Highly flame-retardant sheet molding compound and preparation method thereof

Abstract

The present invention relates to the technical field of highly flame-retardant plastics, specifically disclosing a highly flame-retardant sheet molding compound and a preparation method thereof. The method comprises the following steps: S1: pre-compounding a base resin with aluminum hydroxide to obtain raw material A; S2: stirring raw material A and a low-shrinkage agent at a speed of 700-850 r / min for 2-4 minutes, adding an initiator, polymerization inhibitor, PE powder, release agent, dispersant, wetting agent, and antistatic agent, continuing stirring for 5-10 minutes, adding an inorganic filler, and mixing uniformly at a speed of 900-1100 r / min to obtain a resin paste; S3: adding a thickener and alkali-free glass fiber to the resin paste, stirring uniformly in an SMC machine, and rolling and compacting the mixture to obtain a sheet; S4: aging the sheet at 35-42°C for 12-16 hours, and winding the sheet molding compound.

Description

Technical Field

[0001] The invention relates to the technical field of high flame retardant plastics, in particular to a high flame retardant sheet molding compound and a preparation method thereof. Background Art

[0002] In the existing technology, vinyl resin itself serves as the matrix of flame retardants, and flame retardants (such as glass fiber, graphite, aluminum hydroxide, etc.) and other additives are added to the resin to form flame retardant plastics; however, with the advancement and development of science and technology, people's requirements for the flame retardancy of plastics are constantly increasing, thereby limiting its development in more areas.

[0003] In summary, it is of great significance to prepare a highly flame retardant sheet molding compound. Summary of the Invention

[0004] The object of the present invention is to provide a highly flame-retardant sheet molding compound and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] A method for preparing a highly flame-retardant sheet molding compound comprises the following steps:

[0006] S1: Pre-compounding the base resin and aluminum hydroxide to obtain raw material A;

[0007] S2: Stir raw material A and low shrinkage agent at a speed of 700-850 r / min for 2-4 minutes, add initiator, polymerization inhibitor, PE powder, release agent, dispersant, wetting agent, and antistatic agent, continue stirring for 5-10 minutes, add inorganic filler, and mix uniformly at a speed of 900-1100 r / min to obtain a resin paste;

[0008] S3: Add thickener and alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet;

[0009] S4: Curing the sheet at 35-42° C. for 12-16 hours and rolling it up to obtain a sheet molding compound.

[0010] More optimally, the viscosity of the resin paste is 20,000 to 50,000 CPS; the raw materials of the sheet molding compound include the following components: by weight, 50 to 80 parts of base resin, 50 to 120 parts of aluminum hydroxide, 20 to 40 parts of low shrinkage agent, 0.5 to 1 part of initiator, 0.5 to 1 part of inhibitor, 0.5 to 2 parts of PE powder, 2 to 5 parts of release agent, 0.5 to 2 parts of dispersant, 0.5 to 2 parts of wetting agent, 0 to 50 parts of inorganic filler, 2 to 5 parts of antistatic agent, 1 to 3 parts of thickener, and 50 to 150 parts of alkali-free glass fiber.

[0011] More preferably, the low shrinkage agent includes one or more combinations of polystyrene low shrinkage agents and saturated polyester low shrinkage agents.

[0012] More optimally, the initiator includes one or more combinations of tert-butyl perbenzoate, benzoyl peroxide, tert-butyl peracetate, and tert-amyl perbenzoate; the inhibitor includes one or more combinations of hydroquinone, benzoquinone, trimethylbenzyl ammonium chloride, and bromide.

[0013] More optimally, the release agent includes one or more combinations of zinc stearate, magnesium stearate, and calcium stearate; the antistatic agent includes one or more combinations of carbon nanotubes, graphene, and carbon black; and the thickener includes one or more combinations of calcium oxide, magnesium oxide, calcium hydroxide, and magnesium hydroxide.

[0014] More preferably, the matrix resin is a vinyl resin; the preparation process of the raw material A is as follows: (1) adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene to anhydrous ethanol, heating to 60-65° C., adding hydrogen peroxide, heating to 75-85° C., reacting for 5.5-6.5 hours, purifying, and drying to obtain DOPA;

[0015] (2) 2-amino-1H-imidazole-4-carboxylic acid is added to deionized water, heated to 80-90°C, aluminum hydroxide is added, and the reaction is carried out for 5-6 hours to obtain modified aluminum hydroxide A; DOPA is added to anhydrous ethanol and heated to 55-60°C, modified aluminum hydroxide A is added, and the reaction is carried out for 1-2 hours to obtain modified aluminum hydroxide;

[0016] (3) Heat the modified aluminum hydroxide to 60-70°C, add vinyl resin and styrene, react for 1-2 hours, cool to 45-50°C, add dimethylbenzene peroxide, stir evenly, defoam in vacuum, and react at 120°C for 2 hours to obtain raw material A.

[0017] More optimally, in the DOPA, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene to hydrogen peroxide is 1:(3-3.5).

[0018] More optimally, in the modified aluminum hydroxide A, the mass ratio of 2-amino-1H-imidazole-4-carboxylic acid to aluminum hydroxide is (7.5-8):2.

[0019] More optimally, in the modified aluminum hydroxide, the mass ratio of DOPA to modified aluminum hydroxide A is (11-11.5):8.2.

[0020] More optimally, in the raw material A, styrene accounts for 5-5.5wt% of the vinyl resin, and ditoluyl peroxide accounts for 0.8-1.2wt% of the vinyl resin.

[0021] More optimally, the alkali-free glass fiber is pre-modified to obtain modified alkali-free glass fiber; the modified alkali-free glass fiber and a thickener are added to the resin paste, stirred evenly in an SMC machine, and rolled and compacted to obtain a sheet;

[0022] The preparation method of the modified alkali-free glass fiber is as follows: (1) calcining the alkali-free glass fiber at 300-400° C. for 30-40 minutes, cooling to room temperature, adding the ethanol aqueous solution containing a mercaptosilane coupling agent, reacting for 1-2 hours, purifying, and drying to obtain the mercaptolated glass fiber; (2) placing DOPA in anhydrous ethanol, heating to 55-60° C., adding 1-vinylimidazole, reacting for 1-2 hours, purifying, and drying to obtain the modifier; and (3) placing the mercaptolated glass fiber, the modifier, and azobisisobutyronitrile in tetrahydrofuran, irradiating the solution under ultraviolet light for 2-2.5 hours, purifying, and drying to obtain the modified alkali-free glass fiber.

[0023] More optimally, the mercaptosilane coupling agent accounts for 2-3 wt% of the alkali-free glass fiber; and the mass fraction of the ethanol aqueous solution is 20-30 wt%.

[0024] More optimally, the raw materials of the modifier include the following components: 11.8 to 13 parts by weight of DOPA, 4.5 to 5.5 parts of 1-vinylimidazole, and 35 to 50 parts of anhydrous ethanol;

[0025] More optimized, the raw materials of the modified alkali-free glass fiber include the following raw materials: by weight, 0.6-0.7 parts of mercaptolated glass fiber, 5.8-6.5 parts of modifier, 0.002-0.0032 parts of azobisisobutyronitrile, and 15-25 parts of tetrahydrofuran; the process of irradiation under ultraviolet light is: the emission wavelength is 365nm, the light intensity is 90-115mW / cm 2 .

[0026] Compared with the prior art, the beneficial effect achieved by the present invention is that the raw material A is obtained by pre-compounding the modified aluminum hydroxide with styrene to modify the vinyl resin.

[0027] Among them, aluminum hydroxide itself has good flame retardant properties. At high temperatures, it will decompose and release water vapor, absorb a large amount of heat, and thus prevent the spread of flames. Using aluminum hydroxide to modify vinyl resin can improve the flame retardant properties of the material; in order to further improve the flame retardancy of vinyl resin, the present invention introduces flame retardant elements, nitrogen and phosphorus elements on the surface of aluminum hydroxide through 2-amino-1H-imidazole-4-carboxylic acid and DOPA to obtain modified aluminum hydroxide; and then reacts it with vinyl resin, which not only improves the interface compatibility between aluminum hydroxide and vinyl resin, but also improves the flame retardant properties of vinyl resin; the present invention uses calcium carbonate as a filler to improve the processing performance and stability of the material, and has lower cost than aluminum hydroxide. Therefore, adding calcium carbonate can reduce the production cost of the material without affecting its performance. At the same time, the density of calcium carbonate is relatively high, and after addition, the density of the material can be adjusted to improve its texture and feel.

[0028] The present invention prepares resin paste by uniformly mixing raw material A, low shrinkage agent, initiator, polymerization inhibitor, PE powder, release agent, dispersant, wetting agent and antistatic agent.

[0029] In order to obtain flame-retardant vinyl resin and to make it have antistatic effect, antistatic agents, one or more of graphene, carbon nanotubes and carbon black are added thereto; wherein, high-purity graphene is in a red-hot state after burning in a natural gas flame, but does not diffuse and is quenched after the flame is removed. Graphene has a high electron mobility and a large number of π-π conjugated structures, which can absorb free radicals in the flame and prevent the combustion chain reaction from proceeding, thereby effectively inhibiting the formation and spread of the flame.

[0030] The present invention adds calcium carbonate and PE powder to improve the fluidity and processing performance of the plastic, reduces the friction resistance of the plastic during processing, and thus makes the plastic easier to process in molding, extrusion or injection molding. The addition of calcium carbonate can not only improve the appearance and adjust the fluidity, but also reduce or avoid the shrinkage and cracking of the plastic. Directly adding calcium carbonate and antistatic agents to the matrix resin will result in poor dispersibility in the matrix resin, leading to problems such as interface compatibility, thereby affecting the overall performance of the matrix resin. Considering the economic cost, the present invention adjusts the distribution of the filler and antistatic agent in the material by adding a polymerization inhibitor and dispersibility, thereby improving the uniformity and stability of the material and further enhancing the antistatic effect of the vinyl resin. Using one or more combinations of hydroquinone, benzoquinone, trimethylbenzyl ammonium chloride and bromide as the polymerization inhibitor can also effectively extend the storage time of the sheet molding compound.

[0031] The invention adds a thickener and alkali-free glass fiber to the resin paste, stirs evenly in an SMC machine, and rolls and compacts the mixture to obtain a sheet.

[0032] Using one or more combinations of calcium oxide, magnesium oxide, calcium hydroxide, and magnesium hydroxide as thickeners can effectively increase the viscosity of the thickened resin paste, thereby forming an easy-to-tear film of the sheet molding compound.

[0033] However, the alkali-free glass fiber has poor dispersibility in the resin paste, which affects the flame retardancy of the plastic. The present invention introduces mercapto groups into the alkali-free glass fiber through mercaptopropyltrimethoxysilane. The silane coupling agent can form chemical bonds on the surface of the glass fiber, thereby enhancing the interfacial compatibility between the glass fiber and the vinyl resin, reducing the shear stress of the interface, and improving the mechanical properties and durability of the composite material. The modified glass fiber is then reacted with a modifier prepared from DOPA and 1-vinylimidazole through a click chemistry reaction to obtain a modified glass fiber. While introducing the flame retardant element, the dispersibility of the glass fiber in the resin paste is further improved, thereby enhancing the flame retardancy of the plastic. DETAILED DESCRIPTION

[0034] The following describes preferred implementations of the present invention. Obviously, the described embodiments are only a portion of the embodiments of the present invention, not all of them. It will be apparent to those skilled in the art that all other implementations derived without inventive effort, without departing from the principles of the present invention, are within the scope of protection of the present invention.

[0035] In the following specific embodiments, parts are by weight; it should be noted that the purchase manufacturers of all raw materials involved in the present invention are not subject to any special restrictions and exemplarily include: vinyl resin with the product number Derakane782; low shrinkage agent model DM-818 low shrinkage additive; initiator tert-butyl peroxybenzoate, CAS number 614-45-9; inhibitor benzoquinone, CAS number 106-51-4; release agent zinc stearate, CAS number 557-05-1; dispersant hydroxyethyl ethylene bisstearamide, model DY2012; wetting agent It is a BYK-560 type additive; the thickener is magnesium oxide, with the product number S27399; the product number of PE powder is Y45330; the inorganic filler is calcium carbonate, with the product number S24297; the product number of graphene is A343980; the model of carbon black is N550; the product number of carbon nanotubes is T19281; the model of alkali-free glass fiber is 9606015; the product number of aluminum hydroxide is S30353; the CAS number of 9,10-dihydro-9-oxa-10-phosphaphenanthrene is 35948-25-5; and the CAS number of 1-vinylimidazole is 1072-63-5.

[0036] The preparation method of DOPA is as follows: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene to anhydrous ethanol, heating the temperature to 60-65° C., adding hydrogen peroxide, heating the temperature to 75-85° C., reacting for 5.5-6.5 hours, purifying, and drying to obtain DOPA; the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene to hydrogen peroxide is 1:3.2.

[0037] The preparation method of the modified glass fiber is as follows: (1) calcining the alkali-free glass fiber at 300-400° C. for 30-40 minutes, cooling to room temperature, adding the 25 wt% ethanol aqueous solution containing a mercaptosilane coupling agent, reacting for 1-2 hours, purifying, and drying to obtain the mercaptolated glass fiber; the mercaptosilane coupling agent accounts for 3 wt% of the alkali-free glass fiber; (2) placing 12.2 parts of DOPA in 45 parts of anhydrous ethanol, heating to 55° C., adding 4.8 parts of 1-vinylimidazole, reacting for 1.2 hours, purifying, and drying to obtain the modifier; (3) placing 0.65 parts of mercaptolated glass fiber, 6.2 parts of the modifier, and 0.0025 parts of azobisisobutyronitrile in 25 parts of tetrahydrofuran, irradiating under ultraviolet light for 2 hours, purifying, and drying to obtain the modified alkali-free glass fiber; the process of irradiating under ultraviolet light is as follows: the emission wavelength is 365 nm, the light intensity is 110 mW / cm 2 .

[0038] Example 1: A method for preparing a highly flame-retardant sheet molding compound, comprising the following steps:

[0039] S1: 60 parts of vinyl resin and 25 parts of low shrinkage agent were stirred at 800 r / min for 4 minutes, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, and 5 parts of carbon nanotubes were added, and stirring was continued for 5 minutes. 100 parts of aluminum hydroxide and 20 parts of calcium carbonate were added, and mixed at 1000 r / min for 5 minutes to obtain a resin paste; the viscosity of the resin paste was 30,000 CPS;

[0040] S2: Add 1 part thickener and 100 parts alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0041] S3: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0042] Example 2: A method for preparing a highly flame-retardant sheet molding compound, comprising the following steps:

[0043] S1: 60 parts of vinyl resin and 25 parts of low shrinkage agent were stirred at a speed of 800 r / min for 4 minutes, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, and 5 parts of graphene were added, and stirring was continued for 5 minutes. 100 parts of aluminum hydroxide and 20 parts of calcium carbonate were added, and mixed uniformly at a speed of 1000 r / min for 5 minutes to obtain a resin paste; the viscosity of the resin paste was 30000 CPS;

[0044] S2: Add 1 part thickener and 100 parts alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0045] S3: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0046] Example 3: A method for preparing a highly flame-retardant sheet molding compound, comprising the following steps:

[0047] S1: 60 parts of vinyl resin and 25 parts of low shrinkage agent were stirred at 800 r / min for 4 minutes, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, and 5 parts of carbon black were added, and stirring was continued for 5 minutes. 40 parts of aluminum hydroxide and 20 parts of calcium carbonate were added, and mixed uniformly at 1000 r / min for 5 minutes to obtain a resin paste; the viscosity of the resin paste was 30000 CPS;

[0048] S2: Add 1 part thickener and 100 parts alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0049] S3: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0050] Example 4: A method for preparing a flame-retardant and antistatic sheet molding compound, comprising the following steps:

[0051] S1: 60 parts of vinyl resin and 25 parts of low shrinkage agent were stirred at 800 r / min for 4 minutes, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, and 5 parts of carbon black were added, and stirring was continued for 5 minutes. 100 parts of aluminum hydroxide and 20 parts of calcium carbonate were added, and mixed at 1000 r / min for 5 minutes to obtain a resin paste; the viscosity of the resin paste was 30000 CPS;

[0052] S2: Add 1 part thickener and 100 parts alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0053] S3: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0054] Example 5 is based on Example 3, and further includes the following steps:

[0055] Preliminary raw material preparation: weigh 60 parts of vinyl resin, 25 parts of low shrinkage agent, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, 5 parts of carbon black, 40 parts of aluminum hydroxide, 20 parts of calcium carbonate, 1 part of thickener, and 100 parts of modified alkali-free glass fiber, and set aside;

[0056] S1: (1) 2-amino-1H-imidazole-4-carboxylic acid was added to deionized water, heated to 85°C, and aluminum hydroxide was added and reacted for 5 hours to obtain modified aluminum hydroxide A; the mass ratio of 2-amino-1H-imidazole-4-carboxylic acid to aluminum hydroxide was 7.7:2;

[0057] DOPA was added to anhydrous ethanol, the temperature was raised to 62°C, modified aluminum hydroxide A was added, and the reaction was continued for 1 hour to obtain modified aluminum hydroxide; the ratio of DOPA to modified aluminum hydroxide A was 11.3:8.2;

[0058] (2) heating the modified aluminum hydroxide to 65° C., adding vinyl resin and styrene, reacting for 1 to 2 hours, cooling to 45 to 50° C., adding dimethylbenzene peroxide, stirring evenly, defoaming under vacuum, and reacting at 120° C. for 2 hours to obtain raw material A; styrene accounts for 5 to 5.5 wt% of the vinyl resin, and dimethylbenzene peroxide accounts for 0.8 to 1.2 wt% of the vinyl resin;

[0059] S2: Add 25 parts of low shrinkage agent to raw material A and stir at 800 r / min for 4 minutes. Add 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, and 5 parts of graphene. Continue stirring for 10 minutes. Add 20 parts of calcium carbonate and mix well at 1000 r / min to obtain a resin paste. The viscosity of the resin paste is 30,000 CPS.

[0060] S3: Add 1 part thickener and 100 parts modified alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0061] S4: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0062] Comparative Example 1 is based on Example 2, but no antistatic agent is added.

[0063] S1: 60 parts of vinyl resin and 25 parts of low shrinkage agent were stirred at 800 r / min for 4 minutes, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, and 1 part of wetting agent were added, and stirring was continued for 5 minutes. 40 parts of aluminum hydroxide and 20 parts of calcium carbonate were added, and mixed uniformly at 1000 r / min for 5 minutes to obtain a resin paste; the viscosity of the resin paste was 30,000 CPS;

[0064] S2: Add 1 part thickener and 100 parts alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0065] S3: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0066] Comparative Example 2 is based on Example 2, except that no antistatic agent is added and the amount of calcium carbonate added is increased.

[0067] S1: 60 parts of vinyl resin and 25 parts of low shrinkage agent were stirred at 800 r / min for 4 minutes, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, and 1 part of wetting agent were added, and stirring was continued for 5 minutes. 40 parts of aluminum hydroxide and 120 parts of calcium carbonate were added, and mixed uniformly at 1000 r / min for 5 minutes to obtain a resin paste; the viscosity of the resin paste was 30,000 CPS;

[0068] S2: Add 1 part thickener and 100 parts alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0069] S3: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0070] Comparative Example 3 is based on Example 5, except that the aluminum hydroxide and the vinyl resin are not compounded.

[0071] Preliminary raw material preparation: weigh 60 parts of vinyl resin, 25 parts of low shrinkage agent, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, 5 parts of carbon black, 40 parts of aluminum hydroxide, 20 parts of calcium carbonate, 1 part of thickener, and 100 parts of modified alkali-free glass fiber, and set aside;

[0072] S1: 60 parts of vinyl resin and 25 parts of low shrinkage agent were stirred at a speed of 800 r / min for 4 minutes, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, and 5 parts of graphene were added, and stirring was continued for 10 minutes. 40 parts of aluminum hydroxide and 20 parts of calcium carbonate were added, and mixed at a speed of 1000 r / min to obtain a resin paste; the viscosity of the resin paste was 30,000 CPS;

[0073] S3: Add 1 part thickener and 100 parts modified alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0074] S4: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0075] Comparative Example 4 is based on Example 5, but the glass fiber is not modified.

[0076] Preliminary raw material preparation: weigh 60 parts of vinyl resin, 25 parts of low shrinkage agent, 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, 5 parts of carbon black, 40 parts of aluminum hydroxide, 20 parts of calcium carbonate, 1 part of thickener, and 100 parts of alkali-free glass fiber, and set aside;

[0077] S1: (1) 2-amino-1H-imidazole-4-carboxylic acid was added to deionized water, heated to 85°C, and aluminum hydroxide was added and reacted for 5 hours to obtain modified aluminum hydroxide A; the mass ratio of 2-amino-1H-imidazole-4-carboxylic acid to aluminum hydroxide was 7.7:2;

[0078] DOPA was added to anhydrous ethanol, the temperature was raised to 62°C, modified aluminum hydroxide A was added, and the reaction was continued for 1 hour to obtain modified aluminum hydroxide; the ratio of DOPA to modified aluminum hydroxide A was 11.3:8.2;

[0079] (2) heating the modified aluminum hydroxide to 65° C., adding vinyl resin and styrene, reacting for 1 to 2 hours, cooling to 45 to 50° C., adding dimethylbenzene peroxide, stirring evenly, defoaming under vacuum, and reacting at 120° C. for 2 hours to obtain raw material A; styrene accounts for 5 to 5.5 wt% of the vinyl resin, and dimethylbenzene peroxide accounts for 0.8 to 1.2 wt% of the vinyl resin;

[0080] S2: Add 25 parts of low shrinkage agent to raw material A and stir at 800 r / min for 4 minutes. Add 0.75 parts of initiator, 0.6 parts of polymerization inhibitor, 1 part of PE powder, 2.5 parts of release agent, 1 part of dispersant, 1 part of wetting agent, and 5 parts of graphene. Continue stirring for 10 minutes. Add 20 parts of calcium carbonate and mix well at 1000 r / min to obtain a resin paste. The viscosity of the resin paste is 30,000 CPS.

[0081] S3: Add 1 part thickener and 100 parts alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; control the equipment speed to 10m / min;

[0082] S4: The sheet was aged at 40° C. for 15 hours and rolled up to obtain a sheet molding compound.

[0083] Detection Experiment 1: (1) Two specific electrodes were placed on the surfaces of Examples 1 to 5 and Comparative Examples 1 to 4, the voltage and current of the samples were measured, and the surface resistivity was calculated.

[0084] (2) Examples 1 to 5 and Comparative Examples 1 to 4 were cut into samples of 120 mm × 6.5 mm × 3.2 mm, with 6 samples in each group. The oxygen index (LOI) of the samples was tested according to the ASTM D-2863 test standard.

[0085] Surface resistivity / Ω Oxygen index Example 1 <![CDATA[10 8 ]]> 33 Example 2 <![CDATA[10 6 ]]> 34 Example 3 <![CDATA[10 6 (1.2*10 6 )]]> 29 Example 4 <![CDATA[10 7 ]]> 33.5 Example 5 <![CDATA[10 6 (0.8*10 6 )]]> 36.5 Comparative Example 1 <![CDATA[10 12 ]]> 33 Comparative Example 2 <![CDATA[10 12 ]]> 24 Comparative Example 3 <![CDATA[10 6 ]]> 34 Comparative Example 4 <![CDATA[10 6 ]]> 35

[0086] Table 1

[0087] Conclusion: According to the data in the table, the surface resistivity of the antistatic flame retardant sheet molding compounds prepared in Examples 1 to 5 and Comparative Examples 1 to 5 is between 10 6 and 10 9 It meets the standards of static dissipative anti-static materials.

[0088] Examples 1-2 and Example 4 respectively use carbon nanotubes, graphene, and carbon black as antistatic agents. Table 1 shows that graphene as an antistatic agent exhibits better flame retardancy. Example 3 reduces the amount of aluminum hydroxide added compared to Example 4, which affects the flame retardancy of the plastic. Example 5, based on Example 3, composites aluminum hydroxide with vinyl resin, introduces a flame retardant element, and modifies the alkali-free glass fiber to increase the oxygen index and enhance the flame retardancy of the plastic. Comparative Example 1 is based on Example 2 but without the addition of an antistatic agent. Comparative Example 2 is based on Example 2 but without the addition of an antistatic agent and with an increased calcium carbonate content. The data for these three examples show that the antistatic agent content not only affects the surface resistivity but also the oxygen index. Increasing the calcium carbonate content significantly decreases the oxygen index, and excessively high calcium carbonate content reduces the flame retardancy of the plastic. Comparative Example 3, based on Example 5, does not composite aluminum hydroxide with vinyl resin, which reduces the flame retardancy of the plastic. Comparative Example 4 is based on Example 5, but the glass fiber is not modified, so that the dispersibility of the glass fiber in the resin paste is reduced, resulting in a decrease in the oxygen index.

[0089] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the spirit and principles of the present invention and within the technical scope disclosed in this application should be included in the scope of protection of this application. The embodiments and features of the embodiments of this application can be combined with each other unless there is a conflict. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a highly flame-retardant sheet molding compound, characterized in that: The following steps are included: S1: Pre-compounding the base resin and aluminum hydroxide to obtain raw material A; S2: Stir raw material A and low shrinkage agent at a speed of 700-850 r / min for 2-4 minutes, add initiator, polymerization inhibitor, PE powder, release agent, dispersant, wetting agent, and antistatic agent, continue stirring for 5-10 minutes, add inorganic filler, and mix uniformly at a speed of 900-1100 r / min to obtain a resin paste; S3: Add thickener and alkali-free glass fiber to the resin paste, stir evenly in an SMC machine, and roll compact to obtain a sheet; S4: Curing the sheet at 35-42°C for 12-16 hours and rolling it up to obtain a sheet molding compound; The viscosity of the resin paste is 20,000-50,000 CPS; the raw materials of the sheet molding compound include the following components: by weight, 50-80 parts of base resin, 50-120 parts of aluminum hydroxide, 20-40 parts of low shrinkage agent, 0.5-1 part of initiator, 0.5-1 part of polymerization inhibitor, 0.5-2 parts of PE powder, 2-5 parts of release agent, 0.5-2 parts of dispersant, 0.5-2 parts of wetting agent, 0-50 parts of inorganic filler, 2-5 parts of antistatic agent, 1-3 parts of thickener, and 50-150 parts of alkali-free glass fiber; wherein the inorganic filler is not 0; The matrix resin is a vinyl resin; the preparation process of the raw material A is as follows: (1) adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene to anhydrous ethanol, heating to 60-65°C, adding hydrogen peroxide, heating to 75-85°C, reacting for 5.5-6.5 hours, purifying, and drying to obtain DOPA; (2) 2-amino-1H-imidazole-4-carboxylic acid is added to deionized water, heated to 80-90°C, aluminum hydroxide is added, and the reaction is carried out for 5-6 hours to obtain modified aluminum hydroxide A; DOPA is added to anhydrous ethanol and heated to 55-60°C, modified aluminum hydroxide A is added, and the reaction is carried out for 1-2 hours to obtain modified aluminum hydroxide; (3) Heat the modified aluminum hydroxide to 60-70°C, add vinyl resin and styrene, react for 1-2 hours, cool to 45-50°C, add dimethylbenzene peroxide, stir evenly, defoam under vacuum, and react at 120°C for 2 hours to obtain raw material A; The alkali-free glass fiber is pre-modified to obtain modified alkali-free glass fiber; the modified alkali-free glass fiber and a thickener are added to a resin paste, stirred evenly in an SMC machine, and rolled and compacted to obtain a sheet; The preparation method of the modified alkali-free glass fiber is as follows: (1) calcining the alkali-free glass fiber at 300-400° C. for 30-40 minutes, cooling to room temperature, adding the ethanol aqueous solution containing a mercaptosilane coupling agent, reacting for 1-2 hours, purifying, and drying to obtain a mercaptolated glass fiber; (2) placing DOPA in anhydrous ethanol, heating to 55-60° C., adding 1-vinylimidazole to react for 1-2 hours, purifying, and drying to obtain a modifier; (3) placing the mercaptolated glass fiber, the modifier, and azobisisobutyronitrile in tetrahydrofuran, irradiating the solution under ultraviolet light for 2-2.5 hours, purifying, and drying to obtain a modified alkali-free glass fiber.

2. The method for preparing a highly flame-retardant sheet molding compound according to claim 1, wherein: The low shrinkage agent includes one or more combinations of polystyrene low shrinkage agent and saturated polyester low shrinkage agent; The initiator includes one or more combinations of tert-butyl perbenzoate, benzoyl peroxide, tert-butyl peracetate, and tert-amyl perbenzoate; the inhibitor includes one or more combinations of hydroquinone, benzoquinone, trimethylbenzyl ammonium chloride, and bromide.

3. The method for preparing a highly flame-retardant sheet molding compound according to claim 1, wherein: The release agent includes one or more combinations of zinc stearate, magnesium stearate, and calcium stearate; the antistatic agent includes one or more combinations of carbon nanotubes, graphene, and carbon black; and the thickener includes one or more combinations of calcium oxide, magnesium oxide, calcium hydroxide, and magnesium hydroxide.

4. The method for preparing a highly flame-retardant sheet molding compound according to claim 1, wherein: In the DOPA, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene to hydrogen peroxide is 1:(3-3.5); In the modified aluminum hydroxide A, the mass ratio of 2-amino-1H-imidazole-4-carboxylic acid to aluminum hydroxide is (7.5-8):2; In the modified aluminum hydroxide, the mass ratio of DOPA to modified aluminum hydroxide A is (11~11.5):8.

2.

5. The method for preparing a highly flame-retardant sheet molding compound according to claim 1, wherein: In the raw materials of the raw material A, styrene accounts for 5-5.5 wt % of the vinyl resin, and ditoluyl peroxide accounts for 0.8-1.2 wt % of the vinyl resin.

6. The method for preparing a highly flame-retardant sheet molding compound according to claim 1, wherein: The mercaptosilane coupling agent accounts for 2~3wt% of the alkali-free glass fiber; the mass fraction of the ethanol aqueous solution is 20~30wt%; The raw materials of the modifier include the following components: 11.8-13 parts by weight of DOPA, 4.5-5.5 parts by weight of 1-vinylimidazole, and 35-50 parts by weight of anhydrous ethanol; The raw materials of the modified alkali-free glass fiber include the following: 0.6-0.7 parts of mercaptolated glass fiber, 5.8-6.5 parts of modifier, 0.002-0.0032 parts of azobisisobutyronitrile, and 15-25 parts of tetrahydrofuran, by weight. The process of irradiation under ultraviolet light is: the emission wavelength is 365nm, and the light intensity is 90-115mW / cm 2 .

7. The sheet molding compound prepared according to the method for preparing a highly flame-retardant sheet molding compound according to any one of claims 1 to 6.