JPS61241310A - Production of emulsion of crosslinked polymer - Google Patents

Abstract

PURPOSE:Emulsion polymerization of methyl methacrylate is effected in the absence of a surfactant, a crosslinking monomer bearing a plurality of vinyl groups is added on the way of the polymerization and the addition is stopped at a specific polymerization rate to complete the polymerization, whereby the titled polymer is obtained without formation of coagulums. CONSTITUTION:Emulsion polymerization of methyl methacrylate only or vinyl monomers containing the same is started in the absence of a surfactant. At the time when the polymerization rate reaches 1-40%, a crosslinking monomer having at least 2 vinyl groups is continuously or intermittently added to continue the polymerization. When the polymerization rate reaches within the range from 55 to 90%, the addition of the crosslinking monomer is completed to cease the polymerization reactions. Thus, the objective polymer emulsion is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aqueous emulsion containing methyl methacrylate-based crosslinked electropolymer particles, and more specifically to a soap-free emulsion polymerization method that does not use any surfactant. The present invention relates to a method for producing a stable emulsion of crosslinked aggregate particles by copolymerizing a methyl methacrylate monomer or a vinyl monomer containing methyl methacrylate with a crosslinkable monomer.

Methyl methacrylate is produced using soap-free emulsion polymerization method.
Copolymerization with other vinyl monomers is relatively easy unless the other monomers are crosslinkable, and in fact, many examples can be found in the prior art. However,
When the monomer reacted with methyl methacrylate is a crosslinkable heptamer, in the soap-free emulsion polymerization method, the crosslinked polymer coagulates due to the non-luminous dispersion of the heptad and the polymer in the growth process. This tendency is further exacerbated as the amount of crosslinking monomer used increases, so it is generally not possible to produce a stable emulsion of crosslinked electropolymer particles using the soap-free emulsion polymerization method.

Therefore, when emulsion polymerizing methyl methacrylate and a crosslinkable heptamer, a surfactant is added to the reaction system in order to improve the dispersion of the heptamer and the resulting polymer, and depending on the situation, a surfactant may be added as a dispersion stabilizer. A commonly used method is to perform polymerization by adding a water bath polymer.

According to this method, it is possible to obtain a cross-linked monomer emulsion with satisfactory homogeneity and stability. However, the inclusion of a surfactant in the emulsion is undesirable for the following reasons.

That is, an emulsion of a crosslinked polymer is dried by means such as spray drying, and further crushed into primary particles by an appropriate means such as jet pulverization, and used for pigments, fillers, etc.

If the emulsion contains a surfactant.

- Not only is it difficult to disintegrate into secondary particles, but even if the particles are disintegrated, surfactant is still attached to the particles, so depending on the purpose of the particles, the shadow of the surfactant*t-m We must keep this in mind.

Therefore, the present invention provides a method for producing a stable emulsion of aggregated aiM particles using a soap-free emulsion polymerization method that does not use any surfactant. Ray)t
A vinyl monomer having - is emulsion polymerized in the absence of a surfactant, and when the emulsion ratio reaches a range of 1 to 40%, a crosslinking monomer having at least two vinyl groups is continuously or Add it intermittently to the reaction system to continue the polymerization, and when the 1% ratio reaches the range of 55 to 90%, stop adding the crosslinking monomer, and then complete the 1% reaction. Let be the %-sign.

According to the method of the present invention, emulsion polymerization is initiated by methyl methacrylate or a vinyl monomer containing methyl methacrylate in the absence of any surfactants and crosslinking monomers, and the emulsion polymerization is initiated by a gold catalyst (initiator). ), organic peroxides, azo compounds, persulfates, etc. are used as in the case of ordinary emulsion polymerization. Methyl methacrylate alone may be used as the monomer used at the start of the reaction, but other vinyl monomers can also be used in combination as long as they do not have the 4i11 ability.

Styrene, vinegar i [vinyl,
Acrylic acid, methacrylic acid, alkyl acrylate, radical alkyl methacrylate, acrylamide, methacrylamide, acrylonitrile, N-methylolacrylamide, and the like are included. When using these vinyl monomers together.

The amount used can be arbitrarily selected, but it is generally about 50% or less of the amount of methyl methacrylate. The present invention requires that emulsion polymerization be carried out under conditions that do not contain any surfactant, and does not exclude the use of a water-soluble polymer that functions as a dispersion stabilizer; (It is preferable to use a water-based polymer rather than a water-based polymer. In this case, the amount of the water-based polymer used can be approximately 1 weight or less of the monomer used in the present invention. Molecules include vinyl alcohol, alkali metal polyacrylate, alkali metal polymethacrylate, highly polymerized polyethylene glycol, hydroxyethyl cellulose, calxoxymethyl cellulose,
Methyl cellulose, polystyrene sulfonic acid alkali metal salts, etc. can be used.

Addition of the crosslinking monomer to the reaction system was started when the proportion of methyl methacrylate alone or the vinyl monomer containing methyl methacrylate reached a range of 1 to 40 inches, and reached a range of 55 to 90 inches. leveraged at the point. In other words, the crosslinking 7mer is added continuously or intermittently to the reaction system in which the Togane reaction is progressing, but is not added all at once. The crosslinking monomers used in the present invention include divinylbenzene, divinyltoluene, ethylene glycol dimeta-/! Examples include JV-t, trimethylolpropane trimethacrylate, and allyl methacrylate.

With at least two vinyl groups per molecule, divinylbenzene and ethylene glycol dimethacrylate are typically used. The amount of crosslinking monomer used is the total amount of non-crosslinking monomer used in the present invention (
(weight) can be arbitrarily selected within the range of the same amount or less. As mentioned above, in the method of the present invention, a crosslinking monomer is added continuously or intermittently to the reaction system. It can be diluted with a solvent, and this is useful when a small amount of crosslinking monomer is added,
Effective when solid. After the addition of the crosslinking monomer is completed, the reaction is continued until the unreacted monomer in the system is consumed, and by completing the reaction, an emulsion of crosslinked polymer particles, which is the target product of the present invention, can be obtained. can.

As described above, the method of the present invention involves the use of a crosslinking 7-mer in the so-called soap-free emulsification method that does not use any surfactant. According to the present invention, the crosslinking monomer is not added all at once, after the polymerization rate reaches 1 to 40% and before it reaches 55 to 90%. Stable emulsions of IIIL coalescing particles can be produced. If the emulsion obtained in the present invention is dried and then crushed into secondary particles, the fine powder obtained can contain pigments, without worrying about the influence of surfactants.
It can be used as filler, etc.

EXAMPLES Next, the effects of the present invention will be specifically explained by showing examples together with comparative examples. All "parts" shown in the practical examples and comparative examples mean "parts by weight."

Example 1 400 parts of distilled water and polyethylene glycol α5 were placed in a 50 liter flask equipped with a reflux condenser, a thermometer, a nitrogen blowing tube, a dropping funnel, and a mixing device.
parts, sodium thiosulfate 0.5 parts, methacrylate 20 parts
0 parts and stirred at a constant stirring speed (40O
RPM) and raise the temperature to 50°C. followed by 50℃
When the temperature is reached, add 1 part of potassium persulfate and start 1 cup. One hour after starting polymerization, the polymerization rate was 1.
When it reaches 0%, 30 parts of styrene, ethylene glycol dimeta/! j L/-door 0 parts, ethyl acetate 5
Start dropping 0g of the mixture and stop dropping when the polymerization rate reaches 70g. After completion of the dropwise addition, the reaction was continued for 3 hours at 3°C in 50 parts to complete the reaction.

The emulsion thus obtained was stable and contained almost no agglomerated products, and the average particle size of the dispersed particles was 0.45μ.

Example 2 400 parts of distilled water and 0.0 parts of polysodium methacrylate were placed in a 1-50 flask equipped with a reflux condenser, a thermometer, a nitrogen blowing tube, a dropping funnel, and a mixing device.
5 parts of sodium thiosulfate, 0.57 flll of sodium thiosulfate, and 200 parts of methyl methacrylate were added, and the temperature was raised to 50°C under a nitrogen stream while maintaining a constant stirring speed (400 rpm).

Subsequently, when the temperature reached 50°C, 1 part of potassium persulfate was added to initiate polymerization. When the polymerization rate reached 5% after 30 minutes had passed from the start of polymerization, methyl methacrylate)
A mixture of 20 parts of divinylbenzene and 80 parts of divinylbenzene was started to be added down, and the dropwise addition was stopped when the 1 polymerization rate reached 60%.

After the addition was completed, the reaction was continued for 3 hours at 3°C in 50 parts to complete the reaction. The emulsion thus obtained was very stable, with hardly any agglomerated products or adhesion to the stirring spring, and the average particle diameter of one dispersed particle was 0.55 μm.

Example 3 400 parts of distilled water was placed in an 11-50 flask equipped with a reflux condenser, a thermometer, a 1# nitrogen blower, a dropping funnel, and a grinding type stirring device.

1 part polyethylene glycol, 1 part sodium bisulfite
100 parts of methyl methacrylate and 50 seconds of styrene were added, and stirred at a constant stirring speed (40 rpm) under mk air flow.
) and raise the temperature to 55°C. Subsequently, when the temperature reached 55°C, 2 parts of potassium persulfate was added to start 1 cup.

One hour after starting the polymerization, when the polymerization rate reached 12%, divinylbenzene 1501ti and toluene 5
Start dropping 0 parts of the mixture and stop dropping when the polymerization rate reaches 80 parts.

After finishing the dropwise addition, the reaction was continued for 3 hours at 55±3°C to complete the reaction. The emulsion thus obtained was stable, with almost no agglomeration products, and the average particle size of the dispersed particles was 0.65μ.

Example 4 400 parts of distilled water was placed in an IJ 50 flask equipped with a reflux condenser, a thermometer, a nitrogen blowing tube, a dropping funnel, and a mixing device.

1 part polyethylene glycol, 1 part sodium bisulfite
part, methyl methacrylate 150i1S.

Add 50s of methyl acrylate and 50 parts of acrylonitrile, and stir at a constant stirring speed (30 rpm) under a nitrogen stream.
) and raise the temperature to 55°C.

Subsequently, when the temperature reached 55°C, 2 parts of potassium persulfate was added to initiate polymerization. When the polymerization rate reaches 28%, 45 minutes after starting the polymerization, 50 parts of divinylbenzene is added, and the dropwise addition is stopped when the polymerization rate reaches 85%. 55 minutes after finishing dropping the crosslinking monomer
Continue the reaction at ±3°C for 3 hours to complete the reaction.

The emulsion thus obtained was stable and had almost no aggregates, and the average particle size of the dispersed particles was 0.35μ.

Comparative Example 1 In Example 1, the cross-linking monomer mixture for dropping was put into the flask from the initial stage of polymerization and the polymerization was carried out by charging all at once. However, 80 minutes after the addition of the catalyst, the viscosity increased significantly and the contents of the flask It became immobile.

Comparative Example 2 In Example 2, the crosslinking monomer mixture for addition was put into the flask from the initial stage of polymerization and the polymerization was carried out using a batch charging method. However, 90 minutes after adding the catalyst, the viscosity increased significantly and the contents of the flask did not flow. It became impossible to continue the polymerization.

Comparative Example 3 In Example 4, when divinylbenzene was added at once at a polymerization rate of 35% and polymerization was continued for 6 hours, the emulsion in the flask contained a lot of agglomerated products, and there was also scale adhesion to the flask and stirring spring. There were significantly more. The agglomerated products and scale deposits were scraped off, passed through a 200-mesh wire mesh, dried, and then weighed, and it was found that 45% of the monomer charged was agglomerated products and scale deposits. Ta.

Comparative Example 4 A 50-liter flask K equipped with a reflux condenser, a thermometer, a nitrogen blowing tube, a dropping funnel, and a mixing device, 4005° distilled water, 1 part polyethylene glycol, 111% aqueous sodium sulfite. Add 285 parts of methyl methacrylate and 15 parts of divinylbenzene, and stir under a nitrogen stream while maintaining a constant stirring speed (400 rpm).
Raise the temperature to 5°C. Subsequently, when the temperature reached 55°C, 2 parts of potassium persulfate was added to initiate polymerization. 8 at 55±3℃
Keep time to complete reaction.

The emulsion thus obtained contained a very large amount of agglomerated products (the agglomerated products and scale deposits were removed, the emulsion was passed through a 200-mesh wire mesh, dried, and its weight was measured. It was found that 48 tons were agglomerated products and scale deposits.

Comparative Example 5 In Example 4, when divinylbenzene was started under M at a polymerization rate of 70%, the reaction system increased in viscosity during the dropwise addition of divinylbenzene, and stirring in the flask became impossible.

Claims (1)

[Claims] 1. Emulsion polymerization of methyl methacrylate alone or a vinyl monomer containing methyl methacrylate in the absence of a surfactant, and when the polymerization rate reaches a range of 1 to 40%, at least 2. The reaction is continued by continuously or intermittently adding a crosslinkable monomer having vinyl groups, and when the polymerization rate reaches the range of 55 to 90%, the addition of the crosslinkable monomer is terminated, A method for producing a crosslinked polymer emulsion, which comprises completing the reaction after a certain period of time. 2. The method according to claim 1, wherein the emulsion polymerization is carried out in the presence of a water-soluble polymer. 3. The method according to claim 1, wherein the crosslinking monomer is ethylene glycol dimethacrylate or divinylbenzene.