JPH0667968B2 - Method for producing emulsion polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention can be effectively used as a coating composition, particularly a coating composition for metals, and has excellent adhesiveness, water resistance, corrosion resistance, alkali resistance, and other properties. The present invention relates to a method for producing an emulsion polymer which has low foaming, low odor, and excellent mechanical stability.

[Conventional technology and its problems]

As a method for producing this type of emulsion polymer, a method of emulsion polymerizing various oil-soluble monomers in the presence of a conventional emulsifier is adopted, and the emulsifier is mainly a nonionic or anionic surfactant. Is often used. Here, the emulsifier is used to maintain the dispersion stability of the system during polymerization and to maintain the dispersion stability of the emulsion polymer produced, while the emulsification produced by the presence of the emulsifier. It is well known that the polymer becomes liable to foam, which causes troubles in handling work, and when it is used for coating, for example, the foam causes undesirable effects such as generation of pinholes in the coating film. Has been.
In addition, the emulsifier remains in the emulsion polymer film when it is formed, and adversely affects the properties of the film. That is, it is well known that the water resistance of the film, the adhesion to the substrate, etc. are impaired, and when this emulsion polymer is used as a coating composition, particularly a metal coating composition, corrosion resistance, This causes a defect that physical properties such as alkali resistance are deteriorated.

A method has been proposed for obtaining an emulsion polymer by emulsion-polymerizing only a radical-generating initiator having a sulfate group without using an ordinary emulsifying agent, but in this case as well, the stability of the polymerization system and the emulsion polymer to be produced is proposed. It is obvious that a large amount of an initiator is required to retain the sulphate by the sulfate group, which has a bad influence on the water resistance, and the mechanical stability of the emulsion polymer is not sufficient.

On the other hand, in a mixed solution of a water-soluble organic solvent and water, an ethylenically unsaturated monomer containing an unsaturated carboxylic acid is polymerized using a radical-forming initiator to utilize the carboxyl group of the unsaturated carboxylic acid. Although a method for obtaining an emulsion polymer has been proposed, this generally requires a large amount of a water-soluble organic solvent, and it cannot be said that the problem of odor, the adhesion to metals and the like, and the corrosion resistance are sufficient.

Further, in the conventional production of emulsion polymers, synthetic or natural water-soluble polymeric substances such as polyvinyl alcohol, fibrin ether, polyacrylic acid salt, starch, polyacrylamide and polyester are used as stabilizers without using an emulsifier. Although it has been proposed to obtain an emulsion polymer by emulsion polymerization, such a water-soluble polymer substance, so-called protective colloid, is inferior in its ability to impart stability, so that the polymerizable monomer to be applied is limited. Also, since the amount of such protective colloid is large, the physical properties such as water resistance of the film obtained from the emulsion polymer are inferior as in the case of the emulsifier. In addition, when applied to a metal, the physical properties such as corrosion resistance and adhesion of the coating film are insufficient for these reasons.

[Means for solving problems]

As a means for solving the above-mentioned conventional drawbacks, the present invention replaces an ordinary emulsifier with a part or all of P-OH groups produced by esterifying at least a part of terminal epoxy groups of an epoxy resin with a phosphorus-containing acid. A water-dispersible or water-soluble modified epoxy resin (hereinafter simply referred to as modified epoxy resin) obtained by reacting with

[Action]

A water-dispersible epoxy resin obtained by neutralizing a part or all of P-OH groups produced by esterifying at least a part of terminal epoxy groups of an epoxy resin with a phosphorus-containing acid is used in emulsion polymerization. It was revealed that emulsion polymerization can be carried out with excellent results without the presence of ordinary emulsifiers. Although its role is not clear, it is presumed that it plays a role as a protective colloid similar to a kind of stabilizer, that is, a water-soluble polymer. Also,
The amount used can be widely used from a relatively small amount to a large amount, and the polymerization system and the obtained emulsion polymer are very stable.

The modified epoxy resin used in the present invention not only promotes emulsion polymerization smoothly, but also improves the performance of the film when the emulsion polymer obtained by using it is used as a coating material and a binder. The epoxy resin has excellent physical properties such as rigidity, adhesion, corrosion resistance, and chemical resistance, while the phosphorus-containing acid has a function of improving the adhesion to a metal. For the performance of the film obtained from the coating material using the emulsion polymer obtained by using a modified epoxy resin which is a reaction product of the epoxy resin containing the acid contained in the emulsion polymerization,
It is presumed that not only the above-mentioned properties of the epoxy resin can be imparted, but also the adhesion of the film to the metal is further improved. Furthermore, a polymer obtained by combining these epoxy resins and an ethylenically unsaturated monomer is to impart a flexible and stretchable property to the properties of the epoxy resin by, for example, copolymerizing a (meth) acrylic monomer. It is possible to obtain various physical properties by various combinations according to the purpose.

[Water-dispersible epoxy resin]

Several proposals have been made for the modified epoxy resin (for example, JP-A-58-179273), and the modified epoxy resin used in the present invention can be produced according to such a known method. The outline is as follows.

Epoxy resin The epoxy resin used in the modified epoxy resin of the present invention has the following general formula Suitable are those having more than one substituted or unsubstituted glycidyl ether group shown in the molecule, such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, phenol novolac epoxy resin, and bisphenols. Although various compounds such as diglycidyl ether of alkylene oxide adduct can be used, from the viewpoint of adhesion and corrosion resistance, diglycidyl ether of bisphenol A is preferable.
The epoxy equivalent is not particularly limited, but the epoxy equivalent is preferably about 100 to 1000.

○ Esterification and Neutralization with Phosphorus-Containing Acid The phosphorus-containing acid used as a raw material for the modified epoxy resin is an acid having a phosphorus atom in the molecule, such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, polyphosphoric acid. , Phosphonic acid, phosphinic acid and the like, and orthophosphoric acid is particularly preferable.

The phosphoric acid esterified product of the epoxy resin is obtained by mixing the epoxy resin and the phosphorus-containing acid in a ratio such that the epoxy group remains after the reaction, and heating and reacting in the presence or absence of a solvent. When a solvent is used, it is advisable to add a small amount of a water-soluble solvent such as methyl ethyl ketone or ethyl cellosolve to the extent that the reaction between the epoxy resin and phosphoric acid proceeds smoothly. The heating temperature is not particularly limited, but it is preferable to perform the heating at a temperature at which decomposition of the epoxy resin does not occur and the reaction is completed in an appropriate time.

Neutralization of the phosphoric acid esterified product with a base may be carried out by a known method. For example, it can be carried out by using a base such as ammonia, amine, or an alkali metal compound, but from the viewpoint of corrosion resistance, it is volatilized at room temperature. It is preferable to use ammonia because it does not remain in the film. When the film is dried by heating, a low boiling point amine may be used. There is no particular limitation on the degree of neutralization, but it is suitable to set the pH to 5 or higher. Specific neutralization takes into consideration factors such as the type of monomer to be polymerized and the pH value desired for the polymerization system, and neutralizes some or all of the P-OH groups in the phosphoric acid esterified product. It can be done by things. The modified epoxy resin thus produced is water-dispersible or water-soluble or a mixture thereof, and is preferably used in the present invention.

[Ethylenically unsaturated monomer and emulsion polymerization method]

Examples of the ethylenically unsaturated monomer used in the present invention include the followings, and these are selected according to the use or copolymerizability, and one or more kinds are used.

1) α, β-unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, n-butyl acrylate,
Alkyl esters of acrylic acid or methacrylic acid such as isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate. , Hydroxyalkyl acrylates and methacrylates such as hydroxypropyl acrylate, amino group-containing esters such as dimethylaminoethyl methacrylate, glycidyl group-containing esters such as glycidyl methacrylate and maleic acid,
Fumaric acid and itaconic acid esters.

2) α, β-unsaturated carboxylic acids and sulfonic acids and / or salts thereof, for example, unsaturated-basic acids such as acrylic acid, methacrylic acid, vinylsulfonic acid, vinyltoluenesulfonic acid and salts thereof, itaconic acid, Unsaturated dibasic acids such as fumaric acid and maleic acid, and their half esters and salts.

3) Amides of α, β-unsaturated acids such as acrylamide, methacrylamide, maleic amide and maleic imide.

4) Substituted amides of unsaturated carboxylic acids such as N-methylol acrylamide and methacrylamide, diacetone acrylamide, N-butoxymethyl acrylamide.

5) Vinyl esters such as vinyl acetate, vinyl propionate and vinyl chloride.

6) Nitriles of α, β-unsaturated carboxylic acids such as acrylonitrile and methacrylonitrile.

7) Vinyl ether, such as vinyl ethyl ether.

8) Vinyl ketone, such as vinyl methyl ketone.

9) Vinylamides such as vinylformamide and vinylacetamide.

10) Aromatic vinyl compounds such as styrene and vinyltoluene.

11) Heterocyclic vinyl compounds such as vinyl pyridine and vinyl pyrrolidone.

12) Vinylidene halide compounds, such as vinylidene chloride and vinylidene fluoride.

13) Divinyl compounds such as divinylbenzene and butanediol dimethacrylate.

14) α-olefins such as ethylene and propylene.

15) Diolefins such as butadiene and isoprene 16) Allyl compounds such as allyl acetate, allyl alcohol and diallyl phthalate.

By combining various of these monomers, for example, by combining acrylic ester and methacrylic ester, styrene, etc., it is possible to obtain various types of resins from hard resin to soft resin, from room temperature drying to heat drying type, If a reactive monomer is used, it can be made into a bake-curable resin, and various properties can be obtained in addition to the properties of the epoxy resin.

Further, when a carboxyl-containing monomer such as acrylic acid or methacrylic acid is used, it is possible to further enhance the system stability, chemical stability and mechanical stability of the emulsion polymer by neutralizing with a base later. it can. However, if many hydrophilic monomers such as these carboxy-containing monomers and hydroxy-containing monomers are used, the water resistance of the coating film becomes poor,
It is preferably within 20% by weight of the total amount of monomers.

The amount of the modified epoxy resin used in the method for producing the emulsion polymer according to the present invention can be used in the range of modified epoxy resin / ethylenically unsaturated monomer = 1/99 to 50/50 in weight percentage. , And more preferably 3/97 to 25/75
The range is good. When the amount of the epoxy resin is less than 1/99, not only the dispersion stability of the monomer is insufficient and the polymerization is not smoothly carried out, but also the obtained emulsion polymer does not exhibit the characteristics of the epoxy resin so much. If the amount of epoxy resin is more than 50/50, the amount of epoxy resin is too much and gelation easily occurs during the polymerization.

As a method for producing the emulsion polymer of the present invention, a method according to a known method may be used. As an example, a glass flask is charged with deionized water and a modified epoxy resin, the pH of the system is adjusted to 5.0 to 9.0 suitable for polymerization by a base, and the solid content is 0.1 to 4
Make a 0% dispersion. Then, the mixture is degassed with nitrogen gas, ethylenically unsaturated monomers are sequentially charged while stirring with heating, and a polymerization reaction is carried out according to a conventional method. At this time, the charging method of the monomer may be batch charging or divided charging. As the radical generating catalyst, hydrogen peroxide, t-butyl hydroperoxide, ammonium persulfate, potassium persulfate, etc. are diluted with deionized water and added dropwise or in a batch, and the reaction temperature is preferably 100 ° C. or lower, more preferably 30 ° C. or lower. Polymerize at ~ 90 ° C for 2 hours or more. In this case, sodium sulfite,
If a reducing agent such as ferrous sulfate or Rongalit is used together, the polymerization reaction can proceed smoothly. After completion of the polymerization, the pH is adjusted to 5 to 10 by neutralizing with a base to obtain a stable milky white emulsion polymer. At this time, when ammonia water or amine is used, it is preferable to adjust the pH to 6 to 8 from the viewpoint of odor. The emulsion polymer can be usually obtained at a concentration of 60% by weight or less of solid content.

〔The invention's effect〕

The emulsion polymer obtained by the present invention forms a film having excellent performance by room temperature drying or heat drying, and is also used as a bake-curable type by using the emulsion polymer alone or in combination with a urea resin, a crosslinking agent such as a melamine resin. You can do it.

The emulsion polymer produced by the method for producing an emulsion polymer of the present invention is an emulsion polymer having less foaming, low odor and good mechanical stability as compared with an emulsion polymer using an ordinary emulsifier and the like. The film formed from the emulsion polymer itself has excellent properties such as adhesion, water resistance, corrosion resistance, and alkali resistance, but if necessary, other water-soluble organic resins such as melamine resin and epoxy resin, colloidal It may be used by mixing with a water-soluble inorganic substance such as silica, while titanium oxide,
Pigments such as calcium carbonate, general rust preventive pigments, inhibitors and the like may be added. Further, a thickener, a dispersant, a film forming aid, a defoaming agent, an organic solvent, etc. may be added.

As the use of the emulsion polymer obtained by the method of the present invention,
It can be used for coating glass, wood, metal, plastic, paper moldings or sheets.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Unless otherwise specified, parts and% used below are parts by weight and% by weight, respectively.

[Example 1] 35 parts of bisphenol A / diglycidyl ether (epoxy equivalent 250) was dissolved in 15 parts of ethyl cellosolve, 3 parts of orthophosphoric acid was further mixed in the solution, and the reaction was carried out at 50 ° C for 3 hours. The temperature was raised to 80 ° C. and the reaction was continued for 5 hours to obtain a phosphoric acid esterified epoxy resin. The epoxy resin had a solid content of 70%, a varnish acid value of 140 and a viscosity of 200 cps.
After adding 7 parts of 25% ammonia water to this and stirring well,
1183 parts of deionized water was added, and the pH of the system was adjusted to 8.0 with 25% aqueous ammonia while stirring to disperse the phosphated epoxy resin in water.

The above dispersion liquid was transferred to a 3 liter flask equipped with a stirrer, a cooling tube and a temperature control device, and the temperature was raised to 65 ° C while stirring. While maintaining the temperature at 65 ° C, a solution consisting of 350 parts of n-butyl acrylate, 350 parts of methyl methacrylate and 1.4 parts of diallyl phthalate, an aqueous solution of 3.5 parts of t-butyl hydroperoxide in 53 parts of deionized water and Rongalit. An aqueous solution prepared by dissolving 3.5 parts in 53 parts of deionized water is added dropwise over 4 hours by separate dropping funnels. After completion of the appropriate conditions, stirring and heating were continued for 2 hours to complete the reaction, and a milky white emulsion polymer having a pH of 6.9, a solid content of 35% and a viscosity of 20.5 cps was obtained.

[Example 2] The same method as in Example 1 was used, but the pH of the phosphoric acid esterified epoxy resin aqueous dispersion before monomer addition was adjusted to 6.0 with 25% aqueous ammonia, and the ethylenically unsaturated monomer was used. Was replaced with a solution consisting of 350 parts of n-butyl acrylate, 329 parts of methyl methacrylate, 21 parts of acrylic acid and 1.4 parts of diallyl phthalate, but the same composition and amount were used. After completion of the polymerization, the pH of the system was adjusted with 25% ammonia water. Adjusted to 7.5, solid content 35%, viscosity
A 8.1 cps milky white emulsion polymer was obtained.

Example 3 In the same manner as in Example 2, the monomer was changed to ethyl acrylate 1.40.
Parts, 210 parts of 2-ethylhexyl acrylate, 259 parts of n-butyl methacrylate, 70 parts of styrene, 21 parts of acrylic acid, 0.7 parts of dodecyl mercaptan. Polymerization was carried out using the same composition and amount, except that the solid content was 35 parts. %, Viscosity 22.3 cps
A milky white emulsion polymer of was obtained.

Example 4 Polymerization was carried out in the same manner as in Example 1 except that the catalyst was replaced with a solution prepared by dissolving 0.7 part of ammonium persulfate in 106 parts of deionized water, keeping the temperature at 80 ° C., and using the same composition and amount. PH 3.1, solid content
A milky white emulsion polymer having a viscosity of 35% and a viscosity of 18.7 cps was obtained.

[Example 5] Bisphenol A / glycidyl ether (epoxy equivalent
250) 3.5 parts of ethyl cellosolve are dissolved in 1.5 parts of ethyl cellosolve, 0.3 part of orthophosphoric acid is further mixed in the solution, and the reaction is carried out at 50 ° C. for 3 hours, followed by reaction at 80 ° C. for 5 hours to form a phosphoric ester. A resin was obtained. After adding 0.7 parts of 25% ammonia water to the epoxy resin and stirring well, deionized water 108
Add 0 parts and stir with 25% ammonia water.
The pH of the system was adjusted to 6.0 to obtain a phosphoric acid esterified epoxy resin aqueous dispersion. After that, emulsion polymerization was carried out in the same manner as in Example 2 and using the same composition and amount of the monomer, but the system became milky white after 2 hours from the dropping of the monomer, and the solid content was 35%.
An emulsion polymer of was obtained.

[Example 6] In place of the aqueous dispersion of the phosphoric acid esterified epoxy resin of Example 2, 840 parts of bisphenol A glycidyl ether (epoxy equivalent 250), ethyl cellosolve 360 parts, orthophosphoric acid 71.4 parts, deionized water 6323. Was used in the same manner as in Example 2 to obtain an aqueous dispersion of a phosphoric acid esterified epoxy resin, and monomers were used in the same composition and amount to carry out polymerization in a 9-liter flask. The system gelled.

[Example 7] In place of the phosphoric acid esterified epoxy resin aqueous dispersion of Example 2, 490 parts of bisphenol A / glycidyl ether (epoxy equivalent 250), 210 parts of ethyl cellosolve, 42 parts of orthophosphoric acid, 4403 parts of deionized water. Polymerization was carried out in the same manner as in Example 2 to obtain a phosphoric acid esterified epoxy resin aqueous dispersion, and the monomers were polymerized in a 7-liter flask using the same composition and amount to obtain a milky white emulsion polymer. It was The solid content of the emulsion polymer was 20% and the viscosity was 42.2 cps.

[Comparative Example 1] 700 parts of deionized water was put into a 3 l flask equipped with a stirrer, a cooling pipe and a temperature control device, and the temperature was adjusted to 65 while stirring.
The temperature was raised to ° C. Then, a mixed monomer composed of 350 parts of n-butyl acrylate, 329 parts of methyl methacrylate, 21 parts of acrylic acid and 1.4 parts of diallyl phthalate is an anionic surfactant (25% solution of "Lebenol WZ" manufactured by Kao Atlas). A monomer emulsion pre-emulsified with a homomixer in a solution consisting of 8 parts and 273 parts of deionized water, an aqueous solution of 3.5 parts of t-butyl hydroperoxide in 154 parts of deionized water and 3.5 parts of Rongalit. An aqueous solution prepared by dissolving 154 parts of deionized water is added dropwise for 4 hours by separate dropping funnels. After the dropping was completed, the reaction was completed by stirring and heating for 2 hours, adding 25% ammonia water, and adding pH 7.0.
Adjust to ~ 8.0 to obtain a milky white emulsion polymer.

[Comparative Example 2] 1127 parts of deionized water was placed in a 3 liter flask equipped with a stirrer, a cooling tube and a temperature control device, and the temperature was adjusted to 80 while stirring.
The temperature was raised to ° C. 14 parts of ammonium persulfate is deionized water
Add an aqueous solution dissolved in 154 parts, and after 10 minutes, n-butyl acrylate 350 parts, methyl methacrylate 329 parts, acrylic acid 21
Solution of 1.4 parts of diallyl phthalate was added dropwise over 4 hours, and the temperature was maintained for 2 hours.
The pH is adjusted to 7.0 to 8.0 by adding 25% aqueous ammonia to obtain a milky white emulsion polymer.

Table 1 shows the properties of the emulsion polymers obtained in the respective Examples and Comparative Examples and the performance of the coating films obtained by bar-coating these emulsion polymer compositions on cold-rolled steel sheets. However, the film thickness is 3g / m ² (a), 15g / m ² (b),
The drying temperature is shown as 100 ° C./1 minute as (a) and 100 ° C./30 minute as (b).

As shown in Table 1, the emulsion polymer obtained by the method of the present invention has less foaming and better mechanical stability than the comparative example using an ordinary emulsifier, and the adhesion of the coating film, It can be seen that the alkali resistance, water resistance, and corrosion resistance are all good.

Claims (1)

[Claims] 1. Water obtained by neutralizing a part or all of P-OH groups in a phosphoric acid esterified product obtained by esterifying at least a part of terminal epoxy groups of an epoxy resin with a phosphorus-containing acid with a base. Emulsion polymerization of one or more ethylenically unsaturated monomers in the presence of a dispersible or water-soluble modified epoxy resin, in which case water-dispersible or water-soluble modified epoxy resin and ethylenically unsaturated monomer In the range of 1/99 to 50/50 in terms of weight percentage, the method for producing an emulsion polymer.