JPH11152433A - Composition for electrodeposition and electrodeposition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new heat-resistant composition for electrodeposition giving an electrodeposition film excellent smoothness, storage stability and film thickness uniformity compared to conventional ones, and to provide a method of eletrodeposition using the composition. SOLUTION: This composition for electrodeposition of 0.5-20 wt.% in solid concentration comprises an aromatic polyimide resin bearing pendant-type acid groups, as a reaction product from an aromatic tetracarboxylic acid dianhydride and an aromatic diamine, 0.5-60 wt.% of an oil-soluble solvent soluble for the resin, 2.5-80 wt.% of a water-soluble solvent soluble for the resin, 0.5-80 wt.% of water, and a basic nitrogen-contg. compound for neutralizing the acid groups in the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel electrodeposition composition excellent in heat resistance, chemical resistance, electrical properties and the like, and an electrodeposition method thereof. TECHNICAL FIELD The present invention relates to an electrodeposition composition useful for forming an electrical insulating layer of a body and an electrodeposition method using the same.

[0002]

2. Description of the Related Art Conventionally, most of compositions known as an electrodeposition composition are obtained by dissolving or dispersing an acrylic polymer in water or a mixture of water and an organic solvent. It has been used for surface coating of building materials and the like, and has been used only in limited fields as an electrical insulating material. The advantages of electrodeposition compositions are
The adjustment of the film thickness can be easily performed by controlling the voltage or the current, and the uneven portion or the perforated portion can be coated with a uniform film thickness. However, when the conventional acrylic electrodeposition composition is applied to a wider field of electric and electronic materials, there is a problem in terms of heat resistance.

On the other hand, JP-A-49-52252, JP-A-52-32943, and JP-A-63-11119 attempt to improve the heat resistance of conventional electrodeposition compositions.
No. 9, JP-A-9-124978, etc., describe an electrodeposition aqueous dispersion obtained by adding a poor solvent and water to an organic polar solvent solution of polyamic acid. Since amic acid is easily hydrolyzed, there are problems such as poor stability. In addition, polyamic acid must finally undergo imide ring closure, which involves a dehydration reaction during imidization, and thus has a problem in that when it is electrodeposited with a large film thickness, it foams on the coated surface. Japanese Patent Application Laid-Open No. 9-104839
The heat-resistant polyimide electrodeposition composition not using a polyamic acid described in JP-A No. H10-209, may use a poor solvent for polyimide, and has improved stability when compared with the one using amic acid, An increase in the acid value due to decomposition is observed, resulting in problems such as a change in electrodeposition conditions, and a disadvantage that the film thickness of the coating film is not uniform.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and provides a smoother, more heat-resistant electrodeposition composition.
An object of the present invention is to provide a novel heat-resistant electrodeposition composition excellent in storage stability, film thickness uniformity and the like, and an electrodeposition method thereof.

[0005]

That is, the first aspect of the present invention is as follows.
Is an aromatic polyimide resin which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine and has a pendant acid group, and an oil-soluble solvent in which the resin is soluble.
5 to 60% by weight, water-soluble solvent in which the above resin is soluble
The present invention relates to an electrodeposition composition having a solid content of 0.5 to 20% by weight, comprising 80% by weight, 0.5 to 80% by weight of water and a basic nitrogen-containing compound for neutralizing acid groups of the resin. . A second aspect of the present invention is the first aspect of the present invention, wherein the oil-soluble solvent is 1-acetonaphthone, acetophenone, benzylacetone, methylacetophenone, dimethylacetophenone, propiophenone, valerophenone, anisole, methyl benzoate, benzyl benzoate, Or an electrodeposition composition which is a mixture thereof. Third of the present invention
In the first or second aspect of the present invention, the water-soluble solvent is
The present invention relates to an electrodeposition composition which is N-methylpyrrolidone, N, N-dimethylformamide, dimethylsulfoxide, N, N-dimethylacetamide, sulfolane, or a mixture thereof. A fourth aspect of the present invention relates to the electrodeposition method according to any one of the first to third aspects, wherein the electrodeposition composition is used or stored for electrodeposition at a liquid temperature of 15 ° C. or lower. .

The electrodeposition composition of the present invention comprises, as a base resin, an aromatic polyimide resin which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine and has a pendant acid group. It is characterized by the combined use of an oil-soluble solvent in which the resin is soluble and a water-soluble solvent in which the resin is also soluble, and has excellent storage stability, as well as smoothness and film in electrodeposition. A coating film with excellent thickness uniformity can be formed. In addition, "electrodeposition composition"
Means a mixed solution used for electrodeposition, and may hereinafter be referred to as "electrodeposition solution". Hereinafter, the present invention will be further described.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a condensate having a molecular weight of 5,000 to 100,000 obtained from an aromatic tetracarboxylic dianhydride and an aromatic diamine and having a pendant acid group A solvent-soluble aromatic polyimide resin is used as a base resin for the electrodeposition liquid. The polyimide skeleton may contain an amide acid structural unit of the following formula and a ring-closed imide structural unit, but the amide acid structure is liable to undergo hydrolysis as compared with the imide structure, and changes with time of the electrodeposition composition. Therefore, it is preferable to use one having a small number of amic acid structural units.

[0008]

Embedded image

The above-mentioned "aromatic polyimide resin having a pendant acid group" is a polymer of an aromatic monomer, the main chain structure of which is constituted by imide bonds, and the acid group is a resin of the resin. A polyimide resin that is substituted at an arbitrary position in the main chain in a state of being suspended from the main chain instead of the terminal (pendant type). For example, as shown in the following formula, it is manufactured using an aromatic diamine and an aromatic tetracarboxylic acid having an acid group such as diaminobenzoic acid as a monomer, and an acid group is present on a side chain of a repeating unit having an imide bond. Examples include a polyimide resin having a substituted structure. Carboxylic acid is preferable as the kind of the acid group of the imide resin.

[0010]

Embedded image (However, -X- is a single bond or a divalent group such as -O-.)

As a method for producing the polyimide resin used in the present invention, an aromatic tetracarboxylic dianhydride and an aromatic diamine are used in substantially equal amounts, and heated in an organic polar solvent to carry out polycondensation. Add catalyst if necessary and add 140
A method is used in which water generated by heating to 200 ° C. is removed azeotropically.

The aromatic tetracarboxylic dianhydride used is not particularly limited, but is usually pyromellitic dianhydride,
3,4,3 ', 4'-benzophenonetetracarboxylic dianhydride, 3,4,3', 4'-biphenyltetracarboxylic dianhydride, diphenylsulfonetetracarboxylic dianhydride, bis (3,4 -Dicarboxyphenyl) ether anhydride and the like are used.

The aromatic diamine is used to introduce an acid group into the main chain of the resin in a pendant manner as described above, and an aromatic diamine having an acid group such as aromatic diaminocarboxylic acid was synthesized. It can be used in an amount such that the acid value of 100 g of the polyimide resin is in the range of 30 to 200 mmol. Examples of the aromatic diamine having such an acid group include 3,5-diaminobenzoic acid, 2,4-diaminophenylacetic acid, 2,5-diaminoterephthalic acid, 3,5-diaminoparatoluic acid, and 1,4-diamine. Examples thereof include diamino-2-naphthalene carboxylic acid and 3,5-diamino-2-naphthalene carboxylic acid, and 3,5-diaminobenzoic acid is preferably used.

In order to improve the heat resistance, mechanical strength, rigidity and adhesiveness of the polyimide resin of the present invention, other diamines can be used in combination. The other diamine is not particularly limited, but is generally p, m, o-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, diaminoxylene, diaminodurene,
1,5-diaminonaphthalene, 2,6-diaminonaphthalene, benzidine, 4,4′-diaminoterphenyl,
4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, diaminodiphenylsulfone,
2-bis (p-aminophenyl) propane, 1,2-bisanilinoethane, 3,3′-dimethylbenzidine, 3,3 ′
-Dimethyl-4,4'-diaminodiphenyl ether,
3,3′-dimethyl-4,4′-diaminodiphenylmethane, 4,4′-bis (p-aminophenoxy) biphenyl,
2,2-bis [4- (p-aminophenoxy) phenyl] propane, 4,4'-bis (3-aminophenoxyphenyl)
And aromatic diamines such as diphenyl sulfone.

A solvent-soluble polyimide resin can be obtained by heating and dehydrating an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic polar solvent by using substantially equal amounts thereof. As the organic polar solvent, a water-soluble solvent that dissolves a polyimide resin described later is preferable. By using such a water-soluble solvent, an aromatic polyimide resin as a reaction product is obtained as a polyimide solution dissolved in the solvent.

The concentration of the pendant aromatic polyimide resin having an acid group in the electrodeposition composition is preferably in the range of 0.5 to 20% by weight in terms of solid content. Water is 0.5-
A range of 80% by weight is suitable.

As the water-soluble solvent for dissolving the solvent-soluble polyimide resin used in the present invention, specifically, N-methylpyrrolidone, N, N-dimethylformamide, dimethylsulfoxide, N, N-dimethylacetamide, sulfolane Or a mixture thereof. These water-soluble solvents are used in an amount of from 2.5 to 80 based on the composition for electrodeposition.
It is blended in a ratio of weight%. If the amount is less than this, precipitation of the resin component occurs, and if it is more than this, the effect of adding the oil-soluble solvent described below may be reduced, and neither is preferable. Further, when the above range is exceeded, the stability of the aqueous dispersion or emulsion is lowered, and the smoothness of the coating film is impaired.

In the present invention, an oil-soluble solvent in which a resin is soluble is an essential component in addition to the above-mentioned water-soluble solvent. The oil-soluble solvent is effective in improving the flowability of the polyimide resin deposited on the object to be coated after the electrodeposition and improving the smoothness of the coating film. As a result, the storage stability of the electrodeposition liquid can be improved. Here, the oil-soluble solvent means an organic solvent that is substantially insoluble or hardly soluble in water. Examples of the oil-soluble solvent that dissolves the above resin include 1-acetonaphthone, acetophenone, benzylacetone, methylacetophenone, dimethylacetophenone, propiophenone, valerophenone, anisole, methyl benzoate, benzyl benzoate, and mixtures thereof. .
The oil-soluble solvent is 0.5 to 60% by weight based on the composition for electrodeposition.
In a proportion of If the amount is less than this, the effect of adding the oil-soluble solvent is small. Also, when the above range is exceeded, the stability of the aqueous dispersion or emulsion is lowered, and the smoothness of the coating film is impaired.

In the present invention, a basic nitrogen-containing compound is used to neutralize an acid group present in a pendant form in the resin to convert it into a salt and to maintain the polyimide resin partially water-soluble or water-dispersible. Is necessary. Specific examples include basic nitrogen-containing compounds such as triethylamine, trimethylamine, tripropylamine, tributylamine, pyridine, N-ethylpiperidine, N-methylmorpholine, and triethanolamine. The amount of the basic nitrogen-containing compound used depends on the amount necessary for the polyimide resin to be used to stably disperse or dissolve in the water-solvent system. Accordingly, an arbitrary amount can be appropriately added according to the amount of the acid group or the like of the polyimide resin, but usually, it is sufficient that the amount is 30 mol% or more of the theoretical neutralization amount. In particular,
Usually, by using 1 to 100 parts by weight of the basic nitrogen-containing compound per 100 parts by weight of the resin, the polyimide resin used in the present invention can be stably dispersed or dissolved in water-solvent.

The preparation of the electrodeposition solution comprising the electrodeposition composition can be carried out as follows. For example, a solution of a polyimide resin in a water-soluble solvent is obtained by the above synthesis method, and an oil-soluble solvent that dissolves the resin is added to this solution.
If necessary, a water-soluble solvent is further added, and a basic nitrogen-containing compound is added. Then, water is added dropwise and mixed. Thus, the resin-soluble oil-soluble solvent is 0.5 to 60% by weight, the resin-soluble water-soluble solvent is 2.5 to 80% by weight, and the water is 0.5%.
A composition having a solid content of 0.5 to 20% by weight, preferably 5 to 10%, comprising a basic nitrogen-containing compound which forms a neutralized salt with an acid group of the resin is obtained. The form is either a dispersion, a solution or an emulsion. The order of addition is not particularly limited, and the electrodeposition solution can be prepared by an addition order other than the above.

In addition to the above, other components can be added within a range that does not impair the object of the present invention. Examples of such components include pigments and fillers for the purpose of coloring, hiding, and the like.

In the electrodeposition coating using the composition of the present invention, a conventionally known method can be used as it is. However, when the present invention is used, the liquid temperature during electrodeposition or storage of the electrodeposition liquid can be lowered. That is, when a conventional electrodeposition composition containing no oil-soluble solvent in which the resin is soluble is used, when the electrodeposition is performed at a low temperature of 15 ° C. or less, the resulting coating film has sufficient smoothness. Or no sufficient film thickness was obtained. However, the electrodeposition composition of the present invention can be used for electrodeposition even at a low temperature of 15 ° C. or lower, and can be stored at the same low temperature. This is presumed to be because the hydrolytic stability of the polyimide resin in the electrodeposition composition of the present invention has been dramatically improved.

As a specific electrodeposition coating method, a conductive object to be coated is immersed in the polyimide electrodeposition solution of the present invention as an anode, and a voltage of 20 to 400 V is applied for 30 seconds to 10 minutes. An electrodeposited film is formed on the surface of the conductive coating object. Next, after washing with water and air drying, baking is performed by heating at a temperature suitable for the solvent used in the range of 140 to 350 ° C. for 30 minutes to 1 hour.

The conductive object to which the composition for electrodeposition of the present invention can be applied is not particularly limited to metal, and may be any conductive material. For example, copper, aluminum, iron, stainless steel,
A metal material such as nickel or an alloy is used.
Particularly, the object to be coated which is useful in the present invention is a copper foil or a copper plate, whereby a copper-polyimide substrate for a flexible printed board is obtained. Unlike a conventional method in which an adhesive is sandwiched between a copper foil and a polyimide film and then heat-pressed, a polyimide substrate of various compositions at lower cost can be obtained.

[0025]

The present invention will be described in more detail with reference to the following examples. "%" In the examples is based on weight. <Example 1> (Production of polyimide) A block polyimide was synthesized according to the production method of Example 1 described in JP-A-9-104439 to obtain a polyimide varnish of 20%. The production method is as follows. A glass separable three-necked flask was used, which was equipped with a stirrer, a nitrogen inlet tube, and a water receiver equipped with a stopcock below the cooling tube. The reactor was immersed in a silicone oil bath and heated with stirring while flowing nitrogen to carry out the reaction. The reaction temperature was represented by the temperature of the silicone oil bath. First, add 3,4,3 ',
4'-benzophenonetetracarboxylic dianhydride 64.4
4 g (0.2 mol), bis- [4- (3-aminophenoxy) phenyl] sulfone 42.72 g (0.1 mol), valerolactone 3 g (0.03 mol), pyridine 4.8 g
(0.06 mol), NMP (N-methylpyrrolidone) 4
Then, the mixture was stirred at room temperature for 30 minutes, and then heated to 180 ° C for 1 hour at 200 ° C.
The reaction was performed while stirring at rpm. After the reaction, toluene
30 ml of water distillate was removed. Air-cool the residue,
32.22 g (0.1 mol) of 4,3 ′, 4′-benzophenonetetracarboxylic dianhydride 15.22 g (0.1 mol) of 3,5-diaminobenzoic acid, 2,6-diaminopyridine 11. 01 g (0.1 mol), 222 g of NMP and 45 g of toluene were added and stirred at room temperature for 1 hour (200 rpm).
Then, the mixture was heated and stirred at 180 ° C. for 1 hour.
The reaction was completed by heating and stirring at 180 ° C. for 3 hours while removing the toluene-water distillate (15 ml) and thereafter removing the distillate from the system. Thus, a 20% polyimide varnish was obtained.

The basic skeleton structure of the obtained polyimide is represented by the above structural formula. The acid value of the polyimide was determined by potentiometric titration (using a 0.05N ethanolic KOH solution) to be 90 mmol / 100 g-solids. Of the acid value, the acid corresponding to 63 mmol / 100 g-solids is derived from the carboxyl group of 3,5-diaminobenzoic acid used as the resin monomer, and the carboxyl group is a pendant acid group. The remaining acid value is derived from the remaining amic acid structure and the acid at the terminal of the resin.

(Preparation of Electrodeposition Coating Solution)
Add N-methylpyrrolidone to 0% polyimide varnish,
To 1,000 g of a 15% polyimide varnish, 450 g of acetophenone and 6.5 g of triethylamine were added.
Was added, and 375 g of water was added dropwise with stirring to prepare an aqueous electrodeposition solution, whereby an electrodeposition emulsion composition having a solid content of 8.9% and a pH of 7.7 was obtained. In the following examples, those having almost the same composition were used.

(Electrodeposition experiment) The temperature of the electrodeposition solution was kept at 5 ° C.
50V with 50 × 50 × 1.5mm rolled copper plate as anode
After charging for 60 seconds, the substrate was washed with distilled water. After drying, it was heated at 220 ° C. for 1 hour to obtain an insulated copper plate. The appearance was good without foaming, and a glossy coating film was obtained. The coating film had a thickness of 5.0 ± 0.5 μm on both sides and a surface roughness of ± 0.1 μm. The electrodeposited solution stored at a liquid temperature of 5 ° C. has almost no change in physical properties even after one month.
When electrodeposition was performed under the same conditions, an electrodeposited film having substantially the same thickness was obtained. In addition, the acid value of the electrodeposition solution stored at a solution temperature of 25 ° C. increased after one month. Electrodeposition was carried out under the above conditions for electrodeposition. As a result, only a rough coating film was obtained despite low-temperature electrodeposition.

<Example 2> (Preparation of electrodeposition coating solution) N-methylpyrrolidone was added to the 20% polyimide varnish obtained in Example 1 to prepare a 15% polyimide varnish. And 6.5 g of triethylamine,
While stirring, 375 g of water was added dropwise, and the solid content concentration was 8.9.
%, PH 7.9 was obtained. (Electrodeposition experiment) The electrodeposition liquid was kept at a liquid temperature of 5 ° C.
Using a 1.5 mm rolled copper plate as an anode, a voltage of 200 V was applied, and after charging for 120 seconds, the substrate was washed with distilled water. After drying, it was heated at 220 ° C. for 1 hour to obtain an insulated copper plate. The appearance was good without foaming, and a glossy coating film was obtained. The thickness of the coating film is 11 ± 0.5 μm and the surface roughness is ± 0.1
μm. The electrodeposition solution stored at a temperature of 5 ° C.
Even after one month, there was almost no change in the physical properties of the electrodeposition solution, and an electrodeposition film having substantially the same thickness was obtained by performing electrodeposition under the same conditions.
In addition, the acid value of the electrodeposition solution stored at a solution temperature of 25 ° C. increased after one month. Electrodeposition was carried out under the above conditions for electrodeposition. As a result, only a rough coating film was obtained despite low-temperature electrodeposition.

<Comparative Example 1> (Preparation of Electrodeposition Coating Solution) N-methylpyrrolidone was added to the 20% polyimide varnish obtained in Example 1 to prepare a 15% polyimide varnish. Was added, and 825 g of water was added dropwise with stirring to obtain an electrodeposition emulsion composition having a solid content of 8.9% and a pH of 7.7. (Electrodeposition experiment) The temperature of the electrodeposition solution was kept at 5 ° C, and 150 x 50
A voltage of 50 V was applied using a rolled 1.5 mm copper plate as an anode, and after charging for 60 seconds, the substrate was washed with distilled water. After drying, heating was performed at 220 ° C. for 30 minutes, but the appearance was rough and the coating was not covered with resin.

[0031]

According to the present invention, there is provided a novel electrodeposition composition which is excellent in heat resistance, chemical resistance, and electrical properties and forms a coating film having a smoother and more uniform film thickness than conventional products. Can be. Electrodeposition and storage at low temperatures are possible,
Wide temperature range for use. Therefore, the electrodeposition composition of the present invention is extremely useful as an insulating material in the field of electric and electronic materials.

Claims (4)

[Claims] 1. An aromatic polyimide resin having a pendant acid group, which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and an oil-soluble solvent in which the resin is soluble in a range of from 0.5 to 0.5. 60% by weight, a water-soluble solvent in which the resin is soluble 2.
An electrodeposition composition having a solid content of 0.5 to 20% by weight, comprising 5 to 80% by weight, 0.5 to 80% by weight of water and a basic nitrogen-containing compound for neutralizing acid groups of the resin. 2. The oil-soluble solvent is 1-acetonaphthone, acetophenone, benzylacetone, methylacetophenone, dimethylacetophenone, propiophenone, valerophenone, anisole, methyl benzoate, benzyl benzoate, or a mixture thereof. 1
The composition for electrodeposition according to item 1. 3. The electrode according to claim 1, wherein the water-soluble solvent is N-methylpyrrolidone, N, N-dimethylformamide, dimethylsulfoxide, N, N-dimethylacetamide, sulfolane, or a mixture thereof. Wear composition. 4. An electrodeposition method comprising using or storing the electrodeposition composition according to claim 1 at a liquid temperature of 15 ° C. or lower.