JPS58129492A - Sound absorbing material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound absorbing material used in an exhaust sound absorbing device for an internal combustion engine.

Conventionally, sound absorbing materials used in exhaust silencing devices for internal combustion engines include glass coolers, porous ceramic bodies, porous metal bodies, and the like. However, when these materials are used as sound-absorbing materials, when an internal combustion engine is operated, tar and soot, which are the combustion residues of fuel such as gasoline, adhere to the surface and cause clogging in a relatively short period of time, reducing the sound-absorbing performance. This often resulted in a decrease in noise, intensified noise, and adversely affected the fuel efficiency of the internal combustion engine. In addition, when glass wool or porous ceramic materials are used as sound absorbing materials in exhaust silencers for internal combustion engines, the pressure of exhaust gas is high and the vibrations are large, resulting in the sound absorbing materials becoming powdered or damaged. There were times when it became completely useless. and,
When a porous metal body is used, the temperature of the exhaust gas inside the silencer is as high as 400 to 800°C, and the exhaust gas contains corrosive sulfur oxides and nitrogen oxides, so unless a special heat-resistant alloy is used, However, as corrosion deterioration due to high-temperature oxidation becomes significant, it is inevitable that corrosion products will cause clogging, and the skeleton of the porous material will corrode and disappear, making it useless as a sound absorbing material. As a basic characteristic of the pore diameter is relatively large, there are disadvantages such as the absence of any material with good sound absorption performance.

Conventional sound-absorbing materials have major drawbacks as described above, and none of them can be put to practical use as exhaust silencing devices for internal combustion engines.

This invention eliminates the drawbacks of the conventional products mentioned above, has good sound absorption performance, prevents deterioration of sound absorption performance caused by clogging due to adhesion of tar and soot, and can withstand high temperature oxidation. The present invention provides a sound absorbing material for an exhaust silencer.

That is, the sound-absorbing material of the present invention uses a porous metal material as a sound-absorbing base material without fear of pulverization or breakage, suppresses clogging caused by tar and soot, improves its sound-absorbing properties, and uses its high-temperature It contains a low-temperature oxidation catalyst that has three main purposes: to prevent corrosion deterioration due to oxidation, and graphite fluoride to prevent soot from adhering to the surface of the sound-absorbing substrate. A heat-resistant binder containing at least one of the alkaline agents dispersed therein is applied to a porous metal sound-absorbing base material and cured.

Hereinafter, the details of this invention will be explained according to Examples.

[Example 1. ] As a metal porous sound-absorbing base material, a foamed metal manufactured by Sumitomo Electric Corporation (the surface of which can be seen in an enlarged view in Figure 1) (on one side of the product) was coated with the composition of Composition Example 1 below in a ball mill for about 80% The mixture mixed for minutes was applied uniformly by spray.In Figure 1, (1) is the skeleton of the metal porous body, and (2) is the pores.Furthermore, this was dried at 80°C for 30 minutes. After that, it was baked at 550° C. for 80 minutes to harden it.

(Composition example 1.) Low-temperature oxidation catalyst chromium dioxide 2011 Reducing agent 2Ag powder 22 Layer binder Nialuminum phosphate) 12'fEji% Phosphate-based glassy frit 1211% Additives: Aluminum, bentonite, Water 281B Low surface energy substance: graphite fluoride 61 dB It should be noted that it is difficult for low-temperature oxidation catalysts and reducing agents to form a strong coating film by themselves, so in this invention, they are contained and dispersed in a binder and then applied. It is used by heating and curing to form a porous, strong, and vertical film.

In addition, the additives used here have the effect of improving the adhesion and film performance as a coating material, increasing the strength after the coating film is formed and the adhesion performance to the underlying porous material, and making the film more porous. It has the property of becoming

The sound absorbing material of this invention was manufactured in this way.

The structure is as shown in an enlarged cross section in FIG. 1(6).

That is, (3) consists of particles of a low-temperature oxidation catalyst dispersed on the surface of the skeleton (1) and in the pores (2) of the porous metal body;
4) is the reducing agent particle, (5) is the low temperature oxidation catalyst particle (3)
, a heat-resistant binder (6) which is cured by dispersing graphite particles (7) and reducing agent particles (4), is composition example 1. It is a porous coating formed on the surface by applying a kneaded product of. Composition Example 1 using the sound absorbing material of this invention. Various performances were investigated while comparing with a porous metal material that was not coated with the composition at all.

Figure 2 shows the results of each test at a temperature of 400 to 800°C in air containing sulfur dioxide (phosphorous acid gas) IOPF.
The figure shows the rate of weight change due to corrosion after each 60 cycles at a temperature of 100° C., where one cycle is doffing in which the sample is left to stand for 2 hours and then left to stand at room temperature for 12 hours. Curve a shows the weight change rate of the sound absorbing material of the present invention manufactured as described above, and the curve a shows the weight change rate of the sound absorbing material made of only a metal porous body using the same material. As is clear from FIG. 2, the sound-absorbing material of the present invention can be used at temperatures of 400 to 800°C, which is the exhaust gas temperature in an exhaust silencer for an internal combustion engine, and even in air containing carbon dioxide. It has good corrosion resistance with almost no progress in corrosion. In comparison, with conventional metal porous materials, the weight changes rapidly due to corrosion as the temperature rises, and visual observation shows that yellow-green corrosion products are observed on the surface. Figure 8 shows the normal incidence sound absorption coefficient measured under the same conditions by the in-pipe method (JISA 1405).

Curve C is the characteristic of the sound absorbing material of the present invention, and curve d is the characteristic of the sound absorbing material consisting only of metal porous bodies. From FIG. 8, it is seen that the sound absorbing material of the present invention can have a considerably higher sound absorption coefficient than that of a material made only of porous metal.

This is the result of Composition Example 1 from the surface of the metal porous body. The composition shown in FIG. 1 (6) obtained by coating and curing the composition is also essentially porous, so that air can flow through the interior thereof.

That is, composition example 1. The coated cured product itself forms part of the sound absorbing body, and the sound absorption coefficient can be adjusted to v4 depending on the method of coating.

Next, the above two types of sound absorbing materials were formed into a cylindrical shape to produce an exhaust noise muffling device as shown in the cross-sectional view of FIG.

In Fig. 4, (41) is the casing, (42) is the exhaust gas inlet pipe, (4B) is the exhaust gas passage, (44) is the outlet pipe, (
45) is a sound absorbing material. This exhaust silencing device was installed in a commercially available domestically produced passenger car (exhaust 12,000 cc), and after approximately 10,000 actual runs, the silencing performance was measured according to JISD 1616, and the characteristic diagram comparing each with the initial value before actual driving is shown in Figure 6. As shown in the figure. Song 4es and C! curves 11 and f3 depend on the initial and actual driving times when using the sound absorbing material of the present invention, respectively, and curves 11 and f3 vary at the initial stage and after actual driving when using the conventional sound absorbing material made only of porous metal bodies, respectively. It is % characteristic. As shown in Figure 6, the sound absorbing material of this invention not only has good initial silencing performance, but also shows that the initial performance has not deteriorated even after 10,000 miles of actual driving. On the other hand, in the case of using a sound absorbing material made of only porous metal material, the sound deadening performance deteriorated significantly in all measured frequency bands after 10,000 hours of actual driving. In addition, after measuring the sound-absorbing performance, both sound-absorbing materials were taken out and visually observed.The sound-absorbing material of this invention was almost as clean as the initial one, but the material with only a metal porous material was A large amount of black tar-like and soot-like combustion residue and yellow-green corrosion products had adhered, causing severe clogging.

That is, as can be seen from this result, the sound absorbing material of the present invention has low temperature oxidation catalyst particles dispersed in the sound absorbing base material.
Activated by the temperature of the exhaust gas, the combustion residue is
In addition to automatically purifying and removing the oxidized content (surface combustion) at an exhaust gas temperature that is lower than the temperature at which it actually burns out, it also removes the oxidized components that are mixed in with the catalyst particles. The graphite particles' soot adhesion prevention function and soot adhesion dispersion function were fully demonstrated.

This is thought to be the reason why the initial silencing performance was maintained. The reducing agent contained in this case is considered to have the effect of inhibiting a reaction in which tar-forming components are polymerized by oxidative polymerization on the surface of the sound absorbing material and precipitated as tar.

In other words, once it has precipitated as tar, it may take a long time to purify or remove it with the activation power of the low-temperature oxidation catalyst alone, or it may be difficult to purify it, but tar formation can be prevented. It is considered that the tar-forming component does not turn into a high polymer (t) (high boiling point), making it easier to purify the low-temperature oxidation catalyst.

The above-mentioned buttomized graphite and other components can effectively exhibit their respective functions at 5 to 96% by weight.
Preferably both are 50% by weight.

[Example 2. ] As the metal porous sound-absorbing base material, sintered metal manufactured by Mitsubishi Metals (trade name: Diamond Filter, thickness 6 cm) was used, and the following composition example 2. A mixture of Example 1. After crosstalk as in the case of
Brush coating) is applied onto the sintered metal and baked to harden it.
This is the sound absorbing material of this invention.

(Composition Example 2.) Low-temperature oxidation catalyst Manganese dioxide 2 ott% Nickel oxide 1211% Alkali agent: Sodium aluminate 101 t Potassium silicate 8 ft% Binder: Methylphenyl silicone 15 fl % Phosphate-based glass frit 5 additives : Silica stone, organic bentonite, thinner 20fl-% Low surface energy material: Fluoride graphite 10fl-1% With this sound absorbing material and the same porous metal material as above, composition example 2. Example 1. Various performances were investigated in exactly the same way as in the case of .

As a result, composition example 2. The sound absorbing material of the present invention obtained by applying and curing the composition of the present invention exhibits changes over time in corrosion resistance, sound absorption coefficient, and sound deadening performance due to prevention of clogging. It was found that in all cases, the properties were almost as good as those of Example 1.0 in FIGS. 2, 8, and 6. In particular, in actual vehicle driving tests as an exhaust silencing device, there was no deterioration in the silencing performance, and observation after the test showed almost no tar adhesion. Therefore, composition example 2. It was found that the alkaline agent used in the above-mentioned method also plays the role of preventing the gasoline combustion residue from turning into tar and assisting the action of the low-temperature oxidation catalyst, similar to the reducing agent described above. The tar-inhibiting effect of alkaline agents is due to the neutralization and hydrolysis (saponification) effect on acidic substances and esters that are generated during the process when tar-forming components gradually become polymerized through oxidative polymerization due to heat. This seems to be based on the fact that it prevents further partial molecularization (tar).

As can be seen from these results, in this invention, a reducing agent or an alkaline agent is used together with a low-temperature oxidation catalyst.
For example, composition example 8. Even when used simultaneously as in Example 1. Figures 2 and 8
It was found that excellent corrosion resistance and noise reduction performance were obtained that were almost the same as those shown in Figures 1 and 2.

Low-pitched oxidation catalyst: Copper oxide 28 bean reducing agent:
Stannous sulfate 13 layers Yabu 7/L/Potassium agent: Potassium silicate 12''b Binder: Methylphenyl silicone 2Q] iii% Additives: Alumina, bentonite thinner 20 layers 1 Low surface energy substance: Fluorinated graphite 7 layers 1. By the way, the inventors
We have already proposed a sound absorbing material that is coated and cured with a binder containing a low-temperature oxidation catalyst. Although it cannot be denied that the sound absorbing material of this invention uses more types of mixed chemicals than the previous proposal,
It has even better characteristics. The reason for this is that the sound absorbing material of the present invention is a combination of a catalyst agent that causes low-temperature oxidative decomposition, buttomized graphite that has a soot adhesion inhibiting effect, and a reducing agent or alkaline agent as a chemical (polymerization) reaction inhibitor. This is thought to be due to the fact that

By the way, the low-temperature oxidation catalyst used in this invention is
In addition to those described in Composition Examples 1 to 8, Co3O4,
FetO: +, Ag, 0, metal oxides such as ZnO, PbO, NiCr104, MnCr504, CuCrtO
i, composite gold mmide such as MnFem0a and Pt,
Powders and fine particles of noble metals such as Pd, Rh, Ru, and Ag, which have oxidation catalytic activity and are heat resistant, can be used.

Of course, two or more of these may be used in combination.

Reducing agents used in this invention include those that generally have a reducing effect, such as metal powders, tin salts, ferrous salts, sulfites, and oxalates; alkaline agents include alkali metal silicates, water Examples include those that generally have basicity, such as oxides, alkali metal oxides, and basic oxides.

Furthermore, as the metal porous body used as the base material in this invention, in addition to foamed metals and sintered metals as in the examples, commercially available general-purpose materials such as metal fibers and horizontal fiber reinforced metals can be used. .

The heat-resistant binder used in this invention includes:

Examples include harou (glass frits), alkali metal silicates, tetraidal silica, broidal alumina, metal phosphates, cements, silicone resins (faces), and mixtures thereof.

The graphite used in this invention is a chemically very stable white to gray fine powder in which one fluorine atom is strongly bonded to each carbon atom through a covalent bond. Chestnuts are produced by directly reacting fluorine generated by the electrolysis of butic acid anhydride with carbon. Its properties include low surface energy and a small coefficient of friction.
It has been put into practical use as a solid lubricant. In this invention, the most suitable method for dispersing and layering the bubbly graphite on the surface of a porous material is to apply and bake it dispersed in a resin binder or an inorganic binder, as described in the examples. When metal is used as the porous material as in the present invention, it is also effective to eutectoid plate the surface of the metal porous body with bubbly graphite, which is dispersed in a plating solution together with heat-resistant materials such as Ni and Cr. Met.

It was also effective to use a commercially available spray set in which graphite fluoride was dispersed in a resin binder in the form of No. 4 and a face.

The sound absorbing material of the present invention is intended to be used in an exhaust silencing device for an internal combustion engine, but depending on how it is used, it may also be used as a sound absorbing material in other equipment such as a combustor.

As explained above, a porous metal body is used as a base material, and a heat-resistant binder applied and hardened to the porous metal body contains a low-temperature oxidation catalyst and graphite fluoride, and also contains a reducing agent and an alkali agent. The sound absorbing material of the present invention containing at least one of the above has good sound absorbing performance, excellent high temperature oxidation resistance and corrosion resistance, and when used as a sound absorbing material for an exhaust silencer for an internal combustion engine, It can prevent the adhesion of tar and soot, and it is also great! It is possible to prevent the deterioration of the silencing performance caused by the blockage and maintain the initial good silencing performance. Therefore, because of its high performance and long life, it can be widely used in exhaust silencing devices for internal combustion engines such as automobiles.

[Brief explanation of the drawing]

Fig. 1 is an enlarged view showing the structure of the metal porous body and the sound absorbing material of this invention, Figs. 2, 8 and 5 are characteristic diagrams showing the performance of the sound absorbing material of this invention, and Fig. 4 is an enlarged view of the structure of the sound absorbing material of this invention. This is an application example of In the figure, the same symbols indicate the same or corresponding parts, (1) is the skeleton of the metal porous body, (2) is the pore, (3) is the low-temperature oxidation catalyst particle, (4) is the reducing agent particle, (5) is a binder, (6)
is a porous coating, and (7) is a fumed graphite. Agent Shin Kuzuno (1 other person)

Claims (1)

[Claims] A porous metal body is used as a base material, and a heat-resistant binder coated and cured on the porous metal body contains a low-temperature oxidation catalyst and graphite fluoride, and at least one of a reducing agent and an alkaline agent. A sound-absorbing material characterized by the fact that it also contains