JPH0521155B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a coating composition. More specifically, the present invention relates to a paint composition that has self-healing properties that allow the paint film to regenerate itself when the paint film is damaged by an external force such as an impact. [Prior art and its problems] Conventional paints are made by dissolving or dispersing various resins, cellulose, rubber, etc., which are film-forming elements, in a solvent, and adding various pigments, plasticizers, etc. as necessary. A curing accelerator, a brightening agent, an anticorrosion agent, etc. are further added to the mixture. A strong coating film can be obtained by applying this coating composition and drying or curing it. By the way, the coating film obtained in this way may peel or fall off due to external force such as mechanical impact or rubbing. The scratches formed in this way remain because the paint film does not have self-healing properties, and over a long period of time they deteriorate the aesthetic appearance and can even cause rusting on metal surfaces. Become. [Means for Solving the Problems] The object of the present invention is to provide a coating composition from which a coating film having self-healing properties can be obtained. As a result, damage to the paint film can be repaired because the paint film is regenerated, that is, has self-healing properties, and its performance as a paint film is maintained over a long period of time. That is, the present invention relates to a coating composition containing as components () a polymer having film-forming ability, and () pressure-sensitive microcapsules encapsulating a volatile solvent capable of dissolving the polymer. The invention will be further explained below. The polymer capable of forming a coating film according to the present invention is a non-crosslinked polymer that is normally used in paints and is not subjected to baking or curing. Further, the polymer is soluble in a solvent encapsulated in the microcapsules described below. Specific examples of the above-mentioned polymers include synthetic or semi-synthetic resins such as petroleum resins, polystyrene, xylene resins, acrylic resins, vinyl chloride resins, and nitrocellulose, as well as natural resins such as polyterpene resins, rosin, and shellac. can give. These polymers can be used alone or as a mixture of two or more. In conjunction with the above polymers, pressure sensitive microcapsules are used. This pressure sensitivity means that the capsule is destroyed by pressure and the contained solvent flows out, but it is not destroyed by the minute pressure when compounding the coating composition, and once the coating film is formed, the capsule is This means that the paint film will only break under pressure such that it will be damaged by mechanical impact or pulling. Such adjustment of pressure sensitivity can be easily achieved by adjusting the film-forming substance of the microcapsules, its film thickness, particle size, etc. The pressure-sensitive microcapsules of the present invention encapsulate a volatile solvent. Further, this volatile solvent is a solvent capable of dissolving the polymer forming the coating film described above. Specifically, any solvent can be selected from those commonly used as paint solvents, such as aromatic solvents such as toluene and xylene;
Ester solvents such as ethyl acetate and amyl acetate,
Examples include alcohol solvents such as butanol, ether solvents such as isopropyl ether, and ketone solvents such as methyl isobutyl ketone. When the capsule ruptures, these solvents flow out to the outside, dissolve the polymer around the capsule, and give fluidity to the polymer. As a result, the polymer has self-healing properties and is damaged. The area will be repaired. After repair, it is desirable that the paint film be dry again as before, so the solvent encapsulated in the microcapsules needs to be a volatile solvent. Preferably, a solvent with a low boiling point, for example, a boiling point of 260° C. or less, which dissolves the polymer forming the coating film, is selected from the above-mentioned solvents. The manufacturing method of the microcapsule itself is a known method,
For example, they are prepared by core cervation, in situ polymerization or interfacial polymerization. In addition, the film-forming substance of the capsule is one that does not dissolve or swell in the encapsulating solvent, such as gelatin,
It is appropriately selected from polyurea, polyamide, polyurethane, epoxy resin, polyethylene, polystyrene, etc. If the particle size of the microcapsules is too large, it may cause uneven coating, which is undesirable. Usually 1μ
Capsules with an average particle size of ~500μ are used. In the present invention, 5 to 2,000 parts by weight, preferably 10 to 500 parts by weight of microcapsules as a capsule encapsulating solvent are mixed and used per 100 parts by weight of the polymer as the coating film forming substance.
If it exceeds 2000 parts, the coating film will sag or become sticky when the capsule is broken, which is not preferable. To apply the coating composition of the present invention, the above-mentioned polymer and microcapsules are mixed with a suitable coating solvent and used. This paint solvent can be appropriately selected from common paint solvents as long as it does not dissolve or swell the membrane material of the microcapsules. In this coating solvent, the above-mentioned polymer is dissolved or emulsified with the aid of an emulsifier or the like. For example, aromatic solvents such as toluene and xylene, ester solvents such as ethyl acetate and amyl acetate, alcohol solvents such as butanol, ether solvents such as diisopropyl ether, ketone solvents such as methyl ethyl ketone,
Alternatively, general paint solvents such as mixed solvents thereof can be used. Furthermore, the compositions of the invention can also be used in the form of aqueous emulsions. The amount of paint solvent or water used during emulsion is arbitrarily determined depending on workability during application. The above paint solvent may be the same as the capsule encapsulating solvent, but other appropriate solvents may also be used. Furthermore, the composition of the present invention may contain conventionally known fillers, organic or inorganic pigments, dyes, plasticizers, etc. in arbitrary proportions within the range that achieves the effects of the present invention. In addition, conventionally known rust preventives and the like can also be used. The coating composition of the present invention can be used for coating various materials such as metal, plastic, wood, and concrete in the same way as general coatings. In particular, it is preferable to paint metal because it not only maintains its aesthetic appearance but also further maintains and improves its rust prevention effect. [Effects of the present invention] In the coating composition of the present invention, even if the coating film is damaged by external force, the solvent contained in the coexisting microcapsules flows out due to the destruction of the capsules at the time of damage, and the surrounding area of the capsules is As a result of dissolving the polymer as film-forming substance, the film reformes, ie self-heals. Therefore, a coating film made from the coating composition of the present invention can maintain its beauty even if it is damaged, and when coated on metal, it can also maintain and maintain its antirust effect. [Examples] Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 (Preparation of coating composition-1) The following compositions were mixed to prepare coating composition-1.
was prepared. Note that the petroleum resin was used after being dissolved in toluene. Petroleum resin ^* 33 parts by weight Toluene 50 〃 Solvent-encapsulated microcapsules ^** 17 〃 *Nippon Petrochemical Co., Ltd.'s "Nisseki Neopolymer NP-120" (product name) **Encapsulated solvent: Aromatic solvent (boiling point 184) ~210
℃) [Nisseki Hysol #150 (trade name) manufactured by Nippon Petrochemicals Co., Ltd.] Microcapsule: Polyurea microcapsule average particle size 3μ (Application of composition to steel plate and rusting test) Specified in JIS Z 0236 The above composition was applied to a polished steel plate test piece in an amount of 0.3 g per side, and dried at 50°C for 25 minutes. Six coated test pieces were prepared, three were left as they were, and the remaining three were cut in a 5 mm square grid pattern, with a circumference of 2.5 mm.
(width) with a knife. The cut was deep enough to reach the surface of the steel plate. Each test piece was left at 25°C for 5 hours. Next, each test piece was subjected to a salt spray test according to the method specified in 6.2 of JIS Z 0236, and the occurrence of rust was observed. The results are shown in Table-1. For reference, Table 1 also shows the results of a salt spray test on test pieces of the same shape that were not coated with any of the above compositions. Comparative example 1 (Preparation of coating composition 2) Petroleum resin ^* 40 parts by weight Toluene 60 * "Nisseki Neopolymer NP-120" (trade name) (Application of composition to steel plate and rusting test) Example 1 Similarly, six test pieces were prepared by applying the above composition and drying, and three test pieces were left as they were.
The three sheets were cut in the same way as in Example 1 and subjected to a salt spray test, and the results of testing for rust occurrence are also shown in Table 1.

[Table] (Comparative test of paint film repair ability) The compositions of Example 1 (E) and Comparative Example 1 (R) were applied to a glass plate and dried at room temperature for 16 hours to obtain a dry paint film. Next, a cut was made in the coating film with a knife, and the coating film was left to stand at room temperature, and the recovery of the coating film over time was observed. In the coating film of Example 1 (E), it was clearly observed that the damage caused by the cuts had recovered over time, and after 24 hours, the coating had recovered to the extent that the cuts caused by the knife could hardly be recognized. On the other hand, in the coating film of the comparative example, cuts made by the knife were clearly visible even after 24 hours, and the damaged area had not recovered.

Claims (1)

[Scope of Claims] A coating composition comprising, as one component, () a polymer having film-forming ability, and () pressure-sensitive microcapsules encapsulating a volatile solvent capable of dissolving the polymer. 2. The coating composition according to claim 1, which contains the microcapsules in an amount of 5 to 2000 parts by weight of the volatile solvent per 100 parts by weight of the polymer.