Polyurethane reinforcing material and preparation method thereof

Abstract

The invention discloses a polyurethane reinforcing material and a preparation method thereof, the preparation method comprises the steps of raw material preparation, intermediate material preparation, material mixing and the like, and a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant are respectively added into a component A and a component B to jointly construct a flame retardant system. Meanwhile, stearic acid is adopted to carry out surface coating on magnesium hydroxide for modification, a silane coupling agent is adopted to carry out secondary coating, and a polymer layer with a buffering effect is added between the two layers of coating. According to the invention, the stearic acid is firstly used for primary coating, then the silane coupling agent is used for secondary coating, and meanwhile, a polymer layer with a buffer effect is added between the two layers of coating, so that multilayer coating of magnesium hydroxide is realized. According to the invention, the dispersibility of the multilayer coated magnesium hydroxide in the polyurethane matrix is obviously improved, the phase separation phenomenon is not easy to occur, and the stability of the coating layer can be improved through the middle polymer layer so as to enhance the damage resistance of the coating layer.

Description

Technical Field

[0001] The invention relates to the technical field of composite material preparation methods, in particular to a polyurethane reinforcement material and a preparation method thereof. Background Art

[0002] In the coal mining industry, safe support and reinforcement work in coal mines is of vital importance. Polyurethane reinforcement materials have been widely used in underground mine tunnel support, coal wall reinforcement, etc. due to their good adhesion, flexibility and high strength. However, the underground environment of coal mines is complex, and there are many flammable materials, such as coal itself and some auxiliary materials. The risk of fire always threatens the safe production of mines. Traditional polyurethane reinforcement materials are usually flammable. Once they encounter a fire source, they are very likely to cause combustion, which will not only cause the material itself to lose its reinforcement effect, but may also become a fuse for the fire, causing large-scale mine fires, posing huge safety hazards to coal mine production.

[0003] At present, in order to solve the flame retardancy problem of polyurethane materials, flame retardants can be added to polyurethane materials, but there are still many challenges in the selection of flame retardants, the way of adding flame retardants, and how to ensure the good compatibility of flame retardants with polyurethane materials. Different types of flame retardants vary greatly in terms of flame retardant effects and effects on material properties. For example, a single flame retardant is often difficult to achieve the ideal flame retardant effect, and may have a negative impact on other properties of polyurethane materials, such as mechanical properties and bonding properties.

[0004] At the same time, in terms of preparation technology, how to evenly disperse the flame retardant in the polyurethane material and how to ensure that the flame retardant can play a stable role under different conditions of use are also issues to be solved. In addition, some existing flame retardant modification methods may increase the preparation cost of the material or have problems such as insufficient durability in practical applications.

[0005] Therefore, it has become an urgent need in the field of coal mine safety production to provide a polyurethane reinforcement material and a preparation method thereof to prepare a polyurethane reinforcement material that has good flame retardant properties, can ensure the original reinforcement properties of the material, and has a reasonable preparation process and controllable costs. Summary of the invention

[0006] The purpose of the present invention is to provide a polyurethane reinforcement material and a preparation method thereof. By optimizing the formula and the preparation process, the prepared polyurethane reinforcement material has the advantages of rapid curing, high strength, and good flame retardancy, and can effectively solve the reinforcement and water plugging problems encountered in coal mining, prevent the spontaneous combustion of coal during the reinforcement process, reduce the temperature of the surrounding environment, and inhibit the spread of combustion, thereby improving the safety of coal mine reinforcement materials in the event of fire.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing a polyurethane reinforcement material, comprising the following steps: (1) Raw material preparation: Component A: Select polyether polyol with a molecular weight of 2000-3000, a hydroxyl value of 30-50 mgKOH / g, and a moisture content of less than 0.1%; add 50-70 parts of polyether polyol by weight to a reactor, add 5-10 parts of toluene diisocyanate (TDI), and 0.1-0.5 parts of a catalyst; Component B: prepare 30-50 parts of curing agent, 5-10 parts of plasticizer, 1-5 parts of filler with a particle size between 10-50 μm, and 0.1-0.5 parts of defoamer; (2) Preparation of intermediate materials: Preparation of component A: Heat the reactor containing polyether polyol to 80-100°C, slowly add toluene diisocyanate (TDI) under the condition of stirring at a speed of 200-300r / min, and react for 2-3h; then add the catalyst and continue the reaction for 1-2h until the isocyanate group (-NCO) content of the reaction system reaches 0.5%-2% by weight. After the reaction is completed, cool component A to room temperature and discharge the material for standby use; Preparation of component B: In another reaction kettle, add curing agent, plasticizer, filler and defoamer in sequence, stir evenly at a stirring speed of 100-200 r / min to obtain component B; (3) Material mixing: When in use, component A and component B are mixed in a mixer at a volume ratio of 1:1-1.5, the mixing time is 30-60s, and the stirring speed is 500-800r / min to obtain a polyurethane reinforcement material.

[0008] Preferably, in step (1), two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared as component A; wherein the phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP), and the metal hydroxide flame retardant is magnesium hydroxide (MH). In parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; in step (2), before preparing component A, APP and MH are put into a reaction kettle together with 50-70 parts of polyether polyol, and then the step (2) is continued to prepare component A containing flame retardant.

[0009] Preferably, in step (1), two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared as component B; wherein the phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP) and the metal hydroxide flame retardant is magnesium hydroxide (MH); in parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; in step (2), during the preparation of component B, 30-50 parts of a curing agent are first added, and then 5-10 parts of APP and 10-15 parts of MH are added, and the mixture is stirred at a stirring speed of 100-200 r / min for 30-60 minutes to preliminarily mix the flame retardant and the curing agent, and then 5-10 parts of a plasticizer, 1-5 parts of a filler, and 0.1-0.5 parts of a defoaming agent are added, and the stirring is continued to be uniform to obtain component B containing a flame retardant.

[0010] Preferably, in step (1), two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared. The phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP), and the metal hydroxide flame retardant is magnesium hydroxide (MH). In parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; wherein 40%-60% of the total amount of the flame retardant is added to component A, and the remaining part is added to component B; and then the preparation steps of components A and B in step (2) are followed respectively.

[0011] Preferably, in step (1), the magnesium hydroxide is surface-modified magnesium hydroxide, and the modification method is to coat the surface of the magnesium hydroxide with stearic acid, and the steps are as follows: S1. The amount of stearic acid added is 2%-5% of the mass of magnesium hydroxide. First, stearic acid is slowly added to ethanol and dissolved under stirring. The concentration is controlled at 10%-20%. The stirring speed is 200-300r / min and heated to 40-60°C until the stearic acid is completely dissolved to form a stearic acid solution. S2, adding 10-15 parts of magnesium hydroxide to the above stearic acid solution, reacting at 60-80°C for 1-3h under a stirring speed of 300-500r / min, so that the stearic acid molecules are adsorbed and coated on the surface of the magnesium hydroxide; S3. After the reaction is completed, the product in step S2 is filtered to obtain a coated product, and the coated product is washed 2-3 times with ethanol to remove unreacted stearic acid and other impurities. During each washing, an equal volume of ethanol is used as the product in step S2; S4. Finally, the washed coated product is dried in an oven at 80-100° C. to a constant weight to obtain magnesium hydroxide with the surface coated with stearic acid.

[0012] Preferably, in step (1), the magnesium hydroxide is surface-modified magnesium hydroxide, and the modification method is to first use stearic acid for preliminary coating, and then use a silane coupling agent for secondary coating, and at the same time, add a polymer layer with a buffering effect between the two coating layers, and the steps are as follows: Q1. Dry the magnesium hydroxide powder in an oven at 100-120°C for 2-4h; Q2, using industrial grade stearic acid with a purity of not less than 95%, dissolving the stearic acid in anhydrous ethanol to prepare a stearic acid solution with a mass fraction of 5%-10%, so as to carry out a subsequent coating reaction with magnesium hydroxide; Q3. Prepare the silane coupling agent into an aqueous solution with a mass fraction of 2%-5%, and hydrolyze it for 30-60 minutes before use to activate the active groups of the silane coupling agent; Q4, dissolving the polymer in deionized water to prepare a polymer solution with a mass fraction of 1%-3%; Q5. Preliminary coating with stearic acid: Slowly add the dried magnesium hydroxide powder to the stearic acid solution, and react in a constant temperature water bath at 50-70°C for 1-2h under the condition of stirring at a speed of 300-500r / min; Q6. After the reaction in Q5 is completed, the magnesium hydroxide coated with stearic acid is separated from the solution by centrifugation or filtration, and then repeatedly washed with deionized water for 3-5 times to remove the unreacted stearic acid and organic solvent remaining on the surface, and the washed stearic acid-coated magnesium hydroxide is dried in an oven at 60-80° C. for 2-3 hours to obtain a magnesium hydroxide product preliminarily coated with stearic acid for standby use; Q7, Intermediate layer polymer coating: Adding stearic acid-coated magnesium hydroxide to a polymer solution, reacting at room temperature for 1-1.5 hours under a stirring speed of 200-400 r / min; separating the magnesium hydroxide coated with the intermediate layer polymer by centrifugation or filtration, and then drying in an oven at 50-70° C. for 2-3 hours to obtain an intermediate layer-coated magnesium hydroxide product for standby use; Q8, Silane coupling agent secondary coating: Add the magnesium hydroxide coated with the intermediate layer to the hydrolyzed silane coupling agent solution, and react in a constant temperature water bath at 60-80°C for 2-3h under the condition of stirring speed of 300-500r / min; Q9. After the reaction in Q8 is completed, the magnesium hydroxide coated with the silane coupling agent is separated from the solution by centrifugation or filtration, and then repeatedly washed with deionized water for 3-5 times to remove the unreacted silane coupling agent and solvent remaining on the surface; Q10. Dry the washed silane coupling agent-coated magnesium hydroxide in an oven at 80-100° C. for 3-4 hours to obtain a final multi-layer coated modified magnesium hydroxide product.

[0013] Preferably, in Q1, the average particle size of the magnesium hydroxide powder is 4-6 μm.

[0014] Preferably, in Q2, the purity of the stearic acid is not less than 95%.

[0015] Preferably, in Q3, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550).

[0016] Preferably, in Q4, the polymer used as the intermediate layer material is polyvinyl alcohol (PVA).

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adds two raw materials, phosphorus-nitrogen flame retardant and metal hydroxide flame retardant, to jointly construct a flame retardant system and improve the flame retardant effect. Moreover, adding phosphorus-nitrogen flame retardant and metal hydroxide flame retardant to component A and component B respectively, compared with adding all of them to component A or component B, in terms of flame retardant performance, since the flame retardant is more evenly dispersed in the material system, during combustion, the flame retardant mechanisms such as ammonium polyphosphate forming a carbonized layer and magnesium hydroxide decomposition and absorption of heat can work more effectively and synergistically, improving the flame retardant performance of the whole material, and more effectively preventing the spread of flames, reducing the combustion rate and heat release compared to the flame retardant concentrated in a single component.

[0018] 2. The present invention uses stearic acid to coat the surface of magnesium hydroxide to form surface modification, which can solve the problem that due to the large differences in chemical structure and physical properties between phosphorus-nitrogen flame retardants and metal hydroxide flame retardants, phase separation may occur during the mixing process, resulting in the flame retardant being unable to be evenly dispersed in the material, affecting the flame retardant synergistic effect. It also avoids the problem that when the two flame retardants are mixed, the phosphorus-nitrogen flame retardant and the metal hydroxide flame retardant have poor compatibility in the polyurethane matrix, and after a period of storage, obvious stratification will occur.

[0019] 3. The present invention uses stearic acid for primary coating first, and then uses a silane coupling agent for secondary coating. At the same time, a polymer layer with a buffering effect is added between the two layers of coating to achieve multi-layer coating of magnesium hydroxide. The dispersibility of the multi-layer coated magnesium hydroxide in the polyurethane matrix is ​​significantly improved, and phase separation is not easy to occur. In addition, the stability of the coating layer can be improved through the intermediate polymer layer to enhance the anti-destruction ability of the coating layer. DETAILED DESCRIPTION

[0020] The technical solutions in the present invention will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Embodiment 1: A method for preparing a polyurethane reinforcement material, comprising the following steps: (1) Raw material preparation: Component A: Select polyether polyol with a molecular weight of 2000-3000, a hydroxyl value of 30-50 mgKOH / g, and a moisture content of less than 0.1%; add 50-70 parts of polyether polyol by weight to a reactor, add 5-10 parts of toluene diisocyanate (TDI), and 0.1-0.5 parts of a catalyst; Component B: prepare 30-50 parts of curing agent, 5-10 parts of plasticizer, 1-5 parts of filler with a particle size between 10-50 μm, and 0.1-0.5 parts of defoamer; (2) Preparation of intermediate materials: Preparation of component A: Heat the reactor containing polyether polyol to 80-100°C, slowly add toluene diisocyanate (TDI) under the condition of stirring at a speed of 200-300r / min, and react for 2-3h; then add the catalyst and continue the reaction for 1-2h until the isocyanate group (-NCO) content of the reaction system reaches 0.5%-2% by weight. After the reaction is completed, cool component A to room temperature and discharge the material for standby use; Preparation of component B: In another reaction kettle, add curing agent, plasticizer, filler and defoamer in sequence, stir evenly at a stirring speed of 100-200 r / min to obtain component B; (3) Material mixing: When in use, component A and component B are mixed in a mixer at a volume ratio of 1:1-1.5, the mixing time is 30-60s, and the stirring speed is 500-800r / min to obtain a polyurethane reinforcement material.

[0022] In the present embodiment, the main component of component A is a polyether polyol with a molecular weight of 2000-3000 and a hydroxyl value of 30-50 mgKOH / g and a moisture content of less than 0.1%. The selection of the molecular weight and hydroxyl value range helps to form a polyurethane with appropriate flexibility and strength. In coal mining, this can make the reinforcement material better adapt to the deformation of coal rock and prevent the destruction of the reinforcement material due to the slight movement and deformation of coal rock. Low moisture content ensures the high efficiency and stability of the reaction and avoids the side reaction of moisture and isocyanate affecting the material properties. TDI is a key raw material for forming a polyurethane network structure. It reacts with polyether polyol to generate polyurethane segments, giving the material good strength and adhesion. In coal mining, this high strength and adhesion can enhance the reinforcement effect on coal rock, improve the integrity of coal rock, prevent the slab and roof of coal rock, and ensure the safety of mining operations. Adding 0.1-0.5 parts of a catalyst can accelerate the reaction speed, shorten the reaction time, and improve production efficiency. In coal mining, the rapid preparation of reinforcement materials can promptly process areas that need reinforcement, reduce downtime during the mining process, and improve mining efficiency.

[0023] In component B, 30-50 parts of curing agent can promote the curing process of the material, so that the final reinforcement material can achieve the required mechanical properties faster. In the underground environment of coal mines, rapid curing can play a reinforcing role in a shorter time, improve the bearing capacity of coal rock, and ensure the stability of the tunnel. 5-10 parts of plasticizer can improve the flexibility of the material and prevent the reinforcement material from being brittle due to the dynamic deformation of coal rock. During coal mining, the coal rock will produce certain deformation and vibration due to the impact of mining activities. The presence of plasticizer enables the reinforcement material to withstand these dynamic loads without failure, thereby improving the durability of the reinforcement material. 1-5 parts of filler (particle size between 10-50μm) can reduce costs and adjust the physical properties of the material, such as hardness and density. In coal mining, suitable fillers help adjust the strength and density of the reinforcement material to better match the properties of coal rock and avoid interface damage caused by excessive differences in the properties of the reinforcement material and coal rock. 0.1-0.5 parts of defoamer can eliminate bubbles generated during the reaction and improve the density of the material. Dense reinforcement materials can more effectively resist gas penetration and water erosion in coal mining, and prevent gas outbursts and water damage to the reinforcement materials.

[0024] During the preparation of component A, the appropriate reaction temperature and stirring speed ensure the uniform mixing and full reaction of polyether polyol and TDI to form a stable prepolymer structure. This helps to generate component A with uniform performance and ensure the consistency of the performance of the final reinforcement material. In coal mining, reinforcement materials with consistent performance can provide uniform reinforcement effects and avoid failure of coal rock reinforcement due to local performance differences. Controlling the -NCO content within this range can adjust the hardness and flexibility of the final material to meet the needs of reinforcement materials for different coal seams and mining conditions. Low -NCO content can form a harder material suitable for areas with high stress; while higher -NCO content can provide a certain degree of flexibility to adapt to coal rock areas with certain deformation. The cooling step ensures the stability of the material, which is convenient for storage and subsequent mixing with component B. During transportation and storage underground in coal mines, the stable component A can ensure that its performance is not affected by temperature and can be used for reinforcement operations at any time.

[0025] Prepare component B in another reactor, stir evenly to ensure that each component is evenly distributed in component B, so that component B has consistent properties and ensures the quality stability of the final reinforcement material. In coal mining, a stable component B helps to improve the reliability of the reinforcement effect and reduce the safety hazards caused by fluctuations in material properties. In step (3) material mixing, the appropriate mixing ratio and conditions can ensure that components A and B are fully mixed to form a polyurethane reinforcement material with excellent performance. At the coal mining site, the mixing ratio of components A and B can be adjusted according to different reinforcement requirements to flexibly adjust the performance of the reinforcement material. Fast mixing time and high stirring speed ensure construction efficiency underground, allowing the reinforcement material to be quickly formed and function, reducing the impact on mining operations.

[0026] Example 2: Example 2 is based on Example 1. In Example 1, the reaction between component A and component B is an exothermic reaction, which tends to heat up the coal when it comes into contact with the coal. In addition, fire hazards may occur during coal mining, especially when gas outbursts or electrical equipment failures cause fires.

[0027] In order to solve the above problems, in the step (1) of this embodiment, two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared as component A; wherein the phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP), and the metal hydroxide flame retardant is magnesium hydroxide (MH). In parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; in the step (2), before preparing component A, APP and MH are put into a reaction kettle together with 50-70 parts of polyether polyol, and then the step (2) is continued to prepare component A containing flame retardant.

[0028] In this embodiment, the addition of APP and MH can improve the flame retardant properties of the reinforcement material, prevent the spread of fire, and protect the safety of underground personnel and equipment. Specifically, APP belongs to a phosphorus-nitrogen flame retardant. During the combustion process, it will release acidic substances such as phosphoric acid. These acidic substances can promote the formation of a carbonized layer on the surface of the polyurethane material. This carbonized layer can isolate oxygen and prevent the further progress of the combustion reaction. Magnesium hydroxide (MH) will decompose when heated and absorb a large amount of heat. This process can reduce the temperature of the surrounding environment, and the water vapor produced can also dilute the concentration of combustible gases, thereby inhibiting the spread of combustion and improving the safety of coal mine reinforcement materials in fire conditions.

[0029] Example 3: The technical solution of Example 3 is based on Example 1, and the technical problem to be solved by Example 3 refers to that of Example 2.

[0030] In the step (1) of the present embodiment, two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared as component B; wherein the phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP) and the metal hydroxide flame retardant is magnesium hydroxide (MH); in parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; in the step (2), during the preparation of component B, 30-50 parts of a curing agent are first added, and then 5-10 parts of APP and 10-15 parts of MH are added, and the mixture is stirred at a stirring speed of 100-200 r / min for 30-60 minutes to preliminarily mix the flame retardant and the curing agent, and then 5-10 parts of a plasticizer, 1-5 parts of a filler, and 0.1-0.5 parts of a defoaming agent are added, and the stirring is continued to be uniform to obtain component B containing a flame retardant.

[0031] In this embodiment, when the flame retardant is added to the B component, the flame retardant is added after the curing agent. First, the curing agent plays a key role in the curing reaction in the B component. After the flame retardant is added, it is stirred for 30-60 minutes at a stirring speed of 100-200r / min, mainly for preliminary mixing with the curing agent. In this process, the flame retardant mainly interacts with the curing agent, and does not participate in the reaction of polyether polyol and TDI as in the A component. The mixing of the flame retardant and the curing agent may change the activity of the curing agent, because APP and MH may adsorb or react with the active groups of the curing agent, thereby affecting the curing effect of the curing agent. From the perspective of flame retardant performance, after the flame retardant is added to the B component, its distribution in the polyurethane reinforcement material after mixing with the A component is different from that added to the A component. Since the flame retardant is mixed with other ingredients in the B component and then mixed with the A component, its dispersion uniformity in the material may be slightly worse. During combustion, the effects of APP forming a carbonized layer and MH decomposing and absorbing heat may be limited to a certain extent, because they may not be as tightly combined with the material matrix as in component A. However, through appropriate process operations such as stirring, the flame retardant can still play a certain flame retardant role in the material. In terms of the mechanical properties of the material, after the flame retardant is added to component B, since it mainly interacts with the curing agent first, it will change the properties of the curing agent, thereby affecting the curing process of the material. It may cause incomplete curing or over-curing of the material, affecting the strength, elasticity and other properties of the material. In addition, the presence of flame retardants in component B may affect the effects of other ingredients such as plasticizers, fillers and defoamers, for example, it may change the flexibility of the material (plasticizer effect) or the density of the material (filler effect).

[0032] Example 4: The technical solution of Example 4 is based on Example 1, and the technical problem to be solved by Example 4 refers to that of Example 2.

[0033] In the step (1) of the present embodiment, two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared. The phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP), and the metal hydroxide flame retardant is magnesium hydroxide (MH). In parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; wherein 40%-60% of the total amount of the flame retardant is added to component A, and the remaining part is added to component B; and then the preparation steps of components A and B in step (2) are followed respectively.

[0034] In this embodiment, adding the flame retardant to the A and B components respectively has corresponding advantages compared with adding all of them to the A or B components. Specifically, at the microscopic level, when the flame retardant is added to the A or B components, it is difficult to achieve a highly uniform dispersion of the flame retardant in the entire material system in a short time due to the limitations of the stirring time (30-60s) and stirring speed (500-800r / min) during the mixing process of the A and B components. However, when the flame retardant is added to the A and B components at a ratio of 40%-60%, the flame retardant can be initially dispersed in the reaction system of polyether polyol and toluene diisocyanate (TDI) when the A component is prepared, and the flame retardant can also be fully mixed with the curing agent, plasticizer, etc. when the B component is prepared. In this way, when the A and B components are mixed later, based on the initial uniform dispersion state of each of the two components, the flame retardant can achieve a more ideal microscopic dispersion effect in the final polyurethane reinforcement material, and the uniformity of the overall flame retardant performance of the material is improved. At the macro level, in actual application scenarios, such as coal mine tunnel reinforcement, the range of material coating or filling is large. Since the flame retardant is pre-dispersed in components A and B respectively, after mixing, it can ensure that the flame retardant properties of each part of the material are consistent over a large construction area, avoiding the problem of poor flame retardant effect in some areas due to local concentration or uneven dispersion of the flame retardant. In terms of the impact on the reaction of component A, when some flame retardants are added to component A, ammonium polyphosphate (APP) and magnesium hydroxide (MH) will participate in the reaction process of polyether polyol and TDI. For example, APP may interact with reactive groups, which helps to adjust the molecular structure and cross-linking degree of the product of component A, thereby affecting the thermal stability and mechanical properties of the material. However, if all the flame retardants are added to component A, it may interfere with the reaction excessively and affect the performance of the product. Adding an appropriate amount of flame retardant to component A can not only utilize its beneficial effects on the reaction, but also avoid excessive interference. In terms of the impact on component B and curing, adding the remaining flame retardant to component B can adjust the activity of the curing agent and the curing reaction process when mixed with the curing agent. If all the flame retardants are added to component B, the performance of the curing agent may change too much, affecting the curing effect of the material. Partial addition of component B can ensure that the curing agent works normally while allowing the flame retardant to better integrate into the material structure during the curing process and enhance the overall performance of the material. In terms of mechanical properties, the mechanical properties of the material are optimized by rationally distributing the flame retardant so that components A and B react and mix. In the reaction of component A, the flame retardant participates in adjusting the molecular chain structure and synergizes with the curing agent in component B, so that the material has appropriate hardness, toughness and strength after curing, meeting the requirements of mechanical properties of reinforced materials in coal mines and other scenarios. In terms of flame retardant properties, since the flame retardant is more evenly dispersed in the material system, during combustion, the flame retardant mechanisms such as the formation of a carbonized layer by ammonium polyphosphate and the decomposition and absorption of heat by magnesium hydroxide can work more effectively together to improve the overall flame retardant properties of the material. Compared with flame retardants concentrated in a single component, it can more effectively prevent the spread of flames, reduce the burning rate and heat release.

[0035] Example 5: Based on the above examples 2, 3, and 4, the compatibility of phosphorus-nitrogen flame retardants and metal hydroxide flame retardants in the polyurethane matrix may be poor. Due to the large differences in their chemical structures and physical properties, phase separation may occur during the mixing process, resulting in the flame retardant not being evenly dispersed in the material, affecting the flame retardant synergistic effect. For example, in some experiments, after the two flame retardants were mixed, after a period of storage, obvious stratification occurred.

[0036] In order to solve the above problem, in step (1), the magnesium hydroxide is surface-modified magnesium hydroxide, and the modification method is to coat its surface with stearic acid, and the steps are as follows: S1. The amount of stearic acid added is 2%-5% of the mass of magnesium hydroxide. First, stearic acid is slowly added to ethanol and dissolved under stirring. The concentration is controlled at 10%-20%. The stirring speed is 200-300r / min and heated to 40-60°C until the stearic acid is completely dissolved to form a stearic acid solution. S2, adding 10-15 parts of magnesium hydroxide to the above stearic acid solution, reacting at 60-80°C for 1-3h under a stirring speed of 300-500r / min, so that the stearic acid molecules are adsorbed and coated on the surface of the magnesium hydroxide; S3. After the reaction is completed, the product in step S2 is filtered to obtain a coated product, and the coated product is washed 2-3 times with ethanol to remove unreacted stearic acid and other impurities. During each washing, an equal volume of ethanol is used as the product in step S2; S4. Finally, the washed coated product is dried in an oven at 80-100° C. to a constant weight to obtain magnesium hydroxide with the surface coated with stearic acid.

[0037] In this embodiment, stearic acid coating can improve the surface properties of magnesium hydroxide and improve its dispersibility in the polyurethane system. In coal mine reinforcement materials, better dispersibility can make the flame retardant more evenly distributed and improve the overall flame retardant effect. At the same time, stearic acid coating can reduce the agglomeration of magnesium hydroxide, avoid uneven material properties and local defects caused by agglomeration, and enhance the overall performance and flame retardant effect of the reinforcement material.

[0038] Example 6: Based on the above examples 2, 3, and 4, the dispersibility of the surface-modified magnesium hydroxide in the polyurethane matrix is ​​significantly improved, and phase separation is not easy to occur. However, there are still technical problems of the integrity and stability of the coating layer. A multi-layer coating method can be used to improve the stability of the coating layer to enhance the anti-destruction ability of the coating layer.

[0039] In this embodiment, in order to solve the above technical problems, in the step (1), the magnesium hydroxide is surface-modified magnesium hydroxide, and the modification method is to first use stearic acid for preliminary coating, and then use a silane coupling agent for secondary coating, and at the same time, add a polymer layer with a buffering effect between the two coating layers, and the steps are as follows: Q1. Dry the magnesium hydroxide powder in an oven at 100-120°C for 2-4h; Q2, using industrial grade stearic acid with a purity of not less than 95%, dissolving the stearic acid in anhydrous ethanol to prepare a stearic acid solution with a mass fraction of 5%-10%, so as to carry out a subsequent coating reaction with magnesium hydroxide; Q3. Prepare the silane coupling agent into an aqueous solution with a mass fraction of 2%-5%, and hydrolyze it for 30-60 minutes before use to activate the active groups of the silane coupling agent; Q4, dissolving the polymer in deionized water to prepare a polymer solution with a mass fraction of 1%-3%; Q5. Preliminary coating with stearic acid: Slowly add the dried magnesium hydroxide powder to the stearic acid solution, and react in a constant temperature water bath at 50-70°C for 1-2h under the condition of stirring at a speed of 300-500r / min; Q6. After the reaction in Q5 is completed, the magnesium hydroxide coated with stearic acid is separated from the solution by centrifugation or filtration, and then repeatedly washed with deionized water for 3-5 times to remove the unreacted stearic acid and organic solvent remaining on the surface, and the washed stearic acid-coated magnesium hydroxide is dried in an oven at 60-80° C. for 2-3 hours to obtain a magnesium hydroxide product preliminarily coated with stearic acid for standby use; Q7, Intermediate layer polymer coating: Adding stearic acid-coated magnesium hydroxide to a polymer solution, reacting at room temperature for 1-1.5 hours under a stirring speed of 200-400 r / min; separating the magnesium hydroxide coated with the intermediate layer polymer by centrifugation or filtration, and then drying in an oven at 50-70° C. for 2-3 hours to obtain an intermediate layer-coated magnesium hydroxide product for standby use; Q8, Silane coupling agent secondary coating: Add the magnesium hydroxide coated with the intermediate layer to the hydrolyzed silane coupling agent solution, and react in a constant temperature water bath at 60-80°C for 2-3h under the condition of stirring speed of 300-500r / min; Q9. After the reaction in Q8 is completed, the magnesium hydroxide coated with the silane coupling agent is separated from the solution by centrifugation or filtration, and then repeatedly washed with deionized water for 3-5 times to remove the unreacted silane coupling agent and solvent remaining on the surface; Q10. Dry the washed silane coupling agent-coated magnesium hydroxide in an oven at 80-100° C. for 3-4 hours to obtain a final multi-layer coated modified magnesium hydroxide product.

[0040] More specifically, in Q1, the average particle size of the magnesium hydroxide powder is 4-6 μm.

[0041] More specifically, in Q2, the purity of the stearic acid is not less than 95%.

[0042] More specifically, in Q3, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550).

[0043] More specifically, in Q4, the polymer used as the intermediate layer material is polyvinyl alcohol (PVA).

[0044] In this embodiment, the magnesium hydroxide powder is dried in Q1 to remove moisture and ensure the smooth progress of the subsequent coating reaction. The use of high-purity stearic acid in Q2 can ensure the coating quality and avoid the influence of impurities on the coating effect. The use of hydrolyzed silane coupling agent in Q3 can better react with the hydroxyl groups on the surface of magnesium hydroxide to improve the coating effect. The polyvinyl alcohol (PVA) added in Q4 as an intermediate layer provides a buffering effect, which helps to improve the dispersibility of magnesium hydroxide in the material and its compatibility with the matrix. In the complex environment of coal mining, this multi-layer coating can improve the stability and durability of magnesium hydroxide in the reinforcement material and prevent it from agglomerating and precipitating. Multi-layer coating improves the comprehensive performance of magnesium hydroxide and improves its interface bonding with the polyurethane matrix, so that the reinforcement material can better maintain its flame retardant properties when it is subjected to mechanical stress and chemical erosion during the mining process, while improving the overall strength and stability of the reinforcement material, ensuring the long-term effectiveness of the reinforcement effect.

[0045] In the above embodiment, the quality of the modified magnesium hydroxide can be tested by the following method: 1. Microstructure analysis: Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to observe the microstructure of modified magnesium hydroxide, and the integrity, uniformity and bonding between the coating layers were analyzed. The results are as follows: project sample SEM observation results TEM observation results Examples 1-4 Unmodified magnesium hydroxide Irregular block particles, rough surface, obvious agglomeration, wide particle size distribution, some large particles exceed 10μm / Example 5 Stearic acid coated magnesium hydroxide The surface is relatively smooth, and the agglomeration is reduced. When magnified 5000 times, it can be seen that some particles have a thin coating layer on the surface, but the uniformity is slightly poor, and there is some uncoated surface in some parts. / Example 6 Multilayer coated magnesium hydroxide The particle surface presents a multi-layer structure, which is smooth and has significantly improved uniformity The three-layer structure is clear, from the inside to the outside, it is the magnesium hydroxide core, the middle polymer layer, and the outer silane coupling agent layer. The interface is clear and the coating layer is 20-50nm thick. 2. Thermogravimetric analysis (TGA): TGA is used to test the thermal stability of modified magnesium hydroxide and evaluate the decomposition of the coating at different temperatures to determine the stability of the coating. The results are as follows: project sample Initial decomposition temperature 400℃ weight loss rate 500℃ 600℃ illustrate Examples 1-4 Unmodified magnesium hydroxide About 340℃ About 30% / / Magnesium hydroxide decomposes to produce water and magnesium oxide Example 5 Stearic acid coated magnesium hydroxide About 320℃ About 35% There is still a certain amount of magnesium hydroxide that has not been decomposed / The decomposition of stearic acid causes the initial weight loss to be advanced, and the coating layer has a certain protective effect on magnesium hydroxide Example 6 Multilayer coated magnesium hydroxide About 300℃ About 25% / More residue Multi-layer coating is more effective in delaying the decomposition of magnesium hydroxide and has better stability at high temperatures 3. Dispersibility test: Add modified magnesium hydroxide to the polyurethane matrix, test its particle size distribution in the polyurethane by laser particle size analyzer, and evaluate its dispersibility; at the same time, observe the changes in the appearance and mechanical properties of the material to further verify the effect of the coating on the dispersibility and stability of magnesium hydroxide in the polyurethane matrix. The results are as follows: project sample Average particle size in polyurethane matrix Particle size greater than 50 μm Tensile Strength Elongation at break illustrate Examples 1-4 Unmodified magnesium hydroxide 20μm About 30% About 10MPa About 200% Poor dispersibility affects the mechanical properties of materials Example 5 Stearic acid coated magnesium hydroxide 15μm Down to 15% Increase to 15MPa Increased to 250% Stearic acid coating improves dispersibility and enhances material performance Example 6 Multilayer coated magnesium hydroxide 10μm Almost disappeared Reach 20MPa Reach 300% Multi-layer coating significantly improves dispersion and compatibility, and enhances the mechanical properties of materials Through the above experimental data, microstructure analysis shows that multi-layer coated magnesium hydroxide has a more uniform and complete coating structure, which is beneficial to improve its dispersibility and stability in the polyurethane matrix. Thermogravimetric analysis shows that multi-layer coating can effectively improve the thermal stability of magnesium hydroxide and delay its decomposition, which is of great significance to improving the performance of materials in high temperature environments. The dispersion test directly proves the effect of different coating methods on the dispersion of magnesium hydroxide in the polyurethane matrix. Multi-layer coating significantly improves the mechanical properties of the material, indicating that it has significant advantages in improving material properties. It has important application value for reinforcement materials that need to withstand complex stresses and possible high temperature environments in coal mining.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for preparing a polyurethane reinforcement material, characterized in that: The following steps are involved: (1) Raw material preparation: Component A: Select polyether polyol with a molecular weight of 2000-3000, a hydroxyl value of 30-50 mgKOH / g, and a moisture content of less than 0.1%; add 50-70 parts of polyether polyol by weight to a reactor, add 5-10 parts of toluene diisocyanate (TDI), and 0.1-0.5 parts of a catalyst; Component B: prepare 30-50 parts of curing agent, 5-10 parts of plasticizer, 1-5 parts of filler with a particle size between 10-50 μm, and 0.1-0.5 parts of defoamer; (2) Preparation of intermediate materials: Preparation of component A: Heat the reactor containing polyether polyol to 80-100°C, slowly add toluene diisocyanate (TDI) under the condition of stirring at a speed of 200-300r / min, and react for 2-3h; then add the catalyst and continue the reaction for 1-2h until the isocyanate group (-NCO) content of the reaction system reaches 0.5%-2% by weight. After the reaction is completed, cool component A to room temperature and discharge the material for standby use; Preparation of component B: In another reaction kettle, add curing agent, plasticizer, filler and defoamer in sequence, stir evenly at a stirring speed of 100-200 r / min to obtain component B; (3) Material mixing: When in use, component A and component B are mixed in a mixer at a volume ratio of 1:1-1.5, the mixing time is 30-60s, and the stirring speed is 500-800r / min to obtain a polyurethane reinforcement material.

2. The method for preparing a polyurethane reinforcement material according to claim 1, characterized in that: In the step (1), two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared as component A; Wherein, the phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP), and the metal hydroxide flame retardant is magnesium hydroxide (MH). In parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; In the step (2), before the preparation of component A, APP and MH are placed in a reaction kettle together with 50-70 parts of polyether polyol, and then component A containing a flame retardant is prepared according to step (2).

3. The method for preparing a polyurethane reinforcement material according to claim 1, characterized in that: In the step (1), two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared as component B; Among them, the phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP), and the metal hydroxide flame retardant is magnesium hydroxide (MH); in parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; In the step (2), during the preparation of component B, 30-50 parts of a curing agent are first added, and then 5-10 parts of APP and 10-15 parts of MH are added, and the mixture is stirred for 30-60 minutes at a stirring speed of 100-200 r / min to preliminarily mix the flame retardant and the curing agent, and then 5-10 parts of a plasticizer, 1-5 parts of a filler, and 0.1-0.5 parts of a defoaming agent are added, and the mixture is stirred evenly to obtain component B containing a flame retardant.

4. The method for preparing a polyurethane reinforcement material according to claim 1, characterized in that: In the step (1), two raw materials, a phosphorus-nitrogen flame retardant and a metal hydroxide flame retardant, are prepared. The phosphorus-nitrogen flame retardant is ammonium polyphosphate (APP), and the metal hydroxide flame retardant is magnesium hydroxide (MH). In parts by weight, according to the amount of polyether polyol used in step (1), 5-10 parts of APP and 10-15 parts of MH are prepared; Among them, 40%-60% of the total flame retardant amount is added to component A, and the remaining amount is added to component B; then the preparation steps of components A and B in step (2) are followed respectively.

5. A method for preparing a polyurethane reinforcement material according to any one of claims 2 to 4, characterized in that: In the step (1), the magnesium hydroxide is surface-modified magnesium hydroxide, and the modification method is to coat the surface of the magnesium hydroxide with stearic acid, and the steps are as follows: S1. The amount of stearic acid added is 2%-5% of the mass of magnesium hydroxide. First, stearic acid is slowly added to ethanol and dissolved under stirring. The concentration is controlled at 10%-20%. The stirring speed is 200-300r / min and heated to 40-60°C until the stearic acid is completely dissolved to form a stearic acid solution. S2, adding 10-15 parts of magnesium hydroxide to the above stearic acid solution, reacting at 60-80°C for 1-3h under a stirring speed of 300-500r / min, so that the stearic acid molecules are adsorbed and coated on the surface of the magnesium hydroxide; S3. After the reaction is completed, the product in step S2 is filtered to obtain a coated product, and the coated product is washed 2-3 times with ethanol to remove unreacted stearic acid and other impurities. During each washing, an equal volume of ethanol is used as the product in step S2; S4. Finally, the washed coated product is dried in an oven at 80-100° C. to a constant weight to obtain magnesium hydroxide with the surface coated with stearic acid.

6. A method for preparing a polyurethane reinforcement material according to any one of claims 2 to 4, characterized in that: In the step (1), the magnesium hydroxide is surface-modified magnesium hydroxide, and the modification method is to first use stearic acid for preliminary coating, and then use a silane coupling agent for secondary coating. At the same time, a polymer layer with a buffering effect is added between the two coating layers. The steps are as follows: Q1. Dry the magnesium hydroxide powder in an oven at 100-120°C for 2-4h; Q2, using industrial grade stearic acid with a purity of not less than 95%, dissolving the stearic acid in anhydrous ethanol to prepare a stearic acid solution with a mass fraction of 5%-10%, so as to carry out a subsequent coating reaction with magnesium hydroxide; Q3. Prepare the silane coupling agent into an aqueous solution with a mass fraction of 2%-5%, and hydrolyze it for 30-60 minutes before use to activate the active groups of the silane coupling agent; Q4, dissolving the polymer in deionized water to prepare a polymer solution with a mass fraction of 1%-3%; Q5. Preliminary coating with stearic acid: Slowly add the dried magnesium hydroxide powder to the stearic acid solution, and react in a constant temperature water bath at 50-70°C for 1-2h under the condition of stirring at a speed of 300-500r / min; Q6. After the reaction in Q5 is completed, the magnesium hydroxide coated with stearic acid is separated from the solution by centrifugation or filtration, and then repeatedly washed with deionized water for 3-5 times to remove the unreacted stearic acid and organic solvent remaining on the surface, and the washed stearic acid-coated magnesium hydroxide is dried in an oven at 60-80° C. for 2-3 hours to obtain a magnesium hydroxide product preliminarily coated with stearic acid for standby use; Q7, Intermediate layer polymer coating: Adding stearic acid-coated magnesium hydroxide to a polymer solution, reacting at room temperature for 1-1.5 hours under a stirring speed of 200-400 r / min; separating the magnesium hydroxide coated with the intermediate layer polymer by centrifugation or filtration, and then drying in an oven at 50-70° C. for 2-3 hours to obtain an intermediate layer-coated magnesium hydroxide product for standby use; Q8, Silane coupling agent secondary coating: Add the magnesium hydroxide coated with the intermediate layer to the hydrolyzed silane coupling agent solution, and react in a constant temperature water bath at 60-80°C for 2-3h under the condition of stirring speed of 300-500r / min; Q9. After the reaction in Q8 is completed, the magnesium hydroxide coated with the silane coupling agent is separated from the solution by centrifugation or filtration, and then repeatedly washed with deionized water for 3-5 times to remove the unreacted silane coupling agent and solvent remaining on the surface; Q10. Dry the washed silane coupling agent-coated magnesium hydroxide in an oven at 80-100° C. for 3-4 hours to obtain a final multi-layer coated modified magnesium hydroxide product.

7. The method for preparing a polyurethane reinforcement material according to claim 6, characterized in that: In Q1, the average particle size of the magnesium hydroxide powder is 4-6 μm.

8. The method for preparing a polyurethane reinforcement material according to claim 7, characterized in that: In Q2, the purity of the stearic acid is not less than 95%.

9. The method for preparing a polyurethane reinforcement material according to claim 8, characterized in that: In the Q3, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550); In the above-mentioned Q4, the polymer used as the intermediate layer material is polyvinyl alcohol (PVA).

10. A polyurethane reinforcement material, characterized in that: The polyurethane reinforcement material is prepared according to the method for preparing a polyurethane reinforcement material according to claim 9.