Preparation method of halogen-free flame-retardant microcapsule and halogen-free flame retardant

Abstract

The invention discloses a preparation method of a halogen-free flame retardant microcapsule and a halogen-free flame retardant. According to the invention, the epoxy resin is modified, and flexible chain segments such as polyurethane or polyester are introduced in terms of selection of the epoxy resin, so that the rigidity of the wall material is reduced, and entanglement with molecular chain segments of PVC is enhanced; in the aspect of functional group selection, epoxy resin with higher hydroxyl or carboxylation degree is selected, so that the epoxy resin wall material contains the epoxy resin-PVC block copolymer, and the epoxy resin-PVC block copolymer has better affinity with epoxy resin and PVC. The APP microcapsule is formed by coating and modifying ammonium polyphosphate (APP) with epoxy resin, so that the defects of the APP microcapsule can be effectively overcome, and the application range of the APP microcapsule is expanded. The ammonium polyphosphate (APP) microcapsule with good performance is prepared by adopting a segmented reaction temperature mode, the whole operation process is environment-friendly and pollution-free, most importantly, the method is simple and easy to operate, and industrial application and development are facilitated.

Description

Technical Field

[0001] The present invention relates to a preparation method of a flame retardant material, and specifically to a preparation method of halogen-free flame retardant microcapsules using ammonium polyphosphate and modified epoxy resin as raw materials. The microcapsules can be well compounded with polymers such as polyvinyl chloride (PVC). Background Art

[0002] A flame retardant is a chemical substance that can effectively inhibit the combustion of an object, and is usually divided into halogenated flame retardants and halogen-free flame retardants. Halogenated flame retardants have been widely used due to their advantages of low addition amount, low price, and high flame retardancy efficiency. However, whether burned or not, they are prone to decomposition when heated to produce toxic and harmful gases such as polybrominated dibenzofurans, hydrogen bromide, and carbon monoxide, which has gradually phased them out. Compared with halogenated flame retardants, halogen-free flame retardants do not produce toxic gases during the combustion process, and in addition, they have the outstanding advantages of low price, smokelessness, and suppression of combustion dripping. The current defect of halogen-free flame retardants is poor compatibility with organic substances and low flame retardancy efficiency. Therefore, it is of great significance to study a halogen-free flame retardant with good compatibility with organic substances and good flame retardant effect.

[0003] Among halogen-free flame retardants, phosphorus-based flame retardants have been studied more and are widely used. During the flame retardant process, it effectively promotes the conversion of combustibles into a carbon layer to block the diffusion of heat and oxygen, thereby avoiding the continuous combustion of substances. Ammonium polyphosphate (APP) is an efficient halogen-free flame retardant, which is inexpensive and has advantages such as good compatibility with the matrix and small addition amount. However, APP itself is prone to moisture absorption, difficult to be compounded with polymers, and its insufficient hydrolysis resistance requires optimization and improvement by methods such as surface modification, composite modification, and microencapsulation. Summary of the Invention

[0004] The present invention aims to solve the problem of improving the compounding compatibility of ammonium polyphosphate flame retardant with polymers during processing, especially the poor compatibility during the processing with PVC, and to improve its dispersibility in PVC. For this purpose, the present application proposes a preparation method of halogen-free flame retardant microcapsules using ammonium polyphosphate as a raw material.

[0005] On the other hand, the present invention also provides a halogen-free flame retardant obtained by the above preparation method.

[0006] A preparation method of halogen-free flame retardant microcapsules, which comprises the following steps:

[0007] S1: Add ethanol, modified epoxy resin (EP) and a curing agent into a reactor, and magnetically stir evenly until a clear and transparent pretreatment liquid is obtained;

[0008] The modified epoxy resin (EP) is a modified epoxy resin (EP) synthesized with an epoxy resin-PVC block copolymer; the synthesis method is as follows: 0.1 mmol of CuBr, 0.2 mmol of CuBr / bipyridine (bpy), 0.05 mmol of ethyl α-bromoisobutyrate (EBiB), and 10 mL of toluene are successively added into a Schlenk reaction flask; after purging with nitrogen to displace oxygen, 5 mmol of vinyl chloride monomer is injected, and the reaction is carried out at 70 °C for 6 hours to obtain PVC-Br with a molecular weight of about 10,000 g / mol and a PDI < 1.3; 1 g of the above PVC-Br with 0.1 mmol of end groups is dissolved in 10 mL of N,N-dimethylformamide (DMF), and 0.02 mmol of tetrabutylammonium bromide (TBAB) is added; under nitrogen protection, 10 mmol of epichlorohydrin (ECH) is added dropwise, the temperature is maintained at 40 °C, and the reaction is carried out for 12 hours. The epoxy group is ring-opened to generate an epoxy resin-PVC block copolymer, and the reaction is quenched with 0.1 M hydrochloric acid, and dried to obtain a PVC-b-EP block copolymer;

[0009] S2: Ammonium polyphosphate (APP) and a surfactant are added to the solution in step S1, and ammonium polyphosphate (APP) is dispersed evenly at room temperature using a stirring device;

[0010] S3: The reactor is heated and stirred at a constant temperature;

[0011] S4: The reactor is heated again, the temperature is further increased, and the reaction is carried out at a constant temperature to obtain a reaction product;

[0012] S5: After the reaction is completed, suction filtration and washing are carried out, and finally drying treatment is carried out;

[0013] S6: The dried product is stirred using a pulverizer and packaged and stored using a sealed bag.

[0014] The ethanol is AR anhydrous ethanol, and the dosage is 100-180 mL; the epoxy resin (EP) is bisphenol A epoxy resin EP, with an epoxy equivalent between 184-190 g / eq and an epoxy value of 0.48-0.53, and the dosage is 5-20% of the mass of ammonium polyphosphate (APP).

[0015] The curing agent is one or a combination of aliphatic amines, aromatic amines, acid anhydrides, polyamides, etc., and the dosage is 10-20% of the mass of bisphenol A epoxy resin EP.

[0016] The curing agent is TETA.

[0017] The stirring time in step S1 is 10-30 min.

[0018] The degree of polymerization n of the ammonium polyphosphate (APP) is greater than 1000, and the dosage is 40 - 80 g.

[0019] The surfactant is one or a combination of stearic acid and sodium dodecylbenzenesulfonate, and the dosage is 1 - 5% of the mass of ammonium polyphosphate (APP).

[0020] The stirring time in step S2 is 30 - 60 min.

[0021] The heating in steps S3 - S4 is carried out using a magnetic heater, and the heating rate is 1 - 5 °C / min. First, it is heated to 40 - 60 °C and maintained for 1 - 4 h, and then it is heated to 70 - 80 °C at the same heating rate and maintained for 1 - 4 h.

[0022] The product after the reaction in step S4 is filtered through a complete set of suction filtration devices. The solid product after suction filtration is washed 3 - 4 times with distilled water, and finally dried in a vacuum oven at 80 - 100 °C for 24 h to obtain ammonium polyphosphate flame - retardant microcapsules.

[0023] A halogen - free flame - retardant microcapsule is prepared by the above method.

[0024] The beneficial effects of the present invention are as follows: The present invention modifies epoxy resin. In the selection of epoxy resin, flexible chain segments such as polyurethane or polyester are introduced to reduce the rigidity of the wall material and enhance the entanglement of molecular chain segments with PVC. In the selection of functional groups, epoxy resins with a higher degree of hydroxylation or carboxylation are selected. In this way, the epoxy resin wall material contains an epoxy resin - PVC block copolymer, which has good affinity with both epoxy resin and PVC. By coating and modifying ammonium polyphosphate (APP) with epoxy resin to form APP microcapsules, its disadvantages can be effectively improved and its application scope can be expanded. The present invention adopts a segmented reaction temperature mode to prepare ammonium polyphosphate (APP) microcapsules with good performance. The whole operation process is environmentally friendly and pollution - free. Most importantly, it is simple and easy to operate, which is helpful for industrial application and development. Description of the Drawings

[0025] Figure 1 It is a physical picture of the ammonium polyphosphate flame - retardant microcapsule in Example 1 of the present invention;

[0026] Figure 2 It is a SEM picture of the ammonium polyphosphate flame - retardant microcapsule in Example 2 of the present invention. Detailed Embodiments

[0027] The ammonium polyphosphate in the following embodiments is represented by APP, and the modified epoxy resin (EP) is a modified epoxy resin (EP) synthesized with an epoxy resin-PVC block copolymer; the synthesis method is as follows: 0.1mmol of CuBr, 0.2mmol of CuBr / bipyridine (bpy), 0.05mmol of α-ethyl bromoisobutyrate (EBiB) and 10mL of toluene are added in sequence to a Schlenk reaction bottle; after nitrogen is introduced to replace oxygen, 5mmol of vinyl chloride monomer is injected, and the reaction is carried out at 70°C for 6 hours to obtain PVC-Br with a molecular weight of about 10,000g / mol and PDI<1.3; 1g of the above PVC-Br with 0.1mmol of terminal groups is dissolved in 10mL of N,N-dimethylformamide (DMF), and 0.02mmol of tetrabutylammonium bromide (TBAB) is added; under nitrogen protection, 10mmol of ... l of epichlorohydrin (ECH), maintained at 40°C, reacted for 12 hours to generate epoxy resin-PVC block copolymer through the ring opening of epoxy group, added 0.1M hydrochloric acid to quench the reaction, and dried to obtain PVC-b-EP block copolymer.

[0028] Example 1

[0029] First, add 140 mL of anhydrous ethanol, 6 g of EP, and 0.9 g of curing agent TETA into the reactor.

[0030] Then add 60g of dried APP and 0.6g of sodium dodecylbenzene sulfonate, stir and disperse at room temperature (25°C) for about 30min, set the heating rate to 1°C / min, keep at 40°C for 1h, and then react at 70°C for 1h. After the reaction is completed, filter, wash the precipitate with distilled water, and dry at 80°C for 48h. Finally, use a high-speed mixer to crush the dried product and store it in a sealed bag.

[0031] like Figure 1 Shown is a real picture of the prepared ammonium polyphosphate flame retardant microcapsules, which have a floury texture of white powder after being crushed.

[0032] Example 2

[0033] First, 100 mL of anhydrous ethanol, 4 g of bisphenol A epoxy resin E51, and 0.6 g of curing agent T31 were added to the reaction kettle.

[0034] Then add 40 g of dry APP, and stir and disperse it at room temperature (25 °C). After melting 0.4 g of stearic acid, add it to the suspension under high-speed stirring, and continue stirring for 1 h. Set the heating rate of the heater to 5 °C / min, hold at 80 °C for 4 h, and then raise the temperature to 100 °C and hold for 4 h. After the reaction is completed, pour out the remaining absolute ethanol, stir with distilled water for 10 min, wash 3 times, then filter by suction to obtain the reaction product, and dry it at 100 °C for 24 h. Finally, use a high-speed mixer to crush the dried product and store it in a sealed bag.

[0035] Observed by scanning electron microscope, the ammonium polyphosphate flame-retardant microcapsules were successfully prepared. As Figure 2 shown, a thin film can be clearly seen on the surface of the microcapsules, and the ammonium polyphosphate is completely coated therein, which is crucial for the improvement of performance.

[0036] Example 3

[0037] First, prepare a 500 mL reaction vessel, add 80 g of APP, 7 wt% of EP based on the mass of APP, and the dosage of epoxy resin 593 curing agent is 15 wt% of the mass of EP. Then add 15% of the surfactant glycerol fatty acid ester based on the mass of APP. After mixing all the materials, add 180 mL of absolute ethanol, stir and disperse it with a glass rod without agglomeration, and then stir at a rate of 800 r / min for 1 h until completely dispersed. Set the heating rate of the heater to 2 °C / min, hold at 60 °C for 2 h, and then raise the temperature to 80 °C and hold for 2 h. After the reaction is completed, pour out the remaining absolute ethanol, stir with distilled water for 10 min, wash 3 times, then filter by suction to obtain the reaction product, and dry it at 60 °C for 24 h. Finally, use a high-speed mixer to crush the dried product and store it in a sealed bag.

[0038] The P element content of the ammonium polyphosphate microcapsules was tested as shown in Table 1 below. The content of the P element is about 24%, and the higher the P element, the more excellent the various performances of the ammonium polyphosphate microcapsules.

[0039] Table 1 Test data of P content in microcapsules

[0040]

Claims

1. A method for preparing halogen-free flame-retardant microcapsules, which comprises the following steps: characterized in that: S1: Add ethanol, modified epoxy resin (EP) and curing agent into a reactor, and magnetically stir evenly until a clear and transparent pretreatment liquid is obtained; The modified epoxy resin (EP) is a modified epoxy resin (EP) synthesized with an epoxy resin-PVC block copolymer; its synthesis method is: sequentially add 0.1 mmol of CuBr, 0.2 mmol of CuBr / bipyridine (bpy), 0.05 mmol of ethyl α-bromoisobutyrate (EBiB) and 10 mL of toluene into a Schlenk reaction flask; after purging with nitrogen to displace oxygen, inject 5 mmol of vinyl chloride monomer, and react at 70 °C for 6 hours to obtain PVC-Br with a molecular weight of about 10,000 g / mol and a PDI < 1.3; dissolve 1 g, 0.1 mmol of terminal PVC-Br in 10 mL of N,N-dimethylformamide (DMF), and add 0.02 mmol of tetrabutylammonium bromide (TBAB); under nitrogen protection, dropwise add 10 mmol of epichlorohydrin (ECH), maintain the temperature at 40 °C, and react for 12 hours. The epoxy group is ring-opened to generate an epoxy resin-PVC block copolymer, and 0.1 M hydrochloric acid is added to quench the reaction, and then dried to obtain the PVC-b-EP block copolymer; S2: Add ammonium polyphosphate (APP) and surfactant to the solution in step S1, and disperse ammonium polyphosphate (APP) evenly at room temperature using a stirring device; S3: Heat up the reactor and stir at a constant temperature; S4: Heat the reactor again, continue to heat up, and react at a constant temperature to obtain a reaction product; S5: After the reaction is completed, perform suction filtration, washing, and finally perform drying treatment; S6: Stir the dried product with a pulverizer and package and store it in a sealed bag.

2. The preparation method of a halogen-free flame-retardant microcapsule according to claim 1, characterized in that: The ethanol is AR anhydrous ethanol, and the dosage is 100-180 mL; the epoxy resin (EP) is bisphenol A type epoxy resin EP, with an epoxy equivalent between 184-190 g / eq and an epoxy value of 0.48-0.53, and the dosage is 5-20% of the mass of ammonium polyphosphate (APP).

3. The preparation method of a halogen-free flame retardant microcapsule according to claim 1, characterized in that: The curing agent is one or a combination of aliphatic amines, aromatic amines, acid anhydrides, polyamides, etc., and the dosage is 10-20% of the mass of bisphenol A type epoxy resin EP.

4. The preparation method of a halogen-free flame-retardant microcapsule according to claim 3, wherein: The curing agent is TETA.

5. The preparation method of a halogen-free flame-retardant microcapsule according to claim 1 or 2, characterized in that: The ammonium polyphosphate (APP) has a polymerization degree n greater than 1000, and the dosage is 40-80 g.

6. The preparation method of a halogen-free flame-retardant microcapsule according to claim 1, characterized in that: The surfactant is one or a combination of stearic acid and sodium dodecylbenzenesulfonate, and the dosage is 1-5% of the mass of ammonium polyphosphate (APP).

7. The preparation method of a halogen-free flame retardant microcapsule according to claim 1, wherein: The stirring time in step S1 is 10-30 min; the stirring time in step S2 is 30-60 min.

8. According to claim 1, characterized in that A method for preparing halogen-free flame-retardant microcapsules: The heating in steps S3-S4 is carried out using a magnetic heater, with a heating rate of 1-5 °C / min. First, heat up to 40-60 °C and maintain for 1-4 h, and then heat to 70-80 °C at the same heating rate and maintain for 1-4 h.

9. According to claim 1, characterized in that A preparation method of a halogen-free flame-retardant microcapsule: The product after the reaction in step S4 is filtered through a complete set of suction filtration devices, and the solid product after suction filtration is washed 3-4 times with distilled water, and finally dried in a vacuum oven at 80-100 °C for 24 h to obtain an ammonium polyphosphate flame-retardant microcapsule.

10. A halogen-free flame retardant microcapsule, characterized in that: It is prepared by the method of the halogen-free flame-retardant microcapsule described in any one of claims 1-9 above.

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