ARAMID-BASED PAPER WITH IMPROVED PROPERTIES

Abstract

An aramid-based paper comprising at least 90 wt. % of aramid material, the aramid material including at least one of aramid shortcut and aramid fibrid, the paper including at most 40 wt. % aramid pulp, calculated on the total amount of aramid material, wherein the paper includes 0.1-10 wt. % of polyamido-amine epichlorohydrin (PAE). It has been found that the incorporation of 0.1-10 wt. % of polyamido-amine epichlorohydrin (PAE) into an aramid-based paper including at least 90 wt. % of aramid material calculated on the weight of the paper not including the PAE, the aramid material including at least one of aramid shortcut and aramid fibrid, the paper including at most 40 wt. % aramid pulp, leads to a surprising improvement of the z-strength and the tear strength of the paper.

Claims

1. Aramid-based paper comprising at least 90 wt. % of aramid material, calculated on dry paper components not including the PAE, the aramid material comprising at least one of aramid shortcut and aramid fibrid, the paper comprising at most 40 wt. % aramid pulp, calculated on the total amount of aramid material, wherein the paper comprises 0.1-10 wt. % of polyamido-amine epichlorohydrin (PAE).

2. Paper according to claim 1, which comprises at least 95 wt. % of aramid material.

3. Paper according to claim 1, wherein the amount of PAE is at least 0.5 wt. %, in some embodiments at least 1 wt. % and/or at most 8 wt. %, in some embodiments at most 4.5 wt. %, at most 4.0 wt. %, at most 3 wt. %, or at most 2 wt. %.

4. Paper according to claim 1, wherein paper comprises at least 5 wt. % of aramid shortcut, shortcut calculated on the dry weight of the paper not including the PAE.

5. Paper according to claim 1, comprising at most 35 wt. % of aramid pulp.

6. Paper according to claim 1, which has a grammage of 5 to 1000 g/m2.

7. Paper according to claim 6, which has a grammage of 5-100 g/m2.

8. Paper according to claim 6, which has a grammage in the range of 10-120 g/m2.

9. Paper according to claim 1, comprising 10-60 wt. % of aramid fibrid, in combination with 40-90 wt. % of aramid shortcut, and less than 30 wt. % aramid pulp.

10. Paper according to claim 1, comprising 30-70 wt. % of aramid fibrid, in combination with 20-60 wt. % of aramid shortcut, and optionally up to 40 wt. % aramid pulp.

11. Paper according to claim 1, comprising 10-60 wt. % of aramid fibril, in combination with 10-50 wt. % of aramid shortcut, and optionally up to 40 wt. % aramid pulp.

12. Paper according to claim 1, comprising 10-60 wt. % of aramid fibrid, in combination with 30-90 wt. % of meta-aramid shortcut, and less than 30 wt. % aramid pulp.

13. Use of the paper according to claim 1 in electrical insulation, in separators for batteries or supercapacitors, in three-dimensional products, e.g., sandwich cores, such as honeycombs, folded cores, and corrugated cores, in filtration, or in electronics applications such as printed wiring boards and backings for solar cells.

14. Honeycomb core comprising a plurality of interconnected walls having surfaces that define a plurality of honeycomb cells, wherein the cell walls are formed from paper according to claim 1.

15. Use of 0.1-10 wt. % of polyamido-amine epichlorohydrin (PAE) to improve the z-strength of an aramid-based paper comprising at least 90 wt. % of aramid material, calculated on dry paper components not including the PAE, the aramid material comprising at least one of aramid shortcut and aramid fibrid, the paper comprising at most 40 wt. % aramid pulp, calculated on the total amount of aramid material.

16. Paper according to claim 4, wherein the aramid shortcut is para-aramid shortcut, with at least 10 wt. %,shortcut calculated on the dry weight of the paper not including the PAE.

17. Paper according to claim 9, wherein the aramid fibrid is 20-40 wt. % of para-aramid fibrid, in combination with 60-80 wt. % of para-aramid shortcut.

18. Paper according to claim 10, wherein the aramid fibrid is para-aramid fibrid, in combination with 20-40 wt. % of para-aramid shortcut.

19. Paper according to claim 11, wherein the aramid fibril is 20-50 wt. % of para-aramid fibril, in combination with 10-50 wt. % of para-aramid shortcut.

20. Paper according to claim 12, wherein the aramid fibrid is 20-40 wt. % of para-aramid fibrid, in combination with 60-80 wt. % of meta-aramid shortcut.

Description

[0052] The invention is illustrated by the following examples, without being limited thereto or thereby.

EXAMPLE 1

Improvement of Z-Strength and Tear Strength of Para-Aramid Handsheets

[0053] To show the effect of the present invention, comparative papers were manufactured on a Rapid Koethe (RK) handsheet former according to the method of ISO 5269-2. A paper according to the invention was prepared by adding PAE resin (Kymene 625, ex-Solenis) to the suspension before providing it to the handsheet former. The PAE resin was added in an amount of 4.1 wt. %, calculated on the dry weight of the paper.

[0054] A comparative paper was prepared by a process wherein no PAE was added. Drying was done using the RK-dryer under vacuum at 95° C.

[0055] The papers contained 70 wt. % of para-aramid shortcut with a linear density of 1.1 dtex and length of 6 mm (Twaron® T2000, 6 mm, ex Teijin Aramid, NL) and 30 wt. % never-dried para-aramid fibrids (Twaron® D8016, ex Teijin Aramid, NL). The papers had a grammage of 30 g/m2.

[0056] Z-strength was measured in accordance with Tappi T541. Tear strength was measured by Elmendorf Tear measurement method in accordance with Tappi 414. Grammage was determined in accordance with ASTM D646.

[0057] The results are presented in table 1 below.

TABLE-US-00001 TABLE 1 Z-strength Tear (Fmax) resistance Tear index (kPa) (mN) (mNm2/g) Paper according to the invention 165 723 24 (4.1 wt. % PAE added) Comparative paper 77 423 14 (no PAE)

[0058] As can be seen from the results in Table 1, the addition of 4.1 wt. % PAE resulted in a substantially improved Z-strength, tear resistance, and tear index.

EXAMPLE 2

The Effect of the Amount of PAE

[0059] To show the influence of the amount of PAE, papers with different amounts of PAE were manufactured as follows:

[0060] Never-dried para-aramid fibrids (Twaron® D8016, ex Teijin Aramid, NL) were dispersed in a pulper at a 1.5% consistency for 15 minutes. PAE-resin (Kymene GHP20, ex-Solenis), was dosed to the fibrid dispersion in the amounts mentioned in Table 2, and the system was mixed with a regular agitator for 5 minutes. The fibrid dispersion containing the PAE-resin was added into a tank and further diluted. After a few minutes of continued agitation, para-aramid shortcut with a linear density of 1.7 dtex and a length of 6 mm (Twaron® T1000, 6 mm, ex Teijin Aramid, NL) was added resulting in a final consistency of 0.1%. The solid materials were 30 wt. % p-aramid fibrids and 70 wt. % p-aramid short-cut.

[0061] The resulting dispersion was fed to an inclined wire machine to make paper with a grammage of 30 g/m2.

[0062] Table 2 below provides the amount of PAE dosed to the papers (dry solids based) and the z-strength and tear index.

TABLE-US-00002 TABLE 2 Z-strength Added PAE (Fmax) Tear index (wt. %)* (kPa) (mNm2/g) Comparative 0 85 14 Invention 1 1.5 196 20 Invention 2 2.5 261 25 Invention 3 4.0 250 24 *added amount of PAE, based on dry weight paper

[0063] As can be seen from Table 2,increasing amounts of PAE result in increased z-strength and teat index.

EXAMPLE 3

Improvement of Z-Strength and Tear Strength of Handsheets Comprising Meta-Aramid and Para-Aramid

[0064] To show the effect of the present invention in blended para- and meta-aramid papers, comparative papers were manufactured on a Rapid Koethe (RK) handsheet former according to the method of ISO 5269-2.

[0065] The papers contained 70 wt. % of meta-aramid shortcut with a linear density of 1.7 dtex and length of 6 mm (TeijinConex®, 6 mm, ex Teijin Aramid, TL) and 30 wt. % never-dried para-aramid fibrids (Twaron® D8016, ex Teijin Aramid, NL). The papers had a grammage of 40 g/m2.

[0066] A paper according to the invention was prepared by adding PAE resin (Kymene GHP20, ex-Solenis) to the suspension before providing it to the handsheet former. The PAE resin was added in an amount of 2 wt. %, calculated on the dry weight of the paper. A comparative paper was prepared by a process wherein no PAE was added. Drying was done using the RK-dryer under vacuum at 95° C.

[0067] Z-strength was measured in accordance with Tappi T541. Tear strength was measured by Elmendorf Tear measurement method in accordance with Tappi 414. Grammage was determined in accordance with ASTM D646.

[0068] The results are presented in table 3 below.

TABLE-US-00003 TABLE 3 Z-strength Tear (Fmax) resistance Tear index (kPa) (mN) (mNm2/g) Paper according to the invention 127 1099 27 (2 wt. % PAE added) Comparative paper 87 680 16 (no PAE)

[0069] As can be seen from the results in Table 3, the addition of 2 wt. % PAE resulted in a substantially improved Z-strength, tear resistance, and tear index.