WO2023160495A1 - Intermediate-frequency-sound-absorbing polypropylene composition, and preparation method therefor and use thereof - Google Patents

Abstract

An intermediate-frequency-sound-absorbing polypropylene composition, and a preparation method therefor and the use thereof. The intermediate-frequency-sound-absorbing polypropylene composition comprises the following components in parts by weight: 60-80 parts of polypropylene, 10-20 parts of high-density polyethylene, and 10-20 parts of mesoporous silica microspheres, wherein after the polypropylene is annealed at 120°C for 0.5 h, the ratio of the peak area thereof at 998 cm-1 to the peak area thereof at 973 cm-1 is 0.88-0.92, and the molecular weight distribution index of the polypropylene is 5-15. By means of the screening of an appropriate PP resin and the synergistic effect of same, HDPE and mesoporous silica microspheres, the damping performance of the polypropylene composition is changed, and the polypropylene composition can specifically absorb noise with a frequency of 300-800 Hz by means of resonance sound absorption.

Description

A kind of intermediate frequency sound-absorbing polypropylene composition and its preparation method and application technical field

The invention relates to the technical field of polymer materials, and more specifically, to a polypropylene composition for mid-frequency sound absorption and its preparation method and application.

Background technique

Polypropylene (PP) is widely used in the automotive industry due to its low price, easy processing and molding, low density, chemical corrosion resistance and excellent physical and mechanical properties. There will be a lot of noise during the running of the car, such as engine noise, cooling noise, exhaust noise, tire radiation noise and other mechanical noise. In order to reduce the noise pollution caused by the running of the car, some European and American countries and Japan have formulated relevant regulations and test standards.

Noise with a frequency of 300 to 800 Hz is generally called intermediate frequency noise. During the driving process of the car, the noise radiated to the outside due to the vibration of the body panel is often called solid-borne noise, and the frequency is generally low; and because it is directly transmitted into the car through the holes on the body panel, it is often called air-borne noise. , the main frequency is above 500Hz, which belongs to the intermediate frequency noise.

Generally in the medium and high frequency range, the intermediate frequency noise is in the "sensitive area" of human hearing, which means that the intermediate frequency noise is a special noise with "relatively loudness", which is extremely harmful to the human body. Long-term exposure to medium-frequency noise can easily lead to sluggish human response, distraction, and affect driving safety. Therefore, it is necessary to select materials with excellent noise reduction performance as plastics for automobiles.

In the prior art, the sound insulation performance of polypropylene is generally improved by adding inorganic fillers to obtain a modified polypropylene sound insulation material. Although increasing the amount of inorganic fillers helps to improve the sound insulation performance of polypropylene, it also leads to higher density and higher quality of the polypropylene composition, which is contrary to the development trend of lightweight automobiles; and it does not conduct sound insulation for mid-frequency noise . In addition, the sound insulation material refers to the ability to partially isolate the noise, rather than absorb the noise, and it is easy to cause the reflection of the noise. It does not have sound absorption performance, that is, it cannot silence the sound.

Therefore, it is necessary to develop a polypropylene composition for mid-frequency sound absorption, which can effectively eliminate mid-frequency noise, and has a low material density.

Contents of the invention

In order to overcome the defects of high density and incapable of mid-frequency sound absorption described in the above prior art, the present invention provides a polypropylene composition for mid-frequency sound absorption. By screening specific types of polypropylene resins, synergistic high-density polyethylene ene and low content of mesoporous silica microspheres to obtain a polypropylene composition with excellent mid-frequency sound absorption effect, and the density of the polypropylene composition is ≤1.10g/cm ³ .

Another object of the present invention is to provide a preparation method of the above-mentioned polypropylene composition.

Another object of the present invention is to provide the application of the above-mentioned polypropylene composition.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A medium-frequency sound-absorbing polypropylene composition, comprising the following components by weight:

60-80 parts of polypropylene (PP),

10-20 parts of high-density polyethylene (HDPE),

10-20 parts of mesoporous silica microspheres;

The ratio of the 998cm ^-1 peak area to the 973cm ^-1 peak area of the polypropylene after annealing at 120°C/0.5h is 0.88-0.92; and the molecular weight distribution index (Mw/Mn) of the polypropylene is 5-15.

The inventors have found that due to resonance, different materials have selectivity for the sound absorption frequency, and there is a peak in the sound absorption effect at a specific frequency, and the frequency of the sound absorption peak of the material can be changed by changing the damping performance of the material.

The infrared peak at 998cm ^-1 is mainly the synergistic movement of 11-12 repeating units in the polypropylene crystal region, and 973cm ^-1 corresponds to the 5 repeating units in the amorphous and crystalline chains. Their ratio can determine the isotacticity of the material. When the ratio of 998cm ^-1 peak area to 973cm ^-1 peak area of polypropylene is 0.88～0.92, the crystallinity of polypropylene is relatively low. HDPE itself is relatively compact, and when blended with polypropylene, the crystal of PP is greatly refined, the crystal lattice is perfected, and crystal defects are reduced.

The damping performance of the material is related to the crystallinity and crystal defects of the material. It is generally believed that the crystallinity is low, the crystal defects are small, and the damping performance of the material is large, so that the material produces a sound absorption peak in the frequency range of 300-800Hz, that is, for intermediate frequency noise The volume of absorption is greater.

When the Mw/Mn of polypropylene satisfies 5-15, the dispersibility of polypropylene to mesoporous silica microspheres is better. The mesoporous structure of the mesoporous silica microsphere itself has a certain absorption effect on sound, and it can effectively increase the damping performance of the material in the polypropylene polymer system, so that the sound absorption effect at a specific frequency is significantly enhanced effect.

When the polypropylene resin satisfies the peak area ratio of 0.88-0.92 and the Mw/Mn of 5-15, it helps the polypropylene composition to have an excellent mid-frequency (300-800Hz) sound-absorbing effect.

In the present invention, by screening suitable PP resins, synergizing with HDPE and mesoporous silica microspheres, and then changing the damping performance of the polypropylene composition, it can absorb sound through resonance, and the specific absorption frequency is 300-800Hz noise.

The peak area of polypropylene is measured by FT-IR spectrometer, and the specific method is:

Take a polypropylene sample, heat it on a glass sheet, make a film from the melted sample, anneal at 120°C for 0.5h, remove the film after cooling, and conduct FT-IR test on the film directly; the test resolution is 4cm ^-1 , The number of scans is 32 times, the test range is 400-4000cm ^-1 , and the peak area at the designated position is obtained according to the FT-IR spectrum.

The molecular weight distribution index of polypropylene is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), ie Mw/Mn.

The molecular weight distribution index of polypropylene is obtained by gel permeation chromatography.

Preferably, the ratio of the 998 cm ⁻¹ peak area to the 973 cm ⁻¹ peak area of the polypropylene after annealing at 120° C./0.5 h is 0.89˜0.91.

Preferably, the Mw/Mn of the polypropylene is 9-10.

Preferably, the HDPE has a crystallinity of 40-50%.

The crystallinity of HDPE is tested according to the DSC method. The specific test conditions are: temperature range 30-200°C, heating rate 10°C/min, sample size 5-10mg, nitrogen purge gas, flow rate 50ml/min.

The crystallinity of the polymer is calculated from the heat of fusion ΔHm of the crystalline part in the polymer, and the crystallinity Xc of the sample can be calculated by the following formula:
Xc=△Hm/△Hm ₀ *100%

Where ΔHm is the melting enthalpy of the crystalline part of the sample, and ΔHm ₀ is the melting enthalpy when the sample is 100% crystallized.

Preferably, the melt flow rate of the HDPE under the conditions of 190° C. and 2.16 kg is 5˜10 g/10 min.

The test method for the melt flow rate of HDPE is: ISO 1133-1-2011.

Preferably, the average particle diameter of the mesoporous silica microspheres is 200-800 nm.

More preferably, the average particle diameter of the mesoporous silica microspheres is 400-600 nm.

Preferably, the specific surface area of the mesoporous silica microspheres is 300-600 m ² /g.

More preferably, the specific surface area of the mesoporous silica microspheres is 400-500 m ² /g.

The detection method of the specific surface area of mesoporous silica microspheres is: GB/T 19587-2004.

The specific surface area of mesoporous silica microspheres affects the propagation of sound in the material, thereby improving the sound-absorbing performance of the material, while the particle size determines the dispersion and uniformity of mesoporous silica microspheres in the polypropylene system. In addition, the mesoporous structure of mesoporous silica microspheres also contributes to the polypropylene composition of the present invention having In the case of high sound absorption, keep the density low.

Preferably, the polypropylene composition may further include 0.5-2 parts of a siloxane coupling agent.

The presence of the silane coupling agent helps the components of the polypropylene composition to be combined more closely, and the sound absorption effect is better.

The present invention also protects the preparation method of the above-mentioned polypropylene composition, comprising the following steps:

PP, HDPE, mesoporous silica microspheres and siloxane coupling agent (if any) are mixed, then added to an extruder, melted and mixed, extruded and granulated to obtain the polypropylene composition.

Preferably, the extruder is a twin-screw extruder.

Preferably, the extrusion process of the twin-screw extruder is as follows: the temperature in the first zone is 80-120°C, the temperature in the second zone is 190-210°C, the temperature in the third zone is 210-230°C, the temperature in the fourth zone is 210-230°C, and the temperature in the fifth zone The temperature is 210～230℃, the temperature in the sixth zone is 210～230℃, the temperature in the seventh zone is 210～230℃, the temperature in the eighth zone is 210～230℃, the temperature in the ninth zone is 210～230℃, the speed of the main engine is 250～600rpm; The aspect ratio is 40-48:1.

The present invention also protects the application of the above-mentioned polypropylene composition in the preparation of automobile bumpers, air-conditioning panels, door trim panels, and instrument panel frameworks.

Compared with prior art, the beneficial effect of the present invention is:

The present invention develops a polypropylene composition for intermediate frequency sound absorption. By screening suitable PP resin, it cooperates with HDPE and mesoporous silica microspheres to change the damping performance of the polypropylene composition. It can absorb sound through resonance and specifically It absorbs noise with a frequency of 300-800 Hz, and has a high absorption volume; meanwhile, the density of the polypropylene composition is ≤1.10g/cm ³ .

Description of drawings

Figure 1 is the FT-IR spectrum of polypropylene PP-1 after annealing at 120°C/0.5h. The ratio of the peak area at 998cm ^-1 to the peak area at 973cm ^-1 of PP-1 is 0.89.

Detailed ways

The present invention will be further described below in combination with specific embodiments.

The raw material in embodiment and comparative example all can be obtained by commercially available, specifically as follows:

In the above table, the peak area ratio of polypropylene refers to the ratio of the 998cm ^-1 peak area to the 973cm ^-1 peak area after annealing at 120°C/0.5h.

Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

Examples 1-18

Embodiments 1 to 18 respectively provide a polypropylene composition, the component contents are shown in Table 1, and the preparation method is as follows:

Mix the components according to Table 1, add to a twin-screw extruder, melt and mix, extrude and granulate to obtain a polypropylene composition;

The extrusion process of the twin-screw extruder is as follows: the temperature of the first zone is 80-120°C, the temperature of the second zone is 190-210°C, the temperature of the third zone is 210-230°C, the temperature of the fourth zone is 210-230°C, and the temperature of the fifth zone is 210-230°C ℃, the temperature in the sixth zone is 210-230 ℃, the temperature in the seventh zone is 210-230 ℃, the temperature in the eighth zone is 210-230 ℃, the temperature in the ninth zone is 210-230 ℃, the speed of the main engine is 250-600rpm; the aspect ratio of the twin-screw extruder is 40:1.

The component content (weight part) of table 1 embodiment 1～18 polypropylene composition

Comparative example 1～7

Comparative examples 1 to 7 provide a polypropylene composition respectively, the component contents are shown in Table 2, and the preparation method is as follows:

Mix the components according to Table 2, add to a twin-screw extruder, melt and mix, extrude and granulate to obtain a polypropylene composition;

The extrusion process of the twin-screw extruder is as follows: the temperature of the first zone is 80-120°C, the temperature of the second zone is 190-210°C, the temperature of the third zone is 210-230°C, the temperature of the fourth zone is 210-230°C, and the temperature of the fifth zone is 210-230°C ℃, the temperature in the sixth zone is 210-230 ℃, the temperature in the seventh zone is 210-230 ℃, the temperature in the eighth zone is 210-230 ℃, the temperature in the ninth zone is 210-230 ℃, the speed of the main engine is 250-600rpm; the aspect ratio of the twin-screw extruder is 40:1.

Component content (parts by weight) of the polypropylene composition of Table 2 Comparative Examples 1 to 7

Performance Testing

The polypropylene composition that above-mentioned embodiment and comparative example are made carry out performance test, and concrete method is as follows:

Density: Tested according to the ISO 1183-2019 method, the unit is g/cm ³ ;

Absorption: The polypropylene composition is injection molded into a pipe with a wall thickness of 3mm, a length of 1m, and a pipe diameter of 10mm; the sound source and receiver are placed on both sides of the pipe, and each is 20mm away from the pipe; the frequency of the sound source is 500Hz or 700Hz white noise, resonator resonance frequency: 200±5Hz; absorption volume = volume emitted by the sound source - volume measured by the receiver, the unit is dB; the absorption volume is required to be ≥ 50dB.

The test results of Examples 1-18 are shown in Table 3, and the test results of Comparative Examples 1-6 are shown in Table 4.

The test result of table 3 embodiment 1～18

According to the test results in Table 3, the density of the polypropylene composition prepared in each embodiment of the present invention is low, ≤1.1g/cm ³ ; it has excellent sound absorption effect for intermediate frequency noise of 500Hz and 700Hz, and the absorption volume (500Hz)≥ 50dB, absorption volume (700Hz) ≥ 35dB.

In Examples 1 to 6, the absorption volumes of Examples 1 and 2 are relatively higher. Therefore, the ratio of the peak area of 998 cm ^-1 to the peak area of 973 cm ^-1 after annealing of polypropylene at 120°C/0.5h is preferably 0.89 to 0.91, Mw/Mn of polypropylene is preferably 9-10.

From Example 1 and Examples 7-9, the crystallinity of HDPE is 40-50%, and when the melt flow rate is 5-10g/10min at 190°C and 2.16kg, the absorption volume of the polypropylene composition Relatively higher, the absorption volume can reach more than 58dB at 500Hz, and the absorption volume can reach more than 39dB at 700Hz.

Among Examples 1, 10, and 11, the volume of absorption in Example 10 is relatively higher, the volume of absorption at 500 Hz reaches 62 dB, and the volume of absorption at 500 Hz reaches 43 dB. It can be seen that the sound-absorbing effect of mesoporous silica microspheres is different under different average particle sizes and different specific surface areas. The average particle diameter of the mesoporous silica microspheres is preferably 400-600 nm, and the specific surface area is preferably 400-500 m ² /g.

Compared with Example 1, the sound absorption effect of Example 18 is relatively better, and the density is relatively lower. The addition of the coupling agent contributes to better overall performance of the polypropylene composition.

The test result of table 4 comparative example 1～7

According to the test results in Table 4, in Comparative Examples 1 and 2, when the peak area ratio of polypropylene does not satisfy 0.88 to 0.92, or when the Mw/Mn does not satisfy 5 to 15, the polypropylene composition has a low absorption capacity for intermediate frequency noise, The sound absorption effect cannot meet the requirements.

In Comparative Example 3, non-mesoporous silica spheres were used to replace the mesoporous silica microspheres of the present invention. Not only did the polypropylene composition have poorer absorption volume, but the material density was higher.

In Comparative Example 4, other types of inorganic fillers (talcum powder) were used to replace the mesoporous silica microspheres of the present invention, and it can be seen that the sound absorption effect of the polypropylene composition obtained is poor for intermediate frequency noise, which is far lower than that of the present invention. The required volume of absorption.

In Comparative Example 5, HDPE was not included, but LDPE was substituted. Due to their different properties, the polypropylene composition containing LDPE cannot achieve resonance sound absorption for mid-frequency noise, and the volume of absorption is low.

From Comparative Example 6 and Comparative Example 7, in the absence of HDPE or mesoporous silica microspheres, it is difficult to achieve a good synergistic effect between polypropylene components, and the sound-absorbing effect of the prepared polypropylene composition is not ideal .

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. A medium-frequency sound-absorbing polypropylene composition is characterized in that it includes the following components by weight:

   60-80 parts of polypropylene,

   10-20 parts of high-density polyethylene,

   10-20 parts of mesoporous silica microspheres;

   The ratio of the 998cm ^-1 peak area to the 973cm ^-1 peak area of the polypropylene after annealing at 120°C/0.5h is 0.88-0.92; and the molecular weight distribution index of the polypropylene is 5-15.
2. The intermediate-frequency sound-absorbing polypropylene composition according to claim 1, wherein the ratio of the 998cm ^-1 peak area to the 973cm ^-1 peak area of the polypropylene after annealing at 120°C/0.5h is 0.89-0.91.
3. The intermediate frequency sound-absorbing polypropylene composition according to claim 1, characterized in that the molecular weight distribution index of the polypropylene is 9-10.
4. The medium-frequency sound-absorbing polypropylene composition according to claim 1, wherein the crystallinity of the high-density polyethylene is 40-50%.
5. The medium-frequency sound-absorbing polypropylene composition according to claim 1, wherein the melt flow rate of the high-density polyethylene under the conditions of 190° C. and 2.16 kg is 5-10 g/10 min.
6. The intermediate-frequency sound-absorbing polypropylene composition according to claim 1, wherein the average particle diameter of the mesoporous silica microspheres is 200-800 nm.
7. The intermediate-frequency sound-absorbing polypropylene composition according to claim 1, wherein the specific surface area of the mesoporous silica microspheres is 300-600 m ² /g.
8. The intermediate frequency sound-absorbing polypropylene composition according to claim 1, further comprising 0.5-2 parts by weight of a siloxane coupling agent.
9. The preparation method of the intermediate frequency sound-absorbing polypropylene composition according to any one of claims 1 to 7, characterized in that it comprises the following steps:

   After mixing polypropylene, high-density polyethylene and mesoporous silicon dioxide microspheres, they are added to an extruder, melted and mixed, extruded and granulated to obtain the polypropylene composition.
10. The application of the medium-frequency sound-absorbing polypropylene composition according to any one of claims 1 to 8 in the preparation of automobile bumpers, door trim panels, and instrument panel frameworks.