Flame-retardant polyester fiber and preparation method thereof

Abstract

The invention belongs to the field of polyester fibers, and particularly relates to a flame-retardant polyester fabric, a preparation method of which comprises the following steps: uniformly mixing 80-100 parts of PET polyester chips, 5-15 parts of ionic liquid modified magnesium hydroxide and 1-5 parts of an antioxidant, carrying out blending extrusion through a twin-screw extruder, and carrying out strip drawing and pelletizing to obtain flame-retardant modified polyester master batches; and uniformly mixing 70-90 parts of PET polyester chips and 10-30 parts of flame-retardant modified polyester master batches, and carrying out melt spinning on a double-screw high-speed composite spinning machine to obtain the flame-retardant polyester fiber. The polyester fiber prepared by the invention has excellent flame retardant property and mechanical property.

Description

Technical Field

[0001] The present invention belongs to the field of polyester fibers, and particularly relates to a flame-retardant polyester fiber and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (abbreviated as PET, polyester fiber), as a polymer that was industrialized and widely applied earlier, has been widely used in the fields of clothing, home textiles, decoration, and industry due to its excellent mechanical properties, dimensional stability, heat resistance, and large-scale low cost. It has become the synthetic fiber material with the largest production capacity, the fastest development, and the widest application area among synthetic fibers. Polyethylene terephthalate (PET) is a saturated polyester resin material composed of carbon, hydrogen, and oxygen elements. Currently, terephthalic acid (PTA) and ethylene glycol (EG) are often used to first generate bis(2-hydroxyethyl) terephthalate (BHET) through an esterification reaction, and then BHET is used to carry out a polycondensation reaction under high temperature and high vacuum conditions to prepare it.

[0003] Since polyester fibers themselves only contain a carbon, hydrogen, and oxygen structure, do not contain phosphorus and nitrogen-based flame-retardant groups in their molecular structure, and do not have a highly heterocyclic flame-retardant structure, polyesters belong to flammable materials; at the same time, the semi-crystalline characteristics of polyesters themselves result in poor flame retardancy and easy melting. Therefore, polyester fibers themselves are non-intrinsic flame-retardant polymers. When heated and decomposed, they produce a large amount of combustible volatile components, are prone to combustion and cause fires, and the molten droplets generated after combustion cause secondary combustion, posing a great threat to people's property safety and lives, restricting the wide application of polyester fibers in fields with high flame-retardant grades.

[0004] Magnesium hydroxide, as a kind of inorganic flame retardant, has strong adsorption capacity, thermodynamic stability, non-toxicity, halogen-free, a relatively high humidity for decomposition and dehydration, low calorific value, low corrosion, good smoke suppression effect, and low cost. It is superior to traditional flame retardants in terms of thermochemical reactions, applicable polymers, cracking temperature, smoke elimination effect, flame retardant performance, sensitivity to acids, and toxicity. However, when magnesium hydroxide is used as a flame retardant in textiles, it is often added to polymer composites in the form of an additive, and only when the addition amount of magnesium hydroxide is relatively large can an ideal flame retardant effect be achieved. In addition, the poor hydrophilicity and strong polarity of magnesium hydroxide lead to poor compatibility with non-polar polymer materials, easy uneven dispersion, and thus a certain degree of reduction in the physical and mechanical properties and processing performance of the materials, with a poor flame retardant effect. Based on this, developing polyester fibers that balance flame retardant performance and mechanical properties is a current research hotspot. Summary of the Invention

[0005] The purpose of the present invention is to provide a flame-retardant polyester fiber with excellent flame retardant performance and good mechanical properties and a preparation method thereof. The present invention is achieved through the following technical solutions:

[0006] A preparation method of a flame-retardant polyester fiber, comprising the following steps:

[0007] Step 1: Preparation of ionic liquid-modified magnesium hydroxide

[0008] Add an ionic liquid modifier X, magnesium hydroxide powder and deionized water into a reactor, perform ultrasonic treatment, filter the obtained suspension, and vacuum-dry the filter residue to obtain ionic liquid-modified magnesium hydroxide;

[0009] The structural formula of the ionic liquid modifier X is:

[0010] Step 2: Preparation of flame-retardant modified polyester masterbatch

[0011] By weight, mix 80-100 parts of PET polyester chips, 5-15 parts of the ionic liquid-modified magnesium hydroxide obtained in Step 1, and 1-5 parts of an antioxidant evenly, and perform co-blending extrusion and strand cutting through a twin-screw extruder to obtain a flame-retardant modified polyester masterbatch;

[0012] Step 3: Preparation of flame-retardant polyester fiber

[0013] By weight, mix 70-90 parts of PET polyester chips and 10-30 parts of the flame-retardant modified polyester masterbatch obtained in Step 2 evenly, and then perform melt spinning on a twin-screw high-speed composite spinning machine to obtain a flame-retardant polyester fiber.

[0014] In some embodiments, in Step 1, the mass ratio of the ionic liquid modifier X to the magnesium hydroxide powder is (0.05-0.15):1.

[0015] In some embodiments, in Step 1, the temperature of the ultrasonic treatment is 40-70°C and the time is 0.5-1 h.

[0016] In some embodiments, in Step 2, the antioxidant is selected from one or more of antioxidant HP-136, antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant 1068.

[0017] In some embodiments, in Step 2, the rotation speed of the extruder is 100-200 r / min, the temperature of the first zone of the extruder is 250-270°C, the temperature of the second zone is 280-300°C, the temperature of the third zone is 270-290°C, and the temperature of the fourth zone is 260-280°C.

[0018] In some embodiments, in Step 3, the spinning temperature of the spinning machine is 260-280°C, the screw rotation speed is 400-800 r / min, and the winding speed is 900-1200 r / min.

[0019] In some embodiments, the preparation method of the ionic liquid modifier X comprises the following steps:

[0020] Add compound I, compound II and an organic solvent into a reactor, heat up to 50 - 80 °C and stir for reaction for 1 - 10 h; after the reaction is completed, cool, then dissolve the precipitated solid in methanol, subsequently add acetone to precipitate a white solid, filter, wash the filter residue with acetone, and dry it in a vacuum oven to obtain the ionic liquid modifier X. The reaction formula is as follows:

[0021]

[0022] The present invention has achieved the following beneficial effects:

[0023] 1) The polyester fibers prepared by the present invention have excellent flame retardancy and mechanical properties. When the addition amount of magnesium hydroxide is low, its limiting oxygen index can be as high as 39.5%.

[0024] 2) The carboxyl group in the ionic liquid modifier X of the present invention can interact with the hydroxyl groups on the surface of magnesium hydroxide in the form of chemical bonds, and the imidazole ring can be adsorbed onto the surface of magnesium hydroxide due to its strong polarity, thereby improving the dispersion of magnesium hydroxide in PET polyester. In addition, the ionic liquid modifier X contains flame-retardant elements such as N and Cl, and the magnesium hydroxide modified by the ionic liquid modifier X can form a dense carbon layer on the surface of the polyester. The dense carbon layer can prevent the further penetration of the combustion reaction into the interior of the material, thereby exerting a greater flame retardant effect.

[0025] 3) The alkyl chain on the imidazole of the ionic liquid modifier X can penetrate into PET polyester through physical entanglement and van der Waals interactions, improving the compatibility between magnesium hydroxide and the polymer, thereby enhancing the mechanical properties. Specific Embodiments

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0027] The endpoints and any values of the ranges described in the present invention are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0028] The present invention does not limit the sources of the raw materials used. Unless otherwise specified, the raw materials used in the present invention are all ordinary commercially available products in the technical field.

[0029] Preparation Example 1 Preparation of Ionic Liquid Modifier X

[0030]

[0031] Compound I (0.1 mol), compound II (0.22 mol) and THF (150 mL) were added to a reactor, and the temperature was raised to 60 °C and stirred for reaction for 5 h. After the reaction was completed, it was cooled to 10 °C, and then the precipitated solid was dissolved in methanol (50 ml). Subsequently, acetone (200 mL) was added to precipitate a white solid, which was filtered. The filter residue was washed with acetone (3 x 100 mL) and dried in a vacuum oven to obtain ionic liquid modifier X with a yield of 85.9%.

[0032] 1 1H-NMR (400 MHz, DMSO-d6): δ (ppm): 11.92 (s, 1H), 9.50 (t, 2H), 7.98 (t, 2H), 7.85 (t, 2H), 7.15 (s, 1H), 4.25 (t, 4H), 1.85 - 1.73 (m, 4H), 1.31 - 1.26 (m, 4H), 0.91 (t, 6H).

[0033] Example 1

[0034] A preparation process of flame-retardant polyester fiber, comprising the following steps:

[0035] Step 1: Preparation of ionic liquid-modified magnesium hydroxide

[0036] The ionic liquid modifier X (10.0 g) obtained in Preparation Example 1, magnesium hydroxide powder (100.0 g) and deionized water (100 mL) were added to a flask, ultrasonically treated at 50 °C for 0.5 h, and then the obtained suspension was suction filtered. The filter residue was vacuum dried at 80 °C for 5 h to obtain ionic liquid-modified magnesium hydroxide.

[0037] Step 2: Preparation of flame-retardant modified polyester masterbatch

[0038] By weight, 100 parts of PET polyester chips (grade: Wankai WK-821), 5 parts of the ionic liquid-modified magnesium hydroxide obtained in Step 1, and 2 parts of antioxidant 1010 were mixed evenly and melt-blended and extruded through a twin-screw extruder. The rotation speed of the extruder was 100 r / min, the temperature of the first zone of the extruder was 260 °C, the temperature of the second zone was 290 °C, the temperature of the third zone was 280 °C, and the temperature of the fourth zone was 270 °C. Then, it was drawn into strips and pelletized to obtain a flame-retardant modified polyester masterbatch.

[0039] Step 3: Preparation of flame-retardant polyester fiber

[0040] By weight, 80 parts of PET polyester chips (grade: Wankai WK-821) and 20 parts of the flame-retardant modified polyester masterbatch obtained in Step 2 are mixed evenly, and then melt spinning is carried out on a twin-screw high-speed composite spinning machine. The spinning temperature is 280 °C, the screw speed is 500 r / min, and the winding speed is 1000 r / min to obtain the flame-retardant polyester fiber.

[0041] Example 2

[0042] A preparation process of flame-retardant polyester fiber, comprising the following steps:

[0043] Step 1: Preparation of ionic liquid-modified magnesium hydroxide

[0044] The ionic liquid modifier X (5.0 g), magnesium hydroxide powder (100.0 g) and deionized water (100 mL) obtained in Preparation Example 1 are added to a flask, ultrasonically treated at 50 °C for 0.5 h, and then the obtained suspension is filtered by suction. The filter residue is vacuum dried at 80 °C for 5 h to obtain the ionic liquid-modified magnesium hydroxide.

[0045] Step 2: Preparation of flame-retardant modified polyester masterbatch

[0046] By weight, 100 parts of PET polyester chips (grade: Wankai WK-821), 8 parts of the ionic liquid-modified magnesium hydroxide obtained in Step 1, and 3 parts of antioxidant 1076 are mixed evenly, and co-blending extrusion is carried out through a twin-screw extruder. The rotation speed of the extruder is 100 r / min, the temperature of the first zone of the extruder is 260 °C, the temperature of the second zone is 290 °C, the temperature of the third zone is 280 °C, the temperature of the fourth zone is 270 °C, and then it is drawn into strips and pelletized to obtain the flame-retardant modified polyester masterbatch.

[0047] Step 3: Preparation of flame-retardant polyester fiber

[0048] By weight, 75 parts of PET polyester chips (grade: Wankai WK-821) and 25 parts of the flame-retardant modified polyester masterbatch obtained in Step 2 are mixed evenly, and then melt spinning is carried out on a twin-screw high-speed composite spinning machine. The spinning temperature is 280 °C, the screw speed is 500 r / min, and the winding speed is 1000 r / min to obtain the flame-retardant polyester fiber.

[0049] Comparative Example 1

[0050] On the basis of Example 1, the ionic liquid modifier X is replaced with stearic acid, and other operation methods and parameters are the same as those in Example 1. The specific operation is as follows:

[0051] Step 1: Preparation of stearic acid-modified magnesium hydroxide

[0052] Stearic acid (10.0 g), magnesium hydroxide powder (100.0 g), and deionized water (100 mL) were added to a flask and sonicated at 50 °C for 0.5 h. Then, the resulting suspension was filtered by suction, and the filter cake was dried under vacuum at 80 °C for 5 h to obtain stearic acid-modified magnesium hydroxide.

[0053] Step 2: Preparation of flame-retardant modified polyester masterbatch

[0054] By weight, 100 parts of PET polyester chips (grade: Wankai WK-821), 5 parts of the stearic acid-modified magnesium hydroxide obtained in Step 1, and 2 parts of antioxidant 1010 were mixed evenly and melt-extruded through a twin-screw extruder. The rotation speed of the extruder was 100 r / min, the temperature of the first zone of the extruder was 260 °C, the temperature of the second zone was 290 °C, the temperature of the third zone was 280 °C, and the temperature of the fourth zone was 270 °C. Then, it was drawn into strands and pelletized to obtain the flame-retardant modified polyester masterbatch.

[0055] Step 3: Preparation of flame-retardant polyester fibers

[0056] By weight, 80 parts of PET polyester chips (grade: Wankai WK-821) and 20 parts of the flame-retardant modified polyester masterbatch obtained in Step 2 were mixed evenly, and then melt-spun on a high-speed twin-screw composite spinning machine. The spinning temperature was 280 °C, the screw rotation speed was 500 r / min, and the winding speed was 1000 r / min to obtain the flame-retardant polyester fibers.

[0057] Comparative Example 2

[0058] On the basis of Example 1, the ionic liquid modifier X was replaced with Other operation methods and parameters were the same as those in Example 1, and the corresponding flame-retardant polyester fibers were prepared.

[0059] Performance testing

[0060] The flame-retardant properties and mechanical properties of the polyester fibers obtained in Examples 1-2 and Comparative Examples 1-2 were tested respectively, and the testing methods were as follows:

[0061] Flame-retardant property: The limiting oxygen index of the polyester fabric was detected according to GB / T 5454-1997 "Test Method for Oxygen Index of Combustion Performance of Textiles".

[0062] Mechanical property: The mechanical property was detected according to GB / T 14344-2022 "Test Method for Tensile Properties of Chemical Fiber Filaments". The specific testing conditions were: the pre-tension value was set to 5 cN, the clamping length was set to 250 mm, the tensile rate was set to 250 mm / min, and each group of fiber samples was tested 10-20 times until stable data were obtained, and the CV value was required to be kept within 15%.

[0063] The results are shown in Table 1.

[0064] Table 1 Performance Test Results

[0065]

[0066] As can be seen from Table 1, the polyester fibers prepared by the present invention have excellent flame retardancy and mechanical properties. The improvement of the above properties is mainly due to the modification of magnesium hydroxide with ionic liquid modifier X. The main reasons may be as follows: On the one hand, since the flame-retardant magnesium hydroxide powder is difficult to be uniformly dispersed in the hydrophobic PET polyester, and the ionic liquid modifier X used in the present invention The carboxyl groups in it can interact with the hydroxyl groups on the surface of magnesium hydroxide in the form of chemical bonds, and the imidazole ring can be adsorbed on the surface of magnesium hydroxide due to its strong polarity, thereby improving the dispersibility of magnesium hydroxide in PET polyester. In addition, the ionic liquid modifier X contains flame-retardant elements such as N and Cl, and the magnesium hydroxide modified by the ionic liquid modifier X can form a dense carbon layer on the surface of the polyester. The dense carbon layer can prevent the further penetration of the combustion reaction into the material, thereby exerting a greater flame retardant effect. On the other hand, the alkyl chains on the ionic liquid imidazole can penetrate into the PET polyester through physical entanglement and van der Waals interaction, improving the compatibility between magnesium hydroxide and the polymer, thereby improving the mechanical properties.

[0067] The above embodiments are merely examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications thus derived are still within the protection scope of the present invention.

Claims

1. A method for preparing a flame retardant polyester fiber, comprising the following steps: Step 1: Preparation of ionic liquid modified magnesium hydroxide The ionic liquid modifier X, magnesium hydroxide powder and deionized water are added into a reactor, ultrasonically treated, the obtained suspension is filtered, and the filter residue is vacuum dried to obtain ionic liquid modified magnesium hydroxide; The structural formula of the ionic liquid modifier X is: Step 2: Preparation of flame retardant modified polyester masterbatch By weight, 80 to 100 parts of PET polyester chips, 5 to 15 parts of ionic liquid modified magnesium hydroxide obtained in step 1, and 1 to 5 parts of antioxidant are mixed uniformly, and the mixture is blended and extruded through a twin-screw extruder, and the strands are cut into pellets to obtain a flame-retardant modified polyester masterbatch; Step 3: Preparation of flame retardant polyester fiber By weight, 70 to 90 parts of PET polyester chips and 10 to 30 parts of the flame-retardant modified polyester masterbatch obtained in step 2 are mixed evenly, and then melt-spun on a twin-screw high-speed composite spinning machine to obtain flame-retardant polyester fibers.

2. The preparation method according to claim 1, characterized in that: In step 1, the mass ratio of the ionic liquid modifier X to the magnesium hydroxide powder is (0.05-0.15):

1.

3. The preparation method according to claim 1, characterized in that: In step 1, the temperature of ultrasonic treatment is 40-70° C. and the time is 0.5-1 h.

4. The preparation method according to claim 1, characterized in that: In step 2, the antioxidant is selected from one or more of antioxidant HP-136, antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant 1068.

5. The preparation method according to claim 1, characterized in that: In step 2, the rotation speed of the extruder is 100-200 r / min, the temperature of the first zone of the extruder is 250-270°C, the temperature of the second zone is 280-300°C, the temperature of the third zone is 270-290°C, and the temperature of the fourth zone is 260-280°C.

6. The preparation method according to claim 1, characterized in that: In step 3, the spinning temperature of the spinning machine is 260-280° C., the screw speed is 400-800 r / min, and the winding speed is 900-1200 r / min.

7. The preparation method according to claim 1, characterized in that: The preparation method of the ionic liquid modifier X comprises the following steps: Compound I, compound II and an organic solvent are added to a reactor, and the temperature is raised to 50-80° C. and stirred for reaction for 1-10 hours. After the reaction is completed, the reaction is cooled, and then the precipitated solid is dissolved in methanol, and then acetone is added to precipitate a white solid, which is filtered, and the filter residue is washed with acetone and dried in a vacuum oven to obtain an ionic liquid modifier X. The reaction formula is as follows:

8. The flame-retardant polyester fiber prepared according to the method according to any one of claims 1 to 7.

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