JPH0452478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound absorbing material having excellent sound absorbing performance different from conventional sound absorbing materials made of a vinyl chloride paste resin foam molding.

If the sound absorbing materials currently on the market are classified in terms of sound absorption performance, they can be roughly divided into two types: low frequency sound absorbing materials and high frequency sound absorbing materials. Typical examples of the former include soft polymer sheets and closed foam soft polymer sheets, which exhibit the highest normal incidence sound absorption coefficient in the sound range of 500 to 1000 Hz, and 1000 Hz. It has excellent sound absorption in the low frequency range below Hertz.

On the other hand, the latter has poor sound absorption properties in the low frequency range compared to the former, but the normal incidence sound absorption coefficient increases rapidly in the sound range of 1000 Hz or higher, and its sound absorption properties in the high frequency range are extremely excellent. Most commercially available sound absorbing materials belong to the latter category, and representative examples include polyurethane foam moldings with a thickness of about 1 cm, open porous materials such as glass wool, and foamed concrete. Figure 1 shows typical vertical sound absorption characteristics of both.

The sound absorbing materials currently available on the market are:
Its sound absorption properties are biased towards a specific frequency range, and there is a desire to develop sound absorption materials with well-balanced sound absorption properties.

The inventors of the present application aimed to develop a sheet-like sound absorbing material that has both the sound absorbing properties of conventional low frequency sound absorbing materials and high frequency sound absorbing materials, and arrived at the present invention. That is, the present invention has the following three limited physical property conditions: (1) The apparent Young's modulus at 23°C is 1.5×10 ⁴ N/
m ² to 7.0×10 ⁴ N/m ² , preferably 2.0×10 ⁴
N/m ² to 6.0×10 ⁴ N/m ² (2) Density at 23°C is 80Kg/m ² to 300Kg/m ² ,
Preferably from 100Kg/m ² to 200Kg/m ² (3) Foam molding made to simultaneously satisfy the airflow rate of 40ml/ ^cm2・10mm・min or more, preferably 55ml/ ^cm2・10mm・min or more. This is based on the discovery that a continuous foam molded body of vinyl chloride paste resin from which the skin has been removed has the sound absorption performance of conventional low-frequency and high-frequency sound absorbing materials.

Next, the background of finding the above-mentioned physical property conditions that are the basis of the present invention, and the sound absorption properties of a vinyl chloride paste resin foam molded sheet that satisfies these three physical property conditions will be explained.

Sound absorption by low-frequency sound absorbing materials, such as plasticized vinyl chloride or its closed-cell foam sheets, occurs because sound wave energy is converted into thermal energy by causing viscoelastic vibrations and friction in the surface layer or inside the material. It is believed that.

In general, a viscoelastic body such as a soft polymer material resonates with mechanical vibrations around a specific frequency, and its sound absorption effect increases around the resonance frequency. Factors that influence the sound absorption effect of such materials include:
The elastic modulus of the material, the size and distribution of closed cells, and the cell rate are considered. In particular, the presence of closed cells is effective in improving sound absorption coefficient. According to the research conducted by the inventors of this application, in order to improve the sound absorption function of this type of material,
It is required to have a low elastic modulus, to keep the cell ratio of closed cells within a certain range, and to have a wide distribution of cell sizes.

On the other hand, the sound absorption mechanism of high-frequency sound absorbing materials, that is, open porous sound absorbing materials, is that when a sound wave enters the material, the sound energy is converted into thermal energy through viscous friction between the open cell wall and air vibration. It is said that it is consumed and decays. Therefore, in order to improve the sound absorbing effect of this type of sound absorbing material, it can be considered that the number of open cells should be increased as much as possible. However, according to research by the inventors of the present application, the relationship between the open cell ratio and the sound absorption coefficient is not necessarily proportional, and when the open cell ratio exceeds a certain value, the sound absorption coefficient reaches an equilibrium state.

As can be seen from the above explanation, in order to develop a sound absorbing material that has the sound absorption characteristics of both low frequency sound absorbing materials and high frequency sound absorbing materials: (2) It must be a soft material with a low elastic modulus that maximizes loss, and (2) It must be a foam molded product that has both closed cells and open cells.

(3) The size of closed cells, their distribution, foaming rate, and open cell rate must be controlled within a certain range.

The above condition (1) can be satisfied by using a soft polymer material such as vinyl chloride paste resin, plasticized vinyl chloride resin, ethylene-vinyl acetate copolymer resin, or polyurethane resin, but condition (1) and ( In order to simultaneously and purposefully satisfy 2),
This becomes possible only by using vinyl chloride paste resin and selecting the amount of plasticizer and foaming processing conditions.

The most difficult condition here is condition (3). Condition (3)
relates to the foam cell structure, and its proper control depends on the following factors: (a) the size of the closed cells, (b) their distribution, and (c) the measurement of the closed and open cell fraction. It is necessary to establish a method and quantify it. These foam cell structures can be obtained and measured by observing sections of the foam under an optical microscope, but this requires a great deal of effort and time. In particular, when considering industrialization as a premise, quality control of manufactured products is the most important and absolute condition, but the adoption of optical microscopy as a control method for foam cell structures is difficult due to the complexity of measurement. Not suitable as a quality control measure. Therefore, the inventors of the present invention have researched a simple method for measuring the foam cell structure that can replace the optical microscopy method. You can know it.

The ventilation measuring device shown in Fig. 2 consists of a sample holder A, a cushion tank B, a water absorption bottle C, a water layer D,
It consists of a mercury manometer E, a pressure reduction degree adjustment socket F, and an opening/closing socket G. To measure the amount of ventilation, set the measurement sample H in the sample holder A, close the opening/closing knob G, and adjust the adjustment knob F to maintain the degree of vacuum in the sample holder A at 100 mmHg.
Next, when the opening/closing pot H is opened, water flows from the water layer D into the water absorption bottle C in accordance with the amount of aeration of the sample H. The amount of water flowing from the water layer D into the water absorption bottle C in 30 seconds was defined as the aeration amount of the sample.

In addition, the foaming rate of closed foam and the size of foam cells,
The distribution is based on JIS K 6301 “Physical test method for vulcanized rubber”
Apparent Young's modulus and density measured using a No. 2 dumbbell test piece specified in It was found that there is a correlation. Here, the apparent Young's modulus is determined from the elongation and stress within the elastic limit. Thus, these three
By specifying two physical property factors and materials, it became possible to industrially produce the sound absorbing material intended by the inventors of the present invention. In other words, the apparent Young's modulus at 23°C is 1.5×10 ⁴ N/m ² or less or 7.0×10 ⁴
When N/ ^m2 or more, the density at 23℃ is 80
When the air flow rate is below Kg/m ² or above 300 Kg/m ² , or when the ventilation rate is below 40 ml/cm ² ·10 mm ·min, the foam exhibits only the sound absorption properties of conventional sound absorbing materials. If necessary, within the limits of the physical properties, inorganic or organic fillers with a specific gravity of 4 or less and a particle size of 20 to 1000μ, such as shirasu balloons, perlite, aluminum powder, granular mica, etc.
You may also add wood flour. Alternatively, porous cloth, paper, non-woven fabric, etc. can also be laminated for decorative purposes. Furthermore, if the sound absorbing material of the present invention is laminated with a soft sound insulating material, it can be used as a sound insulating material having both sound absorbing and sound insulating functions. In particular, by laminating the sheet-like sound absorbing material to the sound insulating material, it is possible to improve the transmission loss by 5 dB to 10 dB compared to the sound insulating material alone.

Hereinafter, the effectiveness of the present invention will be explained using Examples, but the present invention is not limited by these.

Example 1 Vinyl chloride paste resin (-1030: 100 parts DOP (dioctyl phosphate): 80 parts Blowing agent (ADCA): 7 parts Stabilizer (Mark FL-21 manufactured by Adeca Argus): 7 parts After kneading for about 5 minutes with a high-speed mixer, it is applied uniformly onto a flame-retardant paper.This is heated in an oven at a temperature of 200°C for 2.25 minutes to obtain a foam.A surface skin layer and a flame-retardant paper are formed from this foam. Removed thickness 12mm
A foam was obtained. The air permeability, apparent Young's modulus, and density of this foam were measured using the method described in the detailed explanation of this application. Air permeability: 68 ml/cm ²・10 mm・min Apparent Young's modulus: 4.8×10 ⁴ N/m ² Density: 130Kg/ ^m2 . All of these physical property values are within the physical property limits defined in the present invention. In addition, the normal incidence sound absorption of the foam was measured using a normal incidence sound absorption coefficient measuring device manufactured by Priel Kjær, Denmark. The results are shown in Figure 3. Compared to 10 mm thick polyurethane foam or 12 mm thick glass wool sheet, product A of the present invention has a smaller frequency dependence of the sound absorption properties of the foam, and has a better sound absorption balance. This is very excellent and shows the effectiveness of the present invention.

Example 2 Vinyl chloride paste resin (degree of polymerization 1030): 100 parts DOP: 80 parts Blowing agent (ADCA): 7 parts Stabilizer (Mark FL-21): 7 parts Shirasu balloon: 40 ml was used in Example 1). The foam was then heated in an oven at a temperature of 205° C. for 200 minutes to obtain a foam. The surface skin layer was removed from this foam to obtain a foam sheet with a thickness of 10 mm. The air permeability, apparent Young's modulus, and density of this foam sheet were measured by the method described in the detailed explanation of this application. Air permeability: 80 ml/cm ² · 10 mm · min Apparent Young's modulus: 4.5 × 10 ⁴ N/m ² Density: 120Kg/ ^m3 . All of these physical property values are within the physical property limits defined in the present invention. The results of the normal incidence sound absorption coefficient are shown in Figure 4, and compared to polyurethane foam and glass wool sheets of similar thickness, the product of this invention exceeds 10% in a wide frequency range from 500 Hz to 3000 Hz. Demonstrates sound absorption performance.

Example 3 Vinyl chloride paste resin (degree of polymerization 1030): 100 parts DOP: 80 parts Blowing agent (ADCA): 7 parts Stabilizer (Mark FL-21): 7 parts Aluminum powder: 30 ml according to Example 1) The foam was obtained by heating in an oven for 2.00 min at a temperature of 205 °C. The surface skin layer was removed from this foam to obtain a foam sheet with a thickness of 10 mm. The air permeability, apparent Young's modulus, and density of this foam were measured by the method described in the detailed explanation of this application. Air permeability: 84 ml/cm ² · 10 mm · min Apparent Young's modulus: 6.2 × 10 ⁴ N/m ² Density: 130Kg/ ^m3 . All of these physical property values are within the physical property limits defined in the present invention. The results of the normal incidence sound absorption coefficient are as shown in FIG. 5, and the foam exhibits excellent sound absorption performance, comparable to that of the foam obtained in Example 2).

Comparative Example 1 Vinyl chloride paste resin (degree of polymerization 1030): 100 parts DOP: 80 parts Foaming agent (ADCA): 7 parts Stabilizer (Mark FL-21): 7 parts Foam molding was carried out under exactly the same conditions as in Example 1) The same foam was obtained. Thickness without removing surface skin layer
When the physical properties of the 12 mm foam were measured, they were as follows: Air permeability: 0 ml/cm ² · 10 mm · min Apparent Young's modulus: 4.8×10 ⁴ N/m ² Density: 130 Kg/m ³ . These physical property values are outside the physical property limits defined in the present invention. The measurement results of the normal incidence sound absorption coefficient are shown in FIG. As shown in the figure, when compared with the claimed invention product,
Its sound absorption properties are significantly inferior in the high frequency range of 1000 Hz or higher.

Comparative Example 2 Vinyl chloride paste resin (degree of polymerization 1070): 100 parts DOP: 60 parts Blowing agent (ADCA): 3 parts Stabilizer (Mark FL-21): 3 parts were flame-proofed in the same manner as in Example 1) Apply it on paper,
A foam was obtained by heating in an oven at a temperature of 190°C for 5 minutes. The surface skin layer was removed from this foam to obtain a foam sheet with a thickness of 10 mm. The air permeability, apparent Young's modulus, and density of this foam were measured using the method described in the detailed description of this application. Air permeability: 35 ml/cm ² · 10 mm · min Apparent Young's modulus: 6.65 × 10 ⁵ N/m ² Density: 160Kg/ ^m3 . Among these physical property values, air permeability and apparent Young's modulus are outside the physical property limits defined in the present invention.
The results of the sound absorption coefficient are shown as E in Fig. 6, and only a low sound absorption coefficient is exhibited in the entire frequency range.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing typical normal incidence sound absorption characteristics of conventional sound absorbing materials. FIG. 2 is a schematic diagram of the airflow measuring device. 3 and 3 are diagrams showing normal incidence sound absorption characteristics of sound absorbing materials according to Examples and Comparative Examples of the present invention. A...Sample holder, C...Water absorption bottle, D...
Water layer, H...sample, A...vinyl chloride paste foam of the present invention, B...polyurethane foam, H...
...Glass wool sheet, D, H...Vinyl chloride paste foam.

Claims (1)

[Claims] 1 An open-circuit polyvinyl chloride paste resin foam, excluding the skin formed during foam molding, whose physical properties are
At 23℃, apparent Young's modulus 1.5×10 ⁴ ~7.0×
10 ⁴ N/m ² , density 80~300Kg/m ³ and airflow rate 40~
Sound absorbing material characterized by 84ml/cm ²・10mm・min.