JPS59177378A - Treatment of iron in ferric phosphate chemical bath for highsolid paint - Google Patents

Abstract

A process for treating ferrous substrates for receiving a high-solids organic solvent-thinned coating by which inadvertent drippage or splashing of the dry phosphated surfaces with the iron phosphating solution does not produce blemishes, discolourations and/or surface imperfections in the final painted surface, comprises employing an aqueous iron phosphating solution devoid of any conventional inorganic oxidants or accelerating agents such as chloride or chlorate and employs an organic oxidizing agent, preferably meta nitrobenzene sulphonic acid or a salt thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention performs an iron phosphate film chemical conversion treatment on a y-grained iron-based substrate of steel, and then performs a high solids solvent type, IK I1
This relates to an improved method for applying one or more coats of paint, which reduces the surface defects of the rock coating and provides a uniform and smooth surface finish with no visible discoloration or roughness. be done.

1l17 strengthens its eating habits and continues? The application of iron sulfate coatings to iron-based substrates to improve the adhesion of T machine coatings or paint has been known and practiced for many years.

For example, saliva salt 1 friend salt,
Various inorganic oxidizing agents such as chlorates, odoropharyngeal salts, molybdates and fluorates have been added to improve the silicone compared to films obtained with alkali metal monophosphates that do not contain any such oxidizing agents. Means have been commonly used to improve the physical properties of the phosphate film, improve the crystal structure, and increase the ae of the film. Iron phosphate containing inorganic compound 1. Although very satisfactory results can be obtained when using a single layer known solvent-based organic paint formulation for the film chemical conversion treatment solution, it is also possible to apply a so-called high-solid type paint that has been put into practical use in the past few years. In some cases, there is a problem that surface discoloration and/or roughening of the organic film and/or reduction in brightness may occur partially.

The reason for the adoption of high solids paints is the Air Pollution Control Regulations, which were further strengthened by the EPA to effectively reduce the release of 41-containing solvents into the air. It depends. While conventional solvent-borne paint formulations have a solids content of less than about 45% by volume, high-solids (or low-bath agent) solvent-borne paint formulations typically have a solids content of about 50% by volume. The solid content is often 60 vol.% or more, or more. Such high solids paint formulations contain polymers of substantially lower molecular weight than the molecular layer of polymers used in conventional solvent-borne paint systems to achieve sprayable viscosities.

Because of the lower molecular weight of the polymer components in high solids paints, these paints are much more sensitive to surface imperfections and tend to create craters around the imperfections, which can be completely offset. .

Part of the reason for this is believed to be that with this binder paint formulation, when the solvent evaporates, it falls off from the high points of the surface and becomes thinner, making the presence of such defects more noticeable.

The problem with using conventional iron sinate coating conversion solutions containing inorganic oxidizers with vine lid type paint formulations is:
A major cause of this is the dripping of iron sinate solutions onto the dry chemically treated surfaces from the racks or conveyor systems in which the parts are transported. Scattering or dripping results in local precipitation of white salts on the chemically treated surface for which the binder paint is applied, causing the precipitated salts to bleed through the final abrasive paint film. This tends to cause a white ring V with a relatively dull appearance to appear in the center of one piece of meat. When such defects occur, the coating preparation must often be reprocessed.

The same problem is also seen when parts that have been sanded are subjected to pyrophosphate conversion treatment to remove surface defects.

According to the method of the present invention, even if an isolid paint formulation is used, such ingress points can be overcome or reduced, and even in this case, the effectiveness of the oxidizing agent is lost during the night in the phosphate film conversion treatment bath. It's not enough.

The benefits and inventive step of this invention reside in that the iron-synthetic-based coating conversion treatment solution contains a constant and highly effective enzyme oxidizing agent in the form of metanitrobenzene sulfonic acid and its hot bath-dissolvable and compatible salts. This can be achieved by a method that provides improved quality coatings at a commercially acceptable rate and eliminates isolide paint even when the debris is splattered or dripped onto the chemically treated surface. The final painted surface using the formulation is free of chips, discoloration and/or defects. In the practice of this invention, the phosphate chemical solution is added in an amount of about 0
．． 1 to about 31! /l of metanitrobenzenesulfonic acid or a salt thereof, the pH of the bath is controlled at about 4.2 to about 6, and the bath temperature is about 70 to about 12
Apply to a clean iron substrate at 0 DEG F. (21-49') for a time sufficient to achieve the desired J thickness. Usually, the sinate chemically treated substrate is rinsed with water, preferably diluted ROM water solution, and then dried. Then apply one or more coats of Norisolid's solvent diluted paint over it. 9 drops of phosphate solution applied on dry phosphate treated surfaces or previously painted remanufactured parts will result in surface imperfections and discoloration caused by inadvertent rust stains. It has been found that this can substantially reduce the incidence of defective products and improve the appearance of the product.

In the method of the present invention, a ferrous substrate, such as steel, is subjected to a series of surface treatments, ultimately forming an article or component having a cross-linked and cured organic paint coating on its surface. The parts are usually cleaned to remove surface contaminants, but this operation may be carried out using a well-known alkaline cleaning bath. If necessary, pickle the surface further to remove surface rust. Then, after rinsing with water, an iron sulfate treatment is carried out, and a uniform phosphate coating is applied thereon. Then, usually after rinsing with water, the hole is sealed using an acidic dilute chromium water bath. After drying, it is then painted using a can of solid organic solvent-based paint, which includes a prime coat followed by one or more top coats or a direct top coat with sicate conversion treatment. It includes a step of applying it to the surface of. This 211 machine paint film is usually heated and baked to completely cure the crosslinking before shipping (this is inspected. If there is a defect on the surface, remove all parts from the rack and sand them.) After removing surface defects, the L111 part is returned to the rank and subjected to the same series of repeat steps described above.

This iron phosphate chemical treatment solution contains an effective amount of alkali metal primary sinate containing ammonium to form the desired iron sinate film on the iron yarn base. Typically, such primary phosphates include sodium dihydrogen phosphate, sodium pyrophosphorobutyrate, and the like, with concentrations ranging from about 3 to about 607/m, preferably from about 4 to about i
present in combination with free phosphoric acid in an amount of o yit.

Some free cynic acid was added according to the known flJ
H may be adjusted and sodium hydroxide or sodium carbonate may also be added for the same purpose to neutralize some or all of the free phosphoric acid. The phosphate coating solution is operated at a p I-I of about 4.2 to 6, preferably about 5.5, and most preferably about 5.

In this phosphate solution, G moss and a certain amount of acid 71
] Also, (iii) organic metanitrobenzenesulfonic acid and/or its bath-soluble/compatible Lg species 75 as an accelerator; contained therein to improve the physical properties of the deposited chemical conversion film.

-g of this metanitrobenzenesulfone salt is about 0.1
~3 yit, preferably about 0.2~1.5F/2
used at a concentration of One formulation of the iron phosphate conversion bath disclosed in U.S. Pat.
Or, if you convert directly with this salt, about 0.5 to about 4% H,,Hj
Corresponding bath promotion was achieved when Qiso salt salts were used.

The aqueous conversion solution is applied by spraying, dipping or flooding onto a clean ferrous substrate for about 5 seconds to several minutes or more, the time being determined depending on the desired film thickness and the properties of the conversion coating to be deposited. The bath temperature is approximately 70℃.
°F (21 °C) to a temperature at which decomposition of metanitrobenzenesulfonic acid and/or salt does not occur, and approximately 70 °F
F to about 120°F (21-49°C) is preferred, about 10
0°F to about 110°F (38-43°C) is typical. Under such conditions, the adhesive phosphoric acid is used, and film car sickness is about 10 mg/ft2 to about 1 ft2 depending on the conditions.
[] Q+ng/ft2 (108M9/m” ~108
0 mg/m”) or more.

The solution may also contain various surfactants and/or emulsifiers commonly used in metal cleaning operations, which are compatible with the forming and oxidizing agents and are It coexists with the process and performs cleaning functions.

Following the chemical conversion step, the treated surface is rinsed with water, usually further rinsed with deionized water, and then subjected to a number of water baths containing preferably hexavalent and/or trivalent chromium ions, as described in U.S. Pat.
, No. 222,226 and No. 3,279.958 are used for chrome sealing.

Following this chrome rinse, the chemically treated substrate is typically rinsed again with water and then dried. After drying, high solid M
The machine paint can be applied as a top coat directly onto the chemically treated substrate, or it can be applied in the form of a residual solid primer paint and then one or more HynoRerad top coats can be applied.

After each coating operation is completed, the coated substrate is hot crosslinked to complete the crosslinking before applying the next coat.

For purposes of this invention as disclosed herein and as described in the accompanying frame, high solids coating formulations have a solids content of at least 50% by volume, and additionally at least about 60% by volume.
Solvent-borne coating systems containing 3% solids by weight are intended to be included. Moreover, the resinous binder component of such binder paints is less than binder contained in conventional solvent-borne coating systems with a solids content of less than 50% by volume, and usually about 45% by volume or less; also has a substantially low molecular weight.

High Solids Coating Technology The other 1ft@ between IC is ``Yamagh-8olids Coatings: Pa
5t, Present.

Future J
Coating Journal.

June 21, 1982 issue) ; r High-8o
lids CoatingsJ (Modern Pa1
nt and Coatings, June 1982 issue]; “Trends in Water-Bo
rne, High-8olidsCoatin
gs J (American Palnt Co.
atingJournal, July 12, 1982
day issue); and “I-Iight-8ol ids Acr.
yl ic 几esins for Bakin
g Enamels J (Modern Palnt
and Coaijngs, April 1981).

Next, the present invention will be described in further detail with reference to Examples.

It will be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention described in the accompanying frame.

EXAMPLE 1 Many plants that handle inorganically accelerated iron sulfate coating solutions use the same bath solution after parts have been sinate coated and/or painted. A 4-inch by 6-inch (10 cm
Two test panels made of steel (2 x 15 mm) were cleaned and then subjected to a commercially available iron phosphate chemical conversion treatment. Operating bath υ about 12 f/l of 75% citric acid, about 4.7 P/l of sodium carbonate in the bath to neutralize the cinic acid to form acidic sulfate, and about 5. It contained 2y/l of sodium chlorate. This solution has a pH of 5 and a temperature of approx.
The panels were sprayed at 60°F (71°C) for approximately 1 minute and then rinsed with tap water. After the panel was air dried, a drop of the same operating bath was applied onto the dried iron sinate film. Place these panels flat in an air circulating oven.
(Bake at 120°F (49°C) for 10 minutes.

Panel (7) - ICrDuracron 200 J
(PPG.

A vinelid white one-response diluted topcoat paint having a composition commercially available under the trade name of Co., Ltd., was applied.

The second panel has r4653J (Sherwin
A high solids black bath agent diluted top coat organic paint having a composition commercially available as - Wi II I ams Inc. (trade name) was applied by spraying. After spraying, place both panels in a circulating air oven at 325°F.
The organic finish was crosslinked and cured by baking for 15 minutes.

In either case, a white ring was visible through the paint layer, and the center of the ring was seen to be cloudy.

Example 2 The same procedure as described in Example 1 was carried out to prepare two test pile T phosphate skins 11! i! Although it has been chemically treated, this chichi phosphate skin! There was no inorganic oxidation in the Hankasei melt, and an M-organic oxidizing agent was used.

This iron phosphate coating solution contains approximately 12.5P/
1 of 75% phosphoric acid, about 4.91/l of sodium carbonate and about 1.8 P/Z of metanitrobenzene sulfonic acid. This operating bath was sprayed onto panels under the same conditions as Example 1, except that the bath temperature was 120°F (49°F).
℃] was there.

After drying the chemically treated panel, a drop of the same cynic acid hot coating chemical conversion treatment solution was applied in the same manner as in Example 1, and then agglomerated, and two types of vinolid top coats were applied under the same conditions as in Example 1. Painted. Inspection of the test panels revealed no discernible rings or discoloration on the paint surface.

Example 3 The same test as described in Example 2 was conducted, but this time the iron sinate film treatment solution contained no inorganic oxidizing agent and further contained approximately 0.717 t of surfactant. In addition to the surfactant, this solution contained 75 of approximately 3.6P/Z.
% cinic acid, about 3.6 F/2 of monosodium sulfate, and about 0.3 P/A of metanitrobenzene sulfonate.

When the same operations and conditions as in Example tlJ 2 were repeated, and the surface of the test panel finally painted was visually observed, no discoloration on the surface that could be observed with the naked eye was observed.

It is clear that a wide variety of embodiments may be constructed without departing from the spirit and scope of this invention, and therefore this invention is not limited to its specific embodiments, except as limited in the accompanying frame. isn't it.

403

Claims (1)

[Scope of Claims] (1) A method for treating a steel substrate to which a high solids coating containing an organic solvent is to be applied, wherein iron paint #Ylt is applied to the substrate surface.
The amount of primary sulfone that forms the I'm film is effective in accelerating the rate of formation of the iron sulfate film as well as the nitrobenzene sulfone present in the salt and its hot bath decomposition.・Process of applying an iron phosphate film chemical conversion water deposit deposit containing a +i' m I7 agent consisting of compatible salts to clean copper-based ground, and rinsing and drying the pond treated with this iron phosphate film chemical conversion treatment. and then applying a high solids paint to the iron sulfate coating and then cross-linking and curing it. (2) The method according to claim 1, further comprising a step of controlling the pH of the iron phosphoric acid coating chemical solution to 4.2 to 141. (6) The iron 9 has a pH of 4.5 to 5.
5. The method according to claim 8'rJ1, further comprising the step of controlling the temperature between 70 and 1.
The method according to any one of claims 1 to 3, further comprising the step of controlling the temperature within the range of 20"F (21 to 49°C). (5) The iron, phosphoric acid Claims 1 to 4 further include the step of subjecting the iron sinate film to a rinse water solution containing chromium, prior to drying the substrate subjected to the salt film chemical conversion treatment. Mt in any one of
How to put it on. (6) 3 to 60 fl/l of salt film chemical water applied to the iron sink
6. The method according to any one of claims 1 to 5, characterized in that the method comprises all of the primary sinate salts. (7) The metanitrobenzenesulfonic acid and the bath OJg compatible salts are present in an amount of 0.1 to 3 P/l. (8) The iron phosphate film conversion aqueous solution is
The method according to any one of items 1 to 7 of the range of patented water characterized by containing all 1β salts in the first column of yit. Calendar/compatible salts in an amount of 0.1 to 1.5 y/l
1. The method according to any one of claims 1 to 8, characterized in that: (10) A method for treating a steel substrate to be coated with a high solids coating containing an organic bath agent, which is clean iron; In a method of painting using a solid organic paint, the sulfate film does not contain any inorganic oxidizing agent, and is coated with an organic metanitrobenzene sulfonic acid agent and its bath, reactive, and compatible salts. An improved method consisting of chemical conversion treatment of a clean steel substrate overnight (11) nucleating agent containing 4 phosphorus in sufficient amounts, 1 simulated aqueous solution (11) containing 0 nucleating agents. .1 to 3 yit. (12) The nucleating agent is present in an amount of 0.2 to 1.5 y/l. A method according to any one of claims 10 to 11.