Flame-retardant epoxy resin composite diatomite soundproof cotton and preparation method thereof

Abstract

The present application relates to the technical field of sound insulation materials, and particularly relates to a flame-retardant epoxy resin composite diatomite sound insulation cotton and a preparation method thereof, which is composed of the following raw materials: epoxy resin, diatomite, composite flame retardant, coupling agent, curing agent, diluent, foaming agent and carbon forming agent; the composite flame retardant at least contains ammonium polyphosphate and melamine; the coupling agent is a silane coupling agent or a titanate coupling agent; the curing agent is methyl tetrahydrophthalic anhydride; the diluent is n-butyl glycidyl ether; the foaming agent is azodicarbonamide; and the carbon forming agent is pentaerythritol. The present application greatly improves the compatibility of diatomite and epoxy resin by optimizing the diatomite modification process and combining physical dispersion and chemical modification means, completely solves the pain point of filler agglomeration in the traditional process, fully releases the porous sound insulation potential of diatomite, and improves the sound absorption and sound insulation performance of the material.

Description

Technical Field

[0001] This invention relates to the field of sound insulation materials technology, specifically to a flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton and its preparation method. Background Technology

[0002] With the continuous improvement of sound insulation and safety requirements in fields such as construction, transportation, and industry, the market demand for flame-retardant sound insulation materials is constantly expanding. Epoxy resin-based foam materials, with their excellent mechanical properties and ease of processing, have become one of the mainstream choices in this field. However, existing products still have many technical shortcomings in practical applications. Traditional epoxy resin sound insulation materials mostly rely on a single matrix or simple filler composites, resulting in limited sound insulation effects and difficulty in meeting the stringent acoustic performance requirements of mid-to-high-end scenarios. Although some products have attempted to introduce diatomaceous earth as a sound insulation filler, the difference in surface polarity between diatomaceous earth and epoxy resin leads to poor compatibility and a tendency for aggregation. This not only fails to fully utilize the porous sound insulation properties of diatomaceous earth but also damages the internal structural integrity of the material, resulting in a decline in mechanical properties.

[0003] In terms of flame retardant performance, existing technologies generally employ single flame retardants or simple binary composite flame retardant systems, resulting in low flame retardant efficiency, poor smoke suppression, and the generation of large amounts of smoke during combustion, often accompanied by dripping, posing serious safety hazards. Simultaneously, the selection of coupling agents is relatively limited, lacking adaptability design for composite systems, further exacerbating problems such as uneven filler dispersion and insufficient interfacial bonding. Furthermore, the raw material ratios of existing products lack scientific justification, and process parameters have not been synergistically optimized, often resulting in a simple superposition of various technical steps. This leads to significant antagonistic effects between sound insulation, flame retardancy, and mechanical properties, making it difficult to achieve a balanced improvement in overall performance and failing to meet the diverse needs of different scenarios. Summary of the Invention

[0004] The primary objective of this invention is to provide a flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton and its preparation method.

[0005] A further objective of this invention is to provide a flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton, composed of the following raw materials: epoxy resin, diatomaceous earth, composite flame retardant, coupling agent, curing agent, diluent, foaming agent, and charring agent; wherein the composite flame retardant contains at least ammonium polyphosphate and melamine; the coupling agent is a silane coupling agent or a titanate coupling agent; the curing agent is methyltetrahydrophthalic anhydride; the diluent is n-butyl glycidyl ether; the foaming agent is azodicarbonamide; and the charring agent is pentaerythritol.

[0006] Preferably, the composite flame retardant further comprises aluminum hypophosphite, and the mass ratio of ammonium polyphosphate, melamine and aluminum hypophosphite is 3-4:2-3:1.

[0007] Preferably, the weight parts of each raw material are: 40-55 parts epoxy resin, 25-40 parts diatomaceous earth, 20-30 parts composite flame retardant, 0.8-2.5 parts coupling agent, 12-16 parts curing agent, 3-8 parts diluent, 2-5 parts foaming agent, and 2-5 parts charring agent.

[0008] Preferably, the silane coupling agent is one or both of KH-550 and KH-560; the titanate coupling agent is NDZ-101.

[0009] Preferably, the epoxy resin is E-51 type epoxy resin.

[0010] A method for preparing the flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton includes the following steps:

[0011] (1) Raw material pretreatment: After drying the diatomaceous earth, crush it and sieve it. Mix the composite flame retardant and the charring agent evenly and then grind them.

[0012] (2) Modification treatment: The pretreated diatomaceous earth is mixed with a coupling agent and surface modified by stirring or ultrasonic-assisted stirring to obtain modified diatomaceous earth;

[0013] (3) Matrix mixing: After heating the epoxy resin, add the diluent and stir evenly. Then add the modified diatomaceous earth, composite flame retardant and charring agent. Heat and increase the speed to continue stirring to obtain composite matrix slurry.

[0014] (4) Foaming molding: After cooling the composite matrix slurry, add curing agent and foaming agent, stir quickly and then inject into the mold, keep at constant temperature to foam and form a foam blank;

[0015] (5) Curing and shaping: Place the foam blank together with the mold into the oven, heat it step by step to cure it, cool it to room temperature, and demold to obtain the product.

[0016] Preferably, in step (1), the diatomaceous earth is dried at a temperature of 105-110℃ for 2-3 hours and then pulverized and passed through a 200-mesh sieve; the composite flame retardant and charring agent are ground to a particle size of ≤50μm.

[0017] Preferably, in step (2), when ultrasonic-assisted stirring is performed, the ultrasonic power is 300-350W, the stirring temperature is 60-70℃, and the stirring time is 30-50min; when high-speed stirring is performed, the stirring speed is 800-900r / min, and the stirring time is 30-35min.

[0018] Preferably, in step (3), the initial temperature of the epoxy resin is 60-70℃, and after adding the filler, the temperature is raised to 80-90℃. The stirring speed is 1000-1500r / min, and the stirring time is 60-90min.

[0019] Preferably, in step (4), the composite matrix slurry is cooled to 50-60℃, the mold temperature is maintained at 60-70℃, and the standing foaming time is 20-30min; in step (5), the step-by-step heating and curing is as follows: first, the temperature is raised to 120-130℃ and cured for 1.5-2.5h, and then the temperature is raised to 150-160℃ and kept for 1-2h.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention optimizes the diatomaceous earth modification process and combines physical dispersion and chemical modification methods to significantly improve the compatibility between diatomaceous earth and epoxy resin, completely solves the problem of filler agglomeration in traditional processes, fully releases the porous sound insulation potential of diatomaceous earth, and qualitatively improves the sound absorption and sound insulation performance of the material.

[0022] 2. This invention achieves a synergistic effect by rationally combining different types of flame retardants, which not only significantly improves flame retardant efficiency and durability, but also effectively inhibits smoke generation during combustion, eliminates dripping, and achieves more comprehensive safety protection, solving the problems of single and inefficient existing flame retardant systems.

[0023] 3. This invention can be adapted to the application requirements of various types of coupling agents, and at the same time, it scientifically defines the raw material ratio range to ensure that the material can maintain stable and excellent performance in different application scenarios, especially to meet the extreme requirements of high sound insulation and high flame retardancy.

[0024] 4. This invention achieves a synergistic improvement in sound insulation performance, flame retardant performance and mechanical performance through in-depth synergistic optimization of various process links such as matrix mixing, foaming molding, curing and shaping, avoiding the sacrifice of other performances caused by single performance optimization, and forming an integrated technical solution.

[0025] 5. The product of this invention has excellent comprehensive performance and a wide range of applications. It is suitable for sound insulation in ordinary buildings and can also meet the safety protection needs of special scenarios such as transportation and industry. It has good prospects for promotion and market value. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] Raw material ratio: 150 parts epoxy resin E-5, 30 parts diatomaceous earth, 3 parts composite flame retardant ammonium polyphosphate APP and melamine MCA by mass ratio of 3:120, 1 part silane coupling agent KH-550, 12 parts curing agent methyltetrahydrophthalic anhydride, 4 parts diluent n-butyl glycidyl ether, 2 parts foaming agent azodicarbonamide, and 3 parts charring agent pentaerythritol.

[0029] Preparation steps:

[0030] Raw material pretreatment: Dry the diatomaceous earth in a 105℃ oven for 2 hours to remove moisture, cool to room temperature, and then pulverize and pass through a 200-mesh sieve for later use; mix the composite flame retardant and charring agent evenly and grind them to a particle size ≤50μm for later use. Drying treatment can avoid the influence of moisture on subsequent mixing and foaming effects, and pulverizing and sieving can ensure that the filler particles are uniform and improve the dispersion effect.

[0031] Modification treatment: The pretreated diatomaceous earth was added to a high-speed mixer at 800 rpm, and coupling agent KH-550 was added. The mixture was stirred at room temperature for 30 minutes to complete the surface modification of the diatomaceous earth, resulting in modified diatomaceous earth. This step, through modification with a silane coupling agent, initially improves the compatibility between diatomaceous earth and epoxy resin, effectively alleviating the diatomaceous earth agglomeration problem commonly found in existing technologies, and laying the foundation for the uniform dispersion of subsequent components.

[0032] Matrix Mixing: Epoxy resin E-51 was added to a stirred tank, heated to 60°C, and stirred at 500 rpm for 10 minutes until the system was homogeneous. Then, modified diatomaceous earth, composite flame retardant, and charring agent were added, the temperature was raised to 80°C, the stirring speed was increased to 1000 rpm, and stirring was continued for 60 minutes to obtain a homogeneous composite matrix slurry. This step uses a step-by-step mixing method, first reducing the viscosity of the epoxy resin with a diluent, and then adding various fillers. This ensures uniform dispersion of each component and avoids localized agglomeration of the flame retardant and diatomaceous earth.

[0033] Foaming molding: Cool the composite matrix slurry to 50℃, add the curing agent and foaming agent, stir rapidly for 20 minutes, then pour the slurry into the mold, maintain the mold temperature at 60℃, and let it stand for 30 minutes to form a foam blank. Controlling the cooling temperature can avoid premature decomposition of the foaming agent due to high temperature, and standing foaming can ensure uniform foam pore size.

[0034] Curing and shaping: Place the foam blank along with the mold in a constant temperature oven, heat to 120℃ and cure for 2 hours, then heat to 150℃ and hold for 1 hour. After completion, cool to room temperature and demold to obtain flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton. Stepwise heating and curing ensures that the matrix is ​​fully cross-linked and cured, improving the mechanical properties and dimensional stability of the product.

[0035] Example 2:

[0036] Raw material ratio: 150 parts epoxy resin E-5, 30 parts diatomaceous earth, 3 parts composite flame retardant APP to MCA by mass ratio of 3:120, 1.5 parts silane coupling agent KH-560, 12 parts curing agent methyltetrahydrophthalic anhydride, 4 parts diluent n-butyl glycidyl ether, 2 parts foaming agent azodicarbonamide, and 3 parts charring agent pentaerythritol.

[0037] Preparation steps:

[0038] Raw material pretreatment: Same as in Example 1, the diatomaceous earth was dried and passed through a 200-mesh sieve, and the composite flame retardant and charring agent were mixed and ground until the particle size was ≤50μm.

[0039] Modification treatment: Pretreated diatomaceous earth was added to deionized water to prepare a 20% (w / w) suspension, which was ultrasonically dispersed for 20 min (300 W, 40 kHz). Then, silane coupling agent KH-560 was added, the temperature was raised to 60°C, and the mixture was stirred at 1000 r / min for 40 min with continuous ultrasonic assistance. After the reaction was complete, the mixture was filtered, and the filter cake was dried in a 110°C oven for 3 h. After cooling, it was pulverized and passed through a 200-mesh sieve to obtain highly dispersible modified diatomaceous earth. Ultrasonic assistance effectively breaks down diatomaceous earth aggregates, increases its specific surface area, and improves the grafting efficiency of the coupling agent. Furthermore, KH-560 contains epoxy groups, resulting in better compatibility with epoxy resins. Compared to the modification method in Example 1, this significantly improves the interfacial bonding force between diatomaceous earth and the matrix.

[0040] Matrix mixing: Similar to Example 1, the epoxy resin was heated to 60°C and a diluent was added, followed by fillers such as modified diatomaceous earth. The mixture was stirred for 60 minutes at 80°C and 1000 r / min. Thanks to the optimized modified diatomaceous earth, the filler dispersion was better, and the system uniformity was significantly improved.

[0041] Foaming molding: Same as in Example 1, add curing agent and foaming agent at 50°C, stir for 20 minutes and then pour into mold. Keep the mold temperature at 60°C and let it stand for 30 minutes to foam.

[0042] Curing and shaping: Same as in Example 1, cure at 120°C for 2 hours, then raise the temperature to 150°C and hold for 1 hour, then demold after cooling.

[0043] Example 3:

[0044] Based on the optimized modification process of Example 2, the binary composite flame retardant system used in Example 2 still has room for improvement in terms of flame retardant efficiency and smoke suppression effect, and there is a slight risk of dripping during combustion. Therefore, this example upgrades the composite flame retardant system by introducing aluminum hypophosphite (AP) as a synergistic flame retardant and adjusting the component ratio to construct a ternary synergistic flame retardant system. This aims to improve flame retardant durability, smoke suppression effect, and anti-dripping performance, while verifying the rationality of the flame retardant dosage range, thus overcoming the limitations of single flame retardant systems and low efficiency in existing technologies.

[0045] Raw material ratio: Epoxy resin E-5145 parts, diatomaceous earth 35 parts, composite flame retardant APP and MCA and AP in a mass ratio of 4:2:125 parts, silane coupling agent KH-560 1.5 parts, curing agent methyltetrahydrophthalic anhydride 14 parts, diluent n-butyl glycidyl ether 5 parts, foaming agent azodicarbonamide 3 parts, charring agent pentaerythritol 2 parts.

[0046] Preparation steps:

[0047] Raw material pretreatment: After drying, diatomaceous earth is passed through a 200-mesh sieve. The composite flame retardants APP, MCA, and AP are mixed and ground with the charring agent until the particle size is ≤50μm to ensure that the three flame retardants are evenly dispersed and to avoid local flame retardant concentrations that are too high or too low, which would affect the flame retardant effect.

[0048] Modification treatment: Similar to Example 2, modified diatomaceous earth was prepared using a composite modification method involving ultrasound assistance and KH-560. The optimized modification process was continued to ensure the basic dispersibility of the filler, guaranteeing the full integration of the flame retardant and the matrix.

[0049] Matrix mixing: Epoxy resin E-51 was added to a stirred tank, heated to 65°C, and diluted with a diluent and stirred for 10 minutes. Then, modified diatomaceous earth, composite flame retardant, and charring agent were added, the temperature was raised to 85°C, the stirring speed was increased to 1200 r / min, and stirring was continued for 70 minutes to ensure the flame retardant and matrix were fully bonded. Compared to Example 2, this example uses an increased amount of flame retardant and has a more complex composition. By appropriately increasing the stirring temperature and speed and extending the stirring time, the dispersion requirements of a high proportion of flame retardant are met, avoiding uneven flame retardant performance caused by flame retardant agglomeration.

[0050] Foaming molding: Cool the composite matrix slurry to 55℃, add the curing agent and foaming agent, stir rapidly for 25 minutes, pour into a mold, maintain the mold temperature at 65℃, and let it stand for 25 minutes to form a foam preform. By adjusting the mold temperature and foaming time, the foaming characteristics of the high flame retardant content system are adapted to ensure uniform foam pore size.

[0051] Curing and shaping: The foam preform is placed in an oven and cured at 125℃ for 1.5 hours, then heated to 155℃ and held for 1.5 hours. After cooling, it is demolded to obtain sound insulation cotton with superior flame retardant properties. By adjusting the curing temperature and time, the curing requirements of the high flame retardant content system are matched to ensure that the matrix is ​​fully cured, thereby improving mechanical properties and flame retardant stability.

[0052] Example 4:

[0053] Based on the optimized flame-retardant system and modification process of Example 3, Examples 2 and 3 both used silane coupling agents. However, the selection of coupling agents in the prior art is relatively limited, and the compatibility of different types of coupling agents with the composite system is not clearly defined. To address this, this example uses titanate coupling agent NDZ-101 to replace the silane coupling agent, while adjusting the dosage range to verify the impact of different types of coupling agents on the overall material performance, expanding the range of raw material selection protection, and further improving the adaptability of the technical solution.

[0054] Raw material ratio: 5 parts epoxy resin E-5, 25 parts diatomaceous earth, 22 parts composite flame retardant APP, MCA and AP in a mass ratio of 4:2:12, 0.8 parts titanate coupling agent NDZ-10, 13 parts curing agent methyltetrahydrophthalic anhydride, 3 parts diluent n-butyl glycidyl ether, 2 parts foaming agent azodicarbonamide, and 3 parts charring agent pentaerythritol.

[0055] Preparation steps:

[0056] Raw material pretreatment: Same as in Example 3, the diatomaceous earth was dried and passed through a 200-mesh sieve, and the composite flame retardant and charring agent were mixed and ground until the particle size was ≤50μm.

[0057] Modification treatment: Diatomaceous earth was added to a high-speed mixer, heated to 70℃, and stirred at 900 rpm. Titanate coupling agent NDZ-101 was added, and the mixture was stirred for 35 minutes to complete the modification. Subsequently, a small amount of diluent was added, and stirring continued for 10 minutes to further improve the compatibility between the modified diatomaceous earth and epoxy resin. Titanate coupling agents and silane coupling agents have different reaction characteristics. This step, by adjusting the modification temperature and stirring time, adapts to the grafting requirements of the titanate coupling agent. Compared to silane coupling agent modification, it can further improve the interfacial bonding strength between the filler and the matrix, and simultaneously verify the compatibility effect when the coupling agent dosage is 0.8 parts.

[0058] Matrix mixing: Similar to Example 3, the epoxy resin was heated to 65°C and a diluent was added, followed by the addition of modified diatomaceous earth, composite flame retardant, and charring agent. The mixture was stirred for 70 minutes at 85°C and a rotation speed of 1200 r / min. Based on the optimized mixing process of Example 3, the diatomaceous earth modified with the titanate coupling agent was ensured to be fully bonded to the flame retardant and the matrix.

[0059] Foaming molding: Same as in Example 3, add curing agent and foaming agent at 55°C, stir for 25 minutes and then pour into mold. Keep the mold temperature at 65°C and let it stand for 25 minutes to foam.

[0060] Curing and shaping: Same as in Example 3, cure at 125°C for 1.5 hours, then raise the temperature to 155°C and hold for 1.5 hours, then demold after cooling.

[0061] Example 5:

[0062] Raw material ratio: 140 parts epoxy resin E-5, 40 parts diatomaceous earth, 30 parts composite flame retardant APP, MCA and AP in a mass ratio of 3:2:130, 2.5 parts silane coupling agent KH-560, 16 parts curing agent methyltetrahydrophthalic anhydride, 8 parts diluent n-butyl glycidyl ether, 5 parts foaming agent azodicarbonamide, and 5 parts charring agent pentaerythritol.

[0063] Preparation steps:

[0064] Raw material pretreatment: After drying, diatomaceous earth is passed through a 200-mesh sieve. The composite flame retardant and charring agent are mixed and ground to a particle size ≤40μm. Using finer particle sizes adapts to the dispersion requirements of systems with high filler content, avoiding performance degradation caused by filler agglomeration.

[0065] Modification treatment: The same ultrasonic-assisted modification method as in Example 2 was adopted, with the ultrasonic power adjusted to 350W and the frequency to 40kHz. The amount of coupling agent was increased to 2.5 parts, and the stirring time was extended to 50min to ensure that the high proportion of diatomaceous earth was fully modified and to solve the dispersion problem under high filler content.

[0066] Matrix mixing: Epoxy resin E-51 was added to a stirred tank and heated to 70°C. Eight parts of diluent (at the upper limit of the mixing ratio) were added to reduce the viscosity of the high-filler system, and the mixture was stirred for 15 minutes. Subsequently, modified diatomaceous earth, composite flame retardant, and charring agent were added, the temperature was raised to 90°C, the stirring speed was increased to 1500 r / min, and stirring was continued for 90 minutes to ensure uniform dispersion of the system. Compared to the previous embodiment, this embodiment, by increasing the stirring temperature, speed, and time, is adapted to the viscous system with high filler and high flame retardant content, effectively solving the problem of mixing uniformity under extreme mixing ratios.

[0067] Foaming Molding: Cool the composite matrix slurry to 60℃, add curing agent and foaming agent. The curing agent dosage is up to 16 parts to match the curing requirements of the low epoxy content system, and the foaming agent dosage is up to 5 parts to ensure the foaming ratio of the high filler system. Stir rapidly for 30 minutes, pour into a mold, maintain the mold temperature at 70℃, and let it stand for 20 minutes to form a foam preform. By adjusting the foaming temperature, time, and mold temperature, the foaming characteristics of the extreme ratio system are adapted to ensure a uniform foam structure and avoid under- or over-foaming.

[0068] Curing and shaping: The foam preform is placed in an oven and cured at 130℃ for 2.5 hours, then heated to 160℃ and held for 2 hours. After cooling, it is demolded to obtain a product that meets the requirements for high sound insulation and high flame retardancy. By adjusting the curing process parameters, extending the curing time, and increasing the curing temperature, the high proportion of additive system is fully cured, ensuring the stability of the product's mechanical properties and flame retardant properties.

[0069] Comparative Example 1:

[0070] Raw material ratio: 180 parts epoxy resin E-5, 3 parts composite flame retardant APP to MCA by mass ratio of 120 parts, 1 part silane coupling agent KH-550, 12 parts curing agent methyltetrahydrophthalic anhydride, 4 parts diluent n-butyl glycidyl ether, 2 parts foaming agent azodicarbonamide, and 3 parts charring agent pentaerythritol.

[0071] This comparative example is a typical solution of existing epoxy resin flame-retardant foam materials, which does not contain diatomaceous earth. It corresponds to existing flame-retardant and sound-insulating materials that do not contain diatomaceous earth, and is used to compare and verify the necessity of diatomaceous earth as the core sound-insulating filler.

[0072] Preparation steps: Except for the absence of diatomaceous earth pretreatment and modification steps, the other steps are the same as in Example 1.

[0073] Comparative Example 2:

[0074] Raw material ratio: 150 parts epoxy resin E-5, 30 parts unmodified diatomaceous earth, 20 parts single flame retardant APP, 1 part silane coupling agent KH-550, 12 parts curing agent methyltetrahydrophthalic anhydride, 4 parts diluent n-butyl glycidyl ether, 2 parts foaming agent azodicarbonamide, and 3 parts charring agent pentaerythritol.

[0075] This comparative example is a simple combination of existing diatomaceous earth modified epoxy resin technology and single flame retardant technology, without using the diatomaceous earth modification process and composite flame retardant system of the present invention, and is used to compare and verify the technical value of the core technical features of the present invention.

[0076] Preparation steps: Except for the diatomaceous earth, which was not modified and was added directly after drying, the other steps were the same as in Example 1.

[0077] Comparative Example 3:

[0078] Raw material ratio: 130 parts epoxy resin E-5, 45 parts diatomaceous earth, 3 parts APP to 135 parts composite flame retardant (mass ratio 3:135), 0.3 parts silane coupling agent KH-550, 7 parts curing agent methyltetrahydrophthalic anhydride, 1 part diluent n-butyl glycidyl ether, and 0.5 parts foaming agent azodicarbonamide.

[0079] The raw material amounts used in this comparative example all exceed the protection range of the formulation of this invention, and do not contain charring agents. This corresponds to unreasonable formulation designs in the prior art and is used to compare and verify the scientific validity of the raw material formulation range of this invention.

[0080] Preparation steps: Same as in Example 1.

[0081] Comparative Example 4:

[0082] Raw material ratio: Same as in Example 2. Although the raw material ratio of this comparative example is the same as that of Example 2, it uses existing conventional preparation processes, does not introduce ultrasonic-assisted modification, and the process parameters deviate from the optimization range of this invention. It is used to compare and verify the necessity of optimizing the process parameters of this invention.

[0083] Preparation steps: Except for the modification treatment which was not ultrasonically assisted, only stirred at room temperature for 40 minutes, and the matrix mixing temperature was 50℃ and the curing temperature was 100℃, the other steps were the same as in Example 2.

[0084] Comparative Example 5:

[0085] Raw material ratio: Same as in Example 3. The raw material ratio of this comparative example is the same as that of Example 3, but it adopts the simple superposition method of diatomaceous earth modification and flame retardant addition in the prior art, without optimizing the synergy of each process step (the modification treatment adopts the single stirring modification of Example 1, and the matrix mixing adopts the process parameters of Example 1). It is used to compare and verify the technical advantages of the integrated optimization scheme of the present invention, indicating that the present invention is not a simple superposition of the prior art.

[0086] Preparation steps: The modification treatment is the same as in Example 1, the matrix mixing is the same as in Example 1, and the foaming molding and curing are the same as in Example 3.

[0087] Comprehensive performance tests were conducted on the products prepared in Examples 1-5 and Comparative Examples 1-5. Typical performance data of similar products in the prior art (including single epoxy resin flame-retardant foam, unoptimized diatomaceous earth composite sound insulation materials, and simple combinations of existing technologies) were collected for reference. Test items covered sound insulation performance (sound absorption coefficient, sound insulation), flame retardancy performance (oxygen index OI, vertical flammability rating UL94, smoke density rating SDR), and mechanical properties (tensile strength, compressive strength). This comprehensive evaluation of the product's overall performance provides reliable data support for verifying the advantages of the present invention. All tests were conducted by qualified third-party testing institutions, and the testing process strictly followed the corresponding standards and specifications, ensuring the authenticity and reliability of the test results.

[0088] Test standards and methods:

[0089] (1) Sound absorption coefficient: The test was conducted in accordance with GB / T18696.2-2002 "Measurement of sound absorption coefficient and acoustic impedance in acoustic impedance tubes - Part 2: Transfer function method" with a test frequency of 125-4000Hz and the average sound absorption coefficient was taken.

[0090] Sound insulation: The test was conducted in accordance with GB / T19889.3-2005 "Acoustic Buildings and Building Components Sound Insulation Measurement Part 3: Laboratory Measurement of Airborne Sound Insulation of Building Components", with a test frequency of 100-3150Hz, and the weighted sound insulation RW was used.

[0091] (2) Oxygen Index (OI): The test was conducted in accordance with GB / T2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test" with an ambient temperature of 23℃±2℃.

[0092] (3) Vertical flammability rating: Tested according to UL94-2013 "Standard Test Method for Flammability of Plastics", with a test sample thickness of 10 mm. The flammability rating is divided into V-0, V-1, V-2 and no rating.

[0093] (4) Smoke density grade SDR: The test was conducted in accordance with GB / T8323.2-2022 "Plastic smoke generation - Part 2: Determination of smoke density by single chamber method", with a test time of 4 minutes, and the highest smoke density grade was taken.

[0094] (5) Tensile strength: The test was conducted in accordance with GB / T1040.1-2006 "Determination of tensile properties of plastics - Part 1: General Rules", with a test speed of 5 mm / min and the sample being dumbbell-shaped.

[0095] (6) Compressive strength: The test was conducted in accordance with GB / T8813-2022 "Determination of compressive properties of rigid foamed plastics". The test speed was 2 mm / min, and the compressive strength was taken when the compression deformation was 10%.

[0096] The test results are shown in Table 1 below:

[0097] Table 1:

[0098]

[0099] The test results in Table 1 are analyzed as follows:

[0100] The performance of each embodiment shows a clear progressive optimization effect, exhibiting excellent overall performance. In Example 2, after optimizing the diatomaceous earth modification method based on Example 1, the average sound absorption coefficient increased by 12.9%, tensile strength increased by 25%, and smoke density level decreased by 6.7%. This demonstrates that the modification process using ultrasonic assistance and a suitable coupling agent can effectively improve the dispersibility and interfacial bonding of the filler, while also improving the smoke suppression effect, thus solving the problem of insufficient modification by simple room temperature stirring.

[0101] Example 3, based on the optimized modification process of Example 2, upgraded the composite flame retardant system by introducing aluminum hypophosphite (AP) to construct a ternary synergistic flame retardant system. This resulted in a 10.8% increase in the oxygen index and a 16.7% decrease in smoke density, achieving a drip-free V-0 flame retardant rating. This significantly improved the flame retardant performance and smoke suppression effect, overcoming the limitation of low efficiency in binary composite flame retardant systems. Example 4, after replacing the titanate coupling agent with NDZ-101, maintained excellent performance across all aspects, with an average sound absorption coefficient of 0.67, an oxygen index of 34.1%, and a tensile strength of 3.2 MPa. This verified the good compatibility of the present invention's technical solution with different types of coupling agents and expanded the selection space for raw materials.

[0102] Example 5 uses the limit value of the raw material ratio protection range, and the average sound absorption coefficient reaches 0.73, the weighted sound insulation reaches 48dB, and the oxygen index reaches 38.5%, all of which are better than the previous examples. This shows that the raw material ratio and process parameters of the present invention can be well adapted to the extreme demand scenarios of high sound insulation and high flame retardancy. The ratio protection range is scientific and reasonable, and the process adaptability is strong.

[0103] The overall performance of each embodiment of the present invention is significantly better than that of the comparative examples. Comparative Example 1, as a diatomaceous earth-free solution, has an average sound absorption coefficient and weighted sound insulation that are much lower than those of the embodiments of the present invention, by 43.5%-52.1% and 33.3%-41.7% respectively, while its smoke density level is 33.3%-66.7% higher. This fully demonstrates the importance of diatomaceous earth as a core sound insulation filler. The present invention effectively improves the problem of insufficient sound insulation performance by introducing diatomaceous earth and optimizing its dispersibility.

[0104] Comparative Example 2 is a simple combination scheme that does not employ the core technology of this invention. It uses unmodified diatomaceous earth and a single flame retardant, with an oxygen index of only 27.5%, no clear flammability rating, and a tensile strength of only 2.1 MPa, which is far inferior to the embodiments of this invention. This shows that the diatomaceous earth modification process and composite flame retardant system of this invention have been carefully optimized and are not simply a combination of technologies. They can achieve a breakthrough improvement in performance and solve the performance antagonism problem.

[0105] Comparative Example 3, which uses raw materials exceeding the protection range of the formulation of this invention and does not contain charring agent, has tensile strength and compressive strength of only 1.8 MPa and 0.8 MPa, respectively, which are far lower than those of the embodiments of this invention, by 31.0%-38.9% and 44.4%-56.3%, respectively. This verifies the scientificity and rationality of the raw material formulation range of this invention. An unreasonable formulation design can easily lead to a decline in product performance.

[0106] Comparative Example 4 uses an unoptimized conventional process without ultrasonic-assisted modification and the process parameters deviate from the optimization range of this invention. Its performance is inferior to that of Example 2, with an average sound absorption coefficient that is 21.4% lower, an oxygen index that is 6.6% lower, and a tensile strength that is 28.6% lower. This shows that the optimization of the process parameters of this invention is of great significance, and conventional processes are difficult to meet the requirements of high dispersibility and synergistic improvement of multiple performances.

[0107] Comparative Example 5 is a simple superposition scheme without optimized process synergy, and its performance is still inferior to Example 3, with an average sound absorption coefficient that is 23.5% lower and a smoke density level that is 48.6% higher. This further shows that the technical solution of the present invention is an integrated solution formed by deep adaptation and synergistic optimization of each process link, which can achieve a better overall performance level.

[0108] Overall, this invention achieves a synergistic improvement in sound insulation, flame retardancy, and mechanical properties by optimizing the diatomaceous earth modification process, constructing a synergistic flame retardant system, and expanding the range of raw material ratios and process adaptability. The various technical links cooperate and work together, resulting in significant comprehensive performance advantages for the product, which has good application value and promotion prospects.

[0109] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton, characterized in that, Composed of the following raw materials: epoxy resin, diatomaceous earth, composite flame retardant, coupling agent, curing agent, diluent, foaming agent, and charring agent; the composite flame retardant is ammonium polyphosphate, melamine, and aluminum hypophosphite, wherein the mass ratio of ammonium polyphosphate, melamine, and aluminum hypophosphite is 3-4:2-3:1; the coupling agent is a silane coupling agent or a titanate coupling agent; the curing agent is methyltetrahydrophthalic anhydride; the diluent is n-butyl glycidyl ether; the foaming agent is azodicarbonamide; and the charring agent is pentaerythritol. The weight parts of each raw material are as follows: epoxy resin 40-55 parts, diatomaceous earth 25-40 parts, composite flame retardant 20-30 parts, coupling agent 0.8-2.5 parts, curing agent 12-16 parts, diluent 3-8 parts, foaming agent 2-5 parts, and charring agent 2-5 parts. The epoxy resin is type E-51 epoxy resin.

2. The flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton according to claim 1, characterized in that, The silane coupling agent is one or both of KH-550 and KH-560; the titanate coupling agent is NDZ-101.

3. A method for preparing flame-retardant epoxy resin composite diatomaceous earth sound insulation cotton as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) Raw material pretreatment: After drying the diatomaceous earth, crush it and sieve it. Mix the composite flame retardant and the charring agent evenly and then grind them. (2) Modification treatment: The pretreated diatomaceous earth is mixed with a coupling agent and surface modified by stirring or ultrasonic-assisted stirring to obtain modified diatomaceous earth; (3) Matrix mixing: After heating the epoxy resin, add the diluent and stir evenly. Then add the modified diatomaceous earth, composite flame retardant and charring agent. Heat and increase the speed to continue stirring to obtain composite matrix slurry. (4) Foaming molding: After cooling the composite matrix slurry, add curing agent and foaming agent, stir quickly and then inject into the mold, keep at constant temperature to foam and form a foam blank; (5) Curing and shaping: Place the foam blank together with the mold into the oven, heat it step by step to cure it, cool it to room temperature, and demold to obtain the product.

4. The preparation method according to claim 3, characterized in that, In step (1), the diatomaceous earth is dried at a temperature of 105-110℃ for 2-3 hours and then pulverized and passed through a 200-mesh sieve; the composite flame retardant and charring agent are ground to a particle size of ≤50μm.

5. The preparation method according to claim 3, characterized in that, In step (2), when ultrasonic-assisted stirring is performed, the ultrasonic power is 300-350W, the stirring temperature is 60-70℃, and the stirring time is 30-50min; when high-speed stirring is performed, the stirring speed is 800-900r / min, and the stirring time is 30-35min.

6. The preparation method according to claim 3, characterized in that, In step (3), the initial temperature of the epoxy resin is 60-70℃, and after adding the filler, the temperature is raised to 80-90℃. The stirring speed is 1000-1500r / min, and the stirring time is 60-90min.

7. The preparation method according to claim 3, characterized in that, In step (4), the composite matrix slurry is cooled to 50-60℃, the mold temperature is maintained at 60-70℃, and the standing foaming time is 20-30min; in step (5), the step-by-step heating and curing is as follows: first heat to 120-130℃ and cure for 1.5-2.5h, then heat to 150-160℃ and keep warm for 1-2h.

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