Boron-containing flame retardant as well as preparation method and application thereof

Abstract

The invention relates to a boron-containing flame retardant as well as a preparation method and application thereof, and belongs to the technical field of materials. The boron-containing flame retardant is prepared from decommissioned thermosetting epoxy resin through boric acid catalytic cracking in the air atmosphere of 300-350 DEG C, and the mass ratio of the decommissioned thermosetting epoxy resin to boric acid is 1: (2-5). Or / and the boron content in the boron-containing flame retardant is more than 5%. The flame retardant disclosed by the invention has good thermal stability and flame retardance.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a boron-containing flame retardant and a preparation method and application thereof. Background Art

[0002] At present, the recycling of industrial thermosetting polymers still faces major challenges. The sustainability of recycling technologies is estimated based on the energy consumption, environmental impact and recycling potential of the products. So far, a number of technologies have been established to recycle epoxy resins. The initial treatment technologies such as incineration and landfill disposal will greatly damage the environment. Subsequently, chemical cracking, pyrolysis, mechanical cracking and other methods have been developed. However, most of these technologies usually require harsh conditions, such as high temperature (450-700 ° C), high pressure (3-27 MPa), strong oxidizing media and expensive customized equipment, and require a lot of energy consumption, which limits the large-scale industrial recycling of epoxy resin thermosetting plastics. Incineration and combustion are the two main thermal waste treatment methods for EP (Epoxy resin) and its fiber-reinforced composites. Incineration involves high-temperature combustion and is only energy recovery. On the other hand, combustion is a controlled process at lower temperatures aimed at recovering fibers and fillers from composite waste. Pyrolysis is a thermochemical process in which organic or inorganic materials are heated to temperatures between 300 and 900 ° C in an oxygen-limited environment to decompose. This process breaks down complex molecules into smaller compounds such as gas, liquid (bio-oil) and solid char by thermal decomposition rather than combustion. Pyrolysis can be used to produce biofuels, convert waste into valuable products, produce syngas and make activated carbon, etc. Traditional pyrolysis includes fixed bed and fluidized bed pyrolysis, and hot steam, catalytic, microwave-assisted and reverse gas pyrolysis have also been developed. A key advantage of pyrolysis is the recovery of fiber and chemical raw materials from resins, although the effect is not necessarily very good. Chemical recovery, also known as solvent decomposition, can be divided into glycolysis, acid digestion and hydrolysis due to different pressures, temperatures, catalysts and solvents. Solvolysis can produce new resin raw materials as well as new polymers, fuels, monomers or chemicals. However, the efficiency of solvent decomposition is affected by the type of resin, so pre-separation of composite types is required. Therefore, it is suitable for processing waste materials with known characteristics. Due to high pressure, high temperature and corrosive solvents, reactors used for solvent decomposition can be costly and may cause environmental problems and health hazards.

[0003] In the past, the main focus of recycling strategies has been to completely decompose the EP network to recover its reinforcing fibers. However, these strategies have overlooked the potential for further utilization of degradation products. Recent advances have shown that these degradation products can actually be used as additive ingredients. However, the large incorporation of degradation products may lead to a decrease in the overall properties of the final material. In addition, the dense cross-linked network and the presence of various CC, CO, and CN bonds in the EP structure make it extremely challenging to recover high-purity and high-quality chemicals or polymers. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a boron-containing flame retardant and a preparation method and application thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present invention provides a boron-containing flame retardant, which is prepared by catalytic cracking of retired thermosetting epoxy resin under an air atmosphere of 300°C-350°C by boric acid, wherein the mass ratio of the retired thermosetting epoxy resin to boric acid is 1:(2-5), or / and, and the boron content in the boron-containing flame retardant is greater than 5%.

[0007] The present invention finds that when boric acid is used as a catalyst for retired epoxy resin, it can not only significantly reduce the thermal degradation temperature of retired epoxy resin, but also the boron atom has a positive effect on flame retardancy. Therefore, the present invention selects boric acid as a catalyst for the pyrolysis of retired thermosetting epoxy resin, and a dark brown solid with a high boron content can be obtained, which is the flame retardant of the present invention, and the present invention names it as FR (Flame-retardant). At the same time, the mass ratio of retired thermosetting epoxy resin to boric acid has an important influence on the performance of the flame retardant formed thereafter. When the mass ratio of retired thermosetting epoxy resin to boric acid is 1: (2-5), the flame retardant has good thermal stability and flame retardancy.

[0008] Preferably, the mass ratio of the retired thermosetting epoxy resin to boric acid is 1:4.

[0009] Preferably, the temperature of the air atmosphere may be 300°C, 310°C, 320°C, 330°C, 340°C, 350°C; more preferably 320°C.

[0010] In a second aspect, the present invention provides a method for preparing a boron-containing flame retardant, comprising the following steps:

[0011] (1) uniformly mixing the retired thermosetting epoxy resin and boric acid to obtain a mixture;

[0012] (2) heating the mixture of step (1) in an air atmosphere at 300° C. to 350° C., and then cooling;

[0013] (3) washing the cooled mixture of step (2) to remove unreacted boric acid;

[0014] (4) dissolving the mixture of step (3) with an organic solvent;

[0015] (5) Recovering the solvent in the mixture of step (4) by evaporation, and vacuum drying the mixture to obtain a dark brown solid, namely the boron-containing flame retardant.

[0016] The present invention recovers retired thermosetting epoxy resins and uses boric acid as a catalyst for the retired epoxy resins, thereby not only reducing the thermal degradation temperature of the retired epoxy resins, but also obtaining a boron-containing flame retardant with good flame retardant properties. Therefore, the present invention opens up a new use for recycling retired thermosetting epoxy resins.

[0017] Preferably, before step (1), the method further comprises the step of crushing the retired thermosetting epoxy resin into powder with a particle size of 3-5 μm.

[0018] Preferably, in step (1), the mass ratio of the retired thermosetting epoxy resin to the boric acid is 1:(2-5).

[0019] Preferably, in step (1), the mass ratio of the retired thermosetting epoxy resin to the boric acid is 1:4.

[0020] Preferably, the heating time in step (2) is 20-30 min; or / and, the organic solvent in step (3) is anhydrous ethanol; or / and, the vacuum drying temperature in step (5) is 70-80° C., and the drying time is 20-24 hours.

[0021] In a third aspect, the present invention provides use of the boron-containing flame retardant in the preparation of a flame-retardant epoxy resin. Preferably, the mass percentage of the boron-containing flame retardant in the flame-retardant epoxy resin is 5%-20%.

[0022] The boron-containing flame retardant of the present invention is used as a raw material for preparing epoxy resin to provide the epoxy resin with flame retardant performance.

[0023] In a fourth aspect, the present invention provides a method for preparing a flame retardant epoxy resin, comprising the following steps:

[0024] (1) E-51, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane and the boron-containing flame retardant are uniformly mixed to obtain a mixed solution; the mass ratio of the boron-containing flame retardant is: E-51:3,3'-dimethyl-4,4'-diaminodicyclohexylmethane:the boron-containing flame retardant=100:30:(5-30);

[0025] (2) removing bubbles in the mixed solution of step (1) by ultrasonication to form a uniform transparent solution;

[0026] (3) pouring the transparent solution of step (2) into a mold for curing to obtain a cured epoxy resin;

[0027] (4) crushing the epoxy resin cured in step (3) to obtain an epoxy resin containing 5-20% of a boron-containing flame retardant.

[0028] In a fifth aspect, the present invention provides the use of retired thermosetting epoxy resin in the preparation of a boron-containing flame retardant.

[0029] The present invention finds that retired thermosetting epoxy resin can be used as a new raw material for flame retardants, so that it can form a boron-containing flame retardant with flame retardant properties under the low-temperature catalysis of boric acid, thus opening up new uses for retired thermosetting epoxy resins.

[0030] Preferably, the retired thermosetting epoxy resin is mixed with boric acid and pyrolyzed at low temperature to prepare a boron-containing flame retardant, and the mass ratio of the retired thermosetting epoxy resin to the boric acid is 1:(2-5).

[0031] In a sixth aspect, the present invention provides the use of boric acid in the preparation of a high-boron content flame retardant.

[0032] The present invention finds that retired thermosetting epoxy resin can form a boron-containing flame retardant with flame retardant properties under low-temperature catalysis of boric acid, and the flame retardant has good flame retardant properties. The present invention develops a new use of boric acid.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention prepares a boron-containing flame retardant by low-temperature pyrolysis of retired epoxy resin with boric acid, realizes high-value utilization of retired epoxy resin, and provides a new material with higher fire safety and thermal stability; adding a proper amount of the flame retardant when preparing epoxy resin will improve the thermal, fireproof and mechanical properties of epoxy resin composite materials. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0036] Comparison table of abbreviations and Chinese names in this invention

[0037] Table 1: Comparison table of abbreviations and Chinese names

[0038]

[0039] DMDC: CAS: 6864-37-5, molecular formula: C 15 H30 N2, molecular weight: 238.4121;

[0040] TPP: CAS: 115-86-6, molecular formula: C 18 H 15 O4P, molecular weight: 326.288;

[0041] BA: CAS: 10043-35-3, molecular formula: H3BO3, molecular weight: 61.833;

[0042] E-51: CAS: 61788-97-4, molecular formula: C 21 H 23 ClFNO2, molecular weight: 375.864, epoxy equivalent: 185-208 g / mol, epoxy value: 0.48-0.54 mol / 100 g;

[0043] EP: Homemade / Grid Decommissioning

[0044] Glossary:

[0045] The retired thermosetting epoxy resin referred to in the present invention refers to: the epoxy resin with DMDC as a curing agent and a similar structure in the composite insulator core rod retired after the operation of the power grid;

[0046] The boron-containing flame retardant of the present invention refers to a boron-containing flame retardant formed by degrading retired thermosetting epoxy resin with boric acid at low temperature, and the boron content in the present invention is more than 5%.

[0047] Example 1

[0048] The present embodiment provides a boron-containing flame retardant, which is prepared by catalytic cracking of retired thermosetting epoxy resin in an air atmosphere at 320° C. using boric acid, wherein the mass ratio of the retired thermosetting epoxy resin to boric acid is 1:4; or / and, the boron content in the boron-containing flame retardant is greater than 5%.

[0049] This embodiment provides a method for preparing a boron-containing flame retardant, which uses boric acid to catalyze and pyrolyze retired thermosetting epoxy resin at low temperature, and the specific steps are as follows:

[0050] (1) washing, drying and crushing the retired thermosetting epoxy resin (EP) into powder with a particle size of 3-5 μm;

[0051] (2) Weigh 1 g of retired thermosetting epoxy resin powder and 4 g of boric acid (BA) and grind them in a mortar for 30 min to mix them evenly;

[0052] (3) The mixed powders were transferred to a magnetic boat, which was then placed in a preheated muffle furnace at 300 °C in an air atmosphere for 30 min;

[0053] (4) collecting the resulting cooled mixture and washing it with hot water to remove unreacted BA;

[0054] (5) dispersing the washed product into anhydrous ethanol and dissolving it;

[0055] (6) The solvent ethanol was recovered by evaporation, and vacuum dried at 80° C. for 24 hours to obtain a dark brown solid, thereby obtaining the flame retardant of the present invention (referred to as Flame-retardant, FR in the present invention).

[0056] The present invention selects boric acid as a catalyst for the pyrolysis of retired thermosetting epoxy resins because boric acid can significantly reduce the thermal degradation temperature of retired epoxy resins (after adding boric acid, the degradation temperature of epoxy resins is reduced from 340°C to 140°C), and boron atoms have a positive effect on flame retardancy. Therefore, the present invention selects boric acid as a catalyst for the pyrolysis of retired thermosetting epoxy resins to obtain a dark brown solid with a high boron content, which is the flame retardant of the present invention, and the present invention names it FR.

[0057] Example 2

[0058] The difference between Example 2 and Example 1 is that the amount of boric acid added is 5 g, and the remaining steps are the same as Example 1.

[0059] Example 3

[0060] The difference between Example 3 and Example 1 is that the amount of boric acid added is 2 g, and the remaining steps are the same as Example 1.

[0061] Comparative Example 1

[0062] The difference between Comparative Example 1 and Example 1 is that the catalyst boric acid is not added, and the remaining steps are the same as those of Example 1. The flame retardant obtained in Comparative Example 1 is named FR-1.

[0063] Comparative Example 2

[0064] The difference between Comparative Example 2 and Example 1 is that oxalic acid is selected as the catalyst, and the remaining steps are the same as those of Example 1. The flame retardant obtained in Comparative Example 2 is named FR-2.

[0065] Comparative Example 3

[0066] The difference between Comparative Example 3 and Example 1 is that sodium borate is selected as the catalyst, and the remaining steps are the same as those of Example 1. The flame retardant obtained in Comparative Example 3 is named FR-3.

[0067] Comparative Example 4

[0068] The difference between Comparative Example 4 and Example 1 is that the amount of boric acid added in Comparative Example 4 is 1 g, and the remaining steps are the same as those in Example 1. The flame retardant obtained in Comparative Example 4 is named FR-4.

[0069] Comparative Example 5

[0070] The difference between Comparative Example 5 and Example 1 is that the amount of boric acid added in Comparative Example 5 is 7 g, and the remaining steps are the same as those in Example 1. The flame retardant obtained in Comparative Example 5 is named FR-5.

[0071] Application Examples

[0072] Application Example 1

[0073] The cured epoxy resin containing 5% FR (EP / FR-5%) was prepared by the following method:

[0074] (1) Add 100g E-51, 30g DMDC and 6.5g FR into a 500ml beaker and stir at 2000rpm for 10min;

[0075] (2) Ultrasonic treatment for 30 min to remove bubbles;

[0076] (3) placing the mixed solution in a vacuum oven at room temperature for 30 minutes to form a uniform transparent solution;

[0077] (4) Finally, the uniform and transparent solution was poured into a mold (10 cm × 10 cm × 2 mm) and cured under curing conditions (80 °C, 2 h and 150 °C, 2 h);

[0078] (5) The cured epoxy resin is crushed into powder to obtain EP / FR-5%.

[0079] Application Example 2

[0080] The cured epoxy resin containing 10% FR (EP / FR-10%) was prepared by the following method:

[0081] (1) Add 100g E-51, 30g DMDC and 13g FR into a 500ml beaker and stir at 2000rpm for 10min;

[0082] (2) Ultrasonic treatment for 30 min to remove bubbles;

[0083] (3) placing the mixed solution in a vacuum oven at room temperature for 30 minutes to form a uniform transparent solution;

[0084] (4) Finally, the uniform and transparent solution was poured into a mold (10 cm × 10 cm × 2 mm) and cured under curing conditions (80 °C, 2 h and 150 °C, 2 h);

[0085] (5) The cured epoxy resin is crushed into powder to obtain EP / FR-10%.

[0086] Application Example 3

[0087] The cured epoxy resin containing 20% ​​FR (EP / FR-20%) was prepared by the following method:

[0088] (1) Add 100g E-51, 30g DMDC and 26g FR into a 500ml beaker and stir at 2000rpm for 10min;

[0089] (2) Ultrasonic treatment for 30 min to remove bubbles;

[0090] (3) placing the mixed solution in a vacuum oven at room temperature for 30 minutes to form a uniform transparent solution;

[0091] (4) Finally, the uniform and transparent solution was poured into a mold (10 cm × 10 cm × 2 mm) and cured under curing conditions (80 °C, 2 h and 150 °C, 2 h);

[0092] (5) The cured epoxy resin is crushed into powder to obtain EP / FR-20%.

[0093] Application Example 4

[0094] The difference between Application Example 4 and Application Example 1 is that the FR in Application Example 4 is replaced by the FR prepared in Example 2, and the rest is the same as Application Example 1.

[0095] Application Example 5

[0096] The difference between Application Example 5 and Application Example 1 is that the FR in Application Example 5 is replaced by the FR prepared in Example 3, and the rest is the same as Application Example 1.

[0097] Comparative application example 1

[0098] Pure EP, without adding any flame retardant, the specific preparation method is as follows:

[0099] (1) Add 100 g E-51 and 30 g DMDC into a 500 ml beaker and stir at 2000 rpm for 10 min;

[0100] (2) Ultrasonic treatment for 30 min to remove bubbles;

[0101] (3) placing the mixed solution in a vacuum oven at room temperature for 30 minutes to form a uniform transparent solution;

[0102] (4) Finally, the uniform and transparent solution was poured into a mold (10 cm × 10 cm × 2 mm) and cured under curing conditions (80 °C, 2 h and 150 °C, 2 h);

[0103] (5) The cured epoxy resin is crushed into powder to obtain pure EP.

[0104] Comparative Application Example 2

[0105] The cured epoxy resin containing 5% TPP (EP / TPP-5%) was prepared by the following method:

[0106] (1) Add 100 g E-51, 30 g DMDC and 6.5 g triphenyl phosphate (TPP) into a 500 ml beaker and stir at 2000 rpm for 10 min;

[0107] (2) Ultrasonic treatment for 30 min to remove bubbles;

[0108] (3) placing the mixed solution in a vacuum oven at room temperature for 30 minutes to form a uniform transparent solution;

[0109] (4) Finally, the uniform and transparent solution was poured into a mold (10 cm × 10 cm × 2 mm) and cured under curing conditions (80 °C, 2 h and 150 °C, 2 h);

[0110] (5) The cured epoxy resin is crushed into powder to obtain EP / TPP-5%.

[0111] Comparative Application Example 3

[0112] The cured epoxy resin containing 10% TPP (EP / TPP-10%) was prepared by the following method:

[0113] (1) Add 100 g E-51, 30 g DMDC and 13 g TPP into a 500 ml beaker and stir at 2000 rpm for 10 min;

[0114] (2) Ultrasonic treatment for 30 min to remove bubbles;

[0115] (3) placing the mixed solution in a vacuum oven at room temperature for 30 minutes to form a uniform transparent solution;

[0116] (4) Finally, the uniform and transparent solution was poured into a mold (10 cm × 10 cm × 2 mm) and cured under curing conditions (80 °C, 2 h and 150 °C, 2 h);

[0117] (5) The cured epoxy resin is crushed into powder to obtain EP / TPP-10%.

[0118] Comparative Application Example 4

[0119] The cured epoxy resin containing 20% ​​TPP (EP / TPP-20%) was prepared by the following method:

[0120] (1) Add 100 g E-51, 30 g DMDC and 26 g TPP into a 500 ml beaker and stir at 2000 rpm for 10 min;

[0121] (2) Ultrasonic treatment for 30 min to remove bubbles;

[0122] (3) placing the mixed solution in a vacuum oven at room temperature for 30 minutes to form a uniform transparent solution;

[0123] (4) Finally, the uniform and transparent solution was poured into a mold (10 cm × 10 cm × 2 mm) and cured under curing conditions (80 °C, 2 h and 150 °C, 2 h);

[0124] (5) The cured epoxy resin is crushed into powder to obtain EP / TPP-20%.

[0125] Comparative Application Example 5

[0126] The difference between Comparative Application Example 5 and Application Example 1 is that FR in Comparative Application Example 5 is replaced by FR-1, and the rest is the same as Application Example 1.

[0127] Comparative Application Example 6

[0128] The difference between Comparative Application Example 6 and Application Example 1 is that FR in Comparative Application Example 6 is replaced by FR-2, and the rest is the same as Application Example 1.

[0129] Comparative Application Example 7

[0130] The difference between Comparative Application Example 7 and Application Example 1 is that FR in Comparative Application Example 7 is replaced by FR-3, and the rest is the same as Application Example 1.

[0131] Comparative Application Example 8

[0132] The difference between Comparative Application Example 8 and Application Example 1 is that FR in Comparative Application Example 8 is replaced by FR-4, and the rest is the same as Application Example 1.

[0133] Comparative Application Example 9

[0134] The difference between Comparative Application Example 9 and Application Example 1 is that FR in Comparative Application Example 9 is replaced by FR-5, and the rest is the same as Application Example 1.

[0135] Test Example 1

[0136] The thermal stability parameters of different samples were measured by thermogravimetric analyzer at a heating rate of 10°C / min in air atmosphere. The results are shown in Table 2:

[0137] Table 2: Thermal stability parameters of different samples

[0138]

[0139]

[0140] Test Example 2

[0141] According to ASTM D7309, the pyrolysis combustion flow calorimeter (PCFC) was used to evaluate the flammability of epoxy resin systems containing different flame retardants by pyrolysis combustion flow calorimetry (MCC) experiment. 3 mg of sample was pyrolyzed at 900 °C at a heating rate of 1 °C / s. The results are shown in Table 3.

[0142] Table 3. Flammability evaluation of different samples

[0143]

[0144] Test Example 3

[0145] The stress relaxation of epoxy resin systems containing different flame retardants in the temperature range of 30 to 250 °C at a heating rate of 5 °C / min was evaluated using a dynamic mechanical analyzer (DMA Q800) in dual cantilever-strain mode. The sample size was 25 mm × 10 mm × 2 mm, the constant frequency was 1.0 Hz, and the amplitude was 15 mm. The results are shown in Table 4.

[0146] Table 4. Storage modulus of different samples

[0147]

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A boron-containing flame retardant, characterized in that: The boron-containing flame retardant is prepared by catalytic cracking of retired thermosetting epoxy resin under an air atmosphere of 300° C.-350° C. via boric acid, wherein the mass ratio of the retired thermosetting epoxy resin to boric acid is 1:(2-5); or / and, the boron content in the boron-containing flame retardant is greater than 5%.

2. A method for preparing a boron-containing flame retardant as claimed in claim 1, characterized in that: The steps include: (1) uniformly mixing the retired thermosetting epoxy resin and boric acid to obtain a mixture; (2) heating the mixture of step (1) in an air atmosphere at 300° C. to 350° C., and cooling; (3) washing the cooled mixture of step (2) to remove unreacted boric acid; (4) dissolving the mixture of step (3) with an organic solvent; (5) Evaporating and recovering the solvent in the mixture of step (4), and vacuum drying the mixture to obtain a dark brown solid, namely the boron-containing flame retardant.

3. The preparation method according to claim 2, characterized in that: Before the step (1), the method further comprises the step of crushing the retired thermosetting epoxy resin into powder with a particle size of 3-5 μm.

4. The preparation method according to claim 2, characterized in that: In the step (1), the mass ratio of the retired thermosetting epoxy resin to the boric acid is 1:(2-5).

5. The preparation method according to claim 4, characterized in that: In the step (1), the mass ratio of the retired thermosetting epoxy resin to the boric acid is 1:

4.

6. The preparation method according to claim 2, characterized in that: In the step (2), the heating time is 20-30 min; or / and, in the step (3), the organic solvent is anhydrous ethanol; or / and, in the step (5), the vacuum drying temperature is 70-80° C., and the drying time is 20-24 hours.

7. Use of the boron-containing flame retardant as claimed in claim 1 in the preparation of flame-retardant epoxy resin.

8. The use according to claim 7, characterized in that The mass percentage of the boron-containing flame retardant in the flame-retardant epoxy resin is 5%-20%.

9. A method for preparing a flame retardant epoxy resin, characterized in that: The steps include: (1) E-51, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and the boron-containing flame retardant according to claim 1 are uniformly mixed to obtain a mixed solution; The mass ratio of the E-51, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane and the boron-containing flame retardant is: E-51:3,3'-dimethyl-4,4'-diaminodicyclohexylmethane:the boron-containing flame retardant=100:30:(5-30); (2) removing bubbles in the mixed solution of step (1) by ultrasonication to form a uniform transparent solution; (3) pouring the transparent solution of step (2) into a mold for curing to obtain a cured epoxy resin; (4) crushing the epoxy resin cured in step (3) to obtain an epoxy resin containing 5-20% of a boron-containing flame retardant.

10. Use of retired thermosetting epoxy resin or boric acid in the preparation of boron-containing flame retardants.

Images