POLYURETHANE ELASTIC FIBER WITH FLAME RETARDANT FUNCTION AND PREPARATION METHOD THEREOF

Abstract

Disclosed are a polyurethane elastic fiber with a flame retardant function and a preparation method thereof. The polyurethane elastic fiber is prepared by using a polyether diol containing phosphorus elements or a polyester diol containing phosphorus elements as a raw material to react with 4,4′-diphenylmethane diisocyanate to prepare a prepolymer, extending the chain using an organic amine to obtain a polyurethane solution, and dry spinning with the polymer solution to prepare the polyurethane fiber. The limit oxygen index of the prepared polyurethane fiber was between 25% and 32%.

Claims

1. A preparation method of a polyurethane elastic fiber with a flame retardant function, comprising: step 1 of reacting a diol containing flame-retardant elements with excess 4,4′-diphenylmethane diisocyanate to prepare a prepolymer end-capped by isocyanate, and dissolving the prepolymer in an organic solvent to form a prepolymer solution; step 2 of adding a diamine or a mixed amine of a diamine and a monoamine to the prepolymer solution for chain extension reaction to obtain a polyurethane solution; and step 3 of mixing the polyurethane solution with an anti-yellowing agent and an antioxidant, followed by curing, filtering, defoaming, and then dry spinning to obtain the polyurethane elastic fiber with flame retardant function.

2. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 1, wherein the diol containing flame-retardant elements in step 1 is a polyether diol containing phosphorus elements or a polyester diol containing phosphorus elements.

3. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 2, wherein the polyether diol containing phosphorus elements contains —P—O— or —P—C— structures, and has a phosphorus content of 0.5 wt % to 5 wt %; and the polyether diol containing phosphorus elements contains phosphate structures, and has a phosphorus content of 0.5 wt % to l0 wt %, and an acid value of 3.0 or lower.

4. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 3, wherein the phosphorus content in the polyether diol containing phosphorus elements is 1 wt % to 3 wt %, the phosphorus content in the polyester diol containing phosphorus elements is 1 wt % to 6 wt %, and the acid value is 2.0 or lower.

5. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 1, wherein in step 1, a molar ratio of the 4,4′-diphenylmethane diisocyanate to the diol containing flame-retardant elements is (1.5:1) to (2.5:1).

6. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 1, wherein the organic solvent in step 1 is N,N-dimethylformamide, N,N-dimethylacetamide, or a mixture thereof.

7. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 1, wherein, in step 2, a molar ratio of amino functional groups in the diamine or the mixed amine of the diamine and the monoamine to the isocyanate at ends of the prepolymer is (1.00:1) to (1.05:1).

8. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 1, wherein in step 2, the diamine is selected from the group consisting of ethylenediamine, 1,2-propanediamine, 1,3-propylenediamine 2-methyl-1,5-pentanediamine, and a combination thereof in any ratio; and the monoamine is selected from the group consisting of dimethylamine, diethylamine, methylethylamine, and a combination thereof in any ratio.

9. The preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 1, wherein, when the mixed amine of the diamine and the monoamine is adopted in step 2, a molar ratio of the monoamine to the diamine is (0.02:1) to (0.15:1).

10. A polyurethane elastic fiber with a flame retardant function, prepared by the preparation method of the polyurethane elastic fiber with the flame retardant function according to claim 1, wherein a limit oxygen index of the polyurethane elastic fiber is 25 wt % to 32 wt %.

Description

DESCRIPTION OF EMBODIMENTS

[0023] The embodiments of the present disclosure are described in further detail below:

[0024] A preparation method of a polyurethane elastic fiber with a flame retardant function, including the following steps:

[0025] (1) A diol containing flame retardant elements with a molecular weight of 1000 to 3000 was reacted with excess 4,4′-diphenylmethane diisocyanate (abbreviated as MDI) to prepare a prepolymer end-capped by isocyanate, and the prepolymer was dissolved in an organic solvent to form a prepolymer solution with a certain concentration;

[0026] The diol containing flame retardant elements is a polyether diol containing phosphorus elements or a polyester diol containing phosphorus elements. The polyether diol containing phosphorus elements contains —P—O— or —P—C— structures, and has a phosphorus content of 0.5 wt % to 5 wt %, preferably 1% to 3%; and the polyester diol containing phosphorus elements contains phosphate structures, and has a phosphorus content of 0.5 wt % to l0 wt %, preferably 1% to 6%, and an acid value of 3.0 or lower, preferably 2.0 or lower; the organic solvent is one or more of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); and a molar ratio of MDI to the diol containing flame-retardant elements is (1.5:1) to (2.5:1);

[0027] (2) a diamine or a mixed amine of a diamine and a monoamine is added to the prepolymer solution for chain extension reaction to obtain a polyurethane solution;

[0028] A molar ratio of an amino functional group in the diamine or the mixed amine of the diamine and the monoamine to the isocyanate at ends of the prepolymer is (1.00:1) to (1.05:1); the diamine is one or more of ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, or 2-methyl-1,5-pentanediamine (MPDA), and serves as an reactive chain extender; the monoamine is one or more of dimethylamine, diethylamine or methylethylamine, and serves as a molecular weight regulator for controlling the reaction viscosity; and a molar ratio of the monoamine to the diamine is (0.02:1) to (0.15:1);

[0029] (3) the polyurethane solution is mixed with various anti-yellowing agents (such as TAS-011, HN-150), antioxidants (such as HW-245, antioxidant 1790) and other additives, followed by curing, filtering, defoaming, and then dry spinning to obtain the polyurethane elastic fiber; the limit oxygen index (LOI) of the polyurethane fiber prepared according to the method reaches 25 wt % to 32 wt %.

[0030] The present disclosure will be further described in detail below in conjunction with embodiments:

[0031] In the embodiments, the following methods are adopted to measure the performances of polyurethane fibers.

[0032] Evaluation of Limit Oxygen Index

[0033] (1) Solution preparation: the prepared polyurethane solution was diluted with a solvent to a polymer solution with a solid content of 10% to 15%; or the prepared fiber was washed to remove the surface oil, followed by drying, dissolving, and then formulating into a polymer solution.

[0034] (2) Film making: after being stirred evenly, the polymer solution was let stand for a period of time to remove bubbles from the solution. Then, the solution was heated to 40° C. to 60° C. and cast on a smooth and clean glass plate to form a film. After being let stand at room temperature for 12 hours, the film was dried at 100° C. for 2 hours. A film with a thickness of approximately 2 mm was obtained.

[0035] (3) Measurement: an oxygen index instrument was adopted to measure the limit oxygen index.

[0036] Evaluation of Elongation at Break

[0037] A Constant-Rate-of-Extension type tensile testing machine was adopted to test the elongation rate of the spandex at break under the condition of a tensile rate of 500 mm/min.

Embodiment 1

[0038] Preparation of Phosphorus-Containing Polyether Diol:

[0039] 800 g of phenylphosphoric acid was put into a 5 L reactor, under the condition of constant stirring and mixing, the reaction temperature was increased up to 90° C., then 696 g of propylene oxide (a first feeding) was added into the reactor within 4 hours, the reaction was continued until the reaction pressure dropped to normal pressure, 20 g of potassium hydroxide was added, and the intermediate product was vacuumed for 1 hour to a degree of vacuum of −0.1 atm. Then, 1722 g of propylene oxide (a second feeding) was added to the reactor within 8 hours, and the reaction was continued until the reaction pressure dropped to normal pressure to obtain the crude product. The crude product was vacuumed for 1 hour to a degree of vacuum of −0.1 atm to completely remove the residual monomers and volatile components in the crude product, neutralized by adding phosphoric acid, adsorbed by diatomaceous earth, and filtered, to finally obtain a viscous transparent liquid product. After testing, the hydroxyl value was 181 mg/gKOH, the acid value was 0.2 mg/gKOH, and the number average molecular weight was 620; and according to calculation based on the feed amount and the product mass, the phosphorus content of the product was 5 wt %.

[0040] Preparation of Polyurethane Fiber:

[0041] The phosphorus-containing polyether diol prepared above and 4,4′-diphenylmethylalkane diisocyanate (MDI) at a molar amount equivalent to 1.5 times that of the phosphorus-containing polyether diol were reacted at 80° C. for 3 hours under the protection of dry nitrogen and mechanical stirring to obtain a prepolymer end-capped by —NCO. After cooling to room temperature, N,N-dimethylacetamide (DMAc) was added to dissolve the prepolymer to form a prepolymer solution.

[0042] The temperature of the above prepolymer solution was lowered to 10° C., and a DMAc solution of a mixed amine of 1,2-propanediamine and diethylamine was added for chain extension to obtain a polyurethane solution. The molar ratio of diethylamine to (1,2-propylenediamine) was 0.15:1, and the molar ratio of amino functional groups in the mixed amine to isocyanate functional groups in the prepolymer (NHx:NCO) was 1.05:1. An anti-yellowing agent TAS-011 accounting for 0.5 wt % of the weight of the polymer and an antioxidant 1790 accounting for 0.5 wt % of the weight of the polymer were added to the polyurethane solution, followed by mixing evenly, then curing, defoaming, and filtering, and then dry spinning to obtain 560 denier (abbreviated as D) polyurethane fiber.

Embodiments 2 to 5

[0043] Preparation of Phosphorus-Containing Polyether Diol:

[0044] According to the preparation method of polyether diol in Embodiment 1, polyether diols containing 3%, 2%, 1%, and 0.5% phosphorus were prepared. In order to control the molecular weight, when preparing a polyether diol with a lower phosphorus content, it was necessary to add diethylene glycol to adjust the molecular weight at the same time when adding potassium hydroxide. The specific feeding amount and performance indicators are shown in Table 1.

TABLE-US-00001 TABLE 1 Feed and performance indicators of phosphorus-containing polyether diol Items Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Feed (g) Phenylphosphoric 800 500 350 172 84 acid Propylene oxide 696 435 304 150 73 (First feeding) Diethylene 0 0 0 0 120 glycol Propylene oxide 1722 2450 2900 3100 3200 (Second feeding) Performance Acid value 0.2 0.1 0.1 0.1 0.1 indicators mgKOH/g Hydroxyl value 181 109 73 37 56 mgKOH/g Number average 620 1030 1540 3000 2000 molecular weight g/mol Phosphorus   5%   3%   2%   1%    0.50% content wt %

[0045] Preparation of Polyurethane Fiber:

[0046] The polyether diol in the above embodiments 2 to 5 was used as the raw material, and according to the preparation method of the polyurethane fiber in Embodiment 1, after the molar ratio of MDI to polyether diol and the type and amount of chain extender were adjusted according to Table 2, a polyurethane solution was prepared, followed by curing, defoaming, filtering, and then spinning to obtain 40D or 560D polyurethane fiber.

[0047] The limit oxygen index and the elongation at break of polyurethane fiber are shown in Table 2.

TABLE-US-00002 TABLE 2 Feed and performance indicators of phosphorus-containing polyether diol based polyurethane fiber Items Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Phosphorus content  5%   3%  2%  1%    0.5% of polyether diol wt % Feed MDI/Diol 1.5 1.5 2 2 2.5 (molar ratio) NHx:NCO 1.05 1 1 1.03 1.05 Monoamine: 0.15 / 0.02 0.10 0.10 Diamine Diamine 1,2- Ethylenediamine Ethylenediamine: 1,2-Propanediamine: 1,2- propanediamine MPDA = 8:2 1,3-propanediamine = propanediamine Monoamine Diethylamine None Diethylamine: 8:2 Methylethylamine Dimethylamine Methylethylamine = 9:1 Performance Fiber size 560D 560D 40D 40D 560D indicators LOI % 32 29 28 26 25 Elongation 360 420 550 580 530 at break %

Embodiment 6

[0048] Preparation of Phosphorus-Containing Polyester Diol:

[0049] 218 g of adipic acid, 2200 g of (2-carboxyethyl)phenylphosphinic acid (CEPPA) and 1248 g of 1,4-butanediol were added into a 5 L reactor, 1.5 g of catalyst tetrabutyl titanate was added, followed by stirring under the protection of nitrogen, and gradually heating up to 125-150° C., the water started to be fractionally distilled out, and the reaction lasted for 2 hours to 8 hours while controlling the reaction temperature in the range; then the temperature was further increased to 180° C., at which temperature the reactor was vacuumed to 20 Pa to 5000 Pa, followed by slowly heating up to 235° C. After reacting for 2-4 hours, the acid value and hydroxyl value were tested every 30 minutes. After the acid value and hydroxyl value were qualified, the heating was stopped. The pressure was relieved with nitrogen and the temperature was lowered. When the temperature dropped to 80° C., the reaction product was taken out to obtain phosphorus-containing polyester diol. After testing, the hydroxyl value was 36 mg/gKOH, the acid value was 1.7 mg/gKOH, and the number average molecular weight was 3000. According to calculation based on the feed amount and product mass, the phosphorus content of the product was 10 wt %.

[0050] Preparation of Polyurethane Fiber:

[0051] The above polyester diol was used as raw material. 560D polyurethane fiber was prepared according to the preparation method of the polyurethane fiber in Embodiment 1. The solvent DMAc was replaced by a mixed solvent of 80 wt % DMF and 20 wt % DMAc, the anti-yellowing agent was replaced by HN-150, and the antioxidant was replaced by antioxidant 245.

Embodiments 7 to 10

[0052] Preparation of Phosphorus-Containing Polyester Diol:

[0053] According to the preparation method of polyester diol in Embodiment 6, the polyester diols containing 6%, 3%, 1%, and 0.5% phosphorus were prepared. The mixed solvent was replaced by pure DMF. See Table 3 for specific feeding amount and performance indicators.

TABLE-US-00003 TABLE 3 Feed and performance indicators of phosphorus-containing polyester diol Items Embodiment 6 Embodiment 7 Embodiment 8 Embodiment 9 Embodiment 10 Feed (g) CEPPA 2200 1420 700 236 115 Adipic acid 218 1100 1680 2100 2100 Butanediol 1248 1490 1604 1672 1776 Performance Acid value 1.7 1.9 1.7 2.0 2.9 indicators mgKOH/g Hydroxyl 36 36 54 54 109 value mgKOH/g Number average 3000 3000 2000 2000 1000 molecular weight g/mol Phosphorus content  10%   6%   3%   1%    0.5% wt %

[0054] Preparation of Polyurethane Fiber:

[0055] The polyester diols in the above Embodiments 7 to 10 was used as raw materials. According to the preparation method of the polyurethane fiber in Embodiment 6, after the molar ratio of MDI to polyether diol and the type and amount of chain extender were adjusted according to Table 4, the polyurethane solution was prepared, followed by curing, defoaming, filtering, and then spinning to obtain 40D or 560D polyurethane fibers.

[0056] The limit oxygen index and the elongation at break of polyurethane fiber are shown in Table 4.

TABLE-US-00004 TABLE 4 Feed and performance indicators of phosphorous-containing polyester diol based polyurethane fiber Items Embodiment 6 Embodiment 7 Embodiment 8 Embodiment 9 Embodiment 10 Phosphorus content of 10%  6%  3%  1%  0.5% polyester diol wt % Feed MDI/Diol 1.5 1.5 2 2 2.5 (Molar ratio) NHx:NCO 1.05 1 1 1.03 1.05 Monoamine: 0.15 / 0.02 0.10 0.10 Diamine Diamine 1,2- Ethylenediamine Ethylenediamine: 1,2-Propanediamine: 1,2- propanediamine MPDA = 8:2 1,3-propanediamine = propanediamine Monoamine Diethylamine None Diethylamine: 8:2 Methylethylamine Dimethylamine Methylethylamine = 9:1 Performance Fiber size 560D 560D 40D 560D 560D indicators LOI% 32 29 27 26 25 Elongation at 480 520 600 570 430 break %

Comparative Embodiment 1

[0057] The flame retardant polyether diol in Embodiment 4 was replaced by polytetrahydrofuran diol (PTMG), and a polyurethane solution was prepared according to the method of Embodiment 4 and spun into 40D polyurethane fiber.

Comparative Embodiment 2

[0058] A polyurethane solution was prepared according to the method of Comparative Embodiment 1, and a high nitrogen flame retardant HT-211 accounting for 2% of the weight of the polymer was added as a flame retardant auxiliary, followed by mixing, curing, filtering, defoaming, and then dry spinning to form 40D polyurethane fiber.

Comparative Embodiment 3

[0059] A polyurethane solution was prepared according to the method of Embodiment 4, and high nitrogen flame retardant HT-211 accounting for 2% of the weight of the polymer was added as a flame retardant auxiliary, followed by mixing, curing, filtering, defoaming, and then dry spinning to form 40D polyurethane fiber.

Comparative Embodiment 4

[0060] A polyurethane solution was prepared according to the method of Embodiment 9, and high nitrogen flame retardant HT-211 accounting for 5% of the weight of the polymer was added as a flame retardant auxiliary, followed by mixing, curing, filtering, defoaming, and then dry spinning to form 560D polyurethane fiber.

TABLE-US-00005 TABLE 5 Feed and performance indicators of different comparative embodiments Comparative Comparative Comparative Comparative Embodiment Embodiment Embodiment Embodiment Items 1 2 3 4 Diol Types PTMG PTMG Polyether-type Polyester-type Phosphorus 0  0 1% 1% content wt % Flame Content 0 5% 2% 5% retardant wt % Performance Fiber size 40D 40D 40D 560D indicators LOI % 18  23  27  28 Elongation 640  540  520 500 at break %