A method for in-situ polymerization of zinc oxide / nylon 6 chips

Abstract

The application relates to the technical field of nylon and discloses a method for preparing zinc oxide / nylon 6 chips by in-situ polymerization, which comprises the following steps: (1) adding zinc oxide and an amino-terminated silane coupling agent into water, grinding after heating and stirring to obtain a zinc oxide dispersion liquid; (2) mixing caprolactam, the zinc oxide dispersion liquid and water and then carrying out a hydrolysis ring-opening reaction; (3) adding a chain extender and a catalyst and then carrying out a polymerization reaction, discharging, granulating, extracting and drying to obtain the zinc oxide / nylon 6 chips. The surface of the zinc oxide is coated by the amino-terminated silane coupling agent, so that the dispersion and compatibility of the zinc oxide in the nylon 6 are improved, the obvious polymerization inhibition phenomenon caused by the addition of the zinc oxide particles is effectively improved, and the zinc oxide is added in the polymerization production stage, so that the nylon 6 is better endowed with the effects of antibiosis, ultraviolet resistance, yellowing resistance and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nylon, and particularly relates to a method for preparing zinc oxide / nylon 6 chip by in-situ polymerization. BACKGROUND

[0002] Nylon 6 as a commonly used high polymer plastic type has the characteristics of high mechanical property, good toughness, wear resistance, shock resistance and easy processing. With the development of the industry, the addition of nano inorganic powder in nylon 6 through copolymerization or blending has become the mainstream to develop nylon 6 to high performance and multi-function. As a commonly used additive, nano zinc oxide can enhance or endow nylon 6 with the ability of antibacterial, anti-ultraviolet and anti-yellowing, and therefore is widely concerned.

[0003] The preparation of zinc oxide / nylon 6 composite mainly includes blending method and in-situ polymerization method. The blending method realizes functional compounding by adding zinc oxide masterbatch in the nylon processing process, and has the advantages of simple operation and flexible production. For example, the patent with the publication number CN103160949A discloses a nano flame-retardant nylon 66 fiber and a preparation method thereof. The method adopts nylon 66 resin powder, organic montmorillonite, nano silicon dioxide, melamine, ammonium polyphosphate and zinc oxide as raw materials for blending, and the raw materials are blended and granulated by a double-screw extruder at a certain temperature. The obtained masterbatch is blended with nylon 66 resin at a weight ratio of 1: (6-9) to obtain a nano flame-retardant nylon 66 fiber with flame-retardant property after spinning. However, the method has the defects of uneven mixing of the masterbatch, easy agglomeration of nano zinc oxide and poor dispersibility. The in-situ polymerization method can produce zinc oxide / nylon 6 chip with uniform dispersion by adding zinc oxide and various auxiliary zinc oxide dispersing agents in the caprolactam ring-opening stage. However, the method still has the following problems: first, the polymerization conditions of nylon 6 are harsh, and the high-temperature and high-pressure polymerization environment puts high requirements on the use of each auxiliary agent, and the dispersion of zinc oxide in the nylon 6 matrix is also affected by various auxiliary agents; second, due to the particularity of zinc oxide, the addition of zinc oxide nanoparticles to caprolactam in the polymerization stage will have obvious polymerization inhibition phenomenon, and zinc oxide is easy to complex with the carboxyl group in aminocaproic acid, thereby inhibiting the catalytic activity of aminocaproic acid and reducing the polymerization rate. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a method for preparing zinc oxide / nylon 6 chip by in-situ polymerization. The surface of zinc oxide is coated by using an amino-terminated silane coupling agent, which can not only improve the dispersion and compatibility of zinc oxide in nylon 6, but also effectively improve the obvious polymerization inhibition phenomenon caused by the addition of zinc oxide particles. Moreover, the surface modification reaction is carried out in water, which minimizes the influence on the traditional polymerization process of nylon 6. Meanwhile, the addition of zinc oxide in the polymerization production stage can improve the binding effect and better endow nylon 6 with the effects of antibacterial, anti-ultraviolet and anti-yellowing.

[0005] The object of the present application is achieved by the following technical solutions.

[0006] The present application provides a method for preparing zinc oxide / nylon 6 chip by in-situ polymerization, comprising the following steps:

[0007] (1) adding zinc oxide and amino-terminated silane coupling agent into water, grinding after heating and stirring to obtain zinc oxide dispersion;

[0008] (2) mixing caprolactam, zinc oxide dispersion and water to perform hydrolytic ring-opening reaction;

[0009] (3) adding chain extender and catalyst to perform polymerization reaction, discharging, granulating, extracting and drying to obtain zinc oxide / nylon 6 chip.

[0010] By adopting amino-terminated silane coupling agent to coat the surface of zinc oxide, the ethoxyl groups in the amino-terminated silane coupling agent can be hydrolyzed to form active silicon hydroxyl groups, which can form chemical bonds with the hydroxyl groups on the surface of zinc oxide through condensation reaction, and the amino groups can chemically react with aminocaproic acid, so that the combination, adhesion and compatibility between the two are improved through the above-mentioned bidirectional reaction. The present application selects silane coupling agent containing two ethoxyl groups because the modification reaction can be carried out in water, and the stability of silane coupling agent containing two ethoxyl groups is better than that of triethoxysilane and methoxysilane, which can avoid the rapid hydrolysis rate in the modification process, leading to poor uniformity of the modification on the surface of zinc oxide and the occurrence of agglomeration.

[0011] In the present application, the zinc oxide is treated with amino groups and can agglomerate with acidic substances. To avoid the mutual adsorption and agglomeration of zinc oxide and catalyst due to electrostatic interaction, and the polymerization environment of the zinc oxide added after ring-opening, the present application adopts the polymerization process of adding zinc oxide dispersion before ring-opening and adding catalyst after ring-opening. In addition, a chain extender is also added after ring-opening. Due to the complexation of zinc oxide and carboxyl groups in nylon 6, the content of carboxyl groups is reduced, the ratio of carboxyl groups to amino groups is unbalanced, the molecular weight of zinc oxide / PA6 grows slowly, and the use of catalyst cannot achieve the ideal polymerization rate and molecular weight. The addition of chain extender in the reaction system can play a chain extension role, further effectively improving the polymerization degree.

[0012] Preferably, in step (1), the amino-terminated silane coupling agent contains primary amino functional groups and two hydrolyzable ethoxyl groups in the molecular structure.

[0013] As preferred, in step (1), the end-amino silane coupling agent comprises 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).

[0014] As preferred, in step (1), the primary particle size of the zinc oxide is < 50 nm.

[0015] As preferred, in step (1), the amount of the end-amino silane coupling agent is 3-8 wt% of the mass of the zinc oxide; the concentration of the zinc oxide in the zinc oxide dispersion liquid is 10-25 wt%.

[0016] As preferred, in step (1), the temperature of the heating and stirring is 75-90℃, and the time is 4-8 h; the grinding is to a particle size D99 < 1 μm.

[0017] As preferred, in step (2), the temperature of the hydrolytic ring-opening reaction is 220-240℃, the pressure is 0.3-1.2 MPa, and the time is 2-4 h.

[0018] As preferred, in step (2), the amount of the zinc oxide dispersion liquid is such that the zinc oxide is 0.5-2 wt% of the mass of the caprolactam.

[0019] As preferred, in step (2), the amount of the water is 5-10 wt% of the mass of the caprolactam, and the amount of the water includes the mass of the water contained in the zinc oxide dispersion liquid.

[0020] As preferred, in step (3), the amount of the catalyst is 0.3-3 wt% of the mass of the caprolactam; the catalyst is one or more of 6-aminohexanoic acid and boric acid.

[0021] As preferred, in step (3), the amount of the chain extender is 0.5-1 wt% of the mass of the caprolactam; the chain extender is a compound containing a double epoxy group.

[0022] The binary epoxy chain extender has high reactivity and good thermal stability, can withstand the high-temperature environment during the intermediate feeding process, and reacts with amino or carboxyl to further increase the molecular weight. If a binary carboxylic acid chain extender is used, experimental verification shows that it has no chain extension effect in the reaction, but plays an end-capping role, which may be due to the long reaction time, low efficiency and incomplete chain extension of carboxylic acid.

[0023] As preferred, in step (3), the chain extender includes one or more of 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)-tetraone (23328-66-7), 2,2'-[1,4-phenylenebis(oxymethylene)]dioxirane (2425-01-6), 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).

[0024] As preferred, in step (3), the temperature of the polymerization reaction is 250-265°C, the pressure is <-0.07 MPa, and the time is 2-8 h.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) The present application performs surface treatment on zinc oxide in a water system, avoids the use of organic solvents, minimizes the influence on the traditional polymerization process of nylon 6, does not change the existing polymerization conditions, and ensures the product quality. The surface modification of zinc oxide has fully considered the agglomeration and sedimentation that may occur in the polymerization process, and the use of surface modification coupling agents is minimized to prevent uncertain factors.

[0027] (2) By adding a binary epoxy substance as a chain extender at a suitable stage, the molecular weight is further improved to eliminate the influence of zinc oxide on the polymerization of nylon and improve the melt viscosity of nylon.

[0028] (3) The zinc oxide particles in the zinc oxide / nylon 6 chip have good dispersibility and small particle size, and can fully exert the antibacterial and ultraviolet resistance of zinc oxide; the light transmittance in the nylon matrix is high, the influence on the color phase of nylon is very small, the influence on the production pipeline during the conversion of varieties is small, and especially when producing matte products, the influence of zinc oxide can be ignored. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The figure is the chip agglomeration particle diagram (magnification is 40 times) in Example 1 of the present application.

[0030] Figure 2A photograph of the agglomerated particles of the cut piece in Invention Comparative Example 5 (magnification: 40 times). DETAILED DESCRIPTION

[0031] The technical solutions of the present application are described below with specific examples, but the scope of protection of the present application is not limited thereto.

[0032] The method for preparing the zinc oxide / nylon 6 cut piece by in-situ polymerization in the present application comprises the following steps:

[0033] (1) Disperse zinc oxide in deionized water, add 3-8wt% of amino-terminated silane coupling agent based on the mass of zinc oxide, heat and stir at 75-90℃ for 4-8h, after the modification, grind to a particle size D99<1μm using a sand mill, and obtain a zinc oxide dispersion liquid with a zinc oxide concentration of 10-25wt%.

[0034] (2) In a high-pressure reactor, add caprolactam, deionized water and zinc oxide (zinc oxide dispersion liquid) in a mass ratio of 100:5-10:0.5-2. After purging the air in the device with nitrogen, introduce 0.2-0.6MPa of nitrogen, raise the internal temperature to 220-240℃, and the pressure to 0.5-1.2MPa, react for 2-3h, then slowly release the water to complete the hydrolysis ring-opening reaction of caprolactam.

[0035] (3) Close the reactor, add 0.5-1wt% of chain extender and 0.3-3wt% of catalyst (diluted with 1-10wt% of water based on the mass of caprolactam) based on the mass of caprolactam in the feeding hopper, and replace the air in the feeding hopper with nitrogen, pressurize the hopper to 0.3-0.5MPa, open the lower valve of the hopper to add the dispersion liquid obtained in step (2) into the system, seal and beat for 20-60min, release the pressure and introduce nitrogen again to replace the air in the device. Then slowly reduce the pressure through a vacuum system to <-0.07MPa within 1h, raise the internal temperature to 250-265℃, and react for 2-8h, then discharge, extract and dry to obtain the zinc oxide / nylon 6 cut piece.

[0036] Example 1

[0037] (1) Disperse 100g of zinc oxide in 900g of deionized water, add 3g of 3-aminopropylmethyldiethoxysilane, heat and stir at 75℃ for 8h, after the modification, grind to a particle size D99<1μm using a sand mill, and obtain a zinc oxide dispersion liquid with a zinc oxide concentration of 10wt%.

[0038] (2) In a high-pressure reactor, 1000 g of caprolactam, 50 g of zinc oxide dispersion liquid, and 10 g of deionized water were added, nitrogen was introduced to remove air in the device, 0.2 MPa of nitrogen was introduced, the internal temperature was raised to 240°C, the pressure was maintained at 0.5 MPa, and after 3 h of reaction, the water was discharged by pressure relief.

[0039] (3) The reactor was closed, 16 g of 3 g of catalyst (boric acid) diluted with water, and 5 g of chain extender (cyclohexane-1,2-dicarboxylic acid diglycidyl ester) were added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.3 MPa. The lower valve of the hopper was opened to add the dispersion liquid obtained in step (2), and after sealing and beating for 30 min, the pressure was released, and nitrogen was introduced again to remove air in the reactor. Then, the pressure was slowly reduced by a vacuum system, and within 1 h, it was reduced to -0.08 MPa, the internal temperature was raised to 250°C, and the reaction was carried out for 2 h. The product was discharged, cut into granules, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0040] Example 2

[0041] (1) 250 g of zinc oxide was dispersed in 750 g of deionized water, 20 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane was added, and the mixture was heated and stirred at 90°C for 4 h. After modification, the sand mill was used to grind to a particle size D99 <1 μm, and a zinc oxide dispersion liquid with a zinc oxide concentration of 25 wt% was obtained.

[0042] (2) In a high-pressure reactor, 1000 g of caprolactam, 40 g of deionized water, and 80 g of zinc oxide dispersion liquid were added, nitrogen was introduced to remove air in the device, 0.6 MPa of nitrogen was introduced, the internal temperature was raised to 220°C, the pressure was maintained at 1.2 MPa, and after 3 h of reaction, the water was discharged by pressure relief.

[0043] (3) The reactor was closed, 80 g of 30 g of catalyst (6-aminohexanoic acid) diluted with 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 lower valve of the hopper was opened to add the dispersion liquid obtained in step (2), and after sealing and beating for 30 min, the pressure was released, and nitrogen was introduced again to remove air in the reactor. Then, the pressure was slowly reduced by a vacuum system, and within 1 h, it was reduced to -0.1 MPa, the internal temperature was raised to 265°C, and the reaction was carried out for 8 h. The product was discharged, cut into granules, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0044] Example 3

[0045] (1) 150 g of zinc oxide was dispersed in 850 g of deionized water, 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane was added, and modification was performed by heating and stirring at 80°C for 6 h. After the modification, a sand mill was used to grind to a particle size D99 < 1 μm, and a zinc oxide dispersion liquid having a zinc oxide concentration of 15 wt% was obtained.

[0046] (2) In a high-pressure reaction kettle, 1000 g of caprolactam and 100 g of the zinc oxide dispersion liquid were added, nitrogen was introduced to remove air in the device, 0.4 MPa of nitrogen was introduced, the internal temperature was raised to 230°C, the pressure was maintained at 0.8 MPa, and after reaction for 3 h, water was discharged by pressure relief.

[0047] (3) The reactor was closed, 22 g of 3 g of catalyst (boric acid) diluted with water and 8 g of chain extender (2,6-bis(oxazolidin-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraone) were added to the hopper, nitrogen replacement was performed on the hopper, the pressure was increased to 0.4 MPa, the lower valve of the hopper was opened to add the dispersion liquid obtained in step (2), the seal was beaten for 30 min, the pressure was released, nitrogen was introduced again to remove air in the reaction kettle. Subsequently, the pressure was slowly reduced by a vacuum system, and within 1 h, it was reduced to -0.1 MPa, the internal temperature was raised to 255°C, and reaction was performed for 4 h. The product was discharged, cut into granules, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0048] Comparative Example 1 (compared with Example 1, zinc oxide was not modified with an amino-terminated silane coupling agent)

[0049] (1) 100 g of zinc oxide was dispersed in 900 g of deionized water, modification was performed by heating and stirring at 75°C for 8 h, and after the modification, a sand mill was used to grind to a particle size D99 < 1 μm, and a zinc oxide dispersion liquid having a zinc oxide concentration of 10 wt% was obtained.

[0050] (2) In a high-pressure reaction kettle, 1000 g of caprolactam and 50 g of the zinc oxide dispersion liquid were added, nitrogen was introduced to remove air in the device, 0.2 MPa of nitrogen was introduced, the internal temperature was raised to 240°C, the pressure was maintained at 0.5 MPa, and after reaction for 3 h, water was discharged by pressure relief.

[0051] (3) The reactor was closed, 16 g of 3 g of catalyst (boric acid) diluted with water and 5 g of chain extender (cyclohexane-1,2-dicarboxylic acid diglycidyl ester) were added to the hopper, nitrogen replacement was performed on the hopper, the pressure was increased to 0.3 MPa, the lower valve of the hopper was opened to add the dispersion liquid obtained in step (2), the seal was beaten for 30 min, the pressure was released, nitrogen was introduced again to remove air in the reaction kettle. Subsequently, the pressure was slowly reduced by a vacuum system, and within 1 h, it was reduced to -0.08 MPa, the internal temperature was raised to 250°C, and reaction was performed for 2 h. The product was discharged, cut into granules, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0052] Comparative Example 2 (compared with Example 1, zinc oxide modified with excess amino-terminated silane coupling agent)

[0053] (1) 100 g of zinc oxide was dispersed in 900 g of deionized water, 10 g of 3- aminopropylmethyldiethoxysilane was added, and modification was performed by heating and stirring at 75°C for 8 h. After the modification, the sand mill was used to grind to a particle size D99 < 1 μm, and a zinc oxide dispersion liquid with a zinc oxide concentration of 10 wt% was obtained.

[0054] (2) In a high-pressure reaction kettle, 1000 g of caprolactam and 50 g of the zinc oxide dispersion liquid were added, nitrogen was introduced to remove air in the device, 0.2 MPa of nitrogen was introduced, the internal temperature was raised to 240°C, the pressure was maintained at 0.5 MPa, and after 3 h of reaction, the water was discharged by pressure relief.

[0055] (3) The reactor was closed, 16 g of 3 g catalyst (boric acid) diluted with water and 5 g of chain extender (cyclohexane-1,2-dicarboxylic acid diglycidyl ester) were added to the hopper, and the hopper was replaced with nitrogen and pressurized to 0.3 MPa. The lower valve of the hopper was opened to add the dispersion liquid obtained in step (2), and after sealing and beating for 30 min, the pressure was released, and nitrogen was introduced again to remove air in the reaction kettle. Then, the pressure was slowly reduced by the vacuum system, and within 1 h, it was reduced to -0.08 MPa, the internal temperature was raised to 250°C, and the reaction was carried out for 2 h. The product was discharged, cut into granules, extracted, and dried to obtain zinc oxide / nylon 6 chips.

[0056] Comparative Example 3 (compared with Example 2, no chain extender added)

[0057] (1) 250 g of zinc oxide was dispersed in 750 g of deionized water, 20 g of N-(2- aminoethyl)-3-aminopropylmethyldiethoxysilane was added, and modification was performed by heating and stirring at 90°C for 4 h. After the modification, the sand mill was used to grind to a particle size D99 < 1 μm, and a zinc oxide dispersion liquid with a zinc oxide concentration of 25 wt% was obtained.

[0058] (2) In a high-pressure reaction kettle, 1000 g of caprolactam, 40 g of deionized water, and 80 g of the zinc oxide dispersion liquid were added, nitrogen was introduced to remove air in the device, 0.6 MPa of nitrogen was introduced, the internal temperature was raised to 220°C, the pressure was maintained at 1.2 MPa, and after 3 h of reaction, the water was discharged by pressure relief.

[0059] (3) Close the reactor, add 60 g of water-diluted 30 g of catalyst (6-aminohexanoic acid) into the hopper, and replace the hopper with nitrogen, pressurize to 0.2 MPa, open the lower valve of the hopper to add the dispersion liquid obtained in step (2), seal and beat for 30 min, then depressurize, and again replace the reactor with nitrogen to remove air. Then slowly depressurize through the vacuum system, to -0.1 MPa within 1 h, raise the internal temperature to 265°C, and react for 8 h. After discharging, pelletize, extract, and dry to obtain zinc oxide / nylon 6 chips.

[0060] Comparative Example 4 (compared with Example 2, excess chain extender is added)

[0061] (1) Disperse 250 g of zinc oxide in 750 g of deionized water, add 20 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and modify at 90°C for 4 h with stirring. After modification, grind to a particle size D99 < 1 μm using a sand mill to obtain a zinc oxide dispersion liquid with a zinc oxide concentration of 25 wt%.

[0062] (2) Add 1000 g of caprolactam, 40 g of deionized water, and 80 g of the zinc oxide dispersion liquid into a high-pressure reactor, replace the device with nitrogen to remove air, and then replace with 0.6 MPa of nitrogen. Raise the internal temperature to 220°C, maintain the pressure at 1.2 MPa, and react for 3 h. After depressurizing to remove water, the reaction is complete.

[0063] (3) Close the reactor, add 60 g of water-diluted 30 g of catalyst (6-aminohexanoic acid) into the hopper, and replace the hopper with nitrogen, pressurize to 0.2 MPa, open the lower valve of the hopper to add the dispersion liquid obtained in step (2), seal and beat for 30 min, then depressurize, and again replace the reactor with nitrogen to remove air. Then slowly depressurize through the vacuum system, to -0.1 MPa within 1 h, raise the internal temperature to 265°C, and react for 8 h. After discharging, pelletize, extract, and dry to obtain zinc oxide / nylon 6 chips.

[0064] Comparative Example 5 (compared with Example 3, the catalyst is added together with the zinc oxide dispersion liquid before ring-opening reaction)

[0065] (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and modify at 80°C for 6 h with stirring. After modification, grind to a particle size D99 < 1 μm using a sand mill to obtain a zinc oxide dispersion liquid with a zinc oxide concentration of 15 wt%.

[0066] (2) In a high-pressure reactor, 1000 g of caprolactam, 100 g of zinc oxide dispersion liquid, 3 g of catalyst (boric acid) were added, nitrogen was introduced to remove air in the device, 0.4 MPa of nitrogen was introduced, the internal temperature was raised to 230°C, the pressure was kept at 0.8 MPa, after 3 h of reaction, the pressure was released to discharge water.

[0067] (3) The reactor was closed, 16 g of water-diluted 8 g of chain extender (2,6-bis(oxazolidine-2-ylmethyl) pyrrolo[3,4-F] isoindole-1,3,5,7(2H,6H)-tetraone) was added to the hopper, and the hopper was replaced with nitrogen, pressurized to 0.4 MPa, the lower valve of the hopper was opened to add the dispersion liquid obtained in step (2), sealed and milled for 30 min, then released the pressure, and nitrogen was introduced again to remove the air in the reactor. Then the pressure was slowly reduced by the vacuum system, reduced to -0.1 MPa within 1 h, the internal temperature was raised to 255°C, reacted for 4 h, discharged, cut into particles, extracted, dried, and zinc oxide / nylon 6 chips were obtained.

[0068] Comparative Example 6 (zinc oxide dispersion liquid added after ring-opening reaction compared with Example 3)

[0069] (1) 150 g of zinc oxide was dispersed in 850 g of deionized water, 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane was added, and the modification was carried out at 80°C for 6 h with stirring. After the modification was completed, the sand mill was used to grind to a particle size D99 <1 μm, and a zinc oxide dispersion liquid with a zinc oxide concentration of 15 wt% was obtained.

[0070] (2) In a high-pressure reactor, 1000 g of caprolactam, 85 g of deionized water, 3 g of catalyst (boric acid) were added, nitrogen was introduced to remove air in the device, 0.4 MPa of nitrogen was introduced, the internal temperature was raised to 230°C, the pressure was kept at 0.8 MPa, after 3 h of reaction, the pressure was released to discharge water.

[0071] (3) The reactor was closed, 100 g of zinc oxide dispersion liquid, 8 g of chain extender (2,6-bis(oxazolidine-2-ylmethyl) pyrrolo[3,4-F] isoindole-1,3,5,7(2H,6H)-tetraone) was added to the hopper, and the hopper was replaced with nitrogen, pressurized to 0.4 MPa, the lower valve of the hopper was opened to add the dispersion liquid obtained in step (2), sealed and milled for 30 min, then released the pressure, and nitrogen was introduced again to remove the air in the reactor. Then the pressure was slowly reduced by the vacuum system, reduced to -0.1 MPa within 1 h, the internal temperature was raised to 255°C, reacted for 4 h, discharged, cut into particles, extracted, dried, and zinc oxide / nylon 6 chips were obtained.

[0072] Comparative Example 7 (chain extender added before ring-opening compared with Example 3)

[0073] (1) 150 g of zinc oxide was dispersed in 850 g of deionized water, 8 g of N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane was added, and the mixture was modified by heating and stirring at 80°C for 6 h. After the modification, the mixture was ground using a sand mill until the particle size D99 was <1 μm to obtain a zinc oxide dispersion liquid having a zinc oxide concentration of 15 wt%.

[0074] (2) In a high-pressure reaction kettle, 1000 g of caprolactam and 100 g of the zinc oxide dispersion liquid were added, and nitrogen was introduced to remove air in the apparatus. Then, 0.4 MPa of nitrogen was introduced, the internal temperature was raised to 230°C, the pressure was maintained at 0.8 MPa, and the mixture was reacted for 3 h. After the reaction, the pressure was released, and water was discharged.

[0075] (3) The reactor was closed, 6 g of 3 g of catalyst (boric acid) diluted with water was added to the hopper, and the hopper was replaced with nitrogen. The hopper was pressurized to 0.4 MPa, and the lower valve of the hopper was opened to add the dispersion liquid obtained in step (2). After sealing and beating for 30 min, the pressure was released, and nitrogen was introduced again to remove air in the reaction kettle. Then, the pressure was slowly reduced to -0.1 MPa by a vacuum system within 1 h, the internal temperature was raised to 255°C, and the mixture was reacted for 4 h. After the reaction, the mixture was discharged, pelletized, extracted, and dried to obtain zinc oxide / nylon 6 pellets.

[0076] Comparative Example 8 (compared with Example 3, the silane coupling agent was replaced with γ-aminopropyltriethoxysilane)

[0077] (1) 150 g of zinc oxide was dispersed in 850 g of deionized water, 8 g of γ-aminopropyltriethoxysilane was added, and the mixture was modified by heating and stirring at 80°C for 6 h. After the modification, the mixture was ground using a sand mill until the particle size D99 was <3 μm to obtain a zinc oxide dispersion liquid having a zinc oxide concentration of 15 wt%.

[0078] (2) In a high-pressure reaction kettle, 1000 g of caprolactam and 100 g of the zinc oxide dispersion liquid were added, and nitrogen was introduced to remove air in the apparatus. Then, 0.4 MPa of nitrogen was introduced, the internal temperature was raised to 230°C, the pressure was maintained at 0.8 MPa, and the mixture was reacted for 3 h. After the reaction, the pressure was released, and water was discharged.

[0079] (3) Close the reactor, add 22 g of 3 g catalyst (boric acid) diluted with water and 8 g of chain extender (2,6-bis(oxazolidin-2-ylmethyl)pyrrolo[3,4-F]isoindole- 1,3,5,7(2H,6H)-tetraone) into the hopper, replace the hopper with nitrogen, pressurize to 0.4 MPa, open the lower valve of the hopper to add the dispersion liquid obtained in step (2), seal and beat for 30 min, then depressurize, and again replace the reactor with nitrogen to remove air. Then slowly depressurize through the vacuum system to -0.1 MPa within 1 h, raise the internal temperature to 255°C, and react for 4 h. After discharging, pelletize, extract, and dry to obtain zinc oxide / nylon 6 chips.

[0080] Comparative Example 9 (compared with Example 3, the silane coupling agent is replaced with 3-aminopropyltrimethoxysilane)

[0081] (1) Disperse 150 g of zinc oxide in 850 g of deionized water, add 8 g of 3- aminopropyltrimethoxysilane, and modify at 80°C for 6 h with stirring. After modification, grind to a particle size D99 < 3 μm using a sand mill to obtain a zinc oxide dispersion liquid with a zinc oxide concentration of 15 wt%.

[0082] (2) Add 1000 g of caprolactam and 100 g of the zinc oxide dispersion liquid into a high-pressure reactor, replace the device with nitrogen to remove air, and then replace with 0.4 MPa of nitrogen. Raise the internal temperature to 230°C, maintain the pressure at 0.8 MPa, and react for 3 h. After depressurizing to remove water, the reaction is complete.

[0083] (3) Close the reactor, add 22 g of 3 g catalyst (boric acid) diluted with water and 8 g of chain extender (2,6-bis(oxazolidin-2-ylmethyl)pyrrolo[3,4-F]isoindole- 1,3,5,7(2H,6H)-tetraone) into the hopper, replace the hopper with nitrogen, pressurize to 0.4 MPa, open the lower valve of the hopper to add the dispersion liquid obtained in step (2), seal and beat for 30 min, then depressurize, and again replace the reactor with nitrogen to remove air. Then slowly depressurize through the vacuum system to -0.1 MPa within 1 h, raise the internal temperature to 255°C, and react for 4 h. After discharging, pelletize, extract, and dry to obtain zinc oxide / nylon 6 chips.

[0084] Table 1 Physical property indexes of zinc oxide / nylon 6 chips of Examples 1-3 and Comparative Examples 1-9

[0085]

[0086] The conventional preparation of nylon 6 is as follows: 1000g caprolactam, 50g deionized water, and 3g boric acid are added to a high-pressure reactor. Nitrogen gas is introduced to purge air from the reactor, followed by the introduction of nitrogen gas at 0.2MPa. The internal temperature is raised to 240℃, and the pressure is maintained at 0.5MPa. After reacting for 3 hours, the pressure is released and water is discharged. Subsequently, the pressure is slowly reduced through a vacuum system to -0.03MPa within 1 hour, and the internal temperature is raised to 260℃. The reaction is continued for 2 hours, and the material is discharged, granulated, extracted, and dried to obtain conventional nylon 6 chips.

[0087] As shown in Table 1, the relative viscosity, carboxyl content, and amino content were tested according to the "GB / T 38138-2019 Test Method for Polycaprolactam (PA6) Slices of Fiber Grade"; the weather resistance test was conducted according to test condition 3 of "GB / T 31899-2015 Weather Resistance Test of Textiles - Ultraviolet Exposure", and the b value was recorded after 9 days of exposure; the Escherichia coli inhibition rate was tested according to "GB-T20944.3-2008 Evaluation of Antibacterial Properties of Textiles - Part 3 - Shaking Method".

[0088] (1) The difference between Comparative Examples 1 and 2 and Example 1 lies in the degree to which zinc oxide is modified with a terminal aminosilane coupling agent, either too low or too high. For example... Figure 1 As shown, the zinc oxide / nylon 6 chips obtained in Example 1 did not contain excessive agglomerated particles. In contrast, the zinc oxide in Comparative Example 1 was not modified with a coupling agent. Due to the lack of coating effect from the coupling agent, the zinc oxide surface was exposed, increasing the probability of contact with caprolactam and resulting in a greater amount of carboxyl groups being complexed. This led to a slightly lower relative viscosity and higher amino content in the nylon 6 chips after in-situ polymerization compared to Example 1. Simultaneously, the lack of an amino coupling agent resulted in poor compatibility between zinc oxide and the nylon 6 substrate, leading to zinc oxide agglomeration and an increased number of agglomerated particles. In Comparative Example 2, the zinc oxide was modified with an excessive amount of coupling agent, resulting in too many small amino coupling agent molecules remaining in the dispersion. This exacerbated the yellowing during the nylon 6 polymerization process and consumed some carboxyl groups, leading to poorer chip color and lower viscosity.

[0089] (2) The difference between Comparative Examples 3 and 4 and Example 2 lies in the amount of chain extender added during the in-situ polymerization process, which may be too little or too much. Comparative Example 3 did not use binary epoxy during polymerization. Due to the complexation of zinc oxide with carboxyl groups, the ratio of amino to carboxyl groups was unbalanced, and the excess amino groups acted as end-capping agents. This resulted in a slow reaction rate for nylon 6 / zinc oxide, and the viscosity stopped increasing in the later stages of the reaction. Maintaining the same polymerization time, the relative viscosity was significantly lower than that of Example 2, which added binary epoxy. Comparative Example 4 used excessive binary epoxy during polymerization. In this case, the excessive binary epoxy also acted as end-capping agents, resulting in excessively low viscosity and a large b-value for the nylon 6 / zinc oxide chips.

[0090] (3) The difference between Comparative Examples 5, 6, and 7 and Example 3 lies in the different addition processes of the catalyst, zinc oxide dispersion, and chain extender. In Comparative Example 5, zinc oxide and the catalyst were added together before ring opening. In the early stage of the reaction, with water present in the system, zinc oxide agglomerated due to electrostatic interaction with boric acid, such as... Figure 2 As shown, a large number of micron-sized agglomerates form within the nylon 6 system, and the excessive number of agglomerated particles affects the use of subsequent materials. In Comparative Example 6, the zinc oxide dispersion was added after ring-opening. The system temperature was high at this time, with the zinc oxide aqueous dispersion rapidly rising from room temperature to over 220°C. This caused the water in the dispersion to evaporate too quickly, leading to the agglomeration of zinc oxide powder and the formation of numerous agglomerated particles. In Comparative Example 7, the chain extender was added before ring-opening. The chain extender was consumed prematurely and could not play its due role, resulting in a still low system viscosity.

[0091] (4) The difference between Comparative Examples 8 and 9 and Example 3 lies in the type of coupling agent used. Comparative Example 8 used triethoxysilane, while Comparative Example 9 used trimethoxysilane. Due to the use of a more easily hydrolyzed coupling agent, its adsorption and reaction on the zinc oxide surface were too rapid, resulting in uneven coating thickness on the powder surface. During grinding, the particle size could only be ground to below 3 μm. Furthermore, due to incomplete coating, the exposed zinc oxide surface had a higher probability of contact with caprolactam, resulting in more carboxyl groups being complexed and an increased probability of agglomeration. After in-situ polymerization, the relative viscosity of the nylon 6 chips was slightly lower than that of Example 3, with a higher amino content and more agglomerated particles.

[0092] (5) The results of ultraviolet exposure showed that after 9 days of testing, the b value of conventional nylon 6 increased by 4.02. The increase in b value of antibacterial nylon 6 after adding zinc oxide was significantly lower than that of conventional nylon 6, with the increase in b value being <2.5. Moreover, when the number of aggregated particles was <1 / mg after the increase in zinc oxide dispersibility, the increase in b value was <1.2. At the same time, the inhibition rate of Escherichia coli after adding zinc oxide was greater than 90%, which showed good antibacterial effect. The antibacterial effect was related to the dispersibility of zinc oxide; the better the dispersibility, the more obvious the antibacterial performance.

[0093] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process for the in-situ polymerization of zinc oxide / nylon 6 chips, characterized in that, The method comprises the following steps: (1) adding zinc oxide and an amino-terminated silane coupling agent into water, the amino-terminated silane coupling agent containing a primary amino functional group and two hydrolysable ethoxy groups in its molecular structure, the amount of the amino-terminated silane coupling agent being 3-8 wt% of the mass of the zinc oxide, heating and stirring, and then grinding to obtain a zinc oxide dispersion; (2) mixing caprolactam, the zinc oxide dispersion and water, and then performing a hydrolytic ring-opening reaction; (3) adding a chain extender and a catalyst, the chain extender being a compound containing a double epoxy group, the amount of the chain extender being 0.5-1 wt% of the mass of the caprolactam, and then performing a polymerization reaction, discharging, granulating, extracting and drying to obtain zinc oxide / nylon 6 chips.

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

3. The process for in-situ polymerization of zinc oxide / nylon 6 chips according to claim 1, characterized in that, In step (1), the concentration of the zinc oxide in the zinc oxide dispersion is 10-25 wt%.

4. The process for the in-situ polymerization of zinc oxide / nylon 6 chips according to one of claims 1 to 3, characterized in that, In step (1), the temperature of the heating and stirring is 75-90°C, and the time is 4-8 h; and the grinding is performed until the particle size D99 is less than 1 μm.

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

6. The process for in-situ polymerization preparation of zinc oxide / nylon 6 chips according to claim 1 or 5, 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 the caprolactam.

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

8. The process for in-situ polymerization of zinc oxide / nylon 6 chips according to claim 1, characterized in that, In step (3), the chain extender includes one or more of 9,9-bis[4-(2,3-epoxypropoxyethoxy)phenyl]fluorene, dipropylene glycol diglycidyl ether, 2,6-bis(oxazolidin-2-ylmethyl)pyrrolo[3,4-F]isoindole-1,3,5,7(2H,6H)-tetraone, 2,2'-[1,4-phenylenebis(oxymethylene)]dioxirane, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, diethylene glycol diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether and 1,4-butanediol diglycidyl ether.

9. The process for in-situ polymerization of zinc oxide / nylon 6 chips according to claim 1 or 7, characterized in that, In step (3), the temperature of the polymerization reaction is 250-265°C, the pressure is <-0.07 MPa, and the time is 2-8 h.

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