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1. WO2021005182 - NONWOVEN FABRIC AND PROCESS FOR THE PRODUCTION THEREOF

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[ EN ]

Claims

1 . A process for producing a nonwoven fabric, the process comprising the following steps:

a) providing a surface-treated calcium carbonate-containing filler material, the surface- treated calcium carbonate-containing filler material comprising a calcium carbonate- containing filler material having prior to the surface treatment

i) a weight median particle size (cf5o) value in the range from 0.1 pm to 7 pm, ii) a top cut (c/98) value of 15 pm or less,

iii) a specific surface area (BET) from 0.5 to 120 m2/g, as measured by the BET method, and

iv) a residual total moisture content from 0.01 wt.-% to 1 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material,

and a surface-treatment layer on at least a part of the surface of said calcium carbonate-containing filler material, wherein the surface-treatment layer is formed by contacting the calcium carbonate-containing filler material with a surface treatment agent in an amount from 0.1 to 3 wt.-%, based on the total dry weight of the calcium carbonate-containing filler material, and wherein the surface treatment agent comprises at least one carboxylic acid and/or a salt or anhydride thereof, b) providing a first polypropylene polymer being an isotactic polypropylene homopolymer having a melt flow rate MFR (230°C / 2.16 kg) in the range of 15 to 40 g/10 min, as measured according to EN ISO 1 133:201 1 ,

c) providing a second polypropylene polymer being an isotactic polypropylene

homopolymer having a melt flow rate MFR (230°C / 2.16 kg) in the range of 15 to 40 g/10 min, as measured according to EN ISO 1 133:201 1 ,

d) forming a masterbatch by compounding the surface-treated calcium carbonate- containing filler material of step a) in an amount of 60 wt.-% to 75 wt.-%, based on the total weight of the masterbatch, with the first polypropylene polymer of step b), e) mixing the masterbatch of step d) with the second polypropylene polymer of step c) to obtain a mixture having a surface-treated calcium carbonate-containing filler material content in the range of 5 wt.-% to 15 wt.-%, based on the total weight of the mixture, f) forming the mixture of step e) into fibers having an average fiber diameter in the range from 1 1 to 30 pm,

g) forming a fibrous web from the fibers of step f), and

h) forming the non-woven fabric by hydroentanglement of the fibrous web of step g), wherein the water pressure during hydroentanglement step h) does not exceed 170 bar and wherein the final bonding step during hydroentanglement is carried out at a water pressure in the range of 80 to 170 bar.

2. The process of claim 1 , wherein the nonwoven fabric has a water vapor transmission rate of at least 1000 g/(m2 day), measured according to ASTM E398-13, preferably of at least 2000 g/(m2 day), and more preferably of at least 3000 g/(m2 day).

3. The process of claim 1 or 2, wherein the surface-treated calcium carbonate-containing filler material of step a) comprises a calcium carbonate-containing filler material having prior to the surface treatment

i) a weight median particle size (cf5o) value in the range from 0.25 pm to 5 pm, preferably from 0.5 to 4 pm, more preferably from 0.5 to 4 pm, most preferably from 1.0 to 3.5 pm, and/or

ii) a top cut (c/98) value of 15 pm or less, preferably of 12.5 pm or less, more preferably of 10 pm or less, most preferably of 7.5 pm or less, and/or

iii) a specific surface area (BET) from 0.5 to 120 m2/g, preferably from 0.5 to 50 m2/g, more preferably from 0.5 to 35 m2/g, most preferably from 0.5 to 15 m2/g, as measured by the BET method, and/or

iv) a residual total moisture content from 0.01 wt.-% to 0.2 wt.-%, preferably from 0.02 wt.-% to 0.15 wt.-%, based on the total dry weight of the at least one calcium carbonate- containing filler material.

4. The process of any of the preceding claims, wherein the surface-treated calcium carbonate- containing filler material of step a) comprises a surface-treatment layer on at least a part of the surface of said calcium carbonate-containing filler material, wherein the surface-treatment layer is formed by contacting the calcium carbonate-containing filler material with a surface treatment agent in an amount from 0.1 to 2.5 wt.-%, preferably 0.1 to 2.0 wt.-%, more preferably 0.1 to 1.0 wt.-%, and most preferably 0.2 to 0.8 wt.-%, based on the total dry weight of the calcium carbonate-containing filler material.

5. The process of any of claims 1 to 4, wherein the surface treatment agent comprises at least one monocarboxylic acid and/or a salt or anhydride thereof, preferably comprises at least one monocarboxylic acid and/or a salt thereof, and most preferably comprises stearic acid and/or a salt thereof.

6. The process of any of claims 1 to 4, wherein the surface treatment agent comprises at least one dicarboxylic acid and/or a salt or anhydride thereof, preferably comprises at least one mono-substituted succinic anhydride and/or mono-substituted succinic acid and/or a salt thereof, and most preferably comprises at least one mono-substituted succinic anhydride.

7. The process of any of the preceding claims, wherein the first polypropylene polymer of step b) and/or the second polypropylene polymer of step c) is an isotactic polypropylene

homopolymer having a melt flow rate MFR (230°C / 2.16 kg) in the range of 20 to 35 g/10 min, preferably 25 to 35 g/10 min, as measured according to EN ISO 1 133:2011 wherein the first polypropylene polymer of step b) and the second polypropylene polymer of step c) are preferably the same polymer.

8. The process of any of the preceding claims, wherein the masterbatch is formed in step d) by compounding the surface-treated calcium carbonate-containing filler material of step a) in an amount of 65 wt.-% to 74 wt.-%, preferably 68 wt.-% to 72 wt.-%, based on the total weight of the masterbatch, with the first polypropylene polymer of step b).

9. The process of any of the preceding claims, wherein the fibers formed in step f) are staple fibers having

an average fiber diameter in the range from 14 to 30 pm, preferably from 14 to 25 pm, and/or

a titer in the range from 1 to 6 dtex, preferably 1.5 to 4 dtex, as measured by EN ISO 2062:2009 and/or

a staple fiber length in the range from 30 to 90 mm, preferably 40 to 60 mm, wherein the staple fibers are preferably formed from the mixture of step e) by a process comprising the steps of multifilament or monofilament extrusion and cutting, and/or wherein the staple fibers are formed into a fibrous web during step g), preferably by carding.

10. The process of any of claims 1 to 8, wherein the fibers formed in step f) are filaments having an average fiber diameter in the range from 14 to 30 pm, preferably from 14 to 25 pm, and/or

a titer in the range from 1 to 6 dtex, preferably 1.5 to 4 dtex, as measured by EN ISO 2062:2009,

wherein the filaments are preferably formed from the mixture of step e) or e2) by spunbonding and/or meltblowing.

11. The process of any of the preceding claims, wherein in hydroentanglement step h)

the pre-bonding step is performed at a water pressure of 50 to 120 bar, preferably 60 to 110 bar, more preferably 65 to 105 bar, and/or

the water pressure does not exceed 160 bar, preferably 155 bar, and/or

the water pressure of the final bonding step is in the range of 90 to 160 bar, preferably 95 to 155 bar, and/or

at least 95 %, preferably at least 98 %, more preferably at least 99 % of the process water is reused, and/or

the nonwoven fabric is dried after the final bonding step at a temperature below 135 °C, more preferably below 120 °C, even more preferably below 100 °C.

12. A nonwoven fabric formed from fibers,

wherein the fibers have an average fiber diameter in the range from 11 to 30 pm and are composed of a mixture comprising

a first polypropylene polymer, being an isotactic polypropylene homopolymer having a melt flow rate MFR (230°C / 2.16 kg) in the range of 15 to 40 g/10 min, as measured according to EN ISO 1 133:201 1

a second polypropylene polymer being an isotactic polypropylene homopolymer having a melt flow rate MFR (230°C / 2.16 kg) in the range of 15 to 40 g/10 min, as measured according to EN ISO 1 133:201 1 and

a surface-treated calcium carbonate-containing filler material, the surface-treated calcium carbonate-containing filler material comprising a calcium carbonate-containing filler material having prior to the surface treatment

i) a weight median particle size (cf5o) value in the range from 0.1 pm to 7 pm, ii) a top cut (d98) value of 15 pm or less,

iii) a specific surface area (BET) from 0.5 to 120 m2/g, as measured by the BET method, and

iv) a residual total moisture content of from 0.01 wt.-% to 1 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material, and a surface-treatment layer on at least a part of the surface of said calcium carbonate-containing filler material, wherein the surface-treatment layer is formed by contacting the calcium carbonate-containing filler material with a surface treatment agent in an amount from 0.1 to 3 wt.-%, based on the total dry weight of the calcium carbonate- containing filler material, and wherein the surface treatment agent comprises at least one carboxylic acid and/or a salt or anhydride thereof;

wherein the surface-treated calcium carbonate-containing material is contained in the mixture in an amount from 5 wt.-% to 15 wt.-%, based on the total weight of the mixture, and wherein the nonwoven fabric has a water vapor transmission rate of at least 1000 g/(m2 day), measured according to ASTM E398-13.

13. The nonwoven fabric of claim 12, wherein the nonwoven fabric has a water vapor transmission rate of at least 2000 g/(m2 day), and preferably of at least 3000 g/(m2 day), measured according to ASTM E398-13.

14. Use of a surface-treated calcium carbonate-containing filler material for the manufacture of a nonwoven fabric having a water vapor transmission rate of at least 1000 g/(m2 day), measured according to ASTM E398-13, preferably of at least 2000 g/(m2 day), and more preferably of at least 3000 g/(m2 day), wherein the surface-treated calcium carbonate-containing filler material comprises a calcium carbonate-containing filler material having prior to the surface treatment i) a weight median particle size (cf5o) value in the range from 0.1 pm to 7 pm, ii) a top cut (d98) value of 15 pm or less,

iii) a specific surface area (BET) from 0.5 to 120 m2/g, as measured by the BET method, and

iv) a residual total moisture content of from 0.01 wt.-% to 1 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material,

and a surface-treatment layer on at least a part of the surface of said calcium carbonate-containing filler material, wherein the surface-treatment layer is formed by contacting the calcium carbonate-containing filler material with a surface treatment agent in an amount from 0.1 to 3 wt.-%, based on the total dry weight of the calcium carbonate-containing filler material, and wherein the surface treatment agent comprises at least one carboxylic acid and/or a salt or anhydride thereof.

15. An article comprising the nonwoven fabric of claims 12 or 13 and/or the nonwoven fabric as obtained in the process according to any of claims 1 to 11.