JP2866140B2 - Additive for high-performance plating - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plating additive used for forming a high-performance plating layer having excellent corrosion resistance, design properties, paintability, workability, and the like. is there.

[Prior art] Metal materials represented by steel sheets are often plated and used for the purpose of improving corrosion resistance and design properties.
Such surface treatment materials are used in a wide range of fields such as automobiles, home appliances, and building materials. As a plating material, a metal material alone such as Zn or a Zn-based alloy has been most widely used, but various ideas have been devised as requirements for a plating function have increased. One such method is to add an additive to the plating solution.

As additives, nonionic acrylamide polymers for obtaining bright plating, polymers having sulfonic acid groups or phosphoric acid groups for obtaining coating adhesion, or oxides for improving lubricity have been used. Fine particles and the like have been studied.

However, when a polymer is used as an additive, sufficient coating film adhesion cannot be obtained depending on the type of coating and the method of coating, or the additive itself tends to deteriorate in a corrosive environment after coating. Has disadvantages. Further, when insoluble fine particles such as oxides are used, it is difficult to uniformly disperse them in a plating solution by a usual method, and there is a disadvantage that process control becomes complicated. Moreover, conventional additives can improve individual properties such as glossiness, coating film adhesion, lubricity, etc., but are sufficiently satisfactory in that they exhibit some of these effects. Was not.

[Problems to be Solved by the Invention] The present invention has been made in view of the above situation, and is uniformly dispersed in a plating solution, hardly deteriorates even after coating, and has a design property of plating and coating. An object of the present invention is to provide an additive capable of improving film adhesion and processability.

[Means for Solving the Problems] The highly functional plating additive of the present invention [Where A is C _n H _2n : n is a positive integer, R ₁ and R ₂ are the same or different and H or an alkyl group] and a functional group represented by an epoxy group-containing compound (meta The point is that the (meth) acrylic polymer has an acrylic ester compound monomer unit of 5 mol% or more in all repeating units.

[Operation] First, the present inventors have studied what properties are necessary for the plating additive to obtain the above-mentioned respective properties, and have obtained the following knowledge.

Stability and dispersibility in plating solution: Depends on the hydrophilicity of the additive, and low hydrophilicity leads to poor stability. Further, when it has self-polymerization at a general plating operating temperature (70 ° C. or less), the stability is further deteriorated.

Designability (brightness): A plating film can be formed uniformly when an additive is adsorbed to an active site at the time of plating deposition.

Coating adhesion and corrosion resistance after coating: If the additive is codeposited in the plating film and forms a bond with the paint component during coating, the bond does not deteriorate even in a corrosive environment.

Workability (press formability): It is desirable that the plating film has a certain degree of hardness and lubricity. For this purpose, the additive has a certain size and is eutectoid in the plating film, which itself has lubricity. Things are advantageous.

As a result of intensive studies based on the above, the plating additive of the present invention having a high function has been completed. The details will be described below.

-C _n H _2n in first plating additives - (n is a positive integer) will be explained and an alkyl group.

-C _n H _2n- , whether linear or branched, typical examples include methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, propylene, ethylethylene, and the like, Particularly preferably, n is 6 or less.

The alkyl group may be linear or branched, and typical examples include methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl, pentyl, hexyl, and the like. It is an alkyl group.

Examples of the (meth) acrylate having an amino-based functional group before the addition of the compound having an epoxy group according to the present invention include dimethylaminoethyl methacrylate, methylethylaminoethyl methacrylate, dimethylaminomethyl methacrylate, and dipropylaminopropyl. Examples include methacrylate, dimethylaminopropyl acrylate, diethylaminoethyl acrylate, and dimethylaminoethyl acrylate. Those exemplified are those in which the terminal amino group is a tertiary amino group, but those having a primary or secondary amino group are also included in the present invention. Further, the compound having an epoxy group added thereto may be either of an ether type or an ester type, such as bisphenol A glycidyl ether, epichlorohydrin, allyl glycyl ether, styrene oxide, and phenyl glycidyl ether. Examples of (meth) acrylic monomers that can be polymer components other than the above monomers include, for example, acrylamide and methacrylamide,
Examples include methyl acrylate and methyl methacrylate.

These combinations are not particularly limited, but those provided with epichlorohydrin as a compound having an epoxy group exhibit particularly excellent effects.

The method of providing the epoxy compound varies depending on the compound. For example, there is a method of homopolymerizing or copolymerizing the above monomers to form a polymer and then reacting the epoxy compound. It is considered that the amino group is quaternized by the addition.

The effect of the present invention can be obtained by allowing the compound having an epoxy group as a monomer unit to be present in the polymer in an amount of 5 mol% or more. Fig. 1 shows the relationship between the content of the epoxy monomer unit and the coating film peeling ratio (coating adhesion), and Fig. 2 shows the relationship between the epoxy monomer unit content and the coating peeling width (corrosion resistance after painting). Indicated. It can be seen that when the content is 5 mol% or less, a sufficient effect cannot be obtained in any of the characteristics. The size of the polymer itself is not particularly limited, but it is desirable that the molecular weight be between 1,000 and 100,000.

The additive of the present invention having the above-mentioned structure is characterized in that the (meth) acrylates are stable in an acid and an alkali, the presence of an ester bond, and furthermore, a hydroxyl group or a quaternary amine formed by addition of an epoxy compound. As a result, the solubility is enhanced, so that it can be stably and uniformly dispersed in the plating solution. Amino functional groups, hydroxyl groups, and the like can be adsorbed at active points during plating deposition, and a glossy plating layer is formed by these effects.
The obtained plating layer has a high coating film adhesion because the epoxy group and the hydroxyl group present in the plating layer form a bond with the paint at the time of coating baking (80 ° C. or higher). Although the plating layer contains (meth) acrylates in the polymer, the corrosion resistance after coating is enhanced, but the quaternary amine is further stabilized by being co-deposited in the plating layer, and is excellent. Shows corrosion resistance after painting. Further, since the additive is a polymer, it is possible to give the plating layer a certain degree of hardness by co-depositing it in the plating layer, and at the same time it is possible to provide the additive itself with lubricity. Therefore, the press formability of the plating layer is greatly improved.

EXAMPLES Hereinafter, examples will be described. However, the present invention is not limited to the following examples, and any appropriate design change based on the gist of the present invention is included in the scope of the present invention.

[Examples] The plating shown in Table 1 was applied to a cold-rolled steel sheet that had been subjected to a pretreatment for fatty acid washing, and its stability, appearance, coating film adhesion, corrosion resistance after coating, and press formability were determined by the following methods. evaluated. As a typical example of the additive according to the present invention, a copolymer having a molecular weight of 200,000 and comprising acrylamide and a compound obtained by adding epichlorohydrin to dimethylaminoethyl methacrylate was used.

(Evaluation method)-Stability Evaluated by the resolubility of the plating solution after drying.

 ：: Completely re-dissolved △: Slightly cloudy ×: Insoluble material precipitated ・ Appearance Evaluated visually.

：: uniform Δ: slight unevenness ×: considerable unevenness ・ Coating film adhesion An alkyd / melamine-based paint was directly applied to the plating, and a crosscut Ericksen tape peeling test was performed to evaluate the coating film peeling rate.

○: Peeling rate of coating film 5% or less △: Peeling rate of coating film 5 to 30% ×: Peeling rate of coating film 30% or more ・ Corrosion resistance after coating Apply alkyd / melamine paint directly to plating, and after 24 hours of cross cut SST A tape peeling test was performed, and evaluation was made based on a peeling width of the coating film.

：: Paint film peeling width 1 mm or less △: Paint film peeling width 1 to 2 mm ×: Paint film peeling width 2 mm or more ・ Press formability A Dlobroid test was conducted to investigate the amount of plating peeling.

：: plating removal amount 0.2 g / m ² or less △: plating removal amount 0.2 to 0.5 g / m ² ×: plating removal amount 0.5 g / m ² or more The results are shown in Table 1.

As shown in Table 1, the examples using the additives according to the present invention are excellent in all of stability, appearance, coating film adhesion, corrosion resistance after coating, and press moldability. On the other hand, the additives of Comparative Examples 1 and 6 had an epoxy monomer content of 5 m.
ol%, sufficient coating film adhesion and corrosion resistance after coating were not obtained, and the additives of Comparative Examples 2, 4 and 5 did not contain an epoxy monomer, so that the coating film adhesion was also sufficient. Properties and corrosion resistance after painting are not sufficient. In Comparative Example 3 in which no additive was added, none of the characteristics was satisfactory.

[Effects of the Invention] The present invention is configured as described above, and the additive of the present invention is stable and uniformly dispersed in a plating solution, and has corrosion resistance after coating, appearance (design), coating film adhesion, It is very useful for obtaining a plating layer having excellent press formability.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the content of epoxy monomer units in the additive and coating film adhesion, and FIG. 2 is a graph showing the relationship between the content of epoxy monomer units in the additive and corrosion resistance after painting. It is.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuki Ikeda 2-3-1 Shinohara Auntoyamayamacho, Nada-ku, Kobe City, Hyogo Prefecture (72) Inventor Atsushi Hisamoto 2-3-3 Shinohara Auntoshinoyamacho, Nada-ku, Kobe City, Hyogo Prefecture -1 (72) Inventor Nagisa Yamamura 4-19-17 Karibadai, Nishi-ku, Kobe-shi, Hyogo (56) References JP-A-61-127887 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , (DB name) C25D 3/00-3/64 C23C 2/00-2/40 C08F 20/00-22/40

Claims (1)

(57) [Claims] (1) [Where A is C _n H _2n : n is a positive integer, R ₁ and R ₂ are the same or different and are H or an alkyl group], and has a group in which a compound having an epoxy group is added to the functional group represented by ( Meta)
An additive for high-performance plating, which is a (meth) acrylic polymer having an acrylic ester compound monomer unit in an amount of 5 mol% or more in all repeating units.