven fabric, the adhesive bonds being relatively strong compared to said cohesive bonds; said non-woven fabric exhibits a specific strength of at least 4.3 N/5 cm per g/m.sup.2 basis weight and a specific initial modulus, measured in the longitudinal direction as tension at 5% elongation, of at least 0.45 N/5 cm per g/m.sup.2 basis weight; said specific strength is defined by dividing the maximum tensile strength (in N/5 cm) of the non-woven fabric by its area density (in g/m.sup.2); and said specific initial modulus is defined by dividing the tensile strength of the non-woven fabric at 5% elongation (in N/5 cm) by its area density (in g/m.sup.2).

2. The method according to claim 1, wherein the drying and thermal treating are carried out at the same time.

3. The method according to claim 1, wherein: said spun-bonded melt-spun synthetic filaments have a first melting point; said binding agent comprises a thermoplastic polymer having a second melting point; and the second melting point is less than the first melting point.

4. The method according to claim 1, wherein the thermally activatable binding agent is applied by employing an air-laying or melt-blown method.

5. The method of claim 3, wherein the second melting point is at least 10 C. lower than the first melting point.

6. The method of claim 1, wherein the synthetic filaments have a titer of 0.7 to 6.0 dTex.

7. The method of claim 1, wherein the synthetic filaments comprise polyester, polyethylene terephthalate (PET), polyethylene napthalate, a copolymer of PET and PEN, a mixture of PET and PEN, and/or a polyolefin.

8. The method of claim 3, wherein the thermoplastic polymer comprises a polyolefin, polyethylene, a copolymer including polyethylene, polypropylene, a copolymer including polypropylene, a copolyester, polypropylene terephthalate, polybutylene terephthalate, a polyamide, and/or a copolyimide.

9. The method of claim 3, wherein the non-woven fabric has a basis weight of 70 g/m.sup.2 to 86 g/m.sup.2.

10. The method of claim 3, wherein applying at least one thin layer of said thermally activatable binding agent to said at least one ply comprises applying particles of said thermoplastic polymer to said at least one ply.

11. The method of claim 3, wherein applying at least one thin layer of said thermally activatable binding agent to said at least one ply comprises applying a melt-blown fibers or fibrils of said thermoplastic polymer to said at least one ply.

12. The method of claim 11, wherein said melt-blown fibers or fibrils are applied to said at least one ply using air.

13. The method of claim 3, wherein applying at least one thin layer of said thermally activatable binding agent to said at least one ply comprises applying melt-blown conjugate fibers comprising said thermoplastic polymer to said at least one ply.

14. The method of claim 1, wherein said fabric comprises a higher number of said cohesive bonds than said adhesive bonds.

15. The method of claim 14, wherein the synthetic filaments have a titer of 0.7 to 6.0 dTex.

16. The method of claim 5, wherein said binding agent is present in an amount ranging from greater than or equal to 9% by weight to less than 15% by weight, relative to the total weight of the non-woven fabric.

17. The method of claim 16, wherein said spun-bonded melt-spun synthetic filaments comprise polyethylene napthalate having a titer of 0.7 dtex to 6 dtex.

18. The method of claim 1, wherein said binding agent is present in an amount ranging from greater than or equal to 7% by weight to less than 15% by weight, relative to the total weight of the non-woven fabric.

Description

EXAMPLE 1

(1) The test machine for the production of spunbonded non-wovens had a width of 1200 mm. It included a spinneret, which extended across the entire width of the machine, two mutually opposed blow walls disposed parallel to the spinneret, and an extraction gap connecting thereto, which in the lower region expanded into a diffuser and formed a non-woven forming chamber. The spun filaments formed a uniform fabric, which is to say a spunbonded non-woven, on a collection belt suctioned downwardly in the non-woven forming region. Said non-woven was pressed together between two rolls and rolled up.

(2) The pre-bonded spunbonded non-woven was unrolled on a test machine for hydroentangling. With the help of an air-laying system, on the surface thereof a thin layer of short bonding fibers was applied, and the two-layer textile was subsequently treated with a plurality of high-energy water jets, thereby hydroentangled and bonded. At the same time, the binding agent was distributed in the textile. Thereafter, the bonded multi-layer non-woven was dried in a drum dryer, wherein in the end zone of the dryer the temperature was adjusted such that the bonding fibers were activated and brought about additional binding.

(3) In this experiment, a spunbonded non-woven was produced from polypropylene. A spinneret was used, which had 5479 spinning holes across the width described above. The raw material used was polypropylene granules from Exxon Mobile (Achieve PP3155), having an MFI of 36. The spinning temperature was 272 C. The extraction gap had a width of 25 mm. The filament titer was 2.1 dtex, measured based on the diameter in the spunbonded non-woven. The production speed was adjusted to 46 m/min. The resulting spunbonded non-woven had a basis weight of 70 g/m.sup.2. On the hydroentangling machine, first a layer of 16 g/m.sup.2 comprising very short conjugate fibers in a shell/core configuration was applied with the aid of a device for non-woven formation under an air current, wherein the core was made of polypropylene and the shell of polyethylene. The weight ratio of the components was 50/50%. Thereafter, the spunbonded non-woven was subjected to the hydroentangling step. The bonding was carried out with the help of 6 manifolds, with alternately acted upon both sides. The water pressure used in each case was adjusted as follows:

(4) TABLE-US-00001 Manifold no. 1 2 3 4 5 6 Water pressure (bar) 20 50 50 50 150 150

(5) During the hydroentangling step, the short fibers were largely drawn into the spunbonded non-woven, so that they did not form a true surface layer.

(6) Thereafter, the spunbonded non-woven treated with water jets was dried in a drum dryer. In the last zone, the air temperature was adjusted to 123 C., so that the polyethylene melted easily and formed thermal bonds. The spunbonded non-woven bonded in this way had the following mechanical values for a basis weight of 86 g/m.sup.2:

(7) TABLE-US-00002 Maximum Maximum tensile Force at 5% Force at 10% tensile force elongation elongation elongation [N/5 cm] [%] [N/5 cm] [N/5 cm] longitudinal 512 85 56 93 transverse 86 105 6.0 11.9

(8) The specific strength in the longitudinal direction was 5.95 N/5 cm per g/m.sup.2 and the specific secant modulus at 5% elongation was 0.65 N/5 cm per g/m.sup.2.

EXAMPLE 2

(9) Polyester granules were used on the same test machine as described in Example 1. These granules had an intrinsic viscosity of IV=0.67. They were thoroughly dried, so that the residual water content was below 0.01% and spinning was carried out at a temperature of 285 C. In the process, as in Example 1, a spinneret having 5479 holes across a width of 1200 mm was used. The polymer throughput was 320 kg/h. In the spunbonded non-woven, the filaments had a visually determined titer of 2 dtex and very low shrinkage. The machine speed was adjusted to 61 m/min, so that the pre-bonded spunbonded non-woven had a basis weight of 72 g/m.sup.2.

(10) The non-woven was placed in the same machine for hydroentangling. A layer of 16 g/m.sup.2 of the same short conjugate fibers (PP/PE 50/50) was placed on the surface of the pre-bonded spunbonded non-woven. Thereafter, the multi-layer material ran through the hydroentangling step using 6 manifolds, which were adjusted as follows:

(11) TABLE-US-00003 Manifold no. 1 2 3 4 5 6 Water pressure (bar) 20 50 80 80 200 200

(12) During the hydroentangling step, the short bonding fibers were largely drawn into the spunbonded non-woven, so that they did not form a true surface layer.

(13) Thereafter, the spunbonded non-woven treated with water jets was dried in a drum dryer. In the last zone, the air temperature was set to 123 C., so that the polyethylene melted easily and formed thermal bonds. The spunbonded non-woven bonded in this way had the following mechanical values for a basis weight of 87 g/m.sup.2:

(14) TABLE-US-00004 Force Maximum Maximum tensile Force at 5% at 10% tensile force elongation elongation elongation [N/5 cm] [%] [N/5 cm] [N/5 cm] longitudinal 530 88 59 96 transverse 93 100 6.1 12.6

(15) The specific strength in the longitudinal direction was 6.09 N/5 cm per g/m.sup.2 and the specific secant modulus at 5% elongation was 0.68 N/5 cm per g/m.sup.2.