CN114833906B

CN114833906B - Preparation method and application of ultrathin wood vibrating diaphragm with excellent acoustic characteristics and dimensional stability

Info

Publication number: CN114833906B
Application number: CN202210487048.4A
Authority: CN
Inventors: 杨蕊; 董安然; 杨锡蔓; 徐硕; 罗婉娟; 朱曦; 孟祥真; 周静; 梁星宇
Original assignee: Nanjing Forestry University
Current assignee: Nanjing Forestry University
Priority date: 2022-05-06
Filing date: 2022-05-06
Publication date: 2023-08-11
Anticipated expiration: 2042-05-06
Also published as: CN114833906A

Abstract

The application discloses a preparation method and application of an ultrathin wood vibrating diaphragm with excellent acoustic properties and dimensional stability, wherein wood is immersed into an sulfamic acid/urea/lactic acid ternary eutectic system, subjected to microwave treatment at a specific temperature, washed by deionized water, and then subjected to hot pressing to obtain the ultrathin wood vibrating diaphragm, and the prepared wood vibrating diaphragm shows excellent acoustic properties and dimensional stability.

Description

Preparation method and application of ultrathin wood vibrating diaphragm with excellent acoustic characteristics and dimensional stability

Technical Field

The application belongs to the technical field of biomass materials, and particularly relates to a preparation method and application of an ultrathin wood vibrating diaphragm with excellent acoustic characteristics and dimensional stability.

Background

With the popularization of audiovisual products, the development of communication technology and the rapid increase of the market size of mobile electronic products, the global earphone market size continues to increase. A core part of the earphone is a sounding unit, the sounding unit is mainly a loudspeaker, the loudspeaker of the earphone is provided with a moving coil and a moving iron, ninety percent of the earphone is provided with the moving coil, and sound is generated through vibration of the vibrating diaphragm, so that the quality of the sound quality is directly influenced by the quality of the vibrating diaphragm.

Most moving coil earphones in the market at present adopt plastic vibrating diaphragms, paper vibrating diaphragms, titanium vibrating diaphragms, aluminum vibrating diaphragms and other metal vibrating diaphragms. But the plastic diaphragm has poor rigidity, small internal resistance and easy distortion. The problems of poor resolution and insufficient dynamics are obvious in hearing, and the phenomenon of slow connection and unsmooth connection easily occurs from the medium frequency to the high frequency. Paper diaphragms are susceptible to air temperature and humidity. The metal diaphragm can perfectly solve the problems of the first two diaphragms, but is always in dispute due to the large weight. And because plastics and metals are difficult to degrade in nature, the post-disposal recycling work of the earphones made of the two materials is also a big problem.

The biological fiber diaphragm which emerges in the last two years is thinner, lighter in inertia, quicker in rebound, finer in sound detail, high in sound restoration degree and popular in virtue of the biological fiber diaphragm which emerges in the last two years is lighter and thinner than other diaphragms. Compared with the vibrating diaphragm made of metal materials, the biological vibrating diaphragm has light weight and can be decomposed, but the main problems existing in the market at present are complex process, high manufacturing cost and high dimensional stability of the vibrating diaphragm; in addition, the thickness of the diaphragm is generally required to be less than 50 μm, and the current wood processing technology is difficult to achieve the requirement, so that the application of the wood diaphragm is limited. Therefore, how to prepare an ultrathin wood diaphragm with good dimensional stability and capable of meeting the thickness requirement is a technical problem to be solved. Meanwhile, reasonable utilization of the biological fiber diaphragm has important significance for relieving environmental pressure and promoting green transformation of related industries.

Disclosure of Invention

This section is intended to outline some aspects of embodiments of the application and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description of the application and in the title of the application, which may not be used to limit the scope of the application.

The application provides a preparation method of an ultrathin wood vibrating diaphragm with excellent acoustic characteristics and dimensional stability, which comprises the following steps,

(1) Heating sulfamic acid, urea and lactic acid in a mixed water bath until solid particles disappear, wherein sulfamic acid: urea: the molar ratio of lactic acid is 1:3: (1-3) preparing a ternary eutectic solvent;

(2) Immersing a wood test piece into the ternary eutectic solvent prepared in the step (1), and carrying out microwave treatment to obtain a modified wood test piece;

(3) Taking out the modified wood test piece in the step (2), and soaking in deionized water to remove residual reaction liquid, wherein the soaking time is 1-2 days;

(4) Taking out the wood test piece obtained in the step (3), and freeze-drying in a freeze dryer to obtain a refined wood test piece;

(5) And (3) carrying out hot pressing on the refined wood test piece obtained in the step (4) to obtain the ultrathin wood vibrating diaphragm.

As a preferable scheme of the preparation method of the ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability, the preparation method comprises the following steps: in the step (1), the mixed water bath is heated, and the water bath temperature is 70-90 ℃.

As a preferable scheme of the preparation method of the ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability, the preparation method comprises the following steps: in the step (2), the temperature of the microwave treatment is 50-90 ℃, the power is 500-1000W, and the treatment time is 5-15 min.

As a preferable scheme of the preparation method of the ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability, the preparation method comprises the following steps: in the step (2), the material of the wood test piece comprises one of bassal wood, fir wood and paulownia wood.

As a preferable scheme of the preparation method of the ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability, the preparation method comprises the following steps: the specification of the wood test piece is as follows: the longitudinal direction X chord direction X radial direction is 1mm X50 mm.

As a preferable scheme of the preparation method of the ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability, the preparation method comprises the following steps: in the step (4), the freeze drying is performed under vacuum, and the temperature is controlled to be-65 to-64 ℃.

As a preferable scheme of the preparation method of the ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability, the preparation method comprises the following steps: in the step (5), the temperature of the hot pressing is controlled to be 100-120 ℃, and the hot pressing pressure is controlled to be 10-20 MPa.

As a preferable scheme of the preparation method of the ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability, the preparation method comprises the following steps: in the step (5), the hot pressing time is 10-20 min.

The application has the beneficial effects that:

1. according to the application, a wood test piece is treated by a ternary eutectic system composed of sulfamic acid, urea and lactic acid, wherein lignin and hemicellulose are partially removed by lactic acid components, wood channels are softened, and spaces between wood cell walls are increased, so that cell collapse is promoted in the compression process. The problems that wastes such as sulfite are difficult to treat, the energy consumption in the treatment process is high, the environment is polluted and the like are avoided by using the traditional sodium hydroxide/sodium sulfite method adopted by the prior delignification and hemicellulose preparation of the wood diaphragm; and the cellulose crystal structure can be well maintained, the elastic modulus is enhanced, and the advantages of high sound conduction rate, low natural attenuation, contribution to high-frequency analysis extension, reduction of segmentation vibration and the like are generated.

2. The sulfamic acid component in the ternary eutectic system adopted by the application is an inorganic solid acid, is formed by treating urea by a mixture of sulfur trioxide and sulfuric acid, and is a common sulfating reagent with low toxicity and low cost; according to the application, negatively charged ions are introduced into sulfonated wood cellulose, the high charge density leads to in-situ self-compaction among cells, and sulfuric acid groups are introduced into the surface of cellulose, so that the sulfated cellulose can be endowed with special properties (strong electronegativity, good solubility, good stability and good film forming property). The final hot pressing process promotes the diaphragm to form a tighter structure, so that the prepared wooden diaphragm has a thickness of less than 10 mu m, and the compact cell structure also prevents the entry of moisture, so that the wooden diaphragm has excellent dimensional stability and good acoustic resonance and vibration spectrum characteristics.

3. Sulfamic acid is an irreplaceable excellent sulfonating agent in the preparation method of the application, but carbonization of cellulose is observed when sulfating is performed in an organic medium using pure sulfamic acid due to the high melting point of sulfamic acid. The presence of urea is therefore an important factor in the sulphation of wood. According to the application, the research shows that the urea and the sulfamic acid can form a eutectic system at a certain ratio, so that the sulfamic acid can react with cellulose at a lower temperature, and a necessary condition is provided for practical application of the application.

4. The temperature and the proportion adopted in the preparation method of the application are irreplaceable, and the mol ratio of sulfamic acid to urea is 1:3, sulfamic acid and urea under other proportioning conditions cannot be mutually fused into transparent clear liquid; and sulfamic acid: urea: the molar ratio of lactic acid is 1:3: (1-3) if the lactic acid amount is too small, hemicellulose and lignin removal rate of the wood is insufficient, and if the lactic acid amount is too large, cellulose structure of the wood is destroyed, which is unfavorable for the subsequent sulfonation treatment. The reaction temperature is controlled to be 70-90 ℃, and the eutectic system is solidified at an excessively low temperature, so that the eutectic system cannot react with a wood sample; too high a temperature can lead to charring of the wood cellulose, which is detrimental to the reaction and sample formation.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:

fig. 1 is an SEM image of a wood diaphragm prepared in each example.

FIG. 2 shows the results of the test of the acoustic performance of the diaphragm according to the embodiments.

Detailed Description

In order that the above-recited objects, features and advantages of the present application will become more apparent, a more particular description of the application will be rendered by reference to specific embodiments thereof.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present application is not limited to the specific embodiments disclosed below.

Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

Example 1:

a preparation method of an ultrathin wood diaphragm with excellent acoustic characteristics and dimensional stability comprises the following steps:

(1) Heating sulfamic acid, urea and lactic acid in a mixed water bath until solid particles disappear, wherein sulfamic acid: urea: the molar ratio of lactic acid is 1:3:1, preparing a eutectic solvent;

(3) Taking out the modified wood test piece in the step (2), and soaking the modified wood test piece in deionized water to remove residual reaction liquid, wherein the soaking time is 1 day in the step;

(4) Taking out the pretreated wood test piece in the step (3), and freeze-drying in a freeze dryer for 12 hours to obtain a refined wood test piece;

(5) And (3) carrying out hot pressing on the refined wood test piece in the step (4) to construct the ultrathin wood vibrating diaphragm.

In step (1), the temperature of the water bath treatment is 80 ℃.

In the step (2), the temperature of the microwave treatment is 70 ℃, the power is 800W, and the treatment time is 10min.

In the step (2), the material of the wood test piece is bassa wood.

In the step (2), the specification of the wood test piece is as follows: the longitudinal direction X chord direction X radial direction is 1mm X50 mm.

In the step (4), the pressure of the freeze drying process is vacuum condition, and the temperature is controlled to be-65 ℃.

In the step (5), the hot pressing temperature in the hot pressing process is 100 ℃, and the hot pressing pressure is controlled to be 10MPa.

In the step (5), the hot pressing time of the hot pressing process is 10min.

Example 2:

(1) Heating sulfamic acid, urea and lactic acid in a mixed water bath until solid particles disappear, wherein sulfamic acid: urea: the molar ratio of lactic acid is 1:3:3, preparing a eutectic solvent;

In step (1), the temperature of the water bath treatment is 80 ℃.

In the step (2), the material of the wood test piece is bassa wood.

In the step (5), the hot pressing time of the hot pressing process is 10min.

Example 3:

a method for preparing an ultra-thin wood diaphragm having excellent acoustic properties and dimensional stability, comprising the steps of:

In step (1), the temperature of the water bath treatment is 80 ℃.

In the step (2), the temperature of the microwave treatment is 70 ℃, the power is 800W, and the treatment time is 15min.

In the step (2), the material of the wood test piece is bassa wood.

In the step (5), the hot pressing time of the hot pressing process is 10min.

Example 4:

In step (1), the temperature of the water bath treatment is 80 ℃.

In the step (2), the material of the wood test piece is bassa wood.

In the step (5), the hot pressing temperature in the hot pressing process is 100 ℃, and the hot pressing pressure is controlled to be 20MPa.

In the step (5), the hot pressing time of the hot pressing process is 10min.

Example 5:

In step (1), the temperature of the water bath treatment is 80 ℃.

In the step (2), the wood test piece is made of paulownia wood.

In the step (5), the hot pressing time of the hot pressing process is 10min.

Example 6:

In step (1), the temperature of the water bath treatment is 80 ℃.

In the step (2), the wood test piece is made of fir.

In the step (5), the hot pressing time of the hot pressing process is 10min.

SEM images of the wood diaphragms prepared in each example are shown in fig. 1.

Dimensional stability test of the diaphragms produced in each example:

dimensional stability test method: according to the requirements of GB/T19282009 chapter 3 sample preparation and test. The sample is soaked in distilled water, the chord length is measured to the size of the sample at 20 ℃ and is accurate to 0.01mm respectively, and the sample is kept in a wet state in the measurement process. After measuring the sample, the sample was placed in a dry gas under conditions specified in chapter 4 of GB/T1928 2009. In the dry gas process, the radial chord is measured to the size of the sample and the mass of the sample are measured respectively according to the accuracy rule, the accuracy is 0.001g, the sample is placed at the temperature of 60 ℃ for 6 hours, then the sample is dried according to the specification of GB/T1931-2009 at 5.2-5.4, the mass and the radial direction of each sample are measured, and in the measuring process, the sample is prevented from cracking or deforming as much as possible.

Table 1 dimensional stability test of each diaphragm sample

Note that: each log sample was the same as the sample of example in specification, and the dimensional stability and thickness thereof were measured after subjecting the log sample to only autoclave treatment.

The thicknesses of the diaphragms produced in each example are shown in Table 2.

TABLE 2 thickness of each diaphragm sample

Sample of	Thickness/mm
		Bassa former wood	0.24
Paulownia log	0.17
		Fir log	0.19
Example 1	0.03
		Example 2	0.03
Example 3	0.04
		Example 4	0.02
Example 5	0.02
		Example 6	0.03

Characterization of the acoustic properties of the diaphragms: to test the performance of the wooden diaphragms prepared in the application, the wooden diaphragms prepared in examples 1 to 6 were cut into a round piece with a diameter of 36mm, the wooden diaphragms and a round gasket were bonded with epoxy resin to prepare round wooden diaphragms, the round wooden diaphragms were placed under a laser vibrometer, white noise with a frequency of 1.5-50kHz was emitted from a loudspeaker, and the acoustic performance test results of the diaphragms of the examples were shown in Table 2 by comparing the output of the vibrometer with the output of a microphone placed beside the diaphragms. Fig. 2 a is an acoustic performance test of a paulownia log diaphragm, and b is an acoustic performance test of a diaphragm prepared in example 5. As is apparent from fig. 2, the sound producing effect of the wood vibration chip provided in example 5 is excellent. The acoustic performance test data for the diaphragm samples of each example are shown in Table 3.

Table 3 test of acoustic properties of samples of diaphragms of various embodiments

As can be seen from Table 3, the acoustic properties of the samples treated by the method of the present application are significantly improved over the log. In particular, although the acoustic properties of the paulownia logs were not optimal, the acoustic properties of the samples treated by the technical solution of example 5 were significantly improved.

It should be noted that the above embodiments are only for illustrating the technical solution of the present application and not for limiting the same, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted without departing from the spirit and scope of the technical solution of the present application, which is intended to be covered in the scope of the claims of the present application.

Claims

1. A method for preparing an ultrathin wood diaphragm with excellent acoustic properties and dimensional stability, which is characterized in that: is composed of the following steps of the method,

(2) Immersing a wood test piece into the ternary eutectic solvent prepared in the step (1), and carrying out microwave treatment to obtain a modified wood test piece; the wood test piece is made of one of bassal wood, fir wood and paulownia wood;

(5) Performing hot pressing on the refined wood test piece obtained in the step (4) to obtain the ultrathin wood vibrating diaphragm;

in the step (1), heating the mixed water bath, wherein the water bath temperature is 70-90 ℃;

in the step (2), the temperature of the microwave treatment is 50-90 ℃, the power is 500-1000W, and the treatment time is 5-15 min;

in the step (5), the temperature of the hot pressing is controlled to be 100-120 ℃, and the hot pressing pressure is controlled to be 10-20 MPa;

in the step (5), the hot pressing time is 10-20 min.

2. The method for producing an ultrathin wood diaphragm having excellent acoustic properties and dimensional stability according to claim 1, characterized in that: the specification of the wood test piece is as follows: the longitudinal direction X chord direction X radial direction is 1mm X50 mm.

3. The method for producing an ultrathin wood diaphragm having excellent acoustic characteristics and dimensional stability according to claim 1 or 2, characterized in that: in the step (4), the freeze drying is performed under vacuum, and the temperature is controlled to be-65 to-64 ℃.

4. The wooden vibrating diaphragm prepared by the preparation method of claim 1 is applied to video and audio products and artificial cochlea products.