Plasma surface modification method for melt-blown polypropylene and application of plasma surface modification method

Abstract

The invention relates to a melt-blown polypropylene plasma surface modification method and application thereof, and the method comprises the following steps: S1, uniformly mixing modified chitosan particles and a modified cellulose compounding agent to obtain a modified mixed material; according to the invention, groups introduced by maleic anhydride grafting are subjected to amidation reaction with modified chitosan, so that the compatibility among components is enhanced, modified chitosan particles and modified cellulose are uniformly dispersed, the former captures small particles by virtue of adsorbability, and the latter is mechanically intercepted by virtue of a three-dimensional network structure; the contact probability of the particles and the melt-blown cloth is greatly increased in combination with multi-stage pores cooperatively constructed by maleic anhydride and plasma; the modified chitosan particles and the modified cellulose form initial pores through steric hindrance and physical support, maleic anhydride reduces surface tension to promote bubble formation and stabilize pore structures through cross-linking, and plasma treatment further optimizes the pores, so that a structure with proper pore size and uniform distribution is cooperatively formed, and a smooth channel is provided for air circulation.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a melt-blown polypropylene plasma surface modification method and application thereof. Background Art

[0002] Meltblown polypropylene is a raw material for preparing meltblown nonwoven polypropylene materials with excellent performance. The meltblown nonwoven process is produced using meltblown nonwoven technology. It relies on high-speed hot air flow to stretch the polymer melt to obtain ultrafine fibers, and then the ultrafine fibers are bonded into a web. Existing meltblown polypropylene is generally prepared by extruder using PP raw materials and initiators.

[0003] At present, although traditional melt-blown polypropylene materials have certain filtering capabilities, there are still many problems in practical applications. Increasing the fiber density or changing the structure to improve the filtering efficiency often leads to a significant increase in the resistance when air passes through, causing the wearer to have difficulty breathing and reducing the practicality of the product. Therefore, a melt-blown polypropylene plasma surface modification method and its application are proposed to solve this problem. Summary of the Invention

[0004] The present invention aims to solve the problems existing in the prior art and provides the following technical solutions:

[0005] The plasma surface modification method of melt-blown polypropylene comprises the following steps:

[0006] S1: uniformly mixing the modified chitosan particles and the modified cellulose compounding agent to obtain a modified mixed material;

[0007] S2: PP particles are melted with maleic anhydride and initiator at 180-200°C and twin-screw extruded to produce PP-g-MAH particles;

[0008] S3: The modified mixture and PP-g-MAH particles are uniformly mixed by ultrasonication to obtain a modified composite material, and then an initiator is added and the modified melt-blown polypropylene crude product is obtained by a twin-screw extruder;

[0009] S4, cooling and drying the crude modified melt-blown polypropylene obtained in step S3 to obtain a finished modified melt-blown polypropylene product;

[0010] S5: placing the modified melt-blown polypropylene finished product in a plasma treatment device, introducing working gas, and performing plasma treatment.

[0011] As an improvement of the above technical solution, the mass ratio of maleic anhydride to PP particles is (1-5):100.

[0012] As an improvement of the above technical solution, the mass ratio of the modified mixed material to the PP-g-MAH particles is (0.03-0.1):1.

[0013] As an improvement of the above technical solution, the mass ratio of the modified chitosan particles to the modified cellulose is (1.1-3.2):(1-2.2).

[0014] As an improvement to the above technical solution, the preparation method of the modified chitosan microparticles comprises dissolving chitosan in an acetic acid solution with a mass fraction of 2-5% to form a uniform chitosan solution, then adding nano-titanium dioxide and a silane coupling agent, wherein the mass ratio of chitosan, nano-titanium dioxide and silane coupling agent is 1:0.1:0.08, stirring and reacting at 40-60°C for 2-4 hours, and after the reaction is completed, obtaining the modified chitosan microparticles by precipitation, washing and drying.

[0015] As an improvement to the above technical solution, the preparation method of the modified cellulose comprises mixing cellulose with a sodium hydroxide solution having a mass fraction of 10-15%, then adding acrylic acid and an initiator, wherein the mass ratio of cellulose, acrylic acid and initiator is 1:0.5:0.03, carrying out a graft copolymerization reaction at 50-70°C for 3-5 hours, then adding a crosslinking agent, wherein the amount of the crosslinking agent is 2% of the mass of the cellulose, and carrying out a crosslinking reaction at 60-80°C for 2-3 hours to form a modified cellulose having a three-dimensional network structure.

[0016] As an improvement of the above technical solution, in step S3, the working gas for the plasma treatment is a mixture of argon and oxygen with a volume ratio of 3:1 to 4:1; the processing power is 100 to 200 W, the processing time is 3 to 5 minutes, and the gas pressure is 20 to 50 Pa.

[0017] An application of the meltblown polypropylene material described above in the field of medicine and health.

[0018] Beneficial effects of the present invention:

[0019] The groups introduced by maleic anhydride grafting undergo an amidation reaction with modified chitosan, enhancing the compatibility between the components and evenly dispersing the modified chitosan particles and modified cellulose. The former captures tiny particles by adsorption, while the latter mechanically intercepts them through a three-dimensional network structure. Combined with the multi-level pores synergistically constructed by maleic anhydride and plasma, the probability of contact between particles and meltblown cloth is greatly increased.

[0020] Modified chitosan particles and modified cellulose form initial pores through steric hindrance and physical support. Maleic anhydride reduces surface tension, promotes bubble formation, and cross-links stabilize the pore structure. Plasma treatment further optimizes the pores. The three work together to create a structure with appropriately sized and evenly distributed pores, providing smooth channels for air circulation.

[0021] The amidation reaction between maleic anhydride and modified chitosan enhances interfacial bonding, making stress transfer more efficient when the material is subjected to external force, reducing the risk of cracks and damage at the interface. At the same time, the evenly dispersed modified chitosan particles and modified cellulose act as fillers and supports, sharing the stress of the polypropylene molecular chains and improving the overall breaking strength of the material. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] Example 1

[0024] S1: uniformly mixing the modified chitosan particles and the modified cellulose compounding agent to obtain a modified mixed material;

[0025] S2: PP particles, maleic anhydride, and initiator are melt-blended at 180° C. and twin-screw extruded to produce PP-g-MAH particles, wherein the mass ratio of maleic anhydride to PP particles is 1:100;

[0026] S3: The modified mixture and PP-g-MAH particles are uniformly mixed by ultrasonication to obtain a modified composite material, and then an initiator is added and the modified melt-blown polypropylene crude product is obtained by a twin-screw extruder;

[0027] S4, cooling and drying the crude modified melt-blown polypropylene obtained in step S3 to obtain a finished modified melt-blown polypropylene product;

[0028] S5: placing the modified melt-blown polypropylene finished product in a plasma treatment device, introducing a working gas, and performing plasma treatment. The working gas is a mixed gas of argon and oxygen with a volume ratio of 3 to 1; the processing power is 100 W, the processing time is 3 minutes, and the gas pressure is 20 Pa.

[0029] Example 2

[0030] S1: uniformly mixing the modified chitosan particles and the modified cellulose compounding agent to obtain a modified mixed material;

[0031] S2: PP particles, maleic anhydride, and an initiator were melt-blended at 190° C. and twin-screw extruded to produce PP-g-MAH particles. The mass ratio of maleic anhydride to PP particles was 3:100.

[0032] S3: The modified mixture and PP-g-MAH particles are uniformly mixed by ultrasonication to obtain a modified composite material, and then an initiator is added and the modified melt-blown polypropylene crude product is obtained by a twin-screw extruder;

[0033] S4, cooling and drying the crude modified melt-blown polypropylene obtained in step S3 to obtain a finished modified melt-blown polypropylene product;

[0034] S5: placing the modified melt-blown polypropylene finished product in a plasma treatment device, introducing a working gas, and performing plasma treatment. The working gas is a mixed gas of argon and oxygen with a volume ratio of 2 to 3; the processing power is 150W, the processing time is 4 minutes, and the gas pressure is 35Pa.

[0035] Example 3

[0036] S1: uniformly mixing the modified chitosan particles and the modified cellulose compounding agent to obtain a modified mixed material;

[0037] S2: PP particles, maleic anhydride, and an initiator are melt-blended at 200° C. and twin-screw extruded to produce PP-g-MAH particles, wherein the mass ratio of maleic anhydride to PP particles is 5:100;

[0038] S3: The modified mixture and PP-g-MAH particles are uniformly mixed by ultrasonication to obtain a modified composite material, and then an initiator is added and the modified melt-blown polypropylene crude product is obtained by a twin-screw extruder;

[0039] S4, cooling and drying the crude modified melt-blown polypropylene obtained in step S3 to obtain a finished modified melt-blown polypropylene product;

[0040] S5: placing the modified melt-blown polypropylene finished product in a plasma treatment device, introducing a working gas, and performing plasma treatment. The working gas is a mixed gas of argon and oxygen with a volume ratio of 1 to 4; the processing power is 200 W, the processing time is 5 minutes, and the gas pressure is 50 Pa.

[0041] Comparative Example 1

[0042] S1: uniformly mixing the modified chitosan particles and the modified cellulose compounding agent to obtain a modified mixed material;

[0043] S3: The modified mixture is uniformly mixed with PP particles by ultrasonic mixing to obtain a modified composite material, and then an initiator is added and the modified melt-blown polypropylene crude product is obtained by a twin-screw extruder;

[0044] S4, cooling and drying the crude modified melt-blown polypropylene obtained in step S3 to obtain a finished modified melt-blown polypropylene product;

[0045] S5: placing the modified melt-blown polypropylene finished product in a plasma treatment device, introducing a working gas, and performing plasma treatment. The working gas is a mixed gas of argon and oxygen with a volume ratio of 2 to 3; the processing power is 150W, the processing time is 4 minutes, and the gas pressure is 35Pa.

[0046] Comparative Example 2

[0047] S1: PP particles, maleic anhydride, and initiator were melt-blended at 190°C and twin-screw extruded to produce PP-g-MAH particles. The mass ratio of maleic anhydride to PP particles was 3:100.

[0048] S3: Add initiator to PP-g-MAH pellets and produce modified melt-blown polypropylene crude product through a twin-screw extruder;

[0049] S4, cooling and drying the crude modified melt-blown polypropylene obtained in step S3 to obtain a finished modified melt-blown polypropylene product;

[0050] S5: placing the modified melt-blown polypropylene finished product in a plasma treatment device, introducing a working gas, and performing plasma treatment. The working gas is a mixed gas of argon and oxygen with a volume ratio of 2 to 3; the processing power is 150 W, the processing time is 4 minutes, and the gas pressure is 35 Pa to obtain a modified melt-blown polypropylene material.

[0051] Among them, the preparation method of the modified chitosan microparticles comprises dissolving chitosan in an acetic acid solution with a mass fraction of 2-5% to form a uniform chitosan solution, then adding nano-titanium dioxide and a silane coupling agent, wherein the mass ratio of chitosan, nano-titanium dioxide and silane coupling agent is 1:0.1:0.08, stirring and reacting at 40-60°C for 2-4 hours, and after the reaction is completed, obtaining the modified chitosan microparticles by precipitation, washing and drying.

[0052] The modified cellulose preparation method comprises mixing cellulose with a sodium hydroxide solution having a mass fraction of 10-15%, then adding acrylic acid and an initiator in a mass ratio of cellulose, acrylic acid and initiator of 1:0.5:0.03, carrying out a graft copolymerization reaction at 50-70°C for 3-5 hours, then adding a crosslinking agent in an amount of 2% of the mass of the cellulose, and carrying out a crosslinking reaction at 60-80°C for 2-3 hours to form a modified cellulose with a three-dimensional network structure.

[0053] The meltblown polypropylenes of Examples 1 to 3 of the present application and Comparative Examples 1 to 2 were used to prepare meltblown fabrics for masks using a meltblown nonwoven fabric equipment, and the filtration efficiency, air resistance, and breaking strength of the meltblown fabrics were tested. The specific results are shown in Table 1 below.

[0054] Among them: the detection of filtration efficiency and air resistance is based on the method of GB / T32610-2016 "Technical Specifications for Daily Protective Masks", and the air resistance is based on the inhalation resistance test;

[0055] Breaking strength: tested according to GB / T24218.3-2010 standard, sample size: 50mm*300mm, tensile rate: 300mm / min.

[0056]

[0057] Table 1

[0058] It can be seen from Examples 1-3 and Comparative Examples 1-2 that the filtration efficiency of the melt-blown polypropylene of the present application is above 99%, the air resistance is less than 20 Pa, and the tensile strength is greater than 13 N. Maleic anhydride introduces a carboxylic acid group (-COOH) on the PP chain through a melt grafting reaction, thereby improving the interfacial binding force with the non-polar PP. The carboxylic acid group (-COOH) of PP-g-MAH undergoes an amidation reaction with the amino group (-NH2) of the modified chitosan to form a covalent bond, thereby improving the interfacial compatibility between the polypropylene and the modified chitosan particles and the modified cellulose. The modified chitosan particles capture tiny particles by adsorption, and the modified cellulose is mechanically intercepted by a three-dimensional network structure. At the same time, maleic anhydride and plasma cooperate to construct multi-level pores. The rich pore structure increases the contact probability between the particles and the melt-blown cloth, effectively improving the filtration efficiency. Polysaccharide particles and modified cellulose form initial pores through steric hindrance and physical support. Maleic anhydride reduces surface tension and promotes bubble formation, and stabilizes the pore structure with the help of cross-linking. Under the action of plasma, the pore structure is further optimized. This good pore structure provides a smooth channel for air circulation, reduces the obstruction of air passage, and thus reduces air resistance. The carboxylic acid groups introduced by maleic anhydride undergo amidation reaction with modified chitosan, which improves the interfacial bonding force between polypropylene and modified chitosan particles and modified cellulose. When the material is subjected to external force, the enhanced interfacial bonding force can more effectively transfer stress and avoid premature cracks and damage at the interface. At the same time, the modified chitosan particles and modified cellulose are evenly dispersed in the polypropylene matrix, playing a filling and supporting role, sharing the stress on the polypropylene molecular chain, and thereby improving the overall breaking strength of the material.

[0059] Based on Example 2 of the present application, the effect on the meltblown polypropylene of the present application was examined by adjusting the ratio of the modified mixture and PP-g-MAH particles.

[0060] Based on Example 2, Examples 4-8 were designed. Except for the addition of the modified mixed material and PP-g-MAH particles, the other components remained unchanged. The specific ratio of the modified mixed material to the PP-g-MAH particles is shown in

[0061] Table 2;

[0062]

[0063] Table 2

[0064] The modified meltblown polypropylene composite materials of Examples 4 to 7 of the present application were used to prepare meltblown fabrics for masks using a meltblown nonwoven fabric equipment, and the filtration efficiency, air resistance, and breaking strength of the meltblown fabrics were tested. The specific results are shown in Table 3 below.

[0065]

[0066] Table 3

[0067] It can be seen from Table 3 that as the addition amount of modified mixed materials increases from 0.03 to 0.1, the filtration efficiency and air resistance of the meltblown cloth show an upward trend and then a downward trend. The modified chitosan particles and modified cellulose components in the modified mixed materials construct a pore network in the meltblown polypropylene through steric hindrance and physical support. As the addition amount increases, the probability of particles contacting the meltblown cloth increases, and it is easier to be intercepted and adsorbed. However, when the addition amount is too high, the local structure of the material may be too dense, reducing the effective filtration area and resulting in a decrease in filtration efficiency. The increase in modified mixed materials increases the porosity of the meltblown cloth, makes the pore size distribution more reasonable, and reduces the air circulation resistance. The internal fiber network and particle gaps provide channels for air, promoting air penetration. When the addition amount is too high, agglomeration or structural disorder may occur inside the material, resulting in partial pore blockage or smaller pore size, and increased air resistance. Modified chitosan particles and modified cellulose are used as reinforcing phases and are evenly dispersed in the polypropylene matrix. They work together with the improved interfacial compatibility of PP-g-MAH to enhance the mechanical properties of the material, share the external force with the reinforcing phase, and effectively transfer stress with the polypropylene molecular chain through hydrogen bonds, physical entanglement, etc., thereby improving the breaking strength. When the addition amount is too high, the modified mixed material is unevenly dispersed, which is easy to form stress concentration points, and ultimately leads to a decrease in breaking strength.

[0068] Based on Example 5 of the present application, the ratio of the modified chitosan particles to the modified cellulose is adjusted to examine the effect of the modified mixed materials on the melt-blown polypropylene of the present application.

[0069] Based on Example 5, Examples 8-12 were designed. Except for the addition of the modified chitosan particles and modified cellulose, the other components and the preparation method remained unchanged. The specific ratios of the modified chitosan particles and modified cellulose are shown in Table 4.

[0070]

[0071] Table 4

[0072] The modified meltblown polypropylene composite materials of Examples 8 to 12 of the present application were used to prepare meltblown fabrics for masks using a meltblown nonwoven fabric equipment, and the filtration efficiency, air resistance, and breaking strength of the meltblown fabrics were tested. The specific results are shown in Table 5 below.

[0073]

[0074] Table 5

[0075] As can be seen from Table 5, when the ratio of the modified chitosan particles to the modified cellulose is (1.1-3.2):2, as the modified chitosan particles increase, the filtration efficiency, air resistance and breaking strength all show a trend of first increasing and then decreasing. For filtration efficiency: the modified chitosan particles adsorb tiny particles by virtue of surface active groups and electrostatic effects, and the modified cellulose mechanically intercepts through a three-dimensional network structure. The ratio of the two is moderate, and the adsorption and interception effects achieve optimal synergy. However, if the modified chitosan particles are too many, they are prone to agglomeration, reducing the effective adsorption sites. For air resistance, a moderate ratio of the two can form a uniform and well-connected pore network, and air can pass smoothly. When the ratio of the modified chitosan particles is too high, the particles agglomerate and block the pores, increasing the air circulation resistance. For breaking strength, the modified chitosan particles and modified cellulose, as reinforcing phases, need to form a good interface bond with the polypropylene matrix to effectively improve the breaking strength. The ratio of the two is coordinated, and the interface compatibility with the polypropylene matrix is optimal, which can evenly disperse stress.

[0076] When the ratio of the modified chitosan particles to the modified cellulose is 2:(1-2.2), as the modified cellulose content increases, the pore distribution between the fibers may become more uniform. As the content increases, agglomeration may occur, forming local dense areas and coarse pores. The former blocks the airflow, and the latter causes leakage. Excessive cellulose may cover the active sites (-NH2) of the chitosan, weakening the ability of electrostatic adsorption of particles. As for air resistance, as the modified cellulose content increases, the excessive cellulose causes the pores to be distorted and the airflow path to be extended, thereby causing The air resistance increases; as for the breaking strength, the interaction between the modified cellulose and the modified chitosan particles and the polypropylene matrix, as the modified cellulose content increases, the excess cellulose occupies the dispersion space of chitosan, reducing the bonding sites between chitosan and PP-g-MAH (the reaction of -COOH and -NH2 is reduced), and the cellulose agglomerates to form defects, which become the starting point of fracture. The ratio of chitosan (toughening) and cellulose (rigidity) is unbalanced, and the rigid-tough synergistic effect is weakened. When the material is subjected to external force, cracks and debonding are more likely to occur at the interface, resulting in a decrease in the overall breaking strength of the material.

[0077] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for plasma surface modification of meltblown polypropylene, characterized in that: The following steps are involved: S1: uniformly mixing the modified chitosan particles and the modified cellulose compounding agent to obtain a modified mixed material; S2: PP particles are melted with maleic anhydride and initiator at 180-200°C and twin-screw extruded to produce PP-g-MAH particles; S3: The modified mixture and PP-g-MAH particles are uniformly mixed by ultrasonication to obtain a modified composite material, and then an initiator is added and the modified melt-blown polypropylene crude product is obtained by a twin-screw extruder; S4, cooling and drying the crude modified melt-blown polypropylene obtained in step S3 to obtain a finished modified melt-blown polypropylene product; S5: placing the modified melt-blown polypropylene finished product in a plasma treatment device, introducing working gas, and performing plasma treatment.

2. The plasma surface modification method for meltblown polypropylene according to claim 1, characterized in that: The mass ratio of the maleic anhydride to the PP particles is (1-5):

100.

3. The plasma surface modification method for meltblown polypropylene according to claim 1, characterized in that: The mass ratio of the modified mixed material to the PP-g-MAH particles is (0.03-0.1):

1.

4. The plasma surface modification method for meltblown polypropylene according to claim 1, characterized in that: The mass ratio of the modified chitosan particles to the modified cellulose is (1.1-3.2):(1-2.2).

5. The plasma surface modification method for meltblown polypropylene according to claim 1, characterized in that: The preparation method of the modified chitosan microparticles comprises dissolving chitosan in an acetic acid solution with a mass fraction of 2-5% to form a uniform chitosan solution, then adding nano-titanium dioxide and a silane coupling agent in a mass ratio of chitosan, nano-titanium dioxide and silane coupling agent of 1:0.1:0.08, stirring and reacting at 40-60°C for 2-4 hours, and after the reaction is completed, obtaining the modified chitosan microparticles through precipitation, washing and drying.

6. The plasma surface modification method for meltblown polypropylene according to claim 1, characterized in that: The modified cellulose preparation method comprises mixing cellulose with a sodium hydroxide solution having a mass fraction of 10-15% to swell the cellulose, then adding acrylic acid and an initiator in a mass ratio of 1:0.5:0.03, carrying out a graft copolymerization reaction at 50-70°C for 3-5 hours, then adding a crosslinking agent in an amount of 2% of the mass of the cellulose, and carrying out a crosslinking reaction at 60-80°C for 2-3 hours to form a modified cellulose with a three-dimensional network structure.

7. The plasma surface modification method for meltblown polypropylene according to claim 1, characterized in that: In step S3 , the working gas for the plasma treatment is a mixture of argon and oxygen with a volume ratio of 3:1 to 4:1; the treatment power is 100 to 200 W, the treatment time is 3 to 5 minutes, and the gas pressure is 20 to 50 Pa.

8. Use of the melt-blown polypropylene material according to any one of claims 1 to 7 in the field of medicine and health.

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