CN103834169A - Flame-retardant benzoxazine resin and preparation method thereof - Google Patents

Abstract

A flame-retardant benzoxazine resin and a preparation method thereof relate to a thermosetting resin. A flame-retardant benzoxazine resin with good flame-retardant effect and heat resistance, and good compatibility between a flame-retardant modifier and a resin matrix and a preparation method thereof are provided. The composition of the flame-retardant benzoxazine resin according to mass ratio is as follows: 100 parts of benzoxazine matrix resin; 1-40 parts of ammonium polyphosphate; 0-150 parts of solvent. Dry method: add ammonium polyphosphate to benzoxazine base resin, stir evenly, after prepolymerization, cool to room temperature to obtain flame retardant benzoxazine resin. The flame-retardant benzoxazine resin prepared by the dry method can be used in adhesives, composite material matrix resins, etc. Wet method: add solvent to benzoxazine base resin, stir well, then add ammonium polyphosphate, stir well, then get flame retardant benzoxazine resin. The flame-retardant benzoxazine resin prepared by the wet method can be used for the preparation of fiber prepregs and the like by the wet method.

Description

A kind of flame-retardant benzoxazine resin and preparation method thereof

technical field

The invention relates to a thermosetting resin, in particular to a flame-retardant benzoxazine resin and a preparation method thereof.

Background technique

Thermosetting resins and their composite materials are widely used in aerospace, automobiles, electronic appliances, construction and other industrial fields due to their excellent dimensional stability, rigidity and heat resistance. Therefore, the flame retardant modification of resins has been extensively studied in recent years.

Epoxy resin and bismaleimide resin are commonly used high-performance thermosetting resin matrices. Epoxy resin has good thermal stability and dielectric properties, and bismaleimide resin has high temperature resistance and chemical resistance. , radiation resistance and excellent mechanical properties, but epoxy resin is easy to burn, and the oxygen index usually does not exceed 25 (Levchik, S.V.; Weil, E.D., Thermal decomposition, combustion and flame‐retardancy of epoxy resins—a review of the recentliterature[J ].Polymer International.2004,53(12),1901-1929), although bismaleimide resin has certain self-extinguishing properties, it needs to be toughened and modified so that its oxygen index is generally less than 24 (Huang Zhixiong, Mei Qi Lin, Qin Yan, et al. Research on Reactive Flame Retardant Modified Bismaleimide Resin. [J] Journal of Wuhan University of Technology. 2002,24(2):5-8). The flame retardant property modification of the original thermosetting resin and the research and development of new flame retardant thermosetting resin are of great value.

Benzoxazine resin is a new type of ring-opening polymerized phenolic resin. It not only has good heat resistance and flame retardancy of traditional phenolic resins, but also has no small molecule release during molding and curing, and its volume is close to zero shrinkage. It has low water absorption and Stable insulation. In addition, the resin synthesis process is simple and low cost. It is reinforced with glass fiber or carbon fiber to prepare composite materials. It has good processability, almost the same as epoxy resin, and its mechanical strength at high temperature (180°C) is comparable to that of double-horse polyimide. The proximity of amines makes benzoxazine resins more and more widely used. The oxygen index of benzoxazine is higher than that of epoxy resin, generally around 30 (M.Sponton, J.C.Ronda, M.Galia`, V.Ca′diz, Studies on thermal and flame retardant behavior of mixtures of bis(m -aminophenyl)methyl-phosphine oxide based benzoxazine and glycidylether ofbisphenol A[J], Polym.Degrad.Stab.2008,93,2158–2165), but it still needs to be modified for flame retardant applications .

Traditional flame retardant modifiers mostly contain halogens. Although these flame retardants have high flame retardant efficiency, they produce a large amount of toxic substances during combustion and seriously pollute the environment. In recent years, they have been gradually replaced by halogen-free flame retardants. As a large category of flame retardants, inorganic flame retardants often have low toxicity, no corrosion, and low price in addition to good flame retardant effects, but they are often used in large amounts and have a great impact on material properties. Gu Yi et al. (Ling Hong, Gu Yi. Magnesium Hydroxide Flame Retardant Polybenzoxazine[J]. Polymer Materials Science and Engineering, 2013,29(7):76-79; Ling Hong, Ye Xiaozhou, Gu Yi. Aluminum hydroxide modified benzoxazine and its flame retardancy [J]. Materials Engineering, 2011, (6): 5-10) adding aluminum hydroxide and magnesium hydroxide as flame retardants to benzene Modified in the oxazine resin, the addition of 20% or more can reach the UL-94V0 level, but the addition of a large amount will affect the combination of the inorganic modifier and the organic resin matrix and affect other properties. Lu Zaijun et al. (Lu Zaijun, Men Weiwei, Zhang Hongchun, et al. Preparation method of diamine-type phosphorus-containing highly flame-retardant benzoxazine resin: China, CN101220152B[P].2010.06.09; Lu Zaijun , Meng Weiwei, Zhang Hongchun, etc. Preparation method of dihydric phenolic phosphorus-containing high flame-retardant benzoxazine resin: China, CN101220153B[P].2010.04.07) The flame-retardant benzoxazine resin invented The phosphorus compound is introduced into the synthesis process of the benzoxazine resin intermediate through chemical reaction, and the flame retardant grade of the prepared flame retardant benzoxazine resin reaches V-0 grade, and has good thermal performance at the same time. This kind of reactive flame retardant method makes the molecular chain contain flame retardant elements or groups, which can avoid the precipitation of the flame retardant and reduce the impact on the physical properties of the matrix, but the reactive flame retardant involves the entire polymerization process. Change is more complicated. As a kind of inorganic phosphorus-based additive flame retardant, ammonium polyphosphate is cheap, low in toxicity, and good in thermal stability. good effect.

Contents of the invention

The object of the present invention is to provide a flame-retardant benzoxazine resin with good flame-retardant effect and heat resistance, and good compatibility between the flame-retardant modifier and the resin matrix and its preparation method.

The composition of the flame-retardant benzoxazine resin according to the mass ratio is as follows:

Benzoxazine matrix resin 100;

Ammonium polyphosphate 1～40;

Solvent 0～150.

The ammonium polyphosphate is type II ammonium polyphosphate crystal, and the degree of polymerization is greater than 1000.

The benzoxazine matrix resin is selected from at least one of diamine-type benzoxazines, bisphenol-type benzoxazines, monocyclic benzoxazines, etc.;

The structural formula of the diamine benzoxazine is:

The structural formula of the bisphenol type benzoxazine is:

The structural formula of the monocyclic benzoxazine is:

The solvent may be selected from at least one of tetrahydrofuran, dichloromethane, chloroform, dimethylsulfoxide, dimethylformamide, acetone, ethyl acetate, benzene, toluene, xylene and the like.

The specific steps of one of the preparation methods (dry method) of the flame-retardant benzoxazine resin are as follows:

Add ammonium polyphosphate into the benzoxazine matrix resin, stir evenly, and cool to room temperature after prepolymerization to obtain the flame-retardant benzoxazine resin. The flame-retardant benzoxazine resin prepared by the dry method can be used in adhesives, composite material matrix resins, etc.

The stirring temperature may be 110-135° C.; the pre-polymerization time may be 3-120 minutes.

The specific steps of the second preparation method (wet method) of the flame-retardant benzoxazine resin are as follows:

Add a solvent into the benzoxazine base resin, stir evenly, then add ammonium polyphosphate, and stir evenly to obtain the flame-retardant benzoxazine resin. The flame-retardant benzoxazine resin prepared by the wet method can be used for the preparation of fiber prepregs and the like by the wet method.

As an inorganic additive flame retardant, ammonium polyphosphate is non-toxic, does not contain halogen, has good thermal stability, and has little environmental pollution. The method has low cost and simple operation, and can meet the requirements of industrial production.

The invention uses ammonium polyphosphate flame-retardant modified benzoxazine resin, adopts wet method and dry method to prepare flame-retardant benzoxazine resin, the flame-retardant effect of the resin is significantly improved, and the original excellent heat resistance of the resin is obtained. It is basically maintained, and the flame retardant modifier has good compatibility with the resin matrix. The flame-retardant benzoxazine resin product of the present invention can be used alone in flame-retardant occasions, and can also be used in combination with reinforcing materials such as glass fiber and carbon fiber. The method is easy to operate and has certain industrial application prospects. In addition to ammonium polyphosphate, the flame retardant preparation method in the present invention is also applicable to the situation where magnesium hydroxide, aluminum hydroxide, antimony trioxide, microencapsulated red phosphorus, and zinc borate are used as flame retardants.

Description of drawings

Figure 1 is the microscopic morphology of ammonium polyphosphate in benzoxazine resin.

Figure 2 is the SEM image of the local fluffy carbon layer after burning the flame retardant benzoxazine resin.

Fig. 3 is an SEM image of the local cell structure of the flame retardant benzoxazine resin after burning.

Figure 4 is the DMTA diagram of the benzoxazine resin before flame retardant modification.

Figure 5 is the DMTA figure after 10% ammonium polyphosphate flame retardant modified benzoxazine resin.

Figure 6 is the DMTA figure after 20% ammonium polyphosphate flame retardant modified benzoxazine resin.

Detailed ways

Example 1

Take 100 parts of benzoxazine matrix resin, add 1 part of ammonium polyphosphate and stir evenly, then raise the temperature to 110°C and stir for 120 minutes to fully mix the molten resin and ammonium polyphosphate, cool to room temperature, and obtain dry flame-retardant benzoxazine Oxazine resins.

The above-mentioned dry-process flame-retardant benzoxazine resin is degassed in vacuum at 125°C, and the temperature is 150±5°C/1h+160±5°C/1h+170±5°C/1h+180±5°C/2h+200± The cast body was prepared by 5°C/2h curing process, and its oxygen index was measured to be 32.5.

Example 2

Take 100 parts of benzoxazine matrix resin, add 10 parts of ammonium polyphosphate and stir evenly, then raise the temperature to 135°C and stir for 3 minutes to fully mix the molten resin and ammonium polyphosphate, cool to room temperature, and obtain dry flame-retardant benzoxazine Oxazine resins. The above-mentioned dry-process flame-retardant benzoxazine resin is degassed in vacuum at 125°C, and the temperature is 150±5°C/1h+160±5°C/1h+170±5°C/1h+180±5°C/2h+200± The cast body was prepared by 5℃/2h curing process, and its oxygen index was measured to be 36.5.

Example 3

Take 100 parts of benzoxazine matrix resin, add 20 parts of ammonium polyphosphate and stir evenly, then raise the temperature to 120°C and stir for 40 minutes to fully mix the molten resin and ammonium polyphosphate, cool to room temperature, and obtain dry flame-retardant benzoxazine Oxazine resins. The above-mentioned dry-process flame-retardant benzoxazine resin is degassed in vacuum at 125°C, and the temperature is 150±5°C/1h+160±5°C/1h+170±5°C/1h+180±5°C/2h+200± The cast body was prepared by 5℃/2h curing process, and its oxygen index was measured to be 40.3.

Example 4

Take 100 parts of benzoxazine matrix resin, add 150 parts of tetrahydrofuran solvent and mix evenly, then add 40 parts of ammonium polyphosphate and stir evenly to obtain wet-process flame-retardant benzoxazine resin. Heat the above wet-process flame-retardant benzoxazine resin to 95°C to remove most of the solvent and then vacuum degassing, according to 150±5°C/1h+160±5°C/1h+170±5°C/1h+180± The cast body was prepared by 5°C/2h+200±5°C/2h curing process, and its oxygen index was measured to be 47.

Example 5

Take 100 parts of benzoxazine base resin, add 80 parts of tetrahydrofuran solvent and mix evenly, then add 20 parts of ammonium polyphosphate and stir evenly to obtain wet-process flame-retardant benzoxazine resin. Heat the above wet-process flame-retardant benzoxazine resin to 95°C to remove most of the solvent and then vacuum degassing, according to 150±5°C/1h+160±5°C/1h+170±5°C/1h+180± The cast body was prepared by 5°C/2h+200±5°C/2h curing process, and its oxygen index was measured to be 40.3.

Example 6

Take 100 parts of benzoxazine base resin, add 60 parts of tetrahydrofuran solvent and mix evenly, then add 10 parts of ammonium polyphosphate and stir evenly to obtain wet-process flame-retardant benzoxazine resin. Heat the above wet-process flame-retardant benzoxazine resin to 95°C to remove most of the solvent and then vacuum degassing, according to 150±5°C/1h+160±5°C/1h+170±5°C/1h+180± The cast body was prepared by 5°C/2h+200±5°C/2h curing process, and its oxygen index was measured to be 36.5.

The flame retardant effect of the flame-retardant benzoxazine resin prepared by using diphenylmethane diamine-type benzoxazine matrix resin and ammonium polyphosphate is significantly improved, and the oxygen index of the modified system with 3% ammonium polyphosphate is reduced from benzo The 31.5 of the oxazine matrix resin increased to 34.5, showing an excellent flame retardant modification effect. The flame retardant modified system produces less smoke than the matrix resin, and the microscopic appearance shows that ammonium polyphosphate has good compatibility and interface properties with the matrix resin (see Figure 1). The inert gas released after combustion makes the surface porous. Bubble structure, the formed carbon layer isolates the polymer from contact with oxygen to play a flame retardant role (see Figures 2 and 3). The flame-retardant benzoxazine resin of the present invention also has excellent heat resistance. When the ammonium polyphosphate addition amount is 10%, the glass transition temperature is 207°C, which is less than that of the base resin at 211°C, and even the addition amount reaches At 20%, the glass transition temperature remains at 203°C (see Figures 4-6).

Claims (8)

1. a flame retardant type benzoxazine colophony, is characterized in that in mass ratio composed as follows:

Benzoxazine matrix resin 100;

Ammonium polyphosphate 1～40;

Solvent 0～150.

2. a kind of flame retardant type benzoxazine colophony as claimed in claim 1, is characterized in that described benzoxazine matrix resin is selected from least one in diamines type benzoxazine, bisphenol type benzoxazine, monocycle benzoxazine;

The structural formula of described diamines type benzoxazine is:

The structural formula of described bisphenol type benzoxazine is:

The structural formula of described monocycle benzoxazine is:

3. a kind of flame retardant type benzoxazine colophony as claimed in claim 1, is characterized in that described ammonium polyphosphate is ammonium polyphosphate crystallization II-type, and the polymerization degree is greater than 1000.

4. a kind of flame retardant type benzoxazine colophony as claimed in claim 1, is characterized in that described solvent is selected from least one in tetrahydrofuran (THF), methylene dichloride, chloroform, dimethyl sulfoxide (DMSO), dimethyl formamide, acetone, ethyl acetate, benzene,toluene,xylene.

5. a kind of preparation method of flame retardant type benzoxazine colophony as claimed in claim 1, is characterized in that its concrete steps are as follows:

In benzoxazine matrix resin, add ammonium polyphosphate, stir, after pre-polymerization, be cooled to room temperature, obtain flame retardant type benzoxazine colophony.

6. a kind of preparation method of flame retardant type benzoxazine colophony as claimed in claim 5, the temperature that it is characterized in that described stirring is 110～135 ℃.

7. a kind of preparation method of flame retardant type benzoxazine colophony as claimed in claim 5, the time that it is characterized in that described pre-polymerization is 3～120min.

8. a kind of preparation method of flame retardant type benzoxazine colophony as claimed in claim 1, is characterized in that its concrete steps are as follows:

In benzoxazine matrix resin, add solvent, after stirring, add again ammonium polyphosphate, then after stirring, obtain flame retardant type benzoxazine colophony.

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