Process to manufacture a mixture of p-aramid pulp with chopped fibers, mixture and its use

Abstract

A process to manufacture a mixture of p-aramid pulp with chopped fibers, wherein the process includes: providing a first mass that includes p-aramid pulp, providing a second mass that includes chopped fibers, guiding the first mass and the second mass into a mixing device, wherein the first mass and the second mass are mixed to yield a mixed mass, guiding the mixed mass on a dewatering device, whereupon the mixed mass is dewatered to yield a dewatered cake, guiding the dewatered cake, either directly or via a passage, through a cake breaker into a drying atmosphere to yield a dried intermediate, and guiding the dried intermediate, either directly or via a passage, through a homogenizing device into an opening device, wherein the dried intermediate is opened to arrive at an opened mixture of p-aramid pulp and chopped fibers. The mixture and its use are also described.

Claims

1. A process to manufacture a mixture of p-aramid pulp with chopped fibers, wherein the process comprises: a) providing a suspension comprising p-aramid pulp in water, b) providing a suspension comprising chopped fibers in water, wherein the chopped fibers comprise p-aramid or carbon, c) guiding the suspension from a) and the suspension from b) into a mixing device, wherein the suspensions are mixed to yield a mixed mass having a solid content of p-aramid pulp and chopped fibers in the range of from 50 wt. % to 95 wt. % of p-aramid pulp and from 5 wt. % to 50 wt. % of chopped fibers, d) guiding the mixed mass on a dewatering device, whereupon the mixed mass is dewatered to yield a dewatered cake, e) guiding the dewatered cake either i) directly, or ii) via a passage through a cake breaker into a drying atmosphere to yield a dried intermediate, and f) guiding the dried intermediate either i) directly, or ii) via a passage through a homogenizing device into an opening device, wherein the dried intermediate is opened to arrive at an opened mixture of p-aramid pulp and chopped fibers, wherein the chopped fibers in the suspension provided in b) either have a single length, wherein the single length has a value in the range of from 3 mm to 12 mm, or have a length distribution, the average value of which is in the range of from 3 mm to 12 mm.

2. A process according to claim 1, wherein the p-aramid pulp in the suspension provided in a) is obtained by at least one refining step.

3. The process according to claim 1, wherein the p-aramid pulp in the suspension provided in a) has a specific surface area in the range of from about 5 m.sup.2/g to 15 m.sup.2/g.

4. The process according to claim 1, wherein in d), the mixed mass is guided via a passage through a refiner on the dewatering device.

5. The process according to claim 1, wherein the chopped fibers in the suspension provided in b) either have a single length, wherein the single length has a value in the range of from 5 mm to 12 mm, or have a length distribution, the average value of which is in the range of from 5 mm to 12 mm.

6. The process according to claim 5, wherein the chopped fibers in the suspension provided in b) exhibit a circular cross-section having a diameter in the range of from 4 m to 50 m.

7. The process according to claim 1, wherein the suspension provided in a), and/or the suspension provided in b), and/or the mixed mass yielded from c) comprises a filler.

8. The process according to claim 1, wherein the dried intermediate resulting from e) exhibits a water content in the range of from 0 wt. % to 20 wt. %.

9. The process according to claim 1, wherein the opening device used in f) is an impact mill, a mill using turbulent air, or a high shear/high agitating mixer.

10. The process according to claim 1, wherein a) to f) are conducted in a single continuous process.

11. A process to manufacture a mixture of p-aramid pulp with p-aramid chopped fibers, wherein the process comprises: a) providing a suspension comprising p-aramid pulp in water, b) providing a suspension comprising p-aramid chopped fibers in water, c) guiding the suspension from a) and the suspension from b) into a mixing device, wherein the suspensions are mixed to yield a mixed mass having a solid content of p-aramid pulp and p-aramid chopped fibers in the range of from 50 wt. % to 95 wt. % of p-aramid pulp and of from 5 wt. % to 50 wt. % of p-aramid chopped fibers, and d) guiding the mixed mass through a refiner and thereafter on a dewatering device, whereupon the mixed mass is dewatered to yield a dewatered cake, wherein the chopped fibers in the suspension provided in b) either have a single length, wherein the single length has a value in the range of from 3 mm to 12 mm, or have a length distribution, the average value of which is in the range of from 3 mm to 12 mm.

12. The process according to claim 11, further comprising e) the dewatered cake resulting from d) is guided either i) directly, or ii) via a passage through a cake breaker into a drying atmosphere to yield a dried intermediate, and f) the dried intermediate is guided either i) directly, or ii) via a passage through a homogenizing device into an opening device, wherein the dried intermediate is opened to arrive at an opened mixture of p-aramid pulp with p-aramid chopped fibers.

Description

EXAMPLE 1: MANUFACTURE OF MIXTURES CONSISTING OF 50/50 [WT.-%/WT.-%] OF P-ARAMID PULP AND P-ARAMID CHOPPED FIBERS WITH DIFFERENT DIAMETERS

EXAMPLE 1A

(1) 1.4 kg of p-aramid pulp (Twaron type 1099 from Teijin Aramid BV, NL) are added to 125 liter water and stirred for two minutes. Then 1.4 kg of p-aramid chopped fibers of 6 mm in length and with a diameter d.sub.chopped fibers of 12 m (Twaron type 1080 from Teijin Aramid BV, NL) are added and the (pulp+chopped fibers+water)mixture is stirred for two minutes. The resulting suspension is then dewatered on a sieve table to yield a dewatered cake. The dewatered cake is dried in an oven overnight at 105 C. to yield a dried cake. 800 g of the dried cake is then opened in a Lodige high-shear mixer for 4 minutes resulting in a mixture A, the properties of which are shown in table 1.

EXAMPLE 1B

(2) This example is performed as example 1a) with the only difference that the p-aramid chopped fibers exhibit a diameter d.sub.chopped fibers 9 m (Twaron type D 2075 from Teijin Aramid BV, NL). The properties of the resulting mixture B are shown in table 1.

COMPARATIVE EXAMPLE 1C

(3) This example is performed as example 1a) with the difference that 2.8 kg of p-aramid pulp (Twaron type 1099 from Teijin Aramid BV, NL) without any chopped fibers were suspended in water, dewatered, dried and opened as described in example 1a). The properties of the resulting pulp P1 are shown in table 1.

(4) TABLE-US-00001 TABLE 1 Kaolin Green filler strength Bulk Jolting Descrip- LL.sub.0.25 Retention [mJ/ volume volume Example tion [mm] [%] mm.sup.2] [ml/g] [ml/g] 1c) 100% n.m. 85 1.4 4.4 2.5 pulp P1 1a) mixture A 2.6 76 2.2 5.3 2.6 d.sub.cf = 12 m 1b) mixture B 2.5 75 2.7 n.m. n.m. d.sub.cf = 9 m

(5) Table 1 shows that both mixture A and mixture B exhibit a green strength which is considerably higher than the green strength of 100% pulp, and a filler retention which is considerably higher than the filler retention of chopped p-aramid fibers and which is only slightly lower than the filler retention of p-aramid pulp P1.

EXAMPLE 2: MANUFACTURE OF MIXTURES CONSISTING OF 50/50 [WT.-%/WT.-%] OF P-ARAMID PULP AND SLIGHTLY FIBRILLATED P-ARAMID CHOPPED FIBERS WITH DIFFERENT DEGREES OF FIBRILLATION

EXAMPLE 2A

(6) 1.4 kg of p-aramid pulp (Twaron type 1099 from Teijin Aramid BV, NL) are added to 125 liter water and stirred for two minutes. Then 1.4 kg of p-aramid chopped fibers of 6 mm in length and 12 m in diameter (Twaron type 1080 from Teijin Aramid BV, NL) are added. The resulting suspension is passed through a Sprout-Bauer 12 lab refiner, wherein a refining energy of 40 kW is applied yielding a refined suspension. The refined suspension is mixed for two minutes and is then dewatered on a sieve table to yield a dewatered cake. The dewatered cake is dried in an oven overnight at 105 C. to yield a dried cake. 800 g of the dried cake is then opened in a Ldige high-shear mixer for 4 minutes resulting in a mixture C, the properties of which are shown in table 2.

EXAMPLE 2B

(7) This example is performed as example 2a) with the only difference that in the refiner a refining energy of 20 kW is applied. The properties of the resulting mixture D are shown in table 2.

(8) TABLE-US-00002 TABLE 2 Kaolin Green filler strength Bulk Jolting Descrip- LL.sub.0.25 Retention [mJ/ volume volume Example tion [mm] [%] mm.sup.2] [ml/g] [ml/g] 2a) mixture C 1.5 78 1.9 4.3 2.5 refining energy 40 kW 2b) mixture D 2.1 71 2.2 5.0 2.5 refining energy 20 kW

(9) Table 2 shows that both mixture C and mixture D exhibit a green strength which is considerably higher than the green strength of 100% pulp (see P1 in example 1c)), and a filler retention which is considerably higher than the filler retention of chopped p-aramid fibers and which is only slightly lower than the filler retention of p-aramid pulp.

EXAMPLE 3: MANUFACTURE OF A MIXTURE CONSISTING OF 72/28 [WT.-%/WT.-%] OF P-ARAMID PULP AND P-ARAMID CHOPPED FIBERS WITH LOW DIAMETER

(10) 2.02 kg of p-aramid pulp (Twaron type 1099 from Teijin Aramid BV, NL) are added to 125 liter water and stirred for two minutes. Then 0.78 kg of p-aramid chopped fibers of 6 mm in length and 9 m in diameter (Twaron type D2075 from Teijin Aramid BV, NL) are added and the (pulp+chopped fibers+water)mixture is stirred for two minutes. The resulting suspension is then dewatered on a sieve table to yield a dewatered cake. The dewatered cake is dried in an oven overnight at 105 C. to yield a dried cake. 800 g of the dried cake is then opened in a Ldige high-shear mixer for 4 minutes resulting in a mixture E, the properties of which are shown in table 3.

(11) TABLE-US-00003 TABLE 3 Kaolin Green filler strength Bulk Jolting Descrip- LL.sub.0.25 Retention [mJ/ volume volume Example tion [mm] [%] mm.sup.2] [ml/g] [ml/g] 3 mixture E 1.8 83 2.3 n.m. n.m. d.sub.cf = 9 m

(12) Table 3 shows that mixture E exhibits a green strength which is considerably higher than the green strength of 100% pulp (see P1 in example 1c)), and a filler retention which almost equals the filler retention of p-aramid pulp.

EXAMPLE 4: MANUFACTURE OF MIXTURES CONSISTING OF 50/50 [WT.-%/WT.-%] OF P-ARAMID PULP AND (SLIGHTLY FIBRILLATED) P-ARAMID CHOPPED FIBERS WITH DIAMETER=12 M

EXAMPLE 4A

(13) 2.25 kg of p-aramid pulp (Twaron type 3091 from Teijin Aramid BV, NL) are added to 200 liter water and stirred for two minutes. Then 2.25 kg of p-aramid chopped fibers of 6 mm in length and 12 m in diameter (Twaron type 1080 from Teijin Aramid BV, NL) are added and the (pulp+chopped fibers+water)mixture is stirred for two minutes. The resulting suspension is then dewatered on a sieve table to yield a dewatered cake. The dewatered cake is dried in an oven overnight at 105 C. to yield a dried cake. 800 g of the dried cake is then opened in a Lodige high-shear mixer for 4 minutes resulting in a mixture F, the properties of which are shown in table 4.

EXAMPLE 4B

(14) 2.25 kg of p-aramid pulp (Twaron type 3091 from Teijin Aramid BV, NL) are added to 200 liter water and stirred for two minutes. Then 2.25 kg of p-aramid chopped fibers of 6 mm in length and 12 m in diameter (Twaron type 1080 from Teijin Aramid BV, NL) are added. The resulting suspension is passed through a Sprout-Bauer 12 refiner, wherein a refining energy of 40 kW is applied yielding a refined suspension. The refined suspension is mixed for two minutes and is then dewatered on a sieve table to yield a dewatered cake. The dewatered cake is dried in an oven overnight at 105 C. to yield a dried cake. 800 g of the dried cake is then opened in a Ldige high-shear mixer for 4 minutes resulting in a mixture G, the properties of which are shown in table 4.

EXAMPLE 4C

(15) Example 4c) is performed as example 4a) with the only difference that a refining energy of 20 kW is applied resulting in a mixture H, the properties of which are shown in table 4.

COMPARATIVE EXAMPLE 4D

(16) Comparative example 4d) is performed as example 4a) with the difference that that 4.5 kg of p-aramid pulp (Twaron type 3091 from Teijin Aramid BV, NL) without any chopped fibers were suspended in water, dewatered, dried and opened as described in example 6a). The properties of the resulting pulp P2 are shown in table 4.

(17) TABLE-US-00004 TABLE 4 Kaolin filler Green Bulk Jolting LL.sub.0.25 SSA Retention strength volume volume Example Description [mm] [m.sup.2/g] [%] [mJ/mm.sup.2] [ml/g] [ml/g] 4d) 100% 0.8 9.4 84 1.3 4.3 2.5 pulp P2 4a) mixture F 2.1 n.m. 71 2.2 5.4 2.6 4b) mixture G 1.3 5.7 73 1.7 4.1 2.4 refining energy 40 kW 4c) mixture H 2.1 5.4 74 2.6 5.3 2.7 refining energy 20 kW

(18) Table 4 shows that mixtures F, G and H exhibit a green strength which is considerably higher than the green strength of 100% p-aramid pulp P2, and a filler retention which is only slightly lower than the filler retention of p-aramid pulp P2.