A kind of hot-rolled non-woven polypropylene staple fiber and preparation method thereof

Abstract

This application discloses a hot-rolled nonwoven polypropylene staple fiber and its preparation method, comprising the following raw materials in parts by weight: 100 parts polypropylene, 0.5-2 parts nucleating agent, and 0.1-1 parts dispersant; the nucleating agent includes sorbitol-based nucleating agents, spherical nucleating agent particles, and needle-shaped nucleating agent particles in a mass ratio of 2-3:1:6-7; the average aspect ratio of the needle-shaped nucleating particles is 10-20; and the average aspect ratio of the spherical nucleating particles is less than 2. The hot-rolled nonwoven polypropylene staple fiber of this application possesses excellent tensile strength and deformation recovery ability, thus enabling the production of nonwoven fabrics with good strength properties, suitable for applications with high material requirements such as construction engineering and highway engineering.

Description

Technical Field

[0001] The present application relates to the field of non-woven fibers, and in particular to a hot-rolled non-woven polypropylene staple fiber and a preparation method thereof. Background Art

[0002] Polypropylene hot-rolled non-woven fabric is an important non-woven material. It uses polypropylene as the main raw material and forms a cloth-like structure by bonding the fibers together through a high-temperature hot-rolling process. It has the advantages of simple production process, large output, and low cost, and has shown broad application prospects in many fields such as home furnishings, automotive interiors, clothing, building materials, and filter materials.

[0003] The application of polypropylene hot-rolled non-woven fabrics in the construction field is growing. For example, its application in highway engineering can effectively reduce rutting deformation, reduce and inhibit reflective cracks, and delay fatigue damage of roads. In soil structure construction, the mesh structure formed by its amorphous fiber tissue can enhance the tensile strength and deformation resistance of the soil, enhance the stability of the building structure, and improve the quality of the soil. This type of application scenario usually places higher requirements on the strength of polypropylene hot-rolled non-woven fabrics and their fiber raw materials. Therefore, how to improve the strength performance and deformation resistance of polypropylene staple fibers is the key to improving the performance of polypropylene hot-rolled non-woven fabrics. Summary of the invention

[0004] The present application provides a hot-rolled non-woven polypropylene staple fiber and a preparation method thereof, which can effectively improve the tensile strength and deformation recovery ability of the polypropylene staple fiber.

[0005] In the first aspect, the present application provides a hot-rolled non-woven polypropylene staple fiber, which includes the following raw materials in parts by mass: 100 parts of polypropylene, 0.5-2 parts of a nucleating agent, and 0.1-1 parts of a dispersant; the nucleating agent includes a sorbitol nucleating agent, spherical nucleating agent particles, and needle-shaped nucleating agent particles in a mass ratio of 2-3:1:6-7; the average aspect ratio of the needle-shaped nucleating particles is 10-20; the average aspect ratio of the spherical nucleating particles is less than 2.

[0006] Preferably, the D50 particle size of the spherical nucleation particles is 1 to 20 μm, and the average length of the needle-shaped nucleation particles is 1 to 20 μm.

[0007] Preferably, the needle-shaped nucleating particles include one or more of needle-shaped calcium carbonate whiskers, needle-shaped talc powder, needle-shaped wollastonite, and needle-shaped zinc oxide whiskers.

[0008] Preferably, the spherical nucleating particles include one or more of calcium carbonate, talc, mica powder, and silicon dioxide.

[0009] The nucleating agent used in the present application can significantly improve the tensile strength and deformation recovery ability of polypropylene fiber in its length direction (axial direction), so that the overall strength of the fiber is significantly improved. Specifically, the nucleating agent is mainly needle-shaped nucleating agent particles. Due to its morphological anisotropy, it will be oriented along the extrusion direction under the pressure of the die mouth during melt extrusion, that is, its length direction is parallel to the extrusion direction, thereby guiding the polypropylene molecular chain to arrange and crystallize in the length direction of the fiber, forming a finer and more uniform grain structure, thereby improving the tensile strength, deformation recovery ability, wear resistance and thermal stability of the fiber.

[0010] It should be noted that the increase in the amount of needle-shaped nucleating agent can certainly improve the crystallinity, but it can also cause the polypropylene molecular chain to be excessively oriented along its length direction, and the fiber brittleness increases, which is unfavorable for the improvement of its tensile strength. For this reason, the application is assisted by part of the ball-forming nucleating agent and the sorbitol nucleating agent, and the isotropic characteristic of the ball-forming nucleating agent crystal nucleus helps to reduce the preferred orientation of the crystal, can make the mechanical properties of the fiber in different directions more balanced, prevent the crystal from being too dense along the fiber length direction orientation and make the fiber brittle. A large amount of alcoholic hydroxyl groups contained in the sorbitol nucleating agent can improve the overall crystallization rate, help to form a smaller and more dense crystal structure. More importantly, the sorbitol nucleating agent can form a network structure with the ball-forming nucleating agent as a connecting node by hydrogen bonding, thereby inducing the polypropylene molecular chain to form a more uniform and dense crystal structure, which is conducive to improving the fiber's strength and toughness in all directions.

[0011] The aspect ratio of the present application is the ratio of the length to the diameter of the needle-shaped nucleating agent. The aspect ratio has a prominent effect in the range of 10 to 20, which is beneficial to orientation along the extrusion direction during extrusion. When the aspect ratio is lower, its orientation effect decreases.

[0012] The D50 particle size of the present application is the median particle size calculated by statistically analyzing the longest particle size of a typical sample of spherical nucleating agent particles. The aspect ratio is the ratio of the longer diameter to the shorter diameter of the spherical nucleating agent particles in the two longest dimensions. The closer the value is to 1, the better the effect.

[0013] It should be noted that the above-mentioned D50 particle size, average length, average length-to-diameter ratio and average aspect ratio can be obtained by randomly selecting a typical sample amount of particles and calculating their arithmetic mean values ​​using a laser particle size analyzer, a scanning electron microscope and other equipment.

[0014] Preferably, the dispersant comprises polyoxyethylene sorbitan fatty acid ester and vinyl silane coupling agent in a mass ratio of 1:1 to 2.

[0015] Preferably, the vinyl silane coupling agent is vinyl trimethoxy silane and / or vinyl triethoxy silane.

[0016] The nucleating agent of the present application has low compatibility with polypropylene and needs to be compounded with a dispersant to improve the dispersibility of the nucleating agent in the polypropylene resin so as to make the crystal distribution more uniform and dense. The above dispersant is compounded with polyoxyethylene sorbitan fatty acid ester and vinyl silane coupling agent, wherein the vinyl silane coupling agent can effectively improve the surface properties of the nucleating agent particles and improve their compatibility. The polyoxyethylene sorbitan fatty acid ester has a good dispersion-promoting effect due to its structural similarity with the sorbitol nucleating agent.

[0017] Preferably, the raw material further comprises 5 to 10 parts of thermoplastic polyolefin elastomer.

[0018] The polypropylene staple fibers of the present application have improved tensile strength and other properties, and their heat resistance is also improved accordingly. During hot rolling, the fibers are not easy to melt and form entanglements and adhesions, which is not conducive to improving the strength performance of non-woven fabrics. To this end, the present application adds thermoplastic polyolefin elastomer (TPO) to increase the physical cross-linking sites between polypropylene fibers during the hot rolling process to enhance the strength of the non-woven fabric.

[0019] Preferably, the sorbitol nucleating agent includes one or more of dibenzylidene sorbitol, methyldibenzylidene sorbitol, and dimethyldibenzylidene sorbitol.

[0020] In a second aspect, the present application provides a method for preparing hot-rolled non-woven polypropylene staple fibers, which is prepared by using any of the above-mentioned raw material ratios and following the following steps:

[0021] The nucleating agent and the dispersing agent are mixed evenly, polypropylene is added, and stirred evenly to prepare a premix;

[0022] The premix is ​​added into an extruder and extruded into filaments through a spinning hole plate, and then pulled and stretched, cooled and solidified, and sheared to obtain polypropylene staple fibers;

[0023] Preferably, during extrusion, the temperature of stage I is 120-150°C, the temperature of stage II is 150-190°C, the temperature of stage III is 190-220°C, and the temperature of the die head is 180-220°C.

[0024] Preferably, the stretching ratio is 6 to 8:1, more preferably 7 to 8:1.

[0025] The use of a higher stretching ratio is beneficial to the preferential orientation of the needle-shaped nucleating agent of the present application, and is conducive to the improvement of strength properties such as tensile strength and deformation recovery ability.

[0026] In summary, this application has the following beneficial effects:

[0027] 1. The present application adopts a compound of sorbitol nucleating agent, spherical nucleating agent particles and needle-shaped nucleating agent particles, which can significantly improve the tensile strength and deformation recovery ability of polypropylene staple fibers, thereby improving the tensile strength and deformation recovery ability and other strength properties of hot-rolled polypropylene non-woven fabrics.

[0028] 2. The present application uses polyoxyethylene sorbitan fatty acid ester and vinyl silane coupling agent as dispersants, which are compounded with nucleating agents, effectively promoting the uniform dispersion of the nucleating agent component in the polypropylene resin to obtain a smaller, more uniform and dense crystal structure, thereby improving the strength performance of fibers and non-woven fabrics.

[0029] 3. The present application, by incorporating thermoplastic polyolefin elastomer, can increase the entanglement and adhesion between fibers of the polypropylene non-woven fabric during hot rolling, increase physical cross-linking points, and thus improve the strength performance of the non-woven fabric. DETAILED DESCRIPTION

[0030] Example

[0031] The polypropylene in the embodiment is a polypropylene homopolymer, and its simply supported beam notched impact strength is 8.0 kJ / m 2 , tensile stress 34MPa, test conditions are temperature 230℃, load 2.16kg. The thermoplastic polyolefin elastomer is TPO Q 300F, its melt index is 0.8g / 10min, and the simply supported beam notched impact strength is 70.0kJ / m 2 , tensile strength at break is 13MPa, the test conditions are temperature 230℃, load 2.16kg.

[0032] Example 1, a hot-rolled non-woven polypropylene staple fiber, prepared according to the following steps: 25g of dibenzylidene sorbitol, 65g of needle-shaped calcium carbonate whiskers (average length of 15μm, average aspect ratio of 15), 10g of spherical calcium carbonate (D50 particle size of 15μm, average aspect ratio of 1.2) are mixed with 15g of polyoxyethylene dehydrated sorbitan fatty acid ester and 25g of vinyl trimethoxy silane couple, stirred for 20min, 10kg of polypropylene and 0.8kg of thermoplastic polyolefin elastomer are added, stirred for 20min, and a premix is ​​prepared.

[0033] The premix is ​​added into a single-screw extruder, heated and melted to obtain a hot melt, the hot melt is extruded into filaments through a spinning hole plate, pulled and stretched, cooled and solidified, and sheared to obtain polypropylene staple fibers (with a diameter of 100 microns); wherein, the temperature of section I of the extruder is 130°C, the temperature of section II is 170°C, the temperature of section III is 200°C, and the temperature of the die head is 200°C; the stretching ratio is 7:1.

[0034] Example 2, a hot-rolled non-woven polypropylene staple fiber is prepared according to the following steps: 18g of dibenzylidene sorbitol, 25g of needle-shaped zinc oxide whiskers (average length of 15μm, average aspect ratio of 10), 6g of spherical calcium carbonate (D50 particle size of 10μm, average aspect ratio of 1.1) are mixed with 10g of polyoxyethylene dehydrated sorbitan fatty acid ester and 20g of vinyl trimethoxy silane couple, stirred for 20min, 10kg of polypropylene and 0.6kg of thermoplastic polyolefin elastomer are added, and stirred for 20min to prepare a premix.

[0035] The premix is ​​added into a single-screw extruder, heated and melted to obtain a hot melt, the hot melt is extruded into filaments through a spinning hole plate, pulled and stretched, cooled and solidified, and sheared to obtain polypropylene staple fibers (with a diameter of 120 microns); wherein, the temperature of section I of the extruder is 140°C, the temperature of section II is 170°C, the temperature of section III is 210°C, and the temperature of the die head is 210°C; the stretching ratio is 7:1.

[0036] Example 3, a hot-rolled non-woven polypropylene staple fiber is prepared according to the following steps: 40g of methyl dibenzylidene sorbitol, 120g of needle-shaped calcium carbonate whiskers (average length of 20μm, average aspect ratio of 20), 18g of spherical calcium carbonate (D50 particle size of 15μm, average aspect ratio of 1.2) are mixed with 30g of polyoxyethylene dehydrated sorbitan fatty acid ester and 65g of vinyl trimethoxy silane couple, stirred for 15min, 10kg of polypropylene and 1kg of thermoplastic polyolefin elastomer are added, and stirred for 15min to prepare a premix.

[0037] The premix is ​​added into a single-screw extruder, heated and melted to obtain a hot melt, the hot melt is extruded into filaments through a spinning hole plate, pulled and stretched, cooled and solidified, and sheared to obtain polypropylene staple fibers (diameter 130 microns); wherein, the temperature of section I of the extruder is 140°C, the temperature of section II is 170°C, the temperature of section III is 190°C, and the temperature of the die head is 190°C; the stretching ratio is 8:1.

[0038] Example 4, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that an equal amount of polyoxyethylene sorbitan fatty acid ester is used to replace vinyl trimethoxy silane.

[0039] Example 5, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that an equal amount of vinyl trimethoxy silane is used to replace polyoxyethylene sorbitan fatty acid ester.

[0040] Example 6, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that an equal amount of fatty alcohol polyoxyethylene ether is used to replace polyoxyethylene sorbitan fatty acid ester.

[0041] Example 7, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that no thermoplastic polyolefin elastomer is added.

[0042] Comparative Example

[0043] Comparative Example 1, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that an equal amount of spherical calcium carbonate (D50 particle size of 15 μm, average aspect ratio of 1.2) is used to replace the needle-shaped calcium carbonate whiskers (average length of 15 μm, average aspect ratio of 15).

[0044] Comparative Example 2, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that the spherical calcium carbonate (D50 particle size of 15 μm, average aspect ratio of 1.2) is replaced by an equal amount of needle-shaped calcium carbonate whiskers (average length of 15 μm, average aspect ratio of 15).

[0045] Comparative Example 3, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that dibenzylidene sorbitol is replaced by an equal amount of spherical calcium carbonate (D50 particle size of 15 μm, average aspect ratio of 1.2).

[0046] Comparative Example 4, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that an equal amount of dibenzylidene sorbitol is used to replace spherical calcium carbonate (D50 particle size is 15 μm, average aspect ratio is 1.2).

[0047] Comparative Example 5, a hot-rolled non-woven polypropylene staple fiber, differs from Example 1 in that an equal amount of spherical calcium carbonate (D50 particle size of 15 μm, average aspect ratio of 1.2) is used to replace the needle-shaped calcium carbonate whiskers (average length of 15 μm, average aspect ratio of 15) and dibenzylidene sorbitol.

[0048] Performance testing

[0049] Test 1: Tensile strength test of polypropylene staple fibers

[0050] The breaking strength of the fiber was measured according to the provisions of GB / T 14344-2008 “Test method for tensile properties of chemical filaments”, and then the tensile strength (MPa) was calculated by breaking strength / cross-sectional area.

[0051] Test 2: Deformation recovery test of polypropylene staple fibers

[0052] The elastic recovery rate (%) of polypropylene fiber was determined according to the provisions of FZ / T 54009-2012 "Polypropylene Stretch Yarn".

[0053] Test 3: Nonwoven fabric breaking strength test

[0054] The polypropylene fiber (average length of 20 cm) obtained above was used as raw material, formed into a web by an air-laid machine, and hot-rolled and bonded by a hot rolling mill (hot rolling temperature of 165-170° C.), to obtain a 80 g / m 2 Polypropylene non-woven fabric. According to FZ / T60005-1991 "Determination of breaking strength and breaking elongation of non-woven fabrics", the breaking strength (N / 5cm) of non-woven fabric samples was tested.

[0055] Table 1. Test results

[0056]

[0057] Analysis of test results:

[0058] (1) It can be seen from Example 1 and Comparative Examples 1 to 5 that the nucleating agent obtained by compounding sorbitol nucleating agent, ball-forming nucleating agent particles and needle-shaped nucleating agent particles can significantly improve the tensile strength and deformation recovery ability (elastic recovery rate) of polypropylene fiber, thereby improving the breaking strength of non-woven fabric. More specifically, it can be seen from Comparative Examples 1 and 5 that the use of needle-shaped nucleating agent plays a key role in improving the fiber strength and deformation recovery ability. At the same time, it can be seen from Comparative Examples 2, 3, and 4 that the ball-forming nucleating agent and sorbitol nucleating agent also play a certain role in improving their performance.

[0059] (2) It can be seen from Examples 4 to 6 that the use of specific dispersant components, polyoxyethylene sorbitan fatty acid ester and vinyl silane coupling agent, also has a significant effect on improving fiber performance.

[0060] (3) It can be seen from Example 7 that the addition of thermoplastic polyolefin elastomer will slightly reduce the strength and deformation recovery of the fiber, but can significantly improve the breaking strength of the non-woven fabric. The reason may be that the thermoplastic polyolefin elastomer will reduce the crystallinity of the fiber, thereby inhibiting the improvement of fiber strength and other properties, but it is beneficial to increase the bonding points between fibers during hot rolling and improve their strength properties.

[0061] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A hot-rolled non-woven polypropylene staple fiber, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of polypropylene, 0.5 to 2 parts of a nucleating agent, and 0.1 to 1 part of a dispersant; the nucleating agent comprises a sorbitol nucleating agent, spherical nucleating agent particles, and needle-shaped nucleating agent particles in a mass ratio of 2 to 3:1:6 to 7; the average length-to-diameter ratio of the needle-shaped nucleating particles is 10 to 20; the average aspect ratio of the spherical nucleating particles is less than 2; the spherical nucleating agent particles are spherical calcium carbonate, and the needle-shaped nucleating agent particles are selected from needle-shaped calcium carbonate whiskers or needle-shaped zinc oxide whiskers.

2. The hot-rolled non-woven polypropylene staple fiber according to claim 1, characterized in that: The D50 particle size of the spherical nucleation particles is 1 to 20 μm, and the average length of the needle-shaped nucleation particles is 1 to 20 μm.

3. The hot-rolled non-woven polypropylene staple fiber according to claim 1, characterized in that: The dispersant comprises polyoxyethylene sorbitan fatty acid ester and vinyl silane coupling agent in a mass ratio of 1:1-2.

4. The hot-rolled non-woven polypropylene staple fiber according to claim 3, characterized in that: The vinyl silane coupling agent is vinyl trimethoxy silane and / or vinyl triethoxy silane.

5. The hot-rolled non-woven polypropylene staple fiber according to claim 1, characterized in that: The raw materials also include 5 to 10 parts of thermoplastic polyolefin elastomer.

6. The hot-rolled non-woven polypropylene staple fiber according to claim 1, characterized in that: The sorbitol nucleating agent includes one or more of dibenzylidene sorbitol, methyldibenzylidene sorbitol, and dimethyldibenzylidene sorbitol.

7. A method for preparing hot-rolled non-woven polypropylene staple fibers, characterized in that: The raw material ratio according to any one of claims 1 to 6 is used and prepared according to the following steps: The nucleating agent and the dispersing agent are mixed evenly, polypropylene is added, and stirred evenly to prepare a premix; The premix is ​​added into the extruder and extruded into filaments through a spinning hole plate, and then pulled and stretched, cooled and solidified, and sheared to obtain polypropylene staple fibers.

8. The preparation method according to claim 7, characterized in that: During extrusion, the temperature of section I is 120-150°C, the temperature of section II is 150-190°C, the temperature of section III is 190-220°C, and the temperature of the die head is 180-220°C.

9. The preparation method according to claim 7, characterized in that: The stretching ratio is 6 to 8:1.

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