JPS5949922B2 - Method for producing synthetic resin emulsion - Google Patents

Description

[Detailed description of the invention] This invention relates to a method for producing a synthetic resin emulsion.

Conventionally, the production of synthetic resin emulsions has required the use of emulsifiers or water-soluble polymers to provide a polymerization site during emulsion polymerization and to stabilize the resulting particles.

However, the emulsifier or water-soluble polymer remains in the film obtained from this type of synthetic resin emulsion, and this acts as a water absorption factor, significantly reducing the water resistance of the film. Therefore, compared to so-called solution-type emulsions in which a polymer is dissolved in an organic solvent, the range of use of the above synthetic resin emulsions is greatly limited. Therefore, attempts have been made to perform emulsion polymerization without using such emulsifiers or water-soluble polymers to obtain synthetic resin emulsions with good water resistance.

This is a method in which a large amount of a radical initiator is used to increase the amount of radicals generated to compensate for the decrease in polymerization rate due to the absence of an emulsifier, and the oligomer molecules produced at this time are used to stabilize the particles. However, in this case,
The radical initiator used in large amounts remains in the film and acts as a water absorption factor, so that the intended purpose of obtaining a film with good water resistance cannot be fully achieved. Moreover, the emulsions produced by this method have extremely poor mechanical stability, freezing stability, etc., and have the disadvantage of not being able to withstand harsh conditions. Regarding the mechanical stability, freezing stability, etc., synthetic resin emulsions obtained by conventional methods using the emulsifier or water-soluble polymer also tend to be relatively poor.

The purpose of this invention is to provide a polymerization site with excellent polymerization stability, that is, to provide a polymerization site during emulsion polymerization, to stabilize the produced particles, and to improve the mechanical stability and freeze stability of the resulting emulsion. The object of the present invention is to provide a new and useful method for producing a synthetic resin emulsion that has excellent water resistance in its epithelial membrane.

For the above purpose, as a result of various studies, the inventors used a water-soluble radical initiator having an electrolytic group consisting of persulfate as a radical initiator, and used a water-soluble radical initiator as a monomer to be emulsion polymerized by hydrolysis. At least a specific hydrophilic monomer capable of producing a carboxylic group is used, and a specific amount of the hydrophilic monomer component is used to form polymer particles as emulsion particles during emulsion polymerization or during and after emulsion polymerization. Hydrolyzes to produce carboxyl groups. Moreover, the present invention was finally completed after learning that the above-mentioned object can be successfully achieved when the pH is adjusted to a specific value during or after the generation.

That is, this invention provides 5 to 100 moles of at least one hydrophilic monomer selected from alkyl esters of (meth)acrylic acid and alcohols having 4 or less carbon atoms, 2-hydroxyethyl acrylate, and acrylamide. , and 95 to 0 mol of another unsaturated monomer having no carboxyl group in the molecule that can be copolymerized with the above monomer, and a water-soluble radical initiator having an electrolytic group consisting of persulfate in water. Emulsion polymerization is carried out in the presence of emulsifiers and water-soluble polymers, and the above hydrophilic monomer components are calculated in terms of total polymers among all the monomer components constituting the polymer particles during or during and after the polymerization. It is hydrolyzed at a rate of 0.05 to 5 mol% to produce carboxyl groups. The present invention also relates to a method for producing a synthetic resin emulsion, which is characterized in that the pH is adjusted to 7 or higher. Hydrophilic monomers used in this invention include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and methyl methacrylate. Alkyl esters of (meth)acrylic acid and alcohols having 4 or less carbon atoms, such as ethyl methacrylate, propyl methacrylate, and butyl methacrylate, 2-hydroxyethyl acrylate, and acrylamide, and one or more of these types You may use it.

In this invention, the above monomers account for 5 to 100 of the total monomers.
mol, that is, the proportion of other unsaturated monomers that do not have a carboxyl group in the molecule that can be copolymerized with this monomer is 9
Emulsion polymerization is carried out at a ratio of 5 to 0 mol, and the above-mentioned hydrophilic monomer components are identified among all the monomer components constituting the polymer particles as emulsion particles during or after the emulsion polymerization. It is hydrolyzed in a proportion to form a predetermined proportion of carboxyl groups in the emulsion.
The carboxyl group formed by this method is reliably coordinated with the electrolytic group of the water-soluble radical initiator used together with the emulsion particle surface, and the electrolytic group and carboxyl group act synergistically to stabilize the polymerization of the emulsion. sex. This results in good mechanical stability, freezing stability, and water resistance of the film. One possible method for simply introducing carboxyl groups into the emulsion is to use acrylic acid, methacrylic acid, itaconic acid, etc., which have free carboxyl groups from the beginning, as comonomers for copolymerization. With this method, it is difficult to reliably coordinate the carboxyl groups on the surface of the emulsion particles, and a large amount of the monomers must be used in order to stabilize the particles. A homopolymer of the monomers is formed, resulting in a significant decrease in the water resistance of the coating. Other unsaturated monomers having no carboxyl group in the molecule that can be copolymerized with the hydrophilic monomer used in this invention include various monomers that can be radically polymerized.

Specifically, esters of alcohols having an alkyl group having 8 to 18 carbon atoms such as 2-ethylhexyl, lauryl, and stearyl and acrylic acid or methacrylic acid. Examples include ethylene, vinyl chloride, vinylidene chloride, butadiene, styrene, and vinyl acetate, and two or more types can be used in combination. The water-soluble radical initiator having an electrolytic group used in this invention is one that is water-soluble and has an electrolytic group that dissociates in water and exhibits anionic or cationic properties. Specifically, potassium persulfate, persulfate, Persulfates such as ammonium sulfate are used.

The amount of catalyst used is sufficient in the usual amount required for emulsion polymerization, and it is preferable that the catalyst be sufficiently decomposed during polymerization so that no undecomposed substances remain that may act as a salting-out agent for the emulsion after polymerization. As mentioned above, the electrolytic group of the water-soluble radical initiator coordinates on the surface of the emulsion particles, contributing to polymerization stability, and because the proportion of the water-soluble radical initiator used is small, decomposition products are formed in the film. It does not have the disadvantage of adversely affecting water resistance when mixed. In the emulsion polymerization of this invention, a predetermined proportion of the above monomers and a water-soluble radical initiator having an electrolytic group are placed in a polymerization tank together with water, and the polymerization reaction is carried out according to a conventional method except that no emulsifier or water-soluble polymer is used. All you have to do is do it. In this invention, a specific amount of the hydrophilic monomer components of all the monomer components constituting the polymer particles are hydrolyzed during the emulsion polymerization or during and after the emulsion polymerization to generate free carboxyl groups. let

In this hydrolysis reaction, since the water-soluble radical initiator with an electrolytic group used is composed of persulfate, its decomposition product acts as an acid catalyst for the hydrolysis reaction. It can be allowed to proceed during emulsion polymerization without addition6, and it can be further allowed to proceed to a desired degree by leaving it to ripen for a predetermined period of time after emulsion polymerization. Of course, during or after the polymerization, a small amount of acid or alkali such as hydrochloric acid, sulfuric acid, nitric acid, 6-oxalic acid,
Ammonia, caustic soda, caustic potash, amine, etc. may be added. The extent of the hydrolysis reaction is 6. The proportion of the above-mentioned hydrophilic monomer components participating in the hydrolysis reaction, that is, being hydrolyzed, is 0.05 to 0.05 in terms of total monomers among all the monomer components constituting the polymer particles. 5 moles? Preferably 0.2 to 5 mol? Adjust so that The effect of the carboxyl group is expressed in such a small amount. In this case, 0.0
5 moles? If it is lower, the mechanical stability of the emulsion will not be satisfied; on the other hand, 5 mol? If it is higher, the water resistance of the film will not be improved. After the hydrolysis reaction is carried out in this manner, an aqueous ammonia solution or the like is added to the polymerization tank to adjust the pH to 7 or more.

Of course, if an alkali is added as a catalyst during the hydrolysis reaction and the pH of the liquid is 7 or higher, an acid may be added as a PH adjuster to adjust the pH to a predetermined value of 7 or higher. Such a regulator may not be intentionally added. When the pH is lower than 7, the mechanical stability and freezing stability of the synthetic resin emulsion will be low. The synthetic resin emulsion thus obtained is extremely stable and has excellent mechanical stability and freezing stability, and the film obtained therefrom has good water resistance. As detailed above, in this invention, a water-soluble radical initiator having an electrolytic group consisting of persulfate is used as a 6-radical initiator without using an emulsifier or a water-soluble polymer, which have conventionally been indispensable. using at least the specific hydrophilic monomer as the polymer, and specifying the hydrophilic monomer component among all monomer components constituting the polymer particles during emulsion polymerization or during and after emulsion polymerization. A synthetic resin emulsion with excellent polymerization stability, mechanical stability 6 and freeze stability can be obtained by hydrolyzing in a proportion to produce a specific amount of carboxyl groups and further adjusting the... to 7 or more. Moreover, the water resistance of the resulting film can be significantly improved compared to the conventional film.

BACKGROUND OF THE INVENTION This invention will be explained in more detail with reference to Examples.

In the following, parts indicate parts by weight. Example 1 30 parts of ethyl acrylate monomer and 70 parts of ion-exchanged water were charged into a four-necked polymerization kettle equipped with a nitrogen gas introduction tube, a stirrer, a thermometer, and a reflux condenser, and the external temperature was adjusted to 70°C. , 0.012 potassium persulfate dissolved in 1 part water
6 parts added with nitrogen stream stirring speed 250 rpm? Polymerization was started.

Approximately 1 hour after the start of polymerization, the external temperature was raised to 80°C, and polymerization was continued for 3 hours. Thereafter, a stable synthetic resin emulsion was obtained by aging at 90° C. for about 1 hour and cooling to room temperature.
The molar ratio of the emulsion after standing was approximately 3.1, indicating that during polymerization and standing, carboxyl groups were generated by hydrolysis reaction of the total monomer component consisting of ethyl acrylate component constituting the polymer particles. The proportion of ethyl acrylate component is approximately 0.15 mol in terms of total mercury. It was moderately hot. A 1N aqueous ammonia solution was added to this emulsion to adjust the pH to 9. Comparative Example 1 In the same manner as in Example 1, pH 3. Obtain l emulsion6
Thereafter, a synthetic resin emulsion is prepared as it is without adding aqueous ammonia.

Comparative Example 2 In Example 1, 1.5 parts of sodium lauryl sulfate was further added as an additive at the initial stage of polymerization, and the polymerization temperature was 70°C.
A synthetic resin emulsion was obtained using the same method and conditions as in Example 1 except that the polymerization time was 6 hours.

Comparative Example 3 In Example 1, a non-electrolytic radical initiator such as hydrogen peroxide or cumene hydroperoxide was used instead of potassium persulfate, and polymerization was carried out under the same conditions as in Example 1. .

In this case, a huge agglomerate formed during the polymerization, making it impossible to obtain a stable emulsion. The mechanical stability, freeze stability, and water resistance of the coatings of the synthetic resin emulsions of Example 1 and Comparative Examples 1 and 2 were investigated, and the results are shown in Table 1 below.

(*l) Mechanical friction test method; MarOn5 (S-H-MarOn, J-N-Vlev
itch: Anal. Chem. ,ιyu 1089(1
953)). Add 50ml of emulsion, pressure 5k9/d, rotation speed 450rp1,-2
After rotating at 0° C. for 5 minutes, it was filtered through cheese cloth (100 mesh), and the weight percentage of the obtained coagulated product based on the total emulsion solid content was evaluated.

(*2) Add 10ml of emulsion and 2 cups of ethylene glycol to an inner diameter of 8mm. Place in a test tube with a stopper, 250 mm long. This is immersed in a methanol-dry ice solution maintained at -20°C, cooled and frozen for 2 hours, and then left at room temperature for 10 hours to melt.

The above operation is repeated three times, and the solidified product generated during the freezing and thawing process is evaluated as a weight percentage of the total emulsion solid content. (*3) Width 2.57E from each emulsion
A sample film with a length of 501 m and a thickness of 0.4 nm is formed.

This film is immersed in ion-exchanged water at 30° C. for 10 days, and the weight increase is evaluated as a weight percentage relative to the original film weight. As is clear from Table 1 above, the synthetic resin emulsion according to Example 1 of the invention method not only has excellent polymerization stability as described above, but also excellent mechanical stability and freezing stability. It can be seen that the water resistance of the resulting film is extremely good.

On the other hand, Comparative Example 1, which was not neutralized with alkali, lacked mechanical stability and freezing stability, and Comparative Example 2, which used a conventional emulsifier, not only had poor freezing stability. The water absorption rate of the film was as high as 90%, indicating how poor its water resistance was. Example 2 2 parts of methyl acrylate and 58 parts of ion-exchanged water were placed in a pressure-resistant polymerization pot, and stirred at 70°C under a nitrogen stream at a stirring speed of 150 rpm.
□, and add 1 part of water in which 0.01 part of potassium persulfate was dissolved to start polymerization.

After 1 hour, it was cooled to 50°C, and 10 parts of styrene, 30 parts of butadiene, and 0.1 part of n-dodecylmercaptan were added. Polymerization is continued by adding an additional 0.1 part of potassium persulfate. After 3 hours, the temperature was raised to 60℃, and after heating for 12 hours, the temperature was 0.
．． A stable emulsion was obtained by adding 0.5 part of a 1N aqueous hydrochloric acid solution, aging at 60° C. for 1 hour, and then cooling to room temperature.

The pH of this emulsion is approximately 2.9, and among the total monomer components consisting of methyl acrylate component, styrene component, and butadiene component constituting the polymer particles, acrylic acid with carboxyl groups generated by a hydrolysis reaction is The proportion of the acid methyl component was approximately 0.3 mol% in terms of total monomers. Finally, add ammonia to the above emulsion and adjust the pH to 9. l
Adjust to. Comparative Example 4 10 parts of styrene. 30 parts of butadiene, 0.1 part of n-dodecylmerkabutane, 1.5 parts of sodium oleate, and 55 parts of ion-exchanged water are charged into a pressure-resistant polymerization kettle, and the external temperature is adjusted to 50°C.

Under a nitrogen stream, at a stirring speed of 150 rpm, 5 parts of ion-exchanged water in which 0.2 parts of potassium persulfate had been dissolved were added, and 50
Heat at ℃ for 12 hours. Finally, it is cooled to form a stable synthetic resin emano resin. Comparative Example 5 In Comparative Example 4, when the same operation as in Comparative Example 4 was carried out without adding sodium oleate, many gel-like aggregates were formed 8 hours after the addition of potassium persulfate. A stable synthetic resin emulsion could not be obtained.

Example 2 and Comparative Example 4 with good polymerization stability
The mechanical stability and freezing stability of the synthetic resin Emulcan and the water resistance of the film obtained from each emulsion were investigated, and the results are shown in Table 2 below.

As is clear from Table 2 above, the synthetic resin emulsion according to the present invention has superior mechanical stability and freeze stability compared to the conventional emulsion (Comparative Example 4).

In particular, excellent mechanical stability means that it is stable against shearing force during use with paint control, application rolls, etc., and because it has little loss, it is economical and easy to handle. It has the advantage of being easy. Moreover, the film obtained from the synthetic resin emulsion according to the method of this invention has significantly better water resistance than the conventional method. This is due to the fact that the water-soluble radical initiator having an electrolytic group used in the method of this invention does not have the disadvantage of leaving a large amount of water-soluble decomposition products in the film. Example 3 10 parts of methyl methacrylate, 30 parts of butyl acrylate, and 70 parts of ion-exchanged water were placed in the same polymerization pot as in Example 1, the external temperature was adjusted to 70°C, and then dissolved in 1 part of water. 0.01 part of ammonium persulfate was added and polymerization was started at a stirring speed of 150 rP1 in 6 nitrogen streams.

4 hours after the start of polymerization. An emulsion was obtained by aging at 90° C. for 1 hour and cooling to room temperature. -0.5 part of 0.2N hydrochloric acid aqueous solution was added to this emulsion and heated to 60°C.
of the total monomer components consisting of methyl methacrylate component and butyl acrylate component constituting the polymer particles. An emulsion was obtained in which the ratio of the methyl acid component and the butyl acrylate component was 0.5 mol % in terms of total monomers, and the pH was further adjusted to 7.5 with an aqueous ammonia solution. Example 4 The number of added parts of the aqueous hydrochloric acid solution in Example 3 was changed to 3 parts, and a hydrolysis reaction was carried out at 60°C for 2 hours to obtain a total monomer consisting of methyl methacrylate component and butyl acrylate component constituting the polymer particles. Among the components, is the proportion of monomer components (methyl methacrylate component and butyl acrylate component) in which carboxyl groups are generated by hydrolysis reaction 2.5 moles in terms of total monomers? An emulsion was obtained, and the pH was further adjusted to pH 8. Adjusted to l.

The mechanical stability and freezing stability of each synthetic resin emulsion obtained in Examples 3 and 4 above, as well as the water resistance of the film obtained from each emulsion, were investigated in the same manner as above, and the results are shown in Table 3 below. In both cases, the same good results as in Examples 1 and 2 were obtained.

Example 5 5 parts of 2-hydroxyethyl acrylate, 25 parts of 2-ethylhexyl methacrylate, and 70 parts of ion-exchanged water were charged into the same polymerization kettle as in Example 1. External temperature 70
After adjusting the temperature to
Polymerization was carried out at rp1 for 10 hours.

After polymerization, add 2 parts of 0.2N caustic soda aqueous solution,
By treating at 70°C for 5 hours, carboxyl groups are generated through a hydrolysis reaction among all the monomer components consisting of 2-hydroxoethyl acrylate component and 2-ethylhexyl methacrylate component that constitute the hexapolymer particles. Is the proportion of 2-hydroxyethyl acrylate component 0.23 mol in terms of total monomers? An emulsion was obtained. Thereafter, the pH of the emulsion was adjusted to 8.0. Example 6 5 parts of acrylic acid amide, 25 parts of 2-ethylhexyl methacrylate, and 70 parts of ion-exchanged water were placed in the same polymerization pot as in Example 1, and the external temperature was adjusted to 70°C. Add 0.023 parts of potassium persulfate dissolved in 1 part of water and add 6
Polymerization was carried out for 10 hours at a nitrogen flow stirring speed of 250 fP1.

After polymerization, add 1 part of 0.2N aqueous solution of caustic soda,
By treating at 50°C for 5 hours, acrylic acid, which is formed by carboxyl groups by hydrolysis reaction, is removed from the total monomer components consisting of acrylic acid amide component and 2-ethylhexyl methacrylate component constituting the polymer particles. Is the ratio of amide component 0.3 moles in terms of total monomers? An emulsion was obtained.

Thereafter, the pH of the emulsion was adjusted to 8.0. The mechanical stability and freezing stability of each synthetic resin emulsion obtained in Examples 5 and 6 above and the water resistance of the film obtained from each emulsion were investigated in the same manner as above, and the results were as follows. } Table 4 shows that good results similar to those of Examples 1 and 2 were obtained in both cases.

Claims (1)

[Claims] 1 At least one selected from alkyl esters of (meth)acrylic acid and alcohols having 4 or less carbon atoms, 2-hydroxyethyl acrylate, and acrylamide.
5 to 100 mol% of a hydrophilic monomer and 95 to 0 mol% of another unsaturated monomer having no carboxyl group in the molecule that can be copolymerized with the above monomer in water from persulfate. Emulsion polymerization is carried out in the presence of a water-soluble radical initiator having an electrolytic group without using an emulsifier or a water-soluble polymer, and during this polymerization, or during and after polymerization, all monomer components constituting the polymer particles have the above-mentioned hydrophilicity. The monomer component is 0.0 in terms of total monomer.
1. A method for producing a synthetic resin emulsion, which comprises hydrolyzing to produce carboxyl groups at a ratio of 0.05 to 5 mol%, and adjusting the pH to 7 or higher.