JP3931266B2 - Method for producing aqueous resin emulsion - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an aqueous resin emulsion, and a film formed from the aqueous resin emulsion obtained by the present invention is excellent in water resistance and stain resistance, and therefore the emulsion is of an aqueous type. It is suitably used as a paint and an adhesive.
[0002]
[Prior art and its problems]
Aqueous resin emulsions are used in a wide range of applications such as paints, adhesives, paper processing agents, textile processing agents, mortar modifiers, taking advantage of their non-polluting properties, good workability, and resource saving. ing. Conventionally, aqueous resin emulsions are most commonly obtained by emulsion polymerization of monomers using low molecular weight compounds such as sodium alkylbenzene sulfonate, polyoxyethylene alkyl allyl ether sodium sulfate or polyoxyethylene nonyl phenyl ether as emulsifiers. It was manufactured by. However, the aqueous resin emulsion produced by the above method has a problem that the water resistance of the film formed by drying is inferior due to the low molecular weight emulsifier.
[0003]
As a method for solving the above problems, a method of emulsion polymerization of a monomer in the presence of a polymer emulsifier, or a reactive emulsifier having a radical polymerizable unsaturated group and being incorporated into a part of the polymer during polymerization (For example, JP-A-5-154369 and JP-A-9-3144).
However, the water resistance of the film formed from the resin emulsion obtained by the above method is still one step. As an example of a reactive emulsifier, polyethylene glycol mono (meth) acrylate was also known, but it was inferior in copolymerizability with other monomers used as the main component of emulsion polymerization and remained unreacted. Since it was easy, the water resistance of the obtained resin emulsion was still not sufficient.
[0004]
[Means for Solving the Problems]
As a result of diligent studies to solve the above problems, the present inventor does not use an emulsifier that has been used conventionally or uses the radically polymerizable macromonomer having a specific configuration. Even if it is less, it has been found that the monomer can be stably emulsion polymerized in an aqueous medium, and according to the emulsion polymerization, it has been found that an aqueous resin emulsion that forms a film with extremely excellent water resistance can be obtained. The present invention has been completed.
That is, the present invention is a method for producing an aqueous resin emulsion, wherein the following macromonomer and other radical polymerizable monomer are copolymerized in an aqueous medium in the presence or absence of an emulsifier.
Macromonomer: (a) a macromonomer having a radical polymerizable group at one end of a silicone or hydrophobic vinyl polymer, (b) polyalkylene glycol mono (meth) acrylate or polyalkylene glycol monoalkyl ether mono (meth) acrylate and A copolymer obtained by copolymerizing (c) other radical polymerizable monomer as desired, wherein the proportion of the macromonomer unit is 40 to 40% based on the total amount of all the structural units. 1% by weight, (b) the proportion of monomer units is 60 to 99% by weight, and (c) the proportion of monomer units is 0 to 15% by weight at one end of the copolymer. Hereinafter, the macromonomer having the above specific structure is referred to as a macromonomer of the present invention. Hereinafter, the present invention will be described in more detail.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The macromonomer of the present invention can be synthesized by a method adopted in the production of a conventionally known radical polymerizable macromonomer.
That is, by radical polymerization using a mercapto compound having a carboxyl group such as mercaptopropionic acid as a chain transfer agent, (a) a macromonomer having a radical polymerizable group at one end of a silicone or hydrophobic vinyl polymer, (b) poly By copolymerizing alkylene glycol mono (meth) acrylate or polyalkylene glycol monoalkyl ether mono (meth) acrylate and optionally (c) other radical polymerizable monomer, the carboxyl group derived from the mercapto compound is converted into a molecule. A copolymer having a chain at one end (hereinafter sometimes referred to as a base polymer) is obtained. Next, the macromonomer of the present invention having a methacryloyl group as a radical polymerizable group at one end is obtained by reacting the copolymer with glycidyl methacrylate and the like.
[0006]
As described above, the ratio of the (a) macromonomer unit, the ratio of the (b) monomer unit, and the ratio of the (c) monomer unit in the macromonomer of the present invention are based on the total amount of them as described above. a) Macromonomer unit; 40 to 1% by weight; (b) Monomer unit; 60 to 99% by weight; and (c) Monomer unit; 0 to 15% by weight.
(A) When the proportion of the macromonomer unit is out of the range of 40 to 1% by weight, the balance between the hydrophobic component and the hydrophilic component is lost, and the surface active ability of the resulting macromonomer is impaired.
The preferred number average molecular weight of the macromonomer of the present invention is 1,000 to 20,000. If the number average molecular weight of the macromonomer is less than 1,000, the property of repelling oil ink and the like tends to be insufficient, while if it exceeds 20,000, unreacted macromonomer remains in the aqueous resin emulsion, When the macromonomer flows out of the formed film by rain water or the like, the stain resistance of the film is likely to be lowered.
[0007]
The component (a) in the present invention is a macromonomer having a radically polymerizable group at one end of a silicone or hydrophobic vinyl polymer, that is, a silicone macromonomer or a hydrophobic vinyl polymer macromonomer.
As the silicone macromonomer, a radical polymerizable group such as a (meth) acryloyl group is present at one end of a polyorganosiloxane molecule represented by polydimethylsiloxane, polydiethylsiloxane, polymethylphenylsiloxane and polydiphenylsiloxane. Examples include bonded macromonomers. Commercially available silicone macromonomers such as AK-5, AK-30, AK-32 manufactured by Toagosei Co., Ltd., and X-22-174DX manufactured by Shin-Etsu Chemical Co., Ltd. can also be used.
The preferred number average molecular weight of the silicone macromonomer is 500 to 10,000. When the number average molecular weight of the silicone macromonomer is less than 500, the stain resistance of the coating film tends to be insufficient, and when it exceeds 10,000, it is difficult to obtain a transparent multi-branched polymer solution.
[0008]
Examples of the hydrophobic vinyl polymer-based macromonomer include macromonomers having a radical polymerizable group at one end of a hydrophobic vinyl polymer such as polymethyl methacrylate or polybutyl methacrylate. Examples of the hydrophobic vinyl polymer serving as the skeleton of the macromonomer include homopolymers or copolymers such as alkyl (meth) acrylate, styrene, acrylonitrile, perfluoroalkylethyl (meth) acrylate, or hydroxyalkyl (meth) acrylate. The number average molecular weight is preferably 1,000 to 10,000.
As the radical polymerizable group, a (meth) acryloyl group and a styryl group are preferable.
[0009]
The component (b) is a polyalkylene glycol mono (meth) acrylate or a polyalkylene glycol monoalkyl ether mono (meth) acrylate (hereinafter may be collectively referred to as a polyalkylene glycol monomer), and is preferably a polyalkylene Examples of glycol mono (meth) acrylates include polyethylene glycol mono (meth) acrylate and polypropylene glycol mono (meth) acrylate.
Polyalkylene glycol monoalkyl ether mono (meth) acrylate) acrylate includes methoxypolyethylene glycol mono (meth) acrylate, ethoxypolyethylene glycol mono (meth) acrylate, butoxypolypropylene glycol mono (meth) acrylate and methoxypolyethylene glycol polypropylene glycol. A mono (meth) acrylate etc. are mentioned.
In addition to the above compounds, methoxypolytetramethylene glycol polyethylene glycol mono (meth) acrylate and benzyloxypolyethylene glycol (meth) acrylate can also be used.
[0010]
The preferable degree of condensation of the alkylene oxide repeating unit in the polyalkylene glycol monomer is 2 to 50, more preferably 3 to 30. If the degree of condensation of the alkylene oxide repeating unit exceeds 50, the water resistance of the film formed from the resulting multibranched polymer tends to decrease.
The number of carbon atoms of the alkylene in the alkylene oxide unit forming the polyalkylene glycol monomer is preferably 2 or 3, particularly preferably 2.
[0011]
In order to form the base polymer in the macromonomer of the present invention, in addition to the above components (a) and (b), other radical polymerizable monomers such as alkyl (meth) acrylate, vinyl carboxylate, (meth) acrylonitrile Styrene, perfluoroalkylethyl (meth) acrylate, perfluoroalkyl (meth) acrylate, and the like may be used.
The amount of other radical polymerizable monomers used is 0 to 15% by weight based on the total amount of all structural units in the base polymer.
[0012]
As described above, the base polymer in the macromonomer of the present invention is produced by radical polymerization of the components (a) to (c) in the presence of a mercapto compound having a carboxyl group.
Examples of the mercapto compound used as the chain transfer agent include mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, and thiomalic acid.
The preferred amount of the mercapto compound used is an amount that is equimolar to the obtained base polymer. Specifically, the base polymer: mercaptocarboxylic acid = 1: (0.8 to 1.3) (molar ratio). It is.
[0013]
The polymerization temperature is preferably 50 to 140 ° C., and the polymerization solvent is preferably ethyl acetate, butyl acetate, methyl isobutyl ketone, toluene or xylene.
Examples of the polymerization initiator include azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanecarbonitrile, benzoyl peroxide, toluoyl peroxide, butyl peroxypivalate, and butyl peroxyoctanoate. The preferable use amount is 0.1 to 3 parts by weight per 100 parts by weight of the monomer.
[0014]
The macromonomer of the present invention can be obtained by reacting the base polymer obtained by the above method with a monomer having a functional group reactive with the carboxyl group, for example, an epoxy group. Examples of the monomer having an epoxy group (hereinafter referred to as an epoxy group-containing monomer) include glycidyl (meth) acrylate or 3,4-epoxycyclohexylmethyl methacrylate.
The base polymer and the epoxy group-containing monomer can be reacted by heating them to 50 to 140 ° C. in the presence of a catalyst in an organic solvent, for example, a base polymer solution obtained by solution polymerization.
The amount of the epoxy group-containing monomer used is at least equivalent to the carboxyl group bonded to one end of the base polymer, specifically 1.0 to 1.5 times the carboxyl group. Mole is preferred.
[0015]
In order to promote the addition reaction of carboxyl group and epoxy group of the base polymer, tertiary amine such as triethylamine, tripropylamine, quaternary ammonium salt such as tetraethylammonium bromide, tetrabutylammonium bromide, triethylbenzylammonium chloride, tetra It is preferable to add an appropriate amount of a quaternary phosphonium salt such as a phosphonium salt as a catalyst.
[0016]
In the present invention, the macromonomer of the present invention and other radical polymerizable monomers are copolymerized in an aqueous medium in the presence or absence of an emulsifier.
The monomer to be copolymerized with the macromonomer naturally varies depending on the use of the obtained aqueous resin emulsion. For example, (meth) acrylic acid ester, vinyl carboxylate, (meth) acrylonitrile, styrene, perfluoroalkyl ( (Meth) acrylate, dimethylaminoethyl (meth) acrylate, N-alkyl (meth) acrylamide, (meth) acrylic acid, maleic acid, itaconic acid, maleic anhydride, styrene sulfonic acid, 2-acrylamide-2-methylpropane sulfonic acid Acid phosphoxyethyl methacrylate and 3-chloro-2-acid phosphoxypropyl methacrylate.
Furthermore, when used in combination with the unsaturated monomer, alkali metal salts, ammonium salts and amine salts of monomers having an acidic group such as a carboxyl group, a sulfo group or a phospho group can also be used.
A preferable copolymerization ratio of the macromonomer and the copolymerizable monomer is 1 to 30% by weight of the macromonomer and 99 to 70% by weight of the copolymerizable monomer based on the total amount thereof.
[0017]
In order to obtain an aqueous resin emulsion suitable as an adhesive, examples of the copolymer monomer of the macromonomer of the present invention include a monomer mixture composed of butyl acrylate, methyl methacrylate, acid phosphoxyethyl methacrylate, and the like. In order to obtain a preferable aqueous resin emulsion for the pressure-sensitive adhesive, a monomer mixture comprising 2-ethylhexyl acrylate, acrylonitrile, itaconic acid and the like can be cited as a copolymerization monomer of the macromonomer, and a paint or a coating agent In order to obtain an aqueous resin emulsion suitable for the above, a monomer mixture composed of styrene, butyl methacrylate, methyl methacrylate, methacrylic acid and the like can be preferably used as the copolymerization monomer.
[0018]
When the above components are copolymerized in an aqueous medium, a nonionic emulsifier, an anionic emulsifier or a nonionic anionic emulsifier may be used. And polyethylene oxide propylene oxide.
Examples of anionic emulsifiers include sulfosuccinic acid alkali metal salts, alkylbenzenesulfonic acid alkali metal salts, and alkylnaphthalenesulfonic acid alkali metal salts. Examples of nonionic anionic emulsifiers include polyoxyethylene lauryl ether sulfate sodium salt and polyoxyethylene octyl phenyl ether sulfate sodium salt.
The preferred amount of the emulsifier is 0.3 to 3% by weight based on the total amount of the macromonomer and the comonomer of the present invention. In the present invention, since a macromonomer having surface active ability is used as a polymerization component, the amount of emulsifier used in combination differs depending on the amount of macromonomer used, but the amount of emulsifier used compared to the case of normal emulsion polymerization. Can be reduced considerably.
[0019]
Examples of the polymerization initiator include potassium persulfate, ammonium persulfate, hydrogen peroxide, cumene hydroperoxide, butyl cumyl peroxide, benzoyl peroxide, toluoyl peroxide, and azobisisobutyronitrile.
In addition, a chain transfer agent such as mercaptoethanol, 2-propanethiol, 1-butanethiol, thiophenol or dodecyl mercaptan may be used to adjust the molecular weight of the obtained polymer.
Applications of the aqueous resin emulsion obtained by the above method include paints, coating agents, adhesives, pressure sensitive adhesives, impregnated reinforcing agents and the like. Examples of the substrate on which this is applied include metal, paper, wood, glass, and concrete.
[0020]
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. “Parts” in each example means “parts by weight”.
○ Production Example 1
A mixed liquid of 100 parts of toluene and 1.8 parts of 3-mercaptopropionic acid was heated to 90 ° C. under a nitrogen stream and stirred, and 80 parts of methoxypolyethylene glycol monomethacrylate (average degree of polymerization of ethylene oxide 9) was added to this liquid. Then, 20 parts of polydimethylsiloxane terminal methacryloyl type macromonomer (X-22-174DX; number average molecular weight of about 5,000, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1 part of azobisisobutyronitrile were added dropwise over 4 hours. By further heating for 2 hours, a toluene solution of a base polymer having a carboxyl group at one end and a number average molecular weight of 7,300 was obtained.
A solution prepared by dissolving 2.65 parts of glycidyl methacrylate, 0.9 part of tetrabutylammonium bromide and 0.05 part of hydroquinone monomethyl ether in 10 parts of toluene was dropped into the above toluene solution, and then blown at 110 ° C. while blowing air. Reacted for hours.
Then, the solvent was removed with a spray dryer to obtain the macromonomer (1) of the present invention. The number average molecular weight was 7,500, and the weight average molecular weight was 17,100.
[0021]
○ Production Example 2
Instead of polydimethylsiloxane terminal methacryloyl type macromonomer in Production Example 1, polymethyl methacrylate terminal methacryloyl type macromonomer (AA-6; number average molecular weight of about 6,000, manufactured by Toagosei Co., Ltd.) was used. In the same manner as in Production Example 1, a toluene solution of a base polymer having a number average molecular weight of 7,500 having a carboxyl group at one end was obtained.
In the same manner as in Production Example 1, the following macromonomer (2) was obtained. The number average molecular weight was 7,700, and the weight average molecular weight was 17,600.
[0022]
[Example 1]
The present macromonomer (1) 20 parts, butyl methacrylate 20 parts, styrene 30 parts, ethyl acrylate 20 parts, methacrylic acid 1 part, hydroxyethyl methacrylate 9 parts and ion-exchanged water 30 parts are mixed with a homomixer to prepare a pre-emulsion. It was adjusted.
In a glass flask equipped with a stirrer, dropping funnel, nitrogen gas inlet tube and thermometer, put 70 parts of ion exchange water, 0.4 part of potassium persulfate and 0.7 part of ammonium carbonate, and replace the gas phase part with nitrogen. After that, the solution was kept at 80 ° C., and the pre-emulsion was dropped over 2 hours. After dropping, the temperature was maintained at 80 ° C. for 1 hour to complete the polymerization. Then, the objective aqueous resin emulsion was obtained by neutralizing until PH became 8 with triethylamine.
With respect to the obtained resin emulsion, the following physical properties were measured. As a result, the results of the storage stability test and the water resistance test were both good, and the amount of grid was as small as 0.05 parts.
a) Storage stability test: After the emulsion was stored at 25 ° C. for 1 week, the appearance was visually evaluated.
b) Water resistance test of coating film: The emulsion was applied to a steel sheet, dried at 25 ° C. for 2 weeks, and then the whitening state after the test piece was immersed in water for 2 days was visually observed.
c) Grid: filtered through a 200-mesh net, weighed after drying aggregates on the net.
[0023]
[Example 2]
Pre-emulsion by mixing 20 parts of the present macromonomer (2), 20 parts of butyl methacrylate, 30 parts of styrene, 20 parts of ethyl acrylate, 1 part of methacrylic acid, 9 parts of hydroxyethyl methacrylate and 30 parts of ion-exchanged water with a homomixer. It was adjusted.
In a glass flask equipped with a stirrer, dropping funnel, nitrogen gas inlet tube and thermometer, put 70 parts of ion exchange water, 0.4 part of potassium persulfate and 0.7 part of ammonium carbonate, and replace the gas phase part with nitrogen. After that, the solution was kept at 80 ° C., and the pre-emulsion was dropped over 2 hours. After dropping, the temperature was maintained at 80 ° C. for 1 hour to complete the polymerization. Then, the objective aqueous resin emulsion was obtained by neutralizing until PH became 8 with triethylamine.
The obtained resin emulsion had good results in both the storage stability test and the water resistance test, and the grid amount was as small as 0.03 part.
[0024]
【The invention's effect】
According to the present invention, an aqueous resin emulsion that forms a film having excellent water resistance is produced by copolymerizing the present macromonomer having a specific chemical structure with another copolymerizable monomer in an aqueous medium. The emulsion is suitable as a paint, a coating material, an adhesive and a pressure-sensitive adhesive.

Claims (1)

A method for producing an aqueous resin emulsion, comprising copolymerizing the following macromonomer and other radical polymerizable monomer in an aqueous medium in the presence or absence of an emulsifier.
Macromonomer: (a) a macromonomer having a radical polymerizable group at one end of a silicone or hydrophobic vinyl polymer, (b) polyalkylene glycol mono (meth) acrylate or polyalkylene glycol monoalkyl ether mono (meth) acrylate and A copolymer obtained by copolymerizing (c) other radical polymerizable monomer as desired, wherein the proportion of the macromonomer unit is 40 to 40% based on the total amount of all the structural units. 1% by weight, (b) the proportion of monomer units is 60 to 99% by weight, and (c) the proportion of monomer units is 0 to 15% by weight at one end of the copolymer. Macromonomer having a group