Method for preparing zinc oxide / nylon 6 slice through in-situ polymerization

Abstract

The invention relates to the technical field of nylon, and discloses a method for preparing a zinc oxide / nylon 6 slice through in-situ polymerization, which comprises the following steps: (1) adding zinc oxide and an amino-terminated silane coupling agent into water, heating, stirring, and grinding to obtain a zinc oxide dispersion liquid; (2) mixing caprolactam, the zinc oxide dispersion liquid and water, and then carrying out hydrolysis ring-opening reaction; and (3) adding a chain extender and a catalyst, carrying out polymerization reaction, discharging, pelletizing, extracting and drying to obtain the zinc oxide / nylon 6 slice. The amino-terminated silane coupling agent is adopted to carry out surface coating treatment on the zinc oxide, so that the dispersion and compatibility of the zinc oxide in nylon 6 can be improved, the obvious polymerization inhibition phenomenon caused by adding zinc oxide particles can be effectively improved, and meanwhile, the zinc oxide is added in the polymerization production stage, so that the production efficiency is improved. The nylon 6 is better endowed with antibacterial, anti-ultraviolet and anti-yellowing effects and the like.

Description

Technical Field

[0001] The invention relates to the technical field of nylon, and in particular to a method for preparing zinc oxide / nylon 6 chips by in-situ polymerization. Background Art

[0002] As a commonly used polymer plastic type, nylon 6 has the characteristics of high mechanical properties, good toughness, wear resistance, shock resistance, and easy processing. With the development of the industry, adding nano inorganic powders to nylon 6 through copolymerization or blending has become the mainstream to develop it in the direction of high performance and multi-function. As a commonly used additive, nano zinc oxide can enhance or give nylon 6 materials the ability to resist bacteria, UV rays, and yellowing, and has attracted widespread attention.

[0003] The preparation of zinc oxide / nylon 6 composite materials mainly includes blending method and in-situ polymerization method. The blending method realizes functional compounding by adding zinc oxide masterbatch during nylon processing. It is easy to operate and flexible in production. For example, the patent with publication number CN103160949A discloses a nano flame-retardant nylon 66 fiber and its preparation method. The method uses nylon 66 resin powder, organic montmorillonite, nano silicon dioxide, melamine, ammonium polyphosphate and zinc oxide as raw materials for blending, and the blending and granulation are carried out by a twin-screw extruder at a certain temperature. The obtained masterbatch is blended and spun with nylon 66 resin at a weight ratio of 1: (6-9) to obtain a nano flame-retardant nylon 66 fiber with flame retardant properties. However, this method has the disadvantages of uneven mixing of masterbatch, easy agglomeration of nano zinc oxide and poor dispersibility. The in-situ polymerization method can produce uniformly dispersed zinc oxide / nylon 6 chips by adding zinc oxide and various auxiliary agents for assisting the dispersion of zinc oxide during the hydrolysis and ring opening stage of caprolactam. However, the following problems still exist: First, the polymerization conditions of nylon 6 are harsh. The high temperature and high pressure polymerization environment puts forward high requirements on the use of each additive, and the dispersion of zinc oxide in the nylon 6 matrix is ​​also affected by various additives; Second, due to the particularity of zinc oxide, adding zinc oxide nanoparticles to caprolactam during the polymerization stage will have obvious inhibition phenomenon. Zinc oxide is easy to react with the carboxyl group in aminocaproic acid to undergo complexation reaction, inhibiting the catalytic activity of aminocaproic acid and reducing the polymerization reaction rate. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing zinc oxide / nylon 6 slices by in-situ polymerization. By using a terminal amino silane coupling agent to perform surface coating treatment on zinc oxide, not only can the dispersion and compatibility of zinc oxide in nylon 6 be improved, but also the obvious inhibition phenomenon caused by the addition of zinc oxide particles can be effectively improved. The surface modification reaction is carried out in water, which minimizes its impact on the traditional polymerization process of nylon 6. At the same time, adding zinc oxide in the polymerization production stage can improve the bonding effect and better give nylon 6 antibacterial, anti-ultraviolet, anti-yellowing and other effects.

[0005] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a method for preparing zinc oxide / nylon 6 chips by in-situ polymerization, comprising the following steps: (1) adding zinc oxide and an amino-terminated silane coupling agent into water, heating, stirring and then grinding to obtain a zinc oxide dispersion; (2) mixing caprolactam, zinc oxide dispersion and water and performing a hydrolysis ring-opening reaction; (3) adding a chain extender and a catalyst to carry out a polymerization reaction, and then pelletizing, extracting, and drying the material to obtain zinc oxide / nylon 6 chips.

[0006] By using an amino-terminated silane coupling agent to perform surface coating treatment on zinc oxide, the ethoxy group in the amino-terminated silane coupling agent will hydrolyze to generate active silanol groups, which will undergo a condensation reaction with the hydroxyl groups on the surface of zinc oxide to form a chemical bond, and the amino group will react chemically with aminocaproic acid, thereby improving the degree of combination, adhesion and compatibility between the two through the above-mentioned two-way reaction. The present invention selects a silane coupling agent containing two ethoxy groups because the modification reaction can be carried out in water, and the stability of the silane coupling agent containing two ethoxy groups is better than that of triethoxysilane and methoxysilane, which can avoid the occurrence of agglomeration caused by excessively fast hydrolysis rate during the modification process, resulting in poor modification uniformity on the surface of zinc oxide.

[0007] In the present invention, zinc oxide will react and aggregate with acidic substances due to the amino treatment. In order to avoid the electrostatic effect between zinc oxide and the catalyst to cause mutual adsorption and agglomeration and the polymerization environment of sudden heating after adding zinc oxide after ring opening, the present invention adopts a polymerization process of adding zinc oxide dispersion before ring opening and adding catalyst after ring opening. In addition, a chain extender is added after ring opening. Due to the complexation of zinc oxide with carboxyl groups in nylon 6, the carboxyl content is reduced, the ratio of carboxyl groups to amino groups is unbalanced, and the molecular weight of zinc oxide / PA6 increases slowly. It is difficult to achieve an ideal polymerization rate and molecular weight using a catalyst. Adding a chain extender in the reaction system can play a role of chain extension, further effectively improving the degree of polymerization.

[0008] Preferably, in step (1), the molecular structure of the amino-terminated silane coupling agent contains a primary amino functional group and two hydrolyzable ethoxy groups.

[0009] Preferably, in step (1), the amino-terminated silane coupling agent includes one or more of 3-aminopropylmethyldiethoxysilane (3179-76-8), (3-aminopropyl)diethoxyethylsilane (20723-29-9), N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane (70240-34-5) and (diethylaminomethyl)methyldiethoxysilane (17961-68-1).

[0010] Preferably, in step (1), the primary particle size of the zinc oxide is less than 50 nm.

[0011] Preferably, in step (1), the amount of the amino-terminated silane coupling agent is 3-8 wt% of the mass of zinc oxide; and the concentration of zinc oxide in the zinc oxide dispersion is 10-25 wt%.

[0012] Preferably, in step (1), the heating and stirring temperature is 75-90° C. and the time is 4-8 h; and the grinding is performed to a particle size D99<1 μm.

[0013] Preferably, in step (2), the temperature of the hydrolysis ring-opening reaction is 220-240° C., the pressure is 0.3-1.2 MPa, and the time is 2-4 h.

[0014] Preferably, in step (2), the zinc oxide dispersion is used in an amount such that the zinc oxide accounts for 0.5 to 2 wt % of the mass of caprolactam.

[0015] Preferably, in step (2), the amount of water used is 5-10 wt % of the mass of caprolactam, and the amount of water used includes the mass of water contained in the zinc oxide dispersion.

[0016] Preferably, in step (3), the amount of the catalyst used is 0.3-3 wt% of the mass of caprolactam; and the catalyst is one or more of 6-aminocaproic acid and boric acid.

[0017] Preferably, in step (3), the amount of the chain extender is 0.5-1 wt% of the mass of caprolactam; and the chain extender is a compound containing a diepoxy group.

[0018] Binary epoxy chain extenders have high reactivity and good thermal stability. They can withstand the high temperature environment during the feeding process and react with amino or carboxyl groups to further increase the molecular weight. If dicarboxylic acid chain extenders are used, experimental verification shows that they have no chain extension effect in this reaction, but play a capping role. This may be due to the long reaction time, low efficiency and incomplete chain extension of carboxylic acids.

[0019] Preferably, in step (3), the chain extender includes 9,9-bis[4-(2,3-epoxypropoxyethoxy)phenyl]fluorene (259881-39-5), dipropylene glycol diglycidyl ether (41638-13-5), 2,6-bis(oxiran-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraketone (23328-66-7), 2,2'-[1,4-phenylenebis(oxymethylene)]bisoxirane (2425-01-6), One or more of cyclohexane-1,2-dicarboxylic acid diglycidyl ester (5493-45-8), 4,5-epoxytetrahydrophthalic acid diglycidyl ester (25293-64-5), diglycidyl ether (2238-07-5), ethylene glycol diglycidyl ether (2224-15-9), neopentyl glycol diglycidyl ether (17557-23-2), 1,6-hexanediol diglycidyl ether (16096-31-4) and 1,4-butanediol diglycidyl ether (2425-79-8).

[0020] Preferably, in step (3), the polymerization reaction temperature is 250-265° C., the pressure is <-0.07 MPa, and the time is 2-8 h.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention performs surface treatment on zinc oxide in a water system, avoids the use of organic solvents, minimizes the impact on the traditional polymerization process of nylon 6, does not change the existing polymerization conditions, and ensures product quality. When zinc oxide is surface modified, the agglomeration and sedimentation phenomena that may occur during the polymerization process are fully considered, and the use of surface modification coupling agents is minimized to prevent uncertainties.

[0022] (2) By adding binary epoxy substances as chain extenders at the appropriate stage, the molecular weight can be further increased to eliminate the effect of zinc oxide on nylon polymerization and increase the nylon melt viscosity.

[0023] (3) The zinc oxide particles in the zinc oxide / nylon 6 slices have good dispersibility and small particle size, which can give full play to the antibacterial and anti-ultraviolet capabilities of zinc oxide; the light transmittance in the nylon matrix is ​​high, and the effect on the nylon hue is very small. When changing varieties, the impact on the production pipeline is small, especially when producing matte products, the impact of zinc oxide can be ignored. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a slice agglutinated particle image in Example 1 of the present invention (magnification is 40 times).

[0025] Figure 2 This is a sliced ​​agglutinated particle image in Comparative Example 5 of the present invention (magnification is 40 times). DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization in the present invention comprises the following steps: (1) Dispersing zinc oxide in deionized water, adding an amino-terminated silane coupling agent accounting for 3 to 8 wt % of the zinc oxide mass, heating and stirring at 75 to 90° C. for modification for 4 to 8 h, and grinding with a sand mill to a particle size D99 <1 μm after modification to obtain a zinc oxide dispersion having a zinc oxide concentration of 10 to 25 wt %.

[0028] (2) Add caprolactam, deionized water, and zinc oxide (zinc oxide dispersion) in a mass ratio of 100:5-10:0.5-2 into the autoclave. After nitrogen is introduced to remove the air in the device, 0.2-0.6 MPa of nitrogen is introduced to increase the internal temperature to 220-240°C and the pressure to 0.5-1.2 MPa. After reacting for 2-3 hours, the pressure is slowly released to discharge water, thereby completing the hydrolysis and ring-opening reaction of caprolactam.

[0029] (3) The reactor is closed, and a chain extender of 0.5-1 wt% of the mass of caprolactam and a catalyst of 0.3-3 wt% of the mass of caprolactam (diluted with water of 1-10 wt% of the mass of caprolactam) are added to the hopper, and the hopper is replaced with nitrogen, and the hopper is pressurized to 0.3-0.5 MPa, and the valve at the bottom of the hopper is opened to add the dispersion obtained in step (2) to the system, and the system is sealed and slurried for 20-60 minutes, and the pressure is released and nitrogen is introduced again to remove air from the device. Subsequently, the pressure is slowly reduced through the vacuum system, and the pressure is reduced to <-0.07 MPa within 1 hour, and the internal temperature is increased to 250-265°C, and the reaction is carried out for 2-8 hours, and the material is discharged, pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0030] Example 1 (1) Disperse 100 g of zinc oxide in 900 g of deionized water, add 3 g of 3-aminopropylmethyldiethoxysilane, heat and stir at 75° C. for modification for 8 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 10 wt %.

[0031] (2) Add 1000 g of caprolactam, 50 g of zinc oxide dispersion, and 10 g of deionized water into a high-pressure reactor, introduce nitrogen to remove air from the device, and then introduce 0.2 MPa of nitrogen, raise the internal temperature to 240° C., maintain the pressure at 0.5 MPa, react for 3 h, and then release the pressure to discharge water.

[0032] (3) Close the reactor, add 3g of catalyst (boric acid) diluted with 16g of water and 5g of chain extender (cyclohexane-1,2-dicarboxylic acid diglycidyl ester) into the hopper, replace the hopper with nitrogen, pressurize to 0.3MPa, open the valve at the bottom of the hopper and add the dispersion obtained in step (2), seal and beat for 30min, then release the pressure, and introduce nitrogen again to remove the air in the reactor. Then slowly reduce the pressure through the vacuum system, reduce to -0.08MPa within 1h, increase the internal temperature to 250℃, react for 2h, discharging, pelletizing, extracting, and drying to obtain zinc oxide / nylon 6 chips.

[0033] Example 2 (1) Disperse 250 g of zinc oxide in 750 g of deionized water, add 20 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, heat and stir at 90° C. for 4 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 25 wt %.

[0034] (2) Add 1000 g of caprolactam, 40 g of deionized water, and 80 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.6 MPa of nitrogen, raise the internal temperature to 220° C., maintain the pressure at 1.2 MPa, react for 3 h, and then release the pressure to discharge water.

[0035] (3) The reactor was closed, 30 g of catalyst (6-aminocaproic acid) diluted with 80 g of water and 10 g of chain extender (dipropylene glycol diglycidyl ether) were added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.2 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 min. Nitrogen was introduced again to remove the air in the reactor. The pressure was then slowly reduced through the vacuum system to -0.1 MPa within 1 h, the internal temperature was increased to 265 ° C, the reaction was carried out for 8 h, the material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0036] Example 3 (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, heat and stir at 80° C. for 6 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 15 wt %.

[0037] (2) Add 1000 g of caprolactam and 100 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.4 MPa of nitrogen, raise the internal temperature to 230° C., maintain the pressure at 0.8 MPa, react for 3 h, and then release the pressure to discharge water.

[0038] (3) The reactor was closed, 3 g of catalyst (boric acid) diluted with 22 g of water and 8 g of chain extender (2,6-bis(oxirane-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraketone) were added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.4 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 minutes. Nitrogen was introduced again to remove the air in the reactor. Subsequently, the pressure was slowly reduced through the vacuum system to -0.1 MPa within 1 hour, and the internal temperature was increased to 255°C. The reaction was continued for 4 hours, and the material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0039] Comparative Example 1 (Compared with Example 1, zinc oxide was not modified with an amino-terminated silane coupling agent) (1) Dispersing 100 g of zinc oxide in 900 g of deionized water, heating and stirring at 75° C. for 8 h, and grinding the mixture with a sand mill to a particle size D99 < 1 μm to obtain a zinc oxide dispersion having a zinc oxide concentration of 10 wt %.

[0040] (2) Add 1000 g of caprolactam and 50 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.2 MPa of nitrogen, raise the internal temperature to 240° C., maintain the pressure at 0.5 MPa, react for 3 h, and then release the pressure to discharge water.

[0041] (3) Close the reactor, add 3g of catalyst (boric acid) diluted with 16g of water and 5g of chain extender (cyclohexane-1,2-dicarboxylic acid diglycidyl ester) into the hopper, replace the hopper with nitrogen, pressurize to 0.3MPa, open the valve at the bottom of the hopper and add the dispersion obtained in step (2), seal and beat for 30min, then release the pressure, and introduce nitrogen again to remove the air in the reactor. Then slowly reduce the pressure through the vacuum system, reduce to -0.08MPa within 1h, increase the internal temperature to 250℃, react for 2h, discharging, pelletizing, extracting, and drying to obtain zinc oxide / nylon 6 chips.

[0042] Comparative Example 2 (Compared with Example 1, zinc oxide was modified with an excess of amino-terminated silane coupling agent) (1) Disperse 100 g of zinc oxide in 900 g of deionized water, add 10 g of 3-aminopropylmethyldiethoxysilane, heat and stir at 75° C. for 8 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 10 wt %.

[0043] (2) Add 1000 g of caprolactam and 50 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.2 MPa of nitrogen, raise the internal temperature to 240° C., maintain the pressure at 0.5 MPa, react for 3 h, and then release the pressure to discharge water.

[0044] (3) Close the reactor, add 3g of catalyst (boric acid) diluted with 16g of water and 5g of chain extender (cyclohexane-1,2-dicarboxylic acid diglycidyl ester) into the hopper, replace the hopper with nitrogen, pressurize to 0.3MPa, open the valve at the bottom of the hopper and add the dispersion obtained in step (2), seal and beat for 30min, then release the pressure, and introduce nitrogen again to remove the air in the reactor. Then slowly reduce the pressure through the vacuum system, reduce to -0.08MPa within 1h, increase the internal temperature to 250℃, react for 2h, discharging, pelletizing, extracting, and drying to obtain zinc oxide / nylon 6 chips.

[0045] Comparative Example 3 (Compared with Example 2, no chain extender was added) (1) Disperse 250 g of zinc oxide in 750 g of deionized water, add 20 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, heat and stir at 90° C. for 4 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 25 wt %.

[0046] (2) Add 1000 g of caprolactam, 40 g of deionized water, and 80 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.6 MPa of nitrogen, raise the internal temperature to 220° C., maintain the pressure at 1.2 MPa, react for 3 h, and then release the pressure to discharge water.

[0047] (3) The reactor was closed, 30 g of catalyst (6-aminocaproic acid) diluted with 60 g of water was added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.2 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 min. Nitrogen was introduced again to remove the air in the reactor. The pressure was then slowly reduced through the vacuum system to -0.1 MPa within 1 h, the internal temperature was increased to 265 ° C, the reaction was carried out for 8 h, the material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0048] Comparative Example 4 (Compared with Example 2, an excess of chain extender was added) (1) Disperse 250 g of zinc oxide in 750 g of deionized water, add 20 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, heat and stir at 90° C. for 4 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 25 wt %.

[0049] (2) Add 1000 g of caprolactam, 40 g of deionized water, and 80 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.6 MPa of nitrogen, raise the internal temperature to 220° C., maintain the pressure at 1.2 MPa, react for 3 h, and then release the pressure to discharge water.

[0050] (3) The reactor was closed, 30 g of catalyst (6-aminocaproic acid) and 20 g of chain extender (dipropylene glycol diglycidyl ether) diluted with 100 g of water were added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.2 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 min. Nitrogen was introduced again to remove the air in the reactor. The pressure was then slowly reduced through the vacuum system to -0.1 MPa within 1 h, the internal temperature was increased to 265 ° C, the reaction was carried out for 8 h, the material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0051] Comparative Example 5 (Compared with Example 3, the catalyst and the zinc oxide dispersion were added together before the ring-opening reaction) (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, heat and stir at 80° C. for 6 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 15 wt %.

[0052] (2) Add 1000 g of caprolactam, 100 g of zinc oxide dispersion, and 3 g of catalyst (boric acid) into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.4 MPa of nitrogen, raise the internal temperature to 230° C., maintain the pressure at 0.8 MPa, react for 3 h, and then release the pressure to discharge water.

[0053] (3) The reactor was closed, 8 g of chain extender (2,6-bis(oxirane-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraketone) diluted with 16 g of water was added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.4 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 minutes. Nitrogen was introduced again to remove the air in the reactor. Subsequently, the pressure was slowly reduced through the vacuum system to -0.1 MPa within 1 hour, and the internal temperature was increased to 255°C. The reaction was continued for 4 hours, and the material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0054] Comparative Example 6 (Compared with Example 3, zinc oxide dispersion was added after the ring-opening reaction) (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, heat and stir at 80° C. for 6 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 15 wt %.

[0055] (2) Add 1000 g of caprolactam, 85 g of deionized water, and 3 g of catalyst (boric acid) to a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.4 MPa of nitrogen, raise the internal temperature to 230° C., maintain the pressure at 0.8 MPa, react for 3 h, and then release the pressure to discharge water.

[0056] (3) Close the reactor, add 100g zinc oxide dispersion and 8g chain extender (2,6-bis(oxirane-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraketone) into the hopper, replace the hopper with nitrogen, pressurize to 0.4MPa, open the valve at the bottom of the hopper and add the dispersion obtained in step (2), seal and beat for 30min, then release the pressure, and introduce nitrogen again to remove the air in the reactor. Then slowly reduce the pressure through the vacuum system, reduce to -0.1MPa within 1h, increase the internal temperature to 255°C, react for 4h, discharging, pelletizing, extracting, and drying to obtain zinc oxide / nylon 6 chips.

[0057] Comparative Example 7 (Compared with Example 3, the chain extender was added before ring opening) (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, heat and stir at 80° C. for 6 h, and grind with a sand mill to a particle size D99<1 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 15 wt %.

[0058] (2) Add 1000 g of caprolactam, 100 g of zinc oxide dispersion, and 8 g of chain extender (2,6-bis(oxirane-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraone) into a high-pressure reactor, introduce nitrogen to remove air from the device, then introduce 0.4 MPa of nitrogen, raise the internal temperature to 230° C., maintain the pressure at 0.8 MPa, react for 3 h, and then release the pressure to discharge water.

[0059] (3) The reactor was closed, 3 g of catalyst (boric acid) diluted with 6 g of water was added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.4 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 minutes, and nitrogen was introduced again to remove the air in the reactor. Then, the pressure was slowly reduced through the vacuum system to -0.1 MPa within 1 hour, and the internal temperature was increased to 255°C, and the reaction was carried out for 4 hours. The material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0060] Comparative Example 8 (Compared with Example 3, the silane coupling agent was replaced with γ-aminopropyltriethoxysilane) (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of γ-aminopropyltriethoxysilane, heat and stir at 80° C. for 6 h, and grind with a sand mill to a particle size D99 < 3 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 15 wt %.

[0061] (2) Add 1000 g of caprolactam and 100 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.4 MPa of nitrogen, raise the internal temperature to 230° C., maintain the pressure at 0.8 MPa, react for 3 h, and then release the pressure to discharge water.

[0062] (3) The reactor was closed, 3 g of catalyst (boric acid) diluted with 22 g of water and 8 g of chain extender (2,6-bis(oxirane-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraketone) were added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.4 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 minutes. Nitrogen was introduced again to remove the air in the reactor. Subsequently, the pressure was slowly reduced through the vacuum system to -0.1 MPa within 1 hour, and the internal temperature was increased to 255°C. The reaction was continued for 4 hours, and the material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0063] Comparative Example 9 (Compared with Example 3, the silane coupling agent was replaced with 3-aminopropyltrimethoxysilane) (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of 3-aminopropyltrimethoxysilane, heat and stir at 80° C. for 6 h, and grind with a sand mill to a particle size D99 < 3 μm to obtain a zinc oxide dispersion with a zinc oxide concentration of 15 wt %.

[0064] (2) Add 1000 g of caprolactam and 100 g of zinc oxide dispersion into a high-pressure reactor, introduce nitrogen to remove the air in the device, then introduce 0.4 MPa of nitrogen, raise the internal temperature to 230° C., maintain the pressure at 0.8 MPa, react for 3 h, and then release the pressure to discharge water.

[0065] (3) The reactor was closed, 3 g of catalyst (boric acid) diluted with 22 g of water and 8 g of chain extender (2,6-bis(oxirane-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraketone) were added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.4 MPa. The valve at the bottom of the hopper was opened to add the dispersion obtained in step (2), and the pressure was released after sealing and beating for 30 minutes. Nitrogen was introduced again to remove the air in the reactor. Subsequently, the pressure was slowly reduced through the vacuum system to -0.1 MPa within 1 hour, and the internal temperature was increased to 255°C. The reaction was continued for 4 hours, and the material was pelletized, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0066] Table 1 Physical properties of zinc oxide / nylon 6 chips of Examples 1 to 3 and Comparative Examples 1 to 9 Conventional nylon 6 is prepared as follows: 1000g of caprolactam, 50g of deionized water, and 3g of boric acid are added to a high-pressure reactor, nitrogen is introduced to remove air from the device, and then 0.2MPa of nitrogen is introduced, the internal temperature is raised to 240°C, the pressure is maintained at 0.5MPa, and after reacting for 3h, the pressure is released and water is discharged. Subsequently, the pressure is slowly reduced through a vacuum system, and the pressure is reduced to -0.03MPa within 1h, the internal temperature is raised to 260°C, the reaction is carried out for 2h, the material is discharged, pelletized, extracted, and dried to obtain conventional nylon 6 chips.

[0067] As shown in Table 1, the relative viscosity, carboxyl content and amino content in the table are tested according to "GB / T 38138-2019 Test method for fiber-grade polycaprolactam (PA6) slices"; the weather resistance test is based on "GB / T 31899-2015 Textile weather resistance test ultraviolet light exposure" experimental condition 3, and the b value after 9 days of exposure is recorded; the Escherichia coli antibacterial rate is tested according to "GB-T20944.3-2008 Evaluation of antibacterial properties of textiles Part 3 Oscillation method".

[0068] (1) The difference between Comparative Examples 1 and 2 and Example 1 is that the degree of modification of zinc oxide with amino-terminated silane coupling agent is too low or too high. Figure 1As shown, there are no excessive agglomerated particles in the zinc oxide / nylon 6 slices obtained in Example 1. However, the zinc oxide in Comparative Example 1 was not modified with a coupling agent. Due to the lack of the coating effect of the coupling agent, the surface of the zinc oxide was exposed, the probability of contact with caprolactam increased, and the amount of carboxyl groups complexed was greater, resulting in the relative viscosity of the nylon 6 slices after in-situ polymerization being slightly lower than that of Example 1, and the amino content was high. At the same time, due to the lack of the effect of the amino coupling agent, the compatibility between zinc oxide and the nylon 6 substrate was poor, resulting in the agglomeration of zinc oxide and an increase in the number of agglomerated particles. The zinc oxide in Comparative Example 2 was modified with an excessive amount of coupling agent, and there were too many small molecules of amino coupling agent remaining in the dispersion. The yellowing was aggravated by heat during the polymerization of nylon 6, and part of the carboxyl groups were consumed, resulting in poor color value of the slices and lower viscosity.

[0069] (2) The difference between Comparative Examples 3 and 4 and Example 2 is that the amount of chain extender added during the in-situ polymerization is too little or too much. In Comparative Example 3, no binary epoxy is used during the polymerization process. Due to the complexation of zinc oxide with carboxyl groups, the ratio of amino groups to carboxyl groups is unbalanced, and the excess amino groups play a capping role. This results in the reaction rate of nylon 6 / zinc oxide being too slow, and the viscosity stops increasing in the later stage of the reaction. The relative viscosity is significantly lower than that of Example 2 in which binary epoxy is added when the polymerization time is maintained at the same level. In Comparative Example 4, an excess of binary epoxy is used during the polymerization process. At this time, the excess binary epoxy also plays a capping role, resulting in the viscosity of the nylon 6 / zinc oxide slices being too low and the b value being large.

[0070] (3) The difference between Comparative Examples 5, 6, and 7 and Example 3 is that the addition process of the catalyst, zinc oxide dispersion, and chain extender is different. In Comparative Example 5, zinc oxide and the catalyst are added together before the ring opening. In the presence of water in the system at the early stage of the reaction, zinc oxide agglomerates due to the electrostatic interaction between zinc oxide and boric acid. Figure 2 As shown, a large number of micron-scale agglomerates will be formed in the nylon 6 system, and too many agglomerated particles will affect the use of subsequent materials. In Comparative Example 6, the zinc oxide dispersion is added after the ring is opened. The temperature in the system is high when the zinc oxide aqueous dispersion is suddenly increased from room temperature to above 220°C. The water in the dispersion evaporates too quickly, causing the zinc oxide powder to agglomerate and form more agglomerated particles. In Comparative Example 7, the chain extender is added before the ring is opened. The chain extender is consumed prematurely and cannot play its due role, resulting in a low viscosity of the system.

[0071] (4) The difference between Comparative Examples 8 and 9 and Example 3 is that the types of coupling agents used are different. Comparative Example 8 uses triethoxysilane, and Comparative Example 9 uses trimethoxysilane. Since a coupling agent that is more easily hydrolyzed is used, its adsorption and reaction on the surface of zinc oxide are too rapid, resulting in uneven thickness of the coating layer on the surface of the powder, and the particle size can only be ground to less than 3 μm during grinding. Due to incomplete coating, the probability of contact between the exposed zinc oxide surface and caprolactam increases, the amount of carboxyl groups being complexed is more, the probability of agglomeration increases, and the relative viscosity of nylon 6 chips after in-situ polymerization is slightly lower than that of Example 3, the amino content is high, and there are many agglomerated particles.

[0072] (5) The results of ultraviolet exposure showed that after 9 days of testing, the b value of conventional nylon 6 increased by 4.02, and the b value increase of antibacterial nylon 6 after adding zinc oxide was significantly lower than that of conventional nylon 6, and the b value increase was <2.5. When the number of agglomerated particles was <1 / mg after the dispersion of zinc oxide increased, the b value increase was <1.2. At the same time, the antibacterial rate of Escherichia coli after adding zinc oxide was greater than 90%, which had a good antibacterial effect. The antibacterial effect was related to the dispersion of zinc oxide. The better the dispersion, the more obvious the antibacterial performance.

[0073] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing zinc oxide / nylon 6 chips by in-situ polymerization, characterized in that: The steps include: (1) adding zinc oxide and amino-terminated silane coupling agent into water, heating, stirring and then grinding to obtain zinc oxide dispersion; (2) mixing caprolactam, zinc oxide dispersion and water to perform a hydrolysis ring-opening reaction; (3) Adding a chain extender and a catalyst to carry out a polymerization reaction, pelletizing, extracting, and drying the material to obtain zinc oxide / nylon 6 chips.

2. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 1, characterized in that: In step (1), the molecular structure of the amino-terminated silane coupling agent contains a primary amino functional group and two hydrolyzable ethoxy groups.

3. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 2, characterized in that: In step (1), the amino-terminated silane coupling agent includes one or more of 3-aminopropylmethyldiethoxysilane, (3-aminopropyl)diethoxyethylsilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane and (diethylaminomethyl)methyldiethoxysilane.

4. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 1, characterized in that: In step (1), the amount of the amino-terminated silane coupling agent is 3-8 wt % of the mass of zinc oxide; the concentration of zinc oxide in the zinc oxide dispersion is 10-25 wt %.

5. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to any one of claims 1 to 4, characterized in that: In step (1), the heating and stirring temperature is 75-90° C. and the time is 4-8 hours; and the grinding is grinding to a particle size D99<1 μm.

6. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 1, characterized in that: In step (2), the temperature of the hydrolysis ring-opening reaction is 220-240° C., the pressure is 0.3-1.2 MPa, and the time is 2-4 h.

7. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 1 or 6, characterized in that: In step (2), the amount of the zinc oxide dispersion is such that the zinc oxide accounts for 0.5-2 wt % of the mass of caprolactam.

8. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 1, characterized in that: In step (3), the amount of the catalyst used is 0.3-3 wt % of the mass of caprolactam; the catalyst is one or more of 6-aminocaproic acid and boric acid.

9. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 1, characterized in that: In step (3), the amount of the chain extender is 0.5-1 wt % of the mass of caprolactam; the chain extender is a compound containing a diepoxy group.

10. The method for preparing zinc oxide / nylon 6 chips by in-situ polymerization according to claim 1, 8 or 9, characterized in that: In step (3), the polymerization reaction temperature is 250-265° C., the pressure is less than -0.07 MPa, and the time is 2-8 hours.

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