Glass fiber reinforced PA double 6 composite material and preparation method thereof

Abstract

The invention discloses a glass fiber reinforced PAdou-6 composite material and a preparation method thereof, belongs to the technical field of PAdou-6 processing, and is used for solving the technical problem that the flame retardant property and the mechanical property of the PAdou-6 composite material in the prior art need to be further improved. The composite material is prepared from the following raw materials in parts by weight: 60-70 parts of PA bis6, 15-20 parts of a modified flame retardant, 20-22 parts of modified glass fibers, 8-10 parts of a modified flexibilizer and 7-10 parts of an auxiliary additive, according to the glass fiber reinforced PAdou-6 composite material prepared by the invention, the PAdou-6 is taken as a matrix, the modified flame retardant, the modified glass fiber and the modified toughening agent are taken as reinforcing materials, and the auxiliary additive is taken as an auxiliary agent, so that the flame retardant property of the PAdou-6 composite material is improved, and the mechanical property of the PAdou-6 composite material is also improved.

Description

Technical Field

[0001] The invention relates to the technical field of PA double 6 composite material processing, and in particular to a glass fiber reinforced PA double 6 composite material and a preparation method thereof. Background Art

[0002] In recent years, polymer materials have become important basic materials for human beings and have an important position in many fields. Broadly speaking, polymer materials are mainly divided into five categories: fiber, plastic, rubber, coating and adhesive. From the manufacture of space shuttles to a piece of clothing, our lives have long been inseparable from polymer materials. Glass fiber reinforced PA double 6 composite material is a composite material with excellent mechanical properties. It is widely used in automobiles, electronics, electrical and industrial fields. The introduction of glass fiber can improve the tensile strength and impact resistance of PA66, but PA double 6 itself is a high-performance polyamide polymerized from adipic acid and hexamethylenediamine. Its molecular chain contains amide groups. The amide bonds are easily broken at high temperatures to generate flammable gases, resulting in insufficient flame retardant properties of glass fiber reinforced PA double 6 composite materials. Although the introduction of glass fiber effectively improves the strength of PA66, the interface bonding force between the glass fiber and the polyamide matrix is ​​limited, especially in high humidity or high temperature environments. The interface bonding force may decrease, resulting in unstable mechanical properties of the composite material, and it is prone to deformation or rupture when subjected to high loads or long-term use.

[0003] PA66 is a highly hydrophilic polyamide material with polar amide groups, while glass fiber is an inorganic material with low surface energy and polarity. The difference between this hydrophilicity and the non-polar surface of glass fiber leads to weak interfacial bonding between the two. In order to improve its interfacial stability, a cross-linking agent is added. However, since the main molecular chain of PA66 is composed of alternating amide bonds and methylene chains, the amide bonds are easily broken at high temperatures and flammable gases are easily generated. By adding flame retardants to improve its flame retardancy, the mechanical properties of PA66 are often reduced due to the poor compatibility of flame retardants with the substrate, and The molecular chain of PA double 6 is composed of alternating rigid amide bonds and flexible methylene chains, showing low toughness. The amide bonds have polarity and hydrogen bonding effects, which make the interaction force between the molecular chains strong, resulting in high rigidity and high brittleness of the material. When impacted, the rigid molecular chain is difficult to absorb energy through deformation and is prone to brittle fracture. Glass fiber is composed of silicate, and its molecular structure is relatively rigid. It lacks the plasticity or ductility like metals or polymers and the molecular chain slip mechanism that can effectively absorb impact energy. Therefore, when subjected to large external forces, glass fiber reinforced PA double 6 composite materials are prone to brittle fracture.

[0004] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0005] The object of the present invention is to provide a glass fiber reinforced PA double 6 composite material and a preparation method thereof, so as to solve the technical problem that the flame retardant properties and mechanical properties of the PA double 6 composite material in the prior art need to be further improved.

[0006] The object of the present invention can be achieved by the following technical scheme: A glass fiber reinforced PA double 6 composite material, comprising the following raw materials in parts by weight: 60-70 parts of PA double 6, 15-20 parts of modified flame retardant, 20-22 parts of modified glass fiber, 8-10 parts of modified toughening agent, and 7-10 parts of auxiliary additives;

[0007] The modified flame retardant is prepared by the following steps:

[0008] A1. Place itaconic acid, diethylenetriamine and N,N-dimethylformamide in a reactor protected by a nitrogen atmosphere, heat to 80-90°C, keep warm for 40-60 minutes, add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and azobisisobutyronitrile, keep warm for 2-3 hours, and post-treat to obtain a modified flame retardant precursor;

[0009] The preparation reaction formula of the modified flame retardant precursor is:

[0010]

[0011] The preparation reaction principle of the modified flame retardant precursor is:

[0012] During the reaction, under the action of high temperature and catalyst, itaconic acid and diethylenetriamine undergo condensation reaction to generate amide. The PH bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide has high activity and undergoes addition reaction with the double bond in itaconic acid to obtain a modified flame retardant precursor.

[0013] A2. Calcium hydroxide, modified flame retardant precursor, deionized water and toluene are placed in a reaction kettle, the temperature is raised to 75-85°C, the reaction is kept warm for 2-3 hours, and the modified flame retardant is obtained by post-treatment.

[0014] The preparation reaction formula of the modified flame retardant is:

[0015]

[0016] The preparation reaction principle of modified flame retardant is:

[0017] During the reaction, the hydroxide ions in calcium hydroxide combine with the carboxyl hydrogen ions in the modified flame retardant precursor to form water molecules and leave. - With Ca 2+ Combined to obtain a modified flame retardant.

[0018] Further, the amount ratio of itaconic acid, diethylenetriamine, N,N-dimethylformamide, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and azobisisobutyronitrile in step A1 is 300-350g:120-130g:2000-3000mL:200-220g:15-20g, and the post-treatment step comprises: after the reaction is completed, the reaction solution is cooled to room temperature, filtered, ethyl acetate is added to the filtrate, washed 1-2 times, and the organic phase is transferred to a rotary evaporator at a temperature of 40-50°C. In the fermenter, rotary evaporation is performed until no liquid is extracted to obtain a modified flame retardant precursor; in step A2, the amount ratio of the calcium hydroxide, the modified flame retardant precursor and toluene is 40-50g:350-400g:800-100mL:3000-3500mL, and the post-treatment step includes: after the reaction is completed, the reaction liquid is cooled to room temperature, filtered, the filtrate is ice-bathed for 1-2h, the filtrate after crystallization is filtered, the filter cake is washed with ethanol 1-2 times, and transferred to a drying oven at a temperature of 60-70°C, and dried to constant weight to obtain a modified flame retardant.

[0019] Furthermore, the modified glass fiber is obtained by the following preparation method:

[0020] B1. Place ethanol solution, KH-550 and microporous calcium silicate in a reaction kettle and perform ultrasonic treatment for 30-60 minutes to obtain a modified solution;

[0021] B2. Immerse the glass fiber in the modifying liquid and dry it to obtain modified glass fiber.

[0022] The preparation reaction principle of modified glass fiber is:

[0023] During the reaction, the silicon-oxygen bonds of KH-550 are hydrolyzed into silanols in an ethanol solution, and the alcoholic hydroxyl groups undergo condensation reactions with the microporous sodium silicate and the hydroxyl groups on the surface of the glass fiber to obtain modified glass fibers modified with a silane coupling agent.

[0024] Furthermore, in step B1, the ethanol solution is composed of ethanol and pure water in a volume ratio of 90-95:5-10, and the dosage ratio of the ethanol solution, KH-550 and microporous calcium silicate is 1000-1200mL:12-15g:8-10g; in step B2, the impregnation operation steps are: dipping the glass fiber in the modified solution twice and rolling it twice, the bath ratio is 1:25-30, and the impregnation rate is 90-100%.

[0025] Furthermore, the modified toughening agent is obtained by the following preparation method:

[0026] C1. Place octamethyltetrasiloxane, tetrabutyl orthosilicate, tetramethyltetravinylcyclotetrasiloxane, sodium dodecylbenzenesulfonate and deionized water in a reaction kettle, perform ultrasonic dispersion for 10-15 minutes, heat to 80-90°C, add sulfuric acid solution, and keep the temperature for reaction for 5-6 hours to obtain intermediate I;

[0027] The preparation reaction principle of intermediate Ⅰ is:

[0028] During the reaction, under the catalysis of sulfuric acid solution, the siloxy groups in the molecules of octamethyltetrasiloxane, tetrabutyl orthosilicate, and tetramethyltetravinylcyclotetrasiloxane undergo hydrolysis reaction to generate silanols, and the silanols further undergo condensation reaction to prepare a three-dimensional polysiloxane with unsaturated olefin double bonds. Under the emulsification effect of sodium dodecylbenzene sulfonate, a seed emulsion intermediate I is obtained.

[0029] C2. Place intermediate I, butyl methacrylate, butyl dimethacrylate, sodium dodecylbenzene sulfonate and deionized water in a reactor protected by a nitrogen atmosphere, stir for 10-12 minutes, add potassium persulfate solution, heat to 60-70°C, keep warm for 4-5 hours, and post-treat to obtain a modified toughening agent.

[0030] The preparation reaction principle of the modified toughening agent is:

[0031] During the reaction, under the catalysis of potassium persulfate solution, the crosslinking agent butyl dimethacrylate and the olefin double bond in the intermediate I molecule undergo free radical polymerization, and the olefin double bond in butyl methacrylate further undergoes free radical polymerization with the other end olefin double bond of the crosslinking agent butyl dimethacrylate to obtain a shell structure, and finally a modified toughening agent with a core-shell structure is obtained.

[0032] Further, in step C1, the concentration of the sulfuric acid solution is 95-98wt%, and the amount ratio of octamethyltetrasiloxane, tetrabutyl orthosilicate, tetramethyltetravinylcyclotetrasiloxane, sodium dodecylbenzenesulfonate, deionized water and sulfuric acid solution is 100-120g:50-60g:20-30g:10-12g:1500-2000mL:50-60mL; in step C2, the potassium persulfate solution is composed of potassium persulfate and pure water in a volume ratio of 5:1, the intermediate I, methyl The dosage ratio of butyl acrylate, butyl dimethacrylate, sodium dodecylbenzene sulfonate, deionized water and potassium persulfate solution is 100-200g:400-500g:50-70g:20-25g:3000-3500mL:10-12g. The post-treatment step comprises: after the reaction is completed, the reaction liquid is cooled to room temperature, filtered, the filter cake is washed with deionized water for 1-2 times, the filter cake is transferred to a drying oven with a temperature of 50-60°C, dried to constant weight, ground, and passed through an 80-mesh sieve to obtain a modified toughening agent.

[0033] Furthermore, a method for preparing a glass fiber reinforced PA double 6 composite material comprises the following steps:

[0034] S1, adding the modified glass fiber to the untwisting and width-opening machine, untwisting and dispersing, and obtaining a modified glass fiber dispersion;

[0035] S2. Evenly mix PA 6, modified flame retardant, modified toughening agent and auxiliary additives, add them into a twin-screw extruder for melt extrusion, add modified glass fiber dispersion from the first exhaust port, melt blend, stretch and water-cool the material strips, and then pelletize them to obtain a PA 6 composite material.

[0036] Furthermore, in step S2, the auxiliary additives are composed of a plasticizer, a stabilizer, a lubricant and an antioxidant in a mass ratio of 10:2:0.5:0.5, the plasticizer is one or more of diisononyl phthalate and tributyl citrate; the stabilizer is one or two of butylated hydroxytoluene and triphenyl phosphite; the lubricant is one or more of calcium stearate and montan wax; the antioxidant is one or more of tetramethyl dihydroxyphenyl acrylate and tri-tert-butyl hydroxyphenyl acrylate, the temperatures of the eight temperature zones of the twin-screw extruder from the feed end to the discharge end are 190°C, 200°C, 210°C, 215°C, 215°C, 215°C, 215°C, 220°C, respectively, and the spindle speed of the twin-screw extruder is 20r / min.

[0037] The present invention has the following beneficial effects:

[0038] 1. The glass fiber reinforced PA double 6 composite material prepared by the present invention uses 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as the main flame retardant effective substance, and is prepared by reacting with itaconic acid, diethylenetriamine and calcium hydroxide to obtain a modified flame retardant, and a modified glass fiber coated with microporous calcium silicate is prepared by a silane coupling agent, and octamethyltetrasiloxane, tetrabutyl orthosilicate and tetramethyltetravinylcyclotetrasiloxane are hydrolyzed and polymerized to obtain a three-dimensional polysiloxane, and a seed emulsion is obtained under the action of an emulsifier sodium dodecylbenzene sulfonate, and the seed emulsion is cross-linked with butyl dimethacrylate and uses butyl methacrylate as a shell structure to prepare a core-shell modified toughening agent, and PA double 6, modified flame retardant, modified glass fiber, modified toughening agent and auxiliary additives are added into a twin-screw extruder, and melt-formed. The modified flame retardant prepared by the present invention introduces nitrogen, calcium and phosphorus in the preparation process, and these substances can generate flame retardants such as phosphoric acid, calcium oxide and polyphosphoric acid when burned, which promote the formation of a dense carbon layer on the surface of the PA double 6 and block the transfer of heat and oxygen. At the same time, the nitrogen element decomposes at high temperature to generate inert gases such as nitrogen and ammonia, which can dilute oxygen and inhibit combustion, thereby improving the flame retardant performance of the PA double 6 composite material. The amide structure of the modified flame retardant has a similar chemical structure to the amide bond in the PA double 6 molecular chain, and can form a good interface bonding with the PA double 6 matrix through hydrogen bonding, thereby improving the mechanical properties of the PA double 6 composite material. The modified flame retardant does not contain halogen, thereby improving the environmental protection performance of the PA double 6 composite material.

[0039] 2. The modified glass fiber prepared by the present invention uses a silane coupling agent as a crosslinking agent, and microporous calcium silicate is modified on the surface of the glass fiber. The microporous calcium silicate has a honeycomb microporous structure, which has a strong adsorption force and can adsorb a large amount of modified toughening agent and PA double 6 on its surface. Since the honeycomb microporous structure itself has a high roughness, the modification on the fiber surface can better improve the roughness of the fiber surface and improve the mechanical bite force of the interface. In addition to the van der Waals force generated by physical adsorption, the microporous structure can generate a large friction force with the existing pits and microcracks on the fiber surface, which helps the modified toughening agent and PA double 6 to adsorb a large amount of modified toughening agent and PA double 6 on its surface. A double 6 is more stably distributed on the surface of the modified fiber, which improves the mechanical properties and toughness of the PA double 6 composite material. At the same time, the amino group of KH-550 reacts with the carboxyl group in the PA double 6 matrix to form a chemical bond, which can improve the interface bonding between the glass fiber and the PA double 6 matrix, and further improve the mechanical properties of the PA double 6 composite material. Microporous calcium silicate has high thermal stability and can maintain structural integrity at high temperatures. Its good interface bonding with the glass fiber and the PA double 6 matrix delays the thermal degradation process of the PA double 6 composite material and improves its aging resistance.

[0040] 3. The modified toughening agent prepared by the present invention is prepared by hydrolyzing and polymerizing octamethyltetrasiloxane, tetrabutyl orthosilicate and tetramethyltetravinylcyclotetrasiloxane to obtain a three-dimensional polysiloxane, and obtaining a seed emulsion under the action of an emulsifier, sodium dodecylbenzene sulfonate. The seed emulsion is cross-linked with butyl dimethacrylate and butyl methacrylate is used as a shell structure to prepare a core-shell modified toughening agent. The polysiloxane core in the core structure has flexibility and elasticity, can deform under stress, absorb the impact energy of the PA double 6 composite material, and inhibit crack propagation. The methyl methacrylate in the shell layer Butyl methacrylate has high toughness and synergistically improves the impact resistance of PA double 6 composite materials. The butyl methacrylate in the shell layer has good compatibility with the PA double 6 matrix and can form a good interface bond through the entanglement of molecular chains and interface interaction. At the same time, the modified toughening agent contains a large amount of silicon-oxygen bond structure. When encountering flames, inorganic substances such as silicon dioxide and silicon carbide are generated. These inorganic substances can form a dense ceramic carbon layer on the surface of the material, blocking the entry of external heat and oxygen, delaying the combustion process, and improving the flame retardant properties of the PA double 6 composite material. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The glass fiber used in the present invention is purchased from Dongguan Yingxiang Plastic Raw Materials Co., Ltd., with a brand name of GF60-01;

[0043] The microporous calcium silicate used in the present invention is purchased from Lingshou County Jingjia Mineral Products Processing Plant, with a purity of 99 and a specification of 25KG / bag;

[0044] The PA double 6 used in the present invention is purchased from Shanghai Jinbo Engineering Plastics Co., Ltd., with a brand number of 54G43 and a specification of 10000mm.

[0045] Example 1

[0046] This embodiment provides a method for preparing a glass fiber reinforced PA double 6 composite material, comprising the following steps:

[0047] S1. Preparation of modified flame retardant

[0048] Weigh: 300g of itaconic acid, 120g of diethylenetriamine and 2000mL of N,N-dimethylformamide, place in a reactor protected by nitrogen atmosphere, heat to 80°C, keep warm for 40min, add 200g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 15g of azobisisobutyronitrile, keep warm for 2h, after the reaction is completed, cool the reaction liquid to room temperature, filter, add ethyl acetate to the filtrate, wash once, transfer the organic phase to a rotary evaporator at a temperature of 40°C, and evaporate until no liquid is extracted to obtain a modified flame retardant precursor;

[0049] Weigh: 40g of calcium hydroxide, 350g of modified flame retardant precursor, 800mL of deionized water and 3000mL of toluene, place in a reactor, heat to 75°C, and keep warm for 2h. After the reaction is completed, wait for the reaction liquid to cool to room temperature, filter, and ice bath the filtrate for 1h. Filter the filtrate after crystallization, wash the filter cake once with ethanol, transfer it to a drying oven at 60°C, and dry it to constant weight to obtain a modified flame retardant.

[0050] S2. Preparation of modified glass fiber

[0051] Ethanol and pure water were mixed evenly in a volume ratio of 90:5 to obtain an ethanol solution for later use;

[0052] Weigh: 1000 mL of ethanol solution, 12 g of KH-550 and 8 g of microporous calcium silicate, put them into a reaction kettle, and ultrasonicate for 30 min to obtain a modified solution;

[0053] The glass fiber is immersed in the modification liquid twice and rolled twice, and then dried to obtain the modified glass fiber.

[0054] S3. Preparation of modified toughening agent

[0055] Mix potassium sulfate and pure water in a volume ratio of 5:1 to obtain a potassium sulfate solution for later use;

[0056] Weigh: 100 g of octamethyltetrasiloxane, 50 g of tetrabutyl orthosilicate, 20 g of tetramethyltetravinylcyclotetrasiloxane, 10 g of sodium dodecylbenzenesulfonate and 1500 mL of deionized water into a reaction kettle, perform ultrasonic dispersion for 10 min, heat to 80° C., add 50 mL of 95 wt % sulfuric acid solution, and keep the temperature for reaction for 5 h to obtain intermediate I;

[0057] Weigh: 100g of intermediate I, 400g of butyl methacrylate, 50g of butyl dimethacrylate, 20g of sodium dodecylbenzene sulfonate and 3000mL of deionized water, place in a reactor protected by nitrogen atmosphere, stir for 10min, add 10g of potassium persulfate solution, heat to 60°C, keep warm for 4h, after the reaction is completed, wait for the reaction liquid to cool to room temperature, filter, wash the filter cake once with deionized water, transfer the filter cake to a drying oven at a temperature of 50°C, dry to constant weight, grind, and pass through an 80-mesh sieve to obtain a modified toughening agent.

[0058] S4. Preparation of PA double 6 composite material

[0059] Diisononyl phthalate, triphenyl phosphite, montan wax and tri-tert-butyl hydroxyphenyl acrylate are uniformly mixed in a mass ratio of 10:2:0.5:0.5 to obtain an auxiliary additive for standby use;

[0060] Weigh by weight: 60 parts of PA double 6, 15 parts of modified flame retardant, 20 parts of modified glass fiber, 8 parts of modified toughening agent, and 7 parts of auxiliary additives for later use;

[0061] Adding the modified glass fiber to an untwisting and width-opening machine, untwisting and dispersing, and obtaining a modified glass fiber dispersion;

[0062] PA double 6, modified flame retardant, modified toughening agent and auxiliary additives are mixed uniformly, added into a twin-screw extruder for melt extrusion, the temperatures of 8 temperature sections from the feed end to the discharge end of the twin-screw extruder are 190°C, 200°C, 210°C, 215°C, 215°C, 215°C, 215°C, 220°C, the main shaft speed of the twin-screw extruder is 20r / min, the modified glass fiber dispersion is added from the first exhaust port, melt blended, the material strips are stretched and water-cooled, and then pelletized to obtain a PA double 6 composite material.

[0063] Example 2

[0064] This embodiment provides a method for preparing a glass fiber reinforced PA double 6 composite material, comprising the following steps:

[0065] S1. Preparation of modified flame retardant

[0066] Weigh: 325g of itaconic acid, 125g of diethylenetriamine and 2500mL of N,N-dimethylformamide, place in a reactor protected by nitrogen atmosphere, heat to 85°C, keep warm for 50min, add 210g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 17g of azobisisobutyronitrile, keep warm for 3h, after the reaction is completed, cool the reaction liquid to room temperature, filter, add ethyl acetate to the filtrate, wash twice, transfer the organic phase to a rotary evaporator at a temperature of 45°C, and evaporate until no liquid is extracted to obtain a modified flame retardant precursor;

[0067] Weigh: 45g of calcium hydroxide, 375g of modified flame retardant precursor, 900mL of deionized water and 3250mL of toluene, place in a reactor, heat to 80°C, and keep warm for 3h. After the reaction is completed, wait for the reaction liquid to cool to room temperature, filter, and ice bath the filtrate for 2h. Filter the filtrate after crystallization, wash the filter cake twice with ethanol, transfer it to a drying oven at a temperature of 65°C, and dry it to constant weight to obtain a modified flame retardant.

[0068] S2. Preparation of modified glass fiber

[0069] Ethanol and pure water were mixed evenly in a volume ratio of 93:7 to obtain an ethanol solution for later use;

[0070] Weigh: 1100 mL of ethanol solution, 13 g of KH-550 and 9 g of microporous calcium silicate, put them into a reaction kettle, and ultrasonicate for 50 min to obtain a modified solution;

[0071] The glass fiber is immersed in the modification liquid twice and rolled twice, and then dried to obtain the modified glass fiber.

[0072] S3. Preparation of modified toughening agent

[0073] Mix potassium sulfate and pure water in a volume ratio of 5:1 to obtain a potassium sulfate solution for later use;

[0074] Weigh: 110 g of octamethyltetrasiloxane, 55 g of tetrabutyl orthosilicate, 25 g of tetramethyltetravinylcyclotetrasiloxane, 11 g of sodium dodecylbenzenesulfonate and 1700 mL of deionized water into a reaction kettle, perform ultrasonic dispersion for 14 min, heat to 85° C., add 55 mL of 95-98 wt % sulfuric acid solution, and keep the mixture for 5.5 h to obtain intermediate I;

[0075] Weigh: 150g of intermediate I, 450g of butyl methacrylate, 60g of butyl dimethacrylate, 23g of sodium dodecylbenzene sulfonate and 3250mL of deionized water, place in a reactor protected by nitrogen atmosphere, stir for 11min, add 11g of potassium persulfate solution, heat to 65°C, and keep warm for 4.5h. After the reaction is completed, wait for the reaction liquid to cool to room temperature, filter, wash the filter cake twice with deionized water, transfer the filter cake to a drying oven at a temperature of 55°C, dry to constant weight, grind, and pass through an 80-mesh sieve to obtain a modified toughening agent.

[0076] S4. Preparation of PA double 6 composite material

[0077] Diisononyl phthalate, triphenyl phosphite, montan wax and tri-tert-butyl hydroxyphenyl acrylate are uniformly mixed in a mass ratio of 10:2:0.5:0.5 to obtain an auxiliary additive for standby use;

[0078] Weigh by weight: 65 parts of PA double 6, 17 parts of modified flame retardant, 21 parts of modified glass fiber, 9 parts of modified toughening agent, and 9 parts of auxiliary additives for later use;

[0079] Adding the modified glass fiber to an untwisting and width-opening machine, untwisting and dispersing, and obtaining a modified glass fiber dispersion;

[0080] PA double 6, modified flame retardant, modified toughening agent and auxiliary additives are mixed uniformly, added into a twin-screw extruder for melt extrusion, the temperatures of 8 temperature sections from the feed end to the discharge end of the twin-screw extruder are 190°C, 200°C, 210°C, 215°C, 215°C, 215°C, 215°C, 220°C, the main shaft speed of the twin-screw extruder is 20r / min, the modified glass fiber dispersion is added from the first exhaust port, melt blended, the material strips are stretched and water-cooled, and then pelletized to obtain a PA double 6 composite material.

[0081] Example 3

[0082] This embodiment provides a method for preparing a glass fiber reinforced PA double 6 composite material, comprising the following steps:

[0083] S1. Preparation of modified flame retardant

[0084] Weigh: 350g of itaconic acid, 130g of diethylenetriamine and 3000mL of N,N-dimethylformamide, place in a reactor protected by nitrogen atmosphere, heat to 90°C, keep warm for 60min, add 220g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 20g of azobisisobutyronitrile, keep warm for 3h, after the reaction is completed, cool the reaction liquid to room temperature, filter, add ethyl acetate to the filtrate, wash twice, transfer the organic phase to a rotary evaporator at a temperature of 50°C, and evaporate until no liquid is extracted to obtain a modified flame retardant precursor;

[0085] Weigh: 50g of calcium hydroxide, 400g of modified flame retardant precursor, 1000mL of deionized water and 3500mL of toluene, place in a reactor, heat to 85°C, and keep warm for 3h. After the reaction is completed, wait for the reaction liquid to cool to room temperature, filter, and ice bath the filtrate for 2h. Filter the filtrate after crystallization, wash the filter cake twice with ethanol, transfer it to a drying oven at a temperature of 70°C, and dry it to constant weight to obtain a modified flame retardant.

[0086] S2. Preparation of modified glass fiber

[0087] Ethanol and pure water were mixed evenly in a volume ratio of 95:10 to obtain an ethanol solution for later use;

[0088] Weigh: 1200 mL of ethanol solution, 15 g of KH-550 and 10 g of microporous calcium silicate, put them into a reaction kettle, and ultrasonicate for 60 min to obtain a modified solution;

[0089] The glass fiber is immersed in the modification liquid twice and rolled twice, and then dried to obtain the modified glass fiber.

[0090] S3. Preparation of modified toughening agent

[0091] Mix potassium sulfate and pure water in a volume ratio of 5:1 to obtain a potassium sulfate solution for later use;

[0092] Weigh: 120 g of octamethyltetrasiloxane, 60 g of tetrabutyl orthosilicate, 30 g of tetramethyltetravinylcyclotetrasiloxane, 12 g of sodium dodecylbenzenesulfonate and 2000 mL of deionized water into a reaction kettle, perform ultrasonic dispersion for 15 min, heat to 90° C., add 60 mL of 98 wt % sulfuric acid solution, and keep the temperature for reaction for 6 h to obtain intermediate I;

[0093] Weigh: 200g of intermediate I, 500g of butyl methacrylate, 70g of butyl dimethacrylate, 25g of sodium dodecylbenzene sulfonate and 3500mL of deionized water, place in a reactor protected by nitrogen atmosphere, stir for 12min, add 12g of potassium persulfate solution, heat to 70°C, and keep warm for 5h. After the reaction is completed, wait for the reaction liquid to cool to room temperature, filter, wash the filter cake twice with deionized water, transfer the filter cake to a drying oven at a temperature of 60°C, dry to constant weight, grind, and pass through an 80-mesh sieve to obtain a modified toughening agent.

[0094] S4. Preparation of PA double 6 composite material

[0095] Diisononyl phthalate, triphenyl phosphite, montan wax and tri-tert-butyl hydroxyphenyl acrylate are uniformly mixed in a mass ratio of 10:2:0.5:0.5 to obtain an auxiliary additive for standby use;

[0096] Weigh by weight: 70 parts of PA double 6, 20 parts of modified flame retardant, 22 parts of modified glass fiber, 10 parts of modified toughening agent, and 10 parts of auxiliary additives for later use;

[0097] Adding the modified glass fiber to an untwisting and width-opening machine, untwisting and dispersing, and obtaining a modified glass fiber dispersion;

[0098] PA double 6, modified flame retardant, modified toughening agent and auxiliary additives are mixed uniformly, added into a twin-screw extruder for melt extrusion, the temperatures of 8 temperature sections from the feed end to the discharge end of the twin-screw extruder are 190°C, 200°C, 210°C, 215°C, 215°C, 215°C, 215°C, 220°C, the main shaft speed of the twin-screw extruder is 20r / min, the modified glass fiber dispersion is added from the first exhaust port, melt blended, the material strips are stretched and water-cooled, and then pelletized to obtain a PA double 6 composite material.

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 2 is that step S1 is omitted, and when the PA double 6 composite material is prepared in step S4, no modified flame retardant is added.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 2 is that, when preparing the modified glass fiber in step S2, no microporous calcium silicate is added.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 2 is that when preparing the PA double 6 composite material in step S4, step S3 is omitted and no modifying toughening agent is added in step S4.

[0105] Performance Testing:

[0106] The impact resistance of the glass fiber reinforced PA double 6 composite materials prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to the standard GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics";

[0107] The tensile strength and elongation at break of the glass fiber reinforced PA double 6 composites prepared in Examples 1-3 and Comparative Examples 1-3 were measured with reference to the standard GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber";

[0108] The vertical burning rating of the glass fiber reinforced PA double 6 composite materials prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to the standard GB / T 26526-2011 "Specification for Thermoplastic Elastomer Low Smoke Halogen-Free Flame Retardant Materials", and the specific data are shown in Table 1;

[0109] After ultraviolet irradiation treatment was performed on the glass fiber reinforced PA double 6 composite materials prepared in Example 1-3 and Comparative Example 1-3 with reference to the standard GB / T 16422.3-2022 "Plastics Laboratory Light Source Exposure Test Method Part 3: Fluorescent Ultraviolet Lamp", the impact resistance of the glass fiber reinforced PA double 6 composite materials prepared in Example 1-3 and Comparative Example 1-3 was tested with reference to the standard GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics"; the tensile strength and elongation at break of the glass fiber reinforced PA double 6 composite materials prepared in Example 1-3 and Comparative Example 1-3 were tested with reference to the standard GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber"; the vertical burning grade of the glass fiber reinforced PA double 6 composite materials prepared in Example 1-3 and Comparative Example 1-3 was tested with reference to the standard GB / T 26526-2011 "Specification for Low-smoke Halogen-free Flame-retardant Materials of Thermoplastic Elastomers", and the specific data are shown in Table 2.

[0110] Table 1-Performance test data of each sample

[0111]

[0112]

[0113] Table 2-Performance test data of each sample

[0114]

[0115] Data Analysis:

[0116] Comparative analysis of the data in Tables 1-2 shows that the elongation at break of the glass fiber reinforced PA double 6 composite material prepared by the present invention is 58.63%, and the cantilever beam impact strength is 24.21 kJ·m -2 The vertical combustion grade is V-0 and the tensile strength is 89.57Mpa. The elongation at break of the glass fiber reinforced PA double 6 composite material after ultraviolet irradiation is 56.28%, and the cantilever beam impact strength is 23.81kJ·m -2 , vertical combustion grade is V-0 and tensile strength is 88.51Mpa, which fully demonstrates that:

[0117] Analysis of the data of Comparative Example 1 and Examples 1-3 shows that the tensile strength, elongation at break, cantilever beam impact strength and vertical burning grade of the PA double 6 composite material prepared in Comparative Example 1 before and after ultraviolet irradiation treatment are all reduced, and it is explained that the modified flame retardant prepared by the present invention introduces nitrogen and phosphorus elements in the preparation process, and these substances can generate flame retardants such as phosphoric acid and polyphosphoric acid when burned, promote the formation of a dense carbon layer on the surface of PA double 6, and block the transfer of heat and oxygen. At the same time, the nitrogen element decomposes at high temperature to produce inert gases such as nitrogen and ammonia, which can dilute oxygen and inhibit combustion, thereby improving the flame retardant properties of the PA double 6 composite material. The amide structure of the modified flame retardant has a similar chemical structure to the amide bond in the PA double 6 molecular chain, and can form a good interface bonding with the PA double 6 matrix through hydrogen bonding, thereby improving the mechanical properties of the PA double 6 composite material.

[0118] The data of comparative example 2 and examples 1-3 are analyzed to show that the tensile strength, elongation at break, cantilever beam impact strength and vertical burning grade of the PA double 6 composite material prepared in comparative example 2 before and after ultraviolet irradiation treatment are all decreased, and the data are quite different, indicating that the modified glass fiber prepared by the present invention uses a silane coupling agent as a cross-linking agent, and microporous calcium silicate is modified on the surface of the glass fiber. The microporous calcium silicate has a honeycomb microporous structure, which has a strong adsorption force and can adsorb a large amount of modified toughening agent and PA double 6 on its surface. Moreover, since the honeycomb microporous structure itself has a high roughness, the modification on the fiber surface can better improve the roughness of the fiber surface, improve the mechanical bite force of the interface, and remove the range generated by physical adsorption. In addition to the dehua force, the microporous structure can generate greater friction with the pits and microcracks on the fiber surface, helping the modified toughening agent and PA double 6 to be more stably distributed on the modified fiber surface, improving the mechanical properties and toughness of the PA double 6 composite material. At the same time, the amino group of KH-550 reacts with the carboxyl group in the PA double 6 matrix to form a chemical bond, which can improve the interface bonding between the glass fiber and the PA double 6 matrix, and further improve the mechanical properties of the PA double 6 composite material. Microporous calcium silicate has high thermal stability and can maintain structural integrity at high temperatures. Its good interface bonding with the glass fiber and the PA double 6 matrix delays the thermal degradation process of the PA double 6 composite material and improves its aging resistance.

[0119] The data of comparative example 3 and examples 1-3 are analyzed to show that the tensile strength, elongation at break, cantilever beam impact strength and vertical burning grade of the PA double 6 composite material prepared in comparative example 3 before and after ultraviolet irradiation treatment are all decreased, indicating that the modified toughening agent prepared by the present invention is obtained by hydrolyzing and polymerizing octamethyltetrasiloxane, tetrabutyl orthosilicate and tetramethyltetravinylcyclotetrasiloxane to obtain a three-dimensional polysiloxane, and a seed emulsion is obtained under the action of an emulsifier, sodium dodecylbenzene sulfonate, and the seed emulsion is crosslinked with butyl dimethacrylate and butyl methacrylate as a shell structure to prepare a core-shell modified toughening agent, and the polysiloxane core in the core structure has flexibility and elasticity, and can be used under stress. It deforms under the action of the impact, absorbs the impact energy of the PA double 6 composite material, and inhibits the expansion of cracks. The butyl methacrylate in the shell has high toughness, which synergistically improves the impact resistance of the PA double 6 composite material. The butyl methacrylate in the shell has good compatibility with the PA double 6 matrix, and can form a good interface bonding through the entanglement of molecular chains and interface interaction. At the same time, the modified toughening agent contains a large amount of silicon-oxygen bond structure. When encountering flames, inorganic substances such as silicon dioxide and silicon carbide are generated. These inorganic substances can form a dense ceramic carbon layer on the surface of the material, blocking the entry of external heat and oxygen, delaying the combustion process, and improving the flame retardant properties of the PA double 6 composite material.

[0120] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A glass fiber reinforced PA double 6 composite material, characterized in that: The invention comprises the following raw materials in parts by weight: 60-70 parts of PA double 6, 15-20 parts of modified flame retardant, 20-22 parts of modified glass fiber, 8-10 parts of modified toughening agent, and 7-10 parts of auxiliary additives; The modified flame retardant is prepared by the following steps: A1. Place itaconic acid, diethylenetriamine and N,N-dimethylformamide in a reactor protected by a nitrogen atmosphere, heat to 80-90°C, keep warm for 40-60 minutes, add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and azobisisobutyronitrile, keep warm for 2-3 hours, and post-treat to obtain a modified flame retardant precursor; A2. Calcium hydroxide, modified flame retardant precursor, deionized water and toluene are placed in a reaction kettle, heated to 75-85°C, kept warm for 2-3 hours, and post-treated to obtain a modified flame retardant.

2. A glass fiber reinforced PA double 6 composite material according to claim 1, characterized in that: In step A1, the amount ratio of itaconic acid, diethylenetriamine, N,N-dimethylformamide, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and azobisisobutyronitrile is 300-350g:120-130g:2000-3000mL:200-220g:15-20g; in step A2, the amount ratio of calcium hydroxide, modified flame retardant precursor, deionized water and toluene is 40-50g:350-400g:800-100mL:3000-3500mL.

3. The glass fiber reinforced PA double 6 composite material according to claim 1, characterized in that: The modified glass fiber is obtained by the following preparation method: B1. Place ethanol solution, KH-550 and microporous calcium silicate in a reaction kettle and perform ultrasonic treatment for 30-60 minutes to obtain a modified solution; B2. Immerse the glass fiber in the modifying liquid and dry it to obtain modified glass fiber.

4. The glass fiber reinforced PA double 6 composite material according to claim 3, characterized in that: In step B1, the ethanol solution is composed of ethanol and pure water in a volume ratio of 90-95:5-10, and the dosage ratio of the ethanol solution, KH-550 and microporous calcium silicate is 1000-1200mL:12-15g:8-10g; in step B2, the impregnation operation steps are: dipping the glass fiber in the modified solution twice and rolling it twice, the bath ratio is 1:25-30, and the impregnation rate is 90-100%.

5. The glass fiber reinforced PA double 6 composite material according to claim 1, characterized in that: The modified toughening agent is obtained by the following preparation method: C1. Place octamethyltetrasiloxane, tetrabutyl orthosilicate, tetramethyltetravinylcyclotetrasiloxane, sodium dodecylbenzenesulfonate and deionized water in a reaction kettle, perform ultrasonic dispersion for 10-15 minutes, heat to 80-90°C, add sulfuric acid solution, and keep the temperature for reaction for 5-6 hours to obtain intermediate I; C2. Place intermediate I, butyl methacrylate, butyl dimethacrylate, sodium dodecylbenzene sulfonate and deionized water in a reactor protected by a nitrogen atmosphere, stir for 10-12 minutes, add potassium persulfate solution, heat to 60-70°C, keep warm for 4-5 hours, and post-treat to obtain a modified toughening agent.

6. The glass fiber reinforced PA double 6 composite material according to claim 5, characterized in that: In step C1, the concentration of the sulfuric acid solution is 95-98wt%, and the amount ratio of octamethyltetrasiloxane, tetrabutyl orthosilicate, tetramethyltetravinylcyclotetrasiloxane, sodium dodecylbenzenesulfonate, deionized water and sulfuric acid solution is 100-120g:50-60g:20-30g:10-12g:1500-2000mL:50-60mL; in step C2, the potassium persulfate solution is composed of potassium persulfate and pure water in a volume ratio of 5:1, and the amount ratio of the intermediate I, butyl methacrylate, butyl dimethacrylate, sodium dodecylbenzenesulfonate, deionized water and potassium persulfate solution is 100-200g:400-500g:50-70g:20-25g:3000-3500mL:10-12g.

7. A method for preparing a glass fiber reinforced PA double 6 composite material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, adding the modified glass fiber to the untwisting and width-opening machine, untwisting and dispersing, and obtaining a modified glass fiber dispersion; S2. Evenly mix PA 6, modified flame retardant, modified toughening agent and auxiliary additives, add them into a twin-screw extruder for melt extrusion, add modified glass fiber dispersion from the first exhaust port, melt blend, stretch and water-cool the material strips, and then pelletize them to obtain a PA 6 composite material.

8. The method for preparing a glass fiber reinforced PA double 6 composite material according to claim 7, characterized in that: In step S2, the auxiliary additives are composed of a plasticizer, a stabilizer, a lubricant and an antioxidant in a mass ratio of 10:2:0.5:0.5, the plasticizer is one or more of diisononyl phthalate and tributyl citrate; the stabilizer is one or two of butylated hydroxytoluene and triphenyl phosphite; the lubricant is one or more of calcium stearate and montan wax; the antioxidant is one or more of tetramethyl dihydroxyphenyl acrylate and tri-tert-butyl hydroxyphenyl acrylate.

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