Preparation method and flame-retardant application of guanidine hypophosphite
By controlling the reaction conditions to prepare guanidine hypophosphite, the problem of limited application of hypophosphite flame retardants in aqueous systems has been solved, achieving high yield and high efficiency in flame retardancy, suitable for materials such as paper and wood.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-03
- Publication Date
- 2026-03-27
AI Technical Summary
The application of existing hypophosphite flame retardants in aqueous systems is limited, and their flame retardant efficiency is lower than that of pentavalent phosphorus flame retardants. Furthermore, their low water solubility restricts their application range.
By controlling the reaction conditions, guanidine hypophosphite aqueous solution was reacted with guanidine carbonate under stirring and heating. The pH value was adjusted between 6.0 and 8.5, and the water volume and temperature were controlled between 90 and 100°C. The mixture was then vacuum dried to prepare guanidine hypophosphite, thereby improving its water solubility and flame retardant efficiency.
A high-yield preparation of guanidine hypophosphate was achieved. It has a neutral pH value and high water solubility, and its flame retardant efficiency is significantly better than similar products. It is suitable for applications such as paper and wood, and its effect is excellent when used in combination with other flame retardants.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of flame retardant technology, specifically to a method for preparing guanidine hypophosphite and its flame retardant applications. Background Technology
[0002] Phosphorus-based flame retardants are highly efficient halogen-free flame retardants that exhibit flame retardant properties in both condensed and gaseous phases, with physical and chemical factors present in both phases. The flame retardant mechanism varies depending on the structure of the phosphorus flame retardant, the type of encapsulation, and the combustion conditions. Generally, phosphorus-containing compounds decompose upon heating to produce acids, such as phosphoric acid and metaphosphoric acid.
[0003] Guanidine salts contain H2NC(=NH)NH3 + Guanidine phosphate is a large class of ionic compounds. Main examples include guanidine phosphate, guanidine carbonate, and guanidine sulfate, which can be used as flame retardants, generally for retardant wood and paper. In 1938, Kiichiro Sugino prepared diguanidine phosphate by reacting diammonium hydrogen phosphate and dicyandiamide at 180℃, but the yield was low, with the highest conversion rate of dicyandiamide reaching only 50%. In his article "Synthesis of Guanidine Phosphate Salts," Jieyu Luo prepared guanidine phosphate using a metathesis reaction of phosphoric acid and guanidine carbonate. Yingjie Liu, in his article "Synthesis and Application Research of Durable Flame Retardant Finishing Agents for Cotton Fibers," demonstrated that monoguanidine phosphate has the molecular formula CH8N3O4P, a relative molecular weight of 157.07, a theoretical phosphorus content of 19.72%, and a theoretical nitrogen content of 26.75%; diguanidine phosphate has the molecular formula C2H... 13 N6O4P, with a relative molecular weight of 216.15, a theoretical phosphorus content of 14.33%, and a theoretical nitrogen content of 38.89%, rapidly reacts with guanidine carbonate in the presence of phosphoric acid under acidic conditions to form diguanidine phosphate. Diguanidine phosphate can then react with excess phosphoric acid to form monoguanidine phosphate. Diguanidine phosphate has a slightly alkaline pH of 8.1, while monoguanidine phosphate has a slightly acidic pH of 3.9. In her article "Research and Application of Novel Phosphorus-Nitrogen-Based Expandable Flame Retardants for Paper Products," Su Yanni synthesized guanidine phosphate using a fast reaction between phosphoric acid and dicyandiamide, demonstrating good flame retardant efficiency. However, the presence of either too high or too low a pH in guanidine phosphate compounds affects their use in pH-sensitive applications.
[0004] Hypophosphites are a class of highly efficient flame retardants, with higher flame retardant efficiency than ordinary pentavalent phosphorus-based flame retardants. They mainly include inorganic salts such as aluminum hypophosphite, calcium hypophosphite, and zirconium hypophosphite, as well as alkyl hypophosphite types such as diethylaluminum hypophosphite. These compounds have low water solubility. Hypophosphites not only have a high phosphorus content, but also consume more oxygen during combustion due to the low valence of phosphorus, resulting in high flame retardant efficiency and wide application. However, due to their low water solubility, their application in aqueous solutions for flame retardancy is limited and not very suitable. Summary of the Invention
[0005] To address the aforementioned technical problems, the present invention aims to provide a method for preparing guanidine hypophosphite for its flame-retardant application. This invention achieves high-yield preparation of guanidine hypophosphite by controlling reaction conditions. The prepared guanidine hypophosphite exhibits high water solubility and significantly superior flame-retardant efficiency compared to similar flame-retardant products, thus possessing significant application value.
[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing guanidine hypophosphatemia is provided, comprising the following steps: Add the hypophosphoric acid aqueous solution to a kneader, dilute with water under stirring, then add guanidine carbonate, and stir under heating with the lid closed for 0.8-1.2 h. Reflux the evaporated water, continue the reaction for another 1.5-2.5 h and remove excess water, and finally vacuum dry to complete the preparation.
[0007] Furthermore, the concentration of the hypophosphite aqueous solution is 50 wt%.
[0008] Furthermore, the molar ratio of hypophosphite to guanidine carbonate in the hypophosphite aqueous solution is 1-1.1:2.
[0009] Furthermore, the mass ratio of water to guanidine carbonate is 1:1.5-2.5.
[0010] Furthermore, the heating temperature is 90-100℃; the stirring speed is 15-25 r / min.
[0011] Furthermore, the pH during the reaction is 6.0-8.5.
[0012] Further, vacuum dry at 105℃ for 4-6 hours.
[0013] The present invention also provides guanidine hypophosphate prepared by the above preparation method.
[0014] This invention also provides the application of the aforementioned guanidine hypophosphite as a flame retardant.
[0015] The present invention also provides a flame retardant comprising the aforementioned guanidine hypophosphatem.
[0016] The present invention has the following beneficial effects: 1. The present invention uses a kneader to react guanidine carbonate and hypophosphite to produce guanidine hypophosphite. By appropriately adjusting the feed ratio, the pH of the reaction system is controlled within the range of 6.0-8.5, and the reaction temperature and water volume are controlled. Heating promotes the timely evaporation of the produced water, reducing the crystallization step in product formation, and achieving high-yield preparation of guanidine hypophosphite.
[0017] 2. The guanidine hypophosphate flame retardant provided by this invention has the characteristics of near-neutral pH, high flame retardant efficiency, and high water solubility. Its flame retardant efficiency is significantly better than that of similar monoguanidine phosphate and guanidine carbonate products, making it more suitable for flame retardant applications in paper, wood, and tape. Furthermore, when used in combination with other specific flame retardants for flame-retardant acrylic cotton paper tape, it exhibits excellent synergistic effects. Detailed Implementation
[0018] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0019] Example 1 A guanidine hypophosphatemoid, the preparation method of which includes the following steps: 2640g of 50% hypophosphite aqueous solution was added to a 5 L kneader. 900g of water was added to dilute the mixture while stirring at 20 r / min. Then, 1800g of guanidine carbonate was added. The mixture was heated at 100℃ with the lid closed and stirred for 1 h. The evaporated water was refluxed and the reaction was continued for another 2 h. Excess water was removed and the mixture was finally vacuum dried at 105℃ for 5 h to complete the preparation. A total of 2479g of the product was discharged.
[0020] Example 2 A guanidine hypophosphatemoid, the preparation method of which includes the following steps: 2640g of 50% hypophosphite aqueous solution was added to a 5 L kneader. 990g of water was added to dilute the mixture while stirring at 20 r / min. Then, 1980g of guanidine carbonate was added. The mixture was heated at 100℃ with the lid closed and stirred for 1 h. The evaporated water was refluxed and the reaction was continued for another 2 h. Excess water was removed and the mixture was finally vacuum dried at 105℃ for 5 h to complete the preparation. A total of 2660g of the product was discharged.
[0021] Example 3 A guanidine hypophosphatemoid, the preparation method of which includes the following steps: 2640g of 50% hypophosphite aqueous solution was added to a 5 L kneader. 900g of water was added to dilute the mixture while stirring at 20 r / min. Then, 1800g of guanidine carbonate was added. The mixture was heated at 90℃ with the lid closed and stirred for 1 h. The evaporated water was refluxed and the reaction was continued for another 2 h. Excess water was removed and the mixture was finally vacuum dried at 105℃ for 5 h to complete the preparation. A total of 2460g of the product was discharged.
[0022] Example 4 A guanidine hypophosphatemoid, the preparation method of which includes the following steps: 2640g of 50% hypophosphoric acid aqueous solution was added to a kneader, and 900g of water was added to dilute it under stirring at 20 r / min. Then, 1800g of guanidine carbonate was added, and the mixture was heated at 90℃ with the lid closed and stirred for 1 h. The evaporated water was refluxed and the reaction was continued for another 2 h, and the excess water was removed. Finally, the mixture was vacuum dried at 105℃ for 5 h to complete the preparation. A total of 2465g of the product was discharged.
[0023] Example 5 A guanidine hypophosphatemoid, the preparation method of which includes the following steps: 2640g of 50% hypophosphoric acid aqueous solution was added to a kneader, and 945g of water was added to dilute it under stirring at 20 r / min. Then, 1890g of guanidine carbonate was added, and the mixture was heated at 100℃ with the lid closed and stirred for 1 h. The evaporated water was refluxed and the reaction was continued for another 2 h, and the excess water was removed. Finally, the mixture was vacuum dried at 105℃ for 5 h to complete the preparation. A total of 2575g of the product was discharged.
[0024] Comparative Example 1 The preparation method of a guanidine hypophosphite differs from that of Example 1 in that the heating temperature during the reaction is 110°C, and the total output is 2100 g.
[0025] Comparative Example 2 The preparation method of a guanidine hypophosphatem is different from that of Example 1 in that the heating temperature during the reaction is 80°C, and the total output is 2430 g.
[0026] Comparative Example 3 Guanidine carbonate flame retardant.
[0027] Comparative Example 4 Guanidine phosphate flame retardant.
[0028] Experimental Example 1 The preparation yields and detection data of Examples 1-5 and Comparative Examples 1-4 are shown in Table 1.
[0029] Table 1 Flame Retardant Data Analysis Table
[0030] As shown in the table, the optimal synthesis temperature is 90-100℃. In Comparative Example 1, the temperature was too high, resulting in a low product yield of only 84%. The high temperature, exceeding 105℃ in the area where hypophosphite contacted the equipment wall, easily led to decomposition of the hypophosphite, reducing the reactant yield. The higher pH compared to the previous example further supports this. In Comparative Example 2, the reaction temperature was too low, resulting in incomplete reaction. The post-reaction system exhibited a stronger acidity of hypophosphite, and the material was highly viscous immediately after discharge, indicating insufficient reaction. Examples 1-5 show relatively high yields of synthesized substances with near-neutral pH, making them suitable for various applications. The solubility of the synthesized product is approximately 50 g / 100 mL of aqueous solution, which is high and meets the requirements for water-soluble flame retardants.
[0031] Meanwhile, flame retardant tests in two different application scenarios showed that the flame retardant efficiency of the synthesized guanidine hypophosphite was higher than that of the same type of guanidine phosphate and guanidine carbonate flame retardants. The flame retardant effect of the synthesized guanidine phosphate in Examples 1-5 was also better than that of the guanidine hypophosphite synthesized at excessively high or low temperatures in the comparative examples, which fully demonstrates that the temperature selected by this technical solution is relatively suitable.
[0032] Since only one phosphorus hydroxyl group in hypophosphite participates in the reaction of guanidine carbonate, monoguanidine phosphate, which also involves only one phosphorus hydroxyl group, was selected for flame retardant comparison tests. The results showed that monoguanidine phosphate was too acidic, had lower water solubility and phosphorus content than guanidine hypophosphite, and its flame retardant performance was also lower than that of neutral guanidine hypophosphite, fully demonstrating the advantages of guanidine hypophosphite over similar flame retardants like monoguanidine phosphate.
[0033] Experimental Example 2 10 g of flame retardants from Example 1, Comparative Example 4, and Comparative Example 2, and commercially available Sichuan Taifeng high-phosphorus water-soluble product TF-303 (phosphorus content 28%) were dissolved in 90 g of water to prepare flame retardant solutions, and 0.5% KH570 was added. Before processing acrylic tape, the cotton paper (20 cm × 15 cm × 0.1 mm) used for tape was treated with this flame retardant solution, soaked for 10 s, and then dried. Oily acrylic adhesive was taken, and 15% of the adhesive mass of a 1:1 mixture of aluminum hypophosphite and melamine hypophosphite flame retardant was added. After stirring evenly, the mixture was evenly coated on both sides of the cotton paper tape using release paper, with a total coating thickness of 0.1 mm. Flame retardant tests were conducted, and the results are shown in Table 2.
[0034] Flame retardancy test results (flame retardancy test: ignite twice with a 2.5 cm butane flame, the first time for 3 seconds and the second time for 10 seconds, calculate the average damaged length of the tape, less than 11.5 cm is considered qualified).
[0035] Table 2 Flame Retardant Test Results
[0036] As can be seen from Example 1 and Comparative Example 4, the flame retardant efficiency of guanidine hypophosphite combined with aluminum hypophosphite and melamine hypophosphite is higher than that of monoguanidine phosphate. As can be seen from Example 1 and Comparative Example 2, the flame retardant effect of the guanidine hypophosphite prepared in Example 1 is significantly better. Comparison between Example 1 and TF-303 flame retardant shows that guanidine hypophosphite has a higher flame retardant efficiency when the phosphorus content (24.6%) is lower than that of pentavalent phosphate (28%), which is related to the dispersion performance of the flame retardant. The average length of the final burn damage of the guanidine hypophosphite prepared in this invention is much shorter than that of other comparative products, and the peel strength of the tape on the steel plate is also much greater than that of other products. The results indicate that the flame retardant efficiency of the guanidine hypophosphite prepared in this invention is superior to that of other products under the same conditions.
[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing guanidine hypophosphite, characterized in that, Includes the following steps: Add the hypophosphoric acid aqueous solution to a kneader, dilute with water under stirring, then add guanidine carbonate, and stir under heating with the lid closed for 0.8-1.2 h. Reflux the evaporated water, continue the reaction for another 1.5-2.5 h and remove excess water, and finally vacuum dry to complete the preparation.
2. The method for preparing guanidine hypophosphite as described in claim 1, characterized in that, The concentration of the hypophosphoric acid aqueous solution is 50 wt%.
3. The method for preparing guanidine hypophosphite as described in claim 1, characterized in that, The molar ratio of hypophosphoric acid and guanidine carbonate in the hypophosphoric acid aqueous solution is 1-1.1:
2.
4. The method for preparing guanidine hypophosphite as described in claim 1, characterized in that, The mass ratio of water to guanidine carbonate is 1:1.5-2.
5.
5. The method for preparing guanidine hypophosphite as described in claim 1, characterized in that, The heating temperature is 90-100℃; the stirring speed is 15-25 r / min.
6. The method for preparing guanidine hypophosphite as described in claim 1, characterized in that, The pH during the reaction is 6.0-8.
5.
7. The method for preparing guanidine hypophosphite as described in claim 1, characterized in that, Vacuum dry at 105℃ for 4-6 hours.
8. Guanidine hypophosphite prepared by the method of any one of claims 1-7.
9. The use of guanidine hypophosphite as a flame retardant as described in claim 8.
10. A flame retardant, characterized in that, Includes guanidine hypophosphate as described in claim 7.