JPH03275709A - Aqueous emulsion of thermosetting resin - Google Patents

Abstract

PURPOSE:To obtain the subject aqueous emulsion for aqueous paint, etc., giving a self-hardened material having excellent toughness, resistance to brine spraying and hardness comprising a modified epoxy resin having a specific structure containing urethane bonding by using cationic surfactant. CONSTITUTION:A bisphenol A type epoxy resin and diamines such as m- xylenediamine are charged in a reaction vessel equipped with a thermometer, stirrer, condenser and dripping funnel and dissolved by adding a solvent such as butyl cellosolve, then reacted in heating, thus alkylene carbonate such as propylene carbonate, etc., is dripped and reacted to give a modified epoxy resin expressed by formula I [R1 is <=5C alkylene or aralkylene, etc.; R2 is H, alkyl or a group expressed by formula II (R3 is H or methyl)]. Next, an aqueous solution of cationic surfactant composed of a modified epoxy resin having tertiary amino group and/or quaternary amino group is added to said resin and mixed to afford the aimed aqueous emulsion.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an aqueous emulsion of a thermosetting resin useful for coating compositions such as paints and binder compositions such as adhesives. It is something.

(Prior art) Water-based emulsion, a thermosetting resin conventionally used industrially, is made of resin-based polyols such as alkyd resins, polyester resins, acrylic resins, and modified epoxy resins, as well as urea resins and melamine resins. Usually, resin-based curing agents such as phenolic resins, phenolic resins, and blocked isocyanate resins are mixed and dispersed in water.

However, in this case, the dispersibility of the resin polyol and the resin curing agent is different, which complicates the selection of a surfactant for emulsification, and the disadvantage is that the stability of the resulting emulsion is likely to be impaired. was there. Even if a coating composition or a binder composition can be obtained by using the aqueous emulsion of the thermosetting resin described above, they do not necessarily have sufficient performance. For example, paint films obtained from acrylic resin polyol emulsions, which are typical aqueous emulsions of thermosetting resins used in paints, and melamine resins lack toughness and salt water spray resistance; The coating film obtained from the block isocyanate emulsion and the block isocyanate emulsion lacks hardness.

A combination of an amine-modified epoxy resin polyol and a blocked isocyanate curing agent is known as a thermosetting aqueous emulsion with high salt spray resistance.For example, a chemically integrated polyol and curing agent has been proposed. has been done. This compound uses a compound with two incyanate groups attached to its aromatic ring, and takes advantage of the difference in reactivity between the two isocyanate groups to react with a monovalent blocking agent to form a half-block incyanate. It is obtained by reacting this with an amine-modified epoxy resin polyol.

Furthermore, in order to increase the toughness of this cured product, aliphatic diisocyanates can be used, but because the difference in reactivity between the two incyanate groups is small, it is difficult to obtain highly pure half-block isocyanates, and amines It has the disadvantage that it tends to gel when reacting with modified resin polyols.

(Problems to be Solved by the Invention) Based on the above background, the present inventor aimed to obtain an aqueous emulsion of a resin that does not require a curing agent and has self-curing properties.
As a result of intensive research, we have completed the present invention.

That is, the present invention provides an aqueous emulsion that provides a cured product with excellent toughness, salt spray resistance, and hardness by using a self-curing thermosetting resin.

(Means for Solving the Problems) The present invention provides an aqueous emulsion of a thermosetting resin containing a modified epoxy resin, wherein the modified epoxy resin (A) has the following structural group. It is an aqueous emulsion, and R2 is a hydrogen atom, an alkyl group, or a hydroxyalkylene carboxylate group with the following structure, and a cationic surfactant is added as a surfactant to the aqueous emulsion of a thermosetting resin. This is an aqueous emulsion of a thermosetting resin characterized in that the cationic surfactant is a modified epoxy resin (B) having a tertiary amino group and/or a quaternary amino group. It is an aqueous emulsion characterized in that the tertiary amino group and/or quaternary amino group of the modified epoxy resin (B) has two or more alkylene groups having 1 to 3 carbon atoms. be.

The configuration of the present invention will be explained in detail below.

The modified epoxy resin (A) used in the present invention has the above structural group (I), and this group contains a β-hydroxyalkyl urethane group, which releases glycol upon heating and recombines with other hydroxyl groups. By doing so, new urethane groups are formed, resulting in condensation and curing, resulting in so-called self-curing performance.

Although the above structural group (1) is hydrophilic, it alone does not have sufficient hydrophilic ability to disperse the resin in water, so it is necessary to use a surfactant in combination for emulsification. In this case, cationic surfactants are most desirable.

As a cationic surfactant, a modified epoxy resin (B) having a tertiary amino group and/or a quaternary amino group is most suitable in that it does not inhibit curability, and A modified epoxy resin in which two or more alkylene groups having 1 to 3 carbon atoms are attached to the group and/or the quaternary amino group is most preferable in terms of emulsion stability. Specific examples of cationic surfactants include tetraalkylammonium salts such as lauryltrimethylammonium salts, stearyltrimethylammonium salts, and alkylbenzyltrialkylammonium salts, which have a tertiary amino group and/or a quaternary ammonium group. Modified epoxy resin (B) is most desirable because it does not inhibit the curability of the emulsion of the present invention. This is modified epoxy resin (B)
It is presumed that this is because there are some hydroxyl groups inside, and these hydroxyl groups react with the hydroxyalkyl urethane groups in the modified epoxy resin (A).

The modified epoxy resin (A) of the present invention is obtained by reacting a bisphenol-based epoxy resin with an excess of diamine to produce a modified epoxy resin with a primary amino group terminal, and then reacting it with ethylene carbonate and/or propylene carbonate. It will be done.

Typical examples of bisphenol-based epoxy resins include:
Examples include bisphenol A-based epoxy resin and bisphenol F-based epoxy resin.

Preferred diamines include alkylene diamines, aralkylene diamines, and metaxylene diamines having 5 or more carbon atoms, such as pentanediamine, hexamethylene diamine, decamethylene diamine, metaxylene diamine, and inphorone diamine. Note that the use of boriakylene polyamines having carbon atoms of 4 or less, such as noalkylene diamines and diethylene triamines, is undesirable because odor is generated when the resulting emulsion is thermally cured.

The modified epoxy resin (B) can be obtained by reacting an epoxy resin with a compound having a secondary amino group or by reacting an epoxy resin with a compound having a tertiary amino group in the presence of an acid. can.

In this case, compounds having a secondary amino group and compounds having a tertiary amino group have 1 to 3 carbon atoms in these amino groups.
Compounds having two or more alkyl groups are most preferred from the viewpoint of emulsifying properties. For example, compounds having a secondary amino group include dimethylamine, methylethylamine,
diethylamine, dipropylamine, etc., and tertiary
Compounds with grade amino groups include triethylamine,
Demethylethanolamine, diethylethanolamine, etc.

Since the modified epoxy resin (B) obtained in this way exhibits surface-active ability in a state where it is neutralized with an acid, it is preferable to use an acid in combination. Examples of acids include organic acids such as formic acid, acetic acid, and lactic acid, and inorganic acids such as hydrochloric acid and phosphoric acid, and any one may be selected from these.

The aqueous emulsion of the present invention is usually produced by combining the modified epoxy resin (A) phase and an aqueous phase containing a cationic surfactant and stirring at high speed, or by combining the cationic surfactant and water stirred at high speed. This is carried out by a method in which the resin (A) phase is dropped into the phase, or a so-called phase inversion emulsification method in which water is added little by little to a mixed phase of the resin (A) and a cationic surfactant. During this production, a solvent may be used for reasons such as adjusting viscosity, and in this case, if necessary, the solvent can be distilled off by heating under reduced pressure after emulsification.

In addition, in order to easily self-cure the aqueous emulsion of the thermosetting resin of the present invention, tin acetate, tin octenoate,
It is preferable to use a tin compound such as dibutyltin dilaurate or a urethanization catalyst such as lead octenoate.

Furthermore, the aqueous emulsion of the thermosetting resin of the present invention may contain various known and commonly used additives such as pigments, antioxidants, fluidity modifiers, etc., if necessary.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 ■ Synthesis of modified epoxy resin (A) 4 equipped with a thermometer, stirrer, condenser, and dropping funnel
316 g of butyl cellosolve in a Tulo flask.

Prepare 272g of meta-xylene diamine and use Ebiclone 8.
40 (Bisphenol A type epoxy resin manufactured by Dainippon Ink & Chemicals Co., Ltd., epoxy fi185, trade name) 3
Add 70 g dropwise over 2 hours. After finishing dropping, 11
Heating at 0°C for 2 hours yields an amine-terminated modified epoxy resin.

Then, 306 g of propylene carbonate is added dropwise over a period of 1 hour, and heated at 110° C. for 2 hours after the addition, to obtain a modified epoxy resin solution having a group represented by chemical structural formula (1). This solution is a viscous, pale yellow solution with a non-volatile content of 75%.

■ Surfactant synthesis 4 equipped with thermometer, stirrer, condenser and dropping funnel
In a Tulo flask, 1900 g of Ebicuron 4050 (bisphenol A type epoxy resin manufactured by Dainippon Ink and Chemicals Co., Ltd., epoxy equivalent weight 950, trade name) and 1900 g of butyl cellosolve were charged and heated to form a uniform solution. To this solution, 146 g of diethylamine was added dropwise, and after the dropwise addition, the mixture was heated at 110° C. for 2 hours to obtain a modified epoxy resin having a tertiary amino group with two ethyl groups at the end.

After adding 180 g of lactic acid and stirring well, 326 g of water was added to obtain a viscous cationic surfactant with a non-volatile content of 50%.

■Synthesis of aqueous emulsion of thermosetting resin Modified epoxy resin (A) 150g, cationic surfactant 150g
Mix well, add 2 g of dibutyltin dilaurate, add 1575 g of water dropwise while mixing, and remove 1 non-volatile content.
An aqueous emulsion of 0% and pH 6.25 was obtained. This emulsion was stable for one month at room temperature.

Example 2 ■ Synthesis of modified epoxy resin (A) The metaxylene diamine of Example 1 ■ replaced with 340 g of inphorone diamine and the propylene carbonate replaced with 264 g of ethylene carbonate were optionally charged together with 325 g of butyl cellosolve. The reaction was carried out in the same manner as above to obtain a modified epoxy resin.

■Synthesis of surfactant The reaction was carried out in the same manner as in Example 1, except that the surfactant diethylamine in Example 1 was changed to 180 g of dimethylamine aqueous solution (50%) and water was changed to 180 g. A cationic surfactant was obtained.

■Synthesis of aqueous emulsion of thermosetting resin The modified epoxy resin (A) obtained in Example 2■ and the cationic surfactant obtained in Example 2■ were mixed, diluted with water, and the non-volatile content was 10%. , an aqueous emulsion with pH 6.6 was obtained.

Example 3 ■ Synthesis of modified epoxy resin (A) Example 1 ■ in which metaxylene diamine was replaced with 236 g of hexamethylene diamine, Ebicuron 840 (trade name) was replaced with Ebicuron 1050 (trade name), 950 g, and butyl cellosolve 1492 g. , Example 1■
A reaction was carried out in the same manner as above to obtain a modified epoxy resin with a non-volatile content of 50%.

■Synthesis of aqueous emulsion of thermosetting resin 180 g of modified epoxy resin (A) obtained in Example 1■, Example 1■
was mixed with 180 g of the cationic surfactant obtained in step 1, and 1440 g of water was added thereto to adjust the non-volatile content to 10% and the pH to 6.5.
An aqueous emulsion was obtained.

Application example: An aqueous emulsion of a thermosetting resin is used as an electrodeposition liquid, two zinc phosphate treated steel plates are used as a cathode and an anode, respectively, a DC voltage of 200V is applied, the process is carried out for 20 seconds, the cathode plate is taken out and washed with water, Bake at 180°C for 20 minutes. The obtained coated steel sheet showed the following performance.

Electrodeposition liquid Aqueous emulsion coating film performance of thermosetting resin
Example 1 2 3 (Effects of the Invention) The aqueous emulsion of the thermosetting resin obtained from the present invention has a cured product obtained by self-curing, which has excellent toughness, salt spray resistance, and hardness. Because of its excellent performance, it is effective as a binder for adhesives or water-based paints, especially cationic electrodeposition paints.

Pencil hardness scratches tear H H H H H H

Claims (1)

[Scope of Claims] 1. An aqueous emulsion of a thermosetting resin containing a modified epoxy resin, wherein the modified epoxy resin (A) has the following structural group. (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R_1 is an alkylene group with 5 or more carbon atoms, an aralkylene group, or a cycloalkylene group, and R_2 is a hydrogen atom, an alkyl group, or a hydroxyalkylene carboxy group with the following structure. 2. A cationic surfactant is added as a surfactant to the aqueous emulsion of the thermosetting resin according to claim 1. An aqueous emulsion of thermosetting resin characterized by its use. 3. The aqueous emulsion of a thermosetting resin according to claim 2, wherein the cationic surfactant is a modified epoxy resin (B) having a tertiary amino group and/or a quaternary amino group. 4. Thermosetting according to claim 2 or 3, wherein the tertiary amino group and/or quaternary amino group of the modified epoxy resin (B) has two or more alkylene groups having 1 to 3 carbon atoms. Aqueous emulsion of synthetic resin.