JPH04372676A - Viscoelastic composition for vibration-damping steel sheet and vibration-damping steel sheet made by coating therewith - Google Patents

Abstract

PURPOSE:To provide a composition having high adhesive strength at high temperature and good water resistance and moisture resistance. CONSTITUTION:This composition is composed mainly of a water-dispersible polyurethane resin (A) made by the chain lengthening of a polyurethane prepolymer formed from a diisocyanate and a polyol with a compound having at least two actzve hydrogen atoms and a water-dispersible epoxy resin (B) comprising a bisphenol A epoxy resin and/or sorbitol polyglycidyl ether epoxy resin, having an epoxy equivalent of 180 to 1,000 at a weight ratio of component A to component B of (99:1) to (90:10).

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a viscoelastic composition, and in particular, it is used to constitute all or part of structures such as home appliances, building materials, and vehicles to reduce vibrations and noise of the structures. The present invention relates to a viscoelastic composition suitable for manufacturing a composite vibration damping material useful for damping.

0002

BACKGROUND OF THE INVENTION In recent years, there has been a trend to regulate noise and vibration in order to improve the working environment in homes and workplaces. In order to respond to these trends, there is a need to add damping properties to metal materials that are sources of noise and vibration, and to improve damping performance, and composite damping materials are being used. be.

[0003] In the composite vibration damping material, a viscoelastic layer converts vibration energy applied to a metal into thermal energy and consumes it, thereby reducing noise generated by vibration. In response to the needs of noise regulations in recent years, this vibration damping material has been used in washing machines,
It has been used in automobile oil pans and building materials such as doors, floors, and shutters. This damping material is usually made by sandwiching a viscoelastic material between metal plates such as metal plates or double metal tubes that face each other.

[0004] Such viscoelastic materials are required to maintain high vibration damping performance and good adhesive performance over a wide temperature range. Conventionally, various means have been used to impart the above-mentioned properties to resins. For example, polyesters include polyesters with a glass transition point (Tg point) of 0 to 60°C made of glycols and phthalates, and compositions in which this resin is mixed with an epoxy resin (Japanese Patent Laid-open No. 5
0-143880). In addition, a composition that attempts to obtain high vibration damping performance over a wide temperature range was published in Japanese Patent Application Laid-open No. 61-60.
It is described in Publication No. 759. In addition, in order to utilize the high vibration damping properties of polyisobutylene over a wide temperature range and improve the adhesion, which is a drawback of the resin, a viscoelastic mixture containing a tackifier, etc. It is disclosed in the publication No. Furthermore, an example in which a hot melt resin film is used as an adhesive layer in addition to vibration damping performance is described in JP-A-59-146837. Furthermore,
An example using urethane resin is disclosed in JP-A-62-74646.
It is stated in the bulletin number.

[0005]

[Problem to be solved by the invention] Among such viscoelastic materials, urethane resins have particularly excellent adhesive performance, but because they are water-insoluble, they are usually supplied dissolved in organic solvents. Because it contains organic solvents, it causes fires during painting, contamination of the working environment, and hygiene problems. Furthermore, when painting with a coil coating line, it is necessary to burn off the organic solvent that dissolves the resin using an incinerator. This is not only a waste of petroleum resources, but also releases carbon dioxide gas, which is not desirable from the standpoint of preserving the global environment. Therefore, in recent years, there has been a strong desire to develop water-dispersible urethane resin viscoelastic compositions from this viewpoint.

[0006] In addition, the first required performance of a viscoelastic composition for a composite vibration damping material is that it has excellent adhesive properties. It shows excellent adhesion at the temperature during processing such as press molding, and after processing, the viscoelastic composition is sometimes subjected to a baking process at a high temperature of about 180°C, so the viscoelastic composition exhibits excellent adhesion at temperatures near the baking temperature. It is necessary that the composition does not flow out and has a certain degree of adhesive strength (usually T-peel strength of 1.0 kg/25 mm or more). Secondly, it is important that the value of the vibration damping property is high. This is expressed by the magnitude of the loss coefficient.

[0007] Therefore, water-dispersed urethane-based resin viscoelastic compositions exhibit a certain degree of adhesive strength not only at room temperature but also at high temperatures of about 180°C, and have excellent performance in terms of vibration damping properties. required.

[0008] Furthermore, as for the water-dispersible urethane resin viscoelastic composition, it is necessary to consider the adhesion to the material, adhesive strength, water resistance, and heat resistance.

[0009] In the case of a urethane resin viscoelastic composition consisting of an aromatic terephthalic acid or isophthalic acid polyester and an aromatic isocyanate such as tolylene diisocyanate, the adhesive strength and adhesion strength to the material are limited. , water resistance is good, but vibration damping properties are poor. On the other hand, in the case of urethane resins made of aromatic terephthalic acid or isophthalic acid-based polyesters and linear aliphatic isocyanates such as hexamethylene diisocyanate, and in the case of aliphatic polyesters synthesized from ethylene glycol and adipic acid and tolylene diisocyanate, Urethane resins made of aromatic isocyanates have good vibration damping properties, but have poor adhesion to materials, adhesive strength, and water resistance.

From this viewpoint, the viscoelastic composition for vibration damping steel plates needs to be blended in a well-balanced manner in terms of vibration damping properties, adhesive strength and water resistance. Further, the urethane resin alone does not provide sufficient water resistance, and the adhesive strength rapidly decreases when immersed in hot water or boiling water, or when left under high temperature and high humidity.

[0011]

[Means for Solving the Problems] Considering the current situation, the present inventor has developed a viscoelastic layer obtained by heating and curing that has the excellent adhesive strength, vibration damping properties, adhesion to materials, and water resistance inherent to urethane resin. We have conducted extensive research to develop a water-dispersible urethane resin composition that can exhibit excellent properties. As a result, they discovered that when a specific water-dispersed epoxy resin is blended with a water-dispersed urethane resin, the adhesive strength, water resistance, and moisture resistance at high temperatures are significantly improved, leading to the completion of the present invention. .

Thus, according to the present invention, (A) a water-dispersible polyurethane resin obtained by chain-extending a polyurethane prepolymer consisting of a diisocyanate and a polyol with a compound having at least two active hydrogens, and (B) a water-dispersible polyurethane resin.
A viscoelastic composition mainly composed of a bisphenol A type water-dispersible epoxy resin and/or a sorbitol polyglycidyl ether type water-dispersible epoxy resin having an epoxy equivalent of 180 to 1000, the composition comprising a water-dispersible polyurethane resin (
A) Weight ratio of water-dispersible epoxy resin (B) to water-dispersible epoxy resin (A)/(
There is provided a viscoelastic composition for damping steel plates, characterized in that B) is 99/1 to 90/10.

The water-dispersed polyurethane resin (A) used in the composition of the present invention is a polyurethane consisting of a polyol such as a polyester polyol or a polyether polyol, and an aromatic, aliphatic, or alicyclic diisocyanate, and a diol, diamine, etc. A polyurethane resin whose chain has been extended by a low molecular weight compound having two or more active hydrogen atoms is stably dispersed or dissolved in water, and a wide variety of known resins can be used. For example, Tokuko Sho 42-24192
No. Publication, Special Publication No. 42-24194, Special Publication No. 49-9 Sho.
86 Publication, Special Publication No. 49-33104, Special Publication No. 1986-15
As is clear from Publication No. 027 and Japanese Patent Publication No. 53-29175, the following method can be used.

(1) A method in which hydrophilicity is imparted by introducing an ionic group such as a hydroxyl group, an amino group, or a carboxyl group to the side chain or end of a polyurethane polymer, and the polyurethane polymer is dispersed or dissolved in water by self-emulsification.

(2) The polymer after the reaction or the terminal isocyanate is converted into oxime, alcohol, phenol,
A method in which a polymer blocked with a blocking agent such as mercaptan, amine, or sodium bisulfite is forcibly dispersed in water using an emulsifier and mechanical shearing force. Furthermore, a method in which a urethane prepolymer with terminal isocyanate groups is mixed with water, an emulsifier, and a chain extender, and mechanical shearing force is used to simultaneously achieve dispersion and polymerization.

(3) A method in which a water-soluble polyol such as polyethylene glycol is used as a polyol as the main raw material for polyurethane, and the polyurethane is dispersed or dissolved in water.

The water-dispersed polyurethane resin (A) used in the composition of the present invention is not limited to a single dispersion or dissolution method as described above, and mixtures obtained by each method may also be used. can.

As the diisocyanate used in the synthesis of the water-dispersed polyurethane resin (A) used in the composition of the present invention, all aromatic and aliphatic diisocyanates are suitable, including the following. Hexamethylene diisocyanate, tetramethylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 1,3-diisocyanatemethylcyclohexanone, 1,4-diisocyanatemethylcyclohexanone , 4,4'-diisocyanate cyclohexanone, 4,4'-diisocyanate cyclohexylmethane, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, Examples include 2,4-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, and 4,4'-diphenylene diisocyanate. Among these, preferably 2,4-
These include tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the like.

Preferred polyols used in the synthesis of the water-dispersed polyurethane resin (A) used in the composition of the present invention include polyethers, polyacetals, polyesters, polyamides, and polyesteramides having a molecular weight of 500 to 8,000. It is a polyhydroxy compound.

Examples of polyethers include polymerization products of ethylene oxide, propylene oxide, tetrahydrofuran, butylene oxide, copolymerization products or graft polymerization products thereof, copolymerization products thereof, and polyhydric alcohols or their Mention may be made of polyethers obtained by condensation of mixtures, as well as polyethers obtained by alkoxylation of polyhydric alcohols, amine polyamines, and amino alcohols. Examples of polyacetals include those synthesized from hexanediol and formaldehyde.

Primarily linear condensations obtained from polybasic saturated and unsaturated carboxylic acids and polyhydric saturated and unsaturated alcohols, amino alcohols, diamine polyamines and mixtures thereof as polyesters, polyesteramides and polyamides things are applied.

[0022] The chain extender having at least two active hydrogens used in the synthesis of the water-dispersed polyurethane resin (A) used in the composition of the present invention includes the following.

(1) Saturated and unsaturated glycols such as ethylene glycol or condensates of ethylene glycol, butanediol, propanediol 1,3, propanediol 1,2, neopentyl glycol and mono- and bis-alkoxylated Aliphatic, cycloaliphatic, aromatic and heterocyclic primary amines, such as N-methyldiethanolamine, N-butyldiethanolamine, N-oleyldiethanolamine, N-cyclohexyldiisopropanolamine.

(2) Aliphatic, cycloaliphatic and aromatic diamines, such as ethylenediamine, hexamethylenediamine, 1,4-cyclohexyldiamine, isomers of phenylenediamine.

(3) Amino alcohols, such as ethanolamine, propanolamine, butanolamine.

(4) Aliphatic, cycloaliphatic, aromatic dicarboxylic acids, such as oxalic acid, malonic acid, succinic acid, adipic acid, pimelic acid, succinic acid, azelaic acid, sebazic acid,
Terephthalic acid, isophthalic acid, maleic acid.

The polyurethane is produced in a manner known per se in the presence of a solvent or water. Generally, the polymeric polyhydroxy compound and the polyisocyanate are first subjected to an addition reaction at 70 DEG to 150 DEG C. in the presence of a solvent or water, and then further reacted in solution at about 50 DEG to 150 DEG C., optionally with a chain extender. It is also possible to premix the hydroxy compound and chain extender.

The reaction can be carried out in the presence of a tertiary amine and a catalyst such as an organometallic compound. The molecular ratio of isocyanate groups to active hydrogen is generally 0.5:
It is between 1 and 1.5:1.

The viscoelastic composition of the present invention has the advantage that a water-dispersible epoxy resin (B) is blended with a water-dispersible polyurethane resin (A) to improve adhesive strength, water resistance, and moisture resistance at high temperatures. It has characteristics.

The water-dispersible epoxy resin (B) constituting the composition of the present invention is a bisphenol A-type water-dispersible epoxy resin having an epoxy equivalent of 180 to 1000, and/or a sorbitol polyglycidyl ether-type water-dispersible epoxy resin. Epoxy resin is used.

[0031] Bisphenol A water-dispersible epoxy resins having an epoxy equivalent of 180 to 1000 include, for example, Epiclon EM-75W (manufactured by Dainippon Ink Chemical Co., Ltd.).

[0032] Sorbitol polyglycidyl ether type epoxy resin is one in which a glycidyl ether group is introduced into the hydroxyl group of sorbitol, such as Epiclon CR-95.
-L (product of Dainippon Ink Chemical Co., Ltd.), etc.

The mixing ratio of the water-dispersible polyurethane resin (A) and the water-dispersible epoxy resin (B) in the composition of the present invention is such that the weight ratio (A)/(B) is 99/1 to 90/10; Preferably, it needs to be in the range of 97/3 to 91/9. When the proportion of the water-dispersible epoxy resin (B) is less than 1, the water resistance of the composition decreases, and when it exceeds 10, the adhesive strength decreases.

The composition of the present invention may further contain fillers such as pigments and metal powders as additives in addition to the above-mentioned resin components, and by blending a conductive substance as an additive, the composition may It is also possible to impart electrical conductivity and make the material formed using it a material that can be spot welded. Examples of conductive materials used for this purpose include metal materials processed into powder, flakes, or fibers such as stainless steel, zinc, tin, copper, brass, and nickel, carbon black, graphite, Examples include conductive carbon materials such as carbon fiber, powdered iron phosphide, and conductive fillers in which a thin film of metallic nickel or carbon black is applied to the surface of fine particles of resin. These fillers can be used alone or in combination with
It is also possible to use a combination of more than one type.

[0035] The composition of the present invention can be prepared by combining each of the above-mentioned components with a disper, attritor, sand mill, pebble mill,
It can be prepared by uniformly mixing using a steel mill, roll mill, etc. When mixing, as appropriate,
Water or a solvent can be added to make the viscosity suitable for mixing.

The viscoelastic composition of the present invention can form a viscoelastic layer on metal by applying it to an object to be coated, such as metal, and curing it by heating. The above heating conditions are not particularly limited, but are generally about 120°C.
The heating time can be about 40 minutes to about 40 seconds at a temperature of about 300°C.

The viscoelastic material formed by curing the composition of the present invention exhibits excellent adhesive strength over a wide temperature range, and at the same time has excellent vibration damping properties in the room temperature range. Even when subjected to a baking process after processing, the viscoelastic layer does not cause significant softening or outflow at temperatures of about 180°C, and has excellent adhesion, even when used as a composite vibration damping material. A product with excellent water resistance and moisture resistance can be obtained without causing the opening phenomenon of the parts. This property is due to the use of water-dispersible epoxy resin in the viscoelastic composition, which contributes to adhesion and vibration damping properties over a wide temperature range, and particularly improves adhesion at high temperatures. This is thought to be because it suppresses the softening and outflow of the viscoelastic layer, prevents the opening phenomenon, and contributes to water resistance and moisture resistance.

[0038] Thus, the composition of the present invention can be widely used in applications for mitigating and attenuating shocks such as vibrations, including composite vibration damping materials.

When manufacturing a composite vibration damping material using the composition of the present invention, the method includes, for example, 0.2 to 1.
The composition of the present invention is applied to a metal plate with a thickness of about 2 m/m using a roll coater or spray coating,
A metal plate with a viscoelastic layer substantially free of water or solvent is created by baking at a temperature of about 280°C for 80 to 40 seconds, and two metal plates with a viscoelastic layer created in this way are prepared. A method of stacking the viscoelastic layers so that their surfaces are in contact with each other and adhering them using a roll or press; a metal plate with a viscoelastic layer prepared as described above and a metal plate without a viscoelastic layer are bonded together. Examples include a method of overlapping and adhering the elastic layers between them.

[0040] The thickness of the viscoelastic layer of the composite damping material to be formed is usually preferably within the range of 30 to 50 μm. If it is less than 30 μm, not only will it not be possible to obtain a uniform resin layer, but also sufficient adhesive strength and vibration damping properties will not be obtained. It not only remains in the resin layer and reduces adhesive strength, but also tends to cause the metal plate to shift during molding.

[0041] Examples of the metal plates used in the composite vibration damping material include cold-rolled steel plates, galvanized steel plates, copper plates, aluminum plates, stainless steel plates, etc., and these metal plates that have been subjected to chromate treatment or It may be any surface-treated board that has been subjected to surface treatment such as phosphate treatment,
Further, the shape may be a cut plate shape, a coil shape, or the like.

The composite vibration damping material prepared using the composition of the present invention can be used not only in the field of building materials that do not require strict molding conditions, but also in home appliances such as washing machines, automobile dash panels, roof panels, It can also be used in fields of application where it has been difficult to use viscoelastic compositions, such as floor panels.

[0043]

[Example] The composition of the present invention will be explained in more detail with reference to Examples below. In the following description, [parts] and [%] mean [parts by weight] and [% by weight], respectively, unless otherwise specified.

Production Example 1 Polytetramethylene ether glycol (OHV56)
90 parts of toluene and 34.8 parts of tolylene diisocyanate were added to 200 parts, and the mixture was stirred at 80°C for 1 hour. Then, the mixture is cooled to room temperature to obtain a urethane polyprimer having isocyanate groups at the ends. When the isocyanate group of this product was measured, it was 2.5%. In another container, 120 parts of acetone, 2.52 parts of diethylenetriamine (0.
0.024 mol) was added to the prepolymer solution, and 68 parts of the prepolymer solution (0.0
20 mol) was gradually added dropwise over a period of 2 hours. Next, 2.20 parts (0.024 mol) of epichlorohydrin was added,
Stir at 50°C for 30 minutes. Then, after cooling to room temperature, 350 parts of 2% aqueous acetic acid was added with stirring to adjust the pH to 5-6. After adjusting the pH, the temperature was raised to 50 to 60°C, the solvent was removed under reduced pressure, and water was added to obtain a stable resin solution (a) with a solid content of 30%. This resin solution was coated on a tin plate so that the film thickness after drying was 40 μm, dried in a dryer at 150°C for 30 minutes, and then peeled off using the mercury amalgam method.The film properties are as follows. there were.

Modulus (kg/cm2) (100%
When extended) 35
(at 300% elongation)
60 Tensile strength (kg/cm2
)
148 Elongation rate (elongation percentage)
495
(*Refer to Special Publication No. 50-15027 Example 3)

Production Example 2 (1) Production of chain extender 1 mole of diethanolamine and 1 mole of phthalic anhydride were collected in a 4-necked flask equipped with a thermometer, a condenser, and a stirrer, and heated at 60°C for 4 hours.
The reaction was carried out for a period of time to produce a polyhydroxy compound of the following chemical formula (I). The product was found to have reacted by more than 90% as determined by acid value measurement.

[0047]

[Chemical formula 1]

(2) Preparation of Polymer The following mixture ratios were reacted under stirring at 60° C. for 3 hours to prepare an NCO group-terminated prepolymer. Tolylene diisocyanate
87g (2,
(80% for 4 bodies, 20% for 2 and 6 bodies) Polypropylene glycol
100g acetone

201g

Next, 65 g of the above chain extender
A solution prepared by dissolving 65 g of dimethylformamide was gradually added dropwise to the prepolymer, and the mixture was reacted at 60° C. for 3 hours. Thereafter, 70 g of a 40% dimethylamine aqueous solution was added, and after stirring, 200 g of water was added and stirred for 20 minutes to obtain a pale yellow resin solution (b). After drying in a dryer at 150° C. for 30 minutes, the film was peeled off using the mercury amalgam method, and the film properties were as follows.

Modulus (kg/cm2) (100%
When extended) 50
(at 300% elongation)
130 Tensile strength (kg/cm2
)
430 Elongation rate (elongation percentage)
370
(*See Example 1 of Special Publication No. 50-126795)

Production Example 3 219 g of adipic acid-hexanediol-nepentyl glycol-polyester (OHV:64) was heated at 120°C/
It is dehydrated at 12 mmHg and reacted with 30.6 g of 1,6-hexane diisocyanate. Stir for 2 hours at 120°C. The melt was dissolved in 330 ml of acetone (55°C), and 32.2 g of a previously prepared 20% taurine-sodium aqueous solution was added while stirring. Then, after adding 320 ml of water, the acetone is evaporated under vacuum. Thus the solids content is 39%
, a water-dispersed resin solution (c) having a pH of 7 was obtained.

The thickness of the film after drying the obtained resin solution is 4
After coating on a tin plate to 0 μm, dry in a dryer at 150℃.
After drying for 30 minutes, the film was peeled off using the mercury amalgam method, and the film properties were as follows.

Modulus (kg/cm2) (100%
when extended) 20
(at 300% elongation)
63 Tensile strength (kg/cm2
)
80 Elongation rate (elongation percentage)
720

0
Example 1 33.4 parts (solid content: 10 parts) of the 30% polyurethane resin solution (a) obtained in Production Example 1 and the 35% polyurethane resin solution (b) obtained in Production Example 2 were placed in a stainless steel beaker. 14
3 parts (solid content 50 parts), 103 parts (solid content 40 parts) of the 39% polyurethane resin solution (c) obtained in Production Example 3, and 18 parts (solid content) of 50% Epicron EM-75W solution dispersed in water. 9 parts) and stirred uniformly to obtain a viscoelastic composition. A composite vibration damping material was created using this composition, and various property tests were conducted. The results are shown in Table 1.

Examples 2 to 9 The same procedure as in Example 1 was carried out except that the formulations shown in Table 1 were used.
Each composition was obtained. The solid content of epoxy resin is 50%.
It was used after being dispersed in water. Further, the blending amount of each resin in Table 1 is expressed as solid content. Various characteristic tests were conducted in the same manner as in Example 1 using these compositions. The results are shown in Table 1.

Test method (1) Preparation of composite damping material: 0.8 x 150 x 300 m
A set of two chromate-treated alloyed galvanized steel sheets (trade name: Pentite PF, manufactured by Nisshin Steel) of 500 mm was used, and the viscoelastic composition shown in Table 1 was coated on one side of each of the two steel sheets using a bar coater. The coating was applied so that the dry film thickness was 23 μm, and the two metal plates were simultaneously placed in a dryer at an ambient temperature of 270° C. and baked for 70 seconds. (However, the ventilation was stopped for the first 30 seconds and continued for the next 40 seconds.) At this time, P
MT (maximum temperature reached by the metal plate) was 240°C. Immediately after the baking process was completed, the surfaces coated with the viscoelastic composition were overlapped and pressed together using a rubber roll to create a composite damping material having a viscoelastic layer between two parallel metal plates.

(2) Vibration damping rate: The prepared composite vibration damping material was measured by electromagnetic vibration method. The measured temperature is 20
The temperature measurement frequencies were 200Hz and 500Hz. Also,
Similar measurements were made on a composite damping material that had been reheated at 180° C. for 20 minutes.

(3) Adhesive strength: The prepared composite damping material was cut into a width of 25 mm, and the T-peel strength and tensile shear strength of this sample were measured. The T-peel strength was measured by T-peeling the sample at a tensile speed of 200 mm/min. The tensile shear strength was measured at a tensile rate of 5 mm/min based on the test method of JIS K-6850. The measurement temperature was 20° C. in both methods. Furthermore, the adhesive strength of the composite vibration damping material reheated at 180° C. for 20 minutes was also measured in the same manner.

(4) T-type peel strength at high temperature: width 25 mm
The composite vibration damping material cut into pieces was heated in a dryer at an ambient temperature of 180° C. for 5 minutes, then taken out and immediately examined for T-peel strength using a spring balance. In order to prevent the end face from opening during the heating process, a strength of approximately 1 kg/25 mm or more is generally required.

(5) T-peel strength after boiling water immersion test:
A composite vibration damping material cut to a width of 25 mm was immersed in boiling water for 24 hours, then taken out and left at room temperature for 24 hours.
The mold peel strength was measured.

(6) T-type peel strength after moisture resistance test: Width 2
Composite vibration damping material cut into 5mm pieces at a temperature of 50℃ and a humidity of 98℃.
After wetting for 480 hours in a humidity tester above %RH,
The sample was taken out and left at room temperature for 24 hours, and the T-peel strength was measured.

As shown in Table 1, when a viscoelastic composition consisting of a water-dispersed urethane resin and a water-dispersed epoxy resin is used in a composite vibration damping material, the adhesive strength is high both initially and after reheating. It exhibited high adhesive strength even at high temperatures, as well as a large vibration damping rate and good vibration damping properties. In addition, no decrease in adhesive strength was observed or the rate of decrease was low in both the boiling water immersion test and the moisture resistance test, which are practical durability tests.

Comparative Examples 1 to 6 Example 1 except that the viscoelastic composition was prepared according to the formulation shown in Table 2.
A composite vibration damping material was created in exactly the same manner as in ~9, and Example 1
Characteristic tests similar to those in 9 to 9 were conducted. The results are shown in Table 2.

As shown in Table 2, when the water-dispersible epoxy resin was not blended with the water-dispersible urethane resin, the heat resistance, water resistance, and moisture resistance of the damping material adhesive strength were significantly reduced. In addition, if 10% or more of water-dispersed epoxy resin is added,
Initial adhesive strength also decreased.

[0065]

[Table 1]

[Table 2]

[Table 3]

[0066]

[Table 4]

[Table 5]

Claims (2)

[Claims] Claim 1: (A) A water-dispersible polyurethane resin obtained by chain-extending a polyurethane prepolymer consisting of a diisocyanate and a polyol with a compound having at least two active hydrogens, and (B) a bisphenol having an epoxy equivalent of 180 to 1000. A viscoelastic composition mainly composed of an A-type water-dispersible epoxy resin and/or a sorbitol polyglycidyl ether-type water-dispersible epoxy resin, the composition comprising a water-dispersible polyurethane resin (A) and a water-dispersible epoxy resin (B). ) weight ratio (A
)/(B) is 99/1 to 90/10, a viscoelastic composition for damping steel plate. 2. A damping steel plate obtained by coating the viscoelastic composition according to claim 1.