US-12617946-B2 - Top coating agent and silvery-white fastening member having protective film formed using said top coating agent

Abstract

The present invention addresses the problem of providing: a top coating agent which forms a protective film demonstrating a beautiful silvery-white appearance, can be adjusted to suppress increases in the friction coefficient even when heat-treated at a high temperature, stabilizes sliding, is strong, and has excellent water resistance, corrosion resistance, and the like; and a fastening member having the protective film formed using said top coating agent. The present invention provides: a top coating agent that includes a polyoxyalkylene amine-based surfactant, a water-soluble modified organopolysiloxane, aluminum flake, and a diluent containing water; and a silvery-white fastening member having a protective film formed using said top coating agent.

Inventors

• Satoshi Takamatsu
• Hiroshi Hirayama
• Mayuko SAKASHITA
• Yoshiki ASAKA
• Bo TONG
• Shinsuke Mochizuki
• Atsushi Murakami
• Hiroyuki Yoshida

Assignees

• DIPSOL CHEMICALS CO., LTD.
• HONDA MOTOR CO., LTD.

Dates

Publication Date

20260505

Application Date

20210401

Priority Date

20200401

Claims (9)

1. 1 . A top coating agent comprising: a polyoxyalkylene amine-based surfactant, a water-soluble modified organopolysiloxane, aluminum flakes, and a diluent containing water.
2. 2 . The top coating agent according to claim 1 , wherein the polyoxyalkylene amine-based surfactant is a polyoxyalkylene amine-based surfactant represented by the following formula: wherein R 1 represents a hydrogen atom or a linear or branched alkyl group or alkenyl group having 1 to 22 carbon atoms, Y each represent a hydrogen atom or a linear or branched alkyl group or acyl group having 1 to 4 carbon atoms, p represents an integer of 1 to 30, q represents an integer of 0 to 30, and at least one of p or q is at least 2.
3. 3 . The top coating agent according to claim 2 , wherein the number of EO moles added (p+q) of the polyoxyalkylene amine-based surfactant is 30 or more.
4. 4 . The top coating agent according to claim 1 , wherein the diluent further contains at least one of water-soluble glycol ethers and water-soluble alcohols.
5. 5 . The top coating agent according to claim 1 , wherein a content of the polyoxyalkylene amine-based surfactant is 20 to 150 g/L.
6. 6 . The top coating agent according to claim 1 , wherein the aluminum flakes are aluminum flakes coated with silica.
7. 7 . The top coating agent according to claim 1 , that is to be formed on a hexavalent chromium-free trivalent chromium chemical conversion film or a chromium-free chemical conversion film to adjust a friction coefficient.
8. 8 . A silvery-white fastening member comprising, on a surface of a metal base plated with zinc: a hexavalent chromium-free trivalent chromium chemical conversion film or a chromium-free chemical conversion film; and a silvery-white protective film on the hexavalent chromium-free trivalent chromium chemical conversion film or the chromium-free chemical conversion film, wherein the silvery-white protective film is a protective film formed using the top coating agent according to claim 1 .
9. 9 . A method for producing a silvery-white fastening member, comprising: coating a fastening member in which a hexavalent chromium-free trivalent chromium chemical conversion film or a chromium-free chemical conversion film is formed on a surface of a metal base plated with zinc, with the top coating agent according to claim 1 , followed by heating and drying at a temperature of 80° C. or more.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national phase of International Application No. PCT/JP2021/014122, filed on Apr. 1, 2021, which claims the benefit of and priority to Japanese Patent Application No. 2020-066100, filed on Apr. 1, 2020, the contents of each of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a top coating agent that imparts excellent slidability, corrosion resistance, and silvery-white appearance, and a silvery-white fastening member using this top coating agent as a protective film. BACKGROUND ART For fastening members, friction coefficients are important for their use. Although fastening members having stable friction coefficients need to be provided, the friction coefficients of fastening members are largely affected particularly by protective films with which the surfaces of the fastening members are coated. For this reason, various friction coefficient stabilizing agents (see Japanese Patent Application Publication No. 2008-37905 and Japanese Patent Application Publication No. 2006-206683, and the like) have been used for protective films of fastening members. However, wax which has been used for stabilizing friction coefficients has a poor dispersibility, and thus there is a problem that sufficiently stable friction coefficients cannot be obtained. In addition, since films formed using top coating agents are of organic substances themselves, there is a problem that such films are susceptible to heat, and thus largely deteriorate when used in an environment where the films are exposed to a high temperature, and thus the functions as protective films for fastening members significantly deteriorate. In order to solve these problems, a top coating agent using a film material mainly composed of a water-soluble modified organopolysiloxane has been developed (see International Publication No. WO2015/029836). Since the film formed by using this top coating agent is mainly composed of a Si—O—Si bond (siloxane bond), the film is resistant to heat, and is thus strong and stable with low deterioration even in an environment where the film is exposed to a high temperature. However, a fastening member coated with this top coating agent has a black appearance. Moreover, this top coating agent tends to impart a higher friction coefficient than organic films, and it is thus necessary to conduct a heat treatment at a high temperature for forming a more stable protective film. In addition, in the case where heat treatment is conducted at a high temperature, there is a problem that the friction coefficient further increases. Hence, the stability of the friction coefficient of the fastening member is not sufficient for use. SUMMARY OF INVENTION Therefore, an object of the present invention is to provide a top coating agent that imparts a beautiful silvery-white appearance, can be adjusted to suppress an increase in friction coefficient even when heat-treated at a high temperature, stabilizes slidability, and forms a protective film strong and excellent in water resistance, corrosion resistance, and the like, and a fastening member having a protective film formed using this top coating agent. The present invention provides a top coating agent described below, and a silvery-white fastening member having a protective film formed using this top coating agent. [1] A top coating agent comprising: a polyoxyalkylene amine-based surfactant, a water-soluble modified organopolysiloxane, aluminum flakes, and a diluent containing water. [2] The top coating agent according to [1], wherein the polyoxyalkylene amine-based surfactant is a polyoxyalkylene amine-based surfactant represented by the following formula: wherein R1 represents a hydrogen atom or a linear or branched alkyl group or alkenyl group having 1 to 22 carbon atoms, Y each represent a hydrogen atom or a linear or branched alkyl group or acyl group having 1 to 4 carbon atoms, p represents an integer of 1 to 30, and q represents an integer of 0 to 30.[3] The top coating agent according to [2], wherein the number of EO moles added (p+q) of the polyoxyalkylene amine-based surfactant is 30 or more. [4] The top coating agent according to any one of [1] to [3], wherein the diluent further contains at least one of water-soluble glycol ethers and water-soluble alcohols. [5] The top coating agent according to any one of [1] to [4], wherein a content of the polyoxyalkylene amine-based surfactant is 20 to 150 g/L. [6] The top coating agent according to any one of [1] to [5], wherein the aluminum flakes are aluminum flakes coated with silica. [7] The top coating agent according to any one of [1] to [6], that is to be formed on a hexavalent chromium-free trivalent chromium chemical conversion film or a chromium-free chemical conversion film to adjust a friction coefficient.[8] A silvery-white fastening member comp