JPS5846242B2 - Method for producing polymer emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel emulsion polymerization method for monomers having specific radically polymerizable unsaturated bonds. The present invention relates to a method for stably producing a polymer emulsion that is chemically and mechanically extremely stable and has a small particle size.

In recent years, regulations on the use of various organic solvents have been tightened from the viewpoint of preventing air pollution, purifying the environment, and saving petroleum resources.

In the paint and adhesive industries, which use relatively large amounts of organic solvents, technical studies are already underway in response to such regulations.
For example, the shift to solvent-free paints, such as powder, water-soluble, emulsion, high-solid, and hot-melt paints, is being promoted.

Among them, emulsion is considered the most effective solution.

However, existing emulsions are not entirely without runners-up.

In particular, residues of conventional emulsifiers used during polymer emulsion polymerization in emulsions can cause problems such as wastewater treatment after emulsion production, foaming problems in the emulsion coating process, pinhole formation due to air bubbles in the formed film, and water resistance of the film. It's posing a big problem.

In order to eliminate such defects caused by emulsifiers, we proposed a method of copolymerizing vinyl chloride and certain acidic monomers to introduce carboxylic acids into the polymer when obtaining vinyl chloride polymer emulsions. (Special Public Interest Publication No. 43-30068
Although this method reduces the amount of emulsifier used, if it is not used, the polymerization system becomes unstable and a large amount of aggregates are formed, and it is difficult to obtain a highly concentrated emulsion. Furthermore, it is difficult to obtain a good emulsion because the polymer particle size in the obtained emulsion is large and the viscosity of the emulsion is also high.

In addition, a method (Japanese Patent Publication No. 47-606) using a certain type of water-soluble polymer instead of a conventional emulsifier is also known, and this method aims to eliminate various defects caused by conventional emulsifiers. However, since it is based on the premise of extracting the polymer from the emulsion, the purpose is only to obtain large polymer particles, and it cannot be used at all for applications where the polymer emulsion is used as it is. It is not possible.

An object of the present invention is to provide a method for stably obtaining an emulsion containing a chemically and mechanically stable polymer with a small particle size, which has not been easily realized using conventional emulsion polymerization methods.

Another object of the invention is to obtain a polymer emulsion which suppresses air bubbles and significantly improves the properties of the film formed, especially the water resistance.

Still other objects of the present invention are for water-based paints, adhesives,
The object of the present invention is to provide a polymer emulsion with significantly improved properties for use in paper processing, fiber modification processing, concrete IJ-1, and mortar mixing.

The present invention provides a water-soluble polymer having a specific polymerization composition, which contains a monomer unit consisting of itaconic acid or a salt thereof, a monomer unit consisting of an ethylenically unsaturated sulfonic acid or a salt thereof, and a methacrylic acid ester. This can be achieved by polymerizing a monomer having a radically polymerizable unsaturated bond in an aqueous medium with a pH of 5 or less using a water-soluble catalyst in the presence of a polymer.

The polymer emulsions prepared according to the present invention have substantially less foaming properties and the foam formed disappears more quickly than similar polymer emulsions prepared using conventional emulsifiers in conventional amounts.

Therefore, in general, the use of an antifoaming agent such as a silicone antifoaming agent is essential in fields of application where foamability is an issue, but antifoaming agents are not necessary for use with the emulsion of the present invention.

The emulsion of the present invention, which does not require an antifoaming agent, has the technical advantage of being able to eliminate defects in physical properties caused by antifoaming agents, and also has economic advantages.

In addition, since the particles in the polymer emulsion obtained by the present invention are extremely fine, when applied to various purposes, they easily penetrate materials, have excellent adhesion, and have excellent film-forming properties. One of the advantages of the present invention is that, as a result, the surface of the film formed during coating becomes very smooth and its gloss can be improved.

Furthermore, since large amounts of hydrophilic or water-soluble dispersants (protective colloid agents) are added to ordinary polymer emulsions for the purpose of stabilizing the dispersion of particles, there is a serious problem with the water resistance of the formed film. there were.

According to the present invention, the amount of the water-soluble polymer used is small and the physical bonding force between the hydrophobic part of the water-soluble polymer and the resin polymer is strong, so that the water resistance of the formed film is improved. is also significantly improved compared to the conventional one.

The water-soluble polymer used in the present invention is a monomer unit consisting of itaconic acid or a salt thereof (component A), a monomer unit consisting of an ethylenically unsaturated sulfonic acid or a salt thereof (component B), and a methacrylic acid ester. It is a copolymer in which (component C) is bound and contained, and the polymerization ratio of (a) component A that can be copolymerized is 30% of the copolymerizable components A, B, and C.
(b) The polymerization ratio of copolymerizable component B is in the range of 5-40% by weight, and (c) The polymerization ratio of copolymerizable component C is 5-40% by weight. range.

No matter which method the water-soluble polymer is obtained, the final composition is A or B within the above composition range.

A water-soluble polymer containing the three components C can be effectively used in the present invention, but in general, the three components A, B, and C can be copolymerized by a well-known method (using water as a polymerization medium). Solution polymerization is preferred).

In addition, the composition ratio of A, B, (J5:) in such a water-soluble polymer varies depending on the type of monomer having a radically polymerizable unsaturated bond to be emulsion polymerized, and it is difficult to define it uniquely. be.

Further, there is no particular restriction on the degree of polymerization of such a polymer, but since the degree of polymerization is correlated with the viscosity of the emulsion obtained, it is desirable to determine the degree of polymerization of the water-soluble polymer according to the required viscosity of the emulsion.

Component B used in the present invention includes sulfonated non-foaming hydrocarbons such as sulfonated styrene, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, and these. Salts, sulfoalkyl esters of acrylic acid or methacrylic acid such as sulfoethyl methacrylate, sulfopropyl methacrylate, and salts thereof can be mentioned.

As component C used in the present invention, methacrylic acid esters such as methyl methacrylate and ethyl methacrylate can be mentioned.

The polymer emulsion of the present invention is produced in the same manner as in conventional emulsion polymerization methods, except that the water-soluble polymer described above is used instead of the emulsifier.

A general manufacturing method is to add the monomer to be polymerized and water in which 1 to 4 weight by weight of the above water-soluble polymer and a predetermined amount of water-soluble catalyst are dissolved in a polymerization system based on the amount of the monomer used. After supplying and adding a chain transfer agent etc. as necessary, the P of the polymerization system is
Polymerization is carried out at a predetermined temperature by batch polymerization or continuous polymerization while maintaining H at 5 or less.

In particular, pH is important in such polymerization, and in order to achieve the purpose of the present invention, it is necessary to employ a pH of 5 or less.

That is, when a polymerization pH higher than 5 is used, the diameter of the produced polymer particles is large and the emulsion tends to aggregate, making it difficult to produce a stable polymer emulsion.

If the amount of water-soluble copolymer used is less than the maximum of 1 monomer per polymer, aggregation of the emulsion tends to occur, and if it exceeds the maximum of 4, the viscosity of the reaction system will increase and the monomer will not dissolve in water. The low speed makes it difficult to produce stable polymer emulsions.

The monomers applied to the polymerization of the present invention include styrene, α-
Aromatic vinyl monomers such as methylstyrene and fluorostyrene; Acrylic acid esters and methacrylic acid esters such as methyl acrylate, ethyl acrylate, and butyl methacrylate; Vinyl chloride, butyl bromide, vinylidene chloride, vinylidene bromide It is a monomer selected from the group consisting of vinyl halides and vinylidenes such as vinyl esters such as vinyl acetate and vinyl propionate, either singly or as a mixture.

Note that some of these monomers may be replaced with other monomers having radically polymerizable unsaturated bonds used in ordinary emulsion polymerization, such as monomers such as ethylene, butadiene, and isoprene. It goes without saying that this does not in any way impede the purpose of the present invention.

Further, as the polymerization catalyst used in the polymerization, any known radical-generating water-soluble polymerization catalyst such as persulfate can be used.

In addition, persulfates and reducing sulfoxy compounds (and/
The object of the present invention can also be sufficiently achieved by using a redox catalyst consisting of a combination of a chlorate or a cyclic sulfoxy compound, or a combination of a chlorate and a cyclic sulfoxy compound.

The emulsion thus obtained according to the present invention is an emulsion consisting of a polymer with an extremely fine particle size,
In addition, it has excellent stability against electrolytes, freezing stability, mechanical stability, etc., so it can be used for water-based paints, adhesives, paper processing, fiber processing/modifiers, and concrete/mortar admixtures. It is possible to produce emulsions which are very advantageous.

Although it is not yet clear why the water-soluble polymer used in the present invention exhibits such an excellent effect as an emulsifier, it is probably because the hydrophobic part of the water-soluble polymer has an unsaturated bond that can be radically polymerized. Radical polymerization of the monomers begins, and the physically and chemically bonded combination of the water-soluble polymer and the oligomer of the polymerization monomer acts as an emulsifier, leading to a chemical reaction called polymerization of the oligomer. This seems to be due to the progression of

Therefore, in order to obtain a stable polymerization state, the selection of an emulsifier is very important in conventional emulsion polymerization methods, and in the present invention, water-soluble polymers that can maximize the effect as an emulsifier are It is considered that it is most important to obtain a physical and chemical bond between the monomer and the oligomer to be polymerized, and the selection of a water-soluble polymer that can induce such a moderate physical and chemical bond. It is thought that the effects of the present invention will be exhibited by this.

The examples described below serve to better explain the invention and are not intended to limit the scope of the invention.

All percentages shown in the examples are based on weight unless otherwise specified, and the water shown in the examples was treated with a positive and anion exchange resin.

Example 1 Itaconic acid, sodium P-styrene sulfonate (NASS) and methyl methacrylate (
A water-soluble copolymer with MMA) was obtained.

Itaconic acid 32 PNASS
24? MMA
24y ammonium persulfate 1
．． 61 Water 3102 A three-hole glass flask with a stirrer and substituted with N2 is charged with 32P itaconic acid and 1772 water.

After adjusting the inside of the flask to 80°C, 101 t of ammonium persulfate dissolved in water was added, and then NAS S and MMA dissolved in 133 t of water were added dropwise using separate dropping funnels.

After 1 hour, the NASS aqueous solution and MMA were added dropwise, and the polymerization was further continued for 1 hour.

This aqueous solution of the polymer was directly diluted with water and used in the next emulsion polymerization.

The polymerization recipe used for emulsion polymerization is as shown below.

Vinyl acetate 20oz Water-soluble polymer 4g Sodium persulfate 0.4z Sodium hydrogen carbonate 0.25P water
2121 19 in a glass three-bottle flask with a stirrer replaced with N2
2z of water, water soluble polymer and sodium bicarbonate were charged.

After adjusting the temperature inside the flask to 65°C while stirring, 20f
? of vinyl acetate monomer was then charged with sodium persulfate, previously dissolved in 205' of water, at this point p.
H was 4.3.

After 10 to 20 minutes, remove the remaining vinyl acetate 180 fI.
was added dropwise over 3 hours to polymerize.

After the dropwise addition was completed, polymerization was continued at 70°C for 1 hour, and then cooled.
The pH of the vinyl acetate emulsion obtained by filtration through a 00 mesh wire mesh was 4.5.

The amount of coagulated material during the polymerization reaction was very small at 0.03% by weight of seven polymers, and the monomer reaction rate was approximately 100%.

The emulsion thus obtained had characteristics such as fine particle size, low foaming property, low foam stability, high water resistance, and low viscosity.

Table 1 shows the physical properties of this emulsion.

Physical property measurement method and measurement conditions 1: Particle size The average particle size was measured using the optical index method or Coulter Counter manufactured by Coulter Electronics.

2. Water resistance The water drop method of JISK6828 was followed.

3. Foaming property Foam height was measured immediately after dropping and 5 minutes after dropping according to the Ross Miles method of ASTM-D1173-53.

4. Ca"+ ion stability Determined by the presence or absence of aggregates when 501 rLl of 10 polycalcium chloride was dropped into 0.5% emulsion 100I711.

5. Freezing stability, dilution stability Compliant with JISK6828.

6. Viscosity Measured using a B-type viscometer at 12r-plm and 24°C.

Comparative Example 1 Polyvinyl alcohol 14 with a saponification degree of 90% was used instead of the water-soluble polymer of Example 1. An emulsion was obtained using the same polymerization recipe and polymerization conditions as in Example 1 except for using the following.

The physical properties of the obtained emulsion are shown in Table 1 together with those of Example 1.

Compared to the emulsion of Example 1, the particle size was larger and the water resistance, foaming properties, and dilution stability δ were inferior.

Comparative Example 2 Instead of the water-soluble polymer of Example 1, a succinic acid emulsifier (
The polymerization recipe was the same as in Example 1 except that 7 g (solid content) of Aerosol A 102) manufactured by Cyanamid was used.
An emulsion was obtained under the polymerization conditions.

Although the particle size of the obtained emulsion was almost the same as that of the emulsion of Example 1, it was significantly inferior in water resistance and foaming properties.

Comparative Example 3 An attempt was made to produce a vinyl acetate polymer emulsion using the same recipe and conditions as in Example 1, except that 44 g of itaconic acid and 12 r of MMA were used.

No emulsification phenomenon occurred.

Comparative Example 4 An attempt was made to produce a vinyl acetate polymer emulsion using the same recipe and conditions as in Example 1, except for using itaconic acid 20ti11MMA36z.

During the dropwise addition of the vinyl acetate monomer, a large amount of solidified material formed, making stirring impossible.

Example 2 Production of a vinyl acetate polymer emulsion using the same recipe and conditions as in Example 1, except that 2-acrylamido-2-methylpropanesulfonic acid, sulfopyropyl methacrylate or sulfoethyl methacrylate was used in place of NASS. I did it.

In each case, a polymer emulsion containing fine polymer particles, low viscosity, and exhibiting a good dispersion state was obtained.

Example 3 Using the water-soluble copolymer obtained in Example 1, a mixed monomer having the composition of ethyl acrylate/methyl methacrylate was emulsion polymerized.

Same recipe as Example 1 except that vinyl acetate monomer was replaced with the above mixed monomer and the polymerization temperature was changed to 80°C.
I went with the conditions.

The resulting copolymer emulsion had low foaming properties and high water resistance, and contained fine copolymer particles with an average particle size of 0.08 microns.

Example 4 Emulsion polymerization was carried out under substantially the same conditions as in Example 31, except that styrene was used in place of the mixed monomer of ethyl acrylate/methyl methacrylate.

In this case, polymerization initiation by a small amount of methyl methacrylate 2
200′ after 0 minutes? of styrene was continuously added dropwise to carry out polymerization.

As a result, a good emulsion was obtained.

Example 5 Using the water-soluble copolymer obtained in Example 1, vinyl acetate/
A vinyl chloride/ethylene terpolymer emulsion was produced.

The compounds and amounts filled in the autoclave are shown below.

Vinyl acetate 490 g Vinyl chloride 234 g Potassium bicarbonate
2.9z ammonium persulfate
5.02 Sodium metabisulfide 5.01 Water-soluble copolymer
24? water 8
10 P ethylene 50 atm (600
G) 6201 water, potassium bicarbonate dissolved in 2 Fl' water and the water-soluble copolymer were placed in a reaction vessel, and after sufficient dissolution 60 ml of vinyl acetate monomer was added.

The pH at this point was 4.5. The reactor was purged with ethylene and heated.

When the temperature was adjusted to 60°C, ammonium persulfate dissolved in 25F water was added and the ethylene pressure was adjusted to 50 atm.

Vinyl acetate and vinyl chloride break down for 4 hours, and
40 i of sodium metabisulfide dissolved in water was pumped into the reaction vessel over a period of 6 hours.

The ethylene pressure was kept constant at 50 atmospheres during the reaction.

The reactants were continuously stirred for 6 hours.

After cooling, unreacted ethylene was discharged.

The pH of the emulsion at this time was 4.5. Analysis of the film of the emulsion obtained by baking revealed that it was a copolymer having a polymer composition of ethylene/vinyl acetate/vinyl chloride=16156/28.

There were almost no coagulated substances formed during the reaction, and the emulsion had a low viscosity and a good dispersion state.

Claims (1)

[Claims] 1. In the presence of a water-soluble polymer containing a monomer unit consisting of itaconic acid or a salt thereof, a monomer unit consisting of an ethylenically unsaturated sulfonic acid or a salt thereof, and a methacrylic acid ester bonded to each other. A method for producing a polymer emulsion, which comprises polymerizing a monomer having a radically polymerizable unsaturated bond in an aqueous medium at pH 5 or lower using a water-soluble catalyst. 2 The water-soluble polymer is 30 to 50 parts by weight of a monomer consisting of itaconic acid or its salt, 5 to 40 parts by weight of a monomer consisting of ethylenically unsaturated sulfonic acid or its salt, and 5 to 40 parts by weight of methacrylic acid ester. A method for producing a polymer emulsion according to claim 1, having a polymerization composition of 3. The method for producing a polymer emulsion according to claim 1 or 2, wherein the amount of the water-soluble polymer used is 1 to 4 percent by weight based on the weight of the monomer having a radically polymerizable unsaturated bond. . 4 One type selected from the group consisting of aromatic vinyl monomers, acrylic esters and methacrylic esters, vinyl halides and vinylidenes, and vinyl esters as a monomer having a radically polymerizable unsaturated bond Claims 1 and 2 using the above monomers
A method for producing a polymer emulsion according to item 3 or 3.