JP5506832B2 - Low VOC electrodeposition coating composition for vehicle parts - Google Patents

Description

  The present invention relates to an electrodeposition coating composition that forms a wear-resistant lubricating film on a vehicle portion having a sliding surface.

  A film containing a solid lubricant such as polytetrafluoroethylene (PTFE), graphite, or molybdenum disulfide is formed on a sliding surface of a machine part that is not suitable for use with a liquid lubricant. Lubricant coatings need to be formed on the surface of parts with complex shapes with a uniform film thickness, so the electrodeposition coating method with excellent throwing power is suitable, and the electrodeposition paint is a water-based paint. Therefore, it can contribute to the reduction of VOC.

  Japanese Patent Application Laid-Open No. 2008-88416 (Patent Document 1) describes a mixture of molybdenum disulfide and PTFE in a weight ratio of 5:95 to 70:30, and a weight ratio of the coating resin solid content of 95: 5 to 50: A paint blended with an alkyd resin-based or polybutadiene resin-based anionic electrodeposition paint so as to be 50 is disclosed. This paint uses PTFE, which has the lowest friction coefficient among solid lubricants, and molybdenum disulfide, which has a lower friction coefficient than PTFE but has a higher usable temperature than PTFE, and has a low friction coefficient and load resistance at high temperatures. It was developed with the intention of achieving a good balance.

JP 2008-88416 A

  The coating is satisfactory in the field of use where its intended performance is required, but it has a lower friction coefficient, wear resistance, and such coating by electrodeposition coating. It would be desirable to provide a coating composition that forms.

  In order to satisfy the above-mentioned demand, the present invention provides an anti-resisting material containing polytetrafluoroethylene particles having a weight ratio of 90:10 to 60:40 of an anionic modified epoxy resin capable of electrodeposition and the solid content of the resin. An anion electrodeposition coating composition for forming an abrasion-resistant lubricating film and an abrasion-resistant lubricating coating film formed by electrodeposition coating of the coating composition are provided.

  The coating composition of the present invention comprises polytetrafluoroethylene (hereinafter abbreviated as PTFE) particles having the smallest coefficient of friction among solid lubricants and an electrodepositable anionic modified epoxy resin serving as a matrix of PTFE particles. It consists of an electrodeposition paint as a vehicle resin.

  PTFE is well known as a solid lubricant and is commercially available. The average particle diameter is preferably in the range of 0.1 to 10 μm from the viewpoint of easy dispersion in the paint.

  The electrodepositable anionic modified epoxy resin used in the present invention is, for example, a bisphenol type epoxy resin or a modified epoxy ester obtained by ring-opening a part of its epoxy group with an unsaturated fatty acid, a glycidyl group-containing vinyl monomer and It is produced by graft copolymerizing a carboxy group-containing vinyl monomer to a polymerizable unsaturated group-containing modified epoxy resin obtained by reacting with an amine. See JP2003-26739A, JP2007-238881, JP2005-120340A, and WO2009 / 066588. This modified epoxy resin has a bisphenol skeleton excellent in anticorrosion properties, and has a polymer graft chain having a large number of pendant carbosyl groups.

  For coating, this resin must be dissolved or dispersed in water containing a neutralizer and optionally a small proportion of a water miscible organic solvent. It is preferable that the PTFE particles are dispersed in the resin before coating, and then water and a neutralizing agent are added to obtain a final electrodeposition coating. Arbitrary inorganic and organic bases can be used as the neutralizing agent, but ammonia, triethylamine, dimethylethanolamine and the like that do not remain in the coating film after baking are preferable. The amount of the neutralizing agent is an amount for adjusting the pH of the paint to 8 to 10 after neutralization. Of course, in addition to PTFE, the paint may contain a color pigment, a rust preventive pigment, a curing agent, for example, a conventional additive such as a melamine resin.

  According to the present invention, the weight ratio of resin solid content: PTFE in the coating is required to be 90:10 to 60:40. Here, “resin solid content” means the total amount of an anionic modified epoxy resin and a curing agent, if present. When the weight ratio of the resin solid content and PTFE is within this range, the wear resistance and the lubricity are well balanced. The total amount of resin solids and PTFE in the paint is preferably 20 to 40 wt%.

  The coating is performed using the object to be coated as an anode, electrodepositing the paint with an applied voltage of 50 to 250 V and an energization time of 2 to 3 minutes, then washing with water and heating to 200 to 250 ° C. to cure the coating film. The film thickness after coating is usually 5 to 20 μm.

  The objects to be coated are mechanical parts that require wear resistance and lubricity, especially vehicle parts such as shafts, joint parts, hinge parts, bearings, plungers, pins, etc., and their materials are iron, aluminum, stainless steel, etc. However, it can also be applied to those obtained by plating or chemical conversion treatment.

  The following examples are illustrative of the invention and are not intended to be limiting. In these, “parts” and “%” are based on weight unless otherwise specified.

Example 1
100 parts of an anionic modified epoxy resin (Arakawa Chemical Industries, trade name KA-1828A, solid content 36%) and 12 parts of PTFE particles are kneaded and uniformly dispersed, and the required amount of water and dimethylethanol are dispersed. An amine was added and stirred to obtain an anionic electrodeposition coating material having a solid content of 20%, pH 9.0, and resin solid content: PTFE = 75: 25.

Example 2
An anionic electrodeposition coating material having a solid content of 20%, pH 9.0, and resin solid content: PTFE = 90: 10 was obtained according to the procedure of Example 1 except that the amount of PTFE particles added was changed to 4 parts.

Example 3
An anionic electrodeposition paint having a resin solid content: PTFE = 60: 40 was obtained according to the procedure of Example 1 except that the amount of PTFE particles added was changed to 24 parts.

Example 4
The coating materials of Examples 1 to 3 were each electrodeposited onto a SPCC steel sheet treated with zinc phosphate in advance by a constant voltage method, washed with water and baked at 230 ° C. for 20 minutes to form a lubricating film having a dry film thickness of about 10 μm. .

  For comparison, PTFE particles are uniformly dispersed in a commercially available solvent-type epoxy resin paint with a resin solid content: PTFE = 70: 30, and air spray-coated on an SPCC steel plate treated in advance with zinc phosphate, at 180 ° C. for 20 minutes. A comparative lubricating film having a dry film thickness of about 22 μm was formed by baking.

  About the lubricating film of the Example and the comparative example, the static friction coefficient and the dynamic friction coefficient were measured by the following method, and the abrasion resistance test was done.

Using a surface property tester (manufactured by Shinto Kagaku Co., Ltd., tribogear type HEIDON 14FW) with a SUS304 ball having a static friction coefficient diameter of 5 mm, slide the ball 10 mm at a load of 1 kg and a speed of 600 mm / min. Then, the coefficient of static friction was measured.

The dynamic friction coefficient was measured by the same method as the measurement method of the dynamic friction coefficient and static friction coefficient.

Wear resistance test Using the same surface property test machine used for static friction coefficient measurement, the ball was reciprocated with a stroke of 10 mm at a load of 1 kg and a speed of 2400 mm / min until the static friction coefficient reached 0.4. Was evaluated.

The results are shown in Table 1.

Discussion Although the lubricating film of the present invention is comparable to the lubricating film of the comparative example in terms of the coefficient of friction, it can be seen that it has excellent wear resistance despite the film thickness being about half.

Claims (4)

An anionic modified epoxy resin that can be electrodeposited and polytetrafluoroethylene particles, wherein the weight ratio of the solid content of the resin: polytetrafluoroethylene is 90:10 to 60:40, and the electrodepositable anionic modification A vinyl group-containing modified epoxy resin obtained by reacting a bisphenol type epoxy resin or a modified epoxy ester obtained by ring-opening a part of its epoxy group with an unsaturated fatty acid with a glycidyl group-containing vinyl monomer and an amine. An anionic electrodeposition coating composition for forming a wear-resistant lubricating film, characterized in that it is a resin having a vinyl polymer chain having a plurality of pendant carboxyl groups introduced thereto by graft copolymerization.   The anion electrodeposition coating composition according to claim 1, wherein the total of the resin solid content and the polytetrafluoroethylene particles is 20 to 40 wt% of the coating. A wear-resistant lubricating film formed on the surface of a metal mechanical part requiring lubricity by the electrodeposition paint of the anionic electrodeposition paint composition of claim 1 or 2 . 4. The lubricious coating according to claim 3 , wherein the metal mechanical part is a vehicle part.