JP2551311B2 - Method for producing graft copolymer by suspension polymerization method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a graft copolymer by an aqueous suspension polymerization method, and the graft copolymer obtained by the present invention is suitable as an adhesive and a molding material.

[0002]

2. Description of the Related Art As one of the methods for synthesizing graft copolymers used for functionalizing polymeric materials,
A method is known in which a high molecular weight monomer having a polymerizable group at one end of a polymer molecule (generally called a macromonomer) is used, and it is copolymerized with another low molecular weight monomer, According to this method, a graft copolymer can be obtained in which the polymer portion of the macromonomer is the branch polymer and the polymer of the other low molecular weight monomer is the trunk polymer.

The macromonomer in the above synthesis method is synthesized by a method of capping the active end of a living polymer obtained by living polymerization with a compound having a polymerizable group such as vinyl group, or by a radical chain transfer method. A method of reacting the obtained polymer having a carboxyl group at one end with a compound having an epoxy group and an ethylenically unsaturated bond in the presence of a quaternary ammonium salt or a quaternary phosphonium salt (hereinafter referred to as radical chain transfer method) The macromonomer synthesized by was commonly used.

The macromonomers prepared by the radical chain transfer method are abundant in their types, since monomers having no living polymerizable property can be used as the monomers constituting the polymer portion serving as the skeleton thereof. The synthetic method also has the advantage of being simple. A graft copolymer solution obtained by copolymerizing the macromonomer with another low molecular weight monomer in an organic solvent is widely used as a paint, an adhesive, and the like. However, when attempting to copolymerize macromonomers and other low molecular weight monomers by radical chain transfer method by aqueous suspension polymerization, blocking of polymerizable particles dispersed in water occurs and stable polymerization cannot be performed. was there.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a method for stably copolymerizing a macromonomer and another low molecular weight monomer by the above radical chain transfer method by aqueous suspension polymerization without causing blocking. The purpose was to.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a quaternary ammonium salt contained in a macromonomer used in the production of a graft copolymer by the suspension polymerization. Further, they have found that the quaternary phosphonium salt adversely affects the dispersion stability of the polymerizable particles in suspension polymerization, and completed the present invention.

That is, the present invention uses the above-described macromonomer from which a quaternary ammonium salt or a quaternary phosphonium salt is removed when suspension polymerization of the following macromonomer and other radical-polymerizable monomer is carried out in an aqueous medium. And a method for producing a graft copolymer by a suspension polymerization method. Macromonomer: A vinyl polymer having a carboxyl group at one end of the molecule (hereinafter referred to as a prepolymer) using a quaternary ammonium salt or a quaternary phosphonium salt as a catalyst,
A macromonomer having a radically polymerizable group at one end of the molecule, which is obtained by reacting with a compound having both a glycidyl group and a radically polymerizable group.

The present invention will be described in more detail below. The prepolymer which is the starting material of the macromonomer in the present invention has a number average molecular weight of 1,000 to 20,0.
A linear polymer of 00 is preferable, and preferable monomers constituting the same include carboxylic acid vinyl esters such as vinyl acetate, vinyl aromatic compounds such as styrene, methyl (meth) acrylate, and (meth) acrylic acid. Ethyl, (meth)
N-butyl acrylate, t-butyl (meth) acrylate,
(Meth) acrylic acid esters such as 2-ethylhexyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate, (meth) acrylonitrile, N-phenylmaleimide, etc. may be mentioned, and these monomers may be used alone or Two or more kinds can be used in combination.

The prepolymer is obtained by radical polymerization of azobisisobutyronitrile or the like with the vinyl monomer in an organic solvent in the presence of a mercaptan chain transfer agent having a carboxyl group such as mercaptoacetic acid or mercaptopropionic acid. It is synthesized by a method of radical polymerization using an initiator. Examples of the organic solvent used for the polymerization include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl isobutyl ketone and isopropyl alcohol.

Examples of the compound having both a glycidyl group and a radically polymerizable group to be reacted with the above prepolymer (hereinafter referred to as a polymerizable group-introducing compound) include glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether and the like.

The reaction between the prepolymer and the polymerizable group-introducing compound is carried out in the prepolymer organic solvent solution obtained by the radical polymerization, and the polymerizable group-introducing compound and the quaternary ammonium salt described below are added to the solution. Add a quaternary phosphonium salt as a catalyst, and add 3 to 60-140 ° C.
A macromonomer is obtained by reacting for 16 hours. As the quaternary ammonium salt or quaternary phosphonium salt, triethylbenzylammonium chloride, trimethylcetylammonium bromide, tetrabutylammonium bromide, trimethylbenzylammonium chloride, triphenylbutylphosphonium bromide, tetrabutylphosphonium bromide and the like are used.

The preferred amount of catalyst used is Prepolymer 1
It is 0.5 to 4 parts by weight per 00 parts by weight, and when using highly active trimethylbenzylammonium chloride, tetrabutylammonium bromide or tetrabutylphosphonium bromide, 0.5 to 1.5 parts by weight is preferable, For other quaternary ammonium salts or quaternary phosphonium salts, 2 to 4 parts by weight are preferable. The macromonomer solution thus obtained usually contains 0.5 to 4% by weight of a quaternary ammonium salt or a quaternary phosphonium salt based on the macromonomer.

In the present invention, a macromonomer obtained by removing an organic solvent from the macromonomer solution,
Although other radically polymerizable monomers are copolymerized by aqueous suspension polymerization, it is necessary to remove the quaternary ammonium salt or quaternary phosphonium salt contained in the macromonomer before the copolymerization. As a method of removing the quaternary ammonium salt or quaternary phosphonium salt from the macromonomer, a method of washing the macromonomer solution with pure water or an aqueous solution of a water-soluble salt is preferable.

The preferred method of washing the macromonomer solution with water is a method commonly used for washing the hydrophobic organic solution, that is, the organic solution and water are mixed in a container such as a separating funnel and then separated into liquids. Is the way. As wash water,
As described above, pure water or an aqueous solution of a water-soluble salt can be used, and when the aqueous solution of a water-soluble salt is used, the salt concentration is preferably 20% by weight or less. The water-soluble salt is used to increase the specific gravity of the wash water and facilitate liquid-liquid separation. Specifically, sodium chloride, sodium sulfate, sodium nitrate, potassium chloride, potassium sulfate, potassium nitrate, lithium chloride. , Lithium sulfate, lithium nitrate and the like are preferable, sodium chloride and sodium sulfate are preferable, and sodium sulfate is particularly preferable.

In the above washing method, the difference in specific gravity between the macromonomer solution and the washing water is preferably 0.05 or more.
When the difference in specific gravity is 0.05 or less, the separation speed between the organic layer and the aqueous layer is slow. When the above washing operation is carried out once, usually about 90% of the quaternary ammonium salt or quaternary phosphonium salt in the macromonomer solution can be removed.
% Can be removed.

The macromonomer solution from which the quaternary ammonium salt or quaternary phosphonium salt has been removed by the above-mentioned method is further subjected to a method such as vacuum distillation or spray drying to remove the organic solvent to give a macromonomer for aqueous suspension polymerization. can get. The concentration of the quaternary ammonium salt or quaternary phosphonium salt in the macromonomer used for suspension polymerization is 0.1% by weight based on the weight of the macromonomer.
The following is preferable, and 0.05% by weight or less is more preferable.

Other radically polymerizable monomers copolymerized with the above macromonomer include vinyl acetate, vinyl chloride, styrene, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, ( Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Examples thereof include acrylonitrile, maleic anhydride, hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate. Preferably, vinyl acetate, vinyl chloride, which is a liquid at room temperature and has water-insoluble properties,
Styrene and alkyl (meth) acrylate.

The preferred use ratio of the macromonomer and the radical-polymerizable monomer in the present invention is 5 to 50% by weight of the macromonomer and 50 to 9 of the other radical-polymerizable monomer.
It is 5% by weight. The preferred concentration of the quaternary ammonium salt or the quaternary phosphonium salt in the monomer mixture composed of the macromonomer and the other radically polymerizable monomer is 0.03% by weight or less. If the concentration exceeds 0.03% by weight, suspension polymerization tends to be unstable.

Dispersants used in suspension polymerization include polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium polyacrylate and high molecular weight compounds of maleic anhydride-vinyl acetate copolymer, and calcium, barium, strontium and magnesium. , Aluminum, iron or cobalt phosphates. The amount of the dispersant used is based on the total amount of the monomer mixture in which the macromonomer and the low molecular weight monomer are combined,
0.1 to 5% by weight is preferable. In the present invention, together with the above dispersant, sodium dodecylbenzene sulfonate,
A suitable amount of a surfactant such as sodium octyl sulfate, sodium sulfosuccinic acid or alkali lauryl sulfate may be used in combination.

As the polymerization initiator, t-butyl perbenzoate, t-butyl peroctoate, azobisisobutyronitrile or the like can be used, and the polymerization temperature is 3
A temperature of 0 to 100 ° C is suitable. The procedure of polymerization is as follows.
Water, a dispersant and a surfactant were charged in a polymerization vessel, and then a solution prepared by dissolving a polymerization initiator in a monomer mixture was added, and fine suspension particles were formed by stirring. Is preferably raised to the polymerization temperature. Polymerization time is usually 3
~ 10 hours.

[0021]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. In addition, all "parts" described in each example are "parts by weight".

Example 1 A 45% toluene solution of the following macromonomer synthesized by the radical chain transfer method was used. Polymethylmethacrylate type macromonomer Polymerizable group: methacryloyl group Number average molecular weight: 5,500 Quaternary ammonium salt (triethylbenzylammonium chloride) content: 0.9% by weight (based on macromonomer solids)

To 100 parts of a 45% toluene solution of the above macromonomer, 50 parts of a 15% aqueous solution of sodium sulfate was added, and the resulting mixed solution was shaken for 30 minutes in a separating funnel to mix, and then allowed to stand overnight. . When the amount of quaternary ammonium salt remaining on the organic layer side is calculated by separating the organic layer and the aqueous layer and measuring the halogen ion concentration in the aqueous layer by titration, the concentration is based on the macromonomer. Was 0.072% by weight. The organic layer was distilled under reduced pressure to remove the solvent, and the obtained solid macromonomer was pulverized,
A powdery macromonomer was obtained, which was subjected to the following aqueous suspension polymerization.

In a glass flask equipped with a stirrer, a reflux condenser and a thermometer, 300 parts of distilled water and calcium phosphate are added.
2.5 parts, 30 parts of macromonomer, 60 parts of styrene, 10 parts of glycidyl methacrylate and 1.5 parts of azobisisobutyronitrile were charged, the temperature was raised to 80 ° C., and polymerization was carried out for 5 hours. Here, the amount of the quaternary ammonium salt contained in the monomer mixture containing the macromonomer was 0.022% by weight. After the obtained polymer powder was dried, coarse particles were separated by a 10-mesh sieve, and the weight ratio of the particles was 2.2%.

[0024]

Comparative Example 1 A toluene solution of the above polymethylmethacrylate type macromonomer containing a quaternary ammonium salt was prepared.
After vacuum distillation as it was to obtain a powdery macromonomer, aqueous suspension polymerization was carried out in the same manner as in Example 1. The obtained polymer powder contained 11% of coarse particles.

[0025]

According to the present invention, a polymerizable dispersion particle comprising a macromonomer and another low molecular weight monomer is excellent in water dispersion stability, and a graft copolymer having a small content of coarse particles is obtained by aqueous suspension polymerization. Obtainable.

Claims (1)

(57) [Claims] 1. A macromonomer from which a quaternary ammonium salt or a quaternary phosphonium salt has been removed is used in suspension polymerization of the following macromonomer and other radically polymerizable monomers in an aqueous medium. A method for producing a graft copolymer by the suspension polymerization method. Macromonomer: Obtained by reacting a vinyl polymer having a carboxyl group at one end of the molecule with a compound having both a glycidyl group and a radical polymerizable group, using a quaternary ammonium salt or a quaternary phosphonium salt as a catalyst.
A macromonomer having a radically polymerizable group at one end of the molecule.