Method for preparing microporous PVA fiber

Abstract

The present application discloses a method for preparing microporous PVA fiber comprising the following steps: Step 1: preparing spinning solution, calcium hydroxide solution, and sodium sulfate solution; Step 2: cooling the spinning solution to 40-60° C., and adding a foaming agent thereto to provide the PVA spinning stock solution; Step 3: spinning into the sodium sulfate solution so that the fiber containing the reaction product of the foaming agent and the mirabilite is dehydrated to provide a primary PVA fiber; Step 4: reacting the fiber with the calcium hydroxide solution to provide a secondary fiber; Step 5: foaming and pore forming; and Step 6: cleaning and drying to provide the final product of microporous PVA fiber.

Claims

1. A method for preparing microporous PVA fiber comprising the following steps: Step 1: preparing a spinning solution: mixing raw material PVA resin with water and heating to dissolve the raw material PVA resin completely to form the spinning solution; preparing a calcium hydroxide solution: mixing calcium hydroxide powder with water to form the calcium hydroxide solution; and preparing a sodium sulfate solution: forming the sodium sulfate solution with a concentration of 35% from mirabilite and water; Step 2: preparing a PVA spinning stock solution: cooling the spinning solution obtained in Step 1 to 40-60° C., and adding a foaming agent thereto to provide the PVA spinning stock solution; Step 3: spinning and first coagulation bath treatment: spinning the PVA spinning stock solution obtained in Step 2, and subjecting a spun fiber to a first coagulation bath treatment in the sodium sulfate solution for dehydration to provide a primary PVA fiber; Step 4: second coagulation bath treatment: reacting the primary PVA fiber obtained in Step 3 with the calcium hydroxide solution to provide a secondary fiber; Step 5: foaming and pore forming: heating to foam the secondary fiber obtained in Step 4 while stretching to form a primary product of microporous PVA fiber; and Step 6: cleaning and drying the primary products of microporous PVA fiber obtained in Step 5 to provide the final product of microporous PVA fiber; wherein the foaming agent is one selected from the group consisting of ammonium carbonate and ammonium bicarbonate.

2. The method for preparing microporous PVA fiber according to claim 1, wherein the foaming agent in Step 2 is ammonium bicarbonate.

3. The method for preparing microporous PVA fiber according to claim 1, wherein, in Step 2, the weight ratio of the PVA resin to the foaming agent is 1:(0.0003-0.001).

4. The method for preparing microporous PVA fiber according to claim 3, wherein, in Step 2, the weight ratio of the PVA resin to the foaming agent is 1:(0.0006-0.0009).

5. The method for preparing microporous PVA fiber according to claim 1, wherein, in Step 3, the temperature of the first coagulation bath treatment is 35-55° C., and the speed of the first coagulation bath treatment is 7-9 m/s.

6. The method for preparing microporous PVA fiber according to claim 5, wherein, in Step 3, the temperature of the first coagulation bath treatment is 40-50° C., and the speed of the first coagulation bath treatment is 7 m/s.

7. The method for preparing microporous PVA fiber according to claim 1, wherein, in Step 1, the weight ratio of water to calcium hydroxide is 1:(0.006-0.02).

8. The method for preparing microporous PVA fiber according to claim 1, wherein, in Step 4, the weight ratio of water to calcium hydroxide is 1:(0.011-0.014).

9. The method for preparing microporous PVA fiber according to claim 1, wherein, in Step 5, the fiber is heated to 180-250° C. for foaming, and the conveying speed of the secondary fiber is 30-40 m/s.

10. The method for preparing microporous PVA fiber according to claim 1, wherein, in Step 5, the temperature of foaming and pore forming is 220-230° C.

Description

DETAILED DESCRIPTION

(1) The application will be further described in detail below in combination embodiments.

Example 1

(2) A method for preparing microporous PVA fiber, includes the following steps:

(3) Step 1: preparing a spinning solution: adding 180 kg of Model 2499 PVA resin and 820 Kg of water into a dissolving kettle, and heating to 95° C. under a slow stirring at a speed of 40 rpm till the PVA resin was completely dissolved to form the spinning solution;

(4) preparing calcium hydroxide solution: thoroughly mixing calcium hydroxide powder and water by a weight ratio of 0.0125:1 to form the calcium hydroxide solution;

(5) preparing sodium sulfate solution: forming sodium sulfate solution with a concentration of 35% from mirabilite and water:

(6) Step 2: preparing PVA spinning stock solution: cooling the spinning solution obtained in Step 1 to 60° C., adding 126 g of ammonium bicarbonate as foaming agent thereto, pressurizing the kettle to 0.3 MPa under a stirring speed of 40 rpm, and stirring for another 30 min to provide the PVA spinning stock solution;

(7) Step 3: spinning and first coagulation bath treatment: conveying the PVA spinning stock solution obtained in Step 2 to a spinneret plate through a pipeline, and subjecting the spinned fiber to a first coagulation bath treatment in the sodium sulfate solution at the temperature of 40° C. and at a treatment speed of 7 m/s, so as to dehydrate the spinned fiber to form a primary PVA fiber;

(8) Step 4: second coagulation bath treatment: reacting the primary PVA fiber obtained in Step 3 with excessive calcium hydroxide solution to provide a secondary fiber;

(9) Step 5: foaming and pore forming: introducing the secondary fiber obtained in Step 4 into a drying channel kept at a temperature of 230° C. for foaming, while stretching the secondary fiber forward at a speed of 35 m/min;

(10) Step 6: cleaning and drying the primary product of microporous PVA fiber obtained in Step 5 to provide the final product of microporous PVA fiber.

Example 2

(11) A method for preparing microporous PVA fiber includes the following steps:

(12) Step 1: preparing spinning solution: adding 190 kg of Model 1799 PVA resin and 810 Kg of water into a dissolving kettle, and heating to 90° C. under a slow stirring at the speed of 40 rpm until the PVA resin was completely dissolved to form the spinning solution;

(13) preparing calcium hydroxide solution: thoroughly mixing calcium hydroxide powder and water by a weight ratio of 0.0125:1 to form the calcium hydroxide solution;

(14) preparing sodium sulfate solution: forming the sodium sulfate solution having a concentration of 35% from mirabilite and water:

(15) Step 2: preparing PVA spinning stock solution: cooling the spinning solution obtained in Step 1 to 41° C., adding 171 g of ammonium bicarbonate as a foaming agent thereto, pressurizing the kettle to 0.3 MPa under a stirring speed of 40 rpm, and stirring for another 30 min to provide the PVA spinning stock solution;

(16) Step 3: spinning and first coagulation bath treatment: conveying the PVA spinning stock solution obtained in Step 2 to a spinneret plate through a pipeline, and subjecting the spinned fiber to a first coagulation bath treatment in the sodium sulfate solution at the temperature of 35° C. by a treatment speed of 7 m/s, so as to dehydrate the spinned fiber to form a primary PVA fiber;

(17) Step 4: second coagulation bath treatment: reacting the primary PVA fiber obtained in Step 3 with excessive calcium hydroxide solution to provide a secondary fiber;

(18) Step 5: foaming and pore forming: introducing the secondary fiber obtained in Step 4 into a drying channel kept at the temperature of 180° C. for foaming, while stretching the secondary fiber forward at a speed of 35 m/min;

(19) Step 6: cleaning and drying the primary product of microporous PVA fiber obtained in Step 5 to provide the final product of microporous PVA fiber.

Example 3

(20) A method for preparing microporous PVA fiber includes the following steps:

(21) Step 1: preparing a spinning solution: adding 180 kg of Model 2499 PVA resin and 820 Kg of water into a dissolving kettle, and heating to 100° C. under a slow stirring at the speed of 40 rpm until the PVA resin was completely dissolved to form the spinning solution;

(22) preparing calcium hydroxide solution: thoroughly mixing calcium hydroxide powder and water by a weight ratio of 0.0065:1 to form the calcium hydroxide solution;

(23) preparing sodium sulfate solution: forming the sodium sulfate solution having a concentration of 35% from mirabilite and water:

(24) Step 2: preparing PVA spinning stock solution: cooling the spinning solution obtained in Step 1 to 60° C., adding 126 g of ammonium bicarbonate as foaming agent thereto, pressurizing the kettle to 0.3 MPa under a stirring speed of 40 rpm, and stirring for another 30 min to provide the PVA spinning stock solution;

(25) Step 3: spinning and first coagulation bath treatment: conveying the PVA spinning stock solution obtained in Step 2 to a spinneret plate through a pipeline, and subjecting the spinned fiber to a first coagulation bath treatment in the sodium sulfate solution at the temperature of 55° C. by a treatment speed of 8 m/s, so as to dehydrate the spinned fiber to form a primary PVA fiber;

(26) Step 4: second coagulation bath treatment: reacting the primary PVA fiber obtained in Step 3 with excessive calcium hydroxide solution to provide a secondary fiber;

(27) Step 5: foaming and pore forming: introducing the secondary fiber obtained in Step 4 into a drying channel kept at the temperature of 250° C. for foaming, while stretching the secondary fiber forward at a speed of 35 m/min;

(28) Step 6: cleaning and drying the primary product of microporous PVA fiber obtained in Step 5 to provide the final product of microporous PVA fiber.

Example 4

(29) A method for preparing microporous PVA fiber includes the following steps:

(30) Step 1: preparing a spinning solution: adding 180 kg of Model 2499 PVA resin and 820 Kg of water into a dissolving kettle, and heating to 90° C. under a slow stirring at the speed of 40 rpm until the PVA resin was completely dissolved to form the spinning solution;

(31) preparing calcium hydroxide solution: thoroughly mixing calcium hydroxide powder and water by a weight ratio of 0.019:1 to form the calcium hydroxide solution;

(32) preparing sodium sulfate solution: forming sodium sulfate solution having a concentration of 35% from mirabilite and water:

(33) Step 2: preparing PVA spinning stock solution: cooling the spinning solution obtained in Step 1 to 60° C., adding 126 g of ammonium bicarbonate as foaming agent thereto, pressurizing the kettle to 0.3 MPa under a stirring speed of 40 rpm, and stirring for another 30 min to provide the PVA spinning stock solution;

(34) Step 3: spinning and first coagulation bath treatment: conveying the PVA spinning stock solution obtained in Step 2 to a spinneret plate through a pipeline, and subjecting the spinned fiber to a first coagulation bath treatment in the sodium sulfate solution at the temperature of 50° C. by a treatment speed of 9 m/s, so as to dehydrate the spinned fiber to form a primary PVA fiber;

(35) Step 4: second coagulation bath treatment: reacting the primary PVA fiber obtained in Step 3 with excessive calcium hydroxide solution to provide a secondary fiber;

(36) Step 5: foaming and pore forming: introducing the secondary fiber obtained in Step 4 into a drying channel kept at the temperature of 220° C. for foaming, while stretching the secondary fiber forward at a speed of 44 m/min;

(37) Step 6: cleaning and drying the primary product of microporous PVA fiber obtained in Step 5 to provide the final product of microporous PVA fiber.

Example 5

(38) A method for preparing microporous PVA fiber, which is different from Example 2 in that, in Step 1, when preparing the spinning solution, 190 kg of Model 1799 PVA resin and 810 kg of water were added to the dissolving kettle, stirred slowly at a stirring speed of 40 rpm and heated to 90° C. or above until the PVA resin was completely dissolved to form the spinning solution. The amount of ammonium bicarbonate used in step 2 was 114 g.

Example 6

(39) A method for preparing microporous PVA fiber, which is different from Example 1 in that, in Step 1, when preparing the spinning solution, 180 kg of Model 2499 PVA resin and 820 kg of water were added to the dissolving kettle, stirred slowly at a stirring speed of 40 rpm and heated to 90° C. or above until the PVA resin was completely dissolved to form the spinning solution. The amount of ammonium bicarbonate used in Step 2 was 54 g.

Example 7

(40) A method for preparing microporous PVA fiber, which is different from Example 1 in that, in Step 1, when preparing the spinning solution, 180 kg of Model 2499 PVA resin and 820 kg of water were added to the dissolving kettle, stirred slowly at a stirring speed of 40 rpm and heated to 90° C. or above until the PVA resin was completely dissolved to form the spinning solution. The amount of ammonium bicarbonate used in Step 2 was 180 g.

Example 8

(41) A method for preparing microporous PVA fiber, which is different from Example 1 in that, in Step 1, the weight ratio of water to calcium hydroxide is 1:0.006.

Example 9

(42) A method for preparing microporous PVA fiber, which is different from Example 1 in that, in Step 1, the weight ratio of water to calcium hydroxide is 1:0.02.

Example 10

(43) A method for preparing microporous PVA fiber, which is different from Example 1 in that, in Step 1, the weight ratio of water to calcium hydroxide is 1:0.011.

Example 11

(44) A method for preparing microporous PVA fiber, which is different from Example 1 in that, in Step 1, the weight ratio of water to calcium hydroxide is 1:0.014.

Example 12

(45) A method for preparing microporous PVA fiber, which is different from Example 1 in that, in Step 1, the foaming agent as added was ammonium carbonate and the use amount of ammonium carbonate was 144 g.

(46) The preparation parameters in the above examples 1-12 are shown in Table 1.

(47) TABLE-US-00001 TABLE 1 Parameters of Examples 1-12 Parameter Weight Weight ratio of ratio of Weight Foaming PVA to calcium ratio of PVA agent foaming hydroxide mirabilite Example (kg) (kg) agent to water to water Example 1 180 0.126 0.0007 0.0125  1 0.35 0.65 Example 2 190 0.171 0.0009 0.0125  1 0.35 0.65 Example 3 180 0.126 0.0007 0.0065  1 0.35 0.65 Example 4 180 0.126 0.0007 0.019   1 0.35 0.65 Example 5 190 0.114 0.0006 0.0125  1 0.35 0.65 Example 6 180 0.054 0.0003 0.0125  1 0.35 0.65 Example 7 180 0.18  0.001  0.0.125 1 0.35 0.65 Example 8 180 0.126 0.0007 0.006   1 0.35 0.65 Example 9 180 0.126 0.0007 0.02   1 0.35 0.65 Example 10 180 0.126 0.0007 0.011   1 0.35 0.65 Example 11 180 0.126 0.0007 0.014   1 0.35 0.65 Example 12 180 0.144 0.0007 0.0125  1 0.35 0.65

Comparison Example 1

(48) A method for preparing PVA fiber, which is different from Example 1 in that, in Step 2, the amount of added ammonium bicarbonate was 80 g.

Comparison Example 2

(49) A method for preparing PVA fiber, which is different from Example 1 in that:

(50) in Step 1, when preparing the calcium hydroxide solution, the calcium hydroxide powder and water were thoroughly mixed by a weight ratio of 0.0031:1; and

(51) in Step 2, the amount of added ammonium bicarbonate was 140 g. [moo] The preparation parameters of the above Comparison Examples 1-2 are shown in Table 2.

(52) TABLE-US-00002 TABLE 2 Parameters for Comparison Examples 1-2 Parameter Weight Weight ratio of ratio of Weight Foaming PVA to calcium ratio of Comparison PVA agent foaming hydroxide mirabilite Example (kg) (kg) agent to water to water Comparison 180 0.08 0.00044 0.0125 1 0.35 0.65 Exm.l Comparison 180 0.14 0.00078 0.0031 1 0.35 0.65 Exm.2

Comparison Example 3

(53) A method for preparing PVA fiber, which is different from Example 1 in that, during the operation, 134 g sodium bicarbonate was used as the foaming agent, instead of ammonium bicarbonate.

Comparison Example 4

(54) A method for preparing PVA fiber, which is different from Example 1 in that, during the operation, sodium hydroxide solution of equal concentration was used instead of calcium hydroxide solution.

Comparison Example 5

(55) A method for preparing PVA fiber, which is different from embodiment 1 in that, ammonium bicarbonate and calcium hydroxide solution were not added.

(56) Test Experiments

(57) The test was made by following reference standard GB/T14335-2008, and the residual sodium sulfate was tested by sintering and weighing method.

(58) Test instruments: a muffle furnace, a chemical fiber fineness analyzer, a fiber length analyzer, a Micronaire instrument, a Model YG008 multifilament strength tester.

(59) Test results: the test results for the Examples are shown in Table 3; and the test results for the Comparison Examples are shown in Table 4.

(60) TABLE-US-00003 TABLE 3 Test results for the Examples Testing indicators Breaking Amount of sodium Void Shrinkage tenacity sulfate residue on Example fraction/% rate/% (1.2 dtex) fiber/% Example 1 21 3 4.9 cN/dtex 0.0029 Example 2 19 3 4.9 cN/dtex 0.0029 Example 3 19 3 4.7 cN/dtex 0.0028 Example 4 20 3 4.8 cN/dtex 0.0029 Example 5 19 3 4.9 cN/dtex 0.0029 Example 6 20 3 4.8 cN/dtex 0.0028 Example 7 20 3 4.9 cN/dtex 0.0027 Example 8 19 3 4.9 cN/dtex 0.0028 Example 9 20 3 4.8 cN/dtex 0.0028 Example 10 19 3 4.8 cN/dtex 0.0028 Example 11 19 3 4.9 cN/dtex 0.0027 Example 12 18 3 4.6 cN/dtex 0.0028

(61) TABLE-US-00004 TABLE 4 Test results for Comparison Examples Testing indicators Void Breaking Amount of sodium Comparison fraction/ Shrinkage tenacity sulfate residue on Exm. % rate/% (1.2 dtex) fiber/% Comparison 7 5 5.7 cN/dtex 0.061 Exm. 1 Comparison 19 6 2.1 cN/dtex 0.0029 Exm. 2 Comparison 11 3 5.1 cN/dtex 0.077 Exm. 3 Comparison 19 5 3.4 cN/dtex 0.0026 Exm. 4 Comparison 0 6 2.0 cN/dtex 0.1 Exm. 5

(62) It can be seen from Table 3 and Table 4 that, in Examples 1-12, the void fraction can reach 19-21%, the shrinkage rate is 3%, the fiber breaking tenacity is 4.7-4.9 cn/dtex, and the amount of sodium sulfate residue on the fiber is 0.0027-0.0029%.

(63) In comparison with Examples 1-12, although the breaking tenacity in the Comparison Example 1 is better than those of Example 1-12, the void fraction in Comparison Example 1 is lower, and the amount of the sodium sulfate residue on the fiber and shrinkage rate are higher, showing that the hydrophilic property of the fiber is poor, and thus it is not suitable for use in the field of medical materials. The main reason for the above difference is that, insufficient amount of ammonium bicarbonate added in the Comparison Example 1 resulted in poor foaming effect, and the insufficient amount of the foaming agent caused more obvious shrinkage since the same sodium sulfate solution as in Examples 1-12 was used.

(64) In comparison with the Examples 1-12, the void fraction and the amount of sodium sulfate residue on the fiber in the Comparison Example 2 are similar to those the Examples 1-12, but the shrinkage rate is too high and the breaking tenacity is too low; and, in despite of the fact that the PVA fiber used as a medical material does not need too high breaking tenacity, a breaking tenacity (1.2 dtex) of only 2.1 cn/dtex makes it difficult to meet the requirements in the field of medical materials. The main reasons for the above differences lie in that, less amount of calcium hydroxide used in the Comparison Example 2 formed a lower concentration of the calcium hydroxide solution, finally resulting in less calcium sulfate formed in the reaction and less adhesion on the surface of the obtained PVA fiber. Therefore, the PVA fiber as obtained tended to have poor dimensional stability, higher shrinkage rate and lower breaking tenacity. Therefore, the concentration of calcium hydroxide solution has a great influence on the mechanical properties and dimensional stability of the finally obtained PVA fiber.

(65) Compared with Examples 1-12, the foaming rate is lower and the amount of sodium sulfate residue on the fiber is higher in Comparison Example 3, resulting in that the formed PVA fiber has a poor hydrophilicity and a great damage to the skin, making it not suitable for use in the field of medical materials. The main reasons for the above differences lie in that, sodium bicarbonate used as foaming agent in Comparison Example 3 can produce foaming effect, but can not produce the foaming effect as good as that of ammonium bicarbonate; moreover, it is difficult to react with sodium sulfate, so that it can not remove sodium sulfate, resulting in more sodium sulfate remained on the surface of PVA fiber. The results show that ammonium bicarbonate or ammonium bicarbonate has better foaming effect, and it is beneficial to reduce the content of residual sodium sulfate remained on the surface of the obtained PVA fiber.

(66) Compared with Examples 1-12, the shrinkage rate is too high and the breaking tenacity is too low in Comparison Example 4, making it difficult to meet the requirements in the field of medical materials. The main reason for the difference is that, it is difficult for the sodium hydroxide solution used in Comparison Example 4 to form a substance attached to the outer surface of PVA fiber and improving the mechanical properties thereof. The results show that the calcium sulfate and calcium carbonate obtained in the process of preparation can improve the breaking tenacity of the PVA fiber.

(67) Compared with Examples 1-12, in Comparison Example 5, the obtained PVA fiber is not foamed, the shrinkage rate is too high, the breaking tenacity is too low, and the amount of the sodium sulfate residue on the fiber makes the obtained PVA have poor hydrophilicity, poor mechanical properties, and damage to the skin when contacting the skin, making it difficult to meet the requirements in the field of medical materials. The main reason for the above difference is that, ammonium bicarbonate and calcium hydroxide solution were not used in Comparison Example 5. The result shows that the coordination of ammonium bicarbonate and calcium hydroxide can improve the foaming effect of PVA fiber, increase its hydrophilicity, and provide it with moderate breaking tenacity, making it suitable for use in the field of medical materials.

(68) These specific examples only represent an explanation to the present application, but not a limitation to the present application. After reading the specification, modifications to the examples based on demands can be made by those skilled in the art based on demands, without paying any creative contribution, which will be protected by the patent law as long as they fall within the scope of the claims of the application.