Anti-aging polypropylene particles for outdoor planting pot production and preparation method of anti-aging polypropylene particles

Abstract

The invention relates to an anti-aging polypropylene particle for outdoor planting pot production and a preparation method thereof, and belongs to the technical field of high polymer materials. The formula of the anti-aging polypropylene particles comprises the following components in parts by weight: 80-90 parts of polypropylene, 3-5 parts of a composite anti-aging agent, 1-2 parts of a stabilizer, 4-6 parts of a flexibilizer, 1-2 parts of a silane coupling agent and 0.5-0.8 part of a lubricant. Wherein the composite anti-aging agent is constructed through a three-step process, firstly, lignin is subjected to alkaline activation to form phenol oxygen anion active sites, secondly, bis (3-aminopropyl) phenylphosphine is subjected to covalent binding to construct a free radical capture network, then tetraethoxysilane is subjected to in-situ hydrolysis, and a silicon dioxide physical barrier is compounded on the surface; the polypropylene particles prepared by the invention have good aging resistance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to an aging-resistant polypropylene particle for the production of outdoor planting pots and its preparation method. Background Technology

[0002] Polypropylene (PP) is widely used in the production of outdoor planting pots due to its low cost, good processing performance, and non-toxicity. However, traditional polypropylene materials are prone to molecular chain breakage when exposed to complex outdoor environments such as ultraviolet radiation, high temperature, and high humidity for extended periods. This leads to brittleness, fading, reduced strength, and a significantly shortened lifespan. While some anti-aging polypropylene materials exist, most suffer from limitations such as single function, high dosage requirements, and insufficient long-term effectiveness, making it difficult to meet the stringent comprehensive performance requirements of outdoor planting pots.

[0003] Current anti-aging technologies on the market have the following limitations: First, ordinary antioxidants and UV absorbers gradually deplete and become ineffective over long-term use, failing to provide lasting protection. Second, while high levels of inorganic fillers can improve weather resistance, they severely impair the material's processing fluidity and impact toughness. Third, single modification methods are insufficient to simultaneously resist the synergistic effects of multiple aging factors such as UV radiation, thermo-oxidative aging, and microbial erosion. For example, conventional anti-aging polypropylene exhibits significant embrittlement and cracking after 1-2 years of outdoor use, leading to sudden breakage of planting pots and causing losses for users.

[0004] Therefore, there is an urgent need to develop an aging-resistant polypropylene granule for the production of outdoor planting pots and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide an aging-resistant polypropylene granule for the production of outdoor planting pots and its preparation method, which has the characteristics of good aging resistance.

[0006] The objective of this invention can be achieved through the following technical solutions: An aging-resistant polypropylene granule for the production of outdoor planting pots, wherein the formulation of the aging-resistant polypropylene granule is as follows, by weight: 80-90 parts polypropylene, 3-5 parts composite anti-aging agent, 1-2 parts stabilizer, 4-6 parts toughening agent, 1-2 parts silane coupling agent, and 0.5-0.8 parts lubricant. The preparation method of the composite anti-aging agent is as follows: S1-1: Add lignin to a 1 mol / L NaOH solution to make the solid-liquid mass ratio 1:(20-30), sonicate for 1-2 h, wash with deionized water and dry to obtain pretreated lignin; S1-2: The pretreated lignin and bis(3-aminopropyl)phenylphosphine were mixed and added to N-methylpyrrolidone, followed by the addition of pyridine. The mixture was stirred for 4-5 h under nitrogen protection and the temperature was controlled at 80-90 °C. The mixture was washed with ethanol and deionized water and then vacuum dried at 80 °C for 12 h to obtain the modified lignin. S1-3: Modified lignin is added to 30-40% ethanol to make a solid-liquid mass ratio of 1:(20-30), tetraethyl orthosilicate is added, and the mixture is ultrasonically dispersed for 30-60 min. Then, 1 M hydrochloric acid is added dropwise until the pH reaches 4.5-5.5. The mixture is reacted at 60-80 °C for 4-6 h, then aged for 10-12 h, washed with deionized water, and freeze-dried at -40--50 °C for 20-24 h to obtain the composite anti-aging agent.

[0007] As a preferred embodiment of the present invention, the toughening agent is one or both of ethylene-octene copolymer and styrene-butadiene-styrene block copolymer.

[0008] As a preferred embodiment of the present invention, the stabilizer is one or both of UV-531 and UV-326.

[0009] As a preferred embodiment of the present invention, the lubricant is zinc stearate.

[0010] As a preferred embodiment of the present invention, the mass ratio of pretreated lignin to bis(3-aminopropyl)phenylphosphine in S1-2 is (3-4):1.

[0011] As a preferred embodiment of the present invention, the amount of pyridine used in S1-2 is 5-8% of the lignin content.

[0012] As a preferred embodiment of the present invention, the amount of tetraethyl orthosilicate added in S1-3 is 5-10% of the modified lignin quality.

[0013] A method for preparing aging-resistant polypropylene granules for outdoor planting pot production, the specific steps of which are as follows. S8-1: Add polypropylene, composite anti-aging agent, stabilizer, toughening agent, silane coupling agent and lubricant to a high-speed mixer and mix for 5-10 minutes to obtain a premix; S8-2: The premixed material is added to a twin-screw extruder for melt dispersion. The screw speed is 200-300 rpm and the feeding speed is 10-15 kg / h. The material is then extruded and granulated to obtain the aging-resistant polypropylene granules.

[0014] As a preferred embodiment of the present invention, the premixing speed in S8-1 is 500-600 rpm.

[0015] As a preferred technical solution of the present invention, the processing temperatures of each zone in the twin-screw extruder of S8-2 are 180-190 ℃ in zone 1, 200-210 ℃ in zone 2, 210-220 ℃ in zone 3, 205-215 ℃ in zone 4, and 195-205 ℃ in zone 5.

[0016] Lignin pretreatment induces the deprotonation of phenolic hydroxyl groups in an alkaline environment, forming phenolic anion active sites and significantly enhancing surface reactivity. The polar aprotic solvent N-methylpyrrolidone is selected, exhibiting good solubility for both lignin and bis(3-aminopropyl)phenylphosphine, and possessing a high boiling point. The solvent polarity matches the reaction requirements, preventing phase separation. Pyridine, as an alkaline catalyst, lowers the activation energy of the dehydrogenation condensation reaction by forming hydrogen bonds with phenolic anions, promoting covalent bonding between phosphine groups and lignin. The reaction temperature is set above the glass transition temperature of lignin to enhance molecular chain mobility and improve reaction efficiency; nitrogen protection inhibits lignin oxidative degradation, ensuring reaction selectivity.

[0017] Bis(3-aminopropyl)phenylphosphine efficiently captures hydroxyl radicals generated during polypropylene degradation through electron transfer via phosphine groups, blocking the photo-oxidation chain reaction. The inherent conjugated carbonyl groups and aromatic structures of lignin absorb ultraviolet light from 280 to 400 nm, reducing polypropylene main chain breakage. The two components, covalently bonded, form a radical-capturing and ultraviolet-shielding dual-function system, significantly improving anti-aging performance compared to single components. After bonding, the lignin particle size decreases and forms a uniform network structure within the polypropylene matrix, enhancing interfacial interaction strength, effectively transferring stress, and inhibiting crack propagation. Furthermore, the rigid filler effect of lignin refines the spherulite size of polypropylene, simultaneously improving tensile strength and flexural modulus. Meanwhile, the polar groups of amino and phosphine do not significantly sacrifice impact strength, achieving a balance between rigidity and toughness. Lignin, derived from plant fibers, is renewable and low-cost, replacing some petroleum-based anti-aging agents; lignin refines polypropylene grains, improving tensile strength and flexural modulus; the introduction of amino and phosphine groups does not significantly reduce the impact strength of polypropylene, balancing rigidity and toughness.

[0018] Ethyl orthosilicate hydrolyzes and forms silica on the surface of modified lignin. Silica acts as a physical barrier, blocking the penetration of ultraviolet light, oxygen, and heat, thus delaying the aging of polypropylene. The composite structure significantly improves aging resistance through the synergistic effect of the photostability of lignin and the thermal stability of silica.

[0019] The beneficial effects of this invention are: This invention utilizes an alkaline environment to deprotonate the phenolic hydroxyl groups of lignin, forming highly active phenolic anions. In N-methylpyrrolidone, pyridine catalyzes the reduction of the phosphine reaction energy barrier, constructing a covalently bonded free radical trapping network. The conjugated structure of lignin absorbs ultraviolet light, synergistically blocking full-band photoaging with the silica generated in situ on the surface, while simultaneously improving thermal stability. The composite can refine polypropylene spherulites, improving tensile strength and flexural modulus, while the amino-phosphine flexible chain maintains impact strength, achieving a balance between rigidity and toughness. Replacing petroleum-based anti-aging agents with renewable lignin has significant environmental and economic advantages. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0021] In the embodiments and comparative examples of this invention: Polypropylene: purchased from Beijing Huawirui Chemical Technology Co., Ltd., melt index 12; Lignin: Purchased from Wuhan Xinxinjiali Biotechnology Co., Ltd.; Bis(3-aminopropyl)phenylphosphine: purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; Pyridine: Purchased from Shandong Minghua New Materials Co., Ltd.; N-Methylpyrrolidone: Purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd.; Ethyl orthosilicate: purchased from Shanghai Zhuorui Chemical Co., Ltd.; Zinc stearate: purchased from Shandong Huishengtang Biomedical Co., Ltd.; Ethylene-octene copolymer (POE): purchased from Hangzhou Jieheng Chemical Co., Ltd. Styrene-butadiene-styrene block copolymer (SBS): purchased from Shanghai Better Chemical Co., Ltd. UV-531: Purchased from Fujian Disheng Technology Co., Ltd.; UV-326: Purchased from Tianjin Lianlong New Materials Co., Ltd.; Silane coupling agent KH550: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0022] Example 1

[0023] An aging-resistant polypropylene granule for the production of outdoor planting pots, wherein the formulation of the aging-resistant polypropylene granule is as follows (by weight): 85 parts polypropylene, 4 parts composite anti-aging agent, 1.5 parts UV-531, 5 parts ethylene-octene copolymer (POE), 1.5 parts silane coupling agent KH550, and 0.6 parts zinc stearate. The preparation method of the composite anti-aging agent is as follows: S1-1: Lignin was added to a 1 mol / L NaOH solution to make the solid-liquid mass ratio 1:25, ultrasonically treated for 1.5 h, washed with deionized water and dried to obtain pretreated lignin; S1-2: Pretreated lignin and bis(3-aminopropyl)phenylphosphine were mixed at a mass ratio of 3.5:1 and added to N-methylpyrrolidone. Then, pyridine at 6% of the mass of lignin was added. The mixture was stirred for 4.5 h under nitrogen protection and the temperature was controlled at 85 °C. The mixture was washed with ethanol and deionized water and then vacuum dried at 80 °C for 12 h to obtain the modified lignin. S1-3: Modified lignin was added to 35% ethanol to make a solid-liquid mass ratio of 1:25. 7% tetraethyl orthosilicate of the modified lignin was added, and the mixture was ultrasonically dispersed for 45 min. Then, 1 M hydrochloric acid was added dropwise until the pH reached 5. The mixture was reacted at 70 °C for 5 h, then aged for 11 h, washed with deionized water, and freeze-dried at -45 °C for 22 h to obtain the composite anti-aging agent.

[0024] A method for preparing aging-resistant polypropylene granules for outdoor planting pot production, the specific steps of which are as follows. S8-1: Add polypropylene, composite anti-aging agent, stabilizer, toughening agent, silane coupling agent and lubricant to a high-speed mixer and mix for 7 min at a premixing speed of 550 rpm to obtain a premix. S8-2: The premixed material is added to a twin-screw extruder for melt dispersion. The processing temperatures of each zone in the twin-screw extruder are 185 ℃ in zone 1, 205 ℃ in zone 2, 215 ℃ in zone 3, 210 ℃ in zone 4 and 200 ℃ in zone 5. The screw speed is 250 rpm and the feeding speed is 12 kg / h. The material is extruded and granulated to obtain the aging-resistant polypropylene granules.

[0025] Example 2

[0026] An aging-resistant polypropylene granule for the production of outdoor planting pots, wherein the formulation of the aging-resistant polypropylene granule is as follows (by weight): 80 parts polypropylene, 3 parts composite anti-aging agent, 1 part UV-326, 4 parts styrene-butadiene-styrene block copolymer (SBS), 1 part silane coupling agent (KH550), and 0.5 parts zinc stearate. The preparation method of the composite anti-aging agent is as follows: S1-1: Lignin was added to a 1 mol / L NaOH solution to make the solid-liquid mass ratio 1:20, ultrasonically treated for 1 h, washed with deionized water and dried to obtain pretreated lignin; S1-2: Pretreated lignin and bis(3-aminopropyl)phenylphosphine were mixed at a mass ratio of 3:1 and added to N-methylpyrrolidone. Then, 5% of the mass of lignin was added with pyridine. The mixture was stirred for 4 h under nitrogen protection and the temperature was controlled at 80 °C. The mixture was washed with ethanol and deionized water and then vacuum dried at 80 °C for 12 h to obtain the modified lignin. S1-3: Modified lignin was added to 30% ethanol to make a solid-liquid mass ratio of 1:20. 5% tetraethyl orthosilicate of the modified lignin was added, and the mixture was ultrasonically dispersed for 30 min. Then, 1 M hydrochloric acid was added dropwise until the pH reached 4.5. The mixture was reacted at 60 °C for 4 h, then aged for 10 h, washed with deionized water, and freeze-dried at -40 °C for 20 h to obtain the composite anti-aging agent.

[0027] A method for preparing aging-resistant polypropylene granules for outdoor planting pot production, the specific steps of which are as follows. S8-1: Add polypropylene, composite anti-aging agent, stabilizer, toughening agent, silane coupling agent and lubricant to a high-speed mixer and mix for 5 min at a premixing speed of 500 rpm to obtain a premix. S8-2: The premixed material is added to a twin-screw extruder for melt dispersion. The processing temperatures of each zone in the twin-screw extruder are 180 ℃ in zone 1, 200 ℃ in zone 2, 210 ℃ in zone 3, 205 ℃ in zone 4 and 195 ℃ in zone 5. The screw speed is 200 rpm and the feeding speed is 10 kg / h. The material is extruded and granulated to obtain the aging-resistant polypropylene granules.

[0028] Example 3

[0029] An aging-resistant polypropylene granule for the production of outdoor planting pots, wherein the formulation of the aging-resistant polypropylene granule is as follows (by weight): 90 parts polypropylene, 5 parts composite anti-aging agent, 2 parts UV-531, 6 parts ethylene-octene copolymer (POE), 2 parts silane coupling agent KH550, and 0.8 parts zinc stearate. The preparation method of the composite anti-aging agent is as follows: S1-1: Lignin was added to a 1 mol / L NaOH solution to make the solid-liquid mass ratio 1:30, ultrasonically treated for 2 h, washed with deionized water and dried to obtain pretreated lignin; S1-2: Pretreated lignin and bis(3-aminopropyl)phenylphosphine were mixed at a mass ratio of 4:1 and added to N-methylpyrrolidone. Then, pyridine (8% by mass of lignin) was added. The mixture was stirred for 5 h under nitrogen protection and the temperature was controlled at 90 °C. The mixture was washed with ethanol and deionized water and then vacuum dried at 80 °C for 12 h to obtain the modified lignin. S1-3: Modified lignin was added to 40% ethanol to make a solid-liquid mass ratio of 1:30. 10% of the mass of modified lignin was added to tetraethyl orthosilicate, and the mixture was ultrasonically dispersed for 60 min. Then, 1 M hydrochloric acid was added dropwise until the pH reached 5.5. The mixture was reacted at 80 °C for 6 h, then aged for 12 h, washed with deionized water, and freeze-dried at -50 °C for 24 h to obtain the composite anti-aging agent.

[0030] A method for preparing aging-resistant polypropylene granules for outdoor planting pot production, the specific steps of which are as follows. S8-1: Add polypropylene, composite anti-aging agent, stabilizer, toughening agent, silane coupling agent and lubricant to a high-speed mixer and mix for 10 min at a premixing speed of 600 rpm to obtain a premix. S8-2: The premixed material is added to a twin-screw extruder for melt dispersion. The processing temperatures of each zone in the twin-screw extruder are 190 ℃ in zone 1, 210 ℃ in zone 2, 220 ℃ in zone 3, 215 ℃ in zone 4 and 205 ℃ in zone 5. The screw speed is 300 rpm and the feeding speed is 15 kg / h. The material is extruded and granulated to obtain the aging-resistant polypropylene granules.

[0031] Comparative Example 1 In the preparation of the composite anti-aging agent, no lignin pretreatment is performed, and the remaining steps are the same as in Example 1.

[0032] Comparative Example 2 The preparation of the composite anti-aging agent does not involve the addition of bis(3-aminopropyl)phenylphosphine, and the remaining steps are the same as in Example 1.

[0033] Comparative Example 3 In the preparation of the composite anti-aging agent, tetraethyl orthosilicate is not added, and the remaining steps are the same as in Example 1.

[0034] Comparative Example 4 The preparation of the composite anti-aging agent does not involve step S1-2; the remaining steps are the same as in Example 1.

[0035] Comparative Example 5 Without adding a compound anti-aging agent, the remaining steps are the same as in Example 1.

[0036] Performance testing The modified polypropylene particles obtained in the examples and comparative examples were made into 80×10×4mm samples and aged at 65 ℃ and 340 nm light for 1000 h. The tensile strength, flexural modulus and cantilever beam notched impact strength of the materials before and after aging were measured.

[0037] Tensile strength was determined according to test standard ISO 527-2-2012 at a tensile speed of 50 mm / min. Flexural modulus was determined according to test standard ISO 178-2010 at a bending speed of 2 mm / min and a span of 64 mm. Notched impact strength of the cantilever beam was determined according to test standard ISO 180.

[0038] Performance change rate % = (Performance before aging - Performance after aging) / Performance before aging × 100% The experimental results are summarized in the table below.

[0039] Group Change rate of tensile strength before and after aging (%) Change rate of flexural modulus before and after aging (%) Change rate of notched impact strength of cantilever beam before and after aging (%) Example 1 5.6 6.2 8.5 Example 2 6.1 7.7 8.9 Example 3 5.9 7.3 8.5 Comparative Example 1 18.6 19.4 25.4 Comparative Example 2 23.1 23.8 30.1 Comparative Example 3 19.3 20.5 27.3 Comparative Example 4 28.5 29.1 34.8 Comparative Example 5 32.0 33.7 39.7 As can be seen from the examples and comparative data, the polypropylene material prepared by the method of the present invention has good aging resistance.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the scope of the present invention.

Claims

1. An aging-resistant polypropylene granule for the production of outdoor planting pots, characterized in that, The formulation of the aging-resistant polypropylene granules is as follows, by weight: 80-90 parts polypropylene, 3-5 parts composite anti-aging agent, 1-2 parts stabilizer, 4-6 parts toughening agent, 1-2 parts silane coupling agent, and 0.5-0.8 parts lubricant. The preparation method of the composite anti-aging agent is as follows: S1-1: Add lignin to a 1 mol / L NaOH solution to make the solid-liquid mass ratio 1:(20-30), sonicate for 1-2 h, wash with deionized water and dry to obtain pretreated lignin; S1-2: The pretreated lignin and bis(3-aminopropyl)phenylphosphine were mixed and added to N-methylpyrrolidone, followed by the addition of pyridine. The mixture was stirred for 4-5 h under nitrogen protection and the temperature was controlled at 80-90 °C. The mixture was washed with ethanol and deionized water and then vacuum dried at 80 °C for 12 h to obtain the modified lignin. S1-3: Modified lignin is added to 30-40% ethanol to make a solid-liquid mass ratio of 1:(20-30), tetraethyl orthosilicate is added, and the mixture is ultrasonically dispersed for 30-60 min. Then, 1 M hydrochloric acid is added dropwise until the pH reaches 4.5-5.

5. The mixture is reacted at 60-80 °C for 4-6 h, then aged for 10-12 h, washed with deionized water, and freeze-dried at -40--50 °C for 20-24 h to obtain the composite anti-aging agent.

2. The aging-resistant polypropylene granules for outdoor planting pot production according to claim 1, characterized in that, The toughening agent is one or both of ethylene-octene copolymer and styrene-butadiene-styrene block copolymer.

3. The aging-resistant polypropylene granules for outdoor planting pot production according to claim 1, characterized in that, The stabilizer is one or both of UV-531 and UV-326.

4. The aging-resistant polypropylene granules for outdoor planting pot production according to claim 1, characterized in that, The lubricant is zinc stearate.

5. The aging-resistant polypropylene granules for outdoor planting pot production according to claim 1, characterized in that, The mass ratio of pretreated lignin to bis(3-aminopropyl)phenylphosphine in S1-2 is (3-4):

1.

6. The aging-resistant polypropylene granules for outdoor planting pot production according to claim 1, characterized in that, The amount of pyridine used in S1-2 is 5-8% of the lignin content.

7. The aging-resistant polypropylene granules for outdoor planting pot production according to claim 1, characterized in that, The amount of tetraethyl orthosilicate added in S1-3 is 5-10% of the modified lignin quality.

8. A method for preparing aging-resistant polypropylene granules for outdoor planting pot production as described in any one of claims 1 to 7, characterized in that, The specific steps of the preparation method are as follows: S8-1: Add polypropylene, composite anti-aging agent, stabilizer, toughening agent, silane coupling agent and lubricant to a high-speed mixer and mix for 5-10 minutes to obtain a premix; S8-2: The premixed material is added to a twin-screw extruder for melt dispersion. The screw speed is 200-300 rpm and the feeding speed is 10-15 kg / h. The material is then extruded and granulated to obtain the aging-resistant polypropylene granules.

9. The method for preparing aging-resistant polypropylene granules for outdoor planting pot production according to claim 8, characterized in that, The premixing speed in S8-1 is 500-600 rpm.

10. The method for preparing aging-resistant polypropylene granules for outdoor planting pot production according to claim 8, characterized in that, The processing temperatures of each zone in the twin-screw extruder of the S8-2 are as follows: Zone 1: 180–190 ℃, Zone 2: 200–210 ℃, Zone 3: 210–220 ℃, Zone 4: 205–215 ℃, and Zone 5: 195–205 ℃.