JPH0116842B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing aqueous polymer emulsions. Aqueous polymer emulsions are now widely used in paints, adhesives, paper and fiber treatment agents, etc.; This is because it is preferable from the viewpoints of circulation maintenance, work environment circulation, resource saving, etc., and is also superior in workability due to its relatively low viscosity even at high concentrations. However, conventional aqueous polymer emulsions are produced in the presence of low molecular weight emulsifiers such as alkyl sulfonates, alkyl sulfates, alkyl carboxylates, etc., and such emulsions are used to form coatings. When the emulsifier remains in the coating, there is a problem that the coating has poor water resistance, heat resistance, weather resistance, etc. In addition, especially when producing an acrylic resin emulsion, there are many aggregates and mechanical There was a problem with stability. In order to solve these problems, methods for producing aqueous emulsions using high molecular weight emulsifiers instead of low molecular weight emulsifiers have been proposed.
Publication No. 43381 discloses a method using maleated polybutadiene as an emulsifier. However, with this method, the resulting film is prone to discoloration and does not have sufficient water resistance or weather resistance.Also, it is necessary to produce a high molecular weight emulsifier prior to emulsion polymerization, making the production process complicated. There were other problems. In view of the above problems, in the process of researching methods for producing aqueous polymer emulsions using various high molecular weight emulsifiers, the present inventors discovered that functional vinyl monomers having a polymerizable unsaturated group and, for example, a hydroxyl group, We obtained the knowledge that a polymer of modified vinyl monomer obtained by esterifying the monomer with a tetrahydrophthalic anhydride-based compound exhibits remarkable emulsifying ability.Based on this knowledge, as a result of intensive research, we found that A method for producing a polymer aqueous emulsion with a simple manufacturing process that provides a film with excellent properties and eliminates the need to polymerize an emulsifier prior to polymerizing an aqueous emulsion unlike conventional high molecular weight emulsifiers. It is. The gist of the method is that a functional vinyl monomer having a polymerizable unsaturated group and at least one of a hydroxyl group, an epoxy group, and an amino group is esterified or amidated with a tetrahydrophthalic anhydride compound. The present invention relates to a method for producing an aqueous polymer emulsion, which comprises carrying out aqueous emulsion polymerization of a radically polymerizable monomer in the presence of the resulting modified vinyl monomer. The functional vinyl monomer is preferably hydroxyethyl (meth)acrylate,
(This means both hydroxyethyl acrylate and hydroxyethyl methacrylate. The same applies hereinafter.) Hydroxyalkyl (meth)acrylates such as hydroxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate Polyalkylene glycol mono(meth)acrylate such as acrylate, N-methylol(meth)
Acrylamide, allyl alcohol, glycidyl (meth)acrylate, aminoethyl (meth)acrylate, etc. are used. The above tetrahydrophthalic anhydride compound is
Refers to a compound whose structural formula is considered to be a derivative of tetrahydrophthalic anhydride.
Δ ⁴ -Tetrahydrophthalic anhydride, cis-3-methyl-Δ ⁴ -tetrahydrophthalic anhydride, 3,6
-Endomethylene- ^Δ4 -tetrahydrophthalic anhydride and the like are preferably used. Esterification or amidation of the functional vinyl monomer with a tetrahydrophthalic anhydride compound can be carried out by a conventional method. For example, in the esterification reaction, the two are mixed and if necessary, a solvent or benzoic acid is added.
50 to 120 in combination with a common esterification catalyst such as triethylamine and a polymerization inhibitor such as hydroquinone.
It progresses easily if heated to a temperature of °C. When emulsion polymerizing the radically polymerizable monomer described below in the presence of the obtained modified vinyl monomer, the polymerization of the modified vinyl monomer that has been polymerized is carried out in parallel with the progress of polymerization of the radically polymerizable monomer. It is thought that the polymer exhibits remarkable emulsifying ability and that the modified vinyl monomer also undergoes some kind of chemical reaction with the radically polymerizable monomer. By using the above-mentioned tetrahydrophthalic anhydride compound, the aqueous polymer emulsion obtained by the method of the present invention has a tetrahydrophthalic acid ring formed in the molecule, which is adjacent to the carbon constituting the carbon-carbon double bond. It is believed that the formed film has excellent air curability because the hydrogen bonded to the carbon is very active. The radically polymerizable monomer is not particularly limited, but specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.
Acrylate, (meth)acrylic acid esters such as glycidyl (meth)acrylate, styrene,
In addition to alkenylbenzenes such as α-methylstyrene and vinyltoluene, vinyl acetate, vinylpyridine, butadiene, isoprene, chloroprene, acrylonitrile, and the like can be mentioned, and these may be used alone or as a mixture of two or more.
If necessary, small amounts of (meth)acrylic acid, itaconic acid, (meth)acrylamide,
(meth)acrylic acid dimethylaminoethyl, N-
Methylol acrylamide, N-butoxymethyl acrylamide, 2-hydroxyethyl (meth)
Acrylate, 2-hydroxypropyl (meth)
Hydrophilic monomers such as acrylate, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid and alkali metal salts of styrenesulfonic acid may be used in combination, and a small amount of ethylene glycol di(meth)acrylate, Poly(meth)acrylates such as tetraethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, A polyfunctional crosslinking agent such as diallyl phthalate may be used in combination. The amount of the modified vinyl monomer used in emulsion polymerization is generally from 1 part by weight to 50 parts by weight per 100 parts by weight of the radically polymerizable monomer.
If the amount of modified vinyl monomer used is too small, the aqueous polymer emulsion obtained will not exhibit sufficient air curability, and the film formed by the emulsion will lack water resistance, while if it is too large, the polymerization stability will deteriorate. Deteriorate. In order to carry out emulsion polymerization in the present invention, conventionally known methods can be employed.
For example, in the presence of the modified vinyl monomer, the radically polymerizable monomer is treated with a radical polymerization initiator in water, if necessary, in combination with the hydrophilic monomer or polyfunctional crosslinking agent described above. Emulsion polymerization at a temperature of ~100°C. The radical polymerization initiator may be water-soluble or oil-soluble, and includes, for example, peroxides such as benzoyl peroxide, cumene hydroperoxide, and hydrogen peroxide, azo compounds such as azobisisobutyronitrile, ammonium persulfate, potassium persulfate, etc. Redox catalysts such as persulfates, perchloric acid compounds, and combinations of persulfuric compounds and reducing sulfoxy compounds can be used. Furthermore, polymerization can also be initiated by irradiation with gamma rays or electron beams. The emulsion obtained by the method of the present invention has a tetrahydrophthalic acid ring formed in the molecule, and it is thought that this carboxyl group contributes to the stability of the aqueous polymer emulsion.
In order to assist and promote the development of emulsion stability due to this carboxyl group, a hydrophilic solvent such as ethanol, propanol, butylcellosolve ethyl acetate, etc. may be added to water as a dispersion medium for emulsion polymerization. Of course. Further, metal ions such as sodium phosphate, cobalt naphthenate, calcium naphthenate, etc. are suitably added to improve the polymerization stability of the radically polymerizable monomer. Furthermore, when the aqueous polymer emulsion produced by the method of the present invention is used as a paint for room temperature or forced drying, a metal desiccant such as cobalt naphthenate or lead naphthenate may be used, and an amino resin or epoxy may be used as a curing agent. It may also be used in baking paints in combination with resins and the like. The method of the present invention is constructed as described above, and according to the present invention, an aqueous polymer emulsion which does not generate aggregates during emulsion polymerization and has excellent storage stability, pigment miscibility, mechanical stability, etc. is obtained,
The coating formed from the emulsion has excellent air curing properties and is excellent in water resistance, weather resistance, etc. Next, examples of the present invention will be shown. In the following, "part" simply means part by weight, and "%" means percent by weight. Example 1 15 parts of styrene, 11.5 parts of butyl acrylate, 1 part of sodium styrene sulfonate, and 2.5 parts of esterified product of cis-3-methyl-Δ ⁴ -tetrahydrophthalic anhydride and 2-hydroxyethyl acrylate in 60 parts of ion-exchanged water. was dispersed in a reactor, and 0.03 parts of potassium persulfate and ion-exchanged water were added under a nitrogen stream.
10 parts of the mixture were added thereto, and the mixture was reacted at 70° C. for 6 hours with stirring to obtain an aqueous polymer emulsion. There were few aggregates in the emulsion, and 0.15 parts of cobalt naphthenate having a cobalt content of 6% was added to the emulsion and dried at 25° C. for 7 days to obtain a film with a thickness of about 150 μm. The water resistance of the coating was good as shown in Table 1. Example 2 Aqueous preparation was carried out in the same manner as in Example 1 except that 3,6-endomethylene-Δ ⁴ -tetrahydrophthalic anhydride was used instead of cis-3-methyl-Δ ⁴ -tetrahydrophthalic anhydride in Example 1. An emulsion and an emulsion coating were obtained. There were few aggregates of the emulsion, and the water resistance of the coating was good as shown in Table 1. Example 3 60 parts of ion-exchanged water, butyl methacrylate
12.9 parts, methyl methacrylate 8.4 parts, butyl acrylate 6 parts, acrylic acid 0.6 parts, 3,6-
2.1 parts of an esterified product of endomethylene- ^Δ4 -tetrahydrophthalic anhydride and 2-hydroxyethyl acrylate was dispersed in a reactor, and 0.03 parts of potassium persulfate and 10 parts of ion-exchanged water were added under a nitrogen stream. The reaction was carried out at 70° C. for 6 hours with stirring to obtain an aqueous polymer emulsion. There were few aggregates in the emulsion, and 0.15 parts of cobalt naphthenate with a cobalt content of 6% was added to this emulsion.
It was heated and dried at ℃ for 20 minutes to obtain a film with a thickness of about 150μ. The water resistance of the coating was good as shown in Table 1. When this film was irradiated with a weatherometer for 250 hours, there was almost no coloration and no change in water resistance.

[Table] In the above table, the water absorption rate of the film and the light transmittance before and after immersion were measured after the film was immersed in pure water at 20℃ for 3 days, and the light transmittance after immersion was calculated as the light transmittance before immersion. It was expressed as a ratio to that of the light beam, that is, a light transmission retention rate.

Claims (1)

[Claims] 1. A functional vinyl monomer having a polymerizable unsaturated group and at least one of a hydroxyl group, an epoxy group, and an amino group is esterified or amidated with a tetrahydrophthalic anhydride compound. 1. A method for producing an aqueous polymer emulsion, which comprises carrying out aqueous emulsion polymerization of a radically polymerizable monomer in the presence of a modified vinyl monomer obtained by. 2. The method for producing an aqueous polymer emulsion according to claim 1, wherein the functional vinyl monomer is hydroxyalkyl acrylate or hydroxyalkyl methacrylate.