RU2745020C1 - Method of manufacture of a noise absorbing material - Google Patents

Abstract

FIELD: insulating materials.

SUBSTANCE: invention relates to a method of manufacture of a noise absorbing material. The method of manufacture of a noise absorbing material containing a non-woven, e.g., porous of fibrous base, consists of the base being submerged into an inorganic compound solution, first into 10 to 21.5% wt. solution of a first salt selected from CuSO₄, CaCl₂, BaCl₂, SrCl₂, AlCl₃, Na₂SiO₃, then a 7.5 to 15.5% wt. solution of a second salt is introduced, the salt selected from NaHCO₃, Na₂CO₃, KH₂PO₄, in an amount between equimolar and 2 to 3% excess from stoichiometry, and allow to stand for 1 to 2 hours. Then the produced material is taken out of the solution, rinsed with distilled water and dried.

EFFECT: invention allows producing a noise absorbing material with high efficiency, especially within the range of low acoustic frequencies between 125 and 1000 Hz.

2 cl, 3 dwg, 1 tbl

Description

The invention relates to methods for eliminating or at least reducing to a safe level of exposure to low-frequency vibration noise on humans and other living organisms. The invention presents the results of one of the directions of research and prospecting work on the creation of noise-absorbing and noise-insulating materials. The materials can be used in the production and repair of vehicles, household machines, in instrument making, in the production and repair of building structures, in other industries.

The known method [RF patent 2579802, IPC F01N 1/24, publ. 04/25/2016] obtaining a noise-absorbing insert for cars with internal combustion engines, made of at least one mineral fibrous material, which has the form of a molded material and is made by winding the material on at least one base. This material contains textured mineral fiber. The material is in the form of a formed web or molded part, and the material does not contain a binder. The disadvantage of this method is that the molding of the material is quite laborious. In addition, no information is provided on the indicators of the efficiency of noise absorption with the help of the obtained material.

In the invention [RF patent 2026869, IPC C08G 8/20, C08L 61/12, publ. January 20, 1995] describes the composition of the binder used to impregnate the fibrous filler, and the sound-absorbing material, with the following ratio of components, wt.%: Fibrous filler, 70-97, phenolic binder - the rest. The binder includes diphenylolpropane, formaldehyde, sodium hydroxide and water in the following ratio of components, wt%: diphenylolpropane, 2.0-15.0, formaldehyde, 0.3-4.0, sodium hydroxide, 0.35-5.1 , water is the rest.

Also known nonwoven material [US patent 10137666, IPC В32В 5 / 022.5 / 12, publ. 11/27/2018], which, in addition to the metal film, has a hum-absorbing layer, including: a) heat-resistant fiber in the amount of 30-100 wt-% of the total weight of the noise-absorbing layer, and b) a binder, characterized in that the nonwoven material contains microcavities ... The material is impregnated with a binder, with the first binder in the same layer as the nonwoven and retaining the three-dimensional structure within the nonwoven, and the first binder maintains and / or forms microcavities in the nonwoven as distributed and attached to the surface of the nonwoven.

This noise-absorbing material contains an adhesive layer comprising a second binder and a silica airgel in a weight ratio of about 1: (0.1-2) based on the solids content, the surface of the silica airgel being modified with a polyethylene glycol fatty acid ester. The refractory fiber has a heat resistance of ≥300 ° C and is selected from the following fibers: aramid, polyphenylene sulfide (PPS), oxidized polyacrylonitrile (oxi-PAN), polyimide (PI), polybenzimidazole (PBI), polybenzoxazole (PBO) (PTFE), polyketone (PK), metal fiber, carbon fiber, glass fiber, basalt, flint and ceramic. Preferably aramid fiber. In this case, the non-woven material is formed by a single-layer aramid fiber with a thickness of 3-20 mm. The binder can also be a thermosetting (epoxy) resin, which is selected from the group consisting of bisphenol diglycidyl ether (A, or B, or AD, F, S), polyoxypropylene, diglycedyl ether, bisphenol A diglycidyl ether polymer, phosphacene diglycidyl ether, epoxy novolac bisphenol A, novolacphenol epoxy, and novolac o-cresol epoxy.

A method of manufacturing a sound-absorbing material consists in immersing a non-woven material containing 30-100 wt-% heat-resistant fiber based on the total weight of the fiber in a binder solution, forming a sound-absorbing layer by drying the nonwoven material and applying a metal film to this layer.

The objective of the claimed invention is to simplify the technology of manufacturing noise-absorbing material of increased efficiency, especially in the range of low acoustic frequencies, 125-1000 Hz, the most harmful and dangerous for human life, while reducing the toxicity of the used intermediates.

The essence of the invention - a method of manufacturing a sound-absorbing material containing a non-woven, for example, a porous or fibrous base, consists in the fact that the base is immersed in a solution of an inorganic compound, first in a solution of the first salt, then a solution of the second salt is introduced in an amount from equimolar to 2-3 % excess from stoichiometry, incubated for 1-2 hours, after which the material is removed from the solution, washed with water and dried.

For impregnation of a nonwoven base by immersion in a solution, the following combinations of salts are selected: CuSO ₄ + NaHCO ₃ , or CaCl ₂ + KH ₂ PO ₄ , or BaCl ₂ + KH ₂ PO ₄ , or SrCl ₂ + KH ₂ PO ₄ , or AlCl ₃ + Na ₂ CO ₃ , or Na ₂ SiO ₃ + NaHCO ₃ .

The specified combinations of salts are taken in an equimolar ratio. The impregnation time is 1-2 hours, depending on the type of non-woven base and the required thickness of the layer of sound-absorbing material.

Non-woven base for impregnation can be selected from the following range: organic or inorganic fiber, polyurethane foam of various (open) porosity, foam and others. The thickness of the material layer is taken in the range, for example, from 15 to 50 mm.

Examples of the implementation of the proposed method.

Example # 1. _{A solution of CuSO 4} salt is poured into a glass container, and a sample of a non-woven base is immersed in the same container. Then add a solution of NaHCO ₃ in 2-3% excess of stoichiometry. Withstand 2 hours under normal ambient conditions, after which the impregnated material is removed from the solution, washed with distilled water and dried. Other experiments are carried out analogously to example No. 1 (see table. 1).

The invention is also illustrated by the following examples, where in FIG. 1 shows (by scanning the sample) the distribution of the substance (compound) particles in the bulk matrix of the porous (foamed) base after impregnation, FIG. 2 - an algorithm of acoustic measurements and a diagram of its implementation using equipment for studying the efficiency of noise absorption of materials manufactured according to the method, as well as materials of analogues and prototype, in a low-frequency acoustic waveguide, FIG. 3 - the efficiency of noise absorption of materials manufactured according to the claimed method, in comparison with the indicators of materials of analogues and prototype in the low-frequency (≤1000 Hz) acoustic spectrum (main indicator: dimensionless absorption coefficient).

As a result of the interaction of combinations of inorganic substances, taken in indicated in the table. 1 concentrations, on the inner and outer surfaces of the structural elements of the nonwoven base, in-situ precipitates of compounds in the form of particles are formed, which are fairly evenly distributed throughout the volume and reliably adhere to the base elements. With the help of tomography (see Fig. 1) of the tetrahedral element, it is shown that the particles of the substance (compound) are evenly distributed over the entire volume of the matrix structure of the base.

Tests illustrating the performance of the proposed method in terms of increasing the efficiency of noise absorption were performed (see Fig. 2) in accordance with the developed algorithm, using a certified measuring complex (Scien Co., Ltd. Acoustic Software development, Republic of Korea), including 100- mm waveguide 1 (System 9301), a set of microphones 2 and a portable system 3 of hardware and software (software), which provides the implementation of procedures for generating and amplifying the input acoustic signal in a given frequency band and a given level, converting the amplified signal into a digital signal for its subsequent spectral analysis by the method of fast Fourier transform (FFT-method), calculation of parameters of noise absorption of sample 4 of the manufactured material, including the main indicator: dimensionless coefficient of [noise] absorption, - as well as processing and graphical presentation of the results of measurements and calculations.

The examples in FIG. 3 illustrate the data of testing the performance of the proposed method to improve the efficiency of noise absorption. Shown here is the change in the noise absorption coefficient of materials of four different types (three with different fibrous and one with a porous base), manufactured according to the claimed method (see solid graphs "application"), in comparison with the quality of materials of analogues and prototype (see dotted graphs "prototype "). In the presented eight samples, the base of each of the corresponding four pairs "prototype" - "application" has the same initial structure. The thickness of the material layer is from 25 to 45 mm.

FIG. 3 shows the results of testing samples of materials impregnated (see table 1) according to example No. 1 (using two different types 1 and 3 of the fiber base) and according to example No. 16 (using the fiber base type 2 and porous base).

FIG. 3 shows that the materials of analogs and prototype are insufficiently effective or ineffective in the frequency band 125-250 Hz, regardless of the layer thickness. Moreover, the materials produced according to the inventive method absorb such noise. With an increase in the thickness of the layer, the efficiency of noise absorption of the manufactured materials significantly increases and exceeds by 2-3 times or more the efficiency of materials of analogues and prototype in the frequency band 250-1000 Hz.

Thus, the inventive method of manufacturing a sound-absorbing material fully provides a solution to the problem, namely, simplifying the technology for manufacturing a sound-absorbing material using available, inexpensive non-toxic starting materials (base), as well as intermediate products (substances) for impregnating the base and, ultimately, in 2-3 times and more significant increase in the efficiency of noise absorption in the range of low acoustic frequencies, 125-1000 Hz, the most harmful and dangerous for human life.

Claims (2)

1. A method of manufacturing a noise-absorbing material containing a non-woven porous or fibrous base, characterized in that the non-woven base is immersed in a solution of an inorganic compound, first in a 10-21.5 wt.% Solution of a first salt selected from CuSO ₄ , CaCl ₂ , BaCl ₂ , SrCl ₂ , AlCl ₃ , Na ₂ SiO ₃ , then a 7.5-15.5 wt.% Solution of the second salt selected from NaHCO ₃ , Na ₂ CO ₃ , KH ₂ PO ₄ is introduced, in an amount from equimolar to 2 -3% excess from stoichiometry, and incubated for 1-2 hours, after which the produced material is removed from the solution, washed with distilled water and dried. 2. The method according to claim 1, characterized in that for the impregnation of the nonwoven base by immersion in a solution, the following combinations of salts are selected: CuSO ₄ + NaHCO ₃ , or CaCl ₂ + KH ₂ PO ₄ , or BaCl ₂ + KH ₂ PO ₄ , or SrCl ₂ + KH ₂ PO ₄ , or AlCl ₃ + Na ₂ CO ₃ , or Na ₂ SiO ₃ + NaHCO ₃ .

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