Thermally foamable microsphere, method of producing the same, and use thereof

Abstract

This invention aims to provide a thermally foamable microsphere which is excellent in heat resistance, has a high expansion ratio, and shows stable foaming behavior; a method of producing the thermally foamable microsphere; and suitable use thereof. This invention provides a thermally foamable microsphere in which an outer shell encapsulating a foaming agent is formed of a copolymer having a polymethacrylimide structure. In particular, this invention provides a thermally foamable microsphere in which monomers capable of forming the polymethacrylimide structure by a copolymerization reaction are methacrylonitrile and methacrylic acid. Moreover, this invention provides a method of producing the thermally foamable microsphere and use of the thermally foamable microsphere as an additive.

Claims

1. A thermally foamable microsphere, comprising: a foaming agent; and outer shell encapsulating the foaming agent, the outer shell capable of forming a copolymer having a polymethacrylimide structure, wherein the copolymer is obtained by polymerizing a mixture of polymerizable monomers, the polymerizable monomers comprise methacrylonitrile and methacrylic acid in a total weight of 90 to 100% by weight based on the total weight of polymerizable monomers, in which a molar ratio of methacrylonitrile to methaerylic acid is 1:9 to 9:1, and the polymerizable monomers comprises no acrylonitrile.

2. The thermally foamable microsphere according to claim 1, wherein the polymerizable monomers comprise methacrylonitrile and methacrylic acid in a total weight of 90 to 98% by weight, in which a molar ratio of methacrylonitrile to methacrylic acid is 1:5 to 5:1, and the mixture of the polymerizable monomers further comprises 2 to 10% by weight of a vinyl monomer capable of copolymerizing with the methacrylonitrile and methacrylic acid.

3. The thermally foamable microsphere according to claim 2, wherein the mixture of the polyrmerizable monomers further comprises 0 to 0.4 mol % of a cross-linkable monomer having two or more functionalities.

4. The thermally foamable microsphere according to claim 1, wherein a b* value after heating at 240 C. for 2 minutes is 100 or lower.

5. The thermally foamable microsphere according to claim 1, wherein a variation in a expanding starting temperature due to heat treatment at a temperature lower than the expanding starting temperature 7% or lower relative to the expanding starting temperature before the heat treatment, and a variation in a maximum expansion temperature due to the heat treatment is 7% or lower relative to the maximum expansion temperature before the heat treatment.

6. A composition, comprising: polymeric material; and the thermally foamable microsphere according to claim 1.

7. A method of producing a thermally foamable mierosphere in which a foaming agent is encapsulated in an outer shell capable of being formed by a copolymer having a polymethacrylimide structure, the method comprising: performing suspension polymerization of a mixture of polymerizable monomers in the presence of the foaming agent in an aqueous dispersion medium containing a dispersion stabilizer, wherein the polymerizable monomers comprise methacrylonitrile and methacrylic acid in a total weight of 90 to 100% by weight based on the total weight of polymerizable monomers, in which a molar ratio of methacrylonitrile to methacrylic acid is 1:9 to 9:1, and the polymerizable monomers comprises no acrylonitrile.

8. The method claim 7, wherein the mixture of the polymerizable monomers comprises at least: 90 to 98% by weight of methacrylontrile and methacrylic acid in which a molar ratio of methacrylonitrile to methacrylic acid is 1:5 to 5:1; 2 to 10% by weight of a vinyl monomer capable of copolymerizing with the methacrylonitrile and methacrylic acid; and 0 to 0.4 mol % of a cross-linkable monomer having two or more functionalities.

9. The thermally foamable microshere according to claim 1, wherein the polymerizable monomers comprise methacrylonitrile and methacrylic acid in a total weight of 100% by weight, in which the molar ratio of methacrylonitrile to methacrylie acid is 1:9 to 9:1.

10. The thermally foamable microshere according to claim 1, wherein the polymerizable monomers comprise methacrylonitrile, methacrylic acid and methyl acrylate in a total weight of 100% by weight, in which the polymerizable monomers comprise 90 to 98% by weight of methacrylonitrile and methacrylic acid and 2 to 10% by weight of methyl acrylate, and the molar ratio of methathacrylonitrile to methacrylic acid is 1:5 to 5:1.

Description

EXAMPLES

(1) Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. First, the measurement method of each parameter will be described.

(2) (1) Expanding Starting Temperature and Maximum Expansion Temperature

(3) Using the TMA-7 model manufactured by PerkinElmer, Inc., TMA measurement was performed. About 0.25 mg of a sample was used, and the temperature was increased at a temperature increase rate of 5 C./minute. Then, the foaming behavior was observed. More specifically, a sample (thermally foamable microsphere) was put in a container, and the temperature was increased at a temperature increase rate of 5 C. /minute. Then, the variation in the height was successively measured. The temperature at which the variation in the height of the sample in the container started was defined as a expanding starting temperature (Tstart) and the temperature at which the height became a maximum was defined as a maximum expansion temperature (Tmax).

(4) (2) Expansion Ratio (Film Coating Method)

(5) To an EVA aqueous emulsion (Concentration: 55% by weight) containing ethylene-vinylacetate copolymer (EVA; ethylene/vinyl acetate=30/70% by weight), the thermally foamable microsphere was added in such a manner that the ratio of the thermally foamable microsphere to the EVA aqueous emulsion was 5:1 in terms of solid content to prepare a coating liquid. The coating liquid was applied to a double-sided art paper by a coater having a gap of 200 pm, and then the resulting product was put in an oven to dry at 90 C. for 5 minutes. The thickness of the coating film after drying was measured. Then, the coating film was put in an oven having a given temperature to heat for 2 minutes for foaming. The thickness of the coating film after foaming was measured, and then the expansion ratio was determined from the coating-film pressure ratio before and after foaming.

(6) (3) Average Particle Diameter

(7) The average particle diameter was measured using a particle size distribution meter SALD-3000J manufactured by Shimadzu Corp.

(8) (4) Measurement of Color Tone

(9) The b* value of the coating film, whose expansion ratio (Film coating method) was measured, was measured using a color difference meter (Color difference meter CR-200, manufactured by Minolta Co., Ltd.). The b* value refers to a b* value of the L*a*b* color system. When the b* value is larger, yellow color tone is strong.

(10) (5) Foamed Particle Density

(11) 0.5 g of microsphere and 2.5 g of silicon oil were weighed out and put in an aluminum cup. After sufficiently mixing, the mixture was foamed under heat in an oven having a given temperature, and then the resultant was taken out. Then, the resultant was put in a 50 ml volumetric flask, and isopropanol was added. Then, the true specific gravity of the foamed microsphere was determined from the sample weight and the flask weight after the addition of isopropanol.

Example 1

(12) (A) Preparation of Aqueous Dispersion Medium

(13) 40 g of 20% by weight colloidal silica, 1.6 g of 50% by weight diethanolamine-adipic acid condensation product (Acid value =78 mgKOH/g), 0.12 g of sodium nitrite, 177 g of sodium chloride, and 565 g of water were mixed. Then, hydrochloric acid was added so that the pH was adjusted to 3.2 to thereby prepare an aqueous dispersion medium.

(14) (B) Preparation of Polymerizable Mixture

(15) 88 g of methacrylonitrile, which is a polymerization monomer (indicated as MAN in Tables), 112 g of methacrylic acid (similarly indicated as MAA in Tables), 60 g of isooctane as a foaming agent, and 2 g of 2,2-azobisisobutyronitril (similarly indicated as V-60 in Tables) as a polymerization initiator were mixed to prepare a polymerizable mixture. In Example 1, the molar ratio of methacrylonitrile to methacrylic acid was 1:1 (see Table 1).

(16) (C) Suspension Polymerization

(17) The aqueous dispersion medium and the polymerizable mixture prepared above were mixed by stirring with a homogenizer to thereby form a minute droplet of the polymerizable monomer mixture in the aqueous dispersion medium. The aqueous dispersion medium containing the minute droplet of the polymerizable mixture was charged in a polymerization can with a stirrer (1.5 L), heated at 60 C. for 15 hours using a hot water bath, and further heated at 70 C. for 9 hours for reaction. After polymerization, a slurry containing the generated thermally foamable microsphere was filtered and washed with water, and dried to thereby obtain a thermally foamable microsphere having an average particle diameter of 40 m (see Table 1).

(18) (D) Evaluation of Foaming Ability

(19) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained above as it was. As a result, the expanding starting temperature was 195 C., the maximum expansion temperature was 217 C., and the difference therebetween was 22 C. The thermally foamable microsphere was heated at 170 C. for 2 minutes, and then the TMA measurement was performed. No changes in both the expanding starting temperature and the maximum expansion temperature were observed. The expansion ratio was 8.4 times at 230 C. (see Table 1).

(20) (E) Measurement of Color Tone

(21) The b* value of the coating film which was heated at 240 C. for 2 minutes to foam in (D) above was 24.5 (see Table 1).

Example 2

(22) Suspension polymerization was performed in the same manner with Example 1 except using 110 g of methacrylonitrile and 90 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 39 m. In Example 2, the molar ratio of methacrylonitrile to methacrylic acid was 1.6:1.

(23) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 186 C., the maximum expansion temperature was 214 C., and the difference therebetween was 28 C. The expansion ratio was 8.4 times at 230 C. and the b* value was 26.8.

Example 3

(24) Suspension polymerization was performed in the same manner with Example 1 except using 132 g of methacrylonitrile and 68 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 41 m. In Example 3, the molar ratio of methacrylonitrile to methacrylic acid was 2.5:1.

(25) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 171 C., the maximum expansion temperature was 255 C., and the difference therebetween was 84 C. The expansion ratio was 10.5 times at 220 C. and the b* value was 27.1.

Example 4

(26) Suspension polymerization was performed in the same manner with Example 1 except using 154 g of methacrylonitrile and 46 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 50 m. In Example 4, the molar ratio of methacrylonitrile to methacrylic acid was 4.3:1.

(27) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 180 C., the maximum expansion temperature was 260 C., and the difference therebetween was 80 C. The expansion ratio was 8.6 times at 220 C. and the b* value was 35.4.

Example 5

(28) Suspension polymerization was performed in the same manner with Example 1 except using 60 g of isopentane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 40 m

(29) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 185 C., the maximum expansion temperature was 240 C., and the difference therebetween was 55 C. The expansion ratio was 4.5 times at 230 C. and the b* value was 25.0.

Example 6

(30) Suspension polymerization was performed in the same manner with Example 2 except using 60 g of isopentane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 49 m.

(31) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 170 C., the maximum expansion temperature was 240 C., and the difference therebetween was 70 C. The expansion ratio was 9.1 times at 220 C. and the b* value was 27.0.

Example 7

(32) Suspension polymerization was performed in the same manner with Example 3 except using 60 g of isopentane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 47 m.

(33) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 155 C., the maximum expansion temperature was 220 C., and the difference therebetween was 65 C. The expansion ratio was 19.2 times at 210 C. and the b* value was 27.5.

Example 8

(34) Suspension polymerization was performed in the same manner with Example 4 except using 60 g of isopentane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 50 m.

(35) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 130 C., the maximum expansion temperature was 210 C., and the difference therebetween was 80 C. The expansion ratio was 17.3 times at 200 C. and the b* value was 36.0.

Example 9

(36) Suspension polymerization was performed in the same manner with Example 3 except using 60 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 31 m.

(37) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 251 C., the maximum expansion temperature was 279 C., and the difference therebetween was 28 C. The expansion ratio was 1.5 times at 230 C. and the b* value was 28.0.

Example 10

(38) Suspension polymerization was performed in the same manner with Example 1 except using 130 g of methacrylonitrile, 66 g of methacrylic acid, and 4 g of methyl acrylate (indicated as MA in Tables) in place of 88 g of methacrylonitrile and 112 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 34 m.

(39) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 171 C., the maximum expansion temperature was 245 C., and the difference therebetween. was 74 C. The expansion ratio was 10.0 times at 220 C. and the b* value was 27.0.

Example 11

(40) Suspension polymerization was performed in the same manner with Example 10 except using 60 g of isopentane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 50 m.

(41) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 150 C., the maximum expansion temperature was 220 C., and the difference therebetween was 70 C. The expansion ratio was 19.1 times at 210 C. and the b* value was 26.9.

Example 13

(42) (A) Preparation of aqueous dispersion medium

(43) 65 g of 20% by weight colloidal silica, 6.5 g of 50% by weight diethanolamine-adipic acid condensation product (Acid value=78 mgKOH/g), 0.24 g of sodium nitrite, 0.04 g of stannous chloride, 177 g of sodium chloride, and 565 g of water were mixed. Then, hydrochloric acid was added so that the pH was adjusted to 3.2 to thereby prepare an aqueous dispersion medium.

(44) (B) Preparation of Polymerizable Mixture

(45) 175 g of methacrylonitrile (MAN), which is a polymerization monomer, 25 g of methacrylic acid (MAA), 60 g of isooctane as a foaming agent, and 2 g of 2,2-azobisisobutyronitril (V-60) as a polymerization initiator were mixed to prepare a polymerizable mixture. In Example 13, the molar ratio of methacrylonitrile to methacrylic acid was 9:1.

(46) (C) Suspension Polymerization was Performed in the Same Manner with Example 1 to thereby obtain a thermally foamable microsphere with an average particle diameter of 27 m.

(47) The evaluation of foaming ability (D) and measurement of color tone (E) were performed using, as a sample, the obtained thermally foamable microsphere as it was in the same manner with Example 1. As a result, the expanding starting temperature was 211 C., the maximum expansion temperature was 218 C., and the difference therebetween was 7 C. The expansion ratio was 6.5 times at 220 C. and the b* value was 41.0.

Example 14

(48) Suspension polymerization was performed in the same manner with Example 13 except using 129 g of methacrylonitrile and 71 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 27 m. In Example 14, the molar ratio of methacrylonitrile to methacrylic acid was 2.3:1.

(49) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 204 C., the maximum expansion temperature was 259 C., and the difference therebetween was 55 C. The expansion ratio was 17.0 times at 230 C. and the b* value was 31.0.

Example 15

(50) Suspension polymerization was performed in the same manner with Example 13 except using 108 g of methacrylonitrile and 92 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 26 m. In Example 15, the molar ratio of methacrylonitrile to methacrylic acid was 1.5:1.

(51) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 189 C., the maximum expansion temperature was 266 C., and the difference therebetween was 77 C. The expansion ratio was 17.6 times at 230 C. and the b* value was 27.0.

(52) Moreover, the heat foamed particle density was 0.0046 at 230 C., 0.0045 at 240 C., and 0.0068 at 250 C. (see Table 2).

Example 16

(53) Suspension polymerization was performed in the same manner with Example 13 except using 88 g of methacrylonitrile and 112 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 31 m. In Example 16, the molar ratio of methacrylonitrile to methacrylic acid was 1:1.

(54) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 199 C., the maximum expansion temperature was 263 C., and the difference therebetween was 64 C. The above-mentioned thermally foamable microsphere was heated at 180 C. for 10 minutes, and then the TMA measurement was performed. Changes in both the expanding starting temperature and the maximum expansion temperature were hardly observed. The expansion ratio was 14.5 times at 230 C. and the b* value was 24.0.

(55) FIG. 1 shows changes (foaming behavior) in the foaming degree between at the expanding starting temperature and at the maximum expansion temperature at the time of TMA measurement. About 0.25 mg of a sample was put in a container, and the temperature was increased at a temperature increase rate of 5 C./minute. Then, the variation in the height was successively measured. The height at each temperature was indicated relative to the height at the maximum expansion temperature (Tmax), which was defined as 1.

(56) As shown in FIG. 1, it is revealed that the thermally foamable microsphere obtained in Example 16 hardly shows changes in the expanding starting temperature and the maximum expansion temperature when not heated and when heated at 180 C. for 10 minutes. In addition, there are no changes in the foaming behavior between at the expanding starting temperature and at the maximum expansion temperature, and a stable foaming ability is maintained.

Example 17

(57) Suspension polymerization was performed in the same manner with Example 16 except using 60 g of lauryl peroxide (indicated as LPO in Tables) isopentane in place of 2 g of 2,2-azobisisobutyronitril as the polymerization initiator to thereby obtain a thermally foamable microsphere with an average particle diameter of 30 m.

(58) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 200 C., the maximum expansion temperature was 250 C., and the difference therebetween was 50 C. The expansion ratio was 7.1 times at 230 C. and the b* value was 23.0.

Example 18

(59) Suspension polymerization was performed in the same manner with Example 17 except using 68 g of methacrylonitrile and 132 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 28 m. In Example 18, the molar ratio of methacrylonitrile to methacrylic acid was 0.7:1.

(60) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 207 C., the maximum expansion temperature was 232 C., and the difference therebetween was 25 C. The expansion ratio was 4.1 times at 230 C. and the b* value was 23.0.

Example 19

(61) Suspension polymerization was performed in the same manner with Example 13 except adding, in addition to 175 g of methacrylonitrile and 25 g of methacrylic acid, 0.4 g of trimethylolpropanetrimethacrylate (indicated as TMPTMA in Tables) to thereby obtain a thermally foamable microsphere with an average particle diameter of 30 m. The blending proportion of trimethylolpropanetrimethacrylate in the polymerizable monomer mixture of Example 19 was 0.04 mol %.

(62) The TMA measurement was prepared using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 213 C., the maximum expansion temperature was 218 C., and the difference therebetween was 5 C. The expansion ratio was 6.7 times at 230 C.

Example 20

(63) Suspension polymerization was performed in the same manner with Example 15 except adding, in addition to 108 g of methacrylonitrile and 92 g of methacrylic acid, 0.2 g of trimethylolpropanetrimethacrylate to thereby obtain a thermally foamable microsphere with an average particle diameter of 26 m. The blending proportion of trimethylolpropanetrimethacrylate in the polymerizable monomer mixture of Example 20 was 0.02 mol %.

(64) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 188 C., the maximum expansion temperature was 250 C., and the difference therebetween was 62 C. The expansion ratio was 10.6 times at 230 C.

Example 21

(65) Suspension polymerization was performed in the same manner with Example 15 except adding, in addition to 108 g of methacrylonitrile and 92 g of methacrylic acid, 0.6 g of trimethylolpropanetrimethacrylate to thereby obtain a thermally foamable microsphere with an average particle diameter of 29 m. The blending proportion of trimethylolpropanetrimethacrylate in the polymerizable monomer mixture of Example 21 is 0.07 mol %.

(66) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 187 C., the maximum expansion temperature was 223 C., and the difference therebetween was 36 C. The expansion ratio was 11.3 times at 230 C.

Example 22

(67) Suspension polymerization was performed in the same manner with Example 15 except adding, in addition to 108 g of methacrylonitrile and 92 g of methacrylic acid, 1.0 g of trimethylolpropanetrimethacrylate to thereby obtain a thermally foamable microsphere with an average particle diameter of 31 m. The blending proportion of trimethylolpropanetrimethacrylate in the polymerizable monomer mixture of Example 22 was 0.11 mol %.

(68) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 185 C., the maximum expansion temperature was 220 C., and the difference therebetween was 35 C. The expansion ratio was 8.0 times at 230 C.

Example 23

(69) Suspension polymerization was performed in the same manner with Example 15 except adding 98 g of methacrylonitrile, 92 g of methacrylic acid, and 10 g of methyl acrylate (indicated as MA in Tables) to thereby obtain a thermally foamable microsphere with an average particle diameter of 27 m. The molar ratio of methacrylonitrile to methacrylic acid was 1.4:1 and the blending proportion of methyl acrylate was 5% by weight in Example 23.

(70) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 189 C., the maximum expansion temperature was 259 C., and the difference therebetween was 70 C. The expansion ratio was 13.4 times at 230 C.

Example 24

(71) Suspension polymerization was performed in the same manner with Example 15 except adding 98 g of methacrylonitrile, 92 g of methacrylic acid, and 10 g of methyl methacrylate (indicated as MMA in Tables) to thereby obtain a thermally foamable microsphere with an average particle diameter of 25 m. The molar ratio of methacrylonitrile to methacrylic acid was 1.4:1 and the blending proportion of methyl acrylate was 5% by weight in Example 24.

(72) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 185 C., the maximum expansion temperature was 242 C., and the difference therebetween was 57 C. The expansion ratio was 14.2 times at 230 C.

Example 25

(73) Suspension polymerization was performed in the same manner with Example 15 except adding 88 g of methacrylonitrile, 92 g of methacrylic acid, and 20 g of methyl methacrylate to thereby obtain a thermally foamable microsphere with an average particle diameter of 27 m. The molar ratio of methacrylonitrile to methacrylic acid was 1.2:1 and the blending proportion of methyl acrylate was 10% by weight in Example 25.

(74) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 186 C., the maximum expansion temperature was 235 C., and the difference therebetween was 49 C. The expansion ratio was 13.3 times at 230 C.

Example 26

(75) Suspension polymerization was performed in the same manner with Example 15 except adding 104 g of methacrylonitrile, 92 g of methacrylic acid, and 4 g of dimethylamino ethyl methacrylate (indicated as DMAEMA in Tables) to thereby obtain a thermally foamable microsphere with an average particle diameter of 24 m. The molar ratio of methacrylonitrile to methacrylic acid was 1.5:1 and the blending proportion of dimethylamino ethyl methacrylate was 2% by weight in Example 26.

(76) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 190 C., the maximum expansion temperature was 251 C., and the difference therebetween was 61 C. The expansion ratio was 11.4 times at 230 C.

(77) TABLE-US-00001 TABLE 1 b* Value Average Expanding Maximum (Yellowness) Particle starting expansion Expansion after Heated Blending Composition of Diameter temperature temperature ratio at 240 C. for Polymerizable Mixture Foaming Agent (m) C. C. (times) 2 minutes Initiator Ex. 1 MAN 88 g Molar Ratio Isooctane60 g 40 Non Heat- Non Heat- 8.4 *1 24.5 V-60 MAA 112 g 1:1 Treated Treated 2 g 195 217 After Heated After Heated at 170 C. for at 170 C. for 2 minutes 2 minutes 195 217 Ex. 2 MAN 110 g Molar Ratio 39 186 214 8.4 *1 26.8 MAA 90 g 1.6:1 Ex. 3 MAN 132 g Molar Ratio 41 171 255 10.5 *2 27.1 MAA 68 g 2.5:1 Ex. 4 MAN 154 g Molar Ratio 50 180 260 8.6 *2 35.4 MAA 46 g 4.3:1 Ex. 5 MAN 88 g Molar Ratio Isopentane60 g 40 185 240 4.5 *1 25 MAA 112 g 1:1 Ex. 6 MAN 110 g Molar Ratio 49 170 240 9.1 *2 27 MAA 90 g 1.6:1 Ex. 7 MAN 132 g Molar Ratio 47 155 220 19.2 *3 27.5 MAA 68 g 2.5:1 Ex. 8 MAN 154 g Molar Ratio 50 130 210 17.3 *4 36 MAA 46 g 4.3:1 Ex. 9 MAN 132 g Molar Ratio Isododecane60 g 31 251 279 1.5 *1 28 MAA 68 g 2.5:1 Ex. 10 MAN 130 g Molar Ratio Isooctane60 g 34 171 245 10.0 *2 27 MAA 66 g 2.5:1 MA 4 g Ex. 11 MAN 130 g Molar Ratio Isopentane60 g 50 150 220 19.1 *3 26.9 MAA 66 g 2.5:1 MA 4 g Ex. 13 MAN 175 g Molar Ratio Isooctane60 g 27 211 218 6.5 *2 41 MAA 25 g 9:1 Ex. 14 MAN 129 g Molar Ratio 27 204 259 17.0 *1 31 MAA 71 g 2.3:1 Ex. 15 MAN 108 g Molar Ratio 26 189 266 17.6 *1 27 MAA 92 g 1.5:1 Ex. 16 MAN 88 g Molar Ratio 31 Non Heat- Non Heat- 14.5 *1 24 MAA 112 g 1:1 Treated Treated 199 263 After Heated After Heated at 180 C. for at 180 C. for 10 minutes 10 minutes 197 266 Ex. 17 MAN 88 g Molar Ratio 30 200 250 7.1 *1 23 LPO MAA 112 g 1:1 3 g Ex. 18 MAN 68 g Molar Ratio 28 207 232 4.1 *1 23 MAA 132 g 0.7:1 Ex. 19 MAN 175 g Molar Ratio 30 213 218 6.7 *1 V-60 MAA 25 g 0.04 mol % 2 g TMPTMA 02. g Ex. 20 MAN 108 g Molar Ratio 26 188 250 10.6 *1 MAA 92 g 0.02 mol % TMPTMA 0.2 g Ex. 21 MAN 108 g Molar Ratio 29 187 223 11.3 *1 MAA 92 g 0.07 mol % TMPTMA 0.6 g Ex. 22 MAN 108 g Molar Ratio 31 185 220 8.0 *1 MAA 92 g 0.11 mol % TMPTMA 1.0 g Ex. 23 MAN 98 g Molar Ratio 27 189 259 13.4 *1 MAA 92 g 1.4:1 MA 10 g 5 parts Ex. 24 MAN 98 g Molar Ratio 25 185 242 14.2 *1 MAA 92 g 1.4:1 MMA 10 g 5 parts Ex. 25 MAN 88 g Molar Ratio 27 186 235 13.3 *1 MAA 92 g 1.2:1 MMA 20 g 10 parts Ex. 26 MAN 104 g Molar Ratio 24 190 251 11.4 *1 MMA 92 g 1.5:1 DMAEMA 4 g 2 parts *1: 230 C., *2: 220 C., *3: 210 C., *4: 200 C., *5: 190 C.

Example 27

(78) Suspension polymerization was performed in the same manner with Example 15 except using 60 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 26 m (See Table 2).

(79) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 232 C., the maximum expansion temperature was 283 C., and the difference therebetween was 51 C. The heat foamed particle density was 0.0612 at 240 C. and 0.0236 at 250 C. (see Table 2).

Example 28

(80) Suspension polymerization was performed in the same manner with Example 15 except using 60 g of isopentane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 31 m.

(81) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 168 C., the maximum expansion temperature was 234 C., and the difference therebetween was 66 C. The expansion ratio was 14.4 times at 230 C. The heat foamed particle density was 0.0116 at 220 C., 0.0072 at 230 C., and 0.0061 at 240 C.

Example 29

(82) Suspension polymerization was performed in the same manner with Example 15 except using 40 g of isobutane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foam able microsphere with an average particle diameter of 27 m.

(83) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 159 C., the maximum expansion temperature was 228 C., and the difference therebetween was 69 C. The expansion ratio was 9.8 times at 230 C. The heat foamed particle density was 0.0108 at 220 C., 0.0104 at 230 C., and 0.0146 at 240 C.

Example 30

(84) Suspension polymerization was performed in the same manner with Example 15 except using 20 g of isobutane and 40 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 26 m.

(85) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 175 C., the maximum expansion temperature was 240 C., and the difference therebetween was 65 C. The expansion ratio was 10.3 times at 230 C. The heat foamed particle density was 0.0097 at 230 C., 0.0108 at 240 C., and 0.0120 at 250 C.

Example 31

(86) Suspension polymerization was performed in the same manner with Example 15 except using 10 g of isobutane and 50 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 26 m.

(87) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 198 C., the maximum expansion temperature was 260 C., and the difference therebetween was 62 C. The expansion ratio was 8.7 times at 230 C. The heat foamed particle density was 0.0123 at 230 C., 0.0113 at 240 C., and 0.0119 at 250 C.

Example 32

(88) Suspension polymerization was performed in the same manner with Example 15 except using 5 g of isobutane and 55 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 25 m.

(89) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 200 C., the maximum expansion temperature was 277 C., and the difference therebetween was 77 C. The expansion ratio was 5.8 times at 230 C. The heat foamed particle density was 0.0221 at 230 C., 0.0205 at 240 C., and 0.0140 at 250 C.

Example 33

(90) Suspension polymerization was performed in the same manner with Example 15 except using 20 g of isopentane and 40 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 25 m.

(91) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 193 C., the maximum expansion temperature was 237 C., and the difference therebetween was 44 C. The expansion ratio was 11.8 times at 230 C. The heat foamed particle density was 0.0080 at 230 C. and 0.0088 at 240 C.

Example 34

(92) Suspension polymerization was performed in the same manner with Example 15 except using 10 g of isopentane and 50 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 24 m.

(93) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 195 C., the maximum expansion temperature was 264 C., and the difference therebetween was 69 C. The expansion ratio was 8.5 times at 230 C. The heat foamed particle density was 0.0127 at 230 C., 0.0117 at 240 C., and 0.0110 at 250 C.

Example 35

(94) Suspension polymerization was performed in the same manner with Example 15 except using 5 g of isopentane and 55 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 22 m.

(95) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 208 C., the maximum expansion temperature was 272 C., and the difference therebetween was 64 C. The heat foamed particle density was 0.0155 at 240 C. and 0.0154 at 250 C.

Example 36

(96) Suspension polymerization was performed in the same manner with Example 15 except using 40 g of isooctane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 25 m.

(97) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 188 C., the maximum expansion temperature was 256 C., and the difference therebetween was 68 C. The expansion ratio was 8.6 times at 230 C. The heat foamed particle density was 0.0125 at 230 C., 0.0116 at 240 C., and 0.0124 at 250 C.

Example 37

(98) Suspension polymerization was performed in the same manner with Example 15 except using 80 g of isooctane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 27 m.

(99) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 187 C., the maximum expansion temperature was 260 C., and the difference therebetween was 73 C. The expansion ratio was 12.4 times at 230 C. The heat foamed particle density was 0.0075 at 230 C., 0.0069 at 240 C., and 0.0068 at 250 C.

Example 38

(100) Suspension polymerization was performed in the same manner with Example 15 except using 100 g of isooctane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 23 m.

(101) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 187 C., the maximum expansion temperature was 260 C., and the difference therebetween was 73 C. The expansion ratio was 12.8 times at 230 C. The heat foamed particle density was 0.0072 at 230 C., 0.0061 at 240 C., and 0.0068 at 250 C.

Example 39

(102) Suspension polymerization was performed in the same manner with Example 15 except adding 110 g of methacrylonitrile, 86 g of methacrylic acid, and 4 g of methyl acrylate, and further adding 22 g of isopentane and 22 g of isooctane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 21 m.

(103) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 176 C., the maximum expansion temperature was 231 C., and the difference therebetween was 55 C. The expansion ratio was 11.0 times at 230 C. The heat foamed particle density was 0.0106 at 210 C., 0.0089 at 220 C., and 0.0094 at 230 C.

Example 40

(104) Suspension polymerization was performed in the same manner with Example 15 except adding 110 g of methacrylonitrile, 86 g of methacrylic acid, and 4 g of methyl acrylate, and further adding 30 g of isopentane and 30 g of isooctane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 24 m.

(105) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 175 C., the maximum expansion temperature was 235 C., and the difference therebetween was 60 C. The expansion ratio was 14.2 times at 220 C. The heat foamed particle density was 0.0093 at 210 C., 0.0062 at 220 C., and 0.0068 at 230 C.

Example 41

(106) Suspension polymerization was performed in the same manner with Example 15 except adding 110 g of methacrylonitrile, 86 g of methacrylic acid, and 4 g of methyl acrylate, and further adding 40 g of isopentane and 40 g of isooctane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 26 m.

(107) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 172 C., the maximum expansion temperature was 241 C., and the difference therebetween was 69 C. The expansion ratio was 16.0 times at 210 C. The heat foamed particle density was 0.0083 at 210 C., 0.0054 at 220 C., and 0.0052 at 230 C.

Example 42

(108) Suspension polymerization was performed in the same manner with Example 15 except adding 110 g of methacrylonitrile, 86 g of methacrylic acid, and 4 g of methyl acrylate, and further adding 50 g of isopentane and 50 g of isooctane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 30 m.

(109) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 168 C., the maximum expansion temperature was 247 C., and the difference therebetween was 79 C. The expansion ratio was 18.2 times at 210 C. The heat foamed particle density was 0.0083 at 210 C., 0.0044 at 220 C., and 0.0047 at 230 C.

(110) TABLE-US-00002 TABLE 2 Average Expanding Maximum b* Value Particle starting expansion Expansion (Yellowness) after Blending Composition of Diameter temperature temperature ratio Heated at 240 C. Polymerizable Mixture Foaming Agent (m) C. C. (times) for 2 minutes Initiator Ex. 15 MAN 108 g Molar Ratio Isooctane 60 g 26 189 266 17.6 *1 230 C.: 0.0046 V-60 MAA 92 g 1.5:1 240 C.: 0.0045 2 g 250 C.: 0.0068 Ex. 27 Isododecane 60 g 23 232 283 Non *1 230 C.: Non Foamed Foamed 240 C.: 0.0612 250 C.: 0.0236 Ex. 28 Isopentane 60 g 31 168 234 14.4 *1 220 C.: 0.0116 230 C.: 0.0072 240 C.: 0.0061 Ex. 29 Isobutane 40 g 27 159 228 9.8 *1 220 C.: 0.0108 230 C.: 0.0104 240 C.: 0.0146 Ex. 30 Isobutane 20 g 26 175 240 10.3 *1 230 C.: 0.0097 Isododecane 40 g 240 C.: 0.0108 250 C.: 0.0120 Ex. 31 Isobutane 10 g 26 198 260 8.7 *1 230 C.: 0.0123 Isododecane 50 g 240 C.: 0.0113 250 C.: 0.0119 Ex. 32 Isobutane 5 g 25 200 277 5.8 *1 230 C.: 0.0221 Isododecane 55 g 240 C.: 0.0205 250 C.: 0.0140 Ex. 33 Isopentane 20 g 25 193 237 11.8 *1 230 C.: 0.0080 Isododecane 40 g 240 C.: 0.0088 250 C.: Ex. 34 Isopentane 10 g 24 195 264 8.5 *1 230 C.: 0.0127 Isododecane 50 g 240 C.: 0.0117 250 C.: 0.0110 Ex. 35 Isopentane 5 g 22 208 272 *1 230 C.: Isododecane 55 g 240 C.: 0.0155 250 C.: 0.0154 Ex. 36 Isooctane 40 g 25 188 256 8.6 *1 230 C.: 0.0125 240 C.: 0.0116 250 C.: 0.0124 Ex. 37 Isooctane 80 g 27 187 260 12.4 *1 230 C.: 0.0075 240 C.: 0.0069 250 C.: 0.0068 Ex. 38 Isooctane 100 g 23 187 260 12.8 *1 230 C.: 0.0072 240 C.: 0.0061 250 C.: 0.0068 Ex. 39 MAN 110 g Molar Ratio Isopentane 22 g 21 176 231 11.0 *1 210 C.: 0.0106 MAA 86 g 1.6:1 Isooctane 22 g 220 C.: 0.0089 MA 4 g 230 C.: 0.0094 Ex. 40 Isopentane 30 g 24 175 235 14.2 *2 210 C.: 0.0093 Isooctane 30 g 220 C.: 0.0062 230 C.: 0.0068 Ex. 41 Isopentane 40 g 26 172 241 16.0 *3 210 C.: 0.0083 Isooctane 40 g 220 C.: 0.0054 230 C.: 0.0052 Ex. 42 Isopentane 50 g 30 168 247 18.2 *3 210 C.: 0.0083 Isooctane 50 g 220 C.: 0.0044 230 C.: 0.0047 *1: 230 C., *2: 220 C., *3: 210 C., *4: 200 C., *5: 190 C.

Example 43

(111) Suspension polymerization was performed in the same manner with Example 15 except using 50 g of 20% by weight colloidal silica in place of 65 g of 20% by weight colloidal silica and adjusting the number of rotation of an emulsifier to 8,500 r/m in preparation of an aqueous dispersion medium to thereby obtain a thermally foamable microsphere with an average particle diameter of 39 m (see Table 3).

(112) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 185 C., the maximum expansion temperature was 266 C., and the difference therebetween was 81 C. The expansion ratio was 11.3 times at 230 C. The heat foamed particle density was 0.0210 at 210 C., 0.0113 at 220 C., and 0.0085 at 230 C. (see Table 3).

Example 44

(113) Suspension polymerization was performed in the same manner with Example 15 except using 40 g of 20% by weight colloidal silica in place of 65g of 20% by weight colloidal silica and adjusting the number of rotation of an emulsifier to 7,500 r/m in preparation of an aqueous dispersion medium to thereby obtain a thermally foamable microsphere with an average particle diameter of 58 m.

(114) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 181 C., the maximum expansion temperature was 232 C., and the difference therebetween was 51 C. The expansion ratio was 11.3 times at 230 C. The heat foamed particle density was 0.0150 at 210 C., 0.0100 at 220 C., and 0.0086 at 230 C.

Example 45

(115) Suspension polymerization was performed in the same manner with Example 15 except using 20 g of 20% by weight colloidal silica in place of 65 g of 20% by weight colloidal silica and adjusting the number of rotation of an emulsifier to 5,500 r/m in preparation of an aqueous dispersion medium to thereby obtain a thermally foamable microsphere with an average particle diameter of 118 m.

(116) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 177 C., the maximum expansion temperature was 201 C., and the difference therebetween was 24 C. The expansion ratio was 2.8 times at 210 C. The heat foamed particle density was 0.0598 at 210 C., 0.0641 at 220 C., and 0.0748 at 230 C.

(117) TABLE-US-00003 TABLE 3 Average Expanding Maximum Number of Particle starting expansion Expansion Foamed Blending Composition of Colloidal Rotation of Diameter temperature temperature ratio Particle Polymerizable Mixture Silica Emulsifier (m) C. C. (times) Density Initiator Ex. 15 MAN 108 g Molar 65 g 9500 r/m 26 189 266 17.6 *1 210 C.: 0.0201 V-60 g MAA 92 g Ratio 1.5:1 220 C.: 0.0074 Isooctane 60 g 230 C.: 0.0046 Ex. 43 50 g 8500 r/m 39 185 266 11.3 *1 210 C.: 0.0210 220 C.: 0.0113 230 C.: 0.0085 Ex. 44 40 g 7500 r/m 58 181 232 11.3 *1 210 C.: 0.0150 220 C.: 0.0100 230 C.: 0.0086 Ex. 45 20 g 5500 r/m 118 177 201 2.8 *3 210 C.: 0.0598 220 C.: 0.0641 230 C.: 0.0748 *1: 230 C., *2: 220 C., *3: 210 C., *4: 200 C., *5: 190 C.

Comparative Example 1

(118) Comparative Example 1 is a test for confirming influences caused by the use of a large amount of acrylonitrile. Suspension polymerization was performed in the same manner with Example 1 except using 45.4 g of acrylonitrile, 45.4 g of methacrylonitrile, and 109.2 g of methacrylic acid in place of 88 g of methacrylonitrile and 112 g of methacrylic acid. As a result, the polymer agglomerated in the middle of polymerization, and thus a normal thermally foamable microsphere was not successfully obtained (see Table 4).

Comparative Example 2

(119) In order to confirm the particle formability of a polymerizable mixture whose composition is similar to that of Examples of Patent Document 2, suspension polymerization was performed in the same manner with Example 1 except using 45.4 g of acrylonitrile, 45.4 g of methacrylonitrile, and 109.2 g of methacrylic acid in place of 88 g of methacrylonitrile and 112 g of methacrylic acid, and further adding 2.72 g of ethylene glycol dimethacrylate (indicated as EGDMA in Table) as a cross linkable monomer. As a result, the polymer agglomerated in the middle of polymerization, and thus a normal thermally foamable microsphere was not successfully obtained.

Comparative Example 3

(120) In order to confirm influences caused by the use of a larger amount of acrylonitrile, suspension polymerization was performed in the same manner with Example 1 except using 66.6 g of acrylonitrile, 66.6 g of methacrylonitrile, and 66.6 g of methacrylic acid in place of 88 g of methacrylonitrile and 112 g of methacrylic acid. As a result, the polymer agglomerated in the middle of polymerization, and thus a normal thermally foamable microsphere was not successfully obtained.

Comparative Example 4

(121) In order to confirm the particle formability of a polymerizable mixture whose composition is similar to that of Examples of Patent Document 2, suspension polymerization was performed in the same manner with Example 1 except using 66.6 g of acrylonitrile, 66.6 g of methacrylonitrile, and 66.6 g of methacrylic acid in place of 88 g of methacrylonitrile and 112 g of methacrylic acid, and further adding 2.86 g of ethylene glycol dimethacrylate as a cross linkable monomer.

(122) As a result, the polymer agglomerated in the middle of polymerization, and thus a normal thermally foamable microsphere was not successfully obtained.

Comparative Example 5

(123) Suspension polymerization was performed in the same manner with Example 1 except using only 200 g of methacrylic acid in place of 88 g of methacrylonitrile and 112 g of methacrylic acid. As a result, the polymer agglomerated in the middle of polymerization.

Comparative Example 6

(124) Suspension polymerization was performed in the same manner with Example 1 except using only 200 g of methacrylonitrile in place of 88 g of methacrylonitrile and 112 g of methacrylic acid to thereby obtain a thermally foamable microsphere with an average particle diameter of 47 gm. The resulted microsphere did not foam. The b* value was 200.

Comparative Example 7

(125) In order to confirm influences of a cross-linkable monomer, suspension polymerization was performed in the same manner with Example 3 except adding 2.72 g of ethylene glycol dimethacrylate as a cross-linkable monomer to thereby obtain a thermally foamable microsphere with an average particle diameter of 50 m. The addition amount of the cross-linkable monomer was 0.5 mol % relative to the polymerizable monomer.

(126) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 169 C., the maximum expansion temperature was 173 C. The expansion ratio was sharply lowered to be 1.1 times at 220 C.

Comparative Example 8

(127) Comparative Example 8 is a test for confirming influences on the foaming behavior. Suspension polymerization was performed in the same manner with Example 1 except using 67 g of acrylonitrile, 31 g of methacrylonitrile, 2 g of methacrylic acid, and 1.5 g of diethyleneglycol dimethacrylate (indicated as DEGDMA in Table) in place of 88 g of methacrylonitrile and 112 g of methacrylic acid, and using 1 g of isopentane, 13 g of isooctane, and 16 g of isododecane in place of 60 g of isooctane as the foaming agent to thereby obtain a thermally foamable microsphere with an average particle diameter of 49 m The addition amount of the cross-linkable monomer was 0.35 mol % relative to the polymerizable monomer.

(128) The TMA measurement was performed using, as a sample, the thermally foamable microsphere obtained as a result of the above manner as it was. As a result, the expanding starting temperature was 204 C., the maximum expansion temperature was 209 C., and the difference therebetween was 5 C. The above-mentioned thermally foamable microsphere was heated at 170 C. for 2 minutes, and then the TMA measurement was performed. The expanding starting temperature was 135 C. and the maximum expansion temperature was 194 C. The expansion ratio after heated at 170 C. for 2 minutes was 8.3 times at 190 C.

(129) FIG. 2 shows changes (foaming behavior) in the foaming degree between at the expanding starting temperature and at the maximum expansion temperature at the time of TMA measurement. It is revealed that the thermally foamable microsphere obtained in Comparative Example 8 is reduced in both the expanding starting temperature and the maximum expansion temperature when not heated and when heated at 170 C. for 2 minutes, and moreover the foaming behavior between at the expanding starting temperature and at the maximum expansion temperature sharply changes (also see FIG. 1).

(130) TABLE-US-00004 TABLE 4 Average Expanding Maximum b* Value Particle starting expansion Expansion (Yellowness) after Blending Composition of Diameter temperature temperature ratio Heated at 240 for Polymerizable Mixture Foaming Agent (m) C. C. (times) 2 minutes Comparative AN 45.4 g Molar Ratio Isooctane 60 g Normal Thermally Foamable microsphere is not Obtained (Formed into a Ex. 1 MAN 45.4 g 0.5:1 Polymer Lump in the middle of Polymerization). MAA 109.2 g 0.00 mol % EGDMA 0 g Comparative AN 45.4 g Molar Ratio Normal Thermally Foamable microsphere is not Obtained (Formed into a Ex. 2 MAN 45.4 g 0.5:1 Polymer Lump in the middle of Polymerization). MAA 109.2 g 0.49 mol % EGDMA 2.72 g Comparative AN 66.6 g Molar Ratio Normal Thermally Foamable microsphere is not Obtained (Formed into a Ex. 3 MAN 66.6 g 1.3:1 Polymer Lump in the middle of Polymerization). MAA 66.6 g 0.00 mol % EGDMA 0 g Comparative AN 66.6 g Molar Ratio Normal Thermally Foamable microsphere is not Obtained (Formed into a Ex. 4 MAN 66.6 g 1.3:1 Polymer Lump in the middle of Polymerization). MAA 66.6 g 0.48 mol % EGDMA 2.86 g Comparative MAA 200 g 0:1 Normal Thermally Foamable microsphere is not Obtained (Formed into a Ex. 5 Polymer Lump in the middle of Polymerization). Comparative MAA 200 g 1:0 47 Not Foamed. 200 Ex. 6 Comparative MAN 132 g Molar Ratio 50 169 173 1.1 *2 Ex. 7 MAA 68 g 2.5:1 EGDMA 2.72 g 0.50 mol % Comparative AN 67 g 0.35 mol % Isopentane 1 g 49 Non Heat- Non Heat- Non *5 Ex. 8 MAN 31 g Isooctane 13 g Treated Treated Foamed MMA 2 g Isododecane 16 g 204 209 DEGDMA 1.5 g After Heated After Heated 8.3 *5 at 170 C. for at 170 C. for 2 minutes 2 minutes 135 194 *1: 230 C., *2: 220 C., *3: 210 C., *4: 200 C., *5: 190 C.

(131) As is clear from the results shown in Table 1 above, in each Example of the thermally foamable microsphere of the present invention, the difference of the expanding starting temperature and the maximum expansion temperature was large. More specifically, the differences of the expanding starting temperature and the maximum expansion temperature in each Example were as follows: Example 1: 22 C., Example 2: 28 C., Example 3: 84 C., Example 4: 80 C., Example 5: 55 C., Example 6: 70 C., Example 7: 65 C., Example 8: 80 C., Example 9: 28 C., Example 10: 74 C., and Example 11: 70 C. This clarifies that the thermally foamable microsphere of the present invention is excellent in the heat resistance.

(132) Moreover, each Example of the thermally foamable microsphere of the present invention has a high expansion ratio. In addition, as shown in Examples 1 and 16, even after heat treated, the expanding starting temperature did not lower, the foaming behavior did not change, and a stable formability was maintained (see Tables 1 and 2, and FIG. 1).

(133) Furthermore, the thermally foamable microsphere of the present invention showed less yellowing at the time of heating. Moreover, in each Example, aggregation did not occur in the middle of polymerization, and thus the thermally foamable microsphere was successfully produced stably.

(134) In contrast, in Comparative Examples 1 and 2 of the monomer mixture in which acrylonitrile was added to methacrylonitrile and methacrylic acid, the mixture was formed into a polymer lump in the middle of polymerization, and thus a normal thermally foamable microsphere was not obtained (see Table 4). Moreover, in Comparative Example 7 in which ethylene glycol dimethacrylate as a cross-linkable monomer was added, the difference between the expanding starting temperature and the maximum expansion temperature was as small as about 4 C. and the expansion ratio also sharply decreased at 220 C. (see Table 4).

(135) Furthermore, in Comparative Example 8, the expanding starting temperature noticeably decreased when the thermally foamable microsphere was not heated and after the thermally foamable microsphere was heated at 170 C. for 2 minutes, and then the foaming behavior sharply changed (see Table 4 and FIG. 2).

INDUSTRIAL APPLICABILITY

(136) The present invention can be used as a technique of producing a thermally foamable microsphere which is excellent in heat resistance and has a high expansion ratio. Making good use of its expandability, the thermally foamable microsphere of the present invention is used as a filler for a paint for automobiles and the like, a foaming agent for wallpaper or foaming ink (for applying relief patterns to T-shirt and the like), a shrink-preventing agents, etc. Moreover, utilizing the volume increase property caused by the foaming, the thermally foamable microsphere of the present invention is used as an additive for the purpose of reducing the weight of polymeric materials such as a synthetic resin (thermoplastic resin, thermosetting resin) and rubber, a paint and various materials making them porous and imparting various functionalities. In particular, the present invention contributes to reducing the weight of interior members or tires of automobiles. Furthermore, the thermally foamable microsphere of the present invention can be suitably used for the fields of a paint, wallpaper, and ink , which are requiring surfaceness and smoothness. The thermally foamable microsphere of the present invention is excellent in processability, and therefore can be suitably used for the fields requiring processing, such as kneading, calendering, extruding, and injection molding.

BRIEF DESCRIPTION OF DRAWINGS

(137) FIG. 1 is a view illustrating changes (foaming behavior) in the degree of expansion between at the expanding starting temperature and at the maximum expansion temperature of a thermally foamable microsphere according to Example 16.

(138) FIG. 2 is a view illustrating changes (foaming behavior) in the degree of expansion between at the expanding starting temperature and at the maximum expansion temperature of a thermally foamable microsphere according to Comparative Example 8.

(139) FIG. 1

(140) 1. Foaming behavior before and after heat treatment (Example 16)

(141) 2. Degree of expansion

(142) 3. Temperature ( C.)

(143) 4. Non heat-treated

(144) After treated at 180 C. for 10 minutes

(145) FIG. 2

(146) 1. Foaming behavior before and after heat treatment (Comparative Example 8)

(147) 2. Degree of expansion

(148) 3. Temperature ( C.)

(149) 4. Non heat-treated

(150) After treated at 170 C. for 2 minutes