JPH04332779A - Aqueous resin dispersion - Google Patents

Abstract

PURPOSE:To provide an aqueous resin dispersion composed of a readily synthesized fluorine-containing copolymer. CONSTITUTION:An aqueous resin dispersion containing a fluorine-containing copolymer in which part or all of carboxyl groups in a copolymer, composed of fluoroolefin monomer units, crotonic acid monomer units, hydroxyalkyl crotonate monomer units or hydroxyalkyl vinyl ether monomer units and vinyl carboxylate monomer units or alkyl vinyl ether monomer units and containing crotonic acid monomer units in an amount of 7-30mol% based on the total amount of the whole monomer units are neutralized with a basic compound as a resin component.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an aqueous resin comprising a fluorine-containing copolymer having a hydroxyl group and capable of being stably dispersed in an aqueous medium, which is useful as an electrodeposition paint or other general aqueous coating material. This relates to dispersions.

0002

[Prior art and its problems] Paints made of fluorine-containing copolymers, which are cured by the combination of crosslinking agents such as polyvalent isocyanate compounds to form coatings with excellent physical properties, are used for building materials,
Widely used in fields such as automobiles. However, since most of the above paints are solution-type paints using organic solvents, a large amount of organic solvent evaporates during coating, which poses environmental pollution or hygiene problems.

[0003] Therefore, in recent years, in the field of fluorine-containing copolymer paints, much research has been done on water-based paints. A method for producing an aqueous fluorine-containing copolymer paint by emulsion polymerization using an acid as a comonomer (Japanese Unexamined Patent Publication No. 2002-240154), or a method for synthesizing a fluorine-containing copolymer having a hydroxyl group by a solution polymerization method. Then, a part of the hydroxyl groups is reacted with a divalent carboxylic acid anhydride to introduce a carboxyl group, and then neutralized with a basic compound to obtain an aqueous resin dispersion of a fluorine-containing copolymer having a hydroxyl group. A method (Japanese Unexamined Patent Publication No. 62-59676) and the like have been proposed. However, in water-based paints obtained by emulsion polymerization, adhesion to the substrate or stain resistance of the paint film surface is poor due to the presence of emulsifiers; on the other hand, hydroxyl group-containing copolymers and divalent carbon According to the method of reacting an acid anhydride, a water-based paint containing no emulsifier and having excellent physical properties can be obtained, but the manufacturing process is complicated and there is a problem that it is inferior in practicality.

In addition, in solution polymerization, generally well-known carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid and itaconic acid are used as comonomers for fluoroolefins, and later As shown below, it has been extremely difficult to introduce a sufficient amount of carboxyl groups into a fluorine-containing copolymer to make the polymer water-soluble by neutralizing it with a basic compound. In other words, the carboxyl group-containing monomers described above have poor copolymerizability with fluoroolefins, and even if subjected to large-scale polymerization, they will form a homopolymer, and the amount introduced into the fluorine-containing copolymer will be limited. is usually up to about 1%, and even when using crotonic acid, which is said to have relatively excellent copolymerizability with fluoroolefins, the copolymerization ratio of crotonic acid in the above-mentioned JP-A-2-240154 is , the maximum content is 5% by weight, and in that case, the physical properties of the coating film are considered to be poor, and preferably 0.1 to 3% by weight.
As stated. As far as the present inventors know, there are no methods for directly copolymerizing a carboxyl group-containing monomer with a fluoroolefin to obtain a fluorine-containing copolymer having a high concentration of carboxyl groups. A method using a carboxyl group-containing monomer having an alkyl vinyl ether structure that has excellent
73873), and even this method has the problem that it is difficult to obtain dihydric carboxylic acid monohydroxyalkyl vinyl ether, which is not a general-purpose chemical raw material, at low cost and with high purity. Ta.

[0005]

SUMMARY OF THE INVENTION The present invention aims to provide an aqueous resin dispersion suitable for paints, which is made of a fluorine-containing copolymer and can be obtained by simple operations without relying on emulsion polymerization. It is something to do.

[0006]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that, as mentioned above, the preferred loading amount in copolymerization with fluoroolefins is at most 3% by weight. When crotonic acid, which was thought to be The present inventors have discovered that by neutralizing with a basic compound, an aqueous resin dispersion that can form a coating film with excellent physical properties can be obtained, and the present invention has been completed. That is, the present invention provides the following monomer units (a
), (b), (c), (d) and optionally other radically polymerizable monomer units, and the proportion of crotonic acid monomer units based on the total amount of all monomer units is 7. This is an aqueous resin dispersion in which the resin component is a fluorine-containing copolymer in which some or all of the carboxyl groups in the copolymer are neutralized with a basic compound in an amount of 30 mol %. (a); Fluoroolefin monomer unit (b); Crotonic acid monomer unit (c); Crotonate hydroxyalkyl monomer unit and/or hydroxyalkyl vinyl ether monomer unit (d); Carboxylic acid vinyl ester Monomer units and/or
or alkyl vinyl ether monomer unit

[0007]
The present invention will be explained in more detail below. First, the synthesis of a copolymer (hereinafter referred to as a crotonic acid-containing copolymer) in which the proportion of crotonic acid monomer units is 7 to 30 mol % in the present invention will be explained. Examples of the fluoroolefins used to obtain the crotonic acid-containing copolymer include vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, etc. From this point of view, tetrafluoroethylene and chlorotrifluoroethylene are preferred, and chlorotrifluoroethylene is particularly preferred. Furthermore, two or more types of fluoroolefins may be used in combination.

As hydroxyalkyl crotonate,
2-hydroxyethyl crotonate, 2-hydroxypropyl crotonate, 3-hydroxypropyl crotonate,
Examples include 3-hydroxybutyl crotonate, 4-hydroxybutyl crotonate, 5-hydroxypentyl crotonate, and 6-hydroxyhexyl crotonate, with 2-hydroxyethyl crotonate being preferred. Examples of hydroxyalkyl vinyl ether include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 6-hydroxyhexyl vinyl ether, 4-hydroxycyclohexyl Examples include vinyl ether and 4-hydroxymethylcyclohexyl vinyl ether.

[0009] Examples of the carboxylic acid vinyl ester include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl versatate, and vinyl stearate. Vinyl acetate and vinyl versatate are preferable. and vinyl pivalate. Particularly preferred is vinyl pivalate, which has a molecular weight that does not significantly reduce the fluorine content in the resulting crotonic acid-containing copolymer and has good hydrolysis resistance. Examples of the alkyl vinyl ether include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-hexyl vinyl ether,
-ethylhexyl vinyl ether, cyclopentyl vinyl ether, cyclohexyl vinyl ether and 4-
Examples include methyl cyclohexyl vinyl ether, and ethyl vinyl ether is preferred in terms of stability of the polymerization solution and heating stability of the polymer solution after polymerization.

[0010] Monomers that may be used as desired include allyl alcohol, ethylene glycol monoallyl ether, diethylene glycol monoallyl ether,
Allyl ethers such as 3-hydroxypropyl allyl ether; olefins such as ethylene, propylene, and 1-butene; alkyl crotonates such as methyl crotonate, ethyl crotonate, and butyl crotonate; vinyl chloride, vinylidene chloride, etc. It will be done.

The preferred proportions of monomer units in the crotonic acid-containing copolymer are: (a) fluoroolefin monomer units;
────30-55 mol% (b) Crotonic acid monomer unit
──── 7-30 〃 (c) Crotonate hydroxyalkyl monomer unit and/or
Hydroxyalkyl vinyl ether monomer unit --- 5 to 16 (d) Carboxylic acid vinyl ester monomer unit and/or
Alkyl vinyl ether monomer unit
─── 25-40〃 (e) Other radically polymerizable monomer units ────
It is 0-30〃. If the content of fluoroolefin monomer units is less than 30 mol%, the weather resistance of the polymer will be poor, while if it exceeds 55 mol%, the polymer will have poor solubility in the polymerization medium and the polymerization will become unstable. Become. If the amount of crotonic acid monomer units is less than 7 mol %, it will be difficult to make it water-soluble, while if it exceeds 30 mol %, the water resistance will be poor. In a polymer in which the amount of carboxylic acid vinyl ester monomer units or alkyl vinyl ether monomer units is less than 25 mol %, it is difficult to introduce 7 mol % or more of the above-mentioned crotonic acid monomer units. If the amount of hydroxyalkyl crotonate monomer units or hydroxyalkyl vinyl ether monomer units is less than 5 mol%, the physical properties of the cured coating formed by using a crosslinking agent such as melamine in combination will be poor; If it exceeds this, the water resistance will be poor.

[0012] The preferred copolymerization ratio of each monomer used to obtain the above-mentioned crotonic acid-containing copolymer is 40 to 70 mol% of fluoroolefin, 10 to 70 mol% of crotonic acid.
40 mol%, hydroxyalkyl crotonate or hydroxyalkyl vinyl ether 5-20 mol%, carboxylic acid vinyl ester or alkyl vinyl ether 25
-40 mol% and other monomers 0-30 mol%. If the charging ratio of crotonic acid is less than 10 mol %, 7 mol % or more of crotonic acid monomer units cannot be introduced into the polymer from the viewpoint of copolymerizability with fluoroolefins. A more preferable amount of carboxylic acid vinyl ester or alkyl vinyl ether to be used is at least the same amount as the amount of crotonic acid used in combination. If the amount of carboxylic acid vinyl ester or alkyl vinyl ether used is less than the amount of crotonic acid used, the copolymerization yield of crotonic acid will be poor.

As the polymerization method, solution polymerization using the following organic solvent and radical-generating polymerization initiator is preferred, and the polymerization temperature and pressure are 0°C, respectively.
-80°C and 3-10 Kg/cm2 are suitable. In polymerization using an aqueous medium, the solubility of crotonic acid in water is high, so the distribution ratio to the oil droplet side formed by other monomers is low, and the desired amount of crotonic acid monomer units is incorporated into the copolymer. Difficult to introduce. Polymerization solvents include toluene, xylene, cyclohexane, n-hexane, ethyl acetate, butyl acetate, methyl isobutyl ketone, cyclohexanone,
Examples include ethanol, n-butanol, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether. As a polymerization initiator, peroxides such as diisopropyl peroxydicarbonate, tertiary butyl peroxypivalate, benzoyl peroxide, and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile are used. etc. Furthermore, in order to capture acids generated from fluoroolefins during polymerization and stabilize polymerization, appropriate amounts of basic compounds, anion exchange resins, hydrotalcites, epoxy compounds, etc. may be added to the polymerization solution. .

[0014] Part or all of the carboxyl groups in the crotonic acid-containing copolymer obtained by the above polymerization are
By neutralizing with a basic compound, a fluorine-containing copolymer that is stably dispersed in an aqueous medium can be obtained. When neutralizing a portion of the carboxyl groups in the crotonic acid-containing copolymer, the preferred degree of neutralization is 50% or more. If the degree of neutralization is less than 50%, it may be difficult to make it aqueous. Specifically, the polymer solution obtained by polymerization is dropped into a large excess of poor solvent, the crotonic acid-containing copolymer is isolated, and the obtained polymer is dissolved in isopropanol, isobutanol, n-butanol, etc. Preferably 50 for organic solvents
Ammonia is dissolved in about % by weight, and then ammonia,
Examples include a method of adding basic compounds such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, diisopropylamine, ethylenediamine, diethylenetriamine, triethanolamine, and methylethanolamine, or a solution thereof in an organic solvent. An aqueous resin dispersion is obtained by adding water to the neutralized polymer solution and diluting it to a solid content concentration of about 10% by weight. The aqueous resin dispersion obtained by the above method contains only a small amount of organic solvent such as isopropanol, isobutanol or n-butanol, and can usually be used as a water-based paint as is, or if necessary, heated to remove the organic solvent. may be removed.

The main uses of the aqueous resin dispersion of the present invention include coating agents, such as melamine resins, benzoguanamine resins, urea resins, which can react with hydroxyl groups or carboxyl groups when used as coating agents.
It is preferable to use a crosslinking agent such as resol, novolac or blocked isocyanate in combination, and additives such as pigments, pigment dispersants, ultraviolet absorbers, leveling agents, and slip agents can also be used. As the coating method, general methods such as spray coating, roll coater coating, electrodeposition coating, etc. can be adopted, and examples of the base material to be coated include metal, plastic, wood, and paper.

[0016]

[Examples] The present invention will be explained in more detail below with reference to Examples and Application Examples. Example 1 The following ingredients were charged into a 1 liter pressure autoclave equipped with a stirrer. xylene
260g vinyl pivalate
119g (0.93mol) Ethyl vinyl ether 33g
(0.46 mol) 2-hydroxyethyl crotonate 60 g (0.46 mol)
46 mol) Crotonic acid
40g (0.46 mol) tert-butyl peroxypivalate 6.
9g IXE-700 (manufactured by Toagosei Kagaku Kogyo Co., Ltd., anion exchanger) 8g Next, after purging with nitrogen and degassing under reduced pressure, 270g of chlorotrifluoroethylene (hereinafter abbreviated as CTFE) (
2.32 mol) was introduced and the temperature was raised. After reacting at 64° C. for 8 hours, unreacted CTFE was removed, the pressure was returned to normal pressure, and the autoclave was opened to obtain a fluoroolefin copolymer solution. After filtering IXE-700, the resulting solution was poured into water to precipitate a copolymer.

The copolymer obtained by vacuum drying at 50°C for 3 days (yield: 80%) has an acid value of 37 (mgKOH/g polymer) and a hydroxyl value of 42 (mgKOH/g polymer). The molecular weight in terms of polystyrene was 10,000, and the fluorine content as determined by the alizarin complexion method was 24% by weight. The amounts of crotonic acid monomer units, 2-hydroxyethyl crotonic acid monomer units, and CTFE monomer units are determined from the acid value, hydroxyl value, and fluorine content, respectively, and the amounts of vinyl pivalate monomer units and ethyl vinyl ether monomer units each have a copolymerization yield of 10
The content in the above copolymer was determined assuming that it was 0%. The results were as follows. CTFE
Monomer unit/vinyl pivalate monomer unit/ethyl vinyl ether monomer unit/2-hydroxyethyl crotonic acid monomer unit/crotonic acid monomer unit = 47/25/1
2/8.5/7.5 (mol%)

Next, 100 g of the above copolymer was dissolved in a mixed solvent consisting of 60 g of isopropanol and 10 g of butyl cellosolve. While stirring the obtained solution, 6.6 g of triethylamine was added dropwise thereto, and then ion-exchanged water was added dropwise to adjust the solid content to 30%. The initial viscosity (Brookfield viscometer, 25°C) of the obtained aqueous resin dispersion was 600 cps, and even after storage at 35°C for one month, the viscosity did not increase to 610 cps, and no agglomerated sediment was observed. .

Example 2 In place of ethyl vinyl ether in Example 1, Ve
ova10 [Shell Chemical Co., Ltd., vinyl ester of carboxylic acid having 10 carbon atoms, which is a mixture of geometric isomers] 92
A copolymer was synthesized in the same manner as in Example 1 except that g (0.46 mol) was used. Monomer ratio of preparation Vinyl pivalate
119g (0.93mol) Veova10 [Shell Chemical Co., Ltd.] 92g
(0.46 mol) 2-hydroxyethyl crotonate 60
g (0.46 mol) Crotonic acid
40g (0.46mol) CTFE
270 g (2.32 mol) The obtained copolymer (yield: 80%) had an acid value of 36 (m
gKOH/g polymer), hydroxyl value is 38 (mgKOH/g polymer),
g polymer), the molecular weight in terms of polystyrene was 8,000, and the fluorine content was 19% by weight. The proportions of each monomer unit in the copolymer, determined in the same manner as in the previous example, are as follows. CTFE monomer unit/vinyl pivalate monomer unit/Veova 10 monomer unit/2-hydroxyethyl crotonate monomer unit/crotonic acid monomer unit = 45/25/13/8.6/8. 4 (mol %) An aqueous resin dispersion was produced in the same manner as in the previous example using 5.7 g of dimethylaminoethanol per 100 g of the above copolymer. The initial viscosity (Brookfield viscometer, 25°C) of the obtained aqueous resin dispersion was 460 cps, and even after storage at 35°C for one month, the viscosity did not increase to 450 cps, and no agglomerated sediment was observed. .

Example 3 Everything was the same as Example 2, except that 40 g (0.31 mol) of 2-hydroxyethyl crotonate and 60 g (0.70 mol) of crotonic acid were used, and ethyl acetate was used as the polymerization solvent. A copolymer was synthesized in the same manner. The obtained copolymer (yield: 80%) had an acid value of 55 (mgKOH/g
polymer), hydroxyl value is 25 (mgKOH/g polymer),
The molecular weight in terms of polystyrene was 8,000, and the fluorine content was 20% by weight. The proportion of each monomer unit in the copolymer is as follows. CTFE monomer unit/vinyl pivalate monomer unit/Veova 10 monomer unit/2-hydroxyethyl crotonate monomer unit/crotonic acid monomer unit = 44/25/13/5.7/12
．． 3 (mol %) An aqueous resin dispersion was produced in the same manner as in the previous example using 8.7 g of dimethylaminoethanol per 100 g of the above copolymer. The initial viscosity of the obtained aqueous resin dispersion was 38
0cps, and even after storage at 35℃ for 1 month, 410cps
There was no increase in PS or viscosity, and no agglomerated sediment was observed.

Example 4 A copolymer was synthesized using the monomers having the following compositions as raw materials in the same manner as in each of the above examples. CTFE
220g (1.89mol) Vinyl pivalate 9
1g (0.71 mol) Vinyl acetate
61g (0.71mol) 2-hydroxyethyl crotonate 92g (0.71mol)
71 mol) Crotonic acid
61 g (0.71 mol) The obtained copolymer (yield: 60%) had an acid value of 82 (m
gKOH/g polymer), hydroxyl value is 85 (mgKOH/g polymer)
g polymer), the molecular weight in terms of polystyrene was 6,500, and the fluorine content was 23% by weight. The proportion of each monomer unit in the copolymer is as follows. CTF
E monomer unit/vinyl pivalate monomer unit/vinyl acetate monomer unit/2-hydroxyethyl crotonate monomer unit/crotonic acid monomer unit = 36.2/19/19/
13.2/12.6 (mol %) An aqueous resin dispersion was produced in the same manner as in the previous example using 14.7 g of triethylamine per 100 g of the above copolymer. The initial viscosity of the obtained aqueous resin dispersion was 850 cps, and even after storage at 35° C. for one month, the viscosity did not increase to 850 cps, and no agglomerated sediment was observed.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 4 except that 0.71 mol of acrylic acid was used in place of crotonic acid. Since the polymer solution obtained after polymerization was cloudy, it was separated into a cloudy substance and a transparent solution by centrifugation. As a result of measuring the infrared absorption spectrum of the cloudy substance, it was found that it was polyacrylic acid. On the other hand, the above transparent solution was poured into a mixed solution of water/methanol = 1/1,
A copolymer was precipitated. The results of determining the proportions of each monomer unit constituting the obtained copolymer were as follows. This shows that acrylic acid was only slightly copolymerized. CTFE monomer unit/vinyl pivalate monomer unit/vinyl acetate monomer unit/2-hydroxyethyl crotonate monomer unit/acrylic acid monomer unit = 40.5/22/22/14.5 /1 (mol%)

Application Examples 1 to 4 Hexamethoxymethylated melamine (Cymel 303 manufactured by Mitsui Cyanamid Co., Ltd.) was 1.5 per 20 g of each of the four types of aqueous resin dispersions obtained in Examples 1 to 4 above.
g was added to prepare a water-based paint, and it was coated on a 0.5 mm thick chromate-treated aluminum plate using a bar coater so that the dry coating film was 20 μm, and then coated in an electric oven at 20 μm.
Baking was performed at 0°C for 10 minutes. All four types of cured coatings obtained were colorless and transparent, and the score was 100/100 in the cross-cut adhesion test according to the method specified by JIS K5400, and even after immersion in boiling water for 1 hour.

[0024]

Effects of the Invention The aqueous resin dispersion of the present invention is a highly pure product obtained by copolymerizing crotonic acid, which is easily available in high purity and has excellent copolymerizability with fluoroolefins, with other monomers. Since the main component is a fluorine-containing copolymer with an acid value, it can be produced by extremely simple operations. Further, since the aqueous resin dispersion of the present invention also contains hydroxyl groups, it can form an excellent cured coating film by using a crosslinking agent such as melamine, and is most suitable as a highly weather resistant aqueous coating agent.

Claims (1)

[Claims] Claim 1: The following monomer units (a), (b), (c),
(d) and optionally other radically polymerizable monomer units, in a copolymer in which the proportion of crotonic acid monomer units is 7 to 30 mol% based on the total amount of all monomer units. An aqueous resin dispersion whose resin component is a fluorine-containing copolymer in which some or all of the carboxyl groups have been neutralized with a basic compound. (a); Fluoroolefin monomer unit (b); Crotonic acid monomer unit (c); Crotonate hydroxyalkyl monomer unit and/or hydroxyalkyl vinyl ether monomer unit (d); Carboxylic acid vinyl monomer unit mer units and/or alkyl vinyl ether monomer units