Composite flame retardant and preparation method thereof

Abstract

The invention discloses a composite flame retardant and a preparation method thereof.The preparation method of the composite flame retardant comprises the steps that phosphorus pentoxide and magnesium chloride hexammine are evenly mixed, then segmented heating polymerization is conducted under the stirring condition, and finally the flame retardant is obtained by smashing the obtained material. According to the composite flame retardant, magnesium hydroxide and ammonium polyphosphate serve as reaction products together, higher mutual dispersibility is achieved, and the defects of a single-system flame retardant are overcome through the synergistic flame retardant effect.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardants, and in particular relates to a composite flame retardant and a preparation method thereof. Background Art

[0002] Ammonium polyphosphate is a non-halogen flame retardant with excellent characteristics such as high flame retardancy, environmental friendliness, small addition amount, and little impact on mechanical properties. It is widely used in flame retardants, refractory materials and fire retardant coatings. The flame retardant mechanism of ammonium polyphosphate is to obtain heat by cutting off combustibles or generating non-combustible substances, thereby preventing combustibles from decomposing under heat to produce combustible substances and causing fires. The raw materials for preparing ammonium polyphosphate are generally divided into the following categories: mainly urea, which is polymerized with phosphoric acid, ammonium phosphate salts, urea phosphate, etc.; mainly phosphorus pentoxide, which is polymerized by passing ammonia or adding ammonium salts and adding condensation agents; less often, polyphosphoric acid and ammonium bicarbonate are used for polymerization.

[0003] However, phosphorus-based flame retardants have the problems of high smoke release during use, poor interfacial compatibility with the wood-plastic composite matrix, resulting in reduced strength, easy precipitation, etc. Therefore, phosphorus-based flame retardants are often used in conjunction with other elemental flame retardants to meet the requirements of material flame retardant treatment.

[0004] Halogen-free flame retardants are valued for their environmental friendliness, which is due to the presence of Al 3+ Mg 2+ Plasma is an effective component of smoke elimination, which is beneficial to the carbonization of the material surface and the formation of an insulating protective layer. The decomposition product is an alkaline porous substance with a large specific surface area. It can adsorb harmful gases and has the dual functions of flame retardancy and smoke suppression, showing good application effects in the flame retardant field.

[0005] The solution disclosed in the document number CN103342833B "A method for preparing an ammonium polyphosphate and magnesium hydroxide nanocomposite material" uses ammonium polyphosphate and magnesium hydroxide as representative halogen-free flame retardants, which can improve the flame retardant properties of the material while also improving the physical properties. However, this method directly mixes magnesium hydroxide into the flame retardant system, resulting in the need for additional ammonia flow and ammonia partial pressure control processes and equipment when preparing ammonium polyphosphate. Summary of the invention

[0006] In order to solve the above technical problems, one of the purposes of the present invention is to provide a composite flame retardant with a simple preparation method, which overcomes the problems of existing phosphorus-based flame retardants, such as large smoke release, poor interfacial compatibility with wood-plastic composite material matrix, resulting in reduced strength, easy precipitation, etc.

[0007] In order to achieve the above purpose, the technical scheme of the present invention is as follows: a method for preparing a composite flame retardant, wherein phosphorus pentoxide and hexaammine magnesium chloride are mixed, and then polymerized by stepwise heating under stirring conditions, and finally the obtained material is crushed to obtain a flame retardant.

[0008] The above technical solution specifically includes the following steps:

[0009] Step 1: Stir phosphorus pentoxide and hexaammine magnesium chloride until they are well mixed to obtain a mixture, heat the mixture to 120-180° C., and pre-react for 1-2 hours;

[0010] Step 2: The pre-reacted mixed material is heated to 230-340°C, kept warm and stirred for 3-6 hours, then the heating is stopped and stirred for 1-2 hours to obtain a flame retardant crude material;

[0011] Step 3: The flame retardant coarse material obtained in step 2 is crushed to obtain the flame retardant.

[0012] In the step 1 described in the above technical scheme, the molar ratio of phosphorus pentoxide to hexaamminemagnesium chloride is 1:1-3.

[0013] In the step 1 described in the above technical solution, a condensation agent is also added during stirring.

[0014] In the above technical solution, the amount of the condensing agent added in step 1 is 1-10% of the sum of the weights of phosphorus pentoxide and hexaammine magnesium chloride.

[0015] The condensing agent in the above technical solution is at least one of urea, ammonium bicarbonate and diammonium hydrogen phosphate.

[0016] The condensing agent in the above technical solution includes urea, ammonium bicarbonate and diammonium hydrogen phosphate.

[0017] The molar ratio of urea:ammonium bicarbonate:diammonium hydrogen phosphate described in the above technical solution is 1-2:1:1.

[0018] The stirring process in step 1 of the above technical solution is carried out in a kneader.

[0019] The second object of the present invention is to provide a composite flame retardant with low smoke release and good interface compatibility with the wood-plastic composite material matrix.

[0020] In order to achieve the above object, the technical solution of the present invention is as follows: a composite flame retardant is prepared by the preparation method as described above.

[0021] The invention has the beneficial effects that: hexaamminemagnesium chloride can be pyrolyzed into magnesium chloride and ammonia, thereby greatly improving the concentration of ammonia in the solid phase reaction, and the ammonia that is not involved in time can also provide ammonia pressure for the reaction atmosphere, further improving the degree of polymerization reaction; the magnesium chloride obtained by decomposition is always stored in the solid phase reaction system, and inorganic flame retardant magnesium hydroxide is generated by absorbing water generated by the polymerization reaction, and the polymerization product is ammonium polyphosphate, and the ammonium polyphosphate and magnesium hydroxide are fully mixed under the action of continuous stirring (since both the ammonium polyphosphate and the magnesium hydroxide are generated in the reaction process, the mixing effect of the two is good), and they are used together as the main components of the flame retardant. DETAILED DESCRIPTION

[0022] The principles and features of the present invention are described below in conjunction with embodiments, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the embodiments in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description and claims.

[0023] This embodiment provides a method for preparing a composite flame retardant, wherein phosphorus pentoxide and hexaammine magnesium chloride are mixed, and then polymerized by stepwise heating under stirring conditions, and finally the obtained material is crushed to obtain the flame retardant.

[0024] Specifically, the above technical solution specifically includes the following steps:

[0025] Step 1: stirring phosphorus pentoxide and hexaammine magnesium chloride in a kneader until uniformly mixed to obtain a mixture, wherein the molar ratio of the two is 1:1-3 (can be any value among 1:1, 1:1.5, 1:2, 1:2.5 and 1:3 or a corresponding range between any two values), heating the mixture to 120-180°C (can be any value among 120°C, 130°C, 140°C, 150°C, 160°C, 170°C and 180°C or a corresponding range between any two values), and pre-reacting for 1-2h (can be any value among 1h, 1.5h or 2h or a corresponding range between any two values);

[0026] Step 2: The pre-reacted mixed material is heated to 230-340°C (can be any value among 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C and 340°C or a corresponding range between any two values), and the mixture is kept warm and stirred for 3-6h (can be any value among 3h, 4h, 5h and 6h or a corresponding range between any two values), and then the heating is stopped, and the stirring is continued for 1-2h (can be any value among 1h, 1.5h or 2h or a corresponding range between any two values) to obtain a flame retardant crude material;

[0027] Step 3: The flame retardant coarse material obtained in step 2 is crushed to obtain the flame retardant.

[0028] In the step 1 of the above technical solution, a condensing agent is further added during stirring, and the amount of the condensing agent added is 1-10% (can be any value among 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% and 10% or a range corresponding to any two values) of the sum of the weights of phosphorus pentoxide and hexaammine magnesium chloride; specifically, the condensing agent is at least one of urea, ammonium bicarbonate and diammonium hydrogen phosphate. Preferably, the condensing agent includes urea, ammonium bicarbonate and diammonium hydrogen phosphate, and the molar ratio of urea: ammonium bicarbonate: diammonium hydrogen phosphate is 1-2:1:1 (it can be any value among 1:1:1, 1.5:1:1 and 2:1:1 or the corresponding range between any two values). In this embodiment, urea, ammonium bicarbonate and diammonium hydrogen phosphate have equivalent performance when used as condensing agents. They can all be pyrolyzed under heating conditions to produce ammonia, thereby providing an ammonia atmosphere for the entire reaction system. However, the amount of ammonia carried by urea is higher, and the effect is better. When the above three materials are used to form a condensing agent, the proportion of urea can be appropriately larger.

[0029] The reaction principle of the composite flame retardant described in this embodiment is as follows:

[0030]

[0031] P2O5+NH3→(NH4) n+2 P n O 3a+1 +H2O Reaction 2;

[0032] MgCl2+H2O+NH3→Mg(OH)2+NH4Cl Reaction equation 3

[0033] The condensing agent described in this embodiment is finally pyrolyzed into gaseous components and discharged. The main components of the flame retardant prepared in this embodiment are ammonium polyphosphate and magnesium hydroxide, and also contain a very small amount of ammonium chloride. When preparing the flame retardant in this embodiment, the exhaust gas discharged mainly contains ammonia, ammonium chloride and carbon dioxide.

[0034] The condensing agent used in the following embodiments and comparative examples is urea.

[0035] Example 1

[0036] This embodiment provides a composite flame retardant, and the preparation method thereof is as follows: Step 1: Take 1000 parts of phosphorus pentoxide and 200 parts of a condensing agent by weight, add them into a kneader, and start stirring for 10 minutes;

[0037] Step 2: Then, 3000 parts of hexaammine magnesium chloride were added to obtain a mixture, and the mixture was stirred and heated to 160° C. for reaction for 2 hours;

[0038] Step 3: Continue heating the mixture to 300°C and continue stirring the mixture for 6 hours;

[0039] Step 4: Stop heating, continue stirring and reacting for 2 hours, discharge the material and crush it to obtain a composite flame retardant.

[0040] Example 2

[0041] The same as Example 1, except that the amount of the condensing agent added in step 1 is 150 parts; the amount of hexaamminemagnesium chloride added in step 2 is 2000 parts, and the stirring temperature in step 2 is 140°C, and the stirring time is 1.5 hours; in step 3, the temperature is raised to 280°C, and the stirring reaction is continued for 5 hours, and in step 4, the heating is stopped and the stirring is continued for 1.5 hours.

[0042] Example 3

[0043] The same as Example 1, except that the amount of the condensing agent added in step 1 is 100 parts; the amount of hexaamminemagnesium chloride added in step 2 is 1000 parts, and the stirring temperature in step 2 is 120°C, and the stirring time is 1 hour; in step 3, the temperature is raised to 260°C, and the stirring reaction is continued for 4 hours, and in step 4, the heating is stopped and the stirring is continued for 1 hour.

[0044] Comparative Example 1

[0045] This comparative example provides a phosphorus-based flame retardant, and the preparation method thereof is as follows: Step 1: Take 1000g of phosphorus pentoxide and 200g of a condensing agent, add them into a kneader, start stirring for 10 minutes, and then add 3000g of ammonium bicarbonate to obtain a mixed material;

[0046] Step 2: Stir and heat to 160℃, keep warm and start ammonia flow, the amount of ammonia flow is 0.7m per 1000g of mixed material 3 / h, the ammonia flow time is 40min, and the reaction is stirred while the ammonia is flowing;

[0047] Step 3: Heat the mixture treated in step 2 to 260°C, keep it warm and increase the ammonia flow rate to 3m3 per 1000g of the mixture. 3 / h, the ammonia flow time is 5h, and the reaction is stirred while the ammonia is flowing. After the reaction is completed, the heating is stopped;

[0048] Step 4: Reduce the amount of ammonia passed through the mixed material after step 3 to 0.3 m3 / 1000 g of the mixed material. 3 / h, continue stirring the reaction for 1.5 hours, then stop passing ammonia;

[0049] Step 5: When the reaction temperature of the mixed material treated in step 4 drops to 160°C, the material is discharged and crushed (the feed rate of the crushing equipment is 250g / min, and the main engine speed is 1000r / min) to obtain ammonium polyphosphate.

[0050] Comparative Example 2

[0051] This comparative example provides a phosphorus-based flame retardant, and the preparation method thereof is as follows: Step 1: Take 2000g of phosphorus pentoxide and 200g of a condensing agent, add them into a kneader, start stirring for 10 minutes, and then add 2000g of ammonium bicarbonate to obtain a mixed material;

[0052] Step 2: Stir and heat to 170℃, keep warm and start ammonia flow, the ammonia flow rate is 0.8m per 1000g of mixed material 3 / h, the ammonia flow time is 35min, and the reaction is stirred while the ammonia is flowing;

[0053] Step 3: Heat the mixture treated in step 2 to 270°C, keep it warm and increase the ammonia flow rate to 4m3 / 1000g of the mixture. 3 / h, the ammonia flow time is 6h, the reaction is continued by stirring while the ammonia is flowing, and the heating is stopped after the reaction is completed;

[0054] Step 4: Reduce the amount of ammonia passed through the mixed material after step 3 to 0.4 m3 / 1000 g of the mixed material. 3 / h, continue stirring and reacting for 2 hours, then stop passing ammonia;

[0055] Step 5: When the reaction temperature of the mixed material treated in step 4 drops to 150°C, the material is discharged and crushed (the feed rate of the crushing equipment is 250g / min, and the main engine speed is 1000r / min) to obtain ammonium polyphosphate.

[0056] Comparative Example 3

[0057] This comparative example provides a phosphorus-based flame retardant, and the preparation method thereof is as follows: Step 1: Take 3000g of phosphorus pentoxide and 200g of a condensing agent, add them into a kneader, start stirring for 10 minutes, and then add 1000g of ammonium bicarbonate to obtain a mixed material;

[0058] Step 2: Stir and heat to 180℃, keep warm and start ammonia flow, the ammonia flow rate is 0.9m per 1000g of mixed material 3 / h, the ammonia flow time is 50min, and the reaction is stirred while the ammonia is flowing;

[0059] Step 3: Heat the mixture treated in step 2 to 280°C, keep it warm and increase the ammonia flow rate to 4.5m3 per 1000g of the mixture. 3 / h, the ammonia flow time is 5.5h, and the reaction is stirred while the ammonia is flowing. After the reaction is completed, the heating is stopped;

[0060] Step 4: Reduce the amount of ammonia passed through the mixed material after step 3 to 0.2 m3 per 1000 g of the mixed material. 3 / h, continue stirring the reaction for 1.5 hours, then stop passing ammonia;

[0061] Step 5: When the reaction temperature of the mixed material treated in step 4 drops to 140°C, the material is discharged and crushed (the feed rate of the crushing equipment is 250g / min, and the main engine speed is 1000r / min) to obtain ammonium polyphosphate.

[0062] Performance comparison table of each embodiment and comparative example product

[0063]

[0064] It can be clearly seen from the table that the composite flame retardants corresponding to Examples 1 to 3 have higher decomposition temperatures and improved polymerization degrees than the ammonium polyphosphates of Comparative Examples 1 to 3, and the corresponding flame retardant efficiency is also higher.

[0065] The invention uses hexaammine magnesium chloride as a raw material, reduces the use of ammonia pipelines, and improves the airtightness of the reactor.

[0066] The present invention uses magnesium hydroxide and ammonium polyphosphate as reaction products, has higher mutual dispersibility, and makes up for the shortcomings of single-system flame retardants through synergistic flame retardancy.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite flame retardant, characterized in that: Phosphorus pentoxide and hexaammine magnesium chloride are mixed, and then polymerized by stepwise heating under stirring conditions, and finally the obtained material is crushed to obtain a flame retardant.

2. The method for preparing a composite flame retardant according to claim 1, characterized in that: The specific steps include: Step 1: Stir phosphorus pentoxide and hexaammine magnesium chloride until they are well mixed to obtain a mixture, heat the mixture to 120-180° C., and pre-react for 1-2 hours; Step 2: The pre-reacted mixed material is heated to 230-340°C, kept warm and stirred for 3-6 hours, then the heating is stopped and stirred for 1-2 hours to obtain a flame retardant crude material; Step 3: The flame retardant coarse material obtained in step 2 is crushed to obtain the flame retardant.

3. The method for preparing a composite flame retardant according to claim 2, characterized in that: In the step 1, the molar ratio of phosphorus pentoxide to hexaamminemagnesium chloride is 1:1-3.

4. The method for preparing a composite flame retardant according to claim 2, characterized in that: In the step 1, a condensation agent is also added during stirring.

5. The method for preparing a composite flame retardant according to claim 4, characterized in that: The amount of the condensing agent added in step 1 is 1-10% of the sum of the weights of phosphorus pentoxide and hexaammine magnesium chloride.

6. The method for preparing a composite flame retardant according to claim 4, characterized in that: The condensing agent is at least one of urea, ammonium bicarbonate and diammonium hydrogen phosphate.

7. The method for preparing a composite flame retardant according to claim 6, characterized in that: The condensing agents include urea, ammonium bicarbonate and diammonium hydrogen phosphate.

8. The method for preparing a composite flame retardant according to claim 7, characterized in that: The molar ratio of urea:ammonium bicarbonate:diammonium hydrogen phosphate is 1-2:1:

1.

9. The method for preparing a composite flame retardant according to claim 2, characterized in that: The stirring process in step 1 is carried out in a kneader.

10. A composite flame retardant, characterized in that: The method is prepared according to any one of claims 1 to 9.

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