Reinforced flame-retardant antistatic PA6 plastic and preparation process thereof

Abstract

The invention discloses a reinforced flame-retardant antistatic PA6 plastic and a preparation process thereof, and belongs to the field of high polymer materials. Through the synergistic effect of the modified graphene, the phosphorus-nitrogen flame retardant, the conductive carbon black-polyethylene glycol antistatic agent and the silane treated glass fiber, the flame retardance, antistatic property and mechanical strength of the material are balanced and improved. The interface bonding force of the composite material is effectively improved through interface chemical bonding of the compatilizer and the glass fibers, and the processing stability is guaranteed through the antioxidant. The material is simple in preparation process, is suitable for industrial production, and can be widely applied to the fields of electronic appliances, automobile parts, industrial equipment and the like with higher requirements on flame retardance, antistatic property and mechanical property.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a reinforced flame-retardant and antistatic PA6 plastic and a preparation process thereof. Background Art

[0002] PA6 is a commonly used engineering plastic with good wear resistance, chemical corrosion resistance and processing performance. However, it has two significant defects: first, it is flammable, with a limiting oxygen index of only about 20%, which makes it easy to drip and cause secondary disasters when burning; second, it has a high surface resistance (usually greater than 1×10 12 Ω), which easily accumulates static electricity, posing a safety hazard in electronic component manufacturing and in flammable and explosive environments. Furthermore, while traditional PA6 composites can be improved by adding flame retardants (such as halogenated flame retardants) and antistatic agents (such as carbon black and surfactants), halogenated flame retardants release toxic gases when burned, which is not environmentally friendly. Conventional antistatic agents are prone to migration and ineffectiveness, and flame retardants and antistatic agents have poor compatibility with the PA6 matrix, often leading to a significant decrease in the material's mechanical properties.

[0003] Glass fiber (GF) is a commonly used reinforcing filler in PA6, but its surface polarity is mismatched with the non-polar PA6 matrix, resulting in weak interfacial bonding and prone to fiber agglomeration and pullout, limiting improvements in mechanical properties. Existing technologies can improve interfacial compatibility by treating glass fiber with coupling agents or adding compatibilizers. However, for PA6 composites that simultaneously exhibit flame retardancy, antistatic properties, and high strength, optimized component ratios and preparation processes are still needed to address synergistic effects and interfacial matching between multifunctional additives. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a reinforced flame-retardant and antistatic PA6 plastic. By modifying graphene, flame retardants, and antistatic agents and co-designing them with glass fiber and compatibilizers, a balance between flame retardancy, antistatic properties, mechanical strength and processing stability is achieved in the material. Another purpose of the present invention is to provide a preparation process for the reinforced flame-retardant and antistatic PA6 plastic.

[0005] Technical solution: A reinforced flame-retardant and antistatic PA6 plastic, characterized by comprising the following components by weight: 60-80 parts of PA6 resin, 5-15 parts of modified graphene, 10-20 parts of phosphorus-nitrogen flame retardant, 5-10 parts of antistatic agent, 10-20 parts of glass fiber, 3-5 parts of compatibilizer, and 0.5-1 part of antioxidant; Among them, PA6 resin is the matrix material, preferably with a relative molecular mass of 1.5-2.5×10 4 Chip-grade resin; The modified graphene is surface-grafted with aminosilane, which includes plasma pretreatment, aminosilane grafting and microwave curing steps; The phosphorus-nitrogen flame retardant is prepared by melt blending and in-situ polymerization of melamine polyphosphate, pentaerythritol diphosphate melamine salt and dimethyl silicone oil; The antistatic agent is prepared by mixing and dispersing conductive carbon black with an average particle size of ≤50nm and polyethylene glycol with a molecular weight of 2000-4000 in a mass ratio of 1:2.

[0006] Preferably, the preparation method of graphene is as follows: placing graphene in a radio frequency capacitively coupled plasma device, using a mixed gas of Ar and O2 with a volume ratio of 5:1 as the working gas, a power of 100-150W, a treatment time of 5-10min, introducing hydroxyl and carboxyl active sites on the graphene surface, dispersing the plasma-treated graphene in anhydrous ethanol, adding an aminosilane coupling agent, wherein the mass ratio of the coupling agent to the graphene is 1.5:1, stirring and reacting at 60°C for 4h, forming a high-density grafted layer through chemical bonding between the plasma-induced active sites and the silane groups, and after the reaction is completed, transferring the mixture to a microwave reactor with a power of 300W and a treatment time of 10min to promote the stabilization of the grafted bond.

[0007] Preferably, the preparation method of the phosphorus-nitrogen flame retardant is as follows: melamine polyphosphate and pentaerythritol diphosphate melamine salt are mixed in a mass ratio of 1:1.5, dimethyl silicone oil with a silicon content of 10% is added, accounting for 10% of the mass of the mixture, and melt blending is carried out at 150°C for 2 hours to form a phosphorus-nitrogen-silicon composite flame retardant, and in situ polymerization enhancement is carried out: a small amount of initiator diisopropylbenzene peroxide is added, accounting for 0.1% to 0.8% of the total mass of the system, and a grafting reaction of the siloxane chain segment and the phosphorus-nitrogen compound is initiated at 200°C to form a three-dimensional cross-linked structure.

[0008] Preferably, the preparation method of the antistatic agent is: first add conductive carbon black to a high-speed mixer, and then add polyethylene glycol, wherein the conductive carbon black and polyethylene glycol are added in a mass ratio of 1:2, set the speed to 600r / min, and mix for 15 minutes to uniformly disperse the conductive carbon black in the polyethylene glycol to obtain the antistatic agent.

[0009] Preferably, the glass fiber is a chopped glass fiber whose surface is treated with a silane coupling agent, with a diameter of 6-15 μm and a length of 3-6 mm. The silane coupling agent is aminosilane or epoxysilane; the compatibilizer is maleic anhydride grafted polypropylene with a grafting rate of 3%-5%. It acts synergistically with the glass fiber to form a chemical bond with the silicon hydroxyl group on the surface of the glass fiber through the maleic anhydride group, so that the tensile strength of the composite material is increased by 25%-40% compared with when no compatibilizer is added.

[0010] Preferably, the antioxidant is 2,6-di-tert-butyl-p-cresol with an industrial grade purity of ≥99%.

[0011] A process for preparing the reinforced flame-retardant and antistatic PA6 plastic according to any one of claims 1 to 6, characterized in that it comprises the following steps: S1. Dry the PA6 resin at 80-100°C for 4-6 hours and set aside; S2. Weigh the modified graphene, phosphorus-nitrogen flame retardant, antistatic agent, glass fiber, compatibilizer, and antioxidant in parts by weight, place them in a high-speed mixer, set the speed to 500 r / min, and mix for 20 minutes to obtain a mixture; S3. Add the dried PA6 resin and the mixed material into a twin-screw extruder, melt-blend at 220-260° C., extrude and granulate to obtain reinforced flame-retardant and antistatic PA6 plastic particles.

[0012] Beneficial effects: 1. Plasma pretreatment increases the density of oxygen-containing functional groups on the graphene surface by more than three times. After plasma pretreatment, aminosilane grafting and microwave curing, the modified graphene has significantly increased active sites and grafting rate, thereby enhancing its interfacial bonding with the PA6 matrix, effectively building a conductive network while improving the mechanical properties of the material.

[0013] 2. Phosphorus-nitrogen flame retardants are formed by melt blending and in-situ polymerization of melamine polyphosphate, pentaerythritol diphosphate melamine salt and dimethyl silicone oil to form a phosphorus-nitrogen-silicon synergistic flame retardant system, which greatly improves the flame retardant efficiency.

[0014] 3. The antistatic agent is a mixture of conductive carbon black with an average particle size of ≤50nm and polyethylene glycol with a molecular weight of 2000-4000 in a mass ratio of 1:2. While constructing a stable conductive path, it ensures the dispersion stability and compatibility in the PA6 matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the data on the improvement of the grafting rate of modified graphene.

[0016] Figure 2 2 is a performance test comparison diagram of the embodiment and the comparative example.

[0017] Figure 3 It is a physical particle map produced. DETAILED DESCRIPTION

[0018] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 (1) Preparation of modified graphene: 20 g of graphene was placed in a radio frequency capacitively coupled plasma device, with a mixed gas of Ar and O2 in a volume ratio of 5:1 as the working gas, a power of 120 W, and a treatment time of 8 min. Active sites such as hydroxyl and carboxyl groups were introduced on the graphene surface. The plasma-treated graphene was dispersed in anhydrous ethanol, and 30 g of aminosilane coupling agent was added. The reaction was stirred at 60 ° C for 4 h. A high-density grafted layer was formed through chemical bonding between the plasma-induced active sites and the silane groups. After the reaction, the mixture was transferred to a microwave reactor with a power of 300 W and a treatment time of 10 min to promote the stabilization of the grafted bonds to obtain modified graphene. (2) Preparation of phosphorus-nitrogen flame retardant: 20 g of melamine polyphosphate was mixed with 30 g of pentaerythritol diphosphate melamine salt, 5 g of dimethyl silicone oil with a silicon content of 10% was added, and the mixture was melt-blended at 150 °C for 2 h to form a phosphorus-nitrogen-silicon composite flame retardant. In-situ polymerization enhancement: 0.2 g of diisopropylbenzene peroxide was added as an initiator, and the grafting reaction of the siloxane chain segment and the phosphorus-nitrogen compound was initiated at 200 °C to form a three-dimensional cross-linked structure. (3) Preparation of antistatic agent: First, add 10g of conductive carbon black into a high-speed mixer, then add 20g of polyethylene glycol, set the speed to 600r / min, and mix for 15 minutes to evenly disperse the conductive carbon black in the polyethylene glycol to obtain an antistatic agent; (4) Dry 100g PA6 resin at 80-100℃ for 4-6 hours and set aside; (5) Weigh 10 g of the modified graphene prepared in step (1), 15 g of the phosphorus-nitrogen flame retardant prepared in step (2), 7.5 g of the antistatic agent prepared in step (3), 15 g of glass fiber, 4 g of a compatibilizer, and 0.8 g of an antioxidant, according to weight, place the mixture in a high-speed mixer, set the speed to 500 r / min, and mix for 20 minutes to obtain a mixture; (6) Add 70 g of the PA6 resin obtained in step (4) after drying and the mixed material into a twin-screw extruder, melt-blend at 220-260°C, and extrude into granules to obtain reinforced flame-retardant and antistatic PA6 plastic granules.

[0020] Example 2 (1) Preparation of modified graphene: 20 g of graphene was placed in a radio frequency capacitively coupled plasma device, with a mixed gas of Ar and O2 in a volume ratio of 5:1 as the working gas, a power of 120 W, and a treatment time of 8 min. Active sites such as hydroxyl and carboxyl groups were introduced on the graphene surface. The plasma-treated graphene was dispersed in anhydrous ethanol, and 30 g of aminosilane coupling agent was added. The reaction was stirred at 60 ° C for 4 h. A high-density grafted layer was formed through chemical bonding between the plasma-induced active sites and the silane groups. After the reaction, the mixture was transferred to a microwave reactor with a power of 300 W and a treatment time of 10 min to promote the stabilization of the grafted bonds to obtain modified graphene. (2) Preparation of phosphorus-nitrogen flame retardant: 20 g of melamine polyphosphate was mixed with 30 g of pentaerythritol diphosphate melamine salt, 5 g of dimethyl silicone oil with a silicon content of 10% was added, and the mixture was melt-blended at 150 °C for 2 h to form a phosphorus-nitrogen-silicon composite flame retardant. In-situ polymerization enhancement: 0.2 g of diisopropylbenzene peroxide was added as an initiator, and the grafting reaction of the siloxane chain segment and the phosphorus-nitrogen compound was initiated at 200 °C to form a three-dimensional cross-linked structure. (3) Preparation of antistatic agent: First, add 10g of conductive carbon black into a high-speed mixer, then add 20g of polyethylene glycol, set the speed to 600r / min, and mix for 15 minutes to evenly disperse the conductive carbon black in the polyethylene glycol to obtain an antistatic agent; (4) Dry 100g PA6 resin at 80-100℃ for 4-6 hours and set aside; (5) Weigh 5 g of the modified graphene prepared in step (1), 10 g of the phosphorus-nitrogen flame retardant prepared in step (2), 5 g of the antistatic agent prepared in step (3), 10 g of glass fiber, 3 g of a compatibilizer, and 0.5 g of an antioxidant, according to weight, place the mixture in a high-speed mixer, set the speed to 500 r / min, and mix for 20 minutes to obtain a mixture; (6) Add 60 g of the PA6 resin obtained in step (4) after drying and the mixed material into a twin-screw extruder, melt-blend at 220-260°C, and extrude into granules to obtain reinforced flame-retardant and antistatic PA6 plastic granules.

[0021] Example 3 (1) Preparation of modified graphene: 20 g of graphene was placed in a radio frequency capacitively coupled plasma device, with a mixed gas of Ar and O2 in a volume ratio of 5:1 as the working gas, a power of 120 W, and a treatment time of 8 min. Active sites such as hydroxyl and carboxyl groups were introduced on the graphene surface. The plasma-treated graphene was dispersed in anhydrous ethanol, and 30 g of aminosilane coupling agent was added. The reaction was stirred at 60 ° C for 4 h. A high-density grafted layer was formed through chemical bonding between the plasma-induced active sites and the silane groups. After the reaction, the mixture was transferred to a microwave reactor with a power of 300 W and a treatment time of 10 min to promote the stabilization of the grafted bonds to obtain modified graphene. (2) Preparation of phosphorus-nitrogen flame retardant: 20 g of melamine polyphosphate was mixed with 30 g of pentaerythritol diphosphate melamine salt, 5 g of dimethyl silicone oil with a silicon content of 10% was added, and the mixture was melt-blended at 150 °C for 2 h to form a phosphorus-nitrogen-silicon composite flame retardant. In-situ polymerization enhancement: 0.2 g of diisopropylbenzene peroxide was added as an initiator, and the grafting reaction of the siloxane chain segment and the phosphorus-nitrogen compound was initiated at 200 °C to form a three-dimensional cross-linked structure. (3) Preparation of antistatic agent: First, add 10g of conductive carbon black into a high-speed mixer, then add 20g of polyethylene glycol, set the speed to 600r / min, and mix for 15 minutes to evenly disperse the conductive carbon black in the polyethylene glycol to obtain an antistatic agent; (4) Dry 100g PA6 resin at 80-100℃ for 4-6 hours and set aside; (5) Weigh 15 g of the modified graphene prepared in step (1), 20 g of the phosphorus-nitrogen flame retardant prepared in step (2), 10 g of the antistatic agent prepared in step (3), 20 g of glass fiber, 5 g of a compatibilizer, and 1 g of an antioxidant, according to weight, place the mixture in a high-speed mixer, set the speed to 500 r / min, and mix for 20 minutes to obtain a mixture; (6) Add 80 g of the PA6 resin obtained in step (4) after drying and the mixed material into a twin-screw extruder, melt-blend at 220-260°C, and extrude into granules to obtain reinforced flame-retardant and antistatic PA6 plastic granules.

[0022] Comparative Example 1 Same as Example 1, except that unmodified graphene is used.

[0023] Comparative Example 2 Same as Example 1, except that aluminum hydroxide is used instead of the phosphorus-nitrogen flame retardant.

[0024] Comparative Example 3 Same as Example 1, except that no antistatic agent is present.

[0025] The composition and preparation process of the reinforced flame-retardant and antistatic PA6 plastics described in Examples 1, 2, and 3 correspond to those in Comparative Examples 1, 2, and 3, respectively, and the composition, formula, and preparation method are essentially the same. The main differences are: (1) the graphene in Comparative Example 1 is replaced by unmodified graphene; (2) the phosphorus-free nitrogen-based flame retardant in Comparative Example 2 is replaced by a commercially available aluminum hydroxide flame retardant; and (3) no antistatic agent is added in Comparative Example 3.

[0026] Performance testing methods Tensile strength: According to GB / T 1040.2-2006 standard; Bending strength: in accordance with GB / T 9341-2008 standard; Oxygen index: in accordance with GB / T 2406.2-2009 standard; Vertical combustion grade: According to GB / T 2408-2021 standard; Surface resistance: Refer to GB / T 1410-2006 standard; Melt index: in accordance with GB / T 3682.1-2018 standard; Calculation of grafting rate: elemental analysis method (grafting rate (%) ≈ (N atom content of modified graphene - N atom content of untreated graphene) ÷ theoretical proportion of N atoms in aminosilane × 100%).

[0027] The performance test comparison results of the above embodiments and comparative examples are as follows: Figure 1 The results show that the reinforced flame retardant and antistatic PA6 plastic provided by the present invention has excellent tensile strength, flexural strength, oxygen index, vertical burning grade, surface resistance and melt index. Examples 1-3: All properties meet the standards, indicating that the component ratio has a synergistic effect within the range of 60-80 parts PA6, 5-15 parts modified graphene; Comparative Example 1: Ordinary graphene has poor compatibility with the PA6 matrix due to the lack of surface modification, resulting in a significant decrease in the tensile and flexural strength of the material, indicating that modified graphene has an auxiliary effect on interface enhancement; at the same time, it is difficult to effectively disperse it in the matrix to form a conductive network, and the surface resistance increases by 1 order of magnitude; Comparative Example 2: Aluminum hydroxide, as a common inorganic flame retardant, decomposes and absorbs heat to exert a flame retardant effect, but lacks gas phase flame retardancy and carbon layer construction capabilities. The oxygen index is greatly reduced to 24%, and the vertical burning grade is only HB grade. The flame retardant effect is far inferior to the phosphorus-nitrogen flame retardant of this patent; Comparative Example 3: In the absence of an antistatic agent, the surface resistance increases by 3 orders of magnitude, indicating that the conductive carbon black-polyethylene glycol system is the core of the antistatic performance.

[0028] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A reinforced flame retardant antistatic PA6 plastic, characterized in that: The composition includes the following components by weight: 60-80 parts of PA6 resin, 5-15 parts of modified graphene, 10-20 parts of phosphorus-nitrogen flame retardant, 5-10 parts of antistatic agent, 10-20 parts of glass fiber, 3-5 parts of compatibilizer, and 0.5-1 part of antioxidant; The PA6 resin is the matrix material, preferably with a relative molecular mass of 1.5-2.5×10 4 Chip-grade resin; The modified graphene is surface-grafted with aminosilane, which includes plasma pretreatment, aminosilane grafting and microwave curing steps; The phosphorus-nitrogen flame retardant is prepared by melt blending and in-situ polymerization of melamine polyphosphate, pentaerythritol diphosphate melamine salt and dimethyl silicone oil; The antistatic agent is prepared by mixing and dispersing conductive carbon black with an average particle size of ≤50 nm and polyethylene glycol with a molecular weight of 2000-4000 in a mass ratio of 1:

2.

2. The reinforced flame retardant antistatic PA6 plastic according to claim 1, characterized in that: The modified graphene is prepared by placing the graphene in a radio frequency capacitively coupled plasma device, using a mixed gas of Ar and O2 in a volume ratio of 5:1 as the working gas, a power of 100-150W, and a treatment time of 5-10 minutes, introducing hydroxyl and carboxyl active sites on the graphene surface, dispersing the plasma-treated graphene in anhydrous ethanol, adding an aminosilane coupling agent, wherein the mass ratio of the coupling agent to the graphene is 1.5:1, stirring and reacting at 60°C for 4 hours, forming a high-density grafted layer through chemical bonding between the plasma-induced active sites and the silane groups, and after the reaction, transferring the mixture to a microwave reactor, treating it at a power of 300W for 10 minutes to promote the stabilization of the grafted bonds.

3. The reinforced flame retardant and antistatic PA6 plastic according to claim 1, characterized in that: The preparation method of the phosphorus-nitrogen flame retardant comprises: mixing melamine polyphosphate and pentaerythritol diphosphate melamine salt in a mass ratio of 1:1.5, adding dimethyl silicone oil with a silicon content of 10%, accounting for 10% of the mass of the mixture, and melt blending at 150°C for 2 hours to form a phosphorus-nitrogen-silicon composite flame retardant; and in-situ polymerization enhancement: adding a small amount of initiator dicumyl peroxide, accounting for 0.1% to 0.8% of the total mass of the system, and initiating a grafting reaction between the siloxane chain segments and the phosphorus-nitrogen compound at 200°C to form a three-dimensional cross-linked structure.

4. The reinforced flame retardant and antistatic PA6 plastic according to claim 1, characterized in that: The preparation method of the antistatic agent comprises the following steps: firstly adding conductive carbon black into a high-speed mixer, then adding polyethylene glycol, wherein the conductive carbon black and polyethylene glycol are added in a mass ratio of 1:2, setting the speed to 600 r / min, mixing for 15 minutes, so that the conductive carbon black is evenly dispersed in the polyethylene glycol, and thus obtaining the antistatic agent.

5. The reinforced flame retardant and antistatic PA6 plastic according to claim 1, characterized in that: The glass fiber is a short glass fiber whose surface is treated with a silane coupling agent, with a diameter of 6-15 μm and a length of 3-6 mm. The silane coupling agent is aminosilane or epoxysilane. The compatibilizer is maleic anhydride grafted polypropylene with a grafting rate of 3%-5%. It works synergistically with the glass fiber to form chemical bonds with the silicon hydroxyl groups on the surface of the glass fiber through the maleic anhydride groups, thereby increasing the tensile strength of the composite material by 25%-40% compared with when no compatibilizer is added.

6. The reinforced flame-retardant and antistatic PA6 plastic according to claim 1, characterized in that: The antioxidant is 2,6-di-tert-butyl-p-cresol, and the industrial grade purity is ≥99%.

7. A process for preparing the reinforced flame retardant and antistatic PA6 plastic according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Dry the PA6 resin at 80-100°C for 4-6 hours and set aside; S2. Weigh the modified graphene, phosphorus-nitrogen flame retardant, antistatic agent, glass fiber, compatibilizer, and antioxidant in parts by weight, place them in a high-speed mixer, set the speed to 500 r / min, and mix for 20 minutes to obtain a mixture; S3. Add the dried PA6 resin and the mixed material into a twin-screw extruder, melt-blend at 220-260° C., extrude and granulate to obtain reinforced flame-retardant and antistatic PA6 plastic particles.

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