JPS636065A - Water-based cationic paint - Google Patents

Abstract

PURPOSE:To provide the title paint which does not cause coloration of reddish brown to dark red even when brought into contact with iron, containing a basic nitrogen-contg. polymer (acid-neutralized product), a specified curing agent and a chelating agent. CONSTITUTION:A basic nitrogen-contg. polymer (A) composed of a basic nitrogen-contg. acrylic monomer (a) (e.g., dimethylaminoethyl methacrylate) and optionally, a copolymerizable monomer (b), or a neutralized product (A) obtd. by partially or wholly neutralizing said polymer with an acid, is blended with a curing agent (B) composed of a benzoguanamine resin and/or a melamine resin having carboxyl groups and an acid value of not lower than 10mg KOH of g of solid by neutralization titration with KOH, in a weight ratio of 60-80:40-20 to obtain a blend. The blend is blended with at least 0.1wt%, pref. 0.5-20wt% (per 100pts.wt. nonvolatile matter of the component B) chelating agent (C) (e.g., ethylenediaminetetraacetic acid). If desired, a pigment, an org. solvent, a surfactant, a leveling agent, an ultraviolet absorber, a plasticizer, etc., are added thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cationic water-based paint having anti-coloring ability.

(Prior Art) The present inventors have discovered that melamine and/or
Alternatively, we proposed an acrylic cationic electrodeposition paint in which benzoguanamine resin was cured simultaneously (Japanese Patent Application No. 12259/1986).
1>.

[Problem that the invention seeks to solve]

It has been found that this invention provides sufficient performance in terms of coating film performance, but as an electrodeposition coating, if it is kept in a container containing iron for a long period of time, the coating will become colored, and the coating will not be colored. Even in this state, when the object to be coated is iron, there are problems with coloring, such as reddish colored areas appearing on some parts of the object, especially when using electrodeposition coating, especially when using white paint or bright colors. It was found that this significantly reduced the commercial value and made it impossible to put it into practical use. The reason for cationic water-based paints is that the acid used as a neutralizing agent may cause the paint to become acidic, but as a result of experiments, we found that acrylic resin alone is used, that is, without the addition of melamine or benzoguanamine resins containing carboxyl groups. When it is made into a paint, the coloration is only pale yellow even if a nail is inserted, and it rarely becomes a reddish or dark red band. On the other hand, if you add a small amount of water to the above-mentioned hardening agent and put a nail in it, it will turn reddish-brown to dark red when left for day and night.This coloring is caused by iron and the above-mentioned hardening agent being in the presence of water. It was found that this phenomenon occurs in water-based paints as long as melamine or benzoguanamine having a carboxyl group is used as a curing agent.

Therefore, an object of the present invention is to provide a cationic water-based paint that uses melamine and/or benzoguanamine resins having carboxyl groups as a curing agent, and which does not cause reddish-brown to dark red coloring even when brought into contact with iron. be.

(Means for Solving the Problems) That is, the present invention comprises: A1 a polymer containing basic nitrogen in the polymer or an acid neutralized product thereof, B, a melamine resin having a carboxyl group, and/or
A cationic water-based paint containing benzoguanamine resin and 0.1% by weight or more of a chelating agent based on 100 parts by weight of C and B nonvolatile components.

The cationic water-based paint of the present invention includes cationic electrodeposition paint,
Refers to paints, etc. that have been added with water.

The basic nitrogen-containing polymer shown in A is a polymer consisting of a monomer containing a basic nitrogen-containing acrylic monomer. A typical example is an acrylic copolymer.

Basic nitrogen-containing acrylic monomers include, for example, aminoethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, moro-propyl (or diisopropyl) aminoethyl acrylate or methacrylate, moro-butyl (or Acrylic acid ester derivatives such as diisobutyl or diisobutyl) aminoethyl acrylate or methacrylate, N
Acrylamide derivatives such as -dimethylaminoethyl acrylamide or methacrylamide, N-diethylaminoethyl acrylamide or methacrylamide, N-moro-propyl (or isobutyl) aminoethylacrylamide or methacrylamide can be used. Monomers copolymerized with the basic nitrogen-containing acrylic monomer include monomers having an OH group such as hydroxyethyl acrylate or methacrylate, hydroxypropyl acrylate or methacrylate, acrylic acid or Acrylic esters or methacrylic esters made from methacrylic acid and alcohol, as well as acrylamides represented by acrylamide, N-methylolacrylamide, n-butoxymethylacrylamide, etc., are used. Those copolymerized with a monomer having an OH group are preferably copolymerized with B since they cure.

Furthermore, as the monomer copolymerized with the basic nitrogen-containing acrylic monomer, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, p-styrene sulfonic acid,
Copolymerizable ethylenically unsaturated carboxylic acids or sulfonic acids, such as vinylsulfonic acid and 2-acrylamido-2methylpropanesulfonic acid, are used. Furthermore, all monomers other than acrylic monomers, such as styrene, vinyltoluene, and vinyl acetate, which can be copolymerized with the aforementioned basic nitrogen-containing acrylic monomers and other acrylic monomers can be used.

Furthermore, as polymers having basic nitrogen, amino-modified epoxy resins currently used in cationic electrodeposition coating can also be used for the purpose of the present invention. For example, a polymer obtained by adding ethylenediamine to "Epon" 1001 corresponds to this.

A neutralized polymer containing basic nitrogen is one that has been partially or completely neutralized with an acid such as acetic acid or lactic acid, and is usually used as a water-soluble polymer.

The melamine resin or benzoguanamine resin having a carboxyl group as shown above is not particularly limited, but is contained in one molecule (wherein, R" is a C1 to C+ alkyl group, R is a C1 to C+ alkyl group, and R is a C1 to C+ alkyl group.
A melamine resin or benzoguanamine resin having at least one alkyl group or oxyalkylene group is preferred.

The carboxylic acid liquor has an acid value of 10 mg KOH/solid content 19 or more, preferably 2 when neutralized and titrated with caustic potassium.
0 to 60 mg KoH/1 g of solid content is suitable.

Examples of such curing agents include "Cymel'1125" and "Cymel" 114 manufactured by American Cyanamid Company.
1 etc. are preferably used.

The polymer A or its acid neutralized product constituting the cationic water-based paint of the present invention and the melamine resin and/or benzoguanamine resin having a carboxyl group B are 60:40 to 60:40.
A weight ratio of 80:20 is preferred.

The chelating agent shown in C is one that forms a chelate compound with a metal, and for example, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, acetylacetone ethylenediimine chelate, and the like are preferably used.

The amount of these chelating agents added is 0.1% by weight or more, preferably 0.5% by weight based on 100 parts by weight of non-volatile content of B.
That's all. If the amount added is less than 0.1% by weight based on 100 parts by weight of non-volatile content of B, the coloring prevention effect will be insufficient.

Regarding the coloring prevention effect, there is no upper limit to the amount added, but from the viewpoint of reducing corrosion resistance, it is preferable to add the nonvolatile component 1C> in the amount B.
It is less than 20% of the O-weighted part.

When the paint according to the invention is used as a one-coat finish paint, it generally contains one or more pigments such as white, black, red, yellow, blue, etc. (e.g. titanium oxide for white). (for black, carbon black, etc.) is used. In addition, this paint contains C2~C1° alcohols and aromatic alcohols (benzyl alcohol, etc.).
, glycols, glycol ethers (e.g., ethyl cellosolve, propyl cellosolve, butyl cellosolve, n-hexyl cellosolve, etc.) or the addition of other organic solvents to the extent that they do not separate or have an adverse effect when dissolved or dispersed in water. However, the effects of the present invention are not hindered in any way. It is also possible to add additives such as surfactants, leveling agents, ultraviolet absorbers, and plasticizers to the present invention to the extent that they do not impede the effects.

〔Example〕

The present invention will be explained with examples.

Examples 1 to 3 10 parts of dimethylamine ethyl methacrylate, 15 parts of 2-hydroxyethyl methacrylate, 15 parts of ethyl acrylate, 20 parts of butyl acrylate, 15 parts of methyl methacrylate, 25 parts of styrene, and 2 parts of azobisisobutyronitrile were added to isopropyl 8 at 80-88°C in the presence of a solvent of 45 parts alcohol and 16 parts butyl cellosolve.
Polymerizes over time. Thereafter, 3 parts of acetic acid was added to neutralize the acrylic polymer, and 20 parts of benzyl alcohol and 15 parts of ion-exchanged water were added and stirred for 30 minutes to form a water-dispersible acrylic polymer with a non-volatile content of 50%. Obtained.

50 parts of the obtained polymer having basic nitrogen, 80 parts of titanium oxide ("Tie Bake" CR-95 manufactured by Gohara Sangyo), 82 parts of ion exchange water, and 1 glass bead for a sand grinder.
Add 50 parts and shake with paint conditioner for about 2 hours to make a pigment paste. This pigment paste has a calculated non-volatile content of 50%.

Acrylic polymer and pigment paste obtained by the above-mentioned process and melamine 1 resin containing carboxyl group (Cymelpa 1141 manufactured by American Cyanamid Co., Ltd. (solid content 85%)
) and carboxyl group-containing benzoguanamine resin (Cymel 1125 (solids content: 80%) manufactured by American Cyanamid) were mixed separately or in combination in the amounts shown in Table 1, and then ethylenediaminetetraacetic acid was added. 0 for each
．． 5 () and further mixed.To these, ion exchange water 8
00fj was gradually added while stirring well to prepare 1000q of a cationic electrodepositing paint with a non-volatile content of about 10%.

These were placed in stainless steel beakers, two nails of about 5 cm in length were placed in each beaker, the lids were placed on the beakers to prevent the solvent from evaporating, and the beakers were left to stand while stirring.

Even after one week, there was no reddish-brown coloring and the paint remained white.

Table 1 Composition of cationic electrodeposition paint Example 1 Example 2 Example 3 Acrylic resin 89.4 (1B9.4 ()
889.4g pigment paste 62.5(] 6
2.5 (362,5g'Cymel" 112528, Ig
9.4Q (non-volatile content 80%) “Cymel” 1141-26.5CI 17
．． 6g (non-volatile content 85%) Ion exchange water 20.0g 21.6g
21゜1g ethylenediamine 0.5g0.5(J
0.5g Tetraacetic acid Bonderite #144 using these paints! Cationic electrodeposition was carried out at 180 V at a bath temperature of 25° C. for 3 minutes using a steel plate as a cathode, followed by baking at 180° C. for 12 minutes. The paint film had no reddish tinge and remained white.

Comparative Examples 1 to 3 The same experiments as in Examples 1 to 3 were conducted except that ethylenediaminetetraacetic acid was used in Examples 1 to 3. After 2 days of stirring, a slight reddish coloring was observed, and after 1 week,
The red color has become stronger. Cationic electrodeposition and baking were performed using this paint in the same manner as in Examples 1 to 3, but the paint film was reddish like the paint.

Example 4 After adding 0.5 g of ethylenediaminetetraacetic acid to each of the paints of Comparative Examples 1 to 3, the mixtures were stirred and left in the same manner as in Examples 1 to 3. After 3 days, the redness gradually disappeared, and after 1 week, the redness of the paint further decreased.

Example 5 Bonderite #144'lla steel plate (15Q mm x 5 Q mm x 0 .8 mm) by cationic electrodeposition to a film thickness of about 30 microns, and baked for 180' of Cl2O. The results of measuring the coating film performance of both films are shown in Table 2, and it was found that there was no decrease in performance even when ethylenediaminetetraacetic acid was added.

Reference Example 1 100g of the acrylic polymer of Example 1 and 20g of ion-exchanged water
0q was gradually added to make a 10% coating without adding a curing agent having a carboxyl group.

A nail similar to that in Example 1 was inserted into this, and the mixture was stirred and left to stand as in Example 1. When observed after one week, there was no red coloring and the color remained pale yellow.

Reference Example 2 50 pieces of "Cymel" 1125 and "Cymel" 1141 were placed in a 100 cc glass bottle, two nails each having a length of 2 cm were added to each bottle, and the bottle was sealed and allowed to stand.

There was no change in color for both "Cymel" 1125 and 1141 even after one week.

Reference Example 3 25C1 each of "Cymel" 1125 and "Cymelpa 1141" were placed in a 100CC glass bottle, and 50C of a mixture of water/acetone = 1/2 (weight ratio) was added to them.
() was added and left to stand. After 2 days, the area in contact with the glaze turned black, and when this was stirred, it turned dark red.

[Effect of the invention] Paints made by mixing melamine resin or benzoguanamine resin and adding water are colored reddish brown or dark red when they come into contact with iron, but when a chelating agent is added as in the present invention, the coloring remains for a long period of time. It also prevents coloring of spray-painted or cationically electrodeposited paint films.

Furthermore, when a chelating agent is added to a paint that has already been colored reddish-brown or reddish-purple, the degree of coloring gradually disappears and eventually the coloring disappears. Moreover, the addition of such a chelating agent does not affect the performance of the coating film. The cationic water-based paint of the present invention can be applied to, for example, a cationic electrodeposition paint, a water-based spray paint, a dipping paint, and the like.

Claims (1)

[Scope of Claims] A, a polymer containing basic nitrogen in the polymer or an acid-neutralized product thereof; B, a melamine resin and/or benzoguanamine resin having a carboxyl group; and C, a nonvolatile content of B. A cationic water-based paint containing 0.1% by weight or more of a chelating agent per 100 parts by weight.