JPS5936954B2 - Vehicle for water-based baking paints - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel vehicle for water-based baking paints.

In recent years, the paint industry has been considering water-based paints, high-solid paints, powder paints, etc. as replacements for organic solvent-based paints from the standpoint of non-pollution and resource conservation.

Among these, water-based paints are attracting attention because they are inexpensive and use harmless water, and their use in the field of top coats for light electrical equipment, automobiles, pre-coated metals, etc. is also being considered. However, when used in these high-grade fields, water bath type paints, although water-based, are
Approximately 30% of hydrophilic organic solvent must be used in combination, and problems remain in terms of corrosion resistance, chemical resistance, and solvent resistance in terms of coating film performance. Also, emulsion-type paints and other water-dispersed paints are 100% water-based or close to it, but the gloss, corrosion resistance, water resistance, and other adhesion to metals of the paint film are better than organic solvent-based paints. The current situation is that none of them has reached the stage of complete practical use. In view of the current situation, the present inventors have conducted intensive research with the aim of developing a vehicle that can be used in the top coat field and can provide a high-performance, non-polluting water-based paint. Obtained by polymerizing a monomer mixture containing as essential monomers a hydroxyalk-alkyl ester of an α3β monoethylenically unsaturated carboxylic acid and an α,β monoethylenically unsaturated carboxylic acid described in detail below. By using as a vehicle a novel self-protecting colloidal aqueous dispersion obtained by adding water to an at least partially neutralized homogeneous resin mixture of a copolymer and a water-insoluble polyepoxy compound. The present invention was completed by discovering that this was possible for the first time.

That is, the vehicle of the present invention is a self-protective colloidal vehicle for water-based baking paints, which contains 1 to 10% by weight of α,β-ethylenically unsaturated carboxylic acid, hydroxyalkyl ester of α,β-ethylenically unsaturated carboxylic acid. 4-40% by weight
A water-insoluble polyexy compound is added to an organic solvent solution of a copolymer obtained by polymerizing a monomer mixture in which the remainder consists of other copolymerizable ethylenically unsaturated monomers in an organic solvent.
Before, after, or at the same time as neutralizing part or all of the carboxyl groups of the copolymer, the copolymer 99-80
It is obtained by preparing a solvent solution of a resin in a proportion of parts by weight and 1 to 20 parts by weight of a water-insoluble polyepoxy compound, and then adding water to the solvent solution of this resin, or by adding a solvent solution of this resin to water. ...7 to 8.5, characterized in that the vehicle component is an aqueous dispersion having a solid content of 30% by weight or more and an organic solvent of 20% by weight or less.

In addition, "self-protecting colloid type" in the present invention refers to polymers that form colloidal particles (approximately 0.001
This means that the particles are dispersed with a size of ~0.1 micron).

Conventional polymers used as vehicles for water-soluble paints use a large amount of water-soluble monomers or hydrophilic monomers as constituent components to provide greater water solubility than solvent-based vehicle polymers. In order to make the polymer solubilized in water through base neutralization, the polymer must be designed with a high acid value and low molecular weight.

These restrictions become a factor that significantly reduces the properties of the resulting coating film, such as corrosion resistance, chemical resistance, and water resistance. On the other hand, conventional emulsion-type paints and other water-dispersible paint vehicles contain additives such as emulsifiers and dispersants to impart water dispersibility. However, even vehicles that do not use these additives have good dispersion stability and film-forming properties, as well as coating properties such as paint, paintability, gloss, corrosion resistance, and water resistance. A major drawback was that it was difficult to provide water-dispersible coatings with good performance. In contrast, the vehicle of the present invention has the advantage of being able to use components, acid values, and molecular weights that are substantially the same as those of copolymers for solvent-based coatings, and as mentioned above, it also has the advantage of being able to use copolymers such as emulsifiers and dispersants. It is a self-protective colloidal water dispersion that does not contain any additives and has excellent film-forming properties. The present invention provides a water-based baking paint that has good suitability and excellent film performance comparable to solvent-based top coat paints. Additionally, in the industry, it has been customary to incorporate water-insoluble polyepoxy compounds such as bisphenol-type epoxy resins and water-insoluble alicyclic polyepoxides as vehicle components in baking paints for top coats to improve coating performance. often done.

The formulation of such polyepoxy compounds improves the adhesion of the coating film,
It significantly improves processability, corrosion resistance, chemical resistance, boiling water resistance, etc. However, when trying to use a water-insoluble polyepoxy compound as a vehicle component of a water-based baking paint, it cannot be used with a water-soluble paint, and conventionally known emulsion-type paints and other water-dispersed paints cannot be used with water-insoluble polyepoxy compounds. It is also possible to add and use an epoxy compound in the form of an emulsion with an emulsifier, but contamination of the emulsifier causes a decrease in coating film performance, making it difficult to achieve the initial objective of improvement. There have also been attempts to directly disperse a water-insoluble polyepoxy compound in a vehicle dispersion, but it is difficult to obtain a stable dispersion with good film-forming properties. The present inventors have overcome all such difficulties. That is, a water-insoluble epoxy compound is uniformly blended in advance into an organic solvent solution of the copolymer,
Then, by dispersing this in water, a stable aqueous dispersion is obtained, and the water-based baking paint using this aqueous dispersion as a vehicle exhibits a much better balance of coating performance than conventionally known paints, and is superior to solvent-based vehicles. They discovered that the effect of adding a polyepoxy compound can be directly expressed.
In the present invention, α used in preparing the copolymer
, β-ethylenically unsaturated carboxylic acids include, for example, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, etc., and one type of these acids or a mixture of two or more types can be used.

This α,β monoethylenically unsaturated (carboxylic acid) is used to impart water dispersibility to the copolymer, and the carboxyl group is partially or partially removed by a basic compound in the subsequent neutralization step. It also serves as an internal acid catalyst in the curing 1 reaction when the vehicle of the present invention is used in combination with a crosslinking agent as an aqueous baking paint.
The amount of α,β monoethylenically unsaturated carboxylic acid used is in the range of 1 to 10% by weight, preferably 2 to 6% by weight of the monomer mixture. This amount used is substantially the same as the amount of internal acid in a copolymer for a container-type acid contact curing baking paint. In water-soluble copolymers, approximately 10% by weight or more of carboxyl group-containing monomers are usually required, and this is a factor that reduces coating film performance such as alkali resistance. Only a small amount is required
It is something that Examples of hydroxyalkyl esters of α,β monoethylenically unsaturated acids include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl arylate, 3-hydroxypropyl acrylate, and 3-hydroxypropyl acrylate. Hydroxypropyl metatarylate, 2-hydroxyethyl monomaleate, 2-hydroxypropyl monomaleate, etc. can be mentioned, and one type of these compounds or a mixture of two or more types can be used.

Since this hydroxyalkyl ester has a hydrophilic group, it is thought that it makes an auxiliary contribution to imparting water dispersibility to the copolymer, and furthermore, when the vehicle of the present invention is used in combination with a crosslinking agent as a water-based baking paint. It plays the role of a functional group component in the curing reaction. The amount of hydroxyalkyl ester of α,β monoethylenically unsaturated acid used is 4 to 40% by weight, preferably 6 to 2% by weight in the monomer mixture.
The amount is in the range of 0% by weight. In the present invention, other copolymerizable ethylenically unsaturated monomers used in preparing the copolymer include, for example, styrene, α-methylstyrene, vinyltoluene, α-methylvinyltoluene, vinyl Monoolefin aromatic compounds such as nylxylene; cyanide olefin compounds such as acrylonitrile, methacrylonitrile, ethacrylonitrile, and vinylidene cyanide; vinyl halides such as vinyl chloride, vinyl bromide, vinyl fluoride, and vinylidene chloride; Jageki [nito, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate,
Examples include esters of atarylic acid or methacrylic acid such as butyl methacrylate, hexyl acrylate, octyl acrylate; vinyl acetate; vinyl propionate; at least one monomer selected from the group of these compounds is effective. used.

The composition ratio of the monomer mixture is 1 to 10% by weight of α,β monoethylenically unsaturated carboxylic acid, and 4 to 40% by weight of hydroxyalkyl ester of α,β monoethylenically unsaturated carboxylic acid.
, and the remainder may be appropriately determined within the above range depending on the ratio of other copolymerizable ethylenically unsaturated monomers, desired dispersion characteristics and coating performance, but for the purpose of the present invention, copolymerizable ethylenically unsaturated monomer It is preferable to set the glass transition temperature of the polymer to be in the range of -20 to 5°C. The copolymer can be easily prepared by radical copolymerizing a monomer mixture by a generally well-known method.

In the present invention, it is effective to prepare the desired copolymer using an organic solvent and following the procedure of a solution polymerization method. At this time, various organic solvents can be used as the organic solvent, but
Hydrophilic organic solvents such as ethanol, propanol, butanol, and alkylene glycol monoalkyl ethers are suitable. It is preferable to consider the amount of organic solvent used so that the amount of organic solvent in the aqueous dispersion finally obtained is 20% or less. As a polymerization catalyst, a free radical catalyst such as azobisisobutyronitrile or benzoyl peroxide is used at a concentration of 0.1% based on the weight of the monomer mixture.
Used in amounts of ~5% by weight. In order to adjust the molecular weight of the copolymer, mercapto compounds such as lauryl mercaptan and mercaptoethanol can be used, and other chain transfer agents can also be used in combination. The polymerization reaction is
The process can be completed by carrying out the reaction at a temperature of about 65 to 140° C. under normal pressure or increased pressure for 6 to 10 hours. The molecular weight of the copolymer is substantially the same as that of the copolymer used in solvent-based baking paints, for example, the weight average molecular weight is 6,
It is in the range of 000 to 5,0000. Examples of water-insoluble polyepoxy compounds include polyglycidyl ethers of bisphenols and polyols, such as commercially available epoxy equivalents such as 6 Epicoat 828, 6 Epicoat 1001-Epicoat 1004'' (all products from Ciel Chemical Co., Ltd.), and the like. 100 to 4,000 bisphenol A type or bisphenol F type polyepoxy compounds; alicyclic polyepoxides, such as commercially available 6 UNOX.2
011 (Union Carbon & Carbide Co. product); Examples include epoxides of esters of unsaturated fatty acids such as drying oils of animals and plants and semi-drying oils of animals and plants, such as epoxidized linseed oil, which can be used as is or as a solution. used in the following conditions.

The amount of water-insoluble polyepoxy compound used is 99% of the copolymer.
The amount is 1 to 20 parts by weight to 80 parts by weight. The solvent solution of the resin in the present invention is prepared by adding a water-insoluble polyepoxy compound to the organic solvent solution of the copolymer before, after, or at the same time as neutralizing part or all of the carboxyl groups of the copolymer. It can be easily prepared by adding and stirring sufficiently to make a uniform resin solution.

At this time, if necessary, heating and stirring can be carried out at a temperature of about 120° C. or lower. The carboxyl groups of the copolymer are partially or completely neutralized with a basic compound.

Basic compounds that can be used include alkylamines such as ethylamine, propylamine, dimethylamine, diethylamine, dibutylamine, and triethylamine; unsaturated amines such as allylamine; aromatic amines such as aniline; cyclic amines such as morpholine and piperidine. Diamines such as hydrazine, ethylenediamine and piperazine; Alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; and ammonia. The amount of the basic compound to be used is determined appropriately depending on the composition of the copolymer, glass transition temperature, molecular weight, amount of water-insoluble polyepoxy compound, etc., but the final aqueous dispersion is 7 to 8.
．． The amount is such that it falls within the range of 5. The neutralization rate is preferably determined in the range of 25 to 100 mol% based on the total carboxyl groups. There are no particular restrictions on the neutralization procedure, and various methods can be employed.

For example, a method in which a water-insoluble polyepoxy compound and a basic compound are simultaneously added to a copolymer solution in an organic solvent and thoroughly stirred, or a method in which a water-insoluble polyepoxy compound is added to a copolymer solution in an organic solvent and the two are thoroughly mixed. Neutralization can be easily carried out by adding a basic compound to a uniform resin solution and stirring thoroughly, or by adding a basic compound to a solution of a copolymer in an organic solvent and stirring thoroughly. .
At this time, if necessary, heating and stirring can be performed at a temperature of about 120° C. or lower. The aqueous dispersion of the present invention can be easily prepared by adding water to a resin solvent solution, or by adding a resin solvent solution to water and stirring thoroughly. At this time, deionized water is used, but tap water can also be used. The amount of water used is such that the total resin solids content of the aqueous dispersion is 30% by weight or more, but since increasing the solids content increases the viscosity, it is necessary to
The amount is preferably in the range of 0 to 45% by weight. There are no particular restrictions on stirring, but in order to reduce the viscosity and facilitate dispersion, heating and stirring can be carried out at a temperature of about 120° C. or lower under normal pressure or increased pressure. At the beginning of the stirring operation, a rapid increase in viscosity is observed, but by continuing stirring, the viscosity stabilizes and a uniform aqueous dispersion is obtained. The aqueous dispersion has a solid content of 7 to 8.5, contains a solid content of 30% by weight or more, preferably 30 to 45% by weight, and an organic solvent of 20% by weight or less, and exhibits a milky white or milky blue colloidal state. It is something that

This dispersion is stable and there is no change in the dispersion form even if it is stored for more than one month, and the change in viscosity is extremely small. Furthermore, it is also extremely good in terms of various stability such as thermal stability, freezing stability, and mechanical stability, as well as film formability. The vehicle of the present invention consists of an aqueous dispersion.

This vehicle, when combined with various crosslinking agents such as thermosetting melamine resins, provides a water-based baking paint with excellent performance. Further, pigments, fillers, various paint additives, etc. can be added as appropriate depending on the use and desired performance. For example, an aqueous baking paint obtained by blending the vehicle of the present invention with a thermosetting melamine resin in an amount of 20 to 40% by weight based on the solid content of the vehicle and kneading the pigment is described in detail in the Examples. As mentioned above, it exhibits excellent paint stability and suitability for spray paints, and the film-forming ability is far superior to that of conventional water-based baking paints, making it suitable as a top coat paint for conventional solvent-based light electrical equipment, automobiles, pre-coated metal, etc. The coating performance is comparable to that of Hereinafter, the present invention will be explained in more detail with reference to Examples.

Note that parts in the examples are parts by weight. Reference Example 1 79 parts of isopropyl alcohol and 21 parts of ethylene glycol monobutyl ether were charged into a reactor equipped with a stirrer, a cooling tube, a thermometer, a nitrogen blowing tube, and a dropping load.

There, 20 parts of acrylic acid, 44 parts of 2-hydroxyethyl methacrylate,
A mixture consisting of 186 parts of styrene, 153 parts of n-butyl acrylate, and 6 parts of azobisisobutyronitrile (polymerization catalyst) was continuously added dropwise over 4 hours, and the polymerization was continued for 4 hours at the same temperature. A polymer solution in an organic solvent (hereinafter referred to as resin liquid I "I") was obtained. This resin liquid 1" has a non-volatile content of 80.0% and a solution acid value of 30.0%.
It was a transparent and viscous resin solution with a viscosity of 3 watts KOH/9 and a viscosity of 85120 poise (B-type viscometer, 25HC). In addition, the glass transition temperature (T9, estimated value) of the copolymer is approximately 18°C,
The weight average molecular weight (as determined by Mwl gel permeation chromatography) was 19,600. Reference Example 2 Into the same reactor as used in Reference Example 1, 80 parts of isopropyl alcohol and 20 parts of ethylene glycol monobutyl ether were charged.

Therein, 20 parts of acrylic acid, 59 parts of 2-hydroxyethyl methacrylate,
A mixture consisting of 121 parts of styrene, 19 parts of ethyl acrylate, 183 parts of n-butyl acrylate, and 6 parts of azobisisobutylronitrile. was continuously added dropwise over a period of 4 hours, and the polymerization was further continued at the same temperature for 4 hours to form a copolymer solution in an organic solvent (hereinafter referred to as "resin liquid").
I got it. This resin liquid "" has a non-volatile content of 79.8%,
Solution acid value is 31.3ηKOH/9, viscosity is 9310 po.
It was a transparent resin solution of 100 ml. The copolymer had a glass transition temperature of about 1° C. and a weight average molecular weight of 18,500. Example 1 Resin liquid 1 "1" 5 was added to a flask equipped with a stirrer and a thermometer.
Add 08 parts of dimethylethanolamine to this and add 12 parts of dimethylethanolamine.
The copolymer was neutralized by stirring at a temperature of 80° C. for 1 hour.

Next, “Epicote 1001” (manufactured by Ciel Chemical Co., Ltd.,
A homogeneous resin mixture was obtained by adding 13 parts of an 80% concentration ethylene glycol monobutyl ether solution of bisphenol A type polyepoxy compound (Bisphenol A type polyepoxy compound) and stirring at a temperature of 80° C. for 1 hour. 509 parts of deionized water was added to this resin mixture, stirred at a temperature of 40 to 50°C for 8 hours, and left to age at room temperature for 1 day, resulting in a nonvolatile content of 40.1% (the amount of organic solvent was 11.2%), viscosity is 15
00 centipoise, pH 7.7, transmittance (sample: resin content 10I) dispersion, cell width: 1? , Wavelength: 620mμ
) was obtained as an opalescent blue colloidal aqueous dispersion having 11.0 fl. Example 2 One [l] of resin liquid was added to the same flask as used in Example 1.
508 parts of dimethylethanolamine were charged, and 1 part of dimethylethanolamine was added
2 parts were added and neutralized as in Example 1.

Next, 25 parts of an 80% concentration ethylene glycol monobutyl ether solution of "Epicote 1001" was added and stirred at a temperature of 80°C for 1 hour to obtain a homogeneous resin mixture.This resin mixture was deionized. By adding 521 parts of water and treating in the same manner as in Example 1, the nonvolatile content was 40.3% (the amount of organic solvent was 11.1 (!)
)), a milky-blue, colloidal aqueous dispersion with a viscosity of 1470 centipoise, a pH of 7.8 and a transmittance of 9.1% was obtained. Example 3 Into the same flask used in Example 1, add resin liquid - "I"
508 parts of dimethylethanolamine were charged, and 1 part of dimethylethanolamine was added
2 parts were added and neutralized as in Example 1.

Next, 51 parts of an 80% concentration ethylene glycol monobutyl ether solution of 6 Epicoat and 100 r was added, and the mixture was stirred at a temperature of 80° C. for 1 hour to obtain a homogeneous resin mixture. 547 parts of deionized water was added to this resin mixture and treated in the same manner as in Example 1, resulting in a non-volatile content of 40.301 parts (organic solvent amount of 11.3 parts).
A milky blue colloidal aqueous dispersion was obtained with a viscosity of 1810 centipoise (1%), a viscosity of 7.8, and a transmittance of 8.7%. Example 4 Into the same flask used in Example 1, add resin ``I'' 5
Add 08 parts of dimethylethanolamine to this and add 12 parts of dimethylethanolamine.
It was neutralized by adding 100% of the total amount.

Next, 6 Unix 201″ (Union Carbon)
Manufactured by And Carbide, alicyclic polyepoxy compound)
A homogeneous resin mixture was obtained by adding 51 parts of an 80% concentration ethylene glycol monobutyl ether solution and stirring at a temperature of 80° C. for 1 hour. By adding 547 parts of deionized water to this resin mixture and treating it in the same manner as in Example 1, the nonvolatile content was 39.8% (the amount of organic solvent was 11.1%) and the viscosity was 1910%. A milky blue colloidal aqueous dispersion with a centipoise of 7.8 and a transmittance of 8.8% was obtained. Example 5 Into the same flask used in Example 1, add 50 ml of resin.
To this, 8 parts of dimethylethanolamine was added and neutralized in the same manner as in Example 1.

Next, 51 parts of an 80% strength ethylene glycol monobutyl ether solution of 6 Epicoat 1001″ is added,
A homogeneous resin mixture was obtained by stirring for 1 hour at a temperature of 80°C. By adding 547 parts of deionized water to this resin mixture and treating it in the same manner as in Example 1, the nonvolatile content was 40.1% (the amount of organic solvent was 10.8%).
, viscosity 590 centipoise, Pll 7.9, transmittance 7
．． A 6% opalescent blue colloidal aqueous dispersion was obtained. Comparative Example 1 In the same flask as used in Example 1, 508 parts of Resin 1[1] was charged, and 12 parts of dimethylethanolamine was added thereto for neutralization in the same manner as in Example 1.

Next, 495 parts of deionized water was added, stirred at a temperature of 40 to 50°C for 8 hours, and left to age at room temperature for 1 day, resulting in a nonvolatile content of 40.8% (the amount of organic solvent was 10%). 9
%), a viscosity of 1850 centipoise, a pH of 7.7, and a transmittance of 10.4%. Comparative Example 2 In Comparative Example 1, non-volatile component force S4O
．． An opalescent blue colloidal aqueous dispersion was obtained with a viscosity of 640 centipoise, a pH of 7.8, and a transmittance of 7.7%.

Example 6 The aqueous dispersions obtained in Examples 1, 2, 3, 4, and 5 and Comparative Examples 1 and 2 were tested for film-forming properties and storage stability.

The results were as shown in Table 1. Comparative Example 3 1015 parts of the aqueous dispersion obtained in Comparative Example 1 was added with ``Epicoat 1''.
25 parts of an 80% strength ethylene glycol monobutyl ether solution of 0017 and 25 parts of deionized water are added,
After stirring at a temperature of 40 to 50°C for 8 hours, it was left to mature at room temperature for 1 day, resulting in a non-volatile content of 40.0% (organic solvent amount: 10.9%), a viscosity of 2020 centipoise,
A colloidal aqueous dispersion with a ... of 7.8 and a transmittance of 10.0% was obtained.

When this aqueous dispersion was tested for film-forming properties in the same manner as in Example 6, a transparent film was not obtained but a cloudy film was obtained. Further, even when the aqueous dispersion was applied onto a glass plate and immediately heated at 100° C. for 2 hours, no transparent film could be obtained. Example 7 Using each of the aqueous dispersions obtained in Examples 1, 2, 3 and 4 and Comparative Examples 1 and 3 as a vehicle component,
Water-based baking paints for painting general equipment and light electrical equipment were prepared with the following formulation and tested for suitability for paint use and film performance.

The results were as shown in Table 2. In addition, the test piece is
Thickness 0.6m77 with parka +144 treatment! The paint was hand-sprayed onto a dull steel plate and baked at a temperature of 170°C for 20 minutes. Blend details: Total non-volatile content = 50%, pigment weight ratio = 40% to vehicle solid dispersion/melamine resin - 75/25 (non-volatile content weight ratio) Example 8 Aqueous dispersion obtained in Example 5 and Comparative Example 2 Using each of these as a vehicle component, water-based baking paints for pre-coated metal were prepared with the following formulations and tested for paint suitability and film performance.

Claims (1)

[Scope of Claims] 1 1 to 10% by weight of α,β-ethylenically unsaturated carboxylic acid, 4 to 40% by weight of hydroxyalkyl ester of α,β-ethylenically unsaturated carboxylic acid, and the remainder is other copolymerizable material. A water-insoluble polyepoxy compound is added to an organic solvent solution of a copolymer obtained by polymerizing a monomer mixture consisting of an ethylenically unsaturated monomer in an organic solvent, and a part of the carboxyl group of the copolymer or Before, after, or at the same time as the total neutralization, the resin is added to form a solvent solution consisting of 99 to 80 parts by weight of the copolymer and 1 to 20 parts by weight of the water-insoluble polyepoxy compound. pH obtained by adding water to a solvent solution of a resin or adding a solvent solution of this resin to water
7 to 8.5, a vehicle for a self-protective colloid type water-based baking paint, the vehicle component of which is an aqueous dispersion having a solid content of 30% by weight or more and an organic solvent of 20% by weight or less. 2. The vehicle for an aqueous baking paint according to claim 1, wherein the amount of α,β-ethylenically unsaturated carboxylic acid in the monomer mixture is in the range of 2 to 6% by weight. 3 The unneutralized copolymer has a glass transition temperature of -20 to 50
°C range and weight average molecular weight from 6,000 to 50,00
2. A vehicle for a water-based baking paint according to claim 1, wherein the vehicle is in the range of 0.0 to 1.0.