High tenacity polypropylene staple fiber and method of making same

Abstract

The application discloses high-toughness polypropylene short fibers and a preparation method thereof, and relates to the technical field of functional polypropylene fibers. The high-toughness polypropylene short fibers are prepared from the following components in parts by mass: 70-85 parts of polypropylene resin, 10-20 parts of polyolefin elastomer, 3-8 parts of maleic anhydride grafted polypropylene, 2-4 parts of plasticizer, 1-3 parts of antioxidant, and 0.5-2 parts of nucleating agent. By introducing a novel plasticizer with a specific structure, the entanglement resistance between polypropylene molecular chains is effectively reduced, the molecular chains are more prone to relative sliding under stress, thereby avoiding the breakage caused by stress concentration, and the tensile and bending resistance of the fibers is significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional polypropylene fibers, in particular to a high-toughness polypropylene staple fiber and a preparation method thereof. BACKGROUND

[0002] As a commonly used synthetic fiber, polypropylene staple fiber has been widely used in many fields such as textiles, packaging, sanitary materials and industrial fabrics due to its light weight, corrosion resistance and low price. However, the toughness of conventional polypropylene staple fiber on the market is generally low, and there are great defects in terms of tensile, bending and wear resistance. These problems lead to the fact that it cannot meet the user's demand in actual application, especially in the scene that requires high strength and high wear resistance, thereby limiting its further development.

[0003] In the prior art, in order to solve the problem of insufficient toughness of polypropylene fiber, methods such as adding plasticizer, modifier or optimizing fiber production process are usually used, but the effect is often limited. On the one hand, the compatibility of traditional plasticizer is poor, which is easy to migrate to the surface of the fiber, resulting in unstable fiber performance; on the other hand, the improved production process often reduces the production efficiency or increases the cost while increasing the toughness of the fiber. In addition, the existing solution method lacks systematicness in improving the toughness of the fiber, and usually optimizes for a single problem without considering the material composition, processing technology and fiber performance.

[0004] Therefore, it has become an important topic in the industry to develop a high-toughness polypropylene staple fiber and a preparation method thereof. By introducing a new plasticizer and optimizing the process parameters, the toughness, impact resistance and wear resistance of the polypropylene staple fiber can be fundamentally improved, thereby expanding its application range and also providing a new direction for further improvement of polypropylene fiber. SUMMARY

[0005] The purpose of the present application is to solve the problem of insufficient toughness of polypropylene staple fiber in the prior art, and to provide a high-toughness polypropylene staple fiber and a preparation method thereof. By introducing a new plasticizer with a specific structure and optimizing the raw material ratio and preparation process, the toughness, impact resistance and wear resistance of the fiber are significantly improved, and the fiber also has good processing stability and application suitability.

[0006] To achieve the above purpose, the technical solution adopted by the present application is: a plasticizer, which is a compound represented by formula 1:

[0007] Formula 1: ;

[0008] R1 in formula 1 is a substituent, and specific R1 is selected from: methyl, ethyl, methoxy, nitro, amino, halogen.

[0009] Further, the plasticizer is any one of the following compounds:

[0010] ;

[0011] ;

[0012] .

[0013] A high-toughness polypropylene staple fiber comprising the plasticizer.

[0014] Further, the polypropylene staple fiber is prepared from the following components by mass parts: polypropylene resin: 70-85 parts, polyolefin elastomer: 10-20 parts, maleic anhydride grafted polypropylene: 3-8 parts, plasticizer: 2-4 parts, antioxidant: 1-3 parts, nucleating agent: 0.5-2 parts.

[0015] Further, the polyolefin elastomer is at least one of ethylene-octene copolymer or ethylene-butene copolymer.

[0016] Further, the grafting rate of the maleic anhydride grafted polypropylene is 0.8-1.5%.

[0017] Further, the antioxidant is at least one of antioxidant 1010 or antioxidant 168; the nucleating agent is at least one of dibenzylidene sorbitol or 1,3:2,4-di-p-methylbenzylidene sorbitol.

[0018] A method for preparing a high-toughness polypropylene staple fiber, comprising the following steps:

[0019] S1. Raw material mixing: under nitrogen protection, the polypropylene resin, polyolefin elastomer, maleic anhydride grafted polypropylene, plasticizer, antioxidant and nucleating agent are added to a high-speed mixer, the rotation speed is controlled at 1000-1500 r / min, and the temperature is controlled at 80-100°C, and the mixture is mixed for 5-10 min to obtain a premix;

[0020] S2. Melt extrusion: the premix is added to a twin-screw extruder, and is melt plasticized at 180-220°C to obtain a spinning melt;

[0021] S3. Spinning forming: the spinning melt is extruded through a spinning assembly, and is cooled and solidified by cold air at 25-35°C to obtain a nascent fiber;

[0022] S4. Stretch setting: the nascent fiber is stretched at 60-110°C, the stretching multiple is 3-5 times, and then is set at 80-110°C for 5-20 min;

[0023] S5. Cutting and packaging: the shaped fibers are cut into 3-10 mm short fibers, and after removing impurities, a high-toughness polypropylene short fiber is obtained.

[0024] Further, the screw length-diameter ratio of the double-screw extruder in the step S2 is 25-30:1, and the temperature distribution of each section of the screw is as follows: the feeding section is 180-190 DEG C, the compression section is 190-210 DEG C, and the homogenizing section is 210-220 DEG C.

[0025] Further, the wind speed of the cold air in the step S3 is 0.5-1.2 m / s, and the spinning speed is 800-1200 m / min; the stretching in the step S4 is two-stage stretching, the first-stage stretching temperature is 60-80 DEG C, and the stretching multiple is 2-3 times; the second-stage stretching temperature is 90-100 DEG C, and the stretching multiple is 1-2 times.

[0026] The plasticizer molecules of the application match the chemical structure of the polypropylene molecular chain (both are mainly non-polar), can be uniformly inserted between the polypropylene molecular chain, replace part of the interchain strong van der Waals force, form weak interaction (such as hydrophobic interaction, van der Waals force), and reduce the entanglement resistance of molecular chain. The plasticizer molecules are equivalent to "molecular lubricant", which reduces the entanglement and friction between polypropylene molecular chains, makes the molecular chain more easily slide when stressed, avoids the fracture caused by stress concentration, and finally improves the fiber toughness (anti-stretching and anti-bending performance). By improving the compatibility of the polypropylene composite system, the interface defects are reduced. The polypropylene short fiber is a multi-component composite system, and the polarity of each component is different, which is easy to form interface separation, resulting in "weak interface" in the fiber, which is easy to break from the interface when stressed. The plasticizer improves the compatibility by "polarity matching", the polar substituent group in the plasticizer molecule can form weak interaction with the polar group of maleic anhydride grafted polypropylene, at the same time, the non-polar group of the plasticizer can be compatible with polypropylene and polyolefin elastomer, reducing the separation between components, eliminating internal defects, making the stress uniform when the fiber is stressed, and further improving the toughness and impact resistance. By adjusting the crystalline structure of polypropylene, the rigid crystal region is reduced. The crystallinity and grain size of polypropylene directly affect the toughness, and the coarse crystalline region is easy to become a stress concentration point, and too high crystallinity will lead to strong rigidity and poor toughness of the material. The plasticizer can synergistically act with the nucleating agent to regulate the crystallization process, and the plasticizer can act as an "auxiliary nucleation point" to promote the formation of fine and uniform crystal grains (instead of coarse grains) with the nucleating agent. The fine crystal grains can disperse the stress when stressed, avoid the breakage of single crystal region to cause overall damage, and finally make the fiber have certain rigidity and high toughness.

[0027] Polypropylene resin as the base material is the skeleton and main body of the entire fiber, providing basic mechanical properties and processability, and is the carrier of all other modified components, and its performance determines the basis of modification. Polyolefin elastomer is the energy absorption and dispersion center. When the material is subjected to external force impact or stretching, these elastomer particles dispersed in the polypropylene matrix can act as "stress concentration points", inducing the surrounding polypropylene matrix to produce phenomena such as crazing and shear band, absorbing a large amount of energy, and preventing further crack propagation. Maleic anhydride grafted polypropylene is an interfacial compatibilizer, which builds a "molecular bridge" between the polyolefin elastomer and the plasticizer and the polypropylene matrix, greatly improving the interfacial compatibility between the components, ensuring uniform dispersion of the elastomer particles and the plasticizer, avoiding interfacial peeling due to poor compatibility, and allowing stress to be effectively transferred from the matrix to the elastomer particles. Antioxidants are the key to ensuring that all the above components can maintain their designed properties and structural integrity after processing, and the protection system will not be damaged at high temperatures. Nucleating agent polypropylene crystallization provides a large number of nucleation points, increases the crystallization temperature, and accelerates the crystallization rate, ultimately forming a larger number of smaller grains, reducing defects and stress concentration points caused by large spherulites.

[0028] Compared with the prior art, the beneficial effects of the present application are:

[0029] 1. Significantly improve the toughness of the fiber: by introducing a new plasticizer with a specific structure, effectively reducing the entanglement resistance between polypropylene molecular chains, making the molecular chains more easily slide when under stress, thereby avoiding the breakage caused by stress concentration, significantly improving the tensile and bending resistance of the fiber.

[0030] 2. Improve the compatibility and dispersibility of the fiber: the plasticizer molecule contains a polar substituent, which can form a weak interaction with the polar groups of maleic anhydride grafted polypropylene, and its non-polar group can be compatible with polypropylene and polyolefin elastomer. Significantly improves the compatibility of the polypropylene composite system, reduces the interfacial defects, makes the stress transfer in the fiber more uniform, and further improves the toughness and impact resistance of the fiber.

[0031] 3. Optimize the crystalline structure of the fiber: the plasticizer and nucleating agent work together to regulate the crystallization process of polypropylene and promote the formation of fine and uniform grains. This fine grain can disperse the stress when under stress, avoiding the overall damage caused by large grains, allowing the fiber to maintain a certain rigidity while having higher toughness. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The plasticizer 1 described in the present application is 1 H NMR chart. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0034] Preparation Example 1

[0035] Preparation of plasticizer 1:

[0036] ;

[0037] First step: under nitrogen atmosphere, 20.00 g of compound A, 25.21 g of compound B, 20.20 g of potassium tert-butoxide and 300 ml of DMSO were added into the reaction system, heated to 85℃ for 16 h; after cooling, the pH of the system was adjusted to neutral with 0.1 mol / L HCl, the organic phase was washed with water for five times, and then washed with saturated NaCl solution for two times; finally, the combined organic phase was dried with anhydrous Na2SO4, rotary evaporation, purified by silica gel column, using a mixture of petroleum ether and ethyl acetate as eluent, rotary evaporation of the solution, 26.11 g of compound C was obtained. Mass spectrum MS [M+H] + = 375.

[0038] ;

[0039] Second step: under nitrogen atmosphere, 21.15 g of triethylamine was added into 200 mL of 1,4-dioxane, then 19.49 g of compound D was added, 26.11 g of compound C was dissolved in 50 mL of 1,4-dioxane, and slowly added into the above solution at a temperature below 10℃, after the addition was completed, it was stirred at 60℃ for 12 h. After the reaction was completed, the mixture was concentrated under reduced pressure to obtain a concentrated solution, purified by column chromatography, using a mixture of n-heptane and ethyl acetate as eluent, rotary evaporation, 28.11 g of plasticizer 1 was obtained. Mass spectrum MS [M+H] + = 554.

[0040] Preparation of plasticizer 1 1 H NMR (Chloroform-d, Figure 1) δ 7.92 (dd, 1H), 7.89-7.83 (m, 2H), 7.80-7.73 (m, 2H), 7.70-7.63 (m, 2H), 7.50-7.38 (m, 5H), 7.13-7.07 (m, 2H), 4.30 (dt, 4H), 2.46 (d, 3H), 1.83-1.72 (m, 2H), 1.54-1.42 (m, 2H), 1.37 (t, 3H), 0.94 (t, 3H).

[0041] Preparation Examples 2-6

[0042] Preparation Examples 2-6 were prepared in sequence, referring to the preparation method of Preparation Example 1, replacing compound B therein, and the rest being the same as Preparation Example 1. See Table 1 for details.

[0043] Table 1.

[0044]

[0045] Example 1

[0046] Preparation of a high-toughness polypropylene staple fiber:

[0047] a Raw material mass parts:

[0048] Polypropylene resin: 80 parts, purchased from Wuxi Feimo New Material Co., Ltd.;

[0049] Polyolefin elastomer: 15 parts, selected from ethylene-octene copolymer, purchased from Hangzhou Jieheng Chemical Co., Ltd.;

[0050] Maleic anhydride grafted polypropylene: 6 parts, purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.;

[0051] Plasticizer: 3 parts, selected from plasticizer 1 prepared in Preparation Example 1;

[0052] Antioxidant: 2 parts, selected from antioxidant 168, purchased from Qingdao Zhen Guang Functional Materials Technology Co., Ltd.;

[0053] Nucleating agent: 1 part, selected from dibenzylidene sorbitol, purchased from Hubei Jusheng Technology Co., Ltd.

[0054] b. Preparation method:

[0055] S1. Raw material mixing: Under nitrogen protection, 80 parts of polypropylene resin, 15 parts of polyolefin elastomer, 6 parts of maleic anhydride grafted polypropylene, 3 parts of plasticizer, 2 parts of antioxidant and 1 part of nucleating agent are added to a high-speed mixer. The speed is controlled at 1200 r / min and the temperature is 90℃ for 8 min to obtain a premix.

[0056] S2. Melt extrusion: The premixed material is added to a twin-screw extruder, and the temperatures of each section of the screw are set as follows: feeding section 185°C, compression section 200°C, homogenization section 215°C. Melt plasticization is carried out at a melting temperature of 200°C, and extrusion is used to obtain a spinning melt.

[0057] S3. Spinning and forming: The spinning melt is extruded through a spinning assembly, cooled and solidified by 30°C cold air at a speed of 0.8 m / s, and the spinning speed is controlled at 1000 m / min to obtain nascent fibers;

[0058] S4. Stretching and Shaping: The nascent fibers are subjected to two-stage stretching. The first stage stretching temperature is 70℃ and the stretching ratio is 2.5 times. The second stage stretching temperature is 95℃ and the stretching ratio is 1.5 times. Then, the fibers are set in hot air at 100℃ for 10 minutes.

[0059] S5. Cutting and Packaging: The shaped fibers are cut into 5mm short fibers, which are then packaged after electrostatic impurity removal to obtain a high-toughness polypropylene short fiber.

[0060] Examples 2-6

[0061] In Examples 2-6, a high-toughness polypropylene staple fiber was prepared sequentially. The preparation method of Example 1 was followed, but the plasticizers were replaced sequentially with plasticizers 2-6, and the rest remained the same as in Example 1.

[0062] Comparative Example 1

[0063] The preparation of a high-toughness polypropylene staple fiber is the same as in Example 1, except that no plasticizer is added.

[0064] Comparative Example 2

[0065] The preparation of a high-toughness polypropylene staple fiber is carried out by referring to the preparation method of Example 1, except that the plasticizer is replaced with dioctyl phthalate (a commonly used plasticizer), and the rest is the same as in Example 1.

[0066] Comparative Example 3

[0067] The preparation of a high-toughness polypropylene staple fiber is carried out according to the preparation method of Example 1, except that the plasticizer is replaced with octyl epoxy stearate (a commonly used plasticizer), and the rest is the same as in Example 1.

[0068] Comparative Example 4

[0069] A high-toughness polypropylene staple fiber was prepared according to the preparation method of Example 1, wherein the polyolefin elastomer was replaced by an ethylene-propylene rubber, and the rest was kept the same as Example 1.

[0070] Comparative Example 5

[0071] A high-toughness polypropylene staple fiber was prepared according to the preparation method of Example 1, wherein the polyolefin elastomer was replaced by a styrene-based block copolymer, and the rest was kept the same as Example 1.

[0072] Performance test

[0073] 1. Tensile property test: The breaking strength and elongation at break of a high-toughness polypropylene staple fiber prepared in the examples and comparative examples were tested according to the standard GB / T 14337-2008 "Chemical fiber staple fiber tensile property test method". At least 10 parallel samples were tested in each group, and the average value was taken. The results are shown in Table 2.

[0074] 2. Abrasion resistance test: The abrasion resistance of a high-toughness polypropylene staple fiber prepared in the examples and comparative examples was tested according to the standard GB / T 21196.3-2007 "Textiles Determination of the abrasion resistance of fabrics by the Martindale method". The polypropylene fiber monofilament was fixed on a reciprocating friction tester, with a pressure of 0.6 cN / dtex, a 400 mesh sandpaper friction head, and a friction frequency of 120 times per minute. The number of frictions when the polypropylene fiber surface appeared obvious fuzz or broke was recorded. At least 10 parallel samples were tested in each group, and the average value was taken. The results are shown in Table 2.

[0075] Table 2.

[0076]

[0077] As can be seen from Table 2, in terms of breaking strength, elongation at break and abrasion resistance, the polypropylene staple fibers prepared by using the specific plasticizer and specified components of the present application (i.e. Examples 1-6) overall perform more outstandingly, with all indicators maintaining at a high level; while the polypropylene staple fibers prepared without adding plasticizer, using traditional plasticizer instead of the specific plasticizer of the present application, or using other types of elastomer instead of the specified polyolefin elastomer (i.e. Comparative Examples 1-5), their performance indicators are significantly lower than the examples, among which the sample without adding plasticizer has the most prominent performance gap, indicating that the plasticizer and specified components described in the present application play a key role in the performance improvement of polypropylene staple fibers.

[0078] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A plasticizer, characterized in that, The plasticizer is a compound represented by Formula 1: Formula 1: ; In Formula 1, R1 is selected from: methyl, ethyl, methoxy, nitro, amino, and halogen.

2. The plasticizer according to claim 1, characterized in that, The plasticizer is any one of the following compounds: ； ； 。 3. A high-toughness polypropylene staple fiber, characterized in that, The polypropylene staple fiber contains the plasticizer described in any one of claims 1-2.

4. The high-toughness polypropylene staple fiber according to claim 3, characterized in that, The polypropylene short fiber is prepared from the following components in parts by weight: polypropylene resin: 70-85 parts, polyolefin elastomer: 10-20 parts, maleic anhydride grafted polypropylene: 3-8 parts, plasticizer: 2-4 parts, antioxidant: 1-3 parts, nucleating agent: 0.5-2 parts.

5. A high-toughness polypropylene staple fiber according to claim 4, characterized in that, The polyolefin elastomer is at least one of ethylene-octene copolymer or ethylene-butene copolymer.

6. The high-toughness polypropylene staple fiber according to claim 4, characterized in that, The grafting rate of the maleic anhydride-grafted polypropylene is 0.8-1.5%.

7. The high-toughness polypropylene staple fiber according to claim 4, characterized in that, The antioxidant is at least one of antioxidant 1010 or antioxidant 168; the nucleating agent is at least one of dibenzylidene sorbitol or 1,3:2,4-di-p-methylbenzylidene sorbitol.

8. A method for preparing a high-toughness polypropylene staple fiber according to any one of claims 3-7, characterized in that, Includes the following steps: S1. Raw material mixing: Under nitrogen protection, polypropylene resin, polyolefin elastomer, maleic anhydride grafted polypropylene, plasticizer, antioxidant and nucleating agent are added to a high-speed mixer. The speed is controlled at 1000-1500 r / min and the temperature is 80-100℃ for 5-10 min to obtain a premix. S2. Melt extrusion: The premixed material is added to a twin-screw extruder, melted and plasticized at 180-220°C, and extruded to obtain a spinning melt; S3. Spinning and forming: The spinning melt is extruded through a spinning assembly and cooled and solidified by cold air at 25-35℃ to obtain nascent fibers; S4. Stretching and setting: The nascent fibers are stretched at 60-110℃ with a stretching ratio of 3-5 times, and then set at 80-110℃ for 5-20 minutes. S5. Cutting and Packaging: The shaped fibers are cut into short fibers of 3-10mm, and after impurity removal, they are packaged to obtain a high-toughness polypropylene short fiber.

9. The method for preparing high-toughness polypropylene staple fiber according to claim 8, characterized in that, In step S2, the screw length-to-diameter ratio of the twin-screw extruder is 25-30:1, and the temperature distribution of each section of the screw is as follows: feeding section 180-190℃, compression section 190-210℃, homogenization section 210-220℃.

10. The method for preparing high-toughness polypropylene staple fiber according to claim 8, characterized in that, In step S3, the wind speed of the cold air is 0.5-1.2 m / s, and the spinning speed is 800-1200 m / min; in step S4, the stretching is a two-stage stretching, with the first stage stretching temperature at 60-80℃ and a stretching ratio of 2-3 times; and the second stage stretching temperature at 90-100℃ and a stretching ratio of 1-2 times.

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