JPH0345704B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a vibration-damping composite steel plate that is excellent in vibration damping and processability. In recent years, noise pollution has become a problem due to the development of road transportation networks and the proximity of factories to residential areas, and measures to reduce noise generated by various transportation systems, machinery, structures, etc. have become important. . In particular, there is a strong desire to reduce noise in parts around automobile engines, metal processing machines, household appliance parts, and the like. One such noise countermeasure is the use of damping composite steel plates, which reduce vibrations by utilizing internal friction caused by shearing deformation of a viscoelastic material used as a damping layer. Since the damping composite steel plate is used to surround the noise generation source as described above, it is not only shaped into a plate but also processed into a desired shape by bending or drawing. [Prior Art] Conventionally, as a resin composition used for vibration damping as an intermediate layer of a damping composite steel sheet, for example, an aqueous dispersion of styrene/acrylic acid ester copolymer + scaly inorganic powder (Japanese Patent Application Laid-open No. 57-167360), crystalline polyolefin modified with unsaturated carboxylic acid or its anhydride + amorphous polymer (JP 59-80454 specification), ethylene acidic copolymer + viscous Various types of elastic materials are known, such as those described in Japanese Patent Publication No. 54-1354. [Problems to be Solved by the Invention] In these conventional technologies, damping composite steel sheets using damping resin compositions have a balance between damping properties and workability such as bending and deep drawing. It wasn't always satisfying. On the other hand, as a result of research conducted by the present inventors, a composition in which a copolymer of an acrylic acid ester and a vinyl aromatic monomer is blended with a crystalline polyolefin, which has excellent heat resistance and rigidity, through copolymerization with a polyolefin. was found to be effective in improving the vibration damping of composite steel plates, but although this also had excellent vibration damping, it was unsatisfactory in workability and adhesion when made into composite steel plates. The present invention improves the workability of a vibration-damping composite steel sheet using a composition of crystalline polyolefin with excellent vibration-damping properties and an acrylic acid ester/vinyl aromatic monomer, and improves vibration-damping properties and mechanical properties. The present invention provides a vibration-damping composite steel plate with an excellent balance of strength, adhesiveness, and workability. [Means for Solving the Problems] As a result of various studies on the damping properties and workability of damping composite steel sheets, the present inventors found that the adhesiveness of the damping layer is important for workability, and that a single It is difficult to maintain both high damping properties and adhesive properties with the damping layer, and even if a modified polyolefin layer is newly provided as an adhesive layer, the thickness of the damping resin layer will become thinner. Regardless, it has been found that the damping properties do not deteriorate compared to a damping resin layer of the same thickness, and the present invention has been achieved. That is, the present invention provides crystalline ethylene polymers, propylene polymers, or butene-1 polymers.
Contains 95 to 10% by weight of A and 5 to 90% by weight of a polymer B derived from an acrylic ester and a vinyl aromatic monomer, and at least one of the acrylic ester and the vinyl aromatic monomer of the polymer B. of
The intermediate layer is made of a resin composition C in which 0.5% or more of the polymer A is copolymerized, and the same type of crystalline polymer A used in the resin composition is grafted with an unsaturated carboxylic acid or its anhydride. This is a vibration-damping composite steel plate characterized in that it is laminated with a steel plate through a layer of modified polyolefin D obtained by modification. The crystalline ethylene polymer, propylene polymer or butene-1 polymer A used in the present invention may be ethylene, propylene alone or a copolymer thereof, or other monomers containing these as main components. It is a copolymer of, for example, low density polyethylene,
High density polyethylene, isotactic polypropylene, polybutene-1, ethylene/propylene copolymer, ethylene/butene-1 copolymer, ethylene/4-methylpentene-1 copolymer, ethylene/hexene-1 copolymer, Ethylene/octene-1 copolymer, propylene/butene-1 copolymer, etc., and from the viewpoint of rigidity and heat resistance, linear polyethylene such as high-density polyethylene, propylene-based polymer, butene-1-based polymer are preferable. In particular, propylene polymers and butene-1 polymers are preferred. On the other hand, polymer B derived from acrylic ester and vinyl aromatic monomer used in the present invention
In addition to a copolymer consisting only of these two, acrylic acid ester and/or vinyl aromatic monomer copolymerized with the above polyolefin is also included. The acrylic ester is an ester of acrylic acid or methacrylic acid, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate. , butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and the like can be used. Further, as the vinyl aromatic monomer, styrene, substituted styrene such as methylstyrene, dimethylstyrene, chlorstyrene, α-substituted styrene such as α-methylstyrene, α-ethylstyrene, etc. can be used. As a method for producing a copolymer consisting only of an acrylic acid ester and a vinyl aromatic monomer, ordinary random polymerization methods such as solution polymerization, emulsion polymerization, and suspension polymerization are suitable. Two or more types of the obtained copolymers may be used in combination. The proportion of acrylic ester in this induced polymer can be appropriately selected so that the temperature at which the maximum value of η occurs matches the operating temperature of the damping composite steel sheet, but it is generally 5 to 95% by weight. . This polymer may further contain a small amount of other monomer as a third component, for example, 30% by weight or less, if necessary. The crystalline ethylene polymer, propylene polymer or butene-1 polymer contains 95 to 10% by weight,
Preferably 80-30% by weight, particularly preferably 70-40%
If it is less than this range, the workability of the vibration-damping composite steel plate will deteriorate, and if it is more than this range, the vibration-damping properties will deteriorate, which is not preferable. Generally, the environmental temperature of the noise source and the frequency range of the generated noise are 0 to 150℃ and 20 to 20℃, respectively.
20000Hz, and the damping composite steel plate must exhibit effective damping properties at the above temperature and frequency. The η of the vibration damping composite steel sheet is required to be 0.05 or more, preferably 0.1 or more in terms of the vibration damping effect, and the polymer derived from the acrylic acid ester and the vinyl aromatic monomer has a η of the vibration damping composite steel sheet. From the point of view of improvement, at least 5 to 90% by weight, preferably 20 to 70% by weight, particularly preferably 30 to 60% by weight is required. If it is lower than this range, η of the vibration-damping composite steel plate will be low, and conversely, if it is higher than this range, the workability of the vibration-damping composite steel plate will deteriorate, which is not preferable. In the resin composition of the present invention, the polymer B derived from an acrylic ester and a vinyl aromatic monomer is co-contained with a crystalline ethylene polymer, a propylene polymer, or a butene-1 polymer A. It also includes polymerized components. That is, the crystalline ethylene polymer, propylene polymer, or butene-1 polymer A used in the composition of the present invention may be used in combination of two or more types, but at least a portion thereof may be It is copolymerized with an acid ester, a vinyl aromatic monomer, or both, and the amount of copolymerization is preferably 0.5% by weight or more, the total amount of polymer B derived from an acrylic ester and a vinyl aromatic monomer. is 1% by weight or more, particularly preferably 3% by weight or more. If the copolymerization amount of the crystalline ethylene polymer, propylene polymer, or butene-1 polymer is less than this amount, the resulting composition will not have the desired mechanical strength, and the forming process of the composite steel sheet will be difficult. The law is also inferior. Examples of copolymerization with crystalline ethylene polymers, propylene polymers, or butene-1 polymers include JP-A-58-198529 and JP-A-59-
Various block copolymerization and graft copolymerization methods described in specifications such as No. 27934 and Japanese Patent Publication No. 58-53003 can be used. The composition of the present invention may be obtained by kneading each of these components using a normal kneading method, but there are some considerations in terms of bending and drawing of the damping composite steel plate and ease of manufacturing the composition. From this point of view, it is obtained by subjecting a crystalline polyolefin and a predetermined amount of an acrylic ester and a vinyl aromatic monomer to graft copolymerization conditions in a suspension system, solution system, or melt system, preferably an aqueous suspension system. Modified products are particularly preferred as compositions of the invention. The composition of the present invention may contain various additives, plasticizers, fillers, elastomers, etc., as long as the purpose of the present invention is not impaired. The plasticizer has the effect of shifting the temperature at which the composition exhibits the maximum value of tan δ to the lower temperature side, adjusting the vibration damping temperature range of the damping composite steel sheet, and also has the effect of making the composition flexible and improving brittleness. Useful. Further, the filler has the effect of keeping the rigidity high at the temperature at which the maximum value of tan δ of the composition occurs, and has the effect of improving η in this respect.
As the elastomer, a styrene/butadiene block copolymer or its hydrogenated product, ethylene/propylene rubber, etc. are preferably blended for the purpose of improving physical properties. The modified polyolefin used for laminating the resin composition on a steel plate in the present invention is the same type of polyolefin as the crystalline ethylene polymer, propylene polymer, or butene-1 polymer A. It is a product grafted with unsaturated carboxylic acid or its anhydride. Examples of the unsaturated carboxylic acid or its anhydride include acrylic acid, methacrylic acid, maleic acid, fumaric acid, maleic anhydride, and the like, with maleic anhydride being the most preferred. The method of graft modification is carried out by a conventional method such as melt grafting or solution grafting of these components in the presence or absence of a radical generator such as a peroxide or an azo compound. The content of unsaturated carboxylic acid or its anhydride in the modified polyolefin is determined from the viewpoint of adhesion to steel sheets.
0.01% by weight or more is required. Further, the MFR of the modified polyolefin is preferably 0.5 to 20 g/10 minutes, particularly preferably 1 to 10 g/10 minutes, from the viewpoint of film formability, workability of vibration-damping composite steel plate, adhesiveness, etc. When the resin composition is ethylene-based, the modified polyolefin is a modified ethylene-based resin, when the resin composition is propylene-based, a modified propylene-based resin, and when the resin composition is butene-1, a propylene-based resin is used. Alternatively, a modified butene-1 resin is preferably used. Furthermore, the composition or modified polyolefin of the present invention may be blended with various conductive fillers such as carbon black and metal fibers in order to impart conductivity for the purpose of improving the weldability and paintability of vibration-damping composite steel sheets. be able to. Furthermore, various flame retardants such as antimony trioxide and aluminum hydroxide may be added for the purpose of improving flame retardancy. The steel sheets used in the present invention include, for example, hot-rolled steel sheets, soft cold-rolled steel sheets, high-strength steel sheets, stainless steel sheets, electrogalvanized steel sheets, hot-dip galvanized steel sheets, and alloyed steel sheets thereof, such as zinc-based alloy-plated steel sheets and zinc chrome metal sheets. Examples include various surface-treated steel sheets such as aluminized steel sheets, nickel-plated steel sheets, and tin-plated steel sheets. Among these, surface-treated steel sheets subjected to anti-corrosion treatment are preferred. The thickness of the steel plate of the vibration damping composite steel plate of the present invention is 0.2~
3.2mm, thickness of modified polyolefin layer is 0.005~0.1
mm, and the thickness of the resin composition layer is 0.03 to 0.5 mm, preferably 0.2 to 2.0 mm, and 0.005 to 0.00 mm, respectively.
0.05mm, 0.03~0.3mm. If the thickness of the modified polyolefin layer is less than the above range, it is difficult to form a film and the stability of adhesion to a steel plate is poor, which is not preferable. On the other hand, if the amount exceeds the above range, vibration damping properties and workability of the composite steel sheet will deteriorate, which is not preferable. If the thickness of the resin composition is less than the above range, vibration damping properties will be poor, which is not preferable. On the other hand, if the amount exceeds the above range, the workability of the composite steel sheet will be poor, which is not preferable. If the thickness of the steel plate is less than the above range, the workability of the composite steel plate will be poor, which is not preferable. On the other hand, if the amount exceeds the above range, the damping properties of the composite steel plate will deteriorate, which is not preferable, and the ratio of the steel plate to the resin layer is preferably 20:1 to 1:1. Various known methods can be employed to manufacture the damping composite steel sheet of the present invention. For example, a method in which a modified polyolefin grafted with an unsaturated carboxylic acid or its anhydride is applied as a solution between steel plates, dried and then thermocompressed with a resin composition film, and a method in which a resin composition and a modified polyolefin are coextruded , or separately formed into a film and then sandwiched between steel plates and laminated using a press or hot roll, or a resin composition and a modified polyolefin are coextruded between steel plates, or separately formed into a film in a molten state. There are methods such as extrusion and lamination. In particular, a method using coextrusion is preferred because the process can be simplified. Furthermore, when laminating the film-like modified polyolefin with a steel plate, the film-like modified polyolefin may be subjected to surface treatment such as corona treatment or flame treatment, and then bonded to the steel plate using an adhesive if necessary. [Operations and Effects] The resin composition and modified polyolefin used in the present invention can be formed into a film in a molten state, so the manufacturing process for vibration-damping composite steel sheets is simplified compared to conventional vibration-damping materials. It is possible to In addition, the damping layer of the vibration-damping composite steel sheet of the present invention is provided with an adhesive resin layer and a vibration-damping resin layer, and as a result, when the composite steel sheet has the same thickness,
Although the thickness of the vibration-damping resin layer becomes relatively thin, no decrease in vibration-damping properties is observed. Therefore, the vibration-damping composite steel sheet according to the present invention can solve the problems caused by lamination with steel plates without reducing the vibration-damping performance, so it is a vibration-damping composite steel sheet with excellent vibration-damping properties and workability. can be designed. [Example] Next, an example will be shown. The vibration-damping composite steel plate in the following example was prepared by forming a composition into a film, and then
It is sandwiched between two steel plates and laminated by compression molding, and the thickness of the steel plates is 0.8 mm, and the thickness of the resin layer is 0.1 mm. η of the damping composite steel plate is the loss coefficient η measured at 1000 Hz by the resonance response method of the mechanical impedance method. The T-peel adhesion (JIS-K6854) and shear adhesion (JIS-K6850) of the composite steel plate were measured at test speeds of 50 mm/min and 4 mm/min, respectively. The method for measuring the monomer copolymerized in polyolefin is to dissolve the obtained modified propylene/ethylene copolymer in boiling xylene, reprecipitate it with acetone, vacuum dry it, and perform infrared analysis. The content of styrene and acrylic ester was determined by the following method. Example 1 Production of graft copolymer 20 kg of pure water, 0.6 kg of tribasic calcium phosphate and 0.06 kg of sodium dodecylbenzenesulfonate as suspending agents were mixed into a 50-capacity autoclave to form an aqueous medium, and a particle size of 3 to 4 mm was added to the aqueous medium. 4 kg of propylene/ethylene copolymer (MFR 4 g/10 min, ethylene content 8% by weight, hereinafter abbreviated as PP) particles were suspended by stirring. Separately, 18 g of benzoyl peroxide was mixed with 4.2 kg of styrene and 2-ethylhexyl acrylate. The solution was dissolved in 1.8 kg and added to the above suspension system, and nitrogen was introduced into the autoclave to replace the inside of the system. Furthermore, the temperature inside the autoclave was raised to 60°C, and the mixture was left at this temperature for 5 hours with stirring to impregnate styrene and 2-ethylhexyl acrylate containing a polymerization initiator into the PP particles. Next, the temperature of this suspension was raised to 80°C, and the polymerization was carried out by leaving it at this temperature for 5 hours while stirring.
The temperature was raised to 90°C to complete polymerization. After cooling, the solid contents were taken out and washed with water to obtain 10 kg of styrene/2-ethylhexyl acrylate modified propylene/ethylene copolymer (hereinafter abbreviated as modified PP) particles. The styrene content in the obtained modified PP was 42% by weight, the 2-ethylhexyl acrylate content was 18% by weight, and their graft copolymerization amount was 8.8%.
It was 3.8% by weight. Using the obtained modified PP particles to which an antioxidant was added, the tensile elongation of the composition was measured and found to be 620%. Manufacture of three-layer film: Maleic anhydride-modified polypropylene (Mitsubishi Yuka Co., Ltd. "Modec P-300M") is used as the inner and outer layers, and the above-mentioned modified PP particles with an antioxidant added are used as the intermediate layer. Inner layer/intermediate layer/outer layer are respectively formed by extrusion 2 resin 3 layer film molding machine.
A three-layer film of 15 μm/70 μm/15 μm was molded. This three-layer film was sandwiched between two 0.8 mm cold-rolled steel plates to form a composite steel plate. The thickness of the intermediate resin layer is
It was 0.1mm. Maximum values (ηmax) of T-peel adhesion, shear adhesion, and vibration damping performance of the obtained composite steel plate at 1000Hz
are shown in Table 1.

[Table] Shows ren/ethylene polymers.
Comparative Example 1 Instead of the three-layer film of Example 1, the above modified film was used.
Using PP with an antioxidant added, a 100 μm single-layer film was formed using a film forming machine and sandwiched between two 0.8 mm steel plates to form a composite steel plate. Maximum values (ηmax) of T-peel adhesion, shear adhesion, and vibration damping performance of the obtained composite steel plate at 1000Hz
are also shown in Table 1. Comparative Example 2 Production of styrene/2-ethylhexyl acrylate copolymer (SAE) 35 kg of pure water and 320 g of polyvinyl alcohol as a suspending agent were mixed into a 50-volume autoclave to form an aqueous medium, and 180 g of benzoyl peroxide was added to this.
was added after being dissolved in 12.6 kg of styrene and 5.4 kg of 2-ethylhexyl acrylate, and the mixture was stirred and suspended. After introducing nitrogen into the autoclave and replacing the system with nitrogen, the temperature inside the autoclave was raised to 6°C.
After prepolymerizing by leaving at this temperature for 5 hours with stirring, the temperature inside the autoclave was raised to 90°C while increasing the stirring speed, and the polymerization was completed by leaving at this temperature for 3 hours while stirring. After cooling, the solid contents were taken out and washed with water to obtain 17.5 kg of styrene/2-ethylhexyl acrylate copolymer (SAE). The styrene content in the obtained SAE was 70% by weight, and the 2-ethylhexyl acrylate content was 30% by weight. The tensile elongation of the composition was measured in the same manner as in Example 1 using 60% by weight of this SAE and 40% by weight of PP used in the production of the graft copolymer in Example 1 with an antioxidant added. The tensile elongation of the composition was 20%. It was hot. Example 2 Production of a graft copolymer 20 kg of pure water, 0.6 kg of calciul triphosphate as a suspending agent, and 0.06 kg of sodium dodecylbenzenesulfonate were mixed into a 50-capacity autoclave to form an aqueous medium, and a particle size of 3 ~4mm ethylene polymer (MFR9g/10min, density 0.95g/ ^cm3 ) (hereinafter referred to as PE
5 kg of particles (abbreviated as ) were suspended by stirring.
Separately, add 15g of benzoyl peroxide to the styrene.
It was dissolved in 3.5 kg and 1.5 kg of 2-ethylhexyl acrylate, and added to the above suspension system, and nitrogen was introduced into the autoclave to replace the system with nitrogen. Furthermore, the temperature inside the autoclave was raised to 60℃, and it was left at this temperature for 5 hours with stirring to dissolve styrene containing a polymerization initiator and 2-ethylhexyl acrylate.
Impregnated into PE particles. Next, the temperature of this suspension was raised to 80°C, and the polymerization was carried out by leaving it at this temperature for 5 hours while stirring.
The temperature was raised to 90°C and maintained for 5 hours to complete polymerization. After cooling, the solid content was taken out and washed with water to obtain 10 kg of styrene/2-ethylhexyl acrylate modified ethylene polymer (hereinafter abbreviated as modified PE) particles. The styrene content in the obtained modified PE was 35% by weight, the 2-ethylhexyl acrylate content was 15% by weight, and their graft copolymers each had 7% by weight.
% by weight, and 3% by weight. The tensile elongation of the composition measured in the same manner as in Example 1 using the obtained modified PE particles to which an antioxidant was added was 450%. Manufacture of 3-layer film Using maleic anhydride modified polyethylene (Mitsubishi Yuka Co., Ltd.'s "Modec H-400M") as the inner and outer layers,
Using the above-mentioned modified PP particles with an antioxidant added as the intermediate layer, the inner layer/intermediate layer/outer layer were each 15μ by a coextrusion two-resin three-layer film molding machine.
A three-layer film of m/70 μm/15 μm was molded. This three-layer film was sandwiched between two 0.8 mm cold-rolled steel plates to form a composite steel plate. The thickness of the intermediate resin layer is
It was 0.1mm. Maximum values (ηmax) of T-peel adhesion, shear adhesion, and vibration damping performance of the obtained composite steel plate at 1000Hz
are shown in Table 2.

[Table] Shows the polymers.
Comparative Example 3 Instead of the three-layer film of Example 2, the above modified film
Using PE with an antioxidant added, a 100 μm single-layer film was formed using a film forming machine and sandwiched between two 0.8 mm steel plates to form a composite steel plate. Maximum values (ηmax) of T-peel adhesion, shear adhesion, and vibration damping performance of the obtained composite steel plate at 1000Hz
are also shown in Table 2. Comparative Example 4 A composition was prepared in the same manner as in Example 2 using 50% by weight of SAE obtained in Comparative Example 2 and 50% by weight of PE used for producing the graft copolymer in Example 2 with an antioxidant added. The tensile elongation of the product was measured and was 10%. Example 3 Production of graft copolymer 20 kg of pure water, 0.6 kg of calciul triphosphate as a suspending agent, and 0.06 kg of sodium dodecylbenzenesulfonate were mixed into a 50-capacity autoclave to form an aqueous medium, and the particle size 3-4 mm butene-1 polymer (MFR4/10 minutes, density 0.90 g/cm ³ ) (hereinafter
5 kg of particles (abbreviated as PB) were suspended by stirring. Separately, 15 g of benzoyl peroxide was dissolved in 3 kg of styrene and 2 kg of 2-ethylhexyl acrylate, and this was added to the suspension system, and the inside of the autoclave was purged with nitrogen. Furthermore, the temperature inside the autoclave was raised to 60°C, and the mixture was left at this temperature for 5 hours while stirring to impregnate styrene and 2-ethylhexyl acrylate containing a polymerization initiator into the PB particles. Next, the temperature of this suspension was raised to 80°C, and the polymerization was carried out by leaving it at this temperature for 5 hours while stirring.
The temperature was raised to 90°C and maintained for 5 hours to complete polymerization. After cooling, the solid contents were taken out and washed with water, and styrene/2-ethylhexyl acrylate modified butene-
1 polymer (hereinafter abbreviated as modified PB) particles 10Kg
I got it. The styrene content in the obtained modified PB is 30
Weight%, 2-ethylhexyl acrylate content is 20
In weight percent, the graft copolymers were 6% and 4% by weight, respectively. The tensile elongation of the composition measured in the same manner as in Example 1 using the obtained modified PB particles to which an antioxidant was added was 500%. Production of three-layer film: Maleic anhydride-modified polypropylene (Mitsubishi Yuka Co., Ltd.'s "Modec P-300M") was used as the inner and outer layers, and the above-mentioned modified PB particles with an antioxidant added were used as the intermediate layer. , the inner layer/intermediate layer/outer layer are formed by a coextrusion two-resin three-layer film molding machine, respectively.
A three-layer film of 15 μm/70 μm/15 μm was molded. This three-layer film was sandwiched between two 0.8 mm cold-rolled steel plates to form a composite steel plate. The thickness of the intermediate resin layer is
It was 0.1mm. Maximum values (ηmax) of T-peel adhesion, shear adhesion, and vibration damping performance of the obtained composite steel plate at 1000Hz
are shown in Table 3.

[Table] Comparative Example 5 Instead of the three-layer film of Example 3, the above modified film was used.
Using PB with an antioxidant added, a 100 μm single-layer film was formed using a film forming machine and sandwiched between two 0.8 mm steel plates to form a composite steel plate. Maximum values (ηmax) of T-peel adhesion, shear adhesion, and vibration damping performance of the obtained composite steel plate at 1000Hz
are also shown in Table 3. Comparative Example 6 In the SAE production of Comparative Example 2, 10.8 kg of styrene
17.5 kg of SAE was obtained in the same manner except that 7.2 kg of 2-ethylhexyl acrylate was used. The styrene content in the obtained SAE was 60% by weight, and the 2-ethylhexyl acrylate content was 40% by weight. The tensile elongation of the composition was measured in the same manner as in Example 3 using the obtained 50% by weight of SAE and 50% by weight of PB used in the production of the graft copolymer in Example 3 with an antioxidant added. The result was 10%.

Claims (1)

[Scope of Claims] 1. Polymer B5 derived from crystalline ethylene polymer, propylene polymer or butene-1 polymer A95 to 10% by weight, acrylic ester and vinyl aromatic monomer 90% by weight of the resin composition C, and 0.5% or more of at least one of the acrylic ester and the vinyl aromatic monomer of the polymer B is copolymerized with the polymer A. is laminated with a steel plate through a layer of modified polyolefin D obtained by graft-modifying the same type of crystalline polymer A as used in the resin composition with an unsaturated carboxylic acid or its anhydride. Vibration-damping composite steel plate. 2 Resin composition C is obtained by treating a crystalline ethylene polymer, propylene polymer, or butene-1 polymer A with an acrylic ester and a vinyl aromatic monomer under graft copolymerization conditions. The damping composite steel sheet according to claim 1, which is the obtained modified product. 3. The vibration-damping composite steel sheet according to claim 1 or 2, wherein the unsaturated carboxylic acid anhydride is maleic anhydride.