Fireproof magnesium oxide plate

Abstract

A fireproof magnesium oxide plate is prepared by mixing the following raw materials: 80-100 parts of magnesium oxide, 20-30 parts of anhydrous magnesium chloride, 10-20 parts of a fireproof heat-insulating flame retardant with water absorption and expansion performance, 20-30 parts of aluminum silicate fiber, 5-10 parts of sawdust, 10-15 parts of fly ash, 8-12 parts of glass magnesium plate crushed powder, 1.5-5 parts of non-woven fabric, and 10-50 parts of water. The fireproof heat-insulating flame retardant with water absorption and expansion performance is prepared from the following components: A component, which comprises elastic waterproof emulsion A, a carbon source, a carbon catalyst, a foaming agent, titanium white, elastic waterproof emulsion B, and appropriate amount of water; and B component, which comprises a water-retaining agent.

Description

Technical Field

[0001] This invention relates to a sheet material, and more particularly to a magnesium oxide sheet material and its manufacturing process. Background Technology

[0002] Magnesium oxide board is a new type of multifunctional building material. It combines the lightweight, flexibility, and reprocessing properties of wood-based organic boards with the fire resistance and water resistance of inorganic boards, making it suitable for use in wall construction, ceiling installation, floor lining, and other areas requiring fire protection. Currently, the main components of magnesium oxide boards are fiberglass mesh (the primary source of strength), magnesium oxide, magnesium chloride, perlite, filler fibers, and modifying additives. However, existing magnesium oxide boards suffer from moisture absorption and efflorescence, as well as embrittlement, affecting product quality and resulting in poor fire resistance and insulation, thus limiting their widespread application. Chinese patent application CN201310232377 attempted to use an expanded foam material composed of melamine, pentaerythritol, and ammonium polyphosphate, achieving a certain degree of flame retardancy. However, the flame retardant performance fails to meet the stringent requirements of the high-end market, such as a fire resistance rating of ≥4 hours.

[0003] Phosphorus-nitrogen intumescent flame retardant (IFR) materials are primarily composed of phosphorus and nitrogen, and contain no halogens. They are a new type of flame retardant material developed from its use as a flame-retardant coating. When IFR-containing polymer materials are heated and burned, a carbonaceous foam layer forms on the surface, providing heat insulation, oxygen barrier, smoke suppression, and preventing dripping. It exhibits excellent resistance to prolonged or repeated exposure to flames.

[0004] However, like other flame-retardant materials, the aforementioned IFR also suffers from poor compatibility with polymer materials and high hygroscopicity, which affects its performance and processing properties. Therefore, how to perform surface treatments on this material, such as microencapsulation or surface coating, is a topic of great interest to researchers.

[0005] East China University of Science and Technology's invention patent CN1847362A discloses a phosphorus-nitrogen-based intumescent flame-retardant material. Through microencapsulation, a dense capsule outer layer is formed on a highly dispersed flame-retardant powder via a reaction, isolating hygroscopic or water-soluble amine salts and phosphorus oxides from the external environment. The patent also discloses the following main types of surface treatment processes for phosphorus-nitrogen-based intumescent flame-retardant materials:

[0006] (1) US6444315 uses alkoxy-containing organosilicon to encapsulate phosphate amines and melamine salt flame retardant powders composed of oxalic acid, phthalic acid, isocyanic acid and borophosphate; the encapsulation method is to directly drip, spray or inject under heating conditions.

[0007] (2)JP-A 3-131 508 uses alkoxy-containing organosilicon to encapsulate polyphosphate amine flame retardant powder; the encapsulation method is to encapsulate it in suspension in the presence of organic solvent;

[0008] (3) CN1379078A uses an unsaturated polyester resin to microencapsulate a nitrogen-phosphorus intumescent flame retardant.

[0009] The methods mentioned in US6444315 and JP-A 3-131 are only applicable to ammonium phosphate and organic melamine materials; the method mentioned in CN1379078A has a complex process and affects the flame retardant properties of the materials.

[0010] Flame retardants containing polyhydroxy alcohols, such as pentaerythritol phosphates, dipentaerythritol phosphates, tripentaerythritol phosphates, pentaerythritol phosphites, and their corresponding melamine salts, which offer better flame retardancy than ammonium phosphates and organic melamine phosphates, also exhibit poor compatibility with polyolefins, high hygroscopicity, and negatively impact material performance and processing properties. Due to the introduction of polyhydroxy alcohols, these flame retardants react with phosphate compounds to form ester compounds. The surface of these materials cannot interact with the alkylalkoxy silicone oils mentioned in US6444315 and JP-A 3-131, thus failing to provide effective coating.

[0011] The inventors discovered in actual production that although the above-mentioned preparation method of phosphorus-nitrogen-based intumescent flame retardants achieves microencapsulation of the intumescent flame retardant, significantly improving its moisture-proof performance and compatibility with polymer substrates, flame retardant performance tests revealed that the silicone coating significantly affects the char-forming expansion of the IFR, resulting in a significantly lower expansion ratio compared to uncoated flame retardants. However, uncoated IFR flame retardants have poor hygroscopicity, and their performance is greatly reduced in water-containing environments over extended periods. Furthermore, the aforementioned material preparation process is relatively complex and costly, resulting in weak market competitiveness and preventing its large-scale application in the actual market to date.

[0012] Patent CN115975446A discloses a high-solids, high-strength fire-retardant coating, in which melamine, pentaerythritol, and ammonium polyphosphate are directly added during the coating preparation process. CN104532588A discloses a composite intumescent flame retardant composed of 50%-65% by weight of an acid source, 10%-20% by weight of an gas source, 15%-20% by weight of a carbon source, and 10%-20% by weight of a smoke suppressant, prepared using a high-speed mixer. It is evident that for phosphorus-nitrogen intumescent flame retardants that have not undergone microencapsulation, in actual production, either they are pre-blended into powder form or the aforementioned three raw materials are directly added during coating preparation. The above-mentioned flame retardants suffer from poor moisture resistance.

[0013] In addition, a fire-resistant and heat-insulating filler for steel fire doors has also appeared on the market, including component A and component B. Component A includes the following components by weight ratio: 57 parts of lightweight heat-insulating material, 11 parts of expandable graphite, 10 parts of bentonite, 10 parts of anhydrous gypsum, and 12 parts of additives. The lightweight heat-insulating material is expanded vermiculite, and the additives include 6 parts of polymeric water-retaining agent and 6 parts of redispersible latex. In this waterproof material, water molecules are retained within the filler by the polymeric water-retaining agent. The anhydrous gypsum hydrates to obtain dihydrate gypsum. When one side of the door panel is exposed to fire, the hardened filler absorbs heat and releases water molecules. The evaporation of these water molecules carries away a large amount of heat, effectively slowing down the heating rate of the entire door panel. At the same time, the expandable graphite expands when heated, filling the voids inside the filler after water is released, ensuring the integrity of the door panel's shape. In this type of coating, the water-retaining agent can absorb heat in the early stage and effectively slow down the heating rate. However, after a period of time, as all the water is consumed and evaporates, it creates voids in the filler, forming more heat conduction channels. This leads to a sharp drop in its fireproof and heat insulation capabilities. Although, as described in the patent, expandable graphite expands when heated and can fill the voids in the filler after water is released, the quantity of expandable graphite is limited, and the heat conduction channels for water vapor release are relatively random. Therefore, the effect of the expanded graphite in filling the voids is limited, and the fireproof and heat insulation effect needs to be further improved.

[0014] Meanwhile, when phosphorus-nitrogen intumescent flame retardants are used in combination with other flame retardants in certain coating or fireproof board formulations, the amount used is small and sparsely dispersed in the fireproof coating. The contact reaction of the charring agent, foaming agent and dehydration charring catalyst is not complete, so the flame retardant effect is poor.

[0015] When fireproof boards use phosphorus-nitrogen intumescent flame retardants, if conventional encapsulated phosphorus-nitrogen intumescent flame retardants are used, not only is the cost higher, but the outer shell also restricts the expansion of the flame retardant, resulting in poor flame retardant effect. Conventional phosphorus-nitrogen intumescent flame retardants also have poor moisture resistance, and their flame retardant effect decreases significantly over time.

[0016] Therefore, the market urgently needs a microencapsulated phosphorus-nitrogen intumescent flame retardant with a simple preparation process, low cost, and certain moisture resistance, and fireproof boards prepared using the above flame retardant. Summary of the Invention

[0017] This invention provides a fire-resistant magnesium oxide board with long-term stable fire resistance. The board is characterized by being composed of the following raw materials in parts by weight: 80-100 parts magnesium oxide; 20-30 parts anhydrous magnesium chloride; 10-20 parts a fire-retardant and heat-insulating agent with water absorption and expansion properties; 20-30 parts aluminum silicate fiber; 5-10 parts sawdust; 10-15 parts fly ash; 8-12 parts pulverized magnesium oxide board powder; 1.5-5 parts non-woven fabric; and 10-50 parts water. The fire-retardant and heat-insulating agent with water absorption and expansion properties is prepared from the following components:

[0018] Component A: Elastic waterproof emulsion A, carbon source, char-forming catalyst, foaming agent, titanium dioxide, elastic waterproof emulsion B, and appropriate amount of water; Component B: water-retaining agent; wherein, according to the mass ratio, the weight ratio of elastic waterproof emulsion A, carbon source, char-forming catalyst, foaming agent, titanium dioxide, and elastic waterproof emulsion B in component A is (1-1.5):(4-8):(1-3):(1-3):(1-3):(0.4-0.6); the carbon source is pentaerythritol, dipentaerythritol, or tripentaerythritol; the char-forming catalyst is ammonium polyphosphate; the foaming agent is dicyandiamide, ammonium oxalate, urea, or hexamethylenetetramine; wherein, emulsion A is tert-vinyl acetate emulsion or acetone emulsion, preferably Wacker EZ3066 emulsion or Rovace 661 emulsion; emulsion B is VAE emulsion, preferably Emultex FR 797; its preparation method is as follows:

[0019] (1) Add the carbon source, carbonization catalyst, foaming agent and titanium dioxide to a grinder in proportion and grind and disperse them;

[0020] (2) Add the powder, elastic waterproof emulsion A and water mixed in step (1) to a high-speed mixer for mixing;

[0021] (3) The mixture obtained in step (2) is subjected to screw extrusion granulation or spray drying granulation to obtain granular flame retardant semi-finished product;

[0022] (4) Place the granular flame retardant semi-finished product obtained in step (3) into a disperser and stir it while spraying the elastic waterproof emulsion B. Then dry it to obtain fireproof and heat-insulating filler A.

[0023] (5) The fireproof and heat-insulating filler A obtained in step (4) is blended with granular water-retaining agent to obtain the final product, fireproof, heat-insulating and flame-retardant agent.

[0024] The manufacturing process of fire-resistant magnesium oxide boards is characterized by the following steps:

[0025] (1) Put magnesium oxide, anhydrous magnesium chloride, flame retardant, and glass magnesium board powder into a mixer according to the weight of the magnesium oxide board and stir. At the same time, gas is introduced into the mixer to form bubbles and stir for 15 minutes.

[0026] (2) Add the aluminum silicate fiber, fly ash, sawdust, and the magnesium oxide board in the specified weight proportions to the mixer, continue mixing, and after uniform mixing for 30 minutes, prepare a slurry.

[0027] (3) Then introduce the prepared template into the press and lay the non-woven fabric.

[0028] (4) Take out the slurry from step (2) and add it to the press feed hopper. Then fill the slurry into the seamless fabric of the template and press it to the required size. After drying for 8-10 hours, it can be demolded.

[0029] (5) Place the cured board and template upside down, gently lift one corner of the mold with your hand, press the cured board with your hand and it will fall off. Then, starting from this corner, remove one side and lift the mold.

[0030] (6) Stack the molded boards together and cure them in the curing room for 3 days. Then put the products in a dry room for 10 days.

[0031] (7) Then cut off the four sides of the dried board according to the specifications.

[0032] The grinding and dispersing time is 1-2 hours.

[0033] In step (2), the high-speed mixer is either a high-speed kneader or a high-speed disperser.

[0034] In step (4), the stirring speed of the disperser is 200-600 r / min.

[0035] In step (4), the time for spraying the elastic emulsion while stirring is 0.5-2 hours.

[0036] In step (5), the mass ratio of fire-retardant and heat-insulating flame retardant to granular water-retaining agent is (2-3):1.

[0037] The water-retaining agent is a polyacrylic acid-based water-retaining agent.

[0038] Among them, the degree of polymerization of ammonium polyphosphate is greater than 600 and less than 1000.

[0039] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0040] (1) When phosphorus-nitrogen intumescent flame retardants are used in combination with other flame retardants in certain fireproof material formulations, the contact reaction of the charring agent, foaming agent and dehydration charring catalyst is not complete due to the small amount used and the sparse dispersion of each component in the fireproof coating. Therefore, the flame retardant effect is poor. In this application, the phosphorus-nitrogen intumescent flame retardant is pre-formed into flame retardant particles through a waterproof elastic emulsion, so that the three components of the phosphorus-nitrogen intumescent flame retardant can effectively contact and react with each other even with a small amount used, resulting in a good flame retardant effect.

[0041] (2) In this application, a waterproof and elastic acetic acid emulsion or acetic acid acrylic emulsion is used as a binder for flame retardant particles. Compared with the adhesive effect of general polymer emulsion, its more important role is that it has a certain degree of waterproofness. The continuously connected adhesive network inside the flame retardant particles can effectively coat most of the ammonium polyphosphate, effectively delaying the hygroscopic hydrolysis of ammonium polyphosphate.

[0042] (3) The flame retardant of this application also contains a water-retaining agent. When exposed to fire, the water molecules evaporate and carry away a large amount of heat, thereby effectively slowing down the heating rate of the entire fireproof material. At high temperatures, compared with semi-expanded vermiculite and expandable graphite, flame retardant A, which is composed of carbon source, char-forming catalyst and foaming agent, will exhibit a flow dynamic before the char-forming reaction. It can flow to the voids generated inside the fireproof material after water is separated, and finally form a carbon layer with a certain strength, ensuring the integrity of the shape and the overall strength of the fireproof material.

[0043] (4) The surface of the granular flame retardant obtained in step (3) is sprayed with elastic waterproof emulsion B and dried. The purpose is to form an elastic waterproof polymer film on the surface of the flame retardant, forming a capsule-like structure, further improving the waterproofness of the flame retardant, and preventing the large amount of water in the water-retaining agent from causing the polyphosphate ammonium to absorb moisture and decompose and become ineffective.

[0044] (5) Waterproof elastic emulsion A and waterproof elastic emulsion B have better overall performance in terms of elasticity and waterproofness compared to general emulsions. For general emulsions, such as acrylic emulsions, although the elasticity is acceptable, the waterproofness is poor. Polyurethane emulsions and epoxy resin emulsions have good waterproofness, but the elasticity is generally poor, which will significantly limit the carbonization and expansion of flame retardants, and have a greater negative impact on the flame retardant effect.

[0045] The technical solution of the invention will be described in detail below with reference to specific embodiments.

[0046] Example 1

[0047] The preparation method of fire-retardant and heat-insulating agent A, which has water absorption and expansion properties, includes the following steps:

[0048] (1) Add the carbon source pentaerythritol, the carbonization catalyst ammonium polyphosphate, the foaming agent dicyandiamide, and titanium dioxide to a grinder in a mass ratio of 4 kg: 2 kg: 2 kg: 2 kg and grind and disperse for 1.5 hours.

[0049] (2) Add the powder, elastic waterproof emulsion A and water mixed in step (1) to a high-speed mixer for mixing; the mass of elastic waterproof emulsion A and water is 1 kg and 0.5 kg respectively, and elastic waterproof emulsion A is EZ3066 emulsion. The high-speed mixer is a high-speed kneader.

[0050] (3) The mixture obtained in step (2) is subjected to screw extrusion granulation to obtain granular flame retardant semi-finished product;

[0051] (4) Place the granular flame retardant semi-finished product obtained in step (3) into a disperser and stir it while spraying 0.5 kg of elastic waterproof emulsion B (Emultex FR 797). Then dry it to obtain fireproof and heat-insulating filler A. The dispersion and stirring speed is 400 r / min.

[0052] (5) The fireproof, heat-insulating and flame-retardant agent obtained in step (4) is blended with granular polyacrylic acid water-retaining agent at a mass ratio of 2:1 to obtain the final product fireproof, heat-insulating and flame-retardant agent A.

[0053] Example 2

[0054] Based on Example 1, the amount of water used in step (2) was adjusted to 6 kg, the high-speed mixer was selected as a high-speed disperser, spray drying granulation was used in step (3), and the other preparation steps were the same to obtain flame retardant B.

[0055] Example 3

[0056] (1) The carbon source pentaerythritol, the carbon-forming catalyst ammonium polyphosphate, the foaming agent dicyandiamide, and titanium dioxide were added to a grinder in a mass ratio of 4 kg: 2 kg: 2 kg: 2 kg and ground and dispersed for 1.5 hours. Then, 5 kg of granular polyacrylic acid water-retaining agent was added and mixed. The mass ratio before and after was 2:1 to obtain the final product fireproof, heat-insulating and flame-retardant agent C.

[0057] Example 4

[0058] Based on Example 1, step (4) is omitted to obtain fireproof, heat-insulating and flame-retardant agent D.

[0059] Example 5

[0060] Based on Example 1, in step (1), 8 kg of expandable graphite and 2 kg of titanium dioxide were added to a grinder and ground and dispersed for 1.5 hours. Other preparation steps were the same to obtain flame retardant E.

[0061] Example 6

[0062] Based on Example 1, the elastic waterproof emulsion A and elastic waterproof emulsion B in steps (2) and (4) were replaced with the commercially available polyurethane waterproof emulsion Dispercoll U53, while the other preparation steps remained the same, to obtain flame retardant F.

[0063] Example 7

[0064] Fire-retardant magnesium oxide boards are prepared from the following raw materials: 90 kg of magnesium oxide; 25 kg of anhydrous magnesium chloride; 15 kg of fire-retardant, heat-insulating, and flame-retardant agent with water absorption and expansion properties; 25 kg of aluminum silicate fiber; 8 kg of sawdust; 12 kg of fly ash; 10 parts of glass magnesium board powder; 5 kg of non-woven fabric; and 30 kg of water. The specific preparation process is as follows:

[0065] (1) Put magnesium oxide, anhydrous magnesium chloride, flame retardant, and glass magnesium board powder into a mixer according to the weight of the magnesium oxide board and stir. At the same time, gas is introduced into the mixer to form bubbles and stir for 15 minutes.

[0066] (2) Add aluminum silicate fiber, fly ash, and sawdust to the mixer according to the weight proportions of the magnesium oxide board, continue mixing, and after uniform mixing for 30 minutes, prepare a slurry.

[0067] (3) Then introduce the prepared template into the press and lay the non-woven fabric;

[0068] (4) Take out the slurry from step (2) and add it to the press feed hopper. Then fill the slurry into the seamless fabric of the template and press it to the required size. After drying for 8-10 hours, it can be demolded.

[0069] (5) Place the cured board and the template upside down, gently lift one corner of the mold with your hand, press the cured board with your hand and it will fall off. Then, starting from this corner, remove one side and lift the mold.

[0070] (6) Stack the molded boards together and cure them in the curing room for 3 days. Then put the products in a dry room for 10 days.

[0071] (7) Then cut off the four sides of the dried board according to the specifications. Among them, fireproof magnesium oxide boards A, B, C, D, E and F are obtained by using fireproof, heat-insulating and flame-retardant agents A, B, C, D, E and F with water absorption and expansion properties prepared in Examples 1-6.

[0072] Fire resistance performance test

[0073] According to GB50045-95, the fire resistance limit (hours) is tested. A specimen reaches its fire resistance limit if any of the following conditions occur: Loss of stability: Axial deformation of the column member exceeds h / 100 (mm) or the axial deformation rate exceeds 3h / 1000 (mm / min). h is the initial fire-exposed height of the column member after loading and before the fire resistance test, in mm.

[0074] Sample type Flame retardant types Fire resistance limit Magnesium oxide sheet A Flame retardant A 5.4h Magnesium oxide sheet B Flame retardant B 5.6h Magnesium oxide sheet C Flame retardant C 3.6h Magnesium oxide sheet D Flame retardant D 4.5h Magnesium oxide sheet E Flame retardant E 3h Magnesium oxide sheet F Flame retardant F 4.4h

[0075] This demonstrates that the flame-retardant properties of fire-resistant magnesium oxide boards with added flame retardants modified by a special process are significantly improved.

Claims

1. A fire-resistant magnesium oxide board, characterized in that, It is composed of the following raw materials, with the following names and weight proportions: 80-100 parts magnesium oxide; 20-30 parts anhydrous magnesium chloride; 10-20 parts a fire-retardant and heat-insulating agent with water absorption and expansion properties; 20-30 parts aluminum silicate fiber; 5-10 parts sawdust; 10-15 parts fly ash; 8-12 parts crushed magnesium oxide board powder; 1.5-5 parts non-woven fabric; and 10-50 parts water. The fire-retardant and heat-insulating agent with water absorption and expansion properties is prepared from the following components. Composition: Component A: Elastic waterproof emulsion A, carbon source, char-forming catalyst, foaming agent, titanium dioxide, elastic waterproof emulsion B, and appropriate amount of water; Component B: water-retaining agent; wherein, according to the mass ratio, the weight ratio of elastic waterproof emulsion A, carbon source, char-forming catalyst, foaming agent, titanium dioxide, and elastic waterproof emulsion B in component A is (1-1.5):(4-8):(1-3):(1-3):(1-3):(0.4-0.6); the carbon source is pentaerythritol, dipentaerythritol, tripentaerythritol, etc. Pentaerythritol; the char-forming catalyst is ammonium polyphosphate; the foaming agent is dicyandiamide, ammonium oxalate, urea or hexamethylenetetramine; wherein, emulsion A is Wacker EZ3066 emulsion or Rovace 661 emulsion; emulsion B is VAE emulsion; the water-retaining agent is polyacrylic acid water-retaining agent; its preparation method is as follows: (1) add carbon source, char-forming catalyst, foaming agent and titanium dioxide into a grinding mill in proportion for grinding and dispersion; (2) add the powder mixed in step (1), elastic waterproof emulsion A and water. (2) Mix the mixture in a high-speed mixer; (3) Granulate the mixture obtained in step (2) by screw extrusion or spray drying to obtain granular flame retardant semi-finished product; (4) Place the granular flame retardant semi-finished product obtained in step (3) in a disperser while stirring and spraying elastic waterproof emulsion B, and then dry to obtain fireproof and heat-insulating filler A; (5) Blend the fireproof and heat-insulating filler A obtained in step (4) with granular water-retaining agent to obtain the final product fireproof and heat-insulating flame retardant.

2. The fire-resistant magnesium oxide board according to claim 1, characterized in that, In step (1), the grinding and dispersing time is 1-2 hours.

3. The fire-resistant magnesium oxide board according to claim 1, characterized in that, In step (2), the high-speed mixer is either a high-speed kneader or a high-speed disperser.

4. The fire-resistant magnesium oxide board according to claim 1, characterized in that, In step (4), the stirring speed of the disperser is 200-600 r / min.

5. The fire-resistant magnesium oxide board according to claim 1, characterized in that, In step (4), the time for spraying the elastic emulsion while stirring is 0.5-2 hours.

6. The fire-resistant magnesium oxide board according to claim 1, characterized in that, The degree of polymerization of ammonium polyphosphate is greater than 600 and less than 1000.