JPS6312482B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an emulsion polymerization method that uses a specific emulsifier when producing a resin emulsion by emulsion polymerizing unsaturated monomers. The method of polymerizing unsaturated monomers by emulsion polymerization is industrially important, and the resulting resin emulsions are used in paints, adhesives, paper processing, fiber processing, etc., or are used to convert polymers from resin emulsions. It is used in a wide variety of ways, including being separated and used as plastics and rubber. and,
The production of such resin emulsions by emulsion polymerization is generally carried out using nonionic emulsifiers, anionic emulsifiers, or mixtures of these emulsifiers. However, by using an emulsifier during emulsion polymerization, the resulting resin emulsion has the property of being inherently prone to foaming when stirred or the like.
This property causes various problems in the process of producing and using resin emulsions. That is, in the process of producing a resin emulsion, the resin emulsion during production generates a large number of bubbles, which reduces heating and cooling efficiency or becomes an obstacle when recovering and removing unpolymerized monomers. In the process of using resin emulsions, for example, when used in paint vehicles, paper processing, or adhesives, the resin emulsion generates many bubbles, leaving air bubbles and pinholes in the resulting film, which impairs the water resistance of the film. This results in a decrease in adhesion, a decrease in finish quality, etc. Furthermore, when a polymer is separated from a resin emulsion, the liquid foams and becomes a hindrance to the treatment. In order to overcome these obstacles, a method has been proposed in which an oxyethylene oxypropylene block copolymer, which is generally considered to have low foaming, is used as an emulsifier, but this method does not allow stable emulsion polymerization. It is often difficult. In addition, antifoaming agents have been added to resin emulsions that foam a lot, but the effect is generally small, and in this application, it causes a decrease in adhesion and a decrease in the finish due to the occurrence of repellency. There is a risk of causing problems such as As a result of intensive research aimed at overcoming the drawbacks of such resin emulsions, the present inventors discovered that by using a specific emulsifier during emulsion polymerization, a resin emulsion with extremely low foaming could be obtained. I've reached it. That is, the present invention provides that when producing a resin emulsion by emulsion polymerizing one or more unsaturated monomers, the general formula (However, in the formula, a and c each represent an integer of 1 or more and 2≦a+c≦300, and b is 1≦
represents an integer satisfying b≦100, and X and Y each represent hydrogen or a salt-forming substance. ) One or two selected from the group of compounds represented by
The present invention relates to an emulsion polymerization method characterized by using at least one species as an emulsifier. The emulsifier in the present invention, that is, the general formula ()
The compound represented by can be prepared by a conventionally known method. Examples of basic substances that can be salt-forming substances include metal radicals, ammonia, and organic amines. By following the method of the present invention using the emulsifier represented by the general formula (), it is possible to stably obtain a resin emulsion with extremely low foaming during manufacturing and usage processes, and overcome the obstacles caused by foaming of the resin emulsion. It is possible. It is not clear why the method of the present invention has such excellent effects. However, the emulsifier used in the present invention is similar to the oxyethylene oxypropylene block copolymer, which is an emulsifier that is conventionally thought to have low foaming, and the hydrophobic group composed of the oxypropylene polymer is the hydrophilic group derived from the oxyethylene polymer. On the other hand, unlike the nonionic oxyethylene oxypropylene block copolymer, it is an anionic emulsifier with carboxyl groups that can be ionically dissociated at both ends of the emulsifier molecule. Because it is a substance,
Due to its ability to solubilize unsaturated monomers in water and to stabilize dispersed particles produced by polymerization of unsaturated monomers,
It is believed that the effects of the method of the present invention will be exhibited. The emulsion polymerization method according to the present invention can be carried out according to conventionally known procedures using the specific emulsifier as described above. That is, in an inert atmosphere, under autogenous pressure or artificially induced pressure in a closed container or in an open container under atmospheric reflux, in the presence of an emulsifier and water, in the presence or absence of a polymerization catalyst, A resin emulsion can be obtained by emulsion polymerization of one or more unsaturated monomers. In this case, the appropriate amount of emulsifier used is 0.05 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the unsaturated monomer. Monomers that can be used in the present invention include, for example, aliphatic unsaturated hydrocarbons such as ethylene and butadiene; halogen-substituted aliphatic unsaturated hydrocarbons such as vinyl chloride; styrene, divinylbenzene, etc. Aromatic unsaturated hydrocarbons; Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic acid and their esters; Vinyl esters such as vinyl acetate; Vinyl ethers; Allyl alcohol and its esters with various organic acids and ethers with various alcohols; unsaturated cyanide compounds such as acrylonitrile; and one or more selected from these groups can be used. When carrying out the emulsion polymerization method of the present invention, conventionally known nonionic emulsifiers, anionic emulsifiers, or protective colloids may be used in amounts that do not impede the advantage of the present invention that a resin emulsion with extremely low foaming can be stably obtained. Can also be used together. As the polymerization catalyst, inorganic peroxides such as ammonium persulfate and hydrogen peroxide; organic peroxides such as t-butyl hydroperoxide; other radical-generating polymerization initiators, etc. can be used.
The amount used is based on 100 parts by weight of unsaturated monomer.
The proportion is from 0.01 to 3 parts by weight, preferably from 0.1 to 1 part by weight. When using peroxides, if it is necessary to increase the polymerization rate or lower the reaction temperature, reducing agents such as soluble sulfites and ascorbic acid or metals that generate heavy metal ions in water such as ferrous sulfate may be used. The compounds can be combined with peroxides to form redox systems. Chain transfer agents such as t-dodecyl mercaptan and carbon tetrachloride can also be used in combination. The emulsion polymerization temperature is appropriately selected depending on the type and composition of the unsaturated monomer, the type of polymerization catalyst, etc.
It is usually in the range of 0 to 100°C. The amount of water during emulsion polymerization is usually 100% of the unsaturated monomer.
The ratio is 300 to 50 parts by weight. According to the emulsion polymerization method of the present invention, a resin emulsion with extremely low foaming can be stably obtained during production and use processes, and various obstacles caused by foaming of the resin emulsion can be overcome. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, in Examples and Comparative Examples, parts indicate parts by weight, and % indicates weight %. Example 1 A glass flask equipped with a stirrer, a thermometer, a dropping funnel, a nitrogen gas inlet, and a reflux condenser was charged with a first
16 parts of the emulsifier shown in the table and 383.6 parts of deionized water were charged, and nitrogen substitution was performed. Then, the temperature was raised to 50°C, 40 parts of 400 parts of an unsaturated monomer mixture consisting of 240 parts of ethyl acrylate, 156 parts of methyl methacrylate, and 4 parts of methacrylic acid were added, and the mixture was heated to 10 parts at 50°C.
Stirring and mixing were performed for a minute. Then 6 parts of a 20% aqueous solution of ammonium persulfate and 2 parts of sodium bisulfite.
% aqueous solution was added to initiate polymerization. 20 minutes after the start of polymerization, the remaining 360 parts of the unsaturated monomer mixture and 24 parts of a 2% aqueous solution of sodium hydrogen sulfite were continuously added over 180 minutes each while maintaining the reaction temperature at 60°C. Emulsion polymerization was allowed to proceed, and after the addition of the unsaturated monomer was completed, stirring was continued for 60 minutes at 60°C to complete the polymerization. The polymerization stability during emulsion polymerization and the foaming properties of the resulting resin emulsions are shown in Table 1, together with the results when conventionally known emulsifiers were used for comparison. The polymerization stability of the resin emulsion obtained by the emulsion polymerization method of the present invention was good, and the foaming property was extremely low.

[Table] Example 2 The unsaturated monomer used in Example 1 was made into a mixture of 240 parts of butyl acrylate, 156 parts of styrene, and 4 parts of methacrylic acid, and an emulsifier was added.
NaOOCCH ₂ O−(C ₂ H ₄ O−) _a −(C ₃ H ₆ O−) _b −(C ₂ H ₄ O
−) _c (CH ₂ COONa (a+c average 16, b average 20)
Emulsion polymerization was carried out under the same conditions as in Example 1, and the polymerization stability and foaming property were measured in the same manner as in Example 1. The polymerization stability was 0.05, and the foaming property was 6.
Therefore, a resin emulsion with extremely low foaming could be stably obtained.

Claims (1)

[Claims] 1. When producing a resin emulsion by emulsion polymerizing one or more unsaturated monomers, the general formula (However, in the formula, a and c each represent an integer of 1 or more and 2≦a+c≦300, and b is 1≦
represents an integer satisfying b≦100, and X and Y each represent hydrogen or a salt-forming substance. ) One or two selected from the group of compounds represented by
An emulsion polymerization method characterized by using at least one species as an emulsifier.