A magnesium hydroxide / epoxy phosphate composite flame retardant, a preparation method and application thereof

Abstract

The application discloses a magnesium hydroxide / epoxy phosphate composite flame retardant and belongs to the field of flame retardant materials, which is prepared from epoxy phosphate and magnesium hydroxide as raw materials. The composite flame retardant is prepared by coating the magnesium hydroxide surface with the epoxy phosphate in a chemical bonding mode, instead of simple physical mixing. Compared with the flame retardant prepared by directly blending the same amount of magnesium hydroxide and epoxy phosphate, the composite flame retardant has better flame retardant effect and better reinforcing and toughening effect. Meanwhile, the magnesium hydroxide / epoxy phosphate composite flame retardant is applied to the preparation of soft PVC, and a soft PVC / MHEPE composite flame retardant material with good compatibility and high flame retardant efficiency can be obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of flame-retardant materials, and particularly relates to a magnesium hydroxide / epoxy phosphate composite flame retardant as well as a preparation method and application thereof. BACKGROUND

[0002] Polyvinyl chloride (PVC) products can be divided into hard, semi-hard and soft according to the content of plasticizers. Among them, hard PVC is difficult to burn or self-extinguish after burning due to its high chlorine content, and the limiting oxygen index (LOI) reaches more than 45%, which belongs to a typical flame-retardant material. The flammability of soft PVC is greatly increased due to the addition of more than 40 parts of ester plasticizers, and the LOI value decreases to about 24%. In addition, soft PVC releases a large amount of toxic smoke (such as HCl, CO, benzene and other chlorine-containing toxic gases, etc.) during combustion, which seriously endangers people's life and property safety and greatly limits the application range of PVC products.

[0003] At present, the research on flame-retardant and smoke-suppressing soft PVC is mainly achieved by adding flame retardants or smoke suppressants, including halogen-based, phosphorus-based, transition metal oxides and salts, metal hydroxides, etc. Among them, halogen-based flame retardants have the advantages of high flame-retardant efficiency and good compatibility with the matrix, but they release corrosive hydrogen halide gas and toxic and carcinogenic substances (such as polybrominated benzoperns and polybrominated dibenzofurans, etc.) during combustion. Phosphorus-based flame retardants mainly include inorganic phosphate, red phosphorus, organic hypophosphite and phosphate esters, etc. On the one hand, phosphoric acid, metaphosphoric acid and polyphosphoric acid generated by thermal decomposition promote the carbonization of PVC matrix, and on the other hand, a large number of PO· free radicals generated by thermal decomposition absorb H·, HO· and other free radicals, blocking the free radical chain growth reaction in the combustion process. There are mainly two ways to flame-retardant soft PVC by using transition metal oxides and salts: ① Lewis acid catalyzing crosslinking to form carbon; ② reducing coupling of low-valence compounds or elements of multi-valence transition metal oxides to form carbon. It should be pointed out that the smoke-suppressing effect of transition metal oxides and salts is very outstanding, but the flame-retardant effect is often poor when used alone.

[0004] Metal hydroxides represented by magnesium hydroxide (MH) are also one of the important flame retardants for soft PVC. This kind of flame retardant reduces the temperature of the matrix by heat absorption and releases a large amount of water vapor, which has the effect of dilution and shielding of oxygen. The metal oxides generated by decomposition also have certain heat insulation and carbon residue enhancement effects. Compared with other flame retardants, MH also has the advantages of environmental protection, non-toxicity, low price and ability to neutralize the acidic gas generated by PVC combustion.

[0005] There are still two problems for using magnesium hydroxide as a flame-retardant and smoke-suppressant for soft PVC: 1) poor interfacial compatibility between magnesium hydroxide and PVC matrix; 2) low flame-retardant efficiency of magnesium hydroxide (limited by flame-retardant mechanism). For problem 1, surface modification or adding a compatibilizer is often used to solve the problem, such as silane coupling agent modification, fatty acid modification, adding maleic anhydride grafted polypropylene, etc., but the introduction of hydrocarbons often leads to a slight decrease in flame-retardant performance. For problem 2, a method of compounding multiple flame retardants is often used to solve the problem. By using different flame-retardant mechanisms of various flame retardants, the synergistic effect between them is used to improve the flame-retardant effect. Common synergistic flame retardants of magnesium hydroxide include organic phosphate ester, microencapsulated red phosphorus, zinc borate / reduced graphene oxide hybrid material, etc., which compensate for the lack of MH in flame-retardant and smoke-suppressant efficiency by mechanisms such as promoting matrix carbonization, forming a flame-retardant protective film, and capturing free radicals, but have little effect on improving the compatibility of magnesium hydroxide with the matrix.

[0006] In the paper "Surface Modification of Magnesium Hydroxide and Its Application in Polymers", a composite material with magnesium hydroxide as a single flame retardant and epoxy resin as a matrix is mentioned. However, the cured EP / MH composite material prepared by the method described in the paper does not have processability and is a completely blocky hard plastic, which cannot be uniformly mixed with each component in the soft PVC formulation, and is even less likely to be remolded after melting (EP is a thermosetting resin). Therefore, a composite flame retardant is needed to modify soft PVC to improve its flame-retardant effect.

[0007] Using epoxy phosphate as a modifier of magnesium hydroxide to construct a magnesium hydroxide / epoxy phosphate composite flame retardant has not been reported at home and abroad. SUMMARY

[0008] In view of the above prior art, the purpose of the present application is to provide a magnesium hydroxide / epoxy phosphate composite flame retardant and its preparation method and application.

[0009] As for PVC, it has good compatibility with polyether and polyester molecules, and many systems can even be completely compatible. Therefore, if polyether or polyester structures can be introduced into the modifier molecules, the interfacial compatibility problem of PVC and magnesium hydroxide can be expected to be solved. Uncured epoxy resin has a linear polyether or polyester structure, such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, linear phenolic polyglycidyl ether, and glycidyl methacrylate. Therefore, designing and synthesizing a modifier with an epoxy resin skeleton structure and introducing a functional group such as phosphate ester with flame-retardant effect is expected to prepare an epoxy phosphate modifier with flame-retardant and compatible functions.

[0010] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0011] The first aspect of the present application provides a preparation method of magnesium hydroxide / epoxy phosphate composite flame retardant, comprising the following steps:

[0012] (1) adding magnesium hydroxide into deionized water, and stirring under ultrasonic wave to obtain a magnesium hydroxide dispersion;

[0013] (2) dissolving epoxy acid phosphate into anhydrous ethanol to obtain an epoxy phosphate-ethanol solution, then adding the epoxy phosphate-ethanol solution into the magnesium hydroxide dispersion under stirring, and heating to 55-70℃ for 0.5-2h, and then cooling to room temperature to obtain a white slurry; the weight ratio of magnesium hydroxide to epoxy phosphate is 100:4-8;

[0014] (3) filtering the white slurry to obtain a filter cake, and washing and drying the filter cake to obtain the magnesium hydroxide / epoxy phosphate composite flame retardant.

[0015] Preferably, the mass of magnesium hydroxide and the volume of deionized water in step (1) are 1-2g:100ml, and the mass of epoxy phosphate and the volume of anhydrous ethanol in step (2) are 1-2g:100ml.

[0016] Preferably, the ultrasonic time in step (1) is 10-25min, and the stirring time is 25-35min; and the drying conditions in step (4) are: temperature 65-75℃, and time 10-12h.

[0017] Preferably, the epoxy phosphate is prepared by the following method:

[0018] Epoxy resin E44 and phosphoric acid are used as raw materials, and acetone is used as a solvent, and the reaction is carried out for 2.5-4.5h, and then the reaction system is cooled to room temperature, and the acetone solvent is removed to obtain a crude epoxy phosphate product, and the epoxy phosphate is obtained after purification.

[0019] The reaction equation of epoxy resin E44 and phosphoric acid is as follows:

[0020]

[0021] Preferably, the weight of epoxy resin E44 and the volume of acetone are 1g:2.5ml; and the molar ratio of epoxy resin E44 to phosphoric acid is 1:1-2.5.

[0022] Preferably, the mass concentration of phosphoric acid is 85%; the method for removing the acetone solvent is: rotary evaporation of the crude epoxy phosphate product at 65℃; and the method for purification is: adding 50ml deionized water into the crude epoxy phosphate product, and then standing and separating the layers, and discarding the water layer.

[0023] The second aspect of the present application provides a magnesium hydroxide / epoxy phosphate composite flame retardant prepared by the above preparation method.

[0024] In a third aspect, the present application provides a use of the magnesium hydroxide / epoxy phosphate composite flame retardant as described above in the preparation of a soft PVC composite flame retardant material.

[0025] In a fourth aspect, the present application provides a soft PVC composite flame retardant material, which is prepared from the following raw materials by weight:

[0026] PVC powder 100 parts, PVC processing aid 4 parts, glycerol monostearate 0.6 parts, dioctyl phthalate 40 parts, liquid paraffin 0.4 parts, organic tin 2 parts and 5-60 parts of the magnesium hydroxide / epoxy phosphate composite flame retardant;

[0027] Preferably, the processing aid is ACR-401.

[0028] Preferably, the PVC composite flame retardant material is prepared by the following method:

[0029] After the raw materials are uniformly mixed, they are mixed at 150°C for 15 minutes to obtain the soft PVC composite flame retardant material.

[0030] The present application has the following advantages:

[0031] 1. The preparation process of the present application is simple, and the epoxy phosphate sample can be prepared by one-pot method without complex and tedious pretreatment or post-treatment process.

[0032] 2. The preparation process of the present application is simple in ingredient, and does not need to add a catalyst, and the mother liquor is easy to handle.

[0033] 3. The present application synthesizes a new flame retardant containing both epoxy resin skeleton structure and phosphate structure, which can solve the problems of poor compatibility and low flame retardant efficiency in soft PVC / MH composite materials.

[0034] 4. The magnesium hydroxide / epoxy phosphate composite flame retardant prepared by the present application has better flame retardant effect than the flame retardant prepared by directly blending the same amount of magnesium hydroxide and epoxy phosphate.

[0035] 5. The magnesium hydroxide / epoxy phosphate composite flame retardant of the present application is coated on the surface of magnesium hydroxide in a chemical bonding manner, rather than simple physical mixing, and has better toughening effect and better compatibility than the flame retardant prepared by directly blending the same amount of magnesium hydroxide and epoxy phosphate. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 NMR spectrum of epoxy phosphate.

[0037] Figure 2 Carbon spectrum of epoxy phosphate.

[0038] Figure 3 : Infrared spectrum of magnesium hydroxide / epoxy phosphate composite flame retardant.

[0039] Figure 4 : Comparison chart of heat release rate (HRR) curves of soft PVC composite materials.

[0040] Figure 5 : Comparison chart of total heat release (THR) curves of soft PVC composite materials. DETAILED DESCRIPTION

[0041] It should be noted that the following detailed description is illustrative only, and is intended to provide further description in order to provide a fuller enabling and complete disclosure of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0042] MH refers to magnesium hydroxide, MHEPE refers to magnesium hydroxide / epoxy phosphate composite flame retardant, and MH / EPE refers to mechanical mixture of magnesium hydroxide and epoxy phosphate.

[0043] The epoxy phosphate used in each of the examples, comparative examples, and application examples is from Preparation Example 1.

[0044] Preparation Example 1: Preparation of epoxy phosphate

[0045] Weigh 20.00 g of bisphenol A type epoxy resin E44 into 50 mL of acetone, stir to dissolve, to obtain an epoxy resin E44-acetone solution; weigh 10.15 g of phosphoric acid into 20 mL of acetone to disperse to obtain a phosphoric acid-acetone solution; under stirring, slowly add the phosphoric acid-acetone solution into the epoxy resin E44-acetone solution, the dropwise addition speed is controlled at 1 drop per second, after the dropwise addition is completed, reflux at 65°C for 4.5 h; remove the acetone solvent by rotary evaporation, remove the unreacted phosphoric acid by water washing, to obtain an epoxy phosphate sample.

[0046] The nuclear magnetic hydrogen spectrum and carbon spectrum of the epoxy phosphate are shown in Figure 1 and Figure 2 , respectively.

[0047] Example 1: Preparation of magnesium hydroxide / epoxy phosphate composite flame retardant

[0048] Take 5.00 g of magnesium hydroxide, add 100 mL of deionized water, ultrasonic for 10 min, then continue to stir for 30 min, to get the initial dispersion of magnesium hydroxide dispersion; Take 0.30 g of epoxy phosphate, add 25 mL of ethanol to dissolve it, to get the epoxy phosphate-ethanol solution; Under the condition of stirring, slowly add the epoxy phosphate-ethanol solution to the magnesium hydroxide dispersion, and heat to 65℃ for 1 h; After the reaction is completed, the white slurry obtained is filtered to obtain a filter cake, which is washed with deionized water and anhydrous ethanol for 5 times respectively, and the filter cake is dried in a 70℃ oven for 10 h, to obtain the magnesium hydroxide / epoxy phosphate composite flame retardant, marked as MH / EPE.

[0049] The infrared spectrum of the magnesium hydroxide / epoxy phosphate composite flame retardant is made, see Figure 3 .

[0050] Example 2: Preparation of magnesium hydroxide / epoxy phosphate composite flame retardant

[0051] Take 5.00 g of magnesium hydroxide, add 100 mL of deionized water, ultrasonic for 15 min, then continue to stir for 25 min, to get the initial dispersion of magnesium hydroxide dispersion; Take 0.20 g of epoxy phosphate, add 25 mL of ethanol to dissolve it, to get the epoxy phosphate-ethanol solution; Under the condition of stirring, slowly add the epoxy phosphate-ethanol solution to the magnesium hydroxide dispersion, and heat to 55℃ for 1.5 h; After the reaction is completed, the white slurry obtained is filtered to obtain a filter cake, which is washed with deionized water and anhydrous ethanol for 5 times respectively, and the filter cake is dried in a 65℃ oven for 11 h, to obtain the magnesium hydroxide / epoxy phosphate composite flame retardant.

[0052] Example 3: Preparation of magnesium hydroxide / epoxy phosphate composite flame retardant

[0053] Take 5.00 g of magnesium hydroxide, add 100 mL of deionized water, ultrasonic for 25 min, then continue to stir for 35 min, to get the initial dispersion of magnesium hydroxide dispersion; Take 0.40 g of epoxy phosphate, add 25 mL of ethanol to dissolve it, to get the epoxy phosphate-ethanol solution; Under the condition of stirring, slowly add the epoxy phosphate-ethanol solution to the magnesium hydroxide dispersion, and heat to 70℃ for 2 h; After the reaction is completed, the white slurry obtained is filtered to obtain a filter cake, which is washed with deionized water and anhydrous ethanol for 5 times respectively, and the filter cake is dried in a 65℃ oven for 12 h, to obtain the magnesium hydroxide / epoxy phosphate composite flame retardant.

[0054] Application Example 1: Preparation of soft PVC / MHEPE composite flame retardant material

[0055] PVC powder 100 parts, PVC processing aid 4 parts, glycerol monostearate 0.6 parts, dioctyl phthalate 40 parts, liquid paraffin 0.4 parts, organic tin 2 parts and 20 parts of MHEPE were mixed uniformly in a high-speed mixer to obtain a premix; the premix was mixed at 150°C for 15 min to obtain the soft PVC composite flame-retardant material, which was marked as PVC / MHEPE composite material.

[0056] The MHEPE was prepared according to Example 1.

[0057] Preparation of soft PVC / MH composite material

[0058] PVC powder 100 parts, PVC processing aid 4 parts, glycerol monostearate 0.6 parts, dioctyl phthalate 40 parts, liquid paraffin 0.4 parts, organic tin 2 parts and 20 parts of magnesium hydroxide were mixed uniformly in a high-speed mixer to obtain a premix; the premix was mixed at 150°C for 15 min to obtain the PVC / MH composite material.

[0059] Preparation of soft PVC / MH / EPE composite material

[0060] PVC powder 100 parts, PVC processing aid 4 parts, glycerol monostearate 0.6 parts, dioctyl phthalate 40 parts, liquid paraffin 0.4 parts, organic tin 2 parts, magnesium hydroxide 19 parts and epoxy phosphate 1 part were mixed uniformly in a high-speed mixer to obtain a premix; the premix was mixed at 150°C for 15 min to obtain the PVC / EPE composite material.

[0061] Determination of flame-retardant properties of soft PVC / MHEPE composite material

[0062] (1) Test method:

[0063] The PVC composite flame-retardant materials prepared in Application Example 1 and Comparative Examples 1-2 were respectively set as soft PVC / 20MHEPE, soft PVC / 20MH and soft PVC / 20MH / EPE, and the heat release rate (HRR) and total heat release (THR) of the three PVC composite materials were determined. The determination method was as follows: the test was carried out according to the test conditions and steps specified in the national standard GB / T16172-2007 “Building materials heat release rate test method”, the sample size was 100mm×100mm×3mm, and the irradiation intensity was 35kW / m 2 .

[0064] (2) Test results:

[0065] The comparison chart of the heat release rate (HRR) and total heat release (THR) curves of the three PVC composite materials is shown in Figures 1 and 2, respectively. Figure 4 and Figure 5 .

[0066] Table 1: Peak value (pHRR) of HRR curve of each composite material

[0067] Sample pHRR (kW / m 2 )]]> Soft PVC / 20MH 253.2 Soft PVC / 20MH EPE 206.0 Soft PVC / 20MH / EPE 241.0

[0068] From Figure 4 and Table 1, it can be seen that the peak value of HRR of the soft PVC / 20MHEPE composite flame-retardant material is not only lower than that of the soft PVC / 20MH composite material, but also lower than that of the soft PVC / 20MH / EPE composite material, indicating that the flame-retardant effect of the soft PVC / 20MHEPE composite flame-retardant material is the best.

[0069] From Figure 5 , it can be seen that the total heat release (THR) of the soft PVC / 20MHEPE composite material is always the smallest after 200s, which indicates that the magnesium hydroxide / epoxy phosphate composite flame retardant has better flame-retardant efficiency than magnesium hydroxide, and the epoxy phosphate coated on the surface of magnesium hydroxide by chemical bonding is more conducive to the improvement of flame-retardant efficiency.

[0070] Test Example 2: Determination of strength and LOI value of soft PVC composite material

[0071] (1) Test method:

[0072] The LOI value, impact strength and tensile strength of soft PVC were determined under different addition amounts (parts) of MH, MHEPE and MH / EPE, and the determination method is as follows:

[0073] LOI value: The test was carried out according to the test conditions and steps specified in the national standard GB / T 2406.2-2009 "Determination of Burning Behavior of Plastics by Oxygen Index Method", and the sample size was 80mm×10mm×4mm.

[0074] Impact strength: The test was carried out according to the test conditions and steps specified in the national standard GB / T 1843-2008 "Plastics Izod Impact Strength Test", and the sample size was 80mm×10mm×4mm without notch.

[0075] Tensile strength: The test was carried out according to the test conditions and steps specified in the national standard GB / T 1040-2006 "Determination of Tensile Properties of Plastics", and the sample type was 1BA type with a size of 75mm×2mm×2mm and a test speed of 10mm / min.

[0076] (2) Test results:

[0077] Table 2: LOI values and strength determination results of different soft PVC composites

[0078]

[0079] As can be seen from Table 2, at the same addition amount, the impact strength and tensile strength of soft PVC / MHEPE and soft PVC / MH / EPE composites are generally higher than those of soft PVC / MH composite, which shows that EPE can effectively improve the interfacial compatibility of MH and soft PVC and improve the interfacial interaction. More importantly, the impact strength and tensile strength of soft PVC / MHEPE composite are generally optimal, which shows the importance of uniform coating of epoxy phosphate on magnesium hydroxide.

[0080] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Use of magnesium hydroxide / epoxy phosphate composite flame retardant in the preparation of soft PVC composite flame retardant material, characterized in that, The magnesium hydroxide / epoxy phosphate composite flame retardant is prepared by the following method: (1) adding magnesium hydroxide into deionized water, ultrasonic stirring to obtain magnesium hydroxide dispersion liquid; (2) dissolving epoxy phosphate into anhydrous ethanol to obtain epoxy phosphate-ethanol solution, then adding the epoxy phosphate-ethanol solution into the magnesium hydroxide dispersion liquid under stirring, heating to 55-70℃ for 0.5-2h, then cooling to room temperature to obtain white slurry; wherein the weight ratio of magnesium hydroxide and epoxy phosphate is 100:4-8; The preparation method of the epoxy phosphate is as follows: taking epoxy resin E44 and phosphoric acid as reaction raw materials, and taking acetone as solvent, reacting for 2.5-4.5h, cooling to room temperature, removing acetone solvent to obtain epoxy phosphate crude product, and purifying to obtain epoxy phosphate; wherein the weight of epoxy resin E44 and the volume of acetone are 1g:2.5mL, and the molar ratio of epoxy resin E44 and phosphoric acid is 1:1-2.5; (3) filtering the white slurry to obtain filter cake, washing and drying to obtain magnesium hydroxide / epoxy phosphate composite flame retardant.

2. Use according to claim 1, wherein In step (1), the mass of magnesium hydroxide and the volume of deionized water are 1-2g:100mL; in step (2), the mass of epoxy phosphate and the volume of anhydrous ethanol are 1-2g:100mL.

3. The use according to claim 1, wherein In step (1), the ultrasonic time is 10-25min, and the stirring time is 25-35min; the drying conditions in step (3) are as follows: temperature 65-75℃, time 10-12h.

4. The use according to claim 1, wherein The purification method is as follows: adding 50mL deionized water into the epoxy phosphate crude product, standing and separating, and discarding the water layer.

5. A flexible PVC composite flame retardant material, characterized in that, The following raw materials are used by weight: PVC powder 100 parts, PVC processing aid 4 parts, glycerol monostearate 0.6 parts, dioctyl phthalate 40 parts, liquid paraffin 0.4 parts, organic tin 2 parts, and 5-60 parts of magnesium hydroxide / epoxy phosphate composite flame retardant; wherein the processing aid is ACR-401; The magnesium hydroxide / epoxy phosphate composite flame retardant is prepared by the following method: (1) adding magnesium hydroxide into deionized water, ultrasonic stirring to obtain magnesium hydroxide dispersion liquid; (2) dissolving epoxy phosphate into anhydrous ethanol to obtain epoxy phosphate-ethanol solution, then adding the epoxy phosphate-ethanol solution into the magnesium hydroxide dispersion liquid under stirring, heating to 55-70℃ for 0.5-2h, then cooling to room temperature to obtain white slurry; wherein the weight ratio of magnesium hydroxide and epoxy phosphate is 100:4-8; The preparation method of the epoxy phosphate is as follows: taking epoxy resin E44 and phosphoric acid as reaction raw materials, and taking acetone as solvent, reacting for 2.5-4.5h, cooling to room temperature, removing acetone solvent to obtain epoxy phosphate crude product, and purifying to obtain epoxy phosphate; wherein the weight of epoxy resin E44 and the volume of acetone are 1g:2.5mL, and the molar ratio of epoxy resin E44 and phosphoric acid is 1:1-2.5; (3) filtering the white slurry to obtain filter cake, washing and drying to obtain magnesium hydroxide / epoxy phosphate composite flame retardant.

6. The soft PVC composite flame retardant material of claim 5, characterized in that, The soft PVC composite flame-retardant material is prepared by the following method: uniformly mixing raw materials, and mixing at 150 DEG C for 15 min.

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