A polyurethane flexible foamed sound absorbing material, sandwich structure sound absorbing material and preparation method

Abstract

The application provides a polyurethane flexible foaming sound-absorbing material, a sandwich structure sound-absorbing material and a preparation method. The preparation raw material of the polyurethane flexible foaming sound-absorbing material comprises the following components: A material, B material, a catalyst and a foaming agent; the A material is polytetrahydrofuran; the B material is diphenylmethane diisocyanate; the mass ratio of the A material, the B material, the catalyst and the foaming agent is 100:60-70:0.02-0.04:0.1-0.15. The polyurethane flexible foaming sound-absorbing material has excellent sound-absorbing capacity, the average sound-absorbing coefficient in the full frequency band of 50-500 KHz is greater than or equal to 0.8, and the polyurethane flexible foaming sound-absorbing material also has good waterproofness and pressure resistance. The sandwich structure sound-absorbing material has lower density and thickness and higher sound-absorbing coefficient, and meanwhile, the support layer provides surplus mechanical properties, so that the demand of the underwater torpedo system for the light weight, high strength and strong sound-absorbing capacity of the platform is met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sound-absorbing materials, and particularly relates to a polyurethane flexible foaming sound-absorbing material, a sandwich structure sound-absorbing material and a preparation method. BACKGROUND

[0002] Due to the fast energy attenuation of electromagnetic waves in water, sound waves become the only energy form capable of long-distance propagation in the ocean and the only information carrier for completing underwater communication, positioning, search and other tasks. Under the complex sound field environment of the ocean, underwater sound-absorbing materials are an important way to eliminate excess sound waves and control the propagation of sound waves, and have important applications in sonar stealth, underwater acoustic communication and other dual-use technologies. The development and progress of sonar detection technology have put forward higher and higher requirements for sound-absorbing materials for ships. The first generation of sound-absorbing materials is mainly made of chlorobenzene rubber and styrene-butadiene rubber sound-absorbing tiles, which mainly rely on the composite cavity structure to attenuate underwater acoustic signals, and the sound absorption coefficient is often small, especially under low frequency conditions, which cannot effectively make the submarine stealth. The second generation of sound-absorbing materials made of polyurethane has the advantages of strong designability, low temperature resistance, corrosion resistance, good impedance matching with water medium, good self-damping performance and the like. It can not only effectively absorb sound energy, but also reduce the propagation of mechanical vibration noise of the ship body, and has the effects of sound absorption and vibration reduction.

[0003] With the in-depth development of sonar detection technology, modern sound-absorbing materials gradually develop in the directions of water pressure resistance: 3-5 MPa, low frequency: 0.5-2 kHz, and wide high frequency band: 50-550 kHz. However, the sound-absorbing performance of the existing sound-absorbing materials in the wide high frequency range is insufficient, the sound-absorbing material has high density and thickness, and the water pressure resistance performance is insufficient when used underwater, which cannot meet the use requirements of the outer protective layer of the underwater weapon in the wide high frequency range. SUMMARY

[0004] The technical problem solved by the present application is to provide a polyurethane flexible foaming sound-absorbing material, a sandwich structure sound-absorbing material and a preparation method. The polyurethane flexible foaming sound-absorbing material has excellent sound absorption capacity, and the average sound absorption coefficient in the full frequency band of 50-500 KHz is greater than or equal to 0.8. Moreover, the sound-absorbing material also has good waterproofness and pressure resistance. The sandwich structure sound-absorbing material has lower density and thickness, and higher sound absorption coefficient. Meanwhile, the support layer provides surplus mechanical properties, which meets the requirements of light weight, high strength and strong sound absorption capacity of the underwater mine system platform.

[0005] In order to solve the above problems, the present application provides a polyurethane flexible foaming sound-absorbing material, and the preparation raw materials thereof comprise the following components:

[0006] A material, B material, catalyst and foaming agent; the A material is polytetrahydrofuran; the B material is diphenyl methane diisocyanate; the mass ratio of A material, B material, catalyst, foaming agent is 100:60-70:0.02-0.04:0.1-0.15.

[0007] Preferably, the density of the polyurethane flexible foaming sound-absorbing material is 0.7-0.9g / cm 3 .

[0008] Preferably, the preparation raw material further comprises a filler; the mass of the filler accounts for 2.5%-15% of the total mass of the preparation raw material; the filler is at least one of hollow microbeads, flaky mica, metal oxide powder and polypropylene fiber.

[0009] The second aspect of the present application provides a preparation method of the above-mentioned polyurethane flexible foaming sound-absorbing material, comprising the following steps:

[0010] Mixing the preparation raw material of the polyurethane flexible foaming sound-absorbing material to obtain a mixed material; then injecting the mixed material into a mold to perform foaming, solidification, and obtaining the polyurethane flexible foaming sound-absorbing material.

[0011] Preferably, further comprising:

[0012] When injecting the mixed material into the mold, the volume of the polyurethane flexible foaming sound-absorbing material is fixed by the mold, and the density of the polyurethane flexible foaming sound-absorbing material is changed by controlling the injection amount of the preparation raw material.

[0013] Preferably, the foaming temperature is 60-70℃;

[0014] Before mixing the preparation raw material of the polyurethane flexible foaming sound-absorbing material, further comprising: loading the raw materials in the preparation raw material except the B material into an A material tank, preheating the A material tank to 48-52℃; loading the B material into a B material tank, and preheating the B material tank to 41-45℃.

[0015] The third aspect of the present application provides a sandwich structure sound-absorbing material, comprising:

[0016] At least two composite material support layers and a polyurethane flexible foaming material layer arranged between the two composite material support layers; the composite material support layer is made of reinforcing fibers and a resin matrix; the polyurethane flexible foaming material layer is made of the above-mentioned polyurethane flexible foaming sound-absorbing material; the thickness of the composite material support layer is 0.1-1mm, and the thickness of the polyurethane flexible foaming material layer is 4-8mm.

[0017] The fourth aspect of the present application provides a preparation method of the above-mentioned sandwich structure sound-absorbing material, comprising the following steps:

[0018] The preparation method comprises the following steps: preparing a prepreg of a composite support layer to obtain a first support layer prepreg; disposing a polyurethane flexible foaming sound-absorbing material on the first support layer prepreg to form a polyurethane flexible foaming material layer; disposing another prepreg of a composite support layer on the polyurethane flexible foaming material layer to obtain a second support layer prepreg; and curing and forming the obtained structure to obtain the sandwich structure sound-absorbing material.

[0019] Preferably, the preparation method further comprises the following steps:

[0020] Before the polyurethane flexible foaming sound-absorbing material is disposed on the first support layer prepreg, the surface of the polyurethane flexible foaming sound-absorbing material in contact with the first support layer prepreg and the second support layer prepreg is polished, and then the surface is treated by using a coupling agent.

[0021] Preferably, the step of preparing the prepreg of the composite support layer comprises the following steps:

[0022] A layer of fiber reinforced material is provided; and a resin glue solution is dip-coated on the layer of fiber reinforced material to obtain the prepreg of the composite support layer.

[0023] The resin glue solution comprises epoxy resin, a curing agent and a diluent; and the mass ratio of the epoxy resin, the curing agent and the diluent is 10:0.5-1.5:1.5-2.5.

[0024] The viscosity of the resin glue solution is 0.35 mPa·s-0.75 mPa·s.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The polyurethane flexible foaming sound-absorbing material is prepared by foaming A material and B material raw materials in a specific ratio in the presence of a catalyst and a foaming agent. The sound-absorbing material has excellent sound-absorbing capacity, with an average sound-absorbing coefficient of ≥0.8 in the full frequency range of 50-500 KHz. In addition, the sound-absorbing material also has good waterproofness and pressure resistance, with a hardness of up to 55A and low density, meeting the use requirements of the sound stealth of the outer protective layer of a wideband high-frequency underwater weapon.

[0027] The sandwich structure sound-absorbing material has lower density and thickness and higher sound-absorbing coefficient than the prior art sound-absorbing material. In addition, the support layer provides surplus mechanical properties, meeting the requirements of lightweight high strength and strong sound-absorbing capacity of the mine system stay platform, and being beneficial to the weight reduction of the mine system stay platform and the further improvement of the sound stealth capacity in the wideband high-frequency range. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a structural schematic diagram of the sandwich structure sound-absorbing material described in the embodiments of the present application.

[0029] 1-composite material support layer; 2-composite material support layer; 3-polyurethane flexible foaming material layer. DETAILED DESCRIPTION

[0030] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0031] The first aspect of the embodiments of the present application provides a polyurethane flexible foaming sound-absorbing material, and the preparation raw materials thereof include the following components:

[0032] A material, B material, catalyst and foaming agent; the A material is polytetrahydrofuran; the B material is diphenylmethane diisocyanate; the mass ratio of the A material, the B material, the catalyst and the foaming agent is 100:60-70:0.02-0.04:0.1-0.15.

[0033] The polyurethane flexible foaming sound-absorbing material is prepared by foaming the A material and the B material in the presence of the catalyst and the foaming agent in a specific ratio. The sound-absorbing material has excellent sound-absorbing capacity, and the average sound-absorbing coefficient in the full frequency range of 50-500 KHz is greater than or equal to 0.8. In addition, the sound-absorbing material also has good waterproofness and pressure resistance, the hardness can reach 55A, the density is low, and the use requirements of the sound-absorbing material for the outer protective layer of the underwater weapon are met.

[0034] Preferably, the polyurethane flexible foaming sound-absorbing material is prepared from the following components:

[0035] A material, B material, catalyst and foaming agent; the A material is polytetrahydrofuran; the B material is diphenylmethane diisocyanate; the mass ratio of the A material, the B material, the catalyst and the foaming agent is 100:65:0.03:0.125.

[0036] Preferably, the density of the polyurethane flexible foaming sound-absorbing material is 0.7-0.9 g / cm 3The present application has found that the sound absorption capacity of the polyurethane flexible foaming sound absorption material changes significantly with the change of density. In the case of the same product formula, the greater the density, the more the number of molecular chains existing in the same volume, the greater the energy loss of entanglement and disentanglement between molecular chains, and the more conducive to the dissipation of sound energy of the material, so as to improve the sound absorption performance of the material. However, when the number of molecular chains in the system is too large, the free volume available for the movement of molecular chains in the system is reduced, and the number of pores is also reduced, which is not conducive to the dissipation of sound waves, so as to reduce the sound absorption performance of the material. It has been found through experimental research that the sound absorption performance of the material is the best when the density is within the above range. Further preferably, the density of the polyurethane flexible foaming sound absorption material is 0.9 g / cm 3 .

[0037] In some embodiments, the raw materials for preparation further include a filler. The addition of the filler in the polyurethane flexible foaming sound absorption material matrix can make the material system exist microcavities, and the polymer network can uniformly distribute the filler particles. When the sound wave acts on the sound absorption material, the polymer network will produce local expansion and compression deformation, which increases the relaxation absorption effect of the material on sound energy, and the addition of the filler can also greatly improve the mechanical properties of the material.

[0038] Preferably, the filler is at least one of hollow microbeads, flaky mica, metal oxide powder, and polypropylene fibers. The addition of the filler can enhance the internal friction of the whole system, thereby increasing the loss of the material to the incident sound wave. Hollow microbeads have the effect of increasing internal friction and scattering sound waves on the synthesized material, can increase the degree of microphase separation, and improve the viscous sound absorption and heat conduction sound absorption effect. In addition, the acoustic filler with a flaky and hollow structure can increase the energy dissipation of the elastomer network structure and the added molecules. In addition, the flaky mica has an orientation effect under the action of external force, which can increase the internal friction between the substrate and the flaky mica, so as to further widen the effective damping temperature range and thus better attenuate sound energy. Most inorganic fillers improve the sound absorption capacity of the substrate by enhancing the interfacial force between the substrate and the filler and the internal friction of the system. Different shapes, types, and sizes of filler particles have different effects on the substrate.

[0039] Preferably, the filler is at least one of hollow microbeads and flaky mica. Further preferably, the filler is hollow microbeads or a mixture of hollow microbeads and flaky mica.

[0040] Preferably, the mass of the filler accounts for 2.5% to 15% of the total mass of the preparation raw materials. The addition of the filler will hinder the collision probability of the reactive groups, inhibit the foaming reaction, and cause a shielding effect. When the amount of the filler is small, the inhibition effect on the foaming reaction is weak, the foaming reaction speed is fast, the foaming amount is large, and the sound absorption performance of the matrix can be improved. When the amount of the filler is gradually increased, the inhibition effect on the foaming reaction is enhanced, but the high loss caused by the filler itself will still improve the sound absorption performance. However, when the improvement reaches a critical value, the inhibition effect becomes more and more obvious, the foaming reaction cannot proceed smoothly, the sound absorption coefficient decreases, and even the sample cannot be formed, and obvious cracks appear on the surface. When the mass percentage is used, the sound absorption performance of the material can be better.

[0041] In some embodiments, the main functions of the catalyst are to promote chain growth reactions, to promote the reaction rate of certain chemical reactions in the reaction system, to adjust the competition reaction, to promote the main reaction, to slow down or inhibit the side reaction, and the like. Commonly used catalysts can be divided into tertiary amine (such as triethylenediamine, N-methyl imidazole, dimethylcyclohexylamine, etc.) and organometallic (such as dioctyltin bisulfate, stannous octoate, dibutyltin dilaurate, etc.) according to ingredients. Most of the catalysts can meet the product use requirements, but in order to ensure sufficient operation time during manual foaming, the catalyst should have a certain delay effect, and the requirement can be appropriately relaxed if machine foaming is used. Preferably, the catalyst is one or a combination of several of triethylenediamine, bis(dimethylaminoethyl) ether, and dimethyl ethanolamine.

[0042] In some embodiments, the foaming agent can be water, fluorine-based foaming agent (such as monofluorodichloroethane), cyclopentane, and physical foaming agent (such as carbon dioxide), etc. Preferably, the foaming agent is water.

[0043] The second aspect of the present application provides a preparation method of the above-mentioned polyurethane flexible foaming sound absorption material, comprising the following steps:

[0044] The preparation raw materials of the polyurethane flexible foaming sound absorption material are mixed to obtain a mixture; then the mixture is injected into a mold to perform foaming, curing, and obtain the polyurethane flexible foaming sound absorption material.

[0045] In some embodiments, before mixing the preparation raw materials of the polyurethane flexible foaming sound absorption material, the following steps are further included: loading the raw materials except the B material into an A material tank, and preheating the A material tank to 48-52℃; loading the B material into a B material tank, and preheating the B material tank to 41-45℃. Among them, the filler is added to the A material tank, and the stirring function is started to stir uniformly.

[0046] In some embodiments, the foaming can be selected according to actual conditions, and the foaming can be manually foamed or foamed by a foaming machine, which is operable and has low operation difficulty. When the foaming machine is used for foaming, the foaming machine needs to be set before foaming, the water tank is heated to 60°C, the pipeline is heated to 40°C, the A material stirring and circulation are turned on, and the B material stirring and circulation are turned on. The mold water circulation heating is turned on, and the temperature is 65°C. The preheating time is 1 hour.

[0047] In some embodiments, before the mixed material is injected into the mold, the inner surface of the mold is coated with an oily release agent, and the coating method can be selected from spraying, wiping or other methods. The mold surface needs to be uniformly and completely coated, which can be coated once or multiple times.

[0048] Preferably, it further comprises: when the mixed material is injected into the mold, the volume of the polyurethane flexible foaming sound-absorbing material is fixed by the mold, and the density of the polyurethane flexible foaming sound-absorbing material is changed by controlling the injection amount of the preparation raw material. The mold volume is fixed, so the volume of the finally prepared polyurethane flexible foaming sound-absorbing material is fixed, and the density of the obtained sound-absorbing material can be adjusted by changing the injection amount of the preparation raw material.

[0049] In some embodiments, when the injection amount of the preparation raw material is controlled, the specific operation is: first, the time required for A material and B material to reach the target weight is calculated according to the flow rate of the foaming machine, then the volume of the sample piece is fixed by using a mold with excellent sealing performance, and the injection time of the raw material is controlled to obtain sound-absorbing materials with different densities.

[0050] Further, when the injection amount of the preparation raw material is controlled, the specific operation is: the determination method of A material and B material flow is: 1. Remove the filling gun head and stirring, set the filling gun head to only A material state, and weigh the outflowing A material as m1. 2. Set the filling gun head to only B material state, and weigh the outflowing B material as m2. 3. According to the foaming density, volume and ratio, calculate the required A material weight as M1, and the required B material weight as M2. 4. According to the estimated value, set the A material flow as a. 5. Calculate the A material flow that should be set as: 6. Calculate the B material flow that should be actually set as: 7. Calculate the B material equipment flow that should be actually set as:

[0051] Preferably, the mold is a steel film. The upper and lower parts of the mold are equipped with a water bath heating system to ensure that the inside of the mold is uniformly heated to the foaming reaction temperature, so as to provide the activation energy required for the reaction to start. At the same time, the surface quality of the mold has a great influence on the surface quality of the sample piece, and the surface finish of the forming surface should reach above △5. In order to ensure that the excess gas released during the reaction can be smoothly discharged instead of forming large size bubbles inside or on the surface of the product, the upper end surface of the mold should be reserved for gas discharge, and the size should be determined according to the mold volume. ​

[0052] In some embodiments, the foaming temperature is 60-70℃. Further preferably, the foaming temperature is 65℃. After clamping, the curing is performed at 65℃ for 20-30min, and then demolding is performed.

[0053] As shown in Figure 1 The third aspect of the embodiment of the present application provides a sandwich structure sound absorption material, comprising:

[0054] At least two composite material support layers 1, 2 and a polyurethane flexible foam material layer 3 arranged between the two composite material support layers 1, 2; the composite material support layer is made of reinforced fibers and a resin matrix; and the polyurethane flexible foam material layer is made of the above-mentioned polyurethane flexible foam sound absorption material.

[0055] Compared with the existing sound absorption material, the sandwich structure sound absorption material has lower density and thickness, higher sound absorption coefficient, and the support layer provides surplus mechanical properties, which meets the requirements of light weight, high strength, and strong sound absorption capacity of the underwater mine system stay platform, and is beneficial to the weight reduction of the mine system stay platform and the further improvement of the sound stealth ability under wide frequency and high frequency.

[0056] In some embodiments, the reinforcing material should be a fiber woven material with no reflection or weak reflection effect on sound waves, and one or more of glass fiber, polyester fiber, carbon fiber, or aramid fiber can be used. Specifically, glass fiber high-strength cloth, quartz fiber fabric, etc. can be used. Preferably, the reinforcing fibers of the composite material support layer are glass fiber high-strength cloth.

[0057] In some embodiments, the resin matrix should be a room temperature curing resin to avoid secondary heating of the foaming core layer and affect the performance of the core layer. Preferably, the resin matrix uses low-cost epoxy resin.

[0058] In some embodiments, the thickness of the glass fiber high-strength cloth can be adjusted. Preferably, the target thickness of the support layer is less than 0.5mm on a single side. Considering that the thickness of the reinforcing layer will increase after the glue liquid is soaked, the thickness of the selected reinforcing material should not exceed 0.3mm on a single side, and 0.2mm is preferred. Further preferably, the thickness of the reinforcing fibers in the two composite material support layers is 0.2mm and 0.1mm, respectively.

[0059] The fourth aspect of the present application provides a preparation method of the above-mentioned sandwich structure sound absorption material, comprising the following steps:

[0060] The prepreg of the composite material support layer is prepared to obtain a first support layer prepreg; the polyurethane flexible foaming sound-absorbing material is arranged on the first support layer prepreg to form a polyurethane flexible foaming material layer; another prepreg of the composite material support layer is arranged on the polyurethane flexible foaming material layer to obtain a second support layer prepreg; and the obtained structure is cured and formed to obtain the sandwich structure sound-absorbing material.

[0061] Preferably, the preparation method further comprises:

[0062] Before the polyurethane flexible foaming sound-absorbing material is arranged on the first support layer prepreg, the surface of the polyurethane flexible foaming sound-absorbing material in contact with the first support layer prepreg and the second support layer prepreg is polished, and then surface treatment is performed using a coupling agent.

[0063] Specifically, the surface of the polyurethane flexible foaming sound-absorbing material is polished using sandpaper. Specifically, the surface of the polyurethane flexible foaming sound-absorbing material is polished to form a cross-shaped pattern using sandpaper with a mesh size of 80-300, which is preferable. After polishing, the dust generated by polishing is cleaned using alcohol or acetone.

[0064] Preferably, when surface treatment is performed using a coupling agent, specifically, a solution of the coupling agent is used for treatment. The solution of the coupling agent includes the coupling agent, ethanol and water, and the ratio of the coupling agent:ethanol:water is 0.2:0.72:0.08. After mixing, the mixture is fully stirred and left to stand for 30 min before use. Further, the coupling agent can be a coupling agent with a model number of kh550.

[0065] Preferably, the prepreg of the composite material support layer specifically comprises the following steps:

[0066] A layer of fiber reinforced material is provided; and a resin glue solution is dip-coated on the layer of fiber reinforced material to obtain the prepreg of the composite material support layer.

[0067] Preferably, the resin glue solution includes an epoxy resin, a curing agent and a diluent; and the mass ratio of the epoxy resin, the curing agent and the diluent is 10:0.5-1.5:1.5-2.5. Further preferably, the mass ratio of the epoxy resin, the curing agent and the diluent is 10:1:2. Further, the epoxy resin can be an epoxy resin with a model number of E51; the curing agent can be tetraethylenepentamine; and the diluent can be a linear epoxy with a model number of 3660. The resin curing speed of this system is relatively fast, and resin coating needs to be completed within 30 min at room temperature.

[0068] The viscosity of the resin glue solution is 0.35 mPa·s-0.75 mPa·s; and the boiling point is between 60℃ and 130℃. In this way, the resin has good wettability and does not appear to be separated during the glue brushing process.

[0069] Preferably, the brush material used for impregnation requires that it is not easy to agglomerate and shed after being impregnated with resin glue, and does not affect the subsequent impregnation effect, such as pig bristles, wool, chemical fiber, nylon cotton fiber, etc.

[0070] Preferably, the obtained structure is cured and formed, and vacuum bag pressing is specifically adopted. Further, when vacuum bag pressing, the system gas is removed by connecting a vacuum pump, and then the vacuum state is kept at room temperature for more than 12 hours before demolding.

[0071] Preferably, the edge part is treated with an angle grinder after demolding.

[0072] Specifically, the preparation method of the sandwich structure sound-absorbing material comprises the following steps: placing a glass fiber high-strength cloth at a suitable position of a steel plate, using a brush to dip prepared resin glue and uniformly coating the resin glue on the surface of the glass fiber high-strength cloth, and removing excess bubbles; placing a polyurethane flexible foaming sound-absorbing material above the glass fiber high-strength cloth, and pressing the polyurethane flexible foaming sound-absorbing material until it is completely attached to the glass fiber high-strength cloth; coating another glass fiber high-strength cloth on the polyurethane flexible foaming sound-absorbing material, using a brush to dip an appropriate amount of resin glue until the glass fiber high-strength cloth is completely infiltrated and there are no excess bubbles; curing and forming the obtained structure to obtain the sandwich structure sound-absorbing material.

[0073] Example 1

[0074] The sandwich structure sound-absorbing material described in this embodiment comprises a first support layer with a thickness of 0.1 mm, a second support layer with a thickness of 0.2 mm, and a polyurethane flexible foaming sound-absorbing material layer arranged between the first support layer and the second support layer.

[0075] The preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer comprise the following components:

[0076] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine) and foaming agent: water. The mass ratio of A material, B material, catalyst, foaming agent is 100:65:0.03:0.125. The density of the polyurethane flexible foaming sound-absorbing material of this embodiment is 0.6 g / cm 3 .

[0077] The preparation method of the sandwich structure sound-absorbing material of this embodiment comprises the following steps:

[0078] 1. Preparation of polyurethane flexible foaming sound-absorbing material:

[0079] (1) According to the mass ratio, the A material, catalyst and foaming agent in the preparation raw materials are placed in the A material tank, and the A material tank is preheated to 50℃; the B material is placed in the B material tank, and the B material tank is preheated to 43℃. Open the mold water bath circulation heating, and preheat for 1 hour until the temperature is 65℃.

[0080] (2) Mold preheating after using the degreasing gauze dipped oil demolding agent, the inner surface of the mold is coated 3 times or more.

[0081] (3) According to the injection of A material: B material is 100:65 ratio, A material tank and B material tank of raw materials are mixed, according to the density of the required polyurethane flexible foaming sound absorbing material, the specific volume of A material and B material reaches the target weight, and then according to the injection time 2s, the foaming machine flow rate required to reach the target weight is calculated. In this embodiment, the density of the sample is 0.6g / cm 3 , according to the formula ratio, the target weight of sample A material is 45.5g, and the weight of B material is 29.5g. Set the injection time to 2s, and calculate the flow rate to be A 22.75g / s and B 14.75g / s. Because there is a deviation between the set flow rate of the equipment and the actual flow rate, the deviation of each machine is different, and the equipment gear position needs to be accurately set according to the deviation relationship between the actual flow rate and the equipment display flow rate. The materials in the A material tank and the B material tank are sent into the foaming machine for mixing, and the mixed material is obtained. The mixed material is injected into the mold for foaming, the mold with excellent sealing performance is used to fix the volume of the sample, the raw material injection time is controlled, and the raw material is injected into the mold for foaming at 65℃. After the mold is closed, it is cured at 65℃ for 30min and then demolded to obtain the polyurethane flexible foaming sound absorbing material.

[0082] (4) After demolding, the weight of the polyurethane flexible foaming sound absorbing material is weighed, and the sample density is calculated. The density is 0.6g / cm 3 .

[0083] 2. Preparation of sandwich structure sound absorbing material

[0084] (1) The surface of the polyurethane flexible foaming sound absorbing material is polished to form a cross pattern with 80-300 mesh sandpaper, and the dust generated by polishing is cleaned with alcohol or acetone. Then, the polyurethane flexible foaming sound absorbing material sample is surface treated with a coupling agent with a brand of kh550 to increase the adhesion. The use ratio of the coupling agent is: kh550: ethanol: water = 0.2:0.72:0.08. After mixing, stir well, stand for 30min, and then brush the surface of the polyurethane sample with a brush, and dry.

[0085] (2) Two pieces of glass fiber high-strength cloth with thicknesses of 0.1 mm and 0.2 mm and sizes of 500*500 mm are cut; the composition and proportion of the resin glue solution for the support layer are epoxy resin (E51): curing agent (tetraethylene pentamine): diluent (3660) = 10:1:2. The viscosity of the resin glue solution is 0.75 mPa*s. Thus, good wettability of the resin can be ensured during the glue brushing process, and precipitation does not occur. The resin curing speed of the system is relatively fast, and resin coating needs to be completed within 30 min at room temperature. The 0.1 mm glass fiber high-strength cloth is placed at a suitable position on the steel plate, the resin glue solution is prepared, and the resin glue solution is evenly coated on the surface of the glass fiber high-strength cloth by using a brush dipped in the resin glue solution, and excess bubbles are removed; the flexible polyurethane flexible foaming sound-absorbing material is placed horizontally above the 0.1 mm glass fiber high-strength cloth, and the polyurethane flexible foaming sound-absorbing material is pressed until it is completely attached to the 0.1 mm glass fiber high-strength cloth; the 0.2 mm glass fiber high-strength cloth is placed above the polyurethane flexible foaming sound-absorbing material, and the resin glue solution is dipped in an appropriate amount until the glass fiber high-strength cloth is completely infiltrated, and there are no excess bubbles.

[0086] (3) The bonded sample is placed at room temperature, and after vacuum bag compression curing for 12 h, it is taken out, and the edge part is polished flat using an angle grinder to obtain a sandwich structure sound-absorbing material.

[0087] Example 2

[0088] The sandwich structure sound-absorbing material described in this example has the same structure composition and preparation method as those in Example 1, except that the density of the polyurethane flexible foaming sound-absorbing material is 0.7 g / cm 3 In the preparation step, the density of the polyurethane flexible foaming sound-absorbing material is controlled by adjusting the injection flow rate of the A material and the B material.

[0089] Example 3

[0090] The sandwich structure sound-absorbing material described in this example has the same structure composition and preparation method as those in Example 1, except that the density of the polyurethane flexible foaming sound-absorbing material is 0.8 g / cm 3 In the preparation step, the density of the polyurethane flexible foaming sound-absorbing material is controlled by adjusting the injection flow rate of the A material and the B material.

[0091] Example 4

[0092] The sandwich structure sound-absorbing material described in this example has the same structure composition and preparation method as those in Example 1, except that the density of the polyurethane flexible foaming sound-absorbing material is 0.9 g / cm 3 In the preparation step, the density of the polyurethane flexible foaming sound-absorbing material is controlled by adjusting the injection flow rate of the A material and the B material.

[0093] Example 5

[0094] The sandwich structure sound absorption material described in this embodiment has the same structure and preparation method as in Embodiment 1, except that the density of the polyurethane flexible foam sound absorption material is 1 g / cm 3 In the preparation step, the density of the polyurethane flexible foam sound absorption material is controlled by adjusting the injection flow rate of the A material and the B material.

[0095] Embodiment 6

[0096] The sandwich structure sound absorption material described in this embodiment has the same structure and preparation method as in Embodiment 1, except that the preparation raw materials of the polyurethane flexible foam sound absorption material layer are different.

[0097] In this embodiment, the preparation raw materials of the polyurethane flexible foam sound absorption material layer include the following components:

[0098] The A material is polytetrahydrofuran; the B material is diphenylmethane diisocyanate; the catalyst is triethylenediamine; the foaming agent is water; and the filler is hollow glass microbeads. The mass ratio of the A material, the B material, the catalyst, and the foaming agent is 100:65:0.03:0.125. The mass of the hollow glass microbeads is 2.5% of the total mass of the preparation raw materials.

[0099] The preparation method of the polyurethane flexible foam sound absorption material in this embodiment has the same steps as in Embodiment 1, except that in step (1), the filler is added to the A material tank in a mass ratio, and the stirring switch is turned on to stir uniformly. The density of the polyurethane flexible foam sound absorption material is controlled to be 0.85 g / cm 3 .

[0100] Embodiment 7

[0101] The sandwich structure sound absorption material described in this embodiment has the same structure and preparation method as in Embodiment 1, except that the preparation raw materials of the polyurethane flexible foam sound absorption material layer are different.

[0102] In this embodiment, the preparation raw materials of the polyurethane flexible foam sound absorption material layer include the following components:

[0103] The A material is polytetrahydrofuran; the B material is diphenylmethane diisocyanate; the catalyst is triethylenediamine; the foaming agent is water; and the filler is hollow glass microbeads. The mass ratio of the A material, the B material, the catalyst, and the foaming agent is 100:65:0.03:0.125. The mass of the hollow glass microbeads is 2.5% of the total mass of the preparation raw materials.

[0104] The preparation method of the polyurethane flexible foam sound absorption material in this embodiment is the same as in Embodiment 6. The density of the polyurethane flexible foam sound absorption material is controlled to be 0.8 g / cm 3 .

[0105] Example 8

[0106] The sandwich structure sound-absorbing material of this example has the same structure and preparation method as that of Example 7, except that the density of the polyurethane flexible foaming sound-absorbing material is controlled to be 0.9 g / cm 3 .

[0107] Example 9

[0108] The sandwich structure sound-absorbing material of this example has the same structure and preparation method as that of Example 1, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0109] In this example, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0110] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads. The mass ratio of A material, B material, catalyst, and foaming agent is 100:65:0.03:0.125. The mass of the hollow glass microbeads is 7.5% of the total mass of the preparation raw materials.

[0111] The preparation method of the polyurethane flexible foaming sound-absorbing material of this example is the same as that of Example 6. The density of the polyurethane flexible foaming sound-absorbing material is controlled to be 0.77 g / cm 3 .

[0112] Example 10

[0113] The sandwich structure sound-absorbing material of this example has the same structure and preparation method as that of Example 1, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0114] In this example, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0115] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads. The mass ratio of A material, B material, catalyst, and foaming agent is 100:65:0.03:0.125. The mass of the hollow glass microbeads is 7.5% of the total mass of the preparation raw materials.

[0116] The preparation method of the polyurethane flexible foaming sound-absorbing material of this example is the same as that of Example 6. The density of the polyurethane flexible foaming sound-absorbing material is controlled to be 0.77 g / cm 3 .

[0117] Example 11

[0118] The sandwich structure sound-absorbing material described in the embodiment has the same structure and preparation method as those of Example 1, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0119] In the embodiment, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0120] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads and aluminum oxide powder. The mass ratio of the A material, the B material, the catalyst and the foaming agent is 100:65:0.03:0.125. The mass of the hollow glass microbeads and the aluminum oxide powder is 5% and 5% of the total mass of the preparation raw materials, respectively.

[0121] The preparation method of the polyurethane flexible foaming sound-absorbing material of the embodiment is the same as that of Example 6. The density of the polyurethane flexible foaming sound-absorbing material is controlled to be 0.8 g / cm 3 .

[0122] Example 12

[0123] The sandwich structure sound-absorbing material described in the embodiment has the same structure and preparation method as those of Example 1, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0124] In the embodiment, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0125] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads and aluminum oxide powder. The mass ratio of the A material, the B material, the catalyst and the foaming agent is 100:65:0.03:0.125. The mass of the hollow glass microbeads and the aluminum oxide powder is 5% and 5% of the total mass of the preparation raw materials, respectively.

[0126] The preparation method of the polyurethane flexible foaming sound-absorbing material of the embodiment is the same as that of Example 6. The density of the polyurethane flexible foaming sound-absorbing material is controlled to be 0.82 g / cm 3 .

[0127] Example 13

[0128] The sandwich structure sound-absorbing material described in the embodiment has the same structure and preparation method as those of Example 1, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0129] In the embodiment, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0130] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: magnetic iron powder. The mass ratio of A material, B material, catalyst, foaming agent is 100:65:0.03:0.125. The mass of magnetic iron powder is 10% of the total mass of the preparation raw materials.

[0131] The preparation method of the polyurethane flexible foamed sound-absorbing material in this embodiment is the same as that in Embodiment 6. The density of the polyurethane flexible foamed sound-absorbing material is controlled to be 0.83 g / cm 3 .

[0132] Embodiment 14

[0133] The sandwich structure sound-absorbing material described in this embodiment has the same structure and preparation method as those in Embodiment 1, except that the preparation raw materials of the polyurethane flexible foamed sound-absorbing material layer are different.

[0134] In this embodiment, the preparation raw materials of the polyurethane flexible foamed sound-absorbing material layer include the following components:

[0135] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads and flaky mica. The mass ratio of A material, B material, catalyst, foaming agent is 100:65:0.03:0.125. The masses of hollow glass microbeads and flaky mica are 5% and 5% of the total mass of the preparation raw materials, respectively.

[0136] The preparation method of the polyurethane flexible foamed sound-absorbing material in this embodiment is the same as that in Embodiment 6. The density of the polyurethane flexible foamed sound-absorbing material is controlled to be 0.82 g / cm 3 .

[0137] Embodiment 15

[0138] The sandwich structure sound-absorbing material described in this embodiment has the same structure and preparation method as those in Embodiment 1, except that the preparation raw materials of the polyurethane flexible foamed sound-absorbing material layer are different.

[0139] In this embodiment, the preparation raw materials of the polyurethane flexible foamed sound-absorbing material layer include the following components:

[0140] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: vermiculite. The mass ratio of A material, B material, catalyst, foaming agent is 100:65:0.03:0.125. The mass of vermiculite is 5% of the total mass of the preparation raw materials.

[0141] The preparation method of the polyurethane flexible foamed sound-absorbing material in this embodiment is the same as that in Embodiment 6. The density of the polyurethane flexible foamed sound-absorbing material is controlled to be 0.79 g / cm 3 .

[0142] Example 16

[0143] The sandwich structure sound-absorbing material described in this example has the same structure and preparation method as that of Example 8, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0144] In this example, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0145] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads. The mass ratio of A material, B material, catalyst, and foaming agent is 100: 60: 0.04: 0.1. The mass of the hollow glass microbeads is 5% of the total mass of the preparation raw materials.

[0146] The preparation method of the polyurethane flexible foaming sound-absorbing material of this example is the same as that of Example 6.

[0147] Example 17

[0148] The sandwich structure sound-absorbing material described in this example has the same structure and preparation method as that of Example 8, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0149] In this example, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0150] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads. The mass ratio of A material, B material, catalyst, and foaming agent is 100: 60: 0.04: 0.1. The mass of the hollow glass microbeads is 5% of the total mass of the preparation raw materials.

[0151] The preparation method of the polyurethane flexible foaming sound-absorbing material of this example is the same as that of Example 6.

[0152] Example 18

[0153] The sandwich structure sound-absorbing material described in this example has the same structure and preparation method as that of Example 8, except that the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer are different.

[0154] In this example, the preparation raw materials of the polyurethane flexible foaming sound-absorbing material layer include the following components:

[0155] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads. The mass ratio of A material, B material, catalyst, foaming agent is 100:55:0.05:0.08. The mass of hollow glass microbeads is 5% of the total mass of the preparation raw materials.

[0156] The preparation method of the polyurethane flexible foamed sound-absorbing material in this embodiment is the same as that in Embodiment 6.

[0157] Embodiment 19

[0158] The sandwich structure sound-absorbing material in this embodiment is the same as that in Embodiment 8 in the remaining structure and the preparation method, except that the preparation raw materials of the polyurethane flexible foamed sound-absorbing material layer are different.

[0159] In this embodiment, the preparation raw materials of the polyurethane flexible foamed sound-absorbing material layer include the following components:

[0160] A material: polytetrahydrofuran; B material: diphenylmethane diisocyanate; catalyst (triethylenediamine); foaming agent: water; filler: hollow glass microbeads. The mass ratio of A material, B material, catalyst, foaming agent is 100:75:0.01:0.18. The mass of hollow glass microbeads is 5% of the total mass of the preparation raw materials.

[0161] The preparation method of the polyurethane flexible foamed sound-absorbing material in this embodiment is the same as that in Embodiment 6.

[0162] The sandwich structure sound-absorbing materials obtained in the above embodiments are tested for sound absorption performance. The size of the sample is 500x500x5mm, the sound absorption coefficient measurement standard is GB / T 14396-2011, and the test method is the free field method. The performance data measured are shown in Table 1.

[0163] As can be seen from the data in Table 1, compared with Embodiments 1-5, the difference is that the densities of the polyurethane flexible foamed sound-absorbing materials are different. The sound absorption capacity of the sample increases with the increase of the density, but when the density continues to increase, the increase of the sound absorption capacity is not obvious, and the significant increase of the material density is not conducive to the application of the sound-absorbing material under water. Therefore, in consideration of the above, the density of the polyurethane flexible foamed sound-absorbing material is preferably 0.7-0.9g / cm 3 .

[0164] Comparing with example 6-15, the difference is the kind and mass content of the added filler. It can be seen that example 6, 8 and 14 all achieve sound absorption coefficient ≥0.8 (50-500KHz) in full frequency band. The flexible polyurethane foam materials prepared by the three formulations have excellent underwater sound absorption performance. The addition of filler can enhance the internal friction of the whole system, thereby increasing the loss of the material to the incident sound wave. Hollow microbeads can increase the internal friction and scatter sound waves of the synthesized material, increase the degree of microphase separation, and improve the viscous sound absorption and heat conduction sound absorption. The acoustic filler with a hollow structure can increase the energy dissipation of the elastomer network structure and the added molecules. When the sound wave enters, it makes the polymer molecular chain move. In addition, the sheet mica has an orientation effect under the action of external force, which increases the internal friction between the substrate and the sheet mica, further widens the effective damping temperature range, and thus can better attenuate sound energy.

[0165] Comparing with example 8, 16-19, the difference is the mass ratio of A material, B material, catalyst and foaming agent. Compared with example 8, 16 and 17, the comprehensive performance is better, which is the preferred formula.

[0166] Table 1

[0167]

[0168]

[0169] Obviously, the above examples are only examples for the sake of clarity, and are not limitations of the embodiments. Based on the above description, other different forms of changes or variations can also be made by those skilled in the art. It is not necessary and impossible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A flexible polyurethane foam sound-absorbing material, characterized in that, Its preparation raw materials consist of the following components: The material comprises component A, component B, catalyst, foaming agent, and filler; component A is polytetrahydrofuran; component B is diphenylmethane diisocyanate; and the foaming agent is water; the mass ratio of component A, component B, catalyst, and foaming agent is 100:65:0.03:0.125; the density of the polyurethane flexible foam sound-absorbing material is 0.82~0.9 g / cm³. 3 The filler is hollow glass microspheres or a mixture of hollow glass microspheres and flaky mica; when the filler is hollow glass microspheres, the mass of the filler accounts for 2.5% to 5% of the total mass of the raw materials; when the filler is a mixture of hollow glass microspheres and flaky mica, the masses of the hollow glass microspheres and flaky mica are 5% and 5% of the total mass of the raw materials, respectively. The preparation method of the polyurethane flexible foamed sound-absorbing material includes the following steps: The raw materials for preparing the flexible polyurethane foam sound-absorbing material are mixed to obtain a mixture; then the mixture is injected into a mold for foaming and curing to obtain the flexible polyurethane foam sound-absorbing material; when the mixture is injected into the mold, the volume of the flexible polyurethane foam sound-absorbing material is fixed by the mold, and the density of the flexible polyurethane foam sound-absorbing material is changed by controlling the amount of mixture injected.

2. A method for preparing the polyurethane flexible foamed sound-absorbing material as described in claim 1, characterized in that, Includes the following steps: The raw materials for preparing the flexible polyurethane foam sound-absorbing material are mixed to obtain a mixture; then the mixture is injected into a mold for foaming and curing to obtain the flexible polyurethane foam sound-absorbing material. When the mixture is injected into the mold, the volume of the polyurethane flexible foam sound-absorbing material is fixed by the mold, and the density of the polyurethane flexible foam sound-absorbing material is changed by controlling the amount of mixture injected.

3. The preparation method according to claim 2, characterized in that: The foaming temperature is 60~70℃; Before mixing the raw materials for preparing the polyurethane flexible foamed sound-absorbing material, the process further includes: loading the raw materials other than material B into material A container and preheating material A container to 48~52°C; loading material B into material B container and preheating material B container to 41~45°C.

4. A sandwich structure sound-absorbing material, characterized in that, include: At least two composite material support layers and a polyurethane flexible foam material layer disposed between the two composite material support layers; The composite material support layer is made of reinforcing fibers and a resin matrix; the polyurethane flexible foam material layer is made of the polyurethane flexible foam sound-absorbing material as described in claim 1; the thickness of the composite material support layer is 0.1-1 mm, and the thickness of the polyurethane flexible foam material layer is 4-8 mm.

5. A method for preparing a sandwich structure sound-absorbing material as described in claim 4, characterized in that, Includes the following steps: A prepreg for preparing a composite material support layer is obtained to form a first support layer prepreg; a flexible polyurethane foam sound-absorbing material is placed on the first support layer prepreg to form a flexible polyurethane foam material layer; another prepreg for a composite material support layer is placed on the flexible polyurethane foam material layer to obtain a second support layer prepreg; the obtained structure is cured and molded to obtain the sandwich structure sound-absorbing material.

6. The preparation method according to claim 5, characterized in that, Also includes: Before placing the flexible polyurethane foam sound-absorbing material on the first support layer prepreg, the surfaces of the flexible polyurethane foam sound-absorbing material that are in contact with the first support layer prepreg and the second support layer prepreg are polished, and then a coupling agent is used for surface treatment.

7. The preparation method according to claim 5, characterized in that: The preparation of the prepreg for the composite material support layer specifically includes the following steps: A fiber-reinforced material layer is provided; a resin adhesive is impregnated onto the fiber-reinforced material layer to obtain a prepreg for a composite material support layer; The resin solution comprises epoxy resin, curing agent, and diluent; the mass ratio of epoxy resin, curing agent, and diluent is 10:0.5~1.5:1.5~2.

5. The viscosity of the resin solution is 0.35 mPa·s to 0.75 mPa·s.

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