Enhanced flame-retardant antistatic PA6 plastic and its preparation process

Abstract

The application discloses a kind of reinforced flame-retardant antistatic PA6 plastics and preparation process thereof, belong to high polymer material field. Through the synergistic effect of modified graphene, phosphorus-nitrogen flame retardant, conductive carbon black-polyethylene glycol antistatic agent and silane treated glass fiber, the balance and promotion of material in flame retardancy, antistatic property and mechanical strength are realized. The interfacial chemical bonding of compatibilizer and glass fiber effectively improves the interfacial bonding force of the composite material, and the antioxidant ensures the processing stability. The material preparation process is simple, suitable for industrial production, and can be widely used in electronic appliances, automobile parts, industrial equipment and other fields with high requirements for flame retardancy, antistatic property and mechanical properties.

Description

TECHNICAL FIELD

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

[0002] PA6 is a commonly used engineering plastic, and has good wear resistance, chemical corrosion resistance and processing performance, but has two significant defects: one is flammability, and the limit oxygen index is only about 20%, and PA6 is easy to drip and cause secondary disasters during combustion; the other is high surface resistance (usually greater than 1x10 12 Ω), and is easy to accumulate static electricity, which poses a safety hazard in the manufacture of electronic components and flammable and explosive environments. In addition, although the traditional PA6 composite material can improve the performance by adding a flame retardant (such as a halogen-based flame retardant) and an antistatic agent (such as carbon black and a surfactant), the halogen-based flame retardant releases toxic gases during combustion, which does not meet environmental protection requirements; the ordinary antistatic agent is easy to migrate and fail, and the poor compatibility of the flame retardant, the antistatic agent and the PA6 matrix often leads to a significant decrease in the mechanical properties of the material.

[0003] Glass fiber (GF) is a commonly used reinforcing filler for PA6, but the surface polarity of the glass fiber does not match the non-polar matrix of PA6, and the interfacial bonding force is weak, which easily causes fiber aggregation and pull-out, limiting the improvement of the mechanical properties. In the prior art, the interfacial compatibility can be improved by treating the glass fiber with a coupling agent or adding a compatibilizer, but for the PA6 composite material with the functions of flame retardation, antistatic and high strength, the component ratio and the preparation process still need to be optimized to solve the problems of the synergistic effect among the multifunctional additives and the interfacial matching. SUMMARY

[0004] The purpose of the application is to provide a reinforced flame-retardant antistatic PA6 plastic, and to achieve a balance among the flame retardation, antistatic property, mechanical strength and processing stability of the material by modifying the graphene, the flame retardant and the antistatic agent and synergistically designing the glass fiber and the compatibilizer. Another purpose of the application is to provide a preparation process of the reinforced flame-retardant antistatic PA6 plastic.

[0005] Technical scheme: A reinforced flame-retardant antistatic PA6 plastic, characterized by comprising the following components in parts by weight: PA6 resin 60-80 parts, modified graphene 5-15 parts, phosphorus-nitrogen flame retardant 10-20 parts, antistatic agent 5-10 parts, glass fiber 10-20 parts, compatibilizer 3-5 parts and antioxidant 0.5-1 part.

[0006] The PA6 resin is a matrix material, and preferably a chip-level resin with a relative molecular mass of 1.5-2.5x10 4 .

[0007] The modified graphene is surface-grafted with amino silane, including the steps of plasma pretreatment, amino silane grafting and microwave curing;

[0008] 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.

[0009] 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 at a mass ratio of 1:2.

[0010] Preferably, the graphene is prepared by the following method: the graphene is placed in a radio frequency capacitive coupling plasma device, a mixed gas of Ar and O2 at a volume ratio of 5:1 is used as working gas, the power is 100-150 W, the processing time is 5-10 min, hydroxyl and carboxyl active sites are introduced on the surface of the graphene, the graphene after plasma treatment is dispersed in anhydrous ethanol, an amino silane coupling agent is added, the mass ratio of the coupling agent to the graphene is 1.5:1, stirring is carried out at 60℃ for 4 h, a high-density grafted layer is formed through chemical bonding of the plasma-induced active sites and the silane groups, and after the reaction is completed, the mixture is transferred to a microwave reactor, the power is 300 W, and the processing time is 10 min to promote the stabilization of the grafted bonds.

[0011] Preferably, the phosphorus-nitrogen flame retardant is prepared by the following method: melamine polyphosphate and pentaerythritol diphosphate melamine salt are mixed at 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, melt blending is carried out at 150℃ for 2 h to form a phosphorus-nitrogen-silicon composite flame retardant, and in-situ polymerization is enhanced by adding a small amount of initiator dicumyl peroxide, accounting for 0.1%-0.8% of the total mass of the system, to initiate the grafting reaction of the siloxane segment and the phosphorus-nitrogen compound at 200℃ to form a three-dimensional cross-linked structure.

[0012] Preferably, the antistatic agent is prepared by the following method: the conductive carbon black is first added to a high-speed mixer, and then the polyethylene glycol is added, the mass ratio of the conductive carbon black to the polyethylene glycol is 1:2, the rotation speed is set to 600 r / min, and the mixing is carried out for 15 min to uniformly disperse the conductive carbon black in the polyethylene glycol to obtain the antistatic agent.

[0013] Preferably, the glass fiber is short-cut glass fiber treated with a silane coupling agent on the surface, the diameter is 6-15 μm, and the length is 3-6 mm; the silane coupling agent is amino silane or epoxy silane; the compatibilizer is maleic anhydride grafted polypropylene with a grafting rate of 3%-5%, which synergistically acts with the glass fiber to form a chemical bond between the maleic anhydride groups and the silicon hydroxyl groups on the surface of the glass fiber, so that the tensile strength of the composite material is increased by 25%-40% compared with when no compatibilizer is added.

[0014] Preferably, the antioxidant is 2,6-di-tert-butyl-p-cresol, industrial grade purity ≥ 99%.

[0015] A preparation process of the reinforced flame-retardant antistatic PA6 plastic according to any one of claims 1-6, characterized by comprising the following steps:

[0016] S1, drying the PA6 resin at 80-100 DEG C for 4-6 hours for standby;

[0017] S2, the modified graphene, phosphorus-nitrogen flame retardant, antistatic agent, glass fiber, compatibilizer, antioxidant are weighed in parts by weight, placed in a high-speed mixer, set the rotation speed to 500 r / min, mixed for 20 minutes, to get the mixture;

[0018] S3, the dried PA6 resin and the mixture are added to a twin-screw extruder, and melt blended at 220-260 DEG C, extruded and granulated to obtain the reinforced flame-retardant antistatic PA6 plastic particles.

[0019] Beneficial effects:

[0020] 1. The plasma pretreatment makes the surface oxygen functional group density of graphene increase by more than 3 times, the modified graphene is treated by plasma pretreatment, amino silane grafting and microwave curing, the active site and grafting rate are significantly improved, the interface bonding force between the graphene and the PA6 matrix is enhanced, the mechanical properties of the material are improved, and the conductive network is effectively constructed.

[0021] 2. The phosphorus-nitrogen flame retardant is formed by melt blending and in-situ polymerization of melamine polyphosphate, pentaerythritol bisphosphate melamine salt and dimethyl silicone oil, forming a phosphorus-nitrogen-silicon synergistic flame retardant system, and the flame retardant efficiency is greatly improved.

[0022] 3. The antistatic agent is a mixture of conductive carbon black with an average particle size of ≤ 50 nm and polyethylene glycol with a molecular weight of 2000-4000 at a mass ratio of 1:2, which can build a stable conductive path and ensure the dispersion stability and compatibility in the PA6 matrix. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the data of the grafting rate of the modified graphene.

[0024] Figure 2 is a performance test comparison result graph of the examples and the comparative examples.

[0025] Figure 3 is a diagram of the actual particles made. DETAILED DESCRIPTION

[0026] In order to make the technical scheme of the present application clearer, the following will further illustrate the present application in combination with the drawings and specific embodiments.

[0027] Example 1

[0028] (1) Preparation of modified graphene: 20 g of graphene was placed in a radio frequency capacitive coupled plasma device, with a mixture of Ar and O2 as working gas at a volume ratio of 5:1, power of 120 W, and processing time of 8 min, to introduce active sites such as hydroxyl and carboxyl groups on the surface of the graphene. The graphene after plasma treatment was dispersed in anhydrous ethanol, 30 g of amino silane coupling agent was added, and the mixture was stirred at 60°C for 4 h. Through the chemical bonding of the active sites induced by plasma and the silane groups, a high-density grafted layer was formed. After the reaction was completed, the mixture was transferred to a microwave reactor, treated at a power of 300 W for 10 min to promote the stabilization of the grafted bonds, and the modified graphene was obtained;

[0029] (2) Preparation of phosphorus-nitrogen flame retardant: 20 g of melamine polyphosphate and 30 g of pentaerythritol bisphosphate melamine salt were mixed, 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 initiator dicumyl peroxide was added to initiate the grafting reaction between the siloxane segment and the phosphorus-nitrogen compound at 200°C, forming a three-dimensional cross-linked structure;

[0030] (3) Preparation of antistatic agent: 10 g of conductive carbon black was first added to a high-speed mixer, and then 20 g of polyethylene glycol was added. The rotation speed was set to 600 r / min, and the mixture was mixed for 15 minutes to ensure uniform dispersion of the conductive carbon black in the polyethylene glycol, obtaining the antistatic agent;

[0031] (4) 100 g of PA6 resin was dried at 80-100°C for 4-6 hours for standby;

[0032] (5) 10 g of modified graphene from step (1), 15 g of phosphorus-nitrogen flame retardant from step (2), 7.5 g of antistatic agent from step (3), 15 g of glass fiber, 4 g of compatibilizer, and 0.8 g of antioxidant were weighed according to the weight parts and placed in a high-speed mixer. The rotation speed was set to 500 r / min, and the mixture was mixed for 20 minutes to obtain a mixture;

[0033] (6) 70 g of PA6 resin from step (4) after drying was added to a twin-screw extruder together with the mixture, and melt blended at 220-260°C to obtain reinforced flame-retardant antistatic PA6 plastic particles.

[0034] Example 2

[0035] (1) Preparation of modified graphene: 20 g of graphene was placed in a radio frequency capacitive coupled plasma device, with a mixture of Ar and O2 as working gas at a volume ratio of 5:1, power of 120 W, and processing time of 8 min. Active sites such as hydroxyl and carboxyl groups were introduced on the surface of the graphene. The graphene after plasma treatment was dispersed in anhydrous ethanol, 30 g of amino silane coupling agent was added, and the mixture was stirred at 60°C for 4 h. Through the chemical bonding of the active sites induced by plasma and the silane groups, a high-density grafted layer was formed. After the reaction was completed, the mixture was transferred to a microwave reactor, treated at a power of 300 W for 10 min to promote the stabilization of the grafting bond, and the modified graphene was obtained;

[0036] (2) Preparation of phosphorus-nitrogen flame retardant: 20 g of melamine polyphosphate and 30 g of pentaerythritol bisphosphate melamine salt were mixed, 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 initiator dicumyl peroxide was added to initiate the grafting reaction between the siloxane segment and the phosphorus-nitrogen compound at 200°C, forming a three-dimensional cross-linked structure;

[0037] (3) Preparation of antistatic agent: 10 g of conductive carbon black was added to a high-speed mixer, followed by the addition of 20 g of polyethylene glycol, and the mixture was mixed at a speed of 600 r / min for 15 min to uniformly disperse the conductive carbon black in the polyethylene glycol, obtaining an antistatic agent;

[0038] (4) 100 g of PA6 resin was dried at 80-100°C for 4-6 hours for standby;

[0039] (5) 5 g of modified graphene from step (1), 10 g of phosphorus-nitrogen flame retardant from step (2), 5 g of antistatic agent from step (3), 10 g of glass fiber, 3 g of compatibilizer, and 0.5 g of antioxidant were weighed according to the weight parts, and placed in a high-speed mixer, set at a speed of 500 r / min, and mixed for 20 min to obtain a mixture;

[0040] (6) 60 g of PA6 resin from step (4) after drying was added to the mixture and fed into a twin-screw extruder, melt blended at 220-260°C, extruded and granulated to obtain reinforced flame-retardant antistatic PA6 plastic particles.

[0041] Example 3

[0042] (1) Preparation of modified graphene: 20 g of graphene was placed in a radio frequency capacitive coupled plasma device, with a mixture of Ar and O2 as working gas at a volume ratio of 5:1, power of 120 W, and processing time of 8 min. Active sites such as hydroxyl and carboxyl groups were introduced on the surface of the graphene. The graphene after plasma treatment was dispersed in anhydrous ethanol, 30 g of amino silane coupling agent was added, and the mixture was stirred at 60°C for 4 h. Through the chemical bonding of the active sites induced by plasma and the silane groups, a high-density grafted layer was formed. After the reaction was completed, the mixture was transferred to a microwave reactor, treated at a power of 300 W for 10 min to promote the stabilization of the grafting bond, and the modified graphene was obtained;

[0043] (2) Preparation of phosphorus-nitrogen flame retardant: 20 g of melamine polyphosphate and 30 g of pentaerythritol bisphosphate melamine salt were mixed, 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 initiator dicumyl peroxide was added to initiate the grafting reaction between the siloxane segment and the phosphorus-nitrogen compound at 200°C, forming a three-dimensional cross-linked structure;

[0044] (3) Preparation of antistatic agent: 10 g of conductive carbon black was first added to a high-speed mixer, followed by the addition of 20 g of polyethylene glycol, and the rotation speed was set to 600 r / min. The conductive carbon black was uniformly dispersed in the polyethylene glycol by mixing for 15 minutes to obtain an antistatic agent;

[0045] (4) 100 g of PA6 resin was dried at 80-100°C for 4-6 hours for standby use;

[0046] (5) 15 g of modified graphene from step (1), 20 g of phosphorus-nitrogen flame retardant from step (2), 10 g of antistatic agent from step (3), 20 g of glass fiber, 5 g of compatibilizer, and 1 g of antioxidant were weighed according to the weight parts and placed in a high-speed mixer. The rotation speed was set to 500 r / min, and the mixture was mixed for 20 minutes to obtain a mixture;

[0047] (6) 80 g of PA6 resin from step (4) after drying was added to the mixture and fed into a twin-screw extruder. The mixture was melt blended at 220-260°C, extruded and granulated to obtain reinforced flame-retardant antistatic PA6 plastic particles.

[0048] Comparative Example 1

[0049] The same as Example 1, except that unmodified graphene was used.

[0050] Comparative Example 2

[0051] The same as Example 1, except that aluminum hydroxide was used instead of phosphorus-nitrogen flame retardant.

[0052] Comparative Example 3

[0053] The difference from Example 1 is that there is no antistatic agent.

[0054] The compositions and preparation processes of the reinforced flame-retardant antistatic PA6 plastics described in Examples 1, 2, and 3 respectively correspond to Comparative Examples 1, 2, and 3, and the compositions and preparation methods thereof are basically the same. The main differences are as follows: (1) in Comparative Example 1, the graphene is changed to unmodified graphene, (2) in Comparative Example 2, the phosphorus-nitrogen-based flame retardant is changed to ordinary aluminum hydroxide flame retardant on the market, and (3) in Comparative Example 3, no antistatic agent is added.

[0055] Performance test method

[0056] Tensile strength: according to GB / T 1040.2-2006 standard;

[0057] Bending strength: according to GB / T 9341-2008 standard;

[0058] Oxygen index: according to GB / T 2406.2-2009 standard;

[0059] Vertical burning grade: according to GB / T 2408-2021 standard;

[0060] Surface resistance: according to GB / T 1410-2006 standard;

[0061] Melt index: according to GB / T 3682.1-2018 standard;

[0062] Grafting rate calculation: elemental analysis method (grafting rate (%) ≈ (modified graphene N atom content - untreated graphene N atom content) ÷ theoretical proportion of N atoms in amino silane × 100%).

[0063] The performance test comparison results of the above examples and comparative examples are as follows: Figure 1The results show that the enhanced flame-retardant antistatic PA6 plastic provided by the application has excellent tensile strength, bending strength, oxygen index, vertical burning grade, surface resistance and melt index performance. Examples 1-3: all performances meet the standards, indicating that the component ratio has a synergistic effect within the range of 60-80 parts of PA6, 5-15 parts of modified graphene, etc.; Comparative Example 1: ordinary graphene lacks surface modification, has poor compatibility with the PA6 matrix, resulting in a significant decrease in the tensile and bending strength of the material, indicating that the modified graphene has an auxiliary effect on interface enhancement; at the same time, it is difficult to effectively disperse 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 play a flame-retardant role, but lacks gas-phase flame-retardant and carbon layer construction ability, the oxygen index is greatly reduced to 24%, the vertical burning grade is only HB grade, and the flame-retardant effect is far inferior to that of the phosphorus-nitrogen flame retardant of the present patent; Comparative Example 3: without 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.

[0064] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the present patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which belong to the protection scope of the present application. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. Reinforced flame-retardant antistatic PA 6 plastic, characterized in that, By weight parts including the following components: PA6 resin 60-80 parts, modified graphene 5-15 parts, phosphorus-nitrogen flame retardant 10-20 parts, antistatic agent 5-10 parts, glass fiber 10-20 parts, compatibilizer 3-5 parts, antioxidant 0.5-1 part; The PA6 resin is a base material, which is a slice-level resin with a relative molecular mass of 1.5-2.5×10 4 ​ The modified graphene is surface-grafted with amino silane, including the steps of plasma pretreatment, amino silane grafting and microwave curing; 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 at a mass ratio of 1:

2.

2. Reinforced flame-retardant antistatic PA6 plastic according to claim 1, characterized in that, The preparation method of the modified graphene is as follows: the graphene is placed in a radio frequency capacitive coupling plasma device, Ar and O2 mixed gas with a volume ratio of 5:1 is used as working gas, the power is 100-150 W, and the treatment time is 5-10 min, so as to introduce hydroxyl and carboxyl active sites on the surface of the graphene; the graphene after plasma treatment is dispersed in anhydrous ethanol, amino silane coupling agent is added, the mass ratio of the coupling agent to the graphene is 1.5:1, stirring is carried out at 60℃ for 4 h, a high-density grafting layer is formed through chemical bonding of the plasma-induced active sites and silane groups, and after the reaction is completed, the mixture is transferred to a microwave reactor, the power is 300 W, and the treatment time is 10 min, so as to promote the stabilization of the grafting bond.

3. Reinforced flame retardant antistatic PA6 plastic according to claim 1, characterized in that, The preparation method of the phosphorus-nitrogen flame retardant is as follows: melamine polyphosphate and pentaerythritol diphosphate melamine salt are mixed at a mass ratio of 1:1.5, 10% silicon-containing dimethyl silicone oil is added, the amount of the dimethyl silicone oil accounts for 10% of the mass of the mixture, melt blending is carried out at 150℃ for 2 h, a phosphorus-nitrogen-silicon composite flame retardant is formed, and in-situ polymerization is carried out to enhance the flame retardant: a small amount of initiator dicumyl peroxide is added, the amount of the initiator accounts for 0.1%-0.8% of the total mass of the system, the grafting reaction of the siloxane segment and the phosphorus-nitrogen compound is initiated at 200℃, and a three-dimensional cross-linked structure is formed.

4. Reinforced flame retardant antistatic PA6 plastic according to claim 1, characterized in that, The preparation method of the antistatic agent is as follows: the conductive carbon black is first added to a high-speed mixer, then the polyethylene glycol is added, the mass ratio of the conductive carbon black to the polyethylene glycol is 1:2, the rotation speed is set to 600 r / min, and the mixing is carried out for 15 min, so that the conductive carbon black is uniformly dispersed in the polyethylene glycol to obtain the antistatic agent.

5. The reinforced flame retardant antistatic PA6 plastic according to claim 1, characterized in that, The glass fiber is short-cut glass fiber treated with a silane coupling agent on the surface, the diameter is 6-15 μm, and the length is 3-6 mm; the silane coupling agent is amino silane or epoxy silane; the compatibilizer is maleic anhydride grafted polypropylene with a grafting rate of 3%-5%, which synergistically acts with the glass fiber to form a chemical bond between the maleic anhydride groups and the silicon hydroxyl groups on the surface of the glass fiber, so that the tensile strength of the composite material is increased by 25%-40% compared with the case where the compatibilizer is not added.

6. Reinforced flame retardant antistatic PA6 plastic according to claim 1, characterized by: The antioxidant is 2,6-di-tert-butyl-p-cresol with an industrial purity of ≥99%.

7. A process for the preparation of a reinforced flame-retardant antistatic PA 6 plastic as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1, drying PA6 resin at 80-100℃ for 4-6 hours for standby use; S2, the modified graphene, phosphorus-nitrogen flame retardant, antistatic agent, glass fiber, compatibilizer, antioxidant, is weighed in parts by weight, placed in a high-speed mixer, set the speed to 500 r / min, mixed for 20 minutes, to get the mixture; S3, the dried PA6 resin and the mixture are added to a twin-screw extruder, melt blended at 220-260℃, extruded and granulated, to get reinforced flame-retardant antistatic PA6 plastic particles.

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