Resin composition for vibration-damping coating material, and production method therefor

Abstract

The invention provides a method for providing a coat having excellent appearance and an excellent vibration damping property in a temperature range of a use environment of vibration damping materials. The invention relates to a vibration damping coating resin composition including an emulsion particle having a multilayer structure, the emulsion particle including an outermost layer and an inner layer located inside the outermost layer, the outermost layer being formed from a resin having a glass transition temperature of 60 C. or higher, the outermost layer being present in a proportion of 1% to 30% by mass in 100% by mass of the emulsion particle.

Claims

1. A vibration damping coating comprising: a vibration damping coating resin composition that contains an emulsion particle having a multilayer structure; and a pigment, the emulsion particle including an outermost layer and an inner layer located inside the outermost layer, the inner layer being formed from a resin, the outermost layer being formed from a resin having a glass transition temperature of 75 C. or higher, the outermost layer being present in a proportion of 1% to 17% by mass in 100% by mass of the emulsion particle, and wherein at least one of the resin forming the outer layer and the resin forming the inner layer comprises a (meth)acrylic polymer.

2. The vibration damping coating according to claim 1, wherein the glass transition temperature of the resin forming the outermost layer is higher than a glass transition temperature of the resin forming the inner layer by 30 C. or more.

3. The vibration damping coating according to claim 1, wherein the glass transition temperature of the resin forming the outermost layer is higher than a glass transition temperature of the resin forming the inner layer by 80 C. or more.

4. The vibration damping coating according to claim 1, wherein a glass transition temperature of the resin forming the inner layer is 30 C. to 40 C.

5. The vibration damping coating according to claim 1, wherein a glass transition temperature of the resin forming the inner layer is 15 C. or higher.

6. The vibration damping coating according to claim 1, wherein a glass transition temperature of the resin forming the inner layer is 10 C. or higher.

7. The vibration damping coating according to claim 1, wherein a glass transition temperature of the resin forming the inner layer is 35 C. or lower.

8. The vibration damping coating according to claim 1, wherein the composition further comprises a component having a sulfosuccinic acid structure or salt thereof and/or a component having a fatty acid structure or salt thereof.

9. The vibration damping coating according to claim 8, wherein the composition comprises a component having a sulfosuccinic acid structure or salt thereof.

10. The vibration damping coating according to claim 8, wherein a total amount of the component having a sulfosuccinic acid structure or salt thereof and the component having a fatty acid structure or salt thereof is 25% by mass or more in 100% by mass of an anionic surfactant in the composition.

11. The vibration damping coating according to claim 8, wherein the total amount of the component having a sulfosuccinic acid structure or salt thereof and the component having a fatty acid structure or salt thereof is 50% by mass or more in 100% by mass of the anionic surfactant in the composition.

12. The vibration damping coating according to claim 8, wherein the total amount of the component having a sulfosuccinic acid structure or salt thereof and the component having a fatty acid structure or salt thereof in the composition is 0.1% to 20% by mass relative to 100% by mass of the entire monomer component used to produce an emulsion.

13. The vibration damping coating according to claim 1, wherein the glass transition temperature of the resin forming the outermost layer is 80 C. or higher.

14. The vibration damping coating according to claim 8, wherein the glass transition temperature of the resin forming the outermost layer is 80 C. or higher.

15. The vibration damping coating according to claim 1, wherein at least one of the resin forming the outer layer and the resin forming the inner layer has a weight average molecular weight of 30000 to 400000.

16. The vibration damping coating according to claim 8, wherein at least one of the resin forming the outer layer and the resin forming the inner layer has a weight average molecular weight of 30000 to 400000.

17. A vibration damping coat obtained from the vibration damping coating according to claim 1.

18. A method for producing a vibration damping coating resin composition containing an emulsion particle having a multilayer structure, the method comprising: polymerizing a monomer component to form a resin-containing inner layer; and polymerizing a monomer component to produce the emulsion particle with an outermost layer formed from a resin having a glass transition temperature of 75 C. or higher and the outermost layer is present at a proportion of 1-17% by mass relative to 100% in the mass of the emulsion particle, wherein at least one of the resin forming the outer layer and the resin forming the inner layer comprises a (meth)acrylic polymer.

19. A vibration damping coating comprising: a vibration damping coating resin composition that contains an emulsion particle having a multilayer structure; and a pigment, the emulsion particle including an outermost layer and an inner layer located inside the outermost layer, the inner layer being formed from a resin, the outermost layer being formed from a resin having a glass transition temperature of 60 C. or higher, the outermost layer being present in a proportion of 1% to 17% by mass in 100% by mass of the emulsion particle, wherein a glass transition temperature of the resin forming the outermost layer is higher than a glass transition temperature of the resin forming the inner layer by 10 C. or more, and wherein at least one of the resin forming the outer layer and the resin forming the inner layer comprises a (meth)acrylic polymer.

20. A method for producing a vibration damping coating resin composition containing an emulsion particle having a multilayer structure, the method comprising: polymerizing a monomer component to form a resin containing-inner layer; and polymerizing a monomer component to produce the emulsion particle with an outermost layer formed from a resin having a glass transition temperature of 60 C. or higher, and the outermost layer is present at a proportion of 1% to 17% by mass relative to 100% in the mass of the emulsion particle, wherein a glass transition temperature of a resin forming the outermost layer is higher than a glass transition temperature of the resin forming the inner layer by 10 C. or more, and wherein at least one of the resin forming the outer layer and the resin forming the inner layer comprises a (meth)acrylic polymer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic side view of a test plate used in the evaluation test of the thermal softening property of a coat on a vertical surface.

EXAMPLES

(2) The following description is offered to demonstrate the invention based on embodiments of the invention. The embodiments should not be construed as limiting the invention. Unless otherwise mentioned, the term part(s) means part(s) by weight and % means % by mass. The inner layer(s) and the outermost layer of an emulsion particle are also referred to as a core(s) and a shell, respectively.

(3) The properties were evaluated as follows in the production examples.

(4) <Average Particle Size>

(5) The average particle size of emulsion particles was measured by dynamic light scattering using a particle size distribution analyzer (FPAR-1000, Otsuka Electronics Co., Ltd.).

(6) <Nonvolatile Content (N.V.)>

(7) About 1 g of the resulting emulsion was weighed and dried in a hot air dryer at 150 C. for one hour. The amount of the residue after drying was measured as the nonvolatile content and expressed as a ratio (% by mass) to the mass of the emulsion before drying.

(8) <pH>

(9) The pH at 25 C. was measured using a pH meter (F-23, Horiba, Ltd.).

(10) <Viscosity>

(11) The viscosity was measured at 25 C. and 20 rpm using a B-type rotary viscometer (VISCOMETER TUB-10, Toki Sangyo Co., Ltd.).

(12) <Weight Average Molecular Weight>

(13) The weight average molecular weight was measured by gel permeation chromatography (GPC) under the following conditions.

(14) Measuring equipment: HLC-8120GPC (trade name, Tosoh Corporation)

(15) Molecular-weight column: TSK-GEL GMHXL-L and TSK-GEL G5000HXL (both produced by Tosoh Corporation) connected in series

(16) Eluent: Tetrahydrofuran (THF)

(17) Calibration curve reference material: Polystyrene (Tosoh Corporation)

(18) Measuring method: A measurement object was dissolved in THF to about 0.2% by mass in terms of solid content, and passed through a filter to obtain a filtrate as a sample to be measured. The molecular weight of the filtrate was measured.

(19) <Glass Transition Temperature (Tg) of Polymer>

(20) The Tg of the polymer was determined from the following equation (1) based on the compositions of the monomers used in the respective stages.

(21) $\begin{array}{cc}\frac{1}{{\mathrm{Tg}}^{}}=\left[\frac{W_1^{}}{T_1}+\frac{W_2^{}}{T_2}+\mathrm{.Math.}+\frac{W_n^{}}{T_n}\right]& \left(1\right)\end{array}$

(22) In the equation, Tg represents Tg (absolute temperature) of the polymer; W.sub.1, W.sub.2, . . . , and W.sub.n each represent the mass fraction of each monomer relative to the entire monomer component; and T.sub.1, T.sub.2, . . . , and T.sub.n, each represent the glass transition temperature (absolute temperature) of the homopolymer of each monomer.

(23) The Tg determined from the compositions of the monomers in all the stages was expressed as total Tg.

(24) The following shows the glass transition temperatures (Tgs) of the homopolymers of the respective polymerizable monomers which were used to calculate the Tg based on the equation (1).

(25) Methyl methacrylate (MMA): 105 C.

(26) Styrene (St): 100 C.

(27) 2-Ethylhexyl acrylate (2EHA): 70 C.

(28) Butyl acrylate (BA): 56 C.

(29) Acrylic acid (AA): 95 C.

(30) Isobornyl methacrylate (IBMA): 180 C.

(31) Acrylamide (AAM): 165 C.

(32) Butyl methacrylate (BMA): 20 C.

1. Examples of the First Aspect of the Invention

(33) The following describes the surfactants used in the below-described examples of the first aspect of the invention.

(34) A polyoxyethylene alkyl ether-sulfosuccinic acid half ester salt is a compound represented by the following formula (i):

(35) ##STR00003##
wherein R represents a C12-C14 secondary alkyl group and n represents the average number of moles added.

(36) Herein, the compound in which n=9 is referred to as a compound (i)-<1a>.

(37) The following describes commercially available surfactants used in the examples and comparative examples.

(38) HITENOL NF-08 (trade name, ammonium polyoxyethylene styrenated phenyl ether sulfate, Dai-Ichi Kogyo Seiyaku Co., Ltd.)

(39) NEOPELEX G-65 (trade name, sodium dodecyl benzene sulfonate, Kao Corporation)

Example 1-1

(40) A polymerization vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen inlet tube, and a dropping funnel was charged with 289.8 parts of deionized water. Then, the internal temperature was increased to 75 C. under stirring and nitrogen flow. Separately, the dropping funnel was charged with a monomer emulsion including 450.0 parts of styrene, 316.0 parts of 2-ethylhexyl acrylate, 125.0 parts of butyl acrylate, 9.0 parts of acrylic acid, 3.0 parts of t-dodecyl mercaptan (also referred to as t-DM) serving as a polymerization chain transfer agent, 135.0 parts of a 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance, and 189.0 parts of deionized water. Then, a 24.0-part portion of the monomer emulsion, 5 parts of a 5% aqueous solution of potassium persulfate serving as a polymerization initiator (oxidant), and 10 parts of a 2% aqueous solution of sodium bisulfite were added to the polymerization vessel with the internal temperature thereof being maintained at 75 C. to start initial polymerization. After 40 minutes, the rest of the monomer emulsion was uniformly added dropwise over 180 minutes with the reaction system being maintained at 80 C. Simultaneously therewith, 70 parts of a 5% aqueous solution of potassium persulfate and 70 parts of a 2% aqueous solution of sodium bisulfite were uniformly added dropwise over 180 minutes. After completion of the dropwise addition, the temperature was maintained for 60 minutes. This gave an aqueous dispersion of an acrylic copolymer having a glass transition temperature of 5 C. forming the core of an emulsion particle having a multilayer structure.

(41) Then, the dropping funnel was charged with a monomer emulsion including 70.0 parts of styrene and 30.0 parts of isobornyl methacrylate as monomers for forming the shell, 0.3 parts of t-DM, 15.0 parts of a 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance, and 21.0 parts of deionized water. The monomer emulsion was uniformly added dropwise over 40 minutes to the aqueous acrylic copolymer dispersion prepared as described above. Simultaneously therewith, 25 parts of a 5% aqueous solution of potassium persulfate and 20 parts of a 2% aqueous solution of sodium bisulfite were uniformly added dropwise over 40 minutes. After completion of the dropwise addition, the temperature was maintained for 120 minutes to form the shell having a glass transition temperature of 120 C. The resulting reaction solution was cooled to room temperature, and 16.7 parts of 2-dimethyl ethanolamine was added thereto. This gave an acrylic emulsion (resin composition 1-1) having a nonvolatile content of 55.0%, a pH of 8.6, a viscosity of 250 mPa.Math.s, an average particle size of 180 nm, and a weight average molecular weight of 70000.

Examples 1-2 to 1-4

(42) Acrylic emulsions (resin compositions 1-2 to 1-4) were obtained as in Example 1-1, except that the ingredients added were changed as shown in Table 1 below.

Example 1-5

(43) The core of an emulsion particle was produced as in

(44) Example 1-1, except that the ingredients of the monomer emulsion for forming the core of an emulsion particle in Example 1-1 were changed as follows: the amount of styrene was changed from 450.0 parts to 460.0 parts, the amount of 2-ethylhexyl acrylate was changed from 316.0 parts to 326.0 parts, the amount of butyl acrylate was changed from 125.0 parts to 155.0 parts, the amount of the 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance was changed from 135.0 parts to 144.0 parts, and the amount of deionized water was changed from 189.0 parts to 198.3 parts; and the amount of the 5% aqueous solution of potassium persulfate and the amount of the 2% aqueous solution of sodium bisulfite which began to be added dropwise simultaneously with the rest of the monomer emulsion were changed from 70 parts to 85 parts and from 70 parts to 80 parts, respectively. This gave an aqueous dispersion of an acrylic copolymer having a glass transition temperature of 8 C.

(45) Then, the shell of an emulsion particle was produced as in Example 1-1, except that the ingredients of the monomer emulsion for forming the shell of an emulsion particle in Example 1-1 were changed as follows: 38.0 parts of methyl methacrylate was used instead of 70.0 parts of styrene, the amount of isobornyl methacrylate was changed from 30.0 parts to 12.0 parts, the amount of the 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance was changed from 15.0 parts to 6.0 parts, and the amount of deionized water was changed from 21.0 parts to 11.7 parts; and the amount of the 5% aqueous solution of potassium persulfate and the amount of the 2% aqueous solution of sodium bisulfite which began to be added dropwise simultaneously with the monomer emulsion were changed from 25 parts to 10 parts and from 20 parts to 10 parts, respectively. Thus, the shell having a glass transition temperature of 120 C. was obtained. Thereafter, the subsequent procedures were performed as in Example 1-1 to obtain an acrylic emulsion (resin composition 1-5) having a nonvolatile content of 55.0%, a pH of 8.5, a viscosity of 290 mPa.Math.s, an average particle size of 170 nm, and a weight average molecular weight of 72000.

Example 1-6

(46) The core of an emulsion particle was produced as in Example 1-1, except that the ingredients of the monomer emulsion for forming the core of an emulsion particle in Example 1-1 were changed as follows: the amount of styrene was changed from 450.0 parts to 350.0 parts, the amount of 2-ethylhexyl acrylate was changed from 316.0 parts to 256.0 parts, the amount of butyl acrylate was changed from 125.0 parts to 85.0 parts, 105.0 parts of a 20% aqueous solution of the compound (i)-<1a>prepared in advance was used instead of 135.0 parts of the 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance, and the amount of deionized water was changed from 189.0 parts to 147.0 parts; and the amount of the 5% aqueous solution of potassium persulfate and the amount of the 2% aqueous solution of sodium bisulfite which began to be added dropwise simultaneously with the rest of the monomer emulsion were changed from 70 parts to 60 parts and from 70 parts to 60 parts, respectively. This gave an aqueous dispersion of an acrylic copolymer having a glass transition temperature of 5 C.

(47) Then, the shell of an emulsion particle was produced as in Example 1-1, except that the ingredients of the monomer emulsion for forming the shell of an emulsion particle in Example 1-1 were changed as follows: 295.0 parts of methyl methacrylate and 5.0 parts of acrylic acid were used instead of 70.0 parts of styrene and 30.0 parts of isobornyl methacrylate, 45.0 parts of a 20% aqueous solution of the compound (i)-<1a>prepared in advance was used instead of 15.0 parts of the 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance, and the amount of deionized water was changed from 21.0 parts to 63.0 parts; the amount of the 5% aqueous solution of potassium persulfate and the amount of the 2% aqueous solution of sodium bisulfite which began to be added dropwise simultaneously with the monomer emulsion were changed from 25 parts to 35 parts and from 20 parts to 30 parts, respectively; and the dropwise addition time of these aqueous solutions were changed from 40 minutes to 60 minutes. Thus, the shell having a glass transition temperature of 105 C. was obtained. Thereafter, the subsequent procedures were performed as in Example 1-1 to obtain an acrylic emulsion (resin composition 1-6) having a nonvolatile content of 54.8%, a pH of 8.6, a viscosity of 320 mPa.Math.s, an average particle size of 160 nm, and a weight average molecular weight of 74000.

Examples 1-7 and 1-8

(48) Acrylic emulsions (resin compositions 1-7 and 1-8) were obtained as in Example 1-1, except that the ingredients added were changed as shown in Table 1 below, and in Example 1-7, 25% ammonia water was added in an amount that gave the acrylic emulsion with a pH of 8.5 instead of 2-dimethyl ethanolamine, and in Example 1-8, no 2-dimethyl ethanolamine was added (no neutralizer was added).

Comparative Example 1-1

(49) An acrylic emulsion (resin composition 1-9) was obtained as in Example 1-1, except that the ingredients added were changed as shown in Table 1 below.

Comparative Example 1-2

(50) The core of an emulsion particle was produced as in Example 1-1, except that the ingredients of the monomer emulsion for forming the core of an emulsion particle in Example 1-1 were changed as follows: the amount of styrene was changed from 450.0 parts to 136.0 parts, the amount of 2-ethylhexyl acrylate was changed from 316.0 parts to 55.0 parts, the amount of butyl acrylate was changed from 125.0 parts to 100.0 parts, the amount of t-DM was changed from 3.0 parts to 1.0 part, 45.0 parts of a 20% aqueous solution of NEOPELEX G-65 (Kao Corporation) prepared in advance was used instead of 135.0 parts of the 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance, and the amount of deionized water was changed from 189.0 parts to 63.0 parts; the dropwise addition time of the rest of the monomer emulsion was changed from 180 minutes to 120 minutes; and the amount of the 5% aqueous solution of potassium persulfate and the amount of the 2% aqueous solution of sodium bisulfite which began to be added dropwise simultaneously with the rest of the monomer emulsion were changed from 70 parts to 35 parts and from 70 parts to 30 parts, respectively. This gave an aqueous dispersion of an acrylic copolymer having a glass transition temperature of 5 C.

(51) Then, the shell of an emulsion particle was produced as in Example 1-1, except that the ingredients of the monomer emulsion for forming the shell of an emulsion particle in Example 1-1 were changed as follows: 650.0 parts of methyl methacrylate was used instead of 70.0 parts of styrene, the amount of isobornyl methacrylate was changed from 30.0 parts to 50.0 parts, the amount of t-DM was changed from 0.3 parts to 2.0 parts, 105.0 parts of a 20% aqueous solution of NEOPELEX G-65 (Kao Corporation) prepared in advance was used instead of 15.0 parts of the 20% aqueous solution of HITENOL NF-08 (Dai-Ichi Kogyo Seiyaku Co., Ltd.) prepared in advance, and the amount of deionized water was changed from 189.0 parts to 147.0 parts; the amount of the 5% aqueous solution of potassium persulfate and the amount of the 2% aqueous solution of sodium bisulfite which began to be added dropwise simultaneously with the monomer emulsion were changed from 25 parts to 60 parts and from 20 parts to 60 parts, respectively; and the dropwise addition time of these aqueous solutions was changed from 40 minutes to 180 minutes. Thus, the shell having a glass transition temperature of 110 C. was obtained. Thereafter, the subsequent procedures were performed as in Example 1-1 to obtain an acrylic emulsion (resin composition 1-10) having a nonvolatile content of 55.1%, a pH of 8.6, a viscosity of 170 mPa.Math.s, an average particle size of 250 nm, and a weight average molecular weight of 65000.

Comparative Example 1-3

(52) A polymerization vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen inlet tube, and a dropping funnel was charged with 310.4 parts of deionized water. Then, the internal temperature was increased to 75 C. under stirring and nitrogen flow. Separately, the dropping funnel was charged with a monomer emulsion including 560 parts of styrene, 270 parts of 2-ethylhexyl acrylate, 150 parts of butyl acrylate, 20.0 parts of acrylic acid, 3.0 parts of t-DM, 150.0 parts of a 20% aqueous solution of NEOPELEX G-65 (Kao Corporation) prepared in advance, and 210.0 parts of deionized water. Then, a 27.0-part portion of the monomer emulsion, 5 parts of a 5% aqueous solution of potassium persulfate serving as a polymerization initiator (oxidant), and 10 parts of a 2% aqueous solution of sodium bisulfite were added to the polymerization vessel with the internal temperature thereof being maintained at 75 C. to start initial polymerization. After 40 minutes, the rest of the monomer emulsion was uniformly added dropwise over 210 minutes with the reaction system being maintained at 80 C. Simultaneously therewith, 95 parts of a 5% aqueous solution of potassium persulfate and 90 parts of a 2% aqueous solution of sodium bisulfite were uniformly added dropwise over 210 minutes. After completion of the dropwise addition, the temperature was maintained for 60 minutes to complete the polymerization.

(53) The resulting reaction solution was cooled to room temperature, and 16.7 parts of 2-dimethyl ethanolamine was added thereto. This gave an acrylic emulsion (resin composition 1-11) having a nonvolatile content of 55.1%, a pH of 8.5, a viscosity of 200 mPa.Math.s, an average particle size of 190 nm, and a weight average molecular weight of 80000.

(54) <Preparation of Coating>

(55) Coatings were prepared according to the following formulation using each of the resin compositions 1-1 to 1-8 in Examples 1-1 to 1-8 and the resin compositions 1-9 to 1-11 in Comparative Examples 1-1 to 1-3. The properties were evaluated (the coat was subjected to evaluation of appearance and vibration damping test) as described below. Table 1 shows the results. Each of resin compositions 1-1 to 1-11: 350 parts Calcium carbonate NN#200.sup.*1: 700 parts Dispersant AQUALIC DL-40S.sup.*2: 6 parts Thickener ACRYSET WR-650.sup.*3: 4 parts *1: Filler produced by Nitto Funka Kogyo K.K. *2: Polycarboxylic acid-based dispersant (active component: 44%) produced by Nippon Shokubai Co., Ltd. *3: Alkali-soluble acrylic thickener (active component: 30%) produced by Nippon Shokubai Co., Ltd.
<Evaluation of Appearance of Coat> (Evaluation of Degree of Preventing Blistering, Cracking, and/or Peeling of Coat)

(56) Each coating was applied to a steel plate (trade name: SPCC-SD, 75 mm in width150 mm in length0.8 mm in thickness, Nippon Testpanel Co., Ltd.) so as to have a thickness of 4 mm. The applied coating was dried using a hot air dryer at 150 C. for 50 minutes. The surface condition of the resulting dry coat was evaluated based on the following criteria. The coating was foamed by heating using a hot air dryer.

(57) (Evaluation Criteria)

(58) Good: No defects were observed in the coat.

(59) Average: Slight blisters and/or cracks were partially observed in the coat.

(60) Fair: Blisters and/or cracks were partially observed in the coat.

(61) Poor: Blisters, peeling, and/or cracks were observed throughout the coat.

(62) (Evaluation of Thermal Softening Property of Coat on Vertical Surface)

(63) The resulting coating was applied to a steel plate (ED steel plate) with dimensions of 0.8 mm70 mm150 mm electrodeposited using a cationic electrodeposition coating ELECRON KG-400 (Kansai Paint Co., Ltd.) so as to have a wet film thickness of 4 mm. Immediately thereafter, the coated surface was made vertical and baked at 110 C. for 30 minutes. After completion of the baking, the test plate was taken out and the thicknesses of the upper end and lower end of the coated area were measured, and the thermal softening index was determined using the following equation. The thermal softening property was evaluated based on the following criteria.

(64) (Calculation Equation of Thermal Softening Index)
Thermal softening index=(Thickness of lower end (mm))/(Thickness of upper end (mm))
(Evaluation Criteria)

(65) Good: 2.5 or smaller

(66) Fair: Greater than 2.5

(67) Poor: The coat partially or entirely peeled away from the steel plate.

(68) <Vibration Damping Test>

(69) Each coating was applied to a cold rolled steel plate (trade name: SPCC, 15 mm in width250 mm in length1.5 mm in thickness, Nippon Testpanel Co., Ltd.) so as to have a thickness of 3 mm, and pre-dried at 80 C. for 30 minutes, followed by drying at 150 C. for 30 minutes. Thus, a vibration damping coat with a surface density of 4.0 kg/m.sup.2 was formed on the cold rolled steel plate. The coating was foamed by heating in pre-drying and in drying after the pre-drying.

(70) The vibration damping property was determined by evaluating the loss coefficients at particular temperatures (10 C., 20 C., 30 C., 40 C., 50 C., and 60 C.) by a cantilever method (loss coefficient measurement system, Ono Sokki Co., Ltd.). The vibration damping property was evaluated based on the total loss coefficient (the sum of loss coefficients at 10 C., 20 C., 30 C., 40 C., 50 C., and 60 C.). A larger total loss coefficient indicates a better vibration damping property.

(71) TABLE-US-00001 TABLE 1 Example Example Example Example Example Example 1-1 1-2 1-3 1-4 1-5 1-6 Core Ingredients (20% aqueous HITENOL NF-08 135 144 solution of emulsifier NEOPELEX G-65 135 prepared in advance) (i)-<1a> 135 135 105 Ingredients MMA 125 (Monomers) St 450 450 450 380 460 350 2EHA 316 316 316 286 326 256 BA 125 125 125 100 155 85 AA 9 9 9 9 9 9 t-DM 3 3 3 3 3 3 Tg ( C.) 5 5 5 5 8 5 Shell Ingredients (20% aqueous HITENOL NF-08 15 6 solution of emulsifier NEOPELEX G-65 15 prepared in advance) (i)-<1a> 15 15 45 Ingredients MMA 38 295 (Monomers) St 70 70 65 88 2EHA 12 AA 5 IBMA 30 30 12 AAM 35 t-DM 0.3 0.3 0.3 0.3 0.3 0.3 Tg ( C.) 120 120 120 66 120 105 Whole Proportion by mass of shell 10% 10% 10% 10% 5% 30% Tg (Tg of shell Tg of core) ( C.) 125.0 125.0 125.0 61.0 128.0 110.0 Nonvolatile content (%) 55.0 55.0 55.1 55.0 55.0 54.8 pH 8.6 8.7 8.5 8.4 8.5 8.6 Viscosity (mPa .Math. s) 250 280 200 230 290 320 Average particle size (nm) 180 150 200 190 170 160 Weight average molecular weight 70000 69000 75000 75000 72000 74000 Results Appearance Thermal softening on Good Good Good Good Good Good vertical surface Prevention degree of Good Fair Good Good Good Good blistering, cracking, and/or peeling Vibration damping 10 C. 0.078 0.07 0.075 0.04 0.077 0.031 property 20 C. 0.096 0.089 0.096 0.07 0.094 0.054 30 C. 0.101 0.097 0.1 0.087 0.097 0.073 40 C. 0.081 0.084 0.091 0.097 0.079 0.088 50 C. 0.06 0.056 0.061 0.086 0.055 0.093 60 C. 0.025 0.027 0.031 0.064 0.02 0.075 Vibration damping property (total) 0.441 0.423 0.454 0.444 0.422 0.414 Comparative Comparative Comparative Example Example Example Example Example 1-7 1-8 1-1 1-2 1-3 Core Ingredients (20% aqueous HITENOL NF-08 144 135 solution of emulsifier NEOPELEX G-65 45 150 prepared in advance) (i)-<1a> 135 Ingredients MMA 125 (Monomers) St 460 450 380 136 560 2EHA 326 316 286 55 270 BA 155 125 100 100 150 AA 9 9 9 9 20 t-DM 3 3 3 1 3 Tg ( C.) 8 5 5 5 7 Shell Ingredients (20% aqueous HITENOL NF-08 6 15 solution of emulsifier NEOPELEX G-65 105 prepared in advance) (i)-<1a> 15 Ingredients MMA 47 650 (Monomers) St 92 84 2EHA 8 16 AA IBMA 3 50 AAM t-DM 0.3 0.3 0.3 2 Tg ( C.) 86 77 56 110 Whole Proportion by mass of shell 5% 10% 10% 70% 0% Tg (Tg of shell Tg of core) ( C.) 94.0 82.0 51.0 115.0 Nonvolatile content (%) 55.0 55.0 55.0 55.1 55.1 pH 8.5 4.2 8.7 8.6 8.5 Viscosity (mPa .Math. s) 290 220 190 170 200 Average particle size (nm) 170 230 200 250 190 Weight average molecular weight 72000 77000 71000 65000 80000 Results Appearance Thermal softening on Good Good Poor Good Poor vertical surface Prevention degree of Good Good Fair Fair Poor blistering, cracking, and/or peeling Vibration damping 10 C. 0.059 0.075 0.039 0.016 0.055 property 20 C. 0.088 0.096 0.063 0.024 0.082 30 C. 0.095 0.099 0.085 0.042 0.097 40 C. 0.078 0.081 0.093 0.063 0.081 50 C. 0.061 0.053 0.074 0.077 0.052 60 C. 0.036 0.027 0.045 0.089 0.03 Vibration damping property (total) 0.417 0.431 0.399 0.311 0.397 2. Examples of the Second Aspect of the Invention

(72) The following describes the surfactants used in the below-described examples of the second aspect of the invention.

(73) A polyoxyethylene alkyl ether-sulfosuccinate-disodium salt is a compound represented by the following formula (i):

(74) ##STR00004##
wherein n represents the average number of moles added. Herein, the compound in which n=8 is referred to as a compound (i)-<1>.

(75) An N-alkyl monoamide disodium sulfosuccinate is a compound represented by the following formula (ii):

(76) ##STR00005##
wherein R represents a C14-C20 alkyl group. Herein, the compound is also referred to as a compound (ii).

(77) A polyoxyethylene alkyl ether-sulfosuccinic acid half ester salt is a compound represented by the following formula (iii):

(78) ##STR00006##
wherein R represents a C12-C14 secondary alkyl group.

(79) In the formula, n represents the average number of moles added. Herein, the compound in which n=9 is referred to as a compound (iii)-<1>.

(80) The following describes commercially available surfactants used in the examples and comparative examples.

(81) NS soap (trade name, sodium soap of partially hydrogenated tallow fatty acid: Kao Corporation)

(82) NEOPELEX G-65 (trade name, sodium dodecyl benzene sulfonate: Kao Corporation)

Example 2-1

(83) A polymerization vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen inlet tube, and a dropping funnel was charged with 286.8 parts of deionized water. Then, the internal temperature was increased to 75 C. under stirring and nitrogen flow. Separately, the dropping funnel was charged with a monomer emulsion including 447 parts of methyl methacrylate, 135 parts of 2-ethylhexyl acrylate, 260 parts of butyl acrylate, 8.0 parts of acrylic acid, 2.0 parts of t-dodecyl mercaptan (also referred to as t-DM) serving as a polymerization chain transfer agent, 105.0 parts of a 20% aqueous solution of the compound (i)-<1>prepared in advance, and 213.0 parts of deionized water. Then, a 24.0-part portion of the monomer emulsion, 5 parts of a 5% aqueous solution of potassium persulfate serving as a polymerization initiator (oxidant), and 10 parts of a 2% aqueous solution of sodium bisulfite were added to the polymerization vessel with the internal temperature thereof being maintained at 75 C. to start initial polymerization. After 40 minutes, the rest of the monomer emulsion was uniformly added dropwise over 180 minutes with the reaction system being maintained at 80 C. Simultaneously therewith, 70 parts of a 5% aqueous solution of potassium persulfate and 70 parts of a 2% aqueous solution of sodium bisulfite were uniformly added dropwise over 180 minutes. After completion of the dropwise addition, the temperature was maintained for 60 minutes. This gave an aqueous dispersion of an acrylic copolymer having a glass transition temperature of 4 C. forming the core of an emulsion particle having a multilayer structure.

(84) Then, the dropping funnel was charged with a monomer emulsion including 148 parts of methyl methacrylate and 2.0 parts of acrylic acid as monomers for forming the shell, 0.3 parts of t-DM, 20.0 parts of a 20% aqueous solution of the compound (i)-<1>prepared in advance, and 17.0 parts of deionized water. The monomer emulsion was uniformly added dropwise over 40 minutes to the aqueous acrylic copolymer dispersion prepared as described above. Simultaneously therewith, 25 parts of a 5% aqueous solution of potassium persulfate and 20 parts of a 2% aqueous solution of sodium bisulfite were uniformly added dropwise over 40 minutes. After completion of the dropwise addition, the temperature was maintained for 120 minutes to form the shell having a glass transition temperature of 105 C. The resulting reaction solution was cooled to room temperature, and 16.7 parts of 2-dimethyl ethanolamine was added thereto. This gave an acrylic emulsion (resin composition 2-1) having a nonvolatile content of 55.1%, a pH of 8.6, a viscosity of 200 mPa.Math.s, an average particle size of 210 nm, and a weight average molecular weight of 125000.

Examples 2-2 to 2-6

(85) Acrylic emulsions (resin compositions 2-2 to 2-6) were obtained as in Example 2-1, except that the ingredients added were changed as shown in Table 2 below.

Example 2-7

(86) The core of an emulsion particle was produced as in Example 2-1, except that the ingredients of the monomer emulsion for forming the core of an emulsion particle in Example 2-1 were changed as follows: the amount of deionized water initially added to a polymerization vessel was changed from 286.8 parts to 290.9 parts, 447 parts of styrene was used instead of 447 parts of methyl methacrylate, and 30.0 parts of a 20% aqueous solution of the compound (iii)-<1>prepared in advance and 100.0 parts of NEOPELEX G-65 (Kao Corporation) were used instead of 105.0 parts of a 20% aqueous solution of the compound (i)-<1>prepared in advance. This gave an aqueous dispersion of an acrylic copolymer having a glass transition temperature of 3 C.

(87) Then, the shell of an emulsion particle was produced as in Example 2-1, except that the ingredients of the monomer emulsion for forming the shell of an emulsion particle in Example 2-1 were changed as follows: 148 parts of styrene was used instead of 148 parts of methyl methacrylate, and 20.0 parts of a 20% aqueous solution of the compound (iii)-<1>prepared in advance was used instead of 20.0 parts of a 20% aqueous solution of the compound (i)-<1>prepared in advance. Thus, the shell having a glass transition temperature of 100 C. was obtained. Thereafter, the subsequent procedures were performed as in Example 2-1 to obtain an acrylic emulsion (resin composition 2-7) having a nonvolatile content of 55.0%, a pH of 8.6, a viscosity of 250 mPa.Math.s, an average particle size of 170 nm, and a weight average molecular weight of 120000.

Reference Examples 2-1 and 2-2

(88) Acrylic emulsions (resin compositions 2-8 and 2-9) were obtained as in Example 2-1, except that the ingredients added were changed as shown in Table 2 below.

Comparative Examples 2-1 and 2-2

(89) Acrylic emulsions (resin compositions 2-10 and 2-11) were obtained as in Example 2-1, except that the ingredients added were changed as shown in Table 2 below.

(90) <Preparation of Coating>

(91) Coatings were prepared according to the following formulation using each of the resin compositions 2-1 to 2-11 in Examples 2-1 to 2-7, Reference Examples 2-1 and 2-2, and Comparative Examples 2-1 and 2-2. The properties were evaluated (the coat was subjected to evaluation of appearance and vibration damping test) as described below. Table 2 shows the results. Each of resin compositions 2-1 to 2-11: 350 parts Calcium carbonate NN#200.sup.*1: 700 parts Dispersant AQUALIC DL-40S.sup.*2: 6 parts Thickener ACRYSET WR-650.sup.*3: 4 parts *1: Filler produced by Nitto Funka Kogyo K.K. *2: Polycarboxylic acid-based dispersant (active component: 44%) produced by Nippon Shokubai Co., Ltd. *3: Alkali-soluble acrylic thickener (active component: 30%) produced by Nippon Shokubai Co., Ltd.
<Evaluation of Appearance of Coat> (Evaluation of Degree of Preventing Blistering, Cracking, and/or Peeling of Coat)

(92) Each coating was applied to a steel plate (trade name: SPCC-SD, 75 mm in width150 mm in length0.8 mm in thickness, Nippon Testpanel Co., Ltd.) so as to have a thickness of 4 mm. The applied coating was dried using a hot air dryer at 140 C. for 50 minutes. The surface condition of the resulting dry coat was evaluated based on the following criteria. The coating was foamed by heating using a hot air dryer.

(93) (Evaluation Criteria)

(94) Excellent: No defects were observed in the coat.

(95) Good: Slight cracks were partially observed in the coat.

(96) Fair: Blisters and/or cracks were partially observed in the coat.

(97) Poor: Blisters, peeling, and/or cracks were observed throughout the coat. (Evaluation of Thermal Softening Property of Coat on Vertical Surface)

(98) The resulting coating was applied to a steel plate (Electro Deposition (ED) steel plate) with dimensions of 0.8 mm70 mm150 mm electrodeposited using a cationic electrodeposition coating Elecron KG-400 (Kansai Paint Co., Ltd.) so as to have a wet film thickness of 4 mm. Immediately thereafter, the coated surface was made vertical and baked at 130 C. for 30 minutes. After completion of the baking, the test plate was taken out and the thicknesses of the upper end and lower end of the coated area were measured, and the thermal softening index was determined using the following equation. The thermal softening property was evaluated based on the following criteria.

(99) (Calculation Equation of Thermal Softening Index)
Thermal softening index=(Thickness of lower end (mm))/(Thickness of upper end (mm)) (Evaluation Criteria)

(100) Excellent: 1.0 or greater and 1.6 or smaller

(101) Good: Greater than 1.6 and 2 or smaller

(102) Fair: Greater than 2

(103) Poor: The coat partially or entirely peeled away from the steel plate.

(104) <Vibration Damping Test>

(105) Each coating was applied to a cold rolled steel plate (trade name: SPCC, 15 mm in width250 mm in length1.5 mm in thickness, Nippon Testpanel Co., Ltd.) so as to have a thickness of 3.5 mm, and pre-dried at 80 C. for 30 minutes, followed by drying at 150 C. for 30 minutes. Thus, a vibration damping coat with a surface density of 4.0 kg/m.sup.2 was formed on the cold rolled steel plate. The coating was foamed by heating in pre-drying and in drying after the pre-drying.

(106) The vibration damping property was determined by evaluating the loss coefficients at particular temperatures (10 C., 20 C., 30 C., 40 C., 50 C., and 60 C.) by a cantilever method (loss coefficient measurement system, Ono Sokki Co., Ltd.). The vibration damping property was evaluated based on the total loss coefficient (the sum of loss coefficients at 10 C., 20 C., 30 C., 40 C., 50 C., and 60 C.). A larger total loss coefficient indicates a better vibration damping property.

(107) TABLE-US-00002 TABLE 2 Example Example Example Example Example Example 2-1 2-2 2-3 2-4 2-5 2-6 Core Ingredients (20% (i)-<1> 105 aqueous solution (ii) 105 105 of emulsifier (iii)-<1> 105 105 prepared in NS soap 105 advance) NEOPELEX G-65 Ingredients MMA 447 (Monomers) St 447 447 447 390 600 2EHA 135 135 135 135 120 85 BA 260 260 260 260 332 163 AA 8 8 8 8 8 2 t-DM 2 2 2 2 2 2 Tg ( C.) 4 3 3 3 6 32 Shell Ingredients (20% (i)-<1> 20 aqueous solution (ii) 20 20 of emulsifier (iii)-<1> 20 20 prepared in NS soap 20 advance) NEOPELEX G-65 Ingredients MMA 148 (Monomers) St 148 148 148 148 148 2EHA BMA AA 2 2 2 2 2 2 t-DM 0.3 0.3 0.3 0.3 0.3 0.3 Tg ( C.) 105 100 100 100 100 100 Whole Proportion by mass of shell 15% 15% 15% 15% 15% 15% Tg (Tg of shell Tg of core) 101.0 97.0 97.0 97.0 106.0 68.0 ( C.) The total amount of component having 100% 100% 100% 100% 100% 100% sulfosuccinic acid (salt) structure and component having fatty acid (salt) structure in anionic surfactant The total amount of component having 12.5% 12.5% 12.5% 12.5% 12.5% 12.5% sulfosuccinic acid (salt) structure and component having fatty acid (salt) structure in the entire monomer component used to produce emulsion Nonvolatile content (%) 55.1 54.9 55.0 55.2 55.0 55.4 pH 8.6 8.5 8.2 8.7 8.5 8.5 Viscosity (mPa .Math. s) 200 170 260 200 250 170 Average particle size (nm) 210 280 180 200 190 230 Weight average molecular weight 125000 110000 105000 120000 115000 115000 Results Appearance Thermal softening on Excellent Excellent Excellent Fair Excellent Good vertical surface Prevention degree of Good Excellent Excellent Good Excellent Excellent blistering, cracking, and/or peeling Vibration 10 C. 0.08 0.085 0.079 0.07 0.096 0.04 damping 20 C. 0.096 0.097 0.091 0.088 0.103 0.051 property 30 C. 0.101 0.103 0.099 0.095 0.098 0.065 40 C. 0.089 0.093 0.092 0.087 0.078 0.077 50 C. 0.065 0.069 0.074 0.069 0.059 0.09 60 C. 0.031 0.036 0.045 0.042 0.02 0.098 Vibration damping property (total) 0.462 0.483 0.48 0.451 0.454 0.421 Reference Reference Comparative Comparative Example Example Example Example Example 2-7 2-1 2-2 2-1 2-2 Core Ingredients (20% (i)-<1> 105 105 aqueous solution (ii) of emulsifier (iii)-<1> 30 105 prepared in NS soap advance) NEOPELEX G-65 100 105 Ingredients MMA 664 (Monomers) St 447 350 0 447 447 2EHA 135 332 48 135 135 BA 260 160 130 260 260 AA 8 8 8 8 8 t-DM 2 2 2 2 2 Tg ( C.) 3 18 52 3 3 Shell Ingredients (20% (i)-<1> 20 20 aqueous solution (ii) of emulsifier (iii)-<1> 20 20 prepared in NS soap advance) NEOPELEX G-65 20 Ingredients MMA 148 (Monomers) St 148 148 123 2EHA 25 13 BMA 135 AA 2 2 2 2 2 t-DM 0.3 0.3 0.3 0.3 0.3 Tg ( C.) 100 100 105 54 10 Whole Proportion by mass of shell 15% 15% 15% 15% 15% Tg (Tg of shell Tg of core) 97.0 118.0 53.0 51.0 7.0 ( C.) The total amount of component having 33% 100% 100% 0% 100% sulfosuccinic acid (salt) structure and component having fatty acid (salt) structure in anionic surfactant The total amount of component having 5.0% 12.5% 12.5% 0.0% 12.5% sulfosuccinic acid (salt) structure and component having fatty acid (salt) structure in the entire monomer component used to produce emulsion Nonvolatile content (%) 55.0 54.8 55.0 55.1 55.4 pH 8.6 8.4 8.5 8.7 8.4 Viscosity (mPa .Math. s) 250 200 190 210 220 Average particle size (nm) 170 250 270 280 200 Weight average molecular weight 120000 105000 110000 120000 10000 Results Appearance Thermal softening on Excellent Fair Good Poor Poor vertical surface Prevention degree of Fair Fair Fair Fair Good blistering, cracking, and/or peeling Vibration 10 C. 0.073 0.089 0.026 0.061 0.081 damping 20 C. 0.09 0.079 0.034 0.079 0.094 property 30 C. 0.092 0.06 0.046 0.088 0.099 40 C. 0.079 0.049 0.055 0.074 0.086 50 C. 0.065 0.038 0.069 0.052 0.059 60 C. 0.049 0.025 0.078 0.041 0.03 Vibration damping property (total) 0.448 0.34 0.308 0.395 0.449