Benzoxazine composition and prepreg and laminate thereof

Abstract

The present invention provides a benzoxazine composition for prepregs, a prepreg thereof, and a laminate. The benzoxazine composition comprises 100 parts of a benzoxazine resin, 10 to 60 parts of a phosphorus-containing flame retardant, 0.1 to 1 part of expandable graphite, and 0.5 to 5 parts of an accelerator. Reinforced fibers are impregnated with the composition to obtain a prepreg. The resin matrix of the present invention has a good impregnation effect on the reinforcing fibers, and the laminate has flame retardant properties that can reach EN45545-2HL3 level, while also having excellent mechanical properties and heat resistance. The preparation process is simple, the material is widely available, the production environment is not demanding, and industrial production is convenient, achieving good technical results.

Description

Technical Field

[0001] The present invention relates to the field of composite materials, in particular to a benzoxazine composition for prepreg, and a prepreg and a laminate thereof. Background Art

[0002] In the rail transit sector, to achieve halogen-free flame retardancy, the industry typically uses epoxy resin as the primary resin, adding phosphorus-containing flame retardants, nitrogen-containing flame retardants, and smoke suppressants for high flame retardancy. However, dissolved flame retardants can compromise heat resistance, while powdered flame retardants can significantly impair the mechanical properties of the laminate.

[0003] Benzoxazine resins are a type of resin with a high nitrogen content (up to 6%). Some benzoxazine grades have intrinsic flame retardancy reaching UL94-V0. Combined with their low cure shrinkage and excellent resistance to moisture and heat, they are widely used in aerospace, electronics, and rail transportation.

[0004] At present, the prepregs that have been publicly reported to meet the EN45545-2 standard are mainly achieved by adding a large amount of organic and inorganic powders to epoxy resin, and their mechanical properties are inevitably greatly reduced.

[0005] Chinese patent application CN110713697A discloses a prepreg for OoA process that meets the EN45545-2 flame retardant standard. The prepreg achieves a flame retardant effect of HL2 level by adding hydroxide, melamine and polyol to epoxy.

[0006] Chinese patent application CN107353775A discloses a flame-retardant surface film for a carbon fiber reinforced resin-based composite material and a preparation method thereof. The flame retardant is composed of one or more of the additive flame retardants triphenyl phosphate, cresyl diphenyl phosphate, pentaerythritol, aluminum hydroxide, melamine phosphate, ammonium polyphosphate, and zinc borate. By adding a high content (40-70 parts) of powdered flame retardant to epoxy to prepare a prepreg for paving on the surface, only the HL2 level can be achieved.

[0007] Therefore, how to achieve the HL3 flame retardant level while ensuring mechanical strength and heat resistance is a recognized difficulty in the industry. Summary of the Invention

[0008] The technical problem addressed by this invention is the inability to balance flame retardancy, mechanical properties, and heat resistance in existing composite laminates. By blending a soluble phosphorus-containing flame retardant with expandable graphite, a flame retardant performance meeting EN45545-2HL3 standards is achieved. Compared to adding powdered flame retardants, this method offers superior heat resistance and mechanical properties, particularly achieving interlaminar shear strength exceeding 70 MPa.

[0009] One of the objects of the present invention is to provide a benzoxazine composition for prepreg, comprising, in parts by mass:

[0010]

[0011] The benzoxazine resin is preferably at least one selected from bisphenol A benzoxazine, bisphenol F benzoxazine, phenolphthalein benzoxazine, diaminodiphenylmethane benzoxazine, and dicyclopentadiene benzoxazine.

[0012] The phosphorus-containing flame retardant is a soluble phosphorus-containing flame retardant, and is preferably at least one selected from bisphenol A type phosphate oligomer, resorcinol type phosphate oligomer A, resorcinol type phosphate oligomer B, and hydroquinone type phosphate oligomer.

[0013] The particle size of the expandable graphite is 75 to 150 μm, preferably 75 to 100 μm.

[0014] The accelerator can be selected from common accelerators in the art, preferably at least one of imidazole accelerators and their derivatives, organic weak acid accelerators, and Lewis acid accelerators, such as adipic acid, 2-methyl-4-ethylimidazole, and the like.

[0015] A second object of the present invention is to provide a benzoxazine prepreg comprising reinforcing fibers and the above-mentioned benzoxazine composition.

[0016] The reinforcing fibers are at least one of inorganic fibers, organic fibers, and metal fibers, or fabrics formed by at least one of inorganic fibers, organic fibers, and metal fibers.

[0017] A third object of the present invention is to provide a method for preparing the prepreg, comprising the following steps:

[0018] (1) heating and melting the benzoxazine resin and keeping the temperature;

[0019] (2) adding the phosphorus-containing flame retardant, expandable graphite, and accelerator to the benzoxazine resin and mixing them evenly;

[0020] (3) uniformly coating the composition obtained in step (2) on release paper to obtain a hot-melt resin film;

[0021] (4) impregnating the reinforcing fibers with a hot-melt resin film, and obtaining the prepreg after cooling and winding.

[0022] In the method for preparing the prepreg,

[0023] In step (1), the benzoxazine resin is heated to 90-120° C. to melt and kept warm for 20-30 minutes;

[0024] In step (2), stirring and mixing at 90-120° C. for 15-60 min;

[0025] In step (3), the resin mixture is applied at 60 to 90° C.;

[0026] In step (4), the impregnation can be carried out using conventional methods and equipment in the art, preferably at 70-150°C.

[0027] A fourth object of the present invention is to provide a laminate prepared from the above-mentioned benzoxazine prepreg.

[0028] A fifth object of the present invention is to provide a method for preparing the laminate, comprising cutting, laying, and heating and curing the benzoxazine prepreg to obtain the laminate.

[0029] In the method for preparing the laminate, the cutting, laying and heating and curing can be carried out using conventional methods and equipment in the art, preferably:

[0030] The laminate laying method can be a laying method of 0°, 0° / 90°, ±45°, 0° / +45° / 90° / -45°, 0° / +45° / -45° / 90°, etc.; the total thickness of the laminate after laying is 1mm to 6mm; the heating and curing adopts a molding process, a vacuum bag process or an autoclave process; the curing temperature is 120 to 200°C, the curing pressure is 0.1 to 1.2Mpa, and the curing time is 1 to 8h.

[0031] The method for preparing the flame-retardant benzoxazine prepreg and the laminate thereof provided by the present invention has the following advantages:

[0032] (1) The heat resistance, mechanical properties and flame retardancy of the laminate can be taken into account, and the flame retardancy can reach EN45545-2HL3 level;

[0033] (2) The preparation process is simple, the raw materials are widely available, and industrial production is convenient.

[0034] By adopting the technical solution of the present invention, the resin matrix has a good impregnation effect on the reinforcing fibers, and the flame retardant performance of the laminate can reach the highest level HL3 of EN45545, while also having excellent mechanical properties and heat resistance. The preparation process is simple, the material source is wide, the production environment requirements are not harsh, and industrial production is convenient, thereby achieving good technical results.

[0035] The present invention will be further described below by way of examples. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0037] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0038] The properties of flame retardant benzoxazine prepreg and its laminate are tested according to the following standard tests and test methods.

[0039] HB 7736.5-2004 Test methods for physical properties of composite prepregs Part 5: Determination of resin content;

[0040] GB / T1447-2005 Test method for tensile properties of fiber reinforced plastics;

[0041] JC / T 773-2010 Determination of interlaminar shear strength of fiber reinforced plastics by short beam method;

[0042] ASTM E1640-2013 Standard Test Method for Glass Transition Temperature by Dynamic Mechanical Analysis;

[0043] EN45545 maximum heat release rate, smoke density Ds.

[0044] According to a preferred embodiment of the present invention, the method for preparing the laminate comprises the following steps:

[0045] (1) heating the benzoxazine resin to 90-120°C to melt and keeping the temperature for 20-30 minutes;

[0046] (2) adding the phosphorus-containing flame retardant, expandable graphite, and curing accelerator to the benzoxazine resin and mechanically stirring at 90-120° C. for 15-60 minutes until the mixture is uniformly mixed;

[0047] (3) uniformly coating the resin mixture on the release paper at a coating temperature of 60° C. to 90° C. using a hot melt coating machine to obtain a hot melt resin film;

[0048] (4) impregnating the reinforcing fibers with a hot melt resin film at 70° C. to 150° C. on a hot melt prepreg machine, and obtaining the flame retardant benzoxazine prepreg after cooling and winding;

[0049] (5) Cutting and laying the flame-retardant benzoxazine prepreg, and heating and curing the prepreg through a molding process, a vacuum bag process, or an autoclave process to prepare a flame-retardant benzoxazine laminate.

[0050] The benzoxazine resin may be one or a mixture of at least two of bisphenol A benzoxazine, bisphenol F benzoxazine, phenolphthalein benzoxazine, diaminodiphenylmethane benzoxazine, and dicyclopentadiene benzoxazine. All of the above benzoxazine resins are commercially available.

[0051] The phosphorus-containing flame retardant can be selected from one or a mixture of at least two of bisphenol A type phosphate oligomer (Japan Daihachi Chemical, brand CR-741), resorcinol type phosphate oligomer A (Japan Daihachi Chemical, brand CR-733S), resorcinol type phosphate oligomer B (Japan Daihachi Chemical, brand PX-200), and hydroquinone type phosphate oligomer (Japan Daihachi Chemical, brand HQDP). Based on 100 parts by weight of the benzoxazine resin, the phosphorus-containing flame retardant is 10 to 60 parts by weight, for example, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, etc.

[0052] The expandable graphite has a particle size of 75 to 150 μm. Based on 100 parts by weight of the benzoxazine resin, the expandable graphite is present in an amount of 0.1 to 1 part, for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, etc.

[0053] [Example 1]

[0054] (1) Add 2000 g of bisphenol A benzoxazine resin into a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0055] (2) 580 g of CR-741, 12.9 g of expandable graphite (particle size 75 μm), and 51.6 g of adipic acid were stirred at 110° C. for 30 min under nitrogen protection.

[0056] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0057] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 1 below:

[0058] Table 1

[0059]

[0060] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0061] The flame retardant benzoxazine prepreg and its laminate properties were tested according to the above standard test methods. The test results are shown in Table 14.

[0062] [Example 2]

[0063] (1) Add 2000 g of bisphenol A benzoxazine resin into a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0064] (2) 460 g of CR733s, 12.5 g of expandable graphite (particle size 75 μm), and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0065] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0066] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 2 below:

[0067] Table 2

[0068]

[0069] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0070] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0071] [Example 3]

[0072] (1) Add 2000 g of bisphenol F-type benzoxazine resin into a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0073] (2) 580 g of CR741, 12.5 g of expandable graphite (particle size 75 μm), and 51.6 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0074] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0075] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 3 below:

[0076] Table 3

[0077]

[0078] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0079] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0080] [Example 4]

[0081] (1) Add 2000 g of bisphenol F-type benzoxazine resin into a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0082] (2) 460 g of CR733s, 12.5 g of expandable graphite (particle size 75 μm), and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0083] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0084] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 4 below:

[0085] Table 4

[0086]

[0087] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0088] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0089] [Example 5]

[0090] (1) Add 2000 g of diaminodiphenylmethane-type benzoxazine resin to a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0091] (2) 580 g of CR741, 20.0 g of expandable graphite (particle size 75 μm), and 51.6 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0092] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0093] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 5 below:

[0094] Table 5

[0095]

[0096] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0097] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0098] [Example 6]

[0099] (1) Add 2000 g of diaminodiphenylmethane-type benzoxazine resin to a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0100] (2) 460 g of CR733s, 20.0 g of expandable graphite (particle size 75 μm), and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0101] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0102] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" sandwich structure with the upper and lower layers being resin film and the middle layer being parallel arranged carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate. The prepreg is wound to obtain a flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 6 below:

[0103] Table 6

[0104]

[0105] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0106] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0107] [Example 7]

[0108] (1) Add 2000 g of diaminodiphenylmethane-type benzoxazine resin to a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0109] (2) 500 g of PX200, 20.0 g of expandable graphite (particle size 75 μm), and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0110] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0111] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 7 below:

[0112] Table 7

[0113]

[0114] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0115] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0116] [Example 8]

[0117] (1) Add 2000 g of dicyclopentadiene-type benzoxazine resin to a 5 L reaction vessel and heat to 110 ° C to melt, and keep warm for 20 minutes;

[0118] (2) 500 g of PX200, 20.0 g of expandable graphite (particle size 75 μm), and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0119] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0120] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate. The prepreg is wound to obtain a flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 8 below:

[0121] Table 8

[0122]

[0123] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0124] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0125] [Example 9]

[0126] (1) Add 2000 g of bisphenol A benzoxazine resin into a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0127] (2) 230 g of CR733s, 2.5 g of expandable graphite (particle size 75 μm), and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0128] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0129] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 9 below:

[0130] Table 9

[0131]

[0132] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0133] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0134] [Comparative Example 1]

[0135] (1) Add 2000 g of phenolic epoxy resin (Dow DEN431, USA) and 400 g of dicyandiamide curing agent into a 5 L reaction vessel and heat to 90 ° C to melt, and keep warm for 20 min;

[0136] (2) Add 1200g of powdered flame retardant Exolit TM OP1248 was added thereto, and the mixture was stirred at 110°C for 30 min under nitrogen protection to obtain epoxy resin with uniformly dispersed powder.

[0137] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0138] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant epoxy resin prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 10 below:

[0139] Table 10

[0140]

[0141] (5) The flame retardant epoxy prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process. The curing process is 120°C / 0.6Mpa / 2h+150°C / 0.6Mpa / 2h to prepare a flame retardant epoxy resin laminate.

[0142] The performance testing method of the obtained flame retardant epoxy resin prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0143] [Comparative Example 2]

[0144] (1) Add 2000 g of bisphenol A benzoxazine resin into a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0145] (2) 580 g of CR741 and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0146] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0147] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 11 below:

[0148] Table 11

[0149]

[0150] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0151] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0152] [Comparative Example 3]

[0153] (1) Add 2000 g of bisphenol A benzoxazine resin into a 5 L reaction vessel and heat to 110 °C to melt, then keep warm for 20 min;

[0154] (2) 12.5 g of expandable graphite (particle size 75 μm) and 50.0 g of 2-methyl-4-ethylimidazole were stirred at 110° C. for 30 min under nitrogen protection.

[0155] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0156] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate. The prepreg is wound to obtain a flame retardant benzoxazine prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 12 below:

[0157] Table 12

[0158]

[0159] (5) The flame-retardant benzoxazine prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process, and the curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame-retardant benzoxazine laminate.

[0160] The performance testing method of the obtained flame-retardant benzoxazine prepreg and its laminate is the same as that of Example 1. The test results are shown in Table 14.

[0161] [Comparative Example 4]

[0162] (1) Add 2000 g of bisphenol A epoxy resin and 534.6 g of diaminodiphenylmethane into a 5 L reaction vessel, heat to 100 ° C and melt, and keep warm for 20 minutes;

[0163] (2) 725 g of CR741 and 15.6 g of expandable graphite (particle size 75 μm) were stirred at 110° C. for 30 min under nitrogen protection.

[0164] (3) Add the low-viscosity prepolymer into the resin tank of the hot-melt coating machine, and evenly coat the prepolymer on the release paper at a coating temperature of 90°C and a coating speed of 5 m / min. After cooling, rewind and obtain a hot-melt resin film.

[0165] (4) The two rolls of resin film obtained in step (3) are placed on the upper and lower unwinding stations of the hot melt prepreg machine respectively. After unwinding, they are compounded with the carbon fiber tow (Toray T700SC-24K) drawn from the creel on the first heating roller to form a "sandwich" structure with the upper and lower layers being resin film and the middle layer being parallel carbon fiber tow. Subsequently, the resin is impregnated into the carbon fiber and the prepolymer is completely reacted through the first heating plate, the second heating roller, the second heating plate, the third heating roller, the third heating plate and the cooling plate to obtain the flame retardant epoxy resin prepreg and its laminate. The specific process parameters of the prepreg machine are shown in Table 13 below:

[0166] Table 13

[0167]

[0168] (5) The flame retardant epoxy resin prepreg is cut and laid in two ways: 0° and 0° / 90°. The prepreg is heated and pressurized by a molding process. The curing process is 150°C / 0.6Mpa / 2h+180°C / 0.6Mpa / 2h to prepare a flame retardant epoxy resin laminate.

[0169] The performance testing method of the flame retardant epoxy resin prepreg and its laminate is the same as that of Example 1. The results are shown in Table 14.

[0170] Table 14 Properties of the prepregs and laminates of the embodiments and comparative examples

[0171]

[0172] Note: EN45545-2 HL3 level requires the maximum heat release rate to be less than 60KW / m 2 , smoke density Ds<300.

[0173] The present invention adopts benzoxazine with high nitrogen content as a matrix resin, adds a soluble phosphate flame retardant, expandable graphite and an accelerator thereto, adopts a hot melt prepreg machine to prepare a prepreg, and the prepreg is cut, stacked, heated and pressurized to cure to obtain a laminate with excellent flame retardant effect, thermal properties and mechanical properties.

Claims

1. A benzoxazine composition for prepreg, comprising, in parts by mass: The phosphorus-containing flame retardant is a soluble phosphorus-containing flame retardant, and is selected from at least one of bisphenol A type phosphate oligomer, resorcinol type phosphate oligomer A, resorcinol type phosphate oligomer B, and hydroquinone type phosphate oligomer.

2. The benzoxazine composition according to claim 1, comprising, in parts by mass:

3. The benzoxazine composition according to claim 1, wherein: The benzoxazine resin is selected from at least one of bisphenol A benzoxazine, bisphenol F benzoxazine, phenolphthalein benzoxazine, diaminodiphenylmethane benzoxazine, and dicyclopentadiene benzoxazine; The particle size of the expandable graphite is 75 to 150 μm; The accelerator is at least one of imidazole accelerators and derivatives thereof, organic weak acid accelerators, and Lewis acid accelerators.

4. The benzoxazine composition according to claim 3, wherein: The particle size of the expandable graphite is 75-100 μm.

5. A benzoxazine prepreg comprising reinforcing fibers and the benzoxazine composition according to any one of claims 1 to 4.

6. The benzoxazine prepreg according to claim 5, characterized in that: The reinforcing fibers are at least one of inorganic fibers, organic fibers, and metal fibers, or fabrics formed by at least one of inorganic fibers, organic fibers, and metal fibers.

7. A method for preparing the prepreg according to claim 5 or 6, comprising the following steps: (1) heating and melting the benzoxazine resin and keeping the temperature; (2) adding the phosphorus-containing flame retardant, expandable graphite, and accelerator to the benzoxazine resin and mixing them evenly; (3) uniformly coating the composition obtained in step (2) on release paper to obtain a hot-melt resin film; (4) impregnating the reinforcing fibers with a hot-melt resin film, and obtaining the prepreg after cooling and winding.

8. The method for preparing the prepreg according to claim 7, wherein: In step (1), the benzoxazine resin is heated to 90-120° C. to melt and kept warm for 20-30 minutes; In step (2), stirring and mixing at 90-120° C. for 15-60 min; In step (3), the resin mixture is applied at 60 to 90° C.; In step (4), the immersion is carried out at 70 to 150°C.

9. A laminated board prepared from the benzoxazine prepreg according to claim 5 or 6.

10. A method for preparing the laminate according to claim 9, comprising cutting, laying out, and heating and curing the benzoxazine prepreg.

11. The method for preparing a laminate according to claim 10, wherein: The total thickness of the laminate after laying is 1mm to 6mm; Heat curing adopts molding process, vacuum bag process or autoclave process; The curing temperature is 120-200°C, the curing pressure is 0.1-1.2 MPa, and the curing time is 1-8 hours.

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