Foamed polyethylene sound absorption material and preparation method thereof

Abstract

The invention relates to a foamed polyethylene sound absorption material and a preparation method thereof, and belongs to the technical field of foamed plastics. The material is prepared from the following raw materials: modified polyethylene resin, a composite foaming agent and a nucleating agent, wherein the modified polyethylene resin is obtained by double-grafting modification of polyethylene resin through a silane coupling agent and a functional carboxylic acid monomer; the polyethylene resin is formed by mixing HDPE and LDPE according to a certain proportion; the composite foaming agent comprises azodicarbonamide, sodium bicarbonate and foaming microspheres according to a certain ratio; the nucleating agent is obtained by reaction of organic quaternary ammonium salt and nano montmorillonite; the specific dosage of the composite foaming agent, the organic quaternary ammonium salt and the nano montmorillonite is calculated according to the mass percent of the polyethylene resin. The sound absorption material provided by the invention is wide in sound absorption frequency band and high in sound absorption coefficient, has relatively good compression resistance, can better keep a uniform and stable foam structure during use, and has a very high application value.

Description

Technical Field

[0001] The invention relates to the technical field of foamed plastics, and in particular to a foamed polyethylene sound-absorbing material and a preparation method thereof. Background Art

[0002] Foamed polyethylene sound-absorbing materials have gradually become an important choice in the field of noise control due to their advantages such as light weight, corrosion resistance and low cost. The core function of this material comes from its unique internal pore structure - countless micron-level closed or open pores are interconnected to form a three-dimensional network. When sound waves enter the material, the elastic vibration of the pore wall, air friction and multiple reflections of the sound waves between the pore walls work together to gradually convert the sound energy into heat energy consumption. It is worth noting that the sound absorption performance of the material is closely related to the uniformity and stability of its pore structure: evenly distributed pores can form a coherent sound wave conduction path, and the stable pores are not easy to collapse under external force, thereby maintaining the continuous effectiveness of the sound absorption mechanism.

[0003] However, the current foamed polyethylene sound-absorbing materials generally have unsatisfactory sound absorption performance, and their compression resistance is insufficient. They are prone to collapse during use, which affects their sound absorption performance. The existing polyethylene sound-absorbing materials have an uneven distribution of pores due to the difficulty in accurately controlling the pore structure, which seriously affects the sound wave conduction and absorption mechanism inside the material, thereby limiting the sound absorption performance of the material. The uneven distribution of pores also reduces the compression resistance of the pores. When squeezed by external forces, the pores are easily deformed or even broken, making it difficult to maintain the stability of the sound wave conduction and absorption path inside the material, resulting in reduced sound absorption performance.

[0004] Aiming at the problems that the current foamed polyethylene sound-absorbing materials generally have insufficient sound absorption performance, poor compression resistance, and easy collapse during use, which in turn affects the sound absorption performance, a new foamed polyethylene sound-absorbing material is provided. Through fine control of the pores, the material has a uniform pore structure and sound absorption effect, and has compression resistance. It has high application prospects in the field of foamed plastics. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a foamed polyethylene sound-absorbing material and a preparation method. The material provided by the present invention has a high sound absorption coefficient and good compression resistance, can better maintain the pore structure, prolong the sound absorption effect, and has high practical value.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a foamed polyethylene sound absorbing material, wherein the raw materials for preparing the foamed polyethylene sound absorbing material include the following components: a modified polyethylene resin, a composite foaming agent and a nucleating agent;

[0008] The modified polyethylene resin is obtained by double graft modification of polyethylene resin with a silane coupling agent and a functional carboxylic acid monomer; the polyethylene resin is a mixture of high-density polyethylene and low-density polyethylene, and the mass ratio of the high-density polyethylene to the low-density polyethylene is 1:(1-3);

[0009] The components of the composite foaming agent include azodicarbonamide, sodium bicarbonate and foaming microspheres, and the mass ratio of azodicarbonamide, sodium bicarbonate and foaming microspheres is azodicarbonamide:sodium bicarbonate:foaming microspheres=(5-8):(1-2):1;

[0010] The nucleating agent is prepared by reacting an organic quaternary ammonium salt and nano-montmorillonite;

[0011] Based on the mass percentage of the polyethylene resin, the dosage of the composite foaming agent is 2-8%, the dosage of the organic quaternary ammonium salt is 0.2-2%, and the dosage of the nano-montmorillonite is 0.5-3%.

[0012] The resin matrix of the foamed polyethylene sound-absorbing material of the present invention is a polyethylene resin double graft-modified with a silane coupling agent and a functional carboxylic acid monomer, and its surface chemical activity is significantly improved: the functional carboxylic acid monomer forms a polymer brush rich in carboxyl groups on the surface of the polyethylene resin, enhancing the interaction between the resin and other additives, and providing a more stable matrix for the fine control of the pores.

[0013] The polyethylene resin itself is obtained by mixing high-density polyethylene and low-density polyethylene in a specific ratio. The ratio of high-density polyethylene to low-density polyethylene significantly affects the density, mechanical properties, and pore formation of the foamed material. At a specific ratio, more uniform and stable pores can be formed, improving the sound-absorbing effect and compression resistance of the foamed polyethylene sound-absorbing material.

[0014] At the same time, the present invention introduces a specific composite foaming agent, including azodicarbonamide, sodium bicarbonate and foaming microspheres. In the preparation of the foamed material, sodium bicarbonate can decompose at 100-140°C to assist early foaming and serve as the initial "seed" for pore formation; the foaming microspheres expand at 160°C, and azodicarbonamide decomposes at 190-210°C to generate a large amount of gas to form the main body of the pores. Under the dosage and ratio defined in the present invention, the synergistic effect of the three foaming agent components can be better realized, providing an appropriate amount of gas for the pore growth of the foamed material at different temperature stages, and significantly improving the performance of the material.

[0015] The nucleating agent used in the present invention is prepared by reacting an organic quaternary ammonium salt and nano-montmorillonite. The nano-montmorillonite sheets have a huge specific surface area, providing a large number of uniform heterogeneous nucleation sites in the polyethylene matrix. The organic quaternary ammonium salt cations enter the interlayers of the nano-montmorillonite sheets, replacing the original inorganic cations, forming an organic-inorganic hybrid structure, which can improve the compatibility between the nano-montmorillonite and polyethylene, enabling it to be uniformly dispersed in the matrix. During the foaming process, a large number of uniformly distributed nucleation sites promote the synchronous nucleation of pores throughout the system. However, when the dosage of the nucleating agent components is inappropriate, it will lead to uneven pore distribution in local areas, affecting the sound absorption and anti-compression effects of the material.

[0016] The foamed polyethylene sound-absorbing material provided by the present invention has excellent sound absorption performance. By controlling the preparation raw materials, fine control of the pores is achieved, enabling the material to have a uniform pore structure, where sound waves can be reflected and absorbed multiple times inside: in the low-frequency range of 125 - 500 Hz, the sound absorption coefficient of the material can reach above 0.4; in the medium-high frequency range of 1000 - 4000 Hz, the sound absorption coefficient of the material can reach above 0.9, and it also has good anti-compression performance, with a compression modulus of above 3.2 MPa. During use, it maintains its physical properties, has relatively good weather resistance, and has high practicality.

[0017] Preferably, the mass ratio of the high-density polyethylene to the low-density polyethylene is one of 1:1, 1:1.5, 1:2, 1:2.5, 1:3 or the range value of any two of them.

[0018] Preferably, based on the mass percentage of the polyethylene resin, the dosage of the composite foaming agent is one of 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8% or the range value of any two of them.

[0019] Preferably, based on the mass percentage of the polyethylene resin, the dosage of the organic quaternary ammonium salt is one of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or the range value of any two of them.

[0020] Preferably, based on the mass percentage of the polyethylene resin, the dosage of the nano-montmorillonite is one of 0.5%, 1%, 1.5%, 2.5%, 3% or the range value of any two of them.

[0021] It should be noted that the selection of the mass ratio of the above-mentioned high-density polyethylene to low-density polyethylene, the dosage of the composite foaming agent, the dosage of the organic quaternary ammonium salt, and the dosage of the nano-montmorillonite is not limited to the above-listed schemes. Those skilled in the art can make other selections within the scope defined by the present invention according to actual needs.

[0022] Preferably, the preparation method of the modified polyethylene resin comprises the following steps:

[0023] Step (1): Dissolve the polyethylene resin by heating in an organic solvent, then add an initiator and a silane coupling agent, and mix and react in a nitrogen atmosphere to obtain a polyethylene resin grafted with siloxane;

[0024] Step (2): Add the polyethylene resin grafted with siloxane, a functional carboxylic acid monomer and an initiator, and mix and react in a nitrogen atmosphere to obtain the modified polyethylene resin.

[0025] As a preferred scheme of the present invention, after the reaction in step (1) is completed, the product is washed with ethanol multiple times to remove unreacted substances, and vacuum dried at 40-70 °C for 8-15 h to obtain the polyethylene resin grafted with siloxane.

[0026] Further preferably, the silane coupling agent is KH570;

[0027] And / or, the functional carboxylic acid monomer is at least one of methacrylic acid, itaconic acid, maleic anhydride, and acrylic acid;

[0028] And / or, based on the mass percentage of the polyethylene resin, the dosage of the silane coupling agent is 2-5%, and the dosage of the functional carboxylic acid monomer is 3-10%.

[0029] Preferably, based on the mass percentage of the polyethylene resin, the dosage of the silane coupling agent is one of 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or the range value of any two of them.

[0030] Preferably, based on the mass percentage of the polyethylene resin, the dosage of the functional carboxylic acid monomer is one of 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or the range value of any two of them.

[0031] It should be noted that the selection of the dosage of the above-mentioned silane coupling agent and functional carboxylic acid monomer is not limited to the above-listed schemes. Those skilled in the art can make other selections within the scope defined by the present invention according to actual needs.

[0032] Further preferably, the initiator in step (1) is benzoyl peroxide, and the dosage of benzoyl peroxide is 0.5-1% based on the mass percentage of the polyethylene resin;

[0033] and / or, the initiator in step (2) is potassium persulfate, and the dosage of potassium persulfate is 1-3% based on the mass percentage of the functional carboxylic acid monomer.

[0034] As a preferred embodiment of the present invention, the heating temperature in step (1) is 100-130 °C;

[0035] and / or, the mixing reaction conditions in step (1) are: stirring reaction at a speed of 100-250 r / min for 2-5 h;

[0036] and / or, the mixing reaction conditions in step (2) are: stirring reaction at a speed of 60-120 r / min for 2-5 h at 50-70 °C.

[0037] Under the preparation conditions of the modified polyethylene resin, the silane coupling agent KH570 is grafted onto the polyethylene molecular chain through a free radical reaction, introducing active siloxane groups on the resin surface; the functional carboxylic acid monomer can undergo a graft polymerization reaction under the initiation of the grafted siloxane groups to achieve double graft modification.

[0038] Preferably, the organic quaternary ammonium salt is at least one of cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and benzyltrimethylammonium chloride.

[0039] As a preferred embodiment of the present invention, the preparation method of the nucleating agent is:

[0040] (Ⅰ) Add the weighed nano-montmorillonite into the reaction kettle, add an appropriate amount of deionized water to prepare a suspension, stir evenly, control the stirring speed at 300-500 r / min to fully disperse the nano-montmorillonite, and then heat up to 60-80 °C;

[0041] (Ⅱ) Under stirring, slowly add the weighed organic quaternary ammonium salt, and continuously stir and react for 2-4 h; after the reaction is completed, filter the reaction product to remove excess water and incompletely reacted impurities;

[0042] (ⅠⅡ) Place the filtered product in a vacuum drying oven at 40-60 °C and dry for 6-8 h to remove residual moisture and obtain a dry nucleating agent.

[0043] The temperature range of the step (I) is conducive to the ion exchange reaction and can accelerate the rate of the organic quaternary ammonium cation entering the interlayer of the nano-montmorillonite. The stirring process in the step (II) enables the full contact between the organic quaternary ammonium salt and the nano-montmorillonite, ensuring the uniform and sufficient progress of the ion exchange reaction.

[0044] Preferably, the raw materials for preparing the foamed polyethylene sound-absorbing material further include the following components: plasticizer, additive, auxiliary agent, and solvent.

[0045] More preferably, the plasticizer includes at least one of tributyl citrate, dioctyl adipate, and dioctyl phthalate;

[0046] and / or, the additive includes micro-scale calcium carbonate whiskers and hollow glass microspheres;

[0047] and / or, the auxiliary agent includes antioxidant and light stabilizer;

[0048] and / or, the solvent is a mixed solvent of dichloromethane and cyclohexanone, and the mass ratio of dichloromethane to cyclohexanone is 1:(1 - 3).

[0049] More preferably, based on the mass percentage of the polyethylene resin, the dosage of the plasticizer is 2 - 5%;

[0050] and / or, the mass of the micro-scale calcium carbonate whiskers accounts for 0.5 - 1.5% of the total mass of the raw materials for preparation, and the mass of the hollow glass microspheres accounts for 1 - 3% of the total mass of the raw materials for preparation;

[0051] and / or, the mass of the antioxidant accounts for 0.2 - 1% of the total mass of the raw materials for preparation, and the mass of the light stabilizer accounts for 0.2 - 1% of the total mass of the raw materials for preparation;

[0052] and / or, the mass ratio of the solvent to the polyethylene resin is 1:(3 - 6).

[0053] Specific toughening agents can reduce the intermolecular force between polyethylene molecular chains, increase flexibility and plasticity, enable the cell walls to be well stretched and expanded during foaming, maintain the cell morphology, and ensure the uniform growth of cells.

[0054] A specific amount of micro-scale calcium carbonate whiskers can enhance the mechanical properties of the material: during the foaming process, the matrix environment around the calcium carbonate particles is relatively stable, which helps the cells to nucleate uniformly around them. The hollow glass microspheres are light in weight and have good noise reduction performance, which can improve the sound-absorbing performance of the material, especially the absorption of low-frequency noise; at a specific addition amount, they can be evenly dispersed in the matrix, providing more space for cell growth, and the interaction with the matrix helps to maintain the uniformity of the cells.

[0055] Among the additives, antioxidants can prevent the oxidative degradation of polyethylene during processing and use, and light stabilizers can absorb ultraviolet rays, improve the weather resistance of materials, and extend the service life.

[0056] Dichloromethane has good solubility, and cyclohexanone can adjust the evaporation rate, make all raw materials mix evenly, reduce the viscosity of the system, and facilitate the dispersion and reaction of each component in the polyethylene matrix.

[0057] In a second aspect, the present invention provides a method for preparing the above-mentioned foamed polyethylene sound-absorbing material, which includes the following steps:

[0058] Step S1: Sequentially add a composite foaming agent, a nucleating agent, a plasticizer, an additive, and an additive to the dried modified polyethylene resin under stirring conditions. After mixing evenly, add a solvent to obtain a mixed solution;

[0059] Step S2: Ultrasonically disperse the mixed solution, and then extrude and mold it using a twin-screw extruder to obtain a blank;

[0060] Step S3: Heat the blank in a mold, apply pressure for foaming, and then keep the pressure and cool it to obtain the foamed polyethylene sound-absorbing material.

[0061] Preferably, the condition for drying the modified polyethylene resin in step S1 is to dry it at 70-90°C for 2-5 hours.

[0062] Preferably, in step S1, the stirring speed is 600-1000 r / min;

[0063] And / or, in step S2, the conditions for ultrasonic dispersion are: power 350-450 W, frequency 30-50 kHz, and time 50-70 min;

[0064] And / or, in step S2, the temperatures of the twin-screw extruder from the hopper end to the head are 140°C, 160°C, 180°C, 200°C, and 210°C in sequence, and the screw speed is 100-140 r / min;

[0065] And / or, in step S3, the temperature of the mold is 160-200°C;

[0066] And / or, in step S3, the applied pressure is 1.5-2.5 MPa, and the pressure holding time is 8-20 min.

[0067] As a preferred solution of the present invention, the pressure holding and cooling specifically are: maintaining the mold pressure, and passing circulating cooling water through the cooling water channel to quickly reduce the temperature to below 40°C.

[0068] The forming of the foamed polyethylene sound-absorbing material of the present invention is mainly divided into several stages:

[0069] Nucleation stage: In the early stage of extrusion molding, when the temperature reaches the decomposition temperature of sodium bicarbonate (100-140°C), sodium bicarbonate first decomposes to produce carbon dioxide gas, forming initial bubble nuclei in the system. At the same time, the foaming microspheres begin to slowly release internal gas at 160°C, further increasing the number of bubble nuclei. At this time, the organic-inorganic hybrid nucleating agent plays a key role, and the large number of nucleation sites on the nano-montmorillonite sheet promotes the uniform distribution of bubble nuclei in the polyethylene matrix. Due to the good interaction between the modified polyethylene resin and the nucleating agent, the nucleating agent is evenly dispersed in the matrix, ensuring that bubble nuclei can be generated synchronously in each area to avoid local nucleation unevenness.

[0070] Growth stage: As the temperature rises to the decomposition temperature of azodicarbonamide (190-210℃), azodicarbonamide decomposes in large quantities to produce nitrogen, carbon monoxide and other gases, and the bubble nucleus begins to expand and grow rapidly. The plasticizer enhances the flexibility of the polyethylene matrix, and the cell wall can be stretched evenly with the increase of gas, preventing the cell from breaking or deforming due to local stress concentration. At the same time, micron-sized calcium carbonate whiskers and hollow glass microspheres are evenly dispersed in the matrix, which play a certain restraining and guiding role in the growth of the cells. The matrix around the micron-sized calcium carbonate particles interacts with the cell wall, so that the cells expand evenly along the gaps between the calcium carbonate particles during the growth process; the hollow glass microspheres provide additional growth space for the cells, and their interaction with the matrix maintains the stability of the cell growth and ensures the uniform growth of the cells.

[0071] Stabilization stage: During the compression foaming process, the mold pressure and temperature further act on the blank. The pressure constrains the cells during expansion to avoid excessive expansion and uneven growth. At this time, the foaming agents work together to accurately control the amount of gas released according to temperature changes to ensure stable cell growth. During the pressure holding time, the cells gradually fuse and reach a stable state. During cooling and shaping, it is preferred to pass circulating cooling water through the mold cooling water channel, and the temperature quickly drops to below 40°C. The modified polyethylene resin molecular chain is gradually fixed and the cell structure is stabilized.

[0072] The foamed polyethylene sound-absorbing material prepared and provided by the invention has uniformly distributed pores, pore diameters mainly concentrated between 50 and 200 μm, and a pore film thickness between adjacent pores between 1 and 5 μm.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] The present invention realizes the fine control of cell pores during the foaming process by performing double graft modification on a specific polyethylene resin and combining a composite foaming agent and a nucleating agent with specific proportions and components, provides a sound-absorbing material with uniform cell pore distribution, a wide sound absorption frequency band, and a high sound absorption coefficient, and also has good compression resistance and can better maintain the uniform and stable cell pore structure during use, solving the key problems of foamed polyethylene sound-absorbing materials in the prior art. The preparation method of the material provided by the present invention is easy to industrialize and has broad market application prospects overall. Description of the Drawings

[0075] Figure 1 It is a cross-sectional view of the foamed polyethylene sound-absorbing material of the present invention in Example 1. Detailed Embodiments

[0076] To better illustrate the purpose, technical solutions, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. The test methods used in the following embodiments are all conventional methods unless otherwise specified.

[0077] In the following embodiments and comparative examples, the sources of some reagents and materials are as follows:

[0078] HDPE: Taiwan Plastics 8010, grade 34;

[0079] LDPE: Maoming Petrochemical, foaming-grade low-density polyethylene, product number 951-050;

[0080] Hollow glass microspheres: Shijiazhuang Runbang New Material Technology Co., Ltd., particle size 10 - 120 μm;

[0081] Calcium carbonate whiskers: Hubei Langbowan Biomedicine Co., Ltd., 20 - 80um, 0.5 - 5μm;

[0082] Foaming microspheres: Boriken, model 186DU30, average particle size 28 - 40 μm;

[0083] Nanometer montmorillonite: Zhejiang Fenghong New Material Co., Ltd., model DK-7, particle size ≤ 20 μm.

[0084] For other materials, reagents, etc. used in the embodiments and comparative examples, they can all be obtained from commercial channels unless otherwise specified.

[0085] Example 1

[0086] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment include modified polyethylene resin, composite foaming agent, nucleating agent, plasticizer, additive, auxiliary agent, and solvent, and the formulation preparation is as follows:

[0087] Preparation of modified polyethylene resin:

[0088] (1) Weigh 333 g of high-density polyethylene (HDPE) and 667 g of low-density polyethylene (LDPE) (i.e., the mass ratio is 1:2), and mix them evenly to obtain a polyethylene resin; add it to a reaction kettle containing toluene solvent, heat it to 110 °C to completely dissolve it, and then add 5 g of benzoyl peroxide (BPO) and 30 g of silane coupling agent KH570; stir and react for 3 h at a rotation speed of 150 r / min under nitrogen protection to complete the graft modification. After the reaction, wash the product with ethanol multiple times and dry it in a vacuum at 50 °C for 10 h to obtain a silicone-grafted polyethylene resin;

[0089] (2) Place the dried silicone-grafted polyethylene resin in a reaction system containing 50 g of acrylic acid, add 1 g of potassium persulfate (KPS), and stir and react for 3 h at a rotation speed of 80 r / min under nitrogen protection at 60 °C to complete the secondary graft polymerization to obtain the modified polyethylene resin.

[0090] Preparation of nucleating agent:

[0091] (Ⅰ) First, weigh 5 g of cetyltrimethylammonium bromide and 7.5 g of nanometer montmorillonite; add the weighed nanometer montmorillonite to the reaction kettle, add an appropriate amount of deionized water to prepare a suspension, stir evenly, control the stirring speed at 400 r / min to fully disperse the nanometer montmorillonite, and then heat it to 70 °C;

[0092] (Ⅱ) Under stirring, slowly add the weighed organic quaternary ammonium salt and continuously stir and react for 3 h; after the reaction, filter the reaction product to remove excess water and incompletely reacted impurities;

[0093] (ⅠⅡ) Place the filtered product in a vacuum drying oven at 50 °C and dry it for 7 h to remove residual water and obtain a dried nucleating agent.

[0094] Preparation of other raw materials:

[0095] Weigh 50 g of azodicarbonamide, 10 g of sodium bicarbonate, and 10 g of foaming microspheres as a composite foaming agent;

[0096] Weigh 30 g of tributyl citrate as a plasticizer;

[0097] Weigh 7.5 g of micron-sized calcium carbonate whiskers and 15 g of hollow glass microspheres as additives;

[0098] Weigh 4 g of antioxidant 1076 and 4 g of light stabilizer UV-770 as auxiliaries;

[0099] Mix dichloromethane and cyclohexanone according to a mass ratio of 1:2 to prepare a mixed solvent, and the mass ratio of the mixed solvent to the modified polyethylene resin is 1:4.

[0100] The preparation method of the foamed polyethylene sound-absorbing material in this embodiment is as follows:

[0101] S1. Pretreatment and mixing of raw materials: The modified polyethylene resin is dried at 80 °C for 3 h. The dried polyethylene resin is added to a high-speed mixer and stirred at a speed of 800 r / min. Meanwhile, each component of the composite foaming agent, nucleating agent, plasticizer, additive, and auxiliary agent are slowly added in sequence and stirred for 30 min, and then a composite solvent is added and stirred for 20 minutes to obtain a mixed solution;

[0102] S2. Ultrasonic-assisted dispersion and extrusion molding: The mixed solution is transferred to an ultrasonic dispersion device and ultrasonically dispersed for 60 min under the conditions of a power of 400 W and a frequency of 40 kHz; The solution after ultrasonic dispersion is transported to a twin-screw extruder, and the temperature is 140 °C, 160 °C, 180 °C, 200 °C, and 210 °C in sequence from the hopper end to the head, the screw speed is 120 r / min, and extrusion is carried out to form a blank with a preliminary cell structure;

[0103] S3. Mold pressing and foaming, cooling: The blank is quickly transferred to a mold preheated to 180 °C, a pressure of 2 MPa is applied, and the pressure is maintained for 15 min; Then, while maintaining the mold pressure, circulating cooling water is introduced through the cooling water channel to quickly reduce the mold temperature to below 40 °C to obtain the finished product of the foamed polyethylene sound-absorbing material.

[0104] The cross-sectional view of the finished product of the foamed polyethylene sound-absorbing material is as Figure 1 shown. It can be seen that a uniformly distributed cell structure is formed in the material.

[0105] Example 2

[0106] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The difference between the preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment and those in Example 1 is only that the polyethylene resin is obtained by mixing 500 g of high-density polyethylene (HDPE) and 500 g of low-density polyethylene (LDPE) (i.e., the mass ratio is 1:1).

[0107] The preparation method of the foamed polyethylene sound-absorbing material in this embodiment refers to Example 1.

[0108] Example 3

[0109] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The difference between the preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment and those in Example 1 is only that in the preparation of the modified polyethylene resin, the dosage of the silane coupling agent KH570 is 20 g (i.e., based on the mass percentage of the polyethylene resin, the dosage of the silane coupling agent changes from 3% to 2%).

[0110] The preparation method of the foamed polyethylene sound-absorbing material in this embodiment refers to Example 1.

[0111] Example 4

[0112] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The difference between the preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment and those in Example 1 is only that in the preparation of the modified polyethylene resin, the amount of the silane coupling agent KH570 is 50 g (that is, based on the mass percentage of the polyethylene resin, the amount of the silane coupling agent changes from 3% to 5%).

[0113] The preparation method of the foamed polyethylene sound-absorbing material described in this embodiment refers to Example 1.

[0114] Example 5

[0115] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The difference between the preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment and those in Example 1 is only that in the preparation of the modified polyethylene resin, the amount of acrylic acid is 30 g (that is, based on the mass percentage of the polyethylene resin, the amount of acrylic acid changes from 5% to 3%).

[0116] The preparation method of the foamed polyethylene sound-absorbing material described in this embodiment refers to Example 1.

[0117] Example 6

[0118] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The difference between the preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment and those in Example 1 is only that in the preparation of the modified polyethylene resin, the amount of acrylic acid is 70 g (that is, based on the mass percentage of the polyethylene resin, the amount of acrylic acid changes from 5% to 7%).

[0119] The preparation method of the foamed polyethylene sound-absorbing material described in this embodiment refers to Example 1.

[0120] Example 7

[0121] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The difference between the preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment and those in Example 1 is only that: 50 g of azodicarbonamide, 15 g of sodium bicarbonate, and 10 g of foaming microspheres are weighed as a composite foaming agent (based on the mass percentage of the polyethylene resin, the amount of the composite foaming agent changes from 7% to 7.5%).

[0122] The preparation method of the foamed polyethylene sound-absorbing material described in this embodiment refers to Example 1.

[0123] Example 8

[0124] An embodiment of the foamed polyethylene sound-absorbing material of the present invention. The difference in the preparation raw materials of the foamed polyethylene sound-absorbing material in this embodiment from those in Example 1 is only that: 20 g of cetyltrimethylammonium bromide is weighed and reacted with 20 g of nano-montmorillonite to prepare a nucleating agent (by mass percentage of the polyethylene resin, the dosages of both cetyltrimethylammonium bromide and nano-montmorillonite are 2%).

[0125] The preparation method of the foamed polyethylene sound-absorbing material in this embodiment refers to Example 1.

[0126] Comparative Example 1

[0127] A foamed polyethylene sound-absorbing material, the difference in its preparation raw materials from those in Example 1 is only that: 12 g of azodicarbonamide, 2 g of sodium bicarbonate, and 1 g of foaming microspheres are weighed as a composite foaming agent (by mass percentage of the polyethylene resin, the dosage of the composite foaming agent changes from 7% to 1.5%).

[0128] The preparation method of this foamed polyethylene sound-absorbing material refers to Example 1.

[0129] Comparative Example 2

[0130] A foamed polyethylene sound-absorbing material, the difference in its preparation raw materials from those in Example 1 is only that: 70 g of azodicarbonamide, 20 g of sodium bicarbonate, and 10 g of foaming microspheres are weighed as a composite foaming agent (by mass percentage of the polyethylene resin, the dosage of the composite foaming agent changes from 7% to 10%).

[0131] The preparation method of this foamed polyethylene sound-absorbing material refers to Example 1.

[0132] Comparative Example 3

[0133] A foamed polyethylene sound-absorbing material, the difference in its preparation raw materials from those in Example 1 is only that: 10 g of cetyltrimethylammonium bromide is weighed and reacted with 4 g of nano-montmorillonite to prepare a nucleating agent (by mass percentage of the polyethylene resin, the dosage of cetyltrimethylammonium bromide is 1% and the dosage of nano-montmorillonite is 0.4%).

[0134] The preparation method of this foamed polyethylene sound-absorbing material refers to Example 1.

[0135] Comparative Example 4

[0136] A foamed polyethylene sound-absorbing material, the difference in its preparation raw materials from those in Example 1 is only that: 30 g of cetyltrimethylammonium bromide is weighed and reacted with 40 g of nano-montmorillonite to prepare a nucleating agent (by mass percentage of the polyethylene resin, the dosage of cetyltrimethylammonium bromide is 3% and the dosage of nano-montmorillonite is 4%).

[0137] The preparation method of this foamed polyethylene sound-absorbing material refers to Example 1.

[0138] Comparative Example 5

[0139] A foamed polyethylene sound-absorbing material, the difference in its preparation raw materials from those of Example 1 is only that the polyethylene resin is obtained by weighing 667 g of high-density polyethylene (HDPE) and 333 g of low-density polyethylene (LDPE) (i.e., the mass ratio is 2:1) and mixing them.

[0140] The preparation method of this foamed polyethylene sound-absorbing material refers to Example 1.

[0141] Effect Example

[0142] To explore the sound-absorbing performance and compression resistance of the foamed polyethylene sound-absorbing material provided by the present invention, performance tests were carried out respectively:

[0143] Sound-absorbing performance: Refer to GB / T 18696.1-2004 "Measurement of Sound Absorption Coefficient and Acoustic Impedance in Acoustic Impedance Tube - Part 1: Standing Wave Ratio Method";

[0144] Compression resistance: Refer to GB / T 1041-2008 "Determination of Compressive Properties of Plastics";

[0145] The sound-absorbing performance and compression resistance results of the foamed polyethylene sound-absorbing materials in the examples and comparative examples are shown in Table 1.

[0146] Table 1 Sound-absorbing performance and compression resistance results of materials in examples and comparative examples

[0147]

[0148] It can be seen from the results in Table 1 that:

[0149] In Examples 1-8, the sound absorption coefficients of the foamed polyethylene sound-absorbing materials provided by the present invention are overall significantly higher than those of the foamed polyethylene sound-absorbing materials in the comparative examples, and they have good sound-absorbing performance in different frequency bands: in the low-frequency band of 125-500 Hz, the sound absorption coefficient of the foamed polyethylene sound-absorbing material can reach above 0.4; in the medium-high frequency band of 1000-4000 Hz, the sound absorption coefficient of the foamed polyethylene sound-absorbing material can reach above 0.9. At the same time, the compression resistance of the foamed polyethylene sound-absorbing materials in Examples 1-8 is also better, and the compression modulus can reach above 3.2 MPa, and the cell morphology can be better maintained during the use of the material, with high practicability.

[0150] Comparing the comparative examples with Comparative Examples 1 and 2, it can be seen that the use amount and ratio of the composite foaming agent defined in the present invention in the examples can better achieve the synergistic effect of the three foaming agent components, accurately provide an appropriate amount of gas for the cell growth of the foaming material at different temperature stages, and significantly improve the performance of the material; while in Comparative Example 1, the use amount of the foaming agent is too low and the ratio of each component is not suitable, the foaming effect is poor, the sound absorption coefficients of the material at different frequency bands are significantly reduced, and the compression modulus becomes smaller; in Comparative Example 2, the use amount of the foaming agent is too high, which may cause the bubbles to merge into large bubbles and the cell structure is uneven, the sound absorption performance of the material deteriorates, and the compression modulus is further reduced.

[0151] Comparing the comparative examples with Comparative Examples 3 and 4, it can be seen that the change of the nucleating agent component has a great influence on the performance of the foamed polyethylene sound-absorbing material of the present invention: when the amount of nano-montmorillonite in the nucleating agent in Comparative Example 3 is too low, it leads to uneven cell distribution and significantly poor foaming effect, the sound absorption coefficients of the material at different frequency bands are significantly decreased, and the anti-compression performance becomes poor; in Comparative Example 4, the overall amount of the components of the nucleating agent is increased, which may cause particle agglomeration, excessive refinement and uneven distribution of the cell structure, and instead reduce the uniformity and mechanical properties of the foaming material, and the sound absorption performance and anti-compression performance are both poor.

[0152] Comparing the comparative examples with Comparative Example 5, it can be seen that when the ratio of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) in the polyethylene resin matrix is changed, and the HDPE is increased and the LDPE is reduced beyond the defined ratio range, the change of the matrix resin ratio causes a significant change in the foaming effect. Although the anti-compression performance of the material is significantly improved and the compression modulus is high, the sound absorption effect is significantly deteriorated and the sound absorption coefficient is greatly reduced, making it difficult to meet the requirements of sound-absorbing materials.

[0153] In summary, the present invention realizes the fine control of the cells by specifically modifying the polyethylene resin and combining specific composite foaming agents and nucleating agents, and prepares a foamed polyethylene sound-absorbing material with both excellent sound absorption effect and good anti-compression performance, solving the key problems of the foamed polyethylene sound-absorbing materials in the prior art. Moreover, its preparation method is easy for industrial production and has broad market application prospects.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A foamed polyethylene sound-absorbing material, characterized in that: The raw materials for preparing the foamed polyethylene sound-absorbing material include the following components: modified polyethylene resin, composite foaming agent and nucleating agent; The modified polyethylene resin is obtained by double grafting modification of polyethylene resin with a silane coupling agent and a functional carboxylic acid monomer; the polyethylene resin is a mixture of high-density polyethylene and low-density polyethylene, and the mass ratio of the high-density polyethylene to the low-density polyethylene is 1:(1-3); The components of the composite foaming agent include azodicarbonamide, sodium bicarbonate and foaming microspheres, and the mass ratio of azodicarbonamide, sodium bicarbonate and foaming microspheres is azodicarbonamide: sodium bicarbonate: foaming microspheres = (5-8): (1-2): 1; The nucleating agent is prepared by the reaction of an organic quaternary ammonium salt and nano-montmorillonite; Calculated by mass percentage of the polyethylene resin, the usage of the composite foaming agent is 2-8%, the usage of the organic quaternary ammonium salt is 0.2-2%, and the usage of the nano-montmorillonite is 0.5-3%.

2. The foamed polyethylene sound absorbing material according to claim 1, characterized in that: The preparation method of the modified polyethylene resin comprises the following steps: Step (1) heating and dissolving a polyethylene resin in an organic solvent, then adding an initiator and a silane coupling agent, and mixing and reacting the mixture in a nitrogen atmosphere to obtain a siloxane-grafted polyethylene resin; Step (2) adding the siloxane-grafted polyethylene resin to a functional carboxylic acid monomer and an initiator, mixing and reacting the mixture in a nitrogen atmosphere to obtain the modified polyethylene resin.

3. The foamed polyethylene sound absorbing material according to claim 2, characterized in that: The silane coupling agent is KH570; And / or, the functional carboxylic acid monomer is at least one of methacrylic acid, itaconic acid, maleic anhydride and acrylic acid; And / or, based on the mass percentage of the polyethylene resin, the amount of the silane coupling agent is 2-5%, and the amount of the functional carboxylic acid monomer is 3-10%.

4. The foamed polyethylene sound absorbing material according to claim 2, characterized in that: The initiator of step (1) is dibenzoyl peroxide, and the amount of dibenzoyl peroxide used is 0.5-1% based on the mass percentage of the polyethylene resin; And / or, the initiator in step (2) is potassium persulfate, and the amount of potassium persulfate used is 1-3% based on the mass percentage of the functional carboxylic acid monomer.

5. The foamed polyethylene sound absorbing material according to claim 1, characterized in that: The organic quaternary ammonium salt is at least one of hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide and benzyltrimethylammonium chloride.

6. The foamed polyethylene sound absorbing material according to claim 1, characterized in that: The raw materials for preparing the foamed polyethylene sound-absorbing material also include the following components: plasticizer, additive, auxiliary agent and solvent.

7. The foamed polyethylene sound absorbing material according to claim 6, characterized in that: The plasticizer includes at least one of tributyl citrate, dioctyl adipate, and dioctyl phthalate; And / or, the additives include micron-sized calcium carbonate whiskers and hollow glass microspheres; And / or, the auxiliary agent includes an antioxidant and a light stabilizer; And / or, the solvent is a mixed solvent of dichloromethane and cyclohexanone, and the mass ratio of dichloromethane to cyclohexanone is 1:(1-3).

8. The foamed polyethylene sound absorbing material according to claim 7, characterized in that: The amount of the plasticizer is 2-5% based on the mass percentage of the polyethylene resin; And / or, the mass of the micron-sized calcium carbonate whiskers accounts for 0.5-1.5% of the total mass of the raw materials, and the mass of the hollow glass microspheres accounts for 1-3% of the total mass of the raw materials; And / or, the weight of the antioxidant accounts for 0.2-1% of the total weight of the raw materials for preparation, and the weight of the light stabilizer accounts for 0.2-1% of the total weight of the raw materials for preparation; And / or, the mass ratio of the solvent to the modified polyethylene resin is 1:(3-6).

9. The method for preparing a foamed polyethylene sound absorbing material according to any one of claims 6 to 8, characterized in that: The following steps are involved: Step S1, adding a composite foaming agent, a nucleating agent, a plasticizer, an additive, and an auxiliary agent to a dried modified polyethylene resin in sequence under stirring, mixing well, and then adding a solvent to obtain a mixed solution; Step S2, ultrasonically dispersing the mixed solution, and then extruding it using a twin-screw extruder to obtain a blank; Step S3, heating the blank in a mold, applying pressure to foam it, and then cooling it under pressure to obtain the foamed polyethylene sound-absorbing material.

10. The method for preparing a foamed polyethylene sound absorbing material according to claim 9, characterized in that: In step S1, the stirring speed is 600-1000 r / min; And / or, in step S2, the conditions of ultrasonic dispersion are: power 350-450W, frequency 30-50kHz, time 50-70min; And / or, in step S2, the temperature of the twin-screw extruder from the hopper end to the die head is 140°C, 160°C, 180°C, 200°C, 210°C, and the screw speed is 100-140r / min; And / or, in step S3, the temperature of the mold is 160-200° C.; And / or, in step S3, the applied pressure is 1.5-2.5 MPa, and the pressure holding time is 8-20 min.

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