JPH06228502A - Automotive muffler coating composition, steel material coated therewith for automotive muffler, and automotive muffler made of this material - Google Patents

Abstract

PURPOSE:To provide an automotive muffler coating composition excellent in heat and corrosion resistances, a steel material coated therewith for an automotive muffler, and an automotive muffler made of the coated steel material. CONSTITUTION:The composition contains a polysilazane having at least one structure of the formula (wherein R is hydrogen, alkyl, alkenyl, cycloalkyl, aryl, alkylamino, alkylsilyl, alkoxyl or another group in which the atom directly bonded to the silicon atom of the main chain is carbon) in the molecule. The material is prepared by coating a steel material with this composition and the muffler is made of the coated steel material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile muffler coating composition having excellent heat resistance and corrosion resistance, a coated steel material for an automobile muffler coated with the coating composition, and an automobile muffler using the same. .

[0002]

2. Description of the Related Art A muffler for an automobile, which has a purpose of reducing exhaust noise from an engine of an automobile, has a double structure of an inner shell (inner box) and an outer shell (outer box) from the viewpoint of improving a sound deadening function. Things are commonly used.

Further, as a use environment of the muffler for automobiles, there is a severe temperature change from a high temperature state (500 ° C. or more in the outer shell) under a high load of the engine to a low temperature state under a light load and at the time of idling, and salt damage due to snow melting salt. It is very strict that it is subject to such problems, and it is necessary for the material used to have the performance to withstand them.

Conventionally, as such a material, a plated steel sheet having a surface of a steel sheet plated with Al or the like, a coated steel sheet, a stainless steel sheet and the like have been used.

[0005]

However, stainless steel sheets are not preferable because they are generally expensive and uneconomical and have a bad appearance due to the occurrence of surface rust. Further, the Al-plated steel sheet and the coated steel sheet were not satisfactory in corrosion resistance after being exposed to high temperature.

The present invention has been made in view of the above-mentioned conventional techniques, and a novel coating composition for forming a coating layer having excellent heat resistance and corrosion resistance on the surface of an outer shell of an automobile muffler. Another object of the present invention is to provide a steel material for an automobile muffler coated with the coating composition and an automobile muffler produced by using the coated steel material.

[0007]

That is, the present invention comprises a composition for coating an automobile muffler, which contains a polysilazane containing at least one structure represented by the following general formula [1] in one molecule. Is provided.

[0008]

[Chemical 2]

(In the formula, R is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an alkylamino group, an alkylsilyl group, an alkoxy group, or a group other than these groups, which is directly bonded to the main chain silicon. Indicates a group that is carbon.)

Further, according to the present invention, a steel sheet coated with the above-mentioned automobile muffler coating composition has a water vapor pressure of 15 mm.
In an atmosphere gas containing water vapor of Hg or less, 300
The present invention provides a steel material for an automobile muffler, characterized by being heat-treated at a temperature higher than ° C. Furthermore, the present invention provides an automobile muffler manufactured by using the steel material.

The present invention will be described in detail below. The composition for coating an automobile muffler used in the present invention (hereinafter, abbreviated as coating composition) has at least one structure represented by the following general formula [1] in one molecule, preferably three or more. , And more preferably, a liquid composition containing 5 to 50 polysilazanes.

[0012]

[Chemical 3]

In the above general formula [1], R is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an alkylamino group, an alkylsilyl group, an alkoxy group, or a silicon atom other than these groups in the main chain silicon. A group in which the directly bonded group is carbon is shown.

Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group,
Examples thereof include a heptyl group, an octyl group and a decyl group. Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group,
Examples thereof include a pentenyl group, a hexenyl group, a heptynyl group, an octenyl group and a decenyl group. Examples of the cycloalkyl group include a cyclohexyl group and a methylcyclohexyl group. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, Examples thereof include a benzyl group and a naphthyl group. Examples of the alkylamino group include a methylamino group and an ethylamino group. Examples of the alkylsilyl group include:
Methylsilyl group, ethylsilyl group, propylsilyl group,
Examples thereof include a butylsilyl group, octylsilyl group and decylsilyl group, and examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group and a heptoxy group.

In addition to these groups, examples of groups in which the group directly bonded to silicon in the main chain is carbon include substituted alkyl groups such as ethyl acrylate and trichlorosilylpropyl.

The polysilazane used in the coating composition of the present invention is a solid substance which is soluble in a solvent. In addition, since the polysilazane used in the coating composition of the present invention contains the structure represented by the general formula [1], it is efficiently cured by dehydrogenative self-condensation between the structures during heat treatment. To form a composition and structure similar to silicon nitride Si ₃ N ₄ , silicon carbide SiC, silicon nitride oxide Si ₃ N _n O _6-1.5n , silicon dioxide SiO ₂ or mixtures thereof. The reason why the coating composition of the present invention is excellent in heat resistance and corrosion resistance is due to the composition and structure similar to this ceramic.

The number average molecular weight of the polysilazane used in the coating composition of the present invention is 200 to 100,000.
It is preferable that it is between. If the low molecular weight is less than 200, there are many volatile components, making it difficult to form a dense film.
If the molecular weight is higher than 10,000, a slight self-crosslinking tends to result in a solvent-insoluble solid, which is unsuitable.

As the above polysilazane, for example, those produced by the following method are used, but not limited thereto, and those produced by other methods can be used.

(1) Polysilazane obtained by reacting dihalosilane and ammonia in an ether or dichloromethane solvent (US Pat. No. 4,397,828). (2) Si-methylpolysilazane obtained by reacting methyldihalosilane and ammonia in a dichloromethane solvent (US Pat. No. 4,482,669). (3) Polysilazane obtained by reacting dihalosilane with a base to form an adduct and then reacting with ammonia (Japanese Patent Publication No. 63-16325). (4) Polysiloxazane obtained by reacting dihalosilane with a base to form an adduct and then reacting ammonia with water (JP-A-62-195024). (5) N-methylpolysilazane obtained by reacting dihalosilane and methylamine in an ether solvent (Table 6
4-500031).

(6) Polysilazane obtained by heating polysilazane in a basic solvent or a solvent containing a basic compound (JP-A-1-138108). (7) Polysilazane obtained by reacting polysilazane with ammonia, hydrazine, amine, or substituted hydrazine under basic conditions (JP-A-1-138107, JP-A-1-203429, JP-A-1-203).
430 publication). (8) Polymetallosilazanes obtained by reacting polysilazanes with metal alkoxides (JP-A-1-221466, JP-A-2-84437, JP-A-2-774)
No. 27). (9) Polyborosilazane obtained by reacting polysilazane with a boron compound (JP-A-2-84437). (10) Copolymerized polysilazane obtained by reacting an inorganic silazane with an organic silazane under basic conditions (JP-A-2-1757).
No. 26).

(11) Copolymerized polysilazane obtained by reacting a complex obtained by reacting an inorganic halosilane and an organic dihalosilane with a base and reacting with ammonia (JP-A-3-31)
No. 326). (12) Polysilazane obtained by bringing polysilazane having Si-H group and N-H group into contact with ammonia in a state of being dissolved in an ether solvent (JP-A-4-240107). (13) Polysilazane obtained by reacting dihalosilane and ammonia in a 1,2-dichloroethane solvent (JP-A-4-240108). (14) Polysilazane obtained by reacting dihalosilane and ammonia in a 1,2-dimethoxyethane solvent (JP-A-4-240109).

The coating composition of the present invention preferably contains a solvent for diluting the polysilazane. As a solvent for dilution, a general organic solvent having no reactivity with polysilazane can be used. Examples of such a solvent include aromatic hydrocarbons such as xylene, toluene and benzene, ethers such as tetrahydrofuran (THF) and diethyl ether, and saturated hydrocarbons such as hexane and heptane.

The mixing ratio of the solvent varies depending on the molecular weight and structure of the polysilazane, but in general, when the amount of the solvent is 0 to 95% by weight, preferably 10 to 50% by weight, coating workability and uniform film thickness control can be achieved. An easy coating composition can be obtained.

If desired, fillers such as fillers, powders and whiskers may be added to and dispersed in the coating composition of the present invention. As the filler, those made of ceramic, glass or metal can be preferably used. For example, silica powder, mica powder, short fiber glass, powder glass, magnesium oxide powder, aluminum powder, zinc powder and the like can be used. The amount of the filler used is preferably 0 to 5 parts by weight with respect to 1 part by weight of polysilazane.

Next, the steel material for automobile muffler of the present invention is
It is obtained by coating a steel material with the above coating composition and then heat treating it. The coating composition is cured (densified) by heat treatment to form a ceramic-like structure,
Exhibits corrosion resistance at high temperatures.

As a coating method for coating the steel material with the coating composition of the present invention, a conventional coating method can be used, and examples thereof include flow coating, spray coating, dip coating and roll coating. .

As the steel material of the substrate used in the present invention, in addition to ordinary carbon steel, alloyed steel sheets such as Ni--Cr steel and Ni--Cr--Al steel, Al plated steel, Al--Si plated steel, Zn.
-Plated steel such as Al plated steel can be used.

The atmosphere gas for the heat treatment after coating can be arbitrarily selected from an inert gas such as nitrogen and argon, an oxidizing gas such as air and oxygen, or a reducing gas such as ammonia. For reasons of preference, it is preferred to choose air or nitrogen. However, it is necessary that the water vapor pressure in the atmosphere gas contains water vapor of 15 mmHg or less, and preferably 10 mmHg or less. If the water vapor pressure in the atmospheric gas is higher than 15 mmHg, the decomposition reaction of polysilazane occurs before polysilazane becomes ceramic, and the densification of the film is hindered, and the corrosion resistance at high temperature is deteriorated, which is not preferable.

The heat treatment temperature must be higher than 300 ° C., preferably 400 ° C. or higher. At a temperature of 300 ° C. or lower, the polysilazane does not densify and the corrosion resistance at high temperature is not exhibited. The upper limit of the temperature of the heat treatment is not particularly limited as long as it is a temperature lower than the temperature at which the steel material of the substrate deteriorates, but it is 10 for economic reasons.
It is preferably lower than 00 ° C.

The automobile muffler of the present invention is made by using the above steel material for automobile muffler to make an outer shell of the automobile muffler, and winding the outer shell around the inner shell with a lock seam or the like, and then, the inner shell, the front end plate and the rear end plate. Can be obtained by winding.

[0031]

The present invention will be described in detail below with reference to Examples and Production Examples.

Production Example 1 A 500 ml four-necked flask was equipped with a gas blowing port, a mechanical stirrer, and a vacuum trap condenser, the inside of the flask was replaced with nitrogen, and 250 ml of dehydrated tetrahydrofuran was charged and cooled to 0 ° C. Next, 50.1 g of dichlorosilane was introduced, and further 0
While maintaining the temperature at 0 ° C, 40.0 g of purified ammonia was added with stirring. After completion of the reaction, the by-product solid was filtered to obtain a clear solution.

When the solvent was removed from this solution under reduced pressure, oily polysilazane was obtained. The number average molecular weight of the obtained polymer was 870 as measured by GPC. Moreover, when the ¹ H-NMR spectrum (TMS standard) was measured, there were three broad absorptions, and the intensity ratio was δ 4.7 ppm (SiH ₂ + SiH) / δ 4.3 p.
pm (SiH ₃ ) / δ 1.5 to 0.5 ppm (NH) =
It was 100/48/78.

From this result, the number of structures represented by the general formula [1] contained in the obtained polysilazane can be determined as follows. When the average unit structure of the obtained polysilazane is R = H in the general formula [1], the polymerization degree is 870/45 = 19.3 from this number average molecular weight. However, the molecular weight of -SiH ₂ -NH- is 45. Also, from the ¹ H-NMR spectrum intensity ratio, 2SiH ₂
== SiH- and -SiH ₃ are produced by the disproportionation reaction in the same amount, the intensity ratio of the ¹ H-NMR spectrum (S
iH ₂ + SiH) / SiH ₃ = 100/48
_{H 2: SiH: SiH 3 =} 0.56: 0.22: 0.2
2 (molar ratio). Therefore, the structure of the above-mentioned general formula [1] contained in one molecule of the obtained polysilazane (R =
The average number of H) is about 11 (19.3 × 0.56 = 1)
0.8).

Production Example 2 Using the same apparatus as in Production Example 1, the inside of the flask was replaced with nitrogen, and 250 ml of pyridine which had been dehydrated in advance was charged to 0.
Cooled to ° C. Next, 50.1 g of dichlorosilane was introduced to form a complex of pyridine and dichlorosilane. Further, while maintaining 0 ° C., 44.2 g of purified ammonia was added with stirring. The by-product solids were filtered to give a clear solution.

The polysilazane obtained by removing the solvent under reduced pressure was oily. The number average molecular weight of the polymer was 980, and the intensity ratio of the ¹ H-NMR spectrum was δ
4.7 ppm / δ 4.3 ppm / δ 1.5 to 0.5 pp
m = 100/26/45. The average number of structures (R = H) of the general formula [1] contained in one molecule of polysilazane obtained by the same method as in Production Example 1 was about 16.

Production Example 3 After the pressure-resistant reaction vessel having an internal volume of 300 ml was replaced with nitrogen, 100 ml of the pyridine solution of polysilazane obtained in Production Example 2 (polysilazane concentration 4.9% by weight) was introduced and further purified ammonia 2 Introduced was 0.6 g. 95 ° C under airtight
It was heated to and held for 2 hours and 50 minutes.

The polysilazane obtained by removing the solvent was solid. The number average molecular weight of the polymer is 342.
0, and the intensity ratio of the ¹ H-NMR spectrum is δ4.
7 ppm / δ 4.3 ppm / δ 1.5 to 0.5 ppm =
It was 100/38/62. The average number of structures (R = H) of the general formula [1] contained in one molecule of polysilazane obtained by the same method as in Production Example 1 was about 47.

Example 1 Using the polysilazane obtained in Production Example 1, a xylene solution having a polysilazane concentration of 20% by weight was prepared to obtain a coating composition. SS41 steel plate (20mm × 40mm × 2m
m) was ultrasonically cleaned in Accenton and dried in a nitrogen stream, and then the above polysilazane solution was applied by brush. A steel plate coated with polysilazane is heated at atmospheric pressure in humidity-controlled air (measured value of water vapor pressure = 2 mmHg) at a temperature rising rate of 10 ° C.
/ Min, heat treatment was performed at a maximum temperature of 450 ° C for 30 minutes, and then the temperature was lowered at 10 ° C / min to prepare a coated steel sheet having a coating film with a thickness of about 0.5 µm.

The coating was transparent and could retain the metallic luster of the substrate. When the film was observed with a microscope, neither cracking nor peeling was observed. This coated steel sheet was introduced into the atmosphere on a rainy day (measured value of water vapor pressure = 20 mmHg).
When heated at 0 ° C. for 1 hour, the film was not cracked or peeled off, and the metallic luster of the substrate of the coated portion could be maintained.

Example 2 Using the polysilazane obtained in Production Example 2, a toluene solution having a polysilazane concentration of 5% by weight was prepared to obtain a coating composition. SS41 steel plate (20mm x 40mm x 2mm)
Was ultrasonically cleaned in Accenton, dried in a nitrogen stream, and then dip-coated with the above polysilazane solution. A steel sheet coated with polysilazane is heat-treated under atmospheric pressure in humidity-controlled air (measured value of water vapor pressure = 3 mmHg) at a temperature rising rate of 10 ° C./min at a maximum temperature of 500 ° C. for 30 minutes, and then at 10 ° C./min. Cool down, thickness about 0.6μ
m coating was formed.

The coating was transparent and was able to retain the metallic luster of the substrate. When the film was observed with a microscope, there was no cracking or peeling. While introducing this coated steel sheet into the atmosphere on a rainy day (measured value of water vapor pressure = 20 mmHg), 5
After heating at 00 ° C. for 1 hour, the film was not cracked or peeled off, and the metallic luster of the substrate of the coated portion could be maintained.

Example 3 Using the polysilazane obtained in Production Example 3, 20% by weight of polysilazane, silica filler (average particle size 0.5 μm)
15 wt% and xylene 65 wt% were mixed by a pot mill to obtain a coating composition.

SS41 steel plate (20 mm x 40 mm x 2 m
m) was ultrasonically cleaned in acetone, dried in a nitrogen stream, and then brushed with the above polysilazane solution. A steel plate coated with polysilazane is heated at atmospheric pressure in humidity-controlled air (measured value of water vapor pressure = 3 mmHg) at a heating rate of 10 ° C. /
After heat treatment for 30 minutes at a maximum temperature of 400 ° C for min,
The temperature was lowered at 10 ° C./min to form a film having a thickness of about 10 μm.

When the film was observed with a microscope, cracks and
There was no peeling. The coated steel sheet was heated at 500 ° C. for 1 hour while introducing the atmosphere (measured value of water vapor pressure = 20 mmHg) on a rainy day, but the film was not cracked or separated, and a good film could be maintained.

Comparative Examples 1 to 3 The coating compositions were prepared in the same manner as in Examples 1 to 3, and coating was performed in the same manner as in Examples 1 to 3 except that the atmosphere during the heat treatment was air with a water vapor pressure of 20 mmHg. A steel plate was produced. By observing the film with a microscope, cracks and peeling of the film were observed in all cases, and it was confirmed that the substrate was discolored brown and oxidized at the peeled portion.

Comparative Examples 4 to 6 Coated steel sheets were prepared in the same manner as in Examples 1 to 3 except that the coating composition was prepared in the same manner as in Examples 1 to 3 and the maximum heat treatment temperature was 200 ° C. did. This coated steel sheet was heated at 500 ° C. for 1 hour while introducing the atmosphere on a rainy day (measured value of water vapor pressure = 20 mmHg), and in both cases, cracking and peeling of the film occurred, and the substrate turned brown in the peeled portion. It was observed that the color changed and oxidized.

Example 4 After forming an outer shell from a muffler steel material, the coating composition was applied to the outer shell in the same manner as in Example 1 and heat treated to form a coating. After inserting the molded inner shell into this, the inner shell and the front end plate and the rear end plate were wound and fastened to manufacture an automobile muffler.

[0049]

As described above, according to the coating composition of the present invention, a coating layer having excellent heat resistance and corrosion resistance can be formed on a steel material. Further, since the steel material for an automobile muffler coated with the coating composition has heat resistance and corrosion resistance, if an outer shell of an automobile muffler is produced using the coated steel material, an automobile muffler having heat resistance and corrosion resistance can be obtained. Obtainable.

Front page continuation (72) Inventor Shigeharu Yoshii 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Inside Aomi Plant of Denki Kagaku Kogyo (72) Inventor Takayuki Shimizu 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Electric Chemical Industry Co. Company Aomi Factory (72) Inventor Tsuguo Suzuki 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Yoshiaki Koizumi 5-24-15 Minamidai, Nakano-ku, Tokyo Calsonitz Co., Ltd.

Claims (3)

[Claims] 1. A composition for coating an automobile muffler, comprising a polysilazane containing at least one structure represented by the following general formula [1] in one molecule. [Chemical 1] (In the formula, R is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an alkylamino group, an alkylsilyl group, an alkoxy group, or a group other than these groups which is directly bonded to silicon of the main chain is carbon. Indicates a group.) 2. A steel sheet coated with the composition according to claim 1 is heat-treated at a temperature higher than 300 ° C. in an atmosphere gas containing water vapor having a water vapor pressure of 15 mmHg or less. Steel materials for automobile mufflers. 3. An automobile muffler produced by using the steel material according to claim 2.