Flame retardant wood-like polyether polyol and preparation method thereof

Abstract

The present invention belongs to the technical field of polyether polyols and their preparation, and specifically relates to flame-retardant polyether polyols for imitating wood and their preparation method. The preparation method of the flame-retardant polyether polyol for imitating wood described in the present invention: melamine is reacted with a carbonyl compound to generate a Schiff base, propylene oxide monomer is continuously added, a polymerization reaction is carried out to obtain a crude polyether polyol, the propylene oxide monomer is removed, and after post-treatment, a flame-retardant polyether polyol for imitating wood is obtained. The obtained flame-retardant polyether polyol for imitating wood has an average functionality of 2-3 and a hydroxyl value of 320-403 mg / KOH. The present invention overcomes the defect of low conversion rate of melamine used to prepare polyether polyols in the prior art, and provides a preparation method of flame-retardant polyether polyol for imitating wood, which has high catalytic efficiency and high conversion rate. The flame-retardant polyether polyol for imitating wood prepared by the preparation method of the present invention has good flame retardant effect and high compressive strength.

Description

Technical Field

[0001] The invention belongs to the technical field of polyether polyols and preparation thereof, and particularly relates to flame-retardant wood-imitation polyether polyols and a preparation method thereof. Background Art

[0002] Wood has been the most commonly used material in building decoration and furniture since ancient times. Wood itself is light in weight, easy to process, and purely natural and renewable, and is deeply favored by the market. In recent years, with the development of the economy and the improvement of people's living standards, the demand for wood has increased. Therefore, it has become an inevitable trend to develop imitation wood materials to replace the use of wood. Polyurethane imitation wood materials have become the mainstream of imitation wood materials on the market due to their good insulation effect, high strength, and strong chemical corrosion resistance. However, there are various defects and deficiencies in the quality and production of imitation wood materials on the market, especially in terms of flame retardancy. Once various imitation wood materials burn, they will bring great harm to public safety. The flame retardancy problem has become a bottleneck in the development of imitation wood materials.

[0003] Melamine plays an important role in providing nitrogen source in flame retardant system due to its thermal stability and special nitrogen-rich molecular structure. By using melamine as an additive or auxiliary agent and physically mixing it into polyether polyol, the obtained polyether polyol has uneven density and poor stability.

[0004] Patent CN101775131A uses melamine and other small molecule polyols as co-initiators, and polymerizes with propylene oxide under the action of an alkali metal catalyst to obtain a new flame retardant rigid foam polyether polyol. However, due to the special structure of melamine, its active hydrogen is more stable than the hydroxyl active hydrogen of other small molecule polyols, and the catalytic efficiency and conversion rate of the reaction are low. More existing polyether polyol products use the above melamine to further react and synthesize the raw material, and then polymerize it into polyether polyols, such as the hydroxymethylation reaction of melamine and formaldehyde to synthesize melamine resin, or the Mannich reaction based on melamine to synthesize polyether polyols. The above products use melamine with low catalytic efficiency, and the yield of more polyether polyol products is low.

[0005] Patent publication CN111423556A mentions a highly flame-retardant polyurethane grafted with reactive nitrogen and phosphorus polyols. Para-hydroxybenzaldehyde is subjected to a substitution reaction with hexachlorocyclotriphosphazene to obtain terminal aldehyde cyclotriphosphazene, which is then subjected to a Schiff base condensation reaction with melamine to obtain an amino-terminated melamine-cyclotriphosphazene polymer, which is finally subjected to a ring-opening reaction with propylene oxide to obtain a melamine polyol-cyclotriphosphazene polymer. The polymer is used as a nitrogen-phosphorus synergistic reaction flame retardant and as a polyol side chain to participate in a polymerization reaction with polyether polyols and isocyanate monomers as the main chain, thereby giving the material excellent flame retardant properties. However, this method is obtained through multi-step synthesis, and the conversion rate and yield are relatively low, the synthesis cycle is long, the manufacturing cost is high, and the initiator prepared by this method has a high degree of unsaturation and is prone to yellowing when preparing polyurethane products. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defect of low conversion rate of melamine used to prepare polyether polyol in the prior art, and provide a preparation method of flame-retardant polyether polyol for wood imitation, which has high catalytic efficiency and high conversion rate. The flame-retardant polyether polyol for wood imitation prepared by the preparation method of the present invention has good flame retardant effect and high compressive strength.

[0007] The preparation method of the flame retardant wood-like polyether polyol of the present invention comprises the following steps: reacting melamine with a carbonyl compound to generate a Schiff base, adding propylene oxide monomer to carry out polymerization reaction to obtain a crude polyether polyol, removing the propylene oxide monomer, and performing post-treatment to obtain a flame retardant wood-like polyether polyol.

[0008] The obtained flame retardant wood-like polyether polyol has an average functionality of 2-3 and a hydroxyl value of 320-403 mg / KOH.

[0009] The specific synthesis process of Schiff base is as follows: melamine, diethylene glycol and hydroxyacetaldehyde are put into a reaction container, alkali metal catalyst 1 is added, the temperature is raised to 60-80°C and the reaction is carried out for 2-4 hours, wherein the reaction temperature is preferably 75°C and the reaction time is 3 hours, then alkali metal catalyst 2 is added, the temperature is maintained at 75-90°C and the reaction is carried out for 1-4 hours, wherein the reaction temperature is preferably 85°C and the reaction time is 2 hours, to obtain Schiff base.

[0010] Furthermore, the molar ratio of melamine to glycolaldehyde is 1:(2.5-4), preferably 1:3.5.

[0011] Furthermore, the alkali metal catalyst 1 is sodium hydroxide or potassium hydroxide, and the added mass is 2-5‰ of melamine, hydroxyacetaldehyde, diethylene glycol, alkali metal catalyst 1, alkali metal catalyst 2, and propylene oxide, preferably solid potassium hydroxide, and the addition ratio is 3‰.

[0012] Furthermore, the alkali metal catalyst 2 is sodium borohydride or potassium borohydride, and the added mass is 1-2.5% of the total mass of melamine, hydroxyacetaldehyde and diethylene glycol, preferably solid potassium borohydride, and the added ratio is 2%.

[0013] The specific steps of the polymerization reaction are: when the temperature of the polymerization reaction system is 80-90°C, add propylene oxide monomer, control the pressure of the polymerization reaction system at 0-0.2MPa, mature for 0.5-1h after the addition is completed, continue to maintain the temperature at 90-110°C, add propylene oxide monomer, control the pressure of the polymerization reaction system below 0.2MPa, and mature for 3-5h after the addition is completed.

[0014] The conditions for removing propylene oxide monomer are: temperature 100-140°C, and vacuum control of the pressure in the reaction container at -0.08 to -0.09 MPa.

[0015] The post-treatment is to reduce the system temperature to 75-85°C, add phosphoric acid and water, stir, then add magnesium silicate, raise the temperature to 100-110°C, vacuum dehydrate to control the pressure in the reaction container at -0.08 to -0.09MPa, detect the moisture content below 0.1%, and filter. The amount of phosphoric acid added in the post-treatment is 0.7% of the mass of the total polyether polyol obtained by the polymerization reaction, the mass of pure water added is 8%, and the mass of magnesium silicate added is 0.2%.

[0016] A flame retardant wood-imitation polyether polyol is prepared by the preparation method of the flame retardant wood-imitation polyether polyol.

[0017] Specifically, the method for preparing the flame retardant wood-like polyether polyol comprises the following steps:

[0018] (1) Input of raw materials and synthesis of Schiff base: Melamine, diethylene glycol and hydroxyacetaldehyde are put into a polymerization reactor, and solid sodium hydroxide or solid potassium hydroxide is added at the same time. The reactor is pressurized to test for leaks. After nitrogen replacement, the pressure is increased to 0.3 MPa, and the temperature is raised to 60-80°C for reaction for 2-4 hours. Then solid sodium borohydride or solid potassium borohydride is added, and the temperature is maintained at 75-90°C for reaction for 1-4 hours to obtain a Schiff base with the structural formula: , molecular weight is 168.

[0019] (2) Polymerization reaction: Control the temperature in the polymerization reactor at 80-90°C, continuously add propylene oxide monomer, and control the pressure in the reactor at a feed rate of 0-0.2 MPa. Add propylene oxide (40% of the total mass of the monomer propylene oxide) until the addition is complete, mature for 0.5-1h, adjust the temperature to 90-110°C, and continuously add propylene oxide monomer (60% of the total mass of the monomer propylene oxide) to ensure that the pressure is controlled below 0.2 MPa during the process until all the propylene oxide is added. Mature for 3-5h to obtain a crude polyether.

[0020] (3) Removal of propylene oxide monomer: Control the temperature in the polymerization kettle to 100-140°C, and control the pressure in the polymerization kettle to -0.08 to -0.09 MPa by vacuuming to remove unreacted propylene oxide.

[0021] (4) Post-treatment: Lower the temperature in the polymerization kettle to 75-85°C, add phosphoric acid and water, stir for 1 hour, add magnesium silicate, raise the temperature to 100-110°C, vacuum dehydrate and control the pressure in the kettle to -0.08 to -0.09 MPa, detect the moisture content to be less than 0.1%, discharge the material and filter, and obtain qualified flame-retardant wood-like polyether polyol.

[0022] The invention adopts melamine and carbonyl compound to generate Schiff base, then uses reducing agent to reduce carbon-nitrogen double bond into single bond, introduces melamine with nitrogen content of 66% into polyether polyol, so as to improve the flame retardant effect of polyether.

[0023] Due to the special structure of melamine, the active hydrogen is more stable than the hydroxyl active hydrogen of other small molecule polyols, so the catalytic efficiency of conventional methods is low and the conversion rate is also low. The present invention uses melamine to synthesize the raw material and then polymerizes it with the monomer, thereby solving the problem that it is difficult to directly polymerize melamine with the monomer by conventional means. The synthesized polyether polyol is mainly used for flame retardant wood-like materials.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The method for preparing the flame-retardant wood-like polyether polyol of the present invention introduces melamine into the polyether polyol by reacting melamine having a nitrogen content of 66% with a carbonyl compound to generate a Schiff base, thereby avoiding the problem of poor reaction effect and low conversion rate when melamine is directly used as an initiator in the polyether; and solving the problem of uneven density of the polyether from top to bottom caused by melamine as an additive.

[0026] (2) The flame retardant wood-like polyether polyol prepared by the method of the present invention has good flame retardant effect and high strength. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments.

[0028] The raw materials and additives used in the following examples and comparative examples are all normal commercially available products.

[0029] Example 1

[0030] The method for preparing the flame retardant wood-like polyether polyol comprises the following steps:

[0031] (1) Input of raw materials and synthesis of Schiff base: 126 g of melamine, 300 g of diethylene glycol and 210 g of hydroxyacetaldehyde were placed in a polymerization reactor, and 4 g of solid potassium hydroxide was added at the same time. The reactor was pressurized to test for leaks. After nitrogen replacement, the pressure was increased to 0.3 MPa, the temperature was raised to 75°C and the reaction was carried out for 3 h. Then, 12.72 g of solid potassium borohydride was added and the temperature was maintained at 85°C for 2 h to obtain a Schiff base.

[0032] (2) Polymerization reaction: Control the temperature in the polymerization reactor at 85±5°C, control the pressure in the reactor at a feed rate of 0.2-0.3 MPa, continuously drop 290 g of propylene oxide monomer, mature for 0.8 h, adjust the temperature to 105±5°C, continuously drop 442 g of propylene oxide monomer, ensure that the pressure is controlled at 0.2-0.3 MPa during the process, until all the propylene oxide is added, mature for 4 h, and obtain a crude polyether.

[0033] (3) Removal of propylene oxide monomer: Control the temperature in the polymerization kettle at 120°C, and control the pressure in the polymerization kettle at -0.08MPa by vacuuming to remove unreacted propylene oxide.

[0034] (4) Post-treatment: Lower the temperature in the polymerization kettle to 80°C, add 9.02g of phosphoric acid and 103.52g of water, stir for 1h, add 2.58g of magnesium silicate, raise the temperature to 105°C, evacuate and dehydrate to control the pressure in the kettle at -0.08MPa, detect the moisture content below 0.1%, discharge and filter, and obtain qualified flame retardant wood-like polyether polyol with a hydroxyl value of 372mg / KOH and a viscosity of 1084mPa·s / 25°C.

[0035] Example 2

[0036] The method for preparing the flame retardant wood-like polyether polyol comprises the following steps:

[0037] (1) Input of raw materials and synthesis of Schiff base: 126 g of melamine, 200 g of diethylene glycol and 150 g of hydroxyacetaldehyde were placed in a polymerization reactor, and 1.95 g of solid potassium hydroxide was added at the same time. The reactor was pressurized for leak test. After nitrogen replacement, the pressure was increased to 0.3 MPa, the temperature was raised to 60°C and the reaction was carried out for 4 h. Then, 4.76 g of solid potassium borohydride was added and the temperature was maintained at 75°C for 4 h to obtain a Schiff base.

[0038] (2) Polymerization reaction: Control the temperature in the polymerization reactor at 80±5°C, control the pressure in the reactor at a feed rate of 0.2-0.3 MPa, continuously drop 190 g of propylene oxide monomer, mature for 1 h, adjust the temperature to 90±5°C, continuously drop 286 g of propylene oxide monomer, ensure that the pressure is controlled at 0.2-0.3 MPa during the process, until all the propylene oxide is added, mature for 3 h, and obtain a crude polyether.

[0039] (3) Removal of propylene oxide monomer: Control the temperature in the polymerization kettle to 100°C, and control the pressure in the polymerization kettle to -0.09MPa by vacuuming to remove unreacted propylene oxide.

[0040] (4) Post-treatment: Lower the temperature in the polymerization kettle to 75°C, add 6.13 g of phosphoric acid and 70.08 g of water, stir for 1 h, add 1.75 g of magnesium silicate, raise the temperature to 100°C, and vacuum dehydrate to control the pressure in the kettle at -0.09 MPa. Detect the moisture content to be less than 0.1%, discharge the material and filter, and obtain qualified flame-retardant wood-like polyether polyol with a hydroxyl value of 403 mg / KOH and a viscosity of 1321 mPa·s / 25°C.

[0041] Example 3

[0042] The method for preparing the flame retardant wood-like polyether polyol comprises the following steps:

[0043] (1) Input of raw materials and synthesis of Schiff base: 126 g of melamine, 320 g of diethylene glycol and 240 g of hydroxyacetaldehyde were placed in a polymerization reactor, and 4.8 g of solid sodium hydroxide was added at the same time. The reactor was pressurized to test for leaks. After nitrogen replacement, the pressure was increased to 0.3 MPa, the temperature was raised to 80°C and the reaction was carried out for 2 h. Then, 17.15 g of solid sodium borohydride was added and the temperature was maintained at 90°C for 1 h to obtain a Schiff base.

[0044] (2) Polymerization reaction: Control the temperature in the polymerization reactor at 90±5°C, control the pressure in the reactor at a feed rate of 0.2-0.3 MPa, continuously drop 400 g of propylene oxide monomer, mature for 1 h, adjust the temperature to 110±5°C, continuously drop 600 g of propylene oxide monomer, ensure that the pressure is controlled at 0.2-0.3 MPa during the process, until all the propylene oxide is added, mature for 5 h, and obtain a crude polyether.

[0045] (3) Removal of propylene oxide monomer: Control the temperature in the polymerization kettle at 140°C, and control the pressure in the polymerization kettle at -0.09 MPa by vacuuming to remove unreacted propylene oxide.

[0046] (4) Post-treatment: Lower the temperature in the polymerization kettle to 85°C, add 11.08 g of phosphoric acid and 126.64 g of water, stir for 1 h, add 3.16 g of magnesium silicate, raise the temperature to 110°C, evacuate and dehydrate to control the pressure in the kettle at -0.09 MPa, detect the moisture content below 0.1%, discharge and filter, and obtain qualified flame retardant wood-like polyether polyol with a hydroxyl value of 326 mg / KOH and a viscosity of 791 mPa·s / 25°C.

[0047] Comparative Example 1

[0048] A method for preparing a polyether polyol comprises the following steps:

[0049] (1) 126 g of melamine, 200 g of diethylene glycol and 3.3 g of solid potassium hydroxide were placed in a reactor, pressurized for leak test, and pressurized to 0.3 MPa after nitrogen replacement.

[0050] (2) The polymerization reaction was controlled at 80°C in the polymerization reactor. The first part of propylene oxide (300 g) was continuously added dropwise. The feed rate was used to control the pressure in the reactor to 0 MPa. After the first part of propylene oxide was completely added dropwise, the reaction mixture was aged for 1 hour. The temperature was raised to 90°C. The second part of propylene oxide (454 g) was continuously added dropwise. The pressure was controlled below 0.2 MPa during the process. After the addition of propylene oxide was completely completed, the reaction mixture was aged for 3 hours. The crude polyether was milky white and turbid, with a large amount of unreacted white melamine solid.

[0051] Comparative Example 2

[0052] A method for preparing a polyether polyol comprises the following steps:

[0053] (1) Add 200g of diethylene glycol and 1.8g of solid potassium hydroxide into the reactor, pressurize and test for leaks, and then replace with nitrogen and pressurize to 0.3MPa.

[0054] (2) The polymerization reaction was controlled at 80°C in the polymerization reactor. 120 g of the first part of propylene oxide was continuously added dropwise. The feed rate was used to control the pressure in the reactor to 0 MPa. After the first part of propylene oxide was completely added dropwise, the reaction mixture was aged for 1 h. The temperature was raised to 90°C. 280 g of the second part of propylene oxide was continuously added dropwise. The pressure was controlled to be below 0.2 MPa during the process. After the propylene oxide was completely added dropwise, the reaction mixture was aged for 3 h to obtain a crude polyether.

[0055] (3) Removal of monomers: Control the temperature in the kettle at 100°C, and control the pressure in the kettle at -0.09 MPa by vacuuming to remove unreacted propylene oxide.

[0056] (4) Post-treatment: Lower the temperature in the reactor to 75°C, add 4.22 g of phosphoric acid and 48.32 g of water, stir for 1 h, add 1.2 g of magnesium silicate, raise the temperature to 100°C, and vacuum dehydrate to control the pressure in the reactor at -0.09 MPa. Detect the moisture content to be less than 0.1%, discharge the material and filter to obtain a polyether polyol with a hydroxyl value of 353 mg / KOH and a viscosity of 1321 mPa·s / 25°C.

[0057] In combination with the above embodiments and comparative examples, the flame retardant wood-like material is composed of component A and component B, and the flame retardant wood-like material is prepared according to the following method, which includes the following steps:

[0058] (1) Component A: Weigh 25 parts of the prepared polyether polyol, 45 parts of polyether polyol 4110 (produced by Shandong Yinuowei New Materials Co., Ltd.), 0.3 parts of PC-8 (N,N-dimethylcyclohexylamine), 1 part of JXP508 (produced by Air Products and Chemicals (Zibo) Co., Ltd.), 0.3 parts of JXP509 (produced by Air Products and Chemicals (Zibo) Co., Ltd.), 0.1 parts of pure water, 1.8 parts of B8870 (produced by Evonik Chemicals), 20 parts of TCPP tris(2-chloropropyl) phosphate, 5 parts of TEP (triethyl phosphate), and 3.5 parts of HFC-365mfc, and mix all the above materials evenly to obtain component A.

[0059] (2) Component B: polyphenyl polymethylene polyisocyanate.

[0060] (3) At 25°C, component A and component B were mixed in a mass ratio of 1:1.6 to make a flame retardant imitation wood material. The product quality indicators were tested. The results are shown in Table 1.

[0061] Table 1 Experimental data analysis table of embodiments and comparative examples

[0062]

[0063] It can be seen from the above table that the flame retardant wood-like polyether polyol prepared by the present invention has good compressive strength and flame retardant index.

Claims

1. A method for preparing a flame retardant wood-like polyether polyol, characterized in that: The melamine is reacted with the carbonyl compound to generate the Schiff base, and the propylene oxide monomer is added to carry out polymerization reaction to obtain the crude polyether polyol, and the propylene oxide monomer is removed and the flame retardant wood-like polyether polyol is obtained after post-treatment; The specific synthesis process of the Schiff base is as follows: melamine, diethylene glycol and hydroxyacetaldehyde are put into a reaction container, an alkali metal catalyst 1 is added, the temperature is raised to 60-80°C for reaction for 2-4 hours, and then an alkali metal catalyst 2 is added, the temperature is maintained at 75-90°C for reaction for 1-4 hours to obtain the Schiff base; the molar ratio of melamine to hydroxyacetaldehyde is 1:(2.5-4); the alkali metal catalyst 1 is sodium hydroxide or potassium hydroxide, and the added mass is 2-5‰ of the total mass of melamine, hydroxyacetaldehyde, diethylene glycol, the alkali metal catalyst 1, the alkali metal catalyst 2 and propylene oxide; the alkali metal catalyst 2 is sodium borohydride or potassium borohydride, and the added mass is 1-2.5% of the total mass of melamine, hydroxyacetaldehyde and diethylene glycol.

2. The method for preparing a flame retardant wood-like polyether polyol according to claim 1, characterized in that: The obtained flame retardant wood-like polyether polyol has an average functionality of 2-3 and a hydroxyl value of 320-403 mg / KOH.

3. The method for preparing the flame retardant wood-like polyether polyol according to claim 1, characterized in that: The specific steps of the polymerization reaction are: when the temperature of the polymerization reaction system is 80-90°C, add propylene oxide monomer, control the pressure of the polymerization reaction system at 0-0.2MPa, mature for 0.5-1h after the addition is completed, continue to maintain the temperature at 90-110°C, add propylene oxide monomer, control the pressure of the polymerization reaction system below 0.2MPa, and mature for 3-5h after the addition is completed.

4. The method for preparing a flame retardant wood-like polyether polyol according to claim 1, characterized in that: The conditions for removing propylene oxide monomer are: temperature 100-140°C, and vacuum control of the pressure in the reaction container at -0.08 to -0.09 MPa.

5. The method for preparing the flame retardant wood-like polyether polyol according to claim 1, characterized in that: The post-treatment is to lower the system temperature to 75-85°C, add phosphoric acid and water, stir, then add magnesium silicate, raise the temperature to 100-110°C, vacuum dehydrate to control the pressure in the reaction container at -0.08 to -0.09MPa, detect the moisture content below 0.1%, and filter.

6. A flame retardant wood-like polyether polyol, characterized in that: The flame retardant wood-like polyether polyol is prepared by the preparation method of any one of claims 1 to 5.

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