Paper comprising microfilaments

Abstract

Paper with a grammage of 10-100 g/m.sup.2 including at least 20 wt. % of microfilaments and at least 20 wt. % of a non-resinous binder, the microfilaments having an average filament length in the range of 2-25 mm and titer less than 1.3 dtex, the non-resinous binder comprising at least one of fibrid or pulp. The paper shows high strength and other attractive properties.

Claims

1. Paper with a grammage of 10-100 g/m.sup.2 comprising at least 20 wt. % of microfilaments and at least 20 wt. % of a non-resinous binder, wherein the microfilaments have an average filament length in the range of 2-25 mm and titer less than 1.3 dtex, wherein the non-resinous binder comprises at least fibrids, wherein the fibrids comprise 10 to 50 wt. % of the paper, and wherein the fibrids are para-aramid fibrids.

2. The paper according to claim 1, wherein the fibrids comprise 20 to 50 wt. % of the paper.

3. The paper according to claim 1, wherein the non-resinous binder further comprises pulp, the pulp comprising at least 20 wt. % of the paper.

4. The paper according to claim 3, wherein the pulp is cellulose pulp.

5. The paper according to claim 1, wherein the microfilaments are aramid microfilaments.

6. The paper according to claim 5, wherein the aramid microfilaments are para-aramid microfilaments.

7. The paper according to claim 1, wherein the length of the microfilaments is at least 3 mm.

8. The paper according to claim 1, wherein the length of the microfilaments is at least 4 mm.

9. The paper according to claim 1, wherein the length of the microfilaments is at most 15 mm.

10. The paper according to claim 1, wherein the length of the microfilaments is at most 8 mm.

11. The paper according to claim 1, wherein the microfilament titer is less than 1.2 dtex.

12. The paper according to claim 11, wherein the microfilament titer is at least 0.3 dtex.

13. The paper according to claim 1, wherein the microfilaments have an average diameter of 1 to 499 nm.

14. The paper according to claim 1, wherein the microfilaments have an average diameter of 50 to 300 nm.

15. The paper according to claim 1, wherein the paper has a grammage of less than 60 g/m.sup.2.

16. The paper according to claim 1, wherein the filaments have an aspect ratio of a least 4 mm/dtex.

17. A fuel cell, a battery, a capacitor, a printed wiring board, a honeycomb, a packaging, a separator for electrical isolation, or a filter comprising the paper according to claim 1.

18. A honeycomb comprising the paper according to claim 1.

Description

EXAMPLE 1: INVESTIGATION OF TENSILE STRENGTH

(1) All papers were made by the process described in ISO 5269-1 for the British sheet mould, ISO 5269-2 for the Rapid Koethe sheet former. The tensile index was measured for all paper according to ISO 1924-2.

(2) The first paper was made by the process outlined above and comprised 30% of microfilaments. The microfilaments were made of para-aramid (Type 2000 produced by Teijin Aramid), had an average length of 6 mm and a titer of 0.9 dtex. In addition, the paper comprised 70% of fibrids (Type 8016 produced by Teijin Aramid) made of para-aramid. The paper was made on the British sheet mould (ISO 5269-1) and the grammage was 40 g/m.sup.2. After the paper making process the wet paper was placed between two blotting papers and calandered between two steel rolls (both 150° C.) to a density of approximately 0.9 g/cm.sup.3.

(3) The second paper distinguished from the first paper only in the content of microfilaments and fibrids. The second paper contained 50% of microfilaments and 50% of fibrids. All other features of the first paper were retained in the second paper.

(4) The third paper distinguished from the first paper in the content of microfilaments and fibrids. The third paper comprised 70% of microfilament and 30% of fibrids. All other features of the first paper were retained in the third paper.

(5) The fourth paper was made by the above-mentioned process and comprised 30% of fibers with an average length of 6 mm and a count of 1.7 dtex. Therefore, these kinds of fibers were no microfilaments in the term of this invention. The fibers were made of para-aramid (Type 1000, produced by Teijin Aramid). The paper comprised also 70% of fibrids (Type 8016) made of para-aramid. The paper was made on the British sheet mould and the grammage was 40 g/m.sup.2. After the paper making process the wet paper was placed between two blotting papers and calandered between two steel rolls (both 150° C.) to a density of approximately 0.9 g/cm.sup.3.

(6) The fifth paper distinguished from the fourth paper only in the content of fibers and fibrids. The fifth paper was made of 50% of fibers and 50% of fibrids. All other features of the fourth paper were retained in the fifth paper.

(7) The sixth paper distinguished from the fourth paper in the content of fibers and fibrids. The sixth paper comprised 70% of fibers and 30% of fibrids. All other features of the fourth paper were retained in the sixth paper.

(8) The fourth, fifth and sixth paper are comparative examples for this invention, whereas the first, second and third paper build up the Examples according the present invention.

(9) TABLE-US-00001 TABLE 1 Paper Tensile Index (Nm/g) 1 92 4 (comparative) 85 2 118 5 (comparative) 101 3 125 6 (comparative) 113

(10) As can be seen from Table 1 the tensile Index of the first paper (92 Nm/g) is higher than the tensile index of the fourth paper (85 Nm/g), which distinguishes from the first paper only in the use of microfilaments instead of fibers. Also the tensile Index of the second paper (118 Nm/g) is higher than the tensile Index of the fifth paper (101 Nm/g) and the tensile Index of the third paper (125 Nm/g) is higher than the tensile Index of the sixth paper (113 Nm/g). The second paper exhibits the same material content as the fifth paper with the exception that in the second paper microfilaments are used instead of fibers (fifth paper). Also the third paper and the sixth paper exhibit the same mixing ratio with the exception, that in the third paper microfilaments are used instead of fibers (like in the sixth paper). Therefore Table 1 shows that the use of microfilaments in a paper increases the tensile strength of a paper. Table 1 shows additionally that the tensile strength increases in respect of the content of microfilaments in the paper—the higher the content of microfilaments, the higher the tensile strength of the paper.

EXAMPLE 2: INVESTIGATION OF TEAR STRENGTH AND ELONGATION AT BREAK

(11) All papers were made on a Rapid Koethe sheet former (ISO 5269-2) and had an areal weight of about 57 g/m.sup.2. The tear strength was measured by ISO 1974. The elongation at break was measured by ISO 1924-2.

(12) The first paper was made of 80% of cellulose pulp (OCC) and 20% of para-aramid microfilaments (type 2000, produced by Teijin Aramid), whereby the microfilaments had an average fiber length of 13 mm and a titer of 0.9 dtex. After the paper making process the paper was not calandered.

(13) The second paper was made of 70% of cellulose pulp (OCC) and 20% of type 1000 para-aramid microfilaments. Also in this paper the microfilaments exhibited an average length of 13 mm and a titer of 0.9 dtex. The second paper exhibited also 10% of para-aramid fibrids (Type 8016 produced by Teijin Aramid). After the paper making process the paper was not calandered.

(14) The third paper distinguished from the first paper by using fibers instead of microfilaments. This means the third paper comprised 80% of cellulose pulp and 20% of para-aramid fibers (Type 1000, produced by Teijin Aramid), whereby the fibers had an average length of 13 mm but a titer of 1.7 dtex (and therefore no microfilaments were present).

(15) The fourth paper distinguished from the second paper also in the use of fibers instead of microfilaments. The fourth paper comprised 70% of cellulose pulp, 20% of para-aramid fibers (Type 1000) and 10% of fibrids (Type 8016). The fibers had an average length of 13 mm and a titer of 1.7 dtex.

(16) The third and the fourth paper are comparative examples for this invention, whereas the first and the second paper build up the Examples according the present invention.

(17) TABLE-US-00002 TABLE 2 Paper Tear Index (mNm.sup.2/g) Elongation at break (%) 1 16.8 0.82 3(comparative) 11.7 0.75 2 34.6 1.33 4 (comparative) 23.6 1.14

(18) Table 2 shows that the use of microfilaments instead of fibers increases the tear index. As can be seen from table 2 also the elongation at break increases by using microfilaments instead of fibers.

(19) In conclusion, the papers comprising microfilaments exhibit therefore a higher tensile strength, a higher tear strength and a higher elongation at break in comparison to papers using fibers instead of microfilaments.

EXAMPLE 3: HONEYCOMBS BASED ON PAPERS ACCORDING TO THE INVENTION

(20) The first paper was made by the process outlined above and comprised 50% of microfilaments (Twaron 2000 produced by Teijin Aramid) with a length of 6 mm and a titer of 0.9 dtex. In addition, the paper comprised 50% of fibrids (Type 8016 produced by Teijin Aramid) made of para-aramid. The paper was made on a paper machine and the grammage was 33.2 g/m.sup.2. The dry paper was calendered between two steel rolls (120° C.) to a density of 0.85 g/cm.sup.3. From this paper, a honeycomb was made with a cell size of 3.4 mm and a density of ca. 53 kg/m.sup.3. This honeycomb was tested in compression according to ASTM-C365 and in shear according to ASTM-C273. The results are given in the table.

(21) The second paper was made according to the first paper, but now the microfilaments were replaced by standard filaments (Twaron 1000 produced by Teijin Aramid) with a length of 6 mm and a titer of 1.7 dtex. The grammage of the paper was 34.0 g/m.sup.2 and the density after steel-steel calendering at 120° C. 0.87 g/cm.sup.3. From this paper, a honeycomb was made with a cell size of 3.4 mm and a density of ca. 53 kg/m.sup.3. The honeycomb was tested on mechanical properties, see table for results.

(22) TABLE-US-00003 TABLE 3 Honeycomb Honeycomb based on Paper based on Paper 2 1 (invention) (comparative) Compression strength (MPa) 2.79 2.78 Shear strength (L-direction) (MPa) 1.85 1.57 Shear strength (W-direction) (MPa) 1.12 0.92 Shear modulus (L-direction) (MPa) 103 98 Shear modulus (W-direction) (MPa) 67 54

(23) From this it is clear that replacing filaments with standard diameter by microfilaments significantly improve the shear properties of the honeycomb.