Melt blown fiber

1. Melt-blown fiber having an average diameter of not more than 5.0 μm, said fiber comprises at least 85 wt.-% of a propylene copolymer, wherein said propylene copolymer is the only polymer in the melt-blown fiber,

and wherein further

(a) said melt blown fiber and/or said propylene copolymer has/have a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of at least 200 g/10 min,

(b) said propylene copolymer has a comonomer content of 0.5 to 5.5 wt.-%, the comonmers are ethylene and/or at least one C 4 to C 20 α-olefin selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene,

(c) the propylene copolymer has <2,1> regiodefects of not more than 0.1 mol.-% determined by 13 C-spectroscopy, and

(d) said melt blown fiber and/or said propylene copolymer fulfill(s) the equation (1)

Tm

⁡

[

°

⁢

⁢

C

.

]

[

°

⁢

⁢

C

.

]

≥

160

-

C

⁢

⁢

2

⁡

[

wt

⁢

⁢

%

]

×

5.25

[

wt

⁢

⁢

%

]

(

1

)

wherein

Tm [° C.] is the melting temperature [given in ° C.] of said melt blown fiber and/or of said propylene copolymer measured according to ISO 11357-3,

C2 [wt %] is the amount [given in weight percentage] of comonomers within said melt blown fiber and/or within said propylene copolymer determined with Fourier transform infrared spectroscopy (FTIR).

2. Melt blown fiber according to claim 1 , wherein said propylene copolymer and/or said melt blown fiber has a melting temperature of at least 140° C.

3. Melt blown fiber according to claim 1 , wherein the fiber comprises at least 90 wt.-% of the propylene copolymer.

4. Melt blown fiber according to claim 1 , wherein the pentad isotacticity of the propylene copolymer is higher than 95 mol.-% determined with 13 C NMR spectroscopy.

5. Melt blown fiber according to claim 1 , wherein the propylene copolymer has a molecular weight distribution (M w /M n ) of 2.0 to 6.0.

6. Melt blown fiber according to claim 1 , wherein the propylene copolymer has been visbroken with a visbreaking ratio [final MFR 2 (230° C.)/initial MFR 2 (230° C.)] of 5.0 to 100.0, wherein

“initial MFR 2 (230° C.)” is the MFR 2 (230° C.) of the propylene copolymer before visbreaking and

“final MFR 2 (230° C.)” is the MFR 2 (230° C.) of the propylene copolymer (R-PP) after visbreaking.

7. Melt blown fiber according to claim 1 , wherein the melt blown fiber and/or the propylene copolymer fulfill(s) the equation (2)

TM

⁡

[

MPa

]

[

MPa

]

≥

1200

-

C

⁢

⁢

2

⁡

[

wt

⁢

⁢

%

]

×

145

[

wt

⁢

⁢

%

]

(

2

)

wherein

TM [MPa] is the tensile modulus [given in MPa] of said melt blown fiber and/or of said propylene copolymer measured according to ISO 527-3 using injection molded specimen as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness),

C2 [wt %] is the amount [given in weight percentage] of comonomers, within said melt blown fiber and/or within said propylene copolymer determined with Fourier transform infrared spectroscopy (FTIR).

8. Melt blown fiber according to claim 1 , wherein the melt blown fiber and/or the propylene copolymer has/have a tensile modulus measured according to ISO 527-3 using injection molded specimen as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness) of at least 850 MPa.

9. Melt blown fiber according to claim 1 , wherein the melt blown fiber has been cooled by water quenching.

10. Melt blown fiber according to claim 1 , wherein said melt blown fiber is formed into a melt blown web comprising said melt blown fibers.

11. Melt blown fiber according to claim 10 , wherein said melt blown web has a tensile strength

(a) of at least 35 N measured 1 h after production of the melt blown web according to ISO 527-1 on rectangular specimens cut from the web having 50 mm width and 140 mm length at a temperature of +23±2° C. and a testing speed of 100 mm/min and/or

(b) of at least 36 N measured 168 h after production of the melt blown web according to ISO 527-1 on rectangular specimens cut from the web having 50 mm width and 140 mm length at a temperature of +23±2° C. and a testing speed of 100 mm/min.

12. Melt blown fiber according to claim 10 , wherein said propylene copolymer is melt blown by using a melt blown plant having a die with holes of 0.3 to 0.5 mm diameter and 10 to 16 holes per cm for the preparation of said melt blown web.

13. Melt blown fiber according to claim 1 , wherein said melt blown fiber is formed into an article comprising said melt blown fiber, said article is selected from the group consisting of filtration medium, diaper, sanitary napkin, panty liner, incontinence product for adults, protective clothing, surgical drape, surgical gown, and surgical wear.

14. Melt blown fiber according to claim 1 , wherein said melt blown fiber is formed into an article comprising a melt blown web comprising said melt blown fiber, said article is selected from the group consisting of filtration medium, diaper, sanitary napkin, panty liner, incontinence product for adults, protective clothing, surgical drape, surgical gown, and surgical wear.

15. Melt blown fiber according to claim 13 , wherein said article further comprises a spunbonded fabric.

16. Melt blown fiber according to claim 14 , wherein said article further comprises a spunbonded fabric.

17. An article comprising,

a spundbonded fabric, and

a melt-blown fiber having an average diameter of not more than 5.0 μm, said fiber comprises at least 85 wt.-% of a propylene copolymer, wherein said propylene copolymer is the only polymer in the melt-blown fiber,

and wherein further

(a) said melt blown fiber and/or said propylene copolymer has/have a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of at least 200 g/10 min,

(b) said propylene copolymer has a comonomer content of 0.5 to 5.5 wt.-%, the comonmers are ethylene and/or at least one C 4 to C 20 α-olefin selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene,

(c) the propylene copolymer has <2,1> regiodefects of not more than 0.1 mol.-% determined by 13 C-spectroscopy, and

(d) said melt blown fiber and/or said propylene copolymer fulfill(s) the equation (1)

Tm

⁡

[

°

⁢

⁢

C

.

]

[

°

⁢

⁢

C

.

]

≥

160

-

C

⁢

⁢

2

⁡

[

wt

⁢

⁢

%

]

×

5.25

[

wt

⁢

⁢

%

]

(

1

)

wherein

Tm [° C.] is the melting temperature [given in ° C.] of said melt blown fiber and/or of said propylene copolymer measured according to ISO 11357-3,

C2 [wt %] is the amount [given in weight percentage] of comonomers within said melt blown fiber and/or within said propylene copolymer determined with Fourier transform infrared spectroscopy (FTIR).

18. Process for the preparation of melt blown fibers, comprising:

providing a propylene copolymer, wherein

(a) said propylene copolymer has a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 of at least 200 g/10 min,

(b) said propylene copolymer has a comonomer content of 0.5 to 5.5 wt.-%, the comonmers are ethylene and/or at least one C 4 to C 20 α-olefin selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene,

(c) the propylene copolymer has <2,1> regiodefects of not more than 0.1 mol.-% determined by 13 C-spectroscopy, and

(d) said propylene copolymer fulfill(s) the equation (1)

Tm

⁡

[

°

⁢

⁢

C

.

]

[

°

⁢

⁢

C

.

]

≥

160

-

C

⁢

⁢

2

⁡

[

wt

⁢

⁢

%

]

×

5.25

[

wt

⁢

⁢

%

]

(

1

)

wherein

Tm [° C.] is the melting temperature [given in ° C.] of said propylene copolymer measured according to ISO 11357-3,

C2 [wt %] is the amount [given in weight percentage] of comonomers within said melt propylene copolymer determined with Fourier transform infrared spectroscopy (FTIR),

melt blowing said propylene copolymer by using a melt blown plant having a die with holes of 0.3 to 0.5 mm diameter and 10 to 16 holes per cm to obtain melt-blown fibers having an average diameter of not more than 5.0 μm, said fiber comprising at least 85 wt.-% of said propylene copolymer, wherein said propylene copolymer is the only polymer in the melt-blown fiber.