Coating composition, preparation method therefor and use thereof

Abstract

A coating composition, a preparation method therefor and use thereof are provided. The coating composition includes at least 60% heat-expandable microspheres having a wall thickness of less than or equal to 5 m, a water-based thermoplastic resin, a water-based thermosetting resin, and a hot-melt filling resin. Thin-shell spheres can be quickly softened and ruptured within a short time in the heat-expansion process, and with the volatilization of an organic solvent, the coating composition cross-links with a resin matrix in the coating to form a cross-linked network structure, thus strengthening the gap support of the coating, and enabling the coating to achieve stepped expansion. After expansion, some polymer materials wrap an airbag and harden to form a stable hollow structure. Therefore, the expanded coating can be used for the fixation of high temperature-resistant parts, and can maintain adhesive stability when placed in a high-temperature environment (140-180 C.) for a long time.

Claims

1. A coating composition, comprising: based on a total weight of the coating composition, no more than 20% by weight of a composition of heat-expandable microspheres, 10%-30% by weight of a water-based thermoplastic resin, 10%-40% by weight of a water-based thermosetting resin, and 10%-35% by weight of a hot-melt filling resin, wherein: at least 60% of the heat-expandable microspheres have a wall thickness5 m; a weight the heat-expandable microspheres having a particle size of 8 mD20 m is no less than 60% of the total weight of the heat-expandable microspheres; each of the heat-expandable microspheres comprises a thermoplastic polymer shell and a liquid alkane enclosed within the thermoplastic polymer shell, the liquid alkane being selected from ethane, propane, isobutane, n-pentane, isopentane, and mixtures thereof; the composition of the heat-expandable microspheres comprises dodecanol ester, an inorganic fiber selected from a nano-aluminosilicate fiber, a carbon fiber, a boron fiber, and mixtures thereof; wherein: the water-based thermoplastic resin is at least one selected from water-based acrylic resin and polyurethane resin; the water-based thermosetting resin is at least one selected from water-based epoxy resin and hydroxyl acrylic acid resin; the hot-melt filling resin is at least one selected from modified chlorinated polyvinyl chloride, polyester resin, polyurethane, polyamide, polyether sulfone, epoxy, and polymethylmethacrylate; a weight ratio of the water-based thermoplastic resin to the water-based thermosetting resin is 1:1-1:2; and a weight ratio of a sum of the water-based thermoplastic resin and the water-based thermosetting resin to the hot-melt filling resin is 1.5:1-2.5:1.

2. The coating composition according to claim 1, wherein a weight ratio of the heat-expandable microspheres to the dodecanol ester is (4-40):1.

3. The coating composition according to claim 1, wherein the coating composition further comprises one or more coating additives selected from a curing agent, a dispersant, a defoamer, a filler, a cross-linking agent, a thickener, and a colorant.

4. The coating composition according to claim 3, wherein the one or more coating additives account for less than 15% of the total weight of the coating composition.

5. The coating composition according to claim 3, wherein the sum of the weight percentages of the composition of heat-expandable microspheres, the water-based thermoplastic resin, the water-based thermosetting resin, and the hot-melt filling resin in the coating composition is 100%.

6. The coating composition according to claim 1, wherein the heat-expandable microspheres have an initial thermal expansion temperature T.sub.1, wherein 100 C.T.sub.1200 C.

7. The coating composition according to claim 1, wherein the heat-expandable microspheres have a maximum heat-resistant temperature T.sub.2, wherein 145 C.T.sub.2215 C.

8. The coating composition according to claim 1, wherein the inorganic fiber and the dodecanol ester are in a weight ratio of 2:1 or less.

9. The coating composition according to claim 1, wherein the composition of the heat-expandable microspheres has an expansion rate of 150%-300%.

10. The coating composition according to claim 1, wherein the coating composition further comprises water.

11. A matrix comprising a coating and a matrix body, wherein the coating has the coating composition according to claim 1.

12. The matrix comprising the coating and the matrix body according to claim 11, wherein the coating has a thickness of 100-300 m.

13. The matrix comprising the coating and the matrix body according to claim 11, wherein the coating is disposed on a surface of the matrix body.

14. A method for preparing a heat-expandable coating, comprising applying the coating composition according to claim 1 to a matrix body, and heating the matrix body to obtain the heat-expandable coating.

15. The method for preparing the heat-expandable coating according to claim 14, wherein the matrix body is a magnetic material.

16. The method for preparing the heat-expandable coating according to claim 14, wherein the heat-expandable coating has a dry film thickness of 100-300 m.

17. A preparation method for the coating composition according to claim 1, comprising mixing a composition of heat-expandable microspheres, a water-based thermoplastic resin, a water-based thermosetting resin, a hot-melt filling resin, and one or more coating additives selected from a curing agent, a dispersant, a defoamer, a filler, a cross-linking agent, a thickener, and a colorant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a photograph of the coating of Example 7 in an unexpanded state (scale: 100 m, 500 magnification).

(2) FIG. 2 shows a photograph of the coating of Example 7 in an expanded state (scale: 100 m, 500 magnification).

(3) FIG. 3 shows a state where a magnet with an expandable coating is assembled to a motor rotor tooling;

(4) in the figure: 1 indicates an expandable coating; 2 indicates a sintered magnet; 3 indicates a reserved gap; 4 indicates a motor tooling.

(5) FIG. 4 shows a comparison of IR spectra of the coating of Example 7 before and after expansion and foaming.

DETAILED DESCRIPTION

(6) The technical solutions of the present disclosure will be further illustrated in detail with reference to the following specific examples. It will be understood that the following examples are merely exemplary illustrations and explanations of the present disclosure, and should not be construed as limiting the protection scope of the present disclosure. All techniques implemented based on the content of the present disclosure described above are included within the protection scope of the present disclosure.

(7) Unless otherwise stated, the starting materials and reagents used in the following examples are all commercially available products or can be prepared using known methods.

(8) The heat-expandable microspheres used in the present disclosure are commercially available, and are, e.g., a composition of two or more selected from 920DU80, 920DU20, 909DU80, 920DU40, and 461DU40 in the Expancel series from AKZO-Nobel.

(9) The following table shows the main parameters of five heat-expandable microspheres in the Expancel series from AKZO-Nobel.

(10) TABLE-US-00001 Initial Maximum heat- expansion resistant Diameter temperature temperature Model (1)/m T.sub.1/ C. T.sub.2/ C. 920DU80 18-24 123-133 185-195 920DU20 5-9 120-145 155-175 909DU80 18-24 120-130 175-190 920DU40 10-16 123-133 185-195 461DU40 9-15 100-107 145-152

Examples 1-5

(11) The expandable microspheres, the dodecanol ester, and the inorganic fiber in the composition of the heat-expandable microspheres are in a weight ratio of 8:1.2:0.8, that is, the weight percentages of the components are as follows: 8 wt % expandable microspheres, 1.2 wt % dodecanol ester, and 0.8 wt % inorganic fiber.

(12) The compositions of heat-expandable microspheres as shown in Table 1 comprise heat-expandable microspheres.

(13) A combination of different heat-expandable microspheres in the Expancel series from AKZO-Nobel was used. The microspheres of model 920DU80 and model 461DU40 were mixed homogeneously in a weight ratio of 1:2 to obtain a composition of heat-expandable microspheres having an initial particle size of 15.50 m (as determined by BFS-MAGIC from sympatec, Germany) and a mean wall thickness of 2 m, with 90% of the microspheres having a wall thickness5 m (Examples 1-5).

(14) The preparation method for the coating compositions of Examples 1-5 comprises the following steps:

(15) firstly, mixing expandable microspheres, a dodecanol ester, and a nano-aluminosilicate fiber to prepare a composition of the heat-expandable microspheres, then adding the composition of the heat-expandable microspheres and other coating additives (a filler of insulating carbon black and a dispersant of ethylene glycol) to a water-based coating resin under stirring at a low shear rate.

(16) Coating composition samples 1-5 were prepared according to the proportions in the table below.

(17) TABLE-US-00002 TABLE 1 Components of coatings Component Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Water-based acrylic resin (wt %) 20 25 15 35 8 Water-based epoxy resin (wt %) 30 25 30 10 26 Polyester resin (wt %) 25 30 30 30 44 Insulating carbon black (wt %) 2 2 2 2 2 Ethylene glycol (wt %) 0.5 0.5 0.5 0.5 0.5 Expandable composition (wt %) 10 10 10 10 10 Water-based organosilicon resin (wt %) 2 1 5 5 4.5 Water (wt %) 10.5 6.5 7.5 7.5 9.5

Examples 6-11

(18) The content, the particle size, and the wall thickness of the expandable microspheres and the components and the content of the high-boiling-point solvent in the composition of the heat-expandable microspheres will affect the performance of the expandable coating, and the amount of the expandable microspheres, the solvent, and the inorganic fiber as the composition of the heat-expandable microspheres will affect the performance of the coating composition, which in turn will affect the performance of the expandable coating made from the coating composition.

(19) In Examples 6-11, coating composition samples 6-11 were prepared by adjusting components of the composition of the heat-expandable microspheres.

(20) Combinations of different heat-expandable microspheres in the Expancel series from AKZO-Nobel were used. The microspheres of model 920DU80 and model 461DU40 were mixed in a weight ratio of 1:2 to obtain a combination of heat-expandable microspheres having an initial particle size of 15.50 m (Example 6);

(21) the microspheres of model 920DU80, model 920DU20, and model 920DU40 were mixed in a weight ratio of 1:1:1 to obtain a combination of heat-expandable microspheres having an initial particle size of 13.10 m (Examples 7, 8, 9, and 10);

(22) the microspheres of model 920DU80, model 909DU80, and model 920DU40 were mixed in a weight ratio of 1:1:1 to obtain a combination of heat-expandable microspheres having an initial particle size of 17.30 m (Example 11).

(23) The coating composition samples 6-11 contain 25 wt % water-based urethane resin, 35 wt % water-based epoxy resin, 15 wt % urethane resin, 10 wt % polymethylmethacrylate, 1 wt % water-based organosilicon resin, 1 wt % dispersant of ethylene glycol, 2 wt % filler of insulating carbon black, 0.5 wt % thickener of acrylic acid, and 0.5 wt % defoamer of polydimethylsiloxane, and their difference in the composition of the heat-expandable microspheres is shown in Table 2 below.

(24) The preparation method for the coating compositions comprises the following steps:

(25) firstly, mixing expandable microspheres, a dodecanol ester, and a nano-aluminosilicate fiber to prepare a composition of the heat-expandable microspheres, then adding the composition of the heat-expandable microspheres and other coating additives (a filler of insulating carbon black, a thickener of acrylic acid, a defoamer of polydimethylsiloxane, and a dispersant of ethylene glycol) to a water-based coating resin under stirring at a low shear rate.

(26) TABLE-US-00003 TABLE 2 Components of compositions of heat-expandable microspheres Sample Sample Sample Sample Sample Sample Component 6 7 8 9 10 11 Content of expandable microspheres 9 8 6 8 8 9 wt % Initial particle size of expandable 15.50 13.10 13.10 13.10 13.10 17.30 microspheres m Proportion % of expandable 82 75 75 75 75 50 microsphere having a particle size of 8 m D.sub.0 20 m of the total weight Proportion % of expandable 60 30 30 30 30 30 microsphere having a particle size of 10 m D.sub.0 15 m of the total weight Mean wall thickness of expandable 2 3.5 3.5 3.5 3.5 3 microspheres .sup.[1] m Proportion % of expandable 90% 70% 70% 70% 70% 50% microsphere having a wall thickness 5 m Dodecanol ester wt % 0.5 1 2 0 2 0.5 Nano-aluminosilicate fiber wt % 0.5 1 2 2 0 0.5 Note: .sup.[1] the mean wall thickness of the heat-expandable microspheres was obtained by testing with a scanning electron microscope (SEM) S-4700 from Japan Hitachi, and was the mean value of the wall thicknesses of all the microspheres (20) on the visual interface.

(27) The coating composition samples of Examples 1-11 were each applied to the surface of a magnetic sheet by roller brush coating, and the surface coating was dried and hardened at room temperature. The hardened coating has certain corrosion resistance, which is convenient for transportation and protection of the magnetic sheet. After the magnetic sheet was transported to the workplace, for example, after the magnetic sheet was transported to a motor rotor assembly site, the magnetic sheet assembly was inserted into a slot of the motor rotor, and the motor rotor assembled with the expandable coating was placed in a high-temperature oven and heated for 10 min when the temperature in the high-temperature oven reached 180 C. The surface of the magnet was coated with a heat-expandable coating, which was softened and expanded after being heated. The expandable microspheres were expanded first after being heated, and then the shell of the expandable microspheres was softened and broken up under the action of a high-boiling-point solvent, and was cross-linked with a resin matrix in the coating to form a coating structure with stable support.

(28) As can be seen from FIGS. 1 and 2, the surface of a sintered neodymium-iron-boron magnet was coated with the coating composition of Example 7, and after curing at room temperature, the magnet coated with an expandable coating was obtained. The results are shown in FIG. 1. The magnet coated with the expandable coating was further heated at 190 C. for 10 min to expand the coating, and a cross-linked coating structure was obtained (see FIG. 2).

(29) As shown in FIG. 3, 1 indicates an expandable coating; 2 indicates a sintered magnet; 3 indicates a reserved gap for motor assembly; 4 indicates a motor tooling. The sintered magnet 2 with the expandable coating 1 (wherein: the sintered magnet has a specification of 40 mm15 mm5 mm) was assembled into the motor tooling 4, the reserved gap for motor assembly was 250 m, and the thickness of one side of the expandable coating was 110 m, and the assembly was performed at an expansion temperature. The coating was expanded when being heated to fill the reserved gap of the motor, so that the magnet was tightly fixed in the motor tooling. In this state, the adhesion thrust of the magnet in the motor tooling at room temperature and at a high temperature of 170 C. was detected.

(30) FIG. 4 shows the results for IR spectrum characterization of the coating of Example 7 before and after expansion and foaming. As can be seen from the figure that: after the expansion of the coating, the peak intensity of the characteristic peaks at a wavelength of 1016.36 cm.sup.1 and a wavelength of 725.74 cm.sup.1 was significantly enhanced, which may be because the resin in the coating reacted again in the high-temperature expansion process of the coating and formed a cross-linked coating structure, so that the coating structure had stable support.

(31) TABLE-US-00004 TABLE 3 Expansion conditions and test conditions Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample 1 2 3 4 5 6 7 8 9 10 11 Expansion 190 190 190 190 190 190 190 190 190 190 190 temperature/ C. Expansion time/min 10 10 10 10 10 10 10 10 10 10 10 Thickness of coating 110 110 110 110 110 110 110 110 110 110 110 film/m Adhesion thrust 1305 1300 1200 1088 1005 1305 1288 1260 1088 1080 1052 (room temperature)/Newton Adhesion thrust 300 305 266 215 200 353 335 306 220 230 188 (170 C.)/Newton

(32) As can be seen from the results in Table 3 that: changing the amount ratio of the water-based thermoplastic resin to the water-based thermosetting resin and/or the amount ratio of the water-based thermoplastic resin and the water-based thermosetting resin to the hot-melt resin will affect the adhesive thrust of the coating after being cured. By reasonably optimizing the amount ratio of the resins described above, the present disclosure surprisingly found that when the amount ratio of the water-based thermoplastic resin to the water-based thermosetting resin was 1:1-1:2, and the amount ratio of the water-based thermoplastic resin and the water-based thermosetting resin to the hot-melt resin was within the range of 1.5:1-2.5:1, the adhesion thrust of the coating at room temperature could be improved, especially the adhesive thrust of the coating after high-temperature expansion, so that the use requirements of the motor under the high-temperature working conditions could be met.

(33) The performance test results for samples 6-11 showed that: changing the amount ratio of the expandable microspheres, the solvent, and the inorganic fiber in the composition of the heat-expandable microspheres will affect the adhesion thrust of the coating after high-temperature expansion.

(34) The embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the embodiments described above. Any modification, equivalent, improvement, and the like made without departing from the spirit and principle of the present disclosure shall fall within the protection scope of the present disclosure.