A flame-retardant and water-resistant magnesium oxysulfate board and its manufacturing process

Abstract

The present invention relates to the field of building materials technology, in particular to a kind of flame retardant and water-resistant magnesium oxysulfate board and its manufacturing process. The present invention discloses the following scheme: light-burned magnesium oxide powder, magnesium sulfate heptahydrate, water, fly ash, citric acid, iminodiacetic acid type chelating resin are mixed to obtain magnesium oxysulfate mixed slurry; using hydrogen-terminated polydimethylsiloxane and 10-undecenal as raw materials, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is grafted after the reaction, and then isophorone diisocyanate is used for end-blocking to obtain an isocyanate-terminated silicon-containing flame retardant; the isocyanate-terminated silicon-containing flame retardant is used for modified epoxy resin, and is mixed with epoxy toughening agent and tetraethylene pentamine to prepare epoxy resin glue; glass fiber cloth is immersed in epoxy resin glue, then combined with magnesium oxysulfate mixed slurry, and solidified to obtain magnesium oxysulfate board. The magnesium oxysulfate board prepared by the present invention has high strength and good flame retardancy and water resistance.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to a flame-retardant and water-resistant magnesium oxysulfate board and a manufacturing process thereof. Background Art

[0002] Magnesium oxysulfate cement is a common inorganic cementitious material used in construction. It is formed by mixing and hardening light-burned magnesium oxide powder and magnesium sulfate solution. Because the calcination temperature of magnesium oxide, the main component of magnesium oxysulfate cement, is much lower than that of Portland cement clinker, it offers the advantages of low energy consumption, simple production process, and low cost. Furthermore, magnesium oxysulfate cement exhibits fire resistance, heat resistance, low density, low thermal conductivity, and strong bonding strength. It is widely used in the production of lightweight wall panels, refractory components, and thermal insulation panels.

[0003] However, magnesium oxysulfate cement has drawbacks such as low strength and poor water resistance, which has limited the development of magnesium oxysulfate boards made from it in the building materials field, especially in long-term high-humidity environments such as swimming pools and bathrooms. Therefore, it is very necessary to invent a new type of magnesium oxysulfate board. Summary of the Invention

[0004] The object of the present invention is to provide a flame retardant and water resistant magnesium oxysulfate board and a manufacturing process thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a flame retardant and water resistant magnesium oxysulfate board and a manufacturing process thereof, comprising the following steps:

[0006] Step 1:

[0007] Mixing light-burned magnesium oxide powder, magnesium sulfate heptahydrate, water, fly ash, citric acid, and iminodiacetic acid type chelating resin to obtain magnesium oxysulfide mixed slurry;

[0008] Step 2:

[0009] S1: Weigh hydrogen-terminated polydimethylsiloxane and 10-undecenal, stir the 10-undecenal and raise the temperature to 45-55°C under nitrogen, then add hydrogen-terminated polydimethylsiloxane, use chloroplatinic acid isopropanol solution as a catalyst, stir and raise the temperature to 85-95°C and maintain for 4-5 hours. After the reaction is completed, remove excess 10-undecenal by rotary evaporation to obtain terminal aldehyde-modified polysiloxane;

[0010] S2: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous toluene, heating to 85-100°C and stirring for 15-30 minutes, then adding terminal aldehyde-modified polysiloxane under nitrogen flow, reacting for 12-15 hours, washing and drying to obtain a silicon-containing flame retardant;

[0011] S3: After drying the silicon-containing flame retardant at 110-120° C. for 2-3 hours, isophorone diisocyanate is added to the silicon-containing flame retardant, and dibutyltin dilaurate is used as a catalyst to react at 50-65° C. for 3-5 hours to obtain an isocyanate-terminated silicon-containing flame retardant;

[0012] S4: mixing an isocyanate-terminated silicon-containing flame retardant and an epoxy resin to obtain a modified epoxy resin; mixing the modified epoxy resin, an epoxy toughening agent, and tetraethylene pentamine to obtain an epoxy resin glue;

[0013] Step 3:

[0014] The glass fiber cloth is calcined at 600-900°C for 30-60 minutes, immersed in epoxy resin glue after cooling, taken out and heated to 80-90°C for curing to obtain a modified glass fiber cloth; the modified glass fiber cloth is laid in a mold, magnesium oxysulfate mixed slurry is poured into it, and then a modified glass fiber cloth is laid on top. After hot pressing treatment, it is demoulded and cured to obtain a flame retardant and water-resistant magnesium oxysulfate board.

[0015] Furthermore, in step 1, the contents of the components in the magnesium oxysulfate mixed slurry are, by weight, 25 to 35 parts of light-burned magnesium oxide powder, 30 to 40 parts of magnesium sulfate heptahydrate, 25 to 30 parts of water, 12 to 16 parts of fly ash, 0.15 to 0.25 parts of citric acid, and 1 to 1.5 parts of iminodiacetic acid type chelating resin.

[0016] Furthermore, in S1, hydrogen-terminated polydimethylsiloxane and 10-undecenal are weighed so that the molar ratio of silicon-hydrogen bonds to carbon-carbon double bonds is 1:(1.1-1.2).

[0017] Furthermore, in S2, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the terminal aldehyde-modified polysiloxane react at a molar ratio of phosphorus-hydrogen bond to aldehyde group of 1:1.

[0018] Furthermore, in S3, the silicon-containing flame retardant and isophorone diisocyanate react at a molar ratio of hydroxyl group to isocyanate group of 1:2.

[0019] Furthermore, in S4, the contents of the components in the modified epoxy resin are, by weight percentage, 10-15% of the isocyanate-terminated silicon-containing flame retardant and 85-90% of the epoxy resin.

[0020] Furthermore, in S4, the modified epoxy resin, the epoxy toughening agent, and tetraethylene pentamine are mixed in a weight ratio of 100:(16-18):(20-30).

[0021] Furthermore, in step 3, the hot pressing treatment time is 30-40 min, the temperature is 110-120° C., and the pressure is 2-3 MPa.

[0022] Furthermore, the demoulding and curing conditions are curing at 20-25°C for 20-28 days.

[0023] Compared with existing technologies, the present invention achieves the following beneficial effects: It provides a method for preparing a flame-retardant and water-resistant magnesium oxysulfate board. Light-burned magnesium oxide powder, magnesium sulfate heptahydrate, water, fly ash, citric acid, and an iminodiacetic acid chelating resin are mixed to produce a magnesium oxysulfate mixed slurry. Glass fiber cloth is then immersed in an epoxy resin adhesive for modification and then bonded to magnesium oxysulfate cement to produce the magnesium oxysulfate board. The glass fiber cloth has excellent mechanical properties and provides a certain load-bearing capacity, thereby reinforcing the magnesium oxysulfate board.

[0024] The magnesium oxysulfate mixed slurry of the present invention contains an iminodiacetic acid-type chelating resin. On the one hand, the chelating resin has good stability in the slurry, can play a filling role, reduce porosity, and optimize the internal structure of the magnesium oxysulfate board. On the other hand, the nitrogen atoms contained in the chelating resin can provide lone pairs of electrons, which combine with the empty orbitals provided by magnesium ions in the slurry layer to produce a coordination effect. The carboxyl carboxylic acid in the chelating resin can react with the hydrated hydroxy magnesium ions generated by the hydrolysis of magnesium oxide to induce the growth of slender needle-rod-shaped crystals 5Mg(OH)2·MgSO4·7H2O and inhibit the formation of flaky Mg(OH)2 phases. The generated 5Mg(OH)2·MgSO4·7H2O interpenetrates to form a dense and strong three-dimensional network structure, filling the gaps and holes in the matrix, making the interior of the magnesium oxysulfate board more dense. In addition, the carboxyl groups in the chelating resin can react with the epoxy resin on the surface of the glass fiber cloth, improving the bonding strength between the glass fiber cloth and the magnesium oxysulfate cement.

[0025] To further enhance the epoxy resin's modification effect on fiberglass cloth, the present invention uses hydrogen-terminated polydimethylsiloxane and 10-undecenal as raw materials to prepare an aldehyde-terminated polysiloxane through a hydrosilylation reaction. The product is then reacted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to obtain a silicon-containing flame retardant. The silicon-containing flame retardant is then reacted with isophorone diisocyanate using the hydroxyl groups generated by the reaction of the aldehyde group and the PH bond to obtain an isocyanate-terminated silicon-containing flame retardant. The isocyanate-terminated silicon-containing flame retardant contains flexible silicon-oxygen bonds. When added to epoxy resin, it can not only increase the epoxy resin's crosslinking density and improve its mechanical properties, but also impart good hydrophobicity and flame retardancy to the epoxy resin, thereby modifying the epoxy resin. During the research and development process, the researchers also found that excessive use of isocyanate-terminated silicon-containing flame retardant will cause it to phase separate from the epoxy resin and affect the modification results. Therefore, when modifying the epoxy resin, the best modification effect is achieved by mixing 10-15% isocyanate-terminated silicon-containing flame retardant and 85-90% epoxy resin by weight. DETAILED DESCRIPTION

[0026] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0027] Materials used in the present invention and their sources: light-burned magnesium oxide powder comes from Haicheng Magnesium Mineral Group Co., Ltd., item number CCM-96; hydrogen-terminated polydimethylsiloxane comes from Ningbo Runhe High-tech Materials Technology Co., Ltd., item number RH-H518; fly ash comes from Lingshou County Chuangwei Mineral Products Processing, item number fmh1100; iminodiacetic acid type chelating resin comes from Tianjin Xinyue Huamei Environmental Protection Technology Co., Ltd., item number D401-5; epoxy resin comes from Wanqian Chemical, item number WSR618 (E51); epoxy toughening agent comes from Guangzhou Good New Materials Technology Co., Ltd., model WD-403; glass fiber cloth comes from Changzhou Chengzhida Fiberglass Products Co., Ltd., item number 1230.

[0028] Example 1: A flame-retardant and water-resistant magnesium oxysulfate board and a manufacturing process thereof, comprising the following steps:

[0029] Step 1:

[0030] 28 kg of light-burned magnesium oxide powder, 36 kg of magnesium sulfate heptahydrate, 27 kg of water, 13 kg of fly ash, 0.18 kg of citric acid, and 1.2 kg of iminodiacetic acid type chelating resin were mixed to obtain a magnesium oxysulfide mixed slurry;

[0031] Step 2:

[0032] S1: Hydrogen-terminated polydimethylsiloxane and 10-undecenal were weighed at a molar ratio of silicon-hydrogen bonds to carbon-carbon double bonds of 1:1.2. Under nitrogen flow, the 10-undecenal was stirred and heated to 45°C. Then, hydrogen-terminated polydimethylsiloxane was added. Using chloroplatinic acid isopropanol solution as a catalyst, the mixture was stirred and heated to 85°C for 4 hours. After the reaction was completed, excess 10-undecenal was removed by rotary evaporation to obtain a terminal aldehyde-modified polysiloxane.

[0033] S2: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous toluene, heating to 85° C. and stirring for 15 minutes, then adding terminal aldehyde-modified polysiloxane while maintaining the temperature under nitrogen flow, reacting for 12 hours, washing and drying to obtain a silicon-containing flame retardant; wherein the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the terminal aldehyde-modified polysiloxane react at a molar ratio of phosphorus-hydrogen bond to aldehyde group of 1:1;

[0034] S3: After drying the silicon-containing flame retardant at 110° C. for 2 hours, isophorone diisocyanate is added to the silicon-containing flame retardant, and dibutyltin dilaurate is used as a catalyst. The reaction is carried out at 50° C. for 3 hours to obtain an isocyanate-terminated silicon-containing flame retardant; wherein the silicon-containing flame retardant and isophorone diisocyanate are reacted at a molar ratio of hydroxyl group to isocyanate group of 1:2;

[0035] S4: mixing an isocyanate-terminated silicon-containing flame retardant and an epoxy resin to obtain a modified epoxy resin, wherein the content of each component in the modified epoxy resin is, by weight percentage, 10% of the isocyanate-terminated silicon-containing flame retardant and 90% of the epoxy resin; mixing the modified epoxy resin, the epoxy toughening agent, and tetraethylene pentamine in a weight ratio of 100:17:25 to obtain an epoxy resin glue;

[0036] Step 3:

[0037] The glass fiber cloth was calcined at 600°C for 30 minutes, immersed in epoxy resin glue after cooling, taken out and heated to 80°C for curing to obtain modified glass fiber cloth; the modified glass fiber cloth was laid in a mold, magnesium oxysulfate mixed slurry was poured into it, and then a modified glass fiber cloth was laid on top. The hot pressing treatment was carried out for 30 minutes at a hot pressing temperature of 110°C and a pressure of 2MPa. After demolding, it was cured at 20°C for 20 days to obtain a flame retardant and water-resistant magnesium oxysulfate board.

[0038] Example 2: A flame-retardant and water-resistant magnesium oxysulfate board and a manufacturing process thereof, comprising the following steps:

[0039] Step 1:

[0040] 28 kg of light-burned magnesium oxide powder, 36 kg of magnesium sulfate heptahydrate, 27 kg of water, 13 kg of fly ash, 0.18 kg of citric acid, and 1.2 kg of iminodiacetic acid type chelating resin were mixed to obtain a magnesium oxysulfide mixed slurry;

[0041] Step 2:

[0042] S1: Weigh hydrogen-terminated polydimethylsiloxane and 10-undecenal at a molar ratio of silicon-hydrogen bonds to carbon-carbon double bonds of 1:1.2. Under nitrogen, stir the 10-undecenal and heat it to 50°C. Then add hydrogen-terminated polydimethylsiloxane. Using isopropanol solution of chloroplatinic acid as a catalyst, stir and heat to 90°C for 4.5 hours. After the reaction is completed, remove excess 10-undecenal by rotary evaporation to obtain terminal aldehyde-modified polysiloxane.

[0043] S2: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous toluene, heating to 90°C and stirring for 25 minutes, then adding terminal aldehyde-modified polysiloxane while maintaining the temperature under nitrogen flow, reacting for 13 hours, washing and drying to obtain a silicon-containing flame retardant; wherein the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the terminal aldehyde-modified polysiloxane react at a molar ratio of phosphorus-hydrogen bond to aldehyde group of 1:1;

[0044] S3: After drying the silicon-containing flame retardant at 115° C. for 2.5 hours, isophorone diisocyanate is added to the silicon-containing flame retardant, and dibutyltin dilaurate is used as a catalyst. The reaction is carried out at 60° C. for 4 hours to obtain an isocyanate-terminated silicon-containing flame retardant; wherein the silicon-containing flame retardant and isophorone diisocyanate are reacted at a molar ratio of hydroxyl group to isocyanate group of 1:2;

[0045] S4: mixing an isocyanate-terminated silicon-containing flame retardant and an epoxy resin to obtain a modified epoxy resin, wherein the content of each component in the modified epoxy resin is, by weight percentage, 13% of the isocyanate-terminated silicon-containing flame retardant and 87% of the epoxy resin; mixing the modified epoxy resin, the epoxy toughening agent, and tetraethylene pentamine in a weight ratio of 100:17:25 to obtain an epoxy resin glue;

[0046] Step 3:

[0047] The glass fiber cloth was calcined at 750°C for 45 minutes, immersed in epoxy resin glue after cooling, taken out and heated to 85°C for curing to obtain modified glass fiber cloth; the modified glass fiber cloth was laid in a mold, magnesium oxysulfate mixed slurry was poured into it, and then a modified glass fiber cloth was laid on top. The hot pressing treatment was carried out for 35 minutes at a hot pressing temperature of 115°C and a pressure of 2.5MPa. After demolding, it was cured at 25°C for 24 days to obtain a flame retardant and water-resistant magnesium oxysulfate board.

[0048] Example 3: A flame-retardant and water-resistant magnesium oxysulfate board and a manufacturing process thereof, comprising the following steps:

[0049] Step 1:

[0050] 28 kg of light-burned magnesium oxide powder, 36 kg of magnesium sulfate heptahydrate, 27 kg of water, 13 kg of fly ash, 0.18 kg of citric acid, and 1.2 kg of iminodiacetic acid type chelating resin were mixed to obtain a magnesium oxysulfide mixed slurry;

[0051] Step 2:

[0052] S1: Weigh hydrogen-terminated polydimethylsiloxane and 10-undecenal at a molar ratio of silicon-hydrogen bonds to carbon-carbon double bonds of 1:1.2. Under nitrogen, stir the 10-undecenal and heat it to 55°C. Then, add hydrogen-terminated polydimethylsiloxane. Using chloroplatinic acid isopropanol solution as a catalyst, stir and heat it to 95°C for 5 hours. After the reaction is completed, remove excess 10-undecenal by rotary evaporation to obtain terminal aldehyde-modified polysiloxane.

[0053] S2: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous toluene, heating to 100° C. and stirring for 30 minutes, then adding terminal aldehyde-modified polysiloxane while maintaining the temperature under nitrogen flow, reacting for 15 hours, washing and drying to obtain a silicon-containing flame retardant; wherein the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the terminal aldehyde-modified polysiloxane react at a molar ratio of phosphorus-hydrogen bond to aldehyde group of 1:1;

[0054] S3: After drying the silicon-containing flame retardant at 120° C. for 3 hours, isophorone diisocyanate is added to the silicon-containing flame retardant, and dibutyltin dilaurate is used as a catalyst. The reaction is carried out at 65° C. for 5 hours to obtain an isocyanate-terminated silicon-containing flame retardant; wherein the silicon-containing flame retardant and isophorone diisocyanate are reacted at a molar ratio of hydroxyl group to isocyanate group of 1:2;

[0055] S4: mixing an isocyanate-terminated silicon-containing flame retardant and an epoxy resin to obtain a modified epoxy resin, wherein the content of each component in the modified epoxy resin is, by weight percentage, 15% of the isocyanate-terminated silicon-containing flame retardant and 85% of the epoxy resin; mixing the modified epoxy resin, the epoxy toughening agent, and tetraethylene pentamine in a weight ratio of 100:17:25 to obtain an epoxy resin glue;

[0056] Step 3:

[0057] The glass fiber cloth was calcined at 900°C for 60 minutes, immersed in epoxy resin glue after cooling, taken out and heated to 90°C for curing to obtain modified glass fiber cloth; the modified glass fiber cloth was laid in a mold, magnesium oxysulfate mixed slurry was poured into it, and then a modified glass fiber cloth was laid on top. The hot pressing treatment was carried out for 40 minutes at a hot pressing temperature of 120°C and a pressure of 3MPa. After demolding, it was cured at 25°C for 28 days to obtain a flame retardant and water-resistant magnesium oxysulfate board.

[0058] Comparative Example 1: The epoxy resin was not modified, and the other parameters were the same as those in Example 1.

[0059] Step 1:

[0060] 28 kg of light-burned magnesium oxide powder, 36 kg of magnesium sulfate heptahydrate, 27 kg of water, 13 kg of fly ash, 0.18 kg of citric acid, and 1.2 kg of iminodiacetic acid type chelating resin were mixed to obtain a magnesium oxysulfide mixed slurry;

[0061] Step 2:

[0062] The epoxy resin, epoxy toughening agent and tetraethylene pentamine are mixed in a weight ratio of 100:17:25 to obtain an epoxy resin glue;

[0063] Step 3:

[0064] The glass fiber cloth was calcined at 600°C for 30 minutes, immersed in epoxy resin glue after cooling, taken out and heated to 80°C for curing to obtain modified glass fiber cloth; the modified glass fiber cloth was laid in a mold, magnesium oxysulfate mixed slurry was poured into it, and then a modified glass fiber cloth was laid on top. The hot pressing treatment was carried out for 30 minutes at a hot pressing temperature of 110°C and a pressure of 2MPa. After demolding, it was cured at 20°C for 20 days to obtain a flame retardant and water-resistant magnesium oxysulfate board.

[0065] Comparative Example 2: The magnesium oxysulfate mixed slurry was prepared without adding the iminodiacetic acid type chelating resin, and the other parameters were the same as those in Example 2.

[0066] Step 1:

[0067] Mix 28 kg of light-burned magnesium oxide powder, 36 kg of magnesium sulfate heptahydrate, 27 kg of water, 13 kg of fly ash, and 0.18 kg of citric acid to obtain a magnesium oxysulfate mixed slurry;

[0068] Step 2:

[0069] S1: Weigh hydrogen-terminated polydimethylsiloxane and 10-undecenal at a molar ratio of silicon-hydrogen bonds to carbon-carbon double bonds of 1:1.2. Under nitrogen, stir the 10-undecenal and heat it to 50°C. Then add hydrogen-terminated polydimethylsiloxane. Using isopropanol solution of chloroplatinic acid as a catalyst, stir and heat to 90°C for 4.5 hours. After the reaction is completed, remove excess 10-undecenal by rotary evaporation to obtain terminal aldehyde-modified polysiloxane.

[0070] S2: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous toluene, heating to 90°C and stirring for 25 minutes, then adding terminal aldehyde-modified polysiloxane while maintaining the temperature under nitrogen flow, reacting for 13 hours, washing and drying to obtain a silicon-containing flame retardant; wherein the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the terminal aldehyde-modified polysiloxane react at a molar ratio of phosphorus-hydrogen bond to aldehyde group of 1:1;

[0071] S3: After drying the silicon-containing flame retardant at 115° C. for 2.5 hours, isophorone diisocyanate is added to the silicon-containing flame retardant, and dibutyltin dilaurate is used as a catalyst. The reaction is carried out at 60° C. for 4 hours to obtain an isocyanate-terminated silicon-containing flame retardant; wherein the silicon-containing flame retardant and isophorone diisocyanate are reacted at a molar ratio of hydroxyl group to isocyanate group of 1:2;

[0072] S4: mixing an isocyanate-terminated silicon-containing flame retardant and an epoxy resin to obtain a modified epoxy resin, wherein the content of each component in the modified epoxy resin is, by weight percentage, 13% of the isocyanate-terminated silicon-containing flame retardant and 87% of the epoxy resin; mixing the modified epoxy resin, the epoxy toughening agent, and tetraethylene pentamine in a weight ratio of 100:17:25 to obtain an epoxy resin glue;

[0073] Step 3:

[0074] The glass fiber cloth was calcined at 750°C for 45 minutes, immersed in epoxy resin glue after cooling, taken out and heated to 85°C for curing to obtain modified glass fiber cloth; the modified glass fiber cloth was laid in a mold, magnesium oxysulfate mixed slurry was poured into it, and then a modified glass fiber cloth was laid on top. The hot pressing treatment was carried out for 35 minutes at a hot pressing temperature of 115°C and a pressure of 2.5MPa. After demolding, it was cured at 25°C for 24 days to obtain a flame retardant and water-resistant magnesium oxysulfate board.

[0075] Comparative Example 3: The amount of the isocyanate-terminated silicon-containing flame retardant was increased, and the other parameters were the same as those in Example 3.

[0076] Step 1:

[0077] 28 kg of light-burned magnesium oxide powder, 36 kg of magnesium sulfate heptahydrate, 27 kg of water, 13 kg of fly ash, 0.18 kg of citric acid, and 1.2 kg of iminodiacetic acid type chelating resin were mixed to obtain a magnesium oxysulfide mixed slurry;

[0078] Step 2:

[0079] S1: Weigh hydrogen-terminated polydimethylsiloxane and 10-undecenal at a molar ratio of silicon-hydrogen bonds to carbon-carbon double bonds of 1:1.2. Under nitrogen, stir the 10-undecenal and heat it to 55°C. Then, add hydrogen-terminated polydimethylsiloxane. Using chloroplatinic acid isopropanol solution as a catalyst, stir and heat it to 95°C for 5 hours. After the reaction is completed, remove excess 10-undecenal by rotary evaporation to obtain terminal aldehyde-modified polysiloxane.

[0080] S2: adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous toluene, heating to 100° C. and stirring for 30 minutes, then adding terminal aldehyde-modified polysiloxane while maintaining the temperature under nitrogen flow, reacting for 15 hours, washing and drying to obtain a silicon-containing flame retardant; wherein the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the terminal aldehyde-modified polysiloxane react at a molar ratio of phosphorus-hydrogen bond to aldehyde group of 1:1;

[0081] S3: After drying the silicon-containing flame retardant at 120° C. for 3 hours, isophorone diisocyanate is added to the silicon-containing flame retardant, and dibutyltin dilaurate is used as a catalyst. The reaction is carried out at 65° C. for 5 hours to obtain an isocyanate-terminated silicon-containing flame retardant; wherein the silicon-containing flame retardant and isophorone diisocyanate are reacted at a molar ratio of hydroxyl group to isocyanate group of 1:2;

[0082] S4: mixing an isocyanate-terminated silicon-containing flame retardant and an epoxy resin to obtain a modified epoxy resin, wherein the content of each component in the modified epoxy resin is, by weight percentage, 30% of the isocyanate-terminated silicon-containing flame retardant and 70% of the epoxy resin; mixing the modified epoxy resin, the epoxy toughening agent, and tetraethylene pentamine in a weight ratio of 100:17:25 to obtain an epoxy resin glue;

[0083] Step 3:

[0084] The glass fiber cloth was calcined at 900°C for 60 minutes, immersed in epoxy resin glue after cooling, taken out and heated to 90°C for curing to obtain modified glass fiber cloth; the modified glass fiber cloth was laid in a mold, magnesium oxysulfate mixed slurry was poured into it, and then a modified glass fiber cloth was laid on top. The hot pressing treatment was carried out for 40 minutes at a hot pressing temperature of 120°C and a pressure of 3MPa. After demolding, it was cured at 25°C for 28 days to obtain a flame retardant and water-resistant magnesium oxysulfate board.

[0085] Experiment: Magnesium oxysulfide board samples were prepared according to the preparation methods in Examples 1 to 3 and Comparative Examples 1 to 3. The size of the magnesium oxysulfide board samples was 40 mm × 40 mm × 160 mm. The performance of the magnesium oxysulfide board samples was tested as follows:

[0086] Flame retardant properties: Tested in accordance with the method in GB / T 5464-2010. Combustion performance classification is based on GB 8624-2012.

[0087] Water absorption performance: Place the magnesium oxysulfate board sample at a constant temperature of 40℃ and dry it to constant weight. Then immerse it in water for 120 hours. After taking it out, wipe off the surface moisture and weigh it again. Calculate the water absorption rate according to the formula: Water absorption rate = (M2-M1) / M1×100%; where M2 is the weight of the sample after immersion in water for 24 hours, and M1 is the weight of the sample when it is dried to constant weight.

[0088] Mechanical properties: Refer to GB / T 17671-2021 to test the compressive strength and flexural strength of magnesium oxysulfate board samples.

[0089]

[0090] Conclusion: The magnesium oxysulfate board prepared by the present invention has good flame retardant and water-resistant properties. The data of Example 1 and Comparative Example 1 show that the magnesium oxysulfate board prepared by impregnating the glass fiber cloth with the modified epoxy resin has higher compressive and flexural strength; the flame retardant and hydrophobic properties of the modified epoxy resin are improved, thus giving the magnesium oxysulfate board good flame retardant and water-resistant properties. The data of Example 2 and Comparative Example 2 show that after adding the iminodiacetic acid type chelating resin, it has good stability in the magnesium oxysulfate mixed slurry, can play a filling role, reduce the porosity, and also can improve the bonding force between the glass fiber cloth and the magnesium oxysulfate cement. The data of Example 3 and Comparative Example 3 show that after increasing the amount of isocyanate-terminated silicon-containing flame retardant, the performance of the modified epoxy resin decreases, and the performance of the prepared magnesium oxysulfate board decreases.

[0091] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A preparation process of a flame retardant and water-resistant magnesium oxysulfate board, characterized by: The following steps are involved: Step 1: Mixing light-burned magnesium oxide powder, magnesium sulfate heptahydrate, water, fly ash, citric acid, and iminodiacetic acid type chelating resin to obtain magnesium oxysulfide mixed slurry; Step 2: Mixing modified epoxy resin, epoxy toughening agent and tetraethylene pentamine to obtain epoxy resin glue; Step 3: The glass fiber cloth is calcined at 600-900°C for 30-60 minutes, immersed in epoxy resin glue after cooling, and then taken out and heated to 80-90°C for curing to obtain a modified glass fiber cloth; The modified glass fiber cloth is laid in a mold, and the magnesium oxysulfide mixed slurry is poured in, and then a modified glass fiber cloth is laid on top. After hot pressing, the mold is demoulded and cured to obtain a flame retardant and water-resistant magnesium oxysulfide board; Preparation method of modified epoxy resin, The following steps are involved: S1: Weigh hydrogen-terminated polydimethylsiloxane and 10-undecenal, stir the 10-undecenal and raise the temperature to 45-55°C under nitrogen, then add hydrogen-terminated polydimethylsiloxane, use chloroplatinic acid isopropanol solution as a catalyst, stir and raise the temperature to 85-95°C and maintain for 4-5 hours. After the reaction is completed, remove excess 10-undecenal by rotary evaporation to obtain terminal aldehyde-modified polysiloxane; S2: Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to anhydrous toluene, heat to 85-100°C and stir for 15-30 minutes, add terminal aldehyde-modified polysiloxane under nitrogen flow, keep the temperature constant, react for 12-15 hours, wash and dry to obtain a silicon-containing flame retardant; S3: After drying the silicon-containing flame retardant at 110-120° C. for 2-3 hours, isophorone diisocyanate is added to the silicon-containing flame retardant, and dibutyltin dilaurate is used as a catalyst to react at 50-65° C. for 3-5 hours to obtain an isocyanate-terminated silicon-containing flame retardant; S4: mixing an isocyanate-terminated silicon-containing flame retardant and an epoxy resin to obtain a modified epoxy resin.

2. The preparation process of a flame retardant and water resistant magnesium oxysulfate board according to claim 1, characterized in that: In step 1, the contents of the components in the magnesium oxysulfate mixed slurry are, by weight, 25 to 35 parts of light-burned magnesium oxide powder, 30 to 40 parts of magnesium sulfate heptahydrate, 25 to 30 parts of water, 12 to 16 parts of fly ash, 0.15 to 0.25 parts of citric acid, and 1 to 1.5 parts of iminodiacetic acid type chelating resin.

3. The preparation process of a flame retardant and water resistant magnesium oxysulfate board according to claim 1, characterized in that: In step 2, the modified epoxy resin, epoxy toughening agent, and tetraethylene pentamine are mixed in a weight ratio of 100: (16-18): (20-30).

4. The preparation process of a flame retardant and water resistant magnesium oxysulfate board according to claim 1, characterized in that: In S1, hydrogen-terminated polydimethylsiloxane and 10-undecenal are weighed so that the molar ratio of silicon-hydrogen bonds to carbon-carbon double bonds is 1:(1.1-1.2).

5. The preparation process of a flame retardant and water resistant magnesium oxysulfate board according to claim 1, characterized in that: In S2, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and terminal aldehyde-modified polysiloxane react at a molar ratio of phosphorus-hydrogen bond to aldehyde group of 1:

1.

6. The process for preparing a flame-retardant and water-resistant magnesium oxysulfate board according to claim 1, characterized in that: In S3, the silicon-containing flame retardant and isophorone diisocyanate react at a molar ratio of hydroxyl group to isocyanate group of 1:

2.

7. The process for preparing a flame-retardant and water-resistant magnesium oxysulfate board according to claim 1, characterized in that: In S4, the content of each component in the modified epoxy resin, calculated by weight percentage, is 10-15% of the isocyanate-terminated silicon-containing flame retardant and 85-90% of the epoxy resin.

8. The process for preparing a flame-retardant and water-resistant magnesium oxysulfate board according to claim 1, characterized in that: In step 3, the hot pressing treatment time is 30-40 minutes, the temperature is 110-120° C., and the pressure is 2-3 MPa; the demolding and curing conditions are 20-28 days at 20-25° C.

9. The flame-retardant and water-resistant magnesium oxysulfate board prepared by the preparation process according to any one of claims 1 to 8.

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