Preparation method and application of surface-modified aluminum phosphite
By adding cationic surfactants and anti-caking agents in the production process of aluminum phosphite, the problem of difficult water content and hygroscopic agglomeration is solved, the dispersion and flame retardant properties are improved, and it is suitable for polymer materials such as polypropylene and nylon 66.
Patent Information
- Application Number
- CN202510217485.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2025-06-03
AI Technical Summary
In the production process of aluminum phosphite, the moisture content is difficult to control, resulting in hygroscopic agglomeration easily after drying, and the screening pass rate is low, which affects its application in polymer materials.
After the synthesis of aluminum phosphite is completed, the pH is adjusted to neutral, the cationic surfactant is added, and washed and dried by suction filtration. Finally, the anti-caking agent is added to the powder and dispersed, and the surface-modified aluminum phosphite powder is screened to obtain surface-modified aluminum phosphite powder.
Through the regulation of anti-caking agents and surfactants, the dispersion and surface performance of aluminum phosphite are improved, the hygroscopic agglomeration problem is solved, the screening pass rate is improved, and its flame retardant performance in polypropylene and nylon 66 is significantly improved.
Smart Images
Figure CN120082103A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of flame retardant synergists. Specifically, it relates to a preparation method and application of surface-modified aluminum phosphite. Background Art
[0002] As a commonly used flame retardant synergist, the flame retardant mechanism of aluminum phosphite involves reactions in both the gas phase and the solid phase. In the gas phase, substances such as phosphates, water, and aluminum oxide decomposed from aluminum phosphite can reduce the combustion temperature and the flame spread rate; in the solid phase, the carbonaceous layer formed by the generated phosphates and aluminum oxide can block the contact between the flame and the material surface. Aluminum phosphite is also involved in chemical heat suppression and heat conduction, catalyzing the process of water-dispersed combustion, etc., reducing the degree of fire hazards. Aluminum phosphite is a colorless or white crystalline powder, soluble in water, capable of forming stable salts with alkali metal ions, having good affinity with organic matrices, and not containing halogens such as those that will release a large amount of toxic gases (such as HCl, HBr, etc.) after combustion; as an efficient, environmentally friendly, and sustainable flame retardant synergist, it is widely used in fields such as construction, electronic products, automobiles, and textiles. As an important flame retardant synergist, improving the uniformity and dispersibility of aluminum phosphite crystals helps its application in more polymer materials. During the synthesis of aluminum phosphite, we add cationic surfactants and anti-caking agents to change the surface properties of aluminum phosphite, making the aluminum phosphite powder have good dispersibility, uniform particle size, and affinity with organic matrices. This method is simple and safe, and the required materials are environmentally friendly, facilitating mass production.
[0003] During the production process of aluminum phosphite, the aqueous crystalline powder of aluminum phosphite is uniform and delicate, but the water content in conventional products is usually controlled at 3 - 5 wt%. In mass production, in order to control the water content of aluminum phosphite, a drying process often needs to be added. After the powder is dried, it is prone to hygroscopic caking during storage. After subsequent particle size screening, the passing rate of powder screening is only 80%, the yield of the first screening is low, and the particle size distribution of the aluminum phosphite powder passing through the screening is also relatively high, affecting its application in polymer materials such as polypropylene. Summary of the Invention
[0004] To solve the above-mentioned problems, the present invention provides a method as follows. After the reaction for synthesizing aluminum phosphite is completed, the pH is adjusted to neutral, a cationic surfactant is added, and then the suspension is obtained as a powder through suction filtration, washing, and drying. An anti-caking agent is added to disperse in the powder, and finally, a powdery solid, namely a surface-modified aluminum phosphite flame retardant material, is obtained through screening.
[0005] Specifically, it includes the following steps:
[0006] (1) Synthesis of aluminum phosphite
[0007] a. Dissolve phosphorous acid (or its salts) in deionized water in a kneading blender, turn on heating and stirring;
[0008] The phosphorous acid or (its salts) described in step a is phosphorous acid (H 3 PO 3 ) and its various phosphites, such as sodium phosphite (Na 2 HPO 3 ), ammonium phosphite ((NH 4 ), 2 HPO 3 ). Preferably, the concentration of phosphorous acid and its salt solution is 30% - 50%, and the stirring speed is 20 - 30 revolutions per minute.
[0009] b. Add a certain weight portion of aluminide, with the molar amount of aluminum ions being 2 / 3 - 3 / 4 of that of phosphite ions, into the aqueous solution of phosphorous acid or (its salts) in batches, and continue stirring and reacting under heating conditions;
[0010] The aluminide described in step b includes aluminum oxide, aluminum salts, aluminum hydroxide, such as aluminum hydroxide (Al(OH) 3 ), aluminum oxide (Al 2 O 3 ), aluminum sulfate (Al 2 (SO 4 ), 3 ), aluminum chloride (AlCl 3 ) and other oxides and aluminum salts. The heating temperature is 60 - 90°C, preferably 80°C, and the stirring speed is 50 - 60 revolutions per minute.
[0011] c. When the reaction reaches a certain time, add a modifier and continue stirring until the reaction ends;
[0012] The modifier described in step c includes but is not limited to mineral modifiers such as stearic acid, silane coupling agent, titanate, Tween - 80, etc. The concentration of the modifier in the system is 1 - 5 wt%. The total reaction time is 1.5 h - 3 h, preferably 3 h. The modifier is added in the middle of the reaction, and the stirring speed is 50 - 60 revolutions per minute.
[0013] d. After the obtained mixture is completely cooled, adjust the pH to neutral, add a cationic surfactant, and stir evenly;
[0014] The cationic surfactant described in step d refers to quaternary ammonium salt - type cationic surfactants: cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride, etc. The addition amount accounts for 0.1 - 0.5 wt% of the weight of the entire reaction system, and the stirring speed is 20 - 30 revolutions per minute.
[0015] e. Remove the excess cationic surfactant by suction filtration and washing to obtain a white powder;
[0016] f. Place the above powder in an oven and dry it by baking at a certain temperature to control the moisture content of the powder at 3 - 5 wt%.
[0017] In step f, the drying temperature is 90 - 240 °C, preferably 110 °C, and the drying time is 2 h - 8 h, preferably 5 h.
[0018] g. Add an anti-caking agent to the white powder, put it into a high-speed mixer and mix evenly to obtain aluminum phosphite with good dispersibility.
[0019] The anti-caking agent described in step g mainly refers to silicon dioxide, and the addition amount is 0.5 - 1.0 wt‰, and the stirring speed is 150 - 300 revolutions per minute.
[0020] h. Screen the product to obtain aluminum phosphite crystal powder with corresponding particle sizes.
[0021] An aluminum phosphite flame retardant material with good dispersibility prepared by the above preparation method.
[0022] The present invention also provides the application of the above aluminum phosphite. The aluminum phosphite is used to prepare a flame retardant material. Specifically, it is added to polypropylene and nylon 66 to prepare a flame retardant material; the aluminum phosphite replaces 30 wt% of PAPP and is added to polypropylene; the aluminum phosphite replaces 4 - 7 wt% of ADPP and is added to nylon 66.
[0023] Use aluminum phosphite for efficacy verification, conduct thermogravimetric experiments, combustion performance tests, glow wire tests of the product, and investigate the influence of aluminum phosphite on the mechanical properties such as tensile strength, elongation at break, and flexural strength of the product; explore the application of aluminum phosphite in polypropylene and nylon 66.
[0024] The preparation method of regulating aluminum phosphite crystals by the anti-caking agent and surfactant provided by the present invention. In large-scale production, the anti-caking agent can more effectively improve the dispersibility of aluminum phosphite, solve the problem of low screening passing rate caused by moisture absorption and caking after product drying; in addition, through the action of the surfactant, the surface properties of aluminum phosphite are adjusted to make its affinity with the organic matrix better, and it is easier to have better binding properties with polypropylene and nylon.
[0025] The beneficial effects of the present invention are as follows:
[0026] (1) The present invention provides a preparation method of regulating aluminum phosphite crystals by an anti-caking agent and a surfactant. The preparation method is simple in operation, low in production cost, and easy for batch production.
[0027] (2) In the preparation process of the present invention, a modifier and a cationic surfactant are added to improve the organic compatibility, and the flame retardant performance is good and it is not easy to precipitate.
[0028] (3) During the preparation process of the present invention, silica anti-caking agent is added to improve the crystal dispersion degree, solve the problem that the product is prone to moisture absorption and caking after drying or during storage, resulting in low screening passing rate, increase the product yield and extend the storage and use cycle of the product.
[0029] (4) The products produced by the preparation method of the present invention are applied in polypropylene and nylon 66, significantly improving the flame retardant properties of the above two polymer materials. Description of the Drawings
[0030] Figure 1 is the thermogravimetric test chart of aluminum phosphite;
[0031] Figure 2 is the thermogravimetric test chart of domestic ADP;
[0032] Figure 3 In, a is the aluminum phosphite powder diagram with anti-caking agent added in Example 1, and b is the aluminum phosphite diagram of commercially available product without anti-caking agent and surfactant;
[0033] Figure 4 is the nylon PA flame retardant masterbatch added with 50wt% aluminum phosphite. Detailed Description of the Invention
[0034] The following further describes the present invention in detail in combination with the implementation cases, but the implementation manners of the present invention are not limited thereto.
[0035] Example 1
[0036] Weigh 200 g of phosphorous acid and add it to a round-bottom flask containing 250 ml of deionized water. Install a kneading mixer, turn on the heating and stirring until the phosphorous acid is completely dissolved, control the temperature at 80 °C, and the stirring speed at 20 revolutions per minute. Weigh 132 g of aluminum hydroxide and add it in three batches. Each time, continue to add after the solution reaction is completed, keep the temperature at 80 °C, and the stirring speed at 50 revolutions per minute. After reacting for 1.5 h, add 3 g of silane coupling agent and continue stirring for 1.5 h. After cooling the obtained solution to room temperature, use sodium hydroxide solution to adjust the pH value to neutral, add 0.3 g of cetyltrimethylammonium bromide, and adjust the stirring speed to 30 revolutions per minute. Filter the above solution, repeatedly wash the precipitate to remove the excess surfactant, obtain a white powder, place the powder in an oven and bake it at 110 °C for 5 h to obtain aluminum phosphite with a moisture content of 3%. Put this product into a high-speed mixer and add 0.15 g of silica anti-caking agent and mix evenly, with a stirring speed of 150 - 300 revolutions per minute. Screen the above aluminum phosphite to obtain aluminum phosphite with good dispersion, and the particle size D50 is between 20 - 30 μm.
[0037] Figure 3Among them, a is the aluminum phosphite powder with an anti-caking agent added in this embodiment, and b is the commercially available aluminum phosphite without an anti-caking agent and a surfactant. It can be clearly seen that the aluminum phosphite with an anti-caking agent and a surfactant added has better dispersibility and no caking phenomenon, while the one without addition shows obvious agglomeration and caking. The screening passing rate of sample a with an anti-caking agent and a surfactant added has increased to 98%, and the screening passing rate of sample b is 83%. After being screened and packaged, the product does not show the problem of moisture absorption and caking even after being stored for six months under dry and ventilated conditions.
[0038] Commercially available aluminum phosphite Aluminum phosphite of Example 1 Screen passing rate 83％ 98％ Storage period Absorbed moisture and caked after 3 months of storage Stable after 6 months of storage
[0039] Example 2
[0040] Using the aluminum phosphite powder prepared in Example 1 as a flame retardant synergist, in a halogen-free flame retardant PP (PAPP system), 30% of PAPP (piperazine pyrophosphate) is replaced by aluminum phosphite and added to the PP material, and the flame retardancy reaches UL94 (V0).
[0041] Comparing the flame retardant performance tests before and after compounding, the results are shown in Table 1 below: The formulation data is in parts by weight.
[0042]
[0043] Table 1
[0044] Afterglow time (T1 + T2 / S): The duration of the afterglow.
[0045] LOI: Limiting oxygen index. A higher index indicates that the material is not easily combustible, and a lower index indicates that the material is easily combustible. Generally, it is considered that materials with an oxygen index < 22% are flammable materials, materials with an oxygen index between 22% - 27% are combustible materials, and materials with an oxygen index > 27% are flame-retardant materials.
[0046] UL94 plastic flame retardant grade V0: After the sample is subjected to two 10-second combustion tests, the flame goes out within 30 seconds, and no combustibles can fall off.
[0047] From the test data in Table 1, it can be seen that when 30% of PAPP is replaced by aluminum phosphite and added to the PP material, the limiting oxygen index increases from 28% to 29%, the flammability of the material decreases, the vertical afterglow combustion time increases by 1 second, and the flame retardant grade UL94 all reaches V0 level.
[0048]
[0049] Table 2
[0050] Table 2 shows the mechanical property test data of aluminum phosphite in halogen-free flame-retardant PP (PAPP system). From the data in the table, it can be seen that compared with the original flame-retardant formula of halogen-free flame-retardant PP, after aluminum phosphite replaces 30% of PAPP, the tensile strength and flexural strength of the PP material slightly decrease, the elongation at break representing the toughness index increases by 144%, and the notched impact strength also slightly increases. The influence on other mechanical properties is not significant.
[0051] Example 3
[0052] Weigh 200 g of phosphorous acid and add it to a round-bottom flask containing 250 ml of deionized water. Install it in a kneading blender, turn on the heating and stirring until the phosphorous acid is completely dissolved, control the temperature at 80 °C, and the stirring speed at 25 revolutions per minute. Weigh 85 g of alumina and add it in three batches. Add it continuously after each solution reaction is completed, keep the temperature at 80 °C, and the stirring speed at 60 revolutions per minute. After reacting for 1.0 h, add 3 g of titanate and continue stirring for 1.5 h. After cooling the obtained solution to room temperature, use sodium hydroxide solution to adjust the pH to neutral, add 0.3 g of cetyltrimethylammonium bromide, and adjust the stirring speed to 30 revolutions per minute. Filter the above solution, repeat washing the precipitate to remove the excess surfactant to obtain a white powder. Place this powder in an oven and bake it at 120 °C for 5 h to obtain aluminum phosphite with a moisture content of 2%. Put this product into a high-speed mixer and add 0.15 g of silica anti-caking agent and mix evenly, with a stirring speed of 150 - 300 revolutions per minute. Screen the above aluminum phosphite to obtain aluminum phosphite with good dispersibility, and the particle size D50 is 20 - 30 μm.
[0053] Using the aluminum phosphite prepared by the above method as a flame-retardant synergist, in the nylon 66 fiber-reinforced system, replace 4 wt% and 7 wt% of domestic ADP (aluminum diethylphosphinate) respectively and add them to the nylon 66 material, and the flame retardancy reaches UL94 (V0). Comparing the flame-retardant performance tests before and after compounding, the results are shown in Table 1 below: The formula data is in parts by weight.
[0054]
[0055]
[0056] Table 3
[0057] It can be seen from the test data in Table 3 that the compounding of aluminum phosphite and ADP can effectively improve the glow wire performance. Replacing 4% of the domestic ADP can enable nylon 66 to maintain the UL94 performance in the non-reinforced system; replacing 7% of the domestic ADP can increase the glow wire from 800 to 825 and maintain the UL94 performance in the non-reinforced system. In the reinforced system, the domestic ADP is not compounded with aluminum phosphite. Although the glow wire performance is increased from 750 to 800, the flame retardant grade UL94 cannot reach V level. After using aluminum phosphite to replace 7% of the domestic ADP, the flame retardant grade UL94 all reaches V0 level.
[0058]
[0059] Table 4
[0060] Table 4 shows the mechanical property test data of the application of aluminum phosphite in the reinforced nylon 66 system. It can be seen from the data in the table that the change of the nylon 66 material property parameters is mainly due to the influence of glass fiber. After replacing 7% of ADP with aluminum phosphite, the elongation at break of the material is increased by 2.2%, and the other index values are very close, which proves that the influence on the other mechanical properties is small.
[0061] Figure 1 is the thermogravimetric test chart of aluminum phosphite, Figure 2 is the thermogravimetric test chart of domestic ADP. There is only one weight loss step for ADP, and the residual mass at 750 °C is 30.44%. There are three weight loss steps for aluminum phosphite, and the residual mass at 750 °C is 94%; neither of them decomposes at 280 °C (thermal weight loss < 1%). Considering the processing temperature of nylon 66 (260 - 280 °C), it has almost no influence on the processing performance. The reason for the synergistic flame retardancy of aluminum phosphite may be to enhance the condensed-phase flame retardancy of ADP.
[0062] Figure 4 is the nylon PA flame retardant masterbatch added with 50wt% aluminum phosphite. It can be seen that the compatibility between aluminum phosphite and nylon PA is good, the surface is smooth, and there are no bad phenomena such as delamination, patterns, and precipitation. At present, the maximum addition amount of aluminum phosphite in the nylon PA flame retardant masterbatch on the market is generally 30wt%. Increasing the addition amount often has problems such as rough surface, delamination or foaming.
Claims
1. A method for preparing surface-modified aluminum phosphite, characterized in that: The preparation method comprises the following steps: (1) After the reaction of synthesizing aluminum phosphite is completed, the pH is adjusted to neutral, a cationic surfactant is added in an amount of 0.1-0.5 wt % of the weight percentage of the entire reaction system, and the mixture is stirred evenly; (2) removing excess cationic surfactant to obtain white powder; (3) placing the above powder in an oven and baking at 90-240° C. to control the moisture content of the powder to be 3-5 wt %; (4) Add an anti-caking agent in an amount of 0.5-1.0 wt‰ and mix well to obtain aluminum phosphite with good dispersion.
2. The method for preparing the surface-modified aluminum phosphite according to claim 1, characterized in that: The cationic surfactant is a quaternary ammonium salt cationic surfactant; or the baking temperature in step (3) is 110° C.; or the anti-caking agent is silicon dioxide.
3. The method for preparing the surface-modified aluminum phosphite according to claim 2, characterized in that: The quaternary ammonium salt type cationic surfactant includes at least one of hexadecyltrimethylammonium bromide and octadecyltrimethylammonium chloride.
4. The method for preparing the surface-modified aluminum phosphite according to claim 1, characterized in that: The steps of synthesizing aluminum phosphite are as follows: a. Dissolve phosphorous acid or its salt in deionized water, turn on heating and stirring, the concentration of phosphorous acid and its salt solution is 30% to 50%, and the heating temperature is 60-90 ℃; b. Add the aluminide in batches to the phosphorous acid or its salt solution, continue stirring the reaction under heating conditions, and the molar amount of aluminum ions is 2 / 3 to 3 / 4 of the phosphite ions; c. Add the modifier in the middle of the reaction and continue stirring until the reaction is completed. The concentration of the modifier in the system is 1-5wt%.
5. The method for preparing the surface-modified aluminum phosphite according to claim 1, characterized in that: The phosphite described in step a is sodium phosphite and / or ammonium phosphite; The aluminide described in step b includes one or more of aluminum oxide, aluminum salt and aluminum hydroxide; The modifier described in step c includes one or more of stearic acid, silane coupling agent, titanate and Tween-80.
6. Use of the aluminum phosphite prepared by the method for preparing the surface-modified aluminum phosphite according to any one of claims 1 to 5 as a flame retardant synergist in the preparation of flame retardant materials.
7. The use according to claim 6, characterized in that The aluminum phosphite is added to polypropylene and nylon 66 to prepare a flame retardant material.
8. The use according to claim 7, characterized in that The aluminum phosphite replaces 30 wt% of PAPP and is added to polypropylene; the aluminum phosphite replaces 4-7 wt% of ADPP and is added to nylon 66.