Nanoscale PU audio film used in mobile phone field, and preparation method and application thereof

Abstract

The invention discloses a nanoscale PU audio film for the field of mobile phones and a preparation method and application of the nanoscale PU audio film. The preparation method comprises the following steps: preparing the nanoscale PU audio film for the field of mobile phones from a polyurethane static spinning solution by using an electrostatic spinning method; the polyurethane static spinning solution comprises linear polyurethane, modified montmorillonite and a solvent. The prepared nanoscale PU audio film in the field of mobile phones is large in specific surface area, sensitive in audio response and wide in frequency response range. The modified montmorillonite forms a nano barrier network, so that the heat resistance is remarkably improved, and the performance is stable through a double-85 long-term environment test. The preparation method is stable in process, repeatable and beneficial to industrial production, the problems that the diameter of traditional PU audio film fibers is difficult to control and the heat resistance is poor are effectively solved, and the requirements of mobile phones for high-quality audio films are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of mobile phone component manufacturing, and in particular relates to a nano-scale PU audio film for use in the mobile phone field, and a preparation method and application thereof. Background Art

[0002] In a mobile phone's audio system, the audio membrane is a key component, and its performance directly affects the sound quality and the overall audio experience of the phone. With the continuous development of mobile phone technology, the requirements for audio membranes are becoming increasingly higher. Not only must they have good audio effects, but they must also be lightweight, thin, and stable.

[0003] While traditional PU audio membranes offer certain advantages in flexibility and processability, they also have significant limitations. Firstly, the difficulty in precisely controlling their fiber diameter at the nanometer level results in a relatively small surface area. This results in a less-than-stellar response to audio signals during vibrations and a limited frequency response range, making it unable to meet the high-quality audio requirements of mobile phones. Secondly, traditional PU audio membranes have poor heat resistance and are susceptible to performance degradation in high-temperature and high-humidity environments, such as those at 85°C (85% relative humidity). This can cause changes in the membrane's physical properties, such as shape changes and a decrease in mechanical properties, which in turn affects the vibration characteristics of the membrane, ultimately leading to a decline in mobile phone audio quality, including sound distortion and unstable volume.

[0004] Electrospinning technology, as an effective method for producing nanofibers, has attracted widespread attention in the field of material preparation. However, applying electrospinning to produce nanoscale PU audio membranes for mobile phones, while ensuring they possess the heat resistance required for long-term dual-85 environmental testing, still presents numerous technical challenges, such as optimizing spinning process parameters and adjusting material formulations. Summary of the Invention

[0005] In view of this, the present invention aims to propose a nano-scale PU audio membrane for use in the mobile phone field, a preparation method and an application thereof, so as to solve at least one technical problem in the background technology.

[0006] This application optimizes the electrospinning process and material formulation to prepare a PU audio membrane with a fiber diameter of 300-900nm, which has good audio performance and significantly improves heat resistance, and can withstand long-term environmental tests of double 85. To achieve the above objectives, the technical solution of the present invention is implemented as follows: A method for preparing a nano-scale PU audio membrane for mobile phones comprises the following steps: preparing a nano-scale PU audio membrane for mobile phones by using an electrostatic spinning method from a polyurethane static spinning solution; The polyurethane static spinning solution comprises linear polyurethane, modified montmorillonite and solvent.

[0007] Furthermore, the molecular weight of the linear polyurethane is 120,000-150,000. The basic PU material of this application uses a linear polyurethane with a number average molecular weight of 120,000-150,000, which has good film-forming properties and mechanical properties and can provide a stable structural foundation for the audio membrane.

[0008] Furthermore, the mass fraction of modified montmorillonite in the polyurethane static spinning solution is 6%-10%. Montmorillonite is a natural layered silicate mineral with a large specific surface area and excellent barrier properties. The montmorillonite is surface-modified using an organic modifier to improve its compatibility with the polyurethane matrix. Cetyltrimethylammonium bromide is used as the organic modifier in an amount of 3%-5% of the montmorillonite mass. The modified montmorillonite is evenly dispersed in the polyurethane matrix, forming a nanoscale barrier layer that effectively hinders heat transfer and molecular chain motion, thereby improving the heat resistance of the PU audio membrane.

[0009] And / or, the mass fraction of the sum of the linear polyurethane and the modified montmorillonite in the polyurethane static spinning solution is 10%-25%.

[0010] Furthermore, the preparation of modified montmorillonite includes surface modification of montmorillonite using hexadecyltrimethylammonium bromide as an organic modifier in an amount of 3%-5% by mass of montmorillonite, adding montmorillonite to hexadecyltrimethylammonium bromide, and ultrasonically vibrating at 75-85°C for 3.5-4.5 hours to ensure that the modification is completed to obtain modified montmorillonite, in which the alkyl chain of hexadecyltrimethylammonium bromide is exposed, causing the surface of the montmorillonite to change from hydrophilic to hydrophobic, thereby improving the interfacial bonding strength with the polymer matrix.

[0011] Further, the solvent includes N,N-dimethylacetamide and tetrahydrofuran; And / or, the volume ratio of N,N-dimethylacetamide to tetrahydrofuran is 3-5:1, preferably 4:1. A mixed solvent of N,N-dimethylacetamide (DMAC) and tetrahydrofuran (THF) is used, with a volume ratio of DMAC to THF of 4:1. This mixed solvent has good solubility for PU, forming a stable jet during the electrospinning process, and facilitating the production of uniform nanofibers.

[0012] A method for preparing a nanoscale PU audio membrane for mobile phones comprises the following steps: S1: adding linear polyurethane and modified montmorillonite into a solvent, heating and stirring to obtain a polyurethane static spinning solution; S2: The polyurethane electrospinning solution obtained in step S1 is loaded into a syringe with a metal needle, and a PU nanofiber membrane is obtained by electrospinning. The PU nanofiber membrane is post-processed to obtain a nano-scale PU audio membrane for mobile phones.

[0013] Furthermore, the temperature of heating and stirring in step S1 is 55-65° C., and the time of heating and stirring is 8-10 h.

[0014] Furthermore, the spinning voltage of the electrospinning in step S2 is 20-35 kV, the receiving distance of the electrospinning is 15-30 cm, and the propulsion speed of the electrospinning is 0.6-1.2 mL / h; and / or, the electrospinning environment in step S2 is at a temperature of 20-30° C. and a relative humidity of 20%-40%; And / or, the post-treatment in step S2 includes vacuum drying the PU nanofiber membrane at 90-110° C. for 3-5 hours.

[0015] The measured amounts of PU and modified montmorillonite were added to a mixture of DMAC and THF and stirred at 55-65°C for 8-10 hours to completely dissolve the PU and evenly disperse the modified montmorillonite, forming a spinning solution with a mass fraction of 18%-22%. The spinning solution was then loaded into a syringe with a metal needle, and the electrospinning parameters were set: spinning voltage of 18-22 kV, receiving distance of 12-16 cm, and propulsion speed of 0.6-1.2 mL / h. During the spinning process, the ambient temperature was maintained at 25-30°C and relative humidity at 30%-40% to ensure spinning stability and fiber quality. The resulting PU nanofiber membrane was vacuum dried at 90-110°C for 3-5 hours to remove residual solvent and further improve membrane density and stability.

[0016] The nano-PU audio membrane produced by the aforementioned method for preparing a nano-PU audio membrane for mobile phones has a fiber diameter of 0.3-1.2 μm and can withstand long-term environmental testing at double 85°C (85°C temperature, 85% relative humidity). Under these conditions, the membrane exhibited good dimensional stability and maintained minimal changes in mechanical and acoustic properties.

[0017] Nano-scale PU audio membranes used in mobile phone fields are used in mobile phone fields.

[0018] Compared with the prior art, the nano-scale PU audio membrane for mobile phones and its preparation method and application described in the present invention have the following advantages: 1. This application can stably produce PU nanofiber membranes with fiber diameters ranging from 300-900nm by precisely controlling electrospinning process parameters, including voltage, receiving distance, propulsion speed, solution concentration, and solvent composition. This nanoscale fiber structure greatly increases the membrane's specific surface area, enabling it to respond more sensitively to audio signals during audio vibrations, effectively improving the membrane's sensitivity and frequency response range, and providing clearer, richer sound quality for mobile phones.

[0019] 2. The modified montmorillonite added in this application forms a good interfacial bond with the PU matrix and is evenly dispersed within the PU matrix, forming an effective nano-barrier network. This network structure can hinder heat transfer and limit the movement of PU molecular chains at high temperatures, thereby significantly improving the heat resistance of the PU audio membrane. Double 85 long-term environmental testing has verified that the PU audio membrane prepared by this invention has good dimensional stability in high temperature and high humidity environments, and the mechanical and acoustic properties of the membrane remain essentially unchanged. It can meet the requirements of long-term stable use of mobile phones in complex environments, greatly improving the reliability and service life of mobile phone audio components.

[0020] 3. By optimizing the material formula and electrospinning process parameters, the preparation method of the present invention has good process stability and repeatability, can realize large-scale industrial production, and provides strong technical support for the widespread application of nano-scale PU audio membranes for mobile phones. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0022] The present invention will be described in detail below with reference to examples.

[0023] Example 1 Material formula: Weigh 12g of linear polyurethane with a number average molecular weight of 130,000 and 0.8g of montmorillonite modified with hexadecyltrimethylammonium bromide (the amount of modifier is 4% of the mass of montmorillonite) and add them to a mixed solvent consisting of 80mL of N,N-dimethylacetamide (DMAC) and 20mL of tetrahydrofuran (THF).

[0024] Preparation process: Stir at 60°C for 9 hours to obtain a spinning solution with a mass fraction of 20%. The solution was loaded into a syringe, and the electrospinning voltage was set to 20kV, the receiving distance was 14cm, and the propulsion speed was 0.8mL / h. Electrospinning was carried out under ambient temperature of 28°C and relative humidity of 35%. After spinning, the fiber membrane was vacuum dried at 100°C for 4 hours. After testing, the average fiber diameter of the prepared PU nanofiber membrane was 550nm. After being placed in a double 85 environment for 1200 hours, the dimensional change rate of the membrane was less than 1%. The audio performance test showed that the sound quality was clear and there was no obvious distortion.

[0025] Example 2 Material formula: Take 15g of linear polyurethane with a number average molecular weight of 140,000, 1.0g of modified montmorillonite (the amount of modifier is 3.5% of the mass of montmorillonite), and the mixed solvent is 90mL DMAC and 22.5mL THF.

[0026] Preparation process: A spinning solution with a mass fraction of 21% was prepared by stirring at 58°C for 10 hours. The electrospinning parameters were set at a voltage of 21 kV, a receiving distance of 15 cm, and a propulsion speed of 1.0 mL / h. The ambient temperature was 27°C and the relative humidity was 38%. The resulting PU nanofiber membrane was vacuum-dried at 105°C for 3.5 hours. The resulting PU nanofiber membrane had an average fiber diameter of 600 nm. After 1500 hours of dual 85°C environmental testing, the membrane showed stable performance and good audio quality.

[0027] Example 3 Material formula: Weigh 13g of linear polyurethane with a number average molecular weight of 120,000 and 0.9g of montmorillonite modified with hexadecyltrimethylammonium bromide (the amount of modifier is 4.5% of the mass of montmorillonite) and add them to a mixed solvent consisting of 76mL DMAC and 19mL THF.

[0028] Preparation process: Stir at 62 ° C for 8.5 hours to obtain a spinning solution with a mass fraction of 19%. The solution was loaded into a syringe, and the electrospinning voltage was set to 19kV, the receiving distance was 13cm, and the propulsion speed was 0.9mL / h. Electrospinning was carried out under ambient temperature of 26 ° C and relative humidity of 33%. After spinning, the fiber membrane was vacuum dried at 95 ° C for 4.5 hours. After testing, the average fiber diameter of the prepared PU nanofiber membrane was 480nm. After being placed in a double 85 environment for 1300 hours, the dimensional change rate of the membrane was less than 1%. The audio performance test showed that the sound quality was clear without obvious distortion.

[0029] Example 4 Material formula: Take 14g of linear polyurethane with a number average molecular weight of 150,000, 1.1g of modified montmorillonite (the amount of modifier is 3.8% of the mass of montmorillonite), and the mixed solvent is 88mL DMAC and 22mL THF.

[0030] Preparation process: Stir at 63 ° C for 9.5 hours to obtain a spinning solution with a mass fraction of 20.5%. The electrospinning parameters are set to a voltage of 20.5kV, a receiving distance of 14.5cm, and a propulsion speed of 1.1mL / h. The ambient temperature is 29 ° C and the relative humidity is 36%. After spinning, the fiber membrane is vacuum dried at 102 ° C for 3.8 hours. The average fiber diameter of the obtained PU nanofiber membrane is 620nm. After 1400 hours of double 85 environmental testing, the membrane performance is stable and the audio effect is good. Example 5 Material formula: Weigh 12.5g of linear polyurethane with a number average molecular weight of 135,000 and 1.05g of montmorillonite modified with hexadecyltrimethylammonium bromide (the amount of modifier is 4.2% of the mass of montmorillonite) and add them to a mixed solvent consisting of 84mL DMAC and 21mL THF.

[0031] Preparation process: Stir at 57 ° C for 9.8 hours to obtain a spinning solution with a mass fraction of 20.8%. The solution was loaded into a syringe, and the electrospinning voltage was set to 21.5kV, the receiving distance was 15.5cm, and the propulsion speed was 1.05mL / h. Electrospinning was carried out under ambient temperature of 25 ° C and relative humidity of 32%. After spinning, the fiber membrane was vacuum dried at 108 ° C for 3.2 hours. After testing, the average fiber diameter of the prepared PU nanofiber membrane was 580nm. After being placed in a double 85 environment for 1100 hours, the dimensional change rate of the membrane was less than 1%. The audio performance test showed that the sound quality was clear and there was no obvious distortion.

[0032] Comparative Example 1 Material formulation: Only 12 g of linear polyurethane with a number average molecular weight of 130,000 was added to a mixed solvent consisting of 80 mL of DMAC and 20 mL of THF, without the addition of modified montmorillonite.

[0033] Preparation process: The spinning and post-treatment process are the same as those in Example 1. The prepared PU fiber membrane has a fiber diameter of 1-2 μm. After being placed in a double 85 environment for 600 hours, the membrane exhibits obvious deformation and the sound is severely distorted in the audio test.

[0034] Comparative Example 2 Material formulation: Add unmodified montmorillonite, and the dosage and other PU and solvent dosage are the same as in Example 1.

[0035] Preparation process: the same as Example 1. The montmorillonite in the obtained fiber membrane was unevenly dispersed, the fiber diameter distribution was wide, and after 800 hours in a double 85 environment, the membrane performance declined and the audio quality was affected.

[0036] Comparative Example 3 Material formula: 12 g of linear polyurethane with a number average molecular weight of 130,000 was added to a mixed solvent consisting of 20 mL of DMAC and 80 mL of THF. No modified montmorillonite was added. The rest was the same as in Example 1.

[0037] Preparation process: same as Example 1.

[0038] The prepared PU fiber membrane has a fiber diameter of 1-2 μm. After being placed in a double 85 environment for 600 hours, the membrane showed obvious deformation and the sound was severely distorted in the audio test.

[0039] Comparative Example 4 Material formula: the solvent is 100 ml of N,N-dimethylacetamide, and the rest are the same as in Example 1.

[0040] Preparation process: the same as Example 1. The obtained fiber membrane has a diameter of 2-3 μm. After being placed in a double 85 environment for 1000 hours, the membrane size change rate is greater than 5%, the sound loss is large, and the audio performance is poor.

[0041] Comparative Example 5 Material formula: the solvent is 100 ml of tetrahydrofuran, and the rest are the same as in Example 1.

[0042] Preparation process: the same as Example 1. The obtained fiber membrane had uneven thickness distribution, wide fiber diameter distribution, large differences in membrane performance at different positions, and unstable audio performance.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a nano-scale PU audio membrane for mobile phones, characterized by: The method comprises the following steps: preparing a nano-scale PU audio membrane for mobile phones by using an electrostatic spinning method for a polyurethane static spinning solution; The polyurethane static spinning solution comprises linear polyurethane, modified montmorillonite and solvent; The preparation of modified montmorillonite includes adding montmorillonite to hexadecyltrimethylammonium bromide, and ultrasonically vibrating at 75-85° C. for 3.5-4.5 hours to obtain the modified montmorillonite; The molecular weight of linear polyurethane is 120,000-150,000; The mass fraction of modified montmorillonite in the polyurethane static spinning solution is 6%-10%; The mass fraction of the sum of the linear polyurethane and the modified montmorillonite in the polyurethane static spinning solution is 10%-25%.

2. The method for preparing a nano-scale PU audio membrane for mobile phones according to claim 1, characterized in that: The mass of hexadecyltrimethylammonium bromide is 3%-5% of the mass of montmorillonite.

3. The method for preparing a nano-scale PU audio membrane for mobile phones according to claim 1, characterized in that: Solvents include N,N-dimethylacetamide and tetrahydrofuran; And / or, the volume ratio of N,N-dimethylacetamide to tetrahydrofuran is 3-5:

1.

4. A method for preparing a nanoscale PU audio membrane for mobile phones according to any one of claims 1 to 3, characterized in that: The steps include: S1: adding linear polyurethane and modified montmorillonite into a solvent, heating and stirring to obtain a polyurethane static spinning solution; S2: The polyurethane electrospinning solution obtained in step S1 is loaded into a syringe with a metal needle; a PU nanofiber membrane is obtained by electrospinning, and the PU nanofiber membrane is post-processed to obtain a nano-scale PU audio membrane for mobile phones.

5. The method for preparing a nano-scale PU audio membrane for mobile phones according to claim 4, characterized in that: The heating and stirring temperature in step S1 is 55-65° C., and the heating and stirring time is 8-10 h.

6. The method for preparing a nano-scale PU audio membrane for mobile phones according to claim 4, characterized in that: The spinning voltage of the electrospinning in step S2 is 20-35 kV, the receiving distance of the electrospinning is 15-30 cm, and the propulsion speed of the electrospinning is 0.6-1.2 mL / h.

7. The method for preparing a nano-scale PU audio membrane for mobile phones according to claim 4, characterized in that: The ambient temperature of the electrospinning in step S2 is 20-30° C. and the relative humidity is 20%-40%.

8. The method for preparing a nano-scale PU audio membrane for mobile phones according to claim 4, characterized in that: The post-treatment of the PU nanofiber membrane in step S2 includes vacuum drying the PU nanofiber membrane at 90-110° C. for 3-5 hours.

9. The nano-scale PU audio film for mobile phones prepared by the method for preparing a nano-scale PU audio film for mobile phones according to any one of claims 5 to 8 is characterized in that: The fiber diameter of the nano-scale PU audio membrane is 0.3-1.2μm.

10. The nano-scale PU audio film for mobile phone field as claimed in claim 9 is used in the mobile phone field.