High-toughness polypropylene short fiber and preparation method thereof

Abstract

The invention discloses a high-toughness polypropylene staple fiber and a preparation method thereof, and relates to the technical field of functional polypropylene fibers. The high-toughness polypropylene short fiber is prepared from the following components in parts by mass: 70 to 85 parts of polypropylene resin, 10 to 20 parts of a polyolefin elastomer, 3 to 8 parts of maleic anhydride grafted polypropylene, 2 to 4 parts of a plasticizer, 1 to 3 parts of an antioxidant and 0.5 to 2 parts of a nucleating agent. By introducing the novel plasticizer with a specific structure, the entanglement resistance among polypropylene molecular chains is effectively reduced, and the molecular chains are easier to relatively slide when being stressed, so that fracture caused by stress concentration is avoided, and the stretching resistance and bending resistance of the fiber are remarkably 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: Formula 1: ; R1 in formula 1 is a substituent, and specific R1 is selected from: methyl, ethyl, methoxy, nitro, amino, halogen.

[0007] Further, the plasticizer is any one of the following compounds: ; ; .

[0008] A high-toughness polypropylene staple fiber comprising the plasticizer.

[0009] 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.

[0010] Further, the polyolefin elastomer is at least one of ethylene-octene copolymer or ethylene-butene copolymer.

[0011] Further, the grafting rate of the maleic anhydride grafted polypropylene is 0.8-1.5%.

[0012] 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.

[0013] A method for preparing a high-toughness polypropylene staple fiber, comprising the following steps: S1. Raw material mixing: under nitrogen protection, the polypropylene resin, polyolefin elastomer, maleic anhydride grafted polypropylene, plasticizer, antioxidant and nucleating agent are added into a high-speed mixer, the rotating speed is controlled at 1000-1500 r / min, and the temperature is controlled at 80-100℃, and mixed for 5-10 min to obtain a premix; S2. Melt extrusion: the premix is added into a twin-screw extruder, and melted and plasticized at 180-220℃ to obtain a spinning melt; S3. Spinning forming: the spinning melt is extruded through a spinning assembly, and cooled and solidified by cold air at 25-35℃ to obtain a nascent fiber; S4. Stretch setting: the nascent fiber is stretched at 60-110℃, and the stretching multiple is 3-5, and then set at 80-110℃ for 5-20 min; S5. Cutting and packaging: the set fiber is cut into 3-10 mm staple fibers, and then packaged after impurity removal to obtain a high-toughness polypropylene staple fiber.

[0014] Further, the screw length-diameter ratio of the twin-screw extruder in step S2 is 25-30:1, and the temperature distribution of each section of the screw is as follows: 180-190 DEG C for the feeding section, 190-210 DEG C for the compression section, and 210-220 DEG C for the homogenizing section.

[0015] Further, the air speed of the cold air in step S3 is 0.5-1.2 m / s, and the spinning speed is 800-1200 m / min; the stretching in 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.

[0016] The plasticizer molecules contain non-polar groups and have a chemical structure matching that 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), reduce the entanglement resistance of molecular chain. The plasticizer molecules are equivalent to "molecular lubricant", reduce the entanglement and friction between the polypropylene molecular chains, make the molecular chain more easily slide when stressed, avoid the fracture caused by stress concentration, finally improve the fiber toughness (anti-stretching, anti-bending performance). By improving the compatibility of the polypropylene composite system, reducing the interface defects. The polypropylene staple fiber is a multi-component composite system, the polarity of each component is different, easy to form interface separation, leading to the existence of "weak interface" in the fiber, easy to break from the interface when stressed, the plasticizer improves the compatibility through "polarity matching", the polar substituent group of the plasticizer molecules can form weak interaction with the polar group of the maleic anhydride grafted polypropylene, at the same time, the non-polar group of the plasticizer can be compatible with polypropylene and polyolefin elastomer, reduce the separation between components, eliminate internal defects, make the stress uniform transmission when the fiber is stressed, further improve the toughness and impact resistance. By regulating the crystalline structure of polypropylene, reducing the rigid crystal region. The crystallinity and grain size of polypropylene directly affect the toughness, 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, 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 whole damage caused by the fracture of single crystal region, finally make the fiber have certain rigidity and high toughness.

[0017] 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 expansion of the crack. 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 enabling 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.

[0018] Compared with the prior art, the beneficial effects of the present application are: 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.

[0019] 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.

[0020] 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, so that the fiber has higher toughness while maintaining a certain rigidity. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The plasticizer 1 described in the present application is 1 H NMR chart. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be clearly and completely described below with reference to the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than 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 effort belong to the scope of protection of the present application.

[0023] Preparation Example 1 Preparation of plasticizer 1: ; Step 1: Under a 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 to the reaction system, heated to 85°C for 16h; after cooling, the pH of the system was adjusted to neutral with 0.1 mol / L HCl, the organic phase was washed with water five times, and then washed with saturated NaCl solution twice; finally, the combined organic phase was dried over anhydrous Na2SO4, rotary evaporation, and purified by silica gel column with a mixture of petroleum ether and ethyl acetate as eluent, and the solution was rotary evaporated to obtain 26.11 g of compound C. Mass spectrum MS [M+H] + = 375.

[0024] ; Step 2: Under a nitrogen atmosphere, 21.15 g of triethylamine was added to 200 mL of 1,4-dioxane, then 19.49 g of compound D was added, and 26.11 g of compound C was dissolved in 50 mL of 1,4-dioxane, which was slowly added to the above solution while keeping the temperature below 10°C, and then stirred at 60°C for 12h. After the reaction was completed, the mixture was concentrated under reduced pressure to obtain a concentrated solution, which was purified by column chromatography with a mixture of n-heptane and ethyl acetate as eluent, and then rotary evaporated to obtain 28.11 g of plasticizer 1. Mass spectrum MS [M+H] + = 554.

[0025] 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).

[0026] Preparation Example 2-Preparation Example 6 Plasticizers 2-6 were prepared in succession in Preparation Examples 2-6, 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.

[0027] Table 1.

[0028] Example 1 Preparation of a high-toughness polypropylene staple fiber: a. Mass of raw materials: Polypropylene resin: 80 parts, purchased from Wuxi Feimo New Material Co., Ltd.; Polyolefin elastomer: 15 parts, selected from ethylene-octene copolymer, purchased from Hangzhou Jieheng Chemical Co., Ltd.; Maleic anhydride grafted polypropylene: 6 parts, purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; Plasticizer: 3 parts, selected from plasticizer 1 prepared in Preparation Example 1; Antioxidant: 2 parts, selected from antioxidant 168, purchased from Qingdao Zhen Guang Functional Materials Technology Co., Ltd.; Nucleating agent: 1 part, selected from dibenzyl sorbitol, purchased from Hubei Jusheng Technology Co., Ltd.

[0029] b. Preparation method: S1. Mixing of raw materials: 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 were added into a high-speed mixer, the rotating speed was controlled at 1200 r / min, and the temperature was controlled at 90°C for 8 min to obtain a premix; S2. Melt extrusion: the premix was added into a twin-screw extruder, the temperature of each section of the screw was set as follows: 185°C for feeding section, 200°C for compression section, and 215°C for homogenization section, melt plasticization was carried out at a melt temperature of 200°C, and a spinning melt was obtained by extrusion; S3. Spinning and forming: the spinning melt was extruded through a spinning assembly, cooled and solidified by 30°C cold air at a wind speed of 0.8 m / s, and the spinning speed was controlled at 1000 m / min to obtain a nascent fiber; S4. Stretching and setting: the nascent fiber was subjected to two-stage stretching, the first-stage stretching temperature was 70°C, the stretching multiple was 2.5 times, the second-stage stretching temperature was 95°C, the stretching multiple was 1.5 times, and then setting was carried out in 100°C hot air for 10 min; S5. Cutting and packaging: the set fiber was cut into 5 mm staple fibers, and then packaged after electrostatic impurity removal to obtain a high-toughness polypropylene staple fiber.

[0030] Examples 2-6 Examples 2-6

[0031] Comparative Example 1 A high tenacity polypropylene staple fiber was prepared according to the preparation method of Example 1, without adding the plasticizer therein, and the rest was kept the same as Example 1.

[0032] Comparative Example 2 A high tenacity polypropylene staple fiber was prepared according to the preparation method of Example 1, replacing the plasticizer therein with dioctyl phthalate (a commonly used plasticizer), and the rest was kept the same as Example 1.

[0033] Comparative Example 3 A high tenacity polypropylene staple fiber was prepared according to the preparation method of Example 1, replacing the plasticizer therein with octyl epoxy stearate (a commonly used plasticizer), and the rest was kept the same as Example 1.

[0034] Comparative Example 4 A high tenacity polypropylene staple fiber was prepared according to the preparation method of Example 1, replacing the polyolefin elastomer therein with ethylene-propylene rubber, and the rest was kept the same as Example 1.

[0035] Comparative Example 5 A high tenacity polypropylene staple fiber was prepared according to the preparation method of Example 1, replacing the polyolefin elastomer therein with styrene-based block copolymer, and the rest was kept the same as Example 1.

[0036] Performance Test 1. Tensile property test: The breaking strength and elongation at break of the high tenacity 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.

[0037] 2. Abrasion resistance test: The abrasion resistance of the high tenacity 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 testing machine, with a pressure of 0.6 cN / dtex, a friction head of 400 mesh sandpaper, and a friction frequency of 120 times per minute. The number of friction times 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.

[0038] Table 2.

[0039] As can be seen from Table 2, the polypropylene staple fibers prepared by using the specific plasticizer and the specified components (i.e. Examples 1-6) have better performance in the three performance indicators of breaking strength, breaking elongation and wear resistance, and each indicator is maintained at a high level. The polypropylene staple fibers prepared by not adding plasticizer, using traditional plasticizer instead of the specific plasticizer of the application, or using other types of elastomer instead of the specified polyolefin elastomer (i.e. Comparative Examples 1-5) have significantly lower performance indicators than Examples, among which the performance gap of the sample without adding plasticizer is the most prominent, indicating that the plasticizer and the specified components described in the application play a key role in the performance improvement of the polypropylene staple fibers.

[0040] Although embodiments of the application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A plasticizer characterized in that, The plasticizer is a compound shown in formula 1: Formula 1: ; R1 in the formula 1 is a substituent, and specific R1 is selected from the group consisting of methyl, ethyl, methoxy, nitro, amino, halogen.

2. A plasticizer as claimed in claim 1, wherein The plasticizer is any one of the following compounds: ； ； 。 3. A high tenacity polypropylene staple fiber, characterized by, The polypropylene staple fiber comprises the plasticizer according to any one of claims 1-2.

4. The high tenacity polypropylene staple fiber according to claim 3, wherein the polypropylene is a copolymer of propylene and 4-methylpentene. 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.

5. The high tenacity polypropylene staple fiber according to claim 4, wherein the polypropylene is a copolymer of propylene and 1-butene. The polyolefin elastomer is at least one of ethylene-octene copolymer or ethylene-butene copolymer.

6. The high tenacity polypropylene staple fiber of claim 4, wherein the polypropylene has a molecular weight of 150,000 to 300,000. The grafting rate of the maleic anhydride grafted polypropylene is 0.8-1.5%.

7. The high tenacity polypropylene staple fiber of claim 4, wherein the polypropylene has a molecular weight of 150,000 to 300,000. The antioxidant is at least one of antioxidant 1010 or antioxidant 168; and the nucleating agent is at least one of dibenzylidene sorbitol or 1,3:2,4-di-p-methylbenzylidene sorbitol.

8. A process for the production of high tenacity polypropylene staple fibre as claimed in any one of claims 3 to 7, wherein the process is characterized in that, The method comprises the following steps: S1. Raw material mixing: under the protection of nitrogen, the polypropylene resin, polyolefin elastomer, maleic anhydride grafted polypropylene, plasticizer, antioxidant and nucleating agent are added into a high-speed mixer, the rotating speed is controlled at 1000-1500 r / min, and the temperature is controlled at 80-100 ℃, and the mixture is mixed for 5-10 min to obtain a premix; S2. Melt extrusion: the premix is added into a double-screw extruder, and is melt-plasticized at 180-220 ℃ to obtain a spinning melt; S3. Spinning forming: the spinning melt is extruded through a spinning assembly, and is cooled and solidified by a cold air at 25-35 ℃ to obtain a nascent fiber; S4. Stretching and setting: the nascent fiber is stretched at 60-110 ℃, and the stretching multiple is 3-5 times, and then is set at 80-110 ℃ for 5-20 min; S5. Cutting and packaging: the fiber after setting is cut into staple fibers with a length of 3-10 mm, and is packaged after impurity removal to obtain a high-toughness polypropylene staple fiber.

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

10. The method for preparing high-toughness polypropylene staple fiber according to claim 8, characterized in that, In the 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; and in the step S4, the stretching is two-stage stretching, the first-stage stretching temperature is 60-80 ℃, and the stretching multiple is 2-3 times; and the second-stage stretching temperature is 90-100 ℃, and the stretching multiple is 1-2 times.

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